Low frequency of BRAFT1796A mutations in childhood thyroid carcinomas.

A high prevalence of the activating BRAF mutation, BRAF(T1796A), is observed in adult papillary thyroid carcinomas (PTCs). The prognosis of childhood PTCs is generally fairly good despite the fact that distant metastases are often documented in these cases. To investigate the differences between the characteristics of childhood and adult PTCs, we analyzed both BRAF(T1796A) and RAS mutations in 31 Japanese and 48 post-Chernobyl Ukrainian thyroid carcinomas. In the 31 Japanese childhood cases, BRAF(T1796A) was found in only one instance (3.2%), and no RAS mutations were detected. In the Ukrainian subjects, of the 15 childhood and the 33 adolescent and young adult PTCs examined, the BRAF(T1796A) mutation was found in zero and eight cases, respectively, and RAS mutations were found in two of the young adult cases. In addition, 17 of the 48 Ukrainian cases showed expression of the RET tyrosine kinase region, indicating the existence of RET/PTC rearrangements. Unlike adult PTCs, we could detect no positive association between BRAF(T1796A) mutations and clinical parameters in the childhood carcinomas, suggesting that a low prevalence of BRAF(T1796A) is a common feature of PTCs in children regardless of radiation exposure levels. The differences in the prevalence of BRAF(T1796A) mutations between childhood and adult cases of PTC may well reflect inherent differences in the clinical features of these cancers between the two age groups.

Low prevalence of BRAF mutations in radiation-induced thyroid tumors in contrast to sporadic papillary carcinomas.

Point mutations of the BRAF gene have been recently described with high prevalence in papillary thyroid carcinomas. However, this molecular alteration has not been studied in radiation-induced thyroid tumors. We analyzed the prevalence of BRAF point mutations and RET/PTC rearrangements in 55 post-Chernobyl papillary carcinomas, compared with 82 sporadic papillary carcinomas. Radiation-induced tumors demonstrated a low prevalence (4%) of BRAF point mutations and high prevalence (58%) of RET/PTC rearrangements. Sporadic papillary carcinomas revealed a clearly distinct pattern, with 37% of tumors harboring BRAF mutations and 20% RET/PTC rearrangements. These results demonstrate a significant difference in the molecular genetic profile of sporadic and radiation-induced thyroid tumors.

Ultrastructural organization of Alicyclobacillus tolerans strain K1T cells.

Electron microscopy examinations of thin sections and freeze-fracture replicas revealed the specific ultrastructural features of Alicyclobacillus tolerans strain K1(T). In particular, the cell wall displayed an ultrastructure typical of gram-positive bacteria and consisted of a thin murein layer (50-60 A in thickness); cells exhibited a surface S-layer constituted by large hexagonally packed (p6-symmetry) rod-shaped subunits of 150-160 A in diameter and 200 A in height. In the cytoplasmic membrane, there were intramembrane vesicular structures that sometimes appeared as large leaflets in the central part. The cytoplasm contained numerous vesicular inclusions covered with a monolayered wall, dissimilar to bilamellar lipid membranes. Endospore coats displayed an intricate structure and consisted of three thick layers; the outer layer had an unusual fine structure; the exosporium was also found.