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  • 1990-1994  (895)
  • 1985-1989  (585)
  • 1880-1889
  • 1992  (895)
  • 1986  (585)
  • 1973
  • Biochemistry and Biotechnology  (1.327)
  • Ultrastructure
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  • 1990-1994  (895)
  • 1985-1989  (585)
  • 1880-1889
  • 1970-1974  (186)
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Annals of hematology 65 (1992), S. 50-52 
    ISSN: 1432-0584
    Schlagwort(e): TNF ; K 562 ; Leukemia ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 50 (1992), S. 459-467 
    ISSN: 1432-0827
    Schlagwort(e): Periodontal ligament fibroblast ; Mineralized nodule ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Comparative clinical pathology 2 (1992), S. 166-169 
    ISSN: 1433-2981
    Schlagwort(e): Erythrocytes ; Flow cytometry ; Frog hibernation ; Image analysis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 421 (1992), S. 351-354 
    ISSN: 1432-2307
    Schlagwort(e): Krabbe's disease ; Eccrine gland storage ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 421 (1992), S. 379-385 
    ISSN: 1432-2307
    Schlagwort(e): Multicystic mesothelial proliferation ; Immunohistochemistry ; Ultrastructure ; DNA analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-2307
    Schlagwort(e): Eosinophilic granuloma of bone ; Eosinophil granule proteins ; Immunostaining ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-2307
    Schlagwort(e): Small cell carcinoma ; Ovary ; Immunohistochemistry ; Ultrastructure ; Literature review
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-2307
    Schlagwort(e): Crystalloid ; Prostatic cancer ; Epithelial membrane antigen ; Phosphotungstic acid hematoxylin stain ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1432-2307
    Schlagwort(e): Islets of Langerhans ; Monocytic phagocytes ; Streptozocin ; Type 1 diabetes ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 420 (1992), S. 459-462 
    ISSN: 1432-2307
    Schlagwort(e): Malignant rhabdoid tumour ; Uterus ; Immunohistochemistry ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 11
    ISSN: 1432-2307
    Schlagwort(e): Diabetes mellitus ; Renovascular hypertension ; Myocardium ; Stereology ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 12
    ISSN: 1432-2307
    Schlagwort(e): Leiomyoma ; Myometrium ; Cytoskeleton ; Ultrastructure ; Immunohistochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Virchows Archiv 420 (1992), S. 219-226 
    ISSN: 1432-2307
    Schlagwort(e): Breast ; Granular cell tumour ; Mammography ; Ultrastructure ; Immunohistochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 14
    ISSN: 1432-2307
    Schlagwort(e): Fetus ; Small intestine ; Ultrastructure ; Malnutrition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 15
    ISSN: 1432-2307
    Schlagwort(e): Eccrine porocarcinoma ; Ultrastructure ; Giant cell ; Elastic fibre ; Globular filamentous body
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 16
    ISSN: 1432-0533
    Schlagwort(e): Spinal cord neurofibrillary tangles ; Parkinsonism-dementia complex on Guam ; Guamanian amyotrophic lateral sclerosis ; Ultrastructure ; Immunoelectron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 83 (1992), S. 408-414 
    ISSN: 1432-0533
    Schlagwort(e): Eosinophilic granular body ; Astrocytoma ; Ultrastructure ; Immunocytochemistry ; αB-crystallin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 84 (1992), S. 117-127 
    ISSN: 1432-0533
    Schlagwort(e): Alzheimer disease ; Amyloid angiopathy ; Pericytes ; Microglia ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 19
    ISSN: 1432-0533
    Schlagwort(e): Creutzfeldt-Jakob disease ; Ballooned neurons ; Ultrastructure ; αB-Crystallin ; Stress-response proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 83 (1992), S. 605-612 
    ISSN: 1432-0533
    Schlagwort(e): Colloid cyst ; Endoderm ; Respiratory epithelium ; Third ventricle ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 185 (1992), S. 271-274 
    ISSN: 1432-0568
    Schlagwort(e): Man ; Spermiogenesis ; Postacrosomal ; sheath ; Silver staining ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 84 (1992), S. 559-569 
    ISSN: 1432-0533
    Schlagwort(e): Neuronal autophagy ; Bovine spongiform encephalopathy ; Lysosomes ; Ultrastructure ; Vactiolation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 23
    ISSN: 1432-0568
    Schlagwort(e): Badger-placenta ; Ultrastructure ; Ferritin ; Iron transfer regulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 24
    ISSN: 1432-0533
    Schlagwort(e): Muscle ; Ultrastructure ; Lysosome ; Metabolic disorder ; Glycogenosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 25
    ISSN: 1432-0533
    Schlagwort(e): Parkinson's disease ; Ultrastructure ; Catecholomines ; Trans-synaptic degeneration ; Axonal dystrophy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 83 (1992), S. 659-663 
    ISSN: 1432-0533
    Schlagwort(e): Eosinophilic inclusion ; Neuroglia ; Astrocyte ; Aicardi's syndrome ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 186 (1992), S. 145-152 
    ISSN: 1432-0568
    Schlagwort(e): Harderian gland ; Tubuloalveolar endpieces ; Serous endpieces ; Ultrastructure ; Opossum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 83 (1992), S. 518-524 
    ISSN: 1432-0533
    Schlagwort(e): Amyotrophic lateral sclerosis ; Upper motor neurons ; Ultrastructure ; Neurofilament ; Ubiquitin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 29
    ISSN: 1432-0533
    Schlagwort(e): Primary leptomeningeal glioma ; Ultrastructure ; Basal lamina ; Laminin ; Heterotopic glial tissue
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 30
    ISSN: 1432-0533
    Schlagwort(e): Peripheral nerve biopsy ; HIV infection ; Ultrastructure ; in situ hybridization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 31
    ISSN: 1432-0533
    Schlagwort(e): Alzheimer's disease ; Tissue culture ; Microglia ; Amyloid ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 84 (1992), S. 238-243 
    ISSN: 1432-0533
    Schlagwort(e): Creutzfeldt ; Jakob disease ; Tubulovesicular structures ; Prion diseases ; Ultrastructure ; Transmissible spongiform encephalopathies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 33
    ISSN: 1432-0568
    Schlagwort(e): Prolactin cell ; Met-enkephalin ; Immunocytochemistry ; Ultrastructure ; Morphometr ; Rat(Sprague-Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 185 (1992), S. 201-206 
    ISSN: 1432-0568
    Schlagwort(e): Development ; Mouse ; Peripheral nerves ; Schwann cells ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 35
    ISSN: 1432-0568
    Schlagwort(e): Mandibular condyle ; Calcified cartilage ; Ultrastructure ; Maturation ; Macaca fascicularis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 284 (1992), S. 259-265 
    ISSN: 1432-069X
    Schlagwort(e): Genodermatoses ; Ultrastructure ; Membrane structures ; Abnormal keratinosomes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 284 (1992), S. 95-99 
    ISSN: 1432-069X
    Schlagwort(e): Chromoblastomycosis ; Host-fungus relationship ; Morphometry ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Archives of dermatological research 284 (1992), S. 275-282 
    ISSN: 1432-069X
    Schlagwort(e): Cherry haemangioma ; Type IV collagen ; Type VI collagen ; Immunohistochemistry ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Planta 188 (1992), S. 403-413 
    ISSN: 1432-2048
    Schlagwort(e): Cyanobacterium ; Gunnera ; Infection process ; Nostoc ; Symbiosis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Planta 188 (1992), S. 155-163 
    ISSN: 1432-2048
    Schlagwort(e): Bradyrhizobium ; Electron microscopy ; Glycine (root nodules) ; High-pressure freezing ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 5 (1992), S. 64-71 
    ISSN: 1432-2145
    Schlagwort(e): Generative cell ; Isolation ; Microtubules ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 5 (1992), S. 27-33 
    ISSN: 1432-2145
    Schlagwort(e): Isolated generative cells ; Ultrastructure ; Microtubule ; Immunofluorescence microscopy ; Allemanda neriifolia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 5 (1992), S. 131-137 
    ISSN: 1432-2145
    Schlagwort(e): Pollen grain ; Generative cell ; Formation and detachment ; Ultrastructure ; Polystachia pubescens ; Orchidaceae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Journal of neurology 239 (1992), S. 191-194 
    ISSN: 1432-1459
    Schlagwort(e): Ghost tangles ; Degenerate neurites ; Astrocytes ; Senile plaques ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 158 (1992), S. 249-255 
    ISSN: 1432-072X
    Schlagwort(e): Sporulation ; Meiosis ; Ultrastructure ; Spindle pole body ; Spo mutants ; Schizosaccharomyces pombe ; Fission yeast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 157 (1992), S. 319-322 
    ISSN: 1432-072X
    Schlagwort(e): Chlorobiaceae ; Spinae ; Chlorobium ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
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  • 47
    ISSN: 1432-2285
    Schlagwort(e): Arbutus unedo ; Laccaria amethystea ; Mycorrhiza ; Synthesis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 270 (1992), S. 395-404 
    ISSN: 1432-0878
    Schlagwort(e): Nucleus sacci vasculosi ; Ultrastructure ; Immunocytochemistry ; Hypothalamus ; Tuberculum posterius ; Scyliorhinus caniculus, Raja undulata (Elasmobranchii)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 267 (1992), S. 483-492 
    ISSN: 1432-0878
    Schlagwort(e): Dental follicle ; Cell culture ; Fibroblasts ; Immunocytochemistry ; Ultrastructure ; Collagen ; Gel-electrophoresis ; Western blotting ; Rat (Sprague-Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 267 (1992), S. 571-582 
    ISSN: 1432-0878
    Schlagwort(e): Crustacean muscle ; Ultrastructure ; Dye coupling ; Flagellum ; Scaphognathite ; Fascicles ; Mitochondria ; Carcinus maenas (Crustacea)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 51
    ISSN: 1432-0878
    Schlagwort(e): Paneth cells ; Ultrastructure ; Morphometry ; Bethanechol ; Fluoride ion ; G-protein ; Mouse (Balb/c)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
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  • 52
    ISSN: 1432-0878
    Schlagwort(e): Primordial germ cell ; Ultrastructure ; Gonadal differentiation ; Cyprinus carpio (Teleostei)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
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  • 53
    ISSN: 1432-0878
    Schlagwort(e): Retinal pigment epithelium ; Ultrastructure ; Organelle differentiation ; Metamorphosis ; Lamprey, Petromyzon marinus (Cyclostomata)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
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  • 54
    ISSN: 1432-0878
    Schlagwort(e): Angiotensin II ; Ovarian follicles ; Theca interna ; Ultrastructure ; Steroidogenesis ; Atresia ; Golden hamster (Rodentia)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 268 (1992), S. 233-238 
    ISSN: 1432-0878
    Schlagwort(e): Alcian blue ; Basement membrane ; Lamina densa ; Meshwork ; Submandibular gland ; Ultrastructure ; Rat (Wistar-Imamichi)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 270 (1992), S. 1-6 
    ISSN: 1432-0878
    Schlagwort(e): Estradiol receptor ; Endometrium ; Ovariectomy ; Immunohistochemistry ; Ultrastructure ; Pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Plant systematics and evolution 181 (1992), S. 233-244 
    ISSN: 1615-6110
    Schlagwort(e): Algae ; Rhodophyta ; Thorea ramosissima ; T. riekei ; Ultrastructure ; pit plugs as a taxonomic character
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 58
    ISSN: 1615-6102
    Schlagwort(e): Cytoskeleton ; Phagotrophic ; Eugienoids ; Immunochemistry ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 59
    ISSN: 1615-6102
    Schlagwort(e): Dactylis glomerata L. ; Orchardgrass ; Sodium chloride tolerance ; Somatic embryo ; Tissue culture ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 60
    ISSN: 1615-6102
    Schlagwort(e): (1→3)-β-Glucose ; Callose ; Cell wall ; Host-parasite interface ; Immunocytochemical ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 166 (1992), S. 165-176 
    ISSN: 1615-6102
    Schlagwort(e): Cuticle ; Humidity ; Leaf structure ; Micropropagation ; Rosa ; Stomata ; Ultrastructure ; Wax
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 166 (1992), S. 67-77 
    ISSN: 1615-6102
    Schlagwort(e): Cuticle ; Cuticular exudations ; Exudations ; Heterodera schachtii ; Ultrastructure ; Host-parasite interactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 168 (1992), S. 125-135 
    ISSN: 1615-6102
    Schlagwort(e): Morphogenesis ; Phagotrophic ; Euglenoids ; Immunocytochemistry ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 64
    ISSN: 1615-6102
    Schlagwort(e): Cell wall ; Lycopersicon esculentum ; Microsporogenesis ; Pollen development ; Prophase I ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 167 (1992), S. 215-230 
    ISSN: 1615-6102
    Schlagwort(e): Lilium ; Freeze substitution ; Pollen tubes ; Rapid freeze fixation ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 171 (1992), S. 19-27 
    ISSN: 1615-6102
    Schlagwort(e): Lysosome ; Morphogenesis ; Trebouxia potteri ; Ultrastructure ; Zoospore formation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    European journal of epidemiology 8 (1992), S. 36-47 
    ISSN: 1573-7284
    Schlagwort(e): Tangier disease ; Aortic morphology ; Ultrastructure ; Atherosclerosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 68
    ISSN: 1573-6822
    Schlagwort(e): Lymphoblasts ; Nickel ; Cytometry ; Ultrastructure ; Membrane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Materialart: Digitale Medien
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  • 69
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 111-116 
    ISSN: 0887-3585
    Schlagwort(e): protein folding ; multiple minima problem ; peptide conformation ; energy calculation ; helices ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We have investigated the conformational properties of a truncated analogue of mastoparan and of mastoparan X, both peptides from wasp venom. The electrostatically driven Monte Carlo method was used to explore the conformational space of these short peptides. The initial conformations used in this study, mainly random ones, led to α-helical conformations. The α-helical conformations thus found exhibit an amphipathic character. These results are in accord with experimental data from NMR and CD spectroscopy.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 70
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992) 
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 71
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 324-330 
    ISSN: 0887-3585
    Schlagwort(e): X-ray diffraction analysis ; hydrogen bonds ; peptide conformation ; 310/α-helix transition ; antiparallel helix packing ; leucyl-leucyl interaction ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The packing of peptide helices in crystals of the leucine-rich decapeptide Boc-Aib-Leu-Aib-Aib-Leu-Leu-Leu-Aib-Leu-Aib-OMe provides an example of ladder-like leucylleucyl interactions between neighboring molecules. The peptide molecule forms a helix with five 5→1 hydrogen bonds and two 4→1 hydrogen bonds near the C terminus. Three head-to-tail NH ċ O = C hydrogen bonds between helices form continuous columns of helices in the crystal. The helicial columns associate in an antiparallel fashion, except for the association of Leu ċ Leu side chains, which occurs along the diagonal of the cell where the peptide helices are parallel. The peptide, with formula C56H102N10O13, crystallizes in space group P212121 with Z = 4 and cell parameters a = 16.774(3) Å, b = 20.032(3) Å and c = 20.117(3) Å; overall agreement factor R = 10.7% for 2014 data with |Fobs| 〈 3σ(F); resolution 1.0 Å.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 72
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 339-344 
    ISSN: 0887-3585
    Schlagwort(e): protein folding ; pro region ; protease inhibition ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: α-Lytic protease, an extracellular bacterial serine protease, is synthesized with a large pro region that is required in vivo for the proper folding of the protease domain. To allow detailed mechanistic study, we have reconstituted pro region-dependent folding in vitro. The pro region promotes folding of the protease domain in the absence of other protein factors or exogenous energy sources. Surprisingly, we find that the pro region is a high affinity inhibitor of the mature protease. The pro region also inhibits the closely related Streptomyces griseus protease B, but not the more distantly related, yet structurally similar protease, elastase. Based on these data, we suggest a mechanism in which pro region binding reduces the free energy of a late folding transition state having native-like structure.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 73
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992) 
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 74
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 1-25 
    ISSN: 0887-3585
    Schlagwort(e): aspartic proteinase zymogen ; molecular replacement ; structure-function ; activation peptide ; acid activation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The structure of porcine pepsinogen at pH 6.1 has been refined to an R-factor of 0.173 for data extending to 1.65 Å. The final model contains 180 solvent molecules and lacks density for residues 157-161. The structure of this aspartic proteinase zymogen possesses many of the characteristics of pepsin, the mature enzyme. The secondary structure of the zymogen consists predominantly of β-sheet, with an approximate 2-fold axis of symmetry. The activation peptide packs into the active site cleft, and the N-terminus (IP-9P) occupies the position of the mature N-terminus (1-9). Thus changes upon activation include excision of the activation peptide and proper relocation of the mature N-terminus. The activation peptide or residues of the displaced mature N-terminus make specific interactions with the substrate binding subsites. The active site of pepsinogen is intact; thus the lack of activity of pepsinogen is not due to a deformation of the active site. Nine ion pairs in pepsinogen may be important in the advent of activation and involve the activation peptide or regions of the mature N-terminus which are relocated in the mature enzyme. The activation peptide-pepsin junction, 44P-1, is characterized by high thermal parameters and weak density, indicating a flexible structure which would be accessible to cleavage. Pepsinogen is an appropriate model for the structures of other zymogens in the aspartic proteinase family. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 75
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992) 
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 76
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 70-85 
    ISSN: 0887-3585
    Schlagwort(e): major histocompatibility complex ; antigenic peptide ; molecular dynamics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Computer simulation of the conformations of short antigenic peptides (5-10 residues) either free or bound to their receptor, the major histocompatibility complex (MHC)-encoded glycoprotein H-2 Ld, was employed to explain experimentally determined differences in the antigenic activities within a set of related peptides. Starting for each sequence from the most probable conformations disclosed by a pattern-recognition technique, several energy-minimized structures were subjected to molecular dynamics simulations (MD) either in vacuo or solvated by water molecules. Notably, antigenic potencies were found to correlate to the peptides propensity to form and maintain an overall α-helical conformation through regular i,i+4 hydrogen bonds. Accordingly, less active or inactive peptides showed a strong tendency to form i,i+3 hydrogen bonds at their N-terminal end. Experimental data documented that the C-terminal residue is critical for interaction of the peptide with H-2 Ld. This finding could be satisfactorily explained by a 3-D Q.S.A.R. analysis postulating interactions between ligand and receptor by hydrophobic forces. A 3-D model is proposed for the complex between a high-affinity nonapeptide and the H-2 Ld receptor. First, the H-2 Ld molecule was built from X-ray coordinates of two homologous proteins: HLA-A2 and HLA-Aw68, energy-minimized and studied by MD simulations. With HLA-A2 as template, the only realistic simulation was achieved for a solvated model with minor deviations of the MD mean structure from the X-ray conformation. Water simulation of the H-2 Ld protein in complex with the antigenic nonapeptide was then achieved with the template-derived optimal parameters. The bound peptide retains mainly its α-helical conformation and binds to hydrophobic residues of H-2 Ld that correspond to highly polymorphic positions of MHC proteins. The orientation of the nonapeptide in the binding cleft is in accordance with the experimentally determined distribution of its MHC receptor-binding residues (agretope residues). Thus, computer simulation was successfully employed to explain functional data and predicts α-helical conformation for the bound peptide. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 77
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 112-119 
    ISSN: 0887-3585
    Schlagwort(e): analytical affinty chromatography ; self-association ; HIV p24gag ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Analytical affinity chromatography (AAC) was used to detect and quantitate the self-association of p24gag, the major structural capsid protein of human immunodeficiency virus (HIV-1). p24gag was immobilized on a hydrophilic polymer (methacrylate) chromatographic support. The resulting affinity column was able to interact with soluble p24, as judged by the chromatographic retardation of the soluble protein upon isocratic elution undernonchaotropic binding conditions. The variation of elution volume with soluble protein concentration fit to a monomer-dimer model for self-association. The soluble p24-immobilized p24 association process was observed using both frontal and zonal elution AAC at varying pH values; the dissociation constant was 3-4 × 10-5 M at pH 7. That p24 monomer associates to dimers was determined in solution using analytical ultracentrifugation. The solution Kd was 1.3 × 10-5 M at pH 7. AAC in the zonal elution mode provides a simple and rapid means to screen for other HIV-1 macromolecules that may interact with p24 as well as for modulators, including antagonists, of HIV p24 protein assembly. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 78
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 132-140 
    ISSN: 0887-3585
    Schlagwort(e): protein stability ; insertion mutations ; substitution mutations ; guanidine hydrochloride denaturation ; conformational changes ; circular dichroism spectroscopy ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: In a previous study, the small protein staphylococcal nuclease was shown to readily accommodate single alanine and glycine insertions, with average losses in stability comparable to substitutions at the same sites (PROT. 7:29-305, 1990). To more fully explore this unexpected adaptability to changes in residue spacing, 2 double amino acid insertions (alanyl-glycine, glycyl-glycine) and 3 additional single amino acid insertions with dissimilar side chains (proline, leucine, and glutamine) were constructed at 10 of the sites previously studied. At 8 of these sites, the type of amino acid side chain on the inserted residue significantly influenced the stability of the mutant protein. However, at 9 of the 10 sites, the double insertions were found to be no more destabilizing than the single alanine or glycine insertions. In contrast, double substitution mutations of staphylococcal nuclease, which replace two adjacent residues with alanine, do not show this striking degree of non-additivity. A comparison of the effects of single glutamine and single glycine insertions with alanyl-glycine insertions indicates that insertion of alanine into the peptide backbone is, on average, less destabilizing than appending the equivalent atoms onto the side chain of a glycine insertion. To explain their very different energetic effects, we propose that, unlike most substitutions, the inserted residue(s) must induce lateral displacements of the polypeptide chain, forcing the folded conformation away from that of wild type. The resulting obligatory shifts in the positioning of residues flanking the insertion generate a large number of degrees of freedom around which the mutant structure can relax. From the many alternative packing and bonding arrangements thus made available to the polypeptide chain, the energetically most favorable is selected. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 79
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 213-223 
    ISSN: 0887-3585
    Schlagwort(e): protein folding ; protein structure ; rotamers ; simulated annealing ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: An unknown protein structure can be predicted with fair accuracy once an evolutionary connection at the sequence level has been made to a protein of known 3-D structure. In model building by homology, one typically starts with a backbone framework, rebuilds new loop regions, and replaces nonconserved side chains. Here, we use an extremely efficient Monte Carlo algorithm in rotamer space with simulated annealing and simple potential energy functions to optimize the packing of side chains on given backbone models. Optimized models are generated within minutes on a workstation, with reasonable accuracy (average of 81% side chain χ1 dihedral angles correct in the cores of proteins determined at better than 2.5 Å resolution). As expected, the quality of the models decreases with decreasing accuracy of backbone coordinates. If the backbone was taken from a homologous rather than the same protein, about 70% side chain X1 angles were modeled correctly in the core in a case of strong homology and about 60% in a case of medium homology. The algorithm can be used in automated, fast, and reproducible model building by homology. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 80
    ISSN: 0887-3585
    Schlagwort(e): protein structure ; protein sequences ; protein design de novo ; protein engineering ; computer algorithms ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: What is the current state of the art in protein design? This question was approached in a recent two-week protein design workshop sponsored by EMBO and held at the EMBL in Heidelberg. The goals were to test available design tools and to explore new design strategies. Five novel proteins were designed: Shpilka, a sandwich of two four-stranded β-sheets, a scaffold on which to explore variations in loop topology; Grendel, a four-helical membrane anchor, ready for fusion to water-soluble functional domains; Fingerclasp, a dimer of interdigitating β-β-α units, the simplest variant of the “handshake” structural class; Aida, an antibody binding surface intended to be specific for flavodoxin; Leather - a minimal NAD binding domain, extracted from a larger protein. Each design is available as a set of three-dimensional coordinates, the corresponding amino acid sequence and a set of analytical results. The designs are placed in the public domain for scrutiny, improvement, and possible experimental verification.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 145-157 
    ISSN: 0887-3585
    Schlagwort(e): thermal diffuse X-ray scattering ; protein disorder ; molecular dynamics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Diffuse scattering data have been collected on two crystal forms of lysozyme, tetragonal and triclinic, using synchrotron radiation. The observed diffraction patterns were simulated using an exact theory for simple model crystals which relates the diffuse scattering intensity distribution to the amplitudes and correlations of atomic movements. Although the mean square displacements in the tetragonal form are twice that in the triclinic crystal, the predominent component of atomic movement in both crystals is accounted for by short-range coupled motions where displacement correlations decay exponentially as a function of atomic separation, with a relaxation distance of ≈ 6 Å. Lattice coupled movements with a correlation distance ≈ 50 Å account for only about 5-10% of the total atomic mean square displacements in the protein crystals. The results contradict various presumptions that the disorder in protein crystals can be modeled predominantly by elastic vibrations or rigid body movements.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 82
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 180-187 
    ISSN: 0887-3585
    Schlagwort(e): fibronectin ; domain ; collagen ; folding ; disulfide ; fluorescence ; GdmCl ; renaturation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The gelatin-binding region of fibronectin is easily isolated as a stable and functional 42-kDa fragment (42-kDa GBF) containing four type I “finger” modules and two type II “kringle-like” modules arranged in the order I6-II1-II2-I7-I8-I9, where the numbers designate the order of these modules in each of the two polypeptide chains. Each module forms an independently folded domain stabilized by two disulfide bonds. Reduction of disulfides caused large changes in the intrinsic fluorescence and abolished the gelatin-binding activity of 42-kDa GBF and two nonoverlapping gelatin-binding subfragments, 30-kDa GBF (I6-II1-II2-I7) and 21-kDa GBF (I8-I9). However, high yields of active material could be regenerated, without diluting the protein, by dialysis into GdmCl followed by slow overnight removal of GdmCl while maintaining the redox potential with a mixture of oxidized and reduced glutathione. Fluorescence spectroscopic analysis indicated that the tertiary structure and thermodynamic stability of the refolded fragments were similar to those of the originals. The refolded fragments were quantitatively indistinguishable from the originals with respect to their dissociation constants for binding to a fluorescent-labeled collagen fragment. The results suggest that all or most of the cystines, a total of 24 in 42-kDa GBF, are correctly paired in the refolded products and that the tertiary structure was completely recovered. The fact that the 30- and 21-kDa fragments bind with a similar affinity proves the existence of at least two nonoverlapping sites in 42-kDa GBF that recognize gelatin.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 83
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 278-298 
    ISSN: 0887-3585
    Schlagwort(e): folding nucleation ; hydrophobic cluster ; conserved loop length ; structure-sequence relationship ; sequence patterns ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The Greek key β-barrel topology is a folding motif observed in many proteins of widespread evolutionary origin. The arthropodan hemocyanins also have such a Greek key β-barrel, which forms the core of the third domain of this protein. The hemocyanin β-barrel was found to be structurally very similar to the β-barrels of the immunoglobulin domains, Cu,Zn-superoxide dismutase and the chromophore carrying antitumor proteins. The structural similarity within this group of protein families is not accompanied by an evolutionary or functional relationship. It is therefore possible to study structure-sequence relations without bias from nonstructural constraints. The present study reports a conserved pattern of features in these Greek key β-barrels that is strongly suggestive of a folding nucleation site. This proposed nucleation site, which we call a “β-zipper,” shows a pattern of well-conserved, large hydrophobic residues on two sequential β-strands joined by a short loop. Each β-zipper strand is near the center of one of the β-sheets, so that the two strands face each other from opposite sides of the barrel and interact through their hydrophobic side chains, rather than forming a hydrogen-bonded β-hairpin. Other protein families with Greek key β-barrels that do not as strongly resemble the immunoglobulin fold - such as the azurins, plastocyanins, crystallins, and prealbumins - also contain the β-zipper pattern, which might therefore be a universal feature of Greek key β-barrel proteins.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 314-323 
    ISSN: 0887-3585
    Schlagwort(e): structure analysis ; graph theory ; protein structure ; β sheet ; retrieval ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: In order to find rules for the secondary structure prediction of proteins which describe the (sequentially) long-range interactions in sheet structures methods of applied graph theory were used. The so called β graph which describes the sheet topology was defined for every protein in the Brookhaven Data Bank containing β sheets. The resemblance of proteins at that topological level is discussed, and four notations and graphic representations of sheets which describe the sequential and topological neighborhoods of the strands were derived. This description level supports the usage of data structures which allow the implementation of efficient algorithms for the analysis and comparison of β structures in proteins. A computer program for the representation and retrieval of bibliographic data and β sheet structures was implemented. Some examples for substructure search illustrate the usefulness of the program. Two graphic catalogues were compiled: one contains all β graphs of PDB proteins and the other all occurring different greek key descriptions.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 85
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 345-364 
    ISSN: 0887-3585
    Schlagwort(e): protein structure ; crystallography ; errors ; φ,ψ distribution ; χ1 angles ; stereochemical parameters ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Methods have been developed to assess the stereochemical quality of any protein structure both globally and locally using various criteria. Several parameters can be derived from the coordinates of a given structure. Global parameters include the distribution of φ,ψ and χ1 torsion angles, and hydrogen bond energies. There are clear correlations between these parameters and resolution; as the resolution improves, the distribution of the parameters becomes more clustered. These features show a broad distribution about ideal values derived from high-resolution structures. Some structures have tightly clustered distributions even at relatively low resolutions, while others show abnormal scatter though the data go to high resolution. Additional indicators of local irregularity include proline φ angles, peptide bond planarities, disulfide bond lengths, and their χ3 torsion angles. These stereochemical parameters have been used to generate measures of stereochemical quality which provide a simple guide as to the reliability of a structure, in addition to the most important measures, resolution and R-factor. The parameters used in this evaluation are not novel, and are easily calculated from structure coordinates. A program suite is currently being developed which will quickly check a given structure, highlighting unusual stereochemistry and possible errors.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
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  • 86
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 12 (1992), S. 382-399 
    ISSN: 0887-3585
    Schlagwort(e): protein secondary structure ; amino acid sequence ; distributions ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The conditional probability, P(σ|x), is a statement of the probability that the value of σ will be found given the prior information that a value of x has been observed. Here σ represents any one of the secondary structure types, α, β, τ, and ρ for helix, sheet, turn, and random, respectively, and x represents a sequence attribute, including, but not limited to: (1) hydropathy; (2) hydrophobic moments assuming helix and sheet; (3) Richardson and Richardson helical N-cap and C-cap values; (4) Chou-Fasman conformational parameters for helix, Pα, for sheet, Pβ, and for turn, Pτ; and (5) Garnier, Osguthorpe, and Robson (GOR) information values for helix, Iα, for sheet, Iβ, for turn, I,τ, and for random structure, Iρ.Plots of P (σ|x) vs. x are demonstrated to provide information about the correlation between structure and attribute, σ and x. The separations between different P (σ|x) vs. x curves indicate the capacity of a given attribute to discriminate between different secondary structural types and permit comparison of different attributes. P (α|x), P (β|x), P (τ|x) and P (ρ|x) vs. x plots show that the most useful attributes for discriminating helix are, in order: hydrophobic moment assuming helix 〉 Pα » N-cap 〉 C-cap ≈ Iα ≈ Iτ. The information value for turns, Iτ, was found to discriminate helix better than turns. Discrimination for sheet was found to be in the following order: Iβ » Pβ ≈ hydropathy 〉 Iρ ≈ hydrophobic moment assuming sheet.Three attributes, at their low values, were found to give significant discrimination for the absence of helix: Iα ≈ Pα ≈ hydrophobic moment assuming helix. Also, three other attributes were found to indicate the absence of sheet: Pβ » Iτ ≈ hydropathy. Indications of the absence of σ could be as useful for some applications as the indication of the presence of σ.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 87
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 26-37 
    ISSN: 0887-3585
    Schlagwort(e): norcamphor ; P450CIA1 ; substrate specificity ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: While cytochrome P-450cam, catalyzes the hydroxylation of camphor to 5-exo-hydroxycamphor with 100% stereospecificity, norcamphor is hydroxylated by this enzyme yielding 45% 5-exo-, 47% 6-exo-, and 8% 3-exo-hydroxynorcamphor (Atkins, W.M., Sligar, S.G., J. Am. Chem. Soc. 109:3754-3760, 1987). The present study describes a 201-psec molecular dynamics (MD) simulation of norcamphorbound cytochrome P-450cam to elucidate the relationship between substrate conformational mobility and formation of alternative products. First, these data suggest that the product specificity is, at least partially, due to the mobility of the substrate within the active site. Second, the high mobility of norcamphor in the active site leads to an average increase in separation between the home iron and the substrate of about 1.0 Å; this increase in separation may be the cause of the uncoupling of electron transfer when norcamphor is the substrate. Third, the active site water located in the norcamphor-bound crystal structure possesses mobility that correlates well with the spin-state equilibrium of this enzyme-substrate complex. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 88
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 57-69 
    ISSN: 0887-3585
    Schlagwort(e): protein conformation ; aromatic contribution ; disulfide contribution ; CD spectra of the main secondary structural elements in proteins ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: A recently developed algorithm, called Convex Constraint Analysis (CCA), was successfully applied to determine the circular dichroism (CD) spectra of the pure β-pleated sheet in globular proteins. On the basis of X-ray diffraction determined secondary structures, the original data set used (Perczel, A., Hollosi, M., Tusnady, G. Fasman, G.D. Convex constraint analysis: A natural deconvolution of circular dichroism curves of proteins, Prot. Eng., 4:-669-679, 1991), was improved by the addition of proteins with high β-pleated sheet content. The analysis yielded CD curves of the pure components of the main secondary structural elements (α-helix, antiparallel β-pleated sheet, β-turns, and unordered conformation), as well as a curve attributed to the “aromatic contribution” in the wavelength range of 195-240 nm. Upon deconvolution the curves obtained were assigned to various secondary structures. The calculated weights (percentages determining the contributions of each pure component curve in the measured CD spectra of a given protein) were correlated with the X-ray diffraction determined percentages in an assignment procedure and were evaluated. The Pearson product correlation coefficients (R) are significant for all five components. The new pure component curves, which were obtained through deconvolution of the protein CD spectra alone, are promising candidates for determining the percentages of the secondary structural components in globular proteins without the necessity of adopting an X-ray database. The CD spectrum of the CheY protein was interesting because it has the characteristic shape associated with the α-helical structure, but upon analysis yielded a considerable amount of β-sheet in agreement with the X-ray structure. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 89
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 120-131 
    ISSN: 0887-3585
    Schlagwort(e): protein folding ; α-helix ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: A computational study of the role of all ionizable groups of the C-peptide in its helix-coil transition is performed within the framework of continuum electrostatics. The method employed in our computations involves a numeric solution of the Poisson equation with the Boundary Element Method. Our calculations correctly predict the experimentally observed trends in the helix-coil equilibrium of the C-peptide, and suggest that the mechanisms involved are more complex than usually presumed in the literature. Our results suggest that electrostatic interactions in the unfolded conformation are often more important than in the helix, total electrostatic contribution to the helix-coil transition due to the side chains of the C-peptide destabilizes the helix, changes in the helix stability produced by the changes in the ionization state of the side chains are dominated by side chain effects, the effect of the helix dipole on the energetics of the helix-coil transition of the C-peptide is either minor or similar to other contributions in magnitude; while the formation of a salt bridge is electrostatically favorable, formation of the hydrogen bond between a charged and a polar side chains is not. Factors limiting the accuracy of the computations are discussed. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 90
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 152-157 
    ISSN: 0887-3585
    Schlagwort(e): Staphylococcus aureus ; bacterial toxins ; structure-function ; protein structure ; crystallography ; pyrogenic toxins ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The Type C staphylococcal enterotoxin produced by Staphylococcus aureus strain FRI-909 has been crystallized using a combination of two precipitants, ammonium sulfate and polyethylene glycol 400, with the addition of small amounts of detergent. Two related crystal forms have been obtained, one triclinic, and one tetragonal, both with one toxin molecule per asymmetric unit. These crystals are stable for at least 75 hr in the X-ray beam and diffract to at least 2.2 and 2.6 Å, respectively. The triclinic crystals have unit cell parameters a = 38.5 Å, b = 43.7 Å, c = 36.9 Å, and interaxial angles α = 99.9°, β = 95.8°, and γ = 98.5°. The tetragonal crystals are of space group P4122 with unit cell parameters a = 43.4 Å and c = 278.0 Å. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 91
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 162-173 
    ISSN: 0887-3585
    Schlagwort(e): protein folding ; folding intermediates ; time resolved fluorescence ; nonradiative excitation energy transfer ; BPTI ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The structure of BPTI and reduced BPTI in concentrated guanidinium HCI (GUHCl) in the presence of glycerol has been probed by measurements of dynamic nonradiative excitation energy transfer between probes attached to its amino groups. Inter probe distance distributions were obtained from analysis of donor fluorescence decay curves and used to characterize local structures in unordered states of the protein. Site specifically fluorescently labeled BPTI derivatives (1-n)BPTI (n = 15, 20, 41, 46) were used, each carrying a 2-methoxy-naphthyl-1-methylenyl group (MNA) at the N-terminal amino group of arg1 and 7-(dimethylamino)-coumarin-4-yl-acetyl residue (DA-coum) at one of its ε-NH2 groups of the lysine side chains. Analysis of donor fluorescence decay kinetics gave the interprobe distance distributions in the native and denatured states.The N-terminal-segment, residues 1-15, is in an extended conformation (with an average interprobe distance of 34 ± 2 Å) in the native state. Upon unfolding by reduction with DTT or β-mercapto ethanol in 6 M GUHCl/glycerol mixture, the conformation of this segment relaxed to a state characterized by a reduced averageinterprobe distance and a larger width of the distances distribution. The average distance between residues 1 and 26, i.e., between the N-terminus and the turn of the twisted β sheet element (residues 18-35), increased upon unfolding. At -30°C in the above solvent, the distribution between these two sites was probably composed of two conformational subpopulations. About 45 ±20% of the molecules were characterized by a short interprobe distance (like the native state) representing a compact conformation, and 55 ± 20% of the molecules showed large interprobe distances representing an expanded (unfolded) conformation.Thus local structures seem to exist in reduced denatured BPTI even underdenaturing conditions in 6 M GUHCl/glycerol mixtures. Some of those structures are unstable in guanidinium isothiocyanate (GUSCN). The method introduced here is suitable for probing local structures and very long range interactions in unfolded folded proteins and for search for folding initiation sites (FISs) and early folding intermediates. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 92
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 206-222 
    ISSN: 0887-3585
    Schlagwort(e): molecular docking ; Monte Carlo ; simulated annealing ; rational drug-design ; dihydrofolate reductase ; proteinase inhibitors ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We present a method to search for possible binding modes of molecular fragments at a specific site of a potential drug target of known structure. Our method is based on a Monte Carlo (MC) algorithm applied tothe translational and rotational degrees of freedom of the probe fragment. Starting from a randomly generated initial configuration, favorable bindingmodes are generated using a two-step process. An MC run is first prformed in which the energy in the Metropolis algorithm is substituted by a score function that measures the average distance of the probe to the targetsurface. This has the effect of making buried probes move toward the targetsurface and also allows enhanced sampling of deep pockets. In a second MC run, a pairwise atom potential function is used, and the temperature parameter is slowly lowered during the run (Simulated Annealing). We repeat this procedure starting from a large number of different randomly generated initial configurations in order to find all energetically favourable docking modes in a specified region around the target. We test this method using two inhibitor-receptor systems: Streptomyces griseus Proteinase B in complex with the third domain of the ovomucoid inhibitor from turkey, and dihydrofolate reductase from E. Coli in complex with methotrexate. The method could consistently reproduce the complex found in thecrystal structure searching from random initial positions in cubes ranging from 25 Å to 50 Å about the binding site. In the case of SGPB, we were also successful in docking to the native structure. In addition, we were successful in docking small probes in a search that included the entire protein surface. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 93
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 272-272 
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 258-271 
    ISSN: 0887-3585
    Schlagwort(e): protein folding ; protein modeling ; knowledge-based prediction ; molecular force field ; statistical mechanics ; globins ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We present an approach which can be used to identify native-like folds in a data base of protein conformations in the absence of any sequence homology to proteins in the data base. The method is based on a knowledge-based force field derived from a set of known protein conformations. A given sequence is mounted on all conformations in the data base andthe associated energies are calculated. Using several conformations and sequences from the globin family we show that the native conformation is identified correctly. In fact the resolution of the force field is high enough to discriminate between a native fold and several closely related conformations. We then apply the procedure to several globins of known sequence but unknown three dimensional structure. The homology of these sequences to globins of known structures in the data base ranges from 49 to 17%. Withone exception we find that for all globin sequences one of the known globinfolds is identified as the most favorable conformation. These results are obtained using a force field derived from a data base devoid of globins of known structure. We briefly discuss useful applications in protein structurlresearch and future development of our approach. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992) 
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 13 (1992), S. 364-368 
    ISSN: 0887-3585
    Schlagwort(e): pancreatic spasmolytic polypeptide ; porcine pancreas ; hanging drop vapor diffusion method ; crystallization ; circular dichroism analysis ; porcine insulin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Pancreatic spasmolytic polypeptide (PSP) isolated from porcine pancreas has been crystallized by the hanging drop vapor diffusion method. Crystals suitable for X-ray diffraction analysis were grown at pH 4.7 from a solution of 6% saturated ammonium sulfate. The space group is orthorhombic I222 or I212121 with unit cell parameters a = 54.38 Å, b = 72.29 Å, and c = 180.85 Å. There are three molecules of PSP per asymmetric unit and a water content of 46.9%. The crystals diffracts to an estimated resolution of 2.7 Å.The far-UV CD spectrum of PSP shows some exceptional features which cannot be accounted for thoroughly in terms of standard secondary structures commonly seen in protein CD spectroscopy. With this limitation, the secondary structure analysis predicts 15% α-helix, between 10 and 20% antiparallel β-strand, 10% parallel β-strand, 15% turn, and 25 to 40% of other structures. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 97
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 1-9 
    ISSN: 0887-3585
    Schlagwort(e): protein engineering ; cassette mutagenesis ; peptide hormone ; molecular modeling ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: By inserting appropriate peptide ligands into surface loops on globular proteins, we expect to develop probes for the location, accessibility, and steric and electrostatic environment of these ligand-binding sites on their membrane-bound receptors. Three residues in a loop on the surface of E. coli alkaline phosphatase were substituted by an 18-residue peptide containing the receptor-binding segment of somatostatin-14 without significantly affecting the catalytic properties of the enzyme. This hybrid protein was then used to investigate the ligand-binding site of somatostatin receptors. Tryptic cleavage of the hybrid protein within the inserted sequence, and binding of the hybrid protein to antisomatostatin antibodies demonstrated the surface accessibility of the guest peptide. Both the wild-type enzyme and the hormone-enzyme hybrid displaced 125I-labeled somatostatin from rat brain membrane receptors only at high concentrations. How-ever, chemical cationization of the hybrid protein, which again did not disturb the phosphatase activity, enhanced its receptor-binding potency to a level only 23 times lower than that of somatostatin itself and 280 times higher than that of the cationized wild-type protein. This alkaline phosphatase/somatostatin hybrid protein appears, therefore, to be a suitable starting point for the development of probes for the steric and electrostatic environment of the ligand-binding site of somatostatin receptors. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 98
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 168-177 
    ISSN: 0887-3585
    Schlagwort(e): protein structure ; helix-turn-helix motif ; Tet represser ; mutagenesis ; structure predictions ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The Tn10derived Tet represser contains an amino acid segment with high homology to the α-helix-turn-α-helix motif (HTH) of other DNA binding proteins. The five most conserved amino acids in HTH are probably involved in structural formation of the motif. Their functional role was probed by saturation mutagenesis yielding 95 single amino acid replacement mutants of Tet repressor. Their binding efficiencies to tet operator were quantitatively determined in vivo. All functional mutants contain amino acid substitutions consistent with their proposed role in a HTH. In particular, only the two smallest amino acids (serine, glycine) can substitute a conserved alanine in the proposed first α-helix without loss of activity. The last position of the first α-helix, the second position in the turn, and the fourth position in the second α-helix require mostly hydrophobic residues. The proposed C-terminus of the first α-helix is supported by a more active asparagine compared to glutamine replacement mutant of the wt leucine residue. The turn is located close to the protein surface as indicated by functional lysine and arginine replacements for valine. A glycine residue at the first position in the turn can be replaced by any amino acid yielding mutants with at least residual tet operator affinity. A structural model of the HTH of Tet repressor is presented. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 191-201 
    ISSN: 0887-3585
    Schlagwort(e): common protein fold ; protein architecture ; close packing ; p-sheet twist ; galactose oxidase ; influenza virus neuraminidase ; methylamine dehydrogenase ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Twisted β-sheets, packed face to face, may be arranged in circular formation like blades of a propeller or turbine. This β-pro-peller fold has been found in three proteins: that in neuraminidase consists of six β-sheets while those in methylamine dehydrogenase and galactose oxidase are composed of seven β-sheets. A model for multisheet packing in the β-propeller fold is proposed. This model gives both geometrical parameters of the β-propellers composed of different numbers of sheets and patterns of residue packing at their sheet-to-sheet interfaces. All the known β-propeller structures have been analyzed, and the observed geometries and residue packing are found to be in good agreement with those predicted by models. It is shown that unusual seven-fold symmetry is preferable to six- or eight-fold symmetry for propeller-like multisheet assembly. According to the model, a six β-sheet propeller has to have predominantly small residues in the β-strands closed to its sixfold axis, but no strong sequence constraints are necessary for a seven-fold β-propeller. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 100
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 178-190 
    ISSN: 0887-3585
    Schlagwort(e): flavoenzymes ; monooxygenase ; FAD ; reduced flavin ; flavin planarity ; Pseudomonas fluorescens ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The crystal structure of the reduced form of the enzyme p-hydroxybenzoate hydroxylase from Pseudomonasm fluorescens, complexed with its substrate p-hydroxybenzoate, has been obtained by protein X-ray crystallography. Crystals of the reduced form were prepared by soaking crystals of the oxidized enzyme-substrate complex in deaerated mother liquor containing 300-400 mM NADPH. A rapid bleaching of the crystals indicated the reduction of the enzyme-bound FAD by NADPH. This was confirmed by single crystal spectroscopy.X-ray data to 2.3 Å were collected on oscillation films using a rotating anode generator as an X-ray source. After data processing and reduction, restrained least squares refinement using the 1.9 Å structure of the oxidized enzyme-substrate complex as a starting model, yielded a crystallographic R-factor of 14.8% for 11,394 reflections. The final model of the reduced complex contains 3,098 protein atoms, the FAD molecule, the substrate p-hydroxybenzoate and 322 solvent molecules.The structures of the oxidized and reduced forms of the enzyme-substrate complex were found to be very similar. The root-mean-square discrepancy for all atoms between both structures was 0.38 Å. The flavin ring is almost completely planar in the final model, although it was allowed to bend or twist during refinement. The observed angle between the benzene and the pyrimidine ring is 2° This value should be compared with observed values of 10° for the oxidized enzyme-substrate complex and 19° for the enzyme-product complex. The position of the substrate is virtually unaltered with respect to its position in the oxidized enzyme. No trace of a bound NADP+ or NADPH molecule was found. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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