Review of Physiological Chemistry

The Effect of Profound Levels of Hypothermia (Below 14°C) on Canine Cerebral Metabolism

“…Since the QlO for most biologic reaction rates is between 2.0 and 3.0 (Harper, 1973), we formulated the following hypothesis: At temperatures between 37 and 27°e, the expected QIO value for eMROz of �2.2 represents primarily the direct effect of tem perature on biologic reaction rates, with little im pact imposed by alteration in neurofunctional activ ity. Between 27 and 17°e, in addition to the direct effect of temperature, there is a major neurofunc tional alteration, culminating in a near isoelectric EEG.…”

“…With rewarming to 37°C, cerebral metabolic variables returned to control It is commonly assumed that the basis for hypo thermia-induced cerebral protection is metabolic suppression. If one assumes that the temperature coefficient (QIO ) for CMR02 is similar to that for most biologic reaction rates of between 2.0 and 3.0 (Harper, 1973), the magnitude of protection clini cally observed at 15-18°C (Tharion et aI., 1982) ex ceeds that which would be predicted on a metabolic basis alone.In two previous studies we examined the effect of temperature on canine CMR02 over the tempera ture range of 14-37°C and demonstrated that the relationship is a complex one, resulting from the combined direct effect of temperature on biologic reaction rates and the effect this has on cerebral function as reflected by the EEG (Steen et aI., 1983;Michenfelder and Milde, 1991 877 levels. Brain biopsies taken at the end of the study yielded normal values for brain energy stores.…”

“…With rewarming to 37°C, cerebral metabolic variables returned to control It is commonly assumed that the basis for hypo thermia-induced cerebral protection is metabolic suppression. If one assumes that the temperature coefficient (QIO ) for CMR02 is similar to that for most biologic reaction rates of between 2.0 and 3.0 (Harper, 1973), the magnitude of protection clini cally observed at 15-18°C (Tharion et aI., 1982) ex ceeds that which would be predicted on a metabolic basis alone.…”

“…If one assumes that the temperature coefficient (QIO ) for CMR02 is similar to that for most biologic reaction rates of between 2.0 and 3.0 (Harper, 1973), the magnitude of protection clini cally observed at 15-18°C (Tharion et aI., 1982) ex ceeds that which would be predicted on a metabolic basis alone.…”

Nutritional homeostasis in carnivorous southern catfish (Silurus meridionalis): is there a mechanism for increased energy expenditure during carbohydrate overfeeding?

“…Generally speaking, the dietary protein had a higher SDA coefficient compared to dietary lipid and carbohydrate in studies on fishes (Tandler and Beamish, 1979;Jobling and Davies, 1980;Peres and Oliva-Teles, 2001). Harper (1971) suggested the SDA coefficients of protein, lipid and carbohydrate were 30%, 13% and 5%, respectively. According to this, the SDA coefficient should decrease with decreasing protein to energy ratio; but in this study, there was no significant difference in SDA coefficient among different dietary treatments.…”