Library

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1995-1999
  • 1970-1974  (2,054)
  • 1970  (2,054)
  • Polymer and Materials Science  (1,970)
  • Engineering  (54)
  • Bone  (30)
  • Nuclear reactions
Material
Years
  • 1995-1999
  • 1970-1974  (2,054)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 183-188 
    ISSN: 1432-0827
    Keywords: Bone ; Enamel ; Apatite ; Hydroxyl ; Composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une méthode de détermination du contenu total en hydroxyle est décrite au niveau l' élément minéral des tissus calcifés. De l'os bovin anorganique et de l'émail dentaire sont dissouts dans un solvant non-aqueux (du chlorure méthanolique hydrogéné) et l'eau formée à partir des ions hydroxyle et carbonate, par dissolution acide du minéral, est déterminée par titration selon la méthode de Karl Fischer. L'eau, formée par réaction avec le carbonate, est calculée et soustraite du montant total de l'eau pour dèterminer la quantité d'eau, dérivée de l'ion hydroxyle. Les éléments inorganiques des échantillons sont ègalement déterminés. En utilisant des équations simultanées, basées sur l'équivalence électrochimique des ions à la surface et dans la maille de l'hydroxyle-apatite, les résultats des études de composition chimique sont utilisés pour calculer les quantités d'hydroxyle dans chaque substance. Le contenu en ion hydroxyle de l'os anorganique, basé sur ce traitement théorique, tenant compte de 2 hydroxyles par molécule, est de 1.40 moles par gramme, alors que, par analyse directe, on trouve 1.01±0.026 (S.E) m moles par gramme. Pour un échantillon d'émail dentaire, d'origine diverse, les valeurs théoriques et les valeurs expérimentales, relevées pour les contenus en hydroxyle, sont respectivement de 1.64 et 1.62 m moles par gramme.
    Abstract: Zusammenfassung Es wird eine Methode zur Bestimmung des gesamten Hydroxylgehaltes im Mineral von verkalkten Geweben beschrieben. Anorganischer Knochen und Zahnschmelz vom Rind wurden in einem wasserfreien Lösungsmittel (Methanolhydrogenchlorid) gelöst und das aus Hydroxyl- und Carbonat-Ionen sich bildende Wasser beim sauren Auflösen des Minerals mit der Titration nach Karl Fischer bestimmt. Das aus der Carbonatreaktion entstehende Wasser wurde berechnet, von der gesamten Wassermenge abgezogen und so der vom Hydroxylion her stammende Wasseranteil ermittelt. Die Proben wurden auf anorganische Bestandteile hin untersucht. Unter Anwendung simultaner Gleichungen, die sich auf die elektrochemische Äquivalenz der Ionen an der Oberfläche und im Kristallgitter von Hydroxyapatit stützten, konnten die Werte der chemischen Zusammensetzung zur Berechnung der Hydroxylmenge in jeder der Substanzen benützt werden. Auf Grund der theoretischen Berechnung und unter Annahme von 2 Hydroxylgruppen pro Molekül fand sich im anorganischen Knochen ein Hydroxylionengehalt von 1,40 mMol/g; durch die direkte Bestimmung konnte ein solcher von 1,01±0,026 (S.E.) mMol/g nachgewiesen werden. In einer gepoolten Zahnschmelzprobe betrug der Hydroxylgehalt theoretisch berechnet 1,64 mMol/g und praktisch bestimmt 1,62 mMol/g.
    Notes: Abstract A method is described for estimation of the total hydroxyl content of the mineral of calcified tissues. Anorganic bovine bone and dental enamel were dissolved in a nonaqueous solvent (methanolic hydrogen chloride) and the water formed from hydroxyl and carbonate ions by acid dissolution of the mineral was determined by the Karl Fischer titration. Water formed by reaction of carbonate was calculated and subtracted from the total amount of water to give the quantity of water derived from hydroxyl ion. The samples were analyzed for inorganic constituents. Using simultaneous equations, based upon the electrochemical equivalence of ions on the surface and lattice of hydroxyapatite, the data of chemical composition were used to calculate the amounts of hydroxyl in each substance. The content of hydroxyl ion of anorganic bone based on this theoretical treatment, assuming 2 hydroxyls per molecule, was 1.40 m moles per gram, and by direct analysis was 1.01±0.026 (S.E.) m moles per gram. With a pooled dental enamel sample, theoretical and determined values for hydroxyl contents were 1.64 and 1.62 m moles per gram, respectively.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 13-20 
    ISSN: 1432-0827
    Keywords: Phospholipids ; Hydroxyapatite ; Bone ; Chelation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé L'association de phospholipides et de la phase minérale de tissus calcifiés est étudiée en équilibrant un mélange de phosphatides avec de l'os anorganique. L'os est élué progressivement avec du chloroforme, chloroforme/méthanol et chloroforme/méthanol/HCl. Dans chaque éluat, les phospholipides sont identifiés par chromatographie quantitative. Les phosphatides acides et neutres sont présents, dans des proportions variables, dans l'éluat chloroformique de l'os anorganique. Ces lipides constituent plus de 80% des phospholipides totaux liés. L'extraction chloroforme/méthanol permit d'isoler un groupe de lipides essentiellement neutres. La composition de cet éluat d'os anorganique est voisin de l'extrait de solvant neutre d'os compact bovin minéralisé. Au troisième stade d'élution, on a pensé que lorsque l'acide du produit d'extraction agit comme un agent de déminéralisation, on pouvait comparer l'éluat avec l'extrait lipidique, obtenu après déminéralisation de l'os compact. Certes il existe des similitudes entre les phospholipides acides de l'extrait obtenu après déminéralisation et le troisième éluat lipidique de l'os. Il est possible que les phospholipides acides soient liés par des liaisons coordonnées aux ions Ca2+ et Mg2+ de la maille apatitique de l'os. En présence d'acide ou d'agent de déminéralisation, ces ions métalliques sont déplacés. Le rôle de ces composés de liaison, en tant que ponts entre les phases organiques et inorganiques des tissus calcifiés, est discuté.
    Abstract: Zusammenfassung Durch Äquilibration eines Gemisches von Phosphatiden mit anorganischen Knochen wurde die Bindung zwischen Phospholipiden und dem Mineralanteil von Hartgewebe untersucht. Der Knochen wurde sukzessive mit Chloroform, Chloroform/Methanol und Chloroform/Methanol/HCl eluiert. Die Phospholipide wurden in jedem der Eluate chromatographisch identifiziert und anschließend quantitativ bestimmt. Sowohl die sauren als auch die neutralen Phosphatide waren in verschiedenen Mengen im Chloroformeluat des anorganischen Knochens vorhanden. Zusammen machten diese Lipide über 80% der gesamtengebundenen Phospholipide aus. Die Extraktion in Chloroform/Methanol entzog dem anorganischen Knochen eine Gruppe von Lipiden mit vorwiegend neutralem Charakter. Die Zusammensetzung dieses zweiten Eluates aus dem anorganischen Knochen war jener ähnlich, wie sie für den Extrakt aus dem mineralisierten kompakten Rinderknochen mit einem neutralen Lösungsmittel beschrieben ist. Bei der dritten Elution wurde erörtert, daß dieses Eluat mit dem nach Demineralisation erhaltenen Lipidextrakt von kompakten Knochen verglichen werden kann, da die Säure des Extraktionsmittels demineralisierend wirkt. In der Tat wurden, was die sauren Phospholipide anbetrifft, Ähnlichkeiten zwischen dem Extrakt nach Demineralisation und dem dritten Lipideluat des Knochens festgestellt. Als Interpretation dieser Resultate wurde vorgeschlagen, daß die sauren Phospholipide koordinativ an Ca2+- und Mg2+-Ionen des Apatitgitters des Knochens gebunden sind. In einem sauren oder einem demineralisierenden Milieu werden die Bindungen zu Metallionen zerstört. Die Rolle solcher koordinativ wirkender Verbindungen als Brücken zwischen organischen und anorganischen Phasen mineralisierter Gewebe wurde besprochen.
    Notes: Abstract The association of phospholipids with the mineral phase of hard tissues was investigated by equilibrating a mixture of phosphatides with anorganic bone. The bone was eluted sequentially with chloroform, chloroform/methanol and chloroform/methanol/HCl. In each of the eluates, the phospholipids were identified chromatographically and were quantitated. Both acidic and neutral phosphatides were present, in variable proportions, in the chloroform eluate of the anorganic bone. Together, these lipids accounted for over 80% of the total bound phospholipids. Chloroform/methanol extraction removed a group of lipids from the anorganic bone which was predominately neutral in character. The composition of this second eluate of anorganic bone resembled the reported neutral solvent extract of mineralized bovine compact bone. At the third elution step, it was argued that as the acid in the extractant acted as a demineralizing agent, this eluate could be compared with the post-demineralized lipid extract of compact bone. With respect to their acidic phospholipids, similarities were noted between the post-demineralized extract and the third lipid eluate of bone. To interpret this finding, it is speculated that acidic phospholipids were bound through co-ordinating bonds to Ca2+ and Mg2+ ions of the apatite lattice of bone. In the presence of either acid or a demineralizing agent, these metal ions were displaced from the ligands. The role of such co-ordinating compounds as bridges between organic and inorganic phases of mineralized tissues is discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 170-182 
    ISSN: 1432-0827
    Keywords: Cartilage ; Bone ; Gonadectomy ; Histochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des coupes de tibias de rats mâles et femelles, gonadectomisés et témoins, sont soumises à divers examens histologiques et histochimiques pour étudier les effets de la gonadectomie au niveau du tissu osseux. Le cartilage épiphysaire proximal des rats castrés et des rattes, ayant subi l'ablation des ovaires, est oblitéré par de l'os 5 mois après l'intervention. En outre, la diaphyse présente une ostéoporose. La matrice intercellulaire du cartilage épiphysaire des rats gonadectomisés est fortement PAS positive, contrairement à la réaction fortement alcian positive de la matrice des animaux témoins. Les travées diaphysaires des rats gonadectomisés se colorent en rouge avec le PAS et contiennent des régions étendues d'ilôts cartilagineux calcifiés. En outre, le cartilage épiphysaire et les travées osseuses de ces animaux se colorent faiblement à la ninhydrine-Schiff. Les réactions colorées suggèrent que la gonadectomie induit une altération dans le degré d'agrégation protéino-mucopolysaccharidique de la matrice organique; ce qui interfère probablement avec la minéralisation osseuse.
    Abstract: Zusammenfassung Tibiaschnitte von unbehandelten und kastrierten männlichen und weiblichen Ratten wurden mit verschiedenen histologischen und histochemischen Techniken untersucht, um die Knochenveränderungen im Anschluß an die Gonadektomie zu bestimmen. Es wurde beobachtet, daß sowohl beim kastrierten Männchen wie beim ovarektomierten Weibchen der proximale Epiphysenknorpel nach dem fünften postoperativen Monat durch Knochen „eingekapselt” ist. Dazu wurde auch eine Osteoporese des Knochenschaftes beobachtet. Der Epiphysenknorpel der kastrierten Ratten zeigte eine intensiv PAS-positive interzelluläre Matrix, im Gegensatz zu der alcianophil reagierenden Matrix von Kontrolltieren. Die Diaphysentrabekel von kastrierten Ratten färbten sich mit PAS rot und enthielten große Bezirke von mineralisierten Knorpelkernen. Dazu färbten sich der Epiphysenknorpel und die Trabekel dieser Tiere nur schwach mit der Ninhydrin-Schiff-Reaktion. Die Resultate der verschiedenen Färbungen zeigten, daß nach Gonadektomie eine Veränderung im Aggregatzustand der Protein-Mucopolysaccharidkomponente der organischen Matrix stattfindet, was zu einer Interferenz im Knochenmineralisationsprozeß führen könnte.
    Notes: Abstract Sections of the tibias from both intact and gonadectomized male and female rats were subjected to various histological and histochemical methods to determine the changes in the bone following gonadectomy. It was observed that both in castrated males and in ovariectomized females, the proximal epiphyseal cartilage became “sealed off” by bone after the fifth post-surgical month. In addition osteoporosis of the shaft of the bone was also observed. The epiphyseal cartilage of the gonadectomized rats exhibited intense PAS positive intercellular matrix in contrast to the alcianophilic ature of the matrix from control animals. The diaphyseal trabeculae from gonadectomized rats stained red with PAS and contained wide regions of calcified cartilage cores. In addition, the epiphyseal cartilage and bony trabeculae from these animals stained faintly in the ninhydrin-Schiff reaction. The staining reactions indicated that in gonadectomy there was an alteration in the state of aggregation of protein-mucopolysaccharide component of the organic matrix, a situation which would result in an interference in the mineralization of the bone.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-0827
    Keywords: Bone ; Epiphyses ; Calcification ; Physiologic ; Phospholipids ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Neuf polets, âgés de huit semaines, ont reçu 1 mCi de32P orthophosphate par voi intrapéritonéale. Ils ont été sacrifiés 2, 14, 38, 86 et 169 heures asprès injection. Les épiphyses des os longs ont été prélevées et séparés en cartilage au repos, cartilage en voie de prolifération, cartilage en voie de calcification et os spongieux primitif. Les lipides sont extraits: chaque tissu est déminéralisé et les lipides sont extraits à nouveau. On détermine ainsi le contenu en lipides totaux et en phospholipides, ainsi que leurs divers types et l'activité spécifique relative: Le contenu lipidique total de tous les tissus épiphysaires est de 1,35 à 4,52% en poids sec de matrice déminéralisée. La fraction phospholipipidique constitue environ la moitié des lipides. Dans les régions à contenu élevé en calcium, plus de phospholipides sont extraits après déminéralisation qu'avant. Des phospholipides neutres constituten 80–90% des phospholipides totaux dans les extraits réalisés avant déminéralisation, et seulement 48–65% dans les extraits après déminéralisation. La quantité des phospholipides, éthanolamine et sérine, est variable dans les diverses zone épiphysaires. La quantité et les types de phospholipides et leur rapport avec le degré de calcification concordent avec les résultats publiés pour les tissus de veaux. Les courbes d'activité spécifique démontrent une activité réduite au niveau de cartilage au repos et des échange très actifs en phospholipides dans les trois autres zones épiphysaires. Les divers types de phospholipides ont des activités métaboliques nettement différentes les uns par rapport aux autres. Les modes d'échanges particuliers de la phosphatidyle ethanolamine, de la phosphatidyle sérine et de la phosphatidyle inositol, au niveau du cartilage en voie de prolifération et de calcification, suggérent un rôle spécial de ces lipides dans le mécanisme de las croissance et de la calcification.
    Abstract: Zusammenfassung Neun achtwöchige Hühner erhielten intraperitoneal 1 mCi32P-Orthophosphat und wurden 2, 14, 38, 86 und 169 Std nach der Injektion getötet. Die Epiphysen der Röhrenknochen wurden seziert und ruhende, proliferierende und verkalkende Knorpel, sowie primäre Spongiosa voneinander getrennt. Die Lipide jeder Zone wurden extrahiert, jedes Gewebe wurde demineralisiert und die Lipide erneut extrahiert. Der Gehalt der Extrakte an Gesamtlipden und Phospholipiden sowie die Art der Phospholipide wurden bestimmt und die relative spezifische Aktivität: gemessen. Der Gehalt an Gesamtlipiden aller epiphysischen Gewebe betrug 1,35–4,52% des Trockengewichtes der demineralisierten Matrix. Phospholipide machten ungefähr die Hälfte der Gesamtlipide aus. In den Zonen mit hohem Calciumgehalt konnten mehr Phospholipide nach der Demineralisation als vorher extrahiert werden. Die neutralen Phospholipide entsprachen in vor der Demineralisation erhaltenen Extrakten 80–90% und in jenen nach der Demineralisation nur 48–65% der gesamten Phospholipide. Die Aethanolamin- und Serinphospholipidmengen variierten bedeutend in den verschiedenen Zonen der Epiphyse. Die Menge und die Art der Phospholipide und ihr Verhältnis in bezug auf Verkalkungsgrad waren in Einklang mit den Werten, die für das Kalb angegeben werden. Die Kurven der relativen spezifischen Aktivität zeigten ein träges metabolisches Muster im ruhenden Knorpel und einen sehr aktiven Phospholipidumsatz in den drei anderen Zonen der Epiphyse. Die verschieden gearteten Phospholipide zeigten untereinander merklich verschiedene metabolische Muster. Die speziellen Eigenschaften der Umsatzsmuster von Phosphatidyläthanolamin, Phosphatidylserin und Phosphatidylinositol in proliferierendem und verkalkendem Knorpel lassen vermuten, daß diese Lipide spezielle Funktionen im Wachstums- oder Verkalkungsprozeß ausüben.
    Notes: Abstract Nine eight-week old chicks were given32P orthophosphate, 1 mCi, intraperitoneally and killed 2, 14, 38, 86, and 169 hours after injection. Long bone epiphyses were dissected and separated into resting cartilage, proliferating cartilage, calcifying cartilages, and primary spongiosa. Lipids were extracted from each zone, each tissue was demineralized, and lipids were extracted again. The extracts were analyzed for total lipid and phospholipid content, types of phospholipids, and relative specific activity. Total lipid content of all epiphyseal tissues was 1.35 to 4.52% of the dry demineralized matrix weight. Phospholipid was about half the total. In the zones with higher calcium content more phospholipid was extracted after demineralization that before. Neutral phospholipids were 80 to 90% of the total phospholipids in predemineralization extracts and only 48 to 65% in extracts after demineralization. The amount of ethanolamine and serine phospholipids varied considerably in different epiphyseal zones. The amount and types of phospholipid and their relation to degree of calcification corroborated data reported for the calf. Relative specific activity curves revealed a sluggish metabolic pattern in resting cartilage and very active phospholipid turnover in the other three epiphyseal zones. The different types of phospholipids had markedly different metabolic patterns from each other. Special features of the turnover patterns of phosphatidyl ethanolamine, phosphatidyl serine, and phosphatidyl inositol in proliferating and calcifying cartilage suggest special roles of these lipids in the growth or calcification process.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 113-119 
    ISSN: 1432-0827
    Keywords: Lipid ; Bone ; Cartilage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Le contenu et la composition des lipides du tissue épiphysaire ont été étudiés chez le poulet. Les valeurs des lipides totaux, des triglycérides et des phospholipides sont, respectivement dans l'os, de 7,50, 1,81 et 1,02 mg/g et, dans le cartilage, de 5,20, 1,46 et 0,53 mg/g. Les principaux acides gras trouvés dans l'os aussi bien que dans le cartilage sont les acides palmitique et oléique, parmi les phospholipides, et les acides palmitique, oléique et linoléique parmi les triglycérides. Quant aux substrats étudiés, l'ordre d'incorporation dans les lipides totaux de l'os et du cartilage a été: palmitate 〉 glucose 〉 acétate 〉 citrate. L'acétate était le principal précurseur dans la synthèse des acides gras, alors que seule une faible protion de glucose a été trouvée dans les acides gras. L'estérification semble donc être la voie prédominante de la synthèse des lipides dans l'os et le cartilage du poulet.
    Abstract: Zusammenfassung Es wurde eine Untersuchung über den Gehalt und die Zusammensetzung der Lipide im Epiphysengewebe von Hühnchen durchgeführt. Es wurden 7,50 mg Gesamtlipide, 1,81 mg Triglyceride und 1,02 mg Phospholipide per Gramm Knochen gefunden. Die entsprechenden Werte per Gramm Knorpel waren 5,20, 1,46 und 0,53 mg. Die hauptsächlichsten Fettsäuren in den Phospholipiden von Knochen- und Knorpelgewebe waren Palmitin- und Ölsäure, in den Triglyceriden Palmitin-, Öl- und Linolsäure. Die untersuchten Verbindungen wurden in nachstehender Reihenfolge in Knochen- und Knorpel-Lipide eingebaut: Palmitin 〉 Glucose 〉 Acetat 〉 Citrat. Acetat war die hauptsächliche Ausgangssubstanz für die Fettsäure-Synthese, während nur ein unbeträchtlicher Teil der Glucose in den Fettsäuren vorgefunden wurde. Veresterung ist anscheinend der vorherrschende Weg der Fettsynthese in Knorpel- und Knochengewebe von Hühnchen.
    Notes: Abstract The content and composition of lipids of chick epiphyseal tissue were investigated. The amounts of total lipids, triglycerides and phospholipids in bone were 7.50, 7.81 and 1.02 mg/g, respectively, and in cartilage, 5.20, 1.46 and 0.53 mg/g, respectively. The main fatty acids of both bone and cartilage were palmitic and oleic in phospholipids, and palmitic, oleic and linoleic in triglycerides. For the substrates studied, the order of incorporation into total lipids of both bone and cartilage was palmitate 〉 glucose 〉 acetate 〉 citrate. Acetate was the main precursor for iatty acid synthesis whereas only a minor portion of glucose was found in the fatty acids. Esterification appeared to be the predominant pathway of lipid synthesis in chick bone and cartilage.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-0827
    Keywords: Bone ; Diabetes ; Osteoporosis ; Mastodon ; Formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Les comptages des densités de population d'ostéones secondaires permettent de déterminer le taux de formation d'os haversien sans utiliser un marquage tissulaire. Cette technique peut être appliquée à des specimens d'os paléontologiques et contemporains. A l'aide de cette technique, combinée à des marquages à la tétracycline, ces taux sont déterminés chez 180 sujets humains normaux, chez 10 diabétiques, 5 patients atteints d'ostéogenèse imparfaite et 17 femmes présentent une ostéoporose typique. La technique décrite ici est utilisée isolément sur de l'os de mastodonte. Chez les sujets normaux, une excellente concordance est observée entre les deux technique utilisées. Chez les diabétiques, les taux de formation, basée sur les comptages de population, sont diminués, mais dans des proportions moindres que celles déterminées par marquage à la tétracycline; une diminution dans la formation de l'os semble accompagner le développement de la maladie; elle ne semble pas exister pendant toute la durée de la vie. Au cours de l'ostéoporose, les taux, mesurés par les deux techniques, tombent au dessous de la normale, semblant ainsi indiquer qu'ils sont bas, au moment de l'apparition et de l'évolution de la maladie. Chez le mastodonte, le taux moyen de formation d'os est identique à celui de l'Homme et du Chien, lorsqu'on considère les moyennes entre la puberté et le milieu de la durée de vie totale.
    Abstract: Zusammenfassung Das Auszählen der Populationsdichte von sekundären Osteonen erlaubt es, die Haverssche Knochenbildungsgeschwindigkeit zu messen, ohne daß ein Gewebemarker eingesetzt werden muß, und zwar sowohl für paläontologische als auch für frische Knochenproben. Durch Anwendung dieser Technik zusammen mit Tetracyclinmarkierungen konnten solche Geschwindigkeiten bei 180 Normalpersonen, 10 Diabetikern, 5 Patienten mit Osteogenesis imperfecta und 17 Frauen mit symptomatischer Osteoporose gemessen werden; die neue Technik allein wurde auf einem Mastodon angewendet. Bei den Normalpersonen stimmten die Werte beider Methoden ausgezeichnet überein. Bei den Diabetikern war die aus der Populationszählung errechnete Bildungsgeschwindigkeit vermindert, jedoch in einem kleineren Ausmaß als die auf der Tetracyclinmarkierung basierende. Daraus ergibt sich, daß die verminderte Knochenbildung eher während der Entwicklung der Krankheit auftritt, als daß sie lebenslang bestehen bleibt. Bei Osteoporosepatienten fällt die mit beiden Methoden gemessene Geschwindigkeit unter die Norm, so daß sie niedrig ist, sowohl während der Entwicklung der Krankheit als auch bei bereits bestehenden Symptomen. Beim Mastodon war die mittlere Knochenbildungsgeschwindigkeit ähnlich wie der Mittelwert von jetzt lebenden Hunden und Menschen, wenn diese Geschwindigkeit in der Zeitspanne zwischen Pubertät und der mittleren Lebenszeit gemessen wird.
    Notes: Abstract Counts of the population densities of secondary osteons allow the determination of the haversian bone formation rate without the use of a tissue marker and can do so in paleontological as well as contemporary bone specimens. Using this technique, together with tetracycline markers, such rates were measured in 180 normal humans, in 10 diabetics, in 5 patients with osteogenesis imperfecta, and in 17 women with symptomatic osteoporosis; the new technique alone was used on a mastodon. In the normals, excellent agreement in values occurred between the tetracycline and population-based techniques. In diabetes, population-based formation rates were decreased, but to a lesser extent than tetracycline-based rates, implying that decreased bone formation accompanied development of the disease rather than existing throughout life. In osteoporosis, the rate fell below normal when measured by both methods, implying that it was low while the disease developed and the same after it had produced symptoms. In the mastodon, the mean bone formation rate was similar to that of comtemporary dogs and man when averaged between puberty and the middle of the total life span.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 254-259 
    ISSN: 1432-0827
    Keywords: Resorption ; Collagen ; Cells ; Bone ; Implant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé De jeunes rats donneurs, de même portée, sont injectés à l'aide de proline3H (1 μ Ci/g) et sacrifiés de 6 heures à 28 jours plus tard. Les omoplates sont prélevées, décalcifiées à l'EDTA et implantées dans la région dorsale sous-cutanée des rats receveurs. Elles sont prélevées 14 jours plus tard avec les tissus environnants, puis elles sont préparées pour l'autoradiographie et colorées à l'hématoxyline-éosine. Dans tous les cas, une prolifération de cellules géantes est observée autour de l'os. Dans les os d'animaux donneurs, prélevés 6 heures après injection de proline, l'isotope est localisé sur les bords de la face d'apposition de l'os et les cellules géantes ne l'éliminent pas. Vingt huit jours après administration de proline, lorsque, par suite de l'apposition et de la résorption, l'isotope est localisé sur le côté de l'os, en voie de résorption, les cellules géantes éliminent l'isotope, sans l'ingérer toutefois. Il apparait, ainsi, que le collagène osseux, formé récemment, est difficilement éliminé, alors que le collagène plus ancien peut être résorbé.
    Abstract: Zusammenfassung Jungen, als Spender verwendeten Ratten aus einem isologen Stamm wurde3H-Prolin (1 μ Ci/g) injiziert; sie wurden 6 std bis 28 Tage später getötet. Die Schulterblätter wurden herauspräpariert, mit EDTA demineralisiert und subcutan am Rücken von Empfängerratten implantiert. 14 Tage später wurden sie mit dem umgebenden Gewebe entfernt, geschnitten, zur Autoradiographie vorbereitet und mit Hämatoxylin-Eosin gefärbt. In allen Fällen fand sich eine Ansammlung von Riesenzellen rund um den Knochen. Knochen, welche 6 Std nach der Prolininjektion von Spendertieren entnommen wurden, enthielten die Markierung am Rande der Anlagerungsseite, und diese Markierung wurde durch die Riesenzellen nicht verdrängt. Knochen, welche 28 Tage nach der Prolininjektion von Spendertieren entnommen wurden, zeigten durch Anlagerung und Resorption die Markierung auf der resorptiven Seite des Knochens; die Riesenzellen entfernten die Markierung, jedoch ohne sie zu phagocytieren. Es scheint daher, wie es auch in der Literatur vorgeschlagen wird, daß neugebildetes Knochenkollagen nur schwer zu entfernen ist, älteres Kollagen jedoch resorbiert werden kann.
    Notes: Abstract Young donor rats of an isogenously related strain were injected with3H proline (1 μ Ci/g) and killed from 6 hours to 28 days later. The scapulae were removed, decalcified with EDTA and implanted subcutaneously into the backs of recipient rats. They were removed 14 days later with the surrounding tissue, sectioned, processed for autoradiography and stained with hematoxylin and eosin. In all cases there was a giant cell response round the bone. In bones removed from the donor animals 6 hours after proline injections, the label was on the edge of the appositional side of the bone and the giant cells did not remove it. By 28 days after proline administration when, due to apposition and resorption, the label was on the resorptive side of the bone, giant cells were seen removing the label, which however they did not ingest. It thus appears, as has been suggested in the literature, that recently formed bone collagen is removed with difficulty, but older collagen can be resorbed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 49-55 
    ISSN: 1432-0827
    Keywords: Bone ; Marrow ; Mast cell ; Parathyroid ; Calcium ; Deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des doses faibles d'hormone parathyroidienne sont administrées pendant 30 jours à des rats sevrés de l'espèce Sprague-Dawley. Chez 7 des 12 animaux utilisés, une hyperplasie des mastocytes est observée dans la moëlle tibiale métaphysaire proximale, sans chute associée du phosphore sérique ou élévation du calcium sérique. En outre, aucun changement de poids corporel ou du poids des cendres squelettiques n'est observé par rapport aux témoins. Un troisième groupe, soumis à une alimentation pauvre en calcium, mais contenant une quantité suffisante de vitamine D, présente une hyperplasie mastocytaire marquée au niveau de la moëlle osseuse de tous les animaux.
    Abstract: Zusammenfassung Entwöhnte Sprague-Dawley-Ratten erhiclten während einer Periode von 30 Tagen niedrige Dosen von Parathyroidhormon. 7 von 12 Tieren zeigten eine Mastzell-Hyperplasie im proximalen Teil des Tibiametaphysenmarks, ohne gleichzeitige Erniedrigung des Serumphosphates oder Anstieg des Serumcalciums. Femer traten im Vergleich zur Kontrollgruppe keine Veränderungen im Körpergewicht oder im Gewicht des Aschenrückstandes des Skelets auf. Eine dritte Gruppe, die eine Calcium-arme, entsprechend mit Vitamin D angereicherte Nahrung erhielt, zeigte eine ausgeprägte Mastzell-Hyperplasie im Knochenmark aller Tiere.
    Notes: Abstract Low doses of parathyroid hormone were administered over a 30-day period to Sprague-Dawley weanlings rats. In 7 of 12 animals, mast cell hyperplasia occurred in the proximal tibial metaphyseal marrow, without an associated fall in serum phosphorus or rise in serum calcium. Further, no alteration occurred in body weight or skeletal ash weight relative to the control population. A third group, on a calcium-deficient diet containing adequate vitamin D, showed marked bone marrow mast cell hyperplasia in all animals.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 146-152 
    ISSN: 1432-0827
    Keywords: Fluorides ; Bone ; Immobilisation ; Citrate ; Mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé L'effet de l'ingestion de fluor chez le rat, sous la forme de fluorure de sodium (NaF) et de monofluorophosphate de sodium (Na2PO3F), est étudié au niveau de tibias immobilisés à l'aide de résine acrylique. Après 4 semaines d'immobilisation, des humérus intacts et des tibias immobilisés et non-immobilisés sont étudiés en ce qui concerne l'épaisseur osseuse, la gravité spécifique et le contenu en citrate, cendre, calcium, phosphore et fluor. Nos travaux reconfirment les résultats antérieurs démontrant que l'administration de fluor augmente la minéralisation osseuse et compense ainsi la diminution de son épaisseur, de son contenu en cendres et de sa gravité spécifique, provoquée par l'atrophie osseuse, sans modifier le rapport Ca/P des cendres. L'augmentation de l'épaisseur osseuse est plus marquée chez les rats traités au Na2PO3F, malgré une incorporation fluorée moindre. Le contenu en cendre est plus faible au niveau des os des rats traités au NaF que dans ceux traités au Na2PO3F et ceux des témoins non fluorés. Des recherches ultérieures sont nécessaires pour étudier les avantages du Na2PO3F.
    Abstract: Zusammenfassung Die Wirkung von Fluorideinnahmen entweder in Form von Natriumfluorid (NaF) oder von Natriummonofluorophosphat (Na2PO3F) wurde bei Ratten verfolgt, indem der Tibiaknochen durch Anwendung von Acrylharz immobilisiert wurde. Nach 4 Wochen der Immobilisation wurden die unbehandelten Humeri und die nicht-immobilisierten und die immobilisierten Tibiae in folgender Hinsicht untersucht: Knochendicke, spezifisches Gewicht, Zitrat-, Asche-, Calcium-, Phosphor- und Fluoridgehalt. Die Resultate bestätigen frühere Befunde: die Fluoridgabe erhöht die Mineralisations-geschwindigkeit der Knochen und wirkt im atrophischen Knochen gegen die Abnahme der Knochendicke, des Aschegehaltes und des spezifischen Gewichts, ohne daß dadurch das Ca/P-Verhältnis der Asche verändert wird. Die Zunahme der Knochendicke war bei Na2PO3F-behandelten Ratten ausgeprägter, obwohl weniger Fluorid eingebaut wurde. Der Zitratgehalt war in den Knochen der mit NaF behandelten Ratten niedriger als in jenen von Tieren, die Na2PO3F erhielten oder die fluoridfrei gehalten wurden. Die erheblichen Vorteile des Na2PO3F rechtfertigen ausgedehntere Forschungen in dieser Richtung.
    Notes: Abstract The effect of fluoride intake in rats as sodium fluoride (NaF) and sodium monofluorophosphate (Na2PO3F) on immobilization of the tibial bone was investigated. After 4 weeks of immobilization intact humeri and non-immobilized and immobilized tibiae were examined for bone thickness, specific gravity, citrate, ash, and calcium, phosphorus and fluoride contents. The results confirm previous findings that administration of fluoride increases the mineralization rate of bones and counteracts the decrease in bone thickness,ash content and specific gravity induced by immobilization, without changing the Ca/P ratio of the ash. The increase in bone thickness was more marked in the Na2PO3F treated rats, in spite of a lower fluoride incorporation. The citrate content was lower in the bones of the NaF-treated rats than in the Na2PO3F-treated and fluoride-free rats. The potential advantage of Na2PO3F appears to justify more extensive investigation.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 277-287 
    ISSN: 1432-0827
    Keywords: Bone ; Enamel ; Hydroxyapatite ; X-ray Diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une étude de microscopie électronique est réalisée pour déterminer si l'élargissement des raies des diagrammes de diffraction aux rayons X, observée après divers procédés de préparation, est liée à la fragmentation des cristaux ou à l'espèce cristalline considérée. Les échantillons d'émail, obtenus par meulage à l'aide de diamants ou de fraises de carbones, tournant à grandes ou à petites vitesses, contiennent de grandes quantités d'émail finement pulvérisé, des quantités relativement grandes de cristaux individuels disséminés et relativement peu de particules (habituellement inférieures à 5 microns), contenant un nombre variable de cristaux intacts. Des échantillons témoins, obtenus par meulage à l'aide de billes, contiennent des cristaux intacts de 5–10 microns. Un meulage prolongé à l'aide de billes donne des quantités importantes de produits fins (inférieurs à 0.025 microns), qui augmentent avec un meulage plus prolongé. Les tailles des particules d'un monocristal d'hydroxyle-apatite synthétique, préparé à l'aide d'une meulette diamantée, tournant à faible vitesse, variant de 〈0.025 microns à 〉5 microns: les particules plus larges prédominent. Le fait de chauffer les cristaux d'os augmente nettement leur taille: par contre ils ne se modifient pas après meulage à l'aide de billes. Un plan de clivage préférentiel n'a pu être mis en évidence dans l'émail. La nature hétérogène et la morphologie cristalline peuvent, par conséquent, être responsables de la fragmentation élevée, qui a pu être constatée. Cette fragmentation cristalline est probablement responsable de l'élargissement des raies de diffraction aux rayons X, bien que l'espèce cristalline considérée puisse également être en cause.
    Abstract: Zusammenfassung Es wurde am Elektronenmikroskop untersucht, ob die Verbreiterung der Röntgendiffraktionsbanden, welche nach verschiedenen Aufbereitungstechniken beobachtet werden konnte, auf eine Kristallzertrümmerung oder auf Druck zurückzuführen ist. Alle Schmelzproben, die durch Zerreiben mit hoch- oder niedrigtourigen Diamantsteinen oder mit Carbidbohrern gewonnen wurden, enthielten große Mengen von feinabgespaltenem Schmelz, eine relativ große Anzahl von verstreuten einzelnen Kristallen und relativ wenig Partikel (gewöhnlich 〈5 μ), die aus einer variablen Anzahl von intakten Kristallen bestanden. Mit dem Kugelbohrer gewonnene Kontrollproben enthielten Aggregate von intakten Kriställchen in der Größe von 5–10 μ. Längeres Zerreiben mit dem Kugelbohrer ergab signifikante Mengen von feinabgespaltenem Material (〈250 Å), das sich mit zunehmendem Zerreiben noch vermehrte. Wurde ein einzelner großer synthetischer Hydroxyapatitkristall mit einem niedrigtourigen Diamantstein zerrieben, so variierte die Größe der Partikel zwischen 〈250 Å und 〉5 μ, wobei die größeren Partikel vorherrschten. Knochenkriställchen erfuhren beim Ausglühen eine merkliche Vergrößerung, blieben jedoch unbeschädigt nach verlängertem Zerreiben in der Kugelmühle. Es konnte nicht bewiesen werden, daß im Schmelz die Abspaltung nach bevorzugten Flächen vorgeht; die komplexe Natur und die Kristallmorphologie können deshalb für die beobachtete starke Zertrümmerung verantwortlich gemacht werden. Die Bandenverbreiterung, die bei der Röntgendiffraktion beobachtet werden konnte, ist wahrscheinlich auf die Zertrümmerung der Kristalle zurückzuführen, obschon auch Druck als Faktor eine Rolle spielen kann.
    Notes: Abstract A study in the electron microscope was carried out to determine if the broadening of X-ray diffraction patterns was related to crystal fragmentation or strain resulting from the preparative technique. All enamel samples, collected either by grinding with high- or low-speed diamond stones or by carbide burs, contained large amounts of finely-divided enamel, a relatively large number of scattered individual crystals and relatively few particles (usually 〈5 μ in size), containing varying numbers of intact crystals. Ball-ground control samples contained aggregates of unbroken crystallites 5–10 μ in size. Prolonged ball grinding produced a significant amount of finely-divided material (〈0.025 μ), the amount increasing with increased grinding. Particle sizes of material ground from a large single crystal of synthetic hydroxyapatite with a low-speed diamond stone ranged from 〈0.025 μ to 〉5 μ, the larger particles predominating. Annealing bone crystallites increased their size appreciably but they remained undamaged despite prolonged grinding in the ball mill. There was no evidence to suggest a plane of preferred cleavage in enamel; the composite nature and crystal morphology may be responsible, therefore, for the severe fragmentation observed. Crystallite fragmentation is probably responsible for the line-broadening observed in the X-ray diffraction pattern, although strain may also be a contributing factor.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 30-38 
    ISSN: 1432-0827
    Keywords: Phospholipids ; Bone ; Cartilage ; Mucopolysaccharides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Les tissus squelettiques de poissons téléostéens (Scomber scombrus, etGadus callaria) et d'élasmobranches (Raja batis etScyllium canicula) sont analysés pour leur contenu en lipides. Plus de phospholipides sont extraits des tissus osseux de téléostéens que des tissus cartilagineux d'élasmobranches. Outre la proportion lipidique plus élevée de l'os de téléostéens, des différences de composition lipidique ont été notées entre les deux tissus. Avant démineralisation, les extraits deGadus et Scomber sont surtout constitués de phospholipides neutres. Par contre, les phosphatides des tissus cartilagineux contiennent des quantités importantes de phospholipides acides. Après déminéralisation de l'os et du cartilage de poissions, les solvants pour lipides neutres éluent á la fois les phosphatides acides et neutres de ces tissus. Après extraction des lipides, le traitement des tissus déminéralisés par des solvant acides extrait à nouveau des lipides. Dans cette fraction finale, un grand nombre de phospholipides ont été retrouvés. A ce stade, d'autres phosphatides, que ceux mis en évidence chez les poissons précités, sont extraits à partir de l'os déminéralisé deScomber. Le principal phosphatide de la fraction finale est constitué par la cardiolipine dont des quantités plus importantes, que celles notées au niveau des autres tissus durs, sont retrouvées dans l'os deScomber.
    Abstract: Zusammenfassung Die Skeletgewebe der Knochenfische (Scomber scombrus undGadus callaria) und der Knorpelfische (Raja batis undScyllium canicula) wurden auf ihren Lipidgehalt untersucht. Es ergab sich, daß mehr Phospholipide aus dem Knochengewebe der Knochenfische extrahiert werden konnte, als dies aus dem Knorpelgewebe der Knorpelfische möglich war. Es wurde nicht nur eine größere Lipidmenge im Knochen der Knochenfische festgestellt, sondern auch noch Unterschiede in der Lipidzusammensetzung der beiden Gewebe beobachtet. Die vor der Demineralisation hergestellten Extrakte von Gadus und Scomber bestanden vorwiegend aus neutralen Phospholipiden. Dagegen enthielten die Phosphatide der Knorpelgewebe ansehnliche Mengen saurer Phospholipide. Nach der Demineralisation von Fischknochen und-knorpel wurden durch neutrale Lipidlösungsmittel sowohl saure als auch neutrale Phosphatide aus diesen Geweben eluiert. Wenn die demineralisierten Gewebe, denen bereits Lipide entzogen wurden, noch mit angesäuerten Lösungsmitteln behandelt wurden, konnten erneut Lipide aus Knochen und Knorpel extrahiert werden. Im letzten Extrakt konnten die verschiedensten Phospholipide nachgewiesen werden. In diesem Stadium konnten verhältnismäßig mehr Phosphatide aus dem demineralisierten Knochen von Scomber entzogen werden, als dies bei anderen Fischarten möglich war. Das wichtigste Phosphatid dieses letzten Extraktes war Cardiolipin. Tatsächlich war mehr Cardiolipin in den Knochen von Scomber vorhanden als in allen andern Hartgeweben.
    Notes: Abstract The skeletal tissues of teleost (Scomber scombrus andGadus callaria) and elasmobranch (Raja batis andScyllium canicula) fish were examined for the presence of lipids. It was found that more phospholipid was removed from the bony tissues of the teleosts than was extractable from the cartilaginous tissues of the elasmobranchs. Apart from there being a greater proportion of lipid associated with teleost bone, differences were also noted in the lipid composition of the two tissues. Before demineralization, inGadus andScomber, the extracts were predominantly of neutral phospholipids. In contrast, the phosphatides of the cartilaginous tissues contained appreciable quantities of acidic phospholipids. After demineralization of piscine bone and cartilage, neutral lipid solvents eluted both acidic and neutral phosphatides from these tissues. When the demineralized lipid extracted tissues were treated with acidified solvents, lipid was again removed from the bone and cartilage. In this final extract, a wide variety of phospholipids was detected. At this stage, more phosphatide was extracted from the demineralized bone ofScomber, compared with the other piscine species. The principal phosphatide of this final extract was cardiolipin. More cardiolipin was present in the bone ofScomber than in any other hard tissue.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 222-235 
    ISSN: 1432-0827
    Keywords: Mechanochemistry ; Bone ; Remodeling ; Stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un mécanisme nouveau tente d'expliquer comment des forces mécaniques augmentées ou diminuées, appliquées à l'os, sont transformées en activité ostéoblastique et/ou ostéoclastique. Une hypothèse mécano-chimique du remaniement osseux, induit par stress mécanique, est émise pour expliquer ce phénomène. L'os répond á un stress mécanique par une croissance différentielle de façon á résister au stress appliqué: par suite le remaniement osseux induit mécaniquement est probablement sous le controle d'un système “feedback” négatif. L'hypothèse consiste dans le fait qu'un changement de charge au niveau de l'os modifie la tension au niveau des cristaux d'apatite de l'os. Ceci modifie la solubilité des cristaux qui fournit ainsi le message de “feedback” négatif nécessaire aux cellules osseuses, sous la forme d'un changement chimique, indiut par un phénomène mécanique. Les cellules aggissent alors pour compenser les modifications de l'activé calcique localisée soit en construisant de l'os pour redistribuer le stress augmenté, ou en résorbant de l'os, qui est en surplus des besoins structuraux, liés à un stress réduit. Pour tester cette hypothèse, des cristaux d'hydroxyleapatite sont soumis à un stress et des changements d'activité ionique du calcium sont enregistrés à l'aide d'une électrode à cation divalent. Les résultats démontrent qu'un effet mécano-chimique peut etre détecté dans les cristaux d'apatite qui, soumis à un stress, engendrent une activité en calcium de 9×10−5 moles/litres et de 7×10−5 moles/litre, dans des conditions sans stress. Les résultats expérimentaux de cette étude et les données de la physiologie cellulaire s'accordent avec l'hypothèse mécano-chimique proposée.
    Abstract: Zusammenfassung Um zu erklären, in welcher Weise auf Knochen applizierte, erhöhte oder verminderte mechanische Stresse zu einer Osteoblasten- und/oder Osteoklastenaktivität führen, wird ein neuer Mechanismus vorgeschlagen. Eine mechanochemische Hypothese der Knochenneubildung, verursacht durch mechanische Stresse, wird besprochen, um dieses Phänomen zu erklären. Knochen reagiert auf mechanische Stresse mit differenziertem Wachstum, um damit dem angewandten Stress zu widerstehen; daraus folgt, daß mechanisch induzierte Knochenneubildung vermutlich durch ein negatives Feedback-System reguliert wird. Die Hypothese besteht darin, daß eine Veränderung der Ladung des Knochens eine Veränderung der Spannung der Hydroxyapatitkristalle im Knochen zur Folge hat. Dies wiederum verändert die Löslichkeit der Kristalle und gibt damit die benötigte negative Feedback-Botschaft an die Knochenzellen in Form einer mechanischinduzierten chemischen Umgestaltung weiter. Die Zellen verhalten sich nun dementsprechend, um der Änderung der örtlichen Calciumaktivität entgegenzuwirken; entweder wird Knochengewebe gebildet, um einen erhöhten Stress neu zu verteilen, oder jener Knochenanteil wird beseitigt, der bei reduziertem Stress einen Überschuß der Strukturbedürfnisse darstellt. Um diese Annahme zu überprüfen, wurden synthetische Hydroxyapatitkristalle einem Stress unterworfen, und die Änderung in der Aktivität der Calciumionen wurde mittels einer divalenten Elektrode zur Messung der Kationenaktivität registriert. Die Resultate zeigen, daß ein mechanochemischer Effekt in den Hydroxyapatitkristallen nachgewiesen werden kann, die unter Stress eine Calciumaktivität von 9·10−5 Mol/Liter, dagegen ohne Stress eine solche von 7·10−5 Mol/Liter erzeugen. Die Ergebnisse dieser Untersuchungen einerseits und die Aussagen der Zellenphysiologie andererseits stimmen mit der hier vorgeschlagenen mechanochemischen Hypothese überein.
    Notes: Abstract A new mechanism is presented to explain how increased or decreased mechanical stresses applied to bone are translated into osteoblastic and/or osteoclastic activity. A mechano-chemical hypothesis for bone remodeling induced by mechanical stress is presented in an attempt to explain this phenomenon. Bone responds to mechanical stress by differential growth so as to resist the applied stress; therefore mechanically induced bone remodeling is probably regulated by a negative feedback system. The hypothesis is that a change in the loading of bone results in an altered straining of the hydroxyapatite crystals in bone. This in turn alters the solubility of the crystals, providing the required negative feedback message to the bone cells in the form of a mechanically induced chemical change. The cells then take appropriate action to compensate for the alteration in the localized calcium activity either by building up bone to redistribute an increased stress, or by removing bone which is surplus to the structural needs imposed by a reduced stress. In order to test the hypothesis, synthetic hydroxyapatite crystals were stressed and changes in calcium ion activity were recorded from a divalent cation activity electrode. The results show that a mechanochemical effect can be detected in hydroxyapatite crystals which, when stressed, generate a calcium activity of 9×10−5 moles/l compared to 7×10−5 moles/l when unstressed. The experimental results in this study and evidence from cellular physiology are consistent with the mechanochemical hypothesis proposed here.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 1432-0827
    Keywords: Bone ; Osteodystrophy ; Hyperparathyroidism ; Resorption ; Osteoclasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La profondeur moyenne de l'os érodé, par unité de temps, au niveau de centres de résorption, est musurée sur des biopsies osseuses, marquées à la tétracycline et prélevées au niveau de 16 patients en dialyse rénale périodique, d'un adolescent présentant un rachitisme rénal et de l'hyperparathyroidie secondaire, et de 2 femmes adultes atteintes d'hyperparathyroidie primitive. L'index de résorption cellulaire est sub-normal au niveau des surfaces d'os haversien de tous les groupes. Il est sub-normal au niveau des surfaces osseuses de l'endoste cortical dans le groupe sous dialyse. Le matériel biopsique était insuffisant pour établir l'index dans les deux autres groupes. Il apparait ainsi que les ostéoclastes individuels, provenant de cas d'hyperparathyroidie de longue durée, résorbent l'os plus lentement que dans des conditions normales.
    Abstract: Zusammenfassung Die mittlere Tiefe von Knochenerosionen, die pro Zeiteinheit in den Resorptionszentren entstanden, wurde in Tetracyclin-markierten Knochenbiopsien gemessen. Die Biopsien stammten von 16 erwachsenen, periodisch hämodialysierten Patienten, ferner von einem Jugendlichen mit renaler Rachitis und sekundärem Hyperparathyreoidismus sowie von zwei erwachsenen Frauen mit erwiesenem Hyperparathyreoidismus. Dieser Index der Resorption auf cellulärer Ebene war in allen Gruppen subnormal, wenn er auf der Innenschicht der Haverschen Kanäle bestimmt wurde. Er war ebenfalls subnormal in der Gruppe dialysierter Patienten auf die cortico-endostale Knochenoberfläche bezogen. Bei den anderen zwei Gruppen konnte der Index für die letztgenannte Oberfläche nicht bestimmt werden, da zu wenig Material vorlag. Diese Resultate lassen vermuten, daß einzelne Osteoklasten in Fällen von langdauerndem Hyperparathyreoidismus beim Menschen den Knochen langsamer resorbieren als dies normalerweise der Fall ist.
    Notes: Abstract The mean depth of bone eroded in unit time at resorption centers was measured in tetracycline-labeled bone biopsies of 16 adult patients on periodic renal dialysis, of one adolescent boy with renal rickets and secondary hyperparathyroidism, and of two adult women with proven primary hyperparathyroidism. This index of cellular-level resorption was subnormal on haversian bone surfaces in all groups, and it was subnormal on cortical-endosteal bone surfaces in the dialysis group; there was insufficient material to evaluate the index on this latter surface in the other two groups. The results suggest that individual osteoclasts resorb bone more slowly than normal in naturally occurring human hyperparathyroid states of long standing.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 1-10 
    ISSN: 1432-0827
    Keywords: Bone ; Dentin ; Enamel ; Lipids ; Calcification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Le but de cette étude est l'analyse des lipides des tissus calcifiés au niveau de la dentine et de l'émail bovins et de l'os cortical humain. Les lipides extraits des tissues pulvérisés sont analysés qualitativement par chromatographie sur colonne. Des échantillons ont été déminéralisés et une seconde extraction a permis de comparer les résultats obtenus avec ceux de la première analyse. Les acides gras des lipides osseux sont étudiés par chromatographie en phase gazeuse et comparés à ceux de l'os spongieux et des expaces médulaires. Les tissus calcifiés contiennent du cholestérol et ses esters, des monoglycérides, des diglycérides, des triglycérides, des acides gras libres et divers phospholipides. A part certains cas, et en particulier l'émail bovin, où l'on n'a pas pu identifier des phospholipides, ces derniers sont constitués par de la lécithine, la lyso-lécithine, l'éthanolamine de phosphatidyle, la sphingomyéline, ainsi que par des substances qui pourraient être de l'acide phosphatidique et de la cardiolipine. La sérine de phosphatidyle a pu être isolée de la dentine bovine, seulement après déminéralisation, mais a pu être extrait de l'os à la avant et, après traitement à l'EDTA. D'autres lipides sont recueillis après déminéralisation à l'EDTA et une seconde dé minéralisation. Les lipides totaux extraits sont d'environ 20.28 mg/100 grammes de dentine, 1.97 mg/100 grammes d'émail et 2005 mg/100 grammes, d'os humain. Le constituant lipidique principal de l'os cortical humain est le triglycéride et la composition en acide gras est identique à celle de l'os spongieux et de la moëlle.
    Abstract: Zusammenfassung Drei verschiedene Materialien wurden untersucht: bovines Dentin, boviner Schmelz und menschliche Corticalis. Die aus den pulverisierten Geweben extrahierten Lipide wurden qualitativ mittels Säulenchromatographie analysiert. Die Proben wurden ebenfalls demineralisiert und ein zweites Mal extrahiert, damit die Resultate mit denjenigen vor der Demineralisation verglichen werden konnten. Die Fettsäuren der Knochenlipide wurden mittels Gaschromatographie untersucht und mit den Fettsäuren der Spongiosa und des Markes verglichen. In den verkalkten Geweben fanden sich Cholesterol, Cholesterolester, Monoglyceride, Diglyceride, Triglyceride, freie Fettsäuren und verschiedene Phospholipide. Mit einigen Ausnahmen, wie z. B. in bovinem Schmelz, wo Phospholipide nicht nachgewiesen werden konnten, bestanden diese Phospholipide aus Lecithin, Lysolecithin, Phosphatidyläthanolamin, Lysophosphatidyläthanolamin, Phosphatidylinositol, Sphingomyelin und Substanzen, welche Phosphatidsäure und Cariolipin sein könnten. Aus bovinem Dentin konnte Phosphatidylserin nur nach Demineralisation extrahiert werden; aus Knochen ließ es sich jedoch sowohl vor wie nach EDTA-Behandlung entfernen. Zusätzliche Lipide wurden aus Proben gewonnen, wenn diese mit EDTA demineralisiert und ein zweites Mal extrahiert wurden. Die gesamte aus den Geweben extrahierte Lipidmenge betrug im Mittel 20,28 mg/100 g Dentin, 1,97 mg/100 g Schmelz und 2005 mg/100 g menschlichen Knochen. Der Hauptteil der Lipide aus menschlicher Corticalis bestand aus Triglyceriden und die Zusammensetzung der Fettsäuren entsprach jener im Mark und in der Spongiosa.
    Notes: Abstract Three different materials were studied: bovine dentin, bovine enamel, and human cortical bone. Lipids extracted from pulverized tissues were analyzed qualitatively by paper chromatography and quantitatively by column chromatography. Sample materials were also demineralized and extracted a second time so that results could be compared to those obtained prior to demineralization. Fatty acids of bone lipids were investigated by vapor phase chromatography and compared to the fatty acids of trabecular bone and bone marrow. Calcified tissues were found to contain cholesterol, cholesterol esters, monoglycerides, diglycerides, triglycerides, free fatty acids, and various phospholipids. With some exceptions, such as bovine enamel where phospholipids could not be identified, these included lecithin, lysolecithin, cephalin, lysocephalin, monophosphoinositide, sphingomyelin, and substances which might be phosphatidic acid and cardiolipin. Phosphatidylserine was extractable from bovine dentin only after demineralization, but was removable from bone both before and after EDTA treatment. Additional lipids were obtained from sample materials if they were demineralized with EDTA and extracted a second time. The total lipids extracted from the tissues averaged 20.28 mg/100 g dentin, 1.97 mg/100 g enamel, and 2,005 mg/100 g human bone. The major portion of human cortical bone lipids was triglyceride and the fatty acid composition was similar to that of marrow and trabecular bone.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 49-54 
    ISSN: 1432-0827
    Keywords: Collagen ; Bone ; Tendon ; Trace Metals ; Spectrographic Analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La composition en éléments métalliques, trouvés à l'état de traces, dans le minéral de l'os humain et dans l'os déminéralisé est mesurée par spectroscopie d'émissions et comparée à celle de l'os original entier et le tendon humain. Le Cu, Fe et Zn restent dans la matrice collagène de l'os et se retrouvent en quantités équivalentes dans le tendon. Il semble donc que ces ions soient liés chimiquement à la matrice collagène de ces tissusin vivo et que cette liaison joue un rôle dans leur activité. La majorité du Pb, Si, Sr, et V de l'os reste dans la fraction minérale, probablement sous la forme d'ions substitués ou interstitiels. Le Zn se répartit entre les phases organiques et minérales.
    Abstract: Zusammenfassung Die natürliche Zusammensetzung der Spurenelemente im menschlichen Knochemineral und im demineralisierten Knochen wurde mittels Emissionsspektroskopie gemessen und mit jener im ursprünglichen, intakten Knochen und in der menschlichen Sehne verglichen. Cu, Fe und Zn blieben in der Kollagenmatrix des Knochens zurück und wurden in ähnlichen Mengen in der Sehne gefunden. Deshalb wird angenommen, daß diese Ionen in vivo chemisch an die Kollagenmatrix dieser Gewebe gebunden sind und daß diese Bindung einen Anteil an ihrer Aktivität hat. Der größte Teil des Pb, Si, Sr und V des Knochens blieb in der Mineralfraktion, vermutlich als substituierte oder interstitielle Ionen. Zn ist gleichmäßig auf die organische und anorganische Phase verteilt.
    Notes: Abstract The natural trace metal compositions of human bone mineral and demineralized bone were measured by emission spectroscopy and compared with those of the original whole bone and human tendon. Cu, Fe and Zn remained in the collagenous matrix of bone and were found in similar quantities in tendon. It is suggested, therefore, that these ions are chemically bound to the collagen matrix in these tissuesin vivo, and that the binding has a part in their activity. Most of the Pb, Si, Sr, and V in bone remained with the mineral portion, probably as substituted or interstitial ions. Zn is divided between the organic and mineral phases.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 70-76 
    ISSN: 1432-0827
    Keywords: Bone ; Soft tissue ; Sodium 22 ; Exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des groupes de jeunes rats sont injectés par voie intraveineuse avec du22Na. Après divers intervalles de temps courts, du sérum et des fragments de foie, de muscle squelettique, de rein et d'os compact soigneusement isolé sont prélevés et étudiés en ce qui concerne les concentrations en sodium stable et isotopique radioactif. La pénétration du22Na dans les tissus mous examinés est très rapide et, après 10 minutes, seule une faible proportion de sodium tissulaire reste relativement inaccessible à la circulation. La vitesse d'absorption de22Na par l'os compact tibial peut être divisée en deux phases: a) une phase rapide qui semble uniquement limitée par la circulation sanguine de l'os et qui est compatible avec la théorie des cycles et b) une phase bien plus lente qui peut s'effectuer par diffusion de l'état solide, recristallisation et remaniement physiologique et qui peut se définir de façon correcte par une formule de fonction de puissance.
    Abstract: Zusammenfassung Gruppen von jungen Ratten erhielten22Na intravenös injiziert. Anschließend wurden nach verschiedenen kurzen Zeitintervallen Proben von Leber, Skelettmuskel, Niere, Serum und saubergereinigten kompakten Knochen entnommen und die Konzentrationen des beständigen und des radioaktiven Natriums gemessen. 22Na drang sehr rasch in die untersuchten Gewebe ein, und nach 10 min blieb nur eine kleine Menge nicht-austauschbares Natrium im Gewebe zurück. Die Geschwindigkeit der22Na-Aufnahme im kompakten Knochengewebe der Tibia konnte in zwei Komponenten aufgeteilt werden: a) Ein rascher Vorgang, der einzig durch die Blutzirkulation im Knochen begrenzt zu sein scheint und der mit dem „cycling concept” vereinbar ist. b) Ein viel langsamerer Vorgang, der eine Diffusion im festen Zustand, eine Rekristallisation und einen physiologischen Umbau einschließen kann und der entsprechend durch eine Potenzfunktion ausgedrückt wird.
    Notes: Abstract Groups of young rats were intravenously injected with22Na. At various short time intervals thereafter samples of liver, skeletal muscle, kidney, serum and thoroughly-cleaned compact bone were removed and assayed for both stable and radioisotopic concentrations of sodium. Penetration of22Na into the analysed soft tissues was very rapid and after 10 minutes only a small amount of tissue sodium remained relatively unavailable to the circulation. The rate of22Na-uptake by the tibial compact bone could be divided into two components: (a) a fast process which appears to be limited only by the blood circulation in bone and is compatible with the cycling concept and (b) a much slower process which may involve solid state diffusion, recrystallisation and physiological remodelling and which is adequately defined by a power function expression.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 103-112 
    ISSN: 1432-0827
    Keywords: Calcium ; Strontium ; Bone ; Exchange ; Equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La réactivité de l'os de rat envers un contenu faible et élevé de strontium a été étudiée par la technique de l'échange radioisotopique dans des conditionsin vitro bien définies. Des courbes d'absorption de solution de45Ca par des poudres d'os, pauvres et riches en strontium, ainsi que celles de solution de85Sr par des poudres d'os, riches en strontium, ont été analysées. Des fonctions exponentielles et de puissance ont été établies. Les résultats indiquent que le strontium en solution atteint un équilibre d'échange dans l'os, à contenu élevé en strontium, en huit heures environ et que le calcium continue à rechercher un état d'équilibre. Il semble, en outre, que les réactions de diffusion et d'échange de surface de la phase solide hydratée soient les mécanismes majeurs observés pendant ces expériences.
    Abstract: Zusammenfassung Die Reaktionsfähigkeit von Rattenknochen mit niederem und hohem Strontiumgehalt wurdein vitro mit der Isotopenaustauschtechnik unter gut definierten Bedingungen untersucht. Kurven, welche die vom Knochenpulver mit niederem und hohem Strontiumgehalt aufgenommene45Ca-Menge, sowie jene von Knochenpulver mit ausschließlich hohem Strontiumgehalt aufgenommene85Sr-Menge wiedergaben, wurden ausgewertet. Die Gleichungen der Exponential- sowie der Potenzfunktionen wurden abgeleitet. Die Interpretation der Ergebnisse dieser Experimente ist, daß das Strontium der Lösung ein Austauschgleichgewicht mit Knochen mit hohem Strontiumgehalt nach einer Periode von etwa 8 Std erreicht, während Calcium fortfährt, sich einem Gleichgewichtsstadium zu nähern. Es wird weiterhin vermutet, daß Diffusion und Oberflächen-Austauschreaktionen der Hydratationsschicht der soliden Phase die vorherrschenden Vorgänge sind, die im Laufe dieser Experimente stattfinden.
    Notes: Abstract The reactivity of rat bone of low- or of high-strontium content was investigated by the technique of radioisotopic exchange under well-defined conditionsin vitro. Analyses of curves depicting the uptake from solution of45Ca by low- and by high-strontium bone powders, and of85Sr by high-strontium bone powder only, were performed. Both exponential and power function expressions were derived. The interpretation of results of these experiments is that strontium of solution reaches exchange-equilibrium with bone of high-strontium content over a period of about eight hours, but that calcium continues to approach a state of equilibrium. Further, it is suggested that diffusion and surface exchange reactions of the hydrated solid phase are the dominant processes operating during the periods of these experiments.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 120-132 
    ISSN: 1432-0827
    Keywords: Vitamin A ; Bone ; Physiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une comparaison du remainiement osseux de la mandibule, du présphénoide et du fémur de veaux, recevant des quantités variables de vitamin A (2 doses carentielles et 2 doses de contrôle) pendant une durée de 16 semaines, a été réalisée. La croissance enchondrale a également été étudiée. Les résultats indiquent une altération du remaniement des os carencés, liée à une déficience de la résorption sous-périostée, cette dernière étant souvent remplacée par de l'apposition. Le traitement eut peu ou pas d'effet au niveau des surfaces périostées, où le remaniement normal ne nécessite pas de résorption. Etant donné que les osteéoclastes ne sont plus visibles au niveau des surfaces périostées au cours de l'état de carence, il semble que la vitamine A soit susceptible d'agir sur la differenciation de la cellule ostéogénique périostée en ostéoclaste.
    Abstract: Zusammenfassung Der Knochenumbau wurde in Unterkiefer, Präsphenoid und Femur von 4 Gruppen von Kälbern verglichen. Diese erhielten während einer Zeitspanne von 16 Wochen verschiedene Vitamin A-Mengen (2 Vitamin A-Mangel- und 2 Kontrollgruppen). Ferner wurde das endochondrale Wachstum grob gemessen. Die Resultate ergaben eine Veränderung des Umbaus von defizienten Knochen wegen der mangelhaften subperiostalen Resorption, die oft durch Wachstum ersetzt wurde. Jene periostalen Oberflächen, wo die Resorption für einen normalen Umbau nicht erforderlicht ist, wurden durch den Vitamin A-Mangel nur wenig beeinflußt. Die Tatsache, daß die Osteoklasten bei Vitamin A-Mangel von den periostalen Oberflächen verschwinden, läßt vermuten, daß Vitamin A die Fähigkeit der periostalen Stammzellen, sich zu Osteoklasten zu differenzieren, beeinflußt.
    Notes: Abstract The drift patterns of the mandible, presphenoid, and femur were compared in calves fed graded levels (2 deficient, 2 control) of vitamin A for 16 weeks. In addition, gross measurements of endochondral growth were recorded. The results indicated that drift of deficient bones was altered because subperiosteal resorption failed and was often replaced by growth. On those periosteal surfaces where resorption was not required for normal modeling, little effect was found due to treatment. In light of the evidence that osteoclasts disappear from the periosteal surfaces during deficiency, it is suggested that vitamin A affects the ability of the periosteal progenitor cell to differentiate as an osteoclast.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 19
    ISSN: 1432-0827
    Keywords: Pyrophosphate ; Orthophosphate ; Phosphonates ; Phosphates ; Parathyroid ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Lors d'essais précédents, nous avons montré que le pyrophosphate minéral (PPi) inhibe in vitro la dissolution de cristaux d'hydroxyapatite et nous avons suggéré que le PPi pourrait être un régulateur physiologique de la résorption osseuse. Dans ce travail, nous avons cherché si le PPi ainsi que d'autres produits phosphorés ont une action inhibitrice sur la résorption osseuse induite par l'hormone parathyroïdienne dans des calottes craniennes de souris et sur l'augmentation du calcium plasmatique induite par l'hormone parathyroïdienne chez des rats thyroparathyroïdectomisés maintenus en régime déficient en calcium. Ni l'orthophosphate, ni le pyrophosphate, ni les polyphosphates, ni deux phosphates polymérisés, inhibiteurs des phosphatases, n'ont inhibé la résorption des calottes craniennes, ni l'augmentation du calcium plasmatique. Par contre, certains phosphonates, contenant la liaison P-C-P, ont réduit la dissolution in vitro de cristaux d'hydroxyapatite et inhibé la résorption osseuse en culture de tissus à une concentration aussi faible que 1,6×10−6 molaire. Certains diphosphonates ont inhibé également l'augmentation du calcium plasmatique chez des rats thyroparathyroïdectomisés. La différence d'activité des produits contenant la liaison P-O-P ou P-C-P peut être attribuée à une plus grande résistance des derniers à une hydrolyse chimique ou enzymatique. Les phosphonates peuvent servier de modèle pour étudier l'action du PPi endogène de l'os. Ils peuvent également être utiles pour éclaircir le mécanisme de la formation et de la destruction osseuse et pourraient jouer un rôle dans la thérapie des maladies présentant une résorption osseuse accrue.
    Abstract: Zusammenfassung Frühere Untersuchungen zeigten, daß anorganisches Pyrophosphat (PPi) die Auflösung von Hydroxyapatit-Kristallenin vitro hemmt; es wurde vorgeschlagen, daß PPi physiologisch die Knochenresorption regulieren könnte. Bei diesem Versuch wurden PPi und andere Phosphatderivate auf ihre Eignung geprüft, die Knochenresorption zu hemmen, welche an Mäusecalvarien durch Parathormon hervorgerufen wurde; ebenso wurde abgeklärt, ob diese Substanzen in thyroparathyreoidektomierten, auf calciumarmer Diät gehaltenen Ratten in der Lage waren, den durch Parathormongaben verursachten Blutcalciumanstieg zu hemmen. Weder Orthophosphat, noch Pyrophosphat, Polyphosphat und zwei polymere Phosphatinhibitoren der Phosphatasen konnten die Resorption von Calvarien oder den Anstieg des Plasmacalciums hemmen. Dagegen verzögerten verschiedene Phosphonate mit P-C-P-Bindungen die Auflösung von Hydroxyapatitin vitro und hemmten dazu in so tiefen Konzentrationen wie 1,6×10−6M die Knochenresorption in der Gewebezucht. Einige Diphosphonate hemmten auch den Plasmacalciumanstieg bei thyroparathyreoidektomierten Ratten. Eine Ursache der unterschiedlichen Wirksamkeit von Substanzen, welche P-O-P- oder P-C-P-Bindungen enthalten, kann darin liegen, daß die letztgenannten einen größeren Widerstand gegenüber chemischer und enzymatischer Hydrolyse entgegenbringen. Phosphonate könnten als Model für die Wirkung des endogenen PPi im Knochen dienen und zudem zur Erläuterung der Mechanismen von Knochenbildung und-resorption nützlich sein; sie könnten auch zur Therapie jener Krankheiten, die eine erhöhte Knochenresorption zur Folge haben, herangezogen werden.
    Notes: Abstract Earlier studies have shown that inorganic pyrophosphate (PPi) inhibits the dissolution of hydroxyapatite crystalsin vitro and it has been suggested that PPi might be a physiological regulator of bone resorption. In this study PP1 and other phosphate compounds have been tested for their ability to inhibit bone resorption induced by parathyroid hormone in mouse calvaria and to inhibit the rise in plasma calcium induced by parathyroid hormone in thyroparathyroidectomised rats on a low calcium diet. Orthophosphate, pyrophosphate, polyphosphate and two polymeric phosphate inhibitors of phosphatases did not inhibit the resorption of calvaria or the rise in plasma calcium. In contrast, several phosphonates containing P-C-P bonds retarded the dissolution of hydroxyapatite crystalsin vitro, and, at concentrations down to 1.6×10−6M, inhibited bone resorption in tissue culture. Some diphosphonates also inhibited the rise in plasma calcium in thyroparathyroidectomised rats. One reason for the difference between the effects of compounds containing P-O-P and P-C-P bonds may be related to the greater resistance of the latter to chemical and enzymic hydrolysis. Phosphonates may provide a model for the effect of endogenous PP1 in bone, and might be of use in elucidating provide a model for the effect of endogenous PP1 in bone, and might be of use in elucidating mechanisms of bone formation and resorption and in the therapy of diseases that involve increased resorption of bone.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 227-238 
    ISSN: 1432-0827
    Keywords: Bone ; Cementum ; Crystallography ; Dentin ; Enamel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une structure périodique, formée de fines striations, a pu être observée au niveau des cristaux d'apatite sous le microscope électronique. Ces strations peuvent s'expliquer comme des projections de plans d'atomes ou de molécules sur le plan image, dont la périodicité est égale à la distance entre ces plans dans la maille cristalline. Des études antérieures indiquent une périodicité de 8.2 Å au niveau de cristaux hexagonaux d'émail de jeunes rats, constituée par la résolution des plans 100 de la maille cristalline de l'apatite. Au cours de cette étude, des striations ont pu être mises en évidence au niveau de l'émail, de la dentine, du cément et de l'os humain. Lorsque le faisceau incident d'électrons est parallèle à l'axe c, les trois types de plans équivalents, parallèles à cet axe, peuvent être mis en évidence simultanément. Même les cristaux de forme externe inhabituelle présentent une ultrastructure comportant une série de lignes droites. Des altérations dans les striations, indiquant une disloocation on un défaut d'alignement dans la maille cristalline, sont parfois notées en particulier près de la ligne médiane des cristaux. Des variations de taille et de forme des cristaux et des défauts de maille cristalline ont pu être démontrés au niveau de cristaux individuels. La cristallinité des apatites d'os et de dents peut être liée à l'ultrastructure des tissues normaux et pathologiques.
    Abstract: Zusammenfassung Im Elektronenmikroskop wird ein sich wiederholendes Muster von winzigen Furchungen innerhalb von Hydroxyapatitkristallen beobachtet. Dieses Randmuster läßt sich als Projektionen von Atom- oder Molekülebenen auf die Bildebene erklären, wobei die Periodizität derjenigen der Abstände zwischen diesen Ebenen im Kristallgitter entspricht. Frühere Untersuchungen ergaben ein Muster mit einer Periodizität von 8.2 Å in hexagonalen Kristallen vom Schmelz junger Ratten; dies stellt die Zerlegung in die 100 Ebenen des Hydroxyapatitkristallgitters dar. In der vorliegenden Untersuchung wurden in Kristallen von menschlichem Schmelz, Dentin, Zement und Knochengewebe Randmuster nachgewiesen. Wenn der einfallende Elektronenstrahl parallel zurc-Achse ist, können die 3 Gruppen von gleichwertigen Gitterebenen, welche parallel zu dieser Achse liegen, gleichzeitig zerlegt werden. Sogar Kristalle mit ungewöhnlicher äußerer Form zeigen eine Substruktur, welche aus Anordnungen von geraden Linien besteht. Defekte im Randmuster, welche Verschiebungen oder Aufbaufehler im Kristallgitter andeuteten, wurden gelegentlich beobachtet, vor allem gegen die Mittellinie der Kristalle. Variationen in der Kristallgröße und-form und das Vorkommen von Gitterdefekten innerhalb einzelner Apatitkristalle, konnten gezeigt werden. Die Kristallinität von Knochen- und Zahnapatiten steht in einer Wechselbeziehung zur feinen Struktur der Gewebe unter normalen und pathologischen Bedingungen.
    Notes: Abstract In the electron microscope, a repeating pattern of minute striations has been observed within hydroxapatite crystals. This fringe pattern can be explained as projections of planes of atoms or molecules on the image plane with a periodicity equal to the spacing between these planes in the crystal lattice. Previous studies have reported a pattern of 8.2 Å repeat periods in hexagonal crystals of young rat enamel, representing the resolution of the 100 planes of the hydroxyapatite crystal lattice. In the present study, fringe patterns were demonstrated in crystals of human enamel, dentin, cementum, and bone tissue. When the incident electron beam was parallel to thec axis, the three sets of equivalent lattice planes parallel to this axis could be resolved simultaneously. Even those crystals which had an unusual external form showed a substructure that consisted of arrays of straight lines. Defects of the fringe pattern indicating dislocations or stacking faults in the crystal lattice were occasionally observed, in particular near the midline of the crystals. Thus, it appears possible to demonstrate visually not only variations in crystal size and shape but also the presence of lattice defects within individual apatite crystals. By high resolution electron microscopy it may prove possible to correlate the crystallinity of bone and tooth apatites to the fine structure of these tissues in normal and pathological conditions.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 280-289 
    ISSN: 1432-0827
    Keywords: Osteocytes ; Bone ; Matrix ; Trabeculae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé L'ultrastructure des ostéocytes et de la matrice osseuse adjacente a des été étudiée au niveau maxillaires de jeunes rats, après décalcification à l'E.D.T.A. Les événements caractéristiques du cycle d'évolution de la cellule et ses effets sur la substance osseuse péricellulaire, peuvent être groupés en 3 stades: 1. La période de formation, pendant laquelle l'ostéocyte, analogue à l'ostéoblaste, montre, cependant, une diminution progressive en ergastoplasme et une réduction de l'appareil de Golgi. 2. La phase de résorption (ostéolyse ostéocytaire) caractérisée par l'apparition des lysosomes et leur activité, provoquant un élargissement de la lacune, où s'accumule du matériel fibrillaire et floconneux. 3. La dégénérescence éventuelle et la mort de la cellule. Une régénérescence cellulaire (“ostéoplasie”) n'a pas été observée.
    Abstract: Zusammenfassung Die Feinstruktur der Osteozyten und der unmittelbar angelagerten Knochenmatrix wurde an den Kiefern junger mit EDTA demineralisierten Ratten untersucht. Die Ereignisse, welche den Lebenszyklus der Zelle und ihre Wirkung auf die pericelluläre Knochensubstanz markieren, wurden in 3 Phasen eingeteilt: 1. die bildende Periode, während welcher der Osteocyt dem Osteoblasten gleicht, jedoch eine stufenweise Abnahme der Menge von endoplasmatischem Reticulum und in der Größe des Golgi-Apparates zeigt; 2. der Resorptionsbeginn (Osteozyten-Osteolyse), welcher durch eine weitere Abnahme der sekretorischen Organellen und das zackige Aussehen der perilacunären Grenze charakterisiert ist; 3. schließlich die Degeneration und der Tod der Zelle. Der Nachweis einer Regeneration („Osteoplasie”) konnte nicht erbracht werden.
    Notes: Abstract The fine structure of the osteocytes and of the immediately adjacent bone matrix has been studied in the jaws of young rats demineralized with EDTA. The events marking the life cycle of the cell and their effects on the pericellular bone substance have been grouped into 3 phases. 1. The formative period, where the osteocyte resembles an osteoblast but shows a gradual decrease in the amount of endoplasmic reticulum and in the size of the Golgi complex. 2. The beginning of resorption (osteocytic osteolysis) which is characterized by a further decrease of the secretory organelles and the jagged appearance of the perilacunar border. Later in this phase there is further development and activity of the lysosomes resulting in increased widening of the lacuna and accumulation in the lacuna of fibrillar and flocculent material. 3. The eventual degeneration and death of the cell. No evidence of regeneration (“osteoplasia”) has been observed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 22
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 189-195 
    ISSN: 1432-0827
    Keywords: Bone ; Pyrophosphatase ; Acid phosphatase ; Alkaline Phosphatase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé L'hydrolyse enzymatique du pyrophosphate et des esters phosphates est étudiée à l'aide d'extraits d'os de jeunes lapins. Les extrémités proximales de l'humérus et les extrémités distales des fémurs sont homogénéisées dans un tampon barbital (7.5 mM) à pH 7.4. L'activité de la pyrophosphatase extraite a des pH optimaux acide et alcalin. L'activité en pyrophosphatase acide, à pH 5.0, est indépendante du magnésium jusqu'à une concentration de 3 mM et est inhibée par un excès de cet ion. Les activités de la pyrophosphatase, à pH 5.0 et 7.4, sont inhibées par le fluorure. La constante de Michaelis de la pyrophosphatase, au pH optimum de 5.0, est de 1.4×10−3M. L'extrait d'os, placé dans une colonne Sephadex G200 et élué avec un tampon barbital (7.5 mM) à pH 7.4, contenant 1% de chlorure de sodium, permet une séparation des deux activités de pyrophosphatase à pH 5.0, l'activité optimale est associée avec une activité de phosphatase acide. L'activité des deux pyrophosphatase alcaline des os de lapins est étudiée de l'age de 5 à 60 jours.
    Abstract: Zusammenfassung Die enzymatische Hydrolyse von Pyrophosphat und Phosphatestern wurde an Knochenextrakten von jungen Kaninchen untersucht. Proximale Humerus- und distale Femurteile wurden in Barbitalpuffer (7.5 mM) bei einem pH von 7,4 homogenisiert. Die somit extrahierte Pyrophosphataseaktivität hatte ein saures und ein alkalisches pH-Optimum. Die saure Pyrophosphataseaktivität bei pH=5,0 blieb durch Magnesiumzusatz bis zu einer Konzentration von 3 mM unbeeinflußt und wurde durch einen Überschuß dieses Ions inhibiert. Beide Pyrophosphataseaktivitäten bei pH 5,0 sowie bei pH 7,4 wurden durch Fluoride inhibiert. Die Michaeliskonstante der Pyrophosphatase mit maximaler Aktivität bei pH=5,0 betrug 1,4·10−3M. Wenn der Knochenextrakt durch eine Sephadex G-200-Säule gegeben und die Kolonne anschließend mit einem Barbitalpuffer (7.5 mM) bei pH 7,4 mit Zusatz von 1% Natriumchlorid eluiert wurde, konnten die beiden Pyrophosphataseaktivitäten getrennt werden; diejenige mit einem Aktivitätsoptimum bei pH 5,0 zeigte ebenfalls die Aktivität einer sauren Phosphatase. Die Resultate der Aktivitätsbestimmung der beiden Pyrophosphatasen und der alkalischen Phosphatase in Kaninchenknochen in der Wachstumsperiode zwischen 5 und 60 Tagen werden mitgeteilt.
    Notes: Abstract A study was conducted of the enzymatic hydrolysis of pyrophosphate and ester phosphates by extracts of bones of young rabbits. The proximal ends of humeri and distal ends of femurs were homogenized in barbital buffer (7.5 mM) at pH 7.4. The extracted pyrophosphatase activity had acid and alkaline pH optima. The acid pyrophosphatase activity at pH 5.0 was independent of magnesium up to a concentration of 3 mM and was inhibited by an excess of this ion. Pyrophosphatase activities at both pH 5.0 and 7.4 were inhibited by fluoride. The Michaelis constant of pyrophosphatase with pH 5.0 optimum activity was 1.4×10−3 M. The bone extract, when loaded on a column of Sephadex G-200 and eluted with barbital buffer (7.5 mM) at pH 7.4 containing 1% sodium chloride, allowed a separation of the two pyrophosphatase activities; that at pH 5.0 optimum activity was associated with acid phosphatase activity. Results of experiments of the two pyrophosphatase activities and alkaline phosphatase in bones of rabbits as they aged from 5 to 60 days are presented.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 23
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 236-246 
    ISSN: 1432-0827
    Keywords: Trabeculum ; Bone ; Vertebra ; Density ; Strength ; Osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé L'objet de ce travail est de déterminer le rapport existant entre une force compressive et la densité osseuse des vertèbres humaines, ainsi que le rapport entre l'orientation des travées et la force de compression et enfin les effets du degré de charge sur la force compressive. Ce travail est effectué sur 71 échantillons prélevés au cours de 23 autopsies. Les densités sont déterminées et 2 types de densités sont calculées: 1. la densité apparente, en poids humide, divisée par le volume total de l'échantillon et 2. la densité réelle, en poids humide, divisée par le volume de la matrice osseuse, déterminé par le déplacement de l'eau. Des mesures de tests de compression sont effectuées sur des échantillons frais en utilisant une machine à tester les matériaux, de type Instron, sous des charges de déformation déterminées. Les résultats indiquent un rapport hautement significatif entre la densité apparente et la force de compression. Des rapports similaires sont trouvés entre le poids sec par volume total d'échantillon et le poids de cendre par volume total d'échantillon et la force compressive. Larsque la densité apparente augmente, la force compressive de l'échantillon diminue. Une régression négative entre la densité réelle et la force compressive est observée dans l'une des séries expérimentales de ce travail, où lorsque la densité de la matrice osseuse augmente, la force de compression de l'échantillon décroit. Ce rapport n'est pas significatif dans les deux autres séries expérimentales. La force de l'os vertébral est significativement plus élevée le long de l'axe supéro-inférieur ou axe vertical que le long des deux autres directions. Certains échantillons présentent une capacité significativement plus élevée de résistance à la compression, lorsque la charge de déformation est de 1 cm par minute, que lorsqu'elle est de 0,01 cm par minute.
    Abstract: Zusammenfassung Das Ziel dieser Untersuchung war, den Zusammenhang zwischen dem Widerstand gegen Kompression und der Dichte menschlicher Wirbel, den Zusammenhang zwischen der Anordnung der Trabekel und dem Kompressionswiderstand sowie die Auswirkung von der Belastung auf den Kompressionswiderstand festzustellen. Insgesamt wurden bei 23 Autopsien 71 Proben entnommen und untersucht. Es wurden Dichtebestimmungen vorgenommen und zwei verschiedene Dichten errechnet: 1. die scheinbare Dichte, bestimmt aus dem Naßgewicht dividiert durch das Gesamtprobenvolumen; 2. die effektive Dichte, bestimmt aus dem Naßgewicht dividiert durch das Volumen der Knochenmatrix, welches mittels Wasserverdrängung festgestellt werden konnte. An frischen Proben wurden Test-Druckmessungen bei verschiedenen bekannten Deformationsgraden mittels eines Instron-Materialprüfgerätes durchgeführt. Die Resultate ergaben eine hochsignifikante Beziehung zwischen der scheinbaren Dichte und dem Widerstand gegen Kompression. Gleiche Beziehungen fanden sich zwischen dem Kompressionswiderstand einerseits und dem Trockengewicht sowie Aschegewicht andererseits, beide auf das Gesamtprobenvolumen bezogen. Bei Zunahme der scheinbaren Dichte nahm der Kompressionswiderstand der Probe ab. Eine negative Regression zwischen effektiver Dichte und Kompressions-widerstand wurde in einer der Versuchsreihen dieser Experimente gefunden, wo bei zunehmender Dichte der Knochenmatrix der Kompressionswiderstand der Proben abnahm. Diese Beziehung war in den andern beiden Versuchsreihen nicht signifikant. Der Widerstand der Wirbelkörper war entlang der vertikalen Achse signifikant höher als in den andern beiden Richtungen. Bei einem Deformationsgrad von 1 cm/min zeigten die Proben eine signifikant höhere Widerstandskraft als bei einem solchen von 0,01 cm/min.
    Notes: Abstract The purpose of this investigation was to determine the relation between compressive strength and density of human vertebral bone, the relation between trabecular orientation and compressive strength, and the effects of the strain rate on compressive strength. A total of 71 samples obtained at 23 post mortem examinations were investigated. Density determinations were made and two different densities were calculated: (1) the apparent density as wet weight divided by the total sample volume; and (2) real density as wet weight divided by the volume of bone matrix determined by water displacement. Compression test measurements were made on the fresh samples using an Instron materials testing machine at controlled deformation rates. The results indicated a highly significant relation between apparent density and compressive strength. Similar relations were found between dry weight per total sample volume and ash weight per total sample volume and compressive strength. As the apparent density increased, the compressive strength of the sample decreased. A negative regression between real density and compressive strength was found in one of the experimental series of this investigation where, as the density of the bone matrix increased the compressive strength of the sample decreased. This relation was not significant in the other two experimental series. The strength of vertebral bone was significantly higher along the superior-inferior axis or vertical axis than along the two other directions. Samples showed a significantly greater ability to withstand compression when the deformation rate was 1 cm per minute than they did when the rate was 0.01 cm per minute.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 24
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 5 (1970), S. 21-29 
    ISSN: 1432-0827
    Keywords: Phospholipids ; Bone ; Calcification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Les phospholipides neutres, tels que la sphingomyéline, la lécithine et la phosphatidyléthanolamine, sont les phosphatides principaux de l'os compact bovin. Ces lipides constituent plus de 90% des phospholipides de l'os, avant déminéralisation, et plus de 60% des phosphatides totaux extraits de ce tissu. Après déminéralisation, les solvants lipidiques neutres extraient des phospholipides neutres et acides de la matrice osseuse. Le traitement final de la matrice osseuse avec un mélange de solvants acides permet de récupérer une faible quantité de phosphatides acides et neutres. Pour expliquer la nécessité d'une déminéralisation au cours de l'extraction lipidique, il est possible que les lipides de l'extrait, obtenu après déminéralisation. soient liés à la phase minérale de l'os. Afin d'exclure la possiblité que cette extraction soit dûe simplement aux cristaux d'apatite, pouvant agir comme obstacle à la diffusion du solvant, l'effet de l'extraction lipidique sur des fractions de particules osseuses de diverses tailles a été étudié. La composition des extraits lipidiques n'est pas liée à la taille des particules: le minéral osseux ne parait done pas constituer un obstacle au passage des solvants lipidiques.
    Abstract: Zusammenfassung Die neutralen Phospholipide Sphingomyelin, Lecithin und Phosphatidyläthanolamin sind die wichtigsten Phosphatide des kompakten Rinderknochens. Zusammengenommen machen diese Lipide über 90% der Phospholipide, welche vor der Demineralisation dem Knochen entzogen worden sind und über 60% der aus diesem Gewebe extrahierten totalen Phosphatide aus. Nach der Demineralisation konnten mit neutralen Lösungsmitteln für Lipide ein weiterer Anteil an neutralen und eine beträchtliche Menge an sauren Phospholipiden aus der Knochenmatrix extrahiert werden. Am Schluß wurde die Knochenmatrix mit einem angesäuerten Lösungsmittelgemisch behandelt, und es konnte eine kleine Menge saurer sowie neutraler Phosphatide aus dem Gewebe extrahiert werden. In Anbetracht der notwendigen Demineralisierung bei der Lipidextraktion wurde vorgeschlagen, daß die Lipide aus dem nach Demineralisation gewonnenen Extrakt an die Mineralphase des Knochens gebunden sind. Um die Möglichkeit auszuschließen, daß dieser Extrakt lediglich durch die Apatit-Kristalle bedingt ist, die die Diffusion des Lösungsmittels verhindern, wurde die Wirkung der Lipidextraktion auf Knochenpulver verschiedener Partikelgrößen geprüft. Jedoch besteht keine Beziehung zwischen der Zusammensetzung des Lipidextraktes und der Größe der Partikel. Daraus folgt, daß das Knochenmineral den Durchgang der Lipidextraktionsmittel in das Gewebe nicht verhindert.
    Notes: Abstract The neutral phospholipids sphingomyelin, lecithin and phosphatidylethanolamine were the principal phosphatides of compact bovine bone. Together, these lipids accounted for over 90% of the phospholipids removed from bone, prior to demineralization, and for over 60% of the total phosphatides extracted from this tissue. Following demineralization, neutral lipid solvents removed a further quantity of neutral, and a considerable number of acidic, phospholipids from the bone matrix. A final treatment of the bone matrix with an acidified solvent mixture removed a small number of acidic, as well as neutral, phosphatides from the tissue. To account for the necessity of the demineralization step in the lipid extraction procedure, it was suggested that lipids of the post-demineralized extract were bound to the mineral phase of bone. To exclude the possibility that this extract was merely due to the apatite crystallites acting as a solvent diffusion barrier, the effect of the lipid extraction of bone of different particle size was examined. However, it was found that the composition of the lipid extracts was not related to the particle area; hence, it was inferred that the bone mineral was not obstructing the passage of the lipid extractants in the tissue.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 25
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 133-142 
    ISSN: 1432-0827
    Keywords: Testosterone ; Dehydroepiandrosterone ; Glucosephosphate-dehydrogenase ; Glucose ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Les effets des androgènes (déhydroépiandrostérone et testostérone) sur le métabolisme des hydrates de carbone ont été étudiés en utilisant deux modèles expérimentaux. Le premier fait appel à la culturein vitro d'os embryonnaires d'oiseaux. Dans le deuxième modèle, on utilise des os non embryonnaires de mammifères, en cours d'ossification enchondralein vivo. Dans les deux cas, on note une augmentation de l'activité de la glucose-6-phosphate déhydrogénase et une oxydation différente de la glucose-1-14C et glucose-6-14C. Ces faits indiquent un changement dans le métabolisme du glucose allant vers la voie oxydative directe. En plus, le traitement provoque une hyperplasie de la couche hypertrophique dans l'épiphyse osseuse chez les souris prépubères.
    Abstract: Zusammenfassung Es wurden die Wirkungen von Androgenen (Dehydroepiandrosteron und Testosteron) auf den Kohlenhydratumsatz von Knochen mittels 2 experimenteller Modelle untersucht: einerseits anin vitro gezüchteten Bindegewebsknochen von Hühnerembryonen und andererseitsin vivo an nichtembryonalen Säugetierknochen mit endochondraler Ossifikation. In beiden Modellen läßt die Aktivitätszunahme der Glucose-6-phosphat-dehydrogenase und die unterschiedliche Oxydation von Glucose-1-14C und Glucose-6-14C eine Verschiebung des Glucosemetabolismus gegen den direkten oxydativen Abbau vermuten. Weiterhin erzeugt eine Behandlung mit diesen Hormonen eine Hyperplasie der hypertrophen Zellschicht an der Epiphysenplatte von vorpubertären Mäusen.
    Notes: Abstract An investigation on the effects of androgens (dehydroepiandrosterone and testosterone) on the carbohydrate metabolism of bone was carried out with two experimental models: avian embryonic membranous bone cultivatedin vitro, and mammal non-embryonic bone of endochondral ossificationin vivo. In both models, the increase in glucose-6-phosphate dehydrogenase activity and the differential oxidation of glucose-1-14C and glucose-6-14C suggest a shift in glucose metabolism toward the direct oxidative pathway. In addition, treatment with these hormones produces hyperplasia of the hypertrophic cell layer at the epiphyseal plate of prepubertal mice.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 26
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 143-150 
    ISSN: 1432-0827
    Keywords: Calcitonin ; Bone ; Atrophy ; Formation ; Tetracycline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La patte arrière gauche de trente rattes Sprague-Dawley a été immobilisée par une attelle plâtrée. Dix rattes témoins ont été utilisées (groupe A): les 30 rattes plâtrées ont été réparties en 4 groupes. Le groupe B n'a pas reçu de traitement. Le groupe C a reçu, par injection sous-cutanée quotidienne, 50 MRC mU de calcitonine (préparée par les auteurs) dans 5% de gélatine. Le groupe D a reçu 5% de gélatine. Le groupe E a reçu 50 MRC mU de calcitonine (Ciba), dans 5% de gélatine par jour, en sous-cutanée. Après 6 jours, les fémurs et tibias ont été pesés, radiographiés et étudiés histologiquement. Les os du groupe A sont normaux. Les os des groupes B, C, D et E présentent une ostéoporose d'immobilisation du coté gauche, avec diminution de l'os trabéculaire, sans traduction radiologique. Le traitement à la calcitonine n'a pas inhibé l'ostéoporose. La pression exercée par les attelles plâtrées a induit une apposition périostée, au niveau de quelques tibias. Après traitement à la calcitonine, une apposition augmentée a été observée au niveau des fémurs et tibias. La gélatine, seule, n'a pas eu d'effet. Bien que la calcitonine n'ait pas agi sur l'ostéoporose d'immobilisation, elle semble pourtant favoriser les processus ostéogéniques provoqués par d'autres mécanismes.
    Abstract: Zusammenfassung 30 weibliche Sprague-Dawley-Ratten erhielten zur Immobilisation der linken hinteren Extremität einen Gipsverband. Die Tiere wurden in folgende 4 Gruppen unterteilt: B) keine Therapie. C) 50 MRC mE Calcitonin (eigene Präparation) in 5% Gelatine täglich s.c. D) Lösungsmittel in 5% Gelatine täglich s.c. E) 50 MRC mE Calcitonin (Ciba) in 5% Gelatine täglich s.c. Zusätzlich diente eine Gruppe ohne Gipsverband sowie ohne Therapie als Kontrolle (A). Nach 6 Wochen Versuchsdauer wurden die Femora und Tibiae geröntgt, gewogen und histologisch untersucht. In der Kontrollgruppe(A) bestand kein Unterschied zwischen rechter und linker Seite. In den Gruppen B, C, D und E hatte sich eine deutliche Immobilisationsosteoporose entwickelt (Rarefizierung der Spongiosa des Femurhalses), die röntgenologisch nicht nachgewiesen werden konnte. Die Therapie mit Calcitonin konnte diese Immobilisationsatrophie nicht verhindern. Der mechanische Reiz des Gibsverbandes erzeugte eine periostale Apposition in einigen Tibiae der Gruppen B und D. Nach Gabe von Calcitonin entwickelte sich diese periostale Neubildung in allen Femora und Tibiae der Gruppen C und E. Außerdem war das Ausmaß der Apposition unter Calcitonintherapie wesentlich größer. Das Lösungs-mittel allein hatte keinen Einfluß auf die beschriebenen Veränderungen. Calcitonin konnte die Entwicklung einer Immobilisationsosteoporose nicht verhindern, die Knochenneubildung nach Auslösung durch mechanische Einflüsse wurde dagegen wesentlich verstärkt.
    Notes: Abstract In thirty female Sprague-Dawley rats the left hind leg was immobilized with plaster casts. According to treatment they were divided into the following groups: A) Control, no casts. B) No treatment. C) 50 MRC mU calcitonin (own preparation) in 5% gelatin subcutaneously per day. D) Vehicle alone subcutaneously. E) 50 MRC mU calcitonin (Ciba) in 5% gelatin subcutaneously per day. In addition, untreated rats without casts served as control (group A). After 6 weeks the femora and tibiae were X-rayed, weighed and examined histologically. The bones of the left and right legs did not differ in control group A. In groups B, C, D, and E a disuse osteoporosis had developed in the left legs (rarefication of trabecular bone volume of femur neck) which could not be seen in X-rays. Calcitonin treatment did not prevent the development of the bone atrophy. However, the pressure of the plaster casts had induced a periosteal apposition in some tibiae, and under calcitonin treatment the extent of this new formation in all femora and tibiae was markedly increased. The vehicle alone was ineffective. It can be concluded that whereas calcitonin is without effect on disuse osteoporosis, it probably favours new bone formation which is induced by other mechanisms.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 27
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 260-264 
    ISSN: 1432-0827
    Keywords: Bone ; Human ; Tissue ; Histology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé De l'os spongieux humain est utilisé pour déterminer la viabilité de cellules osseuses après exposition, pendant un temps déterminé, à l'air et au sérum physiologique. La réaction de Feulgen, ainsi que la culture de tissus sont utilisées pour déterminer la viabilité des cellules osseuses. Il apparait qu'aucun ostéocyte ne survit après 30 minutes d'exposition à l'air et au sérum physiologique. Les cellules de la moëlle ne survivent pas à 2 heures d'exposition ö l'air, ou 6 heures d'exposition au sérum physiologique. Le nombre de cellules qui survivent après action de l'air et du sérum physiologique diminue progressivement en fonction de l'augmentation du temps d'exposition.
    Abstract: Zusammenfassung Poröser Knochen von Erwachsenen wurde zur Bestimmung der Überlebenszeit von Knochenzellen verwendet, nachdem er während bestimmter Zeiten der Luft oder physiologischer Kochsalzlösung ausgesetzt wurde. Um diese Überlebenszeit zu bestimmen, wurde die Feulgen-Reaktion gleichzeitig mit der Gewebekultur durchgeführt. Daraus läßt sich schließen, daß keine Osteocyten überleben, nachdem sie 30 min der Luft oder der Kochsalzlösung ausgesetzt waren. Markzellen überlebten nicht, wenn sie 2 Std der Luft oder 6 Std der Kochsalzlösung ausgesetzt waren. Die Anzahl überlebender Zellen nimmt ab, wenn die Dauer, während welcher sie der Luft oder der Kochsalzlösung ausgesetzt werden, zunimmt.
    Notes: Abstract Adult human cancellous bone was used to determine the viability of bone cells after timed exposure to air and saline. To determine the viability of the bone cells, the Feulgen reaction was used in conjunction with tissue culture. It is concluded that no osteocytes survived after 30 minutes exposure to air or saline. Marrow cells do not survive after 2 hours exposure to air, or 6 hours exposure to saline. The number of surviving cells after exposure to air or saline progressively diminishes as the time of exposure increases.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 28
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 316-328 
    ISSN: 1432-0827
    Keywords: Epiphysis ; Cartilage ; Bone ; Parathyroidectomy ; Histochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des coupes de tibias d'animaux entiers et parathyroidectomisés sont étudiées histologiquement et histochimiquement pour préciser les effets de la parathyroidectomie sur l'os. Les épiphyses cartilagineuses proximales montrent uneaugmentation relative de matrice intercellulaire, une diminution en cellules, et une désorganisation de l'arrangement cellulaire. Le cartilage épiphysaire des rats parathyroidectomisés montre une matrice intercellulaire intensément PAS positive, contrairement aux affinités à l'alcian de la matrice des animaux témoins. Les travées diaphysaires des animaux parathyroidectomisés se colorent en rouge au PAS et contiennent de nombreux ilôts étendus de cartilage calcifié. En outre, le cartilage épiphysaire et les travées osseuses des animaux parathyroidectomisés se colorent moins intensément à la réaction de ninhydrine—Schiff que l'os des témoins. L'étude par les diverses colorations histochimiques, après parathyroidectomie, indique une altération des constituants collagène-protéine et mucopolysaccharide. Ces changements sont susceptibles de produire un trouble de la calcification de l'os.
    Abstract: Zusammenfassung Tibiaschnitte von Kontrollratten und von parathyreoidektomierten Ratten wurden histologisch und histochemisch untersucht, um die nach Parathyreoidektomie aufgetretenen Knochenveränderungen festzustellen. Der proximale Epiphysenknorpel von parathyreoidektomierten Ratten zeigte einerelative Zunahme der intracellulären Matrix, eine Abnahme des Zellgehaltes und eine Veränderung der zellulären Anordnung. Die Epiphysenknorpel der parathyeoidektomierten Ratten wiesen eine intensiv PAS-positive intracelluläre Matrix auf, im Gegensatz zur alcianophilen Reaktion der Matrix der Kontrolltiere. Die Diaphysen-Trabekel der parathyreoidektomierten Tiere ließen sich mit PAS rot färben und enthielten breite Zonen von verkalkten knorpeligen Kernen. Ferner ließen sich die Epiphysenknorpel und die Knochen-Trabekel von parathyreoidektomierten Tieren im Vergleich mit den Kontrolltieren weniger intensiv mit der Ninhydrin-Schiff-Reaktion färben. Die Resultate der verschiedenen histochemischen Reaktionen zeigten, daß die Parathyreoidektomie eine Veränderung der Protein-Mucopolysaccharide des Kollagens zur Folge hat. Diese neuen Bedingungen könnten eine Veränderung der Knochenverkalkung hervorrufen.
    Notes: Abstract Sections of the tibias from intact and from aparathyroid animals were examined histologically and histochemically to determine the changes in bone following parathyroidectomy. The proximal epiphyseal cartilages of parathyroidectomized rats showed arelative increase of intercellular matrix, decrease in cellularity, and disorganization of the cellular arrangement. The epiphyseal cartilages of the aparathyroid rats exhibited an intense PAS-positive intercellular matrix in contrast to the alcianophilic nature of the matrix from control animals. The diaphyseal trabeculae from aparathyroid animals stained red with PAS and contained wide regions of calcified cartilaginous cores. In addition, the epiphyseal cartilages and bone trabeculae from the parathyroidectomized animals stained less intensely to the ninhydrin-Schiff reaction than did the bone from the intact animal. The response to the various histochemical reactions indicated that following parathyroidectomy there was a change in the collagen-protein mucopolysaccharide components. This condition would produce an alteration in the calcification of bone.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 29
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 6 (1970), S. 335-342 
    ISSN: 1432-0827
    Keywords: Calcium ; Phosphate ; Crystals ; Epitaxy ; Bone ; Composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Du phosphate de calcium hydraté monohydrogéné est proposé comme précurseur logique dans la formation de l'hydroxyapatite et une théorie expliquant la formation d'apatiles défectueux, à contenu faible en calcium, est présentée. Les rapports structuraux entre le phosphate de calcium déhydraté monohydrogéné et l'hydroxyapatite indiquent que l'un ou l'autre de ces produits est susceptible de fournir l'édifice atomique nécessaire à la croissance épitaxique de l'un sur l'autre. La formation d'apatite parait être le résultat de deux processus différents au point de vue cinétique: la formation initiale rapide du phosphate de calcium dihydraté monohydrogéné amorphe et la formation lente consécutive d'hydroxyapatite du précipité initial. Les rapports Ca/P des phosphates de calcium, formés à partir des constituants de solution situés dans la région de la phase d'hydroxyapatite, en fonction du temps, permettent une composition variable du phosphate de calcium monohydrogéné dihydraté et de l'hydroxyapatite. Le calcium de phosphate hydraté ponohydrogéné parait être le cristal d'ensemencement nécessaire à la croissance de l'hydroxyapatite dans l'os et les dents à pH physiologique.
    Abstract: Zusammenfassung Hydriertes Calciummonohydrogenphosphat wird als die logische Vorstufe bei der Bildung von Hydroxyapatit vorgeschlagen, und eine vereinheitlichende Theorie für die Bildung von calciumarmen oder defizienten Apatiten wird vorgelegt. Strukturelle Beziehungen zwischen Dihydrocalciummonohydrogenphosphat und Hydroxyapatit zeigen, daß beide Substanzen die Atomanordnung für das epitaxiale Wachstum des einen auf dem anderen liefern können. Die Apatitbildung wird als die Summe von zwei Vorgängen verschiedener Geschwindigkeit dargelegt: die zu Beginn rasch vor sich gehende Bildung von amorphem Dihydrocalciumonohydrogenphosphat und die nachfolgende langsame Bildung von kristallinem Hydroxyapatit aus dem anfänglichen Niederschlag. Das Verhältnis als Zeitfunktion von Ca/P des Calciumphosphates, welches sich aus Lösungen bildet, deren Zusammensetzung im Gebiete liegt, wo das Hydroxyapatit in der stabilen Phase vorkommt, läßt vermuten, daß diese Calciumphosphate eine unterschiedliche Zusammensetzung von Dihydrocalciummonohydrogenphosphate und Hydroxyapatit haben. Es wird vorgeschlagen, daß das Dihydrocalciummonohydrogenphosphat auf Grund der Bildungsgeschwindigkeit und Zusammensetzung des Calciumphosphates sowie der kristallographischen Werte ein notwendiger Nukleator für das Wachstum von Hydroxyapatit in Knochen und Zähnen bei einem physiologischen pH ist.
    Notes: Abstract Hydrated calcium monohydrogen phosphate is proposed as the logical precursor in the formation of hydroxyapatite and a unifying theory for the formation of low calcium, or defect apatites, is presented. Structural relationships between calcium monohydrogen phosphate dihydrate and hydroxyapatite indicate that either material can provide the atomic arrangment for the epitaxial growth of one on the other. The formation of apatite is presented as the summation of two rate processes: the initial fast formation of amorphous calcium monohydrogen phosphate dihydrate and the subsequent slow formation of crystalline hydroxyapatite from the initial precipitate. Ca/P ratios of calcium phosphates, formed from compositions in the phase region of hydroxyapatite as a function of time, suggest a varying composition of calcium monohydrogen phosphate dihydrate and hydroxyapatite. Hydrated calcium monohydrogen phosphate is proposed on the basis of rate and composition of calcium phosphate formed and on crystallographic data to be a necessary seed for growth of hydroxyapatite in bone and teeth at physiological pH.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 30
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 109 (1970), S. 552-565 
    ISSN: 1432-0878
    Keywords: Teleosts ; Bone ; Osteocytes ; Osteoclasts ; Osteolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé Le squelette vertébral de l'Anguille est formé d'os cellulaire: lamellaire compact ou spongieux, suivant les différentes parties de la vertèbre. Nous avons pu y mettre en évidence, chez des animaux physiologiquement normaux, les trois catégories de cellules caractéristiques de l'os des vertébrés supérieurs: ostéoblastes, osteocytes, ostéoclastes. Elles ont les mêmes fonctions que chez ces derniers, les ostéoblastes procèdent à l'élaboration du tissu osseux, alors que les ostéoclastes le détruisent; à cette résorption ostéoclastique s'ajoute une lyse périostéocytaire ou résorption périlacunaire. Les osteocytes, dans ce tissu, nous paraissent être des éléments actifs; néanmoins, leur nombre (par unité de surface) est très inférieur à celui trouvé chez les Mammifères. Le remaniement osseux résultant du jeu de l'apposition et de la résorption est important et comparable à celui existant chez l'Homme. L'os de l'Anguille est, à de nombreux points de vue, très voisin de celui des Mammifères; les Poissons n'ont pas de parathyroïdes en tant que telles mais ils sont pourvus d'autres glandes vraisemblablement impliquées dans la régulation phosphocalcique: corps ultimobranchial et corpuscules de Stannius. Notre but sera donc d'essayer de déterminer comment est réglé le métabolisme de l'os cellulaire des Téléostéens.
    Notes: Summary The vertebral skeleton of the eel consists of cellular bone, either lamellar or spongy, depending on different parts of the vertebra. In this osseous tissue we have found, in physiologically normal animals, three categories of caracteristic cells of the bone of higher vertebrates: osteoblasts, osteocytes, osteoclasts. They have the same functions as in higher vertebrates, osteoblasts form the bone while the osteoclasts which are to be found in “Howship's lacunae” destroy it. In addition, a perilacunar type of bone resorption or “osteocytic osteolysis” can be observed. In this bone, osteocytes seem to be active cells, but the concentration of osteocytes is decidedly lower than that to be found in Mammals. The osseous remodeling produced by apposition and resorption is of the same importance as in human bone. The bone of the eel, in many ways, closely resembles that of mammals. Teleost fish do not have parathyroid glands, but their phosphocalcic regulation seems to be facilitated by the action of two endocrine glands: Ultimobranchial body and the corpuscles of Stannius. The regulation of the cellular bone metabolism of Teleostean fishes is discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 811-824 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The root-mean-square end-to-end distance has been calculated for a model allowing free rotation about glycoside bonds for the general case of polysaccharides having a disaccharide repeating unit. Numerical estimates are given for several naturally occurring structures based on an idealized pyranose unit in the C1 chair conformation. Extrapolation procedures which make use of the intrinsic viscosity [η] in good solvents to obtain unperturbed dimensions do not represent, data for hyaluronic acid very well, especially at low molecular weights. However, order-of-magnitude estimates suggest that this polymer behaves similarly to other polysaccharides, and probably has stiffer local structure than typical non-ionic synthetic polymers. A double logarithmic plot of the product of [η] and M̄w, the weight-average molecular weight, against the degree of polymerization in the range for M̄w of 104 to 2 × 104 permits a straight-line fit of available data for all the glycosaminoglycans, including heparin and the chondroitin sulfates, as well as sodium carboxymethyl cellulose. This result suggests similarity of short-chain hydrodynamic behavior of these polymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 32
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 875-875 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 34
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 865-874 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A common approximation for deriving solutions to the Lamm equation is to neglect diffusion. This paper presents a singular perturbation technique that allows one to estimate the band spreading due to nonzero diffusion coefficient. We illustrate the general mathematical technique by its application to sedimentation when pressure effects are important. Comparison of the approximate solution with accurate numerical solutions shows that the relative errors are of the order of 1% both for concentration and concentration gradient for parameters of chemical interest.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 35
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 891-896 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Glycogen acquires a negative charge in both alkaline and acidic solutions and can move in an electrical field, its mobility being related to the degree of alkalinity or acidity. There is a slight increase in relative viscosity at both ends of the pH spectrum. These effects and the changes in nuclear magnetic resonance as a function of pH are interpreted.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 36
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The viscosity of bovine liver glutamate dehydrogenase solutions was studied at 10 and 20° C in 0.2.M sodium phosphate buffer at pH 7, in the concentration range 0.1-8 mg/ml. A method for the study of the viscosity of very dilute solutions of associating enzymes is described. It was found that the reduced specific viscosity ηsp/c of glutamate dehydrogenase continuously increases with increasing enzyme concentration, from about 4 ml/g at the lowest concentrations to about 16 ml/g at 8 mg/ml. In the presence of 10-3M GTP and 10-3M NADH the viscosity increase is much smaller and the results can be extrapolated to zero enzyme concentration to yield an intrinsic viscosity [η] = 3.2. The values of ηsp/c in phosphate buffer alone apparently extrapolate to the same value of [η], or to a value close to it. We also observe that, in the presence of toluene ηsp/c increases very much more with enzyme concentration: ηsp/c already equals 16 ml/g at a concentration of 0.75 mg/ml. These observations are in good agreement with the hypothesis that the active oligomer of glutamate dehydrogenase (MW = 312,000) associates with increasing enzyme concentration to form linear rodlike polymers of indefinite length. This association is strongly diminished by the addition of 10-3M GTP, 10-3M NADH. Toluene, on the other hand, promotes reversible association to linear polymers of very high molecular weight. The transverse and axial rotary frictional coefficients of macroscopic bodies, similar to a physical model for the structure of glutamate dehydrogenase recently advanced, were determined. Assuming that the viscosity of the model is equal to that of an ellipsoid of rotation with identical frictional coefficients, we calculate [η] = 3.26 ml/g according to Kuhn and 3.20 ml/g according to Simha, for the glutamate dehydrogenase oligomer, in good agreement with the result derived from the study of enzyme solutions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 911-922 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular monolaycrs of poly(β-benzyl L-aspartate) spread at. an air-water interface have been studied. The results obtained both by direct observations on the monlayer and from examination of collapsed films with polarized infrared spectroscopy and electron diffraction are consistent with the presence of right handed α-helices in the mono-layer when the molecular weight is high. When 1% (v/v) isopropanol is present in the subphase the right-handed helix prevails, provided that the monolayer is first spread on water. Monolayers of low molecular weight polymer appear to form the crossed-β structure. Orientated collapsed films of high molecular weight polymer can be converted to the left-handed α-helical and to the ω-conformation, and the mechanisms are discussed. The surface chemistry of this polymer is compared with that of related polymers and a consistent pattern of behavior emerges.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1017-1028 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low-angle light scattering results reported previously demonstrated that measurements on high molecular weight native DNA must be made at angles below 30° in order to obtain correct molecular weights. Earlier light-scattering data obtained on denaturated DNA at angles above 30° showed no change in molecular weight upon denaturation, even though other techniques clearly showed that strand separation occurred. This paper reports low-angle measurements on solutions of calf thymus and T7 DNA denatured under acidic conditions. The results demonstrate that a halving of molecular weight consistent with strand separation is detected by light scattering only when low-angle data are used to obtain correct molecular weights for native material. As expected from theoretical considerations, the scattering from denatured DNA is a linear function of sin2(θ/2), where θ is the angle of observation. This result shows that anticipated experimental artifacts have no significant effect on the low-angle measurements and demonstrates that the curvature in the scattering envelope observed for native DNA below 30° is an inherent property of the native molecule.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 39
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics for the cis-trans isomerization of long-chain poly-L-proline has been studied as a function of pressure, temperature, and solvent composition in the acetic acid + n-propanol solvent system. Our complete kinetic curves were fitted by Monte Carlo techniques, and rate constants for nucleation, growth, and termination were estimated. It was found that for the formation of a cis-helix, high pressure, low temperature, and increased acetic acid content of the solvent, lowered the rate of nucleation relative to growth. The inverse seems to be t rue for the formation of a trans-helix. Molecular models suggest that this behavior of the kinetic constants can be due to the exposure of peptide units to solvent in the transition state for trans nucleation, and the burying of peptide units in the transition state for cis nucleation. It is further suggested from our analysis of complete kinetic curves that at least one of the assumptions usually made in the analysis of relaxation kinetics is invalid for poly-L-proline.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 40
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1039-1047 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solutions of amylose in ethylenediamine yield a crystalline film complex upon evaporation of solvent. The x-ray analysis indicates the presence of a tetragonal-shaped cell with a symmetry approximating that of space group P212121. The amylose sixfold helix has a diameter of 13.3 Å and a translation period of 8.0Å. Chemical and physical analyses support a complexing ratio of one ethylenediamine molecule to every two glucose units. The structure is nearly identical to any amylose-dimethyl sulfoxide complex previously examined. The square mode of packing arrangement appears to result from complexation between amylose chains. Such complexing indicates a much greater degree of amylose interaction than is observed in amylose complex structures having a hexagonal close-packing arrangement.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1049-1058 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: pH titration measurements of poly- S-carboxymethyl-L-cysteine were undertaken in the aqueous Nacl solution in relation to the β form-random coil transition. The titration curves show a marked molecular weight dependence because of the shortened chain length of materials. Comparison of the optical rotatory dispersion parameter a0 with the titration curve reveals that the titration curve apparently reflects a β structure-random coil transition. The β form of this polymer is assumed to be an intramolecular β form, rather than a β structure stabilized by an intermolecular hydrogen bond, at least in the polymer concentration range considered here. The standard free energy change per amino acid residue for the transition from un-ionized random coil to un-ionized β form is estimated to be about -750 cal/mole residue in the range of 0.005-0.2M NaCl concentration.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1059-1077 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism (CD) spectra of the four usual deoxymononucleosides, all sixteen deoxydinucleotides, and a number of trinucleotides have been measured. The dimer spectra are quite different from the sum of the spectra of their constituent monomers. This indicates the presence of base-stacked conformations analogous to those found for ribonucleoside diphosphates. The CD spectra of several deoxytrinucleotide diphosphates and single-strand f 1 DNA can be calculated fairly well by using a semi-empirical nearest-neighbor approach. There is little or no effect of terminal phosphate or of salt concentration on the optical properties of most deoxy oligomers. The possibility of simultaneous analysis of mixtures of deoxypurine or deoxypyrimidine sequence isomers has been examined. This seems to be a viable approach for the analysis of purine runs but cannot promise much success for pyrimidine runs.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 43
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1079-1103 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism spectra of all 16 ribodinudeoside phosphates containing the bases adenine, uracil, cytosine, and guanine have been measured at room temperature and neutral pH. These results are compared with the circular dichroism spectra of the corresponding deoxy compounds. From the optical properties it is clear that the geometry of the base-stacked conformation of ribo compounds must differ substantially from that of deoxy compounds. Because of this, it is not possible to draw firm conclusions about the relative extent of stacking in most ribo and deoxy compounds. The optical rotatory dispersion of about a dozen deoxy and ribodinucleoside phosphates has been studied as a function of temperature. These results confirmed the conclusions drawn earlier from measurements at a single temperature. Several dinucleoside phosphates containing a 2′ → 5′ phosphodiester bond have also been examined. These compounds have a substantial degree of base stacking at room temperature. The geometry of the stacked conformation is different from that of either the normal ribo dimer or the deoxy dimer. The role of the 2′-hydroxyl group in stabilizing base stacked geometries has been examined by studies on C-2′-O-methyl-pC. This compound has optical properties almost identical to those of CpC. This suggests that the effect of the 2′ hydroxyl is felt indirectly through its perturbation of the geometry of the sugar ring rather than directly by hydrogen bonding. It is not possible at present to identify precise conformational differences among deoxy-, ribo-and 2′ → 5′ ribodinucleoside phosphates.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 44
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1119-1124 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1349-1360 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of single-strand breaks on the kinetics of the relaxation of DNA in a solution of low ionic strength has been investigated by a temperature jump method. The relaxation of DNA after a jump of 0.7 °C in the melting region has been monitored by measuring the extinction at 260 nm. For essentially monodisperse T4 DNA (M = 130 × 106) two distinct relaxation times have been observed, that depend markedly on the initial extent of denaturation 1 - θ. The larger relaxation time decreases from 450 sec to about 300 sec, the smaller one from 55 see to 30 when 1 - θ increases from 0.03 to about 0.8. The dependence of these relaxation times on the average number of single-strand breaks per molecule (p) appears to be very small up to p = 100. However, the relative contribution of the slow process decreases sharply when p increases from 0.6 to 30 and remains nearly constant for larger p. The observations are discussed in the light recent theories of the kinetics of denaturation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 46
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1361-1372 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements have been made of the intensity of light scattered from aqueous solutions of calf thymus DNA with and without the application of electric fields. For fields approaching 150 V/cm and frequencies below 2.5 KHz, changes (ΔI) of up to 10% in the residual scattered intensity were observed. In agreement with previous dielectric and electric birefringence measurements, a low frequency dispersion of ΔI was observed, from which a rotary diffusion constant (D) of 1200 s-1 was determined. Interpreting the electric field data in terms of the classical dipolar orientation theory led to values of 2.4 × 10-25 cm (7.4 × 10-14 esu) and 4.3 × 10-25 cm (13 × 10-14 esu) for the permanent dipole moment and the anisotropy of the electric polarisabilities respectively. Furthermore the permanent dipole moment was along the major molecular axis and the particles orientated in the field as rigid entities. The zero field data indicated a molecular shape which was not rodlike but corresponded to the Kratky-Porod “stiffness” parameter of x = 24 for the wormlike coil model. Although curved, the molecules appeared to orientate in low-intensity electric fields as rigid, but not rodlike molecules. The implications of this on recent discrepancies in D determined by two or more dynamic relaxation methods is briefly discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 47
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1391-1402 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The buoyant density of T-4 DNA was determined by equilibrium sedimentation in a density gradient, of mixed solutions of cesium and magnesium chlorides and bromides. The preferential hydration was calculated from these data, allowing appropriately for the exchange equilibrium of DNA with Cs+ and Mg++ ions. The charge and intrinsic solvation of the counterions were found to have no appreciable effect on the hydration of the DNA, the extent of solvation depending only on the thermodynamic, activity of the water. Various reasonable hypotheses are discussed to account for these results.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1373-1389 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of 27 SMS2 RNA with formaldehyde normally results in an unfolded, 13.4 S form. At acidic pH, however, and under the proper ionic conditions, a compact component sedimenting at 36-40 S was obtained. The molecular weight of this species corresponds to a dinner. The formaldehyde concentration was not critical, and approximately the same number of base pairs had been opened in the compact and in the unfolded form. Presumably dimers, which had been specifically formed under defined conditions, were stabilized by formaldehyde-induced crosslinks. Similar dimers were formed by 16 S and by 23 S ribosomal RNA, but not by tRNA.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 445-457 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The change in apparent molal volume φ of DNA on thermal denaturation in carbonate buffer at pH 11.0 has been determined by the dilatometric method. It was found that φ increases sigmoidally during the helix-coil transition. Several methods, including a colorimetric technique that closely simulates the conditions used in the dilatometric experiments, were employed to estimate the protons lost by the DNA during the transition. These measurements indicated that the extent of the proton loss depends on the counterion present, increasing in the order Li+ 〈 Na+ 〈 K+ 〈 Cs+. The major part of the volume changes observed during the denaturation is due to the volume changes expected to accompany the transfer of protons from the bases guanine and thym ne to carbonate ions. As has been previously reported for the denaturation of DNA at neutral pH, the volume change directly due to the change in shape of the polymer molecules is so small as to be experimentally undetectable.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 569-588 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coupling of theoretical optical calculations with experimental data provides a check of the validity of the theory or provides conformational information. The theory was validated by studies in which the approximate conformation was located independently. These studies have shown that a theory restricted to the two lowest energy transitions for each chromophore gives qualitative agreement with experiment. On the other hand, for some of the proline derivatives, the theoretical treatment allows detailed conformational assignments. Both successes and failures in correlating theory with experiment are discussed. The results presented provide a basis for assessing the prospects for relating protein and polypeptide optical activity to their conformations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 51
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethidium bromide inhibits the formation of ultraviolet-induced pyrimidine dimers in DNA. The efficiency of dimer inhibition increases with increasing energy of the exciting photons. The efficiency of energy transfer from the DNA singlet to the dye singlet, as monitored by sensitized fluorescence, is independent of wavelength. The efficiency of singlet-singlet transfer agrees with that for dimer inhibition at photon energies corresponding to excitation of the lowest singlet state of DNA. Our results support a model in which dimers are formed both directly from the singlet state and also from the triplet state, with triplets arising from higher vibrational levels of the singlet.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 689-696 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The intercalation model of DNA-hydrocarbon binding appears reasonable, but rests on indirect evidence only. To test the model, a size criterion for binding has been proposed. The size criterion is based on the assumption that hydrophobic forces play a major role in the binding of hydrocarbons to DNA. It states that hydrocarbons which are small enough to intercalate into DNA and be well protected from contact with the medium, will be found to bind to DNA; those that are too large will not. We report results on the binding of fourteen polycyclic aromatic hydrocarbons to DNA. Predictions based on the size criterion were found to be valid in all cases tested.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 697-715 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dialysis data of Huang and Ts'o for the cooperative binding of adensine to polyuridylic acid are analyzed here using a grand-partition function Ising model method similar to that originally employed for polyelectrolytes by Rice and Nagasawa. An appropriate modification permitting the treatment of the sliding degeneracy of the two polyuridylic acid strands is also included. In addition to the previously estimated stacking energy of about -6 kcal/mole one also obtains the free energy change F̄ for the transfer of a single adenosine molecule from a fixed site in solution to a fixed site on the polyuridylic acid. This binding energy falls in the range F̄ = -140 to +620 cal/mole, indicating that binding in the 1:2 (purine: pyrimidine) complex is either very weak or repulsive. The absence of any comparable cooperative stacking of adenosines in solution at the same concentration together with the likely repulsive character of the binding implies that the stacking energy must contain a significant contribution from other processes than simple stacking of adenosines. A generalization of the theory to treat multicomponent binding and longer-range interactions is effected, and the form applicable to simultaneous binding of both adenosine and guanosine by polyuridylic acid is presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 54
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 739-744 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present communication describes a new way of studying helix-random coil transformations of polypeptide, poly-(γ-benzyl L-glutamate), in benzene-trifluoracetic acid (TFA) and chloroform-TFA systems. The difference between the PMR chemical shift of TFA with and without the polypeptide, measured as Δ, may be used to follow the conformational transition. This technique is particularly useful for concentrated solutions, where the PMR peaks of the polymer are so broad that no valuable information may be derived. As the TFA content increases in the system (at constant polymer concentration), Δ decreases normally whether the polymer is helical or random. However, Δ changes in a different way in the helix-random coil transition region, and actually increases with increasing TFA content. This peculiar behavior is explained in terms of the solvation of the helix and random coil structures.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 745-748 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 56
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 717-738 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new procedure for evaluating u and σ characterizing σ-helix-forming polypeptides in solution was derived from Nagai's theory for the helix-coil transition of such polymers. Here u is the activity for helix formation from random coil, and σ is the helix initiation parameter. The necessary data are the helical content fN at fixed solvent and temperature as a function of N, where N is the degree of polymerization of the polypeptide sample. Such data were obtained from ORD measurements on a number of fractionated samples of poly-N5-(3-hydroxypropyl)-L-glutamine (PHPG) in mixtures of water and methanol covering the complete range of composition and at various termperatures (5-40°C). When analyzed in terms of the proposed procedure, they yielded values of σ which were in the range (3.2 ± 0.6) × 10-4, substantially independent of solvent composition and temperature. These values were much larger than those obtained recently for σ of poly(β-benzyl-L-aspartate) in m-cresol and in a mixture of chloroform and DCA. The data for [η] and s0 (limiting sedimentation coefficient) as functions of molecular weight indicated that the molecular shape of PHPG in pure methanol is essentially rodlike, whereas that in pure water is not entirely randomly coiled but rather may be regarded as an interrupted helix. These indications were consistent with the results from ORD measurements. When plotted against the corresponding values of fN, the values of [η] and [s0] for PHPG in mixtures of water and methanol of various compositions and temperatures formed smooth composite curves, and we attributed these phenomena to the fact that σ of PHPG was nearly constant under these solvent conditions. Here [s0] stands for a reduced limiting sedimentation coefficient which is equal to the inverse friction factor of the solute molecule.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 57
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 765-782 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of purine with DNA, tRNA, poly A, poly C, and poly A. poly U complex was investigated. In the presence of purine, the nucleic acids in coil form (such as denatured DNA, poly A and poly C in neutral solutions, or tRNA) have lower optical rotations. In addition, hydrodynamic studies indicate that in purine solutions the denatured DNA has a higher viscosity and a decreased sedimentation coefficient. These findings indicate that through interaction with purine, the bases along the poly-nucleotide chain are unstacked and are separated farther from each other, resulting in increased assymmetry (and possibly volume) of the whole polymer. Thus, the de-naturation effect of purine reported previously can be explained by this preferential interaction of purine with the bases of nucleic acids in coil form through a hydrophobic-costacking mechanism. Results from studies on optical rotation and helix-coil transition show that the interaction of purine is greater with poly A than with poly C. The influence of temperature, Mg++ concentration, ionic strength, and purine concentration on the effect of purine on nucleic acid conformation has also been investigated. In all these situations the unraveling of nucleic acid conformation occurs at much lower temperatures (20-40°C lower) in the presence of purine (0.2-0.6M).
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 59
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The characteristic ratio of unperturbed cellulose chain was computed as a function of the angle τ at, the bridge oxygen atom and the degree of polymerization. Very high values of the order of 40 or more, depending on the angle at the bridge oxygen atom, have been obtained for this ratio, indicating that cellulose chains are highly extended. The average dimensions of cellulose chains are found to be sensitive even for small changes in the angle at the bridge oxygen, and these chains attain the character of a random coil in very high molecular weight range (degree of polymerization greater than 2000). The large differences in the unperturbed dimensions of cellulosic chains observed in different solvents have been attributed to the possible small changes in the angle τ caused by specific solvent, interactions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 60
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational properties of block copolymers of poly-L-leucine in water have been examined. The degree of polymerization of the poly-L-leucine block was 11 and 21, respectively, for samples prepared by the Merrifield procedure, and 56 for a sample prepared by the polymerization of leucine N-carboxyanhydride. The optical rotatory dispersion parameter b0 was used to obtain the helix content θh at various temperatures. Application of the Lifson-Roig theory gave the following parameters for the transition of a residue from a coil to a helical state: v = 0.05-0.011, ΔH = +100 cal/mole, ΔS = +0.70-1.00 e. u. These parameters, as well as those for other polyamino acids, are accounted for by hydrophobic bonds involving the nonpolar side chains in the helical and randomly coiled forms. From the data for poly-L-alanine and theoretical values of the thermodynamic parameters for hydrophobic bond formation, the parameters for formation of a polyglycine helix are computed. By separating the contributions of the backbone, it is possible to obtain a set of thermodynamic parameters for the side-chain contributions of a number of polyamino acids. Increased size of the nonpolar side chain (with a larger contribution from hydrophobic bonding) makes a larger contribution to the stability of the α-helix which is reflected, among other ways, in a higher helix content at given temperature.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 61
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of DL-β-phenylalanine N-carboxyanhydride (NCA) initiated by poly(N-benzylglycine)diethylamide (DEA) and poly(N-methyl-DL-alanine)DEA has been investigated. As previously reported, polysarcosine DEA, poly-N-ethylglycine DEA, and poly-N-n-propylglycine DEA showed marked accelerations in the polymerization of DL-β-phenylalanine NCA as compared with the polymerization initiated by low molecular weight, amines having similar base strength. However, this phenomenon (the chain effect) was not observed with the two polymer catalysts studied in the present investigation With poly-N-methyl-DL-alanine DEA, adsorption of DL-β-phenylalanine NCA onto the polymer chain takes place, though not so effectively as with other polypeptides, so the absence of chain effect was ascribed to a reduced flexibility of the polymer chain. With poly(N-benzylglycine)DEA, the reactivity of terminal base group was found to be much lower than that of other polymer catalysts. However, the absence of the chain effect would be attributed to the rigidity of polymer chain of poly-N-benzylglycine DEA due to the bulkiness of the N-benzyl group.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 62
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 799-810 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular weights by osmometry (M̄n), light scattering (M̄w), and sedimentation-diffusion (MsD) were determined for selected fractions and unfractionated samples of hyaluronic acid in the molecular weight range 3 × 104-1.7 × 106. For the determination of MsD from the sedimentation coefficient s, a calibration procedure based on the data of Laurent, Ryan, and Pietruszkiewicz gave the following relations in 0.2M NaCl: log (s-1)0 = 14.681 - 0.413 log MsD and log D0 = -3.828 - 0.568 log MsD, where subscript, zero refers to zero concentration and D is the diffusion coefficient. The average Mandelkern-Flory parameter β in 0.2M NaCl is 3.0 × 106. Data for the intrinsic viscosity [η] may be fitted for M 〉 105 by [η] = K′Ma, where K′, a are in 0.2M NaCl, 0.0228, 0.816; in 0.5M NaCl, 0.0318, 0.777; in 0.1 M HCl, 0.0279, 0.763, respectively. Below M = 105, [η] appears to fall below the values calculated, possibly due to non-Gaussian behavior of short chains. The second virial coefficient A2 in 0.5M NaCl approaches the ideal Donnan value, decreasing slightly with increasing molecular weight. The friction parameter P is about 20% smaller than that of uncharged polymers of similar dimensions. The flexible coiling nature of this polymer is confirmed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 63
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 843-864 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of a slowly sedimenting form of 23-S ribosomal RNA from E. coli has been investigated by analytical ultracentrifugation and thermal denaturation in aqueous solution and in formamide. Evidence is presented that the slow form of 23-S arises as a result of nucleate damage to the RNA in the 50-S ribosome. The 30-S ribosome (and 16-S RNA), is unaffected. The slow form of 23-S RNA cannot be demonstrated under conditions of complete denaturation in formamide, but only by partial denaturation in aqueous solution of low ionic strength (〈 0.01M Na). Apparent maintenance of the integrity of 23-S RNA in formamide after nuclease treatment suggests that this may not be a simple linear molecule. An alternative model is suggested containing a circular element in the structure.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 64
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 825-842 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Uniform LiDNA fiber specimens of nearly 20 m length have been prepared with a wet-spinning method developed by the author. Samples immersed in the spinning bath (80% ethyl alcohol containing 0.4M LiCl) have been subjected to mechanochemical study involving stretching, relaxation, and contraction measurements. A special technique was developed to transfer the sample from the Teflon-coated cylinder used in spinning to the sample column of the mechanochemical apparatus without stretching or removing the sample from the spinning bath. Force-strain curves of samples consisting of two fiber bundles showed an initial region of low slope followed by a region of high slope and a second region of low slope up to rupture. Some thicker specimens showed an aging effect which abolished the initial low-slope region and was interpreted as indicative of crystallization. Force-strain curves of two-bundle samples showed a strong influence of temperature with a complete loss of tensile strength of the LiDNA fibers in the spinning bath at about 55°C. Furthermore, samples at zero strain exhibited a contractile force when subjected to temperatures above about 40°C; the contractile process was pronounced with samples kept above 48°C. On contraction these samples obtained a zero-force length 20-30% of the original. These data are taken as evidence for a helix-to-coil transition occurring in the DNA, the low melting temperature being caused by the chemical influence of the ambient aqueous alcohol-LiCl bath.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1029-1038 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular weight of native DNA is shown to decrease by at least a factor of two on denaturation by heat or alkali. This result is obtained only if low-angle (〈30°) light-scattering measurements are used. High-angle measurements (〉30°) do not reveal a decrease in molecular weight on denaturation due to the incorrect value for native DNA. The dn/dc value for both native and denatured DNA is 0.166 ml/g ± 0.003 ml/g. Methods are described for the clarification of native and denatured DNA solutions for light scattering by the use of membrane filters.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 991-1000 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electric dichroism studies on poly(γ-benxyl L-glutamate) show that the addition of small amounts (up to 5%) of trifluoroacetic acid causes complete disappearance of dichroism in contrast to the electric birefringence, which drops to an observable plateau at 20% of its initial value. This loss of dichroism cannot be explained simply by a decrease in the effective dipole moment of the benzyl ester side chains, and the nature of this interaction is explored by nuclear magnetic resonance and infrared spectral studies. Theories of the helix-coil transition which require an initial protonation of the helix backbone to form a more flexible rod consisting of helical segments interrupted by regions of random coil are shown to be inadequate to describe the changes in poly(γ-benzyl L-glutamate) effected by small amounts of trifluoroacetic acid. Rather, trifluoroacetic acid in small amounts interacts with the ester carbonyl oxygen in the side chain, either by hydrogen bonding or protonation, before there is evidence of any effect on the backbone or of loss of helix content.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 67
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1229-1237 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Raman spectra of poly-L-lysine hydrochloride and poly-∊-carbobenzoxy-L-lysine in the solid state have been obtained and are consistent with the presence of an α-helical structure. The Raman spectrum of poly-L-lysine in aqueous solution suggests the presence of random coil structures.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 68
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 70
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nonbonded interaction energy of disaccharides, mannobiose and galactobiose and polysaccharides mannan and galactan have been computed as a function of dihedral angles (φ,ψ). The conformation (40°, -20°) has been preferred for the mannan chain from nonbonded interaction energy considerations. The O5…O3′ type of intramolecular hydrogen bond has been found to be possible in the above conformation. Comparison of the allowed region of mannan with those of cellulose and xylan indicates that the monomer unit, in mannan chain has slightly higher freedom of rotation than that of cellulose and less than that of xylan. As in cellulose and mannan, the freedom of rotation of the monomer units in β-1,4′ galactan is highly restricted. Unlike mannan (which prefers an extended conformation) the β-1,4′ galactan prefers a helical conformation similar to amylose. Just as in amylose the O2…O3′ type hydrogen bond between contiguous residues is also possible in β-1,4′ galactan.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 71
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 23 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 72
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1475-1502 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The predictions of the presently accepted molecular exciton model for the optical activity of helical polypeptides are in reasonable agreement with experimental spectra in the accessible wavelength range. However, crucial verification requires the detect of a significant negative rotatory hand just below the accessible range. A computer-oriented method is utilized to obtain information concerning the inaccessible range. Optical rotatory dispersion computed by evaluation of the Kronig-Kramers integral transform from the experimentally determined circular dichroism of several helical homopolypeptides in solution are compared with the experimentally determined optical rotatory dispersion. Computed and experimental curves are congruent within an uncertainty approaching that of the experimental technique, whatever the polypeptide sample lot, side chains, and solvent. It is shown that t his agreement is not a computational or experimental artifact. These results can be interpreted in two ways: (1) that the predicted band does not exist, and (2) that the perturbation of the predicted band is being negated by other inaccessible bands in the vacuum ultraviolet. Arguments are presented to show that the first of these two possibilities is more probable.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 73
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 1511-1530 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potential problem is formulated for rodlike macroions and reduced to a single dimensionless equation with appropriate boundary conditions. A method of solution based on piecewise linearization of the potential equation is detailed and compared with two other approaches. It is suggested that the present method yields improved estimates of macroion charges. Some numerical results are included, and the relation between electrophoretic charge and macroion charge is considered.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 3-3 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 2-2 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 77
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 5-32 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The program given here assembles and solves symmetric positive-definite equations as met in finite element applications. The technique is more involved than the standard band-matrix algorithms, but it is more efficient in the important case when two-dimensional or three-dimensional elements have other than corner nodes. Artifices are included to improve efficiency when there are many right hand sides, as in automated design. The organization of the program is described with reference to diagrams, full notation, specimen input data and supplementary comments on the ASA FORTRAN print-out.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 78
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 33-43 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the design of a guyed mast the design specification often imposes limits on the allowable deflection of the mast under wind and other lateral loads. While the deflected form of a mast depends on many different design parameters, the guy erection tensions form one of the simplest means of controlling the lateral displacements. The paper describes a procedure for calculating these tensions in the case of a mast required to have a specified set of displacements under a given set of lateral loads. It also discusses the case where specified deflections are not to be exceeded under a number of different loading conditions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 45-59 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper is concerned with the development of a computational algorithm for the solution of the uncoupled, quasi-static boundary value problem for a linear viscoelastic solid undergoing thermal and mechanical deformation. The method evolves from a finite element discretization of a stationary value problem, leading to the solution of a system of linear integral equations determining the motion of the solid. An illustrative example is included.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 80
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 61-71 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The transient field problem of the type encountered in heat conduction problems is formulated in terms of the finite element process using the Galerkin approach. Curved two-dimensional and three-dimensional, isoparametric elements are used in a time-stepping solution and their advantages illustrated by means of several examples.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 81
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The proposed finite element model is based on separate assumptions of interior and interelement displacements and on the assumed boundary tractions of each individual element. The associated variational functional for this model is presented. This method has the same merits of the assumed stress method (References 3 and 4) in that a compatible displacement function at the interelement boundary can be easily constructed, while it can easily be used for shells with distributed loads.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 117-131 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical method for the analysis of field problems is described. The algorithm is based upon the generalized Betti-Maxwell theorem. Using a set of known solutions to problems with similar boundary conditions produces a set of ‘integral’ equations for the required solution. Using any convenient numerical integration formula reduces the problem to the solution of a set of simultaneous algebraic equations. The accuracy of the solution depends upon the accuracy of the integration formula as applied to the problem under consideration and is independent of the known auxiliary solutions. The method is described in detail as applied to harmonic problems.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 83
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 85-98 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Considerable attention has been devoted in the literature on numerical methods towards securing energy convergence of solutions for, say, linearly elastic plate bending problems. Although energy convergence is necessary it by no means follows that the derived bending moments and shearing forces converge uniformly at a given point and it is this kind of feature which the engineer is really seeking.This question is examined in the context of a problem which is of particular interest to the civil engineering field and concerns the bending of a square plate under uniformly distributed load; the plate has simply supported edges and contains a central square hole with free edges. The solution to this multiply connected and mixed boundary value problem is obtained through a recently developed modification to the Rayleigh-Ritz method which has very general application and renders the solution mathematically valid up to the internal corner points where the bending moments are singular. Use is made of triangular equilibrium finite elements in conjunction with continuous eigenfunctions. Although it is already known that the order (i.e. the eigenvalue) of the singularity at the internal corners is available by inspection, it is an interesting feature of the present solution that a good approximation to the amplitude is also obtained by an inspection of the finite element results.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 84
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 99-116 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The convergence rates of eigenvalue solutions using two finite plate bending elements are studied. The elements considered are the well-known 12 degree of freedom, non-conforming rectangular element and the 16 degree of freedom, conforming rectangular element. Three problems are analysed, a square plate simply supported on two opposite sides with the other two sides clamped, simply supported, or free. Closed form, finite element solutions for these problems are obtained by using shifting E-operators.With few exceptions, eigenvalue solutions found with the non-conforming element converge from below the exact answers at an asymptotic rate of n-2, where n is the number of elements on a side. However, since the array size needed for such convergence is very large, little can be said about the convergence rates for practical arrays. The conforming element solutions converge from above at an asymptotic rate of n-4. A comparison of the errors involved in using these two elements shows that the conforming element is far superior to the non-conforming element.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 145-146 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 86
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 146-147 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 88
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 133-144 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a labour-saving method of discretizing irregular and inhomogeneous two-dimensional continua into triangular elements. The method uses a magnetic pen to record node point data and a computer program to generate element data. This technique eliminates the tedium in the manual generation of data and the delay due to mistakes which would otherwise arise frequently for a complex mesh.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 89
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 151-157 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite element formulation which includes the piezoelectric or electroelastic effect is given. A strong analogy is exhibited between electric and elastic variables, and a ‘stiffness’ finite element method is deduced. The dynamical matrix equation of electroelasticity is formulated and found to be reducible in form to the well-known equation of structural dynamics, A tetrahedral finite element is presented, implementing the theorem for application to problems of three-dimensional electroelasticity.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 90
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 175-188 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical method is presented for the solution of the radially symmetric heat conduction problem in a melting sphere. The method employs the embedding technique; this permits the solution to be written in the form of an ordinary integro-differential equation which is readily solved numerically by means of a forward integration scheme. The accuracy of the method is briefly discussed and numerical results for both constant and variable heat inputs are presented.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 91
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 159-174 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper is concerned with the development of general discrete models for the analysis of boundary-value problems in the first strain-gradient theory of elasticity. Extensions of the finite element method are constructed for this purpose, and general equations of motion are derived for finite elements of a class of micro-polar materials which are characterized by strain energy functions involving strains and second gradients of strains or displacements. The notion of generalized nodal doublets is introduced. The problem of a composite consisting of a strain-gradient sensitive microlayer embedded between semi-infinite bodies is examined as an example problem. Some of the results are compared with available exact solutions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 92
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Methods for the analysis of complex, highly redundant structures subjected to intermittent loads causing biaxial membrane stress and stress reversal into the plastic range are presented. The Bauschinger effect in multi-axial stress is taken into account by the use of Ziegler's modification of Pragers kinematic hardening theory. The implementation of this plasticity theory in the discrete element methods involves the application of the loading in small increments. A linear relationship between increments of plastic strain and of stress, arising out of the theory, is used in conjunction with a linear matrix equation that governs the elastic behaviour of the structure. In the latter equation, plastic strains are interpreted as initial strains. A solution to the linear matrix equation, expressed in terms either of stress or of total strain, may be obtained by utilizing one of two alternative procedures. The methods are capable of treating materials which exhibit elastic-plastic behaviour involving ideal plasticity, linear or non-linear strain hardening, or limited strain hardening. Application is made to several representative structures. Comparison of some of the results with existing test data for both monotonic and reversed loading shows good correlation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 93
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 221-228 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A general digital computer method based on a Sturm sequence procedure is described for determining the natural frequencies and associated modes of undamped free vibration of frames and other structures whose stiffness and mass matrices are of band form. A program which uses the method for the analysis of plane multi-storey building frames is outlined, and numerical results are presented for a simple test case and for a 19-storey frame.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 94
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 207-219 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A newly developed numerical Laplace transform inversion technique is described. A derivation of the method, termed the ‘multidata method’, is presented along with a description of a similar collocation method. Similarities and differences between the two numerical methods are described and discussed. Results of parameter studies of both methods are presented which demonstrate the sensitivity to error displayed by the collocation method and the magnitude of the improvement in accuracy obtainable with the multidata method as compared with the collocation method, especially when errors exist in the function to be inverted.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 95
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 229-241 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this study, finite element solution procedures are developed for an elastica problem of inextensible beams. The element stiffness matrices are obtained by using Galerkin's method. Results of a numerical example compare reasonably well with those obtained by using the elliptical integral.Extensions of this research are currently being made to include membrane effects of beams and to develop plate element stiffness matrices for elastica problems of plate structures.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 96
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 243-252 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This report summarizes an experimental application of the finite element approach to two-dimensional inviscid fluid flow.The method results in a matrix equation relating the vector of velocities at the nodal points with the vector of singularities. The singularities, which are concentrated at the nodes, consist of a source and a vortex.On solution of this equation (defining the flow in the region), boundary conditions must te stipulated. This usually involves setting the internal singularities to zero and making certain modifications ro those lying on the boundary of the region.Some results of the application to a particular problem are included in the paper.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 97
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 253-257 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Some typical results of an extensive series of evaluations of parallelogram-shaped plate bending elements with increasing levels of sophistication are presented. It is shown that, contrary to experience in other fields of stress analysis, this sophistication does not lead to striking improvements in accuracy in the solution of simple rectangular and skew plate problems. A computational procedure is described whereby stiffness matrices may be automatically generated from the minimum of input data specifying the displacement modes prescribed for the element.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 98
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 259-264 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A conforming plate bending solution using simple polynomial deflection functions of third-degree inside each triangular element is presented. In order to avoid normal slope discontinuities along the sides of the elements, the plate displacement parameters are subjected to ‘slope continuity conditions’ acting as constraints to the minimum potential energy problem. This is then solved by the classical method of Lagrange introducing multipliers as new auxiliary variables. If a special variational formulation of the problem is used, it can be shown that the Lagrangean multipliers are generalized stress parameters. The suggested solution is therefore basically a ‘mixed’ solution, the unknown variables of the problem being both displacement and stress parameters. Several numerical results are presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 99
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 265-275 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Approximate formulations of non-uniform beam element stiffness matrices for dynamic and elastic instability analysis are derived. Displacement functions for the uniform beam segment are employed in this development. Moment of inertia and area of the element are prescribed by arbitrary powers of the axial co-ordinate. Numerical results are obtained and compared with both analytical solutions and numerical solutions based upon stepped representations using uniform section elements. The significance of the inclusion of taper considerations within individual elements upon solution accuracy and convergence characteristics is also examined. This subject problem and solution approach demonstrates that the upper bound character of minimum energy solutions may be difficult to exploit under practical circumstances.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 100
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 2 (1970), S. 277-282 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This article describes-a new method, suitable for use on a digital computer, for evaluating the singular double integral of Hayes which determines the transonic wave drag of a slender body. Comparison with known exact results and with an earlier computer program described by Eminton shows the present method to be accurate as well as economic in computer time.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...