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Biomedical subjects

K Graf

Publications and source records attributed to K Graf.

At least 73 records · Page 4Linked to original sources
PubMed1993

Degradation of bradykinin by neutral endopeptidase (EC 3.4.24.11) in cultured human endothelial cells.

The presence of neutral endopeptidase 24.11 was demonstrated in human umbilical vein endothelial cells by immunostaining. Enzymatic activity of neutral endopeptidase was determined as 0.167 +/- 0.02 mU/mg protein in the membrane fraction of human umbilical vein endothelial cells, using the fluorogenic peptide substrate, dansyl-D-Ala-Gly-Phe(pNO2)-Gly. No activity was found in the cytosolic fraction of endothelial cells. The role of this peptidase in the degradation of the endogenous vasodilator bradykinin was investigated by incubating human umbilical vein endothelial cell monolayers with bradykinin (10(-8) mol/l). The inhibitor of neutral endopeptidase, phosphoramidon (10(-8) mol/l), decreased the degradation of bradykinin in the supernatant of endothelial cells; the half-life of bradykinin was then increased from 29 +/- 1 to 46 +/- 2 minutes. The angiotensin-converting enzyme inhibitor, lisinopril (10(-8) mol/l), increased the half-life of bradykinin to 244 +/- 20 minutes; the combination of both inhibitors increased the half-life of bradykinin to 381 +/- 51 minutes. Inhibitors of aminopeptidase (amastatin) and carboxypeptidase (2-mercaptomethyl-3-guanidinoethyl-thiopropionic acid) caused no significant effect. The effect of phosphoramidon was small in comparison with that of lisinopril, but was pronounced in combination with lisinopril. Neutral endopeptidase activity is localized in the membranes of human endothelial cells and seems to be involved in the degradation of bradykinin by the vascular endothelium, particularly during angiotensin converting enzyme inhibition.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

Local regulation of vascular tone by bradykinin and angiotensin converting enzyme inhibitors.

Part of the vasodilator response to angiotensin converting enzyme (ACE) inhibitors depends on stimulation of bradykinin receptors, but in most studies the anticipated increase in plasma kinin concentration during ACE inhibition was not detected. We investigated the role of local ACE inhibition on endothelial control of vascular tone. Rings of bovine coronary, renal and tail arteries, as well as human coronary arteries, were mounted in organ chambers so that the isometric force could be recorded. The ACE inhibitors, captopril, fosinoprilat, enalaprilat, lisinopril, and ramiprilat alone had no affect on the vascular tone of bovine coronary arteries with endothelium. However, these ACE inhibitors did potentiate relaxations to bradykinin and the slowly degradable bradykinin derivative [Hyp3-Tyr(Me)8]-bradykinin (3 x 10(-11) M). A similar response was observed in human coronary arteries. The response was not observed in rings of any vessel without endothelium, or after incubation with nitro-L-arginine (10(-4) M), or the bradykinin2-receptor antagonists Hoe 140 (10(-8) M). The sensitivity to bradykinin was higher and the potentiating effect of ACE inhibition larger in the bovine coronary artery than in the renal and tail artery. Thus, ACE inhibition causes selective coronary vasodilation by potentiating the bradykinin-induced release of nitric oxide from the endothelium. The related mechanism underlying these effects must occur at the surface or within the arterial wall and seems to be independent of the degradation of the kinins.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

Regulation of beta-adrenergic receptors on endothelial cells in culture.

This study aimed to determine the density of vascular beta-adrenergic receptors in cultured endothelial cells and to study the regulation of endothelial receptors after exposure to catecholamines and the ACE inhibitors, lisinopril and ramiprilat. Membranes from bovine aortic endothelial cells (BAEC) and bovine pulmonary artery endothelial cells (BPAEC) showed saturable binding of the radioligand [125I]iodocyanopindolol (ICYP). The beta-receptor density and binding affinity were comparable in both types of endothelial cells. Isoproterenol induced significant down-regulation of beta-receptors (-50%; P < 0.01). Incubation (24h) with the ACE inhibitors lisinopril 10(-5) M (+28.8%; P < 0.05) and ramiprilat 10(-5) M (+33.7%, P < 0.09) augmented the beta-receptor density in BAEC, but lower ACE inhibitor doses had no affect. Incubation with lisinopril 10(-5) M for 24 h resulted in significantly lower cAMP baseline levels, but did not affect cAMP concentrations after stimulation with isoproterenol. These results indicate that down-regulation of endothelial beta-receptors occurs during prolonged exposure to beta-stimulation, and that high concentrations of ACE inhibitors may affect the density of endothelial beta-receptors.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

Cultivation and characterization of micro- and macrovascular endothelial cells from the human heart.

In order to investigate processes, such as atherosclerosis and inflammation in vitro, it is necessary to obtain viable and pure endothelial cell cultures from human hearts. To this end, endothelial cells were isolated and cultured from the micro- and macrovasculature of human hearts obtained during heart transplantation. Isolation of capillaries after enzymatic digestion of heart muscle provided a source of microvascular endothelial cells. Contaminating non-endothelial cells were removed by a new technique: paramagnetic beads linked to the lectin ulex europaeus I (UEA-I) were used to select endothelial cells. The resulting cultures contained less than 2% of non-endothelial cells, as judged from immunological staining and fluorescence-activated cell sorting. Both types of endothelial cell displayed typical endothelial properties. They were all positive for factor VIII-related antigen and expressed the endothelial-specific adhesion molecules, CD31 and E-selectin (ELAM-1), after stimulation with cytokines. In addition, they could be labelled with Dil-Ac-LDL, contained angiotensin converting enzyme activity and secreted tissue plasminogen activator, thus demonstrating that typical endothelial functions were preserved in culture.

Capillaries↗
PubMed1992

[Hereditary unilateral deaf-mutism as a variable manifestation of bilateral deaf-mutism or hearing loss].

A total of 2,519 patients with bilateral severe congenital deafness (deaf-mutism) from Central Switzerland were recorded during the period between 1834 to 1979. More recently, 31 persons with unilateral severe deafness were examined. By constructing genealogical charts going back to the 17th century, at least ten of these unilaterally deaf persons were shown to be related to patients with bilateral deafness (pedigrees I-IV). Some of them exhibited a more or less marked Klein- Waardenburg syndrome. The unilateral deafness of those patients was inherited and not acquired. Congenital unilateral deafness may be understood to be the result of the broad variability of the expressivity of acoustic defects.

Deafness↗
PubMed1992

Relaxation of human coronary artery and arteria mammaria by K(+)-channel openers.

Three agents with K(+)-channel-opening activity--nicorandil, bimakalim (EMD 52692), and EMD 56431--were tested for vasorelaxation abilities in human coronary artery and human arteria mammaria. The potency orders were bimakalim = EMD 56431 >> nicorandil for relaxation in human coronary artery and bimakalim = EMD 56431 >> nicorandil in human arteria mammaria. These data demonstrate that K(+)-channel openers are effective vasorelaxant agents in human coronary artery and human arteria mammaria. Bimakalim and EMD 56431 were more potent than nicorandil, a drug that also activates guanylate cyclase.

Benzopyrans↗
PubMed1992

In vivo measurement of endothelium-dependent vasodilation with substance P in man.

Endothelial cells synthesize and metabolize vasoactive substances which are involved in the regulation of vascular tone. Among these factors, the endothelium-derived nitric oxide (NO) appears to be of major importance. Many studies observed an impairment of the generation, release, or the diffusion of endothelial NO across the vascular intima in laboratory animals with various experimental diseases such as hypercholesterolemia, atherosclerosis and hypertension. In human coronary arteries obtained from explanted hearts impaired endothelium-dependent relaxations were measured in atherosclerotic segments. The hypothesis of a decreased NO mediated vasodilation in patients with coronary artery disease was further underscored by in vivo studies in man using intracoronary infusions of the endothelium-dependent vasodilator acetylcholine and quantitative coronary angiographic measurements of the diameter changes. From these observations it was assumed that endothelial dysfunction, in particular a profound inability of the coronary endothelium to relax via NO dependent mechanisms may play an important role in the pathogenesis of abnormal coronary vasomotion. However, further investigations in man reveal that the ability of the coronary endothelium of patients with coronary artery disease or vasospastic angina to produce endothelial NO is less affected as judged from the effects of acetylcholine. In recent investigations a largely preserved endothelial function could be measured in these patients when the endothelium-dependent vasodilator substance P was used as a tool for the measurement of NO dependent relaxation. Thus, endothelial dysfunction does not appear to serve as a major cause of abnormal vasoconstriction in coronary artery disease or vasospastic angina in man.

Acetylcholine↗
PubMed1992

Bradykinin degrading activity in cultured human endothelial cells.

The role of angiotensin-converting enzyme (ACE), neutral endopeptidase 24.11 (NEP), and other peptidases in the endothelial degradation of bradykinin was investigated in cultured human umbilical vein endothelial cells (HUVEC). The major part of the kininase II activity on intact cells was attributed to ACE activity, the minor part to NEP activity. Amastatin, as aminopeptidase inhibitor, and DL-2-mercaptomethyl-3-guanidinoethyl-thiopropionic acid (MGTA), an inhibitor of kininase I, did not affect endothelial kininase activity. The decline of the bradykinin concentrations in the supernatant of intact endothelial monolayer indicated a total kininase activity of 289 +/- 27 fmol/min/dish. The calculated activity of ACE was 223 fmol/min/dish and the neutral endopeptidase activity was 51 fmol/min/dish. Thus, ACE and neutral endopeptidase are the main kininases in the degradation of bradykinin by intact endothelial cells. In contrast to the intact endothelial monolayers, in homogenates additional kininase activity was found which was not affected by either ACE and NEP inhibitors nor by amastatin and MGTA.

3-Mercaptopropionic Acid↗
PubMed1992

Local potentiation of bradykinin-induced vasodilation by converting-enzyme inhibition in isolated coronary arteries.

The interaction of angiotensin-converting enzyme (ACE) inhibitors and bradykinin was investigated in isolated bovine and human coronary arteries. Rings with and without endothelium were mounted in organ chambers for measurement of isometric force. The effects of the ACE inhibitors lisinopril, enalaprilat, fosinoprilat, ramiprilat, and captopril were determined during submaximal stimulation with bradykinin or other vasodilators. Lisinopril and captopril alone did not affect vascular tone; however, in rings with endothelium partially relaxed with bradykinin (> or = 10(-10) M), all ACE inhibitors caused further relaxations. Lisinopril did not affect bradykinin concentrations in the incubation medium. Mechanical removal of the endothelium or incubation with nitro-L-arginine or the bradykinin2-receptor antagonist Hoe 140 prevented the relaxations to bradykinin and lisinopril. Other vasodilators including acetylcholine, adenosine diphosphate, substance P, or SIN-1 did not prime the rings to respond to ACE inhibitors. Endothelium-dependent relaxations to lisinopril were also observed in human coronary arteries treated with bradykinin (> or = 10(-7) M). Thus, ACE inhibitors potentiate endothelium-dependent relaxations to submaximal concentrations of bradykinin in bovine and human coronary arteries. This local mechanism occurs regardless of elevated bradykinin concentrations in the blood and reduced angiotensin II generation.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Endothelium-dependent relaxations are augmented in rats chronically treated with the angiotensin-converting enzyme inhibitor enalapril.

The study was designed to evaluate the effects of chronic inhibition of angiotensin-converting enzyme (ACE) on the reactivity of the endothelium and the smooth muscle to vasoconstrictor and vasodilator stimuli in normal rats. Male rats were treated orally for 6 weeks with enalapril (10 mg/kg/day, n = 10) or with placebo (n = 10). Endothelium-dependent relaxations to acetylcholine and adenosine diphosphate were augmented in aortic rings from rats treated with enalapril compared with controls, whereas the response to the endothelium-independent vasodilator SIN-1 were similar. Contractions induced by phenylephrine and angiotensin II remained unchanged. Thus, the results suggest that chronic ACE inhibition enhances the release of relaxing factors from the endothelium in normotensive rats.

Acetylcholine↗
PubMed1992

Effects of converting enzyme inhibition on endothelial bradykinin metabolism and endothelium-dependent vascular relaxation.

The effects of ACE-inhibitors on bradykinin metabolism and bradykinin-induced endothelium-dependent relaxation were studied in isolated coronary arteries and endothelial cells in culture. The results suggest that ACE-inhibitors affect coronary vascular tone by at least two endothelium-dependent and bradykinin-mediated mechanisms: First, ACE-inhibitors decrease endothelial bradykinin degredation which is accompanied by an augmented bradykinin mediated endothelium-dependent relaxation. Second, ACE-inhibitors evoke endothelium-dependent relaxations in coronary arteries stimulated with threshold concentrations of bradykinin, which cannot be attributed to an inhibition of bradykinin degradation. The effect appears to represent a new mechanism which may be based on an interaction of the bradykinin receptor and the angiotensin converting enzyme on the cellular level.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1991

Beta receptor density in human lymphocyte membranes: changing with aging?

The number of beta adrenergic binding sites (Bmax) in human lymphocyte membranes has been reported to decrease, remain the same, or increase with age. In order to address this issue, we used two highly specific beta receptor ligands with lymphocytes from healthy aged (range: 51-90 years) and young (19-39 years) subjects in two separate studies. Because depression can reduce Bmax, potential aged subjects were excluded if they had high scores on tests for depression. Bmax was higher in the aged group of each study (33% higher in the first, p less than .01, and 72.5% in the second, p less than .02); the results were similar in both studies. Antagonist affinity did not differ between young and aged groups in either study. We suggest that some of the discrepancies in the literature could be due to differences in age ranges used or to inclusion of depressed subjects in prior studies.

Adrenergic beta-Antagonists↗
PubMed1991

[Endothelial protection].

Explore the source record for details and available documents.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1989

Lymphocyte beta-adrenoceptor/effector complex in aging and dementia of the Alzheimer type.

We examined density (Bmax), affinity (Kd), and norepinephrine (NE)-stimulated cyclic adenosine monophosphate (cAMP) generation of the beta-adrenergic receptor on lymphocytes in patients with dementia of the Alzheimer type (DAT, n = 13), in normal aged controls (AGED, n = 27), and in young controls (YOUNG, n = 21). Bmax (fmol/mg protein; mean +/- SD) was significantly lower in YOUNG (48.0 +/- 18.7) than in either AGED (64.8 +/- 22.3) or DAT (63.6 +/- 19.5, p less than 0.05). Receptor sensitivity, i.e., the fold increase of stimulated over basal cAMP generation (S/B), was higher in DAT (8.3 +/- 5.2) than in AGED (5.5 +/- 2.3) or YOUNG (5.4 +/- 2.6, p less than 0.07). This difference was due to a significant increase in S/B in female but not male DAT patients compared with AGED (p less than 0.05). There were no differences in levels of circulating NE between DAT and AGED, nor between sexes. Thus, the present data suggest that in this model of the postsynaptic beta-adrenergic receptor/effector complex, receptor sensitivity was increased in women with DAT.

Adult↗
PubMed1986

[Indications for ligation of ductus arteriosus Botalli persistens in premature infants].

Ligation of patent ductus arteriosus can be safely performed even in the smallest prematures and may be life-saving. Medical treatment with prostaglandin-inhibitors may be substituted in selected cases. From 1976-1985 a total of 215 prematures was treated. 52 of those experienced spontaneous closure. In 68 infants closure occurred following indomethacin-treatment. 48 had operation after failure of medical therapy and 53 with contraindications to indomethacin were primarily operated. The overall mortality reached 20% and was highest among those with combined medical and surgical treatment.

Birth Weight↗