The effect of temperature on the contractile response of cardiac muscle from two frog species, Rana temporaria and Xenopus laevis, at two different calcium concentrations-I. At pH 7.7

Organochlorine residues in two Norwegian puffin (Fratercula arctica) colonies

Residue levels of the chlorinated hydrocarbons hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), alpha-, beta-, and gamma-hexachlorocyclohexane (HCH), oxychlordane, trans-nonachlor, aldrin, and dieldrin in adult puffins (Fratercula arctica) from two colonies in Norway (Røst 67 degrees 30'N and Hornøy 70 degrees 20'N) showing differences in breeding performance were compared in 1982. Furthermore, residue levels in puffin chicks from Røst in 1982, when breeding failed totally, were compared with the corresponding levels in 1983, when breeding was successful. Residue levels of chlorinated hydrocarbons were also measured in eggs from Røst 1982. An autoradiographic study of the distribution of [14C]HCB in adult puffins and chicks from Røst 1982 was included. In general, organochlorine contamination was low, and the results are interpreted to eliminate the organochlorines as a serious factor for impaired reproduction in the Røst colony. Significant differences between the two colonies are discussed in relation to geographical and nutritional aspects. The finding of significantly higher levels of organochlorines in organ tissue from puffin chicks from Røst in 1982 compared to the corresponding levels in 1983 may reflect the dramatic difference in nutritional status between the two years.

Studies on the calcium paradox phenomenon in cardiac muscle strips of poikilotherms

Compared with hearts of homoiotherms at their body temperature, isometric strips from hearts of poikilotherms (G. morhua, P. flesus, R. pipiens, R. temporaria, X. laevis and V. berus) at their physiological temperatures showed an insignificant calcium paradox. In all strips Tmax (maximal contractile tension at Lmax) decreased rapidly upon Ca2+-deprivation. Upon Ca2+-restitution the recovery of Tmax generally decreased--but seldom stopped--with increased length of the Ca2+-free period. Quantitative differences in recovery were observed between the species. P (resting tension) was either unchanged or decreased during Ca2+-deprivation. During Ca2+-restitution P increased initially and thereafter decreased again. In most species the recovery of Tmax was the same at 22 degrees C as at 12 degrees C. Even at 32 and 36 degrees C (V. berus and R. pipiens, respectively) Tmax recovered somewhat. Ultrastructural effects of the Ca2+-deprivation-restitution--studied on R. pipiens--were most marked in the mitochondria, especially at 22 degrees C. At 36 degrees C even the controls were damaged.

The effect of temperature on the contractile response of cardiac muscle from two frog species, Rana temporaria and Xenopus laevis, at two different calcium concentrations-II. At pH 7.0 and pH 6.6

1. Mechanical parameters were recorded from paced ventricular cardiac muscle strips of two amphibian species. Rana temporaria and xenopus laevis. 2. The strips contracted at pH 6.6 and 7.0 with either 1.6 or 3.0 mM Ca2+ while the temperature was changed from 5 to 30 degree C. 3. In the hearts of R. temporaria, but not in those of X. laevis, in increased Ca2+ concentration at low pH could compensate for the effect of lowered pH. 4. It is concluded that during high CO2 tension and/or low pH the myocardium of X. laevis was more temperature dependent, less Ca2+ dependent in the Ca2+ range examined and less sensitive to the pH and/or the CO2 tension during physiological temperature and Ca2+ concentration, than the cardiac muscle of R. temporaria.