Catheter-directed computed tomography angiography: A pictorial essay.

Catheter-directed computed tomography angiography (CDCTA) is an imaging technique where CT images are acquired after selective catheterization of a vessel. Images obtained in this fashion provide several advantages over conventional imaging techniques such as fluoroscopic angiography, digital subtraction angiography, cone-beam CT, and conventional CT angiography. At this point, there is still limited literature on the subject, with prior studies examining a small number of potential uses. The goal of this pictorial essay is to illustrate our single tertiary care center experience using CDCTA.

Baroreflex and chemoreflex controls of sympathetic activity following intermittent hypoxia.

There is a large amount of evidence linking obstructive sleep apnea (OSA), and the associated intermittent hypoxia that accompanies it, with the development of hypertension. For example, cross-sectional studies demonstrate that the prevalence of hypertension increases with the severity of OSA (Bixler et al., 2000; Grote et al., 2001) and an initial determination of OSA is associated with a three-fold increase for future hypertension (Peppard et al., 2000). Interestingly, bouts of intermittent hypoxia have also been shown to affect sympathetic output associated with the baroreflex and chemoreflex, important mechanisms in the regulation of arterial blood pressure. As such, the possibility exists that changes in the baroreflex and chemoreflex may contribute to the development of chronic hypertension observed in OSA patients. The aim of the current article is to briefly review the response of the baroreflex and chemoreflex to intermittent hypoxic exposure and to evaluate evidence for the hypothesis that modification of these autonomic reflexes may, at least in part, support the comorbidity observed between chronic hypertension and OSA.

Direct-detected rapid-scan EPR at 250 MHz.

EPR spectra at 250 MHz for a single crystal of lithium phthalocyanine (LiPc) in the absence of oxygen and for a deoxygenated aqueous solution of a Nycomed triarylmethyl (trityl-CD3) radical were obtained at scan rates between 1.3 x 10(3) and 3.4 x 10(5)G/s. These scan rates are rapid relative to the reciprocals of the electron spin relaxation times (LiPc: T1 = 3.5 micros and T2 = 2.5 micros; trityl: T1 = 12 micros and T2 = 11.5 micros) and cause characteristic oscillations in the direct-detected absorption spectra. For a given scan rate, shorter values of T2 and increased inhomogeneous broadening cause less deep oscillations that damp out more quickly than for longer T2. There is excellent agreement between experimental and calculated lineshapes and signal amplitudes as a function of radiofrequency magnetic field (B1) and scan rate. When B1 is adjusted for maximum signal amplitude as a function of scan rate, signal intensity for constant number of scans is enhanced by up to a factor of three relative to slow scans. The number of scans that can be averaged in a defined period of time is proportional to the scan rate, which further enhances signal amplitude per unit time. Longer relaxation times cause the maximum signal intensity to occur at slower scan rates. These experiments provide the first systematic characterization of direct-detected rapid-scan EPR signals.

Phosphorylation-dependent changes in structure and dynamics in ERK2 detected by SDSL and EPR.

Mitogen-activated protein kinases are regulated by occupancy at two phosphorylation sites near the active site cleft. Previous studies using hydrogen exchange to investigate the canonical mitogen-activated protein kinase, extracellular signal-regulated protein kinase-2, have shown that phosphorylation alters backbone conformational mobility >10 A distal to the site of phosphorylation, including decreased mobility within amino acids 102-105 and increased mobility within 108-109. To further describe changes after enzyme activation, site-directed spin labeling at amino acids 101, 105-109, 111, 112 and electron paramagnetic resonance spectroscopy were used to investigate this region. The anisotropic hyperfine splitting of the spin labels in glassy samples was unchanged by phosphorylation, consistent with previous crystallographic studies that indicate no structural change in this region. At positions 101, 111, and 112, the mobility of the spin label was unchanged by diphosphorylation, consistent with little or no conformational change. However, diphosphorylation caused small but significant changes in rotational diffusion rates at positions 105-108 and altered proportions of probe in a motionally constrained state at positions 105, 107, and 109. Thus, electron paramagnetic resonance indicates reproducible changes in nanosecond side-chain mobilities at specific residues within the interdomain region, far from the site of phosphorylation and conformational change.