Advances in biotreatment of acid mine drainage and biorecovery of metals: 1. Metal precipitation for recovery and recycle

Acid mine drainage (AMD), an acidic metal-bearingwastewater, poses a severe pollution problem attributedto post mining activities. The metals usuallyencountered in AMD and considered of concern for riskassessment are arsenic, cadmium, iron, lead, manganese,zinc, copper and sulfate. The pollution generated byabandoned mining activities in the area of Butte, Montanahas resulted in the designation of the Silver Bow Creek–ButteArea as the largest Superfund (National Priorities List) sitein the U.S. This paper reports the results of bench-scalestudies conducted to develop a resource recovery basedremediation process for the clean up of the Berkeley Pit.The process utilizes selective, sequential precipitation (SSP)of metals as hydroxides and sulfides, such as copper, zinc,aluminum, iron and manganese, from the Berkeley Pit AMDfor their removal from the water in a form suitable foradditional processing into marketable precipitates and pigments.The metal biorecovery and recycle process is based on completeseparation of the biological sulfate reduction step and themetal precipitation step. Hydrogen sulfide produced in the SRBbioreactor systems is used in the precipitation step to forminsoluble metal sulfides. The average metal recoveries usingthe SSP process were as follows: aluminum (as hydroxide) 99.8%,cadmium (as sulfide) 99.7%, cobalt (as sulfide) 99.1% copper(as sulfide) 99.8%, ferrous iron (sulfide) 97.1%, manganese(as sulfide) 87.4%, nickel (as sulfide) 47.8%, and zinc (as sulfide)100%. The average precipitate purity for metals, copper sulfide,ferric hydroxide, zinc sulfide, aluminum hydroxide and manganesesulfide were: 92.4, 81.5, 97.8, 95.6 , 92.1 and 75.0%, respectively.The final produced water contained only calcium and magnesiumand both sulfate and sulfide concentrations were below usablewater limits. Water quality of this agriculturally usable watermet the EPA's gold standard criterion.     

A rapamycin-sensitive pathway down-regulates insulin signaling via phosphorylation and proteasomal degradation of insulin receptor substrate-1

Insulin receptor substrate-1 (IRS-1) is a major substrate of the insulin receptor and acts as a docking protein for Src homology 2 domain containing signaling molecules that mediate many of the pleiotropic actions of insulin. Insulin stimulation elicits serine/threonine phosphorylation of IRS-1, which produces a mobility shift on SDS-PAGE, followed by degradation of IRS-1 after prolonged stimulation. We investigated the molecular mechanisms and the functional consequences of these phenomena in 3T3-L1 adipocytes. PI 3-kinase inhibitors or rapamycin, but not the MEK inhibitor, blocked both the insulin-induced electrophoretic mobility shift and degradation of IRS-1. Adenovirus-mediated expression of a membrane-targeted form of the p110 subunit of phosphatidylinositol (PI) 3-kinase (p110CAAX) induced a mobility shift and degradation of IRS-1, both of which were inhibited by rapamycin. Lactacystin, a specific proteasome inhibitor, inhibited insulin-induced degradation of IRS-1 without any effect on its electrophoretic mobility. Inhibition of the mobility shift did not significantly affect tyrosine phosphorylation of IRS-1 or downstream insulin signaling. In contrast, blockade of IRS-1 degradation resulted in sustained activation of Akt, p70 S6 kinase, and mitogen-activated protein (MAP) kinase during prolonged insulin treatment. These results indicate that insulin-induced serine/threonine phosphorylation and degradation of IRS-1 are mediated by a rapamycin-sensitive pathway, which is downstream of PI 3-kinase and independent of ras/MAP kinase. The pathway leads to degradation of IRS-1 by the proteasome, which plays a major role in down-regulation of certain insulin actions during prolonged stimulation.     

Community dynamic models of two dioecious tree species

The effects of dioecy on community dynamics were examined by using transition matrix models for two dioecious tree species, one a superior competitor with a narrow dispersal range and the other an inferior competitor with a wide dispersal range. The models are based on tree-by-tree replacements in each identical microsite occupied by either male or female canopy trees of the superior competitor and canopy trees of the inferior competitor. Coexistence of the two species is possible not only because of a trade-off between competitive and dispersal abilities but also because of the existence of a competitor gap, which the superior competitor cannot occupy. The competitor gap is created under the male trees of the superior competitor. The inferior competitor occupies the competitor gap because of its wide dispersal range. The relative abundance of the two species depends on the dispersal ability and sex ratios of the superior competitor. The decreasing dispersal ability and the female abundance of the superior competitor increase the competitor gap, which allows the regeneration of the inferior competitor.An erratum to this article can be found at     

Glial cells contribute more to iron and aluminum accumulation but are more resistant to oxidative stress than neuronal cells

Iron (Fe) and aluminum (Al) have been implicated in the pathogenesis of Alzheimer's disease (AD). In this study, we examined neuronal and glial cells to clarify which contributes most to metal accumulation after internalization through the transferrin-independent iron uptake (Tf-IU) systems in primary neuronal and glial predominant (NP and GP) cells from rat cerebral cortex, which affect the accumulation of transition metals in a variety of cultured cells. Al more significantly upregulated the Tf-IU activity in GP cells than in NP cells. GP cells were more resistant to Fe and Al exposure than NP cells. However, a chemiluminescence analysis specific for reactive oxygen species (ROS) showed that ROS levels in Fe- or Al-loaded NP cells were twice as high as in Fe- or Al-loaded GP cells. Northern blot analysis and gel retardation assay showed that the Al and Fe exposure taken up by the cells suppress Tf receptor mRNA expression to a greater extent in GP than NP cells, indicating that Al and Fe more markedly accumulate in glial than in neuronal cells. These results suggest that glial cells rather than neuronal cells contribute to the metal accumulation and are more resistant to oxidative stress caused by metals than neuronal cells. The present study may help to explain the pathogenesis of neurodegeneration in AD disorders caused by metal-generated oxidative stress.     

Silefrin, a sodefrin-like pheromone in the abdominal gland of the sword-tailed newt, Cynops ensicauda

Sodefrin-like female-attracting pheromone was purified from the abdominal glands of male sword-tailed newts, Cynops ensicauda, by gel-filtration chromatography and reversed-phase high-performance liquid chromatography. The final product comprises 10 amino acid residues with the sequence SILSKDAQLK which coincided with the sequence deduced from its precursor cDNA. This peptide was designated silefrin. The sequence of silefrin was different from that of sodefrin by two amino acid residues, with substitutions Leu for Pro and Gln for Leu at positions 3 and 8, respectively. Both native and synthetic silefrin exerted an equipotent activity in attracting conspecific females.     

Molecular Cloning and DNA Analysis of the Orotidine-5′-Phosphate Decarboxylase Gene from the Yeast Saccharomyces exiguus Yp74L-3

The orotidine-5′-phosphate decarboxylase gene of Saccharomyces exiguus Yp74L-3 was cloned as a DNA fragment complementing a ura4 mutation of this yeast. The coding region of the gene is 807 bp in length, and represents 68.7% similarity to the corresponding gene of S. cerevisiae (URA3). The cloned URA4 gene was shown to be located on the 790-kbp Chromosome (chr) VIII of S. exiguus Yp74L-3. The neighbor-joining phylogenetic tree based on the orotidine-5′-phosphate decarboxylase coding sequences indicates that S. exiguus Yp74L-3 is closely related to Kluyveromyces yeasts, as well as to a S. cerevisiae laboratory strain. Received: 4 February 2000 / Accepted: 3 July 2000     

Cloning of a cDNA for Xenopus prolactin receptor and its metamorphic expression profile

A pituitary hormone, prolactin (PRL) shows various effects on cellular metabolism in amphibians, such as stimulation of larval tissue growth and inhibition of metamorphic changes. All these effects are mediated by its cell surface receptor. However, lack of information on PRL receptor (PRL-R) gene expression has made the physiological importance of the PRL/PRL-R system obscure in amphibian metamorphosis. Hence, a Xenopus PRL-R cDNA was cloned, its structure was characterized, and specific binding of PRL to Xenopus PRL-R expressed in COS-7 cells was confirmed. In adult tissues, high level expression was found in the lung, heart, brain, thymus and skin, and low level in the oviduct, kidney and spinal cord. The developmental expression pattern showed that PRL-R messenger ribonucleic acid (mRNA) was expressed in the brain and tail from premetamorphosis and the level increased toward late metamorphosis, suggesting that PRL may inhibit the metamorphic changes in those organs. The level of brain PRL-R mRNA reached a peak just at the start of the metamorphic climax stages and then decreased, whereas in the tail, mRNA expression peaked at late metamorphosis. In the kidney, mRNA expression increased and reached a maximum level at the end of metamorphosis. The results obtained were discussed in relation to metamorphosis.     

Sesterterpenoid from Gentianella alborosea

The structure of a new type of sesterterpenoid, designated as alborosin, isolated from Gentianella alborosea, has been deduced from a spectroscopic investigation.     

Retinoblastoma protein phosphorylation via PI 3-kinase and mTOR pathway regulates adipocyte differentiation

In the early phase of adipocyte differentiation, transient increase of DNA synthesis, called clonal expansion, and transient hyperphosphorylation of retinoblastoma protein (Rb) are observed. We investigated the role of these phenomena in insulin-induced adipocyte differentiation of 3T3-L1 cells. Insulin-induced clonal expansion, Rb phosphorylation and adipocyte differentiation were all inhibited by the PI 3-kinase inhibitors and rapamycin, but not the MEK inhibitor, whereas the MEK inhibitor, but not PI 3-kinase inhibitors or rapamycin, decreased c-fos induction. We conclude that insulin induces hyperphosphorylation of Rb via PI 3-kinase and mTOR dependent pathway, which promotes clonal expansion and adipocyte differentiation of 3T3-L1 cells.     

Molecular Mechanisms of Polymyxin B-Membrane Interactions: Direct Correlation Between Surface Charge Density and Self-Promoted Transport

We have studied the interaction of the polycationic peptide antibiotic polymyxin B (PMB) with asymmetric planar bilayer membranes via electrical measurements. The bilayers were of different compositions, including those of the lipid matrices of the outer membranes of various species of Gram-negative bacteria. One leaflet, representing the bacterial inner leaflet, consisted of a phospholipid mixture (PL; phosphatidylethanolamine, -glycerol, and diphosphatidylglycerol in a molar ratio of 81:17:2). The other (outer) leaflet consisted either of lipopolysaccharide (LPS) from deep rough mutants of PMB-sensitive (Escherichia coli F515) or -resistant strains (Proteus mirabilis R45), glycosphingolipid (GSL-1) from Sphingomonas paucimobilis IAM 12576, or phospholipids (phosphatidylglycerol, diphytanoylphosphatidylcholine). In all membrane systems, the addition of PMB to the outer leaflet led to the induction of current fluctuations due to transient membrane lesions. The minimal PMB concentration required for the induction of the lesions and their size correlated with the charge of the lipid molecules. In the membrane system resembling the lipid matrix of a PMB-sensitive strain (F515 LPS/PL), the diameters of the lesions were large enough (d= 2.4 nm ± 8%) to allow PMB molecules to permeate (self-promoted transport), but in all other systems they were too small. A comparison of these phenomena with membrane effects induced by detergents (dodecyltriphenylphosphonium bromide, dodecyltrimethylammonium bromide, sodiumdodecylsulfate) revealed a detergent-like mechanism of the PMB-membrane interaction. Received: 16 September 1997/Revised: 25 November 1997