Previous studies have indicated that human immunodeficiency virus (HIV) is enclosed with a lipid envelope similar in composition to cell plasma membranes and to other viruses. Further, the fluidity, as measured by spin resonance spectroscopy, is low and the viral envelope is among the most highly ordered membranes analyzed. However, the relationship between viral envelope lipids and those of the host cell is not known. Here we demonstrate that the phospholipids within the envelopes of HIV-1RF and HIV-2-L are similar to each other but significantly different from their respective host cell surface membranes. Further, we demonstrate that the cholesterol-tophospholipid molar ratio of the viral envelope is approximately 2.5 times that of the host cell surface membranes. Consistent with the elevated cholesterol-to-phospholipid molar ratio, the viral envelopes of HIV-1RF and HIV-2-L were shown to be 7.5% and 10.5% more ordered than the plasma membranes of their respective host cells. These data demonstrate that HIV-1 and HIV-2-L select specific lipid domains within the surface membrane of their host cells through which to emerge during viral maturation.Electron microscopic studies (1-3) have demonstrated that the human immunodeficiency virus (HIV) is surrounded by a lipid envelope derived from the host cell plasma membrane. The initial report of the lipid composition of the HIV demonstrated that the envelope phospholipids were similar to those of other enveloped viruses and the erythrocyte plasma membrane (4, 5). The demonstration of high levels of phospholipids normally found in cell surface membranes [sphingomyelin (Sph), phosphatidylethanolamine (PE), phosphatidylcholine (PC), and phosphatidylserine (PS)] supported the electron microscopic observations depicting the enclosure of the viral capsid with a lipid envelope derived from the host cell plasma membrane during the budding process (4, 5). Further, these studies (4, 5) and others (6) indicated that HIV had a low lipid-to-protein (weight) ratio and a high cholesterol-to-phospholipid molar ratio (C/P ratio).Electron spin resonance (ESR) analyses of HIV have indicated that the flexibility of an incorporated spin-labeled probe molecule (a 5-nitroxide derivative of stearic acid; 5-NS) is restricted and that the viral envelope is among the most "ordered" membranes analyzed (5,7,8). Order parameters, which were calculated to be >0.7 (when spectral recordings were made at 37°C), were comparable to those of other enveloped viral systems exhibiting high order parameters (>0.7) and C/P ratios >1.0 (5, 9-11).Although all HIV isolates examined to date exhibit high C/P ratios and elevated order parameters, differences in phospholipid classes have been reported. For example, in HIV isolates LK013, F7529, and 4105 (5) and HZ321 (9) Sph is 25-28 mol %, whereas in isolates HTLV-IIIB and HTLV-The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 so...

900The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

The effect of chronic alcohol consumption on the skeleton was investigated in rats. The treated group received ethanol administered as 38% of caloric intake in a liquid diet (Sustacal) for 10 months. The control rats were pair weighted to the ethanol-treated animals throughout the study; the growth curves of the two groups were the same. The controls were given the same liquid diet except that dextrin:maltose (3:1) was substituted isocalorically for ethanol. Ethanol-treated rats did not differ from the pair-weighted controls in mean serum calcium, phosphorous, or creatinine. In contrast, serum magnesium was reduced (p less than 0.02) in alcohol-treated rats. Ethanol treatment also resulted in changes in the serum concentrations of vitamin D metabolites; serum 25-hydroxyvitamin D3 was increased (p less than 0.001), while serum 1,25-dihydroxyvitamin D3 was decreased (p less than 0.01). Tibial length was reduced in ethanol-treated rats (p less than 0.05) but there was no change in femoral length. Medullary area was increased in tibial diaphyses from alcohol-treated rats compared to weight matched control animals (p less than 0.01), indicating a net increase in resorption. The cross-sectional area of the tibial diaphysis of ethanol-treated rats was the same as the matched controls. Trabecular bone was decreased in the tibial metaphysis of ethanol-treated rats compared to the matched controls (p less than 0.05) indicating a net loss of trabecular bone. Ethanol treatment did not have an effect on the organic weight of the femur but the ash weight was reduced (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

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T1 and T2 relaxation times of agar phantoms containing L-dopa melanin and Fe3+ were measured under MRI conditions. Fe3+ shortened T1 and T2 relaxation times. Melanin influenced relaxation times only in the presence of Fe3+; thus, contrast in MR images of the basal ganglia may depend upon levels of both paramagnetic iron and neuromelanin.

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