Atrial natriuretic peptide decreases aorta stiffness in cholesterol-fed anesthetized rabbits

Aortas from Watanabe heritable hyperlipidemic rabbits show in vitro impaired vasodilatory response to atrial natriuretic peptide (ANP) during atherosclerosis progression. To test a similar reaction in vivo, the effect of ANP administration on pulse wave velocity (PWV, index of aorta stiffness) was investigated in 10 normal and 10 cholesterol-fed (2% cholesterol-loaded feeding for 4 weeks) anesthetized male New Zealand White (NZW) rabbits. Invasively taken carotid and femoral blood pressures (BP) were recorded, simultaneously with ECG, and blood samples for ANP measurement (by RIA) were taken at 0 min and 20, 40, 60 min following an intravenous 20-min administration of either 0.2 microg kg(-1)min(-1) hANP in 5 ml normal saline or only 5 ml saline. Mild to moderate atherosclerosis was found in ascending aorta. BP decreased by ANP only at 20 min in both groups, whereas only in cholesterol-fed rabbits the borderline (p=0.09) increased at 0 min PWV was lowered (p=0.008) in all recording times. With any degree of increase of systolic BP (SBP) PWV increased less in ANP receivers. Atherosclerosis and SBP were the most important determinants of PWV and the effect of ANP was independent of confounding factors. It is concluded that short-term ANP administration in doses to achieve levels approximately threefold the pretreatment ones in normal and mildly to moderately atherosclerotic anesthetized NZW rabbits, causes an improvement of aorta stiffness only in atherosclerotic rabbits.

Physical training in patients on hemodialysis has a beneficial effect on the levels of eicosanoid hormone-like substances

OBJECTIVE

The aim of this study was to evaluate the changes in the levels of vasoactive eicosanoid hormone-like substances PGE2, PGI2 and TXA2 in hemodialysis (HD)patients who were following a long-term physical training program during the hemodialysis session.

DESIGN

A total of 50 patients with Chronic Kidney Disease (CKD) (stage 5)on hemodialysis and 35 healthy individuals who served as controls (C) were evaluated. The 50 CKD patients were divided into two groups: the HD group consisted of 31 patients who received usual care without any physical activity during the hemodialysis sessions, while group HD/Exer included 19 patients who followed a program of physical exercise for six months. Plasma levels of PGE2, 6-Keto-PGF1alpha (the stable derivative of PGI2) and TXB2 (the stable derivative of TXA2) were measured by reliable enzymo-immunoassay methods (EIA) in HD and HD/Exer patients before and after the hemodialysis sessions as well as in the group of C.

RESULTS

The plasma levels of PGE2 and 6-keto-PGF1alpha in group HD Exer/before patients were higher than those in group HDbefore (20.39+/-5.82 and 1449.19+/-553.41 vs 17.68+/-5.36 and 1295.10+/-384.43 pg/ml, p=0.044 and p=0.067, respectively), while the plasma levels of TXB2 were lower in HD Exer/before patients compared to HDbefore(499.76+/-67.51 vs 608.01+/-80.23 pg/ml, p=0.041). The plasma levels of PGE2 and 6-keto-PGF1alpha in group HD Exer/after patients were significantly higher compared to those in HDafter patients (23.01+/-5.70 and 1618.19+/-435.07 vs 16.57+/-4.97 and 1005.44+/-317.16 pg/ml, p<0.001 and p<0.040, respectively). However, significantly lower values in the plasma levels of TXB2 in HD Exer/after compared to HDafter patients (363.10+/-51.91 vs 439.75+/-62.34 pg/ml, p=0.030) were detected. As expected, PGE2 and 6-keto-PGF1alpha values were lower in C than in the groups of patients with CKD.

CONCLUSIONS

The data indicate that exercise training during HD exerts a beneficial effect on the levels of the vasoactive eicosanoid hormone-like substances in patients on HD.

One heart, two bodies: a simulation study of body surface potential differences between donor and recipient of heart transplantation

In cardiac transplantation has been recognized some "abnormalities" in recipient ECG. We investigated the influence of heart geometrical position within the chest cavity as well as somatometric parameters on body surface torso potentials. Two control patients with different Body Mass Index (BMI) were undergone a chest MRI scan. Using specific software we created two tetrahedral meshes that could be applied in our study. A post-mortem human heart was undergone a MRI scan and we also created its tetrahedral mesh. Using second software we extracted the heart mesh of control's torsos and we replaced them with the mesh of the post-mortem heart. The last program also assessed the influence of heart (re)positioning within the thorax, on the body surface potentials. The Finite Elements Method (FEM) was used to solve the forward electrocardiographic problem for both torsos, under the assumption that all the ventricular myocardium of the one post-mortem heart was excited. FEM was also applied in simulating Body Surface Potential Mapping (BSPM) on the first thorax torso for nine different heart positions. For BSPM, FEM has been applied on Poison equation. The results show higher BSPM in patient with lower BMI and significant changes in BSPM when heart was rotated round its long axis. Conversely, the heart shifts (long x- or y- axis) didn't cause significant changes on simulated BSPM.

The combined action of exercise and methylprednisolone sodium succinate on the rat gastrocnemius muscle

1. Methylprednisolone sodium succinate (SM) administration reduces the amount of contractile proteins and increases the collagen in the rat gastrocnemius muscle; it also increases the muscle's isotonic contraction capacity. 2. Exercise in combination with SM treatment reduces this capacity and causes also further reductions of the contractile proteins and increases of collagen. 3. There are no changes of either the relative muscle weight or the number of acetylcholine receptors in any experimental group as compared to controls.