NMDA receptor-independent mechanisms responsible for the rate of rise of cumulative depolarization evoked by trains of dorsal root stimuli on rat spinal motoneurones

The mechanisms responsible for the rate of rise (RR) of cumulative depolarization induced by dorsal root stimulus trains were investigated with intracellular recordings from motoneurones of the rat isolated spinal cord. The NMDA receptor antagonists CPP or APV depressed the cumulative depolarization but not its RR which could still be fast enough to elicit action potential wind-up. RR size was correlated with a slow synaptic potential (detected in CPP or APV solution) with which it shared similar voltage dependence. The NK1 antagonist SR 140333 depressed cumulative depolarization, RR and slow synaptic potentials. It appears that the RR (and the ability to express wind-up) was determined by summation of slow synaptic potentials partly mediated via activation of NK1 receptors.     

Cell Type-specific Effects of the Neural Adhesion Molecules L1 and N-CAM on Diverse Second Messenger Systems

We have previously shown that the neural adhesion molecules L1 and N-CAM influence second messenger systems when triggered with specific antibodies at the surface of the phaeochromocytoma PC12 cell line (Schuch et al., Neuron, 3, 13 - 20, 1989). To determine whether the two molecules are linked to the same intracellular signalling cascades, independent of the cell type expressing them, or whether different neural cell types respond with different signal transduction mechanisms, we have investigated the effects of antibodies to L1 and N-CAM, and the isolated molecules themselves, on second messenger systems in different neural cell types. We have investigated cultures of cerebellar and dorsal root ganglion neurons and transformed Schwann cells and related these results to those obtained with the PC12 cell line. Here we show that addition of L1 and N-CAM antibodies and the isolated molecules themselves elicit cell type-specific responses that can be modulated by the substrate on which the cells are maintained. Depending on the cell type, cells respond to the triggering of L1 and N-CAM with antibodies, or addition of the purified molecules, by either up-regulation or down-regulation of inositol phosphate turnover, by a rise in intracellular Ca2+ levels dependent on or independent of the opening of voltage-gated Ca2+ channels, or by an increase or decrease in intracellular pH. Moreover, cerebellar neurons expressing N-CAM respond to addition N-CAM, but not to N-CAM antibodies, in contrast to the other neural cell types studied, which respond to both triggers. Furthermore, cerebellar neurons were the only cells to show a rise in cAMP levels in response to any of the ligands tested. This stimulation of cAMP production by L1 antibodies depended on the cross-linking of L1 molecules at the cell surface, whereas the other responses did not depend on clustering of L1. Simultaneous addition of L1 and N-CAM antibodies either elicited an additive or more than additive effect on the intracellular responses which, for cerebellar neurons, depends on the substrate on which the cells are maintained. These observations indicate that L1 and N-CAM or their antibodies activate cell type-specific intracellular signalling systems and that the two molecules can act interdependently or independently of each other.     

Developmentally Regulated Expression of HDNF/NT-3 mRNA in Rat Spinal Cord Motoneurons and Expression of BDNF mRNA in Embryonic Dorsal Root Ganglion

Northern blot analysis was used to demonstrate high levels of hippocampus-derived neurotrophic factor/neurotrophin-3 (HDNF/NT-3) mRNA in the embryonic day (E) 13 - 14 and 15 - 16 spinal cord. The level decreased at E18 - 19 and remained the same until postnatal day (P) 1, after which it decreased further to a level below the detection limit in the adult. In situ hybridization revealed that the NT-3 mRNA detected in the developing spinal cord was derived from motoneurons and the decrease seen at E18 - 19 was caused by a reduction in the number of motoneurons expressing NT-3 mRNA. The distribution of NT-3 mRNA-expressing cells in the E15 spinal cord was very similar to the distribution of cells expressing choline acetyltransferase or nerve growth factor receptor (NGFR) mRNA. Moreover, a striking similarity between the developmentally regulated expression of NT-3 and NGFR mRNA was noted in spinal cord motoneurons. A subpopulation of all neurons in the dorsal root ganglia expressed brain-derived neurotrophic factor (BDNF) mRNA from E13, the earliest time examined, to adulthood. These results are consistent with a trophic role of NT-3 for proprioceptive sensory neurons innervating the ventral horn, and imply a local action of BDNF for developing sensory neurons within the dorsal root ganglia.     

Surgical Treatment of Aortic Root Aneurysm Related to Marfan Syndrome in Early Childhood

The prognosis of Marfan syndrome in both adult and pediatric patients is primarily related to the cardiovascular complications. In infantile Marfan syndrome, although involvement of the mitral valve is the most frequently encountered cardiovascular lesion, the aortic root can be more worrisome because of its excessive dilatation, leading to aortic insufficiency or dissection. If the role of elective surgery is relatively well defined for adult patients, it is still debated during childhood. We report two patients, aged 22 months and 5 years, each presenting an aortic root aneurysm related to Marfan syndrome, and each treated with the Bentall procedure without specific age-related mortality or morbidity. These two patients experienced normal growth and were free of any complication for a follow-up period of 8 and 2 years, respectively. More than an absolute value of the aortic root dimension, it is the conjunction of the rate of progression of the aortic root dilatation, the degree and the duration of the aortic valve regurgitation, and its resulting left ventricular dysfunction that must be taken into consideration in choosing the surgical option.     

Risk management and system failure analysis in mental health investigations

This editorial explores the way in which mental health investigations are developing in England and in particular those involving a homicide. A move away from traditional panel inquiries and towards investigations using root cause analysis (RCA) is aimed at shifting the focus from individual blame to identifying system failure. Thus it is envisaged by policy makers that the RCA approach will offer greater learning opportunities for mental health services. The key difficulties associated with panel inquiries are highlighted before describing the intended benefits of the RCA approach. Finally, five key areas where systematic research can support the development of this approach are suggested.     

正畸治疗中上颌中切牙牙根吸收的可疑相关因素分析

目的：通过分析正畸治疗引起的上颌中切牙牙根吸收的可疑相关因素，探讨各因素对牙根吸收影响的程度和大小，以期寻找有效的预测和评估因子。方法：随机选择病例资料完整的64例矫治已经结束的病例为研究对象，采用t检验、相关分析和多元逐步回归方法分析正畸治疗引起的上颌中切牙牙根吸收的可疑相关因素。结果：上颌中切牙牙根吸收的平均值为0．93mm。t检验结果显示上颌中切牙牙根吸收的大小与性别、拔牙与否和安氏分类的类型无关，相关分析结果为上颌中切牙牙根吸收的大小与疗程、方丝弓戴用的时间、根尖垂直向位移显著相关，多元逐步回归分析结果提示各相关因子的预测和评估的效率较低。结论：正畸治疗引起的上颌中切牙牙根吸收数量较小，目前尚无有效的预测和评估因子。     

试管地黄形成过程中形态发生的研究

目的 :研究试管地黄形成的形态发生过程 ,比较试管地黄与自然条件下生长的地黄在形态解剖上的异同。方法 :取离体条件下和自然条件下不同阶段形成的地黄块根 ,染色后制成石蜡切片 ,于显微镜下观察。结果与结论 :试管地黄在形态解剖方面与自然条件下生长的地黄具有一致性 ,说明试管地黄在诱导过程中未发生结构上的变化。     

根管治疗药物及其材料的细胞毒性研究进展

根管治疗中使用的消毒药物和根充材料对人体的安全性历来受到人们的关注。细胞毒性是评价其安全性的重要指标之一。下面就近年来有关常用根管冲洗剂、根管消毒药物、根管充填材料、根尖倒充填材料和髓腔穿孔修复材料的细胞毒性的研究进展作一综述。     

两种桩核系统在残冠残根修复中的临床观察

目的比较石英纤维桩与金属铸造桩在残冠残根修复中的临床效果。方法选择残冠、残根患者145例,合计181颗患牙。经完善的根管治疗后,根据患者意愿,分为A组（纤维桩）和B组（铸造金属桩）,此：较二组患者6～24个月临床复诊疗效情况。结果A组1例桩折,1例桩核松动、脱落,1例根尖周炎,成功率96．94％;B组5例根折,1例桩折,2例桩核松动、脱落,1例根尖周炎,2例牙龈晦暗,成功率86．75％,组间差异有统计学意义（P〈0．05）。结论石英纤维桩应用于残根残冠修复的临床效果优于铸造金属桩。