13 research outputs found
Functional assessment of coronary artery flow using adenosine stress dual-energy CT: a preliminary study
We attempted to assess coronary artery flow using adenosine-stress and dual-energy mode with dual-source CT (DE-CT). Data of 18 patients with suspected coronary arteries disease who had undergone cardiac DE-CT were retrospectively analyzed. The patients were divided into two groups: 10 patients who performed adenosine stress CT, and 8 patients who performed rest CT as controls. We reconstructed an iodine map and composite images at 120Ā kV (120Ā kV images) using raw data with scan parameters of 100 and 140Ā kV. We measured mean attenuation in the coronary artery proximal to the distal portion on both the iodine map and 120Ā kV images. Coronary enhancement ratio (CER) was calculated by dividing mean attenuation in the coronary artery by attenuation in the aortic root, and was used as an estimate of coronary enhancement. Coronary stenosis was identified as a reduction in diameter of >50% on CT angiogram, and myocardial ischemia was diagnosed by adenosine-stress myocardial perfusion scintigraphy. The iodine map showed that CER was significantly lower for ischemic territories (0.76Ā Ā±Ā 0.06) or stenosed coronary arteries (0.77Ā Ā±Ā 0.06) than for non-ischemic territories (0.95Ā Ā±Ā 0.21, PĀ =Ā 0.02) or non-stenosed coronary arteries (1.07Ā Ā±Ā 0.33, PĀ <Ā 0.001). The 120Ā kV images showed no difference in CER between these two groups. Use of CER on the iodine map separated ischemic territories from non-ischemic territories with a sensitivity of 86% and a specificity of 75%. Our quantification is the first non-invasive analytical technique for assessment of coronary artery flow using cardiac CT. CER on the iodine map is a candidate method for demonstration of alteration in coronary artery flow under adenosine stress, which is related to the physiological significance of coronary artery disease
Structure determination of uniformly C-13, N-15 labeled protein using qualitative distance restraints from MAS solid-state C-13-NMR observed paramagnetic relaxation enhancement
Magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) is a powerful method for structure determination of insoluble biomolecules. However, structure determination by MAS solid-state NMR remains challenging because it is difficult to obtain a sufficient amount of distance restraints owing to spectral complexity. Collection of distance restraints from paramagnetic relaxation enhancement (PRE) is a promising approach to alleviate this barrier. However, the precision of distance restraints provided by PRE is limited in solid-state NMR because of incomplete averaged interactions and intermolecular PREs. In this report, the backbone structure of the B1 domain of streptococcal protein G (GB1) has been successfully determined by combining the CS-Rosetta protocol and qualitative PRE restraints. The derived structure has a C alpha RMSD of 1.49 angstrom relative to the X-ray structure. It is noteworthy that our protocol can determine the correct structure from only three cysteine-EDTA-Mn2+ mutants because this number of PRE sites is insufficient when using a conventional structure calculation method based on restrained molecular dynamics and simulated annealing. This study shows that qualitative PRE restraints can be employed effectively for protein structure determination from a limited conformational sampling space using a protein fragment library
Discovery of Potent and Centrally Active 6āSubstituted 5āFluoro-1,3-dihydro-oxazine Ī²āSecretase (BACE1) Inhibitors via Active Conformation Stabilization
Ī²-Secretase
(BACE1) has an essential role in the production
of amyloid Ī² peptides that accumulate in patients with Alzheimerās
disease (AD). Thus, inhibition of BACE1 is considered to be a disease-modifying
approach for the treatment of AD. Our hit-to-lead efforts led to a
cellular potent 1,3-dihydro-oxazine <b>6</b>, which however
inhibited hERG and showed high P-gp efflux. The close analogue of
5-fluoro-oxazine <b>8</b> reduced P-gp efflux; further introduction
of electron withdrawing groups at the 6-position improved potency
and also mitigated P-gp efflux and hERG inhibition. Changing to a
pyrazine followed by optimization of substituents on both the oxazine
and the pyrazine culminated in <b>24</b> with robust AĪ²
reduction in vivo at low doses as well as reduced CYP2D6 inhibition.
On the basis of the X-ray analysis and the QM calculation of given
dihydro-oxazines, we reasoned that the substituents at the 6-position
as well as the 5-fluorine on the oxazine would stabilize a bioactive
conformation to increase potency
Discovery of Potent and Centrally Active 6āSubstituted 5āFluoro-1,3-dihydro-oxazine Ī²āSecretase (BACE1) Inhibitors via Active Conformation Stabilization
Ī²-Secretase
(BACE1) has an essential role in the production
of amyloid Ī² peptides that accumulate in patients with Alzheimerās
disease (AD). Thus, inhibition of BACE1 is considered to be a disease-modifying
approach for the treatment of AD. Our hit-to-lead efforts led to a
cellular potent 1,3-dihydro-oxazine <b>6</b>, which however
inhibited hERG and showed high P-gp efflux. The close analogue of
5-fluoro-oxazine <b>8</b> reduced P-gp efflux; further introduction
of electron withdrawing groups at the 6-position improved potency
and also mitigated P-gp efflux and hERG inhibition. Changing to a
pyrazine followed by optimization of substituents on both the oxazine
and the pyrazine culminated in <b>24</b> with robust AĪ²
reduction in vivo at low doses as well as reduced CYP2D6 inhibition.
On the basis of the X-ray analysis and the QM calculation of given
dihydro-oxazines, we reasoned that the substituents at the 6-position
as well as the 5-fluorine on the oxazine would stabilize a bioactive
conformation to increase potency