Experimental evidence for plasmid-borne nor-nir genes in Sinorhizobium meliloti JJ1c10

In denitrification, nir and nor genes are respectively required for the sequential dissimilatory reduction of nitrite and nitric oxide to form nitrous oxide. Their location on the pSymA megaplasmid of Sinorhizobium meliloti was confirmed by Southern hybridization of its clones with specific structural gene probes for nirK and norCB. A 20-kb region of pSymA containing the nor-nir genes was delineated by nucleotide sequence analysis. These genes were linked to the nap genes encoding periplasmic proteins involved in nitrate reduction. The nor-nir-nap segment is situated within 30 kb downstream from the nos genes encoding nitrous oxide reduction, with a fix cluster intervening between nir and nos. Most of these predicted nor-nir and accessory gene products are highly homologous with those of related proteobacterial denitrifiers. Functional tests of Tn5 mutants confirmed the requirement of the nirV product and 1 unidentified protein for nitrite reduction as well as the norB-D products and another unidentified protein for nitric oxide reduction. Overall comparative analysis of the derived amino acid sequences of the S. meliloti gene products suggested a close relationship between this symbiotic N2 fixer and the free-living non-N2-fixing denitrifier Pseudomonas G-179, despite differences in their genetic organization. This relationship may be due to lateral gene transfer of denitrification genes from a common donor followed by rearrangement and recombination of these genes.     

The influence of geomagnetic variations on the formation of nitric oxide in exhaled air in human

The content of nitric oxide in exhaled air in healthy persons has been studied. It was shown that nitric oxide in exhaled air is formed from saliva nitrite due to the nitrite reductase activity of mouth cavity microflora. A relationship between the nitric oxide level and age, arterial pressure, and geomagnetic field indices was established. It was shown that the level of nitric oxide diminishes with age. A negative correlation between the nitric oxide content in exhaled air and arterial pressure (systolic and diastolic) was found. It was assumed that nitric oxide from the mouth can penetrate into the lungs and then to the blood where it can influence the vessel tonus. It was shown that the negative relationship took place between nitric oxide level in the air and Ki-indices of geomagnetic field on the day of measurement or the day preceding the measurement. The data obtained suggest that nitric oxide is involved in processes causing infarcts and insults in periods of magnetic storms.     

一氧化氮合酶与脓毒症的研究进展

脓毒症在外科临床工作中较常见,治疗相当困难;本文主要概述了一氧化氮合酶的基因定位、结构特点以及一氧化氮合酶与脓毒症的关系,进一步说明由一氧化氮合酶介导的一氧化氮生成与脓毒症关系密切,而选择性一氧化氮合酶抑制剂在脓毒症各阶段恰当的应用可能是有效治疗脓毒症、降低病死率的一个重要途径,也将成为今后研究的热点。     

一氧化氮合酶与脓毒症的研究进展

脓毒症在外科临床工作中较常见,治疗相当困难;本文主要概述了一氧化氮合酶的基因定位、结构特点以及一氧化氮合酶与脓毒症的关系,进一步说明由一氧化氮合酶介导的一氧化氮生成与脓毒症关系密切,而选择性一氧化氮合酶抑制剂在脓毒症各阶段恰当的应用可能是有效治疗脓毒症、降低病死率的一个重要途径,也将成为今后研究的热点。     

Molecular variation in endothelial nitric oxide synthase gene (eNOS) in western Mediterranean populations

Endothelial nitric oxide synthase (eNOS or NOS3) is the main responsible for nitric oxide (NO) production in vascular system and different polymorphisms have been identified in epidemiological studies. Trying to test the eNOS genetic variation in general populations we studied the 27-bp VNTR in intron 4 and G894T substitution in exon 7 markers in 6 Western Mediterranean populations (3 from Iberian Peninsula, 1 from North Africa, and 2 from Sardinia) and a sample from Ivory Coast. The VNTR frequencies in Western Mediterranean and Ivory Coast fit well into the ranges previously described for Europeans and Sub-Saharans respectively, and a typical African allele has been detected in polymorphic frequencies in the Berber sample. The G894T substitution presents the highest frequencies described for the T allele in the North Mediterranean populations. Linkage disequilibrium is present between both markers in all populations except in the Ivory Coast sample. The variation found for these polymorphisms indicates that they may be a useful tool for population studies even at microgeographical level.     

The generation of nitric oxide by G protein-coupled receptors

The highly reactive free radical gas, nitric oxide, serves a variety of biomodulatory functions and has been implicated in a growing array of physiological and pathophysiological states. The striking differences between this labile substance and other, more conventional, signaling molecules highlight the tight degree of nitric oxide regulation that is required in order to maintain appropriate cellular homeostasis. The generation of nitric oxide represents a common component of the signal transduction pathways of a number of chemical signaling molecules that act via binding to G protein-coupled receptors. This review focuses on the relationship between this receptor superfamily, the generation of nitric oxide via the actions of the nitric oxide synthases and some of the inter- and intracellular roles of nitric oxide.     

一氧化氮与肺纤维化的研究进展

肺纤维化是一组由多种因素引起的肺间质性病变,肺纤维化的发病机制迄今尚未完全清楚。近年来,发现在哺乳动物细胞的一氧化氮合酶催化合成的一氧化氮在肺纤维化的发生发展中发挥着重要的作用。因此,阐述一氧化氮与肺纤维化的关系,有着重要的理论意义和潜在的临床应用价值。     

一氧化氮与神经血管单元的关联性及相关药物研究进展

一氧化氮（NO）作为一种重要的信号分子,对中枢神经系统具有重要影响。神经血管单元是近年来提出的从整体上描述中枢神经 系统的新概念,NO对中枢系统的作用是多层次多角度的,NO与神经血管单元这个整体及其各组成单元均密切相关。综述NO及其合成酶 的功能,在中枢神经系统疾病中NO与神经血管单元的相互作用关系及以NO信号通路为靶点的相关药物研究进展。     

Endothelial nitric oxide synthase intron 4 VNTR gene polymorphisms in European and African populations

Endogenous nitric oxide (NO) is a molecule synthesized by endothelium nitric oxide synthase encoded by the ecNOS gene that plays an important role in regulating the systemic, cardiac and pulmonary circulation. Impairment in NO synthesis has been associated to many cardiovascular disorders, including coronary artery disease and hypertension. We investigated the frequency of the intron 4 VNTR ecNOS gene polymorphism in an Ivorian and an Italian population. The frequencies of the ecNOSb/b, ecNOSa/b and ecNOSa/a genotypes were 0.422, 0.476, and 0.102, respectively, for the Ivorian sample, and 0.712, 0.269, and 0.019, respectively, for the Italian population. The frequencies of ecNOS4b and ecNOS4a alleles were 0.660 and 0.340, respectively, for the Ivorian group, and 0.847 and 0.153, respectively, for the studied Italian population. Genotype frequencies were in Hardy–Weinberg equilibrium in both populations. The Ivorian population showed a significantly higher frequency of the ecNOS4a allele compared to other African and non-African populations, while the Italian sample confirmed the high genetic homogeneity of this polymorphism among Europeans. The maldistribution of endothelial ecNOS polymorphisms between populations could be the results of differential exposure to selection pressures in Africa and during the out-of-Africa expansion.     

Nitric oxide synthase in the spinal cord of the frog, Xenopus laevis

The expression of nitric oxide synthase was investigated in the spinal cord of the South African clawed frog by NADPH diaphorase histochemistry and immunohistochemistry. The dorsal field contained many strongly positive neurons and a dense plexus of processes. Only few nitric oxide synthase-positive cells occurred in the lateral and central field. Motoneurons were negative. A dense accumulation of stained neurons was located dorsal and dorsomedial to the motoneurons. The white matter harbored many positive fibers. These were most abundant in the dorsal funiculus, and obviously consist of nonprimary projections to the brainstem. These results suggest that nitric oxide represents a widely used messenger molecule in the frog spinal cord, in particular with respect to the processing of sensory information.     

Effects of thiols, sugars, and proteins on nitric oxide activation of guanylate cyclase.

Purification of soluble guanylate cyclase from rat liver resulted in an apparent loss of enzyme activation by nitric oxide that could be restored by dithiothreitol. methemoglobin, bovine serum albumin, or sucrose. Although hemoglobin also permitted some activation with nitric oxide, the effect of other agents to restore enzyme activation was prevented with hemoglobin. As a result of enzyme purification, there is an alteration of the dose-response relationship for nitric oxide activation. After partial enzyme purification, relatively high concentrations of nitric oxide that were stimulatory in crude enzyme preparations had no effect on enzyme activity. However, partially purified or homogeneous enzyme was activated by lower concentrations of nitric oxide. The bell-shaped dose-response curve for nitric oxide was shifted to the left with guanylate cyclase purification. The addition of dithiothreitol, methemoglobin, bovine serum albumin, or sucrose to enzyme markedly broadens the dose-response curve for nitric oxide. Thus, the apparent loss of responsiveness to nitric oxide with purification is a function of increased sensitivity of guanylate cyclase to nitric oxide. Increased sensitivity to nitric oxide with enzyme purification probably results from the removal of heme, proteins, and small molecules that can serve as scavengers or sinks for nitric oxide and prevent excessive oxidation of the enzyme.     

Interaction between the NOS3 Gene and Obesity as a Determinant of Risk of Type 2 Diabetes: The Atherosclerosis Risk in Communities Study

Endothelial nitric oxide synthase 3 (NOS3) catalyzes the production of nitric oxide from L-arginine in endothelial cells. Obesity is a modifiable risk factor for diabetes, and obese individuals have been reported to have reduced nitric oxide availability compared to controls whose weight is in the normal range. Since homozygous carriers of the NOS3 G894T variant are predicted to have decreased enzyme activity, the association between NOS3 genotype and type 2 diabetes, and possible effect modification by body mass index (BMI) were evaluated. The prevalence of diabetes and BMI was determined at baseline in 14,374 participants 45–66 years of age from the prospective biracial population-based Atherosclerosis Risk in Communities (ARIC) Study of the development of atherosclerosis in four communities in the United States. Individuals with a BMI ≥30 kg/m² were considered obese. Those subjects not meeting the case definition were the comparison groups for the 728 African American and 980 white participants with diabetes. Multivariable logistic regression models adjusted for age, sex, and field center were used to test for main genetic effects and interaction with obesity. Although the NOS3 G894T variant was not independently associated with diabetes in either African Americans or whites, significant interaction between BMI and the NOS3 polymorphism indicated that obesity was an effect modifier of diabetes risk for white individuals with the TT genotype (odds ratio (OR) for interaction = 1.65, p = 0.04). In stratified analyses, homozygosity for the NOS3 T allele in obese white participants but not in those whose BMI <30 kg/m² was associated with an elevated risk of diabetes (OR = 1.47, p = 0.02) when compared to the common GG genotype. These results suggest that interaction between obesity and NOS3 genotype may be a determinant of diabetes case status in whites in the ARIC cohort. Replication in other populations will be required to confirm these observations.     

Ultrastructural localization of nitric oxide synthase and endothelin in coronary and pulmonary arteries of newborn rats

This is the first report on the ultrastructural distribution of nitric oxide synthase and endothelin immunoreactivities in the coronary and pulmonary arteries of newborn Wistar rats. The distribution of nitric oxide synthase and endothelin was investigated using pre-embedding peroxidase-antiperoxidase immunocytochemistry. In both arteries examined, positive labelling for nitric oxide synthase was localized both in the endothelium and smooth muscle, whereas positive labelling for endothelin was localized in the endothelium exclusively. In the coronary artery, approximately 80% and 55% of the endothelial cells examined were positive for nitric oxide synthase and endothelin, respectively, whereas in the pulmonary artery, 77% and 60% of the endothelial cells were positive for nitric oxide synthase and endothelin, respectively. These findings indicate that nitric oxide synthase and endothelin are colocalized in some of the endothelial cells of the newborn rat. In the endothelium, nitric oxide synthase and endothelin immunoreactivities were distributed throughout the cell cytoplasm and in association with the membranes of intracellular organelles. In smooth muscle, a relationship of nitric oxide synthase immunoreactivity to endoplasmic reticulum was observed in the pulmonary artery. In summary, in the newborn rat, endothelial cells of the coronary and pulmonary artery are rich in nitric oxide synthase (neuronal isoform) and endothelin, and it is suggested therefore that they may be substantially involved in vasomotor control of the cardiac and pulmonary circulation during early stages of postnatal development.     

Nitric oxide and changes of iron metabolism in exercise

Accumulated data imply that exercise itself might not lead to a true iron deficiency or 'sport anaemia' in a healthy athlete who has adequate iron intake. The higher prevalence of iron deficiency anaemia in younger female athletes might be not due to exercise itself, but probably results from dietary choices, inadequate iron intake and menstruation. These factors can also induce iron deficiency or anaemia in the general population. However, exercise does affect iron metabolism, leading to low or sub-optimal iron status. The underlying mechanism is unknown. In this review, recent advances in the study of the effect of exercise on iron metabolism and nitric oxide, and the relationship between nitric oxide and iron status in exercise are discussed. A hypothesis that increased production of nitric oxide might contribute to sub-optimal iron status in exercise is proposed.     

Nitric oxide accumulation in Arabidopsis is independent of NOA1 in the presence of sucrose

Nitric oxide signals diverse responses in animals and plants. Whereas nitric oxide synthesis mechanisms in animals are well understood, how nitric oxide is synthesized and regulated in plants remains controversial. NOA1 is a circularly permuted GTPase that is important for chloroplast function and is implicated in nitric oxide synthesis. However, the reported consequences of a null mutation in NOA1 are inconsistent. Whereas some studies indicate that the noa1 mutant has severe reductions in nitric oxide accumulation, others report that nitric oxide levels are indistinguishable between noa1 and the wild type. Here, we identify a correlation between the reported ability of noa1 to accumulate nitric oxide with growth on sucrose-supplemented media. We report that noa1 accumulates both basal and salicylic acid-induced nitric oxide only when grown on media containing sucrose. In contrast, nitric oxide accumulation in wild type is largely insensitive to sucrose supplementation. When grown in the absence of sucrose, noa1 has low fumarate, pale green leaves, slow growth and reduced chlorophyll content. These phenotypes are consistent with a defect in chloroplast-derived photosynthate production and are largely rescued by sucrose supplementation. We conclude that NOA1 has a primary role in chloroplast function and that its effects on the accumulation of nitric oxide are likely to be indirect.     

ADMA-- 一个新的心血管疾病危险因子

非对称性二甲基精氨酸(asymmetric dimethylarginine,ADMA)为内源性一氧化氮合酶(endogenous Nitric-Oxide Synthase,eNOS)竞争性抑制剂,可抑制NOS的活性,减少一氧化氮(nitric oxide,NO)的合成,致使内皮功能障碍。近年来研究认为ADMA是冠心病的独立预测因子,与心功能不全及心血管疾病死亡率明显相关。本文将针对ADMA与心血管疾病的相关性进行综述。     

Salicylic acid activates nitric oxide synthesis in Arabidopsis

The relationship between nitric oxide (NO) and salicylic acid (SA) was investigated in Arabidopsis thaliana. Here it is shown that SA is able to induce NO synthesis in a dose-dependent manner in Arabidopsis. NO production was detected by confocal microscopic analysis and spectrofluorometric assay in plant roots and cultured cells. To identify the metabolic pathways involved in SA-induced NO synthesis, genetic and pharmacological approaches were adopted. The analysis of the nia1,nia2 mutant showed that nitrate reductase activity was not required for SA-induced NO production. Experiments performed in the presence of a nitric oxide synthase (NOS) inhibitor suggested the involvement of NOS-like enzyme activity in this metabolic pathway. Moreover, the production of NO by SA treatment of Atnos1 mutant plants was strongly reduced compared with wild-type plants. Components of the SA signalling pathway giving rise to NO production were identified, and both calcium and casein kinase 2 (CK2) were demonstrated to be involved. Taken together, these results suggest that SA induces NO production at least in part through the activity of a NOS-like enzyme and that calcium and CK2 activity are essential components of the signalling cascade.     

Nitrosation of uric acid induced by nitric oxide under aerobic conditions.

Uric acid is a well-established scavenger of reactive oxygen and nitrogen species such as hydroxyl radical and peroxynitrite. However, little attention has been paid to the relationship between uric acid and nitric oxide. This paper reports the identification and characterization of a reaction product of uric acid induced by nitric oxide. When uric acid was treated with nitric oxide gas in a neutral solution under aerobic conditions, uric acid was consumed, yielding an unknown product. The product was identified as nitrosated uric acid from mass spectrometric data, although the position of the nitroso group on the molecule was not determined. The nitrosated uric acid decomposed to several compounds including uric acid with a half-life of 2.2 min at pH 7.4 and 37 degrees C. The incubation of nitrosated uric acid with glutathione resulted in the formation of S-nitrosoglutathione. Nitrosated uric acid was also formed in the reaction with nitric oxide donors, but not with peroxynitrite. Nitrosated uric acid was detected in human serum and urine by in vitro treatment with a nitric oxide donor. In the reaction of glutathione with the nitric oxide donor, the addition of uric acid caused an increase in the yield of S-nitrosoglutathione. These results indicate that under aerobic conditions nitric oxide can convert uric acid into its nitroso derivative, which can give a nitroso group to glutathione. Uric acid may act as a vehicle of nitric oxide in humans.     

Racial admixture and its impact on BMI and blood pressure in African and Mexican Americans

Admixed populations such as African Americans and Hispanic Americans present both challenges and opportunities in genetic epidemiologic research. Because of variation in admixture levels among individuals, case-control association studies may be subject to stratification bias. On the other hand, admixed populations also present special opportunities both for examining the role of genetic and environmental factors for observed racial/ethnic differences, and for possibly mapping alleles that contribute to such differences. Here we examined the distribution and relationship of individual admixture (IA) estimates with BMI and three measures of blood pressure in two admixed populations in the NHLBI Family Blood Pressure Program (FBPP): African Americans and Mexican Americans. For the African Americans, we observed modest but significant differences in average African IA among four recruitment sites. We observed a slight excess of African IA among hypertensives compared to normotensives, and a positive (non-significant) regression of African IA on blood pressure in untreated participants. Within Mexican Americans, we found no difference in average IA between hypertensives and normotensives, but a positive (marginally significant) regression of African IA on diastolic blood pressure. We also observed a significant positive regression of Caucasian IA (and negative regression of Native American IA) on BMI. Our results are suggestive of genetic differences between Africans and non-Africans that influence blood pressure, but such effects are likely to be modest compared to environmental ones. Excess obesity among Native Americans compared to whites is not consistent with a simple genetic explanation.     

Genetic Polymorphism of NOS3 with Susceptibility to Deep Vein Thrombosis after Orthopedic Surgery: A Case-Control Study in Chinese Han Population

Deep vein thrombosis is one of the common complications of orthopedic surgery. Studies indicated that genetic factors played a considerable role in the pathogenesis of deep vein thrombosis. Endothelial nitric oxide synthase which encoded by nitric oxide synthase 3 (NOS3), can generate nitric oxide in endothelial cells. As a predominant regulator for vascular homeostasis, nitric oxide might be involved in the pathogenesis of thrombosis. It had been proved that the NOS3 polymorphism (rs1799983) was associated with the development of cardiovascular diseases. Our objective was to evaluate the association between the NOS3 polymorphism (rs1799983) and deep vein thrombosis after orthopedic surgery in Chinese Han population. The polymorphism was genotyped in 224 subjects with deep vein thrombosis after orthopedic surgery and 580 controls. Allele and genotype frequencies were compared between subjects with deep vein thrombosis and control subjects. The allele and genotype frequencies of the NOS3 polymorphism (rs1799983) were significantly different between subjects with deep vein thrombosis and control subjects. There were also significant differences when the subjects were stratified by gender, surgery type and hypertension status. These findings suggested that the NOS3 polymorphism (rs1799983) was associated with susceptibility to the deep vein thrombosis after orthopedic surgery in Chinese Han population, and NOS3 might play a role in the development of deep vein thrombosis after orthopedic surgery.