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- Wallin, Gunnar B, 1936, et al.
(författare)
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Two neural mechanisms for respiration-induced cutaneous vasodilatation in humans?
- 1998
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Ingår i: The Journal of physiology. - : Wiley. - 0022-3751. ; 513 ( Pt 2), s. 559-69
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Tidskriftsartikel (refereegranskat)abstract
- 1. In humans, a deep breath is known to induce cutaneous vasoconstriction in the warm state, and vasodilatation in the cold state. To investigate whether vasodilatation in the cold state is related to reduction of sympathetic vasoconstrictor nerve traffic, we studied the effect of a deep breath on vascular resistance in a skin area on the dorsum of the hand, in which release of noradrenaline from sympathetic nerves was blocked by iontophoretic pretreatment with bretylium tosylate. Simultaneous measurements were made in two control areas. In eight healthy subjects, data were obtained from deep breaths taken before bretylium in the warm state, after general cooling to a finger skin temperature below 25 C and after rewarming to above 32 C. 2. In the warm state before bretylium pretreatment, the deep breath evoked short-lasting vasoconstrictions at all sites. In the cold state there was no change of vascular resistance in the bretylium-pretreated area, whereas in the control areas an initial tendency towards vasoconstriction was followed by a significant transient vasodilatation. After rewarming, transient vasoconstrictions reappeared at the control sites, whereas only a transient vasodilatation occurred at the bretylium-pretreated site. 3. In six healthy subjects we also monitored the effects of a deep breath on skin sympathetic nerve activity (recorded by microneurography in the peroneal nerve), and skin vascular resistance within the innervation zone of the impaled nerve fascicle in the foot. Data from thirty deep breaths per subject were averaged. 4. In the cold state, the deep breath induced a strong increase in neural discharge, followed by a transient reduction of nerve traffic lasting approximately 15 s and associated with a subsequent reduction of vascular resistance. 5. We conclude that the deep breath-induced vasodilatation in the cold state is due to reduction of sympathetic vasoconstrictor nerve traffic. The vasodilatation after bretylium treatment in the warm state raises the possibility that a deep breath induces two simultaneous neural reactions, a vasoconstrictor and an active vasodilator component, the latter being weaker and normally masked by the strong vasoconstrictor component.
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- Rafael, E, et al.
(författare)
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Longitudinal studies on the microcirculation around the TheraCyte immunoisolation device, using the laser Doppler technique
- 2000
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Ingår i: Cell transplantation. - : SAGE Publications. - 0963-6897 .- 1555-3892. ; 9:1, s. 107-113
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Tidskriftsartikel (refereegranskat)abstract
- Encapsulation of cellular grafts in an immunoisolation membrane device may make it possible to perform transplantation without having to give immunosuppressive drugs. A common problem is the development of an avascular fibrotic zone around the implants, leading to impaired graft survival. The TheraCyte™ macroencapsulation device has therefore been designed to facilitate neovascularization of the device's surface. In this study, we evaluated the microcirculation around empty TheraCyte™ devices implanted SC in rats at various times after implantation, using a laser Doppler probe introduced via the device port. Studies were performed on day 1 or at 1, 2, and 4 weeks or at 2, 3, and 12 months after implantation. The mean flow was 158 ± 42, 148 ± 50, 133 ± 28, 72 ± 17, 138 ± 41, 165 ± 43, and 160 ± 29 perfusion units (PU), respectively. Thus, the microcirculation around the device was significantly reduced at 4 weeks after implantation (p < 0.01) while, from 2 months onwards the circulation had improved and did not differ significantly from that on day 1. The present study shows time-related changes in the microcirculatory flow around TheraCyte™ macroencapsulation devices that agree with our previous microdialysis studies on in vivo exchange of insulin and glucose between the device and the circulation. Laser Doppler flowmetry seems to provide a reliable technique for screening blood perfusion around macroencapsulation devices.
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