Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P39060 (endostatin)
 2,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Soybean (Glycine max L. Merr.) plants exposed to 10 mM KNO(3) for a 4 d period were used to test the correlation between nitrogenase activity, gene expression and sucrose metabolism. Nitrate caused the down-regulation of sucrose synthase (SS) transcripts within 1 d, although a decline in nodule SS activity and an increase in nodule sucrose content only occurred after 3-4 d. In a second experiment, plants were exposed to (15)N-labelled nitrate for 48 h to determine the time period during which nitrate was taken up, and to relate this to the decline in apparent nitrogenase activity (H(2) production in air) and the reduction in SS gene transcript levels. The peak of nitrate uptake appeared to be between 8 h and 14 h whilst apparent nitrogenase activity began to decline at about 17.5 h. The SS mRNA signal declined markedly between 14 h and 24 h. The correlative association of these factors is clear. However, SS activity per se does not appear to be related to the initial decline in apparent nitrogenase activity as a result of nitrate uptake. These findings, therefore, do not support the hypothesis that the regulation of nodule function is mediated by the regulation of SS activity.
 ...
PMID:Short-term metabolic responses of soybean root nodules to nitrate. 1184 40

Despite a rapidly growing literature on analytical methods and field applications of O isotope-ratio measurements of NO(3)(-) in environmental studies, there is evidence that the reported data may not be comparable because reference materials with widely varying delta(18)O values have not been readily available. To address this problem, we prepared large quantities of two nitrate salts with contrasting O isotopic compositions for distribution as reference materials for O isotope-ratio measurements: USGS34 (KNO(3)) with low delta(18)O and USGS35 (NaNO(3)) with high delta(18)O and 'mass-independent' delta(17)O. The procedure used to produce USGS34 involved equilibration of HNO(3) with (18)O-depleted meteoric water. Nitric acid equilibration is proposed as a simple method for producing laboratory NO(3)(-) reference materials with a range of delta(18)O values and normal (mass-dependent) (18)O:(17)O:(16)O variation. Preliminary data indicate that the equilibrium O isotope-fractionation factor (alpha) between [NO(3)(-)] and H(2)O decreases with increasing temperature from 1.0215 at 22 degrees C to 1.0131 at 100 degrees C. USGS35 was purified from the nitrate ore deposits of the Atacama Desert in Chile and has a high (17)O:(18)O ratio owing to its atmospheric origin. These new reference materials, combined with previously distributed NO(3) (-) isotopic reference materials IAEA-N3 (=IAEA-NO-3) and USGS32, can be used to calibrate local laboratory reference materials for determining offset values, scale factors, and mass-independent effects on N and O isotope-ratio measurements in a wide variety of environmental NO(3)(-) samples. Preliminary analyses yield the following results (normalized with respect to VSMOW and SLAP, with reproducibilities of +/-0.2-0.3 per thousand, 1sigma): IAEA-N3 has delta(18)O = +25.6 per thousand and delta(17)O = +13.2 per thousand; USGS32 has delta(18)O = +25.7 per thousand; USGS34 has delta(18)O = -27.9 per thousand and delta(17)O = -14.8 per thousand; and USGS35 has delta(18)O = +57.5 per thousand and delta(17)O = +51.5 per thousand.
 ...
PMID:Oxygen isotopes in nitrate: new reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration. 1287 83

It is hypothesized that the enterosalivary nitrate circulation encourages nitrate reducing bacteria to reside within the oral cavity. Nitrite production may then limit the growth of acidogenic bacteria as a result of the production of antimicrobial oxides of nitrogen, including nitric oxide. This study was carried out with 10 subjects to characterize oral nitrate reduction and identify the bacteria responsible. Nitrate reduction varied between individuals (mean 85.4 +/- 15.9 nmol nitrite min(-1) with 10 ml 1 mm KNO(3) mouth wash) and was found to be concentrated at the rear of the tongue dorsal surface. Nitrate reductase positive isolates identified, using 16S rDNA sequencing, from the tongue comprised Veillonella atypica (34%), Veillonella dispar (24%), Actinomyces odontolyticus (21%), Actinomyces naeslundii (2%), Rothia mucilaginosa (10%), Rothia dentocariosa (3%) and Staphylococcus epidermidis (5%). Nitrite production rates, using intact and permeabilized cells, of the major tongue nitrate reducers were determined in the presence of methyl and benzyl viologen. Under anaerobic conditions in the presence of nitrate, rates in decreasing order were: A. odontolyticus > R. mucilaginosa > R. dentocariosa > V. dispar > V. atypica. In conclusion, Veillonella spp. were found to be the most prevalent taxa isolated and thus may make a major contribution to nitrate reduction in the oral cavity.
 ...
PMID:Evaluation of bacterial nitrate reduction in the human oral cavity. 1569 24

The NAR2 protein of Chlamydomonas reinhardtii has no known transport activity yet it is required for high-affinity nitrate uptake. Arabidopsis (Arabidopsis thaliana) possesses two genes, AtNRT3.1 and AtNRT3.2, that are similar to the C. reinhardtii NAR2 gene. AtNRT3.1 accounts for greater than 99% of NRT3 mRNA and is induced 6-fold by nitrate. AtNRT3.2 was expressed constitutively at a very low level and did not compensate for the loss of AtNRT3.1 in two Atnrt3.1 mutants. Nitrate uptake by roots and nitrate induction of gene expression were analyzed in two T-DNA mutants, Atnrt3.1-1 and Atnrt3.1-2, disrupted in the AtNRT3.1 promoter and coding regions, respectively, in 5-week-old plants. Nitrate induction of the nitrate transporter genes AtNRT1.1 and AtNRT2.1 was reduced in Atnrt3.1 mutant plants, and this reduced expression was correlated with reduced nitrate concentrations in the tissues. Constitutive high-affinity influx was reduced by 34% and 89%, respectively, in Atnrt3.1-1 and Atnrt3.1-2 mutant plants, while high-affinity nitrate-inducible influx was reduced by 92% and 96%, respectively, following induction with 1 mm KNO(3) after 7 d of nitrogen deprivation. By contrast, low-affinity influx appeared to be unaffected. Thus, the constitutive high-affinity influx and nitrate-inducible high-affinity influx (but not the low-affinity influx) of higher plant roots require a functional AtNRT3 (NAR2) gene.
 ...
PMID:High-affinity nitrate transport in roots of Arabidopsis depends on expression of the NAR2-like gene AtNRT3.1. 1641 12

Five-day-old seedlings of corn (Zealpha mays L.) grown without nitrate were decapitated and exposed to 0.5 mm KNO(3) or 0.5 mm KCl in aerated solutions at 30 C. Uptake of nitrate, chloride, and potassium was determined by replacing solutions hourly and measuring their depletion. Translocation of these ions and of organic nitrogen was determined by hourly analysis of the vascular exudate. Nitrate reduction was estimated by the difference between nitrate uptake and nitrate recovered in the tissue and exudate. Nitrate uptake exhibited its usual pattern of apparent induction resulting in the development of an accelerated uptake phase. Chloride uptake remained fairly constant throughout the experimental period. Translocation of nitrate increased progressively for at least 7 hours whereas chloride translocation reached a maximum about the 3d hour and then declined to a lower rate than nitrate translocation. Nitrate uptake and translocation were restricted by anaerobiosis, by 20 and 40 C relative to 30 C, and by 0.05 mm 6-methylpurine, an RNA-synthesis inhibitor. Accumulation, reduction and translocation of nitrate had different sensitivities to all these factors. The effect of 0.05 mm 6-methylpurine was more detrimental to nitrate translocation and nitrate reduction than to nitrate uptake.Ambient nitrate, relative to chloride, enhanced the exudation volume and the translocation of organic nitrogen within 4 hours from initiation of the experiments. Translocation of nitrate and organic nitrogen decreased shortly after removal of external nitrate. The higher rates of organic nitrogen translocation which occurred during nitrate uptake indicates either (a) rapid translocation of amino acids synthesized from the entering nitrate, or (b) an accelerated rate of protein turnover and a resulting enhancement in translocation of endogenous amino acids.
 ...
PMID:Nitrate translocation by detopped corn seedlings. 1665 46

Root nodule senescence induced by nitrate and ammonium in Pisum sativum L. was defined by determining nitrogenase activity and leghemoglobin content with the acetylene reduction and pyridine hemochrome assays. Root systems supplied with 100 mm KNO(3) or 100 mm NH(4)Cl exhibited a decrease in nitrogenase activity followed by a decline in leghemoglobin content. Increasing the CO(2) concentration from 0.000320 atm to 0.00120 atm had no effect on the time course of root nodule senescence when 20 mm KNO(3) was supplied to the roots; in vitro nitrate reductase activity was detected in leaves and roots, but not bacteroids. Nitrate appeared in leaves, roots, and the nodule cytosol fraction but not bacteroids when 20 mm KNO(3) was supplied to roots. When nitrate entered through the shoots, however, no root nodule senescence was observed, and no nitrate was detected in root or nodule cytosol fractions although nitrate and nitrate reductase were found in leaves. The results suggest that nitrate does not induce root nodule senescence through competition between nitrate reductase and nitrogenase for products of photosynthesis.
 ...
PMID:Induction of Root Nodule Senescence by Combined Nitrogen in Pisum sativum L. 1665 69

A NADH-nitrate reductase inhibitor has been isolated from young soybean (Glycine max L. Merr. Var. Amsoy) leaves that had been in the dark for 54 hours. The presence of the inhibitor was first suggested by the absence of nitrate reductase activity in the homogenate until the inhibitor was removed by diethylaminoethyl (DEAE)-cellulose chromatography. The inhibitor inactivated the enzyme in homogenates of leaves harvested in the light. Nitrate reductases in single whole cells isolated through a sucrose gradient were equally active from leaves grown in light or darkness, but were inhibited by addition of the active inhibitor.The NADH-nitrate reductase inhibitor was purified 2,500-fold to an electrophoretic homogeneous protein by a procedure involving DEAE- cellulose chromatography, Sephadex G-100 filtration, and ammonium sulfate precipitation followed by dialysis. The assay was based on nitrate reductase inhibition. A rapid partial isolation procedure was also developed to separate nitrate reductase from the inhibitor by DEAE-cellulose chromatography and elution with KNO(3). The inhibitor was a heat-labile protein of about 31,000 molecular weight with two identical subunits. After electrophoresis on polyacrylamide gel two adjacent bands of protein were present; an active form and an inactive form that developed on standing. The active factor inhibited leaf NADH-nitrate reductase but not NADPH-nitrate reductase, the bacterial nitrate reductase or other enzymes tested. The site of inhibition was probably at the reduced flavin adenine dinucleotide-NR reaction, since it did not block the partial reaction of NADH-cytochrome c reductase. The inhibitor did not appear to be a protease. Some form of association of the active inhibitor with nitrate reductase was indicated by a change of inhibitor mobility through Sephadex G-75 in the presence of the enzyme. The inhibition of nitrate reductase was noncompetitive with nitrate but caused a decrease in V(max).The isolated inhibitor was inactivated in the light, but after 24 hours in the dark full inhibitory activity returned. Equal amounts of inhibitor were present in leaves harvested from light or darkness, except that the inhibitor was at first inactive when rapidly isolated from leaves in light. Photoinactivation of yellow impure inhibitor required no additional components, but inactivation of the purified colorless inhibitor required the addition of flavin.Preliminary evidence and a procedure are given for partial isolation of a component by DEAE-cellulose chromatography that stimulated nitrate reductase. The data suggest that light-dark changes in nitrate reductase activity are regulated by specific protein inhibitors and stimulators.
 ...
PMID:NADH-Nitrate Reductase Inhibitor from Soybean Leaves. 1666 Apr 85

A method for reversibly regreening and degreening citrus epicarp in vitro using peel segments was developed.Peel segments from mature degreened fruit promptly regreened when kept in light upon agar medium containing low (15 millimolar) concentrations of sucrose. Higher concentrations of sucrose inhibited this regreening, but NO(3) (-) and certain amino acids included in the media overcame the inhibition by sucrose. However, l-serine strongly inhibited regreening. In the presence of nitrogen, sucrose promoted regreening.Peel segments from green fruit remained green on media with low concentrations of sucrose and on media with high concentrations of sucrose and 60 millimolar KNO(3), but degreened in response to high concentrations of sucrose in the absence of nitrogen. Nitrate overcame the degreening effects of high sucrose concentrations in both light and dark. Peel segments were reversibly degreened and regreened by transferring the segments between appropriate media.Nitrate in the media markedly reduced the levels of endogenous sugars in the epicarp and increased endogenous amino acid levels. Sucrose in the media increased endogenous sugar levels and, in the presence of nitrate, increased endogenous amino acid levels. In the absence of nitrogen, high sucrose concentrations reduced endogenous amino acid concentrations.
 ...
PMID:Nutritional control of regreening and degreening in citrus peel segments. 1666 2

Using a new Arabidopsis (Arabidopsis thaliana) mutant (Atnrt2.1-nrt2.2) we confirm that concomitant disruption of NRT2.1 and NRT2.2 reduces inducible high-affinity transport system (IHATS) by up to 80%, whereas the constitutive high-affinity transport system (CHATS) was reduced by 30%. Nitrate influx via the low-affinity transport system (LATS) was unaffected. Shoot-to-root ratios were significantly reduced compared to wild-type plants, the major effect being upon shoot growth. In another mutant uniquely disrupted in NRT2.1 (Atnrt2.1), IHATS was reduced by up to 72%, whereas neither the CHATS nor the LATS fluxes were significantly reduced. Disruption of NRT2.1 in Atnrt2.1 caused a consistent and significant reduction of shoot-to-root ratios. IHATS influx and shoot-to-root ratios were restored to wild-type values when Atnrt2.1-nrt2.2 was transformed with a NRT2.1 cDNA isolated from Arabidopsis. Disruption of NRT2.2 in Atnrt2.2 reduced IHATS by 19% and this reduction was statistically significant only at 6 h after resupply of nitrate to nitrogen-deprived plants. Atnrt2.2 showed no significant reduction of CHATS, LATS, or shoot-to-root ratios. These results define NRT2.1 as the major contributor to IHATS. Nevertheless, when maintained on agar containing 0.25 mm KNO(3) as the sole nitrogen source, Atnrt2.1-nrt2.2 consistently exhibited greater stress and growth reduction than Atnrt2.1. Evidence from real-time PCR revealed that NRT2.2 transcript abundance was increased almost 3-fold in Atnrt2.1. These findings suggest that NRT2.2 normally makes only a small contribution to IHATS, but when NRT2.1 is lost, this contribution increases, resulting in a partial compensation.
 ...
PMID:Dissection of the AtNRT2.1:AtNRT2.2 inducible high-affinity nitrate transporter gene cluster. 1708 7

Nitrate-nitrite poisoning killed four adult alpacas and induced the abortion of a full-term fetus after access to oaten hay (Avena sativa) containing 3.2% KNO(3) equivalent in dry matter. Necropsy findings were cyanosis, dark-coloured blood, and pulmonary congestion and oedema. Aqueous humour from two adults contained 25 mg NO(3)/L and that from the fetus contained 10 mg NO(3)/L. Cyanide poisoning possibly killed two adult wether alpacas that ate a garden-cultivated variety of Osteospermum ecklonis (South African daisy, bietou) with a cyanide potential of 6800 mg HCN/kg dry matter.
 ...
PMID:Alpaca plant poisonings: nitrate-nitrite and possible cyanide. 1924 25


1 2 Next >>