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Biomedical subjects

P S Kumar

Publications and source records attributed to P S Kumar.

At least 19 recordsLinked to original sources
PubMed2003

New bacterial species associated with chronic periodontitis.

Recent investigations of the human subgingival oral flora based on ribosomal 16S cloning and sequencing have shown many of the bacterial species present to be novel species or phylotypes. The purpose of the present investigation was to identify potential periodontal pathogens among these newly identified species and phylotypes. Species-specific ribosomal 16S primers for PCR amplification were developed for detection of new species. Associations with chronic periodontitis were observed for several new species or phylotypes, including uncultivated clones D084 and BH017 from the Deferribacteres phylum, AU126 from the Bacteroidetes phylum, Megasphaera clone BB166, clone X112 from the OP11 phylum, and clone I025 from the TM7 phylum, and the named species Eubacterium saphenum, Porphyromonas endodontalis, Prevotella denticola, and Cryptobacterium curtum. Species or phylotypes more prevalent in periodontal health included two uncultivated phylotypes, clone W090 from the Deferribacteres phylum and clone BU063 from the Bacteroidetes, and named species Atopobium rimae and Atopobium parvulum.

Bacteria↗
PubMed2000

Hepatitis B virus surface (S) transactivator with DNA-binding properties.

Chronic infection with hepatitis B virus (HBV) in humans is strongly linked to the development of hepatocellular carcinoma (HCC). Activation of growth-regulatory genes may play a crucial role in carcinogenesis. Proto-oncogene expression has been shown to be higher in HCC tissue with integrated HBV DNA than in the normal liver. Earlier, we showed that the 3' end of the HBV major surface gene (S) (426-855 nucleotides of the S region) is a transactivator of the X promoter-enhancer regulatory element in co-transfection experiments. This region expresses a truncated carboxy terminal S protein extending from amino acid residues 102 to 226. In this study, the truncated S protein (trc-S) was examined for its enhancing activity on several viral and cellular regulatory elements. The results indicate that trc-S activates rous sarcoma virus long terminal repeat (LTR), human T-lymphotropic virus 2 LTR, human immunodeficiency virus 1 LTR, and the c-jun and c-fos promoters. Electrophoretic mobility shift assays carried out to investigate its DNA-binding properties established that trc-S binds to HBV X promoter and oligonucleotides representing binding sites for the AP1 and TFIID transcription factors. The specificity of this interaction was confirmed by using competition experiments and supershift assays. These experiments suggest that trc-S is a transactivator of several cellular and viral promoters and that this activity is mediated by direct interaction with DNA.

Avian Sarcoma Viruses↗
PubMed1999

Hydrodynamic cavitation for sonochemical effects.

A comparative study of hydrodynamic and acoustic cavitation has been made on the basis of numerical solutions of the Rayleigh-Plesset equation. The bubble/cavity behaviour has been studied under both acoustic and hydrodynamic cavitation conditions. The effect of varying pressure fields on the collapse of the cavity (sinusoidal for acoustic and linear for hydrodynamic) and also on the latter's dynamic behaviour has been studied. The variations of parameters such as initial cavity size, intensity of the acoustic field and irradiation frequency in the case of acoustic cavitation, and initial cavity size, final recovery pressure and time for pressure recovery in the case of hydrodynamic cavitation, have been found to have significant effects on cavity/bubble dynamics. The simulations reveal that the bubble/cavity collapsing behaviour in the case of hydrodynamic cavitation is accompanied by a large number of pressure pulses of relatively smaller magnitude, compared with just one or two pulses under acoustic cavitation. It has been shown that hydrodynamic cavitation offers greater control over operating parameters and the resultant cavitation intensity. Finally, a brief summary of the experimental results on the oxidation of aqueous KI solution with a hydrodynamic cavitation set-up is given which supports the conclusion of this numerical study. The methodology presented allows one to manipulate and optimise of specific process, either physical or chemical.

Journal Article↗
PubMed1998

Effect of liquid-phase properties on ultrasound intensity and cavitational activity.

The intensity of ultrasound is attenuated due to various properties of the liquid, such as viscosity, density, etc. In this paper, a simple method is proposed to measure the combined attenuation and cavitational activity of ultrasound intensity in various organic liquids using standard KI decomposition reaction. A modified experimental attenuation coefficient is proposed and its dependence on liquid viscosity reasonably matches the theoretical predictions made by Stokes [G.G. Stokes, Trans. Camb. Philos. Soc. 8 (1849) 287]. Exploratory work to determine the effect of other liquid properties on cavitational activity is carried out. Correlations are proposed to explain the dependence of the attenuated cavitational activity on various properties of a liquid.

Journal Article↗
PubMed1997

Immunosuppressive effect of honey on the induction of allergen-specific humoral antibody response in mice.

Our study with honey for its possible immunomodulatory activity reveals the immunosuppressive activity on induction of murine humoral antibody responses against different allergens as determined by passive cutaneous anaphylaxis and Ouchterlony double immunodiffusion techniques. Ovalbumin (OVA)-specific IgE antibody responses elicited with various doses were completely suppressed by different sources of commercial honeys. Honey is also found to have suppressed the induction of OVA-specific humoral antibody responses in different strains of mice. The results obtained in this work confirm the immunosuppressive activity of honey and suggest its possible applicability in conditions requiring immunosuppression.

Allergens↗
PubMed1997

Pedicled omental transfer for ischaemic limbs--a 5-year experience.

Chronic occlusive arterial diseases form a single largest entity amongst the peripheral vascular diseases. Current operative methods available for improving circulation often elicit poor results and the patient has to undergo an amputation. The technique of pedicled omental transfer has given hope of saving such unsalvageable limbs. Although symptomatic and clinical improvement has been reported by this method of "biological by-pass revascularisation", there are no simple, objective and easily reproducible tests to assess improvement in circulation. In this study pulse oximetry and stress testing have been used to assess revascularisation. This study comprised 56 patients (78 limbs) suffering from chronic occlusive arterial disease, spanning a period of 5 years. Patients were investigated and subjected to pedicled omental transplantation (omentopexy). Symptomatological assessment showed improvement in intermittent claudication in about 85% of patients, relief from rest pain in 86% and healing of chronic ulcers in 73% of patients. Objective tests of stress testing and pulse oximetry also showed improvement in circulation. Relief from ischaemia was more in cases of Buerger's disease (TAO) than in cases of atherosclerosis obliterans (ASO).

Adult↗
PubMed1995

Changes in tyrosine-phosphorylated p190 and its association with p120 type I and p100 type II rasGAPs during myelomonocytic differentiation of human leukemic cells.

A M(r) 190,000 protein (p190) functions as a GTPase-activating protein (GAP) for Rho and Rac family proteins, which are involved in regulating cytoskeletal actin and membrane ruffling. Tyrosine-phosphorylated p190 also complexes with rasGAP, a regulator of Ras activity, thus possibly linking Ras and Rho pathways. Leukemic cells induced to differentiate along myelomonocytic lineages have increased filamentous actin (as evidenced by phalloidin staining) and extended pseudopodia, and become irregularly shaped and flattened, suggesting altered Rho and Rac function. We, therefore, hypothesized that changes in p190 and its association with rasGAP are an integral part of these shape changes. During phorbol 13-myristate 25-acetate-induced monocytic differentiation of HL60 promyelocytic and RWLeu4 chronic myelogenous leukemic cells, the total amount of p190 decreases rapidly but returns to initial levels by 12 h. In RWLeu4, this was accompanied by commensurate changes in p190 tyrosine phosphorylation and association with p120 type I rasGAP. Association of p190 and type I rasGAP was demonstrated by immunoprecipitation with antibodies to either protein. An additional band at M(r) 100,000 (p100) was detected in immunoprecipitates after 12 h of phorbol 13-myristate 25-acetate treatment. Reverse transcription-PCR and immunoblot analyses suggest that p100 is type II rasGAP, an alternatively spliced product of p120 type I rasGAP. p100 was expressed only in response to direct protein kinase C activators, but all classes of differentiation agents increased tyrosine-phosphorylated p190. Rho and Rac are known to be involved in regulating actin polymerization. The results presented here show that the association of p190 with type I rasGAP parallels increases in actin polymerization and cell adhesion. This suggests a role for p190-rasGAP interactions in phorbol 13-myristate 25-acetate-induced cytoskeletal reorganization.

Base Sequence↗
PubMed1995

Prognosis in intra-abdominal sepsis.

Peritonitis is a common surgical problem with a high mortality rate. Recent advances have not brought down the mortality rate. Eighty six patients with intra-abdominal sepsis were studied for factors affecting prognosis. The factors which significantly affected prognosis were: duration of illness, source of infection and APACHE-II score. Further, among the factors contributing to APACHE II score, statistical analysis using logistic regression identified some factors which individually affect outcome. Our results indicate that mortality rate is high in patients with long duration of illness, postoperative peritonitis and organ system insufficiency.

APACHE↗
PubMed1993

Tyrosine phosphorylated proteins in chronic myelogenous leukemia.

An aberrantly expressed and highly active abl tyrosine kinase (p210bcr-abl) appears critical for the development and pathogenesis of chronic myelogenous-leukemia (CML). CML cells and cell lines each displayed a similar spectrum of phosphotyrosyl proteins. Analysis of these proteins by glycerol-gradient ultracentrifugation showed that many apparently existed as multimeric complexes. Confirming this, several of these proteins co-immunoprecipitated, along with the p210bcr-abl, with antibody to abl. Included were co-precipitating proteins identified as the p120 ras GTPase-activating protein (GAP) and the p62 protein that binds both to GAP and to a number of other tyrosine-phosphorylated proteins having peptide regions homologous to the second domain of src. Because p62, ras GAP and ras are involved in growth-factor and oncogene activation of cells, this pathway may also play an important role in CML.

Fusion Proteins, bcr-abl↗
PubMed1984

Inhibition of mitochondrial oxidative phosphorylation by 2-methyl-4-dimethylaminoazobenzene.

The azodye 2-methyl-4-dimethylaminoazobenzene inhibited oxidation and phosphorylation in tightly coupled rat liver mitochondria. Phosphorylation was more sensitive to the inhibitory action of the azodye than was the oxidation of succinate or ascorbate. The oxidation of NAD+-linked substrate was severely inhibited by the compound. In submitochondrial particles, only NADH oxidation was sensitive. The site of inhibition has been identified to lie between the dehydrogenase flavoprotein and ubiquinone.

Animals↗
PubMed1979

Effect of lipid antioxidants on rat erythrocyte hemolysis.

Lipid antioxidants, DPPD, DAH, BHT, SQ, retinol and alpha-tocopherol were studied for their effects on normal rat erythrocytes. Retinol, BHT and SQ were found to induce hemolysis while DPPD, DAH and alpha-tocopherol were non-hemolytic. Further more the three antioxidants BHT, SQ and retinol showed a synergistic effect on the lysis. Retinol, BHT or SQ alone, and BHT or SQ along with retinol when administered to rats produced a marked modification of the erythrocyte membrane integrity, simultaneously lowering the levels of membrane bound enzymes--acetyl choline esterase and ATPase. It is concluded that the lipid antioxidants may therefore be classified on the basis of their lytic action in vitro.

Animals↗