J.Homer Ferguson

Effects of exercise and cold acclimation on the ventricular and skeletal muscles of white mice (Mus musculus)—I. Succinic dehydrogenase activity

Abstract 1. 1. The effects of acclimation to 6°C and exercise training in a motor-driven running wheel were compared in adult male white mice. 2. 2. Succinic dehydrogenase activity and protein concentration were measured in ventricular, gastrocnemius and masseter muscle. 3. 3. Succinic dehydrogenase activity/mg protein was increased in ventricular muscle by exercise and cold acclimation. Values for skeletal muscle did not differ from control. 4. 4. Protein concentration was below control values in all muscles for both experimental groups. 5. 5. For all parameters examined, greater changes were observed in heart muscles than in skeletal muscle.

Role of thermal stimuli in the diving response of the muskrat (Ondatra zibethica)

Abstract 1. 1. In this investigation we studied the effects of water temperature on diving bradycardiain muskrats. 2. 2. Heart rate was determined by means of an electrocardiogram taken throughout the test period. 3. 3. When submerged in water at 20°C, the heart rate was suppressed to 34% (68 beats/min) of resting heart rate (200 beats/min). At 2 and 35°C the heart rate was 24% (48 beats/min) and 50% (100 beats/min), respectively. 4. 4. These data suggest that the thermal stimuli of water can affect the normal diving reflex of the muskrat.

The effect of cold acclimation upon glucose-6-phosphatase activity in two species of free-living nematodes—I. The effect of pH

Abstract 1. 1. Glucose-6-phosphatase activity was studied in two species of axenically cultured free-living nematodes, Panagrellus redivivus and Turbatrix aceti. Changes in glucose-6-phosphatase activity and in optimal pH for this enzyme were examined in control and cold-acclimated worms. 2. 2. In both the cold-acclimated and the control populations of both species, the optimal pH for glucose-6-phosphatase activity was 6·2. 3. 3. The glucose-6-phosphatase activity was greater in the cold-acclimated populations of P. redivivus than in the controls. No significant difference was observed between cold-acclimated and control T. aceti.

Plasma free fatty acid composition before and after cold exposure in the white rat

Abstract 1. 1. Free fatty acid (FFA) distribution of blood plasma was analyzed by means of gas chromatography in rats acclimated to room temperature (21–22°C). FFA analysis was carried out on an identically treated group of rats after cold exposure. 2. 2. Total plasma FFA concentration increased by 92 % after cold exposure. 3. 3. Concentration changes were not uniform for all fatty acids examined; the greatest percentage increase was found in palmitic acid.

The relationship between body composition and survival time during acute cold exposure in white mice (Mus musculus).

Abstract 1. (i) In this study we compared several body constituents which are useful in predicting survival time during acute cold exposure in mice. 2. (ii) The survival time of adult, male Swiss-Webster mice exposed to intense cold (−18 °C) was determined. 3. (iii) Survival time was analyzed as a function of total body weight, dry weight, basic weight, lipid index, total body fat, total body water, and percentage body water. 4. (iv) Percentage body water and survival time were inversely related. 5. (v) Dry weight was found to be the most significant factor in predicting cold resistance probably because it represents both metabolic capacity (basic weight) and insulative quality (total body fat).

Effect of photoperiod and cold acclimation upon plasma free fatty acid levels in the white rat

1. Animals were acclimated at 3 +/- 1 degrees C and at room temperature (22 degrees C) for 3 weeks. 2. At each acclimation temperature animals were maintained under either an 8:16 L:D cycle or a 16:8 L:D cycle. 3. Blood samples were taken before and after exposure to -38 degrees C for 30 min. 4. Free fatty acid levels were greatest in cold acclimated animals which were maintained on a short light cycle. 5. Interaction between acclimation and photoperiod was apparent.

Effects of acclimation temperature on brown adipose tissue in the red squirrel (Tamiasciurus hudsonicus).

Abstract 1. 1. The effects of temperature on three fat pads in the red squirrel, Tamiasciurus hudsonicus in captivity were studied. 2. 2. Acclimation temperatures of 10, 5 and −10°C resulted in a decrease in total fat pad weight when compared to a normal ambient temperature of 24°C. 3. 3. The interscapular fat body exhibited the largest change in weight. 4. 4. Concomitant with the decrease in weight in the interscapular fat body, the predominant cell type changed from unilocular to a multilocular type. 5. 5. The existence of the multilocular cell type in all three fat pads established the existance of brown adipose tissue in this species.

Oxygen storage capacity and tolerance of submergence of a non-aquatic reptile and an aquatic reptile.

The oxygen storage capacities and the tolerance to submergence of an aquatic snake, Natrix sipedon, and a non-aquatic snake, Crotalus viridis, were determined and compared. C. viridis was found to have a larger oxygen storage capacity, hemoglobin content and blood volume than N. Sipedon. The submergence time for C. viridis was 30.13 min which was less than the estimated time for submergence based on the oxygen storage capacity. N. sipedon exceeded its estimated dive time of 24.00 min and remained submerged for 65.57 min without signs of stress. During submergence, the heart rate of N. sipedon fell to 9% (5 beats/min) of the resting rate, while the heart rate of C. viridis fell to only 75% (27 beats/min) of the resting rate during this activity. These data indicate that N. sipedon responds to submergence via a typical diving reflex and extends its oxygen stores beyond that expected of a non-diver such as C. viridis.

The correlation between colonic cooling and survival time in the acute cold-exposed laboratory mouse: Influence of cold acclimation

Abstract 1. 1.Correlation between survival time and colonic cooling in the mouse has been assessed during acute cold exposure. 2. 2.Mice acclimated to room temperature (22°C) and cold (0°C) environments were acutely exposed to cold temperatures (−18°C). Two colonic temperatures were taken, the first after 30 min of cold exposure, and the second when the mice lost their righting reflex. Time to loss of righting reflex was designated as survival time. 3. 3.In a mouse acclimated to 22°C, colonic cooling and survival time are exponentially related with a high degree of correlation. This relationship also holds true for a cold-acclimated animal but the correlation coefficient of these variables is significantly reduced. 4. 4.In conclusion, colonic cooling is an accurate reflection of the ability of mice to survive acute cold exposure. However, in cold-acclimated mice colonic cooling cannot be considered as reliable for measuring cold resistance as it is in mice acclimated to warmer temperatures.

Relationship between body lipids and resistance to acute cold exposure in mice: Effect of dietary saturated and unsarurated fat☆

Abstract 1. 1. The effect of dietary saturated and unsaturated fat on the relationship of body lipids and tolerance to acute cold exposure was investigated. 2. 2. Male, Swiss-Webster mice were fed rat chow or rat chow with 10% supplements of tripalmitin or safflower oil from weaning (21 days) to 48 days of age. 3. 3. Animals were evaluated for their tolerance to cold by measuring their colonic temperature after 30 min of exposure to intense cold (−22 °C). The mice were immediately sacrificed and total body lipids extracted. 4. 4. The colonic temperature varied directly with lipid index after cold exposure only when mice were fed a diet supplemented with unsaturated fat. 5. 5. The ability to tolerate acute cold exposure is not related to lipid index when mice are fed saturated fat as dietary supplement. 6. 6. In all dietary groups the dry, fat-free weight was a reliable index for predicting the ability of mice to tolerate intense cold.