Partial restoration of impaired alpha1-adrenergic responsiveness in parotid cells of aged rats by S-adenosylmethionine treatment

The age related decrease in alpha₁-adrenergic stimulated inositol 1,4,5 trisphosphate (IP₃) production in parotid cells of aged rats can be partially restored by treatment with S-adenosylmethionine (SAM). This effect is completely blocked by S-adenosyl homocysteine (SAH) and occurs in association with an increase in the conversion of phosphatidylethanolamine to phosphatidylcholine and a decrease in membrane viscosity. In contrast, SAM treatment actually inhibits stimulated IP₃ production in cells of young rats. The membrane viscosity of these cells is lower than that of those from aged rats. Although conversion of phosphatidylethanolamine to phosphatidylcholine is enhanced, no further decrease in membrane viscosity is elicited in young cell preparations. These findings suggest that age changes in the membrane environment may result in impaired alpha₁-adrenergic signal transduction and that such alterations may be at least partially reversible by SAM treatment.     

Enhancement of human immunodeficiency virus type 1 envelope-mediated fusion by a CD4-gp120 complex-specific monoclonal antibody.

The entry of human immunodeficiency virus type 1 (HIV-1) into cells is initiated by binding of the viral glycoprotein gp120-gp41 to its cellular receptor CD4. The gp120-CD4 complex formed at the cell surface undergoes conformational changes that may allow its association with an additional membrane component(s) and the eventual formation of the fusion complex. These conformational rearrangements are accompanied by immunological changes manifested by altered reactivity with monoclonal antibodies specific for the individual components and presentation of new epitopes unique to the postbinding complex. In order to analyze the structure and function of the gp120-CD4 complex, monoclonal antibodies were generated from splenocytes of BALB/c mice immunized with soluble CD4-gp120 (IIIB) molecules (J. M. Gershoni, G. Denisova, D. Raviv, N. I. Smorodinsky, and D. Buyaner, FASEB J. 7:1185-1187 1993). One of those monoclonal antibodies, CG10, was found to be strictly complex specific. Here we demonstrate that this monoclonal antibody can significantly enhance the fusion of CD4+ cells with effector cells expressing multiple HIV-1 envelopes. Both T-cell-line-tropic and macrophage-tropic envelope-mediated cell fusion were enhanced, albeit at different optimal doses. Furthermore, infection of HeLa CD4+ (MAGI) cells by HIV-1 LAI, ELI1, and ELI2 strains was increased two- to fourfold in the presence of CG10 monoclonal antibodies, suggesting an effect on viral entry. These findings indicate the existence of a novel, conserved CD4-gp120 intermediate structure that plays an important role in HIV-1 cell fusion.     

Fatty acid composition of phospholipids of myelin and synaptosomal proteolipid complexes from vertebrate brain.

1. Fatty acid composition of five main phospholipids of vertebrate brain myelin and synaptosomal proteolipids and membranes was studied. 2. Higher content of monoenoic and lower content of saturated and polyenoic fatty acids was found to be characteristic of phospholipids from myelin and myelin proteolipids as compared to phospholipids from synaptosomal proteolipids and membranes of vertebrates (from fishes to mammalians). Fatty acid composition of phospholipids of proteolipid complexes and of the membranes, from which they were isolated, were found to be similar in various species studied. 3. Microviscosity was found to be higher in myelin as compared to synaptosomal membranes of frog Rana temporaria and in rabbit Lepus cuniculus. It appears to be due to the difference in proteolipid content and in lipid composition of myelin and synaptosomal membranes.     

European checkerspots (Melitaeini: Lepidoptera,Nymphalidae) are not aposematic – the point of view of great tits (Parus major)

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The determination of lipopolysaccharide admixtures in protein preparations

A new method for the determination of lipopolysaccharide (LPS) admixtures in protein solutions has been developed. The method includes the periodate oxidation of LPS, biotinylation with biotin hydraside, immobilization on a nitrocellulose membrane and the development of biotinylated LPS in the streptavidin--alkaline phosphatase system. Proteins are previously removed from the solution by treatment with hot phenol. Development with the use of 5-bromoinodyl phosphate and nitrotetrazolium blue makes it possible to detect about 30 pg of LPS immobilized on the nitrocellulose membrane.     

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