The influence of a manipulation of threat on experimentally-induced secondary hyperalgesia

Pain is thought to be influenced by the threat value of the particular context in which it occurs. However, the mechanisms by which a threat achieves this influence on pain are unclear. Here, we explore how threat influences experimentally-induced secondary hyperalgesia, which is thought to be a manifestation of central sensitization. We developed an experimental study to investigate the effect of a manipulation of threat on experimentally-induced secondary hyperalgesia in 26 healthy human adults (16 identifying as female; 10 as male). We induced secondary hyperalgesia at both forearms using high-frequency electrical stimulation. Prior to the induction, we used a previously successful method to manipulate threat of tissue damage at one forearm (threat site). The effect of the threat manipulation was determined by comparing participant-rated anxiety, perceived threat, and pain during the experimental induction of secondary hyperalgesia, between the threat and control sites. We hypothesized that the threat site would show greater secondary hyperalgesia (primary outcome) and greater surface area (secondary outcome) of induced secondary hyperalgesia than the control site. Despite a thorough piloting procedure to test the threat manipulation, our data showed no main effect of site on pain, anxiety, or threat ratings during high-frequency electrical stimulation. In the light of no difference in threat between sites, the primary and secondary hypotheses cannot be tested. We discuss reasons why we were unable to replicate the efficacy of this established threat manipulation in our sample, including: (1) competition between threats, (2) generalization of learned threat value, (3) safety cues, (4) trust, and requirements for participant safety, (5) sampling bias, (6) sample-specific habituation to threat, and (7) implausibility of (sham) skin examination and report. Better strategies to manipulate threat are required for further research on the mechanisms by which threat influences pain.

Dynamic mathematical model development and validation of in vitro Mycobacterium smegmatis growth under nutrient- and pH-stress

Mycobacterium tuberculosis can exist within a host for lengthy periods, tolerating even antibiotic challenge. This non-heritable, antibiotic tolerant "persister" state, is thought to underlie latent Tuberculosis (TB) infection and a deeper understanding thereof could inform treatment strategies. In addition to experimental studies, mathematical and computational modelling approaches are widely employed to study persistence from both an in vivo and in vitro perspective. However, specialized models (partial differential equations, agent-based, multiscale, etc.) rely on several difficult to determine parameters. In this study, a dynamic mathematical model was developed to predict the response of Mycobacterium smegmatis (a model organism for M. tuberculosis) grown in batch culture and subjected to a range of in vitro environmental stresses. Lag phase dynamics, pH variations and internal nitrogen storage were mechanistically modelled. Experimental results were used to train model parameters using global optimization, with extensive subsequent model validation to ensure extensibility to more complex modelling frameworks. This included an identifiability analysis which indicated that seven of the thirteen model parameters were uniquely identifiable. Non-identifiable parameters were critically evaluated. Model predictions compared to validation data (based on experimental results not used during training) were accurate with less than 16% maximum absolute percentage error, indicating that the model is accurate even when extrapolating to new experimental conditions. The bulk growth model can be extended to spatially heterogeneous simulations such as an agent-based model to simulate in vitro granuloma models or, eventually, in vivo conditions, where distributed environmental conditions are difficult to measure.

A partially randomised trial of pretomanid, moxifloxacin and pyrazinamide for pulmonary TB

BACKGROUND: Treatment for TB is lengthy and toxic, and new regimens are needed.METHODS: Participants with pulmonary drug-susceptible TB (DS-TB) were randomised to receive: 200 mg pretomanid (Pa, PMD) daily, 400 mg moxifloxacin (M) and 1500 mg pyrazinamide (Z) for 6 months (6Pa200MZ) or 4 months (4Pa200MZ); 100 mg pretomanid daily for 4 months in the same combination (4Pa100MZ); or standard DS-TB treatment for 6 months. The primary outcome was treatment failure or relapse at 12 months post-randomisation. The non-inferiority margin for between-group differences was 12.0%. Recruitment was paused following three deaths and not resumed.RESULTS: Respectively 4/47 (8.5%), 11/57 (19.3%), 14/52 (26.9%) and 1/53 (1.9%) DS-TB outcomes were unfavourable in patients on 6Pa200MZ, 4Pa200MZ, 4Pa100MZ and controls. There was a 6.6% (95% CI -2.2% to 15.4%) difference per protocol and 9.9% (95%CI -4.1% to 23.9%) modified intention-to-treat difference in unfavourable responses between the control and 6Pa200MZ arms. Grade 3+ adverse events affected 68/203 (33.5%) receiving experimental regimens, and 19/68 (27.9%) on control. Ten of 203 (4.9%) participants on experimental arms and 2/68 (2.9%) controls died.CONCLUSION: PaMZ regimens did not achieve non-inferiority in this under-powered trial. An ongoing evaluation of PMD remains a priority.

Gender differences in tuberculosis treatment outcomes: a post hoc analysis of the REMoxTB study

BACKGROUND

In the REMoxTB study of 4-month treatment-shortening regimens containing moxifloxacin compared to the standard 6-month regimen for tuberculosis, the proportion of unfavourable outcomes for women was similar in all study arms, but men had more frequent unfavourable outcomes (bacteriologically or clinically defined failure or relapse within 18 months after randomisation) on the shortened moxifloxacin-containing regimens. The reason for this gender disparity in treatment outcome is poorly understood.

METHODS

The gender differences in baseline variables were calculated, as was time to smear and culture conversion and Kaplan-Meier plots were constructed. In post hoc exploratory analyses, multivariable logistic regression modelling and an observed case analysis were used to explore factors associated with both gender and unfavourable treatment outcome.

RESULTS

The per-protocol population included 472/1548 (30%) women. Women were younger and had lower rates of cavitation, smoking and weight (all p < 0.05) and higher prevalence of HIV (10% vs 6%, p = 0.001). They received higher doses (mg/kg) than men of rifampicin, isoniazid, pyrazinamide and moxifloxacin (p ≤ 0.005). There was no difference in baseline smear grading or mycobacterial growth indicator tube (MGIT) time to positivity. Women converted to negative cultures more quickly than men on Lowenstein-Jensen (HR 1.14, p = 0.008) and MGIT media (HR 1.19, p < 0.001). In men, the presence of cavitation, positive HIV status, higher age, lower BMI and 'ever smoked' were independently associated with unfavourable treatment outcome. In women, only 'ever smoked' was independently associated with unfavourable treatment outcome. Only for cavitation was there a gender difference in treatment outcomes by regimen; their outcome in the 4-month arms was significantly poorer compared to the 6-month treatment arm (p < 0.001). Women, with or without cavities, and men without cavities had a similar outcome on all treatment arms (p = 0.218, 0.224 and 0.689 respectively). For all other covariate subgroups, there were no differences in treatment effects for men or women.

CONCLUSIONS

Gender differences in TB treatment responses for the shorter regimens in the REMoxTB study may be explained by poor outcomes in men with cavitation on the moxifloxacin-containing regimens. We observed that women with cavities, or without, on the 4-month moxifloxacin regimens had similar outcomes to all patients on the standard 6-month treatment. The biological reasons for this difference are poorly understood and require further exploration.

Accelerated hydrotherapy and land-based rehabilitation in soccer players after anterior cruciate ligament reconstruction: a series of three single subject case studies

Objective. To investigate the effectiveness of accelerated rehabilitation and accelerated hydrotherapy after anterior cruciate ligament (ACL) reconstruction in male athletes participating in soccer. Design. A non-concurrent single subject, multiple baseline design (ABA design) was conducted over 10 weeks. A series of three N=1 studies was conducted to assess the effect of an accelerated hydrotherapy programme on pain, function, and range of motion. Setting. The study was conducted at a private physiotherapy practice in Port Elizabeth, South Africa. Interventions. The land rehabilitation programme was a homebased programme supervised every week by the physiotherapist. The accelerated hydrotherapy consisted of a 6-week programme, and participants attended two treatment sessions of accelerated hydrotherapy per week each of 30 minutes\' duration. Main outcome measures. The knee injury and osteoarthritis outcome scale (KOOS) as a subjective measure of pain, function and quality of life; the goniometer to measure active knee ROM and the 6-minute walking test (6MWT) as an objective measure of function. Results. All three patients demonstrated good improvement during the treatment phase for the KOOS scale and progressed well in terms of their walking ability during the study. Significant improvement was gained during the baseline phase for all three participants with high initial levels of knee flexion while active knee extension improved gradually in all three participants. Conclusion. The study findings indicate that an accelerated landbased and hydrotherapy programme may be useful in improving patient outcomes and that there are no risks for harm. Clinical relevance. The study findings indicate that accelerated hydrotherapy may be a useful and safe adjunct to an accelerated land-based programme after ACL reconstruction South African Journal of Sports Medicine Vol. 20 (4) 2008: pp. 109-114

The effect of polysaccharide-degrading wine yeast transformants on the efficiency of wine processing and wine flavour

Commercial polysaccharase preparations are applied to winemaking to improve wine processing and quality. Expression of polysaccharase-encoding genes in Saccharomyces cerevisiae allows for the recombinant strains to degrade polysaccharides that traditional commercial yeast strains cannot. In this study, we constructed recombinant wine yeast strains that were able to degrade the problem-causing grape polysaccharides, glucan and xylan, by separately integrating the Trichoderma reesei XYN2 xylanase gene construct and the Butyrivibrio fibrisolvens END1 glucanase gene cassette into the genome of the commercial wine yeast strain S. cerevisiae VIN13. These genes were also combined in S. cerevisiae VIN13 under the control of different promoters. The strains that were constructed were compared under winemaking conditions with each other and with a recombinant wine yeast strain expressing the endo-beta-1,4-glucanase gene cassette (END1) from B. fibrisolvens and the endo-beta-1,4-xylanase gene cassette (XYN4) from Aspergillus niger, a recombinant strain expressing the pectate lyase gene cassette (PEL5) from Erwinia chrysanthemi and the polygalacturonase-encoding gene cassette (PEH1) from Erwinia carotovora. Wine was made with the recombinant strains using different grape cultivars. Fermentations with the recombinant VIN13 strains resulted in significant increases in free-flow wine when Ruby Cabernet must was fermented. After 6 months of bottle ageing significant differences in colour intensity and colour stability could be detected in Pinot Noir and Ruby Cabernet wines fermented with different recombinant strains. After this period the volatile composition of Muscat d'Alexandria, Ruby Cabernet and Pinot Noir wines fermented with different recombinant strains also showed significant differences. The Pinot Noir wines were also sensorial evaluated and the tasting panel preferred the wines fermented with the recombinant strains.

Roflumilast, a phosphodiesterase 4 inhibitor, reduces airway hyperresponsiveness after allergen challenge

BACKGROUND

Roflumilast, an oral, once-daily phosphodiesterase 4 inhibitor, is currently in clinical development for the treatment of asthma.

OBJECTIVES

This pilot study examined the effect of roflumilast on allergen-induced airway hyperresponsiveness (AHR) to histamine challenge and asthmatic response to allergen challenge.

METHODS

In a randomized, double-blind, 2-period, crossover trial, 13 patients with mild allergic asthma [mean forced expiratory volume in 1 s (FEV(1)) % predicted = 86%] received a single dose of oral roflumilast 1,000 microg or placebo. Patients were administered roflumilast 60 min before allergen challenge, and asthmatic responses were assessed via change in FEV(1) <or=9 h after allergen challenge. AHR to histamine provocation was measured before and repeated 24 h after allergen provocation. Patients inhaled histamine in doubling concentrations until attaining a decrease in FEV(1) of <or=20% (PC(20)FEV(1)).

RESULTS

Roflumilast had no detectable bronchodilator activity 60 min after administration. Roflumilast significantly attenuated AHR compared with placebo, with a mean change in pre- to postallergen challenge PC(20)FEV(1) ratio of 1.23 +/- 2.75 and 2.51 +/- 2.95 for roflumilast and placebo, respectively (p = 0.002). During the late asthmatic response, roflumilast reduced the mean maximum decrease in FEV(1) from 2 to 9 h after allergen challenge compared with placebo (p = 0.005). Additionally, FEV(1) at 9 h after challenge was significantly higher in patients treated with roflumilast (p = 0.03). Early asthmatic responses to allergen challenge were not significantly reduced by the single dose of roflumilast.

CONCLUSIONS

Roflumilast attenuated allergen-induced AHR in patients with mild asthma. These results support further investigation of roflumilast as an anti-inflammatory treatment of asthma.