苜蓿幼苗对铝胁迫的生理响应及综合评价

为探讨铝胁迫对苜蓿(Medicago sativa)幼苗生长和生理特性的影响,对铝胁迫下苜蓿地上和地下生物量、光合色素及根尖胼胝质含量进行测定,并对根尖结构进行观察,最后采用隶属函数分析法对苜蓿耐铝性进行评价。结果表明,随着铝胁迫的增加,苜蓿地上、地下部分生物量呈降低趋势,低浓度和高浓度铝胁迫使苜蓿生物量显著下降(P0.05);苜蓿的叶绿素含量呈下降趋势,胼胝质积累量增多;中、高浓度铝胁迫使根尖胼胝质含量显著上升。随铝胁迫浓度升高,根尖横切面细胞发生较大变化,尤其在高浓度时,细胞干瘪且排列紊乱。隶属函数分析结果表明,No. 12和No. 18苜蓿材料的耐铝性较好,可在南方酸性富铝化土壤中推广应用。     

车前对铝胁迫生理响应的研究

为探讨车前(Plantago asiatica)对铝胁迫的耐受特性及生理机理,在不同铝浓度及胁迫时间下,对其叶片的渗透调节物质、膜脂过氧化程度和体内保护酶系统进行了研究。结果表明,低浓度铝处理对车前的生理指标无明显影响。随着铝浓度的升高,叶片脯氨酸、可溶性糖、可溶性蛋白质含量呈先升高后下降趋势,细胞质膜透性显著增大、MDA含量显著增加。500 mg L–1的Al3+处理,车前叶片的SOD、CAT、POD活性均明显提高。因此,在铝胁迫下,野生草本植物车前能通过体内的生理保护机制来减少Al胁迫,表现出较强的耐铝特性。     

Aluminum and iron chemistry in the O horizon changed by a shift in tree species composition

In the present study we characterized the buffering system including aluminum in the organic surface horizon (O) of field experiments with replicated plots of pure Norway spruce (Picea abies (L.) Karst) and replicated plots of spruce with a birch (Betula pendula Roth and B. pubescens Ehrh.) admixture. Our results show that a change in tree species composition may have a rather large, short-term (12 years) effect on the concentration of organically bound aluminum in the humus layer (H) of the O horizon. The pure spruce plots had a significantly higher concentration of exchangeable aluminum (Al_e) and organically bound (pyrophosphate extractable) aluminum (Al_P) in the H layer and a lower concentration of each base cation. Furthermore, our results confirm earlier findings that aluminum has base cation properties in acidic organic horizons. Thus, the change in tree species composition did not affect the pH in spite of a change in base saturation, because base cations were mainly compensated for by aluminum. The change in organically bound aluminum was accompanied by a similar change in organically bound pyrophosphate extractable iron (Fe_P). The observed differences between the mixed and pure spruce plots in the amounts of Al_P and Fe_P in the H layer could not be explained by estimated differences in biocycling of Al and Fe either by above-ground litterfall or by root turnover.     

Aluminum tolerance measured by root growth and mucilage protection in Urochloa brizantha and Urochloa decumbens

Aluminum toxicity on root systems was analyzed through comparing root growth and evaluating the protective function of mucilage in Urochloa decumbens and Urochloa brizantha. Seedlings were grown in a solution with different concentrations of AlCl₃ and with mucilage removed or present. The root elongation rate, total length, number of roots and presence of aluminum at the root apex were measured. Root development was inhibited by aluminum and the elongation rate was maintained without any difference between the two species. A significant reduction in root length was found in U. brizantha. Aluminum did not influence root branching in either species and accumulated mostly in the rhizosphere of U. brizantha, where the mucilage has less of a protective function. The greatest aluminum tolerance was found in U. decumbens, observed through maintenance of total root system growth from lower to higher aluminum toxicity.     

Distribution patterns of trace metals and of lipid peroxidation in plasma and erythrocytes of rat exposed to aluminum

Significant decreases of the hematocrit, hemoglobin, and plasma iron levels were observed in rats receiving daily intraperitoneal injections of aluminum at a dose of 27 mg Al/kg body wt for 3 wk, as compared to untreated controls. The activity of alkaline phosphatase was also significantly lower in the treated animals as a result of the accumulation of aluminum in the liver (p<0.05). Following aluminum administration, the plasma concentrations of aluminum and copper were also significantly increased, whereas the plasma zinc levels and oxidative stress measured through thiobarbituric acid reaction products showed nonsignificant differences between the two groups (p>0.05). The erythrocyte concentrations of aluminum, copper, zinc, and iron and of superoxide dismutase activity were found to be significantly higher in the study group as compared to controls. The treated animals also showed evidence of higher oxidative stress in comparison to controls. These results suggest that erythrocyte aluminum accumulation could result in abnormal trace element homeostasis and increasing oxidative stress, which might be a mechanism of aluminum-induced anemia.     

Drosophila melanogaster as a model system of aluminum toxicity and aging

The aim of this study was to investigate the toxic effects of aluminum （A1） on the model organism-Drosophila melanogaster. The study is especially concerned with the effects of aluminum on the fruit fly＇s development, life span, and circadian rhythm in rest and activity. Flies were exposed to aluminum in concentrations from 40 to 280 mg/kg in rearing media or the flies were raised on control medium. Moreover, the life span of insects exposed to aluminum containing 40, 120, or 240 mg/kg of A1 in the medium, only during their larval development, during the whole life cycle and only in their adult life was tested. To check if aluminum and aging cause changes in D. melanogaster behavior, the locomotor activity of flies at different ages was recorded. Results showed that aluminum is toxic in concentrations above 160 mg/kg in the rearing medium. Depending on A1 concentration and time of exposure, the life span of the flies was shortened. At intermediate concentrations （120 mg/kg）, however, A1 had a stimulating effect on males increasing their life span and level of locomotor activity. At higher concentration the aluminum exposure increased or decreased the level of locomotor activity ofD. melanogaster depending on age of flies. In addition, in the oldest insects reared on aluminum supplemented media and in mid-aged flies reared on the highest concentration of A1 the daily rhythm of activity was disrupted.     

Characteristics of Aluminum Biosorption by Sargassum fluitans Biomass

Biomass of nonliving brown seaweed Sargassum fluitans pretreated by different methods is capable of taking up more than 10% (11 mEq/g) of its dry weight in aluminum at pH 4.5. There are indications that the biomass hydroxyl groups were involved in sequestering the aluminum in the form of polynuclear aluminum species. Aluminum-alginate complex (like cotton candy) was formed in the aluminum sorption solution as alginate was partially released from the biomass. Aluminum uptake of S. fluitans biomass was independent of residual alginate content in the biomass. Sodium ion added for pH adjustment was not adsorbed at all in the presence of aluminum ion. Received March 11, 1998; accepted October 9, 1998.     

Effect of aluminum on the binding properties of α-chymotrypsin

 The effect of aluminum ions on the binding properties of α-chymotrypsin has been studied. The results show that aluminum does not affect the catalytic rate constant k _cat, but it acts as an enzyme activator favoring the binding of the substrate to the catalytic site (i.e. decreasing K _m). Furthermore, aluminum binding to α-chymotrypsin displays about a threefold decrease in its affinity for the macromolecular inhibitor bovine pancreatic trypsin inhibitor (BPTI). Altogether, the different effect of aluminum on the binding of synthetic substrates (e.g. N-α-benzoyl-l-tyrosine ethyl ester, BTEE) and macromolecular inhibitors (e.g. BPTI) to α-chymotrypsin suggests the occurrence of an aluminum-linked conformational change in the enzyme molecule which brings about a marked structural change at the primary and secondary recognition sites for substrates and inhibitors. The modulative effect exerted by aluminum on the enzyme hydrolytic activity has been investigated also as a function of pH. The ion-linked effect appears to be dependent on the pH in a complex fashion, which suggests that aluminum binding is controlled by the protonation of at least two classes of residues on the enzyme molecule. Received: 5 December 1996 / Accepted: 11 March 1997     

Aluminum stimulates the proliferation and differentiation of osteoblasts in vitro by a mechanism that is different from fluoride

Summary Micromolar concentrations of aluminum sulfate consistently stimulated [³H]thymidine incorporation into DNA and increased cellular alkaline phosphatase activity (an osteoblastic differentiation marker) in osteoblast-line cells of chicken and human. The stimulations were highly reproducible, and were biphasic and dose-dependent with the maximal stimulatory dose varied from experiment to experiment. The mitogenic doses of aluminum ion also stimulated collagen synthesis in cultured human osteosarcoma TE-85 cells, suggesting that aluminum ion might stimulate bone formation in vitro. The effects of mitogenic doses of aluminum ion on basal osteocalcin secretion by normal human osteoblasts could not be determined since there was little, if any, basal secretion of osteocalcin by these cells. 1,25 Dihydroxyvitamin D₃ significantly stimulated the secretion of osteocalcin and the specific activity of cellular alkaline phosphatase in the human osteoblasts. Although mitogenic concentrations of aluminum ion potentiated the 1,25 dihydroxyvitamin D₃-dependent stimulation of osteocalcin secretion, they significantly inhibited the hormone-mediated activation of cellular alkaline phosphatase activity. Mitogenic concentrations of aluminum ion did not stimulate cAMP production in human osteosarcoma TE85 cells, indicating that the mechanism of aluminum ion does not involve cAMP. The mitogenic activity of aluminum ion is different from that of fluoride because (a) unlike fluoride, its mitogenic activity was unaffected by culture medium changes; (b) unlike fluoride, its mitogenic activity was nonspecific for bone cells; and (c) aluminum ion interacted with fluoride on the stimulation of the proliferation of osteoblastic-line cells, and did not share the same rate-limiting step(s) as that of fluoride. PTH interacted with and potentiated the bone cell mitogenic activity of aluminum ion, and thereby is consistent with the possibility that the in vivo osteogenic actions of aluminum ion might depend on PTH. In summary, low concentrations of aluminum ion could act directly on osteoblasts to stimulate their proliferation and differentiation by a mechanism that is different from fluoride.     

Effect of aluminum on the blood-brain barrier permeability during nitric oxide-blockade-induced chronic hypertension in rats

We examined the effect of aluminum on the permeability of the blood-brain barrier (BBB) during nitric oxide-blockade-induced chronic hypertension in rats. Animals were given the inhibitor of nitric oxide synthase, l-NAME (N ^ω-nitro-l-arginine methyl ester), for 4 wk to induce chronic hypertension. Two groups of rats were given an intraperitoneal injection of aluminum chloride. The integrity of the BBB was assessed by a quantitative measurement for Evans blue (EB) dye. The arterial blood pressure in l-NAME- and l-NAME plus aluminum-treated animals was significantly elevated from 115±2.8 and 110±1.7 mm Hg to 174±5.2 and 175±4.8 mm Hg, respectively (p<0.01). The EB dye content in the brain regions of the rats in the l-NAME group was increased, but there was no statistical significance compared to the saline group. The extravasation of EB dye was significantly increased in the brain regions of the animals treated with aluminum compared to the rats treated with saline (p<0.05). A significantly higher EB dye content in the brain regions was observed in the l-NAME plus aluminium group compared to l-NAME, aluminum, and saline groups (p<0.01). These findings indicate that exposure to a high level of aluminum leads to an additional increase in BBB permeability where nitric oxide-blockade-induced chronic hypertension potentiates the effect of aluminum to enhance BBB permeability to EB dye.     

Aluminum and calcium distribution patterns in aluminum-intoxicated roots of Allium cepa do not support the calcium-displacement hypothesis and indicate signal-mediated inhibition of root growth

The aluminum and calcium distributions in the root tips of aluminum-intoxicated onions, Allium cepa L., were mapped using PIXE (particle-induced X-ray emission) microanalysis. Not enough aluminum was present to have replaced, atom-for-atom, more than a minor fraction of the calcium. Furthermore, no inverse relationship between variations in aluminum and calcium concentrations was observed for pairs of adjacent 30-μm-diameter regions. Our observations, therefore, do not support the hypothesis that aluminum substantially reduces the quantity of bound calcium by competing with calcium for binding sites. Instead we suggest that reductions in calcium content are a non-local and indirect consequence of aluminum-intoxication. We found that aluminum accumulates almost exclusively in a surface layer. Observations of wounded roots indicated that exposed internal tissue binds aluminum avidly, so we contend that the surface accumulation pattern indicates that little aluminum penetrates into the interior of the root. We argue that aluminum does not directly inhibit growth in the interior of the apical root meristem because root growth rate was unaffected by root cap removal which should greatly increase the aluminum concentration in the exposed interior region. We hypothesize that growth inhibition in the interior of the meristem is mediated by a signal initiated or disrupted by excess aluminum in the periphery of the meristem. Received: 29 January 1997 / Accepted: 10 June 1997     

Role of superoxide anion radicals in the bacterial corrosion of metals

It was found that seven strains of bacteria can cause corrosion damage to aluminum, its alloys, and zinc. With respect to the studied metals, the most active bacteria were Proteus vulgaris 1212 and Pseudomonas aeruginosa 969. Superoxide anion radicals were demonstrated to play a role in the initiation of corrosive damage to aluminum and zinc, while bacterial exometabolites participate in the later stages of this process.     

Accumulation of heavy metals by some wood-rotting fungi

Accumulation of aluminum, cadmium, lead and calcium was studied in the wood-roting fungiDaedalea quercina, Ganoderma applanatum, Stereum hirsutum andSchizophyllum commune. The heavy metal content was measured in mycelia cultured in liquid media in the presence of either individual Al, Cd, Pb and Ca salts or of their mixtures. After 8-d cultivations in media containing 1 mmol/L concentration of individual heavy metals, the lead content was maximal in the mycelium ofStereum hirsutum (90.6 mmol/g) while the mycelium ofGanoderna applanatum contained maximal values of cadmium (272 mmol/g), aluminum (600 mmol/g) and calcium (602 mmol/g). When the mycelia were grown on mixtures of all metal salts, lead was the preferentially accumulated ion except inG. applanatum which had a higher affinity for aluminum.     

Axenic aerobic biofilms inhibit corrosion of copper and aluminum

The corrosion behavior of unalloyed copper and aluminum alloy 2024 in modified Baar's medium has been studied with continuous reactors using electrochemical impedance spectroscopy. An axenic aerobic biofilm of either Pseudomonas fragi K or Bacillus brevis 18 was able to lessen corrosion as evidenced by a consistent 20-fold increase in the low-frequency impedance value of copper as well as by a consistent four- to seven-fold increase in the polarization resistance of aluminum 2024 after six days exposure compared to sterile controls. This is the first report of axenic aerobic biofilms inhibiting generalized corrosion of copper and aluminum. Addition of the representative sulfate-reducing bacterium (SRB) Desulfovibrio vulgaris (to simulate consortia corrosion behavior) to either the P. fragi K or B. brevis 18 protective biofilm on copper increased the corrosion to that of the sterile control unless antibiotic (ampicillin) was added to inhibit the growth of SRB in the biofilm. Received: 24 May 1999 / Received revision: 6 July 1999 / Accepted: 1 August 1999     

Aluminum concentrations in tissues of rats: effect of soft drink packaging

Aluminum is a commonly occurring trace element for which no nutritional requirements have been set. Some non-conclusive evidence exists suggesting a need of aluminum for growth, reproduction or health of man and animals. There is concern that exposure or consumption of aluminum may be toxic to humans and animals. The objective of the current study was to compare tissue levels of aluminum of rats fed soft drinks packaged in aluminum cans, glass bottles or distilled water. Thirty male weanling rats (Sprague-Dawley) were divided into three treatment groups of 10 rats each. All rats were fed rodent chow ad libitum throughout the study. Three different fluids, i.e. distilled water, diet soft drinks from aluminum cans and diet soft drinks from glass bottles, were fed for a period of 3 weeks. Aluminum contents of tissues were measured by atomic absorption spectrophotometry. Canned soft drink fed rats had significantly higher blood, liver and bone aluminum concentration than rats that were given glass bottled soft drink. There was a 69% higher bone aluminum concentration and 16% lower femur weight in rats fed aluminum canned soft drinks when compared with rats fed with distilled water.     

Role of aluminum in red-to-blue color changes in <Emphasis Type="Italic">Hydrangea macrophylla</Emphasis> sepals

Red, purple, and blue sepals on selected cultivars of Hydrangea macrophylla were analyzed for their aluminum content. This content was determined to be a function of the sepal color with red sepals possessing 0–10 μg Al/g fresh sepal, purple sepals having 10–40 μg Al/g fresh sepal, and blue sepals containing greater than 40 μg Al/g fresh sepal. Accordingly, the threshold aluminum content needed to change H. macrophylla sepals from red to blue was about 40 μg Al/g fresh sepal. Higher aluminum concentrations were incorporated into the sepals, but this additional aluminum did not affect the intensity or hue of the blue color. These observations agreed with a chemical model proposing that the concentration of the blue Al³⁺-anthocyanin complex reached a maximum when a sufficient excess of aluminum was present. In addition, the visible absorbance spectra of harvested red, purple, and blue sepals were duplicated by Al³⁺ and anthocyanin (delphinidin-3-glucoside) mixtures in this model chemical system.     

Aluminum in lake water and organs of a fish Tribolodon hakonensis in strongly acidic lakes with a high aluminum concentration

Aluminum in lake water and in the organs of the fish Tribolodon hakonensis was investigated in Lake Usoriko (pH 3.6), Lake Inawashiroko (pH 5.0), and the Tenryu River (pH 7.7). The concentration of total soluble aluminum in the water was 0.51 mg l⁻¹ in Usoriko, 0.05 mg l⁻¹ in Inawashiroko, and less than 0.01 mg l⁻¹ in the Tenryu. The chemical forms of soluble aluminum in the acid water were characterized as Al³⁺, AlL²⁺, and AlL^≦1+. More than 90% of soluble aluminum in the water of Usoriko was Al³⁺, whereas AlL²⁺ was dominant in the water of Inawashiroko. The aluminum concentration in the organs of T. hakonensis in Usoriko was 42 μg g⁻¹ wet weight in gills, 4.2 μg g⁻¹ in muscle, 6.9 μg g⁻¹ in bone, 12.7 μg g⁻¹ in liver, 6.0 μg g⁻¹ in kidney, and 6.0 μg g⁻¹ in intestine, indicating accumulation of aluminum in the gills. The aluminum concentration in the organs of T. hakonensis living in Inawashiroko was approximately the same, in spite of the difference in water chemistry of the two acid lakes, especially for pH and aluminum. This suggests that aluminum accumulation might be controlled in the fish living in the acid lakes. In contrast, the aluminum concentration in the gills of T. hakonensis from the Tenryu was 2 μg g⁻¹. Received: May 20, 1999 / Accepted: December 10, 1999     

Loss of Butt-End Leg Bands on Male Wild Turkeys

ABSTRACT We estimated loss of butt-end leg bands on male wild turkeys (Meleagris gallapavo) captured in New York, Ohio, and Pennsylvania (USA) during December-March, 2006–2008. We used aluminum rivet leg bands as permanent marks to estimate loss of regular aluminum, enameled aluminum, anodized aluminum, and stainless steel butt-end leg bands placed below the spur. We used band loss information from 887 turkeys recovered between 31 days and 570 days after release (x̄ = 202 days). Band loss was greater for turkeys banded as adults (>1 yr old) than juveniles and was greater for aluminum than stainless steel bands. We estimated band retention was 79–96%, depending on age at banding and type of band, for turkeys recovered 3 months after release. Band retention was <50% for all age classes and band types 15 months after banding. We concluded that use of butt-end leg bands on male wild turkeys is inappropriate for use in mark-recapture studies.     

Effects of anti-odor automobile air-conditioning system products on adherence of Serratia marcescens to aluminum

Sixteen commercial products for use in automobile air-conditioning systems (ACS), most designated for abatement of malodors presumably of microbial origin, were examined for their potential to inhibit attachment and to detach cells of the Gram-negative bacterium Serratia marcescens on aluminum sections. Numbers of attached cells were appreciably reduced (>60%) following immersion in three alcohol-type and two acrylic-coating-type products. Several products had essentially no effect on the attached cells. Most of the products indicated for alleviation of associated microbial odors from ACS provided only short-term effects. When products were coated onto aluminum prior to exposure to the cells, water-insoluble coatings appeared to provide more consistent inhibition of primary adherence of S. marcescens. The differences in degrees of primary adherence of a selected strain of S. marcescens to variously treated aluminum provided a rapid and reproducible assessment of potential antimicrobial efficacy of ACS products. Received 20 November 2001/ Accepted in revised form 14 June 2002     

Addition of aluminum oxide microparticles to Trichoderma viride My preculture enhances cellulase production and influences fungal morphology

Morphological engineering techniques have recently become popular, since they are used to increase the production of a variety of metabolites and enzymes when fungi are grown in submerged cultures. This study aimed to facilitate cellulase production by adding aluminum oxide to Trichoderma viride My precultures.

The results showed that the highest cellulase activity was achieved when aluminum oxide at 10 g/L was used, and the activities of cellulase for filter paper and endoglucanase activity assays increased from 519.11 to 607.35 U/mL by 17.1%, and from 810.08 U/mL to 917.59 U/mL by 13.3%, compared with the control, respectively. Addition of aluminum oxide decreased the size of T. viride My pellets and increased the final pH. The changes in pellet diameter after the addition of different concentrations of aluminum oxide were fitted using a modified exponential decay model, which could precisely predict the pellet size by controlling aluminum oxide concentration.

The optimum concentration of microparticles, and therefore pellet size, could significantly improve cellulase production, which is an encouraging step towards commercial cellulase production.