The objective of this study is to combine troponin and indicators of cardiac acoustics for synthetically evaluating cardiac fatigue of rabbits, analyzing exercise-induced cardiac fatigue (EICF) and exercise-induced cardiac damage (EICD). New Zealand white rabbits were used to conduct a multi-step swimming experiments with load, reaching an exhaustive state for evaluating if the amplitude ratio of the first to second heart sound (S1/S2) and heart rate (HR) during the exhaustive exercise would decrease or not and if they would be recovered 24-48 h after exhaustive exercise. The experimental end point was to complete 3 times of exhaustions or death from exhaustion. Circulating troponin I (cTnI) were detected from all of the experimental rabbits at rest [(0. 02±0. 01) ng/mL], which, in general, indicated that there existed a physiological release of troponin. After the first exhaustive swim, cTnI of the rabbits increased. However, with 24-hour rest, S1/S2, HR, and cTnI of the tested rabbits all returned toward baseline levels, which meant that the experimental rabbits experienced a cardiac fatigue process. After repeated exhaustion, overloading phenomena were observed, which led to death in 3 out of 11 rabbits, indicating their cardiac damage; the troponin elevation under this condition could be interpreted by pathological release. Evaluation of myocardial damage can not be based on the troponin levels alone, but can only be based on a comprehensive analysis.
Animals ; Fatigue ; Heart ; physiopathology ; Heart Rate ; Myocardium ; pathology ; Rabbits ; Swimming ; Troponin I ; blood

This paper presents a preliminary study of rabbit experiment modality incorporating a new indicator for evaluating cardiac function changes, providing a basis for subsequent study of cardiac fatigue. Using only biochemical indicators, such as troponins, is difficult to make a distinction between exercise-induced cardiac fatigue (EICF) and exercise-induced cardiac damage (EICD). Therefore, some new indicators are needed to evaluate cardiac fatigue synthetically. In our study, we used New Zealand white rabbits to conduct a multi-step swimming experiments with load. We made the rabbits reach an exhaustive state to evaluate whether the amplitude ratio of the first to second heart sound (S1/S2) and heart rate (HR) during the exhaustive exercise would be decreased and whether they would be able to recover after the exhaustive exercise for 24 hours. During the first phase of swimming, S1/S2 and HR were increased, and then decreased at exhaustive state. They were recovered after the exhaustive exercise for 24 hours. Overloading led to deaths of three rabbis, and new phenomena from overloading and related to this kind of death were observed. The experiments proved that Multi-steps swimming experiments with loads by using New Zealand white rabbit is useful for studying cardiac fatigue and premonition of sudden cardiac death.
Animals ; Cardiovascular Physiological Phenomena ; Death, Sudden, Cardiac ; Female ; Heart ; physiology ; Heart Rate ; physiology ; Male ; Muscle Fatigue ; physiology ; Myocardial Contraction ; physiology ; Myocardium ; chemistry ; Physical Endurance ; physiology ; Rabbits ; Stress, Physiological ; physiology ; Swimming

Objective:To explore the effect of clinical conventional fractionated dose radiation on the expression levels of immunogenic cell death (ICD) related proteins in patients with nasopharyngeal carcinoma (NPC).Methods:A total of 38 newly-treated NPC patients admitted to the Affiliated Cancer Hospital of Guizhou Medical University from November 2020 to December 2021 were enrolled, all of whom received induction chemotherapy and concurrent chemoradiotherapy, and another 20 healthy volunteers were selected as controls for a prospective study. The contents of ICD related proteins, namely calreticulin (CRT), high mobility group box 1 protein (HMGB-1) and heat shock protein 70 (HSP70) and the proportion of dendritic cell (DC) in the peripheral blood of patients were detected before treatment, after induction chemotherapy and after concurrent chemoradiotherapy, respectively. The correlation between the above indicators, general clinical data and short-term efficacy was analyzed by statistical methods such as t-test and analysis of variance (ANOVA). Results:The levels of HSP70 and HMGB-1 in peripheral blood of NPC patients before treatment were higher than those of healthy controls (both P<0.05). After concurrent chemoradiotherapy, the content of CRT was significantly higher than that before treatment ( P<0.05), whereas the difference before and after induction chemotherapy and the difference before and after concurrent chemoradiotherapy were not significantly correlated with the short-term efficacy of NPC patients. HSP70 level was significantly decreased after concurrent chemoradiotherapy ( P<0.001). There were no significant differences in the content of HMGB-1 after induction chemotherapy and concurrent chemoradiotherapy (both P>0.05). Conclusion:NPC patients receiving TPF regimen (docetaxel+cisplatin+fluorouracil) for induction chemotherapy and sequential cisplatin concurrent chemotherapy may induce ICD in NPC cells, and CRT has potential value in reflecting the clinical efficacy of NPC.