The palatine bone and its associations in gadoid fishes

The articulation of the palatine bone in gadoid fishes has been thought of as a specialization of that group. It is shown that there are, in fact, three principal types of articulation, two of which are shared with other gadiform groups. The type of palatine articulation in other paracanthopterygians is briefly described and compared with that of various acanthopterygians. The supposed relationships of some gadoids are commented upon in the light of the specialized nature of some types of palatine articulation.     

The postorbital palatoquadrate articulation in elasmobranchs

Although modern hexanchiforms are the only extant elasmobranchs with a postorbital articulation, according to most morphological and molecular cladistic analyses they are not basal, suggesting that Huxley ( 1876 Proc Zool Soc 1876;24–59) correctly identified this articulation as “an altogether secondary connection.” A postorbital articulation is present in many Paleozoic sharks, but differs from that found in hexanchiforms in its morphology, topographic position on the braincase, and inferred ontogenetic origins. Furthermore, a postorbital articulation is absent in hybodonts (the putative extinct sister group to neoselachians). It is proposed that the term amphistylic should be restricted to the modern hexanchiform condition, where the articular facet is located on the primary postorbital process. An identical articulation probably existed in some extinct galeomorphs (e.g., ?Synechodus dubrisiensis, ?Paraorthacodus), but is not widespread within elasmobranchs generally. The term archaeostylic (“ancient pillar”) is proposed here for the suspensorial arrangement in Paleozic sharks with a postorbital articulation on the ventrolateral part of the lateral commissure. Such an articulation is not known in other gnathostomes and may represent a basal chondrichthyan synapomophy (especially if ?Pucapampella is a stem chondrichthyan), suggesting that the autodiastylic pattern is not primitive for chondrichthyans and that holocephalans have secondarily lost a postorbital articulation. The amphistylic condition may have arisen from the archaeostylic, or it could have been acquired independently within neoselachians, but in either case it is most parsimoniously viewed as apomorphic. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

Origin and dispersal of the earliest brachiopods

Brachiopods first appeared at the very beginning of the Phanerozoic together with the first skeletal organisms. Most brachiopod taxa that arose in the first half of the Cambrian had a short temporal range and became completely extinct by the middle of the Middle Cambrian. Rigid articulation of the valves of brachiopods was provided by various structures, which also appeared in the Early Cambrian. This fact points to the importance of this feature for the formation of the whole group and at the same time testifies to the high variability of rigid articulation at the early stages of brachiopod evolution. This is a typical manifestation of archaic diversity in this animal phylum, which appeared very early in the Phanerozoic. Another important property of the archaic diversity of the early brachiopods was the large number of centers of diversification. As for the majority of groups, climatic zonality was the main factor determining the distribution of brachiopods at the beginning of the Phanerozoic. The main ecological types of brachiopods also appeared in the Early Cambrian.     

The Cronin push-back palate repair with nasal mucosal flaps: a speech evaluation

This is a retrospective study of 92 cleft palate patients who had been repaired with the Cronin push-back palate repair with nasal mucosal flaps. The patients were evaluated by a speech pathologist for intelligibility, articulation, and resonance and rated using a 5-point scale devised for this study. Readily intelligible speech was present in 78 percent. Normal articulation was present in 66 percent. Normal resonance was present in 78 percent of the total subject group. Secondary procedures were performed in 14 percent of the group. Repaired clefts of the soft palate achieved a high rate of normal intelligibility, articulation, and resonance. Repaired submucous clefts and short palates achieved the lowest percent of normal articulation and resonance. Educational placement, hearing, and type of structural deformity all appear to influence the ultimate communication outcome.     

Mechanical regulation of secondary chondrogenesis

The development of the skull is characterised by its dependence upon epigenetic influences. One of the most important of these is secondary chondrogenesis, which occurs following ossification within certain membrane bone periostea, as a result of biomechanical articulation. We have studied the genesis, character and function of the secondary chondrocytes of the quadratojugal of the chick between embryonic days 11 and 14. Analysis of gene expression revealed that secondary chondrocytes formed coincident with Sox9 upregulation from a precursor population expressing Cbfa1/Runx2: a reversal of the normal sequence. Such secondary chondrocytes rapidly acquired a phenotype that is a compound of prehypertrophic and hypertrophic chondrocytes, exited from the cell cycle and upregulated Ihh. Pulse and pulse/chase experiments with BrdU confirmed the germinal region as the highly proliferative source of the secondary chondrocytes, which formed by division of chondrocyte-committed precursors. By blocking Hh signalling in explant cultures we show that the enhanced proliferation of the germinal region surrounding the secondary chondrocytes derives from this Ihh source. Additionally, in vitro studies on membrane bone periosteal cells (nongerminal region) demonstrated that these cells can also respond to Ihh, and do so both by enhanced proliferation and precocious osteogenesis. Despite the pro-osteogenic effects of Ihh on periosteal cell differentiation, mechanical articulation of the quadratojugal/quadrate joint in explant culture revealed a negative role for articulation in the regulation of osteocalcin by germinal region descendants. Thus, the mechanical stimulus that is the spur to secondary chondrocyte formation appears able to override the osteogenic influence of Ihh on the periosteum, but does not interfere with the cell cycle-promoting component of Hh signalling.     

Suboccipital muscle of sharpnose sevengill shark Heptranchias perlo and its possible role in prey dissection

Skull and head muscles of Heptranchias perlo were studied. Its distinctive features include the suboccipital muscles, described for the first time, the absence of the palatoquadrate symphysis, a longitudinally extended mouth, and teeth unsuited for dissecting prey in typical method of modern sharks, which is cutting motions powered by head shaking from side to side. The palatoquadrate cartilages of H. perlo and closely related Hexanchidae articulate with the neurocranium via orbital and postorbital articulations, which together allow for lateral expansion of the jaws, but restrict retraction and protraction. We interpret these features as an adaptation to a different method of prey dissection, that is, ripping in a backward pull. It employs the specific postorbital articulation together with the suboccipital muscles as force-transmitting devices, and is powered by swimming muscles which produce a rearward thrust of the tail. During this type of dissection, the anterior part of the vertebral column should experience a tensile stress which explains the replacement of rigid vertebral bodies by a collagenous sheath around the notochord in H. perlo. The backward-ripping dissection could have been common among ancient Elasmobranchii based on the similarly developed postorbital articulation, a longitudinally extended mouth, and the absence of the palatoquadrate symphysis. A biomechanical comparison with the extinct Pucapampella indicates that ancient elasmobranchs could be also specialized in the backward-ripping prey dissection, but their mechanism was different from that inferred for H. perlo. We suggest that in the early evolution of sharks this mechanism was replaced by head-shaking dissection and then later was restored in H. perlo on a new morphological basis. A new position of the postorbital articulation below the vertebral axis is fraught with the braincase elevation when backward ripping the prey, and as a counter-mean, requires formation of suboccipital portions of the axial musculature unknown in other sharks. Homology and origin of these portions is considered.     

Secondary chondrocyte-derived Ihh stimulates proliferation of periosteal cells during chick development

The development of the skull is characterised by its dependence upon epigenetic influences. One of the most important of these is secondary chondrogenesis, which occurs following ossification within certain membrane bone periostea, as a result of biomechanical articulation. We have studied the genesis, character and function of the secondary chondrocytes of the quadratojugal of the chick between embryonic days 11 and 14. Analysis of gene expression revealed that secondary chondrocytes formed coincident with Sox9 upregulation from a precursor population expressing Cbfa1/Runx2: a reversal of the normal sequence. Such secondary chondrocytes rapidly acquired a phenotype that is a compound of prehypertrophic and hypertrophic chondrocytes, exited from the cell cycle and upregulated Ihh. Pulse and pulse/chase experiments with BrdU confirmed the germinal region as the highly proliferative source of the secondary chondrocytes, which formed by division of chondrocyte-committed precursors. By blocking Hh signalling in explant cultures we show that the enhanced proliferation of the germinal region surrounding the secondary chondrocytes derives from this Ihh source. Additionally, in vitro studies on membrane bone periosteal cells (non-germinal region) demonstrated that these cells can also respond to Ihh, and do so both by enhanced proliferation and precocious osteogenesis. Despite the pro-osteogenic effects of Ihh on periosteal cell differentiation, mechanical articulation of the quadratojugal/quadrate joint in explant culture revealed a negative role for articulation in the regulation of osteocalcin by germinal region descendants. Thus, the mechanical stimulus that is the spur to secondary chondrocyte formation appears able to override the osteogenic influence of Ihh on the periosteum, but does not interfere with the cell cycle-promoting component of Hh signalling.     

The Evolution of the Functional Role of Trunk Muscles During Locomotion in Adult Amphibians

SYNOPSIS. The axial musculature of all vertebrates consistsof two principal masses, the epaxial and hypaxial muscles. Theprimitive function of both axial muscle masses is to generatelateral bending of the trunk during swimming, as is seen inmost fishes. Within amphibians we see multiple functional andmorphological elaborations of the axial musculature. These elaborationsappear to be associated not only with movement into terrestrialhabits (salamanders), but also with subsequent locomotor specializationsof two of the three major extant amphibian clades (frogs andcaecilians). Salamanders use both epaxial and hypaxial musclesto produce lateral bending during swimming and terrestrial,quadrupedal locomotion. However during terrestrial locomotionthe hypaxial muscles are thought to perform an added function,resisting long-axis torsion of the trunk. Relative to salamanders,frogs have elaborate epaxial muscles, which function to bothstabilize and extend the iliosacral and coccygeosacral joints.These actions are important in the effective use of the hindlimbsduring terrestrial saltation and swimming. In contrast, caecilianshave relatively elaborate hypaxial musculature that is linkedto a helix of connective tissue embedded in the skin. The helixand associated hypaxial muscles form a hydrostatic skeletonaround the viscera that is continuously used to maintain bodyposture and also contributes to forward force production duringburrowing.     

Functional morphology of synostosial articulations in the crinoid column

The rarest articulation found in the crinoid column is the synostosis, in which adjacent articular facets are essentially planar. 'Synostoses' in the columns of post-Palaeozoic isocrinids are more correctly termed cryptosymplexies. comprising symplectial articulations which have become infilled by secondary calcite. Cryptosymplexial joints are totally inflexible and are the preferred sites of stem autotomy. Synostoses sensu stricto appear to have been limited to early Palaeozoic taxa, but this form of articulation was soon succeeded by the symplexy. Synostoses were probably commonest in meric columns which evolved from hohlwurzels and in which the main flexibility was along meric sutures, rather than between columnals. With the evolution of the holomeric columnal. a more flexible articulation between columnals was a functional necessity in order that the stem did not develop into a stiffened rod. The solution was the evolution of the symplexy. *** Crinoids, columnals. synostosis, functional morphology evolution.     

Development of a model based method for investigating facet articulation

Reported investigations of facet articulation in the human spine have often been conducted through the insertion of pressure sensitive film into the joint space, which requires incision of the facet capsule and may alter the characteristics of interaction between the facet surfaces. Load transmission through the facet has also been measured using strain gauges bonded to the articular processes. While this method allows for preservation of the facet capsule, it requires extensive instrumentation of the spine, as well as strain-gauge calibration, and is highly sensitive to placement and location of the strain gauges. The inherently invasive nature of these techniques makes it difficult to translate them into medical practice. A method has been developed to investigate facet articulation through the application of test kinematics to a specimen-specific rigid-body model of each vertebra within a lumbar spine segment. Rigid-body models of each vertebral body were developed from CT scans of each specimen. The distances between nearest-neighboring points on each facet surface were calculated for specific time frames of each specimen's flexion/extension test. A metric describing the proportion of each facet surface within a distance (2 mm) from the neighboring surface, the contact area ratio (CAR), was calculated at each of these time frames. A statistically significant difference (p<0.037) was found in the CAR between the time frames corresponding to full flexion and full extension in every level of the lumbar spine (L1-L5) using the data obtained from the seven specimens evaluated in this study. The finding that the contact area of the facet is greater in extension than flexion corresponds to other findings in the literature, as well as the generally accepted role of the facets in extension. Thus, a biomechanical method with a sufficiently sensitive metric is presented as a means to evaluate differences in facet articulation between intact and treated or between healthy and pathologic spines.     

Morphology and evolution of the ectethmoid-mandibular articulation in the meliphagidae (Aves)

The ectethmoid-mandibular articulation in Melithreptus and Manorina (Meliphagidae: Aves) consists of the dorsal mandibular process fitting into and abutting against the ventral ectethmoid fossa; it forms a brace for the mandible. This articulation in Melithreptus is a typical diarthrosis with long folded capsular walls. The mandible, thus, has two separate articulations, each with a different axis of rotation. No other genus of Meliphagidae (except Ptiloprora) or any other avian family possesses a similar feature. The jaw and tongue musculature of Melithreptus are described. The two muscles opening the jaws are well developed, while those closing the jaws are small. The tongue muscles show no special developments. A large maxillary gland, presumably muscus secreting, covers the ventral surface of the jaw muscles. Its duct opens into the oral cavity just behind the tip of the upper jaw. The frilled tip of the tongue rests against the duct opening. The ectethmoid-mandibular articulation braces the adducted mandible against dorsoposteriorly directed forces. The mandible can be held closed without a compression force exerted by the mandible on the quadrate, permitting the bird to raise its upper jaw with greater ease and less loss of force. The tongue can be protruded through the slight gap between the jaws, moving against the duct opening and thus be coated with mucus. Presumably, these birds capture insects with their sticky tongue. Hence, the ectethmoid-mandibular articulation is an adaptation for this feeding method; it evolved independently in three genera of the Meliphagidae. The ectethmoid-mandibular articulation demonstrates that a bone can have two articulations with different axes of rotation, that the two articular halves can separate widely, and that articular cartilages can be flat and remain in contact over a large area. Its function suggests that the basitemporal articulation of the mandible found in many other birds has a similar function. And it demonstrates that in the evolution of the mammalian dentary-squamosal articulation, the new hinge did not have to lie on the same rotational axis as the existing quadrate-articular hinge.     

Zur Evolution basicranialer Gelenke bei Vögeln,insbesondere bei Hühner- und Entenvögeln (Galloanseres)

On the evolution of basicranial articulations of birds, especially of fowl and waterfowl (Galloanseres) Basicranial articulations are among the most neglected structures of the avian feeding apparatus. Based on the presented ontogenetic evidence two nonhomologous types of basicranial articulations are distinguished in birds: 1. A basipterygoid articulation developing from an early embryonic quadratopolar comissure, which is homologous to the basipterygoid articulation of other amniotes. This diarthrosis is present in all paleognathous as well as in many juvenile and some adult neognathous birds. 2. A rostropterygoid articulation developing through apposition of the pterygoid on the parasphenoid. This secondary articulation is known from galliform and ansenform birds (Galloanseres). Based on ontogenetic evidence as well as functional analysis following hypothesis explaining the evolution of rostropterygoid articulations in the Galloanseres is proposed: 1. In the groundplan of birds (Aves, sensu Gauthier 1986) a basipterygoid articulation was present continuously during ontogeny. It protected the pterygoid-quadrate articulation against propalineal distortion by controlling the movement of the caudal end of the flexible, but undivided pterygopalatinal bar. This construction is preserved in recent paleognaths. 2. In the groundplan of the Neognathae an intrapterygoid joint subdividing the pterygopalatinal bar was formed in juveniles. Consequently the basipterygoid articulation had lost its function in adults and was therefore developed only in embryonic and juvenile stages. This condition is present in many recent neognaths. 3. In the stemline of the Galloanseres the intrapterygoid joint was already formed in embryos. Since an undivided pterygopalatinal bar is absent in any ontogenetic stage of the Galloanseres, no basipterygoid articulation is being formed. The recent Galloanseres retain this developmental pattern. 4. In the groundplan of the Galloanseres a newly developed rostropterygoid articulation was present providing a support for the pterygopalatinal bar. This articulation could withstand not only pressure but also increasing tension occurring as a consequence of the development of a gliding jaw joint and a firm grip with beak tips, both consequences of increasing herbivory in the Galloanseres. Since the basipterygoid articulation was reduced, a new secondary joint had to be developed.     

Development of the squamosomandibular articulation in the Mongolian gerbil (Meriones unguiculatus). II. Succinate dehydrogenase activity

Synopsis Succinate dehydrogenase activity has been studied, according to the method of Nachlaset al. (1957), in the developing tissues forming the squamosomandibular articulation in the Mongolian gerbil from its inception through the sixth postnatal day. Increased activity was observed in the chondroblasts, osteoblasts and mesenchymal tissues of the developing articulation. The chondroclasts of the developing mandibular condyle displayed intense reaction as did the osteoclasts of the developing bony articulation. Succinate dehydrogenase activity appeared to be related to the functional maturity of the cellular elements of the developing joint.     

Time history of upper-limb muscle activity during isolated piano keystrokes

Playing-related musculoskeletal disorders (PRMDs) in pianists can lead to the cessation of performance-related activities. A better understanding of the impact of performance parameters on muscle activities could help improve prevention of pianists’ PRMDs. The purpose of this study was to assess the effect of touch and articulation (two performance parameters) on muscle activity and to compare analysis based on scalar and time-history values. Activity of nine upper-limb muscles were recorded in 12 professional classical pianists during the performance of slow-paced isolated keystrokes using pressed and struck touch and staccato and tenuto articulation. A two-way (touch and articulation) ANOVA with repeated measures was performed on time history and single-point values of muscle activations. Pressed touch prime mover muscle was the triceps brachii while struck touch entailed progressive deactivation of anti-gravity muscles before the keystroke. Compared to tenuto articulation, staccato articulation induced a muscular burst on shoulder muscles. Our results suggest that warm-up routines aiming to prevent PRMDs should integrate different types of touch and articulation. Staccato articulation appears however to be an important risk factor of PRMDs located at the shoulder structure. Temporal analysis was a more reliable tool to interpret pianists’ muscle activity during keystrokes.     

Unique occipital articulation with the first vertebra found in pristigasterids, chirocentrids, and clupeids (Teleostei: Clupeiformes: Clupeoidei)

This study recognized a W-shaped occipital articulation associated with the first vertebra in pristigasterids, chirocentrids, and clupeids as a unique character among teleosts, based on an evaluation of 43 species within 40 genera of these three families of the Clupeoidei. This occipital articulation is accompanied by an anterior extension of the neural arch bases, which are autogenous with the first vertebral centrum. In chirocentrids and many of the clupeid species examined, the anterior extension occurs on the second vertebra, and similar occipital articulation is found between the first and second vertebrae. The W-shaped occipital articulation is not found in any other teleosts, including Denticeps (suborder Denticipitoidei), which is thought to be a sister group to the suborder Clupeoidei. The W-shaped occipital articulation is absent in the other family of the Clupeoidei, Engraulidae, based on an evaluation of 11 species in 10 genera. Instead, the convex anterior surface of the first vertebral centrum forms a condyle that articulates with the basioccipital, and the neural arches fuse with the centrum behind this condyle. Therefore, it is unclear whether the anterior extension of the first vertebral neural arch bases, which causes the W-shaped occipital articulation, occurs in engraulids. Based on an evaluation of the osteological development of Konosirus punctatus and Engraulis japonicus, the cartilaginous neural arch bases of the first and second vertebrae extend anteriorly at an early developmental stage in the former, whereas no anterior extension of the first vertebral neural arch bases occurs at any developmental stage in the latter. Therefore, the anterior extension of the neural arch bases, which causes the W-shaped occipital articulation, seems to be a unique character of pristigasterids, chirocentrids, and clupeids among teleosts. Within the recent phylogenetic context, this character may be a synapomorphy of these three families.     

Comparative morphology of mandibular structures in lycid larvae and its phylogenetic implications (Polyphaga, Hexapoda)

The morphology of the larval mandibular structures of the family Lycidae (Polyphaga) is characterized by facultative dicondyly, posterior articulation with long mandibular rods, lateral location of the anterior condyle and its articulation with a paired non‐cranial structure. It is compared to that of Eucrustacea, Chilopoda, Entognatha, Microcoryphia and Zygentoma and found to be more reminiscent of the Entognatha. The phylogenetic implications of this conclusion are discussed, with the Pterygota and Dicondylia hypothesized to be non‐monophyletic.     

Speech results of the Zürich approach in the treatment of unilateral cleft lip and palate

The purpose of this study was to describe perceptually the speech articulation, voice quality, and velopharyngeal competency of subjects with complete unilateral cleft lip and palate treated by the Zürich approach. The mean age of the 37 subjects was 10.5 years. Although only one subject had had secondary palatal management, no subject was rated as exhibiting a severe articulation or nasality problem. Subjects were rated as exhibiting adequate to marginal velopharyngeal competency 94.5 percent of the time, and the incidence of compensatory articulation errors was low. In comparison with other studies that evaluated the two-stage palatal repair, the Zürich approach appears to give the better results. The type of initial soft palate repair is probably the significant factor which contributes to the better speech of these subjects.     

Alterations in the adhesion behavior of osteoblasts by titanium particle loading: inhibition of cell function and gene expression

Total joint replacement prostheses are required to withstand corrosive environments and sustain millions of loading and articulation cycles during their term of implantation. Wear debris generation has been implicated as one of the primary causes of periprosthetic osteolysis and subsequent implant loosening in total joint replacements. Particulate debris consisting of metals, polyethylene, ceramics, and bone cement have each been shown to provoke a biological response in joint tissues. The major cell types within the interfacial granulomatous fibrous tissues consist of fibroblasts, macrophages, lymphocytes, and foreign-body giant cells. Osteoblasts are one of the principal cell types in the bone tissue adjacent to prostheses, maintaining physiologic bone remodeling through the balanced coordination of bone formation and resorption in concert with osteoclasts. To date the phenomenon of osteoblast phagocytosis of titanium particles has been suggested, but has not been sufficiently studied or confirmed. This study seeks to clarify the influence of titanium particles on osteoblast adhesion, deformability, proliferation, and gene expression profile. These studies were accomplished by performing biorheological testing, Northern blot analysis and RNase protection assay. The uptake of metallic particles by the osteoblast resulted in a particle-filament complex formation, which induced a series of variations in cell function. Understanding these variations is critical to expanding our knowledge of implant loosening and elucidating the nature of prosthetic joint failure. This study suggests that the impact of titanium particles on osteoblast function and subsequent implant loosening may have been previously underestimated.     

Ontogeny and homology of the basipterygoid articulation in Pantodon buchholzi (Teleostei: Osteoglossomorpha)

The basipterygoid articulation, an articular connection between the base of the braincase and the palatoquadrate, is widespread among gnathostome vertebrates. However, among living teleosts it is present only in the osteoglossomorphs Arapaima , Heterotis , Scleropages , Osteoglossum and Pantodon . Study of the development of the hyopalatine arch and the basipterygoid articulation in Pantodon buchholzi based on an ontogenetic series of cleared and double stained specimens yielded the following results: the symplectic process of the hyosymplectic cartilage never develops and the symplectic is absent; the pars hyomandibularis fuses with the palatoquadrate; the dermopalatine and ectopterygoid originate as separate bones, but fuse subsequently; the basal process is first visible on the pars metapterygoidea of the palatoquadrate at 7.0 mm standard length (SL); at 11.5 mm SL the basipterygoid process appears on the parasphenoid and contacts the basal process, establishing the basipterygoid articulation; the endopterygoid is initially not involved in the articulation, but during subsequent development enlarges and eventually forms an articular groove for the reception of the basipterygoid process of the parasphenoid; the distal tip of the basal process of the metapterygoid, however, still forms the caudolateral part of the articular groove in the adult. We discuss previous hypotheses about the homology of the basipterygoid articulation of osteoglossoids in light of these findings. Based on the numerous shared similarities and its occurrence in all major actinopterygian lineages, we argue that the basipterygoid articulation in osteoglossoids is homologous to that in non teleostean actinopterygians and represents a plesiomorphic character state at the level of Osteoglossomorpha.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 144 , 1−13.     

The relationship between the PD proprioceptor,the propodite‐dactylopodite joint and the dactylopodite flexor muscle in the walking legs of Cancer pagurus

The mechanical arrangement of the PD organ of Cancer has been studied and equations derived which relate its length to the articulation angle of the PD joint and to the angle which the receptor strand makes with the dactylopodite flexor tendon. These relationships are discussed in the light of the anatomy of the PD articulation.