Sex dimorphism in the thyroid gland. IV. Cytologic aspects of sex dimorphism in the rat thyroid gland

This study was designed to explain whether the sex-dependent differences in the structure of the thyroid gland of adult male and female rats depend on quantitative or qualitative changes in the thyroid follicular cells. Absolute thyroid gland weight was similar in male and female rats, but its relative weight was markedly higher in females however. Volume fractions of epithelium and stroma were higher and that of colloid lower in male than in female rats and the epithelium/colloid ratio was higher in the males. Also absolute the volumes (in mm3) of epithelium and stroma were higher in the males; the thyroid gland of females contained more colloid. The average volume of a thyroid follicular cell, estimated by stereology, was higher in males than in females, although the thyroid gland contained similar numbers of follicular cells in both sexes. Also, thyroid glands from both male and female rats contained a similar DNA quantity. Results of the present study show that the sex dimorphism in the rat thyroid depends upon a difference in the mean volume of thyroid follicular cells, with males having larger cells than females. However, in both sexes the thyroid gland contains a similar quantity of these cells.     

State of the rat thyroid gland in coarctation of the abdominal aorta]

In order to study connections between blood vessels and follicular thyrocytes, the method of modulation (a purposeful change of state in one element with registration of states in other elements of the system) was used. In rats chronic increase of blood stream was produced in the thyroid gland; in 15 days it was 54% as high as in the control. The volume of the vascular bed increased by 28% and that of follicles by 26%. Volumetric ratio between the thyroid epithelium and colloid did not changed. Follicular thyrocytes grew high and the nuclear volumes of these cells increased. Thyrocytes greately varied in their height. The number of mast cells in the thyroid gland remained the same. Iodine absorption by the thyroid gland increased as it is dependent on the volume of the vascular bed of the organism (+0.82). The data obtained demonstrate a significant connection existing between the follicular thyrocytes and blood vessels.     

Morphometric studies on the development of human thyroid gland in early fetal life.

Histological and morphometric studies were performed on 30 thyroid glands obtained from normal human fetuses. Their crown-rump length (CRL) ranged from 57 to 190 mm, corresponding to the gestational age of 10-20 weeks. The weight of the thyroid gland increased proportionally in relation to CRL, foot length and fetus weight. The first follicles containing PAS-positive colloid were observed in the peripheral part of the thyroid gland of 57 mm CRL fetus. The number of follicles per 1 mm2 of thyroid surface section increased up to 85 mm CRL and thereafter gradually declined for the end of studied period of fetal life. The volumes (in mm3) of thyroid epithelium, colloid and stroma, beginning from 85 mm increased proportionally to the CRL while the height of epithelial cells did not change. The epithelium/colloid ratio decreased notably to 165 mm CRL and thereafter remained constant. Results of the present study suggest that the thyroid gland of human fetus approaches structural maturity in 17.5 week of gestation.     

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.     

Sex dimorphism in the thyroid gland. I. Morphometric studies on the thyroid gland of intact adult male and female rats

Morphometric studies were performed on thyroid glands of intact adult male and female rats. Thyroid follicular cells are markedly higher in the male rats than in the females during estrus. The volume fraction of the epithelium is larger but the fraction of colloid is less in males than in females. Also epithelium/colloid ratio is higher in male than in female rats.     

Evidence for a functional role of cholecystokinin receptors in the rat thyroid gland.

The aim of the present study was to examine the role of cholecystokinin (CCK) and/or cholecystokinin receptors subtypes (CCK1R and CCK2R) in the regulation of the thyroid gland structure and function. Animals were autopsied after 6 days of treatment with CCK or CCK receptor-specific antagonists (CCK1a--PD 140,548 or CCK2a--PD 135,158) solely or in combination with CCK. Results suggest that CCK exerts a stimulatory effect on follicular thyroid cells manifested by increased epithelium/colloid volume fraction ratio (E/C). Application of selective antagonists of CCK receptor subtypes has demonstrated that CCK acts through the CCK1 receptor subtype at the level of pituitary TSH. The model of endogenous hormone action reveals that thyroid CCK1 is responsible for the thyroid growth. It can be concluded that the physiological activity of CCK1 receptor plays a significant role in a complex interrelationship between TSH, vagal system and CCK1-dependent function of the thyroid gland.     

Decrease of TSH levels and epithelium/colloid ratio in rat thyroid glands following administration of proadrenomedullin N-terminal peptide (12-20).

Adrenomedullin (AM) exerts a potent and long-lasting hypotensive effect and is considered to be an important hormone in blood pressure control. AM is a 52-amino-acid peptide synthesized as part of a 185-amino-acid preprohormone that also contains 20-amino-acid residues in the N-terminus, which has similar biological activity. This sequence is named a proadrenomedullin N-terminal 20 peptide (PAMP). Also, proadrenomedullin N-terminal peptide (PAMP)(12-20) exerts vasodepressor response, however this response is 3-fold less potent than the effect evoked by full-sequence peptide. Both AM and PAMP controls secretory activity of the pituitary gland and adrenal cortex, however, their action on the other endocrine glands is not recognized. Therefore, the aim of the study was to examine whether PAMP(12-20) is able to affect the structure and function of the rat thyroid gland. In adult female rats, subcutaneous PAMP(12-20) administration (1 or 4 nmol/rat/day for 6 days, autopsy 60 min after the last injection) had no effect on the weight of the thyroid gland. Peptide administration however, resulted in a dose-dependent increase in the volume of thyroid colloid, and lowered epithelium/colloid ratio in the gland (3.76 +/- 0.49, 2.66 +/- 0.27, 2.38 +/- 0.26, means +/- SE, n = 6, control, 1 and 4nmol PAMP/rat, respectively). PAMP administration changed neither the length of thyroid capillaries per unit area of surface nor their diameter. Lower dose of PAMP(12-20) significantly lowered blood TSH concentration (p < 0.01) while total and free T3 and T4 concentrations remained unchanged. Collectively, these findings suggest that PAMP(12-20) exerts a mild inhibitory effect on secretory activity of the rat thyroid gland.     

Immunohistochemical localization of thyroid hormone in rat thyroid gland.

Direct and indirect immunofluorescence techniques were used to localize the thyroid hormones triidothyronine (T3) and thyroxine (T4) in adult rat thyroid gland. Optimum dilutions of the antisera were established and four tissue fixatives were investigated for usefulness in this technique. Use of antibodies specific for either T3 or T4 resulted in brilliant fluorescence in the colloid pools and apical cytoplasm of follicular cells. In all cases, the adjacent parathyroid gland was devoid of fluorescence. This report demonstrates that these dipeptide hormones can be localized by using immunofluorescence techniques.     

Structure of the thyroid gland in the rat during hypokinesia and after its elimination

The aim of the investigation is to objectively ascertain and study stages of the processes taking into account the zonal structure of the thyroid gland, that is along the whole distance from the center up to the surface of the lobe. Hypokinesia lasts from 1 to 56 days; rehabilitation begins after 28 days of hypokinesia and lasts 28 days. Morphometric analysis of 8 parameters demonstrating the state of the gland are used. In control animals the structural changes from the center towards the surface of the gland lobe occur gradually, the degree of the changes is different and diversily directed [increasing volumetric part (Vv) of the follicular epithelium, decreasing Vv of the colloid, stable Vv of the vascular component]. When both hypokinesia and rehabilitation develop, all signs change wavily. Natural borders of the waves are defined--5, 16, 28 and 51 days for hypokinesia and 13 and 23 days for readaptation. Different structural components of the gland respond variously to the factors mentioned. Changes of every sign in different zones are also not equal and they can be diversily directed. In the course of rehabilitation for 1 month, there is no return to the normal state.     

Altered mammary gland development in the p53+/m mouse, a model of accelerated aging

The tumor suppressor p53 is important for inhibiting the development of breast carcinomas. However, little is known about the effects of increased p53 activity on mammary gland development. Therefore, the effect of p53 dosage on mammary gland development was examined by utilizing the p53+/m mouse, a p53 mutant which exhibits increased wild-type p53 activity, increased tumor resistance, a shortened longevity, and a variety of accelerated aging phenotypes. Here we report that p53+/m virgin mice exhibit a defect in mammary gland ductal morphogenesis. Transplants of mammary epithelium into p53+/m recipient mice demonstrate decreased outgrowth of wild-type and p53+/m donor epithelium, suggesting systemic or stromal alterations in the p53+/m mouse. Supporting these data, p53+/m mice display decreased levels of serum IGF-1 and reduced IGF-1 signaling in virgin glands. The induction of pregnancy or treatment of p53+/m mice with estrogen, progesterone, estrogen and progesterone in combination, or IGF-1 stimulates ductal outgrowth, rescuing the p53+/m mammary phenotype. Serial mammary epithelium transplants demonstrate that p53+/m epithelium exhibits decreased transplant capabilities, suggesting early stem cell exhaustion. These data indicate that appropriate levels of p53 activity are important in regulating mammary gland ductal morphogenesis, in part through regulation of the IGF-1 pathway.     

Prenatal development of the palatine gland of rats

The present study aimed to elucidate the prenatal development of the rat palatine gland. Parasagittal 5 microm thick serial sections made from Wistar rats at embryonic days (E) 17 to 22 were stained with haematoxylin-eosin (HE), Alcian blue-Kernechtrot or immunohistochemistry for 5-bromo-2'-deoxyuridine (BrdU) as a marker of proliferating cells. Additionally, three-dimensional images of developing glandular parenchyma were reconstructed from serial HE sections with a personal computer. At E 17, several thickenings of the palatal epithelium had appeared which thereafter became the epithelial cords. Branching and lumenization commenced at E 20, and immature acini were observed at E 21. Three-dimensional reconstruction showed that the proximal part of the epithelial cord differentiated into the duct, and the distal part of the epithelial cord differentiated into the acinus. In immunohistochemical staining, there were many BrdU-positive cells in the epithelial cords including thickenings of the palatal epithelium, ducts, and acini. The BrdU labeling index of the cells of the epithelial cord was the highest (statistically significant) of the three in the primitive palatine gland. In conclusion, during the development of the rat palatine gland, epithelial cords with very high proliferative activity arise from the palatal epithelium, and then the proximal part of the epithelial cord differentiates into the duct, and the distal part of the epithelial cord differentiates into the acinus. Proliferation of these glandular parenchyma contributes to the growth of the developing palatine gland.     

Effect of prostaglandin F2alpha on cells of the mammary gland alveoli in mice

In studies on lactating laboratory mice an influence of prostaglandin F2 alpha on the value of transepithelial potential difference and resistance of the alveolar secretory epithelium in the mammary gland, was studied. Prostaglandin F2 alpha did not affect initial level of transepithelial potential difference and resistance in alveoles. In all experiments with the preliminary application of prostaglandin F2 alpha in different concentrations (1 x 10(-5)-1 x 10(-11) M) was registered a reliable increase in an amplitude (before 31 +/- 2%) and duration (before 43 +/- 3%) to return reactions on oxytocin. Prostaglandin F2 alpha caused a reduction of transepithelial resistance in the alveolar secretory epithelium of first phase to return reaction on oxytocin on 28 +/- 22%. The data obtained indicate a possibility of participation of prostaglandin F2 alpha in development of certain stages of shaping a composition of milk.     

Immunoelectron microscopic demonstration of thyroglobulin and thyroid hormones in rat thyroid gland

We have developed a post-embedding immunogold technique for electron microscopic localization and quantitation of thyroglobulin (TG), thyroxine (T4), and triiodothyronine (T3) in rat thyroid. Labeling for TG was located on rough endoplasmic reticulum, Golgi apparatus, exocytotic vesicles, luminal colloid, colloid droplets, and lysosomes, whereas labeling for thyroid hormones was located on luminal colloid, colloid droplets, and lysosomes. We tested different procedures of fixation, dehydration, embedding, polymerization, and immunoincubation to optimize ultrastructural preservation and immunolabeling. Fixation with glutaraldehyde and osmium was possible with retained antigenicity. Dehydration temperature and the choice of embedding resin were the two crucial factors for good immunolabeling. Low-temperature dehydration greatly improved immunolabeling and could be combined with embedding in the methacrylate LR White or the epoxide Agar 100 (equivalent of Epon 812) polymerized at 40-60 degrees C, as the temperature during subsequent embedding and polymerization was of little importance for the immunoreactivity. Labeling on LR White sections was always higher than on Agar 100 sections. Various etching procedures were tested without improved specific labeling. Etching with hydrochloric acid gave nonspecific labeling of certain cell compartments.     

Morphophysiologic status of the rodent thyroid gland in the case of alimentary obesity

The studies were carried out on rodents with different ecology, suffering from alimentary obesity. Their weight was 1.3-1.5 that of control animals. Prolonged (3 months) maintaining of the animals in conditions of obesity led to sharp decrease in inclusion of 131I into thyroid parenchyma, synthesis and excretion of SB 131I into blood. Microscopy study of thyroid gland revealed an inhibition of hormone synthesis, as indicated by flattened epithelium, dense colloid in follicles, and other hypofunctional features. Obesity decreases the quantity of food consumed by the animals and their reproductive abilities. Comparison of data obtained on rodents with different ecology revealed that maximal inhibition of thyroid function at obesity was observed in yellow gopher as compared to rat and gerbil.     

Immunocytochemical localization of prohormone convertases PC1 and PC2 in the mouse thyroid gland and respiratory tract.

We examined immunocytochemical localization of the prohormone convertases, PC1 and PC2, in the thyroid gland and respiratory tract of the adult mouse using the indirect enzyme- and immunogold-labeled antibody methods for light and electron microscopy, respectively. In the thyroid gland, PC1- and/or PC2-immunoreactive cells were cuboidal, scattered in the follicular epithelium and in the interfollicular spaces. When serial sections were immunostained with anti-calcitonin, anti-PC1, anti-calcitonin-gene-related-peptide (CGRP), and anti-PC2 sera, respectively, localization of both PC1 and PC2 was restricted to the calcitonin/CGRP-producing parafollicular cells. In the respiratory tract, only PC1 immunoreactivity was observed in the basal granulated neuroendocrine cells, which were scattered in the tracheal epithelium. Consecutive sections immunostained with anti-PC1 and anti-CGRP sera showed that a subpopulation of these PC1-immunoreactive cells contained CGRP. Double immunogold electron microscopy of the thyroid parafollicular cells revealed that calcitonin- and/or CGRP-immunopositive secretory granules were also labeled with both PC1 and PC2. These findings suggest that procalcitonin is proteolytically cleaved by PC2 alone or by PC2 together with PC1, and that the proCGRP is cleaved by PC1.     

Expression of galectin-1 and galectin-3 in human fetal thyroid gland.

High levels of expression of galectin-1 and galectin-3, the beta-galactoside-binding proteins, have been recently described in malignant thyroid tumors but not in adenomas nor in normal thyroid tissue. However, there are no data about the expression of these galectins during fetal thyroid development. In this study we analyzed immunohistochemically the presence of galectin-1 and galectin-3 in human fetal thyroid glands (16-37 weeks of gestation). Weak to moderate cytoplasmic staining for galectin-1 was observed in follicular cells of all fetal thyroids. Galectin-3 could not be detected in thyroid follicular cells of any fetal thyroid investigated. Both galectins were detected in stromal tissue, but staining for galectin-1 was more intense. The absence of galectin-3 in thyroid cells during fetal development suggests that galectin-3 is expressed de novo during malignant transformation of thyroid epithelium, and that galectin-1 could be considered an oncofetal antigen. The results obtained indicated potential roles for galectin-1 and galectin-3 during the investigated period of human fetal thyroid gland development. Both galectins might participate in developmental processes regarding stromal fetal thyroid tissue organization, whereas galectin-1 might have a function in thyroid epithelium maturation.     

Selenoproteins of the thyroid gland: expression, localization and possible function of glutathione peroxidase 3

The thyroid gland has an exceptionally high selenium content, even during selenium deficiency. At least 11 selenoproteins are expressed, which may be involved in the protection of the gland against the high amounts of H2O2 produced during thyroid hormone biosynthesis. As determined here by in situ hybridization and Northern blotting experiments, glutathione peroxidases (GPx) 1 and 4 and selenoprotein P were moderately expressed, occurring selectively in the follicular cells and in leukocytes of germinal follicles of thyroids affected by Hashimoto's thyroiditis. Selenoprotein 15 was only marginally expressed and distributed over all cell types. GPx3 mRNA was exclusively localized to the thyrocytes, showed the highest expression levels and was down-regulated in 5 of 6 thyroid cancer samples as compared to matched normal controls. GPx3 could be extracted from thyroidal colloid by incubation with 0.5% sodium dodecyl sulfate indicating that this enzyme is (i) secreted into the follicular lumen and (ii) loosely attached to the colloidal thyroglobulin. These findings are consistent with a role of selenoproteins in the protection of the thyroid from possible damage by H2O2. Particularly, GPx3 might use excess H2O2 and catalyze the polymerization of thyroglobulin to the highly cross-linked storage form present in the colloid.     

Hormonal regulation of thermogenesis in goslings. Possible role of the thyroid gland.

The experiments performed on 90 male goslings showed that 6 h cold exposure (5 +/- 1 degree C) of the specimens 3, 10 and 21-day-old increases considerably 131I uptake by their thyroid gland. After single subcutaneous injection of thyroxine (100 mug/kg) no significant alterations of the metabolic rate, during 4 h measurements, in comparison with the pre-injection value were observed. Since, in control birds about 17% decrease of the metabolic rate within the same time occurred, as the effect of fasting, it was concluded that thyroxine does have the calorigenic effect. The metabolic rate of the goslings 5 to 7-day-old treated with thyroxine for four consecutive days (100 mug/kg daily) and the control ones was very similar. In the older goslings (22--24 days) thyroxine treatment significantly elevated the metabolic rate. Direct (extrathyroid) effect of TSH on heat production, did not occur in goslings.     

FNAB thyroid gland: comparison study between pre- and post-operative histological diagnosis

Fine-needle aspiration biopsy is recommended as the first and most important step in the management of nodular thyroid disease. A retrospective study of 520 patients with nodular thyroid disease was done in the north of Jordan, between January 1998 and August 2001. We compared the results of fine-needle aspiration biopsy (FNAB) of thyroid gland with postoperative histological findings. The results are classified into three groups A)-benign, B)-malignant, and C)-suspicious as shown in table II. The results of the FNAB were benign in 96.4% of the cases which include benign colloid nodules (325 cases), multi-nodular goitre (70 cases), diffuse goitre (40 cases), thyroiditis (23 cases) and thyroid cysts (43 cases). A total of 52 patients underwent surgical management, 49 patients found to be accurate with the FNAB. The accuracy of FNAB was 94% (49 patients out of 52), with a specificity of 99% and a sensitivity of 93%. Ultrasound findings showed that 65% (338 patients) had solid nodules, 15% (78 patients) had cystic lesions and 20% (104 patients) had mixed echogenicity lesions. Histological confirmation of malignancy was 10 out of 11 patients with a 91% accuracy rate. FNAB was found to be a highly effective procedure, which can obviate a lot of unnecessary surgery in case of thyroid lesions, and avoid over treatment of benign disease. Surgery was recommended in all suspicious cases. FNAB under ultrasound guidance increases the sensitivity rate which can reach 100%. FNAB accuracy seems to be similar in cold and in hot nodules. Clinically, most of the patients with benign colloid nodules were having goitres suggesting the role played by iodine deficiency is which a prominent feature in that area in Jordan.     

Body, heart, thyroid gland and skeletal muscle weight changes in rats with altered thyroid status

In the present paper we describe changes of anatomical parameters in inbred Lewis strain rats, namely their body weight, body weight gain per week, absolute and relative heart, thyroid gland and skeletal muscle weights, that are assumed to reflect experimentally altered thyroid status. The hyperthyroid state was induced by DL-thyroxine or Na 3,3',5-triiodo-L-thyronine, while methimazole was employed for inducing hypothyroidism. We have found that when compared to euthyroid rats, hypothyroidism resulted in a significantly lower body weight gain, absolute and relative heart weight and, in contrast, in a significant increase of absolute and relative thyroid gland weight. On the other hand, hyperthyroidism led to a significant increase of absolute and relative heart weight and to a significant reduction of absolute and relative thyroid gland weight. However, the body mass was not significantly altered in hyperthyroidism as compared with euthyroid rats. We conclude that our protocol leads to chronic hyper- or hypothyroidism as demonstrated by body, heart and thyroid gland weight changes. These anatomical data can thus be utilized as supplemental criteria for the assessment of the thyroid state of experimental rats.