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R Leiser

Publications and source records attributed to R Leiser.

85 records · Page 5Linked to original sources
PubMed1977

[Adenosine triphosphatases in the bovine endometrium and in the trophoblast during implantation. Microscopic and electron microscopic investigations (author's transl)].

Investigations of the bovine epithelium uteri and trophoblast between the 22nd and 24th day after insemination have been made according to the method of FARQUHAR and PALADE (1966) concerning the activity and microstructural localization of the Mg++-, Ca++- as well as the (Mg++-Na+-K+)-ATPases which may be made active (E. C. 3.6.1.3). The evidence of the ATPases in the so-called free cells during the pre-implantative stage is associated with a production of immunoglobulin A and thus the importance of these cells within the scope of an immunological position of reaction of the endometrium is being discussed. On the epithelium uteri there is a correlation at first between the activity of this hydrolase, which can only be proved at the later pre-contact stage, and the microstructural symptoms of increasing secretion. During the subsequent stage of apposition and after consolidated implantation ATPase-dependent transportations through membranes are likely to serve in the formation of hemotrophs as well as in the hemotroph metabolism. Finally, an attempt is made to give an explanation of the precipitate depositions on the cells of the uterine glands.

Adenosine Triphosphatases↗
PubMed1975

Alkaline phosphatase in the bovine endometrium and trophoblast during the early phase of implantation.

Alkaline phosphatase in the endometrial and chorionic epithelium from the 22nd to 24th day post insemination was investigated according to the method of Hugon and Borgers (1966a, b). In the precontact phase the reaction products of this enzyme were found light microscopically in the caruncular and intercaruncular area in the apical part of the uterine surface epithelium. Although a definite, continuing reaction line between the maternal and fetal epithelium was present in the apposition phase, there was no activity of this phospho-monoesterase ascertainable following consolidated adhesion. Independent of implantation, lead salt precipitate was observed in the apical cytoplasma in the upper third of the uterine epithelial glands. Electron microscopic investigations in the precontact phase demonstrated the localisation of the reaction products of this hydrolase as electron dense grains on the outer plasma lamella of the uterine microvilli. During apposition this reaction appeared on the microvilli of the dark uterine epithelium and the cell membrane of the trophoblast cells. In addition to the existence of alkaline phosphatase on the microvilli of the uterine glandular cells, reaction products were discernable in the kinocilia between the inner lamellar of their plasma membranes and the tubules ring, as well as between the latter and the central tubule pair. There is a possibility that this hydrolase plays a role in the transport of metabolites for the purpose of histiogenic uterine milk production.

Alkaline Phosphatase↗
PubMed1975

Cytochemical establishment of acid phosphatase in the bovine endometrium and trophoblast during implantation.

Acid phosphatase in the endometrial surface epithelium is seen in connection with autophagy and autolysis. In the precontact and initial apposition stage, enzyme-positive Golgi vesicles, lysosomes and secretion granules all indicate autophage performance of the dark uterine epithelial cells in the sense of a histiogene embryotrophe development. At the time of progressing apposition this is joined by cell degradation with the aim of histiolytical uterine milk production. Following the completed implantation in the adhesion phase no activity with autophagy and autolysis-correlated acid phosphatase can be established. In trophoblast giant cells the localisation of acid phosphatase speaks for secretional processes. The incidence of this enzyme in the adhesion stage in "ordinary" trophoblast cells leads to the supposition of autophage processes which must be investigated in more detail. The endometrial gland epithelium shows the same acid phosphatase-dependent autophage indications in the upper third of the glands as shown in the surface epithelium prior to apposition. However, the acid phosphatase activity and the secretion deduced therefrom, thus the histiogene embryotrophe development, is conserved during the whole early gravidity of the cow, independent of the implantation process.

Acid Phosphatase↗
PubMedDate not supplied

Localisation of glycans in the placenta: a comparative study of epitheliochorial, endotheliochorial, and haemomonochorial placentation.

Specimens of mid-term (horse), near-term (pig, cow, sheep, mink) and term (human) placentae and associated tissues have been examined with a panel of 15 biotinylated lectins combined with an avidin-peroxidase revealing system. The aim of this study has been to analyse the expression of glycans at the materno-fetal interface in order to establish whether the morphological diversity exhibited by these six species is reflected by accompanying biochemical diversity, or whether similar types of glycan are expressed in tissues performing similar functions. Lectin staining intensity was scored in the following elements of the interhaemal placental barrier: maternal capillaries, maternal uterine epithelium, the materno-fetal interdigitating microvillous membrane (brush border in the human), trophoblast, and fetal capillaries. A high degree of biochemical diversity was found in the glycan expression of the various placental components within and among placental types. Each layer showed widely differing patterns of lectin binding between species, with only a few findings in common: 1) the relative lack of simple fucosyl termini, 2) the presence of non-bisected bi/tri-antennary N-glycan in most layers, 3) an abundance of terminal N-acetyl galactosamine, and 4) the restriction of high mannose glycans to intracellular granules. This diversity may be a mechanism to avoid hybridisation, although glycan patterns may change between conception and placental development, or it may have evolved as a consequence of morphological changes. It is possible that it may also be part of the cause, rather than the result, of the structural diversity that is so characteristic of mammalian placentation.

Animals↗
PubMedDate not supplied

Carbonic anhydrase activity in different placenta types: a comparative study of pig, horse, cow, mink, rat, and human.

The placenta has multiple functions, being the organ which provides oxygen and nutrients to the developing conceptus. In the placenta, the enzyme carbonic anhydrase (CA) may provide ions for exchange with Na+, K+, and Cl- in transepithelial movement of ions and fluid, as well as facilitating carbon dioxide diffusion. It can also be active in intermediary metabolism, such as gluconeogenesis, urea, and fatty acid synthesis. Placental material from pig, horse, cow, mink, rat, and human was therefore investigated, representing placenta types with variations in shape, internal architecture, and nature of the interhemal barrier. After glutaraldehyde fixation, sections were stained by a histochemical CA-method demonstrating all active isozymes. The most striking feature in common was a positive reaction in the maternal capillaries, when present, as in pig, horse, cow, and mink. In the maternal epithelium, the activation of CA was only observed in the pig, which also exhibited the strongest activity at the maternal interface, which reacted moderately in rat, weakly in horse, and was not visible in cow and human. The trophoblast was positive in pig and rat, whereas it was negative in horse, cow, human, and mink placentae except for few scattered trophoblast cells in pig, horse, and cow, which showed very intense activity. In the fetal capillaries, a positive reactivity was only observed in mink and human. The utilization of CA in placental transfer and metabolism is thus highest in the pig, rat, and mink, compared with horse, cow, and human. It can therefore be concluded that the activation and localization of CA in the placental interhemal barrier varies considerably among species.

Animals↗
PubMedDate not supplied

Vascular interrelationships of near-term mink placenta: light microscopy combined with scanning electron microscopy of corrosion casts.

The microvasculature of the near-term zonary placenta of the mink has been studied using light microscopy and scanning electron microscopy of corrosion casts, prepared from maternal and fetal vessel systems, respectively. The zonary area, most important for placental exchange, includes a characteristic labyrinth. The labyrinth is composed of lobules oriented in a maternal-fetal direction. One maternal stem artery serves as the central axis of a lobule, and about six pairs of fetal stem arteries and stem veins of the chorionic primary villi mark the periphery of the lobule. Viewed from the fetal side of the labyrinth, this lobular structure presents a roughly hexagonal pattern, with the central maternal stem artery and radially oriented arteriolar branches giving the lobule the shape of a star. These arterioles frequently form bridges to neighboring lobular systems; however, the majority continue into the feto-maternally oriented three-dimensional network of maternal capillary sinusoids, which converge on the outlets of the maternal stem veins on the maternal side of the labyrinth. Maternal main crypts are delimited by the rays of the star-shaped lobules containing chorionic primary villi. The latter penetrate into maternal crypts from the fetal side, and are characterized by their axial arterial and venous stem vessels. Fetal secondary villi are arranged at different levels from these stem vessels. The secondary villi are characterized by arterioles and venules branching in pairs from the stem vessels and supply the tributary capillary complexes of terminal villi. The lobular structure of the placental labyrinth provides a three-dimensional framework of vessels where maternal capillary sinusoids and fetal capillaries meet in a one-way cross-current arrangement. The blood flow conditions and the peculiarities of the mink placenta interhemal membrane are compared to those of other carnivores and discussed with respect to the efficiency of the endotheliochorial placenta.

Animals↗
PubMedDate not supplied

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↗
PubMedDate not supplied

Morphogenesis and fine structure of the near-term placenta of Talpa europaea: I. Endotheliochorial labyrinth.

Morphological studies of placentation of Talpa europaea confirm an antimesometrially orientated discoidal and chorioallantoidic placentome. This placentome, near term, shows a villous labyrinthine zone with interspersed haematomal areolae on its fetal side, a centrally located fetomaternal junctional zone, and a uterine gland zone towards the myometrium. As shown by light and electron microscopy the interhaemal membrane in the labyrinthine zone develops to an endotheliochorial placentation type. It consists of a prominent maternal endothelium, a distinct interstitial layer, which contains some endometrial debris and is interrupted by some endotheliochorial contact points, a bilayered trophoblast with a thin syncytial and a larger cytotrophoblastic component, and a small fetal endothelium. Disintegration of endometrial epithelium takes place at the areolar glandular mouths and in the junctional zone where a decidual cell reaction can also be observed, but no decidual cells become integrated into the labyrinth. In the spectrum from epitheliochorial to haemochorial placentation, Talpa europaea exhibits a less endotheliochorial type of placentation than is the case with carnivores.

Allantois↗
PubMedDate not supplied

DNA content and ploidy level of bovine placentomal trophoblast giant cells.

Cytophotometric measurement of the DNA content of Feulgen-stained nuclei in touch preparations of bovine placentomes (n =5) revealed that 8C nuclei occurred in all, 16C nuclei in two, and 32C nuclei in one specimen. The determination of ploidy level by in situ hybridization with a Y-chromosome specific DNA probe showed that the majority of the fetal nuclei in touch preparations of placentomes from male fetuses (n =5) are tetraploid. Generally two tetraploid nuclei lie close together. These findings indicate that polyploidization is a normal feature in the development of the mostly binucleate trophoblast giant cells (TGCs). A new model for the development of these cells is proposed: a primary acytokinetic mitosis leads to a binucleate cell with two diploid nuclei. This cell enters a second acytokinetic mitosis during which the chromosomes of both nuclei form a common metaphase plate. The resulting cell with two tetraploid nuclei undergoes an additional S-phase but does not enter a renewed mitosis. The functional significance of this genome multiplication may be an increased synthetic capacity of bovine TGCs, caused by an increased number of gene copies available for transcription. Since genome multiplication is a property of invasive trophoblast cells of different species, it may be advantageous for trophoblast invasion.

Animals↗
PubMedDate not supplied

Glucose consumption and lactate production of human placental tissue under different conditions of in vitro incubation.

OBJECTIVE: To assess the glycolytic activity of human placental tissue in the third trimester as measured by glucose consumption and lactate production under different conditions of in vitro incubation. METHOD: An incubation technique was used to study the metabolic activity of the human placenta by comparing large blocks (0.3 cm3, T1) and small fragments (explants, 0.03 cm3, T2). Placentas were obtained from premature (28-33 weeks) and term (39-41 weeks) deliveries. In addition, different experimental conditions were used to investigate the influence of incubation medium (Earle's buffer and cell culture medium NCTC = 135), medium oxygen pressure (PO2) (400 and 30 mmHg), and regional sampling of placental tissue (central, intermediate, and peripheral). All media contained glucose (1 g/L). The tissue (2-3 g/25 mL medium, pH 7.2-7.4) was incubated for 3 hours at 37C. 3H-inulin was used for the determination of the extracellular space. RESULTS: Incubation of both tissue forms yielded a higher metabolic activity as measured by glucose consumption and lactate production when incubated with Earle's buffer compared with incubations with NCTC medium. In general, the metabolic activity was consistently higher for small fragments compared with the large blocks. Extracellular space values found for large fragments (25-31%) were significantly lower than for small pieces (39-46%), indicating that an equilibration of the medium with the extracellular space is inadequate with large fragments. Incubation with small fragments showed that 1) there is a tendency for higher metabolic activity during incubation with lower PO2, 2) the metabolically most active part of the placenta is the intermediate tissue region, and 3) placental metabolic activity was significantly higher at 28-33 weeks (n = 5) than at term (n = 6). These differences were not seen with large fragment incubations. CONCLUSION: The smaller tissue fragments are preferable for the in vitro incubation study of placental glucose metabolism. Apparently, there are differences in the metabolic activity with regard to the placental tissue region and gestational age.

Culture Media↗
PubMedDate not supplied

Effect of physiologic perfusion-fixation on the morphometrically evaluated dimensions of the term placental cotyledon.

OBJECTIVE: To estimate the in vivo dimensions of the fetal villous tree of the normal term placenta. METHODS: Dual-circuit perfusion-fixation of a cotyledon from eight normal term placentas was performed with random intra-cotyledon tissue sampling. Stereologic methods were used to derive estimates of villous (intermediate and terminal) surface area and volume, and star volume (a measure of villous volume). RESULTS: Villous surface area (mean 20.9 m2 [standard deviation 1.8]), capillary surface area (12.8 m2 [1.5]), villous volume (469 mL [40]), and capillary volume (80 mL [10]) values were all approximately 50% higher than reported previously. Star volume estimates ranged from 480 to 1350 microns 3. CONCLUSION: Tissue perfusion-fixation more accurately reconstructs the in vivo state, resulting in higher reference values than previously thought for the fetal villous tree dimensions. Up to one-quarter of fetoplacental blood volume is likely to be accommodated within the placenta at term.

Birth Weight↗