Environmental variation at the onset of independent foraging affects full-grown body mass in the red fox

The period following the withdrawal of parental care has been highlighted as a key developmental period for juveniles. One reason for this is that juveniles cannot forage as competently as adults, potentially placing them at greater risk from environmentally-induced changes in food availability. However, no study has examined this topic. Using a long-term dataset on red foxes (Vulpes vulpes), we examined (i) dietary changes that occurred in the one-month period following the attainment of nutritional independence, (ii) diet composition in relation to climatic variation, and (iii) the effect of climatic variation on subsequent full-grown mass. Diet at nutritional independence contained increased quantities of easy-to-catch food items (earthworms and insects) when compared with pre-independence. Interannual variation in the volume of rainfall at nutritional independence was positively correlated to the proportion of earthworms in cub diet. Pre-independence cub mass and rainfall immediately following nutritional independence explained a significant proportion of variance in full-grown mass, with environmental variation affecting full-grown mass of the entire cohorts. Thus, weather-mediated availability of easy-to-catch food items at a key developmental stage has lifelong implications for the development of juvenile foxes by affecting full-grown mass, which in turn appears to be an important component of individual reproductive potential.     

Restricted dispersal reduces the strength of spatial density dependence in a tropical bird population

Spatial processes could play an important role in density-dependent population regulation because the disproportionate use of poor quality habitats as population size increases is widespread in animal populations-the so-called buffer effect. While the buffer effect patterns and their demographic consequences have been described in a number of wild populations, much less is known about how dispersal affects distribution patterns and ultimately density dependence. Here, we investigated the role of dispersal in spatial density dependence using an extraordinarily detailed dataset from a reintroduced Mauritius kestrel (Falco punctatus) population with a territorial (despotic) breeding system. We show that recruitment rates varied significantly between territories, and that territory occupancy was related to its recruitment rate, both of which are consistent with the buffer effect theory. However, we also show that restricted dispersal affects the patterns of territory occupancy with the territories close to release sites being occupied sooner and for longer as the population has grown than the territories further away. As a result of these dispersal patterns, the strength of spatial density dependence is significantly reduced. We conclude that restricted dispersal can modify spatial density dependence in the wild, which has implications for the way population dynamics are likely to be impacted by environmental change.     

Biofilm formation and interactions of bacterial strains found in wastewater treatment systems

Biofilm formation and adherence properties of 13 bacterial strains commonly found in wastewater treatment systems were studied in pure and mixed cultures using a crystal violet microtiter plate assay. Four different culture media were used, wastewater, acetate medium, glucose medium and diluted nutrient broth. The medium composition strongly affected biofilm formation. All strains were able to form pure culture biofilms within 24 h in at least one of the tested culture media and three strains were able to form biofilm in all four culture media, namely Acinetobacter calcoaceticus ATCC 23055, Comamonas denitrificans 123 and Pseudomonas aeruginosa MBL 0199. The adherence properties assessed were initial adherence, cell surface hydrophobicity, and production of amyloid fibers and extracellular polymeric substances. The growth of dual-strain biofilms showed that five organisms formed biofilm with all 13 strains while seven formed no or only weak biofilm when cocultured. In dual-strain cultures, strains with different properties were able to complement each other, giving synergistic effects. Strongest biofilm formation was observed when a mixture of all 13 bacteria were grown together. These results on attachment and biofilm formation can serve as a tool for the design of tailored systems for the degradation of municipal and industrial wastewater.     

Influence of dams and habitat condition on the distribution of redhorse (Moxostoma) species in the Grand River watershed, Ontario

Redhorse, Moxostoma spp., are considered to be negatively affected by dams although this assertion is untested for Canadian populations. One hundred and fifty-one sites in the Grand River watershed were sampled to identify factors influencing the distribution of redhorse species. Individual species of redhorse were captured from 3 to 32% of sites. The most widespread species were golden redhorse, M. erythrurum (30%) and greater redhorse, M. valenciennesi (32%), while river redhorse, M. carinatum, was only found along the lower Grand River. Redhorse were absent from the highly fragmented Speed River sub-watershed and upper reaches of the Conestogo River and the Grand River. Redhorse species richness was positively correlated to river fragment size and upstream drainage area. Generalized additive models (GAMs) were applied to evaluate the influence of river fragment length, connectivity and habitat on species distribution. Principal component analysis reduced habitat data to three axes representing: channel structure, substrate, and pool, riffle and run habitats (PC1); gradient and drainage area (PC2); and cover (PC3). GAMs indicate that PC2 was important for predicting black redhorse and greater redhorse site occupancy and PC1 was important for golden redhorse. River fragment length was important for predicting site occupancy for shorthead redhorse, but not other species.     

Real-time PCR to determine transgene copy number and to quantitate the biolocalization of adoptively transferred cells from EGFP-transgenic mice

Quantitative real-time PCR (qPCR) is a sensitive technique for the detection and quantitation of specific DNA sequences. Here we describe a Taqman qPCR assay for quantification of tissue-localized, adoptively transferred enhanced green fluorescent protein (EGFP)-transgenic cells. A standard curve constructed from serial dilutions of a plasmid containing the EGFP transgene was (i) highly reproducible, (ii) detected as few as two copies, and (iii) was included in each qPCR assay. qPCR analysis of genomic DNA was used to determine transgene copy number in several mouse strains. Fluorescent microscopy of tissue sections showed that adoptively transferred vascular endothelial cells (VEC) from EGFP-transgenic mice specifically localized to tissue with metastatic tumors in syngeneic recipients. VEC microscopic enumeration of liver metastases strongly correlated with qPCR analysis of identical sections (Pearson correlation 0.81). EGFP was undetectable in tissue from control mice by qPCR. In another study using intra-tumor EGFP-VEC delivery to subcutaneous tumors, manual cell count and qPCR analysis of alternating sections also strongly correlated (Pearson correlation 0.82). Confocal microscopy of the subcutaneous tumor sections determined that visual fluorescent signals were frequently tissue artifacts. This qPCR methodology offers specific, objective, and rapid quantitation, uncomplicated by tissue autofluorescence, and should be readily transferable to other in vivo models to quantitate the biolocalization of transplanted cells.     

Anticoagulation intensity and outcomes among patients prescribed oral anticoagulant therapy: a systematic review and meta-analysis

Background

Patients taking oral anticoagulant therapy balance the risks of hemorrhage and thromboembolism. We sought to determine the association between anticoagulation intensity and the risk of hemorrhagic and thromboembolic events. We also sought to determine how under-or overanticoagulation would influence patient outcomes.

Methods

We reviewed the MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials and CINAHL databases to identify studies involving patients taking anticoagulants that reported person-years of observation and the number of hemorrhages or thromboemboli in 3 or more discrete ranges of international normalized ratios. We estimated the overall relative and absolute risks of events specific to anticoagulation intensity.

Results

We included 19 studies. The risk of hemorrhage increased significantly at high international normalized ratios. Compared with the therapeutic ratio of 2–3, the relative risk (RR) of hemorrhage (and 95% confidence intervals [CIs]) were 2.7 (1.8–3.9; p < 0.01) at a ratio of 3–5 and 21.8 (12.1–39.4; p < 0.01) at a ratio greater than 5. The risk of thromboemboli increased significantly at ratios less than 2, with a relative risk of 3.5 (95% CI 2.8–4.4; p < 0.01). The risk of hemorrhagic or thromboembolic events was lower at ratios of 3–5 (RR 1.8, 95% CI 1.2–2.6) than at ratios of less than 2 (RR 2.4, 95% CI 1.9–3.1; p = 0.10). We found that a ratio of 2–3 had the lowest absolute risk (AR) of events (AR 4.3%/yr, 95% CI 3.0%–6.3%).

Conclusions

The risks of hemorrhage and thromboemboli are minimized at international normalized ratios of 2–3. Ratios that are moderately higher than this therapeutic range appear safe and more effective than subtherapeutic ratios.Oral anticoagulant therapy is essential for the treatment and prevention of many thromboembolic disorders. Since anticoagulants can cause serious adverse events,^1–3 physicians monitor the international normalized ratios of patients taking these drugs to ensure that their ratios fall within a target range.An international normalized ratio of 2–3 is the most common target range. Results of previous studies revealed an increased risk of bleeding among patients whose ratios exceeded 4, an increased risk of stroke among patients whose ratios were 1.5–2 and a decreased risk of stroke at a ratio of 2.4.^4,5 However, the evidence supporting the range of 2–3 has some deficiencies. We sought to determine whether the risk of hemorrhagic and thromboembolic events is minimized at an international normalized ratio of 2–3 among patients taking anticoagulants. In addition, it has been observed that patients spend more time with a ratio below 2 than above 3.^6,7 The impact of such systematic underanticoagulation on patient outcomes is unknown. We sought to determine the effect of under-or overanticoagulation on the risk of thromboemboli and hemorrhage.     

Ecological separation in a polymorphic terrestrial salamander

1. When studying speciation, researchers commonly examine reproductive isolation in recently diverged populations. Polymorphic species provide an opportunity to examine the role of reproductive isolation in populations that may be in the process of divergence. 2. We examined a polymorphic population of Plethodon cinereus (red-backed salamanders) for evidence of sympatric ecological separation by colour morphology. Recent studies have correlated temperature and climate with colour morphology in this species, but no studies have looked at differences in diet or mate choice between colour morphs. We used artificial cover objects to assess salamander diet, mating preference and surface activity over a 2-year period at a field site in north-eastern Ohio. 3. We detected differences in diet between two colour morphs, striped and unstriped. The diets of striped individuals were significantly more diverse and were made up of more profitable prey than the diets of unstriped salamanders. 4. Opposite sex pairs were made up of individuals of the same colour morph and striped males were found more often with larger females than were unstriped males. 5. We corroborate findings of earlier studies suggesting that the unstriped form is adapted to warmer conditions. Unstriped individuals were the first to withdraw from the forest floor as temperatures fell in the late fall. We found no evidence that the colour morphs responded differently to abiotic factors such as soil moisture and relative humidity, and responses to surface temperatures were also equivocal. 6. We conclude that the two colour morphs exhibit some degree of ecological separation and tend to mate assortatively, but are unlikely to be undergoing divergence given the observed frequency of intermorph pairings.