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1.
轴突生长诱向因子(Netrin)基因家族研究进展   总被引:4,自引:2,他引:2  
<正> 在神经系统发育过程中,神经与其靶细胞之间精确联系的形成是依靠多种细胞外诱向因子介导实现的。这些因子通过作用于轴突生长锥上的相应受体而诱导或排斥轴突生长,从而决定了轴突的生长路线以及轴突与特定靶细胞的功能联系。Netrin基因家族是此类因子的代表之一,根据位于轴突生长锥上的Netrin受体不同,Netrin在神经发育的不同时  相似文献   

2.
目的研究轴突在三维组织中的定向生长问题,探讨轴突沿非平坦基底定向生长时基底的低起伏程度对轴突的生长速率、成束和解束速率的影响。方法根据实验观察,设轴突生长的牵引力与靶细胞分泌的可扩散吸引分子的浓度梯度成正比,轴突成束和解束的侧向力与生长锥分泌的可扩散吸引分子和排斥分子的浓度梯度成正比,并且,吸引力指向浓度高的方向,排斥力指向浓度低的方向,浓度满足扩散方程。对于非平坦基底,有效力为沿基底轮廓线的切向分量。数值计算采用三维有限差分法和改进的Euler法。结果(1)轴突在三维组织中定向生长的基本特征与在二维培养基实验中的观察是一致的,只是在形态上有三维与二维之分;(2)非平坦基底的低起伏程度影响轴突的生长,随着起伏加剧,生长锥的前进速率减小、侧向速率增加。结论(1)许多基于二维培养实验所揭示的轴突生长的基本规律在三维情况下仍然是成立的;(2)基底的几何性质是影响轴突生长速率的重要因素之一。  相似文献   

3.
生长相关蛋白GAP-43的研究现状   总被引:11,自引:0,他引:11  
在分子水平 ,神经发育和再生时轴突的生长与一组生长相关蛋白 (GrowthAssociatedProteins ,GAPs)的表达有关 ,这些GAPs被认为在神经生长阶段起着特殊作用[1] 。根据其表达与轴突生长的关系可将GAPs分为两类 :一类与远向延伸的轴突本身有关  相似文献   

4.
在神经系统发育或再生过程中,神经元轴突生长锥形成、延伸并与靶细胞形成突触连接,依赖微环境中的多种引导分子吸引或/和排斥作用。近年确定的轴突引导分子要有导素、信号素、Epb相关受体酪氨酸激酶配体和细胞粘附分子等,研究这类分子的作用,将有助于阐明神经系统的发育、网络形成及损伤后再生修复的机理。  相似文献   

5.
Netrins与神经轴突的生长发育   总被引:1,自引:0,他引:1  
神经细胞在胚胎发育过程中形成相互联系 ,须依靠神经轴突正确投射到靶细胞的能力。Netrins是一族高度保守的神经导向分子家族成员 ,在轴突的延长和诱向中发挥了重要作用。轴突对导向分子的反应各不相同 ,即使是同一个生长锥也会在投射路程中改变对相同导向分子的反应。内在和外在的影响因素同时参与了处于发育中的轴突生长锥对Netrins的反应性的变化。本文综述了Netrins的功能及其所涉及的精细的调节机制  相似文献   

6.
轴突导向(axon guidance)是神经细胞发育的一种特殊的运动形式,通过其末端膨大的结构-生长锥(growth cone)表面的受体识别生长路径上不同时间和空间表达的信号分子,寻找到靶标后获得停止前进的信号,使轴突与靶细胞建立突触联系[1]。生长锥诱向(turning)调节轴突延伸,是轴突导向  相似文献   

7.
应用免疫组织化学方法 ,观察了豚鼠臂丛前索损伤与再生过程中脊髓运动神经元生长相关蛋白 ( GAP-4 3 )的表达以及电针、NGF对其表达的影响。结果表明 ,未受损神经的神经元 GAP-4 3呈弱阳性表达 ;但 GAP-4 3在神经损伤初期的表达显著增强 ,随着轴突不断生长 ,表达强度又逐渐减弱 ;电针、NGF能够加快其减弱速度 ,特别是电针能够显著加快 GAP-4 3恢复弱阳性表达。由此可以认为 ,神经元 GAP-4 3含量变化不仅能够反映轴突生长锥生长与靶器官的接触 ,还可表达再生轴突与靶器官之间功能联系的完善程度。电针促进其完善的作用优于 NGF,可能与电针对靶肌肉直接刺激性的调节作用有关  相似文献   

8.
<正> 虽然在正常状态下成熟的外周神经与靶细胞保持隐固的连接,但仍保存若干在发育过程中的细胞行为:继续改变它们的连接形式;产生和输送某些分子到神经终末供神经生长之用;随身体的生长而变长;轴突受损以后,重新生长综述近年有关神经变性和再  相似文献   

9.
在神经系统的发育过程中,轴突的生长具有严格的方向性。轴突沿特定的路线生长、延长,并伸向与它建立突触联系的靶细胞或神经元的胞体、树突或轴突。轴突末端称为生长锥,其扇形膨大部分称作板足,在板足的表面伸出许多细小的突起,称为丝足。板足的细胞骨架主要是由微管构成,丝足的细胞骨架主要是不成束的肌动蛋白(图1)。生长锥对周围环境极其敏感,其表面受体可识别细胞外基质中或周围细胞上的导向分子。这些导向分子中,有的能够吸引生长锥向其生长,有的却是排斥生长锥向其生长,生长锥就在这样一个复杂的环境中,选择一条正确的路径到达目的地。  相似文献   

10.
雪旺细胞与周围神经再生   总被引:7,自引:2,他引:5  
雪旺细胞是周围神经系统的胶质细胞 ,具有多种生理功能。当周围神经损伤时 ,雪旺细胞发生形态行为学的改变 ,对神经再生发挥重要作用。其具体机制有 :(1)分泌神经因子 ,防止受损神经元死亡 ,促进轴突再生 ;(2 )产生促突起生长因子 ,为轴突提供良好的再生环境支持和引导再生轴突 ;(3)与再生轴突形成缝隙连接和紧密连接 ,直接与再生轴突进行物质交换。  相似文献   

11.
12.
In mammals, the oligodendrocyte population includes morphological and molecular varieties. We reported previously that an antiserum against the T4-O molecule labels a subgroup of oligodendrocytes related to large myelinated axons in adult chicken white matter. We also reported that T4-O immunoreactive cells first appear in the developing ventral funiculus (VF) at embryonic day (E)15, subsequently increasing rapidly in number. Relevant fine structural data for comparison are not available in the literature. This prompted the present morphological analysis of developing and mature VF white matter in the chicken. The first axon-oligodendrocyte connections were seen at E10 and formation of compact myelin had started at E12. Between E12 and E15 the first myelinating oligodendrocytes attained a Schwann cell-like morphology. At hatching (E21) 60% of all VF axons were myelinated and in the adult this proportion had increased to 85%. The semilunar or polygonal oligodendrocytes associated with adult myelinated axons contained many organelles indicating a vivid metabolic activity. Domeshaped outbulgings with gap junction-like connections to astrocytic profiles were frequent. Oligodendrocytes surrounded by large myelinated axons and those surrounded by small myelinated axons were cytologically similar. But, thick and thin myelin sheaths had dissimilar periodicities and Marchi-positive myelinoid bodies occurred preferentially in relation to large myelinated axons. We conclude that early oligodendrocytes contact axons and form myelin well before the first expression of T4-O and that emergence of a T4-O immunoreactivity coincides in time with development of a Type IV phenotype. Our data also show that oligodendrocytes associated with thick axons are cytologically similar to cells related to thin axons. In addition, the development of chicken VF white matter was found to be similar to the development of mammalian white matter, except for the rapid time course.  相似文献   

13.
This study describes a 47-year-old woman, gravida 2, para 2, with a uterine polypoid mass. The 25-mm mass, which was growing into the endocervical canal, had a central cavity lined with endometrium and surrounded by smooth muscle layers. It strongly resembled a miniature uterus. It is concluded that the mass represented superficial cervical endometriosis with florid smooth muscle metaplasia of endometrial stromal cells.  相似文献   

14.
Summary We have employed degeneration techniques to study the ontogeny of major projections to the inferior olivary nucleus in the North American opossum, a species which is born 12 days after conception and which enjoys a protracted development in an external pouch. Subsequent to spinal lesions a small amount of axonal degeneration can be produced within the edge of the olive before subnuclei can be distinguished (7 days after birth, 24 mm, snout-rump length). Degenerating axons are present more deeply within the olive in animals operated 12 days after birth (30 mm, snout-rump length) and by at least day 16 (36 mm, snout-rump length), they are found in all of the regions they occupy in the adult animal. Subsequent to lesions which undercut all descending mesencephalic and diencephalic systems, a small amount of axonal degeneration is found at the dorsolateral edge of the olive by day 7 (23 mm, snout-rump length). Degenerating axons fill more of the olive, particularly caudally, after comparable lesions in older animals and by day 17 (38 mm, snout-rump length), degeneration is present in all of the olivary regions innervated by midbrain and thalamic axons in the adult opossum. There is some evidence that spinal, mesencephalic and diencephalic axons follow a caudal to rostral gradient in their intraolivary growth. Lesions which undercut neurites growing out of the cerebellum produce evidence for cerebello-olivary connections by day 17. Axons from the cerebral cortex reach their olivary targets considerably later than those from either the spinal cord, mesencephalon, diencephalon or cerebellum. It is not until approximately postnatal day 30 (55 mm, snout-rump length) that degenerating axons can be traced into the olive after lesions of the cortical mantle. These data indicate that the inferior olive receives major connections early in development and that there is an orderly sequence to their growth.This investigation was supported by U.S.P.H.S. Grants NS-07410 and NS-08798 and The West Virginia University Medical Corporation.  相似文献   

15.
A case of lymphoepithelial cyst of the pancreas is reported. The unilocular cyst was filled with keratin, lined by mature, keratinizing squamous epithelium and surrounded by lymphoid tissue.  相似文献   

16.
基于对称区域生长和边缘梯度的视神经纤维的分割   总被引:1,自引:0,他引:1  
在视神经横切面图像中,将每个神经纤维的内外边界进行精确分割是视神经形态分析的重要环节,提出一种基于对称区域生长和髓鞘边缘梯度的有效分割算法.该算法分两步进行,首先根据交互方式下选取的种子点,由对称区域生长算法实现轴突分割,然后在轴突轮廓模型基础上,髓鞘外轮廓在髓鞘平均边缘梯度引导下进行演化,实现自动分割.与K-均值聚类,局部阈值和水平集等其他算法的实验结果相对照显示,该算法分割获得的轴突和髓鞘轮廓与实际轮廓相吻合,其分割结果可以作为后续神经纤维形态分析的基础.  相似文献   

17.
Ultrastructure of the capillaries of malignant and benign thyroid tumours has been examined. The material consisted of biopsies from six cases of thyroid papillary carcinoma, one case of follicular (foetal type) adenoma and six cases of nodular adenomatous goitre. In the group of nodular adenomatous goitre and in the follicular adenoma, the capillary wall was made up of fenestrated endothelium similar to that of capillaries of normal human thyroid. The fenestrae occupied a large area of the endothelial wall. Micro- and macropinocytotic vesicles were frequent in the endothelial cytoplasm. In the thyroid carcinomas the papillary structures always contained numerous capillaries with fenestrated endothelium. The microfollicular area and the solid tumoral areas of the papillary carcinoma showed occasional capillaries with fenestrated endothelium, but many capillaries were lined with continuous endothelium. The capillaries in all the specimens were surrounded externally by a continuous basement membrane which was frequently bilaminate or multilaminate. This study indicates that capillaries with fenestrated endothelium are characteristic of thyroid tumours which arise from follicular cells.  相似文献   

18.
Uterus-like masses, such as cavities lined by endometrium-type mucosa surrounded by bundles of smooth muscle cells, may strikingly resemble the uterus. In this report, we describe a case of a uterus-like mass of the uterus in a 35-year-old woman.  相似文献   

19.
Congenital oesophageal cysts of foregut origin are rare in animals and human beings. This report describes a case in a 4-year-old cynomolgus monkey with no clinical symptoms. The cyst, which was located within the oesophageal submucosal tissue near the mid-point of the oesophagus, was lined with pseudostratified ciliated epithelium and had a thin layer of submucosal tissue. The cyst was surrounded by a smooth muscle layer which was partly intermingled with the circular muscle layer of the oesophagus. The muscularis mucosae of the oesophagus was not shared with the cyst wall. Simple tubular glands were present, opening into the cyst lumen. No communication between the cyst lumen and the oesophagus was observed. Cartilaginous tissue, which is a diagnostic feature of bronchogenic cysts, was not identified in the cyst wall. On the basis of the histopathological features, a foregut cyst of the oesophagus was diagnosed.  相似文献   

20.
We report an extremely rare case of branchial cleft‐like cysts in Hashimoto's thyroiditis. The patient was a 77‐year‐old man with a growing mass in the anterior neck. Ultrasonography and computed tomography revealed a cystic lesion with septum in the left thyroid and multiple small cystic lesions in the right thyroid. Lymph node swelling of the cervical region, supraclavicular fossa and submandibular region was also observed. Left thyroidectomy and lymph node dissection were performed. Histologically, cysts were lined by stratified squamous epithelium and dense lymphoid tissue having conspicuous follicle formation surrounded the epithelial lining. Solid cell nest (SCN)‐like aggregations were seen in the thyroid parenchyma adjacent to the cyst walls and a small number of thyroid follicles were observed in the fibrous wall. Immunohistochemically, it is suggested that both the cyst lining and SCN‐like aggregations are originally from thyroid follicles. Although, the exact histogenesis of branchial cleft‐like cysts remains unclear, there are probably two different processes for its development, one is of branchial cleft origin and the other is mere squamous metaplasia, while in our case the latter is suggested. Herein, we report our new case and update information about branchial cleft‐like cysts that appears in the literature.  相似文献   

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