Glycerokinase activity was measured in the brown and white adipose tissues compared with that in the liver obese Zucker rats adapted or not adapted to cold. In white adipose tissue total activity was low but higher in the fa/fa rats than in the Fa/ones; cold adaptation did not modify this activity. In brown adipose tissue specific activity was higher than in white; specific activity was twice as high in the fa/fa rats than in the Fa/-. Cold-adaptation induced an increase in the activity in the Fa rats and a decrease in the fa/fa rats. The results are discussed with regard to the cold-induced increase in the energetic efficiency of the tissue.

Adaptation, Physiological↗

PubMedDate not supplied

Magnesium and thermoregulation. I. Newborn and infant. Is sudden infant death syndrome a magnesium-dependent disease of the transition from chemical to physical thermoregulation?

The sudden infant death syndrome (SIDS) remains a leading cause of death during the first year. The common epidemiological and pathological data which characterize SIDS include the curve for age at death (with 3 months as modal age), the stigmata of early maternal intrauterine injury, the seasonal predominance in winter, and the absence of an adequate cause of death at autopsy. Some data characterize risk factor subgroups: for example low socioeconomic level, environmental pollution, stress, and mistakes in baby care. Symptoms before death may be lacking, they may be common and non-specific, or rarely they may be acute, corresponding to "apparent life-threatening events" (ALTE). SIDS may be a magnesium-dependent disease of the transition from chemical to physical thermoregulation. This theory originates from a synthesis of our present knowledge of SIDS, maternal magnesium status, and thermoregulation in the baby. It is consistent with all the epidemiological and pathological prerequisites characterizing SIDS. It eliminates the hiatus between relatively minor thermal stress and induced lethal thermal stroke. Logical scepticism about the role of an implausible lethal superacute magnesium deficiency is no longer justified with regard to well established chronic marginal magnesium deficiency. Further experimental and clinical research will be interesting, i.e. ex vivo studies on brown adipose tissue (BAT) and magnesium deficiency under various conditions of thermal exposure. But even now the theory leads to three therapeutic consequences: (1) the need to define the importance of magnesium deficiency in diagnosis and treatment of ALTE; (2) an assessment of the use of new techniques of rewarming (i.e. extracorporeal circulation) in hypothermia cases to distinguish cot death from "apparent death"; (3) investigation of the prevention of SIDS with magnesium through a blinded and randomized multicentre prospective cooperative study of magnesium supplementation in pregnant and lactating women, followed not only in the mother, fetus, and neonate at birth, but also through the first year of life.

Body Temperature Regulation↗