University of Madras

About: University of Madras is a education organization based out in Chennai, Tamil Nadu, India. It is known for research contribution in the topics: Ring (chemistry) & Lipid peroxidation. The organization has 8496 authors who have published 11369 publications receiving 211152 citations. The organization is also known as: Madras University & University of Chennai.

Inhibition of Leydig cell activity in vivo and in vitro in hypothyroid rats

Abstract: Leydig cell steroidogenic activity under basal and stimulated conditions was studied in hypothyroid rats. Hypothyroidism was induced at a prepubertal age (30 days postpartum) by surgical thyroidectomy, and L-thyroxine (T4) supplementation (6 micrograms/100 g body weight/day for 30 days) to hypothyroid rats was begun after 30 days. Hypothyroidism for 60 days reduced serum LH and FSH without affecting prolactin. Serum and intratesticular testosterone and the specific activity of Leydig cell 3 beta- and 17 beta-hydroxysteroid dehydrogenases diminished in hypothyroid rats. The stimulatory effect of LH on Leydig cell steroidogenic activity and cAMP was also adversely affected in hypothyroid rats. All these changes were reversed by T4 supplementation. The present results suggest that prepubertal hypothyroidism suppresses both basal and stimulated Leydig cell activity in adult rats.

Vinyl polymerization initiated by ceric ion reducing agent systems in sulfuric acid medium

Abstract: Polymerization of the monomers, methyl acrylate (MA) and methyl methacrylate (MMA) was carried out in sulfuric acid medium at 15°C. With the redox initiator system, ceric ammonium sulfate-malonic acid. There was no induction period, and a steady state was attained in a short time. There was found to be no polymerization even after 1 hr. in the absence of the reducing agent R. The initiation was by the radical produced from the Ce 4+ -malonic acid reaction. The rate of monomer disappearance was proportional to [M] 1.5 , [R] 0.5 , and [Ce 4+ ] 0.3-0.5 , and the rate of ceric disappearance was directly proportional to [R] and [Ce 4+ ]. Chain lengths of the polymers were directly proportional to [M] and inversely to [R] ½ and [Ce 4+ ] ½ . The experimental results were explained by a kinetic scheme involving the following steps: (a) oxidation of the substrate to give the primary radical which reacts with Ce 4+ to give the products, (b) initiation by the primary radical, (c) propagation, and (d) termination of the growing polymer radicals by the mutual type. For the polymerization of acrylonitrile (AN) by the redox system, ceric ammonium sulfate-cyclohexanone (CH), in sulfuric acid at 15°C., the scheme was modified to include linear type of termination by Ce 4+ , along with the mutual termination to explain the results especially under conditions with [Ce 4+ ] ≥ [CH].