Objective To investigate the effect of morphine preconditioning on mitochondrial permeability transition pore (MPTP) and its protective mechanism after myocardial ischemia-reperfusion injury. Methods A rat model of ischemia-reperfusion injury was established. Forty rats were injected with 2-3[H] DOG and then divided into 4 groups randomly: a sham operation (S) group, an ischemia-reperfusion injury (IR) group, a morphine preconditioning (Mp+IR) group, and a cyclosporine A preconditioning (CsA+IR) group. We monitored the concentrations of serum creatine kinase-Mb (CK-Mb) and cardiac troponin I (cTnI), and measured myocardial mitochondrial 2-3[H] DOG, cytochrome c content, Ca2+ concentration ([Ca2+]m), the velocity of Ca2+ intake and reaction half time of mitochondrial permeability transition pore (MPTP t1/2) in the 4 groups. Results The concentrations of serum CK-Mb and cTnI decreased more in the Mp+IR group and the CsA+IR group than those of the IR group. The concentrations of 2-3[H]DOG and [Ca2+]m in the IR group were evidently higher but the level of cytochrome c was lower than those of the sham operation group. The concentrations of 2-3[H] DOG and [Ca2+]m in the Mp+IR group decreased whereas the concentration of cytochrome c increased compared with those in the IR group. Mitochondrial 2-3[H]DOG content was positively correlated with the concentration of calcium (r=0.797, P<0.01). The 2-3[H]DOG and [Ca2+]m content were negatively correlated with cytochrome c in the IR group (r=-0.805 and r=-0.648, respectively, P<0.01). MPTP t1/2 in the IR group was shortened evidently, and that in the Mp+IR and CsA+IR group was significantly lengthened. Conclusion Morphine preconditioning may have myocardial protective effect through unburdening the calcium overload and lengthening the MPTP t1/2.

The dot-shaped coagulative necrosis induced by a single HIFU exposure can be considered as a basis for HIFU ablation of tumour. For complete ablation of tumour mass with HIFU, the crucial point is to create a complete line-shaped lesion by way of dot-shaped coagulative necrosis. At the beginning of this in vitro study, a dot-shaped coagulative necrosis with focal width (W) 3mm was induced in ox liver by HIFU (acoustical intensity (I(SAL)) 6500W/cm2; exposure time 1s) at focal depth 2cm. And then, we investigated the formation of line-shaped lesion under two different modes, namely, multiple dot-shaped coagulative necrosis overlapping and linear scanning. Under multiple dot-shaped coagulative necrosis overlapping mode, line-shaped lesion is formed by the combination of multiple dot-shaped coagulative necroses. With acoustical intensity (I(SAL)) 6500W/cm2 and exposure time is for each single exposure, different intervals (D) between two successive single exposures (1mm, 2mm, 2.5mm, 3mm, 4.5mm, 5mm) were applied to obtain line-shaped lesion. Under linear scanning mode, the intensity (I(SAL)) 6500W/cm2 and cycle 1 were set constant, and various scanning speeds (V) 1mm/s, 3mm/s, 6mm/s, 7mm/s were adopted to create line-shaped lesion. After the procedures, the tissues were dissected to obtain the maximum section of the line-shaped lesion. The results were as follows: under multiple dot-shaped coagulative necrosis overlapping mode, a complete line-shaped lesion could be formed when D < or = W, while an incomplete line-shape lesion was formed when D > W; under linear scanning mode, a complete line-shaped lesion could be formed using the scanning speed 3mm/s and cycle 1. The results validate that the complete line-shaped lesion can be created with the dosage and exposure parameters optimized for the dimension of a single dot-shaped coagulative necrosis as shown in this study.
Animals ; Cattle ; Dose-Response Relationship, Radiation ; High-Intensity Focused Ultrasound Ablation ; instrumentation ; methods ; In Vitro Techniques ; Liver ; pathology ; Necrosis

Based on the well-known Pennes' bioheat equation, we analyzed theoretically the temperature rise in tissue during high intensity focused ultrasound(HIFU) irradiation, and measured the focal temperature rise induced by HIFU in the treatment of freshly excised cow liver with different acoustic intensity and exposure time. The results showed that a threshold exposure time always existed under a certain acoustic intensity. Temperature rise was slow when exposure time exceeded the threshold exposure time. The greater the acoustic intensity was, the earlier the threshold time appeared. The focal temperature rise and the relative cumulative thermal dose (RCTD) increased with the increase of acoustic intensity and exposure time. For a certain therapeutic dose, the effects of acoustic intensity on focal temperature rise were more distinct than the effects of exposure time on focal temperature rise. Therefore, the optimal HIFU therapeutic dose should meet the need, i.e. moderate acoustic intensity, and the exposure time be the threshold exposure time under this acoustic intensity.
Animals ; Body Temperature ; Cattle ; Hyperthermia, Induced ; methods ; In Vitro Techniques ; Liver ; diagnostic imaging ; physiology ; Models, Theoretical ; Time Factors ; Ultrasonic Therapy ; methods ; Ultrasonography