Biomedical subjects

P Frykman

Publications and source records attributed to P Frykman.

4 recordsLinked to original sources

PubMed1992

Development of enzymes of glycolysis and gluconeogenesis in human fetal liver.

The activities of two key enzymes of glycolysis and two key enzymes of gluconeogenesis were measured in liver samples from 44 human fetuses ranging in gestational age from 20 weeks to term, from infants to 10 years and from adults from 21 to 58 years. Specific activities of both gluconeogenic enzymes, fructose-1,6-biphosphatase and phosphoenolpyruvate carboxykinase, increased throughout the period of fetal development examined, and rose to near adult levels after birth. The activities of both glycolytic enzymes, phosphofructokinase 1 and pyruvate kinase, were lower in fetal than in pediatric and adult samples. For both of these enzymes, there was a significant reduction in activity of livers from fetuses of 34-37 weeks' gestation. Both enzymes showed hyperbolic kinetics at 24 weeks' gestation, but this changed to sigmoid kinetics during the 34-37 weeks' period of low activity. The data indicate that during the last weeks of gestation, inhibition of the activities of these two glycolytic enzymes, coupled with the rise in the two gluconeogenic enzymes, may reflect a change in liver from a primarily glycolytic role in the first two trimesters to a gluconeogenic role shortly before birth.

Adult↗

PubMed1990

Hormonal and growth factor responses to heavy resistance exercise protocols.

To examine endogenous anabolic hormone and growth factor responses to various heavy resistance exercise protocols (HREPs), nine male subjects performed each of six randomly assigned HREPs, which consisted of identically ordered exercises carefully designed to control for load [5 vs. 10 repetitions maximum (RM)], rest period length (1 vs. 3 min), and total work effects. Serum human growth hormone (hGH), testosterone (T), somatomedin-C (SM-C), glucose, and whole blood lactate (HLa) concentrations were determined preexercise, midexercise (i.e., after 4 of 8 exercises), and at 0, 5, 15, 30, 60, 90, and 120 min postexercise. All HREPs produced significant (P less than 0.05) temporal increases in serum T concentrations, although the magnitude and time point of occurrence above resting values varied across HREPs. No differences were observed for T when integrated areas under the curve (AUCs) were compared. Although not all HREPs produced increases in serum hGH, the highest responses were observed consequent to the H10/1 exercise protocol (high total work, 1 min rest, 10-RM load) for both temporal and time integrated (AUC) responses. The pattern of SM-C increases varied among HREPs and did not consistently follow hGH changes. Whereas temporal changes were observed, no integrated time (AUC) differences between exercise protocols occurred. These data indicate that the release patterns (temporal or time integrated) observed are complex functions of the type of HREPs utilized and the physiological mechanisms involved with determining peripheral circulatory concentrations (e.g., clearance rates, transport, receptor binding). All HREPs may not affect muscle and connective tissue growth in the same manner because of possible differences in hormonal and growth factor release.

Adult↗

PubMed1989

Hypothalamic-pituitary-adrenal responses to short-duration high-intensity cycle exercise.

beta-Endorphin (beta-EP), adrenocorticotropin (ACTH), and cortisol plasma concentrations were examined before and after maximal exercise at four intensities [36, 55, 73, and 100% of maximal leg power (MLP)] by means of a computerized cycle ergometer. All intensities were greater than those eliciting peak O2 uptake for the individual subjects. Blood samples were collected at rest, immediately after exercise, and at 5 and 15 min postexercise. Significant (P less than 0.05) increases were observed at 36% MLP for beta-EP and ACTH immediately after exercise and at 5 and 15 min postexercise. Plasma cortisol increased at 36% MLP at 15 min postexercise. Blood lactate significantly increased at all postexercise collection points for exercise intensities of 36, 55, and 73% MLP and at 5 min postexercise for 100% MLP. beta-EP concentrations at 36% MLP were significantly correlated (r = 0.75) with capillary density (mm-2), and cortisol concentrations at 36% MLP were significantly correlated (r = 0.89) with percentage of type II muscle fibers. No other significant relationships were observed. These data show that brief, high-intensity exercise up to maximal power production results in a nonlinear response pattern in peripheral blood hormone concentrations. Furthermore, blood lactate levels do not appear to be related to hypothalamic-pituitary-adrenal hormone plasma concentrations at high exercise intensities.

Adrenocorticotropic Hormone↗

PubMed1987

Automated data collection and processing for a cycle ergometer.

A system is described for collection and processing of data from a cycle ergometer. Cycle pedals, specially made to withstand the extremely high forces exerted during maximal power cycling, contain transducers to measure pedal angle relative to the crank and foot forces both perpendicular and parallel to the pedal surface. An additional transducer monitors crank position. Output signals are conditioned, amplified, digitized by a 12-bit analog-to-digital converter, fed into a computer at 100 Hz/channel, and mathematically smoothed to attenuate noise. For each sample interval, foot force components perpendicular and parallel to the crank arm are calculated. Power generated on each crank revolution is determined from transducer information. Computer graphics display pedaling parameters vs. crank angle in both rectangular and circular format. Data files containing variables descriptive of pedaling force curves are produced to enable computerized statistical analysis of cycling performance.

Computer Graphics↗