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Biomedical subjects

M Kelm

Publications and source records attributed to M Kelm.

71 records · Page 4Linked to original sources
PubMed1993

Formation and salvage of adenosine by macrovascular endothelial cells.

Contribution of extracellular adenine nucleotide degradation to adenosine formation and internal salvage of adenosine via adenosine kinase were quantified in macrovascular porcine endothelial cells. Microcarrier beads covered with endothelial cells were kept in a perfusion column at a flow rate of 2 ml/min. Total adenine nucleotide (AN) release was quantified with a sensitive firefly luciferin-luciferase assay after enzymatic rephosphorylation of AMP and ADP to ATP. Adenosine (ADO) was measured by radioimmunoassay or high-pressure liquid chromatography (HPLC) techniques. Basal AN and ADO release under steady-state conditions were 2.2 and 13.8 pmol.min-1 x ml column volume (CV)-1, respectively. Inhibition of adenosine deaminase with erythro-9-(2-hydroxy-3-nonyl)adenine (5 x 10(-6) M) enhanced ADO release by 3.3 pmol.min-1 x ml CV-1, and AN release remained unchanged (2.8 pmol.min-1 x ml CV-1). Inhibition of adenosine kinase by 5-iodotubercidine (10(-5) M) greatly enhanced ADO release by 97.7 pmol.min-1 x ml CV-1, while AN release was unaffected. Inhibition of ecto-5'-nucleotidase by alpha,beta-methylene-ADP (5 x 10(-5) M) enhanced AN release from 2.6 to 8.2 pmol.min-1 x ml CV-1 and reduced ADO release by an equivalent extent. Stimulation of endothelial cells with Ca ionophore A23187 dose dependently augmented AN and ADO release to 2,013.2 and 92.5 pmol.min-1 x ml CV-1, respectively. Thrombin (1 U/ml) enhanced AN release from 5.0 to 8.7 pmol.min-1 x ml CV-1, whereas several other endothelium-dependent and -independent vasodilators including acetylcholine, bradykinin, isoproterenol, and norepinephrine were proven to have no significant effect.(ABSTRACT TRUNCATED AT 250 WORDS)

5'-Nucleotidase↗
PubMed1992

Role of phospholamban in NO/EDRF-induced relaxation in rat aorta.

The role of endothelium-derived nitric oxide (NO) to cause smooth muscle phospholamban (PLB) phosphorylation was studied in the isolated perfused rat aorta precontracted with norepinephrine using a back-phosphorylation technique. NO-induced relaxation was associated with increased PLB-phosphorylation while norepinephrine as such was ineffective. Removal of endothelium significantly reduced PLB-phosphorylation in indomethacin treated vessels. Stimulation of NO-formation by ATP augmented PLB-phosphorylation in intact vessels but was ineffective in denuded aortas. The results indicate that PLB-phosphorylation of vascular smooth muscle plays an important role in mediating NO-dependent relaxation by enhancing Ca(++)-uptake into sarcoplasmic reticulum.

Adenosine Triphosphate↗
PubMed1992

Reduced peripheral and coronary vasomotion in systemic hypertension.

In 53 patients with a history of arterial hypertension and 16 normotensive control subjects, coronary blood flow reserve by means of the argon method, and peripheral vascular flow reserve by means of venous occlusion plethysmography, were studied. The coronary flow reserve, expressed as the ratio of coronary vascular resistance under resting conditions to the minimal coronary vascular resistance after the administration of dipyridamole, was 4.34 +/- 0.89 in the normotensive group and 2.18 +/- 0.60 in the hypertensive group. There was no significant difference in forearm peak flow after 3 min of arterial occlusion between normotensive and hypertensive patients, while the peripheral minimal vascular resistance was significantly higher in hypertensive patients (8.8 +/- 3.8 mmHg x ml.min-1 x 100 ml-1 tissue) as compared to normotensive subjects (6.37 +/- 2.37 mmHg x ml.min-1 x 100 ml-1 tissue). Parallel to the reduction in coronary reserve, the peripheral flow reserve, expressed as the ratio of peripheral resting vascular resistance to peripheral minimal vascular resistance after 3 min of arterial occlusion, was significantly lower (P less than 0.01) in hypertensive subjects (3.85 +/- 2.28) as compared to normotensive subjects (5.31 +/- 1.72). These data suggest that in hypertensives an impaired vasodilator reserve of both coronary and peripheral microcirculation exists.

Angina Pectoris↗
PubMed1992

The role of nitric oxide in the regulation of coronary vascular resistance in arterial hypertension: comparison of normotensive and spontaneously hypertensive rats.

Nitric oxide (NO) plays an important role in the regulation of coronary vascular resistance. The aim of the present study was to evaluate the role of NO in the regulation of coronary vascular resistance in isolated hearts from normo- and hypertensive rats, which served as a model for arterial hypertension and hypertensive heart disease. Isolated hearts from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs) were perfused at constant flow, whereas the release of NO into the coronary circulation was measured simultaneously by the oxyhemoglobin technique. Bradykinin, an endothelium-dependent vasodilator, concentration-dependently decreased the coronary perfusion pressure in SHRs by 47 +/- 3% and in WKY rats by 35 +/- 6%. In parallel, the basal NO release increased in both groups, maximally by 154 and 118 pmol/min in SHRs and WKY rats, respectively. Amounts of released NO were sufficient to account for the bradykinin-induced coronary vasodilation. These data indicate that coronary resistance vessels in hearts from hypertensive compared to normotensive rats exhibit a higher sensitivity to the endothelium-dependent vasodilator bradykinin, paralleled by a higher release of NO into the coronary circulation. An enhanced endothelial NO synthesis within the coronary circulation may represent a compensatory mechanism aimed at counterregulating distinct changes in vascular reactivity occurring in arterial hypertension.

Animals↗
PubMed1992

[Prevention with vasoactive drugs].

Arterial hypertension is the most frequent cause of a disturbance of coronary microcirculation. Inspite of having normal epicardial coronary arteries, patients with arterial hypertension often have symptoms of angina pectoris and a positive exercise tolerance test. The angina pectoris symptoms in patients with arterial hypertension are due to functional and structural alterations of the coronary microcirculation. Consequently, an antihypertensive therapy should not only aim at lowering blood pressure and reversing myocardial hypertrophy, but also to improve coronary microcirculation in order to avoid the consequences of chronic ischemia on the myocardium. Until now, only experimental studies have indicated that antihypertensive therapy can improve coronary flow reserve. To determine (also under clinical conditions) if coronary flow reserve can be improved, in 30 hypertensive patients maximal coronary blood flow, minimal coronary resistance, and coronary reserve (dipyridamol) were studied before and after a long-term antihypertensive treatment (9-12 months) with an ACE-inhibitor (enalapril 10-20 mg/d), a calcium channel blocker (diltiazem 120-180 mg/d) and a beta 1-selective beta-receptor-blocker (bisoprolol 5-10 mg/d). To assess the chronic effects rather than the acute effects of the antihypertensive pharmacon, coronary microcirculation was studied after intermission of medical therapy for a period of 1 week. Along with a comparable decrease in LV muscle mass, coronary reserve was improved after enalapril by 48%, after diltiazem by 48%, and after bisoprolol by 22%. It is possible that the observed increase in coronary reserve is related to the reversal of structural vascular abnormalities on the level of the coronary microcirculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Biotransformation of organic nitrates to nitric oxide by vascular smooth muscle and endothelial cells.

The vasodilator action of organic nitrates is thought to be mediated by an increase in the level of cGMP following stimulation of the cytosolic enzyme guanylate cyclase in the vascular smooth muscle cell. However, direct evidence for the formation of the putative active metabolite, nitric oxide (NO) within the different compartments of the vascular wall is still missing. We here demonstrate for the first time that cultured vascular smooth muscle cells as well as endothelial cells from different species actively metabolize organic nitrates to NO. We furthermore present evidence for an outward transport of cGMP from both cell types following stimulation of soluble guanylate cyclase. The rate of NO release closely correlated with the rate of cGMP egression. Biotransformation of organic nitrates to NO appeared to comprise at least two different components, a heat-sensitive enzymatic pathway which is short-lived and prone to rapid desensitization and a second non-enzymatic component which is apparently unsaturable and longer lasting. The marked decrease in the release of NO and cGMP upon the repeated administration of organic nitrates suggests that the phenomenon of "nitrate tolerance" is mainly due to an impaired biotransformation. We propose that the metabolism of nitrates to NO may have important implications for the prevention of atherosclerosis and the therapeutic modulation of blood cell function.

Animals↗
PubMed1991

Protein phosphorylation in intact coronary endothelial cells by bradykinin.

In cultured coronary endothelial cells obtained from guinea pig hearts, bradykinin (10(-6) M) stimulated the 32Pi-incorporation into 5 substrate proteins with molecular weights corresponding to 27, 32, 60, 86 and 100 kDa. The time course of phosphorylation of the 60, 86 and 100 kDa proteins was rapid (within 30 s), but transient (max. within 1-2 min.), while the 32Pi incorporation into the 27 and 32 kDa protein was delayed but increased within 10 minutes. Ca+(+)-ionophore A 23187 (10(-5) M) and 12-O-tetradecanoylphorbol-13-acetate (TPA) (10(-5) M) both mimicked the effects of the bradykinin induced phosphorylation pattern. While A 23187 enhanced the phosphorylation of the 27, 60 and 100 kDa substrates, TPA increased the 32Pi-incorporation into the 32 and 86 kDa proteins. Furthermore the time course of protein phosphorylation elicited by A 23187 and TPA showed marked similarities to those obtained with bradykinin. Our findings are consistent with the view, that stimulation of coronary endothelial bradykinin-receptors activates both Ca+(+)-dependent protein kinases and protein kinase C.

Animals↗
PubMed1991

Release of endothelium derived nitric oxide in relation to pressure and flow.

STUDY OBJECTIVE: Endothelium derived nitric oxide (NO) is an important modulator of resting vascular tone. The aim of the study was to investigate the extent by which the rate of NO release is modulated by the two determinants of vascular conductance: pressure and flow. DESIGN AND EXPERIMENTAL MATERIAL: Porcine macrovascular endothelial cells cultured on microcarrier beads were used as a model in which the rate of NO release was determined photometrically. Columns packed with endothelial cell covered beads were perfused at different flow rates (2, 10, 20 ml.min-1) and perfusion pressures (ranging from 6 to 200 mm Hg). MEASUREMENTS AND MAIN RESULTS: Release of endothelial cell derived NO was continuously quantified under basal and ATP stimulated conditions using a specific difference spectrophotometric assay. Increasing flow flow from 2 to 20 ml.min-1 enhanced the basal NO release from endothelial cells fivefold. ATP (10(-4) M) augmented the NO release from endothelial cells more than 10-fold at each flow level studied. The ATP induced NO release rapidly increased by a factor of 5.8 when flow was enhanced from 2 to 20 ml.min-1 (greater than 180 pmol.min-1.mg endothelial cell protein). Raising perfusion pressure from 6 to 200 mm Hg in endothelial cells did not affect the rate of basal NO release. CONCLUSIONS: (1) The rate of NO release from endothelial cells increases when flow is enhanced. (2) Endothelial cells possess a high capacity for NO production, permitting a rapid adjustment of NO release to changes in flow. (3) The rate of NO release is not causally related to changes in perfusion pressure.

Adenosine Triphosphate↗
PubMed1990

Control of coronary vascular tone by nitric oxide.

A specific difference-spectrophotometric method was used to measure nitric oxide (NO) release into the coronary effluent perfusate of isolated, constant-flow-perfused guinea pig hearts. Authentic NO applied into the coronary circulation decreased vascular resistance dose dependently and enhanced coronary release of cyclic GMP (cGMP) fivefold. Increasing oxygen tension in aqueous solutions from 150 to 700 mm Hg decreased NO half-life (5.6 seconds) by 32%. During single passage through the intact coronary system, 86% of the infused NO was converted to nitrite ions. Oxidation of NO was more than 30 times faster within the heart than in aqueous solution. Endogenously formed NO was constantly released into the coronary effluent perfusate at a rate of 161 +/- 11 pmol/min. The NO scavenger oxyhemoglobin and methylene blue increased coronary resistance and decreased cGMP release (basal release, 342 +/- 4 fmol/min), whereas superoxide dismutase reduced coronary resistance. L-Arginine (10(-5) M) slightly decreased coronary perfusion pressure and enhanced release of cGMP. NG-Monomethyl L-arginine (10(-4) M) reduced basal release of NO and cGMP by 26% and 31%, respectively, paralleled by a coronary vasoconstriction. Bradykinin in the physiological range from 5 x 10(-11) M to 10(-7) M dilated coronary resistance vessels, which was paralleled by the release of NO and cGMP. Onset of NO release preceded onset of coronary vasodilation in all cases. Upon stimulation with bradykinin, amounts of endogenously formed NO were within the same range as the dose-response curves for exogenously applied NO both for changes in coronary resistance and cGMP release. Acetylcholine (10(-5) M), ATP (10(-5) M), and serotonin (10(-8) M) increased the rate of NO and cGMP release, resulting in coronary vasodilation. Our data suggest the following: 1) NO, the most rapidly acting vasodilator presently known, is metabolized within the heart mainly to nitrite and exhibits a half-life of only 0.1 second; 2) in the unstimulated heart, basal formation of NO may play an important role in setting the resting tone of coronary resistance vessels; 3) the kinetics and quantities of NO formation suggest that NO is causally involved in the bradykinin-induced coronary vasodilation; and 4) amounts of NO formed within the heart stimulated with ATP, acetylcholine, and serotonin are effective for vasodilation.

Animals↗
PubMed1989

[Transport of adenosine across the endothelium of the isolated perfused rat aorta].

In order to define the role of vascular endothelium in the transport and metabolism of adenosine, endothelium-intact and denuded isolated rat aortas were perfused with 3H-adenosine. In the physiological concentration range of adenosine (0.01-1 microM) sequestration of adenosine by endothelium was 90-92%. Similar findings were obtained for inosine. Transfer of radioactive purines from the prelabeled endothelium to the underlying smooth muscle was rather small (1% per hour) and most likely proceeds via dephosphorylated purine compounds. Under steady state conditions the transendothelial adenosine gradient is only moderate because underlying vascular smooth muscle metabolize adenosine less rapidly.

Adenosine↗
PubMed1989

Release of the free nitric oxide radical (NO) and EDRF from endothelial cells.

Release of nitric oxide (NO) from cultured macrovascular endothelial cells (EC) and from isolated perfused guinea pig hearts was measured with a specific spectrophotometric assay. Under basal conditions NO was continuously released from cultured cells and from isolated hearts into the coronary effluent perfusate. Bradykinin (10(-7) M) increased rate of NO release maximally two- to three-fold in both experimental models. Onset of NO release always preceded start of vasodilation (less than 15 s). Our results provide evidence that under basal and bradykinin-stimulated conditions. 1) endothelial cells release nitric oxide as a free radical, 2) NO is solely responsible for the vasodilatory properties of EDRF and, 3) under in vivo conditions the endogenous formation of NO is quantitatively sufficient to influence the coronary vascular tone and thus, may play an important role in the regulation of coronary vascular resistance.

Animals↗
PubMed1988

Nitric oxide release from the isolated guinea pig heart.

Nitric oxide (NO) release from isolated guinea pig hearts into the coronary effluent perfusate was measured with a specific spectrophotometric assay. Nitric oxide was continuously released under basal conditions at a rate of 216 +/- 36 pmol/min. Bradykinin (5 X 10(-10)-10(-8) M) stimulated the release of nitric oxide in a dose-dependent manner. The start of NO release preceded coronary vasodilation by 5 +/- 1 s. Our results suggest that the endogenous formation of nitric oxide is quantitatively sufficient to influence the coronary vascular tone and thus may play a significant role in the regulation of coronary vascular resistance.

Animals↗
PubMed1988

Quantitative and kinetic characterization of nitric oxide and EDRF released from cultured endothelial cells.

Endothelial cells (EC) contribute to the control of local vascular diameter by formation of an endothelium derived relaxant factor (EDRF) (1). Whether nitric oxide (NO) is identical with (EDRF) or might represent only one species of several EDRFs has not been decided as yet (2-5). Therefore, we have directly compared in cultured EC the kinetics of NO formation determined in a photometric assay with the vasodilatory effect of EDRF and NO in a bioassay. Basal release of NO was 16, 4 pmol/min/ml packed EC column. After stimulation with bradykinin (BK) and ATP onset of endothelial NO release and maximal response preceded the EDRF-mediated relaxation. Concentrations of NO formed by stimulated EC were quantitatively sufficient to fully explain the smooth muscle relaxation determined in the bioassay. Our data provide convincing evidence that under basal, BK and ATP-stimulated conditions 1. endothelial cells release nitric oxide as free radical, 2. nitric oxide is solely responsible for the vasodilatory properties of EDRF.

Adenosine Triphosphate↗
PubMed1977

Infection of the skin by Mycobacterium marinum: report of five cases.

Five patients 6 to 47 years of age had bacteriologically confirmed Mycobacterium marinum infections of the skin. In four patients the initial lesions were chancriform and were on a finger or a hand; ascending lymphadenitis followed. The other patient had nodular inflammatory lesions on one cheek. Biopsies were performed in four patients; all specimens showed a granuloma, and acid-fast bacilli were identified in one of the four. Four of the five patients were untreated; the fifth was given antituberculous drugs. In all five patients the condition was chronic, with progressive resolution of the lesions during follow-up periods of 1 to 6 years. M. marinum infections of the skin are rare in Canada. This may be due in part of lack of clinical awareness or failure to identify the organism. Biopsy specimens should be obtained under sterile conditions and nondigested material should be inoculated into the footpads of mice.

Adolescent↗
PubMedDate not supplied

Bacteriuria in intermittent catheterization users: the effect of sterile versus clean reused catheters.

Monthly urine cultures were analyzed at the University of Alberta Department of Medical Microbiology and Infectious Diseases to determine whether single-use sterile catheters and clean technique reduced the incidence of bacterial colonization in those using long-term intermittent self-catheterization. Thirty subjects with spina bifida, ages 3 years to 16 years, entered a crossover study with random assignment to 6 months of sterile single-use catheters or clean reused catheters. Seventeen subjects were catheterized by a parent or caregiver; 13 were responsible for self-catheterization and cleaning of the catheters. Six months of descriptive data were also collected at Alberta Children's Hospital from a similar group of subjects with spina bifida who used sterile catheters only. In the crossover group, 38% of all urine cultures were positive regardless of whether sterile single-use or clean reused catheters were employed. The other group using only sterile catheters had a 36% positive culture rate. No difference in positive cultures was found between males and females or between children who catheterized themselves and children whose parents catheterized them. The authors concluded that plastic urethral catheters may be reused.

Adolescent↗
PubMedDate not supplied

Mechanisms of histamine-induced coronary vasodilatation: H1-receptor-mediated release of endothelium-derived nitric oxide.

Although the content of histamine in myocardial tissue is high, its contribution to the regulation of coronary blood flow has not been clearly defined. The aim of the present study was to investigate whether or not nitric oxide (NO), an important modulator of coronary vascular tone, is involved in histamine-induced coronary vasomotion and to characterize which histaminergic receptor subtype mediates this process. Isolated, constant-flow-perfused guinea pig hearts were challenged with histamine, the H1-receptor agonist pyridylethylamine (PYR) and the H2-receptor agonist dimaprit (DIM). Apart from coronary perfusion pressure (CPP), left ventricular pressure (LVP) and the development of contractile force (dp/dt), the release of NO and cyclic GMP (cGMP) were continuously measured. Histamine and DIM induced concentration dependently a coronary vasodilatation with an almost 50% decrease in CPP paralleled by an enhancement of LVP and dp/dt by more than 80%. PYR selectively reduced CPP by 47% without affecting LVP and dp/dt. Histamine- and PYR-induced coronary vasodilatation were paralleled by a more-than-twofold increase in basal cGMP release from isolated hearts, whereas DIM exerted no effects on cGMP release. Oxyhemoglobin (4 microM), an effective scavenger of NO, shifted the concentration-response curve for histamine- and PYR-induced changes in CPP significantly to the right and in parallel inhibited the increase in cGMP release. Histamine and PYR rapidly (within 2 s) decreased CPP, while the onset of DIM-induced coronary vasodilatation followed changes in LVP with a lag period of 10 s. Histamine increased basal NO release concentration dependently by a maximum of 351 +/- 21 pmol/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗