Hox-A2 protein expression in avian jaws cartilages and muscle primordia development

OBJECTIVE

To elucidate the branchial origin of the articular and the square (homology of the malleus and the incus of mammals), we used immunohistochemistry to analyse the expression of the Hox-A2 protein during cephalogenesis in chickens.

MATERIALS AND METHODS

Immunohistochemistry on paraffin sections of embryos from stage HH16 to HH40.

RESULTS

In addition to the columella (equivalent to the mammalian stapes), the joint between the articular and the quadrate bones, and the retro-articular process of the articular (homologous to the short process of the malleus) express Hox-A2, suggesting an intervention of the 2nd arch in their formation. However, we fortuitously observed very intense expression within the early muscle plate of the second arch, which then generalized to all cephalic muscles, and extended to the trunk's myotomes. In the cartilage, the presence of the protein disappeared at stage 35.

DISCUSSION AND CONCLUSION

The present results, while confirming the contribution of the second arch to the development of avian equivalents of the mammalian ear ossicles, strongly suggest that the Hox-A2 gene plays a role in muscle development, which remains to be elucidated by more sophisticated techniques.

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.

Evolution and development of parrot pseudoteeth

Parrot embryos carry peculiar appendages at their developing beak that have been described as pseudoteeth. To better characterize the pattern of development responsible for the emergence of these dental appendages, we examined parrot embryos combining conventional histology and microtomography approaches. Using immunohistochemistry, we observed the epithelial and mesenchymal expression of several proteins involved in tooth development in mammals. Parrot pseudoteeth arose by epithelial and mesenchymal evagination, and their early development was similar to the ontogeny of scales and feathers. There was no enamel tissue, and the evaginations were surrounded by the rhamphotheca. In adults, the rhamphotheca covers entirely the appendages, now represented by bone evaginations, which were more numerous in the lower than in the upper beak, being similar to the osseous teeth of the fossil Pelagornithidae. These embryonic pseudoteeth resembled reptile's first-generation teeth and dental appendages of chicken talpid² mutants. Proteins involved in mammalian odontogenesis, such as SHH, BMP4, PITX2, and PAX9, were found to be generally expressed in beak epithelium and mesenchyme during parrot pseudoteeth development, with clusters of high-level expression in the pseudoteeth rudiments. This suggests that a similar, highly conserved gene expression program gives rise to the appearance of odontode derivatives in numerous species, despite their divergent developmental paths. These results provide new insights into the development and evolution of odontode-derived structures in vertebrates.

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.

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 19^th 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.

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.

Hox-A2 protein expression in mouse embryo middle ear ossicles

The origin of the mammalian middle ear ossicles from mandibular and hyoid pharyngeal arches remains controversial and discussed. Two adverse theories are proposed. The first claims that malleus and incus derive from the Meckel's cartilage of the mandibular arch, and stapes from Reichert's cartilage of the hyoid arch. The second postulates that handle of malleus and long process of the incus are derived from the second arch as well as the stapes. Contradictory analyses support alternatively each theory without any experimental evidence. In order to bring new data, we analyzed by immunohistochemistry the expression of Hox-A2 protein in ossicular anlagen in E11 to 13 mouse embryos. HOXA2 gene is known to be expressed in second arch cells and to be absent from mandibular arch derivatives. Surprisingly, Hox-A2 protein was present in all ossicular primordia, as well in Reichert's cartilage. Meckel's cartilage was free of staining. Unlabeled cells were also present in ossicular blastemata. These results suggest that ossicular condensations could arise from mixed cell populations originated in both mandibular and hyoid pharyngeal arches. However, we cannot exclude that diffuse Hox-A2 immunoreactivity could correspond to a secondary expression in craniofacial mesenchyme independently from the branchial origin of cells.

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.

[Contributions of embryology and comparative anatomy for teaching of cranial nerves]

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.

[The dorsoventral inversion: An attempt of synthesis]

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.

[Morphologic and tomodensitometric comparative analysis of two cyclotocephalic newborns]

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.

[The dental collection Hyacinthe Brabant: A pedagogic and scientific tool]

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.

[A neonate with aprosopia, monomelia and celosomy]

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.

[Immunohistochemical study of Dlx1 and Msx1 expression during cephalic development of Dumbo and Wistar rats. Correlation with morphological data]

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.

[Louis Deroubaix (1813-1897), anatomist, surgeon and rector of the "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.

Expression of Msx1 and Dlx1 during Dumbo rat head development: Correlation with morphological features

The Dumbo rat possesses some characteristics that evoke several human syndromes, such as Treacher-Collins: shortness of the maxillary, zygomatic and mandibular bones, and low position of the ears. Knowing that many homeobox genes are candidates in craniofacial development, we investigated the involvement of the Msx1 and Dlx1 genes in the Dumbo phenotype with the aim of understanding their possible role in abnormal craniofacial morphogenesis and examining the possibility of using Dumbo rat as an experimental model for understanding abnormal craniofacial development. We studied the expression of these genes during craniofacial morphogenesis by RT-PCR method. We used Dumbo embryos at E12 and E14 and included the Wistar strain as a control. Semi-quantitative PCR analysis demonstrated that Msx1 and Dlx1 are expressed differently between Dumbo and Wistar rats, indicating that their low expression may underly the Dumbo phenotype.

[Geldanamycin administration reduces the number of HSP86-positive germ cells in the mouse embryo: preliminary results]

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.

[Early treatment with rapid palatal expander and 3D Quad Action mandibular appliance: evaluation of a comprehensive approach in 22 patients]

The aim of this retrospective study in mixed dentition was to quantify dental arches and radiographic changes with a rapid maxillary expander followed by a transpalatal bar with arms and a 3D Quad action mandibular appliance, at the end of the treatment (T1) and six months afterwards (T2).

MATERIAL AND METHODS

Thirty Class II patients in mixed dentition with tooth size-arch length discrepancies were studied (22 treated). We obtained measurements from dental casts before treatment, at T1 and T2 and radiographic changes at T1. The breathing was appraised.

RESULTS

We found a significant (p < 0.05) increase of maxillary (+7.41 mm) and mandibular (+2.96 mm) dental arch perimeter, of intercanine gingival width (maxillary +3.25 mm, mandibular +1.57 mm) and of intermolar gingival width (maxillary +5.32 mm, mandibular +2.32 mm). There is a statistically significant increase of SNB angle. All posterior cross bites were corrected. We obtained a better position for the maxillary canine on radiography. All patients had nasal breathing at T1. Non treated subjects showed no improvement. In conclusion, this interceptive treatment corrected posterior cross bites, improved breathing and suggests an amelioration of tooth size-arch length discrepancy.

[Learning strategies and anatomy teaching in the Pôle Universitaire Européen Bruxelles-Wallonie]

In order to compare the learning strategies associated to human anatomy courses in student of first, second and third year in medicine, first year in medical biology technologists and first year in nursing, we distributed a questionnaire to the students. The results revealed some similarities, but also several differences, in relationship with local conditions, the content of the courses, and specificities of different student groups, especially in their study choice. Paradoxically, the integration of medical imaging in medical students seems to be difficult, and the medical students are reticent to use another body to ingrate anatomy, although surface anatomy constitutes a part of the anatomical program. This restriction is absent in nursing. These results constitute important data in the field of cognitive research, but also should be useful to improve our pedagogic strategy in specific populations.

HSP110, caspase-3 and -9 expression in physiological apoptosis and apoptosis induced by in vivo embryonic exposition to all-trans retinoic acid or irradiation during early mouse eye development

Apoptosis is an essential physiological process in embryonic development. In the developing eye of vertebrates, three periods of developmental apoptosis can be distinguished: early, intermediate and later. Within the apoptosis pathway, caspases play a crucial role. It has also been shown that HSP110 may have a potential role in apoptosis. The aim of this research was to study the expression of HSP110, caspase-3 and -9 in physiological, retinoic- or irradiation-induced apoptosis during early eye development. Seven pregnant C57Bl/6J mice received 80 mg kg(-1) of all-trans retinoic acid mixed with sesame oil. Seven pregnant NMRI mice received 2 Gy irradiation at the same gestational day. Control mice of both strains (seven mice of each) were not submitted to any treatment. Embryos were harvested at 3, 6, 12 and 24 h after exposition, fixed, dehydrated and embedded. Coronal sections (5 microm) were made. Slide staining occurred alternatively using anti-caspase-3, anti-caspase-9 and anti-HSP110 immunohistochemistry. HSP110 and caspase-3 expression presented similar topographic and chronological patterns, whereas expression of HSP110 was more precocious in retinoic acid-treated embryos. After retinoic exposure, caspase-3- and HSP110-positive cells were increased in the region of the optic vesicle. By contrast, after irradiation, caspase-3- and HSP110-positive cells were noticeably increased in the optic vesicle, peri-optical mesoderm but less in lens placode. HSP110 was expressed before caspase-3. By contrast, caspase-9 was expressed by a very small number of cells in the optic vesicle either under physiological or under teratogenic conditions. Thus, it seems that activation of caspase-9 is dispensable in early eye developmental apoptosis.

Correlation of Hsp110 expression with caspase-3 and -9 during apoptosis induced by in vivo embryonic exposition to retinoic acid or irradiation in early mouse craniofacial development

OBJECTIVE

To analyze the expression and role of three proteins (HSP110, caspase-3 and caspase-9) during craniofacial development.

DESIGN

Seven pregnant C57Bl/6J mice received, by force-feeding at gestation day 9 (E9), 80 mg/kg of all-trans retinoic acid mixed to sesame oil. Seven pregnant NMRI mice received two grays irradiation at the same gestation day. Control mice of both strains (seven mice for each strain) were not submitted to any treatment. Embryos were obtained at various stages after exposition (3, 6, 12 and 24 h), fixed, dehydrated and embedded. Coronal sections (5 microm) were made. Slide staining occurred alternatively using anti-Hsp110, anti-caspase-3 and anti-caspase-9 immunohistochemistry.

RESULTS

Expression of HSP110, caspase-3 and caspase-9 was found in cells of well-known locations of programmed cell death. After retinoic acid exposure, expressions were increased especially in neural crest cells of mandibular and hyoid arches. Quantification of positive cells shows that caspase-9 and Hsp110 were expressed before caspase-3. After irradiation, the expression of the three proteins quickly increased with a maximum 3 h after irradiation. For all three models of apoptosis (physiological, retinoic-induced and irradiation-induced) HSP110 positive cells were more numerous than caspase-3 positive cells. Caspase-3 positive cells were more numerous than caspase-9 positive cells especially in mesectodermal irradiation-induced apoptotic cells.

CONCLUSION

The findings show a potential function of HSP110 in apoptosis during embryo development. Caspase-3-expressing cells are more numerous than cells expressing caspase-9, especially irradiation-induced apoptotic neural crest cells. This suggests that other caspases, still to be identified, may activate caspase-3 in this model.

A case with undescended testis, left pelvic kidney and gut malrotation

We describe here an autopsy case presenting bilateral cryptorchidism, left pelvic kidney and intestinal malrotation, evoking a "reverse rotation" with hypoplasia of the cecum. Furthermore, the colon showed alternate bands of stenosis and dilatation. This association has not yet been described, and is discussed in the light of the embryological events of kidney, gut and gonad development. Two hypotheses can explain gut stenoses (vascular consequences of the malrotation and type Hirschprung aganglionic segments).

[Expression of caspase 3 and p53 during physiological apoptosis and apoptosis induced by three teratologic agents during early craniofacial development of the mouse embryo]

The neural crest-derived mesectoderm gives rise to physiologic apoptosis areas in early vertebrate embryos. Certain teratologic agents increase this phenomenon. The purpose of this work was to detect caspase 3 (which is associated with the apoptosis cascade) and p53 in cell death areas, both during physiological apoptosis and during apoptosis induced by three agents (retinoic acid, methyl-triazene, irradiation). Antibody revelation was performed using the aBC peroxidase kit. Quantifications were also performed on histological sections. We observed caspase 3 uptake on some apoptotic and preapoptotic cells in control embryos, and in the embryos exposed to the three teratogens. Immunoreactivity generally preceded the development of cytological features of apoptosis. However, p53 was expressed only in the embryos exposed to ionizing radiation and methyl-triazene (an alkylating agent), but not significantly in embryos exposed to retinoic acid. The present results throw some light on apoptosis mechanisms in several teratologic conditions.

[Histologic and ultrastructural features of cell death both physiological and induced by two different teratogens in branchial arches of mouse embryo]

AIM OF THE STUDY

To observe and compare cell death process both physiological and associated with the administration of two different teratogens (irradiation and retinoic acid) inside cephalic mesectoderm.

MATERIAL AND METHODS

Irradiated mice: 2 Gy were administered to E 9 embryos. Retinoic acid: 60 mg/kg were gave to E 8 or E 9 embryos. E 9 - 9.5 and E 10 embryos were removed. E 9 - E 9.5 and E 10 control specimens were collected. We used semi-thin sections and ultra-thin sections observed with transmission electron microscope.

RESULTS

The major process is apoptosis, which is increased in experimental embryos compared to control specimens. However, autophagy was observed in retinoic acid-treated embryos, while necrosis can rarely occurs after irradiation.

CONCLUSION

If the common process seems to be apoptosis, both teratological models differs owing to their respective secondary features. These differences should be explained by the specific pathogenesis of both teratological agents: ligand-receptor reaction and Hox system disruption in retinoic acid administration, direct aggression against DNA and diffuse cell death process following irradiation. Furthermore, congenital malformations induced by these teratogens are quite different. This can be partially explained by a specific blow of different cellular subpopulations.

Ectopic stapes: a case report with embryologic correlations

A case report of unilateral congenital stapes misplacement revealed by computed tomography is presented. In addition to this malformation, the malleus was synostosed to the middle ear roof. This kind of stapes ectopia has not been described previously. We have analyzed the malformative pattern in the light of normal and teratologic development of the stapes. In a teratologic model in which retinoic acid is administered to pregnant mice, we have observed an ectopic stapes primordium independent of the otic capsule. We discuss the possible pathogenesis of this abnormality in terms of the genetic events of middle ear development, which can be perturbed by retinoic acid administration.

Differential expression of S100 calcium-binding proteins in epidermoid cysts, branchial cysts, craniopharyngiomas and cholesteatomas

AIMS

To investigate whether epidermoid cysts, branchial cysts, craniopharyngiomas and cholesteatomas express S100 proteins differentially by immunohistochemical assaying the presence of S100A1, S100A2, S100A3, S100A4, S100A5, S100A6 and S100B.

METHODS AND RESULTS

Immunopositivity/negativity was recorded for each S100 protein in a series of 52 cases consisting of 12 epidermoid cysts, 12 branchial cysts, 15 adamantinomatous craniopharyngiomas and 13 acquired cholesteatomas. Except in the case of the craniopharyngiomas, immunoreactivity was assessed independently in the basal membrane and the basal, the internal and the keratin layers. Our data show that in contrast to S100B, which was rarely expressed, S100A1, S100A2, S100A4 and S100A5 were often present in these four types of epithelial lesions. S100A3 and S100A6 and, to a lesser extent, S100A5 were the most differentially expressed proteins across the different histopathological groups analysed. These three proteins are expressed more often in craniopharyngiomas and cholesteatomas, the two more aggressive types of lesions.

CONCLUSIONS

This is the first study to report data on the expression of seven S100 proteins in different histopathological groups of epithelial head and neck lesions, whose precise embryological origins are still a matter of debate. S100 proteins could possibly be used as markers to target this embryonic origin, since our results show that S100A3 and S100A6 (and, to a lesser extent, S100A5) are expressed differentially across these different groups of epithelial lesions.

[Heat shock proteins, embryogenesis and evolution]

We present results about immunohistochemical identification of several heat shock proteins (HSP'S) during mouse normal and teratological embryogenesis. Apoptotic cells express very specifically and precociously HSP 110. This fact permits to identify apoptotic cells before apparition of morphologic features of apoptosis, but also to quantify the process of cell death in some teratological models, particularly administration of retinoic acid. HSP 86 is expressed in some cell populations, and particularly permanent in germ cells. Our observations brought us to discuss the potential protective role of HSP on germ cells, and the consequence of their inactivation in the macroevolution process, as well as the role of apoptosis in teratology.

Computed tomography of a cyclotocephalic neonate

Cyclotocephaly is a very rare malformative lethal condition which associates otocephaly (extreme hypoplasia of the mandibular arch with agnathia) and cyclopy with proboscis. The head of a cyclotocephalic neonate from our Museum of Anatomy and Embryology was examined using computed tomography (CT). Cutaneous and osseous three-dimensional reformations were performed. Severe bony malformations were observed. A single orbital cavity was surrounded by a cartilaginous proboscis and a median fusion of maxillae, temporal and zygomatic bones. The single orbital cavity contained both paramedial eyeballs (synophthalmia). The external auditory meati and the ear pinnae were also parasagittal. No oral cavity and mandible were observed. Despite the poor conservation state of the brain, lobar holoprosencephaly was suspected. The mesencephalon and pituitary gland were absent. This exercise could lead to optimizing ultrasonographic prenatal diagnosis.

Heat shock protein HSP86 expression during mouse embryo development, especially in the germ-line

In addition to appearing in response to biological stresses, heat shock proteins are expressed as 'chaperones' by some cells living in physiological conditions. Among these proteins, the HSP90 family seems to function under normal growth conditions in the pathways of numerous signal transducers, cell-cycle and developmental regulators. The aim of this study was to investigate the immunohistochemical expression and the distribution of the two mammalian cytosolic isoforms of HSP90 (HSP84 and HSP86) during mouse development between E6 and E16. Our immunohistochemical investigations revealed a diffuse and ubiquitous expression of HSP84 distributed throughout the embryo in all stages. On the other hand, HSP86 was specifically noticed in diverse somatic cells such as hepatoblasts and epithelia that could traduce cellular differentiation phenomenon. More interestingly, a strong cytoplasm expression of HSP86 could be demonstrated in primordial germ cells from their appearance on the yolk sac membrane until reaching the genital crest. These results suggested a protective mechanism against the phenotypic expression of mutations induced by environmental changes in vertebrates as has been demonstrated in Drosophila.

Correlation of HSP110 expression with all-trans retinoic acid-induced apoptosis

In a previous study, we observed the strong expression of a stress protein of the HSP100/Clp family (HSP110) in apoptotic mesectodermal cells during early mouse facial development. In the present study, we describe the strong expression of the same HSP110 in mesectodermal cells undergoing apoptosis after all-trans retinoic acid (RA) administration. We used a teratological model known to increase cell deaths mainly in the first and second branchial arches during mammalian cephalogenesis: the treatment of E9 mouse embryos with all-trans RA, which results in craniofacial malformations comparable to those that characterize mandibulofacial dysostosis in man. Pregnant NMRI mice were treated with 60 mg/kg body weight of all-trans RA, given orally on day 9 of gestation; embryos were taken 4, 12 or 24 hr after RA administration. The apoptotic pattern of RA-induced cell deaths was confirmed using the dUTP biotin nick-end labeling (TUNEL) method and transmission electron microscopy (TEM). HSP110 expression was detected using an immunohistochemical approach. The increase in the number of TUNEL-positive cells and HSP110-positive cells after all-trans RA administration was quantified in the first branchial arch using a computerized method. Twelve hours after RA administration, the increase in the number of HSP110-positive cells is greater than the increase in the number of TUNEL-positive cells. Twenty-four hours after RA administration, only TUNEL-positive cells remain strong in number. We suggest that HSP110 expression could represent a biochemical event of apoptotic cell death induced by RA, associated with early stages of the apoptotic process. In order to find out if HSP110 expression resulted from neosynthesis, we performed in situ hybridization, which demonstrated that the expression of HSP110 occurred at the level of mRNA.

Chaperones in the parotid gland: localization of heat shock proteins in human adult salivary glands

Heat shock proteins (HSPs) are expressed or increased in response to various biological stresses. Moreover, these 'stress proteins' seem to be expressed by some cells living in physiological conditions. From then on, they could play an important physiological role in normal cell functioning. The best-known physiological role of these HSP proteins is to act as 'molecular chaperones'. In this context, we have investigated the immunohistochemical expression of HSP27, HSP70, HSP90 and HSP110 in 10 human adult salivary glands. To highlight the presence of RNAm encoding HSP70, an in situ hybridization was performed. In our material, HSP27 was strongly expressed in the cytoplasm of striated duct cells and in some myoepithelial cells. The same localization was less stained for HSP70 and HSP90. The immunocytochemical reaction was weak or negative for HSP110 in striated ducts. HSPs were not expressed in acinic cells. In situ hybridization gave a positive signal in striated ducts with a probe encoding HSP70. Epithelial cells of the striated ducts and myoepithelial cells expressed HSP27, HSP70 and HSP90. These HSPs probably act in part as molecular chaperones for protein synthesis, transport and for several interactions between HSPs and different proteins.

[Expression of heat shock proteins in salivary gland tumors. Immunohistochemical study of HSP27, HSP70, HSP90, and HSP110: apropos of 50 cases]

Heat shock proteins (HSPs) are known to be increased in response to biological stress. Recently some authors described their presence in tumors. Our immunohistochemical investigations revealed the expression of HSP27, HSP70, HSP90 and HSP110 in most of benign tumors of salivary glands (33 cases). In the malignant tumors, the reaction was immunopositive for HSP70 and HSP90 in 13/17 cases; but HSP27 and HSP110 were only expressed in 5/17 cases. In conclusion HSPs were expressed less in malignant than in benign cells. These results suggest that the loss of some HSPs may be a possible sign of malignancy.

Immunocytochemical investigations of heat shock proteins expression during thymic apoptosis induced by glucocorticoids

The aim of our study was to investigate a possible expression of different HSPs in rat's thymuses after hydrocortisone administration. The thymuses of 41 young rats (25 to 45 days age old) were studied immunocytochemically: 12 rats were not injected, 8 received an injection of physiological serum, and 21 received HC (125 mg/kg). HSP27, 70 and 110 expression was investigated following the PAP method. HSPs27 were expressed neither in normal thymic lobules nor in the cortical thymic cells after HC injection. HSPs70 were objectivated only in 1 control animal, but were frankly expressed in cortical thymic cells 1 to 48 hours after HC injection and remained significantly expressed until the 7th day after HC injection. HSPs 110 were present in only 1 control animal and appeared to be distinctly expressed 48 hours after HC injection. HSPs 70 and 110 were never expressed in the regenerated thymuses 14 and 21 days after HC injection. This report objectivates for the first time 70 and 110 kDa "stress proteins" expression during the thymic apoptosis induced by glucocorticoids.

Cytochemical identification of HSP110 during early mouse facial development

Apoptotic cell death constitutes a common phenomenon observed during development. This process plays an important role in the regulation of cell populations and in early differentiation of embryonic organs. Several teratologic situations are considered as resulting in a dramatic increase of the apoptotic process. In mammalian cells, heat shock proteins (HSPs), expressed or increased in response to various stresses, act as molecular chaperones in physiological conditions. In order to determine specific histochemical markers of apoptotic cells in normal craniofacial development, we observed the expression of stress proteins (HSPs) 70, 86, and 110. The apoptotic pattern of mesectodermal cell death areas was confirmed using both nuclear staining (Feulgen) and specific labeling of DNA fragmentation (TUNEL). These areas are localized in the proximal parts of the first and second visceral arches. They are located in mesectodermal and ganglionic cells. Apoptotic mesectodermal populations strongly express HSP110, as shown by the cytochemical identification of HSP110 and by double staining HSP110-TUNEL, suggesting that this protein could be considered as a new marker for apoptotic embryonic cells, and could be used in further teratologic studies to better quantify induced cell death.

[Stress proteins: expression of a universal phenomenon of cell defense]

Heat shock proteins or stress proteins play a role in adaptative thermotolerance. All cells, procaryotic and eucaryotic, are able to respond to different cellular aggressions by the synthesis of these stress proteins. In normal physiological conditions, they are considered as "molecular chaperones" Their actual role in pathology is still unknown; some of these heat shock proteins may be correlated with the degree of aggressiveness of some tumors.

[The role of apoptosis during craniofacial development: concepts and importance in pathology]

Apoptosis is an essential common final pathway in numerous pathological conditions such as malignant tumors, HIV-related CD4 lymphocytes degeneration, neurodegenerative disorders, and in programmed cell death events during normal embryogenesis. Some teratogenic substances for man and laboratory mammals induce an increase of the apoptotic phenomenon, responsible for the occurrence of some precise cranio-maxillo-facial malformations. The study of cell death during normal or teratogenic embryonic development allows to analyse the cellular mechanisms implied in the control of the apoptotic phenomenon, together with its dysregulation ending in pathological processes. We review the cell death phenomenon during cephalogenesis, both during normal embryogenesis, or in teratogenic conditions known to induce cranio-maxillo-facial malformations.

Myxomatous odontogenic tumor of the maxilla. An unusual case with squamous and mucoproducing epithelial component

A tumor attached to the amelo-cemental junction of a third molar impacted in the maxillary tuberosity, consisted histologically of a myxomatous stroma, in which multicystic cavities lined by a columnar epithelium and mucoproducing cells, together with an aggressive squamous epithelial component were present. Although the diagnosis of polyp of the maxillary sinus cannot be excluded, this lesion most likely constitutes an unusual presentation for an odontogenic myxoma of the maxilla, in which an aggressive squamous epithelial component is present, along with a mucosecreting glandular component.

Strong expression of heat shock proteins in growth plate cartilage, an immunohistochemical study of HSP28, HSP70 and HSP110

Heat shock proteins (HSPs) are known to be increased in response to stresses. Our immunohistochemical investigations revealed the strong expression of a wide range of HSPs in the chondrocytes of the tibial growth plate cartilage from young rats. HSP28 and HSP70 are expressed in the upper part of the hypertrophic zone of the growth plate cartilage. HSP110 are found from the proliferating zone to the hypertrophic zone. On the other hand, application of the TUNEL method has already shown apoptotic DNA fragmentation in the lower part of the proliferating zone. From then one, HSP expression in the chondrocytes may be correlated with apoptosis, but its possible relation with the different events occurring during the calcification process cannot be excluded.