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Biomedical subjects

I Singh

Publications and source records attributed to I Singh.

At least 325 records · Page 18Linked to original sources
PubMed1981

alpha-Hydroxylation of fatty acids in brain: characterization of heat-labile factor.

The particulate fraction, heat-labile factor, heat-stable factor, and NADPH are essential for the conversion of lignoceric acid (tetracosanoic acid) to cerebronic acid (alpha-hydroxylignoceric acid). The heat-labile factor was extracted from calf cerebellum and partially purified in four steps: ammonium sulfate precipitation, hydroxylapatite chromatography, isoelectric focusing, and NAD-Agarose affinity chromatography. The specific activity of the heat-labile factor was increased 105-fold during the last three steps, with a yield of 37% of the activity. One major and several minor bands were visible when the preparation was examined by SDS-polyacrylamide gel electrophoresis with Coomassie blue staining. The major band corresponded to a protein of molecular weight 32,700, and the minor bands corresponded to proteins of molecular weights 62,000 and 67,000. The activity was lost when the heat-labile factor was incubated with 1 mM-N-ethylmaleimide. This inhibition was prevented by preincubating the heat-labile factor with 1 mM-NADH. These observations indicate that the heat-labile factor contains a sulfhydryl group which is essential for activity, and that it is located at or near the binding site for the pyridine nucleotide.

Animals↗
PubMed1979

Fatty acid alpha-hydroxylation and its relation to myelination.

alpha-Hydroxylation is an enzymatic reaction by which long-chain fatty acids are converted to their alpha-hydroxy derivatives. This reaction, in animals, can be detected only in developing brain and is the rate-determining step in the synthesis of hydroxycerebroside, which is an indispensable and abundant myelin lipid. In addition to a particulate fraction from brain, two cytoplasmic factors, one heat-stable and the other heat-labile, are required for alpha-hydroxylation. During the past eight years we have been investigating alpha-hydroxylation. Our progress is summarized and discussed here.

Aging↗
PubMed1979

Conversion by rat brain preparation of lignoceric acid to ceramides and cerebrosides containing both alpha-hydroxy and nonhydroxy fatty acids. Effects of compounds which affect sphingolipid metabolism.

Three synthetic compounds which affect sphingolipid metabolism in vitro were examined for their effects on the synthesis in a rat brain system of nonhydroxyceramide, hydroxyceramide, nonhydroxycerebroside, and hydroxycerebroside from [1-14C]ignoceric acid. These compounds are N-octanoyl-D-threo-p-nitrophenylaminopropanediol (Compound I), N-(2,3-epoxydecanoyl)-norephedrine (Compound II), and N-decyl-N'-glucosylthiourea (Compound III). In the presence of up to 0.5 mM Compound I, only the hydroxyceramide fromation increased, while the synthesis of the other three lipids decreased. Compound II strongly inhibited the formation of all four lipids at all concentrations tested (0.1 to 1 mM). Compound III increased the synthesis of both ceramides approximately 2-fold at 1 mM, but the conversion of lignoceric acid to both cerebrosides remained relatively unchanged. Several significant conclusions from these observations are discussed.

Animals↗
PubMed1979

Circulating immune complexes in human osteosarcoma.

Sera from 8 patients with osteosarcoma and 64 normal individuals were examined by C1q and Raji cell radioimmunoassays for the presence of circulating immune complexes. Of the 8 patients with osteosarcoma, 6 had elevated levels of immune complexes in their sera. The elevated levels of immune complexes were demonstrated by both the C1q radioimmunoassay and the Raji cell radioimmunoassay. The amount of immune complexes was quantitated by Raji cell radioimmunoassay; the mean plus or minus the standard error of the amount of aggregated human IgG equivalent per milliliter of serum was 80.12+/-72.64 micrograms for patients with osteosarcoma and 23.07+/-6.2 micrograms for normal individuals. The blocking effect of sera from patients with osteosarcoma on lymphocyte cytotoxicity against cultured osteosarcoma cells (TE-85) was examined. The result indicated that sera with elevated amounts of immune complexes also had increased levels of blocking activity. Sera were fractionated to separate immune complexes from gamma-globulins. No free tumor-specific antibody could be detected in fractionated gamma-globulin fractions from 2 patients with osteosarcoma. The sera of these patients had high amounts of immune complexes and high blocking activities.

Antibodies, Neoplasm↗
PubMed1979

The improvement of technical skills in preclinical courses.

One hundred fifty-four freshmen dental students were administered a fine motor ability test prior to and at the completion of a series of preclinical technique courses. The pre- and posttest performances were compared for each student to determine whether an improvement of technical skill had occurred. The pre- and posttests were also graded using the rank ordered method. The number of students who demonstrated improvement in technical skill was compared to the number of students who improved in grades to establish whether the change in grades was indicative of the observed change in technical skill. Most students improved in technical skill; however, grades did not reflect this improvement.

Curriculum↗
PubMed1979

A model for human osteosarcoma in hamsters.

An animal model for human osteosarcoma was established in newborn Syrian golden hamsters by injecting productively infected TE-85 cells (cultured human osteosarcoma cells) adjacent to the femur. Tumors were palpable 10 to 15 days following cell injection and enlarged progresively until the animal died (mean survival time was 36 days). The tumor take was 100% and all animals developed pulmonary metastases. Osteoid and bone were identified in sections of the tumor by light and electron microscopy. Invasion of the marrow spaces and adjacent skeletal muscle by the malignant osteoblasts, anaplastic sarcoma cells and multinucleated giant cells was frequently observed. The tumor was transplantable. TE-85 cell surface antigens were demonstrable by immunofluorescence on the surface of the cells of the induced tumors. The present tumor model had unique immunologic characteristics in that no antibodies were demonstrable in the sera of the tumored animals.

Animals↗
PubMed1979

Torsion in metacarpal bones and bilateral asymmetry.

A comparison of the relative position of the dorsoventral axes of the bases and heads of the metacarpal bones shows that these do not lie in the same plane, and that torsion can therefore be said to exist in these bones. Torsion is such that the heads of the second and third metacarpals appear to be rotated laterally relative to the base, whereas the heads of the fourth and fifth metacarpals appear to be rotated medially. The usual direction of "rotation" of the head of the first metacarpal is to the lateral side in the right hand and to the medial side in the left hand (P less than 0.001). In addition, there are statistically significant differences in the degree of torsion in other metacarpal bones of the right and left sides: torsion in the second and third metacarpals is greater in the right hand (P less than 0.001), while torsion in the fourth and fifth digits is greater in the left hand (P less than 0.001). All these asymmetries represent a "lateral shift" in the degree of torsion in metacarpal bones of the right side. Torsion in the metacarpal bones appears to facilitate efficiency of the grip: it is apparently an important factor in preventing crowding together of the second to fifth digits during flexion.

Adult↗