Cerebrovascular mental stress reactivity is impaired in hypertension

<p>Abstract</p> <p>Background</p> <p>Brachial artery reactivity in response to shear stress is altered in subjects with hypertension. Since endothelial dysfunction is generalized, we hypothesized that carotid artery (CA) reactivity would also be altered in hypertension.</p> <p>Purpose</p> <p>To compare (CA endothelium-dependent vasodilation in response to mental stress in normal and hypertensive subjects.</p> <p>Methods</p> <p>We evaluated CA reactivity to mental stress in 10 young healthy human volunteers (aged 23 ± 4 years), 20 older healthy volunteers (aged 49 ± 11 years) and in 28 patients with essential hypertension (aged 51 ± 13 years). In 10 healthy volunteers and 12 hypertensive subjects, middle cerebral artery (MCA) PW transcranial Doppler was performed before and 3 minutes after mental stress.</p> <p>Results</p> <p>Mental stress by Stroop color word conflict, math or anger recall tests caused CA vasodilation in young healthy subjects (0.61 ± 0.06 to 0.65 ± 0.07 cm, p < 0.05) and in older healthy subjects (0.63 ± 0.06 to 0.66 ± 0.07 cm, p < 0.05), whereas no CA vasodilation occurred in hypertensive subjects (0.69 ± 0.06 to 0.68 ± 0.07 cm; p, NS). CA blood flow in response to mental stress increased in young healthy subjects (419 ± 134 to 541 ± 209 ml, p < 0.01 vs. baseline) and in older healthy subjects (351 ± 114 to 454 ± 136 ml, p < 0.01 vs. baseline) whereas no change in blood flow (444 ± 143 vs. 458 ± 195 ml; p, 0.59) occurred in hypertensive subjects. There was no difference in the CA response to nitroglycerin in healthy and hypertensive subjects. Mental stress caused a significant increase in baseline to peak MCA systolic (84 ± 22 to 95 ± 22 cm/s, p < 0.05), diastolic (42 ± 12 to 49 ± 14 cm/s, p < 0.05) as well as mean (30 ± 13 to 39 ± 13 cm/s, p < 0.05) PW Doppler velocities in normal subjects, whereas no change in systolic (70 ± 18 to 73 ± 22 cm/s, p < 0.05), diastolic (34 ± 14 to 37 ± 14 cm/s, p = ns) or mean velocities (25 ± 9 to 26 ± 9 cm/s, p = ns) occurred in hypertensive subjects, despite a similar increase in heart rate and blood pressure in response to mental stress in both groups.</p> <p>Conclusion</p> <p>Mental stress produces CA vasodilation and is accompanied by an increase in CA and MCA blood flow in healthy subjects. This mental stress induced CA vasodilation and flow reserve is attenuated in subjects with hypertension and may reflect cerebral vascular endothelial dysfunction. Assessment of mental stress induced CA reactivity by ultrasound is a novel method for assessing the impact of hypertension on cerebrovascular endothelial function and blood flow reserve.</p

Nucleation and crystallization in bio-based immiscible polyester blends

Bio-based thermoplastic polyesters are highly promising materials as they combine interesting thermal and physical properties and in many cases biodegradability. However, sometimes the best property balance can only be achieved by blending in order to improve barrier properties, biodegradability or mechanical properties. Nucleation, crystallization and morphology are key factors that can dominate all these properties in crystallizable biobased polyesters. Therefore, their understanding, prediction and tailoring is essential. In this work, after a brief introduction about immiscible polymer blends, we summarize the crystallization behavior of the most important bio-based (and immiscible) polyester blends, considering examples of double-crystalline components. Even though in some specific blends (e.g., polylactide/polycaprolactone) many efforts have been made to understand the influence of blending on the nucleation, crystallization and morphology of the parent components, there are still many points that have yet to be understood. In the case of other immiscible polyester blends systems, the literature is scarce, opening up opportunities in this environmentally important research topic.The authors would like to acknowledge funding by the BIODEST project ((RISE) H2020-MSCA-RISE-2017-778092

The spatial structure of lithic landscapes : the late holocene record of east-central Argentina as a case study

Fil: Barrientos, Gustavo. División Antropología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Catella, Luciana. División Arqueología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Oliva, Fernando. Centro Estudios Arqueológicos Regionales. Facultad de Humanidades y Artes. Universidad Nacional de Rosario; Argentin