Biomedical science最新文献

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.

The antibiotic bleomycin was examined as a possible component of hybrid molecules composed of an address fragment and a generator of reactive oxygen species. The bleomycin-Fe(II) complex was found to destroy the erythrocyte membrane by generating reactive oxygen. The ability of antioxidants to slow down haemolysis points to a free-radical mechanism for this process. The protective effects of catalase and superoxide dismutase indicate that hydrogen peroxide and the superoxide radical formed on autoxidation of the complex are essential for membrane damage. Haemolytic activity is also exhibited by bleomycin-Fe(III) reduced in the NADPH-cytochrome P450 reductase reaction. The covalent binding of bleomycin to such address molecules as concanavalin A and antierythrocyte immunoglobulin G enhances the ability of the bleomycin-Fe(II) complex to destroy the plasma membrane of erythrocytes.

The composition of the collagen and proteoglycan components of the extracellular matrix in human rib cartilage under normal conditions at different stages of ontogenesis (from 7 weeks of intrauterine development to 60 years of age) has been analysed. Polyacrylamide gel electrophoresis of collagen CNBr-peptides has shown the presence of type I collagen in embryonal cartilage and a gradual decrease in the quantity of this component relative to type II collagen with increasing age. Analysis of reducible and mature collagen cross-links revealed traces of lysylpyridinoline in addition to hydroxylysylpyridinoline in human rib cartilage. The increase in the content of mature cross-links during ontogenesis was accompanied by a decrease in the content of dihydroxylysinonorleucine. Electrophoretic analysis of proteoglycan monomers revealed four fractions of different mobility and the ratio of these fractions altered in the course of ontogenesis. An increase in the glucosamine/galactosamine ratio in the core proteins was observed with increase in age of the donors. During electrophoretic analysis of the link protein fraction a protein of molecular mass 200 kDa was found. This protein first appeared after 9 weeks of intrauterine development and was present in the rib cartilage at all subsequent stages of embryogenesis. This protein has been identified as tenascin by immunoblotting.

Ca2+ ATPase was isolated from rabbit skeletal muscle sarcoplasmic reticulum and used to form structures resembling potential-dependent calcium channels within the membrane lipid bilayer of liposomes. The orientation of these structures in the bilayer was dependent on the conditions used for enzyme incorporation. The results obtained indicate that Ca2+ ATPase may be involved in the passive transport of calcium ions from the sarcoplasmic reticulum which may be regulated by the membrane potential. The membrane potential within the reticulum is probably positive at the moment of calcium ion release.

A mathematical model for the generation of free radicals by mitochondria in ischemia-reperfusion is proposed. Computations show that normally two stable equilibrium states exist: the intact state, and the state characterized by damage to mitochondrial structures and a high rate of radical formation. Transition from one state to another occurs after hypoxia of a certain degree of severity and duration. The model also describes a number of phenomena observed during development of reperfusion injuries and drug therapy.

Parameters of cellular and humoral immunity, and the levels of neurotransmitters and hormones both before and after the administration of various stimulators and blocking agents that affect the immune and neuroendocrine systems were investigated in 100 patients suffering from chronic alcoholism. The results direct attention to the significance of the impairment of interactions between these biological systems during chronic alcoholism.

Enzyme preparations of Rous sarcoma virus (RSV) reverse transcriptase have been isolated from a culture of E. coli HB101(pMF14). The enzyme has been purified to homogeneity and been shown to consist of two subunits, of molecular mass 97.4 and 61.3 kDa, respectively. The optimum conditions for the DNA polymerase and RNAase H activities, fidelity of DNA synthesis on a homogeneous RNA template, and the inhibitory effect of azidothymidine triphosphate have been determined. Data on the use of RSV recombinant reverse transcriptase for cDNA synthesis are given.

An epitope of human leukocyte alpha interferon A (IFN-A), which is recognized by the murine monoclonal antibody NK2, has been mapped by using four successive approaches. Limited proteolysis of the IFN-A chain, followed by electrophoresis, Western blotting, and probing of the proteolytic fragments with NK2 showed that an epitope was located within the sequence residues 110-140. A panel of human IFN subtypes bearing substitutions within the sequence 110-140 was tested for reactivity with NK2 in enzyme-linked immunosorbent assays. The results from these assays suggested that the epitope is within the sequence 112-121. Analysis of a hybrid protein IFN-A(1-92)/F(93-166) revealed that the N-terminal region of IFN-A played no significant role in NK2 binding. Three residues of IFN-F (Asn113, Val114, and Lys121) were substituted for the corresponding residues from IFN-A (Lys113, Glu114, and Arg121) by site-directed mutagenesis of the gene encoding IFN-F. NK2 was able to bind the mutated protein, IFN-F(A 113, 114, 121), as well as unmodified IFN-A. The data show that the epitope recognized by NK2 is located within the C-terminal region of IFN-A (residues 112-121). This epitope consists of the essential residues 114 and 116, and residues 112, 113, 115, 117, and 121 presumably contribute the configuration of the epitope.

Epileptogenic foci were formed in rabbit visual cortex by freezing with liquid nitrogen. RNA isolated from the epileptogenic cortex (RNAepl), or from the frontal lobes (RNAcont) was injected into spontaneously active neurons of the mollusc Planorbarius corneus. The amplitude and duration of the spontaneous action potentials generated following the injection of RNAepl were reproducibly higher than those produced following the introduction of RNAcont. But the time interval between injection and cessation of spontaneous activity was considerably shorter after RNAepl-injection than after RNAcont-injection. Perfusion of neurons with a solution containing puromycin substantially prolonged the period of spontaneous discharge generation in both cases. The addition of Co2+ to the perfusion solution restored the spontaneous rhythmic activity to cells in which the generation of spikes had ceased following the injection of RNAepl. The mechanism underlying these effects is discussed.

It was postulated that similar genetic elements that are 'hot spots' for genetic variation might exist in both the HIV-1 and the human genome. To test this possibility a short repeated sequence from a region of variability in the HIV-1 glycoprotein (env) gene was amplified and used as a probe for blot hybridization with human genome DNA. Human genomic regions were hybridized and characterized by a set of polymorphic restriction DNA fragments. The pattern of the restriction fragments was individual specific. Thus a DNA probe from the HIV-1 env gene can serve as a genetic marker for hybridization with human genome regions and for the identification of individuals.