Family-based association study of serotonin transporter promoter in suicidal adolescents: no association with suicidality but possible role in violence traits

The serotonin transporter-linked promoter region polymorphism (5-HTTLPR) is thought to be associated with some serotonin dysfunction-related psychopathologies such as depression and anxiety disorders. Suicide and suicide-related behaviors such as violence, aggression, and impulsivity have been reproducibly associated with serotonin dysfunction and are partially genetic. This study examined the association of 5-HTTLPR with suicidal behavior and related traits in Israeli suicidal adolescent inpatients using the haplotype relative risk (HRR) method that controls for artifacts caused by population stratification. Forty-eight inpatient adolescents who recently attempted suicide were assessed by structured interviews for detailed clinical history, diagnoses, suicide intent, suicide risk, impulsivity, violence, and depression. Blood samples were collected and DNA extracted from patients and their biological parents. The 5-HTTLPR allele frequencies were tested for association with suicidality by the HRR method. In addition, the relationship between genotypes and phenotypic severity of several clinical parameters was analyzed. No significant allelic association of the 5-HTTLPR polymorphism with suicidal behavior was found (chi square = 0.023; P = 0.88). Analysis of variance of the suicide-related trait measures for the three genotypes demonstrated a significant difference in violence measures between patients carrying the LL and LS genotypes (9.50+/-4.04 vs. 5.36+/-4.03; P = 0.029). This study suggests that the 5-HTTLPR polymorphism is unlikely to have major relevance to the pathogenesis of suicidal behavior in adolescence but may contribute to violent behavior in this population.     

Characterisation of cytotoxicity and DNA damage induced by the topoisomerase II-directed bisdioxopiperazine anti-cancer agent ICRF-187 (dexrazoxane) in yeast and mammalian cells

Background

Bisdioxopiperazine anti-cancer agents are inhibitors of eukaryotic DNA topoisomerase II, sequestering this protein as a non-covalent protein clamp on DNA. It has been suggested that such complexes on DNA represents a novel form of DNA damage to cells. In this report, we characterise the cytotoxicity and DNA damage induced by the bisdioxopiperazine ICRF-187 by a combination of genetic and molecular approaches. In addition, the well-established topoisomerase II poison m-AMSA is used for comparison.

Results

By utilizing a panel of Saccharomyces cerevisiae single-gene deletion strains, homologous recombination was identified as the most important DNA repair pathway determining the sensitivity towards ICRF-187. However, sensitivity towards m-AMSA depended much more on this pathway. In contrast, disrupting the post replication repair pathway only affected sensitivity towards m-AMSA. Homologous recombination (HR) defective irs1SF chinese hamster ovary (CHO) cells showed increased sensitivity towards ICRF-187, while their sensitivity towards m-AMSA was increased even more. Furthermore, complementation of the XRCC3 deficiency in irs1SF cells fully abrogated hypersensitivity towards both drugs. DNA-PK_cs deficient V3-3 CHO cells having reduced levels of non-homologous end joining (NHEJ) showed slightly increased sensitivity to both drugs. While exposure of human small cell lung cancer (SCLC) OC-NYH cells to m-AMSA strongly induced γH2AX, exposure to ICRF-187 resulted in much less induction, showing that ICRF-187 generates fewer DNA double strand breaks than m-AMSA. Accordingly, when yeast cells were exposed to equitoxic concentrations of ICRF-187 and m-AMSA, the expression of DNA damage-inducible genes showed higher levels of induction after exposure to m-AMSA as compared to ICRF-187. Most importantly, ICRF-187 stimulated homologous recombination in SPD8 hamster lung fibroblast cells to lower levels than m-AMSA at all cytotoxicity levels tested, showing that the mechanism of action of bisdioxopiperazines differs from that of classical topoisomerase II poisons in mammalian cells.

Conclusion

Our results point to important differences in the mechanism of cytotoxicity induced by bisdioxopiperazines and topoisomerase II poisons, and suggest that bisdioxopiperazines kill cells by a combination of DNA break-related and DNA break-unrelated mechanisms.     

Neutralization and glorification: Cannabis culture-related beliefs predict cannabis use initiation

Addressing specific pro-cannabis attitudes may be a viable adjunct to school-based substance abuse prevention programs. To study the predictive value of cannabis culture-related beliefs in relation to initiation of cannabis use, a prospective cohort study of 1223 students attending high school or equivalent education programs in Denmark were administered a questionnaire containing demographic information, questions about cannabis use, normative perception and personal beliefs in relation to two dimensions of cannabis culture-related beliefs: (1) beliefs about the negative consequences of cannabis use (neutralization) and (2) beliefs about positive aspects of cannabis use (glorification). Normative perception and glorification were both robustly associated with incidence of cannabis use at the 6- and 12-month follow-up. Neutralization was associated with initiated cannabis use only at the 12-month follow-up. These findings suggest that beliefs about the benefits of cannabis use may be as important in targeted programs to prevent cannabis use as beliefs about whether cannabis use is common or harmful.     

The potential of nasal application for delivery to the central brain-a microdialysis study of fluorescein in rats.

Previous animal studies have shown that various types of nasally administered drugs and model substances can access the central nervous system (CNS) via direct transport across the olfactory epithelium, and thereby circumventing the blood-brain barrier (BBB). These compounds, however, have mainly been identified in the cerebrospinal fluid and the olfactory bulbs which are usually not pharmacologically relevant targets. The aim of the present study was to evaluate the potential of targeting the central brain by olfactory absorption by use of sodium fluorescein as a hydrophilic model substance with limited permeability across the blood-brain barrier. Microdialysis probes were implanted in blood and in right and left side of the brain (striatum) in rats. The pharmacokinetics of sodium fluorescein was studied from 0 to 180min following intravenous and unilateral nasal administration without occlusion of the oesophagus. Pharmacokinetic modelling showed a significantly higher absorption rate and lower T(max) in the ipsilateral striatum (0.097min(-1) and 41min) compared with the contralateral side (0.056min(-1) and 54min). The rate of elimination in brain was significantly lower after nasal administration (0.004min(-1)) compared with intravenous administration (0.012min(-1)). However, the brain to plasma area under the curve ratios of model substance were low (2-3%) and not significantly different between right and left side of the brain, regardless of the route of administration. The results obtained by microdialysis were supported by findings in whole brain homogenates where concentrations of fluorescein were approximately 40% higher in the right striatum compared with the left side initially after nasal administration to the right nostril of rats. Despite some indications of olfactory transport to the central rat brain it was concluded that the drug targeting potential of sodium fluorescein and most likely other hydrophilic compounds is limited.     

Use of anthropometric measurements in assessing risk for coronary heart disease: a useful tool in worksite health screening?

The study examined the association between the anthropometric measurements body mass index (BMI), waist/hip ratio (WHR), and waist/thigh ratio (WTR) and cardiovascular risk factors, and assessed whether a combination of BMI and WHR could be used in routine screening of risk for cardiovascular arteriosclerotic disease at worksites. The data were obtained from a cross-sectional survey designed to assess the nutritional situation, with special reference to cardiovascular risk factors. The study population comprised 372 healthy men working on platforms in the North Sea. Serum cholesterol, triglyceride, fibrinogen, and blood pressure were positively related to the anthropometric variables, while high-density lipoprotein (HDL) was inversely related with them. The relations remained after adjusting for possible confounders, such as age, smoking, physical activity, and an indicator of dietary fat intake. In stepwise multiple linear regression models, BMI, WHR, and WTR were positively related to serum cholesterol, triglycerides, fibrinogen, diastolic blood pressure, and systolic blood pressure, and inversely related to HDL. When controlling for the anthropometric variables WHR and WTR, BMI was not independently related to fibrinogen and risk score. WHR and WTR were not independently related to systolic and diastolic blood pressure, and WTR was in addition not related to triglycerides when controlling for BMI. Overall, the anthropometric variables BMI and WHR were considered the best predictors for CAD risk when taking several risk factors into consideration. A joint variable between BMI and WHR, called body score, constituted the four categories lean, lean android, overweight gynoid, and overweight ovoid. This body score was positively associated with levels of serum lipids, fibrinogen, and blood pressure, and inversely associated with HDL. In stepwise multiple linear regression models, controlling for possible confounding variables, body score was positively related to CAD risk. Dividing the risk score into tertiles, about 51% of the lean were in the first, while 46% of the overweight ovoid were in the third tertile. Those classified as lean android or overweight gynoid had about the same distribution, namely between 31% and 39% in each tertile if the two categories were combined. These data support the hypothesis that BMI, WHR, and WTR are independent predictors for risk factors for CAD among oil workers, and that combinations of BMI and WHR are strong enough predictors to be useful in routine screening for CAD risk at worksites. Based on these findings, supported by data from the literature, a matrix aimed at screening for follow-up at worksites is proposed.     

Activation of Group II Metabotropic Glutamate Receptors Increases Proliferation but does not Influence Neuronal Differentiation of a Human Neural Stem Cell Line

The multiple functions of glutamate include regulation of neural development and stem cells. While the importance of the ionotropic glutamate receptors is well‐established, less is known about the role of metabotropic glutamate receptors (mGluRs). In this study, we examined the effects of pharmacological activation and inhibition of mGluR2/3 on proliferation, differentiation and viability of a human neural stem cell line. Immunofluorescence staining revealed the presence of mGluR2/3 receptors on both proliferating and differentiating stem cells, including cells differentiated into β‐tubulin III‐positive immature neurons and glial fibrillary acidic protein‐positive astrocytes. Stimulation of mGluR2/3 receptors during cell propagation using the agonist (2S,2′R,3′R)‐2‐(2′,3′‐dicarboxycyclopropyl) glycine (DCG‐IV) increased total cell numbers significantly (60% compared to untreated controls). This effect could be inhibited by the specific antagonist (2S)‐2‐Amino‐2‐[(1S,2S)‐2‐carboxycycloprop‐1‐yl]‐3‐(xanth‐9‐yl) propanoic acid (LY341495). The antagonist alone had no effect. No significant decrease in cell death was found following mGluR2/3 stimulation, suggesting that the observed elevation in cell number was not related to cell viability. Subsequent differentiation of the cells resulted in a slight decrease in β‐tubulin III‐positive neurons (5.2–3.2% of total cells) for DCG‐IV pre‐treated cultures. Treatment with DCG‐IV and LY342495 during cell differentiation alone had no such effect. Western blot analysis revealed that the active, dimeric form of mGluR2/3 was mainly present on the proliferating cells, which may explain our findings. This study emphasizes the importance of glutamate and mGluRs on regulation of human neural stem cells and suggests a significant role of mGluR2/3 during cell proliferation.     

A simulation study provided sample size guidance for differential item functioning (DIF) studies using short scales

ObjectiveDifferential item functioning (DIF) analyses are increasingly used to evaluate health-related quality of life (HRQoL) instruments, which often include relatively short subscales. Computer simulations were used to explore how various factors including scale length affect analysis of DIF by ordinal logistic regression.Study Design and settingSimulated data, representative of HRQoL scales with four-category items, were generated. The power and type I error rates of the DIF method were then investigated when, respectively, DIF was deliberately introduced and when no DIF was added. The sample size, scale length, floor effects (FEs) and significance level were varied.ResultsWhen there was no DIF, type I error rates were close to 5%. Detecting moderate uniform DIF in a two-item scale required a sample size of 300 per group for adequate (>80%) power. For longer scales, a sample size of 200 was adequate. Considerably larger sample sizes were required to detect nonuniform DIF, when there were extreme FEs or when a reduced type I error rate was required.ConclusionThe impact of the number of items in the scale was relatively small. Ordinal logistic regression successfully detects DIF for HRQoL instruments with short scales. Sample size guidelines are provided.     

The Wilcoxon–Mann–Whitney test under scrutiny

The Wilcoxon–Mann–Whitney (WMW) test is often used to compare the means or medians of two independent, possibly nonnormal distributions. For this problem, the true significance level of the large sample approximate version of the WMW test is known to be sensitive to differences in the shapes of the distributions. Based on a wide ranging simulation study, our paper shows that the problem of lack of robustness of this test is more serious than is thought to be the case. In particular, small differences in variances and moderate degrees of skewness can produce large deviations from the nominal type I error rate. This is further exacerbated when the two distributions have different degrees of skewness. Other rank‐based methods like the Fligner–Policello (FP) test and the Brunner–Munzel (BM) test perform similarly, although the BM test is generally better. By considering the WMW test as a two‐sample T test on ranks, we explain the results by noting some undesirable properties of the rank transformation. In practice, the ranked samples should be examined and found to sufficiently satisfy reasonable symmetry and variance homogeneity before the test results are interpreted. Copyright © 2009 John Wiley & Sons, Ltd.