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131.
In the present study, “in vitro” evidences are shown for the existence of a highly active 3α-hydroxysteroid dehydrogenase in the crude cytosol of rat muscle homogenates; the use of 5α-dihydrotestosterone (DHT) is therefore compromised in receptor binding measurements because of its extensive metabolism. The synthetic anabolic androgen, methyltrienolone (MT) palliates this disadvantage of DHT. Both steroids, as well as testosterone, appear to be bound to an 8–8.5 S androgen receptor on sucrose density gradient. The androgen receptor in the vastus and the levator ani bulbocavernosus complex (LA/BC) shows similar association constants, but the number of binding sites in LA/BC is about 5 times higher than in vastus. Otherwise, the total number of muscle androgen receptors seems to be invariant in adult and aged rats. The binding to these macromolecules can thus be measured “in vitro” provided specific and sensitive methods are utilized. 相似文献
132.
van Onckelen Henri A.; Caubergs Roland; de Greef Jan A. 《Plant & cell physiology》1977,18(5):1029-1040
The influence of light and endogenous plant-growth regulatorson the evolution of - and ß-amylases in cotyledonsof Phaseolus vulgaris L. was investigated. Both enzymes, whichare not present in ungerminated seeds, appear during germinationof intact seedlings or incubation of excised cotyledons. -Amylaseactivity decreases upon exposure to light. This inhibition iscorrelated with a drastic increase in chlorophyll content anda change in the endogenous gibberellin-inhibitor balance. ß-Amylaseactivity was not affected by light treatment but was by thepresence of endogenous cytokinins. (Received February 3, 1977; ) 相似文献
133.
Fabrice Rebeille Richard Bligny Roland Douce 《Archives of biochemistry and biophysics》1982,219(2):371-378
In view of the importance of Pi in the control of cell metabolism, it was of interest to study the mechanism and regulation of Pi uptake by Acer pseudoplatanus cells grown as cell suspensions. At low external Pi concentrations up to 10 mm, sycamore cells incorporate phosphate against a concentration gradient, by a process which is energy dependent. Under these conditions the intracellular Pi concentration is maintained constant (2–3 mm). On the contrary at high external Pi concentrations, higher than that which counterpoises the cytoplasmic Pi concentration (approximately 10 mm), Pi enters the cell by slow diffusion and the intracellular Pi concentration increases continuously as the extracellular Pi concentration increases from 15 to 50 mm. When sycamore cells are transferred to a phosphate-deficient medium, growth slows down considerably and ceases after 4–5 days. During this time, intracellular Pi concentration falls from 3 to 0.1 mm and phosphate esters from 8 to 2 mm. Phosphate starvation stimulates the uptake indicating that phosphate uptake depends on the intracellular phosphate and/or cytoplasmic ester-P pool. Pi uptake by Pi-starved cells is strongly dependent on the pH of the medium. 相似文献
134.
Asher I. Sapolsky Michael F. Sheff Kunio Matsuta David S. Howell Roland W. Moskowitz Victor M. Goldberg David P. Norby Charles J. Malemud 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1983,762(2):227-231
In addition to releasing collagenase and proteoglycanase activity, rabbit articular chondrocytes in monolayer culture released into the culture medium, latent, neutral enzyme activity which when activated by p-aminophenylmercuric acetate degraded fluorescein-labeled polymeric rat tail tendon Type I collagen and the tropocollagen TCA and TCB fragments of human Type II collagen into smaller peptides at 37°C. Enzyme activity was abolished if p-aminophenylmercuric acetate-activated culture medium was preincubated with 1,10-phenanthroline, a metal chelator. Thus, articular chondrocytes in monolayer culture are capable of producing neutral proteinases which acting together can result in complete degradation of tendon and cartilage collagen to small peptides. 相似文献
135.
Jean Hersovici M. Idriss Bennani-Baiti Roland Montserret Charles Frayssinet Kostas Antonakis 《Bioorganic & medicinal chemistry letters》1991,1(12):721-724
Keto C-glycoside-fatty acid conjugates were synthesized from 6-hydroxy 2- and 4-keto unsaturated D-C-glycosides. These compounds were tested for cytotoxic activity against LFCl2A cells (Rat hepatocarcinoma cells). The introduction of a lipid chain to 2-keto C-glycosides induced a drop in the cyctotoxic activity of these compounds. On the other hand 4-keto unsaturated C-glycoside-fatty acid conjugates possessed IC50 values of 0.7–0.001 μM with 21 being the most potent. 相似文献
136.
Bernard Junod Adrian Griffiths Roland Lüthi Hannes B. St?helin Heikki Savolainen et al. 《International journal of biometeorology》1992,36(3):179-189
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Our Planet, Our Health Report of the who commission on health and environment 相似文献137.
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Long-term telemetry of body temperature with synchronous measurement of metabolic rate in torpid and non-torpid Blue-naped Mousebirds (Urocolius macrourus)相似文献
138.
Specific cleavage of LexA repressor plays a crucial role in the SOS response of Escherichia coli. In vivo, cleavage requires an activated form of RecA protein. However, previous work has shown that the mechanism of cleavage is unusual, in that the chemistry of cleavage is probably carried out by residues in the repressor, and not those in RecA; RecA appears to facilitate this reaction, acting as a coprotease. We recently described a new type of lexA mutation, a class termed lexA (IndS) and here called IndS, that confers an increased rate of in vivo cleavage. Here, we have characterized the in vitro cleavage of these IndS mutant proteins, and of several double mutant proteins containing an IndS mutation and one of several mutations, termed Ind-, that decrease the rate of cleavage. We found, first, that the autodigestion reaction for the IndS mutant proteins had a higher maximum rate and a lower apparent pKa than wild-type LexA. Second, the IndS mutations had little or no effect on the rate of RecA-mediated cleavage, measured at low protein concentrations, implying that the value of Kcat/Km was unaffected. Third, the rate of autodigestion for the double-mutant proteins, relative to wild-type, was about that rate predicted from the product of the effects of the two single mutations. Finally, by contrast, these proteins displayed the same rate of RecA-mediated cleavage as did the single Ind- mutant protein. We interpret these data to mean that the IndS mutations mimic to some extent the effect of RecA on cleavage, perhaps by favoring a conformational change in LexA. We present and analyze a model that embodies these conclusions. 相似文献
139.
Roger S. Holmes Roland A. H. van Oorschot John L. VandeBerg 《Biochemical genetics》1991,29(3-4):163-175
Polyacrylamide gel isoelectric focusing (PAGE-IEF), cellulose acetate electrophoresis, and histochemical techniques were used to examine the tissue and subcellular distribution, genetics and biochemical properties of aldehyde dehydrogenase (ALDH) isozymes in a didelphid marsupial, the gray short-tail opossum (Monodelphis domestica). At least 14 zones of activity were resolved by PAGE-IEF and divided into five isozyme groups and three ALDH classes, based upon comparisons with properties previously reported for human, baboon, rat, and mouse ALDHs. Opossum liver ALDHs were distributed among cytosol (ALDHs 1 and 5) and large granular (mitochondrial) fractions (ALDHs 2 and 5). Similarly, kidney ALDHs were distributed between the cytosol (ALDH5) and the mitochondrial fractions (ALDHs 2, 4, and 5), whereas a major isozyme (ALDH3), found in high activity in cornea, esophagus, ear pinna, tail, and stomach extracts, was localized predominantly in the cytosol fraction. Phenotypic variants of the latter enzyme were shown to be inherited in a normal Mendelian fashion, with two alleles at a single locus (ALDH3) showing codominant expression. The data provided evidence for genetic identity of corneal, ear pinna, tail, and stomach ALDH3 and supported biochemical evidence from other mammalian species that this enzyme has a dimeric subunit structure. 相似文献
140.
Orcadian phase dependency in pharmacokinetics and hemodynamic effects on blood pressure and heart rate of different galenic formulations of nifedipine (immediate-release, sustained-release, and i.v. solution) were studied in healthy subjects or in hypertensive patients. Pharmacokinetics of immediate-release but not sustained-release and i.v. nifedipine were dependent on time of day: immediate-release nifedipine had higher Cmax (peak concentration) and shorter tmax (time-to-peak concentration) after morning than evening application, and bioavailibility in the evening was reduced by about 40%. Orcadian rhythm in estimated hepatic blood flow as determined by indocyanine green kinetics may contribute to these chronokinetics. A circadian time dependency was also found in nifedipine-induced effects on blood pressure and heart rate as monitored by 24-h ambulatory blood pressure measurements. In conclusion, the dose response relationship of oral nifedipine is influenced by the circadian organization of the cardiovascular system as well as by the galenic drug formulation. 相似文献