barx1 is necessary for ectomesenchyme proliferation and osteochondroprogenitor condensation in the zebrafish pharyngeal arches

Barx1 modulates cellular adhesion molecule expression and participates in specification of tooth-types, but little is understood of its role in patterning the pharyngeal arches. We examined barx1 expression during zebrafish craniofacial development and performed a functional analysis using antisense morpholino oligonucleotides. Barx1 is expressed in the rhombencephalic neural crest, the pharyngeal arches, the pectoral fin buds and the gut in contrast to its paralogue barx2, which is most prominently expressed in the arch epithelium. Additionally, barx1 transient expression was observed in the posterior lateral line ganglia and developing trunk/tail. We show that Barx1 is necessary for proliferation of the arch osteochondrogenic progenitors, and that morphants exhibit diminished and dysmorphic arch cartilage elements due to reductions in chondrocyte differentiation and condensation. Attenuation of Barx1 results in lost arch expression of osteochondrogenic markers col2a1, runx2a and chondromodulin, as well as odontogenic marker dlx2b. Further, loss of barx1 positively influenced gdf5 and chordin, markers of jaw joint patterning. FGF signaling is required for maintaining barx1 expression, and that ectopic BMP4 induces expression of barx1 in the intermediate region of the second pharyngeal arch. Together, these results indicate an essential role for barx1 at early stages of chondrogenesis within the developing zebrafish viscerocranium.     

ACCURACY OF AGE DETERMINATION IN THE GREY SEAL HALICHOERUS GRYPUS OF EASTERN CANADA

The ages of 82 grey seals of known age from 1 to 10 yr were determined from growth layer groups in the cementum, readily seen in longitudinal sections 150 μm thick viewed under transmitted light. The sample of teeth was read five times in a series of blind replicates.
With only one reading, an accuracy of 84% was achieved. This increased to 93% on the basis of three readings but improved only marginally to 94% when all five readings were considered. Accuracy was best in the middle range of ages (3–6 yr) which are the critical years for estimating age-specific reproductive rates in population models.     

Odontometry of a Spanish neolithic-Bronze age sample. Comparison with other populations of the iberian peninsula. I.-Permanent teeth

The present study concerns the morphometric characteristics of two hundred permanent teeth from the Neolithic-Bronze Age human remains found in «Galería del Sílex» (Atapuerca Cave, Burgos, Spain). The crown index reveals that all the upper maxillary teeth (except incisors) and the mandibular first incisors, canines and premolars have a vestibulo-lingual diameter greater than the mesio-distal. The dental module and the surface value show that the mandibular teeth (except the molars) are smaller than those of the upper maxillary. These results are very similar to other European populations. Finally, the Sílex Gallery sample was compared with five other series of the Iberian Peninsula which have a chronology from the Mesolithic to the Middle Age. The results indicate a general decrease for both diameters (ØMD and ØVL) throughout time.     

局部放置三七粉对下颌阻生齿拔出术患者的临床疗效

目的：探讨局部放置三七粉对下颌阻生齿拔出术患者的临床疗效。方法：选取我院收治的180例下颌阻生齿拔出术患者,根 据术后治疗方式不同,将患者分为对照组和实验组。对照组患者采用常规治疗方式,实验组患者在此基础上采用局部放置三七粉 治疗。观察并比较两组患者的临床疗效、疼痛情况以及术后并发症的发生情况等。结果：两组患者的并发症相比较,实验组并发症 发生的人数均明显低于对照组（P＜0.05）。两组患者的疼痛、焦虑、抑郁情况比较,实验组明显低于对照组,差异有统计学意义（P＜ 0.05）。结论：局部放置三七粉能够减轻下颌阻生齿拔出后患者的并发症,减轻疼痛,改善患者的心理状态,提高其疗效,值得临床 推广使用。     

PRDC regulates placode neurogenesis in chick by modulating BMP signalling

The epibranchial placodes generate the neurons of the geniculate, petrosal, and nodose cranial sensory ganglia. Previously, it has been shown that bone morphogenetic proteins (BMPs) are involved in the formation of these structures. However, it has been unclear as to whether BMP signalling has an ongoing function in directing the later development of the epibranchial placodes, and how this signalling is regulated. Here, we demonstrate that BMPs maintain placodal neurogenesis and that their activity is modulated by a member of the Cerberus/Dan family of BMP antagonists, Protein Related to Dan and Cerberus (PRDC). We find that Bmp4 is expressed in the epibranchial placodes while Bmp7 and PRDC are expressed in the pharyngeal pouches. The timing and regional expression of these three genes suggest that BMP7 is involved in inducing placode neurogenesis and BMP4 in maintaining it and that BMP activity is modulated by PRDC. To investigate this hypothesis, we have performed both gain- and loss- of-function experiments with PRDC and find that it can modulate the BMP signals that induce epibranchial neurogenesis: a gain of PRDC function results in a loss of Bmp4 and hence placode neurogenesis is inhibited; conversely, a loss of PRDC function induces ectopic Bmp4 and an expansion of placode neurogenesis. This modulation is therefore necessary for the number and positioning of the epibranchial neurons.     

Recent studies of dental development in Neandertals: Implications for Neandertal life histories

Did Neandertals share with modern humans their prolonged periods of growth and delayed ages of maturation? During the past five years, renewed interest in this question has produced dental studies with seemingly contradictory results. Some suggest fast dental growth, 1 , 2 while others appear to suggest a slower, modern‐human dental growth pattern. 3 , 4 Although some apparent contradictions can be reconciled, there remain questions that can be resolved only with additional data and cross‐validation of methods. Moreover, several difficulties are inherent in using dental development to gauge Neandertal life histories. Even with complete data on Neandertal dental development, questions are likely to remain about the meaning of those data with regard to understanding Neandertal life histories.     

Primary teeth in Anura are nonpedicellate and bladed

1. Scanning electron microscop of the dentition of four anuran species (Discoglossus pictus, Bombina orientalis, Rana cyanophlyctis, Rana temporaria) revealed that at least the primary teeth, which are established during metamorphosis, are more or less bicuspid, bladed and nonpedicel-late. Juveniles and adults, however, have pedicellate teeth. 2. Thus, regardin the pedicellate condition, the sequence of stages in tooth development of Anura und Urodela show some similarities, although the primary teeth of urodeles develop already before metamorphosis.     

Folic acid-mediated mitochondrial activation for protection against oxidative stress in human dental pulp stem cells derived from deciduous teeth

Enzymatic antioxidant systems, mainly involving mitochondria, are critical for minimizing the harmful effects of reactive oxygen species, and these systems are enhanced by interactions with nonenzymatic antioxidant nutrients. Because fetal growth requires extensive mitochondrial respiration, pregnant women and fetuses are at high risk of exposure to excessive reactive oxygen species. The enhancement of the antioxidant system, e.g., by nutritional management, is therefore critical for both the mother and fetus. Folic acid supplementation prevents homocysteine accumulation and epigenetic dysregulation associated with one-carbon metabolism. However, few studies have examined the antioxidant effects of folic acid for healthy pregnancy outcomes. The purpose of this study was to elucidate the association between the antioxidant effect of folic acid and mitochondria in undifferentiated cells during fetal growth. Neural crest-derived dental pulp stem cells of human exfoliated deciduous teeth were used as a model of undifferentiated cells in the fetus. Pyocyanin induced excessive reactive oxygen species, resulting in a decrease in cell growth and migration accompanied by mitochondrial fragmentation and inactivation in dental pulp stem cells. This damage was significantly improved by folic acid, along with decreased mitochondrial reactive oxygen species, PGC-1α upregulation, DRP1 downregulation, mitochondrial elongation, and increased ATP production. Folic acid may protect undifferentiated cells from oxidative damage by targeting mitochondrial activation. These results provide evidence for a new benefit of folic acid in pregnant women and fetuses.