Search

Myopericitoma is a rare benign tumor of soft tissue that emerges from perivascular smooth tissue. Myopericitoma primarily derives from soft tissue and skin of the inferior extremities and is rarely found in internal organs. Considering the rare encounter with this neoplasia, it is often misdiagnosed as lipoma or atheroma. Our patient presents with a lump in the lateral region of the Achilles tendon on the right side. On inspection, a small, painful lump of approximately 5 mm×5 mm is noticed without cutaneous changes. In histopathologic examination, branched blood vessels are detected with a characteristic “hemangiopericytoma look-alike” appearance surrounded by prolonged myoid cells.

Multilocular thymic cyst (MTC) and germ cell tumors are common diseases that impact the mediastinum. Correctly diagnosing these diseases can be difficult because several other conditions can mimic them. We report a male patient with MTC associated with mediastinal seminoma. A needle biopsy of the mediastinal tumor revealed numerous epithelioid cell granulomas that mimicked sarcoidosis or mycobacterial infection. However, large atypical cells positive for Oct3/4 and KIT were noted between the granulomas; thus, we diagnosed the patient with mediastinal seminoma. The resected tumor, after chemotherapy, consisted of multiple cystic lesions, and a residual germ cell tumor was first considered. However, thymic medulla-specific elements, namely, POU2F3-positive thymic tuft cells and rhabdomyomatous myoid cells accompanying the epithelium, led to the correct diagnosis of MTC. Our case underscores the importance of recognizing the histological features associated with mediastinal seminoma and provides novel findings for MTC pathogenesis, namely, the presence of thymic tuft cells. [ABSTRACT FROM AUTHOR]

Myoid cells are of common occurrence in the medulla of the thymus of different species, usually identified by electronmicroscopy and/ or immunohistochemistry. Although known from many decades, the role of myoid cells in normal conditions is virtually unknown. Many investigators suggested that myoid cell is a crucial player in myasthenia gravis. Myasthenia gravis is an autoimmune disease, characterized by the production of auto-antibodies that act on the neuromuscular junction further interfering with the transmission of the depolarization wave. Although the exact pathogenesis mechanism of myasthenia gravis is still unknown, myoid cells in the thymus might play an important role in the initiation of this condition. The present article will review the role of myoid cells of the thymus while trying to establish their possible implications in myasthenia gravis.

The thymus prevents autoimmune diseases through mechanisms that operate in the cortex and medulla, comprising positive and negative selection and the generation of regulatory T-cells (Tregs). Egress from the thymus through the perivascular space (PVS) to the blood is another possible checkpoint, as shown by some autoimmune/immunodeficiency syndromes. In polygenic autoimmune diseases, subtle thymic dysfunctions may compound genetic, hormonal and environmental cues. Here, we cover (a) tolerance-inducing cell types, whether thymic epithelial or tuft cells, or dendritic, B- or thymic myoid cells; (b) tolerance-inducing mechanisms and their failure in relation to thymic anatomic compartments, and with special emphasis on human monogenic and polygenic autoimmune diseases and the related thymic pathologies, if known; (c) polymorphisms and mutations of tolerance-related genes with an impact on positive selection (e.g. the gene encoding the thymoproteasome-specific subunit, PSMB11), promiscuous gene expression (e.g. AIRE, PRKDC, FEZF2, CHD4), Treg development (e.g. SATB1, FOXP3), T-cell migration (e.g. TAGAP) and egress from the thymus (e.g. MTS1, CORO1A); (d) myasthenia gravis as the prototypic outcome of an inflamed or disordered neoplastic 'sick thymus'. [ABSTRACT FROM AUTHOR]

Spermatogenesis is fundamental to the establishment and maintenance of male reproduction, whereas its abnormality results in male infertility. Somatic cells, including Leydig cells, myoid cells, and Sertoli cells, constitute the microenvironment or the niche of testis, which is essential for regulating normal spermatogenesis. Leydig cells are an important component of the testicular stroma, while peritubular myoid cells are one of the major cell types of seminiferous tubules. Here we addressed the roles and mechanisms of Leydig cells and myoid cells in the regulation of spermatogenesis. Specifically, we summarized the biological features of Leydig cells and peritubular myoid cells, and we introduced the process of testosterone production and its major regulation. We also discussed other hormones, cytokines, growth factors, transcription factors and receptors associated with Leydig cells and myoid cells in mediating spermatogenesis. Furthermore, we highlighted the issues that are worthy of further studies in the regulation of spermatogenesis by Leydig cells and peritubular myoid cells. This review would provide novel insights into molecular mechanisms of the somatic cells in controlling spermatogenesis, and it could offer new targets for developing therapeutic approaches of male infertility. [ABSTRACT FROM AUTHOR]

The presence of the HGF/Met system in the testicular myoid cells was first discovered by our group. However, the physiological role of this pathway remains poorly understood. We previously reported that HGF increases uPA secretion and TGF-β activation in cultured tubular fragments and that HGF is maximally expressed at Stages VII–VIII of the seminiferous epithelium cycle, when myoid cell contraction occurs. It is well known that the HGF/Met pathway is involved in cytoskeletal remodeling; moreover, the interaction of uPA with its receptor, uPAR, as well as the activation of TGF-β have been reported to be related to the actin cytoskeleton contractility of smooth muscle cells. Herein, we report that HGF induces actin cytoskeleton remodeling in vitro in isolated myoid cells and myoid cell contraction in cultured seminiferous tubules. To better understand these phenomena, we evaluated: (1) the regulation of the uPA machinery in isolated myoid cells after HGF administration; and (2) the effect of uPA or Met inhibition on HGF-treated tubular fragments. Because uPA activates latent TGF-β, the secretion of this factor was also evaluated. We found that both uPA and TGF-β activation increase after HGF administration. In testicular tubular fragments, HGF-induced TGF-β activation and myoid cell contraction are abrogated by uPA or Met inhibitor administration.

Less than 5% of prenatal thymoctes express HLA-DR before week 12 of gestation. However, the number of HLA-DR- positive cells increases during the late second and third trimesters of development. To determine the role of alpha-smooth muscle actin in fetal thymic HLA-DR signaling in different stages of development we examined and compared the immunohistochemical expression of alpha-smooth muscle actin in the myoid cells of the thymic medulla stroma in the 2 nd, and 3rd trimesters of gestation respectively, over the equivalent expression of the protein in the 1 st trimester, in relation with the appearance of HLA-DR-positive thymocytes. Our results demonstrated a quantitative difference in the second and third trimesters of development concerning the expression of alpha-smooth muscle actin in the stromal myoid cells of the thymic medulla over the equivalent expression of the protein in the first (P

The role of the mesonephros in testicular development was re-evaluated by growing embryonic day 11.5 (E11.5) mouse testes devoid of mesonephros for 8-21 days in vivo under the renal capsule of castrated male athymic nude mice. This method provides improved growth conditions relative to previous studies based upon short-term (4-7 days) organ culture. Meticulous controls involved wholemount examination of dissected E11.5 mouse testes as well as serial sections of dissected E11.5 mouse testes which were indeed shown to be devoid of mesonephros. As expected, grafts of E11.5 mouse testes with mesonephros attached formed seminiferous tubules and also contained mesonephric derivatives. Grafts of E11.5 mouse testes without associated mesonephros also formed seminiferous tubules and never contained mesonephric derivatives. The consistent absence of mesonephric derivatives in grafts of E11.5 mouse testes grafted alone is further proof of the complete removal of the mesonephros from the E11.5 mouse testes. The testicular tissues that developed in grafts of E11.5 mouse testes alone contained canalized seminiferous tubules composed of Sox9-positive Sertoli cells as well as GENA-positive germ cells. The seminiferous tubules were surrounded by α-actin-positive myoid cells, and the interstitial space contained 3βHSD-1-positive Leydig cells. Grafts of E11.5 GFP mouse testes into wild-type hosts developed GFP-positive vasculature indicating that E11.5 mouse testes contain vascular precursors. These results indicate that the E11.5 mouse testis contains precursor cells for Sertoli cells, Leydig cells, myoid cells and vasculature whose development and differentiation are independent of cells migrating from the E11.5 mesonephros., (Copyright © 2021 International Society of Differentiation. Published by Elsevier B.V. All rights reserved.)

The suburothelium has received renewed interest because of its role in sensing bladder fullness. Various studies evaluated suburothelial myofibroblasts (MFs), interstitial cells (ICs), interstitial Cajal cells (ICCs) or telocytes (TCs), which resulted in inconsistencies in terminology and difficulties in understanding the suburothelial structure. In order to elucidate these issues, the use of electron microscopy seems to be an ideal choice. It was hypothesized that the cell population of the suburothelial band is heterogeneous in an attempt to clarify the above-mentioned inconsistencies. The suburothelial ICs of the bladder were evaluated by immunohistochemistry (IHC) and transmission electron microscopy (TEM). Bladder samples from 6 Wistar rats were used for IHC and TEM studies and human bladder autopsy samples were used for IHC. Desmin labeled only the detrusor muscle, while all the myoid structures of the bladder wall were positive for α-smooth muscle actin (SMA). A distinctive α-SMA-positive suburothelial layer was identified. A layered structure of the immediate suburothelial band was detected using TEM: (1) the inner suburothelial layer consisted of fibroblasts equipped for matrix synthesis; (2) the middle suburothelial layer consisted of smooth muscle cells (SMCs) and myoid ICCs, and (3) the outer suburothelial layer consisted of ICs with TC morphology, building a distinctive network. In conclusion, the suburothelial layer consists of distinctive types of ICs but not MFs. The myoid layer, with SMCs and ICCs, which could be considered identical to the α-SMA-positive cells in the suburothelial band, seems the best-equipped layer for pacemaking and signaling. Noteworthy, the network of ICs also seems suitable for stromal signaling. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Late-onset myasthenia gravis (LOMG) has become the largest MG subgroup, but the underlying pathogenetic mechanisms remain mysterious. Among the few etiological clues are the almost unique serologic parallels between LOMG and thymoma-associated MG (TAMG), notably autoantibodies against acetylcholine receptors, titin, ryanodine receptor, type I interferons or IL-12. This is why we checked LOMG patients for two further peculiar features of TAMG - its associations with the CTLA4high/gain-of-function +49A/A genotype and with increased thymic export of naïve T cells into the blood, possibly after defective negative selection in AIRE-deficient thymomas. We analyzed genomic DNA from 116 Caucasian LOMG patients for CTLA4 alleles by PCR/restriction fragment length polymorphism, and blood mononuclear cells for recent thymic emigrants by quantitative PCR for T cell receptor excision circles. In sharp contrast with TAMG, we now find that: i) CTLA4low +49G(+) genotypes were more frequent (p = 0.0029) among the 69 LOMG patients with age at onset ≥60 years compared with 172 healthy controls; ii) thymic export of naïve T cells from the non-neoplastic thymuses of 36 LOMG patients was lower (p = 0.0058) at diagnosis than in 77 age-matched controls. These new findings are important because they suggest distinct initiating mechanisms in TAMG and LOMG and hint at aberrant immuno-regulation in the periphery in LOMG. We therefore propose alternate defects in central thymic or peripheral tolerance induction in TAMG and LOMG converging on similar final outcomes. In addition, our data support a 60-year-threshold for onset of 'true LOMG' and an LOMG/early-onset MG overlapping group of patients between 40 and 60. [ABSTRACT FROM AUTHOR]

The majority of investigations on the testis, as the main organ of male reproductive system, have been performed in mammalian species, with few studies on bird species. Thus, the structure of the ostrich testis remains largely unknown. The aim of this study was to investigate the microanatomical characteristics of the testis in five juvenile ostriches. A stereological study was performed according to the Delesse principle. The mean volume fraction of the seminiferous tubules was 0.569, and the mean volume of the seminiferous tubules in an average testis was 1.04 cm. The Paraffin-embedded sections were stained with hematoxylin and eosin, Masson's trichrome, Alcian blue, and periodic acid-Schiff stains. Histological studies revealed that the spermatogonial stem cells and Sertoli cells were localized inside the seminiferous tubules, close to the basement membrane. Inside the tubules a few meiotic cells up to the spermatozoa stage were located in a centripetal manner. Outside the tubules, one to three layers of euchromatic peritubular myoid cells were present, surrounded by loose interstitial connective tissue. A thick tunica albuginea contained many myoid cells and some rete ducts, with the latter extending from the hilus to the free surface of the testis. Straight seminiferous tubules were distributed in the lateral surfaces and hilar portions of the capsule but were rare in the free surface. These capsular rete ducts may participate in testicular fluid transit from the distal tubules through the capsule. [ABSTRACT FROM AUTHOR]

The article presents a study investigating the effect of the consumption of the gossypol rich cottonseed flour (CSF) on immunohistochemical localization of androgen receptors (AR) in rat testes. Gossypol is noted for its cardiotoxic and hepatotoxic effects and has been reported to interfere with male fertility in various species. The results of the study show the adverse effects of CSF and gossypol on AR expression, particularly in the Leydig, Sertoli and peritubular myoid cells, in rat testes, which can lead to infertility.

The main transmission route of Trypanosoma cruzi is by triatomine bugs. However, T. cruzi is also transmitted through blood transfusion, organ transplantation, ingestion of contaminated food or fluids, or is congenital. Sexual transmission, although suggested since the discovery of Chagas’ disease, has remained unproven. Sexual transmission would require T. cruzi to be located at the testes and ovaries. Here we investigated whether T. cruzi is present in the gonads of mice infected with 104 T. cruzi trypomastigotes from the CL strain. Fourteen days after experimental infection, histopathological examination showed alterations in the extracellular matrix of the lamina propria of the seminiferous tubules. Furthermore, amastigotes were present in seminiferous tubules, within myoid cells, and in the adjacencies of the basal compartment. These results indicate that T. cruzi is able to reach seminiferous tubule lumen, thus suggesting that Chagas’ disease could potentially be transmitted through sexual intercourse. Complementary studies are required to demonstrate that Chagas’ disease can be transmitted by coitus. [ABSTRACT FROM AUTHOR]

Abstract: To understand developmental mechanisms of effector B-cells in the hyperplastic MG thymus, we have evaluated immunological roles of IL-2 and the 100-kDa haemopoietic biglycan, because the number of their producers increases pathologically there. When these two factors were added to an immune system together, the number of antibody-producing cells was markedly increased in a synergistic fashion. Further, IL-2 and the conditioned medium of myoid cells induced immunoglobulin isotype switches, suggesting that new B-cell stimulatory microenvironments were generated in the hyperplastic thymus. In relation to this, we also discuss a new biological feature, an immunomodulator, of conventional biglycan and decorin. [Copyright &y& Elsevier]

The anatomy, histology and ultrastructure of the thymus of a dipnoan, the Australian lungfish, Neoceratodus forsteri, was studied by light and transmission electron microscopy. The thymic tissue showed clear demarcation into a cortex and medulla with ample vascularization. Large cells including foamy and giant multinucleated cells with periodic acid Schiff/Alcian blue positive staining properties were localized mainly in the medulla. The major cellular components were epithelial cells and lymphoid cells. The epithelial cells were classified by location and ultrastructure into six sub-populations: capsular cells, cortical and medullary reticular cells, perivascular endothelial cells, intermediate cells, nurse-like cells and Hassall-like corpuscles. Myoid cells were found mainly in the cortico-medullary boundary and medulla. Macrophages and secretory-like cells were also present. These findings will provide a base of knowledge about the cellular immune system of lungfish. [ABSTRACT FROM AUTHOR]

We investigated immune property of a myoid cell line, established from Fisher rat thymus. Immunization of syngeneic rats with the myoid cells induced anti-rat acetylcholine receptor (AChR). Implantation of them into the thymus failed to induce typical thymic pathology of human myasthenia gravis (MG) or anti-AChR responses. We also demonstrated that the myoid cells were able to present exogenous antigens to T cells and induce antigen-specific T cell proliferation. These results suggest that myoid cells have the potential antigenicity to induce anti-AChR and the functions of antigen-presenting cells, but their expansion in the thymus may not directly cause MG. [Copyright &y& Elsevier]

To explore the possible contribution of thymic myoid cells in tolerance induction mechanisms, we quantified by real-time RT-PCR, the expression of 12 muscle genes (the five subunits of acetylcholine receptor, Musk, rapsyn, utrophin, ErbB2, ErbB3, troponin T, and MCK) in a human thymic myoid cell line (MITC), compared to thymic epithelial cells (TEC) and thymocytes. Although expression of all the genes analyzed was detected in TEC and thymocytes, the level of expression in these cells was much lower than in MITC, except for ϵ-AChR, utrophin and ErbB3 genes. Since myoid cells express high level of most muscle genes and are consistently found in the thymic medulla, they may contribute to the mechanisms involved in the induction and maintenance of immune tolerance. [Copyright &y& Elsevier]

Over the years the nomenclature of thymomas has been debated regarding the best manner in which these tumors should be grouped. In every schema presented thus far, the main issue has been the presence or lack of lymphocytes and accordingly, the tumors have been place into a specific category. However, even though this concept applies for most of the cases, there are numerous tumors that do not necessarily fit into those categories as either the thymomas show another cellular proliferation associated with the epithelial cells or the epithelial cell themselves are arranged in a pattern that departs from the conventional features of the classic thymoma. Herein we will emphasize those features, which in some circumstances, mainly with small mediastinoscopic biopsies may pose a considerable problem in interpretation. We do consider that the most important issue is to be familiar with the different growth pattern that these tumors may show in order to avoid misdiagnosis. In addition, we consider that regardless of the growth pattern or cellular composition of the tumor, it is highly recommended that these tumors just like any other be carefully sampled and properly stage. Although we are fully aware of the different growth pattern and specific cellular details that thymoma may show, the discussion of each one of those tumors is beyond the scope of this review. Therefore, we have placed more emphasis in those, which in our judgment are more commonly encountered in the daily practice., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Testicular peritubular cells are located in the lamina propria of seminiferous tubules. These cells, significantly contributing to the basal membrane of seminiferous epithelium, have been studied in a number of species. However, there is a lack of data on the development of the lamina propria in the human testis. The aim of our survey was to investigate the characteristics of the lamina propria and, in particular, peritubular cells in the fetal human testes by immunohistological and stereological methods. Therefore, testes (14-39 weeks of gestation, n=45) were dissected and fixed in a 4% buffered paraformaldehyde solution. Several pieces of each testis were embedded in paraffin and processed for immunohistochemical and stereological analysis. All investigated testes have shown sex cords in the process of development and differentiation. Morphologically, peritubular cells in the lamina propria can be divided into two types: fibroblast-like (FL) and myoid-like (ML) type (cells which much resemble mature myoid cells). By immunohistochemistry, both FL and ML cells are found to be strongly positive for the intermediate filament desmin, but negative for α-smooth actin. While FL cells intensively express Ki-67 demonstrating proliferative activity, ML cells are found to be negative. The basement membrane of sex cords as well as the blood vessels of the interstitium show strong positivity to collagen IV and laminin. Concerning the correlation between the appearance of the investigated antigens with the gestational age, all antigens have been expressed (in the manner described above) already in the 14th week of gestation. The stereological analysis of the number (Nv) and volume (Vv) of peritubular cells indicates a pulsatile development of these cells in the lamina propria of the human fetal testis. While the stereological variables determined for FL cells show a gradual decrease, the same variables determined for ML cells demonstrate a successive increase. It appears that the lamina propria of the fetal human testes shares many of the properties previously discovered in rodents. [ABSTRACT FROM AUTHOR]

The avian thymus and its myoid cells were investigated paying special attention to the developmental and morphological differences between chick and quail. By means of light- and electron microscopy, and immunofluorescence technique using an anti-myosin antibody, the myoid cells were found to express characteristics corresponding to those of skeletal muscle cells. They change their appearance during embryonic development. In the chick the myoid cells become located singly and rounded, and their cross-striation disappears. In the quail they remain small, elongated, cross-striated, and become arranged in long cords. The origin of myoid cells was studied using the quailchick marking technique: Cranial somites and the prechordal mesoderm were grafted from quail into chick embryos. After somite transplantation the host thymus does not contain graft-derived cells. The myoid cells are exclusively derived from the chick. After implantation of prechordal mesoderm, graft-derived quail cells are found in the central cores of all visceral arches and also within the early epithelial anlage of chimeric thymus. These findings indicate that the thymus myoid cells are derived from the axially located prechordal head mesoderm. [ABSTRACT FROM AUTHOR]

We examined 129 colonic biopsies from 21 patients with collagenous colitis, most of whom presented with diarrhoea. Morphometric measurements gave a mean thickness of the subepithelial collagen deposit of 19.5 µ ± 5.1. The trapped fusiform and/or stellate cells within the deposits were identified immunohistochemically as myoid cells, being positive with antibody against smooth muscle cell alpha-actin. Ultrastructurally, these cells have all the characteristic features of myofibroblasts. Similar cells are also present along the crypts, where they were formerly referred to as pericryptal fibroblasts. Although there is still much debate as to the pathogenesis of this condition, we would like to suggest that collagenous colitis is a disease of pericryptal myofibroblasts. During their migration and maturation into the subepithelial region they may synthesize an excess of collagen, under some yet unknown or undefined stimulus/stimuli. [ABSTRACT FROM AUTHOR]

Testes of adult rats, golden hamsters and mice were fixed with paraformaldehyde. Seminiferous tubules were then isolated by collagenase dissociation, stained with fluorescent phallotoxin, and viewed in a confocal laser microscope to observe actin filaments. Bundles of actin filaments in the myoid cells, especially in the rat, were arranged at right angles to each other in relation to the longitudinal axis of the tubule. In the hamster, circumferentially directed bundles were more frequent than longitudinally directed bundles. The actin bundles in the mouse were thinner than those in the rat and hamster, and their lattice network was less prominent. Nuclei of the myoid cells were elliptical and their short diameters were parallel to the long axis of the seminiferous tubules in the animals examined. Areas of myoid cells and of basal junctional portions of Sertoli cells were measured and compared in all animals studied. There were significant differences in the areas among the three species. The golden hamster showed the largest value for myoid-cell area, and the mean value for Sertoli-cell area was highest in the mouse. [ABSTRACT FROM AUTHOR]

Frozen sections of the rat and mouse testes were stained with either FITC-phalloidin or NBD-phallacidin and viewed with conventional fluorescence and confocal laser microscopes in order to demonstrate the arrangment of actin-filament bundles in myoid cells, Sertoli cells and tunica albuginea. Myoid cells are rich in actin-filament bundles crossing at right angles. These bundles running in different directions can also be visualized by means of electron microscopy. Nerve fibers occur in the vicinity of myoid cells, suggesting a neural control of the cell. At Sertoli cell junctions actin filaments occur at the circumference of the cell, where they show a honeycomb pattern. The ratio of the number of Sertoli cells per myoid cell can be calculated by means of confocal microscopy; this technique may provide a new parameter for determining spermatogenic activity. In the tunica albuginea of the juvenile mouse testis, actin filaments are arranged in an alternate fashion. [ABSTRACT FROM AUTHOR]

Testes of Esox lucius and Esox niger were investigated histologically, cytochemically, and ultrastructurally in reproductive fish. Intralobular Sertoli cells possessed numerous lipid droplets in Esox lucius, but not in Esox niger. In both species, interlobular cell types included myoid cells and lipid-negative Leydig cells within the extravascular space. Evidence is presented for a contractile network of myoid cells within the testes of these teleosts. The presence of Leydig cells and myoid boundary cells in the testis of Esox lucius refutes the reported homology between lobule boundary cells and Leydig cells in this species. [ABSTRACT FROM AUTHOR]

Thymic myoid cells (TMC) are sparse muscle-like cells in the thymic medulla, which are believed to trigger the autoimmune response in myasthenia gravis (MG). Ultrastructural investigations have revealed mature, degenerating, and immature TMC, but the number of TMC in MG patients does not differ from that in controls. We examined the turnover of TMC at the subcellular level, performing an immunocytochemical study with muscle-specific anti-desmin labelling of 10 thymuses derived from MG patients with lymphofollicular hyperplasia and from 8 normal controls. All thymuses examined revealed mature, immature, and degenerating TMC. Mature TMC contained desmin filaments in between Z-discs provided the sarcomeres were arranged in register. Morphological features of degenerating TMC included hypercontracted sarcomeres, cytoplasmic granular debris, chromatin clumping and, occasionally, membrane-bound bodies. Macrophages were not involved in the process. Immature TMC were of small diameter and contained myofilaments not arranged in myofibrils. In an MG thymus, small immature TMC were found clustered with dying TMC. It may be that degeneration of TMC is a stimulus for the generation of new TMC with faster turnover. This mechanism may mean that more antigen is available in MG patients than in normal controls, despite constant TMC numbers. [ABSTRACT FROM AUTHOR]

Histochemical and ultrastructural properties of myoid cells in the thymus of the frog were investigated and compared with properties of skeletal muscle fibres. The histochemical reactions of phospholipids, phosphorylase, succinic dehydrogenase and adenosine triphosphatase activities in myoid cells were characterized by considerable variability. Individual myoid cells apparently possess different enzyme activities which correspond to different stages of development, maturity and degeneration of these cells. The mature mononucleated myoid cells have similar enzymatic properties to the fast muscle fibres of the frog. This finding has been extended by ultrastructural observations. Features, typical of fast muscle fibres of the frog, e.g. the presence of the M-line, straight and narrow Z-line and well developed triads were found in the majority of mature myoid cells. [ABSTRACT FROM AUTHOR]

The arrangement and fine structure of peritubular myoid cells was studied in the testes of three species of reptiles ( Lacerta dugesi, Testudo graeca and Natrix natrix) during two short periods of the seasonal cycle (European spring and autumn) and correlated with some ultrastructural properties of Leydig cells. The lamina propria consists of myoid cells, fibroblasts and non-cellular components comprising collageneous and non-striated microfibrils. Both components are arranged in alternating layers surrounding seminiferous tubules. In spring the lamina propria of lacertilian testis shows 1-5 layers of myoid cells which are rich in 50-70 Å filaments and exhibit plasmalemmal and intracellular dense patches, smooth vesicles along the cell membrane and a concentration of organelles in a juxtanuclear position. Leydig cells are rich in smooth ER profiles and have few lipid droplets. In autumn most myoid cells are replaced by fibroblast-like elements. Leydig cells display large numbers of lipid droplets and dense bodies, but only small amounts of agranular ER. Similar changes are noted in Leydig cells of Testudo and Natrix. However, in these species the boundary tissue of seminiferous tubules fails to show significant alterations comparing spring and autumn animals. In both species the lamina propria exhibits a few fibroblast-like cells interspersed among myoid cells. [ABSTRACT FROM AUTHOR]

Mediastinal germ-cell tumors in men are generally thought to be primary at this site and to arise from extragonadal germ cells located in the thymus gland. Recent cytogenetic data have cast some doubt on this hypothesis and revived the alternative possibility of a testicular origin for these lesions. However, a review of the available evidence suggests that a primary mediastinal origin still remains the most likely explanation. The suggestion is made that the difficulties in identifying normal germ cells in the thymus gland may be due to their evolving into some type of somatic cell such as a myoid cell. [ABSTRACT FROM AUTHOR]

A series of 217 trephine bone marrow biopsies from adult patients and specimens from 16 fetuses and 5 infants were examined for the presence of stromal myoid cells (MCs) using a monoclonal antibody recognizing α-smooth muscle actin. In the normal adult bone marrow, stromal cells did not contain α-smooth muscle actin, whereas during fetal life, many α-smooth muscle actin-containing MCs were connected with vascular sinusoids in the primitive bone marrow. This cell type reappeared in various characteristic distribution patterns in adult bone marrow during different neoplastic and non-neoplastic conditions including metastatic carcinoma, Hodgkin's disease, multiple myeloma, hairy cell leukemia, acute myeloid leukemia (FAB M4, 5, 7) and chronic myeloproliferative diseases. In general, the appearance of MCs was associated with a slight to pronounced increase in the deposition of reticulin and collagen fibers. We propose that bone marrow MCs represent a distinct subpopulation of fiber-associated or adventitial reticular cells undergoing cytoskeletal remodeling in response to various stimuli. [ABSTRACT FROM AUTHOR]

The microenvironment of myoid cells (MyCs) was studied in myasthenia gravis (MG) thymitis with lymphoid follicular hyperplasia (LFH) (nine cases) and with diffuse B cell infiltration (one case), and compared with findings in the thymuses of non-myasthenic control subjects (ten cases). Double immunostaining was used to demonstrate MyCs labelled by anti-desmin together with other thymic components such as keratin-positive epithelial cells, Ki-M 1-positive interdigitating reticulum cells (IDCs), Ki-M 4-positive follicular dendritic reticulum cells, Ki-M 6-positive macrophages, CD22-positive B-cells, CD1-positive cells, CD3-positive T-cells or HLA-DR-positive cells. Round or elongated MyCs were confined to the thymic medulla and were surrounded by CD3-positive T-cells and CD22-positive B-cells. In MG thymitis MyCs were localized in the vicinity of, but not inside germinal centres (GCs). MyCs were always HLA-DR-negative, but were invariably embedded in a cellular micromilieu with strong HLA-DR expression. A remarkable feature of MG thymitis was that the great majority of MyCs were in intimate contact with intramedullary IDCs. Morphometric studies confirmed that such contacts were significantly less frequent in thymuses from non-myasthenic subjects. This indicates that an IDC-dependent antigen-presenting process for T-cells may actively involve MyCs in MG thymitis. [ABSTRACT FROM AUTHOR]

Normal fetal and postnatal thymuses, as well as thymuses from patients with myasthenia gravis (MG), were investigated by immunohistochemical and enzyme histochemical techniques and their morphology reviewed. Intrathymic B-cells, detected by ATPase activity, were found to be markedly increased in number in MG thymuses. They were scattered in the medulla and accumulated around the junctional and medullary vessels and Hassall's corpuscles (HCs). Large epithelial cells, singly or within HCs, were found to be unevenly distributed in the medulla of all the thymuses examined. The striated muscle-like nature of some of these cells was revealed by the presence of myoglobin in their cytoplasm. In myasthenics these cells and small developing HCs characteristically surrounded lymph follicles and were in direct contact with the expanded cap of the follicle mantle, without interposition of reticulin fibres. The close association of immune reactive foci (lymphoid follicles, junctional and medullary vessels, and HCs) with structures involved in autoimmune responses in the thymus (muscle-like and true myoid cells, HCs) strongly suggests that the autoimmune reactions against AChR (acetylcholine receptor) and other muscular components, which constitute the basic defects in myasthenia gravis, may begin in the thymus. [ABSTRACT FROM AUTHOR]

Samples of normal human thymus of different ages (4-63 years old) were studied by immunofluorescence microscopy (using antibodies to smooth muscle myosin, to actin from the chicken gizzard, and antibodies to myosin from human striated muscle) as well as by routine electron microscopy. Thymus tissue from myasthenia gravis patients was also investigated for comparative reasons. Epithelial cells reacted with anti-smooth, but not with anti-striated muscle myosin, whereas myoid cells reacted with antibodies to striated, but not to smooth muscle myosin. Both epithelial and myoid cells displayed a strong immunoreactivity with antiactin. Corresponding to this immunoreactivity, both cell types contained bundles of thin, actin-like filaments. Myoid cells occurred in the rounded and elongated variety, and they were a normal constituent of all thymuses investigated in this study. Ultrastructurally, this non-innervated, striated muscle-like cell type possessed bundles of thin and thick filaments as well as Z lines in a rather disorganized arrangement, resembling striated muscle after denervation or various other pathologic conditions. There were no overt differences in the number and structure of myoid cells between healthy and myasthenic patients. [ABSTRACT FROM AUTHOR]

To study the regulation of the development of myoid cells, seminiferous tubules of adult and prepubertal rats were grown in organ culture under the influence of testosterone, HCG and cyproterone acetate. Contractility, EM-structure and histochemical activities of alkaline phosphatase and ATPase of the myoid cells were studied in the adult rat tubules at one week intervals up to 5 weeks in culture, in the prepubertal rat tubules at the age of 15 days and after 15 and 21 days in culture. As in vivo, contractions appear in cultured tubules of prepubertal rats at the age of 15 days. Testosterone and HCG increase the percentage of contractile tubules and the number of filaments of the myoid cells. Cyproterone acetate inhibits both functional and structural development and tends to decrease the enzyme activities. In the cultured adult rat tubules cyproterone acetate causes disappearance of contractility within one week, while contractions normally are found for 3 weeks. Testosterone and HCG have no notable effects on the contractility of adult rat tubules, but they lengthen the persistence of alkaline phosphatase activity. It is concluded that the maturation and also the functioning of the myoid cells are subject to androgenic regulation. [ABSTRACT FROM AUTHOR]

The postnatal development of the seminiferous tubules of Sprague-Dawley rats were studied and the results were correlated with the general development of the animals during 6 months after birth. The following developmental features were observed: [ABSTRACT FROM AUTHOR]

Peritubular stem Leydig cells (SLCs) have been identified from rat testicular seminiferous tubules. However, no stem cells for peritubular myoid cells have been reported in the adult testis so far. In the present study, we tested the hypothesis that the peritubular SLCs are multipotent and able to form either Leydig or myoid cells. Using cultured tubules, we show that in the presence of PDGFAA and luteinizing hormone, SLCs became testosterone-producing Leydig cells, while in the presence of PDGFBB and TGFB, the cells formed α-smooth muscle actin-expressing myoid cells. This multipotency was also confirmed by culture of isolated CD90+ SLCs. These results suggest that these stem cells outside the myoid layer are multipotent and give rise to either Leydig or myoid cells, depending on the inducing factors. These cells may serve as a common precursor population for maintaining homeostasis of both Leydig and myoid cell populations in the adult testis. Image 1 • PDGFAA and PDGFBB stimulate peritubular stem cell proliferation. • PDGFAA stimulates differentiation of peritubular stem cells into Leydig cells. • PDGFBB stimulates differentiation of peritubular stem cells into myoid cells. • Isolated peritubular CD90+ cells can form either Leydig or myoid lineages in vitro. [ABSTRACT FROM AUTHOR]

Ten years ago, the term 'telocyte' was introduced in the scientific literature to describe a 'new' cell type described in the connective tissue of several organs by Popescu and Faussone-Pellegrini (2010). Since then, 368 papers containing the term 'telocyte' have been published, 261 of them in the last five years. These numbers underscore the growing interest in this cell type in the scientific community and the general acceptance of the name telocyte to indicate this interstitial cell. Most of these studies, while confirming the importance of transmission electron microscopy to identify the telocytes with certainty, highlight the variability of their immune phenotypes. This variability was interpreted as due to (i) the ability of the telocytes to adapt to the different sites in which they reside; (ii) the distinct functions they are likely to perform; and (iii) the existence of telocyte subtypes. In the present paper, an overview of the last 10 years of literature on telocytes located in the gut will be attempted, confining the revision to the morphological findings. A distinct chapter will be dedicated to the recently hypothesized role of the telocytes the intestinal mucosa. Through this review, it will be shown that telocytes, despite their variability, are a unique interstitial cell. [ABSTRACT FROM AUTHOR]

Telocytes (TCs), also known as CD34+ stromal/interstitial cells, have recently been identified within the connective tissue of a variety of organs including the normal human testis. Testicular TCs appear to constitute a widespread reticular network distributed either in the peritubular or in the intertubular stromal spaces where they have been suggested to play different roles, such as participation to testis morphogenesis, postnatal preservation of the normal tissue/organ three-dimensional structure, and regulation of spermatogenesis and androgen hormone secretion and release. Although increasing evidence indicates that TCs may be involved in the pathophysiology of various diseases, no study has yet reported possible changes in these cells within the stromal compartment of seminoma, one of the most frequent malignant testicular cancers in humans. Therefore, here we carried out the first investigation of the presence and tissue distribution of TCs/CD34+ stromal cells in human testicular seminoma in comparison with normal human testis using either CD34 immunohistochemistry or CD34/CD31 and CD34/α-smooth muscle actin (α-SMA) double immunofluorescence analyses. In seminoma tissue sections, we observed an overall loss of TCs (CD34+/CD31− stromal cells) accompanying a severe degeneration of the normal architecture of seminiferous tubules and stromal tissue associated with dense cellularity increase and presence of interstitial fibrosis. Noteworthy, in the seminoma tissue the disappearance of TCs was paralleled by an expansion of α-SMA+ myoid cells. Moreover, the CD34+/CD31+ blood vessel network was greatly expanded, while steroidogenic Leydig cells were undetectable in seminoma specimens. Since TCs are emerging as important regulators of tissue and organ homeostasis, collectively the present findings indicate that the possible pathophysiologic implications of the loss of TCs in human testicular seminoma should not be further overlooked. [ABSTRACT FROM AUTHOR]

OBJETIVO: Detectar e quantificar células mióides em timos de pacientes com miastenia grave, estabelecendo possível correlação entre a quantidade de células mióides com variáveis demográficas e clínico-patológicas. MÉTODO: Foram analisados por meio de método imuno-histoquímico com anticorpo antidesmina (clone D33; marca Dako), timos de 22 pacientes (16 mulheres e seis homens, entre 12 e 61 anos) submetidos à timectomia, entre 1981 e 1995, no Serviço de Cirurgia Torácica do Hospital Heliópolis como parte do tratamento de miastenia grave. RESULTADOS: As maiores médias de células mióides foram encontrados em timos dos pacientes da raça negra (29,4:17,8), do sexo feminino (23,2:13,0) e com faixa etária entre 60 e 80 anos (média de 33,0). Pela classificação clínica da Fundação de Miastenia Grave da América (MGFA), a maior média de células mióides (26,7) encontra-se na classe IIIa, sendo do tipo histológico de hiperplasia verdadeira (média 42,0). As células mióides foram identificadas em 11 timos com hiperplasia linfóide, três hiperplasias verdadeiras e em quatro timos normais. Os timomas malignos (três) e um timo normal não apresentaram células mióides. CONCLUSÕES: As células mióides podem ser identificadas e quantificadas pelo método imuno-histoquímico com anticorpo antidesmina, porém não existe correlação entre a quantidade de células mióides e as variáveis demográficas, clínico-patológicas. Elas não foram identificadas no timoma fusocelular.

The mechanism by which noninfectious testicular inflammation results in infertility is poorly understood. Here the infiltration of CD11b+ immunoreactive testicular interstitial cells (neutrophil, macrophages, dendritic cells) in immature (Postnatal Day [PND] 21, 28, and 35) and adult (PND 56) Fischer rats is described at 12, 24, and 48 h after an oral dose of 1 g/kg mono-(2-ethylhexyl) phthalate (MEHP), a well-described Sertoli cell toxicant. Increases of CD11b+ cells are evident 12 h after MEHP exposure in PND 21 and 28 rats. In PND 28 rats, CD11b+ cells remained significantly elevated at 48 h, while in PND 21 rats, it returned to control levels by 24 h. The peak number of CD11b+ cells in PND 35 rat testis is delayed until 24 h, but remains significantly elevated at 48 h. In PND 56 rats, no increase in CD11b+ cells occurs after MEHP exposure. In PND 21, 28, and 35 rats, a significant increase in monocyte chemoattractant protein-1 (MCP-1) by peritubular myoid cells occurs 12 h after MEHP. Interestingly, MEHP treatment of C57BL/6J mice did not incite an infiltration of CD11b+ cells at either PND 21 or 28. The peak level of germ cell apoptosis observed 24 h after MEHP exposure in young rats is not seen in mice at any age or in PND 56 rats. Taken together, these findings implicate MCP-1 released by peritubular myoid cells in provoking the migration of CD11b+ cells into the immature rat testis early after MEHP exposure and point to a role for CD11b+ cells in triggering germ cell apoptosis in an age- and species-dependent manner., (© 2014 by the Society for the Study of Reproduction, Inc.)