Effect of rotating magnetic field on pain threshold in rats' spinal cord:an analysis from processing time and angular velocity / 中华神经医学杂志

Objective To observe the effects of rotating magnetic field on the tail-flick latency (TFL)and mechanical withdrawal threshold(MWT)of rats and analyze it from processing time and angular velocity.Methods Forty-eight female SD rats were randomly assigned to 8 groups(n=6),which would be determined by 8 different time points(before treatment,treating for 10,20,30 and 60 min,10,20 and 30 min after treatment).The magnetic plate rotated near the lumbar of the rat at an angular velocity of 7300 r/min and the TFL and MWT with yon Frey hair test were determined at each time point.The second experiment was carried out on 40 female rats at an angular velocity of 6300,6800,7300 and 7800 r/min,respectively;TFL and MWT were determined 30 min after treatment.The data were statistically analyzed.Results The first experiment was concluded as follows:compared with that before treatment,TFL was statistically increased at treating for 10,20,30 and 60 min(P<0.05).The TFL gradually became shorten after the treatment,but it was still significantly longer 10 and 20 min after the treatment as compared with that before treatment(P<0.05).MWT increased significantly at treating for 30 and 60 min,and 10 min after treatment as compared with that before treatment(P<0.05).The second experiment showed that TFL significantly went up as the angular velocity increased(P<0.05).Significantly difference on MWT was found between the angular velocity of 7800 and 6300 r/min.Conclusion Pain threshold can be increased by rotating magnetic field following the increase of processing time and the angular velocity at a certain range,indicating that the rotating magnetic field might be a potential non-invasive pain alleviating method.

Repair of radius bone defect with the nano-hydroxyapatite/collagen/calcium alginate / 中国医学科学院学报

<p><b>OBJECTIVE</b>To explore the osteogenic potential of the nano-hydroxyapatite/collagen/calcium alginate composite implanted in animals.</p><p><b>METHODS</b>Eighteen 3-month-old New Zealand white rabbits were adopted to prepare 15 mm segmental defect model at the middle part of radius. Rabbit models were randomly divided into experimental group and blank control group. Nano-hydroxyapatite/collagen/calcium alginate was implanted into the defects of experimental group. Four, 8, and 12 weeks after operation, all specimens were examined by X-ray and histological methods.</p><p><b>RESULTS</b>All the 18 rabbit models entered the final analysis. X-ray showed that osteotylus was seen in the whole defect area in the experimental group 12 weeks after operation, during which osteogenesis was more obvious than in weeks 4 and 8 and the bridge grafting of defect area was obviously visible. In the blank control group, osteotylus was only observed at the two ends of the defects, and no osteogenesis was found in the central part of the defect area. Histological examination showed that new osteoid formation was seen in internal porous zone in the experimental group in weeks 4 and 8; in week 12, more woven bone-like tissues were visible and trabecular-like structure was formed.</p><p><b>CONCLUSION</b>The nano-hydroxyapatite/ collagen/calcium alginate has good osteogenic potential.</p>

In vitro drug release from a mitomycin C delivery system and its effect against scar tissue adhesion in vivo / 南方医科大学学报

<p><b>OBJECTIVE</b>To develop a chitosan (CH)/polyethylene glycols succinate acid (PEG-SA)-mediated mitomycin C (MMC) delivery system and investigate its drug release characteristics in vitro and its effect against scar tissue adhesion in vivo.</p><p><b>METHODS</b>Mitomycin C loading in the composite CH/PEG-SA/MMC films was determined using ultraviolet. The freeze-dried films were dispersed in 1 ml PBS (pH7.4) and mitomycin C release in vitro was determined according to the mitomycin C concentration-UV value standard curve. The influence of the film structure on the drug release was evaluated. The drug delivery system was then implanted in SD rats, and 4 weeks later, immunohistochemical and histological examinations were carried out to assess the therapeutic effect on epidural scar tissue.</p><p><b>RESULTS</b>The linear regression equation of the mitomycin C concentration-UV value standard curve was y=0.593x(3)-2.563x(2)+25.944x-0.236 (R(2)=1.000). The film demonstrated good drug delivery capability, and 20 mg of the samples in PBS showed a peak mitomycin C release after 12 days of 14.9616 microg/ml, which was higher than the ID(50) of mitomycin C (10.4713 microg/l) to the fibroblasts. On days 18 and 32, another two drug release peaks occurred (14.4824 microg/ml and 11.4092 microg/ml, respectively), followed by maintenance of slow release. Till day 60, the accumulative mitomycin release reached 0.1793 microg/ml, and the loaded drug was ultimately completely released. Significant differences were noted in the hydroxyproline content in the scar tissues of different groups (F=12.085, P=0.000), and the CH/PEG-SA/MMC DDS reduced the amount of scar tissue and promoted its orderly alignment to control potential scar hyperplasia that may compress the spinal cord and nerve roots.</p><p><b>CONCLUSION</b>The composite film for drug delivery possesses good flexibility and mechanical properties and allows sustained drug release of mitomycin C to prevent epidural scar tissue adhesion following lumbar laminectomy.</p>