Severity: Warning
Message: file_get_contents(https://...@pubfacts.com&api_key=b8daa3ad693db53b1410957c26c9a51b4908&a=1): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 176
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 176
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 250
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3122
Function: getPubMedXML
File: /var/www/html/application/controllers/Detail.php
Line: 575
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 489
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Although intracellular calcium ([Ca(2+)](i)) transients in cardiac cells have been well studied in the uniformly polarized cell membrane, how these transients are modified during field stimulation when the cell membrane is nonuniformly polarized has not been investigated. In this study we characterized the effects of uniform field stimuli on [Ca(2+)](i) transients in isolated guinea pig cardiac cells. Single guinea pig cells were enzymatically isolated, loaded with the [Ca(2+)](i) fluorescent indicator fluo-3, and stimulated along their longitudinal axes with S1 or S1-S2 (S1-S2 = 50 ms) pulses. The fluorescence signals were recorded simultaneously from up to 12 sites along the cell length using a multisite mapping system. S1 pulse, applied during the resting phase of the action potential, induced [Ca(2+)](i) transients that had an earlier onset at the anodal-facing end, suggesting that [Ca(2+)](i) gradients (nabla[Ca(2+)](i)) develop during the rising phase of the [Ca(2+)](i) transients. With the assumption that the peak change in [Ca(2+)](i) is 980 nM, nabla[Ca(2+)](i) was estimated to be approximately 3.4 nM/microm in the anodal half of the cell for a nominal 10 V/cm field and negligible in the cathodal half. The S2 pulse that was applied during the plateau of the action potential also perturbed the [Ca(2+)](i) transients and produced [Ca(2+)](i) gradients directed from the center to either end of the cell. Mean nabla[Ca(2+)](i) in the anodal half of the cell (approximately 4.2 nM/microm) was found to be statistically higher than in the cathodal half (approximately 2.8 nM/microm).
Download full-text PDF |
Source |
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http://dx.doi.org/10.1152/ajpheart.2002.282.1.H72 | DOI Listing |
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