Comparison between high-field 3 Tesla MRI and computed tomography with and without arthrography for visualization of canine carpal ligaments: a cadaveric study

OBJECTIVE:To compare the quality of visualization of canine carpal ligaments by using computed tomography (CT), MRI, CT arthrography (CTA), and magnetic resonance arthrography (MRA). STUDY DESIGN: Prospective descriptive study. STUDY POPULATION: Cadavers from dogs weighing more than 20 kg. METHODS: A 16-slice CT scanner and a 3 Tesla MRI were used for the investigation. A dilute contrast medium was injected into the middle carpal and radiocarpal joints under fluoroscopic control, and CTA and MRA images were acquired. To evaluate the difference between imaging modalities, 3 observers graded carpal ligaments of clinical interest using a scale from 0 to 4 for their quality of visualization. Data were analyzed by using a random-effect ordinal logistic regression with Bonferroni adjustment. The interobserver agreement was calculated by using the weighted Cohen's κ. RESULTS: Normal carpal joints (n = 9) were investigated. Magnetic resonance arthrography improved visualization of the majority of carpal ligaments compared with MRI (P < .05) and offered the best visualization overall. Magnetic resonance imaging and MRA offered better visualization compared with both CT and CTA (P < .05). There was no difference between CT and CTA. Interobserver agreement was discrete (0.2 < κ ≤ 0.4) for all observers. CONCLUSION: Arthrography improved the capabilities of MRI but not of CT for visualization of the canine carpal ligaments. Magnetic resonance arthrography was particularly useful for evaluation of the stabilizers of the antebrachiocarpal joint. CLINICAL SIGNIFICANCE: 3 Tesla MRA and MRI allow excellent visualization of the ligamentous morphology and may be helpful in the diagnostic process of carpal sprains in dogs

Intermembrane distances at the feto-maternal interface in epitheliochorial placentation

Introduction In an epitheliochorial placenta, the apical membranes of trophoblast cells and of uterine epithelial cells are in contact to each other (feto-maternal contact). In addition, there are also folds in which the trophoblast membrane is in contact with itself (feto-fetal contact) and areas where apical uterine epithelial membrane is in contact with itself (materno-maternal contact). Methods We use transmission electron microscopy of placental samples from pigs. (n = 3), cows (n = 2), sheep (n = 2), goat (n = 2) and roe deer (n = 1) to study the intermembrane distance in these three contact types. Results The measured intermembrane distances vary between 8 and 25 nm. One common feature is that the distance at feto-fetal contact sites is about 6–10 nm wider than at materno-maternal sites and feto-maternal sites show intermediate values. Discussion This finding suggests that the membrane distance at feto-maternal contact sites is determined by heterophilic binding of larger fetal to smaller maternal binding molecules. Homophilic binding of smaller maternal or larger fetal molecules lead to the smaller or wider intermembrane distances at materno-maternal or feto-fetal contact sites respectively. The observation that this similar pattern of membrane distances is present in pigs and in ruminants suggest that an evolutionary mechanism is involved in determining the intermembrane distance in epitheliochorial placentas

Relationship between placental surface area and fetal growth rate in artiodactyls and perissodactyls

Gestation periods in mammals are generally in line with scaling laws. There are several exceptions in which species of relatively similar size and degree of neonatal maturation show a significant difference in gestation length. For example the giraffids have a very long gestation period, compared to bovids of similar size. By using published data about the placental surface area at term, we show that in ungulates this surface area is more tightly correlated to the average fetal growth rate than to fetal and placenta weight. These data suggest that, within one type of placenta, gestation length and placental surface area are associated parameters

Centrosome clustering in the development of bovine binucleate trophoblast giant cells

Binucleate trophoblast giant cells (BNC) are the characteristic feature of the ruminant placenta. During their development, BNC pass through 2 acytokinetic mitoses and become binucleate with 2 tetraploid nuclei. In this study, we investigate the number and location of centrosomes in bovine BNC. Centrosomes typically consist of 2 centrioles surrounded by electron-dense pericentriolar material. Duplication of centrosomes is tightly linked to the cell cycle, which ensures that the number of centrosomes remains constant in proliferating diploid cells. Alterations of the cell cycle, which affect the number of chromosome sets, also affect the number of centrosomes. In this study, we use placentomal tissue from pregnant cows (gestational days 80-230) for immunohistochemical staining of γ-tubulin (n = 3) and transmission electron microscopy (n = 3). We show that mature BNC have 4 centrosomes with 8 centrioles, clustered in the angle between the 2 cell nuclei. During the second acytokinetic mitosis, the centrosomes must be clustered to form the poles of a bipolar spindle. In rare cases, centrosome clustering fails and tripolar mitosis leads to the formation of trinucleate "BNC". Generally, centrosome clustering occurs in polyploid tumor cells, which have an increased number of centrioles, but it is absent in proliferating diploid cells. Thus, inhibition of centrosome clustering in tumor cells is a novel promising strategy for cancer treatment. BNC are a cell population in which centrosome clustering occurs as part of the normal life history. Thus, they might be a good model for the study of the molecular mechanisms of centrosome clustering

Intraluminal vesicles of binucleate trophoblast cell granules are a possible source of placental exosomes in ruminants

Introduction: Exosomes are membrane-bound small extracellular vesicles, which play important roles in intercellular communication, including the feto-maternal communication. Placenta-derived exosomes have been identified in maternal blood of a variety of species, including cattle and sheep. Methods: Transmission electron microscopy is used to characterize intraluminal vesicles in binucleate trophoblast cell secretory granules and extracellular vesicles in placentome samples from eight ruminant species of the bovidae and cervidae clades. Results: In all species the secretory granules of binucleate cells contain intraluminal vesicles of 40–70 nm diameter. After fusion of the binucleate trophoblast cells with cells of the uterine epithelium these vesicles are exocytosed together with the granule's secretory proteins. The vesicles are located at the basement membrane of the uterine epithelium and in the connective tissue underneath. Discussion: We suggest that these vesicles function as exosomes. Their function might be either locally in the maternal endometrial stroma or they could have systemic functions after entering the maternal blood. Earlier electron microscopical studies in other ruminants, including species of the most basic ruminant clade (tragulidae), indicate that the intraluminal vesicles are a general feature of ruminant binucleate trophoblast cell granules. Our findings suggest that ruminant BNC are a source of exosomes, which are released into the maternal organism and are thus a newly described type of feto-maternal communication in ruminants

Morphological characterization of basally located uninucleate trophoblast cells as precursors of bovine binucleate trophoblast giant cells

Binucleate trophoblast giant cells (TGCs) are one characteristic feature of the ruminant placenta. In cows, the frequency of TGCs remains constant for most of the duration of pregnancy. As TGCs are depleted by their fusion with uterine epithelial cells, they need to be constantly formed. It is still unclear whether they develop from stem cells within the trophectoderm or whether they can arise from any uninucleate trophoblast cell (UTC). Within the latter, generally accepted theory, a basally located uninucleate cell (BUC) without contact to the feto-maternal interface would represent a transient cell between a UTC and a TGC. So far, no evidence for the existence of such transient cells or for the presence of stem cells has been shown. The aim of the present study is to morphologically characterize the early stages of TGC development. Placentomal tissue of 6 pregnant cows from different gestational stages (gestational days 51-214) was examined for BUCs, UTCs, and TGCs either in serial sections (light and transmission electron microscopy, TEM, n = 3), in single sections (TEM, n = 2), or by serial block face-scanning electron microscopy (n = 1). These investigations revealed the occurrence of BUCs, as well as young TGCs showing contact with the basement membrane (BM), but without apical contact to the feto-maternal interface. The study morphologically defines these 2 cell types as early stages of TGC development and shows that binucleation of TGCs can precede detachment from the BM

Relationship between placental surface area and fetal growth rate in artiodactyls and perissodactyls

Gestation periods in mammals are generally in line with scaling laws. There are several exceptions in which species of relatively similar size and degree of neonatal maturation show a significant difference in gestation length. For example the giraffids have a very long gestation period, compared to bovids of similar size. By using published data about the placental surface area at term, we show that in ungulates this surface area is more tightly correlated to the average fetal growth rate than to fetal and placenta weight. These data suggest that, within one type of placenta, gestation length and placental surface area are associated parameters

Placental contribution to the endocrinology of gestation and parturition

In addition to many other functions, the placenta is a source of a vast number of autocrine, paracrine and endocrine factors. However, the spectrum of placental regulatory factors, their concentrations, gestational profiles and roles may differ considerably even between phylogenetically closely related species. Depending on the species, placental regulatory factors of a broad range of molecule classes have been found including (glyco-)proteins, peptides, steroids and prostaglandins. Local placental regulatory factors are especially important for the dialogue between the fetal and the maternal compartment immediately at the feto-maternal borderline and for the control of growth, differentiation and functions of the placenta itself. Moreover, placental hormones in a proper sense may also have effects in more remote targets within the maternal compartment, serving functions such as pregnancy-specific adaptations of maternal circulation, provision of hemotrophe to the fetus or the development and function of the mammary gland. Functions of placental hormones in the fetus proper are less clear but may be especially important before the establishment of a functional fetal endocrine system and near term within the highly species-specific networks of signals preparing and initiating parturition. This review takes a comparative view on the situation in different domestic animals focusing on ruminants and on placental hormones occurring at significant concentrations in the maternal circulation