Isolation and partial characterization of two porcine spleen ferritin fractions with different electrophoretic mobility.

Ferritin isolated from porcine spleen could routinely be separated in two fractions on nondenaturating gradient gels. Both fractions could be isolated with a purity of 96% when applied to two serially linked columns, each 200 cm in length, packed respectively with Sepharose 4B and Sepharose 6B. Both fractions were similar as judged by electron microscopy.

Effect of sarcomere length and filament lattice spacing on force development in skinned cardiac and skeletal muscle preparations from the rabbit.

Skinned cardiac and skeletal muscle freeze-dried preparations were activated in solutions strongly buffered for Ca2+. The response of single skeletal muscle fibres or thin strips of papillary muscle was investigated in relation to changes in Ca content of the perfusate. Sarcomere length was set and controlled during the experiments.

Caffeine suppresses length dependency of Ca2+ sensitivity of skinned striated muscle.

Freeze-dried skinned cardiac and skeletal muscle preparations of the rabbit were immersed in Ca2+-containing solutions with different concentrations of caffeine. The relation between the negative logarithm of the Ca2+ concentration (pCa) and normalized developed force was studied. The exact position of these Ca2+-sensitivity functions proved to be dependent on both the sarcomere length (monitored by means of laser diffraction) and caffeine concentration.