Influence of castration on development of the thymus in neonatal male rats.

The influence of castration on the development of the thymus in neonatal rats was studied to elucidate when after birth the thymus comes under inhibitory regulation by the testis in rats. The relative and absolute weights of the thymus were measured five days after castration these cases. No excessive changes in the weights of the thymus with castration were observed by 31 days after birth. Significant changes in the thymus appeared in the relative weight at 36-day-castration. The absolute weight of the thymus was also significantly increased after 41-day-castration. These findings suggest that in rats the inhibitory regulation of the thymus by testis development does not appear before at least 31 days of age.     

Epithelial canaliculi of the thymus gland--thymosin-dependent structures

The morphology peculiarities of thymus epithelial canals of 120 Wistar-line rats with thymosin have been observed. Thymosin-5 introduction during 3 days after birth in the dosage of 50 g proved to eliminate the epithelial canals of rat thymus in 3, 7 days of the postnatal period. In this period the epithelial canals have been found in thymus of all intact and control physiological solution injected rats. In 14, 30 days after birth the epithelial canals in experimental rats are found more often than in control ones. Thus, for the first time the evidence of thymosin-dependent characteristics of thymus epithelial canals has been obtained. The possible influence of epithelial canals on the regulation of T-forerunners entrance thymus has been discussed.     

Environmental Influences on Mass Dynamics of the Cotton Rat (Sigmodon hispidus) Thymus Gland

The influence of season on thymus gland mass was examined relative to captivity, gender, and age in 921 cotton rats (Sigmodon hispidus) from free-ranging and laboratory populations. Age-related involution of the thymus gland was evident in free-ranging males and females and captive females. A distinct seasonal cycle in thymus mass dynamics was apparent among adult cotton rats. Mass of the thymus gland was greatest from late fall to early winter before declining 2-4 fold during spring. Thymus gland mass remained low through spring and summer in adult cotton rats when reproductive activity was maximum. No seasonal cycle in thymus mass was apparent among juveniles. Possible involvement of sex hormones in regulating thymus size is discussed.     

A single exposure of rats to water-immersion restraint stress induces oxidative stress more severely in the thymus than in the spleen

Abstract

Objectives

We examined whether a single exposure of rats to water-immersion restraint stress (WIRS) induces oxidative stress in the thymus and spleen.

Methods

Vitamin E, ascorbic acid, reduced glutathione (GSH), and lipid peroxide (LPO) were assayed in the thymus and spleen of rats with and without 6 hours of WIRS.

Results

In unstressed rats, vitamin E, ascorbic acid, GSH, and LPO levels were higher in the thymus than in the spleen. Thymic ascorbic acid level was lower in stressed rats than in unstressed rats. Splenic ascorbic acid level was similar in both groups. Thymic and splenic GSH levels were lower in stressed rats than in unstressed rats but the reduced amount of GSH was lower in the spleen than in the thymus. Thymic vitamin E level was lower in stressed than in unstressed rats. Splenic vitamin E level was higher in stressed rats than in unstressed rats. Thymic and splenic LPO levels were higher in stressed rats than in unstressed rats but the increased amount of LPO was higher in the thymus than in the spleen.

Conclusion

It is indicated that a single expose of rats to WIRS induces oxidative stress more severely in the thymus than in the spleen.     

Effect of thymus polypeptide fractions on the development of rat thymus and spleen in organ culture

Peptides of the thymus--vilon, thymogen and thymalin, alone or in combination with concanavalin A, were used to investigate their effect on organotypic culture of thymus and spleen explants from 1- and 21-day old rats. Vilon, thymogen and thymalin in concentrations of 2 and 10 ng/ml and 5 ng/ml, resp., exerted stimulating effects in thymus and spleen tissue cultures from 21-day old rats as compared to the control explants. Vilon and thymogen showed inhibiting effect in the thymus tissue cultures from 1-day old rats as compared to the control explants. However, the peptides together with concanavalin A in concentration of 10 mkg/ml resulted in decreasing the action of concanavalin A alone. The polypeptide fractions of thymus and their synthetic analogs play different roles in the regulation of thymus and spleen development in rats of different age.     

The role of the thymus in the maintenance of natural killer cells in vivo

This report describes a model for investigating the role of the thymus in regulating natural killer (NK) cell activity in vivo. Evidence is presented that the thymus can regulate NK cells, and that at least some NK cells can develop without thymic help. Marrow from thymectomized rats depleted of circulating T cells by thoracic duct cannulation was transplanted into rats without a thymus (1 degree ATX.BM). These 1 degree ATX.BM rats had NK cell levels above controls 3 months after reconstitution but markedly depressed NK cell levels by 9 months. When 1 degree ATX.BM marrow was used to reconstitute rats with or without a thymus, those without a thymus (2 degrees ATX.BM) exhibited low NK cell levels after 3 months, and a similar result was obtained when 2 degrees ATX.BM marrow was used to reconstitute 3 degrees ATX.BM rats. The low NK cell levels in 2 degrees and 3 degrees ATX.BM rats were due to a deficiency in spontaneously cytotoxic NK cells, as they had normal numbers of interferon-responsive pre-NK cells. Spleen cells from 2 degrees and 3 degrees ATX.BM rats produced less interferon than control spleen cells when cultured with P815 tumor cells in vitro. However, 2 degrees and 3 degrees ATX.BM rats had higher numbers of large granular lymphocytes than controls despite their low NK cell levels. In marked contrast to 2 degrees and 3 degrees ATX.BM rats, spleen cells from 4 degrees ATX.BM rats had higher levels of cytotoxicity and a higher frequency of both spontaneously cytotoxic and pre-NK cells than controls. The 4 degrees ATX.BM rats also had the highest frequency of large granular lymphocytes in the spleen.     

Thymus dependency of neonatal tolerance induction in the absence of detectable suppressor cells

Neonatal thymectomy prevents tolerance induction with bovine serum albumin (BSA) in Wistar Furth (WF) rats whose thymus-derived (T) cell deficit is reconstituted with adult nonadherent peripheral blood lymphocytes (PBL). Sham-thymectomized (STx) rats given PBL become tolerant. To establish whether the adult T cells become tolerant in STx rats, their carrier-reactivity was studied in a cooperative immune response following challenge with methylated BSA (mBSA). The results indicate that carrier-reactive cells, derived from PBL, do become tolerant of BSA in the presence, but not in the absence, of the thymus. To determine whether thymic function during tolerance induction is mediated by suppressor T cells, attempts were made to replace the thymus with various populations of thymocytes or lymphoid cells from neonatal or adult normal rats or neonatal BSA-injected rats. No cell population tried could substitute for the thymus during tolerance induction. In addition, it was found that BSA-tolerant rats with intact thymi do not contain either nonspecific suppressor cells whose activity can be boosted with mBSA or specific suppressor activity demonstrable on transfer to normal rats. Timed thymectomy experiments showed that the thymus is required for more than 2, but less than 5 to 7 days after tolerogen injection for significant tolerance induction. These results imply that the thymus itself is necessary for tolerance induction in a peripheral T-cell population and that its effect is not mediated by suppressor cells. It is suggested that peripheral T helper cells may periodically recirculate through the thymus, at least in young rats, and become tolerant of antigen complexed with Ia antigens in the thymic epithelium. Such a mechanism may be of great importance in the development of self-recognition.     

Activity of antioxidant system enzymes and lipid peroxidation product content in the liver and thymus of rats in the early stages of irradiation]

The activity of enzymes of the antioxidation system and the content of some lipid peroxidation products in the liver and thymus of irradiated (0.21 C/kg) rats have been investigated. Glutathione reductase and glutathione transferase activity in the liver and thymus of rats decreased during the first 24 h after irradiation. There was a phase change in the catalase activity during the initial postirradiation period. The content of malonic dialdehyde increased immediately after irradiation and somewhat decreased during the first 24 h. In 24 h, there observed a radiation-induced increase in the diene conjugate content in the liver and thymus of rats, against the background of low activity of such antioxidation system enzymes as glutathione transferase, glutathione reductase and catalase.     

Inhibition of the endocrine function of the rat thymus by x-irradiation

Whole-body X-irradiation of rats caused inhibition of endocrine function of thymus. The effect was a function of radiation dose and time after irradiation. 72 h following irradiation with doses of 6 and 8 Gy the thymus hormone content of blood serum fell down the level registered in the thymectomized animals. Cellularity of the thymus and spleen concurrently decreased. The kinetics of spontaneous chemiluminescence of blood serum, thymus and spleen cells characterized the hypersecretion of glucocorticoids in response to radiation activation of lipid peroxidation in radiosensitive rat organs.     

Substance P-like immunoreactivity in capsaicin-sensitive structures of the rat thymus

Unlike in mouse and hamster, the thymus of rats or guinea pigs contains measurable amounts of substance P-like immunoreactivity (SP-LI), which, in a HPLC system, eluted as authentic SP or SP sulfoxide. Ontogenetic study showed that in rats the SP-LI content of the thymus increased up to 60 days from birth, and decreased thereafter. Capsaicin, but not 6-hydroxydopamine (6-OHDA) pretreatment completely depleted thymic SP-LI content in both newborn and adult rats. Animals treated with capsaicin as newborns, but not as adults, showed lower thymus weights as compared to controls. Rats pretreated with capsaicin as adults underwent partial time-dependent recovery of thymic SP-LI content. Somatostatin-like immunoreactivity (SST-LI) of rat thymus, eluting in part as authentic SST, was unaffected both by capsaicin or 6-OHDA pretreatment. Taken together, these findings demonstrate the existence of capsaicin-sensitive structures containing SP in the rat thymus. The possible function(s) that capsaicin-sensitive structures could exert in the thymus, among which a trophic action, mediated by the efferent function of sensory neurons, remain(s) to be established.     

Cold acclimation and oxygen consumption in the thymus

Mitochondrial uncoupling protein 1 is usually associated with brown adipose tissue but has recently been discovered in rat and mouse thymus. We wished to establish whether there was a thermogenic role for UCP 1 in thymus and thus examined the effect of 5 weeks cold-acclimation on rat thymus tissue abundance, thymocyte oxygen consumption, thymus mitochondrial abundance, uncoupling protein 1 expression and function. We found that thymocytes from cold-acclimated rats had oxygen consumption rates 8 times less than those from rats held at room temperature and that thymocytes from cold-acclimated rats or rats kept at room temperature were noradrenaline insensitive. In addition, we found that thymus tissue or mitochondrial abundance was not increased after cold-acclimation. However uncoupling protein 1 expression per unit mass of mitochondria was increased after cold-acclimation, as determined by immunoblotting (approximately 1.7-fold) and GDP binding (approximately 1.5-fold). Consistent with our protein expression data, we also observed an increased, state 4 (approximately 1.5-fold), GDP-inhibitable (approximately 1.3-fold) and palmitate activatable (approximately 1.6-fold) oxygen consumption rates in isolated thymus mitochondria. However, extrapolation of our data showed that cold-acclimation only increased the amount of UCP 1 per gram of thymus tissue approximately 1.2-fold. Taken together, we conclude that UCP 1 does not have a thermogenic role in thymus.     

Effect of pentoxyl, ibuprofen and acetylsalicylic acid on the thymus, spleen and adrenals in an experiment]

The effect of acetylsalicylic acid, ibuprofen and pentoxyl on the histological and morphometric pattern of the thymus and the weight of the thymus and spleen was studied in rats. There was decreased function of the thymus and its atrophy with acetylsalicylic acid and ibuprofen. Pentoxyl increased the secretory activity of the thymus. The effect of the drugs on the thymus and spleen was unidirectional.     

Studies of the cellular cure for osteopetrosis by transplanted cells: specificity of the cell type in ia rats.

Spleen cells from normal rats are known to cure osteopetrosis in ia littermates within 3 weeks. In this study cell suspensions from liver, thymus, bone marrow, salivary gland, skeletal muscle and brain from normal rats were tested for their ability to cure osteopetrosis in ia littermates whose ability to reject these cells had been suppressed by whole-body irradiation. Cells from liver, thymus and bone marrow cured the disease as effectively as spleen cells from normal littermates. Mutants that received cells from salivary gland, muscle and brain remained osteopetrotic. These data suggest that some cell found in spleen, liver, thymus and bone marrow of 10-day-old normal rats, such as a lymphoid cell or stem cell, can restore hemopoiesis and bone resorption in osteopetrotic (ia) rats.     

The inhibition of dopamine synthesis in fetuses changes the pattern of T-lymphocyte maturation in the thymus of adult rats

The mRNA for dopamine receptors of type D1, D3, D5, but not type D2, was detected in the thymus of rats starting from day 16 of embryonic development (E16). Dopamine at concentrations of 10^–8–10^?6 M inhibited fetus thymocyte response to mitogen, confirming the functionality of the receptors and the possibility of a direct effect of dopamine on the developing thymus. Pharmacological inhibition of catecholamine synthesis in the crucial period of thymus development leads to long-term changes in the T-system immunity due to increased production of natural regulatory T-lymphocytes. The presence and functional activity of dopamine receptors in the fetal thymus indicates its ability to influence the development of the immune system of rats during ontogeny.     

Cold acclimation and oxygen consumption in the thymus

Mitochondrial uncoupling protein 1 is usually associated with brown adipose tissue but has recently been discovered in rat and mouse thymus. We wished to establish whether there was a thermogenic role for UCP 1 in thymus and thus examined the effect of 5 weeks cold-acclimation on rat thymus tissue abundance, thymocyte oxygen consumption, thymus mitochondrial abundance, uncoupling protein 1 expression and function. We found that thymocytes from cold-acclimated rats had oxygen consumption rates 8 times less than those from rats held at room temperature and that thymocytes from cold-acclimated rats or rats kept at room temperature were noradrenaline insensitive. In addition, we found that thymus tissue or mitochondrial abundance was not increased after cold-acclimation. However uncoupling protein 1 expression per unit mass of mitochondria was increased after cold-acclimation, as determined by immunoblotting (∼ 1.7-fold) and GDP binding (∼ 1.5-fold). Consistent with our protein expression data, we also observed an increased, state 4 (∼ 1.5-fold), GDP-inhibitable (∼ 1.3-fold) and palmitate activatable (∼ 1.6-fold) oxygen consumption rates in isolated thymus mitochondria. However, extrapolation of our data showed that cold-acclimation only increased the amount of UCP 1 per gram of thymus tissue ∼ 1.2-fold. Taken together, we conclude that UCP 1 does not have a thermogenic role in thymus.     

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.     

The ontogenetic evolution of acidic phosphoprotein phosphatase activity in the lymphatic tissue and the liver of the rat.

We have shown that an acidic phosphoprotein phosphatase (APP-ase) has a different pattern of postnatal maturation in the spleen, thymus and liver of rats and mice. The APP-ase activity increases during the first eight months of postnatal life in the spleen of rats (when it attains an 8--10 times higher value than at birth) and up to the sixth month of life in the spleen of mice. It increases considerably during the first two weeks of postnatal life in the thymus of rats and mice; in the liver of rats it reaches maximum activity before birth, but continues to increase up to the sixth month of postnatal life in the liver of mice. The results show also that the APP-ase from the spleen, thymus and liver of rats is equally active in dephosphorylating ATP and phenyl phosphate during the whole life span of rats, but not in relation to beta-glycerol phosphate. After analyzing its substrate specificity, its pH dependence in relation to different substrates, its kinetic properties, as well as its behaviour towards ascorbic acid and different inhibitors (sodium tungstate and sodium molybdate, L-tartrate, L-phenylalanine and L-cysteine) we have come to the conclusion that the rat spleen APP-ase is different from "nonspecific" acid and alkaline phosphatases and very similar to the EC 3.1.3.16 acid phosphoprotein phosphatase.     

Potentiation of autoimmune response in rats infected with Toxoplasma gondii. Effect of the infection route

The aim of this report is to describe the influence of the way of infection with 3 X 10(3) trophozoites of Toxoplasma gondii on the auto- and heteroimmune responses of rats immunized with chemically modified rat male accessory glands (MRAG) and human serum albumin (HSA) 6 and 36 days after infection. The delayed hypersensitivity (DTH) response to MRAG was potentiated in rats infected in thymus proximity (p less than 0.02) when compared with rats only immunized. The parasites introduced intraperitoneally did not modify the cellular autoimmune response. The titers of hemagglutinating antibodies to MRAG were increased in animals infected by both ways (p less than 0.05). The response to HSA did not show significant difference between the infected and uninfected rats. Thymic involution and proliferation of lymphocytes and plasma cells were observed at 6 and 52 days post-infection only in rats infected in thymus proximity (p less than 0.05). A correlation between the potentiation of cellular autoimmune response and the injection of parasites in thymus proximity was observed.     

The effect of hydrocortisone on the alkaline proteinase activity in the target organs of rats]

The effect of hydrocortisone on the thymus and liver proteinases activity in the alkaline pH range was studied on rats. It is shown that the alkaline proteinases are activated in the thymus and inhibited in the liver of hormone-treated animals. Possible relationship between the effect of glucocorticoids on protein metabolism and alkaline proteinases activity is suggested.     

Age-related hyperplasia of the thymus and T-cell system in the Buffalo rat

This report describes the development of hyperplasia of both the thymus and the peripheral T-cell system with advancing age in the Buffalo rat. Buffalo/Mna rats do not show age-related thymic involution, but rather develop thymic hyperplasia with advancing age. This thymic growth is expansile and there is no infiltration of the surrounding tissues. Because the enlarging thymus occupies the thoracic cavity, most of the rats die of respiratory failure by the age of 24 months. Thymic enlargement is due to primary hyperplasia of cortical epithelial cells and the large number of proliferating lymphocytes. The hyperplastic epithelial cells are bizarre in shape and strongly positive when stained with Th-3 monoclonal antibody (MoAb), anti-thymosin antibody and anti-EGF antibody, but negative with Th-4 MoAb. The patterns of distribution of CD-5+, CD-4+ and CD-8+ lymphocytes within the hyperplastic thymus are similar to those seen in young rats of other species. The high level of T-cell emigration from the thymus to the periphery appears to persist throughout life, since the percentage of normal splenic T-cells also increase with advancing age and exceed 70% of the total by 24 months of age. This thymic enlargement with abnormal hyperplasia of cortical epithelial cells can be prevented by hypophysectomy.