Milica Matavulj

Evaluation of rat thyroid gland morphophysiological status after three months exposure to 50 Hz electromagnetic field

Objective of our study was to use morphophysiological criteria in order to determine the sensitivity of male rat thyroid gland to an extremely low frequency electromagnetic field (ELF-EMF) influence and the ability of the gland to repair after period of exposure. Animals were exposed to 50Hz, 50-500 microT ELF-EMF for 3 months when a part of them (group I) were sacrificed, while the rest of animals were subjected to recovery evaluation of the gland and sacrificed after 1 (group II), 2 (group III) and 3 (group IV) weeks. Histological and stereological analyses were performed on paraffin and semifine thyroid gland sections. Serum T3 and T4 were also determined. Histological and stereological analyses showed that the volume density of follicular epithelium and thyroid activation index decreased, while the volume density of colloid and capillary network increased in group I, II and III. The values of all these parameters in group IV were similar to corresponding controls. Serum T3 and T4 concentrations were significantly lower in all exposed animals, except in group I. Results of this study demonstrate that after significant morphophysiological changes caused by ELF-EMF exposure thyroid gland recovered morphologically, but not physiologically, during the investigated repair period.

Light and electron microscopic study of the thyroid gland in rats exposed to power-frequency electromagnetic fields

SUMMARY The effect of 50 Hz electromagnetic field (EMF) on thyroid gland was studied using light and transmission electron microscopes. Two-month-old male rats were exposed to an EMF (100-300 μT, 54-160 V m-1) for 4 h a day, 5 days a week for 1 month. A predominance of microfollicles with less colloid content and dilated blood capillaries was found in the EMF group. Stereological counting showed a statistically significant increase of the volume density of follicular epithelium, interfollicular tissue and blood capillaries as well as the thyroid activation index, as compared to the controls. The volume density of colloid significantly decreased. Ultrastructural analysis of thyroid follicular cells in the EMF group revealed the frequent finding of several colloid droplets within the same thyrocyte with the occasional presence of large-diameter droplets. Alterations in lysosomes, granular endoplasmic reticulum and cell nuclei compared to the control group were also observed. Taken together, the results of this study show the stimulative effect of power-frequency EMF on thyroid gland at both the light microscope and the ultrastructural level.

Histological characteristics of cutaneous and thyroid mast cell populations in male rats exposed to power-frequency electromagnetic fields

Purpose:The objective of this study was to determine whether mast cells (MC) in skin and thyroid gland, cutaneous nerve fibers and eosinophils are sensitive to the influence of electromagnetic fields (EMF). Materials and methods:The experiment was performed on two-month-old Wistar male rats, exposed to 50 Hz EMF (100 – 300 μT, 54 – 160 V/m) for 4 h a day, seven days a week during one month. After sacrifice, samples of skin and thyroid were processed for toluidine blue staining or indirect immunohistochemistry. The M42 grid placed in the ocular of a light microscope and a special microscopic frame placed in the ocular of a fluorescence microscope were used for stereological analysis. Results:The numerical and volume density of intact type A MC in the thyroid of the exposed group was significantly higher compared to the control. A number of MC and immunoreactive nerve fibers were observed in the skin and of histamine-immunoreactive MC in the thyroid of exposed animals. The differences in stereological data were not statistically significant by the Mann-Whitney test. Conclusions:The results indicate certain alterations of cutaneous and thyroid MC in rats exposed to EMF. However, the possible outcome of changes in the MC population under EMF influence on morphophysiological properties of other structures in skin and thyroid requires further investigation.

Electromagnetic Field Effects on the Morphology of Rat Thyroid Gland

The thyroid gland, whose hormones are involved in a broad range of functions is one of the most sensitive organs to ionizing radiation, but the effects of non-ionizing radiation such as an electromagnetic field (EMF) on this gland has been suggested1,2 even if not supported with sufficient data.

Studies on the synergistic effects of extremely low-frequency magnetic fields and the endocrine-disrupting compound atrazine on the thyroid gland

Purpose: The aim of this study was to examine the effect of extremely low-frequency magnetic fields (MF) and the endocrine-disrupting compound atrazine, each separately, on the thyroid gland of juvenile-peripubertal rats, and to investigate the possible synergistic effect of these two factors combined. Materials and methods: The study was performed on male Wistar rats from postnatal day 23–53. Animals were divided into six groups: (1) 4 h/day exposure to MF (50 Hz, 100–300 μT, 54–160 V/m), (2) 20 mg/kg of body weight (bw) of atrazine, (3) 200 mg/kg bw of atrazine, (4) MF with 20 mg/kg bw of atrazine (5) MF with 200 mg/kg bw of atrazine, and (6) control. Results: Light and electron microscopic studies demonstrated no significant alterations in the thyroid structure between the treated groups and the control. Significant outcomes were found regarding the volume density of thyroid follicles and the connective tissue between the MF-exposed group when compared to both atrazine treatments and the combined treatments. The high dose of atrazine significantly affected the number of mast cells compared to the control. Conclusions: No synergistic effect of the MF and the endocrine-disrupting compound atrazine on the thyroid gland has been found. The specific histological alterations of the thyroid parenchyma observed in some treated groups require further investigation.

Acrylamide alters glycogen content and enzyme activities in the liver of juvenile rat.

Acrylamide (AA) is spontaneously formed in carbohydrate-rich food during high-temperature processing. It is neurotoxic and potentially cancer causing chemical. Its harmful effects on the liver, especially in a young organism, are still to be elucidated. The study aimed to examine main liver histology, its glycogen content and enzyme activities in juvenile rats treated with 25 or 50mg/kg bw of AA for 3 weeks. Liver samples were fixed in formalin, routinely processed for paraffin embedding, sectioning and histochemical staining. Examination of haematoxylin and eosin (H&E)-stained sections showed an increase in the volume of hepatocytes, their nuclei and cytoplasm in both AA-treated groups compared to the control. In Periodic acid-Schiff (PAS)-stained sections in low-dose group was noticed glycogen reduction, while in high-dose group was present its accumulation compared to the control, respectively. Serum analysis showed increased activity of aspartate aminotransferase (AST), and decreased activity of alanine aminotransferase (ALT) in both AA-treated groups, while the activity of alkaline phosphatase (ALP) was increased in low-dose, but decreased in high-dose group compared to the control, respectively. Present results suggest a prominent hepatotoxic potential of AA which might alter the microstructural features and functional status in hepatocytes of immature liver.

Atrazine-induced changes in the myocardial structure of peripubertal rats.

The aim of the present study was to investigate the effect of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) on the left ventricle myocardium in juvenile/peripubertal male Wistar rats. Atrazine was administered orally at 50 or 200 mg/kg of body weight dose for 28 consecutive days. In order to assess possible structural alterations, tissue sections were examined histologically and then subjected to quantification analysis using stereological methods. The tissue specimens were routinely processed and stained with Mallory trichrome method in order to clearly distinguish muscle cells from the connective tissue components. A toluidine blue staining method was additionally used for the demonstration of mast cells. Statistically significant increase in length density and numerical density of capillaries were found at both the investigated doses of atrazine compared with the control. The increase in surface density and volume density of capillaries found at lower dosage of atrazine was significant in comparison with the control. The extensive mast cell degranulation was noted on the histological examination at both doses of the applied chemical. No significant changes were demonstrated for the stereological parameters of cardiomyocytes. Based on the available published data and the present results, it can be concluded that atrazine promoted angiogenesis in the rat myocardium, which might be partially mediated by mast cells.

Alterations in jejunal morphology and serotonin-containing enteroendocrine cells in peripubertal male rats associated with subchronic atrazine exposure.

The effect of atrazine on jejunum was investigated by histopathological examination and quantification analysis related to the morphological parameters of the jejunum. The experiment was performed on male Wistar rats from postnatal day 23-51. Atrazine was administered by gavage daily to one group of rats at 50 mg/kg of body weight (bw) dose, to the second at 200 mg/kg bw while the third group was the control. At the end of the experiments after 28 days of treatment, tissue samples were routinely processed and stained with haematoxylin eosin. Additionally, the histochemical staining with periodic acid Schiff-alcian blue was used to demonstrate goblet cells and the immunohistochemistry protocol for serotonin-containing enteroendocrine cells. A significant decrease in the height of epithelial cells covering the intestinal villi, the villus height to total mucosa thickness ratio and the villus height to crypt depth ratio was found at both doses of atrazine. The crypt depth, total mucosa thickness and the thickness of tunica muscularis were significantly increased by the high dose of atrazine only. The number of serotonin-positive endocrine cells significantly decreased in rats treated with the low dose of atrazine. Overall, these results suggest the alterations in intestinal absorption and support the role of atrazine as an endocrine-disrupting compound.

Electromagnetic Field Effects on the Morphometrical Characteristics of Rat Adrenal Glands

Effect of the magnetic field on the biological mechanisms is still poorly known. It was considered for a long time that the effect of magnetic field was identical to the effects produced by high and low temperatures, ultraviolet rays and noise (Nakagawa, 1984). Long-term exposure to LF-EMF induced morphological and morphometrical changes on thyroid gland (Matavulj et al, 1996) and adrenal glands (Uscebrka et al, 1996). Magnetic fields have been shown to influence the release and levels of a number of neurotransmitters (Kavaliers and Ossenkopp, 1987; Zecca et al, 1997) and opioid molecules (Prato and Kavaliers, 1997), with these actions being proposed to involve alterations in neuronal calcium levels and fluxes (and possibly other divalent ions) and in the stability of calcium binding to neuronal membranes (Blackman et al., 1985, Kavaliers and Ossenkopp, 1986).

Atrazine-induced degranulation of thyroid mast cells in peripubertal and adult rats

Atrazine is a commonly used pesticide in the US and the non-EU countries. It is classified as an endocrine-disrupting chemical and is well-known for its reproductive toxicity in mammals and lower vertebrates. The study on atrazine effects on thyroid mast cells was performed on juvenile/peripubertal and adult male Wistar rats orally gavaged with atrazine at doses of 50 mg/kg of body weight (bw) or 200 mg/kg bw. In order to visualize the mast cell population within the thyroid gland, a histochemical staining method of toluidine blue was used. The results of the histological evaluation demonstrated a prominent increase in mast cell degranulation in both age groups and at both atrazine doses. According to the stereological analysis, a statistically significant decrease in the mast cell volume density in the young rats exposed to a higher dose of atrazine was found when compared to the corresponding control. The numerical density of mast cells significantly decreased in a higher-dose atrazine treated adults in comparison to the control. The obtained data suggest that atrazine-affected mast cells would probably have a consequent influence on thyroid follicular cells and/or thyroid microvasculature via paracrine action of released mediators, but might also be involved in already suggested thyroid cancerogenesis.