Sea urchin sperm head plasma membranes: characteristics and egg jelly induced Ca2+ and Na+ uptake.

Sea urchin sperm respond to egg factors with changes in the ionic permeability of their plasma membrane. It has been previously shown that plasma membranes isolated preferentially from sea urchin sperm flagella respond to egg jelly increasing their Ca2+ and Na+ uptake (Darszon et al. (1984) Eur.

The complement fragment C3d facilitates phagocytosis by monocytes.

Two receptors for fragments of C3 are described for human monocytes: CR1 and CR3, which bind C3b and iC3b, respectively. Recently a leucocyte receptor that binds C3dg has also been described, designated CR4. We previously reported that IgM-sensitized sheep erythrocytes that are heavily coated with C3d (EAC3d) can bind to human monocytes that have been cultured in fetal calf serum (FCS).

Response of isolated sperm plasma membranes from sea urchin to egg jelly.

The acrosome reaction in sea urchin sperm is induced by a glycoprotein jelly surrounding the egg and is accompanied by changes in ion permeability of sperm plasma membrane. In an attempt to learn what membrane components are involved in the response to jelly, we have begun to reassemble sperm membrane components into artificial membranes and assay for permeability changes mimicking those that occur in sperm. Jelly in sea water at concentrations that induce the acrosome reaction did not significantly change 45Ca2+ uptake of sonicated unilamellar vesicles made with soybean lipid only (ratio jelly:control uptake = 1.

Adrenal and liver participation in the rat's post-stress diabetic response.

Sixty minutes of restraint stress, preceded by chlorpromazine administration which stimulates somatotrophic hormone secretion (STH), produced an acute post-stress diabetic response (PDR) in normal-intact rats as well as in adrenalectomized rats. This PDR lasted 3 to 4 hours and was evaluated by glucemia and glucosuria determination and by the appearance of an insulin antagonist, alpha2-glycoprotein STH-dependent, called alpha2-inhibitor, which inhibits glucose uptake by isolated tissues. When tested in the suprahepatic blood of animals after stress it showed increased activity, both in normal and in adrenalectomized rats.