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881.
A systematic study of the effect of different ionic conditions on the morphology of the 25–30 nm chromatin fiber from chicken erythrocytes has revealed that, as the ionic strength is increased, knobby fibers with a clear superbead structure are formed in the presence of either Mg++ or Na+, or both. A further increase in ionic strength results in smooth chromatin fibers due to a tight packing of superbeads. Cross-linking such fibers with formaldehyde and reversal of the ionic conditions, demonstrates the superbead structures underlying the smooth fibers observed at high ionic concentrations. The average size of the superbeads is 34 nm along the length of the fibers, in agreement with the value found in embedded sea cucumber chromatin. A second class of superbeads has an average length of 25 nm and probably corresponds to partially disrupted structures. 相似文献
882.
Antonín Vězda 《Folia Geobotanica》1983,18(1):45-70
This paper deals with 19 species of foliicolous lichens collected in the summer months of 1977 to 1980 during several excursions to the vicinity of the spas Sochi, Gagra and Sukhumi on the east shores of the Black Sea (part of the Colchis). Some new taxa and one new combination are proposed:Raciborskiella minor Vězda (sp. n.),Porina colchica Vězda (sp. n.),Gyalectidium caucasicum (Elenk. etWoronich.)Vězda (comb. n.),G. colchicum Vězda (sp. n.),Bacidia vasakii Vězda (sp. n.). Taxonomical, ecological and plant geographical notes to all species are given. 相似文献
883.
884.
The embryotoxic potential of ochratoxin A and citrinin was studied after administering, either subgerminally or intraamniotically, single mounting doses of the mycotoxins to chicken embryos on days 2, 3, and 4. The beginning of the embryotoxicity dose range was found to be between 0.01 to 0.05 microgram for ochratoxin A and 1 to 10 micrograms for citrinin. The maximum response to both mycotoxins occurred after administration on day 3. In addition to significant growth retardation of fetuses, exencephaly, microphthalmia, cleft beak, reduction deformities of the limbs, and abdominal wall and ventricular septal defects were encountered on day 8 of incubation. When 4 micrograms of citrinin was constantly added to ochratoxin A administered in the dose range of 0.03 to 0.5 microgram, a strictly additive effect was seen. It may be supposed that citrinin produced together with ochratoxin A in some strains of Penicillium viridicatum Westling does not potentiate the clear-cut embryotoxic action of the latter mycotoxin. 相似文献
885.
A. Jordá M. Gomez J. Cabo S. Grisolía 《Biochemical and biophysical research communications》1982,106(1):37-43
Streptozotocin induced diabetes in rats increased the activities of the three mitochondrial enzymes, carbamylphosphate synthetase, ornithine transcarbamylase and N-acetylglutamate synthetase, but not of the cytosolic N-acetylglutamate deacylase. Levels of both N-acetylglutamate and arginine, which are activators of carbamylphosphate synthetase and N-acetylglutamate synthetase respectively, increased in diabetes. These results serve to explain the increase both of mitochondrial citrulline and urea formation in hepatocytes and the increased urea excretion in diabetes. 相似文献
886.
The possible presence and properties of the Ca2+-dependent K+ channel have been investigated in the Ehrlich ascites tumor cell. The treatment with ionophore A23187 + CA2+, propranolol or the electron donor system ascorbate-phenazine methosulphate, all of which activate that transport system in the human erythrocyte, produces in the Ehrlich cell a net loss of K+ (balanced by the uptake of Na+) and a stimulation of both the influx and the efflux of 86Rb. These effects were antagonized by quinine, a known inhibitor of the Ca2+-dependent K+ channel in other cell systems, and by the addition of EGTA to the incubation medium. Ouabain did not have an inhibitory effect. These results suggests that the Ehrlich cell possesses a Ca2+-dependent K+ channel whose characteristics are similar to those described in other cell systems. 相似文献
887.
The effects of insulin, cortisol, prolactin, 3,3',5-triiodo-L-thyronine (L-T3) and progesterone on the synthesis of total protein and casein in mammary explants from pregnant goats were studied. In the absence of hormones and in the presence of insulin plus cortisol the rate of incorporation of 14C-leucine into proteins that were precipitated with the anti-casein antibody decreased during culture. The addition of prolactin to hormonal combination of insulin and cortisol caused large stimulation of rates of casein synthesis. Maximum incorporation of leucine was attained between 3 and 5 days of culture in the presence of 0.5 microgram ml-1 of prolactin. Prolactin stimulated-casein and total protein synthesis were not consistently affected by the addition of L-T3 or progesterone. The inhibition of DNA synthesis by hydroxyurea or cytosine-arabinofuranoside had no effect on casein synthesis in mammary explants from pregnant goats. 相似文献
888.
The binding properties of 25 beta-lactam antibiotics to Bacillus megaterium membranes have been studied. The affinities of the antibiotics for the penicillin-binding proteins (PBPs) are also reported. We found that PBP 4 has the highest affinity for nearly all the antibiotics studied whereas PBP 5 has the lowest affinity. Both PBP 4 and PBP 5 appear to be dispensable for the maintenance of bacterial growth and survival and appear to be DD-carboxypeptidases. Only the beta-lactam cefmetazol bound preferentially to PBP 5 and has been used to study the inhibition of DD-carboxypeptidase. Comparative studies with beta-lactam that simultaneously result in (a) binding to PBPs 1 and 3, (b) inhibition of cell growth and (c) lysis, stressed the importance of PBPs 1 and 3 for cell growth and survival. 相似文献
889.
Wiedemann-Beckwith syndrome: clinical, cytogenetical and radiological observations in 39 new cases. 总被引:3,自引:0,他引:3
R Martínez y Martínez R Martínez-Carboney R Ocampo-Campos H Rivera J Gómez Plascencia y Castillo A Cuevas M C Martín Manrique 《Genetic counseling (Geneva, Switzerland)》1992,3(2):67-76
Thirty-nine patients (82% under 1 year of age) with Wiedemann-Beckwith syndrome (WBS) were prospectively studied. To evaluate the somatometric data the normal range was set out at mean +/- 2 SD. The relevant physical findings were a characteristic face, non increased mean height and weight, normal head circumference, defective abdominal wall, a predominance of the upper segment, and tibial bowing. Mental retardation was documented in 5 cases but in only 1 it was related to hypoglycemia. The 32 cases karyotyped were normal. Since neonatal hypoglycemia is frequent (34.3% in our series) and potentially deleterious for the CNS we propose to monitor the glycemia every 6 h during the first 3 days in WBS newborns in order to correct glycemia below of 2.6 mmol/l (46.8 mg/dl) according to recent studies. The comparison with previous large series enabled us to precise the frequency, onset and evolution of the main stigmata. 相似文献
890.
1H-Pyrrolo[2′,3′:4,5]furo[3,2-c]pyridine-2-carboxylic acid (6a) and its 1-methyl (6b) and 1-benzyl (6c) derivatives were synthesized. 3-(5-Methoxycarbonyl-4H-furo[3,2-b]-pyrrole-2-yl)propenoic acid (1) was converted to the corresponding azide 2, which in turn was cyclized to give 3 by heating in diphenylether. The pyridone 3 obtained was aromatized with phosphorus oxychloride, then reduced with zinc in acetic acid to give methyl 1H-pyrrolo[2′,3′:4,5]furo[3,2-c]pyridine-2-carboxylate (5), which by hydrolysis gave the corresponding carboxylic acid 6a. 相似文献