The denitrifier method is widely used as a novel pretreatment method for the determination of nitrogen and oxygen isotope ratios as it can provide quantitative and high-sensitivity measurements. Nevertheless, the method is limited by relatively low measurement accuracy for δ18O. In this study, we analyzed the factors influencing the accuracy of δ18O determination, and then systematically investigated the effects of dissolved oxygen concentrations and nitrate sample sizes on estimates of the δ15N and δ18O of nitrate reference materials. The δ18O contraction ratio was used to represent the relationship between the measured difference and true difference between two reference materials. We obtained the following main results: (1) a gas-liquid ratio of 3:10 (v/v) in ordinary triangular flasks and a shaking speed of 120 r/min produced an optimal range (1.9 to 2.6 mg/L) in the concentration of dissolved oxygen for accurately determining δ18O, and (2) the δ18O contraction ratio decreased as nitrate sample size decreased within a certain range (1.0 to 0.1 μmol). Our results suggested that δ18O contraction is influenced mainly by dissolved oxygen concentrations in pure culture, and provided a model for improving the accuracy of oxygen isotope analysis.
Denitrification ; Nitrates/analysis* ; Oxygen Isotopes/analysis*

OBJECTIVETo study the effect of nitrogen forms on nitrogen metabolism and main chemical composition of Pinellia ternate.

METHODThrough the soilless cultivation experiment and based at the same nitrogen level and different NH4(+) -N/NO3(-) -N ratios, nitrate reductase (NR) activity, glutamine synthetase (GS) activity, the content of nitrate nitrogen and ammonium nitrogen in different parts of P. ternate were determined. The contents of total alkaloid, free total organic acids and guanosine in the tuber were determined. The yield of bulbil and tuber was calculated.

RESULTThe test results showed that, with the NH4(+) -N/NO3(-) -N ratio increasing, the activity of nitrate reductase decreased, the content of nitrate nitrogen in the leaves, petioles and tuber increasing initially, then decreased, and the content of nitrate nitrogen in the root decreased. Meanwhile, with the NH4(+) -N/NO3(-) -N ratio increasing, the activity of glutamine synthetase in the leaves, petioles and root increased, the activity of glutamine synthetase in the tuber increasing initially, then decreased. The contents of ammonium nitrogen in the leaves, tuber and root increased initially, then decreased, and the contents of ammonium nitrogen in the petioles increased with the NH4(+)(-N/NO3(-)-N ratio increasing. The yield of bulbil and tuber were the highest at the NH4(+)-N/NO3(-) -N ratio of 75: 25. The content of total alkaloid and guanosine in the tuber were the highest at the NH4(+)-N/NO3(-) -N ratio of 0: 100, and the contents were 0.245% and 0.0197% respectively. With the NH4(+)-N/NO3(-) -N ratio of 50: 50, the content of free total organic acids was the highest, it reached 0.7%, however, the content of free total organic acids was the lowest at the NH4(+) -N/NO3(-) -N ratio of 0: 100.

CONCLUSIONNitrogen fertilization significant influences the nitrogen metabolism, the yield and main chemical composition of P. ternate.

Fertilizers ; analysis ; Nitrates ; analysis ; Nitrogen ; metabolism ; Pinellia ; chemistry ; growth & development ; metabolism ; Quaternary Ammonium Compounds ; analysis

AIM AND METHODSNew method to analyse nitrate and nitrite concentrations in saliva, serum and urine was developed using high performance liquid chromatography.

RESULTSThe whole isolation process was completed in less than 7 minutes, the determination linearity of nitrate and nitrite were 0.7 ng-100 ng and 5 ng-100 ng, respectively. MINIMUM: Detectable limits of nitrate and nitrite were 0.3 ng and 2 ng, respectively. Nitrate recovery ratio was 99%-102% and nitrite recovery ratio was 99%-104%. The RSD of nitrate and nitrite was 0.8% and 1.7%, respectively.

CONCLUSIONIn comparison with other methods available, the present method seems to be simpler, more sensitive and specific.

Body Fluids ; chemistry ; Chromatography, High Pressure Liquid ; methods ; Nitrates ; analysis ; Nitrites ; analysis

Vegetables are important constituents of the human diet. Heavy metals and nitrate are among the major contaminants of vegetables. Consumption of vegetables and fruits with accumulated heavy metals and nitrate has the potential to damage different body organs leading to unwanted effects. Breeding vegetables with low heavy metal and nitrate contaminants is a cost-effective approach. We investigated 38 water spinach genotypes for low Cd and nitrate co-accumulation. Four genotypes, i.e. JXDY, GZQL, XGDB, and B888, were found to have low co-accumulation of Cd (<0.71 mg/kg dry weight) and nitrate (<3100 mg/kg fresh weight) in the edible parts when grown in soils with moderate contamination of both Cd (1.10 mg/kg) and nitrate (235.2 mg/kg). These genotypes should be appropriate with minimized risk to humans who consume them. The Cd levels in the edible parts of water spinach were positively correlated with the concentration of Pb or Zn, but Cd, Pb, or Zn was negatively correlated with P concentration. These results indicate that these three heavy metals may be absorbed into the plant in similar proportions or in combination, minimizing the influx to aerial parts. Increasing P fertilizer application rates appears to prevent heavy metal and nitrate translocation to shoot tissues and the edible parts of water spinach on co-contaminated soils.
Biomass ; Cadmium/metabolism* ; Chlorophyll/analysis* ; Genotype ; Humans ; Ipomoea/genetics* ; Nitrates/metabolism*

OBJECTIVETo determine the expressions of endothelial nitric oxide synthase traffic inducer (NOSTRIN) and endothelial nitric oxide synthase (eNOS) in the testis tissue of azoospermia patients, and investigate their correlation with the pathogenesis of azoospermia.

METHODSWe detected the expressions of NOSTRIN and NOSTRIN mRNA by immunohistochemistry and RT-PCR respectively, determined the activity of eNOS by spectrophotometry, and measured the stable metabolic end product NO, NO2- / NO3-, by nitrate reductase assay in the testis tissues of 17 patients with idiopathic azoospermia (the azoospermia group) and 10 normal men (the normal group).

RESULTSNOSTRIN and NOSTRIN mRNA were expressed in the spermatogonia, sertoli cells, stromal cells and vascular endothelial cells, more lowly in the azoospermia than in the normal group (0.312 +/- 0.076 versus 0.793 +/- 0.082, P < 0.01). The activity of eNOS was significantly increased in the idiopathic azoospermia patients ([33.727 +/- 3.58] U/mg) compared with the normal men ([17.69 +/- 3.84] U/mg) (P < 0.01). The level of NO2- / NO3- was significantly higher in the azoospermia than in the normal group ([48.56 +/- 8.49] micromol/L versus [25.37 +/- 9.61] micromol/L, P < 0.01). The expression of NOSTRIN showed a significant negative correlation with the activity of eNOS (r = -0.57, P < 0.01) as well as with the level of NO2- / NO3- (r = -0.61, P < 0.01) in the testis tissue of the idiopathic azoospermia patients.

CONCLUSIONThe expression of NOSTRIN is decreased, while the activity of eNOS and the level of NO2- / NO3- increased in the testis tissue of azoospermia patients, which may be associated with the pathogenesis of azoospermia.

Adult ; Azoospermia ; metabolism ; Humans ; Intracellular Signaling Peptides and Proteins ; metabolism ; Male ; Nitrates ; analysis ; Nitric Oxide Synthase Type III ; metabolism ; Nitrites ; analysis ; Spermatogenesis ; Testis ; metabolism

OBJECTIVETo evaluate the bond strength of total-etch or self-etch dentin bonding agents after using two different dentin desensitizers on exposed dentin and investigate the bond interface by scanning electron microscope (SEM).

METHODSThirty intact and non-carious human third molars were used. The occlusal enamel was removed with the use of a slow-speed saw under water cooling. These teeth were divided into three groups using a table of random numbers with 10 teeth each. These three groups were treated with water (Group C), UltraEZ (Group U) and MI Paste (Group M) respectively. Then 10 teeth from each group were divided into A subgroup (n = 5) bonded with Single Bond 2 adhesive system and B subgroup (n = 5) bonded with Xeno III adhesive system according to manufacturers' instructions. A block of composite resin was build up to 4-5 mm. All the teeth were sectioned occluso-gingivally to obtain bar-shaped specimens with bonded surface area about 0.9 mm x 0.9 mm. The tension of the sample was tested by a microtensile tester at 1 mm/min. The mean values of bond strength were compared using one-way ANOVA. Three samples were chosen randomly from each of six groups for SEM investigation.

RESULTSThere were no significant differences between Group U and Group C both in A and B subgroups. While there were significant differences between Group M and Group C in two bonding-agent subgroups. For SEM, the hybrid layer was thin and dense in six groups. Both total-etch and self-etch bonding systems could get fair resin tag infiltration in Group C and Group U. In Group M, the resin tags were relatively shorter and fewer than the anterior mentioned two groups.

CONCLUSIONSUltraEZ had no effect on bond strength of both kinds of dentin bonding agents, while MI paste could diminish bond strength.

Bisphenol A-Glycidyl Methacrylate ; chemistry ; Dental Materials ; Dental Stress Analysis ; Dentin-Bonding Agents ; chemistry ; Humans ; Materials Testing ; Molar, Third ; Nitrates ; chemistry ; Potassium Compounds ; chemistry

To providing evidence about nitrogen adequate application of Platycodon grandiflorum, the pot culture experiment was conducted to study the effect of nitrogen on the growth, physiological metabolism and the quality of P. grandiflorum. The activity of NR, GS and SOD, POD and CAT were determined. And the nitrate and ammonium nitrogen content, photosynthetic characteristics, active components of P. grandiflorum were determined. The results showed that the nitrate nitrogen content and P. biomass reached its maximum value, when NH4(+)-N/NO3(-) -N was 0: 100, the activity of NR. The activity of GS was the highest at the NH4(+) -N/NO3(-) -N ratio of 25:75 and ammonium nitrogen content was the highest at 75:25. The activity of SOD decreased and then increased with the increasing of NO3(-) -N. At the NH4(+) -N/NO3(-) -N ratio of 25: 75, the activity of CAT had its maximum value and the content of MDA had the minimum value. At the same time, the content of platycodon D was the highest at this treatment. The studies had shown that different nitrogen forms and ratio had a significant effect on the characteristics of photosynthetic physiology, nitrogen metabolism and resistance adjustment, growth and the quality of P. grandiflorum. The NH4(+) -N/NO3(-) -N ratio of 25: 75 was a suitable ratio of nitrogen forms for the growth of P. Grandiflorum and accumulating the content of platycodon D.
Ammonium Compounds ; metabolism ; Biomass ; Drugs, Chinese Herbal ; analysis ; metabolism ; Nitrates ; metabolism ; Photosynthesis ; Plant Leaves ; chemistry ; growth & development ; metabolism ; Platycodon ; chemistry ; growth & development ; metabolism

OBJECTIVETo study the effect of NH4(+)-N/NO3(-)-N ratios in the applied supplementary fertilizer on the growth, nitrogen metabolis related enzymes activity and photosynthetic characteristics of Isatis indigotica.

METHODThe sand culture experiment was conducted, and seedling of I. indigotica was fertilized with the mixed nutrition that containing the Hoagland's macro elements and the Aron's micro elements, the additional 63 mmol N was supplementary with the NH4(+)-N/NO3(-)-N ratio of 100:0, 75:25, 50:50, 25:75 and 0:100.

RESULTThe biomass of I. indigotica increased at first when the supplementary N of NH4(+)-N/NO3(-)-N ratio changed from 100:0 to 50:50 and decreased afterwards. The maximum value was at 50:50 and the minimum at 100: 0. With increasing the ratio of NO3(-)-N, the activity of nitrate reductase and glutamine synthetase increased and then decreased and the relationship between the activity and the ratio could be described with an approximate parabola curve. The net photosynthetic rate of I. indigotica was the highest at the NH4(+)-N/NO3(-)-N ratio of 75:25 and the lowest at 100:0.

CONCLUSIONIncreasing the NO3(-)-N ratio properly was beneficial to promote the growth and improve the activity of nitrate reductase and glutamine synthetase and net photosynthetic rate of I. indigotica.

Biomass ; Fertilizers ; analysis ; Isatis ; chemistry ; enzymology ; growth & development ; metabolism ; Nitrate Reductase ; metabolism ; Nitrate Reductases ; metabolism ; Nitrates ; analysis ; metabolism ; Nitrogen ; analysis ; metabolism ; Photosynthesis ; Plant Proteins ; metabolism ; Quaternary Ammonium Compounds ; analysis ; metabolism

Pathophysiological implications of the vascular nitric oxide (NO)/cGMP pathway were investigated in various rat models of hypertension. The expression of brain and endothelial constitutive NO synthases (bNOS, ecNOS) was determined by Western blot analysis, and the biochemical activity of soluble and particulate guanylate cyclases (GC) was assessed by the amount of cGMP generated in the thoracic aortae of rats with deoxycorticosterone acetate (DOCA)-salt, two-kidney, one dip (2K1C), and spontaneous hypertension (SHR). Plasma nitrite/ nitrate levels were decreased in DOCA-salt and 2K1C hypertension, and increased in SHR. The vascular expression of bNOS as well as that of ecNOS was decreased along with tissue nitrite/nitrate contents in DOCA-salt and 2K1C hypertension. The expression of both bNOS and ecNOS was increased in SHR with concomitant changes of tissue nitrite/nitrate contents. The activity of soluble GC was decreased, and that of particulate GC was increased in DOCA-salt hypertension. The soluble GC activity was increased, while the particulate GC activity was not affected in 2K1C hypertension. The soluble GC activity was not significantly changed, but the particulate GC activity was decreased in SHR. These results indicate that the high blood pressure is associated with differentially-altered vascular NO/cGMP pathway in different models of hypertension.
Animal ; Aorta, Thoracic/enzymology ; Atrial Natriuretic Factor/blood ; Blotting, Western ; Desoxycorticosterone ; Guanylate Cyclase/metabolism ; Guanylate Cyclase/analysis* ; Hypertension/enzymology* ; Hypertension/chemically induced ; Isoenzymes/metabolism ; Isoenzymes/analysis* ; Male ; Nitrates/blood ; Nitric-Oxide Synthase/metabolism ; Nitrites/blood ; Rats ; Rats, Inbred SHR ; Rats, Inbred WKY ; Rats, Sprague-Dawley ; Solubility

BACKGROUNDSalivary nitrate is positively correlated with plasma nitrate and its level is 9 times the plasma level after nitrate loading. Nitrate in saliva is known to be reduced to nitrite by oral bacteria. Nitrate and nitrite levels in saliva are 3 - 5 times those in serum in physiological conditions respectively in our previous study. The biological functions of high salivary nitrate and nitrite are still not well understood. The aim of this in vitro study was to investigate the antimicrobial effects of nitrate and nitrite on main oral pathogens under acidic conditions.

METHODSSix common oral pathogens including Streptococcus mutans NCTC 10449, Lactobacillus acidophilus ATCC 4646, Porphyromonas gingivalis ATCC 33277, Capnocytophaga gingivalis ATCC 33624, Fusobacterium nucleatum ATCC 10953, and Candida albicans ATCC 10231 were cultured in liquid medium. Sodium nitrate or sodium nitrite was added to the medium to final concentrations of 0, 0.5, 1, 2, and 10 mmol/L. All of the microorganisms were incubated for 24 to 48 hours. The optical densities (OD) of cell suspensions were determined and the cultures were transferred to solid nutrient broth medium to observe the minimum inhibitory concentration and minimum bactericidal/fungicidal concentration for the six tested pathogens.

RESULTSNitrite at concentrations of 0.5 to 10 mmol/L had an inhibitory effect on all tested organisms at low pH values. The antimicrobial effect of nitrite increased with the acidity of the medium. Streptococcus mutans NCTC 10449 was highly sensitive to nitrite at low pH values. Lactobacillus acidophilus ATCC 4646 and Candida albicans ATCC 10231 were relatively resistant to acidified nitrite. Nitrate at the given concentrations and under acidic conditions had no inhibitory effect on the growth of any of the tested pathogens.

CONCLUSIONNitrite, at a concentration equal to that in human saliva, is both cytocidal and cytostatic to six principal oral pathogens in vitro, whereas nitrate at a similar concentration has no antimicrobial effect on these organisms.

Anti-Infective Agents ; pharmacology ; Candida albicans ; drug effects ; Fusobacterium nucleatum ; drug effects ; Hydrogen-Ion Concentration ; Lactobacillus acidophilus ; drug effects ; Microbial Sensitivity Tests ; Mouth ; microbiology ; Nitrates ; analysis ; blood ; pharmacology ; Nitrites ; analysis ; blood ; pharmacology ; Porphyromonas gingivalis ; drug effects ; Saliva ; chemistry ; Streptococcus mutans ; drug effects