Development of specificity in corticospinal connections by axon collaterals branching selectively into appropriate spinal targets

Corticospinal projections in adult rodents arise exlusively from layer V neurons in the sensorimotor cortex. These neurons are topographically organized in their connections to spinal cord targets. Previous studies in rodents have shown that the mature distribution pattern of corticospinal neurons develops during the first 2 weeks postnatal from an initial widespread pattern that includes the visual cortex to a distribution restricted to the sensorimotor cortex. To determine whether specificity in corticospinal connections also emerges from an intially diffuse set of projections, we have studied the outgrowth of corticospinal axons and the formation of terminal arbors in developing hamsters. The sensitive fluorescent tracer 1, 1′, dioctadecyl-3, 3, 3′, 3′-tetramethylindocarbocyanine perchlorat (DiI) was used to label corticospinal axons from the visual cortex or from small regions of the forelimb or hindlimb sensorimotor cortex in living animals at 4–17 days postnatal. Initially axon outgrowth was imprecise. Some visual cortical axons extended transiently beyond their permanent targets in the pontine nuclei, by growing through the pyramidal decussation and in some cases extending as far caudally as the lumbar enlargement. Forelimb sensorimotor axons also extended past their targets in the cervical enlargement, in many cases growing in the corticospinal tract to lumbar levels of the cord. By about 17 days postnatal these misdirected axons or axon segments were withdrawn from the tract. Despite these errors in axon trajectories within the corticospinal tract, terminal arbors branching into targets in the spinal gray matter were topographically appropriate from the earliest stages of innervation. Thus visula cortical axons never formed connections in the spinal cord, forelimb sensorimotor axons arborized only in the cervical enlargement, and hindlimb cortical axons terminated only in the lumbar cord at all stages of development examined. Corticospinal arbors formed from collaterals that extended at right angles from the shafts of primary axons, most likely by the process of interstitial branching after the primary growth cone had extended past the target. Once collaterals extended into the spinal gray matter, highly branched terminal arbors formed within 2–4 days, beginning at about 4 and 8 days postnatal for the cervical and lumbar enlargements, respectively. These results show that specificity in connectivity is achieved by selectivty growth of axon collaterals in to appropriate spinal targets from the beginning and not by the later remodeling of intially diffuse connections. In contrast, errors occur in the initial outgrowth of axons in the corticospinal tract, which are subsequently corrected. Copyright © 1994 Wiley-Liss, Inc.     

Comparison of the photochemical behavior of four different photoactivatable probes

The most commonly used photoaffinity labeling probes are compared, which are aryl azides, aryl diazirines, α-diazocarbonyls and benzophenone-derivatives. The compounds were used under identical conditions and crosslinking efficiency, influence of water, irradiation requirements, and by-products were investigated. Using the pentapeptide thymopentin (TP5) as a model system, we synthesized four analogues by solid-phase peptide synthesis and partially N-terminal modification to obtain [p-(3-trifluoromethyl)diazirinophenylalanine⁵] TP5, [p-benzoylphenylalanine⁵] TP5, 4-azidobenzoyl-TP5 and 2-diazo-3, 3, 3-trifluoropropionyl-TP5. The peptides were characterized by HPLC and ion-spray mass spectroscopy. Irradiation of the peptides with two different ultraviolet sources was carried out in water, n-propanol and water/n-propanol to imitate both hydrophobic and hydrophilic peptide/protein-interactions as well as the influence of the aqueous environment. Analysis of the products with HPLC, ion-spray MS, HPLC-MS and HPLC-CID-MS revealed that (Tmd)Phe is a highly potent carbene-precursor, which can be transformed easily into uniform crosslinking products by smooth photolysis. However, the electrophilic nature of the intermediate causes a high tendency to react with water molecules. The 4-azidobenzoyl group showed comparable crosslinking efficiency, but the probability to create non-uniform irradiation products (e.g. through rearrangement) is higher, whereas the reaction with water is less dominant. In contrast, Bpa was found to have an extremely low affinity to react with water, whereas prolonged UV irradiation is needed to get complete rearrangement into a variety of products. As the absorption band of α-diazocarbonyls at around 350 nm possesses a low extinction coefficient, 2-diazo-3, 3, 3-trifluoropropionyl-TP5 could not be activated at all with the optimized irradiation conditions that we have chosen for our comparative studies. © Munksgaard 1997.     

Location of motoneurones projecting to the cat distal forelimb. II. Median and ulnar motornuclei

The position of the motornuclei projecting through the median (Mn) and ulnar (Ul) nerves to the cat distal forelimb has been investigated. Horseradish peroxidase (HRP) and fluorescent (Fl) compounds have been used as retrograde tracers. They were either injected into forelimb muscles or applied to the proximal end of transected forelimb nerves. Limb muscles that were not investigated were carefully denervated. The position and the architecture of the individual motornuclei were traced with HRP. The topographical relations between the nuclei were established with application of up to three different Fl compounds in the same animal. The Mn motoneurones had a bimodal distribution in the brachial spinal cord. The motoneurones to the pronator teres and flexor carpi radialis muscles were located in C7 and the other Mn motoneurones were located in C8 and Th1. In C7 the Mn motoneurones occupied a single representation area, which is located some distance medially of the lateral funiculus. In C8 and Th1 two Mn representation areas were found: A dorsal one that contacts the lateral funiculus and is located at the level of the central canal; a ventral one that is located ventrally in the ventral horn. The dorsal area is occupied by the motornuclei projecting to the intrinsic hand muscles and the ventral one by the nuclei projecting to the limb. The Ul motoneurones extend with an unimodal distribution from the caudal C7 to the caudal Th1 segments. They occupy a single, broad representation area. The dorsal part, which contacts the lateral funiculus, is located at the level of the central canal and harbours the nuclei to the intrinsic hand muscles. The other Ul nuclei are located ventromedially deep in the ventral horn. These results, together with those from the companion paper on the location of the deep radial motornuclei, provide important anatomical information for the investigation of the cat brachial enlargement.     

99Tcm直接标记αvβ3受体拮抗剂环形RGD多肽

目的探讨^99Tc^m直接标记αvβ3受体配体——含2个二硫键的精氨酸-甘氨酸-天冬氨酸（RGD）-九肽（RGD-4CK）的可行性和不同标记条件对标记率的影响。方法采用预锡化法^99Tc^m直接标记RGD-4CK，3MM色谱纸层析测定^99Tc^m-RGD-4CK的雕值，计算标记率与比活度。研究各种标记条件对^99Tc^m-RGD-4CK标记率的影响。通过高效液相色谱仪（HPLC）分析，Sep-Pak C18柱层析，进行体外稳定性实验、半胱氨酸置换实验以及血清蛋白结合实验，评价^99Tc^m-RGD-4CK的放射化学性质。结果^99Tc^m-RGD-4CK在以丙酮和V（氨水）：V（乙醇）：V（水）=1：2：5为流动相中的雕值分别为0与0．8～0．9，标记率为（97．8±0．4）％，基础标记条件下的比活度为（11．90±0．05）TBq／mmol。在以下条件下放化纯均〉95％：（1）酒石酸亚锡为150～300μg；（2）预锡化反应pH值为2．0～3．5，温度60℃，保温时间6h以上；（3）^99Tc^mO4^-活度为37～185MBq，体积在200μl内；（4）标记温度为95℃，标记时间30min.^99Tc^m-RGD-4CKHPLC的保留时间与其洗脱液的放射峰基本一致；^99Tc^m-RGD-4CK室温放置6h，放化纯仍〉95％；Sep—Pak C18柱层析测定的^99Tc^m O4^-峰仅比3MM纸层析高0．5％；标记物与300mmol／L半胱氨酸37℃保温1h，^99Tc^m O4^-峰仅增加1．88％；^99Tc^m-RGD-4CK与血清蛋白无明显结合。结论预锡化法^99Tc^m直接标记RGD-4CK方法简便、标记率高，无需分离纯化即可直接应用，还可用于制备冻干品药盒。标记产物^99Tc^m-RGD-4CK具有良好的放射化学性质。     

TrKA和p75神经营养因子受体在嗅神经母细胞瘤的表达

目的 :探讨TrKA和p75神经营养因子受体在嗅神经母细胞瘤的表达及其临床意义。方法 :应用免疫组化和双荧光标记法对 10例鼻腔嗅神经母细胞瘤及 5例正常鼻腔嗅黏膜及 5例鼻咽癌组织进行TrKA和p75神经营养因子受体检测。结果 :免疫组化检测发现 10例鼻腔嗅神经母细胞瘤TrKA和p75蛋白均呈阳性表达 ,5例正常鼻腔嗅黏膜及 5例鼻咽癌组织均为阴性表达 ;双荧光标记显示所有肿瘤组织中TrKA和p75蛋白均在同一细胞表达。结论 :TrKA和p75神经营养因子受体的过度表达可能与嗅神经母细胞瘤的发生和发展有关 ;TrKA和p75神经营养因子受体检测可作为嗅神经母细胞瘤的一种辅助诊断方法     

晚期肺癌的中医证候研究

目的　探讨晚期肺癌的主要中医证候。方法　采用回顾性与前瞻性相结合的方法进行临床观察。结果　经 χ2 检验 ,不同中医证候的晚期肺癌组之间有显著性差异 (P <0 0 1) ,而血瘀证、气虚证、痰证、阴虚证最为多见 ;晚期非小细胞肺癌与晚期小细胞肺癌的中医证型没有显著性差异。结论　晚期肺癌的中医证候以血瘀证、气虚证、痰证、阴虚证为主 ;晚期非小细胞肺癌与小细胞肺癌的中医证候无明显差异。     

MRI of transplanted pancreatic islets.

A promising treatment method for type 1 diabetes mellitus is transplantation of pancreatic islets containing beta-cells. The aim of this study was to develop an MR technique to monitor the distribution and fate of transplanted pancreatic islets in an animal model. Twenty-five hundred purified and magnetically labeled islets were transplanted through the portal vein into the liver of experimental rats. The animals were scanned using a MR 4.7-T scanner. The labeled pancreatic islets were clearly visualized in the liver in both diabetic and healthy rats as hypointense areas on T2*-weighted MR images during the entire measurement period. Transmission electron microscopy confirmed the presence of iron-oxide nanoparticles inside the cells of the pancreatic islets. A significant decrease in blood glucose levels in diabetic rats was observed; normal glycemia was reached 1 week after transplantation. This study, therefore, represents a promising step toward possible clinical application in human medicine.     

微波氚标记法与化合物结构的关系

本文报道了应用微波氚标记了许多不同类型的化合物,这些化合物的放射比度与结构紧密相关,对于在相同条件下研究不同化合物的标记比度提供了一些参考数据。     

基于蒙特利尔病变部位分型的克罗恩病患者临床特征分析

目的 探讨回肠末段型（L1）、结肠型（L2）及回结肠型（L3）克罗恩病（CD）患者的临床特征、实验室检查、疾病行为等方面的差异。方法 回顾性研究2021年1月—2022年6月武汉大学人民医院181例CD患者的临床资料,其中L1型CD患者66例,L2型CD患者20例,L3型CD患者95例。收集患者临床资料和实验室检查结果等,分析3组患者在临床特征和实验室检查结果等方面的差异。多因素二元Logistic回归分析L1、L2和L3型CD患者临床特征。绘制受试者工作特征（ROC）曲线,分析部分临床特征预测CD病变部位的效能。结果 L1组患者平均年龄大于L3组患者（P <0.05）。L1组患者黏液脓血便构成比低于L2和L3组患者（P <0.05）。L1组患者平均血小板计数低于L3组患者（P <0.05）。L1组患者肛周病变构成比低于L2和L3组患者（P <0.05）。多因素二元Logistic回归分析结果显示,L2型CD［O^R =1.017（95% CI：1.004,1.031）］和L3型CD［O^R =1.026（95% CI：1.016,1.037）］与CD疾病活动指数（CDAI）相关（P <0.05）,L3型CD［O^R =7.088（95% CI：2.390,21.018）］与肛周病变风险增加相关（P <0.05）。ROC曲线分析结果显示,与L1型CD比较,当血沉为29.50 mm/h时,L2型CD的ROC曲线下面积（AUC）为0.724（95% CI：0.579,0.868）,此时预测L2型CD敏感性为77.8%（95% CI：0.519,0.926）,特异性为64.1%（95% CI：0.510,0.754）;当血小板计数取临界值307×10⁹/L时,L3型CD的AUC为0.702（95% CI：0.618,0.785）,此时预测L3型CD敏感性为72.3%（95% CI：0.602,0.826）,特异性为65.2%（95% CI：0.554,0.752）。结论 L1型、L2型及L3型CD患者的临床表现、实验室检查、疾病行为等均存在差异,基于这些特征将有助于鉴别CD患者的不同病变部位。     

Transneuronal labeling of cochlear nucleus neurons by HRP-labeled auditory nerve fibers and olivocochlear branches in mice.

Auditory nerve fibers were labeled by extracellular injections of horseradish peroxidase into the spiral ganglion in mice. The labeled fibers were traced in an anterograde direction through the auditory nerve into the cochlear nucleus. In almost half of the injections, the labeled endings of auditory nerve fibers contacted cochlear nucleus neurons that were also labeled with horseradish peroxidase and were presumably transneuronally labeled. Only darkly labeled endings were associated with transneuronally labeled neurons, but not all darkly labeled endings had targets that were transneuronally labeled. Transneuronal labeling occurred almost exclusively in the ventral cochlear nucleus, often between endbulbs and bushy cells. Both "modified" endbulbs and the larger endbulbs of Held transneuronally labeled the bushy cells that they contacted. At the ultrastructural level, transneuronal labeling was evident as a darkening of ribosomes and the membrane surfaces of mitochondria, endoplasmic reticulum, and the nucleus. Transneuronal labeling occurred rarely in octopus, small, and stellate cells, and in neurons of the dorsal cochlear nucleus. Spiral ganglion injections also label olivocochlear fibers, efferent fibers that pass through the ganglion en route to the hair cells. These fibers give off branches to the cochlear nucleus that were rarely associated with transneuronal labeling. In eight instances, the targets of olivocochlear branches were stellate cells or small cells. We suggest that in our mouse preparation, horseradish peroxidase is effective as a transneuronal marker because the short distance from injection site to the cochlear nucleus results in a high concentration of horseradish peroxidase in the endings of the auditory nerve fibers.