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  • 1980-1984  (3.128)
  • 1975-1979
  • 1981  (3.128)
  • Polymer and Materials Science  (3.049)
  • Electron microscopy
  • Nuclear reactions
Materialart
Erscheinungszeitraum
  • 1980-1984  (3.128)
  • 1975-1979
Jahr
  • 1
    ISSN: 1432-2307
    Schlagwort(e): Microfold (membraneous) cells ; Tuft cells ; Electron microscopy ; Horseradish peroxidase ; Sequential uptake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1432-2307
    Schlagwort(e): Electron microscopy ; Effect of various GAG on fibril formation in vitro ; Collagen structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 391 (1981), S. 107-115 
    ISSN: 1432-2307
    Schlagwort(e): Hemangioendothelioma ; Esophagus ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-5233
    Schlagwort(e): Electron microscopy ; Glibenclamide ; Glucose oxidation ; Insulin biosynthesis ; Insulin secretion ; Islets of Langerhans ; Mitochondria ; Morphometry ; Tissue culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 391 (1981), S. 189-205 
    ISSN: 1432-2307
    Schlagwort(e): Crohn's disease ; Electron microscopy ; Ultracytochemistry ; Immunohistology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 392 (1981), S. 231-239 
    ISSN: 1432-2307
    Schlagwort(e): Bronchial gland adenoma ; Oncocytoma ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-2307
    Schlagwort(e): Endocrine tumour ; Pancreas ; Argentaffin reaction ; Immunocytochemistry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-2307
    Schlagwort(e): Labial salivary gland biopsy ; Gougerot-Sjögren's syndrome ; Clinico-pathology ; Histoenzymology ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 394 (1981), S. 31-47 
    ISSN: 1432-2307
    Schlagwort(e): Blood vessel neoplasms ; Electron microscopy ; Histochemistry ; Angiosarcoma ; Breast neoplasms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 390 (1981), S. 11-21 
    ISSN: 1432-2307
    Schlagwort(e): Electron microscopy ; Bladder neoplasms ; Measurement
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 11
    ISSN: 1432-2307
    Schlagwort(e): Liver biopsy ; Renal transplant recipients ; HBs and HBc Ag ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 391 (1981), S. 165-175 
    ISSN: 1432-2307
    Schlagwort(e): Dermatofibrosarcoma protuberans ; Tissue culture ; Electron microscopy ; Fibroblasts ; Fibrosarcoma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 392 (1981), S. 135-145 
    ISSN: 1432-2307
    Schlagwort(e): Malignant fibrous histiocytoma ; Sarcoma ; Soft tissue neoplasms ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of neurology 225 (1981), S. 67-72 
    ISSN: 1432-1459
    Schlagwort(e): Ewing sarcoma ; Epidural tumors ; Spinal cord compression ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 33 (1981), S. 119-124 
    ISSN: 1432-0827
    Schlagwort(e): Avian eggshell ; Microstructure ; Electron microscopy ; Electron diffraction ; Calcite growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 33 (1981), S. 143-151 
    ISSN: 1432-0827
    Schlagwort(e): Calcium transport ; Cytochalasin B ; Dihydrocytochalasin B ; Colchicine ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 33 (1981), S. 381-384 
    ISSN: 1432-0827
    Schlagwort(e): Alcohol ; Electron microscopy ; Growth plate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 33 (1981), S. 529-540 
    ISSN: 1432-0827
    Schlagwort(e): Bone cells ; Electron microscopy ; PTH ; PGE1
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 161 (1981), S. 433-451 
    ISSN: 1432-0568
    Schlagwort(e): Rhombencephalon, rat ; Subependymal cysts ; Morphogenesis ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 53 (1981), S. 165-168 
    ISSN: 1432-0533
    Schlagwort(e): Lewy body ; Neurofibrillary tangle ; Locus ceruleus ; Aged brain ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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).
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 53 (1981), S. 237-248 
    ISSN: 1432-0533
    Schlagwort(e): Thyroxine effect on muscle ; Histochemistry ; Immunopathology ; Electron microscopy ; Diagnostic muscle pathology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 54 (1981), S. 43-53 
    ISSN: 1432-0533
    Schlagwort(e): Uremia ; Kidney transplantation ; Polyneuropathy ; Light microscopy ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 54 (1981), S. 203-210 
    ISSN: 1432-0533
    Schlagwort(e): Retina ; Schwann cell ; Myelinated nerve fibers ; Nodes of Ranvier ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 54 (1981), S. 233-237 
    ISSN: 1432-0533
    Schlagwort(e): Methylmercury ; Mice ; Golgi methods ; Electron microscopy ; Dendrites ; Purkinje cells ; Perivascular glia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 54 (1981), S. 287-292 
    ISSN: 1432-0533
    Schlagwort(e): Mucopolysaccharidoses III ; Sanfilippo's syndrome ; Histochemistry ; Electron microscopy ; Lipofuscin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 55 (1981), S. 77-80 
    ISSN: 1432-0533
    Schlagwort(e): Esthesioneuroepithelioma ; Olfactory neuroblastoma ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 55 (1981), S. 81-87 
    ISSN: 1432-0533
    Schlagwort(e): Canine CNS ; Myelination ; Hypomyelinogenesis ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 55 (1981), S. 89-95 
    ISSN: 1432-0533
    Schlagwort(e): Electron microscopy ; Morphometry ; Sorbitol pathway ; Diabetes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 55 (1981), S. 143-149 
    ISSN: 1432-0533
    Schlagwort(e): Pineal parenchymal neoplasm ; Electron microscopy ; Primitive neuroectodermal cell ; Dense core vesicles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 30
    ISSN: 1432-0533
    Schlagwort(e): Postischemic recirculation ; Complete cerebral ischemia ; Ischemic neuronal injury ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 31
    ISSN: 1432-0533
    Schlagwort(e): Immunochemistry ; Pituitary adenoma ; Electron microscopy ; Mixed eosinophilic-cromophobe ; Gonadotropin ; Thyrotropin-secretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 55 (1981), S. 307-318 
    ISSN: 1432-0533
    Schlagwort(e): Diphtheritic polyneuropathy ; Muscle biopsy ; Intramuscular nerves ; Electron microscopy ; Histochemistry ; Diphtherie-Polyneuropathie ; Muskelbiopsie ; intramuskuläre Nerven ; Elektronenmikroskopie ; Histochemie
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 129 (1981), S. 129-134 
    ISSN: 1432-072X
    Schlagwort(e): Cockroach ; Hindgut ; Distribution ; Microbial morphotypes ; Transmission ; Electron microscopy ; Statistical analysis ; Eublaberus posticus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 130 (1981), S. 339-343 
    ISSN: 1432-072X
    Schlagwort(e): Leptospira ; Halophilic ; Electron microscopy ; X-ray analysis ; Inclusions ; Cytoplasmic tubules
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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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  • 35
    ISSN: 1432-072X
    Schlagwort(e): Ribulose bisphosphate carboxylase ; Quaternary structure ; Molecular weight ; Electron microscopy ; Cyanobacteria ; Synechococcus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    European biophysics journal 7 (1981), S. 209-212 
    ISSN: 1432-1017
    Schlagwort(e): Photosynthetic bacteria ; Electron microscopy ; Planar lattices
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: 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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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Archives of toxicology 47 (1981), S. 101-111 
    ISSN: 1432-0738
    Schlagwort(e): Cerebellar cortex ; Methylmercury ; Toxicity ; Rat ; Morphometry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 130 (1981), S. 125-128 
    ISSN: 1432-072X
    Schlagwort(e): Rhodospirillum rubrum ; Chromatophores ; Reaction centers ; Liposomes ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    International archives of occupational and environmental health 48 (1981), S. 147-157 
    ISSN: 1432-1246
    Schlagwort(e): Diesel exhaust emission ; Liver ; Electron microscopy ; Freeze-fracture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 129 (1981), S. 285-294 
    ISSN: 1432-072X
    Schlagwort(e): Biological control ; Cyanobacteria ; Electron microscopy ; Entrapment ; lysis ; Myxococcus ; Phormidium ; Spherule
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 271 (1981), S. 171-182 
    ISSN: 1432-069X
    Schlagwort(e): Hypomelanotic macule ; Tuberous sclerosis ; Electron microscopy ; Hypomelanotische Macula ; tuberöse Hinrsklerose ; Elektronenmikroskopie
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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.
    Materialart: Digitale Medien
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  • 42
    ISSN: 1432-0711
    Schlagwort(e): Ovary ; FSH ; Inhibin ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Journal of cancer research and clinical oncology 100 (1981), S. 51-58 
    ISSN: 1432-1335
    Schlagwort(e): Electron microscopy ; Rat astrocytomas ; Dibutyryl cyclic AMP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Journal of neurology 224 (1981), S. 171-182 
    ISSN: 1432-1459
    Schlagwort(e): Cerebral amyloidoma ; Congo red birefringence ; IgM immunofluorescence ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 53 (1981), S. 65-74 
    ISSN: 1432-0533
    Schlagwort(e): Hexachlorophene ; Central nervous system ; Mice ; Baboons ; Electron microscopy ; Neurotoxicology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 46
    ISSN: 1432-1106
    Schlagwort(e): Cat-spinocervical tract cells ; Intracellular staining ; Electron microscopy ; Synaptic vesicles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Rheumatology international 1 (1981), S. 21-28 
    ISSN: 1437-160X
    Schlagwort(e): Rheumatoid nodules ; Polymorphonuclear granulocytes ; Electron microscopy ; Collagen degradation products
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 48
    ISSN: 1434-0879
    Schlagwort(e): Dog prostate ; Stereological analysis ; Electron microscopy ; Oestrogen effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Research in experimental medicine 178 (1981), S. 165-175 
    ISSN: 1433-8580
    Schlagwort(e): Perfused rat pancreas ; Insulin secretion ; Uric acid ; Light microscopy ; Electron microscopy ; Rattenpankreasperfusion ; Insulinsekretion ; Harnsäure ; Lichtmikroskopie ; Elektronenmikroskopie
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    European archives of oto-rhino-laryngology and head & neck 230 (1981), S. 161-170 
    ISSN: 1434-4726
    Schlagwort(e): Sudden deafness ; Vertigo ; Neurectomy ; Eighth nerve ; Light microscopy ; Electron microscopy ; Demyelinating disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    European archives of oto-rhino-laryngology and head & neck 233 (1981), S. 271-300 
    ISSN: 1434-4726
    Schlagwort(e): 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
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: 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.
    Notizen: 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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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 220 (1981), S. 555-559 
    ISSN: 1432-0878
    Schlagwort(e): Disaccharidases ; Intestinal brush-border membranes ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The intestinal disaccharidases, lactase, sucrase-isomaltase complex, and glucoamylase are proteins intimately associated with the brush-border membrane of the epithelial cell. These three enzyme activities are found in the intestine of the adult rat; lactase and glucoamylase activities are primarily associated with the intestine of the infant rat. Only glucoamylase and isomaltase activities are detected in the intestine of the California sea lion, Zalophus californianus. The activities of these enzymes are detected only in villus cells, and not in crypt cells. We have carried out electron microscopic studies of negatively stained brush-border preparations of intestinal crypt and villus cells; from the intestine of the 10-day-old rat and from that of the California sea lion. The density of the knob-like structures protruding from the brush-border membranes was not significantly different in any of these preparations. The diameter of the knobs on the preparations from crypt cells was smaller than the diameters of the knobs found on membranes prepared from the other sources. These data are discussed in terms of the relationship between the presence of knob structures and disaccharidase activities associated with the brush-border membranes.
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  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 220 (1981), S. 589-597 
    ISSN: 1432-0878
    Schlagwort(e): Tooth basement membrane ; Ruthenium red ; Tannic acid ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Ruthenium red staining and tannic acid fixation were used to analyse the fine structure of embryonic mouse dental basement membrane in intact first mandibular molars or in EDTA-isolated dental papillae. Preameloblasts are separated from extracellular matrix proper by a basal lamina that contains regularly arranged proteoglycan granules of about 10 nm in diameter. This distribution pattern is particularly evident in the inner and outer lamina rara of the basal lamina associated with EDTA-isolated dental papillae. The plasmalemma of preameloblasts demonstrates electron dense plaques on the inner leaflet. Ruthenium red positive granules (50 nm in diameter) coat non-striated and striated fibrils of the matrix. Hyaluronidase treatment digested the ruthenium red positive granules. Tannic acid fixation allowed the demonstration of filaments within the lamina rara interna, connecting the lamina densa with plasmalemma of preameloblasts. These observations are discussed in the context of the terminal differentiation of odontoblasts.
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 221 (1981), S. 245-256 
    ISSN: 1432-0878
    Schlagwort(e): Monoamines ; Fluorescence histochemistry ; Electron microscopy ; Branchiostoma lanceolatum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Three types of monoamine-containing neurones and fibres can be discriminated in the brain of the lancelet. Two types of elongated cerebrospinal fluid-contacting neurones, located in the ventral and the dorsolateral part of the brain, exhibit formaldehyde-induced catecholamine fluorescence. These neurones contain dense-core vesicles 75–100 nm in diameter. Their apical portion possesses cilia, displaying a 9×2+2 arrangement of their internal tubuli, and projecting into the ventricle. Basal processes from the ventrally situated perikarya abut upon the meninx and may discharge their catecholamines into the circulatory system. Fibres exhibiting catecholamine fluorescence originate from the dorsolaterally situated perikarya and run ventrocaudally to the neuropil, where they form numerous swellings of the bouton en passant type. A third type of perikarya in the posterior part of the brain displays specific green fluorescence. Further, neurones characterized by a specific yellow fluorescence are present in the anterior part of the brain and the anterior part of the neural tube. The rapid photodecomposition of the latter fluorophore indicates that these cells contain an indolamine.
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 221 (1981), S. 311-320 
    ISSN: 1432-0878
    Schlagwort(e): Sertoli cell (rat) ; Testis ; Vesicles ; Morphometry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Membrane-bounded spherical vesicles found in rat Sertoli cells have been examined quantitatively during the cycle of the seminiferous epithelium. Most of the vesicles were localized to the basal and columnar portions of the Sertoli cell cytoplasm. The thin lateral projections of the Sertoli cells contained very few vesicles. Morphometric analysis of the basal portion of the Sertoli cell cytoplasm revealed that the volume density (V v ) of the vesicles changed markedly during the cycle. The V v was at its minimum (0.036) at stage VII and maximum (0.117) at stages XI-I. The vesicles were also smaller at stage VII compared to the vesicles at stages IX-V. The stage-dependent difference in the size of the vesicles was found both in the basal and the columnar portions of the Sertoli cells. At stage VII some of the vesicles appeared to be elongated much like the tubular elements of the smooth endoplasmic reticulum (SER) from which they are probably derived. The stage-dependent differences in volume density and size of the Sertoli cell vesicles may be related to cyclic biochemical variations in the Sertoli cells, and are further indications of a variation in Sertoli cell function during the cycle of the seminiferous epithelium. Whether or not this is due to an “internal” cycle of the Sertoli cell or to influences from adjacent germ cells remains to be determined.
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 219 (1981), S. 69-83 
    ISSN: 1432-0878
    Schlagwort(e): Satellite cells ; Cardiac muscle ; Decapod crustaceans ; Distribution ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The structure and distribution of satellite cells of cardiac muscles were examined in twenty-one species of animals chosen from each tribe within the order Decapoda (Arthropoda, Crustacea). The satellite cells were found in all animals observed. Most of them are morphologically identical with those described in different striated muscles of other species, but some cells have unusual features. The decapod satellite cell occasionally lies right over the region corresponding to the intercalated disc between the apposed cardiac muscle cells. The cell sends cytoplasmic processes into the adjacent muscle cells, enabling the plasma membrane to make close contact with the cleft opening of the intercalated disc, and with the myofibril at the level of the Z-line. Another characteristic feature is the presence of “paired” cells. Such cells are clearly separated from each other over most of the contact area by the respective plasma membranes, which are smooth in appearance and devoid of specialized regions. The significance of the presence of satellite cells in decapod cardiac muscle and its possible role are discussed and compared with those described for other species.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 219 (1981), S. 313-325 
    ISSN: 1432-0878
    Schlagwort(e): Oligodendroglia ; Cell surface antigens ; Electron microscopy ; Immunoperoxidase ; Monoclonal antibodies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Monoclonal antibodies to cell-surface antigens of oligodendrocytes (Sommer and Schachner 1980; Schachner et al. 1980) were used to identify this cell type by immuno-electron microscopy in monolayer cultures of fetal and early postnatal mouse cerebellum. The ultrastructural features of antigen-positive cells confirm that they are immature and mature oligodendrocytes, but not neurons, astrocytes or fibroblasts or fibroblast-like cells. Type I oligodendrocytes are the immature ones with a relatively large amount of moderately electron-lucent cytoplasm, clusters of ribosomes and complex networks of rough endoplasmic reticulum. Large numbers of mitochondria and microtubules, but not intermediate-sized filaments are seen in these cells. They comprise more than 90% of all 0-antigen-positive cells. Type II cells comprise only approximately 5% of all 0-antigen-positive cells. They are characterized by a limited amount of electron-dense cytoplasm, which appears more compact and granular than in type I cells. The rough endoplasmic reticulum is distributed evenly throughout the cytoplasm. Microtubules and mitochondria are present, but more difficult to distinguish due to the compactness of the cytoplasm. Type II cells display the more mature ultrastructural features of oligodendrocytes.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 220 (1981), S. 51-60 
    ISSN: 1432-0878
    Schlagwort(e): Cultured cells ; Detachment procedures ; Nuclear and cell surface ; Cytoskeleton ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Rabbit auricular chondrocytes, SIRC cells, human fibroblasts, and HeLa cells were cultivated in vitro and the fine structural effects of various detachment procedures studied. Treatment with collagenase, trypsin, and trypsin-EDTA caused scalloping of the nuclear envelope, accumulation of phagolysosomes, and an increase in the number of cell surface extensions. Collagenase-EDTA evoked a marked deformation of the nuclei with formation of numerous deep indentations and a redistribution of heterochromatin. Similarly, the cell surface became extensively folded and the vacuolation of the cytoplasm was further increased. These changes were reversible and within 24 h the cells had regained a normal structure. In all cases, chondrocytes and SIRC cells were most prominently affected, whereas fibroblasts and HeLa cells were only slightly changed. Treatment of chondrocytes with colchicine or cytochalasin B did not produce any effects of the type mentioned above. Neither did treatment with the drugs before and during detachment with collagenase-EDTA prevent the structural modification of the cells. It therefore seems unlikely that micro tubules and micro filaments are essential for this process. The structural changes occurring during detachment of cells could represent an adoptive mechanism for disposal of excessive membrane in connection with transition from a flattened to a rounded shape.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 220 (1981), S. 153-161 
    ISSN: 1432-0878
    Schlagwort(e): Cytoplasmic transport ; Insect ovary ; Autoradiography ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ovarioles of Coccinella and Tenebrio are shown to be telotrophic — a characteristic normally associated with hemipterans rather than coleopterans. They possess an anterior region of trophic cells and a chain of oocytes. The trophic cells are connected with the latter by a series of nutritive tubes, and autoradiography has shown that RNA is transported along the tubes to the oocytes. However, the system in these beetles differs markedly from that of hemipterans in that the nutritive tubes do not contain an extensive complement of aligned microtubules. The significance of this to both the mechanism and the selectivity of transport is discussed.
    Materialart: Digitale Medien
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 220 (1981), S. 435-438 
    ISSN: 1432-0878
    Schlagwort(e): Haemocyanin ; Branchial gland ; Electron microscopy ; Eledone moschata ; Cephalopoda
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Polymerized haemocyanin molecules have been identified as rings, about 25 nm in diameter, forming linear arrays within cytoplasmic vesicles, close to the nucleus. They were observed by transmission electron microscopy in the polygonal cells of the branchial gland of Eledone moschata Lamarck. These observations confirm previous data suggesting that haemocyanin is synthetized in the branchial gland cells of Octopoda.
    Materialart: Digitale Medien
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 216 (1981), S. 205-214 
    ISSN: 1432-0878
    Schlagwort(e): Compound eyes ; Insects ; Crustaceans ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 62
    ISSN: 1432-0878
    Schlagwort(e): Gastrin ; CCK ; Median eminence ; Electron microscopy ; Xenopus laevis (Amphibia, Anura)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 217 (1981), S. 211-223 
    ISSN: 1432-0878
    Schlagwort(e): Pituitary gland ; Pars intermedia ; Electron microscopy ; Sheep
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 214 (1981), S. 81-87 
    ISSN: 1432-0878
    Schlagwort(e): Sperm-host glands ; Spermatozoa ; Fowl ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The disintegration of spermatozoa in the infundibular sperm-host glands of the fowl was investigated by electron microscopy. After the 15th day following artificial insemination, secretory granules in the epithelial cells of the sperm-host glands increase in number and size, and subsequently the contents of the granules are released into the glandular lumen, so that the electron density of the lumen increases. At this stage, spermatozoa stored in the glands begin to undergo degenerative changes starting from the head. The heads become distended and chromatin of the nucleus begins to disperse as small masses, simultaneously with the destruction of the acrosome. As the dispersion of chromatin progresses, mitochondria of the middle piece become distended and irregular in shape, and then disintegrate. At the last stage, most of the organelles have disappeared, but the fibrous sheath and axial-filament complex are still identified.
    Materialart: Digitale Medien
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 214 (1981), S. 89-95 
    ISSN: 1432-0878
    Schlagwort(e): Spermatozoa ; Vitelline membrane ; Macrophage ; Fowl ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The fate of spermatozoa that do not participate in fertilization was investigated by electron microscopy. After artificial insemination, we observed several spermatozoa between the fibers of the outer layer of the vitelline membrane of the ovum. One or more spermatozoa were also found in a phagocytic vesicle of macrophages located in the intercellular space of the mucosal epithelium of the infundibulum or in the outer layer of the vitelline membrane. From these observations, we assume that the superfluous spermatozoa in the lumen of the anterior part of the oviduct might be removed by inclusion into the outer layer of the vitelline membrane and by phagocytosis by macrophages.
    Materialart: Digitale Medien
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  • 66
    ISSN: 1432-0878
    Schlagwort(e): Endogenous peroxidase ; Trachea ; Lung ; Electron microscopy ; Guinea pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Endogenous peroxidase activity was demonstrated by cytochemistry in mucous cells of the submucosal glands and tracheobronchial epithelium of guinea pigs. It is localized in the nuclear envelope, in cisternae of rough endoplasmic reticulum, and in secretory granules. It was not seen in Golgi saccules or in the airway lumen. By contrast, all epithelial cells within the lung including mucous (goblet) cells lack activity. Reaction product is also absent from alveolar macrophages and mast cells. The appearance of peroxidase in mucous cells is age-related. No activity was seen at 1.5ms of age. A few mucous cells were positive at 2.5 and 3 ms while the proportion of positive cells increased substantially up to 7 ms. Thus, the age of guinea pigs in HRP transport studies must receive careful consideration in order to avoid misinterpretation of results. The function of mucous cell peroxidase is unknown. The results of this study suggest that it is secreted. Whether it plays a significant role in lung defense through its well documented anti-infectious properties remains to be determined.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 214 (1981), S. 443-448 
    ISSN: 1432-0878
    Schlagwort(e): Chitin synthesis ; Electron microscopy ; Acari ; Tetranychus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Two chitin synthesising systems in Tetranychus urticae are described: one chitosomal system located in the oocytes where spatial and temporal distances are large, and one membrane bound system located in the hypodermis. Similarity of mechanisms of chitin synthesis in animals and plants is suggested.
    Materialart: Digitale Medien
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  • 68
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. A2 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 69
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 11-13 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Quality Control of HDPE Pipes.Trials are reported made with the aim of finding an correlation between creep rupture test results obtained with two different types of testing samples: Pipes under internal pressure and tensile rods cut out of these pipes in a longitudinal direction.
    Notizen: Es wird über Versuche berichtet, eine Korrelation zwischen Ergebnissen aus Zeitstand-Innendruckversuchen an HDPE-Rohren und Zeitstandversuchen an Längszugstäben aus diesen Rohren zu finden.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 70
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 23-31 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Controlled Pickling of Apparatus made of Chemical-Resistant SteelsExamples of material failure and corrosion trials are used to show that the chemical resistance of austenitic steel depends in many ways on the surface condition. Pickling is the best method for removing layers of oxide in preparation for passivation. Internal tensile stresses which are created near the surface by mechanical working, e.g. by turning, drilling and grinding, can assume higher values than those caused by shaping and welding. As a result stress corrosion cracking often occurs only in the region where the surface has been worked. Because the stresses responsible for this phenomenon rapidly fall off below the surface, it is usually possible to reduce them by pickling to the point at which damage of this kind is prevented. The amount of material which must be removed by pickling is determined by trials and pickling must be controlled accordingly.
    Notizen: An Schadensfällen und durch Korrosionsversuche wird gezeigt, daß die chemische Beständigkeit der austenitischen Stähle in mehrfacher Weise von ihrem Oberflächenzustand abhängt. Beim Entfernen von Oxidbelägen, als Voraussetzung für eine gute Passivschicht, liefert das Beizen das beste Ergebnis. Oberflächennahe Zug-Eigenspannungen, die durch eine mechanische Bearbeitung, z. B. Drehen, Bohren, Schleifen, eingebracht werden, können höhere Werte annehmen als die durch Verformen und Schweißen verursachten Spannungen. Als Folge davon tritt oft nur im Bereich einer Oberflächenbearbeitung Spannungsrißkorrosion auf. Weil die zugehörigen Spannungen unter der Oberfläche schnell abfallen, ist es meist möglich, sie durch ein abtragendes Beizen so weit abzubauen, daß Schäden dieser Art unterbleiben. Der notwendige Beizabtrag ist durch Versuche zu ermitteln und das Beizen entsprechend zu überwachen.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
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  • 71
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 90-96 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Crack Growth Behaviour of Structural Steels in SeawaterThe influence of a synthetic seawater environment upon the crack growth behaviour of two structural steels was investigated. The results were presented in terms of the stress intensity fracture toughness parameter. Data were generated in air and in seawater with or without a cathodic protection. Results show that seawater environment and a cathodic protection influence the crack propagation at the applied frequencies of 0,04 and 0,25 Hz. The use of cathodic protection raises questions concerning the resistance to hydrogen embrittlement of the two steels. Some fractographic examinations of selected specimens show the microstructure of the two steels at various test conditions.
    Notizen: Die Kenntnis der Ausbreitungsgeschwindigkeit von Rissen an Materialien in korrosiver Atmosphäre unter Betriebsbelastung ist für die Konstruktionsauslegung von großer Bedeutung. Von den Baustählen X70 sowie St70 ist mittels angeschwungener CT-Proben die Rißausbreitung bestimmt worden. Die Versuchsfrequenzen lagen - bezogen auf realistische Seegangsspektren - bei 0,04 Hz und 0,25 Hz. Durch Aufgabe kathodischer Schutzpotentiale wird bei Vorhandensein von Anrissen die Rißausbreitung stark beschleunigt. Es tritt eine wasserstoffinduzierte Spannungsrißkorrosion auf. Über das Ausmaß der Wasserstoffaufname der Bruchflächen werden Angaben gemacht. Durch REM-Aufnahmen wird das Bruchaussehen dokumentiert.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 72
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 107-108 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 73
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. A28 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 74
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 19-22 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Investigation of Different Welding Processes with Nickel-Alloy NiMo 16 Cr 16 TIThe overall favourable corrosion resistance of the nickel-chromium-molybdenum alloy NiMo 16Cr 16 Ti against attack by powerful oxidizing acids ensures a wide field of applications for this material. The alloy is readily processable using encased rod electrodes and shielded are welding. However, shielded arc welding should be given preference, as there are considerable differences in the analytical results between smelted welded material from encased rod electrodes and bright rods and wires. The different welded materials influence the corrosion resistance and the possibilities of forging welded constructions.
    Notizen: Die allgemeine gute Korrosionsbeständigkeit der Nickelbasislegierung NiMo 16 Cr 16 Ti gegen den Angriff stark oxidierender Säuren sichert diesem Werkstoff ein breites Einsatzgebiet. Die Legierung ist mit umhüllten Stabelektroden und nach Schutzgasschweißverfahren gut zu verarbeiten. Bevorzugt sollte jedoch das Schutzgasschweißen eingesetzt werden, da erhebliche Analyseunterschiede zwischen dem niedergeschmolzenen Schweißgut aus umhüllten Stabelektroden und aus blanken Stäben und Drähten bestehen. Das unterschiedliche Schweißgut hat Einfluß auf das Korrosionsverhalten und die Warmformgebungsmöglichkeiten von geschweißten Konstruktionen.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 75
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. A10 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
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  • 76
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 150-150 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 77
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. A34 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 78
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 256-262 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Anisotropy Effects in Copper Alloy Strip MaterialsThe textures and effects of mechanical anisotropy have been measured in several copper alloy strip materials with commercial hardness levels. In most cases mixed textures have been found with a qualitative correlation to the mechanical effects.The optimum position for spring elements proved to be transverse to rolling direction, especially the relation of the elastic limit in bonding to yield strength has a maximum in this direction.
    Notizen: Bei Bändern aus verschiedenen Kupferlegierungen in handelsüblichen Festigkeitszuständen wurden die Texturen und die mechanischen Anisotropieeffekte gemessen. In den meisten Fällen wurden Mischtexturen festgestellt, welche die mechanischen Anisotropieeffekte qualitativ erklären.Für Federelemente ist die Querlage die günstigste, insbesondere ist in dieser Richtung das Verhältnis Federbiegegrenze zu Streckgrenze am höchsten.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 79
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981) 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 80
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 330-334 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: The Guarantee of Quality for the Steel Hoops of the Refueling Machine of the Nuclear Ship OTTO HAHN by Way of a Special Procedure with UltrasonicThe basic overhaul and renewal of the refueling machine constructed 1965-1967 for the reactor system of the nuclear ship OTTO HAHN required among other things the replacement of the lifting hoops which are necessary for raising the fuel elements and guiding the gripping device. These steel hoops are the critical components of the refueling machine. Therefore the quality assurance of the material was articularly specified.On way of ensuring this guarantee of quality is to carry out tests involving the use of ultrasonic equipment as desired and applied here. The process is explained and its application with the results obtained is described.
    Notizen: Die Grundüberholung und teilweise Erneuerung der in den Jahren 1965-1967 gebauten Brennelement-Wechselmaschine für die Reaktoranalage des NS OTTO HAHN erforderte u.a. die Auswechselung der zur Lastaufnahme und Greifersteuerung dienenden Hubbänder. Diese Stahlbänder sind die kritischen Bauteile der Brennelement-Wechselmaschine. Aus diesem Grunde wurde die Gütesicherung besonders spezifiert. Eine der Gütesicherung dienende zerstörungsfreie Prüfung ist die hier beschriebene und angewendete Impuls-Durchschallung in Tauchtechnik. Das Verfahren wird erklärt und die Durchführung mit dem erzielten Ergebnis beschrieben.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 315-324 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Behaviour of Hip - Joint Endoprostheses under quasi-static and dynamic LoadClinical experience with total-hip endoprostheses has shown that the following problems take priority: - Loosening of the socket (acetabular cup) and the femoral prosthesis - Fracture of the femoral prosthesis - Loosing due to deep infection.Accordingly aims the research at locating the biological and mechanical reasons for the failures as well as testing alternative solutions such as - methods of fixation - construction of protheses - new materials and finishing methods. This publication concerns areas of the mechanical side of the problem.The comparison between the original system of proximal femur and acetabulum and the implanted prosthetic system shows changes in the stiffness of the systems depending on the different types of implanted endoprostheses.The influence of the frequency of loading on the deformation of the system is investigated in a frequency range between quasi-static and dynamically changing loads.The movements between implanted cup and neighbouring pelvic bone during cyclic load is measured.The results of these examinations give clues concerning qualitative and quantitative repercussions from the different endoprosthetic systems under conditions optimal in view of true comparison, and possible or desirable alternative solutions of the problem in view of construction and material.
    Notizen: Aufgrund bisher vorliegender klinischer Erfahrungen mit Hüftgelenks-Totalendoprothesen nehmen folgende Problemstellungen eine gewisse Priorität ein: - Pfannen- und Schaftlockerungen, - Schaftbrüche - Infektlockerungen.Dementsprechend konzentriert sich die Forschung auf die Ermittlung der biologischen und mechanischen Ursachen des Fehlverhaltens sowie auf die Erprobung alternativer Lösungen hinsichtlich - Fixationsmethodik - Konstruktion von Endoprothesen - Werkstoff und Fertigungsmethoden.Die vorliegende Arbeit bezieht sich auf Teile des mechanischen Komplexes dieser Problemstellung.Durch vergleichende Untersuchungen am Original- sowie am Implantatsystem „proximaler Femur/Hüftgelenkspfanne“ wird die Änderung der Steifigkeit infolge Implantation unterschiedlicher Typen von Endoprothesen ermittelt.Der Einfluß der Belastungsfrequenz auf die Deformationsverhältnisse in diesem System wird in einem Frequenzbereich überprüft, der sich von quasi-statischer bis zu dynamisch-wechselnder Belastung erstreckt.Die Relativbewegung zwischen implantierter Hüftgelenkspfanne und benachbartem knöchernen Bereich wird bei zyklischer Belastung erfaßt und messend verfolgt.Die Befunde geben punktuelle Hinweise hinsichtlich qualitativer und quantitativer Auswirkungen unterschiedlicher endoprothetischer Maßnahmen unter Bedingungen optimierter Vergleichbarkeit sowie hinsichtlich möglicher oder zweckmäßiger alternativer Lösungen im konstruktiven und stofflichen Bereich der anstehenden Fragestellungen.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 82
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. A76 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 83
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 335-335 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 84
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 366-374 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Exact and Approximate Calculations of UD-LayersIt is shown that the quasi-elastic solution of layers nearly almost used in practical viscoelastic calculations is an excellent approach. The exact solution achieved with simple integral equations are compared with the quasi-elastic solution and the occuring deviations are described. The creep functions of layers are given the form of the uniaxial creep function of the isotropic viscoelastic material. This makes the creep behaviour of layers very clear and symplifies practical calculations. The given solutions are under no restriction with regard to the chosen form of the uni-axial creep function.
    Notizen: Es wird gezeigt, daß die in der Praxis zur viskoelastischen Berechnung unidirektionaler Laminate verwendete quasielastische Lösung eine hervorragende Näherungslösung darstellt. Die exakten, mit Hilfe einfacher Integralbeziehungen gewonnenen, Lösungen werden mit der quasielastischen Lösung verglichen und es werden die zu erwartenden Abweichungen beschrieben. Die Kriechfunktionen der Laminate werden auf die Form der Kriechfunktion des viskoelastisch-isotropen Materials bei einachsiger Beanspruchung gebracht. Dadurch wird das Kriechverhalten der Laminate besonders deutlich und die praktische Rechnung wird vereinfacht. Die bereitgestellten Lösungen unterliegen keiner Beschränkungen hinsichtlich der funktionalen Form der einachsigen Kriechfunktion.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 85
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 402-407 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Pitting Corrosion at Copper Tubes of Tap Water Systems released by Soldering FluxThe pitting corrosion is the mostly observed reason for getting corrosion damage of copper tubes in tap water systems. In case of loss the reason for corrosion attack is ascribed to rests of cracked drawing compounds at the copper tube wall.The results from own examinations of copper tubes corroded in different tap waters show in case of loss the reason for corrosion damage as cracked soldering flux. This gets by the different described ways into the copper tube and becomes cracked by the soldering temperature. This way formed corrosion attacks often show breaches firstly far away from the soldered joint so that mostly other reasons of damage (cracked drawing compounds) are simulated.
    Notizen: Die häufigste zum Versagen von Kupferrohren in der Trinkwasserinstallation führende Korrosionsart ist die Lochkorrosion. Als schadensauslösend werden dabei in der Literatur die beim Weichglühen der Rohre gecrackten Ziehmittelreste (Kohlenstoffbeläge der Rohrinnenwandungen) und Rückstände von chloridhaltigen Weichlöt-Fluß-mitteln angesehen.Eigene Untersuchungen von Schadensfällen an Kupferrohren der Trinkwasserinstallation zeigen, daß die Ursache, welche zum Versagen der Rohre führt, meistens nicht gecrackte Ziehmittelreste oder eingeflossenes Flußmittel, sondern gecrackte Flußmittel sind. Diese gelangen, auf unterschiedlichste Art und Weise, in das Rohrinnere und werden beim Einwirken der Löttemperatur gecrackt. Da ein so eingeleiteter Korrosionsangriff oftmals erst in relativ weiter Entfernung von der Lötstelle zum Durchbruch führt (Kondensatzone), werden meist andere Schadensursachen (z. B. gecrackte Ziehmittelreste) vorgetäuscht.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 86
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 438-439 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 87
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 88
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 14-18 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Creep Behaviour of Steel × 10 NiCrATi 32 20 at Elevated Temperatures and Over Long Periods.The demands made on the quality of materials for chemical plants are continually increasing. Not only has there been a changeover to large units and an increase in the pressures and temperatures employed, but for technical and financial reasons the properties of the materials must be optimally utilized. In components subjected to the highest stresses due to pressure and temperature, the service life has to be calculated with the aid of creep strength characteristics. On the basis of the austenitic material × 10NiCrAlTi 32 20 an attempt is made, with the aid of creep strength characteristics, which have been determined in our own long-time test, to make a statement regarding the structural states existing at defined times and to draw conclusions for the use of this material.
    Notizen: Die Ansprüche an die Leistungsfähigkeit der Werkstoffe für Chemieanlagen wachsen ständig. So ist neben dem Übergang zu großen Einheiten nicht nur ein Ansteigen der Drücke und Temperaturen zu verzeichnen, sondern aus technischen und wirtschaftlichen Gründen auch ein optimale Ausnutzung der Werkstoffeigenschaften. Bei den durch Druck und Temperatur höchstbeanspruchten Bauteilen muß die Lebensdauer anhand von Zeitstandfestigkeitskennwerten berechnet werden.An dem austenitischen Werkstoff × 10 NiCrAlTi 32 20 wird versucht, anhand von Zeitstandfestigkeitsuntersuchungen, die im eigenen Langzeitversuch ermittelt sind, eine Aussage über die zeitabhängige Gefügeausbildung zu machen und daraus Schlüsse für den Einsatz dieses Werkstoffes zu ziehen.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 89
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. A7 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 90
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 33-39 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Parametric Analysis of Creep Tests under Pressur and Kind of Failure in Thermoplastic Tubes under Chemical LoadCreep tests under pressure are a method to evaluate the long term behaviour of tubes under mechanical, thermic and chemical loading. However, this method does not enclude essential criteria of failure. In form of a parametric analysis this paper proves that “weeping” takes place much earlier than total failure by rupture.Investigations on the different kinds of damage within the tube material using light microscopy and electron scanning microscopy reveal- that it is not correct to transform results of creep tests with small and thin tubes to such of practically used dimensions. This is on the one hand based on the existance of different microstructures which are specific to the semicristalline material and on the macrostructure determined by production process on the other hand.In order to determine failure of tubes sufficiently new test methods are proposed.
    Notizen: Das Zeitstandverhalten von Thermoplastrohren unter mechanischer, thermischer und chemischer Belastung wird durch den Zeitstandinnendruckversuch geprüft.Dabei werden bei der Versuchsdurchführung in der bisher üblichen Form wesentliche Versagenskriterien nicht erfaßt. In dieser Arbeit wird im Rahmen einer Parameteranalyse zum Zeitstandinnendruckversuch am Beispiel des Systems LDPE/H2SO4 nachgewiesen, daß ein Versagen durch Medienaustritt („Schwitzen“) weit vor dem mechanischen Versagen der Prüfkörper durch Bruch stattfindet. Die Betrachtung der Schädigungsmechanismen innerhalb der Rohrwand mit licht- und elektronenmikroskopischen Methoden zeigen, daß die Übertragbarkeit der an relativ kleinen Proberohren ermittelten Zeitstandwerte auf Rohre größerer Dimensionen nicht gegeben sein kann. Dies ist sowohl durch die werkstoffspezifischen Mikrostrukturen teilkristalliner Thermoplaste, als auch durch die herstellungsbedingten Makrostrukturen begründet.Es werden Versuchsanordnungen vorgeschlagen, die es erlauben, das Versagen von innendruckbelasteten Rohrproben hinreichend zu erfassen.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 91
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 72-72 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 92
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 88-90 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Influence of undeformable particles on the extrusion texture of composite materialsThe influence of α-Al2O3 particles on the extrusion texture of Ni-, Cu or CuZn30-composites has been investigated, variing particle size and interparticles spacing.The rods show a 〈100〉-recrystallization texture, which decreases with greater values of the interparticle spacing. In the case of the addition-free Cu and CuZn30 a random orientation distribution of the crystals was found. These results are discussed in comparison with the results found on Al—Al2O3-composites.
    Notizen: Der Einfluß von Teilchengröße und Teilchenabstand einer unverformbaren Phase (α-Al2O3) auf die Texturausbildung einer metallischen Matrix wird an stranggepreßten Verbundstangen mit Nickel-, Kupferoder CuZn30-Matrix untersucht.Alle stranggepreßten Stangen weisen bei kleinem Teilchenabstand (2,5 m̈m) eine scharfe 〈100〉-Rekristallisationstextur auf, die mit zunehmendem Abstand schwächer wird. Im Falle von zusatzfreiem Cu bzw. CuZn30 ist sogar eine regellose Orientierungsverteilung der Kristalle zu beobachten.Die Ergebnisse werden im Vergleich zu den bei Al—Al2O3 Verbundstangen gefundenen diskutiert.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 93
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 160-167 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Separation of Acoustic Emission Signals by Computerized AnalysesFeatures extracted from acoustic emission signals by means of different analysis methods can be evaluated by the application of pattern recognition computer programs. By these methods it can be established, whether the employed features - maximum amplitude, signal rise time, pulse sum, pulse area, pulse energy and mean amplitude as well as simple characteristics of frequency spectra - are capable to distinguish acoustic emission signals or whether combinations of features lead to better results when single features fail.The efficiency of different analyses and the pattern recongnition programs is examined by four simulated types of signals. According to the employed analysis method there are distinct differences regarding the separation of acoustic emission. However, by applying feature combinations signal groups not separable by single analysis methods can be distinguished.
    Notizen: Merkmale, die mit Hilfe verschiedener Analyseverfahren aus Schallemissionssignalen gewonnen werden, können durch den Einsatz von Rechenverfahren zur Mustererkennung bewertet werden. Durch Anwendung dieser Programme kann festgestellt werden, ob die verwendeten Merkmale - maximale Amplitude, Signalanstiegszeit, Schallsumme, Impulsfläche, Impulsenergie und mittlere Amplitude sowie einfache Kenngrößen aus Frequenzspektren - die Schallemissionssignale trennen können oder ob für den Fall, daß ein einzelnes Merkmal diese Aufgabe nicht löst, eine Kombination von Merkmalen zu einem besseren Ergebnis führt.Die Möglichkeiten der verschiedenen Analysen sowie der Mustererkennungsprogramme werden anhand von vier simulierten Signalarten überprüft. Je nach Analyseverfahren ergeben sich dabei deutliche Unterschiede hinsichtlich der Trennung der Schallemissionen. Jedoch kann selbst bei Signalgruppen, die mit einem Analyseverfahren nicht getrennt werden können, durch die Anwendung von Merkmalskombinationen die Unterscheidung verbessert werden.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 94
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 174-181 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Special Methods of Anti-Corrosion Treatment in Heat ExchangersAn anti-corrosion treatment must be adapted to the design of the heat exchanger and the conditions under which it is used. It is often the case, therefore, that highly specialized solutions are found. For the tubular heat exchanger, an organic coating has frequently proved suitable. The results obtained are determined by the construction, the surface characteristics of the components and paying attention to the risk of blister formation. The enamelling is problematic due to the complicated shapes involved and is still at the early stages of development. With water-cooled condensers, cleaning of the tubes while the equipment is running has proved successful. It alleviates the corrosion problem and assists the action of the inhibitors. Equipment made from materials such as titanium and austenitic CrNi steels, which are capable of being passivated, can frequently be retained in a passive state by adding air to the corrosive medium. In such cases, the excessive corrosion would normally necessitate the use of an expensive material. Where damage is caused by gaps and dead spaces it is not always possible to find a constructional remedy. A well-devised construction can subsequently be decisively influenced by manufacturing techniques relating to the structure, the state of internal stress or the surface condition.
    Notizen: Ein Korrosionsschutz muß auf Bauart und Einsatzbedingungen des Wärmetauschers abgestimmt sein, so daß sich oft ganz spezielle Lösungen ergeben. Für den Röhrenwärmetauscher bietet sich häufig eine organische Beschichtung an. Konstruktion, Oberflächenbeschaffenheit des Halbzeugs und Rücksicht auf die Gefahr der Blasenbildung bestimmen den Erfolg. Die Emaillierung ist wegen der komplizierten Formen problematisch und noch am Anfang der Entwicklung. Bei wassergekühlten Kondensatoren hat sich das Rohrreinigungsverfahren unter laufendem Betrieb bewährt. Es entschärft das Korrosionsproblem und unterstützt die Wirkung von Inhibitoren. Apparate aus passivierbaren Werkstoffen, wie Titan und austenitischen CrNi-Stählen, lassen sich häufig durch eine Dosierung von Luft zum angreifenden Medium passiv halten, wo andernfalls infolge zu starker Korrosion ein teureres Material erforderlich wäre. Für Schäden, die durch Spalte und Toträume bedingt sind, läßt sich nicht immer eine konstruktive Abhilfe finden. Eine gut durchdachte Konstruktion kann durch fertigungstechnische Maßnahmen, die das Gefüge, den Eigenspannungs- oder Oberflächenzustand betreffen, noch entscheidend beeinflußt werden.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. A44 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 96
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Influence of Different Degrees of Purity on the Fatigue Strength of Spring Steel 55 Cr 3One of the most important factors for construction and development of high strength springs is the material selection. In this connection the opinion is often represented in bibliography that material defects are the main reason for fractures.Besides surface defects (surface decarburization or rolling defects) essentially nonmetallic inclusions are described as causes of fractures. Therefore high degrees of purity are demanded especially for severe strained springs, which only can be obtained by very expensive special melting processes.By testing specimens of spring steel 55 Cr 3 with different degrees of purity in the present work the quantitative influence of nonmetallic inclusions on the fatigue life was to be examined. About 400 repeated torsion tests with annealed as well as annealed and shotpeened specimens were carried out accompanied by investigations to determine inclusions causing fracture and their size.
    Notizen: Bei der Konstruktion und Entwicklung von Federn spielt die Werkstoffauswahl im Hinblick auf die Dauerschwingfestigkeit eine wichtige Rolle. In diesem Zusammenhang begegnet man im entsprechenden Schrifttum häufig der Auffassung, daß Werkstoffehler als Hauptursache von Brüchen infrage kommen.Neben den äußeren Fehlern, wie Randentkohlung, Walzfehler usw. werden bevorzugt nichtmetallische Einschlüsse als Ursache von Brüchen dargestellt, so daß vor allem bei hochbeanspruchten Federn Reinheitsgrade gefordert werden, die nur mit sehr teueren Sondererschmelzungsverfahren zu erreichen sind.In der vorliegenden Arbeit wurde versucht, an Proben der Federstahlgüte 55 Cr 3 (W.-Nr. 1.7176) mit gezielt unterschiedlich eingestelltem Reinheitsgrad den Einfluß von Größe und Anzahl nichtmetallischer Einschlüsse auf die Lebensdauer von Schwingproben quantitativ zu erfassen. Anhand von etwa 400 Torsionsschwellversuchen an vergüteten und polierten bzw. kugelgestrahlten Probestäben sollten diese Zusammenhänge aufgezeigt und durch begleitende Untersuchungen, insbesondere durch Ermittlung bruchauslösender Einschlüsse und deren Größenbestimmung, ergänzt werden.
    Zusätzliches Material: 20 Ill.
    Materialart: Digitale Medien
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  • 97
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 227-229 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Diffusion Bonding of Silicon CarbidesSilicon carbide is a material that is suitable for high temperature application, especially for heat exchangers at high temperatures.Besides the problem of producing large components out of ceramics a technique for joining silicon carbide has to be developed. At high temperatures the joint has to be gastight und sufficient strength must be guaranteed. Diffusion bonding proved to be a good technique. The temperatures necessary for diffusion bonding are around 1200 °C, inert atmosphere or vacuum was used. The parameters of the procedures are discussed and correlated to strength, microstructure and permeability for gases.
    Notizen: Siliziumcarbid ist ein Werkstoff, der für Hochtemperaturanwendungen, besonders für Hochtemperatur-Wärmetauscher geeignet ist.Neben dem Problem, große Bauteile aus dieser Keramik zu produzieren, muß eine Fügetechnik entwickelt werden. Bei hohen Temperaturen sollen gefügte Teile gasdicht sein und ausreichende Festigkeiten müssen garantiert werden. Diffusionsschweißen hat sich dafür bewährt.Die Temperatur, die für die Diffusionsschweißung in Vakuum oder Schutzgas benötigt worden ist, lag bei 1200 °C. Es werden die Verfahrensparameter in Korrelation zu der Festigkeit des Verbundes, dem Gefüge und der Gasdurchlässigkeit diskutiert.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 98
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. A55 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. A60 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 100
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Influence of a Gradient of Composition on X-Ray Stress AnalysisIn the last years several factors were shown which lead to nonlinear sin2Ψ-distributions in x-ray stress analysis, like rotation of the principal stresses with respect to the normal to surface, steep stress gradients under the surface and a texture in the material under investigation.A fourth factor is revealed which becomes active, when gradients of the composition are present. In case of a chromized Fe-sample the influence on x-ray stress analysis is shown by measurement and theoretically as well. A method of correction is introduced, which is checked by use of a model sample.The x-ray residual stresses of the chromized Fe-sample are in accordance with such ones determined mechanically.
    Notizen: Es wurden in den letzten Jahren verschiedene Einflußfaktoren aufgezeigt, die zu nichtlinearen sin2Ψ-Verteilungen bei röntgenographischen Spannungsmessungen führen. Hierzu gehören eine Drehung der wirksamen Hauptspannungen gegenüber der Probenoberflächennormalen, ein starker Gradient des Spannungszustandes nach der Tiefe unter der Oberfläche sowie das Vorliegen einer Textur im zu untersuchenden Material.Es wird hier ein vierter Einflußfaktor aufgezeigt, der in Kraft tritt, wenn Konzentrationsgefälle der Zusammensetzung auftreten. Anhand des Beispieles einer chromierten Fe-Probe wird meßtechnisch und theoretisch dieser Einfluß auf die röntgenographische Spannungsanalyse erörtert und eine Korrektur ermöglicht. Mit Hilfe eines Modellwerkstoffes wird die Methode überprüft. Es ergibt sich eine gute Übereinstimmung zwischen röntgenographisch und mechanisch ermittelten Werten der Eigenspannungen an dem chromierten Eisen.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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