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Wearable Sensors for Blood Perfusion Monitoring in Patients with Diabetes Mellitus
Published in Andrey V. Dunaev, Valery V. Tuchin, Biomedical Photonics for Diabetes Research, 2023
Evgenii A. Zherebtsov, Elena V. Zharkikh, Yulia I. Loktionova, Angelina I. Zherebtsova, Viktor V. Sidorov, Alexander I. Krupatkin, Andrey V. Dunaev
The main topographic localization sites of the components of regulation of the tone of microvessels of the skin with AVAs are shown in Figure 5.5. As one can see, the oscillatory component of myogenic tone occurs in all muscle-containing microvessels, but, in the zone of precapillary sphincters and precapillaries, it is realized in a relatively “pure” form.
Baroreceptors: Morphology and Mechanics of Receptor Zones and Discharge Properties of Baroafferents*
Published in Irving H. Zucker, Joseph P. Gilmore, Reflex Control of the Circulation, 2020
This kind of hysteretic behavior is to be distinguished from that attributable to wall viscoelasticity merely for its slower time course. Its nature is poorly understood, but it perhaps results from changing myogenic tone (Bayliss, 1902; Peiper et al., 1974), i.e., the inherent property of vascular smooth muscle to constrict on passive stretch or to relax on stretch release. This is a nuisance experimentally since it destabilizes the pressure–volume curves of isolated arteries, which, as in Figure 1, are initially constricted but become more distended with successive stretch–retraction cycles until they finally stabilize when passive elastic behavior prevails (Wezler and Schlüter, 1953; Remington, 1962; Gow, 1972). Since a given pressure may be associated with various diameters, “setting” an isolated artery to the in vivo blood pressure does not ensure that the diameter associated with this “set pressure” would reflect the physiological working conditions for baroreceptors. As is suggested by Figure 1, the diameter of the intact carotid artery of dogs is close to that of the dilated state of the isolated vessel. Note also that this “muscular” artery narrows during the infusion of norepinephrine, but the elastic arteries of cat and humans do not. Thus, in vivo arteries normally operate at relatively large diameters and their response to vasomotor influences depends on species differences in wall architecture.
Structural Cardiovascular Changes in Hypertension
Published in Giuseppe Mancia, Guido Grassi, Konstantinos P. Tsioufis, Anna F. Dominiczak, Enrico Agabiti Rosei, Manual of Hypertension of the European Society of Hypertension, 2019
M. Mulvany, Enrico Agabiti Rosei, H. Struijker-Boudier
Izzard et al. (62) have reviewed the mechanisms of inward eutrophic remodelling of small arteries from essential hypertensive individuals. Their conclusion was that chronic vasoconstriction is the stimulus for a structural reduction in lumen diameter, a conclusion supported by more recent experimental studies (63). The nature of the contractile stimulus is still not fully resolved. Neural or humoral factors may be involved, although Izzard et al. (62) favour the myogenic properties of the small arteries as the underlying mechanism. The myogenic vasoconstriction could serve to maintain wall stress at constant value. Patients with type 2 diabetes show a severely impaired myogenic constriction to increases in intraluminal pressure. In these patients, impaired myogenic tone would increase wall stress and thereby promote small artery hypertrophy (62). The molecular pathways may include tissue transglutaminase (64,65) and ROS-activated MMP9 (66). Schiffrin and co-workers (67) have recently obtained evidence that low-grade inflammation plays an important role in small artery remodelling. In particular, activated T cells may contribute to vascular remodelling directly on blood vessels via effects of the cytokines produced or indirectly by actions on the kidney (67). Similar evidence for a role of angiotensin II type-1 receptor—mediated immune responses in the development of vascular changes in hypertension has been found (68).
Lumen narrowing and increased wall to lumen ratio of retinal microcirculation are valuable biomarkers of hypertension-mediated cardiac damage
Published in Blood Pressure, 2020
Edyta Dąbrowska, Joanna M. Harazny, Eliza Miszkowska-Nagórna, Adrian Stefański, Beata Graff, Katarzyna Kunicka, Ewa Świerblewska, Agnieszka Rojek, Anna Szyndler, Jacek Wolf, Marcin Gruchała, Roland E. Schmieder, Krzysztof Narkiewicz
The second explanation is that microvascular abnormalities of the retina occur in parallel and may be translated to microvascular changes in myocardium. Previous studies have delivered a large body of evidence that coronary and retinal circulations might share the same pathogenic process [39,40]. In response to elevated blood pressures, myogenic tone mediates in resistance vasculature structural changes such as lumen narrowing, wall thickening and then vasocontriction. Hence, myogenic tone plays a key role in blood flow autoregulation and stabilization of capillary pressure protecting from hypertensive injury of target organs [32,41,42]. However, in the course of chronically elevated blood pressures prolonged myogenic vasoconstriction may lead to impairment of vasodilator reserve and capillary rarefaction that both promote tissue hypoperfusion and finally impair organ function [32]. According to the studies showing that alterations in small resistance arteries may be present at the same time in different vascular districts [43,44], structural changes that occur in retinal microvasculature might be automatically expected in microvessels of myocardium, which is exceptionally susceptible to deleterious effect of ischemia.
The emerging significance of circadian rhythmicity in microvascular resistance
Published in Chronobiology International, 2022
Jeffrey T. Kroetsch, Darcy Lidington, Steffen-Sebastian Bolz
The diurnal rhythms in skeletal muscle and cerebral resistance arteries reasonably map to the relevant hemodynamic and perfusion measures. In this regard, skeletal muscle resistance arteries show low myogenic tone during the active phase and elevated tone in the rest phase, which aligns well with the TPR rhythm in non-anaesthetised rats (Figure 2; Smith et al. 1987). Likewise, cerebral artery myogenic tone reasonably maps to measures of cerebral perfusion (Figure 2); (Wauschkuhn et al. 2005). Collectively, these data suggest that the circadian modulation of a local mechanism, myogenic responsiveness, is the most efficient means to individually tailor the blood flow level for each organ.
Vitamin D deficiency and androgen excess result eutrophic remodeling and reduced myogenic adaptation in small cerebral arterioles in female rats
Published in Gynecological Endocrinology, 2019
Leila Hadjadj, Éva Pál, Anna Monori-Kiss, Réka Eszter Sziva, Ágnes Korsós-Novák, Eszter Mária Horváth, Rita Benkő, Attila Magyar, Péter Magyar, Zoltán Benyó, György L. Nádasy, Szabolcs Várbíró
Thickness of the tunica media was significantly reduced in both vitD deficient groups, compared to transdermal testosterone naïve, vitD supplemented group (Figure 5). This result correlates with the reduced myogenic tone detected in both vitD deficient groups.