Fate of the Nasal Capsular Cartilages in Prenatal and Perinatal Tamarins (Saguinus geoffroyi) and Extent of Secondary Pneumatization of Maxillary and Frontal Sinuses

In Utero Exposure to Maternal Electronic Nicotine Delivery System use Demonstrate Alterations to Craniofacial Development

OBJECTIVE

Develop a model for the study of Electronic Nicotine Device (ENDS) exposure on craniofacial development.

DESIGN

Experimental preclinical design followed as pregnant murine dams were randomized and exposed to filtered air exposure, carrier exposure consisting of 50% volume of propylene glycol and vegetable glycine (ENDS Carrier) respectively, or carrier exposure with 20 mg/ml of nicotine added to the liquid vaporizer (ENDS carrier with nicotine).

SETTING

Preclinical murine model exposure using the SciReq exposure system.

PARTICIPANTS

C57BL6 adult 8 week old female pregnant mice and exposed in utero litters.

INTERVENTIONS

Exposure to control filtered air, ENDS carrier or ENDS carrier with nicotine added throughout gestation at 1 puff/minute, 4 h/day, five days a week.

MAIN OUTCOME MEASURES

Cephalometric measures of post-natal day 15 pups born as exposed litters.

RESULTS

Data suggests alterations to several facial morphology parameters in the developing offspring, suggesting electronic nicotine device systems may alter facial growth if used during pregnancy.

CONCLUSIONS

Future research should concentrate on varied formulations and exposure regimens of ENDS to determine timing windows of exposures and ENDS formulations that may be harmful to craniofacial development.

Growth and microanatomy of the paranasal sinuses in two species of New World monkeys

Paranasal sinuses of living apes and humans grow with positive allometry, suggesting a novel mechanism for bone enlargement. Here, we examine the paranasal sinuses of the owl monkey (Aotus spp.) and a tamarin (Saguinus midas) across postnatal development. The prediction that paranasal sinuses grow disproportionately faster than the main nasal chamber is tested. We used diffusible iodine-based contrast-enhanced computed tomography and histology to study sinuses in eight Aotus and three tamarins ranging from newborn to adult ages. Sinuses were segmented at the mucosa-air cavity interface and measured in volume. All sinuses were lined by a ciliated respiratory epithelium, except for the ethmoid air cells in Aotus, which are lined in part by olfactory epithelium. An age comparison indicates that only the maxillary sinus and ethmoid air cells are present in newborns, and two additional sinuses (invading the orbitosphenoid and the frontal bone), do not appear until late infancy or later. Comparing newborns and adults, the main nasal airway is 10 times larger in the adult Aotus and ~ 6.5 times larger in adult Saguinus. In contrast, the maxillary sinus far exceeds this magnitude of difference: 24 times larger in the adult Aotus and 46 times larger in adult Saguinus. The frontal sinuses add significantly to total paranasal space volume in both species, but this growth is likely delayed until juvenile age. Results suggest ethmoid air cells expand the least. These results support our prediction that most paranasal sinuses have a distinctly higher growth rate compared to the main nasal chamber.

3D CT stereoscopic imaging: observations of the frontal and anterior ethmoid sinuses development from birth to early adulthood

Objective: Our objective is to provide observations demonstrated with 3Dimensional Computed x-ray Stereoscopic Imaging (3DCTSI) in the evaluation of the anterior ethmoid and frontal sinus development from birth to age 18. Methods: This is a retrospective evaluation of patient’s CT studies performed over a fifteen-year period, reported as normal studies, and included 53 patients (142 sides) from birth to age 18. Results: At birth, there are two spaces covered by folds, the uncinate and bulla lamellae. The spaces communicate with the Middle Meatus (MM) through the emerging ethmoid infundibulum (EI) and the retrobulbar recess space (RBRS). In the first month after birth, an expansile and breakdown developmental phase blend and continue throughout the growth into the teenage years. The 3D images reveal dark lamellar structures, on the surface of the medial lamina papyracea as well as bridging the broken spatial outlines. The dark lamellae represent the mucosal lamina propria, in unossified lamellae and are the origin of permanent spatial walls. From ages 4 to 18 years, initially, the frontal recess (FR) and later the MM penetrate into the cancellous frontal bone creating the frontal Sinus (FS), the frontal septum (FS), Inter-Frontal Sinus Septal Cell (IFSSC), as well as the Fronto-Ethmoidal and Frontal Bulla Spaces. Conclusion: 3DCTSI is the first intuitive imaging modality to reveal the microanatomical development of the anterior ethmoid and frontal sinus anatomy.

Vertebral pneumaticity is correlated with serial variation in vertebral shape in storks

Birds and their ornithodiran ancestors are unique among vertebrates in exhibiting air-filled sinuses in their postcranial bones, a phenomenon called postcranial skeletal pneumaticity. The factors that account for serial and interspecific variation in postcranial skeletal pneumaticity are poorly understood, although body size, ecology, and bone biomechanics have all been implicated as influencing the extent to which pneumatizing epithelia invade the skeleton and induce bone resorption. Here, I use high-resolution computed-tomography to holistically quantify vertebral pneumaticity in members of the neognath family Ciconiidae (storks), with pneumaticity measured as the relative volume of internal air space. These data are used to describe serial variation in extent of pneumaticity and to assess whether and how pneumaticity varies with the size and shape of a vertebra. Pneumaticity increases dramatically from the middle of the neck onwards, contrary to previous predictions that cervical pneumaticity should decrease toward the thorax to maintain structural integrity as the mass and bending moments of the neck increase. Although the largest vertebrae sampled are also the most pneumatic, vertebral size cannot on its own account for serial or interspecific variation in extent of pneumaticity. Vertebral shape, as quantified by three-dimensional geometric morphometrics, is found to be significantly correlated with extent of pneumaticity, with elongate vertebrae being less pneumatic than craniocaudally short and dorsoventrally tall vertebrae. Considered together, the results of this study are consistent with the hypothesis that shape- and position-specific biomechanics influence the amount of bone loss that can be safely tolerated. These results have potentially important implications for the evolution of vertebral morphology in birds and their extinct relatives.

Inward collapse of the nasal cavity: Perinatal consolidation of the midface and cranial base in primates

Living primates show a complex trend in reduction of nasal cavity spaces and structures due to moderate to severe constraint on interorbital breadth. Here we describe the ontogeny of the posterior end of the primate cartilaginous nasal capsule, the thimble shaped posterior nasal cupula (PNC), which surrounds the hind end of the olfactory region. We used a histologically sectioned sample of strepsirrhine primates and two non-primates (Tupaia belangeri, Rousettus leschenaulti), and histochemical and immunohistochemical methods to study the PNC in a perinatal sample. At birth, most strepsirrhines possess only fragments of PNC, and these lack a perichondrium. Fetal specimens of several species reveal a more complete PNC, but the cartilage exhibits uneven or weak reactivity to type II collagen antibodies. Moreover, there is relatively less matrix than in the septal cartilage, resulting in clustering of chondrocytes, some of which are in direct contact with adjacent connective tissues. In one primate (Varecia spp.) and both non-primates, the PNC has a perichondrium at birth. In older, infant Varecia and Rousettus, the perichondrium of the PNC is absent, and PNC fragmentation at its posterior pole has occurred in the former. Loss of the perichondrium for the PNC appears to precede resorption of the posterior end of the nasal capsule. These results suggest that the consolidation of the basicranial and facial skeletons happens ontogenetically earlier in primates than other mammals. We hypothesize that early loss of cartilage at the sphenoethmoidal articulation limits chondral mechanisms for nasal complexity, such as interstitial expansion or endochondral ossification.

Anatomy of the paranasal sinuses of the common marmoset (Callithrix jacchus Linnaeus, 1758) and radiographic positioning for diagnosis of these structures

BACKGROUND

Callithrix jacchus, it is a species highly targeted by wild animal traffickers and, when apprehended, they need veterinary care. For safe therapeutic procedures, knowledge of anatomy is essential, as well as for diagnostic by imaging, good radiographic positioning is essential.

METHODS

The anatomy of the paranasal sinuses and the radiographic projections was described using 10 carcasses of common marmosets. Radiographs were taken in two panoramic views of their head: profile and frontal-naso. For the anatomical study, paramedian and transverse macroscopic sections and microscopic transverse sections were performed.

RESULTS

On the radiographs, it was possible to identify the frontal recess and maxillary sinuses in profile and frontal-naso incidences. In the anatomical study, the frontal recess and maxillary, sphenoid and ethmoid paranasal sinuses were identified.

CONCLUSIONS

The ethmoidal sinus could be observed only microscopically and the sphenoidal sinus difficult to see on the radiography due to the overlapping adjoining structures.

Fissures, folds, and scrolls: The ontogenetic basis for complexity of the nasal cavity in a fruit bat (Rousettus leschenaultii)

Mammalian nasal capsule development has been described in only a few cross-sectional age series, rendering it difficult to infer developmental mechanisms that influence adult morphology. Here we examined a sample of Leschenault's rousette fruit bats (Rousettus leschenaultii) ranging in age from embryonic to adult (n = 13). We examined serially sectioned coronal histological specimens and used micro-computed tomography scans to visualize morphology in two older specimens. We found that the development of the nasal capsule in Rousettus proceeds similarly to many previously described mammals, following a general theme in which the central (i.e., septal) region matures into capsular cartilage before peripheral regions, and rostral parts of the septum and paries nasi mature before caudal parts. The ossification of turbinals also generally follows a rostral to the caudal pattern. Our results suggest discrete mechanisms for increasing complexity of the nasal capsule, some of which are restricted to the late embryonic and early fetal timeframe, including fissuration and mesenchymal proliferation. During fetal and early postnatal ontogeny, appositional and interstitial chondral growth of cartilage modifies the capsular template. Postnatally, appositional bone growth and pneumatization render greater complexity to individual structures and spaces. Future studies that focus on the relative contribution of each mechanism during development may draw critical inferences how nasal morphology is reflective of, or deviates from the original fetal template. A comparison of other chiropterans to nasal development in Rousettus could reveal phylogenetic patterns (whether ancestral or derived) or the developmental basis for specializations relating to respiration, olfaction, or laryngeal echolocation.

Developmental abnormalities of the otic capsule and inner ear following application of prolyl-hydroxylase inhibitors in chick embryos

BACKGROUND

Naturally hypoxic conditions in amniote embryos play important roles in normal development. We previously showed that a hypoxic condition is required to produce a sufficient amount of neural crest cells (NCCs) during embryogenesis and that promoting a hypoxic response by prolyl-hydroxylase (PHD) inhibitors increases NCCs. Given that PHD inhibitors are considered as a potential treatment for anemia and ischemic diseases, we investigated the phenotypic effect of PHD inhibitors on embryonic development.

METHODS

Chick embryos were administered with PHD inhibitors prior to the induction of NCCs on day 1.5. Three main events relating to hypoxia, NCCs induction, vasculogenesis and chondrogenesis, were examined.

RESULTS

PHD inhibitors caused an increase of Sox10-positive NCCs in vivo. Vasculogenesis was promoted temporarily, although rapid vasculogenesis diminished the effect by day 5 in cephalic and pharyngeal regions. Studies on chondrogenesis at day 7 showed advanced development of the otic capsule, a cartilaginous structure encapsulating the inner ear. Analysis by X-ray micro-computed-tomography (μCT) revealed smaller otic capsule, suggesting premature differentiation. This in turn, deformed the developing semicircular canals within it. Other skeletal structures such as the palate and jaw were unaffected. The localized effect on the otic capsule was considered a result of the multiple effects from the hypoxic responses, increased NCCs and promoted chondrogenesis.

CONCLUSION

Given the wide range of clinical applications being considered for PHD inhibitors, this study provides crucial information to caution and guide use of PHD inhibitors when treating women of childbearing age.

Beyond the sniffer: frontal sinuses in Carnivora

Paranasal sinuses are some of the most poorly understood features of mammalian cranial anatomy. They are highly variable in presence and form among species, but their function is not well understood. The best-supported explanations for the function of sinuses is that they opportunistically fill mechanically unnecessary space, but that in some cases, sinuses in combination with the configuration of the frontal bone may improve skull performance by increasing skull strength and dissipating stresses more evenly. We used CT technology to investigate patterns in frontal sinus size and shape disparity among three families of carnivores: Canidae, Felidae, and Hyaenidae. We provide some of the first quantitative data on sinus morphology for these three families, and employ a novel method to quantify the relationship between three-dimensional sinus shape and skull shape. As expected, frontal sinus size and shape were more strongly correlated with frontal bone size and shape than with the morphology of the skull as a whole. However, sinus morphology was also related to allometric differences among families that are linked to biomechanical function. Our results support the hypothesis that frontal sinuses most often opportunistically fill space that is mechanically unnecessary, and they can facilitate cranial shape changes that reduce stress during feeding. Moreover, we suggest that the ability to form frontal sinuses allows species to modify skull function without compromising the performance of more functionally constrained regions such as the nasal chamber (heat/water conservation, olfaction), and braincase (housing the brain and sensory structures).

The shrinking anthropoid nose, the human vomeronasal organ, and the language of anatomical reduction

Humans and most of our closest extant relatives, the anthropoids, are notable for their reduced "snout." The striking reduction in facial projection is only a superficial similarity. All anthropoids, including those with long faces (e.g., baboons), have lost numerous internal projections (turbinals) and spaces (recesses). In sum, this equates to the loss of certain regions of olfactory mucosa in anthropoids. In addition, an accessory olfactory organ, the vomeronasal organ, is non-functional or even absent in all catarrhine primates (humans, apes, monkeys). In this commentary, we revisit the concept of anatomical reductions as it pertains to the anthropoid nasal region. Certain nasal structures and spaces in anthropoids exhibit well-known attributes of other known vestiges, such as variability in form or number. The cupular recess (a vestige of the olfactory recess) and some rudimentary ethmoturbinals constitute reduced structures that presumably were fully functional in our ancestors. Humans and at least some apes retain a vestige that is bereft of chemosensory function (while in catarrhine monkeys it is completely absent). However, the function of the vomeronasal system also includes prenatal roles, which may be common to most or all mammals. Notably, neurons migrate to the brain along vomeronasal and terminal nerve axons during embryogenesis. The time-specific role of the VNO raises the possibility that our concept of functional reduction is too static. The vomeronasal system of humans and other catarrhine primates appears to qualify as a "chronological" vestige, one which fulfills part of its function during ontogeny, and then becomes lost or vestigial.

Repeated loss of frontal sinuses in arctoid carnivorans

Many mammal skulls contain air spaces inside the bones surrounding the nasal chamber including the frontal, maxilla, ethmoid, and sphenoid, all of which are called paranasal sinuses. Within the Carnivora, frontal sinuses are usually present, but vary widely in size and shape. The causes of this variation are unclear, although there are some functional associations, such as a correlation between expanded frontal sinuses and a durophagous diet in some species (e.g., hyenas) or between absent sinuses and semiaquatic lifestyle (e.g., pinnipeds). To better understand disparity in frontal sinus morphology within Carnivora, we quantified frontal sinus size in relationship to skull size and shape in 23 species within Arctoidea, a clade that is ecologically diverse including three independent invasions of aquatic habitats, by bears, otters, and pinnipeds, respectively. Our sampled species range in behavior from terrestrial (rarely or never forage in water), to semiterrestrial (forage in water and on land), to semiaquatic (forage only in water). Results show that sinuses are either lost or reduced in both semiterrestrial and semiaquatic species, and that sinus size is related to skull size and shape. Among terrestrial species, frontal sinus size was positively allometric overall, but several terrestrial species completely lacked sinuses, including two fossorial badgers, the kinkajou (a nocturnal, arboreal frugivore), and several species with small body size, indicating that factors other than aquatic habits, such as space limitations due to constraints on skull size and shape, can limit sinus size and presence.

Mediation of muscular control of rhinarial motility in rats by the nasal cartilaginous skeleton

The rhinarium is the rostral-most area of the snout that surrounds the nostrils, and is hairless in most mammals. In rodents, it participates in coordinated behaviors, active tactile sensing, and active olfactory sensing. In rats, the rhinarium is firmly connected to the nasal cartilages, and its motility is determined by movements of the rostral end of the nasal cartilaginous skeleton (NCS). Here, we demonstrate the nature of different cartilaginous regions that form the rhinarium and the nasofacial muscles that deform these regions during movements of the NCS. These muscles, together with the dorsal nasal cartilage that is described here, function as a rhinarial motor plant.

Microanatomical variation of the nasal capsular cartilage in newborn primates

The breakdown of nasal capsule cartilage precedes secondary pneumatic expansion of the paranasal sinuses. Recent work indicates the nasal capsule of monkeys undergoes different ontogenetic transformations regionally (i.e., ossification, persistence as cartilage, or resorption). This study assesses nasal capsule morphology at the perinatal age in a taxonomically broad sample of non-human primates. Using traditional histochemical methods, osteopontin immunohistochemistry and tartrate-resistant acid phosphatase procedure, the cartilage of the lateral nasal wall (LNC) was studied. At birth, matrix properties differ between portions of the LNC that ultimately form elements of the ethmoid bone and regions of the LNC that have no postnatal (descendant) structure. The extent of cartilage that remains in the paranasal parts of the LNC varies among species. It is fragmented in species with the greatest extent of maxillary and/or frontal pneumatic expansion. Conversely, greater continuity of the LNC is noted in newborns of species that lack maxillary and/or frontal sinuses as adults. Chondroclasts occur adjacent to elements of the ethmoid bone, along the margin of the nasal tectum, and/or along islands of cartilage that bear no signs of ossification. Chondroclasts are prevalent along remnants of the paranasal LNC in tamarin species (Leontopithecus, Saguinus), which have extensive frontal and maxillary bone pneumatization. Taken together, the morphological observations indicate that the localized loss of cartilage might be considered a critical event at the onset of secondary pneumatization, facilitated by rapid recruitment of chondro-/osteoclasts, possibly occurring simultaneously in cartilage and bone.

The paranasal sinuses: the last frontier in craniofacial biology

This special issue of the Anatomical Record explores the presence and diversity of paranasal sinuses in distinct vertebrate groups. The following topics are addressed in particular: dinosaur physiology; development; physiology; adaptation; imaging; and primate systematics. A variety of approaches and techniques are used to examine and characterize the diversity of paranasal sinus pneumatization in a wide spectrum of vertebrates. These range from dissection to histology, from plain X-rays to computer tomography, from comparative anatomy to natural experimental settings, from mathematical computation to computer model simulation, and 2D to 3D reconstructions. The articles in this issue are a combination of literature review and new, hypothesis-driven anatomical research that highlights the complexities of paranasal sinus growth and development; ontogenetic and disease processes; physiology; paleontology; primate systematics; and human evolution. The issue incorporates a wide variety of vertebrates, encompassing a period of over 65 million years, in an effort to offer insight into the diversity of the paranasal sinus complexes through time and space, and thereby providing a greater understanding and appreciation of these special spaces within the cranium.