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Biomedical subjects

L Garby

Publications and source records attributed to L Garby.

At least 73 records · Page 4Linked to original sources
PubMed1977

Effect of the preceding day's energy intake on the total energy cost of light exercise.

The effect of a variation in the preceding day's dietary energy intake-4, 10 and 18 MJ-on the oxygen consumption and respiratory quotient at rest and at work before and after a test meal (4 MJ) was investigated. 7 normal male subjects were studied at 3 different experimental situations. During the first day the subjects had an energy intake of 10 MJ and normal activity. The following morning measurements of V(O2) and V(CO2) were performed at rest and at work on a bicycle ergometer (36 W) before and after the test meal. The same measurements were performed on the following day but the dietary intake between the two sets of measurement was then either 6, 0 or 14 MJ. No significant effect was found of the preceding day's dietary energy intake on the oxygen consumption or on the energy transformed during rest, during exercise before and after the test meal. The results do not support the conclusions of previously published studies, proposing a significant feed-back mechanism tending to control the body energy content by regulation of the energy expenditure through chemical or mechanical uncoupling.

Adult↗
PubMed1977

The molecular function of hemoglobin as reflected in ligand binding data: analysis of data on erythrocytes.

Hemoglobin oxygen binding data on erythrocytes at diffrent pH, PCO2 and bisphosphoglycerate concentrations have been analyzed in terms of an extended version of the Herzfeld-Stanley model of 1972. The binding of oxygen to subunits when the tetramer is in the quaternary oxy conformation was found to be insensitive to moderate changes in pH and pCO2 (0.71 +/- 0.05 mm Hg-1). Utilizing this circumstance it has been possible to obtain, for the first time, unique estimates of energy parameters related to hemoglobin cooperativity and effector action. At 37 degrees C, pH 7.2 and pCO2 22 mm Hg the following parameter values were obtained: The allosteric constant: (1.5 + 0.4)-10(4); the oxygen binding constant of the deoxy state: (5.4 +/- 0.3).10(-3) mm Hg-1; the 2,3-bisphosphoglycerate binding constants: (3.3 +/- 1.3).10(3)1. mol-1(deoxy), (1.3 +/- 0.5).10(2)1. mol-1 (oxy). Quarternary transition most likely takes place after binding of the second O2 molecule. Following the concepts of Perutz the results suggest that (1) protons and carbon dioxide act as constraint effectors and/or as quaternary effectors; (2) the difference in total conformational energy between the two quaternary ligand-free states is almost exclusively confined to molecular constraints and very little to the difference in quaternary conformational energy. The consistency of the results indicate that the model may be regarded as a useful tool for the description of the functional interrelations in the hemoglobin oxygenation process as reflected in oxygen binding data.

Binding Sites↗
PubMed1976

A theoretical model of the respiratory function of blood.

The model of the respiratory function of blood as outlined here is judged to be a powerful tool for the evaluation of the potential effects of changes in blood as well as tissue parameters upon the supply of oxygen to tissue. The erythrocyte-plasma disequilibria in lung and systemic capillaries which is a consequence of the slowness of plasma CO2 hydrolysis are not significant in terms of the delivery of oxygen to tissue, but result in slightly lower unloading of CO2 in the lungs compared to that which might occur at full equilibration. However, the effects might be of greater interest when relating pH values measured by in vivo sampling to actual values prevailing within the capillaries. The physiological importances of hyperventilation and elevated DPG levels in anemia cannot as yet be clarified. If anything, it appears that increased DPG is a compensatory mechanism to restore proper O2-Hb affinity in alkalosis, while the purpose for an alkalosis is not obvious.

Anemia↗
PubMed1975

The blood oxygen transport system. A numerical simulation of capillary-tissue respiratory gas exchange.

A theoretical model of the process of respiratory gas exchange between capillary and tissue is described, with special reference to the importance of variations in blood properties. The volume of tissue supplied with oxygen from a single vessel, as a function of the blood flowrate (u), hematocrit (h), and 2,3 diphosphoglycerate concentration (DPG), is calculated from a solution to the set of equations governing species distributions in the blood and tissue. The results, which are presented in the form of crossplots of the three blood parameters (u, h, and DPG) at a constant oxygen supply rate, show the possible significance of in vivo variations in the oxygen affinity of hemoglobin as a compensatory mechanism. Of further physiological interest is the sharp increase in venous erythrocyte pH in response to decreases in hematocrit, once the hematocrit is below a certain level. These results, and those relating DPG to hematocrit at constant O2 supply, are consistent with experimental observations of elevated DPG and pH levels in anemic individualts, and the dependence of erythrocyte DPG concentration upon pH.

Capillaries↗