RESUMO
Objective:To explore the changes of dynamic cerebral autoregulation ability in pilots exposed to acute positive acceleration(+ Gz) by transcranial Doppler combined with beat-to-beat blood pressure.Methods:A total of 26 pilots enrolled in the + 8Gz manned centrifuge trial at the Air Force Medical Center, Air Force Medical University from June to October 2022 were prospectively included. Blood pressure and heart rate were monitored in the resting state before the trial and within 5 min after centrifugation. Transcranial Doppler combined with noninvasive continuous beat-to-beat blood pressure monitor were used to detect bilateral middle cerebral artery blood flow velocity and beat-to-beat pulse pressure respectively. The transfer function analysis was applied to derive the parameters of cerebral blood flow autoregulation in each frequency band from 0.02 to 0.50 Hz, and the phase, gain and coherence were calculated. The above parameters were compared between resting state and after acute + 8Gz positive acceleration exposure.Results:Compared with the resting state, in all of the 26 pilots after acute + 8Gz positive acceleration exposure, the systolic and diastolic blood pressure and heart rate increased significantly ( P<0.001), the phase significantly increased and the gain significantly decreased in the ultra-low frequency band (0.02-0.07 Hz) ( P<0.05); whereas there were no statistical differences of gain and phase in the low frequency band (0.07-0.20 Hz) and the high frequency band (0.20-0.50 Hz) (all P>0.05). Conclusions:Transcranial Doppler combined with beat-to-beat pulse pressure can be used for the assessment of changes in immediate dynamic cerebral autoregulation after acute + Gz exposure, and transfer function analysis of ultra-low frequency band parameters is suitable for this type of evaluation.
RESUMO
Objective:To monitor the cerebral vascular blood flow parameters in the early stage of simulated acute exposure to high altitude hypoxia by transcranial color Doppler (TCCD), and to evaluate the change trend of cerebral hemodynamics and cerebrovascular reactivity.Methods:Sixty-four healthy volunteers were selected to observe the changes of peak systolic flow velocity(Vs), end diastolic flow velocity(Vd), mean flow velocity(Vm), resistance index (RI) and pulsatility index (PI) of middle cerebral artery (MCA) 30 minutes after they quickly entered the simulated altitude of 4 500 meters. Combined with breath holding test, breath holding index (BHI) was used to evaluate cerebrovascular reactivity (CVR), and subjects were divided into ≤30 years old group and >30 years old group, and the changes of CVR after hypoxia of the two groups were compared.Results:In the early stage of hypoxic environment, compared with baseline, SpO 2 decreased, heart rate increased, and blood flow velocity of middle cerebral artery(Vs, Vd, Vm) increased significantly, BHI showed a decreasing trend (all P<0.01). After hypoxia, the BHI rate of change in >30 years old was lower than that of the subjects ≤30 years old ( P<0.05). After breath holding, cerebral blood flow velocity increased significantly, PI and RI decreased significantly (all P<0.01). Conclusions:Cerebral blood flow is very sensitive to hypoxia. The application of TCCD technology can evaluate the trend of cerebral blood flow dynamics and cerebrovascular reserve capacity in real time and accurately, which is helpful to provide objective basis and research basis for the prevention and treatment of high altitude hypoxia.
RESUMO
Objective To investigate the effects of the microbubbles combined with different mechanical index ultrasound irradiation on ultrastmcture and migration of colon cancer cells.Methods The experimental study was conducted.Colon cancer cells inn vitro (Lovo ceils) were cultured and divided into 4 groups,ceils in the A group were not treated and cells in the B,C and D groups were treated by microbubbles combined with different mechanical index ultrasound irradiation (mechanical index were 0.20,0.80 and 1.45).The changes of ultrastructure and migration of cells were observed using laser scanning confocal microscope and MilliceIl-PCF cell culturechamber method,respectively.Measurement data with normal distribution were represented as (x)±s.Comparisons among groups were analyzed by the one-way ANOVA.Pairwise comparisons were done by the t test.Results (1)Effects of the microbubbles combined with different mechanical index ultrasound irradiation on ultrastructure of Lovo cells:Lovo cells in the A group showed big nucleus,less plasma,regular arrangement,jagged-like or more irregular varicosity surrounding nucleus,twisted euchmmatin,expansion of nucleus cisternal space,homogeneous distribution and normal development of granular soil and clear mitochondrial ridge-like structures.Lovo cells in the B group showed big nucleus with regular arrangement,obvious nucleolus margination,endoplasmic reticulum dilatation,normal development of mitochondrion and clear mitochondrial ridge-like structures.Lovo cells in the C group showed broadening nucleus space,abnormal nucleus with karyopycnosis,chromatin condensation,a few remaining or obvious dilatation of rough endoplasmic reticulum,typically consisting of different fragments or bubbles,cytoplasmic vacuoles changes and decreasing mitochondrial ridge-like structures.Lovo cells in the D group showed big and irregular nucleus,nucleolus margination,obvious endoplasmic reticulum dilatation,fewer mitochondrion with extended cell area and swelling shape,rare mitochondrial ridge-like structures with disordered or broken arrangement,even disappearing.(2) Effects of the microbubbles combined with different mechanical index ultrasound irradiation on migration of Lovo cells:Millicell-PCF cell culture chamber method showed that number of migration of Lovo cells were respectively 63±7,61±4,21±3 and 19±5 in the A,B,C and D groups,with a statistically significant difference (F=55.040,P＜0.05).There were no statistically significant difference in migration of Lovo cells between group A and B (t =1.571,P＞0.05) and between group C and D (t =2.013,P＞0.05).There were statistically significant differences in migration of Lovo cells between group A and C or D (t=7.861,10.652,P＜0.05) and between group B and group C or D (t=7.161,10.453,P＜0.05).Conclusion Microbubbles combined with high mechanical index ultrasound irradiation can make the ultrastructural alterations in the cancer cells,resulting in tumor cell degeneration and death,ultimately inhibit tumor cell migration and metastasis.