Arhinia revisited

Arhinia is a rare anomaly in which a total absence of the nose and parts of the olfactory system occurs. It is frequently associated with various multiple central nervous system (CNS) and somatic anomalies of different degrees of severity, with high mortality rate. Twelve cases that have been reported in the literature are analyzed according to multiple criteria. The anomalies that have been found to be associated with arhinia are: lack of olfactory bulbs and nerves, missing paranasal sinuses, high arched or cleft palate, various eye anomalies, low set ears - all in a very high incidence. Various degrees of CNS malformations have been found in part of the cases. Somatic anomalies have been reported in 50% of the cases. In two cases chromosome 9 anomalies have been reported. A classification is suggested in which arhinia is classified into arhinia (total absence of the nose and rhinencephalon) and partial arhinia (partial absence of the nose), each may or may not be associated with other malformations (facial, CNS and somatic).

Immunocytochemical demonstration of luteinizing hormone-releasing hormone in optic nerve and nasal region of fetal rhesus macaque

The brain and nasal region of a fetal (124 days) female rhesus macaque (Macaca mulatta) were fixed in situ, decalcified, sectioned and treated for the immunocytochemical demonstration of LHRH. Immunoreactive neurons and fibers were found in expected sites and also in sites not reported to date in primates: there was an abundant distribution along the pathway of the nervus terminalis and clusters of neurons anterior and ventral to the olfactory bulbs and scattered in the nasal septum. Fibers extended into the epithelium lining the nasal septum. Most unexpectedly, LHRH fibers and a few neurons were observed within the optic nerve.

The embryological, developmental and functional importance in the repair of the nasal musculature to reduce the deformity of the cleft lip nose

The latent ability of nasal growth to correct developmental deformities when caused by a deforming force has been shown in nasal dermoids where early surgery by removing the deforming elements allows subsequent growth of the nasal bones and cartilages to correct the abnormality. An embryological study into the nasal musculature has shown both an orbicularis and dilator system to be present. The correction of the abnormal musculature in the cleft lip nose by removing the deforming connections and realigning the muscles allows subsequent growth the possibility of producing normal development. Primary surgery in the cleft lip nose has not shown any detrimental growth patterns and correction of the nasal musculature should therefore be carried out at the time of the primary lip correction.

Small eyes (Sey): a homozygous lethal mutation on chromosome 2 which affects the differentiation of both lens and nasal placodes in the mouse

Small eyes (Sey) is a semidominant, homozygous lethal mutation in the mouse (Roberts, 1967). It is allelic with SeyH, a radiation-induced homozygous prenatal lethal which has been mapped on chromosome 2. The effect of the Sey mutation is apparently limited to the growth and differentiation of the presumptive lens and nasal placodes. Homozygous Sey/Sey embryos can be distinguished as early as 10.5 days post coitum (p.c.); the optic vesicles grow out, but the ectoderm does not give rise to a lens and nasal pits never form. Immunohistochemical studies show that the distribution of the extracellular matrix glycoprotein laminin is not significantly different in the cephalic region of Sey/Sey versus Sey/+ or +/+ embryos. Sey/Sey embryos develop to term but without eyes or nose, and die soon after birth. Further analysis of Sey/Sey embryos may throw light on the mechanisms underlying morphogenesis of craniofacial structures in mammals.

Changes in mesenchymal cell-basal lamina relationships preceding palatal shelf reorientation in the mouse

Two specific regions of the future nasal and oral epithelial surfaces of the secondary palatal shelves increase in cell density during shelf reorientation. The relationships of mesenchymal cells to the basal lamina underlying these regions were examined and compared to those of cells underlying adjacent regions which did not change in cell density. CD-1 mouse fetuses were obtained on day 13.5 of gestation. Some palatal shelves were excised immediately and fixed for electron microscopy; other heads were partially dissected and incubated for 4 hr prior to fixation. Although shelf movement is detected only after 6 hr incubation, the shorter time period was selected in order to detect events which precede reorientation. Electron micrographs were taken of the epithelial-mesenchymal interface of nasal and oral regions known to increase in epithelial cell density (active segments) and of nasal and oral regions which did not increase (inactive segments). Several measurements were made in a 500-nm-wide zone delimited on photographic prints. Distinct differences in mesenchymal cell configuration were found between nasal and oral regions. Active and inactive segments of each region also differed. A filamentous layer attached to the undersurface of the lamina densa was observed to vary in thickness and character between regions as well. After 4 hr incubation, differences in mesenchymal cell configuration and ultrastructure of the sublaminar zone were apparent between regions. These results suggest that local epithelial-mesenchymal interactions, possibly mediated by the extracellular matrix, precede shelf reorientation. Whether these changes in mesenchymal cell configuration actually reflect mesenchymal cell activities that are necessary for shelf reorientation remains to be elucidated.

Nasal glioma and encephalocele: two separate entities. Report of two cases

The term "nasal glioma" is a confusing misnomer as it implies a neoplastic condition with malignant potential, which it is not. Nasal glioma is a rare development abnormality and should be differentiated from glioma, which is a malignant tumor of the brain, and from a primary encephalocele, which is herniation of the cranial contents through a bone defect in the skull, through which it retains an intact connection with the central nervous system. Two cases of nasal glioma, one with and one without intracranial connections, are described and the literature is reviewed.

Light and electron microscopy study of fusion of facial prominences. A distinctive type of superficial cells at the contact sites

The contact site between the medial nasal prominence (MNP) and the lateral nasal prominence (LNP) during the period of primary palate formation in the mouse embryo was examined by light and electron microscopy. Throughout this period, a distinctive type of superficial cell was observed at the contact site. These superficial cells had a large nucleus and abundant cytoplasm as well as structural features characteristic of embryonic cells. At earlier stages, these cells were seen at the transitional region between the surface ectoderm and the epithelia of the nasal pit at the end of the isthmus, where initial contact of opposing MNP and LNP took place. At later stages, these superficial cells appeared to bridge the gap between MNP and LNP at the contact sites, which extended to the bottom of the valley formed by MNP and LNP. These cells were also observed on the surface near the contact sites, that is, the presumptive fusion area. These superficial cells displayed well-developed junctional complexes (intermediate and gap junctions, and desmosomes). Many filaments were observed subjacent to the plasma membranes of these superficial cells, some of which were associated with junctional complexes. These observations suggest that this kind of distinctive superficial cell may play critical roles in the contact of MNP and LNP throughout the fusion process.

Development of human craniofacial morphology during the late embryonic and early fetal periods

After formation of the primary palate during the fifth and sixth weeks postconception (PC), human facial morphology develops rapidly and by 10 weeks PC the face has a typically human appearance. The objective of this study was to review major growth changes associated with development of face shape during this period. Morphometric evaluation of staged human embryos and fetuses in the Carnegie Embryological Collection showed that between 7 and 10 weeks PC when crown-rump (CR) length increased from 18 to 49 mm, facial structures grew predominantly in the sagittal plane, with a four-fold increase in length, a two-fold increase in height, but little change in width. These growth changes altered relations of oronasal structures and at 8 weeks PC the palatal shelves elevated. The sagittal position of the maxilla and the mandible to the anterior cranial base increased by 25 degrees and 30 degrees, respectively, and the mandible was prognathic during secondary palate closure in the first 2 weeks of fetal development. Both the mean cranial base angulation--which remained unchanged at 128 degrees--and the achieved maxillary position of 84 degrees were similar to the angulations present later, prenatally and postnatally. Therefore, human patterns of cranial base angulation and maxillary position appear to develop during the late embryonic period when the chondrocranium and Meckel's cartilage form the continuous craniofacial skeleton. The results suggest that rapid directional growth of the primary cartilages is important to development of normal human facial morphology and that interference with normal growth changes during this early critical period may produce irreversible effects on the face.

Morphometric and autoradiographic analysis of frontonasal development in the chick embryo

Dimensional changes in the nasal processes were measured in chick embryos from Hamburger and Hamilton (1951) stages 20 through 27.5. Transverse measurements in the frontonasal region of freshly fixed embryos were compared to frontal sections of the nasal region of comparably staged embryos. These observations were correlated with autoradiographic studies of cell movement employing an implant labeling technique. Morphometric analysis indicated that between stages 20 and 25 the separation of the nasal pit orifices increased coincidentally with rapid forebrain enlargement. Since the separation of the nasal pit fundi increased more rapidly, the orientation of the nasal pits changed. Autoradiographic studies indicated that lateral movement of medial nasal process mesenchyme into the base of the nasal groove and medial area at the base of the lateral nasal process had occurred. After stage 25, the separation of the nasal orifices declined dramatically, coincidental with rapid orbital enlargement. In contrast, the separation of the nasal pit fundi was maintained. It is proposed that nasal development of the chick embryo may be governed initially by forebrain enlargement and associated lateral movements of mesenchyme in the medial nasal processes, resulting in reorientation of the invaginating nasal placodes; subsequently, orbital enlargement and an associated medial redirection of growth of the lateral nasal processes assumes greater significance to the continued development of the frontonasal region.

The nasopalatine ducts and associated structures in the rhesus monkey (Macaca mulatta): topography, prenatal development, function, and phylogeny

Morphological and developmental characteristics of the rhesus monkey nasopalatine duct system and associated primary palatal structures are described along with functional and phylogenetic considerations. Examination of five adult palates and coronal sections of 13 fetal palates together with dissections of a sixth adult specimen and of a 119-day-old fetal palate reveal that the lateral lobes of the tripartate incisive papilla cover clefts leading into the ducts. The ducts pierce the bony palate to enter the nasal fossae in proximity to the incisive suture. The ontogenetic stability of the duct path reflects the retention of ancient duct and primitive choanae relationships and functionally maintains an optimal oral odorant-to-receptor channel. Sixteen timed pregnancy specimens (35-100 days) provided histological material for documenting rostral nasopalatal development. Duct primordia, identified at 35 days, had by 40 days formed the medial duct walls (conjoined septum-papilla from the primary medial palatal component), the lateral duct walls (maxillary processes), and the rostral walls (fused maxillary-intermaxillary components). The caudal walls derive from the fusion of palatal shelves with the papilla (45 days), thus distinguishing primary and secondary fusion modes. Duct epithelial maturation occurs between 70 and 100 days. The absence of a vomeronasal system is attributed to reduction of olfaction in reproductive behavior, while the presence of the coevolved nasopalatine ducts is linked to the persistence of epiglottal-velar valving. The ducts serve as oral food-odor conduits in otherwise functionally separated respiratory and digestive tracts.

Ultrastructure of initial nasal process cell fusion in spontaneous and 6-aminonicotinamide-induced mouse embryo cleft lip

A search was made for cell ultrastructure differences in the initial fusion process of the medial and lateral nasal processes in mouse embryos of the following types: A/J with 12% cleft lip (CL), CL/Fr with 23% CL--both cleft-lip-predisposed strains, CL/Fr 6-aminonicotinamide (6AN)-treated (94% CL) and controls from the C57BL/6 strain (0% CL) and dancer stock (0% CL). No detectable differences were found between the A/J and CL/Fr strains and the controls in the epithelial cells showing initial contact and fusion. Epithelial surfaces not in contact in controls and where clefts were developing were smooth. Cells approaching or in contact had cell projections, intercellular junctions, desmosomes, and microfilaments demonstrating firm contact between the apposed epithelia. It has been postulated that spontaneous cleft lip was due to a predisposing face shape bringing about a failure of contact in some embryos and in others where contact was achieved fusion was normal. These data support this view. The situation, however, in 6AN-treated embryos is different. A few 6AN-treated embryos showed abnormal contact that appeared malpositioned and tenuous. The teratogen also caused increased cell death and a denser epithelium and mesenchyme. Thus 6AN-induced cleft lip could be due to the epithelial cell changes and/or to the reduction in size of the nasal processes.

Embryonic maturation of sensory terminals of primate facial hairs

The present study examines the sequence of maturation of sensory nerve terminals that can be identified on primate facial guard hairs. At birth, the sensory innervation of both guard and vellus hairs is mature in that lanceolate, Ruffini, and free nerve ending (FNE) terminals can be identified and resemble those of the adult. Presumptive lanceolate terminals can be identified at the beginning of the third trimester of gestation, and other axons present are either Ruffini or FNEs, but definite identification is not possible. In the latter half of the second trimester only axons arranged circumferentially are present, resembling FNE or Ruffini terminals. Some of these axons directly abut the hair follicle and might eventually become lanceolate endings. The earliest nerve terminals associated with hairs cytologically resemble FNE or Ruffini terminals. At the onset of hair differentiation in the early part of the second trimester, nerves were always associated with developing epithelial hair placodes. Branching Schwann cells in the axons radiating toward the epidermis in these youngest embryos studied were best identified by electron microscopy. The early development of afferent nerve fibers in hairy skin provides an anatomical substrate for the known reflexogenic activity of primate embryos. Adequate cytologic criteria are thus available for the identification of sensory terminals in growing, differentiating, and presumably regenerating axons in primate hairy skin.

Origin of hydrocortisone induced orofacial clefts in the chick embryo

The growth and fusion of facial processes were studied in White Leghorn chicken embryos treated with hydrocortisone. This treatment results in complete bilateral cleft beak in 80-100% of cases. The frontonasal complex of the experimental embryos exhibited marked hypoplasia prior to cleft manifestation. During the critical period for cleft beak formation, the maximum mitotic activity was concentrated in the medial nasal processes, which thus became vulnerable to the mitosis inhibiting effect of corticoids. Primary hypoplasia of the facial processes was documented as a causative factor of corticoid-induced cleft beak which is analogous to mammalian cleft lip/palate.

The formation of the primitive choanae and the junction of the primary and secondary palates in the mouse

This study has followed the development of the primary choanae in the mouse and has shown that they originate at the developmentally strategic position of junction between the primordia of the primary and secondary palates and that this basic anatomic relationship is maintained throughout further development. Involution of the oronasal membrane begins late in the 11th day (stage 19) with the formation of interstitial gaps. The gaps enlarge and coalesce so that a completely patent opening between nasal passage and stomodeum is established by 13 days (stage 21). The membrane consists of two layers of simple squamous epithelium which become separated as involution progresses. The form of the choanal antrum changes from a simple funnel-shaped ellipse early in the 13th day to a complex slitlike opening within the following 24 hours. This coincides with the completion of a definitive primary palate and the enlargement and elevation of the shelves of the secondary palate. The maturation of the incisive papilla and interchoanal columella is related to the final stages of choanal morphogenesis. Thus, by stage 22 (14 days) the shape of the primary choanae and their anatomic relationship to the primary and secondary palates are established, and they remain essentially unchanged in later stages.

Primary palatal development in the chick

Seventy-nine chick embryos were examined by light microscopy and scanning electron microscopy to determine the mechanism of primary palatal development. Fusion between two discrete processes, the medial nasal and maxillary prominences, was found to be necessary for formation of a complete primary palate. This was one component of a three-stage process that included: (1) invagination of the nasal pit prior to the appearance of the facial prominences; (2) fusion between the medial nasal and maxillary processes caudal to the nasal groove; (3) rupture of the bucconasal membrane. The lateral nasal and maxillary prominences were found to be part of the same tissue mass. Mergence was proposed as a mechanism for the obliteration of the groove between these two localized prominences. These results were compared with those obtained by other authors for primary palate formation in rodents and man.