Ultrastructural Studies of the Placenta of the Ewe: Phagocytosis of Erythrocytes by the Chorionic Epithelium at the Central Depression of the Cotyledon

Burton, Graham J.; Samuel, Carole A.; Steven, D. H.

doi:10.1113/expphysiol.1976.sp002359

Cited by 46 publications

(24 citation statements)

References 14 publications

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“…First, the capillary of the rabbit provides over 50 % of the total resistance to transplacental passage of ferritin (Thornburg & Faler, 1976). Secondly, electromicroscopic examination of sheep placentae demonstrates extravasation of red blood cells through the maternal capillary but not through the fetal capillary wall (Burton, Samuel & Steven, 1976). Thirdly, proteins produced within the human placenta on the maternal side of the fetal capillary endothelium, such as chorionic gonadotrophin or somatomammotrophin, appear in much higher concentration in the maternal than in fetal plasma.…”

Section: Placental Tissue Spaces and Their Barriersmentioning

confidence: 99%

Volumes of distribution of sodium and albumin in the sheep placenta.

Boyd¹,

Canning²,

Stacey³

et al. 1983

The Journal of Physiology

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SUMMARY1. The volumes of distribution of 22Na and 24Na, 51Cr-EDTA and albumin labelled with 1311 and 1251 were measured in cotyledons and skeletal muscle taken from pregnant sheep and the fetuses near term. Radiolabelled substances were injected through chronically implanted catheters 0-5--32 hr before removal of tissues in 'short-term' experiments and 24-26 hr before in 'long-term' experiments. Volumes of distribution were expressed as percentages of tissue weights.2. Cotyledonary water content was 81 5 + 06 % (S.E. ofmean) ofwet weight (n = 10 sheep). Sodium content was 76-0 + 4-0 m-mole kg-' wet weight (n = 4) and potassium content was 58-8 + 2-4 m-mole kg-' wet weight (n = 4).3. In short-term studies cotyledonary spaces following injection into the fetal circulation were: Na, 20-5 + 0 9 % (n = 10 sheep); Cr-EDTA, 19-5 + 1-2 % (n = 3); and albumin, 2-8 + 0 3 % (n = 11). The equivalent maternal cotyledonary spaces were: Na, 23-5 + 1-6 %, or 22-1 + 1-6 % when 'corrected' for fetal radioactivity (n = 8); and albumin, 4-7 + 0 8 % (n = 8). Maternal and fetal cotyledonary sodium spaces were additive. Larger cotyledons had larger fetal sodium spaces. 4. In long-term studies, the value for maternal albumin spaces was considerably higher 12-3 + 3-2 % (n = 3), whereas that for fetal albumin spaces was only 3 9 + 0 4 % (n = 4). The higher fetal sodium space of 24-9 +1±0 % (n = 4) in the long-term experiments was attributable to rising sodium counts in the maternal circulation. 5. In the short-term experiments maternal skeletal muscle spaces were Na, 135+ 1-3% (n = 7) and albumin, 1-7+0-3% (n = 7), with higher values of 220% (n = 2) and 38 + 0-2 % (n = 3) respectively in long-term experiments.6. In the short-term experiments fetal skeletal muscle spaces were Na, 32-8 + 3-2 % (n = 7) and albumin, 2-5 + 0 3 % (n = 10), with higher values of 39-7 + 7-4 % (n = 4) and 16-2 + 0-6 % (n = 4) respectively in long-term experiments.

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Section: Placental Tissue Spaces and Their Barriersmentioning

confidence: 99%

Volumes of distribution of sodium and albumin in the sheep placenta.

Boyd¹,

Canning²,

Stacey³

et al. 1983

The Journal of Physiology

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“…To reduce the number of false positive counts, BNCs were counted only if O30% of the cytoplasm of a BNC was visible and at least 80% of the randomly selected field of view was covered with placental tissue (Ward et al 2002). BNC localization and distribution was analyzed within three levels, which refer to previously reported zones in a placentome (Burton et al 1976). L1 contained 1, 6, 7, and 8 fields of interest and was taken in the zona intima, closely to the capsule of the placentome.…”

Section: Image Analysismentioning

confidence: 99%

Maternal betamethasone administration reduces binucleate cell number and placental lactogen in sheep

Braun

Li²,

Moss³

et al. 2007

Journal of Endocrinology

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The placenta may mediate glucocorticoid-induced fetal growth restriction. Previous studies have examined effects of fetal cortisol in sheep, which reduces placental binucleate cell (BNC) number; the source of ovine placental lactogen (oPL). The effects of maternal GC are unknown. Therefore, this study examined the effects of maternal betamethasone (BET) administration on BNC number, distribution, placental oPL protein levels, and maternal and fetal plasma oPL levels. Pregnant ewes were randomized to receive injections of saline or one (104 days of gestation; dG), two (104 and 111 dG), or three (104, 111, and 118 dG) doses of BET (0 . 5 mg/kg). Placental tissue was collected before, during, and after the period of BET treatment. Fetal (121-146 dG) and placental (121 dG) weights were decreased after BET when compared with controls. In controls, the mean number of BNCs increased until 132 dG and decreased thereafter. Placental oPL protein levels peaked at 109 dG and remained stable thereafter. Maternal plasma oPL levels in controls increased across gestation; fetal plasma oPL levels decreased. BNCs were reduced by 24% to 47% after BET when compared with controls at all ages studied. Placental oPL protein levels, maternal, and fetal plasma oPL levels were also reduced after BET injections, but recovered to values that were not different to controls near term. BET disrupted the normal distribution of BNCs within the placentome. These data may suggest a placental role in growth restrictive effects of prenatal maternal BET exposure through alterations in placental output of oPL, a key metabolic hormone of pregnancy.

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“…Extravasated blood found near the base of the fetal villi suggests the existence of a small haemophagous organ, as has been described for sheep (Wimsatt, 1950;Steven, 1975) and goats (Harrison & D'Silva, 1956). Electron microscopy of the haemophagus region in sheep indicates the absorption of maternal red blood cells by cells of the chorionic epithelium (Burton et al, 1976). These authors suggest this as one possible route for fetal absorption of iron.…”

Section: Discussionmentioning

confidence: 57%