Molecular basis of perinatal hypophosphatasia with tissue-nonspecific alkaline phosphatase bearing a conservative replacement of valine by alanine at position 406. Structural importance of the crown domain.

Hypophosphatasia, a congenital metabolic disease related to the tissue-nonspecific alkaline phosphatase gene (TNSALP), is characterized by reduced serum alkaline phosphatase levels and defective mineralization of hard tissues. A replacement of valine with alanine at position 406, located in the crown domain of TNSALP, was reported in a perinatal form of hypophosphatasia. To understand the molecular defect of the TNSALP (V406A) molecule, we examined this missense mutant protein in transiently transfected COS-1 cells and in stable CHO-K1 Tet-On cells. Compared with the wild-type enzyme, the mutant protein showed a markedly reduced alkaline phosphatase activity. This was not the result of defective transport and resultant degradation of TNSALP (V406A) in the endoplasmic reticulum, as the majority of newly synthesized TNSALP (V406A) was conveyed to the Golgi apparatus and incorporated into a cold detergent insoluble fraction (raft) at a rate similar to that of the wild-type TNSALP. TNSALP (V406A) consisted of a dimer, as judged by sucrose gradient centrifugation, suggestive of its proper folding and correct assembly, although this mutant showed increased susceptibility to digestion by trypsin or proteinase K. When purified as a glycosylphosphatidylinositol-anchorless soluble form, the mutant protein exhibited a remarkably lower Kcat/Km value compared with that of the wild-type TNSALP. Interestingly, leucine and isoleucine, but not phenylalanine, were able to substitute for valine, pointing to the indispensable role of residues with a longer aliphatic side chain at position 406 of TNSALP. Taken together, this particular mutation highlights the structural importance of the crown domain with respect to the catalytic function of TNSALP.

Nitric oxide modulates elicitation of reflex swallowing from the pharynx in rats.

The pharynx is very important for elicitation of reflex swallowing. The region of the pharynx is innervated by the pharyngeal branch of the glossopharyngeal nerve (GPN-ph). Nitric oxide (NO) plays an important role in various physiological functions. The purpose of this study is to investigate the contribution of NO to reflex swallowing evoked by electrical stimulation of the GPN-ph. Swallowing was evoked in urethane-anesthetized rats by application of repetitive electrical stimulation (10- to 20-microA amplitude, 10- to 20-Hz frequency, 1.0-ms duration) to the central cut end of the GPN-ph or superior laryngeal nerve. Swallowing was identified by electromyographic activity of the mylohyoid muscle. Latency to the first swallow and the interval between swallows were measured. Intravenous administration of N(G)-nitro-L-arginine (L-NNA, 0.6 mg/kg), a nonselective inhibitor of NO synthase (NOS), extremely prolonged latency to the first swallow and the interval between swallows evoked by the GPN-ph. Intraperitoneal administration of 7-nitroindazole (5.0 mg/kg), a selective inhibitor of neuronal NOS, significantly prolonged latency to the first swallow and the interval between swallows evoked by the GPN-ph. Administration of L-arginine (an NO donor, 500 mg/kg) and sodium nitroprusside (an NO releaser, 0.6 mg/kg) restored the suppression of swallowing induced by the NOS inhibitor. Superior laryngeal nerve-evoked swallowing was suppressed by administration of a higher dose of L-NNA (6.0 mg/kg). Swallowing evoked by water stimulation of the pharynx was also suppressed by L-NNA (0.6 mg/kg). These results suggest that NO plays an important role in signal processing for initiation of reflex swallowing from the pharynx.

Anterior crossbite in the primary dentition: proposal for a new analytical method in children.

The aim of this study was to clarify the features of profiles of patients with anterior crossbite in early childhood, using a new method of analysis. Lateral cephalograms of 139 (68 males; 71 females) untreated child patients with anterior crossbite in the primary dentition were assessed. The patients were aged from 3 to 5 years. To evaluate disharmony between the maxilla and the mandible, a proprietary calculating system, the Theoretical Individualized Profile drawing System (TIPS), was applied. Using this system, individualized standard cephalometric values were obtained for normal occlusion. This standard profile, which was harmonized with the cranial base structure of each patient, was compared with the child's original profile. The sizes of the mandibles in the children with anterior crossbite, subclassified into three age groups (3, 4, and 5 years) were greater, both horizontally and vertically, than those in the mean profiles derived from TIPS. The vertical size of the maxilla was smaller than that derived from TIPS in the patients aged 3 years. In contrast, in the patients aged 5 years, the vertical size of the maxilla was larger than that derived from TIPS. These results suggest that, in children with anterior crossbite, the vertical growth of the maxilla is closely related to the variation of morphological conditions with development.

Feeding, artificial sucking habits, and malocclusions in 3-year-old girls in different regions of the world.

PURPOSE: The way babies and young children are reared is important to their health and development. Extensive breast-feeding has also been shown to reduce the development of artificial sucking habits like digit or pacifier-sucking. The aim of this study was to determine feeding methods, artificial sucking habits, and the presence of malocclusions in 3-year-old girls living in different regions of the world. METHODS: Children from the following countries were involved in the present study: (1) Brazil (Porto Alegre); (2) Japan (Niigata); (3) Mexico (Mexico City); (4) Norway (Oslo); (5) Sweden (Falköping); (6) Turkey (Istanbul); (7) and the United States (Iowa City, Iowa). During the interview and examination, the following variables were evaluated and registered: (1) breastfeeding and bottle-feeding; (2) duration and frequency; (3) sucking habits; (4) posterior and anterior crossbites; and (5) other malocclusions/normal occlusion. RESULTS: The prevalence of breast-feeding was very high in all groups, ranging between 78% and 98%. The prevalence of bottle-feeding in the different areas was also high. Except for Iowa City, the prevalence of digit-sucking was relatively low. Pacifier-sucking is fairly popular in most areas, with the exception of Niigata. The prevalence of normal occlusion in different cities ranged from 38% to 98%. CONCLUSIONS: There are considerable differences in feeding, as well as artificial sucking habits, in different areas of the world and at different periods.

Failure of tooth eruption involving a mandibular primary first molar: a case report.

PURPOSE: Primary failure of tooth eruption involving primary teeth is unusual. The purpose of this report was to describe uneruption of a single mandibular primary first molar and the treatment outcome following limited orthodontic care. METHODS: A 5-year, 3-month-old boy was referred to the authors' clinic for treatment of an unerupted primary first molar, 3 months after fenestration by an oral surgeon. Orthodontic traction was performed on the affected molar in the authors' clinic. The affected mandibular primary first molar was fully erupted and in occlusion 16 months after the first fenestration. RESULTS: The histopathological diagnosis of the overlying tissue was pericoronal myxofibrous hyperplasia (PMH) without any calcified obstacles. CONCLUSIONS: Of the 26 primary tooth eruption failure cases treated in the authors' clinic between 1979 and 2003, the present case was the only example of a primary first molar.

Genesis of the decrement of intraluminal pressure in the UES during swallowing in rabbits.

The intraluminal pressure in the upper esophageal sphincter (UES) briefly decreases during swallowing. This decrement in pressure plays an important role in smooth transport of the ingested bolus from the pharynx to the esophagus. It is known that the decrement is caused by cessation of tonic activity of the cricopharyngeus (CP) muscle and also by elevation of the larynx. On the other hand, it is suspected that the recurrent laryngeal nerve (RLN) also contributes to the decrement, since our preliminary study showed for the first time that the decrement in UES pressure was much reduced after the RLN was sectioned. In the present study, we examined the genesis of the decrement of the UES pressure in anesthetized rabbits. When swallowing was elicited by repetitive electrical stimulation of the superior laryngeal nerve, the UES pressure briefly decreased and then abruptly increased. After bilateral sectioning of the RLN, the decrement of the pressure was significantly reduced, whereas the increment was little altered. Sectioning of the pharyngeal branch of the vagus nerve (X-ph) and the RLN mostly eliminated both the decrement and increment of the pressure, and abolished tonic and burst activities of the CP muscle. Electrical stimulation of peripheral end of the RLN decreased the pressure. These results indicate that the RLN and X-ph are involved in the decrement of the UES pressure during swallowing. The RLN generates the decrement by adducting the arytenoid cartilage and closing the glottis. The X-ph contributes to the decrement both by suppressing the tonic activity of the CP muscle and by regulating the laryngeal elevation.

Congenital defect of maxillary primary central incisor associated with exposed pulp and gingival [fibrosis]: case report.

This report describes a rare case of hypoplastic primary incisor in which the pulp was exposed at the crown portion and covered by the gingiva in a 1-year-11-month-old boy. The patient was referred to us due to swelling of his labial cervical gingiva of the maxillary right primary central incisor, and on examination, extended to the hypoplastic labial surface. Radiographically, there was a round radiolucent area on the crown including the edge. Surgical removal of the swollen gingiva revealed a large defect of the labial aspect of the incisor, showing pulpal tissue inside. The tooth was treated by vital pulpotomy. Histopathologically, the removed gingival tissue contained many pieces of dysplastic tooth elements in the lamina propria portion which should have been connected to the exposed pulp. The findings suggested that pulp exposure resulted from focal dental hypoplasia not from resorption of the tooth.

Retarded eruption of maxillary second premolars associated with late development of the germs.

This study focused on five unusual cases with anomalous eruptions of the maxillary second premolars that related to late development of the germs. In four cases, the affected premolars erupted between the ages of 12y3m and 14y6m. In one case, which was suspected to include bilateral anomalies, the eruption of the premolar was excessively late, continuing up to 17y8m old. It was surmised that the degree of tooth formation in the contralateral side might help to predict approximately at what age the late premolars will erupt.

Tensile stress induces alpha-adaptin C production in mouse calvariae in an organ culture: possible involvement of endocytosis in mechanical stress-stimulated osteoblast differentiation.

We previously demonstrated that tensile stress (TS)-induced osteoblast differentiation eventually led to osteogenesis in an organ culture of mouse calvarial sutures. In the present study, we employed RNA-fingerprinting using an arbitrarily primed polymerase chain reaction (RAP-PCR) to identify alpha-adaptin C, a component of the endocytosis machinery AP2, as a TS-inducible gene. Protein production, as well as the gene expression of alpha-adaptin C, was induced by TS as early as 3 h following the initiation of loading. In situ hybridization and immunohistochemical analysis revealed that the induction of alpha-adaptin C mostly occurred in fibroblastic cells in the sutures, suggesting that it precedes TS-induced osteoblast differentiation. Consistent with this result, TS significantly increased the number of coated pits (CPs) and coated vesicles (CVs) in the undifferentiated fibroblastic cells but not in the osteoblastic cells around calvarial bones. Further, TS-induced osteoblast differentiation was suppressed when endocytosis was inhibited by potassium depletion. These results, taken together, suggest that TS accelerates osteoblast differentiation and osteogenesis, possibly through the induction of the alpha-adaptin C expression and consequent activation of receptor-mediated endocytosis.

Occlusal guidance for eruption disturbance of mandibular second premolar: a report of three cases.

This study presents the treatment courses in three impacted cases of mandibular second premolars caused by distal inclination of the tooth germs. In all cases, the second premolars were surgically exposed, but the traction periods until oral emergence differed. The reasons for the differences may be the variation in the severity of the distal inclinations of the tooth germs and the calcified development of the affected germs at fenestration.

Role of the pharyngeal branch of the vagus nerve in laryngeal elevation and UES pressure during swallowing in rabbits.

Elevation of the larynx during swallowing plays an important role in protecting the laryngeal inlet and in the opening of the upper esophageal sphincter (UES). The thyrohyoid (TH) muscle is the most important muscle for laryngeal elevation, and it is thought to be innervated by the thyrohyoid branch. However, in preliminary studies we found that laryngeal elevation was severely disturbed after sectioning of the pharyngeal branch of the vagus nerve (X-ph). In the present study, we examined the role of the X-ph in laryngeal elevation and the contribution of this nerve to UES pressure. Ten male rabbits under anesthesia were used. Sectioning of the X-ph not only abolished the electromyographic activities of the TH and cricopharyngeus (CP) muscles, it also greatly reduced the maximal value of laryngeal elevation during swallowing. On the other hand, sectioning of the hypoglossal nerve, which contains the thyrohyoid branch, produced no appreciable change in the electromyographic activity of either muscle and it reduced the maximal value of the elevation only slightly. These results indicate that the X-ph innervates the TH and CP muscles and suggest that the X-ph plays an important role in elevating the larynx and in regulating the UES pressure in rabbits.

Sour taste stimulation facilitates reflex swallowing from the pharynx and larynx in the rat.

Chemical stimulation of the pharynx and larynx is effective in eliciting reflex swallowing. A sour taste bolus facilitates the onset of swallowing in patients with neurogenic dysphagia, but the mechanism of the facilitation has not been clarified. We investigated the effect of sour solutions on the elicitation of reflex swallowing in anesthetized rats. The main ducts of salivary glands were ligated to avoid the effect of saliva. A small amount of water, sour solutions, and other taste solutions were applied to the mucosa of the pharyngolaryngeal region. Acetic acid and citric acid, which provide a sour taste, had a stronger effect on evoking reflex swallowing as compared with other taste solutions. The effectiveness of these acids increased with increasing concentrations. We also examined the contribution of the superior laryngeal nerve (SLN) and the pharyngeal branch of the glossopharyngeal nerve (GPNph) to reflex swallowing. Acetic acid was greatly effective in evoking swallowing in both the region innervated by the SLN and the GPNph. On the other hand, water was effective in the SLN region but only slightly effective in the GPNph region. The results indicate that stimulation of the pharyngolaryngeal region with sour solutions facilitates reflex swallowing, suggesting that the facilitation may be due to increases of sensory inputs via the SLN and GPNph.

Comparison of SLN-evoked swallows during rest and chewing in the freely behaving rabbit.

Interactions between the swallowing central neural pathway and the chewing central neural pathway were examined in freely behaving, unanesthetized rabbits. Pharyngeal swallows were elicited by electrical stimulation of the superior laryngeal nerve (SLN) and defined by thyrohyoid muscle (TH) activity in the electromyogram (EMG). Recordings were obtained from rabbits at rest and during chewing. The number of swallows elicited by the SLN stimulation was significantly increased (P<0.001) during quiet oral function (at rest) and during chewing. The increased number of swallows from each baseline was similar, signifying that the effect of the SLN stimulation was similar in generating swallowing in both groups. The swallows induced with SLN stimulation were very similar to natural swallows as defined by the temporal pattern of the EMG duration and the timing of EMG activities. Our results suggest that: (1). the peripheral inputs to the swallowing pathway may rarely be modulated by the chewing pathway in the generation of swallows; (2). the swallowing pathway and the chewing pathway may interact at the level of the rhythm generators; (3). each animal has its own threshold for eliciting pharyngeal swallowing, and the threshold may be independent of the number of chews.

Disturbed tooth eruption in osteopetrotic (op/op) mice: histopathogenesis of tooth malformation and odontomas.

BACKGROUND: Odontoma-like structures are formed in the jaw bone of osteopetrotic (op/op) mice, which have a congenital deficiency in osteoclastic differentiation due to the absence of functional macrophage colony-stimulating factor (M-CSF). METHODS: To clarify the histopathogenesis of tooth malformation and odontoma-like structures, a 2-year postnatal process of development of the op/op mandibular incisor was examined radiologically and histologically. At the same time, extracellular matrix (ECM) remodeling around tooth germs was analyzed immunohistochemically. RESULTS: Abnormal forms of op/op tooth germ were noticeable even at 3 days after birth on a radiogram. Histologically, op/op mice were clearly distinguished by the disappearance of dental follicular space at 3 days. With aging, bone trabeculae, which were not remodeled, penetrated into op/op tooth germs and divided them into several daughter germs, which were recognized as odontomas. In mandibular incisor bodies, the immature ECM components, such as heparan sulfate proteoglycan and tenascin, were preserved diffusely in the dental papilla/pulp, which indicates that maturation of the stroma does not take place in op/op mandibular incisors. CONCLUSION: The observation suggests that the disturbed morphogenesis of op/op tooth germs is functionally explained by the disordered immunolocalization of ECM molecules, and that the dental follicular space is essential for normal tooth development because it prevents bone penetration into the tooth germs.

Tooth replantation after traumatic avulsion: a report of ten cases.

This report compares the manner in which the avulsed tooth was handled at home versus at school, and presents the different outcomes of the replanted teeth in both groups. Eighteen of 32 avulsed teeth were not replanted, and four replanted teeth could not be followed. Thus, the material comprised 10 avulsed permanent incisors of 10 traumatized children, aged between 8 and 13 years, who were treated at the Pediatric Dental Clinic of Niigata University Dental Hospital. Half of the patients avulsed the tooth at school and the other half at or near home. Of the five teeth avulsed at school, three were kept under wet conditions. The time until their replantation ranged between 0.5 and 3.5h. Their outcomes were fairly good, except for one incisor that was extracted about 3 years later owing to the undesirable replantation procedures by the dentist. Of the avulsed teeth at or near home, three were left under dry conditions. Their time until replantation ranged scattered between 0.5 and 12h. Of these, two incisors preserved under wet conditions survived without significant root resorption. These results suggested that information about the way to keep the avulsed tooth was relatively well known to school nurse-teachers compared with parents. Depending on the kind of lay people, it appears that it is necessary to select the best way to convey information about the management of avulsed permanent teeth.

Relationship between cranial base structure and maxillofacial components in children aged 3-5 years.

The aim of this study was to clarify the inter-relationships between cranial base angle, the morphological variations of maxillofacial components, and growth of the anterior cranial base length. One hundred and twenty-two Japanese children aged 3-5 years with normal occlusion in the primary dentition were included in this investigation. To analyse the relationship between cranial base structure and maxillofacial components, the subjects were divided into three groups according to facial type (prognathic, orthognathic, or retrognathic) assessed by the magnitude of their NSAr angle (as cranial base angle). These categorized cephalometric profiles suggested that the antero-posterior location of the maxillofacial components corresponded to the NSAr angle. Factor analysis of cephalometric variables showed that the variation of maxillofacial components from the S-N line was strongly related to the cranial base angle. This normal range of morphological variation was distinguished from that of growth by the factor loadings. From these results, theoretical models of cephalometric profiles with normal occlusion were computed by linear regression analysis. Using the models, a standard profile related to an arbitrary cranial base angle was obtained for children with normal occlusion, aged 3-5 years.

External root resorption of the maxillary permanent incisors caused by ectopically erupting canines.

In this study, we analyzed the root resorption of 10 maxillary permanent incisors (two central and eight lateral incisors) in seven cases associated with ectopic eruption of adjacent canines. Two incisors were extracted because of marked root resorption. Two erupted after traction, whereas, five erupted after surgical exposure or without any treatment, although one lateral incisor submerged due to ankylosis. This suggests that self-correction of the ectopic canine occurs in some cases.