Fiber composition and capillarity in growing guinea pigs acclimated to cold and cold plus hypoxia

The central portion of the medial head of the gastrocnemius of control (normoxic and normothermic), hypoxia-, cold-, and cold plus hypoxia-acclimated guinea pigs was analyzed for capillary supply and fiber composition to elucidate changes in capillarity induced by environmental stresses. The muscle was cut at midbelly, frozen, sectioned, and stained for myosin ATPase. Fiber cross-sectional areas; percentages of slow-twitch oxidative (SO), fast-twitch oxidative-glycolytic (FOG), and fast-twitch glycolytic (FG) fibers; and numbers of capillaries around each fiber type were measured. Growth rates of all four guinea pig groups were similar. Capillarity was not affected by acclimation to hypoxia. Cold and cold plus hypoxia acclimation led to increased numbers of capillaries around the fiber in all three fiber types. In addition, significant increases in the percentage of FOG fibers and concomitant decreases in the percentage of FG fibers compared to controls were found in cold and in cold plus hypoxia indicating that a transformation of fiber type from FG to FOG had occurred. The increase in FOGs at the expense of the FGs did not occur in the guinea pigs grown in a hypoxic environment. The increased total capillarity in those muscles studied was the result of more capillaries around all fiber types and was not due to simple transformation of fibers.     

Metabolic effects of exposure to hypoxia plus cold at rest and during exercise in humans

To determine effects on metabolic responses, subjects were exposed to four environmental conditions for 90 min at rest followed by 30 min of exercise: breathing room air with an ambient temperature of 25 degrees C (NN); breathing room air with an ambient temperature of 8 degrees C (NC); hypoxia (induced by breathing 12% O2 in N2) with a neutral temperature (HN); and hypoxia in the cold (HC). Hypoxia increased heart rate (HR), systolic blood pressure (SBP), pulmonary ventilation (VE), respiratory exchange ratio (R), blood lactate, and perceived exertion during exercise while depressing rectal temperature (Tre) and O2 uptake (VO2). Cold exposure elevated SBP, diastolic blood pressure (DBP), VE, VO2, blood glucose, and blood glycerol but decreased HR, Tre, and R. Shivering and DBP were higher and Tre was lower in HC compared with NC. HR, SBP, VE, R, and lactate tended to be higher in HC compared with NC, whereas VO2 and blood glycerol tended to be depressed. These results suggest that cold exposure during hypoxia results in an increased reliance on shivering for thermogenesis at rest whereas, during exercise, heat loss is accelerated.     

Effect of cold acclimation on antioxidant status in cold acclimated skaters

We investigated whether cold acclimation leads to increased activity of the antioxidant defense enzymes and muscle injury. Comparisons were between short track skaters (n=6) and inline skaters (n=6) during rest and at submaximal cycling (65% VO2max) in cold (ambient temperature: 5+/-1 degrees C, relative humidity: 41+/-8%) and warm conditions (ambient temperature: 21+/-1 degrees C, relative humidity: 35+/-5%), during 60 min, respectively, and during the recovery phase. Erythrocyte superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHpx), reduced glutathione (GSH), thiobarbituric substance acid (TBARS), serum creatine kinase (CK), lactate dehydrogenase (LDH), plasma myoglobin (Mb) and cortisol were determined. Activities of CAT and GSHpx and the level of GSH and TBARS in erythrocyte and the level of LDH in serum were elevated in cold acclimated subjects. We suggested that the compensatory increase in antioxidative defense enzymes resulting from long-term cold exposure may reflect the elevated reactive oxygen species (ROS) production and muscle injury at this environment acclimation.     

Enzymatic activity of rodents acclimated to cold and long scotophase

Rodents representative of a diurnal species (Rhabdomys pumilio) as well as a nocturnal species (Praomys natalensis) were acclimated to cold (T_a = 8°C) at a photoperiod of LD 12:12 and a long scotophase (LD 8; 16) at a temperature of 25° C(T_a). Control groups were kept for both species at T_a = 25° C and LD 12:12 and winter acclimated individuals were obtained during July and August to serve as further reference. Blood samples obtained from the tail were analysed for enzymes representative of three major biochemical pathways. The enzymatic activity of LDH (glycolytic pathway), MDH (Krebs cycle) and G6PDH (hexose monophosphate shunt, as an indicator of gonadal activity) were monitored to represent metabolic activity of the respective cycles. Cold acclimated as well as winter acclimatized mice revealed similar enzymatic patterns for both species and significant increases in LDH and MDH were recorded with a concurrent decrease in G6PDH activity. Specimens exposed to long scotophase exhibited similar enzymatic patterns for both species studied, but enzymatic activity was higher than those of cold acclimated individuals. From these results it is concluded that cold as well as long scotophase induce metabolic adaptations through biochemical activity in the experimental animals. The effect of long scotophase is assumed to be an important factor in the induction of winter acclimatization.Present address: University of Haifa, Oramin, P.O. Kiryat Tivon, Israel.Presented at the Eighth International Congress of Biometeorology, 9–14 September 1979, Shefayim, Israel.     

Neuroprotective effects of vitamin E in cold induced cerebral injury in guinea pigs

Significant reduction in hemorrhage (10 v/s 13), necrosis (2 v/s 4), cavitations (7 v/s 13), neuronal degeneration, perivascular and parenchymal inflammatory infiltrate (7 v/s 11) were observed in Vitamin E treated cold induced head injury in guinea pigs, evaluated post injury using the modified Benderson's scale. The results suggest that Vitamin E is highly effective in promoting clinical and histopathological recovery in cold induced head injury in guinea pigs.     

Nasal allergy to fungi in guinea pigs

Sensitized guinea pigs produced specific IgG and IgE antibodies toward Cladosporium and Alternaria. In presence of fungal extracts, nasal mast cells degranulate. Ultrastructural modifications of the cells during degranulation have been established. The ciliary epithelium and the ciliary beating are not affected by fungal allergens.