Increased role of skeletal muscle in the calorigenic response to glucagon of cold-acclimated ducklings.

The site of the calorigenesis observed in birds after glucagon was sought in control and cold-acclimated (CA) ducklings. Twenty-four 6-wk-old muscovy ducklings were reared either at thermoneutrality (TN) (25 degrees C) or in the cold (4 degrees C) from the age of 1 wk. Glucagon-induced calorigenesis (GIC) was estimated at 25 degrees C after a peritoneal glucagon injection (103 nmol/kg).

Increase in cytochrome oxidase capacity of BAT and other tissues in cold-acclimated gerbils.

To determine the effects of cold acclimation on the oxidative capacity of different tissues and their possible role in nonshivering thermogenesis (NST) in a desert rodent, the gerbil (Gerbillus campestris), measurements of cytochrome oxidase activity (COX) were performed on homogenates of liver, brown adipose tissue (BAT), and subsarcolemmal (SS) and intermyofibrillar (IMF) fractions of skeletal muscle. Total organ mass was also measured. Gerbils were maintained either at thermoneutrality (TN) or cold [4 degrees C, ambient temperature (Ta)] for 4 (CA4) or 8 (CA8) wk.

Adaptation to extreme ambient temperatures in cold-acclimated gerbils and mice.

To explain tolerance of heat and cold in gerbils (Gerbillus campestris) in their natural environment, a comparative study was made of thermoregulatory reactions in these animals and white mice (Mus musculus) of the same body mass exposed for 2-3 h to ambient temperatures (Ta) ranging from -23 to 40 degrees C. Metabolic rate (MR), evaporative heat loss (EHL), colonic temperature (Tb), and electromyographic activity (EMG) were measured. Nonshivering thermogenesis (NST) was also evaluated from the increase in MR after norepinephrine injection.

Potentiated muscular thermogenesis in cold-acclimated muscovy duckling.

The capacity for nonshivering thermogenesis (NST) was examined in 26- to 27-day cold-acclimated (CA) muscovy ducklings reared for 21 days at 4 degrees C. Metabolic rate and integrated electromyographic (EMG) muscle activity were measured at ambient temperature ranging from -10 to 28 degrees C. Compared with controls reared at 30 degrees C, CA ducklings were more resistant to cold and had higher peak metabolic rate in extreme cold.

Thermoregulation in the only nocturnal simian: the night monkey Aotus trivirgatus.

The night monkey, a tropical monkey, is the only nocturnal simian; its thermoregulation was studied for comparison with other nocturnal or diurnal primates and other tropical mammals. Resting metabolic rate was 2.6 W (closed-circuit method) and 2.