Showing papers by "Chandra Mohini Chaturvedi published in 2004"

Expression of hypothalamic arginine vasotocin gene in response to water deprivation and sex steroid administration in female Japanese quail.

Abstract: Arginine vasotocin (AVT) is a neurohypophyseal hormone involved in reproductive function and control of osmoregulation in birds. In view of the dual function of AVT, the present experiment was designed to observe the effect of water deprivation (WD) and sex steroid [estradiol benzoate (EB) and testosterone propionate (TP)] treatment independently, as well as simultaneously, on the profile/activity of the hypothalamic AVT system. WD resulted in a significant increase in plasma osmolality, sodium ion concentration and AVT concentration, but administration of sex steroids had no significant influence on these parameters. By contrast, the amount of hypothalamic AVT transcript (northern analysis) and the size of immunoreactive vasotocin (ir-AVT) neurons and hybridization signals (in the form of silver grains), representing AVT mRNA in corresponding neurons of paraventricular nuclei (PVN), increased significantly in all the treated groups compared with controls. Our findings indicate that although sex steroid administration has no effect on plasma osmolality and AVT concentration, unlike water deprivation, it may stimulate the profile/activity of AVT neurons of PVN, supporting the possibility of sex steroid receptors on these neurons. It is concluded that in quail, osmotic stress not only upregulates the expression of the AVT gene in existing neurons but also recruits many more neurons to increase the rate of AVT synthesis and secretion, while sex steroids appear to have a stimulatory effect only on the existing number of neurons and only at the level of transcription/translation and hence may influence/modulate hypothalamic AVT gene expression in response to osmotic stress. This study also suggests an interrelationship between reproduction and AVT system/function in birds.

Age and Sex Dependent Variations in the Arginine Vasotocin Gene in Response to Dehydration in the Chicken and Japanese Quail

Abstract: Age and sexdependent variations in the arginine vasotocin gene in response to dehydration in the chicken and Japanese quail. Zoological Studies 43(1): 86-92. The present study was conducted to investigate and compare age- and sex-dependent central and peripheral effects of osmotic stress (4 d of water deprivation) in 2 poultry species: the chicken (Gallus gallus domesticus) and Japanese quail (Coturnix coturnix japonica). Following dehydration in sexually immature (young) and mature (adult) birds of both sexes, Northern blot analysis was performed, and changes in body weight and plasma osmolality were estimated. Following 4 d of water deprivation, young and adult quail of both sexes exhibited significant losses of body weight and increases in plasma osmolality compared to their hydrated controls. Northern blot analysis revealed 1.24- and 1.95-fold increases in AVT transcripts in water-deprived adult male and female and 1.45- and 1.42-fold increases in young male and female quail, respectively; whereas 1.27- and 1.6- and 1.44- and 1.65-fold increases compared to the controls in water-deprived adult and young, male and female chickens, respectively, were found. We concluded that osmotic stress induced by water deprivation is a potent stimulator for hypothalamic gene expression in the chicken and Japanese quail, and that the response of the AVT system varies with the reproductive age and sex of the birds. In view of the remarkable difference in the amount of hypothalamic AVT transcripts and the peripheral responses of young and adult birds to osmotic stress, the present study suggests a modulatory role of sex steroids in water homeostasis.