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Biomedical subjects

D Hamar

Publications and source records attributed to D Hamar.

6 recordsLinked to original sources
PubMed2003

Effect of head-down bed rest on the neuroendocrine response to orthostatic stress in physically fit men.

The role of neuroendocrine responsiveness in the development of orthostatic intolerance after bed rest was studied in physically fit subjects. Head-down bed-rest (HDBR, -6 degrees, 4 days) was performed in 15 men after 6 weeks of aerobic training. The standing test was performed before, after training and on day 4 of the HDBR. Orthostatic intolerance was observed in one subject before and after training. The blood pressure response after training was enhanced (mean BP increments 18+/-2 vs. 13+/- 2 mm Hg, p<0.05, means +/- S.E.M.), although noradrenaline response was diminished (1.38+/-0.18 vs. 2.76+/-0.25 mol.l(-1), p<0.01). Orthostatic intolerance after HDBR was observed in 10 subjects, the BP response was blunted, and noradrenaline as well as plasma renin activity (PRA) responses were augmented (NA 3.10+/-0.33 mol.l(-1), p<0.001; PRA 2.98+/-1.12 vs. 0.85+/-0.15 ng.ml(-1), p<0.05). Plasma noradrenaline, adrenaline and aldosterone responses in orthostatic intolerant subjects were similar to the tolerant group. We conclude that six weeks of training attenuated the sympathetic response to standing and had no effect on the orthostatic tolerance. In orthostatic intolerance the BP response induced by subsequent HDBR was absent despite an enhanced sympathetic response.

Adult↗
PubMed2002

Effect of simulated microgravity on endocrine response to insulin-induced hypoglycemia in physically fit men.

Adaptation to microgravity is associated with alteration in some endocrine functions. In the present longitudinal study, the counterregulatory hormonal response to insulin-induced hypoglycemia (ITT, 0.1 IU/kg short acting insulin i. v.) was evaluated under simulated microgravity conditions in 15 physically fit subjects. ITT was performed at the beginning of the investigation, and again after completion of 6 weeks of endurance training and after a subsequent period of 4 days of head-down bed rest at a backward tilt of 6 degrees from the horizontal. Endurance training showed a significant increase in maximal aerobic capacity in previously well-trained subjects (increase by 12 %), as well as on attenuation of counterregulatory response of epinephrine to hypoglycemia. After 4 days of bed rest, basal concentrations of plasma norepinephrine was diminished (p < 0.002) and plasma renin activity was enhanced (p < 0.02). After bed rest, decreased responses of the two catecholamines (norepinephrine, p < 0.001; epinephrine, p < 0.001), growth hormone (p < 0.001), and cortisol (p < 0.05) were observed. Response of plasma renin activity after bed rest was increased (p < 0.01). This longitudinal study indicated that 4 days of bed rest in endurance-trained subjects induced increased response of PRA to hypoglycemia and attenuation of other counterregulatory neuroendocrine responses.

Adult↗
PubMed2001

Effects of dietary cholesterol restriction in a feline model of Niemann-Pick type C disease.

A feline model of Niemann-Pick disease type C (NPC) was employed to evaluate the effect of dietary cholesterol restriction on progression of disease. Two NPC-affected treated cats were fed a cholesterol-restricted diet beginning at 8 weeks of age; the cats remained on the diet for 150 and 270 days respectively. The study goal was to lower the amount of low density lipoprotein (LDL) available to cells, hypothetically reducing subsequent lysosomal accumulation of unesterified cholesterol and other lipids. Neurological progression of disease was not altered and dietary cholesterol restriction did not significantly decrease storage in NPC-affected treated cats. One NPC-affected treated cat had decreased serum alkaline phosphatase activity (ALP) and decreased serum cholesterol concentration. Liver lipid concentrations of unesterified cholesterol, cholesterol ester and phospholipids in NPC-affected treated cats were similar to those seen in NPC-affected untreated cats. Ganglioside concentrations in the NPC-affected treated cats and NPC-affected untreated cats were similar. Histological findings in liver sections from NPC-affected treated cats showed a diffuse uniform microvacuolar pattern within hepatocytes and Kupffer cells, in contrast to a heterogeneous macro/microvacuolar pattern and prominent nodular fibrosis in NPC-affected untreated cats. Similar differences in vacuolar patterns were seen in splenic macrophages. Although some hepatic parameters were modified, dietary cholesterol restriction did not appear to alter disease progression in NPC-affected kittens.

Alanine Transaminase↗
PubMed1995

Isokinetic cycle ergometer--application in sports medicine.

Paper deals with application of fully computerized isokinetic cycle ergometer with on-line registration of effective crank force in sports medicine, namely in functional diagnostic and rehabilitation. The system allows to carry out the time and position course analyses of effective pedal force and power produced at various revolution rates. Maximal or mean values of force and power produced by action of right and left leg may be used for the estimation of strength as well as for detection and quantitative assessment of lateral functional deficit for example due to injury. Short term bouts on isokinetic cycle ergometer may be applied as an effective means for the improvement of strength of lower extremities in patients as well as in competitive cyclists. The estimation of individual fluctuation of effective force (i.e. differences between maxima at horizontal and minima at vertical crank position) may be used for the evaluation of pedalling technique. Short term all-out efforts at various cadences allow to register not only peak and mean force and power at particular revolution rates, but also to estimate an optimal individual revolution rate, i.e. those allowing to produce highest power output. Such information can be employed for diagnostic assessment of anaerobic capabilities, namely in cyclists. Isokinetic cycling with self-controlled effort may be also used as a comfortable aerobic exercise. It may be concluded that isokinetic cycle ergometer represents a valuable diagnostic as well as therapeutic tool, which may be utilized in several areas of sports medicine.

Adult↗