K+ excretion rate was measured at normal as well as at rising plasma K+ concentration in intact, in K-depleted, and in acetazolamide-treated dogs submitted to acute blood pH changes. The results indicate that, for any given value of glomerular filtration rate, K+ excretion rate is determined by at least three factors: 1) plasma K+ concentration, 2) blood pH level, and 3) presumably, the H+ gradient across the luminal border of the distal tubule. The data further suggest that most of the filtered K+ is reabsorbed by the proximal tubule, even in conditions of high filtered loads.
The response of rainbow trout Na+ and Cl- uptake systems to acute acidosis was tested by slow infusion of lactic acid into anaesthetized animals. Depression of blood pH by 0–4 pH unit had no effect on influx rates for either ion, and we conclude that gill ion uptake systems do not respond rapidly to blood pH changes.
The effect of temperature on blood pH in embryonic snapping turtles (Chelydra serpentina) was examined to determine whether the blood pH changes in the same manner as the neutral pH of pure water. Eggs were incubated on moistened vermiculite (water potential of −150 or −950 kPa) at 26 or 27 °C. On day 59 of incubation, eggs were placed in individual containers and assigned to incubators set at temperatures between 18.5 and 30 °C. Blood samples were taken on day 60 of incubation. Blood pH of the embryos varied in a manner similar to that observed in adults of this species: blood pH declined with increasing temperature, with a slope of −0.021 pH/°C. The decrease of blood pH with increasing temperature may be accomplished passively, with blood CO2 partial pressure increasing as a result of greater metabolic production of CO2 while the diffusive excretion of this gas remains relatively constant. No effect of substrate water potential on blood pH was observed.
Plasma and erythrocyte Na, K, Cl and water have been determined in hyperventilated dogs cooled to 25°C for periods up to 4 hours, in animals heated to either 41.5°C or 42.5°C for 1 hour and in hyperventilated-normothermic dogs. The induced respiratory alkalemia in both normothermic and hypothermic animals appeared to result in a shift of Na from plasma into red cells. Plasma K was reduced in both normothermic and hypothermic dogs, whereas a K elevation in erythrocytes occurred only in the normothermic animals following hyperventilation. Erythrocyte K remained unchanged in hypothermia. It seems, therefore, that the fall in plasma K which occurs in alkalemic normothermic dogs is due partially to a movement of K into red cells whereas, in hypothermia the K leaving extracellular fluid enters cells other than erythrocytes. The plasma and red cell electrolyte changes observed in the two hyperthermic groups of dogs were all in the direction of an increase. It is concluded that these changes were primarily the result of the increased body temperature and of consequent reductions in plasma and red cell water content, rather than the result of the blood pH changes associated with hyperthermia.
In recent years considerable work has been devoted to the Bacillus species which are pathogenic for insects. Some of these produce a proteinaceous parasporal body or crystal (8) which is toxic to a large number of insect species (11, 13). The effect of a paralytic toxin derived from cultures of Bacillus thuringiensis var. sotto on the silkworm (Bombyx mori L.) has been studied in some detail (2, 3, 4). A similar toxin has been extracted from Bacillus thuringiensis var. alesti by Fitz-James et al. (5), from B. thuringiensis var. thuringiensis by Hannay and Fitz-James (personal communication), and Bacillus entomocidus var. entomocidus Heimpel and Angus (12, also unpublished results).
Lipid-conjugated fluorescent pH sensors for monitoring pH changes in reconstituted membrane systems
