神经根慢性嵌压损伤的动物模型建立

目的：建立一种由自身骨性增生造成神经根慢性嵌压损伤的动物模型，为相关实验提供造模方法一方法：30只健康家猫，手术显露右侧C7、C8和L5、L6冲经根及其椎问孔内口，用牙髓钻破坏椎间孔周围骨皮质后，将“V”形松质骨块沿骨壁嵌于神经根通道的骨性管道内及侧隐窝后方，左侧做正常对照。在造模术前和术后第2、4、8、12、24周行磁刺激运动诱发电位(MEP)检测，每次随机选6只，4～5只行影像学检查，以确定神经根通道的狭窄程度和神经根受压状态，6只均做病理组织学检查和椎间孔截面积测量。结果：术后早期实验侧肢体出现行为异常：而后有不同程度肌萎缩；后期部分肢体远端出现溃疡。影像学检查随着嵌压时间延长．实验侧椎间孔骨痂增多，狭窄加重。神经根受压变形，椎间孔骨性截面积8周后明显减小，与对照侧比较有显著性差异。术后2周，神经根组织学检查主要表现为神经束膜、内膜的水肿。髓鞘肿胀；4周后发生节段性脱髓鞘：8周时神经轴突增粗、断裂，远端瓦勒氏变性；12周后变性冲经结构崩解、吸收，形成空洞：24周时整个神经干纤维化。术后4周时实验侧MEP开始出现潜伏期延长；8周时伴有波形分化不清；12周波幅明显下降：24周MEP的引出困难，部分电位消失。结论：采用椎问孔内自体松质骨植入，造成神经根慢性嵌压性损伤模型成功率高，操作简单，适用于脊柱各个节段，其损伤部位和形式与临床更为接近。     

从ECCE到Phaco的转变--核处理技术的实验研究

目的通过化学方法制成动物核性白内障模型,探讨相对能量复合指数(RECP)与角膜内皮细胞活性的关系。方法将5种化学物质注入晶状体,以透过黑白条纹的清晰程度判断晶状体混浊程度并分级。然后将实验眼球分为6组(Ⅰ组为对照组;Ⅱ-Ⅵ为实验组),行标准超声乳化白内障摘除手术。手术后立即取下角膜,作锥蓝-茜素红联合染色标本和扫描电镜标本。结果晶状体内注入甲醛、冰醋酸、无水乙醇、丙酮和苯扎溴铵均能形成晶状体混浊,其中:冰醋酸致晶状体混浊能力最弱,无水乙醇、丙酮次之,甲醛、苯扎溴铵最强。当RECP≤90时,锥蓝-茜素红双重染色和扫描电镜均表明角膜内皮细胞活性好,其形态和细胞联接均无改变。当RECP=120时,角膜内皮细胞形态尚正常,但是细胞联结和胞膜部分破坏。当RECP=150时,角膜内皮细胞严重损伤。结论用化学方法制作核性白内障模型供过渡训练使用是可行的。当RECP超过某一数值(>90)时,即与角膜内皮细胞的活性成负相关。     

~(60)Co-γ射线照射后HeLa细胞存活曲线和数学模式

本文研究了~(60)Co-γ射线照射后HeLa细胞的存活曲线,比较了两种数学模式拟合的结果.拟合优度以对误差加权的残差平方和(Q)作为统计指标进行评价.结果表明模式的拟合度较模式为优.     

Repression of the embryonic myosin heavy chain phenotype in regenerating chicken slow muscle is dependent on innervation.

Ventricular-like and fast myosin heavy chains (VL-MHC and FMHC) are transiently expressed during slow skeletal muscle development. The influence of innervation on repression of these MHC isoforms is investigated over an 84-day time course in: (1) normal anterior latissimus dorsi (N-ALD) muscles, (2) regenerating ALD (R-ALD) muscles, (3) denervated ALD (D-ALD) muscles, and (4) regenerating and denervated ALD (RD-ALD) muscles. Western blotting demonstrates that the VL-MHC is expressed in R-, D-, and RD-ALD muscles, but not in N-ALD muscles. Expression of the VL-MHC is transient in R-ALD muscles. In contrast, VL-MHC expression persists in RD-ALD muscles, and appears with time in D-ALD muscles. FMHC was not detected in N-ALD muscles by Western blotting. Two FMHCs are seen in R-ALD and RD-ALD muscles, and in 13-day embryonic ALD muscles. The slower migrating FMHC (FMHCA) comigrates with developmentally regulated FMHCs in fast pectoralis muscle, while the faster migrating FMHC (FMHCB) comigrates with the faster migrating FMHC in embryonic ALD muscle (13 days in ovo). FMHCB decreases in amount over the time course in R-ALD muscles, while FMHCA persists. In contrast, substantial levels of both FMHCs persist in RD-ALD muscles, and appear with time in D-ALD muscles. The cellular distribution of MHCs is followed by immunocytochemistry. Regenerating cells expressing VL-MHC and FMHC are replaced by a mature population in R-ALD muscles. Some of the mature myofibers in R-ALD muscles express FMHC, but not VL-MHC. In RD-ALD and D-ALD muscles, both regenerating and mature muscle cells are seen which express VL-MHC and FMHC. Our results indicate that innervation is required for the repression of VL-MHC and FMHCB during regeneration of slow muscle.     

Fiber Matrix Descriptors from Permeability Data Without Requiring Membrane Thickness: Theory,Results, and Optimization

Objective: Permeability of basement membrane and all other barriers contains a term for membrane thickness (Δx). This naturally leads to development of methods for measuring Δx that are imprecise, inaccurate, expensive, subject to preparation artifact, and inattentive to variability. Although height and shape of permeability (P) vs. probe radius (α) curves are sensitive to Δx, ln(P) or ln(P/free diffusivity or D_o) curves have shapes independent of Δx. It should, thus, be possible using such characteristics to determine fiber radius (r_f) and void volume ratio (ε) without Δx. We developed such a method to derive membrane structure by the standard model of Ogston and present its experimental evaluation. Methods: Basement membranes were self-assembled using 1: 1 Matrigel: 0.01 M Tris/150 mM NaCl/1.0 mM CaCl₂ buffer on 0.4-μ polycarbonate supports with transport measured in diffusion chambers using FITC-labeled hydroxyethyl starch probes from 25 to 102 Å in radius. Sampling was at 0.5 hr and then for each hour up to 5. Other membranes were measured 7 days after formation. Results: The best fit of the new technique occurred at 3 hr with R² = 0.949 ± 0.003 SEM, r_f = 36.8 ± 2.4 Å, and ε = 0.87 ± 0.02. Membranes studied for 7 days showed more variability but essentially the same characteristics. Conclusions: Membrane thickness is not necessary to reduce permeability of basement membrane to structure, and optimum sampling time is 3 hr.     

Rising mortality from motor neurone disease in Sweden 1961–1990: the relative role of increased population life expectancy and environmental factors

Recent studies of mortality from motor neurone disease (MND) in Sweden have demonstrated rising levels of mortality from the disease, especially amongst older age groups. Case-control investigations have suggested that certain environmental factors are significantly related to variations in mortality from the disease, and are associated with a probable individual susceptibility to MND. This study applies an innovative epidemiological technique to longitudinal and cohort analysis of Swedish mortality from MND during the period 1961 to 1990. Survival modelling shows that a subpopulation susceptible to MND exists in Sweden, as has been demonstrated in other countries. The increased life expectancy of the Swedish population since 1961 has resulted in more of that susceptible population living to the ages at which MND is expressed, explaining the majority of the increase in mortality from the disease. However, environmental factors may play a role in accelerating the course of MND and may affect the timing of death within the susceptible sub-population.     

Development of commissural neurons in the embryonic rat spinal cord.

Little is known about the development of the various populations of interneurons in the mammalian spinal cord. We have utilized the lipid-soluble tracer DiI in fixed tissue to study the migration and dendritic arborization of spinal neurons with axons in the ventral commissure in embryonic rats. Crystals of DiI were placed in various locations in the thoracic spinal cord in order to label commissural neurons within the dorsal horn, intermediate zone, and ventral horn at E13.5, E15, E17, and E19. Seven different groups of commissural interneurons are present in the spinal cord by E13.5. Migration is relatively simple with groups occupying a position along the dorsoventral axis roughly corresponding to their position of origin along the neuroepithelium. By E15, commissural cells are near their final locations and exhibit characteristic morphology. One striking feature is the tendency of cells with similar morphology to cluster in distinct groups. By E19, at least 18 different types of commissural interneurons can be identified on morphological grounds. Although the situation is complex, some generalities about dendritic morphology are apparent. Commissural neurons located in the dorsal horn are small and have highly branched dendrites oriented along the dorsoventral axis. In more ventral regions, commissural neurons are larger and possess dendritic arbors oriented obliquely or parallel to the mediolateral axis with long dendrites extending toward the lateral and ventral funiculi. The number of primary dendrites of most groups is set by E15 and dendritic growth occurs in the transverse plane by lengthening and branching of these primary processes. This study demonstrates that a large number of classes of commissural interneurons can be recognized on the basis of characteristic morphologies and locations within the dorsal horn, intermediate zone and ventral horn of the embryonic rat spinal cord. This finding is consistent with the fact that commissural neurons project to many different targets and mediate a variety of different functions. The demonstration that dendritic arbors of spinal interneurons with characteristic morphologies can be conveniently labelled with DiI should prove useful in future studies on the development of specific circuits in the mammalian spinal cord.     

Axial tissue diffusion can account for the disparity between current models of hepatic elimination for lipophilic drugs

An assumption of previous models of hepatic elimination is that there is negligible axial diffusion in the liver. We show, by construction of a stochastic model and analysis of published data, that compounds which are readily diffusible and partitioned into hepatocytes may undergo axial tissue diffusion. The compounds most likely to be affected by axial tissue diffusion are the lipophilic drugs for which the cell membranes provide little resistance and which are highly extracted, thereby creating steep concentration gradients along the sinusoid at steady state. This phenomenon greatly modifies the availability of the compound under conditions of altered hepatic blood flow and protein binding. For moderately diffusible compounds, these relationships are similar to those predicted by the simplistic venous-equilibrium model. Hence, the paradoxical ability of the venous-equilibrium model to describe the steady-state kinetics of lipophilic drugs such as lidocaine, meperidine, and propranolol may be finally resolved. The effects of axial tissue diffusion and vascular dispersion on hepatic availability of drugs are compared. Vascular dispersion is of major importance to the availability of poorly diffusible compounds, whereas axial tissue diffusion becomes increasingly dominant for highly diffusive and partitioned substances.This study was supported by the National Health and Medical Research Council of Australia.     

Evaluation of neural fold fusion and coincident initiation of spinal cord occlusion in the chick embryo.

Although it is known that rapid expansion of the vertebrate brain begins near the time that the spinal neurocoel is occluded, it still remains unknown when occlusion occurs in relation to neurulation. Since both morphogenetic events are critical for normal brain growth, it is important to decipher the temporal relationship between the two processes. This study assessed the temporal relationship of the two events with the rationale that if it could be demonstrated that occlusion occurs coincident with the completion of neurulation, then it could be argued that factors shown to direct neurulation could also initiate occlusion. Nearly 600 chick embryos (stages 9- through 12+) were cultured atop egg-agar, the caudal extent of neurulation determined, the cranial five pairs of somites removed and the neurocoels assessed for occlusion. In stage 9- through 10- chicks, neurulation of the spinal cord is incomplete. Stages 10 through 12+ exhibit neurulation and occlusion from the 8th to 19th somites. When lateral tissues were removed in embryos 8 through 10-, the neural folds became dysraphic whereas in embryos stage 10 and older, the folds remained fused dorsomedially and occluded. The only surgical manipulation that was found to prevent occlusion was elimination of the lateral tissues responsible for elevation and closure of the neural folds. Analysis of particular components of the lateral tissues essential for convergence, by treating embryos (n = 75) with chemicals known to degrade tissue-tissue bonds or specific components of the perineural matrix, indicated that more than 75% of the embryos treated with EDTA, EDTA plus Ca2+, trypsin, collagenase, or hyaluronidase exhibited little or no effect on convergence, dorsomedial fusion, and concomitant occlusion.