Cellular localization and seasonal variation of GnRH and Bradykinin in the ovary of Heteropneustes fossilis (Bloch.) during its reproductive cycle.

The present study investigates the distribution and dynamics of gonadotropin-releasing hormone I (GnRH I) and bradykinin in the air-breathing catfish, Heteropneustes fossilis, in relation to the reproductive cycle. Changes in bradykinin, bradykinin B2-receptor, and ovarian GnRH I regulation were demonstrated during the reproductive cycle. The localization of GnRH I, bradykinin, and their respective receptors in the ovaries was investigated by immunohistochemistry, while their levels were quantified by slot/western blot followed by densitometry. GnRH I and its receptor were mainly localized in the cytoplasm of oocytes during the early previtellogenic phase. However, as the follicles grew larger, immunoreactivity was observed in the granulosa and theca cells of the late previtellogenic follicles. The ovaries showed significantly higher expression of GnRH I protein and its receptor during the early to mid-previtellogenic phase, suggesting their involvement in follicular development. Bradykinin and bradykinin B2-receptor showed a distribution pattern similar to that of GnRH I and its receptor. This study further suggested the possibility that bradykinin regulates GnRH I synthesis in the ovary. Thus, we show that the catfish ovary has a GnRH-bradykinin system and plays a role in follicular development and oocyte maturation in H. fossilis.

Adaptive changes in energy reserves and effects of body melanization on thermal tolerance in Drosophila simulans.

Seasonally polyphenic types have been documented in many Drosophilids, which differ significantly during thermal stress. Although Drosophila simulans is a sibling species to Drosophila melanogaster, both thrive in the temperate and tropical climates, but various climatic factors are expected to impact their distribution and abundance. As a result, D. simulans may use phenotypic plasticity to adapt to colder and drier circumstances in temperate zones, although such studies are less known. In the present study, our main aim was to find a link between adaptive plasticity and thermal tolerance in D. simulans. We characterized two morphs in D. simulans flies based on the abdominal melanization collected from the same locality and season, as this trait is highly associated with the larval developmental conditions. Our results suggested that flies reared from dark and light morph showed significant differences in the basal level of proline, carbohydrates (trehalose, glycogen), and lipids (cuticular lipids and total body lipids) within simulated seasons and morph lineages in D. simulans flies. We further showed that D. simulans reared from dark morph are better adapted to cold conditions, whereas light flies are more adapted to warm conditions. The flies, both from light and dark morph lineages, when reared at 15 °C, showed an increase in the level of total body lipids after acclimation at 0 °C but a decrease in the level of proline and carbohydrates (trehalose, glycogen). Heat acclimation increases glycogen levels in the flies from light morph lineage while decreases trehalose and proline.

Central and peripheral neuropeptide RFRP-3: A bridge linking reproduction, nutrition, and stress response.

This article is an amalgamation of the current status of RFRP-3 (GnIH) in reproduction and its association with the nutrition and stress-mediated changes in the reproductive activities. GnIH has been demonstrated in the hypothalamus of all the vertebrates studied so far and is a well-known inhibitor of GnRH mediated reproduction. The RFRP-3 neurons interact with the other hypothalamic neurons and the hormonal signals from peripheral organs for coordinating the nutritional, stress, and environmental associated changes to regulate reproduction. RFRP-3 has also been shown to regulate puberty, reproductive cyclicity and senescence depending upon the nutritional status. A favourable nutritional status and the environmental cues which are permissive for the successful breeding and pregnancy outcome keep RFRP-3 level low, whereas unfavourable nutritional status and stressful conditions increase the expression of RFRP-3 which impairs the reproduction. Still our knowledge about RFRP-3 is incomplete regarding its therapeutic application for nutritional or stress-related reproductive disorders.

Effects of gonadotropin-releasing hormone agonist and antagonist on ovarian activity in a mouse model for polycystic ovary.

PCOS is a major cause of anovulatory infertility in women in their reproductive age. However, its etiology and pathophysiology remain uncertain. The immature mice chronically injected with DHEA, termed as PCO-mice, develop numerous large cystic follicles, high circulating androgen and anovulation similar to PCOS in women. Although PCO-mice show decreased ovarian GnRH I-receptor in immunoblot but show increased immunostaining for GnRH I-receptor in oocytes of cystic follicles. PCO-mice show reduced ovarian LH receptor expression, circulating estradiol and progesterone level compared to normal mice injected with vehicle only. The treatment with low dose of GnRH-Agonist in PCO-mice restores ovarian LH receptor expression to the level of normal mice and promote ovulation and formation of functional corpus luteum. GnRH-Antagonist although cause ovulation in PCO-mice but does not restore LH receptor expression to the level of normal mice, and they show low circulating progesterone and hypertrophied vacuolated corpus luteum. Our study suggests that GnRH-agonist restores ovulation in PCO-mice and produces biphasic and beneficial effect over the use of GnRH-Antagonist.

Immunohistochemical localization of GnRH and RFamide-related peptide-3 in the ovaries of mice during the estrous cycle.

Gonadotropin releasing hormone (GnRH) has now been suggested as an important intraovarian regulatory factor. Gonadotropin inhibitory hormone (GnIH) a hypothalamic dodecapeptide, acts opposite to GnRH. GnRH, GnIH and their receptors have been demonstrated in the gonads. In order to find out the physiological significance of these neuropeptides in the ovary, we aim to investigate changes in the abundance of GnRH I and GnIH in the ovary of mice during estrous cycle. The present study investigated the changes in GnRH I, GnRH I-receptor and RFRP-3 protein expression in the ovary of mice during estrous cycle by immunohistochemistry and immunoblot analysis. The immunoreactivity of GnRH I and its receptor and RFRP-3 were mainly localized in the granulosa cells of the healthy and antral follicles during proestrus and estrus and in the luteal cells during diestrus 1 and 2 phases. The relative abundance of immunoreactivity of GnRH I, GnRH I-receptor and RFRP-3 undergo significant variation during proestrus and thus may be responsible for selection of follicle for growth and atresia. A significant increase in the concentration of RFRP-3 during late diestrus 2 coincided with the decline in corpus luteum activity and initiation of follicular growth and selection. In general, immunolocalization of GnRH I, GnRH I-receptor and RFRP-3 were found in close vicinity suggesting functional interaction between these peptides. It is thus, hypothesized that interaction between GnRH I-RFRP-3 neuropeptides may be involved in the regulation of follicular development and atresia.

Changes in bradykinin and bradykinin B(2)-receptor during estrous cycle of mouse.

The aim of the study was to investigate changes in the abundance of bradykinin and bradykinin B2-receptor in the ovary of mice during its estrous cycle. Changes in the abundance of bradykinin were correlated with changes in bradykinin B(2)-receptor in order to determine the functional significance of this peptide for follicular development, ovulation and luteinization. Bradykinin immunoreactivity was mainly observed in the granulosa cells of antral follicles, especially around the oocytes and lining the antral cavity during proestrus and estrus phases of the cycle. Recently formed corpora lutea showed mild immunoreactivity for both bradykinin and bradykinin B(2)-receptor. During diestrus 1 and diestrus 2, bradykinin and bradykinin B(2)-receptor immunostaining was mainly found in the corpora lutea and mildly in the antral follicles. Immunoblot analysis for bradykinin and bradykinin B(2)-receptor attained a peak during late evening in proestrus, which may be the time of the LH surge. Thereafter bradykinin and bradykinin B(2)-receptor declined sharply during the estrus phase. When the concentration of bradykinin was correlated with bradykinin B(2)-receptor throughout the estrous cycle, they showed strong positive correlation. Thus, this study indicates that the levels of bradykinin and bradykinin B(2)-receptor both simultaneously regulate estrous cycle and are important components for the reproductive process.

Effects of gonadotropin-inhibitory hormone on folliculogenesis and steroidogenesis of cyclic mice.

OBJECTIVE: To evaluate the effects of gonadotropin-inhibitory hormone (GnIH) treatment on ovarian activity of mice. DESIGN: Animal study. SETTING: Reproductive physiology laboratory of university department of zoology. ANIMAL(S): Twelve-week-old female mice of inbred Parkes strain. INTERVENTION(S): Mice treated with different doses of GnIH (control, 100 ng, 500 ng, and 2 µg per day) for 8 days were studied. For in vitro study, the ovaries of proestrus mice were cultured with different doses of GnIH for 24 hours at 37 °C. MAIN OUTCOME MEASURE(S): Folliculogenesis, steroidogenesis, luteogenesis, and apoptosis in the ovaries of control and GnIH-treated mice. RESULT(S): GnIH treatment produced significant changes in body mass, circulating steroid levels, and ovarian activity in the mice. GnIH also caused dose-dependent histologic changes in follicular development and luteinization. The antral follicles showed abnormal changes. The mice treated with increasing dose of GnIH showed significant changes in steroid synthesis owing to inhibitory effects of GnIH on ovarian expression of LH receptor, steroidogenic acute regulatory, and 3ß-hydroxysteroid dehydrogenase proteins. CONCLUSION(S): GnIH inhibited follicular development and steroidogenesis in the ovary of mice. This study thus suggests biologic significance of this neuropeptide in regulating ovarian activity.

Effects of GnRH agonist treatment on steroidogenesis and folliculogenesis in the ovary of cyclic mice.

BACKGROUND: GnRH analogs (both agonist and antagonist) have been extensively used for clinical applications, following the discovery of its direct effects on ovary. With regard to the direct actions of GnRH agonist on ovary, conflicting data are reported. The mechanism through which GnRH agonist affect gonadal functions is still obscure. The aim of present study was thus to investigate the effects of treatment with different doses of GnRH agonist, in vivo and in vitro, on morphological, physiological and functional changes in the ovary of cyclic mice. METHODS: To find out the effect of GnRH agonist on ovarian activity, cyclic mice were treated with different doses for 8 days and its effect on folliculogenesis (morphological changes in follicle, Estrogen receptor, progesterone receptor), steroidogenesis (circulating progesterone level, StAR, LH-receptor, 3ß-HSD), luteinization (Morphology of corpus luteum) and apoptosis (caspase-3, PARP) were observed. To find the in vitro effects of GnRH agonist with or without LH on ovary of mice, changes in the expression of LH-receptor, estrogen receptor, progesterone receptor, 3ß-HSD in the ovary and progesterone level in the culture media were investigated. RESULTS: GnRH agonist treatment produced significant changes in ovarian mass, circulating steroids level and ovarian follicular development, steroidogenesis and apoptosis in the mice. GnRH agonist also caused dose dependent histological changes in follicular development and luteinization. The mice treated with different doses of GnRH agonist showed biphasic effects on steroid synthesis due to its effects on ovarian expression of LH-receptor, StAR, and 3ß -hydroxysteroid dehydrogenase proteins. The high dose showed stimulatory effect, whereas pharmacological dose showed inhibitory effect on ovarian follicular development and steroidogenesis. The in vitro study generally showed inhibitory effects of GnRH agonist on ovarian activities, which may be reversed by the presence of LH. CONCLUSION: Both inhibitory and stimulatory effects found in the present study suggest that GnRH agonist is a versatile tool in the therapy of a variety of gynecological and non-gynecological conditions. This study suggests that the outcome of direct effect of GnRH-ag on ovary depends on LH-responsiveness.

Changes in GnRH I, bradykinin and their receptors and GnIH in the ovary of Calotes versicolor during reproductive cycle.

The aim of this study was to investigate changes in the abundance of gonadotrophin releasing hormone I (GnRH I) and GnRH I receptor in the ovary of Calotes versicolor during the reproductive cycle and correlate them with the changes in gonadotrophin inhibitory hormone (GnIH), bradykinin and bradykinin B(2) receptor in order to understand their interaction during ovarian cycle. GnRH I, bradykinin and their receptors and GnIH, were localized immunohistochemically in the ovary. Relative intensity of these peptides was estimated from the contralateral ovary using slot/Western blot followed by densitometry. The immunostaining of GnRH I, bradykinin and their receptors and GnIH were localized in the granulosa cells of previtellogenic follicles and stroma cells, whereas in the peripheral part of the cytoplasm in oocytes of vitellogenic and ovulatory follicles. The GnRH I immunostaining was relatively higher in inactive phase, but was low during active preovulatory phase suggesting inverse correlation with circulating estradiol level. The study showed a positive correlation between the expression pattern of GnRH I and GnIH, but showed a negative correlation between GnIH with GnRH I receptor in the ovary. This study further suggests a possibility for bradykinin regulating GnRH I synthesis in the ovary. An increase in the immunostaining of both GnRH I and GnIH in the oocyte prior to ovulation suggests their involvement in the oocyte maturation. It is thus concluded that the ovary of C. versicolor possesses GnRH I-GnIH-bradykinin system and interaction between these neuropeptides may be involved in the regulation of follicular development and oocyte maturation.

Localization of gonadotrophin-releasing hormone I, bradykinin and their receptors in the ovaries of non-mammalian vertebrates.

GnRH I and its receptors have been demonstrated in the ovaries of various vertebrates, but their physiological significance in reproductive cascade is fragmentary. Bradykinin is a potent GnRH stimulator in the hypothalamus. In the present study, the presence of GnRH I and its receptor, and bradykinin and its receptor in the ovaries of non-mammalian vertebrates were investigated to understand their physiological significance. GnRH I immunoreactivity in the ovaries of fish, frog, reptile and bird were mainly found in the oocyte of early growing follicles and granulosa cells and theca cells of previtellogenic follicles. Vitellogenic follicles showed mild GnRH immunoreactivity. GnRH I-receptor and bradykinin were localized in the same cell types of the ovaries of these vertebrates. The presence of GnRH I, GnRH I-receptor and bradykinin in the ovaries of these vertebrates was confirmed by immunoblotting. The presence of GnRH I mRNA was demonstrated in the ovary of vertebrates using RT-PCR. The ovaries of reptiles and birds showed significantly higher intensity of immunoreactivity for GnRH I-receptor as compared with the fish and amphibian. This may have a correlation with the higher yolk content in the ovary of reptile and bird. These results suggest the possibility of GnRH I and bradykinin as important regulators of follicular development and vitellogenesis in the vertebrate ovary.