RADIOAUTOGRAPHIC OBSERVATIONS ON VARIATIONS IN DESOXYRIBONUCLEIC ACID SYNTHESIS IN RAT PLACENTA WITH INCREASING GESTATIONAL AGE.
RADIOAUTOGRAPHIC OBSERVATIONS ON VARIATIONS IN DESOXYRIBONUCLEIC ACID SYNTHESIS IN RAT PLACENTA WITH INCREASING GESTATIONAL AGE.
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随着胎龄增加，大鼠胎盘中脱氧核糖核酸合成变化的放射自显影观察。
DOI：
10.1002/aja.1001140109
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发表时间：
1964
期刊：
影响因子：
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通讯作者：
W. Jollie
中科院分区：
文献类型：
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作者：
W. Jollie
大鼠的绒毛膜尿囊胎盘在妊娠16天达到完全大小，由迷宫和交界区组成。后者被定义为滋养层起源的区域，位于基底蜕膜附近，胎儿毛细血管无法穿透（Bridgman, ' 48）。组织学上，接合区由至少三种不同的滋养细胞组成，所有这些细胞都被认为来自植入囊胚的绒毛膜外胎盘锥体：(1)滋养细胞；(2)糖原细胞，(3)滋养细胞巨细胞。此外，迷宫的小梁表面有滋养细胞，也被认为是来自胎盘外锥体。迷路滋养细胞已被证明是细胞性的（而不是先前认为的合胞性的），并且在整个妊娠过程中持续存在，从而使大鼠胎盘具有血液内膜（Dempsey和Wislocki, 1953； Wislocki和Dempsey， 1955），而不是像以前认为的那样具有血液内皮性（Mossman, 1937）。虽然迷宫通常被认为是构成母胎交换发生的“胎盘屏障”（即，在小梁间隙的母体血窦和小梁核心的尿囊毛细血管之间），但越来越多的证据表明，特别是在妊娠早期，连接区充当了交换的替代途径（Amoroso, 55; Dempsey, 59）。在这两个区域，绒毛膜滋养细胞构成屏障的组成部分。在啮齿类动物中，母胎交换的另一个重要部位是卵黄囊的血管移植，其重要性不次于绒毛膜尿囊。的确，在解剖学、发育和功能上，这构成了一个单独的胎盘（Everett, ' 35）。妊娠第16天赖克氏膜破裂，由非胚性滋养外胚层和内胚层组成的卵黄囊连同荚膜残体一起缩回；内脏卵黄囊因此暴露在子宫腔内。后一种膜由含有卵黄循环的内胚层绒毛组成，并作为潜在的转移途径（即在子宫腔和卵黄毛细血管之间），是第三种不含滋养细胞成分的“屏障”。人们早就知道母胎交换是有选择性的。此外，在生理决定的基础上，似乎对大多数物质来说，转移要么仅通过主动转运完成（Hagerman和Villee， ‘ 60），要么通过主动转运和促进扩散共同完成（Widdas, ’ 61）。关于胎盘运输的研究由于以下事实而变得复杂：(1)可运输物质的选择性和运输速率似乎随胎龄而变化（Brambell， 1950年；Feaster, Hansard， Outler和Davis， 1956年；Leissring和Anderson， 1961年）；(2)除某些例外情况外，对特定物质的实际转移地点知之甚少，即，越过上述障碍中的哪一个（Wislocki， Dean和Dempsey， ' 46）。在结带元素的情况下，在电子显微镜水平上，结构的逐步重组
The chorioallantoic placenta of the rat attains full size at 16 days of gestation and consists of a labyrinth and a junctional zone. The latter is defined as the region, trophoblastic in origin, which lies adjacent to the decidua basalis and into which fetal capillaries do not penetrate (Bridgman,’48). Histologically, the junctional zone consists of at least three distinct trophoblastic elements, all of which are believed to be derived from the chorionic ectoplacental cone of the implanting blastocyst:(1) trophospongial cells;(2) glycogen cells, and (3) trophoblast giant-cells. In addition, the trabeculae of the labyrinth are surfaced with trophoblastic elements which also are believed to be derived from ectoplacental cone. Labyrinthine trophoblast has been shown to be both cellular (rather than syncytial, as was previously supposed) and of constant persistence throughout the course of pregnancy, thereby making the rat placenta hemochorial (Dempsey and Wislocki,’53; Wislocki and Dempsey,’55), rather than hemoendothelial, as was previously believed (Mossman,’37). Although the labyrinth is generally credited with constituting the “placental barrier” across which materno-embryonic exchanges take place (viz., between maternal bIood sinuses in the interstices of the trabeculae and allantoic capillaries in the trabecular cores), there is increasing evidence to suggest that, particularly during earlier stages of pregnancy, the junctional zone acts as an alternate route of exchange (Amoroso,’55; Dempsey,’59). In both re-gions chorionic trophoblast constitutes an integral part of the barrier. In rodents another site of materno-fetal exchange, one whose importance is not secondary to the chorioallantois, is the vascularized splanchnopleure of the yolk sac. Indeed, anatomically, developmentally and functionally, this constitutes a separate placenta (Everett,‘35). With rupture of Reichert’s membrane at 16 days of pregnancy, parietal yolk sac consisting of abembryonal trophectoderm and endoderm, together with the remnants of the decidua capsularis retract; and the visceral yolk sac is thereby exposed to the uterine lumen. This last named membrane consists of endodermal villi containing a vitelline circulation and presents as a potential transfer route (viz., between uterine lumen and vitelline capillaries) a third “barrier” which contains no trophoblastic elements. It has long been known that maternofetal exchanges are selective. In addition, on the basis of physiological determinations, it appears that for most substances, transfer is accomplished either by active transport alone (Hagerman and Villee,’60), or by both active transport and facilitated diffusion (Widdas,’61). Studies on placental transport are complicated by the facts that:(1) both selectivity of transportable materials and rates of transport appear to vary with gestational age (Brambell,’50; Feaster, Hansard, Outler and Davis,’56; Leissring and Anderson,’61); and (2) with certain exceptions little is known about the actual site of transfer for particular substances, ie, across which of the barriers described above (Wislocki, Dean and Dempsey,’46). In the case of junctional zone elements, a progressive reorganization of structure at an electron microscopic level with in-