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.     

The effect of gamma irradiation on the direct intercellular interaction (rosette formation) of thymic macrophages with thymocytes]

In experiments with (CBA x C57BL/6)F1 mice, the effect of radiation on rosette formation between thymus macrophages (Th-MPh) and thymocytes (Thc) was studied on days 1, 4, 12, 30, and 60 following gamma irradiation with doses of 0.5, 2, 4, and 8 Gy. The influence of supernatants of thymus epithelial cells (EC) on the rosette formation was estimated. Gamma irradiation with doses of above 2 Gy was shown to cause a dose-dependent inhibition of rosette formation of Th-MPh with Thc in vitro. Recovery of rosette-forming ability of Th-MPh was observed on day 60 of the experiment. Two types of rosette-forming Th-MPh were identified: RFMPhII with low rate of binding to Thc and RFMPhII with high rate of binding to Thc. Radiation affects mainly the RFMPhII content. With radiation doses of 4 and 8 Gy no complete restoration of RFMPhI was observed on day 60. The total population of rosette-forming Th-MPh was restored on day 60 mainly due to cells with low rate of rosette formation. The EC supernatant promoted rosette formation of exposed Th-MPh with Thc. The effect was maximum at early times following irradiation of Th-MPh with a dose of 4 Gy.     

Thymus lipids in continuously irradiated rats.

Male Wistar rats were irradiated continuously with a daily dose of 0.19 Gy (120 days), 0.57 Gy (90 days) and 0.96 Gy (35 days) of gamma rays. An other group of rats was irradiated continuously with graded doses of gamma rays, up to total exposures ranging from 3.83-19.15 Gy. Depending on both the daily dose and total exposure, there was a decrease in phospholipid content in the thymus which correlated well with thymus weight changes. The decrease in triacylglycerol content was a less reliable sign of radiation damage. The phospholipid content reflecting the patterns of organ cellularity is a valuable indicator of the extent as well as recovery from radiation-induced injury to the thymus.     

X-irradiation effects on thymidine kinase (TK): I. TK1 and 2 in normal and malignant cells

Abstract. The effect of radiation on TK is more complicated than would be expected from earlier results on bone marrow cells ( Feinendegen et al. 1984 , Int. J. Radiat. Biol. 45, 205). TK activity increased at 0.01 Gy and then decreased up to 1 Gy in mouse spleen. In contrast to the results for the spleen, an increase in activity at 0.1 Gy was seen in mouse thymus. The activity of dephosphorylated TK1 (TK1a) in both spleen and thymus was reduced to 50% after irradiation at 0.5–1 Gy. The degree of phosphorylation (TK1b/TK1a ratio) changed in spleen, but not in thymus. The activity of TK2 in mouse liver increased at 3 h after 5 Gy by about 60%. In mouse ascites tumour, a dose-independent (1–5 Gy) oscillating TK1 activity was found up to 24 h, especially for TK1a and TK1b. The amount of TK1 was unchanged up to 12 h, but decreased at 24 h. This suggests that the differences in the changes in the degree of phosphorylation of TK1 after irradiation among spleen, thymus and ascites tumour further underline the complexity of the response of TK1 activity to irradiation. The dramatic change in the activities of TK1a and TK1b may illustrate that both of them are more radiosensitive than TK-h, a variant with mixed TK1 and TK2 properties.     

Mechanism of thymocyte death in exposure to ultrahigh doses of gamma radiation

A comparative study was made of the morphological and biochemical indices of rat thymus cells after gamma-irradiation with doses of 4-10 Gy (median), 20 Gy (high), and 200-400 Gy (superhigh). It was shown that 4 h after irradiation with superhigh doses the yield of polydeoxynucleotides (PDN) was twice as low as that observed after doses of 4-10 Gy. 24 h after irradiation the amount of the extracted PDN in thymocytes exposed to superhigh doses was markedly larger than that after 4 hours. After all doses applied chromatin degradation occurred at the internucleosome sites in a strict order, the activity of acid and alkaline nucleases being unchanged. A large number of cells have normal nuclear structure 4 h after irradiation (200-400 Gy), as was demonstrated by the electron microscopy data, while in 24 h no intact cells were virtually found in the thymus which correlated with the changes in the PDN yield. The mechanisms of the lymphoid cell death under the effect of different radiation doses are discussed.     

Effect of myelopeptides on the postradiation recovery of the thymus

The influence of myelopeptides on the postirradiation recovery of thymus was studied by estimating the thymus cellularity, proliferation of thymocytes in vivo, and composition of thymocyte subpopulations characterized by the expression of Thy-1,2 and Sc-1 antigens and receptors for peanut agglutinin. A single intraperitoneal administration of myelopeptide (the optimal dose of 10(-5) mg/mouse) 24 h following 6.5 Gy irradiation gives rise to proliferative and differentiation processes favoring the recovery of thymus.     

转基因MSC对放射损伤胸腺组织修复的研究

目的：探讨转基因MSC能否修复放射损伤的胸腺。方法：雌性BALB/C小鼠120只,随机分为4组：对照组30只,予以假照射;照射组30只,60Coγ射线胸腺单次照射,剂量为9Gy;照射＋MSC组30只,9Gy照射后2小时输注转基因MSC;对照＋MSC组30只,假照射后2小时输注转基因MSC。照射后1、7、14、21、28天检测各组小鼠血像、胸腺指数及胸腺病理。结果：照射＋MSC组血像和胸腺指数在各个时间点均优于照射组,胸腺病理显示组织结构恢复明显加快。结论：转基因MSC能归巢至放射损伤胸腺并能促进胸腺的修复,为干细胞的临床应用提供了实验依据。     

Effects of single gamma-irradiation on the activity of ornithine decarboxylase in the thymus and pulmonary tissue]

In studying the dose (0.1-6 Gy) and time (2 h to 180 days) dependence of ornithine decarboxylase activity, it was found that deviations from the control were more pronounced in the thymus than in the pulmonary tissue. The radiation effect was a function of dose and time after irradiation. A nonmonotonous type of the dose-response curve was observed 7 days after irradiation: the radiation effect with a low dose (0.1 Gy) was opposite to that with sublethal doses (1-6 Gy).     

DNA-protein cross-links in cells of internal organs of rats after fractional irradiation at various doses

The influence of daily fractional irradiation of male Wistar rats for 30 days on DNA-protein cross-links (DPC) in spleen, thymus, and liver cells was studied. The level of DPC depended strongly on the daily dose of irradiation and the studied organ. After irradiation at dose 0.5 Gy per day increased DPC level was detected in all organs. The highest level was in the lymphoid organs and the lowest in the liver. After irradiation at dose 0.3 Gy per day DPC formation was detected only in the thymus. The data suggest the existence of a dose threshold for DPC formation during fractional irradiation.     

Migration of bone marrow cells toward the thymus in C57BL/Ka under fractionated irradiation

Fractionated whole body X-irradiation (4 X 1.75 Gy at weekly intervals) induces a high percentage of thymic lymphomas in C57BL/Ka mice. These tumors develop after a long latency period during which the thymic lymphopoiesis is deeply altered. In the present work, we test wether those modifications are due to lack of prothymocyte homing to preleukemic thymuses. Our results show that the preleukemic state of the thymus don't prevent the homing of normal marrow precursors grafted immediately after an irradiation of 4 Gy. Thus the alterations of thymic lymphopoiesis observed after a leukemogenic irradiation are not due to a modification in the thymus receptivity to thymocyte precursors.     

Endogenous phospholipase hydrolysis in radiation injury of animals

A study was made of the free fatty acid (FFA) content of homogenates of brain, thymus, liver, kidneys, erythrocytes, small intestine mucosa, and spleen of X-irradiated (7.76 Gy) rats. The increased FFA content was exhibited by all the organs under study. The increase was maximum in the thymus. Calcium ions were shown to play a defined role in the radiation enhancement of endogenous phospholipase hydrolysis.     

Synthesis of lipids in the thymocytes of irradiated rats

During the first two hours following whole-body gamma-irradiation of rats with a dose of 7.5 Gy, the content of free cholesterol, phosphatidylcholine and phosphatidylethanolamine in the thymus decreases. Incorporation of 2-14C-acetate into cholesterol and fatty acids of thymus phospholipids in vitro is inhibited. At a dose of 4 Gy, incorporation of 2-14C-acetate into cholesterol and total lipids of thymocytes is activated.     

Changes in lipid metabolism in rats with radiation sickness and a pronounced intestinal syndrome following local irradiation of the abdominal region. Fatty acid composition of the blood and tissue phospholipids

Local irradiation of rat abdomen (13.5 Gy) caused similar changes in fatty-acid composition of phospholipids in the liver, thymus and brain, that is: (a) a decrease in the polyunsaturated fatty acid content in 4 h, (b) a hypercompensatory increase in the content of polyunsaturated fatty acids (excluding thymus) in 24 h, the ratio between essential fatty acids and their derivatives being changed towards accumulation of the latter, and (c) a trend toward normalization in 72 h.     

Modification of the regulatory effects of thymocytes on hematopoiesis in irradiated mice as affected by heterologous immunoglobulin G and low-dose ionizing radiation

The administration of heterologous immunoglobulin G (IgG) and/or exposure of mouse thymocyte donors to 1 and 2 Gy radiation were shown to change the regulatory effects of thymus lymphocytes on the recovery of haemopoiesis in syngeneic recipients irradiated with a median lethal dose of 6 Gy. Thymocytes of exposed (2 Gy) donors produced a stimulatory effect on the restoration of the myelokaryocytes number and increased the number of endogenous splenic colonies and bone marrow CFUs in animals exposed to a median lethal dose, whereas the administration of IgG to thymocyte donors given 2 Gy eliminated the stimulatory effect of thymocytes on the number of myelokaryocytes, and the amount of CFUs in irradiated recipients decreased.     

Structure and repair of rat thymus DNA during long-term irradiation

During long-term fractionated irradiation (0.5 Gy, daily) the molecular weight of single-stranded DNA of the thymus of exposed rats remained the same as that of intact animals till the dose of 25 Gy had been cumulated. The integrity of the DNA structure was ensured by the repair of DNA and elimination of cells with unrepaired lesions. The role of repair decreased and the elimination of cells increased with increasing cumulative dose.     

Regeneration of Gastrocnemius Muscle and State of Immune System in γ-Irradiated Rats under the Influence of He-Ne Laser

We studied the influence of a low-energy He-Ne laser on the regeneration of the transected gastrocnemius muscle and state of the thymus and bone marrow in adult mongrel rats irradiated at 6 Gy using the histological, morphometric, and cytogenetic methods. The laser influence on both rat hind limbs (at total doses of 9.0–10.8 J/cm²) enhanced the regenerative capacity of the viradiated traumatized skeletal muscle, and reduced cytogenetic damage in the bone marrow and thymus cells. The changes in the thymus mass and histostructure suggest that the functional load on the thymus increased under studied the experimental conditions.     

Effect of preincubation irradiation on adenylate cyclase activity and cyclic nucleotide content of the thymus in chick ontogenesis

Adenylate cyclase activity and cAMP and cGMP content of thymus have been studied in intact and irradiated (0.029 Gy, prior to incubation) embryos and chickens. The enzyme activity is stimulated during the postnatal development. The changes in the cyclic nucleotide content are undulatory and oppositely directed. It is suggested that the observed radiation-induced stimulation of adenylate cyclase and the reciprocal changes in the cyclic nucleotide content after hatching are related to the increased specific differentiation of thymus cells.     

Effect of preliminary adaptive irradiation on the concentration of lipid peroxidation products in blood serum and degradation of DNA in thymus of irradiated mice

The animals were irradiated within adaptive dose of 0.1 Gy and 5 hours later with a challenge dose of 2 Gy. The adaptive dose reduced the effects induced by the challenge dose of 2 Gy: the increased content of the products of lipid peroxidation reactive to thiobarbituric acid in blood serum, and the increased number of breaks in thymus DNA of irradiated mice.     

Determination of the radiosensitivity of interphase-dying cells in the thymus, spleen and bone marrow of rats by flow cytometry

The flow cytofluorometry of cells stained with a DNA-specific probe was used to determine the share of dying cells (containing less than 2C DNA) in thymus, spleen and bone marrow cells of irradiated rats. The cell death curves for spleen and bone marrow had a plateau by the 6th h, and for thymus, by the 10th h following irradiation with different doses. On the basis of the dose-response relationship the share of cells dying in the interphase was determined in each organ under study, and dose-response curves shaped. All the curves had no shoulder. Do was 3.0, 3.0 and 3.7 Gy for thymus, spleen, and bone marrow cells, respectively.     

Synthesis of lipids in the thymus of irradiated rats

Changes in the synthesis of total lipids from 14C-glucose and 3H2O and in triacylglycerol concentration in the thymus of rats X-irradiated with a single dose of 14.35 or 6.0 Gy were investigated. Both lipid synthesis and TAG concentration were found to increase in the irradiated rat thymus.