Unique three-dimensional structure of a fish pharyngeal jaw subjected to unusually high mechanical loads.

We examine the structure of the bone of the pharyngeal jaws of a large fish, the black drum (Pogonias cromis), that uses its tooth-jaw complex to crush hard-shelled bivalve mollusks. During mastication huge compressive forces are concentrated in a tiny zone at the tooth-bone interface. We report on the structure of this bone, with emphasis on its contact with the teeth, at different hierarchical levels and in 3D. Micro-CT shows that the molariform teeth do not have roots and are supported by a circular narrow bony rim that surrounds the periphery of the tooth base. The lower pharyngeal jaw is highly porous, as seen by reflected light microscopy and secondary electron microscopy (SE-SEM). Porosity decreases close to the bone-tooth interface and back-scattered electron (BSE-SEM) microscopy shows a slight elevation in mineral density. Focused ion beam - scanning electron microscopy (FIB-SEM) in the serial surface view (SSV) mode reveals a most surprising organization at the nanoscale level: parallel arrays of mineralized collagen fibrils surrounding channels of ~100 nm diameter, both with their long axes oriented along the load direction. The channels are filled with organic matter. These fibril-channel arrays are surrounded by a highly disordered mineralized material. This unusual structure clearly functions efficiently under compression, but the precise way by which this unique arrangement achieves this function is unknown.

Diet versus jaw bones: Lessons from experimental models and potential clinical implications.

The consumption of different types of diets influences not only body health but the bone remodeling process as well. Nutritional components can directly affect maxillary and mandibular alveolar bone microarchitecture. In this review, we focus on the current knowledge regarding the influence of diets and dietary supplementation on alveolar bone. Accumulating evidence from experimental models suggests that carbohydrate- and fat-rich diets are detrimental for alveolar bone, whereas protective effects are associated with consumption of calcium, ω-3, and bioactive compounds. Little is known about the effects of protein-free and protein-rich diets, boron, vitamin C, vitamin E, zinc, and caffeine on alveolar bone remodeling. Adipokines and direct effects of nutritional components on bone cells are proposed mechanisms linking diet and bone. Results from animal models substantiate the role of nutritional components on alveolar bone. It is a well-built starting point for clinical studies on nutritional monitoring and intervention for patients with alveolar bone disorders, especially those who are treatment refractory.

Sarcoglycans and integrins in bisphosphonate treatment: immunohistochemical and scanning electron microscopy study.

Osteonecrosis of the jaw is an adverse outcome associated with bisphosphonate treatment. Bisphosphonates are used in conjunction with antineoplastic chemotherapy for the treatment of hypercalcaemia associated with malignancy, lytic bone metastasis and multiple myeloma. However, it is not known if the osteonecrosis of the jaw lesion originates in the bone or whether it initiates in the gingival epithelium. Two bisphosphonates are commonly used in cancer treatment. One of these is pamidronate disodium, a second-generation bisphosphonate that differs from the first-generation drug because it inhibits bone resorption at a dose that does not affect bone mineralization. The other widely used BP, zoledronate, is a third-generation drug that is the most potent bisphosphonate in clinical use, showing strong anti-osteoclastic activity, similar to pamidronate. The aim of the present study was to evaluate the modifications of human oral mucosa and underlying bone in patients after treatment with these nitrogen-containing bisphosphonates for 24 and 36 months. We analyzed the structural damage of the oral mucosa and damage of the perilesional mandibular bone observing possible correlations from them. Our results allow to express two hypotheses about the mechanism responsible for these results relating to mandible matrix necrosis; first, an increased skeletal microdamage associated with turnover suppression occurred early in treatment and progress with longer treatment duration, second, opening damage in osteonecrosis of the jaw modifies structural morphology of gingival epithelium.

Cartilage, bone, and intermandibular connective tissue in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

The connective tissue that links the bones of the mandible in the Australian lungfish, Neoceratodus forsteri, has been described as an intermandibular cartilage, and as such has been considered important for phylogenetic analyses among lower vertebrates. However, light and electron microscopy of developing lungfish jaws demonstrates that the intermandibular tissue, like the connective tissue that links the bones of the upper jaw, contains fibroblasts and numerous bundles of collagen fibrils, extending from the trabeculae of the bones supporting the tooth plates. It differs significantly in structure and in staining reactions from the cartilage and the bone found in this species. In common with the cladistian Polypterus and with actinopterygians and some amphibians, lungfish have no intermandibular cartilage. The connective tissue linking the mandibular bones has no phylogenetic significance for systematic grouping of lungfish, as it is present in a range of different groups among lower vertebrates.

[The effectiveness of the application of mineral water from the Klyuchi health resort in the programs of combined spa-based rehabilitation of the patients presenting with acquired jaw defects].

The results of the present study give evidence of the well-apparent sanation effect of balneotherapy with the use of therapeutic mineral water (MW) extracted at the Klyuchi health resort. Irrigation of the oral cavity with this mineral water was shown to reduce the number of the strains of opportunistic microorganisms and their virulence potential. It is concluded that the proposed method may be recommended for the treatment and prevention of dysbiosis in the oral cavity of the patients presenting with acquired jaw defects.

Electrically conductive bacterial nanowires in bisphosphonate-related osteonecrosis of the jaw biofilms.

OBJECTIVE: Bacterial biofilms play a role in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (BRONJ). The purpose of this preliminary study was to test the hypothesis that the extracellular filaments observed in biofilms associated with BRONJ contain electrically conductive nanowires. STUDY DESIGN: Bone samples of patients affected by BRONJ were evaluated for conductive nanowires by scanning electron microscopy (SEM) and conductive probe atomic force microscopy (CP-AFM). We created nanofabricated electrodes to measure electrical transport along putative nanowires. RESULTS: SEM revealed large-scale multispecies biofilms containing numerous filamentous structures throughout necrotic bone. CP-AFM analysis revealed that these structures were electrically conductive nanowires with resistivities on the order of 20 Ω·cm. Nanofabricated electrodes spaced along the nanowires confirmed their ability to transfer electrons over micron-scale lengths. CONCLUSIONS: Electrically conductive bacterial nanowires to date have been described only in environmental isolates. This study shows for the first time that these nanowires can also be found in clinically relevant biofilm-mediated diseases, such as BRONJ, and may represent an important target for therapy.

Occlusion on implants - is there a problem?

Oral rehabilitation restores form and function and impacts on general health. Teeth provide a discriminating sense of touch and directional specificity for occlusal perception, management of food with mastication and swallowing, and awareness of its texture and hardness. Peripheral feedback for control of jaw muscles includes the enamel-dentine-pulp complex and mechanoreceptors in the periodontal tissues. The implications of feedback from periodontal and other intra-oral mechanoreceptors as well as changes in central representation are significant for function and adaptation to oral rehabilitation. With implants, in the absence of the periodontium and periodontal mechanoreceptor feedback, fine motor control of mastication is reduced, but patients are still able to function adequately. Further, there is no significant difference in function with full-arch fixed prostheses on teeth in comparison with implants. Predictable implant outcomes depend on bone support. Optimum restoration design appears to be significant for bone remodelling and bone strains around implants with occlusal loading. Finite element analysis data confirmed load concentrations at the coronal bone around the upper section of the implant where bone loss is commonly observed clinically. Load concentration increased with steeper cusp inclination and broader occlusal table and decreased with central fossa loading and narrower occlusal table size. It is recommended that occlusal design should follow a narrow occlusal table, with central fossa loading in intercuspal contact and low cusp inclination to minimise lateral loading in function and parafunction. Acknowledging these features should address potential problems associated with the occlusion in implant therapy.

Ultrastructural analysis of glutamate-immunopositive synapses onto the rat jaw-closing motoneurons during postnatal development.

The excitatory synapses on the jaw-closing (JC) motoneurons mediate the neuronal input that ensures smooth and rhythmic movements of the jaw. Recently, we have shown that the neurotransmitter phenotype of the inhibitory boutons onto JC motoneurons shifts from GABA to glycine, and new inhibitory synapses onto JC motoneurons are continuously formed during postnatal development (Paik et al. [2007] J. Comp. Neurol. 503:779­789). To test whether the developmental pattern of the excitatory synapses onto JC motoneurons differs from that of the inhibitory synapses, we studied the distribution of glutamate-immunopositive boutons onto the rat JC motoneurons during postnatal development by using a combination of retrograde labeling with horseradish peroxidase (HRP), postembedding immunogold staining, and quantitative ultrastructural analysis. The analysis of 175, 281, and 465 boutons contacting somata of JC motoneurons at postnatal days P2, P11, and P31, respectively, revealed that the number of glutamate-immunopositive (Glut(+)) boutons increased by 2.6 times from P2 to P11 and showed no significant change after that, whereas the length of apposition of these boutons increased continuously from P2 to P31, suggesting that the time course for the development of Glut(+) boutons differed from that for Glut(-) boutons, most of which were immunopositive for GABA and/or glycine. Our findings indicate that excitatory and inhibitory synapses onto JC motoneurons exhibit distinctly different developmental patterns that may be closely related to the maturation of the masticatory system.

[Microstructure comparison of jaw sheaths between the Megophryid tadpoles (Amphibia, Anura) by the technology of electron microscope].

The jaw sheaths morphology of eight megophryid larvae were examined using scanning electron microscope. The morphology of jaw sheaths of Leptobrachiinae and Leptolalaginae larvae was similar. Their jaw sheaths were U-shaped and strong keratinized, the serrations were pyramidal, with broad-based and short pointed. While the jaw sheaths of Megophryinae larvae were less curved and weak keratinized, the serrations were ivory-shaped, with narrow-based and long pointed. It has been found that the relationship between serration's diameter and density was negatively correlated, the changing trend reflected the functional significance of serrations. These distinctions among the jaw sheaths of tadpoles most could be related to their specific ecological habits and to their dietary specializations.

Plate-like permanent dental laminae of upper jaw dentition in adult gobiid fish, Sicyopterus japonicus.

Sicyopterus japonicus (Teleostei, Gobiidae) possesses a unique upper jaw dentition different from that known for any other teleosts. In the adults, many (up to 30) replacement teeth, from initiation to attachment, are arranged orderly in a semicircular-like strand within a capsule of connective tissue on the labial side of each premaxillary bone. We have applied histological, ultrastructural, and three-dimensional imaging from serial sections to obtain insights into the distribution and morphological features of the dental lamina in the upper jaw dentition of adult S. japonicus. The adult fish has numerous permanent dental laminae, each of which is an infolding of the oral epithelium at the labial side of the functional tooth and forms a thin plate-like structure with a wavy contour. All replacement teeth of a semicircular-like strand are connected to the plate-like dental lamina by the outer dental epithelium and form a tooth family; neighboring tooth families are completely separated from each other. The new tooth germ directly buds off from the ventro-labial margin of the dental lamina, whereas no distinct free end of the dental lamina is present, even adjacent to this region. Cell proliferation concentrated at the ventro-labial margin of the dental lamina suggests that this region is the site for repeated tooth initiation. During tooth development, the replacement tooth migrates along a semicircular-like strand and eventually erupts through the dental lamina into the oral epithelium at the labial side of the functional tooth. This unique thin plate-like permanent dental lamina and the semicircular-like strand of replacement teeth in the upper jaw dentition of adult S. japonicus probably evolved as a dental adaptation related to the rapid replacement of teeth dictated by the specialized feeding habit of this algae-scraping fish.

Histological and ultrastructural characterization of the alimentary system of solifuges (Arachnida, Solifugae).

Solifuges are voracious and fast predators. Once having captured a prey item, mostly small arthropods or even small vertebrates, they start feeding on their prey by constant chewing movements with their huge chelicerae. At the same time, they squeeze out the soft tissue that passes the anterior lattice-like part of the mouthparts. The digestion of the food takes place in the midgut, which is anatomically highly complex. It consists of the midgut tube from which numerous prosomal and opisthosomal diverticula and tubular lateral branches arise. The dimorphic epithelium of the midgut tube and the diverticula is constituted of digestive and secretory cells. The digestive cells are characterized by an apical tubulus system and contain nutritional vacuoles, lipids, spherites, and glycogen. Secretory cells contain a huge amount of rough endoplasmic reticulum and secretory vacuoles. The lateral branches are ultrastructurally similar to Malpighian tubules and are likely involved in excretion. In contrast to the midgut, the epithelium of the hindgut consists of only one type of cell overlain by a thin cuticle. Digested residuals are stored in the hindgut until defecation.

Jaw morphology and ontogeny in five species of Ophryotrocha.

Detailed scanning electron microscopy of jaws within the genus Ophryotrocha (Dorvilleidae, Annelida) was performed on 871 jaw parts. The investigations resulted in new understandings of the ontogeny and jaw morphology and have systematic implications for the family. Five species in the genus (Ophryotrocha alborana, O. diadema, O. gracilis, O. hartmanni, and O. labronica pacifica) were kept in culture, and the development of the jaws was studied by sampling throughout their life history. Ophryotrocha species have mandibular plates that remain the same throughout ontogeny, whereas the posterior shafts elongate. Both mandibular plate morphology and shaft ontogeny have species-specific distinctions. In Ophryotrocha, the maxillae can be assigned to three to four distinct types, which are replaced by moulting. The maxillary morphology and developmental stages at which moults occur are species specific, although with broad intervals. A redefinition is given for some of the basic jaw elements, and new homologies are proposed for structures that are also present across other dorvilleid taxa.

Importance of microcracks in etiology of bisphosphonate-related osteonecrosis of the jaw: a possible pathogenetic model of symptomatic and non-symptomatic osteonecrosis of the jaw based on scanning electron microscopy findings.

The aim of this study was to evaluate a possible role of microcracks in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (ONJ) and to discuss an etiological model. Bone samples from 35 patients with ONJ were analyzed. Control samples were taken from five patients with osteomyelitis (OM), ten patients with osteoradionecrosis, seven patients with osteoporosis and bisphosphonate medication without signs of ONJ, and six osteoporotic elderly patients. Samples were examined using scanning electron microscopy. In 54% of the bone samples of patients with ONJ, microcracks were seen. Inflammatory and connective tissue reactions within the microcracks were evident in 82% of the cases, indicating that these cracks were not artificial. In contrast, only 29% of samples from patients with oral bisphosphonate medication without ONJ, no sample from patients with OM, none of the osteoradionecrosis group, and only 17% from patients with osteoporosis showed microcracks. Statistically significant differences could be found between the ONJ group and the group after irradiation and the group with OM, respectively. The evidence of microcracks could be a first step in the pathogenesis of bisphosphonate-related ONJ. The accumulation of these microcracks leads to a situation that could be named "non-symptomatic ONJ". Disruptions of the mucosal integrity may then allow bacterial invasion, leading to jawbone infection with exposed bone, fistulas, and pain. This state could be called "symptomatic ONJ". Furthermore, an assumed local immunosuppression as indicated by various studies could explain the severe courses of therapy-resistant ONJ as regularly observed.

Ontogeny of the tessellated skeleton: insight from the skeletal growth of the round stingray Urobatis halleri.

The majority of the skeleton of elasmobranch fishes (sharks, rays and relatives) is tessellated: uncalcified cartilage is overlain by a superficial rind of abutting, mineralized, hexagonal blocks called tesserae. We employed a diversity of imaging techniques on an ontogenetic series of jaw samples to investigate the development of the tessellated skeleton in a stingray (Urobatis halleri). We compared these data with the cellular changes that characterize cartilage calcification in bony skeletons. Skeletal growth is characterized by the appearance of tesserae as well as changes in chondrocyte shape, arrangement and density. Yolk sac embryos (35-56 mm disc width, DW) have untessellated lower jaw tissue wrapped in perichondrium and densely packed with chondrocytes. Chondrocyte density decreases dramatically after yolk sac absorption (histotroph stage: 57-80 mm DW) until the formation of tesserae, which are first visible using our techniques as thin (approximately 60 microm), sub-perichondral plaques. During the histotroph stage, flattened chondrocytes align parallel to the perichondrium at the tissue periphery, where we believe they are incorporated into developing tesserae to form the cell-rich laminae observed within tesserae; in older animals peripheral cells in the uncalcified phase are rounder and less uniformly oriented. By parturition (approximately 75 mm DW), cell density and the number of adjoining chondrocyte pairs (an indicator of cell division) have dropped to less than a third of their initial values; these remain low and tesserae continue to grow in size. The tessellated skeleton is a simple solution to the conundrum of growth in an endoskeleton with external mineralization and no remodeling. Although we see parallels with endochondral ossification (e.g. chondrocytes decreasing in density with age), the lack of chondrocyte hypertrophy and the fact that mineralization is sub-perichondral (not the case in mammalian cartilage) suggest that the similarities end there.

Surface ultrastructure of gill arches and gill rakers in relation to feeding of an Indian major carp, Cirrhinus mrigala.

The surface ultrastructure of the gill arches and the gill rakers of an herbivorous fish, Cirrhinus mrigala was investigated by scanning electron microscopy. These structures show significant adaptive modifications associated with the food and feeding ecology of the fish. Closely lying short gill rakers and narrow inter-raker channels on the gill arches are associated to filter and retain food particles. Prominent epithelial protuberances on the gill rakers and the gill arches enable the taste buds, located at their summit, to project well above the surface of the epithelium. This could increase the efficiency of the taste buds in selective sorting of palatable food. Surface specializations of the postlingual organ are recognized adaptive modifications for selecting, trapping or holding food particles. Prominent molariform teeth born on the lower pharyngeal jaw, and the chewing pad opposite it, are associated to work together as an efficient pharyngeal mill. Mucous goblet cells are considered to elaborate mucus secretions to trap, glue and lubricate food particles for their smooth transport for swallowing.

Morphological specializations of the buccal cavity in relation to the food and feeding habit of a carp Cirrhinus mrigala: a scanning electron microscopic investigation.

The buccal cavity of an herbivorous fish, Cirrhinus mrigala, was investigated by scanning electron microscopy to determine its surface ultrastructure. The buccal cavity shows significant adaptive modifications in relation to food and feeding ecology of the fish. The buccal cavity of the fish is of modest size and limited capacity, which is considered an adaptation with respect to the small-sized food items primarily consumed by the fish that could be accommodated in a small space. Modification of surface epithelial cells, on the upper jaw, into characteristic structures-the unculi-is considered an adaptation to browse or scrap, to grasp food materials, e.g., algal felts, and to protect the epithelial surface against abrasions, likely to occur during their characteristic feeding behavior. Differentiation of the highly specialized lamellar organ on the anterior region of the palate could be an adaptation playing a significant role in the selection, retention, and sorting out of palatable food particles from the unpalatable items ingested by the fish. The filamentous epithelial projections and the lingulate epithelial projections on the palatal organ in the posterior region of the palate are considered to serve a critical function in final selection, handling, maneuvering, and propelling the food particles toward the esophagus. The abundance of different categories of taste buds in the buccal cavity suggests that gustation is well developed and the fish is highly responsive in the evaluation and the selection of the preferred palatable food items. The secretions of mucous cells in the buccal cavity are associated with multiple functions-particle entrapment, lubrication of the buccal epithelium and food particles to assist smooth passage of food, and to protect the epithelium from possible abrasion. These morphological characteristics ensure efficient working of the buccal cavity in the assessment of the quality and palatability of ingested food, their retention and transport toward the esophagus. Such an adaptation may be essential in conducting the function most basic to the survival of the individuals and species-feeding.

Ultrastructure and function of the mastax in Dicranophorus forcipatus (Rotifera: Monogononta).

Rotifers are characterized by a complex set of cuticularized jaw elements in the pharynx. The fine structure of the jaw elements has been the subject of SEM studies for some time, but only very limited information exists on the ultrastructure of the jaw elements and their function beyond taxonomic considerations. Drawing on SEM and TEM techniques, the present study presents a detailed analysis of the mastax in Dicranophorus forcipatus, a carnivorous monogonont rotifer species from freshwater habitats characterized by an extrusible, grasping jaw apparatus. Based on ultrathin serial sections, the jaw elements are reconstructed and, in total, nine paired and two unpaired muscles identified. Possibly homologous muscles in other rotifer species are discussed and functional considerations of the forcipate mastax are suggested.

Central distribution of nociceptive intradental afferent nerve fibers in the rat.

The central distribution of intradental afferent nerve fibers was investigated by combining electron microscopic observations with a selective method for inducing degeneration of the A delta- and C-type afferent fibers. Degenerating terminals were found on the proprioceptive mesencephalic trigeminal neurons and on dendrites in the neuropil of the trigeminal motor nucleus after application of capsaicin to the rat's lower incisor tooth pulp. The results give anatomical evidence of new sites of central projection of intradental A delta- and C-type fibers whereby the nociceptive information from the tooth pulp can affect jaw muscle activity.

Ultrastructure of the maxillary organ of Scutigera coleoptrata (Chilopoda, Notostigmophora): description of a multifunctional head organ.

The maxillary organ of Scutigera coleoptrata was investigated using light microscopy, electron microscopy, and maceration techniques. Additionally, we compared the maxillary organ of S. coleoptrata with those of two other notostigmophoran centipedes, Parascutigera festiva and Allothereua maculata, using SEM. The maxillary organ is located inside the posterior coxal lobes of the first maxillae and extends posteriorly as sac-like pouches. The narrow epidermis of the maxillae is differentiated to form the epithelium of the maxillary organ. Two types of epithelia are distinguishable: a simple cuboidal epithelium of different height and differentiation (types I, II, IV) and a pseudostratified columnar epithelium (type III). These epithelia are covered by a highly specialized cuticle. The pseudostratified epithelium is the most prominent feature of the maxillary organ. It is covered with hundreds of setae, protruding deep into the maxillary organ. Two different types of setae can be distinguished, filiform and fusiform. The maxillary organ communicates with the oral cavity, the maxillary organ gland, the maxillary nephridium, and with a large number of epidermal glands that secrete into the maxillary organ. Epithelium III allows the extension of the maxillary organ when its pouches are filled with secretion. The maxillary organ is a complex multifunctional organ. The organ probably stores excretion from the maxillary nephridia and secretory fluid from the maxillary organ gland and other epidermal glands. The fluid is primarily required as preening fluid. The ammonia of the excretory fluid is thought to evaporate via the setae and the wide opening of the maxillary organ. It is likely that parts of the fluid can be reabsorbed by the animal via the oral cavity.