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30.07.2001 | 9:39 AM

Thyroid hormone–sympathetic interaction and adaptive thermogenesis are thyroid hormone receptor isoform–specific.

In newborns and small mammals, cold-induced adaptive (or nonshivering) thermogenesis is pro- duced primarily in brown adipose tissue (BAT). Heat production is stimulated by the sympathetic nervous system, but it has an absolute requirement for thyroid hormone. We used the thyroid hor- mone receptor-β–selective (TR-β–selective) ligand, GC-1, to determine by a pharmacological approach whether adaptive […]

30.07.2001 | 9:32 AM

Thyroid hormone stimulation of osteocalcin gene expression in ROS 17/2·8 cells is mediated by transcriptional and post-transcriptional mechanisms.

We investigated the mechanism of thyroid hormone regulation of osteocalcin (OC) gene expression in osteoblast-like cells (ROS 17/2·8). Treatment with tri- iodothyronine (T3) (10 8 M) increased OC mRNA levels by 3-fold after 24 h and reached a maximum, 5·4-fold, after 48 h. The mRNA levels of other bone- specific genes, alkaline phosphatase and osteopontin, […]

23.02.2001 | 11:46 AM

Iodine Landmark Paper: Pituitary Nuclear 3,5,3 -Triiodothyronine and Thyrotropin Secretion: An Explanation for the Effect of Thyroxine.

Iodine is an essential component of thyroid hormones. The thyroglobulin-derived iodothyronine molecules contain 3 or 4 iodine atoms that are covalently bound during iodide organification. This process, also known as iodination, is catalyzed by thyroid peroxidase and requires that the thyroid cell concentrate iodide from plasma. Iodine is readily available from the ocean, and salt-water […]

15.02.2001 | 9:44 AM

Regional physiological adaptation of the central nervous system deiodinases to iodine deficiency.

In newborns and small mammals, cold-induced adaptive (or nonshivering) thermogenesis is pro- duced primarily in brown adipose tissue (BAT). Heat production is stimulated by the sympathetic nervous system, but it has an absolute requirement for thyroid hormone. We used the thyroid hor- mone receptor-β–selective (TR-β–selective) ligand, GC-1, to determine by a pharmacological approach whether adaptive […]

09.02.2001 | 9:50 AM

Cloning and functional characterization of an uncoupling protein homolog in hummingbirds.

The cDNA of an uncoupling protein (UCP) homolog has been cloned from the swallow-tailed hummingbird, Eupetomena macroura. The hum- mingbird uncoupling protein (HmUCP) cDNA was amplified from pectoral muscle (flight muscle) using RT-PCR and primers for conserved domains of various known UCP homologs. The rapid amplification of cDNA ends (RACE) method was used to complete […]

30.12.2000 | 9:55 AM

Selective Proteolysis of Human Type 2 Deiodinase: A Novel Ubiquitin-Proteasomal Mediated Mechanism for Regulation of Hormone Activation.

We investigated the mechanism by which T4 regu- lates its activation to T3 by the type 2 iodothyronine deiodinase (D2). D2 is a short- lived (t1/2 50 min), 31-kDa endoplasmic reticulum (ER) integral mem- brane selenoenzyme that generates intracellular T3. Inhibition of the ubiquitin (Ub) activating enzyme, E1, or MG132, a proteasome blocker, inhibits both […]

30.11.2000 | 10:13 AM

Distinct subcellular localization of transiently expressed types 1 and 2 iodothyronine deiodinases as determined by immunofluorescence confocal microscopy.

We compared the subcellular localization of FLAG-epitope tagged Types 1 and 2 deiodinases (D1 and D2) transiently expressed in human embryonic kidney (HEK-293) and mouse neuroblastoma (NB2A) cells. D2 is an integral membrane protein based on resistance to extraction at pH 11 with the NH2 terminus in the endoplasmic reticulum (ER). Immunofluorescence confocal microscopy using […]

30.04.2000 | 10:27 AM

Lack of reduction in body fat after treatment with insulin-like growth factor-I in two children with growth hormone gene deletions.

Two patients with growth hormone (GH) gene deletions were treated with recombinant insulin-like growth factor-I (IGF-I) (80-240 (microg/kg/day) and the effects on bone mass and body composition were compared to administration of GH (0.075 U/kg/day) to 8 patients with idiopathic GH deficiency. Bone mass and body composition were measured by dual photon X-ray absorptiometry (DEXA […]

08.03.2000 | 10:00 AM

Evidence of UCP1-independent regulation of norepinephrine-induced thermogenesis in brown fat.

To study the thermal response of interscapular brown fat (IBF) to nor- epinephrine (NE), urethan-anesthetized rats (1.2 g/kg ip) main- tained at 28–30°C received a constant venous infusion of NE (0–2 104 pmol/min) over a period of 60 min. IBF temperatures (TIBF) were recorded with a small thermistor fixed under the IBF pad. Data were […]

15.02.2000 | 10:33 AM

Substrate-Induced Down-Regulation of Human Type 2 Deiodinase (hD2) Is Mediated through Proteasomal Degradation and Requires Interaction with the Enzyme’s Active Center.

Type 2 iodothyronine deiodinase (D2) catalyzes the first step in thyroid hormone action, the deiodination of T4 to T3 . Endogenous D2 activity is posttranslationally regulated by substrate that accelerates its degradation through the ubiquitin-proteasome pathway. To un- derstand how D2 activity correlates with D2 protein during its normal decay and rT3-induced down-regulation, HEK-293 cells, […]