Does a zone of increased perfusion exist around negative-pressure dressings?

BACKGROUND: Although recent work has demonstrated that perfusion adjacent to a negative-pressure wound therapy dressing is decreased, laser Doppler studies have indicated that there is a zone of increased perfusion a couple of centimeters away. The existence of such a zone of increased perfusion is counterintuitive to the fact that negative-pressure wound therapy has been shown to increase tissue pressure. This study, using an alternative to laser Doppler, evaluated whether such a zone exists. METHODS: Six volunteers were randomized into three groups to test different suction pressures (-75, -125, and -400 mmHg). Each volunteer would have two dressings applied on either side of the lower back. A thermal imaging camera was used to assess perfusion around the dressing during different phases (e.g., "Suction on" and "Suction off"). The mean area under the curve for each phase was compared with those of other phases by means of one-way analysis of variance. Each condition (phase) was compared in a systematic manner with every other by means of Fisher's least significant difference for post hoc comparisons. A Pearson's correlation was determined to test the effects of the different suction pressure groups. RESULTS: No significant difference could be demonstrated for the area under the curve for the different phases. There was no significant correlation between the three suction pressures tested and the difference between the mean area under the curve for "Dressing on, no suction" and the two "Suction on" periods (Pearson correlation = 0.24; p > 0.4). CONCLUSIONS: Thermographic evaluation of tissue around a negative-pressure dressing did not demonstrate a zone of increased perfusion, contrary to other studies, which used laser Doppler. This is in keeping with recent work demonstrating that negative-pressure wound therapy increases tissue pressure while the dressing is applying suction. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

Understanding the yeast host cell response to recombinant membrane protein production.

Membrane proteins are drug targets for a wide range of diseases. Having access to appropriate samples for further research underpins the pharmaceutical industry's strategy for developing new drugs. This is typically achieved by synthesizing a protein of interest in host cells that can be cultured on a large scale, allowing the isolation of the pure protein in quantities much higher than those found in the protein's native source. Yeast is a popular host as it is a eukaryote with similar synthetic machinery to that of the native human source cells of many proteins of interest, while also being quick, easy and cheap to grow and process. Even in these cells, the production of human membrane proteins can be plagued by low functional yields; we wish to understand why. We have identified molecular mechanisms and culture parameters underpinning high yields and have consolidated our findings to engineer improved yeast host strains. By relieving the bottlenecks to recombinant membrane protein production in yeast, we aim to contribute to the drug discovery pipeline, while providing insight into translational processes.

The increasing trend in alcohol-related burns: it's impact on a tertiary burn centre.

INTRODUCTION: The incidence of alcohol-related hospital admissions is a worldwide problem and currently costs the UK National Health Service approximately 4% of its annual budget. 40% of men and 22% of women drink over the recommended UK weekly allowance. The purpose of our study was to examine the trend in alcohol-related admissions to a tertiary burns unit over a 5-year period. METHODOLOGY: All patients admitted were documented for alcohol-related burn, and history of alcohol dependence. RESULTS: 1293 patients admitted between 2003 and 2008 were included in the study. The number of alcohol-related burns were as follows: 2003: 6%; 2004: 10%; 2005: 16%; 2006: 9%; 2007: 19%; 2008: 19%. This increasing trend was highly significant (p<0.0001). Alcohol-related burns had a higher incidence of flame injury (60%) and a subsequent longer length of stay (12.5 vs. 7.9, p=0.04). Alcohol dependence was noted in 54% of all alcohol-related burns and in 5% of the non-alcohol-related burns. DISCUSSION: The number of alcohol-related burns admitted to a tertiary burn unit is increasing and now comprises of nearly 20% of all admissions. This highlights the growing burden of alcohol on health and the need to address it at both a national and regional level.

Developing a scalable model of recombinant protein yield from Pichia pastoris: the influence of culture conditions, biomass and induction regime.

BACKGROUND: The optimisation and scale-up of process conditions leading to high yields of recombinant proteins is an enduring bottleneck in the post-genomic sciences. Typical experiments rely on varying selected parameters through repeated rounds of trial-and-error optimisation. To rationalise this, several groups have recently adopted the 'design of experiments' (DoE) approach frequently used in industry. Studies have focused on parameters such as medium composition, nutrient feed rates and induction of expression in shake flasks or bioreactors, as well as oxygen transfer rates in micro-well plates. In this study we wanted to generate a predictive model that described small-scale screens and to test its scalability to bioreactors. RESULTS: Here we demonstrate how the use of a DoE approach in a multi-well mini-bioreactor permitted the rapid establishment of high yielding production phase conditions that could be transferred to a 7 L bioreactor. Using green fluorescent protein secreted from Pichia pastoris, we derived a predictive model of protein yield as a function of the three most commonly-varied process parameters: temperature, pH and the percentage of dissolved oxygen in the culture medium. Importantly, when yield was normalised to culture volume and density, the model was scalable from mL to L working volumes. By increasing pre-induction biomass accumulation, model-predicted yields were further improved. Yield improvement was most significant, however, on varying the fed-batch induction regime to minimise methanol accumulation so that the productivity of the culture increased throughout the whole induction period. These findings suggest the importance of matching the rate of protein production with the host metabolism. CONCLUSION: We demonstrate how a rational, stepwise approach to recombinant protein production screens can reduce process development time.