Immunohistochemical localization of NPY, VIP and 5-HT in the thyroid gland of the lizard, Podarcis sicula

The thyroid gland of the lizard Podarcis sicula was immunohistochemically studied in adult male specimens using specific antibodies against NPY, VIP and 5-HT and the avidin-biotin peroxidase complex (ABC) procedure to localize the three peptides. Fine beaded VIP-immunoreactive nerve fibers ran between the follicles, and VIP-immunoreactivity was evenly distributed in the apical cytoplasm of follicular cells. NPY-immunoreactive fibers were found around the follicles, and, in the cells, immunoreactivity was localizated only in the cellular apices. Immunoreactivity to 5-HT was observed in the colloid, with a concentration in the follicular lumen exceeding that in the follicular cells. In fact, most follicles showed immunoreactivity in the cytoplasmic bridges formed between the apical portion of the follicular cells and the colloid.     

Immunocytochemical studies on differentiation of the thyroid gland in rabbit fetuses and chick embryos

Summary The morphogenesis of the thyroid gland in rabbit fetuses and chick embryos was investigated using the PAS stain and an immunoperoxidase method with anti-19S-thyroglobulin antiserum. In rabbit fetuses, the reaction for precursor components was firstly detected in the apical portions of follicular cells, arranged in clusters but not yet forming follicles, at 16 days of gestation. Although the first primordial follicles storing colloid droplets were observed on day 18, a drastic increase of follicle formation, the true onset of thyroid function, did not occur until day 22. The colloid in primordial follicles revealed very strong immunoreactivity for 19S-thyroglobulin. The follicles gradually increased in size with age. At 25 days of gestation the cytoplasm of follicular cells was stained densely by slightly diluted 19S-thyroglobulin antiserum, whereas the colloid was stained with highly diluted antiserum; these immunoreactions of follicular cells and colloid were comparable to those of postnatal animals. In chick embryos, significant numbers of primordial follicles were observed throughout the whole thyroid parenchyma at 9 days of incubation. On day 12, the follicles stored more PAS-positive and immunoreactive colloid. At 14 days of incubation follicles with enlarged follicular lumina, having an immunoreactivity similar to mature rollicles, became increasingly common.     

Investigations on the thyroid gland of embryonic larval and adult Ichthyophis glutinosus and Ichthyophis kohtaoensis (Gymnophiona,amphibia)

Summary Different developmental stages of two species of the genus Ichthyophis have been investigated. In the late embryo the follicular cells of the thyroid gland exhibit various degrees of cytodifferentiation. Well differentiated cells show a polar organization and contain numerous granular inclusions, but a colloid-containing lumen is rare. Most cells at this stage contain large lipid inclusions. In young and older larvae the cells contain well-developed rough ER and Golgi systems, numerous mitochondria, and abundant granular and vesicular inclusions. Tentative identifications were made of primary lysosomes, secondary lysosomes, residual bodies, and two types of small apical vesicles—containing resorbed colloid or transporting material into the follicular lumen. In the larvae the number of apical microvilli is relatively high. The thyroid cells of the older larvae seem to contain more granular and vesicular inclusions than those of the younger larvae. In the adult the size of the follicles greatly increases, the height of the epithelium decreases, microvilli become rare, residual bodies are more frequent, and the small primary lysosomes are replaced by larger ones. Colloid droplets have been found only rarely in the cytoplasm of the thyroid cells of adult animals. In the immediate neighbourhood of the follicular epithelium, profiles of nerve fibres were found in all animals. Radioiodide investigations—measurements of conversion ratio and thyroid uptake factor—show, if compared with the results of corresponding studies in other amphibians, only relatively small differences between the larvae on the one hand and larvae and adults on the other. The absolute counts of the thyroid region are lowest in the adult and highest in the older larvae, shortly before metamorphosis. Furthermore our results indicate, on the basis of four animals tested, that in Ichthyophis the activity of the thyroid gland is temperature dependent. The results in Ichthyophis show that the classical stages of metamorphosis, in other amphibians characterized among other things by different levels of thyroid activity, are very indistinct in this animal.We gratefully acknowledge the financial support of the Deutsche Forschungsgemeinschaft (We 380/5; Sto 76/4).     

Structural and ultrastructural differentiation of the thyroid gland during embryogenesis in the grass snake Natrix natrix L. (Lepidosauria, Serpentes)

The differentiation of the thyroid primordium of reptilian species is poorly understood. The present study reports on structural and ultrastructural studies of the developing thyroid gland in embryos of the grass snake Natrix natrix L. At the time of oviposition, the thyroid primordium occupied its final position in the embryos. Throughout developmental stages I-IV, the undifferentiated thyroid primordium contained cellular cords, and the plasma membranes of adjacent cells formed junctional complexes. Subsequently, the first follicular lumens started to form. The follicular lumens were of intracellular origin, as in other vertebrate species, but the mechanism of their formation is as yet unclear. At developmental stages V-VI, the thyroid anlage was composed of small follicles with lumens and cellular cords. Cells of the thyroid primordium divided, and follicles were filled with a granular substance. At developmental stage VI, the cells surrounding the follicular lumen were polarized, the apical cytoplasm contained dark granules and the Golgi complex and the rough endoplasmic reticulum (RER) developed gradually. Resorption of the colloid began at developmental stage VIII. At the end of this stage, the embryonic thyroid gland was surrounded by a definitive capsule. During developmental stages IX-X, the follicular cells contained granules and vesicles of different sizes and electron densities and a well-developed Golgi apparatus and RER. At developmental stage XI, most follicles were outlined by squamous epithelial cells and presented wide lumens filled with a light colloid. The Golgi complex and RER showed changes in their morphology indicating a decrease in the activity of the thyroid gland. At developmental stage XII, the activity of the embryonic thyroid gradually increased, and at the time of hatching, it exhibited the features of a fully active gland.     

The effects of synthetic salmon calcitonin on thyroid C and follicular cells in adult female rats

Structural and morphometric features of thyroid C and follicular cells were studied in adult rat females after treatment with synthetic salmon calcitonin (CT). The animals were chronically treated with either a low (10 IU/kg b.w) or a high (100 IU/kg b.w) dose of CT. A stereological method was applied to determine the volume density and the number of immunoreactive C cells. The height and volume density of follicular epithelium, colloid, interstitium and the follicles (epithelium plus colloid), as well as the index of activation rate were calculated. A significant decrease in body weight, as well as the volume density of immunoreactive C cells and the number of C cells per mm2, was observed in rats treated with both doses of CT. The height and volume density of follicular epithelium and follicles, as well as the index of activation rate were significantly increased in the animals given the high CT dose, while the volume densities of colloid and interstitium were reduced. No significant changes in the examined morphometric parameters were detected after treatment with the low CT dose. According to these results it can be concluded that the structural features of thyroid C and follicular cells were affected by the high dose CT treatment in the opposite manner, while the low dose CT treatment influenced only C cells.     

Morphological changes in the human thyroid gland cultivated in continual flow system

In the present pilot study, the human thyroid gland tissue was cultivated under continuous culture conditions in the culture chambers of the ACUSYST-S system to determine morphological changes as well as the secretion of thyreoglobulin (Tgl) and thyroid hormones. After 24 hours of cultivation the follicular structure of the tissue was preserved in peripheral parts only, and there were regressive changes in the epithelium center. After 72 hours the regressive changes appeared in isolated follicles only; the size of the follicles increased, the height of the follicular epithelium decreased and there were macrophages present with phagocytized cell debris. After 144 hours disintegration of epithelia took place in the centre, while at the periphery the original follicles survived and very tiny new follicles formed, consisting of only 6 to 8 cells each and surrounding in section the homogeneous colloid. The parenchyma picture suggests a possibility of functional regeneration as an expression of adaptation to the conditions newly arisen during cultivation in a culture chamber. There was no significant influencing of the thyroid hormone secretion during cultivation. On the other hand, the Tgl secretion decreased throughout cultivation.     

Alterations within the rat thyroid gland during vitamin A deficiency

Thyroid glands from female rats kept vitamin A deficient for one, two, and three months were examined by electron microscopy. After one month on the diet, no consistent alterations were noted. After two months, the colloid in some follicles displayed a peripheral zone of decreased density. In addition, ultimobranchial follicles within the gland had become keratinized. After two to three months on the diet, cells were seen entering the colloid. Many of these cells were identified as follicular cells since they often occurred in groups and occasionally exhibited remnants of desmosomes. Often the cells within the colloid appeared vacuolated, and by light microscopy were thought to contain lipid. However, electron microscopy revealed that these cells contained many digestive vacuoles rather than lipid droplets. Quantitative and autoradiographic studies indicated that thyroids of vitamin A deficient rats took up less radioiodide than thyroids of control rats. The keratinization of ultimorbranchial follicles in vitamin-A deficiency has been suggested as preliminary in the histogenesis of squamous cell carcinoma. However, an effect of vitamin A deficiency on thyroid follicular cells has not heretofore been reported. It's possible that the presence of follicular cells in the colloid reflects an accelerated turnover of these cells and could indicate an early pathological sign.     

Mixed follicles of the human thyroid gland

Mixed follicles are structures composed of squamous-like and follicular epithelia. Little attention has been generally paid to these peculiar follicles of the human thyroid; thus the aim of the present study was to investigate their prevalence and biological properties by means of systematic autopsy, histochemical and immunohistochemical surveys. Mixed follicles were found to be present in 54% and 81% of the patients with solid cell nests, as well as in 50% and 77% of the total number of the ultimobranchial nests, when one or two histological samples from each solid cell nest were examined, respectively. The follicular lumen of mixed follicles usually contained an eosinophilic and PAS-positive colloid-like material, although in 22% of the cases acid mucins sometimes intermixed with PAS-positive granular material and cell debris were also present within lumina. Follicular cells lining mixed follicles basically did not stain positively for calcitonin. The results indicate that mixed follicles are not rarely found in the human thyroid. The presence of intraluminal mucins and cell debris and the absence of calcitonin-containing cells in the follicular epithelium lining these peculiar follicles suggest that at least some thyroid follicular cells could originate from ultimobranchial tissue.     

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.     

THE ANATOMY OF SECRETION IN THE FOLLICULAR CELLS OF THE THYROID GLAND : II. The Effect of Acute Thyrotrophic Hormone Stimulation on the Secretory Apparatus

This paper reports a study by phase contrast and electron microscopy of changes observed in the thyroid gland of the rat at 1, 2, 12, and 24 hours following an injection of thyrotrophic hormone. Examination by phase contrast microscopy reveals that follicular cells contain numerous colloid droplets 1 and 2 hours after injection. By 12 and 24 hours, the colloid droplets are no longer present, and individual follicles appear to be subdividing into smaller units. The droplets are assumed to contain newly synthesized colloid, and their development was studied by electron microscopy. During the period of active secretion, increase in number of the Golgi vesicles leads to enlargement of this organelle. At its periphery small colloid droplets appear to form from large Golgi vesicles. As they form, their content becomes more adielectronic, and fine dense particles less than 75 A in diameter appear in their matrix. Small- and medium-sized droplets lying in the apical region of the cell contain numerous dense particles scattered in their moderately adielectronic content. Large, mature droplets in the same region have a relatively dielectronic content resembling follicular colloid and no longer contain dense particles. The follicular cells appear to utilize apical pseudopodia to release the content of mature droplets into the follicular lumen. Other droplet-like inclusions occur in follicular cells, but they do not seem to be directly concerned with secretion.     

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.     

Seasonal changes of parafollicular and follicular cells of the dormouse thyroid (Myoxus glis): an ultrastructural and immunocytochemical study

The follicular epithelium of dormouse thyroid consists of two distinct cellular types, follicular and parafollicular cells. Parafollicular cells can be easily identified by their high cytoplasmic dye-affinity for phloxine, round to ovoid shape, basal arrangement and lack of contact with follicular colloid. The wide cytoplasmic matrix is clear and contains many secretory granules of variable electron density whose contents histochemically appears to be proteic with a lean glucidic component. Furthermore immunocytochemical reactions with antibodies against calcitonin and somatostatin showed that both hormones are co-stored in the secretory granules of all parafollicular cells. Both follicular and parafollicular cells show seasonal morphological variations in their secretory activity. Follicular cell activity is high in summer, reaches a peak in late fall or prehibernation and progressively slows down throughout hibernation. Parafollicular cells exhibit a fair synthetic activity in summer, in fall, and in the animals captured during winter hibernating sleep and killed after 12 days stay in laboratory. In winter sleep, granules with interrupted membrane and cottony contents are prevalent and the ultrastructural aspects suggest an intense discharge of secretion. The results are compared with those from other hibernating mammalians and discussed in the light of blood calcium values and seasonal balances of other metabolisms.     

Autoradiographic studies with 3H 1,25 dihydroxyvitamin D3 in thyroid and associated tissues of the neck region

Rats and mice fed a vitamin D-deficient or vitamin D-complete diet were injected with 3H 1,25 (OH)2 vitamin D3. Autoradiograms prepared from cross sections through the neck region revealed nuclear concentration of radioactivity strongest in parathyroid chief cells, occasionally in thyroid follicular epithelial and interfollicular cells, in the epithelium of tubular remnants of the ultimobranchial body, in epithelium of the esophagus, in chondrocytes of tracheal cartilage, and in myoepithelial cells of tracheal glands. In the thyroid, most of the follicle epithelial cells did not show nuclear concentration of radioactivity which occurred only occasionally and predominantly in follicles located in marginal positions. Thyroglobulin in lumina of thyroid follicles contained varying amounts of radioactivity that correspond to the diameter of the follicles, with relatively high amounts in large follicles and little or no radioactivity in small follicles. Competition with excess of unlabeled 1,25 (OH)2 vitamin D3 abolished nuclear radioactivity, but not the radioactivity in the colloid, while 25 (OH) vitamin D3 did not affect either. When a combination of autoradiography and immunohistochemistry was applied, follicular and parafollicular C-cells positive for calcitonin antibodies, did not show nuclear concentration of radioactivity. Tubular remnants of ultimobranchial bodies, however, showed distinct nuclear labeling, but did not stain, or only weakly stain, with antibodies to calcitonin. When 3H 25 (OH) vitamin D3 was injected, no nuclear concentration of radioactivity was noted in any of the tissues.(ABSTRACT TRUNCATED AT 250 WORDS)     

Seasonal variations in the pharyngeal and pronephric thyroid tissues of the fresh water teleost Puntius sophore (Ham).

An attempt has been made to study pharyngeal and pronephric thyroid follicles and contribute seasonal changes in them in a fresh water teleost, Puntius sophore. Their activity has been assessed histologically by the study of size of thyroid follicles, the shape and cell height of epithelial cells and the nature of their colloid. These follicles exhibit notable seasonal changes and record two periods of activity, one in summer months from May to August and the other in November.     

Chronic estradiol exposure modulates thyroid structure and decreases T4 and T3 serum levels in middle-aged female rats

OBJECTIVES: In human medicine, estrogen is applied in prevention and treatment of health problems associated with the menopause. The aim of this study was to examine the effects of chronic estradiol dipropionate (EDP) treatment on thyroid gland structure and function in middle-aged female rats. METHODS: At 14 months of age, Wistar rats received 0.625 mg EDP/kg b.w./day intraperitoneally for 2 weeks. The peripheral and central zones of the thyroid were stereologically analyzed and the following morphometric parameters determined: volume density of follicles, follicular epithelium, interstitium and colloid, epithelial height and the index of activation rate. Serum levels of TSH, T4 and T3 were determined by ELISA. RESULTS: EDP treatment led to significant decreases in volume densities of follicles and follicular epithelium, epithelial height and index of activation rate (by 11%, p < 0.05; 23%, p < 0.005; 11%, p < 0.05 and 21%, p < 0.05, respectively) in comparison to control values. Hyperplasia of thyroid follicular cells was noticed in 25% of EDP-treated animals. Serum levels of T4 and T3 were decreased (by 33%, p < 0.005 and 28%, p < 0.001, respectively), but TSH concentration was not significantly different from that of the controls. CONCLUSION: Chronic estradiol treatment significantly decreased volume density and height of centrally located follicular epithelium, follicular activation index and serum level of total thyroid hormones in middle-aged rats.     

Calcitonin cells and unusual follicles of the thyroid of the indian grey mongoose, Herpestes edwardsi (Geoffroy).

Histological preparations of thyroid, parathyroid and thymus glands of Herpestes edwardsi were examined for calcitonin cells. They reveal that (1) the thyroid calcitonin cells are oval, rounded and rarely elongated in shape; these cells and their nuclei are distinctly larger than those of the follicular cells and their nuclei; (2) calcitonin cells are unevenly distributed in the thyroid, with the result that certain portions of the thyroid are completely devoid of these cells; (3) on an average, calcitonin cells are in a ratio of 10-15 cells/100 follicular cells; (4) the parathyroid and thymus glands do not display calcitonin cells, and (5) the thyroid gland displays unusual follicles of two categories, (a) follicles with ciliated epithelial cells and (b) follicles with squamous epithelium.     

Oocyte growth and follicular hierarchy may be locally controlled by an inhibin-like protein in the lizard Podarcis sicula.

The lizard Podarcis shows an ovarian annual cycle with three to four ovulatory waves between April and July (reproductive period). In August to September, a refractory stage occurs, followed by a nonreproductive period (October to March), during which the oocytes undergo slow growth and prepare themselves for vitellogenesis and ovulation. In the reproductive period, only a certain number of oocytes start growing, giving rise to a follicular hierarchy, which is controlled by still unknown mechanisms. In the present paper, immunoreactive inhibin was detected in previtellogenetic follicles of the reproductive period, and in particular, in the pyriform cells of the follicular epithelium. As the follicle grew and the pyriform cells disappeared, immunostaining shifted to the oocyte cytoplasm. The smaller follicles did not show any immunoreactivity. In the nonreproductive period, no follicles were labeled. We conclude that in the reproductive period, inhibin characterizes the follicles destined to ovulation and might be one of the main factors controlling follicular hierarchy.     

X-ray microanalysis on the thyroid follicle of the hagfish, Eptatretus burgeri and lamprey, Lampetra japonica.

Intracellular dense bodies, cytoplasmic matrices, and luminal colloids in the thyroid follicle of cyclostomes, hagfish and lamprey were examined to identify the distribution of iodine using an energy dispersive X-ray microanalyzer attached to a scanning transmission electron microscope. High level of iodine was detected only in the large dense body of the hagfishes, while it was too slight in quantity to detect by this method in the cytoplasmic matrix as well as in the luminal colloid. In the adult lamprey thyroid, an appreciable amount of iodine was detected in a few large dense bodies. In mice and rats, it is very hard to detect iodine in the luminal colloid, intracellular colloid droplet, and in the lysosomal dense granule by this method, though these structures have been well known to contain a fairly large amount of iodine which is combined with thyroglobulin. These facts mean that intracellular dense bodies in the thyroid follicular epithelium of the cytoclostome, especially of the hagfish have an extremely larger amount of iodine. These bodies are considered to be secondary lysosomes or residual bodies containing reabsorbed colloid materials which are highly condensed.     

Fine needle aspiration of the thyroid. Distinction between colloid nodules and follicular neoplasms using cell blocks and 21-gauge needles

Although fine needle aspiration (FNA) of the thyroid has been found to be useful in selecting patients for surgery in most cases, the cytologic differentiation of cellular colloid nodules from follicular neoplasms has not been possible because of the scanty amount of tissue obtained by this technique and because of the infrequent preparation of cell blocks, thus precluding appreciation of the tissue architecture. Review of the histology of nodular goiters and follicular neoplasms and comparison of their morphology in smears and cell blocks from FNA specimens with the histology of the surgically excised specimens in 74 cases revealed the presence of hyperplastic papillae and fragments of dilated follicles in the aspirates of most cases of colloid nodules. These two features appear to be specific for colloid nodules and are useful for distinguishing colloid nodules from follicular neoplasms. The merits of using a 21-gauge needle and of preparing cell blocks in thyroid studies are also discussed.     

Electron microscopic study on the thyroid gland of the salamander Hynobius nebulosus in the breeding season

Summary The thyroid gland of adult salamanders, Hynobius nebulosus, in the breeding season was studied by electron microscopy. The follicular cells are different in cell height and fine structures; the taller cells with many cell organelles and granules and the lower cells with a few cell organelles and granules are both present in the same follicle. In the cytoplasm, three types of membrane-bounded granules, namely, cytosomes, colloid droplets, and vacuolar bodies and circular membrane complexes occur. The vacuolar bodies are subdivided into two types; the ordinary type having loosely distributed particles and the specific type containing tubules and/or closely packed filaments, crystalloid structures, except for the particles. The chromophobe colloids within the Bensley-cells correspond to extremely large, ordinary type vacuolar bodies, while the Langendorff-colloid cells possess increased numbers of granular cisternae of endoplasmic reticulum and a ribosome-rich, dense cytoplasmic matrix but not extremely large colloid. The intracytoplasmic circular membrane complexes appear in the Golgi area of cytosome-rich cells. It is suggested that they originate from the Golgi apparatus which was activated to produce many cytosomes. Intranuclear inclusions consisting of microtubules and filaments and tight junctions between two adjacent lateral plasma membranes are occasionally encountered.