Alcohol Selection Research Articles

Use of genetic correlations to examine selection bias.

Observational studies are rarely representative of their target population because there are known and unknown factors that affect an individual's choice to participate (the selection mechanism). Selection can cause bias in a given analysis if the outcome is related to selection (conditional on the other variables in the model). Detecting and adjusting for selection bias in practice typically requires access to data on nonselected individuals. Here, we propose methods to detect selection bias in genetic studies by comparing correlations among genetic variants in the selected sample to those expected under no selection. We examine the use of four hypothesis tests to identify induced associations between genetic variants in the selected sample. We evaluate these approaches in Monte Carlo simulations. Finally, we use these approaches in an applied example using data from the UK Biobank (UKBB). The proposed tests suggested an association between alcohol consumption and selection into UKBB. Hence, UKBB analyses with alcohol consumption as the exposure or outcome may be biased by this selection.

Beer Goggles or Liquid Courage? Alcohol, Attractiveness Perceptions, and Partner Selection Among Men.

Perception of physical attractiveness (PPA) is a fundamental aspect of human relationships and may help explain alcohol's rewarding and harmful effects. Yet PPA is rarely studied in relation to alcohol, and existing approaches often rely on simple attractiveness ratings. The present study added an element of realism to the attractiveness assessment by asking participants to select four images of people they were led to believe might be paired with them in a subsequent study. Dyads of platonic, same-sex male friends (n = 36; ages 21-27; predominantly White, n = 20) attended two laboratory sessions wherein they consumed alcohol and a no-alcohol control beverage (counterbalanced). Following beverage onset, participants rated PPA of targets using a Likert scale. They also selected four individuals from the PPA rating set to potentially interact with in a future study. Alcohol did not affect traditional PPA ratings but did significantly enhance the likelihood that participants would choose to interact with the most attractive targets, χ2(1, N = 36) = 10.70, p < .01. Although alcohol did not affect traditional PPA ratings, alcohol did increase the likelihood of choosing to interact with more attractive others. Future alcohol-PPA studies should include more realistic contexts and provide assessment of actual approach behaviors toward attractive targets, to further clarify the role of PPA in alcohol's hazardous and socially rewarding effects.

Health warning labels and alcohol selection: a randomised controlled experiment in a naturalistic shopping laboratory.

Health warning labels (HWLs) on tobacco products reduce smoking. There is an absence of evidence concerning the impact of alcohol HWLs on selection or purchasing in naturalistic settings. Using a commercial-standard naturalistic shopping laboratory, this study aimed to estimate the impact on selection of alcoholic drinks of HWLs describing adverse health consequences of excessive alcohol consumption. A between-subjects randomised experiment with three groups was conducted: group 1: image-and-text HWL; group 2: text-only HWL; group 3: no HWL. A commercial-standard naturalistic shopping laboratory in the United Kingdom. Adults (n=399, 55% female) over the age of 18years, who purchased beer or wine weekly to drink at home. Participants were randomised to one of three groups varying in the HWL displayed on the packaging of the alcoholic drinks: (i) image-and-text HWL (n=135); (ii) text-only HWL (n=129); (iii) no HWL (n=135). Participants completed a shopping task, selecting items from a range of alcoholic and non-alcoholic drinks, and snacks. The primary outcome was the proportion of alcoholic drinks selected. Secondary outcomes included HWL ratings on negative emotional arousal and label acceptability. There was no clear evidence of a difference in the HWL groups for the percentage of drinks selected that were alcoholic compared to no HWL (44%): image-and-text HWL: 46% (odds ratio [OR]=1.08, 95% confidence interval [CI]=0.82, 1.42); text-only HWL: 41% (OR=0.87, 95% CI=0.67, 1.14). Concordant with there being no difference between groups, there was extreme evidence in favour of the null hypothesis (Bayes factor [BF]<0.01). Negative emotional arousal was higher (P<0.001) and acceptability lower (P<0.001) in the image-and-text HWL group, compared to the text-only HWL group. In a naturalistic shopping laboratory, there was no evidence that health warning labels describing the adverse health consequences of excessive alcohol consumption changed selection behaviour.

Impact of health warning labels communicating the risk of cancer on alcohol selection: an online experimental study.

Evidence from tobacco research suggests that health warning labels (HWLs) depicting the adverse consequences of consumption change smoking behaviours, with image-and-text (also known as 'pictorial' or 'graphic') HWLs most effective. There is an absence of evidence concerning the potential impact of HWLs placed on alcohol products on selection of those products. This study aimed to obtain a preliminary assessment of the possible impact of (i) image-and-text, (ii) text-only, and (iii) image-only HWLs on selection of alcoholic versus non-alcoholic drinks. A between-subjects randomised experiment with a 2 (image: present versus absent) × 2 (text: present versus absent) factorial design. The study was conducted on the online survey platform Qualtrics. Participants (n=6024) were adults over the age of 18 who consumed beer or wine regularly (i.e. at least once a week), recruited through a market research agency. Participants were randomised to one of four groups varying in the HWL displayed on the packaging of alcoholic drinks: (i) image-and-text HWL; (ii) text-only HWL; (iii) image-only HWL; and (iv) no HWL. HWLs depicted bowel cancer, breast cancer and liver cancer, which were each displayed twice across six alcoholic drinks. Each group viewed six alcoholic and six non-alcoholic drinks and selected one drink that they would like to consume. The primary outcome was the proportion of participants selecting an alcoholic versus a non-alcoholic drink. Alcoholic drink selection was lower for all HWL types compared with no HWL (image-and-text: 56%; image-only: 49%; text-only: 61%; no HWL: 77%), with selection lowest for HWLs that included an image. Image-and-text HWLs reduced the odds of selecting an alcoholic drink compared with text-only HWLs (OR=0.80, 95% CI=0.69, 0.92), but increased the odds of selecting an alcoholic drink compared with image-only HWLs (OR=1.34, 95% CI=1.16, 1.55). Health warning labels communicating the increased risk of cancers associated with alcohol consumption reduced selection of alcoholic versus non-alcoholic drinks in a hypothetical choice task in an online setting; labels displaying images had the largest effect. Their impact in laboratory and real-world field settings using physical products awaits investigation.

Evaluation of mitochondrial DNA copy number estimation techniques.

Mitochondrial DNA copy number (mtDNA-CN), a measure of the number of mitochondrial genomes per cell, is a minimally invasive proxy measure for mitochondrial function and has been associated with several aging-related diseases. Although quantitative real-time PCR (qPCR) is the current gold standard method for measuring mtDNA-CN, mtDNA-CN can also be measured from genotyping microarray probe intensities and DNA sequencing read counts. To conduct a comprehensive examination on the performance of these methods, we use known mtDNA-CN correlates (age, sex, white blood cell count, Duffy locus genotype, incident cardiovascular disease) to evaluate mtDNA-CN calculated from qPCR, two microarray platforms, as well as whole genome (WGS) and whole exome sequence (WES) data across 1,085 participants from the Atherosclerosis Risk in Communities (ARIC) study and 3,489 participants from the Multi-Ethnic Study of Atherosclerosis (MESA). We observe mtDNA-CN derived from WGS data is significantly more associated with known correlates compared to all other methods (p < 0.001). Additionally, mtDNA-CN measured from WGS is on average more significantly associated with traits by 5.6 orders of magnitude and has effect size estimates 5.8 times more extreme than the current gold standard of qPCR. We further investigated the role of DNA extraction method on mtDNA-CN estimate reproducibility and found mtDNA-CN estimated from cell lysate is significantly less variable than traditional phenol-chloroform-isoamyl alcohol (p = 5.44x10-4) and silica-based column selection (p = 2.82x10-7). In conclusion, we recommend the field moves towards more accurate methods for mtDNA-CN, as well as re-analyze trait associations as more WGS data becomes available from larger initiatives such as TOPMed.

What do we know about the effects of exposure to \u2018Low alcohol\u2019 and equivalent product labelling on the amounts of alcohol, food and tobacco people select and consume? A systematic review

BackgroundExplicit labelling of lower strength alcohol products could reduce alcohol consumption by attracting more people to buy and drink such products instead of higher strength ones. Alternatively, it may lead to more consumption due to a ‘self-licensing’ mechanism. Equivalent labelling of food or tobacco (for example “Low fat” or “Low tar”) could influence consumption of those products by similar mechanisms. This systematic review examined the effects of ‘Low alcohol’ and equivalent labelling of alcohol, food and tobacco products on selection, consumption, and perceptions of products among adults.MethodsA systematic review was conducted based on Cochrane methods. Electronic and snowball searches identified 26 eligible studies. Evidence from 12 randomised controlled trials (all on food) was assessed for risk of bias, synthesised using random effects meta-analysis, and interpreted in conjunction with evidence from 14 non-randomised studies (one on alcohol, seven on food and six on tobacco). Outcomes assessed were: quantities of the product (i) selected or (ii) consumed (primary outcomes - behaviours), (iii) intentions to select or consume the product, (iv) beliefs associated with it consumption, (v) product appeal, and (vi) understanding of the label (secondary outcomes – cognitions).ResultsEvidence for impacts on the primary outcomes (i.e. amounts selected or consumed) was overall of very low quality, showing mixed effects, likely to vary by specific label descriptors, products and population characteristics. Overall very low quality evidence suggested that exposure to ‘Low alcohol’ and equivalent labelling on alcohol, food and tobacco products can shift consumer perceptions of products, with the potential to ‘self-licence’ excess consumption.ConclusionsConsiderable uncertainty remains about the effects of labels denoting low alcohol, and equivalent labels, on alcohol, food and tobacco selection and consumption. Independent, high-quality studies are urgently needed to inform policies on labelling regulations.

Purification and enzymatic characterization of alcohol dehydrogenase from Arabidopsis thaliana

Alcohol dehydrogenases (ADH) catalyze the interconversion between alcohols and aldehydes with the reduction of nicotinamide adenine dinucleotide (NAD+) to NADH. In this study, for the first time we report an over-expression and purification strategy for the Arabidosis thaliana ADH (AtADH), and characterize its enzymatic properties. AtADH was expressed in an Escherichia coli system, the polyhistidine-tag was removed after the recombinant AtADH protein was purified by metal chelating affinity chromatography. Activity assays demonstrated that AtADH has distinct enzymatic properties when compared with many well-known ADHs. It held peak activity at pH 10.5 and showed broad substrate selectivity for primary and secondary alcohols. The kinetic Km parameters for both ethanol and coenzyme were in the order of mM. This relative low affinity may reflect the need of the plant to maintain a supply of NAD+ in nature. Different from yeast ADH, AtADH showed almost the same activity for short straight chain alcohols and reduced activity for secondary alcohols. This broad spectrum in alcohol selection and the observed higher catalytic activity (high Vmax (EtOH)) may result from the requirement of the single enzyme to accommodate many substrates.

Conformation and catalytic properties studies of Candida rugosa Lip7 via enantioselective esterification of ibuprofen in organic solvents and ionic liquids.

Enantioselective esterification of ibuprofen was conducted to evaluate the enzyme activity and ees of lipase from Candida rugosa (CRL7) in ten conventional organic solvents and three ionic liquids. Different alcohols were tested for selecting the most suitable acyl acceptor due to the fact that the structure of alcohols (branch and length of carbon chains; location of –OH functional group) could affect the enzyme activity and ees. The results of alcohol and solvent selection revealed that 1-isooctanol and isooctane were the best substrate and reaction medium, respectively, because of the highest enzyme activity and ees. Compared with the control, conformational studies via FT-IR indicate that the variations of CRL7's secondary structure elements are probably responsible for the differences of enzyme activity and ees in the organic solvents and ionic liquids. Moreover, the effects of reaction parameters, such as molar ratio, water content, temperature, and reaction time, in the selected reaction medium, were also examined.

Physical characterisation and component release of poly(vinyl alcohol)–tetrahydroxyborate hydrogels and their applicability as potential topical drug delivery systems

Poly(vinyl alcohol)–tetrahydroxyborate (PVA–THB) hydrogels are dilatant formulations with potential for topical wound management. To support this contention, the physical properties, rheological behaviour and component release of candidate formulations were investigated. Oscillatory rheometry and texture profile analysis were used at room temperature and 37°C. Results showed that it was possible to control the rheological and textural properties by altering component concentration and modifying the type of PVA polymer used. Hydrogels made using PVA grades with higher degrees of hydrolysis displayed favourable characteristics from a wound healing perspective. In vitro release of borate and PVA were assessed in order to evaluate potential clinical dosing of free species originating from the hydrogel structure. Component diffusion was influenced by both concentration and molecular weight, where relevant, with up to 5% free PVA cumulative release observed after 30min. The results of this study demonstrated the importance of poly(vinyl alcohol) selection for ensuring appropriate gel formation in PVA–THB hydrogels. The benefits of higher degrees of hydrolysis, in particular, included lower excipient release and reduced bioadhesion. The unique physical characteristics of these hydrogels make them an appealing delivery vehicle for chronic and acute wound management purposes.

Approaches for the Isolation ofArabidopsisadh1Regulatory Mutants Using Allyl Alcohol Selection

Allyl alcohol, a suicide substrate for the alcohol dehydrogenase enzyme (EC.1.1.1.1), has been frequently used as a negative selection method for the isolation of alcohol dehydrogenase mutants in plants, animals and microorganisms. This approach led to the isolation of mutants that mapped to the ADH gene itself. We attempted to use allyl alcohol selection for the isolation of adh1 regulatory mutants in Arabidopsis. First we selected at plantlet level on ADH1–GUS transgenic plants. This enabled us to use GUS staining to discriminate between structural and regulatory mutants. Allyl alcohol selection of 50000 EMS-treated seeds did not yield any potential mutants. Secondly we selected EMS and γ-ray-treated seeds of a transgenic line transformed with an additional copy of the ADH1 gene including its own promoter. Fifteen allyl alcohol-resistant plants were selected from the mutagenized seed. Genetic analysis of three putative mutants (adr8, adr10, and adr15) indicated that the ADH1-null phenotype was due to monogenic trans-recessive mutations. But treatment with the demethylating agent 5-azacytidine and analysis of methylation levels of the ADH1 gene indicated that these mutant candidates have increased levels of methylation in the promoter and coding region of ADH1. These results suggest that the allyl alcohol resistance of adr8, adr10, and adr15 is due to silencing of ADH1 rather than to a mutation of a regulatory locus.

Isolation and characterization of a mutant defective in the production of methanol dehydrogenase from a new restricted facultative methanol-oxidizing bacterium.

A new restricted facultative methanol-oxidizing bacterium Methylobacillus sp. strain SK1 (DSM 8269) was subjected to insertion mutagenesis studies with the transposon Tn5 to generate mutants deficient in the production of methanol dehydrogenase (MDH). The transposon was conjugally transferred into the methylotroph by using the triparental mating procedure. The mutants induced by Tn5 were selected directly from a plate containing succinate by using the allyl alcohol selection procedure. The transposition of Tn5 to the bacterium showed a moderate transposition frequency (10(-5) - 10(-6)). Southern hybridization analysis confirmed that the transposon Tn5 was inserted into the chromosomal DNA of the mutants. In addition, the mutants had no RNA transcripts produced from the mdh gene, as judged by Northern blot analysis. The mutants could neither grow on methanol nor produce MDH protein, as determined by Western blot analysis with anti-MDH antibody. These results suggest that Tn5 mutagenesis maybe a useful tool for the molecular analysis of a facultative methanol-oxidizing bacterium.

The influence of gender, expectancy, and partner beverage selection on (meta)perceptions in a “blind” dating situation

There is little question that alcohol plays a role in social situations. Most of the research in this area has used a paradigm designed to understand the effects of consuming alcohol on anxiety and social behavior. Most of the previous studies have looked only at situational factors — with limited focus on personality variables, using confederates to control the social reaction that participants received, with drinking generally occurring in a solitary situation. In the present study we were interested in understanding the interpersonal nature of reactions to alcohol consumption. The focus of this study was on the stimulus value of alcohol rather than anticipated or pharmacological effects of alcohol consumption. In large groups, individuals completed cognitive-personality measures assessing typical alcohol consumption, alcohol expectancies, and social anxiety. In the second part of the study, participants were paired with a member of the opposite sex with whom they had no previous contact; perceptions of their partner and metaperceptions were assessed after 4 and 15 minutes (before and after choosing a beverage — beer, soft drinks, etc.). Results indicate that positive alcohol expectancies interact with partner alcohol selection in predicting changes in metaperceptions of friendliness and relaxation. With friendliness, this result was most pronounced in men. These results are discussed in terms of the role alcohol expectancies may play in filtering alcohol relevant environmental information, and the influence of positive alcohol expectancies in mixed-sex drinking situations.

Genetics of alcoholism: Simultaneous presentation of a chocolate drink diminishes alcohol preference in high drinking HAD rats

Through selective crossbreeding of the N/Nih heterogeneous stock of rats, two genetic lines of rats have been developed that are categorized by their preference for ethyl alcohol as high alcohol drinking (HAD) and low alcohol drinking (LAD) animals. Corresponding to other strains of rat bred for alcohol selection or rejection, they were subdivided on the basis of their intake of a solution of 10% alcohol vs. water. The present experiments were designed to determine whether the HAD-1 and LAD-1 lines are similar to the P and NP rats in their profile of alcohol consumption. Five successive three-bottle preference tests for alcohol drinking in the presence of water were undertaken in both HAD ( n = 9) and LAD ( n = 10) rats as follows: 10% alcohol for 5 days; 3–30% concentrations of alcohol increased over 11 days; the maximally preferred concentration of alcohol for 5 days; this maximally preferred concentration of alcohol plus either chocolate Slender for 5 days, or an aspartame solution for 5 days. The intake of alcohol of the LAD rats during the 10% test was 0.4 g/kg/day, whereas during the 3–30% test, the maximum intake was 1.7 g/kg/day; their maximally preferred concentrations ranged between 7% and 9% alcohol. In contrast, the intake of 10% alcohol of the HAD rats was 6.5 g/kg/day, whereas during the 3–30% test the mean daily intake was 6.6 g/kg/day; the maximally preferred solutions of the HAD rats ranged between 13 to 20%, with the mean maximum intake of 10.57 g/kg/day reached at the 20% concentration. Thus, the use of a single concentration of alcohol such as 10% to ascertain preference for alcohol for these lines of rat is not an optimal procedure. In the presence of both the chocolate drink and aspartame, the intakes of the preferred concentration of alcohol of the HAD rats declined markedly, whereas the limited drinking of the LAD rats was unaffected by either palatable fluid. These results differ with those of the P line of rats which sustained their high preference for alcohol even in the presence of the same palatable solutions. Therefore, gustatory factors associated with the sensory quality of the fluids overrode the characteristic preference of the HAD rats for a pharmacologically efficacious solution of alcohol.

Coenzyme-dependent alcohol dehydrogenases in Candida guilliermondii Y4

Candida guilliermondii Y4 is capable of synthesizing two different alcohol dehydrogenases. ADH1 is constitutive on different carbon sources under shaking or settling conditions and its activity is prominent on gel electrophoresis. ADH2 is only synthesized under shaking condition. Two types of mutants were isolated using an allyl alcohol selection technique. ADH1-deficient mutants had 2.7% ADH activity of the wild type, while ADH2-deficient mutants had an ADH activity as high as that of the wild-type ADH activity. The alcohol dehydrogenases of the mutants differ from those of the wild type in their relative oxidation rates of alcohols. ADH1 appears to possess a functional role mainly in the production of ethanol from acetaldehyde, while ADH2 functions mainly in the oxidation of ethanol to acetaldehyde. However, both enzymes seem to be capable of carrying out the reverse reactions, since mutants lacking either of them still grew satisfactorily on different carbon sources. Key words: Candida guilliermondii, alcohol dehydrogenase, ADH1-deficient mutant, ADH2-deficient mutant.

Genetic and molecular characterization of an Adh-1 null mutant in tomato

Treatment of tomato seeds with ethyl methanesulphonate (EMS) followed by allyl alcohol selection of M2 seeds has led to the identification of one plant (B15-1) heterozygous for an alcohol dehydrogenase (Adh) null mutation. Genetic analysis and expression studies indicated that the mutation corresponded to the structural gene of the Adh-1 locus on chromosome 4. Homozygous Adh-1 null mutants lacked ADH-1 activity in both pollen and seeds. Using an antiserum directed against ADH from Arabidopsis thaliana, which cross-reacts with ADH-1 and ADH-2 proteins from tomato, no ADH-1 protein was detected in seeds of the null mutant. Northern blot analysis showed that Adh-1 mRNA was synthesized at wild-type levels in immature seeds of the null mutant, but dropped to 25% in mature seeds. Expression of the Adh-2 gene on chromosome 6 was unaffected. The potential use of the Adh-1 null mutant in selecting rare transposon insertion mutations in a cross with "mutable" Adh-1+ tomato lines is discussed.

Early experience and the consumption of alcohol by adult C57BL/6J mice

Two types of early experience were examined for their effect on voluntary alcohol consumption by adult C57BL/6J mice: the experiences associated with belonging to a particular litter, and the experience of early postweaning choice between water and a 10% alcohol solution. Males from identified litters were individually caged from arrival at three weeks of age and given a choice between 10% alcohol and water when eight weeks old. Another group without notation of litter was given alcohol-water choice upon arrival at three weeks of age. Alcohol intake was examined by three measures: daily licks of 10% alcohol, alcohol selection (percent alcohol drinking), and volume of alcohol drunk daily. Belonging to a particular litter did affect body weight and growth, but had no effect on adult consumption of alcohol. Postweaning exposure to alcohol choice, however, produced a small but significant and prolonged increase in alcohol consumption by adults. Furthermore, a developmental trend was found in mice offered alcohol choice at an early age: alcohol preference developed as postweaning growth slowed.

Isolation and biochemical analysis of ethyl methanesulfonate-induced alcohol dehydrogenase null mutants of arabidopsis thaliana (L.) Heynh.

Several mutants have been isolated at the Arabidopsis thaliana (L.) Heynh. alcohol dehydrogenase (ADH) gene locus using allyl alcohol selection on ethyl methanesulfonate (EMS)-mutagenized seeds. Eleven mutants were isolated in the ADH1-A electrophoretic allele, and 21 in the ADH1-S allele. These null mutants are characterized by the absence of measurable ADH activity and genetic data showed that the mutations were confined to the ADH1 gene locus of Arabidopsis. Eleven mutants in the ADH1-A background were further characterized at the protein and mRNA level. These experiments revealed striking differences in the ADH protein and mRNA content. Some of the mutants did not synthesize any mRNA or ADH-like protein, whereas some of them had a nearly normal level of ADH protein and mRNA. Others had a very low level of both protein and mRNA. ADH null mutants differed physiologically from the wild type by their higher sensitivity to anaerobic treatment in plants and significantly reduced resistance to acetaldehyde in suspension cultures.

Allyl Alcohol Selection for Lower Alcohol Dehydrogenase Activity in Nicotiana plumbaginifolia Cultured Cells

One cell strain with stable tolerance to allyl alcohol (AA(r)) was selected from 6 x 10(8) suspension cultured Nicotiana plumbaginifolia Viviani cells. The selected strain contained one-half the alcohol dehydrogenase (ADH) activity of the wild type (NP) due to the loss of two of three bands of ADH activity seen on starch gels following electrophoresis of wild-type cell extracts. Anaerobic conditions, simulated by not shaking the suspension cultures, increased the ADH specific activity to more than 3-fold the initial level in both strains but did not change the number of activity bands or the relative levels of activity. The cell strain with decreased ADH activity lost viability more rapidly than the wild type under the anaerobic conditions. The AA(r) cells were 10 times more tolerant to ethanol than the NP cells and were also somewhat more tolerant to acetaldehyde and antimycin A. The substrate specificities of the ADH enzymes from both strains were very similar. Further selection of AA(r) cells with allyl alcohol produced strains with even lower ADH activity and selection under anaerobic conditions produced strains with increased ADH activity. Genetic studies indicate that the N. plumbaginifolia ADH activity bands arise from subunits produced by two nonallelic genes. This is the first example of the use of allyl alcohol to select for decreased ADH using cultured plant cells.

The feasibility of effective psychopharmacological treatments for alcoholism.

SummaryThe effects of lithium, anxiolytics, dopaminergic compounds, serotonin uptake inhibitors, opiates, opiate antagonists, and alcohol‐sensitizing drugs on the alcohol consumption of human alcoholics and laboratory animals are reviewed. There is increasing evidence that each of these classes of drugs might be beneficial in reducing alcohol abuse, including recent controlled studies on alcoholics with lithium, serotonin uptake Mockers, and disefulram. The usefulness of all of the current drugs, however, appears limited, and the ideal drug for use in treating alcoholism awaits discovery. Nevertheless, the fact that some drugs acting on the central nervous system are able to promote abstinence supports the feasibility of psychopharmacological treatment for alcoholism. Furthermore, since the known drugs that appear beneficial against human alcohol abuse also suppress voluntary alcohol selection by experimental animals, it seems likely that studies with animals could be used for screening other potentially effective drugs.

Influence of tryptophan availability on selection of alcohol and water by men.

To study the effects of tryptophan on alcohol selection the tryptophan levels in subjects were altered through the administration of amino acid mixtures. Male social drinkers (N = 45) with no psychiatric or medical problems were divided into three groups and consumed a drink that contained, respectively, a nutritionally balanced amino acid mixture, a tryptophan-supplemented mixture, or a tryptophan-free mixture. After a waiting period of 5 hours, blood samples were taken and subjects participated in an ad-lib taste rating of six--one nonalcoholic and five alcoholic--beverages. Water was also made available to subjects. Although there was a marked effect on total and free plasma tryptophan levels showing a dramatic increase in the case of the tryptophan-supplemented group and a decrease in the tryptophan-free group, altered tryptophan levels did not influence the amount of alcohol subjects ingested. Tryptophan supplementation was found to decrease water intake significantly by an unknown mechanism without affecting alcohol selection.