The Effects of Heatwaves on Human Morbidity in Primary Care Settings: A Case-Crossover Study

Purpose: This study assesses the potential acute effects of heatwaves on human morbidities in primary care settings. Methods: We performed a time-stratified case-crossover study to assess the acute effects of heatwaves on selected morbidities in primary care settings in Flanders, Belgium, between 2000 and 2015. We used conditional logistic regression models. We assessed the effect of heatwaves on the day of the event (lag 0) and X days earlier (lags 1 to X). The associations are presented as Incidence Density Ratios (IDR). Results: We included 22,344 events. Heatwaves are associated with increased heat-related morbidities such as heat stroke IDR 3.93 [2.94–5.26] at lag 0, dehydration IDR 3.93 [2.94–5.26] at lag 1, and orthostatic hypotension IDR 2.06 [1.37–3.10] at lag 1. For cardiovascular morbidities studied, there was only an increased risk of stroke at lag 3 IDR 1.45 [1.04–2.03]. There is no significant association with myocardial ischemia/infarction or arrhythmia. Heatwaves are associated with decreased respiratory infection risk. The IDR for upper respiratory infections is 0.82 [0.78–0.87] lag 1 and lower respiratory infections (LRI) is 0.82 [0.74–0.91] at lag 1. There was no significant effect modification by age or premorbid chronic disease (diabetes, hypertesnsion). Conclusion: Heatwaves are associated with increased heat-related morbidities and decreased respiratory infection risk. The study of heatwaves’ effects in primary care settings helps evaluate the impact of heatwaves on the general population. Primary care settings might be not suitable to study acute life-threatening morbidities.

Extracellular Vesicles Derived from Bone Marrow in an Early Stage of Ionizing Radiation Damage Are Able to Induce Bystander Responses in the Bone Marrow

Ionizing radiation (IR)-induced bystander effects contribute to biological responses to radiation, and extracellular vesicles (EVs) play important roles in mediating these effects. In this study we investigated the role of bone marrow (BM)-derived EVs in the bystander transfer of radiation damage. Mice were irradiated with 0.1Gy, 0.25Gy and 2Gy, EVs were extracted from the BM supernatant 24 h or 3 months after irradiation and injected into bystander mice. Acute effects on directly irradiated or EV-treated mice were investigated after 4 and 24 h, while late effects were investigated 3 months after treatment. The acute effects of EVs on the hematopoietic stem and progenitor cell pools were similar to direct irradiation effects and persisted for up to 3 months, with the hematopoietic stem cells showing the strongest bystander responses. EVs isolated 3 months after irradiation elicited no bystander responses. The level of seven microRNAs (miR-33a-3p, miR-140-3p, miR-152-3p, miR-199a-5p, miR-200c-5p, miR-375-3p and miR-669o-5p) was altered in the EVs isolated 24 hour but not 3 months after irradiation. They regulated pathways highly relevant for the cellular response to IR, indicating their role in EV-mediated bystander responses. In conclusion, we showed that only EVs from an early stage of radiation damage could transmit IR-induced bystander effects.

Acute Effects of Nicotine on Physiological Responses and Sport Performance in Healthy Baseball Players

There is interest in whether nicotine could enhance attention in sporting performance, but evidence on the acute effect of nicotine on physical response and sports performance in baseball players remains scant. This was an observational study to examine whether nicotine gum chewed before exercise could provide acute effects on physiological responses and sport performance. Accordingly, heart rate variability (HRV), saliva cotinine concentration and α-amylase activity, cognitive function, muscle strength, and baseball-hitting performance were measured. Thirteen healthy male non-smoker baseball players were recruited. Conducting two sequences with 7-day intervals, they chewed nicotine gum (nicotine group) or flavor-matched placebo gum (placebo group) for 30 min. HRV and saliva analyses were conducted before gum consumption (S1), after gum consumption (S2), and after test completion (S3). Cognitive, muscle strength, and baseball-hitting performance tests were performed after nicotine or placebo gum chewing. The outcomes of all assessed variables were compared within and between the groups. Significant changes in HRV, α-amylase, testosterone, and cortisol were observed in the nicotine group at S2 and S3 (p < 0.05). Compared with the placebo group, the nicotine group exhibited enhanced motor reaction times, grooved pegboard test (GPT) results on cognitive function, and baseball-hitting performance, and small effect sizes were noted (d = 0.47, 0.46 and 0.41, respectively). Nicotine could induce changes in endocrine and sympathetic nerve activity and enhance cognitive function and baseball-hitting performance. However, no increase in muscle strength was observed after nicotine intake.

Impact of High-Dose Irradiation on Human iPSC-Derived Cardiomyocytes Using Multi-Electrode Arrays: Implications for the Antiarrhythmic Effects of Cardiac Radioablation

Cardiac radioablation is emerging as an alternative option for refractory ventricular arrhythmias. However, the immediate acute effect of high-dose irradiation on human cardiomyocytes remains poorly known. We measured the electrical activities of human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) upon irradiation with 0, 20, 25, 30, 40, and 50 Gy using a multi-electrode array, and cardiomyocyte function gene levels were evaluated. iPSC-CMs showed to recover their electrophysiological activities (total active electrode, spike amplitude and slope, and corrected field potential duration) within 3–6 h from the acute effects of high-dose irradiation. The beat rate immediately increased until 3 h after irradiation, but it steadily decreased afterward. Conduction velocity slowed in cells irradiated with ≥25 Gy until 6–12 h and recovered within 24 h; notably, 20 and 25 Gy-treated groups showed subsequent continuous increase. At day 7 post-irradiation, except for cTnT, cardiomyocyte function gene levels increased with increasing irradiation dose, but uniquely peaked at 25–30 Gy. Altogether, high-dose irradiation immediately and reversibly modifies the electrical conduction of cardiomyocytes. Thus, compensatory mechanisms at the cellular level may be activated after the high-dose irradiation acute effects, thereby, contributing to the immediate antiarrhythmic outcome of cardiac radioablation for refractory ventricular arrhythmias.