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First published online August 17, 2006
Journal of Experimental Biology 209, 3322-3328 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02375

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

Vesna Rajkovic^1,2,*, Milica Matavulj¹ and Olle Johansson²

¹ Department of Biology and Ecology, Faculty of Sciences, Trg Dositeja Obradovica 2, 21000 Novi Sad, Serbia and Montenegro
² Experimental Dermatology Unit, Department of Neuroscience, Karolinska Institute, 171 77 Stockholm, Sweden

View larger version (147K): [in a new window]   Fig. 1. Photomicrographs of frozen sections of the thyroid gland stained with Haematoxylin-Eosin in a control animal (a) and an animal exposed to 50 Hz EMF (b). Thyroid parenchyma is composed mainly of macrofollicles rich in colloid content in a. Follicles of different diameter are present in b with a preponderance of smaller (microfollicles) over larger follicles. Microfollicles have low to very low colloid content in b. The lobular structure is more prominent in b with each lobule completely divided by connective tissue (compared with a). Both photomicrographs are of the same magnification. Scale bar, 200 µm.

View larger version (60K): [in a new window]   Fig. 2. Photomicrographs of frozen sections of the thyroid gland stained with Haematoxylin-Eosin from a control animal (a) and animals exposed to 50 Hz EMF (b,c). Note the difference in follicle size in a compared to b and c. Occasional follicles with a squamous cell lining, probably due to a low activity state can be seen in a-c. There is a prominent increase in connective tissue content in b and c compared to a. All photomicrographs are of the same magnification. Scale bar, 50 µm.

View larger version (116K): [in a new window]   Fig. 3. Photomicrographs of semithin sections of the thyroid gland stained with Toluidine Blue-Cresyl Violet in a control animal (a) and an animal exposed to 50 Hz EMF (b). There is a more extensive capillary bed (carets) in b compared with a. Both photomicrographs are of the same magnification. Scale bar, 25 µm.

View larger version (172K): [in a new window]   Fig. 4. Electron micrographs of a part of the follicle wall showing the ultrastructure of follicular cells in control animals (a,b) and animals exposed to 50 Hz EMF (c,d). In a and b the follicular epithelial cells have euchromatic nuclei (n) and prominent excentrically positioned nucleoli (no). In the treated cells the nuclei are placed basally in the cell (carets in c) and the euchromatin is darker in appearance. The rough endoplasmic reticulum (er) is relatively well developed in both cisternal and vesicular form in a-c. The baso-lateral compartments (bl) of some cells in a, c and d have distended cisternae (er). There are more pleomorphic electron-dense lysosomes (ly) under the apical membrane (am) of thyrocytes in a and b compared with c. Lysosomes of different electron density are seen in c. Note two large colloid droplets (cd) in the apical cytoplasm of the same thyrocyte in c and a large group of droplets of various diameter occupying nearly the entire apical region of one follicular cell (carets in d). c, colloid; bm, basement membrane; pf, parafollicular cell. All photomicrographs are of the same magnification. Scale bar, 1 µm.

View larger version (158K): [in a new window]   Fig. 5. (a-c) Electron micrographs of follicular cells in animals exposed to 50 Hz EMF. The significant features are: a giant colloid droplet (carets) in a; a large colloid droplet (carets) surrounded by lysosomes in the central part of a thyrocyte in b and near the basal membrane (carets) in c; pleomorphic lysosomes (ly) in the apical cytoplasm in b; rough endoplasmic reticulum (er) with amorphous contents of different density and dilated cisternae in a, b and c. c, colloid; am, apical membrane; bm, basement membrane; pf, parafollicular cell. All photomicrographs are of the same magnification. Scale bar, 1 µm.