{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T22:01:23Z","timestamp":1779919283816,"version":"3.53.1"},"reference-count":43,"publisher":"American Physiological Society","issue":"2","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["American Journal of Physiology-Regulatory, Integrative and Comparative Physiology"],"published-print":{"date-parts":[[2008,2]]},"abstract":"<jats:p> Djungarian or Siberian hamsters ( Phodopus sungorus) acclimated to short photoperiod display episodes of spontaneous daily torpor with metabolic rate depressed by \u223c70% and body temperature (T<jats:sub>b<\/jats:sub>) reduced by \u223c20\u00b0C. To study the cardiovascular adjustment to daily torpor in Phodopus, electrocardiogram (ECG) and T<jats:sub>b<\/jats:sub> were continuously recorded by telemetry during entrance into torpor, in deep torpor, and during arousal from torpor. Minimum T<jats:sub>b<\/jats:sub> during torpor bouts was \u223c21\u00b0C, and heart rate, \u223c349 beats\/min at euthermy, displayed marked sinus bradyarrhythmia at \u223c70 beats\/min. Arousal was typically completed within \u223c40 min, followed by a sustained posttorpor inactivity tachycardia (\u223c540 beats\/min). The absence of episodes of conduction block, tachyarrhythmia, or other forms of ectopy throughout the torpor cycle demonstrates a remarkable resistance to arrhythmogenesis. The ECG morphology lacks a distinct isoelectric interval following the QRS complex, and the ST segment resembles the ECG pattern in mice, with a prominent fast transient outward K<jats:sup>+<\/jats:sup> current ( I<jats:sub>to,f<\/jats:sub>) determining the early phase of ventricular repolarization. During low-temperature torpor, the amplitudes of the QRS complex substantially increased, suggesting that in the euthermic state the terminal portion of ventricular depolarization is fused with the beginning of repolarization, low T<jats:sub>b<\/jats:sub> acting to decorrelate the superposition between depolarization and repolarization by delaying the repolarization onset. Atrioventricular and ventricular conduction times were prolonged as function of T<jats:sub>b<\/jats:sub>. In contrast, the QT vs. T<jats:sub>b<\/jats:sub> relationship showed marked hysteresis indicating the operation of nonlinear control mechanisms whereby the rapid QT shortening during arousal results from additional mechanisms (probably sympathetic stimulation) other than temperature alone. <\/jats:p>","DOI":"10.1152\/ajpregu.00496.2007","type":"journal-article","created":{"date-parts":[[2007,11,21]],"date-time":"2007-11-21T20:45:52Z","timestamp":1195677952000},"page":"R639-R650","source":"Crossref","is-referenced-by-count":27,"title":["Cardiac dynamics during daily torpor in the Djungarian hamster (<i>Phodopus sungorus<\/i>)"],"prefix":"10.1152","volume":"294","author":[{"given":"Alexander","family":"Mertens","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Oliver","family":"Stiedl","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stephan","family":"Steinlechner","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"Meyer","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"24","reference":[{"key":"R1","unstructured":"Agduhr F, Stenstrom N. The appearance of the electrocardiogram in heart lesions produced by cod liver oil treatment. Acta Paediatr 8: 493\u2013510, 1929."},{"key":"R2","unstructured":"Antzelevitch C, Dumaine R. Electrical heterogeneity in the heart: physiological, pharmacological and clinical implications. In: Handbook of Electrophysiology: The Heart, edited by Page E, Fozzard H, Solaro RJ. New York: Oxford Univ. Press, 2002, p. 654\u2013692."},{"key":"R3","doi-asserted-by":"publisher","DOI":"10.1111\/j.1540-8167.1999.tb00287.x"},{"key":"R4","doi-asserted-by":"publisher","DOI":"10.1085\/jgp.97.5.973"},{"key":"R5","doi-asserted-by":"publisher","DOI":"10.2307\/1313595"},{"key":"R6","doi-asserted-by":"publisher","DOI":"10.1152\/ajpheart.2001.281.3.H1201"},{"key":"R7","doi-asserted-by":"publisher","DOI":"10.1152\/physrev.00008.2003"},{"key":"R8","doi-asserted-by":"publisher","DOI":"10.1152\/physiolgenomics.00131.2007"},{"key":"R9","doi-asserted-by":"publisher","DOI":"10.1152\/ajpregu.00612.2004"},{"key":"R10","doi-asserted-by":"publisher","DOI":"10.1152\/ajpheart.1987.253.5.H1083"},{"key":"R11","doi-asserted-by":"publisher","DOI":"10.1080\/09687680210139839"},{"key":"R12","doi-asserted-by":"publisher","DOI":"10.1016\/j.hrthm.2005.06.012"},{"key":"R13","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.96.25.14623"},{"key":"R14","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.physiol.66.032102.115105"},{"key":"R15","doi-asserted-by":"publisher","DOI":"10.1007\/BF00387311"},{"key":"R16","doi-asserted-by":"publisher","DOI":"10.1016\/S0022-0736(05)80007-X"},{"key":"R17","doi-asserted-by":"publisher","DOI":"10.1016\/S0022-0736(00)80072-2"},{"key":"R18","doi-asserted-by":"publisher","DOI":"10.1017\/S0033583501003705"},{"key":"R19","doi-asserted-by":"crossref","unstructured":"Heldmaier G, Klingenspor M. Life in the Cold. Berlin: Springer, 2000.","DOI":"10.1007\/978-3-662-04162-8"},{"key":"R20","doi-asserted-by":"publisher","DOI":"10.1152\/ajpendo.1999.276.5.E896"},{"key":"R21","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.physiol.66.032102.115313"},{"key":"R22","doi-asserted-by":"publisher","DOI":"10.1098\/rspa.1998.0193"},{"key":"R23","doi-asserted-by":"publisher","DOI":"10.1161\/01.RES.86.12.1193"},{"key":"R24","doi-asserted-by":"publisher","DOI":"10.1016\/S1054-8807(01)00078-3"},{"key":"R25","doi-asserted-by":"publisher","DOI":"10.1081\/CBI-100101036"},{"key":"R26","doi-asserted-by":"crossref","unstructured":"Lyman CP, Willis JS, Malan A, Wang LCH. Hibernation and Torpor in Mammals and Birds. New York: Academic, 1982.","DOI":"10.1016\/B978-0-12-460420-9.50008-8"},{"key":"R27","doi-asserted-by":"publisher","DOI":"10.1007\/s00421-003-0915-2"},{"key":"R28","doi-asserted-by":"publisher","DOI":"10.1007\/s00285-006-0375-5"},{"key":"R29","doi-asserted-by":"publisher","DOI":"10.1016\/S1095-6433(99)00130-0"},{"key":"R30","doi-asserted-by":"publisher","DOI":"10.1152\/physrev.00002.2005"},{"key":"R31","doi-asserted-by":"publisher","DOI":"10.1161\/hh2301.100349"},{"key":"R32","unstructured":"Osborn JJ. Experimental hypothermia: respiratory and blood pH changes in relation to cardiac function. Am J Physiol 175: 389\u2013398, 1953."},{"key":"R33","doi-asserted-by":"publisher","DOI":"10.1016\/j.physbeh.2004.04.025"},{"key":"R34","doi-asserted-by":"publisher","DOI":"10.1152\/ajpheart.00987.2003"},{"key":"R35","doi-asserted-by":"crossref","unstructured":"Richards AG, Simonson E, Visscher MB. Electrocardiogram and phonocardiogram of adult and newborn mice in normal conditions and under the effect of cooling, hypoxia, and potassium. Am J Physiol 174: 293\u2013298, 1953.","DOI":"10.1152\/ajplegacy.1953.174.2.293"},{"key":"R36","doi-asserted-by":"publisher","DOI":"10.1177\/0748730403254971"},{"key":"R37","doi-asserted-by":"publisher","DOI":"10.1086\/physzool.65.5.30158554"},{"key":"R38","doi-asserted-by":"publisher","DOI":"10.1016\/S0008-6363(00)00051-1"},{"key":"R39","doi-asserted-by":"publisher","DOI":"10.1037\/0735-7044.111.4.703"},{"key":"R40","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.01007.2001"},{"key":"R41","doi-asserted-by":"publisher","DOI":"10.1016\/j.hrthm.2005.06.028"},{"key":"R42","doi-asserted-by":"publisher","DOI":"10.1007\/s00427-004-0403-7"},{"key":"R43","doi-asserted-by":"publisher","DOI":"10.1161\/01.CIR.93.2.372"}],"container-title":["American Journal of Physiology-Regulatory, Integrative and Comparative Physiology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.physiology.org\/doi\/pdf\/10.1152\/ajpregu.00496.2007","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2019,9,8]],"date-time":"2019-09-08T11:53:22Z","timestamp":1567943602000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.physiology.org\/doi\/10.1152\/ajpregu.00496.2007"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2008,2]]},"references-count":43,"journal-issue":{"issue":"2","published-print":{"date-parts":[[2008,2]]}},"alternative-id":["10.1152\/ajpregu.00496.2007"],"URL":"https:\/\/doi.org\/10.1152\/ajpregu.00496.2007","relation":{},"ISSN":["0363-6119","1522-1490"],"issn-type":[{"value":"0363-6119","type":"print"},{"value":"1522-1490","type":"electronic"}],"subject":[],"published":{"date-parts":[[2008,2]]}}}