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Biomedical subjects

R R Tremblay

Publications and source records attributed to R R Tremblay.

At least 145 records · Page 8Linked to original sources
PubMed1976

Comparative binding specificity of methyltrienolone in human and rat prostate.

The binding of methyltrienolone (R 1881) in crude human hyperplastic prostate cytosol was determined by a charcoal assay. Maximum binding was observed after 2-3 h of incubation at 0 degrees C. This binding decreased steadily thereafter and reached 41% of the 2-hour values after 96 h of incubation. In human hyperplastic prostate, the binding of 3H-R 1881 was competed by low concentrations of R 1881, R 5020 and progesterone and by high concentrations of dihydrotestosterone (DHT) and 17 alpha-methyl-DHT. In the rat prostate, on the other hand, this binding was competed by low concentrations of DHT and 17 alpha-methyl-DHT and only by high concentrations of progesterone and R 5020. The apparent association constant (Ka) of R 1881 was determined in three human prostates and found to be 0.2-0.4 X 10(9) liters/mol; the number of binding sites ranged from 101 to 158 fmol per mg of protein. These findings constitute further evidence for the existence of relatively large amounts of a progesterone-binding component in human hyperplastic prostate.

Animals↗
PubMed1976

[Adrenocortical responses to ACTH (author's transl)].

To characterize by a mathematical model the dynamics of adrenocortical responses to ACTH, the concentration of plasma corticosterone was measured following a series of injections and perfusions of ACTH to dexamethasone-treated male rats. A similar slope was observed during the rise of plasma corticosterone following graded pulse inputs, and the steady-state corticosterone secretion rate was shown to increase proportionally to the perfusion rate of ACTH up to saturation corresponding to maximal secretion. The data will be used, concurrently with our model of the dynamics of plasma cortiscosterone, for the identification of a mathematical model of the adrenocortical response to ACTH.

Adrenal Cortex↗
PubMed1975

Effect of sample volume and column length on transcortin determination by sephadex G-25 gel filtration.

When Sephadex G-25 columns are used to separate transcortin-bound corticosterone from free corticosterone, there is a non-linear increase of total binding with increasing plasma volume filtered. However, the specific binding (total binding - unspecific binding) shows a linear relationship with the plasma volume filtered. Furthermore, the specific binding decreases with increasing Sephadex column length and absolute binding values are found by extrapolating to a zero length column.

Chromatography, Gel↗
PubMed1975

Testosterone 5alpha-reductase in rat skin homogenates: measurement in the skin at various anatomical sites in males and females.

Experiments were disigned to find suitable conditions to determine the 5alpha-reducatase activity in rat skin homogenates. The dihydrotestosterone formation was linear until 15 min. The 5alpha- reductase was very heat labile at 37-c in absence of testosterone and NADPH since complete loss of activity occurred after one hour of preincubation. At OC, there was a 20% decrease after 5 hr. The enzyme activiity was measured in the skin at various anatomical sites. It was found to vary with each region in the following order in the male; tail,greater than scrotum greater than ear greater than genital skin greater than dorsum smaller than or equal to thorax greater than sole of the foot. In a few tissues, the enzyme activity was higher than in the prostate. Corresponding female tissues exhibited lower reductase activity except the sole of the foot in which the contrary was found. This significant sex difference indicates that sex hormones may be involved in the control of the levels of that enzyme in rat skin.

Animals↗
PubMed1975

In vivo effects of steroid hormones on the testosterone 5alpha-reductase in skin.

We have studied the hormonal regulation of the levels of testosterone 5alpha-reductase in rat skin by performing surgical manipulations (gonadectomy and/or adrenalectomy) of the rats and by steroid administration to ovariectomized- adrenalectomized rats. Castration significantly increases (P smaller than 0.01) the enzyme activity in the sole of the foot but not in the thoracic skin of male rats. In female rats, significant elevations of the enzyme activity are observed in the thoracic skin (P smaller than 0.01) and in the sole of the foot (P smaller than 0.05) after ovariectomy. Estrogen administration decreases the enzyme activity in thoracic skin, tail skin and vulvar skin of ovariectomized-adrenalectomized rats. Testosterone and dihydrotestosterone decrease the activity in the sole of the foot and increase the activity in vulvar skin. Progesterone and corticosterone administration produce no significant effects in the four skin types studied.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗