Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “THYMUS GLAND”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,027 records · Page 57Linked to original sources
PubMed1981

Analysis of cellular heterogeneity in mouse thymus cultures.

Analysis of 5 to 6 d primary cultures of cells derived from murine thymus glands revealed a heterogeneous population of cells rather than "pure" reticuloepithelial cell cultures as was assumed previously by other investigators. The monolayer cultures consisted of at least three cell types: thymus epithelial cells, macrophagelike epithelioid cells, and fibroblasts. Surprisingly, about 50% of the cells had positive cytochemical staining reactions for acid phosphatase and nonspecific esterase. The sme cells phagocytized carbon particles, latex beads, and yeast. Furthermore, these cells could be removed from the initial cell suspension by phagocytosis of carbonyl iron, followed by magnetic separation, but once they had adhered to the substratum they were resistant to trypsin removal. All of these findings supported the conclusion that about 50% of the cells in the monolayers were macrophages. The other cells present were thymus epithelial cells and a small number of fibroblasts. Both of the latter types of cell were cytochemically negative, did not phagocytize particulate material, and were not removed by carbonyl iron treatment, but were removed by treating the monolayer with trypsin. The findings in this report indicated that epithelioid morphology alone was inadequate to identify correctly the cell types found in thymus cultures and that the use of such cultures as a model to study in vitro the maturation of certain immunological functions has been based on assumptions here shown to be incorrect.

Acid Phosphatase↗
PubMed1980

The thymic mass as a mediastinal dilemma.

Five patients with normal thymus glands whose radiographs were mimicking mediastinal masses are presented; one in an infant with a compressed right upper lobe bronchus and two in adolescents with normal large lobes of the thymus. There were also two patients with regrowth of the thymus, one after severe infection and one after irradiation for secondary malignancies. We discuss the use of various techniques utilised to confirm the diagnosis and avert surgical procedures.

Bronchography↗
PubMed1994

Detection of growth hormone-producing cells in human thymus by immunohistochemistry and non-radioactive in situ hybridization.

It is well recognized that growth hormone (GH) may act as a growth and differentiation factor for the thymus gland. Recently, it has been reported that Pit-1/GHF-1 transcription factor, which controls the expression of both GH and prolactin, is expressed in stromal (not lymphoid) cells of human thymus. Here, we demonstrated by immunohistochemistry and in situ hybridization the presence of distinct GH-producing epithelial cell subsets in human thymus. The cells positive for GH mRNA and GH-immunoreactive substance are both located in the same thymus compartments, i.e., along the thymus capsule, in the subcapsular cortex, and within the septa. Local concentration of GH higher than systemic ones, in combination with other factors, may be important in regulating the thymic microenvironment necessary for T-lymphocyte differentiation.

Child, Preschool↗
PubMedDate not supplied

Alternate sites of lymphopoiesis in the amphibian embryo.

The presumptive ventral blood islands were reciprocally transplanted between chromosomally labelled 72-hour-old leopard frog embryos. At 10 days of development, the differentiating epithelial thymus glands were surgically removed. Following metamorphosis, the spleen and bone marrow from juvenile frogs were analysed cytophotometrically. During normal ontogeny, the vast majority of peripheral lymphocytes are derived from the thymus, not the ventral blood islands. In the absence of the thymus, the ventral blood islands made the major lymphocyte contribution to the peripheral lymphoid organs. Thus, removal of the thymus appears to initiate an alternate pathway of lymphocyte differentiation in the leopard frog.

Animals↗
PubMed1992

In vivo effects of growth hormone on thymus function in aging mice.

It is well demonstrated that the normal functioning of the thymus gland is under neuroendocrine control. Thus, steroid, thyroid, and pituitary hormones can affect distinct structural and/or functional thymic parameters. Particularly growth hormone (GH) was shown to be capable of restoring some thymus functions in old individuals. This prompted us to carry out a multiparametric analysis of the thymus in young, middle-aged, and old mice, subjected to GH treatment lasting 3 or 6 weeks. For that, we treated animals with daily injections of ovine GH (2 micrograms/g BW). Although the general microarchitecture of the thymus remained unchanged following in vivo GH treatment, there was a clearcut increase in thymulin production, independent of the age group analyzed. Regarding the lymphoid compartment, we could not find evidence of changes in total thymocyte numbers nor in the subsets phenotypically defined by the expression of CD3, CD4, and CD8 antigens. Nonetheless, in GH-treated middle-aged and old mice, the concanavalin A-dependent proliferative response of thymocytes, as well as IL-6 production were enhanced compared to age-matched controls. These findings support the notion that GH has a pleiotropic effect upon the thymus, functionally affecting both microenvironmental and lymphoid compartments of the organ.

Aging↗
PubMed1996

Effect of pregnancy on thymic T cell development.

PROBLEM: The thymus gland decreases in size during pregnancy. The significance of this alteration is not known. METHOD: In this report, we examined thymic function by evaluating the development of T lymphocytes in the thymus of pregnant Balb/c mice at 15 and 20 days gestation using multi-color flow cytometry. Comparative analysis was made with non-pregnant mice, post-partum lactating mice, and postpartum non-lactating mice. RESULTS: Progressive reduction of thymic size and cellularity during pregnancy was observed. All of the CD4 and CD8 defined subsets were reduced, with a disproportionate loss of CD4+, CD8+ double positive cells. Examination of the CD4-, CD8- double negative compartment revealed a predominance of TCR alpha, beta+ double negative cells, and a striking loss of precursor cells. The CD3-, CD4-, CD8- triple negative thymic subset was composed almost entirely of the earliest population (CD44+, CD25-), with the remaining maturational stages (CD44+, CD25+; CD44-, CD25+; and CD44-, CD25-) depleted. At 2 weeks postpartum, the subset ratios normalized, and the total cell count showed recovery. CONCLUSION: T cell development is blocked at the precursor level during the mouse pregnancy. These effects are transient, and gradual recovery is observed in the postpartum period.

Animals↗
PubMed1985

Acetylcholinesterase in human thymus cells.

Acetylcholinesterase (AChE) was long thought to be an enzyme found specifically at the sites of nerve synapses and neuromuscular junctions. It has also been found to occur, however, in cells that are not involved with neurotransmission. This study presents the ultrastructural localization of AChE activity in human thymus cells, using the indirect thiocholine method. Cytochemical demonstration of the enzyme was based on the coupling of acetylthiocholine iodide hydrolysis to the precipitation of heavy metal salts. AChE activity was selectively revealed in the perinuclear cisternae, within the endoplasmic reticulum, and in the Golgi complex of thymic lymphocytes and epithelial cells. Evidence of the presence of reaction product in the latter cells was also found in vesicles that opened into the extracellular space. This is the first demonstration of AChE in human thymus cells. Its possible physiologic role in the thymus gland is discussed.

Acetylcholinesterase↗
PubMed2003

Age-dependent changes in thymic macrophages and dendritic cells.

Aging is characterized by the decline and deregulation of several physiological systems, especially the immune system. The involution of the thymus gland has been identified as one of the key events that precedes the age-related decline in immune function. Whereas the decrease in thymocyte numbers and in the thymic output during thymus atrophy has been analyzed by various authors, very little information is available about the age-associated modifications in thymic macrophages and dendritic cells. Here we present evidence that these thymic stromal cell components are only slightly affected by age.

Aging↗
PubMed1992

Alteration of thymic cell subsets by cocaine administration and murine retrovirus infection in protein undernourished mice.

Retrovirus infection, cocaine administration, and nutritional deficiencies are known to individually produce impairment of the immune system. Therefore, we developed a murine model to study the effect of daily cocaine administration, protein malnutrition, and retrovirus infection causing murine AIDS on the lymphoid cell populations of the thymus. C57BL/6 female mice fed a diet containing 4% protein were studied following chronic cocaine administration and LP-BM5 murine leukemia virus (MuLV) infection. Cocaine administration reduced body and thymus weight. Cocaine partially prevented thymus enlargement due to lymphoid cell proliferation induced by murine retrovirus infection. Cocaine treatment affected dramatically the thymus of protein-malnourished mice where the absolute number of Thy 1.2+, CD4+ and CD8+ cells represented only 10% of the control values. Daily saline injection also induced a significant decrease in the number of Thy 1.2+, CD4+ and CD8+ cells per thymus. These results suggest that the thymus glands of mice fed a low protein diet were susceptible to stress. Retrovirus infection provoked a decrease in the percentage and absolute number of Thy 1.2+, CD4+ and CD8+ cells in the thymus. This effect was potentiated by cocaine treatment. Therefore, cocaine was able to potentiate the impairment of the immune system caused by MuLV infection. We consider that cocaine could alter the immune system by altering the expression of T cell differentiation markers after direct interaction with thymocytes or through the neuroendocrine-thymus axis. Moreover, this effect was more dramatic and severe during protein malnutrition.

Animals↗
PubMed2003

Influence of stage of the reproductive cycle and estradiol on thymus cell antigen presentation.

The objective of this study was to determine whether thymus cells present antigen and if endocrine balance influences antigen presentation. We report here that antigen presenting cells (APC) from the thymus glands of male and female rats, when incubated with ovalbumin (OVA)-specific T cells and OVA, are functionally able to present antigen via MHC class II. To determine whether antigen presentation in the thymus is under hormonal control, tissues from female rats at different stages of the estrous cycle were analyzed. Antigen presentation was higher at estrus and proestrus than that seen at diestrus when estradiol levels are low. Estradiol given to ovariectomized animals for 3 days stimulated antigen presentation by adherent thymus cells compared to saline controls. Flow cytometry studies indicated that the adherent thymus cell preparations consisted of DC, T cells, B cells and cells of the myeloid lineage all of which expressed MHC class II, as did a small population of non-leukocytes. Antibody neutralization studies indicated that thymus cell antigen presentation involves the expression of transmembrane proteins B7.1 and B7.2. These studies demonstrate that sex hormones play a central role in regulating antigen presentation in the thymus.

Animals↗
PubMed1986

Defective development of the thymus and immunological abnormalities in the neurological mouse mutation "staggerer".

The autosomal recessive mouse mutation "staggerer" (sg/sg), located on chromosome 9, has been recognized as a neurological mutant because of movement abnormalities and defective cerebellar development. We show here that the sg/sg mutation not only affects the development of the cerebellum, but also causes developmental and regulatory changes of the immune system: We observed, on gross inspection, a marked delay in the development of sg/sg thymus, generally enlarged lymph nodes, and undersized spleens. When immunized with SRBC, the sg/sg mouse generated, in normal proportions, helper T-cells in vivo and antibody-forming B-cells in vitro; however, a delay in terminating the response and a deficiency in generating suppressor cells was noted. This suggests the existence of a defect in regulatory feedback mechanisms. The marked delay in the growth of the thymus gland was associated with the prolonged existence of cell-surface carbohydrate patterns characteristic of immature thymocytes. The prolonged expression of embryonal cell-surface phenotypes was observed on the surface of cerebellum and thymus (and, to some extent, spleen) but not in cells from other organs.

Animals↗
PubMedDate not supplied

Nuclear matrix bound terminal deoxynucleotidyl transferase in rat thymus nuclei. II. Effect of ATP on free and matrix bound TdT.

Endogenous nuclease digestion of thymus nuclei from 3-4 week old rats followed by a step wise extraction with low salt, 0.5 M salt and 1 M salt removed approximately 70-85% of total nuclear terminal deoxynucleotidyl transferase (TdT) whereas approximately 15-30% of the enzyme remained tightly bound to the residual nuclear matrix. The cytoplasmic TdT as well as the bulk of nuclear TdT extracted in low salt and 0.5 M salt was found to be strongly inhibited at low concentration of ATP whereas matrix bound TdT and a significant portion of the enzyme in 1 M salt extract was completely insensitive to this nucleotide. The ATP resistant enzyme in the 1 M salt extract was unstable and slowly converted to ATP sensitive form upon prolonged preincubation on ice whereas under similar conditions it remained unaffected in the matrix bound form. These observations lead us to suggest that ATP resistant matrix bound TdT being capable of discriminating unnatural rNTPs against the natural dNTP substrates, may be the functionally organized form of the enzyme and that free TdT having lost the capability to distinguish between dNTP and rNTP may be the nonfunctional form of the enzyme in the thymus gland.

Adenosine Triphosphate↗
PubMed1975

Combined immunodeficiency disease associated with adenosine deaminase deficiency. Report on a workshop held in Albany, New York, October 1, 1973.

Fifty-five children with CID and known ADA status were studies at a workshop held in Albany, New York. Erythrocyte ADA determinations were performed in 22 of the 55 patients, 13 of whom were ADA negative. The ADA defect appears to be transmitted as an autosomal recessive trait. Some patients with CID and ADA deficiency have characteristic radiologic abnormalities of the skeleton, which are not found in other illnesses. The thymus glands of all patients with CID and ADA deficiency who could be examined have evidence of thymic involution manifested by presence of Hassall's corpuscles and differentiated germinal epithelium; this is in contrast to "classic" thymus findings in CID with normal ADA. Adenosine deaminase probably plays an important, although as yet undefined, role in lymphocyte development and/or function. The deficiency of ADA in CID is the first enzyme defect observed in a deficiency disease of specific immunity.

Adenosine↗
PubMed1987

The human thymus contains a novel population of B lymphocytes.

A study of thymus glands from fetuses, newborn babies, children, and adults has shown a prominent intramedullary B-cell population. These cells have a distinctive phenotype, show evidence of activation, and specifically cluster around Hassall's corpuscles. The thymus can no longer be regarded as an organ exclusively concerned with T-cell function.

Adolescent↗
PubMed1986

Behavioural, physiological and immunological consequences of social status and aggression in chronically coexisting resident-intruder dyads of male rats.

The behavioural and physiological consequences of social status and reciprocal fighting in resident-intruder dyads of Long Evans male rats were evaluated. Before a chronic cohabitation of 10 days, residents and intruders were individually housed for one month to increase their aggressiveness. Control animals included isolates, i.e., animals kept individually housed throughout the experiment and pair-housed rats, i.e., pairs of rats housed together from their rats in the laboratory. In 19 out of 20 dyads, a clear dominance relationship developed with an advantage to the resident in 68% of the cases. Dominants showed more exploratory activity than subordinates in a open-field test at the end of the cohabitation period; subordinates groomed longer than animals from other experimental groups. Dominants had lower pain thresholds than individually and pair-housed animals. Both dominants and subordinates had higher tyrosine hydroxylase enzymatic activities in the left adrenal than isolated and pair-housed rats. Subordinates lost body weight and had higher plasma corticosteroid concentrations than animals from the other experimental groups. In addition, they had smaller thymus glands and reduced spleen lymphocyte responses to mitogenic stimulation in vitro, in comparison to dominant animals. These results show that subordination in the dyadic resident-intruder paradigm leads to a complex syndrome of behavioural and physiological changes, some of which may be modulated by the intensity of aggressive interactions.

Adrenal Glands↗
PubMed1994

Vagal control of lymphocyte release from rat thymus.

The effects of the efferent vagal innervation on the thymus gland of the rat were investigated in vivo by means of section and stimulation experiments. It has been shown that section of the right vagus produces a decrease in the number of lymphocytes released from the thymus into the venous circulation, an effect that disappears after section of the recurrent laryngeal nerve. Vagal stimulation produces a transient increase in the number of lymphocytes released from the thymus, an effect that also disappears after section of the recurrent nerve. The effects of vagotomy are mimicked by nicotinic blocking agents, which also suppress the effects of vagal stimulation, whereas muscarinic blocking agents were ineffective. It is concluded that the vagal fibres running in the recurrent laryngeal nerve exert a tonic and phasic facilitatory influence on the mechanisms responsible for lymphocyte release from the thymus, and that this action is mediated through nicotinic receptors.

Animals↗
PubMed1977

Immunological defect and its correction in the osteopetrotic mutant rat.

Congenital osteopetrosis in the mutant rat "op" is accompanied by early atrophy of the thymus gland. The response of thymocytes to concanavalin A and phytohemagglutinin P was greatly diminished at age 28 days, even before pronounced thymic atrophy could be detected. The response of spleen cells to mitogens that stimulate thymus-derived (T) and bone-marrow-derived (B) cells was diminished as early as 35 days of age. A single injection of a suspension of normal bone marrow, which cures osteopetrosis, increased thymus weight and restored the normal responses of both thymus and spleen to various mitogens. These results add further support to the hypothesis that the thymus is involved in the pathogenesis of osteopetrosis.

Age Factors↗
PubMed1987

Thymocyte/stromal cell chimaerism in allothymus-grafted Xenopus: developmental studies using the X. borealis fluorescence marker.

These experiments employ the X. borealis (quinacrine-fluorescence) cell marker to illustrate that froglet (normal or in vivo-irradiated) thymuses, alloimplanted to 4- to 6-week-old, 7-day-thymectomized hosts, become filled with host lymphoid cells, while a range of thymic stromal cell types (e.g. epithelial derivatives and reticuloendothelial cells) remain donor derived. A time-course study of 4 micron historesin-embedded sections reveals that for normal thymus implants, host cells begin to immigrate in good number only after metamorphosis. In contrast, 3000 rad-irradiated thymus implants begin to be repopulated with host lymphocytes within 2 weeks postimplantation, when hosts are still at a late larval stage of development. Despite rapid colonization by host lymphoid cells, irradiated thymuses remain small and often disappear in early adult life. Donor-derived lymphocytes frequent the blood and both the red pulp and perifollicular regions of the spleen following normal thymus implantation, whereas such thymic emigrants were not seen in the periphery of thymectomized hosts grafted with irradiated thymus glands.

Animals↗