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Although antiserums to lymphocytes and thymus cells have similar effects on lymphocytes and thymocytes in vitro, the antiserum to thymus has more persistent lymphopenic effect in vivo and prolongs allograft survival time more markedly. Since only thymus glands of animals treated with antiserum to thymus showed depletion of small lymphocytes, antibody to thymic humoral factor may be operational.
Atrophy of the thymus gland occurs in rats made diabetic by a single injection of the drug streptozotocin. Histological studies show the presence of thymocytes with pyknotic nuclei in thymus tissue taken from diabetic animals. Analysis of the elemental content of the pyknotic cells was carried out on freeze dried frozen sections of thymus tissue using the technique of X-ray microanalysis. There was no loss of elements from cells which had undergone the early morphological changes characteristic of pyknosis and which showed the condensed chromatin of pyknotic nuclei. However as the cells shrank and lost the clear distinction between nucleus and cytoplasm there was a loss of elements, particularly Mg and K from the cells. The changes in distribution of elements in the dying thymocytes suggest a method of cell death which does not involve disruption of the plasma membrane.
The history of surgery of the thymus gland is presented through highlights and landmark publications ranging from prehistoric times to the present day. The evolution of surgical techniques includes transcervical and transthoracic thymectomy along with other techniques such as current thoracoscopic VATS procedures. The significance of myasthenia gravis, autoimmunity, thymic oncology, adjuvant developments, and speculation on the future is discussed.
We report two rare cases of thymus gland found behind the left brachiocephalic vein, in young women undergoing thymectomy for myasthenia gravis. Our observations are included among the thymic anatomical variants. After a review of the literature on the subject, we discuss both the diagnostic role of new radiological techniques (CT, NRM) and the choice of surgical approach to these variants.
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Chronic treatment with lithium chloride produced significant involution of the thymus gland with histological evidence of reduced cellularity due to loss of thymic lymphocytes and a significant reduction in the weight of the gland in normal and adrenalectomized mice. Lithium also increased corticosterone levels in normal mice without changes in adrenal weights. The involution of the thymus gland is most likely due to an effect of lithium on the gland, and it is not mediated by adrenocortical mechanisms or stress.
The thymus gland of the adult common frog, Rana temporaria, undergoes conspicuous seasonal changes corresponding to the temperature-dependent changes in the annual activity of these animals. During the period of active terrestrial life the thymus is clearly divided into a lymphocyte-rich cortex and an epithelial medulla containing interdigitating-like cells. During hibernation and mating the thymus is depleted of lymphocytes and consists of numerous secretory units (cells and cysts) and degeneration cysts. Rapid release of secretory material is evident at the beginning of the frog active life.
The effect of chronic administration of morphine and abrupt and naloxone-precipitated withdrawal on the levels of beta-endorphin and methionine-enkephalin in spleen, adrenals and thymus glands of Sprague-Dawley rats was determined. Rats were made tolerant to and dependent on morphine by subcutaneous implantation of 6 morphine pellets (75 mg morphine in each) during a 7-day period. The tolerant-dependent (with pellets intact) and abstinent (pellets removed 18 hours earlier) rats were sacrificed. In another group, rats with pellets intact were injected with naloxone and sacrificed 10 min later (precipitated abstinence). The weights of the tissues under any of the above treatments did not change nor did the levels of methionine-enkephalin and beta-endorphin in adrenals. The level of beta-endorphin was elevated in the spleen and thymus of morphine tolerant-dependent rats, while the levels of methionine-enkephalin in rats undergoing abrupt or naloxone-precipitated abstinence were significantly higher than in their respective placebo controls. The levels of methionine-enkephalin in the thymus gland of rats with placebo and morphine pellets left intact did not differ. It is concluded that in morphine tolerant-dependent rats the levels of beta-endorphin in spleen and thymus are elevated. During abrupt and naloxone-precipitated abstinence, the levels of methionine-enkephalin in the thymus gland are significantly elevated possibly due to an inhibition of their release. Since these opioid peptides have been implicated in immunomodulation, and alterations were seen in organs controlling immune function, the present results may be helpful in explaining altered immune function in morphine dependent and abstinent states.
Thymus excised from 68 patients suffering from juvenile myasthenia was subjected to histological, histochemical and electron microscopy studies. The changes in the thymus involved hyperplastic immune response in the form of lymphoid follicles with the germinal centers and focal plasmocytic infiltration. In myasthenia, the permanent characteristic of the thymus was activation of epithelial cells and Hassal bodies. A direct relationship was discovered between the efficacy of thymectomy and intensity of hyperplasia of the glandular lobules of the thymus. The lobule number of lymphoid follicles with the germinal centers did not affect the results of the surgical treatment of patients suffering from myasthenia.
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Innervation of the mammalian thymus gland by both cholinergic and catecholaminergic neuronal projections has been documented. The present results reveal that the inhibitory neurotransmitter, gamma amino butyric acid is also present in the mouse thymus and that it is significantly elevated following challenge with a T-cell dependent antigen. A possible immunomodulatory role for the neurotransmitter is discussed.
The article comprises a survey of the literature data on histophysiology of the thymus gland and a discussion of results of the authors' own observations of this gland in rats line "Vistar" in normalcy and in the presence in the organism of a transplanted tumour RS-1. Problems associated with histophysiology of the thymus, including such as differentiation of thymocytes, their relationships with the reticuloepithelial cells, the capacity of the latter for secretion, the role of the stratified epithelial bodies, the hematothymus barrier, etc., are discussed.
The effect of a purified bovine thymus gland extract (Dr. Kurt Mulli, GmbH, Hamburg, West Germany) was studied in 12-week old male Wistar rats on the following: thyroid weights and morphology, T3-T4 serum levels, thyroid lactic dehydrogenase, ATP-ase, acid phosphatase, and non-specific esterase activities. Thymus extract was administered intramuscularly daily for 21 days at doses of 0.5, 1.0 and 2.0 ml/kg. Measurements were made on day 3, 7, 14 and 21 of treatment. Thyroid histology and enzyme activity were studied only on 21-day specimens. Thymus extract significantly decreased average thyroid gland weights in a dose-dependent manner irrespective of treatment duration. T3 serum levels were consistently lower in thymus-treated rats irrespective of treatment dose or duration. Changes from control levels were not statistically significant due to large standard deviations. T4 serum levels were significantly lower than control levels in rats treated with thymus extract for 14 and 21 days. Histology of thyroids from 21-day treated animals revealed a marked reduction in both thyroid follicle size and colloid content with an increase in connective tissue, resorption vacuoles and hyperemia. Histochemical study of thyroid enzyme activity showed lactic dehydrogenase increase in follicle epithelial cells, acid phosphatase increase in follicle epithelial cells and decrease in interstitium, ATP-ase increase in granular storage area and non-specific esterase increase in follicle epithelial cell. The data suggest the presence of an unidentified specific anti-thyroid factor(s) in the thymus gland extract.
We studied the entire thymus gland by step-serial sections in four fatal cases of acquired immunodeficiency syndrome (AIDS) in children. The location, configuration, and blood vessels of the thymus gland were normal. The weight was reduced. There was severe depletion of both lymphocytes and Hassall's corpuscles. Because of the normal location, configuration, and blood vessels and the seemingly less severe lymphocytic depletion than is seen in congenital immunodeficiency syndromes and because of the clinical and epidemiologic features, we concluded that this syndrome in children represents AIDS. We postulated that the epithelial cells of the Hassall's corpuscles may be the primary site of thymic injury in AIDS.
In European common frogs, Rana temporaria, leading an active land life at high external temperatures (May-October), the thymus glands are clearly divided into lymphocyte-rich cortex and mainly epithelial medulla ('summer' appearance). In contrast, thymuses of hibernating and mating frogs (at low temperatures, October-April) are typically endocrine organs with an abundant population of secretory cells, small number of thymocytes and lack cortico-medullary division ('winter' appearance). Thymuses of experimental animals kept from September until January at a high temperature tend to change their appearance from the 'summer' type to the 'winter' one. Thymuses of experimental frogs kept from the end of May until the end of June in refrigerator preserve their 'summer' appearance. These results show that the annual rhythm of the frog thymus gland is difficult to alter by simple changes of external temperature.