Chandra Mohini Chaturvedi

Bio: Chandra Mohini Chaturvedi is an academic researcher from Banaras Hindu University. The author has contributed to research in topics: Quail & Vasotocin. The author has an hindex of 19, co-authored 92 publications receiving 1161 citations. Previous affiliations of Chandra Mohini Chaturvedi include University of Arkansas for Medical Sciences.

Testosterone modulates pituitary vasotocin receptor expression and adrenal activity in osmotically stressed chicken.

Abstract: Regulation of arginine vasotocin (AVT), avian neurohypophyseal hormone, is an important component of the hypothalamo-pituitary-adrenal axis. Changes in plasma osmolality levels and sex steroids are known to affect AVT gene expression. The present study reports the effect of water deprivation and testosterone treatment independently, as well as simultaneously, on the pituitary vasotocin receptor VT2R expression and adrenal steroidogenic activity in sexually immature male chicken (Gallus gallus). Birds were divided into four groups- control, water deprived (WD), testosterone injected (TE) and TE treated water deprived (TE+WD). WD decreased and TE treatment alone or in combination with WD (TE+WD) increased VT2R expression compared to the control. Expression of pro-opiomelanocortin (POMC) was also studied since this gene is a polypeptide precursor of ACTH and is under the negative feedback of adrenal corticoids. TE treatment as well as WD separately or when coupled together decreased the POMC mRNA expression in the pituitary but stimulated adrenal steroidogenic activity. Further, VT2R expression decreased in TE+WD compared to TE group, but it was not different from the vehicle treated control group suggesting that the suppressive effect of WD on VT2R expression was inhibited by the stimulatory effect of testosterone. Similarly, although both TE and WD decreased POMC expression and increased steroidogenic activity, no further decrease or increase in these parameters was observed when these two (WD and TE) treatments were combined together. Although, the exact mechanism is not clear, data indicate a stimulatory action of testosterone on VT2R expression and adrenal function despite a decreased expression of POMC mRNA. Results also suggest that testosterone treatment to sexually immature birds, in addition to its effect on hypothalamic AVT neurons (earlier study) and pituitary VT2R expression (present study), masks or inhibits osmotic stress-induced alterations in pituitary-adrenal activity.

Seasonal changes in immune function.

Abstract: Winter is energetically demanding Physiological and behavioral adaptations have evolved among nontropical animals to cope with winter because thermoregulatory demands increase when food availability decreases Seasonal breeding is central within the suite of winter adaptations among small animals Presumably, reproductive inhibition during winter conserves energy at a time when the adds of producing viable young are low In addition to the well-studied seasonal cycles of mating and birth, there are also significant seasonal cycles of illness and death among many populations of mammals and birds in the field Challenging winter conditions, such as low ambient temperatures and decreased food availability, can directly induce death via hypothermia, starvation or shock In some cases, survival in demanding winter conditions puts individuals under great physiological stress, defined here as an adaptive process that results in elevated blood levels of glucocorticoids The stress of coping with energetically demanding conditions can also indirectly cause illness and death by compromising immune function Presumably, the increased blood concentrations of adrenocortical steroids in response to winter stressors compromise immune function and accelerate catabolic mechanisms in the field, although the physiological effects of elevated glucocorticoids induced by artificial stressors have been investigated primarily in the laboratory However, recurrent environmental stressors could reduce survival if they evoke persistent glucocorticoid secretion The working hypothesis of this article is that mechanisms have evolved in some animals to combat seasonal stress-induced immunocompromise as a temporal adaptation to promote survival Furthermore, we hypothesize that mechanisms have evolved that allow individuals to anticipate periods of immunologically challenging conditions, and to cope with these seasonal health-threatening conditions The primary environmental cue that permits physiological anticipation of season is the daily photoperiod; however, other environmental factors may interact with photoperiod to affect immune function and disease processes The evidence for seasonal fluctuations in lymphatic organ size, structure, immune function, and disease processes, and their possible interactions with recurrent environmental stressors, is reviewed Seasonal peaks of lymphatic organ size and structure generally occur in late autumn or early winter and seasonal minima are observed prior to the onset of breeding Although many of the field data suggest that immune function and disease processes are also enhanced during the winter, the opposite seasonal pattern is also observed in some studies We propose that compromised immune function may be observed in some populations during particularly harsh winters when stressors override the enhancement of immune function evoked by short day lengths Because so many factors covary in field studies, assessment of our proposal that photoperiod mediates seasonal changes in immune function requires laboratory studies in which only photoperiod is varied A review of the effects of photoperiod on immune function in laboratory studies reveals that exposure to short day lengths enhances immune function in every species examined Short day exposure in small mammals causes reproductive inhibition and concomitant reduction in plasma levels of prolactin and steroid hormones, as well as alterations in the temporal pattern of pineal melatonin secretion These hormones affect immune function, and influence the development of opportunistic diseases, including cancer: however, it appears that either prolactin or melatonin secretion is responsible for mediating the effects of photoperiod on immune function Taken together, day length appears to affect immune function in many species, including animals that typically do not exhibit reproductive responsiveness to day length

Gene regulation in the magnocellular hypothalamo-neurohypophysial system.

Abstract: The hypothalamo-neurohypophysial system (HNS) is the major peptidergic neurosecretory system through which the brain controls peripheral physiology. The hormones vasopressin and oxytocin released from the HNS at the neurohypophysis serve homeostatic functions of water balance and reproduction. From a physiological viewpoint, the core question on the HNS has always been, "How is the rate of hormone production controlled?" Despite a clear description of the physiology, anatomy, cell biology, and biochemistry of the HNS gained over the last 100 years, this question has remained largely unanswered. However, recently, significant progress has been made through studies of gene identity and gene expression in the magnocellular neurons (MCNs) that constitute the HNS. These are keys to mechanisms and events that exist in the HNS. This review is an inventory of what we know about genes expressed in the HNS, about the regulation of their expression in response to physiological stimuli, and about their function. Genes relevant to the central question include receptors and signal transduction components that receive and process the message that the organism is in demand of a neurohypophysial hormone. The key players in gene regulatory events, the transcription factors, deserve special attention. They do not only control rates of hormone production at the level of the gene, but also determine the molecular make-up of the cell essential for appropriate development and physiological functioning. Finally, the HNS neurons are equipped with a machinery to produce and secrete hormones in a regulated manner. With the availability of several gene transfer approaches applicable to the HNS, it is anticipated that new insights will be obtained on how the HNS is able to respond to the physiological demands for its hormones.