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Biomedical subjects

R Clayton

Publications and source records attributed to R Clayton.

At least 55 records · Page 3Linked to original sources
PubMed1987

Cultured mammary carcinoma cells contain gonadotropin-releasing hormone-like immunoreactivity, GnRH binding sites and chorionic gonadotropin.

Immunoperoxidase staining and radioimmunoassay were used to identify gonadotropin-releasing hormone (GnRH) and chorionic gonadotropin (hCG) in 4 mammary carcinoma cell lines. GnRH-like immunoreactivity was found in all cell lines; 2 lines also contained hCG. Binding of a GnRH agonist was demonstrated by radioreceptor assay in cultured mammary carcinoma cells. In cell column perfusion of the same cells, exogenous GnRH did not stimulate release of hCG.

Binding Sites↗
PubMed1987

Modification of food cariogenicity in rats by mineral-rich concentrates from milk.

Dairy products, including milk, cheese, and casein, can reduce the caries-causing potential of cariogenic substrates as measured in various animal, plaque acidity, and in vitro systems. Although the mechanisms responsible for protection are not completely identified, substances containing Ca and P may contribute to the protective potential by reducing demineralization and/or promoting remineralization of enamel. Casein may reduce demineralization by forming a protective coat on the enamel surface. By means of a rat model, this study evaluated the ability of three casein-free milk mineral concentrates with various levels of whey protein, calcium, and phosphate to modify the cariogenicity of a powdered diet containing 20% sucrose. Analysis of these data indicates that there were no significant differences among groups for weight gain, total food consumption, or feeding frequency, as monitored by a computer-based infrared activity monitor. All three mineral concentrates significantly reduced buccal caries, and two of the three reduced sulcal caries by from 10 to 30%. The analysis further shows that casein-free milk mineral fractions can modify the cariogenicity of sucrose-containing foods in a rat model.

Animals↗
PubMed1986

Regulation of testicular steroidogenesis by gonadotropin-releasing hormone agonists and antagonists.

Clinical and experimental studies are described on the effects of a gonadotropin-releasing hormone (GnRH) agonist (A) and antagonist (Ant.) on testicular endocrine function. Testicular effects of long-term gonadotropin suppression by GnRH-A were assessed during treatment of prostatic cancer patients. The testis tissue removed after 6 months of A treatment had less than 5% of the testosterone(T)-producing capacity in comparison to testis tissue removed from untreated control patients. However, the LH receptors (R) and responsiveness of T output to LH stimulation in vitro were unchanged. FSH-R decreased by 70%. Hence, despite suppression of gonadotropins and testicular androgen production during long-term GnRH-A treatment the responsiveness to exogenous gonadotropins is maintained. The testicular effects of a gonadotropin suppression induced with GnRH-Ant. and testicular GnRH-R blockade were studied in rats. Besides decreases of gonadotropins and testicular T, systemic Ant. treatment decreased testicular Prl-R, but had no effect on LH-R or FSH-R. Bromocriptine-induced hypoprolactinemia, in contrast, decreased LH-R but had no effect on Prl-R. The results indicate reciprocal regulation of LH-R and Prl-R, and that testicular steroidogenesis and LH-R are under differential regulation, the former by LH, the latter by Prl. In another study, testicular GnRH-R, and consequently the action of a putative testicular GnRH-like factor, were blocked by unilateral intratesticular infusion of Ant. (1 week, Alzet osmotic pumps). The treatment resulted in 90% occupancy of testicular GnRH-R in the Ant.-infused testes, and this was associated with decreased levels of R for LH, FSH and Prl, and of T. The results indicated that the testicular GnRH-R have a physiological function in subtle stimulation of Leydig cell functions.

Acid Phosphatase↗
PubMed1985

Altered concentrations of gonadotrophin, prolactin and GnRH receptors, and endogenous steroids in the abdominal testes of adult unilaterally cryptorchid rats.

Testicular descent was prevented unilaterally in newborn rats by cutting the gubernaculum testis. At 100 days of age, the number of Leydig and Sertoli cells per testis, the concentration of receptors for LH, FSH, prolactin and GnRH, and endogenous concentrations of progesterone and testosterone were determined. The weight of the abdominal testes was reduced by 80%, but in spite of this they contained as many Sertoli (32.8 +/- 1.3 X 10(6), mean +/- s.e.m., n = 6) and Leydig (28.2 +/- 1.7 X 10(6) cells as did scrotal testes (32.1 +/- 2.5 X 10(6) and 24.3 +/- 1.2 X 10(6) respectively). The numbers of receptors for LH (3.2 +/- 0.2 and 1.0 +/- 0.2 pmol/testis, mean +/- s.e.m., n = 11), FSH (358 +/- 11.0 and 96.3 +/- 12.6 fmol/testis) and prolactin (535 +/- 32.7 and 92.4 +/- 13.2 fmol/testis) were reduced (P less than 0.001) in abdominal testes, but the number of GnRH receptors was unaffected (8.9 +/- 1.4 and 12.1 +/- 1.8 fmol/testis, n = 6). Testicular testosterone concentration (30.9 +/- 4.4 vs 15.4 +/- 3.2 ng/g, n = 11, P less than 0.001), but not that of progesterone (0.87 +/- 0.10 vs 1.01 +/- 0.21 ng/g), was decreased in abdominal testes. The decreased receptor and androgen values reflect functional disturbances in the abdominal testes. The changed local milieu within abdominal testes may reduce hormone receptor concentrations which are then involved in the observed Leydig cell dysfunction.

Animals↗
PubMed1983

Beneficial effect of 15% azelaic acid cream on acne vulgaris.

Patients treated with azelaic acid (15%) cream for chloasma reported simultaneous improvement of acne lesions within the treated areas. This prompted an open study of its effect in cases of acne without chloasma. One hundred patients with acne vulgaris were treated for 3-9 months by twice-daily application of the cream with significant improvement in every case.

Acne Vulgaris↗
PubMed1983

Studies of lens enzyme activities in relation to cataract type and plasma constituents.

The specific activities of glutathione reductase (GR), EC 1.6.4.2, and aldolase, (ALD) EC 4.1.2.13, were determined in the homogenates of 60 cataractous lenses. Concentrations of certain plasma constituents and the morphological types of cataract of the patients were known. Investigations were aimed at establishing a possible correlation between enzyme activities and plasma constituents as well as between the specific activities of GR and ALD and type of cataract. A correlation between the specific activity of GR and the urea content of the blood could be identified. Results also indicated a relationship between the decrease in GR activity and the formation of cortical cataracts.

Alkaline Phosphatase↗