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PublicationArticle Temporal and periovulatory changes in ovarian catecholamines in the catfish Heteropneustes fossilis(Academic Press Inc., 2010) V. Singh; R. Chaube; T.K. Chourasia; K.P. JoyA high performance liquid chromatography-fluorescence detection method was employed to demonstrate temporal and periovulatory changes in ovarian catecholamines in the catfish Heteropneustes fossilis. Tyrosine, l-DOPA, dopamine (DA), norepinephrine (NE) and epinephrine showed significant seasonal and diurnal changes during the reproductive cycle. A high concentration of tyrosine was detected, the values increased in day and decreased in night during recrudescence from preparatory to spawning phases. Similarly, l-DOPA increased during the breeding phase giving the day value concentration peak in the spawning phase and the night value peak in the postspawning phase. DA activity or turnover index (calculated as a ratio of DA to 3,4-dihydroxyphenylacetic acid, DOPAC) showed a bimodal pattern with the major activity peak in the postspawning phase and the minor one in the prespawning phase, the spawning phase registered the lowest activity. NE activity or turnover index (ratio of NE to normetanephrine, NME) increased during the recrudescent phase to give the peak in the spawning phase and decreased in the quiescent phase. Epinephrine elicited an inverse relationship in the day-night pattern, the day values increased to the peak in the spawning phase. All the study correlates showed significant periovulatory changes after hCG treatment. DA activity dropped to the nadir at 8. h but recovered at 16 and 24. h. NE activity showed only a marginal decrease up to 16. h but decreased drastically at 24. h. Epinephrine levels remained unchanged but only to increase at 24. h. The seasonal patterns and periovulatory changes strongly point to important functions for catecholamines in the ovary. The occurrence of tyramine (an invertebrate neurotransmitter) suggests the presence of alternate catecholamine pathway in fish ovary. © 2010 Elsevier Inc.PublicationArticle Functional interactions between vasotocin and prostaglandins during final oocyte maturation and ovulation in the catfish Heteropneustes fossilis(Academic Press Inc., 2013) K.P. Joy; V. SinghFunctional interactions between vasotocin (VT) and prostaglandins (PGs) in the regulation of final oocyte maturation (FOM) and ovulation were investigated in the catfish Heteropneustes fossilis. Incubation of post-vitellogenic follicles with VT resulted in significant increases of both PGF2α and PGE2 at 8 and 16h intervals. The rise was higher at 16h except in the 1000nM VT group, in which the PG levels decreased compared to the 100nM group (biphasic effect). VT was more effective to increase the PG levels in comparison to hCG or IT. The co-incubation of the follicles with both hCG (20IU/ml) and VT (100nM) increased significantly PGF2α level at 8h, higher than that elicited by each when incubated alone. Pre-incubation of the follicles with V1 receptor antagonist, alone or in co-incubation with VT, significantly inhibited the VT-stimulated PGF2α and PGE2 levels. Under similar conditions, V2 receptor antagonist did not affect the PGE2 levels. Both VT (100nM) and PGs stimulated FOM (germinal vesicle breakdown) and ovulation in a dose- and duration dependent manner, PGF2α was more effective. Incubation of postvitellogenic follicles with indomethacin (a non selective cyclooxygenase inhibitor) per se did not affect FOM and ovulation but significantly decreased VT and PG effects upon pre-incubation. The results suggest that the VT stimulation of PGs may be mediated mainly through the V1 receptor though the involvement of V2 receptor cannot be excluded. The article also discussed the positive interplay of gonadotropin, maturation-inducing steroid, VT and PG during FOM and ovulation. © 2013.PublicationArticle Relative in vitro seasonal effects of vasotocin and isotocin on ovarian steroid hormone levels in the catfish Heteropneustes fossilis(Academic Press Inc., 2009) V. Singh; K.P. JoyIn the present investigation, catfish (Heteropneustes fossilis) ovarian tissues were incubated in vitro with vasotocin (VT) or isotocin (IT) to demonstrate their effects on estradiol-17β (E2), progesterone (P4), 17α-hydroxy-4-pregnene-3, 20-dione (17-P) and 17α, 20β-hydroxy-4-pregnen-3-one (17, 20β-DP). Parallel incubations with human chorionic gonadotropin (hCG) alone or in combination with VT were used for a comparison. In pre-vitellogenic phase (preparatory phase, GSI-0.48 ± 0.03%), both VT and hCG stimulated E2 significantly, VT in a biphasic manner and hCG in a dose-dependent manner. In pre-spawning (post-vitellogenic, GSI-9.05 ± 0.11%) and spawning (post-vitellogenic, GSI-8.01 ± 0.12%) phases, both hormones decreased E2 levels in a dose- and duration-dependent manner; the VT effect being biphasic in the spawning phase. The co-incubation with VT + hCG stimulated E2 in the preparatory phase but inhibited it in the pre-spawning and spawning phases. The incubations with VT or hCG increased P4 levels in a dose- and duration-dependent manner, the magnitude of the effect was higher in the pre-spawning and spawning phases. The co-incubation with VT + hCG stimulated P4 without any additive effect. The P4 derivatives (17-P and 17, 20β-DP) showed similar changes except 17-P in the spawning phase which decreased at 16 h of the incubation. The incubations with IT produced similar but low responses. In conclusion, like hCG, VT has differential effects on ovarian steroidogenesis and may be involved directly or indirectly in ovarian functions, as a paracrine/autocrine factor or a neurohormone. © 2009 Elsevier Inc.PublicationArticle Effects of hCG and ovarian steroid hormones on vasotocin levels in the female catfish Heteropneustes fossilis(Academic Press Inc., 2009) V. Singh; K.P. JoyEffects of hCG, ovariectomy and estradiol replacement on brain, plasma and/or ovarian vasotocin in vivo, and estradiol, progesterone, 17α, 20β-hydroxy-4-pregnen-3-one and hCG on ovarian vasotocin in vitro were investigated in the catfish. A 100 IU/fish of hCG induced ovulation and elicited both periovulatory and post-ovulatory changes in vasotocin concentrations with a significant increase up to 8 h in the brain and up to 16 h in both plasma and ovary. After stripping the fish at 16 h, the peptide concentration decreased significantly with time, up to 4 days. Ovariectomy in early pre-spawning phase resulted in a duration-dependent significant reduction of both brain and plasma vasotocin. Estradiol replacement in 3-week ovariectomized fish produced dosage-dependent biphasic effects: the lower dosage (0.1 μg/g) restored the vasotocin level while the higher dosage (0.5 μg/g) decreased it significantly below the control level. In vitro incubation of ovarian tissues with estradiol produced season-dependent effects on vasotocin. The incubation of pre-vitellogenic ovarian pieces with estradiol (1, 10, and 100 ng/ml) elevated vasotocin level in a dose- and duration-dependent manner while that of post-vitellogenic follicles resulted in a significant decrease. The incubation of intact post-vitellogenic follicles or follicular envelope with progesterone and 17α, 20β-hydroxy-4-pregnen-3-one (1 μg/ml) or hCG (20 IU/ml) for 8 and 16 h significantly increased vasotocin in a duration-dependent manner. The results show that both gonadotropin and ovarian steroids modulate vasotocin titer, which may influence follicular growth, ovulation and spawning in the catfish. © 2009 Elsevier Inc.PublicationArticle Annual and periovulatory changes in tyrosine hydroxylase activity in the ovary of the catfish Heteropneustes fossilis(Academic Press Inc., 2010) T.K. Chourasia; R. Chaube; V. Singh; K.P. JoyIn the present study, tyrosine hydroxylase (TH, the rate-limiting enzyme in catecholamine synthesis) activity was demonstrated in the ovary of the catfish to elucidate the possible physiological role of catecholamines in the gonad. The ovary is innervated by seven pairs of nerves, originating from the paired sympathetic chain lying dorsal to the posterior kidney. Ovarian TH activity showed a significant annual variation (P< 0.001, one-way ANOVA), correlating with gonado-somatic index. Activity was low from December to February (resting phase), increased from March to July (recrudescent phase) and then decreased in post-spawning phase (August-November). The annual pattern was similar to that of the brain. An intraperitoneal injection of 100. IU hCG/fish induced significant periovulatory changes in TH activity with the peak rise at 16 h, and the activity decreased after egg-stripping (P<0.001, one-way ANOVA). Brain TH activity showed similar periovulatory changes. The results suggest that catecholamine synthesis is increased during both ovarian recrudescence and spawning of the annual reproductive cycle, implying a functional role in ovarian growth, maturation and ovulation. © 2009 Elsevier Inc.