Release of an endothelial cell growth factor from cultured porcine thyroid follicles

It has been proposed from in vivo studies that thyroid angiogenesis during thyroid enlargement may be due to paracrine mitogenic factors released by epithelial thyroid cells. To study this paracrine growth regulating communication between thyroid cells and endothelial cells in vitro, culture medium from isolated porcine thyroid follicles was investigated for a growth promoting effect on porcine aortal endothelial cells. Serum-free conditioned medium (CM) from thyroid follicles in suspension culture contains a dose-related mitogenic activity which stimulates endothelial cell growth up to 197%. Stimulation of the thyroid follicles with TSH (1 mU/ml) significantly reduced the mitogenic activity for endothelial cells in CM to 131%. Thyroid hormones had no influence on mitogenic activity in CM. When follicles were treated with iodide (20 microM) during CM production, no proliferation of endothelial cells was observed by this CM. In contrast, CM from epidermal growth factor-treated thyroid follicles significantly enhanced the mitogenic activity for endothelial cells up to 235%. The mitogenic activity was precipitable by saturated ammonium sulfate, showed high affinity to heparin by chromatography on heparin-sepharose, and was abolished after treatment of CM with trypsin. On gel electrophoresis the heparin-binding fraction showed a double band with a mol wt of 15 and 15.5 k. These data show a paracrine mitogenic activity on endothelial cells released by thyroid follicles which is regulated by TSH, epidermal growth factor, and iodide in parallel with the direct effect of these substances on thyroid cell growth. The data suggest that the mitogenic factor is a polypeptide, which belongs to the heparin-binding growth factors.     

Morphological and histochemical changes of ultimobranchial follicles of the rat thyroid in the course of postnatal life.

Morphological and histochemical changes of ultimobranchial follicles of thyroid have been investigated in rats from newborn to 18 months of age. The first well-delimited ultimobranchial follicles, though with no lumen, were detected in the thyroid gland of 10-day-old rats. At 30 days of age, follicles possessing regular lumina were present in the thyroid. With age, the follicles gradually increased in volume assuming extreme dimensions in adult age. The follicles displayed varying shapes from simple cysts to bizarre forms. From the age of 50 days the cells of the follicular wall are separated from the cell debris contained in the lumen. The latter gave a PAS positive reaction. The cells of the ultimobranchial follicles did not exhibit argyrophilia and metachromasia showing that they differ considerably from the C-cells likewise of ultimobranchial origin, which are known to give marked argyrophilic and metachromatic reactions.     

Thyroid hormones in small ruminants: effects of endogenous, environmental and nutritional factors

Appropriate thyroid gland function and thyroid hormone activity are considered crucial to sustain the productive performance in domestic animals (growth, milk or hair fibre production). Changes of blood thyroid hormone concentrations are an indirect measure of the changes in thyroid gland activity and circulating thyroid hormones can be considered as indicators of the metabolic and nutritional status of the animals. Thyroid hormones play a pivotal role in the mechanisms permitting the animals to live and breed in the surrounding environment. Variations in hormone bioactivity allow the animals to adapt their metabolic balance to different environmental conditions, changes in nutrient requirements and availability, and to homeorhetic changes during different physiological stages. This is particularly important in the free-ranging and grazing animals, such as traditionally reared small ruminants, whose main physiological functions (feed intake, reproduction, hair growth) are markedly seasonal. Many investigations dealt with the involvement of thyroid hormones in the expression of endogenous seasonal rhythms, such as reproduction and hair growth cycles in fibre-producing (wool, mohair, cashmere) sheep and goats. Important knowledge about the pattern of thyroid hormone metabolism and their role in ontogenetic development has been obtained from studies in the ovine foetus and in the newborn. Many endogenous (breed, age, gender, physiological state) and environmental factors (climate, season, with a primary role of nutrition) are able to affect thyroid activity and hormone concentrations in blood, acting at the level of hypothalamus, pituitary and/or thyroid gland, as well as on peripheral monodeiodination. Knowledge on such topics mirror physiological changes and possibly allows the monitoring and manipulation of thyroid physiology, in order to improve animal health, welfare and production.     

Cholinergic nerves in the thyroid gland

Summary The cholinergic innervation of the thyroid gland has been studied in the human. AChE positive nerve fibers are localized in the wall of the thyroid artery, arranged in two plexuses, a superficial (adventitial) and a deep one (medial). The glandular tissue is provided with cholinergic nerve fibers, localized between and around thyroid follicles. The present results suggest that the endocrine activity of the thyroid gland is also under the control of the autonomic nervous system.     

Ontogeny of the Thyroid Glands During Larval Development of South American Horned Frogs (Anura,Ceratophryidae)

The role of thyroid hormone (TH) in anuran metamorphosis has been documented from a variety of approaches, but the sequence of morpho-histological development of the thyroid glands that produce the secretion of the hormone was assumed invariant from studies of relatively few species even when the effects of environmental influences on larval development and metamorphosis have been largely documented. There are anurans in which developmental and growth rates diverge, and the resulting heterochrony in growth and development produces giant/miniature tadpoles, and or rapid/delayed metamorphosis suggesting changes of the activity of the thyroid glands during larval development. Herein, we analyze the morpho-histological variation of the thyroid glands in larval series of Ceratophrys cranwelli, Chacophrys pierottii, Lepidobatrachus laevis and L. llanensis that share breeding sites along semiarid environments of the Chaco in South America, belong to a monophyletic lineage, and present accelerated patterns in growth and development in order to have a morphological evidence about a possible shift of TH physiology. We describe gross morphology and histology of the thyroid glands and find features shared by all studied species such as the presence of supernumerary heterotopic follicles; changes in the volume and number of follicles towards the metamorphic climax, and cuboidal epithelia with occasional intra-cellular vacuoles as signs of low glandular activity without a manifest peak at the climax as it was assumed for anurans. We discuss different lines of evidence to interpret sources of extra supplement of TH to support the rapid metamorphosis. These interpretations highlight the necessity to design a research program to investigate the endocrine variation during development of ceratophryids taking in account their morphology, physiology and ecology in order to learn more about the effects of environmental and developmental interactions involved in the anuran evolution.     

Thyroidal modulation following hypo- and hyper-thermia in the soft-shelled turtle Lissemys punctata punctata Bonnoterre

The aim of the current study was to investigate the effects of ambient temperature on thyroid activity of the soft-shelled turtle (Lissemys punctata pucntata). Turtles exposed to low ambient temperature (10 degrees C for 15 days) showed a significant decrease in relative thyroid weight, follicular cell size (cell became squamous from cuboidal type) and epithelial height in both the peripheral and central follicles of the gland, with the appearance of homogeneous colloid materials in the follicular lumen. Thyroid peroxidase activity declined significantly. In contrast, high ambient temperatures (32/34 degrees C for 15 days) caused reverse changes to those observed after exposure with low ambient temperature. No significant difference was marked in thyroid activity between 32 and 34 degrees C temperature treatments. The findings provide evidence that low ambient temperature inhibits thyroid activity and high ambient temperature stimulates the gland activity in soft-shelled turtles. Ambient temperature acts presumably via the hypothalamo-hypophysial (TRF-TSH) axis which in turn alters thyroid function in turtles.     

Seasonal changes in the activity of rhodanese in frog (Rana temporaria) liver.

1. The investigators studied annual changes in rhodanese activity in mitochondria and cytosol of frog liver cells (Rana temporaria) and found that the value of the enzyme-specific activity was higher in mitochondria than in cytosol, showing significant seasonal fluctuations. 2. The character of changes in the rhodanese activity in mitochondria, regardless of the sex of the studied animal, was demonstrated to be dependent upon the seasonal changes in frog thyroid gland function. 3. In the supernatant fraction of R. temporaria liver homogenate, seasonal changes of rhodanese specific activity seemed to be related to changes in hepatic function.     

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.     

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.     

Spatial organization of the follicles of the thyroid gland in newborn infants

By means of multilayered plastic reconstruction using serial semithin epoxide sections, it has been demonstrated that besides typical follicles there are some other ones in the thyroid gland of newborns: follicles that have a local thickening on one side, follicles that have reniform proliferates with a cavity, and also follicles with two cavities. The variants mentioned are considered as separate stages of the process for newly formed follicles from the wall proliferates of the preceding ones. While studying 150 interfollicular islets in serial semithin sections, as well as by means of plastic reconstruction, it has been found that they are sections of the follicular wall cut tangentially, and as independent structures in the thyroid gland, they are absent.     

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.     

Age-dependent different action of curcumin in thyroid of rat

The aging is associated with alterations in the hypothalamic-pituitary-thyroidal axis which can lead to hypothyreosis. Our previous investigations has shown that polyphenol curcumin can enhance the manifestation of hypothyreosis in rats simultaneous treated with propylthiouracil. The aim of the study was to investigate the relationship between age-related changes and curcumin action in the thyroid of old rats. To this end, morphometric and radioimmunological methods were used. The study was conducted on 3- and 18-month-old male Wistar rats. The experimental rats were treated daily for 30 days by gavage with 100 mg/kg b.w. of curcumin. There were observed age-related changes in morphology and endocrine function of the thyroid. It was increase in the percentages of large follicles and significant decrease in FT3 level in 18-month-old rats in comparison to 3-month ones. Curcumin treatment lead to significant increase in FT3 and FT4 levels in 3-month-old experimental rats, but the level of FT3 significantly decreased in 18-month-old rats after curcumin administration. Our results show that curcumin activity depends on the functional condition of the rat thyroid which changes with age. This compound exerts stimulatory influence on the secretory function of the thyroid gland in young rats, but has rather weak antithyroid activity in old animals.     

The distribution of labelled iodine in the tissues of wild and laboratory animals with differing functional activity of the thyroid

The dynamics of radioactive iodine accumulation in some organs and tissues of experimental and wild rodent has been studied. The data obtained indicate the seasonal changes in accumulation investigated. These changes correlate with the dynamics of thyroid gland functional state.     

Functional properties of normal and inverted rat thyroid follicles in suspension culture

Rat thyroid follicles in both the normal and the inverted configuration have been cultured in suspension. It has been found that normal follicles (i.e., those having a structural organization similar to the follicles in vivo) express most functional properties of the thyroid gland. They trap iodide, synthesize, secrete, and iodinate thyroglobulin, and secrete thyroid hormone into the culture medium. On the contrary, in inverted follicles (i.e., those having a cell polarity reversed with respect to normal) we were unable to detect expression of some of these functions. We conclude that both the follicular organization and the proper cell polarity are needed for the full expression of thyroid functional properties.     

Postnatal fate of the ultimobranchial remnants in the rat thyroid gland

The ultimobranchial follicles (UBFs) are considered embryonic remnants from the ultimobranchial body (UBB). They are follicular structures that vary in size and appearance depending on the age of the rat. The main objective of this article was to study the progressive changes in shape, size, and frequency of the UBFs in the postnatal rat, from birth to old‐age. To accomplish that objective, a systematic morphometric and incidental study of the UBF has been carried out in 110 Wistar rats of different ages and both sexes, divided into three groups: 1) young rats (5–90‐day‐old); 2) adult rats (6–15‐month‐old), and 3) old rats (18–24‐month‐old). The glands were serially sectioned and immunostained for calcitonin at five equidistant levels. According to our results, UBFs were observed in all thyroid glands but a more exhaustive sampling was occasionally necessary in male rats. In young rats, immature UBFs predominantly appeared whereas in adult rats, mature UBFs with cystic appearance and variable luminal content prevailed. We frequently found spontaneous anomalous UBFs in old rats, which we have termed as “ultimobranchial cystadenomata.” Additionally, in young rats, UBF areas significantly increased with age and they were larger when compared to that of normal thyroid follicles. Likewise, in adult rats, UBFs were significantly larger than normal thyroid follicles but only in female rats. In general, UBFs in females were also significantly larger than those found in male rats. Finally, all these differences related to UBFs together with a higher incidence in females of UB cystadenomata suggest a sexual dimorphism in regard to the destiny of these embryonic remnants during postnatal thyroid development. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

Moulting cycles

Moulting in mammals is a cyclic phenomenon which often occurs in a wave–like pattern. The moult cycle depends upon an inherent rhythm of activity in the hair follicles, which may be modified by systemic factors. In laboratory rodents a number of hormones affect the timing of the moult, as well as affecting the amount of hair produced and the loss of club hairs.
In Microtus agrestis a seasonal moult results in a sparse coat with coarse hairs in summer and a dense coat with fine hairs in winter. The moult appears to be adjusted to the environment by way of the endocrine system, with adrenal and thyroid hormones, as well as sex hormones, involved in the regulation. The importance of such adaptive coat changes are discussed.     

A novel model for lymphocytic infiltration of the thyroid gland generated by transgenic expression of the CC chemokine CCL21

Lymphocytic infiltrates and lymphoid follicles with germinal centers are often detected in autoimmune thyroid disease (AITD), but the mechanisms underlying lymphocyte entry and organization in the thyroid remain unknown. We tested the hypothesis that CCL21, a chemokine that regulates homeostatic lymphocyte trafficking, and whose expression has been detected in AITD, is involved in the migration of lymphocytes to the thyroid. We show that transgenic mice expressing CCL21 from the thyroglobulin promoter (TGCCL21 mice) have significant lymphocytic infiltrates, which are topologically segregated into B and T cell areas. Although high endothelial venules expressing peripheral lymph node addressin were frequently observed in the thyroid tissue, lymphocyte recruitment was independent of L-selectin or lymphotoxin-alpha but required CCR7 expression. Taken together, these results indicate that CCL21 is sufficient to drive lymphocyte recruitment to the thyroid, suggest that CCL21 is involved in AITD pathogenesis, and establish TGCCL21 transgenic mice as a novel model to study the formation and function of lymphoid follicles in the thyroid.     

Accumulation of cytochrome P450 induced by proteasome inhibition during cardiac ischemia

Although differences in size of the right and left thyroid lobes are well defined, differences in morphology, follicles structure, cAMP production, thyrotropin receptor, and protein involved in cell signalling have not previously been reported. This study provides morpho-functional data of right and left thyroid lobes by biochemical, immunohistochemistry, immunoblotting and immunofluorescence analysis. We demonstrate that, in comparison with the left lobe, the right lobe has a higher activation index, is more sensitive to thyrotropin treatment, is rich in thyrotropin receptor and caveolin 1 involved in thyroid hormone synthesis as well as in epithelial thyroid cell homeostasis, is characterised by a high content of molecules involved in cell signalling such as stat3, raf1, sphingomyelinase and sphingomyelin-synthase whose activity ratio is necessary for epithelial cell activity and finally has more areas calcitonin-dependent. The relation between structure/function of right lobe and its susceptibility to the higher risk of pathological modifications with respect the left lobe is discussed.     

Morphochemical investigation of the thyroid gland of guinea pig in experimental acute anaphylactic shock

Some morphochemical changes were observed in the thyroid glands of guinea pigs in acute anaphylactic shocks (AAS). The growth of intensity of reactions for the enzymes of active transport was found. The vacuolisation of the cytoplasm of thyreocytes (as well as colloid) and numerous lesions of follicles were found together with the increase of activity of lysosomal enzymes. The changes of activity of oxidoreductive enzymes in ASS also presented and discussed.     

Activities of oxidative enzymes in thyroid follicles of Xiphophorin fishes.

The activity of some intracellular oxidative enzymes was studied histochemically in the cells of the thyroid follicles of teleost fishes of the genus Xiphophorus. The experimental material consisted of animals of the red swordtail and Mexican swordtail breeds of Xiphophorus helleri and of melanotic Xiphophorus maculatus fishes. Observations were carried out on adult specimens of both sexes, including pregnant femals of Mexican swordtail. Moreover, immature Mexican swordtails of both sexes were examined. Thyroid follicles were found to be present in the subpharyngeal region of all fishes studied. The distribution of these follicles as well as their number and form depended on sex, age and on the analysed stage of prenancy. A smaller number and size of thyroid follicles were characteristic of immature specimens, whereas they were most numerous in the thyroids of pregnant fishes. The follicles were arranged in characteristic dense aggregations, especially in the melanotic platyfish. The follicular eipthelium in the fishes under study was usually cubical, but pregnant and non-pregnant adult females also contained a considerable number of larger follicles with flattened epithelium. Besides, thyroid follicles of multilayer epithelium were rather frequently encountered, especially in male fishes, irrespective of their age. The thyroid follicle cells of these fishes demonstrated invariably high activities of reduced NAD and NADP dehydrogenases and of beta-hydroxybutyrate dehydrogenase, and a low activity of succinat dehydrogenase. The intensities of alpha-glycerophosphate and lactate dehydrogenases and of cytochrome oxidase varied with sex, age and breed of the studied fishes. The immature and pregnant fishes showed the most clearly pronounced differences in the intensity of enzymic activity, the thyroid follicles of immature specimens revealing a high activity of lactate dehydrogenase and low activity of cytochrome oxidase, an inverse picture being seen in pregnant fishes. The adult forms of both sexes exhibited an enhanced activity of cytochrome oxidase and a decline in that of lactate dehydrogenase. The observed differences in the intensities of enzymic acitivities in the thyroids of the studied fishes are related with functions of this gland which in the period of growth are different from those in the period of sexual maturity, and certainly also with individual metabolic characteristics of the studied fishes.