An unrecognized dietary factor for guinea pigs associated with the fibrous fractions of plant products.

The growth rate of guinea pigs was used to assess the nutritional value of plant materials and to characterize the active component(s). Weanlings were fed for 28 days a purified diet based on soybean protein. Addition of 10 to 20% of wood pulp improved the growth rate beyond that supported by 0 to 5%. Subsequently, the basal diet contained 15% of wood cellulose. Raw cabbage, ad libitum, 5% of wheat straw and 5% of mature alfalfa, collected and dried in the laboratory, increased growth rate significantly. Several other plant products tested were inactive. Holocellulose (2.5%) prepared from alfalfa improved the growth rate while that from cabbage was minimally active. Afalfa holocellulose fractions enriched in hemicellulose and alpha-cellulose were inactive. Lyophilized cabbage and the residue which remained after extraction of frozen raw cabbage with ethyl acetate and acetone stimulated growth when fed at a level of 10%. Treatment of holocellulose with KOH, with pancreatin at pH 8 or with 0.1 m KHCO3 caused loss of activity. Storage of dry alfalfa meal for a period of 1 year resulted in loss of activity. It is concluded that a labile component of alfalfa associated with the fibrous fraction confers unique nutritional value to the fiber. Cabbage also contains a labile growth stimulant which may be associated with the fibrous fraction.     

Interactions of alfalfa plant and sprout saponins with cholesterol in vitro and in cholesterol-fed rats

The in vitro interactions of saponins from alfalfa plant and alfalfa sprouts with cholesterol and the effects of alfalfa plant and sprout and saponin-free alfalfa plant on diet-induced liver cholesterol accumulation, bile acid excretion, and jejunal and colonic morphology were examined. Cholesterol-saponin interactions have been suggested as mechanisms for the observed hypocholesterolemic effects of alfalfa as well as the changes in intestinal morphology. Alfalfa plant saponins bound significant quantities of cholesterol both from ethanol solution and from micellar suspension. Alfalfa sprout saponins interacted with cholesterol to a lesser but significant extent. Sprout saponins also inhibited growth of Trichoderma viride significantly, another measure of saponin-cholesterol interaction. Bile acid adsorption was greatest for alfalfa plant and was not reduced by removal of saponins from the plant material. The ability of alfalfa to reduce liver cholesterol accumulation in cholesterol-fed rats was enhanced by removal of saponins and alfalfa sprouts did not prevent accumulation. Removal of saponins from alfalfa reduced the changes in intestinal morphology previously reported, but interaction with membrane cholesterol did not appear to be the cause of this effect of saponins. Saponin-cholesterol interaction is an important part of the hypocholesterolemic action of alfalfa but interaction of bile acids with other components of alfalfa may be of equal importance.     

Preliminary description of antigenic components characteristic of Stachybotrys chartarum

The objective of this study was to characterize preliminarily immunogenic components characteristic of Stachybotrys chartarum to be used later for the development of a detection method for the fungus in environmental samples. The procedure for S.chartarum extract preparation was first optimized related to the age of the culture, culture type, and growth medium, and the antigenic composition of S. chartarum cultured in two different media was then characterized by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting method. Cross-reactivity of S. chartarum antigenic components with 10 other fungal species was identified by the inhibition immunoblotting method. The 10-day-old S. chartarum culture extract cultured in malt extract broth revealed a wider selection of proteins and antigenic components than the 30-day-old culture extract or the culture medium extracts. When cultured in cellulose broth, S. chartarum produced a higher number of proteins and antigenic components than in malt extract broth. The most dominant immunogenic components of S. chartarum cultured in cellulose broth were those of 65, 50, 37, and 27 kDa. The components of 65 and 50 kDa proved to be the most characteristic of this fungus according to the inhibition immunoblotting analyses. Several of the S. chartarum components were identified as glycoproteins. Carbohydrate moieties of the S. chartarum components also possessed an antibody binding activity.     

SS培养基实验室质量控制的探讨

摘要:目的　为了保证检验质量,使实验室能够提供准确的实验结果,对市售的商品化SS培养基,从质量性能测试及制成平皿后不同条件存放下肠道致病菌的生长情况两个方面对培养基进行实验观察。方法　依据国标GB4789.28-2013《食品微生物学检验 培养基和试剂的质量要求》。结果　4种SS干燥培养基,鼠伤寒沙门氏菌ATCC14028和福氏志贺氏菌［CMCC（B）51572］在1号和4号上的生长率为23.0%～26.8%,基本达到使用要求,2号和3号的生长率为3.3%～7.6%,存在着目标菌生长率过低的质量问题。4种培养基生长率越高,其选择因子G也呈现偏高的趋势。配置倾注的SS平皿,在密封条件下4℃～8℃冰箱内存放5 d内,其肠道菌的检出率仍可达96％以上,对肠道致病菌的检测效果无明显影响,而恒温保存的平皿检测效果逐日下降。结论　实验室对SS培养基的质量控制应从多方面综合考虑。     

Effect of feeding alfalfa and refined plant fibers on the toxicity and metabolism of T-2 toxin in rats

Experiments were conducted to determine the effect of dietary fibers on T-2 toxicosis in rats. Weanling rats were fed varying levels of cellulose, hemicellulose, lignin and pectin with and without T-2 toxin (3 micrograms/g feed) for 2 weeks. Only lignin showed promise of overcoming feed refusal and growth depression in animals fed T-2 toxin. Further experiments feeding alfalfa meal (0, 5, 10, 15, 20 or 25%) with and without T-2 toxin indicated that this lignin-rich feedstuff could largely overcome feed refusal and growth depression caused by the toxin. There was no effect of diet, however, on the activity of hepatic esterase, the enzyme believed to catabolize T-2 toxin. Rats were fed diets containing 0, 5, 12.5 or 20% alfalfa for 2 weeks and then dosed orally with [3H]T-2 toxin. Dietary alfalfa increased fecal excretion of 3H, whereas urinary excretion was unaffected. Residual 3H in kidney and muscle was reduced with alfalfa feeding when [3H]T-2 toxin was administered orally. Residual 3H in the digesta in the intestinal lumen increased. Alfalfa feeding was found to reduce intestinal transit time. It was concluded that the feeding of alfalfa reduced T-2 toxicosis in rats by binding the toxin in the intestinal lumen thereby promoting fecal excretion.     

Evaluation of serum-free culture conditions for primary human nasal epithelial cells

Defined culture conditions are essential for the interpretation of effects caused by volatile substances on human nasal epithelial cells (HUNEC) cultured in vitro. Conventionally, serum-containing media are used. However, the results of these experiments are of restricted value as serum contains many unknown and undefined substances. Not all serum-free media on the market are suitable for culturing primary HUNEC. Therefore, serum-free defined cell culture media were compared to evaluate optimal conditions for HUNEC and their cell lines. HUNEC were generated by trypsin digestion of mucosal tissue of the inferior turbinate. Cells were cultured on uncoated polystyrene dishes adding pre-warmed medium. Viability was controlled by trypan blue dye exclusion; colony forming units and cell morphology were controlled microscopically. The expression of different cytokeratins was studied immunocytochemically. Dulbecco's modified Eagle's medium was not suitable to grow HUNEC and passage them. HUNEC cultured in bronchial epithelial growth medium presented a more homogeneous cell morphology compared to other media and had a doubling time of 1.2 days. The maximum number of cell passages was 11 with bronchial epithelial growth medium.     

Nutrition influence on copper accumulation by Brassica pekinensis Rupr

Effect of nutrition status in the growth medium on Cu accumulation and plant growth were tested in Brassica pekinensis grown in hydroponic culture in a cultural facility. Cu concentration in the roots and shoots increased with increasing external Cu in the culture solution. On the other hand, it decreased with increasing Hoagland's solution (HS) strength. Interaction between external Cu and HS strength was also observed to affect Cu concentration in the tissues. A low level of external Cu could lead to a high Cu concentration in the plant at low HS strength, while to obtain a high Cu concentration in the plant at high HS strength, a high level of external Cu was needed. Partial nutrient experiments showed an important role of Fe and P in governing Cu accumulation. The influence of nutrients on Cu accumulation were mainly attributed to the osmolarity of the nutrient solution, antagonism between nutrients and Cu, pH change, and cation transporter induction. Root length and shoot biomass were negatively related to Cu concentration in the plant, suggesting an adverse effect of Cu in the tissue on plant growth. Root biomass showed less response to Cu concentration in the plant. This was presumably due to plant resource allocation between shoot and root, by which more resources were shifted to the Cu-stressed roots. The results might have important implications in understanding the sterility of the growth media of plants on Cu fate and effect in the ecosystem.     

Water-soluble contrast media in obstructed in ischemic small intestine. A clinical and experimental study

In this study the attention was focused on the possible application of the new low-osmolar water-soluble contrast media in already existing routines for radiologic diagnostic work-up and management of the abdominal emergencies of simple intestinal obstruction and ischemia: Iohexol was a good, or better, alternative to sodium diatrizoate regarding taste acceptance and patient reactions: Seventy-five per cent of patients characterized the taste of iohexol as good or neutral, while 52% gave sodium diatrizoate similar scores. The scores were also consistently in favor of iohexol as compared with sodium diatrizoate for the other chosen criteria; nausea, vomiting and diarrhea, but a larger number of patients may be needed for conclusive evaluation. Water-soluble media may have therapeutic effects on intestinal obstruction when preceded by conventional gastric suction using a short gastric tube: Twenty-three of 25 patients with subtotal small bowel obstruction due to peritoneal adhesions improved following the ingestion of either iohexol or sodium diatrizoate. Hyperosmolar contrast media might stimulate peristalsis and dilute the bowel contents, hence, easing the passage through a subtotally obstructed bowel. In rats, a direct relationship was found between contrast medium osmolality and the degree of intestinal distension, fluid influx to the bowel lumen and the speed of contrast medium progression. The water-soluble, low-osmolar contrast media seem promising as diagnostic aids in examination of the gastrointestinal tract: The low-osmolar contrast media gave better intestinal details on films than both barium sulphate and sodium diatrizoate in rats with intestinal obstruction or ischemia when high volumes of radiopaques were employed. Also in patients iohexol retained its radiographic density in the small bowel better than sodium diatrizoate. The diagnostic efficacy of the water-soluble radiographic media varied directly with their osmolality and the resulting fluid influx to bowel lumen. Hyperosmolality stimulated contrast medium progression and bowel distension, and reduced the radiographic density of the contrast media and the alignment to the bowel wall. Water-soluble contrast media may aid the diagnosis of bowel ischemia and the evaluation of the degree of ischemic injury: No bladder opacification, following absorption of water-soluble contrast media from the simply obstructed bowel, was observed in the majority of the animals and was only faintly present in 8%. Distinct radiographic opacification of the urinary bladder in rats with intestinal ischemia was demonstrated as early as 1-2 hours after the administration of contrast medium.(ABSTRACT TRUNCATED AT 400 WORDS)     

Physiological effect of anatase TiO(2) nanoparticles on Lemna minor

Manufactured metal oxide nanoparticles (NPs) are being used on a large scale, and these particles will inevitably reach a body of water through wastewater and urban runoff. The ecotoxicological study of these NPs on hydrophyte is limited at present. Lemna minor was exposed to media with different concentrations of titanium dioxide (TiO(2) ) NPs or bulk TiO(2) for 7 d. The changes in plant growth, chlorophyll, antioxidant defense enzymes (peroxidase [POD], catalase [CAT], and superoxide dismutase [SOD] activities), and malondialdehyde (MDA) content were measured in the present study. The particle size of TiO(2) NPs and the zeta potential of TiO(2) NPs and of bulk TiO(2) in the culture media were also analyzed to complementally study the toxicity of these materials on duckweed. The results showed that the effect of TiO(2) NPs on plant growth was more obvious than bulk TiO(2.) Titanium dioxide NPs stimulated plant growth in low concentrations, but inhibited plant growth at high concentrations. The POD, SOD, and CAT activity of Lemna minor increased when TiO(2) NP concentration was lower than 200?mg/L to eliminate accumulated reactive oxygen species in plant cells. The SOD activity decreased when the TiO(2) NP concentration was higher than 200?mg/L, and the plant cell membrane encountered serious damage from 500?mg/L TiO(2) NP concentration in the culture media. Environ. Toxicol. Chem. 2012; 31: 2147-2152. ? 2012 SETAC.     

The effect of extracellular matrix molecules on mouse preimplantation embryo development in vitro

The extracellular matrix (ECM) molecules, laminin (LN), chondroitin sulfate (CS), fibronectin (FN), hyaluronic acid (HA), mucin (MUC) and heparan sulfate proteoglycan (HS), were investigated as supplements to culture medium to improve the in vitro development of mouse 1-cell zygotes to blastocysts. Development was also compared with that in medium supplemented with bovine serum albumin (BSA) to determine the potential for ECM molecules as suitable alternatives to serum albumin in culture medium. Supplementation of sequential culture media with LN at all concentrations examined failed to result in more than 70% of zygotes developing to blastocysts; therefore, LN was considered unsuitable as a replacement for BSA and was not examined further. The optimal concentration of the remaining ECM molecules was used to supplement sequential culture media and the effect on blastocyst quality was assessed by determining the differential cell numbers of blastocysts grown in BSA-supplemented medium. Development to blastocyst was similar, regardless of the macromolecule used. The number of inner cell mass cells was significantly higher in HS-supplemented medium compared with controls. Trophectoderm cell numbers were similar to control values for all ECM molecules examined except CS for which there were fewer trophectoderm cells. It is concluded that ECM molecules, FN, HA, MUC and HS may be used as substitutes for serum protein supplementation of culture media EG0/G2 for mouse preimplantation embryo development. Heparan sulfate proteoglycan increases inner cell mass numbers and this may be due to interactions with the growth factors fibroblast growth factor 4 (FGF-4) and granulocyte-macrophage colony-stimulating factor.     

Dietary psyllium fiber increases intestinal heat shock protein 25 expression in mice

Heat shock proteins (HSPs) protect intestinal epithelial cell function, integrity and viability against many forms of stress. We hypothesized that dietary fibers (DFs) in the diet may increase HSP expression, since DFs are known to exhibit beneficial effects on intestinal health. The present study investigated the regulation of intestinal HSP expression by DFs, particularly psyllium fiber. Feeding psyllium fiber for 5 d increased HSP25 expression, but not HSP32 and HSP70 expression in the jejunum, ileum, and colon of mice at both the protein and mRNA levels. The increases in HSP25 expression did not correlate with cecal organic acid production by microbial fermentation. The water-insoluble fraction of psyllium fiber largely contributed to the induction of HSP25 expression, but feeding with other water-insoluble DFs from beet, wheat, and oats failed to induce intestinal HSP25 expression. Although the water-holding capacity of psyllium fiber was much higher than those of the other water-insoluble DFs examined, the increase in HSP25 expression induced by feeding polycarbophil, which possesses a high water-holding capacity similar to that of psyllium fiber, was much lower than that induced by psyllium fiber. Finally, induction of malondialdehyde production by hydrogen peroxide, an oxidant, in the colon of mice fed psyllium fiber was lower than that in mice fed with the control diets. Taken together, feeding psyllium fiber, especially the water-insoluble fraction, increases intestinal HSP25 expression and suppresses oxidant-induced malondialdehyde production.     

不同类型蛋白胨支持大肠菌群生长效果评价

目的 快速、准确评价不同类型蛋白胨支持大肠菌群的生长效果,为优化大肠菌群快速生长培养基选择适宜原材料。方法 选择不同类型的蛋白胨和大肠菌群代表性菌株,应用全自动生长曲线测定仪进行浊度测量,用原材料再配制培养基,通过测定培养基支持大肠菌群的生长能力验证原材料筛选方法的可靠性。结果 多价蛋白胨支持大肠菌群生长能力较好;大肠菌群快速生长的蛋白胨评估与配制培养基后的实验结果一致,即培养24 h后最大A值均为1.18。结论 不同类型蛋白胨支持大肠菌群的生长能力存在差异,生长曲线测定仪可作为培养基原材料选择的有力工具。     

不同培养基对阪崎肠杆菌侵袭作用影响的分析

目的分别使用脑心培养基、普通肉汤培养基、CAYE培养基增菌的阪崎肠杆菌新疆分离株侵袭ICR乳鼠,对其组织器官病变特征进行分析。方法阪崎肠杆菌新疆分离株经不同培养基培养后,对3-4日龄ICR乳鼠灌胃4 d、7 d后,无菌解剖取乳鼠肠、肝、脾、肾等组织,石蜡切片,HE染色,光镜观察。结果脑心培养液组、普通肉汤组病变特征相似,均出现肝组织弥漫性点状坏死,肾组织可见鲍曼囊消失,近曲管上皮细胞嗜酸性变化较轻;CAYE培养基组肝组织病变与脑心培养液组、普通肉汤组病变特征相似,肾组织有明显的近曲管上皮细胞嗜酸变性、崩解,结肠、直肠黏膜上皮细胞嗜酸变性,黏膜下层血管扩张充血。结论阪崎肠杆菌新疆分离株经CAYE培养后,对乳鼠器官产生损伤较为严重,尤以肝广泛点状坏死为著,推测其对人体具有潜在危害。     

食蟹猴精原干细胞分离纯化及鉴定

目的掌握食蟹猴精原干细胞 (spermatogonial stem cells,SSCs) 体外培养生长特性,建立食蟹猴精原干细胞分离、纯化、培养及初步鉴定的方法。 方法经手术获取2岁14天食蟹雄猴单侧睾丸,采用三步酶消化法分离获得单细胞悬液和差异贴壁法富集精原干细胞。将细胞培养于经丝裂酶素C处理的STO细胞层上,使用添加神经胶质细胞源性的神经营养因子(GDNF)、碱性成纤维细胞生长因子(bFGF)、GDNF家族受体α (GFRa1) 三种重要生长因子的无血清培养液体外培养,20d后采用CDH1标记分子免疫荧光染色和RT-PCR对培养的食蟹猴细胞进行SSCs初步鉴定。 结果通过差异贴壁法分离纯化富集的SSCs,接种到丝裂霉素C处理的STO饲养层细胞上,第2天开始分裂增殖。用含有生长因子的培养基培养2 d细胞形成小集落,5 d后细胞集落明显。培养20 d后,SSCs呈葡萄串状细胞簇,符合SSCs的形态特征,这些细胞经CDH1标记分子免疫荧光染色和RT-PCR均呈阳性表达。 结论本研究成功建立食蟹猴精原干细胞的分离纯化及鉴定体系。基于STO饲养细胞的添加GDNF、bFGF和GFRa1三种生长因子的无血清培养体系可用于食蟹猴精原干细胞培养,CDH1可作为食蟹猴精原干细胞鉴定的标志物。     

Formulation of a complex serum-free medium (CSM) for use in the co-culture of mouse embryos with cells of the female reproductive tract

Co-culture of pre-implantation embryos with cells of the reproductive tract requires a medium that is beneficial to both embryos and cells. However, many studies in this area utilize media originally formulated for specific cell lines. In the present study, a complex serum-free medium (CSM) was formulated on the basis of the ionic compositions of existing embryo culture media and mouse oviductal fluid as well as the concentrations of growth factors that appear to benefit mouse embryo development. The study began by investigating the effect of altering the concentrations of K+ ions (0-40 mM) and sulfate ions (0-10 mM) in embryo culture media on the development of 2-cell mouse embryos. Mouse embryos showed improved cell numbers at the blastocyst stage when cultured in 10 mM K+ compared with Whittingham's T6 medium. Embryos were also cultured in T6 supplemented with bovine serum albumin (BSA) containing various concentrations of insulin, insulin-like growth factors I and II, fibroblast growth factor, and epidermal growth factor. Insulin concentrations of 100 ng mL-1 significantly (P less than 0.05) improved the cell numbers of 2-cell embryos cultured to the morulae and blastocyst stages compared with those cultured in T6 + BSA alone. CSM was formulated on the basis of the results of these experiments and was found to support both improved development of 2-cell mouse embryos and the culture of mouse fibroblast and mouse oviduct cells.     

Vasoactive intestinal peptide influences hatching of ovine blastocysts

Expanded blastocysts collected from superovulated Sarda ewes were divided at random into four groups for culture in a simple medium that does not support blastocyst hatching (CZB) or a complex medium that is permissive to hatching (TCM 199), with or without vasoactive intestinal peptide (VIP), a known embryo mitogenic peptide. Plasminogen activator (PA) secretion after 24 h of culture, and the number of cells, diameter of blastocysts and hatching rate after 48 h of culture were compared. The results showed an increase in hatching rate (78.6 v. 6.7%; P<0.01), diameter and number of cells (220.89 v. 210.44 microm, P<0.01 and 246 v. 232, P<0.01 respectively) and caseinolytic areas (1.33 v. 0.92 cm, P<0.01) of blastocysts cultured in TCM 199 compared with those cultured in CZB. Supplementation of the culture media with VIP increased these parameters in CZB (P<0.01) and partially in TCM 199. In particular, cell number, diameter and PA activity were significantly higher (P<0.01) after culture with VIP in both media. Immunoneutralization of exogenous VIP in culture with anti-VIP antibody caused a decrease in the hatching rate (P<0.01) of embryos cultured in medium with VIP, similar to the rate in unsupplemented CZB (P<0.01). These results suggest a receptor-mediated response. In immunohistochemical studies, VIP was shown to bind receptors in hatched blastocysts demonstrating the VIP-receptor interaction, and VIP receptors of approximately 150 kDa were revealed by electrophoretic studies. In conclusion, ovine preimplantation embryos exhibit VIP receptors, providing a basis for a receptor-mediated influence of VIP in the hatching of ovine blastocysts.     

Influence of cooking duration of cabbage and presence of colonic microbiota on the excretion of N-acetylcysteine conjugates of allyl isothiocyanate and bioactivity of phase 2 enzymes in F344 rats

Isothiocyanates have been implicated in the cancer-protective effects of brassica vegetables. When cabbage is consumed, sinigrin is hydrolysed by plant or microbial myrosinase partly to allyl isothiocyanate (AITC), which is mainly excreted as N-acetylcysteine conjugates (NAC) of AITC in urine. The effect of cooking cabbage on the excretion of NAC of AITC, and glutathione-S-transferase (GST) and uridine 5'-diphospho-glucuronosyl transferase (UGT) activity in rat liver and colon was investigated. Germ-free (GF) and human faecal microbiota-associated (HFM) rats were fed a control diet containing 20 % raw, lightly cooked, or fully cooked cabbage for 14 d. When plant myrosinase was present, excretion of NAC of AITC/24 h was increased by 1.4 and 2.5 times by the additional presence of microbial myrosinase after consumption of raw and lightly cooked cabbage respectively. When plant myrosinase was absent, as after consumption of fully cooked cabbage, excretion of the AITC conjugate was almost zero in GF and HFM rats. None of the cabbage diets modified hepatic GST activity. When microbiota was absent, colonic GST was 1.3-fold higher after fully cooked cabbage, and hepatic UGT was increased by 1.4-1.8-fold after all cabbage diets, compared with the control feed. There were no differences in GST or UGT following cabbage consumption when microbiota was present. It is possible that other constituents of cabbage, rather than metabolites of glucosinolates per se, may be responsible for changes in phase 2 enzyme activity. The main effect of cooking cabbage and altering colonic microbiota was on excretion of NAC of AITC.     

新型淋巴细胞培养基配制及其性能比较评价

目的 比较大鼠淋巴细胞在不同培养基中的生长及增值状况,筛选最佳新型淋巴细胞培养基。方法 分离培养大鼠胸腺淋巴细胞,分别采用新配方培养基、无血清RPMI-1640培养基和无血清新配方培养基培养细胞,用倒置显微镜观察细胞的生长状态,MTT 比色法检测细胞增殖活性。结果 镜下观察,接种24 h后不同培养基中细胞均匀大量贴壁并伸展,5 d细胞生长数量减少,出现衰退;含0.1 mmol的蛋氨酸脑非肽（MEK）的新型淋巴细胞基可大幅度提高淋巴细胞生长,细胞生长状态良好,新型培养基中淋巴细胞增殖活性与传统RPMI-1640比较差异均有统计学意义（P<0.05）;在RPMI1640培养基、新配方2培养和无血清新配方2培养基中淋巴细胞增殖活性分别为99.9%、103.1%和96.6%。结论 新型培养基较 RPMI-1640 更适合淋巴细胞生长及增殖。     

The sterility of hospital-prepared Soffban bandages

An evaluation of the sterility of hospital-prepared Soffban bandages was undertaken. Discs of Bacillus stearothermophilus were inserted into the bandage rolls, prior to sterilization in "porous load" autoclaves. The discs were subsequently removed and placed in culture media, with growth of the organism indicating failure of sterilization. It was demonstrated that Soffban could not be sterilized reliably using standard hospital autoclave techniques.     

Phytotoxic effects of copper on nitrogen metabolism and plant growth in Brassica pekinensis Rupr

Copper (Cu) from various anthropogenic and natural sources is one of the major heavy metal contaminants in the environment. To study Cu-induced nitrogen (N) metabolism damage in the popular vegetable Chinese cabbage (Brassica pekinensis Rupr.), aquatic culture experiments with this plant were performed. Two Cu levels (0.3 micromol/L (control) and 10.3 micromol/L) and two N levels (0.05- and 1-fold Hoagland's solution) were used for the aquatic culture experiments. The results demonstrated adverse effects of Cu on N metabolism and plant growth. Cu exposure elevated Cu concentration and decreased nitrate reductase (NR) activity in the roots and shoots and reduced total chlorophyll content. It also shortened root length and produced fewer leaves and lower plant biomass. However, Cu exposure increased total free amino acid content in the leaves. The results also demonstrated effects of N deficiency on N metabolism and plant growth. N deficiency increased the root/shoot ratio of biomass and the total free amino acid content and decreased the nitrate contents and NR activity in roots and leaves. In addition, there were interactive effects between Cu exposure and N level on plant biomass, root/shoot ratio, and chlorophyll and nitrate content in leaves. The results suggested that Cu toxicity to the plant was at least partly due to an influence on N metabolism.