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ACE inhibition has been shown to improve left ventricular (LV) and myocardial blood flow. Previous data regarding changes in capillary density and angiogenesis during ACE inhibition are controversial. The aim of the following study was to determine myocardial microcirculation and heart function in the rat after coronary stenosis using non invasive MR imaging techniques. MR spin labeling and cine techniques have been performed in female Wistar rats 2weeks after coronary artery stenosis. In one group, animals were treated with quinapril in a dose of 6mg/kg/day. Perfusion, relative blood volume (RBV), LV mass and function were determined non-invasively 2weeks after treatment. Finally, fibrosis and capillary density were analyzed histologically. Additionally, hemodynamic measurements were realized in a further group in order to calculate systemic vascular resistance (SVR). Quinapril resulted in a significant increase in perfusion at rest in the remote and the poststenotic myocardium with improved systolic function and a decrease in SVR compared to the non treated control group. Additionally, maximum perfusion and RBV were slightly elevated whereas capillary density was unchanged among the groups. MRI allows for non-invasive quantification of functional microcirculation and heart function. In addition to the well known effect of ACE inhibition on systolic function, treatment with the tissue specific ACE inhibitor quinapril revealed an important microvascular improvement, especially at arteriolar level. These findings may support the use of tissue ACE inhibitors to improve cardiac microcirculation after ischemia., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Objectives: Left ventricular (LV) remodeling after myocardial infarction (MI) is characterized by myocyte hypertrophy and a disproportional capillary growth. We developed a hypothetical model of capillary remodeling mechanisms based on quantitative data of microcirculation determined by magnetic resonance (MR) imaging techniques and histology., Methods: Perfusion and regional capillary blood volume (RBV) were quantified 8 and 16 weeks after MI (mean 27.0+/-2.9% of the left ventricle 16 weeks post MI) or sham operation in rats using MR imaging and were correlated with morphometric data., Results: Maximum perfusion (ml/(g min)) in the remote area decreased from 5.69+/-0.63 to 3.48+/-0.48 compared to sham animals (5.33+/-0.31, p

Changes in the microcirculation may compensate for the reduction of perfusion supplied by the stenotic vessel. The objective of this study was to determine functional adaptive processes in the microcirculation by magnetic resonance imaging (MRI) during coronary stenosis in the rat heart. Left coronary artery (LAD) narrowing (cross-sectional area 49.8 +/- 3.5%; n = 14) or sham operation (n = 10) was induced in rats. Myocardial perfusion and relative intracapillary blood volume (RBV) at rest and during vasodilatation 1 and 2 weeks after surgery were quantified using MRI. Coronary stenosis in vivo was verified by 3D MR angiography. Foci of fibrosis were found in the poststenotic myocardium. In this area, perfusion at rest was significantly reduced (1.79 +/- 0.11 ml/g/min, p < 0.001) despite a maintained perfusion reserve during adenosine (3.12 +/- 0.20 ml/g/min compared to the remote myocardium (3.07 +/- 0.12 and 5.24 +/- 0.24 ml/g/min, respectively) and the sham operated group (3.22 +/- 0.07 and 5.28 +/- 0.24 ml/g/min, respectively). Poststenotic RBV at rest (12.63 +/- 0.42 %) and during vasodilatation (22.42 +/- 0.81 %) were not significantly different (p > 0.05) from RBV of the remote myocardium (12.92 +/- 0.33 and 23.32 +/- 0.52 %, respectively). Coronary stenosis in the rat leads to foci of tissue injury with impaired perfusion at rest despite a partially maintained perfusion reserve distal to the stenosis. RBV remains constant in order to maintain blood supply. These functional changes reflect adaptive processes that may compensate for ischemic tissue loss.

Noninvasive characterization of microcirculation at the level of both coronary conductance and resistance vessels is of major importance for the understanding of microvascular adaptive processes in the heart. The objective of this study was to determine simultaneously myocardial perfusion and microvessel diameters in the myocardium by magnetic resonance (MR) imaging within the same heart. A MR imaging method is presented which combines high-resolution perfusion measurement (140 x 140 microm2) by spin labeling with flow-weighted MR microscopy of coronary microvessels (phi > 140 microm). We determined changes in myocardial perfusion and vessel diameters of isolated beating rat hearts (n = 10) at rest and during administration of nitroglycerin (0.5 mg/min). Alterations in perfusion were validated by microsphere measurements. Under the influence of nitroglycerin an increase in perfusion (+2.51 +/- 0.4 ml x min(-1) x g(-1), mean +/- SEM) and vessel diameters (+14.22 +/- 1.92%) could be observed. Endocardial perfusion revealed a modest enhanced susceptibility to nitroglycerin in comparison to epicardial perfusion. Analysis of vessels according to their diameters showed no significant differences. MR imaging allows the noninvasive and simultaneous determination of conducting arteries and smaller resistance vessels in one and the same beating rat heart. Due to an excellent spatial resolution of these methods, transmural characterization of both parameters at rest and during vasodilation is feasible., (Copyright 2001 Academic Press.)

Although the investigation of coronary microcirculation is of great importance, available methods have severe restrictions. They do not allow the study of vasodynamics of resistance vessels and microscopic conductance vessels simultaneously in the isolated beating rat heart. We now demonstrate that the combined measurement of perfusion which reflects the state of resistance vessels and cross-sections of microscopic conductance vessels is feasible in the model of the isolated constant flow perfused rat heart. Perfusion measurement was based on injection of coloured microspheres. Cross-sections of microscopic conductance vessels (diameter >140 micron) were determined by NMR-microscopy by flow weighted imaging. Both methods were established recently by our group. The combined measurement was applied to hearts which were subjected to ischaemia and reperfusion (group 1: n=5, 15 min ischaemia/group 2: n=7, 30 min ischaemia/measurements before ischaemia and 15/30 min after reperfusion), 200 pmol endothelin-1 bolus application (group 3: n=6/measurements before and 5 min after drug application), continuous infusion of the endothelin-1 antagonist BQ 610 (group 4: n=6/measurements before and 20 min after onset of infusion), and 200 pmol endothelin-1 application superimposed on 20 min of continuous BQ 610 infusion (group 5: n=7/combined measurement before BQ 610 infusion and 5 min after endothelin-1 application). In group 1, 15 min reperfusion restored the pre-ischaemic perfusion state, whereas conductance vessels were dilated (80.8+/-2.6%), after 30 min reperfusion pre-ischaemic conditions were also restored for conductance vessels. In group 2, a redistribution of perfusion from left ventricular endocardium to the right ventricular wall was observed. Post-ischaemic rhythm disturbances made NMR-imaging in this group impossible. In group 3, a shift of perfusion from the left ventricular myocardium to the right ventricular wall was observed. Similarly, the cross-section of left ventricular conductance vessels decreased (-32.6+/-2.1%), whereas size of right ventricular vessels increased. In group 4, BQ 610 had no effect on perfusion nor on vessel size and antagonized the effect of endothelin-1 on perfusion and vessel size in group 5., (Copyright 1997 Academic Press Limited.)

Myocardial perfusion measurement with colored microspheres may become an alternative for radioactive microsphere techniques. We use and validate a spectrophotometric method that has been previously established for large animals in the isolated perfused rat heart. The perfusion system was adapted for use in a NMR microscope. Hearts were perfused with constant coronary flow that was adjusted to a coronary perfusion pressure of 100 mmHg. Homogeneous coronary inflow of microspheres was represented by equal distribution of microspheres of two different colors after simultaneous injection. Mean regional myocardial blood flow was 17.76 +/- 5.01 ml/min/g, mean wet heart weight was 1.13 +/- 0.34 g and mean global flow was 20.06 +/- 0.60 ml/min. Heart rate was 296 +/- 8.9 beats/min and left ventricular pressure was similar 5 min before (149.1 +/- 14.27 mmHg) and after (147.1 +/- 13.49 mmHg) microsphere injection. Microspheres of four colors that were injected sequentially, at various coronary flows, demonstrated linearity and reproducibility of the technique. A cumulative use of less than 90 000 microspheres showed no effect on hemodynamics especially on left ventricular pressure.

The coronary vascular effect of atrial natriuretic peptide is controversial: Coronary vasodilator as well as constrictor effects have been reported. The controversy may originate from interference of atrial natriuretic peptide with the renin-angiotensin system and/or tachyphylaxis of the effect of atrial natriuretic peptide. The effect of alpha-human atrial natriuretic peptide bolus application on changes of coronary flow was examined in the isolated, constant-pressure perfused rat heart. Six groups were considered: (1) control group; groups in which the renin-angiotensin system was modulated by pretreatment with continuous infusion of: (2) angiotensin II, (3) the angiotensin converting enzyme inhibitor captopril (4) the angiotensin II receptor blocker saralasin; and groups in which tachyphylaxis was examined by pretreatment with ANP, (5) as continuous infusion and (6) as bolus application. First, in control hearts, dose-response curves were obtained for single ANP dosages of 1-100 nmol. The effect of high dosages (40 and 100 nmol) was biphasic, with an initial vasodilator and subsequent long-lasting vasoconstrictor component. Hearts in which coronary flow was reduced by approximately 18% through continuous angiotensin II infusion showed an enhanced early vasodilator response after ANP administration, whereas the vasoconstrictor effect was no longer observable. Angiotensin converting enzyme inhibition and angiotensin II receptor blockade reduced the vasodilator effect of ANP. In addition, saralasin nearly abolished ANP-induced vasoconstriction, whereas vasoconstriction was unaltered by pretreatment with captopril. Captopril or saralasin alone did not change coronary flow, heart rate and left ventricular developed pressure. In groups (5) and (6). ANP bolus application showed significantly reduced vasomotor activity. We conclude that in the isolated rat heart. ANP has a biphasic effect with early vasodilation and late vasoconstriction. Both effects can be modulated by inhibition of the renin-angiotensin system at different levels indicating that vasomotor ANP effects result from interaction of ANP with the local renin-angiotensin system. ANP effects can be markedly reduced by tachyphylaxis.

A major vaccinia virus core protein, designated VP8, has been purified from virions to homogeneity through DEAE-cellulose, CM-cellulose, and hydroxyapatite chromatography. VP8 migrates as a 25-kDa band in SDS-polyacrylamide gel electrophoresis and sediments as a monomeric species in neutral sucrose gradient centrifugation. This protein is a significant constitutent of the virion, comprising about 6.5% of the total viral polypeptides by mass. Analysis by filter binding and by sucrose gradient centrifugation shows that VP8 binds to double-stranded as well as to single-stranded DNA at low salt concentrations (25 mM NaCl). At higher salt concentrations (100 mM NaCl), the protein binds with a relatively greater affinity to single-stranded DNA. The results from sucrose gradient centrifugation indicate that VP8 probably binds noncooperatively to all structural forms of DNA. The protein is likely to be a component of the viral nucleoprotein complex.

We have obtained antiserum against highly purified vaccinia virus structural protein VP8, a major DNA binding protein present in the viral core particle. The antiserum has been used to monitor the course of the biosynthesis of this protein. The protein can first be detected in extracts of infected cells at 4 hr postinfection (p.i.). Its synthesis increases significantly at 5 hr p.i. and is maintained at about the same level up to 11 hr. The requirement of viral DNA replication for VP8 synthesis indicates that it is a viral late protein. This protein is synthesized in the form of a 28-kDa precursor, which is then processed to a 25-kDa product. The half-life of the precursor is about 2 hr. Comparing the N-terminal amino acid sequence of this purified protein with those derived from the published DNA sequence of the vaccinia viral genome [J.P. Weir and B. Moss (1984) J. Virol. 51, 662-669], it is found that VP8 maps to the HindIII L fragment of the viral genome. The cleavage site at which processing takes place lies between amino acids 32 (Gly) and 33 (Ala) from the N-terminal end of the precursor.

One of the major DNA binding proteins contained in vaccinia virus is an 11-kDA species denoted VP11. The biosynthesis of VP11, a late polypeptide, occurs subsequent to the initiation of viral DNA replication. In particular, VP11 synthesis is blocked by cytosine arabinoside, a specific inhibitor of DNA synthesis. We show here that VP11 is specifically phosphorylated subsequent to translation. Phosphorylated VP11 is present both in viral core particles and in the cytoplasm of virus-infected cells. Kinetic analysis reveals that the total amount of phosphorylated VP11 species increases rapidly and remains approximately constant for as long as 17 hr postinfection. Phosphorylation occurs at two different serine residues, progressing from either site singly to the diphosphorylated product. Under steady-state conditions, the phosphorylated derivative constitutes approximately 85% of total VP11 in extracts of vaccinia virus-infected cells. Even though 15% of the VP11 remains unphosphorylated in cell extracts, only phosphorylated VP11 is found in mature viral cores.