Journal of Anatomy最新文献

Rheumatoid arthritis (RA) is an autoimmune disease that primarily affects hyaline cartilage, except in the case of the temporomandibular joint (TMJ), which is covered by fibrocartilage. This study compared the progression of RA in these two types of cartilage by examining the TMJ and knee joints of rats in both the acute and chronic phases of the disease. Forty-eight male Wistar rats were divided into groups: Control (animals without RA in the TMJ or knee), RA-24h, and RA-7d (animals with RA in the TMJ or knee, euthanized 24 h or 7 days after the last intra-articular injection, respectively). The rats were sensitized with subcutaneous injections containing complete/incomplete Freund's adjuvant and methylated bovine serum albumin (mBSA), followed by three intra-articular mBSA injections (one per week) into either the TMJ or knee. Euthanasia was performed 24 h (acute phase) or 7 days (chronic phase) after the third injection. The following parameters were assessed: nociceptive thresholds, cellular influx in synovial fluid, histopathology, immunohistochemistry for metalloproteinase-9 (MMP-9), and birefringence of collagen fibers in articular cartilage. A significant reduction in the nociceptive threshold was observed in arthritic animals in both joints compared to the control groups. Additionally, a significant increase in cellular influx in the synovial membrane was noted in both joints after the third mBSA injection, as well as in the knee after 7 days. Histopathological analysis revealed reduced metachromasia, increased MMP-9 immunoexpression, and higher levels of type III collagen in the articular cartilage compared to the respective controls (p < 0.05). The nociceptive response was similar in both joints during the acute and chronic phases of RA. However, evidence of articular repair was observed in the TMJ, accompanied by a sustained reduction in the nociceptive threshold, suggesting central sensitization without ongoing peripheral damage.

This study investigates the organization of pancreatic endocrine islets in lizard embryos before hatching. Immunohistochemical staining was performed on "pre-hatching" embryos from three species representing major squamate clades: Lacerta agilis (Lacertoidea), Eublepharis macularius (Gekkota), and Anolis sagrei (Iguania). Four distinct endocrine cell types were identified within the pancreas of the studied species: glucagon-producing α-cells, insulin-producing β-cells, somatostatin-producing δ cells, and pancreatic polypeptide (γ) cells. Each of these cell types exhibited a unique distribution pattern across the upper, lower, and splenic lobes, as well as within the pancreatic head. The observed variation in the spatial distribution of endocrine cells appears to be related to several factors, including the developmental origins of the pancreatic regions from specific embryonic primordia, their subsequent differentiation driven by distinct developmental mechanisms, and paracrine interactions. The marked interspecific variations in islet cell topography and composition of the analyzed species could represent adaptations to dietary specialization or other ecological pressures. It has been proposed that the anatomical variation of the pancreas and, consequently its topographical relationship with the other organs, may be, to some extent, evolutionarily conservative within certain major squamate clades. In fact, at least some of the endocrine cell distribution patterns among the investigated species appear to be related to the proximity of certain pancreatic regions to the spleen, determined by pancreas shape. This suggests a potential regulatory influence on pancreatic islet differentiation and implies an indirect phylogenetic influence on endocrine cell distribution through the diverse pancreatic morphology. Further comparative research is required to clarify the potential phylogenetic, ecological, and developmental impact on pancreatic islet formation and composition.

A variety of bird species engage in complicated, elaborate courtship displays to impress potential mates. Such displays include wing flaring, aerial acrobatics, choreographed dances, and tail fanning. Though these behaviors are often well studied, the underlying musculature facilitating them is poorly understood. Exemplars of unique avian courtship behaviors include species of the North American sage-grouse (Centrocercus). Each spring, males gather in leks where they perform courtship displays which incorporate species-specific sound production, nape feather movement, and importantly, the raising and spreading of their rectricial fan for prolonged periods of time. Here we describe the tail myology of the lekking sage-grouse species Ce. minimus (Gunnison sage-grouse). We compare the tail myology of this species to that of other, either closely related or similarly sized, bird species which do not engage in rectricial displays. Results indicate tail myology in Ce. minimus is adapted for unique courtship behaviors. Muscles of the rectricial apparatus in Ce. minimus have greater proportional mass relative to body mass compared to other species examined here, and nearly all other species previously examined. In particular, both overall mass and the mediolateral width of the origination surface of the m. levator caudae are hypertrophied compared to other species which do not incorporate a raised tail fan during courtship displays. Additionally, the muscles that primarily spread the tail fan have relatively more extensive origin surfaces in Ce. minimus. Our results provide evidence that the specialized courtship behaviors of Ce. minimus have a clear influence on the tail myology morphology of this species, and suggest that sexually selected displays alter the corresponding underlying musculature across birds.

Muscle architecture [i.e. physiological cross-sectional area (PCSA), fascicle length and pennation angle] changes significantly during childhood. Previous studies have described the architecture of selected muscles in small samples of children over narrow age ranges, but a comprehensive analysis of the distribution of muscle architectural parameters during childhood development is currently lacking. The primary aim of this study was to estimate age- and sex-conditional distributions (reference curves) of architectural parameters of seven lower leg muscles (soleus, medial gastrocnemius, lateral gastrocnemius, tibialis anterior, tibialis posterior, flexor digitorum longus and flexor hallucis longus) in typically developing children aged 5-15 years. We used anatomical and diffusion-weighted magnetic resonance imaging to quantify the three-dimensional architecture and aponeurosis dimensions of seven lower leg muscles in 192 typically developing children aged 5-15 years. Quantile regression with b-splines was used to estimate muscle- and sex-specific reference curves for PCSA, fascicle lengths and pennation angles. In the median 15-year-old, PCSAs were 3.0-4.7 times (range is across muscles and sexes), and fascicle lengths were 1.1-1.7 times that of the median 5-year-old, respectively. Thus, lower leg muscle volumes (product of PCSA and fascicle length) increase primarily through transverse growth, rather than longitudinal growth, especially in children above 5 years of age. There was considerable overlap in PCSA, fascicle length and pennation angle distributions between boys and girls at all ages. Further analysis showed that longitudinal growth of muscle-tendon units is achieved primarily by lengthening of intramuscular aponeuroses and that aponeurosis surface areas scale in proportion with PCSA. The reference curves presented here provide normative data for muscle architecture in children and provide insights into the mechanisms of childhood muscle growth.

During endochondral bone development, pericytes differentiate into septoclasts, a mononuclear cartilage-resorbing cells, and contribute to the forming primary ossification center. To clarify the origin of the pericyte-septoclast lineage, the present study investigated the chronological localization of pericytes, septoclasts, and perichondrial cells during the early developmental stage of mouse tibiae using specific histochemical markers: platelet-derived growth factor receptor beta (PDGFRβ) for pericytes, epidermal-type fatty acid-binding protein (E-FABP, FABP5) for septoclasts, distal-less homeobox 5 (DLX5) for perichondrial cells, and von Kossa method and periostin for the periosteum. Before blood vessel invasion and septoclast appearance, PDGFRβ and DLX5 were commonly expressed in pericytes and in the cells of the outer layer of the perichondrium (OPC). Moreover, DLX5 positive OPC cells projected inward and were continuous with pericytes in the mid-portion of the cartilaginous templates. After the onset of blood vessel invasion and septoclast appearance, DLX5 was localized in both pericytes and septoclasts, suggesting that pericytes originated from OPC cells and differentiated into DLX5-expressing septoclasts. Based on the localization of von Kossa-positive calcified substrates and periostin immunoreactivity, OPC cells were transformed into the periosteum. Immunoreactivity of PDGFRβ, which mediates pericyte migration or recruitment, was relatively weak in the perichondrium compared to that observed before blood vessel invasion. In conclusion, the present results suggest that the pericyte-septoclast lineage originates from perichondrial cells during the initial developmental stage of endochondral bone formation.

A growing body of evidence suggests that lizards are promising model organisms for studying various developmental processes. However, knowledge of pancreatic islet distribution in non-ophidian squamates remains limited. The most comprehensive accounts available to date lack three-dimensional reconstructions and often show inconsistencies. In this study, we aimed to address both aspects: first, by evaluating squamate embryos as model systems for understanding general mechanisms of pancreatic islet morphogenesis in vertebrates, and second, by conducting a comparative analysis of islet development in squamates from an evolutionary perspective. In this study, we analyzed embryos of four non-ophidian squamates representing three major evolutionary lineages: Iguania-the brown anole Anolis sagrei; Gekkota-the leopard gecko Eublepharis macularius and the mourning gecko Lepidodactylus lugubris; and Lacertidae-the sand lizard Lacerta agilis. Three-dimensional reconstructions were created from thick serial sections and high-resolution semithin sections. Pancreatic islet cells in lizards originate from ductal epithelium. Early in development, precursor cells leave the duct walls to form buds that give rise to primary islets, a process evolutionarily conserved across vertebrates. Subsequent growth involves both the fusion of islet buds and the fission of larger agglomerates. Analyzed species differ in islet distribution: The brown anole islet remains restricted to the splenic lobe, whereas the sand lizard, leopard gecko, and mourning gecko also form islets in remaining regions. In studied gekkotans, small- and medium-sized islets tended to be concentrated in close proximity to the spleen. Medium-sized islets dominate the splenic lobe in the sand lizard. Interestingly, we observed a varanid-like condition in the brown anole, characterized by the formation of a single large islet within the splenic lobe, accompanied by a concurrent reduction in islet size throughout the remaining pancreatic regions. This pattern may reflect a broader trend within Toxicofera, a clade identified through molecular studies, toward splenic lobe islet enlargement and a reduction in the size of the islets in the remaining parts of the pancreas. While the phylogenetic position may influence these patterns, our findings suggest that the spatial relationship between the spleen and pancreas, particularly the formation of large islets near the spleen, could play a more direct, possibly inductive, role in islet formation. Further detailed studies, particularly focusing on representatives of Iguania and Anguimorpha, are essential to test this hypothesis.

Sauropods were the most gigantic land animals that ever lived on the Earth, and dominated herbivorous niches in many terrestrial ecosystems from the Jurassic to the end of the Cretaceous. Other than their great size, the elongated neck was the most remarkable feature of the sauropod bauplan and has been suggested as a key factor underpinning their evolutionary success. The necks of dicraeosaurid sauropods are particularly unusual, exhibiting extremely long neural spines and often being relatively short for sauropod necks, raising questions about their feeding strategies. In this regard, there are still many unknowns regarding the structure and function of the sauropod neck, especially concerning the soft tissues. Craniocervical muscles are particularly important, since they are responsible for the movement of the head relative to the neck, strongly implicated in the feeding behavior. The braincase of Amargasaurus cazaui, a dicraeosaurid from the Lower Cretaceous of Argentina, represents a chance to reconstruct the craniocervical muscles in a sauropod and, in turn, shed light on the feeding behavior. In this study, the insertions of the muscles are reconstructed using the extant phylogenetic bracket (EPB) approach, based on the anatomy of extant archosaurs and then compared with other studies performed on other groups of dinosaurs. There are several differences due to the disparity in the identification of the attachment areas and/or differences in the homologies of the muscles of the extant archosaurs. In the light of our findings, we discuss the high and low browsing modes for food acquisition and propose a three-step mechanism to explain the importance of the craniocervical muscles during animal feeding. This contribution represents the first complete reconstruction of the neck muscles inserting in the occiput for Dicraeosauridae.

Conflicting anatomical descriptions and functional interpretations have emerged regarding glandular structures located in the nasopharynx, particularly near the Eustachian tube. While some studies describe them as microscopic submucosal or tubal glands, others propose a distinct gland potentially salivary in nature. However, the majority of existing research has relied on imaging or histological analysis, with limited gross anatomical exploration. In view of these divergent perspectives and the paucity of macroscopic data, the present study aims to investigate this region through detailed cadaveric dissection, supplemented by microscopic validation, to clarify the structural identity and anatomical consistency of the glandular tissue in question. The study was conducted on 118 sides of embalmed adult cadaveric head specimens. Morphological and morphometric characteristics of the gland were recorded via dissection. Microscopic features were evaluated on 10 cadaver sides using Hematoxylin & Eosin and special stains to validate the macroscopic findings. A well-defined, lobulated glandular structure with a translucent covering was consistently identified deep to the mucosa of the tubal elevation and salpingopharyngeal fold, extending variably into the oropharynx, often reaching the lower border of the soft palate. The gland appeared as an elongated, triangular structure in this region. A distinct macroscopic duct was observed arising from the posterior aspect of the gland, coursing toward the pharyngeal recess; its presence and orientation were subsequently confirmed through histological examination. Microscopically, the gland exhibited a compound tubuloalveolar architecture, predominantly composed of mucous acini, along with a well-developed ductal system and the presence of myoepithelial cells. The duct opening was located near the junction of the nasopharynx and oropharynx, as indicated by the transition in epithelial lining between these two regions. This cadaveric study establishes the consistent presence of a well-defined glandular structure located beneath the mucosa of the tubal elevation and salpingopharyngeal fold, with variable extension into the oropharynx. For the first time, a macroscopic excretory duct was documented, arising from its posterior aspect and opening into the pharyngeal recess. The gland exhibited a distinct shape, reproducible location, and could be excised in toto, affirming its status as a discrete anatomical entity. Histological validation confirmed a compound tubuloalveolar architecture with mucous predominance and a well-developed ductal system. While its precise physiological role remains to be determined, these findings provide a definitive anatomical framework that can guide future radiological, functional, and clinical investigations.

In fishes and aquatic-stage amphibians, mechanosensory neuromasts are arranged in characteristic lines in the skin of the head and trunk, with afferent innervation from anterior or posterior lateral line nerves. In electroreceptive non-teleost jawed fishes and amphibians, fields of electrosensory ampullary organs flank some or all of the cranial neuromast lines, innervated by the anterior lateral line nerve. Like the mechanosensory hair cells found in neuromasts and the inner ear, electroreceptor cells in ampullary organs across vertebrates form specialised ribbon synapses with afferent nerve terminals. Ribbon synapses in hair cells are distinct from other glutamatergic synapses, including the ribbon synapses in photoreceptors: In hair cells, synaptic vesicles are loaded with glutamate by vGlut3 and otoferlin is the Ca²⁺ sensor for synaptic vesicle exocytosis. We previously showed that the genes encoding vGlut3 and otoferlin are expressed by ampullary organs as well as neuromasts in a chondrostean ray-finned fish, the Mississippi paddlefish (Polyodon spathula), suggesting that electroreceptor ribbon synapses are very similar to those in hair cells. In this study, we selected additional synapse-related candidate genes from our previously published dataset of putatively lateral line organ-enriched genes from late-larval paddlefish, and examined their expression in developing lateral line organs in a more experimentally tractable chondrostean, the sterlet sturgeon (Acipenser ruthenus). We found that sterlet ampullary organs express genes encoding vGlut3 (as expected from paddlefish) and the high-affinity glutamate re-uptake transporter EAAT1 (GLAST). Sterlet ampullary organs also express Otof (also expected from paddlefish, though we identified one Otof transcript variant maintained in ampullary organs but not neuromasts) and two other hair cell synapse-associated genes, Apba1 (Mint1) and Rab3a. Genes encoding the presynaptic cell adhesion molecule Nrxn3, the calcium-independent synaptotagmin Syt14, the calmodulin regulator protein PCP4 (PEP-19) and cell adhesion molecule DSCAML1 were expressed in both neuromasts and ampullary organs. In contrast, Cbln18, encoding a secreted trans-synaptic scaffolding protein, was only expressed in neuromasts and Tulp1, encoding tubby-related protein 1 (required for the development and function of photoreceptor ribbon synapses), was only expressed in ampullary organs. Overall, our results support electroreceptor ribbon synapses in non-teleost ray-finned bony fish being glutamatergic and suggest further commonalities, but also some differences, with hair cell ribbon synapses.