No abstract

The stress of routine transport practices on hatchery‐reared brook trout Salvelinus fontinalis, lake trout Salvelinus namaycush, and splake S. fontinalis × S. namaycush was evaluated by measuring changes in plasma levels of the stress hormone cortisol, the key stress metabolite glucose, and the plasma electrolytes Na+ and Cl–, and by measuring net ion and ammonia exchanges with the water in the transport tanks. We examined actual transport trips and standardized net confinement stress in the laboratory to quantify differences in stress response among the species. Brook trout were the least sensitive to both transport stress and net confinement, and responded in a similar fashion to both treatments. Splake responded to transport like brook trout but were the most sensitive to net confinement. Species differed most in their ability to maintain ion exchanges with the water under stress. Lake trout experienced ion losses during transport that were about 10‐fold higher than losses from brook trout and splake. Trip duration (3.5–11 h) had only a minor effect on physiological responses, and wide variations in loading density (6.9–17 kg/100L) had no significant effect. Increasing O2 levels in the water (due to oxygenation rather than aeration of the tanks) proved to be moderately stressful to brook trout, based on elevations in plasma cortisol levels. Our results permit an evaluation of the relative contributions of different transport variables to the transport stress imposed on salmonids.

Offspring of diabetic mothers have an increased incidence of neonatal polycythemia, decreased oxygen tension in cord blood at delivery, and elevated plasma erythropoietin levels at birth. Experimental fetal hyperinsulinemia has been associated with reduced fetal oxygen content and increased erythropoietin concentration. To test the hypothesis that prolonged fetal hyperinsulinemia results in increased fetal erythropoiesis and red cell volume during gestation, we infused insulin or placebo for 11 +/- 0.2 (+/- SE) days into chronically catheterized fetal sheep, beginning at 124 days of gestation. Indices of fetal erythropoiesis, red cell and blood volume were measured before and during the infusions. Insulin infusion resulted in increased plasma insulin, decreased plasma glucose, and decreased oxygen saturation values. The nucleated red blood cell (RBC) and RBC counts were significantly higher in the insulin- compared with the placebo-treated fetal sheep after 6-8 and 9-12 days of infusion, respectively. Although erythropoietin concentration did not differ between the groups, red cell volume expressed as a change from the base-line value was significantly higher in the insulin-treated group. We conclude that prolonged fetal hyperinsulinemia augmented erythropoiesis and red cell volume during late gestation in fetal sheep.