Removal of toluene in a vapor-phase bioreactor containing a strain of the dimorphic black yeast Exophiala lecanii-corni.

Stricter regulations on volatile organic compounds and hazardous air pollutants have increased the demand for abatement technologies. Biofiltration, a process in which contaminated air is passed through a biologically active bed, can be used to remove these pollutants from air streams. In this study, a fungal vapor-phase bioreactor containing a strain of the dimorphic black yeast, Exophiala lecanii-corni, was used to treat a gas stream contaminated with toluene. The maximum toluene elimination capacity in short-term tests was 270 g m(-3) h(-1), which is 2 to 7 times greater than the toluene elimination capacities typically reported for bacterial systems. The fungal bioreactor also maintained toluene removal efficiencies of greater than 95% throughout the 175-day study. Harsh operating conditions such as low moisture content, acidic biofilms, and nitrogen limitation did not adversely affect performance. The fungal bioreactor also rapidly reestablished high toluene removal efficiencies after an 8-day shutdown period. These results indicate that fungal bioreactors may be an effective alternative to conventional abatement technologies for treating high concentrations of pollutants in waste gas streams.     

Resistance to Alpha/Beta Interferons Correlates with the Epizootic and Virulence Potential of Venezuelan Equine Encephalitis Viruses and Is Determined by the 5′ Noncoding Region and Glycoproteins

We compared the alpha/beta interferon (IFN-α/β) sensitivities of the TC-83 vaccine strain and 24 enzootic and epizootic Venezuelan equine encephalitis (VEE) isolates. The IFN-resistant or -sensitive phenotype correlated well with epizootic or enzootic potential. IFN-α/β resistance of Trinidad donkey (TRD) virus correlated with virulence determinants in the 5′ noncoding region and glycoproteins. Infection of mice lacking a functional IFN system with the IFN-sensitive TC-83 virus resulted in disease equivalent to that produced by the virulent, IFN-resistant TRD virus, further demonstrating that IFN resistance contributes to VEE virus virulence and is a biological marker of epizootic potential.     

Oxytetracycline age validation of an adult shortfin mako shark Isurus oxyrinchus after 6 years at liberty

This study presents findings on an oxytetracycline injected adult male shortfin mako Isurus oxyrinchus recaptured in waters off of southern California after 6 years at liberty. During the period at liberty, the vertebral band‐pair deposition rate was validated at one per year. This result indicates that from a time at or near sexual maturity, male I. oxyrinchus in the north‐east Pacific Ocean exhibit a band‐pair deposition rate of one band pair per year, while deposition rates for juveniles in the area have been validated at two band pairs per year.     

Fixed and random effects selection in linear and logistic models

We address the problem of selecting which variables should be included in the fixed and random components of logistic mixed effects models for correlated data. A fully Bayesian variable selection is implemented using a stochastic search Gibbs sampler to estimate the exact model-averaged posterior distribution. This approach automatically identifies subsets of predictors having nonzero fixed effect coefficients or nonzero random effects variance, while allowing uncertainty in the model selection process. Default priors are proposed for the variance components and an efficient parameter expansion Gibbs sampler is developed for posterior computation. The approach is illustrated using simulated data and an epidemiologic example.     

Capitalizing on multi-element interactions through bal-anced nutrition——A pathway to improve nitrogen use efficiency in China,India and North America

A viable option for increasing nitrogen (N) use efficiency and mitigation of negative impacts of N on the environment is to capitalize on multi-element interactions through implementation of nutrient management programs that provide balanced nutrition. Numerous studies have demonstrated the immediate efficacy of this approach in the developing regions like China and India as well as developed countries in North America. Based on 241 site-years of experiments in these countries, the first-year N recovery efficiency (RE) for the conventional or check treatments averaged 21% while the balanced treatments averaged 54% RE, for an average increase of 33% in RE due to balanced nutrition. Effective policies to promote adoption are most likely those that enable site-specific approaches to nutrient management decisions rather than sweeping, nation-wide incentives supporting one nutrient over another. Local farmers, advisers and officials need to be empowered with tools and information to help them define necessary changes in practices to create more balanced nutrient management.     

Discovery of GlyT1 inhibitors with improved pharmacokinetic properties

Glycine transporter 1 (GlyT1) represents a novel target for the treatment of schizophrenia via the potentiation of glutamatergic NMDA receptors. The discovery of 4,4-disubstituted piperidine inhibitors of GlyT1 which exhibit improved pharmacokinetic properties, including oral bioavailability, is discussed.     

Functional Characterization of Phospholipid N-Methyltransferases from Arabidopsis and Soybean

Phospholipid N-methyltransferase (PLMT) enzymes catalyze the S-adenosylmethionine-dependent methylation of ethanolamine-containing phospholipids to produce the abundant membrane lipid phosphatidylcholine (PtdCho). In mammals and yeast, PLMT activities are required for the de novo synthesis of the choline headgroup found in PtdCho. PLMT enzyme activities have also been reported in plants, yet their roles in PtdCho biosynthesis are less clear because most plants can produce the choline headgroup entirely via soluble substrates, initiated by the methylation of free ethanolamine-phosphate. To gain further insights into the function of PLMT enzymes in plants, we isolated PLMT cDNAs from Arabidopsis and soybean (Glycine max) based upon primary amino acid sequence homology to the rat PLMT, phosphatidylethanolamine N-methyltransferase. Using a heterologous yeast expression system, it was shown that plant PLMTs methylate phosphatidylmonomethylethanolamine and phosphatidyldimethylethanolamine but cannot utilize phosphatidylethanolamine as a substrate. Identification of an Arabidopsis line containing a knock-out dissociator transposon insertion within the single copy AtPLMT gene allowed us to investigate the consequences of loss of PLMT function. Although the accumulation of the PLMT substrates phosphatidylmonomethylethanolamine and phosphatidyldimethylethanolamine was considerably elevated in the atplmt knock-out line, PtdCho levels remained normal, and no obvious differences were observed in plant morphology or development under standard growth conditions. However, because the metabolic routes through which PtdCho is synthesized in plants vary greatly among differing species, it is predicted that the degree with which PtdCho synthesis is dependent upon PLMT activities will also vary widely throughout the plant kingdom.Phosphatidylcholine (PtdCho)2 is the most abundant phospholipid in most non-plastid membranes of eukaryotes. PtdCho biosynthesis has been studied intensively in plants not only because of its importance as a structural membrane lipid, but also because of its role as a precursor to important lipid-based signaling molecules, such as phosphatidic acid, and phospholipase A₂-derived free fatty acids (1). The choline headgroup of PtdCho serves multiple functions as well. In addition to being an essential human nutrient (2), in many plant species choline can be oxidized to produce the potent osmoprotectant glycine betaine (3, 4).For over 2 decades it has been apparent that there are fundamental differences between the manner in which PtdCho is produced in plants versus how it is synthesized in mammals and fungi. In the latter two systems, PtdCho can be formed through two distinct pathways as follows: (a) the “nucleotide pathway” in which free choline is incorporated in PtdCho using CDP-choline as an intermediate, and (b) the “methylation pathway” whereby PtdCho is produced directly from phosphatidylethanolamine (PtdEtn) via three sequential methylation reactions using S-adenosylmethionine (AdoMet) as the methyl donor (5, 6). In contrast, PtdCho biosynthesis in plants occurs through a branched pathway that utilizes components of both the nucleotide and methylation pathways (7). The greatest distinction between the contrasting mechanisms of PtdCho biosynthesis can be attributed to the presence of plant enzymes that are capable of converting ethanolamine headgroups to choline at the phospho-base level, activities that are absent in mammals and yeast. Conversely, mammals and fungi possess methylation enzymes that act directly on PtdEtn, a reaction that cannot be detected in most plant systems investigated (reviewed in Ref. 7).A diagram of the most widely accepted model of phosphoamino alcohol biosynthesis in plants is shown in Fig. 1. Similar to animals and yeast, free choline can be directly incorporated into PtdCho via nucleotide pathway enzymes in plants. In the absence of choline, however, the methylation of Etn-phosphate represents the first committed step in PtdCho biosynthesis. The resulting monomethylethanolamine-phosphate (MMEtn-P) metabolite can be further methylated at the phospho-base level to produce Cho-P. Alternatively, MMEtn-P can be incorporated into phosphatidylmonomethylethanolamine (PtdMMEtn) via the cytidylyltransferase and amino alcohol phosphotransferase activities of the nucleotide pathway and then methylated at the phosphatidyl-base level to complete the synthesis of PtdCho (Fig. 1). The extent with which PtdCho is formed by the flow of metabolites through phospho-bases as opposed to phosphatidyl-bases varies greatly among different plant species. In most higher plants, it is likely that the methylation of the phosphoamino alcohol headgroups involves the flow of metabolites through both branches of the pathway, as has been shown in species such as barley, carrot, and tobacco (3, 8, 9). Nevertheless, examples have also been reported where only one of the branches appears to be utilized. In Lemna paucicostata, for example, the methylation steps in PtdCho biosynthesis were shown to occur almost exclusively at the phospho-base level (10). At the other end of the spectrum is soybean, where all methylations beyond the initial formation of MMEtn-P were reported to occur on phosphatidyl-bases (8, 11). The tremendous variability observed among plants with regard to PtdCho formation is also exemplified by a study conducted by Williams and Harwood (12) where it was shown that the predominant route of PtdCho synthesis in olive culture cells involved the first two methylation reactions taking place at the phospho-base level (producing dimethylethanolamine phosphate) and the final methylation occurring on a phosphatidyldimethylethanolamine (PtdDMEtn) substrate.Open in a separate windowFIGURE 1.Phosphatidylcholine biosynthetic pathways. Steps common to plants, mammals, and yeast are indicated by black arrows. Dashed arrows indicate pathways specific to plants. Methylation of PtdEtn, which occurs in mammals and yeast, is indicated by on open arrow. Enzymes catalyzing phosphoamino alcohol methylation reactions in plants, mammals, and yeast are indicated.Our understanding on the mechanisms by which plants synthesize PtdCho and regulate its accumulation has been further enhanced as the genes encoding the various steps of the phosphoamino alcohol pathway have been isolated and characterized. For example, molecular characterizations led to the conclusion that all of the amino alcohol phosphotransferase reactions depicted in Fig. 1 can be mediated by the product of a single gene (designated AAPT1) that displays a broad substrate specificity (13, 14). Similarly, it was the isolation of the phosphoethanolamine methyltransferase (PEAMT) genes from Arabidopsis and spinach that led to the discovery that all three phospho-base methylation reactions could be catalyzed by a single enzyme (15, 16). Inhibition of PEAMT gene function in Arabidopsis through T-DNA insertion or co-suppression revealed unexpected associations between the phosphoamino alcohol pathway and root development, salt hypersensitivity, and male sterility (17, 18).Although most of the reactions depicted in Fig. 1 have been characterized at the molecular genetic level, conspicuously absent is information on the plant genes/enzymes responsible for the methylation reactions conducted at the phosphatidyl-base level. In contrast, these reactions are among the most well characterized in animals and yeast, catalyzed by enzymes commonly referred to as phospholipid N-methyltransferases (PLMTs). In mammals, the 18-kDa integral membrane protein phosphatidylethanolamine N-methyltransferase (PEMT) is a PLMT that is expressed primarily in the liver (19). PEMT catalyzes all three of the methylation reactions needed to convert PtdEtn to PtdCho. Yeast uses two distinct PLMT enzymes to catalyze the three methylation reactions as follows: Cho2p/Pem1p that mediates the direct methylation of PtdEtn to produce PtdMMEtn (20, 21), and Opi3p/Pem2p, an enzyme homologous to the mammalian PEMT, that primarily catalyzes the methylation of PtdMMEtn to PtdDMEtn and PtdDMEtn to PtdCho, the final two steps of the methylation pathway (20, 22). PLMT activities are critical in both of these systems. Mice possessing pemt knock-out mutations are completely dependent on dietary choline for survival, and they display abnormal levels of choline metabolites within the liver and develop hepatic steatosis even when fed diets supplemented with choline (23). Yeast lacking PLMT activities (cho2/opi3 double mutants) are obligate choline auxotrophs, unable to synthesize PtdCho de novo in the absence of exogenous choline.To gain a greater understanding of the specific function of PLMT reactions in higher plants, and their contribution toward PtdCho biosynthesis, we cloned and characterized PLMT homologs from Arabidopsis and soybean. By expressing the candidate cDNAs in yeast, we were able to confirm that they encoded functional PLMT activities as well as to establish their substrate specificities. We also identified a mutant Arabidopsis line containing a knock-out allele in the single copy PLMT gene found in the Arabidopsis genome, allowing us to characterize the consequences of loss of gene function in this model species.     

Peripartum Cardiomyopathy Presenting With Ventricular Tachycardia: A Rare Presentation

A 25-year-old previously asymptomatic pregnant woman at 36 weeks'' gestation was noticed to have repetitive monomorphic ventricular tachycardia. A dilated left ventricle with moderately reduced systolic function was found on echocardiographic examination. This is a very rare presentation of peripartum cardiomyopathy (PPCMP) presenting with repetitive monomorphic ventricular tachycardia.