Bibliothek

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • 1980-1984  (6.764)
  • 1980  (6.764)
  • Chemistry  (6.408)
  • Engineering  (233)
  • Ultrastructure  (122)
  • Nuclear reactions
Materialart
Erscheinungszeitraum
  • 1980-1984  (6.764)
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    European archives of oto-rhino-laryngology and head & neck 226 (1980), S. 239-250 
    ISSN: 1434-4726
    Schlagwort(e): Enchondrale Schicht ; Labyrinthknochen ; Ultrastruktur ; Vergleichende Anatomie ; Endochondral layer ; Labyrinthine bone ; Ultrastructure ; Comparative anatomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary The endochondral layer of labyrinthine bone of dog (Canis f. intermedius Woldrich) is examined by means of light and transmission electron microscopy. The osteocytes of the fine-fibred, alamellar “embryonic skein bone” (Meyer 1927) are surrounded by a fibre-less matrix. They correspond to osteocytes in long bones. Some of them are producing microfibrils according to formation of preosseous tissue which is called “intraosseous osteogenesis” (Knese 1970). Others are characterized by signs of micropetrosis or indicate osteocytic osteolysis. In the perivascular mesenchym of some vessels giant cells are visible which according to their ultrastructural characteristics are identified as osteoclasts. The occurrence of an embryonic type of bone in endochondral layer of otic capsule throughout life is discussed considering oxygenation via perivascular canalizition as well as biomechanical aspects.
    Notizen: Zusammenfassung Unseres Wissens ist dies die erste transmissionselektronenmikroskopische Untersuchung des normalen Labyrinthknochens. Hier wird die enchondrale Schicht beim Hund (Canis f. intermedius Woldrich) betrachtet, da menschliche Felsenbeine sich aufgrund postmortaler Veränderungen nicht für ultrastrukturelle Studien eignen. Im „zeitlebens embryonalen Strähnenknochen“ (Meyer 1927) sieht man Zellen, die in einem fibrillenfreien, perizellulären Hof unterschiedlicher Ausdehnung liegen. Diese entsprechen den Osteozyten in anderen Knochen. Einige dieser Zellen bilden Mikrofibrillen und sind zu einer „intraossären Osteogenese“ (Knese 1970) fähig. Andere Zellen bieten das Bild einer osteozytären Osteolyse. Auch kommt eine Mikropetrosis in nicht kanalisierten, perivaskulären Regionen vor. Im perivaskulären Mesenchym erkennt man vereinzelt Riesenzellen, die aufgrund ihrer Ultrastruktur als Osteoklasten zu bezeichnen sind. Das lebenslange Vorkommen des embryonalen Strähnenknochens in der Labyrinthkapsel wird unter Berücksichtigung biomechanischer Gesichtspunkte diskutiert. Dabei wird auch auf die perivaskuläre Kanalisierung des Strähnenknochens eingegangen.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Neurosurgical review 3 (1980), S. 151-158 
    ISSN: 1437-2320
    Schlagwort(e): Diffuse hypertrophy of the cerebellum ; Dysplastic cerebellar gangliocytoma ; Epilepsy ; Granule cell hypertrophy ; Hamartoma of the cerebellum ; Lhermitte-Duclos disease ; Megalencephaly ; Ultrastructure ; Diffuse Hypertrophie des Kleinhirns ; Dysplastisches Kleinhirn-Gangliozytom ; Epilepsie ; Granuläre Zellhypertrophie ; Hamartom des Kleinhirns ; Lhermitte-Duclos'sche Krankheit ; Megalencephalie ; Ultrastruktur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird über zwei Fälle von Lhermitte-Duclos'scher Erkrankung bzw. diffuser Hypertrophie des Kleinhirns berichtet. Histopathologisch handelt es sich dabei um umschriebene Dysmorphien des Kleinhirns, die so charakteristisch sind, daß sie bei chirurgischer Exploration vom bloßen Auge erkannt werden können. Die vergröberten, hypertrophen Kleinhirnläppchen heben sich zudem durch eine unterschiedliche Färbung vom normalen Kleinhirn ab (Fig. 1). An Stelle der Körnerschicht gibt es dicht beieinanderliegende, dysplastische Ganglienzellen verschiedenen Typs (Fig. 3), die myelinisierte Axone (Fig. 7) in die dadurch stark myelinisierte Molekularschicht schicken. Die Purkinjezellschicht fehlt, die Marklamellen sind stark verschmälert. Die Läsion wird als Hamartom aufgefaßt; klinisch kann sie als Raumforderung der hinteren Schädelgrube in Erscheinung treten. Die Mehrzahl der Patienten mit diffuser Kleinhirnhypertrophie haben zusätzlich andere gehäuft vorkommende Läsionen wie Megalencephalie, Schädelund Skelettanomalien, benigne und maligne extracerebrale Tumoren u. a. m. Bei dem ersten Fall handelt es sich um einen 39jährigen Mann, der neben der diffusen Kleinhirnhypertrophie ein megalencephales Gehirn (2320 g) hatte, und an einem metastasierenden Coloncarcinom ad exitum gekommen ist. Im Alter von 34 Jahren ist eine 540 g schwere Struma entfernt worden. Die Ganglienzellnatur der dysplastischen Zellen der Körnerschicht ließ sich anhand des Nachweises von Synapsen (Fig. 6) und großen Nisslschollen (Fig. 5) elektronenmikroskopisch beweisen. Bei dem zweiten Fall handelt es sich um eine 74jährige Frau, deren Kleinhirnläsion — wie im ersten Fall — klinisch nicht in Erscheinung getreten ist. Die Aetiopathologie ist nicht bekannt. Die organoide Struktur der cerebellären Läsion, die häufige Vergesellschaftung mit Megalencephalie und anderen Mißbildungen, sowie das Vorkommen von familiären Fällen macht es wahrscheinlich, daß es sich dabei um eine Entwicklungsstörung handelt. Die Lhermitte-Duclos'sche Erkrankung ist selten. Meines Wissens sind zur Zeit insgesamt 42 Fälle bekannt geworden.
    Notizen: Summary Two cases of Lhermitte-Duclos disease or diffuse hypertrophy of the cerebellum are presented. This brings the total number of such cases reported in the literature to 42. Pathologically the disease is characterized by a circumscribed cerebellar lesion consisting of thickening of the cortex with closely packed dysplastic ganglion cells in the granular layer and with large myelinated axons in the molecular layer. Purkinje cells are missing and the central white matter is greatly reduced. The first patient, a man 39 years of age, had, in association to the cerebellar lesion, a megalencephalic brain (2320 g). He had suffered from epilepsy since he was 24-years-old and died with metastasizing colon carcinoma. An electron microscopic study of the cerebellar lesion disclosed perikarya containing large amounts of rough endoplasmic reticulum, cell processes filled with coated and dense core vesicles. In addition, there were numerous enlarged myelinated axons in the molecular layer. The second patient, a woman 74 years of age, had a small area of diffuse hypertrophy of the left cerebellar hemisphere measuring one centimeter in diameter. Specific symptoms were very scant in the first case and absent in the second one indicating a very slow evolution — if any — of the disease process. The etiology and pathogenesis remain unknown. However, the organoid structure of the lesion, the frequent association of megalencephaly and other congenital abnormalities, and the occurrence of familiar cases would favor the disease being basically a developmental disorder.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Archives of gynecology and obstetrics 230 (1980), S. 123-135 
    ISSN: 1432-0711
    Schlagwort(e): Clip ; Bleier-Clip ; Tube ; Histologie ; Sterilisation ; Ultrastruktur ; Clip ; Bleier clip ; Fallopian tube ; Histology ; Sterilization ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary A bilateral salpingectomy was performed at the time of vaginal hysterectomy in a pregnant patient sterilized 20 months earlier by application of Bleier clips to the fallopian tubes. Clip application to the left tube had been incomplete. Undisturbed tissue (left tube) and clipped tissue (right tube) were examined and compared by light and scanning electron microscopy. The segment of tube fully grasped by the clip had a completely detached lining epithelium with coarse and flattened mucosa, a loose stroma, and disorganized muscular bundles. The left tubal mucosa was normal, whereas the right tube was stenosed at the site of clip placement, with rigid walls and a 0.175 mm luminal diameter. With progressively greater stenosis toward the clip site, mucosal destruction increased. Polypoidal mucosal folds were seen, as well as fibrous adhesions between mucosal folds. These observations indicate that tissue damage is extensive enough after clip application to require excision of the damaged segment of tube and microsurgical re-anastomosis for reversal of sterilization.
    Notizen: Zusammenfassung Das Untersuchungsgut, über welches hier eingehend berichtet wird, stammt von einer 37jährigen Schwangeren (8. Woche), bei welcher 20 Monate zuvor eine Sterilisation mit Bleier-Clips versucht worden war. Es ergab sich eine Indikation zur Hysterektomie mit bilateraler Salpingektomie, was uns erlaubte, die gewebliche Reaktion einer Tube, an der ein Bleier-Clip korrekt saß, mit der an der kontralateralen Tube, über welche die Schwangerschaft eingetreten war, zu vergleichen. Die Präparate wurden rasterelektronenmikroskopisch und anschließend an identischen Stellen desselben Blocks lichtmikroskopisch untersucht („post-scanning histology“). In der voll gefaßten rechten Tube war das luminale Epithel streckenweise von der Unterlage abgehoben, das Faltenrelief der Mucosa distal und proximal der Clipmarke vergröbert oder abgeflacht, das subepitheliale Bindegewebe aufgelockert und die Bündel der Muscularis auseinandergedrängt. Die nur partiell mitgefaßte und daher noch ausreichend durchgängige linke Tube war zwar stenosiert, jedoch abgesehen von Schwangerschaftszeichen ohne markante Veränderung des Epithels. In der durch der korrekt sitzenden Clip verschlossenen rechten Tube verengte sich die Stenose der Clipmarke trichterförmig von proximal wie von distal, ein solider Epithelstrang war lichtmikroskopisch jedoch durchgehend nachzuweisen. Schleimhautmikropolypen und narbige Überbrückungen des Faltenreliefs in unmittelbarer Nachbarschaft des korrekt sitzenden Clips veranschaulichen, ebenso wie die narbigen Veränderungen der Tubenwand, daß eine funktionsfähige Wiederherstellung der Tubenkontinenz nach Entfernung eines zur temporären Sterilisierung applizierten Bleier-Clip kaum anders als durch eine mikrochirurgische Reanastomosierung nach Resektion der narbigen Stenose erwartet werden kann.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Archives of gynecology and obstetrics 230 (1980), S. 49-75 
    ISSN: 1432-0711
    Schlagwort(e): Ovarian Sertoli-Leydig cell tumors ; Ultrastructure ; Histogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Ovarian Sertoli-Leydig cell tumors are rare, most of them being endocrinologically active and causing virilization. Their histogenesis and nomenclature are still under discussion. Six such tumors were identified in the Laboratory for Histopathology of the University Women's Hospital, Zürich. The clinical data as well as the macroscopic, microscopic and ultrastructural features of these tumors are analysed and discussed. In an attempt to clarify their histogenesis, the ultrastructural features of these tumors have been compared with those of two granulosa cell tumors as well as with those of a testis in a patient with testicular feminization. Our own results and a study of published data suggest that Sertoli-Leydig cell tumors arise from ovarian stroma. Because of their obvious morphological similarities to testicular structures they should be termed “gonadal stromal tumors of android type”.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 15 (1980), S. 79-101 
    ISSN: 1432-1432
    Schlagwort(e): Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 38 (1980), S. 125-135 
    ISSN: 1432-1106
    Schlagwort(e): Ventromedial thalamic nucleus ; Cerebellar degenerating boutons ; Ultrastructure ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Terminal degeneration of cerebellar afferents in the ventral medial thalamic nucleus (VM) was studied in cats at the ultrastructural level after uni- or bilateral lesions in the brachium conjunctivum (BC). To achieve discrete lesions within the BC, a new very accurate stereotaxic technique was used. Numerous large terminals belonging to a population of so-called LR boutons were observed degenerating in the VM. The boutons displayed a wide variety of degenerative changes. Some revealed the features of the classical neurofilamentous type of degeneration. Others, although containing a slightly increased number of neurofilaments, featured much more prominently large numbers of coated vesicle shells and heavy accumulations of a flocculent electrondense material. Degeneration in a third group of boutons similar to some extent to the light type of degeneration was characterized by tight clumping of enormously swollen or distorted synaptic vesicles within a light matrix. At later stages, however, all these boutons were believed to become shrunken and electron-dense since intermediate stages between the light- and dark-appearing boutons were observed. The degenerating cerebellar boutons formed asymmetrical synaptic contacts. Groups of 3 or 4 boutons terminated upon dendrites of projection neurons synapsing more frequently on spines than on dendritic stems. The synaptic contacts between cerebellar boutons and the vesicle-containing dendrites of local circuit neurons were encountered as often if not more than the contacts on projection neuron dendrites. Triads consisting of cerebellar boutons and dendrites of both types of neurons were observed very regularly. This synaptic arrangement provides the anatomical basis for the modification of cerebellar input in the VM by interneurons.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    ISSN: 1432-2307
    Schlagwort(e): Cortisol ; Myocardium ; Ultrastructure ; Morphometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Male Wistar rats were treated with high cortisol doses for 1 week. The dose administered daily was 15 mg per animal in group 1 (7 animals) and 30 mg in group 2 (7 animals). 7 rats served as control group. After cortisol treatment the body weights decreased due to skeletal muscle catabolism and the heart weights increased. Morphometric analysis of the left ventricular posterior papillary muscles gave evidence that the increased heart weights resulted from an increased number of mitochondria and an increased volume of the cytoplasm, whereas the myofibrillar mass was not affected. The surface area of inner mitochondrial membranes (+cristae mitochondriales) per myofibrillar unit volume increased from 15.7 μ2/μ3 to 21.3 μ2/μ3 in group 1 and 21.4 μ2/μ3 in group 2. Ultrastructural changes indicating myocardial cell damage were absent. Similar quantitative results have been reported to occur in the early phase of cardiac overload. For elucidating the hemodynamic effects of glucocorticoid a second experiment was performed: 7 Wistar rats were treated with cortisol in the same way as group 1, 7 others of the same body weight served as control. The systolic arterial pressure was significantly elevated in the cortisol group. Though myocardial tissue is known to be able to accumulate large quantities of glucocorticoids our results indicate that the application of high cortisol doses for a short time does not produce myocardial cell damage and does not suppress the myocardial adaption to the glucocorticoid-induced hypertension, i.e. hypertrophy. On the contrary, it seems to be possible that the adaption process is itself facilitated or accelerated by the presence of high cortisol concentrations in the heart. This thesis is supported by the considerably higher relative heart weights in the cortisol groups and is in agreement with observations reported by other authors.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 8
    ISSN: 1432-2307
    Schlagwort(e): Parathyroid carcinoma ; Tumour progession ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A case of parathyroid carcinoma in a 74-year-old female patient was studied by light and electron microscopy. The malignancy of the parathyroid tumour was confirmed by local recurrence and infiltration of adjacent structures. The tumour was composed of uniform chief cells without mitoses. Ultrastructurally, the cells were characterized by tortuous plasma membranes, numerous secretion granules, an extensive rough endoplasmic reticulum and lack of lipid vacuoles, all indicating hyperactivity, but not malignancy. At death, the autopsy revealed local recurrence of tumour tissue, but no distant metastases. Both light and electron microscopy showed that considerable dedifferentiation of the tumour tissue had occurred. The tumour cells were now characterized by a marked nuclear pleomorphism and a coarse clumping of the chromatin. The presence of secretion granules alone suggested a parathyroid origin. Thus, at death there was unequivocal histological evidence of a carcinoma, whereas no such diagnosis could be made from the early biopsy. The clinical course alone indicated the malignant nature of the lesion.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 9
    ISSN: 1432-2307
    Schlagwort(e): Pituitary adenoma ; Prolactin ; Ultrastructure ; Immunohistochemistry ; Morphometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Fifteen cases of pituitary adenoma, 14 of which were associated with hyperprolactinemia, were studied by observation and granule morphometry of electron micrographs, immunohistochemistry and sequential observation of in vitro release with regard to hormone production, storage and secretion. Adenoma cells of 6 cases with marked elevation of plasma prolactin were sparsely granulated, showed characteristic ultrastrucures including the presence of small secretory granules, well developed Golgi and rough membranes, misplaced exocytosis, and positive or negative immunostaining for prolactin. These adenomas also showed vigorous release of the hormone into the circulation and/or culture medium. In vitro studies showed that negative immunostaining of adenoma cells did not preclude the production and secretion of the hormone. One densely granulated adenoma containing cells with numerous lactotroph type granules showed moderate release of prolactin into the circulation. In an acromegalic case associated with both high plasma growth hormone and prolactin, some cells were shown by immunohistochemistry to store both hormones. There were 4 adenomas which could not be shown to produce, store and secrete prolactin by any method available.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 387 (1980), S. 279-288 
    ISSN: 1432-2307
    Schlagwort(e): Pituitary ; Ultrastructure ; Hypophysectomy ; Regeneration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Male Wistar rats were partially hypophysectomized and sacrificed at intervals of from 2 days to 1 year following the operation. The resected material was examined under the light microscope and the residual pituitary under the light and electron microscope. Neither regeneration nor an anatomical restoration of the adenohypophysis occurred even one year after partial hypophysectomy. An increased number of small chromophobe stem cells and juvenile chromophil cells were found in the residual pituitary. The amount of mitoses were not significantly increased. The ACTH, FSH and prolactin producing cells demonstrated electron microscopically distinct changes which were interpreted as signs of intensified activity. This can be seen as a “functional regeneration” to maintain vital pituitary function for the organism.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 387 (1980), S. 353-369 
    ISSN: 1432-2307
    Schlagwort(e): Granulosa cell tumors ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The ultrastructural features of three granulosa cell tumors are presented. The neoplastic non-luteinized granulosa cells are characterized at sub-microscopical level by severely indented nuclei with prominent nucleoli, sparse to moderately developed predominantly granular endoplasmic reticulum, scanty lipids and lysosomes, small mitochondria with lamellar cristae and abundant intracytoplasmic filamentous material. The luteinized cells display a strongly developed tubular agranular endoplasmic reticulum and mitochondria with tubular cristae. These findings are compared with those of previous reports and discussed in relation to the well-known hormonal activity of these tumors.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 12
    ISSN: 1432-2307
    Schlagwort(e): Eosinophilic granuloma ; Frontal lobe ; Histiocytosis-X ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The clinical symptoms, pathological findings and surgical treatment of a case of primary frontal lobe eosinophilic granuloma are presented. Initially a frontal mass was detected that clinically seemed like a low-growth tumor. After operation, the histological, cytochemical and ultrastructural studies showed positive acid phosphatase, α-naftil-esterase, oil-red and PAS reactions of tumoral cells and the presence of rod-shaped bodies in proliferative histiocytes, all which confirmed the pathological diagnosis of eosinophilic granuloma. Other osseous or visceral histiocytosis-X signs were not observed. The patient remains asymptomatic after a postoperative follow-up of 2 years.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 389 (1980), S. 1-11 
    ISSN: 1432-2307
    Schlagwort(e): Soft tissue sarcoma ; Myofibroblasts ; Ultrastructure ; Host response
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A series of 129 soft tissue sarcomas was examined ultrastructurally to determine in which neoplasms and to what extent myofibroblasts could be demonstrated. Twenty cases of fibromatosis and fasciitis served as controls. Myofibroblasts were identified in all 30 cases of malignant fibrous histiocytoma and all 4 cases of well-differentiated sclerosing liposarcoma. Though most numerous in areas of desmoplasia, in no instance did myofibroblasts constitute the dominant cellular constituent of either neoplasm. Myofibroblasts were identified with lesser frequency and in smaller numbers in fibrosarcoma, synovial sarcoma, malignant hemangiopericytoma and neuroblastoma. None were observed in a wide assortment of diverse sarcomas in which desmoplasia was not a feature. In comparison each lesion judged by light microscopy to represent either fibromatosis or fasciitis was composed principally of myofibroblasts. The demonstration of abundant myofibroblasts within a soft tissue lesion which has been subjected to wide sampling strongly suggests a benign proliferative process as opposed to a malignant neoplasm. It is hypothesized that myofibroblasts observed within collagenized regions of soft tissue sarcomas may constitute an expression of host response to neoplasia.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 389 (1980), S. 27-41 
    ISSN: 1432-2307
    Schlagwort(e): Chondrosarcoma ; Clear-cell chondrosarcoma ; Glucosaminoglycans ; Histochemistry ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Two cases of clear-cell chondrosarcoma located in the upper end of the right femur of men aged 30 and 40 years are reported. The roentgenologic appearances suggested a chondroblastoma. Both patients are alive, one and four years after surgical removal of the tumor. Glucosaminoglycans were studied with cationic dyes at different pH, with and without pretreatment with testicular hyaluronidase, and with the Scott technique at the light-microscopic level. Ultrastructurally, the glucosaminoglycans were studied with the high iron diamine and dialyzed iron techniques and glycogen with the PATCH-method. Light-microscopically, the tumors were characterized by clear vacuolated cells with distinct cytoplasm boundaries and scattered multinucleated giant cells of osteoclast type. Histochemical studies at the light-microscopic level indicate the presence of chondroitin 4- and 6-sulphate but no keratosulphate. Ultrastructurally, the predominant clear-cells showed features characteristic for chondroblasts. The cytoplasm showed areas lacking organelles and containing a low-density, finely granular matrix. These areas are considered to correspond to the clear cytoplasmic vacuoles seen under the light microscope. Most of the organelles were seen in the perinuclear region. The irregular tumor cells formed delicate protruding cytoplasmic extensions, which delineated intercellular spaces appearing as vacuoles under the light microscope. The benign multinucleated giant cells had an ultrastructural appearance typical of osteoclasts. Histochemical analysis at the electron-microscopic level showed the presence of sulphated glucosaminoglycans in the intercellular matrix and in association with the cytoplasmic membrane. Glycogen and non-sulphated acid glucosaminoglycans were found within the cytoplasm of the clear-cells.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 15
    ISSN: 1432-2307
    Schlagwort(e): Congenital Nephrotic Syndrome of Finnish type ; Histochemical ; Placentomegaly ; Trophoblast basement membrane alteration ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary We have studied the morphological aspects of a thirty-six week gestational age placenta in the Congenital Nephrotic Syndrome of Finnish type. The study, conducted with histological, histochemical, morphometric and ultrastructural methods, demonstrates the presence of primary disorders of placentation consisting of persistent embryonic villi, arrested ramification and chorionangiomatosis. The villous development is compatible with the first-second trimester of pregnancy. Vasculo-syncytial membranes are quantitatively increased. Histochemical findings document placental immaturity further: Perls' reaction was positive for the trophoblast basement membrane (this is normally not observed beyond the second trimester), Alcian Blue positivity at pH 1 was also evident and was observed in three month gestational age placentae and in controls. Periodic Acid Silver Methenamine and Thioaldehyde Fuchsin documented abnormal thickenings of the trophoblast basement membrane. Electron microscopic observation reveals that the trophoblast basement membrane is thickened. Osmiophilic bodies are distributed throughout the trophoblast basement membrane and also within the basement membrane like material. Abundant microfibrils are present in the villous stroma. Lamination of basement membrane like material is observed in a subendothelial position. On the basis of their findings and in conjunction with the data in the literature regarding biochemical alterations of renal glomerular basement membranes in Congenital Nephrotic Syndrome Finnish type, the Authors suggest that a primitive membranopathy forms the basis for this pathological condition.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 389 (1980), S. 59-77 
    ISSN: 1432-2307
    Schlagwort(e): Ethanol ; Myocardium ; Ultrastructure ; Morphometry ; Mitochondria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Male Wistar rats were fed with ethanol for 33 weeks. Ethanol was administered in a liquid diet containing 33% of the calories as ethanol. In the control group ethanol was isocalorically replaced by glucose. Light and electron microscopic investigation of the hearts did not indicate significant structural abnormalities, in contrast to the results of some other groups. Nevertheless, morphometric analysis revealed considerable quantitative changes. The number of mitochondria was remarkably reduced and the volume of an average single mitochondrion nearly doubled, whereas the volume fractions of mitochondria and myofibrils were unaltered. The analysis of the mitochondrial subcompartments indicated a slight decrease of the surface area of inner mitochondrial membranes per unit volume of mitochondria and a slight increase of the volume fraction of the mitochondrial matrix space. Myocardial cell hypertrophy or atrophy were not observed. We believe that the mitochondrial changes are the expression of an impaired biogenesis of these organelles. The increased number of capillaries in the ethanol-fed group is possibly caused by functional ethanol effects which may be partly similar to effects of chronic hypoxia. Ethanol- or acetaldehyde-induced damage of heart mitochondria may play an important role in the pathogenesis of alcoholic cardiomyopathy.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 389 (1980), S. 103-117 
    ISSN: 1432-2307
    Schlagwort(e): Gonadal dysgenesis ; H-Y antigen ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The gonads of 4 phenotypically female individuals with XY chromosomal constitution and signs of virilisation were examined by light microscopy. Electron microscopic examination was also performed in two cases. Serological analysis of H-Y antigen titer yielded positive results. The matrix of the gonads is shown to be ovarian stroma, in which tubular and follicular structures are embedded. The epithelia of the follicles resemble granulosa cells of the ovary, the tubular epithelia are resemble Sertoli cells. Tubules and follicles both show extensive regressive changes. A varying number of Leyding cells/stroma lutein cells were found in each gonad. The different degree of development of testicular and ovarian structures in the dysgenetic gonads might be explained by a defect of the gonadal specific receptor for the H-Y antigen, this defect varying in time of occurrence, duration and severity.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 389 (1980), S. 287-305 
    ISSN: 1432-2307
    Schlagwort(e): Myeloproliferative disease ; Osteomyelofibrosis ; Bone marrow biopsy ; Blast crisis ; Ultrastructure ; Basophilic leukaemia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The clinical and morphological findings are presented in two patients suffering from myelofibrosis and osteomyelosclerosis which terminated in an acute blastic crisis. Clinical follow-up data and light microscopy of the bone marrow however, revealed a chronic megakaryocytic-granulocytic myelosis (CMGM) with progression into myelofibrosis during the course of disease. In one patient the blastic transformation involved predominantly basophils, and in the other, neutrophils, with an accompanying abnormal proliferation of megakaryocytes in both cases. Electron microscopy of this cell population demonstrated remarkable atypicalities of the neutrophilic, basophilic and megakaryocytic cell lines. These abnormalities consisted of a nuclear-cytoplasmic asynchrony and a partial arrest of maturation, sometimes resulting in bizarre cell forms. Our investigations support the hypothesis of a mixed cellularity type of myelosis with a gradual and insiduous progression into osteomyelofibrosis/-sclerosis and a potential blastic crisis. In the evolution of blastic crisis all cell lines may be transformed, but with predominance of one population — basophils and neutrophils in our two cases — in addition to atypicalities of megakaryocytes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 385 (1980), S. 283-291 
    ISSN: 1432-2307
    Schlagwort(e): Hodgkin's disease ; Myofibroblasts ; Ultrastructure ; Nodular sclerosis ; Host response
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Ten cases of nodular sclerosing Hodgkin's disease involving lymph nodes were studied by electron microscopy to determine the ultrastructural composition of the nodule-stromal interphase and the collagenized regions. In addition to a few lymphocytes, rare eosinophils and neutrophils, abundant filamentous and granular electron dense material, collagen fibers and myofibroblasts were observed in all instances. Since myofibroblasts possess contractile and synthetic properties, it is likely they contribute to the retraction and sclerosis which together represent one of the morphologic hallmarks of the disease. The dense fibrosis and contractile state of such tissue may constitute a beneficial host response to contain and limit local and vascular invasion by the neoplastic cellular population, thus contributing to the relative benignity of this form of Hodgkin's disease.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 158 (1980), S. 167-178 
    ISSN: 1432-0568
    Schlagwort(e): Placenta (human) ; Villous stroma ; Intercellular junctions ; Endothelium ; Ultrastructure ; Freeze-fracturing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Intercellular junctions within the villous stroma and the cytotrophoblastic layer of the human full term placenta were investigated using thin sectioning and freeze-fracturing. Numerous maculae adherentes (desmosomes) were found between the cytotrophoblast cells and the syncytiotrophoblast. This junction type was also seen connecting adjacent cytotrophoblast cells. Large gap junctions were frequently observed in contact areas of perikarya or at processes of adjacent fibroblasts. They often exhibited a peculiar pattern of their particles on the P-face of the membrane. Small rows of junctional particles were found on the P-faces of interconnected smooth muscle cells and gap junctions frequently bridged myoendothelial and interendothelial contact zones. The significance of the junctional complexes is discussed in relation to functional systems within the villous stroma of the human full term placenta.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 49 (1980), S. 43-49 
    ISSN: 1432-0533
    Schlagwort(e): Rat ; Peripheral nerve ; Macrophage ; Ultrastructure ; Histochemistry ; Acid phosphatase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The cellular content of the endoneurium in peripheral nerves of normal adult rats was studied. Endoneurial cells with high light-microscopical activity of acid phosphatase were usually located close to blood vessels or near the perineurium. Cells with the ultrastructural appearance of macrophages showed the same distribution and accounted for 2–4% of the endoneurial cell nuclei profiles. These cells rapidly endocytosed carbon particles after endoneurial administration of colloidal carbon in vitro.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 51 (1980), S. 65-70 
    ISSN: 1432-0533
    Schlagwort(e): Morphometry ; Glial cells ; Portocaval anastomosis ; Ultrastructure ; Corpus striatum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The ultrastructure of astrocytes and oligodendrocytes was investigated in rats 10 days, 30 days, and 10 weeks after portocaval anastomosis (PCA). Cell and nuclear sizes were measured by planimetry on randomly sampled cells magnified×24,000. The volume fractions of mitochondria, glia fibrils, and lipofuscin granules were measured in astrocytes by electronic image analysis. The mitochondrial profile area distribution and oligodendrocyte mitochondrial content were likewise estimated. All PCA animals had an increased astrocyte cell and cytoplasmic area, and after correction for cytoplasmic edema all groups had an enhanced mitochondrial fraction and mitochondrial number. The mitochondrial sizes were increased in all PCA groups. The mitochondrial profile area distribution curves did not suggest more than one group of mitochondria. All PCA groups had increased fractions of lipofuscin granules and glia fibrils. The oligodendrocytes had a slight fall in cell, nuclear, and cytoplasmic area after 30 days of shunting, and the mitochondrial fraction was diminished. After 10 weeks of PCA, all changes were reversed to normal values. It is concluded that the astrocytes are the active cells in the brain metabolism of ammonium. The oligodendrocytes seem to be dependent on neuronal integrity and do not contribute to the brain ammonium metabolism. The increase in astrocyte lipofuscin granules content may be explained by a beginning neuronal loss.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 51 (1980), S. 113-117 
    ISSN: 1432-0533
    Schlagwort(e): Peroxisomes ; Catalase ; d-amino-acid oxidase ; Glial tumors ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Morphologically and cytochemically defined peroxisomes (microbodies) were demonstrated in a series of 11 human glial tumors. The cytochemical methods used were the diaminobenzidine method for catalase and a tetrazolium salt-phenozine methosulfate method ford-amino-acid oxidase. Ultrastructurally, the peroxisomes were found as single membrane limited organelles with a granular matrix. Marginal plates as well as continuities with the smooth endoplasmic reticulum could be demonstrated. Peroxisomes were found most abundantly in subependymal giant cell astrocytomas, to a lesser number in astrocytomas and least abundantly in glioblastomas.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 52 (1980), S. 157-159 
    ISSN: 1432-0533
    Schlagwort(e): Neurons ; Thalamus ; Inclusions ; Ultrastructure ; Myotonic dystrophy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Intracytoplasmic cosinophilic inclusions were found by light microscopy in the thalamic neurons of 35 consecutive normal adult brains and in a case of myotonic dystrophy, but not in six newborn children, including one with myotonic dystrophy. Histochemical tests suggested a protein composition. Ultrastructurally, the inclusions were composed of stacks of parallel alternating dark and light rectilinear profiles not surrounded by a limiting membrane. Such inclusions are a virtually constant finding in the adult human thalamus and probably represent sites of neuronal protein storage.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 49 (1980), S. 75-78 
    ISSN: 1432-0533
    Schlagwort(e): Lamellar bodies ; Rough endoplasmic reticulum ; Purkinje neurons ; Adenohypophysis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Lamellar bodies are stacks of parallel cisternae of approximately regular spacing derived from ergastoplasm. Their occurrence was studied in various nervous and epithelial cells of different animal species in both normal and diseased subjects. This organelle appears to be, at least for some cell types, a normal cytoplasmic feature. The number of lamellar bodies increases in some pathologic conditions and when the cell metabolism is elevated.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 50 (1980), S. 81-83 
    ISSN: 1432-0533
    Schlagwort(e): Cerebral neuroblastoma ; Desmoplastic variant ; Dense core vesicles ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A desmoplastic primary cerebral neuroblastoma originating in the frontal lobe of a boy who died at the age of 6 years contained dense core vesicles within the cytoplasm of neoplastic cells as evidence of neuronal differentiation. Sarcomatous transformation had occurred at the time of recurrence. At autopsy, he also had cerebrospinal and extraneural metastases.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 51 (1980), S. 99-105 
    ISSN: 1432-0533
    Schlagwort(e): Skeletal muscle ; Senescence ; 65 to 89-year-old people ; Histopathology ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Biopsies for histochemical and ultrastructural studies were taken from the M. vastus lateralis of 45 healthy sedentary men and women aged 65–89 years. With increasing age the histochemical reactions reveal changes in the fibre type distribution characterized by a decrease in the percentage and predominant atrophy of type II fibres. The most frequent changes in the oldest subjects are: targetoid fibres, type I fibre predominance, and type grouping phenomena; expressions of denervation. Myopathic alterations are observed unusually. Electron microscopic findings are characterized by myofibrillar disorder, streaming of Z line and rod formation, and dilatation and increase of sarcoplasmic reticulum. As the age increases, the fibres become richer in intracellular lipid droplets and lysosomes. Intramuscular microcirculatory alterations, consisting of arteriolosclerotic changes and increase in width of the capillary basement membrane, are also observed and discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 160 (1980), S. 11-27 
    ISSN: 1432-0568
    Schlagwort(e): Sertoli cells ; Rat ; Fetal and postnatal life ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Sertoli cells have various functions: mechanical (creation of two compartments in the seminiferous tubules, migration of germinal cells), secretory (secretion of anti-Müllerian hormone, inhibin, androgen-binding-protein and estrogen) and phagocytic. We report an ultrastructural study of the rat Sertoli cell during maturation and consider possible correlations between the acquisition of certain morphological characteristics and certain functions. During fetal life, the Sertoli cell possesses differentiated zones of junction with the gonocytes and seems to have a role in the migration of the gonocytes towards the periphery of the seminiferous tubule. The Sertoli cell performs the phagocytosis of the gonocytes which degenerate during their migration, and seems to be the site of production of protein granules, whose presence can be related to the synthesis of anti-Müllerian hormone. After birth and before puberty, when the inclusions resembling secretory granules disappear, the Sertoli cell membranes in contact with spermatocytes II and spermatids differentiate, forming, through the differentiated junctional complexes, two compartments (adluminal and luminal) in the seminiferous tubules. Finally, they acquire the characteristics of active secretory cells, capable, in particular, of steroid synthesis.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 160 (1980), S. 275-284 
    ISSN: 1432-0568
    Schlagwort(e): Adenohypophyseal rudiment ; Follicular cells ; Ultrastructure ; Culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The epithelial rudiment of 4 day-old quail embryo adenohypophysis, cultivated in vitro under conditions allowing glandular differentiation, displays peripheral cells that progressively acquire follicular cell features. They elongate, develop numerous microvilli, junctional complexes, interlocking membranes and bundles of microfilaments. These follicular-like cells derive from peripheral epithelial cells that, in situ, become glandular. These results show that follicular cells can develop from undifferentiated cells. They undergo this pathway of development, in all likelihood, as a result of perturbations in their microenvironment.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 159 (1980), S. 277-288 
    ISSN: 1432-0568
    Schlagwort(e): Megakaryocyte ; Bone marrow ; Steel mice ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The megakaryocytes in the bone marrow of steel mutant mice (Sl/Sld) and their normal littermates (+/+) were studied by light and electron microscopy with special emphasis on their maturity and distribution in the hematopoietic cords. A higher percentage of megakaryocytes lying against the sinus wall, a higher percentage of the sinus perimeter covered by megakaryocytes and a higher percentage of large megakaryocytes were found in Sl/Sld mice than in +/+ mice. In addition, more large megakaryocytes as well as senile megakaryocytes were observed in the spleen of Sl/Sld mice than in that of +/+ mice. These observations suggest that more platelets are produced in Sl/Sld mice than in +/+ mice on the basis of per unit area of the marrow tissue. Heretofore, the fate of the senile megakaryocytes in the marrow was not known. However, in Sl/Sld mice senile megakaryocytes were often found entering the marrow sinuses from the hematopoietic cords. They were also seen in the lung and the spleen where degradation of senile megakaryocytes was observed. These observations suggest that senile megakaryocytes in Sl/Sld mice leave the marrow and are removed by the reticuloendothelial system outside the marrow.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 159 (1980), S. 289-305 
    ISSN: 1432-0568
    Schlagwort(e): Placenta (rat) ; Development ; Intercellular junctions ; Ultrastructure ; Freeze-fracturing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The differentiation of chorionic layers II and III and alterations of intercellular junctions within the developing placental labyrinth were investigated in rats. Between the 14th and 16th day of gestation, the trabecular structures of the labyrinth alter and increasing numbers of primary, secondary, and tertiary lamellae develop. Trophoblastic layer I remains multicellular. Layer III rearranges and cytoplasmic fusions result in a continuous cytoplasmic barrier intervening between the already syncytial trophoblastic layer II and fetal capillaries. Simultaneously, most of the “undifferentiated” cells within the labyrinth disappear. Thin sectioning anf freeze-fracturing reveal multiple images of intercellular junctions, particularly gap and tight junctions in the cellular and syncytial parts of layers II and III. Continuous and regularly arranged tight junctions occur as well as fragmented structures which are spaced irregularly. Gap junctions are occasionally found between the juxtasinusoidal regions of layers II and III on the 14th day. More often they occur within restricted areas near the center of the trabeculae, integrated within extensive tight junctional strands. Gap junctions increase in later stages of pregnancy and eventually become distributed between the interfaces of layers II and III in the primary lamellae.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 267 (1980), S. 275-282 
    ISSN: 1432-069X
    Schlagwort(e): Allergic contact dermatitis ; Epidermal cell changes ; Ultrastructure ; Allergische Kontaktdermatitis ; epidermale Zellveränderungen ; Ultrastruktur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Frühe epidermale Veränderungen bei allergischer Kontaktdermatitis wurden im Elektronenmikroskop untersucht. Gesunde freiwillige Testpersonen wurden mit DNCB sensibilisiert und in der Folge Kontaktreaktionen hervorgerufen. Epidermale Zellveränderungen nach 3 h waren unter anderem: Auftreten kleiner Vakuolen mit oder ohne Membran, stellenweise Erweiterung des Intercellularraums und eine Veränderung des Tonofilaments in kurze, gehäufte Bündel. Nicht sensibilisierte Haut, auf die DNCB appliziert wurde, zeigte auch kleine Vacuolen mit oder ohne Membran. Monocyten drangen in den Intercellularraum ein, der nicht ausgedehnt wurde. Die benachbarten Tonofilamente der Keratinocyten blieben normal.
    Notizen: Summary Early epidermal lesions of allergic contact dermatitis were examined by electron microscopy. Normal human volunteers were sensitized to DNCB, and contact reactions were elicited sequentially. Epidermal cell changes at 3 h included: the occurrence of small vacuoles with or without membrane, focal dilatation of intercellular spaces, and the alteration of tonofilaments into short, aggregated bundles. Non-sensitized skin to which DNCB was applied also showed small vacuoles with or without membrane. Monocytes infiltrated into the intercellular spaces which were not dilated, and the neighboring tonofilaments of keratinocytes remained normal.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 267 (1980), S. 283-290 
    ISSN: 1432-069X
    Schlagwort(e): Allergic contact dermatitis ; Infiltrating cells ; Monocytes ; Lymphocytes ; Ultrastructure ; Allergische Kontaktdermatitis ; Infiltratzellen ; Monocyten ; Lymphocyten ; Ultrastruktur
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Art und Feinstruktur mononuklearer Zellen, die bei allergischer Kontaktdermatitis nach ungefähr 6 h in der Epidermis auftreten, wurden im Elektronenmikroskop untersucht. Es handelte sich um Monocyten und Lymphocyten, die in ungefähr gleicher Zahl auftraten. Die Ultrastruktur der Monocyten war die gleiche wie die normaler Monocyten im Blut. Offenbar in aktiver Bewegung, erweitern sie die intercellulären Verbindungen der Keratinocyten. Die Lymphocyten zeigten einen runden oder ovalen Kern mit einigem elektronendichten Cytoplasma, das Ribosomen und Polysomen enthielt, aber nur fallweise Mitochondrien und Golgi-Komplexe.
    Notizen: Summary The kind and fine structure of mononuclear cells appearing in the epidermis at about 6 h of allergic contact dermatitis were examined by electron microscopy. They were monocytes and lymphocytes, the number being about equal. The ultrastructure of monocytes was that described for normal ones in blood, and apparently actively moving, streching the intercellular connections of the keratinocytes. Lymphocytes displayed a round or oval nucleus with some electron-dense cytoplasm which contained ribosomes and polysomes but only occasional mitochondria and Golgi complexes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 49 (1980), S. 225-230 
    ISSN: 1432-0533
    Schlagwort(e): Human pituitary adenomas ; Tissue culture ; Cell culture ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Pituitary adenomas of 120 patients were investigated in tissue and in cell cultures. Under different conditions of culture, the biopsies revealed different rates of growth. In tissue cultures 66% of the samples could be propagated while tumour specimens explanted in cell suspensions proliferated in 80% of the cases. Attempts to establish subcultures were also more successful when specimens were put into cell cultures primarily. Further differences of growth characteristics were observed in connection with the histological types of the parent tissues. According to the old terminology cells of mixed type adenomas had the longest life-span both in tissue and in cell cultures. Considering the proliferative activity, this type of tumour could be most frequently subcultured. Concerning the relationship of different cell components of the biopsies it was proven that survival and proliferation of adenoma cells may occur without fibroblasts. The appearance of fibroblast-like cells in older cultures is a morphological manifestation of the senescence of the specific cell types. Qualitative features of cultured adenoma cells showed that on the basis of cytomorphological properties “chromophobe” samples could be separated from the other types. Cells of acidophil and mixed type growths had the capacity of developing in vitro various migratory shapes, while “chromophobe” cells did not possess this ability. The histological diagnoses made independently from cultures confirmed the tissue culture findings. Differences of in vitro characteristics correlated also with the ultrastructural features of the cultured adenoma cells.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 51 (1980), S. 249-250 
    ISSN: 1432-0533
    Schlagwort(e): Neurons ; Mitochondria ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Ultrastructural study of the cerebral cortex and spinal anterior horns disclosed periodically repeating processes located in the envelope space or in the intracristal space of neuronal mitochondria. The alteration was observed in postmortem cases in which fixation was delayed either voluntarity or involuntarily, but was not present in postmortem or surgical specimens in which fixation was prompt. The change is interpreted as an artifact due to delayed fixation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 36
    ISSN: 1432-0533
    Schlagwort(e): Aging ; Hypertension ; Blood-brain barrier ; Ultrastructure ; Blood vessels
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary This study demonstrates that markedly different patterns of age-related changes in blood pressure and body weight occur among normotensive Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats and spontaneously hypertensive rats (SHR). In addition, a variety of age-related structural alterations occurred in the walls of arterioles, capillaries, and venules of the frontal cortex. These changes include: (1) an increase in the thickness of the vascular wall by deposits of collagen and basal lamina which, in some cases, extended into the surrounding neuropil; (2) the presence of a flocculent material in the adventitia of intracerebral arterioles; (3) vesicular inclusions in perivascular macrophages, pericytes and smooth muscle cells which were labelled with i.v. administered horseradish peroxidase (HRP); (4) fragmentation of smooth muscle cells; and (5) accumulation of lipofuscin-like pigments in perivascular glial processes. The hypertensive rats exhibited these changes, but they were more advanced and more widely distributed throughout the cerebral cortex. The aged hypertensive rats occasionally had large bundles of 10 nm diameter, intermediate filaments in the endothelial cells. Whereas no change in blood-brain barrier permeability to HRP was observed in the aged normotensive rats, all age groups of the hypertensive rats exhibited increased permeability to HRP in the initial segment of penetrating arterioles in laminae I and II of the cerebral cortex.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Pure and applied geophysics 118 (1980), S. 128-151 
    ISSN: 1420-9136
    Schlagwort(e): Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 188 (1980), S. 65-73 
    ISSN: 1432-041X
    Schlagwort(e): Nuclear migration ; Cleavage ; Microtubules ; Ultrastructure ; Gall midge
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In the eggs ofWachtliella persicariae the cleavage nuclei move relative to the surrounding ooplasm. This ‘active’ migration is caused by an organelle whose ultrastructure was studied throughout the mitotic cycle. It consists of a greatly enlarged polar cytaster derived from the mitotic apparatus, linked to the nucleus by 100 Å filaments. The microtubules of the cytaster were found only during periods of active nuclear migration, i.e., from the onset of anaphase to the early prophase of the next mitotic cycle. They are always solitary and follow the course of the astral rays, which are known to temporarily adhere to peripheral structures of the egg cell and to exert tractive forces. In contrast to the cytaster microtubules, the microtubules in the spindle are bundled and persist from early metaphase through late telophase. During ontogenesis the first migration cytaster is built up between 3 and 12 min after oviposition near the anterior egg pole, in the vicinity of the sperm nucleus. In non-inseminated eggs time lapse films show a migration cytaster to develop autonomously in a region free from nuclei, but it does not follow the normal path of the male pronucleus. In several cases the female pronucleus, which remains without a cytaster of its own, was observed to move to the cytaster generated in the absence of the male pronucleus. Whether or not it is adhering to a nucleus, the cytaster divides into two at the correct time, i.e, corresponding to the first cleavage division in fertilized eggs. In some non-inseminated eggs this type of ‘pseudocleavage’ has been observed to occur repeatedly, giving rise to an increasing number of anucleate cytasters.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 188 (1980), S. 163-177 
    ISSN: 1432-041X
    Schlagwort(e): Yolk sac ; Ultrastructure ; Embryogenesis ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Changes at the ultrastructural level during germ band extension in the embryo ofDrosophila melanogaster are described. Cytoplasmic connections between cells and the yolk sac are present during initial cellular movements. At this time, a continuous system of microfilaments is present adjacent to the membranes in the connections and at the periphery of the yolk sac. As germ band extension progresses, this system becomes discontinuous, and microfilaments are apparent only in the immediate vicinity of the connections. Cytoplasmic connections are disassembled at approximately the midpoint of extension; at the same time, extensive membrane associations develop between germ band cells and between these cells and adjacent yolk sac membranes. Positioning and orientation of cytoplasmic connections suggest that the yolk sac, via these connections, is actively involved in the cellular movements of early germ band extension.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 31 (1980), S. 93-108 
    ISSN: 1432-0827
    Schlagwort(e): Calculus ; Ultrastructure ; Apatite ; Transmission ; Scanning
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Using transmission and scanning electron microscopy, we have studied the ultrastructure of a number of urinary calculi, mainly composed of calcium phosphate. Three fundamental kinds of calcium phosphates were detected: nonstoichiometric carbonate apatite, nonhexagonal octacalcium phosphate, and calcium-magnesium whitlockite. The influence that the organic matter, substitutions in the phosphate lattice of CO3 and Mg, and apatitic stoichiometry have on the ultrastructure of the calcium phosphate calculi has been detailed. An originating apatitic unity named U2 is assumed to be the responsible for all the different structures of calcium apatites appearing in renal calculi. On the basis of our observations, a mechanism whereby apatites grow is postulated; magnesium functions as an inhibitor for the growing mechanism.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 30 (1980), S. 27-34 
    ISSN: 1432-0827
    Schlagwort(e): Ultrastructure ; Calcium ; Cartilage ; Vesicles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The potassium pyroantimonate technique was utilized for the selective subcellular localization of calcium in the mandibular condylar cartilage of 1-day-old rats. Electron dense calcium pyroantimonate precipitates were localized principally in mitochondria and at the cell membrane of the chondrocytes. In addition, small intracellular vesicles 0.1–0.2µm in diameter were observed in proximity to the cell membrane of chondrocytes of the mid-hypertrophic zone. The results suggest that these vesicles were being extruded from the cell into the extracellular matrix. Energy-dispersive analysis by X-rays confirmed that calcium is the principal cation of the electron-dense precipitates.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 42
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 134 (1980), S. 69-74 
    ISSN: 1432-1076
    Schlagwort(e): Achondrogenesis type I ; Ultrastructure ; Chondrocytes ; Cytoplasmic inclusions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The light- and electron-microscopic structure of articular and costal cartilage in a case of achondrogenesis type I has been described. The most characteristic ultrastructural change in the chondrocytes was conspicuous dilatation of the rough endoplasmatic reticulum (RER) which contained amorphous electronopaque material. This change in the RER was accompanied by marked hypertrophy of the Golgi apparatus; the matrix was basically unchanged.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 43
    ISSN: 1432-0738
    Schlagwort(e): Ultrastructure ; Morphometry ; Ageing ; Pentachlorophenol ; Liver
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Altersabhängige Unterschiede im Reaktionsverhalten der Leber bei männlichen Wistarratten nach intraperitonealer Applikation von 30 mg technischem Pentachlorphenol (PCP) pro Kilogramm Körpergewicht über 15 Tage wurden feinstrukturell-morphometrisch ausgewertet. Neben einer altersabhängigen Erhöhung des relativen Lebergewichts und einer Abnahme des Körpergewichts konnten umfangreiche Alterationen an den Hepatocytenzellkernen und Zellorganellen festgestellt werden. Die Ergebnisse belegen, da β PCP neben Veränderungen an den Mitochondrien und Microbodies eine Proliferation der Membranen des glatten ER und eine Verminderung von Membranen des rauhen ER hervorruft.
    Notizen: Abstract Age-dependent effects of technical pentachlorophenol (PCP) on male rat livers were investigated after a 15 day treatment with PCP, 30 mg/kg/d body weight. The liver tissues were investigated morphometrically at light and electron microscopical levels. Statistically significant alterations of nuclei and organelles of the hepatocytes were described.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular medicine 58 (1980), S. 501-510 
    ISSN: 1432-1440
    Schlagwort(e): Primärer Hyperparathyreoidismus, klinische und klinisch-chemische Befunde ; Akuter Hyperparathyreoidismus ; Ultrastruktur ; Hypercalciämie ; Parathormonspiegel ; Primary hyperparathyroidism, clinical and laboratory findings ; Acute hyperparathyroidism ; Ultrastructure ; Hypercalcemia ; Parathormone, blood level
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary In a series of 6 patients out of 47 cases with extrarenal hyperparathyroidism we investigated the clinical, laboratory and ultrastructural peculiarities of acute hyperparathyroidism. It was found that there are characteristic differences between both entities which, however, are fluid. Clinically more severe were neuromuscular psychiatric and mental signs. In the laboratory parameters PTH determined by radio-immunoassay and calcium were higher whereas hemoglobin was lower. The weights of the adenomas did not differ in both groups and this was also true for light microscopy findings. Electron microscopy revealed accelerated hormone extrusion and autodigestion of retrieved membrane material in the cases of acute hyperparathyroidism similar to characteristics of parathyroid cells stimulated by hypocalcemia in tissue culture.
    Notizen: Zusammenfassung Bei 6 Kranken mit akutem Hyperparathyreoidismus werden klinische Befunde, Labordaten und Besonderheiten in der Ultrastruktur der Nebenschilddrüsen den Daten von 47 Kranken mit extrarenalen Hyperparathyreoidismus gegenübergestellt. Typische Unterschiede konnten aufgezeigt werden, die Übergänge sind aber fließend. Beim klinischen Verlauf waren neuromuskuläre Zeichen, psychiatrische und Störungen des Bewußtseins deutlicher in der ersten Gruppe. Beim Vergleich der Labordaten war radioimmunchemisches Parathormon höher in der akuten Gruppe und das Hämoglobin niedriger. Das Gewicht der Adenome und die lichtmikroskopischen Befunde waren nicht unterschiedlich in beiden Gruppen. Die elektronenmikroskopischen Studien des Adenomgewebes zeigten eine erhöhte Hormonausschüttung mit einer deutlichen Beschleunigung der Autodigestion von Membranmaterial. Diese Veränderungen entsprechen etwa denen, wie sie an Nebenschilddrüsengewebe in der Gewebekultur nach Stimulation durch Hypocalciämie gefunden werden.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 45
    ISSN: 1432-072X
    Schlagwort(e): Mating tube ; Microtubule ; Tremella ; Ultrastructure ; Yeast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Ultrastructure of the mating tube formed in yeast haplont of the heterobasidiomycete Tremella mesenterica was studied by electron microscopy. Cell wall of the mating tube emerged as evagination of the inner layers, rupturing outer layers of the mother cell wall. Comparison with budding cells suggested that the tube emergence place at bud scar and the process of tube emergence was the same as that of bud emergence. Electron transparent vesicles of 0.1 μm diameter were scattered in the cytoplasm of the mating tube. Nucleus-associated organelle was located at one side of the nuclear envelope which extended towards the mating tube. A few microtubules were detected in the mating tube, but their association with a nucleus was not clear. The cytoplasmic structure of the mating tube was discussed in comparison with that of hyphae of the filamentous fungi.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 46
    ISSN: 1432-072X
    Schlagwort(e): Claviceps purpurea ; Ultrastructure ; Development ; Sclerotium ; Oleosomes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The development of sclerotia of Claviceps purpurea was investigated by light and electron microscopy. During the first days after infection sterigma and conidiospores are formed. The spores show a moderately developed vacuolar system, they are thick walled and contain about 20% lipid (related to the cell volume) embedded in glycogen. The sterigma are cylindrical unicellular hyphae with electron dense cytoplasm and isolated strongly contrasted lipid droplets. In maturing sclerotia the hyphae become septated with increasingly thick cell walls and a large lipid content. The lipid forms small droplets in young cells, while in the mature sclerotium it occurs in the form of very large drops, occupying the major part of the cell. Simultaneously the composition of the lipid is changed. The mature cells have several nuclei. They are partially connected by osmiophilic substances, forming a network of intercellular spaces.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 47
    ISSN: 1432-2048
    Schlagwort(e): Boron ; Foliar nutrition ; Nuclear reactions ; Transport (boron) ; Trifolium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The growth of white clover (Trifolium repens L.) is severely inhibited by boron starvation, but a foliar treatment with boric acid can transitorily alleviate the deficiency symptoms. The 10B(n ,α)7 Li nuclear reaction has been used to study boron transport in the plant after foliar application. More than 98% of the boron supplied remained at the point where it was applied to the leaves, and less than 2% was useful to the growth of the treated plant. This small “efficient” portion of boron was quite mobile. It was distributed to the different parts of the plant, then was transferred from the oldest parts to the newly formed leaves. Physiological and agronomical implications of these data are discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 389 (1980), S. 307-324 
    ISSN: 1432-2307
    Schlagwort(e): Polycythemia vera ; Secondary polycythemia ; Histopathology ; Ultrastructure ; Cytogenetics ; Bone marrow biopsy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Clinical and morphological studies including light microscopy, electron microscopy and karyotyping of the bone marrow, were performed on a total of 164 patients with polycythemic conditions. A final diagnosis was obtained from clinical findings and histopathology of plastic embedded core biopsies of the bone marrow including sequential examinations. 51 patients revealed a secondary polycythemia whereas 113 displayed polycythemia vera (P. vera). In this last group 83 cases have persisting P. vera. 30 showed a transgression towards chronic myeloid leukemia with or without accompanying myelofibrosis — osteomyelosclerosis (so called chronic megakaryocytic-granulocytic myelosis — CMGM). The histopathology of the bone marrow in P. vera revealed consistent alterations which are useful in distinguishing this disorder from secondary polycythemia (SP) and CMGM: depletion of iron storage, increased neutrophilic granulopoiesis but no gross atypia in maturation, polymorphism of megakaryocytes with conspicuous giant forms and dilatation and increased branchings of venous sinusoids. Electron microscopic findings were in agreement and showed further abnormalities of cytological maturation in the erythrocytic and granulocytic lineage. Cytogenetic studies in 27 non-treated patients with P. vera revealed the Philadelphia chromosomes in 2 cases, whereas in SP only minor chromosomal anomalies have been encountered in a few patients. It is concluded that histopathology of trephine biopsies of the bone marrow is an invaluable aid to establish a correct diagnosis, differentiating P. vera from the other potentially polycythemic disorders and helping to detect a possible progression towards leukemia at an early stage. Cytogenetic investigations may show early structural and numerical abnormalities of the karyotype and possibly precede a presumptive transgression towards myeloid leukemia (CMGM). A simultaneously performed histological and chromosomal examination of bone marrow samples is therefore desirable in each case of a polycythemic condition.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 389 (1980), S. 325-341 
    ISSN: 1432-2307
    Schlagwort(e): Polycythemia vera ; Myeloid leukemia ; Histopathology ; Ultrastructure ; Cytogenetics ; Survival
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Of 113 Patients with polycythemia vera (P. vera) who had been followed for the last 8 years, 30 cases (27%) developed myeloid leukemia with fibrosis of the bone marrow. Core biopsies of the bone marrow including sequential examinations in several cases revealed neoplastic proliferation of neutrophil granulopoiesis and an atypical megakaryopoiesis with accompanying fibrosis of varying degrees. These alterations were consistent with a subtype of chronic myeloid leukemia — the so called chronic megakaryocytic-granulocytic myelosis (CMGM) — and correspond to (agnogenic) myeloid metaplasia with osteomyelofibrosis/-sclerosis. 5 of those 30 patients showed spontaneous transgression into myeloid leukemia, none of them had received any ionizing radiation or cytostatic therapy. A blast crisis or so called acute leukemia in P. vera was seen only in one patient who was treated by an overdose of radioactive phosphorus and later evolved into osteomyelosclerosis with blastic transformation. These findings of a chronic leukemia or CMGM arising from P. vera was further confirmed by atypia of ultrastructure and particularly by our cytogenetic evaluation. Chromosomal studies showed a Ph′-chromosome to be present in 5 of 8 patients with CMGM and myelofibrosis. Clinical and statistical evaluation of survival times showed a median survival expectation of all P. vera patients of 15 years. Life expectancy of the patients who still displayed P. vera was more favorable than those cases with transformation into CMGM, disregarding any therapy. Transformation of P. vera into CMGM occurred about 8 years after the onset of disease and following transgression into leukemia, half of these patients were dead after 2.5 years. Our results demonstrate that P. vera represents a “panmyelosis” with an inherent malignant nature, or a neoplastic proliferation of all three cell lines. This concept is supported by several facts: atypia of cytological differentiation as observed by light- and electron microscopy of the bone marrow, chromosomal anomalies with aneuploidy and an infrequent Ph'-marker, spontaneous transgression into chronic myeloid leukemia or its subtype CMGM without relevant therapy and a clonal evolution as shown by enzymatic studies reported in the literature.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 206 (1980), S. 95-114 
    ISSN: 1432-0878
    Schlagwort(e): Lateral eyes ; Scorpion ; Ultrastructure ; Retina ; Arhabdomeric cells
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The dioptric apparatus of the lateral eyes of the scorpion, Androctonus austrails, consists of a cuticular lens, but lacks a vitreous body. The retina is formed by (1) retinula cells displaying a contiguous network of rhabdoms; (2) arhabdomeric cells bearing a distal dendrite that contacts retinula cells via numerous projections and ends before the rhabdomere of the retinula cells; (3) pigment cells that ensheath retinula and arhabdomeric cells with the exception of the contact regions; and (4) neurosecretory fibres possibly originating in the supraesophageal ganglion. The ratio of the number of retinula to arhabdomeric cells is determined to be close to 2 ∶ 1 in the three larger anterolateral eyes, in contrast to the median eyes where the ratio is 5 ∶ 1. The construction of the dioptric apparatus as well as the anatomy of the retina imply that in the lateral eyes of Androctonus australis visual acuity is reduced. A certain degree of spatial discrimination, however, may be retained by the presence of a relatively high number of arhabdomeric cells. It is suggested that the lateral eyes of A. australis mainly function as light detectors, e.g., for Zeitgeber stimuli.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 206 (1980), S. 123-138 
    ISSN: 1432-0878
    Schlagwort(e): Ultrastructure ; Sense organs ; Compound eyes ; Interfacetal mechanoreceptor ; Coleoptera
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The structure of the compound eyes of adult Cicindela tranquebarica Herbst was examined by use of light, scanning, and transmission electron microscopy. Each ommatidium of these photopic eyes is eucone and has a “subcorneal layer” situated between the corneal lens and crystalline cone. A distal rhabdomere consisting only of microvilli from retinula cell seven, a more proximal, rectangular, fused rhabdom formed from six retinula cells, and a basal, eighth retinula cell with a spherical rhabdomere comprise the light sensitive portions of the ommatidium. The “subcorneal layer” consists of lamellae of endocuticular microfibrils and, in surface view, shows 11 concave polygons. Proximal extensions of the crystalline thread form inter-retinular fibres containing microtubules between retinula cells 1/2, 3/4, 5/6, and 7/1. The primary pigment cells are devoid of pigment granules, but are rich in rough endoplasmic reticulum. Proximal to each retinula cell nucleus are two basal bodies, one perpendicular to the other. The more proximal basal body extends two fibrillar feet proximally which fuse to form a horizontally-banded ciliary rootlet extending the length of the retinula peripheral to the rhabdom. Each ommatidium is surrounded by 16 secondary pigment cells. Interfacetal mechanoreceptors between some adjacent lenses each have a single bipolar neuron, with a dendritic sheath, tubular body, cilium, outer and inner sheath cells, and an axon surrounded by a neurilemma sheath cell.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 52
    ISSN: 1432-0878
    Schlagwort(e): Somatostatin cells ; Calcitonin cells ; Ontogeny ; Ultrastructure ; Thyroid (rat)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Calcitonin cells are relatively numerous in the thyroid gland of the rat. In contrast, somatostatin cells are very scarce except at the time of birth and a few days thereafter, when they are conspicuously numerous. Somatostatin cells of the thyroid gland, which are ultrastructurally similar to somatostatin cells in gut and pancreas, also contain immunoreactive calcitonin. It is not clear whether somatostatin cells in the rat thyroid gland produce calcitonin or accumulate calcitonin from the environment.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 211 (1980), S. 73-82 
    ISSN: 1432-0878
    Schlagwort(e): Preputial glands ; Nude mice ; Ultrastructure ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The preputial glands of male nude (nu/nu) mice were analyzed by a combination of electron microscopy and gas chromatography to determine whether or not they are affected, like developing hairs and nails, by the nu/nu genotype. Results of the analyses revealed no differences between the glands of nude and normal male mice in either their ultrastructural characteristics or lipid secretory products.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 211 (1980), S. 105-115 
    ISSN: 1432-0878
    Schlagwort(e): Rat ; Preovulatory follicle ; Ultrastructure ; Degeneration ; Atresia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary To identify and describe ovarian follicles committed to undergo follicular degeneration (atresia), immature rats were primed with pregnant mare serum gonadotropin (PMSG). After PMSG treatment, preovulatory follicles develop but subsequently degenerate. Prior to the appearance of pyknotic nuclei (Stage I of atresia), degenerative changes were observed in focal areas of the granulosa cell layer. These changes include “blebbing” of the cytoplasm and alterations in the shape of the granulosa cells. The appearance of these degenerative changes coincides with a decrease in ovarian concentrations of estradiol and testosterone. Since estrogens and androgens maintain the follicle, the decline in estradiol and testosterone could be responsible for the further degenerative alterations that lead to complete deterioration of the preovulatory follicle. In Stage I atretic follicles, lysosome-derived autophagic vacuoles develop and macrophages invade both the thecal and granulosa cell layers. The combined actions of the autophagic vacuoles and macrophages could destroy both the granulosa-cell and thecal layers and thereby transform the preovulatory follicle into an ovarian cyst.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 212 (1980), S. 241-255 
    ISSN: 1432-0878
    Schlagwort(e): Glomerulogenesis ; Glomerular capillaries ; Kidney development ; Corrosion casts ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Kidneys of 2 to 10 day-old rats of Wistar and Sprague-Dawley strains were fixed with glutaraldehyde by retrograde vascular perfusion and then prepared for observation in TEM and SEM. In addition methacrylate casts of differentiating glomerular capillaries were examined by SEM. Although the glomerular vascular pattern differs from one glomerulus to another, its differentiation proceeds according to the following general plan. First the glomerular capillary splits longitudinally, finally to form 3 to 5 lobules consisting of a capillary network, sustained centrally by the mesangium. In the present study the differentiation of glomerular capillaries is described in five successive arbitrarily selected stages. At Stage I a capillary loop penetrates between the lower limb and the middle segment of the S-shaped body, the rudimentary nephron. At Stage II the capillary undergoes a first subdivision, establishing the primitive lobulation of the glomerulus. At Stage III the vascular and urinary poles differentiate. At Stage IV the glomerulus assumes the aspect of a spherical body, and the capillaries in each lobule undergo subdivision. In Stage V the glomerular vascular pattern approaches its adult appearance, although the maturation processes continue for an extended period of time. Hence in the 10 day-old rat the best-differentiated glomeruli are half the size of adult glomeruli, and their capillary loops are proportionally less well-developed. The capillaries of adjacent lobules may communicate with each other, but a direct vascular shunt between the afferent and efferent vessels cannot be demonstrated.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 56
    ISSN: 1432-0878
    Schlagwort(e): Stannius bodies ; Secretory cell types ; Teleosts (Fundulus, Carassius) ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The Stannius bodies of killifish and goldfish were ultrastructurally investigated after exposure of the fish to media of different osmolality and calcium content. In both species two structurally different secretory cell types are found. Type-1 cells predominate. They contain an extensive granular endoplasmic reticulum, some large Golgi areas, and secretory granules with a mean diameter of about 0.4 μm. These cells are activated by transfer of freshwater fish to seawater, but not by transfer to low-calcium seawater. Type-2 cells often contain cytoplasmic processes that penetrate between the type-1 cells and are ending on the basal lamina. In this contact area granule release takes place. Type-2 cells contain some strands of granular endoplasmic reticulum, several small Golgi areas, and secretory granules with a mean diameter between 0.15 and 0.20 μm. Type-2 cells are not activated after transfer of fish to seawater. In killifish seawater exposure leads to a reduction of type-2 cells. The differences between the reactions of both cell types to different media point to functional differences between their secretory products. Type-1 cells may produce a hypocalcemic factor. It is concluded that type-2 cells are typical for freshwater fish or euryhaline fish spending part of their life cycle in freshwater. The proper function of these cells is unclear.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 212 (1980), S. 307-314 
    ISSN: 1432-0878
    Schlagwort(e): Thymus (Mammalia) ; Erythropoiesis ; Macrocytes ; Anaemia ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The thymus of wild young and adult bank voles (Clethrionomys glareolus) was examined by histological methods for the presence of developing erythroid cells. Nucleated erythroid cells were observed in 26% of the glands examined by light microscopy and in 69% of the glands examined by electron microscopy. The largest number of developing erythroid cells was observed in the thymus of pregnant females, also showing raised reticulocyte counts (3.1–10.2%). However, erythropoiesis could also be found in breeding and non-breeding, first year and older animals. Erythroid cells were mainly located in the cortex, sometimes in small groups interspersed between lymphoid cells, and also randomly scattered in the cortex. Occasionally, macrocytic erythroid cells were also present. Pyknotic cells were commonly present, and granulopoiesis was frequently observed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 208 (1980), S. 123-133 
    ISSN: 1432-0878
    Schlagwort(e): Lesioned axons ; Ultrastructure ; Crayfish
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The distal stumps of severed medial giant axons (MGAs) and of non-giant axons (NGAs) in the CNS of the crayfish Procambarus clarkii show long-term (5–9 months) survival associated with disorientation of mitochondria and thickening of the glial sheath. However, the morphological responses of the two axonal types differ in that neither the proximal nor the distal stump of severed MGAs ever fills with mitochondria as is observed in some severed NGAs. Furthermore, the adaxonal glial layer never completely encircles portions of MGA axoplasm as occurs in many severed NGAs; in fact, ultrastructural changes in the adaxonal layer around severed MGAs are often difficult to detect. No multiple axonal profiles are ever seen within the glial sheath of the proximal or distal stumps of severed MGAs whereas these structures are easily located within severed NGAs.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 211 (1980), S. 223-234 
    ISSN: 1432-0878
    Schlagwort(e): Neurosecretion, insect ; Median neurosecretory cells ; Melanogryllus desertus ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Based on the nature of their granules, eight principal types of neurons, six of which are thought to be neurosecretory, are recognized in the median neurosecretory cell group of the brain of Melanogryllus desertus. Most of the neurosecretory cells contain granules with diameters of 200–300 nm. In a few the granules are smaller with diameters varying from 60–100 nm. Most of the cells have well developed Golgi areas and dense bodies of different sizes. Dense bodies are closely associated with neurosecretory granules. Accumulations of electron-dense granular material occur in expanded cisterns of endoplasmic reticulum, particularly in type-I cells.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 60
    ISSN: 1432-0878
    Schlagwort(e): Ultrastructure ; Fluorescence histochemistry ; Prevertebral ganglia ; Ageing ; 5-hydroxydopamine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Sympathetic post-ganglionic neurones in the coeliac-superior mesenteric ganglion (CSMG) complex of aged (24 month) rats have been studied by glyoxylic acid-induced fluorescence and electron microscopy. Comparisons have been made with the CSMG of young adult (4 month) rats. In the aged rats the noradrenaline fluorescence of the majority of neuronal perikarya was very low or absent and few intraganglionic fluorescent varicosities were seen. Lipofuscin pigment was very prominent at the nuclear pole region of neurones and also in dendrites and axonal processes. Ultrastructural studies revealed large accumulations of residual bodies at the nuclear poles and in axons and dendritic profiles. Within the perikarya many mitochondria were distorted or swollen, the rough endoplasmic reticulum was disarranged and much dilated as were Golgi cisternae. Primary lysosomes were encountered throughout the neurone perikaryon and its axonal or dendritic processes. In contrast to the young adult CSMG, no evidence for loading of transmitter storage vesicles with an identical dose level of 5-hydroxydopamine was detected in any part of the neurones of aged rats. This might reflect an impairment of the uptake mechanisms and/or storage of noradrenaline in aged sympathetic neurones and their axonal and dendritic processes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 205 (1980), S. 273-287 
    ISSN: 1432-0878
    Schlagwort(e): Human neurohypophysis ; Ultrastructure ; Pituicytes ; Ependyma ; Choristoma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The pars nervosa of the neurohypophysis from 12 patients undergoing hypophysectomy for palliative treatment of advanced carcinoma was studied electron microscopically. Special attention was given to the cellular elements, the pituicytes. Five different classes of pituicytes, with various transitional forms, were elucidated based on their ultrastructural characteristics: (1) The most common type, referred to as “major pituicytes”, is reminiscent of astrocytes. (2) “Dark pituicytes” are thought to represent different functional stages of the “major pituicytes”. (3) “Ependymal pituicytes” are believed to provide ultrastructural evidence that human pituicytes are phylogenetically derived from ependymal cells. (4) “Oncocytic pituicytes” were observed in all cases and are of unknown significance. (5) The ultrastructural features of “granular pituicytes” suggest the existence of an active uptake and catabolism of extracellular material by pituicytes, probably through “ultraphagocytosis” or “endocytosis”. These five classes of pituicytes are considered to represent different functional forms of one cell line that originates phylogenetically from the ependyma.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 205 (1980), S. 361-370 
    ISSN: 1432-0878
    Schlagwort(e): Enamel organ ; Human foetus ; Tooth germ ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The fine structure of external enamel epithelium, stellate reticulum and stratum intermedium in primary tooth germs (bell stage) from four human foetuses was investigated. Characteristically, the cells of the differentiated external enamel epithelium, stellate reticulum and stratum intermedium exhibit many free ribosomes, few rough endoplasmic reticulum cisterns, well-developed Golgi complexes, many coated and smooth vesicles, often in relation to the cell membranes, and many bundles of tonofilaments. The cells are connected by numerous desmosomes and gap junctions. A parallel differentiation of stratum intermedium — external enamel epithelium, and the ameloblast layer is demonstrated. The morphology of the cells of the three layers indicates that these have secretory, transport and supporting functions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 206 (1980), S. 487-500 
    ISSN: 1432-0878
    Schlagwort(e): Trophamnion ; Coelenterate, Polypodium hydriforme ; Ultrastructure ; Planula ; Parasitism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The larval stage of Polypodium hydriforme is planuliform and parasitic inside the growing oocytes of acipenserid fishes. The larva has inverted germ layers and a special envelope, the trophamnion, surrounding it within the host oocyte. The trophamnion is a giant unicellular provisory structure derived from the second polar body and performing both protective and digestive functions, clearly a result of adaptation to parasitism. The trophamnion displays microvilli on its inner surface, and irregular protrusions anchoring it to the yolk on its outer surface. Its cytoplasm contains long nuclear fragments, ribosomes, mitochondria, microtubules, microfilaments, prominent Golgi bodies, primary lysosomes, and secondary lysosomes with partially digested inclusions. The cells of the larva proper are poorly differentiated. No muscular, glandular, neural, interstitial, or nematocyst-forming cells have been found. The entodermal (outer layer) cells bear flagella and contain rough endoplasmic reticulum; the ectodermal (inner layer) cells lack cilia and contain an apical layer of acid mucopolysaccharid granules. The cells of both layers contain mitochondria, microtubules, and Golgi bodies; their nuclei display large nucleoli with nucleolonema-like structure, decondensed chromatin, and some perichromatin granules. At their apical rims, the ectodermal cells form septate junctions; laterally, the cells of both layers form simple contacts and occasional interdigitations. The lateral surfaces of entodermal cells are strengthened by microtubules.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 210 (1980), S. 257-267 
    ISSN: 1432-0878
    Schlagwort(e): Ultrastructure ; Smooth muscle ; Connective tissue ; Portal vein ; Rabbit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The smooth muscle of rabbit portal vein was studied by electron microscopy with particular emphasis on the mechanical linkage between the muscle cells and on the distribution of connective tissue. The media of this vein is composed of inner circular and outer longitudinal muscle layers which are orientated almost perpendicularly to each other. The muscle of the inner circular layer shows very irregular contours with much branching and anastomosing of the cytoplasmic processes, which often make membrane contacts with neighbouring cells to form an extensive network of cytoplasmic processes. The muscle cells of the outer longitudinal layer are arranged in densely packed bundles and are spindle-shaped, with no branching processes. Opposing dense areas from neighbouring cells, with variable gap distances (30–100 nm) and close membrane contacts (intermediate junctions) with a gap of 11 nm were observed in both circular and longitudinal muscle layers. In the terminal regions of muscle cells in both circular and longitudinal layers a specialized anchoring structure was present which was closely related to extracellular elastic tissue. Muscle cells in the longitudinal layer showed the most elaborate structure, the tapering end of the muscle cell showing a honeycomb-like structure penetrated by columns of connective tissue compounds. The functional implications of these structures are discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 210 (1980), S. 339-347 
    ISSN: 1432-0878
    Schlagwort(e): Seasonal breeding ; Leydig cells ; Ultrastructure ; Bat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Leydig cells of the bat, Myotis adversus, have been examined by electron microscopy throughout fourteen months. During the breeding season the Leydig cells become hypertrophied and are characterised by prominent areas of agranular endoplasmic reticulum and numerous small, membrane-bound granules. Microperoxisomes are also observed. During the period of testicular regression. Leydig cell size and the number of membrane-bound granules are greatly reduced. Lipid droplets and dense bodies are more numerous.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 210 (1980), S. 417-433 
    ISSN: 1432-0878
    Schlagwort(e): Pinealocytes ; Ultrastructure ; Malaysian rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé Les pinéalocytes d'un Rat de Malaisie (Rattus sabanus), un animal vivant près de l'équateur donc dans une zone où les variations annuelles de la longueur des jours sont minimes, examinés au microscope électronique ont été comparés à ceux d'autres Mammifères. Une seule population de pinéalocytes a été observée. La présence d'un grand nombre de vésicules granulaires et de rubans circonscrits par des vésicules est la caractéristique premi`ere des pinéalocytes de cette espèce. Les rubans circonscrits par des vésicules ont été plus spécialement observés dans les terminaisons des prolongements des pinéalocytes où ils sont nombreux et la plus souvent en contact directe avec l'espace périvasculaire. L'importance physiologique de ces rubans circonscrits par des vésicules et des vésicules granulaires est discuté.
    Notizen: Summary The ultrastructure of the pinealocytes of the Malaysian rat (Rattus sabanus), a mammal inhabiting a zone near the equator where the annual variations of daylength are inconspicuous, was examined and compared with that of pinealocytes of other mammals. On the basis of the presence of granular vesicles, only one population of pinealocytes was found. A large number of granular vesicles and vesicle-crowned rodlets is characteristic of the pinealocytes of this equatorial species. Vesicle-crowned rodlets are especially numerous in the endings of the pinealocyte processes and; they most often found in direct topographical connection with the perivascular spaces. The physiological significance of the presence of such large amounts of vesicle-crowned rodlets and of the secretory process characterized by the formation of granular vesicles is discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 67
    ISSN: 1432-0878
    Schlagwort(e): Growth hormone-release-inhibiting factor (somatostatin) ; Sympathetic ganglia ; Ultrastructure ; Guinea pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The superior cervical ganglia (SCG), celiac superior mesenteric ganglia (CMG), and splanchnic nerve of unoperated guinea pigs, as well as both proximal and distal stumps of a previously transected branch of the postganglionic plexus of the CMG, were immunostained for somatostatin (SS). In addition, the PAP technique was adapted for fine-structural visualization of SS. A greater proportion of cells were labeled for SS in the CMG than in the SCG. PAP molecules were present in one type of intraganglionic axons. Only two labeled axons were found in the splanchnic nerve. Neither proximal nor the distal stump of the transected CMG postganglionic nerve contained labeled axons. The present results support the hypothesis that the intraganglionic axons labeled for SS arise from SS-containing intraganglionic neurons.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 68
    ISSN: 1432-0878
    Schlagwort(e): Sturgeon ; Muscle fibres ; Ultrastructure ; Morphometry ; Vascularisation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructure and vascular supply of the different fibre types in the lateral muscles of the sturgeon Acipenser stellatus were studied by light- and electron microscopy and morphometry. Three fibre types form separate layers without intermingling. The red fibres are superficial, the white fibres deep and the intermediate fibres between them. From morphometric analyses, the mitochondrial volume fraction in red fibres is 30%, in intermediate fibres 3.7% and in white fibres 0.7%. Z lines are most fuzzy in the red fibres. Triads of the sarcotubular system are always situated at the level of the Z discs. In red fibres the three elements are arranged in a series along the myofibrils, whereas in white fibres they are arranged transversely and in the intermediate fibres they are aligned obliquely. The number of capillaries surrounding each fibre is 2.3, 0.9 and 0.2 for the red, intermediate and white fibres, respectively. In red fibres 16% of the surface is directly covered by capillaries. The corresponding percentages for intermediate and white fibres are 5 and 1, respectively. Per unit volume of the fibre, the directly vascularised fibre surface in red fibres is about ten times larger than that of white fibres. The degree of vascularisation of the fibre types is directly related to the volume fraction of mitochondria, and thus to their aerobic capacities.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 69
    ISSN: 1432-0878
    Schlagwort(e): Calcergy ; Calcification ; Cutaneous calcinosis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In rats a subcutaneous injection of KMnO4 leads to the calcification of the connective tissue. During mineral deposition, both intra- and extracellular changes are observed in the connective tissue. The intracellular phase is characterized by the formation of intramitochondrial granules and cytoplasmic vesicles, both in fibroblastic and extrinsic cells. In the extracellular phase, numerous heterogeneous matrix vesicles appear in the extracellular matrix. At the same time, globular particles which are resistant to microincineration, are observed between the collagen fibrils. The mineralization of the extracellular matrix takes place in two stages. The first stage comprises the appearance of needle-like structures and round aggregates. The needle-like structures are observed occasionally in the matrix vesicles and often in the extracellular matrix where they appear isolated or diverging from a central point. The round aggregates, composed of dense particles, are seen in the ground substance between the collagen fibrils. The second stage is characterized by a progressive mineralization of the collagen fibrils and the elastic fibers, without formation of extended calcified plaques.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 70
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 213 (1980), S. 221-235 
    ISSN: 1432-0878
    Schlagwort(e): Peripheral blood lymphocyte ; Density separation ; T cell depleted rabbits ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Density separation of purified peripheral blood leucocytes from T-cell depleted rabbits on a linear Ficoll-metrizoate gradient has been applied to obtain different leucocyte fractions. Two lymphocyte fractions separated on density seem to have different characteristics, both morphologically and immunologically. In this study these two fractions have been characterized ultrastructurally by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and a relationship has been established between the surface architecture (SEM), the cell size (SEM/TEM) and surface-Ig/C3-receptors (LM, light microscopy). Finally three types of lymphocytes have been described in the two lymphocyte fractions separated on density. Morphometric information such as cell size, cell shape, eu-/heterochromatin ratio in the nucleus and the nucleus-/cell ratio have been correlated to the stage of activation of the B lymphocyte in a representative density separation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 208 (1980), S. 183-196 
    ISSN: 1432-0878
    Schlagwort(e): Sinus node ; Atrium ; Ultrastructure ; Caveolae ; Freeze fracture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Caveolae or membrane vesicles are commonly observed in smooth and skeletal muscle as well as in working heart muscle. Using sections of fixed tissue and replicas of freeze-cleaved material, we show in this study that caveolae are also very numerous in sinus node cells of the rabbit, and to a lesser degree, in the atrial cells. Caveolae increase the plasma membrane surface area by 115% in the leading sinus node, and by 56% in the atrial cells. In these two cell types, the membrane of the caveolae contains four times fewer intramembranous particles than the rest of the plasma membrane, and this difference applies to both PF and EF faces. The role of the caveolae is still unclear, but it does not seem that they have a pinocytotic function.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 72
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 207 (1980), S. 171-182 
    ISSN: 1432-0878
    Schlagwort(e): Nephridia ; Anatomy ; Ultrastructure ; Tardigrada
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The excretory system of Macrobiotus richtersi consists of one dorsal and two lateral components and shows a high degree of structural complexity. In each of these a tricellular external lobe and a column can be distinguished, the two parts being connected distally. The surface of the lobe cells is increased by deep basal infoldings and fingerlike processes which form a labyrinth next to the basal lamina. Their cytoplasm contains numerous mitochondria, a well developed rough endoplasmic reticulum, dictyosomes, and granules in amounts depending on the physiological state of the animal. Excretory crystals occur in caveolae located in the lobe: between the fingershaped processes of the cell and in the space enclosed by the basal lamina on one side and the column on the other. The column faces an extracellular channel meandering along its whole length which is surrounded on the outside by a basal lamina. Morphologically the column is similar to the protonephridial channel of Rotifera. At the ultrastructural level, the cytoplasm of the column shows numerous mitochondria, rough endoplasmic reticulum, lysosomes, and a well developed Golgi apparatus. The lumen of the channel is coated by glycocalyx. At the base of the column several small cells form the proximal part of a duct that communicates with the gut. The morphology and ultrastructure of the excretory system of M. richtersi have been compared with similar a system in Isohypsibius megalonyx (Greven, 1979), and on these grounds a proposal is put forward to call the excretory organs of Tardigrada “nephridia” instead of “Malpighian tubules”.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 210 (1980), S. 85-94 
    ISSN: 1432-0878
    Schlagwort(e): Hypothalamus ; Domestic fowl ; Preoptic area ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Numerous secretory parvocellular perikarya were found in the preoptic region of the domestic fowl (Gallus gallus). The dense-core secretory vesicles belong to two categories: vesicles with a diameter of (i)80–90 nm and (ii) 110–140nm. Scattered magnocellular elements display larger dense-core granules. The parvocellular neurons form unit-like clusters, showing also zones of direct apposition of neuronal membranes. The surrounding neuropil is rich in synaptic structures, formed by at least three types of axon terminals, distinguishable on the basis of vesicular morphology. These observations confirm the findings in other avian species. The hypothetical function of this system of peptidergic neurons in the rostral hypothalamus of birds is discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 210 (1980), S. 121-132 
    ISSN: 1432-0878
    Schlagwort(e): Glycoproteins ; Ultrastructure ; Tunicamycin ; Colonic epithelium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Glycoproteins are associated with several structures of colonic absorptive cells of the mouse. These include the cell coat, Golgi apparatus and vesicles that transport the glycoproteins from the apparatus to the cell surface (Michaels and Leblond 1976). In many in vitro systems, the antibiotic tunicamycin inhibits the glycosylation of asparagine residues yielding carbohydrate-poor glycoproteins. In the present in vivo study, tunicamycin was injected into mice. The murine colonic epithelial cells were prepared routinely for electron microscopy and cytochemistry. Cells from the experimental and control animals were similar morphologically. However, staining by the periodic acid-chromic acid-silver methenamine technique, revealed differences in the distribution of glycoproteins. In animals that received the higher dosages of tunicamycin there was a substantial reduction in silver staining in both the Golgi apparatus and the vesicles of colonic epithelial cells compared to these structures in cells of identically treated control tissues, whereas the staining over the cell coat was not significantly altered. Possible explanations for the staining of the cell coat in the treated animals were provided in the text. This report demonstrates the feasibility of using tunicamycin in vivo and detection of the changes obtained by the silver methenamine method.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 75
    ISSN: 1432-0878
    Schlagwort(e): Transmitter-dualism ; Multipotential neuron ; Heart innervation ; Ultrastructure ; SEM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The segmental heart nerves of Caligo beltrao Illiger (Brassolidae) were examined by transmission and scanning electron microscopy. Heart and alary muscles are innervated by branching processes of single multinucleate neurons (MNNs). There is one MNN situated at each segmental fan-shaped group of alary muscles. The main nerve of the MNN consists of a bundle of processes. This nerve extends centripetally toward the CNS and corresponds to the dorsal portion of the transverse nerve. However, neither axo-somatic nor axo-axonic synapses were found, the presence of which might suggest that this nerve contains axons of different neuronal origin. The synaptic contacts of the MNN with axons originating from the CNS are therefore assumed to be established beyond the spiracular region. In addition to the neuro-muscular junctions of the smaller centrifugal axon branches there are neurohaemal release sites along the entire length of all MNN axon bundles. Axon terminals are packed with either dense-cored or multigranular vesicles. Both morphological types of vesicles are, however, found side by side in the large axons and in the perikaryon, often at the same Golgi element. These morphological findings may support the concept that more than one transmitter is produced in a single neuron. Questions that arise in reference to dual or polyfunctional neurons and to the control of cardiac activity are discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 212 (1980), S. 415-427 
    ISSN: 1432-0878
    Schlagwort(e): Cerebellum ; Purkinje axon ; Ultrastructure ; Axotomy ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Transection of Purkinje cell axons in adult male rats made 1.5 mm or further from the cell body does not lead to the death of the neuron and results in compensatory structural alterations of the surviving axonal portions of the nerve cell. Near to, and at the emergence of recurrent collaterals of Purkinje cell axons, huge varicosities filled with filaments, granular material, lysosomes and mitochondria develop. Terminals of recurrent axon collaterals also exhibit different degrees of structural changes. Most striking of the morphological alterations is the regular presence of nematosomes in the hypertrophic axonal branches, especially in synaptic terminals. Since nematosomes were shown to contain RNA in other types of neurons, their presence in recurrent collaterals may indicate an enhanced synthetic activity in Purkinje axonal processes and endings after axotomy.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 77
    ISSN: 1432-0878
    Schlagwort(e): Ecdysteroids ; Moulting hormones ; Xyleborus ferrugineus pupae ; Ultrastructure ; Prothoracic gland
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The prothoracic glands of female pupae of Xyleborus ferrugineus at three ages (0-h, 48-h and 72-h-old) were examined for ultrastructural changes that correlate with high titers of ecdysteroids in the entire pupa. In all three ages, the prothoracic gland cells appear compact with a prominent nucleus. Lysosome-like structures with concentrically oriented internal membrane are observed in both 0-h and 72-h-old gland cells. Mitochondria are abundant in the glands of both ages, and rough endoplasmic reticulum is relatively sparse. Numerous microtubules are present in the prothoracic gland cells of 48-h-old female pupae that contain relatively high titers of ecdysteroids. Rough endoplasmic reticulum also is especially abundant at this age of the pupa. Ecdysone titers, estimated by the radioimmunoassay method (RIA), were 161.04±22.61 pg/mg, 704.25±69.02 pg/mg and 298.72±26.80pg/mg body weight in 0-h, 48-h and 72-h-old female pupae, respectively.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 213 (1980), S. 149-157 
    ISSN: 1432-0878
    Schlagwort(e): Trophic chamber ; Nutritive cord ; Ultrastructure ; Homoptera
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Each ovariole of the coccidian Aspidiotus hederae contains a single oocyte connected by means of a nutritive cord to the trophic chamber. The trophic chamber consists of three nurse cells characterized by an enlarged, ramified nucleus with a prominent nucleolus. The perinuclear cytoplasm contains nuage material, large amounts of free ribosomes, and scattered mitochondria. Occasional cisternae of the rough endoplasmic reticulum and bacteroids are found in trophocyte cytoplasm. The nutritive cord contains many microtubules in parallel array interspersed with numerous free ribosomes and a few mitochondria. The nutritive cord is strengthened by trophocyte projections which surround it. Microtubules in the projections are oriented perpendicular to the long axis of the cord.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 79
    Digitale Medien
    Digitale Medien
    Springer
    European archives of oto-rhino-laryngology and head & neck 226 (1980), S. 161-176 
    ISSN: 1434-4726
    Schlagwort(e): Otosklerose ; Histochemie ; Ultrastruktur ; Lysosome ; Oxytalanfaser ; Otosclerosis ; Histochemistry ; Ultrastructure ; Lysosomes ; Oxytalan fibres
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary In a histochemical and electron microscopical study the pathogenesis of Otosclerosis was investigated. The morphological changes in the extra- and intracellular space indicated a complex metabolic disturbance of all tissue components. The observed chondrocytic chondrolysis stressed the role of the cartilage remnants in the otic capsule as an etiological factor. There was morphological evidence of a superimposed enzymatic defect.
    Notizen: Zusammenfassung In einer histochemischen und ultrastrukturellen Untersuchung werden die pathologischen Bindegewebsveränderungen bei der Otosklerose analysiert. Die Erkrankung führt zu einer komplexen Schädigung aller Bindegewebskomponenten. Es finden sich morphologische Anhalte für einen Enzymdefekt, der dem initialen pathologischen Reiz aufgelagert sein kann. Die beobachtete chondrozytäre Chondrolyse unterstreicht die Bedeutung der Knorpelreste in der otischen Kapsel als pathogenetischen Faktor der Otosklerose.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 80
    Digitale Medien
    Digitale Medien
    Springer
    European archives of oto-rhino-laryngology and head & neck 229 (1980), S. 45-53 
    ISSN: 1434-4726
    Schlagwort(e): Vitamin A-Mangel bei jungen Ratten ; Ultrastruktur ; Akustische Sinnenzellen ; Ganglion spirale cochleae ; Vitamin A deficiency in young rats ; Ultrastructure ; Acoustic sensory receptor ; Ganglion cell
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary Microscope studies of the inner ear in rats with chronic vitamin A deficiency have rendered contradicting results. In our electron microscope study of the sensory cells of the inner ear in young rats with vitamin A deficiency we found that the cuticle is missing in outer hair cells. In the inner hair cells the cuticle is subtotally lacking. Furthermore, we found changes in the reticular system of the intermediate zone and massive degenerative changes in the afferent nerve system including the ganglion cells of the ganglion spirale cochleae. These morphological changes together with the recent findings of high concentrations of vitamin A in Corti's organ support the hypothesis that the acoustic sensory receptors contain of functionally depend upon vitamin A.
    Notizen: Zusammenfassung Histologische Untersuchungen über die Auswirkung eines chronischen Vitamin A-Mangels auf die Strukturen des Innenohres hatten widersprüchliche Ergebnisse gebracht. Nach einem sechswöchigen Vitamin A-Mangel bei jungen Ratten fanden wir in äußeren Haarzellen ein Fehlen der elektronendichten, homogenen Cuticula. In den inneren Haarzellen kam es ebenfalls zu einer deutlichen Auflösung der Cuticula. Weiter fanden wir eine Fragmentierung und Verminderung des reticulären Systems der Intermediärzone. Deutliche Degenerationszeichen fanden sich bei den afferenten Nervenendigungen und in den Ganglienzellen des Ganglion spirale cochleae. Die Ergebnisse weisen auf eine spezielle Bedeutung des Vitamin A für die Funktionsfähigkeit der Sinneszellen hin.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 81
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 823-831 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of the DNA-binding oligopeptide distamycin A on the B to A transition of DNA in ethanol/water solutions has been studied by means of CD. (The overbars indicate that it does not matter which particular form of the corresponding families is considered.) The results show that increasing the concentration of distamycin A reverses the A conformation (in 82% ethanol) to the B conformation due to its strong binding and stabilization of the latter. In accordance with previous data for pure aqueous solutions, a site size of 3.5 base pairs is obtained from the studies in water/ethanolic solutions. From the data on the B to A transition in the presence of distamycin A, we estimated the length of the cooperativity ν0 = 10 base pairs.The results demonstrate that the oligopeptide systems of distamycin, as well as those of netropsin, are effective stabilizers of the DNA B-conformation.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 82
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Tetrapeptides with proline in position 2, asparagine or leucine in position 3, and glycine in positions 1 and 4, with end groups free or blocked on the N-terminal side, were studied in their various ionic states in 2H2O and in Me2SO-d6 by 1H- and 13C-nmr. In order to clarify or refine some details, successive substitutions of the residues in these peptides with amino acids enriched to 85% in 13C, or to 85% 13C plus 97% 2H were carried out. The 1H and 13C chemical shifts as well as the 1H-1H, 13C-13C, and 13C-1H coupling constants and the signal intensities show strong similarity of behavior between the tetrapeptides of asparagine and leucine. The main conformational characteristics are (1) the almost total stabilization of the trans conformer in the type I β-turn structure when the peptide is in the zwitterion state dissolved in Me2SO. This is deduced from the 3JC3αH-N3H and the 3JC2′-H3α coupling constants, which both furnish a dihedral angle of φ3 = -90°, and from the positive value of the temperature coefficient of the glycine-4 amide protons, which suggests a type 4 → 1 hydrogen bond; (2) the evolution of cis and trans isomer fractions which change with the ionic state of the peptides in Me2SO, whereas they remain constant in aqueous solution; and (3) the conformation of the pyrrolidine ring as it follows the variations in cis:trans isomer populations together with the side-chain rotamer fractions of the residue in position 3. In the β-turn conformation the isomer cis is less abundant and the pyrrolidine ring is more flexible; this explains the perfect accommodation of the proline residue in position 2 of a bend. The interdependence of these phenomena where interactive forces play a predominant role underlines the importance of cooperative effects in the molecule. The results also suggest that the cis isomer of proline can adapt itself just as well as the trans isomer to position 2 of a type I β-turn.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 83
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An algorithm is presented for the Monte Carlo simulation of the decay of fluorescence polarization from segmentally flexible molecules. Based on the random walk model of Brownian motion, the treatment explicitly follows the stochastic changes in the diffusion coefficients as the molecule bends. It includes the effects of a linear restoring force opposing the bending and the effects of hydrodynamic coupling between the translational, rotational, and bending motions. One application is presented: the simulation of anisotropy decay curves for hinged rods. A variety of decay curves are obtained, including single- and multiexponential behavior, and the following conclusions are reached: (1) increasing the flexibility is usually, but not always, accompanied by a more rapid rate of depolarization; (2) reducing the size of the fluorescent subunit will usually, but not always, increase the rate of depolarization; and (3) the complex interplay between the effects of molecular shape, relative sizes of the subunits, restoring force, and orientation of the transition dipoles renders it unlikely that any simple method can be used to interpret anisotrophy data without simulation. In particular, it is not possible to determine the extent of bending by fitting the data with the two-exponential approximation used by some investigators in the past.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 84
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 977-990 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 13C-nmr spectra of red seaweed galactans, belonging to the agar and carrageenan groups or having the “intermediate” type of structure, were interpreted on the basis of 13C-nmr spectra of model compounds. Signal assignments have been made for most of the known extreme structures of such galactans. 13C-nmr spectroscopy was shown to be a rapid and convenient method of structural analysis, which permits one to determine the type of galactan structure, the absolute configurations of its constituents (galactose and 3,6-anhydrogalactose), and the positions of the sulfate and O-methyl groups in a polysaccharide molecule.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 85
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 931-944 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The dielectric response of human umbilical cord hyaluronic acid in various environments has been studied at microwave frquencies using a resonant microwave cavity as a probe. Both the real and imaginary parts of complex dielectric constant and the loss tangent for hyaluronate solutions are obtained by utilizing equations for perturbation of a resonant cavity. Dielectric changes at room temperature have been observed in aqueous solutions of hyaluronic acid as a function of concentration ranging from 0 to 350 mg/ml. The data indicate the existence of ordered phases in hyaluronate solutions at selective concentrations, that is, exhibiting lyotropic-type transitions. Hyaluronate solutions at 1.5 and 3 mg/ml concentrations have been studied at various pH in the range of 6-8 and at constant ionic strength 0.1. A temperature-dependent transition in hyaluronate solution of 120 mg/ml concentration has been observed at physiological temperature. It is shown that this temperature-dependent behavior can be related to the orientational polarizability term in the Debye theory of polar molecules in liquids.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 86
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 945-964 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In 1974, Zimm described a theory which predicts that the sedimentation coefficient of high-molecular-weight DNA will decrease as the rotor speed of measurement increases. In 1979, this theory was revised, and the new formula predicts speed-dependence effects that are substantially smaller than the predictions of the original version. This report describes the results of subjecting both the original and the revised versions of the theory to quantitative tests using a well-defined sucrose-gradient system and a DNA of known molecular weight (T4c DNA). T4c bacteriophage is a mutant, whose DNA contains the unmodified base cytosine, instead of the glucosylated hydroxymethylcytosine characteristic of the T-even bacteriophages, and has a molecular weight of 115 ± 3 × 106. The DNA of the wild-type phage (T4D+) was also used in some experiments.In addition to the quantitative tests, the experiments test for an effect first observed by Rubenstein and Leighton, which showed that the sedimentation coefficient measured for T2 DNA depended on the composition of the centrifuge tube used for the measurement (tube composition effect). It can be inferred from this observation that an interaction occurs between particle and tube wall during sedimentation, and this leads to a reduction in sedimentation velocity independent of the reduction in S described by Zimm's theory.The results show that in the range of 25,000-50,000 rpm, the original but theoretically incorrect form of the theory quite accurately describes the sedimentation behavior of both T4c and T4D+ DNA, although T4D+ was a special case in some respects. The revised (corrected) form of the theory predicts much less of a speed-dependence effect than that actually observed. The discrepancy between corrected theory and observation suggests that other factors (perhaps arising from the use of the swinging bucket rotor geometry) are causing the additional observed reduction in S20,w. However, the experiments show that the tube composition effect does not seem to be one of these.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 87
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1299-1309 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The fixation of cis (NH3)2Cl2Pt(II) to poly(I)·poly(C) leads to the formation of two complexed species. One involves coordination to a single base (accounting for about 70% of the total platinum bound over the rb range 0.07-0.25) and the other to two bases which are not adjacent to each other but may be on the same strand and separated by a loop. Reaction of the platinum compound with poly(I) gives in addition to the above two species a minor one (about 15%, independent of rb over the range 0.05-0.30) in which the platinum is bound to two adjacent bases. The availability of such coordination reduces the dominance of the 1:1 species, which, however, remains the major one (ca. 55%).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 88
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1329-1344 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The complex of CH3Hg(II) with the accessible cysteines of glyceraldehyde-3-phosphate dehydrogenase (GAPD, EC 1.2.1.12) from rabbit muscle has been studied by phosphorescence and optically detected magnetic resonance (ODMR) spectroscopy. The wavelength dependence of the phosphorescence decay kinetics has also been measured. Comparison of CH3Hg(II)-GAPD with GAPD by these methods shows that a specific optically resolved tryptophan site of GAPD is perturbed by the interaction with a nearby mercury atom. The perturbation on the luminescence and ODMR properties is typical of an external heavy-atom effect. Based on the x-ray diffraction structure of the lobster enzyme, it is proposed that the heavy-atom effect results from the interaction of tryptophan-310 with CH3Hg(II) bound to cysteine-281 in the rabbit muscle enzyme.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 89
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1415-1434 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The energy of interaction of a spermine molecule with the A- and B-forms of DNA has been calculated, assuming that the molecule of spermine is fixed in the narrow groove of the DNA helix with the formation of hydrogen bonds between the amino groups of spermine and the phosphate groups of DNA. The atom-atom potentials method was used. Optimal structures for the A-DNA-spermine and B-DNA-spermine complexes are suggested. It is shown that, in agreement with the experimental data, the interaction of the spermine molecule with the A-DNA is energetically more favorable than that with the B-DNA. Two main factors are responsible for this: (1) the distance between neighboring phosphates of the chain in A-DNA (which is about 1 Å less than that in B-DNA) corresponds better to the distance between the amino groups of the propyl part of spermine; and (2) the orientation of phosphate groups in A-DNA inside the groove is preferable for complex formation with spermine to the outside groove arrangement of the phosphates in B-DNA. These conclusions are further confirmed by the calculations for DNA-propane diamine complexes.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 90
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1517-1534 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The crystal structure of a synthetic analog of valinomycin, cyclo[-(D-Ile-Lac-Ile-D-Hyi)3-] (C60H102N6O18), has been determined by x-ray diffraction procedures. The crystals are orthorhombic, space group P212121, with cell parameters a = 11.516, b = 15.705, c = 39.310 Å, and Z = 4. The atomic coordinates for the C, N, O atoms were refined in the anisotropic thermal motion approximation and for the H atoms in the isotropic approximation. Values of standard (R) and weighted (Rw) reliability factors after refinement are 0.073 and 0.056, respectively. The structure is completely asymmetric. The cyclic molecular backbone is stabilized by six intramolecular hydrogen bonds N—H…O=C, five bonds being of the 4→1 type and one being of the 5→1 type. The side chains are located on the molecular periphery. The conformational state of isoleucinomycin in the crystal is intermediate between the corresponding crystalline states of valinomycin and meso-valinomycin. The observed conformation suggests that complexation could proceed via entry of the ion at the face possessing the L-Lac residues, the less crowded face.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 91
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1555-1566 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Possible conformations of lacto-N-tetraose, lacto-N-neotetraose, related disaccharides, and other milk oligosaccharides have been studied by an energy-minimization procedure using empirical potential functions. Lacto-N-tetraose favors a “curved” conformation, while lacto-N-neotetraose favors an approximately “straight” conformation. These two conformations differ mainly in the position of the terminal galactose residue with respect to the rest of the molecule. This difference explains the greater strength of lacto-N-neotetraose compared with lacto-N-tetraose in its ability to inhibit the cross-reaction of blood group P1 fractions with Type XIV pneumococcal antipolysaccharide. Although the favored conformation of lacto-N-tetraose (inactive) agrees with the model proposed by the earlier workers, that for lacto-N-neotetraose (active) differs. The favored conformations for the disaccharides galactose-β(1-4)-N-acetylglucosamine, galactose-β(1-3)-N-acetylglucosamine, and lactose are similar in overall shape, differing only in the nature and orientation of the side groups. This explains their nearly equal inhibitory activity. These theoretical models also explain the increased activity of lacto-N-fucopentaose I over that of lacto-N-tetraose and the relative activities of the substituted lactoses. The present studies suggest that it is the overall shape of the molecule which is important for activity, rather than the terminal β(1-4)-linked galactose residue alone.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 92
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1571-1585 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 13C spin-lattice relaxation times of poly(L-lysine) have been obtained at 67.9 MHz in aqueous solution and in a mixed solvent (40% methanol/60% water). A concomitant determination of the conformation by CD permits the correlation of conformation and rotational diffusion of the polymer. The dependence on pH of the spin-lattice relaxation times of the 13Cα and the side-chain carbon resonances reflects the diffusional motion in the random-coil conformation, in the helix-coil transition, and in the conformation of the α-helix. In the mixed solvent the reorientational correlation time of the Cα-Hα vector increases from τ = 0.37 nsec (random coil) to τ = 12.0 nsec (α-helix). In aqueous solution the correlation time of this vector increases from τ = 0.33 nsec (random coil) to τ ≫ 11 nsec. The reorientation rates of the side-chain methylene groups in the two solvents are markedly different. The reorientation of all methylene groups is reduced in the mixed solvent.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 93
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The solid-state conformation of copolymers of β-benzyl-L-aspartate [L-Asp(OBzl)] with L-leucine (L-Leu), L-alanine (L-Ala), L-valine (L-Val), γ-benzyl-L-glutamate [L-Glu(OBzl)], or ∊-carbobenzoxy-L-lysine (Cbz-L-Lys) has been studied by ir spectroscopy and circular dichroism (CD). The ir spectra in the region of the amide I and II bands and in the region of 700-250 cm-1 have been determined. The results from the ir studies are in good agreement with data obtained by CD experiments. Incorporation of the amino acid residues mentioned above into poly[L-Asp(OBzl)] induces a change from the left-handed into the right-handed α-helix. This conformational change for the poly[L-Asp(OBzl)] copolymers was observed in the following composition ranges: L-Leu, 0-15 mol %; L-Ala, 0-32 mol %; L-Val, 0-8 mol %; L-Glu(OBzl), 3-10 mol %; and Cbz-L-Lys, 0-9 mol %.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 94
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1667-1673 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Dry purified ligamentum nuchae elastin has been investigated for physical aging. The samples were quenched from a temperature (197°C) close to the softening point to a number of measuring temperatures ranging from -20 to +180°C. At each temperature, the small-strain torsional creep properties were determined at a number of elapsed intervals after the quench. Aging effects were found over the whole temperature range, and the creep and aging behavior of elastin turned out to be very similar to that of synthetic polymers.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 95
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 96
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1705-1713 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Covalently closed circular DNA can exist in different configurations known as circular, toroidal, and interwound. Changes among these forms can be made in several ways, including the insertion of dye molecules between adjacent base pairs, which tends to untwist the double-helical structure. The aim of this paper is to discuss these configurations, and the changes among them, in the context of classical elastomechanics. The concepts of twisting, linkage and writhing are explained. Simple experiments on a twisted linear-elastic rod are described, and it is shown that although the circular and interwound forms may be modeled in this way, the toroidal form does not occur, being mechanically unstable. Theoretical energy calculations by Levitt on bent and twisted DNA show that DNA exhibits a particular kind of nonlinear elasticity in which there is an unusual coupling between bending and twisting. The aim of the paper is to show qualitatively that this special kind of elasticity can stabilize the toroidal form of closed circular DNA.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 97
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1357-1374 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Light-scattering, viscosity, and sedimentation experiments on aqueous solutions of k-carrageenan show that this sulfated polygalactose is an expanded flexible random coil. This expansion is due to long-range interactions that are predominantly electrostatic. Extrapolation of viscosity data to infinite ionic strength provided values for the intrinsic viscosity which were subjected to the Stockmayer-Fixman analysis, giving a value for the Mark-Houwink coefficient under theta-conditions, Kθ, of 0.27. The characteristic ratio, C∞, under these conditions is 7.8, and the conformation factor σ is 2. In a solution of 0.118 ionic strength, where a Mark-Houwink exponent aη of 0.86 is found, the radii of gyration calculated from viscosity data are lower than those found from the angular dependence of scattered light. On the other hand, the radius of gyration found from the sedimentation rate agrees well with the light-scattering radius. The relations between molecular parameters are corrected for the poly-dispersity of the sample.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 98
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1407-1414 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 99
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 100
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1475-1489 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An approximate analytic expression for the translational friction coefficient of a toroid modeled as a continuous shell of frictional elements is derived using the Kirkwood approximation. The accuracy of this expression was determined by comparing the friction coefficients predicted by it to those predicted by extrapolated shell-model calculations using the modified Oseen tensor. To show that these calculations do indeed yield the correct friction coefficients, actual translational friction coefficients were determined by observing settling rates of macroscopic model rings or toroids in a high-viscosity silicone fluid. Our conclusion is that the approximate expression yields friction coefficients that are about 1.5-3% low for finite rings. For thin rings, a comparison is also made with the exact result of Yamakawa and Yamaki [J. Chem. Phys. 57, 1572 (1972); 58, 2049 (1973)] for the translational friction of plane polygonal rings. This comparison shows that the approximate expression yields results which are low by 2-3% unless the rings are extremely thin, in which case the error is larger. In the limit of an infinitely thin ring the approximate expression reduces to the Kirkwood result [J. Polym. Sci. 12, 1 (1954)], which is low by 8.3%. We discuss briefly how this work may be useful in determining the structure of DNA compacted by various solvent-electrolyte systems and polyamines.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...