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Biomedical subjects

A Kumar

Publications and source records attributed to A Kumar.

At least 739 records · Page 41Linked to original sources
PubMed1998

Alternative approach and evaluation of three potency assay methods for testing adsorbed tetanus toxoid.

Thirteen batches of adsorbed Tetanus Toxoid (TT) from different manufacturers were tested for potency by three different methods viz: (i) An Antibody Induction Method (AIM) developed in mice: (ii) WHO lethal challenge in mice; and (iii) Conventional Antibody Induction (I.P). Method in guinea pigs. The potency results obtained in AIM, by serological evaluation of immunized mice were found identical and correlated significantly with those obtained by WHO recommended lethal challenge test in mice. The potency data obtained in the present study was found comparable with other studies. An AIM in mice thus offers an alternative to lethal challenge tests and can replace guinea pig model. Out of 107 serum samples obtained from immunized guinea pigs in the conventional antibody induction method, 90% samples contained more than 4 units of tetanus antitoxin per ml. End point titres of 42 serum samples belonging to 5 batches of TT also showed much higher tetanus antitoxin content when determined by TN test. The potency data obtained thus suggest revision of the minimum requirement in Indian Pharmacopoeia which is too low and which may be increased as indicated by the present study.

Adsorption↗
PubMed1998

Quantitation of tetanus and diphtheria antitoxins in mouse sera by indirect haemagglutination.

Serum samples obtained from 75 groups of mice immunized with various doses of adsorbed tetanus vaccine, adsorbed diphtheria-tetanus vaccine and adsorbed diphtheria-tetanus-pertussis vaccine were titrated for tetanus antitoxin content by an in-vitro indirect haemagglutination (IHA) and by toxin neutralization test (TN) in mice. From these serum samples of 49 groups of mice which were immunized with combined vaccine containing diphtheria toxoid were titrated for their diphtheria antitoxin content by IHA and by i.d. toxin neutralization test (TN) in guinea pigs. Good correlations were found between the estimates obtained by in-vitro IHA and in vivo TN tests in both tetanus and diphtheria antitoxin titrations. The minimum level of tetanus or diphtheria antitoxin detectable by IHA was 0.00039 IU/ml. It is concluded that IHA is a simple, sensitive and reproducible alternative test which can replace the animal TN tests for the estimation of tetanus and diphtheria antitoxins and could reliably be used in the potency assay of tetanus and diphtheria toxoids of combined vaccines based on antibody induction in mice.

Animals↗
PubMed1998

Some AIDS-related policy issues and nursing students' willingness to provide AIDS care.

Two thirty three diploma students from a Nursing School, in Delhi were surveyed anonymously to seek their opinion on some AIDS-related policy issues and willingness to provide AIDS care. More than one fourth of students opinionated that health personnel should be given a choice to refuse care to the AIDS patients and an equal proportion felt that authorities should be empowered to terminate the services of such personnel. Majority were in favour of making HIV testing compulsory for various high risk groups, indoor patients and health workers. Perceiving the risk of HIV infection, 41.2% students felt that girls might not opt for nursing career, whereas few (10.7%) were considering even to leave the profession. However, majority (58-72%) were willing to nurse the high risk individuals, if adequate training and preventive measures were provided in the health care settings. The study implies framing of an AIDS policy taking in to consideration the views of health professionals and imparting comprehensive training to the nursing students in order to promote a humane approach towards AIDS care.

AIDS Serodiagnosis↗
PubMed1998

Primary amenorrhoea: analysis of 48 cases.

The clinical analysis of 48 patients of primary amenorrhoea seen at All India Institute of Medical Sciences, New Delhi for a period of 3 years, was performed. Twenty-six patients (54.2%) had muellerian anomalies, 11 (22.9%) had hypogonadotropic hypogonadism, 8 (16.6%) had hypergonadotropic hypogonadism and 3 (6.3%) had genital tuberculosis. The study highlights the role of transabdominal sonography in the work up of these cases. It suggests the reproductive potential of these cases by visualising the genital organs and makes laparoscopy and intravenous pyelography obsolete and selects the cases who deserve to be further investigated.

Adolescent↗
PubMed1998

Diagnosis of vertebrobasilar insufficiency: time to rethink established dogma?

As isolated symptoms, vertigo, dizziness and imbalance are not regarded by neurologists as reflections of transient ischemia in the vertebrobasilar circulation. The purpose of this retrospective study was to demonstrate that these symptoms can and do occur in isolation. To this end, we analyzed the symptoms, stroke risk factors and diagnostic algorithms in 27 patients with a diagnosis of transient vertebrobasilar ischemia. None of the 27 patients included in the review complained of any associated neurologic symptoms. Against the reference standard of brain imaging, the site of the pathologic lesion was defined in the brainstem/cerebellum with the Torok monothermal caloric test, with a sensitivity greater than 86%. Vestibular decruitment and hyperactive caloric responses were of particular diagnostic value. Thus, we recommend that the neurologic dogma with regard to brainstem cerebellar ischemia be rethought.

Adolescent↗
PubMed1998

Virulence factors of aeromonads--an emerging food borne pathogen problem.

Aeromonas spp. possess a number of virulence properties which are considered responsible for intestinal and extra-intestinal infections in human beings and also for a wide variety of infections in animals. The paper discusses current status of colonization and toxic factors of Aeromonas spp., especially in relation to food and biochemical markers. Future research needs are also identified.

Aeromonas↗
PubMed1997

Remodeling and neointimal formation in the carotid artery of normal and P-selectin-deficient mice.

BACKGROUND: Inflammatory reactions such as leukocyte activation with platelet adherence and release of inflammatory mediators occur after percutaneous transluminal coronary angioplasty and may play a role in restenosis. Vascular remodeling with neointimal formation was studied in normal C57Bl/J6 and P-selectin-deficient mice. METHODS AND RESULTS: The left common carotid artery was ligated just proximal to the carotid bifurcation. Four weeks later, left carotids and contralateral controls were snap-frozen. Computer-aided morphometry was performed to measure ratios of neointimal to medial area (NI/M) in 10 sections per animal as a measure of the thickness of the neointimal lesion. For normal mice, NI/M was 1.13+/-0.2 (n=20), whereas NI/M was reduced by 76% to 0.27+/-0.1 (n= 19) in P-selectin knockout mice. Vascular constriction (as measured by the length of external elastic lamina) was the same in both groups, but the circumference of the lumen in knockout mice was 26% larger. Also, normal and P-selectin-deficient mice were killed at 3 and 7 days after ligation (n=6 for each group per time point). Histological staining and immunostaining for CD45 showed no inflammatory cell presence in P-selectin knockout mice. However, in normal mice, leukocyte infiltration was observed in the adventitia, media, and developing neointima. Also, P-selectin immunostaining was observed in media and developing neointima of normal mice. CONCLUSIONS: These data suggest that P-selectin is involved in processes leading to cell migration and proliferation associated with vascular remodeling, presumably by mediating leukocyte recruitment and the interaction between platelets and leukocytes.

Adaptation, Physiological↗
PubMed1997

Simultaneous analysis of lignocaine and bupivacaine enantiomers in plasma by high-performance liquid chromatography.

A sensitive analytical procedure is described for the simultaneous determination of lignocaine and the enantiomers of bupivacaine in biological fluids using diazepam as an internal standard. After solvent extraction into hexane, the local anaesthetics were separated using an alpha1-acid glycoprotein (AGP) column and detected at 214 nm. Calibration curves were linear (r2>0.99) in the concentration range of 5 to 500 ng/ml for the enantiomers of bupivacaine and 12.5 to 1000 ng/ml for lignocaine. The corresponding limits of detection were 4 ng/ml and 10 ng/ml, respectively. The method was applied to the analysis of plasma from a healthy woman undergoing tubal ligation.

Anesthetics, Local↗
PubMed1997

Identification of the subunits and target peptides of pig heart NAD-specific isocitrate dehydrogenase modified by the affinity label 8-(4-bromo-2,3-dioxobutylthio)NAD.

Pig heart NAD-dependent isocitrate dehydrogenase reacts with 8-(4-bromo-2,3-dioxobutylthio)-NAD (8-BDB-TNAD) with incorporation of 1.21 mol of reagent/mol of average subunit when the enzyme reaches the limit of 25% residual activity (Kumar, A., and Colman, R. F., Arch. Biochem. Biophys. 308, 357-366, 1994). Inclusion of NADPH decreases both the extent of inactivation and the reagent incorporation to 0.55 mol/mol of average subunit. We have now isolated the peptides labeled by radioactive 8-(4-bromo-2,3-dioxobutylthio)-[2-3H]NAD and have located them within the sequence of pig heart NAD-dependent isocitrate dehydrogenase. The enzyme is composed of three types of subunits, present as alpha 2 beta gamma. We have separated the subunits from unmodified and 8-BDBT[2-3H]NAD-modified enzymes by HPLC on a C4 reverse-phase column, after pretreatment of the enzymes with sodium dodecyl sulfate or urea, and compared the subunit sequences of the porcine enzyme with those of the corresponding subunits from other mammalian NAD-dependent isocitrate dehydrogenases. The predominant radioactivity of 8-BDBT[2-3H]NAD is observed in the alpha and gamma peaks, and the NADPH-protected enzyme exhibits marked reduction in incorporation into these peaks. However, evidence based on recombination of subunits from modified and unmodified enzymes indicates that only labeling of the alpha-subunit is responsible for inactivation by 8-BDB-TNAD. Cyanogen bromide was used to cleave the modified enzyme, and we purified one labeled peptide from the alpha-subunit (amino acids 84-177) as well as one from the gamma-subunit (amino acids 67-186). In the alpha-subunit, decreased modification by [7-14C]-phenylglyoxal of Arg88 and Arg98 after prior labeling of the enzyme by 8-BDB-TNAD indicates that these residues are the critical target sites of the reactive nucleotide analogue. We conclude that alpha subunit's Arg88 and Arg98 are both at or near the allosteric NADPH sites of the pig heart isocitrate dehydrogenase.

Affinity Labels↗
PubMed1997

Therapeutic effects of interleukin-4 gene transfer in experimental inflammatory bowel disease.

Inflammatory bowel disease (IBD) is characterized by altered immunoregulation and augmented intestinal synthesis of nitric oxide. The purpose of this study was to determine the effects of exogenous IL-4, introduced by a recombinant human type 5 adenovirus (Ad5) vector, on the tissue injury associated with an experimental model of colonic immune activation and inflammation. Colitis was induced in rats by the intrarectal administration of trinitrobenzene sulfonic acid (TNB) dissolved in 50% ethanol, and control rats received saline via the same route. 1 h later, all rats were randomized into two groups. The first group was injected intraperitoneally (ip) with 3.0 x 10(6) plaque forming units (PFUs) of Ad5 transfected with murine interleukin-4 (Ad5IL-4) and the second group was injected ip with the same amount of Ad5 expressing the Escherichia coli Lac Z gene (Ad5LacZ). One-half of the colitic and control rats were injected again with 3.0 x 10(6) PFUs of Ad5IL-4 or Ad5LacZ on day 3 of the 6-d study. When introduced once or twice via the peritoneal route into control rats, Ad5LacZ was localized to the serosal lining of the peritoneal cavity, the diaphragm and the liver on day 6. One or two injections of Ad5IL-4 into rats also produced measurable levels of circulating IL-4. TNB-colitis in both Ad5LacZ-treated groups was associated with pronounced elevations in serum IFN-gamma, and mucosal ulceration of the distal colon. Myeloperoxidase and inducible nitric oxide synthase II (NOS II) synthetic activity were also increased by 30- and fivefold, respectively, above control levels in the distal colon. However, two injections of Ad5IL-4 into colitic rats caused the overexpression of IL-4, and significantly inhibited tissue damage, serum and colon IFN-gamma levels and myeloperoxidase activity in the distal colon. In addition, NOS II gene expression and NOS II nitric oxide synthesis was significantly inhibited. No therapeutic effect was observed in rats injected once with Ad5IL-4. Thus, IL-4, introduced by Ad5, is therapeutic during acute inflammation in the rat colon. The therapeutic effect of IL-4 was associated with an inhibition of inducible nitric oxide expression and a reduction in nitric oxide synthesis.

Adenoviruses, Human↗
PubMed1997

Sanguinarine (pseudochelerythrine) is a potent inhibitor of NF-kappaB activation, IkappaBalpha phosphorylation, and degradation.

The nuclear factor NF-kappaB is a pleiotropic transcription factor whose activation results in inflammation, viral replication, and growth modulation. Due to its role in pathogenesis, NF-kappaB is considered a key target for drug development. In the present report we show that sanguinarine (a benzophenanthridine alkaloid), a known anti-inflammatory agent, is a potent inhibitor of NF-kappaB activation. Treatment of human myeloid ML-1a cells with tumor necrosis factor rapidly activated NF-kappaB, this activation was completely suppressed by sanguinarine in a dose- and time-dependent manner. Sanguinarine did not inhibit the binding of NF-kappaB protein to the DNA but rather inhibited the pathway leading to NF-kappaB activation. The reversal of inhibitory effects of sanguinarine by reducing agents suggests a critical sulfhydryl group is involved in NF-kappaB activation. Sanguinarine blocked the tumor necrosis factor-induced phosphorylation and degradation of IkappaBalpha, an inhibitory subunit of NF-kappaB, and inhibited translocation of p65 subunit to the nucleus. As sanguinarine also inhibited NF-kappaB activation induced by interleukin-1, phorbol ester, and okadaic acid but not that activated by hydrogen peroxide or ceramide, the pathway leading to NF-kappaB activation is likely different for different inducers. Overall, our results demonstrate that sanguinarine is a potent suppressor of NF-kappaB activation and it acts at a step prior to IkappaBalpha phosphorylation.

Alkaloids↗
PubMed1997

Defective TNF-alpha-induced apoptosis in STAT1-null cells due to low constitutive levels of caspases.

Signal transducers and activators of transcription (STATs) enhance transcription of specific genes in response to cytokines and growth factors. STAT1 is also required for efficient constitutive expression of the caspases Ice, Cpp32, and Ich-1 in human fibroblasts. As a consequence, STAT1-null cells are resistant to apoptosis by tumor necrosis factor alpha (TNF-alpha). Reintroduction of STAT1alpha restored both TNF-alpha-induced apoptosis and the expression of Ice, Cpp32, and Ich-1. Variant STAT1 proteins carrying point mutations that inactivate domains required for STAT dimer formation nevertheless restored protease expression and sensitivity to apoptosis, indicating that the functions of STAT1 required for these activities are different from those that mediate induced gene expression.

Apoptosis↗
PubMed1997

Inhibition of T7 RNA polymerase: transcription initiation and transition from initiation to elongation are inhibited by T7 lysozyme via a ternary complex with RNA polymerase and promoter DNA.

The mechanism of transcription repression of T7 RNA polymerase by T7 lysozyme was investigated using a combination of kinetic and equilibrium methods. HPLC gel-filtration experiments demonstrated complex formation between T7 lysozyme, T7 RNA polymerase, and promoter DNA. The interactions between the two proteins were quantitated by measuring in real time the changes in protein fluorescence upon binary complex formation using stopped-flow kinetics. Complex formation between T7 lysozyme and the RNA polymerase was found to occur by a one-step process, with a bimolecular association rate constant of 38 microM-1 S-1 and a dissociation rate constant of 3.5 S-1. These constants provided an equilibrium dissociation constant, Kd, of 92 nM for the polymerase lysozyme complex. The interactions of the polymerase with the DNA were studied by stopped-flow kinetics and nitrocellulose equilibrium DNA binding experiments in the absence and in the presence of T7 lysozyme. The results showed that T7 lysozyme did not prevent or change the kinetic or thermodynamic interactions of the RNA polymerase with the DNA. T7 lysozyme by itself did not bind to the DNA, but since it bound to the RNA polymerase as well as to the polymerase DNA complex, transcription repression must involve the formation of the ternary complex between T7 lysozyme, T7 RNA polymerase and the promoter DNA. The effect of T7 lysozyme was most striking on runoff product synthesis which was greatly inhibited whereas the steady-state synthesis of abortive products, limited by polymerase cycling or RNA dissociation, was relatively unaffected by the presence of T7 lysozyme. Investigation of the pre-steady-state kinetics of transcription in the presence and absence of T7 lysozyme indicated that the inhibition of runoff product synthesis was largely due to inhibition of transcription initiation and transition from initiation to elongation.

Bacteriophage T7↗
PubMed1997

Diverse aspects of metanephric development.

Mammalian nephrogenesis constitutes a series of complex developmental processes in which there is a differentiation and rapid proliferation of pluripotent cells leading to the formation of a defined sculpted tissue mass, and this is followed by a continuum of cell replication and terminal differentiation. Metanephrogenesis ensues with the intercalation of epithelial ureteric bud into loosely organized metanephric mesenchyme. Such an interaction is reciprocal, such that the intercalating ureteric bud induces the conversion of metanephric mesenchyme into an epithelial phenotype, while the mesenchyme stimulates the iterations of the ureteric bud. The induced mesenchyme then undergoes a series of developmental stages to form a mature glomerulus and tubular segments of the kidney. Coincidental with the formation of these nephric elements, the developing kidney is vascularized by the process of vasculogenesis and angiogenesis. Thus, the process of metanephric development is quite complex, and it involves a diverse group of molecules who's biological activities are inter-linked with one another and they regulate, in a concerted manner, the differentiation and maturation of the mammalian kidney. This diverse group of molecules include extracellular matrix (ECM) proteins and their receptors, ECM-degrading enzymes and their inhibitors, growth factors and their receptors, proto-oncogenes and transcription factors. A large body of literature data are available, which suggest a critical role of these molecules in metanephric development, and this review summarizes the recent developments that relate to metanephrogenesis.

Animals↗
PubMed1997

Percutaneous transvenous mitral commissurotomy using an Inoue balloon in children with rheumatic mitral stenosis.

Percutaneous transvenous mitral commissurotomy (PTMC) using the Inoue technique was performed in 557 patients with rheumatic mitral stenosis. Of these, 107 were children aged 10-18 years (mean +/- SD 14.5 +/- 2.3). All patients were symptomatic New York Heart Association (NYHA) Class II (n = 78) and Class III (n = 29). All were in sinus rhythm. Following PTMC, the mitral valve area (MVA) increased from 0.73 +/- 0.18 to 1.7 +/- 0.53 cm2 (P < 0.001). There was a significant fall in mean transmitral gradient from 15.6 +/- 5.2 to 5.1 +/- 2.3 mmHg, and in mean pulmonary artery pressure from 41 +/- 15 to 28.4 +/- 10 (P < 0.001). Cardiac tamponade developed in one patient. One patient developed severe mitral regurgitation requiring emergency mitral valve replacement. Five patients (4.7%) developed moderate mitral regurgitation. There was no mortality or cerebral embolism in any of the children. Four patients (3.7%) had oximetry evidence of atrial septal defect. Mean mitral valve area and transmitral gradient at 14 months mean follow up was 1.68 +/- 0.4 cm2 and 6 +/- 3.5 mmHg, respectively, and were comparable to the immediate post-PTMC results. Two patients (1.8%) developed restenosis. The immediate haemodynamic results in children were compared to 450 adult patients who underwent PTMC in the same period. The outcome was similar in both groups. Children were found to have significantly higher pulmonary artery pressure compared to adults. We found that PTMC using an Inoue balloon is very effective and safe in children, and consider that it should be the procedure of choice for young patients with symptomatic rheumatic mitral stenosis.

Adolescent↗