Development of stratified normative data and reference equations for the timed up and down stairs test for healthy children 6-14 years of age.

OBJECTIVES: To generate normative data on healthy children aged 6-14 years for the timed up and down stairs (TUDS) test, and to provide reference equations. DESIGN AND SETTING: Cross-sectional study at two primary schools. PARTICIPANTS: Healthy children 6-14 years of age. MAIN OUTCOMES MEASURES: Anthropometric data and Minnesota Leisure-Time Physical Activity Questionnaire from children were collected before the start of the TUDS test. Heart rate, blood pressure and perceived exertion were measured at the beginning and at the end of the test. Two trials of the TUDS test were performed with 15-minute of rest on the same day and the better of the two trials was used in the analyses. The reference equations were established using the anthropometric variables as possible predictors of the TUDS test. RESULTS: Two hundred fifty eight children (125 boys and 133 girls) were assessed. The mean TUDS test score decreased significantly from 6 to 14 years of age in boys and girls alike, with statistically significant differences between the three age range groups. A significant difference was found between girls and boys in TUDS test score. The 56% of the variation in TUDS test score could be explained by age, height, and weight in boys [TUDSsec score=(9.967-(0.182×Ageyears)+(0.025×Weightkg)-(2.546×Heightm)], while 50% could be explained in girls [TUDSsec score=10.553-(0.194×Ageyears)+(0.019×Weightkg)-(2.406×Heightm)]. The inclusion of physical level activity increased the variability explained (boys: 59%; girls: 51%). CONCLUSIONS: TUDS score improved as the age of the children increased, with boys achieving better values than girls within each age group. TUDS test score can be easily predicted from age, height, and weight. The inclusion of the child's physical activity level increased the variance explained by the equation.

Unexpected behavior of irradiated spider silk links conformational freedom to mechanical performance.

Silk fibers from Argiope trifasciata and Nephila inaurata orb-web weaving spiders were UV irradiated to modify the molecular weight of the constituent proteins. Fibers were characterized either as forcibly silked or after being subjected to maximum supercontraction. The effect of irradiation on supercontraction was also studied, both in terms of the percentage of supercontraction and the tensile properties exhibited by irradiated and subsequently supercontracted fibers. The effects of UV exposure at the molecular level were assessed by polyacrylamide gel electrophoresis and mass spectrometry. It is shown that UV-irradiated fibers show a steady decrease in their main tensile parameters, most notably, tensile strength and strain. The combination of the mechanical and biochemical data suggests that the restricted conformational freedom of the proteins after UV irradiation is critical in the reduction of these properties. Consequently, an adequate topological organization of the protein chains emerges as a critical design principle in the performance of spider silk.

Molecular characterization of sea bass gonadotropin subunits (alpha, FSHbeta, and LHbeta) and their expression during the reproductive cycle.

Reproduction is controlled by two pituitary gonadotropin hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). This study reports the cloning, sequence analysis, and gene expression of gonadotropin (GTH) subunits from the European sea bass (Dicentrarchus labrax). The GTH subunits were cloned from a sea bass brain-pituitary cDNA library. The nucleotide sequences of the common alpha, the FSHbeta, and the LHbeta subunit cDNAs were 625, 521, and 591 base pair (bp) long, respectively, encoding for mature peptides of 94, 105, and 115 amino acids (aa), respectively. Sequence analysis showed that sea bass FSHbeta is more similar to higher vertebrate FSHbeta's (35-37%) than to LHbeta's (26-30%), whereas sea bass LHbeta is more similar to LHbeta's (40-53%) than to FSHbeta's (26-41%). Phylogenetic analysis of fish GTH sequences grouped the beta subunits into two groups, FSH and LH, distributed into four classes, corresponding to the accepted divisions of Elopomorphs, Ostariophysis, Salmonids, and Percomorphs. A dot-blot technique was developed to analyze GTH pituitary mRNA levels during the reproductive cycle of male sea bass. From October (initiation of gametogenesis) to February (spermiation), the expression of all three subunits in the pituitary increased in parallel, concomitantly with the gonadosomatic index (GSI) and the accumulation of LH protein in the pituitary, all values declining sharply at post-spermiation. This study demonstrates that the pituitary of sea bass contains two gonadotropin hormones and that both gonadotropins are probably involved in the control of gametogenesis, gamete maturation, and spermiation.

Regulation of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) gene expression by gonadotropin-releasing hormone (GnRH) and sexual steroids in the Mediterranean Sea bass.

The secretion of gonadotropins, the key reproductive hormones in vertebrates, is controlled from the brain by the gonadotropin-releasing hormone (GnRH), but also by complex steroid feedback mechanisms. In this study, after the recent cloning of the three gonadotropin subunits of sea bass (Dicentrarchus labrax), we aimed at investigating the effects of GnRH and sexual steroids on pituitary gonadotropin mRNA levels, in this valuable aquaculture fish species. Implantation of sea bass, in the period of sexual resting, for 12 days with estradiol (E2), testosterone (T) or the non-aromatizable androgen dihydrotestosterone (DHT), almost suppressed basal expression of FSHbeta (four to 15-fold inhibition from control levels), while slightly increasing that of alpha (1.5-fold) and LHbeta (approx. twofold) subunits. Further injection with a GnRH analogue (15 microg/kg BW; [D-Ala6, Pro9-Net]-mGnRH), had no effect on FSHbeta mRNA levels, but stimulated (twofold) pituitary alpha and LHbeta mRNA levels in sham- and T-implanted fish, and slightly in E2- and DHT-implanted fish (approx. 1.5-fold). The GnRHa injection, as expected, elevated plasma LH levels with a parallel decrease on LH pituitary content, with no differences between implanted fish. In conclusion, high circulating steroid levels seems to exert different action on gonadotropin secretion, inhibiting FSH while stimulating LH synthesis. In these experimental conditions, the GnRHa stimulate LH synthesis and release, but have no effect on FSH synthesis.