David Penney

Effects of prolonged diving anoxia on the turtle, Pseudemys scripta elegans.

Abstract 1. 1. This species of fresh water turtle sustains non-voluntary diving in deoxygenated water at 22°C for periods of at least 24 hr. 2. 2. Under these conditions bradycardia occurs, although its onset may not be rapid and it may be broken during the dive by periods of rapid heart beat. 3. 3. Extensive glycogen depletion occurs in heart (95 per cent) and liver (83 per cent) as a result of submersion, while lactate increases in these two organs (eight times). 4. 4. Blood glucose levels rise fivefold, while blood lactate rises thirty-seven times. 5. 5. Coelomic fluid shows no change in either glucose or lactate concentration. 6. 6. Liver, but not heart, accumulates succinic acid (1–54 μmoles/g wet wt.).

Anaerobic glycolysis and lactic acid accumulation in cold submergedRana pipiens

SummaryWinter frogs acclimated to 5 °C for 2–8 weeks were submerged in deoxygenated water at 5 °C.2.Under these anoxic conditions survival time as judged by persistence of cardiac activity was in excess of 120 hours.3Cardiac glycogen decreased to 1.9% of that of aerobic controls, while whole body glycogen fell 25%.4.At the same time there was a rise in blood (2×) and lymph (7.5×) glucose levels.5.Blood and lymph lactic acid levels rose dramatically under anoxia (33× and 56×, respectively), while levels in heart and whole body also showed increases (3× and 6×, respectively).6.Less than 5% of the total lactic acid produced was recovered in the water in which the animal was immersed, suggesting very low rates of lactate loss from the cold anoxic frog.7.Body weight gain of 16.1%, mainly in the form of lymph, was observed following submersion. This coupled with the large increase in lymph lactic acid concentration during anoxia suggests that lymph may act as a major repository of lactate in the cold anoxic frog.

Lactate dehydrogenase and pyruvate kinase in rat heart during sideropenic anemia

Abstract Lactate dehydrogenase isozyme pattern and activity and pyruvate kinase activity were studied in animals with severe sideropenic anemia. This condition was induced by feeding rats a diet of non-fat dry milk-sucrose from the time of weaning. Anemia was indicated by the lowering of blood hemoglobin levels to 25 and 20% of normal in two groups after 30 and 85 days, respectively. In both anemic groups there was accompanying cardiac enlargement and retardation of body weight gain. Statistically significant increases in cardiac lactate dehydrogenase (25–33%) and pyruvate kinase (25%) activity were observed in both groups relative to controls. An alteration of the normal myocardial lactate dehydrogenase isozyme pattern in the direction of increased lactate dehydrogenase-5 took place in both groups of anemic rats. This resulted from a dramatic increase in the M-lactate dehydrogenase subunit contribution (45–54%) to total lactate dehydrogenase activity.

Effects of physical training on several glycolytic enzymes in rat heart

In response to a program of daily swimming for 16 weeks, the activities of pyruvate kinase and lactate dehydrogenase increased significantly in the hearts of young male rats. The isozyme composition in M of cardial lactate dehydrogenase increased from 28.5 to 32.7% in the trained animals. Phosphofructokinase activity and glycogen content were unchanged. The hearts of the exercising animals were 28% heavier than those of sedentary paired weight controls.

Lactate dehydrogenase subunit and activity changes in hypertrophied heart of the hypoxically exposed rat

Abstract Rats were exposed to an atmospheric pressure as low as 342 mm Hg (6220 m) for 57 days. This resulted in marked increases in blood hemoglobin concentration and heart weight relative to sea level controls. The lactate dehydrogenase electrophoretic isozyme pattern was visibly altered in extracts from such hearts, showing increased staining density of cathodal components amounting to an 11.8% shift toward greater M-subunit composition. This resulted in such hearts from a more than 2-fold increase in M-subunit, while H-subunit increased only slightly. The sum of both subunit changes produced a 37.5% increase in total cardiac lactate dehydrogenase activity in hypoxically exposed animals as compared to controls.

Thyroxine and oxygen consumption in Pseudemys scripta elegans

Abstract 1. 1. Thyroxine dramatically increases oxygen utilization in Pseudemys. 2. 2. The effect of thyroxine on oxygen utilization shows a strong temperature dependence, enhancement being greatest between 6 and 16°C and above 26°C. 3. 3. No increase in oxygen utilization is seen at ambient temperatures of 21–26°C or at 2°C or below.

Behavior of phosphofructokinase during the aerobic-anaerobic transition period in the isolated perfused turtle (Pseudemys scripta elegans) heart

Abstract 1. 1. Turtle hearts were perfused in a recirculating system at 22°C. Levels of intermediates of the phosphofructokinase (PFK) reaction were monitored during the aerobic-anaerobic changeover. 2. 2. ADP increased three-fold and remained elevated following initiation of anaerobiosis, while ATP increased slightly to a plateau during the same period. 3. 3. F-6-P decreased transiently upon initiation of anaerobiosis, while F-1,6-diP increased transiently at the same time in reciprocal fashion. 4. 4. The mass action ratio of the reaction catalyzed by PFK increased sharply from 2·83 × 10 −2 immediately before the changeover to 18·37 × 10 −2 15 min after changeover, returning to 7·04 × 10 −2 60 min after changeover. 5. 5. A nine-fold increase in the rate of lactate production was observed beginning 10 min after changeover, when oxygen tension reached a near minimal level. Lactate continued to accumulate in the perfusate at a constant rate throughout the period of anaerobiosis.

Activities, intracellular localization and kinetic properties of phosphoenolpyruvate carboxykinase, pyruvate kinase and malate dehydrogenase in turtle (Pseudemys scripta elegans) liver, heart and skeletal muscle

Abstract 1. 1. Intracellular localization studies show that in turtle ( Pseudemys scripta elegans ) liver and heart, 99 and 85 per cent of the pyruvate kinase (PK) and malate dehydrogenase (MDH) activities, respectively, are extramitochondrial (24,500 g supernate), while 71 per cent of the liver and 93 per cent of the heart phosphoenolpyruvate carboxykinase (PEPCK) activities are extramitochondrial. 2. 2. Of the three enzymes assayed, PK shows the highest activity in both liver and heart; PEPCK shows the lowest activity in both organs, While MDH is intermediate in activity. 3. 3. PK and MDH are only one-fourth as active in liver as in heart, while PEPCK is over twice as active in liver as in either heart or skeletal muscle. 4. 4. The apparent K m( PEP ) values for liver (81 μM) and heart (48 μM) PEPCK are smaller than K m( PEP ) values for liver (2141 μM) and heart (172 μM) PK. 5. 5. In the presence of 100 μM fructose-1,6-diphosphate the K m( PEP ) of liver PK decreases to 214 μM.

Effect of starvation on fructose diphosphatase, glucose-6-phosphatase and phosphoglucomutase activities in organs of Pseudemys (Chrysemys) scripta elegans.

Abstract 1. 1. The glycogen content of liver, kidney, heart and skeletal muscle remains unchanged in turtles following 18–22 weeks of fasting. 2. 2. Liver shows the highest fructose diphosphatase (FDPase) and glucose-6-phosphatase (phosphohydrolase) (G6Pase) activity, followed by kidney, skeletal muscle and heart. Skeletal muscle, however, shows the highest phosphoglucomutase (PGM) activity, followed by liver, kidney and heart. 3. 3. Heart has little or no measurable FDPase activity, but shows PGM and G6Pase activity. 4. 4. FDPase, PGM and G6Pase reside mainly in the cytosol of the organs examined with little or no activity in the mitochondrial fraction. 5. 5. Fasting (5–9, 7–14 and 8–22 weeks) results in no significant changes in the activities of these enzymes.

Kinetic properties of turtle heart phosphofructokinase

Abstract 1. 1. The kinetic properties of turtle [ Pseudemys ( Chrysemys ) scripta elegans ] ventricle phosphofructokinase (PFK) were examined. 2. 2. At pH 7·28, PFK demonstrates a high degree of co-operativity with respect to F-6-P. This co-operativity is enhanced with increased ATP concentration or addition of citrate and is reduced by addition of ADP at 0·2 mM or by decreasing H + concentration. 3. 3. The enzyme shows a hyperbolic activity curve with respect to ATP; however, increased ATP or addition of citrate inhibits the enzyme. Increased pH, F-6-P concentration, enzyme concentration, addition of ADP or 5′AMP at 0·2 mM, or maintaining the Mg 2+ and ATP concentration equal, reduces ATP inhibition. 4. 4. At 2·5 mM ATP, PFK is activated by Pi, 5′AMP and ADP, but ADP loses its capacity to activate at ADP concentrations above 0·5 mM. 5. 5. At 1·0 mM ATP, PFK is inhibited by citrate and ADP. 5′AMP activates less at 5′AMP concentrations greater than 0·1 mM, while Pi has no effect. Citrate inhibition is decreased by a high F-6-P concentration (3·0 mM).