共查询到20条相似文献,搜索用时 93 毫秒
1.
Camila de Moraes Ana Paula Couto Davel Luciana Venturini Rossoni Edson Antunes Angelina Zanesco 《BMC physiology》2008,8(1):1-8
Background
Obesity has been associated with a variety of disease such as type II diabetes mellitus, arterial hypertension and atherosclerosis. Evidences have shown that exercise training promotes beneficial effects on these disorders, but the underlying mechanisms are not fully understood. The aim of this study was to investigate whether physical preconditioning prevents the deleterious effect of high caloric diet in vascular reactivity of rat aortic and mesenteric rings.Methods
Male Wistar rats were divided into sedentary (SD); trained (TR); sedentary diet (SDD) and trained diet (TRD) groups. Run training (RT) was performed in sessions of 60 min, 5 days/week for 12 weeks (70–80% VO2max). Triglycerides, glucose, insulin and nitrite/nitrate concentrations (NOx -) were measured. Concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP) were obtained. Expression of Cu/Zn superoxide dismutase (SOD-1) was assessed by Western blotting.Results
High caloric diet increased triglycerides concentration (SDD: 216 ± 25 mg/dl) and exercise training restored to the baseline value (TRD: 89 ± 9 mg/dl). Physical preconditioning significantly reduced insulin levels in both groups (TR: 0.54 ± 0.1 and TRD: 1.24 ± 0.3 ng/ml) as compared to sedentary animals (SD: 0.87 ± 0.1 and SDD: 2.57 ± 0.3 ng/ml). On the other hand, glucose concentration was slightly increased by high caloric diet, and RT did not modify this parameter (SD: 126 ± 6; TR: 140 ± 8; SDD: 156 ± 8 and TRD 153 ± 9 mg/dl). Neither high caloric diet nor RT modified NOx - levels (SD: 27 ± 4; TR: 28 ± 6; SDD: 27 ± 3 and TRD: 30 ± 2 μM). Functional assays showed that high caloric diet impaired the relaxing response to ACh in mesenteric (about 13%), but not in aortic rings. RT improved the relaxing responses to ACh either in aortic (28%, for TR and 16%, to TRD groups) or mesenteric rings (10%, for TR and 17%, to TRD groups) that was accompanied by up-regulation of SOD-1 expression and reduction in triglycerides levels.Conclusion
The improvement in endothelial function by physical preconditioning in mesenteric and aortic arteries from high caloric fed-rats was directly related to an increase in NO bioavailability to the smooth muscle mostly due to SOD-1 up regulation. 相似文献2.
eNOS protects from atherosclerosis despite relevant superoxide production by the enzyme in apoE mice
Ponnuswamy P Schröttle A Ostermeier E Grüner S Huang PL Ertl G Hoffmann U Nieswandt B Kuhlencordt PJ 《PloS one》2012,7(1):e30193
Background
All three nitric oxide synthase (NOS) isoforms are expressed in atherosclerotic plaques. NOS enzymes in general catalyse NO production. However, under conditions of substrate and cofactor deficiency, the enzyme directly catalyse superoxide formation. Considering this alternative chemistry, the effects of NOS on key events in spontaneous hyperlipidemia driven atherosclerosis have not been investigated yet. Here, we evaluate how endothelial nitric oxide synthase (eNOS) modulates leukocyte/endothelial- (L/E) and platelet/endothelial- (P/E) interactions in atherosclerosis and the production of nitric oxide (NO) and superoxide by the enzyme.Principal Findings
Intravital microscopy (IVM) of carotid arteries revealed significantly increased L/E-interactions in apolipoproteinE/eNOS double knockout mice (apoE−/−/eNOS−/−), while P/E-interactions did not differ, compared to apoE−/−. eNOS deficiency increased macrophage infiltration in carotid arteries and vascular cell adhesion molecule-1 (VCAM-1) expression, both in endothelial and smooth muscle cells. Despite the expression of other NOS isoforms (inducible NOS, iNOS and neuronal NOS, nNOS) in plaques, Electron Spin Resonance (ESR) measurements of NO showed significant contribution of eNOS to total circulating and vascular wall NO production. Pharmacological inhibition and genetic deletion of eNOS reduced vascular superoxide production, indicating uncoupling of the enzyme in apoE−/− vessels.Conclusion
Overt plaque formation, increased vascular inflammation and L/E- interactions are associated with significant reduction of superoxide production in apoE−/−/eNOS−/− vessels. Therefore, lack of eNOS does not cause an automatic increase in oxidative stress. Uncoupling of eNOS occurs in apoE−/− atherosclerosis but does not negate the enzyme''s strong protective effects. 相似文献3.
The placental cholinergic system: localization to the cytotrophoblast and modulation of nitric oxide
Background
The human placenta, a non-neuronal tissue, contains an active cholinergic system comprised of acetylcholine (ACh), choline acetyltransferase (ChAT), acetylcholinesterase (AChE), and high affinity muscarinic receptors. The cell(s) of origin of placental ACh and its role in trophoblast function has not been defined. These studies were performed to define the cellular location of ACh synthesis (ChAT) in the human placenta and to begin studying its functional role.Results
Using immunohistochemical techniques, ChAT was observed primarily within the cytotrophoblasts of preterm placentae as well as some mesenchymal elements. Similar intense immunostaining of the cytotrophoblast was observed for endothelium-derived nitric oxide synthase (eNOS) suggesting that ACh may interact with nitric oxide (NO)-dependent signaling pathways. The ability of carbamylcholine (CCh), an ACh analogue, to stimulate a rise in intracellular Ca++ and NO production in trophoblasts was therefore tested using the BeWob30 choriocarcinoma cell as a model system. First, CCh significantly increased intracellular calcium as assessed by fluorescence microscopy. We then examined the ability of CCh to stimulate NO production by measuring total nitrite/nitrate production in conditioned media using chemiluminescence-based analysis. CCh, alone, had no effect on NO production. However, CCh increased measurable NO approximately 100% in the presence of 10 nM estradiol. This stimulatory effect was inhibited by 1 (micro)M scopolamine suggesting mediation via muscarinic receptors. Estradiol, alone, had no effect on total NO or eNOS protein or mRNA.Conclusion
These data demonstrate that placental ChAT localizes to the cytotrophoblast and some mesenchymal cells in human placenta. It further suggests that ACh acts via muscarinic receptors on the trophoblast cell membrane to modulate NO in an estrogen-dependent manner. 相似文献4.
Novensà L Novella S Medina P Segarra G Castillo N Heras M Hermenegildo C Dantas AP 《PloS one》2011,6(9):e25335
Aims
Aging is among the major causes for the lack of cardiovascular protection by estrogen (E2) during postmenopause. Our study aims to determine the mechanisms whereby aging changes E2 effects on nitric oxide (NO) production in a mouse model of accelerated senescence (SAM).Methods and Results
Although we found no differences on NO production in females SAM prone (SAMP, aged) compared to SAM resistant (SAMR, young), by either DAF-2 fluorescence or plasmatic nitrite/nitrate (NO2/NO3), in both cases, E2 treatment increased NO production in SAMR but had no effect in SAMP. Those results are in agreement with changes of eNOS protein and gene expression. E2 up-regulated eNOS expression in SAMR but not in SAMP. E2 is also known to increase NO by decreasing its catabolism by superoxide anion (O2 -). Interestingly, E2 treatment decreased O2 − production in young females, while increased O2 − in aged ones. Furthermore, we observed that aging changed expression ratio of estrogen receptors (ERβ/ERα) and levels of DNA methylation. Increased ratio ERβ/ERα in aged females is associated to a lack of estrogen modulation of NO production and with a reversal in its antioxidant effect to a pro-oxidant profile.Conclusions
Together, our data suggest that aging has detrimental effects on E2-mediated benefits on NO bioavailability, partially by affecting the ability of E2 to induce up regulation of eNOS and decrease of O2 −. These modifications may be associated to aging-mediated modifications on global DNA methylation status, but not to a specific methylation at 5′flanking region of ERα gene. 相似文献5.
Background
Low Emission Zones (LEZs) are areas where the most polluting vehicles are restricted from entering. The effectiveness of LEZs to lower ambient exposures is under debate. This study focused on LEZs that restricted cars of Euro 1 standard without appropriate retrofitting systems from entering and estimated LEZ effects on NO2, NO, and NOx ( = NO2+NO).Methods
Continuous half-hour and diffuse sampler 4-week average NO2, NO, and NOx concentrations measured inside and outside LEZs in 17 German cities of 6 federal states (2005–2009) were analysed as matched quadruplets (two pairs of simultaneously measured index values inside LEZ and reference values outside LEZ, one pair measured before and one after introducing LEZs with time differences that equal multiples of 364 days) by multiple linear and log-linear fixed-effects regression modelling (covariables: e.g., wind velocity, amount of precipitation, height of inversion base, school holidays, truck-free periods). Additionally, the continuous half-hour data was collapsed into 4-week averages and pooled with the diffuse sampler data to perform joint analysis.Results
More than 3,000,000 quadruplets of continuous measurements (half-hour averages) were identified at 38 index and 45 reference stations. Pooling with diffuse sampler data from 15 index and 10 reference stations lead to more than 4,000 quadruplets for joint analyses of 4-week averages. Mean LEZ effects on NO2, NO, and NOx concentrations (reductions) were estimated to be at most −2 µg/m3 (or −4%). The 4-week averages of NO2 concentrations at index stations after LEZ introduction were 55 µg/m3 (median and mean values) or 82 µg/m3 (95th percentile).Conclusions
This is the first study investigating comprehensively the effectiveness of LEZs to reduce NO2, NO, and NOx concentrations controlling for most relevant potential confounders. Our analyses indicate that there is a statistically significant, but rather small reduction of NO2, NO, and NOx concentrations associated with LEZs. 相似文献6.
Background
Nitrate and nitrite (jointly referred to herein as NOx) are ubiquitous environmental contaminants to which aquatic organisms are at particularly high risk of exposure. We tested the hypothesis that NOx undergo intracellular conversion to the potent signaling molecule nitric oxide resulting in the disruption of endocrine-regulated processes.Methodology/Principal Findings
These experiments were performed with insect cells (Drosophila S2) and whole organisms Daphnia magna. We first evaluated the ability of cells to convert nitrate (NO3 −) and nitrite (NO2 −) to nitric oxide using amperometric real-time nitric oxide detection. Both NO3 − and NO2 − were converted to nitric oxide in a substrate concentration-dependent manner. Further, nitric oxide trapping and fluorescent visualization studies revealed that perinatal daphnids readily convert NO2 − to nitric oxide. Next, daphnids were continuously exposed to concentrations of the nitric oxide-donor sodium nitroprusside (positive control) and to concentrations of NO3 − and NO2 −. All three compounds interfered with normal embryo development and reduced daphnid fecundity. Developmental abnormalities were characteristic of those elicited by compounds that interfere with ecdysteroid signaling. However, no compelling evidence was generated to indicate that nitric oxide reduced ecdysteroid titers.Conclusions/Significance
Results demonstrate that nitrite elicits developmental and reproductive toxicity at environmentally relevant concentrations due likely to its intracellular conversion to nitric oxide. 相似文献7.
Masafumi Hidaka Aina Gotoh Taiki Shimizu Kiwamu Minamisawa Hiromi Imamura Takafumi Uchida 《The Journal of biological chemistry》2016,291(5):2260-2269
Nitrate (NO3−) and nitrite (NO2−) are the physiological sources of nitric oxide (NO), a key biological messenger molecule. NO3−/NO2− exerts a beneficial impact on NO homeostasis and its related cardiovascular functions. To visualize the physiological dynamics of NO3−/NO2− for assessing the precise roles of these anions, we developed a genetically encoded intermolecular fluorescence resonance energy transfer (FRET)-based indicator, named sNOOOpy (sensor for NO3−/NO2− in physiology), by employing NO3−/NO2−-induced dissociation of NasST involved in the denitrification system of rhizobia. The in vitro use of sNOOOpy shows high specificity for NO3− and NO2−, and its FRET signal is changed in response to NO3−/NO2− in the micromolar range. Furthermore, both an increase and decrease in cellular NO3− concentration can be detected. sNOOOpy is very simple and potentially applicable to a wide variety of living cells and is expected to provide insights into NO3−/NO2− dynamics in various organisms, including plants and animals. 相似文献
8.
Background
The aging gene p66Shc, is an important mediator of oxidative stress-induced vascular dysfunction and disease. In cultured human aortic endothelial cells (HAEC), p66Shc deletion increases endothelial nitric oxide synthase (eNOS) expression and nitric oxide (NO) bioavailability via protein kinase B. However, the putative role of the NO pathway on p66Shc activation remains unclear. This study was designed to elucidate the regulatory role of the eNOS/NO pathway on p66Shc activation.Methods and Results
Incubation of HAEC with oxidized low density lipoprotein (oxLDL) led to phosphorylation of p66Shc at Ser-36, resulting in an enhanced production of superoxide anion (O2 -). In the absence of oxLDL, inhibition of eNOS by small interfering RNA or L-NAME, induced p66Shc phosphorylation, suggesting that basal NO production inhibits O2 - production. oxLDL-induced, p66Shc-mediated O2- was prevented by eNOS inhibition, suggesting that when cells are stimulated with oxLDL eNOS is a source of reactive oxygen species. Endogenous or exogenous NO donors, prevented p66Shc activation and reduced O2- production. Treatment with tetrahydrobiopterin, an eNOS cofactor, restored eNOS uncoupling, prevented p66Shc activation, and reduced O2- generation. However, late treatment with tetrahydropterin did not yield the same result suggesting that eNOS uncoupling is the primary source of reactive oxygen species.Conclusions
The present study reports that in primary cultured HAEC treated with oxLDL, p66Shc-mediated oxidative stress is derived from eNOS uncoupling. This finding contributes novel information on the mechanisms of p66Shc activation and its dual interaction with eNOS underscoring the importance eNOS uncoupling as a putative antioxidant therapeutical target in endothelial dysfunction as observed in cardiovascular disease. 相似文献9.
Introduction
Glucocorticoids are commonly used as therapeutic agents in many acute and chronic inflammatory and auto-immune diseases. The current study investigated the effects of methylprednisolone (a synthetic glucocorticoid) on aortic distensibility and vascular resistance in lipopolysaccharide-induced chronic inflammation in male Wistar rats.Methods
Chronic inflammation was induced by implanting a subcutaneous slow-release ALZET osmotic pump (1 mg kg−1 day−1 lipopolysaccharide) for either 2 or 4 weeks. Arterial wave transit time (τ) was derived to describe the elastic properties of aortas using the impulse response function of the filtered aortic input impedance spectra.Results
Long-term lipopolysaccharide challenge enhanced the expression of advanced glycation end products (AGEs) in the aortas. Lipopolysaccharide also upregulated the inducible form of nitric oxide synthase to produce high levels of nitric oxide (NO), which resulted in vasodilation, as evidenced by the fall in total peripheral resistance (Rp). However, lipopolysaccharide challenge did not influence the elastic properties of aortas, as shown by the unaltered τ. The NO-mediated vascular relaxation may counterbalance the AGEs-induced arterial stiffening so that the aortic distensibility remained unaltered. Treating lipopolysaccharide-challenged rats with methylprednisolone prevented peripheral vasodilation because of its ability to increase Rp. However, methylprednisolone produced an increase in aorta stiffness, as manifested by the significant decline in τ. The diminished aortic distensibility by methylprednisolone paralleled a significant reduction in NO plasma levels, in the absence of any significant changes in AGEs content.Conclusion
Methylprednisolone stiffens aortas and elastic arteries in lipopolysaccharide-induced chronic inflammation in rats, for NO activity may be dominant as a counteraction of AGEs. 相似文献10.
Yi Yu Yuyan Xiong Jean-Pierre Montani Zhihong Yang Xiu-Fen Ming 《Journal of visualized experiments : JoVE》2016,(108)
Endothelium-derived nitric oxide (NO) produced from endothelial NO-synthase (eNOS) is one of the most important vasoprotective molecules in cardiovascular physiology. Dysfunctional eNOS such as uncoupling of eNOS leads to decrease in NO bioavailability and increase in superoxide anion (O2.−) production, and in turn promotes cardiovascular diseases. Therefore, appropriate measurement of NO and O2.− levels in the endothelial cells are pivotal for research on cardiovascular diseases and complications. Because of the extremely labile nature of NO and O2.−, it is difficult to measure NO and O2.− directly in a blood vessel. Numerous methods have been developed to measure NO and O2.− production. It is, however, either insensitive, or non-specific, or technically demanding and requires special equipment. Here we describe an adaption of the fluorescence dye method for en face simultaneous detection and visualization of intracellular NO and O2.− using the cell permeable diaminofluorescein-2 diacetate (DAF-2DA) and dihydroethidium (DHE), respectively, in intact aortas of an obesity mouse model induced by high-fat-diet feeding. We could demonstrate decreased intracellular NO and enhanced O2.− levels in the freshly isolated intact aortas of obesity mouse as compared to the control lean mouse. We demonstrate that this method is an easy technique for direct detection and visualization of NO and O2.− in the intact blood vessels and can be widely applied for investigation of endothelial (dys)function under (physio)pathological conditions. 相似文献
11.
Short-term (10 minutes) measurements of plasmalemma NO3− influx (oc) into roots of intact barley plants were obtained using 13NO3−. In plants grown for 4 days at various NO3− levels (0.1, 0.2, 0.5 millimolar), oc was found to be independent of the level of NO3− pretreatment. Similarly, pretreatment with Cl− had no effect upon plasmalemma 13NO3− influx. Plants grown in the complete absence of 13NO3− (in CaSO4 solutions) subsequently revealed influx values which were more than 50% lower than for plants grown in NO3−. Based upon the documented effects of NO3− or Cl− pretreatments on net uptake of NO3−, these observations suggest that negative feedback from vacuolar NO3− and/or Cl− acts at the tonoplast but not at the plasmalemma. When included in the influx medium, 0.5 millimolar Cl− was without effect upon 13NO3− influx, but NH4+ caused approximately 50% reduction of influx at this concentration. 相似文献
12.
Sai Wang Seto Smriti M. Krishna Hongyou Yu David Liu Surabhi Khosla Jonathan Golledge 《PloS one》2013,8(3)
Objective
The angiotensin II (AngII)-infused apolipoprotein E-deficient (ApoE−/−) mouse model is widely used to study atherosclerosis and abdominal aortic aneurysm. An increase in blood pressure has been reported in this model however the underlying mechanism has not been fully explored. In this study, we investigated whether vasomotor dysfunction develops in AngII-infused ApoE−/− mice and the underlying mechanism involved.Methods
ApoE−/− mice were infused with vehicle (distilled water) or AngII subcutaneously for 14 days. Blood pressure and heart rate were measured using the non-invasive tail cuff method. Aortic vascular reactivity and expression of key proteins (endothelial nitric oxide synthase (eNOS), phospho-eNOS and caveolin-1) were assessed using tension myography and Western blotting respectively. Plasma nitric oxide (NO) level was estimated using a colorimetric assay.Results
AngII infusion caused a time-dependent increase in blood pressure (P<0.001). Aortas from AngII-infused mice were significantly less responsive to acetylcholine-induced endothelium-dependent relaxation when compared to aortas from mice infused with vehicle control (P<0.05). Contractile responses to phenylephrine (P<0.01) and potassium chloride (P<0.001) were significantly enhanced in aortas from AngII-infused mice. eNOS phosphorylation was significantly decreased in the aorta of AngII-infused mice (P<0.05). Aortic caveolin-1 protein expression was significantly increased in AngII-infused mice (P<0.05). Plasma nitrate/nitrite level was significantly reduced in AngII-infused mice (P<0.05). Pharmacological disruption of caveolae using methyl-β-cyclodextrin (MβCD) in isolated aortas from AngII-infused mice caused a significant leftward shift of the acetylcholine-induced relaxation concentration-response curve when compared to vehicle control (P<0.05).Conclusion
Upregulation of caveolin-1 protein expression and reduced NO bioavailability contributes to aortic endothelial dysfunction in AngII-infused ApoE−/− mice. 相似文献13.
Achromobacter denitrificans YD35 is an NO2−-tolerant bacterium that expresses the aconitase genes acnA3, acnA4, and acnB, of which acnA3 is essential for growth tolerance against 100 mm NO2−. Atmospheric oxygen inactivated AcnA3 at a rate of 1.6 × 10−3 min−1, which was 2.7- and 37-fold lower compared with AcnA4 and AcnB, respectively. Stoichiometric titration showed that the [4Fe-4S]2+ cluster of AcnA3 was more stable against oxidative inactivation by ferricyanide than that of AcnA4. Aconitase activity of AcnA3 persisted against high NO2− levels that generate reactive nitrogen species with an inactivation rate constant of k = 7.8 × 10−3 min−1, which was 1.6- and 7.8-fold lower than those for AcnA4 and AcnB, respectively. When exposed to NO2−, the acnA3 mutant (AcnA3Tn) accumulated higher levels of cellular citrate compared with the other aconitase mutants, indicating that AcnA3 is a major producer of cellular aconitase activity. The extreme resistance of AcnA3 against oxidation and reactive nitrogen species apparently contributes to bacterial NO2− tolerance. AcnA3Tn accumulated less cellular NADH and ATP compared with YD35 under our culture conditions. The accumulation of more NO by AcnA3Tn suggested that NADH-dependent enzymes detoxify NO for survival in a high NO2− milieu. This novel aconitase is distributed in Alcaligenaceae bacteria, including pathogens and denitrifiers, and it appears to contribute to a novel NO2− tolerance mechanism in this strain. 相似文献
14.
Wei Yu Jiliang Wu Fei Cai Jizhou Xiang Wenliang Zha Dan Fan Shuang Guo Zhangyin Ming Chao Liu 《PloS one》2012,7(12)
Objectives
Diabetic cardiomyopathy (DCM), characterized by myocardial structural and functional changes, is an independent cardiomyopathy that develops in diabetic individuals. The present study was sought to investigate the effect of curcumin on modulating DCM and the mechanisms involved.Methods
An experimental diabetic rat model was induced by low dose of streptozoticin(STZ) combined with high energy intake on rats. Curcumin was orally administrated at a dose of 100 or 200 mg·kg−1·d−1, respectively. Cardiac function was evaluated by serial echocardiography. Myocardial ultrastructure, fibrosis area and apoptosis were assessed by histopathologic analyses. Metabolic profiles, myocardial enzymes and oxidative stress were examined by biochemical tests. Inflammatory factors were detected by ELISA, and interrelated proteins were measured by western blot.Results
Rats with DCM showed declined systolic myocardial performance associated with myocardial hypertrophy and fibrosis, which were accompanied with metabolism abnormalities, aberrant myocardial enzymes, increased AGEs (advanced glycation end products) accumulation and RAGE (receptor for AGEs) expression, elevated markers of oxidative stress (MDA, SOD, the ratio of NADP+/NADPH, Rac1 activity, NADPH oxidase subunits expression of gp91phox and p47phox ), raised inflammatory factor (TNF-α and IL-1β), enhanced apoptotic cell death (ratio of bax/bcl-2, caspase-3 activity and TUNEL), diminished Akt and GSK-3β phosphorylation. Remarkably, curcumin attenuated myocardial dysfunction, cardiac fibrosis, AGEs accumulation, oxidative stress, inflammation and apoptosis in the heart of diabetic rats. The inhibited phosphorylation of Akt and GSK-3β was also restored by curcumin treatment.Conclusions
Taken together, these results suggest that curcumin may have great therapeutic potential in the treatment of DCM, and perhaps other cardiovascular disorders, by attenuating fibrosis, oxidative stress, inflammation and cell death. Furthermore, Akt/GSK-3β signaling pathway may be involved in mediating these effects. 相似文献15.
Kristína Simon Klenovics Peter Boor Veronika Somoza Peter Celec Vincenzo Fogliano Katarína ?ebeková 《PloS one》2013,8(1)
Introduction
Infant formula-feeding is associated with reduced insulin sensitivity. In rodents and healthy humans, advanced glycation end product (AGE)-rich diets exert diabetogenic effects. In comparison with human breast-milk, infant formulas contain high amounts of AGEs. We assessed the role of AGEs in infant-formula-consumption-associated insulin resistance.Methods
Total plasma levels of Nε-(carboxymethyl)lysine (CML), AGEs-associated fluorescence (λex = 370 nm/λem = 445 nm), soluble adhesion molecules, markers of micro- binflammation (hsCRP), oxidative stress (malondialdehyde, 8-isoprostanes) and leptinemia were determined, and correlated with insulin sensitivity in a cross-sectional study in 166 healthy term infants aged 3-to-14 months, subdivided according to feeding regimen (breast-milk- vs. infant formula-fed) and age (3-to-6-month-olds, 7-to-10-month-olds, and 11-to-14-month-old infants). Effects of the consumption of low- vs. high-CML-containing formulas were assessed. 36 infants aged 5.8±0.3 months were followed-up 7.5±0.3 months later.Results
Cross-sectional study: 3-to-6-month-olds and 7-to-10-month-old formula-fed infants presented higher total plasma CML levels and AGEs-associated fluorescence (p<0.01, both), while only the 3-to-6-month-olds displayed lower insulin sensitivity (p<0.01) than their breast-milk-fed counterparts. 3-to-6-month-olds fed low-CML-containing formulas presented lower total plasma CML levels (p<0.01), but similar insulin sensitivity compared to those on high-CML-containing formulas. Markers of oxidative stress and inflammation, levels of leptin and adhesion molecules did not differ significantly between the groups. Follow-up study: at initial investigation, the breast-milk-consuming infants displayed lower total plasma CML levels (p<0.01) and AGEs-associated fluorescence (p<0.05), but higher insulin sensitivity (p<0.05) than the formulas-consuming infants. At follow-up, the groups did not differ significantly in either determined parameter.Conclusions
In healthy term infants, high dietary load with CML does not play a pathophysiological role in the induction of infant formula-associated insulin resistance. Whether a high load of AGEs in early childhood affects postnatal programming remains to be elucidated. 相似文献16.
Background
We have previously reported that high glucose impairs coronary vasodilation by reducing voltage-gated K+ (Kv) channel activity. However, the underlying mechanisms remain unknown. Advanced glycation end products (AGEs) are potent factors that contribute to the development of diabetic vasculopathy. The aim of this study was to investigate the role of AGEs in high glucose-induced impairment of Kv channels-mediated coronary vasodilation.Methods
Patch-clamp recording and molecular biological techniques were used to assess the function and expression of Kv channels. Vasodilation of isolated rat small coronary arteries was measured using a pressurized myograph. Treatment of isolated coronary vascular smooth muscle cells (VSMCs) and streptozotocin-induced diabetic rats with aminoguanidine, the chemical inhibitor of AGEs formation, was performed to determine the contribution of AGEs.Results
Incubation of VSMCs with high glucose reduced Kv current density by 60.4 ± 4.8%, and decreased expression of Kv1.2 and Kv1.5 both at the gene and protein level, whereas inhibiting AGEs formation or blocking AGEs interacting with their receptors prevented high glucose-induced impairment of Kv channels. In addition, diabetic rats manifested reduced Kv channels-mediated coronary dilation (9.3 ± 1.4% vs. 36.9 ± 1.4%, P < 0.05), which was partly corrected by the treatment with aminoguanidine (24.4 ± 2.2% vs. 9.3 ± 1.4%, P < 0.05).Conclusions
Excessive formation of AGEs impairs Kv channels in VSMCs, then leading to attenuation of Kv channels-mediated coronary vasodilation. 相似文献17.
The comparative induction of nitrate reductase (NR) by ambient NO3− and NO2− as a function of influx, reduction (as NR was induced) and accumulation in detached leaves of 8-day-old barley (Hordeum valgare L.) seedlings was determined. The dynamic interaction of NO3− influx, reduction and accumulation on NR induction was shown. The activity of NR, as it was induced, influenced its further induction by affecting the internal concentration of NO3−. As the ambient concentration of NO3− increased, the relative influences imposed by influx and reduction on NO3− accumulation changed with influx becoming a more predominant regulant. Significant levels of NO3− accumulated in NO2−-fed leaves. When the leaves were supplied cycloheximide or tungstate along with NO2−, about 60% more NO3− accumulated in the leaves than in the absence of the inhibitors. In NO3−-supplied leaves NR induction was observed at an ambient concentration of as low as 0.02 mm. No NR induction occurred in leaves supplied with NO2− until the ambient NO2− concentration was 0.5 mm. In fact, NR induction from NO2− solutions was not seen until NO3− was detected in the leaves. The amount of NO3− accumulating in NO2−-fed leaves induced similar levels of NR as did equivalent amounts of NO3− accumulating from NO3−-fed leaves. In all cases the internal concentration of NO3−, but not NO2−, was highly correlated with the amount of NR induced. The evidence indicated that NO3− was a more likely inducer of NR than was NO2−. 相似文献
18.
Background and Aims
Modellers often define growth as the development of plant structures from endogenous resources, thus making a distinction between structural (WS) and total (W) dry biomass, the latter being the sum of WS and the weight of storage compounds. In this study, short-term C and N reserves were characterized experimentally (forms, organ distribution, time changes) in relation to light and nutrition signals, and organ structural growth in response to reserve levels was evaluated.Methods
Tomato plants (Solanum lycopersicum) were grown hydroponically in a growth room with a 12-h photoperiod and an adequate supply of NO3− (3 mol m−3). Three experiments were carried out 18 d after sowing: [NO3−] was either maintained at 3 mol m−3, changed to 0·02 mol m−3 or to 0 mol m−3. Plants were sampled periodically throughout the light/dark cycles over 24–48 h. Organ WS was calculated from W together with the amount of different compounds that act as C and N resources, i.e. non-structural carbohydrates and carboxylates, nitrate and free amino acids.Key Results
With adequate nutrition, carbohydrates accumulated in leaves during light periods, when photosynthesis exceeded growth needs, but decreased at night when these sugars are the main source of C for growth. At the end of the night, carbohydrates were still high enough to fuel full-rate growth, as WS increased at a near constant rate throughout the light/dark cycle. When nitrate levels were restricted, C reserves increased, but [NO3−] decreased progressively in stems, which contain most of the plant N reserves, and rapidly in leaves and roots. This resulted in a rapid restriction of structural growth.Conclusions
Periodic darkness did not restrict growth because sufficient carbohydrate reserves accumulated during the light period. Structural growth, however, was very responsive to NO3− nutrition, because N reserves were mostly located in stems, which have limited nitrate reduction capacity.Key words: Solanum lycopersicum, tomato, nitrogen, carbon, structural growth, reserves, nitrate, amino acids, carbohydrate, carboxylate 相似文献19.
20.
Most studies of bacterial denitrification have used nitrate (NO3−) as the first electron acceptor, whereas relatively less is understood about nitrite (NO2−) denitrification. We isolated novel bacteria that proliferated in the presence of high levels of NO2− (72 mM). Strain YD50.2, among several isolates, was taxonomically positioned within the α subclass of Proteobacteria and identified as Ochrobactrum anthropi YD50.2. This strain denitrified NO2−, as well as NO3−. The gene clusters for denitrification (nar, nir, nor, and nos) were cloned from O. anthropi YD50.2, in which the nir and nor operons were linked. We confirmed that nirK in the nir-nor operon produced a functional NO2− reductase containing copper that was involved in bacterial NO2− reduction. The strain denitrified up to 40 mM NO2− to dinitrogen under anaerobic conditions in which other denitrifiers or NO3− reducers such as Pseudomonas aeruginosa and Ralstonia eutropha and nitrate-respiring Escherichia coli neither proliferated nor reduced NO2−. Under nondenitrifying aerobic conditions, O. anthropi YD50.2 and its type strain ATCC 49188T proliferated even in the presence of higher levels of NO2− (100 mM), and both were considerably more resistant to acidic NO2− than were the other strains noted above. These results indicated that O. anthropi YD50.2 is a novel denitrifier that has evolved reactive nitrogen oxide tolerance mechanisms.Environmental bacteria maintain the global nitrogen cycle by metabolizing organic and inorganic nitrogen compounds. Denitrification is critical for maintenance of the global nitrogen cycle, through which nitrate (NO3−) or nitrite (NO2−) is reduced to gaseous nitrogen forms such as N2 and nitrous oxide (N2O) (19, 47). Decades of investigations into denitrifying bacteria have revealed their ecological impact (9), their molecular mechanisms of denitrification (13, 25, 47), and the industrial importance of removing nitrogenous contaminants from wastewater (31, 36). Bacterial denitrification is considered to comprise four successive reduction steps, each of which is catalyzed by NO3− reductase (Nar), NO2− reductase (Nir), nitric oxide (NO) reductase (Nor), and N2O reductase (Nos). The reaction of each enzyme is linked to the electron transport chain on the cellular membrane and accompanies oxidative phosphorylation, implying that bacterial denitrification is of as much physiological significance as anaerobic respiration (25, 47). Most denitrifying bacteria are facultative anaerobes and respire with oxygen under aerobic conditions. Because denitrification is induced in the absence of oxygen, it is considered an alternative mechanism of energy conservation that has evolved as an adaptation to anaerobic circumstances (13, 47).Nitrite and NO are hazardous to bacteria, since they generate highly reactive nitrogen species (RNS) under physiological conditions and damage cellular DNA, lipid, and proteins (28, 37). Denitrifying bacteria are thought to be threatened by RNS since they reduce NO3− to generate NO2− and NO as denitrifying intermediates. Furthermore, denitrifying bacteria often inhabit environments where they are exposed to NO2− and NO and hence high levels of RNS. Recent reports suggest that pathogenic bacteria invading animal tissues are attacked by NO generated by macrophages (12). Such bacteria involve denitrifiers, and some of them, for example, Neisseria meningitidis (1) and Pseudomonas aeruginosa, acquire resistance to NO by producing Nor (44). The utilization (reduction) of NO by Brucella increases the survival of infected mice (2). These examples suggest that production of a denitrifying mechanism affects bacterial survival of threats from both endogenous and extracellular RNS. However, the mechanism of RNS tolerance induced by denitrifying bacteria is not fully understood.Ubiquitous gram-negative Ochrobactrum strains are widely distributed in soils and aqueous environments, where they biodegrade aromatic compounds (11), organophosphorus pesticides (45), and other hydrocarbons (38) and remove heavy metal ions such as chromium and cadmium (24). Having been isolated from clinical specimens, Ochrobactrum anthropi is currently recognized as an emerging opportunistic pathogen, although relatively little is known about its pathogenesis and factors contributing to its virulence (7, 30). Manipulation systems have been developed to investigate these issues at the molecular genetic level (33). Some O. anthropi strains have been identified as denitrifiers (21), although the denitrifying properties of these strains have not been investigated in detail. This study was undertaken to examine the denitrifying properties of O. anthropi in more detail. O. anthropi YD50.2 was selected for this study and was isolated herein. The strain denitrified high levels of NO2− (up to 40 mM) to dinitrogen under anaerobic conditions. The strain was highly resistant to acidified NO2− under nondenitrifying aerobic conditions. These results indicate that O. anthropi YD50.2 has mechanisms that produce tolerance to RNS. 相似文献