Rudolf Leiser

Intrauterine growth restriction with absent end-diastolic flow velocity in the umbilical artery is associated with maldevelopment of the placental terminal villous tree

OBJECTIVE Our purpose was to evaluate the structure of placental terminal villi and their capillaries in pregnancies complicated by intrauterine growth restriction with absent end-diastolic flow velocity in the umbilical artery. STUDY DESIGN Glutaraldehyde-perfusion-fixed villous tissue and a plastic cast of the vessels in at least two cotyledons were prepared from 10 cases with intrauterine growth restriction and 9 gestational age-matched control placentas. The structure and dimensions of 20 terminal capillary loops per cast were determined by scanning electron microscopic examination, and their appearances were correlated with the peripheral villi of the perfusion-fixed villous tissue. RESULTS Capillary loops in the growth-restricted cases were sparse in number and significantly longer than in the control cases (218 microns [72] vs 137 microns [30], mean and SD, p < 0.05). They exhibited fewer branches (4.0 [1.9] per loop vs 6.1 [2.2], p < 0.05) and a majority of loops were uncoiled (79% vs 18%, p < 0.05). The villous tissues from the growth-restricted cases demonstrated elongated villi, consistent with the cast findings. The trophoblast surface was wrinkled and in some areas covered by fibrin plaques. CONCLUSIONS The terminal villous compartment of the placenta appears to be maldeveloped in preterm intrauterine growth restriction pregnancies where absent end-diastolic flow velocity is demonstrated in the umbilical artery before delivery. These findings are consistent with an increase in fetoplacental vascular impedance at the capillary level and may account for the impaired gas and nutrient transfer in this disorder.

The fetal vascularisation of term human placental villi

SummaryVessel arrangement and vessel structure of the intermediate and terminal villi of 50 human normal term placentas have been studied by means of semithin histology, three-dimensional reconstruction of serial sections as well as scanning electron microscopy of vessel casts. The reliability of the methods applied has been checked by a morphometrical comparison of the luminal diameters obtained. The mature intermediate villi are characterized by the presence of 1 to 2 terminal arterioles as well as 1 to 2 postcapillary venules, and a few moderately coiled, mostly narrow capillaries, some of which belong to the so-called paravascular network. The remaining capillaries are continuous with the capillary loops of the terminal villi. The fetal vessels of the terminal villi are represented by capillary loops only, parts of which are sinusoidally dilated, reaching diameters up to 50 μm. Depending on the method, the mean vessel diameter of the terminal villi is 12.3 (vessel casts) or 14.5 μm (semithin sections). The capillaries of the terminal villi are arranged in such a way that 3 to 5 terminal villi are supplied by the same, multiply coiled capillary loop. The average capillary length of the paravascular net is 1,000 to 2,000 μm, that of the terminal villus capillary loops 3,000 to 5,000 μm. The extent of sinusoidal dilation rises with increasing capillary length, indicating that the main functional importance of the sinusoids in the reduction of blood flow resistance.

The fetal vascularisation of term human placental villi. I. Peripheral stem villi.

SummaryThe fetal vascularisation of the most peripheral three generations of stem villi has been studied by means of semithin serial sectioning and scanning electron microscopy of vessel casts in 50 human term placentas. The vessel types have been classified according to the structure of the vessel walls. Stem villi with a diameter of 200–400 μm are characterized by one smaller artery and one small vein, some arterioles and venules and capillaries of the paravascular net. Stem villi of about 150 μm diameter contain arterioles and muscular venules besides the paravascular capillary network. The last generation of stem villi measuring 80 to 100 μm in diameter exhibit a terminal arteriole and a collecting venule as well as up to ten paravascular capillaries. The luminal width of the arterial and venous stem vessels is considerably smaller than described for other vascular beds. This may partly be due to postpartal vascoconstriction. The capillaries of the paravascular net normally to not show sinusoidal dilation. They are arranged as long, hairpin-like, poorly branched loops connecting the arterial and venous stem vessels to each other.

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 μm3. 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.

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

SummaryAlkaline 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 lamella 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.

Spatial topography of the excurrent duct system in the bovine testis

SummaryThe rete testis of the bull is situated within an axial mediastinum and consists of approximately 30 longitudinally arranged, anastomosing rete channels. At the cranial testicular pole all rete channels empty into a common space, the area confluens reds, which is subdivided by small septa and narrow chordae retis. The area confluens always contains numerous spermatozoa and is connected with the bulbous initial portions of the efferent ductules by short, often tortuous rete tubules. Since the connection between rete and efferent ductules is situated within the tunica albuginea, the bovine excurrent duct system is not provided with an extratesticular rete as in many other mammals.Straight testicular tubules merge from all directions to connect with superficial rete channels, but the inlets are not evenly distributed. In the periphery each straight tubule begins with a cup-like structure followed by a narrow stalk region and a heavily folded portion opening either immediately into a rete channel or into a tube-like lateral rete extension.In close contiguity to the rete testis lie extremely coiled arterial portions connecting the centripetal and the centrifugal branches of the testicular artery. Since intrinsic musculature is scarcely developed in the mediastinum, and transport of rete content relies primarily on massage due to external pressure changes, the pulsatile blood flow through these coiled arteries may influence conveyance processes within the rete testis.An intimate spatial association between area confluens reds and adjacent large, thin-walled lymph vessels may facilitate a transfer of androgens into the fluid of the rete testis.

Cytochemical establishment of acid phosphatase in the Bovine endometrium and trophoblast during Implantation

SummaryAcid 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.

Production of protein hormones by cultured trophoblast cells isolated from term and early placentae.

PROBLEM: To compare the capacity of de novo hormone synthesis by cultured trophoblast cells isolated from early and term placenta as cytotrophoblast, and to determine the ability of these cells to proliferate in culture.
 METHOD OF STUDY: Cytotrophoblast cells were isolated from term (TP, 38–42 weeks) and early placentae (EP, 8–13 weeks) by enzymatic digestion and subsequent purification on a percoll gradient. The net synthesis of the hormones human placental lactogen (hPL) and human chorionic gonadotropin (hCG) was determined as the release during culture+cell content after culture−cell content before culture. Proliferation was determined using a dedicated colorimetric reagent (CellTiter 96TM).
 RESULTS: Using a percoll gradient we were able to isolate three cell bands with densities of 1.051, 1.058, and 1.063 g/mL, which were predominantly cytotrophoblast cells as shown by immunocytochemical analysis. The cytotrophoblast cells with the highest density (1.063 g/mL) were used because they were found to release the highest amount of hormones and have shown the lowest rate of cell death after 6 days in culture. Both hCG and hPL showed different patterns of release during the first 2–3 days of culture between TP and EP. While the release by EP cytotrophoblast cells continued during 6 days of culture (n=4), the concentrations for TP cytotrophoblast (n=4) reached a plateau between 4 and 6 days. Net de novo synthesis calculated for 3×104 TP trophoblast cells cultured for 6 days (mean±SD, n=4) was 8.65±9.05 mU for hCG and 0.95±0.45 ng for hPL. For EP, it was 395.5±265.5 mU for hCG and 148.8±84.2 ng for hPL. Net synthesis of hCG was>10‐fold (TP) and>70‐fold (EP) higher than the initial cell content. While at term, hPL synthesis was only a fraction of the initial cell content, production by EP cytotrophoblast was 106 times the initial cell content. The extent of cell death after 6 days in culture was significantly ( P<0.02) higher for term (30–40%) than for early trophoblast (10–20%). Using a proliferation detection agent during the first 3 days of culture with first trimester cytotrophoblast cells, we did not find any changes in the proliferative activity.
 CONCLUSIONS: There are differences in the functional activity between trophoblast cells obtained from first and third trimester. The in vitro findings are difficult to reconcile with the different patterns of plasma concentrations of the two hormones observed in vivo during the course of pregnancy.

Morphological Studies of Lacunar Formation in the Early Rabbit Placenta

Lacunae are maternal blood vessels, bordered by trophoblast cells, which begin to develop during late implantation. They are typical of hemochorial placentation. As shown in this comparative study by high resolution light microscopy and SEM micrographs of vessel casts, lacunae are formed from the preimplantational endometrial vasculature by the loss of vessel walls and partly by changing of the vessel’s architecture.