Comparison of ternary complexes of Pneumocystis carinii and wild-type human dihydrofolate reductase with coenzyme NADPH and a novel classical antitumor furo[2,3-d]pyrimidine antifolate.

The novel furopyrimidine N-(4-{N-[(2,4-diaminofuro[2,3-d]pyrimidin-5-yl)methyl]methylamino}benzoyl)-L- glutamate (MTXO), a classical antifolate with antitumor activity comparable to that of methotrexate (MTX), has been studied as inhibitor-cofactor ternary crystal complexes with wild-type Pneumocystis carinii (pc) and recombinant human wild-type dihydrofolate reductase (hDHFR). These structural data provide the first direct comparison of the binding interactions of the same antifolate inhibitor in the active site for pc and human DHFR. The human ternary DHFR complex crystallizes in the rhombohedral space group R3 and is isomorphous to the ternary complex reported for a gamma-tetrazole methotrexate analogue, MTXT.

Parabola-doublet aplanat becomes anastigmatic when second doublet is inserted near focus.

A doublet of choice glasses may be located in the converging focal cone of the infinity-focused parabola to yield an aplanatic telescope or camera. The resulting angular field is limited by high astigmatism but is significantly larger than that of the coma-limited parabola. The spherical and chromatic aberrations are so well corrected and the coma so well balanced that the doublet may be used unaltered with a parabola of arbitrary focal length and speed with excellent results for the unvignetted rays.

Houghton anastigmatic telescope containing aspheric mirrors that allows corrector position as a free parameter.

A family of catadioptric telescopes is investigated, characterzied with two-element, full-aperture afocal corrector lenses and aspherical, focusing, primary mirrors or primary-secondary mirror combination. Third-order aberration and design equation are provided for anastigmatic systems in which corrector position must be a free parameter, forcing the consideration of aspherics on the mirrored surfaces.

Experience with 2-chlorodeoxyadenosine in previously untreated children with newly diagnosed acute myeloid leukemia and myelodysplastic diseases.

Purpose: To develop more effective chemotherapy regimens for childhood acute myelogenous leukemia (AML).

Patients And Methods: Between June 1991 and December 1996, we administered the nucleoside analog 2-chlorodeoxyadenosine (2-CDA) to 73 children with primary AML and 20 children with secondary AML or myelodysplastic syndrome (MDS). Patients received one or two 5-day courses of 2-CDA (8.

Lack of correlation between cigarette mainstream smoke particulate phase radicals and hydroquinone yield.

Evidence suggests that when compared with non-smokers, cigarette smokers are exposed to an increased burden of free radicals from both the vapor phase and particulate phase of the cigarette smoke aerosol. In this study, primary emphasis was placed on the free radicals found in the particulate phase. Published reports hypothesize that the particulate phase free radicals of cigarette mainstream smoke (MS) condensate consist of a hydroquinone/semiquinone/quinone shuttle.