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PubMedDate not supplied

Intermediates of stigmasterol metabolism in Spodoptera littoralis.

Stigmasterol-24,28-epoxide, 22E-stigmasta-5,22,24(28E)-trien-3 beta-ol, and 22E-cholesta-5,22,24-trien-3 beta-ol were identified as normal metabolites of [3H]stigmasterol in Spodoptera littoralis larvae. Relative concentrations of all three of these metabolites increased when a diazasterol inhibitor was fed in combination with stigmasterol in the artificial diet. Identification of these sterols as intermediates in the conversion of stigmasterol to cholesterol in this insect indicates that intermediates analogous to fucosterol and fucosterol-24,28-epoxide in the conversion of sitosterol to cholesterol are produced in the metabolism of stigmasterol. This is the first published identification of stigmasterol-24,28-epoxide and 22E-stigmasta-5,22,24(28E)-trien-3 beta-ol as intermediates in this pathway in an insect.

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PubMedDate not supplied

Brain arteriovenous malformations: assessment with dynamic MR digital subtraction angiography.

BACKGROUND AND PURPOSE: Conventional catheter angiography (CCA) is the current reference standard for the diagnosis, assessment, and management of pial brain arteriovenous malformations (AVMs). The purpose of this study was to develop an MR angiographic technique that produces dynamic images comparable to those provided by CCA and to apply the technique to the investigation of pial brain AVMs. METHODS: Twenty patients with brain AVMs referred for stereotactic radiosurgery were recruited. All patients had CCA performed on a 1.5-T superconducting system. Sixty images were obtained at a rate of one image per second. Slices were orientated to produce Towne, lateral, and anteroposterior projections. A set of mask images was taken and then a series during the passage of a bolus of contrast material. MR examinations were assessed independently by neuroradiologists blinded to the conventional catheter angiographic findings. RESULTS: The nidus of the AVMs was depicted in 19 of the 20 patients, and correlation with CCA was excellent for measurements of maximum diameter. Venous drainage was correctly assessed in 18 of 19 cases. CONCLUSION: MR digital subtraction angiography shows promise as a noninvasive, dynamic angiographic tool for planning stereotactic radiosurgery of AVMs already delineated by catheter angiography. At present, it suffers from temporal and spatial resolution, which impede the assessment of some brain AVMs.

Adolescent↗