Changes in skin blood flow, respiration and blood pressure in participants reporting motion sickness during sinusoidal galvanic vestibular stimulation.

NEW FINDINGS: What is the central question of the study? We have previously shown that sinusoidal galvanic vestibular stimulation induces greater modulation of skin sympathetic nerve activity, but not muscle sympathetic nerve activity, in participants who report nausea during simulated motion, but the effects on skin blood flow and blood pressure are unknown. What is the main finding and its importance? During vestibular stimulation, nausea was associated with a greater increase in skin blood flow and a progressive reduction in skin sympathetic nerve activity, but no changes in muscle sympathetic nerve activity. This emphasizes the differential changes in sympathetic outflow to different tissues during nausea. ABSTRACT: We tested the hypothesis that galvanic vestibular stimulation, which produces illusions of side-to-side swaying, causes a greater reduction in skin blood flow in participants who report stimulation-induced nausea. A retrospective analysis was performed on data obtained in 30 participants. Bipolar sinusoidal galvanic vestibular stimulation (sGVS) was applied across the mastoid processes (±2 mA, 0.08 Hz) for 21 min. ECG, continuous blood pressure, respiration and skin blood flow were recorded. Muscle sympathetic nerve activity was recorded in 17 participants and skin sympathetic nerve activity in 12. Ten participants reported motion sickness, whereas 20 did not. Both groups showed an initial reduction in skin (finger) blood flow during sGVS, followed by a sustained increase and a subsequent return towards baseline levels throughout the stimulation; the increase was greater in those who experienced nausea. The increase fits with the progressive reduction in skin sympathetic nerve activity observed in the nauseous group. Mean blood pressure was significantly lower in those who experienced nausea and showed a much larger increase at the onset of sGVS, compared with those who did not. Moreover, the respiratory rate was higher at the outset for the subjects who experienced nausea, decreasing progressively during sGVS, whereas respiratory rate remained constant in those who did not experience nausea. Heart rate was more labile in the subjects who experienced nausea, showing a sustained increase towards the end of stimulation. We have shown that several autonomic parameters change during the nausea induced by vestibular stimulation, but a sustained decrease in skin blood flow is not a hallmark of incipient motion sickness.

Mosquito biodiversity and mosquito-borne viruses in the United Arab Emirates.

BACKGROUND: In the last 50 years, the United Arab Emirates (UAE) has experienced rapid population growth and urbanization. Urbanization is known to influence biodiversity, and there appears to be a link between the emergence of arboviruses and urban growth. Very little is known about the UAE mosquito species richness and dominant vectors. We performed a mosquito survey comparing peri-urban sites in Dubai and Al Ain to a protected, natural site in Fujairah emirate. We measured mosquito biodiversity and species composition, and screened mosquito pools for common arboviruses to measure arbovirus activity in the region. RESULTS: We report ten species of mosquitoes from the UAE, with highest species diversity in the natural site, a protected wadi near the eastern coast. The predominant mosquito was Culex perexiguus, and was associated with peri-urban habitats. The site with lowest mosquito species diversity but relatively high species richness was the peri-urban site of Al Ain Zoo, where we identified Bagaza virus and Barkedji virus, two flaviviruses, in pools of Cx. perexiguus. CONCLUSIONS: Decreased mosquito biodiversity was associated with increased levels of urbanization. The predominance of two species at peri-urban sites was related to the availability of their larval habitats. Arboviruses were associated with the presence of a single predominant mosquito species, Cx. perexiguus.