Identification and characterization of two novel lymphocyte function-associated antigens, L24 and L25

We describe the function and cell distribution of two novel cell surface antigens, L24 and L25. These antigens are broadly distributed on human lymphocytes. Monoclonal antibodies specific for these molecules block lysis by Class I- and II-specific cytotoxic T lymphocytes, but do not affect any other T cell functions tested. Anti-L24 antibody immunoprecipitates a molecule composed of two disulfide-linked monomers of 140 kd each. Anti-L25 antibody immunoprecipitates three proteins of 150, 85, and 75 kd. The study of these and other function associated molecules may provide insight into mechanisms of cytotoxic T lymphocyte recognition and/or function.     

Anti-sense peptide recognition of sense peptides: direct quantitative characterization with the ribonuclease S-peptide system using analytical high-performance affinity chromatography

The ability of peptides coded by the anti-sense strand of DNA to interact specifically with peptides coded by the sense strand has been evaluated. The sense peptide examined, ribonuclease S-peptide, was immobilized on a coated silica affinity chromatographic matrix. Anti-sense peptides were synthesized on the basis of the anti-sense DNA sequence for the S-peptide region in native pancreatic ribonuclease A. The interaction of synthetic anti-sense peptides with sense peptide was quantitated from the degree of retardation during chromatographic elution on the sense peptide affinity matrix in buffers with and without soluble competing sense peptide. Sense/anti-sense peptide interactions were found to occur with significant affinities with each of two anti-sense 20-residue peptides of opposite amino-to-carboxyl orientations and to weaken progressively with decreasing length of anti-sense peptide. The substantial chromatographic retardation of anti-sense peptides was specific, since it decreased as expected with increasing concentration of the soluble competing S-peptide, could not be mimicked by the elution of several control peptides (including S-peptide itself) on the S-peptide matrix, and did not occur with a blank chromatographic matrix (no S-peptide attached). The stoichiometry of anti-sense peptide binding to immobilized sense peptide was found to be far greater than 1:1, and at least 4-5:1, for the two 20-mer anti-sense peptides. In sum, the analytical affinity chromatographic experiments have established quantitatively that anti-sense peptide binding to sense peptides occurs in the ribonuclease S-peptide case and have identified some structural elements that govern these interactions.(ABSTRACT TRUNCATED AT 250 WORDS)     

De novo and maintenance DNA methylation by a mouse plasmacytoma cell DNA methyltransferase

A DNA methyltransferase of Mr = 140,000 that is active on both unmethylated and hemimethylated DNA substrates has been purified from the murine plasma-cytoma cell line MPC 11. The maximal rate of methylation was obtained with maintenance methylation of hemimethylated Micrococcus luteus or M13 DNAs. At low enzyme concentrations, the highest rate of de novo methylation occurred with single-stranded DNA or relatively short duplex DNA containing single-stranded regions. Strong substrate inhibition was observed with hemimethylated but not unmethylated DNA substrates. Fully methylated single-stranded M13 phage DNA inhibited neither the de novo nor the maintenance reactions, but unmethylated single-stranded M13 DNA strongly inhibited the maintenance reaction. The kinetics observed with hemimethylated and single-stranded substrates could be explained if the enzyme were to bind irreversibly to a DNA molecule and to aggregate if present in molar excess. Such aggregates would be required for activity upon hemimethylated but not single-stranded DNA. For de novo methylation of duplex DNA, single-stranded regions or large amounts of methyltransferase appear to be required. The relative substrate preference for the enzyme is hemimethylated DNA greater than fully or partially single-stranded DNA greater than fully duplex DNA.     

Dietary soya lecithin decreases plasma triglyceride levels and inhibits collagen- and ADP-induced platelet aggregation

Elevated plasma lipid concentrations and increased platelet activation are risk factors in the development of atherosclerosis. Nine patients with type IIa hyperlipoproteinemia and nine patients with type IV hyperlipoproteinemia were given soya lecithin, 12 g/day, for 3 months. Plasma cholesterol and triglycerides were reduced by 15 and 23%, respectively, and HDL-cholesterol increased by 16% in the hypercholesterolemic patients. Platelet function was unchanged. In the hypertriglyceridemic patients, total cholesterol fell by 18%, triglycerides by 36%, and HDL-cholesterol increased by 14%. There was a 27% reduction in platelet aggregation (P less than 0.01). Seventeen hypertriglyceridemic patients then received increasing doses of soya lecithin for 1-month periods (6, 12, and 18 g/day). The optimal lipoprotein-lowering effect was achieved with a daily dose of 12 g soya lecithin per day. Both low-density lipoprotein and very-low-density lipoprotein levels were reduced, and HDL-cholesterol and apolipoprotein levels were reduced, and HDL-cholesterol and apolipoprotein A-I concentrations were increased. Platelet aggregation in response to collagen and ADP was significantly reduced, parallel with the reduction in triglyceride level. Soya lecithin supplementing the diet may be useful in the management of the hypertriglyceridemic patient.     

Notes on the food of feral mink Mustela vison in England and Wales

There is some apprehension about the possible effect of the introduced American mink Mustela vison upon the indigenous British fauna, either as a predator exerting new and excessive pressure upon native prey species, or as a carnivore competing for prey resources against native carnivores. Concern is also felt by preservers of game, and by keepers of small domestic animals (poultry and rabbits) about the mink's potential as a pest. To investigate the food habits of the mink in England and Wales the alimentary canals of 1165 trapped animals were examined, yielding 204 samples for analysis. The resulting information provides a general picture of the mink's diet, including seasonal variations. Comparisons were possible with similar work carried out in other countries, and with the diets of other British carnivores. Tentative conclusions were reached regarding the broad pattern of food relationships between the mink and other British animals, wild and domestic.