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Biomedical subjects

J Lutz

Publications and source records attributed to J Lutz.

At least 127 records · Page 7Linked to original sources
PubMed1977

[Determination of acid-base parameters by means of programmable pocket calculators (author's transl)].

The possibility to calculate parameters of acid-base status derived by common laboratory devices without built-in computers is described. The calculation is carried out faster and more exactly than it is possible by nomograms, which is especially suitable when a great quantity of dates occurs. The number of programmable steps in some inexpensive pocket calculators is sufficient for this purpose; this type of "microcomputers" offers advantages of economy and small size so that calculations can be carried out immediately at the site where measurements are taken.

Acid-Base Equilibrium↗
PubMed1975

Oxygen supply and uptake in the liver and the intestine.

The oxygen supply to the liver was found to be dependent on the total blood flow only and not on the ratio of arterial to portal contribution. The mean value of O2-uptake in the liver, related to a blood flow of 110 ml/min - 100 g liver, amounted to 6.08 +/- 0.2 ml O2/min - 100 g liver (mean +/- S.E.M.). O2-uptake of the intestine was found to be 1.95 +/- 0.13 ml O2/min - 100 g tissue, related to a normal blood flow of 50 ml/min - 100 g tissue. With low oxygen supply O2 extraction in the liver reaches values of 97%, whereas the intestinal extraction does not surpass 75%. A rise in oxygen supply surmounting normal values does not increase the O2-consumption. Contrary to the intestinal circulation the liver showed no postocclusive vasodilatation. The oxygen debt was payed back by a greater extraction. The portal oxygen supply to the liver can markedly increase due to intestinal metabolic hyperemia. High O2-extraction capacity, rather than vasodilatation, is the main mechanism for matching hepatic oxygen supply with requirements. The hepatic venous blood may leave the liver with an extremely low O2-content.

Animals↗
PubMed1975

Calculation of O2 saturation and of the oxyhemoglobin dissociation curve for different species, using a new programmable pocket calculator.

The degree of O2 saturation and different data of acid-base status are determined from pO2, pH, and pCO2 values bya programmable pocket calculator. Since the operating program should be usable for different species and also in the range of very low O2 saturations, obviously the usual Hill equation for calculating the oxygen dissociation curve of hemoglobin is not applicable; the same is true is some cases for the Adair equation. Thus a 3-fold subdivision of the dissociation curve was undertaken and programmed. Suitable programs for several species could be established despite the limited number of program steps in the new calculator, giving systematic deviations in calculated O2 saturations of less than or equal to +/- 0.9 saturation precent over the full range of dissociation curves. A reverse procedure for calculation of pO2 from saturation is added. In situations where pCO2 or base excess are not known or only estimated, limits of the arising error are stated. In the acid-base program 7 parameters are evaluated partially using empirical formulae derived from nomograms. The programmable pocket calculator offers advantages of small size, economy, and independence of line voltage compared to much more spacious units and a precision equal or superior to nomograms.

Animals↗
PubMed1975

Stimulated amino acid imbalance and histidine transport in rat brain slices.

Histidine concentration in the brain decreases rapidly when rats are fed a low protein diet in which an amino acid imbalance is created by addition of an amino acid mixture devoid of histidine. Competition for histidine transport into the brain was suggested as an explanation for this effect. Therefore, animo acid mixtures simulating composition of plasma from rats fed basal or histidine-imbalanced diets were added to media to evaluate their effects on uptake of histidine by brain slices during a 60-min incubation period. At the concentrations actually found in plasma, the unbalanced mixture decreased histidine uptake significantly more than did the basal mixture. Two distinct inhibition patterns were observed with different groups of amino acids: a linear decrease in histidine uptake with a mixture of the small neutral, hydroxyl, basic, and acidic amino acids, and a hyperbolic decrease with a mixture of large neutral amino acids, and a hyperbolic decrease with a mixture of large neutral amino acids. Inhibition of histidine transport by the complete mixtures reflected these two effects. Plasma patterns and concentrations of competitive amino acids as well as the concentration of histidine appear to be factors involved in decreasing histidine transport into the brain.

Alanine↗