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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim was to determine whether the fetal vasculature of the human placenta adapts in a uniform manner to different forms of hypoxic stress. Stereological analyses were performed on the intermediate and terminal villi of placentae obtained from each of the following conditions; high altitude (up to 2800 m), maternal iron-deficiency anaemia and pre-eclampsia. These conditions were taken to represent hypoxic, anaemic and ischaemic hypoxia, respectively. In each situation, there was a trend for the volume fraction of the fetal capillaries to be higher than in the controls, although the differences were statistically significant only for the cases of hypoxic and anaemia hypoxia. This was due, in part, to capillaries being of larger diameter. Evidence for capillary proliferation was inconsistent. At high altitude there was a trend for the capillary length density to be raised, but there was no change in the ratio of capillary:villous length. In both maternal anaemia and pre-eclampsia the capillary length density remained constant, but the ratio of capillary:villous length was significantly raised in the former. These results suggest that dilatation of the capillary sinusoids, with accompanying thinning of the villous membrane, is the principal adaptation to hypoxia under the conditions studied.
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PMID:Stereological evaluation of vascular adaptations in human placental villi to differing forms of hypoxic stress. 871 Aug 13

The spiral artery (=SA) is an important muscular artery, which controls the blood volume to the placenta. Preeclampsia is thought to be induced by the failure of the placenta by dysfunction of SA. To clarify the function of SA, we examined forty-eight placentae and its morphological and biological characteristics: 36 normal placentae and 12 placentae with preeclampsia. Gestational age of normal placentas was between 19 and 40 weeks and placentae with preeclampsia was between 31-36 weeks. The wall of the placental segment of SA by both light and electron microscope, and the wall width of SA and gestation age were compared each other. The wall of SA, with the invasion of trophoblast, was thin, but SA without trophoblasts was thick in width. At normal placenta, the diameter of SA was dilative constantly, but the width of the wall showed a tendency of getting thinning as advances. Ultrastructually, we found the trophoblast of thin wall of SA with dilated lumen. These ultrastructual alternations were consistence with the light microscopical findings. In preeclampsia, the lumen of SA between normal pregnancy and one with preeclampsia was almost same, but the wall width was thick, compared with normal pregnancy (P<0.05). We concluded that trophoblastic invasion control the functions of SA.
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PMID:Spiral artery of placenta: development and pathology-immunohistochemical, microscopical, and electron-microscopic study. 1191 50

The influence of oxygen pressure on placental and villous vascular development is reviewed and considered relative to the natural experiment afforded by residence at high altitude. Data obtained from normal high altitude pregnancies are compared with those from IUGR and preeclampsia, conditions believed to be caused by placental hypoxia. High altitude placentas are characterized by increased villous vascularization, thinning of the villous membranes, proliferation of the villous cytotrophoblast, and reduced perisyncytial fibrin deposition relative to low altitude placentas. The significance of reduced fibrin deposition is unknown; it could be explained by less apoptosis along the barrier membrane, less syncytiotrophoblast turnover, or altered ratios of local proversus anticoagulant production. Increased villous capillary density and thinning of the villous membranes increases oxygen diffusion capacity and is generally considered a beneficial adaptation. Nonetheless, there is evidence that hypoxia and/or reduced blood flow reduce placental nutrient transporter densities, and this may act in additive or synergistic fashion to reduce birth weight at high altitude. The available literature on high altitude placentas derives from less than 100 pregnancies from three different continents and six different ethnic groups, and were acquired in pregnancies ranging from 2500 to 4300 m in altitude. Thus differences between studies are likely to be due to variation in altitude and/or to ethnic variation, which in turn may be due to differences in population history of residence at high altitude (e.g., Andeans vs. Europeans). Nonetheless, systematic examination of human placental development under conditions of lowered maternal arterial oxygen pressure (high altitude > 2700 m) may provide useful insights into the etiology of pathological conditions believed to be associated with placental hypoxia.
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PMID:The placenta at high altitude. 1285 50

A 27-year-old pregnant female underwent cesarean section due to preeclampsia. Two days after the delivery, she presented with acute onset of blurred vision in the left eye. Optical coherence tomography (OCT) revealed characteristic findings of acute macular neuroretinopathy (AMN) in both eyes. During the follow-up, her vision improved gradually, but outer nuclear layer thinning with disruption of ellipsoid zone was identified from OCT. OCT angiography was arranged and revealed both vascular defect in superficial and deep vascular plexus, which correlated with previous AMN lesions in both eyes. Subsequent microvascular change in AMN was found to involve both superficial and deep vascular plexus, which is different from the current consensus that AMN mainly involved deep vascular plexus. By using the OCT angiography, we can better visualize the detail retinal vascular structure and may identify the real mechanism in this rare retinal disorder.
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PMID:Microvascular change in acute macular neuroretinopathy by using optical coherence tomography angiography. 3119 71

An interstitial pregnancy that continues beyond the second trimester is a rare phenomenon. We report a patient with an interstitial pregnancy undiagnosed until the third trimester. A multiparous woman was referred to us because of preeclampsia at 26 weeks of gestation. The placental position was the right fundus, and color Doppler ultrasound revealed myometrial thinning and subplacental hypervascularity, leading to a suspicion of placenta accreta spectrum (PAS). Emergency cesarean section was performed at 281/7 weeks of gestation due to severe preeclampsia. The right tubal horn to the isthmus of the fallopian tube bulged with placental adhesion and a part of the tube had ruptured, with the omentum adhering to the ruptured part. Interstitial and tubal isthmic pregnancy with uterine rupture was diagnosed.
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PMID:Interstitial Pregnancy in the Third Trimester with Severe Preeclampsia: A Case Report and Literature Review. 3245 34