Arun K. Ray

Bio: Arun K. Ray is an academic researcher from Bose Institute. The author has contributed to research in topics: Heteropneustes fossilis & Catfish. The author has an hindex of 19, co-authored 56 publications receiving 976 citations.

The biology of triploid fish

Abstract: This review deals with major areas of triploidy research in fish. It includes not only methods for induction and detection of triploidy but also the impact of triploidy on morphology, anatomy, growth, haematology, energetics, behaviour, endocrinology and gonads in various species of fish, studied so far. The future prospects of research on triploid fish are discussed inviting researchers with diverse areas of interest in fish biology.

Effect of ethanol extract of Piper betle Linn leaf on healing of NSAID-induced experimental ulcer--a novel role of free radical scavenging action.

Abstract: Treatment with ethanol extract of leaf of P. betle at a dose of 150 mg/kg body weight daily for 10 days, after induction of peptic ulcer by NSAID in albino rats, produced significant healing effect. During healing process, on treatment with the extractive, antioxidative factor, e.g. superoxide dismutase and catalase activity, mucus and total gastric tissue sulfhydryl group were increased. In contrast, oxidised lipid and oxidatively modified proteins were reduced to near normalcy, within 7 to 10 days, however, change in the untreated group was not significant. The extract also showed significant in vitro free radical scavenging action. The results suggest that the antioxidant or free radical scavenging activity of the plant extract, may be responsible for its healing action.

Molecular aspects of thyroid hormone actions.

Abstract: Cellular actions of thyroid hormone may be initiated within the cell nucleus, at the plasma membrane, in cytoplasm, and at the mitochondrion. Thyroid hormone nuclear receptors (TRs) mediate the biological activities of T3 via transcriptional regulation. Two TR genes, α and β, encode four T3-binding receptor isoforms (α1, β1, β2, and β3). The transcriptional activity of TRs is regulated at multiple levels. Besides being regulated by T3, transcriptional activity is regulated by the type of thyroid hormone response elements located on the promoters of T3 target genes, by the developmental- and tissue-dependent expression of TR isoforms, and by a host of nuclear coregulatory proteins. These nuclear coregulatory proteins modulate the transcription activity of TRs in a T3-dependent manner. In the absence of T3, corepressors act to repress the basal transcriptional activity, whereas in the presence of T3, coactivators function to activate transcription. The critical role of TRs is evident in that mutations of th...

7 The Gonadal Steroids

Abstract: Publisher Summary This chapter discusses that the gonads potentiality to produce steroids, and the regulation of the syntheses. The nature, shape, and intensity of a hormonal signal, ready to be received by a target cell, is the result of an intricate series of positive and negative regulations. In the case of hormonal steroids in fish, only some aspects of this complex have been considered. Once a steroid is secreted, several mechanisms may inactivate it before it reaches its target. Little is known of catabolism of sexual steroids in teleosts. Most available data are concerned with the total radioactivity found in tissues after fish are fed labeled steroid. The biological significance of glucuronidation or sulfonation remains to be explored. Although the conjugated steroids are usually considered to be inactive, recent studies attribute a pheromonal role to glucuronides. In other respects, the binding to plasma proteins may lead to a reversible inactivation, although, in mammals, it has been suggested that steroid secretion may be enhanced by the presence of serum steroid-binding proteins. Finally, the conversion of plasma steroids into biologically active metabolites can occur in some target tissues. The actual physiological role of gonadal steroids in fish is discussed with emphasis on gametogenesis.

5 Vitellogenesis and Oocyte Assembly

Abstract: Publisher Summary This chapter describes the different aspects of vitellogenesis and oocyte assembly The major components of fish oocytes are derived from the blood-borne high-molecular-weight compound, vitellogenin, which is synthesized in the liver of oviparous vertebrates The classification of vitellogenin as a phospholipoglycoprotein indicates the crucial functional groups that are carried on the protein backbone of the molecule—namely, lipids, some carbohydrates, and phosphate groups In the rainbow trout, estrone administration leads to the induction of vitellogenin synthesis in the liver and its release into the bloodstream, but estrone displays only 5%–12% of the potency of estradiol The biochemical information concerning vitellogenin clearly indicates that a great deal of posttranslational modification must occur in the liver cell to reach the finished product seen in the serum An integral part of estradiol action is the observed hypercalcemia in vitellogenic fish, which can largely be ascribed to the calcium-binding properties of phosphorylated and highly charged, components of the native vitellogenin molecule