Sharma AK

References (22)

Title : Heterologous expression, biochemical characterization and prospects for insecticide biosensing potential of carboxylesterase Ha006a from Helicoverpa armigera - Kaur_2024_Pestic.Biochem.Physiol_200_105844
Author(s) : Kaur H , Rode S , Lonare S , Demiwal P , Narasimhappa P , Arun E , Kumar R , Das J , Ramamurthy PC , Sircar D , Sharma AK
Ref : Pestic Biochem Physiol , 200 :105844 , 2024
Abstract : Enzymes have attracted considerable scientific attention for their crucial role in detoxifying a wide range of harmful compounds. In today's global context, the extensive use of insecticides has emerged as a significant threat to the environment, sparking substantial concern. Insects, including economically important pests like Helicoverpa armigera, have developed resistance to conventional pest control methods through enzymes like carboxyl/cholinesterases. This study specifically focuses on a notable carboxyl/cholinesterase enzyme from Helicoverpa armigera (Ha006a), with the goal of harnessing its potential to combat environmental toxins. A total of six insecticides belonging to two different classes displayed varying inhibitory responses towards Ha006a, thereby rendering it effective in detoxifying a broader spectrum of insecticides. The significance of this research lies in discovering the bioremediation property of Ha006a, as it hydrolyzes synthetic pyrethroids (fenvalerate, lambda-cyhalothrin and deltamethrin) and sequesters organophosphate (paraoxon ethyl, profenofos, and chlorpyrifos) insecticides. Additionally, the interaction studies between organophosphate insecticides and Ha006a helped in the fabrication of a novel electroanalytical sensor using a modified carbon paste electrode (MCPE). This sensor boasts impressive sensitivity, with detection limits of 0.019 microM, 0.15 microM, and 0.025 microM for paraoxon ethyl, profenofos, and chlorpyrifos, respectively. This study provides a comprehensive biochemical and biophysical characterization of the purified esterase Ha006a, showcasing its potential to remediate different classes of insecticides.
ESTHER : Kaur_2024_Pestic.Biochem.Physiol_200_105844
PubMedSearch : Kaur_2024_Pestic.Biochem.Physiol_200_105844
PubMedID: 38582571
Gene_locus related to this paper: helam-d5g3e0

Title : Editorial Expression of Concern: Cholinesterase inhibitors ameliorate spatial learning deficits in rats following hypobaric hypoxia -
Author(s) : Muthuraju S , Maiti P , Solanki P , Sharma AK , Singh SB , Prasad D , Ilavazhagan G
Ref : Experimental Brain Research , : , 2023
PubMedID: 36692527

Title : Azo-Stilbene and Pyridine-Amine Hybrid Multifunctional Molecules to Target Metal-Mediated Neurotoxicity and Amyloid-beta Aggregation in Alzheimer's Disease - Rana_2022_Inorg.Chem__
Author(s) : Rana M , Cho HJ , Arya H , Bhatt TK , Bhar K , Bhatt S , Mirica LM , Sharma AK
Ref : Inorg Chem , : , 2022
Abstract : Neurodegenerative diseases such as Alzheimer's disease (AD) are associated with progressive neuronal cell death, and they are commonly correlated with aberrant protein misfolding and aggregation of Abeta peptides. Transition metal ions (Cu, Fe, and Zn) have been shown to promote aggregation and oxidative stress through formation of Abeta-metal complexes. In this context, integrating molecular scaffolds rationally is used here to generate multifunctional molecules as modulators for metal-induced abnormalities. This work encompasses two azo-stilbene (AS)-derived compounds (AS-HL1 and AS-HL2), the rationale behind the design, their synthesis, characterization, and metal chelation ability [Cu(II) and Zn(II)]. The molecular frameworks of the designed compounds consist of stilbene as an Abeta-interacting moiety, whereas N,N,O and N,N,N,O donor atoms are linked to generate the metal chelation moiety. Furthermore, we went on exploring their multifunctionality with respect to (w.r.t.) (i) their metal chelating capacities and (ii) their utility to modulate the aggregation pathways of both metal-free and metal-bound amyloid-beta, (iii) scavenge free radicals, and (iv) inhibit the activity of acetylcholinesterase and (v) cytotoxicity. Moreover, the compounds were able to sequester Cu(2+) from the Abeta-Cu complex as studied by the UV-visible spectroscopic assay. Molecular docking studies were also performed with Abeta and acetylcholinesterase enzyme. Overall, the studies presented here qualify these molecules as promising candidates for further investigation in the quest for finding a treatment for Alzheimer's disease.
ESTHER : Rana_2022_Inorg.Chem__
PubMedSearch : Rana_2022_Inorg.Chem__
PubMedID: 35768324

Title : Comparative susceptibility of Rhipicephalus microplus collected from the northern state of India to coumaphos, malathion, deltamethrin, ivermectin, and fipronil - Bisht_2021_Trop.Anim.Health.Prod_53_460
Author(s) : Bisht N , Kumar S , Sharma AK , Nandi A , Singh K , Fular A , Nagar G , Ghosh S
Ref : Trop Anim Health Prod , 53 :460 , 2021
Abstract : The chemical-based tick management method is gradually losing its clutch due to the establishment of resistant ticks. For development of region-specific tick management strategies, the present study was aimed to evaluate the comparative resistance profile of Rhipicephalus microplus isolates collected from seven districts of Uttar Pradesh, a northern state of India. Comparative analysis of the dose-response data using adult immersion test (AIT) against coumaphos, malathion, deltamethrin, ivermectin, and fipronil revealed that all the isolates were resistant to discriminating concentration of deltamethrin having LC(50) of 295.12-436.52 ppm with a resistance ratio of 22.02-32.58. An emerging low level of ivermectin resistance (resistance ratio, RR(50) = 1.03-2.26) with LC(50) in the range of 22.39-48.98 ppm was found across the isolates. The coumaphos was highly effective against all except Amethi (AMT) isolate. Similarly, malathion was efficacious against most of the isolates except Pratapgarh (PRT) and Sultanpur (SUL) isolates showing LC(50) of 5128.61 and 5623.41 ppm, respectively. All the isolates were responsive to fipronil. Comparative detoxifying enzymes profiles revealed a significant correlation between the increased activity of esterase and deltamethrin resistance. The GST activity was 51.2% correlated with RR(50) of malathion while esterase activity was significantly correlated (68.9%) with RR(50) of coumaphos. No correlation between the ivermectin resistance and enzyme activity was established. Multiple sequence analysis of S4-5 linker region of the sodium channel gene of all the isolates revealed a point mutation at 190th position (C190A) which is associated with deltamethrin resistance. The possible tick management strategies in this part of the country are discussed.
ESTHER : Bisht_2021_Trop.Anim.Health.Prod_53_460
PubMedSearch : Bisht_2021_Trop.Anim.Health.Prod_53_460
PubMedID: 34542704

Title : Characterization of deltamethrin, cypermethrin, coumaphos and ivermectin resistance in populations of Rhipicephalus microplus in India and efficacy of an antitick natural formulation prepared from Ageratum conyzoides - Kumar_2021_Ticks.Tick.Borne.Dis_12_101818
Author(s) : Kumar S , Sharma AK , Kumar B , Shakya M , Patel JA , Bisht N , Chigure GM , Singh K , Kumar R , Srivastava S , Rawat P , Ghosh S
Ref : Ticks Tick Borne Dis , 12 :101818 , 2021
Abstract : Rhipicephalus microplus is posing a serious threat to productive animal husbandry. Excessive use of synthetic chemicals in tick management has led to the development of resistant tick populations. Characterization of resistance to deltamethrin, cypermethrin, coumaphos and ivermectin in ticks is necessary to develop a suitable and sustainable control strategy. Based on adult immersion test and larval packet test, the resistance ratios (RR(50)) for adults and larvae of R. microplus populations from two Indian states ranged from 3.8 to 19.4 and 1.35-25.0 against deltamethrin, 0.061-26.3 and 0.22-19.2 against cypermethrin, and 0.2-9.5 and 0.01-3.1 against coumaphos, respectively, were recorded. Moreover, the RR(50) for adults ranged from 0.212 to 3.87 against ivermectin. The RR(50) for different acaricides was significantly (p<0.01) correlated with esterases, Glutathione S-transferase and monooxygenase activity. A point mutation at the 190th position of the domain II S4-5 linker region of the sodium channel gene in synthetic pyrethroids (SP) resistant populations was also detected. An antitick natural formulation prepared from the plant Azeratum conyzoides and containing two major compounds, Precocene-I (7methoxy-2, 2-dimethyl 2H-chromene) and Precocene II (6, 7-dimethoxy-2, 2-dimethyl- 3-chromene), was developed and tested against the resistant ticks. The LC(50) values of the natural formulation against the resistant populations were in the range of 4.31-5.33% irrespective of their RR(50) values. Multi-acaricide resistant populations of R. microplus are established in India and the A. conyzoides based natural formulation can be used for its management.
ESTHER : Kumar_2021_Ticks.Tick.Borne.Dis_12_101818
PubMedSearch : Kumar_2021_Ticks.Tick.Borne.Dis_12_101818
PubMedID: 34537543

Title : Pharmacological and pharmacognostical valuation of Canna indica leaves extract by quantifying safety profile and neuroprotective potential - Chigurupati_2021_Saudi.J.Biol.Sci_28_5579
Author(s) : Chigurupati S , Abdul Rahman Alharbi N , Sharma AK , Alhowail A , Vardharajula VR , Vijayabalan S , Das S , Kauser F , Amin E
Ref : Saudi J Biol Sci , 28 :5579 , 2021
Abstract : The current study primarily focused on the pharmacognostical and phytochemical screening of Canna indica and further analyzing the leaves extract for toxicological profile and neuroprotective potential. The microscopic, dry powder properties of the leaf material and phytochemical, physicochemical analysis was evaluated for pharmacognostical assessment. Dry leaves of C. indica were extracted using methanol and then further studied for both in vitro and in vivo toxicological study. The acute toxicity was measured by estimating the antioxidant defense system and anatomical impairment in the rat's organs. Also, the neuroprotective activity of the plant extract was assessed using anticholinesterase enzymatic inhibitory assay. The extract was found to be hemocompatible and showed absences of induction of behavioural changes. Likewise, no changes were seen on the anatomical structure of the rat's organs. The methanolic extract portrayed a significant upsurge in the reduced glutathione level and showed a comparable acetylcholinesterase inhibition in a dosedependent manner with an IC50 value of 14.53 microg/mL compared to the standard Donepezil with an IC50 value of 13.31 microg/mL. C. indica has compelling pharmacognostical characteristics, good safety reports, and significant antioxidant as well as the neuroprotective potential that shows great potential for its further in-depth research for pharmacological use.
ESTHER : Chigurupati_2021_Saudi.J.Biol.Sci_28_5579
PubMedSearch : Chigurupati_2021_Saudi.J.Biol.Sci_28_5579
PubMedID: 34588868

Title : A chemical-genetic screen identifies ABHD12 as an oxidized-phosphatidylserine lipase - Kelkar_2019_Nat.Chem.Biol_15_169
Author(s) : Kelkar DS , Ravikumar G , Mehendale N , Singh S , Joshi A , Sharma AK , Mhetre A , Rajendran A , Chakrapani H , Kamat SS
Ref : Nat Chemical Biology , 15 :169 , 2019
Abstract : Reactive oxygen species (ROS) are transient, highly reactive intermediates or byproducts produced during oxygen metabolism. However, when innate mechanisms are unable to cope with sequestration of surplus ROS, oxidative stress results, in which excess ROS damage biomolecules. Oxidized phosphatidylserine (PS), a proapoptotic 'eat me' signal, is produced in response to elevated ROS, yet little is known regarding its chemical composition and metabolism. Here, we report a small molecule that generates ROS in different mammalian cells. We used this molecule to detect, characterize and study oxidized PS in mammalian cells. We developed a chemical-genetic screen to identify enzymes that regulate oxidized PS in mammalian cells and found that the lipase ABHD12 hydrolyzes oxidized PS. We validated these findings in different physiological settings including primary peritoneal macrophages and brains from Abhd12(-/-) mice under inflammatory stress, and in the process, we functionally annotated an enzyme regulating oxidized PS in vivo.
ESTHER : Kelkar_2019_Nat.Chem.Biol_15_169
PubMedSearch : Kelkar_2019_Nat.Chem.Biol_15_169
PubMedID: 30643283
Gene_locus related to this paper: human-ABHD12

Title : Molecular mechanism of synthetic pyrethroid and organophosphate resistance in field isolates of Rhipicephalus microplus tick collected from a northern state of India - Nagar_2018_Exp.Appl.Acarol_75_319
Author(s) : Nagar G , Sharma AK , Kumar S , Saravanan BC , Kumar R , Gupta S , Ghosh S
Ref : Exp Appl Acarol , 75 :319 , 2018
Abstract : The frequently used chemical control method to manage Rhipicephalus microplus is limited by the emergence of resistance populations. Understanding of resistance mechanisms is essential to develop strategy for sustainable management. The present study was focused on working out the molecular mechanisms of resistance against synthetic pyrethroids (SPs) and organophosphates (OPs) in field isolates of R. microplus collected from six districts of Uttar Pradesh, India. Adult immersion test with discriminating concentrations (AIT-DC) was used to determine resistance status of isolates to SPs (deltamethrin, cypermethrin) and OPs (diazinon, coumaphos). All the six isolates were found resistant to SPs with resistance factor (RF) of 2.9-58.6 and to one of the OP compounds, diazinon having RF of 3.5-13.7 but susceptible to coumaphos (RF < 1.4). Three R. microplus genes, viz. para-sodium channel domain II S4-5 linker, carboxylesterase (372 bp) and acetylcholinesterase 2 (1692 bp) were sequenced and compared with respective sequences of reference susceptible IVRI-I, reference OP resistant population (IVRI-III), IVRI-IV and multi-acaricide resistant population (IVRI-V) of R. microplus. A C190A mutation in the domain II S4-5 linker region of sodium channel gene leading to L64I amino acid substitution was detected in all six isolates. The G1120A mutation in the carboxylesterase gene could not be detected in any isolate. Five nucleotide substitutions viz., G138A, G889A, T1090A, C1234T and G1403A were identified in the acetylcholinesterase 2 gene leading to four amino acid substitutions. The findings of the study corroborate the role of mutation in sodium channel and acetylcholinesterase 2 genes in SP and OP resistance in this part of India.
ESTHER : Nagar_2018_Exp.Appl.Acarol_75_319
PubMedSearch : Nagar_2018_Exp.Appl.Acarol_75_319
PubMedID: 29846851
Gene_locus related to this paper: boomi-ACHE2

Title : Establishment of a multi-acaricide resistant reference tick strain (IVRI-V) of Rhipicephalus microplus - Fular_2018_Ticks.Tick.Borne.Dis_9_1184
Author(s) : Fular A , Sharma AK , Kumar S , Nagar G , Chigure G , Ray DD , Ghosh S
Ref : Ticks Tick Borne Dis , 9 :1184 , 2018
Abstract : Tick-borne diseases is a global threat and tick resistance to commonly used acaricides is a growing problem, thus calling for improved resistance monitoring tools. To aid in monitoring of resistance in field tick populations, a resistant colony of Rhipicephalus microplus was characterized with the aim to establish a reference multi-acaricide resistant tick strain. Using a standardized adult immersion test, the Lethal Concentration(LC)50 values for deltamethrin, cypermethrin, fenvalerate and diazinon against the laboratory selected resistant tick (LSRT) strain were determined as 306.7ppm, 2776.9ppm, 30262.1ppm and 9458.7ppm. Relative to the susceptible IVRI-I tick strain, the LSRT strain showed 4.78- and 5.84-fold increases in activity of esterases, a 6-fold increase for monooxygenases and a 2.24 fold increase for glutathione S-transferase. In the acetylcholinesterase 2 gene, 22 single nucleotide polymorphisms (SNPs) were identified in the LSRT strain. Four of these SNPs lead to amino acid substitutions and were consistently found in resistant field populations in India. A C190A mutation in the domain II S4-5 linker region of sodium channel gene resulting in a L64I amino acid substitution was recorded in the LSRT strain. Monitorable indicators for the maintenance of the strain, designated as the reference IVRI-V tick strain and representing the first established multi-acaricide resistant tick strain in India, were identified.
ESTHER : Fular_2018_Ticks.Tick.Borne.Dis_9_1184
PubMedSearch : Fular_2018_Ticks.Tick.Borne.Dis_9_1184
PubMedID: 29730262

Title : Characterization and establishment of a reference deltamethrin and cypermethrin resistant tick line (IVRI-IV) of Rhipicephalus (Boophilus) microplus - Ghosh_2017_Pestic.Biochem.Physiol_138_66
Author(s) : Ghosh S , Gupta S , Ajith Kumar KG , Sharma AK , Kumar S , Nagar G , Kumar R , Paul S , Fular A , Chigure G , Nandi A , Manjunathachar HV , Mohammad A , Verma MR , Saravanan BC , Ray D
Ref : Pestic Biochem Physiol , 138 :66 , 2017
Abstract : The problem of ticks and tick borne diseases is a global threat and growing reports of resistance to commonly used insecticides further aggravated the condition and demands for country specific resistance monitoring tools and possible solutions of the problem. Establishment of standard reference is prerequisite for development of monitoring tools. For studying possible role of different mechanisms involved in development of resistance in Rhipicephalus (Boophilus) microplus population and to develop newer drug to manage the problem of resistance, a deltamethrin exposed and selected tick colony, referred to as IVRI-IV, was characterized using reference susceptible IVRI-I tick line as control. The RF values of IVRI-IV ticks against deltamethrin, cypermethrin and diazinon were determined as 194.0, 26.6, 2.86, respectively, against adults. The esterase enzyme ratios of 2.60 and 5.83 was observed using alpha-naphthyl and beta-naphthyl acetate while glutathione S-transferase (GST) ratio was 3.77. Comparative analysis of IVRI-I and IVRI-IV carboxylesterase gene sequences revealed 13 synonymous and 5 non synonymous mutations, reported for the first time. The C190A mutation in the domain II S4-5 linker region of sodium channel gene leading to leucine to isoleucine (L64I) amino acid substitution was also detected in the IVRI-IV population. In the present study, monitorable indicators for the maintenance of the reference IVRI-IV colony, the first established deltamethrin and cypermethrin resistant tick line of India, were identified.
ESTHER : Ghosh_2017_Pestic.Biochem.Physiol_138_66
PubMedSearch : Ghosh_2017_Pestic.Biochem.Physiol_138_66
PubMedID: 28456306

Title : Esterase mediated resistance in deltamethrin resistant reference tick colony of Rhipicephalus (Boophilus) microplus - Gupta_2016_Exp.Appl.Acarol_69_239
Author(s) : Gupta S , Ajith Kumar KG , Sharma AK , Nagar G , Kumar S , Saravanan BC , Ravikumar G , Ghosh S
Ref : Exp Appl Acarol , 69 :239 , 2016
Abstract : Monitoring of acaricide resistance is considered as one of the important facets of integrated tick management. In an attempt of development of resistance monitoring indicators, in the present study two reference tick lines of Rhipicephalus (Boophilus) microplus maintained in the Entomology laboratory, Indian Veterinary Research Institute (IVRI), Izatnagar, India, were studied to determine the possible contributing factors involved in development of resistance to deltamethrin. Electrophoretic profiling of esterase enzymes detected high activities of EST-1 in reference resistant tick colony designated as IVRI-IV whereas it was not detectable in reference susceptible IVRI-I line of R. (B.) microplus. Esterases were further characterized as carboxylesterase or acetylcholinesterase based on inhibitor study using PMSF, eserine sulphate, malathion, TPP and copper sulphate. It was concluded that an acetylcholinesterase, EST-1, possibly plays an important role for development of deltamethrin resistance in IVRI-IV colony of R. (B.) microplus.
ESTHER : Gupta_2016_Exp.Appl.Acarol_69_239
PubMedSearch : Gupta_2016_Exp.Appl.Acarol_69_239
PubMedID: 26979585

Title : Survey of acaricides resistance status of Rhipiciphalus (Boophilus) microplus collected from selected places of Bihar, an eastern state of India - Ghosh_2015_Ticks.Tick.Borne.Dis_6_668
Author(s) : Ghosh S , Kumar R , Nagar G , Kumar S , Sharma AK , Srivastava A , Ajith Kumar KG , Saravanan BC
Ref : Ticks Tick Borne Dis , 6 :668 , 2015
Abstract : Monitoring acaricide resistance in field ticks and use of suitable managemental practices are essential for controlling tick populations infesting animals. In the present study, the acaricide resistance status in Rhipicephalus (Boophilus) microplus ticks infesting cattle and buffaloes of five districts located in the eastern Indian state, Bihar were characterized using three data sets (AIT, Biochemical assays and gene sequences). Adult immersion test (AIT) was adopted using seven field isolates and their resistance factor (RF) was determined. Six isolates (DNP, MUZ, BEG, VSH, DRB and SUL) were found resistant to both deltamethrin and diazinon and except VSH all were resistant to cypermethrin. One isolate (PTN) was susceptible with a RF below 1.5. To understand the possible mode of resistance development, targeted enzymes and gene sequences of the para sodium channel and achetylcholinesterase 2 (AChE2) were analyzed. The esterase, monooxygenase and glutathione-S-transferase (GST) activity of reference susceptible IVRI-I line was determined as 2.47+/-0.007nmol/min/mg protein, 0.089+/-0.0016nmol/mg of protein and 0.0439+/-0.0003nmol/mg/min respectively, which increased significantly in the resistant field isolates. However, except esterases, the fold increase of monooxygenase (1.14-2.27 times) and GST (0.82-1.53 times) activities were not very high. A cytosine (C) to adenine (A) nucleotide substitution (CTC to ATC) at position 190 in domain II S4-5 linker region was detected only in one isolate (SUL) having RF of 34.9 and in the reference deltamethrin resistant line (IVRI-IV). However, the T2134A mutation was not detected in domain IIIS6 transmembrane segment of resistant isolates and also in reference IVRI-IV line despite of varying degree of resistance. The flumethrin specific G215T and the recently identified T170C mutations were also absent in domain II sequences under study. Four novel amino acid substitutions in AChE2 gene of field isolates and in organophosphate (OP) resistant reference IVRI-III line were identified which can possibly have a role in resistance development.
ESTHER : Ghosh_2015_Ticks.Tick.Borne.Dis_6_668
PubMedSearch : Ghosh_2015_Ticks.Tick.Borne.Dis_6_668
PubMedID: 26117183
Gene_locus related to this paper: boomi-ACHE2

Title : Acaricide resistance status in Indian isolates of Hyalomma anatolicum - Shyma_2012_Exp.Appl.Acarol_58_471
Author(s) : Shyma KP , Kumar S , Sharma AK , Ray DD , Ghosh S
Ref : Exp Appl Acarol , 58 :471 , 2012
Abstract : The multi host tick, Hyalomma anatolicum, is the commonest Hyalomma species in India and cattle serves as the main host of this species. A study to evaluate the acaricide resistance of H. anatolicum to deltamethrin, cypermethrin and diazinon was conducted in 20 areas located in three agro climatic regions known to have abundance of the species. Results obtained by the "larval packet test" (LPT) showed a low grade resistance (level-I, RF <5) in the tick species to both deltamethrin and cypermethrin in 10 areas and higher grade resistance (level-II, RF <25) to deltamethrin in one area, where intensive use of synthetic pyrethroids are practiced for tick control. Low grade resistance to diazinon (level I) was recorded in six areas where organophosphates compounds are extensively used for agricultural practices allowing increased exposure of the moulting instars of the ticks to these chemicals. Biochemical analysis of the samples suggested involvement of esterase and alterations of acetylcholinesterase in the resistance mechanisms.
ESTHER : Shyma_2012_Exp.Appl.Acarol_58_471
PubMedSearch : Shyma_2012_Exp.Appl.Acarol_58_471
PubMedID: 22760859

Title : Possible role of cholinesterase inhibitors on memory consolidation following hypobaric hypoxia of rats - Muthuraju_2011_Int.J.Neurosci_121_279
Author(s) : Muthuraju S , Maiti P , Solanki P , Sharma AK , Pati S , Singh SB , Prasad D , Ilavazhagan G
Ref : International Journal of Neuroscience , 121 :279 , 2011
Abstract : High altitude (HA) generates a deleterious effect known as hypobaric hypoxia (HBH). This causes severe physiological and psychological changes such as acute mountain sickness (AMS) and cognitive functions in terms of learning and memory. The present study has evaluated the effect of cholinesterase inhibitors on memory consolidation following HBH. Adult male Sprague Dawley rats (80-90 days old) with an average body weight of 250 +/- 25 g were used. Rats were assessed memory consolidation by using Morris water maze (MWM) for 8 days. After assessment of memory consolidation, rats were then exposed to HBH in stimulated chamber for 7 days at 6,100 m. After exposure to HBH, the memory consolidation of rats has been assessed in MWM. The results showed that there was memory consolidation impairment in HBH-exposed rats as compared to normoxic rats in terms of time spent in quaradents, rings, and counters. The rats which have been treated with physostigmine (PHY) and galantamine (GAL) showed better time spent in quaradents, rings, and counters as compared with hypoxic rats. In conclusion, the cholinesterase inhibitors could ameliorate the impairment of memory consolidation following HBH.
ESTHER : Muthuraju_2011_Int.J.Neurosci_121_279
PubMedSearch : Muthuraju_2011_Int.J.Neurosci_121_279
PubMedID: 21348795

Title : Role of cholinergic markers on memory function of rats exposed to hypobaric hypoxia - Muthuraju_2011_Eur.J.Pharmacol_672_96
Author(s) : Muthuraju S , Maiti P , Pati S , Solanki P , Sharma AK , Singh SB , Prasad D , Ilavazhagan G
Ref : European Journal of Pharmacology , 672 :96 , 2011
Abstract : Hypobaric hypoxia is encountered at high altitude. It has a deleterious effect on cognitive functions. An important cause of memory impairment at high altitude is the impairment of neurotransmission. The present study investigates the role of cholinergic markers in hypobaric hypoxia-induced memory impairment. Rats were exposed to hypobaric hypoxia at 6,100 m for 7 days in a simulated-decompression chamber. Memory performance was assessed using the Morris water maze task. Cholinergic markers such as acetylcholine, acetylcholinesterase, choline acetyltransferase, alpha-7-nicotinic acetylcholine receptor and M(1) muscarinic acetylcholine receptor were also evaluated along with neuronal morphology and DNA fragmentation. We found impairment in memory function along with a decrease in acetylcholine levels, increase in acetylcholinesterase activity, down regulation of choline acetyltransferase, alpha-7-nicotinic acetylcholine receptor and M(1) muscarinic acetylcholine receptor. We also found that cellular damage is associated with a significant increase in DNA fragmentation. However, administration of acetylcholinesterase inhibitors, such as physostigmine and galantamine, resulted in amelioration of the hypobaric hypoxia induced deleterious effects. It improved acetylcholine level, decreased acetylcholinesterase activity and increased the synthesis of acetylcholine by increasing choline acetyltransferase activity. Also, the acetylcholinesterase inhibitors improved neuronal morphology, perhaps by increasing the expression of alpha-7-nicotinic acetylcholine receptor and by reducing the acetylcholinesterase level in the cortex and the hippocampus. Therefore, our results suggest cholinergic dysfunction is one of the mechanisms involved in hypobaric hypoxia-induced memory impairment and that acetylcholinesterase inhibitors were able to restore cholinergic function and thus improve memory function.
ESTHER : Muthuraju_2011_Eur.J.Pharmacol_672_96
PubMedSearch : Muthuraju_2011_Eur.J.Pharmacol_672_96
PubMedID: 21924263

Title : Effect of phosphamidon on convulsive behavior and biochemical parameters: modulation by progesterone and 4'-chlorodiazepam in rats - Joshi_2010_Naunyn.Schmiedebergs.Arch.Pharmacol_382_311
Author(s) : Joshi V , Arora T , Mehta AK , Sharma AK , Rathor N , Mehta KD , Mahajan P , Mediratta PK , Banerjee BD , Sharma KK
Ref : Naunyn Schmiedebergs Arch Pharmacol , 382 :311 , 2010
Abstract : Phosphamidon (PHOS) has been shown to affect nervous system adversely. The present study was designed to explore the modulation of the effects of PHOS on convulsions by neurosteroids, progesterone (PROG), and 4'-chlorodiazepam (4'-CD), in both acute and chronic seizure models. In acute study, seizures were induced by either pentylenetetrazole (PTZ) injection or maximal electroshock seizures, while in the chronic study, kindling was induced by injecting PTZ (30 mg/kg, s.c.) on alternate days three times in a week. Oxidative stress was assessed in the brain by measuring the levels of malondialdehyde (MDA), acetylcholinesterase (AChE), and non-protein thiol (NP-SH). PROG and 4'-CD were able to modulate the PHOS-induced convulsions in acute PTZ convulsions as well as in chronic kindling model. However, they failed to reverse the derangements in oxidative stress parameters of MDA and NP-SH produced by PHOS in kindled animals. PROG significantly increased the AChE activity in untreated rats, while PROG and 4'-CD reversed the AChE activity inhibition induced by PHOS. The study indicates a possible anticonvulsive mechanism of neurosteroids, since both PROG and 4'-CD reversed PHOS-induced inhibition of AChE activity. The neurosteroids seem to play a protective role in PHOS-induced convulsions besides their antioxidant property.
ESTHER : Joshi_2010_Naunyn.Schmiedebergs.Arch.Pharmacol_382_311
PubMedSearch : Joshi_2010_Naunyn.Schmiedebergs.Arch.Pharmacol_382_311
PubMedID: 20737266

Title : Cholinesterase inhibitors ameliorate spatial learning deficits in rats following hypobaric hypoxia - Muthuraju_2010_Exp.Brain.Res_203_583
Author(s) : Muthuraju S , Maiti P , Solanki P , Sharma AK , Singh SB , Prasad D , Ilavazhagan G
Ref : Experimental Brain Research , 203 :583 , 2010
Abstract : Cognitive functions especially learning and memory are severely affected by high altitude (HA) exposure. Hypobaric hypoxia (HBH) encountered at HA is known to cause oxidative stress, alterations of neurotransmitters and cognitive impairment. We hypothesized that alteration in cholinergic system may be involved in HBH-induced learning impairment. The present study has investigated the cholinergic dysfunctions associated with simulated HBH-induced impairment of learning in rats and protective role of acetylcholine esterase inhibitors (AChEIs). Male Sprague-Dawley rats were exposed to HBH equivalent to 6,100 m for 7 days in a simulated decompression chamber. After stipulated period of exposure, learning ability was assessed using Morris water maze (MWM) task. Cholinergic markers like acetylcholine (ACh) and acetyl cholinesterase (AChE) were evaluated from cortex and hippocampus. Morphological changes were evaluated from cortex, CA1, and CA3 region of hippocampus by Nissle staining and by electron microscopy. We found that exposure to HBH led to impairment of learning ability in MWM task, and it was accompanied by decrease in ACh level, increase in AChE activity, and revealed critical cellular damage. Administration of AChEIs like physostigmine (PHY) and galantamine (GAL) resulted in amelioration of the deleterious effects induced by HBH. The AChEIs were also able to restore the neuronal morphology. Our data suggest that cholinergic system is affected by HBH, and AChEIs were able to improve HBH-induced learning impairment in rats.
ESTHER : Muthuraju_2010_Exp.Brain.Res_203_583
PubMedSearch : Muthuraju_2010_Exp.Brain.Res_203_583
PubMedID: 20458473

Title : Acetylcholinesterase inhibitors enhance cognitive functions in rats following hypobaric hypoxia - Muthuraju_2009_Behav.Brain.Res_203_1
Author(s) : Muthuraju S , Maiti P , Solanki P , Sharma AK , Amitabh , Singh SB , Prasad D , Ilavazhagan G
Ref : Behavioural Brain Research , 203 :1 , 2009
Abstract : Hypobaric hypoxia (HBH) can produce neuropsychological disorders such as insomnia, dizziness, memory deficiencies, headache and nausea. It is well known that exposure to HBH cause alterations of neurotransmitters and cognitive impairment in terms of learning and memory. But the mechanisms are poorly understood. The present study aimed to investigate the cholinergic system alterations associated with simulated HBH induced cognitive impairment. Male Sprague-Dawley rats were exposed to HBH equivalent to 6100 m for 7 days in a simulation chamber. The cognitive performance was assessed using Morris Water Maze (MWM) task. Cholinergic markers like acetylcholine (ACh) and acetylcholinesterase (AChE) were evaluated in hippocampus and cortex of rats. Neuronal damage was also studied through morphological changes. Exposure to HBH led to impairment in relearning ability and memory retrieval and it was accompanied by decrease in ACh level and increase in AChE and led to morphological damage. Administration of AChE inhibitor (AChEI), physostigmine (PHY) and galantamine (GAL) to rats during HBH exposure resulted in amelioration of the deleterious effects induced by HBH. The AChEIs were able to improve the cholinergic activity by restoring the level of ACh by blocking the AChE activity. In addition, the AChEIs also prevented neurodegeneration by reducing the AChE level in cortical and hippocampal neurons.
ESTHER : Muthuraju_2009_Behav.Brain.Res_203_1
PubMedSearch : Muthuraju_2009_Behav.Brain.Res_203_1
PubMedID: 19446892

Title : Evolution of rhodopsin ion pumps in haloarchaea - Sharma_2007_BMC.Evol.Biol_7_79
Author(s) : Sharma AK , Walsh DA , Bapteste E , Rodriguez-Valera F , Ford Doolittle W , Papke RT
Ref : BMC Evol Biol , 7 :79 , 2007
Abstract : BACKGROUND: The type 1 (microbial) rhodopsins are a diverse group of photochemically reactive proteins that display a broad yet patchy distribution among the three domains of life. Recent work indicates that this pattern is likely the result of lateral gene transfer (LGT) of rhodopsin genes between major lineages, and even across domain boundaries. Within the lineage in which the microbial rhodopsins were initially discovered, the haloarchaea, a similar patchy distribution is observed. In this initial study, we assess the roles of LGT and gene loss in the evolution of haloarchaeal rhodopsin ion pump genes, using phylogenetics and comparative genomics approaches. RESULTS: Mapping presence/absence of rhodopsins onto the phylogeny of the RNA polymerase B' subunit (RpoB') of the haloarchaea supports previous notions that rhodopsins are patchily distributed. The phylogeny for the bacteriorhodopsin (BR) protein revealed two discrepancies in comparison to the RpoB' marker, while the halorhodopsin (HR) tree showed incongruence to both markers. Comparative analyses of bacteriorhodopsin-linked regions of five haloarchaeal genomes supported relationships observed in the BR tree, and also identified two open reading frames (ORFs) that were more frequently linked to the bacteriorhodopsin gene than those genes previously shown to be important to the function and expression of BR. CONCLUSION: The evidence presented here reveals a complex evolutionary history for the haloarchaeal rhodopsins, with both LGT and gene loss contributing to the patchy distribution of rhodopsins within this group. Similarities between the BR and RpoB' phylogenies provide supportive evidence for the presence of bacteriorhodopsin in the last common ancestor of haloarchaea. Furthermore, two loci that we have designated bacterio-opsin associated chaperone (bac) and bacterio-opsin associated protein (bap) are inferred to have important roles in BR biogenesis based on frequent linkage and co-transfer with bacteriorhodopsin genes.
ESTHER : Sharma_2007_BMC.Evol.Biol_7_79
PubMedSearch : Sharma_2007_BMC.Evol.Biol_7_79
PubMedID: 17511874
Gene_locus related to this paper: 9eury-a7u103

Title : Hypobaric hypoxia induces oxidative stress in rat brain - Maiti_2006_Neurochem.Int_49_709
Author(s) : Maiti P , Singh SB , Sharma AK , Muthuraju S , Banerjee PK , Ilavazhagan G
Ref : Neurochem Int , 49 :709 , 2006
Abstract : High altitude exposure results in decreased partial pressure of oxygen and an increased formation of reactive oxygen and nitrogen species (RONS), which causes oxidative damage to lipids, proteins and DNA. Exposure to high altitude appears to decrease the activity and effectiveness of antioxidant enzyme system. The antioxidant system is very less in brain tissue and is very much susceptible to hypoxic stress. The aim of the present study was to investigate the time dependent and region specific changes in cortex, hippocampus and striatum on oxidative stress markers on chronic exposure to hypobaric hypoxia. The rats were exposed to simulated high altitude equivalent to 6100 m in animal decompression chamber for 3 and 7 days. Results indicate an increase in oxidative stress as seen by increase in free radical production, nitric oxide level, lipid peroxidation and lactate dehydrogenase levels. The magnitude of increase in oxidative stress was more in 7 days exposure group as compared to 3 days exposure group. The antioxidant defence system such as reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutase (SOD) and reduced/oxidized glutathione (GSH/GSSG) levels were significantly decreased in all the three regions. The observation suggests that the hippocampus is more susceptible to hypoxia than the cortex and striatum. It may be concluded that hypoxia differentially affects the antioxidant status in the cortex, hippocampus and striatum.
ESTHER : Maiti_2006_Neurochem.Int_49_709
PubMedSearch : Maiti_2006_Neurochem.Int_49_709
PubMedID: 16911847

Title : The genome of Salinibacter ruber: convergence and gene exchange among hyperhalophilic bacteria and archaea - Mongodin_2005_Proc.Natl.Acad.Sci.U.S.A_102_18147
Author(s) : Mongodin EF , Nelson KE , Daugherty S , DeBoy RT , Wister J , Khouri H , Weidman J , Walsh DA , Papke RT , Sanchez Perez G , Sharma AK , Nesbo CL , Macleod D , Bapteste E , Doolittle WF , Charlebois RL , Legault B , Rodriguez-Valera F
Ref : Proc Natl Acad Sci U S A , 102 :18147 , 2005
Abstract : Saturated thalassic brines are among the most physically demanding habitats on Earth: few microbes survive in them. Salinibacter ruber is among these organisms and has been found repeatedly in significant numbers in climax saltern crystallizer communities. The phenotype of this bacterium is remarkably similar to that of the hyperhalophilic Archaea (Haloarchaea). The genome sequence suggests that this resemblance has arisen through convergence at the physiological level (different genes producing similar overall phenotype) and the molecular level (independent mutations yielding similar sequences or structures). Several genes and gene clusters also derive by lateral transfer from (or may have been laterally transferred to) haloarchaea. S. ruber encodes four rhodopsins. One resembles bacterial proteorhodopsins and three are of the haloarchaeal type, previously uncharacterized in a bacterial genome. The impact of these modular adaptive elements on the cell biology and ecology of S. ruber is substantial, affecting salt adaptation, bioenergetics, and photobiology.
ESTHER : Mongodin_2005_Proc.Natl.Acad.Sci.U.S.A_102_18147
PubMedSearch : Mongodin_2005_Proc.Natl.Acad.Sci.U.S.A_102_18147
PubMedID: 16330755
Gene_locus related to this paper: salrd-q2ryx4 , salrd-q2ryz7 , salrd-q2rz15 , salrd-q2rz19 , salrd-q2rz52 , salrd-q2rz84 , salrd-q2rzy1 , salrd-q2s0e4 , salrd-q2s1i8 , salrd-q2s1v7 , salrd-q2s1v9 , salrd-q2s2d6 , salrd-q2s2y7 , salrd-q2s5a6 , salrd-q2s5k5 , salrd-q2s5u7 , salrd-q2s6g6 , salrd-q2s039 , salrd-q2s117 , salrd-q2s215 , salrd-q2s287 , salrd-q2s400 , salrd-q2s402 , salrd-q2s473 , salrd-q2s516 , salrd-q2s564

Title : Properties of a thermostable and solvent stable extracellular lipase from a Pseudomonas sp. AG-8 - Sharma_2001_J.Basic.Microbiol_41_363
Author(s) : Sharma AK , Tiwari RP , Hoondal GS
Ref : J Basic Microbiol , 41 :363 , 2001
Abstract : An extracellular lipase isolated from Pseudomonas sp. AG-8, had an optimal activity at 45 degrees C and pH 8.0-8.5. It retained more than 80% of its initial activity after keeping for 1 h at 65 degrees C. The enzyme was stable in 5 M NaCl and 6 M urea. Triton X-100 increased the lipase activity by 2.4 fold. Ca2+ ions activated the enzyme, while Zn2+, Fe2+, Fe3+ strongly inhibited its activity. Ethanol, methanol and acetone at 20% (v/v) enhanced the lipase activity by 2.9, 3.6 and 4.5 fold respectively. Dimethylsulphoxide at 90% (v/v) enhanced the enzyme activity up to 5.7 fold.
ESTHER : Sharma_2001_J.Basic.Microbiol_41_363
PubMedSearch : Sharma_2001_J.Basic.Microbiol_41_363
PubMedID: 11802546