Detection of antituberculous activity in plant extracts

Ten of 408 ethanolic extracts of plants inhibited growth of Mycobacterium tuberculosis H37Rv at dilutions of 1 in 160 to 1280 and a high proportion of the other extracts inhibited growth at lower dilutions. Some of the plants, after purification, may be therapeutically useful. In view of the environmental threat to many plant species, screening of such plants for potential therapeutic properties, including antituberculous and other antimicrobial activities, are urgently required before they are lost forever.     

Kinetic properties of "soluble" adenylyl cyclase. Synergism between calcium and bicarbonate

"Soluble" adenylyl cyclase (sAC) is a widely expressed source of cAMP in mammalian cells that is evolutionarily, structurally, and biochemically distinct from the G protein-responsive transmembrane adenylyl cyclases. In contrast to transmembrane adenylyl cyclases, sAC is insensitive to heterotrimeric G protein regulation and forskolin stimulation and is uniquely modulated by bicarbonate ions. Here we present the first report detailing kinetic analysis and biochemical properties of purified recombinant sAC. We confirm that bicarbonate regulation is conserved among mammalian sAC orthologs and demonstrate that bicarbonate stimulation is consistent with an increase in the V(max) of the enzyme with little effect on the apparent K(m) for substrate, ATP-Mg(2+). Bicarbonate can further increase sAC activity by relieving substrate inhibition. We also identify calcium as a direct modulator of sAC activity. In contrast to bicarbonate, calcium stimulates sAC activity by decreasing its apparent K(m) for ATP-Mg(2+). Because of their different mechanisms, calcium and bicarbonate synergistically activate sAC; therefore, small changes of either calcium or bicarbonate will lead to significant changes in cellular cAMP levels.     

Synergism of endoenzyme and exoenzyme on hydrolysis of soluble cellulose derivatives

A kinetic model that represents the reaction of hydrolysis of water-soluble cellulose derivatives by a mixed endo- and exoenzyme system is proposed with the following assumptions: at an early stage of the reaction, endoenzymes split the substrate molecule in order to supply the newly formed nonreducing ends to exoenzymes until the molecular weight of the substrates reaches a low value; after that point, the reaction kinetics obeys only the rate equation of the reaction of the exoenzymes in which the reaction parameters change linearly with decrease of the molecular weight of the substrates. Hydrolysis experiments of soluble cellulose derivatives, carboxymethyl cellulose and hydroxyethyl cellulose, were carried out with endo-and exoenzymes separated from Trichoderma Koningii cellulase. The critical molecular weight of the substrate, from that point the action of endoenzyme can be neglected, was determined from the experimental data. That was ca. 4000 D. With that value, the model fits well the experimental data. Synergism of both enzymes appears as enhancement of the rate of the reaction at the early stage of the reaction.     

Calcium-independent and cAMP-dependent modulation of soluble guanylyl cyclase activity by G protein-coupled receptors in pituitary cells

It is well established that G protein-coupled receptors stimulate nitric oxide-sensitive soluble guanylyl cyclase by increasing intracellular Ca(2+) and activating Ca(2+)-dependent nitric-oxide synthases. In pituitary cells receptors that stimulated adenylyl cyclase, growth hormone-releasing hormone, corticotropin-releasing factor, and thyrotropin-releasing hormone also stimulated calcium signaling and increased cGMP levels, whereas receptors that inhibited adenylyl cyclase, endothelin-A, and dopamine-2 also inhibited spontaneous calcium transients and decreased cGMP levels. However, receptor-controlled up- and down-regulation of cyclic nucleotide accumulation was not blocked by abolition of Ca(2+) signaling, suggesting that cAMP production affects cGMP accumulation. Agonist-induced cGMP accumulation was observed in cells incubated in the presence of various phosphodiesterase and soluble guanylyl cyclase inhibitors, confirming that G(s)-coupled receptors stimulated de novo cGMP production. Furthermore, cholera toxin (an activator of G(s)), forskolin (an activator of adenylyl cyclase), and 8-Br-cAMP (a permeable cAMP analog) mimicked the stimulatory action of G(s)-coupled receptors on cGMP production. Basal, agonist-, cholera toxin-, and forskolin-stimulated cGMP production, but not cAMP production, was significantly reduced in cells treated with H89, a protein kinase A inhibitor. These results indicate that coupling seven plasma membrane-domain receptors to an adenylyl cyclase signaling pathway provides an additional calcium-independent and cAMP-dependent mechanism for modulating soluble guanylyl cyclase activity in pituitary cells.     

Antibacterial activity of soluble pyridinium-type polymers.

Cross-linked poly(N-benzyl-4-vinylpyridinium halide) (designated insoluble BVP) was previously reported to capture bacterial cells alive by contact with them. The corresponding linear polymer poly(N-benzyl-4-vinylpyridinium salt) (designated soluble BVP) was found to exhibit antibacterial activity. This soluble pyridinium-type polymer showed strong antibacterial activity against gram-positive bacteria, whereas it was less active against gram-negative bacteria. The antibacterial activity of this cationic, polymeric disinfectant was considerably greater than that of the corresponding monomeric compound and was approximately equal to that of conventional disinfectants such as benzalkonium chloride and chlorohexidine.     

Capillary electrophoresis method for simultaneous determination of penicillin G, procaine and dihydrostreptomycin in veterinary drugs

Capillary electrophoresis method for identification and simultaneous determination of procaine, dihydrostreptomycin and penicillin G, present in multiantibiotic veterinary preparations, was elaborated. The influence of pH (5.0-9.75) and concentration of disodium tetraborate decahydrate in running buffers (0.02-0.1 M) as well as temperatures (25-40 degrees C) on separation efficacy were analyzed. For quantitative analysis, 0.08 M borate buffer (pH 8.0) at 35 degrees C and 15 kV were chosen. Method was validated, selectivity, precision, linearity, LOD, LOQ, accuracy and specificity of capillary zone electrophoresis (CZE) were evaluated.     

Complementation of soluble phosphofructokinase activity in yeast mutants.

We describe here the genetic and biochemical analyses of two classes of mutations in the soluble phosphofructokinase (PFK I) of Saccharomyces cerevisiae: those leading to the loss of activity and those giving rise to a kinetically altered enzyme. Complementation and allele-testing between these two classes of mutants show that loss of enzyme activity in vitro can come about not only by mutations in the catalytic subunit but also in the regulatory subunit. Also, a mutation in the catalytic subunit can give rise to an enzyme altered in its kinetic properties in a manner phenomenologically similar to that caused by a mutation in the regulatory subunit. The results of the complementation studies in diploids suggest that, in spite of their distinct functions, both the subunits are essential for activity to be detected in vitro. This is confirmed by the reconstitution of an active PFK I enzyme by mixing cell-free extracts of two complementing parents, each of which lacks the enzyme activity. PFK activity appears in the mixture, reaching a maximum value of 60-100% of that of the diploid in 15-30 min at 24 degrees C. Unlike the catalytic subunit which exists in various multimeric states in cell-free extracts of the mutant bearing only this subunit, the regulatory subunit exists largely as a monomer in a mutant devoid of the catalytic subunit. The reconstituted enzyme, however, is indistinguishable from that of the wild type, as analysed by sedimentation studies and Western blot analysis, demonstrating that only the heteromeric complex of the two subunits is active, while neither of the individual subunits displays activity in vitro.