Connectome-wide structure-function coupling models implicate polysynaptic alterations in autism

Autism spectrum disorder (ASD) is one of the most common neurodevelopmental diagnoses. Although incompletely understood, structural and functional network alterations are increasingly recognized to be at the core of the condition. We utilized multimodal imaging and connectivity modeling to study structure-function coupling in ASD and probed mono- and polysynaptic mechanisms on structurally-governed network function. We examined multimodal magnetic resonance imaging data in 80 ASD and 61 neurotypical controls from the Autism Brain Imaging Data Exchange (ABIDE) II initiative. We predicted intrinsic functional connectivity from structural connectivity data in each participant using a Riemannian optimization procedure that varies the times that simulated signals can unfold along tractography-derived personalized connectomes. In both ASD and neurotypical controls, we observed improved structure-function prediction at longer diffusion time scales, indicating better modeling of brain function when polysynaptic mechanisms are accounted for. Prediction accuracy differences (∆prediction accuracy) were marked in transmodal association systems, such as the default mode network, in both neurotypical controls and ASD. Differences were, however, lower in ASD in a polysynaptic regime at higher simulated diffusion times. We compared regional differences in ∆prediction accuracy between both groups to assess the impact of polysynaptic communication on structure-function coupling. This analysis revealed that between-group differences in ∆prediction accuracy followed a sensory-to-transmodal cortical hierarchy, with an increased gap between controls and ASD in transmodal compared to sensory/motor systems. Multivariate associative techniques revealed that structure-function differences reflected inter-individual differences in autistic symptoms and verbal as well as non-verbal intelligence. Our network modeling approach sheds light on atypical structure-function coupling in autism, and suggests that polysynaptic network mechanisms are implicated in the condition and that these can help explain its wide range of associated symptoms.

Stability-indicating HPLC assays for the determination of piritramide and droperidol in PCA solution

WHAT IS KNOWN AND OBJECTIVE

A mixture of morphine and droperidol is a well-established antiemetic for reducing the risk of postoperative nausea and vomiting. A mixture of piritramide and droperidol has not yet been evaluated in this context. Our objectives were to develop a high-performance liquid chromatographic assay for piritramide and droperidol in 0·9% saline, and to establish their stability under defined storage conditions.

METHODS

The separation and assay of both drugs were attempted by high performance liquid chromatography (HPLC) using a RP-select B column and a mobile phase of 57:43% v/v methanol-monosodium phosphate solution 0·05 M at a flow rate of 1·2 mL/min. UV detection at 205 and 246 nm for piritramide and droperidol were used, respectively.

RESULTS AND DISCUSSION

The HPLC method was successful. Linearity was shown for piritramide from 0·075 to 0·013 mg/mL and for droperidol from 0·8 to 0·2 mg/mL. The intra- and inter-day relative standard deviation (RSD, %) was 0·27% and 0·54% for piritramide and droperidol, respectively. The two drugs were stable for at least 72 h when stored under ambient light at room temperature.

WHAT IS NEW AND CONCLUSION

Seventy-five milligrams piritramide and 2·5 mg droperidol diluted to 50 ml with 0·9% saline should be suitable for clinical use. At this dilution, a Dipidolor(®) and Xomolix(®), mixture, was stable when stored under ambient light exposure at room temperature for at least 72 h.

Relationship between body mass index, diet, exercise and gastro-oesophageal reflux symptoms in a community

BACKGROUND

Body mass index (BMI) is a risk factor for gastro-oesophageal reflux but may simply be explained by diet and lifestyle.

AIM

We aimed to determine the contribution of BMI, diet and exercise to GER.

METHODS

Community subjects (n = 211, mean age = 36 years, 43% males) completed validated questionnaires on gastro-oesophageal reflux, energy expenditure (Harvard Alumni Activity Survey), dietary intake (Harvard Food Frequency Questionnaire) and measures of personality and life event stress. Diet, exercise, BMI and other potential risk factors for reflux were analysed using logistic regression analyses.

RESULTS

The overall mean (+/- s.d.) BMI was 26.6 (+/- 5.7); 79 (37%) reported infrequent (< weekly) reflux and 16 (8%) reported frequent (> or = weekly) reflux. The median caloric intake was 2097 cal/day and the median daily energy expenditure was 1753 cal/day. Among those with BMI > 25, 10% reported frequent reflux compared to 4% of those with BMI < or = 25. In a model which included age, sex and Symptom Checklist-90 somatisation T-score, BMI was associated with reflux (OR per 5 units = 1.9, 95% CI: 1.2, 3.0). In models which included diet and exercise variables, BMI but not diet or exercise was associated with reflux.

CONCLUSION

BMI may be associated with symptomatic gastro-oesophageal reflux independent of diet and exercise.

The effect of new diagnostic criteria for irritable bowel syndrome on community prevalence estimates

The 'Rome' criteria for irritable bowel syndrome (IBS) have evolved over 15 years with four published versions. The impact of these changes on community prevalence rates is not known. Study aims were to estimate the prevalence of IBS using the four Rome criteria and agreement between Rome II and previous criteria. Questionnaires were mailed to a random sample of Olmsted County, Minnesota residents in 1992. Age- and gender-adjusted prevalence estimates were calculated for Rome II (1999), Rome I (1992), Rome (1990), and Rome (1989) criteria. Per cent agreement and kappa values were calculated to assess agreement. Of 892 eligible subjects, 643 (72%) responded. The age- and gender-adjusted prevalence of IBS was 5.1% [95% confidence interval (CI): 3.1, 7.0], 6.8% (95% CI: 4.7, 8.9), 5.1% (95% CI: 3.2, 7.1) and 27.6% (95% CI: 23.6, 31.5), respectively. In comparison with Rome II criteria, per cent agreement and kappa values were 97.2% and 0.78 (95% CI: 0.69, 0.88), 96.4% and 0.68 (95% CI: 0.55, 0.80), and 79.0% and 0.29 (95% CI: 0.19, 0.40), respectively. Thus, although differences were seen with the older criteria, compared with the Rome I criteria, good agreement was seen and community prevalence estimates were similar with the Rome II criteria.