The derivation of human embryonic stem (hES) cells establishes a new avenue to approach many issues in human biology and medicine for the first time. To meet the increased demand for characterized hES cell lines, we present the derivation and characterization of six hES cell lines. In addition to the previously described immunosurgery procedure, we were able to propagate the inner cell mass and establish hES cell lines from pronasetreated and hatched blastocysts. The cell lines were extensively characterized by expression analysis of markers characteristic for undifferentiated and differentiated hES cells, karyotyping, telomerase activity measurement, and pluripotency assays in vitro and in vivo. Whereas three of the cell lines expressed all the characteristics of undifferentiated pluripotent hES cells, one cell line carried a chromosome 13 trisomy while maintaining an undifferentiated pluripotent state, and two cell lines, one of which carried a triploid karyotype, exhibited limited pluripotency in vivo. Furthermore, we clonally derived one cell line, which could be propagated in an undifferentiated pluripotent state. Stem

ISRCTN38014610.

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Turner syndrome (TS) is caused by a sex chromosome aberration. The aim was to study the prevalence and incidence of thyroid disease in adults with TS. Women with TS (n = 91; mean age, 37.7 +/- 11 yr) were compared with an age-matched female random population sample (n = 228). At baseline, 15 (16%) TS women were treated for hypothyroidism, and elevated serum TSH was found in another eight (9%). As a result, hypothyroidism was more common in women with TS (25%) than in controls (2%; P < 0.0001). Serum free T4 was lower (P = 0.02), and serum TSH was higher (P < 0.0001) in TS women than in age-matched controls. Of all TS women with hypothyroidism, 10 (43%) had an elevated thyroid peroxidase antibody titer vs. 15 (22%) of those without hypothyroidism (P < 0.05), evenly distributed between the karyotype 45,X and mosaicism. A high body mass index, but not a family history or blood lipids, was associated with hypothyroidism in TS. After the 5-yr follow-up, an additional 11 (16%) developed hypothyroidism, of whom four (36%) had elevated thyroid peroxidase. Altogether, 34 (37%) TS women had hypothyroidism after the 5-yr follow-up. Autoimmune hypothyroidism was common, with an annual incidence of 3.2% in TS. Thyroid function should be checked regularly in TS.

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Mosaicism seems to mitigate the TS phenotype and the cardiovascular risk factor profile. Mosaics were diagnosed 8 years later than 45,X cases. This emphasizes the necessity for a stricter genotype categorization not only in the clinic but also in research on TS than previously adopted.

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