Rotational Diffusion of Rhodopsin-Digitonin Micelles Studied by Transient Photodichroism

The transient photodichroism induced by a 0.80 sec plane-polarized light flash in a rhodopsin-digitonin mixture at about -70°C was compared with a theoretical description of the effect. It was concluded that the transient dichroism is entirely due to rotational diffusion of the pigment molecules. When the rhodopsin-digitonin micelles are assumed to be rotationally symmetric it was found from the observed relaxation time that the axial ratio is probably less than 2. The initial photodichroism after each flash as a function of the number of flashes was shown to obey an equation derived for the photochemical equilibrium reaction between rhodopsin, lumirhodopsin, and isorhodopsin. The absolute quantum efficiency of the transition of rhodopsin to lumirhodopsin was found to be equal, within experimental error, to the quantum efficiency of bleaching rhodopsin at room temperature

Observer Variability in Evaluating Pisotriquetral Osteoarthritis using Pisotriquetral View

A pisotriquetral (semilateral) view of the wrist may improve the assessment of pisotriquetral osteoarthritis (OA), but its reliability and reproducibility are unclear. The purpose of this cross-sectional observer study was to investigate (1) the inter- and intraobserver agreement of evaluating pisotriquetral OA using pisotriquetral views with a special focus on sclerosis, joint space width (JSW) narrowing and osteophyte formation, and (2) the incidence of these latter radiographic features in patients suspected for pisotriquetral OA. Five independent observers rated independently at two different occasions 27 pisotriquetral views from patients treated for ulnar-sided wrist pain suspected for pisotriquetral OA requiring a pisiform resection. The agreement was calculated using kappa statistic. Agreement between observers ranged from 0.38 (fair) to 0.56 (moderate). Average intraobserver agreement ranged from 0.43 (moderate) to 0.52 (moderate). In 36% of the ratings, JSW narrowing was observed, followed by osteophyte formation (30%) and sclerosis (28%). Observers found it especially difficult to detect JSW narrowing. Despite the availability of a pisotriquetral view to enhance visualization of the pisotriquetral joint, assessment of the specific features indicating pisotriquetral OA leads to only fair-to-moderate agreement. This limits the applicability of a radiographic assessment. A rationale for a more reliable radiologic approach in assessing the level of pisotriquetral OA is needed, which may require the use of more advanced imaging technique

Simple assessment of the efficacy of peritoneal transport in continuous ambulatory peritoneal dialysis patients

The efficacy of peritoneal transport was assessed in 13 permeability studies in 11 continuous ambulatory peritoneal dialysis (CAPD) patients. During each study the in situ intraperitoneal volume was measured as well as the dialysate and plasma concentrations of various solutes with a molecular weight range from 60 to 5,500. As clearance estimations are unsuitable for the purpose of permeability studies, mass transfer area coefficients were used. By applying a simple mathematical model assuming first-order kinetics, these coefficients were calculated for urea, lactate, creatinine, glucose, kanamycin, and inulin. The accuracy of the calculations is indicated by their r values. After pooling these correlation coefficients, the mean approached 1.00 for all solutes with high confidence limits, indicating the usefulness of the model. A further simplification was tested using only an initial- and end-dialysate sample and two blood samples, without the measurement of the in situ intraperitoneal volume. Except for inulin the results of this simplification correlated well with the results described above. The reproducibility of the simplified mass transfer area coefficient calculations was investigated on 15 occasions in 3 other CAPD patients. The coefficients of variation of low molecular weight solutes varied between 15 and 20%. It is concluded that mass transfer area coefficient estimations using the latter method can be performed in any CAPD patient and probably yield sufficient information to establish the efficacy of the membrane transport mechanism during clinical follow-u

Intraobserver and interobserver variability in diagnosing scapholunate dissociation by cineradiography

To evaluate the intraobserver and interobserver variability in diagnosing scapholunate dissociation (SLD) by wrist cineradiography. A musculoskeletal radiologist, hand surgeon, and trauma surgeon assessed the records of 50 consecutive wrist cineradiographies performed in 25 patients. Fluoroscopy was performed on the unaffected and affected wrist and consisted of radiographer-controlled passive flexion-extension and passive radial-ulnar deviation in both posteroanterior and lateral projections. To determine the intraobserver variability, the 3 reviewers reassessed all wrist cineradiographies 6 months after their first assessment. The kappa coefficient for interobserver agreement was calculated using the jackknife method. The Cohen kappa was used to assess intraobserver variability. The interobserver variability for diagnosing SLD by cineradiography was excellent (κ = 0.84). The intraobserver variability for the hand surgeon was excellent (κ = 0.80), and was good for the radiologist (κ = 0.72) and the trauma surgeon (κ = 0.76). Cineradiography is a promising and helpful, noninvasive tool for diagnosing SLD. It is widely available and has relatively low costs. Conventional radiographs remain essential in the primary workup for suspected SLD. However, we recommend cineradiography when an SLD is clinically suspected. Diagnostic II