Browsing by Author "S.K. Chaube"

Now showing 1 - 5 of 5

Calcium ionophore-induced egg activation and apoptosis are associated with the generation of intracellular hydrogen peroxide
(2008) S.K. Chaube; Sabana Khatun; S.K. Misra; T.G. Shrivastav
The present study was designed to investigate whether calcium ionophore-induced activation and apoptosis are associated with the generation of hydrogen peroxide (H2O2) in rat eggs cultured in vitro. Culture of metaphase-II (M-II) arrested eggs in Ca2+/Mg2+-deficient medium did not induce egg activation, while a second polar body was observed in 20% of eggs when cultured in Ca2+/Mg2+-supplemented medium. In Ca2+/Mg2+-deficient medium, lower concentrations of calcium ionophore (0.2,0.4 and 0.8 μm) not only induced egg activation in a dose-dependent manner but also generation of intracellular H2O2 (84.40 ± 0.50 ng/egg) when compared to control eggs (80.46±1.34 ng/egg). The higher concentration of calcium ionophore (1.6 μm) induced apoptosis and pronounced generation of intracellular H2O2 (92.43±0.93 ng/egg) in treated eggs. Conversely, cell-permeant antioxidant such as 2(3)-tert-butyl-4-hydroxyanisole (BHA) reduced intracellular H2O2 level (81.20±1.42 ng/ egg) and protected against calcium ionophore-induced morphological changes characteristics of egg activation and apoptosis. These results clearly suggest that calcium ionophore-induced activation and apoptosis are associated with the generation of intracellular H2 O2 in rat eggs.
Evidence for the stimulation of cyclic AMP phosphodiesterase in catfish (Clarias batrachus) oocytes by 17α,20β-dihydroxy-4-pregnen-3-one
(1997) S.K. Chaube; S. Haider
A decrease in cyclic AMP (cAMP) level within the catfish follicle occurs during oocyte maturation (Haider and Chaube [1995] Comp. Biochem. Physiol., 112A:379-385). Experiments described in this report were performed to evaluate the modulations in oocyte phosphodiesterase (PDE) activity during maturation in the catfish Clarias batrachus. An increase in PDE activity was found in extracts of oocytes which were incubated for 36 hr with different concentrations of 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DP; the naturally occurring maturation-inducing steroid of this catfish), and this increase was in a dose-dependent manner. Evaluation of the time course of response to 1 μg/ml 17α,20β-DP revealed that PDE activity increased in a time-dependent manner. A minimum detectable PDE activity was observed at 2 hr, the half-maximal activity at 6 hr, and maximum at 36 hr of incubation of oocytes with 17α,20β-DP. The two different known inhibitors (isobutylmethylxanthine and theophylline) inhibited catfish oocyte PDE activity in a dose-dependent manner. These studies suggest that the 17α,20β-DP-induced increase in PDE is involved in the decrease in cAMP in catfish oocytes during maturation.
Extracellular calcium protects against verapamil-induced metaphase-II arrest and initiation of apoptosis in aged rat eggs
(2009) S.K. Chaube; Anima Tripathi; Sabana Khatun; S.K. Mishra; P.V. Prasad; T.G. Shrivastav
Non-specific L-type calcium channel blockers, such as verapamil (≥50 μM), induce metaphase-II (M-II) arrest and apoptosis in aged rat eggs cultured in Ca2+-deficient medium. However, the effects of extracellular Ca2+ on verapamil-induced M-II arrest and apoptosis have not yet been reported. We have demonstrated that postovulatory aging induced exit from M-II arrest by extruding a second polar body, a morphological sign of spontaneous egg activation (SEA). Verapamil inhibited SEA and induced egg apoptosis in a dose-dependent manner in Ca2+-deficient medium. The initiation of apoptotic features was observed at 50 μM of verapamil. Extracellular Ca2+ (1.80 mM) reduced intracellular H2O2 level, bax protein expression, caspase-3 activity, DNA fragmentation and protected against 50 μM, but not higher concentrations of ≥100 μM in verapamil-induced egg apoptosis. These results suggest that extracellular Ca2+ ions have a role during SEA and protect against verapamil-induced apoptosis in aged rat eggs. © 2009 International Federation for Cell Biology.
Intracellular levels of hydrogen peroxide and nitric oxide in oocytes at various stages of meiotic cell cycle and apoptosis
(2009) Anima Tripathi; Sabana Khatun; A.N. Pandey; S.K. Mishra; Radha Chaube; T.G. Shrivastav; S.K. Chaube
The objective was to find out the functional roles of hydrogen peroxide (H2O2) and nitric oxide (NO) during various stages of meiotic cell cycle and apoptosis in rat oocytes. For this purpose, 30 oocytes from each stage such as diplotene, metaphase-I (M-I), metaphase-II (M-II) and apoptosis were collected and intracellular H2O2, total nitrite level and inducible nitric oxide synthase (iNOS) expression were analysed. This study demonstrated that generation of a tonic level of H2O2 induces meiotic resumption in diplotene-arrested oocytes and further increase may lead to apoptosis. Conversely, reduction in iNOS expression and total nitrite level are associated with meiotic resumption in diplotene-arrested oocytes, but induce apoptosis in aged oocytes. These results suggest that generation of a tonic level of H2 O2, reduced iNOS expression and total nitrite level are associated with meiotic resumption, while more generation of H2O2 and sustained reduced total nitrite level are linked with oocyte apoptosis in rat.
Long-term melatonin administration attenuates low-LET γ-radiation- induced lymphatic tissue injury during the reproductively active and inactive phases of Indian palm squirrels (Funambulus pennanti)
(2010) S. Sharma; C. Haldar; S.K. Chaube; T. Laxmi; S.S. Singh
A comparative analysis of low linear energy transfer (LET) γ-radiationinduced damage in the lymphatic tissue of a tropical seasonal breeder, Indian palm squirrel (Funambulus pennanti), during its reproductively active phase (RAP) and inactive phase (RIP) was performed with simultaneous investigation of the effects of long-term melatonin pre-treatment (100 mg/100 g body weight). A total of 120 squirrels (60 during RAP and 60 during RIP) were divided into 12 groups and sacrificed at 4, 24, 48, 72 and 168 h following 5 Gy c-radiation exposure; control groups were excluded fromexposure. Total leukocyte count and absolute lymphocyte count (ALC) and melatonin only of peripheral blood, stimulation index, thiobarbituric-acid-reactive substances (TBARS) level, superoxide dismutase (SOD) activity, and the apoptotic index of spleen as analysed by terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick-end labelling (TUNEL) noted at observed time-points were significantly reduced in melatonin pre-treated groups during RAP and RIP. Long-term melatonin pretreatment mitigated radiation-induced alterations more prominently during RIP, as assessed by ALC, TBARS, SOD, TUNEL and caspase-3 activity, at some time-points. Our results demonstrate an inhibitory role of melatonin on caspase-3 activity in splenocytes during RAP and RIP following γ-radiation-induced caspase-mediated apoptosis. Hence, we propose that melatonin might preserve the viability of immune cells of a seasonal breeder against background radiation, which is constantly present in the environment. © 2010 The British Institute of Radiology.