The effect of pyrazines on the metabolism of tryptophan and nicotinamide adenine dinucleotide in the rat Evidence of the formation of a potent inhibitor of aminocarboxy-muconate-semialdehyde decarboxylase from pyrazinamide

The intraperitoneal or oral administration of pyrazinamide and pyrazinoic acid (pyrazine 2-carboxylic acid) resulted in a marked increase of the NAD content in rat liver. The injections of pyrazine and pyrazine 2,3-dicarboxylic acid exhibited no significant effect on the hepatic NAD content. The boiled extract obtained from liver and kidney of rat injected with either pyrazinamide or pyrazinoic acid exhibited a potent inhibitory effect on the aminocarboxymuconate-semialdehyde decarboxylase (EC 4.1.1.45) activity in either liver or kidney, although pyrazinamide or pyrazinoic acid per se did not inhibit the enzyme activity. The unknown inhibitor of aminocarboxymuconate-semialdehyde decarboxylase was dialysable and heat-stable, and mostly excreted in urine by 6 and 12 h after injection of pyrazinoic acid and pyrazinamide, respectively. Pyrazine 2,3-dicarboxylic acid, pyrazine, nicotinamide, nicotinic acid, tryptophan, anthranilic acid, 5-hydroxyanthranilic acid and quinolinic acid exhibited no significant effect on the aminocarboxymuconate-semialdehyde decarboxylase activity in liver and kidney at the concentration of 1 mM in the reaction mixture. The expired ¹⁴CO₂ from l-[benzen ring-U-¹⁴C]tryptophan was markedly decreased by the pyrazinamide injection, while the urinary excretion of ¹⁴C-labeled metabolites from l-tryptophan, mainly quinolinic acid, was markedly increased. These results suggest that the glutarate pathway of l-tryptophan was strongly inhibited by the inhibitor produced after the administration of pyrazinoic acid and pyrazinamide. Pyrazinamide but not pyrazinoic acid also exhibited a significant inhibition of the nuclear enzyme poly(ADP-ribose) synthetase in rat liver.     

Quercetin metabolites and protection against peroxynitrite-induced oxidative hepatic injury in rats

Quercetin has strong antioxidant potency. Quercetin-3′-O-sulphate (Q3′S) and quercetin-3-O-glucuronide (Q3GA) are the main circulating metabolites after consumption of quercetin-O-glucoside-rich diets by humans. However, information about how these quercetin metabolites function in vivo is limited. Hence, this study evaluated the efficacy of Q3′S and Q3GA for the protection of oxidative injury using in vitro and in vivo experiments. Peroxynitrite-mediated hepatic injury in rats was induced by administration of galactosamine/lipopolysaccharide (GalN/LPS). Twenty-four hours after GalN/LPS treatment, plasma ALT and AST levels δ increased significantly. However, pretreatment with 4^G-α-D-glucopyranosyl rutin, a quercetin glycoside (30 mg/kg body weight), prevented these increases and reduced nitrotyrosine formation, indicating that consumption of quercetin glycosides prevent oxidative hepatotoxicity. Moreover, physiological levels of Q3′S and Q3GA (1 µM) effectively prevented peroxynitrite-induced nitrotyrosine formation in human serum albumin in in vitro experiments. These findings indicate peroxynitrite-induced oxidative hepatotoxicity is protected by the in vivo metabolites of quercetin, Q3′S and Q3GA.     

Consequences of Sphaeropsis tip blight disease for the phytohormone profile and antioxidative metabolism of its pine host

Phytopathogenic fungi infections induce plant defence responses that mediate changes in metabolic and signalling processes with severe consequences for plant growth and development. Sphaeropsis tip blight, induced by the endophytic fungus Sphaeropsis sapinea that spreads from stem tissues to the needles, is the most widespread disease of conifer forests causing dramatic economic losses. However, metabolic consequences of this disease on bark and wood tissues of its host are largely unexplored. Here, we show that diseased host pines experience tissue dehydration in both bark and wood. Increased cytokinin and declined indole‐3‐acetic acid levels were observed in both tissues and increased jasmonic acid and abscisic acid levels exclusively in the wood. Increased lignin contents at the expense of holo‐cellulose with declined structural biomass of the wood reflect cell wall fortification by S. sapinea infection. These changes are consistent with H₂O₂ accumulation in the wood, required for lignin polymerization. Accumulation of H₂O₂ was associated with more oxidized redox states of glutathione and ascorbate pools. These findings indicate that S. sapinea affects both phytohormone signalling and the antioxidative defence system in stem tissues of its pine host during the infection process.     

Enzymatic syntheses of GlcNAcβ1-2Man and Galβ1-4GlcNAcβ1-2Man as components of complex type sugar chains

GlcNAc1-2Man and GlcNAc1-6Man were synthesized using the reverse hydrolysis activity of -N-acetylglucosaminidase from both jack beans and Bacillus circulans. In turn, Gal1-4GlcNAc1-2Man and Gal1-4GlcNAc1-6Man were synthesized regioselectively using the transglycosylation activity of -galactosidase from Diplococcus pneumoniae and B. circulans, respectively. These di- and trisaccharides are important components of complex type sugar chains and will be used as intermediates in our synthetic studies. Abbreviations: pNp--GlcNAc, p-nitrophenyl 2-acetamido-2-deoxy--D-glucopyranoside; pNp--Gal, p-nitrophenyl -D-galacto-pyranoside     

Relationship between gyrA Mutations and Quinolone Resistance in Flavobacterium psychrophilum Isolates

Flavobacterium psychrophilum is the causative agent of the fish diseases called bacterial cold-water disease and rainbow trout fry syndrome. It has been reported that some isolates of F. psychrophilum are resistant to quinolones; however, the mechanism of this quinolone resistance has been unexplained. In this study, we examined the quinolone susceptibility patterns of 27 F. psychrophilum strains isolated in Japan and the United States. Out of 27 isolates, 14 were resistant to both nalidixic acid (NA) and oxolinic acid (OXA), and the others were susceptible to NA and OXA. When amino acid sequences deduced from gyrA nucleotide sequences of all isolates tested were analyzed, two amino acid substitutions (a threonine residue replaced by an alanine or isoleucine residue in position 83 of GyrA [Escherichia coli numbering] and an aspartic acid residue replaced by a tyrosine residue in position 87) were observed in the 14 quinolone-resistant isolates. These results strongly suggest that, as in other gram-negative bacteria, DNA gyrase is an important target for quinolones in F. psychrophilum.     

Triterpenoids from enkianthus campanulatus

From the leaves of Enkianthus campanulatus were isolated three new triterpenes, 3-oxo-19,23,24-trihydroxyurs-12-en-28-oic acid, 3β,6β, 19,23-tetrahydroxyurs-12-en-28-oic acid and 3β,6β,23-trihydroxyurs-12-en-28-oic acid.     

Oral lipase activities and fat-taste receptors for fat-taste sensing in chickens

It has been reported that a functional fat-taste receptor, GPR120, is present in chicken oral tissues, and that chickens can detect fat taste in a behavioral test. However, although triglycerides need to be digested to free fatty acids to be recognized by fat-taste receptors such as GPR120, it remains unknown whether lipase activities exist in chicken oral tissues. To examine this question, we first cloned another fat-taste receptor candidate gene, CD36, from the chicken palate. Then, using RT-PCR, we determined that GPR120 and CD36 were broadly expressed in chicken oral and gastrointestinal tissues. Also by RT-PCR, we confirmed that several lipase genes were expressed in both oral and gastrointestinal tissues. Finally, we analyzed the lipase activities of oral tissues by using a fluorogenic triglyceride analog as a lipase substrate. We found there are functional lipases in oral tissues as well as in the stomach and pancreas. These results suggested that chickens have a basic fat-taste reception system that incorporates a triglycerides/oral-lipases/free fatty acids/GPR120 axis and CD36 axis.     

A Novel Nectin-mediated Cell Adhesion Apparatus That Is Implicated in Prolactin Receptor Signaling for Mammary Gland Development

Mammary gland development is induced by the actions of various hormones to form a structure consisting of collecting ducts and milk-secreting alveoli, which comprise two types of epithelial cells known as luminal and basal cells. These cells adhere to each other by cell adhesion apparatuses whose roles in hormone-dependent mammary gland development remain largely unknown. Here we identified a novel cell adhesion apparatus at the boundary between the luminal and basal cells in addition to desmosomes. This apparatus was formed by the trans-interaction between the cell adhesion molecules nectin-4 and nectin-1, which were expressed in the luminal and basal cells, respectively. Nectin-4 of this apparatus further cis-interacted with the prolactin receptor in the luminal cells to enhance the prolactin-induced prolactin receptor signaling for alveolar development with lactogenic differentiation. Thus, a novel nectin-mediated cell adhesion apparatus regulates the prolactin receptor signaling for mammary gland development.