Browsing by Author "Rahul K. Singh"

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Effect of dilution of both A-and B-sites on the multiferroic properties of spinal Mott insulators
(Institute of Physics Publishing, 2015) Prashant Shahi; Rahul K. Singh; Rajesh K. Singh; Shiv Kumar; A. Tiwari; A. Tripathi; J. Saha; S. Patnaik; A.K. Ghosh; Sandip Chatterjee
The structural, magnetic, electrical and transport properties of FeV2O4, by doping Li and Cr ions in A and B sites, respectively, have been studied. Dilution of the A site by Li doping decreases the V-V distances which in effect increases the A-V coupling. This increased coupling enhances the ferrimagnetic ordering temperature and reduces the ferroelectric transition temperature. Furthermore, since Li is non-magnetic the A-V coupling is also decreased. The increase in A-V coupling dominates over the decrease in A-V coupling with Li doping. On the other hand, Cr doping increases the ferrimagnetic ordering temperature but does not alter the ferroelectric transition temperature, which is due to the fact that the polarization originates from the presence of almost non-substituted regions. © 2015 IOP Publishing Ltd.
Estrogen regulation of brain vasotocin secretion in the catfish Heteropneustes fossilis: An interaction with catecholaminergic system
(Academic Press Inc., 2012) Radha Chaube; Rahul K. Singh; Keerikkattil P. Joy
Vasotocin (VT) is a basic neurohypophysial nonapeptide in non-mammalian vertebrates and is involved in diverse functions like osmoregulation, reproduction, metabolism and behavior. In this study, we report that estradiol-17β (E2) regulates brain and plasma VT secretion through the involvement of the catecholaminergic (CA) system. To demonstrate this, E2 level was altered through ovariectomy (OVX, 3weeks) and replacement study with low and high E2 doses (0.1 and 0.5μg/g body weight). CA activity was inhibited by treatment with α-methylparatyrosine (α-MPT; 250μg/g body weight), a competitive inhibitor of tyrosine hydroxylase. VT was assayed by an enzyme immunoassay method. In the sham group, the low E2 dose produced 82% and 104% increase, respectively, in brain and plasma VT levels. The high E2 dose decreased the VT levels significantly. The low E2 dose decreased brain E2 but elevated plasma E2. In the high E2 group, the E2 level increased further in both brain and plasma. OVX resulted in a significant inhibition (69% and 25%, respectively) of both brain and plasma VT, which was correlated with low E2 levels. The low E2 dose not only reversed the inhibition, but increased the VT level in both brain and plasma in comparison to the sham groups. The high E2 replacement inhibited VT levels further low in both brain and plasma. The α-MPT treatment inhibited VT levels significantly in both sham and OVX groups. The drug treatment abolished partially the restorative effect of the low E2 dose in the ovariectomized fish. In the high E2 dose group, α-MPT decreased brain and plasma VT levels further low compared to the sham+0.5μg E2 group or OVX+0.5μg E2 group except the brain VT level, which increased in the OVX+0.5μg E2 group. It is inferred that E2 may exert biphasic effects on VT through the mediation of the CA system. © 2011 Elsevier Inc.
In search of an ideal test for diagnosis and prognosis of Kala-azar
(International Center for Diarrhoeal Disease Research, 2010) Dharmendra P. Singh; Rahul K. Goyal; Rahul K. Singh; S. Sundar; Tribhuban M. Mohapatra
The latex agglutination test (KAtex), direct agglutination test (DAT), and the rK39 immuno-chromatographic strip test (dipstick test) were evaluated for their role in the diagnosis and prognosis of visceral leishmaniasis (kala-azar) in India. Sera and urine samples from 455 subjects-150 confirmed visceral leishmaniasis cases, 160 endemic controls, 100 non-endemic controls, and 45 other febrile diseases-were included in the study. The sensitivity of the KAtex, DAT, and rK39 strip test was 87% [95% confidence interval (CI) 80-96], 93.3% (95% CI 88-100), and 98% (95% CI 93-100) respectively. The specificity of these tests was 98% (95% CI 93-100), 93% (95% CI 87-100), and 89% (95% CI 82-97) for the KAtex, DAT, and rK39 strip test respectively. Fifty cases were followed up and subjected to the KAtex, DAT, and rK39 strip test after 30 days of successful treatment. The DAT and rK39 strip test showed positive results in all the 50 cases whereas the KAtex showed no positive reaction in any case. Based on the results, it is concluded that the sensitivity and specificity of the DAT and rK39 strip test are comparable but the greater convenience of use of the strip test makes it a better tool for the diagnosis of visceral leishmaniasis in the peripheral areas of endemic regions whereas the sensitivity of the KAtex needs to be improved to promote its use as a first-line diagnostic test in the field-setting. It may be used for the prognosis of the disease as antigen becomes undetectable in urine after 30 days of the completion of the treatment. Alternatively, it can be used as an adjunct with rK39 for sero-epidemiological surveys. © International Centre for Diarrhoeal Disease Research, Bangladesh.
In vitro effects of cadmium chloride on steroid profiles of post-vitellogenic ovary in the catfish heteropneustes fossilis
(2013) Radha Chaube; Surabhi Mishra; Rahul K. Singh
Cadmium (Cd) is a known endocrine disruptor with the ability to affect the production of hormones involved in the regulation of reproductive processes. The purpose of this study was to evaluate invitro effects of cadmium chloride (CdCl2) exposure on steroid levels in post-vitellogenic follicles of catfish ovary. Pieces of ovarian tissues (500mg) were incubated in culture medium in the presence or absence (control) of CdCl2 (0,0.01,0.1,1,3 and 10μg/ml) for 12 or 24hr. Estradiol-17f3 (E) and testosterone were measured by ELISA. Other steroids like progestins (progesterone -P; 17-OH-progesterone -17-P and 17,20fi-dihydroxyprogesterone -17,20f3-DP) and corticosteroids (cortisol, 21-deoxycortisol, corticosterone and deoxycorticosterone) were quantified by High Performance Liquid Chromatography. The results show that Cd produced biphasic effects on E, T, P4, 17,20f3-DP, cortisol, deoxycorticosterone, and 21-deoxycortisol, stimulatory at lower concentrations and inhibitory at higher concentrations. In contrast, 17-P and corticosterone were inhibited in a dose-dependent manner. Thus, Cd can influence ovarian steroidogenesis adversely, affecting gametogenesis and ovulation resulting in the decline of fish population.
In vitro effects of lead nitrate on steroid profiles in the post-vitellogenic ovary of the catfish Heteropneustes fossilis
(2010) Radha Chaube; Surabhi Mishra; Rahul K. Singh
Heavy metals are endocrine disruptors with the ability to cause hormonal imbalances, affecting various physiological processes such as reproduction. In this study, in vitro effects of exposure (12 or 24h) of lead nitrate [Pb(NO3)2] (0, 0.01, 0.1, 1, 3 and 10μg/ml) on steroid levels in post-vitellogenic catfish (Heteropneustes fossilis) ovary was investigated. Steroids were assayed by HPLC/ELISA. Lead (Pb) elicited biphasic effects on estradiol-17β, testosterone and cortisol: stimulatory at lower concentrations and inhibitory at higher concentrations. In contrast, progesterone, 17-hydroxyprogesterone, 17,20β-dihydroxyprogesterone, corticosterone, 21-deoxycortisol and deoxycorticosterone were inhibited in a dose-dependent manner. Thus, the present results suggest that short-term Pb response can be a potent endocrine disruptor of normal follicular steroidogenesis. The stimulatory effect on E2 suggests that Pb in trace amounts may be beneficial. The cortisol elevation may be indicative of the metal/stress insult. Nevertheless, further studies are required to understand the mechanism of action of lead toxicity. © 2010 Elsevier Ltd.
Toxicopathological impact of sub-lethal concentrations of lead nitrate on the gill of the catfish Heteropneustes fossilis
(Elsevier GmbH, 2022) Archisman Mahapatra; Arup Mistri; Priya Gupta; Sumanta Kar; Swati Mittal; Rahul K. Singh
In recent studies, fish are heavily used as biomarkers of aquatic pollution, and heavy metals are among the main contributors to water pollution. In the present study, we investigated histopathological changes along with alterations in localization and activity of enzymes alkaline phosphatase (ALP), acid phosphatase (ACP), catalase (CAT), peroxidase (PER) and Na+/K+-ATPase in the gill tissues of Indian stinging catfish Heteropneustes fossilis exposed to two different concentrations (0.4 and 4 mg/L) of lead nitrate for 15 days. Histopathological examination of gill tissues revealed hypertrophy and swelling of epithelial cells, the fusion of epithelium of gill filaments and secondary lamellae, and alteration of secondary lamellae structure. Biochemical assays and histochemical localization show a pronounced effect on enzyme alkaline phosphatase activity and acid phosphatase in the gills of both groups of treated groups. In contrast, a significant decrease was noticed in the enzymatic response including catalase and peroxidase activity. Being a vital organ gill reflects the fish's physiological condition and the severity of the contamination in the surrounding environment. Gill is also the prime organ of osmoregulation in teleosts. Decreased activity of Na+/K+-ATPase suggests lead as a potent inhibitor of Na+/K+-ATPase that causes sodium hyperregulation. Alteration in the activity of metabolic enzymes reflects the level of tissue damage and metabolic disruption. At the same time, the increased activity of antioxidant enzymes states the condition of oxidative stress. Haematological parameters also altered with the lead nitrate exposure, reflecting metal toxicity and immune response against it. Meanwhile, this study also provides a potential use of H. fossilis as a biomarker for aquatic pollution. © 2022