Behavioural flexibility in migratory behaviour in a long-lived large herbivore.

Migratory animals are predicted to enhance lifetime fitness by obtaining higher quality forage and/or reducing predation risk compared to non-migratory conspecifics. Despite evidence for behavioural flexibility in other taxa, previous research on large mammals has often assumed that migratory behaviour is a fixed behavioural trait. Migratory behaviour may be plastic for many species, although few studies have tested for individual-level flexibility using long-term monitoring of marked individuals, especially in large mammals such as ungulates. We tested variability in individual migratory behaviour using a 10-year telemetry data set of 223 adult female elk (Cervus elaphus) in the partially migratory Ya Ha Tinda population in Alberta, Canada. We used net squared displacement (NSD) to classify migratory strategy for each individual elk-year. Individuals switched between migrant and resident strategies at a mean rate of 15% per year, and migrants were more likely to switch than residents. We then tested how extrinsic (climate, elk/wolf abundance) and intrinsic (age) factors affected the probability of migrating, and, secondly, the decision to switch between migratory strategies. Over 630 individual elk-years, the probability of an individual elk migrating increased following a severe winter, in years of higher wolf abundance, and with increasing age. At an individual elk level, we observed 148 switching events of 430 possible transitions in elk monitored at least 2 years. We found switching was density-dependent, where migrants switched to a resident strategy at low elk abundance, but residents switched more to a migrant strategy at high elk abundance. Precipitation during the previous summer had a weak carryover effect, with migrants switching slightly more following wetter summers, whereas residents showed the opposite pattern. Older migrant elk rarely switched, whereas resident elk switched more frequently to migrate at older ages. Our results show migratory behaviour in ungulates is an individually variable trait that can respond to intrinsic, environmental and density-dependent forces. Different strategies had opposing responses to density-dependent and intrinsic drivers, providing a stabilizing mechanism for the maintenance of partial migration and demographic fitness in this population.

Dynamic breast MRI in the course of neoadjuvant chemotherapy: standardized evaluation of tumor size and enhancement parameters in correlation to different histopathologic characteristics.

RATIONALE AND OBJECTIVES: Basic exploratory data analysis to evaluate enhancement and tumor size (SIZE) in contrast-enhanced breast magnetic resonance imaging (CE-MRI) during chemotherapy. Correlation with histopathology (human epidermal growth factor receptor (HER2/neu) status and estrogen receptor (ER) score). MATERIALS AND METHODS: Sixty-five women (mean age 47 +/- 10 years) with locally advanced breast cancer (mean SIZE 25 mL) had CE-MRI (three-dimensional fast low angle shot (FLASH); repetition time = 9.1 ms, echo time = 4.8 ms, flip angle (FA) 25 degrees, matrix size 256 x 256 pixels, field of view 350 mm, slice thickness 2 mm, number of slices = 32, one precontrast and five postcontrast series) before and after chemotherapy. Lesion segmentation and subsequent SIZE and enhancement analysis including maximum enhancement (MAX), area under the curve (AUC), time-to-peak (TTP), and maximum upslope (MUS) were performed. Correlation with histopathology (ER score and HER2/neu status). RESULTS: SIZE reduced significantly during therapy (25 mL vs. 5 mL, P < .0001). AUC, MAX, MUS decreased (P < .0001), TTP increased (P < .0001). SIZE and MAX were independent parameters (r(2) = .22). No correlation (P > .01) in any of the parameters with either ER score or HER2/neu status was found. HER2/neu score equal 2+pos. or 3+ showed significantly stronger changes in SIZE (P < .01), MAX (P < .01) and AUC (P < .05) compared to lower HER2/neu score (0 to 2+neg.). CONCLUSIONS: From routine MRI protocol and semiquantitative analysis of signal enhancement curves, information about size, and hemodynamic status of tumors under treatment may be extracted. Reduction in size and maximum enhancement were complementary parameters. In the course of therapy, size and enhancement may develop differently in clinically relevant histopathological subgroups.

Regeneration of the donor side after autogenous fibula transplantation in 53 patients: evaluation by dual x-ray absorptiometry.

We determined the degree of fibular regeneration at the donor site, using radiographs and dual x-ray absorptiometry, in 53 patients who underwent autogenous nonvascularized fibular transplantation for tumor reconstruction in long bones (mean follow-up 15 (3-26) years). Logistic regression was used to determine whether gender, age at transplantation, time since transplantation, bone mineral density (BMD), and length of the graft were associated with fibular regeneration. 26 patients had spontaneous complete bone regeneration. Younger age at transplant was the only predictor of fibular regeneration. In predicting fibular regeneration, sensitivity was 96% and specificity 74%, using 15 years of age as a cut-off. In the long-term follow-up, we found only gradual changes in the BMD and the values ranged from 24% to 217%. We found no correlations of bone mineral density with age, gender, length of the graft, or time since transplantation.