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Hypoxic vasodilation
Başlık:
Hypoxic vasodilation
Yazar:
Ebeigbe, Anthony B., author.
ISBN:
9780438057333
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (193 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: Sheila Jennett.
Özet:
Responses of isolated blood vessels from different systemic sites to hypoxia have been studied to find out if a direct effect of hypoxia on the smooth muscle cell may provide an explanation for in vivo hypoxic vasodilatation. The vessels studied were rat portal, rabbit ear artery, rabbit common carotid artery and rabbit aorta. Mechanical, 45 calcium uptake, ultrastructural, and histochemical studies have been carried out. Mechanical studies were on vessel strips suspended in a 5ml bath of krebs solution, under an initial load of 500 - 1000 mg and bubbled alternatively with normoxic or hypoxic gas mixtures. Strips were stimulated with either noradrenaline or KCL. Portal vein and ear artery strips responded with similar rapidities to PO2 changes, though the magnitude of responses was greater in portal vein. Aortic and carotid artery strips relaxed less to hypoxia, and much more slowly too. Carotid artery strips often showed paradoxical responses. Preliminary exposure (for 1 - 2 hours) to hyperoxia diminished hypoxic relaxations in all strips from different sites. The speed of relaxation to cyanide was similar for all strips from different sites. Additional relaxations to hypoxia were still observed after maximal CN- effect. Relaxations to hypoxia, following iodoacetic acid (IAA) - treatment, was only partially reversed (Ear Artery), or not reversed (Portal Vein) by reoxygenation. The time course of relaxation to hypoxia of strips from i any given site, was similar to their respective time course of I relaxation to calcium removal. Thus, a similar mechanism may operate in both cases. The effect of hypoxia on 45calcium movement in aortic smooth muscle was studied using the "Lanthanum-Method". Results showed that hypoxia increased uptake in unstimulated specimens, but decreased uptake in Noradrenaline- and K+-stimulated specimens. Ultrastructural studies were carried out on spontaneously contracting rat portal veins. Changes observed in hypoxic specimens compared with normoxic ones are: Increase in number of Surface Vesicles (SV) per unit membrane length; decrease in number of cell-to-cell contracts per unit membrane length; enlargement of mitochondria; more frequent occurence of SRPSV - Mitochondria association; and loss of intramitochondrial granules. The loss of intramitochondrial granules suggests redistribution of calcium in hypoxia. Histochemical estimation of glycogen in normoxic and hypoxic (30 min. duration) portal veins, showed significant decrease in hypoxia, suggesting a possible mobilization of glycolytic energy reserve in hypoxia.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684592.1) | 684592-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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