Background:Previous reports have highlighted the high prevalence of blood culture negative endocarditis (BCNE) in South Africa. Methods:The Tygerberg Endocarditis cohort (TEC) study is a prospective cohort study of patients with con rmed or suspected IE presenting to Tygerberg Academic Hospital,
Atrial natriuretic peptide is stored by atrial myocytes in secretory granules, known as atrial specific granules, and is released from these granules by exocytosis. We have isolated a group of atrial proteins by affinity chromatography that bind to atrial specific granules in a calcium-dependent manner. The two major proteins isolated (32.5 kd and 67 kd) are calcium-binding proteins and have been identified as annexins V and VI by immunoblotting with specific antisera. The calcium dependence of their binding to atrial specific granules has been characterized in vitro and indicates that this interaction takes place at micromolar levels of calcium. In addition, the group of proteins isolated includes another calciumbinding protein of 20 kd, as well as GTP-binding proteins of 22 to 26 kd. Membrane interactions during exocytosis are presumably mediated by the interaction of specific proteins with the granule membrane. The properties of the proteins described here, and their ability to bind to atrial specific granules in a calcium-dependent manner, make them likely candidates in the search for regulatory proteins mediating atrial natriuretic peptide secretion. (Hypertension 1991;18:648-656) A trial natriuretic peptide (ANP), a potent natri-/ \ uretic, diuretic, and vasorelaxant factor, is A. A . secreted from the mammalian heart. 1 Electron-dense granules present in atrial myocytes, 2 known as atrial specific granules (ASG), are now recognized as the intracellular storage sites for ANP. 3 These secretory granules therefore form part of the regulated secretory pathway for ANP.In other endocrine organs, such as the adrenal medulla, calcium plays an important role in the control of the secretory pathway. 4 -5 Various studies have indicated that calcium is also involved in the regulation of ANP secretion from the heart. 6 -10 The regulatory role of calcium during hormone secretion in many noncardiac endocrine organs is mediated by calcium-binding proteins. 11 Calmodulin, the ubiquitous calcium-binding protein, has been extensively studied in this regard. 12 Although ANP is present in In this study, calcium-dependent affinity chromatography with immobilized ASG was used to isolate atrial cytosolic proteins that may interact with atrial secretory granules during the regulated secretion of ANP. Proteins isolated include annexins V and VI, and their calcium-dependent binding to ASG has been characterized. Methods Granule IsolationAtria were obtained from female Sprague-Dawley rats (weight 250-275 g) after decapitation. Granules were isolated essentially as reported earlier. 3 Batches of 30 atria (from 15 rats) were processed and pooled. They were rinsed, minced, and homogenized in 0.25 M sucrose, 10 mM tris (hydroxymethyl) aminomethane
The calcium dependence of the atrial natriuretic peptide (ANP) secretory system is controversial. Some studies clearly support a stimulatory role, whereas others favor an inhibitory role for calcium in this endocrine system. We demonstrate that calcium is involved in both a positive modulatory role and a negative modulatory role, thereby providing some explanation for the seemingly irreconcilable findings previously published. The negative modulatory role performed by calcium is evident during basal secretion, whereas the positive modulatory role is especially evident in the sustained phase of the secretory response to stimulation. Furthermore, we demonstrate the calcium dependence of processing of the prohormone to the mature circulating form in a cell culture system. This supports the concept that processing is a function of the atrial myocyte rather than of the mesenchymal cells of the atrium. We have demonstrated previously that calcium is important for packaging of the prohormone into secretory granules. Together these findings support a multifaceted role for calcium in the regulation of the secretory apparatus for ANP.
The research presented in this paper serves to provide a tool to autonomously screen for cardiovascular disease in the rural areas of Africa. With this tool, cardiovascular disease can potentially be detected in its initial stages, which is essential for effective treatment. The autonomous auscultation system proposed here utilizes recorded heart sounds and electrocardiogram signals to automatically distinguish between normal and abnormal heart conditions. Patients that are identified as abnormal by the system can then be referred to a specialist consultant, which will save a lot of unnecessary referrals. In this study, heart sound and electrocardiogram signals were recorded with the prototype precordial electro-phonocardiogram device, as part of a clinical study to screen patients for cardiovascular disease. These volunteers consisted of 28 patients with a diagnosed cardiovascular disease and, for control purposes, 34 persons diagnosed with healthy hearts. The proposed system employs wavelets to first denoise the recorded signals, which is then followed by segmentation of heart sounds. Frequency spectrum information was extracted as diagnostic features from the heart sounds by means of ensemble empirical mode decomposition and auto regressive modelling. The respective features were then classified with an ensemble artificial neural network. The performance of the autonomous auscultation system used in concert with the precordial electro-phonocardiogram prototype showed a sensitivity of 82% and a specificity of 88%. These results demonstrate the potential benefit of the precordial electro-phonocardiogram device and the developed autonomous auscultation software as a screening tool in a rural healthcare environment where large numbers of patients are often cared for by a small number of inexperienced medical personnel.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.