Increased cholesterol efflux in apolipoprotein AI (ApoAI)-producing macrophages as a mechanism for reduced atherosclerosis in ApoAI((-/-)) mice.

The concentration of apolipoprotein (apo) AI in the artery wall is thought to enhance cellular cholesterol efflux and protect against atherosclerosis. It has been shown that although macrophages do not make apoAI, they respond to it by increased cholesterol efflux. We hypothesized that macrophage production of apoAI would increase cholesterol efflux and reduce atherogenesis. In this study, we produced mice expressing human apoAI under the control of the macrophage-specific scavenger receptor-A promoter (mphi-AI). Human apoAI was detectable in the serum HDL fraction of mphi-AI transgenic mice at concentrations too low to affect serum cholesterol or HDL levels. Immunoblotting showed the presence of human apoAI in transgenic macrophage culture supernatants, mostly as lipoprotein-free protein, with a small component associated with HDL-like particles. Atherosclerosis studies using apoAI((-/-)) mice transplanted with mphi-AI bone marrow showed that in the absence of macrophage-derived apoE, local expression of apoAI reduced diet-induced lesions in the proximal aorta. Additionally, mphi-AI macrophages showed a 40% increase in cholesterol efflux compared with control macrophages. These data support the hypothesis that apoAI production by macrophages in the artery wall is protective against atherosclerosis. This protection is likely mediated by increased cholesterol efflux and decreased foam cell formation in vivo.

The technique of administering enteral nutrition. Practical pointers for ensuring correct placement, avoiding complications.

Many critically ill patients require nutritional support to avoid protein-calorie malnutrition. Enteral administration is preferred because it is less expensive than parenteral nutrition and is associated with fewer complications. Nasogastric insertion is the route most often used; however, oral insertion is required for intubated patients. Administration of a promotility agent increases the chances that the feeding tube will migrate transpylorically; it also improves gastric emptying. To lower the risk of aspiration, check the level of gastric residuum before initiating, or increasing the level of, nutritional support. Diarrhea is not an indication for stopping enteral nutrition.

Allergens in Hymenoptera venom. XX. Isolation of four allergens from imported fire ant (Solenopsis invicta) venom.

Commercial Solenopsis invicta (Sol i) venom was fractionated by gel filtration and high-performance cation exchange chromatography. Four proteins were isolated and purified to homogeneity. The four proteins were tested with a panel of sera from patients allergic to fire ant venom; all proteins had significant allergenic activity. These proteins corresponded to four of the bands we previously reported to be allergenic by immunoblot analysis. Sol i I has an apparent molecular weight of 37,000 daltons and yields bands of 18,000, 16,500 and 14,000 daltons in sodium dodecyl sulfate-polyacrylamide gel electrophoresis; cation-exchange chromatography indicates that there are three charge forms. Sol i II has a native molecular weight of 28,000 daltons and appears to be easily cleaved into half molecules; it is a phospholipase structurally unlike either bee or wasp phopholipases. Sol i III has a native and denatured molecular weight of 26,000 daltons. Sol i IV has an apparent native molecular weight of 20,000 daltons and gives a single chain of 15,000 daltons in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sol i II and III are the major proteins in the venom; there are only small amounts of Sol i I and IV. All are significant allergens, and patients are found who react most strongly with each. Regression analysis of RAST data with highly purified allergens indicated that the IgE responses to the allergens were not related to each other. Amino acid compositions indicated that the four allergens were distinct and that the allergens were structurally different from each other. Four proteins identical to Sol i I to IV were isolated from hand-milked pure venom.

Allergens in Hymenoptera venom. XXI. Cross-reactivity and multiple reactivity between fire ant venom and bee and wasp venoms.

The relationships between fire ant venom and bee and wasp venoms were explored by studying sera from five groups of subjects. Group 1 included adults not allergic to any venoms and who were not exposed to fire ants. Group 2 included adults with fire ant exposure who were not allergic to venoms. Group 3 included patients with recent systemic reactions to fire ant venom. Group 4 included patients allergic to bee and vespid venoms with no fire ant exposure. Last, group 5 included patients allergic to bee and vespid venoms with fire ant exposure. None of the serum samples from group 1 was RAST reactive to fire ant venom, but 24% of those from group 2 were fire ant positive, as were 100% of those from group 3, 51% of those from group 4, and 87% of those from group 5. The RAST-positive patients in groups 2 and 5 were also skin test positive. RAST inhibition studies demonstrated cross-reactivity in some cases and multiple reactivity in others. The serum samples were further investigated via nondenaturing electrophoretic immunoblot studies and RAST with highly purified allergens. Serum samples from group 4 reacted to a single band on immunoblots and with only one of the four purified allergens from fire ant venom (Solenopsis invicta I, or Sol i I). Serum samples from groups 2, 3, and 5 showed various patterns of allergen reactivity. All serum samples from patients allergic to fire ant venom who also reacted to bee and/or vespid venoms by RAST contained IgE antibodies binding to Sol i I.(ABSTRACT TRUNCATED AT 250 WORDS)