Lectin histochemistry in the developing oto-maxillo-facial primordia of the mouse embryo

The binding sites of several lectins (Con-A, SBA, WGA, PNA, RCA-I, UEA-I, DBA) were studied in the different tissues involved in mouse visceral cephalogenesis. As compared to various other lectins which have only a weak affinity for precartilaginous rudiments, PNA preceded by neuraminidase treatment shows a very strong fixation in the precartilaginous blastemata and their immediate environment. PNA receptors exist also on the enamel epithelium and mesenchymal sac. RCA affinity for blood vessels has also enabled detailed observations on the vascularization of the palatal shelves, particularly in area 3. Various other localizations have been described and correlated with other histochemical data.Les sites de fixation de différentes lectines (Con-A, SBA, WGA, PNA, RCA-I, UEA-I, DBA) ont été étudiés dans les différents tissus impliqués dans la céphalogenèse viscérale de la souris. En comparaison avec les autres lectines qui présentent une faible affinité pour les précartilages, l’étude de la fixation de la PNA précédée d’une pré-incubation à la neuraminidase montre une forte fixation sur les blastèmes précartilagineux et leur environnement immédiat. Des récepteurs à la PNA sont également relevés dans l’organe adamantin, alors que la RCA se fixe dans la zone périphérique du mésenchyme odontogène et sur le sac mésenchymateux. La fixation de la RCA sur la paroi des vaisseaux permet d’intéressantes observations relatives à la vascularisation des crêtes palatines, particulièrement dans la zone 3. De nombreuses autres localisations sont décrites et mises en corrélation avec d’autres données histochimiques

Etude in toto de l’activité cholinestérase dans le viscérocrâne de l’embryon de souris

In toto analysis of cholinesterase activity in the cephalic extremity of 9- to 14-day old mouse embryo permits to define four different stages. Stage 1 corresponds to activity in the cephalic neural crest-derived cells. Stage 2 is characterized by activity in the proximal part of both first branchial arches and in the oculomotor blastemata. Stage 3 corresponds to a decrease of the activity, which appears in the area of fusion of several facial processes. Stage 4 corresponds to activity in nervous and muscular blastemata. Cholinesterase activity is thus chronologically varying and implies several differentiating cell populations.L’analyse in toto de l’activité cholinestérase dans l’extrémité céphalique d’embryons de souris de 9 à 14 jours permet de définir 4 stades. Le stade 1 correspond à la présence d’une activité dans les cellules dérivées des crêtes neurales céphaliques. Le stade 2 se caractérise par une activité dans la partie proximale des deux premiers arcs branchiaux et dans les blastèmes oculomoteurs. Le stade 3 voit l’activité décroître et intéresser la zone de fusion de certains bourgeons faciaux. Le stade 4 correspond à une activité répartie dans les ébauches nerveuses et musculaires. L’activité cholinestérase s’avère donc variable dans le temps et concerne diverses populations cellulaires en voie de différenciation

Tératogénicité de l’acide 13-cis rétinoïque sur les ébauches mandibulo-optiques de l’embryon de souris: approche histologique et histochimique

Oral administration of 400 mg/kg of 13-cis retinoic acid to 9 day pregnant mice gives rise to important maxillo-facial malformations. The first manifestation of teratogenic effect is an increase of density of cell death arising in the dorsal part of the first two branchial arches at day 9.5. These two arches become hypoplastic at days 10 and 11, and the preskelettic anlagen appear too late in comparison to control embryos. Meckel’s cartilage is too curvilinear and medially situated. Pre-ossicular and pre-mandibular blastemata develop with spatial distorsions which are well analyzable at days 16 and 17. They give some arguments to discuss several features of normal early development of this area.L’administration orale de 400 mg/kg d’acide 13-cis rétinoïque à des souris gestantes à 9 jours de gestation est responsable d’importantes malformations de la sphère oto-maxillo-faciale. Le premier signe consiste en une augmentation de la densité des nécroses observées dans la partie dorsale des deux premiers arcs à 9.5 jours. Ceux-ci se caractérisent ultérieurement par une hypoplasie relative par rapport aux témoins et les ébauches présquelettiques y apparaissent avec retard. Le cartilage de Meckel apparaît d’emblée trop arciforme et médialement situé. Les blastèmes pré-ossiculaires et prémandibulaires subissent une importante distorsion spatiale et leurs déformations, bien observables à 16 et 17 jours, permettent de discuter certains aspects de la morphogenèse précoce normale de ces éléments

Early development of the malleus and incus in humans.

It is widely accepted by developmental biologists that the malleus and incus of the mammalian middle ear are first pharyngeal arch derivatives, a contention based originally on classical embryology that has now been backed up by molecular evidence from rodent models. However, it has been claimed in several studies of human ossicular development that the manubrium of the malleus and long process of the incus are actually derived from the second arch. This 'dual-arch' interpretation is commonly presented in otolaryngology textbooks, and it has been used by clinicians to explain the aetiology of certain congenital abnormalities of the human middle ear. In order to re-examine the origins of the human malleus and incus, we made three-dimensional reconstructions of the pharyngeal region of human embryos from 7 to 28 mm crown-rump length, based on serial histological sections from the Boyd Collection. We considered the positions of the developing ossicles relative to the pharyngeal pouches and clefts, and the facial and chorda tympani nerves. Confirming observations from previous studies, the primary union between first pharyngeal pouch and first cleft found in our youngest specimens was later lost, the external meatus developing rostroventral to this position. The mesenchyme of the first and second arches in these early embryos seemed to be continuous, but the boundaries of the developing ossicles proved to be very hard to determine at this stage. When first distinguishable, the indications were that both the manubrium of the malleus and the long process of the incus were emerging within the first pharyngeal arch. We therefore conclude that the histological evidence, on balance, favours the 'classical' notion that the human malleus and incus are first-arch structures. The embryological basis of congenital ossicular abnormalities should be reconsidered in this light.This is the author accepted manuscript. The final version is available from Wiley via https://doi.org/10.1111/joa.1252

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

Pure Second Arch Syndrome

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Le larynx: phylogenèse, ontogenèse et généralités anatomiques

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Development of the stapes and associated structures in human embryos

The objective of this study was to clarify the development of the stapes in humans and its relationship with the cartilage of the second branchial arch. The study was carried out in 25 human embryos between 6 and 28 mm crown–rump length. The stapes develops at the cranial end of the second branchial arch through an independent anlage of the cartilage of this arch. Between the stapedial anlage and the cranial end of the Reichert's cartilage there is a formation called the interhyale, the internal segment of which gives rise to the tendon of the stapedial muscle. The stapedial anlage is a unique formation with two distinct parts: the superior part that will comprise the base and the inferior part that will be crossed by the stapedial artery during embryonic development and will constitute the limbs and the head of the stapes. According to the results, the otic capsule is not involved in formation of the base of the stapes