In vitro assessment of cardiac performance after irradiation using an isolated working rat heart preparation.

The effect of irradiation on cardiac function was assessed using an isolated working rat heart preparation. The animals were given single doses of X-rays in the range 15-30 Gy to their hearts. Cardiac output (CO = aortic flow + coronary flow), heart weight and body weight were followed for a period of 10 months after treatment. Irradiation led to a decrease in cardiac function. This reduction was dose-dependent and progressive with time after treatment. The shape of the Frank-Starling curves constructed for irradiated hearts suggests a loss of contractile function of the myocardium. Coronary flow rates measured in 'working' hearts and in 'Langendorff' hearts were not significantly changed by the irradiation treatment. The isolated working rat heart preparation proved to be a simple and suitable animal model for the investigation of irradiation-induced cardiotoxicity.     

MR imaging of coronary artery flow in isolated and in vivo hearts.

Methods for imaging flow in coronary arteries with magnetic resonance (MR) imaging techniques are demonstrated in isolated heart preparations and live animal models. Coronary artery flow was first imaged with a flow-compensated gradient-echo pulse sequence in isovolumic and working perfused rat hearts and then in vivo. A bolus tracking technique was used to measure flow velocity in the coronary arteries. Ultrafast gradient-echo imaging techniques were then applied, with high resolution obtained by combining the information from several cardiac cycles. A stimulated-echo pulse sequence was demonstrated as a method for performing coronary angiography by flow tagging in isovolumic perfused hearts. This report describes the results of coronary flow MR imaging in isolated rat hearts and live mice and rats. The general approach has proved useful in evaluating new methods for coronary MR angiography and should permit well-controlled studies of pathologic conditions. This ability to image coronary flow in isolated hearts and in small animals should permit integrated MR studies of coronary flow, myocardial perfusion, myocardial metabolism, and cellular ionic status.     

Echo planar imaging of isolated perfused rat hearts at 4.7 T: a comparison of Langendorff and working heart preparations

The implementation of echo planar imaging at 4.7 T is demonstrated using a homebuilt gradient and radiofrequency assembly. The application of such a technique to the study of the isolated perfused rat heart is demonstrated. Langendorff and working heart perfusion preparations are compared and changes in the left ventricular volume shown are to be much larger in the working heart preparation. Such a methodology is expected to provide a useful model for the study of cardiac function and dynamics in the normal and diseased states under controlled perfusion conditions.     

离体心脏灌注模型的制备

目的 通过制备大鼠离体心脏灌注模型,探讨模型制备的方法及注意事项.方法 健康成年大鼠20只,雌雄不限,取离体心脏,制备Langendorff模型及离体工作心脏灌注模型.结果 实验中成功18例(成功率90%).心脏均能持续稳定搏动,心脏收缩有力,左室内压为7.1～10.5 kPa,处于生理范围(6.3～10.3 kPa),心率250～300 /min,心律齐,心脏可平稳跳动6 h以上.结论 Langendorff模型及离体工作心脏灌注模型操作方便、稳定,是比较符合生理特性的离体心脏灌注模型.     

Contractile function of the heart of guinea pigs after long-term continuous stress

Guinea-pigs exposed to 60- and 100-day biosocial stress were used to examine the contractile function of the heart in the whole body and in an isolated state. A 60-day stress effect caused adaptation which included increases in the intensity of heart contractility and in its weight unit by 29% and 38%, respectively. Measurement of resistance of such an adapted heart to isometric load produced by a short-term aortic occlusion showed increases in maximal rates of its contraction and relaxation by 34-35%. After a 100-day stress-effect the strength and velocity of heart contraction and resistance to isometric load returned to normal; however, the intensity of the function of the weight unit increased by 27-32%. The effect of adaptation was also seen in an isolated heart: after a 100-day exposure the isolated hearts did not lose their ability to react to a greater preload according to Starling's law; moreover at the filling pressure 15 cm H2O their cardiac output increased by 50% as compared to the baseline. This observation suggests that the process of adaptation of guinea-pig hearts to chronic stress involves not only activation of central mechanisms of regulation but also enhancement of mechanisms of self-regulation but also enhancement of mechanisms of self-regulation.     

Proton electron double resonance imaging (PEDRI) of the isolated beating rat heart.

Proton electron double resonance imaging (PEDRI) is a double resonance technique where proton MRI is performed with irradiation of a paramagnetic solute. A low-field PEDRI system was developed at 20.1 mT suitable for imaging free radicals in biological samples. With a new small dual resonator, PEDRI was applied to image nitroxide free radicals in isolated beating rat hearts. Experiments with phantoms showed maximum image enhancement factors (IEF) of 42 or 28 with TEMPONE radical concentrations of 2-3 mM at EPR irradiation powers of 12W or 6W, respectively. In the latter case, image resolution better than 0.5 mm and radical sensitivity of 5 microM was obtained. For isolated heart studies, EPR irradiation power of 6W provided optimal compromise of modest sample heating with good SNR. Only a small increase in temperature of about 1 degrees C was observed, while cardiac function remained within 10% of control values. With infusion of 3 mM TEMPONE an IEF of 15 was observed enabling 2D or 3D images to be obtained in 27 sec or 4.5 min, respectively. These images visualized the change in radical distribution within the heart during infusion and clearance. Thus, PEDRI enables rapid and high-quality imaging of free radical uptake and clearance in perfused hearts and provides a useful technique for studying cardiac radical metabolism.     

Cardioprotective effect of spontaneous activity

In the perspective of giving a better understanding of the cardioprotective effects attributable to the tandem low caloric intake and training, Lou/C rats would be an interesting model since these animals exhibit spontaneously these two characteristics for months, without any dietary manipulations or stressor stimuli. No information was so far available on their cardiac function. Therefore, the aim of this pilot study was (i) to document cardiac function before and after ischemia in this strain, and (ii) to investigate whether spontaneous wheel-running activity can improve the ability of cardiac muscle to recover its function after an ischemic period. Cardiac mechanical and metabolic functions were measured in isolated Langendorff hearts from Wistar sedentary, Lou/C sedentary, and Lou/C wheel-running male rats submitted to a 20-min low-flow ischemia and 20-min reperfusion. In Lou/C sedentary rats, rate-pressure product, an index of cardiac work, was decreased before ischemia as compared to Wistar sedentary animals (- 24 %, p < 0.05). After ischemia, cardiac mechanical function recovery did not significantly differ between these two groups. Nevertheless, flux of non-oxidative glycolysis was lower before and after ischemia in Lou/C sedentary animals than in Wistar sedentary rats. In Lou/C rats, during normoxic perfusion, wheel-running activity significantly decreased heart rate (- 15 %), oxygen consumption (- 2.2 %) and cardiac efficiency (- 37 %), whereas coronary flow and flux of non-oxidative glycolysis were significantly increased (+ 15 % and + 263 %, respectively). After ischemia, recovery of cardiac mechanical function and cardiac efficiency were improved in Lou/C wheel-running rats versus Lou/C sedentary animals (p < 0.05). In conclusion, the impact of ischemia-reperfusion is similar between Lou/C- and Wistar sedentary rats. Spontaneous wheel-running activity decreases cardiac efficiency before ischemia and confers a protection against ischemia- and reperfusion-induced injury in isolated Lou/C rat hearts.     

Myocardial kinetics of 99m technetium-Q agents: studies in isolated cardiac myocyte, isolated perfused rat heart, and canine regional myocardial ischemia models.

OBJECTIVE: Based on reports of high cellular uptake and low plasma binding of nonreducible mixed ligand Tc(III) cations (Q complexes) and high linear uptake versus blood flow of 99mTc-Q3 in canine hearts, the authors hypothesized that the two Q complexes, 99mTc-Q63 and 99mTc-Q64, would have high cell uptake and better differentiation between ischemic and nonischemic myocardium compared with other 99mTc-based compounds. METHODS: Uptake and retention kinetics of 99mTc-Q63 and 99mTc-Q64 were measured in isolated rat cardiac myocytes, isolated perfused rat hearts, and intact canines and compared with previously reported Q-based compounds, a clinically available 99mTc perfusion agent (sestamibi), and 201Tl. RESULTS: Uptake of Q63, Q64, and sestamibi by isolated cardiac myocytes was similar. Maximum extraction (Emax) of Q64 by isolated perfused rat hearts was greatest among the 99mTc agents (P < 0.02), but net extraction (Enet) of Q64 was not different from Q63 or sestamibi 3 minutes after tracer injection. By 15 minutes, 201Tl Enet was lower than Q63, Q64, and sestamibi (P < 0.05). Among 99mTc agents, the uptake versus flow of Q3, Q63, and Q64 by canine heart was superior to Q12 and sestamibi (P < 0.05). CONCLUSIONS: The activity of Q63 and Q64 in the myocardium is related to actual myocardial blood flow over a broad, clinically relevant range of flows. The ischemic-to-normal zone activity distributions of Q63 and Q64 approximate actual flow in a manner more like that of 201Tl than sestamibi or Q12. These results provide a rational foundation in support of further evaluation of Q63 and Q64 in humans.     

The Differential Response of the Skin in Young and Old Rats to a Combination of X-rays and ‘Wet’ or ‘Dry’ Hyperthermia

Summary

The left hind feet of groups of female rats aged 7, 14 and 52 weeks were irradiated at three dose levels of X-rays (20, 25 or 30 Gy). Hyperthermia (42·5°C for 1 h) was carried out immediately following irradiation using either ‘wet’ or ‘dry’ heat, achieved by immersion in either water or fluorocarbon liquid.

The results demonstrated that ‘wet’ heat produced a consistently greater enhancement of the irradiation damage than ‘dry’ heat. The thermal enhancement ratio for irradiation plus ‘wet’ heat was approximately 1·5 and for irradiation plus ‘dry’ heat it was in the range 1·17 to 1·39. Immersion of the feet in fluorocarbon liquid at 37°C did not significantly modify the irradiation response of the skin. The lower thermal enhancement ratios obtained using immersion in fluorocarbon liquid at 42·5°C are close to those obtained in large animal studies and also similar to the limited amount of data from clinical studies where microwave or ultrasound heating techniques were used.

It has been demonstrated that there are large age-related differences in the response of the rat foot skin to irradiation alone. It has also been shown in the present study, using rats of the same age, that the response to irradiation plus hyperthermia was less age dependent. This finding may reflect the differing methods by which damage occurs in tissue after irradiation or hyperthermia.     

三种波段电磁辐射对大鼠心脏组织形态的影响

目的 探讨3种不同波段电磁辐射[X波段、S波段、电磁脉冲(EMP)]对大鼠心脏损伤的病理学改变及损伤程度差异。方法 采用二级Wistar大鼠180只,应用电脑随机法分为对照组(36只)、EMP辐照组(48只)、S波段微波辐照组(48只)、X波段微波辐照组(48只)。分别于照后6 h、1、3、7、14、28 d、6和12个月活杀,切取大鼠心脏组织标本行组织学及组织化学观察。结果 与对照组比较3种波段辐照组大鼠心脏呈现不同程度损伤,变化规律相似,以6 h~7 d心脏损伤呈加重趋势,心肌纤维排列紊乱,糖原颗粒减少,核染色质浓缩,蒲肯野纤维溶解,间质水肿,心肌间有浆液渗出。14~28d后心脏呈修复恢复期。6~12个月心脏组织与对照组基本相似。比较同一时间点3种波段辐照组X波段辐照心脏损伤最重、S波段次之、EMP组最轻。正常对照组心脏组织结构基本正常。结论 3种不同波段的电磁辐射均会造成不同程度的心脏损伤,X波段>S波段>EMP,提示波长越短、频率越高致心脏损伤越重,且恢复时间越长。     

Evaluation of cardiac beta-adrenoreceptors in the isolated perfused rat heart using (S)-11C-CGP12388.

(S)-(11)C-CGP12388 ((11)C-CGP12388) was recently developed as an in vivo PET tracer for the evaluation of cardiac beta-adrenergic receptors. The purpose of this study was to evaluate the myocardial kinetics of (11)C-CGP12388 using the perfused rat heart model. METHODS: Normal rat hearts were cannulated for retrograde perfusion according to the Langendorff method. Studies were performed using constant coronary flow rates of 12 mL/min (high flow: n = 6) and 6 mL/min (low flow: n = 6). Beta-adrenergic-blocking studies were also done using propranolol (blocking: n = 6). Two bolus injections of (11)C-CGP12388 were administered at a 25-min interval, and time-activity curves were measured using bismuth germanate detectors. The beta-adrenergic receptor density (B(max)) and total distribution volume (DV(tot)) were estimated using compartmental modeling. After the experiment, B(max) in vitro was measured for all hearts using (3)H-CGP12177, and the values were compared with the B(max) estimated in isolated hearts. RESULTS: DV(tot) was significantly lower in the blocking group than in the high-flow group (P < 0.01), and there was no significant difference in DV(tot) between the high- and the low-flow groups. B(max) values estimated from (11)C-CGP12388 kinetics were 5.05 +/- 0.90 pmol/g under the high-flow model and 5.20 +/- 0.63 pmol/g under the low-flow model. The B(max) results in isolated hearts correlated significantly with the measured in vitro B(max) values (r(2) = 0.69; P < 0.001). CONCLUSION: Beta-adrenoreceptor density in the isolated rat heart can be quantified using (11)C-CGP12388 and a 2-injection protocol. The binding of the tracer was flow independent, with low nonspecific binding. These results suggest that (11)C-CGP12388 is a promising PET tracer that may be applicable to human studies.     

Three-Dimensional gated EPR imaging of the beating heart: Time-resolved measurements of free radical distribution during the cardiac contractile cycle

In vivo or ex vivo EPR imaging, EPRI, has been established as a powerful technique for determining the spatial distribution of free radicals and other paramagnetic species in living organs and tissues. While instrumentation capable of performing EPR imaging of free radicals in whole tissues and isolated organs has been previously reported, it was not possible to image rapidly moving organs such as the beating heart Therefore instrumentation was developed to enable the performance of gated-spectroscopy and imaging on isolated beating rat hearts at L-band. A synchronized pulsing and timing system capable of gated acquisitions of up to 256 images per cycle, with rates of up to 16 Hz was developed. The temporal and spatial accuracy of this instrumentation was verified using a specially designed beating heart-shaped isovolumic phantom with electromechanically driven sinusoidal motion at a cycle rate of 5 Hz. Gated EPR imaging was performed on a series of isolated rat hearts perfused with nitroxide spin labels. These hearts were paced at a rate of 6 Hz with either 16 or 32 gated images acquired per cardiac contractile cycle. The images enabled visualization of the time-dependent alterations in the free radical distribution and anatomical structure of the heart that occur during the cardiac cycle.     

Facteurs de la variation de la fréquence cardiaque maximale: hypothèse «enképhalinique

To try to explain the decrease in maximal heart rate under different situations (ie, chronic hypoxia, ageing, proteino-energetic malnutrition), cardiac concentration and flow of leucine-encephalin peptide in isolated and perfused hearts were studied in rats. The heart leucine-encephalin concentration which was 301 ± 60 fmol/g before perfusion, increased up to 543 ± 125 fmol/g after perfusion (1 h). The total release during perfusion was four times the initial concentration. Concerning the antagonism of leucine-encephalin on cardiotropic adrenergic effects on isolated cardiomyocytes, it is possible to propose this mechanism to explain totally or partially the decrease in maximal heart rate under particular situations.     

低G预适应对重复+10Gz应激大鼠左心室收缩功能和心肌内皮素与前列环素含量的影响

目的 进一步验证低G预适应对 Gz应激致心肌损伤的防护效应。方法 42只雄性Wistar大鼠随机分为3组(每组n=14)：A( 1Gz)组、B( 10Cz)组和C(低G预适应)组。B组实验条件为： 10Gz峰值暴露30s，5次／d(间隔 1Gz 1min)，3(1／wk，共3wk；A组仅受 1Gz作用5min；C组在每日 10Cz暴露前约1h受 2Gz作用5min，其余处理同B组。于末次 Gz实验后次日断头处死大鼠，速取心脏离体观察左室收缩压的变化；另取心肌组织测定其内皮素与前列环素含量。结果与A组相比，B组心肌收缩功能明显降低，心肌内皮素含量显著升高；而低G预适应使 10Gz应激大鼠左室收缩压明显增加，心肌内皮素含量明显降低。结论 低G预适应对重复高G应激大鼠左室功能和心肌血管内皮细胞分泌功能均有一定的保护作用。     

基础心功能状况与急性放射性心脏损伤的相关性研究

目的 探讨胸部放疗基础心功能状况对急性放射性心脏损伤的影响,评价急性期内患者心功能的变化。方法 分析109例胸部肿瘤患者放疗后基础心功能状况对急性放射性心脏损伤的影响,并观察放疗前及急性观察期内心功能的变化。结果 全组患者急性放射性心脏损伤发生率为79.8%,患者临床因素及基础心功能各项指标与急性放射性心脏损伤发生均无明显相关(P>0.05)。放射治疗后急性期内出现左室收缩功能减低24例,舒张功能减低15例;瓣膜病变24例,全部为二尖瓣和(或)主动脉瓣改变,其中反流(轻、中度反流)23例、狭窄(轻度)1例,未见三尖瓣和(或)肺动脉瓣反流与狭窄。左房前后径、主动脉流速、E/A值在放疗前、放疗结束、自放疗开始3个月差异有统计学意义(F=8.552、0.017、0.003,P<0.05)。左房前后径、主动脉流速、E/A值放疗结束较放疗前分别下降了9.19%、7.56%、17.5%,自放疗开始3个月较放疗结束分别恢复7.05%、4.14%、7.58%,其中E/A下降和恢复变化幅度最大。结论 临床因素及基础心功能状况与急性放射性心脏损伤发生无明显相关。放疗导致的瓣膜病变以二尖瓣和(或)主动脉瓣轻、中度反流多见,并可引起左室收缩和舒张功能改变。左房前后径、E/A值放疗后首先降低,随着时间延长逐渐改善,但急性期内未能恢复到正常水平。急性观察期内放疗对心脏舒张功能的影响较收缩功能明显。     

Effect of myocardial perfusion and metabolic interventions on cardiac kinetics of phenylpentadecanoic acid (IPPA) I 123

The effect of regional myocardial perfusion and flow-independent adrenergic stimulation, as well as lactatemediated inhibition of cardiac lipolysis, on cardiac IPPA uptake and metabolism was examined in canine hearts (flow studies) and in the isolated perfused Langendorff rat heart (metabolic interventions). In both normal and ischaemic myocardium, local perfusion is a major determinant of cardiac IPPA uptake. In pacing-induced hyperaemia, the strict flow-dependence of cardiac IPPA uptake is not preserved. Adrenergic stimulation raises the rate of oxidation of both palmitic acid ¹⁴C and IPPA. This change is reflected by increased metabolite production released into the perfusate and radioactivity clearance recorded externally. Lactate in high concentrations exerts the opposite effect on cardiac free fatty acid oxidation. IPPA is stored in this condition preferentially in tissue phospholipids and triglycerides.

     

Protective Effects of Repetitive Injections of Radiographic Contrast Media on the Subsequent Tolerance to Ischemia in the Isolated Rat Heart

Purpose: Despite detailed knowledge of the effects of X-ray contrast media on cardiac function, no studies have examined the effect of contrast media injections on the subsequent tolerance to ischemia in the heart. Methods: Isolated perfused rat hearts were exposed to repetitive injections of iohexol, iodixanol, or ioxaglate before 30 min of global ischemia and 120 min of reperfusion. These groups were compared with control (no pretreatment) and ischemic preconditioning known to reduce infarct size. Physiologic variables and infarct size were measured Results: Pretreatment with iodixanol reduced infarct size significantly compared with control and thus afforded protection against ischemia. Injections with iohexol and ioxaglate reduced infarct size, although not significantly, compared with control. Conclusion: Pretreatment of the isolated rat heart with commonly used contrast media enhances the cardiac tolerance to subsequent ischemia. The mechanism behind this protective effect could not be determined, but could involve stretching of the heart and/or generation of nitric oxide.     

Intracellular Volume Measurement and Detection of Edema: Multinuclear NMR Studies of Intact Rat Hearts during Normothermic Ischemia

The present study describes the cell volume dynamics in intact rat hearts, during ischemia and after reperfusion. Cell volumes were measured in isolated hearts by either ¹³C or ⁵⁹Co NMR of mannitol or cobalticyanide, respectively, as extracellular markers and ¹H NMR of water as the aqueous space marker. A constant volume chamber was built inside a 15-mm NMR tube; the contents of the chamber were measured with and without a heart. The intracellular volume of isolated rat hearts was estimated to be 2.45 ± 0.13 ml/g dry weight. In the perfused heart, adenosine triphosphate (ATP) and phosphocreatine (PCr) concentrations were calculated to be 12.2 ± 0.7 and 16.1 ± 1.0 mM, respectively. Consecutive volume measurements showed cell swelling of 16% during 30 min of ischemia, which was reduced at reperfusion to 7%. After 30 min of reperfusion, ATP and PCr concentrations were 4.5 ± 0.8 and 8.1 ± 0.9 mM. It is concluded that: (1) cell swelling is an ischemic event, which is partially reversed by reperfusion; and (2) continuous measurement of cell volumes provides intracellular molar concentrations of metabolites, which are the physiologically significant parameters.     

心脏保存液种类及保存时间对离体鼠心低温保存效果的对比研究

目的研究3种心脏保存液[HTK液、FWM液和St.Thomas-Ⅱ(ST-Ⅱ)]在低温条件下保存离体鼠心的效果。方法54只雄性SD大鼠随机均分为HTK组、FWM组、ST-Ⅱ组(n=18),各组再根据低温保存时间分为4、6、8h3个亚组(n=6)。采用Langen-dorff装置进行心脏保存前后的灌注,各实验组分别使用不同保存液灌停心脏并在低温条件下保存4、6、8h,于灌停前及复灌后测定心率(HR)、冠脉流量(CF)、左心室收缩压(LVSP)、左心室内压最大上升速率(+dp/dtmax)、左心室内压最大下降速率(-dp/dtmax)等指标,并计算各指标的恢复率。灌注结束后,取心肌组织制作光镜标本,观察心肌组织结构变化。结果在相同的低温保存时间下,与ST-Ⅱ组相比,HTK组与FWM组心功能各指标恢复率明显较高,光镜下心肌组织结构变化较小。随保存时间延长,使用HTK液保存的鼠心心功能恢复率下降,组织结构发生改变,8h亚组与4、6h亚组间比较差异显著(P<0.05),而4h亚组与6h亚组间无显著差异(P>0.05)。结论在保存时间相同的条件下,HTK液及FWM液的心肌保存效果明显优于ST-Ⅱ液。HTK液保存效果随低温...     

Gadolinium-DTPA-enhanced magnetic resonance imaging of the isolated rat heart after ischemia and reperfusion.

The objective of this study was to assess the potential of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) to identify myocardial ischemia and reperfusion in the isolated rat heart model. Ischemia was induced by reducing the perfusion pressure from 80 to 30 mm Hg for 2 hours. Hearts were not reperfused, or were reperfused for 20 minutes or for 2 hours. Perfusion was performed with Evans blue dye and/or Gd-DTPA for 3 minutes. Twenty isolated rat hearts were perfused according to the Langendorff method, and divided into five groups according to the perfusion status and the use of Gd-DTPA and/or Evans blue as perfusion markers. The Evans blue distribution in the hearts was assessed by point-counting volumetry. The Gd-DTPA distribution was assessed by magnetic resonance microimaging at 6.3 T field strength. Evans blue staining clearly identified areas with "no flow" or "no reflow." Perfusion with Gd-DTPA enhanced signal intensity significantly, both in ischemic and reperfused myocardium. Signal intensity in hearts reperfused for 2 hours was increased significantly compared to nonreperfused ischemic hearts, but not to ischemic hearts reperfused for 20 minutes. Magnetic resonance imaging with the aid of Gd-DTPA can identify ischemia and reperfusion in the isolated rat heart, dependent on residual perfusion.