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PubMed1975

Fungal fimbriae. I. Structure, origin, and synthesis.

Fine hair-like appendages on the cell walls of the another smut Ustilago violacea are described. These hairs are termed fimbriae because of their close similarity to the fimbriae (pili) found on certain Gram-negative bacteria. Cells of U. violacea may carry more than 200 fimbriae varying in length from about 0.5 mum to over 10 mum, and having a diameter of about 60-70 A. Some fimbriae produce knobs similar to those found on bacterial sex fimbriae. Log-phase cells are the most densely fimbriated, while stationary phase cells are devoid of fimbriae. The cells can be defimbriated by sonication, high-speed agitation, or centrifugation through a 40% sucrose solution. The fimbriae can regenerate in these defimbriated cells in about 1 h. This regeneration is inhibited by both cycloheximide and rifampin, but not by chloramphenicol and therefore appears to depend on de novo protein synthesis on cytoplasmic ribosomes. Similar long fimbriae are found on U. maydis and Leucosporidium (Candida) scottii. Short fimbriae, about 0.5 mum long, were found on all the other species of yeast-like fungi examined (Rhodotorula, Saccharomyces, Schizosaccharomyces, Hansenula, Lipomyces, Nadsonia, and Torulopsis spp.).

Cell Wall↗
PubMed1984

Extracellular calcium ion depletion induces release of glycoproteins by canine trachea.

The effect of depletion of extracellular Ca2+ on the release by canine trachea in vitro of [14C]glucosamine-labeled trichloroacetic-phosphotungstic acid-precipitable glycoproteins was evaluated. Incubation in Ca2+,Mg2+-free medium containing ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA, 10(-3) to 10(-5) M) induced a time-dependent increase in base-line release of high molecular weight, radiolabeled glycoprotein that was not blocked by 10(-5) M atropine, propranolol, or phentolamine. Maximal increase was proportional to EGTA concentration and was augmented by preincubation with methacholine chloride. The secretory response was reversed by reincubation of explants in medium containing Ca2+, Sr2+, or Ba2+ but not Mg2+. Assessment of explants denuded of epithelium or cartilage indicated that the secretory response to depletion of Ca2+ originated in the tracheal submucosa, probably the submucosal glands. Quantitative autoradiographic analyses showed, however, that incubation in Ca2+,Mg2+-free medium had no effect on radiolabel release from mucous or serous cells in the tracheal submucosal glands. Increased radiolabeled glycoprotein release in Ca2+,Mg2+-free medium was accompanied by exfoliation of the surface epithelium, though the two effects were apparently unrelated. The secretory response was not due to cell lysis or increased release of radiolabeled glycosaminoglycans, and the finding that the specific activity (ratio of bound radiolabel to protein content) of the glycoprotein released was not changed in Ca2+,Mg2+-free medium showed that it was not due to a change in the rate of glycoprotein synthesis. A model is proposed in which depletion of Ca2+ increases the rate of flow of mucus from the duct lumens of the tracheal glands.

Animals↗
PubMed1994

Presence or absence of glycogen-beta particles in sinoatrial node cells.

The sinoatrial node is formed by specialized cells, the main ultrastructural differences of which, as compared with ordinary atrial myocardium, are a pale cytoplasm and sparse myofibrils. Moreover, nodal cells have been described to contain large amounts of glycogen particles in their pale cytosol; these glycogen inclusions are often used as the main criterion for identifying nodal cells. Nevertheless, the presence of glycogen cytosolic inclusions has been discussed by several authors. This paradox was solved by the description of some undesirable effects of uranyl acetate when used en bloc. To prove the presence of glycogen granules in nodal cells and the effects of uranyl acetate en bloc, we performed an ultrastructural study of the sinoatrial node in rats of different ages using different staining techniques. Our results do not reveal any beta-particles in nodal cells in tissues processed by either general or glycogen-specific methods. Uranyl acetate staining did not cause any change of appearance in the nodal or ordinary myocardium. From these results, one could conclude that, on the one hand, sinoatrial nodal cells do not show deposits of beta-particles of glycogen which can be detected with ultrastructural techniques, and, on the other hand, that uranyl acetate does not cause any morphological artifacts.

Aging↗
PubMed1995

Fine structure of the epidermal basement membrane of the lip: applications of dithiothreitol separation and ultrathin frozen sectioning.

The fine structure of the epidermal basement membrane at the electron-microscopic level has already been defined. To obtain more details, two techniques, dithiothreitol separation and ultrathin frozen sectioning, were applied either alone or in combination. Negatively stained ultrathin sections showed a much thicker lamina densa than ordinary plastic-embedded sections. In the lamina lucida, bridging filaments and subbasal dense plates were observed in negative images. After the treatment with dithiothreitol, the lamina densa could be peeled off mechanically from the underlying dermis, and the anchoring fibrils were pulled off the dermis, preserving the connection with the lamina densa. With this specimen, bundles of anchoring fibrils were observed clearly and their lengths could be measured. Negatively stained ultrathin sections of dithiothreitol-separated specimens showed the fine structure of the lamina lucida. Bridging filaments in the lamina lucida were resolved by negative staining.

Animals↗
PubMed1984

Ultrastructure of human eosinophils genetically lacking peroxidase.

The structure of human eosinophils genetically lacking peroxidase is described. Structural changes were discerned in the specific granules of the deficient eosinophils as compared to normal eosinophils. Apart from the inhibition of peroxidase formation, this mutation also affects the structure of the specific granules - primarily the interrelationship between the matrix and the core.

Cytoplasmic Granules↗
PubMed1996

Simplified model of krypton laser-induced thrombotic distal middle cerebral artery occlusion in spontaneously hypertensive rats.

BACKGROUND AND PURPOSE: The effects of thrombotic occlusion of the middle cerebral artery on compromised ischemic tissue may be different from and more severe than those of cerebral ischemia induced by mechanical occlusion of the artery. Photothrombosis, which is based on photochemical damage to the endothelium and subsequent platelet aggregation, is an efficient method to induce thrombosis in vivo. This study aimed to improve and simplify this unique method for an ischemia model of middle cerebral artery occlusion in rats. METHODS: Male spontaneously hypertensive rats (5 to 6 months old, 300 to 450 g) were anesthetized with halothane, endotracheally intubated, and mechanically ventilated. A krypton laser operating at 568 nm was used to irradiate the exposed distal middle cerebral artery with an intact dura above the rhinal fissure. The photosensitizing dye rose bengal (20 mg/kg body wt) was administered intravenously over 90 seconds starting simultaneously with 4 minutes of laser irradiation at a power of 20 mW to cause thrombotic occlusion of this artery. RESULTS: The irradiated middle cerebral artery was completely occluded by intraluminal thrombi within 3 minutes after simultaneous laser irradiation and rose bengal infusion. Thrombosed materials were not stained by phosphotungstic acid-hematoxylin stain (ie, aggregated platelets lacked apparent fibrin). The mean volume of 3-day-old infarction, indicated by the lack of staining with 2,3,5-triphenyltetrazolium chloride, was 84.8 +/- 17.4 mm3 (mean +/- SD, n = 6). CONCLUSIONS: We demonstrated a reproducible and minimally traumatic model of brain infarction induced by the thrombotic distal middle cerebral artery occlusion in rats.

Animals↗
PubMed1998

Two-kidney, two clip renovascular hypertensive rats can be used as stroke-prone rats.

BACKGROUND AND PURPOSE: The cerebrovascular lesions in stroke-prone spontaneously hypertensive rats are not only dependent on high blood pressure but partly related to pressure-independent genetic factors. The aim of the present study was to observe whether spontaneous stroke occurred in renovascular hypertensive rats without a genetic deficiency. METHODS: The 1-kidney, 1 clip (1k1c); 2-kidney, 1 clip (2k1c); and 2-kidney, 2 clip (2k2c) methods were used to induce hypertension in male Sprague-Dawley rats with a ring-shaped silver clip. Sham-operated rats were used as controls. Blood pressure and neurological symptoms were observed in the rats without any artificial inducement. Brain sections stained with hematoxylin-eosin and phosphotungstic acid-hematoxylin were examined under a microscope to determine stroke foci. RESULTS: The attack rate of stable hypertension was 100% (55/55) in the 2k2c group, which was significantly higher than that in the 1k1c (23/30, 76.7%) and 2k1c (21/30, 70%) groups (P<0.01). None of the rats in the 2k2c group died of acute renal failure or suffered from diffuse cerebral lesions postoperatively. Forty weeks after renal artery constriction, the incidence of spontaneous stroke in the 2k2c group was 61.8% (34/55), which was significant higher than that in the 1k1c (7/30, 23.3%) and 2k1c (5/30,16.7%) groups (P<0.01). Stroke foci were not observed in normotensive controls. CONCLUSIONS: We conclude that 2k2c renovascular hypertensive rats with proper renal artery constriction can be used as stroke-prone renovascular hypertensive rats independent of a genetic deficiency.

Animals↗