Search PubMed⌕ Search

Biomedical subjects

S Shuster

Publications and source records attributed to S Shuster.

At least 235 records · Page 13Linked to original sources
PubMed1978

Sensitive new in vitro bioassay for melanocyte-stimulating activity using the skin of Anolis carolinensis.

An accurate, highly reproducible and sensitive bioassay for melanocyte-stimulating hormone (MSH) using the skin of Anolis carolinensis in vitro is described. The time taken for green Anolis skin fragments to change to a specific, visually assessed, green-brown color is dose-related, and this forms the basis of the new assay. The method is simple to perform, and 1 person may assay 20 samples in a day using the dorsal skin from a single adult lizard. The mean dose-response ranges between 48 X 10(-12) and 375 X 12(-12) M (38 to 625 pg/ml). Using the assay, alpha-MSH, beta-MSH, ACTH (4-10), and ACTH (1-10) were equipotent on a molar basis. For repeated bioassay of rat pituitary extracts, the dose-response curves were highly significant, and only 1 of the 9 pituitary dose-response curves deviated significantly from the slope of the standard alpha-MSH curve. The index of precision, lambda, for the 9 pituitary bioassays ranged between 0.037 and 0.081, while the mean 95% fiducial limits were -6.6 and 7.1% on either side of the estimated potency. The new rate method is compared with an earlier quantal method which also uses the isolated skin of Anolis carolinensis. The quantal method does not have dose-response characteristics and is therefore less accurate and reproducible than the new method; the coefficient of variation for repeated bioassay of the same pituitary extracts ranged from between 12 to 20% for the quantal method and between 2.9 to 5.7% for the new rate method.

Adrenocorticotropic Hormone↗
PubMed1978

Plasma immunoreactive beta-melanocyte-stimulating hormone in chronic liver disease and fulminant hepatic failure.

Hyperpigmentation believed to be due to melanin, is a feature of chronic liver disease, especially primary biliary cirrhosis and hemochromatosis. Normal plasma concentrations of immunoreactive beta-melanocyte-stimulating hormone (beta-MSH) have been found in both these conditions; thus elevation of plasma beta-MSH plays no role in the pathogenesis of hepatic pigmentation. Normal levels are also found in hepatocellular failure, which supports the hypothesis that the kidney and not the liver is the site of metabolism of this hormone.

Chronic Disease↗
PubMed1978

Increased sebaceous gland activity in the adult rat after alpha-melanocyte-stimulating hormone treatment during early life.

Sebum secretion was measured in adult female and male rats given alpha-melanocyte stimulating hormone (alpha-MSH) during early life. Daily treatment with 40 microgram alpha-MSH/100 gm body weight for the first 5 weeks of life increased sebum secretion in female and male rats at 8, 11, and 15 weeks of age. A lower dose of alpha-MSH (10 microgram/100 gm body weight) produced similar changes in male but not in female rats. No effect on sebum secretion was found in female and male rats aged between 8-28 weeks when alpha-MSH was given (1) from the day of birth to 3 weeks; (2) 3--5 weeks; (3) 1st and 5th weeks and (4) 7--12 weeks. Apparently alpha-MSH must be given throughout the first 5 weeks of life in order to produce a sustained effect on the sebaceous glands. The fact that males appear to be more sensitive than females, in that they responded to a lower dose of alpha-MSH, may indicate that MSH acts by enhancing the response to androgen. Early alpha-MSH treatment failed to alter the sebaceous gland response to testosterone in adult female and male rats but the possibility that alpha-MSH enhances the action of androgen in early life cannot be ruled out.

Age Factors↗
PubMed1978

Dermatoglyphics in dermatitis herpetiformis.

In a dermatoglyphic study of 101 patients with dermatitis herpetiformis, comparison was made with their normal relatives and several random normal series. The results of the several comparisons are quite consistent, considering the nature of the data, for the all point to an attenuation of qualitative and quantitative digital and palmar traits in the patients. It is argued that these differences are associated with the disease itself, and that some of the female relatives have an inherited tendency to the disorder, but do not express it. The findings suggest the involvement of genetic factors in the aetiology, and possibly intrauterine environmental influences as well.

Dermatitis Herpetiformis↗
PubMed1978

Melanocyte-stimulating hormone--mimetic action of the phenothiazines.

We have compared the melanophore-stimulating action of four phenothiazines, trifluoperazine, perphenazine, chlorpromazine, and prochlorperazine, with alpha-MSH on the skin of the lizard Anolis carolinensis, using a new rate method of bioassay. The dose-response curves for the phenothiazines were parallel to that of alpha-MSH, and when given together alpha-MSH and chlorpromazine were additive. The phenothiazines may therefore stimulate melanosome dispersion in the lizard skin by the same mechanism as alpha-MSH; a MSH-mimetic action of phenothiazines may similarly explain their pigmentary action in man. The pigmentary potency of the phenothiazines corresponded with their therapeutic potency in man; this is in keeping with a neuro-regulatory role for MSH peptides and suggests a possible therapeutic use for them.

Animals↗
PubMed1978

Effect of progesterone on the sebaceous glands.

The effect of progesterone on the rate of sebum secretion was examined in intact and gonadectomized male and female rats. In intact adult male rats, progesterone administered for 3 weeks decreased sebum secretion, whereas in intact adult female rats, progesterone slightly increased sebum production. In castrated adults progesterone increased sebum secretion in both sexes, a greater response occurring after castration at 21 days of age than after castration at 10 weeks. Thus, the response to progesterone in the adult rat differs in intact males and females and is affected by changes in the endocrine environment induced by gonadectomy, especially near the time of puberty.

Animals↗
PubMed1977

Immunoreactive beta-melanocyte-stimulating hormone in cerebrospinal fluid and plasma in hypopituitarism: evidence for an extrapituitary origin.

Immunoreactive beta-melanocyte-stimulating hormone (beta-MSH) was measured in the plasma of 19 patients with hypopituitarism and in the cerebrospinal fluid (CSF) of five of these patients. In neither plasma nor CSF were the beta-MSH concentrations significantly different from those in normal controls. These observations raise the possibility that beta-MSH may be produced by and secreted from neural tissue; this is supported by the findings of beta-MSH in high concentrations in many parts of the brain.

Brain Chemistry↗
PubMed1977

Chloasma, oral contraceptives, and plasma immunoreactive beta-melanocyte-stimulating hormone.

Plasma immunoreactive beta-melanocyte stimulating hormone (beta-MSH) has been measured in patients taking a progestogen-only oral contraceptive and in patients taking combined estrogen-progestogen therapy, of whom some had chloasma. Plasma levels did not differ significantly from those in a group of age- and sex-matched controls. It is concluded that the pigmentation of chloasma is not due to increased plasma concentrations of immunoreactive beta-MSH.

Contraceptives, Oral↗
PubMed1977

The measurement of the cell cycle time in squamous epithelium using the metaphase arrest technique with vincristine.

In squamous epithelia with a single layer of germinative cells, the age distribution of cells in the cell cycle is shown to depend on the direction of the mitotic axis (i.e. a line joining the nuclei of daughter cells) relative to the plane of the basal layer. When axes are in the plane of the basal layer the age distribution is exponential; when cells divide at right angles to the plane of the basal layer, the age distribution is rectangular. When there is a ratio of vertical to horizontal axes, the age distribution is intermediate but can be calculated from knowledge of the proportion of axes in the plane of the layer. Squamous epithelia can be classified according to this arrangement of axes. When there are multiple layers of germinative cells, as in psoriasis, the age distribution is shown to be exponential to a good approximation, whatever the direction of the mitotic axes in the several layers. The importance of these observations is demonstrated by analysing metaphase arrest experiments with vincristine in the single layer of germinative cells in the mouse oesophagus, and in the several layers found in psoriatic epidermis. Choice of the wrong age distribution leads to an error of 6 h in the oesophagus and 23 h in psoriatic epidermis, when the mean cell cycle time is calculated. It is concluded that, in squamous epithelium, it is most important to know the age distribution before calculating the cell cycle time by methods involving measurement of the rate of entry of cells into mitosis or DNA synthesis.

Animals↗