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Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, AV. Combatients de Malvinas 3105, 1427 Buenos Aires, Argentina
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Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, AV. Combatients de Malvinas 3105, 1427 Buenos Aires, Argentina
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Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, AV. Combatients de Malvinas 3105, 1427 Buenos Aires, Argentina
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Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, AV. Combatients de Malvinas 3105, 1427 Buenos Aires, Argentina
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Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, AV. Combatients de Malvinas 3105, 1427 Buenos Aires, Argentina
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Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, AV. Combatients de Malvinas 3105, 1427 Buenos Aires, Argentina
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Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, AV. Combatients de Malvinas 3105, 1427 Buenos Aires, Argentina
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Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, AV. Combatients de Malvinas 3105, 1427 Buenos Aires, Argentina
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Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, AV. Combatients de Malvinas 3105, 1427 Buenos Aires, Argentina
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Introduction Homeostatic regulation of immunity involves factors that are traditionally considered outside the immune system, including hormones and neurotransmitters. Thyroid hormones play critical roles in differentiation
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SUMMARY
Thyroid hormone binding capacity in serum was measured indirectly by a [131I]tri-iodothyronine (T3) resin uptake method in 36 patients with trophoblastic tumours.
A low [131I]T3 resin uptake (raised thyroid hormone-binding capacity) was found in approximately one-third of the patients but none showed clinical or other evidence of hypothyroidism. There was no correlation between [131I]T3 resin uptake test and gonadotrophin excretion. The results suggest that the increased thyroid-hormone binding capacity found in some patients with trophoblastic tumours may be related to oestrogen secretion and further study is required to establish this.
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( Decuypere et al . 1990 ). During this important phase of development, plasma thyroid hormone (TH) concentrations change markedly–with a profound increase toward the end of embryogenesis – and contribute to the critical events taking place around hatching
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The anterior pituitary is active mitotically and apoptotically under basal conditions and in response to a variety of physiological and pathophysiological stimuli. Hypothyroidism in man is associated with a modest but very occasionally dramatic increase in overall pituitary size. The mechanisms underlying this reversible phenomenon remain obscure. In the present study we have examined young adult rat anterior pituitary following surgical thyroidectomy and subsequent thyroid hormone treatment and withdrawal using an extremely accurate system for quantifying directly identified mitotic and apoptotic events. Despite the expected increase in the number and/or proportion of immunohistochemically identifiable thyrotrophs three weeks after thyroidectomy, mitotic and apoptotic activity remained unchanged, as did pituitary wet weight, in comparison with sham-operated and intact controls. In contrast, mitotic but not apoptotic activity was enhanced by treatment of thyroidectomized animals with thyroid hormones (triiodothyronine (T3) and thyroxine (T4) 1.8 microg and 3.6 microg/100 g body weight per day respectively), and once again declined to levels seen in intact animals within 72 h of subsequent thyroid hormone withdrawal. Thyroid hormone-induced enhancement of mitotic activity was also seen in intact rats treated with similar doses of thyroid hormones for 7 days and in thyroidectomized rats treated for a similar period with very low dose thyroid hormone replacement at a level that had no effect on raised hypothalamic TRH- or pituitary TSHbeta-transcript prevalence (0.018 microg T3 plus 0.036 microg T4/100 g body weight per day). Thus changes in mitotic and apoptotic activity are unlikely to be the principle mechanism for the apparent increase in thyrotrophs up to 4 weeks after thyroidectomy. In contrast, the data indicate that thyroid hormones have a permissive effect on anterior pituitary mitotic activity in thyroidectomized male rats. Thyroid hormone-induced enhancement of mitotic activity in intact rats further suggests that in euthyroid rats, ambient thyroid hormone levels are a limiting factor for anterior pituitary mitotic activity. In summary, this time course study of young, male rats has shown for the first time that thyroidectomy, thyroid hormone replacement and subsequent withdrawal has no significant effect on anterior pituitary apoptotic activity. Secondly, it has shown that the anterior pituitary mitotic response to thyroidectomy is blocked by complete thyroid hormone deprivation, but can be restored by very low level thyroid hormone replacement, and thirdly that in intact animals thyroid hormone levels significantly limit anterior pituitary mitotic activity.
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Introduction Thyroid hormones (TH) are potent modulators of lipid metabolism ( Abrams et al . 1981 , Erem et al . 1999 , Hashimoto et al . 2006 ), and hypothyroidism is associated with higher serum lipids ( Erem et al . 1999 ). Most of the
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ABSTRACT
Studies were made on the effect of thyroid hormones on the level of acetylcholine receptors (AChR) in cultured rat skeletal muscle. Treatment of differentiated myotubes in vitro with thyroxine (T4; 2 × 10−7 mol/l) for 2–3 days caused a marked decrease in the amount of AChR (P<0·05) and an increase in activity of Na+-K+-ATPase (P<0·05). There was no significant effect of hormone treatment on other muscle proteins, such as creatine kinase and acetylcholinesterase. Measurements of the turnover rate of AChR in T4-treated myotubes showed only a very slight effect of T4 on the rate of AChR degradation. To study the mechanism by which the hormone exerts its effect, muscle cells were labelled with radioactive amino acid and the rate of its incorporation into AChR protein was measured. The AChR was then isolated using anti-AChR antibodies. The specific activity of labelled AChR was lower in hormone-treated cells. These experiments suggest that the decreased level of AChR in response to thyroid hormone treatment is due to a partial suppression of receptor synthesis.
J. Endocr. (1984) 101, 141–147
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Thyroid hormones has its main role in controlling metabolism, but it can also modulate extracellular fluid Volume (ECFV) through its action on the expression and activity of Na(+) transporters. Otherwise, chloride is the main anion in the ECFV and the influence of thyroid hormones in the regulation of chloride transporters is not yet understood. In this work, we studied the effect of thyroid hormones in the expression of ClC-2, a cell Volume-, pH- and voltage-sensitive Cl(-) channel, in rat kidney. To analyze the modulation of ClC-2 gene expression by thyroid hormones, we used hypothyroid (Hypo) rats with or without thyroxine (T(4)) replacement and hyperthyroid (Hyper) rats as our experimental models. Total RNA was isolated and the expression of ClC-2 mRNA was evaluated by a ribonuclease protection assay, and/or semi-quantitative RT-PCR. Renal ClC-2 expression decreased in Hypo rats and increased in Hyper rats. In addition, semi-quantitative RT-PCR of different nephron segments showed that these changes were due exclusively to the modulation of ClC-2 mRNA expression by thyroid hormone in convoluted and straight proximal tubules. To investigate whether thyroid hormones action was direct or indirect, renal proximal tubule primary culture cells were prepared and subjected to different T(4) concentrations. ClC-2 mRNA expression was increased by T(4) in a dose-dependent fashion, as analyzed by RT-PCR. Western blotting demonstrated that ClC-2 protein expression followed the same profile of mRNA expression.
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Growth hormone cell differentiation normally occurs between day 14 and day 16 of chicken embryonic development. We reported previously that corticosterone (CORT) could induce somatotroph differentiation in vitro and in vivo and that thyroid hormones could act in combination with CORT to further augment the abundance of somatotrophs in vitro. The objective of the present study was to test our hypothesis that endogenous thyroid hormones regulate the abundance of somatotrophs during chicken embryonic development. Plasma samples were collected on embryonic day (e) 9-14. We found that plasma CORT and thyroid hormone levels increased progressively in mid-embryogenesis to e 13 or e 14, immediately before normal somatotroph differentiation. Administration of thyroxine (T4) and triiodothyronine (T3) into the albumen of fertile eggs on e 11 increased somatotroph proportions prematurely on e 13 in the developing chick embryos in vivo. Furthermore, administration of methimazole, the thyroid hormone synthesis inhibitor, on e 9 inhibited somatotroph differentiation in vivo, as assessed on e 14; this suppression was completely reversed by T3 replacement on e 11. Since we reported that T3 alone was ineffective in vitro, we interpret these findings to indicate that the effects of treatments in vivo were due to interactions with endogenous glucocorticoids. These results indicate that treatment with exogenous thyroid hormones can modulate somatotroph abundance and that endogenous thyroid hormone synthesis likely contributes to normal somatotroph differentiation.
Departamento de Biología de la Reproducción, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No. 186, Mexico City 09340, México
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Departamento de Biología de la Reproducción, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No. 186, Mexico City 09340, México
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Departamento de Biología de la Reproducción, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No. 186, Mexico City 09340, México
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Departamento de Biología de la Reproducción, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No. 186, Mexico City 09340, México
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Departamento de Biología de la Reproducción, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No. 186, Mexico City 09340, México
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Introduction Sex hormones, prolactin (PRL), and thyroid hormones (TH) modulate, in a synergistic or antagonistic manner, several aspects of reproductive physiology ( Longcope 2000 a , 2000 b , Cooke et al. 2004 ). The prostate is
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Gene (Rmmp1) of matrix metalloproteinase 1 (MMP1) of the bullfrog, Rana catesbeiana, has been shown previously to contain a thyroid hormone response element (TRE)-like sequence in its 5'-upstream region. The present study aimed to determine whether this TRE-like sequence is functional in vivo as a true TRE, and to characterize the sequences of the 5'-upstream region with respect to the regulation of the activity of the TRE when the TRE-like sequence was proved to be a true TRE. With this aim, various sequences of TRE-like sequence-containing 5'-upstream region were constructed and fused to the enhanced green fluorescent protein gene as a reporter gene. The fusion constructs were bombarded to the skin of bullfrog tadpoles and the activity of the TRE was quantitatively determined by measuring increased intensities of fluorescence when the animals were exposed to thyroid hormone. The present study clearly demonstrated that the sequence of Rmmp1 is a biologically active TRE in vivo. In addition, a unique 36 bp long sequence directly flanked to the 3'-end of the TRE was identified which worked co-operatively with TRE to regulate the transcriptional promoter activity. It should be emphasized that the presence of TRE in the Rmmp1 gene is unique, because its presence has not been reported in the known promoter region of vertebrate MMPs.
