R.R.J. Chaffee

Restorative effects of spermine on oxidative phosphorylation and respiration in heat-aged mitochondria.

Abstract Samples of fresh rat liver mitochondria were heat-aged in 37°C isotonic sucrose sufficiently to cause approximately a 30% reduction in the ADP:O ratio when using beta-hydroxybutyric acid as substrate. Subsequent polarographic assays showed spermine concentrations between 0.0157 and 0.250 mM to cause a striking linear restoration of the ADP:O ratio. Spermine also improves both the respiratory rate during the conversion of ADP to ATP and the respiratory control ratio of heat-aged mitochondria. The effects of spermine on the respiratory rate after ADP to ATP conversion vary depending on the spermine concentration. Spermine has no significant effects on mitochondrial respiration prior to addition of ADP.

The possible role of intracellular polyamines in mitochondrial metabolic regulation

Abstract Studies were made on the effects of very low concentrations of the polyamine, spermine, on rat liver mitochondrial metabolism associated with β-hydroxybutyrate. The respiratory control ratio and the rate of respiration during ADP-ATP conversion are significantly altered with shifts in spermine concentrations of as little as 15.7 nMoles/ml within the physiological Mg++ concentration range. These spermine concentration changes are small compared to the estimated hepatic intracellular levels of spermine which have been reported to be between 200 and 1200 nMoles/gm wet weight under normal conditions. There is now evidence that exposure of an animal to certain environmental conditions induces changes of 164 nMoles/gm wet weight in intracellular levels of liver spermine in a few hours. Also there is evidence that the concentration of intracellular polyamines is influenced by endocrines since the levels of the enzymes responsible for their synthesis are markedly affected by hormonal changes. Therefore, alterations of polyamine levels may play a role in mitochondrial metabolic regulation in vivo .

Polyamine effects on succinate-linked and αketoglutarate-linked rat liver mitochondrial respiration

Summary At 0.6–1.17 mM Mg ++ , physiological spermine levels strikingly enhance respiratory control ratios of rat liver mitochondria with αketoglutarate by suppressing respiration which occurs after added ADP is converted to ATP. Respiration with added ADP is enhanced at 0.6 but not at 1.17 mM Mg ++ . Conversely, with succinate, spermine at high concentrations depresses respiratory control ratios but only slightly affects respiration. Spermidine with αketoglutarate increases respiratory control ratios but suppresses respiration both during and after added ADP-ATP conversion. However, suppression is greater after this conversion. With succinate, spermidine also increases respiratory control but its effects on respiration during or after added ADP-ATP conversion vary with Mg ++ concentration. Thus, polyamines seem to affect mitochondrial metabolism.

Studies on thermogenesis in brown adipose tissue in temperature-acclimated Macaca mulatta

Abstract 1. 1. Adult male Macaca mulatta were acclimated for 12–24 months at two environmental temperatures (5 ± 1°C and 35 ± 1°C). 2. 2. Body weights in the two temperature groups were the same. The axillary brown adipose tissue (ABAT) wet weight of the cold-acclimated animals was 211 per cent greater, and the total ABAT protein content 1330 per cent greater than that of heat-acclimated animals (P ⩽ 0·05). 3. 3. The calculated total rates of oxygen consumption of homogenates of ABAT of cold-acclimated animals were greater (P ⩽ 0·05) than that of the heat-acclimated animals by 5363 per cent with succinate, 610 per cent with glutamate, 1613 per cent with a-ketoglutarate, 1955 per cent with β-hydroxybutyrate and 6104 per cent with α-glycerophosphate. 4. 4. Both brown and yellow adipose tissue were darker in the cold-acclimated animals.

Metabolic and biochemical aspects of heat acclimation in the deer mouse, Peromyscus maniculatus sonoriensis*

Abstract o 1. Adult deer mice (Peromyscus maniculatus sonoriensis) were acclimated to 24 ± 1 and 35 ± 1°C for 2 months. 2. At ambient temperatures between 20–30°C, body temperatures of heat-acclimated deer mice were significantly below those of controls (P 3. Metabolic rates of heat-acclimated deer mice were 9–27% lower than those of control mice over the temperature range studied. 4. The body weight of heat-acclimated deer mice was significantly below that of controls (P 5. Heat acclimation produced significant decreases in kidney BOH oxidase activity and liver serine and threonine dehydrase activities; a significant increase in liver mitochondrial P/O ratio with BOH as substrate; and no significant changes in either liver or kidney succinoxidase activity. Brown fat mass, protein content and QO2 all decreased in the heat. 6. The combined metabolic, biochemical and organ wt changes seen in heat-acclimated deer mice provide further evidence of decreased total heat production in a hot environment and support the hypothesis that chemical thermosuppression occurs during heat acclimation.

Evidence of kidney chemical thermosuppression in temperature-acclimated hamsters

Abstract 1. 1. Adult male golden hamsters (Mesocricetus auratus) were acclimated at three environmental temperatures ( 35±0·5, 23±0.·5 and 6±1° C ) for 3–6 months. 2. 2. the body weight of the heat-acclimated hamsters was significantly lower than that of the controls, whereas there was no difference between the weight of the controls and cold-acclimated animals ( P ). The kidney weight ratios in each temperature group were significantly different ( P⩽0·001 ), being highest in the cold and lowest in the heat. 3. 3. The total kidney protein was highest in the cold-acclimated animals and lowest in the heat-acclimated animals ( P⩽0·001 ). 4. 4. The specific and total kidney alpha-glycerophosphate dehydrogenase activity was elevated during cold acclimation and reduced during heat acclimation. 5. 5. The total kidney activity of isocitric dehydrogenase was significantly higher in the cold than in the control and heat-acclimated animals which were equal. 6. 6. The results support the concept that there are physiological-chemical-metabolic feedback mechanisms that increase the thermogenic response during cold acclimation and suppress it during heat acclimation.

Effects of cold acclimation, hibernation and temperature on succinoxidase activity of heart homogenates from hamster, rat and squirrel monkey☆

Abstract 1. 1. The effects of temperature on heart homogenate succinoxidase activity have been studied in preparations from hamsters (Mesocricetus auratus), rats and squirrel monkeys (Saimiri sciureus). 2. 2. Squirrel monkey heart homogenates show a greater temperature sensitivity between 5 and 15°C than preparations from rodents. This suggests that these animals may prove to be more susceptible to severe hypothermia than either rats or hamster. Q 10 values between 15 and 37°C were similar in all three species. 3. 3. No depression of succinoxidase activity was seen in heart homogenates from hibernating compared with active hamsters. 4. 4. There were no significant differences in the temperature sensitivities of homogenates from hamsters and rats which might account for the greater tolerance of the hibernator heart to hypothermia.

Effects of temperature on oxidative phosphorylation of liver mitochondria from hamster, rat and squirrel monkey.

Abstract 1. 1. The effects of temperature on succinoxidase activity have been measured using liver mitochondria from hamsters (Mesocricetus auratus), rats and squirrel monkeys (Saimiri sciurea). 2. 2. These studies reveal changes in the temperature sensitivity of this enzyme system in mitochondria from hibernating hamsters which distinguish them from mitochondria of rats, monkeys and active hamsters. 3. 3. At low temperatures, Q 10 values for monkey and rat mitochondria are higher than those for control or hibernating hamsters. 4. 4. At 20–34°C, the Q 10 for mitochondria from hibernating hamsters is higher than that for non-hibernating animals. 5. 5. Hamster liver mitochondria have a higher ADP/O ratio than rat or monkey liver mitochondria when assayed at low temperatures. 6. 6. These changes may be of adaptive significance both in maintenance of functional integrity of liver cells during hibernation and in contributing to rapid rewarming during arousal.

A comparative study of oxidative enzymatic potential of Sphermophilus lateralis and Spermophilus tereticaudus

Abstract 1. 1. Adult Spermophilus lateralis and Spermophilus tereticaudus were examined for possible differences in cellular metabolic potential as indicated by oxidative enzyme levels. 2. 2. The body weight of S. tereticaudus was 38% smaller than S. lateralis. The body to organ weight ratios of the two species were not significantly different except for the kidney which was higher in S. tereticaudus. 3. 3. The specific and total activity of succinoxidase in the heart, brown adipose tissue (BAT), muscle and kidney was greater (P ⩽ 0.05) in S. lateralis. 4. 4. The specific and total activity of glutamic acid oxidase was greater (P ⩽ 0.05) in kidney, muscle and liver of S. lateralis, but no differences were observed in BAT or heart. 5. 5. The total cytochrome oxidase activity of BAT was higher in S. lateralis; but there were no differences in the α-glycerophosphate dehydrogenase activity. 6. 6. These results indicate potential metabolic differences exist in two closely related but ecologically diversified scuirids.

A comparative study of brown adipose tissue oxidative metabolism among temperature-acclimated spermophilus lateralis, spermophilus tereticaudus and Amnospermophilus leucurus.☆

Abstract 1. 1. Brown adipose tissue (BAT) oxidative enzyme activities levels, mass and protein content were determined for control and heat- and cold-acclimated Spermophilus lateralis, Spermophilus tereticaudus and Amnospermophilus leucurus. 2. 2. S. lateralis and S. tereticaudus respond to prolonged temperature stress by undergoing compensatory changes in oxidative enzyme levels that may facilitate greater nonshivering thermogenesis in the cold and increased chemical thermosuppresion in the heat. 3. 3. S. tereticaudus and A. leucurus , but not S. lateralis , showed significant changed in BAT mass. 4. 4. S. tereticaudus and S. lateralis , but not A. leucurus , showed significant changes in protein per g BAT. 5. 5. The similarity of BAT enzymatic responses between S. lateralis and S. tereticaudus and dissimilarity of the BAT response of A. leucurus suggest an intrinsic physiological difference between hibernators and non-hibernators rather than between desert and mountain species.