Search PubMed⌕ Search

Biomedical subjects

S Lieberman

Publications and source records attributed to S Lieberman.

At least 109 records · Page 6Linked to original sources
PubMed1973

Improved estimation of body masses and turnover of cholesterol by computerized input--output analysis.

In 23 patients, the decay curves of serum cholesterol specific activity after a single intravenous dose of radioactive cholesterol were measured for 16-66 wk and were subjected to computerized input-output analysis. Of 17 patients with decay curves followed for longer than 50 wk, a three-exponential curve fit was better in 12, and a two-exponential curve fit in 5, according to computerized F tests. Of six patients with decay curves followed for less than 50 wk, a two-exponential curve fit was better in five and a three-exponential curve fit in one. In the 13 patients who exhibited three-exponential curve fits, the third exponential appeared after 13-43 wk of observation (average, 25 wk). In 12 patients of this group who were followed for 50 wk or more, turnover rates and exchangeable masses of cholesterol were measured at maximum lengths of the curves (50-66 wk), and these parameters were then compared with measurements made with curves successively shortened down to 10-12 wk. The average differences between analyses of the minimum vs. the maximum lengths of the curves were: It (input rate: absorbed dietary plus biosynthesized cholesterol), 14% larger (1.24 vs. 1.09 g/day); M(a) (rapidly exchangeable mass of cholesterol), no change (34 vs. 33 g); M (total exchangeable mass), 26% smaller (67 vs. 91 g); M - M(a) (remaining exchangeable mass), 39% smaller (40 vs. 65 g). Significant differences in It, M, and M - M(a) (minimum vs. maximum curve lengths) were found in both normolipidemic and hypercholesterolemic patients, and the differences were of similar magnitude in the two groups. Since only 12 of 17 patients followed for 50 wk or longer demonstrated three-exponential curve fits, various means were sought by which it might be predicted at the outset whether a given patient must be studied for so long a time; none was found. However, in the group with two exponentials the value of M(a) was significantly larger than those with three-exponential curve fits, and this difference was apparent at as early as 10-12 wk.

Adolescent↗
PubMed1972

Long-term kinetics of serum and xanthoma cholesterol radioactivity in patients with hypercholesterolemia.

In four patients with hypercholesterolemia (type II hyperlipoproteinemia) and xanthomatosis the decay of serum cholesterol specific activity was followed for 53-63 wk after pulse labeling. Specific activity of biopsied xanthoma cholesterol was measured four times in the course of the study. The xanthoma specific activity curve crossed and thereafter remained above the serum specific activity curve. The average ratio of xanthoma to serum specific activity was 4.7 at the end of the study. The final half-time of the xanthoma decay curves was significantly greater (average: 200 days) than the slowest half-time of serum specific activity decay (average: 93 days). The data were analyzed by input-output analysis and yielded the following results. The average value for the total input rate of body cholesterol (I(T)) (sum of dietary and biosynthesized cholesterol) was 1.29 g/day. The average size of the rapidly miscible pool of cholesterol (M(a)) was 55.7 g. and of the total exchangeable body mass of cholesterol (M) 116.5 g. The average value of M - M(a) (remaining exchangeable mass of cholesterol) was 60.8 g. The derived values for exchangeable masses of cholesterol, in the present patients with marked hypercholesterolemia, were significantly larger than in a group of patients with normal serum lipids in previous studies. One of the four patients died of a sudden acute myocardial infarction 53 wk after pulse labeling. Specific activity of aortic wall and atheroma cholesterol was 3.12 times that of serum. The ratio was close to 2 for adipose tissue and spleen, and was slightly above 1 or was close to unity in most other organs studied, with the exception of brain which showed a ratio of 0.19.

Adolescent↗
PubMed1970

Steroidal free radicals as possible intermediates in the biosynthesis of C19-delta 16-steroids.

Treatment of deoxycorticosterone with reagents that abstract a hydrogen atom from the C-21-hydroxyl group leads to the formation of androsta-4,16-dien-3-one. In vitro incubations of [1,2-(3)H]deoxycorticosterone with homogenates of boar testis tissue produce the tritiated dienone. This reaction can be formulated as an abstraction of hydrogen from the C-21-hydroxyl group to form a C-21-alkoxy radical, followed by a 1,5-H.shift from the C-16 atom and beta-scission of the C-16-alkoxy radical leading to the loss of a C(2) fragment (C-20 and C-21) with the formation of the double bond between C-16 and C-17. Both the chemical model and the in vitro experiment support further the thesis [Lieberman, S., L. Bandy, V. Lippman, and K. D. Roberts, Biochem. Biophys. Res. Commun., 34, 367 (1969)] that biosynthetic reactions in which molecular oxygen reacts with steroids (for example, side-chain cleavage or hydroxylation) involve steroidal free radicals.

Androstanes↗