Embryogenesis of the Uropygial Glands in the Laysan Albatross (Phoebastria immutabilis (Rothschild, 1893): Procellariiformes).

An avian uropygial gland is located on the mid-dorsum of the tail, and is the only external gland found in birds. Most studies have focused on the function, gross anatomy and chemical nature of this gland, with little research on its ontogeny. The purpose of this study was to examine the development of this gland in a series of Laysan Albatross (Phoebastria immutabilis) embryos. Specimens were examined anatomically and histologically. It was found that grooves preceded glandular development by many stages. The embryogenesis of the uropygial gland was divided into 6 phases: preinception, groove inception, mesodermal separation, migrating mesodermal cells, oval shaped "depressions", constriction and finally glandular inception. No other gland is known to develop similarly, though there may be parallels with femoral gland development. In comparison to other bird species, the length of the development period in the Albatross, as well as other compounding factors, make it difficult to determine the significance of these observations. The development of a mesodermal band, soon to be a connective tissue capsule, is more complex than originally described in ducks. Thus, the unique nature of this gland is established, but the significance of the observations required further studies into uropygial gland development. Anat Rec, 300:1420-1428, 2017. © 2017 Wiley Periodicals, Inc.

Transforming Growth Factor-ß3 Therapy Delays Postoperative Reossification and Improves Craniofacial Growth in Craniosynostotic Rabbits.

Postoperative reossification is a common clinical correlate following surgery. It has been suggested that an underexpression of transforming growth factor-ß3 (TGF-ß3) may be related to craniosynostosis and postoperative reossification. Adding TGF-ß3 may delay reossification and improve postoperative growth. The present study was designed to test this hypothesis. Thirty 10-day-old New Zealand white rabbits with hereditary coronal suture synostosis were divided into three groups: (1) suturectomy controls (n = 14), (2) suturectomy treated with bovine serum albumin (n = 8), and (3) suturectomy treated with TGF-ß3 protein (n = 8). At 10 days of age, a 3-mm × 15-mm coronal suturectomy was performed, and serial three-dimensional (3D) computed tomography (CT) scans and cephalographs were taken at 10, 25, 42, and 84 days of age. Calvaria were harvested at 84 days of age for histomorphometric analysis. Mean differences were analyzed using a group by age analysis of variance. Analysis of the 3D CT scan data revealed that sites treated with TGF-ß3 had significantly (P < .05) greater defect areas and significantly (P < .05) greater intracranial volumes through 84 days of age compared with controls. Histomorphometry showed that sites treated with TGF-ß3 had patent suturectomy sites and significantly (P < .001) less new bone in the suturectomy site compared with controls. Serial radiograph data revealed significant (P < .05) differences in craniofacial growth from 25 to 84 days in TGF-ß3-treated rabbits compared with controls. Data show that TGF-ß3 administration delayed reossification and improved craniofacial growth in this rabbit model. These findings also suggest that this molecular-based therapy may have potential clinical use.

Quality standards for DNA sequence variation databases to improve clinical management under development in Australia.

Despite the routine nature of comparing sequence variations identified during clinical testing to database records, few databases meet quality requirements for clinical diagnostics. To address this issue, The Royal College of Pathologists of Australasia (RCPA) in collaboration with the Human Genetics Society of Australasia (HGSA), and the Human Variome Project (HVP) is developing standards for DNA sequence variation databases intended for use in the Australian clinical environment. The outputs of this project will be promoted to other health systems and accreditation bodies by the Human Variome Project to support the development of similar frameworks in other jurisdictions.

Development of the Lacrimal Apparatus in the Rabbit (Oryctolagus cuniculus) and Its Potential Role as an Animal Model for Humans.

Rabbits have been proposed as a model organism for the human lacrimal apparatus (LA), including the nasolacrimal duct (NLD), based principally on comparative studies of adult morphology; however, little is known about its development. The NLD first appears as an incomplete primordium in the subcutaneous region of the primordial eyelid and subsequently elongates to reach the naris. One posterior and three anterior orbital glands are present fetally although one of the anterior glands is soon lost. The NLD follows a tortuous path and passes through a bony canal consisting of lacrimal, maxilla, and maxilloturbinal bones at different regions. Although early developmental similarities exist to haplorhine primates, the narial opening of the NLD resembles strepsirrhines. This distinction, along with the ductal and glandular differences at the orbital end of the NLD, indicates that rabbits may be a poor model for LA drainage in primates, specifically humans.

Relationship of premaxillary bone and its sutures to deciduous dentition in nonhuman primates.

OBJECTIVE: The relationship of the human premaxillary bone (Pmx) to neighboring craniofacial structures is clouded by its embryonic union with the maxillary bone proper. Only humans among all primates have such early fusion of the premaxillomaxillary suture (PS). This study surveyed the relationship of the PS to the upper deciduous dentition in nonhuman primates, and describes the distribution of bone cells along the osseous margins of the Pmx. METHOD: Twenty-eight subadult primates were studied using gross, CT, and histologic observations. Location of the anterior deciduous dentition relative to the PS was assessed. In sections of selected specimens, observations of bone cells on the osseous boundaries of the Pmx were made. Osteopontin (OPN) immunohistochemistry was used to isolate osteoclastic binding sites along the Pmx boundaries. RESULTS: The PS was consistently found between deciduous incisor and canine in strepsirrhines of all ages, whereas the suture passed variably closer to the incisor or canine in haplorhines. In all species, the anterior part of the Pmx was nonarticulating and mostly osteoblastic, except for osteoclastic margins adjacent to dentition and the nasal fossa. Superolaterally, the osteogenic fronts of the PS were osteoblastic, while more inferiorly, at the level of the deciduous canine, the PS was often osteoclastic. Results from OPN immunohistochemistry support the findings on bone cell distribution. CONCLUSION: Bone cell distribution patterns in perinatal nonhuman primates resemble those described for the prenatal human Pmx, suggesting that differences among species relate to magnitude rather than the pattern of osteogenesis.

General mutation databases: analysis and review.

Databases of mutations causing Mendelian disease play a crucial role in research, diagnostic and genetic health care and can play a role in life and death decisions. These databases are thus heavily used, but only gene or locus specific databases have been previously reviewed for completeness, accuracy, currency and utility. We have performed a review of the various general mutation databases that derive their data from the published literature and locus specific databases. Only two--the Human Gene Mutation Database (HGMD) and Online Mendelian Inheritance in Man (OMIM)--had useful numbers of mutations. Comparison of a number of characteristics of these databases indicated substantial inconsistencies between the two databases that included absent genes and missing mutations. This situation strengthens the case for gene specific curation of mutations and the need for an overall plan for collection, curation, storage and release of mutation data.

Comparison of hind limb muscle mass in neonate and adult prosimian primates.

Little ontogenetic data exist to indicate whether muscular organization of neonates reflects adult locomotion (e.g., leaping) or infant activities like clinging or the initial quadrupedal phase of locomotion that typifies most infant primates. In the present study, five species of primates with contrasting modes of locomotion were examined. Twenty-eight preserved neonatal and adult cadavers were studied by careful dissection of the hip, thigh, and leg muscles. Wet weights were taken of limb muscles after removal, and the muscles were combined into major functional groups (e.g., flexors, extensors) of each limb segment. Results demonstrate that the distribution of muscle mass within the thigh and within the leg are similar between neonates and adults for all species, with major groups varying by 5% or less in all but two age comparisons. Crural indices of the neonates are nearly identical to those of the adults, but leg/thigh muscle mass ratios were higher in the neonates. Species vary greatly in the percentage of adult limb segment muscle mass present in neonates, with Tarsius syrichta having the greatest percentage for all segments and two lemurids showing the least. These results primarily track differences in relative body mass at birth rather than developmental differences. The adaptive distribution of muscle, as discussed previously for adult prosimians, appears to be established at birth. Neonates of leaping species already have much larger quadriceps muscles than quadrupeds. Differences between large- and small-bodied leapers (e.g., pronounced superficial plantarflexor masses in tarsiers and pronounced deep plantarflexor masses in sifakas) also are present in neonates. Ratios of muscle mass over body mass are smaller in all neonates than in their adult counterparts, suggesting that the neonates are relatively poorly muscled, and that muscle mass must increase with positive allometry during growth.

Alligator tears: a reevaluation of the lacrimal apparatus of the crocodilians.

The Harderian gland is a poorly understood anterior ocular gland that occurs in most terrestrial vertebrates. Numerous extraorbital functions have been ascribed to the Harderian gland, principally based on its association with the nasolacrimal duct. Few studies have centered on archosaurs and the majority of those available focused solely on the Harderian gland of birds. Little is known about the lacrimal apparatus of the crocodilians. We examined the lacrimal apparatus of several specimens of Alligator mississippiensis anatomically, histologically, and histochemically and studied the embryogenesis of this system. The nasolacrimal duct possesses a distal secretory area, which is more convoluted than that of typical mammals or lepidosaurs. The alligator Harderian gland possesses a unique combination of characteristics found in lepidosaurs, birds, and mammals. Like that of both mammals and lepidosaurs, it is a large, tuboloacinar gland that appears to secrete both mucoprotein and lipids. However, the presence of blood vessels and immune cells is reminiscent of that of the avian Harderian gland. The immunogenesis of the alligator Harderian gland appears to be tied to the development of the vascular system. The presence of a distinct palpebral gland in the anterior aspect of the ventral eyelid is a feature unique to alligators. Based on position, this gland does not appear to be homologous to the anterior lacrimal gland of lepidosaurs. Lymphatic aggregations were also found in the palpebral gland. The presence of interstitial immune cells in the orbital glands of alligators suggests that the alligator lacrimal apparatus, like that of birds, may play a role in the head-associated lymphatic tissue system.

Histochemical localization of enzymes and lipids in the ovary of a vespertilionid bat, Scotophilus heathi, during the reproductive cycle.

The present study describes seasonal changes in delta5 3beta hydroxysteroid dehydrogenase (3beta-HSD), glusose-6 phosphates dehydrogenase (G-6-PD), and lipids in the ovary of a vespertilionid bat, Scotophilus heathi. Total lipids and 3beta-HSD activity are restricted to thecal and interstitial cells of the ovary. The total lipids, 3beta-HSD, and G-6-PD significantly increase during recrudescence, and remain high during winter dormancy and breeding as compared to the other reproductive phases. High incidence of lipids and enzyme activity in interstitial cells during the breeding period and at the time of ovulation clearly suggests that these cells are actively involved in steroidogenesis. A decline in enzymes and lipid activity during winter dormancy, which correlates with the declining levels of steroidogenesis, might be the factors responsible for prolonged survival of the Graafian follicle in the ovary of S. heathi.

Histochemical localization of enzymes and lipids in the ovary of a vespertilionid bat, Scotophilus heathi, during the reproductive cycle

O presente estudo descreve as mudanças sazonais na D5 3b hidroxiesteróide desidrogenase (3b-HSD), glicose-6 fosfato desidrogenase (G-6-PD), e lipídios no ovário de um morcego vespertilionidae, Scotophilus heathi. As atividades totais dos lipídios e do 3b-HSD estão restritas às células tecais e intersticiais do ovário. Os lipídios, 3b-HSD e G-6-PD totais, aumentaram significantemente durante a recrudescência, e permaneceram elevados durante a dormência de inverno e o período de acasalamento, quando comparados a outras fases reprodutivas. A alta incidência de atividade de lipídios e enzimas nas células intersticiais durante o período de acasalamento e durante o período de ovulação sugere claramente que estas células estão ativamente envolvidas na esteroidogênese. O declínio da atividade dos lipídios e enzimas durante a dormência de inverno, o qual se correlaciona com os níveis decrescentes da esteroidogênese, podem ser o fator responsável pela longa sobrevivência do folículo de De Graaf no ovário do S. heathi.

Observations on the vomeronasal organ of prenatal Tarsius bancanus borneanus with implications for ancestral morphology.

Adult primates have at least five known phenotypes of vomeronasal organ (VNO), ranging from the typical morphology seen in most other mammals to complete absence. With such morphological disparity, the phylogenetic value and any inferences on ancestral VNO morphology of the primate VNO are left uncertain. The present study investigated the VNO of embryonic and fetal Tarsius bancanus borneanus (n = 4) in comparison with prenatal specimens from four other species of primates in an effort to clarify adult morphological variations. In all except one of the fetal primates, the VNO communicated to the nasopalatine duct. One exception occurred in the largest fetal Tarsius (25 mm crown-rump length), in which the VNO communicated with the nasal cavity alone. The vomeronasal neuroepithelium was well differentiated from a thinner, non-sensory epithelium in all Tarsius and New World monkeys studied, as well as late embryonic and fetal Microcebus myoxinus. In anterior sections, this neuroepithelium was found in a more superior location in Tarsius and New World monkeys compared with Microcebus myoxinus. In all primates, masses of cell bodies were found superior to the VNO, intermingled with nerve fibres. These morphologically resembled luteinizing hormone-releasing hormone neurons described in other mammals, including humans, suggesting that a primitive association of these neurons with the VNO may exist in all primate taxa. The present study revealed that prenatal similarities exist in Tarsius and New World primates in VNO epithelial morphology. However, these are transient stages of morphology. If tarsiers and anthropoids do represent a clade (Haplorhini), then the atypical morphology seen in adult tarsiers and New World monkeys probably represents the adult VNO morphology of a haplorhine common ancestor.

Size of the vomeronasal organ in wild Microtus with different mating strategies.

Most studies on mammalian vomeronasal organ (VNO) have been on laboratory-bred animals. Our present study examines the VNO in wild-caught meadow voles (Microtus pennsylvanicus: n=16) and prairie voles (M. ochrogaster: n=15). These species vary in their mating strategies and degree of parental care by males. M. ochrogaster exhibits pair bonding and more paternal care compared to M. pennsylvanicus, a promiscuous species. We hypothesize that sexual dimorphism will occur in the promiscuous species based on previous studies which suggest that those who exhibit more aggressive or masculine behavior have larger VNOs. Our results support our original finding that VNOs are not different in size in wild Microtus spp. that vary in male parental tendencies. However, the present study also indicates that M. pennsylvanicus, the species exhibiting more disparate parental tendencies, exhibited larger VNOs in females than males. This is the reverse of previous findings on rats, and we hypothesize that this difference may be due to mate selectivity and/or maternal aggression.

Cranial base changes following coronal suturectomy in craniosynostotic rabbits.

It has been suggested that surgical release of synostosed sutures may ameliorate various cranial base abnormalities in craniosynostotic patients. The present study was designed to test this hypothesis in a rabbit model with familial coronal suture synostosis (CSS). Data were collected from 56 New Zealand White rabbits: 32 unaffected controls, 11 with unoperated CSS, and 13 with CSS released by suturectomy performed at 25 days of age. Serial radiographs were taken at 25, 42 and 84 days. Linear, angular and triangular shape cranial base measurements were compared using ANOVA and tensor biometric analysis. Results revealed that at 84 days, both groups of CSS rabbits had significantly (p < 0.05) different anterior and total cranial base lengths, flatter cranial base angles, and dysmorphic anterior cranial base shapes when compared with normals. Significant (p < 0.05) differences were noted only for palatal and cranial base angles and posterior cranial base shape between CSS rabbits with and without suturectomy. However, significant (p < 0.05) changes were noted between pre- and postoperative measurements in posterior and total cranial base lengths and anterior and posterior cranial base shapes in CSS rabbits with suturectomy. Results revealed that surgical release of synostosed coronal sutures through suturectomy did not normalize cranial base growth patterns in CSS rabbits. These findings may be explained by the relatively late age of surgical release or suturectomy site resynostosis with continued dysmorphic cranial base growth. Alternatively, cranial base abnormalities seen in CSS rabbits may be early primary malformations, not secondary deformations amenable to surgical modification.

Anatomical position of the vomeronasal organ in postnatal humans.

In the last decade or so, there has been a renewed interest in the adult human vomeronasal organ (VNO). Studies have yielded sometimes disparate findings about the microscopic structure of the organ and its supporting tissues. Such varied descriptions may be due to examination of different regions of the VNO, individual variation of VNOs among humans, or the presence of multiple, non-homologous structures that bear false resemblance to the human VNO. A histological description of the spatial relationship of the human VNO to other nasal septal elements is needed to ensure that all investigators are examining the same regions and homologous structures. Histologically sectioned nasal septa from, 22 human cadavers (1 child, 21 adults) were examined grossly and by light microscopy for the VNO. Using histological sections, the position of the VNO relative to other structures was estimated. Sections containing the VNO were retrospectively compared to scaled photographic slides of the unsectioned septa to identify surface landmarks. Human VNOs varied in anteroposterior and superoinferior position relative to the anterior nasal spine and the nasal cavity floor. In the absence of a visible duct opening, the only reliable surface marker, no consistent surface markings were noted for precise location. VNOs were frequently found superior to swellings associated with the paraseptal and/or septal cartilages. Such findings demonstrate that the human VNO is positionally variable, which may have contributed to previous conflicting findings on presence versus absence. Furthermore, our findings support recent suggestions that the VNO may have been misidentified by some investigators, and that its opening can be easily confused with other structures.

Cranial base growth and morphology in second-trimester normal human fetuses and fetuses with cleft lip.

OBJECTIVE: The present radiographic study describes the size and shape of the cranial base from the sagittal aspect for a sample of 77 second-trimester "normal" control fetuses (n = 61) and fetuses (n = 16) exhibiting isolated, unilateral clefts of the lip (CL), ranging in fertilization age from 10 to 22 weeks. METHODS: Fetuses were placed in a cephalostat, and standardized, lateral head radiographs were taken. The radiographs were traced, and 15 cephalometric landmarks were identified and digitized for analysis. Growth curves for cranial base lengths, angles, and areas were compared between control and CL groups. Also, cranial base triangles were constructed and shape comparisons were made using tensor biometric analysis. RESULTS: No significant differences (p >.05) in regression line slopes were noted for any comparisons between the control and CL samples. Tensor biometric analysis also revealed no significant differences in the shapes of various cranial base triangles between the control and CL samples. CONCLUSION: This report presents second-trimester baseline growth curves for various cranial base components in CL human fetal specimens, and these data suggest that CL fetuses may also be used as an appropriate control sample for prenatal growth comparison studies of cleft lip and palate and cleft palate.

Endocranial vascular patterns in a familial rabbit model of coronal suture synostosis.

OBJECTIVE: The present study investigates the potential relationship between craniosynostosis and any changes in endocranial vasculature. The hypothesis that crania from rabbits with familial, nonsyndromic coronal suture synostosis and crania from rabbits with experimental immobilization of the coronal suture are associated with altered form of the middle meningeal vessels and dural venous sinuses is tested. DESIGN: Silicone rubber endocasts from 14 adult New Zealand white rabbits (Oryctolagus cuniculus) with familial nonsyndromic coronal suture synostosis (five with bilateral coronal suture synostosis and nine with unilateral coronal suture synostosis) were made to assess middle meningeal vessel and dural venous sinus form. For comparative purposes, endocasts were made from 25 rabbits with normal, patent coronal sutures and 10 rabbits with experimental immobilization of the coronal suture. Impressions of the dural venous sinuses were assessed for depth and width. The area of the confluens of sinuses was also assessed. Impressions of the middle meningeal vessels were assessed for depth, width, and degree of convolution. For width of the dural venous sinuses and area of the confluens of sinuses, comparisons among groups were made with a one-way analysis of variance (ANOVA). For depth of the dural venous sinuses and impressions of the middle meningeal vessels, comparisons among groups were made using a Kruskal-Wallis one-way ANOVA. RESULTS: Crania with familial coronal suture synostosis had significantly (p <.05) reduced posterior dural venous sinus dimensions when compared with both crania from rabbits with experimental immobilization of the coronal suture and rabbits with normal coronal sutures. Crania with both coronal suture synostosis and experimental immobilization had significant increases in dimensions of the middle meningeal vessels relative to normal crania. In addition, casts from rabbits with unicoronal suture synostosis showed marked asymmetry in the dural venous sinuses. CONCLUSIONS: These results support the hypothesis that craniosynostosis is associated with alterations in endocranial vasculature. These changes are most likely a secondary response to synostosis rather than a causal factor and may reflect increased intracranial pressure, decreased intracranial volume, and local accumulations and reductions of cerebrospinal fluid in the posterior region of the skull and immediately deep to the coronal suture.

The human vomeronasal organ. III. Postnatal development from infancy to the ninth decade.

The large literature on the human vomeronasal organ (VNO) offers little consensus as to its persistence in the adult. We have already documented the existence of the VNO from embryonic day 33 through the neonatal stages. This has now been extended to human adults: 27 cadaver nasal septa, aged 2-86 y, were either dissected or decalcified, serially sectioned, stained and examined. The consistent presence of the VNO is reported as a homologue, in the form of a duct-like structure on the nasal septum at all ages. Also reported are size variability, pronounced bilateral asymmetry, a nonchemosensory pseudostratified ciliated epithelium with considerable structural variation and generally without medial-lateral differentiation, nasal septal glands opening into the VNO lumen, a lack of correlation between postnatal age and VNO size, visualisation of the human VNO with certainty by histological means alone, and a minute opening as its only visible surface feature. The human VNO is a discrete structure that should not be confused with the nasopalatine fossa, the septal mucosal pits or VNO openings.

Reappraisal of the vomeronasal system of catarrhine primates: ontogeny, morphology, functionality, and persisting questions.

The vomeronasal organ (VNO) is a chemosensory organ that functions in sociosexual communication in many vertebrates. In strepsirhine primates and New World monkeys, the bilateral VNOs are traditionally understood to exist as a well-developed chemosensory epithelial unit. In contrast, the VNOs of catarrhine primates are thought to be absent or exist only as reduced epithelial tubes of uncertain function. However, the VNO of New World monkeys shows substantial variation in the extent of sensory epithelium. Recent findings that the chimpanzee (Pan troglodytes) possesses a VNO similar to humans suggest the variability of the VNO among haplorhine primates may be more extensive than previously thought, and perhaps more at par with that observed in chiropterans. The atypical histologic structure and location of the human/chimpanzee VNO suggest accessory glandular secretion and transport functions. Other catarrhine primates (e.g., Macaca spp.), may truly be characterized by VNO absence. Unique aspects of facial growth and development in catarrhine primates may influence the position or even presence of the VNO in adults. These recent findings demonstrate that previous investigations on some catarrhine primates may have missed the VNO and underestimated the extent of variability. As an understanding of this variation increases, our view of VNO functionality and associated terminology is changing. Further investigations are needed to consider phylogenetic implications of VNO variability and the association of craniofacial form and VNO anatomic position in primates.

Correction of coronal suture synostosis using suture and dura mater allografts in rabbits with familial craniosynostosis.

OBJECTIVE: Resynostosis following surgical correction of craniosynostosis is a common clinical correlate. Recent studies suggest that the dura mater is necessary to maintain suture patency. It has also been hypothesized that dura mater from synostotic individuals may provide aberrant biochemical signals to the osteogenic fronts of the calvaria, which result in premature suture fusion and subsequent resynostosis following surgery. This study was designed to test this hypothesis by surgically manipulating the coronal suture and dura mater in rabbits with familial craniosynostosis to prevent postsurgical resynostosis. DESIGN: Craniofacial growth and histomorphometric data were collected from 129 rabbits: 72 normal controls and 57 rabbits with bilateral coronal suture synostosis (15 unoperated on controls; 13 surgical controls; 9 dura mater transplant only; 10 suture transplant only; and 10 suture and dura mater transplant). At 10 days of age, all rabbits had radiopaque amalgam markers placed on either side of the coronal, frontonasal, and anterior lambdoidal sutures. At 25 days of age, 42 synostosed rabbits had a 3 to 5-mm wide coronal suturectomy. Coronal sutures and/or underlying dura mater allografts were harvested from same-aged, wild-type, isohistogenic control rabbits and transplanted onto the dura mater of synostosed host rabbits. Serial radiographs were taken at 10, 25, 42, and 84 days of age, and the suturectomy sites were harvested at 84 days of age in 44 rabbits and serially sectioned for histomorphometric examination. RESULTS: Results revealed that cranial vault growth was significantly (p < .05) improved following surgical release of the fused coronal suture compared with synostosed rabbits who were not operated on but was still significantly different (p < .05) from that of normal control rabbits. By 84 days of age, significant (p < .05) differences were noted in calvarial suture marker separation, cranial vault shape indices, and cranial base angles between rabbits with and without dura mater allografts, probably as a result of resynostosis of the suturectomy site or suture-only allografts. Qualitative histological examination revealed that at 84 days of age rabbits with suture and dura allografts had patent coronal sutures, suture-only allografts had fused coronal sutures with extensive endosteal hyperostosis, dura mater-only allografts had some new bone in the suturectomy site that resembled rudimentary osteogenic fronts, and suturectomy controls had extensive endosteal bone formation and resynostosis of the suturectomy site. Significantly (p < .05) more bone was found in the suturectomy sites of rabbits without dura mater allografts compared with rabbits with dura mater allografts. CONCLUSIONS: Results support the initial hypothesis that normal dura mater allografts will maintain suture or suturectomy site patency and allow unrestricted craniofacial growth. However, it is still unclear whether the dura mater from normal rabbits was providing biochemical signals to the transplanted sutures or suturectomy sites or simply acting as a barrier to prevent abnormal biochemical signals from the dura mater of synostosed rabbits from reaching the calvaria. The clinical and therapeutic implications of these procedures are discussed.