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One current strategy to deal with the serious issue of antibiotic resistance is to use biosurfactants, weak antimicrobials in their own right, with antibiotics in order to extend the efficacy of antibiotics. Although an adjuvant effect has been observed, the underlying mechanisms are poorly understood. To investigate the nature of the antibiotic and biosurfactant interaction, we undertook a scanning electron microscopy (SEM) and atomic force microscopy (AFM) microscopic study of the effects of the tetracycline antibiotic, combined with sophorolipid and rhamnolipid biosurfactants, on Methicillin-resistant Staphylococcus aureus using tetracycline concentrations below and above the minimum inhibitory concentration (MIC). Control and treated bacterial samples were prepared with an immersion technique by adsorbing the bacteria onto glass substrates grafted with the poly-cationic polymer polyethyleneimine. Bacterial surface morphology, hydrophobic and hydrophilic surface characters as well as the local bacterial cell stiffness were measured following combined antibiotic and biosurfactant treatment. The sophorolipid biosurfactant stands alone insofar as, when used with the antibiotic at sub-MIC concentration, it resulted in bacterial morphological changes, larger diameters (from 758 ± 75 to 1276 ± 220 nm, p-value = 10-4) as well as increased bacterial core stiffness (from 205 ± 46 to 396 ± 66 mN/m, p-value = 5 × 10-5). This investigation demonstrates that such combination of microscopic analysis can give useful information which could complement biological assays to understand the mechanisms of synergy between antibiotics and bioactive molecules such as biosurfactants.

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CONTEXT: Prompt reperfusion therapy in acute ST-segment elevation myocardial infarction (STEMI) improves outcomes and is therefore a key part of the management of affected patients. Primary percutaneous coronary intervention (PPCI) is preferred over thrombolysis; however, when PPCI is not available within an acceptable time frame, thrombolysis should be administered without delay. When thrombolysis is contraindicated, this can lead to delays in achieving coronary artery reperfusion, and making therapeutic decisions is more challenging. ISSUES: A 57-year-old woman with hereditary haemorrhagic telangiectasia (HHT) presented with chest pain to local medical services on a Scottish island. Initial assessment including 12-lead ECG was performed without delay and led to a diagnosis of infero-lateral STEMI. Initial treatment was with antiplatelets, nitrate and opiate analgesia. Immediate reperfusion therapy with thrombolysis was considered; however, this was contraindicated due to the diagnosis of HHT. Following discussion with the regional centre she was treated with heparin and urgently transferred to the nearest catheterisation laboratory for PPCI. Unfortunately delays in transfer were caused by inclement weather conditions, which precluded the use of an air ambulance. The patient reached a cardiac catheterisation laboratory by road. A total occlusion of a distal branch of the circumflex artery was found to be the culprit lesion and despite wiring and ballooning good blood flow was not restored. However, she made a good recovery and was discharged home on secondary prevention therapy, which was modified to take into account her increased bleeding risk associated with her pre-existing HHT. LESSONS LEARNED: In this case, the patient presented early to medical services following the onset of symptoms and was immediately assessed, resulting in a prompt accurate diagnosis at first medical contact. Despite this, the presence of HHT, and the particularities of living in a remote area compounded by unfavourable weather conditions, resulted in a delay in definitive treatment that would have been available to a similar patient presenting in an urban setting. In remote regions where reperfusion therapy for acute STEMI relies more often on thrombolysis, an increased awareness of the issues around the contraindication of thrombolysis, together with early discussion with a regional cardiology service leads to the most efficient way of establishing the best treatment plan for individual patients. Despite this, rural patients may remain at a disadvantage.

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Extreme sports such as paragliding are increasing in popularity, providing continued challenges for the development of safe practice techniques. In January and February 2013, the Wings of Kilimanjaro expedition aimed to launch 95 paragliders from the summit of Mount Kilimanjaro, 5790 m above sea level. A safe launch was paramount but risked being impaired by adverse environmental conditions, in particular the pathophysiological effects of high altitude. There are no existing scores to assess fitness for high-altitude paraglider launches present in the literature. A novel scoring system, the Kilimanjaro Score, was therefore developed to rapidly assess pilots pre-flight. The Kilimanjaro Score aimed to assess cognition, memory, and visual-spatial skill within the context of standard pre-flight checks. Further testing, including the Lake Louise Score, was to be performed if the pilot's Kilimanjaro Score was deemed unsatisfactory. We present the Kilimanjaro Score here for comment and refinement, and we invite other parties to consider its use in the field for high altitude paragliding activities.

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OBJECTIVES: To investigate the effect of Antarctic residence on energy dynamics and aerobic fitness over the course of a year in over-wintering personnel. STUDY DESIGN: A prospective longitudinal observational study. METHODS: A convenience sample of personnel over-wintering at Rothera Research Station in Antarctica was studied. Body weight, body fat, food intake, activity and aerobic fitness were recorded every 30 days for 1 year. Body weight, body fat and food intake were measured using weighing scales, skinfold callipers and diet records, respectively; activity was measured using accelerometer-based activity trackers and aerobic fitness using a treadmill protocol. Climate markers of temperature and sunlight hours were also recorded. RESULTS: Twenty-one subjects took part in the study over the 12-month period. A statistically significant increase in body weight and body fat in winter was observed (p=0.012 and p=0.049, respectively). There were no statistically significant trends in activity, food intake or aerobic fitness. CONCLUSIONS: There were significant seasonal changes in body weight and body fat, with both measures increasing in winter but no significant changes in the other main outcome measures.

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OBJECTIVE: To review the current literature that describes the effect of Antarctic residence on energy dynamics and aerobic fitness. STUDY DESIGN: Literature review. METHODS: Published literature on energy dynamics and aerobic fitness in the polar environment was reviewed. Energy dynamics were represented by body weight, body fat, food intake and energy expenditure. Consideration was given to seasonal variation and possible explanations for the apparent high metabolic cost of Antarctic residence. The influence of cold exposure was discussed and comment was made on the differences between temperate and polar residence. RESULTS: Food intake and energy expenditure are found to increase with Antarctic residence. There is often an associated increase in body weight and body fat. Seasonal variation is common but not universal, with an increase in body weight and body fat in winter. Variation in aerobic fitness appears to be related to the specific study sample rather than Antarctic residence per se. CONCLUSIONS: In most instances, Antarctic residence has effects on energy dynamics and aerobic fitness. Explanations for the observed changes may include physiological adaptations, such as a raised basal metabolic rate and increased thermogenesis. However, cold-induced changes are less likely when cold exposure is minimized by heated buildings and insulated clothing. Activity patterns related to work and leisure thus represent a more likely cause. The majority of the research is several decades old; further research would help to elucidate the patterns of energy dynamics of modern Antarctic workers.

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Ventilatory control undergoes profound changes on ascent to high altitude. We hypothesized that the fall in citric acid cough threshold seen on ascent to altitude is mediated by changes in the central control of cough and would parallel changes in central ventilatory control assessed by the hypercapnic ventilatory response (HCVR). Twenty-five healthy volunteers underwent measurements of HCVR and citric acid sensitivity at sea level and during a 9 day sojourn at 5200m. None of the subjects had any evidence of respiratory infection. Citric acid cough threshold fell significantly on ascent to 5200m. The slope, S, of the HCVR increased significantly on ascent to 5200m and during the stay at altitude. There was no correlation between citric acid sensitivity and HCVR. We conclude that the change in citric acid cough threshold seen on exposure to hypobaric hypoxia is unlikely to be mediated by changes in the central control of cough. Sensitivity to citric acid may be due to early subclinical pulmonary edema stimulating airway sensory nerve endings.

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OBJECTIVE: Dizziness is a symptom of acute mountain sickness (AMS). This study tested whether immediate fall in systolic blood pressure (BP) on standing was more severe at altitude and whether this was associated with symptoms of dizziness. METHODS: Eighty-five lowlanders flew into La Paz, Bolivia (3650 m), and after 4 to 5 days of acclimatization ascended in 90 minutes to the Chacaltaya Laboratory (5200 m) by road. Blood pressure was measured on 5 occasions, 3 times at 5200 m and twice at sea level, before and after the expedition using a mercury sphygmomanometer. Both a supine and an erect (within 15 seconds of standing) BP measurement were recorded. Participants recorded whether they felt dizzy on standing. A mixed-effect model was used to test for a difference in the change in BP for time and altitude. RESULTS: The immediate fall in systolic BP observed on standing was significantly greater (P < .001) on all 3 altitude study days (18.2, 23.4, and 20.7 mm Hg) than at sea level (12.2 and 12.4 mm Hg). There was no significant difference in the change in diastolic BP or change in mean arterial BP between sea level and altitude. CONCLUSIONS: The immediate drop in systolic BP observed on standing was greater at altitude. However, mean arterial pressure was maintained, and we found no association between the degree of immediate fall in BP and dizziness or AMS.

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BACKGROUND: Both tissue hypoxia in vitro, and whole-body hypoxia in vivo, have been found to promote the release of reactive oxygen species (ROS) that are potentially damaging to the cardiovascular system. Antioxidant systems protect against oxidative damage by ROS and may exhibit some degree of responsiveness to oxidative stimuli. Production of urate, a potent soluble antioxidant, is increased in hypoxic conditions. We aimed to determine whether urate is an important antioxidant defense in healthy subjects exposed to hypoxia. METHODS: We conducted a cohort study of 25 healthy lowland volunteers during acute exposure to high altitude (4 days at 3,600 m, followed by 10 days at 5,200 m) on the Apex high-altitude research expedition to Bolivia. We measured markers of oxidative stress (8-isoprostane F2), serum urate concentration, and total plasma antioxidant activity by two techniques: 2,2'-amino-di-[3-ethylbenzthiazole sulfonate] spectrophotometry (total antioxidant status [TAS]) and enhanced chemiluminescence (ECL). RESULTS: On ascent, F2-isoprostane levels were significantly elevated compared with those at sea level (p < 0.01). After 1 week at high altitude, plasma antioxidant capacity (AOC) by both TAS and ECL, and serum urate concentration were significantly elevated (each p < 0.01 vs sea level), and F2-isoprostane levels were reduced to values at sea level. There was a highly significant correlation between plasma urate and AOC at this stage (ECL, r(2) = 0.59, p = 0.0001; TAS, r(2) = 0.30, p = 0.0062). CONCLUSIONS: Our results support the hypothesis that urate may act as a responsive endogenous antioxidant in high-altitude hypoxia.

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PURPOSE: To demonstrate the influence of radiographic positioning on the assessment of stent-graft migration using plain radiographs following endovascular abdominal aortic aneurysm repair. METHODS: Equations were derived to correct for artifactual stent-graft migration introduced by geometric distortion due to variations in positioning between radiographs acquired at different times. A phantom system was used to validate the equations. RESULTS: Errors in stent position increase with (1) the distance of the aortic stent-graft from the midline and (2) differences in radiographic centering points in the craniocaudal direction; other variables have little effect. For typical stent positions, errors are small if the centering changes by <8 cm. Consistent radiographic positioning to within 4 cm on successive imaging studies limits errors to 1.5 mm. Even if artifactual migration is large, the true migration can be reliably calculated to within 2 mm. CONCLUSIONS: Artifactual migration due to variation in radiographic centering is not usually clinically significant if care is taken to center radiographs consistently. Radiographs in which artifactual migration may be important are readily identified, and mathematical correction is straightforward.

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