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.     

Metyrapone - reduced cytochrome P-450 complex: A specific method for the determination of the phenobarbital inducible form of rat hepatic microsomal cytochrome P-450

Using homogeneous cytochrome P-450, we have shown that the well-known metyrapone-dithionite reduced cytochrome P-450 complex is specific for the cytochrome P-450b induced by phenobarbital. A linear relationship was observed between the absorbance of metyrapone-reduced cytochrome P-450 complex and the one of CO-reduced cytochrome P-450 complex, the usual method for the determination of cytochrome P-450. A method has been proposed for the specific determination of the cytochrome P-450b.     

Properties of the selenium-containing moiety of nicotinic acid hydroxylase from Clostridium barkeri

The nicotinic acid hydroxylase from Clostridium barkeri is a selenoenzyme, as evidenced by the copurification of selenium with enzyme activity. This conclusion is supported by data showing a 23-fold increase in nicotinic acid hydroxylase activity when C. barkeri was cultured in media supplemented with selenium. A labile, selenium-containing compound was released from the native protein by treatment with either chaotropic agents and heat or by heating alone. A stable selenium compound was formed when the enzyme was alkylated prior to denaturation. This compound had the same chromatographic properties as dialykyl selenide in a number of systems. The formation of dialkyl selenide upon alkylation is not consistent with the selenium moiety being selenocysteine. Thus, nicotinic acid hydroxylase represents a new type of selenoenzyme.     

Molecular control of rabbit follicular testosterone production. Role of protein and RNA after stimulation with luteinizing hormone.

The time and dose dependence of the relationship between uptake of labelled precursors into protein and RNA and production of testosterone by rabbit follicles was examined. Although testosterone production was stimulated by luteinizing hormone at concentrations between 0.1 and 10 microgram/ml, the uptake of [3H]leucine into protein was significant only when the concentration of luteinizing hormone was greater than 2.5 microgram/ml. Increased production of testosterone was observed within 15 min of stimulation with luteinizing hormone whereas uptake of [3H]leucine was only significant at 90 min. Puromycin (40 microgram/ml) and cycloheximide (10 microgram/ml) in the presence of luteinizing hormone inhibited the synthesis of both testosterone and protein. However, lower concentrations of puromycin (0.1, 1 and 10 microgram/ml) and cycloheximide (1 microgram/ml) had no effect on luteinizing hormone-induced testosterone production but significantly inhibited protein synthesis by 58, 37, 31 and 71%, respectively. Actinomycin D (20, 80 and 160 microgram/ml) alone and in combination with 5 microgram luteinizing hormone/ml severely inhibited uptake of [3H]uridine into RNA without affecting testosterone production. However, with 1 microgram actinomycin/ml, testosterone production was significantly (P less than 0.01) greater than in the presence of luteinizing hormone alone. These results cast doubt on the obligatory role of RNA and protein synthesis in rabbit ovarian follicular steroidogenesis.