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.

The effects of testosterone on craniosynostotic calvarial cells: a test of the gene/environmental model of craniofacial anomalies.

INTRODUCTION: The gene-environmental interaction model for craniofacial development proposes that if a genetic predisposition for an anomaly is coupled with an environmental factor that can exacerbate this predisposition, more severe phenotypes will result. Here, we utilize cells derived from our non-syndromic rabbit model of craniosynostosis to test the hypothesis that an insult, testosterone (TP) administration (exogenous source) will alter the osteogenic activity of these cells. DESIGN: Calvarial cells from wild-type (WT) (N=13) or craniosynostotic (CS) rabbits (N=11) were stimulated with TP, an androgen receptor blocker, flutamide, and combined treatments. Proliferation and differentiation assays were conducted after 7 days. anova and t-tests were used to determine differences in stimulation and cell type. RESULTS: The CS cells had significantly greater proliferation after TP administration compared to WT. There were no appreciable changes in differentiation after TP stimulation. Flutamide administration or combined TP and flutamide administration decreased both proliferation and differentiation for both cell types similarly. CONCLUSIONS: Testosterone exposure caused an increase in cell proliferation for CS osteoblast cells. However, a therapy targeted to mitigate this response (flutamide therapy) similarly affected CS and WT cells, suggesting that the administration of flutamide or TP in the presence of flutamide decreases osteogenesis of these cells. Thus, although our data support a mechanism of gene-environmental interaction, these results would not support a therapeutic intervention based on this interaction.

Oral Sciences PhD Program Enrollment, Graduates, and Placement: 1994 to 2016.

For decades, dental schools in the United States have endured a significant faculty shortage. Studies have determined that the top 2 sources of dental faculty are advanced education programs and private practice. Those who have completed both DDS and PhD training are considered prime candidates for dental faculty positions. However, there is no national database to track those trainees and no evidence to indicate that they entered academia upon graduation. The objective of this study was to assess outcomes of dental school-affiliated oral sciences PhD program enrollment, graduates, and placement between 1994 and 2016. Using the American Dental Association annual survey of advanced dental education programs not accredited by the Commission on Dental Accreditation and data obtained from 22 oral sciences PhD programs, we assessed student demographics, enrollment, graduation, and placement. Based on the data provided by program directors, the average new enrollment was 33, and graduation was 26 per year. A total of 605 graduated; 39 did not complete; and 168 were still in training. Among those 605 graduates, 211 were faculty in U.S. academic institutions, and 77 were faculty in foreign institutions. Given that vacant budgeted full-time faculty positions averaged 257 per year during this period, graduates from those oral sciences PhD programs who entered academia in the United States would have filled 9 (3.6%) vacant faculty positions per year. Therefore, PhD programs have consistently generated only a small pipeline of dental school faculty. Better mentoring to retain talent in academia is necessary. Stronger support and creative funding plans are essential to sustain the PhD program. Furthermore, the oral sciences PhD program database should be established and maintained by dental professional organizations to allow assessments of training models, trends of enrollment, graduation, and placement outcomes.

Craniofacial morphology in myostatin-deficient mice.

GDF-8 (myostatin) is a negative growth regulator of skeletal muscle, and myostatin-deficient mice are hypermuscular. Muscle size and force production are thought to influence growth of the craniofacial skeleton. To test this relationship, we compared masticatory muscle size and craniofacial dimensions in myostatin-deficient and wild-type CD-1 control mice. Myostatin-deficient mice had significantly (p < 0.01) greater body (by 18%) and masseter muscle weight (by 83%), compared with wild-type controls. Significant differences (p < 0.05) were noted for cranial vault length, maxillary length, mandibular body length, and mandibular shape index. Significant correlations were noted between masseter muscle weight and mandibular body length (r = 0.68; p < 0.01), cranial vault length (r = -0.57; p < 0.05), and the mandibular shape index (r = -0.56; p < 0.05). Masticatory hypermuscularity resulted in significantly altered craniofacial morphology, probably through altered biomechanical stress. These findings emphasize the important role that masticatory muscle function plays in the ontogeny of the cranial vault, the maxilla, and, most notably, the mandible.

The effects of guided tissue regeneration (GTR) on modified Le Fort I osteotomy healing in rabbits.

Osteogenesis following surgery depends on the osteoblasts at the wound site. Fibrous nonunions may be the result of differential and rapid migration of fibroblasts compared to osteoblasts into the wound. The present study was designed to test this hypothesis through the use of guided tissue regeneration (GTR) in a rabbit model. Bilateral, Le Fort I osteotomies (n=20) were produced in the maxillae of 10 New Zealand White rabbits. The segments were advanced 6mm and rigidly fixed using microplates and screws. One side was covered with a resorbable collagen membrane or left uncovered. Rabbits were followed for four weeks with radiographs and the maxillae were harvested for histology. Cephalometry revealed that membrane-covered defects had significantly (P<0.01) reduced defect area (by approximately 70%) compared to uncovered defects. Histologically, membrane-covered defects showed more organized osteogenesis and less fibrous tissue than uncovered defects. Histomorphometry revealed that membrane covered defects had significantly (P<0.05) reduced defect areas (by approximately 20%) compared to uncovered defects. While findings suggest that GTR can facilitate osseous wound healing in Le Fort I osteotomies, results also caution against relying exclusively on two-dimensional radiography to assess bony wound healing in lieu of three-dimensional imaging and evaluations.

Searching for the vomeronasal organ of adult humans: preliminary findings on location, structure, and size.

The adult human vomeronasal organ (VNO) has been the focus of numerous recent investigations, yet its developmental continuity from the human fetal VNO is poorly understood. The present study compared new data on the adult human "VNO" with previous findings on the fetal human VNO. Nasal septa were removed from twelve adult human cadavers and each specimen was histologically sectioned. Coronal sections were stained with hematoxylin-eosin and periodic acid-Schiff-hematoxylin. The sections were examined by light microscopy for the presence of VNOs and the anterior paraseptal cartilages (PC). VNOs were quantified using a computer reconstruction technique to obtain VNO length, volume, and vomeronasal epithelium (VNE) volume. Histologically, VNOs and PCs were identified in eleven specimens. VNOs had ciliated, pseudostratified columnar epithelium with goblet cells. Variations (e.g., multiple communications to the nasal cavity) were observed in several specimens. Quantification was possible for 16 right or left VNOs. Right or left VNOs ranged from 3.5 to 11.8 mm in length, from 1.8 to 33.8 x 10(-4)cc in volume, and from 2.7 to 18.1 x 10(-4)cc in VNE volume. Results indicated that the adult human VNO was similar in VNE morphology, lumen shape, and spatial relationships when compared to human fetal VNOs. By comparison with previous fetal VNO measures, mean VNO length, volume, and VNE volume were larger in adult humans. These results support previous suggestions that postnatal VNO growth occurs. Findings on location and spatial relationships of the adult VNO were similar to those seen in human fetuses, but critical questions remain regarding the ontogeny of the vomeronasal nerves and VNE.

Tuned aperture computed tomography to evaluate osseous healing.

Quantification of osseous healing is a challenging task, requiring expensive advanced imaging modalities. To improve diagnostic osseous imaging, we undertook this prospective study to explore the potential of Tuned Aperture Computed Tomography. Eighty defects in 20 rabbit mandibles, randomly carrying an osteoblast suspension or a polymer matrix or a combination thereof or no treatment, were imaged at 3, 6, 9, and 12 weeks post-surgery. TACT slices, iteratively restored TACT, and conventional digital radiographs were evaluated. Mean-gray-value distribution within regions of interest was correlated with histomorphometric data. Lesions treated with osteoblast/polymer-matrix delivery systems demonstrated the highest mean gray-value, while the diagnostic efficacy of TACT-IR was significantly better than that of other imaging modalities (p < 0.001). Thus, TACT is an accurate imaging modality for non-destructive quantification of osseous dynamics.

Rabbit calvarial wound healing by means of seeded Caprotite scaffolds.

Autologous bone is the most successful bone-grafting material; however, limited supply and donor site morbidity are problematic. Synthetic bone substitutes are effective, but healing is slow and unpredictable. Osseous wound healing may be enhanced if bone substitutes are combined with autologous bone marrow cells. To test this hypothesis, we created 40 calvarial defects in 20 12-week-old New Zealand White rabbits, divided into four groups: (1) unrepaired controls, (2) autologous bone grafts, (3) unseeded Caprotite (a polymer-ceramic composite) grafts, and (4) Caprotite grafts seeded with autologous bone marrow stromal cells. CT scans were obtained at 0, 6, and 12 weeks post-operatively, and defects were harvested for histology. Defects repaired with autologous bone had significantly (p < 0.05) more bone than the other three groups, although seeded Caprotite defects showed different wound-healing sequelae. Results suggest that seeded Caprotite scaffolds did not significantly enhance osseous defect healing compared with controls.

Development of plagiocephaly in rabbits with unicoronal synostosis.

Human unicoronal synostosis results in plagiocephaly of the cranial vault due to predictable compensatory growth patterns of the contralateral coronal, sagittal, and ipsilateral squamosal sutures. The present study describes the development of plagiocephaly and tests compensatory growth predictions in a naturally occurring rabbit model of uncorrected unicoronal synostosis. Cranial vault and sutural growth data were collected from serial x-ray films in 70 normal rabbits and 19 rabbits with congenital unicoronal synostosis from 1.5 to 18 weeks of age. One-way analysis of variance results revealed that rabbits with unicoronal synostosis had significant (p < 0.05) growth inhibition at both coronal sutures and the contralateral frontonasal suture and a significantly wider (p < 0.05) cranial vault compared to controls. Paired Student's t-tests between affected and unaffected sides of the vault in rabbits with synostosis revealed significant (p < 0.05) asymmetry, with ipsilateral coronal sutures growing less than contralateral ones. Gross qualitative examination of the adult brains revealed severe asymmetry and anteroposterior reduction on the ipsilateral side. These results demonstrate that this congenital rabbit model effectively simulates human cranial vault growth predictions from unicoronal synostosis and produces a plagiocephalic morphology.

The relationship between lip pressure following lip repair and craniofacial growth: an experimental study in beagles.

In the present study with beagles, various states of lip pressure (decreased and increased) following surgical creation of the lip and palatal defects and subsequent lip repair were found to be significantly related to craniofacial growth aberrations and disproportions. These aberrations are discussed in terms of an imbalanced functional skeletal-soft-tissue matrix. Significantly elevated lip pressure following lip repair in group III animals was found to be more detrimental to craniofacial growth than decreased lip pressure resulting from the surgical creation of a defect left unrepaired. Results of the study present, for the first time, documented evidence of a significant relationship between lip pressure following lip repair and craniofacial growth. Caution should be employed in extending these conclusions to the clinical setting, yet the findings underscore the need for well-controlled clinical studies designed to assess the influence of cleft lip repair on craniofacial growth.

Development of the orbicularis oris muscle in normal and cleft lip and palate human fetuses using three-dimensional computer reconstruction.

As part of an ongoing study of cleft lip and palate fetal morphology, normal and dysmorphic development of the human fetal orbicularis oris muscle was studied in a cross-sectional sample of 29 human fetuses (20 "normal" and 9 cleft lip and palate) ranging in age from 8 to 21 postmenstrual weeks. The specimens were embedded in celloidin and sectioned at 20 microns, and every tenth section was stained with hematoxylin and eosin. A computer reconstruction technique was applied to produce three-dimensional representations of the orbicularis oris muscle. The orbicularis oris muscle in the normal fetal sample with discernible lip fibers (N = 15) increased symmetrically in both fiber density and complexity from 12 to 21 weeks. Metrically, muscle volume and thickness growth curves were consistent with qualitative observations. In contrast, the unilateral cleft lip and palate fetal specimens with discernible lip fibers (N = 3) exhibited a 3.5-week delay in overall muscle development, asymmetrical fiber distribution, and abnormal fiber insertions. However, quantitatively, no significant (p greater than 0.05) differences were noted in orbicularis oris muscle thickness or volume between the normal and cleft lip and palate fetal specimens through 21 weeks. Findings suggest that orbicularis muscle deficiency, noted clinically in cleft lip and palate neonates, may be a result of perinatal functional dysmorphogenesis rather than congenital mesenchymal reduction or deficiency.

Pharmacologic manipulation of postoperative labial wound contraction and midfacial growth in rabbits.

Recent experimental work has suggested that increased lip pressure and scar contraction following lip repair with wide soft-tissue undermining may, in part, contribute to midfacial growth inhibition. The present study was designed to test this hypothesis through the application of pharmacologic agents reported to minimize scar contraction. Thirty-six 6-week-old rabbits were divided into six groups: unoperated controls, rabbits with surgically created defects left unrepaired (surgical controls), and four groups of rabbits with surgically created defects with lip repair and wide undermining on the maxillary surface. Animals with lip repair received either no injections or labial subcutaneous injections of distilled water (route-of-injection controls), normal saline, or papaverine hydrochloride for 2 weeks postoperatively. Rabbits with lip repair and saline or papaverine injections showed significantly (p less than 0.05) decreased lip pressure, relatively hypotonic orbicularis oris muscle EMG activity on the cleft lip side, and greater anteroposterior facial growth (assessed radiologically) from 2 to 24 weeks postoperatively compared with rabbits with lip repair and postoperatively compared with rabbits with lip repair and no injections or distilled water injections. Preliminary results suggest that wound contraction following lip repair and soft-tissue undermining may contribute to mid-facial growth inhibition, which may be reduced by pharmacologic manipulations in the rabbit model.

Lip pressure changes following lip repair in infants with unilateral clefts of the lip and palate.

The present study was designed to quantitatively assess lip pressure changes following cleft lip repair in infants with unilateral cleft lip, alveolus, and palate. Lip pressure measurements were taken using an electronic transducer system developed especially for this study. Lip pressure was monitored from 3 months (preoperatively) through 2 years of age in cleft and normal control children. Findings from the present study confirm the hypothesis that lip repair in infants with unilateral cleft lip and palate significantly increases lip pressure and that increased lip pressure remains significantly higher than in normal control children for the 2-year duration of the study. Thus increased lip pressure when the palate is unrepaired has to be considered as a factor modulating subsequent craniofacial growth.

Traction, prenatal development, and the labioseptopremaxillary region.

Twenty-nine human fetuses ranging in age from 8 to 22 weeks were coronally sectioned for gross light microscope analysis of the labioseptopremaxillary region. In "normal" fetuses from 8 to 15 weeks, the septopremaxillary ligament was present. The horizontal and oblique fibers of the orbicularis oris muscle were poorly developed initially and increased in density with age. The anterior nasal spine and the alveolar process of the maxillae were present and in the same coronal plane. From 15 to 22 weeks, the horizontal and oblique fibers were well developed and inserted into the perichondrium of both alar and nasal cartilages. The septopremaxillary ligament was thus obliterated or more difficult to define, and the anterior nasal spine was located anterior to the alveolar process. In the cleft fetuses from 8 to 15 weeks, the nasal septum was absent or horizontally rotated. No septopremaxillary ligament or orbicularis oris fibers were noted, and the anterior nasal spine was not distinguishable. From weeks 15 to 20, the fibers of the orbicularis oris muscle were poorly differentiated, inserting asymmetrically into the perichondrium of the lateral alar cartilage on the noncleft side, the septopremaxillary ligament was absent, and the anterior nasal spine and the premaxillae were in the same coronal plane. These results suggest that the midfacial deficiencies seen in some cleft patients might have an origin in prenatal dysmorphology.

Internal calvarial bone distraction in rabbits with experimental coronal suture immobilization: effects of overdistraction.

This study was designed to assess the effects of overdistraction of an experimentally immobilized coronal suture using an internal appliance on craniofacial growth in rabbits. Fifty-three, 1.5-week-old rabbits were used. Markers were placed on either side of the calvarial sutures. Thirty-nine rabbits had bilateral coronal suture immobilization using methyl methacrylate; 14 rabbits served as normal controls. At 6 weeks of age, the 39 immobilized rabbits were randomly assigned to four groups: (1) immobilized controls (n = 14); (2) suturectomy (n = 6); (3) suturectomy with distraction (n = 9); and (4) suturectomy with overdistraction (n = 10). Lateral head radiographs were taken at 1.5, 6, 12, and 18 weeks of age. Results revealed that, by 18 weeks of age, rabbits with overdistraction exhibited significant compensatory growth abnormalities in the cranial vault, midface, and anterior cranial base compared with the other groups. Results indicate that overdistraction may contribute to craniofacial anomalies through altered growth vectors and compressive tension-stress forces at adjacent sutures and suggest that it may be important to keep "pace" with the growing coronal suture and neurocapsular matrix during distraction to reestablish normal craniofacial morphology.

Age related changes in intracranial volume in rabbits with craniosynostosis.

Neurocapsular growth is highly heritable and determines neurocranial form. Although craniosynostosis alters brain growth direction, resulting in compensatory changes in the neurocranium, it is believed that such compensations occur without reduction in intracranial volume. This hypothesis was tested in a rabbit model with nonsyndromic, familial coronal suture synostosis. Skulls of 56 rabbits (20 normals, 20 with delayed onset synostosis, and 16 with complete synostosis) were scanned using three-dimensional computed tomography at 6 and 18 weeks of age. Intracranial contents were reconstructed, and indirect intracranial volume was calculated. Qualitatively, re-formations of intracranial contents from completely synostosed rabbit skulls exhibited the typical "copper beaten" morphology. Quantitatively, intracranial volume was significantly (p < 0.05) reduced in rabbit skulls with complete synostosis compared with both control rabbit skulls and rabbit skulls with delayed onset synostosis at 6 weeks by 11 percent and 14 percent, respectively). By 18 weeks, intracranial volume in rabbit skulls with synostosis was significantly (p < 0.05) reduced (by 12 percent in complete synostosis and 8 percent in delayed onset synostosis) compared with normal rabbits. Results suggest that in rabbits with uncorrected craniosynostosis, compensatory changes in the neurocranium were not adequate to allow normal expansion of the neurocapsular matrix. Further research is needed to determine whether reduction in intracranial volume was a result of neural tissue deficiency or cerebrospinal fluid (i.e., ventricular or subarachnoid) space compression in this model.

Internal calvarial bone distraction in rabbits with delayed-onset coronal suture synostosis.

Recent studies have identified a subpopulation of craniosynostotic individuals who exhibit progressive or delayed-onset synostosis and mild craniofacial growth abnormalities. These individuals may be good candidates for nonextirpation, distraction osteogenesis therapy. The present study was designed to test this hypothesis by using internal calvarial bone distraction in a rabbit model with familial delayed-onset craniosynostosis. Data were collected from 159 rabbits: 71 normal controls, 72 with delayed-onset coronal suture synostosis, 8 with delayed-onset coronal suture synostosis and coronal suturectomy, and 8 with delayed-onset coronal suture synostosis and distraction. At 10 days of age, all rabbits had amalgam markers placed on both sides of the frontonasal, coronal, and anterior lambdoidal sutures. At 25 days of age, correction was accomplished through either a 5-mm-wide suturectomy or distraction osteogenesis. An internal distraction appliance was fixed to the frontal and parietal bones and percutaneously and intermittently activated at an average of 0.10 mm/day for 42 days (4.11 mm total). Serial radiographs were taken at 10, 25, 42, and 84 days of age. Results revealed that rabbits with delayed-onset synostosis had significantly (p < 0.01) reduced coronal suture growth rates (0.04 mm/day) compared with the other three groups (0.07 mm/day). Rabbits with suturectomy and rabbits with distraction showed similar coronal suture responses. However, from 42 to 84 days of age, rabbits with distraction showed reduced growth at the vault sutures and abnormal growth patterns in cranial vault width, cranial vault shape, and cranial base angulation compared with the other three groups. Results demonstrated that, although the normal coronal suture growth rate was maintained in rabbits with delayed-onset synostosis using intermittent distraction osteogenesis, normal adult craniofacial structure was not achieved. Such anomalous growth was probably a result of altered growth vectors and compressive forces at adjacent sutures during distraction. These findings suggest that distraction osteogenesis without corticotomy may be a treatment alternative in individuals with progressive, delayed-onset synostosis, but that internal appliances that generate low-level, continuous distractive forces should be investigated and developed.

Degradation kinetics of biodegradable DL-polylactic acid biodegradable implants depending on the site of implantation.

A recently developed biodegradable system made of DL-polylactic acid (DL-PLA) for internal fixation of non-weight-bearing bones of the craniofacial skeleton was investigated. The plates were used for rigid fixation of experimental nasal bone fractures in 20 New Zealand white rabbits. In addition, prebent plates were placed in subcutaneous pockets in the backs of the animals. The material was removed after 7, 14, 28, and 42 days, and bending angles, plate stability, molecular weights (MW), and histologic analyses were studied. A significant decrease of MW over time and a difference in MW loss, showing a faster degradation subcutaneously, were observed. Plate stability did not decrease during the interval of 6 weeks, but a loss of bending angle was found in all prebent implants. This effect was caused by memory of DL-PLA. The results suggest that memory of biodegradable materials should be investigated before clinical application and that degradation rates differ according to the site of implantation.

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.

Postnatal presence of paraseptal cartilages in humans: a description of morphology and size.

Paraseptal cartilages (PCs) have been the subject of controversy, in that some authors believe them to be absent or rarely present, while others have described them to exist at predictable locations in adult human tissue specimens. This study seeks to determine the presence or absence of PCs in humans and describe their morphology and size. Nasal septal tissue from 19 adults and 1 child were paraffin embedded, coronally sectioned, placed on slides, and stained for microscopic observation. For all specimens, PCs were identified and lengths were calculated. Selected PCs were also digitized in order to calculate volume. Results demonstrated that PCs were present in all 20 tissue specimens and assumed a common morphology. In each, PCs were found to begin as hyaline cartilage lobes that extend projections in a superolateral direction as an anteroposterior course is followed. The projections were found to rotate inferiorly until each PC was found to assume a position that extended below the nasal septum. Length measures in adults ranged from 8,725 to 19,000 microm (x = 14,188.9 microm) and volumes ranged from 7.7 to 24.2 (x = 13.2) x 10(-3) ml. A quantitative comparison to foetal data from a previous study suggests prenatal and/or postnatal growth of PCs. Results from this study support the presence of PCs in adult humans as well as prenatal/postnatal growth of PCs.