Impaired neural drive in patients with low back pain.

BACKGROUND: Control of trunk movement relies on the integration between central neuronal circuits and peripheral skeletomuscular activities and it can be altered by pain. There is increasing evidence that there are deficits within the central nervous system controlling the trunk muscles in people with low back pain (LBP). However, it is unclear how LBP impacts upon neural drive to back muscles at different levels of voluntary contraction. Therefore, the purpose of this study was to investigate if neural drive is impaired in these patients. METHODS: Seventeen patients with LBP and 11 healthy controls were recruited. Bilateral electromyographic (EMG) recordings were obtained from the erector spinae (ES) muscles at two vertebral levels (T12 and L4). Participants performed a series of brief isometric back extensions (50-100% maximum voluntary contraction - MVC), during which transcranial magnetic stimulation was delivered. The size of the evoked (superimposed) twitch was measured using dynamometry. RESULTS: The size of the superimposed twitch decreased linearly with increasing contraction strength in the controls; however, this linear relationship was not observed in the patients. Additionally, patients had larger superimposed twitches and longer time-to-peak amplitudes during MVCs than those observed in controls. Furthermore, patients had lower MVC and root-mean-square EMG activity of ES muscles during MVCs. CONCLUSIONS: A decline of central neural drive to the back muscles at high level of voluntary contraction was observed in patients with LBP. These results suggest that it might be pertinent to include neuromuscular facilitation programmes and therapeutic exercise utilizing high voluntary contractions for patients with LBP.

Anosognosia, neglect and quality of life of right hemisphere stroke survivors.

BACKGROUND AND PURPOSE: Anosognosia and neglect may coexist in stroke patients. Neglect patients often report poor quality of life (QOL), whereas patients suffering from other cognition disorders with poor insight report better QOL. This study investigates the relationship between anosognosia, neglect and QOL amongst stroke survivors. METHODS: Stroke survivors who met the criteria were used as a sampling pool. Sixty stroke patients were observed in this study, amongst whom 20 patients with anosognosia and neglect (A+N+), 20 patients with neglect but not anosognosia (A-N+) and 20 patients with neither anosognosia nor neglect (A-N-) were selected from the sampling pool based on demographic characteristics matched with the A+N+ group. A questionnaire (SS-QOL) was used to collect the QOL perceived by the stroke survivors. RESULTS: The perceived QOL of the A+N+ group was significantly better than those of the other groups, including the subscales of self-care, mobility, work/productivity, upper extremity, mood, family role and social role. However, the A+N+ group had poor balance level and more fall incidents were reported. CONCLUSION: The A+N+ group perceived better QOL but had more falls and poorer balance than the other groups. Health providers should work with caregivers aggressively in preventing accidents.

Blood pressure and age associated with silent autonomic dysreflexia during urodynamic examinations in patients with spinal cord injury.

STUDY DESIGN: An observational study. OBJECTIVES: To investigate the factors associated with silent autonomic dysreflexia (AD) during urodynamics (UD) in spinal cord injury (SCI) patients. SETTING: Taichung city, Taiwan, ROC. METHODS: Blood pressure (BP) and symptoms of AD were continuously monitored during UD, and systolic blood pressure (SBP) elevations >20 mmHg was considered an AD reaction. AD patients were divided into a symptomatic group and a silent group (without AD symptoms), and variables (basic demographic data, hemodynamic data and UD parameters) were compared. RESULTS: A total of 42 patients, 21 in symptomatic and 21 in silent AD groups, were analyzed. Symptomatic group had significantly greater diastolic blood pressure (DBP) increment and rates of SBP/DBP changes (change of BP divided by duration) as compared to the silent group (29.5 vs 21.7 mmHg; 4.8 vs 2.3 mmHg min(-1) and 2.8 vs 1.4 mmHg min(-1)) (P<0.05). The cutoff points of these three variables, determined by receiver operating characteristic analysis, are: DBP increment of 21 mmHg and rates of SBP/DBP change of 2.27 and 1.16 mmHg min(-1). Age had a weak negative correlation with DBP change (Pearson's r=-0.377, P=0.048) and the silent group was significantly older than the symptomatic group (49.4 vs 40.1 years, P<0.05). CONCLUSION: Patients with more symptomatic AD tended to have significant DBP elevation and more rapid SBP/DBP increments, and this was negatively correlated with age. Aging decreases AD symptoms and the magnitude of DBP elevation, possibly through the mechanism of decreased baroreceptor sensitivity. BP monitoring during UD and other invasive procedures is strongly recommended, especially for elderly SCI patients.

Atomic structure of the Ag/Ge(111)-(sq.rt.(3) x sq.rt.(3)) surface: From scanning tunneling microscopy observation to theoretical study.

The atomic structure of the Ag/Ge(111)-(sq.rt.(3) x sq.rt.(3))R30 degrees surface is studied by scanning tunneling microscopy (STM) and the density functional theory (DFT) calculations. Our STM images have shown a structure which is different from the widely accepted honeycomb-chained-triangle (HCT) model before. The structure is similar to the inequivalent triangle (IET) model found for the Ag/Si(111)-(sq.rt.(3) x sq.rt(3))R30 degrees surface. This model proposed two types of silver triangles with different sizes in the unit cell, corresponding to the bright spots and the dark spots in the STM image. A distinguishable hexagonal pattern of the IET structure was well disclosed in the temperature range from 100 to 473 K in our STM studies for Ag/Ge(111)-(sq.rt.(3) x sq.rt.(3))R30 degrees. Furthermore, the result of the DFT calculations showed that the IET structure is 0.20 eV energetically more stable than the HCT model. Besides, the Ge triangles, which were not disclosed in earlier STM research, are found in this study.

A scanning tunneling microscopy study of distyrylbenzene on Ag/Ge(111)-(sqr rt of 3 x sqr rt of 3)R30 degrees.

The adsorption and self-organized monolayers of trans,trans-distyrylbenzene (tt-DSB) and cis,cis-distyrylbenzene (cc-DSB) on Ag/Ge(111)-(sqr rt of 3 x sqr rt of 3)R30 degrees (Ag/Ge(111)-sqr rt of 3) were studied by low-temperature scanning tunneling microscopy (STM) in ultrahigh vacuum. tt-DSB and cc-DSB overlayers were prepared by vapor deposition at a substrate temperature of 200 K and imaged after the samples were cooled to 100 K. High-resolution images allow identification of the internal structure of individual tt-DSB molecules with three phenyl rings and their molecular arrangements on the Ag/Ge(111)-sqr rt of 3 surface. It is found that the intermolecular distance between two terminal phenyl rings in tt-DSB is about twice the lattice constant of Ag/Ge(111)-sqr rt of 3. Such a lattice match makes Ag/Ge(111)-sqr rt of 3 an ideal substrate for tt-DSB self-organization and the formation of a (3 x 1) overlayer unit cell. The structural model and the molecule registry corresponding to STM images for the adlayers of tt-DSB on Ag/Ge(111)-sqr rt of 3 are proposed and discussed. For cc-DSB adsorption on Ag/Ge(111)-sqr rt of 3, uniform molecular overlayers with two discernible molecular images corresponding to two major types of cc-DSB conformers were observed. The coexistence of multiple conformers and the mismatch of molecular dimension of cc-DSB with the substrate unit cell length limit the growth of large cc-DSB domains.

The nature of cation-pi binding: interactions between tetramethylammonium ion and benzene in aqueous solution.

A combined quantum mechanical and molecular mechanical Monte Carlo simulation method was used to determine the free energy of binding between tetramethylammonium ion (TMA+) and benzene in water. The computed free energy as a function of distance (the potential of mean force) has two minima that represent contact and solvent-separated complexes. These species are separated by a broad barrier of about 3 kJ/mol. The results are in good accord with experimental data and suggest that TMA+ binds to benzene more favorably than to chloride ion, with an association constant of about 0.8 M-1.