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Biomedical subjects

M Parsons

Publications and source records attributed to M Parsons.

At least 145 records · Page 8Linked to original sources
PubMed1978

Detection of genetic variation with radioactive ligands. III. genetic polymorphism of transcobalamin II in human plasma.

We detected genetically determined, electrophoretic variants of vitamin B12 binding proteins, most probably transcobalamin II, in human plasma. Polymorphic variants were observed in all populations tested; the two most common alleles (of at least four detected to date) attain frequencies of greater than 40% in Caucasians and Orientals. The variants are autosomally inherited and are seen as doublets in homozygotes, and four-banded patterns, the sum of two dissimilar homozygote patterns, in heterozygotes. The technique used in this survey, polyacrylamide gel electrophoresis (PAGE) autoradiography of plasma and serum labeled in vitro with 57Co-vitamin B12 is particularly applicable to the study of trace proteins such as the transcobalamins (10(-9)M). Possible functional variation in the TC II allele products is described, and the selective significance of this worldwide polymorphism is considered.

Autoradiography↗
PubMed1976

Purine uptake by azaguanine-resistant Chinese hamster cells.

In this study the resistance of a number of lines of Chinese hamster ovary cells to azaguanine is examined. Those which are drug resistant by virtue of a deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT) fail to take up any exogenous hypoxanthine or azaguanine. A second class of drug resistant cells which grow in the reverse selective HAT medium and have levels of HPRT in the range of the wild type parent line take up these purines at lower rates than the nonresistant cells and incorporate smaller amounts of them into trichloracetic acidinsoluble constituents. The results suggest that their basis for resistance resides in lowered incorporation of azaguanine into DNA and RNA, possibly due to a mofified HPRT molecule which accepts hypoxanthine, but not azaguanine as a substrate.

Amino Acids↗
PubMed1975

An analysis of a performance feedback system: the effects of timing and feedback, public posting, and praise upon academic performance and peer interaction.

In the first experiment, after establishing baseline composition rates in each classroom, timing (announcing time limits) and feedback (student self-scoring) were introduced followed by the introduction, removal, and reintroduction of public posting of highest scores. Timing and feedback improved story writing performance and public posting of highest scores improved performance even further in both classrooms. Teacher praise produced further improvement in one classroom but had no effect on performance in the other. Changes in on-task behavior paralleled changes in writing rate. Comments made by children concerning their own work or work of their peers were recorded throughout the experiment. Although the baseline rate of performance comments was almost zero, the introduction of each variable markedly increased the rate of performance comments. In the second experiment, baseline rates on reading and language exercises were established in a fifth-grade classroom. The entire performance feedback system was introduced on a multiple baseline across the two behaviors and then removed during the final phase of the experiment. Introducing the system improved performance on both tasks. These results further increased the generality of some of the findings of the previous experiment and of previous research on the efficacy of the experimental package of timing, feedback, public posting, and praise.

Journal Article↗