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Biomedical subjects

J Roberts

Publications and source records attributed to J Roberts.

At least 649 records · Page 36Linked to original sources
PubMed1975

The effect of experimental anaemia on the levels of glutathione and glycolytic enzymes of the erythrocytes of normal and glutathione-deficient Merino sheep.

The effects of experimental anaemia on the levels of reduced glutathione (GSH) and the activity of glycolytic enzymes in the erythrocytes of normal and GSH-deficient Merino sheep were investigated. There was a rise in red cell GSH levels in both groups of sheep; the magnitude of this response was, however, quite different. When expressed as a percentage of the initial value, the rise in GSH level was 18% in normal and 263% in GSH-deficient animals. There was also an increase in the activities of various enzymes following phlebotomy but this increase was similar in the two groups of sheep.

Anemia↗
PubMed1975

Factor-VIII-related antigen: multiple molecular forms in human plasma.

Analysis of Factor-VIII-related antigen (vWAg) in normal plasma by crossed immunoelectrophoresis reveals an asymmetric pattern indicative of molecular heterogeneity. This asymmetric pattern apparently results from the presence of multiple molecular forms of VWAg with distinct, though partially overlapping, mobilities on crossed immunoelectrophoresis. Evidence for this conclusion has been obtained by separating these forms, one from another, utilizing cryoprecipitation, agarose gel chromatography, and ion-exchange chromatography. Variation in the relative destribution of VWAg forms in liver disease and disseminated intravascular coagulation suggests that the processes which govern generation and/or breakdown of these forms can be altered by disease.

Antigens↗
PubMed1975

Processing of E. coli tRNA precursors.

Our results indicate that RNase P has a very general role in the processing of tRNA precursors in E. coli, being responsible for the cleavage of virtually all precursor molecules at a site corresponding to the 5' end of the mature tRNA, and that at least two other RNases play specific roles in precursor processing. One of these, which may be RNase II, is responsible for removing extra nucleotides from the 3' end of tRNA precursors. The other, which we call RNase P2, is an endonuclease that cleaves precursors in spacer regions between different tRNA sequences; this enzyme is involved in the processing of large multimeric precursors.

Base Sequence↗
PubMed1975

Effects of aging on ionic movements of atrial muscle.

The effect of age on ion concentrations and fluxes in cardiac muscle was examined. Left atria from rats of 1, 3, 6, 12, 24, and 28 months of age were analyzed for content of total water, sodium and potassium, for 14C-inulin space and for 22Na and 42K influx and efflux rates. Animals of 3 and 24 months of age showed a small but significantly greater water content than those of the other age groups. The inulin space, after a small nonsignificant fall between 1 and 3 mo, increased significantly at 6 mo, then leveled off through 28 mo. Intracellular sodium (Na)1, and potassium (K)1 concentrations were calculated. (Na)1 showed a significant increase from 1 to 3 mo, decreased significantly at 6 mo, and then leveled off. (K)1 exhibited an initial significant decrease from 1 to 3 mo followed at 6 mo by a significant increase which remained unchanged through 28 mo. Trend analyses of the Na influx rates showed that a significant increase with age occurred, except for a decrease at 24 mo. Potassium influx rates remained relatively constant at all ages. Sodium efflux appeared to be multiexponential, with at least two distinct rate constants (k1 and k2). Potassium efflux steadily decreased as a function of age. The results are discussed with reference to possible consequences of aging on cardiac physiology and reactivity to pharmacological agents.

Aging↗
PubMed1975

Influence of the adrenal medulla on cardiac rhythm disturbances following acute coronary artery occlusions.

The present study was designed to examine the relationship between epinephrine secreted from the adrenal medulla and acute occlusion of the left anterior descending (LAD) coronary artery in alpha-chloralone-anesthetized cats. Occlusion of the LAD artery produced arrhythmia in all of the animals, with 39% developing ventricular fibrillation (VF). Epinephrine content in the adrenal venous blood increased 5-fold immediately after occlusion and was associated with the development of arrhythmia and VF. The adrenal venous epinephrine levels increased 8-fold after occlusion in the animals that developed VF while, in those that did not develop VF, the epinephrine levels increased only 1.5-fold. Bilateral ligation of the adrenal veins 1 hour prior to occlusion of the LAD artery did not alter the pattern of development of arrhythmia but prevented the occurrence of VF. Pretreatment of animals with either practolol or sotalol 15 min prior to LAD artery occlusion also did not affect the occurrence of arrhythmia but prevented the incidence of VF. The data indicate that acute occlusion of the LAD coronary artery produces a sharp rise in epinephrine from the adrenal medulla and that epinephrine is a major factor in producing VF but does not seem to be involved to any great extent in the production of less ominous ventricular arrhythmias.

Adrenal Medulla↗