人胎海马发育的研究 Ⅱ、电镜观察

在电镜下观察了4-10个月人胎儿海马CA_2亚区多形细胞层突触复合体的发育。结果,4个月胎儿即见到含少量、分散的圆形无芯小泡的对称型轴-树突触。数量不多但结构非常典型。突触前成分内还可见到结构不发达的线粒体。此时,在数量上占优势的突触前身结构构成突触样接触,即膜的相接近部分发生特化的增厚,间隙清楚可辨,但无突触小泡。随着胎龄的增大,出现下述一系列变化:(1) 突触前身结构的数量优势逐渐被典型突触所代替;(2) Ⅰ型突触出现,并逐渐增多;(3) 突触形式由低胎龄时的简单突触逐渐出现并联突触和突触群;(4) 突触小泡数量增加,并向突触前膜靠拢,在10个月材料还见到扁平小泡和圆形小泡共存;(5) 线粒体的数量和结构也日趋增多和典型。基于上述发现,作者认为(1)人胎海马CA_2亚区内突触的个体发育经历了突触前身结构和典型突触两个连续过程;(2) 该部的突触具有简单突触、并联突触和突触群等多种形式;(3) 参与海马活动的神经递质至少应具有兴奋和抑制两类。

RESEARCH ON HIPPOCAMPUS DEVELOPMENT IN HUMAN FETUS Ⅱ. ELECTRON MICROSCOPIC OBSERVATION

The development of synaptic complex at stratum oriens of CA_2 subarea of hippocampus in human fetus aging from four to ten month have been researched under electron microscope. The results show that in the four month sample the axo-dendritic synapses were seen with non-core-circular vesicles but a large, number of prosynaptic structures which have specialized membrane without synaptic vesicle were seen at the same time. As the time goes, a series of change appeared that the classical synapses were gradually replaced the prosynaptic structure; that type Ⅰ synapses appeared and inereasee in number; that the form of simple synapse in the early of development and gradually was replaced by parallel synapse as well as synaptic groups in the late stage of development; that the vesicles increased in number and gradually migrated toward the presynaptic membrane and coexistence of spherical and flattend vesicles were seen in nine and ten month that mitochondria gradually increased in number and became identifiable in structure.