Imaging of haemophilic arthropathy in growing joints: pitfalls in ultrasound and MRI.

The purpose of this review was to summarize the current knowledge on the utilization of magnetic resonance imaging (MRI) and ultrasound (US) for assessing arthropathy in children and adolescents with haemophilia and to recognize the limitations of each imaging modality and pitfalls in the diagnosis of soft tissue and osteochondral abnormalities. Awareness of MRI and US limitations and pitfalls in the assessment of joints in persons with haemophilia is essential for accurate diagnosis and optimal management of haemophilic arthropathy.

IV. Synthesis and assay of analogs of adenosine 3',5'-diphosphate as inhibitors of bovine adrenal estrogen sulfotranferase.

Analogs of adenosine 3',5'-diphosphate are described which aid in the characterization of the inhibition of estrone sulfurylation by 3'-phosphoadenosine 5'-phosphosulfate as mediated by bovine adrenal estrogen sulfotransferase (3'-5'-phosphosulfate:estrone 3-sulphotransferase, EC 2.8.2.4). The facile conversion of ribonucleosides to 2',3'-cyclic phosphate 5'-phosphate in neat pyrophosphoryl chloride is utilized to provide a reliable route to the requisite intermediates for enzymatic regiospecific conversion to ribonucleoside 3',5'- and 2',5'-diphosphates. The importance of the 3'-phosphate ester to inhibition of estrone sulfurylation is confirmed by Ki measurements. Replacement of the 6-amino group by hydrogen or oxygen leads to considerable loss in affinity for the enzyme as does also dimethylation of the exocylic amino group. Alterations in the pyrimidine ring are not well tolerated by the sulfotransferase but modifications in the imidazole ring as in tubercidin (7 -deazaadenosine) and 8-bromoadenosine 3',5'-diphosphate lead to an enhanced affinity. The latter findings are discussed in terms of an hypothesis of stacking of the aromatic ring of the estrogen substrate and the purine moiety and its analogs.

Studies on bovine adrenal estrogen sulfotransferase. Inhibition and possible involvement of adenine-estrogen stacking.

The inhibition of bovine adrenal estrogen sulfotransferase has been studied utilizing representative androgens and estrogens with structural changes in rings A, B, and D. These investigations have shown oxygen functions in positions 3, 16, or 17 to be required for the binding of estrogens or androgens to the enzyme. 5alpha-Androstanes (all transfused rings) are weak noncompetitive inhibitors and bind more tightly than the 5beta isomers (cis-fused A and B rings). The competitive inhibition observed with the estrogens does not require a free 3-phenolic hydroxyl, however, groups larger than 3-methoxy limit binding. While the product, estrone sulfate, is not inhibitory, phosphate esters on positions 3- or 17beta or a sulfate moiety on the 17beta-hydroxyl group of estrogens slightly inhibit the enzyme. The stacking of adenine (in adenosine 3'-phosphate-5'-phosphosulfate) with the A ring of estrogens is postulated for the enzyme-bound transition state. This structure, which facilitates the hydrogen bonding between the 6-amino group of adenine and the 4-nitro, 4-bromo, or 6-keto substituents on estrogens, readily explains the unusual substrate and inhibitory properties of these compounds. Certain of these estrogen derivatives, which possess little or no hormonal activity, are efficient inhibitors of estrogen sulotransferase.

Studies on bovine adrenal estrogen sulfotransferase. III. Facile synthesis of 3'-phospho- and 2'-phosphoadenosine 5'-phosphosulfate.

A practical synthesis of 3'-phosphoadenosine 5'-phosphosulfate (IV) in yields of 68-72% from adenosine 2',3'-cyclic phosphate 5'-phosphate (II) is described. Reaction of II with triethylamine-N-sulfonic acid affords adenosine 2',3'-cyclic phosphate 5'-phosphosulfate (III) which, on treatment with ribonuclease-T2, provides IV. Spleen phosphodiesterase, on the other hand, converts III to 2'-phosphoadenosine 5'-phosphosulfate (V). The biological activity of IV, measured by sulfate transfer to [6,7-3H2]estrone as mediated by bovine adrenal estrone sulfotransferase (3'-phosphoadenylyl-sulfate:estrone 3-sulfotransferase, EC 2.8.2.4), is identical with that obtained with a sample of IV prepared by an established biochemical procedure. By contrast, V exhibits approximately one-third the activity of the natural isomer.