Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
Filter
  • 1990-1994  (1,071)
  • 1980-1984
  • 1992  (1,071)
  • Engineering  (757)
  • Physical Chemistry  (227)
  • Nuclear reactions
  • Ultrastructure
Source
Material
Years
  • 1990-1994  (1,071)
  • 1980-1984
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    TNF induces cytoplasmic vesicles in actinomycin D-treated K 562 cells (1992)
    Springer
    Annals of hematology 65 (1992), S. 50-52 
    Details
    ISSN: 1432-0584
    Keywords: TNF ; K 562 ; Leukemia ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We report here that tumor necrosis factor alpha (TNF) induces peculiar cytoplasmic vesicles in the human erythromyeloid leukemia cell line K 562, sensitized to the cytotoxic action of TNF by a treatment with the inhibitor of transcription actinomycin D. These vesicles are well delineated ultrastructurally. The formation of these vesicles is characteristic for the combination of actinomycin D with TNF and precedes the changes of apoptosis and cellular disintegration. These vesicles correspond to an intermediate step in the cytotoxicity caused by TNF and may indicate that reactive metabolites are involved in the mechanism of action of TNF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01715127
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    In vitro formation of mineralized nodules by periodontal ligament cells from the rat (1992)
    Springer
    Calcified tissue international 50 (1992), S. 459-467 
    Details
    ISSN: 1432-0827
    Keywords: Periodontal ligament fibroblast ; Mineralized nodule ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The purposes of this study were to determine whether periodontal ligament (PDL) cells are capable of producing mineralized nodules in vitro and to analyze ultrastructural features of the nodules. Rat PDL cells were obtained from coagulum in the socket at 2 days after tooth extraction and cultured at confluence in standard medium containing Dulbecco's Modified Eagle's Medium supplemented with 10% FBS and antibiotics. To test mineralized nodule formation, cells were further cultured for an additional 3 weeks in the standard medium containing (1) ascorbic acid (50 μg/ml) and sodium β-glycerophosphate (10 mM), (2) ascorbic acid, sodium β-glycerophosphate, and dexamethasone (5 μM), or (3) ascorbic acid alone. Cells were then fixed in 2.5% glutaraldehyde, postfixed in 1% OsO4, and prepared for light and electron microscopy. Threedimensional nodules containing mineralized matrices were formed only when the cells were cultured in the presence of ascorbic acid and dexamethasone. They were composed of multilayered fibroblasts (up to 13 layers), and highly organized collagen fibrils with 64 nm cross-banding patterns between the cell layers. The fibroblasts in the nodules exhibited an elongated shape with a high degree of cytoplasmic polarity throughout the nodule, and have the morphological features of PDL fibroblasts as seen in vivo. Mineral deposition with needle-like crystals was initiated on collagen fibrils located in intercellular spaces of the upper cell layers and became increasingly heavier towards the bottom half of the nodules. X-ray microanalysis and electron diffraction analysis confirmed that mineral deposition contained calcium and phosphate in the form of immature hydroxyapatite. These nodules contained neither osteoblasts nor osteocytes, and have their own morphological organization and characteristics which differ from those formed by bone cells in culture. Therefore, these data suggest that PDL cells are capable of forming mineralized tissue in vitro with the morphological characteristics different from bone mineralized nodules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296778
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructure and cytochemistry of circulating erythrocytes during the annual cycle of Rana esculenta L. (1992)
    Springer
    Comparative clinical pathology 2 (1992), S. 166-169 
    Details
    ISSN: 1433-2981
    Keywords: Erythrocytes ; Flow cytometry ; Frog hibernation ; Image analysis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Morphometrical (image analysis of cell and nuclear shape factor), morphological (electron microscopy) and cytochemical (acridine orange fluoro-chromasia and propidium iodide-DNA flow cytometry) features of circulating red blood cells were investigated during two periods of the annual cycle of Rana esculenta: the active phase (July) and the underground hibernating phase (January). The results showed that the hibernating phase is marked by more homogeneity of the red cells, both at nuclear (strongly condensed chromatin) and cytoplasmic level (loss of intact organelles and acridine orange fluorochromasia). The almost complete disappearance of the ‘immature’ erythrocytes from the circulation, during the hibernating phase, should be related to a decrease of haemopoietic activity and to an increase of life span accompanied by uncommon storage in different organs both at vascular and intracellular level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00426172
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Eccrine gland involvement in Krabbe's disease (1992)
    Springer
    Virchows Archiv 421 (1992), S. 351-354 
    Details
    ISSN: 1432-2307
    Keywords: Krabbe's disease ; Eccrine gland storage ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Lysosomal storage inclusions were observed in skin eccrine gland secretory and myoepithelial cells in three cases of Krabbe's disease. In addition to storage there were numerous degenerative changes, occasionally resulting in cell necrosis. These findings suggest a generalized nature of the storage process in this lysosomal enzymopathy and point to high galactocerebroside turnover in eccrine gland epithelium. This knowledge may be of value in the biopsy diagnosis of Krabbe's disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01660983
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Multicystic mesothelial proliferation (1992)
    Springer
    Virchows Archiv 421 (1992), S. 379-385 
    Details
    ISSN: 1432-2307
    Keywords: Multicystic mesothelial proliferation ; Immunohistochemistry ; Ultrastructure ; DNA analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We investigated the clinicopathological findings in five cases of multicystic mesothelial proliferation (MMP). All masses consisted of multiloculated cysts attached to pelvic organs and sometimes growing into the upper abdominal cavity. The cystic spaces were lined by flattened or cuboidal cells. The stroma showed fibrosis, oedema and chronic inflammation. Immunohistochemistry revealed strong positive staining for cytokeratin and epithelial membrane antigen, and focal positivity for vimentin and carcinoembryonic antigen. The endothelial markers were negative. Electron microscopy showed abundant surface microvilli and well-developed basal lamina. DNA analysis identified euploid cell populations in all cases. All but one case had a previous history of abdominal surgery. Despite the worrying appearance the clinical outcome was favourable in all cases; there was one recurrence. Clinical and pathological data support the hypothesis that MMP represent a reactive mesothelial proliferation and not a neoplastic process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01606909
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Immunopathological study of eosinophils in eosinophilic granuloma of bone: Evidence for release of three cationic proteins and subsequent uptake in macrophages (1992)
    Springer
    Virchows Archiv 421 (1992), S. 255-261 
    Details
    ISSN: 1432-2307
    Keywords: Eosinophilic granuloma of bone ; Eosinophil granule proteins ; Immunostaining ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eosinophils from two patients with eosinophilic granuloma of bone (EGB) were studied by combined immunohistochemical and immuno-ultrastructural methods with antibodies directed against three eosinophil granule proteins: major basic protein, eosinophil cationic protein, and eosinophil peroxidase. Immunohistostaining showed the presence and distribution of large numbers of eosinophils in the granuloma. Immuno-ultrastructural methods showed alterations of eosinophil fine structure associated with some steps in the release of granule proteins. No granule extrusion was seen, but rather cationic proteins diffused within cytoplasmic tubulo-vesicular structures. Furthermore, the three granule proteins were found within phagolysosomes of surrounding macrophages, suggesting an interaction between eosinophils and phagocytic cells at the destructive stage of EGB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01611183
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Small cell carcinoma of the ovary: An immunohistochemical and ultrastructural study with a review of the literature (1992)
    Springer
    Virchows Archiv 421 (1992), S. 263-270 
    Details
    ISSN: 1432-2307
    Keywords: Small cell carcinoma ; Ovary ; Immunohistochemistry ; Ultrastructure ; Literature review
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This is an immunohistochemical and ultrastructural study of two small cell carcinomas of the ovary with a review of the literature. These cases showed a dimorphic population of small and large cells sharply demarcated from each other. Cytokeratin 18 and vimentin were mainly expressed in the large tumour cells, some of which also stained for alpha-smooth muscle actin. Periodic-acid-Schiff-positive, alpha-1-antitrypsin-positive hyaline globules were present in one case. Ultrastructural findings included filamentous nucleolonema as well as evidence of smooth muscle differentiation. Some of these observations have not been previously reported. Certain of the above features seem to support a germ cell origin of small cell carcinoma, but they cannot be considered specific for germ cell neoplasms. Thus, small cell carcinoma of the ovary cannot be classified into one of the known categories of ovarian tumours at the present time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01611184
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Immunohistochemical and ultrastructural studies of intraluminal crystalloids in human prostatic carcinomas (1992)
    Springer
    Virchows Archiv 421 (1992), S. 421-425 
    Details
    ISSN: 1432-2307
    Keywords: Crystalloid ; Prostatic cancer ; Epithelial membrane antigen ; Phosphotungstic acid hematoxylin stain ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intraluminal crystalloids (ICr) observed in 19 cases of incidental or invasive human prostatic carcinoma (PCa) and in a case of benign prostatic hyperplasia were examined extensively by immunohistochemistry and electron microscopy. They were brilliantly eosinophilic with haematoxylin and eosin, manifesting needlelike, triangular, rectangular, hexagonal and irregular lump-like in shape. They were strongly positive, dark blue, with phosphotungstic acid -haematoxylin (PTAH) stain in all cases examined. Among the human antibodies tested, epithelial membrane antigen (EMA) gave specifically positive immunostainability with ICr in all cases. Annual ring-like lamellar or concentric structures were detected by electron microscopy. Positive staining of ICr with PTAH and anti-EMA antibody is very useful as a diagnostic marker for PCa in human prostatic tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01606915
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Ultrastructural observations on cytotoxic effector cells infiltrating pancreatic islets of low-dose streptozocin treated mice (1992)
    Springer
    Virchows Archiv 420 (1992), S. 5-10 
    Details
    ISSN: 1432-2307
    Keywords: Islets of Langerhans ; Monocytic phagocytes ; Streptozocin ; Type 1 diabetes ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of this study was to observe the ultrastructural events, during the onset of diabetes mellitus in the low-dose streptozocin (LDS)-treated mouse model with emphasis on the infiltrating elements. Forty male C57 BL/6J mice were given 40 mg/streptozocin on 5 consecutive days and killed 5, 6, 7, 8, 9, 10, 15, and 18 days after the first injection. Results demonstrated that islet infiltration occurring in LDS-treated mice is characterized by a very early pre-infiltration state in which mononuclear phagocytes in islet capillary vessels were considerably increased in number. A new histopathological time sequence for the early insulitis is described, in which attraction of blood mononuclear phagocytes into the islet capillary lumen is the first step. During the successive stage, occurring on days 6–8 we observed that mononuclear phagocytes migrate through capillary and venule walls into the islet parenchyma, where they differentiate into tissue macrophages. It was only later (step 3) that these macrophages acquired novel properties, typical of their “activated state” and started to phagocytose islet beta-cell debris. These data suggest that during the pre-infiltration and early insulitis the mononuclear phagocyte system plays a key role in the onset of LDS diabetes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01605977
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Malignant rhabdoid tumour of the uterus: an immunohistochemical and ultrastructural study (1992)
    Springer
    Virchows Archiv 420 (1992), S. 459-462 
    Details
    ISSN: 1432-2307
    Keywords: Malignant rhabdoid tumour ; Uterus ; Immunohistochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Malignant rhabdoid tumours (MRTs) are highly aggressive neoplasms which most frequently occur in the kidney of young children. Several cases of primary MRT occurring in extra-renal sites have been reported, particularly in the soft tissues. We report a case of primary MRT of the uterus, a very rare site for this neoplasm, with morphological, immunohistochemical and ultrastructural features corresponding to restrictive morphological criteria for MRT. The possible differential diagnoses were considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600519
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 11
    Electronic Resource
    Electronic Resource
    Effects of combined renovascular hypertension and diabetes mellitus on myocardial cells, non-vascular interstitium and capillaries: a stereological study on rat hearts (1992)
    Springer
    Virchows Archiv 420 (1992), S. 499-506 
    Details
    ISSN: 1432-2307
    Keywords: Diabetes mellitus ; Renovascular hypertension ; Myocardium ; Stereology ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of combined renovascular hypertension and diabetes mellitus on the rat heart were investigated in order to detect possible synergistic effects of the two conditions. Hypertensive diabetic and hypertensive non-diabetic animals were compared to diabetic and non-diabetic controls. Hypertension was established for 12 weeks by a surgical stenosis of the left renal artery; diabetes mellitus was maintained for 8 weeks by a single intraperitoneal injection of 60 mg/kg streptozotocin. Light microscopic stereology did not reveal significant divergences between diabetic hypertensives and non-diabetic hypertensives. Hypertension induced a focal perivascular and interstitial fibrosis with increased volume densities of non-vascular interstitium and fibrosis (P〈0.001). Capillary density (QA) was decreased in transverse sections (P〈0.01) and increased in longitudinal sections (P〈0.01). This indicates a three-dimensional remodelling of the capillary bed with an increased number of obliquely running capillaries. At least the length density (LV) of capillaries (mm/mm3) tends to be normalized in long-term renovascular hypertension. At the ultrastructural level, a synergism of hypertension and diabetes mellitus was observed: the volume ratio of mitochondria to myofibrils was significantly decreased in hypertensive diabetics, but not in non-diabetic hypertensives or in diabetics. This may enhance the risk of cardiac deterioration. We conclude that the primary target of the synergistic damage in hypertensive diabetic heart muscle disease is the myocardial cell and not the cardiac interstitium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600254
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Cytoskeletal filaments in the smooth muscle cells of uterine leiomyomata and myometrium: An ultrastructural and immunohistochemical analysis (1992)
    Springer
    Virchows Archiv 420 (1992), S. 51-58 
    Details
    ISSN: 1432-2307
    Keywords: Leiomyoma ; Myometrium ; Cytoskeleton ; Ultrastructure ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The filamentous components of the cytoskeleton in smooth muscle cells of leiomyomata and normal myometrium were studied by immunohistochemistry and electron microscopy. Fourteen patients hysterectomised for non-malignant disease provided leiomyomata of conventional histological type and histologically normal myometrium: four samples of fetal myometrium were studied by immunohistochemistry alone. All samples of leiomyoma and myometrium were strongly positive for α-smooth muscle actin and desmin, the latter often as paranuclear columns or granules. Vimentin was also stained in most samples but less intensely, while cytokeratin stained in about half the samples with an intensity comparable to that of vimentin. By electron microscopy, myofilaments with focal densities were abundant in both normal myometrium and leiomyomata. Intermediate filaments corresponding to the desmin and vimentin demonstrated by immunohistochemistry were also recognised in a variety of architectural arrangements. At one extreme, comparatively small numbers of filaments were loosely distributed around membranous organelles; at the other, filaments formed conspicuous aggregates, largely excluding other organelles and corresponding to the paranuclear granules seen by immunohistochemistry. A comparison of these findings with those of the literature and comments on the possible significance and origin of these aggregates are provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01605984
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Granular cell tumour of the breast (1992)
    Springer
    Virchows Archiv 420 (1992), S. 219-226 
    Details
    ISSN: 1432-2307
    Keywords: Breast ; Granular cell tumour ; Mammography ; Ultrastructure ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eight cases of benign granular cell tumour of the breast are reported. Seven patients were women and one was male. The age at the time of the excision ranged from 17 to 73 (average 40.1) years. All tumours were positive for S-100 protein and negative for keratin, myoglobin and gross cystic disease fluid protein. In two cases ultrastructural studies revealed findings identical to those in the previously reported cases of granular cell tumours. None of these cases were diagnosed preoperatively. In six cases the clinical and mammographic findings, and in one case the frozen section, led to an erroneous diagnosis of malignancy. The clinico-pathological features of the cases are delineated in order to draw attention to a benign condition which closely simulates malignancy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600274
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Ultrastructural anomalies in the fetal small intestine indicate that fetal swallowing is important for normal development: an experimental study (1992)
    Springer
    Virchows Archiv 420 (1992), S. 305-312 
    Details
    ISSN: 1432-2307
    Keywords: Fetus ; Small intestine ; Ultrastructure ; Malnutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fetal swallowing is established early in development and if fetal ingestion is prevented, the gastrointestinal (GI) tract fails to grow normally. In this article we describe the ultrastructural features of GI tissues developing in the absence of swallowing, in the fetal sheep. We have noted a number of defects in enterocyte morphology. These include abnormal or absence of microvilli, inappropriate cell extrusion, glycogen accumulation and altered lysosomal morphology. Many of these changes resemble those seen in malnourished infants. It is possible that fetal ingestion provides a significant source of nutrients, ensuring adequate GI tract growth in utero, in addition to specific growth factors which may be present in ingested fluid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600209
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    A histopathological and ultrastructural study of eccrine porocarcinoma with special reference to its subtypes (1992)
    Springer
    Virchows Archiv 420 (1992), S. 395-401 
    Details
    ISSN: 1432-2307
    Keywords: Eccrine porocarcinoma ; Ultrastructure ; Giant cell ; Elastic fibre ; Globular filamentous body
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Five cases of eccrine porocarcinoma were studied by light and electron microscopy. Histopathologically, these could be classified into two types; the common and the giant cell type. The common type was characterized by almost uniform medium-sized cuboidal tumour cells and a formation of well-developed intracytoplasmic lumina. A broad diversity of histopathological and ultrastructural features was seen in these tumours. The tumours of the giant cell type consisted of mononu-clear polygonal cells and bizarre giant cells. This type was considered to be an undifferentiated form of porocarcinoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600510
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Ultrastructural identification of neurofibrillary tangles in the spinal cords in Guamanian amyotrophic lateral sclerosis and parkinsonism-dementia complex on Guam (1992)
    Springer
    Acta neuropathologica 83 (1992), S. 277-282 
    Details
    ISSN: 1432-0533
    Keywords: Spinal cord neurofibrillary tangles ; Parkinsonism-dementia complex on Guam ; Guamanian amyotrophic lateral sclerosis ; Ultrastructure ; Immunoelectron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The immunohistochemical and ultrastructural characteristics of spinal cord neurofibrillary tangles (NFTs) were examined in Guamanian amyotrophic lateral sclerosis and in parkinisonism-dementia complex on Guam. The spinal cord NFTs reacted with antibodies to tau protein (tau-2), ubiqitin and paired helical filaments (PHFs). Ultrastructurally, the components of the NFTs were seen as randomly arranged fibrils which were often associated with osmiophilic granules; small bundle-like arrangements were also occasionally observed. Individual NFT fibrils appeared as straight fibrils with a diameter of approximately 15 nm and constricted fibrils with a periodicity of approximately 80 nm. Ultrastructural microscopic examination of specimens stained by the modified Bielschowsky method and with the antibodies revealed silver particles and the products of the tau, ubiquitin and PHF immunoreactions on the NFT fibrils. This is the first demonstration of the fine structure of the spinal cord NFTs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296790
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Immunocytochemical and ultrastructural studies of eosinophilic granular bodies in astrocytic tumors (1992)
    Springer
    Acta neuropathologica 83 (1992), S. 408-414 
    Details
    ISSN: 1432-0533
    Keywords: Eosinophilic granular body ; Astrocytoma ; Ultrastructure ; Immunocytochemistry ; αB-crystallin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eosinophilic granular bodies (EGBs) are studied immunocytochemically and ultrastructurally in a case of low-grade and a case of high-grade astrocytoma. EGBs are recognized as brightly eosinophilic round bodies of variable size in hematoxylin and eosin-stained sections. Immunocytochemically some EGBs are positive for antibodies raised against αB-crystallin, ubiquitin and glial fibrillary acidic protein with the staining patterns for each being different from one another. Ultrastructurally EGBs consist of membrane-bound round body of various diameter ranging from 50 nm to 20 μm. Small EGBs contain electron-dense homogeneous material with occasional myelin figures, while large EGBs contain small EGB-like structures within electron-dense homogeneous material or loose granular profiles. Our studies demonstrate (1) ultrastructural variety of EGB; (2) and αB-crystallin epitope in EGB; and (3) the presence of EGB in high-grade as well as low-grade astrocytoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713533
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Ultrastructural studies of the cells forming amyloid in the cortical vessel wall in Alzheimer's disease (1992)
    Springer
    Acta neuropathologica 84 (1992), S. 117-127 
    Details
    ISSN: 1432-0533
    Keywords: Alzheimer disease ; Amyloid angiopathy ; Pericytes ; Microglia ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ultrastructural studies of serial sections of the vessels with amyloid deposits in the brain cortex of patients with Alzheimer's disease showed that cells in the position of pericytes — perivascular cells - and perivascular microglial cells are producers of amyloid fibrils in the vascular wall. Three types of changes from normal are distinguishable in the vessel wall: (1) semicircular or circular thickening of vascular wall containing a large amount of amorphous material and various number of amyloid fibrils, (2) tuberous amyloid deposits containing both amorphous material and amyloid fibrils, some of the fibrils being arranged in strata and others arranged radially, and (3) amyloid star composed of a predominantly radial arrangement of bundles of amyloid fibrils and a less prominent amorphous component. A mixture of amorphous material and amyloid fibrils is present in cell membrane envaginations of perivascular cells, and occasionally perivascular microglial cells. Bundles of amyloid fibrils are found in altered cisternae of the endoplasmic reticulum and in the channels confluent with the infoldings of the plasma membrane of perivascular microglial cells. The amyloid deposition in the wall of the vessel causes degeneration of endothelial cells and the reduction of, and in some vessels obliteration of, the vessel lumen. In areas affected by amyloid angiopathy, extensive degeneration both of the neuropil and of neurons was observed. These changes were accompanied by astrogliosis. This study demonstrates similarities in amyloid formation in amyloid angiopathy and in β-amyloid plaques in the neuropil and suggests that cells of the mononuclear phagocyte system of the brain (perivascular cells and perivascular microglia) are engaged in amyloid fibril formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311383
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Ultrastructural and immunohistochemical studies on ballooned cortical neurons in Creutzfeldt-Jakob disease: expression of αB-crystallin, ubiquitin and stress-response protein 27 (1992)
    Springer
    Acta neuropathologica 84 (1992), S. 443-448 
    Details
    ISSN: 1432-0533
    Keywords: Creutzfeldt-Jakob disease ; Ballooned neurons ; Ultrastructure ; αB-Crystallin ; Stress-response proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This report concerns ultrastructural and immunohistochemical studies on ballooned neurons of ten patients with Creutzfeldt-Jakob disease (CJD). While abundant ballooned neurons and severe white matter degeneration was seen in six Japanese cases, only occasional ballooned neurons and no white matter degeneration was observed in four cases from the files of Montefiore Medical Center. Ultrastructurally, the ballooned neurons contained granule-coated fibrils of 25 to 40 nm in width and 10-nm neurofilaments. The immunohistochemical studies revealed that most ballooned neurons expressed αB-crystallin, with deposits of reaction products observed in the cytoplasm. A similar intracellular staining pattern was also seen with the antibody to phosphorylated neurofilament proteins (pNFP). Although the proportion of stained ballooned neurons was less, a positive reaction was also observed with antibodies against ubiquitin, stress-response protein 27 (srp 27) and synptophysin, but not with an antibody to srp 72. Our findings suggest that expression of pNFP and synaptophysin by ballooned neurons may reflect axonal impairment and that the presence of αB-crystallin, srp 27 and ubiquitin may be related to the degenerative processes that neurons undergo in CJD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227673
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Colloid cysts of the third ventricle: ultrastructural features are compatible with endodermal derivation (1992)
    Springer
    Acta neuropathologica 83 (1992), S. 605-612 
    Details
    ISSN: 1432-0533
    Keywords: Colloid cyst ; Endoderm ; Respiratory epithelium ; Third ventricle ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The histogenesis of colloid cyst of the third ventricle remains unsettled. Ultrastructural and immunohistochemical analyses have suggested the following possible origins: (a) neuroepithelium, including paraphysis, ependyma, choroid plexus and tela chorioidea; and (b) endoderm, including respiratory and enteric epithelium. This report describes the ultrastructural features of the lining epithelium in four cases of colloid cyst. Six distinct cell types were recognized: (1) ciliated cells with occasional abnormal cilia; (2) non-ciliated cells with microvilli coated with granulofibrillary material; (3) goblet cells showing discharge of secretory granules; (4) basal cells with prominent tonofilaments and desmosomes; (5) basal-located cells with elongated electron-lucent cytoplasm and scattered membrane-bound dense-core granules (150–350 nm); and (6) small undifferentiated cells with scanty organelles. Junctional complexes were present in the former four cell types but absent in the latter two. The types of epithelial cells and their topographic distribution within the epithelium are both very similar to those of normal respiratory epithelium and to the lining epithelium of intraspinal bronchogenic cyst. The observations made in the present study are compatible with the hypothesis that colloid cysts of the third ventricle originate from the endoderm, most likely the respiratory epithelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299409
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 21
    Electronic Resource
    Electronic Resource
    Silver staining of the postacrosomal sheath during human spermiogenesis (1992)
    Springer
    Anatomy and embryology 185 (1992), S. 271-274 
    Details
    ISSN: 1432-0568
    Keywords: Man ; Spermiogenesis ; Postacrosomal ; sheath ; Silver staining ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Applying the silver staining technique, it could be shown that in the early phase of spermiogenesis a layer of argyrophilic material accumulated at the base of the acrosomal vesicle and at the outer side of the nuclear envelope opposite that region, and, later, at the inner side of the plasma membrane near the base of the acrosomal vesicle. During further development of the postacrosomal region of the spermatozoon head, the argyrophilic material associated with the plasmalemma grew caudally to form the postacrosomal dense lamina, while the argyrophilic material associated with the nuclear envelope, staying the same size, shifted to the caudal end of the postacrosomal dense lamina to form the postnuclear band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211825
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 22
    Electronic Resource
    Electronic Resource
    Ultrastructural features of spongiform encephalopathy transmitted to mice from three species of bovidae (1992)
    Springer
    Acta neuropathologica 84 (1992), S. 559-569 
    Details
    ISSN: 1432-0533
    Keywords: Neuronal autophagy ; Bovine spongiform encephalopathy ; Lysosomes ; Ultrastructure ; Vactiolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructural neuropathology of mice experimentally inoculated with brain tissue of nyala (Tragelaphus angasi; subfamily Bovinae), or kudu (Tragelaphus strepsiceros; subfamily Bovinae) affected with spongiform encephalopathy was compared with that of mice inoculated with brain tissue from cows (Bos taurus: subfamily Bovinae) with bovine spongiform encephalopathy (BSE). As fresh brain tissue was not available for nyala or kudu, formalin-fixed tissues were used for transmission from these species. The effect of formalin fixation was compared with that of fresh brain in mice inoculated with fixed and unfixed brain tissue from cows with BSE. The nature and distribution of the pathological changes were similar irrespective of the source of inoculum or whether the inoculum was from fresh or previously fixed tissue. Vacuolation caused by loss of organelles and swelling was present in dendrites and axon terminals. Vacuoles were also seen as double-membrane-bound and single-membrane-bound structures within myelinated fibres, axon terminals and dendrites. Vacuoles are considered to have more than one morphogenesis but the structure of vacuoles in this study was nevertheless similar to previous descriptions of spongiform change in naturally occurring and experimental scrapie, Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker syndrome and kuru. Other features of the ultrastural pathology of the transmissible spongiform encephalopathies including dystrophic neurites and scrapie-associated particles or tubulovesicular bodies were also found in this study. Neuronal autophagy was a conspicuous finding. It is suggested that excess prion protein (PrP) accumulation, or accumulation of the scrapie-associated protease-resistant isoform of PrP, may lead to localised sequestration and phagocytosis of neuronal cytoplasm and ultimately to neuronal loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00304476
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 23
    Electronic Resource
    Electronic Resource
    Placental iron transfer regulation in the haemophagous region of the badger placenta: ultrastructural localization of ferritin in trophoblast and endothelial cells (1992)
    Springer
    Anatomy and embryology 185 (1992), S. 175-179 
    Details
    ISSN: 1432-0568
    Keywords: Badger-placenta ; Ultrastructure ; Ferritin ; Iron transfer regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The haemophagous region of the badger (Meles meles L.) placenta is involved in iron transfer, and maternal erythrocytes are the only source of iron for the fetus. This ultrastructural study provides morphological evidence of placental ferritin iron storage intervening if haem-iron uptake exceeds fetal needs. Such placental ferritin is assumed to play an active role in iron transfer regulation. In this paper we demonstrate that this regulatory process of iron transfer by storage in placental ferritin occurs on at least two levels: the cytotrophoblast and the fetal endothelium. The latter could then act as a final monitor in the transfer of iron into the fetal circulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185919
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 24
    Electronic Resource
    Electronic Resource
    “Reducing body”-like inclusions in skeletal muscle in childhood-onset acid maltase deficiency (1992)
    Springer
    Acta neuropathologica 85 (1992), S. 111-115 
    Details
    ISSN: 1432-0533
    Keywords: Muscle ; Ultrastructure ; Lysosome ; Metabolic disorder ; Glycogenosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Unusual inclusions with some of the features of “reducing bodies” were encountered in the skeletal muscle biopsy of a 2.5-year-old boy with childhoodonset acid maltase deficiency. The biopsy revealed a vacuolar myopathy with lysosomal storage of glycogen and eosinophilic refractile inclusions in myofibers, which appeared dark blue with the menadione-nitroblue tetrazolium reaction. The significance of the association of inclusions with reducing properties in the setting of acid maltase deficiency is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00304641
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 25
    Electronic Resource
    Electronic Resource
    Caudate nucleus pathology in Parkinson's disease: ultrastructural and biochemical findings in biopsy material (1992)
    Springer
    Acta neuropathologica 83 (1992), S. 352-360 
    Details
    ISSN: 1432-0533
    Keywords: Parkinson's disease ; Ultrastructure ; Catecholomines ; Trans-synaptic degeneration ; Axonal dystrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ultrastructural and biochemical properties of caudate nucleus (CN) biopsies in two patients with advanced Parkinson's disease (PD) were compared with three CN specimens removed during surgery for intracranial tumors. An additional two specimens from neurologically intact patients (59 and 86 years old) were removed during autopsy (performed 3 and 4 h post mortem, respectively) for electron microscopic studies. Dopamine levels in PD were reduced to less than 15% of control values. Both PD patients showed frequent dystrophic neurites and transsynaptic degeneration of neurons and neuritic processes. These changes were not found in CN from the four control individuals. Only a few dystrophic neurites were noticed in one 67-year-old control patient. The development of neuroaxonal dystrophy in CN is consistent with a dying-back process, probably accompanying abnormalities of axonal transport in PD. Transsynaptic degeneration of neurons in CN very likely represents a morphological marker of disease severity. The occurrence of this change may account for the poor clinical response of patients with advanced PD to intracerebral implantation of dopaminergic tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713525
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 26
    Electronic Resource
    Electronic Resource
    Novel eosinophilic inclusion in astrocytes (1992)
    Springer
    Acta neuropathologica 83 (1992), S. 659-663 
    Details
    ISSN: 1432-0533
    Keywords: Eosinophilic inclusion ; Neuroglia ; Astrocyte ; Aicardi's syndrome ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intracytoplasmic and brightly eosinophilic inclusions within neuroglias are reported in a patient with Aicardi's syndrome. Most inclusion-bearing neuroglias were protoplasmic astrocytes in the cerebral cortex. Compared with similar eosinophilic and intracytoplasmic inclusions in other studies using both light and electron microscopy, the inclusions in this report are regarded as being novel and not previously described. Ultrastructually, the inclusions were composed of electron-dense granules and amorphous substances, and were not surrounded by a limiting membrane. They were numerous in the cerebral cortex, especially in part of the microgyrus, but absent in the deep cerebral white matter, subcortical nuclei, brain stem and the cerebellum. Therefore, they may be closely associated with brain malformation and congenital astrocytic dysfunction. They also suggested a functional difference in protoplasmic astrocytes themselves, according to the differentiation of related gray matter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299417
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 27
    Electronic Resource
    Electronic Resource
    Morphological observations on the Harderian gland of the North American opossum (Didelphis virginiana) (1992)
    Springer
    Anatomy and embryology 186 (1992), S. 145-152 
    Details
    ISSN: 1432-0568
    Keywords: Harderian gland ; Tubuloalveolar endpieces ; Serous endpieces ; Ultrastructure ; Opossum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The Harderian gland of the North American opossum (Didelphis virginiana) is large and well developed, despite the absence of a nictitating membrane in the adult of this species. The elongate glands are surrounded by a delicate connective tissue capsule from which thin septae extend, subdividing the gland into numerous lobules. The secretory units of the opossum Harderian gland are drained by a well defined but not extensive intralobular and interlobular duct system. Most of the secretory end pieces consist of tubuloalveolar units with widely dilated lumina filled with secretory product. Numerous intact lipid vesicles suspended within an amorphous material constitute the luminal contents. Cells lining the tubuloalveolar secretory endpieces are usually columnar in shape, and characterized by numerous lipid-containing secretory vesicles and aggregations of polytubular complexes 40–60 nm in diameter. In addition, these cells contain numerous large irregularly shaped mitochondria, whose matrix is of considerable electron density. Intralobular and interlobular ducts are lined by electron-lucent epithelial cells that lack both the lipid-containing vesicles and the large mitochondria, although typical smaller mitochondria are found scattered within the cytoplasm. Both secretory endpieces and ductal elements are invested by an abundance of myoepithelial cells. A second, smaller serous type of secretory unit may occur near the centre of some Harderian gland lobules. In these units secretory tubules and acini are compactly arranged surrounding a narrow lumen. Serous cells are pyramidal in shape and the cytoplasm is characterized by numerous electron-dense secretory granules and scattered profiles of rough endoplasmic reticulum. Basolateral cell membranes show extensive infoldings and intercellular canaliculi are present. The overall size of cells forming the serous secretory units is much less than that comprising the tubuloalveolar secretory endpieces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174952
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 28
    Electronic Resource
    Electronic Resource
    Immunocytochemical and ultrastructural studies of upper motor neurons in amyotrophic lateral sclerosis (1992)
    Springer
    Acta neuropathologica 83 (1992), S. 518-524 
    Details
    ISSN: 1432-0533
    Keywords: Amyotrophic lateral sclerosis ; Upper motor neurons ; Ultrastructure ; Neurofilament ; Ubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The pathological alterations in upper motor neurons were investigated in 27 cases of adult-onset sporadic amyotrophic lateral sclerosis (ALS). No signficant cytoskeletal alterations were found in the Betz cells of any of the cases except one, although cytoskeletal pathology was consistently present in lower motor neurons. The one case had severe circumscribed atrophy of the precentral gyrus and, microscopically, had argentophilic intracytoplasmic inclusions in Betz cells and other pyramidal neurons in the primary motor area as eell as in the lower motor neurons. Immunocytochemically these inclusions contained the epitope of phosphorylated neurofilament and ubiquitin and ultrastructurally consisted of granule-associated filaments with neurofilaments. This is the first demonstration of alterations of cytoskeleton and ubiquitination in the giant cells of Betz, an established subset of upper motor neurons in ALS. Thus, although uncommon, cytoskeletal changes can be found in upper motor neurons in some ALS cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310029
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 29
    Electronic Resource
    Electronic Resource
    Primary leptomeningeal glioma: ultrastructural and laminin immunohistochemical studies (1992)
    Springer
    Acta neuropathologica 83 (1992), S. 538-542 
    Details
    ISSN: 1432-0533
    Keywords: Primary leptomeningeal glioma ; Ultrastructure ; Basal lamina ; Laminin ; Heterotopic glial tissue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We studied a case of primary leptomeningeal glioma (PLG) on the left parietal lobe of a 74-year-old woman and compared the tissue with heterotopic glial tissue from another case. The PLG tumor consisted of spindle-shaped cells with marked nuclear atypism, which tended to be arranged in a fascicular pattern, and the majority of its cells were positive for glial fibrillary acidic protein. Ultrastructural examination demonstrated that most of the tumor cells contained intermediate filaments and often junctional complexes were present on their plasma membranes. Frequently, basal lamina-like structures surrounding the tumor, cell surfaces were observed. Laminin immunohistochemistry clearly demonstrated a fine network of linear positive staining around the cytoplasm and processes of the tumor cells. The ultrastructure of the heterotopic glial tissue consisted of many astrocytes partially surrounded by basal lamina. These findings strongly suggest that PLG is a distinct tumor, which arises from the heterotopic astrocytes within the subarachnoid space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310033
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 30
    Electronic Resource
    Electronic Resource
    Morphological findings on peripheral nerve biopsies in 15 patients with human immunodeficiency virus infection (1992)
    Springer
    Acta neuropathologica 83 (1992), S. 618-623 
    Details
    ISSN: 1432-0533
    Keywords: Peripheral nerve biopsy ; HIV infection ; Ultrastructure ; in situ hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A peripheral nerve biopsy was performed in 15 patients with human immunodeficiency virus (HIV) infection and polyneuropathy. Two cases [1 asymptomatic, 1 AIDS-related complex (ARC)] presented with chronic inflammatory demyelinating polyneuropathy; there was 1 case (asymptomatic) of mononeuropathy multiplex and 12 cases (1 asymptomatic, 1 ARC, 10 AIDS) with distal symmetrical polyneuropathy. Epi- or endoneurial microvasculitis was observed in 6 cases. Electron microscopy showed that nerve fiber lesions were mainly axonal. Severe segmental demyelination was also present in both cases of chronic inflammatory demyelinating polyneuropathy, with characteristic features of active demyelination in one. Numerous plasmacytoid cells were found in the endoneurium in 4 patients. Tubuloreticular inclusions were present in endothelial cells in the 10 cases with AIDS but absent in the other patients. Direct immunopathological examination with anti-immunoglobulin sera was negative in all cases. HIV was evidenced by in situ hybridization in 2 AIDS patients; no Epstein-Barr virus or cytomegalovirus was detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299411
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 31
    Electronic Resource
    Electronic Resource
    Ultrastructure of the microglia that phagocytose amyloid and the microglia that produce β-amyloid fibrils (1992)
    Springer
    Acta neuropathologica 84 (1992), S. 225-233 
    Details
    ISSN: 1432-0533
    Keywords: Alzheimer's disease ; Tissue culture ; Microglia ; Amyloid ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The function of microglia associated with β-amyloid deposits still remains a controversial issue. On the basis of recent ultrastructural data, microglia were postulated to be cells that form amyloid fibrils, not phagocytes that remove amyloid deposits. In this electron microscopic study, we examined the ability of microglia to ingest and digest exogenous amyloid fibrils in vitro. We demonstrate that amyloid fibrils are ingested by cultured microglial cells and collected and stored in phagosomes. The ingested, nondegraded amyloid remains within phagosomes for up to 20 days, suggesting a very limited effectiveness of microglia in degrading β-amyloid fibrils. On the other hand, we showed that in microglial cells of classical plaques in brain cortex of patients with Alzheimer's disease, amyloid fibrils appear first in altered endoplasmic reticulum and deep infoldings of cell membranes. These differences in intracellular distribution of amyloid fibrils in microglial cells support our observations that microglial cells associated with amyloid plaques are engaged in production of amyloid, but not in phagocytosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227813
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 32
    Electronic Resource
    Electronic Resource
    Tubulovesicular structures in Creutzfeldt-Jakob disease (1992)
    Springer
    Acta neuropathologica 84 (1992), S. 238-243 
    Details
    ISSN: 1432-0533
    Keywords: Creutzfeldt ; Jakob disease ; Tubulovesicular structures ; Prion diseases ; Ultrastructure ; Transmissible spongiform encephalopathies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary By electron microscopy tubulovesicular structures (TVS) have been consistently observed in brain tissue of transmissible spongiform encephalopathies such as natural and experimental scrapie, bovine spongiform encephalopathy and experimentally induced, but not naturally occurring, Creutzfeldt-Jakob disease (CJD). For the first time we report here the presence of TVS in human brains with CJD as detected by transmission electron microscopy. TVS were observed in all three CJD specimens (two biopsies, one autopsy), but they were rare and were found only in one or two location(s) per grid. TVS were seen in distended pre- and postsynaptic terminals and measured approximately 35 nm in diameter; they were smaller and of higher electron density than synaptic vesicles. Their occurrence in all types of transmissible spongiform encephalopathies irrespective of the affected host and the strain of the infectious agent suggests their biological significance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227815
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 33
    Electronic Resource
    Electronic Resource
    Morphometrical variations of prolactin cells in response to prolonged and systemic administration of Met-enkephalin in female rats (1992)
    Springer
    Anatomy and embryology 186 (1992), S. 99-105 
    Details
    ISSN: 1432-0568
    Keywords: Prolactin cell ; Met-enkephalin ; Immunocytochemistry ; Ultrastructure ; Morphometr ; Rat(Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A stimulatory effect on prolactin secretion had been describe after acute and systemic administration of met-enkephalin, but the effects of this opioid after chronic administration has not been reported, and the response of mammotroph cells is not clear. As a complement to previous studies, a morphometric analysis (light and electron microscopy) was carried out on prolactin cells from female rats treated chronically with met-enkephalin. Clear features of cellular hyperactivity appeared after chronic and systemic administration of the opioid, and these persisted for two weeks. The changes consisted in increases of cellular, cytoplasmic and nuclear areas, volume and surface densities of the Golgi complex and rough endoplasmic reticulum, as well as the numbers of exocytotic figures. These morphological alterations were paralleled by an increase in serum prolactin levels as detected by RIA. It is concluded that the increase in the synthesis and secretory activity of prolactin cells following chronic and systemic administration of met-enkephalin is very similar to those observed after acute and intraventricular administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00710406
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 34
    Electronic Resource
    Electronic Resource
    Electron microscopic investigations on the growing tip of nerve fibres in the developing distal forelimb of the mouse (1992)
    Springer
    Anatomy and embryology 185 (1992), S. 201-206 
    Details
    ISSN: 1432-0568
    Keywords: Development ; Mouse ; Peripheral nerves ; Schwann cells ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The distal course of the sensory nerve fibres on the palmar side of the hand of 12-day-old mouse embryos was followed by serial ultrathin cross-sections of conventionally fixed tissue. Small nerves fibres are to be found in the space between the layer of the cutaneous blood vessels and the epidermis. A special arrangement of the tissue which is traversed by the nerve fibres is not visible. In most cases the nerve fibres are in intimate contact with fibroblasts. More distally the nerve fibres consist only of one axon encircled by a Schwann cell. The sheath of the Schwann cell decreases gradually, and finally disappears completely. The distal tips of the naked axons are a few μm ahead. In some cases they are considerably enlarged and contain only a fine fuzzy material without special cell organelles. Other axons may end in a more finger-like fashion, and contain also in the naked parts many cell organelles. Also the naked axons contact fibroblasts over long ranges. Collagen was not found aligned to the distal nerve fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185922
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 35
    Electronic Resource
    Electronic Resource
    Light and electron microscopic morphology of the temporomandibular joint in growing and mature crab-eating monkeys (Macaca fascicularis): the condylar calcified cartilage (1992)
    Springer
    Anatomy and embryology 185 (1992), S. 189-199 
    Details
    ISSN: 1432-0568
    Keywords: Mandibular condyle ; Calcified cartilage ; Ultrastructure ; Maturation ; Macaca fascicularis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In an attempt to show maturational alterations in the calcified cartilage, mandibular condyles of four growing and four adult male monkeys (Macaca fascicularis) were studied using light microscopy as well as transmission and scanning electron microscopy. All specimens were initially fixed by perfusion in the presence of ruthenium red. For examination of the hard tissue surfaces in the scanning electron microscope, uncalcified tissues were removed with sodium hypochlorite. In growing animals, almost the entire hard tissue surface in the joint region of the condyle was formed by calcified cartilage, while in adult animals, calcified cartilage was confined to load-bearing regions. In growing animals, the appearance of the calcified cartilage surface suggested a continuously advancing mineralizing front similar to that seen in the epiphyseal plate. Chondrocytes mostly exhibited a terminal stage of hypertrophy, and seemed to die and get lost through vascular invasion and subsequent endochondral ossification. In adult animals, most of the calcified cartilage surface appeared comparatively stable, and resembled the tidemark of articular cartilage. Chondrocytes were usually small and appeared viable. However, on the adult condyles, there were always circumscribed islands where chondrocytes and the pattern of mineralization resembled those seen in growing animals. In these regions, prominent chondroclastic activity indicated extensive articular remodelling. These observations suggest that at the end of somatic growth, condylar calcified cartilage undergoes considerable maturation from a type reminiscent of hyaline growth cartilage to a type resembling articular cartilage. Concomitantly, chondrocytes appear to change their developmental program, in that they stop enlarging and lose their commitment to death. However, they may be able to retain, or switch back to, a more immature stage, in case there is need for extensive articular remodelling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185921
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 36
    Electronic Resource
    Electronic Resource
    Clinical, light and electron microscopic features of recessive ichthyosis congenita type III (1992)
    Springer
    Archives of dermatological research 284 (1992), S. 259-265 
    Details
    ISSN: 1432-069X
    Keywords: Genodermatoses ; Ultrastructure ; Membrane structures ; Abnormal keratinosomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The recessively inherited congenital ichthyoses have ultrastructural features which indicate abnormal epidermal lipid metabolism. The ultrastructural markers of the three recessive congenital ichthyosis groups are lipid droplets in horny layers (type I), cholesterol clefts (type II) and membrane structures (type III). We describe six patients from five families belonging to the last group. The variable clinical phenotype alone does not allow the delineation of this disease, but together with the ultrastructural characteristics the subtype is unequivocal. In addition to the membrane structures, half of the cases showed abnormal keratinosomes and vesicular complexes. Membrane-bound vacuoles and needle-like slits were exceptionally found. The onset of the ichthyosis was variable, in contrast to other patients described under the heading recessive congenital ichthyosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00372578
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 37
    Electronic Resource
    Electronic Resource
    Relationship between tissue reactions and morphological changes of the fungi in chromoblastomycosis: morphometry and electron microscopy (1992)
    Springer
    Archives of dermatological research 284 (1992), S. 95-99 
    Details
    ISSN: 1432-069X
    Keywords: Chromoblastomycosis ; Host-fungus relationship ; Morphometry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To investigate the histological distribution and the morphology of the fungi and the tissue reactions in chromoblastomycosis, especially in the process of trans-epidermal elimination, cutaneous lesions of two patients with this disease were studied morphometrically and ultrastructurally. In the dermis, most of the fungal elements appeared as sclerotic cells and their cell wall showed an irregular, worm-eaten leaf-like appearance; they seemed to be continuously attacked by polymorphonuclear neutrophils. The epidermis eliminated 10–20% of all the organisms in the skin lesions, and the hypha-forming activity tended to be higher in the epidermis than in the dermis. Ultrastructurally, basal keratinocytes facing the dermal abscess containing fungal elements frequently appeared as dark cells, suggesting an increased proliferation activity. Spinous keratinocytes facing intraepidermal microabscesses containing fungal elements showed an abnormal accumulation of tonofilaments and further early keratinization in the spinous cell layer. All of the morphological changes of the dermis and epidermis are regarded as defence reactions against the fungi existing in the skin lesions. There is a close relationship between tissue reactions and morphological changes of fungi in chromoblastomycosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373377
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 38
    Electronic Resource
    Electronic Resource
    Increase in types IV and VI collagen in cherry haemangiomas (1992)
    Springer
    Archives of dermatological research 284 (1992), S. 275-282 
    Details
    ISSN: 1432-069X
    Keywords: Cherry haemangioma ; Type IV collagen ; Type VI collagen ; Immunohistochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The capillaries in cherry haemangiomas show perivascular hyalinized sheaths. In order to clarify the nature of this sheath material, the extracellular matrix of cherry haemangiomas from 20 normal volunteers (age range 30–64 years) was investigated using immunohistochemical and electronmicroscopical methods. Antibodies against collagen types III, IV and VI and laminin were used. Hyaluronic acid was visualized using the hyaluronic acid binding region of the cartilage proteoglycan as ligand. Electronmicroscopically, the sheaths contained multilaminated basement membrane-like material, collagen fibres 20–25 nm thick with a periodicity of 67 nm and broad-banded aggregates with a periodicity of 100 nm (zebra bodies or fibrous long-spacing fibres). Immunohistochemically, type IV collagen was stained throughout the whole sheath material. Staining for laminin was more confined to the endothelial side of the sheath. Intense staining for type III collagen and hyaluronic acid was found in the connective tissue of the subpapillary layer and between the cherry haemangioma capillaries. Much weaker staining for type III collagen and no staining for hyaluronic acid were found invariably in an area 4–10 Μm thick directly around the capillaries. Both sheath material and intercapillary connective tissue of the haemangiomas showed pronounced staining for collagen type VI. Immunogold staining revealed that type VI collagen was localized to microfibrils 5–6 nm thick and to the broad-banded aggregates with 100 nm periodicity. These findings further underline the assumption that the broad-banded aggregates consist of type VI collagen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00372581
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 39
    Electronic Resource
    Electronic Resource
    Early events during the establishment of the Gunnera/Nostoc symbiosis (1992)
    Springer
    Planta 188 (1992), S. 403-413 
    Details
    ISSN: 1432-2048
    Keywords: Cyanobacterium ; Gunnera ; Infection process ; Nostoc ; Symbiosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The symbiosis between Gunnera and Nostoc was reconstituted using G. chilensis Lam. and G. manicata Linden, respectively, and three different Nostoc strains. Six stages characterised by specific modifications in both the cyanobiont and the host were recognised during the infection process. Mucilage-secreting stem glands developed on the Gunnera stems independent of the presence of cyanobacteria (Stage I). Soon after addition of the Nostoc isolates to the plant apices, an abundant differentiation of motile hormogonia commenced. The cyanobacteria accumulated in the mucilage on the surface of the gland (Stage II), and the hormogonia then proceeded into the stem tissue through intercellular channels (Stage III). At the channel bases, Nostoc was detected between the cell walls of small, densely cytoplasmic Gunnera cells and also in elaborate folds of these (Stage IV). The Gunnera cell walls subsequently dissolved adjacent to the cyanobacteria and Nostoc entered the host cells (Stage V). Once the intracellular association was formed, a high proportion of the vegetative Nostoc cells differentiated into heterocysts (Stage VI). Nostoc changed from being rich in inclusions (particularly cyanophycin) while on the gland surface into a comparatively “non-storing” form during penetration and the early intracellular stages. Bacteria were numerous on the gland surface, fewer in the channels, and were never detected within the Gunnera cells, indicating the existence of specific recognition mechanisms discriminating between conceivable microsymbionts. Mechanisms behind mutual adaptations and interactions between the two symbionts are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192808
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 40
    Electronic Resource
    Electronic Resource
    High-pressure freezing of soybean nodules leads to an improved preservation of ultrastructure (1992)
    Springer
    Planta 188 (1992), S. 155-163 
    Details
    ISSN: 1432-2048
    Keywords: Bradyrhizobium ; Electron microscopy ; Glycine (root nodules) ; High-pressure freezing ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract High-pressure freezing of chemically untreated nodules of soybean (Glycine max (L.) Merr.), in sharp contrast to chemical fixation and prefixation, appears to preserve the ultrastructure close to the native state. This is supported by the observation that the peribacteroid membrane of high-pressure-frozen samples is tightly wrapped around the bacteroids, a finding that is fully consistent with the current views on the physiology of oxygen and metabolite transport between plant cytosol and bacteroids. In soybean root nodules, the plant tissue and the enclosed bacteria are so dissimilar that conventional aldehyde-fixation procedures are unable to preserve the overall native ultrastructure. This was demonstrated by high-pressure freezing of nodules that had been pre-fixed in glutaraldehyde at various buffer molalities: no buffer strength tested preserved all ultrastructural aspects that could be seen after high-pressure freezing of chemically untreated nodules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216809
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 41
    Electronic Resource
    Electronic Resource
    The microtubule cytoskeleton and the rounding of isolated generative cells ofNicotiana tabacum (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 64-71 
    Details
    ISSN: 1432-2145
    Keywords: Generative cell ; Isolation ; Microtubules ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Upon squashing of the pollen grain, the isolated generative cell ofNicotiana tabacum looses its spindle shape to become spherical; this phenomenon is independent of the sucrose concentration used. The time necessary for this change can vary from 1 min (0% sucrose) to 20 min (30% sucrose). The microtubular cytoskeleton was studied by means of immunofluorescence and electron microscopy. Just after isolation, 5 to 15 clearly visible bundles in microtubules organized in a basket-like structure are present. After 15 min in medium with 15% sucrose, the microtubular cytoskeleton disappears, and a diffusely spread tubulin can be observed. Neither the addition of 10–20 μM taxol to the medium, nor the omission of Ca2+ to the medium has any effect on the changes in cell shape and loss of microtubular bundles after isolation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714559
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 42
    Electronic Resource
    Electronic Resource
    Ultrastructure and microtubule organization of isolated generative cells ofAllemanda neriifolia at interphase and prophase (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 27-33 
    Details
    ISSN: 1432-2145
    Keywords: Isolated generative cells ; Ultrastructure ; Microtubule ; Immunofluorescence microscopy ; Allemanda neriifolia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of isolated generative cells ofAllemanda neriifolia at interphase and prophase was studied. The microtubule organization of the isolated cells was also investigated by immunofluorescence microscopy with a monoclonal anti-α-tubulin. After the generative cells had been isolated from the growing pollen tubes by osmotic shock, most of the cells were at prophase and only a few were at interphase. The interphase cell is spindle shaped and contains an ellipsoidal nucleus. In addition to the usual organelles, the cytoplasm of the interphase cell contains numerous vesicles (each measuring 40–50 nm in diameter) and two sets of longitudinally oriented microtubule bundles — one in the cortical region and the other near the nucleus. Most of the prophase cells are spherical in shape. Based on the ultrastructure and the pattern of microtubule cytoskeleton organization three types of prophase cells can be recognized. (1) Early prophase cell, which contains the usual organelles, numerous vesicles, and a spherical nucleus with condensed chromosomes. Longitudinally oriented microtubule bundles can no longer be seen present in the early prophase cell. A new type of structure resembling a microtubule aggregate appears in the cytoplasm. (2) Mid prophase cell, which has a spherical nucleus containing chromosomes that appear more condensed than those seen in the early prophase cell. In addition to containing the usual organelles, the cytoplasm of this cell contains numerous apparently randomly oriented microtubules. Few vesicles are seen and microtubule aggregates are no longer present. (3) Late prophase cell, typified by the lack of a nuclear envelope. Consequently, the chromosomes become randomly scattered in the cytoplasm. Microtubules are still present and some become closely associated with the chromosomes. The changes in the ultrastructure and in the pattern of microtubule organization in the interphase and prophase cells are discussed in relation to the method of isolation of the generative cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714555
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 43
    Electronic Resource
    Electronic Resource
    The formation of the generative cell in Polystachia pubescens (Orchidaceae) (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 131-137 
    Details
    ISSN: 1432-2145
    Keywords: Pollen grain ; Generative cell ; Formation and detachment ; Ultrastructure ; Polystachia pubescens ; Orchidaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The formation and nature of the generative cell wall and the detachment mode of the generative cell from the intine in Polystachia pubescens were observed by LM and TEM. Vesicles evenly positioned within the phragmoplast fuse to form a cell plate that divides the microspore into the generative and vegetative cell. This cell plate consists of callose. Before the generative cell leaves the intine, however, the callose is completely resorbed and is not replaced by any other substance. The generative cell becomes detached from the intine by moving towards the centre of the pollen grain. A constriction formed thereby gives the generative cell a bulb-like appearance and leads ultimately to the generative cell being pinched off. Plasma-filled vesicles originating from the generative cell remain between the intine and the plasma membrane of the vegetative cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194872
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 44
    Electronic Resource
    Electronic Resource
    Ultrastructural and immunohistochemical study of degenerate neurite-bearing ghost tangles (1992)
    Springer
    Journal of neurology 239 (1992), S. 191-194 
    Details
    ISSN: 1432-1459
    Keywords: Ghost tangles ; Degenerate neurites ; Astrocytes ; Senile plaques ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Some ghost tangles in the brains of Alzheimer patients were accompanied by many small argyrophilic structures which were electron microscopically confirmed to be degenerate neurites. In these ghost tangles, roughly dispersed 15 nm straight and occasional twisted tubules were penetrated by proliferated astrocytic processes. Immunohistochemically, these ghost tangles lost immunoreactivities to anti-NFT, -tau and -ubiquitin antibodies, but were thioflavine-S fluorescent, though antigenicity to β-protein was not proved. This similarity in composition of degenerate neurite-bearing ghost tangles to senile plaques might be induced by the amyloid nature of tubules, which probably provokes the reaction of neuropils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00839138
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 45
    Electronic Resource
    Electronic Resource
    Electron microscopic examination of sporulation-deficient mutants of the fission yeast Schizosaccharomyces pombe (1992)
    Springer
    Archives of microbiology 158 (1992), S. 249-255 
    Details
    ISSN: 1432-072X
    Keywords: Sporulation ; Meiosis ; Ultrastructure ; Spindle pole body ; Spo mutants ; Schizosaccharomyces pombe ; Fission yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A homothallic haploid strain of the fission yeast Schizosaccharomyces pombe initiates sexual reproduction (mating, meiosis and sporulation) in nitrogen-free sporulation medium. Cellular fine structures of eleven sporulation-deficient mutants (spo2, spo3, spo4, spo5, spo6, spo13, spo14, spo15, spo18, spo19 and spo20) of S. pombe in sporulation medium were examined by serial section-electron microscopy. The striking features of these spo mutants were: 1) the disappearance of the spindle pole bodies (SPBs) after the second meiotic division, and 2) the accumulation of unorganized structures. Based on histochemical staining, these structures were presumably unorganized spore wall precursors. In some mutants (spo3, spo5, spo6, spo19 and spo20), diploid zygotes contained four spore-like bodies which had walls similar to complete spore walls but failed to enclose any nuclei. After completion of the second meiotic division the nuclei were abnormally distributed in zygotic diploid cells. In the spo5, spo13, spo14, spo15 and spo19 mutants, the nuclei remained attached to each other. In spo5 and spo19, the inner membrane of the nuclear envelope was separated, but its outer membrane was shared by two sister nuclei. These observations suggest that the spo+ gene products play important roles in spatial and temporal organization of cellular structures during ascospore development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00245240
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 46
    Electronic Resource
    Electronic Resource
    Frequency and structure of spinae on Chlorobium spp. (1992)
    Springer
    Archives of microbiology 157 (1992), S. 319-322 
    Details
    ISSN: 1432-072X
    Keywords: Chlorobiaceae ; Spinae ; Chlorobium ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several Chlorobium species have been observed to possess spinae. Spinae are non-prosthecate, helically wound, rigid structures that extend from the outer bacterial cell surface into the external environment. Spinae length was variable within and between Chlorobium species. Spinae width was fairly consistent within species but varied between species (39.4 ± 2.6 nm to 82.6 ± 8.0 nm). The number of spinae per cell varied. The spinae did not penetrate the bacterial cell envelope and were randomly located on the cell surface. Spinae were not geographically restricted. The observation of spinae on pure cultures of Chlorobium spp. maintained for 25–30 years suggests that spinae may be of significant use to the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248675
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 47
    Electronic Resource
    Electronic Resource
    Ultrastructural investigations of Arbutus unedo-Laccaria amethystea mycorrhiza synthesized in vitro (1992)
    Springer
    Trees 7 (1992), S. 40-47 
    Details
    ISSN: 1432-2285
    Keywords: Arbutus unedo ; Laccaria amethystea ; Mycorrhiza ; Synthesis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Anatomy and ultrastructure of the arbutoid mycorrhiza of Arbutus unedo-Laccaria amethystea from axenic culture are described. In comparison to non-inoculated roots, the rhizodermal cells of mycorrhizas are of greater volume, their nuclei are enlarged and show an irregular shape, plasmalemma and cytoplasm with mitochondria, plastids, endoplasmic reticulum and dictyosomes are increased. Several ontogenetical states are documented. The arbutoid mycorrhiza as a connecting link between ectomycorrhiza and ericoid mycorrhiza is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225230
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 48
    Electronic Resource
    Electronic Resource
    Immunocytochemical and electron-microscopic study of the elasmobranch nucleus sacci vasculosi (1992)
    Springer
    Cell & tissue research 270 (1992), S. 395-404 
    Details
    ISSN: 1432-0878
    Keywords: Nucleus sacci vasculosi ; Ultrastructure ; Immunocytochemistry ; Hypothalamus ; Tuberculum posterius ; Scyliorhinus caniculus, Raja undulata (Elasmobranchii)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The elasmobranch nucleus sacci vasculosi was studied by means of electron microscopy (in the dogfish) and immunocytochemistry (in the dogfish and the skate) by using antibodies against tyrosine hydroxylase, alpha-melanocyte-stimulating hormone, somatostatin, serotonin, and substance P. Ultrastructural study of the dogfish nucleus sacci vasculosi shows the presence of medium-sized cells that possess numerous mitochondria but that have no dense-core vesicles in the cytoplasm or in cell processes. Fibres of the conspicuous tractus sacci vasculosi have a beaded appearance and form conventional synapses with dendrites and cell perikarya of the nucleus sacci vasculosi. The perikarya of this hypothalamic nucleus were not immunoreactive to any of the antibodies tested, and fibres immunopositive to tyrosine hydroxylase, alpha-melanocyte-stimulating hormone, somatostatin, serotonin, and substance P were scarce within this nucleus, in both the dogfish and the skate. Dorsal to the nucleus sacci vasculosi, there are numerous positive neuronal processes in addition to many small neurons that show immunoreactivity to alpha-melanocyte-stimulating hormone, somatostatin and tyrosine hydroxylase. Two types of neuron occur in this dorsal region, displaying dense-core vesicles of either 100–160 nm or 60–100 nm diameter in their cytoplasm; they were identified as peptide-containing and monoamine-containing neurons, respectively. The neuropil of this region has a significantly different ultrastructure from that of the nucleus sacci vasculosi, with many processes containing dense-core vesicles. This group of neurons, located dorsal to the nucleus sacci vasculosi and showing (a) immunoreactivity to neuropeptides or to monoamine-synthesizing enzyme, and (b) cytoplasm with dense-core vesicles, was considered not to be a part of the nucleus sacci vasculosi but rather part of the nucleus tuberculi posterioris. These results support the non-peptidergic and non-aminergic character of the nucleus sacci vasculosi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328023
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 49
    Electronic Resource
    Electronic Resource
    Culture and characterization of dental follicle cells from rat molars (1992)
    Springer
    Cell & tissue research 267 (1992), S. 483-492 
    Details
    ISSN: 1432-0878
    Keywords: Dental follicle ; Cell culture ; Fibroblasts ; Immunocytochemistry ; Ultrastructure ; Collagen ; Gel-electrophoresis ; Western blotting ; Rat (Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Because the dental follicle is necessary for the eruption of teeth of limited eruption, it was the objective of this study to determine if the cells of the follicle could be cultured in vitro. To achieve this, dental follicles and associated enamel organs were dissected from the first and second mandibular molars of 6–7-day-old rats (secretory stage of amelogenesis), and then cultured in a medium that promotes fibroblast growth — the predominant cell type of the dental follicle. The cultured cells grew to confluency and were kept through 3 passages before experimentation. The cultured cells were fibroblastic in shape, elongate with processes, and transmission electron microscopy revealed that they contained an abundant rough endoplasmic reticulum, but did not form desmosomes. Immunofluorescent staining for anti-vimentin showed that all the cells stained and electron-microscopic immunogold labeling indicated that the antibody was associated with intermediate filaments. As revealed by SDS-polyacrylamide gel electrophoresis and Western blotting, the cultured cells synthesized and secreted the extracellular matrix molecules fibronectin and procollagens. Subsequent immunofluorescence staining of permeabilized and non-permeabilized cells confirmed the presence of fibronectin and type I collagen both intra- and extracellularly. Thus, based on all the above characteristics, the cultured cells appeared to be fibroblasts derived from the dental follicle, although a few of the fibroblasts may be derived from undifferentiated mesenchymal cells interposed between the alveolar bone and follicle. Experiments now can be conducted to determine how these cultured cells respond directly to growth factors that alter the rates of tooth eruption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319370
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 50
    Electronic Resource
    Electronic Resource
    Structural organization of two fast, rhythmically active crustacean muscles (1992)
    Springer
    Cell & tissue research 267 (1992), S. 571-582 
    Details
    ISSN: 1432-0878
    Keywords: Crustacean muscle ; Ultrastructure ; Dye coupling ; Flagellum ; Scaphognathite ; Fascicles ; Mitochondria ; Carcinus maenas (Crustacea)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The organization of the flagellum abductor muscle and of a scaphognathite levator muscle of the green crab, Carcinus maenas, has been compared quantitatively using light and electron microscopy. These muscles are rhythmically active at relatively high frequencies and for long durations. Fibers of both muscles are interconnected to form fascicles of 50 or more fibers within which there is cytoplasmic continuity. A single muscle is made up of 8–12 fascicles. Individual fibers consist of a peripheral rind of densely packed mitochondria, a thick region of glycogen granules, and myofibrils arranged into scattered central islands. Less than half the volume-density of these muscles is contractile material, the balance being largely mitochondria and glycogen. The fibers within a muscle are structurally similar. They have short sarcomeres (about 2 μm), thin to thick filament ratios of about 3:1, and junctions between the sarcoplasmic reticulum and the transverse tubules at the M line. Sarcoplasmic reticulum occupies about 10% of the myofibrillar volume-density. A well developed sarcoplasmic reticulum appears to underlie the capacities of these two muscles for high frequency contraction; extensive mitochondria and glycogen stores should confer fatigue resistance under both aerobic and anaerobic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319380
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 51
    Electronic Resource
    Electronic Resource
    Bethanechol and a G-protein activator, NaF/AlCl3, induce secretory response in Paneth cells of mouse intestine (1992)
    Springer
    Cell & tissue research 269 (1992), S. 213-220 
    Details
    ISSN: 1432-0878
    Keywords: Paneth cells ; Ultrastructure ; Morphometry ; Bethanechol ; Fluoride ion ; G-protein ; Mouse (Balb/c)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Paneth cells located at the bottom of intestinal crypts may play a role in controlling the bacterial milieu of the intestine. Using morphometry to clarify the secretory mechanism of the Paneth cells, we studied the ultrastructural changes in mouse Paneth cells produced following intra-arterial perfusion with Hanks' balanced salt solution containing a cholinergic muscarinic secretagogue (bethanechol), a neuroblocking agent (tetrodotoxin), or a G-protein activator (NAF/AlCl3). Bethanechol (2×10-4 mol/l) induced Paneth-cell secretion. Many Paneth cells massively exocytosed their secretory material into the crypt lumen; the enhanced secretion caused degranulation and vacuole formation. However, tetrodotoxin (2×10-6 mol/l) did not prevent the bethanechol-enhanced secretion by the Paneth cells. NaF (1×10-2 mol/l) and AlCl3 (1×10-5 mol/l) induced massive exocytosis of the Paneth cells; the exocytotic figures were similar to those observed in mice stimulated by bethanechol. G-protein activation was followed by a sequence of intracellular events, resulting in exocytosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319611
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 52
    Electronic Resource
    Electronic Resource
    Ultrastructural changes in primordial germ cells during early gonadal development of the common carp (Cyprinus carpio L., teleostei) (1992)
    Springer
    Cell & tissue research 267 (1992), S. 337-346 
    Details
    ISSN: 1432-0878
    Keywords: Primordial germ cell ; Ultrastructure ; Gonadal differentiation ; Cyprinus carpio (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A description is given of primordial germ cell (PGC) differentiation and gonadal development in carp from hatching until the age of 6 weeks. This period was chosen as the PGCs are mitotically silent before they start to proliferate rapidly after week 6. The PGCs increased in size between week 2 and week 4 after fertilization. Ultrastructurally, the perinuclear dense bodies present in PGCs from hatching onwards increased in size and formed the ‘cement’ between mitochondria. Moreover, from week 2 onwards, an elaborate Golgiapparatus was present in PGCs, indicating synthetic activity that may be related to PGC enlargement. During the observation period, gonadal tissue was gradually formed around the PGCs. From the age of 4 and 5 weeks onwards, two somatic cell types could be distinguished; the central type had a light appearance and was closely associated with the PGCs, the other type being darker and forming the peripheral layer of the developing gonads. Thus, during the period of mitotic quiescence, the PGCs and the gonads actively differentiate in preparation for the fast PGC proliferation that occurs after 6 weeks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302972
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 53
    Electronic Resource
    Electronic Resource
    Ultrastructural study of the retinal pigment epithelium during metamorphosis in the sea lamprey (Petromyzon marinus L.) (1992)
    Springer
    Cell & tissue research 267 (1992), S. 375-384 
    Details
    ISSN: 1432-0878
    Keywords: Retinal pigment epithelium ; Ultrastructure ; Organelle differentiation ; Metamorphosis ; Lamprey, Petromyzon marinus (Cyclostomata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The sequence of morphological changes in the retinal pigment epithelium during the metamorphic period of the sea lamprey Petromyzon marinus L. has been investigated using electron microscopy. At early metamorphic stages (stages I and II), photoreceptors are present in a small zone of the retina. During these stages, the lateral surface of the epithelial cells shows zonulae occludentes and adhaerentes. The degree of cell differentiation varies throughout the retinal pigment epithelium. Cells covering the differentiated photoreceptors in the central retina have phagosomes, whereas pigment granules appear only in the retinal pigment epithelium dorsal to the optic nerve head. Most epithelial cells have myeloid bodies; their morphology is more complex around the optic nerve head. At stage III, when photoreceptors develop over the whole retina, the distribution of cytoplasmic organelles is almost homogeneous in the retinal pigment epithelium. Subsequently, the basal plasma membrane of the epithelial cells becomes progressively folded and their apical processes enlarged. In addition, extensive gap junctions develop between retinal pigment cells. In late metamorphic stages, noticeable growth of myeloid bodies occurs and consequently the retinal pigment epithelium resembles that of the adult. This study also describes, for the first time, the presence of wandering phagocytes in the retinal pigment epithelium of lampreys; their role in melanosome degradation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302976
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 54
    Electronic Resource
    Electronic Resource
    In-vitro effects of angiotensin II on steroid production by hamster ovarian follicles and on ultrastructure of the theca interna (1992)
    Springer
    Cell & tissue research 268 (1992), S. 191-196 
    Details
    ISSN: 1432-0878
    Keywords: Angiotensin II ; Ovarian follicles ; Theca interna ; Ultrastructure ; Steroidogenesis ; Atresia ; Golden hamster (Rodentia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Angiotensin II (AII) is present in the mammalian ovary and has been correlated with atresia in follicles. Since the theca interna may be one site at which atresia is intiated, we wished to determine whether AII exerts an effect on theca interna from explanted ovarian follicles of hamsters. Hamsters were sacrified on the morning of proestrus, and ovaries were removed. Preovulatory follicles were excised from the ovaries, and cultured with one of the following components: medium alone (control); medium plus AII (1x10-6 M); the AII-receptor antagonist [Sar1, Ile8] AII (1x10-4 M); or AII plus antagonist. After 72 h, the follicles were processed for transmission electron microscopy (to determine quantities of theca interna organelles involved in the steroid synthetic pathway) or for protein determination (to normalize steroid production rates). The incubation medium was drawn off and analyzed by radioimmunoassay for progesterone, androstenedione, or estradiol-17β. There was a significant positive correlation (r=0.92, P〈0.01) between follicular androstenedione secretion and area comprising theca interna smooth endoplasmic reticulum. In the theca interna, AII induced a two-fold and 1.6-fold increase in lipid droplet number and area comprising smooth endoplasmic reticulum, respectively (P〈0.05). Excess antagonist negated the increase in cell or-ganelles and also reduced androstenedione secretion compared with AII alone (P〈0.05). Most importantly, AII significantly augmented the ratio of androstenedione: estradiol-17β secretion by 44% over that of control. The ultrastructural changes observed in this study and the increase in the andostenedione: estradiol-17β production ratio are consistent with atresia-like changes in ovarian follicles. We believe, therefore, that AII is involved, possibly at its membrane receptor, in an aspect of the overall process of follicular atresia, operating in part at the level of the theca interna.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338068
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 55
    Electronic Resource
    Electronic Resource
    Ultrastructure of the basement membrane and its precursor in developing rat submandibular gland as shown by alcian blue staining (1992)
    Springer
    Cell & tissue research 268 (1992), S. 233-238 
    Details
    ISSN: 1432-0878
    Keywords: Alcian blue ; Basement membrane ; Lamina densa ; Meshwork ; Submandibular gland ; Ultrastructure ; Rat (Wistar-Imamichi)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the epithelial basement membrane and membrane precursor was studied in rat submandibular rudiment and a model system of the reconstructed basement membrane, by transmission electron microscopy following alcian blue staining. Directly beneath the epithelial plasma membrane, a meshwork layer was found to consist of anastomosing thin fibers arranged as a three-dimensional meshwork (100–400 nm in thickness). Straight strands (5–10 nm in diameter) could sometimes be seen to pass through the meshwork. Adjacent to this layer, a coarse network composed of threads (20–40 nm in diameter) connected the meshwork layer with collagen fibers of the underlying connective tissue. The earliest precursors recognized in the reconstruction-model system were part of the fine-meshwork structure, and showed this structure to be a fundamental component of the basement membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318791
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 56
    Electronic Resource
    Electronic Resource
    Immunogold labelling of the cytoplasmic estradiol receptor in resting porcine endometrium (1992)
    Springer
    Cell & tissue research 270 (1992), S. 1-6 
    Details
    ISSN: 1432-0878
    Keywords: Estradiol receptor ; Endometrium ; Ovariectomy ; Immunohistochemistry ; Ultrastructure ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Serial sections of resting porcine endometrium were analyzed with the monoclonal antibody 13H2 using goat antimouse IgG/5 nm gold as secondary reagent or with either polyclonal antibodies from goat #402 or the rat monoclonal antibody H222, both in combination with protein G/12 nm gold. A modestly higher labelling of nuclei than of cytoplasm was seen only with the monoclonal antibody H222. Polyclonal #402 and monoclonal 13H2 showed fewer attachments over nuclear than over cytoplasmic areas. The highest densities of attachment and of predominantly cytoplasmic labelling were obtained with the monoclonal antibody 13H2. The results confirm the earlier assumption of a restricted accessiblity of estradiol receptor in the cytoplasm of resting cells for immunoreagents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00381873
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 57
    Electronic Resource
    Electronic Resource
    Electron microscopical studies ofThorea ramosissima (Thoreaceae, Rhodophyta): Taxonomic implications ofThorea pit plug ultrastructure (1992)
    Springer
    Plant systematics and evolution 181 (1992), S. 233-244 
    Details
    ISSN: 1615-6110
    Keywords: Algae ; Rhodophyta ; Thorea ramosissima ; T. riekei ; Ultrastructure ; pit plugs as a taxonomic character
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The thallus ofThorea ramosissima was studied electron microscopically. The cells of the medulla, the cortex and the assimilatory hairs differ not only in size and number of plastids and their equipment with thylakoids but also in cell wall structure, the number of mitochondria and the activity of the Golgi apparatus, with dictyosomes transforming complete cisternae into Golgi vesicles with mucilaginous contents in the outer region of the cortex. The pit connections have plugs with a distinct plate—like (not dome-like) outer cap layer. BecauseT. riekei was reported to have dome-like outer cap layers and because this character was the main reason to place theThoreaceae into theBatrachospermales (Pueschel & Cole 1982),T. riekei was reinvestigated, too. A distinct outer cap could not be detected. The reliability of pit plug structure as a taxonomic character and the taxonomic position ofThorea is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00937447
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 58
    Electronic Resource
    Electronic Resource
    Biochemical and immunological characterization of intermicrotubular cement in the feeding apparatus of phagotrophic eugienoids:Entosiphon, Peranema, andPloeotia (1992)
    Springer
    Protoplasma 168 (1992), S. 113-124 
    Details
    ISSN: 1615-6102
    Keywords: Cytoskeleton ; Phagotrophic ; Eugienoids ; Immunochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A monoclonal antibody (IIID12) obtained from mice immunized against the entireEntosiphon cytoskeleton highlights the feeding apparatus ofEntosiphon, Peranema, andPloeotia by IF. IGS at the ultrastructural level shows that it labels the cementing material surrounding the microtubular bundles in the three species studied. InEntosiphon additional structures, such as the supplementary plaque, the scaffold structure and the lenticular structure or canal thickening, are also detected by the antibody. Immunoblotting analysis after SDS-PAGE reveals a positive reaction with this antibody to the 58 and 66kDa protein bands inEntosiphon, 82 and 84kDa inPeranema, and 56 and 60kDa inPloeotia. These results demonstrate biochemical homologies in the proteins of the cement material in the three heteronematal eugienoids studied. The possible role of these proteins in microtubule assembly and stabilization is discussed, as well as the role of the cementing material in the mode of the feeding apparatus motion during the ingestion of food.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666257
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 59
    Electronic Resource
    Electronic Resource
    Ultrastructural characterization of somatic embryos regenerated from NaCl selected and nonselected calli ofDactylis glomerata (1992)
    Springer
    Protoplasma 170 (1992), S. 177-185 
    Details
    ISSN: 1615-6102
    Keywords: Dactylis glomerata L. ; Orchardgrass ; Sodium chloride tolerance ; Somatic embryo ; Tissue culture ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Calli were induced from leaf expiants of aDactylis glomerata L. (orchardgrass) genotype which has a high capacity for somatic embryogenesis. After 7 months culture on SH medium containing NaCl, a line was selected which was tolerant to 200 mM NaCl. When both selected and nonselected calli were maintained for 56 days on media containing 0 to 300 mM NaCl, the selected line showed significantly higher regeneration capacity than nonselected calli when placed on media containing more than 50 mM NaCl. Ultrastructural features of control somatic embryos not exposed to the salt were compared to those from nonselected and selected embryos cultured on 200 mM NaCl medium. In the presence of NaCl there were changes in the appearance of cell walls and mitochondria, accumulation of lipids and a higher degree of vacuolation in cells of nonselected embryos compared to control and selected embryos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01378792
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 60
    Electronic Resource
    Electronic Resource
    Immunocytochemical localization of callose in root cortical cells parasitized by the ring nematodeCriconemella xenoplax (1992)
    Springer
    Protoplasma 171 (1992), S. 1-6 
    Details
    ISSN: 1615-6102
    Keywords: (1→3)-β-Glucose ; Callose ; Cell wall ; Host-parasite interface ; Immunocytochemical ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Polyclonal antibodies specific to (1→3)-β-glucose were used to localize callose around stylets ofCriconemella xenoplax in parasitized cortical cells in root explants of carnation, crimson clover, and tomato. The nematode's stylet was inserted 5–6 μm through the wall of the parasitized cell without piercing the plasma membrane, which became invaginated around the stylet tip. A layer of electron-transparent callose was localized by immunogold labelling between the invaginated plasma membrane and the inserted stylet, except at the stylet orifice. The callose was continuous with the inner surface of the wall of the parasitized cell around the site where the stylet penetrated. When the parasitized cell was located in the second layer of the cortex, the nematode's stylet first passed through a subepidermal cortical cell. The integrity of the plasma membrane of the transected cell was maintained and callose was deposited around the portion of the nematode's stylet that traversed the cell. We suggest that callose deposition around nematode stylets in parasitized cells is a common wound response elicited when plant-parasitic nematodes feed from cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01379274
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 61
    Electronic Resource
    Electronic Resource
    Rose leaf structure in relation to different stages of micropropagation (1992)
    Springer
    Protoplasma 166 (1992), S. 165-176 
    Details
    ISSN: 1615-6102
    Keywords: Cuticle ; Humidity ; Leaf structure ; Micropropagation ; Rosa ; Stomata ; Ultrastructure ; Wax
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Mme Isaac Pereire rose was investigated in an attempt to establish how micropropagated roses might best be weaned into normal growth conditions. Leaves of in vitro grown plants, weaned plants and the stock plant were studied, using light microscopy and different scanning and transmission electron microscopical techniques. Features that varied in the different growing conditions were leaf size and thickness, amount of wax, thickness of cuticle and external epidermal cell wall, number and aperture of the stomata, size of the epidermal cells, number of layers of the palisade cells, and size of the chloroplasts in the mesophyll. The rose in the present study had wax on the in vitro cultured plants; this wax was of similar ultrastructural appearance to that of the stock plant, even though in smaller quantities. Weaned plants had an intermediate amount of wax. The cuticle was thin, ranging from 0.04 μm on plants growing in vitro to 0.3-0.6 μm on weaned plants and stock plants. Stomata were always wide-open on leaves taken from cultures with a relative humidity of 100%. After four weeks in a humidity lowered to 85% stomata had closed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322779
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 62
    Electronic Resource
    Electronic Resource
    Ultrastructure of cuticular exudations in parasitic juvenileHeterodera schachtii, as related to cuticle structure (1992)
    Springer
    Protoplasma 166 (1992), S. 67-77 
    Details
    ISSN: 1615-6102
    Keywords: Cuticle ; Cuticular exudations ; Exudations ; Heterodera schachtii ; Ultrastructure ; Host-parasite interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development ofHeterodera schachtii inside roots of a cruciferous host plant grown under monoxenic conditions in an agar medium was observed with video-enhanced contrast light microscopy. One to 6 days after inoculation, roots were excised and processed for electron microscopic observations. Exudates were present on the cuticle surfaces of J 2 and early J 3 juveniles located at feeding sites. Fibrillar exudations were correlated with similar fibrillar patterns in the epicuticle, exocuticle, intermediate zone, and the striated endocuticle. Secretion vesicles assembled at many Golgi sites in the hypodermis, appeared to coalesce and form large electron translucent vesicles in the cytoplasm. We propose that secretion vesicles migrate toward the cuticle, contact the plasmalemma and transfer their contents by exocytosis or a similar mechanism to a secretion accumulation site. These contents are associated with cuticle structure and emerge as surface exudations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320145
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 63
    Electronic Resource
    Electronic Resource
    Morphogenesis of the feeding apparatus ofEntosiphon sulcatum (1992)
    Springer
    Protoplasma 168 (1992), S. 125-135 
    Details
    ISSN: 1615-6102
    Keywords: Morphogenesis ; Phagotrophic ; Euglenoids ; Immunocytochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The disruption and development of the siphon during division ofEntosiphon have been followed by immunofluoresence with both an anti-cement MAb (IIID12) and an anti-tubulin MAb. (IVA10), by nuclear DNA labelling and by electron microscopy of serial section. The disruption of the parental siphon begins at the reservoir level where two new transversely orientated daughter siphons arise. In the degenerating bundles the cement disappears, first liberating the microtubules which then depolymerize. The first structure which surrounds the anterior part of the two young siphons is a loop of 5 microtubules linked to the reservoir membrane. From around this loop a row of perpendicular microtubules sink in the cytosplasm; they will form the primary row of microtubules in the definitive bundles. Inside the loop, reinforced microtubules are seen beneath the membrane, they will generate the future vanes, and also penetrate into the cytosplasm. Amorphous material surrounds the young siphons and may correspond to cement material. The growth of the siphons proceeds as they adopt a central longitudinal position in the cell. The cement material progressively condenses on structures such as the primary row of microtubules. The bundles, the supplementary plaque, and the scaffold. After flagellar partition each of the canals becomes distinct and cytokinesis occurs from the anterior end. These observations indicate that the microtubular loop could be the source of microtubule-organizing centre (MTOC) proteins initiating the assembly of the primary row of microtubules. Bundle microtubules start to assemble at the anterior end and extend backwards. The microtubules of the loop could be linked to roots associated with the basal bodies which double in number before division. The cement later condenses, linking and stabilizing the structures. Microfibrils play an important role in basal body and siphon separation and positioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666258
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 64
    Electronic Resource
    Electronic Resource
    Ultrastructural changes in the cell wall, nucleus and cytoplasm of pollen mother cells during meiotic prophase I inLycopersicon esculentum (Mill.) (1992)
    Springer
    Protoplasma 169 (1992), S. 139-147 
    Details
    ISSN: 1615-6102
    Keywords: Cell wall ; Lycopersicon esculentum ; Microsporogenesis ; Pollen development ; Prophase I ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Throughout the premeiotic to late prophase I stages of meiosis in the anthers of tomato (Lycopersicon esculentum) extensive changes occurred in the ultrastructure of pollen mother cells (PMCs). During early prophase, the wall of each PMC developed a layered appearance and was broadened both by the widening of the middle lamella as well as by intensive deposition of microfibrils in the wall. By late prophase, however, the microfibrils adjacent to the plasmalemma dissipated. At the same time, callose was deposited between the wall and the plasmalemma. The nucleus of the PMCs also underwent changes. During early prophase, the nucleolus consisted of a linear series of three segments, with a separation of the granular and fibrillar portions. By late prophase, the nucleoli were less distinct as the nucleus was highly vacuolate. Mitochondria were initially simple with lightly stained matrix and few cristae but, during the course of prophase, they acquired a more densely-stained matrix with dilated cristae. Plastids remained relatively undifferentiated and, at late prophase, many were convoluted in appearance and constricted at intervals indicating their division. Cytoplasmic connections between adjacent PMCs were broad enough to permit the passage of organelles and were retained through to metaphase I. These cytological and wall changes appear to be a prerequisite for the subsequent development of microspores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323613
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 65
    Electronic Resource
    Electronic Resource
    Ultrastructure of freeze-substituted pollen tubes ofLilium longiflorum (1992)
    Springer
    Protoplasma 167 (1992), S. 215-230 
    Details
    ISSN: 1615-6102
    Keywords: Lilium ; Freeze substitution ; Pollen tubes ; Rapid freeze fixation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In view of the importance of the lily pollen tube as an experimental model and the improvements in ultrastructural detail that can now be attained by the use of rapid freeze fixation and freeze substitution (RF-FS), we have reexamined the ultrastructure of these cells in material prepared by RF-FS. Several previously unreported details have been revealed: (1) the cytoplasm is organized into axial “slow” and “fast” lanes, each with a distinct structure; (2) long, straight microtubule (MT) and microfilament (MF) bundles occur in the cytoplasm of the fast lanes and are coaligned with every organelle present; (3) the cortical cytoplasm contains complexes of coaligned MTs, MFs, and endoplasmic reticulum (ER); (4) the cortical ER is arranged in a tight hexagonal pattern and individual elements are closely appressed to the plasma membrane with no space between; (5) mitochondria and ER extend into the extreme apex along the flanks of the pollen tube, and vesicles and ER are packed into an inverted cone-shaped area at the center of the apex; (6) MF bundles in the tip region are fewer, finer, and in random orientation in comparison to those of the fast lanes; (7) the generative cell (GC) cell wall complex contains patches of plasmodesmata; (8) The GC cytoplasm contains groups of spiny vesicles that are closely associated with and seem to be fusing with or pinching off from mitochondria, and (9) the vegetative nucleus (VN) contains internal MT-like structures as well as numerous cytoplasmic MTs associated with its membrane and also located between the VN and GC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403385
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 66
    Electronic Resource
    Electronic Resource
    Changes in the lysosome structure during the formation of zoospores inTrebouxia potteri (1992)
    Springer
    Protoplasma 171 (1992), S. 19-27 
    Details
    ISSN: 1615-6102
    Keywords: Lysosome ; Morphogenesis ; Trebouxia potteri ; Ultrastructure ; Zoospore formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Changes in the lysosome structures were examined by electron microscopy during the formation of zoospores inTrebouxia potteri. Lysosomes in vegetative cells were homogeneously filled with electron-dense material. At the beginning of zoospore formation, lysosomes invaginated or evaginated to take up mitochondria, ER, or cytoplasmic ground plasma. The ingested organelles became disorganized within the lysosomes. During this disruption of these organelles, the lysosomal contents became heterogeneous, suggesting a decrease in the amount of enzymes within the lysosomes. Golgi bodies and ER seemed to be involved with the disruption of the organelles, probably supplying some substances necessary for the functioning of the lysosomes. Amount of electron-dense materials decreased and, finally, only one to three small spherical aggregates remained in the lysosomes. Then the lysosomes appeared to shrink via loss of watery substances or cutting off of electron-transparent regions. After these changes in lysosome structure, nuclei started to divide successively for formation of the zoospores. The possibility is proposed that the drastic cytoplasmic changes operated by lysosomes trigger the following morphogenetic events in the formation of zoospores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01379276
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 67
    Electronic Resource
    Electronic Resource
    Aortic features in tangier disease and pathogenetic considerations — Part I. Fatty dots and streaks (1992)
    Springer
    European journal of epidemiology 8 (1992), S. 36-47 
    Details
    ISSN: 1573-7284
    Keywords: Tangier disease ; Aortic morphology ; Ultrastructure ; Atherosclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Morphological studies of aortic fatty dots and streaks, and the adjacent normally appearing intima, in a 5 3/4-year-old boy who died of pneumonia, showed several hitherto unreported features. In lesions, lipid vacuoles and/or other cytoplasmic “inclusions” (ultrastructurally considered to present complex forms of lipids) were present on occasion in the endothelium but consistently involved the (intimal) smooth muscle cells (SMC). Similar changes were present in the adjacentintima, but were here less prominent and “tapered off” distally. A moderate number of macrophages also contained cytoplasmic lipids but such cells entirely free of lipid inclusions were observed, too. Most surprisingly, dilated and manycisternae of rough-surfaced endoplasmicreticulum (ER) in the SMC of lesions were associated spatially with cytoplasmic droplets and other forms of lipids. The results of these studies question the generally accepted central role of macrophages as being primarily involved in the pathogenesis of tissue changes in Tangier disease. It is possible that in view of the absence or paucity of high-density lipoproteins (HDL) and alterations of (their) apo A-I and apo A-II (as well as of other lipids), the arterial SMC may be in some way involved in the metabolism of the above substances in this disorder. Support of this tentative (and highly speculative) assumption must await further work utilizing tissues and cells other than those containing macrophages and other derivatives of reticuloendothelial system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00145348
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 68
    Electronic Resource
    Electronic Resource
    Cytometric and electron microscopic studies of the direct interaction of divalent nickel with intact and chemically modified HuT-78 lymphoblasts (1992)
    Springer
    Cell biology and toxicology 8 (1992), S. 27-41 
    Details
    ISSN: 1573-6822
    Keywords: Lymphoblasts ; Nickel ; Cytometry ; Ultrastructure ; Membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Cytometric and ultrastructural studies on 24 hr cultures of intact, 1.0 mM H5I06, and 0.1 mM SeO2-oxidized HuT-78 lymphoblasts were performed after their direct, 30 min interaction with 1.0 mM NiCl2. Except for moderately depressed cell viability, divalent nickel did not alter the progression of intact and oxidized target cells through the phases of the cell cycle. Although the plasma membrane remained structurally intact, marked distortion of mitochondria structure and increased osmiophilia were an invariable attribute of all nickel-pulsed cells. Moreover, numerous electron-opaque, intracellular depositions were detected in SeO2-oxidized, nickel-pulsed cells. It is concluded that the initial state of plasma membrane, and the interaction of nickel with other trace elements, have jointly determined the response of HuT-78 cells to brief and direct, divalent nickel pulses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119293
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 69
    Electronic Resource
    Electronic Resource
    Projection methods in flexible multibody dynamics. Part II: Dynamics and recursive projection methods (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1941-1966 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In Part I of this paper the kinematic relationships between the absolute, elastic and joint accelerations are developed. In this paper, these kinematic equations are used with the generalized Newton-Euler equations and the relationship between the actual and generalized reaction forces to develop a recursive projection algorithm for the dynamic analysis of open-loop mechanical systems consisting of a set of interconnected rigid and deformable bodies. Optimal matrix permutation, partitioning and projection methods are used to eliminate the elastic accelerations while maintaining the inertia coupling between the rigid body motion and the elastic deformation. Recursive projection methods are then applied in order to project the inertia of the leaf bodies onto their parent bodies. This leads to an optimal symbolic factorization which recursively yields the absolute and joint accelerations, and the joint reaction forces. The method presented in this paper avoids the use of Newton-Raphson algorithms in the numerical solution of the constrained dynamic equations of open-loop kinematic chains since the joint accelerations are readily available from the solution of the resulting reduced system of equations. Furthermore, the method requires only the inversion or decomposition of relatively small matrices and the numerical integration of a minimum number of co-ordinates. Open-loop multibody robotic manipulator systems are used to compare the results and efficiency of the recursive methods with that of the augmented formulations that employ Newton-Raphson algorithms.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351003
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 70
    Electronic Resource
    Electronic Resource
    Coupling finite elements and magnetic networks in magnetostatics (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1991-2002 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper a new method for computing non-linear magnetostatic fields is introduced, which allows the simultaneous coupling of a finite element structure with a magnetic network. Combining the advantages of both methods while avoiding their drawbacks, this coupling yields both an accurate and time-efficient computation.The traditional method of the unknown mesh fluxes is applied for the solution of the magnetic network. The finite element solution, on the other hand, is based on a classical first-order interpolation of the unknown vector potential. The coupling is established by a proper organization of the unknowns on the boundary common to the finite element and network regions. In this way, a single system of non-linear equations is obtained.Moreover, it is shown that the coupled system of equations is equivalent to a single finite element system if generalized base functions are allowed. Consequently, various results from finite element theory may be applied. For instance, the matrix governing the iteratively linearized system of equations can directly be shown symmetrical and positive definite.Finally, the field inside a permanent magnet motor is calculated with the coupled method. Although the number of unknowns is dramatically reduced compared to a full FE calculation, the same level of accuracy is achieved. Hereby, the benefit of the coupled method is clearly proved.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351005
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 71
    Electronic Resource
    Electronic Resource
    A consistent model for first-order moderate rotation plate theory (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 2049-2066 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The first-order shear deformation plate theory can be used in the small strain and moderate rotation non-linear elasticity by defining correctly the displacement vector form. In this paper, the problem of the consistency between the displacement vector form and the finite strain tensor approximation is analysed. Then, a new moderate rotation theory is proposed. The variational form of the governing equations is derived for the beam and the plate problems in a consistent way. Then, an iterative numerical procedure based on the finite element method and the secant striffness matrix is developed in order to solve the non-linear differential equation problem. Computations are made for one- and two-dimensional structures, in order to assess the performance of the von Kármán, finite elasticity, classical and the proposed moderate rotation theories.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351008
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 72
    Electronic Resource
    Electronic Resource
    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 2103-2104 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351012
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 73
    Electronic Resource
    Electronic Resource
    Direct evaluation of singular boundary integrals in two-dimensional biharmonic analysis (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 2067-2078 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Development of techniques to provide rapid and accurate evaluation of the integrations required in boundary element method (BEM) formulations are receiving more attention in the literature. In this work, a series of direct expressions for surface integrals, required for a boundary element solution of the non-homogeneous biharmonic over a general two-dimensional curvilinear surface, are presented. The concept of an isoparametric representation, usually applied to the variation of the field variables and the geometry, is extended to the parametric mapping of the curvilinear geometry. The result renders the typically complicated Jacobian function into a series of polynomial expressions based on the shape function set and several discrete Jacobian values. An application of the isoparametric approximation of the Jacobian for a quadratic element representation is developed. Implementation of this approximation significantly improves the accuracy of the boundary integral solution by eliminating error associated with numerical quadrature. Overall computational efficiency is improved by reducing the time necessary to calculate individual surface integrals and evaluate field variables at internal points. A numerical solution of the boundary integral equations of phenomena governed by the biharmonic equation is presented and compared with an exact analysis.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351009
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 74
    Electronic Resource
    Electronic Resource
    An infinite boundary element formulation for three-dimensional potential problems (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 2079-2100 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An infinite boundary element (IBE) is presented for the analysis of three-dimensional potential problems in an unbounded medium. The IBE formulations are done to allow their coupling with the finite element (FE) matrices for finite domains and to obtain the overall matrices without destroying the banded structure of the FE matrices. The infinite body is divided into a number of zones whose contributions are expressed in terms of the nodal quantities at FE nodes by employing suitable decay functions and performing mainly analytical integrations of the boundary element kernels. The continuity and compatibility conditions for the potential and the flux at the FE-IBE interface are developed. The relationships for the contributions of the IBE flux vectors to the FE load vectors are given. The final equations for the IBE are obtained in the usual FE stiffness-load vector form and are easily assembled with the FE matrices for the finite object. A series of numerical examples in heat transfer and electromagnetics were solved and compared with alternative solutions to demonstrate the validity of the present formulations.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620351010
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 75
    Electronic Resource
    Electronic Resource
    Creep deformation structural analysis using an efficient numerical algorithm (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1427-1442 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a fast numerical algorithm for the implementation of material models for creep into finite element codes. First, an overview of existing algorithms for transient and steady-state creep is given. Next, a new formulation is presented which reduces the constitutive integration to the solution of a scalar non-linear algebraic equation. A solution is shown to exist without the need for subincrementation. Details of the numerical algorithm are then discussed. The paper closes with several numerical examples which illustrate the speed, robustness and accuracy of the proposed procedure as implemented in the Lawrence Livermore National Laboratory finite element codes NIKE2D and NIKE3D.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350704
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 76
    Electronic Resource
    Electronic Resource
    How to recognize the order of infinitesimal mechanisms: A numerical approach (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1351-1395 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Structures presenting kinematical inderterminacy are usually called mechanisms. This paper is entirely concerned with assemblies which reveal themselves to be mechanisms at a null value of the load. Among them a first distinction is made between infinitesimal and finite ones, the former being characterized by one or several directions of lower (but not zero) stiffness, whereas the latter show at least one finite admissible displacement for which none of the bars undergoes any elongation. Moreover, there exists the possibility to make a further distinction among the infinitesimal mechanisms, according to which is the order of the stiffness along the direction considered above. The way of evaluating this order is to perform a local analysis of the strain energy of the assembly, once the displacement field is parametrized in terms of a suitable parameter. By means of a finite element technique, this analysis can be easily performed through the numerical approach presented in this report.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350702
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 77
    Electronic Resource
    Electronic Resource
    Solutions to shape and topology eigenvalue optimization problems using a homogenization method (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1487-1502 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A solution strategy to find the shape and topology of structures that maximize a natural frequency is presented. The methodology is based on a homogenization method and the representation of the shape of the structure as a material property. The problem is formulated as a reinforcement problem in which a given structure is reinforced using a prescribed amount of material. Two dimensional, plane elasticity problems are considered. Examples are presented for illustration.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350707
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 78
    Electronic Resource
    Electronic Resource
    Announcements (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992), S. 1541-1542 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350710
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 79
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 35 (1992) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620350901
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 80
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330101
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 81
    Electronic Resource
    Electronic Resource
    Numerical solution of integral equations with a logarithmic kernel by the method of arbitrary collocation points (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 143-148 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An integral equation whose kernel presents logarithmic singularity is numerically solved by the method of arbitrary collocation points (ACP). As a first step a Gaussian quadrature of order n (hence of polynomial accuracy 2n- 1) is employed for the numerical approximation of the integral. Until now the collocation, which follows, was performed on special points x̄k, determined as roots of appropriate transcedental functions, in order to retain the 2n - 1 degree of polynomial accuracy of the Gaussian quadrature. In this paper an appropriate interpolatory technique is proposed, so that xk may be arbitrary and yet the high (2n - 1) accuracy of the Gaussian quadrature is retained.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330110
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 82
    Electronic Resource
    Electronic Resource
    Stabilized rapidly convergent 18-degrees-of-freedom flat shell triangular element (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 149-162 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A rank-sufficient flat triangular shell element with drilling degrees-of-freedom is described. A variational basis for this element has been provided by a three-field variational principle with relaxed interelement compatibility and traction continuity conditions. A generalized spurious mode control procedure has been developed in order to stabilize zero energy kinematical modes. Excellent performance has been found in an obstacle course and buckling problems.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330111
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 83
    Electronic Resource
    Electronic Resource
    Some comments on: Benchmark problems and testing of a finite element code for solidification in investment castings (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 213-215 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330114
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 84
    Electronic Resource
    Electronic Resource
    Computational structural mechanics and optimal control - the simulation of substructural chain theory to linear quadratic optimal control problemsJoint project of the Natural Science Foundation of China and the Royal society. (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 197-211 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The theory of optimal control and the theory of a substructural chain in static structural analysis are mutually simulated issues. From the minimum potential energy variational principle of the substructural chain, the generalized variational principle with two kinds of variables is derived first. By comparing that generalized variational principle with the variational principle in LQ control theory, the simulation relation is established. Based on that relation, the potential energy and mixed energy formulation of the algebraic Riccati equations are derived, then iterative algorithms are proposed which give the upper and lower bounds to the solution matrix. By using the solutions of the positive and negative co-ordinate algebraic Riccati equations, the canonical transformation matrices for the eigenproblems of the substructural chain and LQ control are constructed respectively, which reduce the eigenproblem to half-size. The properties of the solutions are analysed, which establishes the basis for expansion solutions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330113
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 85
    Electronic Resource
    Electronic Resource
    Computer-aided analysis and design of electromagnetic devices, by S. Rantajeevan H. Hoole, Elsevier Science Publishing company, New York. 1989. ISBN 0-444-01327-x (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 217-219 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330116
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 86
    Electronic Resource
    Electronic Resource
    Reliability in computational mechanics, edited by J. T. Oden, Elsevier Science Publications, NY, 1990. No. of pages: 388. Price: $192.25. ISBN 0-444-88560-9 (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 220-220 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330117
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 87
    Electronic Resource
    Electronic Resource
    Conference diary (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 221-222 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330118
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 88
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992) 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330201
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 89
    Electronic Resource
    Electronic Resource
    Free vibration of axisymmetric and beam-like cylindrical shells, partially filled with liquid (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 235-268 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A theory is presented for the determination of the free vibration characteristics of anisotropic thin cylindrical shells, partially or completely filled with liquid, for two circumferential wave numbers, n = 0, axisymmetric and n = 1, beam-like. The method used was a combination of finite element analysis and classical shell theory. The shell was subdivided into cylindrical finite elements and the displacement functions were obtained using the shell equations. Expressions for the mass and stiffness matrices for a finite element and for the whole structure were obtained. A finite element was developed for the liquid in cases of potential flow. The natural frequencies of the shell, both empty and partially filled, were obtained and compared with existing experiments and other theories.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330203
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 90
    Electronic Resource
    Electronic Resource
    Effective modelling of spatial buckling of beam assemblages, accounting for warping constraints and rotation-dependency of moments (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 469-502 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple, two-noded, finite element model for the three-dimensional buckling analysis of beam assemblages is developed. The underlying generalized-beam theory employed accounts for all coupled significant modes of deformations, including stretching, bending, shear and torsion, as well as warping. Its mixed formulation is of the two-field type, utilizing linear and constant interpolants for displacements and strain fields. Due considerations are given to the effect off inite rotations in space on the non-linear kinematic descriptions as well as the configuration-dependent behaviour of externally applied moment vectors of the conservative and non-conservative types. The performance of the model, and particularly the accuracy of its geometric and load-correction stiffnesses, is assessed in a fairly complete set of numerical simulations.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330303
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 91
    Electronic Resource
    Electronic Resource
    Finite element calculation of energy release rate for 2-D rubbery material problems with non-conservative crack surface tractions (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 907-927 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The energy release rate G for 2-D rubbery material problems with non-conservative crack surface tractions is calculated by a modified version of virtual crack extension method with finite element solutions. The formulation is demonstrated to be ‘patch-independent’ and therefore a complicated finite element model around the crack tip is not required.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330503
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 92
    Electronic Resource
    Electronic Resource
    A numerical technique for the analysis of cracks subjected to normal compressive stresses (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 929-942 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The purpose of the present paper is the development of a numerical method for the evaluation of the Stress Intensity Factor in mode II at the tips of closed cracks subjected to compressive normal stresses and monotonically increasing shear stresses. A hybrid Boundary Element Technique, originally developed for the analysis of open cracks, has been suitably modified. The Stress Intensity Factor is evaluated directly on the basis of the displacement discontinuities computed at the crack tip element, by taking into account the development of frictional resistance on the crack surfaces. A limited number (10-15) of displacement discontinuity elements is found to be sufficient for an accurate evaluation of the Stress Intensity Factor. Some basic aspects of the mechanical behaviour of closed cracks are also investigated on the basis of the proposed method.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330504
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 93
    Electronic Resource
    Electronic Resource
    A thick-thin triangular plate element (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 963-973 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple and efficient triangular finite element is introduced for plate bending applications. The element is a three-node triangular one with three basic degrees of freedom per node and two internal rotation degrees of freedom, using selective reduced integration. Numerical examples indicate that, despite its simplicity, the element is not only competitively accurate, but also useful as a thick-thin triangular plate bending element. It is also pointed out that this element using selective reduced integration is in fact a mixed element.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330506
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 94
    Electronic Resource
    Electronic Resource
    An integration scheme for Prandtl-Reuss elastoplastic constitutive equations (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 943-961 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: We investigate the Generalized Midpoint Rule for the time integration of elastoplastic constitutive equations for pressure-independent yield criteria. The incremental equations are divided into one scalar hydrostatic pressure/dilation rate equation, and a stress deviator/strain rate deviator tensorial equation, the solution of which reduces to one single scalar equation in the plastic multiplier. The existence and uniqueness of an incremental solution is discussed. The pressure/deviator decomposition is the basis for reduced integration of the pressure term in the Principle of Virtual Work, in order to avoid locking and spurious pressure oscillations. It is also shown that an optimal choice of the parameter of the Midpoint Rule can be computed by reference to the analytical solution of the equations assuming no work hardening. A benchmark test shows that this choice allows increased time steps. This formulation is applied to two classical problems: bulging of a tube under internal pressure and tension test on a notched specimen, and a comparison with the analytical solution is performed. Finally, the hypothesis which sustains these formulations of elastoplasticity (constant strain rate during an increment) is discussed with reference to elastic unloading and residual stress computation.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330505
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 95
    Electronic Resource
    Electronic Resource
    Delaunay's mesh of a convex polyhedron in dimension d. application to arbitrary polyhedra (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 975-995 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a method for creating a Delaunay triangulation connected to a set of specified points. The theoretical aspect is recalled for an arbitrary dimension and the method is discussed in order to derive a practical approach, valid for dimensions 2 and 3, which is simple, robust and well adapted to computation. Convex polyhedral and arbitrary polyhedral situations are introduced.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330507
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 96
    Electronic Resource
    Electronic Resource
    Theoretical development and numerical verification of a geometrically non-linear, 3-D based finite element for composite materials (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1119-1138 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A geometrically non-linear thin shell element made from classical laminated materials is developed from three dimensional continuum concepts that admits arbitrarily large displacements and rotations. The development shows how explicit integration through the thickness of the element can be accomplished without sacrificing significant accuracy of the element.Computations obtained via the present formulation are compared with four test problems for which numerical data are available. All computations were carried out using the Crisfield-Riks arc length continuation algorithm with a full Newton-Raphson iterative scheme. Excellent agreement is observed for each test problem.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330603
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 97
    Electronic Resource
    Electronic Resource
    A new explicit variable time-integration self-starting methodology for computational structural dynamics (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1165-1180 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new explicit variable time-integration methodology and architecture which possesses self-starting attributes, eliminates the need to involve acceleration computations, and which has improved accuracy characteristics in comparison to the traditional central-difference-type formulations customarily advocated is described for applicability to computational structural dynamics. To sharpen the focus of the present study, an explicit variable time-integration architecture which is relatively simple, yet effective, is described. Unlike variable explicit time-integration formulations adopted in the past, the present self-starting variable time-integration architecture and implementation aspects facilitate a simplified representation and a straightforward and effective approach for combining finite element meshes requiring different time steps in a single analysis. Numerical test cases are provided which demonstrate the applicability of the proposed formulations.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330605
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 98
    Electronic Resource
    Electronic Resource
    An optimal method for the solution of the constrained eigenvalue/response problem for large structures comprising rigidly-connected substructures (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1139-1163 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Dynamic substructuring or modal synthesis is established as a powerful means by which the computational effort required to perform dynamic analyses of large structures comprising many degrees of freedom can be reduced. For the case where the substructures are rigidly connected a method of synthesis is proposed which gives very substantial improvements in efficiency over existing methods both in terms of the number of floating-point operations which must take place and the on-board computer memory required. The proposed method makes use of a stable co-ordinate transformation which reduces the mass matrix for the constrained composite-system to the identity matrix and makes the stiffness matrix banded. The bandwidth is exactly equal to twice the total number of constraints plus 1. This is usually very small in comparison with the total number of degrees of freedom in the constrained composite-system. The proposed method is ideal for combining a number of substructures into a single new substructure in an efficient way without necessarily disposing of any degrees of freedom. Approximate formulae are presented which give the ratios of the number of operations required for established methods compared with the number needed for the proposed method. These formulae determine when it is appropriate to use the method proposed here.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330604
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 99
    Electronic Resource
    Electronic Resource
    Non-singular boundary integral representation of potential field gradients (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1181-1195 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper we derive the non-singular boundary integral representation of the field gradients for two-dimensional problems of classical potential field theory. Numerical implementation of this representation is developed too. The proposed method eliminates the most inaccurate influence coefficients which arise when singular integral representations are used and the internal point approaches the boundary. Since the integrands in this new method are finite at any internal point, accurate numerical results are achieved even in that portion of a solid which is very close to a discretized boundary. Two test problems are analysed in which the numerical results computed by strongly singular, weakly singular and non-singular integral representations are compared mutually and with exact solutions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330606
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 100
    Electronic Resource
    Electronic Resource
    Computing alternative optimal collapse mechanisms (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1197-1216 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Optimal plastic designs for structural frames can be obtained via static or kinematic considerations, each leading to a mathematical model requiring solution by linear programming. In both cases a mechanism can be found which satisfies the Foulkes optimality condition. However, this mechanism generally has many degrees of freedom and is most unlikely to be the actual collapse mode of the frame. A simple algorithm based on the method of redundant forces is presented for the automatic generation of the alternative optimal collapse mechanisms, any of which may be the actual collapse mode.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330607
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...