Sado Marine Biological Station, Faculty of Science, Niigata University, 952-21, Niigata, Japan.
Fish Physiol Biochem. 1990 Sep;8(5):355-64. doi: 10.1007/BF00003367.
The hypophysis of early larval stages, from the moment of hatching on the 18th day after fertilization to the 101st day of larval life, of the arctic lamprey Lampetra japonica was studied with scanning and transmission electron microscopes. A solid cord of cells of the distal part of the nasopharyngeal duct represents the early adenohypophysis. On the 20th day after fertilization, several of the epithelial cells of this structure showed first indications of secretory activity with an extensive Golgi apparatus and small electron-dense secretory granules. On the 26th day, non-secretory, stellate (=supporting) cells and secretary cells can be distinguished. Already on the 39th day, two different parts can be distinguished in the adenohypophysis: the pars distalis with cells containing small dense granules, and the pars intermedia with cells containing larger granules of medium density. The number of granulated cells increases steadily; on the 101st day two pars distalis cell types can be distinguished. The neurohypophysis consists of a thin anterior and a thick posterior part. Already on the 20th day single nerve terminals in the ependymal layer of the diencephalic (=infundibular) floor contain dense elementary granules. The number of granule-containing terminals increases steadily; on the 101st day almost all terminals contain granules. The present observations suggest an early secretory function of the lamprey hypophysis.
我们以扫描和透射电子显微镜研究了刚孵化的日本七鳃鳗幼体（受精后第 18 天至第 101 天）早期阶段的脑下垂体。鼻咽导管远侧部分的细胞索代表早期腺垂体。受精后第 20 天，该结构的一些上皮细胞开始表现出分泌活动的迹象，出现了广泛的高尔基体和小而密集的电子致密分泌颗粒。受精后第 26 天，可区分非分泌的星状（=支持）细胞和分泌细胞。受精后第 39 天，腺垂体可分为两部分：含有小而密集颗粒的远侧部和含有中等密度较大颗粒的中间部。颗粒细胞的数量稳步增加；在第 101 天，可区分两种腺垂体细胞类型。神经垂体由薄的前叶和厚的后叶组成。受精后第 20 天，神经下丘间脑（漏斗）地板的室管膜层中的单个神经末梢已经含有密集的初级颗粒。含颗粒的末梢数量稳步增加；在第 101 天，几乎所有末梢都含有颗粒。目前的观察结果表明七鳃鳗脑下垂体具有早期分泌功能。
