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Biomedical subjects

B Brouwer

Publications and source records attributed to B Brouwer.

At least 19 recordsLinked to original sources
PubMed2002

Women with spinal cord injury and the impact of aging.

OBJECTIVES: The objectives of this study were to describe what women with longstanding spinal cord injury (SCI) feel they are experiencing as they age, how they are coping and what they require in order to ensure their continued social and economic participation in society. STUDY DESIGN, METHODS AND SETTING: :A naturalistic approach was taken, incorporating three focus groups (n=10) and key informant interviews (n=19) of women with SCI ranging in age from 31 to 70 years and living in rural and urban communities in Ontario, Canada. RESULTS: The women feel isolated and sense many of their key concerns are ignored or dismissed by health care and service providers. The common physical changes and concerns were gynecological/sexual and bowel and bladder issues. Socio-emotional changes with age included impact of their age-related changes on important relationships and re-evaluation of personal priorities. They articulated worries including declining health, increasing dependency and financial stresses. Additional resources they need to age successfully include improved environmental accessibility, assistive devices, more flexible and responsive attendant and household support, access to recreation and fitness opportunities and peer and psychological support. CONCLUSIONS: Many of the issues raised by the women were consistent with the authors' previous examination of aging in men with SCI and women with disabilities. The most striking difference was their profound sense of isolation and perceptions that health care and service providers were unprepared or unwilling to address the unique issues they face as women living and now aging with SCI.

Adaptation, Psychological↗
PubMed2001

Tracking ability in subjects symptomatic of cumulative trauma disorder: does it relate to disability?

Symptoms of upper extremity cumulative trauma disorders (CTDs) often include weakness, discomfort, pain, numbness and stiffness, which are generally assessed clinically by using static tests or isolated movements. Little is known about the dynamic, functional ability of the upper extremity in CTD, yet, more than impairment, performance variables may relate to disability. The objectives of this study were to determine whether a manual tracking task was sensitive to the presence of symptoms associated with CTD and whether tracking performance related to disability. Forty-five volunteers who had frequently experienced one or more symptoms consistent with upper extremity CTD for at least 1 year and 22 control subjects performed the manual tracking task. Using a hand-held stylus over a digitizing tablet, subjects tracked a target that moved pseudo-randomly and was displayed on a computer screen. The root mean square error of the linear difference between target and stylus positions provided a measure of overall performance accuracy. Quadrant specific performance was also calculated to determine whether the location of the target (hence hand and wrist position) influenced performance. Additionally, the symptomatic group completed the Disability of the Arm, Shoulder and Hand (DASH) questionnaire reflecting physical disability level. Performance accuracy was poorer in symptomatic subjects than controls (p<0.001) and was influenced by target location (p<0.0001). The overall performance was associated with physical disability (r = 0.54). The findings suggest that tracking performance is sensitive to the presence of CTD symptoms and related to disability level. Further validation is required to determine whether the performance measure is sensitive to disease progression or intervention-induced changes.

Adolescent↗
PubMed2001

Asymmetry of motor cortex excitability during a simple motor task: relationships with handedness and manual performance.

Transcranial magnetic stimulation (TMS) was used to assess the relative contribution of the corticospinal (CS) pathway in activating the first dorsal interosseous (FDI) muscle in each hand of 16 right- (RH) and 16 left-handed (LH) subjects with varied degrees of hand preference. It was hypothesised that asymmetry in corticospinal activation of the two hands may be related to hand preference and interlimb differences in manual performance. Subjects performed isometric index finger abduction at force levels of 0.5 N, 1 N and 2 N while TMS was applied at resting threshold intensity (T), 0.9T, or 0.8T. The amount of contraction-induced facilitation of the muscle evoked potential (MEP) was used as an estimate of corticospinal involvement in the task. Patterns of MEP facilitation in each hand were compared with measures of manual performance (finger tapping speed, Purdue pegboard, maximal FDI strength). Threshold TMS intensities for an MEP in FDI at rest were similar in LH and RH subjects, and did not vary between hands. Facilitation of the MEP with voluntary activation was larger overall on the left side (P<0.05), but the asymmetry was dependent on the degree of lateralisation of hand preference. For subjects with consistent hand preference (either LH or RH), MEP facilitation in active FDI was larger for the left hand. For non-consistent RH subjects, contraction-induced MEP facilitation was larger in the right FDI muscle than the left. Asymmetry of MEP facilitation was not correlated with differences between hands in finger tapping speed or performance in the pegboard task, but was associated with relative differences in FDI strength. MEP facilitation tended to be larger in the stronger FDI muscle of the pair. We conclude that corticospinal involvement in the command for index finger abduction is generally greater when the left hand is used, although in RH subjects the asymmetry is influenced by the degree of lateralisation of hand preference. The corticospinal asymmetry is not related to speed or dexterity of finger movements, but the association with muscle strength suggests that it may be influenced in part by preferential use of one hand for tasks which strengthen the FDI muscle.

Adult↗
PubMed2000

Reduced interhemispheric inhibition in musicians.

In vivo magnetic resonance imaging has revealed that the anterior half of the corpus callosum is larger in musicians trained intensively from an early age than in untrained subjects. The corpus callosum is crucial for the coordination of bimanual motor activity, but neurophysiological correlates of morphological differences in the corpus callosum of musicians are not known. In the present study we have used transcranial magnetic stimulation (TMS) to assess interhemispheric inhibition in six adult professional musicians who began musical training at an early age. Conditioning TMS was applied to the hand area of the motor cortex of one hemisphere, followed 4-16 ms later by a test stimulus applied to the other hemisphere. Tests were performed at rest, and with the first dorsal interosseous muscle contralateral to the conditioning hemisphere voluntarily active. Conditioning TMS in musicians was 29% less effective at reducing the size of the test MEP at rest, and 63% less effective in the active condition, compared with control subjects. We conclude that transcallosal interhemispheric inhibitory circuits activated by TMS are less effective in musicians than in controls.

Adult↗
PubMed2000

Changes in muscle responses to stimulation of the motor cortex induced by peripheral nerve stimulation in human subjects.

The aim of this study was to determine whether prolonged, repetitive mixed nerve stimulation (duty cycle 1 s, 500 ms on-500 ms off, 10 Hz) of the ulnar nerve leads to a change in excitability of primary motor cortex in normal human subjects. Motor-evoked potentials (MEPs) generated in three intrinsic hand muscles [abductor digiti minimi (ADM), first dorsal interosseous (FDI) and abductor pollicis brevis (APB)] by focal transcranial magnetic stimulation were recorded during complete relaxation before and after a period of prolonged repetitive ulnar nerve stimulation at the wrist. Transcranial magnetic stimuli were applied at seven scalp sites separated by 1 cm: the optimal scalp site for eliciting MEPs in the target muscle (FDI), three sites medial to the optimal site and three sites lateral to the optimal stimulation site. The area of the MEPs evoked in the ulnar-(FDI, ADM) but not the median-innervated (APB) muscles was increased after prolonged ulnar nerve stimulation. Centre of gravity measures demonstrated that there was no significant difference in the distribution of cortical excitability after the peripheral stimulation. F-wave responses in the intrinsic hand muscles were not altered after prolonged ulnar nerve stimulation, suggesting that the changes in MEP areas were not the result of stimulus-induced increases in the excitability of spinal motoneurones. Control experiments employing transcranial electric stimulation provided no evidence for a spinal origin for the excitability changes. These results demonstrate that in normal human subjects the excitability of the cortical projection to hand muscles can be altered in a manner determined by the peripheral stimulus applied.

Adult↗
PubMed1999

Muscle strengthening and physical conditioning to reduce impairment and disability in chronic stroke survivors.

OBJECTIVE: To evaluate the impact of a program of muscle strengthening and physical conditioning on impairment and disability in chronic stroke subjects. DESIGN: A randomized pretest and posttest control group, followed by a single-group pretest and posttest design. SUBJECTS: Thirteen community-dwelling stroke survivors of at least 9 months. INTERVENTION: A 10-week (3 days/week) program consisting of a warm-up, aerobic exercises, lower extremity muscle strengthening, and a cool-down. MAIN OUTCOME MEASURES: Peak isokinetic torque of the major muscle groups of the affected lower limb, quadriceps and ankle plantarflexor spasticity, gait speed, rate of stair climbing, the Human Activity Profile (HAP), and the Nottingham Health Profile (NHP) were recorded twice for the treatment group and three times for the control group. RESULTS: Significant improvements were found for all the selected outcome measures (HAP, NHP, and gait speed) for the treatment group (p < .001). In terms of overall training effects, the 13 subjects demonstrated increases in strength of the affected major muscle groups, in HAP and NHP profiles, and in gait speed and rate of stair climbing without concomitant increases in either quadriceps or ankle plantarflexor spasticity. CONCLUSIONS: The 10-week combined program of muscle strengthening and physical conditioning resulted in gains in all measures of impairment and disability. These gains were not associated with measurable changes of spasticity in either quadriceps or ankle plantarflexors.

Activities of Daily Living↗
PubMed1998

Determination of embutramide and pentobarbital in meat and bone meal by gas chromatography-mass spectrometry.

An analytical procedure, consisting of multiple steps, was developed for the analysis of meat and bone meal for two veterinary drugs, embutramide and pentobarbital, used for euthanasia. After a combined extraction, embutramide was converted to its trimethylsilylether derivative and pentobarbital was methylated. Both analytes were determined by gas chromatography-mass spectrometry in the electron impact or chemical ionisation mode. Limits of determination and identification were between 50 and 100 micrograms kg-1 depending on the compound and the ionisation technique applied. Particular attention was focused on the identification of the analytes.

Amides↗
PubMed1998

Normal variability of postural measures: implications for the reliability of relative balance performance outcomes.

The reliability of outcome measures obtained using the Balance Master and the limits of stability in anterior, posterior, and lateral directions were evaluated in 70 healthy subjects aged 20 to 32 years. Data relating to static sway and the ability to shift the centre of gravity to preset targets were collected on three occasions one week apart. The centre of gravity position and limits of stability were determined over three trials and data converted from a relative reference system to absolute displacements from vertical. Intraclass correlation coefficients revealed fair to poor reliability of static and dynamic sway measures (coefficients < or = 0.55) and excellent reliability of limits of stability measures and the position of the centre of gravity (coefficients > or = 0.75). The variability in outcome measures from tests which do not maximally challenge the postural control system may be a hallmark of normal balance performance. Further, the intersubject variation in resting centre of gravity position and in limits of stability supports the use of absolute performance measures as the interpretive value of data expressed relative to standard norms is limited.

Adult↗
PubMed1998

Reflex excitability and isometric force production in cerebral palsy: the effect of serial casting.

During passive dorsiflexion, the angle of stretch-reflex onset was earlier in the dorsiflexion range for children with spastic cerebral palsy (CP) (N=10) compared with controls (P<0.001) at comparable velocities of stretch. Isometric plantar-flexor force was lower in children with CP (P<0.0001) and a leftward shift in the length-tension curve reflected that peak forces were produced in greater plantar flexion in children with CP than in controls (P<0.0001). Seven children with CP underwent 3 weeks of serial casting resulting in increased dorsiflexion at postcasting and at 6 weeks follow-up (P<0.002). There was no associated loss in plantar-flexor strength (P>0.32), but increased reflex threshold (P<0.03) and a decline in restraint to imposed stretch (P<0.002) were evident. A rightward shift in the length-tension curve illustrated that peak tension was generated in dorsiflexion rather than plantar flexion following casting (P<0.001). The gains were still evident at follow-up although generally to a lesser extent.

Adolescent↗
PubMed1998

Comparison of five isometric exercises in the recruitment of the vastus medialis oblique in persons with and without patellofemoral pain syndrome.

Strengthening of the vastus medialis oblique (VMO) has been advocated as a treatment for patellofemoral pain syndrome (PFPS), as weakness of this component of the quadriceps is postulated to contribute to malalignment of the patella. This study investigated the surface electromyographic activity (EMG) of the VMO relative to the vastus lateralis (VL) during five isometric exercises in eight PFPS female subjects and 19 controls. The area under the EMG curve of each muscle was normalized to the EMG area acquired while subjects performed a submaximal isometric contraction (50% of maximum voluntary contraction), and the "normalized" outcome measure was expressed as a proportion (VMO:VL). A two-factor repeated measures analysis of variance indicated no differences in the VMO:VL proportion between the control group and PFPS participants across the five exercises (p > .05). The VMO:VL proportions for medial tibial rotation and knee extension combined and knee extension alone were significantly greater than for the other three exercises (p < 0.005). Hip adduction or the combination of hip adduction and knee extension did not result in greater recruitment of the VMO compared with the VL.

Adult↗
PubMed1997

Motor cortical mapping of proximal upper extremity muscles following spinal cord injury.

Focal transcranial magnetic stimulation was used to map the motor cortical representations of the relaxed and gently contracted biceps brachii, deltoid and triceps muscles in 22 subjects comprised of 12 controls, five subjects with complete and five with incomplete cervical spinal cord lesions (SCI). Motor evoked potentials (MEPs) were rarely observed during the resting condition (3/30 muscles tested; SCI group) which precluded detailed analysis of these data. With background facilitation, the mean number of scalp stimulation sites producing MEPs varied according to muscle (P < 0.001); biceps yielded the largest maps and triceps the smallest. The cortical representations of proximal upper extremity muscles were largest for the control group and smallest for the incomplete SCI group although differences were not significant (P > 0.09). The optimal site of stimulation (that which produced the largest MEP) was always surrounded by an area producing submaximal MEPs, but was variable across subjects and groups. There was extensive overlap in the motor cortical representation areas corresponding to the three muscles of interest. Following maximal intensity stimulation at the optimal site, the mean MEP amplitudes (normalized) were largest for the biceps muscle and smallest or absent in triceps (P < 0.02). No differences were detected between groups (P > 0.50). The threshold stimulus intensity was highest for those with incomplete SCI and lowest amongst control subjects (P < 0.05), with biceps then deltoid muscles generally having lower thresholds than triceps (P < 0.001). The findings suggest that cortical map areas and MEP characteristics are not significantly altered in gently contracting muscles innervated by nerve roots rostral to the lesion. Only activation thresholds are higher following SCI, particularly incomplete lesions, although there is no apparent association with sensorimotor function. The inability to elicit MEPs in the relaxed muscles of patients with SCI fail to support previous reports of expanded motor cortical representations associated with muscles innervated by roots rostral to the lesion.

Adult↗
PubMed1996

Corticospinal input onto motor neurons projecting to ankle muscles in individuals with cerebral palsy.

Cross-correlograms between voluntarily active soleus (SOL) and tibialis anterior (TA) motor units were generated from seven control subjects and six subjects with spastic cerebral palsy (CP). Short-duration central peaks were observed in three subjects with spastic diplegia only. All subjects demonstrated reciprocal inhibition in TA following electrical stimulation of group I afferents to SOL, and all subjects with CP demonstrated strong activation of both TA and SOL in response to transcranial magnetic stimulation. Responses in SOL were stronger than those observed from controls. These data support the existence of abnormal corticospinal projections to soleus motor neurons in individuals with spastic CP. In spastic diplegia, short-term discharge synchrony between SOL and TA motor units may reflect abnormal interneuronal modulation at the spinal level. Abnormal corticospinal projections and/or modulation of spinal interneurons may contribute to the disordered movement patterns and co-activation observed in this population.

Ankle↗
PubMed1995

Alginate regulatory and biosynthetic gene homologs in Pseudomonas putida WCS358: correlation with the siderophore regulatory gene pfrA.

A previous study [Venturi et al., Mol. Microbiol. 10 (1993) 63-73] demonstrated that the siderophore regulatory gene pfrA of Pseudomonas putida (Pp) WCS358 is highly similar and interchangeable with the alginate regulatory gene algQ (algR2) of P. aeruginosa (Pa). The algQ gene is physically linked to two other alginate regulators in the Pa chromosome, namely algR (algR1), a response regulator, and algP (algR3), a histone-like gene. In this study, we have identified the same genes and a similar genetic organization in the Pp chromosome. The two genes linked to pfrA, designated pprA and pprB, are similar to algR and algP, respectively. Chromosomal mutants of pprA and pprB were constructed showing that unlike pfrA, the two newly identified regulators are not involved in siderophore regulation. The pprA gene complemented a Pa algR mutant phenotype, suggesting that it could be involved in alginate gene regulation. The WCS358 strain is not producing alginate, but we demonstrated by Southern analysis that it also possesses, in addition to pprA and pprB, algD and algU (algT) gene homologs, two genes essential for alginate biosynthesis. Using an algD-xylE transcriptional fusion, we observed that the algD promoter is active in strain WCS358 and absolutely requires pfrA. The possibility that all five genes of Pp WCS358 are involved in alginate biosynthesis is discussed.

Alginates↗
PubMed1995

Characteristics and variability of lower limb motoneuron responses to transcranial magnetic stimulation.

The characteristics and variability of the short latency responses to transcranial magnetic stimulation (TMS) were examined in 188 single lower limb motor units. Information about the cortically evoked postsynaptic potentials was derived from peristimulus time histograms generated from the discharge times of single, rhythmically active, motor units. Tibialis anterior (TA) motoneurons were almost exclusively facilitated and response magnitudes were consistent within a motoneuron pool as indicated by low coefficients of variation (CV). The net cortical effect on soleus (SOL) and medial gastrocnemius (MG) motoneurons was significantly weaker than in TA (P < 0.001) and the responses were non-homogeneous within a motoneuron pool, both in terms of response amplitude and direction. The occurrence of strong facilitatory and inhibitory responses or an absence of a response within a given MG motoneuron pool was associated with CVs about 13 times that of TA and 4 times that of SOL. The large CVs may be indicative of the existence of subgroups of motoneurons differentiated by their response to TMS. Examination of only excitatory responses resulted in comparable CVs across the muscles tested. It is suggested that the degree of non-homogeneity within a motoneuron pool reflects the ability of the cortex to modulate other inputs. Selective cortical activation of specific groups (or subgroups) of motoneurons may set up appropriate conditions suited to a particular volitional task.

Adult↗
PubMed1994

Fatigue secondary to chronic illness: postpolio syndrome, chronic fatigue syndrome, and multiple sclerosis.

Estimates of the percentage of patients with postpolio syndrome, chronic fatigue syndrome, and multiple sclerosis who experience fatigue range from approximately 75% to 100%. In this study we describe the severity of fatigue and its impact on subjects with these three diagnoses. The Fatigue Severity Scale, the Human Activity Profile, and the Nottingham Health Profile were used to measure fatigue, activity, and health status respectively of each diagnostic group as well as a control group. Using a Kruskal-Wallis one-way analysis of variance followed by a Bonferroni-adjusted Mann Whitney U test all diagnostic groups reported significantly higher levels (p = .0000 to p = .002) of fatigue and lower perceived health status than the control group. Subjects with chronic fatigue and multiple sclerosis also had significantly reduced activity levels (p = .002 to p = .01) compared with the control group. Further attention should be directed toward understanding the relationship between fatigue and ability to engage in activities as well as strategies for remediation and/or compensation of the fatigue.

Adult↗
PubMed1994

Determination of anabolic esters in oily formulations and plasma in husbandry using high-performance liquid chromatography and gas chromatography-mass selective detection.

Two different analytical methods are described for the analysis of anabolic steroid esters in oily formulations for veterinary use and animal plasma samples, respectively. For the determination of anabolic steroid esters in oily formulations (at mg kg-1 levels) a reversed-phase high-performance liquid chromatographic method with gradient elution is described. Gradient elution is performed owing to the relatively large variations in polarity of the investigated anabolic steroid esters. For the analysis of anabolic steroid esters in plasma (at ng ml-1 levels) two different strategies are applied. After solid-phase extraction, the plasma samples are introduced into the high-performance liquid chromatography (HPLC) system where the obtained fractions are then analysed by using gas chromatography-mass selective detection (GC-MSD). An alternative method is direct analysis of plasma samples after solid-phase extraction by using GC-MSD without any further clean-up procedure. Prior to GC-MSD the samples are derivatized to corresponding trifluoroacyl (TFA) derivatives. The calibration graph for HPLC is rectilinear over the range 25-150 ng ml-1 plasma and the analytical recoveries for medroxyprogesterone acetate (MPA) and testosterone propionate (TP) are more than 95%. The detection limits for both analytes in GC-MS are 2.5 ng ml-1 plasma for MPA and 0.5 ng ml-1 plasma for TP with an acceptable signal-to-noise ratio (calculated for the derivatized relative molecular mass). In the analysis of plasma obtained from animal experiments concentrations of 6.5 ng ml-1 are found for MPA by using GC-MSD and 5.0 ng ml-1 are found for nortestosterone laurate (NL) by using HPLC.

Anabolic Agents↗
PubMed1992

Corticospinal projections to lower limb motoneurons in man.

The projections of cortical neurons activated by transcranial magnetic stimulation to single lower limb spinal motoneurons were examined in 34 normal subjects. Peristimulus time histograms of the discharge times of single, voluntarily activated motor units were used to derive information about postsynaptic potentials in single spinal motoneurons produced by magnetic stimuli applied over the contralateral scalp. All tibialis anterior motor units and the majority of motoneurons innervating the small muscles of the foot showed strong short latency facilitation. About half of the motoneurons of proximal lower limb muscles showed this facilitation. Short latency facilitation of the motoneurons of soleus and medial gastrocnemius was only rarely observed and when present was weak. The short latency facilitation is attributed to the projections of the fast corticospinal pathway with monosynaptic projections to motoneurons. The relative strength of the facilitation in different motoneuron pools is considered to reflect the density of corticospinal projections to that motoneuron pool. The observed pattern of projections in man shows some differences from the pattern of projections in subhuman primates that might reflect the different use of the limb.

Cerebral Cortex↗