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At least 109 records · Page 6Linked to original sources
PubMed1995

Increased deposition of extracellular matrix components in the thymus gland of MDX mouse: correlation with the muscular lesion.

The present work describes the expression of extracellular proteins in the thymus and skeletal muscle of the X-linked dystrophic MDX mouse which corresponds to an experimental model for the human disease Duchenne muscular dystrophy. MDX dystrophic mice showed marked alterations in the thymic cytoarchitecture including cortical atrophy that was paralleled by denser epithelial cell network with intense immunolabelling for cytokeratins pair 8/18 and increased vascularization assessed with monoclonal antibody anti-desmin. Consistent augmentation of intrathymic extracellular matrix components (ECM) was observed especially at weaning and by the onset of disease. Interestingly, the amount of ECM elements in the gastrocnemius muscle of MDX wild-type dystrophic mice also showed a prominent difference as compared to age-matched non-dystrophic BALB/cAn animals. A marked but uneven overdeposition of reticulin and collagen fibres (type I, type IV), laminin and fibronectin were often present in the skeletal muscle of dystrophic mice, mostly around lesioned fibres. Alterations in both organs positively correlated with the degree of dystrophy thus suggesting that similar stimuli may be enhancing ECM production in both thymus and skeletal muscle. Although the thymus gland might not be directly involved in the development of the murine X-linked muscular dystrophy, it should be considered as a further target in this disease.

Animals↗
PubMed1970

Doxynucleotide-polymerizing enzymes of calf thymus gland. IV. Inhibition of terminal deoxynucleotidyl transferase by metal ligands.

The polymerization of deoxynucleoside triphosphates, catalyzed by terminal deoxynucleotidyl transferase from calf thymus gland, is strongly inhibited by various metal chelators. The reaction appears to be first order with respect to enzyme, deoxynucleoside triphosphate, and initiator, indicating that there is only one catalytic center for each enzyme molecule. The presence of metal chelator does not affect the molecular state of the enzyme or the order of reaction. An analysis of the kinetics of o-phenanthroline inhibition demonstrates that the ligand is noncompetitive with nucleoside triphosphate substrate and strictly competitive with oligodeoxynucleotide initiator. These results, obtained in the presence of millimolar Mg(++), suggest that the initiator binds to the enzyme through a transition metal atom and ligand inhibition occurs at that site. The precise spatial arrangement of the coordination orbitals around a metal atom provides a model to visualize the specificity of the enzyme for the 3'-OH end of the growing polynucleotide chain.

Animals↗
PubMed1980

[Unique microscopic picture of the thymus gland in myasthenic thymoma].

In the course of microscopic examination of 535 thymuses excized from patients with myasthenia (among them 60 with thymoma) the authors came across only one case in which there were numerous large foreign bodies granulomas in the thymus. Despite such a polymorphous structure of the thymus, the clinical course of the underlying disease did not show any specific features.

Humans↗
PubMed1976

Some endocrine aspects of the thymus gland.

In studies of the mouse thymus, lymphocyte mitoses are seen to be most frequent in the thymus cortex. There is evidence from thymic grafts that a hypothetical factor, thymopoietin, may stimulate mitosis of thymic lymphocytes. It is a factor which is postulated to act in conjunction with the PAS-positive mesenchymal reticular cells and epithelial reticular cells of the cortex. The thymus medulla is necessary for the integrity of thymic grafts, and may also elaborate a secretion for maintaining the cellular functions of the gland. Thymectomy has been used as a gauge for judging normal thymic function and results, in the mouse, in lymphopenia, degeneration of spleen and lymph nodes, delayed rejection of skin allografts, reduced ability of spleen cells to mount the graft versus host reaction, and reduced primary immune response to certain antigens. Correction of these deficiencies offers a means of evaluating various thymic extracts and grafts. Lymphocytosis-stimulating hormone (LSH) is known to maintain the peripheral lymphoid organs and cause lymphocytosis in the thymectomized animal. Diffusion chamber studies of thymic grafts also show restored lymphoid tissue by a cell-free factor (CIF). These two factors may be the same and probably represent the basis of the highly purified lymphocyte-stimulating proteins, LSHr and LSHh, which restore the L/P ratio in thymectomized animals and may stimulate lymphopoiesis in spleen and lymph nodes. LSHr, unlike LSHh, increases the total lymphocyte count. LSHr has been found to increase the humoral antibody response in neonatal mice both by the PFC technique and by direct hemolysis of sheep erythrocytes. Homeostatic thymic hormone (HTH) is a thymic extract of small molecular weight and contains nucleic acid. In the thymectomized guinea pig it has been found to maintain normal levels of lymphocytes in the blood, spleen and lymph nodes, to restore antibody titers to typhoid H antigen and to restore the toxic allergic reaction. Thymic humoral factor (THF) is of smaller molecular weight (less than 1,000) and probably is not a protein. It also enhances lymphoid proliferation in neonatally thymectomized mice. There is evidence that THF participates in humoral antibody formation because it stimulates PFC formation from neonatally thymectomized mice after inoculation with sheep erythrocytes. Its effects on cell-mediated immunity are seen from findings that injection of THF restores the ability of thymectomized mice to reject skin allografts. THF enables spleen cells from thymectomized or neonatal animals to mount the graft versus host reaction, and causes maturation of bone marrow cells and spleen or lymph node cells so that they can participate in the graft versus host reaction. It has been reported to stimulate lymphocytes to kill isogeneic tumor cells in vitro. Thymosin is protein extracted from the thymus. It has been found to alleviate leukopenia slightly and provide some improvement in lymphoid histology in thymectomized mice...

Aging↗
PubMed1988

[Comparative ultrastructural characteristics of epithelial cells of the parenchyma of the thymus gland and thymoma].

Comparative ultrastructural investigation of the parenchyma was performed for human thymus (7 specimens) and thymoma (34 specimens). For thymic parenchyma eight types of epithelial cells were identified. These may be represented by three different histogenetic lines: 1) spindle-shaped appendiceal cortical cells (type 1-4) 2) medullary cells showing signs of squamous-epithelium differentiation (type 5-6) 3) medullary cells with signs of glandular differentiation (type 7-8). Thymomas demonstrated cells ultrastructurally similar to thymic parenchyma and exhibiting features of either cortical or medullary epithelial cells. These findings served the basis for dividing thymomas into 3 major groups: 1) with cortical cell differentiation 2) with cortical and medullary cell differentiation 3) with medullary cell differentiation.

Adolescent↗
PubMed1999

Primary carcinomas of the thymus gland.

Carcinomas of the thymus are now well recognized as distinctive but rare entities, and several clinicopathologic variants of such neoplasms have been described. These include keratinizing squamous cell carcinoma, nonkeratinizing squamous cell carcinoma, lymphoepithelioma-like carcinoma, neuroendocrine carcinoma, adenosquamous carcinoma, mucoepidermoid carcinoma, clear-cell carcinoma, papillary adenocarcinoma, adenocarcinoma not otherwise specified, basaloid carcinoma, and sarcomatoid carcinoma. The application of electron microscopy, immunohistology, and other adjunctive pathological techniques is effective in refining the differential diagnosis between primary thymic carcinoma (PTC) and several other histological simulators. However, the distinction between PTC and carcinomas that involve the thymic region by metastasis from other sites is a difficult one, and ultimately must be predicated on detailed clinical and radiographic information. Well-differentiated squamous carcinoma, low-grade mucoepidermoid carcinoma, and basaloid carcinoma of the thymus usually are associated with a favorable prognosis, but other variants are aggressive and require multimodality treatment approaches.

Aged↗
PubMedDate not supplied

[Thymus gland scan in myasthenia gravis: experience in 52 patients].

A firm relationship has been established between thymus gland pathology and myasthenia gravis. The most frequent changes observed in this gland consist in simple hyperplasia of germinal centers or thymoma. In order to detect these alterations it is necessary to have a suitable reliable technique, beside routine radiological exams: thymus scan has been proposed as an useful tool. Since 1968 we submitted 52 patients to this procedure; we used as a tracer 75Se-Seleniomethionine in most cases, 57Co-bleomycin and 67Ga-citrate in a few cases. The scan was found positive in 22 cases (42%) showing either localized or diffuse uptake in the region of the sternum. Thymus changes were subsequently examined in 26 cases: 22 cases after thymectomy in 4 cases at autopsy. We found a good correlation between positive scan and pathological changes of the gland such as thymoma or germinal center hyperplasia. However in 4 patients with negative scan that previously received radiation therapy or immunosuppressive therapy such pathology was missed: 3 cases of hyperplasia and 1 residual thymoma. We conclude that thymic scan an useful and highly specific diagnostic procedure and should be done before any kind of treatment which affects thymus.

Adolescent↗
PubMed1980

Changes within the thymus gland as induced by high doses of hydrocortisone--histological and histochemical aspects.

The investigations were carried out on mature male Wistar rats. Hydrocortisone was administered intramuscularly for the period of 10 or 20 days. Histological findings showed that within the thymus gland the compact and fat connective tissue was proliferated, including both cortical and medullar zones. In the medullar part large vesicular forms filled with a substance of a basic character could be observed. Studying the thymus sections from the histochemical point of view, one could note numerous cells filled up with the Gomori-positive substance. The cells, mainly grouping in the cortical zone were often of a giant size.

Animals↗
PubMed2000

[Echographic evaluation of the thymus gland in childhood].

INTRODUCTION: The thymus is a linphoepithelial organ located mostly in the anterior mediastinum and, for a smaller part, in the neck. The gland is particularly developed in the fetus and in children, while it shrinks in young adults following an involution process. We investigated the US appearance of the thymus in normal pediatric subjects to gather information for use in pediatric patients with suspected thymus conditions, using a safe, irradiation-free, technique. MATERIAL AND METHODS: We performed a US examination of the anterior mediastinum and the neck in 30 children (14 males and 16 females) ranging in age 6 months to 11 years. We used a Sonora LOGIC 700 MD General Electrics unit with 7.5-13 MHz linear probes and acquired transverse and longitudinal scans on the chest wall and the neck, integrated with intercostal scans. RESULTS: The thymus had the same echogenicity as the liver parenchyma in 22 children (73.3%), lower echogenicity in 2 (6.6%, age range 6-12 months) and higher echogenicity with heterogeneous structure in 6 children (20%, age range 8-11 years). The gland was in central and symmetric localization in 20 children (66.6%) while it exhibited a slight deviation leftwards in 7 (23.3%) and rightwards in 3 children (10%). We considered as normal the following values: in the right lobe, 1.4 cm for the AP diameter and 2.5 cm for the longitudinal one; in the left lobe, 1.4 cm for the AP diameter and 2.9 cm for the longitudinal one. DISCUSSION AND CONCLUSION: Radiological studies of the thymus are really difficult to perform because the gland is extremely variable in size, extension and shape. The thymus has the same echogenicity as the liver parenchyma and lower echogenicity than the thyroid parenchyma. We believe that US is an effective technique for studying the thymus in all its involution stages and that provides similar information to CT and MRI. Also, US does not use radiations and needs no sedation, which improves safety for young patients.

Child↗