The H-2 dm1 mutation and Qa antigens

The effect of the H-2dm1 mutation on Qa-m2 expression was examined. The mutant strain B10.D2-H-2dm1 showed a fourfold increase in Qa-m2 expression when compared with the parental strain B10.D2. Qa-m2 molecules immunoprecipitated from B10.D2-H-2dm1, C57BL/10, and B10.D2 spleen cells were identical by two-dimensional (2-D) gel electrophoresis [isoelectric focusing (IEF) followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE]). It is likely therefore that the increased Qa-m2 expression is not due to gross structural alterations of the Qa-m2 molecule; in the present study, alternative explanations are discussed.     

Isolation and characterization of a collagen-binding glycoprotein from chondrocyte membranes

A collagen-binding glycoprotein was isolated from purified chick chondrocyte surface membranes by affinity chromatography on type II collagen-Sepharose. The purified glycoprotein has an apparent mol. wt. of 31,000 and binds to native chick collagen types I, II, III, V and M. Although it contains 30% carbohydrates, the majority of which is fucose, it is hydrophobic and soluble only in detergents. The integral membrane protein character of the 31-K protein became apparent from its ability to insert into lecithin vesicles. Liposome-inserted 31-K protein binds 125I-labelled type II collagen in the presence of 0.5 M NaCl, while detergent-solubilized 31-K protein is dissociated from type II collagen by 0.05-0.1 M NaCl. Electron microscopic studies employing the rotary shadowing technique indicate that 31-K protein particles bind to the ends of collagen molecules. We propose that this glycoprotein serves as anchorage site for extracellular collagen to the chondrocyte membrane and thus may be involved in cell-matrix interactions in cartilage.     

Analysis of the myogenic lineage in chick embryos

Abstract. Probabilistic and programmed lineage models for the generation of terminally differentiated skeletal muscle cells were tested in a clonal culture assay. Myogenic cells from the breast muscles of 10-day chick embryos were plated at an initial density of 250–1000 cells per 60 mm dish. Well-isolated individual cells were marked with a ring on the underside of the dishes, and clones arising from only these cells were followed. The presence of post-mitotic myoblasts in clones was assayed by peroxidase-antiperoxidase (PAP) and fluorescence immunocytochemical staining for both M-type creatine kinase (MCK) and skeletal muscle myosin heavy chain (MHC). Clones were fixed at intervals up to 76 h and were scored for the number of cells per clone and the number of MCK+ and MHC+ cells per clone. Quantitative and kinetic data were obtained indicating that post-mitotic myoblasts occurred overwhelmingly in homogeneous clones (all cells MCK⁺ and MHC⁺) which contained 2ⁿ cells ( n =0, 1, 2, 3, 4). This result does not support either probabilistic models of myogenesis or the existence of 'proliferative' mitoses at the end stages of differentiation. Rather, it indicates that myogenic precursor cells are a heterogeneous population, within which individual cells are predetermined to undergo a set number of symmetrical mitoses prior to yielding terminally differentiated progeny. These findings are strong evidence for a programmed, cell cycle-dependent lineage in the end stages of muscle differentiation.     

The accumulation of 65Zn and other Radionuclides by Tubificid Worms

Tubificid worms did not accumulate radionuclides bound to sediments, but did accumulate dissolved radionuclides. The level of accumulation of dissolved ⁶⁵Zn by the worms was dependent upon temperature and concentration of the radionuclide. This paper is based on work performed under United States Atomic Energy Commission Contract AT(45-1)-1830. This paper is based on work performed under United States Atomic Energy Commission Contract AT(45-1)-1830.     

Translation of pure feather keratin mRNA in a wheat embryo cell-free system

Highly purified feather keratin mRNA, prepared by dissociation of mRNP particles in Na dodecyl sulphate, was translated in a wheat embryo cell-free system with similar efficiency to rabbit globin mRNA and RNA purified from cucumber mosaic virus. The only detectable products of translation of the keratin mRNA were keratin chains, which were identical to native keratin chains as judged by several different criteria. These results support previous conclusions that the keratin mRNA can be obtained in a pure state.     

Does New Guinea cannibalism have nutritional value?

This paper examines the question of the nutritional value of cannibalism. Although other authors have concluded that the practice does not have such value, we argue that this cannot properly be determined except in the context of the total subsistence economy and local human ecology. The paper also presents a format for the empirical investigation of foodgetting and new ethnographic information about New Guinea cannibalism. Our major conclusion is that this practice does have nutritional value for certain human groups, specifically tropical peoples living at lowmedium population densities and exploiting a diverse range of animal foods.     

Separation and properties of human brain hexosaminidase C

Hexosaminidase C was separated from human brain supernatant by immunoadsorption of the A and B forms on to a column of immobilized antibody followed by preparative starch-block electrophoresis. There were some differences in the properties of hexosaminidase C preparations after each of these stages, shown by comparison of their heat-inactivation characteristics and filtration through Bio-Gel P-200. The C form prepared by both separation steps had properties which differed markedly from those of the A and B isoenzymes; its molecular weight was much larger, greater than 200000, it had optimum activity between pH6 and 7 and could not be successfully eluted from DEAE-cellulose, even with high salt concentrations, or from Sephadex G-200. These results seem to support the proposal that the C form is under a separate genetic control from the others.     

Evidence for a Reductive Pathway for the Anaerobic Metabolism of Benzoate

Evidence is presented for a reductive pathway for the anaerobic metabolism of benzoate by Rhodopseudomonas palustris.     

Influence of Bacterial Infection on Serum Enzymes of White Rats

Infection of white rats with Francisella tularensis (Pasteurella tularensis) and Salmonella typhimurium and exposure to the endotoxin of S. typhimurium stimulated significant increases in various serum enzymes including aldolase, lactate dehydrogenase, phosphohexose isomerase, isocitrate dehydrogenase, and glutamate-oxalacetate transaminase. The rates of changes in enzymatic activity after infection were directly related to the size of infecting dose and to the type of infective agent employed. Tularemic infection stimulated excessive changes in enzyme activity, whereas salmonellosis and endointoxication elicited less pronounced alterations of relatively short duration. Changes observed in serum enzymes after exposure to these agents reflect the severe liver damage and extensive systemic involvement noted in tularemia as opposed to more localized and less intensive tissue damage occurring during salmonellosis and endointoxication.