GLYCERINATED SKELETAL AND SMOOTH MUSCLE: CALCIUM AND MAGNESIUM DEPENDENCE

Contractions of glycerinated skeletal (striated) and vascular (smooth) muscles are similar in their calcium dependence but differ in their magnesium dependence. The threshold concentration of free Ca(++) for contraction of either muscle was 1.8 x 10(-7)M; maximum tension developed when the concentration of free Ca(++) was slightly greater than 10(-6)M. The Mg concentration required for contraction of smooth muscle was at least ten times as great as that for skeletal muscle.

EFFECT OF ANAEROBIOSIS AND CELL POISONS ON GLUCOSE UPTAKE OF HEMIDIAPHRAGMS AND EPIDIDYMAL FAT PADS IN VITRO

An attempt has been made to repeat the observations that anaerobiosis, 2:4-DNP, and the sodium salts of cyanide, arsenite, arsenate, and salicylate all stimulate the glucose uptake of hemidiaphragms in vitro in a way that has been postulated to be analogous to the action of insulin. The glucose uptakes of hemidiaphragms and fat pads have been measured in bicarbonate and phosphate buffers. In no case did anaerobiosis stimulate glucose uptake. Anaerobiosis reduced but did not abolish the effect of insulin.

The effects of the cell poisons were diverse and appeared to be related to both the tissue used and the medium employed. The sodium salts of cyanide, arsenite, and arsenate stimulated the glucose uptake of hemidiaphragms in bicarbonate buffer, whereas, only arsenate was effective in phosphate buffer. When fat pads were incubated in bicarbonate buffer, arsenate and cyanide increased glucose uptake; in phosphate buffer only arsenate was effective. In addition, 2:4-DNP markedly inhibited the glucose uptake of hemidiaphragms in both bicarbonate and phosphate buffers but was without effect on the fat pads. Most of the cell poisons reduced or abolished the effect of added insulin.

These results are discussed with relation to the theory that insulin acts to divert energy away from a process that restricts the entry of glucose into the cell under basal conditions.

THE ELUTION OF S35-LABELLED C'1 FROM ANTIGEN-ANTIBODY-S35 COMPLEMENT PRECIPITATES

C′₁ haemolytic activity and radioactivity were detected in EDTA eluates of immune precipitates formed in the presence of either whole guinea-pig serum or euglobulin fraction labelled with ³⁵S in vivo. Eluted C′₁ and ³⁵S were fixed by sensitized sheep cells which subsequently lysed on exposure to guinea-pig C′ reagents lacking C′₁. The dissociated material contributed only a minute fraction of the protein N taken up by Ag—Ab precipitates from fresh C′.