The metabolism of leukotrienes in blood plasma studied by high-performance liquid chromatography

The metabolism of leukotrienes (B4, C4, D4, and E4) within human plasma was studied and a simple sample preparation is presented. It was demonstrated that leukotriene E4 and leukotriene B4 were stable during incubation at 37 degrees C using the in vitro system. In contrast, leukotriene C4 was metabolized by gamma-glutamyl transpeptidase activities into leukotriene D4 which was further metabolized by dipeptidase activities of plasma into leukotriene E4. The transition state inhibitor of gamma-glutamyl transpeptidase L-serine-borate decreased the metabolism of leukotriene C4 in plasma. Dilution of plasma demonstrated that the dipeptidase was more active compared to the gamma-glutamyl transpeptidase. The metabolizing activities of plasma were functionally characterized by fractionating the plasma proteins.     

Pathway of acetate assimilation in autotrophic and heterotrophic methanococci.

The autotroph Methanococcus maripaludis contained high levels of acetate-coenzyme A ligase, pyruvate synthase, pyruvate, water dikinase, pyruvate carboxylase, and the enzymes of the incomplete reductive tricarboxylic acid cycle. Phosphoenolpyruvate carboxykinase, citrate synthase, and isocitrate dehydrogenase were not detected. In contrast, the heterotroph Methanococcus sp. strain A3 contained acetate kinase, and acetate coenzyme A ligase was virtually absent.     

THE LOCOMOTION OF LIMAX : I. TEMPERATURE COEFFICIENT OF PEDAL ACTIVITY.

Pedal progression of the slug Limax maximus was studied to obtain relations between wave velocity on the sole of the foot, wave frequency, the advance due to a single wave, and the velocity of vertically upward creeping. Each of the first three quantities is directly proportional to the simultaneous velocity of progression. Under comparable conditions, that is when work is done at a constant rate, the frequency of pedal waves is influenced by the temperature according to the equation of Arrhenius, with µ = 10,700 (Q ₁₀ for 11° to 21° = 2.1). The velocity of a single wave must have very nearly the same "temperature characteristic," which is found also in another case of nerve net transmission (in Renilla).     

Tissue distribution and kininogen gene expression after acute-phase inflammation

A kinin-directed monoclonal antibody to kininogens has been developed by the fusion of murine myeloma cells with mouse splenocytes immunized with bradykinin-conjugated hemocyanin. The hybrid cells were screened by an enzyme-linked immunosorbent assay (ELISA) and a radioimmunoassay (RIA) for the secretion of antibodies to bradykinin. Ascitic fluids were produced and purified by a bradykinin-agarose affinity column. The monoclonal antibody (IgG1) bound to bradykinin, Lys-bradykinin, Met-Lys-bradykinin, and kininogens in ELISA. Further, this target-directed monoclonal antibody recognized purified low and high molecular weight bovine, human, or rat kininogens and T-kininogen in Western blotting. After turpentine-induced acute inflammation, rat kininogen levels increased dramatically in liver and serum as well as in the perfused pituitary, heart, lung, kidney, thymus, and other tissues, as identified by the kinin-directed kininogen antibody in Western blot analyses. The results were confirmed by measuring kinin equivalents of kininogens with a kinin RIA. During an induced inflammatory response, rat kininogens were localized immunohistochemically with the kinin-directed monoclonal antibody in parenchymal cells of liver, in acinar cells and some granular convoluted tubules of submandibular gland, and in the collecting tubules of kidney. Northern and cytoplasmic dot blot analyses using a kinin oligonucleotide probe showed that kininogen mRNA levels in liver but not in other tissues increase after turpentine-induced inflammation. The results indicated that rat kininogens are distributed in various tissues in addition to liver and only liver kininogen is induced by acute inflammation. The target-directed kininogen monoclonal antibody is a useful reagent for studying the structure, localization, and function of kininogens or any protein molecule containing the kinin moiety.     

The Chlamydomonas cell wall degrading enzyme, lysin, acts on two substrates within the framework of the wall

The Chlamydomonas cell wall is a multilayered, extracellular matrix containing 20-25 proteins and glycoproteins, many of which are highly enriched in hydroxyproline. 80-90% of the wall protein is located in a crystalline portion of the wall that is soluble in sarkosyl-urea solutions as well as in chaotropic salts. Although the wall has no cellulose it contains a noncrystalline, highly insoluble framework portion that is responsible for the integrity and overall shape of the wall. In the present report we show that the framework of the wall is composed of two components that are acted upon by lysin, a wall degrading enzyme released by mating gametes. One, which makes up the major portion of the framework, is insoluble upon boiling in SDS-PAGE sample buffer. Lysin treatment of this portion leads to its physical degradation and the concomitant appearance of several SDS-dithiothreitol-soluble polypeptides ranging in relative molecular mass from greater than 400,000 to less than 60,000. The second component is the flagellar collar. This hollow cylinder composed of striated fibers aligned in parallel array serves as the tunnel in the wall through which the flagella protrude. Our evidence indicates that the primary collar polypeptide is a 225,000-Mr molecule that itself has at least two functional domains. One domain, contained in a 185,000-Mr fragment, permits the self-association of the molecules to form the main body of the collar. The second part of the molecule anchors the collar to the wall framework via sarkosyl-urea-insensitive, SDS-dithiothreitol-sensitive linkages.