Stimulation of synthesis of free chondroitin sulfate chains by beta-D-xylosides in cultured cells.

Beta-Xylosides stimulate 2- to 6-fold the synthesis of glycosaminoglycans by three types of nonconnective tissue cells (RG-C6, NB41A, and rat hepatoma cells, and normal and simian virus 40 (SV40)-transformed normal human skin fibroblasts. The effect, which is specific for the anomeric linkage and the glycone, is observed in the presence and absence of puromycin. Beta-Xylosides may substitute for xylosylated core protein as initiators of synthesis of chondroitin sulfate chains. No stimulation of synthesis of heparan sulfate was observed. With the use of a fluorogenic xyloside, 4-methylumbelliferyl-beta-D-xyloside, it was demonstrated that the free chondroitin sulfate chains secreted into the medium bear the xyloside at the reducing end, and have an average molecular weight of 16,500.     

The subunit fine structure of isolated, purified Na,K-adenosine triphosphatase : Freeze-fracture study

The ultrastructural features of a purified fraction of Na⁺,K⁺-adenosine triphosphatase (ATPase) isolated from dog kidney medulla were compared with those of the initial crude microsomal fraction in the purification sequence. Although both fractions consist of vesicular structures, the purified fraction is more homogeneous with respect to overall size and intramembrane protein particle size and distribution. Polyacrylamide gel electrophoresis profiles of both fractions reveal multiple proteins in the microsomal fraction but only two in the final purified fraction. The membranes of the pure fraction comprised one class of particles roughly 95–120 Å in diameter which represent the in vitro configuration of Na⁺,K⁺-ATPase.     

Antigenic relationships between Candida albicans and various yeasts as reflected by immunoglobulin-class specificity.

A group of guinea pigs was inoculated into the foot pads with a single dose of Candida albicans in complete Freund's adjuvant, while another group was similarly inoculated once in the foot pads but also several times intramuscularly, with Candida alone. All guinea pigs were bled at different intervals after immunization and sera were separated chromatographically into IgG and IgM fractions. In order to study the antigenic relationships as reflected by immunoglobulin-class specificity, IgG and IgM fractions and whole sera obtained from guinea pigs differently immunized, were tested for the presence of agglutinins against C. albicans, six other species of Candida, and species of the ascosporogenous genera Saccharomyces, Kluyveromyces and Schizosaccharomyces. The results show that (1) only IgG fractions of the different sera prepared contained the specific anti-C. albicans antibodies; (2) IgG and IgM fractions of the sera obtained from a single inoculation did not reveal a specific pattern expressing antigenic relationships of the yeast studied, and (3) the IgM fractions of the sera obtained from several inoculations had a more homogenous pattern of reactivity, since mainly these contained the agglutinins against the ascosporogenous yeast species.     

Lattice simulations of aggregation funnels for protein folding.

A computer model of protein aggregation competing with productive folding is proposed. Our model adapts techniques from lattice Monte Carlo studies of protein folding to the problem of aggregation. However, rather than starting with a single string of residues, we allow independently folding strings to undergo collisions and consider their interactions in different orientations. We first present some background into the nature and significance of protein aggregation and the use of lattice Monte Carlo simulations in understanding other aspects of protein folding. The results of a series of simulation experiments involving simple versions of the model illustrate the importance of considering aggregation in simulations of protein folding and provide some preliminary understanding of the characteristics of the model. Finally, we discuss the value of the model in general and of our particular design decisions and experiments. We conclude that computer simulation techniques developed to study protein folding can provide insights into protein aggregation, and that a better understanding of aggregation may in turn provide new insights into and constraints on the more general protein folding problem.     

Separation of endocytic from exocytic coated vesicles using a novel cholinesterase mediated density shift technique

Coated vesicles isolated from rat liver perfused with diisopropylfluorophosphate (DFP) to inactivate endogenous cholinesterase contained newly synthesized secretory cholinesterase after a 30 min recovery. The cholinesterase is found in coated vesicles of presumed endocytic origin following DFP treatment and perfusion for 3 min with galactosylated cholinesterase, a ligand for the asialoglycoprotein receptor. Highly enriched populations of endocytic and exocytic coated vesicles can be separated by use of a novel cholinesterase mediated density shift technique. The two coated vesicle classes have very similar polypeptide compositions but differ significantly in the ratio of cholesterol to phospholipid.     

Anti-DNA antibodies and the problem of autoimmunity

Several different classes of autoreactive antibodies are known to exist: those that are stimulated by bacterial infection (e.g., streptococci/rheumatic fever), those that react with tissue-specific antigens (e.g., thyrotropin receptor/Graves' disease), and those that bind to ubiquitous autoantigens (e.g., DNA/systematic lupus). The origin of the last kind of autoantibody is unknown, but it now seems that their production is an inherent property of the normal immune system. Indeed, it would appear that autoantibodies of the lupus variety actually have a physiological role in normal immunity. The development of the autoimmune disease may occur when there is an "escape" from the normal function of lupus autoantibodies.     

Introduction of active enzymes into intact Escherichia coli cells by means of liposomes. Phenotypic suppression of uvr A and pol A mutants

Summary Genetically deficient cells were supplied with the missing enzymes, purified from an independent source. The introduction of exogenous enzymes into the cells was effected by two independent methods: plasmolysis and liposome transformation. The latter procedure yielded a homogenous cell population which had been rescued from the defect even if the molecular weight of the enzyme amounted to 70 KD (Kilodaltons).