Theophylline, fatigue, and diaphragm contractility: cellular levels of 45Ca and cAMP.

The relationship between variations in diaphragmatic contractility and corresponding changes in total tissue levels of 45Ca and adenosine 3',5'-cyclic monophosphate (cAMP) was examined. The contractile performance of perfused contracting rat diaphragms was manipulated with theophylline (10(-4) M), induced fatigue, or both. The increased contractility associated with theophylline was related to significant increases in 45Ca levels without changes in cAMP levels. Fatigue-diminished contractility was associated with increases in both 45Ca and cAMP levels. The increased 45Ca and cAMP levels associated with fatigue persisted, even in the presence of theophylline. Calcium channel blockade with 10(-4) M verapamil blocked the positive inotropic influence of theophylline as well as the theophylline-associated increase in 45Ca levels. Verapamil had no effect on either the fatigue-associated decreases in contractility or the fatigue-enhanced 45Ca uptake. The results of this study strongly suggest that the enhanced contractility associated with theophylline is related to its influence on cellular calcium metabolism. The elevated level of isotopic calcium measured in fatigued muscle probably represents calcium sequestered in the sarcoplasmic reticulum, the result of cAMP-enhanced Ca-adenosine triphosphatase activity.     

Ornithogenic soils of the cape bird adelie penguin rookeries,Antarctica

Summary The activity of soil-forming processes in the ornithogenic soils under the adelie penguin rookeries at Cape Bird, Ross Island, Antarctica, is limited by low temperatures and aridity, and is dominated by the influence of organic input from the penguins. A study of soil chemistry, biochemistry and biology of ornithogenic soils was carried out during the austral summers of 1981/1982 and 1983/1984. For the study, five sites were used to represent a relative age sequence in biological activity, from a presently occupied colony, a recently (previous season) abandoned colony, a re-worked guano site, and a long abandoned (many years) colony, to compare with a site that apparently had never been occupied by penguins. The sites were selected by the apparent age of the guano based on its morphology. Characteristics of the soils and guanos within the sequence are now described and illustrated, to complement the chemistry, biochemistry and biology of these sites, results of which have been published previously in this journal. A conventional radiocarbon age of 8 080±160 years BP (14C No. 5990) was obtained from a penguin bone in the long abandoned colony guano. A few temperature records indicated that soil temperatures were higher from soils with guano cover than from adjacent soils without guano cover. This difference in temperature should contribute to the increased biological and biochemical activity in the guano soils.