Colonography by computed tomography.

Computed tomographic colonography ('virtual colonoscopy') has shown promising results in the detection of large (> or = 10 mm) polyps in populations with a high prevalence of polyps. Recent studies in low prevalence populations, however, show variable results in sensitivity, ranging from 55% to 94% for the detection of patients with polyps measuring 10 mm or longer. Therefore questions have been raised about computed tomographic colonography as a screening method, probably the most valuable use of this technique.

The integration of a woman's perspective in hysterectomy decisions.

It has been argued, based on a limited amount of research data, that patient participation in decision-making regarding surgery, results not only in more patient satisfaction, but also in better surgery outcomes. Especially in a procedure such as hysterectomy, with far-reaching consequences and many potential side effects, it may therefore be relevant to promote an active role of the patient in the decision-making process. The article identifies contextual elements that might promote this active role.

Remarkable features in lattice-parameter ratios of crystals. II. Monoclinic and triclinic crystals.

The frequency distributions of monoclinic crystals as a function of the lattice-parameter ratios resemble the corresponding ones of orthorhombic crystals: an exponential component, with more or less pronounced sharp peaks, with in general the most important peak at the ratio value 1. In addition, the distribution as a function of the monoclinic angle beta has a sharp peak at 90 degrees and decreases sensibly at larger angles. Similar behavior is observed for the three triclinic angular parameters alpha, beta and gamma, with characteristic differences between the organic and metal-organic, bio-macromolecular and inorganic crystals, respectively.

Remarkable features in lattice-parameter ratios of crystals. I. Orthorhombic, tetragonal and hexagonal crystals.

The investigation of the lattice-parameter ratios of tetrahedral and hexagonal-rhombohedral inorganic compounds, as reported by Constant & Shlichta [(2003), Acta Cryst. A59, 281-282], has been extended to the structural data found for organic and metal-organic compounds (CSD), for bio-macromolecular crystals (PDB) and for inorganic materials (ICSD). In this first part of the series, the frequency distribution of orthorhombic, tetragonal and hexagonal crystals is presented.

Nonvisual ocular photoreception in the mammal.

Rodents blind from outer retinal (rod and cone) degeneration still retain several light-dependent phenomena, including entrainment of the circadian clock and pupillary light responsiveness. This paradox is explained by the presence of intrinsically photosensitive retinal ganglion cells in the inner retina. These cells have unique properties, including a novel action spectrum, resistance to bleaching and adaptation under continuous light, and resistance to vitamin A depletion.

IrII(ethene): metal or carbon radical?

One-electron oxidation of [(Me(n)tpa)Ir(I)(ethene)]+ complexes (Me(3)tpa = N,N,N-tri(6-methyl-2-pyridylmethyl)amine; Me(2)tpa = N-(2-pyridylmethyl)-N,N,-di[(6-methyl-2-pyridyl)methyl]-amine) results in relatively stable, five-coordinate Ir(II)-olefin species [(Me(n)tpa)Ir(II)(ethene)](2+) (1(2+): n = 3; 2(2+): n = 2). These contain a "vacant site" at iridium and a "non-innocent" ethene fragment, allowing radical type addition reactions at both the metal and the ethene ligand. The balance between metal- and ligand-centered radical behavior is influenced by the donor capacity of the solvent.

Method for the computational comparison of crystal structures.

A new method for assessing the similarity of crystal structures is described. A similarity measure is important in classification and clustering problems in which the crystal structures are the source of information. Classification is particularly important for the understanding of properties of crystals, while clustering can be used as a data reduction step in polymorph prediction.

Colorectal cancer screening and surveillance with CT colonography: current controversies and obstacles.

Computed tomographic (CT) colonography has been advocated as an alternative colorectal screening method because studies in populations with a high prevalence of polyps have demonstrated that sensitivity for patients with large (> or =10 mm) polyps is generally high (approximately 90%). In three recent studies in low-prevalence populations, however, these values vary from 55% to 94%. Many questions have been raised as to the cause of this remarkable variability, which hampers the implementation of CT colonography in colorectal cancer screening and surveillance.

Diastereoselective synthesis of (2S,5R)-5-hydroxypipecolic acid and 6-substituted derivatives.

[reaction: see text] Herein, we report a diastereoselective synthesis of the natural product (2S,5R)-5-hydroxypipecolic acid and 6-substituted derivatives thereof. The key step in the synthetic sequence is a novel highly diastereoselective epoxidation reaction of an enantiomerically pure cyclic enamide intermediate.

Effect of vitamin A depletion on nonvisual phototransduction pathways in cryptochromeless mice.

Mice exhibit multiple nonvisual responses to light, including 1) photoentrainment of circadian rhythm; 2) "masking," which refers to the acute effect of light on behavior, either negative (activity suppressing) or positive (activity inducing); and 3) pupillary constriction. In mammals, the eye is the sole photosensory organ for these responses, and it contains only 2 known classes of pigments: opsins and cryptochromes. No individual opsin or cryptochrome gene is essential for circadian photoreception, gene photoinduction, or masking.

Nonvisual photoreception in the chick iris.

The embryonic chicken iris constricts to light ex vivo, but with characteristics atypical of visual phototransduction. The chick iris was most sensitive to short-wavelength light, demonstrating an action spectrum consistent with cryptochrome rather than with opsin pigments. Pupillary responses did not attenuate after saturating light exposure, but showed paradoxical potentiation.

CT colonography and colonoscopy: assessment of patient preference in a 5-week follow-up study.

Purpose: To prospectively evaluate short- and midterm patient preference of computed tomographic (CT) colonography relative to colonoscopy in patients at increased risk for colorectal cancer and to elucidate determinants of preference.

Materials And Methods: Consecutive patients at increased risk for colorectal cancer underwent CT colonography prior to scheduled colonoscopy. Patient experience and preference were assessed both directly after the examinations and 5 weeks after the examinations.

Resetting the clock: Dexras1 defines a path.

The signaling pathways by which light and activity shift the circadian clock are not well understood. In this issue of Neuron, Cheng et al. analyze mice lacking Dexras1 (a Ras family GTPase protein) and demonstrate an important role for G(i/o) signaling mediating both photic and nonphotic phase shifts of the circadian clock.

Computed tomographic colonography compared with colonoscopy in patients at increased risk for colorectal cancer.

Background & Aims: To date, computed tomographic (CT) colonography has been compared with an imperfect test, colonoscopy, and has been mainly assessed in patients with positive screening test results or symptoms. Therefore, the available data may not apply to screening of patients with a personal or family history of colorectal polyps or cancer (increased risk). We prospectively investigated the ability of CT colonography to identify individuals with large (>or=10 mm) colorectal polyps in consecutive patients at increased risk for colorectal cancer.

CT colonography: feasibility of substantial dose reduction--comparison of medium to very low doses in identical patients.

In a feasibility study, the authors compared polyp detection and interobserver variability at computed tomographic (CT) colonography in 15 patients with doses ranging from medium to very low (12.00-0.05 mSv).

Efficient preparation of a 1,3-diazidocyclitol as a versatile 2-deoxystreptamine precursor.

A synthesis route toward 2-deoxystreptamine, a common structure in many of the clinically important aminoglycosides, is presented. Starting from p-benzoquinone and cyclopentadiene, 2-deoxystreptamine is synthesized with key steps involving Pd(0)-catalyzed rearrangement, a retro-Diels-Alder by flash vacuum thermolysis, and Yb(III)-directed regioselective epoxide opening. The obtained diazidocyclitol 17 is a suitable 2-deoxystreptamine precursor, conveniently protected for incorporation in new aminoglycoside entities.

Admission blood glucose level as risk indicator of death after myocardial infarction in patients with and without diabetes mellitus.

Background: High admission blood glucose levels after acute myocardial infarction (AMI) are common and associated with an increased risk of death in subjects with and without known diabetes. Recent data indicate a high prevalence of abnormal glucose metabolism in patients with unknown diabetes at the time of AMI. We investigated the predictive value of admission blood glucose levels after AMI for long-term prognosis in patients with and without previously diagnosed diabetes mellitus, particularly in those with unknown diabetes but with blood glucose levels in the diabetic range.

Amidopalladation of alkoxyallenes applied in the synthesis of an enantiopure 1-ethylquinolizidine frog alkaloid.

A palladium-catalyzed amidation of alkoxyallenes has been developed for the construction of linear allylic N,O-acetals under basic conditions involving (cyclic) amides, sulfonamides, carbamates, and amidophosphates. Application of the methodology provided access to the enantiopure 1-ethylquinolizidine structural motif, which is a key synthon in the synthesis of the naturally occurring poisonous frog quinolizidine 233A and derivatives such as the 1-epi-isomer of quinolizidine 207I.

Diiminoisoindoline: tautomerism, conformations, and polymorphism.

Two polymorphs of the industrially important compound diiminoisoindoline occur in the amino tautomeric form as a conformational isomorph with a 1 : 1 mixture of the syn- and anti-isomers, and a conformational polymorph containing only the syn-isomer.

Sleep disturbances in young subjects with visual dysfunction.

Purpose: To determine whether the type of ophthalmic disease is predictive of sleep and wakefulness disturbances in young subjects with visual dysfunction.

Design: Prospective cohort study.

Participants And Controls: Twenty-five subjects (ages 12-20) were recruited from the Missouri School for the Blind.

Recent insights into mammalian circadian rhythms.

This short review highlights recent progress in understanding the mammalian circadian clock. Advances in the understanding of the neuroanatomy of circadian rhythms, the molecular biology of the core clock mechanism, mechanisms of light entrainment of the circadian clock, clock synchronization among multiple tissues, and recent work on the relationship of the mouse circadian clock and cancer are discussed. This review is intended as an overview of recent research activity for the interested sleep disorders clinician or researcher.