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At least 775 records · Page 43Linked to original sources
PubMed1990

A sensitive and specific assay for superoxide anion released by neutrophils or macrophages based on bioluminescence of polynoidin.

Using the luminescent protein polynoidin, present in the bioluminescent system isolated from the marine annelid Harmothoe lunulata, we have developed a new method to measure, specifically, superoxide anion (O2-) released by macrophages or neutrophils. A small quantity of an aqueous crude extract of polynoidin is used to detect O2- released by stimulated cells. Light emission is linearly dependent on the number of cells over a wide range (10(3) to 10(7) cells), and the assay is thus more sensitive than either luminol or ferricytochrome c reduction. Luminescence is enhanced 20% by mannitol, 80% by catalase, and is totally quenched by superoxide dismutase. For the same number of cells, neutrophils showed a threefold higher release of O2- and a twofold faster first-order light decay than stimulated macrophages, in accordance with data obtained by other methods.

Animals↗
PubMed1984

Enzymatic defenses against oxygen toxicity in the hydrothermal vent animals Riftia pachyptila and Calyptogena magnifica.

Two deep-sea hydrothermal vent organisms, the tube worm Riftia pachyptila and the clam Calyptogena magnifica, contain superoxide dismutase, dianisidine peroxidase, and glutathione peroxidase. The tube worm trophosome exhibits an iron-containing superoxide dismutase, ordinarily associated with prokaryotes and not previously seen in an animal tissue, in accord with the presence of symbiotic bacteria in this tissue. The enzymes which provide a defense against oxygen toxicity are thus present in these animals.

Animals↗
PubMed1984

Structure and function of hemoglobin from Urechis caupo.

The hemoglobin of the erythrocytes of Urechis caupo is tetrameric. Three chromatographic fractions have been isolated. Fractions F-I (the major fraction) and F-II are each composed of at least five electrophoretic components. Minor fractions F-III has an amino acid composition which is very different from those of fractions F-I and F-II. Amino acid analysis and peptide mapping suggests that fractions F-I and F-II are very similar, and may differ only in a few post-translational modifications. The major fraction, F-I, appears to consist of tetramers in which all subunits are almost identical. Oxygen binding is noncooperative, with a pressure of half-saturation (p50) of 12 mm Hg at 20 degrees C and pH 7.5 in Tris buffers. The oxygen equilibria of undialyzed lysate and of hemoglobin purified by chromatography on Sephadex G-100 are identical. This observation indicates that no allosteric modulator is present. The oxygen equilibrium is not significantly affected by ATP, Cl-, Ca2+, Mg2+, or CO2. The pH dependence of oxygen binding is extremely small: delta Log p50/delta pH is only +0.06 between pH 6 and 7.5. The p50 value changes by no more than 15% between 6.8 microM and 4.3 mM (heme). The apparent enthalpy of oxygenation, delta H, is -11 kcal/mol. Deoxygenation, oxidation, dilution, or pH changes have no significant effect on the state of aggregation. These oxygen-binding properties are consistent with the suggestion that the primary function of the hemoglobin is to store oxygen during the hypoxia which occurs in the burrows of the animal at low tide.

Amino Acid Sequence↗
PubMed1989

Expression of human plasminogen cDNA in a baculovirus vector-infected insect cell system.

A cDNA that encodes the human plasminogen (HPg) amino acid sequence has been inserted adjacent to the polyhedrin promoter in the genome of the baculovirus, Autographa californica nuclear polyhedrosis virus, which was then used to infect cultured cells of the farm armyworm, Spodoptera frugiperda. Under the conditions of cell growth employed, recombinant (rec)-HPg was secreted into the medium after 24 h postinfection (p.i.), at which point virtually no rec-HPg antigen remained inside the cells. At 48 h p.i., a maximal level of intact rec-HPg was present in the medium, which underwent substantial proteolytic digestion after that time. The rec-HPg produced by this expression system possessed a molecular weight equivalent to that of plasma [Glu1]-plasminogen. In addition, the rec-HPg adsorbed to Sepharose-lysine, and was eluted with epsilon-aminocaproic acid (EACA). The recombinant protein also interacted with polyclonal antibodies generated to plasma HPg, as well as with a monoclonal antibody directed against a distinct region (kringle 1-3) of the plasma HPg molecule. Finally, the insect-expressed rec-HPg was activatable to plasmin (HPm) by urokinase. The results demonstrate that this expression system produces a full-length functional single-chain rec-HPg, which can be isolated intact from the culture medium, with some consideration for the temporal events that occur in secretion and longer-term degradation of the protein. The fact that this rec-HPg was converted to HPm with a plasminogen activator, and that it interacted with anti-plasma HPg polyclonal and monoclonal antibodies, as well as with the ligand, EACA, indicates that the molecule retains many of its important functional properties and is folded in an integral manner.

Animals↗