Kinematics of cranial vault growth in rabbits

To characterize mathematically the spatial rearrangement of cranial vault bones of the rabbit during growth, a longitudinal study was undertaken from age 4-20 weeks. Initially, at least three nonlinear tantalum bone markers were implanted in the parietal, frontal, and the combined nasal bones. Thereafter, the animals were followed regularly with roentgen stereophotogrammetrical analysis. The parietal bones were found to rotate laterally upward (3 degrees), while the frontal bones rotated downward (2 degrees) relative to their contralaterals. The frontal bones rotated rostrally upward (12 degrees) and outward (3 degrees) as well as laterally downward (5 degrees) in relation to the parietal bones. Due to the morphology of the rabbit head, the examination positioning used in this study, and the direction of the growth process, growth at the coronal suture correlated fairly well with longitudinal axis translations; but the growth at the frontonasal suture relative to the frontal bones was directed about 45 degrees downward. This points to the importance of the bone-marker positioning, so that their connecting line is directed along the axis of growth. Also, this approach makes it possible to obtain new information on the development and treatment of craniofacial aberrations.     

DSA-Based Quantitative Assessment of Cerebral Hypoperfusion in Patients with Asymmetric Carotid Stenosis

Digital subtraction angiography (DSA) is often used to evaluate the morphological and pathological changes of cerebral arteries in clinical practice. This study aims to explore the possibility of assessing cerebral hypoperfusion with DSA in patients with carotid stenosis. Thirty patients with a mild to severe stenosis on one side, and a mild stenosis on the other side of the carotid artery were recruited. Frontal, parietal, temporal and occipital lobes were chosen as regions of interest for measuring the quantitative perfusion parameters from their time-density curves (TDCs) of DSA images. The perfusion parameters were compared between the two hemispheres by using paired t-test. In addition, the bilateral asymmetry of these parameters was calculated and its correlation with the bilateral asymmetry in stenosis was analyzed. The parameters included mean transit time (MTT), time of contrast uptake (TU), time taken to the half peak value (1/2TMAX), area under the curve (AUC) were significantly prolonged at the severe stenosis side than those at the mild stenosis side in frontal lobe (P=0.013; P=0.041; P=0.009; P=0.027) and parietal lobe (P=0.008; P=0.041; P=0.002; P=0.012). The asymmetric ratios of MTT and AUC showed statistically significant correlations with stenosis asymmetry in all four lobes. MTT, TU, 1/2TMAX and AUC could reflect the bilateral asymmetry of the cerebral perfusion. These DSA parameters, therefore, may be used for the evaluation of cerebral hypoperfusion caused by carotid stenosis.     

FGF9 can induce endochondral ossification in cranial mesenchyme

Background  

The flat bones of the skull (i.e., the frontal and parietal bones) normally form through intramembranous ossification. At these sites cranial mesenchymal cells directly differentiate into osteoblasts without the formation of a cartilage intermediate. This type of ossification is distinct from endochondral ossification, a process that involves initial formation of cartilage and later replacement by bone.     

An Enlarged Parietal Foramen in the Late Archaic Xujiayao 11 Neurocranium from Northern China,and Rare Anomalies among Pleistocene Homo

We report here a neurocranial abnormality previously undescribed in Pleistocene human fossils, an enlarged parietal foramen (EPF) in the early Late Pleistocene Xujiayao 11 parietal bones from the Xujiayao (Houjiayao) site, northern China. Xujiayao 11 is a pair of partial posteromedial parietal bones from an adult. It exhibits thick cranial vault bones, arachnoid granulations, a deviated posterior sagittal suture, and a unilateral (right) parietal lacuna with a posteriorly-directed and enlarged endocranial vascular sulcus. Differential diagnosis indicates that the perforation is a congenital defect, an enlarged parietal foramen, commonly associated with cerebral venous and cranial vault anomalies. It was not lethal given the individual’s age-at-death, but it may have been associated with secondary neurological deficiencies. The fossil constitutes the oldest evidence in human evolution of this very rare condition (a single enlarged parietal foramen). In combination with developmental and degenerative abnormalities in other Pleistocene human remains, it suggests demographic and survival patterns among Pleistocene Homo that led to an elevated frequency of conditions unknown or rare among recent humans.     

Activation of FGF signaling mediates proliferative and osteogenic differences between neural crest derived frontal and mesoderm parietal derived bone

Background

As a culmination of efforts over the last years, our knowledge of the embryonic origins of the mammalian frontal and parietal cranial bones is unambiguous. Progenitor cells that subsequently give rise to frontal bone are of neural crest origin, while parietal bone progenitors arise from paraxial mesoderm. Given the unique qualities of neural crest cells and the clear delineation of the embryonic origins of the calvarial bones, we sought to determine whether mouse neural crest derived frontal bone differs in biology from mesoderm derived parietal bone.

Methods

BrdU incorporation, immunoblotting and osteogenic differentiation assays were performed to investigate the proliferative rate and osteogenic potential of embryonic and postnatal osteoblasts derived from mouse frontal and parietal bones. Co-culture experiments and treatment with conditioned medium harvested from both types of osteoblasts were performed to investigate potential interactions between the two different tissue origin osteoblasts. Immunoblotting techniques were used to investigate the endogenous level of FGF-2 and the activation of three major FGF signaling pathways. Knockdown of FGF Receptor 1 (FgfR1) was employed to inactivate the FGF signaling.

Results

Our results demonstrated that striking differences in cell proliferation and osteogenic differentiation between the frontal and parietal bone can be detected already at embryonic stages. The greater proliferation rate, as well as osteogenic capacity of frontal bone derived osteoblasts, were paralleled by an elevated level of FGF-2 protein synthesis. Moreover, an enhanced activation of FGF-signaling pathways was observed in frontal bone derived osteoblasts. Finally, the greater osteogenic potential of frontal derived osteoblasts was dramatically impaired by knocking down FgfR1.

Conclusions

Osteoblasts from mouse neural crest derived frontal bone displayed a greater proliferative and osteogenic potential and endogenous enhanced activation of FGF signaling compared to osteoblasts from mesoderm derived parietal bone. FGF signaling plays a key role in determining biological differences between the two types of osteoblasts.     

南京2号人类头骨化石的复位和形态

南京2号人类头骨化石仅保留部分的额骨、顶骨、枕骨和颞骨,为一不完整的颅盖骨。其顶骨和枕骨有数条断裂缝,各断块之间有程度不一的错动,致使该颅盖骨显得外形异常。本项研究是对该颅盖骨的错动部分进行复位,结果表明,南京2号头骨有较大的顶骨、较小的上枕鳞相对宽度、可能较大的颅容量。这些形态提示该头骨与直立人有所不同而与早期智人相近。该头骨所具有的角圆枕、颞鳞顶缘形状、枕骨圆枕发育程度、枕骨的枕平面与项平面过渡情况、枕内隆突点与枕外隆突点的距离、头骨骨壁厚度、脑膜中动脉分支情况、头骨枕面观之轮廓线样式等形态细节,还很难作为可靠的依据把南京2号头骨鉴定为直立人。南京2号头骨很大可能是属于智人亚种(Homo sapiens sapiens)中的一员。     

Mechanical Properties of Calvarial Bones in a Mouse Model for Craniosynostosis

The mammalian cranial vault largely consists of five flat bones that are joined together along their edges by soft fibrous tissues called sutures. Premature closure of the cranial sutures, craniosynostosis, can lead to serious clinical pathology unless there is surgical intervention. Research into the genetic basis of the disease has led to the development of various animal models that display this condition, e.g. mutant type Fgfr2^C342Y/+ mice which display early fusion of the coronal suture (joining the parietal and frontal bones). However, whether the biomechanical properties of the mutant and wild type bones are affected has not been investigated before. Therefore, nanoindentation was used to compare the elastic modulus of cranial bone and sutures in wild type (WT) and Fgfr2^C342Y/+mutant type (MT) mice during their postnatal development. Further, the variations in properties with indentation position and plane were assessed. No difference was observed in the elastic modulus of parietal bone between the WT and MT mice at postnatal (P) day 10 and 20. However, the modulus of frontal bone in the MT group was lower than the WT group at both P10 (1.39±0.30 vs. 5.32±0.68 GPa; p<0.05) and P20 (5.57±0.33 vs. 7.14±0.79 GPa; p<0.05). A wide range of values was measured along the coronal sutures for both the WT and MT samples, with no significant difference between the two groups. Findings of this study suggest that the inherent mechanical properties of the frontal bone in the mutant mice were different to the wild type mice from the same genetic background. These differences may reflect variations in the degree of biomechanical adaptation during skull growth, which could have implications for the surgical management of craniosynostosis patients.     

A tale of two cities: The genetic mechanisms governing calvarial bone development

The skull bones must grow in a coordinated, three‐dimensional manner to coalesce and form the head and face. Mammalian skull bones have a dual embryonic origin from cranial neural crest cells (CNCC) and paraxial mesoderm (PM) and ossify through intramembranous ossification. The calvarial bones, the bones of the cranium which cover the brain, are derived from the supraorbital arch (SOA) region mesenchyme. The SOA is the site of frontal and parietal bone morphogenesis and primary center of ossification. The objective of this review is to frame our current in vivo understanding of the morphogenesis of the calvarial bones and the gene networks regulating calvarial bone initiation in the SOA mesenchyme.     

The subdivisions and fusions of the exoskeletal skull bones ofDiscosauriscus austriacus (Makowsky 1876) and their possible homologues in rhipidistians

Two localities in the Boskovice Furrow region of Moravia (Czecho-Slovakia) have produced new, well preserved material of the Lower Permian tetrapodDiscosauriscus austriacus (Makowsky 1876). A relatively large number of specimens have been found with some dermal skull roof bones partly or fully subdivided, and/or fused. These are the first records of such subdivisions and fusions in this tetrapod and the following bones are discussed: frontal, postfrontal, parietal, intertemporal, supratemporal, tabular and postparietal. The subdivided bones within the skull roof ofDiscosauriscus (and some dissorophoids) are situated at the same places as those found in Devonian rhipidistians, and may relate to the homology of the bones of the cranial exoskeletal roof inDiscosauriscus and in osteolepiforms. It shows that the “orthodox” terminology of the skull roof bones used in osteolepiforms is correct.     

Surface Vulnerability of Cerebral Cortex to Major Depressive Disorder

Major depressive disorder (MDD) is accompanied by atypical brain structure. This study first presents the alterations in the cortical surface of patients with MDD using multidimensional structural patterns that reflect different neurodevelopment. Sixteen first-episode, untreated patients with MDD and 16 matched healthy controls underwent a magnetic resonance imaging (MRI) scan. The cortical maps of thickness, surface area, and gyrification were examined using the surface-based morphometry (SBM) approach. Increase of cortical thickness was observed in the right posterior cingulate region and the parietal cortex involving the bilateral inferior, left superior parietal and right paracentral regions, while decreased thickness was noted in the parietal cortex including bilateral pars opercularis and left precentral region, as well as the left rostral-middle frontal regions in patients with MDD. Likewise, increased or decreased surface area was found in five sub-regions of the cingulate gyrus, parietal and frontal cortices (e.g., bilateral inferior parietal and superior frontal regions). In addition, MDD patients exhibited a significant hypergyrification in the right precentral and supramarginal region. This integrated structural assessment of cortical surface suggests that MDD patients have cortical alterations of the frontal, parietal and cingulate regions, indicating a vulnerability to MDD during earlier neurodevelopmental process.     

Effect of hatchery environment on cranial morphology and developmental stability of Atlantic salmon (Salmo salar L.) from North‐West Russia

The study addresses the effect of hatchery rearing on morphological variation and developmental stability of Atlantic salmon parr from North‐West Russia. Totally, we collected nine samples. Four wild samples were collected from each of the rivers Kola, Umba, Keret’ and Shuia. Five samples of hatchery‐reared parr were the first‐generation progeny of wild adults from these rivers reared separately at the four hatcheries (one hatchery was represented by two samples). Ten meristic and 48 morphometric cranial characters were analysed. We studied the morphological divergence between wild and hatchery fishes of the same river of origin. To analyze developmental stability we used fluctuating asymmetry (random deviations from perfect bilateral symmetry). It was found that hatchery‐reared parr significantly differ from wild parr in both meristic characters and the shape of cranial bones. Different hatcheries caused similar effect on morphological variation in all populations. Fluctuating asymmetry in morphometric characters was significantly higher in hatchery fish than in wild from the Shuia River, indicating a higher level of developmental instability. However, wild parr from the Keret’ River had significantly higher fluctuating asymmetry than cultivated parr of the same origin, possible due to a high infection pressure of the parasite Gyrodactylus salaris Malmberg which has led to significant decline of the wild salmon population in this river, or from genetic changes caused by cultivation. The obtained results indicate a notable effect of hatchery environment on Atlantic salmon’s phenotype.     

Congruence of individual cranial bone morphology and neutral molecular affinity patterns in modern humans

Recent studies have demonstrated that the shape of the human temporal bone is particularly strongly correlated with neutral genetic expectation, when compared against other cranial regions, such as the vault, face, and basicranium. In turn, this has led to suggestions that the temporal bone is particularly reliable in analyses of primate phylogeny and human population history. While several reasons have been suggested to explain the temporal bone's strong fit with neutral expectation, the temporal bone has never systematically been compared against other individual cranial bones defined using the same biological criteria. Therefore, it is currently unknown whether the shapes of all cranial bones possess reliable information regarding neutral genetic evolution, or whether the temporal bone is unique in this respect. This study tests the hypothesis that the human temporal bone is more congruent with neutral expectation than six other individual cranial bones by correlating population affinity matrices generated using neutral genetic and 3D craniometric data. The results demonstrate that while the temporal bone shows the absolute strongest correlation with neutral genetic data compared with all other bones, it is not statistically differentiated from the sphenoid, frontal, and parietal bones in this regard. Potential reasons for the temporal bone's consistently strong fit with neutral expectation, such as its overall anatomical complexity and/or its contribution to the architecture of the basicranium, are examined. The results suggest that future phylogenetic and taxonomic studies would benefit from considering the shape of the entire cranium minus those regions that deviate most from neutrality. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

The mechanical properties of cranial bone: The effect of loading rate and cranial sampling position

Linear and depressed skull fractures are frequent mechanisms of head injury and are often associated with traumatic brain injury. Accurate knowledge of the fracture of cranial bone can provide insight into the prevention of skull fracture injuries and help aid the design of energy absorbing head protection systems and safety helmets. Cranial bone is a complex material comprising of a three-layered structure: external layers consist of compact, high-density cortical bone and the central layer consists of a low-density, irregularly porous bone structure.In this study, cranial bone specimens were extracted from 8 fresh-frozen cadavers (F=4, M=4; 81±11 years old). 63 specimens were obtained from the parietal and frontal cranial bones. Prior to testing, all specimens were scanned using a μCT scanner at a resolution of 56.9 μm. The specimens were tested in a three-point bend set-up at different dynamic speeds (0.5, 1 and 2.5 m/s). The associated mechanical properties that were calculated for each specimen include the 2nd moment of inertia, the sectional elastic modulus, the maximum force at failure, the energy absorbed until failure and the maximum bending stress. Additionally, the morphological parameters of each specimen and their correlation with the resulting mechanical parameters were examined.It was found that testing speed, strain rate, cranial sampling position and intercranial variation all have a significant effect on some or all of the computed mechanical parameters. A modest correlation was also found between percent bone volume and both the elastic modulus and the maximum bending stress.     

南京1号直立人头骨与肯尼亚KNM-ER 3733人类头骨化石的形态比较

KNM-ER 3733人类头骨化石的年代为距今1.78百万年,1975年发现于肯尼亚。Walker和Leakey注意到这具头骨与周口店直立人的在脑颅形态上很相近,但二者在年代上相差大约1百万年,故认为直立人形态在这1百万年期间是稳定的。长期来此观点缺乏更多的人类化石证据来支持。1993年在中国发现了南京1号人类头骨化石。该头骨与KNM-ER 3733头骨一样兼具脑颅和面颅,且都属于成年女性个体,但南京1号人类头骨化石的年代比KNM-ER 3733人类头骨化石的要晚大约1百万年。因此,南京1号人类头骨是目前所知的可用来验证直立人头骨形态是否在1百万年期间保持稳定的唯一合适的人类头骨化石材料。形态比较表明,这两个人类头骨化石的脑颅虽然在眶上圆枕上沟的发育程度、眶后收缩的程度、额骨横向隆起的程度、角圆枕和乳后突的发育与否、顶骨形状以及骨壁厚度的表现上有所差异,但有更多的形态性状显示出相近。这些相近表现在脑颅的长、宽、高值上;颅容量上;脑颅的低矮性上;脑颅最大宽之位置上;额骨、顶骨、枕骨之矢弧值的比例上;眶上圆枕的纤细上;顶骨的大小和矢向扁平性上;颞线位置和颞鳞顶缘的形状上;枕鳞的低宽形状上;上枕鳞与下枕鳞之间的转折形状和比例上;枕骨圆枕和枕骨圆枕上沟的发育程度上等。这两具头骨的面颅虽然有同属突颌型的面角、皆发育有鼻骨间嵴、两鼻骨组成的上部宽度与下部宽度皆差别很大,但有更多的形态性状显示出差别。这些差别表现在面型上、颜面上部扁平度上、眶形和眶型上、上颌额突外侧面的朝向上、鼻骨横向隆起程度上、鼻梁外突程度上、鼻型上、颧骨下缘外展程度上、颊高上、颧上颌下缘的形状上、上颌颧突基部的位置上以及颧结节的位置上等。因此,南京1号头骨与KNM-ER 3733头骨之间在脑颅上显示出较多的相近性状,在面颅上则显示出较多的相异性状。脑颅方面的相近性状大多具有分类上的鉴别价值。这两个头骨脑颅形态的相近支持把KNM-ER 3733头骨鉴定为"直立人"的观点;也提示了南京1号头骨的脑颅似乎保持着1百多万年前的"祖先"形态。如果直立人的某些成员在至少1百万年期间保持着形态稳定的话,则这种形态上的稳定主要是表现在脑颅形态上。这两具头骨的面颅形态上较大差异的意义,目前尚不清楚。     

Asymmetric vault modification in Hopi crania

Cradleboarding was practiced by numerous prehistoric and historic populations, including the Hopi. In this group, one result of cra-dleboarding was bilateral or asymmetric flattening of the posterior occipital. We test whether cradleboarding had significant effects on the morphology of the cranial vault, cranial base, and face. Additionally, we examine associations between direction of flattening and asymmetric craniofacial growth. A skeletal sample of Hopi from the Old Walpi site includes both nonmodified (N = 43) and modified individuals (N = 39). Three-dimensional coordinates of 53 landmarks were obtained using a diagraph. Thirty-six landmarks were used to define nine finite elements in the cranial vault, cranial base, and face. Finite element scaling was used to compare average nonmodified individuals, with averages of bilaterally, right, and left modified individuals. The significance of variation among “treatment” groups was evaluated using a bootstrap test. Pearson product-moment correlations test the association of asymmetry with direction of modification. Hopi cradleboarding has a significant effect on growth of the cranial vault, but does not affect morphology of the cranial base or face. Bilateral flattening of the cranial vault leads to decreased length and increased width of the cranial vault. Flattening of the right or left cranial vault results in ipsilaterally decreased length and width coupled with a corresponding increased length and width on the contralateral side of the cranial vault. There is a significant correlation of size asymmetry with direction of modification in the cranial vault, but not with size or shape change in the cranial base or face. © 1995 Wiley-Liss, Inc.     

Strain patterns in the horncores, cranial bones and sutures of goats (Capra hircus) during impact loading

The design of bovid horns and skulls for the function of head-to-head fighting has been well studied using mechanical and kinematic analyses, but actual strain measurements from the horncores, cranium and sutures during impact loading have never been made. During in vitro impact loading of one or both horns on the heads of female domestic goats, principal strains were measured from the surfaces of the horncore bases, frontal and parietal bones, and interfrontal and frontoparietal sutures. Impact produced a bending moment at the bases of the horncores, with compressive strains on the posterior surfaces more than doubling the anterior tensile strains. These ratios of compression to tension exceed our predictions (and those in the literature) based on curved beam theory. Principal strains in the cranial bones dropped by as much as 50% crossing the sutures, which acted like springs or hinges to allow cranial bone movement. Sutures also experienced very high strain magnitudes, being more than 10 times greater than those of the surrounding cranial bones. Sutural strains during impact loading of the horns also greatly exceeded the strain levels recorded during mastication in other studies. The decrease in strain between adjacent cranial bones across a suture and the large strains at the sutures indicate that the sutures function as shock absorbers during impact.     

Geometric morphometrics and paleoneurology: brain shape evolution in the genus Homo

Paleoneurology concerns the study and analysis of fossil endocasts. Together with cranial capacity and discrete anatomical features, shape can be analysed to consider the spatial relationships between structures and to investigate the endocranial structural system. A sample of endocasts from fossil specimens of the genus Homo has been analysed using traditional metrics and 2D geometric morphometrics based on lateral projections of endocranial shape. The maximum and frontal widths show a size-related pattern of variation shared by all the taxa considered. Furthermore, as cranial capacity increases in the non-modern morphotypes there is a general endocranial vertical stretching (mainly centred at the anterior ascending circumvolution) with flattening and relative shortening of the parietal areas. This pattern could have involved some structural stress between brain development and vault bones at the parietal midsagittal profile in the heavy encephalised Neandertals. In contrast, modern humans show a species-specific neomorphic hypertrophy of the parietal volumes, leading to a dorsal growth and ventral flexion (convolution) and consequent globularity of the whole structure. Brain tensors such as the falx cerebri have been hypothesised to represent one of the main physical constraints on morphogenetic trajectories, with additional influences from cranial base structures. The neurofunctional inferences discussed here stress the role of the parietal areas in the visuo-spatial coordination and integration, which can be involved in higher cerebral functions and related to conceptual thinking.     

Revision of <Emphasis Type="Italic">Rhabdolepis macropterus</Emphasis> (Bronn, 1829) (Osteichthyes,lower Actinopterygii; Lower Permian,SW Germany)

The neotype of Rhabdolepis macropterus is revisited. Together with additional material, a new reconstruction of the skull in lateral view is presented. Main characters of this species of the family Elonichthyidae are a ventral accessory operculum which completely separates the operculum from the suboperculum, and further the border between the frontal (parietal) and the parietal (postparietal) bones lying anterior to the border between the dermosphenotic and the dermopterotic bones. The diagnosis of genus Rhabdolepis is renewed. The species Rh. macropterus is compared with the sympatric elonichthyid species Rhabdolepis saarbrueckensis and Elonichthys fritschi.     

Cell lineage in mammalian craniofacial mesenchyme

We have analysed the contributions of neural crest and mesoderm to mammalian craniofacial mesenchyme and its derivatives by cell lineage tracing experiments in mouse embryos, using the permanent genetic markers Wnt1-cre for neural crest and Mesp1-cre for mesoderm, combined with the Rosa26 reporter. At the end of neural crest cell migration (E9.5) the two patterns are reciprocal, with a mutual boundary just posterior to the eye. Mesodermal cells expressing endothelial markers (angioblasts) are found not to respect this boundary; they are associated with the migrating neural crest from the 5-somite stage, and by E9.5 they form a pre-endothelial meshwork throughout the cranial mesenchyme. Mesodermal cells of the myogenic lineage also migrate with neural crest cells, as the branchial arches form. By E17.5 the neural crest-mesoderm boundary in the subectodermal mesenchyme becomes out of register with that of the underlying skeletogenic layer, which is between the frontal and parietal bones. At E13.5 the primordia of these bones lie basolateral to the brain, extending towards the vertex of the skull during the following 4-5 days. We used DiI labelling of the bone primordia in ex-utero E13.5 embryos to distinguish between two possibilities for the origin of the frontal and parietal bones: (1) recruitment from adjacent connective tissue or (2) proliferation of the original primordia. The results clearly demonstrated that the bone primordia extend vertically by intrinsic growth, without detectable recruitment of adjacent mesenchymal cells.     

Cranial thickness of modern and neolithic populations in Japan

Cranial vault thicknesses were measured directly with a spreading caliper at six anatomical reference points in the modern Japanese and Neolithic Jomon series. Because no statistically significant correlation was found between age and cranial thickness in our study, the age-related change in thickness was not indicated in the modern Japanese. The cranial thicknesses at the frontal and parietal eminences were significantly greater in the female than in the male in modern Japanese. In the male series the cranial thickness of the Neolithic Jomon was significantly greater than that of modern Japanese. It is suggested that the temporal change that has occurred in Japan during the last 2000 years is consistent with the trend toward decreasing cranial thickness during the last 10,000 years in many parts of the world.