Biomedical subjects

H Hegeman

Publications and source records attributed to H Hegeman.

4 recordsLinked to original sources

PubMed1997

Early pharmacologic intervention may prevent the deterioration in endothelial function after experimental myocardial infarction in rats: effects of ibopamine and captopril.

BACKGROUND: Endothelial function is progressively disturbed after myocardial infarction (MI), which may be related to both neurohumoral activation and hemodynamic alterations. Consequently, it may be suggested that drugs that favorably affect these factors may also have a positive effect on endothelial function. METHODS AND RESULTS: Rats underwent coronary ligation (n = 24) or remained unoperated (n = 21), and were randomized to captopril (25 mg/kg/d) or ibopamine (10 mg/kg/d) or remained untreated. Treatment was started following MI and lasted 8 weeks, after which rats were sacrificed for in vitro studies. Left ventricular end-systolic pressure was higher in rats treated with captopril (83 +/- 6 mmHg) and ibopamine (80 +/- 3 mmHg), as compared with untreated MI rats (48 +/- 6 mmHg, P < .01 for both). Increased plasma norepinephrine levels in MI rats were reduced by captopril and ibopamine (both P < .05). Infarct size was smaller in rats treated with captopril (26.7 +/- 3.6%, P < .05) and ibopamine (31.4 +/- 4.3%, P = NS), as compared with untreated rats (41.7 +/- 2.4%). Maximal endothelium-dependent relaxation (Emax; % precontraction) and the concentration of methacholine causing 50% Emax, expressed as negative log(pIC50) were significantly reduced in aortic rings from MI control subjects (pIC50 = 6.15 +/- 0.06 mol/L, Emax = 32.0 +/- 4.2%), as compared with normal control subjects (pIC50 = 6.57 +/- 0.07 mol/L, P < .001; Emax = 50.0 +/- 4.9%, P = .022). Captopril (pIC50 = 6.30 +/- 0.08 mol/L, Emax = 45.1 +/- 7.0%) and ibopamine (pIC50 = 6.60 +/- 0.08 mol/L, Emax = 43.8 +/- 5.2%) improved these parameters in MI rats. CONCLUSION: The results demonstrate preservation of endothelial function by early pharmacologic intervention after experimental MI in rats in the setting of concomitant reduction in infarct size.

Animals↗

PubMed1995

Relation between myocardial beta-adrenoceptor density and hemodynamic and neurohumoral changes in a rat model of chronic myocardial infarction: effects of ibopamine and captopril.

OBJECTIVES: The purpose of this study was to investigate the changes in beta-adrenoceptor density (Bmax) and distribution in a model of chronic myocardial infarction in rats, and to relate possible changes to hemodynamic and neurohumoral abnormalities. In addition, we examined the effects of 8 weeks treatment with ibopamine and captopril. METHODS: There were 3 experiments: (1) Bmax and plasma catecholamines were examined (n = 46), (2) Bmax was compared in infarcted and non-infarcted tissue (n = 13), and (3) contractile function was evaluated by isolated heart perfusion (n = 40). Of rats in Expts. (1) and (3), 50% had myocardial infarction induced by coronary ligation and 50% were controls. Each group was divided between ibopamine, ibopamine and captopril, or standard (no drug) treatment. RESULTS: Bmax was not decreased in rats with myocardial infarction (10.8 +/- 0.8 fmol/mg protein), compared to normal rats (11.4 +/- 0.6 fmol/mg protein), and the ratio beta 1/beta 2 was also unaffected. In infarcted tissue, Bmax was significantly (P = 0.03) lower than in non-infarcted tissue. Baseline left ventricular pressure, systolic and diastolic dP/dT were all impaired (P < 0.001), and plasma norepinephrine levels were elevated in rats with myocardial infarction (16.03 +/- 230 vs. 1287 +/- 83 pg/ml; P < 0.05), compared to normals. Both ibopamine alone and in combination with captopril reduced the elevated plasma norepinephrine levels in infarcted rats (P < 0.001), but only the combination of the 2 drugs significantly increased Bmax in infarcted rats (14.7 +/- 0.8 fmol/mg protein; P = 0.03 vs. untreated myocardial infarction), while ibopamine alone had no significant effect (13.1 +/- 1.1 fmol/mg protein; p = ns). Also, active drug treatment had no significant effect on the hemodynamic changes. CONCLUSIONS: In this coronary artery ligation model of myocardial infarction in rats, no beta-adrenoceptor down-regulation is observed, despite marked abnormalities in baseline left ventricular function and plasma norepinephrine levels. The combination of ibopamine and captopril significantly increases Bmax in infarcted rats, which is accompanied by a reduction in plasma norepinephrine levels, but not by an improvement in hemodynamic parameters.

Adrenergic beta-Agonists↗

PubMed1994

Effect of ibopamine on ventricular remodeling after experimental myocardial infarction: a comparison with captopril.

Remodeling after myocardial infarction (MI) is influenced not only by hemodynamic but possibly by neurohumoral factors as well. Ibopamine is an orally active dopamine agonist (DA) with both hemodynamic and neurohumoral properties in humans. The latter property prevails in rats. To study the dose-dependent effect of ibopamine on myocardial remodeling and compare it with the effect of captopril, we randomized rats with (n = 27) or without (n = 27) experimental MI to captopril (25 mg/kg/day), low-dose ibopamine (10 mg/kg/day), high-dose ibopamine (30 mg/kg/day), or no treatment. After 8-week treatment, hearts were isolated and left ventricular (LV) function, LV cavity volume, and infarct size (IS) were evaluated. Both ibopamine and captopril significantly reduced plasma norepinephrine (NE) levels in rats with MI. In untreated but not in treated infarcted rats, LV function was significantly reduced as compared with that of controls. IS was reduced in all three active treatment groups as compared with untreated rats. LV cavity volume was significantly increased in untreated rats with MI as compared with controls. This dilatation was attenuated by both ibopamine and captopril. Ibopamine, comparable to captopril, administered early after coronary ligation reduced IS and subsequent ventricular dilatation, resulting in preservation of cardiac function in this rat model. This observation suggests a major role for neurohumoral activation in the process of remodeling.

Animals↗

PubMed1990

Genomic integration system based on pBR322 sequences for the cyanobacterium Synechococcus sp. PCC7942: transfer of genes encoding plastocyanin and ferredoxin.

Synechococcus sp. PCC7942 recipient strains were constructed for the chromosomal integration of DNA fragments cloned in any pBR322-derived vector, which carries the ampicillin resistance (ApR) marker. The construction was based on the incorporation of specific recombination targets, the so-called 'integration platforms', into the chromosomal metF gene. These platforms consist of an incomplete bla gene (ApS) and the pBR322 ori separated from each other by a gene encoding an antibiotic (streptomycin or kanamycin) resistance (SmR or KmR). Recombination between a pBR322-derived donor plasmid and such a chromosomal platform results with high frequency in restoration of the bla gene and replacement of the chromosomal marker (SmR or KmR) by the insert of the donor plasmid. The integration into the platform depends on recombination between pBR322 ori and bla sequences only and is therefore independent of the DNA insert to be transferred. The desired recombinants are found by selection for a functional bla gene (ApR) and subsequent screening for absence of the chromosomal antibiotic marker. Gene transfer with this integration system was found to occur efficiently and reliably. Furthermore, the presence of the pBR322 ori in the platform allowed for 'plasmid rescue' of integrated sequences. The system was applied successfully for the transfer of the gene encoding plastocyanin (petE1) from Anabaena sp. PCC7937 and for the integration of an extra copy of the gene encoding ferredoxin I (petF1) from Synechococcus sp. PCC7942 itself.

Blotting, Northern↗