Speciation of inorganic arsenic and selenium in leachates from landfills in relation to water quality assessment

Speciation of arsenic and selenium was carried out on water samples taken from rivers used as water intake points in the vicinity of landfill areas used for land-based waste disposal system. Leachates from these landfill areas may contaminate the river water through underground seepage or overflowing, especially after a heavy downpour. Preconcentration of the chemical species was done using a mixture of ammonium pyrrolidinethiocarbamate-chloroform (APDTC-CHCl₃). Because only the reduced forms of both arsenic and selenium species could be extracted by the preconcentrating mixture, suitable reducing agents such as 25% sodium thiosulfate for As(III) and 6M HCl for Se(IV) were used throughout the studies. Care was taken to exclude the interfering elements such as the alkali and alkali earth metals from the inorganic arsenic and selenium species by introducing 12% EDTA solution as the masking agent. The extracted mixture was irradiated in a thermal neutron flux of 4 × 10¹²/cm/s from a TRIGA Mk.II reactor at the Malaysia Institute of Nuclear Technology Research (MINT). Gamma rays of 559 keV and 297 keV from⁷⁶As and⁷⁵Se, respectively, were used in the quantitative determination of the inorganic species. Mixed standards of As(III) and Se(IV) used in the percentage efficiency procedure were prepared from salts of Analar grade. The water quality evaluation was viewed from the ratio of the inorganic species present.     

Expressed sequence tags (ESTs) from desiccated Tortula ruralis identify a large number of novel plant genes.

The desiccation-tolerant moss Tortula ruralis [Hedw.] Gaerten., Meyer & Scherb. has both a constitutive protection system and an active rehydration induced recovery mechanism apparently unique to bryophytes. Immediately following rehydration, desiccated T.ruralis gametophytes produce a set of polypeptides whose synthesis is unique to the rehydrated state. We report the construction of a cDNA expression library from the polysomal mRNA of desiccated gametophytes and the single-pass sequencing of randomly selected clones. 152 expressed sequence tags (ESTs) were generated representing more than 60,000 bp of non-redundant DNA sequence. 44 ESTs (29%) demonstrated significant homology to previously identified nucleotide and/or polypeptide sequences, such as ribosomal proteins, desiccation-related peptides, early light-inducible proteins and a V-type ATPase. Analysis of a subset of these homologous ESTs reveals that codon preference in T.ruralis is similar to that of vascular plants, particularly the Magnoliopsida. 108 ESTs (71%) demonstrated no significant homology to deposited sequences and represent a large number of novel plant genes. Analysis of these ESTs will define the range of genes involved in cellular repair and recovery and may provide greater insight to the complex phenotype of vegetative desiccation-tolerance.     

Gravitropism of hypocotyls of wild-type and starch-deficient Arabidopsis seedlings in spaceflight studies

The major purpose of this spaceflight project was to investigate the starch-statolith hypothesis for gravity perception, and a secondary goal was to study plant growth and development under spaceflight conditions. This research was based on our ground studies of gravity perception in the wild type and three starch-deficient (one starchless and two reduced starch) mutants of Arabidopsis thaliana (L.) Heynh. Dark-grown seedlings that developed in microgravity were given one of several (30 min, 60 min, or 90 min) 1-g stimuli by an on-board centrifuge, and additional controls for seedling development also were performed. These latter control experiments included a morphological study of plants that developed in space in microgravity (F μg), in space on a centrifuge (F 1g), on the ground (G 1g), and on a rotating clinostat on the ground. Since elevated levels of ethylene were reported in the spacecraft atmosphere, additional controls for morphology and gravitropism with added ethylene also were performed. While exogenous ethylene reduced the absolute magnitude of the response in all four strains of Arabidopsis, this gas did not appear to change the relative graviresponsiveness among the strains. The relative response of hypocotyls of microgravity-grown seedlings to the stimuli provided by the in-flight centrifuge was: wild type > starch-deficient mutants. Although the protoplast pressure model for gravity perception cannot be excluded, these results are consistent with a statolith-based model for perception in plants. Received: 12 February 1999 / Accepted: 9 March 1999     

Molecular cloning of some components of the translation apparatus of fission yeast Schizosaccharomyces pombe and a list of its cytoplasm ic proteins genes]

Full-length cDNAs of four new genes encoding cytoplasmic ribosomal proteins L14 and L20 (large ribosomal subunit) and S1 and S27 (small ribosomal subunit) were isolated and sequenced during the analysis of the fission yeast Schizosaccharomyces pombe genome. One of the Sz. pombe genes encoding translation elongation factor EF-2 was also cloned and its precise position on chromosome I established. A unified nomenclature was proposed, and the list of all known genetic determinants encoding cytoplasmic ribosomal proteins of Sz. pombe was compiled. By now, 76 genes/cDNAs encoding different ribosomal proteins have been identified in the fission yeast genome. Among them, 35 genes are duplicated and three homologous genes are identified for each of the ribosomal proteins L2, L16, P1, and P2.     

Pain.

Advances in our understanding of the activation of peripheral damage-sensing neurons (nociceptors) over the past year have been complemented by electrophysiological and imaging studies of central nervous system pain-related centres. The manipulation of gene expression in a reversible and cell type specific way combined with imaging and electrophysiological studies holds promise for helping us to identify the spatial and molecular substrates of pain perception with increasing precision and gives hope for improved analgesic therapies.     

Polyglutamine pathogenesis.

An increasing number of neurodegenerative disorders have been found to be caused by expanding CAG triplet repeats that code for polyglutamine. Huntington's disease (HD) is the most common of these disorders and dentatorubral-pallidoluysian atrophy (DRPLA) is very similar to HD, but is caused by mutation in a different gene, making them good models to study. In this review, we will concentrate on the roles of protein aggregation, nuclear localization and proteolytic processing in disease pathogenesis. In cell model studies of HD, we have found that truncated N-terminal portions of huntingtin (the HD gene product) with expanded repeats form more aggregates than longer or full length huntingtin polypeptides. These shorter fragments are also more prone to aggregate in the nucleus and cause more cell toxicity. Further experiments with huntingtin constructs harbouring exogenous nuclear import and nuclear export signals have implicated the nucleus in direct cell toxicity. We have made mouse models of HD and DRPLA using an N-terminal truncation of huntingtin (N171) and full-length atrophin-1 (the DRPLA gene product), respectively. In both models, diffuse neuronal nuclear staining and nuclear inclusion bodies are observed in animals expressing the expanded glutamine repeat protein, further implicating the nucleus as a primary site of neuronal dysfunction. Neuritic pathology is also observed in the HD mice. In the DRPLA mouse model, we have found that truncated fragments of atrophin-1 containing the glutamine repeat accumulate in the nucleus, suggesting that proteolysis may be critical for disease progression. Taken together, these data lead towards a model whereby proteolytic processing, nuclear localization and protein aggregation all contribute to pathogenesis.     

Laterality of expression in portraiture: putting your best cheek forward.

Portraits, both photographic and painted, are often produced with more of one side of the face showing than the other. Typically, the left side of the face is overrepresented, with the head turned slightly to the sitter''s right. This leftward bias is weaker for painted male portraits and non-existent for portraits of scientists from the Royal Society. What mechanism might account for this bias? Examination of portraits painted by left- and right-handers and of self-portraits suggests that the bias is not determined by a mechanical preference of the artist or by the viewer''s aesthetics. The leftward bias seems to be determined by the sitters and their desire to display the left side of their face, which is controlled by the emotive, right cerebral hemisphere. When we asked people to portray as much emotion as possible when posing for a family portrait, they tended to present the left side of their face. When asked to pose as scientists and avoid portraying emotion, participants tended to present their right side. The motivation to portray emotion, or conceal it, might explain why portraits of males show a reduced leftward bias, and also why portraits of scientists from the Royal Society show no leftward bias.     

The effects of elevated summer temperature and sublethal pollutants (ammonia, low pH) on protein turnover in the gill and liver of rainbow trout (Oncorhynchus mykiss) on a limited food ration.

Protein synthesis, degradation and growth of the liver and gills were determined in juvenile rainbow trout (Oncorhynchus mykiss) fed a limited ration and exposed for 90 days to normal or elevated summer temperatures (+2 degrees above ambient) and either low pH (5.2) in softwater or 70 microM total ammonia in hardwater. The limited ration resulted in low rates of growth (< 0.80% per day) and protein synthesis in all fish. In softwater, whole-body growth was significantly inhibited by elevated temperature but stimulated by low pH, although tissue protein metabolism was generally unaffected by these treatments. There was no significant difference in final size between the groups of fish in hardwater, but liver protein synthesis and degradation were significantly lower at +2 degrees C, the reduction in synthesis being due to an inhibition of both the capacity for protein synthesis, Cs and the RNA translational efficiency, kRNA. Gill protein metabolism was unaffected by the experimental treatments in trout in hardwater. The authors conclude that a global warming scenario would be detrimental to protein synthesis and growth in freshwater fish under conditions of food limitation in summer, and when late summer temperatures approached the upper thermal limit of the species, regardless of food availability.