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51.
Transection of the third cervical hindlimb dorsal column nerve fibers in the spinal cord leads to a partial deafferentation atrophy of the neurons of the ascending dorsal column-medial lemniscal neural network (DC-ML) up to the cortex. We now examine the alteration of the steady-state level mRNA coding for the synaptic vesicle protein, dynamin I, and the cytoskeletal protein β-actin as early indicators of direct and trans-synaptic changes in the relay nuclei of the DC-ML. Rats were sacrificed at 6, 24, 72, and 240 hr after C3 hindlimb dorsal column or sham lesion. By 24 hr, there are changes in the steady-state levels of mRNA coding for both dynamin I and β-actin in regions of the brain containing the first (nucleus gracilis of medulla) and third synaptic relays (cortex). β-actin mRNA is increased at both 6 and 24 hr in the nucleus gracilis. The changes in dynamin I mRNA in the nucleus gracilis are early and biphasic, elevated at 6 hr but decreased compared to sham by 24 hr. In both regions, the initial fluctuations of dynamin I and β-actin mRNA levels are transient. By 72 hr, the levels are no different from those of sham-lesioned animals. In the somatomotor cortex, there is an additional increase in β-actin mRNA levels at 240 hr. The increased steady-state levels of dynamin and actin mRNA following a hindlimb dorsal column lesion suggest that increased synaptic vesicle recycling and actin cytoskeleton rearrangement are some of the early responses to deafferentation made by the neurons of the DC-ML synaptic relays. © 1996 Wiley-Liss, Inc.  相似文献   
52.
The scope of this paper is to investigate analytically and numerically the influence of shear cap size and stiffness on the distribution of shear forces in flat slabs in a slab–column-connections-reinforced concrete structure. The effect of support (shear cap) stiffness on the calculation of the length of the shear control perimeter according to the available methods is presented. Based on the analysis, the authors indicate in what range of support stiffness the corner concentrations become important in the calculation of the punching resistance. For shear caps with high flexibility (α1 ≤ 0.5), the concentration of internal forces in the corners does not occur. The authors compare the numerical results obtained from the calculation methods and indicate the correlations, which can be useful guidance for structural designers. In the case of large shear caps, the simplified MC2010 method gives a significantly lower value of the effective control perimeter length compared to more accurate methods. This paper is intended to provide scientists, civil engineers, and designers with guidelines on which factors influence punching shear load capacity of the slab–column connections with shear caps.  相似文献   
53.
At present, the existing standards (AISC360-16, EN1994-1-1:2004, and JGJ138-2016) lack relevant provisions for steel-reinforced concrete (SRC) composite columns with high-strength steel. To investigate the axial compressive mechanical performance of short high-strength steel-reinforced concrete (HSSRC) columns, the axial load test was conducted on 12 short composite columns with high-strength steel and ordinary steel. The influences of steel strength, steel ratio, and the section form of steel on the failure modes, bearing capacity, and ductility of the specimens were studied. Afterward, the experimental data were compared with the existing calculation results. The results show: compared with the specimens with Q235 steel, the bearing capacity of the specimens with Q460 steel increases by 7.8–15.3%, the bearing capacity of the specimens with Q690 steel increases by 13.2–24.1%, but the ductility coefficient increases by 15.2–202.4%; with the increase of steel ratio, the bearing capacity and ductility of specimens are significantly improved. A change of the steel cross-section could influence the ductility of SRC columns more than their bearing capacity. Moreover, the calculation results show that present standards could not predict the bearing capacity of HSSRC columns. Therefore, a modified method for determining the effective strength of steel equipped in HSSRC columns was proposed. The results of the ABAQUS simulation also showed that the addition of steel fibers could significantly improve the bearing capacity of Q690 HSSRC columns. The research results provide a reference for engineering practices.  相似文献   
54.
55.
Plain film imaging remains important for the diagnosis and surveillance of scoliosis, as well as for the detection of complications after surgery. Advances in CT and MR imaging have greatly improved the ability to detect or confirming nonidiopathic causes of scoliosis, including abnormalities within the spinal canal. Three-dimensional thinking has become more important in evaluating and understanding scoliosis.  相似文献   
56.
Nanoscale titanium dioxide (nTiO2 (Hombikat UV 100 WP)) was applied to sewage sludge that was incinerated in a large-scale waste treatment plant. The incineration ash produced was applied to soil as fertilizer at a realistic rate of 5% and investigated in pilot plant simulations regarding its leaching behavior for nTiO2. In parallel, the applied soil material was subject to standard column leaching (DIN 19528) in order to test the suitability of the standard to predict the leaching of nanoscale contaminants from treated soil material. Relative to the reference material (similar composition but without nTiO2 application before incineration) the test material had a total TiO2 concentration, increased by a factor of two or 3.8 g/kg, respectively. In contrast, the TiO2 concentration in the respective leachates of the simulation experiment differed by a factor of around 25 (maximum 91.24 mg), indicating that the added nTiO2 might be significantly mobilisable. Nanoparticle specific analysis of the leachates (spICP-MS) confirmed this finding. In the standard column elution experiment the released amount of TiO2 in the percolates between test and reference material differed by a factor of 4 to 6. This was also confirmed for the nTiO2 concentrations in the percolates. Results demonstrate that the standard column leaching, developed and validated for leaching prediction of dissolved contaminants, might be also capable to indicate increased mobility of nTiO2 in soil materials. However, experiments with further soils are needed to verify those findings.  相似文献   
57.
In decerebrate-decerebellate cats, dorsal column stimulation (DCst) rostral to selective dorsal funicular cuts, to prevent antidromic activation of afferent DC fibers, produced primary afferent depolarization and modulated reflexes at the lower spinal level. These findings indicate the importance of a DC-brainstem-spinal loop in explaining the effects of DC stimulation in man and experimental animals.  相似文献   
58.
Studies of sensory pathways in several species indicate that the extent and form of reorganization resulting from deafferentation early in life vs. adulthood are not the same. The reasons for such differences are not well understood. To gain further insight into age-dependent mechanisms of reorganization, this study compared the consequences of neonatal vs. adult forelimb amputation in rats at multiple levels of the sensory pathway, including primary somatosensory cortex, brainstem, and dorsal root ganglia. At the cortical level, the average area of the functional forelimb-stump representation from rats amputated as adults was significantly smaller (P < 0.05) than that of neonatally amputated rats (4.3 +/- 1.3 mm(2) vs. 6.6 +/- 1.5 mm(2), respectively). At the brainstem level, neonatally amputated rat cuneate neurons possessed the following responsivities: 20% stump responsive, 40% responsive to both stump and hindlimb, 30% responsive to another body region, and 10% unresponsive. In contrast, cuneate neurons of adult amputated rats were 70% stump responsive, 2% responsive to both stump and hindlimb, and 30% unresponsive. A significantly (P < 0.001) greater percentage of the C(6)-C(8) dorsal root ganglia neurons of adult amputated rats were unresponsive to peripheral stimulation vs. neurons from neonatally amputated rats (48% vs. 16%, respectively). These results indicate that the reorganization that occurs in response to forelimb amputation at birth vs. adulthood is distinctly different at each of these levels of the dorsal column-medial lemniscal pathway. Possible mechanisms to account for these differences are considered.  相似文献   
59.
目的探讨颈胸段脊柱脊髓损伤的临床特点及后路椎板减压、植骨、椎弓根螺钉内固定术的治疗作用。方法 8例颈胸段脊柱损伤患者,损伤部位为第6颈椎至第1胸椎,损伤类型为椎体爆裂性骨折2例,椎体压缩性骨折5例,压缩性骨折伴脱位1例。分析上述患者的临床表现,并分别经后路颈胸段椎板减压椎弓根或侧块螺钉内固定术。结果所有患者随访6~20个月,植骨均在3~4个月完全融合,所有患者术后脊髓神经功能均有不同程度症状改善,伴有交感神经节刺激症状者有所缓解。结论颈胸段后路椎板开窗减压植骨融合内固定术对颈胸段脊柱脊髓损伤具有较好的疗效。后路椎弓根螺钉及侧块螺钉固定系统有助于植骨节段融合、重建和稳定颈胸段脊柱。  相似文献   
60.
During embryogenesis, limb‐innervating lateral motor column (LMC) spinal motor neurons (MN) are generated in excess and subsequently nearly half of them die. Many motor neuron survival factors (MnSFs) have been shown to suppress this default programmed cell death (PCD) program through their receptors (MnSFRs), raising the possibility that they are involved in matching specific MNs with their target muscles. Published observations suggest a combinatorial model of MnSF/Rs function, which assumes that during the PCD phase, MNs are expressing combinations of MnSFRs, whereas the limb muscles innervated by these MNs express cognate combinations of MnSFs. We tested this model by expression profiling of MnSFs and their receptors in the avian lumbosacral spinal cord and limb muscles during the peak PCD period. Our findings highlight the complexity of MnSF/Rs function in the control of LMC motor neuron survival. Developmental Dynamics 239:965–979, 2010. © 2010 Wiley‐Liss, Inc.  相似文献   
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