Научная статья на тему 'Effect on the experimental hypothyroidism morphological and morphometric parameters of thymus'

Effect on the experimental hypothyroidism morphological and morphometric parameters of thymus Текст научной статьи по специальности «Фундаментальная медицина»

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Ключевые слова
THYMUS / THYROID GLAND / MERCAZOLILUM / THYMOCYTES

Аннотация научной статьи по фундаментальной медицине, автор научной работы — Yuldasheva Mokhigul Turdialievna

The aim of the work was to study the morphological and morphometric characteristics of the thymus at experimental hypothyroidism in adolescencerats. Experiments were carried out on rats weighing 70-80 g, hypothyroidism caused by adding food merkazolil in dose 0.5 mg/100 gbody weight for 14 days. Then the animals received during the month maintenance dose of the drug 0.25 mg/100 g body weight. Thymus was examined using morphological and morphometric techniques. It was found that long-term hypothyroidism contributes to a significant reduction in the area of cortical areas and a decrease in the density and ofthe mitotic activity of thymocytes. The degree of destruction of thymocytes significantly increases. Conclusion: Experimental hypothyroidism in the adolescence rats leads to inhibition of proliferation of thymocytes and increases their death in the thymus. Therefore, thyroid hormones play a key role in maintaining tissue homeostasis in the thymus in a postnatal ontogenesis

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Текст научной работы на тему «Effect on the experimental hypothyroidism morphological and morphometric parameters of thymus»

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DOI: http://dx.doi.org/10.20534/ESR-16-11.12-110-112

Yuldasheva Mokhigul Turdialievna, Tashkent Medical Academy, Uzbekistan E-mail: parizod70@mail.ru

Effect on the experimental hypothyroidism morphological and morphometric parameters of thymus

Abstract: The aim of the work was to study the morphological and morphometric characteristics of the thymus at experimental hypothyroidism in adolescencerats. Experiments were carried out on rats weighing 70-80 g, hypothyroidism caused by adding food merkazolil in dose 0.5 mg/100 gbody weight for 14 days. Then the animals received during the month maintenance dose of the drug 0.25 mg/100 g body weight. Thymus was examined using morphological and morphometric techniques. It was found that long-term hypothyroidism contributes to a significant reduction in the area of cortical areas and a decrease in the density and ofthe mitotic activity of thymocytes. The degree of destruction of thymocytes significantly increases. Conclusion: Experimental hypothyroidism in the adolescence rats leads to inhibition of proliferation of thymocytes and increases their death in the thymus. Therefore, thyroid hormones play a key role in maintaining tissue homeostasis in the thymus in a postnatal ontogenesis.

Keywords: thymus, thyroid gland, Mercazolilum, thymocytes.

The urgency of the problem. In the process of evolutionary development of the organism there are new coordination mechanisms, leading to the formation of structural and functional relationships. These relationships enable the integration of the various organs and systems. The close relationship between the immune and endocrine systems is shown in several studies [1]. It has been established that various endocrine organs lesions are accompanied by certain immune changes in the body and, in turn, certain immune disorders lead to disturbances of the endocrine functions of the body [2; 3]. In this regard, the relationship of the thyroid with the immune system are particularly noteworthy. Clinical observations suggest that at the diseases of the thyroid gland in patients with various immune disorders develop, the severity of which depends on the level of thyroid hormones [4].

It was revealed that in patients with autoimmune thyroiditis in combination with hypothyroidism secondary immunode ficiencies are observed to varying degrees [5]. The change in the immune system generally correspond to the level of serum thyroid hormones. Reducing the level of thyroxine (T4) and triiodothyronine (T3),

often accompanied by a decrease in the total amount of co-lymphocytes change in the ratio of T-suppressor/helper, a violation of antibody processes and the emergence ofhigh-titer auto-antibodies [6; 7]. '

Objective. Identification of morphological and morphometric characteristics of the thymus in rats with experimental hypothyroid-ism caused in the prepubescent period.

Material and methods. The experiments were conducted on rats — males weighing 70-80 grams, which corresponded to the period of prepubescent or adolescent development. Rats were divided into three groups. Two groups of animals received the experimental diet Mercazolilum together with a dose of 0.5 mg. 100 gr. of body weight during the 14 days, then received within a month merkazolila maintenance dose of 0.25 mg. Per 100 g body weight. Further experimental groups of animals were divided into two subgroups. The first subgroup continued to receive merkozolil (short-term hypothyroidism). This class was used for the study of the natural regression of hypothyroidism in the juvenile period. Animals with similar body weight merkozolila instead received sterile

Effect on the experimental hypothyroidism morphological and morphometric parameters of thymus

physiological saline throughout the experiment served as control. At the end of experiments 90 hours as control and experimental animals were killed by decapitation under light ether anesthesia. We determine the mass of the thymus and its relation to body weight. Morphological studies were conducted on 7-10 micron thick sections stained with hematoxylin and eosin. In addition, sections of the thymus morphometric method determines the average area of the lobules, their cortical and brain areas, counted the number of mitotically dividing and destructive thymocytes. All digital data is processed by the method of variation statistics using computer software package, reliable differences were considered satisfying P <0.05. For electron microscopic examination of the thymus pieces were fixed in 2.5% glutaraldehyde solution and focused in 1% solution of osmium tetroxide. After dehydration in alcohols of increasing concentration bits embedded in Araldite. Ultrathin sections were obtained on ultramicrotome LKB-V, after

double staining with uranyl acetate and lead citrate viewed under an electron microscope JEM-100SX.

Results and its discussion. It was found that the thymus morphological changes in experimental hypothyroidism are directly dependent on the duration of thyroid suppression. The development of hypothyroidism in experimental animals has been proven to study serum tireoidnyhgormonov. The greatest reduction of thyroxine (T4) and triiodothyronine (T3) (more than 3-fold) was observed in rats with long hypothyroidism, and observed under short hypothyroidism relatively moderate (1.6-fold) decrease of thyroid hormones in comparison with control. Mass, as well as the index of thymus weight in both groups of experimental animals decreased compared with the control significantly. The greatest decrease in thymus weight observed in the group of rats with a long hypothyroidism. Results of morphological studies of different areas of the thymus zones are shown in Table 1.

Table 1. - Average square lobes, areas of cortical and cerebral zones of the thymus at Experimental hypothyroidism (M ± m, xlQ5 mm 2)

Animal group Area

The total area of cloves crustal zone brain area

Max. % Max. %.

Control (n=22) 21,5±0,6 15,9±0,2 74 5,6±0,1 26

Short-term hypothy-roidism (n=16) 19,7±0,3* 12,4±0,3*** 63 7,3±0,2*** 37

Prolonged hypothy- roidism (n=18) 118,5±0,5*** 11,1±0,2*** 60 7,4±0,2*** 40

Note: * - the difference relative to the control group significant data (* - P <0,05, *** - P <0,001)

It is seen that hypothyroidism resulted in a significant de- thyroidism in the exponent decreased by 14% of control. crease in the average area of slices. These animals with long hypo-

Table 2. - The average density of the cells in the lobules of the thymus location at Experimental hypothyroidism (M ± m, xlQ 5 mkm 2)

Animal group Area

crustal zone brain area

Control (n=22) 19,1±0,28 9,7±0,17

Short-term hypothy-roidism (n=16) 17,8±0,31** 8,9±0,23**

Prolonged hypothy- roidism (n=18) 16,5±0,27***AAA 8,6±0,22***

Note:* — the difference relative to the control group significant data (** — P <0,01, *** — P <0,001), A — differences with respect to short-term data giaotireoz significant (AAA — P <0,001)

In separate research areas of different zones revealed that hypothyroidism contributed to a significant reduction in the area of cortical areas on 22-30% of the control. In contrast, the brain area with hypothyroidism area increased by 30-32% of the control. Both short and long-term hypothyroidism resulted in a decrease in the average cell arrangement density in areas of thymic lobules (table 2).

The cell density in the cortical area, depending on the duration of hypothyroidism decreased by 7-13,7%, and in the brain area — on 8,3-11,4% of the control. It is found that reducing the concentration of thyroid hormone adversely affects thymocyte proliferation activity, while increasing the degree of destruction of thymus cells (Table 3).

Table 3. - Number of mitotically dividing and destructive thymus cells in experimental hypothyroidism (M ± m 1Q 3 cells)

Animal group Cells

mitotic destructive

cortical brain cortical brain

Control (n=22) 52,8±1,5 10,2±1,3 16,5±1,2 4,8±0,3

Short-term hypo-thy-roidism (n=16) 43,4±1,3*** 8,6±0,9 27,8±1,4*** 8,7±0,5***

Prolonged hypothy- roidism (n=18) 21,7±1,1*** 5,4±1,2** 48,3±1,6*** 10,5±0,9***

As the table shows, the largest decrease in the mitotic activity of thymus cells is observed for prolonged hypothyroidism. The number of mitoses in these animals in the cortical and medullary zones was respectively of 41% and 53% of control. For short hypothyroidism decrease the number of mitoses were not so pronounced and the number of proliferating cells in this case was

82-87% of control. Reducing the number of mitosis in hypothyroidism accompanied with an increase in the number of cells in the areas of destructive thymus. Table 3 shows that the greatest increase in the amount of degradation observed in the cortical area in which intermittent 1.77 hypothyroidism, and prolonged hypothyroidism — 2.9 times the control parameters. Similarly, but

to a lesser extent, increased the degree of destruction in the brain area. The most pronounced morphological and submicroscopic thymus changes occurred in rats with long hypothyroidism. In the majority of cortical slices zone acquires the character of a narrow strip, where portions of closely spaced thymocytes interspersed with light areas that do not contain cells.

The cortical area is often identified large bright pockets containing destructive thymocytes. Hypothyroidism, especially long, accompanied by a significant ultra-structural changes of thymocyte and thymic microenvironment cells. Often identified with signs of thymocytes lysis of the cytoplasm and nucleus pyknosis. Macrophages thymus were characterized by large size, in their cytoplasm often phagocytized thymocytes were found in various stages of destruction.

All this indicated that under the conditions of thyroid hormone deficiency is amplified degree of degradation and death of thymocytes, macrophages are absorbed rapidly. So, conducted studies have shown a direct correlation with postnatal growth of the thymus thyroid condition. We have found that the longer the duration of hypothyroidism, the deeper manifested morphological and morphometric changes in the thymus. Status of the thymus in a violation of thyroid function has been insufficiently studied. In the works of Ukrainian authors demonstrated that the removal of the thyroid gland is accompanied by inhibition of the secretory activity of the thymus in terms of production of thymic hormones. It is known that these hormones are key regulators of the process

of proliferation and differentiation of T lymphocytes and their subpopulations. From our data show that at short hypothyroidism, hypothyroidism and long — lead to a greater extent to decrease the proliferative activity of thymocytes. The degree of degradation is significantly increased in the thymus. This, in turn, contributes to thymic hypoplasia as to reduce its weight and performance of different zones of the thymus lobes. The development of premature thymic involution can be attributed to deficiency of thyroid hormones that have a regulating influence-of the synthesis and secretion of thymic peptides. It is possible that in the pathogenesis of structural and functional disorders of the thymus in a hypothetical-reoza important role played by thyroid and growth hormone anterior pituitary, and thyrotropin-releasing hormone produced by the hypothalamus. From here, it follows that for the natural formation and functioning of the thymus is necessary to have normal levels of thyroid hormones. Prevention of hypothyroidism in childhood and adolescence is one of the important conditions for the normal functioning of the immune system in the adult body.

Conclusions

1. Hypothyroidism develops in the prepubescent period, leading to hypoplastic thymus, the degree of which depends on the duration of the hypothyroid state.

2. Inhibition of activity of the thyroid gland reduces the pro-liferative processes in the thymus and increases the degradation of thymocytes that entails a violation of the processes of T-lymphocy-topoiesis in the body.

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DOI: http://dx.doi.org/10.20534/ESR-16-11.12-112-116

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