Identification of murine leukemia viral antigens detected on mouse cells by H-2 alloantisera

H-2 alloantisera have been previously reported to contain antibodies against murine leukemia viral antigens, but the nature of the viral antigens on mouse cells which interact with these antibodies has not been established. We have found that H-2 alloantisera recognize components of molecular weight 70 000-80 000 mouse lymphocytes and leukemia cells. These components were also detected by a goat antiserum against the murine leukemia virus (MuLV) glycoprotein (gp 70) and are therefore closely related to or identical with that viral protein. Although most H-2 alloantisera detected gp 70-like molecules on lymphocytes and leukemia cells from a great variety of mouse strains, only one H-2 alloantiserum was found to interact with a gp 70 component on cells from C57BL/10 and C57BL/6 mice. Animals such as C57BL/10 mice that lacked the component reacting with most H-2 alloantisera showed increased serum levels of anti-MuLV antibodies after injection of B10.A spleen cells having a gp 70 component detectable by other H-2 alloantisera. In contrast, strains with cells reactive to antiviral antibodies in the H-2 alloantisera had low responses to MuLV antigens after a similar immunization procedure. Serum levels of anti-MuLV antibodies in both groups of mice, however, were increased after injection of Freund's adjuvant. These observations suggest that anti-MuLV antibodies in mouse alloantisera may arise from a response to viral antigens on the immunizing cells and general stimulation of the immune system.

Subunit structure, cell surface orientation, and partial amino-acid sequences of murine histocompatibility antigens

Detergent and papain solubilized murine histocompatibility (H-2) antigens have been compared by gel exclusion chromatography, ultracentrifugation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and amino-acid sequence analysis. From these data, we propose a molecular model for the H-2 antigens that includes the size and arrangement of the subunits on the cell surface and in solution, and we provide evidence for the orientation of these molecules on the cell surface. Detergent solubilized H-2 antigens (molecular weight 116,000) consist of two disulfide-linked heavy chains (46,000 daltons) and two monocovalently associated light chains (12,000 daltons). Alkylation with iodoacetamide prior to extraction prevented the formation of a disulfide linkage between the two heavy chains. A water-soluble 51,000-dalton molecule (Fs) consisting of a 39,000-dalton fragment (FH) of the heavy chain and one intact light chain was obtained by papain digestion of cells or detergent extracts. Therefore, the disulfide linkage between the heavy chains is located in the remaining membrane-associated portion (Fm). Amino-acid sequence analysis of the FH fragment of H-2Kb by radiochemical techniques showed that it is identical to the detergent solubilized H-2Kb heavy chain in eight positions for the three amino acids tested. These data indicate that the fragment FH derives from the amino-terminus of the heavy chain and suggest that it projects outward from the cell surface, while the carboxyl-terminal region is associated with the plasma membrane. The described amino-terminal sequence data have been found constant in H-2Kb, H-2Kd, H-2Kk, H-2Db, and H-2Dd gene products. These data support the hypothesis that the K and D products of the major histocompatibility antigen complex have evolved by gene duplication.

pH gradient across the lysosomal membrane generated by selective cation permeability and Donnan equilibrium

The pH within isolated Triton WR 1339-filled rat liver lysosomes was determined by measuring the distribution of [14C]methylamine between the intra- and extralysosomal space. The intralysosomal pH was found to be approximately one pH unit lower than that of the surrounding medium. Increasing the extralysosomal cation concentration lowered the pH gradient by a cation exchange indicating the presence of a Donnan equilibrium. The lysosomal membrane was found to be significantly more permeable to protons than to other cations. The relative mobility of cations through the lysosomal membrane is H+ greater than Cs+ greater than Rb+ greater than K greater than Na+ greater than Li+ greater than Mg2+, Ca2+. The presented data suggest that the acidity within isolated Triton WR 1339-filled lysosomes is maintained by: (1) a Donnan equilibrium resulting from the intralysosomal accumulation of nondiffusible anions and (2) a selective permeability of the lysosomal membrane to cations.

Systemic haemodynamics in mild arterial hypertension before and after physical training

1. Five men with borderline, latent arterial hypertension of the hyperkinetic type were studied haemodynamically at rest and during dynamic exercise before and after a 6-week period of supervised physical training.

2. Tendencies to lower heart rate, cardiac output and arterial blood pressure, both at rest and during a standardized work-load, were observed after the training period, with significant differences between paired observations for the heart rate and mean arterial blood pressure during exercise. The systemic vascular resistance being unchanged, there was a certain trend to an increased widening of the arteriovenous oxygen difference, both at rest and during exercise.

3. The present findings from a small number of subjects indicate that physical conditioning of patients with latent hypertension of the hyperkinetic type contributes to a normalization of their circulation toward a normokinetic one, thereby also normalizing their blood pressure level and achieving a more economic energy expenditure in the cardiovascular system.