An on-ice aerobic maximal multistage shuttle skate test for elite adolescent hockey players.

The aim of this study was to design an on-ice test to predict V.O (2max) in ice hockey players. 30 elite hockey players (age 14.7 +/- 1.5 years) participated in this study. The oxygen uptake was assessed at submaximal and maximal velocities during an on-ice intermittent maximal multistage shuttle skate test with a 1-min/0.5-min work/rest ratio. The procedure consisted of skating back and forth on a distance of 45 m (stop and go) while following a pace fixed by an audible signal: initial velocity of 3.5 m . s (-1) with increments of 0.2 m . s (-1) every stage. The skating multistage aerobic test (SMAT) enabled the prediction of the V.O (2max) (ml . kg (-1) . min (-1)) from the maximal velocity (m . s (-1)) by means of the following regression equation: V.O (2max) = 18.07 x (maximal velocity) - 35.596 (r = 0.97, SEE = 3.01). The test-retest correlation was 0.92 and SEE = 0.56 stage (n = 23). Following the SMAT validation, an additional group of 112 elite male (age = 14.2 +/- 1.3 years) and 31 elite female (age = 14.0 +/- 1.2 years) ice hockey players performed both the 20-m shuttle run test and the SMAT, which was more specific and accurate to predict V.O (2max). The overall results suggest that the SMAT is highly specific, valid and reliable for the prediction of V.O (2max) of ice hockey players.

Estimate of the degree of inhomogeneity of the refractive index of dielectric films from spectroscopic ellipsometry.

Dielectric thin films often present microstructures that give rise to a variation of the refractive index with the distance from the substrate. We propose a method of analysis of ellipsometric data for homogeneous and slightly inhomogeneous films that are deposited on transparent substrates. Assuming a linear refractive-index gradient, we are able to determine not only the average index and the thickness but also the degree of inhomogeneity of the films by spectroscopic ellipsometry at variable angles of incidence. We apply this method to titanium dioxide films deposited on glass, which present different degrees of inhomogeneity depending on the preparation conditions.

Modification of guanine nucleotide-regulatory components in brain membranes. II. Relationship of guanosine 5'-triphosphate effects on opiate receptor binding and coupling receptors with adenylate cyclase.

Guanine nucleotides couple receptors to stimulate or inhibit adenylate cyclase as well as regulate binding of neurotransmitters. To explore the relationship between these different functions of guanosine 5'-triphosphate (GTP), rat brain membranes were preincubated in 50 mM sodium acetate, pH 4.5, which increased GTP regulation of 3H-opiate agonist binding. Assay of adenylate cyclase in the low pH-pretreated membranes revealed no loss of basal activity but a dramatic loss in fluoride- and guanylyl-5'-imidodiphosphate-stimulated activity, thus suggesting a loss in stimulatory guanine nucleotide coupling function. Manganese stimulation, which presumably occurs on the catalytic subunit of adenylate cyclase directly, was not affected by low pH treatment. In striatum, dopamine-stimulated adenylate cyclase was eliminated, but inhibition of adenylate cyclase by D-Ala2-Met5-enkephalinamide (D-Ala enk) was increased by low pH treatment. The effect of low pH on sodium fluoride-stimulated and D-Ala enk-inhibited adenylate cyclase could be reversed by addition of either cis-vaccenic acid or phosphatidylcholine to treated membranes, but the effect on GTP regulation of binding was not reversed by lipid incorporation. These results suggest that fundamental differences exist between membrane components which couple receptors to adenylate cyclase and those that regulate neurotransmitter binding.

Autoradiographic characterization of beta adrenergic receptors in coronary blood vessels and myocytes in normal and ischemic myocardium of the canine heart.

This light microscopic autoradiographic study was performed to test the hypotheses that (a) the density of beta adrenergic receptors (BAR) may differ in various components of the heart and (b) BAR in certain components of the heart may exhibit a selective response to pharmacologic and pathological stimuli. Blocks of canine left ventricle were frozen and tissue sections cut and incubated in (-)[3H]dihydroalprenolol (DHA) to label the BAR. For total and nonspecific binding, serial sections were incubated with and without 10(-5) M (+/-)propranolol. Scintillation spectrometry of sections demonstrated rapid binding, saturability, stereospecificity, a dissociation constant (KD) of 3.2 +/- 0.5 nM (SD) (n = 3), and a maximal binding of 31.3 +/- 3.1 fmol/mg of tissue protein. Isoproterenol was 12.5 times more effective than norepinephrine in displacing DHA. Sections incubated with 10(-5) - 10(-8) M metoprolol, a beta one selective antagonist, demonstrated a KD of 0.7 X 10(-6) M. For autoradiography, emulsion-coated coverslips were attached to the slides. After exposure, the slides were developed and stained, and grain density quantified. Specific BAR binding (n = 4 dogs) was 1,047 +/- 131 (SEM) grains/10(-2) mm2 for myocardial arterioles, 219 +/- 30 for myocardial arteries, 31 +/- 12 for the proximal left anterior descending coronary artery (LAD), and 231 +/- 34 for cardiac myocytes. Specific binding in the presence of 10(-5) M metoprolol was reduced approximately 75% for both arterioles and myocytes. However, at 10(-6) M metoprolol, the percent reduction in specific DHA binding was greater for myocytes (50%) than for arterioles (0%), and at 10(-7) M metoprolol, the percent reduction in specific DHA binding was 17% for myocytes with no reduction over arterioles. After 1 h of LAD occlusion, a selective increase (18%) in BAR density occurred over cardiac myocytes, but not over blood vessels in the ischemic myocardium. Thus, (a) specific BAR binding was five times greater in arterioles than in small arteries and myocardium and 34 times greater than in the proximal LAD; (b) BAR of myocytes were more sensitive than those of arterioles to displacement by the beta one selective antagonist, metoprolol; and (c) a selective increase in BAR occurs in cardiac myocytes but not in blood vessels after 1 h of ischemia in this experimental model.

Fatness and fat patterning among athletes at the Montreal Olympic Games, 1976.

Six skinfold measurements for male and female athletes (N=456) at the 1976 Montreal Olympic Games were analyzed to identify principal components of fatness and anatomical distribution of fat, i.e., fat patterning. As in non-athletes, two principal components were evident among the athletes. All skinfolds were correlated positively with the first component, which was termed fatness, while extremity fat measurements were correlated positively and trunk measurements were correlated negatively with the second principal component, which was termed an extremity/trunk ratio component. The two principal components accounted for about 85% of the variance. The first component was related to control variables in order of descending contribution to its variance as follows: sex (21-31%), sport (19%), ethnicity (3%), and age (1-3%). Likewise, the second component (extremity/trunk ratio) was related to the control variables: sex (20-35%), age (4-7%), ethnicity (2%), and sport (2%). Fatness is more influenced by sport and by inference training than is the anatomical distribution or patterning of fat on the extremities relative to the trunk. The latter characteristic may be more dependent on biological or environmental factors unrelated to sport and training.

Age at menarche, family size, and birth order in athletes at the Montreal Olympic Games, 1976.

Age at menarache, family size, and birth order in 145 athletes at the Montreal Olympic Games, 1976, were determined through interview. The athletes represented 27 countries, but 76% came from Canada, Great Britain and the United States. On the average, athletes attained menarche later than the general population in their respective countries, the mean age at menarche for the sample of 139 athletes who had attained menarche at the time of the survey being 13.66 +/- 0.12 years. Six athletes had not yet attained menarche at the time of the survey. Gymnasts, runners and rowers attained menarche significantly later than swimmers, but gymnasts, runners, rowers and jumpers/hurdlers did not differ significantly among themselves in the age at menarche. Correlations between age at menarche and family size and birth order were significant, but low to moderate in magnitude. Athletes from larger families tended to have, on the average, later menarche than those from smaller families, this trend being more apparent in rowers and track and field athletes.