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  • 1990-1994  (3)
  • Semiconductor  (1)
  • Ultrastructure  (1)
  • pharmacokinetics  (1)
  • 1
    ISSN: 1432-2145
    Keywords: Cytoplasmic male sterility ; Ultrastructure ; Mitochondria morphometry ; Beta vulgaris L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of microspore mother cells (MMC) and tapetum in male-fertile and male-sterile anthers of Beta vulgaris L. was compared at the electron microscope level. These studies were complemented by morphometric analyses of mitochondria in both tissues through successive stages of microsporogenesis. The earliest irregularities in the ultrastructure of male-sterile anthers were noted within the tapetum at the tetrad stage. These disturbances were initially expressed by a slight reduction in mitochondrial size and the appearance of concentric configurations of endoplasmic reticulum. As development proceeded, a further decrease in mitochondrial size become more conspicuous and was accompanied by a reduction in ribosome population and a failure of the tapetum to produce Ubisch bodies. This failure to produce Ubisch bodies is reflected in the underdevelopment of sterile microspore exine.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 69 (1994), S. 59-64 
    ISSN: 1432-0738
    Keywords: Key words Tetraethoxysilane ; Semiconductor ; Time course study ; Renal toxicity ; Blood silicon concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  To clarify the time course of toxicological effects of tetraethoxysilane [Si(OC2H5)4, TEOS] on the kidney and the relationship between blood silicon levels (Si-B) and the effects, 250 mg/kg or 500 mg/kg TEOS was intraperitoneally administered to ten 5-week-old male ICR mice (SPF grade) in each group, and morphological and functional changes of the kidney were assessed at 12 h, 24 h, 3 days and 2 weeks after administration of TEOS. Injury to tubular epithelial cells was observed in mice killed 12 and 24 h after administration, and its severity increased with increasing dosage. The mean values of blood urea nitrogen exhibited dose-related increase in mice sacrificed 24 h after the administration. The concentrations of Si-B increased in order of the administered doses of TEOS, and then decreased steadily. The results of Si-B were consistent with the concept that renal toxicity of TEOS is mediated by siliceous compounds. The kidney was recovering from injury 3 days after administration, and had developed tubulointerstitial nephritis, which could be regarded as repaired lesion of acute injury, by 2 weeks after administration.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1041
    Keywords: propranolol ; chronopharmacology ; exercise-induced tachycardia ; pharmacokinetics ; healthy volunteers ; gastio-intestinal absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Following a cross-over design propranolol 20 mg p.o. was given to 7 healthy subjects at 09.00 h and 21.00 h at an interval of 1 week. Heart rate (HR) during submaximal ergometer exercise was measured at four intervals during 10 h after treatment. Plasma propranolol concentrations were also determined. The suppressive effect (%R) of propranolol on the rise in HR during exercise after the morning dosage was significantly greater at 1.5 h and tended to be greater 3 h after administration than at comparable times in the evening trial. Mean plasma propranolol concentrations during the early phase were higher after the morning than the evening dose. The maximum plasma concentration (Cmax), area under the plasma concentration-time curve from 0 to 10 h (AUC (0–10)) and absorption rate constant (ka) were significantly greater after the morning dose. The time to maximum concentration (tmax) and elimination half-life (t1/2) of the morning and evening dosages did not differ. A significant correlation was observed between plasma propranolol concentration and %R in HR during exercise in the morning (r=0.74) and evening (r=0.63) trials, and the regression lines of the morning and evening treatments did not differ. The data indicate that the suppressive effect of propranolol on exercise-induced tachycardia was relatively greater after a morning than an evening dose; that propranolol was more rapidly absorbed from the gastrointestinal tract after the morning than the evening dosage; that diurnal changes in the activity of propranolol depend in part on the time of administration and its subsequent effect on plasma concentrations of the drug; and that the antagonist activity of propranolol relative to a given drug concentration may not differ between morning and evening treatments.
    Type of Medium: Electronic Resource
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