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Clostridium difficile infections (CDI) are caused by colonization and growth of toxigenic strains of C. difficile in individuals whose intestinal microbiota has been perturbed, in most cases following antimicrobial therapy. Determination of the protective commensal gut community members could inform the development of treatments for CDI. Here, we utilized the lethal enterocolitis model in Syrian golden hamsters to analyze the microbiota disruption and recovery along a 20-day period following a single dose of clindamycin on day 0, inducing in vivo susceptibility to C. difficile infection. To determine susceptibility in vitro, spores of strain VPI 10463 were cultured with and without soluble hamster fecal filtrates and growth was quantified by quantitative PCR and toxin immunoassay. Fecal microbial population changes over time were tracked by 16S ribosomal RNA gene analysis via V4 sequencing and the PhyloChip assay. C. difficile culture growth and toxin production were inhibited by the presence of fecal extracts from untreated hamsters but not extracts collected 5 days post-administration of clindamycin. In vitro inhibition was re-established by day 15, which correlated with resistance of animals to lethal challenge. A substantial fecal microbiota shift in hamsters treated with antibiotics was observed, marked by significant changes across multiple phyla including Bacteroidetes and Proteobacteria. An incomplete return towards the baseline microbiome occurred by day 15 correlating with the inhibition of C. difficile growth in vitro and in vivo. These data suggest that soluble factors produced by the gut microbiota may be responsible for the suppression of C. difficile growth and toxin production. [ABSTRACT FROM AUTHOR]

Objective: Animal models of hindlimb ischemia are critical to our understanding of peripheral vascular disease and allow us to evaluate therapeutic strategies aimed to improve peripheral collateral circulation. To further elucidate the processes involved in revascularization following ischemia, we evaluated the temporal association between tissue ischemia, vascular endothelial cell growth factor (VEGF) release, angiogenesis (capillary sprouting), arteriogenesis (growth of the larger muscular arteries), and reserve blood flow (functional collateral flow). Methods: New Zealand White rabbits (male 3–4 kg) were evaluated at specific days (0, 5, 10, 20 or 40) following femoral artery removal for measurement of hindlimb blood flow, skeletal muscle lactate production and VEGF content, capillary density (a marker of angiogenesis), and angiographic score (a marker of arteriogenesis). Results: Maximal capillary sprouting occurred within 5 days of femoral artery removal and was temporally associated with reduced resting hindlimb blood flow, increased lactate release and detectable levels of skeletal muscle VEGF. The growth of larger angiographically visible collateral vessels occurred after 10 days and was not temporally associated with ischemia or skeletal muscle VEGF content, but did coincide with a large functional improvement in the reserve blood flow capacity of the limb. Conclusions: Following femoral artery removal in the rabbit, the time course of angiogenesis and arteriogenesis were clearly distinct. Tissue ischemia and/or VEGF may stimulate capillary sprouting, but this response does not translate to a significant improvement in collateral flow. The growth and development of the larger collateral vessels was correlated with a large functional improvement in collateral flow, and occurred at a time when VEGF levels were undetectable. [ABSTRACT FROM PUBLISHER]

Blood collection from conscious, unanesthetized mice is often performed during the drug development process. The site of collection may influence the parameter(s) of interest. To investigate the potential influence of collection site on plasma glucose and insulin, a study was conducted to compare plasma glucose and insulin concentrations in blood samples collected without anesthesia from the retroorbital sinus versus the tail vein in 10- to 12-week-old female C57BL/6 mice. Two experiments were performed. In the first experiment, mice were randomized to be bled from the tail vein then the retroorbital sinus or vice-versa in a balanced two-period crossover design. In this experiment, the retroorbital and tail vein bleeds were performed a few minutes apart. The second experiment was similar to the first, except the bleeds were performed 1 week apart. Overall, retroorbital collection yielded lower glucose levels (p, 0.001) and higher insulin levels (p, 0.001) than did tail vein collection. The minimum difference in measured glucose in a retroorbital collection versus a tail vein collection, after adjusting for the effect of sequential bleeding was -97 mg/dl; the maximum was 98 mg/dl. We estimate that about 98% of observations taken under similar conditions would fall in this interval. The minimum difference in measured insulin in a retroorbital collection versus a tail vein collection was -0.6 ng/ml; the maximum was 7.3 ng/ml. We estimate that about 98% of observations taken under similar conditions would fall in this interval.