Effect of diurnal rhythm of body temperature on muscular work

The effect of the diurnal rhythm of body temperature on the metabolic and thermoregulatory response to moderate work was studied in eight healthy, adult males. Work bouts were conducted at the occurrence of each subject's morning minimum (approx 0700 h) and afternoon maximum (approx. 4600 h) diurnal rhythm of body temperature. No significant differences were found between these time periods for resting and exercise oxygen uptakes, respiratory minute volume, metabolic heat production, or heart rates. However, resting and exercise rectal, mean skin, and mean body temperatures, and evaporative heat loss were significantly higher in the afternoon. The importance of the diurnal temperature rhythm on modifying the response of body temperature to exercise is discussed.     

Metabolic responses to light arm and leg exercise when sitting

Seven male subjects performed progressive exercises with a light work load on an upper limb or bicycle ergometer in the sitting position. At any comparable work load above zero, arm exercise induced higher oxygen uptake, ventilation, heart rate, oxygen pulse, respiratory rate and tidal volume than leg exercise. At similar levels of VO2 above 0.45 1 X min-1, heart rate and ventilation were higher during arm exercise. A close linear relationship between carbon dioxide output and oxygen uptake was observed during both arm and leg exercises, the slope for arm work being steeper. The ventilatory equivalent for VCO2 (VE/VCO2) gradually decreased during both types of exercise. The ventilatory equivalent for VO2(VE/VO2) remained constant (arm) while it rose (leg) to a peak at 9.8 W and then gradually decreased. Ventilation in relation to tidal volume had a linear relationship with leg exercise, but became curvilinear with arm exercise after tidal volume exceeded 1100 ml. The observed differences in response between arm and leg exercises at a given work load appear to be influenced by differences in sympathetic outflow due to the greater level of static contraction of the relatively small muscle groups required by arm exercise.     

Enhanced leptin-stimulated Pi3k activation in the CNS promotes white adipose tissue transdifferentiation

The contribution of different leptin-induced signaling pathways in control of energy homeostasis is only partly understood. Here we show that selective Pten ablation in leptin-sensitive neurons (Pten^ΔObRb) results in enhanced Pi3k activation in these cells and reduces adiposity by increasing energy expenditure. White adipose tissue (WAT) of Pten^ΔObRb mice shows characteristics of brown adipose tissue (BAT), reflected by increased mitochondrial content and Ucp1 expression resulting from enhanced leptin-stimulated sympathetic nerve activity (SNA) in WAT. In contrast, leptin-deficient ob/ob-Pten^ΔObRb mice exhibit unaltered body weight and WAT morphology compared to ob/ob mice, pointing to a pivotal role of endogenous leptin in control of WAT transdifferentiation. Leanness of Pten^ΔObRb mice is accompanied by enhanced sensitivity to insulin in skeletal muscle. These data provide direct genetic evidence that leptin-stimulated Pi3k signaling in the CNS regulates energy expenditure via activation of SNA to perigonadal WAT leading to BAT-like differentiation of WAT.     

Understanding network concepts in modules

Background  

Network concepts are increasingly used in biology and genetics. For example, the clustering coefficient has been used to understand network architecture; the connectivity (also known as degree) has been used to screen for cancer targets; and the topological overlap matrix has been used to define modules and to annotate genes. Dozens of potentially useful network concepts are known from graph theory.     

Thoughts for food: brain mechanisms and peripheral energy balance

The past decade has witnessed dramatic advancements regarding the neuroendocrine control of food intake and energy homeostasis and the effects of peripheral metabolic signals on the brain. The development of molecular and genetic tools to visualize and selectively manipulate components of homeostatic systems, in combination with well-established neuroanatomical, electrophysiological, behavioral, and pharmacological techniques, are beginning to provide a clearer picture of the intricate circuits and mechanisms of these complex processes. In this review, we attempt to provide some highlights of these advancements and pinpoint some of the shortcomings of the current understanding of the brain's involvement in the regulation of daily energy homeostasis.     

Development of a versatile procedure based on natural transformation for marker-free targeted genetic modification in Streptococcus thermophilus

A versatile natural transformation protocol was established for and successfully applied to 18 of the 19 Streptococcus thermophilus strains tested. The efficiency of the protocol enables the use of in vitro-amplified mutagenesis fragments to perform deletion or insertion of large genetic fragments. Depending on the phenotype linked to the mutation, markerless mutants can be selected either in two steps, i.e., resistance marker insertion and excision using an adapted Cre-loxP system, or in one step using a powerful positive screening procedure as illustrated here for histidine prototrophy.