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  • 1980-1984  (3,128)
  • 1975-1979  (2,754)
  • 1981  (3,128)
  • 1976  (2,754)
  • Polymer and Materials Science  (5,675)
  • Electron microscopy  (207)
  • Nuclear reactions
Material
Years
  • 1980-1984  (3,128)
  • 1975-1979  (2,754)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Rheumatology international 1 (1981), S. 21-28 
    ISSN: 1437-160X
    Keywords: Rheumatoid nodules ; Polymorphonuclear granulocytes ; Electron microscopy ; Collagen degradation products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Necrotic areas of rheumatoid nodules were investigated electron microscopically. PMNs in different stages of disintegration were present in all cases. Granular material, sometimes in a fiberlike orientation, and small fibrils without periodicity were detected between the collagenous fibers. It is assumed that granular material and fibrillar remnants represent degraded collagen. Often these degradation products were present in the neighborhood of disintegrating PMNs. From this morphological relationship it is concluded that enzymes of PMNs may in part be responsible for the fibrinoid necrosis in rheumatoid nodules.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0711
    Keywords: Ovary ; FSH ; Inhibin ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of a highly purified preparation of human follicular fluid inhibin (hFF-Inhibin) on the ovary of immature rats have been studied. The highly purified preparation was obtained by gel and ion-exchange chromatography and ultrafiltration of the acetone dried extract of human follicular fluid. Administration of 5, 10, or 20 μg of inhibin daily for 10 days starting from day 11 postnatum resulted in (1) a significant reduction of basal FSH levels by the 20 μg dose but not by lower doses, (2) atresia of preantral and antral follicles in an apparently dose-related manner, (3) hyperplasia of the theca interna, and (4) degeneration of the granulosa cells, maximum damage being in the group treated with 20 μg. In inhibin-induced atretic follicles there were no signs of (a) granulosa cell-luteinisation, (b) connective tissue invasion, (c) hyalinisation of the basement membrane, or (d) vascularisation. Simultaneous administration of human menopausal gonadotrophin (hMG) led to luteinisation of the atretic follicles. However, the other structural alterations mentioned above (b-d), and those of the theca cells could not be overcome by hMG. In addition, there was no significant difference in the ovarian weight of animals treated with hMG when compared to those treated with inhibin and hMG, but the serum levels of the oestradiol in the latter were significantly lower. Our results suggest that hFF-inhibin acts not only at the pituitary, but also at the ovarian level.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2307
    Keywords: Liver biopsy ; Renal transplant recipients ; HBs and HBc Ag ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A prospective series of 45 liver biopsies taken from 22 renal transplant patients was investigated for the presence of hepatitis B antigen core (HBc) and surface (HBs) components by electron microscopy. At the time of each biopsy serum HBs Ag was sought by radioimmunoassay. Sections were taken for the detection of HBs Ag by immunofluorescence. In seropositive patients, intravesicular tubular structures resembling HBs Ag were found in 61% of biopsies while the intranuclear core HBc was present in 69%. No correlation could be made between the ultrastructural pattern of the viral components and the intensity of the histological liver damage. During the follow up, there was an accumulation of both HBs and HBc Ag even in a period as short as 1 year. The 9 liver specimens examined after three years of transplantation showed a marked accumulation of both antigens. Thus the expression of HB Ag at the hepatocellular level seems to correlate better with the duration of antigenaemia than with the histological pattern. Lastly, on matched semithin and ultrathin sections, the ground glass appearance of cytoplasm appeared to correlate with smooth endoplasmic reticulum distorsion, irrespective of the simultaneous presence or absence of intravesicular tubular structures. The sanded nuclei expressed a rare massive accumulation of core antigen.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 391 (1981), S. 165-175 
    ISSN: 1432-2307
    Keywords: Dermatofibrosarcoma protuberans ; Tissue culture ; Electron microscopy ; Fibroblasts ; Fibrosarcoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dermatofibrosarcoma protuberans has been considered to be of fibrohistiocytic or fibroblastic origin. The purpose of this paper is to identify the original cell strain from which this neoplasm derives, using tissue culture and electron microscopic methods. Thirteen cases of DFSP characterised by clinical, topographical, histological and behavioral criteria were explanted. The emigrating cells were bipolar with two opposed processed and showed a radial arrangement in respect to the expiants. After the second week the distal processes tended to curve back towards the cell body forming flame-like structures. This cell morphology and cellular orientation persisted during the whole life of the culture. Electron microscopy was performed in three cases; the newly grown cells maintained an electron microscopic picture similar to that found in the original tumors. This pattern of behaviour is characteristic of fibroblastic tumors and has been found in explants of normal fibroblasts, of fibromatosis and of fibrosarcomas used as controls. On this basis, we believe that DFSP is a fibrosarcoma of the skin of low grade malignancy.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 390 (1981), S. 11-21 
    ISSN: 1432-2307
    Keywords: Electron microscopy ; Bladder neoplasms ; Measurement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of urothelium from 4 patients with no evidence of tumour was compared with that taken from 22 patients with bladder neoplasms of different grade and stage. Two features were quantified: the percentage of reduplication of the basal lamina and the percentage of discontinuous basal lamina. Tumours showed a lower percentage of reduplicated basal laminae than normal tissues, the difference being significant in 3 out of 4 types of tumours. The difference in frequency between normal tissues and non-recurring tumours was not significant, but there was a significant difference between normals and recurring tumours. All types of tumours showed discontinuities in the basal lamina, including 80% of those staged non-invasive by light microscopy. None of the normal tissues showed these. The percentage of discontinuities seen in non-recurrent tumours was half that seen in recurrent ones, but both groups were significantly higher than normals. Loss of continuity of the basement membrane distinguishes invasive from non-invasive tumours. However, there is a high probability of these being missed by light microscopy alone. Therefore, electron microscopic studies on recurrent bladder tumours would increase the accuracy of staging and prognosis.
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  • 6
    ISSN: 1432-2307
    Keywords: Microfold (membraneous) cells ; Tuft cells ; Electron microscopy ; Horseradish peroxidase ; Sequential uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 79 NMRI mice and Wistar rats were used for ultrastructural investigations of the sequential uptake of horseradish peroxidase (HRP) by M cells. In addition the ultrastructure of the so-called tuft-cells was reported. HRP, a foreign protein antigen, was applied either by injection (Owen 1977), or by stomach tube. After variable exposure times (5 min to 3 h) segments of the distal small intestine, containing Peyer's patches, mesenteric lymph nodes and liver tissue were removed. After fixation, they were reacted with H2O2-3,3′-diaminobenzidine tetrachloride and were examined by light and electron microscopy for HRP reaction products. The uptake of HRP mainly occurs through the M cells in the dome epithelium of Peyer's patches with a continual transport of the antigenic material into lymphoid cells, macrophages, and dendritic reticulum cells. In the 3 h specimens a few single HRP-positive lymphoid cells can be observed within the efferent lymphatics of Peyer's patches. In addition, a continual uptake of HRP by necrobiotic enterocytes was observed. It has also been shown that after 3 h HRP is located inside the Kupffer cells of the liver. These findings also support the presumption that antigenic material can be transmitted via the portal circulation. However, definite, quantitatively and permanently recorded uptake of HRP by brush border cells was not be observed. To exclude a toxic effect of the applied HRP on the enterocytic epithelium additional resorptive-physiological investigations were performed using the in vivo-perfusion-recirculation method and in vitro-accumulation of L-phenylalanine.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 391 (1981), S. 107-115 
    ISSN: 1432-2307
    Keywords: Hemangioendothelioma ; Esophagus ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The histology and electron-microscopy of a malignant hemangioendothelioma of the esophagus wall appearing in a 42 year old male is presented. By light microscopy the tumor is composed of vessels and capillary-like structures of an anastomosing nature covered by atypical endothelial cells. These cells infiltrate the intersticial spaces growing into the posterior mediastinal area. Electron microscopy confirms the endothelial nature of the neoplastic cells, showing characteristics of the cell type, as is the presence of Weibel-Palade bodies, filaments and active pinocytosis. Hemangioendothelioma should be differentiated from other vascular tumors (angiosarcoma) as are hemangiopericytoma or hemangioblastoma, being composed exclusively of malignantly transformed endothelial cells.
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  • 8
    ISSN: 1432-2307
    Keywords: Crohn's disease ; Electron microscopy ; Ultracytochemistry ; Immunohistology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Immunohisto- and ultracytochemical studies were carried out on surgical and biopsy specimens from 27 patients suffering from Crohn's disease of the ileum or colon. Control specimens were obtained from 16 patients with nonspecific proctitis or neoplastic disorders of the caecum or rectum. Our results suggest that the initial lesions in Crohn's disease are associated with a typical humoral immune response. In non-ulcerated mucosa a uniform increase of IgA-, IgG- and IgM-cells was found (numbers of IgA-cells: IgG-cells ∼14.4), whereas disproportional increases of IgG- and IgE-cells were observed in ulcerated mucosa (IgA:IgG ∼0.7). The IgE-cell multiplication in ulcerated areas suggests the possibility of local hypersensitivity reactions. Macrophages and granulocytes contained IgG, which was also demonstrated in multinucleated giant cells. The granulomas contained extracellular IgG, acid phosphatase and peroxidase. The finding of potentially harmful extracellular lysosomal enzymes may be of pathogenetic significance in view of the hypothesis of Weissmann (1964). Micro-ulcerations of the dome epithelium of hyperplastic Peyer's patches were seen by electron microscopy a finding which can be interpreted as an early lesion through which luminal antigens gain uncontrolled access to Peyer's patches. This could lead to (1.) overstimulation of the local immune system, (2.) disturbance of local immune homeostasis, (3.) imbalanced Ig-production with disproportional increases in IgG and IgE. We were not able to detect Clq or C3 bound to epithelial or vascular basement membranes, and no electron dense deposits were found. Viral particles or bacteria in any of the specimens were not demonstrated by electron microscopy. The type of immune response in Crohn's disease and its pathogenetic significance with remain unclear until more is known about the specificity of the locally produced antibodies.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 392 (1981), S. 135-145 
    ISSN: 1432-2307
    Keywords: Malignant fibrous histiocytoma ; Sarcoma ; Soft tissue neoplasms ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructural findings in 17 cases of malignant fibrous histiocytoma (MFH) are described. The tumors consisted of fibroblast-like cells and histiocyte-like cells in different proportions in different cases. Intermediate, undifferentiated, xanthomatous and multinucleated giant cells were also identified. In 12 of 17 cases myofibroblasts were evident. Acid phosphatase activity was detected cytochemically in the Golgi zone, endoplasmic reticulum and lysosomes (GERL) mainly within histiocyte-like cells, in three cases. These observations indicate that the GERL of the tumor cells are engaged in the formation of lysosomes. The polymorphic cellular composition, including undifferentiated cells, lends support to the concept that the MFH originates from a primitive multipotent undifferentiated mesenchymal cell.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 392 (1981), S. 231-239 
    ISSN: 1432-2307
    Keywords: Bronchial gland adenoma ; Oncocytoma ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Benign adenomas derived from the bronchial mucous glands are uncommon. Probably the least common variety is the oncocytomatous adenoma, this case being the second known example. The tumour was situated in the right main bronchus in a man aged 75. An oncocytomatous adenoma should be clearly distinguished from the common oncocytomatous change which affects the normal bronchial mucous gland cells seen in adults. The eosinophilic, columnar tumour cells seen by light microscopy contained numerous and prominent mitochondria by electron microscopy and granules of serous secretion. Other tumour cells contained microfilaments and were perhaps of myoepithelial origin. The true oncocytomatous mucous gland adenoma needs to be distinguished from an oncocytomatous bronchial carcinoid tumour the cells of which contain dense core granules of neurosecretory type. The bronchial oncocytomatous adenoma appears to be a benign tumour with a close similarity to its counterpart occuring in the salivary glands.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 394 (1981), S. 31-47 
    ISSN: 1432-2307
    Keywords: Blood vessel neoplasms ; Electron microscopy ; Histochemistry ; Angiosarcoma ; Breast neoplasms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A total of five haemangiosarcomata and two benign haemangiomas arising in the mammary gland have been studied electron microscopically and by histochemical techniques. Malignant tumors were mainly composed of endothelial cells reactive to alkaline phosphatase and adenosine triphosphatase, and of pericytes and undifferentiated mesenchymal elements. A juvenile haemangioma showed a more structured wall with an increase of endoplasmic reticulum and filaments, and a diminution of membrane modulations and rod-like tubular bodies. A cavernous haemangioma showed an ultrastructure very similar to normal vessels. The ultrastructural and histochemical data suggest a blood vessel origin of mammary angiosarcomas and show that vascular neoplasms of the breast, benign or malignant, are composed of a combined proliferation of the different cell types present in the vessel wall, as described in other organs.
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  • 12
    ISSN: 1432-2307
    Keywords: Labial salivary gland biopsy ; Gougerot-Sjögren's syndrome ; Clinico-pathology ; Histoenzymology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 119 cases of Sjögren's syndrome are described. Clinically, the female sex predominates (83% of cases); the average age is 56 years. Isolated sicca syndrome is noted in 31 % of cases; it is more often associated with rheumatoid polyarthritis (64%) or with another collagen disease (5%). In addition, in 5 patients, we have found a malignant lymphoproliferative disease in an accessory or a main salivary gland (4 non-Hodgkin malignant lymphomas, 1 chronic lymphoid leukaemia). In all cases, a biopsy from accessory labial glands or from a main salivary gland, corroborates the diagnosis. Histologically, epi-myoepithelial islets are always lacking in accessory glands. We classified labial gland injuries in three groups based on striated duct distention: first, some tubular ectasia with interstitial lymphoid cells; second, much ectasia associated with many lymphoid cells and the beginning of pericanalar sclerosis; third, intensive ectasia, scarce lymphocytes, severe peri- and intralobular sclerosis and extensive destruction of acini. This grading is positively correlated with that of parotid biopsies and also with abnormalies on numerous parotid sialographic radiograms performed simultaneously. The histoenzymological study demonstrates decreased activity of oxydative enzymes in striated duct epithelia and of ATPases in myoepithelial cells. The ultrastructural study confirms these findings. Even at an early stage of the disease, tubular alterations are observed: epithelial cell degeneration (vacuolated mitochondria, loss of cytoplasmic lateral membrane foldings) and myoepithelial cell damage (in particular disappearance of myofilaments). These findings explain tubular ectasia by the loss of contractile function. Simultaneously, intensive regeneration from the intercalated ducts by young “totipotent” cells, sometimes differentiating into epidermoid, secretory or myoepithelial cells, are observed. Lesions in acinar cells are less marked: conglomeration of secretory granules, some autophagosomes and rarely true necrosis. In the interstitial tissue, amongst lymphocytes, plasmocytes and mastocytes, numerous myoepithelial cells are present: young pseudo-fibroblastic cells with poor ergastoplasm and some myoid organelles (a few myofilaments, dark zones and endocytosis vacuoles on cell membrane; degenerated myoepithelial cells whose scanty dark cytoplasm is filled with lipid droplets). Thus, by analogy with the myoepithelial islets observed in parotid biopsies, the myoepithelial cell damage seems to have a specific signification in Sjögren's disease. Regeneration from the intercalated ducts fails to repair these cells and to restore their physiological contractile function. Furthermore, this leads to extratubular migration of young myoid cells which are responsible for progressive accumulation in the interstitial tissue of membranoid material and later collagen sclerosis.
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  • 13
    ISSN: 1434-0879
    Keywords: Dog prostate ; Stereological analysis ; Electron microscopy ; Oestrogen effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The stromal tissue of the prostate in normal castrated dogs and castrated and oestrogen treated dogs were studied by quantitative morphological methods. Quantitative morphological (=stereological) procedures provide values of volume, surface and number of tissue and cell components. The stereological data show an activation of the smooth muscle cell of the stromal tissue in the oestrogen treated dog compared with the control group; related to the unit volume of smooth muscle cell cytoplasm, a threefold increase of the endoplasmic reticulum was observed in castrated and oestrogen treated dogs.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Research in experimental medicine 178 (1981), S. 165-175 
    ISSN: 1433-8580
    Keywords: Perfused rat pancreas ; Insulin secretion ; Uric acid ; Light microscopy ; Electron microscopy ; Rattenpankreasperfusion ; Insulinsekretion ; Harnsäure ; Lichtmikroskopie ; Elektronenmikroskopie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es ist bekannt, daß die Methylxanthine Coffein und Theophyllin die Insulinsekretion positiv beeinflussen. Im Rahmen von Perfusionsversuchen sollte untersucht werden, ob die Inselzellfunktion auch dem Einfluß der chemisch eng verwandten Harnsäure unterliegt. Zugleich sollte eine Destruktion von Inselzellstrukturen durch Harnsäure ausgeschlossen werden, da die chemisch ähnlich configurierte Substanz Alloxan bekanntlich Inselzellnekrosen verursacht. Dazu wurden isolierte Rattenbauchspeicheldrüsen mit Glukosekonzentrationen von 100 mg/100 ml und 300 mg/100 ml stimuliert. In einem Teil der Fälle wurde dem Perfusat Harnsäure in der Konzentration von 12 mg/100 ml zugegeben. Es zeigte sich, daß Harnsäure die Insulinsekretion bei Stimulation mit Glukose in der Konzentration von 100 mg/100 ml nicht beeinflußt. Werden die B-Zellen jedoch mit einer Glukosekonzentration von 300 mg/100 ml stimuliert, so steigert Harnsäure die Hormonfreisetzung im Sinne eines glukosepotenzierenden Effektes um mehr als 100%. Anhand charakteristischer Sekretionsphänomene sowie lichtoptischer und elektronenmikroskopischer Untersuchungen konnte nachgewiesen werden, daß es sich hierbei um eine echte Mehrsekretion handelt und nicht etwa um einen Auslaufeffekt als Folge einer Destruktion von Inselzellstrukturen durch eine alloxanähnliche Wirkung der Harnsäure.
    Notes: Summary Methylxanthines, such as caffeine and theophylline, show effects increasing the secretion of insulin. Perfusion experiments were intended to find out whether insulin secretion is even influenced by uric acid, which is chemically closely related. Besides, it was to be demonstrated that uric acid causes no damages to islet cell structures for it is well established that alloxan, which is chemically related to uric acid, produces necroses in B cells. Isolated rat pancreata were stimulated by glucose at concentrations of 100 mg/100 ml and 300 mg/100 ml. In part of the experiments uric acid was added to the perfusion medium at a concentration of 12 mg/100 ml. We found that uric acid has no influence on insulin secretion if it is stimulated by glucose at a concentration of 100 mg/100 ml. However, if B cells are stimulated by glucose at a concentration of 300 mg/100 ml insulin secretion is enhanced by the addition of uric acid by more than 100%. This indicates that this substance exhibits a glucose-potentiating effect. The characteristic dynamics of insulin secretion demonstrate together with light- and electron-microscopic investigations that uric acid causes a real additional secretion and no leaking of intracellular insulin as a result of destruction of islet cell structures by an effect of uric acid similar to that of alloxan.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 54 (1981), S. 203-210 
    ISSN: 1432-0533
    Keywords: Retina ; Schwann cell ; Myelinated nerve fibers ; Nodes of Ranvier ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Myelination of axons in the nerve fiber layer (NFL) of the retina occurs as a sporadic abnormality in several mammalian species including man, monkey, cat and rat. All of these species have vascularized retinae and, in the latter three, ultrastructural studies have demonstrated the pattern of medullation to be similar to Schwann cell myelination in the peripheral nervous system. This contrasts with an oligodendrocytic pattern of myelination normally present in the avascular retina of the rabbit. One possible explanation for this difference is that the pattern of myelination is related to the presence or absence of retinal blood vessels. The present investigation provides the first evidence of NFL myelination in another avascular retina, that of the guinea pig. Myelination in the guinea pig retina was observed in a single bundle of axons and involved only large diameter fibers. With several axons, myelin sheaths terminated at hemi-nodes of Ranvier and in all such cases this occurred in association with marked paranodal infolding. Morphological characteristics of the myelination include (1) a one to one relationship between axon and myelinating cell, (2) cytoplasm between myelin sheath and plasma membrane, (3) basal lamina surrounding the myelinating cell, (4) collagen fibers in the adjacent extracellular space and (5) double intraperiod lines. These morphological features are characteristic of peripheral nerve myelination by Schwann cells. Thus, in all species so far described in which retinal medullation is abnormally present, the pattern of myelination has been Schwann cell in nature rather than oligodendrocytic. The reasons for this Schwann cell predominance remain undefined.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 54 (1981), S. 233-237 
    ISSN: 1432-0533
    Keywords: Methylmercury ; Mice ; Golgi methods ; Electron microscopy ; Dendrites ; Purkinje cells ; Perivascular glia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neonatal C57BL/6J mice were injected with 5 mg/kg body weight of203Hg-labeled methylmercuric chloride on postnatal days 3, 4, and 5, totaling 15 mg/kg body weight per animal. The experimental and control animals were sacrificed on postnatal day 15. Whole body radioactivity of203Hg progressively increased during the 3-day injection period and reached the peak level and remained at peak levels until the time of sacrifice. This indicates a lack of clearance of203Hg by neonatal mice during the period examined in this study. Golgi preparations of cerebella of MeHg-treated animals revealed significant reduction in dendritic arborization of Purkinje cells. Ultrastructurally, the vascular endothelium showed attenuation with increased electron density and frequent vacuolization of cytoplasm. Marked swelling of perivascular glia was noted in most of the capillaries throughout the cerebella of MeHg-treated animals.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 55 (1981), S. 77-80 
    ISSN: 1432-0533
    Keywords: Esthesioneuroepithelioma ; Olfactory neuroblastoma ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A rare case of esthesioneuroepithelioma infiltrating the right frontal lobe is reported in a 41-year-old man. This tumor composed of compact lobules with tubular arrangements, ultrastructurally showed two different cell types, both devoid of neurosecretory granules and reminiscent of neurons and sustentacular cells of the olfactory epithelium. These features are distinguished from those generally observed in olfactory neuroblastomas.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 55 (1981), S. 89-95 
    ISSN: 1432-0533
    Keywords: Electron microscopy ; Morphometry ; Sorbitol pathway ; Diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Galactose neuropathy is characterized by progressive endoneurial edema manifested by a gradual increase in endoneurial fluid pressure. Edema accumulates via a unique mechanism of osmotic force generated by products of the polyol pathway, synthesized within the endoneurial compartment. This paper presents morphologic findings showing firstly, that blood nerve barrier permeability to horseradish peroxidase complexes appears unchanged and secondly, peripheral nerve edema in this condition is restricted to extraganglionic endoneurium sparing the spinal ganglia and adjacent roots. Thirdly, mast cells accumulated in significant numbers and electron microscopy revealed degranulation. There was no evidence of edema in Schwann cell cytoplasm, the putative site of galactitol accumulation via the sorbitol pathway. These findings are discussed with respect to diabetic neuropathy for which galactose intoxication is a useful experimental model.
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  • 19
    ISSN: 1432-0533
    Keywords: Postischemic recirculation ; Complete cerebral ischemia ; Ischemic neuronal injury ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The neuronal response to complete cerebral ischemia (CCI) of 5–15 min duration was evaluated at the light and electron microscopic level subsequent to postischemic recirculation periods of up to 60 min. Following postischemic reperfusion, the homogeneous neuronal changes characteristic of permanent CCI were modified into a heterogeneous pattern of selectively vulnerable neuronal responses. Four basic types of neuronal injury were represented within this heterogeneous neuronal population. The Type I neuronal response was most numerous and consisted of chromatin clumping, nucleolar condensation and a breakdown of polysomes. This response may represent a reversal of some of the neuronal changes observed after permanent CCI. In addition to the above changes, Type II neurons contained swollen mitochondria and Golgi saccules which appeared as microvacuoles under the light microscope. Type III neurons displayed varying degrees of neuronal shrinkage and numerous swollen mitochondria. Type IV neurons were markedly shrunken and electron-dense with few identifiable subcellular structures. The distribution of Type I neurons was random but the other neuronal responses occurred in “selectively vulnerable” brain regions. The number of Type II, III, and IV neurons increased with extended insult durations but were unaffected by the length of recirculation. Ten minutes of CCI represented the threshold for a significant increase in the number of severely altered neurons. These findings suggest that considerable neuronal injury may be present after 10–15 min of CCI, and the lack of a recirculation period following CCI appears to afford the brain parenchyma an extensive degree of structural protection.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 53 (1981), S. 65-74 
    ISSN: 1432-0533
    Keywords: Hexachlorophene ; Central nervous system ; Mice ; Baboons ; Electron microscopy ; Neurotoxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A study on hexachlorophene encephalopathy in mice and baboons is reported. By light microscopy, a severe spongiform lesion of the central nervous system (CNS) was localized in the white matter, without myelin breakdown or cellular reaction. By electron microscopy, the myelin alteration was characterized by wide intralamellar spaces or “splitting” developed in the intraperiod line of compact sheaths. The acute changes described were induced by administration of the drug by the digestive or cutancous routes at various dosage levels in an aqueous solution or in talcum powder. The toxic effects depended on the age of the animals, the survival times and the concentrations of hexachlorophene, i.e., 6%, 3%, and 0.5%. The findings are compared with previous reports on the neurotoxicity of hexachlorophene and other chemicals in humans and experimental animals. Hexachlorophene cannot be recommended for use in young infants because of its neurotoxicity in very low doses as demonstrated in the present report.
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  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 53 (1981), S. 165-168 
    ISSN: 1432-0533
    Keywords: Lewy body ; Neurofibrillary tangle ; Locus ceruleus ; Aged brain ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The presence of Lewy body and neurofibrillary tangle in the locus ceruleus neurons of aged brain is described. Ultrastructural study revealed that in some Lewy bodies the presence of “twisted tubules” or “paired helical filaments” amongst the filaments of the Lewy body. A quantitative analysis of serial sections of locus ceruleus from aged brain, incidences of the Lewy body and neurofibrillary change were 0.07% (9/11,515) and 6.6% (15/11,515), respectively. The incidence of neurons containing both structures was 0.008% (1/11,515).
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  • 22
    Electronic Resource
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    Springer
    Acta neuropathologica 54 (1981), S. 43-53 
    ISSN: 1432-0533
    Keywords: Uremia ; Kidney transplantation ; Polyneuropathy ; Light microscopy ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eighteen patients, ten with clinical uremia and eight with functioning kidney transplants, were studied clinically for neuropathy and were subsequently subjected to a sural nerve biopsy. The biopsy specimens were studied using light and electron microscopic and morphometric methods. The clinical polyneuropathy was qualitatively and quantitatively most severe in the hemodialysis group. These results conformed with the light and electron microscopic observations. Clinical, morphological and morphometric indications of recovery from uremic neuropathy were observed in the transplant recipients. The pathophysiology of uremic peripheral neuropathy was marked axonal degeneration. Pathologic Schwann cells were also frequently found. Axonal degeneration and Schwann cell damage seemed to exist independently of each other. In morphometric analysis, axonal atrophy and abnormal myelin sheath thickness were observed in all patient groups. A close relationship was found between axonal atrophy and low conduction velocity. Unexpectedly low nerve conduction velocities were also observed, which cannot be explained by either loss of nerve fibers or demyelination. The findings of damaged endoneural blood capillaries supported the ischemic theory as one mechanism in the pathogenesis of uremic neuropathy.
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  • 23
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    Anatomy and embryology 161 (1981), S. 433-451 
    ISSN: 1432-0568
    Keywords: Rhombencephalon, rat ; Subependymal cysts ; Morphogenesis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A bilaterally symmetrical cystic cavity is situated in the subependymal neuropil of the rostral rhombencephalon of the rat during the perinatal period of ontogeny. These cysts are formed by the confluence of enlarged extracellular spaces in this region between E18 and E20. The cysts are present for about 2 weeks but disappear on about P15 without trace. They have a maximal volume of about 0.004 to 0.006 mm3 on P2, with a rostrocaudal extension of about 200 μm. Their shape is characterized by a medial convexity and a lateral concavity, and they have their maximal circumference at about the middle of the rostrocaudal axis. The caudal portion is juxtaposed to the subependyma, while the rostral part lies in the neuropil of the presumptive griseum centrale pontis. In the lumen and the wall of the cysts are found numerous macrophages, hlioblasts and some degenerating axons and dendrites. The significance of these cysts in the context of morphogenesis and the origin of the numerous macrophages within them are both unresolved.
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  • 24
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    Acta neuropathologica 53 (1981), S. 237-248 
    ISSN: 1432-0533
    Keywords: Thyroxine effect on muscle ; Histochemistry ; Immunopathology ; Electron microscopy ; Diagnostic muscle pathology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Proximal myopathy and different types of neuromuscular syndromes are frequently observed in hyperthyroid patients with complicated thyrotoxicosis. Conflicting reports on the changes seen in muscle biopsies range from no abnormalities to muscle necrosis with the fibers being replaced by connective tissue and fat. On the basis of 21 skeletal muscle biopsies from chronic thyrotoxic myopathic patients, coupled with studies in experimentally induced triiodothyronine myopathy in rats, the histological, histochemical, immunofluorescent, and electron-microscopic findings diagnostic for thyrotoxic myopathy are defined. These criteria include: clumping of nuclei, los of cross-striation, vacuolar degeneration, and fatty infiltration of endo- and perimysium, presence of giant mitochondria, increased number of mitochondria, disorganization of contractile elements, swelling of transverse tubules, presence of microtubular aggregations, and a significant increase of lipofuscin granules. Both muscle fiber types or in some cases selective type II fibers display atrophy with signs of reinnervation. These alterations are polyfocal and polyphasic and, therefore, polychronous and stereotyped rather than pathognomonic. However, they are related to the severity of thyrotoxic myopathy and the duration of disease. The results of muscle biopsies have a predictive value in determining the reversibility or irreversibility of pathologic changes with therapeutic consequences.
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  • 25
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    Acta neuropathologica 55 (1981), S. 143-149 
    ISSN: 1432-0533
    Keywords: Pineal parenchymal neoplasm ; Electron microscopy ; Primitive neuroectodermal cell ; Dense core vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The fine structure of two pineal parenchymal neoplasms has been described. The tumors contained a predominance of small, poorly differentiated cells with prominent nuclei and scanty cytoplasm. These cells were similar to those found in medulloblastomas, primitive cerebral neuroectodermal tumors, and fetal cerebellum and cerebrum. Some cells contained 9+0 cilia, dense core vesicles, and processes containing microtubules and numerous dense core and clear vesicles, suggesting neuronal differentiation. Astrocytic elements were also present. This study suggests that the predominant cells of these tumors are primitive neuroectodermal elements which have the potential to differentiate along several different lines.
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  • 26
    ISSN: 1432-0533
    Keywords: Immunochemistry ; Pituitary adenoma ; Electron microscopy ; Mixed eosinophilic-cromophobe ; Gonadotropin ; Thyrotropin-secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Twenty-nine pituitary adenomas were studied by histologic, electron-microscopic, and immunohistochemical techniques. By conventional histological stains, 19 cases were considered chromophobe, five cosinophilic, and five mixed chromophobe and eosinophilic adenomas. Immunohistochemistry, with specific antibodies against human GH, PRL, FSHβ, LHβ, and TSHβ showed, clearly, secreting and non-secreting groups of tumors: growth hormone-secreting adenomas (four cases), prolactin-secreting adenomas (eight cases), thyrotropin and/or gonadotropin-producing tumors (seven cases), and non-secreting adenomas (ten cases). Electron microscopy showed secretory granules of varying numbers, sizes, and shapes in all tumor cells in all 29 cases. The endoplasmic reticulum appeared markedly increased in 5/8 of the prolactin producing tumors; mitochondria also appeared markedly increased in 3/7 of the thyrotropin-gonadotropin group. These three cases could be considered “oncocytomas” by electron-microscopic criteria. Patients with prolactin-secreting adenomas had high serum prolactin and typical clinical symptoms associated with such tumors. One patient with large numbers of TSH-containing cells in her tumor and some cells with growth hormone and FSH had overt thyrotoxicosis. Although the remaining six tumors stained specifically for one hormone or another, no clinical correlation was possible. Conventional electron microscopy has some value in the generic identification of puritary tumor cells, but no value in the recognition of specific secretory products or specific cell types. Conventional histopathology is the least reliable method to correctly identify a specific type of pituitary adenoma, beyond the identification of the adenomatous changes. This study demonstrates the existence of gonadotropin- and/or thyrotropin-secreting pituitary adenomas, among so-called chromophobe adenomas, or “undifferentiated adenomas”.
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  • 27
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    Acta neuropathologica 55 (1981), S. 307-318 
    ISSN: 1432-0533
    Keywords: Diphtheritic polyneuropathy ; Muscle biopsy ; Intramuscular nerves ; Electron microscopy ; Histochemistry ; Diphtherie-Polyneuropathie ; Muskelbiopsie ; intramuskuläre Nerven ; Elektronenmikroskopie ; Histochemie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Biopsien aus Extremitätenmuskeln von vier Kranken mit schwerer tetraplegischer Form der Diphtherie-Polyneuropathie konnten nahe dem Höhepunkt der Erkrankung gewonnen und mit modernen Methoden einschließlich Histochemie, Elektronenmikroskopie und morphometrischer Verfahren untersucht werden. Vergleichbare Studien wurden bisher nicht veröffentlicht. Die Muskulatur bot vorwiegend neurogene Veränderungen mit disseminierten angulierten Fasern, eine besonders die Typ-2B-Fasern betreffende, mehr generaliierte Atrophie sowie Targetoidherde oder „Cores” in Typ-1-Fasern. Darüber hinaus fanden sich eindeutige myogene Veränderungen mit unterschiedlichen Degenerationsphänomenen bis zur totalen Nekrose, offenbar — wie am Herzmuskel —toxischer Herkunft. Das neurogen-myogene Mischbild entsprach den elektromyographischen Befunden. Die intramuskulären Gefäße waren unauffällig bis auf vereinzelte perivaskuläre, vorwiegend mononukleäre Zellinfiltrate mit reichlich zerebriformen lymphoiden Zellen, wahrscheinlich T-Lymphozyten. An 11 intramuskulären Nerven und zwei motorischen Endplatten waren eindeutig auf die Diphtherie zu beziehende Veränderungen nicht aufzudecken. Dies kann als Hinweis auf eine vorwiegend proximale Entmarkung bei der Diphtherie-Polyneuropathie des Menschen gedeutet werden, die damit eher der experimentellen Form des Kaninchens als der des Meerschweinchens entspricht.
    Notes: Summary Mucle biopsies from the lower extremities of four patients with severe tetraplegic form of diphtheritic polyneuropathy were examined by modern techniques including histochemistry, electron microscopy and morphometric procedures. Until now comparable studies have not been published. The biopsies were removed during the acute stage of the polyneuropathy. We found scattered small angulated muscle fibers beside a more generalized slight atrophy predominantly of type 2B fibers and targetoid-phenomenons or cores in type 1 fibers. Beside this neurogenic pattern there also were, corresponding with the results of electromyography, primary myogenic alterations with different degenerative phenomenons, suspicious of toxic origin as in cardiac muscle. The intramuscular vessels showed no abnormalities except some perivascular predominantly mononuclear cellular reactions with a remarkable number of cerebriform lymphoid cells, probably T-lymphocytes. No specific pathological alterations could be detected in 11 intramuscular nerves and two motor endplates. This may reflect the more proximal demyelination of human peripheral neurons by the diphtheria toxin as found in experimental diphtheria of the rabbit in contrast to the more distal type of the guinea pig.
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  • 28
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    Acta neuropathologica 54 (1981), S. 287-292 
    ISSN: 1432-0533
    Keywords: Mucopolysaccharidoses III ; Sanfilippo's syndrome ; Histochemistry ; Electron microscopy ; Lipofuscin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A histochemical and ultrastructural study was made on the brain of a 23-year-old man with Sanfilippo's syndrome. In accordance with previous reports the cortical nerve cells contained a PAS-positive lipid storage substance. This showed intense autofluorescence in UV-light and was positive with various stains for lipofuscin. The storage material appeared ultrastructurally as inclusion bodies composed of short lamellated membranes, granular material, and vacuoles. In addition, concentrically and transversely lamellated membranous cytoplasmic bodies were observed in the nerve cells. It is concluded that the PAS-positive lipid storage material in the neurons was composed partly of lipofuscin in addition to other lipids presumably glycosphingolipids.
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  • 29
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    Acta neuropathologica 55 (1981), S. 81-87 
    ISSN: 1432-0533
    Keywords: Canine CNS ; Myelination ; Hypomyelinogenesis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of myelin deficiency in Chow Chow dogs was studied in the spinal cord of a 15-month-old and a 3-year-old animal. It was found that myelination progresses with age in these dogs but is still deficient at the age of 3 years. The findings included axons with thin or uncompacted myelin sheaths, separated from each other by massive astrocytosis, and bizarre myelin formations. Normal numbers of morphologically normal oligodendrocytes were present in the myelin-deficient areas. The disease in these Chow Chow dogs consists of a strongly retarded myelination which is possibly due to a dysfunction or delay in glial maturation.
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  • 30
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    Archives of dermatological research 271 (1981), S. 171-182 
    ISSN: 1432-069X
    Keywords: Hypomelanotic macule ; Tuberous sclerosis ; Electron microscopy ; Hypomelanotische Macula ; tuberöse Hinrsklerose ; Elektronenmikroskopie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Hypomelanotische Maculae der Haut bei der tuberösen Hirnsklerose (TS) werden verursacht durch einen komplizierten Prozeß, in den die Synthese und Reifung von Melanosomen verwickelt sind. Weil die Charakterisierung von Hautbiopsien aus hypomelanotischen Maculae bei TS-Patienten zur Zeit nicht ausreichend ist, haben wir eine quantitative Methode entwickelt, durch die die Reifung der Melanosomen in den Melanocyten erforscht wird. Diese Methode wurde anhand von Biopsien aus hypomelanotischer und der angrenzenden Haut von sechs Patienten mit erwiesener TS geprüft und mit bekannten Methoden verglichen. Bei allen sechs Patienten wurde in der hypomelanotischen Macula eine statistisch signifikant niedrigere Zahl von pigmentierten Melanosomen pro melanocytärem Perikaryon und dendritischem Zellprozeß festgestellt als in der angrenzenden Haut. Die relative Anzahl von Stadium III- und IV-Melanosomen hatte in der hypomelanotischen Macula abgenommen, die von Stadium II-Melanosomen zugenommen (auch statistisch signifikant). Durch Verwendung unserer Methode kann die Hypomelanose der TS zuverlässig charakterisiert werden, was möglicherweise aus diagnostischer Sicht wichtig ist. Die Resultate der Melanosomengrößenmessung oder die des DOPA-Verfahrens dagegen waren statistisch nicht signifikant.
    Notes: Summary Hypomelanotic macules of the skin in tuberous sclerosis (TS) are caused by a complex process, involving the synthesis and maturation of melanosomes. A quantitative method was developed to investigate the maturation of the melanosomes at the level of the melanocytes. The method was tested on biopsies of hypomelanotic and adjacent normomelanotic skin from six patients with definite TS, and compared with other methods. In all patients, a statistically significant lower number of pigmented melanosomes was found per cross-sectioned melanocytic perikaryon and dendritic cell process in the hypomelanotic as compared to the normomelanotic skin. The relative numbers of stage III and IV melanosomes were decreased, and of stage II melanosomes increased in the hypomelanotic macule (also statistically significant). This indicates that it is possible to characterize the hypomelanosis in TS reliably, which may have diagnostic importance. In our hands, assessment of the size of the melanosomes did not show a statistically significant difference between hypo- and normomelanotic skin; the difference found with the DOPA technique was more evident, although not statistically significant.
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  • 31
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    Calcified tissue international 33 (1981), S. 143-151 
    ISSN: 1432-0827
    Keywords: Calcium transport ; Cytochalasin B ; Dihydrocytochalasin B ; Colchicine ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary In vivo calcium absorption was studied in normal and rachitic chicks. Cytochalasin B (CB) at a concentration of 25 µg/ml added to the medium inside the duodenal lumen inhibited calcium absorption (20 min) from 82.5±1.9% of calcium absorbed in the controls to 59.2±3% in normal and from 70.0±2.3% to 47.0±2.1% in rachitic chicks. In vitro studies by everted ileal sacs of young rabbits also showed an inhibition of active transport of calcium due to CB. Whereas in the controls the ratio of45Ca concentrations in serosal and mucosal media (60 min) was 7.2±0.32, the ratios were 5.24±0.52; 4.40±0.36; 3.40±0.42; 5.77±0.52; 1.38±0.08; and 1.06±0.02 in the presence of CB at concentrations of 5, 10 and 25 µg/ml; colchicine 10−4M, Na citrate 0.02M, and heat-devitalized conditions, respectively.45Ca concentration in the mucosal scrapings was also affected. It showed an increase from controls (15,101±404 cpm/mg) and correlated with CB concentration: 17,378±489, 19,015±1000, and 20,201±362 at 5, 10, and 25 µg/ml, respectively. Dihydrocytochalasin B also inhibited active calcium transport and caused an increase in45Ca concentration in the mucosal scrapings. Correlated electron microscopic studies showed certain changes in the brush border, especially in some actin microfilaments in the terminal web region. It seems that these morphological alterations may be related to transcytoplasmic movement of calcium.
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  • 32
    ISSN: 1432-0827
    Keywords: Alcohol ; Electron microscopy ; Growth plate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary We have previously demonstrated that ethanol has a direct toxic effect on the rat skeleton characterized by decreased trabecular bone volume. In the present study, we examined the ultrastructure of the distal radial epiphyseal growth plates in these same animals. Eight weeks of ethanol administration to 12 male rats results in serum alcohol levels of 140 mg/dl but did not alter the width or light microscopic appearance of the radial growth plate. Quantitative electron microscopy failed to demonstrate morphologic evidence of toxicity in the skeletal cells. We conclude that although ethanol appears to have a direct effect on rat bone characterized by enhanced resorption, toxicity is not attended by ultrastructural changes in the skeletal cells.
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  • 33
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    Calcified tissue international 33 (1981), S. 529-540 
    ISSN: 1432-0827
    Keywords: Bone cells ; Electron microscopy ; PTH ; PGE1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Four different cell populations—designated PF, OB, OC, and PC—were isolated from calvaria of 18-day-old chick embryos for analysis of the effects of hormones on bone tissue. The cell populations were studied with histological and biochemical methods. Apart from the well-known cell types present in calvaria, a new cell type was found in the noncalcified organic matrix between the osteoblastic layer and the calcified matrix. These cells were provisionally called osteocytic osteoblasts. They represent the “transition state” between osteoblasts and osteocytes. On the basis of histological studies with light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), the PF population was considered to originate primarily from the periosteal fibroblasts, the OB population from the osteoblasts and osteocytic osteoblasts. The population of cells still present in calvaria after removal of periosteal fibroblasts and osteoblasts was called the OC population. This cell population was very much enriched with osteocytes. The fourth isolated population (PC) was a mixed population of fibroblasts, osteoblasts, and preosteoblasts. On exposure to parathyroid hormone (PTH), all four cell populations showed increased lactate production, but only the OB and OC populations displayed increased cAMP production. Prostaglandin E1 (PGE1) stimulated cAMP production in both OB and PF cells. From the results of this study it was concluded that PTH receptors are present on all of the cell types studied, but that occupancy of the receptor induces adenylate cyclase stimulation only in osteocytes and fully differentiated osteoblasts.
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  • 34
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    Calcified tissue international 33 (1981), S. 119-124 
    ISSN: 1432-0827
    Keywords: Avian eggshell ; Microstructure ; Electron microscopy ; Electron diffraction ; Calcite growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The eggshell of the domestic fowl has been studied by transmission electron microscopy and diffraction. Thin sections of shell were prepared by chemical and ion-beam thinning techniques. Each calcite column of the palisade layer consisted of crystallites of diameter 20 to 30 µm with some tendency for crystallite alignment within a single column. Evidence indicates that there was no significant preferred orientation in the palisade layer as a whole. Only in the surface layer was any preferred orientation detected, and here {1014} planes tended to lie parallel to the surface. The results are compared with previously published data, and calcite nucleation and growth are discussed.
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  • 35
    ISSN: 1432-1246
    Keywords: Diesel exhaust emission ; Liver ; Electron microscopy ; Freeze-fracture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The livers of Syrian golden hamsters were examined with the light and electron microscope using the techniques of thin sectioning and freeze-fracture following 5 months of exposure to various concentrations of diluted diesel exhaust gases. The light microscopical examination showed enlarged sinusoides with activated Kupffer's cells and slight changes in the cell nuclei. In the electron microscopical examination the most striking changes were seen in the mitochondria, which frequently showed a loss in cristae. In addition, the mitochondria exhibited pleomorphic character. The microbodies were of the same size as mitochondria. An increase in the number of lysosomes was observed especially in the tissue surrounding the narrow bile canaliculi. The various alterations corresponding to the different concentrations of exhaust gases could be seen especially well in the sinusoides, the mitochondria and the microbodies. In general the hepatocytes appeared to be moderately enlarged. The zonulae occludentes showed a more irregular outline and large maculae tight junctions were found on the lateral region of the plasmalemma of hepatocytes. The gap junctions exhibited a wide range of structural diversity. The intramembranous particles on the P fracture face of the plasmalemma of hepatocytes are aggregated.
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  • 36
    ISSN: 1432-1106
    Keywords: Cat-spinocervical tract cells ; Intracellular staining ; Electron microscopy ; Synaptic vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Synaptic vesicles in initial collateral terminals of two feline Spinocervical tract cells have been investigated after intracellular staining with horseradish peroxidase. A total of 5325 vesicles in 52 axodendritic and 26 axo-somatic terminals were analysed after aldehyde-osmium fixation. The greatest length and longest perpendicular width of each vesicle were measured, and the ratio and geometric mean of the diameters (gm-diameters) were calculated. The vesicles were divided into classes with round, elliptical and flat organelles. The variations in vesicle length, gm-diameter, and diameter ratio were statistically analysed by means of one- and two-way analyses of variance and t-tests. The diameter ratio, the length of round vesicles, and the gm-diameters of round and elliptical vesicles differed significantly between the cells. The length and gm-diameter of the elliptical vesicles differed significantly between the groups of axo-dendritic and axo-somatic terminals of each cell. Round vesicles were significantly longer in the axosomatic than in the axo-dendritic terminals of each cell, and the gm-diameter showed this relation for both round and elliptical vesicles. It is assumed that a one-size vesicle could not account for all the measured profiles. The variability of synaptic vesicles within and between the functionally similar cells emphasize the difficulties in using the morphology of synaptic vesicles for a discrimination of axon terminals of different origin.
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  • 37
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    European biophysics journal 7 (1981), S. 209-212 
    ISSN: 1432-1017
    Keywords: Photosynthetic bacteria ; Electron microscopy ; Planar lattices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The thylakoids of Rhodopseudomonas viridis have been studied by freeze-fracturing whole cells. Depending on growth conditions and treatment before freezing, three different types of particle arrangements in the photosynthetic membrane are reported: a random arrangement, an isometric (quadratic) lattice arrangement with a lattice constant of 12.5 ± 0.8 nm, and a hexagonal lattice arrangement with a lattice constant of 12.5 ± 0.8 nm.
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  • 38
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    Archives of toxicology 47 (1981), S. 101-111 
    ISSN: 1432-0738
    Keywords: Cerebellar cortex ; Methylmercury ; Toxicity ; Rat ; Morphometry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A single dose of 10 mg methylmercury chloride per kg body weight was given to 30 days old rats and to adult rats (180–200 g). This resulted in brain levels of 1.4–2.2 μg Hg/g wet weight. In the young rats electron microscopic morphometry showed swelling of the granule cells. The extent of changes was more pronounced in the cerebellar hemispheres than in the vermais and flocculus. At 7 days after giving the methylmercury the granule cells appeared to have returned to normal. Methylmercury produced both light and electron microscopic changes in cerebellar neurons of adult (180–200 g) rats 3 days after dosing. 2.5–10% of the granule cells appeared dark and condensed in toluidine blue stained semithin sections of perfusion fixed and plastic embedded material. In control animals the comparable percentage never exceeded 1. By electron microscopic morphometry the dark cells proved to be shrunken to 70%, whereas the remaining light granule cells were swollen to 130% of the normal cell volume. The heterochromatin and mitochondrial volumes per cell remained constant in both dark and light cells from methylmercury treated animals. In the Purkinje cells from both young and adult rats, geometrical changes in the cisternae of the granulated endoplasmic reticulum were evident. The swelling and shrinkage of the granule cells is supposed to be due to impaired electrolyte control and the disorganized granulated endoplasmic reticulum of the Purkinje cells may be related to the deleterious effects on protein synthesis.
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  • 39
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    Journal of neurology 225 (1981), S. 67-72 
    ISSN: 1432-1459
    Keywords: Ewing sarcoma ; Epidural tumors ; Spinal cord compression ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Es wird ein Ewing-Sarcom, welches sich außerhalb des Skelettes bei einem Kind entwickelte, geschildert. Klinisch manifestierte es sich als epidurale Masse. Bei der chirurgischen Exploration zeigte sich ein brüchiges Gewebe, welches 2–3 cm lang war und nicht vom Knochen ausging. Lichtmikroskopisch und elektronenmikroskopisch ließ sich die Diagnose eines Ewing-Sarcoms stellen. Es werden morphologische Aspekte und differentialdiagnostische Überlegungen in Zusammenhang mit Tumoren des Epiduralraumes diskutiert.
    Notes: Summary The clinicopathological findings in a child with extraskeletal Ewing sarcoma are described. The patient complained of pain in the lower back and difficulty walking. An extraskeletal, epidural, friable tumor, 2–3 cm long was removed from the epidural space. It had no relationship with the bone structures. Light and electron microscopic examination of the tumor led to the diagnosis of Ewing sarcoma. The morphological aspects of this neoplasia and the problem of the differential diagnosis with other small cell tumors of the epidural space are discussed.
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  • 40
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    Journal of neurology 224 (1981), S. 171-182 
    ISSN: 1432-1459
    Keywords: Cerebral amyloidoma ; Congo red birefringence ; IgM immunofluorescence ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Eine fast walnußgroße, intra- und subcortical gelegene Masse von Congo-Rot-färbbarem Amyloid mit einigen umgebenden Lympho-Monozyten, Plasmazellen und mehrkernigen Elementen sowie doppelbrechenden plumpen Plaques und fein dispers verteilten Amyloidpräzipitaten innerhalb eines unmittelbar angrenzenden kleinen Rinden-Restgewebes wurde operativ aus dem Occipitallappen entfernt. Aufgrund der typischen grüngelblichen Doppelbrechung im Congo-Rot-Präparat, der Thioflavin-Fluoreszenz, der positiven PAS-Reaktion, Bindegewebsfaserfärbungen und des elektronenmikroskopischen Nachweises charakteristischer unverzweigter 10 nm-Fibrillen kann die Diagnose eines cerebralen Amyloidtumors (Amyloidom) gestellt werden. Bei nur schwacher Anfärbung des vielfach deutlich appositionell gewachsenen Substrates mit Anti-Bence-Jones-Proteinserum (λ-Kette) reagierten die Perikarya der mononukleären lymphoiden Zellen und der Plasmocyten im indirekten Immunfluoreszenztest besonders mit Anti-IgM (FITC-markiert). — Die Trägerin, eine 46jährige Hausfrau, hatte jahrelang recidivierende depressive Episoden und in den letzten 4 Jahren fortschreitende neurologische Symptome nach Art eines chronischen raumfordernden Prozesses ohne jegliche Anzeichen einer Systemerkrankung oder Gammopathie. Sie erholte sich nach der Operation ziemlich gut. Es wird angenommen, daß es sich — analog zum tumorförmigen Amyloid in Haut, Lunge oder anderen Organen — hier um eine isolierte cerebrale Form von Paramyloid oder nodulärer primärer Amyloidose (Amyloid L) im Sinne von Reimann et al. (1935), Cohen (1967), Azar (1973), Langer und Missmahl (1980), Glenner (1980) u. a. handelt.
    Notes: Summary An almost walnut-sized tumor was removed surgically from the left occipital lobe of a 46-year-old woman, who had suffered for 4 years from progressive visual loss with scotoma and finally from hemianopia, associated with attacks of headaches and recurrent episodes of depression each lasting for some weeks or months. Neuropathological examination, including polarization, thioflavine fluorescence, immunofluorescence staining, and electron microscopy, revealed an amyloidoma, which consisted of broad appositionally grown amyloid deposits surrounded by some plasma cells, monocytic or foreign body cell types. The massive accumulations, often associated not only with blood vessels or perivascular collagenous fibers but also lying in the cerebral tissue not unlike senile plaques in the cortical gray matter, corresponded to gradually growing masses as seen in the repeated CT scans. This unique lesion in the brain of a patient who did not show any evidence of systemic disorder, seems to confirm that the spontaneous tumor-like amyloid, which gave an immunofluorescent staining mainly with anti-IgM, is a special variant of primary amyloidosis (amyloid L) or of so-called paramyloid (Reimann et al. 1935; Cohen 1967; Azar 1973; Langer and Missmahl 1980).
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  • 41
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    Archives of microbiology 130 (1981), S. 125-128 
    ISSN: 1432-072X
    Keywords: Rhodospirillum rubrum ; Chromatophores ; Reaction centers ; Liposomes ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In freeze-fractures of chromatophores of Rhodospirillum rubrum the reaction centers are seen as hexagonal arranged particles of 13 nm diameter with a density of around 5,500 particles per μm2. Similar regions on the cytoplasmic membrane suggest that these parts are the prospective invagination sites. Isolated reaction centers are easily incorporated into liposomes. In freeze fractures of liposomes particles similar in shape and size, although less dense as in chromatophores are observed. In negative staining much smaller units of only 5 nm in diameter are found indicating that reaction centers occur in the membrane as tri- or tetramers. There is a strong correlation between particle density in chromatophores and titratable reaction centers remaining in these membranes after extraction of reaction centers by detergents; both values are in good agreement with the yield of reaction centers at a given detergent concentration.
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  • 42
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    Archives of microbiology 129 (1981), S. 129-134 
    ISSN: 1432-072X
    Keywords: Cockroach ; Hindgut ; Distribution ; Microbial morphotypes ; Transmission ; Electron microscopy ; Statistical analysis ; Eublaberus posticus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relative numbers of fourteen microbial morphotypes in transmission electron micrographs of the hindgut of a cockroach, Eublaberus posticus, were counted and their distribution was analyzed statistically. The microbiota of three wall-associated regions (the anterior paunch, the posterior paunch, and the black band region) was clearly different from that of the gut lumen. The three wall fractions were also significantly different from each other. Only one of the fourteen types, prosthecate bacteria, appeared to be distributed randomly in the four fractions. The five main wall-associated morphotypes individually constituted up to 41% of the microbes in some micrographs. They included one type with the characteristic morphology of Methanospirillum. Six morphotypes rarely made up over 2% of the population, but were consistently present. The numbers of the remaining three morphotypes were quite variable between micrographs and between individual insects, but when present often made up 5–10% of the population.
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  • 43
    ISSN: 1432-072X
    Keywords: Biological control ; Cyanobacteria ; Electron microscopy ; Entrapment ; lysis ; Myxococcus ; Phormidium ; Spherule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A Myxococcus xanthus isolate from a farm drainage ditch, designated strain PCO2, is capable of rapidly inducing lysis of both agar and liquid-grown cultures of the cyanobacterium, Phormidium luridum, var. olivacea. Microscopic studies of the predator-prey interaction demonstrate that lysis of the cyanobacterium occurs within clumps and spherules formed by the cells of M. xanthus PCO2. In the earliest stage, one sees the formation of irregular microclumps of bacteria and cyanobacterial filaments. As these clumps mature, colonies 1 to 6 mm in diameter develops. The center of these densely green colonies contains cyanohacteria in various stages of degradation, while the periphery is almost exclusively a tightly woven mass of myxobacterial cells. Electron microscopy shows that long extrusions from the outer membrane of the M. xanthus PCO2 cells are involved in the formation both of initial clumps and of mature colonial spherules. These extrusions appear to efficiently entangle the cyanobacterial filaments in the culture environment. Predator-to-prey ratios of 1/10, 1/100 and 1/1,000 have resulted in cyanobacterial lysis. Because the entrapment and lysis of P. luridum filaments by M. xanthus PCO2 appears to be independent of any other heterotrophic nutritional requirement, as well as of environmental agitation, this system has potential as a biological control technique for undesirable aquatic cyanobacteria.
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  • 44
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    Archives of microbiology 130 (1981), S. 339-343 
    ISSN: 1432-072X
    Keywords: Leptospira ; Halophilic ; Electron microscopy ; X-ray analysis ; Inclusions ; Cytoplasmic tubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The morphology of cells of strain Muggia, a slightly halophilic leptospire, was examined by the negative staining technique. The ultrastructure of the cells was rather similar to that of cells of Leptonema illini, i. e. the cells possessed cytoplasmic tubules. The basal complex of their flagella, however, was similar to the corresponding part of flagella on Gramnegative bacteria. The interior of the cells was densely packed with inclusions, except for the two outermost wavelengths at each end where these inclusions were absent. X-ray microanalysis showed that the inclusions contained sodium and chlorine as their main constituents. The inclusions disappeared upon storage of the cultures at room temperature.
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  • 45
    ISSN: 1432-072X
    Keywords: Ribulose bisphosphate carboxylase ; Quaternary structure ; Molecular weight ; Electron microscopy ; Cyanobacteria ; Synechococcus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ribulose bisphosphate (RuP2) carboxylase from the marme cyanobacterium, Synechococcus sp., comprised both large (57,000 dalton) and small (12,000 dalton) subunits. The undissociated, purified enzyme was considerably smaller than the spinach enzyme when compared by pore-gradient electrophoresis, gel filtration and density-gradient centrifugation. This suggested that the cyanobacterial enzyme might have a hexameric (L6S6) subunit structure, unlike the enzymes from spinach and many other organisms which are octamers (L8S8). However, the molecular weight of the Synechococcus enzyme was measured by equilibrium sedimentation and found to be 530,000, which is within the range observed for L8S8-type enzymes. Furthermore, electron microscopic studies of negatively stained preparations of both the native enzyme, and a preparation depleted of 87% of its small subunits by repeated mild-acid precipitation, revealed four-fold symmetry characteristic of an octameric, cubical structure. Synechococcus RuP2 carboxylase therefore must be an L8S8 octamer and its anomalous pore-penetration behaviour may be due to an asymmetric shape. Some support for the latter possibility was provided by electron miscoscopic observations of two different types of images which may be different views of the molecule in two planes.
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  • 46
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    Journal of cancer research and clinical oncology 100 (1981), S. 51-58 
    ISSN: 1432-1335
    Keywords: Electron microscopy ; Rat astrocytomas ; Dibutyryl cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two cloned rat astrocytoma cell lines, 36 B-10 and 40 A-2, maintained in vitro were treated with 1 mM dibutyryl cyclic AMP. This treatment induced arborization of cellular processes and rounding-up of cell bodies in both cell lines and was associated with increased microvillous development in 40 A-2. There were no detectable concomitant changes in either (a) the quantity or organization of microtubules or 80–100 nm microfilaments, or (b) the intensity of glial fibrillary acidic protein indirect immunofluorescence staining.
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  • 47
    ISSN: 1432-5233
    Keywords: Electron microscopy ; Glibenclamide ; Glucose oxidation ; Insulin biosynthesis ; Insulin secretion ; Islets of Langerhans ; Mitochondria ; Morphometry ; Tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to evaluate long-term effects of sulphonylureas on pancreatic islet structure and function, isolated mouse islets were maintained in tissue culture for one week at various glucose concentrations, and in the absence or presence of glibenclamide. When the islets were cultured at 3.3 or 5.5 mmol/1, but not at 16.7 mmol/1 glucose, it was found that the drug stimulated insulin secretion into the culture medium during the initial 3 days of culture. During the remainder of the culture period no such enhancement of secretion was demonstrated. Insulin release due to glibenclamide apparently resulted in rapid depletion of intracellular insulin stores. The finding of an enlarged B-cell Golgi apparatus in the drug-treated islets was probably associated with granule discharge. The failure of glibenclamide to promote insulin secretion during the whole culture period could reflect the adverse effects of the drug on islet insulin biosynthesis as indicated by short-term experiments performed after culture. Similar experiments showed that the impaired insulin biosynthesis could not be restored by withdrawal of the drug from the culture medium for 3 days. Furthermore, the capacity for insulin release in response to an acute glucose challenge at the end of the culture period, was abolished by culture in the presence of glibenclamide. The drug effects on insulin biosynthesis and intracellular insulin stores, which were most pronounced at 5.5 mmol/1 glucose, possibly resulted from changes in B-cell metabolism as suggested by the diminished islet glucose-oxidation rate. The spatial characteristics of islet mitochondria indicated that these changes might involve an adaptation to substrates other than glucose. In conclusion, our findings suggest that sulphonylureas have an insulinotropic effect, which is however transient. Indeed, it rather seems as if long-term exposure of islet B-cells to sulphonylureasin vitro were accompanied by functional deficiency.
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  • 48
    ISSN: 1432-2307
    Keywords: Electron microscopy ; Effect of various GAG on fibril formation in vitro ; Collagen structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Proteoglycans (PG) and glycosaminoglycans (GAG) bind to collagen, and thus influence fibril formation. Polysaccharides interfere with the aggregation of collagen molecules and affect pattern formation. The morphological structure of type I and type II collagen was studied after adding different GAG to collagen solutions in test tubes in vitro. Electron microscopical investigations suggest that sulfated GAG change the aggregation behaviour of collagen molecules. Thus, the cross-striation pattern is changed. This effect seems to be based on the degree of sulfatation and not on the molecular weight of the GAG. Furthermore, GAG appear to have a stabilizing influence on the in vitro fibril formation.
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  • 49
    ISSN: 1432-2307
    Keywords: Endocrine tumour ; Pancreas ; Argentaffin reaction ; Immunocytochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An endocrine pancreatic tumour that had not caused any endocrine symptoms was examined by histological, immunocytochemical and electron microscopic techniques. The majority of the tumour cells were argentaffin and contained secretory granules of the enterochromaffin cell type. Immunocytochemically a minority of tumour cells reacted to antisera against β-endorphin, met- and leu-enkephalin, gastrin, somatostatin and ACTH. The tumour was thus multihormonal, and appeared to be more closely related to the classic Carcinoid tumours of the mid-gut than to most pancreatic endocrine tumours.
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  • 50
    ISSN: 1432-0878
    Keywords: Pancreatic islets ; Adrenergic innervation ; Insulin secretion ; Chemical sympathectomy ; Adrenalectomy ; Fluorescence histochemistry ; Immunohistochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Morphological changes in the adrenergic innervation of pancreatic islets after chemical sympathectomy by use of 6-hydroxydopamine and the influence of the sympatho-adrenal system on insulin secretion were investigated in the mouse and rat. Fluorescence histochemistry revealed a clear-cut reduction in the number of adrenergic nerve fibers in the pancreatic islets 2 days after administration of 6-hydroxydopamine; the reduction was more pronounced in the rat than in the mouse. In the rat, a partial regeneration was seen after 6 weeks. In the pancreas of the mouse, after administration of 6-hydroxydopamine, a severe damage of unmyelinated nerve fibers was revealed electron microscopically. However, no ultrastructural or immunohistochemical alterations could be demonstrated in the endocrine cells of the islets. 6-Hydroxydopamine induced a depression of basal plasma insulin concentrations in mice and an elevation in rats. Adrenalectomy depressed basal plasma insulin levels in mice. The α-adrenoceptor antagonist phentolamine enhanced insulin secretion in normal mice. The secretory response of insulin to phentolamine was diminished by chemical sympathectomy and almost abolished by adrenalectomy or the combination of chemical sympathectomy and adrenalectomy. Thus, the effect of phentolamine is probably mediated by liberated catecholamines. It is concluded that basal insulin secretion is partially regulated by the sympatho-adrenal system and that species differences exist in this respect. In addition, the results suggest that endogenous catecholamines have the ability to promote insulin secretion.
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  • 51
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    Cell & tissue research 216 (1981), S. 471-479 
    ISSN: 1432-0878
    Keywords: Ovulation ; Perfusion ; Graafian follicle (Rabbit) ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the present investigation the ultrastructure of isolated rabbit ovaries, perfused with different media for various time periods, was studied. The steroid hormone production by the perfused ovary was also determined. Perfusion with Medium 199 results in prominent interstitial ovarian oedema which increases with perfusion time. Even after the addition of 6–10 % Dextran T40, oedema appears in the interstitial tissue of the ovary. Perfusion solutions with osmotically active colloid particles of large molecular size (Dextran T70; average molecular weight 70,000 and bovine serum albumin), cause less distortion in the ovarian structure, and ultrastructurally the ovarian tissues appear essentially the same as in the control ovaries. The results indicate that the perfused rabbit ovary, under strictly controlled conditions, can be used as an experimental model for studies of various aspects of ovarian function, including follicular rupture.
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  • 52
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    Cell & tissue research 216 (1981), S. 205-214 
    ISSN: 1432-0878
    Keywords: Compound eyes ; Insects ; Crustaceans ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The basement membrane of the compound eye of four insect species and three crustacean species was investigated employing electron microscopy. The basement membrane consists of an extracellular (basal lamina) and a cellular portion, the latter being composed of the flattened terminal extensions of cone cells and accessory pigment cells in insects and distal pigment cells in crustaceans. Other cells can also contribute to the basement membrane. It is thus a complex structure in all well-developed compound eyes. The cellular contributions vary in different species and were found to correlate to specific taxonomic units.
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  • 53
    ISSN: 1432-0878
    Keywords: Gastrin ; CCK ; Median eminence ; Electron microscopy ; Xenopus laevis (Amphibia, Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary By use of an anti-gastrin serum and colloidal gold- or ferritin-labelled sheep anti-rabbit γ-globulins, nerve fibres and nerve terminals containing a gastrin-like substance were characterized at the ultrastructural level in the median eminence of Xenopus laevis. These immunoreactive fibres contain neurosecretory granules displaying medium to high electron density and a mean diameter of 75 nm. Labelling intensity varies from granule to granule. This is the first demonstration at the ultrastructural level of the precise location of a gastrin-like hormone in the median eminence of a vertebrate.
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  • 54
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    Cell & tissue research 217 (1981), S. 211-223 
    ISSN: 1432-0878
    Keywords: Pituitary gland ; Pars intermedia ; Electron microscopy ; Sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Light microscopy of coronal sections of the sheep pars intermedia revealed a compact, incompletely lobulated V-shaped region about 15–20 cells thick, situated between the pars distalis and the pars nervosa. A prominent hypophysial cleft and follicles containing a colloid-like substance were seen. Using electron microscopy, five cell types could be distinguished: pars intermedia glandular cells, pars distalis-like glandular cells, interstitial cells, follicular cells and cleft lining cells. The polyhedral to pear-shaped pars intermedia glandular cells predominated. They contained dense-cored, membrane-bound granules near the Golgi complex, and larger, irregular vesicles with finely granular contents of varying electron density throughout the remaining cytoplasm; exocytotic release of granules was occasionally observed. Smaller numbers of cells resembling those seen in the pars distalis were scattered throughout the pars intermedia. Interstitial cells usually possessed elongated cytoplasmic processes which extended between the glandular cells, and were characterized by deeply indented nuclei, elaborate junctional complexes and an absence of cytoplasmic granules. Cells lining the follicles resembled the interstitial cells. The major cells bordering the hypophysial cleft were triangular in section and bore irregular microvilli on their free surface. The pars intermedia appeared to be less vascular than the remainder of the hypophysis and only occasional fenestrated capillaries were seen. Nerve profiles were rare.
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  • 55
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    Cell & tissue research 215 (1981), S. 643-649 
    ISSN: 1432-0878
    Keywords: T-lymphocytes ; Blast cells ; Autoradiography ; Electron microscopy ; Stereology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary As a companion to an earlier study, the morphometric attributes of stimulated (blast-derived) lymphocytes in mouse axillary lymph nodes have been established using stereological and autoradiographic methods. Blast transformation was induced in vivo with dinitrochlorobenzene (DNCB) and stimulated cells were labelled with tritiated thymidine. Random samples of cells were taken for light and electron microscopic morphometry. In comparison to the unstimulated lymphocyte, the stimulated cell increased in size and possessed a greater plasma membrane surface area. Increase in cell size was the result of increases in the volumes of all measured subcellular compartments both in the nucleus and the cytoplasm. Heterogeneity of the stimulated cell population precludes firm conclusions regarding the significance of all these ultrastructural changes, though alterations in cell surface are discussed in the context of known biochemical differences accompanying blastogenesis.
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  • 56
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    Cell & tissue research 216 (1981), S. 557-568 
    ISSN: 1432-0878
    Keywords: Electron microscopy ; Neuroglia ; Silver impregnation ; Brain ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The silver-impregnation procedure of Tsujiyama is suitable for demonstration of all three classical types of neuroglial cells; in the present study it was used for electron microscopic identification of neuroglial cells in the brain of the cat. The aim of the present study was 1) to determine impregnated structural correlates of neuroglial cells at the light- and electron-microscopic levels, and 2) to determine whether the method of Tsujiyama is applicable for the electron microscopic identification of the single types of neuroglial cells. Silver deposits were observed over the cytoplasm and processes of astrocytes where numerous glial filaments were present. Oligodendrocytes and microglial cells may be precisely differentiated by use of Tsujiyama's silver impregnation method at the electron microscopic level due to the pattern of silver-deposition in these two basic types of cells. This silver-impregnation method combined with electron microscopy is thus suitable for a precise identification of neuroglial cells; the technique may prove to be very helpful in identification of such categories of neuroglial cells that encompass also the images of cells which cannot be classified by use of the standard methods.
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  • 57
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    European archives of oto-rhino-laryngology and head & neck 233 (1981), S. 271-300 
    ISSN: 1434-4726
    Keywords: Neurogenic sarcoma ; Neurofibrosarcoma ; Malignant schwannoma ; Head and neck ; Tumors of the peripheral nervous system ; Histopathology ; Electron microscopy ; Differential diagnosis ; Case reports ; Computerized X-ray-tomography ; Prognosis ; Therapy ; Neurogenes Sarkom ; Neurofibrosarkom ; Malignes Schwannom ; Kopf- und Halsbereich ; Tumoren des peripheren ; Nervensystems ; Histopathologie ; Elektronenmikroskopie ; Differentialdiagnose ; Fallberichte ; Computertomografie ; Prognose ; Therapie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Das neurogene Sarkom ist ein insgesamt seltenes malignes Neoplasma, das sich von den Hüllen des peripheren Nerven ableitet. Entwickelt sich diese Geschwulst aus einem solitären oder multiplen Neurofibrom, so wäre nomenklatorisch auch die Bezeichnung Neurofibrosarkom gerechtfertigt, während alle anderen Synonyma für diese Geschwulst, insbesondere das maligne Schwannom, aus histogenetischen Gründen verlassen werden sollten. Für die Klassifizierung aller Tumoren des peripheren Nervensystems ist heute ein von der WHO (1969) akzeptierter Vorschlag zugrunde zu legen. Ein tabellarischer Literaturüberblick zeigt, daß in den letzten 50 Jahren nur über wenig mehr als 100 Fälle von neurogenen Sarkomen im Kopf-Halsbereich berichtet wurde. Die Differentialdiagnose dieses malignen Tumors umfaßt nahezu alle anderen malignen Weichgewebsgeschwülste und manchmal sogar ein anaplastisches Karzinom. Die Histopathologie, einschließlich der Elektronenmikroskopie, wird allgemein und an drei eingehenden Falldemonstrationen aufgezeigt, wobei auch den drei mikromorphologischen Varianten Rechnung getragen wird. Neben der feingeweblichen Untersuchung, die nur beim zusätzlichen Vorliegen einer Neurofibromatose oder bei der Identifizierung des Ursprungsnerven hundertprozentig gesichert werden kann, sind konventionelle und computertomografische Röntgentechniken zur Diagnosestellung hilfreich. Zum Schluß werden die Grundsätze der Therapie sowie die Prognose diskutiert.
    Notes: Summary The neurogenic sarcoma is a neoplasm found seldom. It descends from the sheaths of peripheric nerves. If this tumor develops from a solitary or multiple neurofibroma, it might also be called a neurofibrosarcoma. All other synonyms, especially that of the malignant schwannoma, should better be abandoned for histogenetic reasons. Today the classification of all tumors of the peripheral nervous system is based on a suggestion of the WHO from 1969. The tabular summary of the literature shows that only a little more than a hundred cases of neurogenic sarcoma of the head and neck were reported during the last 50 years. Differential diagnosis of this malignant tumor includes nearly all other malignant neoplasms of soft tissue, sometimes even anaplastic carcinoma. Histopathology, including electron microscopy, is described in general and also in detail with regard to three cases. Three forms of micro-morphological variants are dealt with, too. For diagnosis histological examination will be absolutely successful only in cases of neurofibromatosis or in cases where the nerve from which the tumor originates may be identified. Otherwise, conventional and computerized X-ray tomography may be helpful. Finally, some therapeutic and prognostic principles are discussed.
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  • 58
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    European archives of oto-rhino-laryngology and head & neck 230 (1981), S. 161-170 
    ISSN: 1434-4726
    Keywords: Sudden deafness ; Vertigo ; Neurectomy ; Eighth nerve ; Light microscopy ; Electron microscopy ; Demyelinating disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A patient initially presenting typical symptoms of idiopathic sudden deafness later developed disabling episodic vertigo, which led to translabyrinthine eighth nerve transection. Morphological examination of the removed cochlear nerve specimen revealed a demyelinating process in the neuroglial portion of the nerve. The major part of the peripheral, neurolemmal portion of the cochlear nerve was normal. The inferior vestibular nerve was fibrotic. The major part of the superior vestibular nerve was normal. Some of its peripheral bundles showed increased endoneurial fibrosis. It is suggested that a demyelinating process was the cause of the patient's symptoms.
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  • 59
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    Biopolymers 20 (1981), S. 169-185 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The IR data for the R1 CO-O-CHR2-CO-NHR3 derivatives are interpreted in terms of a H…π interaction involving the N—H bond and the π orbitals of the ester function and giving rise to a high ν(C=O) frequency and a low ν frequency. The resulting molecular conformation corresponds to the angular values φ # -90°, ψ # 0°. The H…π interaction in MeCO-L-Lac-NHMe is highly destabilized by water and aprotic solvents but is retained in methanol. Considering the high ν(C=O) ester or amide frequency of the middle function in β-folded depsipeptide or peptide sequences, it may be supposed that the residue indexed i + 2 in β turns experiences a H…π interaction which has a stabilizing effect on β turns. Some examples concerning valinomycin and some model compounds are discussed.
    Additional Material: 8 Ill.
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  • 60
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    New York : Wiley-Blackwell
    Biopolymers 20 (1981) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 61
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    Biopolymers 20 (1981), S. 251-268 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The difference between the theories of Manning, on the one hand, and of Odijk and Skolnick and Fixman, on the other, for the polyelectrolyte contribution to the persistence length of DNA is shown to arise entirely from a subtle geometrical error in the theory of Manning. The corrected theory of Manning predicts a negligible polyelectrolyte contribution in 1.0M NaCl and only 33 Å in 0.01M NaCl, thus giving a change in total persistence length by a factor of only 1.07 over that range, in agreement with Odijk. Pertinent data in the literature indicate that the persistence length must change by a factor of ≤ 1.6 between 1.0 and 0.01M NaCl, and very likely by less than a factor of 1.4. Evidently, the intrinsic rigidity of the uncharged double-strand filament dominates the bending rigidity at NaCl concentrations above 0.01M.
    Additional Material: 1 Ill.
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  • 62
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structures of L-3,4-dehydroproline, t-butoxycarbonyl-L-3,4-dehydroproline amide, and acetyl-L-3,4-dehydroproline amide have been determined. L-3,4-Dehydroproline is orthorhombic with a = 16.756, b = 5.870, c = 5.275 Å, and Z = 4; t-butoxycarbonyl-L-3,4-dehydroproline amide is orthorhombic with a = 6.448, b = 8.602, c = 21.710 Å, and Z = 4; acetyl-L-3,4-dehydroproline amide is monoclinic with a = 4.788, b = 10.880, c = 7.785 Å, β = 105.25°, and Z = 2. The final R value for the L-3,4-dehydroproline is 0.046 based on 529 reflections; for t-butoxycarbonyl-L-3,4-dehydroproline amide, 0.050 based on 792 reflections; and for acetyl-L-3,4-dehydroproline amide, 0.058 based on 632 reflections. The structures clearly establish that the free amino acid exists in the zwitterionic form in the crystalline state. The molecular conformations of the t-Boc and acetyl derivatives consist of two planes: one involving the primary amide and the other the remaining atoms of the molecule. The acetyl-L-3,4-dehydroproline amide contains a tertiary amide bond in the cis conformation. To the best of our knowledge, this is the first example of a cis bond in an acetyl derivative of an amino acid or peptide. At variance with the previously reported proline amides, which present φ and ψ values corresponding to those of a right-handed α-helical conformation (conformation A), the t-Boc and acetyl derivatives both have φ and ψ values corresponding to a collagenlike conformation (conformation F).
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  • 63
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    Biopolymers 20 (1981), S. 359-371 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of thermally denatured Type I collagen has been studied using laser light scattering. The results indicate that the diffusion coefficients of α-chains and β- and γ-components are 1.550 ± 0.08 × 10-7, 1.000 ± 0.05 × 10-7, and 0.835 ± 0.04 × 10-7 cm2/sec, respectively, at temperatures between 20 and 40°C. It is concluded from diffusion data that these species have hydrodynamic radii of about 13.8 nm (α-chain), 21.5 nm (β-component), and 25.7 nm (γ-component), consistent with previous studies of thermal denaturation by light scattering. It is also concluded, based on volume calculations, that a large volume increase occurs when the triple helix unfolds. Homodyne correlation functions for two component mixtures of α-chains and β-and γ-components appeared to decay exponentially. In all but one case discussed the correlation function could be fitted with a single component having a translational diffusion coefficient which was an intensity weighted average of the diffusion coefficient of each component present.
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  • 64
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    Biopolymers 20 (1981), S. 387-397 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichroic spectra and oscillator strengths of the π-π transition near 190 nm are calculated for helical (Gly)6 and (Ala)6 at 30° intervals of the backbone torsion angles (φ,ψ) over the range -180° ≤ φ ≤ -60°, -60° ≤ ψ ≤ 180°, using the partially dispersive normal mode treatment of the dipole interaction model. Polarizabilities of atoms and the NC′O group are those determined semiempirically in previous studies. Calculations for (Ala)6 at (φ,ψ) angles corresponding to the α-helix, the poly(Pro) II helix, a collagen single helix, a poly-(MeAla) helix, and single β-helices are found to agree well with most of the available experimental data.
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  • 65
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of the fluorinated antimalarial drug fluoroquine [7-fluoro-4-(diethyl-amino-1-methylbutylamino)quinoline] with DNA, tRNA, and poly(A) has been investigated by optical absorption, fluorescence, and 19F-nmr chemical-shift and relaxation methods. Optical absorption and fluorescence experiments indicate that fluoroquine binds to nucleic acids in a similar manner to that of its well-known analog chloroquine. At low drug-to-base pair ratios, binding of both drugs appears to be random. Fluoroquine and chloroquine also elevate the melting temperature (Tm) of DNA to a comparable extent. Binding of fluoroquine to DNA, tRNA, or poly(A) results in a downfield shift of about 1.5 ppm for the 19F-nmr resonance. The chemical shift of free fluoroquine depends on the isotopic composition of the solvent (D2O vs H2O). The solvent isotope shift is virtually eliminated by fluoroquine binding to any one of the nucleic acids. 19F-nmr relaxation experiments were carried out to measure the spin-lattice relaxation time (T1), 19F{1H} nuclear Overhauser effect (NOE), off-resonance intensity ratio (R), off-resonance rotating-frame spin-lattice relaxation time (T1ρoff), and linewidth for fluoroquine in the nucleic acid complexes. By accounting for intramolecular proton-fluorine dipolar and chemical-shift anisotropy contributions to the fluorine relaxation, all of the relaxation parameters for the fluoroquine-DNA complex can be well described by a motional model incorporating long-range DNA bending on the order of a microsecond and an internal motion of the drug on the order of a nanosecond. Selective NOE experiments indicate that the fluorine in the drug is near the ribose protons in the RNA complexes, but not in the DNA complex. Details of the binding evidently differ for the two types of nucleic acids. This study provides the foundation for an investigation of fluoroquine in intact cells.
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  • 66
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    Biopolymers 20 (1981), S. 345-357 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In carbonate buffer at pH 10.5, a transparent solution of poly(L-lysine HBr) was obtained up to fairly high concentration of 3 g/dl at room temperature. The hydrodynamic behavior of the solution has been studied by sedimentation analyses and viscosity measurements. A dimer form for high concentrations and a monomer form for low concentrations were inferred. The dimer and monomer forms were assigned to a β-structure and α-helix, respectively, based on the CD and optical rotary dispersion spectra. Using CD spectroscopy, a reversible transition between α-helix and β-structure was observed as a function of either poly(L-lysine HBr) concentration or temperature. An aggregated form which was assigned to the antiparallel pleated sheet appeared at 50°C on the basis of its ir spectrum.
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  • 67
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    Biopolymers 20 (1981), S. 707-718 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Observations of induced circular dichroism (CD) bands in chloroform solution demonstrate the formation of specific, asymmetric complexes of the aromatic ligands 2-pyridone and 2,6-dichlorobenzoic acid with cyclic dipeptides of the general formula cyclo(L-Pro-X). The induced CD changes sign with the configuration of X due to subtle influences of the side chain on the geometry of the complex. Computations of interaction energies suggest that a plausible model for the complex of an aromatic ligand with the -CONH- of the cis secondary amide is a nearly planar arrangement of six heavy atoms in a ring containing two hydrogen bonds. The observed CD is matched by that computed for a tilt of the aromatic ligand toward the side chain of X. Binding constants were determined from the induced CD as a function of ligand concentration. For dichlorobenzoic acid these are about 450m-1 for the secondary amide and 50m-1 for the tertiary amide. For pyridone the binding constant is about 45m-1 for either the secondary or tertiary amide. For comparison self-dimerization constants determined by vapor-pressure osmometry in chloroform solution at 25°C are 870, 350, 50, and 20m-1 for pyridone, benzoic acid, dichlorobenzoic acid, and cyclo(L-Pro-Gly), respectively.
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  • 68
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    Biopolymers 20 (1981), S. 803-816 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton and phosphorus nmr have been used to investigate the double-helical structures of polyriboadenylic acid [poly(A)] formed in acidic solutions (pH 〈 6). The results obtained at low pH (∼4.5) are consistent with the model for the acid poly(A) double helix proposed by Rich [Rich, A., Davies, D. R., Crick, F. H. C. & Watson, J. D. (1961) J. Mol. Biol. 3, 71-86]. Other models that have been proposed are inconsistent with the nmr data. The nmr measurements have also been used to examine the conformation of poly(A) helix in the half-protonated state. Although the base-stacking arrangement of this state is similar to that observed in the more extensively protonated low-pH state, the phosphate backbone conformation is different from that found in either the neutral or low-pH structures.
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  • 69
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    Biopolymers 20 (1981) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 70
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    Biopolymers 20 (1981), S. 39-51 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the effects of some organic cosolvents (monohydric alcohols and amides) on the reaction of hemoglobin with oxygen. We present evidence showing that our data can be analyzed within the framework of the Monod-Wyman-Changeux model and that the main effect of cosolvents is to alter the T ⇄ R conformational equilibrium of hemoglobin, without significantly affecting the intrinsic oxygen dissociation constants. Following a previously described phenomenological approach, the overall effects have been separated into effects related to the variation of the bulk dielectric constant of the solvent and effects not related to the variation of this constant.
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  • 71
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    Biopolymers 20 (1981), S. 65-88 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The spectroscopic properties (uv, CD, nmr) of histidine, glycylhistidine, histidylglycine, glycylhistidylglycine have been investigated in water and methanol in the temperature range 200-320 K in order to obtain information about their conformational equilibria. This analysis has been carried out for the different ionic forms of the compounds, in order to evaluate the influence of the ionization state of the carboxyl, histidyl, and amino groups on the rotamer distribution of the histidyl side chain (as evaluated from proton nmr analysis) and on the overall molecule (as judged from CD spectra). On the basis of certain approximations and from the temperature dependence of the proton nmr resonance, the thermodynamic parameters (ΔH° and ΔS°) characterizing the conformational equilibrium of the hystidyl side chain have been evaluated for the different structures and ionization states. Relatively large entropy differences between the rotamers are obtained in some cases. The data of the sidechain rotamer population, as determined by nmr, have been analytically correlated with the CD data, and in the case of hystidine and histidylglycine in basic solution, first-approximation values for the ellipticity of the single conformers have been evaluated. Finally, in the example of glycylhistidine and histidylglycine in basic solution, it is shown how the data obtained from the different experimental approaches (nmr and CD), as well as from theoretical energy calculations, converge to characterize the most stable conformation in solution.
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  • 72
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photon-correlation spectroscopy is a powerful technique for measuring the translational diffusion coefficient of particles and macromolecules in solution. In the study described here, this technique was used to analyze a specific dimerization process involving the association of two tRNA molecules through complementary anticodons. The tRNAs used in the analysis were E. coli tRNA2Glu and yeast tRNAPhe. The experimental data on the concentration dependence of the observed diffusion constants are shown to agree well with theoretical predictions. From these data, the equilibrium constant of the association reaction was determined for dimers formed over a wide range of temperatures and in several different solution conditions. In solutions of 0.1M ionic strength at 22°C, the equilibrium constants vary from 1 × 105M-1 in the absence of magnesium to 1.5 × 106M-1 in 10 mM Mg+2. The enthalpy and entropy changes for dimer formation in the absence and presence, 5 and 10 mM, of magnesium have been obtained from the temperature dependence of the equilibrium constant. The results show that both ΔH and ΔS contribute to the free energy of binding and that their relative contributions are similar for each solution condition evaluated.
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  • 73
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    Biopolymers 20 (1981), S. 231-235 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 74
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    Biopolymers 20 (1981), S. 237-240 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 75
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    Biopolymers 20 (1981), S. 243-247 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 76
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A conformational quantum-mechanical study of (Gly-Phe-Pro) and (Gly-Pro-Phe) repeating tripeptide sequences has been carried out with the PCILO method. Using appropriate molecules as a model, we investigated the conformational possibilities of each in situ residue. Computations have been done taking into account the two typical pyrrolidine ring puckering and the most favorable orientations of the phenylalanyl side chain. Major conclusions drawn from this study are that the phenylalanyl can be accommodated at both second and third positions in the sequence without preventing the formation of triple-helix conformation. However, the analogy observed between the rotational possibilities around the second residue of Gly-Pro-Pro and Gly-Phe-Pro indicates that phenylalanyl in the second position favors the triple-helix formation.
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  • 77
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    Biopolymers 20 (1981), S. 327-343 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of the nucleosome core particle in solution has been studied by neutron scattering using the full-contrast variation technique, which reduces the experimental spectra to three fundamental scatter functions holding information on shape and structure. Systematic calculations of the fundamental scatter functions expected from proposed core-particle models have been compared with the observed functions and show that the neutron-scattering criteria severely restrict the number of models which can be valid for the structure in solution. The best model for the core particle in solution has a hydrophobic histone core about which 1.7 ± 0.1 turns of DNA are wrapped at a pitch between 3.0 and 3.5 nm. This core contains most of the histone and has an average thickness of 4 nm and diameter 6.4-7.5 nm. While solution scattering is not able to specify uniquely the actual shape of the core to high resolution, all models which are possible for the shape of the core to a resolution justified by the data have been considered. It is clear that cylindrical or wedge shapes compatible with the above dimensions are valid structures. A hole probably penetrates the histone core, but the data do not allow a diameter greater than 1 nm. Available evidence suggests that about a quarter of the total histone is outside the core.
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  • 78
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relationship between published vicinal proton-proton coupling constants and the pseudorotation properties of the pyrrolidine ring in L-proline, 4-hydroxy-L-proline, 4-fluoro-L-proline, and several linear and cyclic model proline peptides is investigated. Compared to earlier studies, several important improvements are incorporated: (1) a new empirical generalization of the classical Karplus equation is utilized, which allows a valid correction for the effects of electronegativity and orientation of substitutents on 3JHH; (2) an empirical correlation between proton-proton torsion angles and the pseudorotational parameters P and τm is derived; and (3) the best fit of the conformational parameters to the experimental coupling constants is obtained by means of a computerized iterative least-squares procedure. Two pseudorotation ranges were considered, classified as type N (χ2 positive sign) and type S (χ2 negative sign). The conformational equilibrium is fully described in terms of four geometrical parameters (PN, τN, PS, τS) and the equilibrium constant K. The present results indicate that, in general, the geometrical properties found in x-ray studies of proline and hydroxyproline residues are well preserved in solution. Several novel features are encountered, however. It is demonstrated that the proline ring occurs in a practically 1:1 conformational equilibrium between well-defined N- and S-type forms. Introduction of an amide group at the C-terminal end has no observable effect on this equilibrium, but the formation of a peptide bond at the imino nitrogen site results in a pronounced, but not exclusive, preference for an S-type form which is roughly 1.1 kcal/mol more stable than its N-type counterpart. The hydroxyproline ring system in neutral or acidic medium displays a pure N-type state, but N-acetylation results in the appearance of a minor (S-type) conformation. Cyclic proline dipeptides similarly exist in a biased conformational equilibrium. The major form (77-88%) corresponds to the N-type conformer observed in the solid state; the minor S-form has not been observed before. In contrast, cyclic hydroxyproline dipeptides display complete conformational purity. Ranges of endocyclic torsion angles deduced for the various classes of pyrrolidine derivatives in solution are presented. Each torsion appears confined to a surprisingly narrow range, comprising about 4°-8° in most cases. In all, the proline ring is far less “floppy” than hitherto assumed.
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  • 79
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurement of the equilibrium distribution of persistence length fragments of DNA in high concentration in the ultracentrifuge shows that the reduced osmotic pressure rises much faster than linearly. From analysis of the data in terms of the Zimm cluster integral we infer that the net interactions between helices are purely repulsive at all distances. A theoretical equation of state derived from scaled particle theory with one adjustable parameter is in excellent agreement with the experimental data so long as the salt concentration is not excessively low. The parameter represents the hard-core radius in a simplified approximation to the potential function for the electrostatic repulsion between helices. Its value depends on the salt concentration, and it shrinks at high salt to a radius in close agreement with direct structural estimates. At a particular value of the osmotic pressure that is only slightly salt dependent, the solution undergoes a reversible transition to a denser, turbid, optically anisotropic phase. The relation between DNA volume fraction, including the electrostatic radius, at the transition point and the effective asymmetry of the molecules as a function of salt is in approximate correspondence with various theoretical treatments. However, the experimental function extrapolates to the correct limit for spherical particles. The work needed to bring DNA to a high concentration is estimated. The results suggest that the phase transition is first order.
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  • 80
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    Biopolymers 20 (1981), S. 2121-2136 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This report presents a quantitative test of the ability of the counterion condensation theory to describe the proton-induced lowering of DNA melting temperature. From a general approach of Record et al. [Record, M. T., Anderson, C. F. & Lohman, T. H. (1978) Q. Rev. Biophys. 11, 103-178], we have obtained an expression that may be computer-fitted to the experimental data by numerical minimization of χ2. To do this, in addition to the assumptions made by Record et al., it was necessary to suppose that the interchange between protons and sodium is independent of pH and, due to the absence of data, take the enthalpies of protonation as thermally independent over the experimental temperature range. The dependences of the enthalpy of denaturation at neutral pH on sodium concentration and on G + C content were taken from literature. In the fitting process we have used 250 melting temperatures obtained at different pH and sodium concentrations for various natural DNAs. The theoretical expression gives a good quantitative description of the G + C and sodium concentration influences on the phenomenon but is only qualitative with respect to the dependence of dT/d log[Na+] on the pH. The adjusted pK values for the bases in denatured DNA agree with those for isolated deoxynucleosides. Interchange between sodium and protons is found to be less than 1:1. Calculated protonation enthalpies are ill-defined because of their low numerical influence. In short, it appears that the theory gives a good description of most of the aspects of the phenomenon even if it has some shortcomings, perhaps due to the great number of assumptions.
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  • 81
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    Biopolymers 20 (1981), S. 2137-2142 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the kinetics of replacement of O2 by CO in hemoglobin in the presence and absence of organic cosolvents (methanol, ethanol, iso-propanol, n-propanol, formamide, acetamide, N-methyl-formamide) and at 10 and 25°C. Quantitative analysis of the results indicates that these cosolvents do not affect the intrinsic binding constants of ligands to the heme when hemoglobin is in the R conformation. The present results confirm the previously reported suggestion that the effects of the above cosolvents on the oxygen affinity of hemoglobin are related to effects on the T ⇄ R conformational equilibrium.
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  • 82
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    Biopolymers 20 (1981), S. 2195-2202 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparations have been made of acid-soluble collagens whose telopeptides have suffered different levels of proteolytic attack. The collagens with more intact telopeptides form fibrils more rapidly than those with degraded telopeptides. In addition, we have shown that a high molecular weight aggregate rich in the carboxyterminal CNBr peptide, α1CB6, can be found in cyanogen bromide digests of fibrils formed from intact collagen. A similar aggregate is found in CNBr digests of native tendons. The aggregate formed in fibrils assembled in vitro can be stabilized by reduction, and its generation is strongly dependent on the presence of intact telopeptides. The latter point is the most objective evidence that to reproduce the characteristics of native fibrils in vitro, the collagen telopeptides must be preserved from proteolysis.
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  • 83
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    Biopolymers 20 (1981), S. 2225-2241 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present an alternative to the common lattice model for nonspecific DNA-protein interactions by using ligands that translate freely along the polynucleotide instead of binding to distinct lattice sites along the polynucleotide chain. The general model we present corresponds to a one-dimensional continuum gas and is referred to as the “continuum model” to distinguish it from the general lattice model. Explicit expressions are obtained for the binding isotherm equation for two version of the continuum model, including the effects of binding-site exclusion and attractions between bound ligands. Theoretical results are compared to those obtained from the McGhee-von Hippel (1974) analysis of the lattice model with cooperative interactions between ligands occupying more than one lattice site. Practical applications of the continuum model are illustrated by analyzing (i) the noncooperative binding to single-stranded DNA by RNase (Jensen and von Hippel, 1976), and (ii) the highly cooperative binding to poly(rA) by a proteolyzed fragment of the gene 32 protein of phage T4 (Lonberg et al., 1981).
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  • 84
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of water and its interaction energy with a fragment of B-DNA composed of 12 base pairs and of the corresponding 24 sugar and 22 phosphate units and Na+ ions (one at each phosphate group) are analyzed using Monte Carlo simulations. The sample of water molecules, at the simulated temperature of 300 K, is composed of 447 water molecules. The results are discussed either in terms of statistical analyses over the 2,000,000 simulated conformations (after equilibration) or with reference to an “average configuration.” Comparison is made to a simulation previously presented for the same system but without counterions. Isotherm at different relative humidity, hydration, and reactivity scales for different sites, the hydration number at each site, the structure of intraphosphate and interphosphate hydrogen-bonded filaments of water are reported and discussed. The stabilization of the B-conformation induced by the solvent with counterion (“ion-induced compression effect”) is analyzed on the base of the above findings. A preliminary model to predict conformational transition in DNA is presented. The analyses reported are very detailed to allow refined interpretations of spectroscopic (infrared, Raman, and nmr) and scattering (x-ray and neutron beam) data on DNA insolution.
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  • 85
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational response of calf thymus DNA to solvent conditions altered by varying amounts of ethanol and NaCl has been monitored by circular dichroism (CD). These measurements, which extend over a much greater range of conditions than previously examined, reveal (above critical concentrations of ethanol and salt) a condensed form of the macro-molecule with unusually large positive ellipticity in the 250-300-nm region [the Ψ(+) state]. Mere increase in NaCl concentration at constant 35% (v/v) concentration of ethanol suffices to convert such Ψ(+) samples - via a series of intermediate forms with CD spectra resembling those of A-DNA, then B-DNA - into Ψ(-) states having anomalously large negative ellipticity similar to the well-known Ψ(-) forms produced by above-critical concentrations of poly-(ethylene oxide) and salt. These ethanol/salt-induced transitions are all completely reversible and can occur without formation of any visible precipitates. We suggest that they represent predominantly tertiary structural changes of B-form DNA molecules analogous to the changes which occur in several other systems where Ψ(+) ⇌ Ψ(-) interconversion has been reported. A “skein-of-yarn” model for the condensed tertiary (and quaternary, i.e., aggregated) state of the DNA affords one possible explanation for the inversions of ellipticity in all these cases. Such a model accords well with the accepted description of cholesteric liquid crystals.
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  • 86
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    Biopolymers 20 (1981), S. 2623-2633 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H-Nmr was used to measure the rate of cis-trans interconversion of X-Pro bonds in linear and cyclic oligopeptides. k(cis → trans) = 2.5 × 10-3 s-1 at 25°C was found for the zwitterionic form of H-Ala-Pro-OH, in good agreement with earlier measurements. Replacement of Ala by Phe, Tyr, or Trp resulted in a 10-fold slower interconversion rate, whereas after substitution of Ala by His or Glu, the rate decreased only slightly. Independent of the residues X, the interconversion rate was increased by a factor of ca. 20 when the peptide chain was elongated by addition of Ala to the C-terminal Pro. An additional increase by a factor of 6 was observed when going from the protected linear peptide CF3CO-Gly-Gly-Pro-Ala-OCH3 to the closely related cyclic compound c[-Gly-Gly-Pro-Gly-Ala-]. These data are evaluated with regard to their possible use in future studies on the role of X-Pro cis-trans isomerization in the kinetics of protein folding.
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  • 87
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As a model compound for the growing chain in the activated-NCA type of polymerization of α-amino acid N-carboxyanhydride (NCA), 3-[ω-acetylglycyl-poly(α-amino acid) acyl]-α-amino acid NCA (called the prepolymer) having various degrees of polymerization (DPs) was synthesized by the polymerization of Phe, Val, Glu(OEt), and Asp(OBzl) NCA in the presence of AcGly NCA by the tertiary amine. Activated (S)-Phe, Val, Glu(OEt), and Asp(OBzl) NCA were added to the terminal cyclic group of the corresponding (S)- or (R)- prepolymer, and the enantiomer selectivity in the reaction was investigated. With prepolymers having DPs ranging from 1 to 15, the addition reaction always took place preferentially between species having the same configuration, and the degree of the enantiomer selection increased with increasing DP of the prepolymer. With prepolymers having DP = 1 and 2, we found contributions from the chiral terminal unit and the chiral penultimate unit to the enantiomer selection, respectively. Prepolymer having DP = 5 was shown to take a β-type conformation, which led to higher enantiomer selection; and prepolymers having DP = 10 and 15 were shown to take an α-helix conformation, which led to much higher enantiomer selection than did the β-type conformation. In the present investigation the mechanisms of terminal-unit control, penultimate-unit control and conformational control of the enantiomer selection in the activated-NCA type of polymerization were clearly observed.
    Additional Material: 7 Ill.
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  • 88
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The helix-coil transition and conformational structure of poly(8-bromoadenylic acid) [poly(8BrA)] have been investigated using 1H- and 13C-nmr, CD, and ir spectroscopy. The results have been compared with the structure of the related 5′-mono- and polynucleotides. The chemical shifts of H(2′), H(3′), C(2′), and C(3′) nmr signals show an interesting correlation with both the puckering of ribose ring and glycosidic bond torsion angle. Poly(8BrA) shows an upfield shift of the C(3′) signal and a downfield shift of the H(3′) signal compared to the chemical shifts in poly(A). These shifts are consistent with a C(3′) endo-syn conformation for poly(8BrA). A similar effect has been reported previously and is also observed here on the C(2′) and H(2′) signals when the preferred conformation is C(2′)endo-syn (e.g., in 5′-8BrAMP). The chemical-shift parameters thus act as a probe for studying syn ⇄ anti and N ⇄ S equilibria in solutions. The three-bond 1H-′13C coupling constants between H(1′) and C(8) and C(4) have been measured in poly(8BrA) and 5′-8BrAMP and their structural implications have been discussed. The observed preference of a C(3′)endo-syn conformation for poly(8BrA), coupled with other evidence, throws doubt on the validity of a correlation previously reported whereby a syn conformation is associated with a C(2′)endo ribose pucker. The backbone conformation of randomly coiled poly(8BrA) is very similar to the structures found in polyribonucleotides: poly(A) and poly(U). All three polymers show strong preferences for the backbone angles found in RNA helices. The CD spectrum of poly(8BrA) has a striking relationship to that of poly(A). The signs of all extrema are inverted, and the magnitudes are related by a constant factor. We suggest that these differences result from a change in the angle between coupled transition moment vectors in the two polymers. Infrared spectra of poly(8BrA) in H2O and D2O solution are reported for the frequency range below 1400 cm-1. The antisymmetric 〉PO2- stretching vibration is observed at an unusually low frequency in the helix (1214 cm-1). The symmetric 〉PO2- stretch occurs at ∼1095 cm-1 but is not resolved from a ring vibration near this frequency. A conformationally sensitive band, characteristic of helical RNA structures, is observed at 817 cm-1 and disappears when the helix is melted. This observation confirms the conclusion that ordered poly(8BrA) has a regular helical structure with an RNA backbone conformation. A stereochemical explanation is provided for the failure of poly(8BrA) (or other syn polymers) to form double helices with anti-polyribonucleotides.
    Additional Material: 11 Ill.
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  • 89
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    Biopolymers 20 (1981), S. 1103-1112 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The arginine and lysine residues of calf thymus histone H1 were modified with large molar excesses of 2,3-butanedione and O-methylisourea, respectively. Kinetic study of the modification reaction of the arginine residue revealed that the reaction is divided into the two pseudo-first-order processes. About a third (1 Arg) of the total arginine residues of the H1 molecule was rapidly modified without causing any detectable structural change of the molecule, and the slow modification of the remaining arginine residues (2 Arg) led to a loss of the folded structure of H1. In the case of lysine residue modification, 93% (56 Lys) of the total lysine residues of the H1 was modified with the same rate constant, while 7% (4 Lys) of lysine residue remained unmodified. When the reaction was performed in the presence of 6M guanidine-HCl, all of lysine residues were modified. It is concluded that the 2 arginine and 4 lysine residues resistant to modification are buried in interior regions of the H1 molecule and play an important role in the formation of the H1 globular structure, while the other 1 arginine and 56 lysine residues are exposed to solvent.
    Additional Material: 5 Ill.
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  • 90
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    Biopolymers 20 (1981), S. 1191-1209 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molar Kerr constants mK, molar refractions mR, and dipole moments μ are reported for the N-methylacetamides CX3CONHCH3 (X = H, CH3, F. CI, Br) and acetamides CX3CONH2 (X = H, F, Cl, Br). The components of the polarizability tensor α are deduced for N-methylacetamide and acetamide on the basis of the bond additivity approximation. This α is found to be considerably more anisotropic than was indicated in previous determinations by other methods. The data for N-methylacetamide were used to calculate mK, μ, and γ2 (anisotropy squared) of N-acetyl-N′-methylglycine amide and N-acetyl-N′-methyl-alanine amide as functions of the torsional angles (φ,Ψ). The statistical mechanical averages of mK, μ, and γ2 were calculated from conformational energies obtained by the methods of Scheraga.
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  • 91
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    Biopolymers 20 (1981), S. 1247-1260 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The physical properties of single, 5-8-μm diameter, water-swollen elastin fibers have been investigated on a microtest apparatus attached to a polarizing microscope. Analysis of the mechanical and optical properties at extensions below 100% indicate that the elastic modulus (G) has a value of 4.1 × 105 N m-2, the average molecular weight of chains between crosslinks is in the range of 6000-7100, and the stress optical coefficient (C′) is 1 × 10-9 m2 N-1 at 24°C. Analysis of the temperature dependence of the stress optical coefficient indicates that the polarizability of the random link decreases with increasing temperature, with an apparent activation energy for this process of the order of 1.6 kcal/mol. Analysis of the non-Gaussian mechanical and optical properties at extensions above about 100% suggest that the chains between crosslinks contain approximately 10 “effective” random links, with each link consisting of 7-8 amino acid residues. These parameters for the random chains in the elastin network have been used to predict the dimensions of other random proteins. The close correlation of these predictions with published values for the dimensions of a series of proteins in solution in 6M guanidinium hydrochloride provides an independent test of the appropriateness of our analysis.
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  • 92
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    Biopolymers 20 (1981), S. 1333-1335 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 93
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    Biopolymers 20 (1981), S. 1399-1411 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heavy meromyosin binding to F-actin saturated with tropomyosin is studied theoretically. The problem is formulated as a special case of n-mer adsorption to a one-dimensional Ising lattice which is divided into m-site-long blocks.
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  • 94
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    Biopolymers 20 (1981), S. 1481-1502 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Monte Carlo analysis is presented which establishes a relationship between the rotational diffusion coefficients and the flexibility (persistence length, P) of short, wormlike chains. The results of this analysis are presented in terms of experimentally observable quantities; namely, the rotational relaxation times for the field-free decay of optical anisotropy. The pertinent theoretical quantity is R, defined as the ratio of the longest rotational relaxation time of a wormlike chain to the transverse rotational relaxation time of a rigid cylinder having the same axial length (L) and segmental volume. R, so defined, is essentially independent of the axial ratio of the cylinder for any value of L/P within the range of validity of the present analysis (axial ratio 〉 20; 0.1 〈 L/P 〈 5). It is pointed out that P can be determined with reasonable accuracy even in the absence of a precise knowledge of the local hydrodynamic radius of the chain.
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  • 95
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    Biopolymers 20 (1981), S. 1537-1547 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvents which accelerate DNA renaturation rates have been investigated. Addition of NaCl or LiCl to DNA in 2.4M Et4NCl initially increases renaturation rates at 45°C and then leads to a loss of second-order behavior. The greatest accelerations are seen with LiCl and dilute DNA. Volume exclusion by dextran sulfate is the most effective method of accelerating DNA renaturation with concentrated DNA. Addition of dextran sulfate beyond 10-12% in 2.4M Et4NCl fails to increase the acceleration beyond approximately 10-fold. Accelerations of 100-fold may be achieved with 35-40% dextran sulfate in 1M NaCl at 70°C. No other mixed solvent system was found to be more effective, although acceleration may be achieved in solvents containing formamide or other denaturants. The acceleration in 2M NaCl occurs without loss of the normal concentration and temperature dependence of DNA renaturation and is also independent of dextran sulfate concentration if sufficient dextran sulfate is used. Dextran sulfate may be selectively precipitated by use of 1M CsCl.
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  • 96
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    Biopolymers 20 (1981), S. 1503-1535 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the preceding article, a Monte Carlo analysis was presented which provides a quantitative numerical relationship between the rotational diffusion coefficients, as measured by the decay of optical anisotropy following an electric field pulse, and the flexibility (persistence length) of short, wormlike chains. In the present article, the results of the foregoing analysis are applied to the observed rates of decay of birefringence for a series of sequenced DNA fragments ranging in size from 104 to 910 base pairs. Under the conditions used in this study, the DNA fragments exist as native, duplex molecules. Furthermore, conditions are defined in which the observed relaxation times are not dependent on DNA concentration, field strength, or the duration of the pulse. It is pointed out that the ionic atmosphere associated with a wormlike polyion does not exert any significant (direct) influence on the rotational diffusion of the polyion and, therefore, that the rotational relaxation times are a true measure of the configurations of the DNA molecules in solution. Moreover, excluded-volume effects are shown not to be significant for the moderately short molecules employed in this study. The major conclusion of this study is that there is no strong ionic strength dependence of the persistence length for ionic strengths above 1 mM and that the persistence length, under conditions where electrostatic contributions are negligible, is approximately 500 Å. For ionic strengths significantly lower than 1 mM, electrostatic contributions to the stiffness of DNA become significant.
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  • 97
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    Biopolymers 20 (1981), S. 1575-1588 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aqueous and hydroalcoholic solutions of the heptenic macrolide amphotericin B display strong and variable signals in CD and absorption spectroscopies in the range of the π* ← π transition. An interpretation of the spectroscopic changes is proposed based on the equilibrium between two forms of the intermolecular organization: the aggregated one (A) with strong excitonic interaction and the nonaggregative one (B) whose spectra are like those of linear conjugated polyenes in true solution with a well-developed vibrational structure. The intermediate spectra are fitted by linear combination of the A- and B-form spectra. A two-level organization of the aggregates is proposed for the A-form: (1) a close packing of few molecules, which is the origin of the absorption maxima hypsochromic shift; and (2) interaction between the preceding small units inside the aggregates, which is spectroscopically expressed by the intense CD couplet.
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  • 98
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    Biopolymers 20 (1981), S. 1625-1633 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polypeptides of dicarboxylic amino acids having the monomer units linked in α- and ω-peptide bonds contain two kinds of carboxyls of different acidity. How well potentiometric titration can distinguish these two carboxyls and so characterize the nature of the peptide bonds is evaluated critically. An analysis of the equation describing the dependence of pH on the degree of neutralization based on neglecting the polymer effect and a discussion of the dissociation behavior of polyanions show that the method of evaluating experimental data found in the literature is incorrect. Nevertheless, if a conformational transition does not interfere, some useful and reliable information may be gained by this method; namely, an indication of the presence of two different peptide bonds, their mole ratio, and an approximate pK value for the carboxyl of the amino acid linked in the ω-peptide bond. The presence of two types of carboxyls complicates the evaluation of the titration curves in the conformation studies.
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  • 99
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    Biopolymers 20 (1981), S. 1707-1725 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational analysis of antiparallel double-helical polynucleotides with Watson-Crick base pairing was reduced to a four-dimensional problem using original mathematical methods. In the four-dimensional conformational space the family of structures, characterized by the base-pair stacking with the most stable conformations in water solution as well as in the solid state, was localized. For the C′2-endo sugar pucker, both right-handed and left-handed structures were found; right-handed structures only, however, seem to be allowed for the C′3-endo pucker, the only possible one for ribonucleotides with base stacking.
    Additional Material: 7 Ill.
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  • 100
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Angiotensin II and its competitive inhibitor [Sar1, Ile8]-angiotensin II, as well as several analogs of these two compounds specifically chosen for their well-defined pharmacological properties, were studied by circular dichroism and nuclear magnetic resonance methods at various pH values in aqueous solution and in d6-dimethylsulfoxide. The results were compared with their biological activities. This allowed us to establish relationships between conformation and pressor activity, explaining most of the properties of angiotensin II, its inhibitor, and the analogs successively substituted in positions 3 and 5.
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