Carl Wight

Reversible activation-inactivation of cholesterol 7α-hydroxylase possibly due to phosphorylation-dephosphorylation

Abstract The activity of microsomal cholesterol 7α-hydroxylase is shown to be increased in vitro by ATP, Mg 2+ , and a cytosolic protein fraction. There was a loss of enzyme activity in the presence of E. coli alkaline phosphatase which was proportional to the amount of phosphatase. Much of this loss was recovered upon addition of ATP, Mg 2+ , and a cytosolic protein fraction.

Thyrotropin-Releasing Hormone (TRH)-Induced Growth Hormone (hGH) Responses In Cirrhotic Men

The plasma growth hormone (hGH) responses to an intravenous challenge of 400 micrograms of thyrotropin-releasing hormone (TRH) were evaluated in 14 normal controls and in 29 chronic alcoholic men. The normal controls had either a minimal or no hGH response to TRH, having basal hGH levels of 0.9 +/- 0.2 ng per ml and peak hGH levels of 2.0 +/- 0.5 ng per ml. In contrast, the chronic alcoholic men had a basal hGH level of 2.8 +/- 0.4 ng per ml, 3 times the basal level of the normal controls (P less than 0.01). The peak hGH response of the alcoholic men was 7.4 +/- 1.5 ng per ml (P less than 0.01). The 29 alcoholic men could be divided into two groups based upon the presence or absence of cirrhosis as determined by liver biopsy. The 16 alcoholic men with cirrhosis had greater basal hGH levels (3.5 +/- 0.6 ng per ml) and peak hGH levels (9.5 +/- 2.3 ng per ml) than did the 13 alcoholic men without cirrhosis (basal hGH 2.1 +/- 0.6 ng per ml, peak hGH 4.9 +/- 1.5 ng/ml). Plasma estradiol levels were similar in the normal controls and in the alcoholic men. In contrast, plasma estrone was greater in the alcoholic men (32.2 +/- 3.5 pg per ml) than in the normal controls (18.9 +/- 1.8 pg per ml) (P less than 0.05). However, when the plasma estrone levels of alcoholic men with cirrhosis were compared to those of the alcoholic men without cirrhosis no difference existed. Thus it is difficult to ascribe the increased hGH responses of the cirrhotic alcoholic men when compared to those of the noncirrhotic alcoholic men as being a result of increased basal estrogen levels.

On the differential suppression of cholesterol synthesis by low density lipoprotein in B and T lymphocytes

Cholesterol synthesis and its suppression by low density lipoprotein cholesterol were measured in purified B and T peripheral blood lymphocytes. After preincubation for 53 h in lipoprotein-deficient serum, both B and T cells exhibited increased cholesterol synthesis as compared with synthesis measured in cells immediately after their isolation from blood and without preincubation with lipoprotein-deficient serum. The magnitude of this increase was far greater in T cells in comparison with that in B cells in all subjects studied. But, whereas there was an immediate and progressive suppression of cholesterol synthesis in lipoprotein-deficient serum-incubated T cells as the concentration of low density lipoprotein cholesterol in the medium was increased, synthesis in lipoprotein-deficient serum-incubated B cells remained insensitive to the presence of low density lipoprotein in the medium. Hydroxymethylglutaryl-CoA reductase activity was observed also to follow a similar pattern in both cell types. These observations may imply that one or more events, including binding of low density lipoprotein to its receptor, internalization and degradation of low density lipoprotein receptor complex finally leading to suppression of hydroxymethylglutaryl-CoA reductase activity and cholesterol synthesis, fail to take place in B cells.

Estriol determination in pregnancy urine by gas chromatography

Abstract Determination of free estriol in pregnancy urine by gas chromatography is described and data are presented to support the accuracy of this procedure as compared to the gas chromatography of estriol triacetate. Data from infrared and nuclear magnetic resonance spectroscopy and from mass spectrometric studies on estriol and estriol triacetate obtained after passage through gas Chromatographic columns indicate no structure modifications in these compounds.

Gas-liquid chromatography of underivatized steroids: simultaneous determination of urinary 17-ketosteroids, pregnanediol, pregnanetriol, and pregnanetriolone☆

Abstract A gas—liquid Chromatographic procedure is described for estimating major urinary 17-ketosteroids, pregnanediol, pregnanetriol, and pregnanetriolone without formation of their derivatives. The concentrations of these steroid metabolites are calculated with a simple computer program.

Cholesterol synthesis in rat intestine: effect of fasting and of porphyrogenic chemical allylisopropylacetamide

Abstract (a) Administration of allylisopropylacetamide to fasting rats stimulates intestinal sterol synthesis as measured by incorporation of 14 C from [1- 14 C]sodium acetate. Stimulatory effect of AIA is confined to the acetate to mevalonate segment of cholesterol biosynthetic pathway. (b) It is also shown that the suppression of sterol synthesis in the ileum of intact rats produced by fasting is of the same order of magnitude as that observed for liver sterol synthesis due to fasting.