Ethmoid Plate Research Articles

Histone deacetylase-4 is required during early cranial neural crest development for generation of the zebrafish palatal skeleton

BackgroundHistone deacetylase-4 (Hdac4) is a class II histone deacetylase that inhibits the activity of transcription factors. In humans, HDAC4 deficiency is associated with non-syndromic oral clefts and brachydactyly mental retardation syndrome (BDMR) with craniofacial abnormalities.ResultsWe identify hdac4 in zebrafish and characterize its function in craniofacial morphogenesis. The gene is present as a single copy, and the deduced Hdac4 protein sequence shares all known functional domains with human HDAC4. The zebrafish hdac4 transcript is widely present in migratory cranial neural crest (CNC) cells of the embryo, including populations migrating around the eye, which previously have been shown to contribute to the formation of the palatal skeleton of the early larva. Embryos injected with hdac4 morpholinos (MO) have reduced or absent CNC populations that normally migrate medial to the eye. CNC-derived palatal precursor cells do not recover at the post-migratory stage, and subsequently we found that defects in the developing cartilaginous palatal skeleton correlate with reduction or absence of early CNC cells. Palatal skeletal defects prominently include a shortened, clefted, or missing ethmoid plate, and are associated with a shortening of the face of young larvae.ConclusionsOur results demonstrate that Hdac4 is a regulator of CNC-derived palatal skeletal precursors during early embryogenesis. Cleft palate resulting from HDAC4 mutations in human patients may result from defects in a homologous CNC progenitor cell population.

Subdural haematoma after endoscopic skull base surgery: Case report and lesson learned

We report a case of a left fronto-temporo-parietal subdural haematoma that emerged as a complication of an endonasal endoscopic resection of a sinonasal adenocarcinoma of the left ethmoidal region. During the first surgical intervention, following oncological principles, the dura mater above the ethmoidal plate was removed and a skull base plasty was performed. In the post-operative phase a massive cerebrospinal fluid leak was observed and a revision duraplasty was performed the following day. Subsequently the patient was discharged on day 8 with no signs of CSF leakage. At the three month follow-up MR examination a subdural haematoma was observed and then treated by the neurosurgeon in a standard fashion. The collection was quite asymptomatic and discovered accidentally. We strongly advise the role of early post-op neuroimaging in every patient undergoing skull base procedures. We maintain that a massive CSF leak, that causes a significant reduction of intracranial pressure, should be managed as a surgical emergency, in order to reduce the risk of subdural haematoma.

Zebrafish wnt9a is expressed in pharyngeal ectoderm and is required for palate and lower jaw development

Wnt activity is critical in craniofacial morphogenesis. Dysregulation of Wnt/β-catenin signaling results in significant alterations in the facial form, and has been implicated in cleft palate phenotypes in mouse and man. In zebrafish, we show that wnt9a is expressed in the pharyngeal arch, oropharyngeal epithelium that circumscribes the ethmoid plate, and ectodermal cells superficial to the lower jaw structures. Alcian blue staining of morpholino-mediated knockdown of wnt9a results in loss of the ethmoid plate, absence of lateral and posterior parachordals, and significant abrogation of the lower jaw structures. Analysis of cranial neural crest cells in the sox10:eGFP transgenic demonstrates that the wnt9a is required early during pharyngeal development, and confirms that the absence of Alcian blue staining is due to absence of neural crest derived chondrocytes. Molecular analysis of genes regulating cranial neural crest migration and chondrogenic differentiation suggest that wnt9a is dispensable for early cranial neural crest migration, but is required for chondrogenic development of major craniofacial structures. Taken together, these data corroborate the central role for Wnt signaling in vertebrate craniofacial development, and reveal that wnt9a provides the signal from the pharyngeal epithelium to support craniofacial chondrogenic morphogenesis in zebrafish.

Anatomical variation of the nasal septum: Correlation among septal components

The nasal septum consists of multiple components with various developmental origins and is considered a mosaic structure. Few studies have focused on anatomical relationships among the components of the nasal septum, even though they are essential for clinical assessments of morphological abnormalities in the nasal septum. This study was performed to evaluate anatomical correlations among components of the nasal septum using computed tomography (CT) of the paranasal sinus. We studied images from CT scans of 168 paranasal sinuses collected at a secondary referral hospital between July 2008 and February 2009. The area of each component of the nasal septum was measured using median sagittal images of CT scans after three-dimensional reconstruction using computer software. The area of the cartilaginous septum decreased with age, whereas the area of the total nasal septum remained constant. The area of the perpendicular plate of ethmoid increased with age at the expense of the area of the septal cartilage.

Development of the ethmoidal structures of the endocranium in Discoglossus pictus (Anura: Discoglossidae)

We use histological techniques and computer-aided three-dimensional reconstructions made from serial histological sections to describe the ontogeny of the ethmoidal endocranium of discoglossid frog Discoglossus pictus. We identify a pattern of development for the suprarostral cartilage that differs from previous findings and probably represents the ancestral anuran pattern. The nasal cartilages, including the inferior prenasal cartilage, are de novo adult structures. The only larva-derived structures of the adult nasal capsules are the posterior aspects of the solum nasi and septum nasi. We also identify patterns of development for the ethmoid plate and postnasal wall that occur during early in ontogenesis. These patterns are associated with development events during metamorphic climax. The pattern of timing of chondrification of the anterior nasal cartilages more closely coincides with that of the neobatrachian species than that recorded for the pelobatid frog Spea. In addition, this study supports a sister taxon relationship between Discoglossus and Alytes.

Sandwich technique in nasal dorsal augmentation

Tutoplast fascia lata (TFL) has been used as an onlay graft for nasal dorsal augmentation in open approach rhinoplasty; however, insertion of layers of moist TFL in the closed approach is technically challenging. We have presented a "sandwich" technique which facilitates graft insertion in a closed approach rhinoplasty. The available autologous graft (cartilage or perpendicular plate of ethmoid) is sandwiched and secured between layers of TFL (sandwich technique) prior to insertion of the graft for nasal dorsal augmentation in a closed rhinoplasty approach. All our cases of nasal dorsal augmentation were reviewed in a 2year period. Eight cases of nasal dorsal augmentation in secondary rhinoplasty through a closed approach were reviewed. The ease of insertion and the subsequent manipulation of the graft were noted in all the cases. Good aesthetic results have been noticed in all the cases after an average of 14months follow-up. The sandwich technique ensures ease of the graft insertion and the subsequent manipulation in a closed approach secondary rhinoplasty for dorsal augmentation.

Cranial architecture of tube‐snouted gasterosteiformes (Syngnathus rostellatus and Hippocampus capensis)

The long snout of pipefishes and seahorses (Syngnathidae, Gasterosteiformes) is formed as an elongation of the ethmoid region. This is in contrast to many other teleosts with elongate snouts (e.g., butterflyfishes) in which the snout is formed as an extension of the jaws. Syngnathid fishes perform very fast suction feeding, accomplished by powerful neurocranial elevation and hyoid retraction. Clearly, suction through a long and narrow tube and its hydrodynamic implications can be expected to require certain adaptations in the cranium, especially in musculoskeletal elements of the feeding apparatus. Not much is known about which skeletal elements actually support the snout and what the effect of elongation is on related structures. Here, we give a detailed morphological description of the cartilaginous and bony feeding apparatus in both juvenile and adult Syngnathus rostellatus and Hippocampus capensis. Our results are compared with previous morphological studies of a generalized teleost, Gasterosteus aculeatus. We found that the ethmoid region is elongated early during development, with the ethmoid plate, the hyosymplectic, and the basihyal cartilage being extended in the chondrocranium. In the juveniles of both species almost all bones are forming, although only as a very thin layer. The elongation of the vomeral, mesethmoid, quadrate, metapterygoid, symplectic, and preopercular bones is already present. Probably, because of the long and specialized parental care which releases advanced developmental stages from the brooding pouch, morphology of the feeding apparatus of juveniles is already very similar to that of the adults. We describe morphological features related to snout elongation that may be considered adaptations for suction feeding; e.g. the peculiar shape of the interhyal bone and its saddle-shaped articulation with the posterior ceratohyal bone might aid in explosive hyoid retraction by reducing the risk of hyoid dislocation.

The use of topical intranasal fluorescein in endoscopic endonasal repair of cerebrospinal fluid rhinorrhea

Background The CSF rhinorrhea is a kind of common clinical disease. The preoperative diagnosis and intraoperative localization of CSF fistulas are critical to treatment of CSF rhinorrhea. At present, intrathecal fluorescein regarding endoscopic transnasal cerebrospinal leakage repair is a common method for localization of the fistula; however, it has some disadvantages because it needs a specific endoscope, and the trauma from lumbar puncture as well as the potential complications of intrathecal fluorescein, as a result, widely limited its clinical use. Topical intranasal fluorescein can avoid the above-mentioned shortcoming. The aim of this work was to describe the use of topical fluorescein in the intraoperative localization of CSF fistulas and to screen its use in preoperative diagnosis of CSF rhinorrhea. Methods Fifteen patients with CSF rhinorrhea were treated with an endoscopic endonasal technique. Topical intranasal 5% fluorescein for preoperative diagnosis and intraoperative localization of the site of the leak was placed in middle turbinate meatus, the roof of the ethmoid plate, and sphenoethmoidal recesses. A change in the color of the fluorescein from brown to green fluorescence denoted the presence of CSF, and the site of the leak could be traced. The accuracy rate of diagnosis and leak site identification was made by comparison with glucose analysis, intraoperative findings, and follow-up. Results The cause of the leak was accidental trauma in 5 patients and spontaneous in 10 patients. The preoperative use of fluorescein-soaked cotton was 100% accurate in diagnosing CSF rhinorrhea. The intraoperative use of topical intranasal fluorescein was also 100% accurate in locating the site of the CSF fistula when compared with the surgical findings. It had achieved 100% success rate in sealing the CSF fistulas in our 15 patients with no recurrence detected during the follow-up period (mean, 2-24 months). No complications have been reported. Conclusion In the presence of a clinically diagnosed CSF leakage and location of the leakage fistula, topical fluorescein is a very easy, sensitive, safe, and highly accurate tool in the intraoperative localization of the site and extent of CSF fistulas. It should be considered as a viable noninvasive alternative to intrathecal fluorescein.

17β-Estradiol inhibits chondrogenesis in the skull development of zebrafish embryos

17β-Estradiol (E2) plays important roles in the development and differentiation of the gonad and central nervous systems, but little is known regarding the effects of exogenous E2 on chondrogenesis in skeletal development. In the present study, we found that treatment with E2 1–5 days post-fertilization (dpf) at concentrations above 1.5 × 10 −5 M increased the mortality rate in zebrafish embryos. Morphological analysis showed that treatment with E2 1–5 dpf caused abnormal cartilage formation in a dose-dependent manner at concentrations above 5 × 10 −6 M. E2 1–5 dpf at 1.5 × 10 −5 M caused defects of the ethmoid plate, parallel cleft of the trabecular cartilage, and hypoplasia of Meckel's cartilage and the ceratohyal cartilage. The sensitivity of embryos to E2 depended on the developmental stage. In early chondrogenesis (1–2 dpf), the embryos were highly sensitive to E2, leading to hypoplasia of the cartilage. In situ hybridization studies showed that expression levels of patched1 ( ptc1) and patched2 ( ptc2) receptor mRNAs were markedly decreased by exposure to 2 × 10 −5 M E2 1–2 dpf. However, the expression levels of sonic hedgehog ( shh) and tiggywinkle hedgehog ( twhh) mRNAs were constant in the E2-treated embryos. In addition, the estrogen receptor antagonist ICI 182,780 did not completely abolish the effects of E2, suggesting that E2 may not inhibit chondrogenesis through its nuclear estrogen receptor. These results suggest that exposure to exogenous E2 possibly inhibits chondrogenesis via inhibition of the hedgehog (Hh) signal transduction system.

Application of topical intranasal fluorescein in endoscopic endonasal repair of cerebrospinal fluid leakage

To investigate the effects of topical fluorescein on the preoperative diagnosis of rhinorrhea of cerebrospinal fluid (CSF) and intraoperative localization of CSF fistula. Cotton pads soaked with 5% fluorescein were placed in the middle turbinate meatus, roof of ethmoid plate, and sphenoethmoidalis recesses via endoscopic endonasal technique of 15 patients with CSF rhinorrhea, 5 caused by accidental trauma and 10 spontaneous. Change of the color of fluorescein from yellow to green fluorescence denoted the presence of CSF, and thus the site of the leak could be traced. The accuracy rates of diagnosis and leak site identification by this technique were compared with those by glucose analysis, intraoperative findings, and follow-up. The preoperative diagnosis rate of CSF rhinorrhea and the CSF fistula site localization rate by fluorescein-soaked cotton pad were both 100%. No recurrence was found during the follow-up for 2 - 24 months. No complication had been reported. Application of topical fluorescein is an easy, sensitive, safe, and highly accurate tool in the intraoperative localization of the site and extent of CSF fistulas and should be considered a viable noninvasive alternative to intrathecal fluorescein technique.

S261 – Development of the Ethmoidal Fovea during Intrauterine Life

Objectives To analyze embryological development of the ethmoidal fovea and the horizontal ethmoidal plate and measure the thickness of the latter during the various stages of gestation, and whether to determine if, during the intrauterine life, there are different types of fovea according to the Keros classification. Methods A retrospective, descriptive, and comparative study was made using 92 human fetuses. Morphometry was made and inferential statistics and correlations and autocorrelations during different stages were done. Results The morphological structures of the fovea are recognized during the 14th week. In 32-week-old fetuses measurements of the fovea did not vary in proportion to the rest of the structures. In all the specimens studied, the type of roof was type I, agreeing with Keros' classification. As for the measurements of the thickness of the fovea, width and length of the crista Galli apophysis, they were significant (p <0,001), strongly supporting their growth in relation to the crown-caudal length. Conclusions As for the various anatomic variants that are observed in the adults, according to Keros' classification, there were no variants in all the fetuses studied as such variants we can assure, at least in the population studied, that these appear until after birth upon development of the middle third of the face.

Are Cross-hatching Incisions Mandatory for Correction of Cartilaginous Septal Deviation?

ObjectivesCross-hatching incisions have been considered mandatory for correcting cartilaginous septal deviation. We evaluated the clinical outcome of septoplasty without cross-hatching incisions to determine the necessity for making septal cartilage incisions.MethodsThe reconstructed septal components during septoplasty were categorized into four anatomical areas: vomer, maxillary crest, perpendicular plate of ethmoid (PPE) and septal cartilage (the area for cross-hatching incisions). During septoplasty, we attempted to complete the surgery only by removing or fracturing the bony part of the septum without cross-hatching incisions on the cartilage. Only in the cases that the deviation was not immediately corrected, the cross-hatching incisions were made onto the cartilage at the end of the procedure. We analyzed the frequency of manipulating the septal components. The changes of symptoms were evaluated using a modified nasal obstruction symptom evaluation (NOSE) scale and a visual analog scale (VAS) preoperatively, 1 and 3 months after the surgery.ResultsSeventy five percents of the deviated septums were immediately corrected only by removing or fracturing of the bony septal components. In decreasing order of frequency, the sepal components for correcting septal deviation were the vomer (59%), maxillary crest (49%), septal cartilage (cross-hatching only: 25%) and PPE (15%). The modified NOSE scale and the VAS demonstrated significant improvement of the nasal symptoms postoperatively (P<0.05).ConclusionMost of septal deviations could be corrected by manipulating only the bony septum. The results of this procedure were not different from conventional septoplasty with cross-hatching incisions. Our data suggest cross-hatching incisions during septoplasty might have been overemphasized and that the main cause for cartilaginous deviation may be the extrinsic forces that are generated by the neighboring bony structures.

Post-embryonic remodelling of neurocranial elements: a comparative study of normal versus abnormal eye migration in a flatfish, the Atlantic halibut.

The process of eye migration in bilaterally symmetrical flatfish larvae starts with asymmetrical growth of the dorsomedial parts of the ethmoid plate together with the frontal bones, structures initially found in a symmetrical position between the eyes. The movement of these structures in the future ocular direction exerts a stretch on the fibroblasts in the connective tissue found between the moving structures and the eye that is to migrate. Secondarily, a dense cell population of fibroblasts ventral to the eye starts to proliferate, possibly cued by the pulling forces exerted by the eye. The increased growth ventral to the eye pushes the eye dorsally. Osteoblasts are deposited in the dense cell layer, forming the dermal part of the lateral ethmoid, and at full eye migration this will cover the area vacated by the migrated eye. When the migrating eye catches up with the previous migrated dermal bones, the frontals, these bones will be remodelled to accommodate the eye. Our findings suggest that a combination of extremely localized signals and more distant factors may impinge upon the outcome of the tissue remodelling. Early normal asymmetry of signalling factors may cascade on a series of events.

Management of an isolated orbital blow-out fracture

Fracture of the orbital floor (57.4%) can occur from zygomatico-maxillary complex fracture in middle third facial skeletal injuries. However, isolated orbital floor fracture-the term coined as ‘blow out fracture’ represents upto 21.4% [1]. Anatomically, the antero-medial 3rd of the floor is formed by orbital surface of maxilla, where as the postero-medial part is formed by palatine bone and lateral 3rd is formed by zygoma. The medial wall of the orbit is formed anterior to posterior, by frontal process of the maxilla behind its lacrimal crest, lacrimal bone, orbital plate of ethmoid and body of sphenoid. The ‘blow out’ fracture of orbit usually involves the medial wall and floor of the orbit being the thinnest. Absolute indications for reconstruction of orbital floor are diplopia with muscle entrapment, enopthalmos and large defect [2]. Many materials have been described for the reconstruction of orbital floor defects with varying rate of success. They include autogenic, allogenic and alloplastic material. This article reports management of a case of orbital blow-out fracture using autogenous iliac crest bone graft to reconstruct the defect of the orbital floor.

Desenvolvimento osteológico de Hippocampus reidi Ginsburg (Pisces, Syngnathiformes, Syngnathidae), em laboratório: II. Período juvenil

The sequence of events of the ossification process in the newly bom specimens of Hippocampus reidi Ginsburg, 1933 up to 37 days of life has been described, mainly the ossification in the ethmoid plate, palatine, pectoral girdle, and postorbital bones and bony structures such as mesoethmoid, articular and six suborbitals. Observation on adult specimens are presented too.

The Chondrocranium of the Mexican Burrowing Toad, Rhinophrynus dorsalis

-The chondrocranium of Rhinophrynus dorsalis is described and illustrated. Autapomorphies of R. dorsalis are the presence of the symplectic cartilage and a cartilaginous process on the ascending process of the palatoquadrate. Synapomorphies of Rhinophrynus shared with the Pipidae are: (1) early formation of the lower jaw and (2) presence of a suprarostral plate. Alternative developmental pathways for the formation of the suprarostral plate are considered. Histological data indicates that the suprarostral plate forms from: (1) the early fusion of the cornua trabeculae with the suprarostral cartilages, (2) an anterior growth of the ethmoid plate, and (3) subsequent fusion of the cornua trabeculae and the anterior process of the ethmoid plate. The larval crista parotica of R. dorsalis resembles the one described for microhylid taxa. Taylor (1942) described pipid-like anuran larvae from a sample of tadpoles collected in Guerrero, Mexico. However, these larvae remained unidentified until the tadpole of Rhinophrynus dorsalis was described by Orton (1943). Orton's description included a few chondrocranial characteristics, particularly focusing on the jaw apparatus. She noted the early formation of the lower jaw and suggested that this early development may be correlated with a macrophagous diet. Subsequently, Sokol (1977, 1981) made references to the chondrocranial anatomy for Rhinophrynus dorsalis larvae while evaluating the use of larval characteristics in systematics. The sequence of cranial ossification for Rhinophrynus larvae was described by Trueb, 1985. Description of adult osteology has been previously described (Trueb, 1973; Trueb and Cannatella, 1982). Hay et al. (1995) placed Rhinophrynus as the sister group to Pipidae based on 12S and 16S rRNA sequence data. Previous morphological studies suggested the following synapomorphies for the Pipoidea: absence of mentomeckelian bones, lack of parasphenoid alae, presence of a single frontoparietal, greatly enlarged otic capsules, and larvae with paired spiracles and lacking comified beaks and denticles (Ford and Cannatella, 1993). Of the approximately 28 species of the Pipoidea, the chondrocranium has been described thoroughly for Xenopus laevis (Trueb and Hanken, 1992) and partially for Rhinophrynus dorsalis, Pipa carvalhoi, and Xenopus tropicalis (Sokol, 1975). Herein we provide a complete description and illustration of the chondrocranium of Rhinophrynus dorsalis. 1 Corresponding Author. MATERIALS AND METHODS Thirty tadpoles of the Mexican Burrowing Toad, Rhinophrynus dorsalis, representing Neiuwkoop and Faber (1956) stages 48-62 were cleared and double-stained for bone and cartilage using standard procedures. Drawings were obtained with the help of a Wild M3C stereomicroscope with camera lucida attachment. Collection localities of specimens used in this study are: Guanacaste, Costa Rica (USNM 515945515958); and Aguacate Lagoon, Cayo District, Belize (USNM 515959-515974). Collection numbers, measurements, and stages of material examined are given in Table 1. Nieuwkoop and Faber's (1956) staging table for Xenopus was used to stage Rhinophrynus tadpoles. The similarity of external morphology of Xenopus and Rhinophrynus during development makes this table preferable to the Gosner's (1960) staging table. Chondrocranial terminology follows De Jongh (1968), Haas (1995), and Trueb and Hanken (1992).

Autologus ethmoid splint for nasal septal reconstruction

Otolaryncologic literature is full of techniques described to correct the deviated nasal septum. The popular operation of submucosal resection has several potential complication. Moreover the dorsal and caudal septal deflections cannot be corrected by it. The modern trend is towards nasal septal reconstruction, so that the whole septum can be approached and reconstructed. We have used the autologous perpendicular plate of ethmoid as permanent nasal septal splint. The ethmoid plate is rigid enough to be used as splint at the same time it is thin and does not add to the bulk. The Ethmoid splints are effective in correcting septal deviation and prevent redeviation of the reconstructed septum. The technique was successfully used in over 100 patients without any significant complication.

Development of the cranium ofNeoceratodus forsteri, with a discussion of the suspensorium and the opercular apparatus in Dipnoi

The ontogeny of the cranium of Dipnoi is restudied. The investigation especially refers to the basic components of the dipnoan cranium and several functional and developmental aspects of the structure of the larval skull ofNeoceratodus. There are fundamental differences even in the early development and composition of the chondrocranium ofNeoceratodus and Lepidosirenidae. This result, and comparison with several osteichthyans and Tetrapoda, requires a reinterpretation of the components of the dipnoan skull base. The pterygoid processes are not reduced, but incorporated into the cranial base early in ontogeny. The characteristic elongate trabecular rods, which in Gnathostomata usually bridge the ethmoidal plate and the orbito-temporal base of the chondrocranium, are much delayed in development inNeoceratodus, or even seem absent inLepidosiren andProtopterus. Accordingly, in Dipnoi no typical basitrabecular junction is formed in early ontogeny. Instead, the pars quadrata is fused to the mesodermal basis cranii posteriorly. InNeoceratodus a mesially directed basal process of the palatoquadrate is recognizable, which topographically corresponds to the basal process of Urodela and the pseudobasal process of anuran larvae. The ethmosphenoid region of the dipnoan skull also develops quite differently. In Lepidosirenidae, the palatoquadrates are interconnected anteriorly by a distinct commissura palatoquadrati, whereas inNeoceratodus a continuous planum ethmoidale (“trabecular plate”) is formed. The primary embryonic quadrato-trabecular connection persists as a commissura quadratocranialis anterior below the foramen opticum, at the root of the ectethmoid process. The formation of the skull base in living Amphibia appears to provide the best model for comparison, though it is difficult to propose any undisputable shared derived character states of the cranium of Dipnoi and Tetrapoda beyond this similarity. A similar difficulty presents the phylogenetic interpretation of the hyoid arch. In contrast to the absence of any dorsal hyoid arch elements inLepidosiren, the small hyomandibula ofNeoceratodus is surprisingly complete. In larvae it consists of a laterohyale, an epihyal part, and a processus symplecticus. A stylohyal cartilage is present, which forms rather late in ontogeny. The major chondral components of the hyoid arch are thus comparable to those of living Actinopterygii, except that a distinct symplecticum is not separated off, the components are relatively smaller, and they do not ossify. In view of the early-immobilized palatoquadrate, the hyomandibula ofNeoceratodus has no suspensorial function, but represents part of an opercular hinge and opening mechanism. The hamuloquadrate knob at the posterior face of the quadrate body is comparable to the processus hyoideus in some Urodela. It provides a pivoting joint for the ceratohyale, and therefore functions in buccal expansion. The closed spiracular canals include mechanoreceptive lateral line organs, which probably represent proprioreceptive organs for adjustment of mandibular, hyoid, and opercular movements. It is concluded that considerable differences between the skull architecture of Dipnoi and other Osteognathostomata (Teleostomi) can be assigned to the fact that palatoquadrate and trabecular anlagen fail to separate, resulting in a dramatic and highly adaptive change of palatoquadrate development in early ontogeny. Though these differences include several characters that suggest a plagiostomate condition of the jaw apparatus, this can be explained as a secondary acquisition. The multitude of retained plesiomorphies observed in the cranium of Dipnoi do not exclude a sister group-relationship to Tetrapoda. However, the ancestral osteognathostome suspensorial pattern still presents a problem of interpretation, for we lack a detailed survey of the development and significance of different quadrato-neurocranial connections.

Craniofacial Dysmorphia of Frontal Proboscis in Holoprosencephaly

ABSTRACTWe have examined eleven cases of holoprosencephaly with special emphasis on the frontal proboscis. Although the nostril appears blind ended grossly, the proboscis has a single slender midline nostril lined with squamous mucosa containing numerous sebaceous glands. It is actually connected to a poorly formed but definite nasal cavity microscopically. The inner portion of the nostril tunnel is lined by olfactory mucosa containing numerous subjacent secretary glands. Despite the absence of olfactory bulbs and tracts the cartilaginous nasal capsule is identified along with abnormal nasal cavity. However, the nasal capsule is hypoplastic, and has an aberrant nasal septum and no concha. In severe form of holoprosencephaly, i.e., cyclopia, the nasal capsule is noted above the level of the ethmoid plate, in which case the nasal cavity dose not communicate with nasopharynx because it is too distant from the hypoplastic maxilla. Therefore, choanal atresia is resulted. Although unique maxillary bone comprises the whole upper jaw, the failure of fusion between vomeronasal septum and palatal processes in holoprosencephaly results in abnormal maxillary bone which is characterized by a narrow palate without palatal arch form. Nevertheless, through serial microscopic sections we could find a space between the posterior maxilla and the sphenoid bone, which is composed of adipose tissue and is similar in shape to the nasal capsule. This space is thought to be made for the nasal capsule during early developmental period. The present study suggests that the frontal proboscis in holoprosencephaly is an undescended nose. In most cases it is connected to the aberrant nasal cavity which is located beneath the proboscis. The level of proboscis descends gradually toward normal nose position as the severity of holoprosencephaly decreased from cyclopia, ethmocephaly, cebocephaly, to premaxillary agenesis. Key words: frontal proboscis, holoprosencephaly, craniofacial dysmorphia

Development of the ethmoidal structures of the endocranium in the anuran Pipa pipa.

Investigation of eight developmental stages by means of serial sections and subsequent graphic or wax model reconstructions, as well as by means of cleared-and-stained and dissected material, revealed that the ethmoidal endocranium in Pipa pipa consists in early states of a single horizontal ethmoid plate lacking labial cartilages. Later in the course of development, structures comparable with those in other anurans appear, though modified and of reduced size. These adult structures arise from the new cartilaginous tissue located above the former larval ethmoid plate, whereas the latter entirely disappear. This phenomenon can be observed also in P. carvalhoi and in Xenopus laevis; hence, it supposedly occurs in all pipids. On the other hand, in anuran larvae, which develop cornua trabecularum in the ethmoidal region, these persist in adults as part of the nasal septum. Positional and developmental differences suggest that, although the ethmoid plate and the cornua trabecularum arise from the same region of the cranial neural crest, they are not fully corresponding structures. Comparison with adults of other pipid genera confirmed the conclusion of some earlier investigators that P. pipa is the most specialized among pipids.