1,791 research outputs found
Vitamin A affects flatfish development in a thyroid hormone signaling and metamorphic stage dependent manner
Vitamin A (VA) and retinoid derivatives are known morphogens controlling vertebrate development. Despite the research effort conducted during the last decade, the precise mechanism of how VA induces post-natal bone changes, and particularly those operating through crosstalk with the thyroid hormones (THs) remain to be fully understood. Since effects and mechanisms seem to be dose and time-dependent, flatfish are an interesting study model as they undergo a characteristic process of metamorphosis driven by THs that can be followed by external appearance. Here, we studied the effects of VA imbalance that might determine Senegalese sole (Solea senegalensis) skeletogenetic phenotype through development of thyroid follicles, THs homeostasis and signaling when a dietary VA excess was specifically provided during pre-, pro-or post-metamorphic stages using enriched rotifers and Artemia as carriers. The increased VA content in enriched live prey was associated to a higher VA content in fish at all developmental stages. Dietary VA content clearly affected thyroid follicle development, T3 and T4 immunoreactive staining, skeletogenesis and mineralization in a dose and time-dependent fashion. Gene expression analysis showed that VA levels modified the mRNA abundance of VA- and TH-specific nuclear receptors at specific developmental stages. Present results provide new and key knowledge to better understand how VA and TH pathways interact at tissue, cellular and nuclear level at different developmental periods in Senegalese sole, unveiling how dietary modulation might determine juvenile phenotype and physiology.Ministry of Education and Culture (MEC) of the Spanish Government [AGL2005-02478]; [SFRH/BPD/82049/2011]info:eu-repo/semantics/publishedVersio
Thyroglossal cyst our experience
This study shares our experiences in managing patients with thyroglossal cysts. These are common midline tumors of neck. Characteristically these masses move on protrusion of tongue due to their intimate relationship with hyoid bone. Adults commonly presented with this lesion eventhough literature review suggests it to be common in children. All these patients underwent surgerybecause of the presence of mass rather than any symptoms. All 30 patients taken up in this study had a normal functioning thyroid in the normal position in addition to the cystic lesion.
Anatomy of Larynx A Review
This article attempts to review anatomical aspects of larynx from a surgeon’s perspective. Anatomically larynx is designed to protect the lower air way from oropharyngeal secretions. Vocalisation happens to be the beneficial offshoot of its pro-tective function
Pre-autoimmune thyroid abnormalities in the biobreeding diabetes-prone (BB-DP) rat: a possible relation with the intrathyroid accumulation of dendritic cells and the initiation of the thyroid autoimmune response
Thyroid autoimmune reactions start with an accumulation of mainly
dendritic cells in the thyroid. There is increasing evidence that, apart
from being antigen-presenting cells, they are also able to control the
growth and hormone synthesis of neighbouring endocrine cells. The
questions thus arise: are dendritic cells accumulating in the
pre-autoimmune thyroid in response to an altered proliferative or
metabolic activity of thyrocytes, and do cytokines, monocyte
chemoattractants, or both, have a role in their accumulation? We have
investigated these questions in thyrocytes of the biobreeding
diabetes-prone (BB-DP) rat in relation to the start of the intrathyroid
accumulation of dendritic cells--that is, at about 9 weeks of age. BB-DP
rats and Wistar rats (controls) were studied from 3 to 20 weeks of age.
Hyperplastic goitre development was studied by assessing the thyroid
weight and by measuring the number of thyrocyte nuclei per 0.01 mm2
thyroid section. In addition, the in situ expression of interleukin-6
(IL-6), tumour necrosis factor-alpha (TNF-alpha), monocyte-chemotactic
protein-1 (MCP-1), and intercellular adhesion molecule-1 (ICAM-1) were
studied by immunohistochemistry. The in vitro proliferative capacity of
BB-DP and Wistar thyrocytes was measured by tritiated-thymidine ([3H]TdR)
and bromodeoxyuridine (BrdU) incorporation into reconstituted, TSH- and
non-TSH-stimulated, cultured thyroid follicles. Further in vitro studies
consisted of measurement of the production of thyroxine (T4),
triiodothyronine (T3), thyroglobulin, IL-6, TNF-alpha and MCP-1 by the
thyroid follicles. BB-DP rats developed a small hyperplastic goitre
between the ages of 9 and 12 weeks. The in vitro proliferative rate of
thyrocytes isolated from hyperplastic BB-DP thyroids was significantly
lower than that of Wistar thyrocytes. This phenomenon also occurred in
follicles isolated from BB-DP rats before hyperplastic goitre development,
which produced significantly less T4, but more T3, than did Wistar
follicles of the same age. At the time of and after hyperplastic goitre
development, BB-DP follicles exhibited altered metabolic behaviour and
produced significantly more T4, but equal amounts of T3 compared with both
Wistar follicles of the same age and follicles of younger BB-DP rats (both
under basal conditions and TSH-st
Antigen-presenting dendritic cells as regulators of the growth of thyrocytes: a role of interleukin-1beta and interleukin-6
An accumulation of antigen-presenting dendritic cells (DC) in the thyroid
gland, followed by thyroid autoimmune reactivity, occurs in normal Wistar
rats during iodine deficiency, and spontaneously in diabetic-prone
Biobreeding rats. This intrathyroidal DC accumulation coincides with an
enhanced growth rate and metabolism of the thyrocytes, suggesting that
both phenomena are related. Because DC are known to regulate the hormone
synthesis and growth in other endocrine systems (i.e. the pituitary, the
ovary, and the testis), we tested the hypothesis that DC, known for their
superb accessory cell function in T cell stimulation, act as regulators of
thyrocyte proliferation (and hormone secretion). We investigated the
effect of (Nycodenz density gradient) purified splenic DC from Wistar rats
on the growth rate of and thyroid hormone secretion by Wistar thyroid
follicles (collagenase dispersion) in culture. Various numbers of DC and
follicles were cocultured during 24 h. The proliferative capacity of
thyrocytes was measured by adding tritiated thymidine (3H-TdR) and
bromodeoxyuridine, the hormone secretion into the culture fluid was
measured by using a conventional T3 RIA. Furthermore, antibodies directed
against interleukin-1beta (IL-1beta), IL-6, and tumor necrosis
factor-alpha (TNF-alpha) were added to these cocultures to determine the
role of these cytokines in a possible DC regulation of thyrocyte growth.
Cocultures were also carried out in the presence of antimajor
histocompatibility complex-class I (MHC I), anti-MHC II, antiintercellular
adhesion molecule-1 (ICAM-1), and antilymphocyte function-associated
antigen-1alpha (LFA-1alpha) antibodies to possibly interfere with
DC-thyrocyte interactions. The addition of DC to thyroid follicles clearly
inhibited their 3H-TdR uptake, particularly at a 10:1 ratio, in comparison
to follicle cultures alone, both under basal conditions and after TSH
stimulation (75 +/- 7% and 49 +/- 11% reduction, respectively, n = 4). The
follicle T3 secretion (after TSH stimulation) was also suppressed by DC in
this system, but to a lesser extent (at best at an 1:1 ratio, 25 +/- 7%
reduction, n = 4). The DC-induced inhibition of thyroid follicle growth
was totally abrogated after addition of anti-IL-1beta antibodies;
anti-IL-6 only had effect on the DC inhibition of non-TSH-stimulated
thyrocytes, whereas anti-TNF-alpha demonstrated no effect at all. The
antibodies to MHC and to adhesion molecules had also no effect on this
DC-induced growth inhibition. The effect of the different anti-cytokine
and anti-adhesion antibodies on the T3 secretion from thyroid follicles
was not investigated. The cl
Histological investigations on the thyroid glands of marine mammals (Phoca vitulina, Phocoena phocoena) and the possible implications of marine pollution
In 1988 and 1989, thousands of harbor seals (Phoca vitulina) died in the North Sea from phocine distemper infection. The morphology of thyroid glands from 40 harbor seals found dead on the North Sea coastlines of Schleswig-Holstein, Federal Republic of Germany, during an epizootic of phocine distemper, was compared with the morphology of thyroid glands from five healthy harbor seals collected in Iceland. Thyroid glands from seven harbor porpoises (Phocoena phocoena) found dead in 1990 on the North Sea coastlines also were evaluated. Colloid depletion and fibrosis were found in the thyroid glands of harbor seals which died during the epizootic, but not in animals from Iceland. Thyroid glands of the porpoises showed similar lesions, but to a lesser degree, than those observed in the North Sea seals
Thyroid gland in Clarias batrachus (Linnaeus): a morphohistological and histochemical study
Relatamos as mudanças morfo-histo1ógicas e histoquímicas que ocorrem na glândula tireóide do peixe teleosteo, Clarias batrachus (Lin.). Com base nos conteúdos coloídais e atividades secretorias, os folículos da tireóide do peixe sob estudo podem ser divididos em 5 estágios (quiescente, não-secretório, secretório, secretório ativo e atrofiado). Foram feitas tentativas para correlacionar as mudanças morfo-histológicas e histoquímicas de vários folícolos da tireóide com sua atividade secretória
Histological organization of thyroid and interrenal glands of the pearl mullet, Alburnus tarichi (Cypriniformes: Cyprinidae) from Lake Van Basin of Turkey
In this study, histological organizations of the thyroid and interrenal glands were first investigated in pearl mullet (Alburnus tarichi Güldenstädt, 1814), living in the Lake Van basin in Turkey. The serial sections taken from the subpharyngeal region and kidney were stained with hematoxylin and eosin, Mallory’s trichrome and periodic acid-Schiff/hematoxylin and then examined. The histological examinations showed that the thyroid gland of pearl mullet was unencapsulated and the thyroid follicles were scattered diffusely in the subpharyngeal region, located at the dorsal and lateral aspects of the ventral aorta. The follicles had colloid-filled lumens and were surrounded by simple follicular epithelial cells varying in shapes (squamose, cuboidal and cylindrical). Thyroid follicles were not found in any areas of the kidney. The interrenal and chromaffin tissue were observed to be associated with postcardinal vein with its branches in the head of the kidney. The interrenal cells having a deeply eosinophilic cytoplasm were determined adjacent to branches in the head kidney. The eosinophobic chromaffin cells were found to show two different distributions. They were observed as being intermingled with the interrenal cells and formed separate groups surrounded by a thin connective tissue in the walls of the major veins. Both interrenal and chromaffin cells displayed a negative periodic acid-Schiff reaction
Involvement of the hypothalamic-pituitary-thyroid axis and its interaction with the hypothalamic-pituitary-adrenal axis in the ontogeny of avian thermoregulation: a review
The emergence of thermoregulation in avian species is a complex matter in which neural as well as hormonal processes are involved. In a previous paper, the neural aspects of primary avian thermoregulation were discussed. In this paper the role of the hypothalamus-pituitary-thyroid axis (HPT-axis) and the hypothalamus-pituitary-adrenal axis (HPA-axis) in the ontogeny of avian thermoregulation is evaluated. The regulatory mechanisms and different important hormones of both axes, which have stimulatory or inhibitory effects, are discussed. Because the onset of functionality of the thermoregulatory system is of great interest, the ontogeny and functionality of the hormonal axes are clarified. There is a great difference between precocial and altricial birds in hormonal events as well as in neural processes which are involved in the emergence of thermoregulation. In precocial avian species the HPT-axis becomes functional during the mid- to late embryonic period while the same axis only becomes fully functional during the first week post-hatch in altricial avian species. As early as the sixties, the emergence of homeothermy in chickens was investigated. It was concluded that the thyroid gland plays an important role in the thermoregulatory mechanisms of newly hatched chicks. More recent studies however were not able to show any direct effect of the thyroid hormones on the thermoregulation of day-old chicks, although blocking the conversion of T4 to T3 caused a decrease in body temperature in young chicks. Thyrotropin releasing hormone (TRH) is known to act in thermoregulation in mammals and several authors have found an effect of TRH on the metabolism of young and older chicks. However, the exact mechanism still remains unclear. Because the HPT- and the HPA-axis show close relationships, the role of the HPA-axis in the ontogeny of thermoregulation is also taken into consideration in this review. In mammals as well as in birds, corticotropin releasing hormone (CRH) is involved in the primary thermoregulation. We conclude that the HPT-axis has an important role in the ontogeny of avian thermoregulation. The exact role of the HPA-axis remains largely unclear although at least CRH is definitely of some importance
Cell Polarity and Water Transport in Thyroid Epithelial Cells in Separated Follicles in Suspension Culture
Separated thyroid follicles maintained in suspension culture can be used to study the properties of thyroid epithelium in the virtual absence of other cell types and to study the effect of extracellular materials on the follicles. They can be prepared by enzymatic separation of thyroid into single cells followed by reaggregation of the epithelial cells and also by collagenase treatment of thyroids to release follicles and sheets of epithelia that can be separated from other materials by differential filtration. The follicles can exist with normal orientation or inverted (inside out). The follicles are inverted in the presence of high serum concentrations (5%) but can have normal orientation when embedded in a type I collagen gel, even at high serum concentrations. When normally oriented follicles invert, the polarity of the epithelial cells reverses while they are connected to neighbors. During inversion, bipolar cells are observed having microvilli- bearing surfaces at both lumen and medium. Inverted follicles can revert to normal orientation when embedded in collagen gel. Various functional properties of normally oriented follicles are similar to those of follicles in vitro. However, inverted follicles do not concentrate iodide, although they synthesize thyroglobulin and secrete it into the medium. Mutants are available in established cell lines. They have functional and organizational properties that differ from those of normal cells and demonstrate a lack of coupling between functional properties and organization. Inverted follicles transport water from medium into the lumen, although at rates somewhat less than MDCK cells
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