Central orchestration of peripheral nutrient partitioning and substrate utilization: implications for the metabolic syndrome

Energy homoeostasis is maintained through a complex interplay of nutrient intake and energy expenditure. The central nervous system is an essential component of this regulation, as it integrates circulating signals of hunger and satiety to develop adaptive responses at the behavioural and metabolic levels, while the hypothalamus is regarded as a particularly crucial structure in the brain in terms of energy homoeostasis. The arcuate nucleus (ARC) of the hypothalamus contains at least two intermingled neuronal populations: the neurons that produce neuropeptide Y (NPY); and the Agouti-related protein (AgRP) produced by AgRP/NPY neurons situated below the third ventricle in close proximity to proopiomelanocortin (POMC)-producing neurons. POMC neurons exert their catabolic and anorectic actions by releasing α-melanocyte-stimulating hormone (α-MSH), while AgRP neurons oppose this action by exerting tonic GABAergic inhibition of POMC neurons and releasing the melanocortin receptor inverse agonist AgRP. The release of neurotransmitters and neuropeptides by second-order AgRP neurons appears to take place on a multiple time scale, thereby allowing neuromodulation of preganglionic neuronal activity and subsequent control of nutrient partitioning - in other words, the coordinated regulation of conversion, storage and utilization of carbohydrates vs. lipids. This suggests that the function of AgRP neurons extends beyond the strict regulation of feeding to the regulation of efferent organ activity, such that AgRP neurons may now be viewed as an important bridge between central detection of nutrient availability and peripheral nutrient partitioning, thus providing a mechanistic link between obesity and obesity-related disorders.

Natural and synthetic oviposition stimulants forCatolaccus grandis (Burks) females

Oviposition behavior was elicited fromCatolaccus grandis (Burks) (Hymenoptera: Pteromalidae) females, an ectoparasitoid of the boll weevil,Anthonomus grandis Boheman (Coleoptera: Curculionidae), by smears of freshly cut cotton bolls or smears of extracts prepared with boll weevil damaged or undamaged cotton boll tissues. Oviposition behavior was also elicited fromC. grandis females by smears made withn-pentane,n-hexane,n-heptane, and isooctane. This is the first report of oviposition behavior elicited for any parasitoid by these short-chain saturated hydrocarbons (alkanes), introducing a new concept on the chemical mediation of parasitoid behavior during host selection. Oviposition behavior was also elicited fromC. grandis females by volatiles emanating from an artificial diet devoid of insect components that was specifically developed for the in vitro rearing of ectoparasitoids. The possible use of a synergistic combination ofn-hexane and diet to optimize the mechanized production of noncontaminated eggs is also discussed.

Postnatal Growth Patterns in a Chilean Cohort: The Role of SES and Family Environment

Objective. This study examined how family environmental characteristics served as mediators in the relationship between socioeconomic conditions and infant growth in a cohort of Chilean infants. Methods. We studied 999 infants, born between 1991 and 1996, from a longitudinal cohort which began as an iron deficiency anemia preventive trial. SES (Graffar Index), the Life Experiences Survey, and the Home Observation for Measurement of the Environment (HOME) were assessed in infancy. Using path analysis, we assessed the relationships between the social factors, home environment, and infant growth. Results. During the first year, weight and length gain averaged 540 grams/month and 6.5 cm/month, respectively. In the path analysis model for weight gain, higher SES and a better physical environment were positively related to higher maternal warmth, which in turn was associated with higher average weight gain. Higher SES was directly related to higher average length gain. Conclusions. In our cohort, a direct relationship between SES and length gain developed during infancy. Higher SES was indirectly related to infant weight gain through the home environment and maternal warmth. As the fastest growing infants are at risk for later obesity, new strategies are needed to encourage optimal rather than maximal growth.

Deciphering the genetic determinism of bud phenology in apple progenies: a new insight into chilling and heat requirement effects on flowering dates and positional candidate genes

The present study investigates the genetic determinism of bud phenological traits using two segregating F(1) apple (Malus × domestica) progenies. Phenological trait variability was dissected into genetic and climatic components using mixed linear modeling, and estimated best linear unbiased predictors were used for quantitative trait locus (QTL) detection. For flowering dates, year effects were decomposed into chilling and heat requirements based on a previously developed model. QTL analysis permitted the identification of two major and population-specific genomic regions on LG08 and LG09. Both 'chilling requirement' and 'heat requirement' periods influenced flowering dates, although their relative impact was dependent on the genetic background. Using the apple genome sequence data, putative candidate genes underlying one major QTL were investigated. Numerous key genes involved in cell cycle control were identified in clusters within the confidence interval of the major QTL on LG09. Our results contribute towards a better understanding of the interaction between QTLs and climatic conditions, and provide a basis for the identification of genes involved in bud growth resumption.