The mechanisms of thermogenesis and thermoregulation were studied in the tree shrew (Tupaia belangeri) and greater vole (Eothenomys miletus) of the subtropical region, and Brandt’s vole (Microtus brandti), Mongolian gerbil (Meriones unguiculatus), Daurian ground squirrel (Spermophilus dauricus) and plateau pika (Ochotona curzoniae) of the northern temperate zone. Resting metabolic rate (RMR) and non-shivering thermogenesis (NST) increased significantly in T. belangeri, E. miletus, M. brandti and M. unguiculatus after cold acclimation (4ºC) for 4 weeks. In T. belangeri, the increase in RMR and thermogenesis at liver cellular level were responsible for enhancing the capacity of enduring cold stress, and homeothermia was simultaneously extended. Stable body temperature in M. brandti, E. miletus, M. unguiculatus and O. curzoniae was maintained mainly through increase in NST, brown adipose tissue (BAT) mass and its mitochondrial protein content, and the upregulation of uncoupling protein (UCP1) mRNA, as well as enhancement of the activity of cytochrome C oxidase, α-glycerophosphate oxidase and T4 5′-deiodenase in BAT mitochondria. The RMR in O. curzoniae and euthermic S. dauricus was not changed, while NST significantly increased during cold exposure; the former maintained their stable body temperature and mass, while body temperature in the latter declined by 4.8ºC. The serum T3concentration or ratio of T3/T4 in all the species was enhanced after cold acclimation. Results indicated that: (1) the adaptive mechanisms of T. belangeri residing in the subtropical region to cold are primarily by increasing RMR and secondly by increasing NST, and the mechanisms of thermogenesis are similar to those in tropical mammals; (2) in small mammals residing in northern regions, the adaptation to cold is chiefly to increase NST; (3) the mechanism of cold-induced thermogenesis in E. miletus residing in subtropical and high mountain regions is similar to that in the north; (4) a low RMR in warm environments and peak RMR and NST in cold environments enabled M. unguiculatus to tolerate a semi-desert climate; (5) O. curzoniae has unusually high RMR and high NST, acting mainly via increasing NST to adapt to extreme cold of the Qinghai-Tibet Plateau; (6) the adaptation of euthermic S. dauricus to cold is due to an increase in NST and a relaxed homeothermia; and lastly (7) the thyroid hormone is involved in the regulation of cold adaptive thermogenesis in all the species studied. © 2001 Elsevier Science Inc. All rights reserved.

We studied the effect of dietary vitamin C on growth, liver vitamin C and serum cortisol levels in stressed and unstressed juvenile soft-shelled turtles. Turtles were fed with vitamin C supplementation at dosages of 0, 250, 500, 2500, 5000 or 10 000 mgykg diet for 4weeks. Vitamin C supplementation exerted significant effects on specific growth rate and liver vitamin C concentrations. The specific growth rate peaked in the group fed at 500 mgykg diet, while liver vitamin C levels increased with increasing dietary vitamin C levels. Serum cortisol concentrations did not differ between groups of turtles fed diets supplemented with vitamin C in the range of 0–10 000 mgykg. After acid stress, hepatic vitamin C levels were unaffected, while serum cortisol in the control group was significantly elevated (P-0.01). The other five groups of turtles did not show significant changes in serum cortisol compared with pre-stress levels. © 2003 Elsevier Science Inc. All rights reserved.

The 24-, 48- and 96-h LC50 of nitrite and the effects on reactive oxygen intermediates (ROIs) in haemocytes and muscle, superoxide dismutase (SOD) activity, catalase (CAT) activity, glutathione peroxidase (GPX) activity, in muscle of Macrobrachium nipponense exposed to ambient nitrite were investigated. The 24-, 48- and 96-h LC50 values of nitrite at pH 8.0 were 46, 26 and 13.3 mg l-1. A significantly increased ROIs value was found in prawn (P<0.05) exposed to nitrite shock and increased with increased ambient nitrite concentration. Exposure to a sublethal concentration of nitrite for 24 h, increased ROIs by 97% compared with that of prawn exposed to control nitrite concentration, whereas SOD, CAT and GPX activity decreased 67%, 80.6% and 82.7%, respectively. The results showed that an imbalance between prooxidant forces and antioxidant defenses is one of the toxicity mechanisms of nitrite on prawn.

This paper deals with the developmental process of thermoregulation. From an ecologicalp oint of view, it establishes a mathematical model for postnatal development of thermoregulation, and proposes a new index of homeothermy ability. The model is used to predict homenthermy ability at any time of postnatal development for root vole and other species.

l. Oxygen consumption and body temperatures of 32 juvenile root voles (Microtus oeconomus) of different ages (in days) were measured at ambient temperatures (Ta) of 10, 20 and 30