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Articles by Ashok Kumar
Total Records ( 11 ) for Ashok Kumar
  Neeraj Kathuria , Anuj Tripathi , Kamal K Kar and Ashok Kumar
  Elastic chitosan–gelatin cryogels of varying concentration of polymer precursors have been synthesized using glutaraldehyde as a crosslinking agent. The optimum co-polymer ratio of chitosan to gelatin was found to be 1:4 at the temperature of –12 °C for synthesis of chitosan–gelatin hybrid cryogels. chitosan–gelatin cryogels synthesized with low viscosity chitosan were morphologically better than those formed with medium and high viscosity chitosan. Pore diameters of chitosan–gelatin cryogels as measured by scanning electron microscopy (SEM) was in the range of 30–100 μm. While mercury porosimetry analysis revealed the majority of pores of the scaffold lying in the range of 30–50 μm. Porosity of chitosan–gelatin cryogels was found to be greater than 90% using Archimedes’s principle. Unconfined compression tests showed significant elasticity of chitosan–gelatin cryogels and maintained their physical integrity even after compressing them up to 80% of their original length. The elastic modulus varied in the range of 36–39 kPa. Cyclic deformation analysis performed by compression of chitosan–gelatin cryogels with varying strains (10, 20 and 40%) showed no cracking or any significant deformation. The degradation of chitosan–gelatin cryogels was found up to 13.58 ± 1.52% at 37 °C within 8 weeks of incubation under sterile conditions and the cryogels swelled up to 90% of their capacity within two min. Efficient cell adherence, proliferation and extracellular matrix (ECM) secretion was observed by growing fibroblast (Cos-7) cell line on chitosan–gelatin hybrid cryogels which indicate potential of the material for tissue engineering applications.
  Ashok Kumar , Vinay Medhekar , Michael P. Harold and Vemuri Balakotaiah
  A systematic study over Pt/Al2O3 powder and monolith catalysts is carried out using temporal analysis of products (TAP) to elucidate the transient kinetics of NO decomposition and NO reduction with H2. NO pulsing and NO–H2 pump-probe experiments demonstrate the effect of catalyst temperature, NO–H2 pulse delay time and H2/NO ratio on N2, N2O and NH3 selectivity. At lower temperature (150 °C) decomposition of NO is negligible in the absence of H2, indicating that N–O bond scission is rate limiting. At higher temperature NO decomposition occurs readily on reduced Pt but the rate is inhibited by surface oxygen as reaction occurs. The reduction of NO by a limiting amount of H2 at lower temperature indicates the reaction of surface NO with H adatoms to form N adatoms, which react with adsorbed NO to form N2O or recombine to form N2. In excess H2, higher temperatures and longer delay times favor the production of N2. The longer delay enables NO decomposition on reduced Pt with the role of H2 being a scavenger of surface oxygen. Lower temperatures and shorter delay times are favorable for ammonia production. The sensitive dependence on delay time indicates that the fate of adsorbed NO depends on the concentration of vacant sites for NO bond scission, necessary for N2 formation, and of surface hydrogen, necessary for hydrogenation to ammonia. A mechanistic-based microkinetic model is proposed that accounts for the experimental observations. The TAP experiments with the monolith catalyst show an improved signal due to the reduction of transport restrictions caused by the powder. The improved signal holds promise for quantitative TAP studies for kinetic parameters estimation and model discrimination.
  Thadiyam Puram Ramees , Ramswaroop Singh Rathore , Prashanth Suresh Bagalkot , Hosakote Venkatappa Mohan , Ashok Kumar and Kuldeep Dhama
  In recent years, the frequency of isolation and detection of Arcobacter organisms from animals and humans with enteritis and food samples, highlights the importance of arcobacters worldwide as emerging food-borne pathogens. Reports are very scanty regarding prevalence of arcobacters from India. Therefore, the present study aimed to know the prevalence of Arcobacter spp. (Arcobacter butzleri and Arcobacter cryaerophilus) in humans and foods of animal origin by employing cultural and multiplex PCR (mPCR) methods. A total number of 353 samples were collected from human hospitals, retail meat shops and milk suppliers [human stools (102), chicken meat (151), milk (100)] from in and around Bareilly region, Uttar Pradesh, India. By cultural method the overall prevalence rate of Arcobacter spp. was found to be 10.20% (36/353) while it was 18.13% (64/353) with mPCR which revealed mPCR to be a more efficient technique in detecting arcobacters. The highest prevalence rate was observed in chicken meat, followed by human stool and milk samples with A. butzleri having more prevalence. For simultaneous detection and differentiation of arcobacters at species level the cultural methods possess limitations while mPCR gave rapid and confirmatory detection of A. butzleri and A. cryaerophilus species. The results of the study add to the epidemiological data available for arcobacters. Extensive epidemiological studies employing the utility of mPCR are suggested for knowing the magnitude of Arcobacter infection animals, humans and various food sources in the country. This would help in designing appropriate prevention and control strategies for this important pathogen having public health concerns.
  Hosakote Venkatappa Mohan , Ramswaroop Singh Rathore , Kuldeep Dhama , Thadiyam Puram Ramees , Anil Patya , Prashanth Suresh Bagalko , Mohd. Yaqoob Wani , Kiran Narayan Bhilegaonkar and Ashok Kumar
  Arcobacter is an important emerging food and water borne pathogen having worldwide public health concern. The present study reports the prevalence of Arcobacter spp. in humans, animals and foods of animal origin based on cultural isolation, antibiogram, Polymerase Chain Reaction (PCR) and multiplex PCR detection. A total of 400 samples were collected as human diarrheal stool (50), faecal swabs of poultry (50), pig (50), cattle (50) and foods of animal origin [Raw milk (60), chicken meat (60), beef (40) and pork (40)]. The overall prevalence rate of Arcobacter spp. was found to be 6.75% (27/400) by cultural isolation with highest prevalence in pig faeces (12%), followed by cattle faeces (10%), chicken meat (10%), poultry faeces (8%), beef (5%), pork (5%), human diarrheal stools (2%) and milk (1.67%). PCR screening revealed prevalence of Arcobacter spp. to be 7.75% (31/400) with highest in pig faeces (12%), followed by cattle faeces (12%), chicken meat (11.67%), poultry (10%), beef (7.5%), pork (5%), human stools (2.00%) and raw milk (1.67%). Multiplex PCR assay enabled detection of A. butzleri (21/27) and A. skirrowii (6/27). In vitro antibiotic sensitivity profile of 27 Arcobacter isolates revealed most of these to be sensitive to azithromycin, gentamycin, nalidixic acid, kanamycin, streptomycin, ciprofloxacin and tetracycline. Higher resistance was observed for cephalothin, novobiocin and vancomycin with notable intermediately resistance against erythromycin and chloramphenicol. The present study demonstrated high prevalence of Arcobacter spp. in pig, cattle and poultry faecal samples which may play important role in contamination of environment, water and human food chain, thus could be of public health concerns. The PCR was found to be more rapid, sensitive, specific and efficient than cultural methods for detection of Arcobacter spp.
  Manoj Jinu , R.K. Agarwal , B. Sailo , M.A. Wani , Ashok Kumar , K. Dhama and M.K. Singh
  The aim of the study was to compare Polymerase Chain Reaction (PCR) and conventional method for detection of Salmonella from field poultry samples (n = 510, poultry blood and faeces 255 each). The prevalence rate of Salmonella in chicken was found to be 5.09% using conventional method and 5.88% by PCR assay. Serotyping of 26 Salmonella isolates revealed 57.69% Salmonella Typhimurium, 19.23% rough type, 15.38% Salmonella Enteritidis and 7.69% untypable. Among Salmonella Typhimurium isolates, 73.33% were from poultry blood and 26.66% from faeces samples. All isolates belonging to Typhimurium and Enteritidis serotypes were confirmed by PCR targeting of Salmonella Typhimurium (typh) and Salmonella Enteritidis (ent) specific genes. However, 4 isolates found to be rough type also turned out to be positive for ent gene. The PCR employed for detection of Salmonella was found 100% sensitive for poultry blood but its sensitivity was very less (77.77%) for faeces samples as compared with culture method. However, PCR was 100% specific with regard to faeces samples. The specificity from blood samples was 97.89% by PCR. The positive predictive values of PCR from blood and faecal samples were 77.27 and 100% with a concordance of 98.03 and 99.21%, respectively. The negative predictive values from blood and faecal samples were 100 and 99.19%. The study demonstrated usefulness of genus specific PCR for detection of Salmonella in poultry clinical samples. Owing to its robustness and rapidity it can be used for wide epidemiological studies. Serotype specific PCR detection of Typhimurium and Enteritidis serotypes has added advantage in identifying them even where there is loss of O antigen.
  Ashok Kumar , Linda D. Hazlett and Fu-Shin X. Yu
  Pseudomonas aeruginosa is a common organism associated with bacterial keratitis, especially in extended-wear contact lens users. In the present study, we determined that pretreatment of cultured human corneal epithelial cells with flagellin isolated from the P. aeruginosa PAO1 strain attenuated cytokine production when the cells were challenged with a cytotoxic strain (ATCC 19660), suggesting a potential use of bacterial flagellin to downregulate infection-associated inflammation in vivo. Administration of flagellin via the subconjunctival and intraperitoneal routes 24 h prior to Pseudomonas inoculation significantly improved the disease outcome, preserved structural integrity and transparency, and thus maintained vision in otherwise perforated corneas of C57BL/6 (B6) mice. The flagellin pretreatment resulted in suppression of polymorphonuclear leukocyte infiltration at a late stage of infection but not at an early stage of infection, decreased the expression of proinflammatory cytokine genes (genes encoding interleukin-1β [IL-1β], macrophage inflammatory protein 2, IL-12, and gamma interferon), and greatly enhanced bacterial clearance in the corneas of B6 mice probably through induced expression of the cathelicidin-related antimicrobial peptide and inducible nitric oxide synthase. This is the first report that describes the protective mechanisms induced by a Toll-like receptor agonist that not only curbs the host inflammatory response but also eliminates invading bacteria in the B6 mouse cornea.
  Arunava Das , Yahya Mazumder , Biman Kumar Dutta , Bibek Ranjan Shome , Komal Molla Bujarbaruah and Ashok Kumar
  This paper reports the investigation of necrotic enteritis (NE) in six broiler chickens of age two to three weeks old, died in Jowai poultry farm, Meghalaya, India. Initially, scanning electron microscopy (SEM) was performed to observe the morphological changes within the intestine. Intestinal contents and liver samples from dead chicken were investigated for isolation of bacteria and their virulence determinant. The SEM analysis of infected intestine revealed massive necrosis and complete destruction of the intestinal villi within the intestinal mucosa. Bacterial isolation confirmed the causative agent as C. perfringens in NE. All the isolates harboured single and double plasmid deoxyribonucleic acid with identical 45.2kb common plasmid. In polymerase chain reaction (PCR) assay all 10 clinical isolates harboured alpha toxin gene (cpa) of C. perfringens, however, four isolates also carried additional beta2 toxin gene (cpb2). None of the isolates were positive for beta, epsilon, iota and enterotoxin genes. PCR analysis revealed that all isolates derived from NE belonged to C. perfringens type A. The partial cpa gene sequence analysis showed 97.6 to 100% homology among the C. perfringens isolates. The study confirmed that C. perfringens type A is the most predominant one associated with necrotic enteritis in broiler chickens in Meghalaya, India and the alpha toxin (CPA) might play a significant role in the pathogenesis of the disease in broiler chicken.
  Kirti Walia , Vijay Dhir , S.N. Panda and Ashok Kumar
  A lot of studies have been carried out to secure the network coding. Network coding can be defined as the transmission mode over any network. For a secure transmission a dynamic key is generated and these two are then mixed to secure the cipher text. These network coding are characterized into two groups: weakly secure shannon secure. The difference between these two groups is that weakly secure doesn’t allow any outflow of meaningful information where as shannon secure didn’t allow any kind of outflow of information. In this study, the security approach of improved secured network segmentation and dynamic key exchange has been blended, so as to reduce the attacks and threats to a network. It has also increased the efficiency of the network. We have also demonstrated the same in wireless sensor network scenarios under dynamic key exchange.
  Reena Negi , Deepti Pande , Ashok Kumar , Sriparna Basu , Ranjana S. Khanna and Hari D. Khanna
  Pregnancy while not a disease is often accompanied by a high energy demand of many bodily functions. Neonates are said to be more susceptible to oxygen radical injury. The objective of the present study was to measure cord blood levels of 8-OHdG, malondialdehyde, protein carbonyl and total antioxidant status in premature low birth weight infants to analyze the status of oxidative stress in relation to the degree of prematurity and birth weight of neonates. Umbilical cord blood samples were obtained at the time of delivery. 8-OHdG has been measured as oxidative DNA damage marker in preterm LBW newborns by competitive in vitro Enzyme-Linked Immunosorbent Assay (ELISA) along with malondialdehyde as marker of lipid peroxidation, protein carbonyl as marker of protein oxidation and total antioxidant status to study the oxidative stress. Significant elevation in the levels of 8-OHdG along with malondialdehyde, protein carbonyl has been noted in preterm LBW newborns. Serum 8-OHdG is found to be significantly and negatively correlated with birth weight (r = -0.834, p<0.001) and gestational age of the newborn (r = -0.626, p<0.001). These results provide evidence of increased oxidative stress in the form of DNA damage, protein oxidation and lipid peroxidation in premature LBW newborns which may be responsible for different complications associated with prematurity.
  Ashok Kumar , V.M.S. Sriwastwa , S. Lata and R.K. Tiwari
  It is known that humidity enhances the growth of mites in carpets, mattresses and other household items. The association between exposure to house dust and diseases such as asthma, chronic rhinitis and atopic dermatitis has been shown in many individuals. Large quantities of carpet dyes are used in carpet industry located in Eastern Uttar Pradesh India. Nearly 90% of the carpets are manufactured in Eastern Uttar Pradesh and remaining 10% is produced in Kashmir and other places of India. Therefore, this area is important in huge dyeing and washing industry in which nearly 760 metric tons of dyes and dye supporting chemicals as well as washing chemicals are used per year. Present study has been conducted to see the adverse health effects of carpet dye black T supra which is being greatly used in carpet industry. In the present study, Gram mixed with 20 mg kg-1 of b.wt. day-1 sub-lethal dose of Black T Supra carpet dye was fed to Rattus norvegicus for three months and the symptoms of dermatitis in the form of hair fall in patches on surface of body started from fifth week onward. The area of patches of hair fall increased between 6-12th weeks. In controls, such effect was not observed. In addition, a little increase in body weight, cataract in eyes and desperate walking in experimental animals were observed after fifth week of feeding Black T Supra dye. In some cases, the correlation between exposure to carpet dye black T supra and symptoms is obvious.
  B.R. Maurya , Ashok Kumar , Richa Raghuwanshi and Vimal Singh
  Azotobacter and Azospirillum are known as non symbiotic free living nitrogen fixing biofertilizer microorganisms which actively participate in nutrients cycles. In eastern Uttar Pradesh of India, there is a great diversity in various cropping systems that may possess variation in these important biofertilizer microorganisms. The present study was conducted in order to chalk out the diversity of Azotobacter and Azospirillum sp. in different districts of eastern Uttar Pradesh in India with respect to the prevailing cropping system. Sixty two soil samples were collected from different crop rotations namely rice-wheat, vegetables, agroforestry and grassland for enumerating the diversity of Azotobacter and Azospirillum. The result showed that the Azotobacter population in rice-wheat, vegetables, agroforestry and grassland based crop rotations varied from 10x105 -13x105, 12x105-16.5x105, 9x105-15.5x105 and 7x105-10.5x105 CFU g-1 soil, respectively. Population of Azospirillum in rice-wheat, vegetables, agroforestry and grassland based crop rotations varied from 5.5x105-10.5x105, 6.5x105-12x105, 5x105-13x105 and 4.5x105-10x105 CFU g-1 soil, respectively. The diversity in population density of Azotobacter was maximum in soil of agroforestry followed by vegetables, grassland and lowest in rice-wheat based crop rotations, while in case of Azospirillum diversity was maximum in agroforestry and the lowest was observed in the rice-wheat but similar diversity present in vegetables and grassland crop rotations soil of eastern Uttar Pradesh. Overall maximum diversity of both the biofertilizer micro-organisms occurred in agroforestry based crop rotation.
 
 
 
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