On the composition and characteristics of microvessels isolated from the rabbit and bovine brain

Brain capillaries (microvessels) were isolated from the rabbit and bovine brain. Extensive morphological examinations were performed at the light and electron microscopical levels. The relative contribution of endothelium (52%), basal membrane (32%) and pericytes (16%) to the composition of the microvessel was assessed. The ability of the endothelium from bovine brains to maintain a membrane potential, i.e. to accumulate the lipophilic cation [³H]TPMP, was shown. The transmitter catabolizing enzymes MAO and AchE were shown to be, and COMT and GABA-T not to be associated with the microvessel fraction isolated from rabbits.     

Ligand effects on the dephosphorylation of heart and skeletal muscle specific phosphorylases

Pseudo first order rate constants were determined for the dephosphorylation of heart and skeletal muscle specific phosphorylase a isoenzymes isolated from rabbit and pig using rabbit muscle phosphorylase phosphatase (mol. wt 34,000). The rate constants determined in the absence of ligands, were 4-5 fold lower for heart specific phosphorylases than for skeletal muscle specific ones. Glucose 6-phosphate (0.5-1 mM) enhances the rate of dephosphorylation of heart specific isophosphorylases 3-fold and suspends inhibition by 10(-5) M AMP, however, it has no significant effect on the dephosphorylation of skeletal muscle specific enzymes under the same conditions. Our data support characteristic functional differences between heart and skeletal muscle specific phosphorylases both in rabbit and pig.     

Compounds in urban air compete with 2,3,7,8-tetrachlorodibenzo-p-dioxin for binding to the receptor protein

Acetone extracts of filter-collected urban airborne particulate matter contain compounds which can competitively inhibit 2,3,7,8-[1,6-3H]tetrachlorodibenzo-p-dioxin (TCDD) binding to the rat liver TCDD-receptor protein. The concentration of conventional polycyclic aromatic hydrocarbons (PAHs) or chlorinated dioxins and dibenzofurans cannot account for more than 1-30% of the observed competition for [3H]TCDD binding to the receptor protein. The difference in potency between samples collected in urban areas during different periods of the year and a background sample is 25-400-fold. Collecting samples in the presence of increased concentrations of nitrogen dioxide, nitrous acid, nitric acid or ozone did not increase the amount of compounds with receptor affinity. However, with nitrogen dioxide and especially with nitric acid, a substantial increase of the mutagenic effects in the Ames Salmonella assay in the absence of mammalian activation as well as a degradation of several PAHs were noted. Affinity for the TCDD-receptor protein, mutagenicity in the absence of mammalian metabolic activation in the Ames Salmonella assay and PAH-content are characteristics of urban particulate matter showing the presence of compounds, that represent potential health risks. The compounds with affinity for the receptor may constitute a group of substances different from both conventional PAHs and direct-acting mutagens.     

Histocompatibility Gene Organization and Mixed Lymphocyte Reaction

TRANSFORMATION of allogenic lymphocytes in mixed cultures depends chiefly on an incompatibility between the lymphocyte donors at the major histocompatibility locus in man (HL-A), mouse (H-2) and rat (H-l)¹. Although the mouse H-2 locus can be divided into several regions each of which controls one or more antigenic specificities² and two or more subloci control HL-A antigens in man³, it is not known whether all parts of the major histocompatibility locus are equally important in eliciting transformation in mixed lymphocyte cultures. We now show that capacity to elicit lymphocyte transformation is different for different parts of the mouse H-2 locus.     

Interactions between Marek's Disease Herpesvirus and Avian Leucosis Virus in Tissue Culture

A GROUP B herpesvirus is important in the aetiology of Marek's disease, a highly contagious lymphoproliferative disease of chickens^1,2. Chicks inoculated with enveloped Marek's disease herpesvirus (MDHV), extracted from feather follicle epithelium of chickens with the disease, developed tumour-like aggregates of lymphoid cells in the viscera and frequently in the peripheral nerves^3,4. Cultures of chicken embryo fibroblast (CEF) cells infected with MDHV develop discrete foci of altered cells⁵. Our data show that MDHV infection of cultures of CEF cells, previously infected with an avian leucosis virus (RAV-2), results in both a reduction in the number of MDHV foci and an increase in the complement fixing avian leucosis antigen (COFAL)⁶ titre.     

Convergence of signals of various sensory modalities on the neurons of the sensorimotor zone of the rabbit cerebral cortex

The responses of the neurons to electrocutaneous stimulation, light flashes, and clicks in the cortical region of the motor representation of the rabbit forelimb were investigated by means of intra- and quasiintracellular recordings. In unanesthetized animals, in only eight out of 65 neurons did postsynaptic potentials (PSP) with a short (10–30 msec) latent period arise in response to light and sound. In 15 neurons, long latency (50–150 msec) responses to one or both of these stimuli were recorded. In most of the cells, short latency stable responses to stimulation of the contralateral forelimb and unstable long latency responses to light and/or sound, frequently of the nature of an increase in the background "synaptic noise," were observed. Under deep chloralose narcosis, the type of convergence was sharply changed: in most of the neurons, short latency responses to all the stimuli used appeared. However, the picture of convergence differed from that described earlier [5,6] for the motor cortex of the cat under chloralose narcosis. The responses to various stimuli were less similar to one another; the somesthetic modality substantially "predominated" (judging by the stability and nature of the interaction of the response).Brain Institute, Academy of Medical Sciences of the USSR. Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 5, pp. 474–483, September–October, 1971.     

The distribution of sulphate residues in the chondroitin sulphate chain

1. Electrophoresis of chondroitin sulphate, before and after partial degradation with testicular hyaluronidase, revealed charge heterogeneity of the degraded but not of the intact polymer. 2. Hyaluronidase-treated chondroitin sulphate was fractionated by gel chromatography. Two subfractions which were essentially monodisperse with regard to molecular weight (values of 8600 and 4800, respectively) were separated further by chromatography on Dowex 1. The resulting subfractions differed considerably with respect to their sulphate/disaccharide molar ratios. 3. Amino acid and neutral-sugar analyses of the Dowex 1 subfractions showed that the less sulphated fragments contained the carbohydrate-protein linkage region, whereas the high-sulphated fragments essentially lacked this constituent. It was concluded that chondroitin sulphate contains relatively less sulphate in the vicinity of the carbohydrate-protein linkage region than in the more peripheral portion of the polysaccharide chain.