Personality and the genetic risk for alcohol dependence

The extent to which the genetic risk for alcohol dependence (AD) and conduct disorder (CD) and their common genetic risk overlap with genetic factors contributing to variation in dimensions of personality was examined in a study of 6,453 individuals from 3,383 adult male and female same-sex and unlike-sex twin pairs from the Australian Twin Registry. The associations between the personality dimensions of positive emotionality, negative emotionality, and AD and CD risk were modest. whereas the associations between behavioral undercontrol and AD and CD risk were substantially higher. Genetic influences contributing to variation in behavioral undercontrol accounted for about 40% of the genetic variation in AD and CD risk and about 90% of the common genetic risk for AD and CD. These results suggest that genetic factors contributing to variation in dimensions of personality, particularly behavioral undercontrol. account for a substantial proportion of the genetic diathesis for AD and most of the common genetic diathesis for AD and CD among both men and women.

Genetic and environmental contributions to cannabis dependence in a national young adult twin sample

Background. This paper examines genetic and environmental contributions to risk of cannabis dependence. Method. Symptoms of cannabis dependence and measures of social, family and individual risk factors were assessed in a sample of 6265 young adult male and female Australian twins born 1964-1971. Results. Symptoms of cannabis dependence were common: 11(.)0% of sample (15(.)1% of men and 7(.)8% of women) reported two or more symptoms of dependence. Correlates of cannabis dependence included educational attainment, exposure to parental conflict, sexual abuse, major depression, social anxiety and childhood conduct disorder. However, even after control for the effects of these factors, there was evidence of significant genetic effects on risk of cannabis dependence. Standard genetic modelling indicated that 44(.)7% (95% CI = 15-72(.)2) of the variance in liability to cannabis dependence could be accounted for by genetic factors, 20(.)1% (95 CI = 0-43(.)6) could be attributed to shared environment factors and 35(.)3% (95% CI = 26(.)4-45(.)7) could be attributed to non-shared environmental factors. However, while there was no evidence of significant gender differences in the magnitude of genetic and environmental influences, a model which assumed both genetic and shared environmental influences on risks of cannabis dependence among men and shared environmental but no genetic influences among women provided an equally good fit to the data. Conclusions. There was consistent evidence that genetic risk factors are important determinants of risk of cannabis dependence among men. However, it remains uncertain whether there are genetic influences on liability to cannabis dependence among women.

Genetics of Serum Dehydroepiandrosterone Sulfate and Its Relationship to Insulin in a Population-Based Cohort of Twin Subjects

Previous studies have shown a significant effect of insulin administration on serum dehydroepiandrosterone sulfate (DHEA-S) concentration and its metabolic rate, with evidence for the effect in men, but not in women. This could lead to differences in the sources of variation in serum DHEA-S between men and women and in its covariation with insulin concentration. This study aimed to test whether these hypotheses were supported in a sample of healthy adult twins. Serum DHEA-S (n=2287) and plasma insulin (n=2436) were measured in samples from adult male and female twins recruited through the Australian Twin Registry. Models of genetic and environmental sources of variation and covariation were tested against the data. DHEA-S showed substantial genetic effects in both men and women after adjustment for covariates, including sex, age, body mass index, and time since the last meal. There was no significant phenotypic or genetic correlation between DHEA-S and insulin in either men or women. Despite the experimental evidence for insulin infusion producing a reduction in serum DHEA-S and some effect of meals on the observed DHEA-S concentration, there were no associations between insulin and DHEA-S at the population level. Variations in DHEA-S are due to age, sex, obesity, and substantial polygenic genetic influences.

Growth of subtropical ECM fungi with different nitrogen sources using a new floating culture technique

Eight species of ectomycorrhizal (ECM) fungi in the genera Amanita. Gymnoboletus, Lactarius, and Russula were isolated from subtropical plant communities in eastem Australia. Two species were isolated from each of rainforest, Nothofagus forest, Eucalyptus forest, and Eucalyptus dominated wallum (heath) forest. These communities differ strongly in their soluble soil nitrogen (N) composition. The ability of the fungi to use inorganic (nitrate, ammonium) and organic (amide, peptide, protein) nitrogen sources was determined. As the fungi did not grow in liquid culture, a 'floating culture' technique was devised that allows hyphal growth on a screen floating on liquid medium. With some exceptions, fungal biomass production in floating culture closely reflected fungal growth on solid media assessed by total colony glucosamine content. Most isolates grown in floating culture had similar glucosamine concentrations on all N sources, with isolate specific concentrations ranging from 6 to 12 mug glucosamine g(-1) DW. However, Russula spp. had up to 1.7-fold higher glucosamine concentrations when growing with glutamine or ammonium compared to nitrate, glutathione or protein. Floating cultures supplied with 0.5, 1.5. 4.5, or 10 mm N mostly produced greatest biomass with 4.5 mM N. In vitro nitrate reductase activity (NRA) ranged from very low (0.03 mumol NO2- g(-1) fw h(-1)) in Russula sp. (wallum) to high (2.16 mumol NO2- g(-1) fw h(-1)) in Gymnoboletus sp. (rainforest) and mirrored the fungi's ability to use nitrate as a N source. All Russula spp. (wallum, Nothofagus and Eucalyptus forests), Lactarills sp, (rainforest) and.4manita sp. (wallum) utilized ammonium and glutamine but had little ability to use other N sources. In contrast,Amanita species (Nothofagus and Eucalyptus forests) grew on all N sources but produced most biomass with ammonium and glutamine. Only Gymnoboletus sp. (rainforest) showed similar growth with nitrate and ammonium as N sources. Fungal N source use was not associated with taxonomic groups, but is discussed in the context of soil N sources in the different habitats.

Longitudinal study of veterinarians from entry to the veterinary course to ten years after graduation: career paths

Objective To map out the career paths of veterinarians during their first 10 years after graduation, and to determine if this could have been predicted at entry to the veterinary course. Design Longitudinal study of students who started their course at The University of Queensland in 1985 and 1986, and who completed questionnaires in their first and fifth year as students, and in their second, sixth and eleventh year as veterinarians. Methods Data from 129 (96%) questionnaires completed during the eleventh year after graduation were coded numerically then analysed, together with data from previous questionnaires, with SAS System 7 for Windows 95. Results Ten years after they graduated, 80% were doing veterinary work, 60% were in private practice, 40% in small animal practice and 18% in mixed practice. The equivalent of 25% of the working time of all females was taken up by family duties. When part-time work was taken into account, veterinary work constituted the equivalent of 66% of the group working full-time. That 66% consisted of 52% on small animals, 7% on horses, 6% on cattle/sheep and 1% on pigs/poultry. Those who had grown up on farms with animals were twice as likely to be working with farm animals as were those from other backgrounds. Forecasts made on entry to the veterinary course were of no value in predicting who would remain in mixed practice. Conclusions Fewer than one-fifth of graduates were in mixed practice after 10 years, but the number was higher for those who grew up on farms with animals. Forecasts that may be made at interview before entry to the course were of little value in predicting the likelihood of remaining in mixed veterinary practice.

Longitudinal study of veterinarians from entry to the veterinary course to 10 years after graduation: attitudes to work, career and profession

Objective To describe the attitudes of veterinarians to their work, career and profession during the 10 years after graduation. Design Longitudinal study of students who started their course at The University of Queensland in 1985 and 1986, and who completed questionnaires in their first and fifth year as students, and after one, five and 10 years as veterinarians. Methods Data from 129 (96%) questionnaires completed after 10 years as a veterinarian were coded numerically then analysed, together with data from previous questionnaires, with SAS System 7 for Windows 95. Results After 10 years, almost all respondents were either very glad they had done the veterinary course (57%) or generally glad, though with some misgivings (37%). Despite this, only 55% would definitely become a veterinarian if they 'had to do it over again'. The responses for about one-third were different from those given five years earlier. The views of many were related to the level of support and encouragement received in their first job after graduation. There were 42% who were working less than half-time as veterinarians, and their main reasons were, in order, raising children, long hours of work, attitudes of bosses and clients, and poor pay. A majority was concerned about the ethics and competence of some colleagues, and almost all believed that consideration of costs must influence the type of treatment animals receive. Conclusions Most veterinarians were glad to have done the veterinary course, but for about one-quarter their career had not lived up to expectations and almost half would not do it again in another incarnation. Stress, hours of work, difficulties in balancing personal life with career and low income were important concerns for many. Low income may contribute to the low number of males entering the veterinary profession.

Accuracy of Mothers' Retrospective Reports of Smoking During Pregnancy: Comparison with Twin Sister Informant Ratings

Retrospective assessment of maternal smoking or substance use during pregnancy is sometimes unavoidable. The unusually close relationship of twin sister pairs permits comparison of self-report data versus co-twin informant data on substance use during pregnancy. Information about smoking during pregnancy has been gathered from a series of mothers from an Australian volunteer twin panel (576 women reporting on 995 pregnancies), supplemented in many cases by independent ratings of their smoking by twin sister informants (821 pregnancies). Estimates of the proportion of women who had never smoked regularly (56-58%), who had smoked but did not smoke during a particular pregnancy (16-21%), or who smoked throughout the pregnancy (16-18%), were in good agreement whether based on self-report or twin sister informant data. However, informants underreported cases who smoked during the first trimester but then quit (1-3% versus 7-9% by self-report). Women who smoked throughout pregnancy (by informant report) rarely denied a history of regular smoking (

Zygosity Diagnosis in the Absence of Genotypic Data: An Approach Using Latent Class Analysis

For zygosity diagnosis in the absence of genotypic data, or in the recruitment phase of a twin study where only single twins from same-sex pairs are being screened, or to provide a test for sample duplication leading to the false identification of a dizygotic pair as monozygotic, the appropriate analysis of respondents' answers to questions about zygosity is critical. Using data from a young adult Australian twin cohort (N = 2094 complete pairs and 519 singleton twins from same-sex pairs with complete responses to all zygosity items), we show that application of latent class analysis (LCA), fitting a 2-class model, yields results that show good concordance with traditional methods of zygosity diagnosis, but with certain important advantages. These include the ability, in many cases, to assign zygosity with specified probability on the basis of responses of a single informant (advantageous when one zygosity type is being oversampled); and the ability to quantify the probability of misassignment of zygosity, allowing prioritization of cases for genotyping as well as identification of cases of probable laboratory error. Out of 242 twins (from 121 like-sex pairs) where genotypic data were available for zygosity confirmation, only a single case was identified of incorrect zygosity assignment by the latent class algorithm. Zygosity assignment for that single case was identified by the LCA as uncertain (probability of being a monozygotic twin only 76%), and the co-twin's responses clearly identified the pair as dizygotic (probability of being dizygotic 100%). In the absence of genotypic data, or as a safeguard against sample duplication, application of LCA for zygosity assignment or confirmation is strongly recommended.

Direction of Causation Modeling Between Cross-Sectional Measures of Parenting and Psychological Distress in Female Twins

Under certain conditions, cross-sectional analysis of cross-twin intertrait correlations can provide important information about the direction of causation (DOC) between two variables. A community-based sample of Australian female twins aged 18 to 45 years was mailed an extensive Health and Lifestyle Questionnaire (HLQ) that covered a wide range of personality and behavioral measures. Included were self-report measures of recent psychological distress and perceived childhood environment (PBI). Factor analysis of the PBI yielded three interpretable dimensions: Coldness, Overprotection, and Autonomy. Univariate analysis revealed that parental Overprotection and Autonomy were best explained by additive genetic, shared, and nonshared environmental effects (ACE), whereas the best-fitting model for PBI Coldness and the three measures of psychological distress (Depression, Phobic Anxiety, and Somatic Distress) included only additive genetic and nonshared environmental effects (AE). A common pathway model best explained the covariation between (1) the three PBI dimensions and (2) the three measures of psychological distress. DOC modeling between latent constructs of parenting and psychological distress revealed that a model which specified recollected parental behavior as the cause of psychological distress provided a better fit than a model which specified psychological distress as the cause of recollected parental behavior. Power analyses and limitations of the findings are discussed.