Cardiac Rhythms and Variation in Hibernating Arctic Ground Squirrels.

AbstractThe dramatic decrease in heart rate (HR) during entrance into hibernation is not a mere response to the lowering of core body temperature (Tb) but a highly regulated fall, as the decrease in HR precedes the drop in Tb. This regulated fall in HR is thought to be mediated by increased cardiac parasympathetic activity. Conversely, the sympathetic nervous system is thought to drive the increase of HR during arousal. Despite this general understanding, we lack temporal information on cardiac parasympathetic regulation throughout a complete hibernation bout. The goal of this study was to fill this gap in knowledge by using Arctic ground squirrels implanted with electrocardiogram/temperature telemetry transmitters. Short-term HR variability (root mean square of successive differences [RMSSD]), an indirect measure of cardiac parasympathetic regulation, was calculated in 11 Arctic ground squirrels. RMSSD, normalized as RMSSD/RR interval (RRI), increased fourfold during early entrance (from 0.2±0.1 to 0.8±0.2, P<0.05). RMSSD/RRI peaked after HR dropped by over 90% and Tb fell by 70%. Late entrance was delineated by a decline in RMSSD/RRI while Tb continued to decrease. During arousal, HR started to increase 2 h before Tb, with a concurrent decrease in RMSSD/RRI to a new minimum. As Tb increased to a maximum during interbout arousal, HR declined, and RMSSD/RRI increased. These data suggest that activation of the parasympathetic nervous system initiates and regulates the HR decrease during entrance into hibernation and that withdrawal of parasympathetic activation initiates arousal. We conclude that cardiac parasympathetic regulation persists throughout all phases of a hibernation bout-a feature of the autonomic nervous system's regulation of hibernation that was not appreciated previously.

Circulating adipose stromal cells as a response biomarker in phase II energy balance trials of obese breast cancer survivors and high-risk women.

PURPOSE: Circulating adipose stromal cells (CASC) are thought to be increased in obesity and facilitate angiogenesis, and tumor metastases. METHODS: CASC were identified from buffy coat peripheral blood mononuclear cells (PBMCs) by flow cytometry as CD34brightCD31- CD45- and CASC frequency was compared to adiposity measures in 33 women at increased risk for breast cancer. Feasibility of CASC as a response biomarker for a diet and exercise intervention in ten breast cancer survivors was then explored. RESULTS: For 33 high-risk women, median CASC frequency was 9.7 per million PBMCs and trended positively with body mass index, fat mass index (FMI), and percent android fat. Correlation was significant when BMI was dichotomized at > versus < 35 kg/m2 (p = 0.02). For ten breast cancer survivors with a median BMI of 37 kg/m2, median CASC frequency was 16.4 per million PBMCs. In univariate analyses, change in BMI, total fat and visceral fat were significantly correlated with change in CASC frequency. On multivariate analysis, change in visceral adipose had the strongest association with change in CASC frequency (p < 0.00078). CONCLUSIONS: The association between the reduction in visceral adipose tissue and the decrease in frequency of circulating adipose stromal cells suggests that the latter might be a useful biomarker in clinical trials of obese breast cancer survivors undergoing a weight loss intervention.

Application of risk factors for venous thromboembolism in patients with multiple myeloma starting chemotherapy, a real-world evaluation.

INTRODUCTION: Within the first year of diagnosis, up to 1 in 3 multiple myeloma (MM) patients will experience a venous thromboembolism (VTE). The International Myeloma Working Group (IMWG) has thromboprophylaxis guidelines that stratify patients into low or high risk for thrombosis and subsequently recommend thromboprophylaxis, but it is unknown if these recommendations are being followed or if they are effective. The purpose of this study was to assess efficacy of the IMWG guidelines and investigate other potential VTE risk factors. METHODS: Study participants were treated at the University of Kansas Medical Center between 2007 and 2013, and charts were reviewed to extract data. Cases (MM and VTE) were matched to controls (MM and no VTE) at approximately 1:3 ratio based on gender, age (±5 years), and time of MM diagnosis (±5 years). RESULTS: A total of 80 cases and 211 controls were matched. Most patients (82%) were considered high risk for experiencing a VTE at the time of their MM diagnosis and 18% were considered low risk. Neither risk category (P = 0.16) nor thromboprophylaxis at baseline (P = 0.37) predicted VTE, though cases were more likely than controls to have an increased risk of thrombosis at the time of clot compared to their baseline risk (P = 0.09). CONCLUSION: Our results suggest that IMWG guidelines are not being consistently followed and therefore could not be validated. Additional risk factors were not identified, but risk for VTE may change over time suggesting patients may require ongoing assessment of VTE risk and thromboprophylaxis throughout the disease course.