PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Thymus Gland”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1979

Functional relationship of macrophages and basophils to the thymus gland.

Human thymus epithelium, depleted of thymocytes and macrophages by means of organ culture, was used in chemotaxis experiments with peripheral blood cells. Such cultured thymus epithelium can attract specifically macrophages and basophils. T-lymphocytes were attracted only by short-term (8 day) cultured thymus tissue which still retains some of the original macrophage population. Thymic macrophages formed rosette structures with thymocytes. In other experiments 'activated' rabbit macrophages had the capability to destroy thymocytes, whether autochthonous or allogeneic. The possible role of macrophages and basophils in thymus function is discussed.

Animals↗
PubMed1979

Ultrastructural and histochemical features of the thymus glands of the adult lungless salamander, Plethodon glutinosus (Caudata: Plethodontidae).

The thymus glands of adult slimy salamanders (Plethodon glutinosus) were examined by light and electron microscopy with the objective of describing the populations of epithelial cells believed to be secretory. The results of various histochemical procedures designed to demonstrate nucleic acids, proteins, lipids, and mucosubstances were evaluated by light microscopy. Each thymus is incompletely subdivided into a variable number of interconnected lobules by trabeculae extending inward from a thin capsule composed of connective tissues. The thymic parenchyma lacks distinct cortical and medullary regions, although developing lymphocytes and plasma cells tend to accumulate in larger numbers in the outermost portions of the glands. Basophils are found regularly in the capsule and trabeculae, but only very rarely within the thymic parenchyma. The epithelial cells of the thymus can be classified into five categories: epithelial reticular cells; three varieties of granulated cells (types I, II, and III), and myoid cells. Epithelial reticular cells form a three-dimensional network which extends throughout all portions of the thymus. Type I and type II granulated cells can be distinguished from one another by various morphological criteria at the ultrastructural level, but only small differences in the composition of their inclusions can be demonstrated histochemically. Both types of granules are composed principally of a proteinaceous material containing an abundance of primary amino and guanidyl groups. In addition, most type I inclusions possess a lipid component that cannot be demonstrated in type II granules. Type III granulated cells possess very small cytoplasmic inclusions resembling those of gastroenteric endocrine cells. Myoid cells contain concentrically arranged myofibrils composed of sarcomeres. In favorably oriented material, small cysts can be identified whose walls are composed of mixtures of type I cells, type II cells, and epithelial reticular cells. Groups of degenerating epithelial cells form lamellated structures corresponding to Hassall's (thymic) corpuscles.

Animals↗
PubMed1975

Purification of terminal riboadenylate transferase from calf thymus gland.

A poly(A) polymerase has been purified from the soluble protein fraction of calf thymus gland. The activity is cytoplasmic and nonparticulate. Mn-2+ATP is the preferred substrate. On the basis of disc gel electrophoresis in sodium dodecyl sulfate-acrylamide gels, gel filtration, and sedimentation velocity in sucrose gradients, the enzyme has a molecular weight of 62,000 and appears to consist of one polypeptide chain. The enzyme preparation is shown to be nearly homogeneous by disc gel electrophoresis and isoelectric-focusing. The activity has a pI of about 7.4. The specific activity of the enzyme is about 1700 mumol per hour per mg of protein, giving a turnover number of about 1800 mol of substrate per mol of enzyme min- minus 1. The activity is highly specific for ATP and is inhibited by other ribonucleoside triphosphates. It is sensitive to high levels of RNA-polymerase inhibitors. Km for oligoadenylate is 50 muM in the presence of Mn-2+ and 200 muM in Mg-2+ and equivalent Vmax is achieved with either metal ion. The initiator function may be filled by a variety of oligoribonucleotides having a free 3'-OH.

Adenine Nucleotides↗
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↗
PubMed1977

[Cytological structure of the thymus gland in mature monkeys].

Histological sections of the thymus were studied morphometrically in 5 rhesus monkeys and 3 hamadryas baboons. The ratio of square surfaces of the cortical and cerebral substance, the percentage of Hassall's corpuscles and cellular elements (lymphocytes, stromal elements, blasts etc.) were established in the organ. Individual and species peculiarities of the structure of thymus elements were found. Less amount of parenchyma and growth of the stroma in baboons and a greater mitotic complex in rhesus monkeys show more pronounced involution processes in baboons.

Animals↗
PubMed1978

[Changes in the cellular elements of the thymus gland in experimental destructive pulmonary tuberculosis].

Lymphoid elements of the thymus were studied by scanning electron microscopy in rabbits susceptible to tuberculosis. The complete Freund adjuvant causes in the thymus a 3-fold decrease in the number of cells with the properties of T-lymphocytes, and an appearance of a new type of cell elements (polygonal shape, with cytoplasmic outgrowths). Formation of a focus of tuberculosis and the development of destructive changes in the lungs occur under conditions of a progressive decrease in the number of T- and B-lymphocytes in the thymus. Delimitation of the pathological process in the lung is characterized by an increase in the number of T- and B-lymphocytes and considerable predominance of polygonally shaped cells with cytoplasmic outgrowths of different lengths and their subsequent replacement by a cell form transitory between T- and B-lymphocytes. A relatively favourable course of the process in the lungs is observed when the cell elements in the thymus differentiate towards B-lymphocytes.

Animals↗
PubMed1979

[Histoenzymological characteristics of changes in the thymus gland in xenogenous form of graft vs host reaction].

The structural and functional lesions in the thymus of newborn animals in which xenogeneic graft versus host reaction was produced. Against the background of thymus hypoplasia, a decrease in mitogenesis and a reduction in the number of metabolically active lymphocyte forms were found. At the same time, activation of reticuloepithelial cells, macrophages, and giant cells was observed. It is assumed that such changes in the thymus may reflect an adaptative reaction of the host directed at making up the deficiency of peripheral T-lymphocytes developing in GVHR.

Animals↗
PubMed1979

[Effects of ionizing radiations on the ultrastructure of the thymus gland].

Different doses of gamma rays induce ultrastructural alterations in limphoid and epithelial cells of the chick thymus which exhibit a different temporal evolution after the treatment. The main changes which occur in lymphoid cells treated with 50 rads disappear 48 hours after the irradiation, while with 100 rads the radiation damage is still evident in epithelial cells.

Animals↗
PubMed1977

[Effect of a low-molecular humoral factor of the thymus gland on the lymphocyte sensitivity to phytohemagglutinin].

The preincubation of mouse spleen lymphocytes with a low molecular lymphocytosis-stimulating substance from the thymus (LSS), or the addition of the LSS to the cultures caused inhibition of the mitotic response of lymphocytes to phytohemagglutinin (PHA). LSS induced transformation of murine thymocytes to the blast cells capable of mitotic division. This transformation was depressed by PHA. The lymphocytes of the mice injected LSS in vivo responded weakly to PHA at first, but in 5 days a significant intensification on the response to PHA was observed. It is concluded that LSS may activate the T-cells responding to PHA.

Animals↗
PubMed1978

[Lesion of the thymus gland in infants caused by cytomegalovirus].

In the autopsy materials of 1972-1976, cytomegaly was diagnosed in 47 infants dying in the first year of life; two of them were found to have cytomegalovirusinvolvement of the thymus. The clinical course of the disease depended on the intensity of pathological lesions in organs and tissues associated with secondary infection. In the thymus, alongside with marked accidental involution, cytomegaloviral metamorphosis of the reticular epithelium and epithelium of Hassal bodies was found. Foci of calcinosis were observed in the parenchyma of the thymus. During the disease hypogammaglobulinemia was observed. A possible role of cytomegalovirus infection in the development of acquired immunodeficiency conditions in infants under one is suggested.

Agammaglobulinemia↗
PubMed1978

[Methods of determination of toxicity of pertussis vaccine. 1. Change in the weight of the thymus gland and the spleen in mice after administration of pertussis vaccine].

Experiments were conducted on mice, strain NIH, line HSFS/N, immunized with pertussis vaccine. Determination of thymocyte pool proved to be a more sensitive method of detection of the stress effect of the vaccine than determination of the thymus weight. The test can be used for the elaboration of the method of assessment of the toxicity of pertussis preparations.

Animals↗