Is the impact of fatigue related to walking capacity and perceived ability in persons with multiple sclerosis? A multicenter study.

BACKGROUND: The relationship between fatigue impact and walking capacity and perceived ability in patients with multiple sclerosis (MS) is inconclusive in the existing literature. A better understanding might guide new treatment avenues for fatigue and/or walking capacity in patients with MS. OBJECTIVE: To investigate the relationship between the subjective impact of fatigue and objective walking capacity as well as subjective walking ability in MS patients. METHODS: A cross-sectional multicenter study design was applied. Ambulatory MS patients (n = 189, age: 47.6 ±â€¯10.5 years; gender: 115/74 women/men; Expanded Disability Status Scale (EDSS): 4.1 ±â€¯1.8 [range: 0-6.5]) were tested at 11 sites. Objective tests of walking capacity included short walking tests (Timed 25-Foot Walk (T25FW), 10-Metre Walk Test (10mWT) at usual and fastest speed and the timed up and go (TUG)), and long walking tests (2- and 6-Minute Walk Tests (MWT). Subjective walking ability was tested applying the Multiple Sclerosis Walking Scale-12 (MSWS-12). Fatigue impact was measured by the self-reported modified fatigue impact scale (MFIS) consisting of a total score (MFIStotal) and three subscales (MFISphysical, MFIScognitive and MFISpsychosocial). Uni- and multivariate regression analysis were performed to evaluate the relation between walking and fatigue impact. RESULTS: MFIStotal was negatively related with long (6MWT, r = -0.14, p = 0.05) and short composite (TUG, r = -0.22, p = 0.003) walking measures. MFISphysical showed a significant albeit weak relationship to walking speed in all walking capacity tests (r = -0.22 to -0.33, p < .0001), which persisted in the multivariate linear regression analysis. Subjective walking ability (MSWS-12) was related to MFIStotal (r = 0.49, p < 0.0001), as well as to all other subscales of MFIS (r = 0.24-0.63, p < 0.001), showing stronger relationships than objective measures of walking. CONCLUSIONS: The physical impact of fatigue is weakly related to objective walking capacity, while general, physical, cognitive and psychosocial fatigue impact are weakly to moderately related to subjective walking ability, when analysed in a large heterogeneous sample of MS patients.

Epifluorescence microscopy with a pulsed nitrogen tunable dye laser source.

This paper describes an epifluorescence system that uses a pulsed laser source as an excitation source for quantitative fluorescence measurements. A 1 micron diameter portion of the sample can be illuminated with high intensity, short light pulses and the fluorescence can be measured with a fast detection system. Selective excitation is possible at 337 nm and from 357 to 710 nm by using different dyes in the laser system. The spectral bandwidth is 0.1-3 nm. Several advantages over the commonly used systems with continuum spectral sources are indicated, especially when measured intensities are low, as in the case of intrinsic fluorescence of the sample, and where reflection of unwanted excitation light may cause appreciable errors when using conventional light sources.

Characterization of laser-induced fluorescence in the canine retinal pigment epithelium.

The adult retinal pigment epithelium (RPE) exhibits fluorescence caused by various cytoplasmic flurophors and by lipofuscin. Microscopic investigations of fluorescence generally utilize continuum excitation sources (xenon, mercury) and varying filter combinations. Consequently, discrepant emission characteristics are often encountered in the literature. In the present study, an epi-fluorescence microscope linked to a laser source with defined excitation characteristics was used to examine fluorescence in normal, adult canine RPE. Excitation at 337 nm produced maximal fluorescence at 450 nm (blue), while excitation at 439 nm induced 550 nm (yellow) fluorescence. Continuous exposure of cells to 439 nm light caused an initial rapid reduction of intensity, with a subsequent slower decrease of the signal. After solvent extraction, fluorescence at 600 and 650 nm showed no major alterations relative to the values recorded at 550 nm. Our findings demonstrate that varying excitation wavelengths produce discrepant fluorescence data from RPE cells and indicate caution in direct comparisons between experiments where different excitation sources and filter combinations are used.