Bony Plates Research Articles

Morphology and mechanical properties of the dorsal bony plates in the Chinese sturgeon (Acipenser sinensis).

The morphology, composition, and mechanical properties of the dorsal bony plates in the Chinese sturgeon (Acipenser sinensis) were determined in this study. Scanning electron microscopy images of the bony plates revealed a ridge-like shape similar to that of traditional Chinese architecture and displayed hierarchical microstructures whose the degree of mineralization decreased from the surface layer to the internal layer. Moreover, the crests in the central part of the bony plates displayed porous characteristics. Composition analysis of the bony plates revealed that they were primarily composed of Ca, P, O, and C, demonstrating that hydroxyapatite was the main constituent. Mechanical experiments including nanoindentation, penetration, and tension tests confirmed that the bony plates have excellent mechanical properties and present high specific tensile strength that is comparable to that of 304 stainless steel. This study may provide a new bionic design template for lightweight and high-strength body armor.

Synergistic Effects of Silicon/Zinc Doped Brushite and Silk Scaffolding in Augmenting the Osteogenic and Angiogenic Potential of Composite Biomimetic Bone Grafts.

Cell instructive scaffolding platforms displaying synergistic effects by virtue of their chemical and physical cues have tremendous scope in modulating cell phenotype and thus improving the success of any graft. In this regard, we report here the development of Si- and Zn-doped brushite cement composited with silk scaffolding that hierarchically emulated the cancellous bone. The composite scaffolds fabricated exhibited an open porous network capable of enhanced osteoblast survival as attested by increased alkaline phosphatase activity and also sustaining osteoclast activity affirmed by tartrate resistant acid phosphatase staining. Moreover, the chemical cues presented by dissolutions products from the composite scaffold enabled the osteoblasts to secrete proangiogenic factors which favored better endothelial cell survival, confirmed through in vitro experiments. Moreover, the efficacy of these composite biomimetic scaffolds was validated in vivo in volumetric femur defects in rabbits, which revealed that these matrices influenced vascular cell infiltration and favored the formation of matured bony plate. Fluorochrome labeling studies and microtomography analysis revealed that at the end of three months, the implanted composite scaffolds had completely resorbed, leaving behind neo-osseous tissue and vouching for clinical translation of these composite matrices as viable and affordable bone-graft substitutes.

Assessment of changes in the micro-nano environment of intervertebral disc degeneration based on Pfirrmann grade

BACKGROUND CONTEXTPfirrmann grading can be used to assess intervertebral disc degeneration (IVDD). There is growing evidence that IVDD is not simply a structural disorder but also involves changes to the substructural characteristics of the disc. Whether Pfirrmann grade can accurately represent these micro-nano environmental changes remains unclear. PURPOSEWe aimed to assess the micro-nano structural characteristics of the degenerative disc to provide more specific biomechanical information than the Pfirrmann score. STUDY DESIGNA micro- and nano-level structural analysis of degenerative discs of rat tails. METHODSIn this study, 12-week-old adult male Sprague-Dawley rats were divided randomly into five groups: control (no intervention to the intervertebral disc of the tail) and four intervention groups that all had caudal vertebrae immobilized using a custom-made external device to fix four caudal vertebrae (Co7–Co10) but with variable subsequent compression of Co8 and Co9 for 2, 4, 6, or 8 weeks. Magnetic resonance imaging detection of rat coccygeal vertebrae was conducted at each time node of the experiment, and the T2 signal intensity and disc space were evaluated. Animals were euthanized and the caudal vertebrae were harvested for further analysis. Histopathology, glycosaminoglycan (GAG) content, histologic score, end plate structure, and elastic modulus of the intervertebral discs were evaluated. RESULTSIVDD was observed at an earlier Pfirrmann grade (Pfirrmann II) under the microscope. With an increase in Pfirrmann grade to III–V, the pore structure of the bony end plate changed significantly and the number of pores decreased gradually. Furthermore, the total GAG content of the nucleus pulposus decreased from an average of 640.33 μg GAG/ng DNA in Pfirrmann grade I to 271.33 μg GAG/ng DNA in Pfirrmann grade V (p < .0001). At the early stage of clinical degeneration of intervertebral discs (Pfirrmann grades II and III), there were significant changes in mechanical properties of the outer annulus fibrosus compared with the inner layer (p < .05). Further, the fibril diameters exhibited significant changes compared with the control group (p < .05). CONCLUSIONSOur study found that the Pfirrmann grading system combined with intervertebral disc micro-nano structural changes more comprehensively reflected the extent of disc degeneration. These data may help improve our understanding of the pathogenesis and process of clinical disc degeneration.

Morphometric and Topographic Study of Foramen Ovale in Indian Skulls

Foramen ovale is an important foramen for neurosurgeons and used for percutaneous trigeminal rhizotomy in trigeminal neuralgia. The present study was undertaken to study anatomic variations in appearance, dimensions of foramen ovale and its location in relation to the zygomatic arch. The study was conducted on 50 dry human skulls of known sex, available in the museum of Anatomy Dept. in G.S.V.M. Medical College, Kanpur. The shape of foramen ovale and presence of any accessory bony structure like spur, spine, tubercle or bony plate were observed on both sides. The length and width of foramen ovale and its distance from articular tubercle and the anterior root of Zygomatic Arch was measured on both sides. The metric data was statistically analysed for bilateral symmetry and sexual dimorphism. The shape of foramen ovale was typically oval in most of the skulls (66%). In 40% sides any accessory bony structure was not seen while bony plate in 45% sides, spine in 6% and bridge like bony septa dividing the foramen into two compartments in 2% was observed. The mean length and width of foramen ovale in male skulls was 7.50+/-0.90 mm and 4.20+/-0.70 mm and 7.7+/-1.00 mm and 3.9+/-0.80 mm in the female skulls. The mean distance of foramen ovale from articular tubercle on Zygomatic arch was 32.8 +/- 2.8 mm in males and 31.1 +/- 2.4 mm in females. The mean distance from anterior root of Zygomatic arch was 21.4 +/- 1.9 mm in males and 21.6 +/- 1.7 mm in females. There was no significant difference in measurements of various metric parameters between right and left sides of foramen ovale (p&gt;0.05) but highly significant difference was observed between male and female dimensions of all metric parameters.(p&lt;0.001). Thus the foramen ovale does not exhibit bilateral symmetry but the sexual dimorphism is evident. The data is helpful for surgical practices.

A New Orbito-Zygomatic Complex Reconstruction Technique Using Computer-Aided Design and Manufacturing–Assisted Harvest of Autologous Calvarial Bone in Cases of Orbito-Zygomatic Benign Tumor

The orbito-zygomatic complex (OZC) includes several key structures, and its destruction leads to the impairment of functional activities such as nutrition, communication, nasal support, and vision.Management of benign tumors of the OZC is therefore a surgical challenge because of the necessity for reconstruction of these elements. Autogenous bone is considered the gold standard for reconstruction. Nevertheless, there is difficulty related to the complex anatomy and distorted skeletal anatomic landmarks, which require precise work in the case of bone grafts. The aim of this report is to propose a new reconstruction technique consisting of OZC reconstruction with computer-aided design and manufacturing of autologous calvarial bone. Three cases are presented. After performing tumor resection using computer-aided design and manufacturing cutting guides, we used a piezotome to perform osteotomies and preserve the periosteum and sinus mucosa.The SinpliciTi system (Materialise, Châtillon, France) allowed us to make cutting guides and a 3-dimensional surgical plan of the shapes and ideal positions of the calvarial bony plates for the OZC reconstruction. Calvarial osteotomies were performed using a piezotome through the polyamide calvarial cutting guide to obtain the shapes designed beforehand. Once the samples were collected, the shapes could be assembled exvivo and then put in place through a minimally invasive approach. We discuss the advantages and limitations of our reconstruction method and its place in the management of OZC reconstruction.

Parturition and Morphological Development of Larvae and Juvenile in Hippocampus kuda from Korea

The newborn, Hippocampus kuda larvae were 6.97-8.81, standard length (SL) mm (mean 7.89 mm) and mouth and anuse were open. Dorsal fin rays 15-18 and pectoral fin-rays were counted 8 and had 10-11+21 myotomes, body's bony plate ring being developed strongly in the central axis of myotomes part. 4 days after bearing, the SL was 7.02-9.47 mm (mean 8.24 mm) and nostrils began to open. 12 days after bearing, larvae attained to 8.91-11.2 SL mm (mean 10.0 mm). From this time, their unique predation habit appeared. 21 days bearing, larvae attained to 12.1-14.8 SL mm (mean 13.4 mm) the and thorn of back was enlarged among the plate formed around ring. 41 days bearing, seahorses attained to 17.1-17.8 SL mm (mean 17.4 mm) and the number of body's bony plate ring of the top of rings trunk was 11 and on the tail of them was 33-36, similar to figure of adult.

Controlled immobilization-traction based on intervertebral stability is conducive to the regeneration or repair of the degenerative disc: an in vivo study on the rat coccygeal model

Previous studies have shown the potential for intervertebral disc tissue regeneration is very limited. While in vivo and in vitro studies have shown that traction can restore disc height and internal pressure, in many clinical studies it was shown that axial mechanical traction for the treatment of low back pain is ineffective. The aim of this study was to identify how the disc could be distracted, how to define the state of traction, and to further examine the feasibility of regenerating or restoring the degenerative disc by means of traction. A macro- and microlevel structural analysis of degenerative discs of rat tail before and after controlled immobilization-traction. In this study, 49 6-month-old male Sprague-Dawley rats were randomly assigned to one of seven groups. Group A was the sham control group in which caudal vertebrae were instrumented with K-wires only. In Group B (model group), caudal vertebrae were immobilized using a custom-made external device to fix four caudal vertebrae (Co7-Co10) and Co8-Co9 underwent 4 weeks of compression to induce moderate disc degeneration. In Group C, vertebrae Co8-Co9 underwent 4 weeks of compression to induce moderate disc degeneration, followed by removal of the external apparatus. Rats in the other four groups (Groups D-G), Co8-Co9 underwent 4 weeks of compression to induce moderate disc degeneration followed by 2 weeks, 4 weeks, 6 weeks, and 8 weeks of distraction, respectively. Caudal vertebrae were harvested and disc height, T2 signal intensity of the discs, disc morphology, total glycosaminoglycan content of the nucleus pulposus and the structure of the Co8-Co9 end plate were evaluated. After 4 weeks of compression, the intervertebral height and T2 signal intensity of Co8-Co9 vertebrae of rats in Groups B to G were significantly reduced compared with Group A (sham group, all p<.0001). Histological scores of rats in Group B averaged 10.14 and the total glycosaminoglycan (GAG) of nucleus pulposus averaged 238.21μg GAG/ng DNA. The bony end plate structure showed significant changes in comparison with the control Group. After 2 weeks to 8 weeks of traction, the disc space and T2 signal intensity of Co8-Co9 vertebrae in Group E were significantly recovered compared to that of rats in Group B (p<.0001), and the intervertebral height of the Co8-Co9 in Group D, Group F, and Group G when compared with Group B (p<.0001). Meanwhile, the T2 signal intensity of Co8-Co9 in Group D, F, and G when compared with Group B (p<.001). Histological scores dropped from an average of 10.14 in Group B to 5.57 in Group E, and 5.86 in Group F (all p<.0001). Furthermore, the total GAG content of the nucleus pulposus increased from an average of 238.21μg GAG/ng DNA in Group B to 601.02μg GAG/ng DNA in Group E (p<.0001). The number of pores of end plates in rats in Groups D and E both were significantly increased when compared to that of rats in Group B (Groups D vs Groups B, p<.05; Groups E vs Groups B, p<.0001). A mechanical degenerative model was successfully established by using a custom-made device. We demonstrated that disc degeneration is a cascade of biochemical, mechanical, and structural changes mediated by cells in an abnormal mechanical environment. Not all levels of disc degeneration can be regenerated or repaired. Regeneration or recovery of disc degeneration requires specific conditions. Based on the immobilization-traction mode, the cascade cycle of disc degeneration is interrupted. Traction of 2 to 6 weeks is a sensitive period for regeneration of the degenerative disc. Moreover, the duration and extent of the traction loading must be moderately controllable, and beyond the limits that can lead to significant degeneration. These data may help improve our understanding of the pathogenesis of clinical disc degeneration and how to optimize the use of traction devices for possible regeneration.

Comparative Functional Analysis of the Anatomy of the appendicular skeleton in two reptilian species

Aim of the work: the present study aimed to illustrate the osteological characters of the appendicular skeleton of two Egyptian lizard species, Acanthodactylus boskianus and Ptyodactylus guttatus and clarify the relationship between characteristics of the appendicular skeleton and mode of their locomotion of the two species. A. boskianus is diurnal insectivorous lizard forage in open area and it is a generalized ground-dwelling species and P. guttatus is a diurno-nocturnal omnivorous gecko which is a highly specialized climbing on vertical substrates. Material and methods: in the present study we used Alizarin red and Alcian blue as double skeletal staining to investigate the the bony and cartilaginous pattern of limbs and girdles of A. boskianus and P. guttatus. Results: in P. guttatus, the pectoral girdle was characterized by the presence of the interclavicles was dagger in shape and partially fused with clavicles, while it was cruciform and completely fused with the clavicles in A. boskianus. In P. guttatus, the epicoraoid was well developed, broad bony plates and fused with the interclavicles, while in A. boskianus it was narrow cartilaginous, plates and overlap in the mid-line. Moreover, in P. gutattus two fenestrae were appeared within coracoid and scapula with un-fenestrated cartilaginous sternum, while one fenestra appeared in both coracoid and sternum of A. boskianus. On other hand, the pelvic girdle of P. guttatus had complete fusions between the pubis, ischium and ilium, while in A. boskianus the pubis articulated poster-omedially with the ischium. In both P. gutattus and A. boskianus, the forelimbs posture was in horizontal plane, while the hind limbs were in vertical plane. In P. gutattus both the fore and hind limbs were relatively equal in length, while the fore limb in A. boskianus was greatly shorter than the hind limb. Conclusion: the P. gutattus is considered as a one of climbers species which have stout appendicular skeleton to support the climbing process on the vertical surface with relatively short limbs, while A. Boskianus is ground-dwellers and also good climbers and use their claws to walk and climbing on rocky areas and these abilities of locomotion depend on the flexibility of skeletal elements of its appendicular skeleton.

Comparative Functional Analysis of the Anatomy of the appendicular skeleton in two reptilian species

Aim of the work: the present study aimed to illustrate the osteological characters of the appendicular skeleton of two Egyptian lizard species, Acanthodactylus boskianus and Ptyodactylus guttatus and clarify the relationship between characteristics of the appendicular skeleton and mode of their locomotion of the two species. A. boskianus is diurnal insectivorous lizard forage in open area and it is a generalized ground-dwelling species and P. guttatus is a diurno-nocturnal omnivorous gecko which is a highly specialized climbing on vertical substrates. Material and methods: in the present study we used Alizarin red and Alcian blue as double skeletal staining to investigate the the bony and cartilaginous pattern of limbs and girdles of A. boskianus and P. guttatus. Results: in P. guttatus, the pectoral girdle was characterized by the presence of the interclavicles was dagger in shape and partially fused with clavicles, while it was cruciform and completely fused with the clavicles in A. boskianus. In P. guttatus, the epicoraoid was well developed, broad bony plates and fused with the interclavicles, while in A. boskianus it was narrow cartilaginous, plates and overlap in the mid-line. Moreover, in P. gutattus two fenestrae were appeared within coracoid and scapula with un-fenestrated cartilaginous sternum, while one fenestra appeared in both coracoid and sternum of A. boskianus. On other hand, the pelvic girdle of P. guttatus had complete fusions between the pubis, ischium and ilium, while in A. boskianus the pubis articulated poster-omedially with the ischium. In both P. gutattus and A. boskianus, the forelimbs posture was in horizontal plane, while the hind limbs were in vertical plane. In P. gutattus both the fore and hind limbs were relatively equal in length, while the fore limb in A. boskianus was greatly shorter than the hind limb. Conclusion: the P. gutattus is considered as a one of climbers species which have stout appendicular skeleton to support the climbing process on the vertical surface with relatively short limbs, while A. Boskianus is ground-dwellers and also good climbers and use their claws to walk and climbing on rocky areas and these abilities of locomotion depend on the flexibility of skeletal elements of its appendicular skeleton.

Changes in human intervertebral disc biochemical composition and bony end plates between middle and old age.

ObjectiveThis study evaluates molecular, nutritional and biochemical alterations in human intervertebral discs between middle and old age.MethodsTwenty-eight human lumbar intervertebral discs from donors were evaluated and separated into two groups: Middle-aged (35–50 years old, relatively non-degenerate discs of Pfirrmann grades 1–3, n = 15) and Old-aged (≥80 years old, all degenerate Pfirrmann grade 4 or 5, n = 13). Parameters which might be expected to to be related to nutrient supply and so the health of disc cells (eg the porosity of the vertebral endplate, cell viability and cell density) and to disc extracellular composition (ie quantification of glycosaminoglycan disaccharides and hyaluronic acid molecular weight) and collagen organization, were analyzed. Three regions of the intervertebral disc (anterior annulus fibrosus, nucleus pulposus, and posterior annulus fibrosus) were examined.ResultsThe old-aged group showed a decrease in content of sulphated and non-sulphated glycosaminoglycans relative to middle-aged and there were also alterations in the proportion of GAG disaccharides and a decrease of collagen fiber size. Hyaluronic acid molecular weight was around 200 kDa in all regions and ages studied. The anterior annulus differed from the posterior annulus particularly in relation to cell density and GAG content. Additionally, there were changes in the bony endplate, with fewer openings observed in the caudal than cranial endplates of all discs in both groups.ConclusionsResults show the cranial vertebral endplate is the main vascular source for the intervertebral discs. Hylauronic acid molecular weight is the same through the intervertebral disc after age of 50 years.

Diagnostics of Gymnocanthus pistilliger (Pallas, 1814) and G. galeatus Bean, 1881 (Scorpaeniformes: Cottidae) in their Cohabitation Areas

Sex-independent characters for identification of Gymnocanthus pistilliger and G. galeatus in their cohabitation areas were revealed: the presence, position, and arrangement of rough bony plates on the interorbital space, as well as the total spine and ray count for all fins (dorsals and anal; doubled number of rays in pectoral). The interorbital space of G. galeatus is completely covered by bony plates; the spine and ray count for all fins is 82−89. In G. pistilliger, the interorbital space is naked (26%) or has only a few bony plates that never extend onto the rim of the orbit; the spine and ray count for all fins is 74−81. In the eastern part of the Sea of Okhotsk, G. galeatus is not common and perhaps might be found here only occasionally.

First record of the Bignose Unicornfish, Naso vlamingii (Perciformes, Acanthuridae) from Korea

Naso vlamingii (Valenciennes, 1835) is reported from Korea for the first time and a morphological description is provided. A single specimen of N. vlamingii was collected from the southeastern coast of Jeju Island, Korea in September 2017. This species is characterized by the presence of 2 bony plates on the middle of the caudal peduncle, 6 dorsal and 2 anal fin spines, and a rounded, convex, swollen snout. This species is the fifth species of the genus Naso Lacepède, 1801 in the Korean fish fauna, and the newly proposed Korean name for the species is “Keun-ko-pyo-mun-jwi-chi”.

Reposition of the bone plate over the antrostomy in maxillary sinus augmentation: A histomorphometric study in rabbits.

To test if repositioning the bony plate secured with a cyanoacrylate over the antrostomy in maxillary sinus augmentation was superior to covering the antrostomy with a collagen membrane in terms of the bone augmentation area and the bone density. After the exposure of the nasal bone in eighteen rabbits, a rectangular access window was prepared with a sonic instrument, and the bony plate was removed. A bilateral sinus mucosa elevation was performed, and the space was filled with a resorbable xenograft. On the test side, the bone plate was repositioned over the antrostomy and fixed with a cyanoacrylate. On the control side, a collagen membrane was placed over the opening. Per group, six animals were sacrificed after 2, 4, and 8weeks of healing, respectively. Histological ground sections were prepared. The augmented area after elevation decreased between 2 and 8weeks from 9.4±1.8 to 4.8±2.8 mm2 at the test and from 9.5±2.6 and 5.1±1.6 mm2 at the control sites. Small amounts of new bone were seen after 2weeks in both groups (~1.6%-2.5%) forming from the bony sinus walls. New bone density increased over time in both groups reaching~10%-11% and~23%-25% after 4 and 8weeks, respectively. No statistically significant differences were found. Small residual defects were present both at the test sites in the margin of the bone plate, and at the control sites in the center of the antrostomy. The bone healing in the elevated sinus space was similar irrespective of the coverage of the antrostomy. After 8weeks, the bone plate repositioned on the antrostomy was incorporated while at the control sites the healing was still incomplete. Residual defects were still present in both groups.

Ossicular Involvement and Types of Pathology in Chronic Otitis Media Squamous Active Disease

Background: Chronic otitis media (COM) squamous type is commonly as­sociated with cholesteatoma. In COM squamous type with active disease, there is retraction of pars flaccida or pars tensa with retention of squamous epithelial debris and is associated with inflammation and production of pus. It is potentially dangerous because it can cause resorption of bone, leading to ossicular erosion and destruction of bony plates of middle ear. The objective of this study is to determine the effect of chronic otitis media squamous type on the ossicular chain as well as to observe the types of pathology in this disease.&#x0D; Methods and materials: Fifty cases of chronic otitis media squa­mous type who underwent surgical management were included. The status of ossicular chain was evaluated intraoperatively. The type of pathology in­volving middle ear was also studied. Cases admitted for revision surgery were excluded from the study.&#x0D; Results: Of the total fifty cases, ossicular changes were observed in forty eight cases and in two cases all ossicles were intact. Long process of incus is the most frequently involved ossicle. The most common pathology was found to be mixed type (52%).&#x0D; Conclusion: The conclusion of this study is that ossicular chain is commonly involved in chronic otitis media squamous type and mixed pathology consisting of cholesteatoma and granulation tissue is the most frequent pathology.

Proximate causes of variation in dermal armour: insights from armadillo lizards

Although it is widely assumed that body armour in animals evolved to thwart predator attacks, assessing the role that predators may play in shaping defensive morphologies has proven to be difficult. Recent studies suggest that body armour might be influenced by additional factors besides predation, and/or even by sexual selection. We investigated variation in dermal armour in 13 populations of armadillo lizards Ouroborus cataphractus, spanning the entire distribution range of the species. We obtained thickness measurements of osteoderms – bony plates embedded in dermal layer of the skin – using micro‐ and nano‐computed tomography. Using these data, we examined the effects of predation pressure/risk and climatic variables on dermal armour variation and addressed sexual and ontogenetic influence. Our results show that climate is the only factor affecting variation in dermal armour. Populations inhabiting more arid environments, characterized by low summer precipitation and mild winter temperatures, are relatively more armoured than those present in less arid environments. In contrast to our expectations, predation pressure or perceived predation risk was not associated with osteoderm thickness. The results of our study support the idea that the evolution of defensive traits might not be driven exclusively by predator–prey interactions, but could be moulded by environmental factors. In particular, we highlight the role of dermal armour as a potentially important mechanism to reduce evaporative water loss in arid environments.

Analyzing nature's protective design: The glyptodont body armor.

Many animal species evolved some form of body armor, such as scales of fish and bony plates or osteoderms of reptiles. Although a protective function is often taken for granted, recent studies show that body armor might comprise multiple functionalities and is shaped by trade-offs among these functionalities. Hence, despite the fact that natural body armor might serve as bio-inspiration for the development of artificial protective materials, focussing on model systems in which body armor serves a solely protective function might be pivotal. In this study, we investigate the osteoderms of Glyptotherium arizonae, an extinct armadillo-like mammal in which body armor evolved as protection against predators and/or tail club blows of conspecifics. By using a combination of micro-computed tomography, reverse-engineering, stress simulations and mechanical testing of 3D printed models, we show that the combination of dense compact layers and porous lattice core might provide an optimized combination of strength and high energy absorption.

Vascularization and odontode structure of a dorsal ridge spine of Romundina stellina Ørvig 1975.

There are two types of dermal skeletons in jawed vertebrates: placoderms and osteichthyans carry large bony plates (macromery), whereas chondrichthyans and acanthodians are covered by small scales (micromery). Fin spines are one of the last large dermal structures found on micromeric taxa and offer a potential source of histology and morphology that can be compared to those found on macromeric groups. Dermal fin spines offer a variety of morphology but aspects of their growth modes and homology are unclear. Here, we provide detailed descriptions of the microstructure and growth of a dorsal ridge spine from the acanthothoracid placoderm, Romundina stellina, using virtual three-dimensional paleohistological datasets. From these data we identify several layers of dentine ornamentation covering the lateral surfaces of the spine and reconstructed their growth pattern. We show that this spine likely grew posteriorly and proximally from a narrow portion of bone located along the leading edge of the spine. The spine is similarly constructed to the scales with a few exceptions, including the absence of polarized fibers distributed throughout the bone and the presence of a thin layer of perichondral bone. The composition of the spine (semidentine odontodes, dermal bone, perichondral bone) is identical to that of the Romundina dermal plates. These results illustrate the similarities and differences between the dermal tissues in Romundina and indicate that the spine grew differently from the dentinous fin spines from extant and fossil chondrichthyans. The morphology and histology of Romundina is most similar to the fin spine of the probable stem osteichthyan Lophosteus, with a well-developed inner cellular bony base and star-shaped odontodes on the surface. Results from these studies will undoubtedly have impact on our understanding of fossil fin spine histology and evolution, contributing to the on-going revision of early gnathostome phylogeny.

Proposal of a Novel Natural Biomaterial, the Scleral Ossicle, for the Development of Vascularized Bone Tissue In Vitro.

Recovering of significant skeletal defects could be partially abortive due to the perturbations that affect the regenerative process when defects reach a critical size, thus resulting in a non-healed bone. The current standard treatments include allografting, autografting, and other bone implant techniques. However, although they are commonly used in orthopedic surgery, these treatments have some limitations concerning their costs and their side effects such as potential infections or malunions. On this account, the need for suitable constructs to fill the gap in wide fractures is still urgent. As an innovative solution, scleral ossicles (SOs) can be put forward as natural scaffolds for bone repair. SOs are peculiar bony plates forming a ring at the scleral-corneal border of the eyeball of lower vertebrates. In the preliminary phases of the study, these ossicles were structurally and functionally characterized. The morphological characterization was performed by SEM analysis, MicroCT analysis and optical profilometry. Then, UV sterilization was carried out to obtain a clean support, without neither contaminations nor modifications of the bone architecture. Subsequently, the SO biocompatibility was tested in culture with different cell lines, focusing the attention to the differentiation capability of endothelial and osteoblastic cells on the SO surface. The results obtained by the above mentioned analysis strongly suggest that SOs can be used as bio-scaffolds for functionalization processes, useful in regenerative medicine.

Dorsal spine evolution in threespine sticklebacks via a splicing change in MSX2A

BackgroundDorsal spine reduction in threespine sticklebacks (Gasterosteus aculeatus) is a classic example of recurrent skeletal evolution in nature. Sticklebacks in marine environments typically have long spines that form part of their skeletal armor. Many derived freshwater populations have evolved shorter spines. Changes in spine length are controlled in part by a quantitative trait locus (QTL) previously mapped to chromosome 4, but the causative gene and mutations underlying the repeated evolution of this interesting skeletal trait have not been identified.ResultsRefined mapping of the spine length QTL shows that it lies near the MSX2A transcription factor gene. MSX2A is expressed in developing spines. In F1 marine × freshwater fish, the marine allele is preferentially expressed.Differences in expression can be attributed to splicing regulation. Due to the use of an alternative 5 ′ splice site within the first exon, the freshwater allele produces greater amounts of a shortened, non-functional transcript and makes less of the full-length transcript. Sequence changes in the MSX2A region are shared by many freshwater fish, suggesting that repeated evolution occurs by reuse of a spine-reduction variant.To demonstrate the effect of full-length MSX2A on spine length, we produced transgenic freshwater fish expressing a copy of marine MSX2A. The spines of the transgenic fish were significantly longer on average than those of their non-transgenic siblings, partially reversing the reduced spine lengths that have evolved in freshwater populations.ConclusionsMSX2A is a major gene underlying dorsal spine reduction in freshwater sticklebacks. The gene is linked to a separate gene controlling bony plate loss, helping explain the concerted effects of chromosome 4 on multiple armor-reduction traits. The nature of the molecular changes provides an interesting example of morphological evolution occurring not through a simple amino acid change, nor through a change only in gene expression levels, but through a change in the ratio of splice products encoding both normal and truncated proteins.

When natural armour does more than protect

![Graphic][1] A range of animals, from dinosaurs to armadillos, have a natural form of chain mail armour that is composed of bony plates in the skin called osteoderms. Individual osteoderms each act as miniature shields that are linked together through flexible connections, forming a