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While haemoconcentration due to loss of plasma volume is well established during cycling, the existence of similar changes during running remains contentious. This study compared the changes in plasma volume and associated blood indices during 60 min of running and cycling at the same relative intensity (approximately 65% $$\dot VO_{2 max} $$ ), with all(More)
The present study examined the roles of the renin-angiotensin and autonomic nervous systems in cardiovascular homeostasis during slow progressive haemorrhage (20% of measured blood volume over 1h) in fetal (128-132 and 143-148 days gestation) and neonatal (5-9 and 12-20 days post-natal) sheep. Basal plasma renin activity (PRA) was not significantly(More)
1. The effects of vascular infusions of acetylcholine, angiotensin II, noradrenaline and prostaglandin F2 alpha on the baroreceptor reflex were studied in the anaesthetized greyhound. 2. Vertebral artery infusions of low doses of angiotensin II, but not of acetylcholine or prostaglandin F2 alpha, resulted in a significant reduction in the depressor response(More)
Cholecystokinin octapeptide (CCK-8) administered i.v. to urethane-anaesthetized rats or added to the perfusion stream of isolated rat hearts produced an immediate bradycardia. The size of this response was dose-related. Studies in vivo and in vitro using atropine and propranolol indicated that the response to CCK-8 was largely due to a direct action of the(More)
Blood volume has been measured in fetal and neonatal sheep using red blood cells labelled with 99mTc. The calculated volumes were highly correlated with simultaneous measurements made using the standard 51Cr labelled red cell method, although in absolute terms the 99m Tc method provided volumes which on average exceeded by a small percentage those(More)
In fetal and neonatal sheep intravenous injections of angiotensin I, angiotensin II and noradrenaline each increased mean blood pressure and decreased heart rate in a dose-dependent manner. Blood pressure responses to given doses of angiotensin I and II were larger in neonatal than fetal animals while the reverse was true for noradrenaline. In both sheep(More)
Intravenous injections of PGI2 (1.5-12 X 10(-5) nmol/ml blood volume) caused hypotensive responses which increased with dose in both fetal and neonatal sheep. In the fetus, as gestation advanced and basal heart rate declined, the predominant heart rate response to PGI2 changed progressively from bradycardia to tachycardia. In the neonate, PGI2 always(More)
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