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111.
Kim YS 《Journal of biochemistry and molecular biology》2002,35(5):443-451
Malonate is a three-carbon dicarboxylic acid. It is well known as a competitive inhibitor of succinate dehydrogenase. It occurs naturally in biological systems, such as legumes and developing rat brains, which indicates that it may play an important role in symbiotic nitrogen metabolism and brain development. Recently, enzymes that are related to malonate metabolism were discovered and characterized. The genes that encode the enzymes were isolated, and the regulation of their expression was also studied. The mutant bacteria, in which the malonate-metabolizing gene was deleted, lost its primary function, symbiosis, between Rhizobium leguminosarium bv trifolii and clover. This suggests that malonate metabolism is essential in symbiotic nitrogen metabolism, at least in clover nodules. In addition to these, the genes matB and matC have been successfully used for generation of the industrial strain of Streptomyces for the production of antibiotics. 相似文献
112.
Edwards A Vincken JP Suurs LC Visser RG Zeeman S Smith A Martin C 《The Plant cell》2002,14(8):1767-1785
Amyloses with distinct molecular masses are found in the starch of pea embryos compared with the starch of pea leaves. In pea embryos, a granule-bound starch synthase protein (GBSSIa) is required for the synthesis of a significant portion of the amylose. However, this protein seems to be insignificant in the synthesis of amylose in pea leaves. cDNA clones encoding a second isoform of GBSSI, GBSSIb, have been isolated from pea leaves. Comparison of GBSSIa and GBSSIb activities shows them to have distinct properties. These differences have been confirmed by the expression of GBSSIa and GBSSIb in the amylose-free mutant of potato. GBSSIa and GBSSIb make distinct forms of amylose that differ in their molecular mass. These differences in product specificity, coupled with differences in the tissues in which GBSSIa and GBSSIb are most active, explain the distinct forms of amylose found in different tissues of pea. The shorter form of amylose formed by GBSSIa confers less susceptibility to the retrogradation of starch pastes than the amylose formed by GBSSIb. The product specificity of GBSSIa could provide beneficial attributes to starches for food and nonfood uses. 相似文献
113.
Hormone trajectories leading to human birth 总被引:5,自引:0,他引:5
The mechanisms regulating human parturition and labor remain unknown. This ignorance is expensive as preterm birth is responsible for 70% of neonatal mortality and 50% of cerebral palsy. Methods for the prediction of preterm birth and treatments for women in preterm labor have poor efficacy reflecting our limited knowledge of the mechanisms involved. Recent research has supported the view that parturition is a cascade of events that commences early in pregnancy and involves the mother, fetus, placenta, membranes, cervix and myometrium. Although a number of the key hormones and proteins involved have been identified, the relationships between these factors in time and tissues remain unclear. Placental production of Corticotropin-releasing hormone (CRH) is proposed as an early event regulating the cascade of events. Central to the onset of parturition will be a mechanism for progesterone withdrawal and estrogen activation in human. Two forms of progesterone receptor with opposing actions exist in the human myometrium. Progesterone receptor A (PR-A) is a dominant negative repressor of progesterone receptor B (PR-B). Preliminary studies strongly support the hypothesis that the onset of human parturition is initiated by rising concentrations of PR-A in the myometrium. 相似文献
114.
The mite-pathogenic fungus Neozygites floridana Fisher (Entomophthorales: Neozygitaceae) is considered to have potential for the biological control of the cassava green
mite, Mononychellus tanajoa (Bondar). However, its activity is sporadic and laboratory data suggest a strong dependence on night-time saturation deficits
for transmission. We report on an epizootic of this fungus in a mite population in northeastern Brazil. During the epizootic,
host populations appeared to be limited by a combination of the pathogen and a predatory mite Neoseiulus idaeus (Acari: Phytoseiidae). When temperatures increased, the epizootic finished and the host population began to grow. Abiotic
conditions could not explain the variation in host mortality following pickup of infective propagules in this epizootic. However,
night-time saturation did help to explain the variation in transmission from infective cadavers to newly killed hosts. This
supports laboratory observations that horizontal transmission between hosts is determined mainly by saturation deficits, while
the process of infection is little affected by abiotic conditions. A further field observation was the near-absence of resting
spores in dead mites (ca. 0.1% of cadavers), suggesting that the pathogen population was unsuccessful in producing inoculum
to infect future M. tanajoa populations. The implications are that this pathogen will only be effective as a biological control agent in periods of high
relative humidity, and establishment in new areas may be limited by resting spore formation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
115.
116.
Detection and characterization of the Gloeosporium gloeosporioides growth inhibitory compound iturin A from Bacillus subtilis strain KS03 总被引:4,自引:0,他引:4
The Bacillus subtilis strain KS03 was isolated, and identified as a biological control agent that inhibits the anthracnose disease fungus Gloeosporium gloeosporioides. The antifungal compound was purified from its culture broth through butanol extraction, diethylaminoethyl (DEAE) Sepharose CL-6B chromatography, and preparative thin layer chromatography. Tandem mass spectrometric analyses (MS/MS), with matrix-assisted laser desorption ionization (MALDI) time-of-fight/time-of-flight (TOF/TOF) mass spectrometry, showed that the antifungal compound was iturin A, a cyclic lipopeptide antibiotic. The major compound, with a molecular mass of 1042 Da, was identified as iturin A(2). 相似文献
117.
Stilbenes from the roots of Pleuropterus ciliinervis and their antioxidant activities 总被引:1,自引:0,他引:1
Two stilbene glycosides, pieceid-2"-O-gallate and pieceid-2"-O-coumarate, were isolated from the MeOH extract of the roots of Pleuropterus ciliinervis Nakai (Polygonaceae), together with two known compounds, resveratrol and pieceid. Their structures were determined spectroscopically, particularly by 2D NMR spectroscopic analysis. The antioxidant activities of stilbenes isolated were determined in vitro against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, superoxide radicals and by determining their lipid peroxidation inhibitory activities. Among the compounds isolated, pieceid-2"-O-gallate had the most potent inhibitory scavenging effect on DPPH, superoxide radicals and upon lipid peroxidation inhibition with IC50 values of 16.5, 23.9 and 5.1 microM, respectively. 相似文献
118.
119.
Dalm VA van Hagen PM van Koetsveld PM Achilefu S Houtsmuller AB Pols DH van der Lely AJ Lamberts SW Hofland LJ 《American journal of physiology. Endocrinology and metabolism》2003,285(2):E344-E353
Increasing evidence suggests that neuropeptides play a role in the regulatory mechanisms between the neuroendocrine and immune systems. A differential expression of the five known somatostatin (SS) receptors (sst1-5) has been demonstrated in human immune cells and tissues. However, little is known concerning regulation and expression of sst1-5 and the peptide SS. Therefore, we investigated the expression and the time-dependent regulation of sst1-5, SS, and cortistatin (CST), a novel SS-like peptide, in human monocytes (MO), monocyte-derived macrophages (MP), and dendritic cells (DC) in the basal and lipopolysaccharide (LPS)-activated state. MO, MP, and DC selectively expressed sst2 mRNA. SS mRNA was not detectable, whereas all samples expressed CST mRNA. Expression levels of sst2 and CST mRNA showed marked differences and were in the rank order of MP>DC>MO. LPS stimulation did not induce expression of SS or sst1,3,4,5. However, sst2 mRNA expression was upregulated significantly by stimulation with LPS. CST mRNA was upregulated as well. During differentiation of MO in MP or DC, time-dependent, significantly increasing sst2 and CST mRNA levels were found. By confocal microscopy, the presence of sst2 receptors was demonstrated on MP, but not on DC. This study demonstrates for the first time a selective and inducible expression of the recently discovered CST, as well as sst2, in human monocyte-derived cells, suggesting a role for a CST-sst2 system rather than a SS-sst2 system in these immune cell types. 相似文献
120.