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Biomedical subjects

A Kamath

Publications and source records attributed to A Kamath.

At least 19 recordsLinked to original sources
PubMed2001

Human V gamma 2V delta 2 T cells produce IFN-gamma and TNF-alpha with an on/off/on cycling pattern in response to live bacterial products.

Whereas cytokine production in alphabeta T cells is rapidly regulated by exposure to peptide Ag, the mechanisms regulating cytokine production by gammadelta T cells are unknown. In this study, we demonstrate that human Vgamma2Vdelta2 T cells produce IFN-gamma and TNF-alpha as early as 2 h after Ag exposure, and that they produce these cytokines in a dose- and time- dependent manner in response to stimulation with a live bacterial product, iso-butylamine (IBA), but not to dead bacteria or LPS. gammadelta T cells began, ceased, and then resumed IFN-gamma and TNF-alpha generation in an on/off/on cycling pattern, both in vitro and in vivo, depending on the presence or absence of IBA. IFN-gamma and TNF-alpha, whose optimum production was dependent on IBA-stimulated gammadelta T cells, were critical for monocyte-mediated killing of Escherichia coli. By limiting cytokine production to periods of direct contact with live bacteria, gammadelta T cells focus their resources at the site of infection, while limiting systemic immunopathology. Thus, human gammadelta T cells may mediate innate resistance to extracellular bacteria via tightly regulated cytokine production without necessarily expanding in number.

Animals↗
PubMed2001

Vgamma2Vdelta2 T-cell receptor-mediated recognition of aminobisphosphonates.

Aminobisphosphonates, potent derivatives of bisphosphonates, are frequently used for the treatment of conditions such as osteoporosis and bone metastases that are characterized by excessive osteoclastic bone resorption. Using T-cell receptor (TCR) transfer studies, we show that recognition of antigenic aminobisphosphonates that are known to stimulate human gammadelta T cells in vitro and in vivo (potency: risedronate > alendronate > pamidronate) requires expression of the Vgamma2Vdelta2 TCR and is thus Vgamma2Vdelta2 TCR-dependent. Myeloma cells or monocytes pulsed with risedronate and then washed rendered these target cells sensitive to lysis by a Vgamma2Vdelta2 T-cell clone or cell line. These results suggest that Vgamma2Vdelta2 TCR-dependent recognition leading to direct cytolysis of aminobisphosphonate-sensitized osteoclast or tumor targets may be a mechanism whereby aminobisphosphonate treatment of cancers metastatic to bone decreases osteoclastic activity and tumor burden and also may account for the decreased osteoclastic activity associated with successful treatment of osteoporosis.

Alendronate↗
PubMed2001

The dendritic cell populations of mouse lymph nodes.

The dendritic cells (DC) of mouse lymph nodes (LN) were isolated, analyzed for surface markers, and compared with those of spleen. Low to moderate staining of LN DC for CD4 and low staining for CD8 was shown to be attributable to pickup of these markers from T cells. Excluding this artifact, five LN DC subsets could be delineated. They included the three populations found in spleen (CD4(+)8(-)DEC-205(-), CD4(-)8(-)DEC-205(-), CD4(-)8(+)DEC-205(+)), although the CD4-expressing DC were of low incidence. LN DC included two additional populations, characterized by relatively low expression of CD8 but moderate or high expression of DEC-205. Both appeared among the DC migrating out of skin into LN, but only one was restricted to skin-draining LN and was identified as the mature form of epidermal Langerhans cells (LC). The putative LC-derived DC displayed the following properties: large size; high levels of class II MHC, which persisted to some extent even in CIITA null mice; expression of very high levels of DEC-205 and of CD40; expression of many myeloid surface markers; and no expression of CD4 and only low to moderate expression of CD8. The putative LC-derived DC among skin emigrants and in LN also showed strong intracellular staining of langerin.

Animals↗
PubMed2001

Antibacterial effect of human V gamma 2V delta 2 T cells in vivo.

V gamma 2V delta 2 cells, a class of T cells found only in primates, are reactive to nonpeptide organophosphate and alkylamine antigens secreted by bacteria and parasites. These cells make up 2-5% percent of human peripheral blood T cells but expand to make up 8-60% of peripheral blood T cells during bacterial and parasitic infections. We show here, using a chimeric severe combined immunodeficiency (SCID) mouse (hu-SCID) model, that human V gamma 2V delta 2 T cells mediate resistance to extracellular gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli and Morganella morganii) bacteria, as assessed by survival, body weight, bacterial loads, and histopathology. Surprisingly, this bacterial resistance was evident 1 day after infection, and bacteria were cleared well before gamma delta T cell expansion was detected 6 days after infection. Decreased resistance in V delta 2 T cell-depleted hu-SCID mice correlated with decreased serum IFN-gamma titers. Intravenous treatment of infected, reconstituted hu-SCID mice with pamidronate, a human V gamma 2V delta 2 T cell-specific aminobisphosphonate antigen, markedly increased the in vivo antibacterial effect of V gamma 2V delta 2 T cells. Therefore, this large pool of antigen-specific, yet immediately reactive memory human V gamma 2V delta 2 T cells is likely to be an important mediator of resistance against extracellular bacterial infection and may bridge the gap between innate and acquired immunity.

Animals↗
PubMed2001

Vaccination with DNA of the Mycobacterium tuberculosis 85B antigen protects mouse foot pad against infection with M. leprae.

A DNA vaccine composed of the gene for the common mycobacterial secreted protein antigen 85B was demonstrated to protect the mouse foot pad against infection with Mycobacterium leprae. The protective effect was demonstrated by a 61%-88% reduction in the bacterial number, a protective effect less than that of BCG. The same DNA vaccine has been shown to protect mice against M. tuberculosis infection, and the importance of testing other candidate tuberculosis vaccines for their potential to protect against leprosy is discussed.

Acyltransferases↗
PubMed2000

Histamine alters endothelial barrier function at cell-cell and cell-matrix sites.

To determine how histamine regulates endothelial barrier function through an integrative cytoskeletal network, we mathematically modeled the resistance across an endothelial cell-covered electrode as a function of cell-cell, cell-matrix, and transcellular resistances. Based on this approach, histamine initiated a rapid decrease in transendothelial resistance predominantly through decreases in cell-cell resistance in confluent cultured human umbilical vein endothelial cells (HUVECs). Restoration of resistance was characterized by initially increasing cell-matrix resistance, with later increases in cell-cell resistance. Thus histamine disrupts barrier function by specifically disrupting cell-cell adhesion and restores barrier function in part through direct effects on cell-matrix adhesion. To validate the precision of our technique, histamine increased the resistance in subconfluent HUVECs in which there was no cell-cell contact. Exposure of confluent monolayers to an antibody against cadherin-5 caused a predominant decrease in cell-cell resistance, whereas the resistance was unaffected by the antibody to cadherin-5 in subconfluent cells. Furthermore, we observed an increase predominantly in cell-cell resistance in ECV304 cells that were transfected with a plasmid containing a glucocorticoid-inducible promoter controlling expression of E-cadherin. Transmission electron microscopy confirmed tens of nanometer displacements between adjacent cells at a time point in which histamine maximally decreased cell-cell resistance.

Cadherins↗
PubMed1999

Neovascularization of nucleus pulposus. A diagnostic feature of intervertebral disc prolapse.

STUDY DESIGN: Seventy-five surgically excised prolapsed intervertebral discs were histopathologically evaluated. Fifteen prospective normal cadaveric discs were used as control specimens. OBJECTIVE: To compare the morphologic features between the prolapsed and normal discs. SUMMARY OF BACKGROUND DATA: The histologic criteria were edge neovascularization of the fibrocartilage, chondrocyte cloning, fibrillation with fraying, and granular change. METHODS: Sections stained with hematoxylin and eosin, Van Gieson's, and toluidine blue were studied. The presence or absence of edge neovascularization was noted. The other criteria were graded based on a semiquantitative scoring system. RESULTS: Edge neovascularization was observed in 56% of the discs in the test group and in none of the control specimens. Fibrillation with fraying was the most significant finding in the test group (P < 0.001). Although the mean grades were higher in the test group, they did not predict the presence of edge neovascularization. CONCLUSIONS: Edge neovascularization was the most significant finding to confirm disc prolapse. Fibrillation with fraying, was observed more frequently in prolapsed intervertebral discs and the grades of fibrillation with fraying, chondrocyte cloning, and granular change were significantly higher in the test group. Pathologists can usually agree on the presence or absence of a particular histologic characteristic but are rarely consistent when they estimate the degree. Simple, reproducible agreed-on criteria are needed before semiquantitative evaluations become reliable.

Adolescent↗
PubMed1998

Seroprevalence of hepatitis A virus in Mumbai, and immunogenicity and safety of hepatitis A vaccine.

OBJECTIVES: Since epidemiologic trends of hepatitis A are changing worldwide, we studied its seroprevalence in Mumbai, which is thought to be a high-endemicity area. The immunogenicity and safety of a hepatitis A vaccine were also studied. METHODS: Six hundred and seventy subjects (456 men; age range 6 mo-60 y) answered a questionnaire on social and medical history. Qualitative analysis of total anti-HAV was performed in all subjects by ELISA. One hundred and seven of 147 anti-HAV negative subjects received hepatitis A vaccine at months 0, 1 and 6. Subjects were followed up (months 1, 2, 6, 7) to look for side-effects and seroconversion. RESULTS: The seroprevalence of HAV was 523/670 (78%); 38% of children < 5 years were anti-HAV negative. Seroprevalence rates of 80% were reached by 15 years. Prevalence was lower in the higher socio-economic group (151/234; 64.5%) compared with the lower socio-economic group (372/436; 85%) (p < 0.001). One month after doses 1, 2 and 3 of the hepatitis A vaccine, seropositivity was 92%, 99% and 100%, respectively. Minor self-limited side-effects occurred in 19.5% of subjects; there were no major side-effects. CONCLUSIONS: The seroprevalence of anti-HAV is high in Mumbai. Seroprevalence is lower in the higher socio-economic groups. The hepatitis A vaccine is safe and immunogenic.

Adolescent↗
PubMed1997

Isometric tension of cultured endothelial cells: new technical aspects.

In this paper new technical aspects are discussed in the measurement of the low amount of force typically expressed in cultured endothelial cells. We illustrate how potential background noises interfere with signal acquisition. We present a new generation prototype that measures isometric tension in vitro in multiple samples and in more than on isometric vector. We report that thrombin increases isometric tension in at least two separate vectors that are directed in opposite directions. We also report that phorbol ester dibutyrate can randomly mediate a false relaxation (anisotropic contraction) in cultured PPAEC, when the force vector is directed opposite to the referenced isometric vector of the transducer. In contrast, stimulation of cultured HUVEC with the cAMP agonists, theophylline and forskolin, decreased isometric force in both vectors. Thus direction of the force vector needs to be considered when interpreting isometric tension in cultured endothelial cells.

Animals↗
PubMed1997

Distribution of malarial parasites: effect of gender of construction workers.

The city of Mangalore in South India was having increasing number of malaria cases from 1990. Concerned over the import of cases through migrant construction workers, a screening was done among them using clinical and parasitological methods. This demonstrated 6.28% slide positivity rate with statistically insignificant difference in prevalence of infection between males and females. There were many asymptomatic individuals reporting positive only on peripheral smear examination. Yet, clinical symptoms like fever were found to have good predictive value on logistic regression. It was more so with the P. falciparum which is a relatively new entrant to Mangalore.

Adolescent↗
PubMed1989

Role of yeast elongation factor 3 in the elongation cycle.

Investigation of the role of the polypeptide chain elongation factor 3 (EF-3) of yeast indicates that EF-3 participates in the elongation cycle by stimulating the function of EF-1 alpha in binding aminoacyl-tRNA (aa-tRNA) to the ribosome. In the yeast system, the binding of the ternary complex of EF-1 alpha.GTP.aa-tRNA to the ribosome is stoichiometric to the amount of EF-1 alpha. In the presence of EF-3, EF-1 alpha functions catalytically in the above mentioned reaction. The EF-3 effect is manifest in the presence of ATP, GTP, or ITP. A nonhydrolyzable analog of ATP does not replace ATP in this reaction, indicating a role of ATP hydrolysis in EF-3 function. The stimulatory effect of EF-3 is, in many respects, distinct from that of EF-1 beta. Factor 3 does not stimulate the formation of a binary complex between EF-1 alpha and GTP, nor does it stimulate the exchange of EF-1 alpha-bound GDP with free GTP. The formation of a ternary complex between EF-1 alpha.GTP.aa-tRNA is also not affected by EF-3. It appears that the only reaction of the elongation cycle that is stimulated by EF-3 is EF-1 alpha-dependent binding of aa-tRNA to the ribosome. Purified elongation factor 3, isolated from a temperature-sensitive mutant, failed to stimulate this reaction after exposure to a nonpermissive temperature. A heterologous combination of ribosomal subunits from yeast and wheat germ manifest the requirement for EF-3, dependent upon the source of the "40 S" ribosomal subunit. A combination of 40 S subunits from yeast and "60 S" from wheat germ showed the stimulatory effect of EF-3 in polyphenylalanine synthesis (Chakraburtty, K., and Kamath, A. (1988) Int. J. Biochem. 20, 581-590). However, we failed to demonstrate the effect of EF-3 in binding aa-tRNA to such a heterologous combination of the ribosomal subunits.

Fungal Proteins↗
PubMed1986

Protein synthesis in yeast. Purification of elongation factor 3 from temperature-sensitive mutant 13-06 of the yeast Saccharomyces cerevisiae.

An altered form of the elongation factor 3 (EF-3) has been purified to near homogeneity from a thermolabile yeast mutant ts 13-06. The isolation procedure involved chromatography on DEAE-Sephadex, CM-Sepharose, and hydroxylapatite columns. The final purification of this protein was obtained by affinity chromatography on an ATP-Sepharose column. Because of the extreme lability of the mutant protein, the yield was very poor. Silver stain analysis of the sodium dodecyl sulfate electrophoretograms indicated that the affinity-purified protein was better than 90% pure. From the studies of the physical and biochemical properties, the following characteristics of the purified wild type and the mutant protein have been established. The two proteins were indistinguishable by their molecular weight, amino acid composition, and isoelectric point. Purified mutant EF-3 was rapidly inactivated between 37 and 39 degrees C. Under this condition, wild type EF-3 was completely stable. Ribosome-dependent GTPase and ATPase activities of the mutant EF-3 were heat sensitive; GTPase activity was more labile than the ATPase activity. Mutant EF-3, after exposure to a nonpermissive temperature, failed to stimulate binding of the ternary complex of EF-1 X GTP X aminoacyl-tRNA to ribosome. The wild type protein was fully active under this condition. Other biochemical and physical properties of these two proteins are under current investigation.

Adenosine Triphosphatases↗
PubMed1986

Protein synthesis in yeast. Identification of an altered elongation factor in thermolabile mutants of the yeast Saccharomyces cerevisiae.

Cell-free extracts from the wild type yeast strain (A364A) and from a group of noncomplementing mutants that are conditionally defective in translation were preincubated at a restrictive temperature prior to incubation at a permissive temperature for protein synthesis. Results of these experiments showed that upon exposure to the restrictive temperature (39 degrees C), all five of the noncomplementing mutants lost ability to incorporate amino acid into protein. The wild type parent strain retained better than 80% of the activity under identical conditions of heat treatment. Mutant extracts could be revived to incorporate amino acid by the addition of the purified yeast elongation factor 3. Factors 1 and 2 had no effect. The heat-treated extract from one mutant did not supplement the activity of the other mutant. Although all five of the mutants were inactivated by preincubation at 39 degrees C, each showed a variable rate and extent of thermolability. Heat-treated mutant extracts were fully active in polyphenylalanine synthesis with liver ribosomes but not with the yeast ribosomes. Since liver ribosomes do not require factor 3, this assay then confirms that factor 3 is the thermolabile component in this group of noncomplementing mutants.

Fungal Proteins↗
PubMed1986

Pepsinogen activation: genesis of the binding site.

Previous experiments have suggested that a substrate binding site may appear relatively early in the sequence of transformations that pepsinogen undergoes during its unimolecular activation. To test this possibility, tert-Boc-L-valyl-[3(S)-hydroxy-4(S)-amino-5-(2-naphthyl) pentanoyl]-L-alanylisoamylamide, a fluorescent analogue of pepstatin, has been used to measure the rate of appearance of the binding site. This probe is a potent inhibitor of pepsin, and its naphthyl group is an environmentally sensitive fluorophore that permits binding to be detected by fluorescence spectroscopy. In stopped-flow experiments, the fluorescence change following acidification of pepsinogen due to binding of the probe was found to obey a two-term exponential decay law. Analysis of the data obtained at various pH values permits us to rule out a sequential model for the kinetics. Rather, we were able to demonstrate that a concurrent model, with two species undergoing simultaneous transformation at different rates, is consistent with the results. The two species are related to each other by the protonation of a single site with a pKa of approximately 2.2. We obtained essentially identical results in an analysis of the early events observed in the acidification of pepsinogen labeled with 6-(p-toluidinyl)naphthalene-2-sulfonyl chloride (Auer & Glick, 1984). The protonic equilibrium probably occurs early after exposure to acid and is proposed to lead to a conformational change that freezes the distribution between the two species. It may be that these two conformers persist as identifiable entities at later stages of activation as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Exponential model for weight using 'RJ index'.

We screened a sample of 204 children between the age of 3 months to 5 years and 3 months were during a general health survey conducted by the Department of Community Medicine, Kasturba Medical College, Mangalore from March 1992 to December 1993 at Kumpala village under PHC Ullal about 10 kms from Mangalore City. We developed a new index RJ as RJ = Mid upper Arm Circumference x (Height)2 x 10(-4) and tested the correlation of RJ index and weight for age. We found the correlation coefficient (r = 0.8) to be very significant (P < 0.001). Thus we propose the model as Weight = A x exp (RJ x B). We found that the available data fit in this model. We hope that this study will be a new step in looking at arm circumference as a tool in estimating weight of pre-school children.

Anthropometry↗
PubMedDate not supplied

Safety and radiosensitizing efficacy of sanazole (AK 2123) in oropharyngeal cancers: randomized controlled double blind clinical trial.

UNLABELLED: Oropharynx is an important site of cancer in India. Global comparison indicates higher incidences in India. Radiotherapy remains an important treatment modality. Efforts to improve loco-regional treatment and prolong survival are areas of focus. Radiosensitizers in hypoxic tumors have shown promise. AIM: To study the safety and radiosensitizing efficacy of sanazole in oropharyngeal squamous cell carcinoma (stage T2-4, N0-3, M0) as phase-II double blind controlled trial in patients treated with conventional radiotherapy. SETTINGS AND DESIGN: Single institutional, randomized, double-blind, placebo-controlled trial. MATERIALS AND METHODS: Group 1 (control; n = 23) received normal saline infusion, group 2 (test; n = 23) received sanazole biweekly 1.25 g intravenous infusion 15 minutes before radiotherapy. Surrogate end points of efficacy were tumor and nodal size; safety parameters were mucositis, salivary and skin reactions, dysphagia, vomiting, dysgeusia and neurological deficit. Investigators blinded to the trial evaluated patients, weekly during treatment for six weeks and thereafter monthly for three months. STATISTICAL METHODS: Non-parametric, Friedman's, Chi square, Mann-Whitney U tests. RESULTS: In the test, 15 (65%) patients had complete response, five (22%) partial/no response, two (9%) died, one (4%) lost to follow up. In the control, five (22%) patients had complete response, 16 (70%) partial/no response, one (4%) died, one (4%) lost to follow up. Short-term loco-regional response was better in the test (DF = 3, 95% Confidence Interval 0.418, 0.452, P = 0.0048). In the test group significant vomiting and one case of grade 3 neurological deficit was observed. CONCLUSION: The study validates the usefulness of sanazole for initial loco-regional control in oropharyngeal cancers.

Adult↗