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Biomedical subjects

D L GILBERT

Publications and source records attributed to D L GILBERT.

At least 19 recordsLinked to original sources
PubMed1960

Magnesium equilibrium in muscle.

Isolated frog sartorii were immersed in Ringer's solution, which had a 2 mM magnesium concentration containing Mg(28). The uptake of the radioactive magnesium was measured under steady state conditions. Although the biological variability was fairly large, it was observed that the uptake proceeded in three stages lasting respectively about 0.5, 30, and 300 minutes and accounting respectively for about 0.21, 0.71, and 0.67 millimole magnesium/kg. muscle. It was assumed that the first stage represents surface adsorption, the second stage represents extracellular water and connective tissue phases, and the third stage entry inside the cell. It is estimated that the maximum intracellular magnesium concentration is about 1.1 mM and that only about 0.6 millimole magnesium/liter intracellular water is exchanged per hour. The maximum energy required per hour to pump the magnesium out of the cell against the electrochemical gradient is calculated to be only 1.5 cal./kg. muscle. About 75 to 80 per cent of the magnesium in muscle is non-exchangeable and difficult to remove by diffusion. It appears from previous work that the exchangeable magnesium behaves similarly to exchangeable calcium.

Animals↗
PubMed1958

The production of hydrogen peroxide by high oxygen pressures.

Hydrogen peroxide is formed in solutions of glutathione exposed to oxygen. This hydrogen peroxide or its precursors will decrease the viscosity of polymers like desoxyribonucleic acid and sodium alginate. Further knowledge of the mechanism of these chemical effects of oxygen might further the understanding of the biological effects of oxygen. This study deals with the rate of solution of oxygen and with the decomposition of hydrogen peroxide in chemical systems exposed to high oxygen pressures. At 6 atmospheres, the absorption coefficient for oxygen into water was about 1 cm./hour and at 143 atmospheres, it was about 2 cm./hour; the difference probably being due to the modus operandi. The addition of cobalt (II), manganese (II), nickel (II), or zinc ions in glutathione (GSH) solutions exposed to high oxygen pressure decreased the net formation of hydrogen peroxide and also the reduced glutathione remaining in the solution. Studies on hydrogen peroxide decomposition indicated that these ions act probably by accelerating the hydrogen perioxide oxidation of glutathione. The chelating agent, ethylenediaminetetraacetic acid disodium salt, inhibited the oxidation of GSH exposed to high oxygen pressure for 14 hours. However, indication that oxidation still occurred, though at a much slower rate, was found in experiments lasting 10 weeks. Thiourea decomposed hydrogen peroxide very rapidly. When GSH solutions were exposed to high oxygen pressure, there was oxidation of the GSH, which became relatively smaller with increasing concentrations of GSH.

Glutathione↗
PubMed1957

Calcium equilibrium in muscle.

1. A study of the calcium equilibrium in isolated frog muscle has been attempted. 2. When sartorius muscles were immersed in Ca(45) Ringer's solution, the surface phase took up the Ca(45) in about 1 minute; the extracellular water space and connective tissue in about 30 minutes; and the intracellular space in about 300 minutes. 3. The percentages of total calcium in the whole muscle immersed in Ringer's solution was as follows: 10 per cent in the surface phase; 12 per cent in the extracellular water space; 17 per cent in the dry connective tissue; 24 per cent in the intracellular space; and 37 per cent as non-exchangeable calcium. 4. The exchange constants of isolated frog sartorius muscle to calcium has been determined. The flux of intracellular calcium in the steady state was approximately 0.8 mM/(liter hr). 5. It appears that there is a calcium pump pushing calcium out of the cell against an electrochemical gradient of about 4 cal./mM of calcium. However, since the flux is low, the maximum energy required per hour to pump calcium out of the cell against this high gradient is only about 2 cal./kg. muscle or about 1 per cent of the resting energy.

Animals↗