Browsing by Author "Lawrence E. Cornett"

Now showing 1 - 8 of 8

A sexual dimorphism in hypothalamic arginine vasotocin (AVT) gene expression and avt plasma levels in the Japanese quail (Coturnix coturnix japonica) in response to water deprivation
(Academic Press Inc., 2000) Chandra Mohini Chaturvedi; Adity Chowdhary; P. Timothy Wall; Thomas I. Koike; Lawrence E. Cornett
To examine a possible sexual dimorphism in the osmotic control of arginine vasotocin (AVT) release in birds, age-matched male and female Japanese quail were subjected to water deprivation. The observed increased plasma osmolalities were accompanied by increased plasma AVT levels. Plasma mesotocin levels did not change with water deprivation. The sensitivity of the osmotic control of AVT release as determined by the slope of the relationship between plasma AVT levels and plasma osmolalities was significantly (P < 0.05) higher in males than in females. By Northern blot analysis, levels of hypothalamic AVT gene transcripts were increased 2.3 ± 0.14- and 3.5 ± 0.13-fold in water-deprived male and female Japanese quail, respectively, compared to normally hydrated birds. Our data suggest gender- related differences in the osmotic control of AVT release and in hypothalamic AVT gene expression in the Japanese quail.
Age-dependent expression of AVT and its oxytocic-like receptor VT3 in the shell gland of Japanese quail, Coturnix coturnix japonica
(Academic Press Inc., 2010) Rashmi Srivastava; Lawrence E. Cornett; Chandra Mohini Chaturvedi
The avian neurohypophyseal hormone AVT is an important regulatory hormone involved in many physiological processes including oviposition; an age-related phenomenon, through its action on the shell gland. In this study, immunohistochemistry and in situ hybridization was performed to study the expression of immunoreactive (ir) AVT and its oxytocic-like receptor VT3 transcript in the ovary/shell gland of Japanese quail representing sexually immature, mature and old condition. Our results indicate that ir-AVT is present in the ovary of sexually active adult only, but in the shell gland it is observed in both sexually active adult and sexually quiescent old quail. Further, VT3 gene transcript although not detected in the shell gland of sexually immature birds, has been found abundantly in the myometrium of shell gland of sexually active adult quail with a slight decrease in old birds. It is concluded that in addition to the ovarian function and shell gland activity, the expression of AVT and VT3 receptor in the shell gland also varies with the age dependent reproductive/egg laying performance of the Japanese quail. Our findings also suggest that (i) local synthesis of AVT and the expression of its oxytocic-like VT3 receptors is estrogen dependent and (ii) shell gland AVT upregulates its VT3 receptor (paracrine role) in advance to facilitate the role of neurohypophyseal AVT during oviposition. © 2009 Elsevier Inc.
Corticosterone- or metapyrone-induced alterations in adrenal function and expression of the arginine vasotocin receptor VT2 in the pituitary gland of domestic fowl, Gallus gallus
(Academic Press Inc., 2009) Dharmendra Sharma; Lawrence E. Cornett; Chandra Mohini Chaturvedi
The avian neurohypophyseal hormone arginine vasotocin (AVT) is known to be involved in the regulation of adrenocorticotropin (ACTH) release by interacting with the VT2 receptor (VT2R), which is homologous to the mammalian vasopressin V1b receptor (V1bR). To study the role of glucocorticoid in the expression and regulation of the VT2R, corticosterone (1 or 5 mg/bird/day) or metapyrone (10 or 50 mg/kg body weight/day) were administered daily for 8 days to white leghorn chickens. While low doses were ineffective, a high dose of corticosterone upregulated, while metapyrone downregulated, pituitary VT2R mRNA expression and ir-VT2 in the cephalic lobe of the anterior pituitary. Further, although no change was observed in the expression of POMC mRNA, adrenal activity (as judged by the changes in total cholesterol, 3β HSD, cortical cord width and cortico-medullary ratio) exhibited suppression or stimulation following treatment with corticosterone or metapyrone, respectively. In view of the classical negative feedback effect of glucocorticoids at the level of hypothalamic CRH neurons and pituitary corticotrophs, high corticosterone level-induced suppression of the CRH-ACTH axis may have been masked by VT2R-mediated stimulation of corticotrophs, and hence the POMC mRNA level did not change. The same argument could be used for metapyrone. It is concluded that expression of the VT2 receptor is regulated by glucocorticoids in chicken. These findings confirm a role for AVT, mediated by the VT2 receptor, in regulating ACTH secretion during stress and suggest that corticotroph VT2 receptor levels may be dynamically regulated depending on the HPA axis activity. © 2009 Elsevier Inc. All rights reserved.
Effect of estrogen and its antagonist on the expression of arginine vasotocin (AVT) and its oxytocic-like receptor VT3 in the shell gland of Japanese quail, Coturnix coturnix japonica
(Elsevier Inc., 2008) Rashmi Srivastava; Lawrence E. Cornett; Chandra Mohini Chaturvedi
Avian neurohypophysial hormone arginine vasotocin (AVT) is known to regulate shell gland contractility during oviposition. While studying the role of estrogen in the expression and regulation of AVT and its oxytocic-like receptor VT3, using in situ hybridization and immunohistochemistry, it was observed that the expression of AVT and its receptor was not detected in the shell gland of sexually immature Japanese quail. However, administration of estrogen to these birds not only stimulates the growth and activity (as assessed by increased mucosal fold length, total protein content and alkaline phosphatase level) of the shell gland but also upregulates the expression of AVT and VT3. Further, administration of estrogen antagonist tamoxifen to sexually mature bird shows opposite results. On the other hand, localization of ir-AVT, observed in the ovary of sexually mature bird, was not detected in the estrogen treated sexually immature quail. It is concluded that estrogen not only affects the growth and differentiation of avian oviduct, but also regulates the expression of shell gland AVT and its receptor VT3. Present findings suggest that the locally synthesized AVT acts in a paracrine way to upregulate VT3 receptor and thus facilitates the endocrine function of neurohypophysial AVT during oviposition. © 2008 Elsevier Inc. All rights reserved.
Effect of photoperiod and estrogen on expression of arginine vasotocin and its oxytocic-like receptor in the shell gland of the Japanese quail
(Elsevier Inc., 2007) Rashmi Srivastava; Lawrence E. Cornett; Chandra Mohini Chaturvedi
The avian neurohypophysial hormone arginine vasotocin (AVT) is an important regulatory hormone involved in many physiological processes including fluid balance, blood pressure regulation, stress responses and reproductive events including oviposition. The mechanisms by which AVT stimulates myometrial contraction during oviposition are not well established in birds. In the present study, immunohistochemistry and in situ hybridization were used to localize AVT and the oxytocin-like VT3 receptor in the shell gland of Japanese quail (Coturnix coturnix japonica). Using an AVT-specific antibody, immunoreactive AVT (ir-AVT) was observed in the myometrium of both photosensitive and photorefractory birds. Similarly, VT3 receptor gene transcripts were detected in the myometrial layer of the shell gland of both photosensitive and photorefractory birds. Body mass, shell gland mass and length of mucosal folds of the shell gland of photosensitive birds was higher compared to that of photorefractory birds. Treatment of photorefractory birds with estrogen increased shell gland activity (mass and length of mucosal folds) and levels of both AVT and VT3 receptor mRNA, whereas treatment of photosensitive birds with the estrogen antagonist tamoxifen decreased shell gland activity and levels of both AVT and VT3 receptor mRNA. Our results suggest that shell gland contractility in response to AVT may be regulated during the reproductive cycle of the Japanese quail and that, in part, this regulation is estrogen-dependent. © 2007 Elsevier Inc. All rights reserved.
Impact of estrogen and photoperiod on arginine vasotocin and VT3 receptor expression in the shell gland of quail
(Frontiers in Bioscience, 2018) Rashmi Srivastava; Lawrence E. Cornett; Chandra Mohini Chaturvedi
Role of estrogen and photoperiod is well-established in avian reproduction. In addition, the distribution and the expression of arginine vasotocin (AVT) and its receptor VT3 to ensure reproductive/ breeding conditions in Japanese quail influenced by them has been the main focus of this review. To consider this aspect the mRNA expression of VT3 receptor and its ligand AVT in the shell gland has been emphasized. In birds, AVT performs a dual role as an anti-diuretic hormone and the functions accomplished by oxytocin in mammals. The physiological actions of AVT in birds are mediated through its diverse receptor subtypes VT1, VT2, VT3 and VT4. Dynamic alteration of VT3 expression during different reproductive and photo-sexual conditions of quail can be modulated by estrogen. In addition to the endocrine effect of AVT, the shell gland is complemented by its paracrine action via its receptors. Evidences indicate that the expression of shell gland AVT modulated by estrogen appears to play a priming role by modulating the availability of VT3 receptor for the required action of neurohypophysial AVT during oviposition. © 1996-2018
Osmotic stress induced alteration in the expression of arginine vasotocin receptor VT2 in the pituitary gland and adrenal function of domestic fowl
(Academic Press Inc., 2009) Dharmendra Sharma; Lawrence E. Cornett; Chandra Mohini Chaturvedi
The role of arginine vasotocin in the regulation of the pituitary-adrenal axis of domestic fowl was analyzed by studying the expression of its recently cloned pituitary receptor VT2 and adrenal activity following osmotic stress. Four days of water deprivation induced an increase in plasma osmolality-a known stimulator of AVT synthesis and release from hypothalamic magnocellular neurons. Water deprivation also decreased pituitary mRNA levels for both the VT2 receptor and for pro-opiomelanocortin (POMC). Despite a decrease in the expression of VT2 mRNA, immunoreactive-VT2 receptor levels in the pituitary increased, suggesting a possible role for post-transcriptional mechanisms in the regulation of this receptor. Further, adrenal activity (as judged by adrenal weight, cholesterol content, 3β hydroxysteroid dehydrogenase, cortical cord width and cortico-medullary ratio) showed stimulation in water-deprived chicken as compared to control. On the basis of present findings, it is concluded that water deprivation down regulates the mRNA expression of AVT receptor VT2 as well as POMC but stimulates adrenal function. It is also suggested that in addition to the release of magnocellular AVT into the neurohypophysis to act as antidiuretic hormone following water deprivation, AVT may also modulate HPA axis to cope with the osmotic stress. © 2008 Elsevier Inc.
Water deprivation and circadian changes in plasma arginine vasotocin and mesotocin in the domestic hen (Gallus domesticus)
(2001) Chandra Mohini Chaturvedi; Adity Chowdhury; Lawrence E. Cornett
Possible circadian variations in plasma levels of arginine vasotocin (AVT) and mesotocin (MT) were assessed in domestic hens (Gallus domesticus) under a 12h:12h light-dark (LD) schedule. Blood samples were taken at 4h intervals, and neurohypophyseal hormone levels were determined by radioimmunoassay. Marked circadian changes in both AVT and MT were observed in hens provided free access to water. Minimal and maximal AVT levels occurred at 08:00 and 20:00, respectively. Minimal MT levels occurred at 20:00, whereas maximal MT levels occurred over a broad time period of 04:00 to 12:00. In water-deprived hens, plasma AVT levels were elevated at each time point, and the circadian variations in plasma AVT and MT levels were attenuated. These results demonstrate that rhythmicity in neurohypophyseal function in a lower vertebrate species, like that in mammals, is disrupted by osmotic stress.