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Biomedical subjects

R M Arendt

Publications and source records attributed to R M Arendt.

At least 19 recordsLinked to original sources
PubMed1999

Endothelin in coronary endothelial dysfunction early after human heart transplantation.

BACKGROUND: Cytokines and growth factors released as part of the immune response to alloantigenic stimuli are capable of regulating endothelin-1 expression in the allograft. Endothelin plays a significant role as a modulator of coronary vascular reactivity in the early stages of atherosclerosis and may be important as a participant in and marker for cardiac allograft vasculopathy. METHODS: We characterized a possible relationship between morphological and functional coronary changes, transcardiac plasma endothelin level and myocardial endothelin-mRNA expression in 33 cardiac transplant recipients in the early, stable phase 5+/-3 months after orthotopic heart transplantation. Coronary microvascular function was determined as endothelium-dependent with acetylcholine and endothelium-independent with adenosine using intracoronary Doppler-FloWire. The percentage of the epicardial diameter changes was measured using quantitative coronary angiography. Intravascular ultrasound was performed to quantify intimal hyperplasia. Cardiac endothelin uptake or release was determined by measuring plasma endothelin levels in the coronary sinus and aorta. Myocardial endothelin-gene expression was determined using semiquantitative RT-PCR. RESULTS: The aortic endothelin levels were significantly increased in transplant recipients compared to nontransplanted patients (11.8+/-2.2 vs 7.2+/-0.9 fmol/mL; P < 0.001). Endothelin uptake was noticed in the majority of patients, and the amount of endothelin uptake was correlated to microvascular (r = 0.37; P < 0.05) and epicardial (r = 0.41; P < 0.03) endothelium-dependent vasodilatation. High mRNA signal intensity was associated with significantly reduced coronary flow response to acetylcholine compared to patients with low myocardial gene expression (coronary flow reserve 2.4+/-0.9 vs 3.4+/-0.8, respectively; P < 0.005). Morphological coronary changes early after transplantation were not correlated to endothelin plasma levels or myocardial gene expression. CONCLUSION: Coronary endothelial vasomotor dysfunction after cardiac transplantation is associated with an increased myocardial endothelin mRNA expression and decreased endothelin-uptake by the heart. We postulate that early activation in the endothelin system may have a pivotal role in the acceleration of the atherosclerotic process in transplant patients.

Adult↗
PubMed1998

Cocaine increases the endothelial release of immunoreactive endothelin and its concentrations in human plasma and urine: reversal by coincubation with sigma-receptor antagonists.

BACKGROUND: Cocaine-associated vascular events are not completely explained by adrenergic stimulation. The purposes of this study were to investigate whether vasoconstrictive endothelin-1 is released by cocaine and to elucidate the mechanisms involved. METHODS AND RESULTS: Endothelin-1 was measured by radioimmunoassay and high-performance liquid chromatography (1) in the supernatant of porcine aortic endothelial cells after treatment with cocaine (10(-7) to 10(-4) mol/L) and a sigma-receptor antagonist, haloperidol (10(-6) mol/L) or ditolylguanidine (10(-5) mol/L) and (2) in plasma and urine of 12 cocaine-intoxicated patients and 13 healthy control subjects. Radioligand binding assays were performed on endothelial membrane preparations. In cell culture, cocaine significantly increased endothelin accumulation above baseline at 3 to 24 hours; endothelin release rates per hour increased dose-dependently, reaching a plateau of 175+/-23% of control at hour 4 to 5. Coincubation of cocaine with haloperidol or ditolylguanidine abolished or reduced cocaine-induced endothelin release. Endothelial membrane preparations specifically and displaceably bound the highly selective sigma-ligand [3H]ditolylguanidine (25x10(-9) mol/L), with 1400 binding sites estimated per cell. Endothelin-1 levels in plasma (22.7+/-5.6 versus 7.3+/-0.8 pmol/L) and urine (41.5+/-10.1 versus 12.7+/-3.8 pmol/L) of cocaine-intoxicated patients were significantly increased compared with control values. CONCLUSIONS: The data suggest that cocaine increases the endothelin-1 release in vitro and in vivo. The cocaine-induced vasoconstriction/vasospasm may therefore be facilitated by the release of endothelin-1. Cocaine appears to be an exogenous stimulator at endothelial sigma-receptors. The endogenous ligands of this antiopioid system may prove to play a role in vasospastic angina, acute myocardial infarction, and sudden cardiac death.

Acute Disease↗
PubMed1998

Endothelin B receptor-mediated increase of cerebral blood flow in experimental pneumococcal meningitis.

Study investigates the role of endothelin (ET) receptors in mediating early changes in cerebral blood flow--as measured by laser Doppler flowmetry (CBFLDF)--during experimental pneumococcal meningitis. Meningitis was induced with heat-killed pneumococci and confirmed by a significant increase in CBFLDF (baseline 100%; 225.3 +/- 21.8% after 6 hours; mean +/- SD), intracranial pressure (ICP), brain water content, and white blood cell count in the CSF. Intravenous administration of the selective endothelin B (ETB) receptor antagonist BQ-788 immediately before pneumococcal challenge (but not 4 hours afterward) significantly attenuated these pathophysiologic alterations (e.g., CBFLDF 6 hours after pneumococcal challenge: 116.7 +/- 17.4%). Pretreatment with BQ-123, a selective endothelin A receptor antagonist, had no significant effect on ICP and brain water content, but augmented the increase in CBFLDF and CSF white blood cell count. Since ET is known to trigger the release of nitric oxide (NO) by ETB receptor activation, we examined specific ET-NO interactions in primary rat cerebromicrovascular endothelial cells after stimulation with heat-killed pneumococci. Pneumococci induced a significant increase in both ET and NO concentrations in endothelial cell culture medium. Treatment with phosphoramidon, an inhibitor of the endothelin-converting enzyme, prevented the production of endothelin and markedly reduced NO generation. Our data provide evidence that ET is involved as a mediator in early pneumococcal meningitis in the rat and contributes to the increase in CBFLDF, ICP, brain water content, and CSF pleocytosis, presumably through ETB receptor-mediated NO production.

Animals↗
PubMed1997

[Necrotizing fasciitis].

Necrotizing fasciitis has changed considerably over time. The disease used to be due to group A streptococci and affected otherwise quite healthy or traumatized subjects. Today we see multibacterial infections in polymorbid or immunocompromised patients. Rapid and resolute surgery is of critical prognostic value. Early clinical recognition may be difficult. Sometimes frozen-section biopsy proves helpful. Septic immune response and organ failure develop rapidly in these patients. After vigorous staged necrosectomy, extensive plastic reconstruction is mostly required.

Debridement↗
PubMed1996

Prevention of hyperacute rejection by human decay accelerating factor in xenogeneic perfused working hearts.

As a potential source of organs for xenotransplantation, pigs that are transgenic for human decay accelerating factor (DAF) have been bred in order to overcome hyperacute rejection. We investigated the protective effect of human DAF in a porcine working heart model perfused by human blood. Hearts of normal landrace pits served as controls. The following parameters were measured: stroke work index, coronary flow and arteriovenous oxygen consumption, 6-keto prostaglandin F1alpha and prostaglandin E2 as markers of endothelial cell activation; creatine phosphokinase and lactate dehydrogenase for evaluation of the extent of myocardial damage; TNFalpha and IL-6 as markers of mononuclear cell activation. Histological and ultrastructural investigations from myocardial tissue sections were done at the end of perfusion. Human (h) DAF appeared to inhibit complement-mediated endothelial cell activation of transgenic pig hearts successfully. This was in contrast to landrace pig hearts, which had a sixfold increase of prostaglandin levels during perfusion with human blood. The cardiac weight increase during perfusion time due to interstitial edema tended to be less in the hDAF group. Myocardial damage was minimal in transgenic hearts, whereas normal pig hearts produced a threefold increase of creatine phosphokinase and lactate dehydrogenase levels. In these hearts, electron microscopy revealed single cell necrosis of myocytes and vacuolization of mitochondria with cristae rupture. According to the results obtained in the working heart model, the breeding of pigs that are transgenic for hDAF represents a promising step to making heart xenotransplantation a clinical reality in the future.

Acute Disease↗
PubMed1995

Bidirectional effects of endogenous opioid peptides on endothelin release rates in porcine aortic endothelial cell culture: mediation by delta opioid receptor and opioid receptor antagonist-insensitive mechanisms.

The effects of opioid peptides on immunoreactive endothelin (ir ET) release from cultured porcine aortic endothelial cells over a 1-hr period (4-5 or 23-24 hr) were determined by radioimmunoassay and high-performance liquid chromatography after treatment for either 4 or 23 hr. Endogenous opioids, the synthetic delta opioid [D-Pen2,5]enkephalin and, for comparison, atrial and brain natriuretic peptides were added to the culture medium in concentrations ranging from 10(-12) to 10(-7) M. Thrombin (0.1-10 U/ml) served as a stimulatory reference. 1) Brain natriuretic peptide displayed only insignificant effects on ir ET release at 5 hr, but strongly inhibited ir ET release at 24 hr. 2) Opioids modulated release rates at 5 hr but did not display significant effects at 24 hr: metorphamide with predominant mu/kappa and weak delta opioid receptor activity stimulated release in a dose-dependent manner, whereas [Met5]enkephalin-Arg6-Phe7 with mu/delta activity and the delta agonists [Leu5]enkephalin, sulfated [Leu5]enkephalin and [D-Pen2,5]enkephalin decreased release rates; [Leu5]enkephalin was the most potent of the latter drugs. 3) Coincubation with either the nonselective opioid receptor antagonist naloxone (10(-5) M) or the delta receptor-selective antagonist ICI-174,864 (N,N-bisallyl-Tyr-D-Ala-Aib-Aib-Phe-Leu-OH) (10(-5) M) abolished all opioid-induced inhibitory effects, but rather potentiated or unmasked stimulatory effects of opioid peptides on ir ET release rates at 5 hr and also at 24 hr in the case of the delta agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Increased endothelin plasma concentrations in patients with coronary artery disease or hyperlipoproteinemia without coronary events.

Endothelins are made by endothelial cells, macrophages, and vascular smooth muscle cells, among others, and are the most potent endogenous vasoconstrictors yet discovered, with additional growth-promoting properties. A locally increased endothelin production in coronary artery disease or other atherosclerotic diseases may increase circulating endothelin plasma concentrations before symptoms of disease are manifest. We determined endothelin plasma concentrations (1) in 43 patients suffering from coronary artery disease (CAD); (2) in 43 patients with hyperlipoproteinemia without coronary artery disease (HLP); (3) in 29 healthy control subjects (C), by means of a novel extraction procedure and radioimmunoassay followed by chromatographic separation. Plasma concentrations in HLP and C overlapped, but were still significantly different (29 +/- 10 vs 21 +/- 8 fmol/ml, ANOVA and Duncan's test). Significantly increased plasma concentrations were also found in patients with CAD, with the highest levels in a subgroup of 8 patients presenting with unstable angina (43 +/- 12 vs 53 +/- 15 fmol/ml). There were no statistically significant differences between CAD groups with (n = 28) or without hyperlipoproteinemia (n = 15) (42 +/- 14 vs 41 +/- 16 fmol/ml; n.s.). Likewise there was no relationship between endothelin plasma concentration in any of the patients studied and lipid fractions in serum. Increased endothelin plasma concentrations in HLP patients without evidence of coronary artery disease are thus not related to the hyperlipidemic state per se, but may rather indicate presence of an increased vasoconstrictor tonus, pre-clinical or silent atherosclerotic disease.

Chromatography, Gel↗
PubMed1990

Different behaviour of the N-terminal and C-terminal fragment of proatrial natriuretic factor in plasma of healthy subjects as well as of patients with cirrhosis.

N-terminal (atrial natriuretic factor (ANF) 1-98) and C-terminal (ANF 99-126) fragments of proatrial natriuretic factor (NTA and CTA, respectively) were determined in plasma of healthy subjects adopting different postures and in patients with cirrhosis. Seven healthy subjects were investigated while seated and 30 min after assuming a horizontal position. NTA plasma concentrations increased in subjects in the horizontal position (from 734 +/- 250 (SE) fmol/ml to 902 +/- 227 fmol/ml; p less than 0.05). In contrast, CTA plasma concentrations remained unchanged (9.2 +/- 1.3 fmol/ml vs 8.9 +/- 1.6 fmol/ml). In 10 patients with cirrhosis of the liver, NTA concentrations were markedly (p less than 0.001) elevated compared to 11 healthy subjects (2334 +/- 291 fmol/ml vs 743 +/- 155 fmol/ml). However, there was no difference of CTA plasma levels between cirrhotic patients and healthy subjects (8.7 +/- 1.3 fmol/ml vs 8.2 +/- 0.9 fmol/ml). These data demonstrate changes of the plasma concentration of the N-terminal fragment of proatrial natriuretic factor by posture and in liver disease, in contrast to unchanged levels of the C-terminal fragment.

Adult↗
PubMed1989

Atrial natriuretic factor and renin-aldosterone in volume regulation of patients with cirrhosis.

The role of the atrial natriuretic factor and of the main counteracting sodium-retaining principle, the renin-aldosterone system, in acute volume regulation of cirrhosis of the liver has been investigated. Central volume stimulation was achieved in 21 patients with cirrhosis, 11 without and 10 with ascites, and 25 healthy controls by 1-hr head-out water immersion. Immersion prompted a highly significant (p less than 0.001) increase of atrial natriuretic factor plasma concentrations in cirrhotic patients without ascites from 8.5 +/- 1.3 fmoles per ml to 16.5 +/- 2.6 fmoles per ml, comparable to the stimulation in control subjects (6.0 +/- 0.6 fmoles per ml to 13.6 +/- 2.6 fmoles per ml). In cirrhotic patients with ascites, atrial natriuretic factor increase (from 7.7 +/- 1.3 fmoles per ml to 11.4 +/- 2.3 fmoles per ml) was blunted (p less than 0.05). Plasma renin activity and plasma aldosterone concentration were elevated in cirrhotic patients, especially in the presence of ascites. Following immersion, plasma renin activity and plasma aldosterone concentration were reduced similarly in all groups. Water immersion induced a more pronounced natriuresis and diuresis in control subjects than in cirrhotic patients. Neither atrial natriuretic factor nor plasma renin activity nor plasma aldosterone concentration alone correlated to sodium excretion. However, atrial natriuretic factor to plasma aldosterone concentration ratios were closely correlated to basal and stimulated natriuresis in cirrhotic patients, particularly in those with ascites. These data suggest that atrial natriuretic factor and the renin-aldosterone system influence volume regulation in patients with cirrhosis.

Adult↗
PubMed1989

Atrial natriuretic factor-like immunoreactivity in spinal cord and in primary sensory neurons of spinal and trigeminal ganglia of guinea-pig: correlation with tachykinin immunoreactivity.

Atrial natriuretic factor (ANF) is a cardiac hormone with various functions in body homeostasis. It is also processed in the brain and in the peripheral nervous system where it appears to play a role as a neuromodulator. Little is known about the presence of ANF throughout the spinal cord of the guinea-pig. We therefore examined the distribution of ANF and its possible interrelation with primary sensory afferents in this species. Using enzyme-and fluorescence-immunohistochemistry on deparaffinized sections. ANF-like immunoreactivity was found to be present in nerve fibers in laminae I/II of the spinal cord and in neurons of spinal and trigeminal ganglia. Tachykinins and ANF coexisted in very few fibers of the spinal cord but did not coexist in primary sensory spinal or trigeminal neurons. Our results indicate that spinal ANF-immunoreactive fibers are of dual origin, primary sensory and non-primary sensory. The possibly heterogeneous source of the non-primary sensory ANF, its possible coexistence with other co-transmitters and functional implications are discussed.

Animals↗
PubMed1989

Immunoreactive atrial natriuretic peptide (ANP) in endoscopic biopsies of the human gastrointestinal tract.

The human gastrointestinal tract, important for body salt and water balance, was investigated by endoscopic biopsy for the presence of atrial natriuretic peptide (ANP). Using immunohistochemistry, ANP-immunoreactive cells were identified in the lamina epithelialis mucosae of stomach, duodenum, jejunum, colon, and rectum. The findings indicate that ANP plays a role in intestinal salt and water regulation in man. ANP measurements in tissue specimens reached by endoscopic biopsy may be of major interest for future investigations on (patho-)physiological and pharmacological aspects of ANP.

Adult↗
PubMed1989

Human atrial natriuretic peptide in non-dialyzed patients with chronic renal failure.

The role of human atrial natriuretic peptide (alpha-hANP) in the regulation of blood pressure (BP) and extracellular fluid volume (ECFV) remains elusive. This is of particular interest in chronic renal failure, in which first, increased sodium and water retention plays a major pathogenetic role in the development of hypertension, and second, altered secretion and/or metabolism of alpha-hANP may contribute to fluid volume and BP regulation. In the present study the relationship between renal function, BP, and circulating alpha-hANP was investigated in 16 non-dialyzed patients with stable chronic renal failure (CRF) without edema. Analysis of potential molecular heterogeneity of immunoreactive (ir) ANP was performed by gel permeation chromatography of plasma extracts from normotensive patients with CRF. Serum creatinine concentrations averaged 435 +/- 76 mumol/l ranging from 127 to 1187 mumol/l, systolic and diastolic BP averaged 158 +/- 4 and 94 +/- 2 mmHg, respectively. Plasma alpha-hANP concentrations ranged from 5 to 75 with a mean of 23 +/- 4 pmol/l as compared to a mean of 10 +/- 1 pmol/l in healthy volunteers (p less than 0.05). A significant linear correlation between plasma alpha-hANP and serum creatinine concentrations (r = 0.92) was observed; a weaker correlation was found between mean arterial pressure and alpha-hANP (r = 0.66). Chromatographic analysis revealed considerable amounts of higher molecular weight circulating ir-ANP, approximately 15,000 Da, in addition to the biologically active small mol wt ANP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Presence of the atrial natriuretic factor (ANF) in human ascitic fluid.

Presence of atrial natriuretic factor (ANF)-like material was demonstrated by radioimmunoassay in ascitic fluid of 14 patients with cirrhosis of the liver. Immunoreactive ANF concentrations (M +/- SEM) were 2.4 +/- 0.5 fmol/ml in ascites, significantly lower (p less than 0.001) than the corresponding plasma concentrations of 15.5 +/- 2.6 fmol/ml. High performance gel permeation chromatography and reverse phase high performance chromatography of the ascitic ANF immunoreactivity showed correspondence to the alpha human ANF (99-126). ANF levels in ascites were significantly (p less than 0.01) correlated to levels in plasma (r = 0.66).

Ascites↗
PubMed1988

Acute and chronic effects of nitrendipine on hemodynamics and myocardial ischemia in patients with combined angina pectoris and hypertension.

To examine the antianginal and antihypertensive efficacy of nitrendipine, a new calcium channel blocking agent, 25 patients with chronic stable angina pectoris (NYHA I-III) and systemic hypertension underwent cardiac catheterization and treadmill exercise tests. Acute hemodynamic results were obtained before and 2 h after oral administration of 20 mg nitrendipine. They showed a significant decrease in aortic pressure (162.1 +/- 27.4/80.0 +/- 12.1 vs. 134.9 +/- 23.5/74.2 +/- 13.1 mm Hg), pulmonary arterial pressure (25.4 +/- 5.4/11.3 +/- 3.7 vs. 21.9 +/- 5.4/9.9 +/- 3.7 mm Hg), and pulmonary wedge pressure (10.0 +/- 4.4 vs. 6.6 +/- 3.8 mm Hg). Cardiac index (+31%) and stroke volume (+33%) increased markedly, whereas heart rate remained unchanged (66.9 +/- 11.4 vs. 66.8 +/- 10.8 beats/min). Chronic hemodynamic results and exercise tolerance tests were obtained before and 8 weeks after oral nitrendipine therapy. A significant decrease in arterial blood pressure was observed (167 +/- 22/86 +/- 10 vs. 126 +/- 32/76 +/- 19 mm Hg). Exercise tolerance improved concerning test duration (+22%) and total exercise capacity (+37%). Maximal ST-segment depression decreased by 30% (0.2 +/- 0.03 vs. 0.14 +/- 0.02 mV) and subsequently the anginal frequency was reduced from 7.8 +/- 2.1 to 3.8 +/- 1.7 attacks/week (-50%). The maximal rate-pressure product during exercise remained unchanged. Plasma levels of cholesterol, triglycerides, and LDL- and HDL-cholesterol did not show any significant alterations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗