Characterization and Utilization of the Flexor Digitorum Brevis for Assessing Skeletal Muscle Function

Abstract Background The ability to assess skeletal muscle function and delineate regulatory mechanisms is essential to uncovering therapeutic approaches that preserve functional independence in a disease state. Skeletal muscle provides distinct experimental challenges due to inherent differences across muscle groups, including fiber type and size that may limit experimental approaches. The flexor digitorum brevis (FDB) possesses numerous properties that offer the investigator a high degree of experimental flexibility to address specific hypotheses. To date, surprisingly few studies have taken advantage of the FDB to investigate mechanisms regulating skeletal muscle function. The purpose of this study was to characterize and experimentally demonstrate the value of the FDB muscle for scientific investigations. Methods First, we characterized the FDB phenotype and provide reference comparisons to skeletal muscles commonly used in the field. We developed approaches allowing for experimental assessment of force production, in vitro and in vivo microscopy, and mitochondrial respiration to demonstrate the versatility of the FDB. As proof-of principle, we performed experiments to alter force production or mitochondrial respiration to validate the flexibility the FDB affords the investigator. Results The FDB is made up of small predominantly type IIa and IIx fibers that collectively produce less peak isometric force than the extensor digitorum longus (EDL) or soleus muscles, but demonstrates a greater fatigue resistance than the EDL. Unlike the other muscles, inherent properties of the FDB muscle make it amenable to multiple in vitro- and in vivo-based microscopy methods. Due to its anatomical location, the FDB can be used in cardiotoxin-induced muscle injury protocols and is amenable to electroporation of cDNA with a high degree of efficiency allowing for an effective means of genetic manipulation. Using a novel approach, we also demonstrate methods for assessing mitochondrial respiration in the FDB, which are comparable to the commonly used gastrocnemius muscle. As proof of principle, short-term overexpression of Pgc1α in the FDB increased mitochondrial respiration rates. Conclusion The results highlight the experimental flexibility afforded the investigator by using the FDB muscle to assess mechanisms that regulate skeletal muscle function

Genes Required for Growth at High Hydrostatic Pressure in Escherichia coli K-12 Identified by Genome-Wide Screening

Despite the fact that much of the global microbial biosphere is believed to exist in high pressure environments, the effects of hydrostatic pressure on microbial physiology remain poorly understood. We use a genome-wide screening approach, combined with a novel high-throughput high-pressure cell culture method, to investigate the effects of hydrostatic pressure on microbial physiology in vivo. The Keio collection of single-gene deletion mutants in Escherichia coli K-12 was screened for growth at a range of pressures from 0.1 MPa to 60 MPa. This led to the identification of 6 genes, rodZ, holC, priA, dnaT, dedD and tatC, whose products were required for growth at 30 MPa and a further 3 genes, tolB, rffT and iscS, whose products were required for growth at 40 MPa. Our results support the view that the effects of pressure on cell physiology are pleiotropic, with DNA replication, cell division, the cytoskeleton and cell envelope physiology all being potential failure points for cell physiology during growth at elevated pressure

The Prospective Oral Mucositis Audit: relationship of severe oral mucositis with clinical and medical resource use outcomes in patients receiving high-dose melphalan or BEAM-conditioning chemotherapy and autologous SCT

The Prospective Oral Mucositis Audit was an observational study in 197 patients with multiple myeloma (MM) or non-Hodgkin's lymphoma (NHL) undergoing, respectively, high-dose melphalan or BEAM chemotherapy and autologous SCT at 25 European centres. We evaluated the relationship between severe oral mucositis (SOM; WHO Oral Toxicity Scale grade 3-4) and local and systemic clinical sequelae and medical resource use. SOM occurred in 44% of patients. The duration of SOM (mean 5.3 days) correlated with time to neutrophil engraftment. The following parameters increased gradiently with maximum grade of oral mucositis: duration of pain score >or=4, opioid use, dysphagia score >or=4, total parenteral nutrition (TPN) use, incidence and/or duration of fever and infection, and duration of antibiotic use. SOM increased the duration of TPN use by 2.7 days (P<0.001), opioids by 4.6 days (P<0.001), and antibiotics by 2.4 days (P=0.045). SOM prolonged hospital stay by 2.3 days (P=0.013) in MM patients, but not in NHL patients (who tended to have a longer hospital stay). In conclusion, this analysis of prospectively collected observational data provides important insight into the scope and impact of SOM in the European transplant setting