These results indicate that the increased frequency of chronic anaemia in patients with ATD is essentially due to the presence of concomitant autoimmune gastrointestinal diseases.

The regulation of expression of type II deiodinase (D2) is a critical mechanism to maintain appropriate intracellular concentrations of tri-iodothyronine in selected tissues. One of the major regulators of D2 concentrations is cAMP, which potently increases human type II deiodinase (hD2) gene transcription in some tissues via a conserved cAMP response element (CRE) located in the promoter region. In addition, the regulatory region of the hD2 gene contains several TATA box/transcription start site (TSS) units, suggesting the presence of different transcripts that might be characterised by different biological properties. However, it is still unclear whether one ore more TATA box/TSS units are needed in response to cAMP or to other signals able to modulate hD2 transcription. In this study we have analysed the ability of cAMP to regulate hD2 in JEG3 cells, a human choriocarcinoma cell line highly responsive to cAMP. Transient transfection assays of different hD2 gene promoter constructs revealed that cAMP induces transcription starting from the most 58 TSS, located about 80 nucleotides from the CRE. RT-PCR studies have revealed that cAMP activates the expression of a long-lived transcript in JEG3 cells. Site-directed mutagenesis and deletion analysis of promoter constructs have shown that a single CRE/TATA box/TSS unit is needed to confer responsiveness to cAMP. By using chromatin immunoprecipitation studies, we have also demonstrated that the response to cAMP involves the binding of transcription factor CRE binding protein (CREB) to the CRE located in the hD2 promoter. In summary, in JEG3 cells cAMP induces transcription of a long-lived hD2 RNA via CREB and a single CRE/TATA box/TSS unit. This study provides new insights to the regulation of expression of hD2 in placenta.

Objective: The selenoenzyme type 2 iodothyronine 5 H deiodinase (DII) catalyzes the conversion of thyroxine into its active form tri-iodothyronine (T3), modulating thyroid hormone homeostasis in a local, tissue-speci®c manner. The amphibian, rodent and human cDNAs encoding this enzyme have been recently cloned and expressed. At present, little information regarding the genomic structure of mammalian DII is available. Design and methods: The complete structure, including intron±exon junctions, of the human DII (hDII) gene was obtained by long PCR and rapid ampli®cation of cDNA ends (RACE). Chromosomal assignment of the hDII gene was performed by¯uorescence in situ hybridization using a highly speci®c probe. Results and conclusions: Our data demonstrated that hDII is a single copy gene located on chromosome 14, position 14q24.3. The gene spans over 15 kb, and the 7 kb transcript is encoded by three exons of 149 bp, 273 bp and 6.6 kb separated respectively by two 274 bp and 7.4 kb introns. A restriction map of the hDII gene is also reported. These data will help in further studies of the role of DII in the maintenance of peripheral thyroid hormone homeostasis.

Objective: The prevalence of platelet-associated IgG (paIgG) in nonthrombocytopenic patients with autoimmune thyroid disease (AITD) alone or associated with autoimmune polyglandular syndrome (APS) has been studied. Subjects: A total of 164 individuals were enrolled in this study: 81 patients with AITD alone, 33 patients with APS, and 50 healthy controls. Results: The presence of paIgG was recorded in 41 of 81 patients with AITD (51%) as compared with 2 of 50 control subjects (4%, p < 0.0001). The prevalence of paIgG in patients with APS was higher even when compared with patients with AITD alone (25/33, 76%; p = 0.02). The presence of paIgG was not related to the functional thyroid parameters. The prevalence of paIgG was higher in the older than in the younger patients (75 vs. 47%, p = 0.0037). Conclusions: The results indicate that the prevalence of paIgG in patients with AITD is higher than previously thought, namely in elderly patients and in patients with APS, and not related to the thyroid function.

Objective: We have studied the effect of tryptophan on cellular [125 I]tri-iodothyronine (T3) uptake by mouse thymocytes. Materials and methods: Mouse thymocytes (20´10 6 cells/ml) were suspended in Krebs±Ringer solution buffered by Tris±HCl and incubation (23 8C at pH 7.45 6 0.6), in the presence or absence of 1 mM tryptophan, was started by adding 25 pM [125 I]T3. At the end of incubation, samples were cooled in ice, centrifuged over a 30% sucrose cushion and the cell-associated radioactivity was measured in the pellet. Results: Tryptophan reduced both the total and the saturable fraction of [125 I]T3 uptake by 44% (P 0.0009) and 60% (P 0.0006) respectively, following 1 min of incubation. This effect was speci®c and dose-dependent, being maximal at 5 mM concentration (À82%). In contrast, the preexposure of cells to tryptophan for up to 2 h had no effect on the subsequent uptake of 125 I]T3 uptake was exerted in both the presence and the absence of sodium. In fact, the inhibitory effect of tryptophan on T3 transport was greater and signi®cantly different (P 0.0046) from that obtained by sodium depletion alone. Conclusions: Tryptophan interferes with both the sodium-dependent and -independent components of [ 125 I]T3 uptake by a dose-dependent, non-competitive mechanism which operates in cis-modality at the plasma membrane level of mouse thymocytes.