How mechanistic in silico modelling can improve our understanding of TB disease and treatment.

TB is one of the top 10 causes of death worldwide and the leading cause of death from a single infectious agent. Decreasing the length of time for TB treatment is an important step towards the goal of reducing mortality. Mechanistic in silico modelling can provide us with the tools to explore gaps in our knowledge, with the opportunity to model the complicated within-host dynamics of the infection, and simulate new treatment strategies. Significant insight has been gained using this form of modelling when applied to other diseases - much can be learned in infection research from these advances.

First Report of Root Rot of Field Pea Caused by Aphanomyces euteiches in Alberta, Canada.

In recent years, root rots have severely impacted yields of field pea (Pisum sativum L.) in the Canadian province of Alberta. Above-normal precipitation levels in the springs of 2011 to 2013 led to the hypothesis that Aphanomyces euteiches Drechsler may play a role in root rot in water-saturated pea fields. To determine causal agent(s) of root rot, 145 pea fields were surveyed at flowering in July 2013 (1). Symptoms of root rot were abundant; the most prominent included red vascular streaking and dark brown rot of the tap root, indicative of Fusarium spp., but brown discoloration and cortical decay of lateral roots, indicative of A. euteiches, was also observed. Total genomic DNA was extracted from diseased root samples from each field, using the Qiagen DNeasy Plant kit, and amplified with species-specific primers for A. euteiches (2). Fusarium spp. were present in all fields, but seven fields located within a 200-km radius yielded a positive reaction for A. euteiches. Five fields were re-visited in May 2014 to collect soil for a bait test (3). Tests were performed using surface-sterilized pea seeds (cv. CDC Meadow) treated with Allegiance FL (Bayer, a.i. metalaxyl) at a rate of 110 ml/kg of seed. Five seeds per pot were planted into field soils in 10-cm pots with 12 replicate pots per field. Soils were irrigated as needed until the second-node stage and then kept at saturation for 14 days. Thirty day-old pea roots were evaluated for root rot symptoms; plated onto cornmeal agar amended with metalaxyl, benomyl, and vancomycin (MBV) without surface sterilization; and visualized microscopically for presence of oospores in the roots. Roots from three out of the five field soils showed symptoms typical of A. euteiches infection, including honey-brown discoloration, degradation of the root cortex, and presence of oospores. Root rot symptoms from the remaining fields were characteristic of Fusarium root rot, and oospores were not observed in roots. Fungal cultures with fast-growing, white, aerial mycelia characteristic of A. euteiches on MBV, were recovered from roots with Aphanomyces root rot symptoms, and transferred to PDA. To confirm pathogen identity, total DNA was extracted from 7-day-old cultures growing on PDA using the Qiagen DNeasy Plant Kit. The ribosomal DNA internal transcribed spacer (ITS) region was amplified using the primer pair ITS1 and ITS4 and sequenced (4). The sequences, deposited in GenBank with accession numbers KM486065, KM486066, and KM486067, were 100% identical to the ITS rDNA sequence of several isolates of A. euteiches using a BLASTn query. Fusarium spp. were also recovered from all root samples in the soil bait test. Total DNA extracted from roots was used in PCR assays with A. euteiches-specific primers as described above. PCR amplification of root DNA was successful only from the same three fields that showed Aphanomcyces root rot symptoms, further verifying presence of A. euteiches. The inability to detect or recover A. euteiches from two fields that had tested positive in the survey was likely due to patchy distribution of this pathogen and emphasizes the importance of rigorous soil collection methods to accurately detect pathogens. Although this is the first record of A. euteiches on field pea in Alberta, the distribution of A. euteiches within a 200-km radius in southern Alberta indicates that it has likely been present in soils for several years. The interaction between A. euteiches and Fusarium spp. infection in the root rot complex of field pea and their impact on field pea production in Alberta is currently being investigated. References: (1) S. Chatterton et al. Can. Plant Dis. Surv. 94:189, 2014. (2) C. Gangneux et al. Phytopathology 104:1138, 2014. (3) D. Malvick et al. Plant Dis. 78:361, 1994. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

The reduction in postprandial lipemia after exercise is independent of the relative contributions of fat and carbohydrate to energy metabolism during exercise.

A single session of exercise several hours before a high-fat meal reduces postprandial lipemia. The purpose of the present study was to test the hypothesis that this effect is independent of substrate metabolism during exercise. Twelve men aged 21 to 36 years underwent three oral fat tolerance tests with intervals of at least 1 week. On one occasion, only activities of daily living were allowed the preceding day (control). On the other two occasions, subjects ran on a treadmill for 90 minutes on the afternoon preceding the fat tolerance test; 90 minutes before running, they ingested either acipimox, an inhibitor of lipolysis in adipose tissue, or placebo. Acipimox abolished the increase in the nonesterified fatty acid (NEFA) concentration observed during the run after placebo and reduced lipid oxidation (placebo, 37 +/- 7 g; acipimox, 21 +/- 3 g; P < .05, mean +/- SEM), but had no effect on gross energy expenditure (placebo, 4.86 +/- 0.20 MJ; acipimox, 4.83 +/- 0.18 MJ). Before each of the three fat tolerance tests, subjects reported to the laboratory after an overnight fast. Blood samples were obtained in the fasted state and for 6 hours after consumption of a high-fat meal (per kilogram of body mass: 1.2 g fat, 1.2 g carbohydrate, and 61 kJ energy). Plasma concentrations of NEFA were higher postprandially with acipimox, compared with control and placebo (P < .05), as were glucose concentrations measured over the first 4 hours. The insulin response to the meal was lower in placebo compared with control and acipimox (P < .05). Despite these counterregulatory responses, postprandial lipemia was reduced to the same degree (compared with control, P < .05) by exercise preceded by acipimox and by exercise preceded by placebo (area under the plasma triacylglycerol concentration v time curve: control, 8.77 +/- 1.17 mmol/L x 6 h; placebo, 6.95 +/- 0.97 mmol/L x 6 h; acipimox, 6.81 +/- 0.81 mmol/L x 6 h). These findings suggest that some factor other than the nature of the metabolic substrate used during exercise determines the attenuating effect of prior exercise on postprandial lipemia.