Are birds pseudoteeth and denticulations related to touch papilla? An investigation in parrot, goose, and chicken.

We first studied the morphology and the development of goose denticulations, which develop mainly by a ripple process, and the touch papillae of the bill tip organ, which appears through an evagination process at the end of the beak. During their development, we observed the specific expression of PAX9, PITX2, and BMP4, while SHH was expressed mainly in the basal layer of the epithelium in a non-specific manner. Adult goose denticulations are associated with numerous columns. The goose denticulations and columns were filled with numerous Herbst and Grandry corpuscles, as well the touch papillae of the bill tip organ. Histological analysis of adult parrot pseudoteeth revealed that the osseous pseudoteeth were extended by similar columns filled with Herbst and Grandry corpuscles. We also examined adult and embryonic chicken beaks. During ontogeny, we observed a process of rostral evagination with folding associated with discrete ripples in the anterior part of the beak rudiment, in which PAX9, PITX2, and BMP4 are expressed. In the corresponding adult areas, there were numerous sensory corpuscles with rostral columns, which were similar to the features observed in goose. These observations support the hypothesis that pseudoteeth and denticulations constitute sensory organs, and that the touch papillae exhibit some similarities with pseudoteeth.

Effects of HSP90 inhibition on primordial germ cells migration: A study in the gonad of the chick embryo.

INTRODUCTION: Primordial Germ Cells (PGCs) differentiate into spermatozoa or oocytes. They appear early during embryonic development before migrating to the gonadal ridges. Because of their long migration, PGCs have been proposed as a valuable model to study long distance cell migration. Some species also present a vascular phase in the migration of the germline and could therefore be compared to metastatic migration. HSP90 is a heat shock protein involved in the stabilization of several client-proteins, including oncoproteins. HSP90 inhibition has been proved to decrease PGCs migration in mouse and zebrafish. MATERIAL AND METHODS: We investigated the effect of geldanamycin on PGCs migration in a species with a vascular phase, the chicken. Geldanamycin was injected in the egg at 48h of incubation, PGC's were detected in blood using of blood smears, and in the embryo by immunohistochemistry using anti-HSP90 antibody. RESULTS: The effects of the treatment were similar to those observed in mouse and zebrafish. We show the presence of ectopic germs cells in the vasculature and in the dorsal mesentery, and some deformities of the gonads. CONCLUSION: Inhibition of HSP90 decreases the migration of PGCs and proposed the migration of PGCs in the chick embryo as an interesting model to study metastatic invasion.

Is Vasa such a highly specific marker for primordial germ cells? A comparison of VASA and HSP90 proteins expression in young chicken embryos.

INTRODUCTION: Primordial germ cells (PGCs) have been studied since the 19th century with several different methods. The earliest works were based on the morphological criteria of these cells associated or not with a particular staining. Different markers have been proposed in immunohistochemistry among which we can quote the Stage-specific embryonic antigene-1 (SSEA-1), the embryonic mouse antigen-1 (EMA-1) or the heat shock protein 90. Unfortunately, none of them are germline specific. The VASA protein is considered as one of the most reliable marker for PGCs by some authors with its expression being considered to limited to the germ cells. However, other studies have reported its expression in somatic cells. Here, we described the expression of the heat shock protein, HSP90, and the VASA protein in the early chick embryo. MATERIAL AND METHODS: Embryos from stages Hamburger-Hamilton (HH) 19, 21 and 28 were collected. Embryos were dissected and fixed in Serra's medium. Sections were placed on slides for PAS staining and for double immunohistochemistry with HSP90 and VASA. RESULTS: VASA and HSP90 expression have been observed in germ cells but as well in other cell lineages with a spatio-temporal gradient in respect to the characteristics of development of each organ. The conclusion is that VASA expression is not limited to the germ line in chick embryo.

A reviewed chronology of primordial germ cells migration in the chick embryo.

INTRODUCTION: Primordial Germ Cells (PGCs) are present in all sexually reproducing animals. They differentiate into spermatozoa or oocytes and are therefore responsible for the transmission of genetic and epigenetic information across generations. In birds, PGCs are first observed in the center of the blastodisc at stage Eyal-Giladi X. With the formation of the primitive streak, germ cells are translocated anteriorly to the germinal crescent. At stage Hamburger- Hamilton 10-12, they enter the vasculature before migrating through the dorsal mesentery towards the genital ridges. MATERIAL AND METHODS: Embryos from stages Hamburger-Hamilton (HH) 16 to 22 were collected. Blood samples were taken from the dorsal aorta and from the heart in order to perform blood smears and PAS staining. Embryos were dissected and fixed in Serra's medium. Sections were placed on slides for PAS staining. A sample of each embryo was collected for DNA extraction and PCR in order to determine the sex of the embryos. RESULTS: PGCs were observed in blood circulation until stage HH 20 on blood smears and until stage HH 19 on histological sections. The first PGCs arrived in the genital ridges were observed from stage HH 17. A few germ cells were still migrating in the dorsal mesentery at stage HH 22. The aim of this study was to review the chronology of the migration of PGCs in chick embryos.

External and computed tomography analysis of a strophocephalic lamb.

CONTEXT: The Museum of Anatomy and Embryology Louis Deroubaix attached to the Laboratory of Anatomy, Biomecanics and Organogenesis, ULB, Brussels, possesses in its liquid collections a cephalic extremity of a lamb suffering from strophocephaly. The origins have not been determined. The trunk and the limbs are resected. MATERIAL AND METHODS: The piece has been studied and photographed. A volumic computed tomography acquisition has been performed with a Siemens Volume Zoom. For pedagogic and museological purposes, surface reconstructions and 3D printing have been obtained. RESULTS: An otocephaly is observed. Both ears are located in place of the oral cavity. The mandible is welded to the braincase. The eyeballs are close together (synophtalmia) which confirms the presence of a cyclotocephaly. They are surmounted by a rudimentary snout rather than a proboscis. The presence of this muzzle allows the anomaly to be classified as a strophocephaly, a malformation already described in sheeps. CT slices of the brain show a semi-lobar holoprosencephaly with incomplete division of the cerebral hemispheres and ventricules. DISCUSSION AND CONCLUSION: The CT examination allows the facial anomalies to be allocated to a holoprosencephaly. The singularity of this case, compared to the human cyclotocephalies, is the presence of a differentiated muzzle rather than a simple proboscis. The holoprosencephaly is uncomplete. Such anomalies have been associated with an entire absence of cerebral differentiation but with a complete absence of the muzzle. The tridimensional printing represents an interesting educational tool easily transportable in contrast to the original specimen.

[Contributions of embryology and comparative anatomy for teaching of cranial nerves]. / Apports de l'embryologie et de l'anatomie comparée à l'enseignement des nerfs crâniens.

Some authors propose a global approach, including imaging, to describe cranial nerves from a clinical point of view. If we can agree to a certain extent with this proposal, we consider that the use of a medical point of view can neglect histological and embryological features which contribute to a better understanding of nerve function. For example, it is false to consider totally "nerves" I and II as "sensory cranial nerves". They are not true nerves, but derive manly from direct expansions of the central nervous system. They differ fundamentally from cranial nerves, except for the fibers present at the roof of olfactory fossa. The cranial nerve nuclei arise from "Herrick's columns", which originate from alar and basal plates. These columns, which correspond to "functional components" of these nerves are extremely important for the understanding of cranial nerve functions (as "viscero-efferent", "somato-afferent", etc.), which also helps students to memorize these nerves. The usual classification of cranial nerves neglect the terminal nerve, present in adult humans and associated to the vomero-nasal organ. It includes in the cranial nerves a trunk nerve secondary associated with the head, the hypoglossal nerve, and creates a supernumerary cranial nerve (the accessory nerve) by fusion of vagous fibers with cervical roots. Close consideration of the development and the comparative anatomy can lead to a new synthesis useful to understand the cranial nerves from a general biological point of view and can facilitate their study.

Expression of Wnt and beta-catenin in mouse tooth germs and chick facial primordia: a comparison / Expresión de Wnt y beta-catenina en gérmenes de dientes de ratón y primordios faciales de polluelos: una comparación

In order to compare Wnt/ beta-catenin expression in mouse and chick facial primordia during development, we performed an immunohistochemical analysis of both protein expressions in E12 to E17 mouse embryos and in E3 and E10 chick embryos. During odontogenesis, from bud to bell stage, both proteins exhibit similar fixation patterns, with epithelial and mesenchymal immunoreactivity, consistant with literature data. Double labelling demonstrates that the same cells express both antigens, even in undifferentiated mesenchyme. The enamel knot, and the ameloblastic and odontoblastic layers are stained at the same manner. In the chick, Wnt and beta-catenin are diffusely present on craniofacial mesenchyme. In both species, premuscular blastemata express Wnt and b-catenin, but Wnt is specifically expressed on the perichondrium and ossification centers, suggesting a role independent from beta-catenin pathway.

Geldanamycin administration reduces the amount of primordial germ cells in the mouse embryo.

INTRODUCTION: Heat shock proteins (HSPs) are expressed or overexpressed in response to exposure to stress. They act as molecular chaperones, ensuring the correct folding of numerous client proteins. HSP90 is one of the most conserved HSPs. Its role extends beyond stress tolerance. HSP90 also contributes to development, differenciation, apoptosis and oncogenesis. Numerous tumors are associated with an overexpression of HSP90 and this expression can be used to evaluate its metastatic capacity. Primordial germ cells (PGCs) exhibit HSP90 expression under normal conditions. PGCs arise early in development and migrate by a combination of passive and active movements towards the gonads. The aim of this work was to study the impact of an inhibition of HSP90 on the migration of the PGCs. Geldanamycin, a well established HSP90 inhibitor with potent antitumor properties was used to achieve this inhibition. MATERIEL AND METHODS: 5mg of Geldanamycin were administered to E8 pregnant mice. E17 embryos were removed and fixed for staining and Immunohistochemistry with anti-HSP90 and anti-VASA antibodies. RESULTS: Geldanamycin-treated mouse embryos exhibited less VASA-immunopositive cells compared to the non-treated ones. These results suggest that geldanamycin administration at the time of PGCs migration reduces the number of PGCs in the gonads. HSP90 and VASA stainings were identical. We therefore expressed the idea that HSP90 could be used as a reliable marker for PGCs.

[The dorsoventral inversion: An attempt of synthesis]. / L'inversion dorsoventrale : un essai de synthèse.

The invertebrates, with known exception of echinoderms, are hyponeurian and protostomian. By contrast, echinoderms, chordates and vertebrate are epineurian and deuterostomian. Convinced of the uniqueness origin of all species, Etienne Geoffroy Saint Hilaire (1772-1844), had postulated a complete inversion of body plan to explain this difference. He had to face up to the hostility of the fixist Georges Cuvier (1763-1832). Much later, famous embryologists such as Maurice Caullery still believed that this idea was erroneous. However, the progress of comparative embryology and of developmental biology gradually contributed to validate this idea. Based upon ancient and recent literature review, and re-examination of arthropods (Acanthoscelides obtectus Say), amphibians (Discoglossus), echinoderms (sea urchin) and mammals (rodents) embryos, we can raise up difference and common points of the gastrulation processes. The dorsoventral gradient is ensured by the couple Dpp (dorsal in arthropods)/SOG/chordin (ventral in arthropods), which appears as "inverted" in epineurians. Blastopore invagination occurs in arthopods in the ventral region, opposite to the vitellus mass (initially diffuse, then predominant on the dorsal side), whereas it occurs at the vegetative side in other hyponeurians and epineurians. It has been accepted that the BMP inhibits oral development in protostomian, whereas it activates it in Chordates. Therefore we assume, as Lowe does, that the oral cavity of deuterostomians might constitute a new structure related to the branchial system. The comparative analysis of the blastopore' orientation, the sperm penetration site, and the polarity axes of various embryos species allows to follow the different modifications and to hypothesize their relative chronology during evolution.

[The dental collection Hyacinthe Brabant: A pedagogic and scientific tool]. / La collection dentaire Hyacinthe Brabant: un outil pédagogique et scientifique majeur.

Among the numerous specimens preciously preserved in the Anatomical and Embryological Museum of ULB, there lies also a dental collection assembled by Professor Hyacinthe Brabant. This collection, previously unlabelled, shows several dental anomalies and pathologies as well as tumours. The objective of our study was to conduct an inventory of this collection and to set up an electronic iconographic tool through the Iconography website of ULB. A descriptive study was carried out and it was based on the analysis of 125 models and 90 extracted human teeth. The inspection of the models showed some non-odontological tumours as well as multiple dental anomalies. The extracted teeth showed generalised, coronal or radicular anomalies. The conducted inventory allowed us to classify and label the specimens and therefore to showcase this dental collection which is unique owing to its rich content and didactic display. Finally, the iconographic site will be a useful tool to raise awareness about several dental pathologies and anomalies among students and young practionners.

[Morphologic and tomodensitometric comparative analysis of two cyclotocephalic newborns]. / Analyse morphologique et tomodensitométrique comparée de deux nouveau-nés affectés d'une cyclotocéphalie.

Two specimens of cyclotocephalic newborns, coming from museum collections, have been the subject of a comparative morphologic analysis. This one comprised an external examination and a CT scan exploration. If the craniofacial features were similar, one had a quasi-normal brain, while the second specimen displayed alobar holoprosencephaly. This observation relatively surprising is discussed in the light of current knowledge on the developmental genetics of this family of malformations.

[A neonate with aprosopia, monomelia and celosomy]. / Un cas de nouveau-né affecté d'une aprosopie, d'une monomélie et d'une célosomie.

The specimen of which it is a matter here takes part of the heritage of the Museum of Anatomy and Embryology of the Faculty of Medicine of the Université Libre de Bruxelles. Its medical history is completely unknown, because it takes part of an ancient collection of pathological anatomy saved from destruction and recovered by the laboratory of Anatomy and Embryology. The specimen is strongly folded up on itself ("in extension"), its length so arranged is about 25 cm; unfolded, it develops to 45 cm. Cranial perimeter is of 31 cm. Unfortunately, the brain was removed during the initial analysis, and only the examination of the braincase allows to draw some conclusions on the probable state of the encephalon. The face is rudimentary, without any orbit, and the oral cavity is limited to a vertical slit, revealing small strongly tipped up maxillary bones. A double proboscis is present. The trunk is characterised by a rather broad celosomy, with exhibition of the intestines, the liver and the pancreas. Anal atresia is observed, and the external sexual organs are hypoplastic and ambiguous. The whole left lower limb is absent, including the left half of the pelvis, corresponding to a left unilateral complete ectromelia. The neck is in hyperextension, so that the occipital region seems extremely welded in the cervical spine. However, CT examination does not confirm the presence of such fusion, but on the other hand, reveals a severe axial diversion of the spine with hyperextension. Extremely rare in humans, the aprosopia is more readily present in some animals (sheep). Its association with a monomelia and a celosomy seems not yet described.

[Phylogenetic interpretation of aortic arches and outflow tract partitioning]. / Interprétation phylogénétique des anomalies des arcs aortiques et de la septation bulbaire.

The great thoracic and cervical vessels come from the complex metameric system, formed of the dorsal and ventral aortas and aortic arches. From the branchial respiratory system of fish to the mammalian configuration, numerous changes have occurred in parallel with the evolution of cardiac septation, which imposes constraints on the vascular system. In addition, an important cell population is involved with the partioning of the arterial bulb: the cardiac neural crests originating from the head. The examination of abnormalities of arterial bulb septation, considered as neurocristopathies, within certain limitations, demonstrates an association of abnormal features with ancestral configurations. Some aortic arch malformations can be considered as a continuation of ancient embryonic transient vessels, which should have disappeared. Exemplative malformations, such as the "tetralogy of Fallot", are similar to reptilian configuration of great vessels, associated with incomplete partition of both ventricles with an absence of sub-endocardial cushions. However, the presence in reptiles of two systemic arches and a pulmonary artery (in fact, 3 vessels arising from the arterial bulb) has no malformative equivalent in mammals. Arteria lusoria, double aortic arch, dextroaortia, corresponds to the persistence of aortic arches intended to disappear, and could be considered as a haemodynamic response to the early and untimely regression of another arch.

[Immunohistochemical study of Dlx1 and Msx1 expression during cephalic development of Dumbo and Wistar rats. Correlation with morphological data]. / Étude immuno-histochimique de l'expression des protéines Dlx1 et Msx1 durant la céphalogenèse des rats Wistar et Dumbo Corrélation avec les données morphologiques.

The Dumbo rat is characterized by a short snout, low ears and relative hypoplasia of maxillar and zygomatic bones. It corresponds to an autosomal recessive genotype. Previous study demonstrated a global deficit of Dlx1 and Msx1 genes expression in comparison to Wistar embryos as considered as control animals. We performed a histological study of cephalic development of Dumbo rats compared to Wistar embryos and an immunohistochemical analysis of Dlx1 and Msx1 protein expression during cephalogenesis. Our data indicate that the pattern of expression of both genes is similar in both strains, but that quantitative differences in gene expression can be the result of delayed organogenesis in Dumbo rat in comparison to Wistar. Some data about gene expressions are discussed at the light of the postulated function of Dlx1 and Msx1 in cephalic development.

The Dumbo rat mutant: a cytogenetic, morphologic and sagittal morphometric analysis.

OBJECTIVE: To study the possibility of use Dumbo rat as, experimental model for understanding abnormal craniofacial development. DESIGN: We investigated craniofacial morphogenesis in the Dumbo rat by morphologic and morphometric technics. We also performed a cytogenetic study of this rat. Wistar strain was considered as control. For morphologic and morphometric studies, we used Dumbo and Wistar embryos at E15 to 21. We stained these embryos in toto with alcian blue and alizarin red. The skeletons of the embryos were examined and drawn under a Lucida camera, and the following sagittal measurements were taken: zygomatic length and thickness, length of the mandible and its anterior and posterior thicknesses, length of the maxillary, and petrous bone height. Statistical analyses were realized using Mann Whitney test in SPSS. For cytogenetic study, chromosome spreads were prepared from lymphocyte cultures obtained from the blood of adult rats of both strains. RESULTS: The Dumbo embryos exhibited hypoplasia of the zygomatic, maxillar and mandibular bones, and micrognathia, evoking some human dysmorphogenesis . Moreover, the position of the preliminary ear was abnormally low. The differences in the measurements of the craniofacial structures between the two groups of rats are significant. However, the cytogenetic study did not reveal any differences between the two strains. CONCLUSION: Our data indicate that the considerable morphometric differences between the craniofacial structures of Dumbo and Wistar rats might be due to genetic mutations that are undetectable by chromosome mapping. Further histologic and genetic analyses might contribute to elucidate the early determinism of the Dumbo phenotype.

[Geldanamycin administration reduces the number of HSP86-positive germ cells in the mouse embryo: preliminary results]. / L'administration de geldanamycine réduit le nombre de gonocytes exprimant l'HSP86 chez l'embryon de souris: premiers résultats.

5 mg of Geldanamycin, an inhibitor of stress protein HSP86 which express on mammalian germ cells, were administered to E8 pregnant mice. E17 embryos were removed, and a quantitative analysis of HSP90-immunoreactive cells in the gonad was performed, in comparison to control embryos. First, we observed that the number of germ cells is lower in male than in female embryos, as well in control and experimental embryos. External features of experimental and control embryos did not display any difference. Embryos exposed to geldanamycin exhibit a significant decrease of immunoreactive germ cells. In two embryos, we observed a group of ectopic immunoreactive cells in the pelvic area. We conclude that geldanamycin inhibits germ cells migration, and suggest that this inhibition can lead to ectopic germ cell populations, similar to teratomas.

[Louis Deroubaix (1813-1897), anatomist, surgeon and rector of the "Université Libre de Bruxelles"]. / Louis Deroubaix (1813-1897), anatomiste, chirurgien et recteur de l'Université Libre de Bruxelles.

Louis Deroubaix was professor of human anatomy in the "Université Libre de Bruxelles" between 1841 and 1894. He founded the museum of human anatomy and created outstanding dissections, still presently in use. He was also surgeon, and developed new technics and original instrumentation. He was elected rector of the University, and consacrated himself to social medicine, even though he received a lot of academic hounours.