González Santander R, Martínez Cuadrado G, González-Santander Martínez M, Toledo Lobo M V, Martínez Alonso F J
Department of Morphological Science and Surgery, Faculty of Medicine, University of Alcalá de Henares, Madrid, Spain.
Histol Histopathol. 1992 Jul;7(3):353-61.
The ultrastructure of the dorsal periaqueductal nucleus capillaries of the mesencephalon in the cat was studied under the electron microscope in relation to the hematoencephalic barrier, and its four structural levels: 1. Endothelium; 2. Basal membrane; 3, Pericytes; and 4. Glial prolongations. An analysis was performed of what occurs in these four components (in a non-experimental histophysiological state, and without manipulation by markers) in the thinnest capillaries of the centre of the mesencephalic neuronal nucleus. Special attention was placed on the first diffusion barrier formed by the endothelium capillary as the intimate guardian of the Central Nervous System (C.N.S.) neurons. The C.N.S. capillaries are formed from the continuous endothelium, with no fenestrations, and hermetic joining complexes, without pinocytosis vesicles on both sides of the plasmatic membrane (adluminal and external), and surrounded by a continuous basal membrane. The non-fenestrated capillaries of the C.N.S. are less permeable than those with similar characteristics located in other areas. In the C.N.S. these capillaries form a selective physiological barrier which determines the size of the molecules that are permitted to cross the capillary wall. It is suggested that the electron-dense globules found in the endothelium cytoplasm may be molecules assimilated from the blood, which might represent the first level or step to the selective diffusion entrusted to the hematoencephalic barrier. It is also suggested that the elongated electron-dense particles found in the endothelium cytoplasm and basal membrane may be macromolecules which are normally retained for an active defensive function. They would represent the first and second level or steps of the retention performed by the hematoencephalic barrier which blocks their passage to the confined space of the perivascular capillary.
在电子显微镜下研究了猫中脑导水管周围背侧核毛细血管的超微结构与血脑屏障的关系，及其四个结构层次：1. 内皮；2. 基底膜；3. 周细胞；4. 神经胶质突起。对中脑神经元核中心最细毛细血管的这四个组成部分（处于非实验性组织生理状态且未用标记物处理）所发生的情况进行了分析。特别关注由内皮毛细血管形成的第一道扩散屏障，它是中枢神经系统（CNS）神经元的紧密守护者。中枢神经系统的毛细血管由连续的内皮形成，无窗孔，有紧密连接复合体，质膜两侧（管腔侧和外侧）无胞饮小泡，并被连续的基底膜包围。中枢神经系统的无窗孔毛细血管比其他区域具有类似特征的毛细血管渗透性更低。在中枢神经系统中，这些毛细血管形成了一个选择性生理屏障，决定了允许穿过毛细血管壁的分子大小。有人认为，在内皮细胞质中发现的电子致密小球可能是从血液中吸收的分子，这可能代表了血脑屏障选择性扩散的第一级或第一步。也有人认为，在内皮细胞质和基底膜中发现的细长电子致密颗粒可能是通常保留用于发挥主动防御功能的大分子。它们将代表血脑屏障进行的保留的第一级和第二级或步骤，该保留阻止它们进入血管周围毛细血管的受限空间。
