PubMed · 5379126
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A Naszlady, L Kiss. 1969. Haemodynamic analogue computer model.. https://pubmed.ncbi.nlm.nih.gov/5379126/
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Adaptation of saphenous vein to the hemodynamic stresses of the arterial circulation is critical to the maturation of vein bypass grafts. We have investigated early adaptive responses of venous endothelium by placing excised human saphenous vein in a bypass circuit with either venous or arterial flow conditions, using external stenting to resolve the effects of longitudinal (shear) from circumferential stress. Endothelial protein concentrations were assessed by immunostaining area (ratio of protein/CD31) and Western blotting of endothelial cell lysates (staining ratio protein/vWf). In both unstented and stented veins nitric oxide synthase increased after 90 min of arterial flow: twofold increase of immunostaining area (P = 0.001), four- to fivefold increase by Western blotting (P = 0.02), and increased A23187mediated maximum endothelium-dependent relaxation of vein rings (P = 0.01). In unstented veins, ICAM-1 concentration was increased after 45 min of arterial flow: twofold increase by immunostaining (P = 0.001) and Western blotting (P = 0.038), with maximum fibrinogen-mediated endothelium-dependent relaxation increasing from 55.9+/-4.9 to 97+/-2.1% (P = 0.01). In contrast, in unstented veins there was a threefold decrease of VCAM-1 and no change in P-selectin after arterial flow for 45 and 90 min, respectively. However, no changes in ICAM-1 and VCAM-1 were observed in stented veins. The flow-induced alterations in nitric oxide synthase, ICAM-1, and VCAM-1 were abolished when 3 mM tetraethylammonium ion (K+ channel blocker) was included in the vein perfusate. The very rapid changes in ICAM-1 and VCAM-1 expression are a response to circumferential stress, whereas the slower upregulation of nitric oxide synthase is a response to longitudinal (shear) stress. Similar changes could influence the adhesiveness of endothelium in newly implanted saphenous vein bypass grafts.
The aim of this study was to evaluate the role of uterine artery Doppler velocimetry performed at 20 and 24 weeks gestation in predicting gestational hypertension and small-for-gestational age babies in a population of nulliparous women. Four hundred and fifty-six patients without risk factors for pregnancy complications and with fetuses free from structural abnormalities at ultrasonographic examination at 20 weeks gestation were considered in the study. During the routine 20 weeks ultrasound a continuous-wave Doppler examination of the uterine arteries was performed. The patients with abnormal uterine Resistance Index (RI) repeated the Doppler evaluation at 24 weeks by means of Colour Doppler equipment. Among the 419 women who completed the study an abnormal Doppler uterine arteries velocimetry was found in 8.6% of the patients. Pregnancy complications (gestational hypertension and/or small-for-gestational age babies) were observed in 56% of the patients presenting high uteroplacental RI versus 10% of those with normal uterine artery velocimetry (P = 0.0001). In the group of patients with an abnormal RI value, the presence of a diastolic notch in one or both of the uterine arteries identified a population of pregnant women at higher risk for pregnancy complications when compared with patients without notch (78% vs. 33%, P = 0.007). The knowledge of the uteroplacental resistance can help in identifying a subgroup of patients at higher risk of hypertensive disorders and small-for-gestational age babies that could benefit from prophylaxis with low dose aspirin.
Oxygen transport capacity is the most important determinant of maximum oxygen uptake (V(O2) max) in healthy subjects, however, its role is controversial in patients with chronic heart failure (CHF). The aim of this study was to clarify whether the oxygen transport capacity is an actual determinant of exercise capacity in CHF patients. Thirteen CHF patients underwent two maximum exercise tests, i.e., a graded protocol test and a fixed protocol test, measuring expiratory gases, leg blood flow (LBF), and arterial and venous blood gases. The workload of the fixed protocol was set to exceed the peak workload obtained by the graded protocol. Exercise with the fixed protocol caused significantly larger peak V(O2) compared to the graded protocol (813+/-194 to 971+/-203 ml/min, P<0.001). Peak LBF increased by 17%, while the peak leg arterio-venous oxygen difference increased by 5% from the graded protocol to the fixed protocol. The linear correlation between leg venous partial oxygen pressure and peak V(O2) was more clearly manifested in the fixed protocol (r=0.60, P<0.05) than in the graded protocol (r=0.47, NS). In conclusion, the exercise with graded protocol did not always conduct the upper limit of oxygen demand/supply relationship in CHF patients, whereas, the fixed protocol with a larger workload produced larger peak V(O2) and manifested the mechanism to limit V(O2) by oxygen transport capacity.