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Biomedical subjects

S Segal

Publications and source records attributed to S Segal.

At least 631 records · Page 35Linked to original sources
PubMed1973

Interrelationship of glutathione-cystine transhydrogenase and glutathione reductase in developing rat intestine.

1. Glutathione reductase and glutathione-cystine transhydrogenase activity in supernatant fractions of whole homogenates and homogenates of mucosal and muscular layers were determined in developing rat intestine after determination of the optimum conditions for assay of the two enzymes. In jejunum from adult rat, the K(m) values for GSSG reductase and GSH-cystine transhydrogenase activities were 0.25mm-GSSG and 0.23mm-cystine respectively. 2. The two activities could be differentiated by stability studies since GSSG reductase was stable at 60 degrees C for 10min and could be stored at 4 degrees C for 24h without loss of activity. GSH-cystine transhydrogenase, on the other hand, was denatured at 60 degrees C and completely inactive after 24h storage at 4 degrees C. 3. Based on calculations of total activities, both enzymes increased from the eighteenth day until the animals were young adults. 4. Total GSSG reductase activity increased at a greater rate with age than total GSH-cystine transhydrogenase activity as evidenced by activity ratios for GSH-cystine transhydrogenase/GSSG reductase of 0.44 and 0.12 in ileum from suckling and adult rats respectively, and 0.31 and 0.24 in jejunum from suckling and adult rats respectively. 5. In mucosa from adult rats GSSG reductase was more active in the ileum than in the jejunum, whereas GSH-cystine transhydrogenase activity was higher in the jejunum. 6. GSH-cystine transhydrogenase was active only in the muscle cells of the ileum of 7-day-old rats but became localized primarily in the mucosal layer in the adult rat. However, GSSG reductase activity was distributed evenly between the two layers throughout the intestine.

Aging↗
PubMed1973

Cellular accumulation of L-cystine in rat kidney cortex in vivo.

Cellular accumulation of L-cystine in rat kidney cortex in vivo has been studied using L-[(35)S]cystine. The L-[(35)S]cystine radioactivity in plasma decreases to less than 10% of the initially calculated value by 15 min. Four (35)S-containing intracellular products of L-cystine metabolism were identified including cystine, cysteine, reduced glutathione, and an as yet unidentified compound. The latter is probably taurine, cysteinesulphinate, or cysteic acid. Cellular accumulation of these products was found to be more rapid in vivo than in vitro. Cellular accumulation of the products of L-cystine metabolism was found to be essentially unchanged in the presence of ureter ligation. Unlabeled L-lysine administered simultaneously with L-[(35)S]cystine, in both the presence and absence or ureter ligation, enhanced the cellular accumulation of intracellular metabolic products of L-[(35)S]cystine. Simultaneous (35)S cellular accumulation and L-cystine clearance studies were performed both in the presence and absence of L-lysine. L-Lysine enhanced cellular accumulation of (35)S-products despite an accompanying increase in L-cystine clearance. The results are interpreted as evidence for a dissociation between cellular accumulation and transepithelial transport. This evidence for independent luminal transport and peritubular cellular accumulation could explain the apparent paradox in the disease cystinuria where there appears to be a luminal transport defect for L-cystine, but no defect for cellular accumulation of L-cystine metabolic products in vitro.

Animals↗
PubMed1972

Thymus-derived lymphocytes: humoral and cellular reactions distinguished by hydrocortisone.

Lymphocytes derived from the thymus (T cells) take part in the induction of humoral antibody and also effect cell-mediated graft-versus-host reactions. Preliminary treatment of mice with hydrocortisone caused an inhibition of T-cell function in humoral immunity, while enhancing the graft-versus-host reactivity of the same population of spleen cells. This suggests that different types of T cells participate in cellular and humoral immune reactions.

Animals↗