Yujiro Sakamoto

Morphological influence of ascorbic acid deficiency on endochondral ossification in osteogenic disorder Shionogi rat

The influences of chronic deficiency of L‐ascorbic acid (AsA) on the differentiation of osteo‐chondrogenic cells and the process of endochondral ossification were examined in the mandibular condyle and the tibial epiphysis and metaphysis by using Osteogenic Disorder Shionogi (ODS) rats that bear an inborn deficiency of L‐gulonolactone oxidase. Weanling male rats were kept on an AsA‐free diet for up to 4 weeks, until the symptoms of scurvy became evident. The tibiae and condylar processes of scorbutic rats displayed undersized and distorted profiles with thin cortical and scanty cancellous bones. In these scorbutic bones, the osteoblasts showed characteristic expanded round profiles of rough endoplasmic reticulum, and lay on the bone surface where the osteoid layer was missing. Trabeculae formation was deadlocked, although calcification of the cartilage matrix proceeded in both types of bone. Scorbutic condylar cartilage showed severe disorganization of cell zones, such as unusual thickening of the calcification zone, whereas the tibial cartilage showed no particular alterations (except for a moderately decreased population of chondrocytes). In condylar cartilage, hypertrophic chondrocytes were encased in a thickened calcification zone, and groups of nonhypertrophic chondrocytes occasionally formed cell nests surrounded by a metachromatic matrix in the hypertrophic cell zone. These results indicate that during endochondral ossification, chronic AsA deficiency depresses osteoblast function and disturbs the differentiation pathway of chondrocytes. The influence of scurvy on mandibular condyle cartilage is different from that on articular and epiphyseal cartilage of the tibia, suggesting that AsA plays different roles in endochondral ossification in the mandibular condyle and long bones. Anat Rec 268:93–104, 2002.

Spatial relationships between masticatory muscles and their innervating nerves in man with special reference to the medial pterygoid muscle and its accessory muscle bundle

The relationships between the positional arrangement of the surrounding and innervating nerves of the muscles supplied by the mandibular nerve, in particular those medial to the main trunk of the nerve, were examined in 24 head halves from 12 Japanese cadavers by dissection from the inside after removal of the bony elements except for the mandible. In ten sides of five heads, the lingual nerve pierced the medial pterygoid muscle, and the bundle lateral to the nerve was found to be separated as an accessory muscle bundle. The accessory bundle was frequently attached to the mylohyoid muscle. In addition, the inferior alveolar nerve and the lingual nerve frequently communicated, and in four specimens a branch from the lingual nerve entered the mylohyoid to communicate with the proper nerve. The innervation pattern indicated that the medial pterygoid muscle consists of the anteromedial and the posterolateral main parts, and sometimes has an accessory bundle. Based on the present findings and the previous studies of the positional relationships between the muscles and nerves by our research group, we propose that the muscles innervated by the mandibular nerve could be classified as an inner group (the lateral pterygoid) and an outer group (the other muscles). A possible scheme of the positional relationships between the muscles and nerves is presented.

An Immunohistochemical Study of Matrix Proteins in the Craniofacial Cartilage in Midterm Human Fetuses

Immunohistochemical localization of collagen types I, II, and X, aggrecan, versican, dentin matrix protein (DMP)-1, martix extracellular phosphoprotein (MEPE) were performed for Meckel’s cartilage, cranial base cartilage, and mandibular condylar cartilage in human midterm fetuses; staining patterns within the condylar cartilage were compared to those within other cartilaginous structures. Mandibular condylar cartilage contained aggrecan; it also had more type I collagen and a thicker hypertrophic cell layer than the other two types of cartilage; these three characteristics are similar to those of the secondary cartilage of rodents. MEPE immunoreactivity was first evident in the cartilage matrix of all types of cartilage in the human fetuses and in Meckel’s cartilage of mice and rats. MEPE immunoreactivity was enhanced in the deep layer of the hypertrophic cell layer and in the cartilaginous core of the bone trabeculae in the primary spongiosa. These results indicated that MEPE is a component of cartilage matrix and may be involved in cartilage mineralization. DMP-1 immunoreactivity first became evident in human bone lacunae walls and canaliculi; this pattern of expression was comparable to the pattern seen in rodents. In addition, chondroid bone was evident in the mandibular (glenoid) fossa of the temporal bone, and it had aggrecan, collagen types I and X, MEPE, and DMP-1 immunoreactivity; these findings indicated that chondroid bone in this region has phenotypic expression indicative of both hypertrophic chondrocytes and osteocytes.

Spatial relationships between the morphologies and innervations of the scalene and anterior vertebral muscles

The prevertebral muscles are innervated by the cervical ventral rami. However, little information is available on the spatial relationships between the muscles and the supplying branches. This gross anatomical study investigated the prevertebral muscles and the nerves in 26 cadavers to elucidate their spatial interrelationships and the nerve pathways to each muscle. These muscles were characterized by the variations in the vertebral attachments. The scalenus medius was divisible into the dorsal and ventral parts. The scaleni anterior and medius attached to both the anterior and posterior tubercles of the cervical transverse processes. The oblique fibers arising from the transverse processes joined the vertical part of the longus colli. The rectus capitis anterior, the longus capitis and the scalene anterior and minimus were innervated by the ventromedial branches of the cervical ventral rami, and the branches passed between the origins of the proximal muscles to supply the longus colli. The rectus capitis lateralis and the scalenus medius were innervated by their dorsolateral branches, and the branches pierced the medius to the scalenus posterior. The roots of the brachial plexus passed between the scalenus anterior and the ventral part of the medius. The penetrations by the upper roots and the interconnecting fibers passing between the roots were found in the muscle bundles arising from the fourth or fifth cervical vertebrae. Their anomalies are the possible causes of the cervical-brachial disorders, and the knowledge of the innervation and the variations in this study seems to be useful for surgical and non-surgical treatments.

Classification of pharyngeal muscles based on innervations from glossopharyngeal and vagus nerves in human.

PurposeThe pharyngeal muscles are innervated by the glossopharyngeal and vagus nerves. However, their spatial interrelationships with the innervating branches have been unclear. This study examined the pharynx to elucidate their precise relationships for the anatomical evidence of the functional diagnosis.MethodThe muscles and nerves were dissected under a binocular microscope in 44 sides of 22 cadavers fixed with 8% formalin.ResultsThe pharyngeal muscles overlapped each other, and the pharyngeal constrictors sometimes linked to adjacent muscles. The uppermost part of the superior constrictor arose from the soft palate, and sometimes contained the fibers attaching to the petrous part of the temporal bone. Anomalous bundles were frequently found between the superior and middle constrictors and the stylopharyngeus. The stylopharyngeus and the glossopharyngeal part of the superior constrictor were innervated by the glossopharyngeal nerve, which occasionally penetrated the stylopharyngeus. The pharyngeal plexus not only spread onto dorsolateral surface of the pharynx but also sent branches between the constrictors. The plexus supplied the superior constrictor and salpingo- and palatopharyngei from their dorsal surface and the middle and inferior constrictors from their ventral and dorsal surfaces. The inferior constrictor received additional innervations from the laryngeal nerves.ConclusionsThe innervations pattern suggests that the pharyngeal muscles comprise four groups: the first innervated by the glossopharyngeal nerve, the second and third by the pharyngeal plexus, and the fourth by the plexus and the laryngeal nerves. The stylopharyngeus descends between the second and third groups, and its penetration may cause the anomalous bundles between them.

Supernumerary muscle bundles in the submental triangle: their positional relationships according to innervation.

The positional relationships between the supernumerary muscle bundles within the submental triangle and their innervating branches from the mylohyoid nerve were investigated. Ten heads of Japanese cadavers that showed aberrant muscle bundles within the submental triangle were examined. Three additional heads without such aberrant bundles were used for comparison. All cadavers were fixed with 8% formalin and preserved in 30% ethanol. After the examination of the origin and insertion of the muscles, the bony elements were removed, and then their innervating branches from the mylohyoid nerve were examined in detail under a binocular microscope. In 11 head-halves of six cadavers unilateral supernumerary bundles were found. Right and left mylohyoid nerves gave off branches that crossed the inner surface of the bundles of each respective side. Supernumerary bundles ran across the median line in two heads. In one head, the twigs from the mylohyoid nerve of the same side as the mandibular origin entered the inner surface of the bundles. The other head received double innervation from right and left nerves. Three heads showed supernumerary bundles that attached to the mandible or the hyoid bone at one end and joined the mylohyoid muscle at the other end. The branches from the mylohyoid nerve of the digastric side entered the inner surface of the bundles, and those of the mylohyoid side entered their outer surface. After giving off branches to the muscles, the mylohyoid nerve continued as a cutaneous nerve of the submental region. Based on the innervation patterns of the aberrant bundles within the submental triangle, it was suggested that these bundles result from the combination of the remnants of the primordia of the mylohyoid muscle and the anterior belly of the digastric.

Histological features of endomysium, perimysium and epimysium in rat lateral pterygoid muscle

The distribution of the endomysium, perimysium, and epimysium and their constituent connective tissue fiber types in the mature rat lateral pterygoid muscle was examined with the light microscope. The endomysium and perimysium were relatively thin and consisted mainly of reticular fibers. The epimysium was thicker than the intramuscular sheaths and consisted of both collagen and reticular fibers; however, the thickness and constituent connective tissue fiber types of these sheaths varied regionally. Near the articular capsule and disc, the endomysium, perimysium, and epimysium were all thicker than in other regions of the muscle and consisted of collagen, reticular, and elastic fibers. The perimysium bound the bundles of muscle fibers together and frequently included blood vessels and nerves. As the superior head of the pterygoid muscle approached its insertion, sheaths of perimysium divided this head into smaller and smaller bundles of muscle fibers. In the inferior head, some of the perimysial sheaths and part of the epimysium were aponeurotic, and many muscle fibers attached to them. There were few such aponeurotic regions in the superior head.

Development of a liquid culture system for megakaryocyte terminal differentiation: fibrinogen promotes megakaryocytopoiesis but not thrombopoiesis

Summary. Megakaryocyte differentiation is composed of three distinct stages: formation of erythromegakaryocytic progenitor cells, maturation of megakaryocytes and production of platelets. We have developed a liquid culture system for megakaryocyte terminal differentiation from haematopoietic stem cells into proplatelets. In this system, CD34+ cells isolated from human cord blood, differentiated to CD41+ cells, were classified either as propidium iodide (PI)+ cells (large) or PI– cells (small) by fluorescence‐activated cell sorting analysis on the late‐stage CD41+ cells. Transmission electron microscopy showed that the cultured small cells were morphologically identical to platelets isolated from normal peripheral blood. Moreover, the number of differentiated cells that were CD42b‐positive attained an approximately 60‐fold expansion over that of the primary CD34+ cells in this culture system. Furthermore, gene expression of megakaryocytopoietic transcriptional factors, GATA‐1 and NF‐E2, and several megakaryocytic markers such as glycoprotein (GP)IIb and thromboxane synthase was observed in the individual differentiation stage. Treatment with fibrinogen, a ligand of GPIIb/IIIa, increased the number of CD41+/PI+ cells, but treatment in the late stage suppressed CD41+/PI– cell formation, suggesting that fibrinogen promotes megakaryocytopoiesis, but not thrombopoiesis. We conclude that this liquid culture system using human CD34+ cells may be used to mimic the physiological development from haematopoietic stem cells into megakaryocytes, as well as promote subsequent thrombopoiesis.

Spatial relationship between the palatopharyngeus and the superior constrictor of the pharynx

PurposeThe palatopharyngeus and the superior constrictor act during swallowing. However, because they overlap one another, their morphologies have been controversial. This study examined these muscles to clarify their configuration and interrelationships.MethodsThe attachments and the fiber arrangement of the superior constrictor and the palatopharyngeus were gross anatomically examined in 28 Japanese cadavers.ResultsThe most superior fibers of the superior constrictor arose from the palate and interfused with the lateral fibers of the palatopharyngeus. Consequently, their origins and insertions were arranged in a continuous line, respectively, and these flat muscles formed a sheet. The palatopharyngeus rotated 90 degrees, from the origin to the insertion, about its long axis, and its superior and inferior surfaces turned into internal and external, respectively. Its lateral fibers passed on the internal surface of the superior constrictor, and these two muscles were inserted into the pharyngeal raphe with an overlap, indicating that the muscular sheet was folded back. Its medial fibers consisted of two layers at the origin and were interdigitated with the insertion of the levator veli palatini. The superior layer was joined by the salpingopharyngeus and dispersed into the pharyngeal wall. The inferior one was joined by the stylopharyngeus and descended along the palatopharyngeal arch to be inserted into the thyroid cartilage and the epiglottis.ConclusionsThese two muscles formed a sheet that was partially folded back. It is suggested that the superior constrictor and the lateral fibers cooperate as sphincters, and the medial fibers and the stylopharyngeus as elevators.

Gross anatomical observations of attachments of the middle pharyngeal constrictor

The pharyngeal muscles overlap each other and some of their parts have different areas of origin. Such arrangements make the interrelationships among pharyngeal muscles complicated. This study investigated the attachments of the middle constrictor to clarify its configuration and re‐examine its functions. The gross anatomies of the pharyngeal and neighboring muscles were examined in 41 cadavers. The middle constrictor arose from the stylohyoid ligament and the hyoid bone, and its fibers were divided into three overlapping groups. The anterosuperior group ascended posterosuperiorly from the ligament and the lesser horn and fanned out. The middle group ascended posterosuperiorly from the greater horn and fanned out. The posteroinferior group fanned out from the posterior part of the greater horn, while the middle constrictor arose internally to the hyoglossus; some fibers often passed externally, and their fibers sometimes intersected around the lingual artery, which ran between them. Some fibers attached to the hyoglossus, occasionally to the stylohyoid and the posterior belly of the digastric, but seldom to the lingual artery and the triticeal cartilage in the thyrohyoid ligament. The three groups were inserted into the pharyngeal raphe, and the descending fibers joined the longitudinal pharyngeal muscles. The ascending and descending fibers rarely reached the top of the pharynx and the thyroid cartilage, respectively. The fiber arrangement suggested that, besides constriction of the pharynx, the ascending and descending fibers of the middle constrictor can act as an elevator muscle, and the irregular attachments could affect the functions of the muscles and vessels. Clin. Anat. 603–609, 2014.