外源NO对Cu胁迫下番茄Cu的亚细胞分布和化学形态的影响

采用营养液培养方法,研究外源NO供体硝普钠(SNP)处理对50 μmol·L^-1Cu²⁺胁迫下番茄幼苗Cu的亚细胞分布和化学形态的影响.结果表明： Cu胁迫下,番茄幼苗的生物量和株高显著降低33.7%和23.1%,外源NO能够显著缓解这种抑制作用,但各器官中Cu的含量和累积量仍显著升高.Cu胁迫下,番茄幼苗各器官的Cu含量和累积量大小依次为根系>叶片>茎>叶柄,幼苗根系吸收的Cu向地上部的转运大幅降低,外源NO只能缓解而不能消除这种作用.外源NO可以使Cu胁迫下幼苗各器官的液泡和细胞壁中Cu含量显著上升,细胞器中Cu含量降低,从而减轻过多Cu对胞质生理生化代谢的伤害,增强组织细胞对Cu的耐性.外源NO可以提高番茄幼苗根系中醋酸提取态铜（F_HAc）、茎中氯化钠提取态铜（F_NaCl）、叶柄中F_HAc、叶片中乙醇提取态铜（F_E）和F_NaCl的含量,降低水溶态铜（F_W）的含量与比例,以降低过多铜的生物毒性.     

Effects of extended growth periods on subcellular distribution,chemical forms,and the translocation of cadmium in Impatiens walleriana

Impatiens walleriana plants accumulate sufficiently high concentrations of cadmium (Cd) for this species to be considered a potential Cd hyperaccumulator. Rooted cuttings were grown hydroponically for 25 and 50 days in solutions spiked with various Cd concentrations. The subcellular distribution and chemical forms of Cd in different organs were analyzed, and its upward translocation was also assessed. The plants accumulated large amounts of Cd; the Cd concentration in the roots and shoots reached 120–1900 and 60–1600 mg/kg, respectively. Regardless of the growth period, the Cd accumulated in the roots was primarily compartmentalized in the soluble fraction or ethanol and deionized water extractable chemical forms with high migration abilities. Translocation to the shoots was followed by an association of Cd mainly in the cell wall or with pectate and protein. The roots’ Cd showed a high migration capacity for predicting the shoots’ Cd concentrations. Different exposure periods significantly affected the subcellular distribution of Cd in the stems, and thus the upward translocation.     

Subcellular distribution,chemical forms,and physiological response to cadmium stress in Hydrilla verticillata

This study investigated the subcellular distribution and chemical forms of cadmium (Cd) in Hydrilla verticillata and the physiological mechanism underlying H. verticillata responses to Cd stress. Hydrilla verticillata was grown in a hydroponic system and was treated with various Cd concentrations (0, 10, 50, 100, 125, and 150?µM) for 7?days. Cadmium analysis of the leaves at the subcellular level showed that Cd was mainly stored in the soluble fraction (77.98–83.62%) and in smaller quantities in the cell wall fraction (11.99–17.30%) and the cell organelles (4.30–4.88%). The Cd taken up by H. verticillata was in different chemical forms. In the leaves and stems, the Cd was mostly extracted using 1?M NaCl and smaller amounts of Cd were extracted using 2% acetic acid. The malondialdehyde content significantly increased at all Cd concentrations, which indicated oxidative stress. The superoxide dismutase, guaiacol peroxidase, and catalase activities were enhanced. The proline, ascorbate, and glutathione contents increased at lower Cd concentrations, but decreased consistently as the Cd concentration rose. These results suggest that H. verticillata can be successfully used in the phytoremediation of Cd-contaminated water.     

Nonprotein amino acids in edible lentil and garden pea seedlings

Summary. Commercial edible seedlings of garden pea (Pisum sativum L.) and lentil (Lens culinaris L.) contain high concentration of nonprotein amino acids and trigonelline. Both seedlings grown in the laboratory or purchased in a supermarket were studied by HPLC. Samples from both origins contained trigonelline, α-aminoadipic acid, homoserine, β-(isoxazolin-5-on-2-yl)-alanine (BIA), and γ-glutamyl-BIA. Garden pea seedlings also contained a uracil-alanine derivative (isowillardiine) in substantial amount. Some of these compounds such as BIA and α-aminoadipic acid have neurotoxic activity. Received December 17, 1999 Accepted February 15, 2000     

Changes in protein and amino acid contents in two cultivars of rice seedlings with different apparent tolerance to cadmium

Changes in protein and amino acid contents in Cd-treated rice (Oryza sativa L.) seedlings of two cultivars were investigated. By assessing the decrease in chlorophyll content in the second leaves as an indicator of Cd toxicity, it was seen that cv. Tainung 67 (TNG 67) seedlings were apparently more tolerant to Cd than cv. Taichung Native 1 (TN 1). Following treatment with CdCl₂, protein content decreased with a progressive and substantial increase of protease activity and total amino acids in TN 1, but not in TNG 67. The patterns of individual amino acids in Cd-treated leaves of both cultivars were examined and, only in cv. TN 1 a substantial increase in the content of all amino acids analysed, except for methione, was recorded. The role of these changes in endogenous amino acids in Cd toxicity of TN 1 leaves is discussed.     

Effect of exogenous amino acids on Cu uptake and translocation in maize seedlings

This study aimed to assess the effects of four contrasting proteinogenic amino acids on copper (Cu) uptake and translocation in maize (Zea mays L.) seedlings grown in a modified Hoagland solution. Glycine, aspartic acid and lysine at three concentrations (10, 25 and 100 μM) did not have any significant effect on Cu uptake and translocation in maize seedlings over a two-day experimental period. However, cysteine (a reductive amino acid) at the three concentrations increased very significantly (P < 0.01) Cu accumulations in the root symplast and the shoots of maize seedlings in comparison to the control. Cu uptake in the whole plant and Cu translocation from root to shoot were also increased in the cysteine treatments. In the 25 μM cysteine treatment, where cysteine was in moderate excess, the Cu uptake in the whole plant and Cu translocation from root to shoot were significantly (P < 0.01) higher than those of the 10 or 100 μM cysteine treatments, where the concentration of cysteine was equivalent to that of Cu(II) or in great excess according to the stoichiometry of the redox reaction of cysteine with Cu(II). It is hypothesized that the cysteine-induced oxidation state alteration from Cu(II) to Cu(I) could be responsible for the increased Cu uptake and Cu translocation, on the ground that Cu(I), as free cuprous ion or cysteine cuprous complex, may be more available to maize roots than Cu(II).     

Subcellular distribution,chemical forms and thiol synthesis involved in cadmium tolerance and detoxification in Siegesbeckia orientalis L.

Siegesbeckia orientalis L. is a promising species for cadmium (Cd) phytoextraction with large biomass and fast growth rate, while little information about their intracellular mechanisms involved in Cd tolerance and detoxification has been explored. A soil pot experiment with total target Cd concentrations of 0, 10, 50, 100, and 150 mg kg^?1 were designed to investigate the subcellular distribution, chemical forms and thiol synthesis characteristics of Cd in S. orientalis. More than 90% of Cd was bound to the soluble fractions (48.4–76.5%) and cell walls (19.9–46.3%). Increasing soil Cd concentrations enhanced Cd sequestration into the cell walls. Most of the Cd (69.8–82.7%) in the plant organ was mainly in the forms of pectate and protein integrated Cd and undissolved Cd phosphate, while a minor portion (6.8–20.9%) was in the forms of the inorganic Cd and the water soluble Cd. Nonprotein thiols and phytochelatins significantly increased with increasing soil Cd treatment levels, while glutathione concentrations had no obvious change trends. Therefore, intracellular detoxification mechanisms of Cd in S. orientalis mainly rely on formation of less toxic Cd chemical forms, store of a large amount of Cd in cell wall and synthesis of thiol compounds.     

Distribution and phytotoxicity of cadmium in tomato seedlings

Thirty-day-old seedlings of tomato (Lycopersicon esculentum cv. Kwangsoo) were treated with various cadmium (Cd) concentrations (0, 10, 50, 100, and 500 μM) for up to 20 days, and the detailed distribution of absorbed Cd and its phytotoxicity in different plant parts (root, stem, and leaves) were investigated. The accumulation of Cd in plants increased with external Cd concentrations and Cd was strongly retained by roots, with less than 30% of the absorbed Cd being transported to shoots. Among the leaves, the lower positioned older leaves accumulated more Cd than the younger leaves. Furthermore, Cd-exposure not only reduced the dry weight and length of both shoot and root, chlorophyll levels in leaves, and levels of photosynthesis, but also enhanced the concentration of malondialdehyde (a lipid peroxidation product) in all plant parts. Our results indicate that the physiological impairment of tomato seedlings exposed to toxic levels of Cd may be related to the internal distribution of absorbed Cd, prolonged exposure, and oxidative stress in different plant parts.     

Physiological mechanism of hypertolerance of cadmium in Kentucky bluegrass and tall fescue: Chemical forms and tissue distribution

Kentucky bluegrass (Poa pratensis) and tall fescue (Festuca arundinacea) are hypertolerant grasses to soil cadmium contamination. Little information is available on their tolerance mechanism. A sand culture and a hydroponic culture experiment were designed to investigate the Cd chemical form changes and its translocation in different tissues. The results showed that Kentucky bluegrass and tall fescue can tolerate 50–200 mg kg⁻¹ of soil Cd stresses and accumulate as high as 4275 and 2559 mg Cd kg⁻¹ DW, respectively, in their shoots without the loss of shoot biomass. Their Cd hypertolerance was correlated with an increase of the undissolved Cd phosphates in the leaves in both grass species, as determined by sequential solvent extraction procedures. The superior Cd tolerance of tall fescue to Kentucky bluegrass was associated with less Cd translocation into the stele of roots and less Cd transported to leaves. The pectate- and protein-integrated Cd forms may be involved in the symplastic translocation of Cd from cortex into stele, and this may lead the higher Cd concentrations in the stele of roots and then above ground leaves via long-distance transport in Kentucky bluegrass.     

稀土对蚯蚓体内氨基酸含量的影响

采用滤纸接触染毒法,分别进行了氯化稀土、氯化镧与土居动物蚯蚓接触染毒不同时间和不同浓度的试验。研究其对蚯蚓体内氨基酸含量的影响变化。结果表明。Re、La对蚯蚓体内的氨基酸含量影响较显著,在低浓度时总体表现为促进蚯蚓体内氨基酸的形成,而在高浓度状态下则使蚯蚓体内氨基酸含量下降,产生抑制作用,两种稀土在400mg·L^-1浓度时,蚯蚓体内氨基酸含量除脯氨酸外开始上升,随着作用时间延长,氨基酸含量逐渐下降,在100～1200mg·L^-1浓度范围,两种稀土均引起蚯蚓体内脯氨酸含量的下降,产生抑制作用。     

Effects of carbohydrate feedings on plasma free tryptophan and branched-chain amino acids during prolonged cycling

Brain serotonin (5-hydroxytryptamine, 5-HT) has been suggested to be involved in central fatigue during prolonged exercise. Changes in the ratio of plasma free tryptophan (free Trp) to branched-chain amino acids (BCAA) are associated with altered brain 5-HT synthesis. The purposes of this study were to describe systematically the effects of prolonged exercise on changes in plasma free Trp and BCAA and to examine the effects of carbohydrate (CHO) feedings on these same variables. Eight well-trained men [VO2max = 57.8 (SE 4.1) ml kg-1 min-1] cycled for up to 255 min at a power output corresponding to VO2 at lactate threshold (approximately 68% VO2max) on three occasions separated by at least 1 week. Subjects drank 5 ml kg-1 body wt-1 of either a water placebo, or a liquid beverage containing a moderate (6% CHO) or high (12% CHO) concentration of carbohydrate beginning at min 14 of exercise and every 30 min thereafter. Exercise time to fatigue was shorter in subjects receiving placebo [190 (SE 4) min] as compared to 6% CHO [235 (SE 10) min] and 12% CHO [234 (SE 9) min] (P < 0.05). Glucose and insulin decreased in the placebo group, and free Trp, free-Trp/BCAA, and free fatty acids increased approximately five- to sevenfold (P < 0.05). These changes were attenuated in a dose-related manner by the carbohydrate drinks.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of protein fractions and amino acids in ensiled alfalfa treated with different chemical additives

Formic acid, formaldehyde, tannic acid or mixtures of two were studied on their effects on ensiled alfalfa (Medicago sativa L.) amino acids and N fractions by the Cornell Net Carbohydrate and Protein System (CNCPS). The alfalfa forage was a second cut and was wilted to a mean over-dry dry matter (DM) content of 330 g/kg. All silages were prepared as mini-silos using 100 ml polypropylene centrifuge tubes (50 g) on a small laboratory-scale, with the additives added in 20 ml aliquots/kg herbage fresh weight (FW). After 35 d of ensiling, most of forage true protein was converted to fraction A and all of the added additives reduced fraction A content in the ensiled forages (P<0.05). The content of fraction B₁ in all of the additive-treated silages was higher (P<0.05) than that in control silage. Large proportions of true protein in the tannic acid/formaldehyde- and formic acid/formaldehyde-treated silages were fractions B₂ and B₃, respectively. No difference was observed on fraction C content between the control silage and silages treated with additives except for the formaldehyde or tannic acid-treated silages. Amino acids were well preserved in additive-treated silages compared with the control silage. Concentration of total amino acid was higher in formic acid-treated silages than that in the control and the other additive-treated silages (P<0.05). The pattern of changes in individual amino acid in all of the silages indicated that branched chain amino acids and methionine were relatively well preserved during fermentation but the basic and acidic amino acids were not.     

Subcellular distribution and chemical forms of cadmium in Morus alba L.

Morus alba L. (mulberry) is a perennial woody tree and a species with great potential for Cd phyremediation owing to its large biomass and extensive root system. The mechanisms involved in Cd detoxification were investigated by analyzing the subcellular distribution and chemical forms of Cd in mulberry in the present study. These results indicated that 53.27–70.17% of Cd mulberry accumulated was stored in the root and only about 10% were in the leaves. Lots of the Cd was located in the cell wall of the mulberry root and in soluble fraction of the mulberry leaf. Moreover, in roots, the largest amount of Cd was in the form of undissolved Cd-phosphate. While in mulberry leaves and stems, most of the Cd was extracted by 2% Acetic acid and 0.6 M HCl, representing Cd-phosphate and Cd-oxalate. It could be concluded that the Cd combination with peptides and organo-ligands in vacuole of leaf or complexed with proteins or cellulose in the cell wall of root might be contributed to the tolerance of mulberry to Cd stress. The mulberry could be used to remediate the Cd polluted farmland soils.     

Levels of amino acids in 52 discrete areas of postmortem brain of adult and aged humans

Summary In a series of studies we have analyzed the regional distribution of the free amino acid pool in 52 discrete areas of postmortem brain of adult and aged humans. Here we show the distribution of eleven amino acids: alanine, methionine, valine, leucine, isoleucine, glutamine, asparagine, lysine, arginine, ornithine, and histidine. As found previously for other amino acids, the distribution of these amino acids was seen to be heterogeneous, the level of the area of highest level being 3.4 to 10.7 times that of the area of the lowest level. On average we found a five- or six-fold difference in concentration between the highest and lowest level areas in the brain samples from adult and old respectively. The distribution patterns were found to be different for each amino acid; they were not similar even in the same class (amides, branched chain, basic amino acids), and they were different from those recently found in rat brain. Only a few changes, mostly increases, were found in the aged brain, such as increases in alanine and valine levels in cortical areas. In studies of changes in cerebral amino acid levels, the great regional heterogeneity of distribution has to be taken into account since changes in whole brain values may not reflect regional changes. The functional significance and the control of this regional heterogeneity are under investigation.     

Development of a protocol for the automated analysis of amino acids in brain tissue samples and microdialysates

An automated precolumn derivatisation method has been developed for the measurement of fourteen amino acids in brain tissue and microdialysate samples. The method involves labelling amino acids with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide (CN⁻). The resulting highly stable N-substituted 1-cyanobenz[f]isoindole (CBI) derivatives were separated using a binary gradient elution profile and detected fluorometrically. The order of elution of the derivatised amino acids was confirmed by using liquid chromatography with fluorescence and mass spectrometric detection in tandem. Linear calibration plots were obtained for all amino acids in the range studied (0.2–12.5 μM). The limit of detection for CBI derivatives of amino acids was in the range 5–20 fmol (S/N=2) using a 5 μl injection volume. The method has been used for the measurement of amino acids in microdialysates from rat brain and tissue homogenates from different regions of mouse brain.     

Parameter determination involved in phytotoxicity and transport of cadmium in rice seedlings

Hydroponic experiments were conducted with rice seedlings to determine parameters involved in phytotoxicity and transport of Cadmium (Cd). Results showed that a linear decrease in relative growth rate and water use efficiency was observed in rice seedlings with increasing Cd concentrations. More severe inhibitory effects on both parameters were found at the 4-d treatment. The effective concentrations (EC) were estimated using the Levenberg–Marquardt Algorithm. The EC values obtained from the relative growth rate were always smaller than these from water use efficiency, indicating that the former was more sensitive to change of Cd than the latter. Phyto-transport of Cd was apparent, but the distribution of Cd in different parts of rice seedlings was different and roots were the dominant sink for Cd accumulation (p < 0.05). Although the translocation of Cd into shoots was detectable, more Cd was detected in shoots at the 4-d treatments than that at the 2-d treatments (p < 0.05). The partial correlation analysis suggested that the total accumulation rate of Cd was highly related to the doses of Cd supplied (p < 0.05). In conclusion, Cd is problematic at relatively low concentrations for rice seedlings, and inhibitory effects are highly dependent on the selected response endpoints and the duration of exposure periods.     

Studies on lysine analogs,aspartate-derived amino acids,and attempted mutant selection on oat seedlings

The lysine analogs S-2-aminoethyl-L-cysteine (AEC) and DL--hydroxylysine (DHL) caused severe growth inhibition in dark-grown oat seedlings (Avena sativa L. and A. nuda L.) at similar concentrations while L-lysine methyl ester (LME) had little effect. Lysine, arginine, and ornithine reversed the inhibition caused by AEC and DHL, the order of effectiveness being lysine>arginine>ornithine. Of aspartate-pathway amino acids, tested individually and in combinations for inhibitory effects on seedling growth, lysine and combinations containing lysine were the most inhibitory, but the inhibition was much less than that produced by AEC. Only slight synergistic effects occurred when oat seedlings were grown in the presence of paired combinations of aspartatepathway endproduct amino acids.Ca. 54,000 seeds obtained from 3,463 plants grown from ethyl-methanesulfonate (EMS) treated seed were screened for resistance to AEC. Three resistant variants were identified but the resistance was not recovered among their self-pollinated progeny.Abbreviations AEC S-2-aminoethyl-L-cysteine - DHL DL--hydroxylysine - EMS ethyl methanesulfonate - LME L-lysine methyl ester Paper No. 10351, Scientific Journal Series, Minnesota Agricultural Experiment Station     

Effect of hyperammonemia on brain amino acids in young and adult ferrets

Summary Effects of arginine deficiency and hyperammonemia on the brain concentrations of amino acids and urea cycle enzyme activities in young and adult ferrets were investigated. Only young ferrets developed hyperammonemia and encephalopathy immediately after consuming the arginine-free diet. Brain ornithine and citrulline concentrations in young ferrets fed arginine containing diet were significantly lower than those in adult ferrets. Compared to rats and other animals, young and adult ferrets had lower concentrations of brain glutamic acid and glutamine. Unlike in other species, brain glutamine was not elevated in young, hyperammonemic ferrets. Brain arginase and glutamate dehydrogenase activities were significantly increased in young ferrets fed arginine-free diet. Young ferrets provide a useful animal model for investigating the neurotoxicity of acute hyperammonemia.Abbreviations ACD Arginine-containing diet - AFD Arginine-free diet This work was presented, in part, at the annual meeting of the Midwest Society for Pediatric Research, Chicago, IL, 1991.     

Effects of amino acids on methionine-sulfoximine-induced heterocyst formation in Anabaena

Heterocyst development in ammonia-grown cultures of Anabaena variabilis and Anabaena 7120 was fully induced by the amino-acid analog methionine sulfoximine (MSO) at concentrations of 0.5–1.0 M. Glutamine, glutamate, aspartate, and alanine at 0.5 mM blocked the induction of heterocysts by MSO in A. variabilis. With Anabaena 7120, glutamine and glutamate were fully effective and alanine partially effective in preventing MSO-induced heterocyst formation. In MSO-treated algae, glutamine synthetase activity was reduced to less than 15% of control values within 4–6 h. Inactivation of the enzyme was prevented by all four amino acids tested.     

Use of amino acids by Plasmodium relictum oocysts in vitro.

A comparison was made of the in vitro growth of the gut of Culex tarsalis in Grace's insect culture medium, supplemented with fetal bovine serum in the presence of dividing cells of Antheraea eucalypti, with a similar preparation of a gut infected with oocysts of the avian parasite, Plasmodium relictum. In the latter case, after 16 hr, significant decreases occurred in the concentration of arginine, asparagine, and glutamine combined, glutamic acid, glycine, histidine, lysine, proline, and serine. Lower and less marked decreased concentrations of alanine, β-alanine, cystine, isoleucine, leucine, methionine, ornithine, phenylalanine, threonine, tryptophane, tyrosine, and valine also took place. This indicated utilization of certain amino acids by the developing oocysts of P. relictum in the presence of metabolizing insect cells.