Biomedical science最新文献

Proteins of human chorionic villi from the first trimester of pregnancy were studied by high-resolution two-dimensional gel electrophoresis. One hundred and ninety-eight proteins spots were identifiable and allowed the plotting of a two-dimensional map of the proteins of human chorionic villi from the eighth week of pregnancy. The proteins of human chorionic villi from the twelfth week of gestation and of villi from term placenta were also studied. A comparison of protein compositions at different gestational ages was made. The findings from two-dimensional electrophoretic analysis of villi proteins have been summarized and stored in a computer data base.

The interactions of tumour cells with membrane molecules of T-cell subsets, as well as methods directed towards the enhancement of antitumour immunity, are reviewed in this paper. Special attention is given to the cytotoxic function of lymphokine-activated tumour-infiltrating lymphocytes, to tumour-specific suppressor T cells, and to various causes of decreased expression of histocompatibility antigens on the surface of tumour cells. The different mechanisms underlying selective antitumour immunodeficiencies and possible approaches to the correction of immunodeficiency, to the enhancement of tumour immunogenicity, and to specific immunotherapy are considered in more detail.

A comparison of a new method of searching for functionally important sites in proteins and peptide hormones with a previously published method is presented. All methods are based on information theory that holds that rare oligomers contain much information and, thus, are likely to be important for specific functional activity. Twenty-five proteins and peptide hormones with known receptor-binding sites were studied; the new method showed good predictive ability. However, taking into account short-range sequential preferences in protein structures, the predictive ability of methods based on information theory, at least for the receptor-binding site predictions, was not greatly improved.

Six monoclonal antibodies to the components of the rabbit multienzyme aminoacyl-tRNA synthetase complex were generated and characterised. Two, F7 and F31 were directed against arginyl-tRNA synthetase, two, F8 and F25 against glutamyl-tRNA synthetase, and two, F6 and F12 recognised 38 and 43 kDa polypeptides, respectively. All antibodies were species-specific and failed to affect the activity of the respective enzymes.

The isoform composition and type of Na(+)-K+ ATPase functional complexes in a number of calf brain membranes were determined. Functionally active enzymes were obtained from microsomes from calf cerebral cortex grey matter, brain stem, and stem axolemma by two different methods involving (1) the selective removal of contaminating proteins according to Jorgensen (1974) and (2) the selective solubilization of the enzyme with subsequent reformation of the membrane structure according to Esmann (1988). The protein components of the isolated preparations were separated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, transferred to an immobilon membrane [poly(vinylidene difluoride) membrane] by electroblotting, and subjected to structural analysis. The N-terminal amino acid sequences of the alpha- and beta-subunits (alpha 1, alpha 2, alpha 3, beta 1, beta 2) and the isoform composition and type of alpha n beta m functional complexes present in the different microsome preparations were determined. Brain grey matter Na(+)-K+ ATPase was characterized by biphasic kinetics with respect to ouabain inhibition (Ki approximately 10(-6) M and -1.5 x 10(-8) M) and comprised a set of isozymes with subunit compositions of alpha 1 beta 1, alpha 2 beta m, and alpha 3 beta m (where m = 1 and/or 2), with the alpha 1 beta 1 form clearly predominating. Na(+)-K+ ATPase from brain stem and axolemma consisted mainly of a mixture of the isozymes alpha 2 beta 1 and alpha 3 beta 1, which had identical ouabain inhibition constants (Ki approximately 10(-7) M), but in the axolemma there was a large quantity of the alpha 3 beta 1 isozyme. The catalytic subunit alpha 3 within the untreated enzyme complex had increased sensitivity towards endogenous proteolysis. It was therefore possible to isolate enzyme containing the alpha 3 catalytic subunit only in the presence of the protease inhibitor diisopropyl fluorophosphate (DIPF). In the absence of this inhibitor there was a specific fragmentation of the polypeptide chain, resulting in the formation of an extremely stable N-terminal fragment of molecular mass 55 kDa.

Immunofluorescent flow cytometric examination of one hundred and eighty-five children with different primary immunodeficiency syndromes and sixty-nine control patients revealed twenty-six cases with a bimodal distribution of antigens CD5 and CD7. Such abnormalities were most frequently found in patients with total antibody deficiency, namely those with common variable hypogammaglobulinaemia (10/24 patients) and congenital agammaglobulinaemia with lack of B cells (10/40), but were never seen in normal controls. Two-colour flow immunofluorescence demonstrated that antigen CD4 was expressed only on intensely fluorescent CD5+ cells, irrespective of the immunodeficiency state. Antigen CD4 was detected on cells with both high and low expression of antigen CD7, but a small percentage (2%-5%) of CD4+ lymphocytes did not belong to the CD7+ population. Antigen CD8 was found equally on intensely and weakly fluorescent CD5+ and CD7+ cells. In some immunodeficient patients suffering from ataxia-telangiectasia (12/36) and in some with Wiskott-Aldrich syndrome (2/6) there was a significant excess (greater than 20%) of CD7+ over CD5+ cells. In these patients a considerable number of the CD8+ cells were not part of the CD5+ population, but were always part of the CD7+ population. Cell populations with the phenotype CD5-, CD7+ consisted mainly of lymphocytes showing weak expression of antigen CD8.

A fibre-optic oxygen sensor is described which is based on an oxygen-sensitive luminescent film made from platinum octaethylporphyrin and polystyrene. The luminescence and quenching characteristics of such films were studied for their use in a fibre-optic oxygen biosensor. A prototype oxygen sensor was made from this material, and was tested in aqueous solutions and in the gaseous phase at physiological oxygen concentrations. Measurements of luminescence intensity and decay time were employed to determine oxygen concentration from luminescence quenching. The main working characteristics of this prototype oxygen sensor were studied.

Genome sizes of eleven strains of eight species of Mollicutes Mycoplasmataceae were investigated by pulsed-field gel electrophoresis. Mycoplasma genomic sizes were determined from the sum of the sizes of fragments obtained after digestion of genomic DNA with restriction endonucleases. The sizes of the fragments were determined by comparison of their electrophoretic mobilities with those of lambda DNA concatemers. Specific restriction endonucleases were chosen so that after digestion three to ten fragments were obtained. The values for genome size derived by this method showed a continuous distribution that ranged from approximately 650 kb for Mycoplasma hyorhinis BTS-7 to 1600 kb for Acholeplasma laidlawii FHM.

Exposure to X rays (20 impulses of 4 Hz frequency, total dose 0.6-1.1 mGy) increased the epileptic activity of a focal area, which was produced in the visual cortex of rabbit brain by freezing with liquid nitrogen, and by stimulating with flashes of light at frequencies of 5-6 Hz. The number of seizure complexes during photostimulation for 5 s increased by 80% compared with the initial level, and this effect continued for 15 min. In control animals (with no epileptic foci), a decrease was observed in the main frequencies of the delta rhythm and the theta rhythm (by 90% and by 10%, respectively) over the cortex as a whole. In rabbits with experimental epilepsy, the delta rhythm decreased only in the frontal lobes and in the lateral geniculate body (by 30%), whereas the theta rhythm decreased only in the visual cortex (by 10%). Possible mechanisms for these effects are discussed.

Two lectin fractions (FI and FII) were obtained from seeds of Butea frondosa by affinity chromatography on a sorbent of macroporous glass coupled to the disaccharide alpha-D-GalNAc-(1----3)-beta-D-Gal. Both of these fractions, although different in their sugar specificity, were found on SDS-PAGE to consist of two polypeptide chains of 33 kDa and 35 kDa. In the native state the subunits associated to form a 250 kDa complex, possibly comprising four molecules of the 33 kDa polypeptide and four molecules of the 35 kDa polypeptide. The presence of a faint 70 kDa band when the 250 kDa complex was subjected to SDS-PAGE may indicate the existence of a sequential mechanism of aggregation. N-terminal amino acid sequence analysis revealed extensive homology between these lectins and those of other Leguminosae.