Tirosielurie by geestelik vertraagde pasiënte

Abstract

Various aspects of the blood physiology in mudfish Labeo aapeneis acclimated to winter and summer temperatures (8°C & 23°C) have been investigated. Occationally unacclimated fish, referred to as winter and summer fish, were used during winter and summer times respectively. Hematocrit, hemoglobin concentration and oxygen capacity of whole blood were higher in the cold-acclimated fish. It was concluded that Labeo aapensis raises its blood oxygen capacity in response to increasing temperature by erithropoiesis and not by increasing the amount of hemoglobin molecules in the circulating cells. Mudfish regulate their acid-base balance by altering plasma bicarbonate concentration when temperature changes. Plasma Na and Cl concentrations also increase with temperature increase and this effect is considered to have adaptive value for plasma bicarbonate regulation. Standard oxygen consumption was measured in relation to weight and temperature. When expressed on a logarithmic grid, standard oxygen uptake increased linearly with weight at both 8°C and 23°C. The mean slope values of the regressions are less than unity, meaning a higher metabolic rate for smaller than for larger fish. Summer fish at 23°C have a greater ability to maintain a constant oxygen uptake rate than winter fish at 8°C. The standard rate of oxygen consumption found for mudfish in this investigation more closely relates to that of active fishlike trout and is much higher than figures obtained for carp in the literature. Oxygen dissociation curves were constructed for whole blood, hemolysate and hemoglobin stripped of organic phosphates and inorganic ions. The cooperative binding of hemoglobin to oxygen was found to be dependent on temperature and pH as well as on organic phosphate concentrations in the red cells. ATP is the major nucleocide triphosfate in mudfish blood. GIP is also present and, although it is present in minor amounts, it has a greater effect on oxygen affinity than ATP. The total nucleocide triphosphate concentration in molar ratio to hemoglobin decreases when temperature increases. This effect can be mainly attributed to the increase of ATP and seems to have great adaptive value in regulating oxygen transport to the tissues. Electrophoretic studies showed that mudfish have four hemoglobin components of which one is cathodal. The relative concentrations of these hemoglobins showed minor changes with temperature and is considered to have no significant adaptive value in oxygen transport. The experimental results is discussed in relation to the ability of the fish to survive during great environmental changes in oxygen availability and temperatures.