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  • 1990-1994  (10,033)
  • 1980-1984
  • 1955-1959
  • 1990  (10,033)
  • Chemistry  (9,691)
  • Analytical Chemistry and Spectroscopy  (1,434)
  • Atomic, Molecular and Optical Physics  (269)
  • Nuclear reactions
  • Ultrastructure
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  • 1990-1994  (10,033)
  • 1980-1984
  • 1955-1959
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Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Biology and ultrastructure of the mycophagus, soil testate amoeba, Phryganella acropodia (Rhizopoda, Protozoa) (1990)
    Springer
    Biology and fertility of soils 9 (1990), S. 101-109 
    Details
    ISSN: 1432-0789
    Keywords: Phryganella acropodia ; Testate amoeba ; Growth rate ; Rhizopoda ; Feeding ; Fungal species ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Clones of Phryganella acropodia were cultivated under different trophic conditions with bacteria as the food source. The doubling time was estimated to be 3 days. The edibility of four species of fungi, Aspergillus niger, Cunninghamella echinulata, Penicillium echinulatum and Stilbella bulbicola, was tested, but only Penicillium enchinulatum and Stilbella bulbicola were eaten and digested by the amoeba. An ultrastructure examination showed that there are two contractile vacuoles, many dictyosomes, a single nucleus with several nucleoli, and peroxisomes. The pseudopodia are filiform when attached to the substrate but change to lobose when the animal is floating. A thin organic membrane covers the aperture of resting forms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335791
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  • 2
    Electronic Resource
    Electronic Resource
    Differing microvasculature in the two major types of gastric carcinoma: a conventional, ultrastructural and ultrastructural immunolocalization study of von Willebrand factor (1990)
    Springer
    Virchows Archiv 417 (1990), S. 29-35 
    Details
    ISSN: 1432-2307
    Keywords: Gastric carcinoma ; Capillaries ; von Willebrand factor ; Ultrastructure ; Immuno-electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The microvasculature of the stroma of human gastric carcinoma was studied by immuno-electron microscopy for factor VIII/von Willebrand factor (vWF) and conventional electron microscopy. In differentiated type (intestinal) gastric carcinoma (9 cases), capillaries were distributed more densely around carcinoma cell nests. vWF was localized in endothelial cells and neighbouring stroma. Ultrastructurally, capillary endothelial cells showed considerable hypertrophic changes with well-developed rough endoplasmic reticulum (rER). vWF was localized in well-developed rER, granules, Weibel-Palade bodies (WPB), in the vascular lumen as clusters, and diffusely deposited in the subendothelium. This indicates that endothelial cells in this group are transformed into a state of active protein production. In undifferentiated type (diffuse) gastric carcinoma (12 cases), capillaries were uniformly distributed and endothelial hypertrophic changes were less remarkable. vWF was localized in WPB, scanty rER and subendothelial matrix. Solid capillary buds were observed in both types; they were composed of a solid strand of endothelial cells without a visible lumen. Our results reveal that the microvasculature in tumour stroma differs significantly according to its histological type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600106
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  • 3
    Electronic Resource
    Electronic Resource
    Small mucus-granule-containing ciliated cells in the human gastric mucosa: a transitional form to metaplastic ciliated cells (1990)
    Springer
    Virchows Archiv 417 (1990), S. 37-41 
    Details
    ISSN: 1432-2307
    Keywords: Mucus-granule-containing ciliated cell ; Ciliated metaplasia ; Transitional form ; Gastric mucosa ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ciliated cells were found in the gastric mucosa in close association with intestinal metaplasia, mainly in the pyloric mucosa, of Japanese patients. The occurrence of ciliated cells is believed to be an acquired phenomenon and is considered to be a type of metaplasia; the term “ciliated metaplasia” is used to describe this phenomenon. Ciliated cells are found in the basal part of the glands among normal-looking mucous cells, mucous neck cells and neuroendocrine cells, but never on the surface or in foveolar epithelium. In ciliated cellcontaining glands, mitoses were noted in the neck region and the ultrastructural features of these cells were identical to those of undifferentiated neck cells. However, cell metaplasia from undifferentiated cells to metaplastic ciliated cells has never been demonstrated previously. The small mucus-granule-containing ciliated cells found in our present study may arise subsequent to division of undifferentiated neck cells into mucous cells with some daughter cells then exhibiting differentiation characteristics specific to ciliated cells. Thus they contain a mixture of both small mucus granules and numerous basal bodies and cilia, at the same time as a transitional form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600107
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  • 4
    Electronic Resource
    Electronic Resource
    Morphometric comparison of mitochondria and myofibrils of cardiomyocytes between hypertrophic and dilated cardiomyopathies (1990)
    Springer
    Virchows Archiv 416 (1990), S. 473-478 
    Details
    ISSN: 1432-2307
    Keywords: Cardiomyopathies ; Ultrastructure ; Morphometry ; Mitochondria ; Myofibrils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We performed an ultrastructural, morphometric comparison of mitochondria and myofibrils of cardiomyocytes using endomyocardial biopsy specimens in hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Biopsies came from the right ventricular side of the interventricular septum in nine patients with HCM, nine with DCM, and nine controls with arrhythmia and/or ST depression. Morphometric analysis was carried out using electron microscopic photographs and an image analyser. Mitochondria were significantly greater in number and smaller in size in HCM than in the control group. In DCM, the size of mitochondria was also significantly smaller than in the control group, although their number was similar to that of the control group. No statistically significant difference was found regarding the size of mitochondria between HCM and DCM. The percentages of both mitochondrial and myofibrillar areas in cytoplasm were smaller in the DCM than the HCM and control groups, though no difference was seen between the latter two. The ratio of mitochondrial area to myofibrillar area was almost the same in each group. These results suggest increased mitochondrial function to match hypertrophic cardiomyocytes in HCM, and decreased mitochondrial function and cardiomyocytic contractility in DCM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600297
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  • 5
    Electronic Resource
    Electronic Resource
    So-called minute chemodectoma of the lung (1990)
    Springer
    Virchows Archiv 417 (1990), S. 113-118 
    Details
    ISSN: 1432-2307
    Keywords: Minute chemodectoma ; Lung ; Ultrastructure ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary So-called minute pulmonary chemodectoma is a curious, small lung tumour found mainly in women. The nature and origin of the proliferating cells are still obscure. In the first report on the tumour, the component cells were described as resembling chemoreceptor cells and the tumour was named chemodectoma. However, electron microscopic studies of the tumour have revealed no evidence of neuronal characteristics and have shown a close resemblance to meningothelial cells. In this study, the electron microscopic findings were similar to those previously reported but in one of the two cases, tumour cells were filled with abundant cytofilaments, giving them an occasional dense, patch-like appearance. Immunostaining for myosin and vimentin was positive in all tumour cells, but epithelial membrane antigen staining was not seen. These findings indicate that the tumour might have its origin from muscle cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02190528
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  • 6
    Electronic Resource
    Electronic Resource
    The ultrastructure of signet-ring cell non-Hodgkin's lymphoma (1990)
    Springer
    Virchows Archiv 417 (1990), S. 395-404 
    Details
    ISSN: 1432-2307
    Keywords: Ultrastructure ; Non-Hodgkin's lymphoma ; Signet-ring cell ; Endoplasmic reticulum ; Multivesicular body
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary New ultrastructural findings are reported from two lymphomas of vacuolar signet-ring cell morphology (SR+), one of B cell and one of T cell lineage. When these lymphomas were compared ultrastructurally a difference in the relationship of the endoplasmic reticulum (ER) to the vacuole was noted, although the fine structure of the vacuoles themselves was similar and they were interpreted as giant multivesicular bodies (mvbs). Smooth ER was found near the vacuoles in both cases. Dark mvbs with a complex, reticulate form are emphasised as readily identified but hitherto unreported cell components in these tumours. A further B cell lymphoma of centroblastic/centrocytic type which was SR− was found to be rich in mvbs and may be a transitional form between SR− and SR+ lymphomas. In addition, the occurrence of mvbs has been studied quantitatively in a number of other lymphomas and in B and T lymphocytes in reactive nodes. Although increased numbers of mvbs were found in neoplastic compared with reactive lymphocytes, and in T compared with B cell lymphomas, these differences were not statistically significant. The possible roles of endoplasmic reticulum and mvbs in the generation of SR+ change are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01606028
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  • 7
    Electronic Resource
    Electronic Resource
    Occurrence and prevention of contraction bands in Purkinje fibres, transitional cells and working myocardium during global ischaemia (1990)
    Springer
    Virchows Archiv 417 (1990), S. 463-471 
    Details
    ISSN: 1432-2307
    Keywords: Purkinje fibres ; Transitional cells ; Working myocardium ; Global ischaemia ; Ultrastructure ; Contraction state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Contraction bands usually occur in the intramural working myocardium following post-ischaemic reperfusion. In the subendocardium, however, they are found during ischaemia. Thus, we ascertained the contraction states of Purkinje fibres, transitional cells, subendocardial and intramural parts of the working myocardium during 30 min global ischaemia at 25° C. The effects with and without myocardial protection were compared. At the onset of pure ischaemia contraction bands are completely lacking in all cell types. During pure ischaemia contraction bands are found in all subendocardial cell types but not in the intramural working myocardium. A peak of pathological contraction states is found in the intramural working myocardium at the onset (0 min), in the subendocardial working myocardium at 10 min, in the transitional cells and Purkinje fibres at 30 min of pure ischaemia. Histidine-, tryptophan-, ketoglutarate-enriched (HTK) cardioplegia prevents contraction bands completely at the onset of ischaemia and prevents both contraction bands and pathological contraction states during ischaemia almost completely. Striking differences in the physiological contraction states are seen only in the working myocardium: HTK cardioplegia brings about dominance of relaxation during ischaemia. These findings may be due mainly to the effects of global ischaemia on the one hand and to catecholamines, calcium and oxygen on the other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01625725
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  • 8
    Electronic Resource
    Electronic Resource
    Well-differentiated papillary mesothelioma of the peritoneum: A borderline mesothelioma (1990)
    Springer
    Virchows Archiv 417 (1990), S. 443-447 
    Details
    ISSN: 1432-2307
    Keywords: Mesothelioma ; Pathology ; Ultrastructure ; Peritoneum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Well-differentiated papillary mesothelioma (WDPM) is considered to be a distinct subtype of peritoneal mesothelioma. Although the WDPM is usually qualified as benign, the natural history of this lesion has not been clearly established. This report relates to two WDPMs which were found incidentally. In a 51-year-old man the WDPM developed over a period of 5 years into a typically malignant diffuse mesothelioma. Thus, although the WDPM morphologically lacks signs of malignancy, it should be regarded as a borderline mesothelioma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01606033
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  • 9
    Electronic Resource
    Electronic Resource
    Cytoplasmic argyrophilic inclusions in neurons of pontine nuclei in patients with olivopontocerebellar atrophy: immunohistochemical and ultrastructural studies (1990)
    Springer
    Acta neuropathologica 79 (1990), S. 584-594 
    Details
    ISSN: 1432-0533
    Keywords: Olivopontocerbellar atrophy ; Argyrophilic inclusion ; Pontine nucleus ; Ubiquitin ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Patients with olivopontocerebellar atrophy (OPCA) were studied, and cytoplasmic inclusions were observed in some of the remaining neurons of the pontine nuclei, nuclei reticularis tegmenti pontis and arcuate nuclei. The cytoplasmic argyrophilic inclusions were demonstrated by silver impregnation techniques such as Bielschowsky and Bodian staining. With hematoxylin and eosin stain, the inclusions were sharply demarcated and appeared pale. The inclusions were not stained by the following routine histological methods: Klüver-Barrera, phosphotungstic acid hematoxylin, Holzer, periodic acid-Schiff, Mallory azan, alcian blue, nile blue, Masson trichrome, Congo red, thioflavine S, oil red O and Sudan black B stains. Immunohistochemistry with anti-ubiquitin antiserum showed that these inclusions were ubiquitinated. However, the inclusions did not react with any of the following antibodies (Abs) or antisera: anti-phosphorylated neurofilament (NF) Ab, anti-nonphosphorylated NF Abs (160 and 200 kDa), anti-paired helical filament antiserum, anti-tau antiserum, anti-tubulin Abs (alpha and beta), anti-microtubule-associated proteins antiserum, anti-glial fibrillary acidic protein antiserum, anti-vimentin Ab, anti-desmin Ab, anti-cytokeratin Abs (low and high molecular weights), anti-actin antiserum, anti-skeletal myosin antiserum and anti-myelin basic protein Ab. Ultrastructurally, the inclusion bodies noted in OPCA were composed primarily of fibrils having a width ranging from about 24 to 40 nm, which were entirely coated with osmiophilic granular material along their whole length. They were occasionally intermingled with a few filaments about 10 nm in width. Electron microscopical examination on silver-impregnated specimens revealed that each granule-coated fibril had a great affinity for silver particles. In elucidating the pathogenesis of OPCA, it was considered to be an important neuropathological finding that some of the remaining pontine neurons affected by OPCA developed characteristic cytoplasmic argyrophilic inclusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294235
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  • 10
    Electronic Resource
    Electronic Resource
    A study of the morphology of the gills of an extreme alkalinity and hyperosmotic adapted teleost Oreochromis alcalicus grahami (boulenger) with particular emphasis on the ultrastructure of the chloride cells and their modifications with water dilution (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 83-98 
    Details
    ISSN: 1432-0568
    Keywords: Chloride cell ; Teleost ; Gills ; Ultrastructure ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The general gill morphology of Oreochromis alcalicus grahami, a teleost adapted to high salinity and hyperosmosis, is basically similar to that of other teleostean fish. The species has four pairs of gill arches, all of which have well developed filaments. Each of the arches (holobranchs) has two rows of filaments (hemibranchs). Bilaterally situated secondary lamellae branch from the central axis of the filaments. The lamellae reach their maximum size at the middle of the filament, gradually decrease in size and eventually disappear towards the tip of the filament, which is bare. The leading edge of the gill filament and the immediate interlamellar space is covered by a stratified epithelium consisting of pavement cells, mucous cells, chloride cells and undifferentiated cells. The surface of these cells is made up of concentric microridges. The chloride cells were found only on the primary epithelium (filamental epithelium) and very rarely on the secondary epithelium (lamellar epithelium). Two types of chloride cells were observed in the gills of Oreochromis. The superficial chloride cells have fewer mitochondria concentrated towards the basal aspect of the cell, and a network of tubules towards the apical surface and are less electron dense. These cells intercommunicate with the water through an apical pore. The deep chloride cells have numerous diffuse mitochondria intercalated between a fine profuse tubular network and are more electron dense. These cells are covered by one or more layers of pavement cells and thus do not have access to the external surface. After gradual dilution of the lake water in which the fish were kept, both types of chloride cells remained topographically and ultrastructurally distinct. However, in both kinds of cell the mitochondria decreased in number and size. Initially there was an increase in the diameter and the degree of interdigitation of the tubules followed by a gradual decrease. An increase in the quantity of rough endoplasmic reticulum, particularly at the perinuclear region of the cell, was noted. The morphometric analysis of the branchial system indicated that the gills of Oreochromis are well adapted for gas exchange by having numerous and relatively long gill filaments with a high lamellar density. These features provide a large surface for gas exchange which, when coupled with the notably thin water-blood barrier of an average thickness of only 0.83 μm, would facilitate efficient absorption of oxygen by the gills. Oreochromis alcalicus was observed to be incapable of adapting to freshwater. This may have been due to the progressive degeneration of the chloride cells. Also the arrangement of the chloride cells as a continuum from the central venous compartments to the free epithelial surface is a structural feature which may not be amenable to radical functional changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189731
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  • 11
    Electronic Resource
    Electronic Resource
    Developmental cell death: morphological diversity and multiple mechanisms (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 195-213 
    Details
    ISSN: 1432-0568
    Keywords: Cell death ; Degeneration ; Embryo ; Development ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Physiological cell death is a widespread phenomenon in the development of both vertebrates and invertebrates. This review concentrates on an aspect of developmental cell death that has tended to be neglected, the manner in which the cells are dismantled. It is emphasized that the dying cells may adopt one of at least three different morphological types: “apoptotic”, “autophagic”, and “non-lysosomal vesiculate”. These probably reflect a corresponding multiplicity of intracellular events. In particular, the destruction of the cytoplasm in these three types appears to be achieved primarily by heterophagy, by autophagy and by non-lysosomal degradation, respectively. The various mechanisms underlying both nuclear and cytoplasmic destruction are reviewed in detail. The multiplicity of destructive mechanisms needs to be born in mind in studies of other aspects of cell death such as the signals which trigger it, since different signals probably trigger different types of cell death.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174615
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  • 12
    Electronic Resource
    Electronic Resource
    Involvement of extraocular muscle in mitochondrial encephalomyopathy (1990)
    Springer
    Acta neuropathologica 80 (1990), S. 118-122 
    Details
    ISSN: 1432-0533
    Keywords: Mitochondrial encephalomyopathy ; Extraocular muscle ; Ultrastructure ; Mitochondrial myopathy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We carried out a histological examination of the extraocular muscles (EOMs) in a case of myoclonus epilepsy associated with ragged-red fibers (MERRF) and two cases of mitochondrial myopathy, encephalopathy, laetic acidosis, and stroke-like episodes (MELAS), which did not manifest external ophthalmoplegia clinically. By light microscopy, many granular and vesicular fibers were seen associated with endomysial fibrosis. Electron microscopy revealed that the fibers showed prominent accumulation of abnormal mitochondria, extensive loss of myofibrils, proliferation of free sarcoplasmic reticulum and an increased amount of lipid vacuoles. These changes were more pronounced in MELAS than in MERRF. Hirano bodies were often seen in the subsarcolemmal area of muscle fibers and also in the intramuscular myelinated nerve fibers and axon terminals. These findings suggest the presence of mitochondrial myopathy of the EOMs in cases of MELAS and MERRF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308913
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  • 13
    Electronic Resource
    Electronic Resource
    Ultrastructural investigation of the CA1 region of the hippocampus after transient cerebral ischemia in gerbils (1990)
    Springer
    Acta neuropathologica 80 (1990), S. 487-492 
    Details
    ISSN: 1432-0533
    Keywords: Cerebral ischemia ; Delayed neuronal death ; Gerbil ; Hippocampus ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ultrastructural damage leading to delayed neuronal death was investigated in the mid-CA1 region of the hippocampus from the stratum (str.) moleculare to oriens after transient bilateral forebrain ischemia in Mongolian gerbils. After ischemia for 5 min without recirculation, mild swelling of the peripheral part of the apical and basal dendrites was already apparent in the str. moleculare and str. oriens. Mitochondria in the dendrites were also swollen in the same area. During recirculation for 12 h to 3 days, swelling of the dendritic cytoplasm persisted with formation of microvacuoles, but swelling of mitochondria receded. Microvacuolation and loss of microtubules were also observed in the proximal part of the dendrites during this period, and swelling and disruption of internal cristae were observed in mitochondria after recirculation for 3 days. The dendrites became severely degenerated after recirculation for 4 days. In the pyramidal cell bodies, no abnormality was observed at the end of ischemia for 5 min, but disaggregation of polyribosomes and swelling of the endoplasmic reticulum were observed 12 h after recirculation. Proliferation of the endoplasmic reticulum in parallel arrays occurred after recirculation for 1 day and persisted. Severe degeneration of the pyramidal cell bodies was obvious after recirculation for 4 days. The findings observed in the present investigation suggested that the neuronal structure most vulnerable to ischemia was the peripheral part of the dendrites and postischemic neuronal damage occurred early in this part of the dendrites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294608
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  • 14
    Electronic Resource
    Electronic Resource
    Type C retroviral expression in spontaneous feline olfactory neuroblastomas (1990)
    Springer
    Acta neuropathologica 80 (1990), S. 547-553 
    Details
    ISSN: 1432-0533
    Keywords: Feline ; Olfactory neuroblastoma ; Type C retrovirus ; Immunocytochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three cases of spontaneous olfactory neuroblastoma (ONB) in domestic cats were morphologically and immunocytochemically characterized. Diagnostic light microscopic features included Flexner and Homer-Wright rosettes, while ultrastructurally the cells had neuritic processes, intracellular intermediate filaments, and intercellular junctions. Immunocytochemically, the tumors stained positively for neuron-specific enolase, cytokeratins, and S-100 protein antigens. In each case, a key finding was the identification of numerous mature type C retroviral particles within the tumors. In one case, budding of viral particles from the plasmalemma of tumor cells suggested the source of mature particles. This cat and one other were tested, and both were serologically positive for feline leukemia virus (FeLV). The virus in the tumors was identified as FeLV by polymerase chain reaction and immunocytochemistry. No other neoplasms were found in any of the cats, nor was there similar evidence of active viral infection in other non-tumor tissues, including the brain. Although the relationship between FeLV infection and ONB is uncertain, our findings indicate that FeLV should be investigated as an etiologic agent of ONB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294617
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  • 15
    Electronic Resource
    Electronic Resource
    Chronic progressive and relapsing neuromyopathy with massive dilatations of endoplasmic reticulum in muscle fibers (1990)
    Springer
    Acta neuropathologica 80 (1990), S. 611-617 
    Details
    ISSN: 1432-0533
    Keywords: Intranuclear inclusions ; Endoplasmic reticulum ; Hyaline inclusions ; Striated muscle ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Large intracytoplasmic inclusions arising from the endoplasmic reticulum and nuclear envelope were found in the muscle fibers of a 32-year-old individual with a life-long, chronic and progressive sensory-motor neuropathy. The morphological features of the inclusions were similar to that occasionally reported in the striated muscles in several unrelated conditions as well as to “hyaline” or “colloid” inclusions commonly seen in motor neurons of the brain stem and spinal cord. The chemical nature of the inclusions is not known. Their occurrence in the muscle fibers is probably secondary to chronic denervation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307628
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  • 16
    Electronic Resource
    Electronic Resource
    Characterization of intracellular amyloid fibrils in the human choroid plexus epithelial cells (1990)
    Springer
    Acta neuropathologica 80 (1990), S. 597-603 
    Details
    ISSN: 1432-0533
    Keywords: Choroid plexus ; Amyloid ; Intracellular inclusions ; Ultrastructure ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intracellular inclusions with staining properties of amyloid are very common in the aging choroid plexus epithelial cells. In many ways these inclusions show similarities with the neurofibrillary tangles, found in cerebral cortical neurons in patients with Alzheimer's dementia. We have now designed a purification method for choroid plexus amyloid and performed a transmission and scanning electron miscroscopic study. This shows that one form of choroid plexus inclusions, the Biondi ring, is a homogeneous globule covered with a thin layer of amyloid fibrils. Partial immunochemical characterization of the choroid plexus amyloid reveals that it is different from the neurofibrillary tangles although there are similarities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307626
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  • 17
    Electronic Resource
    Electronic Resource
    Re-evaluation of fibroblasts and fibroblast-like cells (1990)
    Springer
    Anatomy and embryology 182 (1990), S. 103-112 
    Details
    ISSN: 1432-0568
    Keywords: Fibroblast ; Myofibroblast ; Interstitial cell ; Vitamin A storing cell ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Scanning electron microscopic observations of connective tissue cells show a new aspect of the nature of fibroblasts, and the subsequent broad survey of references makes clear that fibroblasts of many tissues have various features which are regarded as atypical of fibroblasts, and at the same time that various connective tissue cells in different organs have features typical of fibroblasts. Both morphological and functional features of fibroblasts are more or less common to those of fibroblast-like cells, and differences among these cells are quantitative rather than qualitative. Therefore, it is almost impossible to set clear-cut criteria for distinguishing genuine fibroblasts from a large population of fibroblast-like cells. The majority of cells sharing features of fibroblasts, if not all, seem to belong to the same population of cells. They are probably adapted to special functional needs in their own micro-environment that are peculiar to local or pathological or experimental conditions. It is proposed to categorize these cells into subtypes depending on their main functions: 1, fibrogenesis; 2, tissue skeleton or barrier; 3, intercellular communication system; 4, gentle contractile machinery; 5, endocrine activity; and 6, vitamin A-storing. Re-evaluation of fibroblasts and fibroblast-like cells is required to facilitate their better understanding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174011
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  • 18
    Electronic Resource
    Electronic Resource
    The gap junction family: structure, function and chemistry (1990)
    Springer
    Anatomy and embryology 182 (1990), S. 517-528 
    Details
    ISSN: 1432-0568
    Keywords: Gap junction ; Structure ; Function ; Molecular biology ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Gap junctions are aggregates of transmembranous channels which bypass the extracellular space by transporting messenger molecules and ions from one cytoplasmic source to an adjacent cytoplasmic interior. The channels join the plasma membranes of adjacent cells by bridging the extracellular space between them. Thereby, cellular “compartments” which were once considered to be individual units are, in actuality, interconnected by a system of pathways which form a functional cellular syncytium. The evolutionary importance of a generalized intercellular communication system can be appreciated when one considers the widespread prevalence of gap junctions within animals of all multicellular phyla, and within almost all tissues of vertebrates. Only a few population of cells such as skeletal muscle cells (which are fused to form functional syncytia) and circulating blood cells are not equipped with gap junctions. This paper provides a brief review of the diverse structural, molecular and functional aspects of gap junctions as revealed by current research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00186458
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  • 19
    Electronic Resource
    Electronic Resource
    Structural aspects of oocyte maturation in the blue fox (Alopex lagopus) (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 325-331 
    Details
    ISSN: 1432-0568
    Keywords: Oocyte maturation ; Ultrastructure ; Fox ; Ovulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Blood samples were taken weekly from seventeen mature blue fox vixens (average age five years), from late anoestrus until pro-oestrus, and then taken daily. The vixens were sacrificed at various stages of oestrus, and oocytes were collected from ovarian follicles by aspiration, and/or from oviducts by flushing. The structural features of oocyte maturation were related to the time of the luteinizing hormone (LH) peak. On days 1–2 after the LH peak the oocyte nucleus migrated from a central to a peripheral position in the ooplasm and assumed a flattened appearance. The cumulus investment expanded simultaneously and ovulation took place around day 2. On days 2–3 the oocyte nuclear envelope broke down, the nucleoli disappeared, the metaphase of the first meiotic division was reached, the Golgi complexes decreased in size, the perivitelline space enlarged, and all junctional contact between cumulus cell projections and oocyte was disrupted. On days 3–5 the first polar body was extruded, the metaphase of the second meiotic division was reached, and the cumulus cells degenerated. On day 5 the release of cortical granule content was occasionally seen, and from day 6 the oocytes showed signs of degeneration. In a few animals deviant oocyte maturation was noticed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00186904
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  • 20
    Electronic Resource
    Electronic Resource
    Optic nerves in plethodontid salamanders (amphibia, urodela): neuroglia, fiber spectrum and myelination (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 37-48 
    Details
    ISSN: 1432-0568
    Keywords: Axons ; Astrocytes ; Oligodendrocytes ; Ultrastructure ; Paedomorphosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In five species of lungless salamanders, family Plethodontidae, which all show highly developed visual abilities, the ultrastructure of the optic nerve was investigated and the total number of retinal ganglion cell axons, the percentage of myelinated axons, and the volume densities of glia and axons were determined. More than 80% of all axons were smaller than 0.4 μm and only 2–3% were larger than 0.8 μm. In individual nerves the degree of myelination varied between 1 and 9% which is in the range reported for other amphibian species. The miniaturized and highly paedomorphic species Batrachoseps attenuatus was an exception because only very few or even no myelinated axons were present in the nerve, which is unique among gnathostome vertebrates. The five investigated species had total numbers of axons ranging from 26000 in Batrachoseps attenuatus to about 50000 in Plethodon jordani. These numbers are the lowest found among vertebrates with an elaborated visual system. The amount of glial material in the optic nerve varied between 25 and 50%, with larger nerves possessing more glia than smaller ones. Ultrastructural analysis revealed that the optic nerve of each species contained both astrocytes and oligodendrocytes, although often in immature form. In Batrachoseps attenuatus the glia showed features of both astrocytes and oligodendrocytes which reflect an undifferentiated state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189726
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  • 21
    Electronic Resource
    Electronic Resource
    An ultrastructural study of early chorionic villus formation in the marmoset monkey (Callithrix jacchus) (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 59-66 
    Details
    ISSN: 1432-0568
    Keywords: Ultrastructure ; Marmoset ; Chorionic villi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructural morphology of developing chorionic villi in the marmoset monkey (Callithrix jacchus) placenta was studied in pregnant monkeys at known time intervals after ovulation. In samples obtained at 45 days after ovulation the mesoderm, which consists of primitive foetal blood vessels, is seen to extend down into cytotrophoblast columns. Syncytiotrophoblast completely surrounds maternal blood vessels and both basal laminae and endothelial cells of maternal origin show signs of disorganisation and degradation. Syncytiotrophoblast is first observed to breach the maternal circulation in samples collected from animals at 60 days after ovulation; this results in discrete haemochorial villi randomly distributed throughout the placental bed. Samples obtained at 80 days after ovulation and term placental samples (145 days after ovulation) exhibit tertiary haemochorial villi throughout the placenta, similar to those seen randomly distributed at 60 days after ovulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189728
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  • 22
    Electronic Resource
    Electronic Resource
    Early development and myogenesis of the posterior anuran lymph hearts (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 75-82 
    Details
    ISSN: 1432-0568
    Keywords: Anuran lymph hearts ; Development ; Ultrastructure ; Myogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The early development of anuran posterior lymph hearts studied by light- and electron-microscopy in frog larval stages 25–29 (Gosner 1960) can be subdivided into three phases. In phase I, mesenchymal myogenic cells are found, each possessing a single 9 + 0 cilium and numerous filopode-like processes aggregated near the vena caudalis lateralis, forming up to three metameric organ anlagen arranged like a cuff around the preexisting lymphatics (stages 26/27). In phase II, cell proliferation starts at stage 28 within the lymph heart wall as does the formation of primarily polynuclear myofibres by fusion of several myoblasts. At this stage immature myofibres show a vast sarcoplasm, a poorly developed SR and only few myofibrils with not yet distinguishable A- and I-bands. In phase III, the afferent and efferent valves are formed at the onset of pulsation in stage 29. Contractile myofibres contain large glycogen fields and a considerable amount of myofibrils which frequently branch and show distinct Z-lines, A-, I-, H- and M-bands; 1–3 cilia were found lying within a channel-like cell invagination. The peculiarities of organogenesis and myofibre development are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189730
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  • 23
    Electronic Resource
    Electronic Resource
    Rosenthal fibres: an immunohistochemical, ultrastructural and immunoelectron microscopic study (1990)
    Springer
    Acta neuropathologica 79 (1990), S. 456-460 
    Details
    ISSN: 1432-0533
    Keywords: Rosenthal fibers ; Immunohistochemistry ; Ultrastructure ; Neoplastic and reactive astrocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The nature of Rosenthal fibres (RF) was investigated in eight cases each of low-grade astrocytoma and reactive gliosis using immunohistochemical (IH) staining for glial fibrillary acidic protein (GFAP), electron microscopy (EM) and immunoelectron microscopy (IEM) by immunogold labelling technique. By IH under light microscopy (LM), three types of RF were seen, uniformly positive (type I), rim positive (type II) and completely negative (type III). EM showed variation in structural pattern of RF. Some RF contained large amount of glial filaments (GF) intermingled with RF while others with a large amount of electron dense material and less GF. Thus, the presence and amount of GF in RF appear to be responsible for the different types of IH staining under LM. IEM showed that all RF including the ones consisting of entirelh amorphous material possess immunoreactivity for GFAP. It is suggested that RF formation is a two-stage process, staring with excessive accumulation of GF within astrocytic processes followed by their gradual alteration into electron-dense amorphous material under the influence of some unknown metablic or other factors. The quantitative analysis of different types of RF suggests a difference in the rate of formation of RF in neoplastic and reactive conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308723
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  • 24
    Electronic Resource
    Electronic Resource
    Alphaherpesvirus saimiri infection in rabbits (1990)
    Springer
    Acta neuropathologica 79 (1990), S. 551-557 
    Details
    ISSN: 1432-0533
    Keywords: Cutaneous nerves ; Neuropathy ; Ultrastructure ; Herpesvirus ; Rabbits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A light and electron microscopic study was undertaken to determine pathological changes in cutaneous spinal nerves of rabbits following intradermal inoculation with alphaherpesvirus saimiri (αHVS) isolate KM 322. Infected rabbits were killed at 3, 10, 17, 45 days and 2 years after infection. No abnormalities were seen at 3 days postinoculation. In the nerves of the rabbits killed at 10, 17 and 45 days after infection, axonal (Wallerian-type) degeneration was the main pathological feature. Regeneration, manifested by axonal sprouting, was observed in the nerves of the rabbits killed at 45 days post-inoculation. Neural fibrosis and paucity of unmyelinated axons was the final outcome. The severity of the neural damage not only varied according to the progression of the disease but between nerves taken from the same rabbit. This was probably associated with variation in the numbers of virus particles that had reached the dorsal root ganglion of the dermatome served by a particular nerve. Since αHVS (isolate KM 322) provides a model system for the study of virus latency in dorsal root ganglia, and consequently for the study of varicellazoster infection in man, these findings give further insight into the pathology of herpetic neuropathy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296116
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  • 25
    Electronic Resource
    Electronic Resource
    Histological, ultrastructural and chromatographical discrimination of phospholipids in meningiomas (1990)
    Springer
    Acta neuropathologica 80 (1990), S. 255-259 
    Details
    ISSN: 1432-0533
    Keywords: Meningioma ; Phospholipid ; Psammoma ; Ultrastructure ; Chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Phospholipids in meningiomas were studied by light and electron microscopy, and by high-performance liquid chromatography. They were microscopically demonstrated in six of the ten cases by Sudan III staining after the fixation with potassium dichromate. However, the conventional ultrastructural fixation with glutaraldehyde and osmium tetroxide failed to confirm phospholipids, as most of them were dissolved during dehydration. In contrast, the specimens pretreated with tannic acid before osmication ultrastructurally retained phospholipids which were represented by multilamellar bodies or ribbon-like rings. Both were found in 23 of the 30 cases within the cytoplasm, among the plasma membranes and in the extracellular matrices. The outermost lamella or ribbon showed a direct continuity from the neighbouring plasma membranes of the cytoplasm or the mitochondria. The multilamellar bodies showed an overall distribution, while the ribbon-like rings were predominantly distributed around the psammoma bodies. Precipitation of hydroxyapatite crystals within the ribbon-like rings resulted in matrix minerals of psammoma bodies. Chromatographical analyses of meningiomas disclosed phospholipids including phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl serine, sphingomyelin and phosphatidyl inositol in that order. Psammomatous meningiomas contained a higher percentage of phosphatidyl serine than non-psammomatous tumors. Ultrastructural study of synthetic phospholipids adequately treated with tannic acid showed that the multilamellar bodies were similar to phosphatidyl choline, while the ribbon-like rings were similar to phosphatidyl serine. The role of phospholipids in meningiomas is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294642
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  • 26
    Electronic Resource
    Electronic Resource
    Hyperplastic and hypertrophic growth of lateral muscle in Dicentrarchus labrax (L.) (1990)
    Springer
    Anatomy and embryology 182 (1990), S. 1-10 
    Details
    ISSN: 1432-0568
    Keywords: Fish ; Muscle growth ; Hyperplasia ; Hypertrophy ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In this EM study of lateral muscle in Dicentrarchus labrax, we observed that during the larval period, growth of the presumptive red and white muscle layers occurs both by hypertrophy (as fibres already present at hatching complete their maturation) and by production of new fibres in germinal zones specific to the two muscle layers. In the first half of larval life the presumptive white muscle increases in thickness by the addition, superficially, of new fibres derived from a germinal zone of presumptive myoblasts lying beneath the red muscle layer. In the second half of larval life new fibres produced in this same zone form the intermediate (or pink) muscle layer. Dorsoventrally the myotome grows throughout larval life, largely by addition of new fibres from germinal zones at the hypo- and epi-axial extremities. Towards the end of larval life all these germinal zones are becoming exhausted, but another source of fibres arises as satellite cells, associated with large-diameter presumptive white muscle fibres, are activated to produce new fibres. The addition of small, new fibres gives the white muscle its mosaic appearance. Morphometric analysis of fibre diameters in the white muscle confirms that whereas these hyperplastic processes are important during the larval and juvenile periods, when growth is very rapid, they have ceased by the time the adult stage is attained. By contrast, fibre hypertrophy continues through into adult life. The presumptive red muscle consists initially of a monolayer of fibres present only near the lateral line, and during larval life it grows hypo- and epi-axially by addition of fibres derived from myoblasts already present in these areas at hatching. Lying superficially to the presumptive red muscle monolayer there is a near-continuous layer of external cells with a “flattened” profile. During the second half of larval life, differentiation of these external cells into myoblasts provides the source of new fibres which are added to the red muscle layer. This process, which occurs initially in the region around the lateral line and later spreads outwards, is responsible for the increase in thickness of the red muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187522
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  • 27
    Electronic Resource
    Electronic Resource
    Pronephric regression during larval life in the sea lamprey, Petromyzon marinus L. (1990)
    Springer
    Anatomy and embryology 182 (1990), S. 41-52 
    Details
    ISSN: 1432-0568
    Keywords: Lamprey ; Pronephros ; Ultrastructure ; Regression ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The regression of the pronephric kidney of the lamprey, Petromyzon marinus, is described using histochemical and ultrastructural techniques. Regression begins in the third year of larval life, and by the time the animal enters metamorphosis the tubules have all disappeared. The nephrostomes and the renal corpuscle, however, persist for the remainder of the life cycle and undergo little change in the larva. Iron is present within the tubular epithelium prior to the beginning of degeneration, but as degeneration proceeds iron is observed within the tubule lumina. Acid phosphatase is noted within the tubule epithelia prior to degeneration, but as degeneration proceeds acid phosphatase is also observed within the intertubular area. Features of tubular regression include a prominent and highly folded basal lamina, numerous cytoplasmic inclusions, and dense bodies in the epithelia and lumina. The intertubular region is invaded by lymphocytes, granulocytes, plasma cells, and macrophages. The process of pronephric regression possesses many features of the process of apoptosis, which has been noted in the regression of larval organs in other vertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187526
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  • 28
    Electronic Resource
    Electronic Resource
    Distribution of serotonin in the caudal neurosecretory complex (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 491-498 
    Details
    ISSN: 1432-0568
    Keywords: Serotonin ; Ultrastructure ; Caudal Neurosecretory Complex ; Neuroendocrine ; Monoamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The caudal neurosecretory complex (CNc) of poecilids has previously been shown to receive serotonergic inputs. In the present study, immunohistochemical techniques were applied at the light and electron microscopic levels to characterize serotonergic terminals in the neuroendocrine nucleus. A dense plexus of varicose fibers observed in the rostral CNc neuropil was absent in the spinal cords of deafferented fish, indicating that the origin of this input was extranuclear. Ultrastructural study revealed no direct contacts between labeled structures and neuroendocrine cells. Non-synaptic terminals (varicosities) were the predominantly labeled structures in the neuropil. Synaptic terminals were observed on cellular and axonal targets in the CNc. Small cells containing 70 nm dense-core vesicles received serotonergic input on their perikarya. Labeled synapses were also found on unlabeled axon terminals which made axoaxonal synapses on neuroendocrine processes. Non-synaptic terminals may be responsible for a variety of serotonin-mediated effects in the CNc. Synaptic interactions with local catecholaminergic and afferent cholinergic inputs to the CNc are likely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02433796
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  • 29
    Electronic Resource
    Electronic Resource
    Light and electron microscopic morphology of the temporomandibular joint in growing and mature crab-eating monkeys (Macaca fascicularis): the condylar articular layer (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 499-511 
    Details
    ISSN: 1432-0568
    Keywords: Mandibular condyle ; Articular tissue layer ; Ultrastructure ; Maturation ; Load-dependence ; Macaca fascicularis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In an attempt to establish maturational alterations in the morphology of the articular tissue layer, mandibular condyles of four immature and four mature male monkeys (Macaca fascicularis) were studied using light microscopy as well as scanning and transmission electron microscopy. Specimens were fixed in situ by perfusion in the presence of ruthenium red to stabilize proteoglycans. Preparations intended for observation in the scanning electron microscope were first dehydrated and sputtered for the examination of articular surfaces, and afterwards treated with trypsin to expose the spatial arrangement of collagen fibrils. Gross anatomical relations between joint components indicated that the anterior and central, but not the posterior region of the condylar articular surface can be subject to compressional load. Load-bearing and non-load-bearing regions differed with respect to the morphology of the articular layer. Load-bearing surfaces were covered by a prominent articular surface lamina similar to that observed on articular cartilage. This lamina seemed to constitute an integral part of the articular layer, distinct from the lining of synovial fluid, and to be composed largely of proteoglycans. It was unaffected by maturation. The subjecent, load-bearing articular layer differed markedly in structure, both from articular cartilage, and between immature and mature animals. Articular cells of immature animals were classified as fibroblastlike, but unlike typical fibroblasts, were surrounded by a thin, often incomplete halo of fibril-free pericellular matrix, presumably consisting of proteoglycans. In mature animals, articular cells closely resembled chondrocytes, but exhibited prominent nuclear fibrous laminae, which usually are found only in fibroblasts. Thus, the load-bearing part of the articular layer seems to undergo a maturation-dependent metaplastic conversion, from a dense connective tissue with some features of fibrocartilage, to a fibrocartilage-like tissue containing chrondrocytelike cells with some features of fibroblasts. This conversion might reflect an adaptation to a maturation-associated increase in articular stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02433797
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  • 30
    Electronic Resource
    Electronic Resource
    The ultrastructure of dysplastic naevi: comparison with superficial spreading melanoma and common naevocellular naevi (1990)
    Springer
    Archives of dermatological research 282 (1990), S. 353-362 
    Details
    ISSN: 1432-069X
    Keywords: Dysplastic naevi ; Superficial spreading melanoma ; Naevocellular naevi ; Ultrastructure ; Melanosomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eleven dysplastic melanocytic naevi with various degrees of dysplasia, as judged by light microscopy, were studied by transmission electron microscopy, and their intra-epidermal melanocytes compared with those of five superficial spreading melanomas and seven common benign naevocellular naevi. Intra-epidermal melanocytes in dysplastic naevi exhibited signs of cellular atypia, which were most pronounced in the dysplastic naevi with histological high-grade dysplasia. A correlation between the degree of dysplasia at the light microscopic level and the degree of cytological atypia at the ultrastructural level was noted, and melanocytes in dysplastic naevi with a high degree of dysplasia had ultrastructural features similar to the melanocytes in superficial spreading melanomas. Our observations support the concept that dysplastic naevi fill the biological gap between benign naevocellular naevi and malignant melanomas and suggest that at least some of the dysplastic naevi must be regarded as potential precursor lesions of malignant melanoma, particularly those exhibiting a high degree of histological dysplasia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00372084
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  • 31
    Electronic Resource
    Electronic Resource
    Skin changes in variegate porphyria (1990)
    Springer
    Archives of dermatological research 282 (1990), S. 108-114 
    Details
    ISSN: 1432-069X
    Keywords: Porphyria ; Dermal vessels ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The skin of 20 patients with variegate porphyria (VP) was studied using light, fluorescent, and electron microscopy. Twelve patients had skin symptoms and markedly increased fecal protoporphyrin excretion. Their sun-exposed skin was characterized by homogeneous PAS-positive thickening and IgG deposition in the vessel walls. The basic ultrastructural change was thickening of the vascular walls caused by reduplication of the basal lamina and perivascular deposition of amorphous material. Qualitatively similar but less prominent histopathological changes occurred in sun-protected skin in some of the patients. Six patients had no skin symptoms but an increased porphyrin excretion. The light microscopical changes were comparable to those in the patients with skin symptoms, but the ultrastructural changes were less severe. No abnormal histopathological changes occurred in two symptomless patients who had low lymphocyte protoporphyrinogen oxidase activity but normal fecal porphyrin excretion. These results show that the primary site of skin damage in VP is the vessel wall, and that histopathological changes of the skin also occur in porphyric patients who have never had skin symptoms. Factors determining the occurrence of skin symptoms in VP are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00493468
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  • 32
    Electronic Resource
    Electronic Resource
    Dynamic ultrastructural changes of the connective tissue sheath of human hair follicles during hair cycle (1990)
    Springer
    Archives of dermatological research 282 (1990), S. 434-441 
    Details
    ISSN: 1432-069X
    Keywords: Hair cycle ; Human hair follicle ; Connective tissue sheath ; Hyaline membrane ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ultrastructural changes of the connective tissue sheath (CTS), including the hyaline membrane, of human hair follicles during the hair cycle, were studied in normal scalp skin specimens. In early anagen, the CTS was composed of a thin basal lamina and surrounding collagen tissue. The collagen tissue gradually thickened during the development of the hair and hair follicle. In mature anagen hair follicles, the collagen tissue was separated into three layers. The inner collagen layer, just outside the basal lamina, was thin and composed of collagen fibres running longitudinally parallel to the hair axis. The middle collagen layer was very thick with its collagen fibres running transversely against the hair axis and surrounding the inner hair tissue. Many fibroblasts were present among the collagen fibres in the middle layer, whereas the inner layer contained almost none. In the outer collagen layer, collagen fibres ran in various directions parallel to the outer surface of the outer root sheath cells. In late anagen, the basal lamina became very thick. In catagen, the basal lamine and the inner collagen layer became corrugated and showed oedematous change and degeneration. Surrounding fibroblasts showed active production of new collagen fibres, which seemed to fill the spaces left by the retraction of the hair follicle and hyaline membrane. These ultrastructural changes of the CTS show that there may be dynamic metabolic changes of the connective tissue around human hair follicles during the hair cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402618
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  • 33
    Electronic Resource
    Electronic Resource
    Intercellular structure in a many-celled magnetotactic prokaryote (1990)
    Springer
    Archives of microbiology 154 (1990), S. 18-22 
    Details
    ISSN: 1432-072X
    Keywords: Intercellular junctions ; Multicellularity in prokaryotes ; Bacterial magnetotaxis ; Ultrastructure ; Bacterial co-ordination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A many-called magnetotactic prokaryote obtained from brackish water was observed to possess intercellular connections at points of contact between the outer membranes of constituent cells. Each aggregate organism consisted of 10 to 30 individual Gram-negative cells containing material with the appearance of poly-β-hydroxybutyrate and magnetosomes of unusual arrangement, structure and composition. The aggregate, which possessed prokaryotic-type flagella arranged at the outwards surfaces of each cell, showed motility indicative of co-ordination between individual component cells. These results suggest that this organism could be a multicellular prokaryote.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249172
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  • 34
    Electronic Resource
    Electronic Resource
    The vascular architecture of human xenotransplanted tumors: histological, morphometrical, and ultrastructural studies (1990)
    Springer
    Journal of cancer research and clinical oncology 116 (1990), S. 517-524 
    Details
    ISSN: 1432-1335
    Keywords: Tumor vascularization ; Tumor blood flow ; Xenograft ; Nude mouse ; Vascular corrosion cast ; Ultrastructure ; Electron microscopy ; Heterogeneity ; Vessel morphology ; Morphometry ; Necrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study was designed to examine the vascular system of human xenotransplanted tumors on nude mice with different complementary morphometrical and morphological methods. The vascular system shows a chaotic arrangement. There is an extreme heterogeneity in the vascular distribution and density. Large avascular regions could be identified in several non-necrotic tumors. There was no clear difference in the vascular density between the center and the periphery of the tumors, nor was there any zonal correlation for the distribution of the necrosis. With three-dimensional corrosion casts it could be demonstrated that clusters of vessels were directly beneath areas almost free of vessels. In the center, vessels often form a sinusoidal system with numerous blind ends without clearly discernible endothelial cells. Numerous irregular tumor-cell-lined sinusoids are visible next to endothelial-lined vessels with transmission electron microscopy. With scanning electron microscopy it could be demonstrated that large-calibre endotheliazed vessels were found in the direct vicinity or in the center of non-viable zones. Even large-calibre vessels have a capillary wall structure. Sometimes, a basement membrane cannot be observed at all or only incompletely. There are numerous indications of vascular discontinuities and leaks with a widespread intercellular occurrence of blood cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01613005
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  • 35
    Electronic Resource
    Electronic Resource
    Effects of endogenous and exogenous cholesterol on the ultrastructure and steroid secretion of undifferentiated rat adrenocortical cells in primary culture (1990)
    Springer
    Cell & tissue research 259 (1990), S. 421-427 
    Details
    ISSN: 1432-0878
    Keywords: Adrenal cortex ; Tissue culture ; Corticosterone ; Ultrastructure ; Lipoproteins ; Mevinolin ; Rat (Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The present study was undertaken to define the effects of lipoprotein-derived cholesterol and endogenous, de novo synthesized cholesterol on the ultrastructure and function of undifferentiated rat adrenocortical cells [lipoprotein (HDL3 and LDL) receptor-negative, zona glomerulosa-like adrenocortical cells] in primary culture. For this purpose human plasma high density lipoprotein (HDL3) or low density lipoprotein (LDL) was added to culture medium devoid of cholesterol. Steroid secretion remained at the low basal level even after addition of lipoproteins, and the amount of intracellular lipid droplets did not increase. When mevinolin (0.96 µg/ml), an inhibitor of cholesterol synthesis, was added to the culture medium, a low secretion of corticosterone was measured both in serum-free and serum-containing media. Ultrastructurally, lipid droplets disappeared after treatment with mevinolin in both media used. At this concentration of mevinolin cell proliferation was similar to that in the controls, but at higher concentrations (4.8 or 9.6 µg/ml) proliferation was inhibited to 42% and 26% in serum-free medium, and 20% and 12% in serum-supplemented medium, respectively. This study demonstrates that cell proliferation and synthesis of corticosterone by undifferentiated rat adrenocortical cells is identical in the absence or presence of exogenous lipoprotein cholesterol. Inhibition of de novo cholesterol synthesis by mevinolin over a period of 7 days does not inhibit corticosterone secretion or proliferation of cells but decreases the amount of intracellular lipid droplets, thus suggesting utilization of intracellular cholesterol esters. However, higher concentrations of mevinolin inhibit proliferation of cells both in serum-free and serum-containing media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01740768
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  • 36
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    Electronic Resource
    Organization of a phyllobranchiate gill from the green shore crab Carcinus maenas (Crustacea, Decapoda) (1990)
    Springer
    Cell & tissue research 260 (1990), S. 495-505 
    Details
    ISSN: 1432-0878
    Keywords: Cuticle ; Epithelium, branchial ; Gills ; Hemocoel ; Histology ; Ultrastructure ; Carcinus maenas (Crustacea)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The phyllobranchiate gills of the green shore crab Carcinus maenas have been examined histologically and ultrastructurally. Each gill lamella is bounded by a chitinous cuticle. The apical surface of the branchial epithelium contacts this cuticle, and a basal lamina segregates the epithelium from an intralamellar hemocoel. In animals acclimated to normal sea water, five epithelial cell types can be identified in the lamellae of the posterior gills: chief cells, striated cells, pillar cells, nephrocytes, and glycocytes. Chief cells are the predominant cells in the branchial epithelium. They are squamous or low cuboidal and likely play a role in respiration. Striated cells, which are probably involved in ionoregulation, are also squamous or low cuboidal. Basal folds of the striated cells contain mitochondria and interdigitate with the bodies and processes of adjacent cells. Pillar cells span the hemocoel to link the proximal and distal sides of a lamella. Nephrocytes are large, spherical cells with voluminous vacuoles. They are rimmed by foot processes or pedicels and frequently associate with the pillar cells. Glycocytes are pleomorphic cells packed with glycogen granules and multigranular rosettes. The glycocytes often mingle with the nephrocytes. Inclusion of the nephrocytes and glycocytes as members of the branchial epithelium is justified by their participation in intercellular junctions and their position internal to the epithelial basal lamina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297229
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    Electronic Resource
    Electronic Resource
    The ultrastructure of the intestinal nerve of Remak in the domestic fowl (1990)
    Springer
    Cell & tissue research 260 (1990), S. 601-616 
    Details
    ISSN: 1432-0878
    Keywords: Autonomic ganglia ; Catecholamines ; Intestines ; Innervation ; Ultrastructure ; Domestic fowl (Aves)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An ultrastructural study was made of the neurons, satellite cells and vesiculated axons of the intestinal nerve of the domestic fowl. Broad membrane-to-membrane contacts between adjacent nerve cell bodies were sometimes observed. The cell bodies and processes were not always separated from the extracellular space by a capsule of satellite cells. Following fixation using potassium permanganate, catecholamine (CA)-containing neurons in the intestinal nerve, unlike those in the lumbar parasympathetic ganglia, did not possess any small granular vesicles (SGV). Following exposure to noradrenaline, SGV could be demonstrated in the cell bodies of the juxta-ileal ganglia but not the juxta-rectal ganglia of the intestinal nerve. Non-CA axons were examined in tissue from birds that had been pretreated with 6-hydroxydopamine. Approximately one half of the non-CA axons formed axo-somatic contacts. Most of the non-CA axons contained varying proportions of small clear vesicles, large clear vesicles and large granular vescles. Statistical analysis showed that the non-CA axons could not be subdivided according to their vesicle content. CA-axons contained many SGV and were found in close apposition to neuronal somata and processes, and in the neuropil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297241
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  • 38
    Electronic Resource
    Electronic Resource
    Histochemical and ultrastructural studies on the enterochromaffin-like cell in the gastric mucosa of the opossum Didelphis albiventris (Marsupialia) (1990)
    Springer
    Cell & tissue research 262 (1990), S. 425-430 
    Details
    ISSN: 1432-0878
    Keywords: Stomach ; Enteroendocrine cells ; Enterochromaffin-like (ECL) cell ; Enterochromaffin cell (EC) ; Histamine ; Ultrastructure ; Secretory granules ; Didelphis albiventris (Marsupialia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An ultrastructural study of enterochromaffin-like (ECL) cells in the gastric mucosa of the white-belly opossum Didelphis albiventris (Marsupialia) was carried out. In parallel, histochemical methods were used at the light-microscopical level to demonstrate argentaffin cells, argyrophilic cells, and serotonin- and histamine-immunoreactive elements. Argentaffin and serotonin-immunoreactive cells were scattered, and argyrophilic cells were numerous, within the full thickness of the mucosa. Argyrophilic cell distribution was similar to that of histamine-immunoreactive elements. At the electron-microscopical level, the oxyntic mucosa of D. albiventris presented endocrine cells with secretory granules morphologically similar to those of the ECL cell of eutherian mammals. However, in this marsupial, the ECL cell exhibited a variable mixture of two distinct types of secretory granules: (1) granules with the morphological appearance of the eutherian ECL cell, and (2) granules morphologically similar to those of the eutherian enterochromaffin (EC) cells. Based on this morphological pattern of the ECL cell granules, it is proposed that in the oxyntic mucosa of the opossum D. albiventris, the EC and ECL cells represent distinct steps in the same line of cell differentiation; the ECL cell should also be a site of histamine storage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305239
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  • 39
    Electronic Resource
    Electronic Resource
    Effects of mevinolin, an inhibitor of cholesterol synthesis, on the morphology and function of differentiating and differentiated rat adrenocortical cells in primary culture (1990)
    Springer
    Cell & tissue research 261 (1990), S. 125-132 
    Details
    ISSN: 1432-0878
    Keywords: Adrenal cortex ; Differentiation ; Tissue culture ; Mevinolin ; Steroids ; Ultrastructure ; Rat (Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mevinolin, an inhibitor of cholesterol synthesis, was used to study the effect of endogenous cholesterol synthesis on the morphology and function of differentiating and differentiated fetal rat adrenocortical cells grown in primary culture. Upon adrenocorticotrophic hormone (ACTH) stimulation under conditions in which endogenous cholesterol synthesis was inhibited but exogenous (lipoprotein) cholesterol was available, the cells differentiated normally from glomerulosa-like to fasciculata-like cells; the steroid hormone secretion was maximally induced. Under conditions in which cholesterol synthesis was maximally inhibited by mevinolin and the cells had no access to exogenous cholesterol, the cells did not differentiate into fasciculata-like cells; the ACTH-induced steroid response was highly suppressed under these conditions. The addition of either human low-density lipoprotein (LDL) or high-density lipoprotein (HDL3) to the culture medium restored the ACTH-induced differentiation and steroid secretion. Thus, in the absence of exogenous cholesterol, endogenous cholesterol synthesis was a prerequisite for differentiation. In cultures grown in the presence of exogenous cholesterol and ACTH with mevinolin-inhibited cholesterol synthesis and high steroid output, an increase in cytoplasmic lipids was evident, suggesting upregulation of LDL and HDL receptors. The results also demonstrated that induction of phenotypic differentiation from glomerulosalike into fasciculata-like cells can proceed in the presence of a cholesterol synthesis inhibitor like mevinolin; this differentiation in the absence of endogenous cholesterol synthesis is accompanied by the appearance of cytoplasmic cholesterol ester droplets, typical of fasciculata cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329445
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  • 40
    Electronic Resource
    Electronic Resource
    Qualitative and quantitative analysis of granules in atrial appendage cardiocytes in different physiological states (1990)
    Springer
    Cell & tissue research 259 (1990), S. 529-534 
    Details
    ISSN: 1432-0878
    Keywords: Atrial appendage ; Atrial-specific granules ; Atrial natriuretic polypeptides ; Exocytosis ; Ultrastructure ; Rat (Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Atrial appendage cardiocytes of mammals, including man, contain multiple cytoplasmic granules that vary in number in different physiological states. Using morphologic and comprehensive morphometric techniques, these granules were assessed in Sprague-Dawley rats following dehydration for 5 days, volume-loading by substituting 1% NaCl as drinking water for 7 days, unilateral nephrectomy plus volume-loading for 7 days, and in late term pregnant animals (18–20 days; term ≈21 days). Although principally located in the paranuclear region, granules were observed throughout the sarcoplasm. Cytological features indicative of synthetic activity and granule formation were readily apparent in all groups with the exception of pregnant rats where they were infrequently observed. Granule contents were released by exocytosis and observed in the right appendage of control, dehydrated and nephrectomy/volume-loaded groups and left appendage of volumeloaded animals. Exocytosis was not observed in pregnant animals. By point counting, the proportional volume of cardiocytes occupied by granules (V v ) in controls was significantly greater for right than for left appendage (2.12±0.22% vs 1.29±0.16%; mean±SEM;p〈0.05). A significantly similar difference was found for nephrectomy/volume-loaded animals. There was no significant difference inV v for right appendage between the control and experimental groups; for left appendage there was a significant increase inV v to 2.42±0.09% (p〈0.05) for volume-loaded animals only. Estimation of the maximum diameter of granule profiles in control animals was 238±9 nm and 230±6 nm for right and left appendages, respectively. The profile diameters in the left appendages of dehydrated (202±9 nm) and pregnant (200±7 nm) animals were significantly (p〈0.05) less than those of the control animals. The morphometric findings did not correlate with predictions based upon published biochemical data. In the course of this study, a previously unreported bimembranous, circular to ovoid structure was observed in the cardiocyte sarcoplasm of all animals; the nature and function of this structure is unknown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01740780
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  • 41
    Electronic Resource
    Electronic Resource
    Fine structural and volumetric changes of lamprey photoreceptor cells during light and dark periods (1990)
    Springer
    Cell & tissue research 259 (1990), S. 33-41 
    Details
    ISSN: 1432-0878
    Keywords: Photoreceptor cells ; Ultrastructure ; Volumetric change ; Light/dark cycle ; Lampetra japonica (Cyclostomata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Short photoreceptor cells of the lamprey retina exhibited a 30% increase in the width of the myoid process and a 20% increase in that of the axonal process during a 12-h light period, compared to the measurements obtained during a 12-h dark period. An increase in the amount of cytoplasm, dilation of ER cisterns, and swelling of the nucleus appeared to cause the enlargement of the myoid parts. Accumulation of synaptic vesicles occurred concurrently with a thickening of the axonal process. These morphological changes presumably represent a phase of the diurnal cycle and current synaptic activity of the short cell. By contrast, the long photorecpetor cell showed neither measurable changes nor any indication of “retinomotor movement”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571427
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  • 42
    Electronic Resource
    Electronic Resource
    The paraventricular and posterior recess organs of elasmobranchs: A system of cerebrospinal fluid-contacting neurons containing immunoreactive serotonin and somatostatin (1990)
    Springer
    Cell & tissue research 259 (1990), S. 463-473 
    Details
    ISSN: 1432-0878
    Keywords: Cerebrospinal fluid-contacting neurons ; Paraventricular organ ; Posterior recess organ ; Somatostatin ; Serotonin ; Ultrastructure ; Immunocytochemistry ; Dogfish,Squalus acanthias skate,Raja radiata (Elasmobranchii)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The paraventricular organ (PVO) and the posterior recess organ (PRO) of two elasmobranch species, the spiny dogfish,Squalus acanthias, and the skate,Raja radiata, were investigated by use of scanning and transmission electron microscopy and immunocytochemistry employing a series of primary antisera. The PVO and PRO contained four types of cerebrospinal fluid (CSF)-contacting neurons. One type was free of secretory granules and projected a dendrite-like process into the ventricle. The other three types were distinguished according to the size of their secretory granules. The ventricular extensions of these cells were filled with secretory granules. By means of immunocytochemistry three types of CSF-contacting neurons were observed in the PVO and PRO. Type I contained only serotonin; type 2 displayed only somatostatin; type 3 was endowed with both serotonin and somatostatin. Type I dominated in the PRO, whereas type 3 was the most frequent in the PVO. The latter cells appear to be the site of origin of a loose tract formed by serotonin- and somatostatinimmunoreactive fibers projecting from the PVO into the neuropil of the PRO. Compact bundles formed exclusively by serotonin fibers were also shown to extend between the PVO and PRO. The basal processes of the CSF-contacting neurons of the PRO penetrated into the underlying neuropil. This neuropil is rich in synapses and can be regarded as an integrative area to which the basal processes of the local CSF-contacting neurons, serotonin and somatostatin fibers from the PVO, and fibers containing immunoreactive thyrotropin-releasing hormone of unknown origin, support a conspicuous input. The present findings indicate that the PVO and PRO of elasmobranchs are functionally integrated structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01740772
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  • 43
    Electronic Resource
    Electronic Resource
    Topographical relationships between catecholamine-and neuropeptide-containing fibers in the median eminence of the newt,Triturus alpestris (1990)
    Springer
    Cell & tissue research 259 (1990), S. 561-566 
    Details
    ISSN: 1432-0878
    Keywords: Median eminence ; Catecholamines ; Neuropeptides ; Immunocytochemistry ; Double labeling ; Ultrastructure ; Triturus alpestris (Urodela)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Dopaminergic and peptidergic nerve fibers were simultaneously demonstrated with a double-labeling technique at the ultrastructural level. The first antibody, raised against tyrosine hydroxylase, was applied during the preembedding phase and visualized with the peroxidase method. The second antibody, raised against one of the peptides met-enkephalin, somatostatin or gonadotropin-releasing hormone (GnRH), was applied to the ultrathin sections and visualized with gold-labeled goat anti-rabbit IgG. The fibers of both categories were present in the zona externa of the median eminence, frequently contacting the basal lamina of the portal vessels. In addition, topographical relationships between different types of nerve fibers were observed in the perivascular areas, although there were no morphological signs of synaptic specializations. Using serial sections, it could be established that one GnRH-fiber contacted both a dopaminergic fiber and a fiber immunoreactive for met-enkephalin. The observations support earlier physiological data concerning the regulation of the hypothalamo-hypophyseal axis, with special emphasis on the release of neurohormones in the median eminence of the newt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01740784
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  • 44
    Electronic Resource
    Electronic Resource
    Ultrastructural study of crystalloids in Sertoli cells of the three-toed sloth (Bradypus tridactylus) (1990)
    Springer
    Cell & tissue research 259 (1990), S. 599-602 
    Details
    ISSN: 1432-0878
    Keywords: Crystalloids ; Filaments ; Sertoli cells ; Testis ; Ultrastructure ; Three-toed sloth,Bradypus tridactylus (Edentata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Crystalloids were found in Sertoli cells of the testis of the three-toed sloth by examination at the lightand electron-microscopic levels. Needle-, or spindle-shaped crystalloids, varying in length, were located in the basal part of the Sertoli cells. They consisted of bundles of filaments each measuring ~ 11 nm in diameter. Several filaments were packed hexagonally to form a bundle. The center-to-center distance between individual filaments of a bundle was ~ 17 nm. Periodical lateral projections emanated from the filaments. Cross sections of crystalloids showed that the projections radiated from each filament in three directions, forming an equilateral triangle with a side length of ~ 15 nm. Scattered polyribosomes were found between and around the bundles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01740789
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  • 45
    Electronic Resource
    Electronic Resource
    Organization of testicular interstitial tissue of an Australian rodent, the spinifex hopping mouse, Notomys alexis (1990)
    Springer
    Cell & tissue research 260 (1990), S. 469-477 
    Details
    ISSN: 1432-0878
    Keywords: Testis ; Interstitial tissue ; Leydig cells ; Lymphatics ; Ultrastructure ; Spinifex hopping mouse ; Notomys alexis (Rodentia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The organization of testicular interstitial tissue of the spinifex hopping mouse, Notomys alexis differs from that of other rodents. It comprises between 10.3% and 17.3% (average 15.0%) of the total testicular volume, and is variable in its organization both at different locations within the testis of the one animal and among different individuals. Abundant, closely packed Leydig cells are usually present; however, in some regions large, thick-walled blood vessels and extensive peritubular lymphatic spaces, often lacking an endothelium adjacent to the Leydig cells, are also prominent. The Leydig cells in contact with the large blood vessels and lymphatics, unlike those in regions where lymph is sparse, are not densely packed and sometimes contain numerous lipid droplets. Ultrastructure of Leydig cells is typical of steroid-producing cells; however, mitochondria are often extremely large, unusual in shape or bizarely arranged in relation to one another. Also electrondense bodies displaying a paracrystalline-like internal structure of parallel, electron-dense filaments arranged in a lattice pattern occur in the cytoplasm of many cells. The significance of these unusual ultrastructural features and the organization of the interstitial tissue remain to be determined conclusively, but may relate to steroid synthesis, secretion and uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297226
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  • 46
    Electronic Resource
    Electronic Resource
    Immunoreactive atrial natriuretic peptide in the fish heart and blood plasma examined by electron microscopy, immunohistochemistry and radioimmunoassay (1990)
    Springer
    Cell & tissue research 260 (1990), S. 235-247 
    Details
    ISSN: 1432-0878
    Keywords: Atrial natriuretic peptide ; Heart ; Freshwater fish ; Seawater fish ; Immunohistochemistry ; Ultrastructure ; Radioimmunoassay ; Cyprinus carpio (Teleostei) ; Narke japonica (Elasmobranchii) ; Eptatretus burgeri (Cyclostomata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The immunoreactivity of atrial natriuretic peptide and ultrastructure of cardiocytes were examined in 5 species each of freshwater and seawater teleosts, as well as in 2 species each of elasmobranchs and cyclostomes. Immunoreactivity was strong in the atria of Cyprinus carpio, Anguilla japonica and Conger myriaster, rather weak in atria of Channa maculata, Lepomis macrochirus, Salmo gairdneri, Oplegnathus fasciatus and Eptatretus burgeri, very weak in atria of Pagrus major, Trachurus japonicus and Triakis scyllia, and not detectable in atria of Hexagrammos otakii, Narke japonica and Lampetra japonica. The immunoreactivity of the atrial cardiocytes was generally stronger in freshwater than seawater fish. Ventricular immunoreactivity was detected only in 7 species, always being weaker than that observed in the atrium. Ultrastructurally, however, secretory granules were found in atria and ventricles of all species examined, being more frequent in the former than the latter. By radioimmunoassay, immunoreactive ANP was detected in the extracts of blood plasma and both atrial and ventricular tissues of all species examined. There were no statistically significant differences in the values between freshwater and seawater species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318627
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  • 47
    Electronic Resource
    Electronic Resource
    Ultrastructural changes of liver parenchyma following digitonin-pulse perfusion of rat liver (1990)
    Springer
    Cell & tissue research 261 (1990), S. 423-430 
    Details
    ISSN: 1432-0878
    Keywords: Hepatocytes ; Liver ; Ultrastructure ; Digitonin perfusion ; Metabolic zonation ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary It has been shown that pulse perfusion of rat liver with a digitonin-containing medium results in a highly zonated hepatocyte permeabilization, allowing selective sampling of cytosolic constituents from periportal and perivenous (centrolobular) hepatocytes “in situ”. In the present paper we provide an ultrastructural evaluation of the perfusion method. Identical changes in hepatocytes from affected periportal and perivenous zones are found. Affected hepatocytes appear light (electron-lucent) in electron micrographs with a sharp transition to normal hepatocytes. The most conspicuous ultrastructural findings are: (1) transformation of the sinusoidal part of the light hepatocytes, the lipocyte processes and the endothelium of affected zones apparently unifying into a continuous layer dominated by disrupted plasma membranes and 7-nm filaments; (2) deposition of osmiophilic digitonin-cholesterol complexes along the sinusoidal plasma membranes of affected zones; and (3) reduction of the cytoplasmic matrix (cytosol) in the light hepatocytes, a dilation of the mitochondrial intermembrane space with a preserved mitochondrial matrix, and a dilation of cisternae of the granular endoplasmic reticulum. The ultrastructural findings are consistent with marker-enzyme activity measured in eluates from digitonin-perfused livers, except that lysosomes appear intact, apparently contrasting with the observed eluation of amyloglucosidase (Quistorff et al. 1985).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313520
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  • 48
    Electronic Resource
    Electronic Resource
    Effect of carbamylcholine on Harderian gland morphology in rats (1990)
    Springer
    Cell & tissue research 261 (1990), S. 451-459 
    Details
    ISSN: 1432-0878
    Keywords: Harderian gland ; Ultrastructure ; Morphometry ; Carbamylcholine ; Secretion ; Rat (Slc: SD)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary To determine the effect of cholinergic secretagogue on the Harderian gland of rats, several light- and electron-microscopic parameters were morphometrically assessed at different time intervals after carbamylcholine injection. In controls, two types of glandular cells (type A cells having 40–55 large vacuoles per cell profile and type B cells containing 30–38 smaller vacuoles per cell profile) and myoepithelial cells were recognized. At 5 min after injection of carbamylcholine, when rats secreted “bloody tears”, many alveoli showing narrower lumina and exocytotic figures in both types of cells were observed. Some vacuoles, which were covered by thin cytoplasmic sheets, protruded into the alveolar lumina. However, there was no evidence of apocrine or holocrine secretion. At 30 min and 120 min after injection, most of the alveolar lumina were dilated, and a pronounced decrease in the number of vacuoles in the glandular cells was observed. At 300 min after injection, the secretory vacuoles in both cell types reaccumulated. Transitional forms between the two cell types were not observed. The two types of Harderian gland cells can therefore be considered independent populations rather than different secretory stages of the same cell. It appears that the secretory process of the Harderian gland of rat is affected by cholinergic stimulation of the two types of glandular cells and of myoepithelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313523
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  • 49
    Electronic Resource
    Electronic Resource
    Effects of visible and ultraviolet radiation on the ultrastructure of zooxanthellae (Symbiodinium sp.) in culture and in situ (1990)
    Springer
    Cell & tissue research 261 (1990), S. 501-508 
    Details
    ISSN: 1432-0878
    Keywords: Photoadaptation ; Stereology ; Ultrastructure ; Accumulation bodies ; Zooxanthellae ; Symbiodinium sp. ; Protozoa ; Dinoflagellata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Quantitative ultrastructural studies on the effects of visible and ultraviolet radiation on zooxanthellae in culture and in situ showed an inverse relationship between the volume fraction of chloroplast and irridiance. An independent effect of ultraviolet radiation was detected in cultured zooxanthellae only. The volume fraction of chloroplasts in cultured zooxanthellae and zooxanthellae in situ were the same, while the surface density of thylakoid lamellae relative to chloroplast volume in cultured zooxanthellae was less than in zooxanthellae in situ for all irradiances. Additionally, zooxanthellae in situ showed an effect of ultraviolet radiation on surface density of thylakoid lamellae. The response to different irradiances suggests a limit to photoadaptation by means of changing chloroplast volume, and that changes in thylakoid density are responsible for the continued photoadaptive plasticity observed. Flow cytometry and stereological studies show that the volume fraction of accumulation bodies within zooxanthellae increases with irradiance and ultraviolet radiation. Ultrastructurally, accumulation bodies do not resemble plant peroxisomes or glyoxysomes, while other inclusions observed in this stydy are suggestive of peroxisomes. This evidence suggests that accumulation bodies are not peroxisomes, but does support the previous assumptions concerning their role in autophagic processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313529
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  • 50
    Electronic Resource
    Electronic Resource
    Urinary bladder of rat: fine structure of normal and hypertrophic musculature (1990)
    Springer
    Cell & tissue research 262 (1990), S. 67-79 
    Details
    ISSN: 1432-0878
    Keywords: Urinary bladder ; Smooth muscle ; Hypertrophy ; Ultrastructure ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the muscle of the urinary bladder in female rats is similar to that of other visceral muscles, although it is arranged in bundles of variable length, cross-section and orientation, forming a meshwork. When distended, the musculature is 100–120 μm thick, with some variation and occasional discontinuity. Extended areas of cell-to-cell apposition with uniform intercellular space occur between muscle cells, whereas attachment plaques for mechanical coupling are less common than in other visceral muscles. There are no gap junctions between muscle cells. Many bundles of microfilaments and small elastic fibres run between the muscle cells. After chronic partial obstruction of the urethra, the bladder enlarges and is about 15 times heavier, but has the same shape as in controls; the growth is mainly accounted for by muscle hypertrophy. The outer surface of the hypertrophic bladder is increased 6-fold over the controls; the muscle is increased 3-fold in thickness, and is more compact. Mitoses are not found, but there is a massive increase in muscle cell size. There is a modest decrease in percentage volume of mitochondria, an increase in sarcoplasmic reticulum, and no appreciable change in the pattern of myofilaments. Gap junctions between hypertrophic muscle cells are virtually absent. Intramuscular nerve fibres and vesicle-containing varicosities appear as common in the hypertrophic muscle as in controls. There is no infiltration of the muscle by connective tissue and no significant occurrence of muscle cell death.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327747
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  • 51
    Electronic Resource
    Electronic Resource
    Changes in renal morphology and renin secretion in the golden-mantled ground squirrel (Spermophilus lateralis) during activity and hibernation (1990)
    Springer
    Cell & tissue research 262 (1990), S. 99-104 
    Details
    ISSN: 1432-0878
    Keywords: Hibernation ; Ultrastructure ; Plasma renin activity ; Renal changes ; Spermophilus lateralis (Rodentia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Chronological changes in renal glomerular morphology and plasma renin activity were investigated during active and hibernating periods in the golden-mantled ground squirrel Spermophilus lateralis. The objective of this study was to determine whether the glomerular endothelium, visceral epithelium (podocytes), basement membrane, mesangial cells, proximal convoluted tubule cells and plasma renin activity exhibit measurable sequential differences between as well as within active and hibernating states at various time points. Limitations in the size of the experimental population prevented an evaluation of changes in these parameters during other important periods such as periodic arousal between hibernation bouts. In this study, glomerular endothelial pore number and epithelial filtration slit number significantly decreased by early hibernation when compared to those during summer activity, and then they increased back toward summer levels by late hibernation. In contrast, podocytic pedicel width along the glomerular basement membrane increased from summer activity to early hibernation, before significantly decreasing again by late hibernation. Mesangial cell and proximal convoluted tubule cell activity appeared increased during hibernation as compared to summer activity, whereas the width of the glomerular basement membrane showed no significant alterations throughout. Plasma renin activity significantly increased during early hibernation and mid-hibernation when compared to summer levels but had decreased by late hibernation toward summer values. The glomerular and plasma renin activity changes observed in this study clearly illustrate the drastic structural and functional adjustments which hibernating species make during torpor and also correlate well with the reported decrease in renal perfusion pressure and urine formation during hibernation. The observed morphological changes during hibernation do not appear to be temperature-dependent, because significant alterations in most of the parameters studied occurred during this period despite the fact that cold-room temperatures were kept constant throughout. The chronological approach to this study and its morphometric evaluation represent a pilot attempt at accurately documenting these changes during two critical states in the hibernator's cycle and may eventually lead to the characterization of these changes during the entire circannual cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327750
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    Organelle loss in the endosymbiont ofGymnodinium acidotum (Dinophyceae) (1990)
    Springer
    Protoplasma 153 (1990), S. 178-185 
    Details
    ISSN: 1615-6102
    Keywords: Cryptophyceae ; Dinoflagellate ; Dinophyceae ; Endosymbiosis ; Gymnodinium ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The freshwater dinoflagellateGymnodinium acidotum is known to harbor a cryptomonad endosymbiont whose chloroplasts give the organism its blue-green coloration. Every cell examined from a wild population possessed chloroplasts, mitochondria, and other organelles which are of endosymbiotic origin. Transmission electron microscopy and fluorescence microscopy revealed that only 33% of these cells possessed the nucleus of the endosymbiont. The lack of a cryptomonad nucleus in some cells did not appear to affect the cells' ability to photosynthesize or move in response to varying levels of illumination. This represents the first report of a host/endosymbiont relationship in which a significant number of individuals from a given population lack a major endosymbiont organelle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01354002
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    In situ degradation of cellulose fibres by the entodiniomorph rumen ciliatePolyplastron multivesiculatum (1990)
    Springer
    Protoplasma 154 (1990), S. 122-131 
    Details
    ISSN: 1615-6102
    Keywords: Cellulose degradation ; Ultrastructure ; Rumen ciliate ; Polyplastron multivesiculatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The feeding behaviour of the rumen ciliatePolyplastron multivesiculatum has been studied with scanning and transmission electron microscopy. In contrast to other large entodiniomorphs,Polyplastron scarcely attaches to plant substrata such as straw or alfalfa; however, it readily phagocytes cellulose fibres (like epidermal bristles of alfalfa) suspended in the rumen fluid. The different stages of ingestion and intracellular degradation of this particular substrate are described at the ultrastructural level. Engulfment involves active movements of the vestibular lips. The digestion follows a peculiar pattern (“permeative” way): the cellulose substrate is gradually decomposed in situ inside the primary digestive vacuole without large fragmentation or pinching off of small vesicles. Thus degradation products are not stored in secondary vesicular systems as they are for other plant substrates (“cytotic” way). Thus, there is no single or general pattern of cellulosic structures lysis in entodiniomorph rumen ciliates. Rather, several pathways can be observed, probably according to the nature of the ingested plant material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01539839
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  • 54
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    Direct cytoplasm-cytoplasm connection: an unusual host-parasite interaction of the tremelloid mycoparasiteTetragoniomyces uliginosus (1990)
    Springer
    Protoplasma 154 (1990), S. 157-160 
    Details
    ISSN: 1615-6102
    Keywords: Basidiomycetes ; Cytoplasmic connections ; Host-parasite interaction ; Tetragoniomyces uliginosus ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cellular interaction ofTetragoniomyces uliginosus andRhizoctonia sp. was restudied by transmission electron microscopy. During the first stages of interaction a body of medium electron density is visible at the center of the haustorial apex in close association with the plasmalemma. A single micropore is produced between the haustorial filament and the host cell. Cytoplasmic connection via the pore always occurred. The pore membrane is continuous with the plasmalemma of both cells. The protoplasts of both the haustorium and the host cell fuse via the micropore. An electron transparent to dense body occlude the pore. Among basidiomycetes, direct connection between the parasite and host protoplasts represents a hitherto unknown type of parasitic interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01539843
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  • 55
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    Selenium deficiency in Crustacea (1990)
    Springer
    Protoplasma 154 (1990), S. 25-33 
    Details
    ISSN: 1615-6102
    Keywords: Selenium deficiency ; Culture medium ; Crustacea ; Daphnia magna ; Ultrastructure ; Cytopathology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of selenium deprivation onDaphnia magna was examined under controlled rearing conditions in a synthetic culture medium. After three generations, fertility was significantly reduced in deprived (Se−) animals. Growth and mortality of parent daphnids and development of parthenogenetic eggs were not affected during this period. In the fourth generation Se− daphnids rejected parts of their second antennae. At the ultrastructural level antennal muscle tissue was severely affected. Animals deprived of selenium had mitochondria and sarcoplasmic reticulum with myelin-like alterations. Giant lysosomes were present and complete lysis of muscle fibrils was observed in antennal muscle cells. These alterations are characteristic features of peroxidic damage in tissues. This interpretation is consistent with the function of selenium as a constituent of the enzyme glutathione peroxidase which protects cells from peroxidation. Selenium should be included in synthetic culture media for daphnids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01349532
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  • 56
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    Ultrastructure of ascospore delimitation in freeze substituted samples ofAscodesmis nigricans (Pezizales) (1990)
    Springer
    Protoplasma 156 (1990), S. 94-102 
    Details
    ISSN: 1615-6102
    Keywords: Ascodesmis nigricans ; Ascosporogenesis ; Freeze substitution fixation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Freeze substitution proved to be a valuable technique for studying the early stages of ascosporogenesis inAscodesmis nigricans. Our observations indicate that the ascus vesicle originated from the ascus plasma membrane. Invaginations of the plasma membrane produced ascus vesicle initials consisting of two closely spaced unit membranes. The appearance of the outer leaflet of each of these membranes was identical to that of the inner leaflet of the ascus plasma membrane. Apparent points of continuity between ascus vesicle initials and the plasma membrane were observed. Ascus vesicle initials accumulated in the ascus cytoplasm near the plasma membrane and then coalesced to form the ascus vesicle, a peripheral, cylinder-like structure consisting of two closely spaced unit membranes that extended from the ascus apex to the ascus base. The ascus vesicle then became invaginated in a number of regions and subsequently gave rise to eight sheet-like segments, or ascosporedelimiting membranes, that encircled uninucleate segments of cytoplasm forming ascospore initials. Like the ascus vesicle, each ascospore-delimiting membrane consisted of two closely spaced unit membranes, the inner of which became the ascospore plasma membrane. The ascospore wall then developed between the spore plasma membrane and the outer membrane. Many details of ascospore maturation were clearly visible in freeze substituted samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666510
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  • 57
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    Effects of temperature on cytomorphogenesis and ultrastructure ofMicrasterias denticulata Bréb (1990)
    Springer
    Protoplasma 157 (1990), S. 3-18 
    Details
    ISSN: 1615-6102
    Keywords: Chilling ; Cytomorphogenesis ; Heat ; “Heat shock granules” ; Micrasterias ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Exposure of growingMicrasterias cells to high (32°–36°C) and low (3°–10°C) temperatures produces changes in morphology that are accompanied by several ultrastructural alterations. Whereas low temperatures essentially cause simplification of cell ornamentation, a variety of cell malformations result from high temperature treatment. These are the loss of cell symmetry leading to markedly aberrant cell shapes and an increase of “main lobes” with reduced degree of differentiation. Preliminary studies indicate that a shift in the distribution of membrane-associated Ca2+ by elevated temperatures probably underlies these abnormal cytomorphogenetic events. Both, low and high temperature cause a reduction in size of the young half cell and affect cytoplasmic streaming. Moreover, nuclear migration is retarded and chloroplast arrangement is influenced by temperature treatment at both ranges. Growth velocity of primary wall responsible for cell shaping is increased at high and slowed down at low temperatures compared to cells grown at 20°C. The main ultrastructural alterations induced by high temperatures are an increase in amount and length of ER cisternae, the appearance of “heat shock granule” aggregations localized in the cytoplasm, a reduced number of ribosomes and polysomes, the presence of oil bodies in growing cells and a varying thickness of the primary wall. Influences of low temperatures on ultrastructure are less pronounced. They are manifested in the formation of large aggregations of ER cisternae slightly differing from those found in untreated cells, a disturbed arrangement of the microtubule system surrounding the nucleus and a decrease of the number of cell wall forming cytoplasmic vesicles. It is thought that most of the temperature effects are due to an influence on membranes probably an alteration of ionic currents and, in addition, a modulation of normal protein synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322635
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    Ultrastructure of esophageal glands and their secretory granules in the root-knot nematodeMeloidogyne incognita (1990)
    Springer
    Protoplasma 156 (1990), S. 9-18 
    Details
    ISSN: 1615-6102
    Keywords: Esophageal glands ; Plant-parasitic nematodes ; Secretory granules ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The dorsal and subventral esophageal glands and their secretory granules in the root-knot nematodeMeloidogyne incognita changed during parasitism of plants. The subventral esophageal glands shrank and the dorsal gland enlarged with the onset of parasitism. While secretory granules formed by both types of glands were spherical, membrane-bound, and Golgi derived, the granules differed in morphology and size between the two types of glands. Subventral gland extensions in preparasitic second-stage juveniles were packed with secretory granules which varied in diameter from 700–1,100 nm and had a finely granular matrix. Within the matrix of each subventral gland granule was an electron-transparent core that contained minute spherical vesicles. The size and position of the core varied within different granules. Few granules were present in the dorsal gland extension in preparasitic juveniles. The matrix of dorsal gland secretory granules formed during parasitism was homogeneous and more electron-dense than the matrix of subventral gland granules. Subventral gland secretory granules of parasitic juveniles and adult females appeared degenerate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666501
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  • 59
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    Polysaccharide and protein secretion by grass microhairs (1990)
    Springer
    Protoplasma 156 (1990), S. 45-56 
    Details
    ISSN: 1615-6102
    Keywords: Cytochemistry ; Grasses ; Microhairs ; Partitioning membranes ; Polysaccharides ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Secretory activities of bicellular microhairs from grasses belonging to the subfamilies Chloridoideae, Arundinoideae, Panicoideae, and Bambusoideae, and including the “chloridoid”, “panicoid” and “Enneapogon” microhair morphological types, have been investigated. Light microscopic histochemistry indicated that all microhairs studied secrete polysaccharide and protein (or glycoprotein), including those which also secrete salt. Localization of polysaccharide at ultrastructural level using periodic acid-thiocarbohydrazidesilver proteinate staining revealed that in “panicoid type” microhairs dictyosomes are involved in polysaccharide secretion, whereas in the “chloridoid” and “Enneapogon” types “partitioning membranes” seem to be involved instead.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666505
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    Isolation, purification, and characterization of flagellar scales from the green flagellateTetraselmis striata (Prasinophyceae) (1990)
    Springer
    Protoplasma 156 (1990), S. 103-112 
    Details
    ISSN: 1615-6102
    Keywords: Tetraselmis striata ; Prasinophyceae ; Flagellar scales ; Isolation ; Purification ; Ultrastructure ; Biochemical composition ; 2-keto-sugar acids ; Polypeptide composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Flagellar scales from the green flagellateTetraselmis striata (Prasinophyceae) were isolated, purified by isopycnic cesium chloride-gradient and zonal sucrose gradient centrifugation and their structure and biochemical composition investigated. Three types of flagellar scales were purified to more than 90% purity, a fourth type up to 75% purity. In addition to the previously known types of flagellar scales (pentagonal scales, rod-shaped scales, hair-scales), a novel scale type (i.e., the knotted scales) was discovered. New information about the asymmetric structure of the rod-shaped scales is presented and consequently they are renamed “man scales”. Flagellar scales consist mainly of carbohydrate (50–70%), significant amounts of protein (11% of dry weight) were found only in pentagonal scales. The main sugars (90%) of the pentagonal and man scales are the unusual 2-keto-sugar acids 3-deoxy-5-O-methyl-2-octulosonic acid (5 OMeKDO), 3-deoxy-2-heptulosaric acid (DHA), and 3-deoxy-2-octulosonic acid (KDO), the knotted scales contain as major sugars galactose and arabinose in addition to KDO and 5 OMeKDO but lack DHA. 13 major polypeptides were identified in flagellar scales by one-dimensional SDS-PAGE, 11 of these are of high molecular mass (〉116 kDa). While the majority of polypeptides was found associated with pentagonal scales, at least 4 polypeptides were tentatively assigned to the hair-scales and knotted scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666511
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    Systematics and evolution within theCompositae, seen with the eyes of a chemist (1990)
    Springer
    Plant systematics and evolution 171 (1990), S. 1-14 
    Details
    ISSN: 1615-6110
    Keywords: Angiosperms ; Compositae ; Chemistry ; systematics ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The broad knowledge of the chemistry of theCompositae allows the discussion of its relevance for the systematics and evolution within the family. Furthermore a separation into subfamilies can be supported by the observed differences in the distribution of the main constituents in the tribes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00940593
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    Ultrastructural pathology of the vestibule in patients with acoustic neurinomas: secondarily operated cases after posterior fossa operation (1990)
    Springer
    European archives of oto-rhino-laryngology and head & neck 247 (1990), S. 93-96 
    Details
    ISSN: 1434-4726
    Keywords: Vestibule ; Acoustic neurinoma ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The vestibular sensory epithelia from two patients with acoustic neurinomas were examined ultrastructurally. Both patients had first undergone posterior fossa operations 8 months and 3 years before residual tumors in the acoustic canals were removed by a secondary translabyrinthine operation. Labyrinthine sensory tissues were also removed for microscopic studies. In case 1, the utricular macula and the lateral and anterior cristae were observed, with all sensory epithelia showing fairly normal findings. Myelinated nerve fibers below the sensory epithelia also appeared normal. In case 2, only the utricular macula could be observed. The sensory epithelium showed severe degeneration, disappearing sensory cells and increasing cytoplasmic filaments of both the sensory cell and the supporting cell. Myelinated nerve fibers below the sensory epithelia were only rarely found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00183175
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    Ultrastructural localization of Ca2+-binding sites in the middle ear mucosa of the rat (1990)
    Springer
    European archives of oto-rhino-laryngology and head & neck 247 (1990), S. 156-160 
    Details
    ISSN: 1434-4726
    Keywords: Calcium distribution ; Rat middle ear mucosa ; Electron spectroscopic imaging ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cations were precipitated with potassiumpyroantimonate in the middle ear mucosa of the rat and the distribution of the formed precipitates was studied by electron microscopy. The precipitate density in various cells of the different epithelia of the middle ear mucosa was determined on electron micrographs by counting the number of precipitates per unit area. Electron spectroscopic imaging was also performed to obtain information about the spatial distribution of the precipitates and their elemental composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175968
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  • 64
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    Ciliary ultrastructure in a child with Kartagener's syndrome (1990)
    Springer
    European archives of oto-rhino-laryngology and head & neck 248 (1990), S. 49-52 
    Details
    ISSN: 1434-4726
    Keywords: Kartagener's syndrome ; Immotile cilia ; Ultrastructure ; Tannic acid ; Dynein arm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Kartagener's syndrome has been characterized by a primary ultrastructural abnormality of the cilia which consequently impairs their movements. We used transmission electron microscopy with tannic acid staining to investigate the fine structure of the cilia from the nasal mucosa of a 7-year-old girl with Kartagener's syndrome. The staining technique employed was useful for visualizing the dynein arms and protofilaments of the microtubules of the cilia. Although 15% of the cilia examined demonstrated microtubular disarrangements, these findings were considered to be acquired changes due to chronic sinusitis. No abnormal ciliary ultrastructures specific to Kartagener's syndrome, such as absence of dynein arms, were detected in this study. In such cases without any abnormal ciliary ultrastructures, it is conceivable that some other unknown factor may be involved in the impaired ciliary movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00634781
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    Constancy of synaptic ribbon numbers in the retina of the arctic chary, Salvelinus alpinus (1990)
    Springer
    Environmental biology of fishes 27 (1990), S. 131-137 
    Details
    ISSN: 1573-5133
    Keywords: Diurnal ; Histology ; Photoperiod ; Cones ; Rods ; Ultrastructure ; Fish vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis At high latitudes, such as in Iceland, the daily photoperiod varies from almost continuous darkness in winter to virtually constant light in summer. Previous studies of detailed retinal structure in vertebrates have shown significant daily and annual effects of photoperiod. We sampled arctic charr in Iceland during the summer, including fish that were both light- and dark-adapted, during both day and night. We observed retinomotor responses characteristic of light- and dark-adaptation, but found no difference in the number of synaptic ribbons in the retina. The morpho-physiological changes, appearing as retinomotor responses, are thus not expressed at the synaptic level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00001942
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    Modelling the kinetics of the precipitation polymerization of acrylic acid (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 107-116 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zur Beschreibung der Polymerisationsgeschwindigkeit der radikalischen Fallungspolymerisation von Acrylsäure in Toluol wurde ein Modell entewickelt. Die experimentelle Überprüfung des Modells erfolgte durch Messungen in einem isotherm betriebenen Reaktionskalorimeter. Das Modell beschreibt die Polymerisationsgeschwindigkeit bis zum vollständigen Umsatz in einem Temperaturbereich von 40 bis 60°C.
    Notes: A kinetic model for the free-radical precipitation polymerization of acrylic acid in toluene was developed and verified experimentally by using an isothermal reaction calorimeter. The model predicts the rate of polymerization accurately up to complete conversion in the temperature range of 40 to 60°C.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051750109
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    The influence of electron irradiation on the mechanical properties of polypropylene/EPDM rubber blends (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 157-168 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird über Untersuchungen an Legierungen aus isotaktischem Polypropylen und EPDM-Elastomer berichtet, die mit hochenergetischen Elektronen bestrahlt worden waren. Die Mischungsverhältnisse in den Proben überstrichen sowohl den für elastomermodifizierte Thermoplaste typischen Bereich als auch den der thermoplasticschen Elastomeren. Eine Vernetzung der Komponenten über die Grenzfläche hinweg wurde nachgewiesen. Diese grenzflächenübergreifende Vernetzung bewirkte eine merkliche Verbesserung der mechanischen Eigenschaften insbesondere des thermoplastischen Elastomeren.
    Notes: Blends of isotactic polypropylene and EPDM rubber have been treated by electron irradiation in the composition range of rubber modification and in the thermoplastic rubber composition range as well. Mutual crosslinking of the components through the interface could be detected. This intercrosslinking caused a remarkable improvement of the mechanical properties particularly of the thermoplastic rubber.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051750113
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    Mitteilungen (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 205-205 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051750117
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    Mechanisms of photooxidation of polyolefinsPaper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers”, in Prague (Czechoslovakia), July 25 - 27, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 27-42 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanisms of photooxidation usually envisaged, are perfected by taking into account photoreactions of peroxy radicals. They involve interaction of a peroxy radical with the polymer to yield a hydroperoxy radical and a pair of macroradicals. After peroxidation, this pair will usually undergo bimolecular termination. The influence of such a reaction on photooxidation kinetics is particularly important for polyethylene. Then, chain termination occurs mainly by interaction of two hydroperoxy radicals or of a hydroperoxy radical with a macroperoxy radical. The reaction does not only affect kinetics of photooxidation but also the nature of the photooxidation products. The latter is more important for polypropylene than for polyethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760102
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    Ageing behaviour of hot-water pipes of polybutene-1Paper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 55-63 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Isothermal Differential Thermal Analysis was used to test the thermooxidative stability of pipes of polybutene during internal pressure tests at 110°C. At low hoop stresses and long testing times pipe failure was exclusively caused by thermooxidative degradation of the polymer.The stabilizer distribution in the initial state and its alteration during the pressure tests could easily be measured by isothermal DTA. Leaching of antioxidants from pipe walls could be detected. The decrease of residual thermooxidative stability was degressive.Degradation of pipe material started from the exterior pipe wall. Molecular weight of polybutene decreased rapidly after stabilizer exhaustion which could be observed by isothermal DTA.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760104
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    Possibilities for predicting the change in properties of polyolefins at natural ageingPaper presented at the 19th Colloquim of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 79-86 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A base of experimental data on the ageing of commerial grade plastics is created. In includes assorted physical and chemical properties of plastics and their changes at natural ageing. An automated system for storing and processing of the experimental data is designed. Processing involves mathematical modeling of the changes in properties that aids in empirical prediction. The possibilities of the system are verified with experimental results from a 5-year ageing period of PE-LD and PE-HD. The results show a good agreement between the predicted and real data for selected models.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760106
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    Weld lines in injection moulded polypropylene parts. Mechanical properties morphology relationships (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 179 (1990), S. 35-56 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Morphologie von Polypropylen-Spritzgußteilen mit Bindenaht wurde mit Röntgenweit-und Kleinwinkelstreuung, Lichtstreuung und Polarisationsmikroskopie untersucht. Die erhaltenen morphologischen Daten wurden mit mechanischen Werten aus Zugversuchen korreliert. Es wird gefunden, daß die mechanischen Eigenschaften der untersuchten Proben im wesentlichen von der sphärolithstruktur beeinflußt werden. Anhäufungen von Sphärolithen mit Kristallen der hexagonalen β-Modifikation und eine starke Inhomogenität der Sphärolithstruktur senkrecht zur Bindenaht sind der wesentliche Grund für die verschlechterten mechanischen Eigenschaften. Diese Sphärolithstruktur wird durch die Temperatur des Spritzgußwerkzeugs stark beeinflußt. Die Lamellen-Überstruktur hat dagegen einen vernachlässigbar kleinen Einfluß auf das mechanische Verhalten.
    Notes: The morphology of polypropylene plaques containing a weld line, has been investigated by x-ray wide and small angle scattering, light scattering and polarization microscopy. The results are correlated to mechanical values obtained from tensile tests. While the lamellar morphology is of neglectable influence, it is found, that the mechanical properties of the samples are strongly influenced by the spherulitic structure. Clustering of β-type spherulites and strong morphological inhomogeneities in the vicinity of the weld line are the primary reason for the mechanical weakening of the plaques. The temperature of the mould has a strong effect on the spherulitic structure and thus on the tensile properties of the samples.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051790104
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    Studies of the surface structure of plasma-modified fillers and their application in PVC and PP compounds (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 179 (1990), S. 77-85 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Füllstoffe für PVC- und PP-Formmassen wurden mit Mikrowellenplasma behandelt. Photoakustische FT-IR-Spektren zeigen, daß die Plasma-Polymerhülle auf der Füllstoffoberfläche —C=C—, —CH2—, CH3— und andere Gruppen enthält. Aus Röntgenelektronenspektren geht hervor, daß zwischen Siliciumdioxid und der organischen Beschichtung chemische Bindungen existieren. Durch Compoundieren von plasmabehandelten Füllstoffen mit PVC und PP werden Materialien mit guten mechanischen Eigenschaften bei niedrigen Kosten erhalten.
    Notes: Fillers for PVC and PP compounds have been treated by microwave plasma. FT-IR photoacoustic spectroscopy studies show that the plasma polymer sheath on filler's surface contains —C=C—, —CH2—, —CH3 groups, etc. X-ray photoelectron spectroscopy studies reveal that interfacial chemical bondings exist between silica and the organic coating. Application of plasma-treated fillers in PVC and PP compounds gives rise to materials of good mechanical properties and low cost.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051790106
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    Alcoholysis of esterlinkages in solution (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 179 (1990), S. 135-148 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly-(alkylenadipat)-diole mit Molmassen von 1500, 2000 und 3000 wurden bei Temperaturen von 25 und 60°C in Gegenwart verschiedener Alkohole und unterschiedlicher PUR-Katalysatoren (1,4-Diazabicyclo[2.2.2]octan (DABCO), Dibutylzinndilaurat (DBTL),Dibutylzinndiethoxid (DBTEO) und Dibutylzinnoxid (DBTO)) in Ethylacetat bzw. Toluol gelagert und die Alkoholyse verfolgt. Die erhaltenen Ergebnisse werden mit dem Alkoholyseverhalten verschiedener Dialkyladipate sowie des Lösungsmittels Ethylacetat unter den selben Bedingungen verglichen. Die Alkoholyse verlauft in Gegenwart der zinnorganischen Verbindungen etwa mit gleicher Geschwindigkeit, ohne daß diese selbst signifikant zersetzt werden, wahrend DABCO praktisch inaktiv ist. Die Aktivitat der Alkohole ist starker von ihrer sterischen Struktur als von ihrer Basizitat abhangig. Die Stabilität der Polyalkylenadipate gegenüber einer Umesterung nimmt mit der Lange der Diolalkyleneinheiten des Polyols zu. Die Umesterung von Adipinsäuredialkylestern findet auch partiell in Anwesenheit eines großen Uberschusses an Ethylacetat statt.
    Notes: Poly(alkylene adipate)diols having molar masses of 1500, 2000 and 3000 were stored at temperatures of 25 and 60°C in the presence of low amounts of different alcohols and some polyurethane (PUR) catalysts, such as dibutyltindilaurate (DBTL), dibutyltindiethoxide (DBTEO), dibutyltinoxide (DBTO), and 1,4-diazabicyclo[2.2.2]octane (DABCO). Alcoholysis was studied using either ethyl acetate (EA) or toluene as solvent. The results were compared with those obtained by examining the behaviour of several dialkyl adipates and ethyl acetate under identical conditions. The alcoholysis in the presence of the tin catalysts proceeds at the same reaction rate without significant decomposition of the catalyst, whereas DABCO is practically inactive. The nucleophilic activity of the alcohols depends on their bulk size rather than their basicity. The resistance of polyalkylene adipates to transesterification increases with the increasing alkyl chain length of diol units in polyester. A partial transesterification of dialkyl adipates takes place too, in spite of ethyl acetate being present in excess.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051790110
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    Separation of liquid mixtures by using polymer membranes. II. Water-alcohol separation by pervaporation through porous PVA membranesPart 1 cf.25. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 179 (1990), S. 157-171 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde das Permeations- und Trennverhalten von Alkohol/Wasser-Systemen durch poröse PVA-Membranen untersucht. PVA-Membranen mit unterschiedlicher Anzahl und Große von Poren wurden über Mischungen in Lösung mit verschiedenen synthetisierten Polymeren und Copolymeren, wie Polyacrylsäure, Polyacrylnitril, Polyacrylamid, Poly(Methylmethacrylat-co-Maleinsäureanhydrid) etc., anschließendes Gießen von Filmen und Extraktion der Polymeren oder Copolymeren durch Lösungsmittel hergestellt. Die Abhängigkeit der Durchlässigkeit und Trennwirkung von der Größe und Form der permeierenden Moleköle wurde qualitativ diskutiert. Des weiteren wurde die Selektivität der Trennwirkung in Abhangigkeit von der Zusammensetzung von Alkohol/Wasser-Gemischen und von der Größe und Anzahl der Poren untersucht. Es wurde gefunden, daß die Selektivität von der Menge und dem Molekulargewicht der in die Membranen eingebrachten Polymeren abhängt. Wenn der Gewichtsanteil des verwendeten Polymeren größer als 0,1 war, permeierte bevorzugt der Alkoholanteil bei methanolischen Msungen, wobei der Trennfaktor mit steigender Methanolkonzentration anstieg. In Gemischen mit anderen Alkoholen zeigten die Membranen andererseits eine selektive Durchlässigkeit für Wasser. Der Einfluß der Versuchsbedingungen wurde ebenfalls untersucht.
    Notes: The permeation and separation characteristics of alcohol/water systems through porous PVA membranes were investigated. Porous PVA membranes with different pore size and number were prepared by solution blending of PVA with several synthesized polymers or copolymers, such as polyacrylic acid, polyacrylamide, polyacrylonitrile, and methylmethacrylate-co-maleic anhydride, etc. Then casting, and finally extracting the blended polymers or copolymers by solvent from the membranes. The dependency of both permeation and separation on the molecular size and shape of the permeating species was dicussed qualitatively. Moreover, the permselectivity was investigated with attention to the feed composition of alcohol/water mixture and the effect of pore size and number. The selectivity was found to depend on the weight ratio and the molecular weight of polymer introduced to the membrane. When the weight ratio of polymer introduced into the membrane was larger than 0.1, methanol was permeated through membrane preferentially in methanol/water system, and the separation factor increased with increasing the methanol feed concentration. On the other hand, membrane had a selective permeability for water in the other alcohol/water systems. The influence of operating conditions was also studied.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051790112
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    Temperature dependence of proton spin-lattice and spin-spin relaxation times in isotactic polypropylene. Effect of atactic fraction (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 29-38 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Temperatur des T1-Minimums für die Segmentbewegung in Polypropylen, das einen hohen ataktischen Anteil besitzt, ist niedriger als die in isotaktischem Polypropylen. Ein kurzes T1, T1s, tritt bei beiden Materialien auf. Bei Temperaturerhöhung nimmt T2a (T2 der beweglichen amorphen Bezirke) stark und T2m (T2 der dazwischen liegenden Bezirke) leicht zu, während sich T2c (T2 der steifen kristallinen Bezirke) kaum ändert. T2a in Polypropylen mit hohem ataktischem Anteil ist länger als in isotaktischem Polypropylen.Der Massenbruch der kristallinen Bezirke, Fc, nimmt bei Temperaturerhöhung ab und der der amorphen Bezirke, Fa, zu. Die Relaxationsgeschwindigkeit, 1/ (T1min), steigt linear mit Zunahme des amorphen Anteils an, außer bei der mit siedendem n-Heptan extrahierten Probe. Mit Zunahme der Peaktemperatur von tan δ fällt T2a nahezu linear ab, während die Temperatur des T1-Minimums zunimmt.
    Notes: The temperature of the T1 minimum for the segmental motion in polypropylene containing a lot of atactic fraction is lower than that in isotactic polypropylene. A short T1, T1s, appears for both materials. As the temperature is raised, there is a large increase in T2a (T2 of the mobile amorphous regions), and a mild increase in T2m (T2 of the intermediate regions), while there is no substantial change in T2c (T2 of the rigid crystalline regions). T2a in polypropylene containing a lot of atactic fraction is longer than that in isotactic polypropylene.The mass fraction of crystalline regions, Fc, decreases and that of the amorphous regions, Fa, increases as the temperature is raised. There is a linear increase in the relaxation rate, 1/(T1min), as the amorphous fraction is increased, except for the sample extracted with boiling n-heptane. With increase of the peak temperature of tanδ, T2a decreases nearly linearly, while the temperature of the T1 minimum increases.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051750103
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    Wettability and surface chemistry of irradiated PTFE (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 180 (1990), S. 191-198 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Bestrahlung von PTFE mit Elektronen niedriger Energie führt zur Abspaltung von Fluor und zum Einbau von Sauerstoff in die Polymeroberfläche. Es wird gezeigt, daß das Ausmaß der Oberflächenveränderungen hauptsächlich von der Zahl und kaum von der Energie der Elektronen abhängt, die die Oberfläche erreichen. Änderungen in der Oberflächenenergie resultieren in unterschiedlichem Benetzungsverhalten. Kontaktwinkelmessungen und Kurvenanalysen der C-1s-Peaks aus Röntgenphotonenspektroskopiemessungen zeigen, daß der am wenigsten benetzbare Teil der bestrahlten Oberflächen in den meisten Fällen aus —CF2 —CF-Einheiten besteht. Werden bei der Bestrahlung nahezu alle Fluoratome abgespalten, bleiben nur isolierte —CF2-oder —CF-Gruppen zurück. Die „receding“-Winkel werden mit zunehmender Sauerstoffkonzentration in der Oberfläche kleiner, was auf die Bildung stark oxidierter Bereiche hinweist. Die Unabhängigkeit der Kontaktwinkel von der Alterungsdauer deutet auf eine sehr geringe Beweglichkeit der Makromoleküle hin, was mit einer starken Vernet-zung an der Oberfläche zusammenhängen könnte.
    Notes: Low energy electron irradiation of PTFE induced fluorine depletion and introduction of oxygen on the surface. The effect on surface chemistry was shown to be dependent mostly on the amount of electrons reaching the sample, rather than on their energy.Changes in surface energy resulted in different wetting behaviors. The measurement of advancing water contact angles and the analysis of XPS C-1s peak shapes showed that the least wettable portion of irradiated surfaces is made in most cases of —CF2—CF — units. When the treatment caused a nearly complete fluorine depletion, only isolated —CF2— or —CF— groups are present. Receding angle values decreased linearly depending on the amount of oxygen introduced on the sample during the treatment, suggesting the formation of strongly oxidized polymer islets. The invariance of contact angles with aging time indicated very low macromolecular mobility, probably related to extensive surface crosslinking.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051800114
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    Herstellung von dispersionen anionischer polyurethane mit COO- -gruppen und NH4+ -gegenionen (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 41-52 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In aqueous dispersions of anionic polyurethanes containing the triethylammonium salt of 2,2-dimethylol propionic acid as chain extender, triethylamine can be largely replaced by ammonia. For electrostatic reasons, NH4+ is namely more tightly bound in the ion pairs located in the Stern layer than NH(C2H5)3+. Thermal treatment of films leads to a loss of base, whereby ammonia is more rapidly released than triethylamine. Therefore, crosslinking with partially methylated hexamethylolmelamine proceeds the faster the more triethylamine is replaced by ammonia.
    Notes: In Dispersionen aus anionischen Polyurethanen, die das Triethylammoniumsalz der 2,2-Dimethylolpropionsäure als Kettenverlängerungsmittel enthalten, läßt sich durch Zugabe von Ammoniak eine weitgehende Verdrängung des Triethylamins erreichen. Aus elektrostatischen Gründen ist nämlich in den in der Sternschen Schicht lokalisierten Ionenpaaren NH4+ fester gebunden als NH(C2H5)3+. Bei der thermischen Behandlung der Filme tritt Basenabspaltung ein, dabei erfolgt die Abgabe von Ammoniak deutlich schneller als die von Triethylamin. Die Spannungswerte der mit teilmethyliertem Hexamethylolmelamin vernetzten Proben sind daher um so höher, je mehr Triethylamin durch Ammoniak ersetzt wurde.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810103
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    Compression creep of molten polystyrene (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 53-66 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Viskoelastizitäts-Parameter von geschmolzenem Polystyrol (PS) wurden mit einem Instron-Kapillarrheometer gemessen.Die Drucknachgiebigkeit B(t) zeigt ein Plateau sowohl im Schmelze (B1)- als auch im Glaszustand (Bg); beide nehmen mit abnehmender Spannung ab. Durch Verschiebung der B(t)-Kurven werden Master-Kurven erhalten, mit denen das Gesamtdruckverhalten (überlagerte elastische und viskose Deformationen) analysiert werden kann. Die stationäre Nachgiebigkeit (Bs) erlaubt eine Beschreibung des elastischen Energieanteils und scheint mit der Extrusions-Strangaufweitung (Bcs/Bds) korreliert zu sein. Die Volumenviskosität (ηk) nimmt mit zunehmender Spannung (P), zunehmender Belastungsgeschwindigkeit (k) und abnehmender Temperatur ab.
    Notes: Viscoelastic parameters of polystyrene (PS) melt in compression creep have been measured in an lnstron capillary-rheometer.Bulk compression creep compliance B(t) shows plateau regions in the molten state (B1) and the glassy state (Bg), both decreasing with increasing stress. Shifting of B(t) curves provides master curves suitable to analysing the total (superposed elastic and viscous deformations) bulk compression behaviour. The steady-state creep compliance (Bs) allows to describe the recoverable elastic energy (Be) and seems to be related to the extrusion die swell (Bcs/Bds). Volume viscosity (ηk) decreases with decreasing stress (P), increasing compression rates (k) and decreasing temperature (T).
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051810104
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    Variation in molecular weight and molecular weight distribution of aged iPP filaments as revealed by HTGPC (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 67-74 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurden Untersuchungen über Molekulargewichtsänderungen an physikalisch bei Raumtemperatur gealterten isotaktischen Polypropylenfilamenten (iPP) mit Hilfe der Hochtemperaturgelpermeationschromatographie (HTGPC) durchgeführt. Das Ergebnis der Untersuchungen weist auf eine sehr unbedeutende Änderung des Molekulargewichts des Materials während der Alterung hin.Das Materialgranulat wurde als Bezugsstandard gewählt. Basierend auf der Uneinheitlichkeit D = Mw/Mn des Granulats wurden Filamente der Handelsprodukte GYE 47 und PXC 31399 charakterisiert, deren Alterungsdauer zwischen 2 Wochen und 8 Monaten lag. Bei den Filamenten der Qpe GYE 47 verringerte sich die Breite der Molekulargewichtsverteilung D um durchschnittlich 12%. Andererseits zeigen die Filamente des PXC 31399-vps einen weniger eindeutigen Trend zur Änderung, jedoch im Mittel hat sich die Breite der Verteilung um etwa 20% erniedrigt. Bei letzterem ist die Verteilung iiber die Alterungsdauer stark gestreut. Der GYE 47-Typ zeigt eine nahezu asymptotische Abnahme. Es wird angenommen, daß die Ungleichartigkeit in der Ändenz der Anderung von D zwischen beiden Proben in ihrer unterschiedlichen thermodynamischen Stabilitat liegen ktinnte; PXC 31399 ist weniger stabil.
    Notes: Experiments on the molecular weight variations of physically, room temperature aged isotactic polypropylene (iPP) filaments were done using the High Temperature Gel Permeation Chromatography (HTGPC). Evidence emanating from the studies indicates a very marginal change in molecular weight of the materials during aging.The granules of the materials were chosen as the reference standard. Based on the polydispersity D = Mw/Mn of the granules, filaments of commercial grades GYE 47 and PXC 31399 were characterized between an aging period ranging from 2 weeks to 8 months. The filaments of the GYE 47 grade have their distributions D lowered on the average by about 12%. On the other hand, those of the PXC 31399 grade have a less definite trend in change, but on the average, D is lowered by about 20%. The distributions of this latter grade are highly scattered over the period of aging. The GYE 47 grade shows a reduction in the distribution of a near asymptotic nature. It is believed that the disparity in the trend of change of D between the two samples could be attributed to their relative thermodynamic stability with the PXC 31399 grade being less stable.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051810105
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    The photocopolymer rod of ethyleneglycol dimethacrylate with methylmethacrylate (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 1-10 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Photopolymerisation von Ethylenglykoldimethacrylat (EGDMA) mit Methylmethacrylat (MMA) wurde mit Benzoinmethylether (BME) als Initiator in einem Glasrohr durchgeführt, um einen lichtfokussierenden Plastikstab (Radius Rp) mit parabolischer Brechungsindex-Verteilung (Verteilungskonstante A) in der Nähe der Stabachse (bis zum Radius Rc) herzustellen. Die Abhängigkeit von A und Rc/Rp vom Monomerenverhältnis MMA/EGDMA der Ausgangsmischung, der Einfluß der BME-Konzentration auf die Brechungsindex-Verteilung und die Reproduzierbarkeit der Photopolymerisationen wurden untersucht. Das Rc/Rp-Verhältnis stieg mit dem Monomerenverhältnis MMA/EGDMA bei BME = 1,0 Gew.-% und der Geschwindigkeit der UV-Lampe von V = 0,58 mm/min an. Andererseits stieg Rc/Rp bei BME = 0,6 Gew.-% und V = 0,735 mm/min bis zum Monomerenverhältnis von 0,2 an und fiel dann deutlich zwischen 0,20 und 0,25 ab. Die Plastikstäbe, die hier durch Photopolymerisation hergestellt wurden, haben Linseneigenschaften und sind gut reproduzierbar.
    Notes: The photocopolymerization of ethyleneglycol dimethacrylate (EGDMA) with methylmethacrylate (MMA) containing benzoin methyl ether (BME) as initiator was carried out in a glass tube to fabricate a light-focusing plastic rod (radius Rp) with a parabolic refractive index distribution (distribution constant A) in the region near the center axis (radius Rc). The dependence of A and Rc/Rp on MMA/EGDMA feed ratio, influence of BME concentration on the refractive index distribution, and the reproducibilities of the photopolymerizations were investigated. The Rc/Rp increased with the feed ratio used under BME = 1.0 wt.-% at velocity of UV lamp V = 0.58 mm/min. On the other hand, Rc/Rp increased with the feed ratio to 0.2 and then decreased remarkably with the feed ratio in the range of 0.2-0.25 with BME = 0.6 wt.-% at V = 0.735 mm/min. Plastic rods fabricated in the investigation using photopolymerization have lens characteristics and good reproducibilities.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051740101
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    Effects of drawing conditions on the properties of optical fibers made from polystyrene and poly(methyl methacrylate)Dedicated to Prof. Dr. O. Wichterle on the occasion of his 75th birthday (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 25-39 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polystyrol- und Polymethylmethacrylateinzelfäden mit verschiedenen Graden von Doppelbrechung wurden durch die kontinuierliche Änderung der Ziehgeschwindigkeit, der Temperatur der Polymerschmelze und des Molekulargewichts von Polystyrol (PS) und Polymethylmethacrylat (PMMA) gewonnen. Der “brittle to ductile” Übergangspunkt (Übergang des Polymeren vom spröden zum ziehbaren Zustand) wurde für das optisch reine Polystyrol im Bereich der Doppelbrechungszahlen -0,6 · 10-3 bis -2,6 · 10-3 gefunden. Höhe und Lage dieses Punktes werden durch das Molekulargewicht, die Molekulargewichtsverteilung und die Temperatur der Polymerschmelze beeinflußt. Die Werte des Doppelbrechungsindexes von PS sind um zwei Zehnerpotenzen höher als von PMMA. Bei PMMA wurde der “brittle to ductile” Übergangspunkt nicht beobachtet. Die mechanischen und optischen Eigenschaften hängen nicht nur vom mittleren Wert des durch die Doppelbrechung charakteri-sierten Orientierungsgrades ab, sondern auch davon, welcher Teil des Relaxations-spektrums des Polymeren vorzugsweise orientiert ist. Beim Ziehen der PS- und PMMA-Einzelfäden bilden sich in der Mitte des Fadens Risse (crazes), die jedoch nicht an die Oberflache des Fadens treten.
    Notes: Monofilaments possessing various degrees of birefringence were obtained by changing the drawing rate, the molten polymer temperature, and the molecular weight of polystyrene (PS) and poly(methyl methacrylate) (PMMA). The “brittle-toductile” transition point of optically pure PS was found in the range of birefringences of -0.6 · 10-3 to -2.6 · 10-3. Both the height and position of this point are influenced by M̄w, molecular weight distribution, and polymer melt temperature. The birefringence of PS is higher by two orders of magnitude than that of PMMA in which this transition point has not been observed. The mechanical and optical properties depend not only on the average amount of orientation characterized by the birefringence but on what portion of the relaxation spectrum of the polymer is preferentially oriented. During the drawing of PS and PMMA monofilaments crazes are formed in the centre of the fibers and do not reach the surface.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051740103
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    Ataktisches polypropylen als pfropfgrundlage für die monomeren vinylacetat und vinylchlorid. Herstellung undeigenschaften der pfropfprodukte (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 174 (1990), S. 105-117 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The possibility of the application of atactic polypropylene is investigated as graft base for the preparation of graft copolymers of vinyl acetate and vinyl chloride respectively graft copolymers from vinyl acetate onto polypropylene as graft base for the preparation of graft copolymers of vinyl chloride in relation to the composition of the original mixture.After compounding of the graft products with polyvinyl chloride or ABS/polyvinyl-chloride mixtures selected mechanical properties are presented in relation to the quantity and composition of the incorporated graft copolymers.
    Notes: Die Möglichkeiten des Einsatzes von ataktischem Polypropylen als Pfropfgrundlage zur Herstellung von Pfropfcopolymerisaten des Vinylacetates und Vinylchlorids bzw. von Polypropylen-Vinylacetat-Pfropfprodukten als Pfropfgrundlage zur Herstellung von Pfropfcopolymerisaten des Vinylchlorids werden in Abhängigkeit von der Ausgangsgemischzusammensetzung untersucht.Nach Abmischung der Pfropfprodukte mit Polyvinylchlorid bzw. ABS/Polyvinylchlorid-Mischungen werden ausgewählte mechanische Eigenschaften sowohl in Abhängigkeit von der Menge des enthaltenen Pfropfproduktes als auch von der Zusammensetzung der Pfropfpolymerisate dargestellt.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051740109
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    Eine spektroskopische Methode zur Messung der Ammoniak-Permeabilität in PolymerfilmenHerrn Prof. Dr. Herward Pietsch zum 60. Geburtstag gewidmet (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 179 (1990), S. 5-19 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: A new spectroscopic method for determining the permeability of ammonia in transparent polymer layers is presented. It is based on the quantitative proof of the ammonia passing the test layer into a sensor layer, containing 4-nitrophenol as an NH3-sensitive probe, which is placed under the test film. The permeability (P) of the test layer is calculated from the slope of extinction with time in the sensor layer. The lag time (t1) gives the diffusion coefficient (D). The suitability of this method is confirmed by comparison with literature values. Diffusion coefficients obtained from t1 correspond well to those obtained by the sorption method.The temperature dependence of P and D in more than five different polymers (CDA, PVB, PVAc, PVC and different polyvinyl alcohols) demonstrates that peculiarities in the temperature dependence of the permeability result from the behaviour of the NH3-solubility (P/D) which is strongly dependent on the polymer structure.
    Notes: Es wird eine neuartige spektroskopische Methode zur Messung der Ammoniak-Permeabilität in transparenten Polymerfilmen vorgestellt. Sie beruht auf dem quantitativen Nachweis des den Testfilm durchdringenden Ammoniaks in einer darunter befindlichen Sensorschicht mit Hilfe der NH3-empfindlichen Sonde 4-Nitrophenol. Aus dem Anstieg der Extinktion mit der Zeit (ΔE/Δt) in der Sensorschicht wird die Permeabilität (P) und aus der Verzögerungszeit (lag time (t1)) der Diffusionskoeffizient (D) berechnet. Die Eignung der Methode wird durch Vergleich mit Literaturwerten belegt. Die aus t1 zugänglichen Diffusionskoeffizienten stimmen sehr gut mit denen überein, die mit der Sorptionsmethode gefunden werden.Die Temperaturabhängigkeiten von P und D in mehr als fünf verschiedenen Polymeren (CDA, PVB, PVAc, PVC und in verschiedenen Polyvinylalkoholen) zeigen, daß Besonderheiten im Temperaturgang der Permeabilität aus dem vom Aufbau des Polymeren stark abhängigen Verhalten der NH3-Löslichkeit (P/D) resultieren.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051790102
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    SBS/VP homograft membrane for oxygen enrichment (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 179 (1990), S. 99-111 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die strahleninduzierte Pfropfung von 4-Vinylpyridin (VP) auf Styrol-Butadien-Styrol-Copolymere (SBS) in Gegenwart von gelöstem Sauerstoff untersucht. Pfropfcopolymer-Membranen mit unterschiedlichen Pfropfgraden wurden durch Gießen aus benzolischer Lösung hergestellt. Die mechanischen Eigenschaften, die Gaspermeabilität sowie der Einfluß der Temperatur auf die Gasdurchlässigkeit wurden untersucht. Der höchste Pfropfgrad von 8,4% wurde bei einer Bestrahlungszeit von 15,5 herreicht. Sowohl bei kürzeren als auch längeren Bestrahlungszeiten war der Pfropfgrad  -  bedingt durch Störung durch den vorhandenen Sauerstoff  -  niedriger. Reißfestigkeit und Reißdehnung von SBS-g-VP waren vergleichbar rnit SBS. Die Spannungsrelaxation von SBS-g-VP war langsamer als bei SBS, was auf der Bildung von starren Polyvinylpyridin(DVP)-Mikrophasen beruhen könnte, die als permanente Vernetzungspunkte wirken und die Spannungsrelaxation beeinträchtigen könnten.Da SBS eine hohe Gasdurchlässigkeit und PVP eine hohe O2/N2-Selektivität aufweisen, wurde die Gasdurchlässigkeit der Pfropfmembranen untersucht. Die Selektivitat der SBS-g-VP-Membranen stieg mit steigendem Pfropfgrad, allerdings auf Kosten der Permeabilität, Bei Erhöhung der Temperatur nahm die Durchlässigkeit zu, das Verhältnis O2/N2, aber ab. Die Aktivierungsenergie (Ep) der Gasdurchlässigkeit stieg mit dem Pfropfgrad. Für eine nichtgepfropfte SBS-Membran betrug Ep 5,5 kcal/mol für Sauerstoff und 7,2 kcal/mol für Stickstoff. Für eine SBS-g-VP-Membran mit einem Pfropfgrad von 8,4% waren die Ep-Werte für Sauerstoff und Stickstoff 6,5 bzw. 8,1 kcal/mol.
    Notes: The grafting of 4-vinyl pyridine (VP) onto styrene-butadiene-styrene triblock copolymers (SBS) by homografting irradiation with dissolved oxygen was studied. Homograft membranes of various degree of grafting were prepared from a casting solution of grafted copolymer in benzene. The mechanical properties of membranes, gas permeability, and the effect of operating temperature on gas permeation were investigated.The degree of grafting of 8.4% was the largest at an irradiation time of about 15.5 h. It was smaller at both shorter and longer duration because of the interference of dissolved oxygen. It was found that the tensile strength and elongation of SBS-g-VP were similar to those of SBS. The stress relaxation of SBS-g-VP was slower than that of SBS, and this might be due to the formation of rigid microphase separation domain of poly(4-vinyl pyridine), which acted as permanent crosslinking points to reduce the stress relaxation.Using the properties of high flux of SBS and high O2/N2 selectivity of poly(4-vinyl pyridine), the performance of gas permeation of 4-vinyl pyridine homografted SBS membrane was studied. The selectivity of SBS-g-VP membrane increased with increasing degree of grafting. However, it was done at the expense of a decrease in the gas permeability.When the operating temperature of gas permeation increased, the permeability of oxygen and nitrogen increased, and the O2/N2 permeability ratio decreased. The activation energy (Ep) for gas permeation through different degree of grafting of SBS-g-VP membrane (obtained by the Arrhenius law) increased with increasing degree of grafting. For ungrafted SBS membrane, Ep was 5.5 kcal/mol for oxygen and 7.2 kcal/mol for nitrogen. For 8.4% grafting degree SBS-g-VP membrane, Ep for oxygen and nitrogen, were 6.5 and 8.1 kcal/mol, respectively.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051790108
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  • 86
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    Anhäufung von bruchstellen in polydispersen polymeren unter dauerbelastung (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 13-27 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The change of molecular mass and long-term strength of high and low density polyethylene under tensile load in surface-active medium was studied. It is shown that long-term strength of polyethylene depends on the molecular mass. The influence of polydispersity on strength was investigated.
    Notes: Es wird über die Untersuchungsergebnisse von Lebensdauer und Molmassenänderung an polydispersen Proben von HDPE und HDPE in einem breiten M̄v-Bereich im Zugversuch in einem oberflächenaktiven Medium berichtet.Die Arbeit enthält auch die Darstellung der quantitativen Änderung der Molmasse von Hochdruck- und Niederdruck-Polyethylen unter Dauerbeanspruchung und die Analyse der Lebensdauer in Abhängigkeit von den unterschiedlichen Molmassen (MM) (M̄w, M̄n, M̄v); die Unterschiede in Abhängigkeit von der Lebensdauer von M̄v für Proben und polydisperse Muster sowie die Vorstellungen über den dualen Einfluß der Polydispersität auf die Lebensdauer mit einer Interpretation der auftretenden Erscheinungen werden beschrieben.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051750102
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    Partikelgrößenanalyse von dispersen farbstoffsystemen I. Grundlagen zur partikelgrößenanalyse mittels photonen-korrelations-spektroskopieHerrn Dr. Gerhard Heidemann zum 60. Geburtstag gewidmet (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 51-67 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: One constitutive property for the description of dyeing polyester-materials with disperse dyes is the particle size distribution in the dye bath. To measure particle sizes below one micrometer in situ, special techniques are required. One of these is the so called photon-correlation-spectroscopy, depending on the scattering of laser light by suspended small particles in a fluid. The mathematical and physical principles of the photon-correlation-technique are explained in this article.
    Notes: Eine zur Beschreibung des Färbevorganges von Polyestermaterialien mit Dispersionsfarbstoffen wesentliche Größe stellt die Partikelgrößenverteilung im Farbebad dar. Partikelgrößen unterhalb eines Mikrometers lassen sich in situ nur mit wenigen Meßtechniken bestimmen. Dazu zählt u. a. die Photonen-Korrelations-Spektroskopie, die auf Streuung von Laserlicht an kleinen, in einer Flüssigkeit suspendierten Teilchen basiert. Die mathematischen und physikalischen Grundlagen dieser Meßtechnik werden in diesem Artikel erläutert.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051750105
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    SAXS and WAXS investigations of the crystallinity in polymers (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 81-97 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Kristallinität von Polyethylen, Polyethylenterephthalat und Polypropylen wurde mit Hilfe der Röntgenweitwinkel(WAXS)-und-kleinwinkel(SAXS)streuung gemessen. Die mittels der letzteren Methode erhaltenen Kristallinitätswerte sind deutlich größer als die durch WAXS. Es wird vermutet, daß die Unterschiede mit der Schicht zusammenhängen, die zwischen den amorphen und kristallinen Bereichen liegt. Daraus wurde geschlossen, daß die Röntgenkleinwinkelstreuung nicht als unabhängige Routinemethode zur Kristallinitätsbestimmung angewendet werden kann.
    Notes: The crystallinity of polyethylene, polyethyleneterephthalate, and polypropylene was measured with the aid of wide angle (WAXS) and small angle (SAXS) X-ray scattering methods. The values of crystallinity evaluated using the latter method are distinctly larger than those ones given by the WAXS method. The differences are supposed to be associated with the transition layer existing between the amorphous and crystalline regions. It was concluded that small angle X-ray scattering cannot be employed as an independent routine method of crystallinity determination.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051750107
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    SEC on cellulose nitrate: DP-Ve relationship and evaluation of different methods to determine the calibration parameters (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 117-128 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Für das System Cellulosenitrat-μ-Styragel-THF wurde die DP-Ve-Beziehung sowie die Ausarbeitung der betreffenden Eichparameter einer genaueren Betrachtung unterzogen. Die etwa dreißig Eichpräparate waren durch definierten säurekatalysierten Abbau von Baumwollcellulose und anschließende Nitrierung hergestellt worden und umfaßten einen DP-Bereich von 150 〈 DP 〈 8000. Es wird gezeigt, daß mit steigendem DP die DP-Ve-Beziehung drei verschiedene Phasen aufweist. Bei der Anwendung der SEC auf Cellulosenitrat müssen daher bezüglich der Eichung zwei Fehlerquellen in Betracht gezogen werden: eine bezieht sich auf die Methode der Ausarbeitung der Eichparameter als solche, und die andere auf die Nichtbeachtung des Vorhandenseins dreier Abschnitte in der DP-Ve-Beziehung. Die Auswirkung dieser Fehler auf die Genauigkeit der aus den Elutionsdiagrammen abgeleiteten Verteilungskurven und DP-Mittelwerte wird diskutiert.
    Notes: The calibration behaviour of the system cellulose nitrate-μ-Styragel-THF has been studied using about 30 different calibration samples prepared by defined acid catalyzed degradation of cotton cellulose. The samples covered a range of DP between 150 〈 DP 〈 8000. It is shown that the DP-Ve relationship is characterized by the existence of three subsequent stages. Consequently, two sources of errors in the DP-Ve calibration must be taken into consideration. One refers to the methods as such to elaborate the calibration parameters, and the other one arises by neglecting that the DP-Ve relationship involves 3 distinct stages. The extent of the two classes of errors in regard to the exactness of the determined molecular weight averages and molecular weight distributions is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051750110
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  • 90
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    Water-Soluble polyamides as potential drug carriers. I. Poly(α,β-D,L-asparthydrazide-CO-D,L-ornithine) (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 141-156 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bei der Polycondensation von d,l-Asparaginsäure mit Nδ-phthaloyl-L-ornithin in Phosphorsäure bei 185°C entstehen statisticsche Copolymere (Ausbeute 60  -  70%) aus Poly(d,l-succinimid-co-Nδ-phthaloyl-d,l-ornithin), Formel 6, mit inhärenten Viskositäten (DMF) von 5 bis 15 ml g-1. Copolyimide der selben Zusammensetzung 6 und vergleichbarer Kettenlänge werden aus Asparaginsäure und dem Kupferchelat des Phthaloylornithins erhalten. Die Behandlung des Copolymeren 6 mit Hydrazinhydrat fuhrt zur Öffnung der Succinimid-Kettenglieder unter Bildung von Hydrazid-Seitengruppen. Die resultierenden Polyamide sind Poly(α,β-d,l-asparaginsäurehydrazid-co-d,l-ornithin), Formel 7. Kürzere Reaktionszeiten bedingen unvollständige Ringöffnung, und die verbleibenden Succinimid-Gruppen werden bei der folgenden Aufarbeitung hydrolytisch gespalten unter Bildung von Asparaginsaüre-Gruppen; die sogebildeten Polyamide besitzen die Struktur 8. Beide Polymere, 7 und 8, sind in Wasser loslich und zeigen in Wasser inharente Viskositiiten von 5 bis 14 ml g-l. Die Fahigkeit dieser Polyamide zur Arzneimittelverankerung wird durch Ankoppeln von Carbonsau- ren als Modellsubstanzen gezeigt.
    Notes: The polycondensation of d,l-aspartic acid with Nδ-phthaloyl-l-ornithine in phosphoric acid at 185°C gives rise to the formation, in 60  -  75% yield, of random copolymers of the poly(d,l-succinimide-co-Nδ-phthaloyl-D,L-ornithine) type 6 possessing inherent viscosities (DMF) in the range of 5  -  15 ml g-1. Copolyimides of the same compositions 6 and comparable chain lengths are obtained from aspartic acid and the copper chelate of the phthaloylornithine. Treatment of copolymers 6 with hydrazine hydrate in DMF leads to N-deprotection and opening of the intrachain succinimide rings with formation of hydrazide side groups. The resultant polyamides are of the poly(α,β-d,l-asparthydrazide-co-d,l-ornithine) type 7. Shorter reaction periods give incomplete hydrazinolytic ring opening, and the remaining succinimide units are cleaved hydrolytically during the subsequent aqueous workup, thereby transforming into aspartic acid units. The polyamides so formed possess the general poly(α,β-d,l-asparthydrazide-co-α,β-d,l-aspartic acid-co-d,l-ornithine) structure 8 Both types 7 and 8 are soluble in water and, in this medium, give inherent viscosities of 5  -  14 ml g-1. The potential drug-anchoring capabilities of these amine-functionalized polyamides are demonstrated by coupling reactions with model carboxylic acids.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051750112
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    Antioxidants and stabilizers, 111Part 110 cf. Polym. Degrad. Stab., in press.. Regeneration mechanism of the antioxidant action of N-isopropyl-N′-phenyl-1,4-phenylenediamine (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 169-180 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Im Zusammenhang mit Arbeiten über den Wirkungsmechanismus von Antioxidantien in Kohlenwasserstoffpolymeren unter Sauerstoffmangel wurde die Abfangreaktion des Modellradikals 1-Cyano-1-methylethyl (R°) mit N-Isopropyl-N′-phenyl-1,4-phenylendiamin (Ia) und seinem Oxidationsprodukt IIa untersucht. Reines Ia und IIa reagieren kaum mit R′, eine Mischung aus beiden ist jedoch ein effektiver Fänger fur R′, wobei R′ entweder am Stickstoffatom zwischen den aromatischen Ringen unter Bildung von VIa gebunden wird, oder unter Substitution mit dem Phenylenring reagiert, wobei VIIIa entsteht. Verbindung VIa ist labil, bei Vulkanisationstemperatur spaltet sie im neutralen Medium Olefin unter Regenerierung von Ia ab. In Gegenwart von Säuren lauft diese Reaktion auch bei niedrigerer Temperatur ab. Im Produkt VIIIa ist R′ fest gebunden, durch die Nitrilgruppe tritt jedoch eine säurekatalysierte Cyclisierung zum Indolinderivat X ein. Die Bildung von VIIIa ist ein Modell für die Entstehung einer „nichtextrahierbaren Fraktion“ des Antioxidants Ia bei der Stabilisierung von Kohlenwasserstoffpolymeren.
    Notes: In connection with the investigation of the mechanism of antioxidant action of antidegradants in hydrocarbon polymers under the conditions of a relative deficiency of oxygen, scavenging of a model alkyl (1-cyano-1-methylethyl,R°) was studied with Nisopropyl-N′-phenyl-1,4-phenylenediamine (Ia)For abbreviations see p. 11. and its oxidation product, i.e. Nisopropyl-N′-phenyl-1,4-benzoquinonediimine (IIa). While pure Ia and IIa do not react with the radical R° almost at all, their mixture is able to scavenge R° effectively. The reaction is further accelerated with acids. The alkyl R° combines with the antidegradant molecule in two ways, one of which leads to the substitution at the nitrogen atom between the aromatic rings, giving rise to VIa, while the other consists in the substitution of phenylene, leading to VIIIa. The product VIa is labile, and at vulcanization temperatures it readily splits off olefin in a neutral medium, being regenerated to Ia. In the presence of acids this reaction proceeds even at lower temperatures. In the other product, i.e. in VIIIa, the alkyl R° is bound firmly, but due to the presence of the nitrile group, VIIIa is readily cyclized by the effect of acids, and an indoline derivative X is formed. The formation of VIIIa is a model of the formation of an “unextractable fraction” of antidegradant Ia in the stabilization of hydrocarbon polymers. Investigations based on the isolation of reaction products bear at the same time evidence of the possibility of regeneration of an effective antioxidant in the stabilized substrate.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051750114
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    Wetterbeständigkeit von polymeren: Messung der photochemischen abbauprozesse und der schutzwirkung anorganischer pigmente mittels physikalischer untersuchungsmethodenHerrn Prof. Dr. Hans Rudolph zum 60. Geburtstag gewidmetVortrag anläßlich des 19. Donauländergesprächs über “Atmosphärische Alterung und Stabilisierung von Polymeren” in Prag (Tschechoslovakei) vom 24. - 29. Juli 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 1-25 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photochemical degradation of polymers (commonly known as UV degradation) takes place in two stages: First, there is the primary process comprising the rapid formation of radicals caused by quanta of visible light; this involves the dissociation of polymer chain molecules and/or the activation of polymer chain molecules respectively of additives, colorants and impurities contained in the polymer. The secondary process consists in oxidation reactions with singulett-oxygen generated by energy-transfer and/or between the polymer radicals thus formed and adsorbed oxygen, as a result of which gradual degradation of the polymer takes place.An investigation of these individual reactions using a combination of selected physical test methods leads to an unterstanding of the entire reaction sequence involved in photo-oxidative degradation. This knowledge provides a basis for systematically improving the weather-resistance of polymers by modifying their basic polymeric structure or through the controlled use of UV absorbers, quenchers, radical interceptors and antioxidants.The physical test methods themselves are divided into two categories: techniques used for investigating the primary processes (ultra short-time spectroscopy, ESR) and those used to investigate the secondary processes (XPS, FT-IR, UV/VIS et al.).With pigmented polymers, attention is focussed on borderline cases in the use of photoactive and photoinactive pigments: as a result of “photocatalytic oxidation”, photoactive pigments (e.g. TiO2 anatase) lead to additional degradation reactions which take place at the same time as the UV degradation reaction. Photoinactive pigments (e.g. high-grade TiO2-rutile and iron oxide pigments), on the other hand, exhibit negligible or no photocatalytic oxidation and, by absorbing UV radiation, provides better protection for the polymer against UV degradation.This paper gives an overview of the above-mentioned physical methods of investigating primary and secondary photochemical processes, taking a thermoplastic material (Polycarbonate) as an example. A description is also given of the photocatalytic oxidation reations which can take place if pigmented polymers are used, and there is a discussion of the degradation-inhibiting effects of inorganic pigments.
    Additional Material: 7 Ill.
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    Investigation of the thermal ageing of polyethylene and polystyrene with the purpose of predicting their shelf-lifePaper presented at the 19th Colloqium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24 - 29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 87-92 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The aim of the present work is to predict the warehouse storage life of polyethylene low-density, polyethylene high-density and polystyrene impact-resistent, using the method of temperature-time superposition. The properties, most representative for thermal ageing, are the relative elongation at break for polyethylene and the impact resistance for polystyrene. The validity of the predicted shelf-life is verified by estimating the change of these properties under real conditions of warehouse storage.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1990.051760107
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    Thermal and UV degradation of impact-resistant polystyrene (II)Paper presented at the 19th Colloquium of Danubian Countries on “Atmospheric Aging and Stabilization of Polymers” in Prague (Czechoslovakia), July 24-29, 1989 (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 176 (1990), S. 105-112 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A commercial type of impact-resistant polystyrene was investigated. Two types of antioxidants, Irganox 245 and Irganox PS-800 were added to polystyrene in ammounts of 0,05 to 0.20%. Films, dumbbells and straight test pieces were subjected to thermal and u.v. ageing. Films of 250 μ thickness were thermally treated at 100°C and separately u.v. irradiated at 360 nm for 24, 72, 120 and 168 hours. Dumbbells and straight test pieces were only thermally aged at 100°C for 7, 14, 21, 28 and 35 days. Mechanical properties were determined. The spectra of samples were recorded using Perkin-Elmer, model 1750 FTIR and Perkin-Elmer data station 7700. Colour changes of all dumbbells were measured using Elrepho apparatus in u.v.-visible region. (Changes of the content of carbonyl and hydroxyl groups, as well as of polybutadiene (PB) unsaturation in films were recorded on i.r. spektrophotometer Perkin-Elmer 257 between 4000 and 625 cm-1 and were published in the first part of this study1).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051760109
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  • 95
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    Electronic Resource
    New resin system for low-pressure moulding compounds with special properties (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 181 (1990), S. 85-91 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Formstoffe aus aromatischen Polyepoxiden, aromatischen Polyaminen mit hochtemperaturbeständigen Strukturelementen sowie pulverförmigen Füllstoffen besitzen hervorragende Eigenschaften, wie hohe Glasübergangstemperatur, hohemechanische Festigkeit, kleinen thermischen Ausdehnungskoeffizienten und Schwerbrennbarkeit ohne Zugabe von Flammschutzmitteln. Über die Synthese dieser aromatischen Polyamine, die Herstellung und Verarbeitung der Niederdruckpreßmassen sowie die Eigenschaften der Formstoffe wird berichtet.
    Notes: Moulded materials produced from aromatic epoxide resins, aromatic polyamines with high-temperature-resistant structure units and powdered mineral fillers possess outstanding properties like high glass transition temperatures, high mechanical strength, low linear thermal expansion coefficient, and reduced flammability without the addition of flame retardants. An account is given of the synthesis of aromatic polyamines, the preparation and working of moulding materials and the properties of the finished products.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051810107
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  • 96
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    Lichtinduzierte Umorientierung der optischen Achse in LC-Farbstoff-CopolymerenHerrn Prof. Dr. D. Braun zum 60. Geburtstag gewidmetVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker über “Polymere und Licht”. in Bad Nauheim vom 7. bis 9. Mai 1990. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 103-113 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The influence of linearly and circularly polarized light on the state of order of nematic dye-copolymers is investigated. For a nematic model system we have shown that the optical axis of these systems can be reorientated with linearly polarized light in a well defined manner. Furthermore these investigations prove that the isomerisation cycles of the azo dye is responsible for the described properties. By selection of circularly polarized light the same transmission behaviour as shown by selectively reflecting materials, i. e. cholesteric liquid crystals, was observed.
    Notes: Untersucht wird der Einfluß von linear und zirkular polarisiertem Licht auf den Ordnungszustand von nematischen Farbstoff- Copolymeren. Am Beispiel eines Modellsystems wird gezeigt, daß mit linear polarisiertem Licht die optische Vorzugsachse dieser Systeme gezielt reorientiert werden kann. Die Untersuchungen zeigen, daß der Isomerisierungszyklus des Azofarbstoffes für diese Eigenschaft des Materials verantwortlich ist Nach Bestrahlen der Probe mit zirkular polarisiertem Licht wird für das Polymere das gleiche Transmissionsverhalten beobachtet. Wie es auch selektivreflektierende Materialien, z. B. cholesterische Flüssigkristalle, aufweisen.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830105
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  • 97
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    Electronic Resource
    Anwendung organischer Resistmaterialien in der SynchrotronlithographieVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker über “Polymere und Licht”. in Bad Nauheim vom 7. bis 9. Mai 1990. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 123-132 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830107
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  • 98
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    HERSTELLUNG VON MIKROSTRUKTURPRODUKTEN DURCH TIEFENLITHOGRAFIE UND SPRITZGUSSPaper presented at the meeting of the GDCh-Fachgruppe “Makromolekulare Chemie” on “Polymers and Light” in Bad Nauheim (West Germany), May 7 - 9, 1990. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 133-150 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: For fabricating microstructures with extreme structural heights a technology has been developed which is based on deep-etch lithography and subsequent replication processes. A particularly high precision is achieved if the lithographic process is carried out by means of synchrotron radiation. Electroforming and molding processes are used for the replication of microstructures from a large variety of materials. The field of application comprises micromechanics, microoptics, electrical and optical microconnectors as well as sensors and actuators.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830108
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  • 99
    Electronic Resource
    Electronic Resource
    Critical requirements for non linear optical polymeric materials in active optical devices: The present state and prospects for the futurePaper presented at the meeting of the GDCh-Fachgruppe “Makromolekulare Chemie” on “Polymers and Light” in Bad Nauheim (W-Germany) May 7 - 9, 1990. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 151-166 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830109
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  • 100
    Electronic Resource
    Electronic Resource
    Photoconductive polymers: Structure, mechanisms and propertiesPaper presented at the meeting of the CDCh-Fachgruppe “Makromolekulare Chemie” on “Polymers and Light” in Bad Nauheim (W-Germany) May 7-9, 1990. (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 183 (1990), S. 197-220 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Charge carrier transport properties of organic polymers can vary over a wide range. The paper shows that the electron- and hole mobilities of polymers with pendant photoconductive groups (i. e. carbazole) are on the order of 10-6 cm2/Vs. In these materials the flow of electronic charge is maintained by the overlap of the π-orbitals of the pendant molecular groups. The large variation of this short-range interaction, depending on the local configurations encountered in polymer glasses, leads to a large variation of hopping probabilities and, hence, to wide rate-distributions. These distributions are reflected in the slow algebraic decay characteristics of the observed photocurrents. The typical time exponents α (α 〈 1) are shown to carry a great deal of physical information, if the dynamical range of the experiments is sufficiently large. The paper also refers to quasi-conjugated polymers (polysilanes) whose dynamic transport parameters are about 103 times better (faster) as compared to polymers with pendant groups. These new materials open interesting aspects for the development of new polymeric materials with better transport parameters and, hence, shorter 'switching times'.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051830111
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