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At least 127 records · Page 7Linked to original sources
PubMed1978

[Evaluation of sino-atrial function using the method of extrasystole induced by constant-relative premature impulses. 2. Application in 50 normal and abnormal studies].

The total immediate sino-atrial conduction time (SACT) as calculated by constant relative pacing, 40 or 50% of the immediate sinus cycle (SC), normally varies inversely with the SC. 50 patients were investigated by this method. In 38 patients without sino-atrial block (SAB) on the surface ECG, it was found that the mean slope of correlation between SACT and SC varied with the shape of the curve of Strauss and with the presence or absence of a post-pacing depression. The smallest slope was found in the group in which the curve of Strauss was horizontal in zone II, and in which there was no depression. In the groups with a rising zone II, comparative use of pacing with a fixed relationship in milliseconds suggested a phenomenon of decreasing retrograde conduction. In cases with sinus arrhythmia and a Strauss curve with scattered coordinates, the relationship between SACT and SC was maintained. 1st degree right-sided SAB should therefore be defined as a function of the immediate SC. In 12 other patients with SAB on the surface ECG, the immediate SACT was greatly lengthened so as to be immeasurable, and bore no relationship to the SC.

Adolescent↗
PubMed1981

Left atrial function in acute mitral regurgitation. Factors which modify the regurgitant volume.

Dynamic geometry of the left atrium was studied in open-chest dogs instrumented with ultrasonic dimension gauges for the measurement of the transverse diameter together with left ventricular dimensions and left atrial and ventricular pressures. Three definite phasic changes of the left atrial diameter were observed during the cardiac cycle at the control state; shortening of left atrial diameter with atrial contraction, continuous chamber expansion during ventricular ejection, and either a reduction in the diameter or a plateau during mitral valve opening to onset of the next atrial contraction. Acute onset of mitral regurgitation initially induces a remarkable augmentation of atrial shortening with chamber dilation as a result of an optimal use of the Frank-Starling mechanism of the atrial muscle. When mitral regurgitation is progressively increased, the extent of the atrial shortening and expansion is diminished despite the geometrical advantage of a further increase in atrial diameter, indicating that this extreme dilation no longer provokes the Frank-Starling response and the atrial myocardium is made to operate on a descending limb of function. The amount of regurgitation is highly dependent on the geometry of the mitral orifice and a decrease in regurgitation with vasodilator therapy or with positive inotropic agents may be largely related to a decrease in the size of the left heart cavity, which brings closer together components of the mitral apparatus and increases its competence.

Animals↗
PubMed1983

Effect of the ouabain-quinidine interaction on left ventricular and left atrial function in conscious dogs.

The effect of the ouabain-quinidine interaction was examined in 10 conscious dogs. Left ventricular (LV) pressure, LV dP/dt, LV diameter and left atrial (LA) diameter were measured with high-fidelity micromanometers and sonomicrometer crystals. Ouabain, 0.025 mg/kg, significantly (p less than 0.05) increased LV dP/dt, LV and LA fractional shortening and LV and LA velocity of circumferential fiber shortening (Vcf). In a separate experiment, quinidine was administered as a bolus dose, 3.85 mg/kg, followed by an infusion, 0.28 mg/kg/min. This resulted in steady-state quinidine concentrations that produced no change in wall motion or hemodynamics. When ouabain was given 1 hour into the quinidine infusion, only LV dP/dt increased significantly (p less than 0.05). Ouabain alone increased LV dP/dt 26.4 +/- 3.5%, whereas ouabain during the quinidine infusion increased it by 9.5 +/- 2.3%. Similar differences were seen in the responses to ouabain in the absence and presence of quinidine: LV Vcf, 22.4 +/- 4.9% vs 6.0 +/- 2.1%, LV fractional shortening, 23.1 +/- 4.6% vs 5.8 +/- 2.1%, LA Vcf, 22.7 +/- 5.9 vs 4.6 +/- 2.0% and LA fractional shortening, 21.8 +/- 7% vs 7.8 +/- 3.3%. Thus, in the presence of quinidine the increase in intropy usually seen with ouabain was markedly attenuated. These data suggest that the quinidine-induced increase in digoxin serum concentrations is accompanied by a decrease in the contractile response of the heart to digoxin.

Animals↗
PubMed1995

[Stroke in pacemaker users for sinus node disease. Relevance of atrial function and clinical characteristics].

Several studies reported that the annual incidence of stroke in patients with sick sinus syndrome ranges from 6 to 10% while the incidence of stroke in patients with atrial fibrillation is about 2-4% and about 0.1% in the normal population. We evaluated the prevalence of cerebral ischemia and peripheral embolism and investigated the predictor factors in a population of 80 patients paced for sick sinus syndrome. The implanted pacemakers were 40 ventricular and 40 physiological stimulation mode was based on the physicians judgement. All patients had cerebral computed tomography scan at the time of implant and after 24 months. Statistical analysis included log-rank test and actuarial curve calculated with Mantel-Haenszel method. At the end of follow-up the end-point occurred in 15 patients: 2 patients had asymptomatic cerebral infarction, 2 had fatal stroke, 2 developed peripheral embolysm, 1 to the lower limb and 1 abdominal; in 4 patients a transient ischemic attack occurred, in 2 a minor stroke and in 3 a non invalidant stroke. No statistically significant difference was found among the subgroups; with different pacing modality. In conclusion, multivariate analysis underlines the role of age > 65 years, history of cerebral ischemia, low atrial ejection force and spontaneous echo contrast in the development of embolic episodes.

Aged↗
PubMed1981

Experimental evaluation of atrial function in right atrium--pulmonary artery conduit operation for tricuspid atresia.

Right ventricular bypass operations were performed in dogs by right atrium--pulmonary artery (RA-PA) conduits with closure of the tricuspid valve. Atrial fibrillation (AF) was induced in prebypass (control) and postbypass (postconduit) studies. Six dogs tolerated the procedure and had postoperative sinus rhythm (SR). In the postconduit studies, AF resulted in significant decline in both mean arterial pressure (73 +/- 2 to 65 +/- 2 mm Hg [mean +/- SEM], p less than 0.05) and pulmonary blood flow (1,050 +/- 160 to 880 +/- 110 ml/min, p less than 0.05). However, there were no significant differences between the magnitude of these changes and those during control studies. Mean right atrial pressure was markedly elevated (17.3 +/- 1.3 mm Hg) during SR after the conduit operations, but it did not increase significantly with AF. In volume load studies, pulmonary blood flow increased in proportion to rises between 15 and 30 mm Hg in mean right atrial pressure. The results suggest that right atrial contraction is not critical to the maintenance of pulmonary blood flow following RA-PA conduit operations.

Animals↗
PubMed1988

Bovine adrenal medullary cells contain functional atrial natriuretic peptide receptors.

The recent report that bovine adrenal chromaffin cells synthesized and secreted atrial natriuretic peptide, ANP, suggested that the peptide may have binding sites in the gland itself. Studies in bovine adrenal medulla membranes did reveal a single class of high affinity [125I]-ANP binding sites with a KD of 94 pM and a density of 1.7 pmol/mg protein. Binding was very rapid (association half-time: 2.5 min), and specific in that only unlabelled ANP displaced bound [125I]-ANP. Application of ANP to bovine chromaffin cells in culture, resulted in a concentration-dependent increase in cGMP synthesis. The data suggest the presence of biologically functional ANP receptors in adrenal chromaffin cells.

Adrenal Cortex↗
PubMed1984

Echocardiographic evaluation of atrial function after Senning and Mustard correction for transposition of the great arteries.

Two groups of six children who had undergone either Senning or Mustard repair for uncomplicated transposition of the great arteries were studied with M mode echocardiography derived from a phased array sector scanner picture. The newly created atria were visualised from the subxiphoid region and the upper systemic venous inflow was selected for a simultaneous M mode registration with a subsequent wall motion analysis with a commercially available computer. In the Mustard group of patients the atrial walls seemed to move passively with the overall heart movements, while abrupt atrial wall excursions of both atria synchronous with heart action were noted in all patients after Senning repair. In this group also slow cyclic changes followed respiration. The atrial wall movements were significantly superior (p = 0.001) in the Senning group of patients. It is concluded that, in contrast to the Mustard method, the Senning operation seems to lead to a viable atrium with the capability of increasing and diminishing atrial diameter and with subsequent potential for growth.

Adolescent↗
PubMed1996

The H295R human adrenocortical cell line contains functional atrial natriuretic peptide receptors that inhibit aldosterone biosynthesis.

The inhibitory effect of atrial natriuretic peptide (ANP) on angiotensin II (AII)-stimulated aldosterone secretion has been previously studied in rat and bovine adrenal zona glomerulosa cells in primary culture. However the understanding of the mode of action of ANP at the molecular level has been hampered by limitations of those primary cell culture systems and by the lack of cell lines from human adrenal cortex. Here we demonstrate the presence of fully functional ANP receptors in the recently characterized AII-responsive adrenocortical carcinoma cell line H295R. Specific saturable binding of 125I-rANP to H295R cell membrane preparations revealed a single class of high affinity binding sites with a density of 20 fmol/mg of protein. The pharmacological profile of this ANP receptor was documented by competitive binding of 125I-rANP with naturally occurring natriuretic peptides. rANP was the most potent with a Kd of 42 pM. pBNP32 was less potent with a Kd of 174 pM. 125I-rANP binding was not competed by pCNP (NPRB-specific ligand) nor by C-ANF (NPRC-specific ligand). Photoaffinity labeling of membrane preparations with 125I-BPA-ANP revealed a single specific protein of molecular weight around 130 kDa. This protein was further identified by immunodetection with a specific antibody directed to the human ANP-specific receptor NPRA. Natriuretic peptides stimulated cGMP production by the receptor-coupled guanylate cyclase with the same specificity. Aldosterone production by AII-stimulated H295R cells was dose-dependently inhibited by rANP with an ED50 of 1.5 nM. In addition, we used this model to test two chimeric analogs of ANP and BNP. pBNP1 and pBNP3 were, respectively, 4- and 2-fold more potent than rANP in competing for 125I-rANP binding with Kd of 10 and 20 pM. pBNP1 was 24-fold more potent in inhibiting AII-stimulated aldosterone production with ED50 of 63 pM. pBNP1 is therefore the most potent natriuretic peptide analog tested. In summary, the human H295R cell line contains NPRA receptors positively coupled to the particulate guanylate cyclase and that antagonize angiotensin II stimulation of aldosterone secretion.

Adrenal Cortex↗
PubMed1993

Human small cell lung cancer cell lines express functional atrial natriuretic peptide receptors.

Small cell lung cancer cell (SCLC) lines, NCI-H82, NCI-H660, and NCI-H1284, and HeLa cells were analyzed for the presence of atrial natriuretic peptide (ANP) receptors. In these SCLC cell lines and HeLa cells, ANP A receptor mRNA was identified by Southern blot analyses of polymerase chain reaction products and RNase protection assays using poly(A)(+)-selected RNA. Saturable binding assays revealed that HeLa cells had 2000 to 5000 high affinity atrial natriuretic peptide receptors per cell with a dissociation constant of 140 pM. In the SCLC cell lines, the binding was saturable but too low to accurately estimate the number of binding sites. After addition of human ANP, radioimmunoassays revealed accumulation of cyclic GMP in SCLC cells as well as HeLa cells in a dose-dependent fashion. The half-maximal stimulation concentration of cyclic GMP accumulation in HeLa and these SCLC cell lines was approximately 2 nM. Tetrazolyl blue assays and tritiated thymidine incorporation did not show any remarkable growth inhibition or growth stimulation of SCLC cell lines after addition of human ANP up to 3.3 microM, more than 1000-fold greater than the half-maximal stimulation concentration of cyclic GMP accumulation. Our results indicate that human SCLC cells express functional ANP receptors but ANP addition produced no detectable change in their growth pattern.

Atrial Natriuretic Factor↗
PubMed1976

Functionally atrialized parchment-like right ventricle with extensive myocardial fibrosis of left ventricle.

A 18-year-old female with unusual type of parchment-like right ventricle died of intractable congestive heart failure was reported. A catheter study revealed the absence of systolic contraction of the right ventricle. The pressure tracing curve in the right ventricle was virtually the same as in the right atrium. At autopsy, there was an extensive myocardial fibrosis of the left ventricle in addition to the almost total absence of the myocardium of the right ventricle. The case was considered to be a unique type of idiopathic cardiomyopathy.

Adolescent↗
PubMed1991

Effects of hyperglycaemia on kidney function, atrial natriuretic factor and plasma renin in patients with insulin-dependent diabetes mellitus.

In normoalbuminuric patients with insulin-dependent diabetes mellitus, plasma atrial natriuretic factor (ANF), cyclic GMP and active renin and the renal clearances of [99Tcm]-diethylenetriaminepentaacetic acid (DTPA) lithium and sodium were studied on a hyperglycaemia day and a euglycaemia day. Baseline euglycaemia was achieved by an overnight variable insulin infusion, which during study days was fixed at the rate necessary to maintain euglycaemia in the morning. After a baseline euglycaemic clearance period of 90 min, measurements were repeated in a new 90-min period beginning 150 min later. On the hyperglycaemia day i.v. infusion of 20% glucose was started at the end of the euglycaemic baseline period, increasing blood glucose (5.3 +/- 1.3 vs 12.1 +/- 1.2 mmol l-1, p less than 0.01). On the euglycaemia day blood glucose declined (5.1 +/- 1.0 vs 4.2 +/- 1.0 mmol l-1, p less than 0.02). Glomerular filtration rate (GFR) was unchanged by acute hyperglycaemia (127 +/- 16 vs 129 +/- 24 ml min-1, NS), but nearly normalized during maintained euglycaemia on the euglycaemia day (124 +/- 17 vs 105 +/- 16 ml min-1, p less than 0.01). When comparing the hyperglycaemic study period with the similarly timed period on the euglycaemia day, GFR was elevated by hyperglycaemia (129 +/- 24 vs 105 +/- 16 ml min-1, p less than 0.01), while the renal clearances of lithium and sodium were similar. Consequently, the calculated absolute proximal reabsorption rate of sodium and water was elevated during hyperglycaemia. Hyperglycaemia reduced the slight decline in plasma concentrations of ANF and cyclic GMP observed on the euglycaemia day. Active renin, glucagon and plasma osmolality were unchanged. In conclusion, marked changes in glomerular filtration rate are induced by changes in blood glucose concentration, but the effect is delayed and thus not directly related to renal tubular transport of glucose. Hyperglycaemia does not affect renal clearances of lithium and sodium, while proximal tubular reabsorption is markedly stimulated. These changes are not related to changes in ANF, renin, glucagon or plasma osmolality.

Adult↗
PubMed1989

Functional atrial natriuretic peptide receptor in human adrenal tumor.

The effects of synthetic human atrial natriuretic peptide (ANP) on the release of catecholamines, aldosterone, or cortisol were observed in human adrenal tumors obtained surgically from patients with pheochromocytoma, primary aldosteronism, or Cushing's syndrome, respectively. Each tumor tissue or adjacent normal cortical tissue was sectioned into slices, which were incubated in medium-199 in the presence or absence of adrenocorticotrophin (ACTH) and ANP. The amounts of epinephrine, norepinephrine, aldosterone, or cortisol released into the medium were measured. Existence of ANP receptors on the adrenal tissues was examined by binding assays, affinity labeling, and immunohistochemistry. Release of catecholamines from pheochromocytoma tissues was inhibited by ANP, and the presence of the ANP receptor on pheochromocytoma was further demonstrated by both binding assays and affinity labeling; Scatchard analysis revealed a single class of binding sites for ANP with a Kd of 1.0 nM and a Bmax of 0.4 pmol/mg of protein and the molecular size was estimated as 140 and a 70 kDa under nonreducing and reducing conditions, respectively. The presence of ANP receptors in pheochromocytoma was demonstrated by immunohistochemistry. ANP inhibited both basal and ACTH-stimulated aldosterone secretion in the slices of normal cortex, and localization of ANP receptors in zona glomerulosa cells was also demonstrated. However, ANP did not inhibit basal and ACTH-stimulated aldosterone and cortisol secretion in both tissue slices from aldosteronoma and Cushing's adenoma. Consistent with these observations, the absence of ANP receptors in adenoma tissues was determined by binding assays, affinity labeling, and immunohistochemistry.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex↗