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Biomedical subjects

R Srinivasan

Publications and source records attributed to R Srinivasan.

At least 163 records · Page 9Linked to original sources
PubMed1991

Acridine orange staining in early diagnosis of mycotic keratitis.

We have assessed the comparative sensitivities of acridine orange staining and 10% potassium hydroxide wet mount in the examination of corneal scrapings from one hundred and sixty-one clinically suspected cases of mycotic keratitis. The sensitivity of acridine orange was found to be 76% as compared to that of potassium hydroxide (65%). The predictive value for culture result was also seen to be higher. Although both the values were not statistically significant (P greater than 0.05), acridine orange staining was a rapid and simple technique with an added advantage of detecting inflammatory cells in corneal scrapings.

Acridine Orange↗
PubMed1990

Endurance to starvation by the immatures of Toxorhynchites splendens.

Studies on the endurance to starvation by the immatures of T. splendens showed that the III instar larvae survived longer than the I and II instar larvae. The IV instar larvae even in the absence of food pupated and emerged into adults. The irregular supply of food did not affect the perpetuation of the predator in the habitat.

Animals↗
PubMed1989

Role of IFN-gamma in lethal and nonlethal malaria in susceptible and resistant murine hosts.

IFN-gamma plays an important role in host defense against microbial disease. Here, we studied the role of IFN-gamma in lethal and nonlethal murine malaria. Administration of recombinant murine IFN-gamma resulted in a dose-dependent protection of SW, BALB/cByJ, and CBA/J mice from the lethal variant of Plasmodium yoelii 17x (PyL) but had little effect on the course of the nonlethal variant of this parasite (PyNL). Administration of recombinant IFN-gamma also resulted in the activation of peritoneal macrophages for increased phagocytosis of malaria-infected erythrocytes and release of H2O2, as measured in vitro. The ability of spleen cells from infected mice to produce endogenous IFN-gamma and release H2O2 during the course of malaria was also studied. In BALB/cByJ mice, which are relatively susceptible to PyL and PyNL, there was an initial burst of IFN-gamma only in response to PyNL whereas in CBA/J mice, which are relatively resistant to these parasites, there was an initial burst of IFN-gamma in response to both PyL and PyNL. The kinetics of H2O2 release corresponded to that of IFN-gamma. In all infections, levels of IFN-gamma declined as parasitemia increased; however, nonlethal infections were characterized by a recovery of both IFN-gamma activity and H2O2 release as parasitemia declined. These data suggest that IFN-gamma may play an important role in modulating the course of malaria infections by activating macrophages for both intracellular and extracellular parasite destruction.

Animals↗
PubMed1989

Humoral immune responses in dapsone treated M. leprae infected mice.

Humoral responses in M. leprae infected mice were studied through 52 weeks and were found to be directly related to the bacterial load. However, treatment with dapsone (DDS) in the last 12 weeks of infection resulted in an initial enhancement of the humoral responses followed by a gradual decrease, though they were still significantly high at the end of the study.

Animals↗
PubMed1988

Mechanism of formation of bound alpha-iminoglutarate from alpha-ketoglutarate in the glutamate dehydrogenase reaction. A chemical basis for ammonia recognition.

Two mechanisms have been postulated for the formation of bound alpha-iminoglutarate intermediate during the glutamate dehydrogenase-catalyzed reductive amination of alpha-ketoglutarate; one involves the nucleophilic attack of ammonia on a covalently bound Schiff base in the enzyme-NADPH-alpha-ketoglutarate complex, and the other involves the reaction of ammonia with the carbonyl group of alpha-ketoglutarate in the ternary complex. We have measured the rates of carbonyl oxygen exchange in the complex to unambiguously distinguish between these two mechanisms. We find that the loss of label in the carbonyl oxygen-labeled ternary complex is at least 10(5) times slower than the rate of the reductive amination reaction. Therefore, the former mechanism cannot be operative. We also find that (i) the carbonyl oxygen exchange in free alpha-ketoglutarate proceeds without any significant catalysis by its gamma-carboxylate group; (ii) this exchange reaction has energy parameters which are comparable to those observed for the hydration of simple aliphatic ketones; and (iii) the carbonyl oxygen exchange in bound alpha-ketoglutarate is slower than that in the free keto acid over a wide pH range. We conclude that the oxygen exchange in the free and bound alpha-ketoglutarate must occur via a gem-diol intermediate. The observation that the enzyme inhibits the reaction of water with alpha-ketoglutarate while it catalyzes the reaction of ammonia with the same keto acid points to an extraordinary recognition of ammonia by the enzyme. We interpret this observation by assuming that the enzyme-NADPH-alpha-ketoglutarate complex exists in two forms, a predominant form which is produced rapidly upon mixing the components together and an unstable form which is produced in trace amounts from the predominant form via a gem-diol intermediate. These two forms are presumed to differ in the spatial relationship of the carbonyl group to the enzyme functional groups. The carbonyl group in the unstable form is assumed to be surrounded by the same enzyme groups as the iminium ion is in the bound iminoglutarate complex. We ascribe the remarkable catalysis of the ammonia reaction and the inhibition of the water reaction by the enzyme to the opposing interactions of the iminium and carbonyl groups with these surrounding enzyme groups.

Algorithms↗
PubMed1988

Predicting the response to cytotoxic therapy for childhood nephrotic syndrome: superiority of response to corticosteroid therapy over histopathologic patterns.

To determine the utility of steroid response in classifying childhood nephrotic syndrome, we reviewed 119 biopsies in 92 children aged 1 to 16 years who had been followed for a mean of 7.2 years. Steroid responses were classified as steroid resistant, steroid dependent, and frequent relapser as defined by the International Study of Kidney Disease in Children. Biopsy specimens were classified as showing focal glomerulosclerosis (FSGS) in 39 children, as showing lipoid nephrosis in 28, and as questionable in another 25 with either focal global sclerosis, IgM nephropathy, or mesangial prominence and tubular changes. A strong agreement (p less than 0.01) was found between children whose FSGS was steroid resistant and children whose lipoid nephrosis resulted in frequent relapses. The length of the remission after therapy with chlorambucil or cyclophosphamide was determined in 84 children. A significantly shorter length of remission after cytotoxic drug therapy (p less than 0.05) was identified for patients with FSGS versus those with lipoid nephrosis; this difference became more significant for steroid-resistant patients in comparison with those who were steroid dependent or were frequent relapsers (p less than 0.005). Among all steroid-resistant patients, those with FSGS had shorter remissions than patients with other histologic changes (p less than 0.001). The data suggest that patterns of response to corticosteroid therapy correlate with the histologic abnormality. Thus steroid-sensitive patients need not undergo renal biopsy before receiving cytotoxic drugs. Steroid-resistant patients would benefit from a biopsy, because the findings tend to predict the outcome.

Adolescent↗
PubMed1988

Engineering, mosquitoes and filariasis: a case report.

The results of larval surveys were used to assess the relative numbers of mosquitoes breeding in different types of habitat and in different parts of the town of Pondicherry, India. The results illustrate an effective method to set priorities for mosquito control by identifying the most significant breeding sites in a town, and show that they are not necessarily the most obvious, the most extensive or those intuitively most likely.

Animals↗
PubMed1988

Comparison of the compression strength of human vertebral bodies with the mass and density of apatite: a study by 31P NMR spectroscopy.

The force needed to fracture individual human thoracic and lumbar vertebral bodies is compared with the mass and density of apatite. 31P NMR spectrometry was used to quantify the apatite, because it permits the mineral content of bone to be determined noninvasively with minimal nonspecific interference from the organic matrix or from variations in composition of the marrow. Experiments were performed with bones of similar structure and function from a single individual with no history of trabecular fractures, to compensate for the effects of the other variables that affect bone strength. The coefficient of correlation between compression strength and the volume density (i.e., g/cm3) of apatite was 0.95. The correlation of strength with the mass (i.e., grams) of apatite in a vertebral body also was reasonably good, r = 0.82, but correlations with areal density (i.e., g/cm2) and linear density (i.e., g/cm) were much poorer.

Apatites↗
PubMed1988

Simultaneous administration of measles-mumps-rubella vaccine with booster doses of diphtheria-tetanus-pertussis and poliovirus vaccines.

The safety and efficacy of simultaneous administration of measles-mumps-rubella (MMR), diphtheria-tetanus-pertussis (DTP), and trivalent oral poliovirus (OPV) vaccines in a test group of 405 children were compared with the safety and efficacy of sequential administration of the same vaccines in a control group of 410 children given MMR followed by booster doses of DTP and OPV 2 months later. The study was double blind and placebo controlled with respect to DTP and OPV. Seroconversion rates to measles, mumps, and rubella exceeded 96% in both groups. Geometric mean titers to measles (P = .05) and rubella (P = .004) were higher in the test group, and titers of antibodies to the other seven antigens were similar in both groups. Clinical reaction data were analyzed in 248 of 405 test children and 249 of 410 control children. The rates of serious vaccine-associated reactions were low and similar in the two groups. Some minor side effects were reported more frequently in the test group, but these differences were judged to be related to study design rather than to differences in the safety of the two vaccine schedules. The results indicate that the safety and serologic efficacy of administering MMR simultaneously with reinforcing doses of DTP and OPV in the second year of life is equivalent to the safety and efficacy observed after administering these antigens separately.

Antibodies↗
PubMed1988

In vivo 31P nuclear magnetic resonance spectroscopy of bone mineral for evaluation of osteoporosis.

The mineral content of stationary bone samples can be quantified by 31P nuclear magnetic resonance (NMR) spectroscopy. The assay can be performed in regions of the anatomy that pose problems for absorptiometric techniques, because the mineral content is measured within a selected volume without concern for the geometry of the bone. In vivo 31P NMR spectra of the bones in human fingers and wrist are reported. Soft tissue such as marrow and skeletal muscle contributes little to the 31P NMR spectra of human fingers and wrist and thus should not seriously affect the accuracy of the mineral assay. 31P NMR spectrometry should prove helpful for confirming rapid bone mineral loss in those at risk and for monitoring response to treatment.

Bone and Bones↗