Thermogenesis in Birds

The article discusses the importance of avian skeletal muscle as a source for heat generation by means of both shivering and non-shivering. Non-shivering thermogenesis in birds is still a polemic issue. Recent evidence at the molecular/cellular level indicates, however, that this type of heat generation may also exist among birds. The involvement of the sarcoplasmic reticulum calcium ATPase in non-shivering thermogenesis is discussed in-depth.     

In Vivo Ubiquinone Reduction Levels during Thermogenesis in Araceae

In vivo ubiquinone (UQ) reduction levels were measured during the development of the inflorescences of Arum maculatum and Amorphophallus krausei. Thermogenesis in A. maculatum spadices appeared not to be confined to a single developmental stage, but occurred during various stages. The UQ pool in both A. maculatum and A. krausei appendices was approximately 90% reduced during thermogenesis. Respiratory characteristics of isolated appendix mitochondria did not change in the period around thermogenesis. Apparently, synthesis of the required enzyme capacity is regulated via a coarse control upon which a fine control of metabolism that regulates the onset of thermogenesis is imposed.     

A Glutamatergic Hypothalamomedullary Circuit Mediates Thermogenesis,but Not Heat Conservation,during Stress-Induced Hyperthermia

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Brown Adipose Tissue Thermogenesis During Aging and Senescence

We have found that cold- and norepinephrine-induced brown adipose tissue (BAT) nonshiveringthermogenesis (NST) is significantly lower in old male Fischer 344 rats and is associatedwith the decreased ability of these animals to maintain homeothermy. This decline in BATthermogenesis is not as great in females. Although the mechanism(s) underlying this genderdifference in the age-related decrease in brown fat NST are not completely elucidated, theydo not appear to reflect decreased sympathetic neural activity of BAT in the older males vs.females. Rather, our investigations, strongly suggest that the blunted cold-induced heatproduction of BAT reflects less functional BAT. The fact that the older animals have less functionalBAT than do their younger counterparts may predispose them to the accumulation of excessbody fat. Our studies have also found that near the end of the natural life of these rats, theyenter a state of senescence that can be identified by spontaneous rapid body weight loss,resulting from decreased food intake. In this state, the rats are considerably more susceptibleto cold than are comparably aged presenescent (body weight stable) rats of the samechronological age. The greater hypothermia exhibited by the senescent vs. presenescent rats during coldexposure is associated with a significant reduction in the amount of functional brown fat andin the amount of heat each brown fat cell can generate. It is the intent of this review to discussthe findings of these investigations.     

Gene transfer during surgical procedures with molecular surgical suture

Over the last decades, there has been an explosion of interest in plasmid DNA for gene therapy with reports of their efficacy in the fight against cancer, vascular diseases, and inherited diseases caused by specific gene defects (Srivastava, 2003). DNA plasmids present several advantages over the use of recombinant viruses concerning their production and safety issues. Plasmid DNA vectors can be constructed easily and economically, and they are free of size constraints imposed by viral packaging, obviating the need for an infectious vector and lessening the likelihood of toxicity and immunogenicity (Davis, 1993). Plasmids have a relative low cost, long shelf life and allow repetitive administration of the therapeutic gene without generating an immune response against the delivery vector (Donnelly, 2003). Finally, plasmids can be injected directly into tissues, such as heart (Sarkar, 2002), muscle (Neumeister, 2001, Dan, 2000) and tumors (De Marco, 2003, Sasaki, 2002).     

Circadian Modulation of Cold-Induced Thermogenesis in the Golden Hamster

The relationship between the circadian and homeostatic control of body temperature was studied in golden hamsters maintained under a 14:10 LD cycle. Telemetric records of body temperature showed that body temperature oscillates daily with a low phase during the light section of the LD cycle and a high phase during the dark section. The low phase of the temperature rhythm was found to start two hours after lights on and to last about 8 hours. The high phase was found to start immediately after lights off and to last about 8 hours also. Metabolic heat production was measured by indirect calorimetry during the high phase and the low phase of the body temperature rhythm. Heat production in a thermoneutral environment was higher during the high phase of the body temperature rhythm than during the low phase, but cold-induced thermogenesis was greater during the low phase than during the high phase. This finding suggests that the autonomic thermoregulatory system is more responsive to cold stress during the low phase than during the high phase. Consequently, the daily oscillation of body temperature cannot be explained by an elevation of the thermoregulatory set point during the high phase of the rhythm. The homeostatic and circadian control of body temperature seem to be exerted separately from each other.