PubMed Health⌕ Search

Biomedical subjects

F J Giblin

Publications and source records attributed to F J Giblin.

64 records · Page 4Linked to original sources
PubMed1979

The effects of X-irradiation on lens reducing systems.

Studies have been made of the effects of X-ray on various lens reducing systems, including the levels of NADPH and glutathione (GSH), the activity of the hexose monophosphate shunt (HMS) and of certain enzymes, including GSH reductase, GSH peroxidase, and glucose-6-phosphate dehydrogenase (G-6-PG). It was found that during several weeks following X-irradiation but prior to cataract formation, there was very little change in the number of reduced -SH groups per unit weight of lens protein but that, with the appearance of cataract, there was a sudden loss of protein -SH groups. In contrast, the concentration of GSH in the X-rayed lens decreased throughout the experimental period. Similarly, the concentration of NADPH in the X-rayed lens was found to decrease significantly relative to controls 1 week prior to cataract formation, and the ratio of NADPH to NADP+ in the lens shifted at this time period from a value greater than 1.0 in the control lens to less than 1.0 in the X-rayed lens. A corresponding decrease occurred in the activity of the HMS in X-rayed lenses as measured by culture in the presence of 1-14C-labeled glucose, G-6-PD was partially inactivated in the X-rayed lens. Of the eight enzymes studied, G-6-PD appeared to be the most sensitive to X-irradiation. The data indicate that X-irradiation results in a steady decrease in the effectiveness of lens reducing systems and that when these systems reach a critically low point, sudden oxidation of protein -SH groups and formation of high-molecular-weight protein aggregates may be initiated.

Animals↗
PubMed1976

Glutathione and lens epithelial function.

The relationship of the concentration of glutathione (GSH) in lens epithelium to the transport of cations in the lens was studied by decreasing the level of GSH in the epithelium and monitoring subsequent effects in the lens on the distribution of cations, the activity of Na+-K+ ATPase and the uptake and efflux of 86Rb. Oxidation of GSH in cultured rabbit lenses was accomplished by the use of 1 mM tertiary butyl hydroperoxide (TBHP), a reagent which appears to be suitable for the specific oxidation of GSH in this tissue. The concentration of GSH found in the normal lens epithelium was estimated to be 64 mum per gram wet weight or nearly six times that present in the whole lens. A decrease in the concentration of GSH in lens epithelium of 60 per cent or more leads to an increase in hydration, a shift in the distribution of Na+, K+, and Cl-, a decrease in the activity of Na+-K+ ATPase, and a decrease in the active transport, and an increase in the passive diffusion of 86Rb. In the TBHP-treated lenses there is a rapid decrease in the production of lactate, possibly as a result of the inhibition of Na+-K+ ATPase, but the effect on the level of lens ATP is delayed and less pronounced. It appears that the adverse effect on membrane permeability caused by the oxidation of GSH is partially reversed when a high level of GSH returns to the epithelium. However, the decrease in active transport of 86Rb and the inactivation of Na+-K+ ATPase are not reversed by either regeneration of GSH in the tissue or by treatment with exogenous dithiothreitol and may indicate an irreversible conformational change in the enzyme initiated by the loss of the protective effect of GSH. The data indicate that a critical level of GSH is required in the lens epithelium for the maintenance of normal cation transport.

Adenosine Triphosphatases↗
PubMed1975

The erythrocyte transport and transfer of methylmercury to the tissues of the rainbow trout (Salmo gairdneri).

Methylmercury (MeHg) was found to be taken up rapidly and almost completely by trout red blood cells (RBC) both in vitro and in vivo. The binding of MeHg within the RBC was freely reversible both in vitro, as shown by the efflux of MeHg from RBCs suspended in protein solutions, and in vivo following intracardial (i.c.) injection of RBC-bound MeHg. Hemoglobin (Hb) appeared to be the main MeHg transport protein in trout blood since it bound 90% of whole blood Hg following an intragastric dose of Me203HgCl. MeHg, injected i.c. as MeHgS-cysteine, was found to be present in blood bound almost completely to hemoglobin 10 days post-injection. This suggests an ability of hemoglobin to compete for and bind MeHg bound to other sulfhydryl (-SH) compounds. The number of reactive -SH groups per molecule of trout Hb was determined to be 4 by amperometric titration with MeHgCl. The concentration of Hb reactive -SH groups in the trout RBC was calculated to be at least 20 mM. This accounts for the high affinity of the RBC for MeHg.

Animals↗
PubMedDate not supplied

Toxic effects of hydrogen peroxide on corneal endothelium.

We have measured the effects of hydrogen peroxide on the ability of the isolated rabbit cornea to maintain normal hydration during perfusion, on the structure of the endothelial cells, and on the redox state of glutathione and the activity of the hexose monophosphate shunt in these cells. Swelling of isolated corneas was immediate and severe upon exposure to 50 microM H2O2 in the absence of glucose, or to 200 microM H2O2 in the presence of glucose. The presence of glucose with 50 microM H2O2 delayed the onset of swelling for two hours and markedly decreased its severity. The concentration of glutathione in the endothelium, and its redox state, were unaltered by 50 microM H2O2 in the presence of glucose, but in its absence glutathione loss was significant and the fraction in the oxidized state was greatly increased. H2O2 was removed from the medium by reaction with the cornea at a concentration-dependent rate. It was calculated that the reaction rate at 50 microM H2O2 was about twice that which could be accounted for by the increased yield of NADPH generated by the stimulation of the hexose monophosphate shunt. H2O2 may also react with endothelial cell membranes, which could account for the marked changes in cell structure seen in the scanning electron microscope.

Animals↗