Beginning Of Immersion Research Articles

Effect of physical fitness on vanillylmandelic acid excretion during immersion.

The effects of 4--6 h head-out immersion on excretion of vanillylmandelic acid (VMA), blood pressure and plasma volume were estimated in 8 endurance-trained (TR) and 8 untrained (UT) subjects. In the trained only a slight increase of VMA excretion occurred (4 h value: +2.7 +/- 10.9 ng/ml GFR), but there was a highly significant increase in the UT (+29.0 +/- 17.2 ng/ml GFR). VMA values during control experiments in supine position tended to decrease in both groups. Systolic and diastolic blood pressure fell by 20 mm Hg after beginning of immersion; in the UT plasma volume was reduced while it remained constant in TR. The results indicate that orthostatic intolerance (o.i.) after immersion is not effected by decreased sympathetic innervation of vessels; in contrast it seems to be partly compensated for by an elevated sympathetic activity at least in the UT. As a main cause for the post-immersion o.i. one might suggest a decrease in renin activity.

Estimation of low chlorpromazine concentrations by surfacing and sinking reaction of minnows (Gambusia affinis).

Surfacing and sinking reactions of minnows (Gambusia affinis) allow the determination of chlorpromazine in aqueous solutions down to concentrations of 0.1 μg/ml. In a given volume of solution, neither sex nor number of the fish per tube have any effect on their response to the low doses. A twenty-fold augmentation in volume causes a two-fold increase in sensitivity. The time elapsing, from the beginning of immersion until onset of surfacing, increases with decreasing drug concentration. Partial recovery from the drug is obtained after washing of fish with tap water. Adaptation occurs when the fish are immersed for more than 48 hrs.