Evaluation of Soft Tissue and Airway Changes in Individuals Treated with Mini-Implant Assisted Rapid Palatal Expansion (MARPE).

INTRODUCTION: Mini-implant assisted rapid palatal expansion (MARPE) is gradually becoming the treatment of choice to correct the transverse dimension, exceeding the limitations of conventional RME devices. One of the key factors for orthodontic diagnosis and treatment planning apart from a stable occlusion is a balanced and aesthetic facial profile that is influenced by maxillary expansion. Similarly, it also affects the anatomy and physiology of the nasal cavity since nasal airflow is a continuous stimulus for lowering of the palate and for lateral maxillary growth. Hence, there is a need to conduct further research on the effects of MARPE on the facial soft tissues as well as the airway, enabling the orthodontist to reach a more accurate diagnosis as well as aid in the treatment planning process. AIMS AND OBJECTIVES: This retrospective three-dimensional study was planned and designed with the objective of measuring facial soft tissue and airway changes in individuals treated with mini-implant assisted rapid palatal expansion (MARPE) using CBCT. MATERIALS AND METHODS: This study was carried out on CBCT records of 10 patients in the age group of 18-30 years. These records were then imported into Romexis software and calibrated. The facial soft tissue and airway parameters were measured for each individual at selected landmarks and compared before and after expansion. RESULT: Statistically significant differences in the soft tissue parameters were observed, which included an increased H-angle, increased soft tissue subnasal to H-line and a decreased soft palate surface area after MARPE.

Runx2-Twist1 interaction coordinates cranial neural crest guidance of soft palate myogenesis.

Cranial neural crest (CNC) cells give rise to bone, cartilage, tendons, and ligaments of the vertebrate craniofacial musculoskeletal complex, as well as regulate mesoderm-derived craniofacial muscle development through cell-cell interactions. Using the mouse soft palate as a model, we performed an unbiased single-cell RNA-seq analysis to investigate the heterogeneity and lineage commitment of CNC derivatives during craniofacial muscle development. We show that Runx2, a known osteogenic regulator, is expressed in the CNC-derived perimysial and progenitor populations. Loss of Runx2 in CNC-derivatives results in reduced expression of perimysial markers (Aldh1a2 and Hic1) as well as soft palate muscle defects in Osr2-Cre;Runx2fl/fl mice. We further reveal that Runx2 maintains perimysial marker expression through suppressing Twist1, and that myogenesis is restored in Osr2-Cre;Runx2fl/fl;Twist1fl/+ mice. Collectively, our findings highlight the roles of Runx2, Twist1, and their interaction in regulating the fate of CNC-derived cells as they guide craniofacial muscle development through cell-cell interactions.

Dynamic activation of Wnt, Fgf, and Hh signaling during soft palate development.

The soft palate is a key component of the oropharyngeal complex that is critical for swallowing, breathing, hearing and speech. However, complete functional restoration in patients with cleft soft palate remains a challenging task. New insights into the molecular signaling network governing the development of soft palate will help to overcome these clinical challenges. In this study, we investigated whether key signaling pathways required for hard palate development are also involved in soft palate development in mice. We described the dynamic expression patterns of signaling molecules from well-known pathways, such as Wnt, Hh, and Fgf, during the development of the soft palate. We found that Wnt signaling is active throughout the development of soft palate myogenic sites, predominantly in cells of cranial neural crest (CNC) origin neighboring the myogenic cells, suggesting that Wnt signaling may play a significant role in CNC-myogenic cell-cell communication during myogenic differentiation in the soft palate. Hh signaling is abundantly active in early palatal epithelium, some myogenic cells, and the CNC-derived cells adjacent to the myogenic cells. Hh signaling gradually diminishes during the later stages of soft palate development, indicating its involvement mainly in early embryonic soft palate development. Fgf signaling is expressed most prominently in CNC-derived cells in the myogenic sites and persists until later stages of embryonic soft palate development. Collectively, our results highlight a network of Wnt, Hh, and Fgf signaling that may be involved in the development of the soft palate, particularly soft palate myogenesis. These findings provide a foundation for future studies on the functional significance of these signaling pathways individually and collectively in regulating soft palate development.

Regulatory Mechanisms of Soft Palate Development and Malformations.

Orofacial clefting is the most common congenital craniofacial malformation, appearing in approximately 1 in 700 live births. Orofacial clefting includes several distinct anatomic malformations affecting the upper lip and hard and soft palate. The etiology of orofacial clefting is multifactorial, including genetic or environmental factors or their combination. A large body of work has focused on the molecular etiology of cleft lip and clefts of the hard palate, but study of the underlying etiology of soft palate clefts is an emerging field. Recent advances in the understanding of soft palate development suggest that it may be regulated by distinct pathways from those implicated in hard palate development. Soft palate clefting leads to muscle misorientation and oropharyngeal deficiency and adversely affects speech, swallowing, breathing, and hearing. Hence, there is an important need to investigate the regulatory mechanisms of soft palate development. Significantly, the anatomy, function, and development of soft palatal muscles are similar in humans and mice, rendering the mouse an excellent model for investigating molecular and cellular mechanisms of soft palate clefts. Cranial neural crest-derived cells provide important regulatory cues to guide myogenic progenitors to differentiate into muscles in the soft palate. Signals from the palatal epithelium also play key roles via tissue-tissue interactions mediated by Tgf-ß, Wnt, Fgf, and Hh signaling molecules. Additionally, mutations in transcription factors, such as Dlx5, Tbx1, and Tbx22, have been associated with soft palate clefting in humans and mice, suggesting that they play important regulatory roles during soft palate development. Finally, we highlight the importance of distinguishing specific types of soft palate defects in patients and developing relevant animal models for each of these types to improve our understanding of the regulatory mechanism of soft palate development. This knowledge will provide a foundation for improving treatment for patients in the future.

Growth Effects on Velopharyngeal Anatomy From Childhood to Adulthood.

Purpose The observed sexual dimorphism of velopharyngeal structures among adult populations has not been observed in the young child (4- to 9-year-old) population. The purpose of this study was to examine the age at which sexual dimorphism of velopharyngeal structures become apparent and to examine how growth trends vary between boys and girls. Method Static 3-dimensional magnetic resonance imaging velopharyngeal data were collected among 202 participants ranging from 4 to 21 years of age. Participants were divided into 3 groups based on age, including Group 1: 4-10 years of age, Group 2: 11-17 years of age, and Group 3: 18-21 years of age. Nine velopharyngeal measures were obtained and compared between groups. Results Significant sex effects were evident for levator length ( p = .011), origin to origin ( p = .018), and velopharyngeal ratio ( p = .036) for those in Group 2 (11-17 years of age). Sex effects became increasingly apparent with age, with 7 of 9 variables becoming significantly different between male and female participants in Group 3. Boys, in general, displayed a delayed growth peak in velopharyngeal growth compared to girls. Conclusion Results from this study demonstrate the growth of velopharyngeal anatomy with sexual dimorphism becoming apparent predominantly after 18 years of age. However, velopharyngeal variables displayed variable growth trends with some variables presenting sexual dimorphism at an earlier age compared to other velopharyngeal variables.

Fetal and early postnatal development of the porcine tonsils of the soft palate.

Tonsils are mucosa-associated lymphoid tissues located at the openings of the gastrointestinal and respiratory tracts, which play a key role in the surveillance of inhaled or ingested pathogens and can concurrently be reservoirs of infectious agents. Therefore, tonsils are important for the immunology and hygiene management of domestic animals, including pigs. However, the process of their fetal developmental has been poorly described, at least in part, because rodents lack tonsils. Therefore, we performed a histological analysis of porcine tonsils of the soft palate from 60 to 100 days of gestation (DG) and from 2 to 14 days post partum (DP). This analysis showed that lymphoid aggregations first appear at DG65, gradually develop during the fetal stage, and expand after birth. In addition, the mRNA expression of chemokine genes involved in lymphoid aggregation and localization was analyzed. CCL19 expression showed the most marked increase and a sharp peak after birth. CCL21 expression changed moderately but showed an interesting bimodal pattern. CXCL13 expression steadily increased throughout the study period. Thus, we demonstrated the mRNA expression of chemokine characteristically changed accompanying tonsillar development.

Evaluation of a Sample of Patients With Unilateral Cleft Lip and Palate Treated With a Two-Stage Protocol.

The aim of this paper was to assess growth, speech, and aesthetic results at the completion of growth in patients with unilateral cleft lip and palate treated with the 2 stages Milan surgical protocol.Craniofacial growth was evaluated with cephalometric analysis and a theoretical need for orthognathic surgery.Nasolabial appearance was qualitatively assessed using the Asher McDade Aesthetic Index.Speech was assessed using the Gos.Sp.Ass '98 modified for Italian language scoring system.Burden of care was recorded in terms of number of secondary surgical procedures. All of the patients were treated and evaluated at San Paolo Hospital, Smile House, Milan.Fifty-two consecutive patients treated by the same surgeon were recalled, 12 patients did not come for assessment.The first surgical step (average age of 6 months) was cheilorhinoplasty (Millard modified Delaire technique) and soft palate rapair (Pigott). The second step (average age of 35 months) was hard palate and alveolar repair performed simultaneously with an early secondary gengivo alveolo plasty. Fifty-six percent of the patients did not need further surgery after the 2-stage surgery protocol.The 2-stage surgical protocol of Milano, Smile House, seems to be effective for treatment of unilateral cleft lip and palate, with good results in terms of speech, labial appearance, and alveolar cleft management. Nevertheless, maxillary growth was moderately impaired by the protocol.

Age-Related Changes Between the Level of Velopharyngeal Closure and the Cervical Spine.

The primary focus of this study was to assess age-related changes in the vertical distance of the estimated level of velopharyngeal closure in relation to a prominent landmark of the cervical spine: the anterior tubercle of cervical vertebra 1 (C1). Midsagittal anatomic magnetic resonance images were examined across 51 participants with normal head and neck anatomy between 4 and 17 years of age. Results indicate that age is a strong predictor (P = 0.002) of the vertical distance between the level of velopharyngeal closure relative to C1. Specifically, as age increases, the vertical distance between the palatal plane and C1 becomes greater resulting in the level of velopharyngeal closure being located higher above C1 (range 4.88-10.55 mm). Results of this study provide insights into the clinical usefulness of using C1 as a surgical landmark for placement of pharyngoplasties in children with repaired cleft palate and persistent hypernasal speech. Clinical implications and future directions are discussed.

Pharyngeal airway dimensions: a cephalometric, growth-study-based analysis of physiological variations in children aged 6-17.

OBJECTIVE: The aim was to assess pharyngeal airway dimensions and physiological changes based on lateral cephalometric radiographs from healthy untreated children aged 6-17 years. MATERIALS/METHODS: The sample consisted of 880 lateral cephalograms (412 females and 468 males) of the Zurich Craniofacial Growth Study. Statistical analyses on cephalometric measurements of airway dimensions (distances 'p': shortest distance between soft palate and posterior pharyngeal wall and 't': shortest distance between tongue and posterior pharyngeal wall) and craniofacial parameters were performed. To disclose differences between different age groups, a Kruskal-Wallis test was applied. The influence of gender on 'p' and 't' was analysed by a Mann-Whitney U-test for each age group separately. The Spearman correlation was computed in order to investigate associations between craniofacial parameters. Variables associated with 'p' and 't' were chosen for multiple regression model investigation. RESULTS: The results demonstrated high interindividual variations. A slight influence of age on 'p' (P = 0.034) could be attested (+1.03 mm) but not on 't' (P = 0.208). With the exception of the 9-year age group, no significant differences between the genders were found. Correlation analysis revealed several statistically significant correlations between 't' or 'p' and antero-posterior cephalometric variables. All correlation coefficients were, however, very low and the adjusted coefficient of determination also revealed the regression model to be very weak. CONCLUSIONS: The high interindividual variations of 'p' and 't' render the use of reference values problematic. Contrary to other craniofacial structures, neither age-related changes nor sexual dimorphism were found for 'p' and 't'. Any associations to antero-posterior cephalometric characteristics seem low.

Upper airway changes in Pierre Robin sequence from childhood to adulthood.

OBJECTIVES: To investigate pharyngeal airway changes in patients with Pierre Robin sequence (PRS) longitudinally from childhood to adulthood. SETTING AND SAMPLE POPULATION: Cleft Lip and Palate Unit, Clinic of Orthodontics, University of Zurich. Twenty-four patients born between 1970 and 1990 with non-syndromic PRS. MATERIALS AND METHODS: Lateral cephalograms at age 5 (T1), 10 (T2), 15 (T3) and 20 (T4) years were available. Variables describing pharyngeal airway dimensions, soft palate morphology, tongue and hyoid position, skeletal morphology and head posture were assessed. RESULTS: A significant increase in nasopharyngeal depth was found over the entire observation period (T1 10.7 to T4 19.1 mm, p < 0.001), especially between T2 and T3 (change 3.8 mm, p < 0.001), and was mainly due to adenoid recession (r = -0.75, p < 0.001; variation explained by 56%). Increase in velopharyngeal depth mainly took place between T3 and T4 (change 2.3 mm, p < 0.01). It was due to more anterior tongue posture (r = 0.65, p < 0.001; 42.5% of variation explained), in turn allowing the soft palate to take a more vertical position (r = -0.52, p < 0.001). Increase in oropharyngeal depth was associated with head extension and anterior mandibular positioning (36% of variation explained). However, significance was not reached (T1 8.3 to T4 9.8 mm, p > 0.05). CONCLUSIONS: Upper airway dimensions in children with PRS improve with time, except for the oropharyngeal airway. Despite large interindividual variation, the mean remained in the lower reaches of normality described in other studies. Thus, further research should investigate the prevalence of obstructive sleep apnoea in adults with PRS.

Implications of peripheral muscular and anatomical development for the acquisition of lingual control for speech production: a review.

OBJECTIVES: Normally developing children learn to produce intelligible speech during rapid, non-uniform growth of their articulators and other vocal tract structures. The purpose of this review is to focus attention on the consequences of peripheral growth and development for the acquisition of lingual control for speech production. This paper (1) reviews physiological underpinnings of tongue shaping and movements that are likely to be changing in young children; (2) estimates, from previously published studies, the net consequences of growth of multiple vocal tract structures on lingual control; (3) integrates our findings with the example of [R] production, and (4) highlights areas where further investigations would be most helpful. PATIENTS AND METHODS: The authors searched the literature, including the PubMed database, for studies of the development of muscle proteins, muscle fibers, and motor units of the tongue, and of the growth of the tongue, jaw, adenoids, soft and hard palates, oral and pharyngeal cavities, and the vocal tract as a whole. CONCLUSIONS: Substantial anatomical and muscular data sets focused on children from 1-4 years of age, and rigorous definitions of the tongue boundaries are needed.

Expression of the basal cell markers of taste buds in the anterior tongue and soft palate of the mouse embryo.

Although embryonic expression of Shh in the fungiform papilla placodes has a critical role in fungiform papilla patterning, it remains unclear whether its appearance indicates the differentiation of the basal cells of taste buds. To examine the embryonic development of the basal cells, the expression of Shh, Prox1, and Mash1 was determined in the anterior tongue and soft palate in mouse embryos by in situ hybridization. In the anterior tongue, Prox1 was coexpressed with Shh from the beginning of Shh expression in the fungiform papilla placodes at E12.5. Shh was expressed in the soft palate in a band-like pattern in the anteriormost region and in a punctate pattern in the posterior region at E14.5. The number (21.4 +/- 4.3, at E14.5) of locations where Shh was observed (i.e., spots) rapidly increased and reached a peak level (54.8 +/- 4.0 at E15.5). Also in the soft palate, Prox1 was coexpressed with Shh from the beginning of Shh expression. These results suggest that basal cell differentiation occurs synchronously with the patterning of Shh spots both in the anterior tongue and in the soft palate. In contrast, Mash1 expression lagged behind the expression of Shh and Prox1 and began after the number of Shh spots had reached its peak level in the soft palate. Furthermore, immunohistochemistry of PGP9.5 and Shh revealed that epithelial innervation slightly preceded Mash1 expression both in the tongue and in the soft palate. This is the first report describing the time courses of the embryonic expression of basal cell markers of taste buds.

Quantitative study of taste bud distribution within the oral cavity of the postnatal mouse.

The aim of this study was to investigate the age-related developmental changes of taste bud distribution within the subpopulations at different postnatal ages in the mouse oral cavity. Developmental changes of taste bud distribution on the soft palate, fungiform, foliate and circumvallate papillae in the mouse oral cavity were examined histologically at different postnatal ages. After paraffin embedding, complete serial sections at 10mum thickness were made and stained by routine hematoxylin-eosin staining methods. Digitised images for each section were examined carefully. The existence of a taste pore was used to identify mature taste buds. A two-way analysis of variance (group versus age) was used to analyse differences in taste bud number and characteristics for each of the developmental changes. An independent measures t-test was used to compare two means. No taste buds with pores were observed at birth within circumvallate and foliate papillae. However, 61% of the circumvallate and 58% of the foliate taste buds contained taste pores at 2 weeks after birth. In contrast, at birth, 55% of the taste buds on the soft palate and only 22% of the taste buds within fungiform papillae contained taste pores. Then, the number of mature taste buds (taste buds with pores) increased rapidly 1 week after birth, resulting in 90% of soft palate taste buds and 32% of fungiform taste buds containing taste pores. These results suggests that the earlier maturation of soft palate taste buds compared with the other populations in the oral cavity raises evidence of their significant role in the taste mechanism, especially in the early life of the mouse.

Developmental changes of pharyngeal airway structures from young to adult persons.

This cross-sectional study investigated developmental changes of pharyngeal airway structures. The materials were comprised of 120 lateral cephalometric radiographs and were divided into three stages according to the dental age. Results indicated that the upper pharyngeal depth increased with age, whereas, the lower pharyngeal depth was established early in life. The pharynx increases its capacity predominantly by vertical expansion. The developmental changes in pharyngeal structures were signficantly greater in males than in females.

Relations of the pterygoid hamulus and hard palate in children and adults: anatomical implications for the function of the soft palate.

We investigated spatial relations of the pterygoid hamuli to the hard palate on 65 skull bases: 31 disarticulated sphenoidal bones from the newborn up to 9 years of age, 19 skulls of adult skeletons (21-59 age group), and 15 skulls aged 60-100 years. We measured: (a) width of the hard palate in the choanal region, (b) length of the hamulus, (c) inclination of the hamulus from the perpendicular line, and (d) distance between the tips of the contralateral hamuli. The width of the hard palate in the choanal region was smallest in children (mean +/- standard deviation, 21.5 +/- 2.6 mm) compared with adult skulls (26.8 +/- 2.3 mm in the 21-59 age group and 25.4 +/- 1.9 mm in the 60-100 age group; P<0.05, one-way analysis of variance (ANOVA) and Student-Newman-Keuls post hoc test). Children had the shortest hamulus (3.6 +/- 1.5mm), and its length increased in the adult age group to 6.9+1.7mm (P<0.05), and then again decreased to 5.0 +/- 1.9 mm in the 60-100 age group (P<0.05 vs. adults and children). The distance between the tips of the contralateral hamuli and their lateral inclination from the perpendicular plane were also greater in the adult age group (38.0 +/- 2.7mm and 35.9 +/- 13.7 degrees, respectively) than either in children (31.0 +/- 3.7mm and 19.6 +/- 12.1 degrees) or the elderly (32.7 +/- 3.9mm and 19.7 +/- 10.3 degrees) (P<0.05). Our study showed that the anatomical measures of the pterygoid hamulus and its relation to the surrounding structures change with age, and occur with the changes in the function of pharyngeal and palatal muscles in deglutition. These changes may have clinical relevance for sleep apnoea and snoring.

Role of vocal tract morphology in speech development: perceptual targets and sensorimotor maps for synthesized French vowels from birth to adulthood.

The development of speech from infancy to adulthood results from the interaction of neurocognitive factors, by which phonological representations and motor control abilities are gradually acquired, and physical factors, involving the complex changes in the morphology of the articulatory system. In this article, an articulatory-to-acoustic model, integrating nonuniform vocal tract growth, is used to describe the effect of morphology in the acoustic and perceptual domains. While simulating mature control abilities of the articulators (freezing neurocognitive factors), the size and shape of the vocal apparatus are varied, to represent typical values of speakers from birth to adulthood. The results show that anatomy does not prevent even the youngest speaker from producing vowels perceived as the 10 French oral vowels /i y u e phi o epsilon oe [symbol: see text] a/. However, the specific configuration of the vocal tract for the newborn seems to favor the production of those vowels perceived as low and front. An examination of the acoustic effects of articulatory variation for different growth stages led to the proposed variable sensorimotor maps for newbornlike, childlike, and adultlike vocal tracts. These maps could be used by transcribers of infant speech, to complete existing systems and to provide some hints about underlying articulatory gestures recruited during growth to reach perceptual vowel targets in French.

Linear dimensions of the upper airway structure during development: assessment by magnetic resonance imaging.

The upper airway undergoes progressive changes during childhood. Using magnetic resonance imaging (MRI), we studied the growth relationships of the tissues surrounding the upper airway (bone and soft tissues) in 92 normal children (47% males; range, 1 to 11 yr) who underwent brain MRI. None had symptoms of sleep-disordered breathing or conditions that impacted on their upper airway. MRI was performed under sedation. Sequential T1-weighted spin echo sagittal and axial sections were obtained and analyzed on a computer. We measured lower face skeletal growth along the midsagittal and axial oropharyngeal planes. In the midsagittal plane the mental spine-clivus distance related linearly to age (r = 0.86, p < 0.001). Along this axis, the dimensions of tongue, soft palate, nasopharyngeal airway, and adenoid increased with age and maintained constant proportion to the mental spine-clivus distance. Similarly, a linear relationship was noted for mandibular growth measured along the intermandibular line on the axial plane and age (r = 0.78, p < 0.001). In addition, the intertonsillar, tonsils, parapharyngeal fat pads, and pterygoids widths maintained constant proportion to intermandibular width with age. We conclude that the lower face skeleton grows linearly along the sagittal and axial planes from the first to the eleventh year. Our data indicate that soft tissues, including tonsils and adenoid, surrounding the upper airway grow proportionally to the skeletal structures during the same time period.

Longitudinal investigation of soft palate and nasopharyngeal airway relations in different rotation types.

The relationship between the soft palate and the nasopharyngeal airway in different mandibular growth rotation models was investigated. A total of 72 lateral cephalograms were obtained three years longitudinally from 24 individuals. The subjects had a mean age of 10.7 +/- 1.2 years and showed a normal (n = 8), posterior (n = 8), and anterior (n = 8) mandibular rotation pattern. Linear and angular measurements of the soft palate and nasopharyngeal airway were recorded by using PORDIOS computer program and were examined by means of descriptive statistics and paired t-tests. A linear increase in the soft palate length (SPL) was observed in all groups, with the posterior mandibular rotation group showing the largest increase within the observation period (28.56 +/- 4.83 to 34.98 +/- 2.87; P < .01). According to the paired t-test, palatal plane (ANS-PNS)/soft palate tip (SPT) angle showed a statistically significant decrease in the posterior rotation group (P < .01). The ratio between SPL and superior nasopharyngeal space (SPS) did not show a statistically significant difference among the groups. Although various amounts of soft palate and nasopharyngeal airway growth occurred in the different mandibular rotation types, the ratio between SPL and SPS (SPL/SPS), which plays an indispensable role in velopharyngeal functions, did not show a statistically significant difference in the groups. This assured velopharyngeal closure throughout the active growth period.

Development and maturation of taste buds of the palatal epithelium of the rat: histological and immunohistochemical study.

Palatal taste buds are intriguing partners in the mediation of taste behavior and their spatial distribution is functionally important for suckling behavior, especially in the neonatal life. Their prenatal development has not been previously elucidated in the rat, and the onset of their maturation remains rather controversial. We delineated the development and frequency distribution of the taste buds as well as the immunohistochemical expression of alpha-gustducin, a G protein closely related to the transduction of taste stimuli, in the nasoincisor papilla (NIP) and soft palate (SP) from the embryonic day 17 (E17) till the postnatal day 70 (PN70). The main findings in the present study were the development of a substantial number of taste pores in the SP of fetal rats (60.3 +/- 1.7 out of 122.8 +/- 5.5; mean +/- SD/animal at E19) and NIP of neonatal rats (9.8 +/- 1.0 out of 44.8 +/- 2.2 at PN4). alpha-gustducin-like immunoreactivity (-LI) was not expressed in the pored taste buds of either prenatal or newborn rats. The earliest expression of alpha-gustducin-LI was demonstrated at PN1 in the SP (1.5 +/- 0.5 cells/taste bud; mean +/- SD) and at PN4 in the NIP (1.4 +/- 0.5). By age the total counts of pored taste buds continuously increased and their morphological features became quite discernible. They became pear in shape, characterized by distinct pores, long subporal space, and longitudinally oriented cells. Around the second week, a remarkable transient decrease in the total number of taste buds was recorded in the oral epithelium of NIP and SP, which might be correlated with the changes of ingestive behaviors. The total counts of cells showing alpha-gustducin-LI per taste bud gradually increased till the end of our investigation (14.1 +/- 2.7 in NIP and 12.4 +/- 2.5 in SP at PN70). We conclude that substantial development of taste buds began prenatally in the SP, whereas most developed entirely postnatal in the NIP. The present study provides evidence that the existence of a taste pore which is considered an important criterion for the morphological maturation of taste buds is not enough for the onset of the taste transduction, which necessitates also mature taste cells. Moreover, the earlier maturation of palatal taste buds compared with the contiguous populations in the oral cavity evokes an evidence of their significant role in the transmission of gustatory information, especially in the early life of rat.

Maturation of taste buds on the soft palate of the postnatal rat.

Taste bud distribution on the soft palate and within three types of tongue papillae (fungiform, foliate, and circumvallate) were examined histologically in the rat at different postnatal ages. After paraffin embedding, serial sections (10 microm) were made and stained by HE, and digitized images of each section were examined. The existence of a taste pore was used to identify mature taste buds. At birth, 53% (68 of 127 observed) of the taste buds on the soft palate, but only 14% (14 of 110 observed) within fungiform papillae, contained a taste pore. One week after birth, the number of mature taste buds increased rapidly, resulting in 90% of soft palate taste buds and 80% of fungiform taste buds containing taste pores. In contrast, no taste buds with pores were observed at birth within foliate and circumvallate papillae; however, at two weeks after birth 52% (71 of 132 observed) of the foliate and 68% (180 of 267 observed) of the circumvallate taste buds examined contained taste pores. These results suggest that taste buds within the soft palate play an important role in the detection of nutrients in the neonatal rat.