Maximal oxygen uptake in Danish adolescents 16-19 years of age

A random sample of schoolchildren, 119 boys and 153 girls, was tested in the fall of 1983. The data presented here are anthropometric data (height, weight, fat % and vital capacity) and oxygen uptake directly measured on a bicycle ergometer. The mean height and weight for boys were 179.1 cm and 67.7 kg, and those for girls were 168.0 cm and 59.6 kg. The mean fat content was 9.1% for boys and 19.1% for girls, and their mean vital capacities were 4.91 and 3.61 respectively. The boys had a high maximal oxygen uptake (51.7 ml X kg-1 X min-1) showing no reduction over the age span studied. The girls' maximal oxygen uptake was lower (overall mean 40.0 ml X kg-1 X min-1) with a small reduction from 16 to 19 years of age. When comparing maximal oxygen uptake per kg lean body mass in the two sexes, the boys had 18.4% higher values than the girls, indicating that girls of this age have the lower fitness level. The results of maximal aerobic power measurement in the boys compare well with findings from other investigations using direct measurements, indicating that the fitness of teenage boys is kept at a high level. Comparable data from various countries for girls show different pictures, but it appears that in general they have a low fitness level.     

On the heterogeneous glycosylation of the membranes of the trans Golgi network in rabbit luteal cells

In rabbit luteal cells the transmost element (G2) of the Golgi apparatus bears cytochemical resemblances to the limiting membrane of lysosomes and it was suggested that lysosomal membranes may originate from the above element. But in the normal Golgi apparatus it cannot be made out whether the considered molecules are indeed membrane bound. Perfusing the rabbit ovary with buffer containing monensin or ammonium chloride allowed to vesiculate the trans Golgi network (G2-G1) selectively. Controls showed a well-preserved ultrastructure. Parts of the limiting membrane of the vacuoles derived from the transmost reticulum (G2) were spiny coated and carried an osmiophilic inner layer. They also showed a heavy precipitate for acid phosphatase (AcPase) and were strongly stained with phosphotungstic acid (PTA) at low pH. By neutralizing the acidic groups, involved in the PTA-staining, it was possible to show that the same membranes were more heavily glycosylated. The MvB's and the limiting membrane of lysosomes showed the same staining characteristics. The other membrane domains revealed a gradient in PTA staining and in AcPase activity. It is concluded that the trans Golgi network (G2-G1) is an acidic compartment. The presence of differentially glycosylated membranes reveals a sorting mechanism for membranous components. The highly glycosylated membrane stretches seem to be involved in endocytosis and in the formation of lysosomal membranes.     

Voltage dependence of Na-Ca exchanger conformational currents.

Properties of a transient current (Icont) believed to reflect a conformational change of the Na-Ca exchanger molecules after Ca2+ binding were investigated. Intracellular Ca2+ concentration jumps in isolated cardiac myocytes were generated with flash photolysis of caged Ca2+ dimethoxynitrophenamine, and membrane currents were simultaneously measured using the whole-cell variant of the patch-clamp technique. A previously unresolved shallow voltage dependence of Icont was revealed after developing an experimental protocol designed to compensate for the photoconsumption of the caged compound. This voltage dependence can be interpreted to reflect the distribution of Na-Ca exchanger conformational states with the Ca2+ binding site exposed to the inside of the cell immediately before the flash. Analysis performed by fitting a Boltzmann distribution to the observed data suggests that under control conditions most exchanger molecules reside in states with the Ca2+ binding site facing the outside of the cell. Dialysis of the cytosol with 3',4'-dichlorobenzamil, an organic inhibitor of the Na-Ca exchange, increased the magnitude of Icont and changed the voltage dependence, consistent with a parallel shift of the charge/voltage curve. This shift may result from intracellular DCB interfering with an Na(+)-binding or Na(+)-translocating step. These observations are consistent with Icont arising from a charge movement mediated by the Na-Ca exchanger molecules after binding of Ca2+.     

Epstein-Barr virus transformation of human B lymphocytes despite inhibition of viral polymerase.

Epstein-Barr virus transformed human lymphocytes despite the presence of up to 500 microM acyclovir [9-(2-hydroxyethoxymethyl)guanine], a viral DNA polymerase inhibitor. The transformed cells contained multiple Epstein-Barr virus genome copy numbers. Functional viral DNA polymerase is probably not required for cell transformation and the initial amplification of the viral genome.