Hormonas Tiroideas y Cerebro. Notas Sobre La Relación Bocio y ...

More documents

Recommendations

Info

12. Bakke JL, Lawrence N, Robinson S 1972 Late effects of thyroxine injected into the hypothalamus of the neonatal rat. Neuroendocrinol 10:183-195 13. Bakke JL, Lawrence N, Wilber JF 1974 The late effects of neonatal hyperthyoridism upon the hypothalamicpituitary-thyroid axis in the rat. Endocrinology 95:406-411 14. Hernandez A, Fiering S, Martinez E, Galton VA, St. Germain DL 2002 The gene locus encoding iodothyronine deiodinase type 3 (Dio3) is imprinted in the fetus and expresses antisense transcripts. Endocrinology 143:in press 15. Hernandez A, Martinez ME, Fiering S, Galton VA, St Germain D 2006 Type 3 deiodinase is critical for the maturation and function of the thyroid axis. Journal of Clinical Investigation 116:476-484 16. Reik W, Walter J 2001 Genomic imprinting: parental influence on the genome. Nature Reviews Genetics 2:21-32 17. Hernandez A, Fiering S, Martinez E, Galton VA, St. Germain DL 2002 The gene locus encoding the iodothyronine deiodinase type 3 (Dio3) is imprinted in the fetus and expresses antisense transcripts. Endocrinology 143:4483-4486 18. Buiting K, Barnicoat A, Lich C, Pembrey M, Malcolm S, Horsthemke B 2001 Disruption of the bipartite imprinting center in a family with Angelman syndrome. American Journal of Human Genetics 68:1290-1294 19. Ohta T, Gray TA, Rogan PK, Buiting K, Gabriel JM, Saitoh S, Muralidhar B, Bilienska B, Krajewska-Walasek M, Driscoll DJ, Horsthemke B, Butler MG, Nicholls RD 1999 Imprinting-mutation mechanisms in Prader-Willi syndrome. American Journal of Human Genetics 64:397-413 20. Weaver IC, Cervoni N, Champagne FA, D'Alessio AC, Sharma S, Seckl JR, Dymov S, Szyf M, Meaney MJ 2004 Epigenetic programming by maternal behavior.[see comment]. Nature Neuroscience 7:847-854 21. Waterland RA, Jirtle RL 2004 Early nutrition, epigenetic changes at transposons and imprinted genes, and enhanced susceptibility to adult chronic diseases. Nutrition 20:63-68 22. Dolinoy DC, Weidman JR, Waterland RA, Jirtle RL 2006 Maternal genistein alters coat color and protects Avy mouse offspring from obesity by modifying the fetal epigenome. Environmental Health Perspectives 114:567-572 23. Jirtle RL, Skinner MK 2007 Environmental epigenomics and disease susceptibility. Nature Reviews Genetics 8:253-262 24
Action of Thyroid Hormone in Brain Juan Bernal Instituto de Investigaciones Biomédicas, CSIC-UAM, and Center for Biomedical Research on Rare Diseases, Madrid, Spain Introduction. Thyroid hormones (thyroxine, T 4 ; and 3,5,3′-triiodothyronine, T 3 ) have major effects on developmental and physiological processes and act on most tissues, but the central nervous system is one of the most important targets. Altered supply of thyroid hormones in developing humans may cause irreversible mental retardation and neurological deficits (1). In adults, thyroid hormones influence mood and behavior, and thyroid diseases can lead to psychiatric manifestations. During brain maturation, thyroid hormones influence a wide range of developmental processes such as myelination, and neuronal and glial cell differentiation and migration; genes involved in these processes have been identified as being regulated by thyroid hormones. The source and metabolism of thyroid hormones in the brain. Both, T4 and T3 enter the brain through the blood-brain barrier and the blood-CSF barrier. Specific transporters are present to facilitate the passage of hormones. The transcriptionally active hormone (T 3 ) in brain arises from thyroidal secretion, and it is also generated locally from T 4 by type 2 deiodinase (D2). This enzyme is expressed in glial cells of two types: astrocytes, and tanycytes which are specialized glial cells lining the walls of the third ventricle (2). T 4 and T 3 are metabolized to rT 3 and to T 2 , respectively, by type 3 deiodinase (D3), which is expressed in neurons (3). During the first half of human pregnancy the contribution of thyroid hormones from the mother is very important for development of the fetal brain before the fetal thyroid gland is fully active (4). Despite low circulating fetal concentrations of T 4 and T 3 brain T 3 greatly increases in the cerebral cortex during the second trimester. This increase takes place in parallel with increasing activity of type 2 deiodinase. It appears likely that expression of type 2 deiodinase is one important regulatory factor during the early action of T 3 in brain, by locally generating the TR ligand from the T 4 substrate. Although the relative contributions of mother and fetus to brain T 4 levels before term are not known, it is likely that the mother provides a significant fraction of the fetal T 4 pool during the first half of pregnancy. Effects of thyroid hormone on brain gene expression. Thyroid hormones regulate the expression of genes encoding functionally diverse proteins, from myelin, cytoskeleton, neutrophins and receptors, extracellular matrix, etc (5,6). For most of these, the control is temporally and regionally restricted, but the molecular basis of such restriction is not known. Most genes are regulated during the first two postnatal weeks in the rats, with few genes known to be thyroid hormone dependent in the fetal brain. Thyroid hormone receptors in brain. The main cellular site of thyroid hormones action is the nucleus, where chromatin-associated thyroid hormone receptors (TRs) are present (7). TRs are transcription factors with ligand-modulated activity. TRs influence gene expression by interacting with regulatory sites in target genes, in a similar way as other members of the nuclear receptor superfamily. In brief, TRs and other class II nuclear receptors, such as retinoic acid receptors, bind to DNA in the absence or presence of the hormone. 25
Page 1 and 2: Hormonas Tiroideas y Cerebro. Notas
Page 3 and 4: Uno de los libros más importantes
Page 5 and 6: ocio (struma). Las observaciones de
Page 7 and 8: Thyroid hormone synthesis Peter Kop
Page 9 and 10: eferred to as microsomal antigen in
Page 11 and 12: It has been proposed that TG mutati
Page 13 and 14: Thyroid Hormone Transporters Theo J
Page 15 and 16: References 1. Bianco AC, Kim BW 200
Page 17 and 18: T 4 T 3 I HO- I I I HO- -O- -R I I
Page 19 and 20: 1 of every 2 molecules of T 4 . Thu
Page 21 and 22: The Type 3 Deiodinase (D3) and the
Page 23: parental origin (16). Thus, using t
Page 27 and 28: Hormonas Tiroideas y Migración Neu
Page 29 and 30: Como ya se mencionó, las hormonas
Page 31 and 32: Función fetal y materna. Un panora
Page 33 and 34: Nacer EDAD GESTACIONAL (semanas) ED
Page 35 and 36: Este fenómeno ha sido observado in
Page 37 and 38: 14. Ausó E, Lavado.Autric R, Cueva
Page 39 and 40: solicita un perfil tiroideo complet
Page 41 and 42: Referencias. 1. Money J, Clarke FC,
Page 43 and 44: • Concentraciones de T4: lograr c
Page 45 and 46: 9. Fisher DA. 2000 The importance o
Page 47 and 48: starting dosage are ever fully norm
Page 49 and 50: and release. Brain structures havin
Page 51 and 52: 31. Rovet JF, Williamson M, Nash K,
Page 53 and 54: Restricción neonatal de alimento e
Page 55 and 56: expresión de la mielina retarda su
Page 57 and 58: 6. Eayrs JT, Taylor SH 1951 The eff

Hormonas Tiroideas y Cerebro. Notas Sobre La Relación Bocio y ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?