About

Ramesh Ramachandran is a Professor of Reproductive Biology and holds the title of Walther H. Ott Professor in Avian Biology at the Department of Animal Science at Pennsylvania State University. He serves as the Director of Graduate Studies and is based in the Animal, Veterinary and Biomedical Sciences Building in University Park, PA. His areas of expertise include endocrinology, ovarian cancer research, and reproductive biology. Dr. Ramachandran's educational background includes a Ph.D. and M.S. from the University of Maryland, College Park, and a B.V.Sc (DVM) from Madras Veterinary College in India. His research focuses on reproductive endocrinology, with particular attention to ovarian function, the effects of metabolic factors such as metformin on reproductive health, and the molecular mechanisms underlying ovarian cancer and reproductive processes in poultry. His work has contributed to understanding how metabolic and hormonal factors influence egg production, ovarian health, and disease in avian species, with implications for both animal health and broader reproductive biology.

Research topics

• Internal medicine
• Endocrinology
• Medicine

Selected publications

• Evaluation of the Central Effects of Systemic Lentiviral-Mediated Leptin Delivery in Streptozotocin-Induced Diabetic Rats

  International Journal of Molecular Sciences · 2021 · 2 citations

  • Internal medicine
  • Endocrinology
  • Medicine

  Type 1 diabetes (T1D) is characterized by hyperphagia, hyperglycemia and activation of the hypothalamic-pituitary-adrenal (HPA) axis. We have reported previously that daily leptin injections help to alleviate these symptoms. Therefore, we hypothesized that leptin gene therapy could help to normalize the neuroendocrine dysfunction seen in T1D. Adult male Sprague Dawley rats were injected i.v. with a lentiviral vector containing the leptin gene or green fluorescent protein. Ten days later, they were injected with the vehicle or streptozotocin (STZ). HPA function was assessed by measuring norepinephrine (NE) levels in the paraventricular nucleus (PVN) and serum corticosterone (CS). Treatment with the leptin lentiviral vector (Lepvv) increased leptin and insulin levels in non-diabetic rats, but not in diabetic animals. There was a significant reduction in blood glucose levels in diabetic rats due to Lepvv treatment. Both NE levels in the PVN and serum CS were reduced in diabetic rats treated with Lepvv. Results from this study provide evidence that leptin gene therapy in STZ-induced diabetic rats was able to partially normalize some of the neuroendocrine abnormalities, but studies with higher doses of the Lepvv are needed to develop this into a viable option for treating T1D.

  PublisherOA PDFDOI

• Development, validation, and utilization of a novel antibody specific to the type III chicken gonadotropin-releasing hormone receptor

  Domestic Animal Endocrinology · 2010-10-21 · 9 citations

  article
  PublisherDOI

• Gonadotropin-inhibitory hormone receptor signaling and its impact on reproduction in chickens

  General and Comparative Endocrinology · 2009-03-30 · 82 citations

  reviewSenior author
  PublisherDOI

• Plasma kisspeptin levels in hypertensive diseases of pregnancy and the identification of kisspeptin in amniotic fluid

  Society for Endocrinology BES 2009 · 2009-03-01 · 1 citations

  article
  Publisher

• Gonadotropin-inhibitory hormone (GnIH) receptor gene is expressed in the chicken ovary: potential role of GnIH in follicular maturation

  Reproduction · 2008-01-31 · 104 citations

  articleOpen accessSenior author

  Gonadotropin-inhibitory hormone (GnIH), an RFamide peptide, has been found to inhibit pituitary LH secretion in avian and mammalian species. The gene encoding a putative receptor for GnIH (GnIHR) was recently identified in the chicken and Japanese quail brain and pituitary gland. GnIHR appears to be a seven-transmembrane protein belonging to a family of G-protein-coupled receptors. In the present study, we have characterized the expression of GnIHR mRNA in the chicken ovary and demonstrate that GnIHR may exert an inhibitory effect on ovarian follicular development. By RT-PCR, we detected GnIHR mRNA in the chicken testis and in the ovary, specifically both thecal and granulosa cell layers. Real-time quantitative PCR analysis revealed greater GnIHR mRNA quantity in theca cells of prehierarchial follicles compared with that of preovulatory follicles. GnIHR mRNA quantity was significantly decreased in sexually mature chicken ovaries versus ovaries of sexually immature chickens. Estradiol (E(2)) and/or progesterone (P(4)) treatment of sexually immature chickens significantly decreased ovarian GnIHR mRNA abundance. Treatment of prehierarchial follicular granulosa cells in vitro with chicken GnIH peptide significantly decreased basal but not FSH-stimulated cellular viability. Collectively, our results indicate that the ovarian GnIHR is likely to be involved in ovarian follicular development. A decrease in ovarian GnIHR mRNA abundance due to sexual maturation or by E(2) and/or P(4) treatment would implicate an inhibitory role for GnIHR in ovarian follicular development. Furthermore, GnIH may affect follicular maturation by decreasing the viability of prehierarchial follicular granulosa cells through binding to GnIHR.

  PublisherOA PDFDOI

• Gonadotrophin‐Inhibitory Hormone Receptor Expression in the Chicken Pituitary Gland: Potential Influence of Sexual Maturation and Ovarian Steroids

  Journal of Neuroendocrinology · 2008-07-11 · 83 citations

  articleSenior author

  Gonadotrophin-inhibitory hormone (GnIH), a hypothalamic RFamide, has been found to inhibit gonadotrophin secretion from the anterior pituitary gland originally in birds and, subsequently, in mammalian species. The gene encoding a transmembrane receptor for GnIH (GnIHR) was recently identified in the brain, pituitary gland and gonads of song bird, chicken and Japanese quail. The objectives of the present study are to characterise the expression of GnIHR mRNA and protein in the chicken pituitary gland, and to determine whether sexual maturation and gonadal steroids influence pituitary GnIHR mRNA abundance. GnIHR mRNA quantity was found to be significantly higher in diencephalon compared to either anterior pituitary gland or ovaries. GnIHR mRNA quantity was significantly higher in the pituitaries of sexually immature chickens relative to sexually mature chickens. Oestradiol or a combination of oestradiol and progesterone treatment caused a significant decrease in pituitary GnIHR mRNA quantity relative to vehicle controls. GnIHR-immunoreactive (ir) cells were identified in the chicken pituitary gland cephalic and caudal lobes. Furthermore, GnIHR-ir cells were found to be colocalised with luteinising hormone (LH)beta mRNA-, or follicle-stimulating hormone (FSH)beta mRNA-containing cells. GnIH treatment significantly decreased LH release from anterior pituitary gland slices collected from sexually immature, but not from sexually mature chickens. Taken together, GnIHR gene expression is possibly down regulated in response to a surge in circulating oestradiol and progesterone levels as the chicken undergoes sexual maturation to allow gonadotrophin secretion. Furthermore, GnIHR protein expressed in FSHbeta or LHbeta mRNA-containing cells is likely to mediate the inhibitory effect of GnIH on LH and FSH secretion.

  PublisherDOI

• EXPRESSION OF ADIPONECTIN AND ITS RECEPTORS, Adipor1 AND Adipor2, IN THE CHICKEN TESTIS

  Biology of Reproduction · 2007-07-01

  articleSenior author

  Adiponectin (ADN) is an adipokine hormone known to affect multiple metabolic processes, including glucose utilization, insulin sensitivity, energy homeostasis and lipid synthesis. In humans, plasma ADN level is inversely correlated to body mass index. Models of diminished ADN, such as obesity in humans, have been found to be associated with the development of insulin resistance, type 2 diabetes and cardiovascular diseases. Although ADN was once thought to be exclusively secreted from adipose tissue, we identified the expression of ADN and its receptors, AdipoR1 and AdipoR2, in multiple chicken tissues, including ovaries. However, the role of ADN and its receptors in reproduction has not been understood. Similar to ADN, AdipoR1 and AdipoR2 expression in the ovary, we hypothesized that ADN and its receptors will be expressed in the chicken testis and that ADN, AdipoR1, and AdipoR2 gene expression would be higher in 8 week-old broiler testis compared with 4 week-old broiler testis. The objectives of the present study are to characterize the cellular expression of ADN, AdipoR1 and AdipoR2 genes and protein in the chicken broiler testis and to quantify the mRNA encoding ADN, AdipoR1, and AdipoR2 in the testis of 4 week-old and 8 week-old broiler chickens. RT-PCR analyses of RNA isolated from broiler testis revealed the presence of ADN, AdipoR1 and AdipoR2 mRNA. Immunohistochemical studies utilizing anti-sera raised against a synthetic chicken AdipoR1, AdipoR2 peptides or recombinant chicken ADN protein confirmed that ADN, AdipoR1 and AdipoR2 are localized in sertoli cells and spermatogonial cells within the seminiferous tubule as well as in the leydig cells in the testis of 9 week-old broiler chicken. Quantitative real-time PCR analyses revealed that ADN, AdipoR1 and AdipoR2 gene expression is upregulated by 1.9-, 2.4-, 1.9-fold, respectively, in 8 week-old versus 4 weekold broiler testis (n=4-5; P<0.01). The physiological role of testicular ADN and its receptors are presently unknown. We speculate that sexual maturation is possibly affecting testicular ADN or its receptors gene expression, as it has been shown that plasma ADN levels are 4-fold higher in sexually mature versus sexually immature mice. In addition, systemic or testicular ADN and its receptors may be involved in steroidogenesis, as ADN has been shown to increase steroidogenic acute regulatory protein mRNA expression and phosphorylation of MAPK-ERK 1/2 in porcine granulosa cells in vitro, both involved in testicular testosterone production. (poster)

  PublisherDOI

• Identification of Calcitonin Expression in the Chicken Ovary: Influence of Follicular Maturation and Ovarian Steroids1

  Biology of Reproduction · 2007-06-20 · 21 citations

  articleSenior author

  Calcitonin (CALCA), a hormone primarily known for its role in calcium homeostasis, has recently been linked to reproduction, specifically as a marker for embryo implantation in the uterus. Although CALCA expression has been documented in several tissues, there has been no report of production of CALCA in the ovary of any vertebrate species. We hypothesized that the Calca gene is expressed in the chicken ovary, and its expression will be altered by follicular maturation or gonadal steroid administration. Using RT-PCR, we detected Calca mRNA and the calcitonin receptor (Calcr) mRNA in the granulosa and theca layers of preovulatory and prehierarchial follicles. Both CALCA and Calca mRNA were localized in granulosa and thecal cells by confocal microscopy. Using quantitative PCR analysis, F1 follicle granulosa layer was found to contain significantly greater Calca mRNA and Calcr mRNA levels compared with those of any other preovulatory or prehierarchial follicle. The granulosa layer contained relatively greater Calca and Calcr mRNA levels compared with the thecal layer in both prehierarchial and preovulatory follicles. Progesterone (P(4)) treatment of sexually immature chickens resulted in a significantly greater abundance of ovarian Calca mRNA, whereas estradiol (E(2)) or P(4) + E(2) treatment significantly reduced ovarian Calca mRNA quantity. Treatment of prehierarchial follicular granulosa cells in vitro with CALCA significantly decreased FSH-stimulated cellular viability. Collectively, our results indicate that follicular maturation and gonadal steroids influence Calca and Calcr gene expression in the chicken ovary. We conclude that ovarian CALCA is possibly involved in regulating follicular maturation in the chicken ovary.

  PublisherDOI

• Calcitonin is expressed in the chicken pituitary gland: influence of gonadal steroids and sexual maturation

  Cell and Tissue Research · 2006-11-08 · 10 citations

  articleSenior authorCorresponding
  PublisherDOI

Frequent coauthors

• Sreenivasa R. Maddineni

  Pennsylvania State University

  8 shared

• Susan M. Krzysik-Walker

  National Institutes of Health

  6 shared

• Gilbert L. Hendricks

  Western University

  6 shared

• Olga M. Ocón-Grove

  Pennsylvania State University

  6 shared

• Grégoy Y. Bédécarrats

  University of Guelph

  2 shared

• Heather McFarlane

  University of Guelph

  2 shared

• P.S. MohanKumar

  University of Georgia

  2 shared

• Sheba M.J. MohanKumar

  Michigan State University

  2 shared

Education

• Ph.D.

  University of Maryland, College Park, Maryland

• M.S.

  University of Maryland, College Park, Maryland

• Other

  Madras Veterinary College, Madras, India