Developmental associations between traits of autism spectrum disorder and attention deficit hyperactivity disorder: a genetically informative, longitudinal twin study

BACKGROUND

Autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), and associated subclinical traits, regularly co-occur with one another. However, the aetiology of their co-occurrence remains poorly understood. This paper provides the first genetically informative, longitudinal analysis of the interaction between traits of ASD and ADHD, and explores their genetic and environmental overlap.

METHOD

Parents of approximately 5000 twin pairs completed questionnaires assessing traits of ASD and ADHD when twins were aged 8 and 12 years. Cross-lagged longitudinal modelling explored their developmental association, enabling a consideration of phenotypic-driven processes. Overlapping aetiological influences on traits at age 12 years were explored using bivariate twin modelling.

RESULTS

Traits of ADHD at age 8 years were more strongly predictive of traits of ASD at 12 years than traits of ASD at 8 years were of traits of ADHD at 12 years. Analysis of traits by subscales assessing specific symptom domains suggested that communication difficulties were most strongly associated with traits of ADHD. Bivariate modelling suggested moderate genetic overlap on traits in males (genetic correlation = 0.41), and a modest degree of overlap in females (genetic correlation = 0.23) at age 12 years.

CONCLUSIONS

Traits of ADHD at age 8 years significantly influence traits of ASD at age 12 years, after controlling for their initial relationship at age 8 years. In particular, early ADHD traits influenced later communication difficulties. These findings demonstrate the dynamic nature of co-occurring traits across development. In addition, these findings add to a growing body of literature suggesting that traits of ASD and ADHD may arise via similar aetiological processes.

Monitoring agricultural rodenticide use and secondary exposure of raptors in Scotland

Despite the documented risk of secondary poisoning to non-target species by anticoagulant rodenticides there is no statutory post-approval monitoring of their use in the UK. This paper presents results from two Scottish monitoring schemes for the period 2000-2010; recording rodenticide use on arable farms and the presence of residues in raptor carcasses. More than three quarters of arable farms used anticoagulant rodenticides; predominately the second generation compounds difenacoum and bromadiolone. There was widespread exposure to anticoagulant rodenticides in liver tissues of the raptor species tested and the residues encountered generally reflected agricultural use patterns. As found in other studies, Red Kites (Milvus milvus) appeared to be particularly vulnerable to rodenticide exposure, 70 % of those sampled (n = 114) contained residues and 10 % died as a result of rodenticide ingestion. More unexpectedly, sparrowhawks (Accipiter nisus), which prey almost exclusively on birds, had similar exposure rates to species which prey on rodents. Although, with the exception of kites, confirmed mortality from rodenticides was low, the widespread exposure recorded is concerning. Particularly when coupled with a lack of data about the sub-lethal effects of these compounds. This raises questions regarding whether statutory monitoring of use is needed; both to address whether there are deficiencies in compliance with approval conditions or whether the recommended risk management procedures are themselves adequate to protect non-target wildlife.

Hypothermic Perfusion Preservation of Pancreas for Islet Grafts: Validation Using a Split Lobe Porcine Model

The demand for high-quality islets for transplantation in type I diabetics will increase as the current clinical trials transition into standard of care. The mode of preservation of donor pancreata is critical to this mission since islets are very sensitive to ischemic injury. Hypothermic perfusion preservation (HPP) is being investigated for extended pancreas preservation in light of the beneficial effects reported for other organs. The present pilot study aimed to establish the potency of porcine islets isolated from pancreata after 24 h of HPP at 4-8°C. The study design included a split-lobe pancreas model that permitted paired comparisons of islets isolated from 24-h HPP splenic lobes with nonperfused, fresh control duodenal/connecting lobes stored at 4°C for <3 h. Prior to transplantation, islet viability was assessed in vitro using the ratio of oxygen consumption rate to DNA (OCR/DNA) assay and correlated with subsequent in vivo function by transplantation in diabetic immunodeficient mice. The OCR/DNA (mean ± SD) measured after 7 days of culture and immediately prior to transplantation for islets from the 24-h HPP group was 269 ± 19 nmol/min/mg DNA, which was higher but not statistically different to the mean of 236 ± 43 for the counterpart control group. All four nude mice transplanted with islets from the 24-h HPP group showed diabetes reversal, compared with five of six transplants from the control group. In conclusion, islets isolated from adult porcine pancreata after 24-h HPP exhibited high viability as measured by OCR/DNA and were able to consistently reverse diabetes in a nude mouse bioassay.

Cold-Storage of Synthetic Human Epidermis in HypoThermosol

There is a growing need for engineered tissues in a wide variety of medical applications and as alternatives to animal tissues for in vitro toxicology testing. While techniques for the preparation of a variety of synthetic tissue constructs have been devised, little attention has been focused upon the optimum conditions necessary for storage and shipping of these tissue devices. This study investigates the effects of hypothermic storage on synthetic human epidermis (EpiDerm, MatTek Corp., Ashland, MA) and specifically examines the quality of storage in keratinocyte growth medium (KGM), a standard skin culture medium, compared with storage in HypoThermosol, a new hypothermic preservation solution. EpiDerm samples were immersed in HypoThermosol for 1 to 13 days at 4 degrees C and were assayed using the noninvasive, viability indicator dye, Alamar Blue (AB). Samples immersed for 1 to 9 days in HypoThermosol retained their viability subsequent to warming to 37 degrees C and for at least 7 days thereafter in culture. During this time samples previously stored in HypoThermosol continued to generate a stratum corneum and their ultrastructural characteristics were similar to EpiDerm that were not exposed to hypothermic solutions. This profile, however, was not apparent in EpiDerm maintained for 1 to 13 days in KGM and subsequently warmed. These samples appeared viable immediately upon warming in most cases, but viability was not retained thereafter. EpiDerm maintained in KGM and allowed to recover at 37 degrees C appeared necrotic and failed to continue to differentiate. The conclusions of this study are the following: (1) HypoThermosol protects the viability of EpiDerm during cold-storage, (2) HypoThermosol preserves EpiDerm's ability to differentiate subsequent to warming, and (3) the inferior preservation of samples stored in KGM was most apparent 24 h after warming.

Issues in online patient self-reporting of health status

Patient self-reporting of symptoms and quality of life following surgical interventions is generally delivered in the form of paper-based questionnaires to be completed in the outpatient clinic or at home. A commonly used tool for patient self-reporting of quality of life is the EQ5D health status questionnaire which, while limited in scope, has general applicability across a range of health interventions. In this article we examine the issues relating to online patient self-reporting using this questionnaire and the wider implications for the online reporting of health status.

Evidence for a spin-aligned neutron-proton paired phase from the level structure of (92)Pd

Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus (92)Pd. Gamma rays emitted following the (58)Ni((36)Ar,2n)(92)Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.

HIV-associated neurocognitive disorders persist in the era of potent antiretroviral therapy: CHARTER Study

OBJECTIVES

This is a cross-sectional, observational study to determine the frequency and associated features of HIV-associated neurocognitive disorders (HAND) in a large, diverse sample of infected individuals in the era of combination antiretroviral therapy (CART).

METHODS

A total of 1,555 HIV-infected adults were recruited from 6 university clinics across the United States, with minimal exclusions. We used standardized neuromedical, psychiatric, and neuropsychological (NP) examinations, and recently published criteria for diagnosing HAND and classifying 3 levels of comorbidity (minimal to severe non-HIV risks for NP impairment).

RESULTS

Fifty-two percent of the total sample had NP impairment, with higher rates in groups with greater comorbidity burden (40%, 59%, and 83%). Prevalence estimates for specific HAND diagnoses (excluding severely confounded cases) were 33% for asymptomatic neurocognitive impairment, 12% for mild neurocognitive disorder, and only 2% for HIV-associated dementia (HAD). Among participants with minimal comorbidities (n = 843), history of low nadir CD4 was a strong predictor of impairment, and the lowest impairment rate on CART occurred in the subset with suppressed plasma viral loads and nadir CD4 ≥200 cells/mm(3) (30% vs 47% in remaining subgroups).

CONCLUSIONS

The most severe HAND diagnosis (HAD) was rare, but milder forms of impairment remained common, even among those receiving CART who had minimal comorbidities. Future studies should clarify whether early disease events (e.g., profound CD4 decline) may trigger chronic CNS changes, and whether early CART prevents or reverses these changes.

Lack of effect of citalopram on magnetic resonance spectroscopy measures of glutamate and glutamine in frontal cortex of healthy volunteers

Magnetic resonance spectroscopy (MRS) is a non-invasive imaging technique that can provide localised measures of brain chemistry in vivo. We previously found that healthy volunteers receiving the selective serotonin reuptake inhibitor, citalopram, daily for 1 week showed higher levels of a combined measure of glutamate and glutamine (Glx) in occipital cortex than those receiving placebo. The aim of this study was to assess if a similar effect could be detected in the frontal brain region. Twenty-three healthy volunteers randomised to receive either citalopram 20 mg or a placebo capsule daily for 7-10 days were studied and scanned using a 3T Varian INOVA system before and at the end of treatment. Standard short-TE (echo time) PRESS (Point-resolved spectroscopy) (TE = 26 ms) and PRESS-J spectra were acquired from a single 8-cm(3) voxel in a frontal region incorporating anterior cingulate cortex. Glutamate and total Glx levels were quantified both relative to creatine and as absolute levels. Relative to placebo, citalopram produced no change in Glx or glutamate alone at the end of the study. Similarly, no effect was seen on other MRS measures studied: myo-inositol, choline, N-acetylaspartate and creatine. These data suggest that the effects of serotonin reuptake to modify cortical glutamatergic MRS measures may be regionally specific. This supports the potential for MRS in assessing neuroanatomically specific serotonin-glutamate interactions in the human brain.

Increased neural response to fear in patients recovered from depression: a 3T functional magnetic resonance imaging study

BACKGROUND

Previous imaging studies have revealed that acute major depression is characterized by altered neural responses to negative emotional stimuli. Typically, responses in limbic regions such as the amygdala are increased while activity in cortical regulatory regions such as the dorsolateral prefrontal cortex (DLPFC) is diminished. Whether these changes persist in unmedicated recovered patients is unclear.

METHOD

We used functional magnetic resonance imaging to examine neural responses to emotional faces in a facial expression-matching task in 16 unmedicated recovered depressed patients and 21 healthy controls.

RESULTS

Compared with controls, recovered depressed patients had increased responses bilaterally to fearful faces in the DLPFC and right caudate. Responses in the amygdala did not distinguish the groups.

CONCLUSIONS

Our findings indicate that clinical recovery from depression is associated with increased activity in the DLPFC to negative emotional stimuli. We suggest that this increase may reflect a compensatory cortical control mechanism with the effect of limiting emotional dysregulation in limbic regions such as the amygdala.

Group specific optimisation of fMRI processing steps for child and adult data

Motion is a major issue in functional magnetic resonance imaging (fMRI) dataseries and causes artifacts or increased overall noise obscuring signals of interest. It is particularly important to be able to control for and correct these artifacts when dealing with child data. We analysed the data from 35 children (4-8 years old) and 13 adults (18-30 years old) during an emotional face paradigm. The children were split into low and high motion groups on the basis of having less or more than an estimated maximal movement of one voxel (3.75 mm) and one degree of rotation in any motion direction between any pair of scans in the run. Several different preprocessing steps were evaluated for their ability to correct for the excess motion using agnostic canonical variates analysis (aCVA) in the NPAIRS (Nonparametric, Prediction, Activation, Influence, Reproducibility, re-Sampling) framework. The adult dataset was reasonably stable whereas the motion-prone child datasets benefited greatly from motion parameter regression (MPR). Motion parameter regression had a strong beneficial impact on all datasets, a result that was largely unaffected by other preprocessing choices; however, motion correction on its own did not have as much impact. The low motion child group subjected to MPR had reproducibility values at par with those of the adult group, but needed almost twice as many subjects to achieve this result, indicating weaker responses in young children. The aCVA showed greater sensitivity to the task response pattern than the mixed effects general linear model (mGLM) in the expected face processing regions, although the mGLM showed more responses in some other areas. This work illustrates that preprocessing choices must be made in a group-specific fashion to optimise fMRI results.