Muscle glycogen depletion during exercise at 9 degrees C and 21 degrees C

This study compared glycogen depletion in active skeletal muscle after light and moderate exercise in both cold and comfortable ambient conditions. Twelve male subjects (Ss) were divided into two groups equally matched for the submaximal exercise intensity corresponding to a blood lactate concentration of 4 mM (W4) during cycle exercise. On two separate days Ss rested for 30 min at ambient temperatures of either 9 degrees C or 21 degrees C, with the order of temperature exposure being counter-balanced among Ss. Following rest a tissue specimen was obtained from the m. vastus lateralis with the needle biopsy technique. Six Ss then exercised on a cycle ergometer for 30 min at 30% W4 (range = 50 - 65 W) while the remaining group exercised at 60% W4 (range = 85 - 120 W). Another biopsy was taken immediately after exercise and both samples were assayed for glycogen content. Identical procedures were repeated for the second environmental exposure. No significant glycogen depletion was observed in the Ss exercising at 30% W4 in 21 degrees C, but a 23% decrease (p = 0.04) was observed when the same exercise was performed at 9 degrees C. A 22% decrease (p = 0.002) in glycogen occurred in the 60% W4 group at 21 degrees C, which was not significantly different from that observed during the same exercise at 9 degrees C. The results suggest that muscle substrate utilization is increased during light exercise in a cold environment as compared to similar exercise at a comfortable temperature, probably due to shivering thermogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bovine plasma progesterone levels at programmed circadian temperatures of 17 to 21 degrees C and 21 to 34 degrees C

Eight Angus heifers were subjected to control ambient temperatures (diurnal variation of 17 to 21°C) and experimental ambient temperatures (diurnal variation of 21 to 34°C). There was no significant difference (P > 0.05) in progesterone levels between the two environmental regimes or blood samples collected at 0800 and 1600 hr.     

Chloroethene biodegradation in sediments at 4 degrees C

Microbial reductive dechlorination of [1,2-14C]trichloroethene to [14C]cis-dichloroethene and [14C]vinyl chloride was observed at 4 degrees C in anoxic microcosms prepared with cold temperature-adapted aquifer and river sediments from Alaska. Microbial anaerobic oxidation of [1,2-14C]cis-dichloroethene and [1,2-14C]vinyl chloride to 14CO2 also was observed under these conditions.     

In vitro survival of Echinococcus granulosus protoscolices in several media, at +4 degrees C and +37 degrees C

As a first step towards hydatid disease control, the in vitro survival of protoscolices of Echinococcus granulosus was investigated for various media and temperatures. Higher percentage survival was obtained than previously reported: at 4 degrees C, 100% survival was obtained for 20 days in medium 199 (GIBCO) and for 25 days in hydatid fluid from the host of origin. Maximal survival was 30% at 55 days in these conditions. Flame cell activity was the criterion of choice for viability. At 37 degrees C survival rates were lower and morphological changes in protoscolices were observed.     

Metabolic and cardiovascular adjustment to work in air and water at 18, 25, and 33 degrees C.

By use of successive increments of discontinuous work with an arm-leg cycle ergometer the VO2, Q, SV, and HR were studied in six male subjects at rest and during exercise in air and in water at 18, 25, and 33 degrees C. The Q values obtained by CO2 rebreathing were reproducible. VO2 was linearly related to work with the plots for air and 33 degrees C water being similar. However, during work in 25 and 18 degrees C water, the VO2 averaged 9.0% (150 ml) and 25.3% (400 ml) higher, respectively, than values observed in 33 degrees C water, with the largest differences observed in leaner subjects. The plot of HR-VO2 was linear and almost identical during work in air and 33 degrees C water, but shifted significantly to the right in cooler water. VO2 averaged 250-700 ml higher in cold water compared to air and 33 degrees C water at a given mean heart rate. The Q vs. VO2 line was similar during work in air and in water with no effect of water or temperature. At similar levels of VO2, SV was significantly larger (P less than 0.05) in 25 and 18 degrees C water than in air or 33 degrees C water. Consequently, the reduction in heart rate during work in cold water was entirely compensated for by a proportionate increase in the SV of the heart. Q was therefore maintained at similar levels of energy expenditure in air and in 18, 25, and 30 degrees C water.     

Survival of bovine embryos stored at 4 degrees C

These experiments were designed to test the efficacy of storing bovine embryos at 4 degrees C. Of particular interest were the age of embryo at which maximum post-storage survival could be achieved and longevity at 4 degrees C. A greater proportion of day 8 blastocysts developed in vitro at 37 degrees C following refrigeration for 48 hr than did embryos collected 2, 4 or 6 days after estrus (P<0.01). Survival of blastocysts stored at 4 degrees C for 48 hr was similar to that of nonstored blastocysts. In a subsequent experiment, day 8 blastocysts were recovered nonsurgically and assigned to one of the following treatments: (a) immediate transfer; (b) culture at 37 degrees C; or (c) storage at 4 degrees C for 1, 2, 3 or 5 days. Post-storage viability was assessed by either development in culture at 37 degrees C or embryo survival following nonsurgical transfer to synchronized recipients. In vitro survival of nonstored embryos and embryos stored 1 day did not differ. Survival decreased after storage for 2 days (P<0.10) or longer (P<0.05). Similar results were observed for survival after transfer, but embryo viability decreased even more rapidly with increasing duration of storage. In vitro survival was approximately 50% for blastocysts stored for 3 and 5 days, but few pregnancies resulted from transfer of embryos stored for these periods. In another experiment survival after transfer of blastocysts stored at 4 degrees C for up to 2 days was similar to that of nonstored blastocysts.     

Short-term storage of rabbit embryos at 4 degrees C

A simple method for storing preimplantation mammalian embryos was tested under conditions which could be easily maintained inside an ordinary refrigerator set at 4 degrees C. No significant loss of viability occurred when rabbit embryos were stored at 4 degrees C for 7 days and either cultured in vitro at 37 degrees C or transferred to recipient does. Significant losses occurred when embryos were stored for 10 days or longer before culture at 37 degrees C (P < .01). Stored embryos transferred to recipients had a significantly longer average gestation period than embryos transferred without cold storage (P < .05).     

3T3 cell motility in the temperature range 33 degrees C to 39 degrees C

The phenomena of mammalian cell motility in tissue culture is an integrated function of many cellular components. As such, cell motility is very sensitive to external stimuli and perturbation. In this article we report the effect of temperature in the range 33 degrees C to 39 degrees C on cell motility. For this 3T3 cells were plated in plastic tissue culture flasks. A large number of individual cells (60 per experiment) were tracked as a function of time by means of an automated device, the Cell Analyzer. The data show a peak in the average cell speed in the range 36.5 degrees C to 38.5 degrees C, falling off sharply at lower and higher temperatures. The average rate of cell motility closely correlates to the average cell proliferation rate in the range 33 degrees C to 39 degrees C.     

Post-mortem changes in cytochemical localization and enzymological measurement of marker enzymes of the mitochondria, SDH and Mg-ATPase, of porcine muscle stored at 4 degrees C, -18 degrees C, or -80 degrees C

As a series of studies on postmortem changes in the fine structure of porcine muscle, activity of two mitochondrial marker enzymes, succinate dehydrogenase (SDH) and magnesium dependent adenosine triphosphatase (Mg-ATPase), was measured and localized in cardiac, red and white muscles stored at 4 degrees C, -18 degrees C or -80 degrees C. The postmortem loss of SDH activity was most remarkable in cardiac muscle. The variation of SDH activity was proportional to the amount of absolute activity. The postmortem change of Mg-ATPase was more variable than SFH, though the activity was well preserved up to 15 weeks in all three types of porcine muscle stored at -80 degrees C. The loss of Mg-ATPase was most remarkable in red muscle stored at -18 degrees C or -80 degrees C. Cytochemical localization of SDH was between the outer and the inner mitochondrial membranes while that of Mg-ATPase was on the inner surface or matrix side of the inner membrane. Those localization was not altered by the difference in temperature and the duration of storage.