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Biomedical subjects

S Friedman

Publications and source records attributed to S Friedman.

At least 505 records · Page 28Linked to original sources
PubMed1973

Isolation and characterization of mitochondrial DNA from Drosophila melanogaster.

Mitochondrial DNA (MtDNA) with a neutral buoyant density of 1.681 g/cm(3) has been isolated from unfertilized eggs of Drosophila melanogaster. This DNA is a circular molecule with an average length of 5.3 microm; it reassociates with a low C(0)t(1/2) after denaturation, and in alkaline isopycnic centrifugation it separates into strands differing in density by 0.005 g/cm(3). MtDNA isolated from purified mitochondria of unfertilized eggs or from total larval DNA melts with three distinct thermal transitions. The three melting temperature values suggest that the molecule may have three regions differing in average base composition. DNA isolated from unfertilized eggs of D. melanogaster contains approximately equal amounts of MtDNA and another DNA with a buoyant density of 1.697 g/cm(3), slightly less dense than main peak DNA. The possibility that the heavier DNA fraction consists of amplified ribosomal DNA was excluded by hybridization experiments, but otherwise nothing is known of its origin or function.

Animals↗
PubMed1973

Beta-thalassemia in the American Negro.

In Italian patients with high hemoglobin A(2) beta-thalassemia trait, the synthesis of beta-chains of adult hemoglobin in the peripheral blood is approximately one-half that of alpha-chains. In this study the relative rates of beta- and alpha-chain synthesis were determined in 26 Negro heterozygotes and five homozygotes for beta-thalassemia in six families. The beta/alpha ratio of globin synthesis was decreased in only 15 heterozygotes, whereas in the other 11, beta/alpha globin synthesis was in the normal range or was slightly increased. These unusual findings did not appear to be due to the presence of alpha-thalassemia or a hyperactive "normal" beta-allele. This study demonstrates that the beta/alpha ratio of globin synthesis in the peripheral blood is normal in some patients with beta-thalassemia trait. In five Negro homozygotes with relatively mild clinical disease the beta/alpha ratios were similar to those of Caucasians with Cooley's anemia. Further studies are needed to explore the relationship between normal synthesis ratios in many Negro heterozygotes and milder clinical disease in homozygotes in the same families.

Adolescent↗
PubMed1972

Ultrafiltration of lipoproteins through a synthetic membrane. Implications for the filtration theory of atherogenesis.

To investigate the interaction of lipoproteins with semipermeable membranes, solutions of low density lipoproteins (LDL), very low density lipoproteins (VLDL), mixtures of the two, and diluted, normal, and hyperlipidemic serum were ultrafiltered through a synthetic membrane (500 A nominal pore diameter) using a stirred laboratory ultrafiltration cell. The pressure dependence of ultrafiltrate flux showed that a concentrated layer of lipoproteins was built up at the membrane surface (concentration polarization) and that VLDL was more subject to polarization than LDL. This phenomenon controlled the observed lipoprotein transport behavior. Whereas true membrane rejection (the fraction of the solute on the membrane surface which does not pass through the membrane) was greater than 0.95 for both LDL and VLDL, observed solute rejection varied from nearly 0 to 1.0, depending upon experimental conditions. If concentration polarization occurs in the arterial system, these results suggest that lipoprotein transport into arterial wall may be influenced not only by arterial blood pressure and the properties of the arterial wall, but also by local hemodynamic conditions and by the relative as well as absolute magnitudes of LDL and VLDL concentration.

Arteriosclerosis↗