Beyo Reston S, Divya Lekha, Oommen Oommen V, Akbarsha Mohammad A
Department of Zoology, University of Kerala, Kariavattom, Thiruvananthapuram, Kerala 695581, India.
J Morphol. 2008 Nov;269(11):1412-24. doi: 10.1002/jmor.10670.
There is a paucity of information on the female reproductive biology of the caecilian amphibians when compared with the other vertebrate groups. Hence, the accumulation of nutrient reserves in the form of yolk and formation of yolk platelets were studied in Gegeneophis ramaswamii, adopting light microscopic histological and transmission electron microscopy analysis. Previtellogenic as well as vitellogenic follicles were observed in appropriate preparations. On the basis of the source and the routes of entry, we identified four types of yolk precursor materials, precursors 1 to 4. The earliest material appearing in the oocyte consists of abundant lipid vesicles during the previtellogenic phase, i.e., much before the follicular epithelium is fully established. This is a contribution from the oocyte mitochondria, which we identified as yolk precursor material 1, and it is autosynthetic. Once the follicle cell-oocyte interface is fully established, there is an accumulation of the principal component of the heterosynthetic yolk by sequestration from the blood through the intercellular spaces between follicle cells in a pinocytic process. This we identified as yolk precursor material 2. There was also an indication of a lipidic yolk material synthesis in the follicle cells sequestered from maternal blood through the follicle cells in an endocytic process in which the macrovilli of follicle cells and the microvilli of the oocyte play a role. This we identified as yolk precursor material 3. Contribution to the yolk of peptidic, glycosidic, and/or lipidic material synthesized in the vitellogenic oocyte was also indicated. This we identified as yolk precursor material 4. The sequential development of intercellular associations and indications of synthesis/sequestration of the yolk have been traced. Thus, we report the mechanistic details of synthesis/sequestration of the yolk materials in a caecilian.
与其他脊椎动物类群相比，关于蚓螈两栖动物的雌性生殖生物学的信息匮乏。因此，采用光学显微镜组织学和透射电子显微镜分析方法，对拉氏吉纳螈（Gegeneophis ramaswamii）中以卵黄形式存在的营养储备积累和卵黄小板的形成进行了研究。在合适的标本中观察到了卵黄发生前期以及卵黄发生期的卵泡。根据来源和进入途径，我们确定了四种卵黄前体物质，即前体1至4。在卵黄发生前期，即在卵泡上皮完全形成之前很久，最早出现在卵母细胞中的物质是大量的脂质小泡。这是卵母细胞线粒体的贡献，我们将其确定为卵黄前体物质1，并且它是自体合成的。一旦卵泡细胞 - 卵母细胞界面完全建立，通过吞噬作用从血液中通过卵泡细胞之间的细胞间隙螯合，就会积累异源合成卵黄的主要成分。我们将其确定为卵黄前体物质2。在通过卵泡细胞从母体血液中螯合的卵泡细胞中，也有脂质卵黄物质合成的迹象，这一过程涉及卵泡细胞的大绒毛和卵母细胞的微绒毛，是一个内吞过程。我们将其确定为卵黄前体物质3。还表明了在卵黄发生期的卵母细胞中合成的肽类物质、糖苷类物质和/或脂质类物质对卵黄的贡献。我们将其确定为卵黄前体物质4。已经追踪了细胞间联系的顺序发展以及卵黄合成/螯合的迹象。因此，我们报告了蚓螈中卵黄物质合成/螯合的机制细节。
