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  • 1985-1989  (626)
  • 1970-1974
  • 1945-1949
  • 1840-1849
  • 1987  (626)
  • Biochemistry and Biotechnology  (560)
  • Electron microscopy
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Years
  • 1985-1989  (626)
  • 1970-1974
  • 1945-1949
  • 1840-1849
Year
  • 1
    ISSN: 1437-160X
    Keywords: Chondrocalcinosis ; Calcium pyrophosphate dihydrate crystals ; Polymorphonuclear leukocyte ; Articular cartilage ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Electron microscopy was used to investigate the characteristics of calcium pyrophosphate dihydrate (CPPD) crystals in chondrocalcinosis (pseudogout syndrome). Crystals in midzone cartilage were frequently seen adjacent to chondrocytes. Great variation in crystal size and shape was observed. Most of the pyrophosphate crystals that had been phagocytosed by polymorphonuclear leukocytes of synovial fluid from patients with acute pseudogout were small (≦1 μm), indicating that small crystals can cause intense inflammation. Large numbers of polymorphonuclear leukocytes became attached to the eroded articular surface and phagocytosed microcrystals. Interaction of polymorphonuclear leukocytes with CPPD crystals in the superficial region of articular cartilage may stimulate the release of inflammatory mediators.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 65 (1987), S. 144-146 
    ISSN: 1432-1440
    Keywords: Campylobacter pyloridis ; Duodenal ulcer ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of campylobacter-like organisms found within duodenal biopsy specimens from 7 of 24 patients (28%) with active duodenal ulcer is described. Their curved shape and variable size are similar to what has previously been reported in descriptions of light microscopies. The organisms were found at the edge of active duodenal ulcers exclusively near neutral-mucous producing antral cells, to which they can adhere. The presence of these bacteria within cells and in the intercellular fluid implies that they can penetrate through the cell membrane or through tight intercellular junctions. The occurrence of these bacteria as well as numerous polymorphonuclear leukocytes in the afflicted regions suggests that the bacteria originally described by Warren and Marshall are indeed pathogenic and that their influence on ulcer healing should be included in designing treatment protocols.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 26 (1987), S. 347-357 
    ISSN: 1432-1432
    Keywords: Ribosome structure ; Electron microscopy ; Image analysis ; Evolutionary lineages
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Multivariate statistical analysis and classification techniques are powerful tools in sorting noisy electron micrographs of single particles according to their principal features, enabling one to form average images with an enhanced signal-to-noise ratio and a better reproducible resolution. We apply this methodology here to determining the characteristic views of the large (50S) ribosomal subunits from the eubacteriumEscherichia coli and the archaebacteriaMethanococcus vannielii, Sulfolobus solfataricus, andHalobacterium marismortui. Average images were obtained of the subunit in the common crown and kidney projections, but views of the particle in orientations intermediate between these two extremes were also elucidated for all species. These averages show reproducible detail of up to 2.0 nm resolution, thus enabling the visualization and interspecies comparison of many structural features as a first step toward comparing the actual three-dimensional structures. Our results disprove evolutionary lineages recently postulated on the basis of electron microscopical images of ribosomal subunits.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 410 (1987), S. 83-92 
    ISSN: 1432-2307
    Keywords: Buschke-Loewenstein tumour ; Giant condyloma ; Anogenital region ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Results on the light- and electron microscopic studies of six cases of Buschke-Loewenstein tumour are presented. The role of chronic irritation is emphasized in the aetiology of the tumour. Fistulas and abscesses arising in the tumour are dangerous as they give rise to chronic sepsis. In two perianal tumours, in situ or invasive carcinoma developed. Electron microscopy revealed varying degrees of differentiation of keratinocytes. As a result of the defective desmosomes, the tumour cell underwent segregation, with widened intercellular spaces containing oedema, erythrocytes and leucocytes. This phenomenon is probably responsible for frequent bleeding and fistula formation. The investigations disclosed that the Buschke-Loewenstein tumour is a special form of squamous carcinoma and therefore, radical surgical excision must be attempted even in case of a benign histological picture.
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  • 5
    ISSN: 1432-2307
    Keywords: Thrombocytopenic purpura ; Idiopathic thrombocytopenic purpura ; Liver sinusoidal fibrosis ; Electron microscopy ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 10 patients with thrombocytopenic purpura (TP) underwent splenectomy. Eight of these patients had idiopathic TP (certain or probable). All had normal liver function tests. Liver histology of the surgical biopsy was normal with the exception of a non specific mild portal infiltration in 6 cases. On Sirius red staining the perisinusoidal network was normal in 3 cases, mildly or moderately increased in 5 cases and often associated with perivenular fibrosis. Collagen types I, III, IV, laminin and fibronectin were increased in the 8 biopsies tested. On semi-thin sections, numerous Kupffer cells were observed. Under the electron microscope, sinusoidal abnormalities were very similar in all 7 patients studied: numerous Kupffer cells containing abundant lysosomes, numerous collagen bundles in the Disse space, active endothelial cells, transformation of some perisinusoidal cells into cells with some of the characteristics of fibroblasts (increased RER) and myofibroblasts (peripheral condensations of the filamentous network), increased fragments of basement membrane-like material. In two cases there was an increase in the number of perisinusoidal cells loaded with lipids. The similarity of the lesions and the absence of other fibrogenic causes (except in 2 cases) suggest that TP may represent another group of diseases with perisinusoidal fibrosis. The aetiology of fibrosis remains unknown but platelet derived growth factor and activated macrophages may play a major role.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 176 (1987), S. 251-258 
    ISSN: 1432-0568
    Keywords: Decidua ; Involution ; Electron microscopy ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Involution of the antimesometrial decidua was analysed by electron microscopy on days 9, 10 and 11 of pregnancy in the mouse. During this period, the width of the antimesometrial decidua decreases considerably. Involution begins in the decidual cells situated closest to the embryo (internal decidua) and proceeds towards the myometrium. The cells of the internal decidua showed signs of deterioration characterized by accumulation of clumps of chromatin in the nuclei and dilation of the perinuclear cisterna and endoplasmic reticulum cisternae. Autophagosomes and heterophagosomes accumulated in the cytoplasm of these cells. Cells particularly strongly affected became spherical and were devoid of their plasma membrane. Some cells near the trophoblast as well as the mature decidual cells situated farther from the embryo showed a normal morphology. The trophoblastic cells established close contact with healthy decidual cells and engulfed fragments of disorganized decidual cells. It is suggested that the death of decidual cells is a type of programmed cell death and that it is not due to a direct lytic action by the trophoblast.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 73 (1987), S. 370-378 
    ISSN: 1432-0533
    Keywords: Electron microscopy ; Factor VIII ; Glial fibrillary acidic protein ; Hemangioblastoma ; Tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The histogenesis of stromal cells in capillary hemangioblastoma has been the subject of debate. The light and electron microscopic studies of hemangioblastomas presented here showed pericytic and leiomyoblastic features in stromal cells. Cells cultured by the monolayer method showed similar features to those of the original tumors. Immunohistochemical studies for glial fibrillary acidic protein and factor VIII/von Willebrand factor indicated that stromal cells were antigenically distinct from astrocytes and endothelial cells. These findings suggest that stromal cells are closely related to pericytes and smooth muscle cells, and support Rhodin's speculation that pericytes serve as a precursor to smooth muscle cells.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 88 (1987), S. 142-146 
    ISSN: 0942-0940
    Keywords: Electron microscopy ; immunohistochemistry ; pituitary ; rhabdomyosarcoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intracranial extension of rhabdomyosarcoma from the face, nasopharynx or middle ear is rare. A 16-year-old boy presented with deterioration of vision and headache. CT scan revealed a soft tissue mass occupying the sphenoid and ethmoid sinuses, extending to the suprasellar fossa and impinging on the optic chiasm. The tumour, mimicking pituitary carcinoma, was removed by transsphenoidal craniotomy. Morphologic studies, including immunohistochemistry and electron microscopy, revealed that the tumour was a rhabdomyosarcoma. This case stresses the value of immunohistochemical and ultrastructural studies in the diagnosis of tumours occurring in the region of the sella turcica. The origin of this tumour was thought to be the sphenoid or ethmoid sinus. The pituitary gland appeared intact.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 75 (1987), S. 131-139 
    ISSN: 1432-0533
    Keywords: Cerebral ischemia ; Hyperglycemia ; Substantia nigra ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Preischemic hyperglycemia induced by feeding or glucose infusion worsens the brain damage and the clinical outcome following ischemia of a given duration and density, and characteristically causes postischemic seizure activity. Light microscopy has previously showed that, in the rat, transient hyperglycemic ischemia induced by bilateral carotid occlusion in combination with arterial hypotension causes a uni- or bilateral lesion in the pars reticulata of the substantia nigra. Since this region has a central role in preventing seizure discharges the present study was carried out to determine the ultrastructural characteristics of this lesion. In rats with 10 min of transient hyperglycemic ischemia followed by recirculation for 1 to 18 h, the pars reticulata of the substantia nigra showed signs of status spongiosus, as well as extensive nerve cell alterations. These changes were observed after all recovery periods studied. The spongiotic appearance was mainly caused by swelling of dendrites and, to a lesser degree, by astrocytic swelling. The dendrites were expanded at all recovery times but the severity increased during the later periods of recirculation. These swollen dendrites contained severely expanded mitochondrias and endoplasmic reticulum. The cytoskeletal elements showed disordered lining of microtubules. Two major types of nerve cell alterations were present: a “pale” and a “dark” variety. The pale type was the most frequent cell alteration. It occurred in all experimental groups and at all time points. Redistribution of the nuclear chromatin and of cytoplasmic organelles as well as swelling of the same type as in the dendrites were the essential changes. The dark neurons were much fewer in number and occupied a peripheral position in the pars reticulata. Astrocytic foot processes appeared to be dilated around the dark neurons. Swelling of astrocyte processes was most pronounced in the 1 h recovery animals. Both types of neurons showed severe mitochondrial alterations of the type observed in dendrites. Occasionally, mitochondrial alterations were found in astrocytic processes as well. Blood vessel alterations were lacking. Previous studies have shown that in this model of ischemia the substantia nigra has a relatively well-preserved blood perfusion. In view of this the extensive histopathological lesions are surprising. We speculate that the lesions primarily involve excitotoxic damage to dendrites, with pronounced lactic acidosis playing a contributory role in causing axonal and glial pathology as well.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 176 (1987), S. 145-154 
    ISSN: 1432-0568
    Keywords: Neurological mutant mice ; ‘Purkinje cell degeneration’ (pcd) ; Weaver ; Neural transplants ; Cerebellum ; Light microscopy ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Embryonic cerebellar grafts from genetically normal donors were implanted into the cerebellomedullary cistern of adult ‘Purkinje cell degeneration’ (pcd) and weaver mutant mice, which are respectively characterized by the selective loss of Purkinje and granule cells. Grafts placed into both mutant recipients exhibited a layered cellular organization reminiscent of the normal cerebellar cortex. Molecular, Purkinje, and granule cell layers were identifiable. Grafted Purkinje cells displayed characteristic cytological features, such as hypolemmal cisterns in association with mitochondria in the perikaryon, and lamellar structures in their axons. The cytological features of granule cell somata in the grafts appeared similar to those of mature granule cells. Electron microscopic examination of the molecular layer of the grafts revealed the presence of parallel fibers, which were not oriented in a parallel fashion; axon terminals of such fibers were often presynaptic to dendritic spines. The number of parallel fibers was markedly reduced in grafts implanted into both mutants compared to the normal cerebellar cortex; however, this phenomenon is commonly seen in cerebellum in tissue culture and in cerebellar transplants into normal hosts. It is concluded, therefore, that the environment of the mutant hosts does not affect the survival of Purkinje or granule cells and that transplantation of solid cerebellar grafts in the neurological mutants studied does not seem to pose any apparent limitations beyond those inherent to the process of cerebellar growth and differentiation outside its normal environment.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 176 (1987), S. 525-530 
    ISSN: 1432-0568
    Keywords: Placenta ; Guinea pig ; Labyrinth ; Syncytiotrophoblast ; Tracers ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The permeability of the materno-fetal barrier in the chorioallantoic placenta was studied in guinea pigs with gestation at term applying a variety of electron-opaque tracers via maternal circulation. None of the tracers tested was seen permeating the syncytiotrophoblast in the materno-fetal direction up to a 20 min interval when the fine structure of the placenta was satisfactorily preserved. The lanthanum chloride, cationized ferritin and horseradish peroxidase bound to the trophoblast surface, apparently due to electrostatic forces more than to specific receptors, and no uptake of these probes was detected in the cytoplasm. Albumin-colloidal gold complex, also used as a tracer, yielded similar results. As reported in other species with more complex syncytiotrophoblastic organization, this layer investing maternal lacunae is a highly selective permability barrier.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 279 (1987), S. S30 
    ISSN: 1432-069X
    Keywords: Cicatricial pemphigoid ; Vegetating lesions ; Immunopathology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case with widespread vegetating-pustular skin lesions, oral erosions, ulcerations and scarring, and conjunctival synechiae is reported. Clinically, histopathologically, and by immunofluorescence and electron microscopy this patient combined the features of pemphigoid vegetans, as described by Winkelmann and Su, and the mucocutaneous type of cicatricial pemphigoid. This observation suggests that a third subset of cicatricial pemphigoid can now be added to the two existing ones, the mucocutaneous and Brunsting-Perry types, and the designation vegetating cicatricial pemphigoid is proposed for this heretofore undescribed condition.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 75 (1987), S. 116-122 
    ISSN: 1432-0533
    Keywords: Rat ; Lead ; Brain edema ; Electron microscopy ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Newborn rats were exposed to daily intraperitoneal injections of 10 mg lead nitrate per kg body weight for the first 15 postnatal days. The growth and mortality of the lead-exposed animals did not differ from their control litter-mates, injected with vehicle only. In our previous studies, focal hemorrhages and spongy areas as well as breakdown of blood-brain barrier to plasma proteins were shown by light microscopy in the cerebellar parenchyma of 15-day-old rats exposed to this dose. In spite of these signs of edema, measurements of brain tissue specific gravity did not show increased water content. In the present investigation we examined the ultrastructure of the brain lesions in these rats with low-dose lead encephalopathy, focusing on signs of edema, and evaluated astroglial reaction by immunocytochemical staining for glial fibrillary acidic protein (GFAP). The electron microscopic findings were compatible with extracellular edema in the cerebellum of 15-day-old lead exposed rats. The number of GFAP-positive cell bodies in the gray substance of the cerebellar cortex was increased in the 15-day-old lead-exposed rats as compared with the controls of the same age, a finding which is presumably related to the leakage of plasma proteins. Both these findings were lacking at 20 days of age, suggesting reversibility of the lead-induced changes.
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  • 14
    ISSN: 1432-0533
    Keywords: Pleomorphic xanthoastrocytoma ; Epithelial properties ; Circumscribed growth ; Electron microscopy ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three cases of pleomorphic xanthoastrocytoma (PXA), one of which showed anaplastic evolution, are described. In all three the PXA tumors were well circumscribed and could be totally removed. Light-microscopically, pleomorphic tumor cells clustered gregariously and often formed alveolar structures. Electron microscopy revealed various epithelial properties, such as junctions and interdigitations between apposing tumor cells, and prominent basal laminae surrounding tumor nests. The circumscribed growth of PXA, as contrasted with an infiltrative growth of usual astrocytoma, can be attributed to the cellular cohesion based on the epithelial properties of the tumor cells. In the third patient, tumor recurred 6 months postoperatively. Although the recurrent tumor retained the alveolar structures, pleomorphism and various degenerative features of the tumor cells diminished with advance in the proliferative activities.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 74 (1987), S. 169-178 
    ISSN: 1432-0533
    Keywords: Cerebral gangliocytoma ; Parieto-frontal lobe ; Intracytoplasmic inclusion bodies ; No synapse ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We report a case of cerebral gangliocytoma (GC) with a variety of unusual structures in the tumor cells. Light microscopically, the tumor consisted of typical ganglion cells, atypical cells which has argyrophilic granules in the cytoplasm, and a few astrocytes. Electron microscopically, the tumor cells showed typical gangliocytic features, which had abundant rough endoplasmic reticula, ribosomes and cored vesicles of 90–150 nm diameter, a few 50-nm-diametered non-cored vesicles, and other common organelles in their cytoplasm. Furthermore, neoplastic ganglion cells contained a variety of abnormal structures, including membranous cytoplasmic bodies (MCB), Zebra bodies (ZB), tubular structures, branched tubular structures (BTS), concentrical laminated bodies and curvilinear bodies (CB). The MCB, ZB and CB resembled those in GM2 gangliosidosis (GMG), and the BTS that in infantile neuroaxonal dystrophy (INAD). Although the significance of these inclusions is still unknown, it is considered that some common mechanism might play a role in the metabolism of both neoplastic neuronal cells and degenerating neurons (GMG and INAD). Synapses could not be observed anywhere despite complete neuronal differentiation of many tumor cells.
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  • 16
    ISSN: 1432-0533
    Keywords: Hypoglycemia ; Rat striatum ; Glutamate ; Excitotoxic nerve cell injury ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In rat striatum severe hypoglycemia causes an irreversible nerve cell injury, which does not become manifest until during the post-insult recovery period. This injury can be ameliorated by lesions of the glutamatergic cortico-striatal pathway, which suggests that an “excitotoxic” effect mediated by the glutamatergic input is the likely cause of the posthypoglycemic nerve cell destruction. In this paper we further characterize the protective effect of abolishing the glutamatergic innervation to striatum at the ultrastructural level. Two weeks after a unilateral cortical ablation rats were subjected to 30 min of severe hypoglycemia with isoelectric EEG and killed either immediately after the insult or following 60 min of recovery induced by restoring the blood glucose levels. Immediately after the hypoglycemic insult the structure of striatum was similar on both sides (except for the changes attributable to the ablation); i.e., the neurons and their dendrites had pale cytoplasm with condensed mitochondria, sparse RER and pinpoint ribosomes. After 60 min restitution numerous striatal neurons on the non-protected, non-ablated side had turned variably dark and condensed, whereas under-neath the ablation they remained similar as immediately after hypoglycemia. This sequence indicates that the most likely cause of nerve cell destruction on the non-protected side is the “excitotoxic” effect mediated by the glutamatergic innervation, which is superimposed on the action of the hypoglycemic insultper se. Furthermore, the primary condensation of neurons and their dendrites indicate existence of another type of acute “excitotoxic” nerve cell injury which differs from the previously described injury characterized by neuronal swelling.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 72 (1987), S. 341-348 
    ISSN: 1432-0533
    Keywords: Carbon disulphide neuropathy ; Pacinian corpuscles ; Denervation and reinnervation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Adult Wistar rats were exposed to carbon disulphide vapours at a concentration of 2.4 mg/l of air for 5 days a week (6 h a day), and the ultrastructure of Pacinian corpuscles and their nerve supply was investigated after 6 months of exposure. Both degenerative and regenerative changes were observed in sensory axons and the corpuscles. In a sample of corpuscles examined, 30% were denervated and about 60% showed clear signs of reinnervation. Some of the reinnervated corpuscles were supplied by unmyelinated axons. In others, one to three myelinated axons were already found at the nerve entry. The axons branched and formed three to eight terminals in the inner core. Due to continuous intoxication, most regenerated terminals were again undergoing degeneration. In peripheral nerves, the evidence of axonal regeneration has been reported in various toxic distal axonopathies. However, the reinnervation of Pacinian corpuscles has not been described before. It can be expected that reinnervation of Pacinian corpuscles and other end-organs also occurs in other axonopathies, if not during continuous poisoning, then at least after its cessation.
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  • 18
    ISSN: 1432-0533
    Keywords: Herpes simplex virus type 2 ; Genital infection ; Avidin-Biotin Method ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mice were infected by the vaginal route with the MS strain of herpes simplex virus type 2 (HSV-2). Serial vaginal cultures were used to confirm infection and to select mice for this study. Two mice were killed by perfusion on days 2–6 post infection (p.i.) and lumbar and sacral cord with cauda were fixed and embedded for electron microscopy. Semithin Epon-sections were stained for viral antigen using a rabbit anti-HSV-2 antiserum and the Avidin-Biotin (ABC) method. Thin sections from antigen-positive blocks were examined by electron microscopy, and the number and types of infected cells detected by these two methods were compared. A good correlation was found between detection of infected cells by these methods. Infected cells included neurons of dorsal root ganglia and spinal cord, satellite cells of dorsal root ganglia, non-myelinating Schwann cells, astrocytes, oligodendrocytes and arachnoidal cells. Infected cells were first detected in the cauda on day 3 p.i. and in the spinal cord on day 5 p.i. The temporal and spatial distribution of infected cells was consistent with neural spread to and within the CNS. The pathological lesions showed a good correlation with the distribution and number of infected cells and are probably due to a direct virus effect. The similar sensitivity of the Epon-ABC method to electron microscopy in detecting infected cells indicates that this method may have useful applications in both experimental and diagnostic work.
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  • 19
    ISSN: 1432-0533
    Keywords: Cerebral calcification ; Fahr's disease ; Electron microscopy ; Histochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of idiopathic nonarteriosclerotic cerebral calcification was studied post mortem by histochemical and scanning and transmission electron microscopic methods. Calcification was found bilaterally in the basal ganglia, cerebral cortex, granular layer and white matter of the cerebellum. Histochemical examination revealed that deposits were composed of a mixture of glycoproteins, mucopolysaccharides, calcium salts and iron. Transmission electron microscopy revealed minute deposits mainly in the cytoplasm of adventitial cells of blood vessels and sometimes in the cytoplasmic processes of glial cells. Scanning electron microscopy showed that some of the spherical and hemispherical bodies, which were formed in the adventitial cells of blood vessels, were connected with filamentous cytoplasmic processes of surrounding cells. Small uncalcified deposits occurring in the cytoplasm of the adventitial cells had subsequently had minerals deposited in them. Some kind of impairment of the pericytes may play an important role at the onset of this disease.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 279 (1987), S. 270-272 
    ISSN: 1432-069X
    Keywords: Atopic eczema ; Hyperlinear palms ; Autosomal dominant ichthyosis vulgaris ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 279 (1987), S. 167-172 
    ISSN: 1432-069X
    Keywords: Morphometry ; Electron microscopy ; Cytological atypia ; Nevus cells ; Melanoma cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cytological atypia, revealed in the course of routine light microscopy, is considered a valuable indicator of malignancy in melanocytic lesions. A clear definition of the term cytological atypia, however, is lacking. Therefore, by morphometric analysis of ultrathin sections of 11 malignant melanomas (7 invasive, 3 in situ, and 1 lentigo maligna melanoma) and 10 compound nevi, we evaluated the discriminating power of the various facets of cytological atypia, i. e., nuclear area, area of the nucleolus, area of the total cell, and nuclear irregularity. In each case, at least 50 intraepidermal melanocytic cells were examined. The two-sided U-test showed significant differences between intraepidermal nevus and melanoma cells, with regard to the mean values (x) and standard deviations (s) of the nuclear area (x and s, p=0.00011), area of the nucleolus (x, p=0.00043; s, p=0.00011), and area of the total cell (x, p=0.00011; s, p=0.00093). However, only the mean values and standard deviations of the nuclear area allowed a clear distinction in each individual case. The area of the nucleus can be estimated in the course of routine histology. We therefore think that the size and variation of the nuclear area should be considered in the histological differential diagnosis between malignant melanomas and benign nevi.
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  • 22
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 279 (1987), S. 308-314 
    ISSN: 1432-069X
    Keywords: Congenital cutis laxa ; Collagen synthesis ; Electron microscopy ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of congenital cutis laxa (CCL) of unclear mode of inheritance associated with multiple pulmonary artery branch stenosis was extensively investigated to assess possible correlations between clinical, ultrastructural, and biochemical features. Light microscopy revealed that elastic fibers were absent in the papillary dermis, while hypoplastic elsewhere. Transmission electron microscopy showed a poor elastin matrix content in some elastic fibers, variable diameters of collagen fibrils, and abundant glycogen granules in most dermal cells. Measurement of collagen fibril diameters, using an image analyzer, was carried out in the patient and two age- and site-matched controls. A biomodal distribution was found in the upper reticular dermis of the patient. In vitro analysis of collagen in skin fibroblast cultures of the patient showed increased collagen synthesis with a balanced production of type I and type III procollagens. Our study confirms that CCL represents a disorder both of collagen and elastic connective tissue.
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  • 23
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 85 (1987), S. 56-62 
    ISSN: 0942-0940
    Keywords: Electron microscopy ; erythropoietin ; haemangioblastoma ; immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Immunohistochemical studies for erythropoietin were carried out in six capillary haemangioblastomas, three of which were also studied by electron microscopy. The immunohistochemical studies showed that positively stained cells were scattered in the vicinity of capillaries, and that neither endothelial cells nor stromal cells were stained. In their morphology and distribution, the positively stained cells were identical to mast cells as observed by electron microscopy. In one case, erythropoietin was demonstrated in the cyst fluid of the tumour. These findings suggest that mast cells with abundant secreting granules in haemangioblastomas are capable of producing erythropoietin.
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  • 24
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cancer research and clinical oncology 113 (1987), S. 392-399 
    ISSN: 1432-1335
    Keywords: Paget's disease of bone ; Osteosarcoma ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The authors report 12 cases (8 men and 4 women) of sarcomatous degeneration in Paget's bone disease, with an average age of 72.3 years. Sarcomatous degeneration occurred often in polyostotic Paget's disease, and osteitis deformans was seen in 4 cases. Femur and pelvis were the most affected bones. Pain was a constant feature, whereas tumefaction and fracture were less common. Osteolytic lesions were more frequent than condensed or mixed lesions and radiological signs of malignancy were usually found. Seven cases were histologically clasiified as osteogenic sarcoma and 3 cases as fibrosarcoma. Electron microscopy was performed on 2 osteogenic sarcomas and in 1 case revealed microcylindrical inclusion in Pagetic osteoclasts and in multinucleated giant tumor cells, but none in mononucleated tumor cells. The average survival time for the patients in this study was only 4.5 months.
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  • 25
    ISSN: 1432-1106
    Keywords: Ventral mesencephalic grafts ; Electron microscopy ; Afferent synapses ; Tyrosine hydroxylase immunocytochemistry ; Dopaminergic neurons ; Dopaminergic boutons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In adult rats with a unilateral 6-hydroxydopamine-induced lesion of the nigrostriatal dopamine pathway, grafts of embryonic ventral mesencephalon can establish extensive efferent connections with the previously denervated host neostriatum and can compensate for motor and sensorimotor asymmetries induced by the lesion. The object of this study was to examine the afferent synaptic inputs to grafted dopaminergic neurons, implanted into a cortical cavity overlying the previously denervated caudate-putamen, using electron microscopic immunocytochemistry. The dopaminergic neurons of the grafts in the same animals had previously been shown to re-innervate the host neostriatum, to form synaptic connections therein and to attenuate the lesion-induced motor asymmetry that occured in response to amphetamine (Freund et al. 1985). In the light microscope, the grafts were found to contain numerous tyrosine hydroxylase-immunoreactive perikarya, dendrites, axons and axonal swellings which had distinct distributions. In addition axons and axonal swellings that were immunoreactive for either substance P or glutamate decarboxylase were present. Electron microscopic analysis of the boutons contacting tyrosine hydroxylase-immunoreactive neurons in the grafts revealed the presence of at least five distinct types of afferent synaptic boutons based on their immunochemistry, morphology, or types of membrane specialization. One type was itself immunoreactive for tyrosine hydroxylase; such synapses are extremely rare in the intact substantia nigra, none were found in the contralateral substantia nigrae or the substantia nigra of a control rat. Three of the remaining types had ultrastructural features that were similar to synaptic terminals that were immunoreactive for substance P or glutamate decarboxylase. These synapses were similar to the types of synapses found contacting dopaminergic neurons in the substantia nigra contralateral to the graft or the substantia nigra of a control rat. The results demonstrate that, in the absence of the normal extrinsic afferent inputs, the intracortical mesencephalic grafts have a well-developed local synaptic circuitry. It is suggested that local circuit regulation of dopaminergic neurons within the graft may, at least in part, be responsible for the maintenance of a normal or close to normal functional activity.
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  • 26
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    Experimental brain research 66 (1987), S. 175-184 
    ISSN: 1432-1106
    Keywords: Dorsal column nuclei ; Gracile nucleus ; Inferior olive ; Dorsal accessory olive ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study examined the termination pattern within the dorsal accessory subdivision of the cat inferior olive of axons arising from the gracile nucleus. The gracile terminals were labeled by anterograde transport of wheat germ agglutinin complexed to horseradish peroxidase and visualized with tetramethyl benzidine. Gracile terminals were found to contain round synaptic vesicles and form asymmetric synaptic contacts. Of particular interest was the finding that gracile axons, like axons from the spinal cord, terminate primarily outside of synaptic glomeruli. Yet most of the gracile terminals did not synapse on isolated dendritic elements. Rather, the majority contacted distal dendrites which directly contacted other dendritic elements, forming simple complexes termed dendritic thickets. Typically the dendritic thickets were composed of two or three dendrites that received input from more than one round vesicle-containing synaptic terminal. Only one terminal per thicket was labeled by injections in the gracile nucleus. This clustering of pre-and postsynaptic elements within the thickets provides opportunities for many of the same interactions allowed by synaptic glomeruli, in particular divergence and convergence of information.
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  • 27
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    Experimental brain research 67 (1987), S. 380-390 
    ISSN: 1432-1106
    Keywords: Adrenal medulla ; Periaqueductal gray ; Neural implants ; Analgesia ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recent findings in our laboratory indicate that adrenal medullary grafts produce significant alterations in pain sensitivity. Electron microscopic studies were undertaken to correlate these behavioral changes with the neural interactions of the host and graft tissue in the periaqueductal gray. A striking change found 8 weeks after transplantation is that pronounced myelination has taken place both in the graft and in the host tissue. The new myelin formation in the graft has the typical appearance of PNS myelination and, in the host the appearance of CNS myelination. The endothelial cells of the capillaries in the grafted tissue are attenuated and fenestrated in contrast to those of the surrounding parenchymal tissue of the host. By 8 weeks, the graft becomes heavily encapsulated with collagen, while the host CNS tissue develops layers of glial processes outlining the graft. However, collagen and glial layers apparently do not form an absolute barrier to either cellular or humoral interaction between the host and graft tissue. Chromaffin cells can be found protruding into the host CNS tissue and sometimes forming synapses with presumably the host neuronal processes. Grafted chromaffin cells may participate as both postsynaptic and, less often, as presynaptic components of synaptic junctions. The behavioral relevance of these synaptic contacts is unclear, since similar implants of adrenal medullary tissue into the dorsal spinal cord subarachnoid space, which also induce potent analgesia, do not contain synapses. Thus, it is more likely that behavioral changes are brought about by diffusion of neuroactive substances from grafted chromaffin cells to host receptors.
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  • 28
    ISSN: 1432-0983
    Keywords: Electron microscopy ; Replicative intermediates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Some physicochemical properties of the mitochondrial DNAs (mtDNA) from plants of flax, broad bean and mung bean, and from tissue culture cells of jimson weed, soybean, petunia and tobacco were determined. Circular molecules were observed in electron microscope preparations of each mtDNA. In soybean, petunia, broad bean and mung bean mtDNAs, the circular molecules had a continuous distribution of lengths (ranges between 1 to 36 kb, and 1 to 126 kb), heavily skewed toward smaller molecules. Eighty-six percent of the flax circular molecules were from 27 to 54 kb in size, and 78% of the jimson weed circular molecules were from 4 to 15 kb. Replicative forms of 1.2–1.6 kb circular molecules were observed in electron microscope preparations of broad bean mtDNA.
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  • 29
    ISSN: 1432-0738
    Keywords: Isopropyl alcohol ; Tracheal mucosa ; Ciliary activity ; Recovery process ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The toxicity of isopropyl alcohol (IPA) on the tracheal mucosa was studied experimentally with special reference to the recovery process of the organ. The results showed that 400 ppm IPA has an acute effect on the mucociliary system in the tracheal mucosa, and that recovery from such degeneration can occur in 2 weeks. When functional and morphological damage was induced by a higher level (5500 ppm) of IPA, recovery did not occur in 2 weeks. The conclusion is that the present allowable level of IPA is reasonable from the viewpoint of the effects of short-term exposure to IPA on the tracheal mucosa. In addition, a higher level of IPA exposure has longer-term effects on the tracheal mucosa, and workers exposed to such a higher level of IPA vapor should be given careful otolaryngological follow-up observations.
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  • 30
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    Archives of toxicology 59 (1987), S. 385-390 
    ISSN: 1432-0738
    Keywords: Lung ; Methyl isocyanate ; Gas poisoning ; Electron microscopy ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The static exposure of rats to 0.25 mg/l methyl isocyanate for 1 h resulted in damage to the epithelium of the proximal bronchioles and upper airways. Bronchiolar cells exhibited both nuclear and cytoplasmic damage; many epithelial cells, particularly in the bronchi and trachea, were killed and/or dislodged from the basement membrane. A “raft” of cell debris and fibrin lined most of the airways during the 1st week after exposure but repair to the underlying epithelium was well advanced within 2–3 days. The majority of airways were lined by a normal epithelium within 3 weeks of exposure, but isolated foci of hyperplasia and occluded airways probably accounted for continued respiratory impairment.
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  • 31
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    Child's nervous system 3 (1987), S. 74-80 
    ISSN: 1433-0350
    Keywords: Medulloblastoma ; GFAP-positivity ; Electron microscopy ; Postoperative follow-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Eighty-four cases of medulloblastoma were examined immunohistochemically and 12 by electron microscopy to assess differentiation in these tumors. Based upon the largest series of medulloblastoma studied to date, we demonstrated glial fibrillary acidic protein (GFAP) positivity, in 25% (21/84) of these tumors showing glial differentiation. GFAP-positive cells were seen more frequently in the desmoplastic variant of medulloblastoma (7/10). Under electron microscopy, the major part of the 12 tumors studied appeared primitive and undifferentiated. In 7 cases, groups of cells were found with primitive neuronal and/or glial features. GFAP positivity was confirmed at light microscopy level in all cases where cells showed glial differentiation in the form of glial-like filaments in cytoplasma. However, a follow-up questionnaire study of those patients who had received only surgical treatment revealed no difference in mean survival time between GFAP-positive and GFAP-negative medulloblastoma.
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  • 32
    ISSN: 1432-2013
    Keywords: Sugar transport ; Electron microscopy ; Chicken cecum and jejunum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have investigated the possible relation between the phloridzin-sensitive influx of α-methyl-D-glucoside (concentration 5 mmol/l) and the brush border surface area, in chicken isolated enterocytes. The intestinal regions studied were: jejunum and proximal cecum (both with high affinity sugar transport sites), medial cecum (with a low affinity transport system) and distal cecum (which lacks any transport ability). Cell apical surface measured by electron microscopy gave the following results; jejunal cells (0.41 μm2) 〉proximal cecal cells (0.23 μm2)〉medial cecal cells (0.15 μm2)=distal cecal cells (0.14 μm2). This parameter is mainly determined by the length of microvilli. Sugar influx studies showed that the concentration of the substrate in cell water (in mmol/l) was jejunum (7.1)〉proximal cecum (2.9) 〉medial cecum (1.7)〉distal cecum (not different from zero). The decline in influx rate from proximal to distal cecum may be explained both by changes in surface and by the different carriers involved (differentK m). Results of sugar concentration in the distal cecal cells do not correlate with the other segments studied since the substrate enters in these cells by a passive process. It is concluded that the degree of development of microvilli should be taken into account when estimating nutrient transport rates in different intestinal segments.
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  • 33
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    Virchows Archiv 411 (1987), S. 311-314 
    ISSN: 1432-2307
    Keywords: Human pituitary adenomas ; Granules ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Light bodies are large cytoplasmic granules originally described in the gonadotrophic cells of the rat pituitary gland. In order to determine whether similar bodies occur in the human anterior pituitary gland, 89 pituitary adenomas and periadenomatous tissue from 20 cases were examined by transmission electron microscopy. Double membrane bound bodies with filamentous internal structure identical to rodent light bodies were identified in 10 hormone-producing adenomas: 5 PRL, 1 PRL-GH, 2 GH, and 2 ACTH-producing tumours. No light bodies were found in the remaining 79 tumours nor in the pituitary cells in periadenomatous tissue from 20 cases. These results show that some human pituitary adenomas may contain light bodies identical to those seen in gonadotrophs of rat pituitary.
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  • 34
    ISSN: 1432-0878
    Keywords: Mammary gland ; Tissue culture ; Collagen gel ; Electron microscopy ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Fragments of human breast epithelium, devoid of all stromal and basal lamina components, which maintain their in vivo topological organisation can be cultured for up to 28 days within a reconstituted rat-tail-derived collagen matrix. These organoids initially undergo a loss of structural and 3-dimensional organisation, typified by loss of lumina formed by epithelial cells, and myosin from myoepithelial cells. Their subsequent reorganisation is dependent on the presence of serum, insulin, hydrocortisone, and cholera toxin in tissue culture medium. After this preliminary phase, a reduction in the concentration of serum, insulin, hydrocortisone, and cholera toxin is necessary to allow the structural differentiation of epithelial and myoepithelial cells. The myoepithelial cells also regain their ability to produce the basal lamina component laminin. The use of bovine-dermal collagen as the matrix, rather than rat-tail-derived collagen is shown to result in more stable organisation and differentiation of the organoids. The successful use of single-cell pellets (derived by trypsinisation of the organoids) in place of organoids in such cultures illustrates that there is no requirement for pre-existing cell/ cell contact or topological organisation of cells prior to embedding within the collagen matrix.
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  • 35
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    Cell & tissue research 247 (1987), S. 457-459 
    ISSN: 1432-0878
    Keywords: Vomeronasal glands ; Autonomic innervation ; Electron microscopy ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphological evidence for a direct autonomic innervation of the mouse vomeronasal glands is presented. Axonal varicosities containing a few densecore vesicles and numerous clear vesicles (36–60 nm in diameter) make synaptic contacts with the secretory cells at the base of the glandular acini. The axonal presynaptic membrane is associated with a distinct dense material and it is separated from the secretory cell by a synaptic cleft of about 12–14 nm. At the postsynaptical level, coated vesicles can be found. Additional postsynaptical specializations have not been observed.
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  • 36
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    Cell & tissue research 248 (1987), S. 49-54 
    ISSN: 1432-0878
    Keywords: Enterochromaffin cells ; Serotonin ; Duodenum ; Immunocytochemistry ; Electron microscopy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Enterochromaffin cells of the rat duodenum have been studied immunocytochemically by use of a specific antiserum to serotonin. At the light-microscopic level serotonin immunoreactivity was observed in enterochromaffin cells located in the epithelium of the duodenal mucosa. Most of the serotonin-immunoreactive material was localized to the basal portion of the enterochromaffin cells, but small amounts of immunoreactive material were regularly observed in the apical portion. At the electron-microscopic level serotonin immunoreactivity in enterochromaffin cells was found to be concentrated over the dense cores of the cytoplasmic granules. The majority of these granules was located in the basal cytoplasm of the enterochromaffin cells, but serotonin-immunoreactive granules were also observed in the apical cytoplasm immediately beneath the microvilli. These observations indicate that duodenal enterochromaffin cells are bipolar and that they secrete serotonin both basally, to the circulation, and apically, to the gut lumen. Rat duodenal enterochromaffin cells thus appear to have an exocrine as well as an endocrine function.
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  • 37
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    Cell & tissue research 248 (1987), S. 675-682 
    ISSN: 1432-0878
    Keywords: Molluscan muscles ; Innervation ; Chromatophores ; Cephalopods ; Electron microscopy ; Eledone cirrhosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cephalopod chromatophores are made of a central pigment cell surrounded by 10 to 20 radially arranged muscle fibres under direct nervous control. Innervation of these muscle fibres was studied with anterograde cobalt fills of peripheral nerve bundles and light and electron microscopy. Individual axons branch repeatedly to innervate the muscles of chromatophores scattered over several millimeters. Axons contained in several dermal nerves converge to innervate the same chromatophores. Among the chromaophores, axons were found running either singly or in small bundles, often accompanied by sheath cells. Single chromatophore muscles were innervated by at least one axon running across or along its length. Since nerves terminating on chromatophore muscles are very rare, neuromuscular contact seems to be made “en passant”. Varicosities of the axons apposed to the muscles are thought to be presynaptic sites. However, morphological differentiations of the pre-or post-synaptic membranes were not visible. Two types of innervating processes were found containing either electron-clear or a mixture of electron-clear and dark-core synaptic vesicles.
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  • 38
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    Cell & tissue research 248 (1987), S. 393-398 
    ISSN: 1432-0878
    Keywords: Adrenaline ; Phenylethanolamine-N-methyl transferase ; Immunocytochemistry ; Electron microscopy ; Central nervous system ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of adrenergic axon terminals was examined in the paraventricular nucleus of the thalamus (PNT) and in the hypothalamic arcuate nucleus-median eminence (ARC-ME) complex by use of phenylethanolamine-N-methyl transferase (PNMT) immunocytochemistry. In the PNT, immunoreactive terminals formed a dense and well-circumscribed plexus. In the ARC, labeled varicosities were less numerous and more evenly distributed. In the ME, they were scarce and confined to the inner zone. In all these areas, the diameter of immunoreactive varicosities ranged between 0.2 and 1.3 μm; in the ME and in the transitional zone between the ARC and the ME, a population of larger boutons (〉2 μm) was also visible. All immunoreactive varicosities exhibited densely packed small, clear vesicles associated with a few large granular vesicles. In the PNT and the ARC, but not in the ME, they formed synaptic contacts with dendritic elements and were occasionally apposed to neuronal cell bodies. These axo-somatic appositions showed no junctional specializations. In the ME and transitional zone, immunoreactive terminals were frequently juxtaposed to, and occasionally established differentiated synaptic contacts with, tanycytes. These data support a transmitter role for adrenaline in the diencephalon and suggest that adrenaline plays a role in hypothalamo-hypophysiotropic regulation through interactions with neural and glial elements.
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  • 39
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    Cell & tissue research 248 (1987), S. 169-180 
    ISSN: 1432-0878
    Keywords: M-band structure ; Fibre type ; Skeletal muscle ; Cryo ultramicrotomy ; Electron microscopy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the M-band in soleus (SOL) and extensor digitorum longus (EDL) muscles in newborn and four-week-old rats was studied using electron-microscopic techniques. In newborn rats, all myotubes and fibres in both muscles had an identical myofibrillar appearance. A five-line M-band pattern was seen in longitudinal sections and distinct M-bridges in cross-sections. The Z-discs were of medium width. On the other hand, in four-week-old rats, different muscle fibre types were observed on the basis of their myofibrillar pattern. In SOL two fibre types were distinguished in longitudinal sections. One had a four-line M-band pattern and very broad Z-discs, whereas the other type had five lines in the M-band and broad Z-discs. In EDL, three different myofibrillar patterns were observed. The M-bands were composed of three, four or five lines. Fibres had either thin, broad or medium Z-disc widths, respectively. In cross-sections of the SOL muscle one group of fibres showed indistinct M-bridges, whereas distinct M-bridges were seen in the other fibres and in all observed EDL muscle fibres. We conclude that initially there seems to be a single intrinsic program for M-band genesis; this program becomes modified upon the induction of functionally differentiated fibres.
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  • 40
    ISSN: 1432-0878
    Keywords: Human growth hormone-releasing factor (hGRF) ; Paraventricular nucleus ; Immunocytochemistry ; Electron microscopy ; Synapses ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary By means of a preembedding immuno-electronmicroscopic technique, a large number of nerve endings containing a substance related to human growth hormonereleasing factor (hGRF) have been demonstrated in the paraventricular nucleus of the guinea pig. They made synaptic contacts primarily with dendritic shafts: 80% of these contacts were symmetrical. The immunoprecipitate was located mainly in large granules and around small clear vesicles. These findings suggest that a peptide related to hGRF may play a role in neural communication in the paraventricular nucleus.
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  • 41
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    Cell & tissue research 247 (1987), S. 167-177 
    ISSN: 1432-0878
    Keywords: Arteriovenous anastomoses ; Autonomic innervation ; Synaptic vesicles ; Histochemistry ; Electron microscopy ; Tongue ; Dog
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The innervation of the arteriovenous anastomoses in the dog tongue has been investigated. At the lightmicroscopic level, the vessels were found to be densely supplied with adrenergic and AChE-positive nerve plexuses and less densely with the quinacrine-binding nerve plexus. At the electron-microscopic level, at least two apparently different types of axon profiles were identified: 1) Small vesicle-containing axons, characterized by many small granular vesicles, variable numbers of small clear vesicles and large granular vesicles. Storage of endogenous amines and uptake of exogenous amines into most small granular vesicles and many large granular vesicles was demonstrated. These axons stained only lightly with reaction products for AChE activity and thus seemed to be adrenergic in nature. Some axons contained numerous large granular vesicles, whose cores occasionally stained with uranyl ions; this suggests a co-localization of ATP or peptides as neurotransmitters. 2) Small granular vesicle-free axons, containing small clear vesicles and large granular vesicles in variable ratio. Most cores of these large granular vesicles were heavily stained with uranyl ions. No storage or uptake of amine into the synaptic vesicles was detected. Some axons appeared to be typically cholinergic, some, typically non-adrenergic, noncholinergic, and the rest, intermediate between the two. All axons stained heavily with reaction products for AChE activity, suggesting their cholinergic nature.
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  • 42
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    Cell & tissue research 247 (1987), S. 573-582 
    ISSN: 1432-0878
    Keywords: Seminal vesicle ; Histology ; Histochemistry ; Electron microscopy ; Physiology ; Clarias gariepinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The seminal vesicle of the African catfish, Clarias gariepinus, consists of 36–44 fingerlike lobes built up of tubules in which a fluid is secreted containing acid polysaccharides, acid-, neutral- and basic proteins, and phospholipids. In this fluid sperm cells are stored. The seminal vesicle fluid immobilizes the sperm cells. After ejaculation, it prolongs the period of sperm activity. The seminal vesicle fluid is secreted by the epithelium lining the tubules. The tubules in the proximal part of the lobes are predominantly lined by a simple cylindrical and those of the distal part by a simple squamous epithelium. These epithelial cells contain enzymes involved in energy-liberating processes, the enzyme activites being proportional to the height of the cells. Interstitial cells between the tubules have enzyme-histochemical and ultrastructural features indicative of steroid biosynthesis. Similar characteristics are found in testicular interstitial cells. The most rostral seminal vesicle lobes and the most caudal testicular efferent tubules form a network of tubules that opens at the point where the paired parts of the sperm ducts fuse with each other. The tubules of most seminal vesicle lobes, however, form a complex system that fuses with the unpaired part of the sperm duct.
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  • 43
    ISSN: 1432-0878
    Keywords: Microtubules ; Terminal web ; Small intestine ; Electron microscopy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The terminal web (TW) region of mature absorptive cells in the small intestine of the rat contains an elaborate cytoskeleton which supports the apical microvillus membrane. In studies regarding the structural organization of the cytoskeleton and associated proteins in the small intestine, microtubules have not been mentioned as components of the TW. By transmission electron microscopy of conventional resin-embedded sections of rat small intestine, we observe many microtubule profiles in the TW of mature absorptive cells. These microtubules are found in various orientations, although most course parallel to the long axis of the cell, and many microtubule profiles are seen in close association with smooth-surfaced vesicles.
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  • 44
    ISSN: 1432-0878
    Keywords: Alpha-bungarotoxin ; Autoradiography ; Cholinergic receptors ; Electron microscopy ; Suprachiasmatic nucleus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of (125I) alpha bungarotoxin (α-BTX) binding sites in the suprachiasmatic nucleus (SCN) of the adult female rat was examined by electron-microscopic autoradiography. The ultrastructural distribution of silver grains was analysed by line source, direct point count, and 50% probability circle methods. Real grain distribution was significantly different from that of randomly generated hypothetical grains. Line source analysis demonstrated two populations of sources: one associated with membranes, and one inside neuronal structures. Probability circle analysis of shared grains indicated that membrane-bound-radioactive sources were mainly asssociated with axo-dendritic appositions. Only a small proportion of labeled neuronal interfaces exhibited synaptic differentiations in the plane of section. However, the compartment containing synaptic terminals was the most enriched when comparing real to hypothetical grains. Probability circle analysis of exclusive grains demonstrated that sources that were not associated with neuronal plasma membranes were likely to be within nerve cell bodies and dendrites. It is concluded that the majority of specifically labeled α-BTX binding sites in the SCN is membrane bound, and may be associated with axodendritic synaptic transmission. The presence of a significant proportion of the label in the soma and dendrites of suprachiasmatic neurons 24 h after ventricular infusion suggests that some of the labeled binding sites (junctional or nonjunctional) may be internalized within these two compartments.
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  • 45
    ISSN: 1615-6102
    Keywords: Cytoskeleton ; Contractile proteins ; Lowicryl ; LR White ; Polyvinylalcohol ; Immunogold staining ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three embedding media have been compared with respect to post-embedding immunolabeling of contractile and cytoskeletal antigens in aldehyde-fixed smooth muscle tissue: the methacrylate derivates lowicryl K4M (cured at −35 or 60°C) and LR White (cured at 0 or 60°C) and the water soluble resin, polyvinylalcohol (dried at 60°C). Measurements of intensity of labeling of ultrathin sections in the fluorescence microscope showed that five antigens (actin, myosin light chain, tropomyosin, filamin and vinculin) reacted more or less equally with their respective antibodies in all the embedding media, including those cured at 60°C. One antibody (anti-light meromyosin) reacted well only with polyvinylalcohol-embedded tissue. In contrast to the relative invariance of antibody reactivity between media clear differences in the preservation of ultrastructural integrity were observed. Embedding in polyvinylalcohol (dried at 60°C) and in Lowicryl (cured at −35°C) resulted in superior preservation as compared to Lowicryl or LR White cured at 60°C. Examples of uitrastructural immunocytochemistry with the antibodies against filamin and myosin light chain, using the immunogold staining procedure are presented: the sites of localization by these antibodies were the same with all the media tried. The relative merits of the different methods are discussed.
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  • 46
    ISSN: 1615-6102
    Keywords: Cytopathology ; Rhabdovirus ; Development ; Electron microscopy ; Cuscuta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Electron microscopic examination ofCuscuta odorata, used for transmission trials, revealed mycoplasma-like organisms (MLO) as well as rhabdovirus-like particles, unknown toCuscuta. The virus infection is confined to certain phloem-parenchyma cells and a 1–2 cell thick layer of parenchyma cells with thickened walls surrounding the central cylinder. Virus particles, mostly bacilliform, could be detected mainly in the nucleus but also in the cytoplasm. They reach a length of 350–400 nm and a diameter of approximately 75 nm. Virus assembly takes place exclusively in the nucleus. Virus maturation occurs in membrane bound areas within the nucleus, which have no connection with the perinuclear space. Formation of nucleocapsids is always associated with a nuclear viroplasm. Envelopment of virus particles occurs in these membrane bound areas. Budding into the perinuclear space does not occur. Virus infection leads to degeneration and finally to death of the protoplast.
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  • 47
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    Protoplasma 140 (1987), S. 100-109 
    ISSN: 1615-6102
    Keywords: Actin ; Conifer ; Electron microscopy ; Picea glauca ; Somatic embryo ; Tissue culture ; Ultrastructure ; White spruce
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Somatic embryos in embryogenic callus cultures derived from Immature zygotic embryos ofPicea glauca (White spruce) were examined by light and electron microscopy. Somatic embryos consist of an embryonic region of small densely cytoplasmic cells subtended by a suspensor consisting of long highly vacuolated cells. Mitotic figures are frequent in the embryonic cells but are not observed in the suspensor. Cell divisions in the embryonic region apparently produce rows of cells which elongate to form the suspensor. The presence of abundant polysomes, coated membranes and dictyosomes in the cytoplasm of embryonic and upper suspensor cells suggests rapid growth of the embryo. In contrast the basipetal suspensor cells appear to be senescing. While only a few scattered microfilaments are present in the meristematic cells, the upper suspensor cells contain numerous bundles of longitudinally oriented microfilaments. These bundles correspond to actin cables observed in light microscope preparations stained with rhodamine labelled phalloidin and are oriented parallel to the direction of active streaming in these cells.
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  • 48
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    Colloid & polymer science 265 (1987), S. 855-859 
    ISSN: 1435-1536
    Keywords: Electron microscopy ; polyethylenemelt ; fine structure ; artifact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract There are still two opinions on the fine structure of polymer melts and glasses: (a) that the structure is similarly homogeneous to that in lower molecular weight materials and (b) that the structure shows larger short-range order regions (2–20 nm), which consist of bundeled segments of the chain molecules. Whereas opinion a relies more on indirect methods of investigation, opinion b is based mainly on fine granular structures which become visible in electron microscope investigations of surfaces of glassy solidified polymers. Such a fine structure can now be observed directly in a polyethylene melt. However, the structure is exposed as an artifact, so opinion a is supported.
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  • 49
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    European archives of oto-rhino-laryngology and head & neck 244 (1987), S. 180-184 
    ISSN: 1434-4726
    Keywords: Localized laryngeal amyloidosis ; Light microscopy ; Electron microscopy ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We performed light and electron microscopic studies in a case of localized supraglottic laryngeal amyloidosis involving a 55-year-old woman. Tissue specimens were stained with hematoxylin and eosin, and alkaline Congo red with or without permanganate (KMnO4) treatment, and were also examined with peroxidase-antiperoxidase immunohistochemistry. Biopsy specimens from the epiglottis showed diffuse replacement of the subepithelial region by amyloid, which showed a typical green birefringence under polarized light. Tissue affinity for Congo red was persistent after the KMnO4 treatment. However, the tissue sections showed a positive reaction only to the anti-P component antibody. Electron microscopic studies revealed some disorders of the plasma cells, suggesting that these cells play an important role in focal production of amyloid fibrils.
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  • 50
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    European archives of oto-rhino-laryngology and head & neck 244 (1987), S. 30-35 
    ISSN: 1434-4726
    Keywords: Central venous hemangioma ; Mandible ; Immunohistochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To date, 96 cases of central hemangiomas of the jawbones have been described in the literature. Of these cases, the mandible has been more affected than the maxilla, while approximately 50% of all cases occur in the first and second decades of life. Histopathologically, cavernous and capillary types are often found, in contrast to the central venous type, which is rare. We have recently treated a 44-year-old man, who was found to have a central venous hemangioma in his mandible. Immunohistochemical studies were performed using factor-VIIIrelated antigen as well as various lectins as markers for tumor endothelial cells. Our results showed that four kinds of lectins (UEA-I, PNA, ConA, and DBA) were useful for the marker as factor-VIII-related antigen. Scanning electron microscopic findings of this tumor demonstrated that the lumina of the blood vessels were more rough, while the lining endothelial cells were more irregular when compared with those of the normal vascular system.
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  • 51
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    European archives of oto-rhino-laryngology and head & neck 243 (1987), S. 361-365 
    ISSN: 1434-4726
    Keywords: Human inner ear ; Congenital anomalies ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We performed light and electron microscopic studies on the temporal bones of a patient with genetic aplastic deafness, in which the right ear had a Mondini-type defect and the left ear a Michel-type anomaly. The round window of each ear was absent. The stapedial foot plate of the right ear was depressed at its central part and was covered by thin membrane. The course of the internal auditory meatus of the left ear was deviated ventrally. There was total aplasia of the cochlea in the left ear, while that of the right ear showed only three-quarters of a turn. In this ear, three sites of spherical bulging were found and were believed to represent outer hair cells. Other structures of the normal cochlear duct were not present. The modiolus of the left ear was round and dome-shaped, contained sparse nerve fibers and a primitive spiral ganglion. The saccule, utricle and semicircular canals of each ear were missing, so that a common cavity of the vestibular system was present. Several otoliths could be seen under the surface of the membrane covering the common cavity. No sensory cells or their related tissues could be found in either ear.
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  • 52
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    European archives of oto-rhino-laryngology and head & neck 243 (1987), S. 382-386 
    ISSN: 1434-4726
    Keywords: Experimental tympanosclerosis ; Calcium antagonists ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of calcium antagonists in experimental tympanosclerosis following infection with Streptococcus pyogenes and vitamin D3 intoxication has been analyzed in a rat animal model. Compared with untreated animals, calcium antagonists exert a positive effect on the degenerative process and on secondary calcification in the subepithelial layer. This effect could be substantiated planimetrically.
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  • 53
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    Proteins: Structure, Function, and Genetics 2 (1987) 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 54
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 13-19 
    ISSN: 0887-3585
    Keywords: two-dimensional electrophoresis ; ethylnitrosourea ; somatic mutations ; structural variants ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The feasibility of detecting human somatic structural gene mutations by two dimensional electrophoresis has been investigated. A lymphoblastoid cell line was grown as a mass culture in the presence of ethylnitrosourea, after which cells were regrown as single cell clones. A total of 257 polypeptide spots were analyzed in gels derived from 186 clones. Four structural mutations were detected by visual analysis of the gels. Computer analysis of gels corresponding to the mutant clones was also undertaken. At a spot size threshold of 200 spots to be matched using a computer algorithm, all four mutant polypeptides were detected. These results indicate the usefulness of the two-dimensional approach for mutagenesis studies at the protein level.
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  • 55
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 1-12 
    ISSN: 0887-3585
    Keywords: protein crystallography ; protein refinement ; empirical energy simulations ; error analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The uncertainties in the refined parameters for a 1.5-Å X-ray structure of carbon-monoxy (FeII) myoglobin are estimated by combining energy minimization with least-squares refinement against the X-ray data. The energy minimization, done without reference to the X-ray data, provide perturbed structures which are used to restart conventional X-ray refinement. The resulting refined structures have the same, or better, R-factor and stereochemical parameters as the original X-ray structure, but deviate from it by 0.13 Å rms for the backbone atoms and 0.31 Å rms for the sidechain atoms. Atoms interacting with a disordered sidechain, Arg 45 CD3, are observed to have larger positional uncertainties. The uncertainty in the B-factors, within the isotropic harmonic motion approximation, is estimated to be 15%. The resulting X-ray structures are more consistent with the energy parameters used in simulations.
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  • 56
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 20-33 
    ISSN: 0887-3585
    Keywords: calmodulin ; peptide ; calmodulin-binding peptide ; peptide design ; hydrophobic moment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A basic, amphiphilic α helix is a structural feature common to a variety of inhibitors of calmodulin and to the calmodulin-binding domains of myosin light chain kinases. To aid in recognizing this structural feature in sequences of peptides and proteins we have developed a computer algorithm which searches for sequences of appropriate length, hydrophobicity, helical hydrophobic moment, and charge to be considered as potential calmodulin-binding sequences. Such sequences occurred infrequently in proteins of known crystal structure. This algorithm was used to find the most likely site in the catalytic (γ) subunit of phosphorylase b kinase for interaction with calmodulin (the δ subunit). A peptide corresponding to this site (residues 341-361 of the γ subunit) was synthesized and found to bind calmodulin with approximately an 11 nM dissociation constant. A variant of this peptide in which an aspartic acid at position 7 in its sequence (347 of the γ subunit) was replaced with an asparagin was found to bind calmodulin with approximately a 3 nM dissociation constant.
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  • 57
    ISSN: 0887-3585
    Keywords: proteolytic cleavage ; immunological cross-reaction ; amber fragment ; temperature-sensitive mutant ; stationary growth-phase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Immunological cross-reaction was employed for identification of proteolytic fragments of E. coli RNA polymerase genered both in vitro and in vivo. Several species of partially denatured but assembled RNA polymerase were isolated, which were composed of fragments of the two large subunits, β and β′, and the two small and intact subunits, α and σ. Comparison of the rate and pathway of proteolytic cleavage in vitro of unassembled subunits, subassemblies, and intact enzymes indicated that the susceptibility of RNA polymerase subunits to proteolytic degradation was dependent on the assembly state.Using this method, degradation in vivo was found for some, but not all, of the amber fragments of β subunit in merodiploid cells carrying both wild-type and mutant rpoB genes. Although the RNA polymerase is a metabolically stable component in exponentially growing cells of E. coli, degradation of the full-sized subunits was found in two cases, i.e., several temperature-sensitive E. coli mutants with a defect in the assembly of RNA polymerase and the stationary-phase cells of a wild-type E. coli. The in vivo degradation of RNA polymerase was indicated to be initiated by alteration of the enzyme structure.
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  • 58
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 54-63 
    ISSN: 0887-3585
    Keywords: domain association ; protein folding ; viscosity dependence ; solvent effects ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The equilibria and kinetics of ureainduced unfolding and refolding of the α subunit of tryptophan synthase of E. coli have been examined for their dependences on viscosity, pH, and temperature in order to investigate the properties of one of the rate-limiting steps, domain association. A viscosity enhancer, 0.58 M sucrose, was found to slow unfolding and accelerate refolding. This apparently anomolous results was shown to be due to the stabilizting effect of sucrose on the folding reaction. After accounting for this stabilization effect by using linear free-energy plots, the unfolding and refolding kinetics were found to have a viscosity dependence. A decrease in pH was found to stabilize the domain association reaction by increasing the refolding rate and decreasing the unfolding rate. This effect was accounted for by protonation of a single residue with a pK value of 8.8 in the native state and 7.1 in the intermediate, in which the two domains are not yet associated. The activation energy of unfolding is 4.8 kcal/mol, close to the diffusion limit. The negative activation entropy of unfolding, -47 cal/deg-mol, which controls this reaction, may result from ordering of solvent about the newly exposed domain interface of the transition state. These results may provide information on the types of noncovalent interactions involved in domain association and improve the ability to interpret the folding of mutants with single amino-acid substitutions at the interface.
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  • 59
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 34-41 
    ISSN: 0887-3585
    Keywords: adrenergic receptors ; affinity chromatography ; electron microscopy ; oligomeric structure ; target size analysis ; HPLC digest mapping ; receptor evolution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have characterized the structure of purified beta-adrenergic receptors by a combination of photoaffinity labeling, high performance liquid chromatography (HPLC)-tryptic mapping, CNBr fragmentation, target size analysis, and electron microscopy of purified receptor molecules. Guinea pig lung beta-adrenergic receptors purified by affinity chromatography, ion exchange chromatography, and HPLC size exclusion chromatography or photoaffinity labeled with [125]-iodocyanopindolol diazirine displayed mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) that corresponded to Mr = 68,000. Purified, radioiodinated guinea pig lung beta-receptors were subjected to complete trypsin digestion and subsequent reverse-phase HPLC analysis, which revealed nine peptides. Active site labeling and tryptic digestion of partially purified hamster lung beta-receptors produced one peptide, whereas CNBr digestion of the same material produced two labeled fragments, yielding information about the location of the active site within the primary sequence. Purified guinea pig lung receptors were examined with transmission electron microscopy. Electron micrographs revealed slightly asymmetric, rod-shaped structures with an average length of 13 nm and width of 3.4 nm. Many receptors were arranged as apparent dimeric structures. These findings confirm data obtained from target size analysis of guinea pig lung beta-receptors in situ which suggest that receptors may exist as oligomeric arrays in the native membrane. Taken together, these data provide information about putative functional domains of the beta-adrenergic receptor and its quaternary structure.
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  • 60
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    Keywords: intrahelical ion pairs ; frequency of ion pairs in exposed helices ; alpha-helix stabilization ; protein tertiary structure stabilization ; protein-folding pathway ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A survey of 47 globular proteins was made to determine the probability of occurrence of ion pairs separated by 1, 2, 3, … and 8 residues in the alpha helices. As a control, the probability of occurrence of like charged pairs was also determined. The survey showed that ion pairs of the type i, i±3 and i, i±4 are the most predominant. Such a preference was not observed for like charged pairs. The observed frequency of ion pairs is significantly greater than their expected frequency. The normalized frequencies of occurrence of the ion pairs were also found to increase generally with the helix length. These results indicate that the ion pairs may contribute to the stability of solvent-exposed alpha helices. Since the stabilization of protein secondary structure, these results may throw light on the mechanism of protein folding.
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  • 61
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    Proteins: Structure, Function, and Genetics 2 (1987) 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 62
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 79-80 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 63
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 72-77 
    ISSN: 0887-3585
    Keywords: CO equilibrium constants ; des-(Arg 141α)HbA ; heme proteins ; high-affinity state ; kinetics ; ligand binding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A few years ago we reported that histidine (HC3) 146β plays a major role in the pH-dependent propeties of the R-state of human hemoglobin, accounting for close to 50% of the R-state Bohr effect. We have extended these studies by examining the role of arginine 141α, another group known to affect the overall Bohr effect. We have compared the pH dependencies of the rate constants for the dissociation and combination of the fourth carbon monoxide molecule, I4 and I′4, respectively, for native hemoglobin A (HbA) and a control reconstututed HbA, and des-(Arg 141α) HbA, the hemoglobin molecule resulting from the enzymatic removal of the C-terminal arginine of the α-chain of human Hb. From these kinetic contants the pH dependence of L4, by about 80% between pH 6 and 8, where the aldkaline Bohr effect normally occurs, The sum of the effects of the removal of His 146β and of Arg 141α is grater than 100%. This suggests that at least one of these modifications altrs the contrubutions of other residues of this Bohr effect.
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  • 64
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    Keywords: hybrid immunologlobulin ; compatible plasmids ; transfection ; mouse IgG1 ; mouse IgG2a ; dansyl ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have produced a series of hybrid IgG1-IgG2a mouse immunoglobulins with identical light chains (L) and variable regions to facilitate the identification of structural features associated with functional differnces between immunoglobulin isotypes. Hybrid heavy chain (H) constant region gene segments were generated by genetic recombination in Escherichia coli between plasmids carrying mouse γ1 and γ2a gene segments. Crossovers occured through out these segments although the frequency was highest in regions of high nucleotide sequence homology. Eleven variant immunoglobulins produced by transfected hybridoma cell lines are assembled into H2L2 tetramers and properly glycosylated. In addition, all 11 immunoglbulins have identical antigen combining sites specific for the fluorescent hapten ε-dansyll-L-lysine. Protein A binding was used as probe of the structural integrity of the Fc portion of the variant antibodies. Differeneces in protein A binding between IgG1 and IgG2a appear to be due to amino acid differances at postions 252 (Thr→Met) and 254 (Thr→Ser) of the heavy chain (EU numbering).
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  • 65
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 111-117 
    ISSN: 0887-3585
    Keywords: crystallography ; antigen ; glycoprotein ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Neuraminidases from different subtypes of influenza virus are characterized by the absence of serlogical cross-reactivity and an amino acid sequence homology of approximately 50%. The three-dimensional structure of the neuraminidase antigen of subtype N9 from an avian influenza virus (A/tern/Australia/G70c/75) has been determined by X-ray crystallography and shown to be folded similarly to neuraminidase of subtype N2 isolated from a human influenza virus. This result demontrates that absence of immunological cross-reactivity is no measure of dissimilarity of polypeptide chain folding. Small differences in the way in which the subunits are organized around the molecular fourfold axis are observed. Insertions and deletions with respect to subtype N2 neuraminidase occur in four regions, only one of which is located within the major antigenic determinants around the enzyme active site.
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  • 66
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 90-110 
    ISSN: 0887-3585
    Keywords: compact units ; coefficient of compactness ; folding intermediates ; protein structural hierarchy ; primitive units ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The coefficient of compactness was recently introduced and used to locate domains in lysozyme and ribonuclease (Zehfus and Rose: Bio-chemistry 25:5759-5765, 1986). Nineteen additional proteins now have been analyzed by using this measure. Complete listings of compact units and plots showing their hierarchic organization are presented for all twenty-one proteins. Large compact units correspond well to protein domains; however, many smaller compact structures of equal or better compactness are also found. Since small compact units could represent subdomains or protein-folding intermediates, their structural composition is further examined.
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  • 67
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 118-129 
    ISSN: 0887-3585
    Keywords: homologous proteins ; hydropathy index ; chain flexibility ; α/β barrels ; tryptophan ; synthase aplha subunit ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The amino acid sequences of the α subunits of tryptophan synthase form ten different microorganisms were alingned by standard procedures. The α helics, β strands and turns of each sequence were predicted separately by two standard prediction algorithms and averaged at homologous sequence positions. Additional evidence for conserved secondary structure was derived form profiles of average hydropathy and chain flexibility values, leading to a joint prediction. There is good agreement between (1) predicted β strands, maximal hydropathy and minimal flexibility, and (2) predicted loops, great chain flexibility, and protein segments that accept insertions of various lengths in individual sequences. The α subunit is predicted to have eight repeated β-loop-α-loop motifs with an extra N-terminal α helix and an intercalated segment of highly conserved residues. This pattern suggests that the teritiary structure of the α subunit is an eightfold α/β barrel. The distribution of conserved amino acid residues and publilshed data on limited proteolysis, chemical modification, and mutagenesis are consistent with the α/β barrel structure. Both the active site of the α subunit and the combining site for the β2 subunit are at the end of the barrel formed by the carboxyl-termini of the β strands.
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  • 68
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 153-161 
    ISSN: 0887-3585
    Keywords: accessbility ; hydrophobic effect ; protein conformation ; Boltzmann statistics ; maximum likelihood ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Globular proteins fold into compact particles with interior amino acid residues shielded from the surounding aqueous environment. An early hypothesis holds that entropic hydophobic forces dirve this phenomenon. However, previous analyses based on a binary description of the accesible surfaces of amino acid residues in proteins did not support theis hypothesis. This report shows that a complete description of accessible surface areas is given by parametric distribution fuctions with three modes. The modes are formed by partitioning the available accessible surface area of the amino acids into three segments; the data for each segment are characterized by a mode-specific model. In the “repulsive” mode, probabilities of accessibility decrease exponentially with exposed surface area, as predicted by the hydrophobic hypothesis. A distinct “buried” mode is needed to account for an excess of residues at or near zero accessibility for most amino acids, consistent with the use of binary descriptions of accessibility. A third mode exists which is termed “near neutral” because it is described by a nearly uniform distribution of accessibility for the hydrophiliic amino acids. Empirical energies calculated for the repulsive mode correlate well with measured free energies of transfer of amino acids from water to organic solvents, while those from the buried mode correlate well with measured free energies of hydration of the side chains. Poor cross correlations between these energies give an explanation for the previous conflict in interpreting these data.
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  • 69
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 162-166 
    ISSN: 0887-3585
    Keywords: protein folding ; secondary structure prediction ; tertiary structure prediction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In recent years, the protein-folding problem has attracted the attention of molecular biologists. Efforts have focused on developing heuristic and energy-based algorithms to predict the three-dimensional structure of a protein from its amino acid sequence. We have applied a series of heuristic algorithms to the sequence of human growth hormone. A family of five structures which are generically right-handed fourfold α-helical bundles are found from an investigaion of ∼108 structures. A plausible receptor binding site is suggested. Independent crystallographic analysis confirms some aspects of these predictions. These methods only deal with the “core” structure, and conformations of many residues are not defined. Further work is required to identify a unique set of coordinates and to clarify the topological alternatives available to α-helical proteins.
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  • 70
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 130-152 
    ISSN: 0887-3585
    Keywords: amino acid hydophobicity scale ; QSAR ; amino acids ; peptide side chains ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The fragment method of calculation partition coefficients (P) has been extended to include the common amino acids (AAs). The results indicate that polar and charged side chains influence the hydrophobicity of atoms in the side chain in a predictable manner. Feild effects, as evidenced through polar proximity factors and bond factors, need to be considered for accurate estimation of transfer phenomena. The calculated log P and ΔG°′ values of the 20 AAs agree well with the observed values. Pro calculates to be more hydrophilic than the observed log P. Hydrophobicity scales for peptide side chain residues are compared and evaluated in terms of suitability. Calculated π values for nonpolar side chain residures agree well with the observed values; calculated values for uncharged polar side chain residues deviate by about 0.6 log units except for Gln and Cys; and polar side chain residues with charged side chains calculate as too hydorphilic. Reasons for the differences are explored. We also suggest that tightly bound water to polar moieties in amino acids and peptides may be transferred into the octanol phase during partitioning experiments. A quantitative methodology is persented which characterizes the thermodynamic partitioning of groups and individual atoms in amino acids and proteins.
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  • 71
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    Proteins: Structure, Function, and Genetics 2 (1987) 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 72
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 177-187 
    ISSN: 0887-3585
    Keywords: evolution ; protein structure ; nucleotide binding domain ; gene sequence ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The intron/exon organization of the human gene for glycogen phosphorylase has been determined. The segments of the polypeptide chain that corresponds to the 19 exons of the gene are examined for relationships between the three-dimensional structure to the protein and gene structure. Only weak correlations are observed between domains of phosphorylase and exons. The nucleotide binding domains that are found in phosphorylase and other glycolytic enzymes are examined for relationships between exons of the genes and structures of the domains. When mapped to the three-dimensional structures, the intron/exon boundaries are shown to be widely distributed in this family of protein domains.
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 188-201 
    ISSN: 0887-3585
    Keywords: NMR ; NOE ; protein conformation ; structure data base ; structure fragments ; modelling ; distance matrices ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A method to build a three-dimensional protein model from nuclear magnetic resonance (NMR) data using fragments from a data base of crystallographically determined protein structures is presented. The interproton distances derived from the nuclear Overhauser effect (NOE) data are compared to the precalculated distances in the known protein structures. An efficient search algorithm is used, which arranges the distancs in matrices akin to a Cα diagonal distance plot, and compares the NOE distance matrices for short sequential zones of the protein to the data base matrices. After cluster analysis of the fragments found in this way, the structure is built by aligning fragments in overlapping zones. The sequentially long-range NOEs cannot be used in the initial fragments search but are vital to discriminate between several possible combinations of different groups of fragments. The method has been tested on one simulated NOE data set derived from a crystal structure and one experimental NMR data set. The method produces models that have good local structure, but may contain larger global errors. These models can be used as the starting point for further refinement, e.g., by restrained molecular dynamics or interactive graphics.
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  • 74
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 167-176 
    ISSN: 0887-3585
    Keywords: icosahedral ; insect ; virus ; structure ; evolution ; nodavirus ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We report the first atomic resolution structure of an insect virus determined by single crystal X-ray diffraction. Black beetle virus has a bipartite RNA genome encapsulated in a single particle. The capsid contains 180 protomers arranged on a T = 3 surface lattice. The quaternary organization of the protomers is similar to that observed in the T = 3 plant virus structures. The protomers consist of a basic, crystallographically disordered amino terminus (64 residues), a β-barrel as seen in other animal and plant virus subunits, an outer protrusion composed predominantly of β-sheet and formed by three large insertions between strands of the barrel, and a carboxy terminal domain composed of two distorted helices lying inside the shell. The outer surfaces of quasi-threefold related protomers form trigonal pyramidyl protrusions. A cleavage site, located 44 residues from the carboxy terminus, lies within the central cavity of the protein shell.The structural motif observed in BBV (a shell composed of 180 eight-stranded antiparallel β-barrels) is common to all nonstatellite spherical viruses whose structures have so far been solved. This highly conserved shell architecture suggests a common origin for the coat protein of spherical viruses, while the primitive genome structure of BBV suggests that this insect virus represents an early stage in the evolution of spherical viruses from cellular genes.
    Additional Material: 6 Ill.
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  • 75
    ISSN: 0887-3585
    Keywords: myosin light chain kinase ; trace acetylation ; label selection ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A method is described for rapidly surveying the effects of modifying individual amino acid residues of a protein on its ability to interact specifically with another macromolecule. The procedure has been used to examine the individual roles of the seven lysyl residues of calmodulin in its ability to bind to smooth muscle myosin light chain kinase; previous studies by Jackson et al. (J. Biol. Chem. 261:1226-12232, 1986) have suggested that certain lysines may be located close to the interaction site. Trace [3H]-acetylated calmodulin, consisting predominantly of molecules acetylated at single sites together with unmodified protein, was incubated in excess (five- to 20-fold) with smooth muscle MLC kinase to allow the modified and unmodified molecules to compete for binding to the enzyme. Subsequently, the calmodulin-enzyme complex was separated from unbound calmodulin, and the level of acetylation of each of the seven lysines of the bound fraction of calmodulin was determined and compared to that of each corresponding group of the starting preparation. Significant changes were found at only two of the lysines, 21 and 75, where the extent of acetylation in the bound fraction was three- and fivefold lower, respectively, than that in the original preparation. These results were reproducible in three separate selection experiments employing both chicken and turkey gizzard MLC kinase. It is concluded that acetylation of calmodulin at either lysine 21 or 75 markedly reduces its affinity for MLC kinase, but acetylation at any of the other lysines (13, 30, 77, 94, or 148) has only minor effects. This finding supports the proposal that the face of the central helix containing lysine 75 is involved in interaction with MLC kinase and suggests also that additional contact near Ca2-binding site 1 occurs.
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  • 76
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 210-224 
    ISSN: 0887-3585
    Keywords: protein folding ; circular dichroism ; protein secondary structure ; heuristic prediction of protein structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The tertiary structure of the α-subunit of tryptophan synthase was proposed using a combination of experimental data and computational methods. The vacuum-ultraviolet circular dichroism spectrum was used to assign the protein to the α/β-class of supersecondary structures. The two-domain structure of the α-subunit (Miles et al.: Biochemistry 21:2586, 1982; Beasty and Matthews: Biochemistry 24:3547, 1985) eliminated consideration of a barrel structure and focused attention on a β-sheet structure. An algorithm (Cohen et al.: Biochemistry 22:4894, 1983) was used to generate a secondary structure prediction that was consistent with the sequence data of the α-subunit from five species. Three potential secondary structures were then packed into tertiary structures using other algorithms. The assumption of nearest neighbors from second-site revertant data eliminated 97% of the possible tertiary structures; consideration of conserved hydrophobic packing regions on the β-sheet eliminated all but one structure. The native structure is predicted to have a parallel β-sheet flanked on both sides by α-helices, and is consistent with the available data on chemical cross-linking, chemical modification, and limited proteolysis. In addition, an active site region containing appropriate residues could be identified as well as an interface for β2-subunit association. The ability of experimental data to facilitate the prediction of protein structure is discussed.
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  • 77
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 225-235 
    ISSN: 0887-3585
    Keywords: allosteric ; tissue-specific isozymes ; protein structure ; AMP ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Glycogen phosphorylases catalzye the regulated breakdown of glycogen to glucose-1-phosphate. In mammals, glycogen phosphorylase occurs in three different isozymes called liver, muscle and brain after the tissues in which they are prefer entially expressed. The muscle isozyme binds and is activated cooperatively by AMP. In contrast, the liver enzyme binds AMP noncooperatively and is poorly activated. The amino acid sequence of human liver phosphorylase is 80% identical with rabbit muscle phosphorylase, and those residues which contact AMP are conserved. Using computer graphics software, we replaced side chains of the known rabbit muscle structure with those of human liver phosphorylase and interpreted the effects of these changes in order to account for the biochemical differences between them. We have identified two substitutions in liver phosphorylase potentially important in altering the cooperative binding and activation of this isozyme by AMP.
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  • 78
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 290-297 
    ISSN: 0887-3585
    Keywords: mutants ; structural function relationships ; protein folding and stability ; catalysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Uniquely among class A β-lactamases, the RTEM-1 and RTEM-2 enzymes contain a single disulfide bond between Cys 77 and Cys 123. To study the possible role of this naturally occurring disulfide in stabilizing RTEM-1 β-lactamase and its mutants at residue 71, this bond was removed by introducing a Cys 77 → Ser mutation. Both the wild-type enzyme and the single mutant Cys 77 → Ser confer the same high levels of resistance to ampicillin in vivo to Echerichia coli; at 30°C the specific activity of purified Cys 77 → Ser mutant is also the same as that of the wild-type enzyme. Also, neither wild-type enzyme nor the Cys 77 → Ser mutant is inactivated by brief exposure to p-hydroxymercuri-benzoate. However, above 40°C the mutant enzyme is less stable than wild-type enzyme. After introduction of the Cys 77 → Ser mutation, none of the double mutants (containing the second mutations at residue 71) confer resistance to ampicillin in vivo at 37°C; proteins with Ala, Val, Leu, Ile, Met, Pro, His, Cys, and Ser at residue 71 confer low levels of resistance to ampicillin in vivo at 30°C. The use of electrophoretic blots stained with antibodies against β-lactamase to analyze the relative quantities of mutant proteins in whole-cell extracts of E. coli suggests that all 19 of the doubly mutant enzymes are proteolyzed much more readily than their singly mutant analogues (at Thr 71) that contain a disulfide bond. Thus, the disulfide bond of the RTEM-1 β-lactamase seems able to reduce the destabilizing effect of mutations at Thr 71. These results also emphasize the unique and essential role that Thr 71 performs in the stable folding of RTEM-1 β-lactamase and presumably the other class A β-lactamases.
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  • 79
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 298-307 
    ISSN: 0887-3585
    Keywords: α-bungarotoxin ; neurotropism ; rhabdo-virus ; α-subunit ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Peptides corresponding to portions of loop 2 of snake venom curare-mimetic neurotoxins and to a structually similar region of rabies virus glycoprotein were synthesized. Interaction of these peptides with purified Torpedo electric organ acetylcholine receptor was tested by measuring their ability to block the binding of 125I-labeled α-bungarotoxin to the receptor. In addition, inhibition of α-bungarotoxin binding to a 32-residue synthetic peptide corresponding to positions 173-204 of the α-subunit was determined. Neurotoxin and glycoprotein peptides corresponding to toxin loop 2 inhibited labeled toxin binding to the receptor with IC50 values comparable to those of nicotine and the competitive antagonist d-tubocurarine and to the α-subunit peptides with apparent affinities between those of d-tubocurarine and α-cobratoxin. Substitution of neurotoxin residue Arg37, the proposed counterpart of the quatenary ammonium of acetylcholine, with a negatively charged Glu residue reduced the apparent affinity about 10-fold. Peptides containg the neutotoxin invarint residue Trp29 had 10- to 100-fold higher affinites than peptides lacking this residue. These results demonstrate that relatively short synthetic peptides retain some of binding ability of the native protein from which they are derived, indicating that such peptides are useful in the study of proetin interactions. The ability of the peptides to compete α-bungarotoxin binding to the receptor with apparent affinites comparable to those of other cholinergic ligands indicates that loop 2 of the neurotoxins and the strucually similar segment of the rabies virus glycoprotein act as recognition sites for the acetylcholine receptor. Invarient toxin residues Arg37 and Trp29 and their viral homologs play important, although not essential, roles in binding, possibly by interaction with complementary anionic and hydrophobic subsites on the acetylcholine receptor. The α-subunit peptide most likely contains all of the determinants for binding of the toxin and glycoprotein peptides present on the α-subunit, because these peptides bind to the 32-residue α-subunit peptides with the same or greater affinity as to the intact subunit.
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  • 80
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 308-329 
    ISSN: 0887-3585
    Keywords: conformational dynamics ; normal mode analysis ; Young's modulus ; rigid structural elements ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The normal mode analysis of conformational fluctuation is carried out for a small globular protein, bovine pancreatic trypsin inhabitor. Results are analyzed mainly to reveal the mechanical construction of the protein molecule. We take dihedral angles, including peptide ω angles, as independent variables for the normal mode analysis. There are 306 such angles in this molecule. Motions in modes with frequencies lower than 120 cm-1 are showned to involve atoms in the whole protein molecule, and spatial change of displacement vectors is continues, i.e., those of atoms near in space are similar. To quantitate the observation of the continuity, a correlation function of direction vectors of atomic displacement is calculated. From this function we define a Quantity that is interpreted as the wave length of an equivalent elastic plane wave. From this Quantity we deduce eefective young's modulus for each mode. For the mode with the lowest frequency 4.4 cm-1, it terned out to be 0.8 × 109 dyn cm-2, the value two orders magnitude softer than, for instance, α-helices. Prompted by this observation, the four lowest frequency modes and also the harmonic motions in the thermal equilibrium are analyzed further mainly to detect relatively rigid structural elements in the molecule. From this analysis emerges a mechanical picture of the protein molecule that is made up of relatively rigid elements held together by very soft parts.
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  • 81
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 236-259 
    ISSN: 0887-3585
    Keywords: atomic probability distributions of proteins ; anisotropy and anharmonicity of motions in proteins ; multiple occupancy of atomic positions in proteins ; molecular dynamics simulation ; lysozyme ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Positional probability density functions (pdf) for the atomic fluctuations are determined from a molecular dynamics simulation for hen egg-white lysozyme. Most atoms are found to have motions that are highly anisotropic but only slightly anharmonic. The largest deviations from harmonic motion are in the direction of the largest rms fluctuations in the local principal axis frame. Backbone atoms tend to be more nearly harmonic than sidechain atoms. The atoms with the largest anharmonicities tend to have pdfs with multiple peaks, each of which is close to harmonic. Several model pdfs are evaluated on the basis of how well they fit probability densities from the dynamics simulations when parameterized in terms of the moments of the distribution. Gram-Charlier and Edgeworth perturbation expansions, which have been successful in describing the motions of small molecules in crystals, are shown to be inadequate for the distributions found in the dynamics of proteins. Multipeaked distribution functions are found to be more appropriate.
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  • 82
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 260-261 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 83
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    Proteins: Structure, Function, and Genetics 2 (1987) 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 84
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 263-272 
    ISSN: 0887-3585
    Keywords: picornavirus ; capsid structure ; homology ; sequence comparisons ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An attempt has been made to build a model of human rhinovirus 2 (HRV2) based on the known human rhinovirus 14 (HRV14) structure. HRV2 was selected because its amino acid sequence is known and because it belongs to the minor rhinovirus receptor class as compared to HRV14, which belongs to the major class. Initial alignment of HRV2 with HRV14 based on the primary sequence and the knowlege of the three-dimensional structure of HRV14 showed that most probable position of the majority of insertions and deletions occurred in the vicinity of the neutralizing immunogenic sites (NIm). Out of a total of 855 amino acids present in one copy of each of the capsid proteins VP1 through VP4 of HRV14, 411 are different between the two viruses. There are also 6 amino acids residues inserted and 14 residues deleted in HRV2 relative to HRV14. Examination of amino acid interactions showed several cases of conservation of function, e.g., salt bridges or the filling of restricted space. The largest variation amongst the residues lining the canyon, the putative receptor binding site, was in the carboxy-terminal residues of VP1.
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  • 85
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 273-282 
    ISSN: 0887-3585
    Keywords: protein-DNA interactions ; hydroxylamine mutagenesis ; dimerization ; protein structure-function ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: EcoRI endonuclease mutants were isolated in a methylase-deficient background following in vitro hydroxylamine mutagenesis of plasmid pKG2 (Kuhn et al.: Gene 44:253-263, 1986). Mutants which survived high-level endonuclease expression (IPTG induction) were termed null mutants. Sixtytwo of 121 null mutants tested by Western blot contained normal levels of endonuclease cross-reacting protein. The complete endonuclease gene was scquenced for 27 null mutants. This group was found to consist of 20 signle base-change missense mutations, 6 double mutations, and 1 triple mutation. Ten of the 20 signle mutations were clustered between residues 139 and 144. When examined with respect to the structure of the EcoRI-DNA complex (McClarin et al.: Science 234:1526-1541, 1986), these alterations werre found to fall predominantly into two classes: substitutions at the protein-DNA interface or substitutions at the protein-protein (dimer) interface. Protein from several of the mutants was purified and sized by using HPLC. Wild-type EcoRI endonuclease and protein from three of the DNA interface mutations (A1a139→Thr, Gly140→Ser, Arg203→Gln) appeared to be dimeric, while protein from subunit interface mutations (Glu144→Lys, Glu152→Lys, Gly210→Arg) migrated as monomers.
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  • 86
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 283-289 
    ISSN: 0887-3585
    Keywords: bent DNA ; electrostatics ; base-pair rolls ; finite difference calculations ; gene activation ; DNA-protein complex ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two observations suggest that DNA, upon binding to E. coli catabolite gene activator protein (CAP), is sharply bent by a total angle of at least 100-150 degrees: (1) The electrostatic protential field of CAP shows regions of positive potential that from a ramp on 3 sides of the protein. (2) The DNA binding site size as determined by DNA ethylation interference with binding, (Majors: “Control of the E. coli Lac Operon at the Molecular Level.” Ph.D. Thesis, Harvard University, Cambridge, 1977) and by relative affinities of DNA fragments of various lengths (Liu-Johnson et al.: Cell 47:995-1005, 1986) requires severe bending of the DNA to maintain its favorable electrostatic contact with the protein.
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  • 87
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 330-339 
    ISSN: 0887-3585
    Keywords: van der Waals radii ; conformation ; amino acid residue ; dipeptide approximation ; molecular modeling ; systematic conformationl search ; N-alkyl amino acid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Effective van der Waals radii were celebrated in such a way that molecular models built from standard bond lengths and bond angels reproduced the amino acid conformations observed by crystallography in proteins and peptides. The celebrations were based on the comparision of the Ramachandbran plots prepared from high-resolution X-ray data of protins and peptides with the allowed φ,ψ torsional angel space for the depeptide molecular models. The celebrated radii are useful as criteria with which to filter energetically improbable conformations in molecular modeling studies of proteins and peptides.
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  • 88
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 340-358 
    ISSN: 0887-3585
    Keywords: artificial intelligence ; expert systems ; constraint satisfaction ; protein solution structure ; PROTEAN ; Nuclear Overhauser Effect ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A new method for the analysis of NMR data in terms of the solution structure of proteins has been developed. The method consists of two steps: first systematic search of the conformational space to define the region allowed by the initial set of experimental constraints, and second, the narrowing of this region by the introduction of aaditional constraint and optional refinement procedures. The search of the conformational space is guided by heuristics to make it computationally feasible. The method is therfore called the heuristic refinement method and is coded in an expert system called PROTEAN. The paper describe the validation of the first step of the method using an artificial NMR data set generated from the known crystal structure of sperm whale carbon monoxymyoglodin. It is shown that the initial search procedure yields a low-resolution structure of the myoglobin molecule, accurately reproducing its main topological features, and that the precision of the structure depend on the quality of the intial data set.
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  • 89
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    Biotechnology and Bioengineering 29 (1987), S. 187-194 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Let us consider the modeling of a cascade reactor for the production of ethanol. The rates of reaction in alcoholic fermentation are modeled so that it can assume both ethanol and substrate inhibition, in relation to the observed results.A nonstructured model, based on biomass, substrate, and ethanol concentrations, is developed and identified. It is a complex model, this being due to the nonlinearity between the specific rate of ethanol production and the growth rate and, on the other hand, the study of the static optimization of ethanol fermentation is performed.
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  • 90
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    Biotechnology and Bioengineering 29 (1987), S. 421-428 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments using Pichia yeast grown on n-paraffins have been conducted in laboratory 10-L airlift fermenters and in a 640-L module of commercial scale. Results confirmed the design concept of combining oxygen transfer and fermenter cooling with low-pressure air. However, in the absence of mass transport constraints, the build up of toxic factors in the fermenter appeared to be a major variable limiting cell productivity. Foaming in the large fermenter also presented a serious problem, which must be solved before low-pressure airlift fermenters become practical.
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  • 91
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The suitability of using annually grown, carrot-sized buffalo gourd (Cucurbita foetidissima) roots as a feedstock for alcoholic fermentation was explored. Roots grown in 1982 and 1983 were slurried, dextrinized and saccharified using Takatherm™ and Diazyme™ (commercial enzymes manufactured by Miles Laboratories), and fermented by the action of Saccharomyces cerevisiae. These processes were monitored in detail and results were compared with those displayed by controls formulated using potato tubers. The preparation of gourd root slurries with suitable viscosity characteristics for enzymatic digestion required the addition of water (at least 50% by weight) which reduced the proportion of fermentable sugars in the resulting saccharified suspensions. The resulting slurries were well-suited to enzymatic conversion of starch to sugar. Estimates of enzymatic efficiency in gourd root suspensions did not suggest the presence of naturally occurring amylase or glucosidase inhibitors in these plant materials. Saccharified gourd root mashes supported yeast growth well and produced ethanol yields at 82.2-86.5% of the theoretically maximum efficiency.
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  • 92
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    Biotechnology and Bioengineering 29 (1987), S. 476-481 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Available electron methods are presented and used to estimate theoretical energetic growth yields for photoautotrophic, mixotrophic, and photoheterotrophic growth of algae and photosynthetic bacteria. The theoretical yields are compared to experimental values reported previously. For photoautotrophic and mixotrophic growth of algae experimental values that approach and even exceed the theoretical values have been reported in the literature. For photosynthetic bacteria experimental yields are much smaller than thetheoretical maximum values.
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  • 93
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    Biotechnology and Bioengineering 29 (1987), S. 488-492 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We describe a first-principles analysis of a system for the continuous culture of the green alga Scenedesmus obliquus under light-limiting conditions. According to this analysis, the productivity of the algal culture is given by the relation Y = EmI0AK(1 - e-αcl) - GRcV, where Y = yield (g cells/h), Em = 0.20 (the maximum attainable photosynthetic conversion on an energy basis), A = illuminated area (m2), K = 0.156[(g cells/h/W), the energy equivalent of the algae], I0 = light intensity (W/m2), α = extinction coefficient (L/cm/g),c = cell concentration (g/L), I = light path (cm), R = respiration rate (g carbon/g cells/h), V = culture volume (L), and G = ratio of g cells to g carbon (2.04). This formula is completely determined and has no free adjustable parameters. Using parameter values determined independently, the model accurately predicted the relationship of productivity to cell density in the culture system.
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  • 94
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    Biotechnology and Bioengineering 29 (1987), S. 513-519 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Temperature shifting was investigated as a means of improving cloned-gene product yields form a recombinant Escherichia coli containing the temperature-sensitive plasmid, pOU 140. In a series of shaker flask fermentations recombinant cells were thermally induced for different time periods. The growth, stability, and plasmid product levels were followed, and the results indicate the existence of an induction time period that maximizes product yield. A sustained thermal induction results in recombinant cell death and instability, while exposure to a runaway temperature for minimal time periods does not give sufficiently high product yields. At intermediate cycling times, however, the recombinant cells remain stable, and the plasmid replication region is activated, resulting in higher product yields.
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  • 95
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    Biotechnology and Bioengineering 29 (1987), S. 747-752 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to carry out an effective enzyme reaction, the preparation of soluble-insoluble immobilized enzyme was investigated. Proteases were selected as model enzymes, and their immobilization was carried out by using an enteric coating polymer as a carrier. Among the polymers tested, methacrylic acid-methylacrylate-methylmethacrylate copolymer (MPM-06) gave the most active soluble-insoluble immobilized papain. This immobilized papain showed insoluble from below pH 4.8 and soluble form above pH 5.8; it was also soluble in water-miscible organic solvent. It was reusable and more stable with heat and water-miscible organic solvents than native proteases. Furthermore, various proteases could be immobilized by using MPM-06 with high activity. Chymotrypsin immobilized by this method catalyzed the effective peptide synthesis in a heterogeneous reaction system containing water-miscible organic solvent.
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  • 96
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 657-671 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model for radial flow mammalian cell culture has been developed. Two situations, one with permeable hollow fibers and the other with a porous matrix in the annulus, were considered. The hollow fibers were modeled as continuously distributed sinks. Numerical solutions are presented for the complete model as well as limiting analytical solutions. The analysis identified the importance of various kinetic, transport, and design dimensionless groups for maintenance of radial flow cell culture systems under uniform conditions. The important design parameter was the depth of the bed and the important operating parameter was a modified Damkohler number, both of which should be maintained low for gradient free systems. Dispersion was included in the analysis but substrate consumption was relatively independent of dispersion. Preliminary separation of a low-and high-molecular-weight product was also modeled, and shown to be strongly dependent on the permeability of the fibers, as well as the aspect ratio and the magnitude of the transmembrane flux.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 672-678 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cycling in feed substrate concentration and dilution rate is examined as a means of modifying the final fate of a mixed culture. It is shown for the case where the specific growth rate of one species is always greater than that of the second that no cycling strategy will provide the desired extinction of the faster growing species unless time delay is included in the modeling. To account for the time lag in adjusting organism metabolic activities to environmental changes, an adaptability parameter is introduced. Numerical simulations are carried out and an operating diagram indicating the conditions under which the desired extinction occurs is constructed. Cycling in feed substrate concentration and dilution rate are both found to produce the desired result.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 679-689 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 690-695 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It has been demonstrated that Thiobacillus denitrificans may be readily cultured aerobically in batch and continuous flow reactors on H2S(g) under sulfide limiting conditions. Under these conditions sulfide concentrations in the culture medium were less than 1μM resulting in very low concentrations of H2S in the reactor outlet gas. Biomass yield under aerobic conditions was much lower than previously reported for anaerobic conditions, presumably because of oxygen inhibition of growth. However, biomass yield was not affected by steady state oxygen concentration in the range of 45μM-150μM. Biomass yield was also observed to be essentially independent of specific growth rate in the range of 0.030-0.053 h-1. Indicators of reactor upset were determined and recovery from upset conditions demonstrated. Maximum loading of the biomass for H2S oxidation under aerobic conditions was observed to be 15.1-20.9 mmol/h/g biomass which is much higher than previously reported for aerobic conditions. Other aspects of the stoichiometry of aerobic H2S oxidation are also reported.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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