Browsing by Author "Vikas Kumar Roy"

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Carnitine-mediated antioxidant enzyme activity and Bcl2 expression involves peroxisome proliferator-activated receptor-γ coactivator-1α in mouse testis
(CSIRO, 2017) Vikas Kumar Roy; Rachna Verma; Amitabh Krishna
The protective effects of carnitine have been attributed to inhibition of apoptosis, alleviating oxidative stress and DNA repair mechanism by decreasing oxidative radicles. Carnitine also increases mitochondrial biogenesis via peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α). The role of carnitine in testicular PGC1α expression has not been documented. We hypothesised that the effects of carnitine as an antioxidant, inhibitor of apoptosis and controller of steroidogenesis in mouse testis may involve PGC1α as a regulator. The present study was designed to evaluate the localisation of PGC1α and the effects of carnitine treatment on the expression of PGC1α, Bcl2 and antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)) in mouse testis and serum testosterone concentrations. PGC1α was primarily immunolocalised to the Leydig cells and primary spermatocytes. Western blot analysis showed that carnitine (50mgkg-1 and 100mgkg-1 for 7 days) significantly increased PGC1α and Bcl2 expression in the testis in a dose-dependent manner. In addition, carnitine treatment significantly increased antioxidant enzyme (CAT, SOD and GPx) levels. The carnitine-induced changes in PGC1α in the testis were significantly correlated with changes in serum testosterone concentrations, as well as with changes in Bcl2 expression and antioxidant enzyme activity in the testis, as evaluated by electrophoresis. Therefore, the results of the present study suggest that carnitine treatment of mice increases PGC1α levels in the testis, which may, in turn, regulate steroidogenesis by increasing expression of Bcl2 and antioxidant enzymes. © 2017 CSIRO.
Changes in glucose and carnitine levels and their transporters in utero-tubal junction in relation to sperm storage in the vespertilionid bat, Scotophilus heathi
(2013) Vikas Kumar Roy; Amitabh Krishna
Prolonged sperm storage over winter is a common feature of reproduction in some bats. In order to understand how sperm storage in the female genital tract of the vespertilionid bat, Scotophilus heathi (Greater yellow bat), is controlled, we compared concentrations of glucose and the fatty-acid carrier carnitine in the blood, and carnitine concentrations and levels of expression of the glucose transporters (GLUTs) and the carnitine transporter OCTN2 in the utero-tubal junction of females during non-storage (early winter) and sperm-storage periods (late winter-early spring). During the sperm-storage period (December-January) blood glucose concentrations declined, as did the expression of GLUT3 and GLUT5 in the utero-tubal junction. At the same time there were increases in the concentration of carnitine, and expression of OCTN2 and hormone-sensitive lipase (HSL) in the utero-tubal junction. These results suggest that prolonged sperm storage is enhanced by decreased glucose availability but increased free fatty acid availability at the site of sperm storage. Increases in expression of GLUT4 and GLUT8 in late winter suggest a role for these GLUTs in increasing sperm motility prior to fertilization. © 2013 Wiley Periodicals, Inc.
Changes in the expression of HSL and OCTN2 in the female reproductive tract of the bat, Scotophilus heathii in relation to sperm storage
(2012) Vikas Kumar Roy; Amitabh Krishna
The aim of this study was to compare the changes in the expression of hormone sensitive lipase (HSL) and organic cation transporter 2 (OCTN2) in different regions of the female reproductive tract of bats (. Scotophilus heathii) during the period of sperm storage. Western blot analysis revealed that both HSL and OCTN2 showed elevated expression in the utero-tubal junction, the site of sperm storage, compared to the vagina, cervix and uterus. An immunohistochemical study showed localization of HSL and OCTN2 in the cytoplasm of luminal epithelial cells in the utero-tubal junction of . S. heathii, which suggests a role of fatty acids metabolism at the site of sperm storage. Furthermore, this study showed the presence OCTN2 immunostaining in the tail of stored sperm, which suggests a direct role of carnitine in sperm physiology. However, the role of carnitine in sperm storage needs further investigation. It is hypothesized that the utero-tubal junction may be finely tuned with fat depletion to support sperm storage in the female genital tract of . S. heathii. © 2011 Elsevier GmbH.
Evidence of androgen-dependent sperm storage in female reproductive tract of Scotophilus heathi
(Academic Press Inc., 2010) Vikas Kumar Roy; Amitabh Krishna
The aim of present study was to investigate the role of androgen in sperm storage in the female genital tract of Scotophilus heathi. Spermatozoa were observed in the distal part of oviduct and utero-tubal junction of all the female bats collected between January and early March. Increase in circulating testosterone level coincided with the arrangement of sperm with their head oriented towards the epithelial lining of reproductive tract. Immunocytochemical and Western blot analysis revealed the presence of androgen receptor (AR) only in the distal part of the oviduct and utero-tubal junction, the site of sperm storage. Localization of AR in the cytoplasm of luminal epithelial cells in utero-tubal junction of S. heathi suggests non-genomic action of androgen at the site of sperm storage. Further study showed the presence of intense immunoreactivity of androgen binding protein (ABP) in the glandular epithelial cells of utero-tubal junction. It is hypothesized that androgen creates a unique microenvironment e.g. secretion of ABP within lumen of utero-tubal junction which helps to store spermatozoa for prolonged period in the female genital tract of S. heathi. © 2009 Elsevier Inc. All rights reserved.
Hormones and reproductive cycles in bats
(Elsevier, 2024) Amitabh Krishna; Vikas Kumar Roy; Arnab Banerjee
Highly diversified bats are shown to evolve numerous unusual reproductive specializations. Bats have a high basal metabolic rate, and energy produced is utilized mainly for flight. As a result, only limited energy is spared for reproduction. Majorities of bats are seasonal breeders due to insufficient availability of energy. Reproduction in temperate-zone bats initiated following arousal in spring coincides with the period of active food intake. Reproduction in these bats is suppressed during hibernation. Nonhibernating tropical bats show one or more breeding cycles, depending upon the availability of food. Temperate male bats exhibit a unique feature of reproductive asynchrony between spermatogenesis and functioning of accessory sex glands and libido because sufficient energy is not available to support both activities simultaneously. Many neotropical bats produce spermatozoa at a very high rate. Prolonged sperm retention in epididymis, prolonged lifespan, geographical variation in reproduction, and menstruation are some unusual features of the bat. Gonadal hormones together with metabolic hormones affect reproductive activities by regulating energy homeostasis. Female bats are unusually sensitive to environmental changes resulting in a variety of reproductive delays, such as delayed ovulation, sperm storage, delayed implantation, and development. The delays allow young to be born at an energetically favorable time. Detailed knowledge of the reproductive characteristics of this unique and ecologically important group of mammal is essential for their conservation. © 2024 Elsevier Inc. All rights reserved.
Mechanisms of prolonged sperm storage in female bats
(Nova Science Publishers, Inc., 2011) Amitabh Krishna; Vikas Kumar Roy
Prolonged sperm storage is an adaptation to the reproductive cycle that is most highly developed in microchiroptera, where sperm may be stored up to ~198 days and still retain fertilizing capacity. The aim of this review is to describe the mechanism and molecules necessary for sperm to become efficiently stored in the female genital tract. Perpendicular orientation of sperm with their head towards the reproductive tract epithelium are characterized in all sperm-storing bat species so far investigated, suggesting that such relationships are an integral part of the mechanism of prolonged storage of sperm. Recent study suggests that the ultimate controls of the mechanism underlying sperm storage are hormonal. It has been demonstrated that sperm-storing female bats contain a high circulating level of androgen during the period of sperm storage. It is suggested that androgen creates a unique microenvironment that facilitates prolonged sperm storage. The identification of the specific molecules responsible for prolonged sperm storage may suggest a mechanism to keep sperm viable for a prolonged period for use in assisted reproductive techniques. © 2011 Nova Science Publishers, Inc. All rights reserved.
Regulation of leptin synthesis during adipogenesis in males of a vespertilionid bat, Scotophilus heathi
(2011) Vikas Kumar Roy; Amitabh Krishna
The aim of this study was to elucidate the hormonal regulation of leptin synthesis by the white adipose tissue (WAT) during the period of fat accumulation in male Scotophilus heathi. An in vivo study showed a significant correlation between the seasonal changes in serum insulin level with the circulating leptin level and with the changes in body fat mass in S. heathi. An in vitro study showed insulin induced a significant increase in expression of leptin protein in WAT. The insulin-stimulated increase in leptin expression was associated with increased uptake of glucose in the WAT. Two glucose transporters (GLUT4 and GLUT8) are utilized for transport of glucose in the WAT during adipogenesis in the bat. The bats showed high insulin and glucose levels, but a reduction in insulin receptor protein during the period of fat deposition, suggesting insulin resistance, which improved in late winter (January) when most of the fat has been utilized as a metabolic fuel. The in vitro study confirmed that insulin enhanced leptin and GLUT4 expression in WAT. The in vitro study further showed that the expression of leptin is directly proportional to the amount of glucose uptake by the WAT. The expression of GLUT4 and GLUT8 were also shown to be differentially regulated by insulin during adipogenesis. The insulin-stimulated increase in leptin synthesis by WAT is mediated through phosphorylation of MAPK in S. heathi. The specific role of GLUT4 and GLUT8 in the regulation of leptin synthesis during adipogenesis needs further investigation. © 2011. Published by The Company of Biologists Ltd.
Role of leptin in seasonal adiposity associated changes in testicular activity of vespertilionid bat, Scotophilus heathi
(Academic Press Inc., 2010) Vikas Kumar Roy; Amitabh Krishna
The aim of this study was to investigate changes in circulating level of leptin in natural population of male bat, Scotophilus heathi in relation to seasonal changes in body mass, adipose tissue mass and testicular activity. The peak serum leptin level coincided with the period of maximum body mass due to heavy accumulation of adipose tissue. The in vivo study showed both inhibitory and stimulatory effects on testicular activity depending on circulating level of leptin. Moderate increase in circulating concentration of leptin coincided with the stimulatory effect on testicular activity in October, whereas peak circulating concentration of leptin coincided with suppressed testicular activity in December. Immunohistochemical and Western blot analysis confirmed expression of leptin receptors (Ob-R) in the testis, particularly in Leydig cells during different reproductive stages suggesting the direct action of leptin in regulation of testicular steroidogenesis. The in vitro study confirmed the in vivo observations of inhibitory effect of leptin on testosterone production through dose-dependent StAR expression in the testis. This study further showed that the leptin affects testicular activity through STAT3 mediated regulation of StAR expression. Thus, increased adiposity associated rise in circulating leptin level during winter dormancy impairs testicular activity by suppressing StAR mediated testosterone production in S. heathi. These results are suggestive of a link between the adipocyte derived leptin and testicular function. © 2010 Elsevier Inc.
Sperm storage in the female reproductive tract of Scotophilus heathii: Role of androgen
(2011) Vikas Kumar Roy; Amitabh Krishna
The aim of the present study was to investigate the mechanism of androgen-mediated, prolonged sperm-storage in the female reproductive tract of the bat, Scotophilus heathii. The bat treated in vivo with flutamide, an androgen antagonist, showed loss of spermatozoa at the storage site, utero-tubal junction. Immunocytochemistry and Western blot analysis revealed the presence of increased expression of Bcl2 in the epithelial cell lining of the utero-tubal junction during the period of sperm-storage. Treatment with testosterone in vitro caused a significant dose-dependent increase in expression of the survival factor Bcl2, whereas treatment with flutamide together with testosterone caused a significant decline in Bcl2 in the utero-tubal junction of S. heathii. Together with the expression of Bcl2, the utero-tubal junction also expresses the death signal, caspase3. Expression of caspase3 decreased during January, but increased in February during the late stage of sperm storage. Androgen stimulated Bcl2 synthesis in the utero-tubal junction via the non-genomic MAP kinase signaling pathway. In conclusion, this study suggests that androgen promotes sperm storage in S. heathii by stimulating the survival factor Bcl2 in the utero-tubal junction. It is further hypothesized that a balance between the survival factor, Bcl2, and the death signal, caspase3, determines the duration of sperm storage in S. heathii. © 2011 Wiley-Liss, Inc.
Status of visfatin in female reproductive function under normal and pathological conditions: a mini review
(Springer Science and Business Media B.V., 2024) Lalrawngbawli Annie; Pranay Punj Pankaj; Rajesh Kumar Kharwar; Ajit Singh; Vikas Kumar Roy
Adipokines are now well-known to regulate reproduction. Visfatin is an adipokine expressed in the hypothalamus, pituitary, ovary, uterus, and placenta of different species, and since it has been found to modulate the endocrine secretion of the hypothalamus, pituitary gland and ovary, it may be considered a novel regulator of female reproduction. Although the majority of the literature explored its role in ovarian regulation, visfatin has also been shown to regulate uterine remodeling, endometrial receptivity and embryo development, and its expression in the uterus is steroid dependent. Like other adipokines, visfatin expression and levels are deregulated in pathological conditions including polycystic ovary syndrome. Thus, the present mini-review focuses on the role of visfatin in female reproduction under both physiological and pathological conditions. © The Author(s), under exclusive licence to Springer Nature B.V. 2024.
The expression pattern of the glucose transporter GLUT-5 in the testis during the spermatogenic cycle of the vespertilionid bat Scotophilus heathi
(Academic Press Inc., 2013) Vikas Kumar Roy; Amitabh Krishna
The aims of this study were to investigate the localization and rate of expression of GLUT-5 protein during the spermatogenic cycle of Scotophilus heathi and to determine whether the expression of testicular GLUT-5 was under androgenic control. This study showed localization of GLUT-5 mainly in the spermatogonia, spermatids, spermatozoa and Leydig cells of the testis in S. heathi. Western blot analysis showed marked variation in the rate of expression of GLUT-5 protein in the testis during the reproductive cycle, in which peak expression of GLUT-5 in the testis coincided with the period of peak spermatogenesis and mating. Treatment with flutamide (an anti-androgen) caused a dose-dependent decrease in the expression of GLUT-5 protein in the testis that suggested that the expression of GLUT-5 was under androgenic control. We propose that GLUT-5 plays an important role in the transport into spermatozoa of the fuel that is required for prolonged storage in the female genital tract in S. heathi. © 2013 Elsevier Inc.