Toxicokinetics of Vitexin Injection in Beagle Dogs / 中国药学杂志

OBJECTIVEP: To investigate the toxicokinetic and tissue distribution of vitexin in Beagle dogs. METHODS: Beagle dogs were randomly divided into three groups, and received vitexin injection at small, medium and big doses of 50, 20 and 8 mg•kg-1. They were given medicine once a day for consecutive 3 months by intravenous drip. The blood samples of Beagle dogs were drawn at different time points on the first and last day of administration, and concentrations in plasma were detected by HPLC method. RESULTS: Intravenous drip the vitexin injection at the doses of 8, 20 and 50 mg•kg-1, the blood concentration of vitexin linearly metabolized in Beagle dogs when given medicine for 1, 22, 44 and 83 d. Vitexin was significantly accumulated in Beagle dogs, and the accumulation was disappeared, and the exposure decreased with the prolonged time at the dose of 50 mg•kg-1; at the dose of 8 and 20 mg•kg-1, vitexin did not accumulate in Beagle dogs, and the exposure decreased with prolonged administration time. CONCLUSION: There is no accumulation of repeated drug delivery in the Beagle dog's body by intravenous drip at the doses of 8 and 20 mg•kg-1.

Mechanical properties of human enamel based on resonant ultrasound spectroscopy / 医用生物力学

Objective To investigate the mechanical properties of human enamel based on resonant ultrasound spectroscopy (RUS). Methods The rectangular parallelepiped specimens of human enamel were processed. The theoretical resonant frequencies of specimens were estimated and paired with the experimental resonant frequencies measured from RUS experiments. An iterative procedure was used to adjust elastic constants of enamel until the theoretical frequencies corresponded to the experimental frequencies based on minimum mean-squared error criterion. In addition, elastic modulus, shear modulus and Poisson’s ratio were calculated respectively. Results The elastic modulus, shear modulus and Poisson’s ratio ranged from 61.52 to 80.46 GPa, 21.51 to 51.86 GPa and 0.18 to 0.43, respectively. Eliminating the effect of large specimen variances, the average of elastic modulus, shear modulus and Poisson’s ratio was 72.84 GPa, 31.94 GPa and 0.27, respectively. Conclusions RUS performs a feasibility of measuring the mechanical properties of human enamel with repeatable and nondestructive advantages. All the elastic constants and mechanical parameters can be estimated through a signal experiment. The results provide references for the development of biomimetic dental restoration materials.

Mechanical properties of human enamel based on resonant ultrasound spectroscopy / 医用生物力学

Objective To investigate the mechanical properties of human enamel based on resonant ultrasound spectroscopy (RUS).Methods The rectangular parallelepiped specimens of human enamel were processed.The theoretical resonant frequencies of specimens were estimated and paired with the experimental resonant fre quencies measured from RUS experiments.An iterative procedure was used to adjust elastic constants of enamel until the theoretical frequencies corresponded to the experimental frequencies based on minimum mean-squared error criterion.In addition,elastic modulus,shear modulus and Poisson's ratio were calculated respectively.Results The elastic modulus,shear modulus and Poisson's ratio ranged from 61.52 to 80.46 GPa,21.51 to 51.86 GPa and 0.18 to 0.43,respectively.Eliminating the effect of large specimen variances,the average of elastic modulus,shear modulus and Poisson's ratio was 72.84 GPa,31.94 GPa and 0.27,respectively.Conclu sions RUS performs a feasibility of measuring the mechanical properties of human enamel with repeatable and nondestructive advantages.All the elastic constants and mechanical parameters can be estimated through a sig nal experiment.The results provide references for the development of biomimetic dental restoration materials.

Triphasic mechanical properties of osteoarthritis cartilage with different pathological grades / 医用生物力学

Objective To obtain the axial elastic modulus of rabbit articular cartilage based on the ultrasound swelling observation technique and the triphasic theory, and to explore the triphasic mechanical properties of the osteoarthritis cartilage with different pathological grades. Methods The articular cartilage samples from rabbit knees were assessed according to the different pathological grades. The swelling strains were recorded based on the high frequency transient ultrasound measurement technique. The axial elastic modulus of the cartilage samples was extracted based on the fixed charge density, the water volume fraction and the triphasic model. Correlation analysis was also made. Results There were both significant differences in axial elastic modulus between the normal cartilages and among the osteoarthritis cartilage with different pathological grades (P<0.05). The value of axial elastic modulus decreased with the increase of osteoarthritis grades. For normal cartilage samples, the average axial elastic modulus was (15.87±6.30) MPa. For osteoarthritis cartilages of grade 1, 2 and 3, the value of axial elastic modulus were (11.33±5.21), (9.15±5.68) and (6.05±4.99) MPa, respectively. Conclusions This study showed there are significant differences in triphasic mechanical properties of the articular cartilage with different osteoarthritis grades, which may provide some new thought for the quantitative assessment of osteoarthritis grade based on mechanical properties of cartilage.

Correlation study on bone density, microstructure and acoustic parameters of cancellous bone at different stages of decalcification / 医用生物力学

Objective To study changes and correlations in ultrasound acoustic parameters, bone density and microstructure of the cancellous bone at different stages of decalcification. Methods Fifteen defatted porcine cancellous bone specimens were decalcified at different decalcification stages, and the bone density, microstructure and acoustic parameters were measured by Micro CT and ultrasound system, respectively, before and after the decalcification. Correlations between acoustic parameters, bone density and microstructure were investigated. Results With the loss of calcium in bone specimens, BMD (bone mass density), BS/TV and BV/TV decreased continuously. Microstructure parameters SMI and BS/BV increased, while Tb.Th and Tb.N decreased with Tb. Sp increasing. Degree of anisotropy (DA) increased. Acoustic parameter SOS increased at first, and then decreased, with nBUA slightly decreasing. High correlation was found between acoustic parameters, BMD and bone microstructure parameters. Conclusions Ultrasound acoustic parameters are correlated with BMD and bone microstructure. This study may provide some reference information for the early diagnosis of osteoporosis based on ultrasound.

Effects of location training and orientation training on the visual-motor coordination under up-down reversed vision / 医用生物力学

Objective To compare the effects of location and orientation training on the improvement of visual motor coordination under up down reversed vision, provide reference for the preventation of space motion sickness and the design of adaptation training for sensory conflict. Method Sixteen subjects were instructed to complete the maze task wearing the up down reversing prism spectacle before and after the location training and the orientation training. Both trainings lasted 30 minutes respectively. The error rate and the executing time during the maze test were analyzed and compared. Results Both trainings significantly decreased the error rate and the executing time. In addition, the results of different training methods had significant difference, and the effects of the orientation training was better than that of the location training under up-down reversed vision. Conclusions Under the sensory conflict environment arising from the visual change, the adaptation induced by some task training could also be of benefit to some other task training so as to improve the ability of visual-motor coordination and the adaption to the sensory conflict. However, different trainings could have various degrees of improvement.