Asbestos-induced decomposition of hydrogen peroxide.

Decomposition of H2O2 by chrysotile asbestos was demonstrated employing titration with KMnO4. The participation of OH radicals in this process was delineated employing the OH radical scavenger dimethyl sulfoxide (DMSO). A mechanism involving the Fenton and Haber-Weiss reactions as the pathway for the H2O2 decomposition and OH radical production is postulated.

Inhibition of lymphocyte capping by fatty acids in mouse and man.

Lipid-enriched diets have been related to a high cancer incidence in experimental animals for many years, and more recently, to assorted defects on the immune response. We investigated the effect of incubating human or murine (C3H/HEJ) lymphocytes with saturated (16:0) and unsaturated (18:1, 18:2, 18:3, 20:4) fatty acids (12 micrograms for each 10(7) cells), on the ability to cap with antihuman or antimouse anti-IgM, mu-chain specific antibody. Capping was also tested in obese (ob/ob, C57BL/6J) mice. Capping at 30 and 60 min was reduced by fatty acid incubation to 10-30% of control values in humans (p less than .001), and to 30% of control values in mice (p less than .01), regardless of degree of unsaturation. ob/ob capped normally. A lymphocyte membrane effect caused by fatty acids is observed in these experiments. Whether this is related to the dysimmunity caused by lipid diets cannot be assessed from our data, especially since all fatty acids, regardless of unsaturation, reduced the capping phenomenon.

Protection of organs during experimental ischemia.

Cell death complicating ischemia has profound local or systematic effects on the organism. We have tried to protect the small intestine and severed extremities from the effects of ischemia by using various drugs and techniques. Occlusion of the superior mesenteric artery for 1.5 hours in anesthesized, fed rats had a 97 per cent mortality. This was improved by pretreatment with methylprednisolone and amplicillin given together. Histologic preservation was seen in treated survivors. Chlorpheniramine, diphenylhydantion and methylprednisolone or amplicillin given alone had little, if any, effect. In dogs, reimplantation of severed extremities subjected to a 1.5 to two hour warm ischemic period resulted in toxic systemic picture, and 100 per cent mortality. This was improved by perfusion with Collins solution and postoperative injection of methylprednisolone. The incidence of gangrene was decreased. The judicious use of some drugs and preservation techniques may protect organs and the organism from the consequence of ischemia.

The immunoregulatory role of cholesterol and other lipids: a hypothesis.

Membrane lipids play an important role in cellular responses to exogenous signals. In immunocompetent lymphocytes, marked changes in the concentrations of membrane lipids occur following cell-antigen interaction. These changes lead to an increase in membrane fluidity, thus facilitating the microaggregation of receptor-antigen complexes. This event constitutes the inductive signal for lymphocytes. Lipid profile alterations leading to increased concentration of membrane cholesterol, of polyunsaturated lipids, or of both, bring about a decrease in membrane fluidity. The latter interferes with receptor displacement preventing delivery of an inductive signal to the responding cell. Interference with microaggregation is readily brought about in interactions involving low affinity antigens, such as tumoral antigens. We postulate that in hyperlipidemic and hypercholesterolemic states there is decreased immune responsiveness to weak antigens due to the aformentioned lipid profile alterations in the membranes of immunocompetent cells. The manner in which an increase in the concentration of the lipids mentioned can lead to decreased immune responsiveness and hence to an increased incidence of malignancies in hyperlipidemic and hypercholesterolemic states is the hypothesis presented in this paper.