单端固定式下颌骨修复体的应力分析

目的:针对包括一侧髁状突的下颌骨缺损,通过有限元应力分析,了解单端固定式下颌骨修复体在功能运动时的受力与变形规律,以期寻求更加合理的修复体的设计和固定方式。方法:建立下颌骨断端和修复体的简易三维模型,模拟咀嚼运动,施加垂直方向载荷,进行有限元法应力分析,计算出该模型各组成部分的应力分布和受力变形。结果:在该模型加载时,延伸板基部和近断端处上部的螺钉颈部是应力集中的部位,近断端处下部的螺钉颈部和修复体的远端舌侧为形变最大的部位。结论:单端固定式下颌骨修复体在加载时,延伸板的基部和靠近断端的固定螺钉是应力集中的部位,修复体远离固定的一侧是变形最大的部位,提示我们应将延伸板形态设计为尽可能加宽,并应增加下颌骨下缘处的固定,使修复体与下颌骨断端受力更加合理,变形也尽可能缩小。     

Albumin preservation in fossil bones and systematics of Malpaisomys insularis (Muridae,Rodentia), an extinct rodent of the Canary Islands

Collagen and albumin were extracted from subfossil bones of the extinct rodent Malpaisomys insularis; the radiocarbon age of the sample was at least 1.73 Ka. Electrophoretic and immunological techniques indicate the preservation of albumin while collagen is revealed as degraded fragments. Immunological comparisons between Malpaisomys albumin and albumin antisera of four extant rodents indicate that Malpaisomys is more closely related to Mus than to Acomys and Uranomys and that Cavia is the most divergent taxon studied. The branching order of the fossil and the extant rodents is discussed with respect to the relationships derived from morphological criteria.     

Comparison of lactase persistence polymorphism in ancient and present-day Hungarian populations

The prevalence of adult-type hypolactasia varies ethnically and geographically among populations. A C/T-13910 single nucleotide polymorphism (SNP) upstream of the lactase gene is known to be associated with lactase non-persistence in Europeans. The aim of this study was to determine the prevalence of lactase persistent and non-persistent genotypes in current Hungarian-speaking populations and in ancient bone samples of classical conquerors and commoners from the 10th-11th centuries from the Carpathian basin; 181 present-day Hungarian, 65 present-day Sekler, and 23 ancient samples were successfully genotyped for the C/T-13910 SNP by the dCAPS PCR-RFLP method. Additional mitochondrial DNA testing was also carried out. In ancient Hungarians, the T-13910 allele was present only in 11% of the population, and exclusively in commoners of European mitochondrial haplogroups who may have been of pre-Hungarian indigenous ancestry. This is despite animal domestication and dairy products having been introduced into the Carpathian basin early in the Neolithic Age. This anomaly may be explained by the Hungarian use of fermented milk products, their greater consumption of ruminant meat than milk, cultural differences, or by their having other lactase-regulating genetic polymorphisms than C/T-13910. The low prevalence of lactase persistence provides additional information on the Asian origin of Hungarians. Present-day Hungarians have been assimilated with the surrounding European populations, since they do not differ significantly from the neighboring populations in their possession of mtDNA and C/T-13910 variants.     

Fibroblast growth factor 10 regulates Meckel's cartilage formation during early mandibular morphogenesis in rats

Fibroblast growth factors (FGF) are pluripotent growth factors that play pivotal roles in the development of various organs. During mandibular organogenesis, Meckel's cartilage, teeth, and mandibular bone differentiate under the control of various FGF. In the present study, we evaluated the role of FGF10 in rat mandibular chondrogenesis and morphogenesis using mandibular organ culture and mandibular cell micromass culture systems. The overexpression of Fgf10 induced by the electroporation of an FGF10 expression vector not only altered the size and shape of Meckel's cartilage, but also upregulated the expression of the cartilage characteristic genes Col2a1 and Sox9 in a mandibular organ culture system. Meckel's cartilage was deformed, and its size was increased when Fgf10 was overexpressed in the lateral area of the mandible. Meanwhile, no effect was found when Fgf10 was overexpressed in the medial portion. In the mandibular cell micromass culture, recombinant FGF10 treatment enhanced chondrogenic differentiation and endogenous ERK (extracellular signal-regulated kinase) phosphorylation in cells derived from the lateral area of the mandible. On the other hand, FGF10 did not have significant effects on mandibular cell proliferation. These results indicate that FGF10 regulates Meckel's cartilage formation during early mandibular morphogenesis by controlling the cell differentiation in the lateral area of the mandibular process in rats.     

Variation in fibular robusticity reflects variation in mobility patterns

During hominin plantigrade locomotion, the weight-bearing function of the fibula has been considered negligible. Nevertheless, studies conducted on human samples have demonstrated that, even if less than that of the tibia, the load-bearing function of the fibula still represents a considerable portion of the entire load borne by the leg. The present study assesses whether variation in habitual lower limb loading influences fibular morphology in a predictable manner. To achieve this, both fibular and tibial morphology were compared amongst modern human athletes (field hockey players and cross-country runners) and matched sedentary controls. Peripheral quantitative computed tomography was used to capture two-dimensional, cross-sectional bone images. Geometric properties were measured at the midshaft for each bone. Results show a trend of increased fibular rigidity from control to runners through to field hockey players. Moreover, relative fibular robusticity (fibula/tibia) is significantly greater in hockey players compared with runners. These results are likely the consequence of habitual loading patterns performed by these athletes. Specifically, the repeated directional changes associated with field hockey increase the mediolateral loading on the lower leg in a manner that would not necessarily be expected during cross-country running. The present study validates the use of the fibula in association with the tibia as a mean to provide a more complete picture of leg bone functional adaptations. Therefore, the fibula can be added to the list of bones generally used (tibia and femur) to assess the correspondence between mobility patterns and skeletal morphology for past human populations.     

An in situ hybridization study of MMP-2, -9, -13, -14, TIMP-1, and -2 mRNA in fetal mouse mandibular condylar cartilage as compared with limb bud cartilage

The main purpose of this in situ hybridization study was to investigate MMPs and TIMPs mRNA expression in developing mandibular condylar cartilage and limb bud cartilage. At E14.0, MMP-2, -14, TIMP-1 and -2 mRNAs were expressed in the periosteum of mandibular bone, and in the condylar anlage. At E15.0 MMP-2, -14, TIMP-1 and -2 mRNAs were expressed in the perichondrium of newly formed condylar cartilage and the periosteum of developing bone collar, whereas, expression of MMP-14 and TIMP-1 mRNAs were restricted to the inner layer of the periosteum/perichondrium. This expression patterns continued until E18.0. Further, from E13.0 to 14.0, in the developing tibial cartilage, MMP-2, -14, and TIMP-2 mRNAs were expressed in the periosteum/perichondrium, but weak MMP-14 and no TIMP-1 mRNA expression was recognized in the perichondrium. These results confirmed that the perichondrium of condylar cartilage has characteristics of periosteum, and suggested that MMPs and/or TIMPs are more actively involved in the development of condylar (secondary) cartilage than tibial (primary) cartilage. MMP-9-positive cells were observed in the bone collar of both types of cartilage, and they were consistent with osteoclasts/chondroclasts. MMP-13 mRNA expression was restricted to the chondrocytes of the lower hypertrophic cell zone in tibial cartilage at E14.0, indicating MMP-13 can be used as a marker for lower hypertrophic cell zone. It was also expressed in chondrocytes of newly formed condylar cartilage at E15.0, and continuously expressed in the lower hypertrophic cell zone until E18.0. These results confirmed that progenitor cells of condylar cartilage are rapidly differentiated into hypertrophic chondrocytes, which is a unique structural feature of secondary cartilage different from that of primary cartilage.     

Expression pattern of Kmt2d in murine craniofacial tissues

Formation of the calvaria is a multi-staged process and is regulated by multiple genetic factors. Disruption of normal calvarial development usually causes craniosynostosis, a prevalent birth defect characterized by premature fusion of calvarial bone. Recent studies have identified mutations of KMT2D allele in patients with craniosynostosis, indicating a potential role for Kmt2d in calvarial development. KMT2D mutations have also been implicated in Kabuki syndrome, which features a distinct facial appearance, skeletal abnormality, growth retardation and intellectual disability. However, the expression pattern of Kmt2d has not been fully elucidated. In the present study we examined the expression pattern of Kmt2d at multiple stages of embryo development in mice, with a focus on the craniofacial tissues. Our in situ hybridization results showed that Kmt2d mRNA is expressed in the developing calvarial osteoblasts, epithelia and neural tissues. Such an expression pattern is in line with the phenotypes of Kabuki syndrome, suggesting that Kmt2d plays an intrinsic role in normal development and homeostasis of these craniofacial tissues.     

A biochemical strategy for simulation of endochondral and intramembranous ossification

Following the assumption that parathyroid hormone related protein and Indian hedgehog form a biochemical regulatory loop for the endochondral process and bone morphogenetic protein 2 and Noggin in the intramembranous process, this paper implements these regulatory mechanisms. For this purpose, we use a set of reaction–diffusion equations that are widely used in morphogenesis, in which biochemical factors are assumed to be secreted by precursor cells, mesenchymal cells and chondrocytes, in endochondral and intramembranous ossification, respectively. The solution leads to the so-called Turing patterns, which represent these processes of ossification in a very approximate way.     

Stature estimation from complete long bones in the Middle Pleistocene humans from the Sima de los Huesos, Sierra de Atapuerca (Spain)

Systematic excavations at the site of the Sima de los Huesos (SH) in the Sierra de Atapuerca (Burgos, Spain) have allowed us to reconstruct 27 complete long bones of the human species Homo heidelbergensis. The SH sample is used here, together with a sample of 39 complete Homo neanderthalensis long bones and 17 complete early Homo sapiens (Skhul/Qafzeh) long bones, to compare the stature of these three different human species. Stature is estimated for each bone using race- and sex-independent regression formulae, yielding an average stature for each bone within each taxon. The mean length of each long bone from SH is significantly greater (p < 0.05) than the corresponding mean values in the Neandertal sample. The stature has been calculated for male and female specimens separately, averaging both means to calculate a general mean. This general mean stature for the entire sample of long bones is 163.6 cm for the SH hominins, 160.6 cm for Neandertals and 177.4 cm for early modern humans. Despite some overlap in the ranges of variation, all mean values in the SH sample (whether considering isolated bones, the upper or lower limb, males or females or more complete individuals) are larger than those of Neandertals. Given the strong relationship between long bone length and stature, we conclude that SH hominins represent a slightly taller population or species than the Neandertals. However, compared with living European Mediterranean populations, neither the Sima de los Huesos hominins nor the Neandertals should be considered ‘short’ people. In fact, the average stature within the genus Homo seems to have changed little over the course of the last two million years, since the appearance of Homo ergaster in East Africa. It is only with the emergence of H. sapiens, whose earliest representatives were ‘very tall’, that a significant increase in stature can be documented.     

Geometric morphometric analysis of mandibular shape diversity in Pan

The aim of this research is to determine whether geometric morphometric (GM) techniques can provide insights into how the shape of the mandibular corpus differs between bonobos and chimpanzees and to explore the potential implications of those results for our understanding of hominin evolution. We focused on this region of the mandible because of the relative frequency with which it has been recovered in the hominin fossil record. In addition, no previous study had explored in-depth three-dimensional (3D) mandibular corpus shape differences between adults of the two Pan species using geometric morphometrics. GM methods enable researchers to quantitatively analyze and visualize 3D shape changes in skeletal elements and provide an important compliment to traditional two-dimensional analyses.Eighteen mandibular landmarks were collected using a Microscribe 3DX portable digitizer. Specimen configurations were superimposed using Generalized Procrustes analysis and the projections of the fitted coordinates to tangent space were analyzed using multivariate statistics. The size-adjusted corpus shapes of Pan paniscus and Pan troglodytes could be assigned to species with approximately 93% accuracy and the Procrustes distance between the two species was significant. Analyses of the residuals from a multivariate linear regression of the data on centroid size suggested that much of the shape difference between the species is size-related. Chimpanzee subspecies and a small sample of Australopithecus specimens could be correctly identified to taxon, at best, only 75% of the time, although the Procrustes distances between these taxa were significant. The shape of the mandibular symphysis was identified as especially useful in differentiating Pan species from one another. This suggests that this region of the mandible has the potential to be informative for taxonomic analyses of fossil hominoids, including hominins. The results also have implications for phylogenetic hypotheses of hominoid evolution.