Browsing by Author "Dhruv Kumar"

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Biochemical characterization of a shikimic acid‐resistant mutant of Nostoc linckia
(1989) Dhruv Kumar
The growth of Nostoc linckia was significantly inhibited by shikimic acid concentrations greater than 4.0 μg ml−1 and was completely inhibited at 10.0μg ml−1. Shikimic acid increased the duration of the lag phase and the doubling time and hastened the onset of the retardation phase of growth. A mutant (NLshi) capable of growing in presence of 50 μg ml−1 shikimic acid, was isolated by nitrosoguanidine mutagenesis from the wild type population at a frequency of about 1 × 10−5 to 1 × 10−6. The mutant grew slower than the wild type. Both the wild type and the mutant strain grew photoheterotrophically in light, with and without 3 (3–4 dichlorophenyl) 1,1‐dimethyl urea (DCMU) and in darkness when provided with glucose. Glucose supplementation promoted ammonium uptake from the medium, when wild type and mutant were grown in an ammonium‐supplemented medium. Glucose stimulated heterocyst production and nitrogenase activity in both the strains. As compared to wild type, this mutant showed higher heterocyst frequency and nitrate reductase activity but its ammonium uptake activity was lower. No significant difference in glutamine synthetase and nitrogenase activities of the mutant were observed. The mutant was stable and retained its resistance even after several subcultures through medium free of shikimic acid. Copyright © 1989 Wiley‐VCH
Effect of light quality on the acetylene reducing activity of the isolated heterocysts of anabaena sp. Strain CA
(1989) Dhruv Kumar
Metabolically active heterocysts isolated from Anabaena sp. strain CA showed high rates of light-dependent nitrogenase activity. When these active heterocysts were incubated under light of various wavelengths, they were most active under blue light, followed by yellow and red light respectively. Involvement of phycobiliproteins in transferring light energy to photosystem I in isolated heterocysts is discussed. Aldolase, phosphofructokinase and catalase activities were also studied in extracts of vegetative cells as were heterocysts from Anabaena sp. strain CA. © 1989, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.
Effects of amitrol on cyanobacterium nostoc linckia
(1986) Dhruv Kumar
The effect of 3-amino-1,2,4-triazole (amitrol), an uncoupler of the Q of photosystem II, on growth, heterocyst frequency, H2 production, acetylene reduction (nitrogenase activity) and photosynthetic 02 evolution was studied in Nostoc linckia. Whereas amitrol inhibited growth, acetylene reduction and 02 evolution, it increased heterocyst frequency and H2 production. Exposure of Nostoc linckia to higher concentrations of amitrol caused pronounced fragmentation of filaments into 5- to 10-celled trichomes. The observed effects on growth and other physiological processes may be due to the reduction in reductant and ATP pool(s). © 1986, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.
Effects of some inhibitors and carbon sources on acetylene reduction and hydrogen production of isolated heterocysts of anabaena sp. (strain ca)
(1990) Dhruv Kumar; Har Darshan Kumar
Metabolically active heterocysts isolated from wild-type Anabaena sp. strain CA showed high rates of light dependent acetylene reduction and H2 evolution. Fructose and erythrose significantly stimulated nitrogenase activity but not H2 evolution. DCMU and cyanide were not effective. DBMIB significantly inhibited both nitrogenase and nitrogenase-catalysed H2 evolution. This inhibition was overcome by a catalytic amount of TMPD. These data suggest that in the isolated heterocysts all electrons, irrespective of source, must pass through the plastoquinone pool before reducing ferredoxin, which in turn can reduce dinitrogen to ammonia. © 1990 Taylor & Francis Group, LLC.
Factor regulating acetylene reduction in the isolated heterocysts of anabaena sp. strain CA
(1989) Dhruv Kumar
[No abstract available]
Hydrogen production by several cyanobacteria
(1992) Dhruv Kumar; Har Darshan Kumar
Twenty species belonging to eleven genera of nitrogen-fixing and non-nitrogen-fixing cyanobacteria were screened for production of hydrogen. Only one species each of Nostoc and Anabaena showed light- and nitrogenase-dependent aerobic hydrogen production. The highest rate of aerobic hydrogen production was recorded in Anabaena sp. strain CA. When incubated anaerobically under 99% Ar + 1% CO2, all the tested strains produced hydrogen. Nickel supplementation completely abolished hydrogen production both under aerobic and anaerobic conditions, except in Anabaena sp. strain CA, where only the rate of production was decreased. Species of Plectonema, Oscillatoria and Spirulina showed methyl viologen-dependent (hydrogenase-dependent) hydrogen production. Other physiological activities were also studied with a view to selecting a suitable organism for large-scale production of hydrogen. © 1992.
Novel 3,4-diarylpyrazole as prospective anti-cancerous agents
(Elsevier Ltd, 2020) Vivek Pandey; Garima Tripathi; Dhruv Kumar; Abhijeet Kumar; Pawan K. Dubey
Cancer is a leading cause of death globally. Despite therapeutic advancements the mortality rate of cancer is continuously increasing. Thus, it is important to identify and design potential therapeutic agents which can specifically bind with most common targets of cancer and inhibit tumor progression. The present work discloses the potential therapeutic application of the novel 3,4-diaryl 1H-pyrazoles as prospective anti-cancerous agent. The in silico molecular docking studies performed with 3,4-disubstituted pyrazoles as ligand with targets including DNA, BCL-2 and F1-ATP Synthase revealed strong binding affinity with DNA (-7.5 kcal/mol), BCL-2 (-8.1 kcal/mol) and F1-ATP Synthase (-7.2 kcal/mol). Furthermore, the in silico finding was validated with the in vitro cytotoxicity assay with human breast cancer cell line (MDA-MB-231). MDA-MB-231 cells treated with 3,4-diarylpyrazole resulted in an increase in annexin-V positive cells, production of reactive oxygen species (ROS), dissipation of the mitochondrial membrane potential and activation of caspase-3. Taken together, this study demonstrate that a novel synthesized 3,4-diarylpyrazoles, showed strong binding affinity against DNA, anti-proliferative activity and executed apoptosis through ROS-dependent caspase-3-mediated mitochondrial intrinsic apoptotic pathway against MDA-MB-231 cells. These findings increase our understanding of the molecular mechanism (s) by which 3,4-diarylpyrazoles can exert their anticancer activity and may contribute towards development of novel therapeutic agent against breast cancer. © 2020 The Author(s); Pyrazole; Molecular docking; Apoptosis; Reactive oxygen species; MDA-MB-231; Chemistry; Organic chemistry; Pharmaceutical chemistry; Biological sciences; Cell biology; Bioinformatics © 2020 The Author(s)
Protection of nitrogenase levels in dark-incubated cultures of anabaena sp. Strain ca by various carbon sources, and restoration of nitrogenase activity by oxygen
(1990) Dhruv Kumar; Har Darshan Kumar
Photoautotrophically grown, nitrogen-fixing cultures of Anabaena sp. strain CA lost nitrogenase activity completely after 4 h of incubation in the dark. The original level of nitrogenase activity was restored within 3 h of re-illumination and was apparently dependent on de novo protein synthesis. Several organic carbon sources protected nitrogenase activity. The heterocysts isolated from photoautotrophically grown cultures incubated in the dark (35 min) showed negligible nitrogenase activity. When these heterocysts were exposed to oxygen, glucose or fructose during isolation, normal activity was observed only with 02. Oxygen also enhanced the rate of initial H2 evolution from isolated heterocysts. © 1990 The British Phycological Society.
Reductant supply in isolated heterocysts of anabaena sp. strain CA
(1991) Dhruv Kumar
Metabolically active heterocysts isolated from wild type Anabaena sp. strain CA under hydrogen incubation showed high endogenous acetylene-reducing activity with or without nickel supplementation. The acetylene reducing activity of Ar-incubated heterocysts was significantly enhanced by fructose, erythrose, and reduced glutathione. The possible pathways related to reductant supply to heterocysts are discussed. © 1991, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.
The role of microRNA-21 in the onset and progression of cancer
(Future Medicine Ltd., 2021) Ashutosh Singh; Ashutosh Kumar Singh; Rajanish Giri; Dhruv Kumar; Rohit Sharma; Martin Valis; Kamil Kuca; Neha Garg
MicroRNAs (miRNAs), a class of small noncoding RNA, posttranscriptionally regulate the expression of genes. Aberrant expression of miRNA is reported in various types of cancer. Since the first report of oncomiR-21 involvement in the glioma, its upregulation was reported in multiple cancers and was allied with high oncogenic property. In addition to the downregulation of tumor suppressor genes, the miR-21 is also associated with cancer resistance to various chemotherapy. The recent research is appraising miR-21 as a promising cancer target and biomarker for early cancer detection. In this review, we briefly explain the biogenesis and regulation of miR-21 in cancer cells. Additionally, the review features the assorted genes/pathways regulated by the miR-21 in various cancer and cancer stem cells. © 2021 Newlands Press.
Xenobiotics in Chemical Carcinogenesis: Translational Aspects in Toxicology
(Elsevier, 2022) Akhileshwar Kumar Srivastava; Dhruv Kumar; Divya Singh; Rajesh Kumar Singh
Xenobiotics in Chemical Carcinogenesis: Translational Aspects in Toxicology covers the translational toxicology of xenobiotics substances in carcinogenesis by explaining the toxicokinetic and toxicodynamic, toxicogenomic, biotransformation, and resistance mechanisms in the human body. The book begins with a historical review and link to future prospects for chemical carcinogenesis. It discusses major environmental xenobiotics and their risks in inducing cancer, along with content on toxic xenobiotics and their routes of exposure in humans, the role of xenobiotic metabolism in carcinogenesis, and the toxicokinetic and toxicodynamic of xenobiotics in cancer development. Lastly, the book explores current achievements such as using toxicogenomics for predicting the carcinogenicity of xenobiotic substances and the challenges posed by carcinogenic xenobiotic substances when examining preventive methods, diagnosis, and the development of anticancer drugs for specific toxicants. © 2022 Elsevier Inc. All rights reserved.