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Biomedical subjects

V Dantzer

Publications and source records attributed to V Dantzer.

80 records · Page 5Linked to original sources
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Placental vascular corrosion cast studies: a comparison between ruminants and humans.

The microvasculature of both the ruminant placentomes of cattle, sheep, and goats and the human placenta were compared, using corrosion casts of blood vessels and scanning electron microscopy. The fetal vascular trees of ruminant and human placenta differ in form and size, which correlates with the degree of ramification; however, their architecture of stem, intermediate, and terminal villi is similar. In the human, the system of serially linked capillary convolutions of terminal villi is longer than that in ruminants. Therefore, in guaranteeing blood flow against flow resistance, the human vessels particularly need a straight course, anastomoses, and sinusoidal dilations. Specifically in the ruminants studied, the venous vessels outweigh the arterial ones by volume and by number. They are suggested to be absorptive for substances metabolized in the zone of the capillary complex. The most extreme interspecies difference relates to the maternal vasculature, which, in contrast to the fetal system, is a closed system in the ruminant septas and an open lacunal intervillous space in the human. Converging and differing morphological vascular phenomena of ruminants and human placenta are discussed in terms of maternofetal exchange related to placental efficiency. In summary, the ruminant placenta, concerning the fetal vascular tree, in many aspects is workable as a model for the human.

Animals↗
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Macroscopic and microscopic aspects of collared peccary and white-lipped peccary placenta.

This study examines middle and late gestational placentae from 13 Tayassu tajacu (collared peccary) and 3 Tayassu pecari (white-lipped peccary), which are Artiodactyla belonging to the Family Tayassuidae. The chorionic sac of Tayassu species is diffuse and chorioallantoic. These epitheliochorial placentae show no trophoblast invasion into the uterine epithelium and there is interdigitation between fetal and maternal microvilli. Two distinct regions of the fetomaternal interface can be identified: the interareolar and the areolar regions. The uterine epithelium has eosinophilic cytoplasm with dispersed, basophilic and electron-dense granules. Trophoblast cells are irregularly cuboidal on top of the fetal ridges and columnar on troughs, where cells have cytoplasmic vesicles and large basal vacuoles, surrounded by whorls of smooth membranes. Capillaries indent the trophoblast cells forming a placental barrier 3 microm or less thick. The columnar uterine glandular epithelium has a subpopulation of granules staining with Perl's Prussian blue reaction, suggesting iron secretion. In areolar areas, the trophoblast cells show apical microvilli, a basophilic cytoplasm with electron-dense intracellular vacuoles and cisternae. The placenta can therefore be classified as non-deciduate. The ultrastructural aspects of this study reveal features that have not previously been described and extend our knowledge of functions relating to materno-fetal transport in these species.

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Perfusion in vivo of the porcine placenta. Fixation for EM.

A method for vascular perfusion in vivo, especially for EM fixation, was developed with the porcine placenta. The effect of fixation at varying parameters was studied. Nine multiparous Danish Landrace sows ranging in gestation from 33 to 112 days and in body weight from 160 to 257 kg were used. After general and local anaesthesia laparotomy was undertaken on the left flank and the uterine horn was perfused through a. uterina with buffered glutaraldehyde. Local perfusion through a. umbilicalis was undertaken in one case, and installation of concentrated glutaraldehyde into the allantoic cavity was performed in five cases. Perfusion-fixed and fresh tissue samples were fixed in OsO4 and processed for electron microscopy. The osmolarity of the buffer was varied between 470 and 660 mOsm. At high tonicity cytoplasm was well preserved but the intercellular spaces of the uterine epithelium was dilated. At about 575 mOsm the preservation was still good and the spaces were occluded. At lower tonicity damage occurred in the cytoplasm. The trophoblast was generally better preserved than the uterine epithelium. A rapid perfusion flow was beneficial for fixation.

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An electron microscopic study of histiotrophe in the interareolar part of the porcine placenta.

Placentae from nine sows covering gestational stages from 33 to 112 days were examined by light and electron microscopy. Deeply stainable electron-dense histiotrophe was demonstrated in the interareolar placenta. Focal accumulations of cell debris with profiles of organelles were demonstrated in the intermicrovillous space between uterine epithelium and trophoblast. In addition, small expansions of amorphous histiotrophe were found between the microvilli. Furthermore, histiotrophe with profiles of cytomembranes was shown in intercellular spaces in columnar trophoblast between the microvillar border and tight junctions. Dense bodies were demonstrated in the uterine epithelium, and endocytic vesicles and branched tubular structures with dense contents were found in the columnar trophoblast. It is concluded that focal accumulations of cell debris are derived from degenerating epithelial cells in the endometrium and chorion, and that amorphous histiotrophe arises by secretory activity of uterine epithelium. It is further concluded that the histiotrophe is absorbed by columnar trophoblast of the chorionic fossae.

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An extensive lysosomal system in the maternal epithelium of the porcine placenta.

The material comprised 64 placentae from 19 Danish Landrace sows representing gestational stages from 16 to 112 days. The maternal epithelium was examined by means of light and electron microscopy to describe the morphology of the irregular electron-dense bodies and membrane whorls and their relation to gestational stages. Incubation for acid phosphatase demonstrated their lysosomal nature. Electron micrographs of serial sections followed by reconstructions and freeze-fracturing demonstrated their three-dimensional structure and relation to transfer tubules. In the early stages, during the development of fetal vascularization, the maternal epithelium was dominated by inclusions of lipids and glycogen, which can easily be transferred to and utilized by the embryo. The development of an extensive lysosomal system, consisting of irregular electron-dense bodies, membrane whorls and transfer tubules, indicates that cellular digestion is an important factor in the transfer and subsequent fetal utilization of maternal nutriments in the last two-thirds of gestation, and that this development is apparently related to anatomical and physiological changes during gestation.

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High densities of angiotensin II subtype 2 (AT2) receptors in the porcine placenta and fetal membranes.

The present study was undertaken in order to characterize and determine angiotensin (Ang) II receptors and renin in the porcine placenta and fetal membranes. High densities of Ang II receptors of subtype 2 (AT2 receptors) were demonstrated in all parts of the placenta and fetal membranes throughout gestation. AT1 receptors (subtype 1) were only found in the first part of the gestation and only in the allantochorion-endometrium at low densities. The total Ang II receptor density was increased in the allantochorion-endometrium in the last stage of gestation. Except for this finding the Ang II receptor density did not vary during gestation. Some of the highest receptor densities were found in the allantoamnionic membrane. The Ang II receptor densities did not correlate with the duration of the gestation in any part of the placenta. Enzymatically active renin was found in all parts of the porcine placenta and fetal membranes in concentrations similar to those found earlier in the blood plasma. The renin concentrations did not correlate with the Ang II receptor densities or the duration of the gestation in any part of the placenta. Compared with the human placenta, where the Ang II receptors are almost exclusively AT1 receptors and low receptor densities are found in the fetal membranes, the present results indicate profound species differences in the expression and function of the renin-angiotensin system in the placenta and fetal membranes.

Angiotensin Receptor Antagonists↗