Developmental anatomy of the mouse stapediovestibular and temporomandibular joints.

The genesis, development and growth of the mouse stapediovestibular joint (SVJ), which contains the annular ligament, and the temporomandibular joint (TMJ) were examined in an attempt to study the stress-bearing articular tissue that is thought to be derived from embryonic mesenchyme; the findings were also compared with those in the ossicular joints. The following conclusions were obtained: 1) The articular cartilage of the mandibular condylar process, stapedial foot plate and otic capsule is derived from fetal fibrous articular tissue. 2) The fetal TMJ developed into a typical double diarthroses containing an articular disc. 3) The fetal syndesmodial SVJ differentiated into the annular ligament containing characteristic palisade-like fibroblasts and hammock-like fibers; no interzone formation or synovial cavities were observed in the completed and mature syndesmodial SVJ. 4) Like the TMJ, the major elastic system fibers in the annular ligament were also mechanical-resistant elaunin. 5) Elastogenesis was closely related to functional and mechanical factors in the auditory ossicular chain, TMJ and annular ligament; the mature incudomalleal and incudostapedial joints contained mainly mature elastic fibers, but the mature SVJ and immature TMJ contained mainly pre-elastic elaunin fibers. 6) Stress elastosis, turnover of the fibrillar component and age changes in cellular and fibrous components were not evident in either the mature SVJ or the young functional TMJ.

Scanning electron microscopy of the organelles of rat incisor odontoblasts--in particular the tubulo-vesicular elements.

The fine structure of rat odontoblasts (OBs) showing the developmental sequence of cellular maturation along the long axis of the incisor was studied. The cytomorphological changes and relationships of the intracellular components, particularly the membranous component, were investigated mainly by scanning electron microscopy (SEM) using the AODO (A: aldehyde prefixation; O: osmium tetroxide postfixation; D: dimethyl sulfoxide (DMSO) freeze-fracture; O: osmium tetroxide maceration) method and transmission electron microscopy (TEM) using the conventional methods. The following results were obtained: 1) The elongated young OBs were highly polarized and characterized by well-developed concentric cisternal granular (rough) endoplasmic reticulum (rER) layers and Golgi complex. SEM showed the rER was continuous to the agranular (smooth) ER (sER). 2) Transformation of the concentric rER to a tubular network was closely related to the maturation and secretory activity of the OBs. 3) Many branched and elongated tubular mitochondria were observed in the supranuclear region of young OBs. On the other hand, many round-to-ovoid mitochondria were observed particularly in the distal clear area of old OBs. 4) SEM also revealed tubulo-vesicular elements, which are believed to be structures relating to secretory and absorptive functions, composed of secretory granules and small tubules, having connections with the cell membrane in both young and old OBs. Furthermore, the small tubules were continuous with the larger sER tubules in the distal clear area and cell process of the OBs. 5) Using TEM, long lysosomes, various cytosomes and multivesicular bodies (MVBs) were usually observed in the peripheral region and in the distal cytoplasm and major processes of the OBs. The present SEM and TEM studies indicated the MVBs were closely associated with sER tubules of the tubulo-vesicular elements. 6) Both TEM and SEM showed cytosegresomes containing laminated ER and other organelles particularly in the distal clear area of old OBs. 7) SEM also showed some thin lateral branchings of the OBs running along the fine matricial fibrils, as well as matrix-vesicle-like structures deeply invaginated at the basal portion of the cell processes and distributed in the predentine. The present morphological study demonstrated a three-dimensional configuration of the structures relating to secretory and absorptive functions of young and old OBs.

Comparative histological contributions to the development of the ear-ossicular joints and the temporomandibular joint in the mouse.

The genesis, differentiation, development and growth of the ear-ossicular joints and temporomandibular joint (TMJ) in the Slc-ICR mouse were studied by means of light and transmission electron microscopy. The differentiation of the ossicular joints and TMJ anlagen was initiated during the fetal stages. Although morphogenesis, development and growth of the TMJ were already evident in the prenatal stages, the joint-cleaving associated with the occurrence of interzones in the cartilaginous ossicular chain was observed during the neonatal stages. However, the simple diarthrodial ossicular joints were completed and became mature earlier than the double synovial TMJ having an articular disc in early postnatal life. TEM examinations revealed that the articulating epiphyseal cartilage of the ossicular joints consisted of hyaline cartilage, while the intracapsular structures in the TMJ were composed of fibrocartilage. The synovium of the diarthroidal joints was supplied by blood vessels, nerve fibers, collagen and elastic fibers. No distinct aging in the cellular and fibrous components of the synovial tissue of the completed TMJ and ossicular joints was evident in the present study.

Immunohistochemical localization of certain inducers related to the proliferation of the pituitary gland and a study on cell contacts between the presumptive neurohypophysis and the adenohypophysis in the foetal mouse.

Optic and confocal laser scanning microscopy (CLSM) and the LsAB method were used to immunolocalize TGF alpha, EGF, FGF-2 and their related receptors, which are involved in the regulation of organogenesis in the mouse hypophysis. Internalization of the above receptors and the active proliferation of the presumptive adenohypophysis and neurohypophysis were observed during the mid-foetal stage. CLSM images were used to map the distribution of Cx32 in the proliferating hypophysis, particularly between the closely apposed neuro- and adenohypophyses. Using conventional transmission electron microscopy, gap junctions were observed at the boundary of these structures. The results suggest that cell coupling via gap junctions may provide positional information that is then used to control the differentiation of the hypophyseal cells.

Early organogenesis and cell contacts in the proliferating hypophysis of the developing mouse.

The mouse foetal hypophysis which contains the diencephalic downgrowth (Dd) and Rathke's pouch (Rp) was examined using morphological and immunocyto/histo-chemical methods to study the cell-cell and cell-extracellular matrix (ECM) interactions that occur during early organogenesis. While many studies have described that the differentiation of ACTH cells precedes the proliferation of other endocrine cells in the Rp, light and conventional transmission electron microscopic (TEM) investigations have failed to differentiate between the various endocrine cell types in the proliferating distal lobe at the late mid-foetal stage. Conversely, TEM studies have shown that the occurrence of dense secretory vesicles in glandular cells of the presumptive pars intermedia in close apposition with the presumptive neural lobe by a basal lamina, is the earliest sign of endocrine activity in the foetal hypophysis. However, a confocal laser scanning microscopy (CLSM) and fine structure study did not observe direct cell-to-cell contacts between the Dd, Rp and their associated mesenchyme at the late mid-foetal stage. Using CLSM and TEM, we detected active cell turnover with programmed cell death in the proliferating Rp, Dd and their associated cephalic mesenchyme. Morphological findings indicated that apoptosis in the cephalic mesenchyme subsequently brings neurohypophyseal pituicytes and adenohypophyseal precursor stem cells into closer proximity, and alternations in the boundary cell surfaces might initiate signal transduction mediated via the intervening ECM at the proliferation stage.

A histological study of the organic elements in the human enamel focusing on the extent of the odontoblast process.

Topographic and tomographic studies were conducted on the organic elements occluded in the enamel of premolars removed from young orthodontic patients by using light (transmitted) microscopy, confocal scanning laser microscopy (CLSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) on ultrathin sections and freeze-etching replicas, and energy dispersive spectroscopy (EDS) X-ray microscope (EDX) analysis. The present fine structure study aimed in particular to determine the fine structure of the enamel spindle and the extent of the odontoblast process. Organic elements in the ground-sectioned enamel corresponding to simple projections and enamel rods/spindles, enamel tufts and lamellae were identified by conventional light microscopy and subsequently examined by CLSM. Both light microscopy and CLSM indicated that a number of enamel spindles were measured about 50 microns in length, some 4-7 microns in thickness and were mostly confined to the cuspal summits and conformed to previous descriptions. SEM examination revealed some simple projections extending from the dentine into the enamel as well as clearly identifiable enamel spindles; the enamel spindles were structures intervening enamel prisms and showing morphological complexity by branching and convergence of the distal endings of the invading organic structure from dentinal tubules. EDX-analysis revealed that enamel tufts, lamellae, and spindles contained less phosphorus and calcium elements than enamel prisms. The enamel spindles had a higher content than tufts or lamellae, but this may be the result of contamination from surrounding enamel. Both conventional ultrathin-section and freeze-etching replica TEM evaluation of the dentino-enamel boundaries in particular suggested that simple projections and enamel rods/spindles were extensions of the odontoblast processes trapped in the enamel during early amelogenesis. In contrast, both SEM and TEM observations failed to identify dentinal tubule, peritubular (intratubular) dentine, membranous structures or lamina limitans surrounding the enamel spindles and simple projections occluded in the human enamel.

Scanning electron microscopy of elastic system fibers in the articular disc of the rat mandibular joint.

Elastic system fibers (ESFs), i.e., microfibrils (putative oxytalan fibers), elaunin and elastic (true elastin) fibers, in the rat mandibular joint were studied mainly using scanning electron microscopy (SEM) and light microscopy (LM) with the aid of image processing. The present quantitative analysis using LM showed that the articular disc and capsule, which are the sites that receive physical compressive force during mastication, contained more ESFs than the articular cartilage of the mandibular joint. In addition, oxytalan fibers were the principal ESFs in all the articular components (capsule, articular disc, supraossous layer of articular surfaces and articular cartilage). Subsequently, ESFs in the articular disc, which contained more thick ESFs, were closely examined by SEM using both collagen- and elastin-digestion methods. SEM showed networks of microfibrils beneath the articular surfaces (superior and inferior layers) in the thin central portion of the articular disc; the principal microfibrils ran at nearly right angles to the collagen fibers. The microfibrils were cemented with amorphous elastin, thickened and shifted towards interconnecting oblique fibers and many main ESF trunks, which were oriented in the direction of the layered wavy collagen fibers and parallel to the direction of applied force, to sustain the mechanical force. From the superior and inferior layers, the main ESFs shifted towards the middle portion of the disc, transitional zone (synovial osteochondral junction) and the other articular components, showing no specific directivity. Transmission mission electron microscopy revealed that the thick main ESFs in the elastic network were elaunin fibers. The present study indicated that ESFs unite, branch and therefore construct an extensive and complicated protective stretchable network, which is interposed with the less tensible collagen network in the mandibular articular disc.

Immunohistochemical localisation of epidermal growth factor, transforming growth factor alpha and EGF receptor during organogenesis of the murine hypophysis in vivo.

In previous study of melanocyte-stimulating hormone (MSH) cell development in the proliferating pars intermedia, which is in close apposition to the presumptive pars nervosa, no direct cell-to-cell contact was found between the boundary neurohypophyseal pituicytes (PIC), adenohypophyseal precursor stem cells (PSC) and the related diencephalic mesenchymal cells. Here, we have used immunohistochemistry to examine cytokine expression in the development of the hypophysis during foetal stages II-IV. Light and confocal laser scanning microscopy indicated diffuse expression of both TGF alpha and EGF in the hypophysis at different foetal stages. While no findings indicative for temporary changes of TGF alpha and EGF patterns were found in the foetal hypophysis, a temporary increment of EGF molecules was distinct in the diencephalic mesenchyme at stages III and IV. On the other hand, light microscopy intensively immuno-localized EGFR in the adenohypophysis and neurohypophysis at different developmental stages. Immunoreactivity of EGFR in the cytoplasm and nucleus suggested active proliferative events in the PIC and PSC of stages II-IV mouse pituitaries.

Histological study of the circulatory system of human dental pulp from individuals under local anesthesia and electro-acupuncture.

A transmission electron microscopic (TEM) study was conducted on dental pulp obtained from patients under acupuncture or infiltration local analgesia. It was difficult to differentiate lymphatic circulation in the dental pulp that received infiltration anesthesia, because the vessels were constricted, congested, and showed stasis and thrombosis. On the other hand, the dental pulp that received acupuncture showed normal arterioles, capillaries, and venules, as well as some lymph capillaries and small efferent lymphatic vessels that measured about 8 microns and 100 microns in diameter, respectively. The lymphatic endothelial walls had many intercellular gaps, an imperfect basal lamina, and a few discontinuous pericytes. Between the openings in the lymphatic vessels, there were bundles of junctional filaments extending towards the dental pulp connective tissue. Therefore, the lymphatic system, which contains mainly B-3-alpha capillaries, is a leaky tissue for regulating fluid in the dental pulp.

Observation of the internal configuration of rat incisor odontoblasts by scanning electron microscopy using the AODO method.

The internal configuration of rat incisor odontoblasts was studied mainly by scanning electron microscopy (SEM) using the AODO method (low concentration aldehyde prefixation, osmium tetroxide postfixation, dimethyl sulfoxide (DMSO) freeze-fracture, osmium tetroxide maceration). The present SEM findings were compared with the results obtained by conventional transmission electron microscopy (TEM) of epon-embedded specimens. The following results were obtained: 1) Functioning odontoblasts were characterized by a concentric, laminar rough endoplasmic reticulum (rER) with many long mitochondria interposed. 2) A network of tubular smooth endoplasmic reticulum (sER) was observed in the odontoblast process and distal portion of both functioning and resting odontoblasts. 3) The tubulo-vesicular elements which have been found to present a modified Golgi-GERL organelle with secretory and absorptive functions were demonstrated in both the functioning and resting odontoblasts. Structurally they consist of the sER network and strings of granules and vesicles. 4) Various types of cytoplasmic bodies, e.g., lysosomes, cytosomes and multivesicular bodies, related to the sER were also noted in both functioning and resting odontoblasts. 5) Microapocrine secretion of membranous vesicles of various sizes into the predentin and along the lateral branchings of odontoblast processes in the circumpulpal dentin was observed during the matrix apposition stage of the odontoblasts. The present morphological study revealed the three-dimensional configuration of the intra- and extra-cellular structures related to dentinogenesis by odontoblasts.

A preliminary study on inherited tooth morphology characters of Japanese and Chinese young adults--with special reference to the Carabelli tubercle.

A comparative study on inherited tooth morphology characters, in particular the incidence of Carabelli tubercles in the maxillary dentition, was conducted on standardized stone casts obtained from 240 Japanese (124 males (male) and 116 females (females)) and 160 Chinese (74 male, 86 female) young adults. The following results were obtained: 1) No significant differences in the incidence of Carabelli tubercles according to sex or body height were found between the two groups. 2) However, significant differences in the incidence of Carabelli tubercles according to sex were found in both groups. The tubercles occurred more frequently in males. 3) Significant differences between the bilateral and unilateral occurrence of Carabelli tubercles were observed in both the Japanese (p < 0.05) and Chinese (p < 0.01) groups; Carabelli tubercles on upper first molars were always bilateral. 4) The highest incidence of Carabelli tubercles was found in individuals with a body height of 166 approximately 175 cm in both groups, and a significant difference (p < 0.05) between the 156 approximately 165 cm and 166 approximately 175 cm groups was particularly evident in the Japanese adults. The authors postulate that bilateral occurrence of Carabelli tubercles was originally an inherited character in the molar region, but that the character was inhibited during the process of evolution of the masticatory system and regression of the molar dentition.

[Quantitative measuring method for fibers using image processing and analysis].

Previously, the radioisotope labeling and morphometric techniques have been used for the quantitative determination of growth of mandibular condyle by measuring the DNA synthesis or the increased number of cells. However, it is difficult to analyze the dynamics of ESFs (Elastic System Fibers) in the mandibular condyle related to aging, because of changes in the amount, distribution, number of fibers, and density of ESFs. In the present study, therefore, the video-scanning image analyzing technique was used for the quantitative measurement of ESFs in the mouse mandibular condyle. The objects under selected suitable illumination are scanned and focused by the TV camera and lens. The focused image is converted and amplified to obtain the most reliable electric signal by sequential scanning with the relative electronic beam. The original shaded image (electric signals) generated and converted by photo electric converter was filtered by the input slope (detective sensitivity) to detect the relative objects. Next, by inputted contrast, a secondary black-and-white image was detected. Meanwhile, a suitable compensation was also used to eliminate electric noise and dusts by inputting size discrimination. The next step was designed to obtain various quantitative data by measuring areas and diameters of the relative objects after treatment and analyzing of the secondary image, which was outputted from the photo electric converter. The connected LED display showed the measured and counted data, and at the same time the obtained data was automatically printed out for recording. There are many samples that are impossible to distinguish without using specific staining methods, like the ESFs.(ABSTRACT TRUNCATED AT 250 WORDS)

Scanning electron microscopy of intracellular organelles in the young odontoblasts of rats.

Intracellular structures of the odontoblasts were studied by scanning electron microscopy (SEM) using a modified AODO (aldehyde prefixed-osmium-DMSO-osmium) method. Well-developed flattened and layered rER (rough endoplasmic reticulum), paved with its associated ribosomes on its outer surface, were clearly observed in the odontoblast. Branched tubular mitochondria with nodules and swollen endings, interposing between and passing through the fenestrated layered rER, were demonstrated in the functional cells. Oblique and cross-sections of both the rER system and tubular mitochondria showed orthodox configurations similar to those usually described in transmission electron microscopy (TEM) studies. Many finger-like projections constructing the cristae directing towards the inner mitochondrial chamber were observed, and external chamber extending into the tubular cristae was also demonstrated.

SEM study on the dentin and cementum of oreodont teeth.

An SEM study on the dental hard tissue was conducted on the canines and molars removed from a fossil oreodont. The orthodentin was densely distributed with dentinal tubules measuring 2.2 microns in diameter; the tubules were filled with their related odontoblastic processes. They coursed in a parabolic fashion from the pulpal aspect towards the tooth surface. There were many fine lateral offshoots that branched from the tubules, such that the mantle dentin measuring 50 microns in thickness was mostly distributed with these terminal branches measuring 0.7 micron in diameter. However, they did not intrude into the enamel to form spindles and rods. SEM study indicated that the uneven surface of the tubular wall was due to a crisscross of the underneath dentinal matricial fibers, and the peritubular dentin was not observed. The superficial circumpulpal dentin was distributed with interglobular dentin, while the radicular dentin beneath the cementum was additionally distributed with a granular layer. We also observed concentric lamellae corresponding to incremental lines in the dentin, as well as a flat wavy dentinoenamel junction. We noticed the radicular dentin was covered with an acellular cementum except at the apical portion, where it was paved with cellular cementum.

Fine structure of cartilage elastic system fibers, in particular those of the mandibular condyle.

Light microscopy of the mandibular joint tissues from fetal mice show a distribution of fibrillar structures in the articular fibrous capsule covering the condylar head. Further SEM and TEM studies were conducted on autoclaved xiphoid and mandibular condylar processes of the fetuses for observation of the elastic system fibers in these cartilaginous tissues. SEM showed that non-collaginous fibers branched and united to form a complicated network in the cartilage. A fine structure study on diameter distribution of the fibers indicated elastogenesis in the differentiating cell layer and fiber maturation in the articular surfaces and calcification layer, thus suggesting a sequential development, growth, and degeneration of the cellular and fibrillar components in the cartilage, as well as bidirectional cell differentiation in the growing mandibular joint. A further TEM study on these autoclaved connective tissues showed the elastic system fibers in the network to be composed of fine microfibrils and amorphous elastin. The elastic fibers in the condylar cartilage were a loose network having many tortuous main and oblique elastic fibers, and coiling oxytalan fibers.