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Biomedical subjects

R Srinivasan

Publications and source records attributed to R Srinivasan.

At least 199 records · Page 11Linked to original sources
PubMed1983

Configurational, conformational, and solvent effects on the reduction of a Schiff base by reduced pyridine nucleotide analogs.

The rate of reduction of the Schiff base, delta 1-pyrroline-2-carboxylic acid, by beta-NADH has previously been shown to be 6.8 times smaller than that calculated from the substituent effects in 1-substituted 1,4-dihydronicotinamides. The factors governing this anomalous rate have been studied by measuring the reduction rate with a number of reduced pyridine nucleotides in water and water-methanol mixtures. The beta-configuration for the nicotinamide-ribosidic linkage was found to be responsible for 75% of the anomaly; the same reduced coenzyme with alpha-linkage, however, behaves normally. It was also shown that the low reactivities of the reduced coenzymes with beta-configuration are entirely the result of their abnormal thermodynamic stabilities. Conformational effects (the folding of beta-NADH) account for only 20% of the reduction rate anomaly. Addition of organic solvents causes only a modest decrease in the overall rate. These solvent effects are interpreted in terms of the opposing effects of solvents on the basicity of the Schiff base and on the reduction step itself. Specific solvation effects appear important in controlling the reduction rates.

Kinetics↗
PubMed1983

Excimer laser surgery of the cornea.

The excimer laser, which produces light in the far-ultraviolet portion of the spectrum, allows precise removal of corneal tissue through a photochemical laser-tissue interaction. This interaction is not thermal and does not involve optical breakdown; rather, it directly breaks organic molecular bonds without tissue heating. We used this process of ablative photodecomposition to remove corneal tissue in a series freshly enucleated cow eyes. Applying the far-ultraviolet light in short intense pulses permitted us to control the depth of the incision with great precision. We found that 1 joule/cm2 ablates corneal tissue to a depth of 1 micron. Adjacent tissue suffered no thermal damage and the stromal lamellae adjacent to the incision showed no evidence of disorganization.

Animals↗
PubMed1983

Central serous retinopathy in leprosy.

The involvement of fundus is rare in leprosy. More so fundus lesions, if any, are not very well visualized because of anterior segment lesions and the pupillary adhesions. A case of central serous retinopathy is recorded in association with progressive lepra reaction (type II) in a case of leprosy.

Adult↗
PubMed1982

Glutamate dehydrogenase catalyzes the reduction of a Schiff base (delta 1-pyrroline-2-carboxylic acid) by NADPH.

alpha-Iminoglutarate has long been postulated as an obligatory intermediate in the glutamate dehydrogenase catalyzed reaction, but direct proof of its participation is lacking. We report here the glutamate dehydrogenase catalyzed reduction of delta 1-pyrroline-2-carboxylic acid (a cyclic-alpha-imino acid) to proline (an alpha-amino acid). The catalysis occurs at the normal catalytic site of the enzyme. The imine and the enzyme-NADPH complex are the active oxidant and reductant, respectively. The latter is about 500 times more reactive than NADPH itself. These findings provide direct evidence that the glutamate dehydrogenase catalyzed reaction does indeed proceed by way of an enzyme-bound form of an alpha-iminocarboxylic acid.

Animals↗
PubMed1981

The median-ulnar anastomosis (Martin-Gruber) in normal and congenitally abnormal fetuses.

The median-ulnar anastomosis (Martin-Gruber) of the forearm was present in 15% of the normal fetuses dissected. Among the congenitally abnormal fetuses, all the cases of trisomy 21 had the anastomosis in both forearms. The anastomosis is usually between the anterior interosseous nerve and the ulnar nerve and could be classified into six basic patterns.

Abnormalities, Multiple↗
PubMed1981

Primary closure of excisional defects of the breast with local flaps: a problem in the treatment of advanced carcinoma of the breast in developing countries.

Large, advanced, fungating breast tumours are a special problem in developing countries. The surgical treatment is often confined to rescue and relief and primary closure of the excisional defect is highly desirable. Split-skin grafts are often unsatisfactory for many reasons. Full thickness local flaps, cut as thickly as possible, give the best results and the "sheet anchor" in skin cover is the medially based deltopectoral flap. Myocutaneous flaps can be useful in treating low inner quadrant growths and lesions which leave no room for a deltopectoral flap.

Breast Neoplasms↗
PubMed1981

Computed tomography of the carpal tunnel: a radioanatomical study.

Cross-sectional anatomy of the carpal tunnel was evaluated by computed tomography (CT) on eight cadavers. Prior to CT, the wrists were marked and, subsequently, anatomical cross sections of the specimens were carefully made along the markers. The anatomical section planes closely correlated with the levels of the CT images. Photographs of one of the specimens were taken for comparative studies.

Autopsy↗
PubMed1981

Primary carcinoma of the fallopian tube.

Primary carcinoma of the fallopian tube is a rare condition and not easy to diagnose. On a smear taken from the vagina of a 73-year-old woman, cells consistent with adenocarcinoma were detected even though the patient was asymptomatic. The specimen from endometrial curettage was normal on microscopic examination. The patient was readmitted, 2 months after dilatation and curettage, with a right pleural effusion. Examination of the pleural fluid revealed adenocarcinomatous cells. Laparotomy disclosed a primary carcinoma (stage IV) of the left fallopian tube. Thiotepa (45 mg) was instilled into the chest cavity and medroxyprogesterone (100 mg tid) and melphalan (6 mg/d for 4 days over 6 weeks) were given. Although the life expectancy for stage IV primary carcinoma of the fallopian tube is less than 2 years this patient has no clinical evidence of disease 2 1/2 years after operation.

Adenocarcinoma↗
PubMed1981

On the Colton model for clinical trials with delayed observations -- normally-distributed responses.

The Colton model for the choice between two medical treatments is studied, with the additional assumption that there is a time lag between the administration of the treatments and the availability of the responses. Two simple procedures are suggested for dealing with patients who arrive during the waiting period, caused by the lag, between the trial and treatment stages of the model. The relative performance of the procedures in the Bayesian framework is discussed when the responses to the treatments are normally distributed with unknown means and a common known variance.

Bayes Theorem↗
PubMed1980

Double-blind placebo controlled crossover evaluation of levamisole in rheumatoid arthritis.

During levamisole therapy, 14 of 20 patients with previously unresponsive rheumatoid arthritis had significant improvement (P less than 0.05) in clinical measures of disease activity, erythrocyte sedimentation rate, and rheumatoid factor titer in a 32-week double-blind placebo controlled crossover trial. Levamisole was shown to alter antibody responses to tetanus and typhoid antigens, lymphocyte blastogenesis to phytohemagglutinins, and the number of null cells in peripheral blood. Agranulocytosis and rash resulted in discontinuation of the drug in one patient in each group. Though clearly effective, routine use of levamisole as a disease suppressant in rheumatoid arthritis must await more complete clarification of its association with agranulocytosis.

Adult↗
PubMed1980

Origin of the preganglionic visceral efferent fibers to the glands in the rat tongue as demonstrated by the horseradish peroxidase method.

A study was made to identify the cells which give origin to the preganglionic visceral efferent fibers to the 'intralingual' glands in the tongue of the albino rat by the horseradish peroxidase (HRP) method. The medium-sized multipolar neurons whose cell bodies were filled with HRP were located in the lateral reticular formation at the level between the facial motor nucleus and the superior olivary nucleus. These HRP-labeled neurons were identified as belonging to the superior salivatory nuclear complex. There was no discernible topographical separation within the superior salivatory nucleus for the submandibular glands and 'intralingual' glands.

Animals↗