Interspecific and intraspecific comparisons of the period locus in the Drosophila willistoni sibling species

The period (per) locus has received much attention in molecular evolution studies because it is one of the best studied "behavioral genes" and because it offers insight into the evolution of repetitive sequences. We studied most of the coding region of per in Drosophila willistoni and confirmed previously observed patterns of conservation and divergence among distantly related species. Five regions are so highly diverged that they cannot be aligned, whereas a region encompassing the PAS domain is very conserved. Structural and nucleotide polymorphism patterns in the willistoni group are not the same as those observed in previously studied species. We sequenced the region homologous to the highly polymorphic threonine-glycine repeat of D. melanogaster in multiple strains of D. willistoni, as well as in other members of willistoni group, and found an unusual amount of conservation in this region. However, the next nonconserved region downstream in the sequence is quite variable and polymorphic for the number of repeated glycines. The glycine codon usage is significantly different in this glycine repeat as compared to other parts of the gene. We were able to plot the directionality of change in the glycine repeat region onto a phylogeny and find that the addition of glycines is the general trend with the diversification of the willistoni group.      

Deficiency in the mitochondrial apoptotic pathway reveals the toxic potential of autophagy under ER stress conditions

Endoplasmic reticulum (ER) stress-induced cell death is normally associated with activation of the mitochondrial apoptotic pathway, which is characterized by CYCS (cytochrome c, somatic) release, apoptosome formation, and caspase activation, resulting in cell death. In this study, we demonstrate that under conditions of ER stress cells devoid of CASP9/caspase-9 or BAX and BAK1, and therefore defective in the mitochondrial apoptotic pathway, still undergo a delayed form of cell death associated with the activation of caspases, therefore revealing the existence of an alternative stress-induced caspase activation pathway. We identified CASP8/caspase-8 as the apical protease in this caspase cascade, and found that knockdown of either of the key autophagic genes, ATG5 or ATG7, impacted on CASP8 activation and cell death induction, highlighting the crucial role of autophagy in the activation of this novel ER stress-induced death pathway. In line with this, we identified a protein complex composed of ATG5, FADD, and pro-CASP8 whose assembly coincides with caspase activation and cell death induction. Together, our results reveal the toxic potential of autophagy in cells undergoing ER stress that are defective in the mitochondrial apoptotic pathway, and suggest a model in which the autophagosome functions as a platform facilitating pro-CASP8 activation. Chemoresistance, a common problem in the treatment of cancer, is frequently caused by the downregulation of key mitochondrial death effector proteins. Alternate stress-induced apoptotic pathways, such as the one described here, may become of particular relevance for tackling the problem of chemoresistance in cancer cells.     

Ventilatory anaerobic threshold in healthy children. Age and sex differences

The ventilatory anaerobic threshold (VAT) during graded exercise was defined as the oxygen uptake (VO2) immediately below the exercise intensity at which pulmonary ventilation increased disproportionally relative to VO2. Since VAT is considered to be a sensitive and noninvasive measure for evaluating cardiorespiratory endurance performance, the purpose of the present study was to determine normal values in children. We examined 257 healthy children (140 boys and 117 girls) varying in age from 5.7 to 18.5 years, during treadmill exercise. The data were analyzed in relation to sex and age. In boys the lowest VO2max (ml X min-1 X kg-1) was found in the youngest age group (5-6 year). In girls, on the other hand, no significant increase occurred with age. For VAT, expressed as ml O2 X min-1 X kg-1 or as a percent of VO2max, a significant decrease was found in boys and girls with age. This suggests an increase in lactacid anaerobic capacity during growth. In contrast to observations in adults, only low correlations were found between VO2max and VAT (r = 0.28 in boys and r = 0.52 in girls), which suggests that the development of the underlying physiological mechanism does not occur at the same rate in growing children. These data provide normal values for VAT that can be used for clinical exercise testing in the pediatric age group.