Mathematical model insights into arsenic detoxification

Background

Arsenic in drinking water, a major health hazard to millions of people in South and East Asia and in other parts of the world, is ingested primarily as trivalent inorganic arsenic (iAs), which then undergoes hepatic methylation to methylarsonic acid (MMAs) and a second methylation to dimethylarsinic acid (DMAs). Although MMAs and DMAs are also known to be toxic, DMAs is more easily excreted in the urine and therefore methylation has generally been considered a detoxification pathway. A collaborative modeling project between epidemiologists, biologists, and mathematicians has the purpose of explaining existing data on methylation in human studies in Bangladesh and also testing, by mathematical modeling, effects of nutritional supplements that could increase As methylation.

Methods

We develop a whole body mathematical model of arsenic metabolism including arsenic absorption, storage, methylation, and excretion. The parameters for arsenic methylation in the liver were taken from the biochemical literature. The transport parameters between compartments are largely unknown, so we adjust them so that the model accurately predicts the urine excretion rates of time for the iAs, MMAs, and DMAs in single dose experiments on human subjects.

Results

We test the model by showing that, with no changes in parameters, it predicts accurately the time courses of urinary excretion in mutiple dose experiments conducted on human subjects. Our main purpose is to use the model to study and interpret the data on the effects of folate supplementation on arsenic methylation and excretion in clinical trials in Bangladesh. Folate supplementation of folate-deficient individuals resulted in a 14% decrease in arsenicals in the blood. This is confirmed by the model and the model predicts that arsenicals in the liver will decrease by 19% and arsenicals in other body stores by 26% in these same individuals. In addition, the model predicts that arsenic methyltransferase has been upregulated by a factor of two in this population. Finally, we also show that a modification of the model gives excellent fits to the data on arsenic metabolism in human cultured hepatocytes.

Conclusions

The analysis of the Bangladesh data using the model suggests that folate supplementation may be more effective at reducing whole body arsenic than previously expected. There is almost no data on the upregulation of arsenic methyltransferase in populations chronically exposed to arsenic. Our model predicts upregulation by a factor of two in the Bangladesh population studied. This prediction should be verified since it could have important public health consequences both for treatment strategies and for setting appropriate limits on arsenic in drinking water. Our model has compartments for the binding of arsenicals to proteins inside of cells and we show that these comparments are necessary to obtain good fits to data. Protein-binding of arsenicals should be explored in future biochemical studies.

Associations of plasma selenium with arsenic and genomic methylation of leukocyte DNA in Bangladesh

BACKGROUND

Global hypomethylation of DNA is thought to constitute an early event in some cancers and occurs in response to arsenic (As) exposure and/or selenium (Se) deficiency in both in vitro and animal models. In addition, antagonism between As and Se, whereby each reduces toxicity of the other, has been well documented in animal models. Se status may therefore modify the health effects of As in As-exposed populations.

OBJECTIVE

The primary objectives of our study were to test the hypothesis that Se deficiency is associated with genomic hypomethylation of lymphocyte DNA and to determine whether Se levels are associated with blood As (bAs) and urinary As (uAs) concentrations in adults exposed to As-contaminated groundwater in Bangladesh. A secondary objective was to explore the relationships between plasma Se and As metabolites.

DESIGN

We assessed plasma Se concentrations, As metabolite profiles in blood and urine, and genomic methylation of leukocyte DNA in a cross-sectional study of 287 adults.

RESULTS

After adjustment for potential confounders, we observed an inverse association between Se (micrograms per liter) and genomic DNA methylation (disintegrations per minute per 1-µg/L increase in Se): β = 345.6; 95% confidence interval (CI), 59-632. Se concentrations were inversely associated with total As concentrations (micrograms per liter) in blood (β = -0.04; 95% CI, -0.08 to -0.01) and urine (β = -20.1; 95% CI, -29.3 to -10.9). Se levels were negatively associated with the percentage of monomethylarsinic acid (β = -0.59; 95% CI, -1.04 to -0.13) and positively associated with the percentage of dimethylarsinic acid (β = 0.53; 95% CI, 0.04 to 1.01) in blood.

CONCLUSIONS

Our results suggest that Se is inversely associated with genomic DNA methylation. The underlying mechanisms and implications of this observation are unclear and warrant further investigation. In addition, Se may influence bAs and uAs concentrations, as well as relative proportions of As metabolites in blood.

Genome-wide shRNA screen reveals increased mitochondrial dependence upon mTORC2 addiction

Release from growth factor dependence and acquisition of signalling pathway addiction are critical steps in oncogenesis. To identify genes required on mammalian target of rapamycin (mTOR) addiction, we performed a genome-wide short hairpin RNA screen on a v-H-ras-transformed Pten-deficient cell line that displayed two alternative growth modes, interleukin (IL)-3-independent/mTOR-addicted proliferation (transformed growth mode) and IL-3-dependent/mTOR-non-addicted proliferation (normal growth mode). We screened for genes required only in the absence of IL-3 and thus specifically for the transformed growth mode. The top 800 hits from this conditional lethal screen were analyzed in silico and 235 hits were subsequently rescreened in two additional Pten-deficient cell lines to generate a core set of 47 genes. Hits included genes encoding mTOR and the mTOR complex 2 (mTORC2) component rictor and several genes encoding mitochondrial functions including components of the respiratory chain, adenosine triphosphate synthase, the mitochondrial ribosome and mitochondrial fission factor. Small interfering RNA knockdown against a sizeable fraction of these genes triggered apoptosis in human cancer cell lines but not in normal fibroblasts. We conclude that mTORC2-addicted cells require mitochondrial functions that may be novel drug targets in human cancer.

Evaluation of the potential use of adipose-derived mesenchymal stromal cells in the treatment of canine atopic dermatitis: a pilot study

Stem cells and their potential therapeutic uses in human and veterinary medicine have generated considerable interest. These cells have a number of potentially unique immunologic properties; most notable are their reported regenerative and antiinflammatory capabilities. The aim of this prospective pilot study was to evaluate the efficacy of intravenously administered autogenous adipose-derived mesenchymal stem cells (AD-MSCs) in the treatment of canine atopic dermatitis. AD-MSCs administered intravenously at a dose of 1.3 million cells/kg did not significantly reduce the clinical signs of canine atopic dermatitis or the owner-assessed pruritus level.

Influence of cobalamin on arsenic metabolism in Bangladesh

BACKGROUND

Arsenic is a carcinogen to which 35 million people in Bangladesh are chronically exposed. The enzymatic transfer of methyl groups to inorganic As (iAs) generates monomethylarsonic (MMA) and dimethylarsinic acids (DMA) and facilitates urinary As (uAs) elimination. This process is dependent on one-carbon metabolism, a pathway in which folate and cobalamin have essential roles in the recruitment and transfer of methyl groups. Although DMA(V) is the least toxic metabolite, increasing evidence suggests that MMA(III) may be the most cytotoxic and genotoxic As intermediary metabolite.

OBJECTIVE

We examined the associations between plasma cobalamin and uAs metabolites.

METHODS

We conducted a cross-sectional study of 778 Bangladeshi adults in which we over-sampled cobalamin-deficient participants. Participants provided blood samples for the measurement of plasma cobalamin and urine specimens for As measurements.

RESULTS

Cobalamin was inversely associated with the proportion of total uAs excreted as iAs (%iAs) [unstandardized regression coefficient (b) = -0.10; 95% confidence interval (CI), -0.17 to -0.02; p = 0.01] and positively associated with %MMA (b = 0.12; 95% CI, 0.05 to 0.20; p = 0.001). Both of these associations were stronger among folate-sufficient participants (%iAs: b = -0.17; 95% CI, -0.30 to -0.03; p = 0.02. %MMA: b = 0.20; 95% CI, 0.11 to 0.30; p < 0.0001), and the differences by folate status were statistically significant.

CONCLUSIONS

In this group of Bangladeshi adults, cobalamin appeared to facilitate the first As methylation step among folate-sufficient individuals. Given the toxicity of MMA(III), our findings suggest that in contrast to folate, cobalamin may not favorably influence As metabolism.

mTOR-what does it do?

Target of rapamycin (TOR) is a highly conserved serine/threonine kinase that controls cell growth and metabolism in response to nutrients, growth factors, cellular energy, and stress. TOR, which was originally discovered in yeast, is conserved in all eukaryotes including plants, worms, flies, and mammals. The discovery of TOR led to a fundamental change in how we think about cell growth. It is not a spontaneous process that just happens when building blocks (nutrients) are available, but rather a highly regulated, plastic process controlled by TOR-dependent signaling pathways. TOR is found in 2 structurally and functionally distinct multiprotein complexes, TORC1 and TORC2. The 2 TOR complexes, like TOR itself, are highly conserved. Mammalian TORC1 (mTORC1) is rapamycin sensitive and contains mTOR, raptor, and mLST8. TORC1 in yeast and mammals mediates temporal control of cell growth by regulating several cellular processes, including translation, transcription, ribosome biogenesis, nutrient transport, and autophagy. mTORC2 is rapamycin insensitive and contains mTOR, rictor, mSIN1, PRR5, and mLST8. TORC2 in yeast and mammals mediates spatial control of cell growth by regulating the actin cytoskeleton. Thus, the 2 TOR complexes constitute an ancestral signaling network conserved throughout eukaryotic evolution to control the fundamental process of cell growth. As a central controller of cell growth, TOR plays a key role in development and aging and has been implicated in disorders such as cancer, cardiovascular disease, obesity, and diabetes. The challenge now is to understand the role of mTOR signaling to coordinate and integrate overall body growth in multicellular organisms.

Folate, Cobalamin, Cysteine, Homocysteine, and Arsenic Metabolism among Children in Bangladesh

BACKGROUND

Approximately 35 million people in Bangladesh are chronically exposed to inorganic arsenic (InAs) in drinking water. Methylation of InAs to monomethylarsonic (MMA) and dimethylarsinic acids (DMA) relies on folate-dependent one-carbon metabolism and facilitates urinary arsenic (uAs) elimination.

OBJECTIVES

We examined the relationships between folate, cobalamin, cysteine, total homocysteine (tHcys), and uAs metabolites in a sample of 6-year-old Bangladeshi children (n = 165).

METHODS

Children provided blood samples for measurement of tHcys, folate, cobalamin, and cysteine, and urine specimens for the measurement of total uAs and As metabolites.

RESULTS

Consistent with our studies in adults, mean tHcys concentrations (7.9 micromol/L) were higher than those reported among children of similar ages in other populations. Nineteen percent of the children had plasma folate concentrations < 9.0 nmol/L. The proportion of total uAs excreted as InAs (%InAs) was inversely correlated with folate (r = -0.20, p = 0.01) and cysteine (r = -0.23, p = 0.003), whereas the correlations between %DMA and both folate (r = 0.12, p = 0.14) and cysteine (r = 0.11, p = 0.15) were positive. Homocysteine was inversely correlated (r = -0.27, p = 0.009) with %MMA in males, and the correlation with %DMA was positive (r = 0.13, p = 0.10).

CONCLUSIONS

These findings suggest that, similar to adults, folate and cysteine facilitate As methylation in children. However, the inverse correlation between tHcys and %MMA, and positive correlation with %DMA, are both opposite to our previous findings in adults. We propose that upregulation of one-carbon metabolism, presumably necessary to meet the considerable demands for DNA and protein biosynthesis during periods of rapid growth, results in both increased tHcys biosynthesis and increased As methylation.

A 22-y prospective study of fish intake in relation to prostate cancer incidence and mortality

BACKGROUND

Fish and seafood n-3 fatty acids may prevent or delay the progression of prostate cancer, but epidemiologic studies do not uniformly support this hypothesis.

OBJECTIVE

We examined the relation of fish and seafood n-3 fatty acid intakes with prostate cancer incidence and mortality.

DESIGN

We conducted a prospective cohort study among 20,167 men participating in the Physician's Health Study who were free of cancer in 1983.

RESULTS

During 382 144 person-years of follow-up, 2161 men were diagnosed with prostate cancer and 230 died of prostate cancer. Fish intake was unrelated to prostate cancer incidence. Survival analysis among the men diagnosed with prostate cancer revealed that those consuming fish >or=5 times/wk had a 48% lower risk of prostate cancer death than did men consuming fish less than once weekly [relative risk (RR) = 0.52; 95% CI: 0.30, 0.91; P for trend = 0.05]. A similar association was found between seafood n-3 fatty acid intake and prostate cancer mortality (RR(Q5 versus Q1) = 0.64; 95% CI: 0.42, 0.99; P for trend = 0.02). These associations became stronger when the analyses were restricted to clinically detected cases.

CONCLUSION

These results suggest that fish intake is unrelated to prostate cancer incidence but may improve prostate cancer survival.

A 22-year prospective study of fish, n-3 fatty acid intake, and colorectal cancer risk in men

BACKGROUND

Fish is the main dietary source of long-chain n-3 fatty acids, which have been suggested to play a protective role in colorectal cancer development in laboratory and animal studies. Human studies have not shown consistent results. We examined the association between intakes of fish and n-3 fatty acids from fish and colorectal cancer risk in men enrolled in the Physicians' Health Study.

METHODS

The Physicians' Health Study began as a randomized trial to examine the effect of aspirin and beta-carotene supplementation on cancer and cardiovascular disease. Fish intake was assessed at the 12-month follow-up with an abbreviated food-frequency questionnaire. Cox proportional hazards models were used to estimate multivariate relative risks for colorectal cancer for the categories of fish intake and quartiles of n-3 fatty acid intake.

RESULTS

During 22 years of follow-up, 500 men had a confirmed diagnosis of colorectal cancer. Fish intake was inversely associated with colorectal cancer risk [multivariate relative risk (95% confidence interval) for highest versus lowest category, 0.63 (0.42-0.95); P trend = 0.02] [corrected] The inverse association was observed for both colon and rectal cancers. Our findings for n-3 fatty acids were similar to those for fish; the multivariate relative risk (95% confidence interval) of total colorectal cancer for the highest versus lowest quartile of n-3 fatty acids was 0.74 (0.57-0.95; P trend = 0.01).

CONCLUSIONS

Our results from this long-term prospective study suggest that intakes of fish and long-chain n-3 fatty acids from fish may decrease the risk for colorectal cancer.

Blood levels of long-chain polyunsaturated fatty acids, aspirin, and the risk of colorectal cancer

BACKGROUND

N-3 fatty acids may decrease risk of colorectal cancer by inhibiting the cyclooxygenase-2 enzyme and production of proinflammatory eicosanoids derived from arachidonic acid (20:4n-6). Aspirin also inhibits the cyclooxygenase-2 enzyme and may share with n-3 fatty acids a potential mechanism to decrease the risk of colorectal cancer.

METHODS

We conducted a nested case-control analysis using blood samples collected from the Physicians' Health Study participants in 1982 to 1984. N-3 and n-6 fatty acid levels were measured using gas-liquid chromatography for 178 men who developed colorectal cancer through December 31, 1995 and 282 age- and smoking-matched controls. We used conditional logistic regression to examine associations. All statistical tests were two-sided.

RESULTS

Total long-chain n-3 fatty acids were nonsignificantly inversely associated with colorectal cancer risk [relative risk (RR) for highest versus lowest quartile, 0.60; 95% confidence interval (95% CI), 0.32 to 1.11; P(trend) = 0.10], after adjustment for possible confounders. We observed potential interaction between randomized aspirin assignment and long-chain n-3 fatty acid levels (P(interaction) = 0.04). Among men not on aspirin, RRs (95% CI) for increasing quartiles of long-chain n-3 fatty acids were 1.00 (reference), 0.60 (0.28-1.28), 0.51 (0.22-1.17), and 0.34 (0.15-0.82), P(trend) = 0.006. For participants taking aspirin, there was no additional benefit of increasing n-3 fatty acid levels. The RR (95% CI) for the highest versus lowest quartile of n-6 fatty acids was 0.64 (0.35-1.17).

CONCLUSIONS

Blood levels of long-chain n-3 fatty acids were associated with decreased risk of colorectal cancer among men not using aspirin. N-6 fatty acids were nonsignificantly inversely associated with colorectal cancer risk.

TOR: the first 10 years

TOR was discovered and christened 10 years ago. On the occasion of this anniversary, we revisit the discovery of TOR and chronicle subsequent breakthroughs in S. cerevisiae that contributed to an understanding of TOR function in yeast and higher eukaryotes. In particular, we discuss findings that led to the realization that the function of TOR is to control cell growth in response to nutrients.

Evidence for a coupling of synthesis and export of an outer membrane protein in Escherichia coli

We describe a lesion, lamB701-708, affecting the hydrophilic portion of the lambda receptor signal sequence. The C to A transversion of the sixth codon of the signal sequence changes a positively charged arginine to a neutral serine. The phenotype conferred by this alteration is unique among previously described signal sequence mutations. The results suggest an essential role for the charged amino acids of the hydrophilic segment in the initial interaction between a nascent secreted protein and a membrane export site. The results further suggest that synthesis of lambda receptor is coupled to its export.

TIP41 interacts with TAP42 and negatively regulates the TOR signaling pathway

In Saccharomyces cerevisiae, the rapamycin-sensitive TOR kinases negatively regulate the type 2A-related phosphatase SIT4 by promoting the association of this phosphatase with the inhibitor TAP42. Here, we describe TIP41, a conserved TAP42-interacting protein involved in the regulation of SIT4. Deletion of the TIP41 gene confers rapamycin resistance, suppresses a tap42 mutation, and prevents dissociation of SIT4 from TAP42. Furthermore, a TIP41 deletion prevents SIT4-dependent events such as dephosphorylation of the kinase NPR1 and nuclear translocation of the transcription factor GLN3. Thus, TIP41 negatively regulates the TOR pathway by binding and inhibiting TAP42. The binding of TIP41 to TAP42 is stimulated upon rapamycin treatment via SIT4-dependent dephosphorylation of TIP41, suggesting that TIP41 is part of a feedback loop that rapidly amplifies SIT4 phosphatase activity under TOR-inactivating conditions.

The GATA transcription factors GLN3 and GAT1 link TOR to salt stress in Saccharomyces cerevisiae

One of the most recent functions assigned to the TOR signaling pathway in yeast is the coordination of the transcription of genes involved in nutrient utilization. Here we show that transcription of ENA1, a gene encoding a lithium and sodium ion transporter essential for salt tolerance in yeast, is controlled by the TOR signaling pathway. First, ENA1 expression is strongly induced under TOR-inactivating conditions. Second, the absence of the TOR-controlled GATA transcription factors GLN3 and GAT1 results in reduced basal and salt-induced expression of ENA1. Third, a gln3 gat1 mutant displays a pronounced sensitivity to high concentrations of lithium and sodium. Fourth, TOR1, similar to ENA1, is required for growth under saline stress conditions. In summary, our results suggest that TOR plays a role in the general response to saline stress by regulating the transcription of ENA1 via GLN3 and GAT1.

Updating and refining prevalence estimates of disordered gambling behaviour in the United States and Canada

BACKGROUND

This study updates prevalence estimates of gambling-related disorders in the United States and Canada, identifies differences in prevalence estimates among population segments, and identifies changes in prevalence over the past 25 years.

METHOD

A meta-analytic strategy guided the synthesis of 180 estimates derived from 146 prevalence studies.

RESULTS

Prevalence estimates among adolescent samples were significantly higher than estimates among adult samples for both clinical (level 3) and sub-clinical (level 2) measures of disordered gambling within both lifetime and past-year time frames. Among adults, level 3 prevalence estimates continue to increase significantly.

CONCLUSIONS

Membership in youth, treatment, and prison population segments is significantly associated with experiencing gambling-related disorders. Understanding sub-clinical gamblers provides a meaningful opportunity to lower the public health burden associated with gambling disorders. Prospective studies of incidence are necessary to determine whether the prevalence of disordered gambling continues to increase among the adult general population and how adolescent gambling experiences change as this cohort ages.

HEAT repeats mediate plasma membrane localization of Tor2p in yeast

The subcellular distribution of Tor1p and Tor2p, two phosphatidylinositol kinase homologs and targets of the immunosuppressive drug rapamycin in Saccharomyces cerevisiae, was analyzed. We found that Tor protein is peripherally associated with membranes. Subcellular fractionation and immunofluorescence studies showed that Tor1p and Tor2p associate with the plasma membrane and a second fraction that is distinct from Golgi, vacuoles, mitochondria, and nucleus and may represent vesicular structures. Pulse-chase experiments showed that association of Tor protein with plasma membrane and the second compartment is fast, does not appear to involve components of endocytic, secretory, or Golgi to vacuole transport pathways, and is not affected by the immunosuppressive drug rapamycin. Deletion analysis reveals that two domains within Tor2p independently mediate localization to both compartments. These domains are composed of HEAT repeats that are thought to act as protein-protein interaction surfaces. Our studies therefore place Tor proteins at the site of action of their known downstream effectors and suggest that they may be part of a multiprotein complex.

TOR, a central controller of cell growth

Cell growth (increase in cell mass) and cell proliferation (increase in cell number) are distinct yet coupled processes that go hand-in-hand to give rise to an organ, organism, or tumor. Cyclin-dependent kinase(s) is the central regulator of cell proliferation. Is there an equivalent regulator for cell growth? Recent findings reveal that the target of rapamycin TOR controls an unusually abundant and diverse set of readouts all of which are important for cell growth, suggesting that this conserved kinase is such a central regulator.

FAP1, a homologue of human transcription factor NF-X1, competes with rapamycin for binding to FKBP12 in yeast

The immunosuppressive drug rapamycin binds to the peptidyl-prolyl cis-trans isomerase FKBP12, and this complex arrests growth of yeast cells and activated T lymphocytes in the G1 phase of the cell cycle. In yeast, loss-of-function mutations in FPR1, the gene encoding FKBP12, or dominant gain-of-function mutations in TOR1 and TOR2, the genes encoding the physical targets of the FKBP12-rapamycin complex, confer rapamycin resistance. Here, we report the cloning and characterization of a novel gene, termed FAP1, which confers resistance to rapamycin by competing with the drug for binding to FKBP12. FAP1 encodes a member of an evolutionarily conserved family of putative transcription factors that includes human NF-X1, Drosophila melanogaster shuttle craft and previously undescribed homologues in Caenorhabditis elegans, Arabidopsis thaliana and Schizosaccharomyces pombe. We provide genetic and biochemical evidence that FAP1 interacts physically with FKBP12 in vivo and in vitro, and that it competes with rapamycin for interaction. Furthermore, mutations in the FKBP12 drug binding/active site or surface residues abolish binding to FAP1. Our results suggest that FAP1 is a physiological ligand for FKBP12 that is highly conserved from yeast to man. Furthermore, prolyl isomerases may commonly bind and regulate transcription factors.

Smoking behavior among casino employees: self-report validation using plasma cotinine

The veracity of behavioral self-reports is often challenged, particularly when the motivation to avoid stigma and win social approval holds potential to introduce bias into the data collected. This study employed plasma cotinine tests to validate the self-reports of tobacco use collected from 3,841 casino employees as part of a comprehensive health survey. Rates of discordance were calculated by comparing employee self-reports with results from plasma colinine tests. This study provides evidence that casino employees can provide valid self-report data. Further, discordance rates of self-reported tobacco use vary according to operational definitions of tobacco use. These findings highlight the methodological importance of recognizing the inherent heterogeneity of smoking behavior.

Eap1p, a novel eukaryotic translation initiation factor 4E-associated protein in Saccharomyces cerevisiae

Ribosome binding to eukaryotic mRNA is a multistep process which is mediated by the cap structure [m(7)G(5')ppp(5')N, where N is any nucleotide] present at the 5' termini of all cellular (with the exception of organellar) mRNAs. The heterotrimeric complex, eukaryotic initiation factor 4F (eIF4F), interacts directly with the cap structure via the eIF4E subunit and functions to assemble a ribosomal initiation complex on the mRNA. In mammalian cells, eIF4E activity is regulated in part by three related translational repressors (4E-BPs), which bind to eIF4E directly and preclude the assembly of eIF4F. No structural counterpart to 4E-BPs exists in the budding yeast, Saccharomyces cerevisiae. However, a functional homolog (named p20) has been described which blocks cap-dependent translation by a mechanism analogous to that of 4E-BPs. We report here on the characterization of a novel yeast eIF4E-associated protein (Eap1p) which can also regulate translation through binding to eIF4E. Eap1p shares limited homology to p20 in a region which contains the canonical eIF4E-binding motif. Deletion of this domain or point mutation abolishes the interaction of Eap1p with eIF4E. Eap1p competes with eIF4G (the large subunit of the cap-binding complex, eIF4F) and p20 for binding to eIF4E in vivo and inhibits cap-dependent translation in vitro. Targeted disruption of the EAP1 gene results in a temperature-sensitive phenotype and also confers partial resistance to growth inhibition by rapamycin. These data indicate that Eap1p plays a role in cell growth and implicates this protein in the TOR signaling cascade of S. cerevisiae.

"Computer addiction": a critical consideration

Problems related to intemperate Internet use are examined within the conceptual framework of addiction. It is argued that empirical support for the construct validity of computer addiction has yet to emerge, that defining the construct as a unique psychiatric disorder is therefore premature, and that, in most cases, excessive computer use may be symptomatic of other, more primary disorders. Greater caution and rigor are urged in investigating and treating problems related to intemperate computer use.

Social workers employed in substance abuse treatment agencies: a training needs assessment

This article describes the results of an assessment of the substance abuse treatment training needs of social workers working in randomly selected substance abuse treatment facilities in New England. This assessment revealed that clinical supervision related to substance abuse treatment had not been available to a significant percentage of the respondents throughout their careers. Despite limited previous training experience and considerable barriers to current training, social workers surveyed in this study reported significantly higher levels of knowledge and skill than other substance abuse treatment providers in 10 of 12 substance abuse treatment areas investigated. Despite these high levels of knowledge and skill, respondents reported considerable need for and interest in additional substance abuse treatment training. This study identified the areas of assessment, advanced clinical techniques, and dual diagnosis as priorities for future training among social workers working in substance abuse treatment facilities.

Analysis of deletion phenotypes and GFP fusions of 21 novel Saccharomyces cerevisiae open reading frames

As part of EUROFAN (European Functional Analysis Network), we investigated 21 novel yeast open reading frames (ORFs) by growth and sporulation tests of deletion mutants. Two genes (YNL026w and YNL075w) are essential for mitotic growth and three deletion strains (ynl080c, ynl081c and ynl225c) grew with reduced rates. Two genes (YNL223w and YNL225c) were identified to be required for sporulation. In addition we also performed green fluorescent protein (GFP) tagging for localization studies. GFP labelling indicated the spindle pole body (Ynl225c-GFP) and the nucleus (Ynl075w-GFP) as the sites of action of two proteins. Ynl080c-GFP and Ynl081c-GFP fluorescence was visible in dot-shaped and elongated structures, whereas the Ynl022c-GFP signal was always found as one spot per cell, usually in the vicinity of nuclear DNA. The remaining C-terminal GFP fusions did not produce a clearly identifiable fluorescence signal. For 10 ORFs we constructed 5'-GFP fusions that were expressed from the regulatable GAL1 promoter. In all cases we observed GFP fluorescence upon induction but the localization of the fusion proteins remained difficult to determine. GFP-Ynl020c and GFP-Ynl034w strains grew only poorly on galactose, indicating a toxic effect of the overexpressed fusion proteins. In summary, we obtained a discernible GFP localization pattern in five of 20 strains investigated (25%). A deletion phenotype was observed in seven of 21 (33%) and an overexpression phenotype in two of 10 (20%) cases.