Protein dynamics and imidazole binding in cytochrome P450 enzymes.

P450 (cytochrome P450) enzymes have major roles in the biosynthesis of endogenous factors such as steroids and eicosanoids, in the termination of the action of endogenous factors such as retinoic acid, in the metabolism of most drugs and xenobiotics and in the generation of toxic and carcinogenic products. Understanding the determinants of the substrate and inhibitor specificities of these enzymes is important for drug design. The crystallographic analysis of the deformability of two bacterial P450 active sites associated with the binding of azole (a class of inhibitors with an imidazole or triazole ring that co-ordinates to the haem iron) inhibitors described in the present study illustrates the importance of protein conformational malleability in the binding of imidazole derivatives.

AquaLite bioluminescence assay of thyrotropin in serum evaluated.

We studied a new commercially available thyrotropin (TSH) assay, the AquaLite Bioluminescence TSH-Immunoassay (SeaLite Inc.). This assay has a detection limit of 0.005 mIU/L and a functional sensitivity of 0.017 mIU/L and meets the requirements of a third-generation TSH assay. Using this assay, we measured serum TSH in 153 euthyroid individuals and in the following patients: 32 primary hypothyroids; 38 primary hyperthyroids; 35 with thyroid cancer receiving suppressive therapy with levothyroxine (L-T4); 33 receiving replacement L-T4 aimed at reaching and maintaining a euthyroid status; 23 with subclinical hyperthyroidism; and 52 hospitalized for nonthyroidal illnesses (NTI). The AquaLite TSH assay perfectly discriminated hypothyroid and untreated hyperthyroid patients from euthyroid subjects and clearly discriminated between overtly and mildly hyperthyroid patients. Intermethod comparisons showed that the AquaLite and the Nichols assays were more effective than the ACS-180 and the TOSOH assays in discriminating among hyperthyroid patients, including patients over-treated with L-T4.

Wilms tumor arising in horseshoe kidney.

Tumors originating in horseshoe kidneys are rare; only 21 cases of Wilms tumor reported in horseshoe kidneys. A seven-month-old girl with Wilms tumor arising from the isthmus of a horseshoe kidney is reported. The literature is reviewed, and surgical considerations are discussed.

Acute megakaryoblastic leukemia in early childhood.

Two girls, each less than 2 yr of age, developed acute megakaryoblastic leukemia (malignant myelosclerosis). Both presented with anemia, severe thrombocytopenia, and a low percentage of blasts in their peripheral blood. Their marrow showed marked reticulin fibrosis with an increase in blasts and immature megakaryocytes. The blasts stained negatively for myeloperoxidase and Sudan Black B, but showed acid phosphatase (ACP) and alpha-naphthyl acetate esterase (ANAE) activity inhibitable by sodium fluoride. They were identified as megakaryoblasts by the platelet peroxidase reaction. Cytogenetic studies showed multiple chromosomal abnormalities in both cases. Chemotherapy with vincristine, prednisone, and L-asparaginase was without effect, while daunorubicin and cytosine arabinoside induced a complete remission in one case. The second case responded to a combination of cytosine arabinoside, daunorubicin, and 6-thioguanine. This article documents that acute megakaryoblastic leukemia occurs in early childhood and describes its clinical, pathologic, and cytogenetic features. Previous reports of childhood "myelofibrosis" are reviewed, and their possible relationship with acute megakaryoblastic leukemia is discussed.