Tolerance of chronic hypercapnia by the European eel Anguilla anguilla

European eels were exposed for 6 weeks to water CO2 partial pressures (PCO\ub7) from ambient (approx.0.8\ub7mmHg), through 15\ub11\ub7mmHg and 30\ub11\ub7mmHg to 45\ub11\ub7mmHg in water with a total hardness of240\ub7mg\ub7l\u20131 as CaCO3, pH 8.2, at 23\ub11\ub0C. Arterial plasma PCO\ub7 equilibrated at approximately 2\ub7mmHg above water PCO\ub7 in all groups, and plasma bicarbonate accumulated up to 72\ub7mmol\ub7l\u20131 in the group at a water PCO\ub7 of 45\ub7mmHg. This was associated with an equimolar loss of plasma Cl\u2013, which declined to 71\ub7mmol\ub7l\u20131 at the highest water PCO\ub7. Despite this, extracellular acid\u2013base compensation was incomplete; all hypercapnic groups tolerated chronic extracellular acidoses and reductions in arterial blood O2 content (CaO\ub7), of progressive severity with increasing PCO\ub7. All hypercapnic eels, however, regulated the intracellular pH of heart and white muscle to the same levels as normocapnic animals. Hypercapnia had no effect on such indicators of stress as plasma catecholamine or cortisol levels, plasma osmolality or standard metabolic rate. Furthermore, although CaO\ub7 was reduced by approximately 50% at the highest PCO\ub7, there was no effect of hypercapnia on the eels\u2019 tolerance of hypoxia, aerobic metabolic scope or sustained swimming performance. The results indicate that, at the levels tested, chronic hypercapnia was not a physiological stress for the eel, which can tolerate extracellular acidosis and extremely low Cl\u2013 levels while compensating tissue intracellular pH, and which can meet the O2 requirements of routine and active metabolism despite profound hypoxaemia

Evidence of intestinal binding of prion protein in fish

Intestinal uptake of abnormal prion protein (PrPSc), the infectious agent involved in transmissible spongiform encephalopaties (TSEs), has been investigated in rainbow trout (Oncorhynchus mykiss). Experimental procedures were conducted in vitro, both by immunoblotting, in isolated everted intestine, after PrPSc perfusion, and by immunohistological PrPSc localization, in isolated intestine and pyloric caeca, after static perfusion of infected material. Results indicated that PrPSc has been bound by intestinal mucosa, though no evidences sustained PrPSc crossing of intestinal barrier

Fish as model in pharmacological and biological research

Fish represent the oldest and most diverse classes of vertebrates, comprising around the 48% of the known member species in the subphylum Vertebra. There are many scientific fields that use fish as models in research, including respiratory and cardiovascular research, cell culture, ecotoxicology, ageing, pharmacological and genetic studie