Browsing by Author "N. Dubey"

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Carbon, oxygen and strontium isotope geochemistry of Proterozoic carbonate rocks of the Vindhyan Basin, central India
(2002) B. Kumar; S. Das Sharma; B. Sreenivas; A.M. Dayal; M.N. Rao; N. Dubey; B.R. Chawla
Carbon, oxygen and strontium isotope compositions of carbonate rocks of the Proterozoic Vindhyan Supergroup, central India suggest that they can be correlated with the isotope evolution curves of marine carbonates during the latter Proterozoic. The carbonate rocks of the Lower Vindhyan Supergroup from eastern Son Valley and central Vindhyan sections show δ13C values of ∼ 0% (V-PDB) and those from Rajasthan section are enriched up to + 2.8‰. In contrast, the carbonate rocks of the Upper Vindhyan succession record both positive and negative shifts in δ13C compositions. In the central Vindhyan section, the carbonates exhibit positive δ13C values up to + 5.7‰ and those from Rajasthan show negative values down to -5.2‰. The δ18O values of most of the carbonate rocks from the Vindhyan Supergroup show a narrow range between -10 and -5‰ (V-PDB) and are similar to the 'best preserved' 18O compositions of the Proterozoic carbonate rocks. In the central Vindhyan and eastern Son Valley sections, carbonates from the Lower Vindhyan exhibit best-preserved 87Sr/86Sr compositions of 0.7059 ± 6, which are lower compared to those from Rajasthan (0.7068 ± 4). The carbonates with positive δ13C values from Upper Vindhyan are characterized by lower 87Sr/86Sr values (0.7068 ± 2) than those with negative δ13C values (0.7082 ± 6). A comparison of C and Sr isotope data of carbonate rocks of the Vindhyan Supergroup with isotope evolution curves of the latter Proterozoic along with available geochronological data suggest that the Lower Vindhyan sediments were deposited during the Mesoproterozoic Eon and those from the Upper Vindhyan represent a Neoproterozoic interval of deposition. © 2002 Elsevier Science B.V. All rights reserved.
Existence of a nitric oxide synthase/nitric oxide system in fish testis and its role in modulation of androgenesis
(Kluwer Academic Publishers, 2013) B. Lal; N. Dubey
Fish testis is equipped with different isoforms of nitric oxide synthase (NOSs) and is capable of producing nitric oxide (NO). Cellular sources of NO in the catfish testis are germ cells, Leydig cells, and macrophages. Production of testicular NO is under endocrine inhibitory control. Expression of NOSs exhibits seasonality and that depends on the reproductive status of fish. Leydig cells are highly sensitive to chemical as well as biological NO. NO inhibits testosterone production by the testis in vivo as well as by the isolated Leydig cells in vitro. © 2012 Springer Science+Business Media B.V.
Further investigations towards luminescence dating of diatoms
(Elsevier Ltd, 2022) P. Morthekai; P. Tiwari; M.K. Murari; P. Singh; B. Thakur; M.C. Manoj; S.N. Ali; V.K. Singh; K. Kumar; J. Rai; N. Dubey; P. Srivastava
Following up on previous attempts to date diatom frustules, further investigations were made on 1) extracting diatom frustules devoid of inorganic luminescent grains, 2) developing an equivalent dose estimating protocol based on the diatomite luminescence characterization, and 3) testing the applicability of this protocol on two lacustrine profiles. Diatom frustules were extracted in such a way that they are almost devoid of non-biogenic polymineral grains, confirmed by field emission scanning electron microscope (FE-SEM) observation and energy dispersive X-ray (EDX) analysis. The presence of opal was confirmed by X-ray diffraction (XRD) spectrometric analysis. The optimized luminescence signal that could be used for equivalent dose estimation was blue stimulated UV emission with a preheat temperature of 200 °C. The thermoluminescence glow curve peaking at 245 °C might be the source of this signal. In this study the characteristic dose was found to be ∼1500 Gy. Two sediment profiles were explored for luminescence dating, fading rates and a-values were found different between profiles. This discrepancy can be resolved 1) by measuring luminescence characteristics across different regions, or/and 2) by using species-specific luminescence measurements. This attempt has yielded an encouraging set of luminescence ages, with diatom frustule ages comparable to fine grain polymineral ages. © 2022 Elsevier Ltd
Traditional formulation-Vanari Gutika treatment improves the testosterone biosynthesis and sperm quality in adult male mice
(Walter de Gruyter GmbH, 2025) Arti Rajpoot; Anupam Yadav; Shubhanshu Yadav; Nikita Nikita; N. Dubey; G. Chaubey; Raghav Kumar Mishra
Objectives: Vanari Gutika (VG), an Indian traditional formulation containing Mucuna pruriens as a principal component, is traditionally used for the management of male reproductive disorders. However, there is a significant lack of evidence-based research validating its effects on male fertility and testosterone biosynthesis. This study aimed to investigate the impact of VG on testicular steroidogenesis, lipid peroxidation, and sperm quality in male mice. Methods: Adult male mice were orally administered VG at 75, 150, or 300 mg/kg body weight/day for 35 days. Testicular function was assessed through sperm morphology and viability, lipid peroxidation and expression of key steroidogenic and oxidative stress-related proteins. Results: VG at 150 and 300 mg/kg significantly increased testis weight and serum testosterone, with a concurrent reduction in estradiol. VG (150 mg/kg) improved normal sperm morphology and reduced abnormalities. Markers of oxidative stress status improved, evidenced by reduced LPO and increased Nrf-2 expression. VG treatment enhanced the expression of steroidogenic markers (SF-1, CYP11A1, 3β-HSD, StAR, and 17β-HSD) at higher doses. Conclusions: Higher doses of VG (150 and 300 mg/kg BW) promote testicular androgenesis, reduces oxidative stress, and improves sperm quality. Consequently, our results provide robust and compelling evidence supporting its potential as a dietary supplement for boosting the testosterone level and sperm quality. © 2025 Walter de Gruyter GmbH, Berlin/Boston.