Objective To evaluate the effect of acute hypervolemic hemodilution (AHH) on myocardial damage in severely burned rabbits.Methods Eighteen healthy adult rabbits,weighing 2.0-2.5 kg,were randomly divided into 3 groups (n =6 each) using a random number table:control group (group C),burn group (B group) and AHH group.Rabbits were subjected to 3rd degree burn covering 40％ of the total body surface area.After the model was established,6％ hydroxyethyl starch 130/0.4 was infused intravenously,and the target Hct was 25％ in AHH group.Before AHH (To) and at 2,4 and 8 h after AHH (T1-3),left ventricular systolic pressure (LVSP),left ventricular end-diastolic pressure (LVEDP),+dp/dtmax and-dp/dtmax were recorded,and blood samples from femoral veins were taken to determine the concentration of serum cardiac troponin I (cTnI) by ELISA.The rabbits were sacrificed at T3,and myocardial specimens were removed for microscopic examination of pathological changes with light microscope.Results Compared with group C,the serum cTnI concentration and LVEDP were significantly increased,LVSP and +dp/dtmaxwere decreased at T1-3 in B and AHH groups,and-dp/dtmax at T1-3 in group B and-dp/dtmax at T3 in group AHH were decreased.Compared with group B,LVSP,+dp/dtmax and-dp/dtm,x were significantly increased at T1-3,and no significant change was found in serum cTnI concentration and LVEDP in group AHH.There was no significant difference in the pathological changes between group B and group AHH.Conclusion AHH can not aggravate the early myocardial damage in severely burned rabbits.

Objective To investigate the changes of morphology of injured nerve after pulsed radiofrequency (PRF) and radiofrequency thermocoagulation (RFTC) on rats. Methods 55 male Wistar rats were selected, in which 5 were allocated to control group (group C) and the other 50 were randomly divided into group PRF (n=25) and group RFTC (n=25). The specimens were analyzed both with light microscopy and electron microscopy at immediate, and 1, 7, 14 and 28 d after operation. Results In group PRF, the nerve function of rats maintained after operation. The edema among nerve fibers was found under light microscope, while myelin lamellar structure disorder and myelin balls shaped, and compensatory hyperplasia of ultrastructure under electron microscopic level. Those effects were more pronounced 1 d after operation. In group RFTC, the nerve function of rats disappeared and autophagy behaviors happened, meanwhile Waller's degeneration and nerve regeneration appeared under both light microscopy and electron microscopy. Conclusion PRF and RFTC can produce destruction of nerve, but PRF was minor and recoverable.

Objective To investigate the changes in cerebral hemodynamics in different body positions in healthy volunteers.Methods Sixty right-handed healthy male volunteers,aged 22-26,height 167-178 cm,weighing 51-67 kg,were randomly divided into 4 groups ( n =15 each): 15 degrees head-down tilt group (group Ⅰ ),30 degrees head-down tilt group (group Ⅱ ),15 degrees head-up tilt group (group Ⅲ) and 30 degrees head-up tilt group (group Ⅳ ).Blood flow signals of right middle cerebral artery (MCA) and extracranial internal carotid artery (EICA) were detected by transcranial Doppler and systolic blood flow velocity (Vs),diastolic blood flow velocity (Vd ),mean blood flow velocity (Vm),pulsatility index (PI) and resistance index (RI) were recorded at supine position (baseline),immediately,10 and 30 min after body position change(T1-3 ).Lindegaard index was calculated.Results Compared with the baseline,in group [Ⅱ Lindegaard index was increased at T2,while Vs and Vm of MCA were decreased at T2,3,in group Ⅳ Vs of MCA and PI of EICA at T2,Vd and Vm of MCA at T2,3 were decreased ( P ＜ 0.05),while there was no significant difference in the variables mentioned above in the other two groups ( P ＞ 0.05 ).Conclusion In healthy adults,cerebral blood flow velocity decreases in 30 degrees headdown and head-up tilt positions,however there is no change in cerebral blood flow velocity in 15 degrees headdown and head-up tilt positions.

Objective To explore the activation of the primary somatosensory cortex (S_Ⅰ) and secondary somatosensory cortex (S_Ⅱ) undermild and moderate pain. Methods 7 healthy right-handed volunteers accepted electrostimulation of 1 and 2 times pain threshold respectively.The severity of pain was determined with the Visual Analogue Score (VAS), and they received functional magnetic resonance imaging(fMRI) simultaneously. Results 1 and 2 times pain threshold electrical stimulation caused mild and moderate pain respectively. Bothmild and moderate pain activated contralateral S_Ⅰ similarly, and bilateral S_Ⅱ with pain intensity. Conclusion S_Ⅰ and S_Ⅱ respond to the mildand moderate pain in different ways.