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Biomedical subjects

K Singh

Publications and source records attributed to K Singh.

At least 595 records · Page 33Linked to original sources
PubMed1980

Photoelectric conversion by bacteriorhodopsin in charged synthetic membranes.

Photoelectroactivity of oriented purple membrane layers attached to an ion exchange film has been investigated. The action spectrum of the photocurrent followed the absorption spectrum of bacteriorhodopsin. The intactness of structure and function of bacteriorhodopsin was demonstrated by studies of absorption and photocycle kinetics. The direction of the photocurrent suggests that the extracellular surface of purple membrane is more positive. Photocurrents as high as 20 microA cm-2 were obtained in some preparations. The dependence of steady-state photocurrents on intensity of illumination and temperature was also studied. The initial rate of build-up of photocurrent depends linearly on the intensity of illumination while the off rate does not exhibit any dependence on the intensity of illumination. With rise in temperature an increase in the steady state photocurrent has been observed. This dependence was found to be linear when increase of the photocurrent due to proton translocation alone was considered.

Bacteriorhodopsins↗
PubMed1979

A simple and sensitive nonradioactive method for the detection of urinary human chorionic gonadotropin and diagnosis of early human pregnancy. II. Single-unit test.

A simple, sensitive, and reliable single-unit nonradioactive method for the detection of human chorionic gonadotropin (hCG) in concentrated urine and the diagnosis of early pregnancy is reported. This unit, presently termed the Ayerst pregnancy test kit (APTK), consists of four components: a sampler-filter paper cone, an ultrafilter-concentrator to which a vial holder is attached, a support stand with a mirror, and an immunologic reagent vial. In the APTK, 5 to 6 ml of urine were sampled, filtered, and concentrated, and the hCG in the retentate was detected by Ayerst immunologic reagents [APTK(AY)] and by the Pregnosticon "All In" [APTK(P)]. Some of the unconcentrated urine samples (0.1 ml) were also tested in hemagglutination inhibition tests (HIT) using Ayerst [HIG(AY)] and Pregnosticon "All In" [HIT(P)] reagents. Urine samples from pregnant, nonpregnant (ovulating and nonovulating), perimenopausal, and menopausal women were tested. It was found that the APTK(AY) and APTK(P) were significantly more sensitive and reliable than the HIT(AY) and HIT(P) in detecting low levels of urinary hCG for early diagnosis of pregnancy. The sensitivity and specificity of the APTK(AY) were better than those of the APTK(P). The APTK(AY) give significantly more correct positive and negative results than the other tests performed simultaneously. The APTK(AY) is simpler and safer than the serum radioimmunoassays and radioreceptor assay presently used to detect low levels of hCG for the early diagnosis of pregnancy and other hCG-producing states.

Chorionic Gonadotropin↗
PubMed1979

Rapamycin (AY-22,989), a new antifungal antibiotic. IV. Mechanism of action.

Rapamycin, an antifungal antibiotic produced by Streptomyces hygroscopicus showed a strong candicidal activity, which could not be reversed by sterols. It has no effect on efflux of K+, Pi ir U.V. absorbing materials and cell permeability of Candida albicans. Thus, in its action it differs from the polyenes. Mechanism of action of rapamycin appears to be different from many known antifungal agents. In C. albicans, rapamycin at the minimum growth inhibitory concentration inhibited: 1) phosphate incorporation into nucleic acids, 2) acetate incorporation into lipids and 3) substrate respiration of amino acids. The effect on amino acid metabolism was expressed as inhibition of oxidative deamination. At low concentrations rapamycin caused degradation of P32-labeled intracellular macromolecules. Inhibition of threonine incorporation into cell wall and leucine incorporation into cellular protein was observed at relatively higher concentrations of rapamycin. The antibiotic showed no effect on cell-free protein synthesizing systems of Escherichia coli, rat liver and C. albicans and in the mitochondrial enzyme systems. Whether the lethal action of rapamycin on C. albicans is primarily due to one of the above effects or is the result of combined effect on some of these biosynthetic parameters remains to be established.

Amino Acids↗
PubMed1978

Two regimes with the same TDF but differing morbidity used in the treatment of stage III carcinoma of the cervix.

As an alternative to five daily fractions per week, one large fraction per week has been used to treat patients with stage III carcinoma of the cervix. This regime was greatly appreciated by our village women who could attend for weekly treatment from their homes. The weekly dose was matched with our previously acceptable daily fractionation using NSD, TDF and CRE values. In 24 patients the early reactions and tumour response were acceptable. Late rectal complications commencing seven months after treatment have, however, developed in all surviving patients with the new regime. The complications have been far more severe than those of a matched group of 24 patients treated with daily fractions and the schedule using one fraction per week has been abandoned. "Iso-effective" doses for the two techniques were selected from the NSD, TDF and CRE tables. This study clearly indicates that for one fraction per week the doses predicted are not "iso-effective" as far as the normal tissues of the pelvis are concerned.

Adult↗
PubMed1978

Hematology of the common Indian frog Rana tigrina. III. Hemoglobin and hematocrit.

The hemoglobin and hematocrit values studied in two years averaged 6.22 and 3.87 g/100 ml and 31.8 and 19.5 percent in female and male Rana tigrina respectively. The peak values in females and males are observed in May and June respectively. The breeding season is characterized by low hemoglobin and hematocrit values. The starvation upto 28 days is observed to cause a decrease in hemoglobin level.

Animals↗