Light- and electron-microscopic study of the near-term paraplacenta of the domestic cat

Abstract

The entire chorioallantoic paraplacenta of the near-term domestic cat shows cytological evidence of maternal-fetal substance transfer, but there are probably qualitative and quantitative differences and increased transfer progressing from the poles to the placenta! border. In the interfetal polar zone, the cytotrophoblast remains proliferative, is squamous to columnar and shows only a small amount of pinocytotic activity. However, in the adjacent ring of the free polar zone, where the trophoblast is cuboidal or columnar and loosely apposed to the endometrium, material of uterine origin (histotroph) appears to be transferred from the columnar uterine surface epithelium to the trophoblast. The remaining paraplacenta extends from the polar zone to the girdle, forming an extravasate zone that is composed of hematomal areas containing extravasates of maternal blood, and interposed relatively unmodified paraplacental junctional areas. The trophoblast in this hematomal area is columnar and constitutes chorionic villi which face a. surface formed by maternal symplasma, degenerative uterine tissue, and disintegrating blood, thus providing ‘histolytic’ and ‘hemolytic’ embryotroph to this hemophagous cytotrophoblast. When the junctional area is just forming, a cuboidal cytotrophoblast consisting of resting cells, opposite to the endometrial folds, appears to have both the capacity for digestion and transformation. However, during the recessive junctional stage, this cytotrophoblast is proliferative and absorptive only. Both sources of cuboidal trophoblast may give rise to syncytial trophoblast, which is presumably the invasive form that erodes the uterine tissue, including the interstitial layer and maternal endothelium. As long as there is firm junction of the fetal and maternal tissues, there appears to be a transfer of secretion products to form embryotroph. However, with the regression of the junctional area more products of cell breakdown (histolytic products) are absorbed by the cuboidal cytotrophoblast in the chorionic fossae.

Histological Changes of the Feline Cervix, Endometrium and Placenta after Mid‐gestational Termination of Pregnancy with Aglepristone

“…The process of placental detachment seems to occur suddenly, as the foetuses aborted were alive. This sudden detachment might be the result of a certain ‘destabilization’ of the foetal–maternal connection, probably facilitated through haemorrhage that developed as the result of several ‘leaky’ maternal venules, which could not be observed in the intact pregnant queens of this study and several previous investigations (Leiser and Enders 1980a,b; Leiser and Koob 1993).…”

Transplacental Transfer of Iron in the Water Buffalo (Bubalus bubalis): Uteroferrin and Erythrophagocytosis

“…1979, 1984; Myagkaya and De Bruijn 1982; Santos et al. 1996), carnivores (Wislocki and Dempsey 1946; Gulamhusein and Beck 1975; Leiser and Enders 1980; Dumartin and Canivenc 1991) and insectivores (King et al. 1978).…”

“…It is frequently suggested that the haemophagous areas or ‘placental hematomes’ contribute to iron transfer from mother to foetus, based on studies using light and transmission electron microscopy, immunohistochemistry and electron immunomicroscopy with markers of iron transport, X‐ray microanalysis and injection of Fe 59 into the maternal circulation (Hoyes 1972; Burton et al. 1976; Leiser and Enders 1980; Myagkaya and De Bruijn 1982; Murai and Yamauchi 1986; Latshaw 1987; Santos et al. 1996).…”

Placental iron transfer regulation in the haemophagous region of the badger placenta: ultrastructural localization of ferritin in trophoblast and endothelial cells

“…Ultrastructural studies of uptake and subsequent degradation of maternal erythrocytes have been made in the cat (Malassin~ 1977(Malassin~ , 1982Leiser and Enders 1980), sheep (Burton et al 1976;Myagkaya and Vreeling-Sindelarova 1976;Myagkaya etal. 1979;Myagkaya and Schellens 1981), shrew (King et al 1978) and seals (Sinha and Erikson 1974).…”