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Morphological and functional features of thyroid gland of posterity under in utero and early postnatal exposure to pesticides
of myopia, is one of the pathogenetic mechanisms of the myopia progression.
Conservative general therapy of patients with juvenile glaucoma occurring on the base of progressive myopia, regardless of the stage of development of glaucomatous process, requires
the inclusion of pathogenetically directed treatment, the purpose of which is to slow and/or stabilization of the intensity of the destruction of collagen ECM system, prescribing substitution therapy and stimulating collagen formation on the base of antihy-pertensive therapy.
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DOI: http://dx.doi.org/10.20534/ESR-17-3.4-33-34
Zokirova Nargiza Bakhodirovna, Senior Researcher of Tashkent Medical Academy E-mail: [email protected]
Morphological and functional features of thyroid gland of posterity under in utero and early postnatal exposure to pesticides
Abstract: The effect of prenatal and early postnatal exposure to pesticides of new generation (cyhalothrin and fipronil) on the postnatal dynamics of the formation of pituitary-thyroid system of offspring has been studied. It was found that the impact of pesticides through the mother's body slows down the rate of formation of thyroid follicles offspring. Violation of the pituitary-thyroid system is manifested in the form of hypothyroidism. All this leads to a thorough monitoring of thyroid function in pregnant women and newborns at increased risk of environmental pollution by pesticides.
Keywords: pesticides, thyroid gland, pituitary-thyroid system, postnatal ontogenesis.
Introduction. Many chemicals that are widely used in households, agriculture and industry have a negative effect on the endocrine system. They are now united under the name of "endocrine-disrupting substances, EDs or endocrine disruptors, ED" [5; 6]. This term together those chemicals that in humans and animals change the processes of synthesis, secretion, transport, metabolism of natural hormones and thus lead to a breach of the hormonal homeostasis [5]. That action has a number of pesticides, including the latest generation, household chemicals, some drugs [3; 4; 5]. The high sensitivity of the thyroid to the EDs has caused the need for a separate group of chemical substances (thyroid-disrupting chemicals), which predominantly inhibit the processes of synthesis, transport and receptor function of thyroid hormones [7; 9]. To date, can be considered a proven role of EDs in the pathogenesis of several diseases, such as obesity, atherosclerosis, hypertension and coronary disease, some of reproductive dysfunction and other related metabolic disorders and hormonal homeostasis [5; 6; 9]. Analysis of the literature shows that the majority of studies on the mechanisms and effects of EDs on the endocrine system, unfortunately, animals and adults carried out on mature individuals [3; 4]. There are only a
few reports that such ED substances have a more pronounced pathogenic effect in childhood and adolescence, disrupting the growth and formation of the body in the postnatal period [8]. However, many questions of adverse effects of environmental chemicals on the developing human body and animals remain unsolved.
The purpose of research is identifying the structural and functional features of postnatal growth and the formation of the thyroid gland in the offspring in terms of pesticide exposure via the mother's body.
Materials and methods. Experiments were performed on nul-liparous, white adult female rats, which were divided into 3 groups of 30 animals each. Two groups of animals for 30 days daily per os obtained respectively pesticides cyhalothrin or fipronil. The third group receiving only the same volume of sterile saline served as a control. The following day, the females were coupled with healthy males for fertilization. Exposure of pesticides was continued incessantly during pregnancy and until the end of the lactation period. Pregnancy was monitored for the presence of sperm in vaginal smears. Offspring obtained from the experimental and control females were examined in dynamics on days 3,7,14, 21 and 30 after
Section 5. Medical science
birth. Thyroid gland (TG) was studied by morphometric and electron microscopic techniques [1; 2]. Furthermore, in the offspring was determined level of thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone (TSH) of pituitary. All figures are statistically processed using the software package with the calculation criteria Student, reliable differences were considered satisfying P < 0.05.
Results and discussion. It was revealed that chronic intoxication the mother's body significantly reduces the growth rate and the formation of the thyroid in a postnatal ontogenesis. Starting from 1-3 days after birth, the average total number of follicles on the cut area in the experimental animals was significantly lower compared with the control. The areas of follicles were also significantly lower than the control. In the dynamics ofpostnatal growth the formation of morphometric parameters of thyroid in all studied groups, respectively, increased. However, the rate of growth of the thyroid as a whole, the formation of new follicles in the gland in the experimental animals lagged significantly from the control. Of particular note is the low specific indicators thyrocytes in all terms of the study, indicating a decrease in the secretory activity of the cells. The resulting morphometric data were fully confirmed by the results of electron microscopic studies.
Under the electron microscope the thyroid follicles of control animals at all stages of observation were typical structure. Thyrocytes of control animals were in various stages of the secretory cycle and generally characterized by ultrastructural signs of high activity and lysosomal synthetic devices. The cytoplasm of individual thyrocytes contained a considerable amount of granular endoplasmic reticulum cisterns. The nuclei of cells in the heart or were slightly shifted to the basal part of thyrocytes. The results of electron microscopic studies of thyroid in progeny derived from experimental animals, revealed the existence of certain submicroscopic changes in general reveal a violation of certain phases of the secretory cycle thyrocytes. Along with thyrocytes with intact ultrastructure, they are often in the wall of the follicle cells were found with obvious signs of disorganization profiles granular endoplasmic reticulum in the form of excessive expansion and reduce the density of the internal content.
Sometimes the cytoplasm of individual thyrocytes looked like a giant vacuole with a light content, the kernel and a few organelles were pushed to the cell periphery. Often detected thyrocites with
marked swelling of mitochondria with enlightenment of their matrix and disorganization of the cristae or with their complete vacuolization. Much less in some thyrocytes failed to note the emergence of a few lipid droplets of different sizes, which hardly occurred in the control group. Finally, in the progeny of the experimental animals more frequently in comparison with the control were determined thyrocytes with clear signs of apoptosis and destruction of cytoplasmic organelles. It can be concluded on the basis of electron microscopy data, and in the formation of thyroid growth in chronic intoxications, along with a reduction in the proliferation of thyrocytes, there is a strong upset their differentiation process. This is indicated by the signs of destruction submicroscopic organelles responsible for synthesis, transport and cleavage of thyroglobulin. All of this eventually leads to thyroid dysfunction and disruption of metabolic processes in the developing offspring. Functional disorders in the pituitary-thyroid system offspring have been confirmed by determining the level of T4, T3 and TSH in the offspring in the dynamics of postnatal development. It was shown, that in the offspring, subjected to the pesticide through the mother (in utero and through breast milk) developing thyroid dysfunction, it appears as hypothyroidism, despite the fact that the concentration of pituitary TSH significantly exceeds the control group. Comparative evaluation of the negative effect of the studied pesticides showed that fipronil has a stronger negative impact on the structure and function of the thyroid gland offspring compared to cyhalothrin.
Conclusions:
1. The impact of the new generation of pesticides (cyhalothrin and fipronil) through the mother's body leads to structural and functional impairment of formation of the pituitary-thyroid system offspring. This significantly slowed down the pace of the formation of thyroid follicles offspring.
2. Identified disorganization granular endoplasmic reticulum and mitochondria destruction of thyrocytes represent morphological substrate of developing thyroid dysfunction.
3. Violation of the functions of the authority manifests itself in the form of hypothyroidism with decreased levels of thyroid hormones T4 and T3, in spite of the increase in the concentration of thyroid-stimulating hormone pituitary.
4. All this necessitates careful monitoring of thyroid function in pregnant women and newborns in a high risk of environmental pollution by pesticides.
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