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981.
982.
Biomechanics of increased exposure to lumbar injury caused by cyclic loading: Part 1. Loss of reflexive muscular stabilization 总被引:6,自引:0,他引:6
STUDY DESIGN: The recording of electromyographic responses from the in vivo lumbar multifidus of the cat, obtained while cyclic loading was applied as in occupational bending/lifting motion over time. OBJECTIVES: To determine whether the effectiveness of stabilizing reflexive muscular activity diminishes during prolonged cyclic activity; the recovery of lost muscle activity by a 10-minute rest; and whether such diminished muscular activity is caused by fatigue, neurologic habituation, or desensitization of mechanoreceptors in spinal viscoelastic tissues resulting from its laxity. SUMMARY OF BACKGROUND DATA: The literature repeatedly confirms observation that cyclic occupational functions expose workers to a 10-fold increase in episodes of low back injury and pain. The biomechanical evidence indicates that creep in the viscoelastic tissues of the spine causes increased laxity in the intervertebral joints. The impact of cyclic activity on the function of the muscles, which are the major stabilizing structures of the spine, is not known. METHODS: Electromyography was performed from the L1 to L7 in vivo multifidus muscles of the cat, while cyclic passive loading of 0.25 Hz was applied to L4-L5. Cyclic loading was applied for 50 minutes, followed by 10 minutes rest and a second 50-minute cyclic loading session. A third 50-minute cyclic loading period also was applied after the preload was reset to 0.5 N to offset the effect of laxity. RESULTS: Reflexive muscular activity was recorded from the multifidus muscles of all lumbar levels at the initiation of the first 50 minutes of cyclic loading. Activity recorded on electromyography quickly diminished with each cycle during the first 8 minutes of loading to 15% of its initial value. A slower decrease in muscular activity was evident throughout the remaining period, settling at 5% to 10% of its initial level by the end of 50 minutes. A 10-minute rest provided a 20% to 25% recovery of the electromyographic activity, but that was lost within the first minute of cycling. Offsetting the laxity in the spine resulted in full restoration of the electromyographic activity at all lumbar levels. CONCLUSIONS: The creep induced in the viscoelastic tissues of the spine as a result of cyclic loading desensitizes the mechanoreceptors within, which is manifest in dramatically diminished muscular activity, allowing full exposure to instability and injury, even before fatigue of the musculature sets in. 相似文献
983.
Spontaneous regression of periodontoid pannus mass in psoriatic atlantoaxial subluxation. Case report 总被引:4,自引:0,他引:4
STUDY DESIGN: A case report of a 41-year-old man with psoriasis who had cervical myelopathy caused by atlantoaxial subluxation and periodontoid pannus mass. OBJECTIVE: To describe the possible mechanism underlying the periodontoid pannus formation and the optimal treatment for such cases. SUMMARY OF BACKGROUND DATA: Atlantoaxial subluxation causing spinal cord compression at the craniocervical junction may develop in patients with rheumatoid or psoriatic arthritis. Periodontoid pannus formation plays an important role in compromising the anteroposterior diameter of the spinal canal and in causing neurologic deficits. Transoral transpharyngeal excision of the pannus is sometimes thought necessary for anterior decompression of the spinal cord. Spontaneous resolution of the periodontoid pannus after posterior atlantoaxial fusion and fixation has been documented in rheumatoid arthritis, but not in psoriatic arthritis. METHODS: The patient underwent posterior atlantoaxial fusion and Halifax fixation. RESULTS: The patient experienced clinical improvement. Regression of the periodontoid pannus mass was observed on magnetic resonance imaging. CONCLUSIONS: Posterior fusion and instrumentation resulted in spontaneous regression of the pannus mass and symptomatic relief. This report provides evidence that atlantoaxial instability may be the sine qua non for the formation of periodontoid pannus, and that amelioration of such instability leads to spontaneous resolution of the pannus mass. 相似文献
984.
烫伤后脂多糖受体CD14和肿瘤坏死因子-α基因表达的变化规律 总被引:2,自引:0,他引:2
目的 观察烫伤后机体主要脏器脂多糖受体CD14(CD14)和肿瘤坏死因子-α(TNF-α)mRNA的表达的变化规律及二者的相互关系。方法 采用大鼠35%Ⅲ度烫伤模型,分别于伤前,伤后12,24,48,72小时活杀动物,留取组织标本或分离腹腔巨噬细胞,检测组织或巨噬细胞CD14,TNF-αmRNA表达。结果 烫伤后肝,肺,肾,肠等组织CD14mRNA水平均有不同程度增高,分别于伤后12小时和48小时 相似文献
985.
986.
游离骨膜与复合rhBMP2的异种骨联合移植修复骨缺损的实验研究 总被引:6,自引:0,他引:6
目的 探讨复合基因重组人BMP2(rhBMP2)的异种骨与游离骨膜(FP)联合移植修复节段性骨缺损的效果。方法 将rhBMP2与去抗原牛松质骨载体(BCB)复合,制成rhBMP2/BCB;选用新西兰大耳白兔28只,制成烧骨干15mm缺损动物模型,分别行FP和rhBMP2/BCB复合移植(n=6)、rhBM2/BCB移植(n=6)和单纯BCB移植(n=2);术后4、8、12、16周取材,通过X线、生 相似文献
987.
988.
Inactivated hepatitis A virus (HAV) vaccine was administered to 55 healthy seronegative adult volunteers to evaluate the immunogenicity and adverse reactions of two doses of HAV vaccination (25 units) in comparison with a three-dose regimen. The volunteers were randomly assigned to receive one of the two regimens: 26 were vaccinated with two doses at 0 and 24 weeks (Group 1), and 29 were vaccinated with three doses at 0, 2, and 24 weeks (Group 2). The vaccine was well tolerated and there was no serious adverse reaction. In both groups, the seroconversion rate was 100% at week 28. At week 52, all remained positive for anti-HAV regardless of a two- or three-dose regimen. No statistically significant difference in seroconversion rates and geometric mean titers could be demonstrated between the two groups. Thus, the two-dose regimen may be favorable to save cost and time for active immunization against hepatitis A. 相似文献
989.
伽玛刀的医学技术评估 总被引:9,自引:0,他引:9
伽玛刀是世界上最昂贵的医疗设备之一,我国从1992年开始引进。1995年卫生部等联合发文暂缓装备。为了规范提供方和患方的行为,以及为卫生行政部门提供决策依据,我们开展了伽玛刀的技术评估。在评估前拟定评估步骤,然后确定评估内容与方法。评估结果,国外1994年有56台伽玛刀,平均每台治疗190例,治疗病种是:动静脉畸型病人占32%,肿瘤病人占65%,功能性疾病占2%。我国13台伽玛刀到1995年底共治病人7000例,前6位病种是转移瘤等,虽然比例和顺位与世界有差异,但病例分析结果完全一致。 相似文献
990.
食品中分离的李斯特氏菌的致病基因分析 总被引:3,自引:0,他引:3
1996—1997年作者对全国12个省市的7类食品共3746份进行了李斯特氏菌的污染调查,共分离出李斯特氏菌165株。用PCR技术对分离菌株中李斯特氏菌的2种主要致病因子李氏溶血素O和内化素的基因进行了检测,其中57株仅有内化素基因,27株同时具有内化素基因和李氏溶血素O基因。两种致病基因均未检出的共有81株。本研究说明判断单增李氏菌的主要指标是小鼠毒力试验阳性而不是其溶血反应,同时检测溶血素O和内化素2种基因对单增李氏菌有鉴别意义。 相似文献