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Biomedical subjects

B Conrad

Publications and source records attributed to B Conrad.

At least 91 records · Page 5Linked to original sources
PubMed1995

Influence of baclofen upon the alpha-motoneuron in spasticity by means of F-wave analysis.

Intrathecal baclofen dramatically improves severe spastic syndromes. This improvement is likely related to reduced excitability of alpha-motoneurons. To investigate the influence of baclofen upon the alpha-motoneuron, we analyzed F-waves before and after intrathecal baclofen bolus injection (usually 50 micrograms) as well as after administration of different, constantly delivered doses (60-200 micrograms/day). Intrathecal baclofen bolus decreased the maximum F-wave amplitude (Fp) from an initial value of 9% of the maximum M amplitude (Mmax) (= F/M-ratio) to 2.4% of the Mmax after 130-180 min, reduced the mean F-wave amplitude 60% within 150 min, and shortened the mean duration by 40-60% after 130-180 min. Constantly delivered baclofen of 100 micrograms/day reduced the F/M-ratio from 5% to 2%, the mean F-wave amplitude by 40-80%, and the F-wave mean duration by 40-80%. The minimum F-wave latency did not change after bolus or during steady state administration. The findings indicate that the F-wave mean and maximum amplitude as well as the mean duration are altered in a quantifiable manner following intrathecal baclofen application.

Baclofen↗
PubMed1995

Dynamics of cerebral blood flow velocities during normal human sleep.

Bilateral flow patterns of the middle cerebral artery (MCA) were recorded continuously throughout the night in 18 healthy male subjects (mean age 27.4 years) by a computer-assisted pulsed Doppler (2 MHz) system together with simultaneous polysomnography. After inception of sleep, mean flow velocity (MFV) decreased steadily during deepening sleep stages reaching -15.0 +/- 3.6% (p < 0.001) in the right MCA and -16.2 +/- 3.4% in the left MCA (p < 0.001) in stage 4 of the first sleep cycle compared to the waking state. Lowest MFV values were found in stage 2 preceding the last REM period (right MCA: -19.2 +/- 4.1%: left MCA: -19.7 +/- 5.1%). Changing from non-REM into REM sleep, a sudden rise of MFV, which varied from 8.9% (first sleep cycle, left MCA) to 18% (last sleep cycle, right MCA), could be consistently detected indicating a coupling of cerebral electrical activity and cerebral perfusion in REM sleep. During non-REM sleep this concomitant change of MFV and EEG activity was only found in the first sleep cycle, whereas no parallel changes could be observed in later sleep cycles. These results indicate a decoupling of EEG measured cerebral electrical activity and perfusion and suggest that factors other than metabolic mechanisms contribute to the regulation of cerebral perfusion during human non-REM sleep.

Adult↗
PubMed1995

Comparison of various coils used for magnetic stimulation of peripheral motor nerves: physiological considerations and consequences for diagnostic use.

We compared the ability of 4 magnetic coils to activate peripheral nerves in healthy subjects. No differences in motor threshold intensities were found between the coils, but the intensities needed to elicit maximum compound muscle action potential (CMAP) amplitudes were different. For superficial nerves maximum CMAPs in comparison with electrical stimulation were usually but not always found. CMAPs were at their maximum only when the direction of induced current flowed from proximal to distal and when a certain part of the coil was over the nerve. Distal nerve stimulation was time consuming. Due to artifacts many stimuli were necessary and sometimes no maximum CMAP could be elicited. CMAPs were much less sensitive to position changes of the coil than to changes in an electrical stimulator. Small circular coils were superior to larger coils in terms of the lower intensities necessary to elicit maximum CMAPs, better focusing of the stimulus, and less artifacts. For deep nerves amplitudes were always submaximal. Coactivation of nearby nerves and underlying muscles was another main drawback especially at proximal sites and for coils of large diameter. Despite better focusing, double coils are less useful due to their great diameter. Magnetic stimulation cannot replace electrical neurography at the moment, even if different coils are used at different sites of stimulation.

Action Potentials↗
PubMed1995

Temperament in toddlerhood.

The purpose of this article is to describe how toddler temperament can affect parent-child relations using a goodness-of-fit framework. Nursing considerations for assessing toddler temperament with families and providing parental guidance for managing toddlers with difficult temperament styles are discussed. Emphasis is placed on helping parents to understand their toddler's temperament-based behavior and to devise strategies that maximize compatibility between the toddler's temperament and parental expectations.

Child, Preschool↗
PubMed1995

Cerebral perfusion during sleep-disordered breathing.

Snoring, a leading symptom of the sleep apnoea syndrome (SAS), has been reported to be one of the risk factors for sleep-related cerebral strokes. Episodes of apnoea are accompanied by hypoxaemia as well as hypercapnia. As CO2 constitute a major regulatory factor controlling cerebral blood flow, it is likely that changes in cerebral perfusion are to be found in patients with SAS, which may be related to nocturnal stroke. A computer-assisted pulsed (2 mHz) Doppler ultrasonography system has been modified for continuous long-term and on-line recording of cerebral haemodynamics together with simultaneous polysomnography, continuous blood pressure recordings, and measurement of the end-expiratory CO2. The dynamics of cerebral blood flow velocity (CBFV) during sleep were measured in the right middle cerebral artery in 10 SAS patients. CBFV showed a characteristic nocturnal pattern with decreases during non-rapid eye movement (NREM) sleep and increases during REM sleep. Changes in sleep stage patterns as well as awakenings from NREM sleep were not regularly accompanied by corresponding changes in CBFV. Dramatic increases in CBFV could be observed during apnoeic episodes, with maximum increases during REM sleep. CO2 reactivity and changes in CBFV related to apnoea duration were markedly increased during sleep compared with the waking state in SAS patients. The dynamic feature of CBFV in relation to sleep patterns reflects quantitative uncoupling between cerebral electrical activity and cerebral perfusion during sleep in SAS patients as has been previously reported for normal subjects (Hajak et al. 1994). It supports a dissociation in the activity of central regulatory mechanisms during human sleep which might cause abnormal cerebral perfusion under certain circumstances. The increased CO2 reactivity during sleep in SAS suggests a 'hypersensitivity' of intracranial vasoactive receptors and/or disturbances in the central autonomic control of cerebrovascular functions. It may be concluded that, under certain conditions, the interaction of decreased cerebral perfusion in SAS patients with sleep-related cerebral perfusion patterns and haemodynamic changes during apnoeic episodes might lead to a critical reduction in cerebral perfusion.

Journal Article↗
PubMed1995

Clinical phenotype associated with terminal 2q37 deletion.

Three children with deletions of the terminal portion of the long arm of chromosome 2 [del (2) (q37)] are described and their clinical findings compared to published cases of 2q terminal deletions. Common clinical findings include development delay, macrocephaly, frontal bossing, depressed nasal bridge and cardiac anomaly. Hypotonia and repetitive behavior are also seen during different times of development. The facial characteristics of children with 2q terminal deletions are not uniform, but development delay is a constant finding. Chromosomal analysis of such children using high resolution banding may uncover the diagnosis of a small chromosomal deletion.

Abnormalities, Multiple↗
PubMed1995

[Rockwood capsulorrhaphy in shoulder instability. A clinical follow-up study].

Rockwood described a capsulorrhaphy technique for operative treatment of multidirectional shoulder instability with anterior dislocation. We have used this technique mainly in patients with severe multidirectional instability and now have 8 years' experience with it, which is reported below. The surgical technique involves refixation of the Bankart lesion with transosseous suture and double breasting of the anterior capsule. No transposition of the subcapularis muscle was performed. A functional rehabilitation program without immobilization was used in all patients. The daily activity level, the degree of discomfort upon shoulder-related activities and the subjective assessment of outcome were recorded for each patient. General outcome was determined with reference to Rowe's score. A clinical examination was performed as well as radiography. Strength was evaluated by standardized bilateral dynamometry. Follow-up examination was possible in 73 out of 82 patients. The mean age at follow up was 32.7 +/- 4.1 years, and the mean follow-up time, 4.3 years. The reason for surgery was recurrent dislocation in 81% of patients, pain in 4% and both pain and dislocation in 15% of patients. In 8 patients (10.9%) multiple (up to 4) previous surgical attempts by various methods had been unsuccessful. Postoperatively 59% (n = 44) were able to take part in sports without restrictions, 27.4% could take part only in sports not involving the shoulder, and 13.5% (n = 10) did not engage in any sports postoperatively. The redislocation rate was 12.3% (n = 9), and there was 1 traumatic redislocation. A deficit in abduction/elevation by 10-60 degrees was found in 4 patients (5.4%) and by > 60 degrees in 2 patients (2.7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Evidence for superantigen involvement in insulin-dependent diabetes mellitus aetiology.

Insulin-dependent diabetes mellitus (IDDM) is a T-cell-mediated autoimmune disease whose onset is believed to be triggered by unknown environmental factors acting on a predisposing genetic background. Islet-infiltrating T (IIT) cells from two IDDM patients, who had died at the onset of the disease from brain swelling as a complication of ketoacidosis, were analysed. The results provided evidence for the involvement of a pancreatic islet cell membrane-bound superantigen as a diabetes aetiopathogenetic factor. There was a selective expansion of a T-cell receptor (TCR) variable segment of the beta-chain (V beta 7) in these IIT cells in association with unselected V alpha-chain segments; extensive junctional diversity of the TCR V beta 7 chains; and evidence of positive selection, after exposure to diabetic islet cell membrane preparations, of V beta 7+ T-cell clones among peripheral blood lymphocytes from non-diabetic individuals.

Amino Acid Sequence↗
PubMed1994

Magnetically induced muscle contraction is caused by motor nerve stimulation and not by direct muscle activation.

When magnetically stimulating peripheral nerves, a local cocontraction of muscle under the coil is observed. We assessed whether this contraction results from: (1) magnetic stimulation of motor nerves, or (2) direct depolarization of the muscle membrane. Wrist extensor muscles of normal subjects were magnetically stimulated with the coil placed directly above the muscle. Neuromuscular transmission was then blocked by atracurium using a technique of local curarization. As a reference, the radial nerve was stimulated electrically. Magnetic and electrical stimuli were applied alternatingly every 10 s. Twitch force of wrist extension was measured isometrically over a period of about 70 min including the phase of complete neuromuscular block. Twitch amplitudes elicited by magnetic and electrical stimuli were equivalent during the whole experiment. These results suggest that muscle cocontraction following magnetic stimulation results from depolarization of terminal motor nerve branches.

Action Potentials↗
PubMed1994

Dysfunctional activation of subcortical nuclei in palatal myoclonus detected by high-resolution MRI.

Magnetic resonance images that were sensitized to changes in cerebral blood oxygenation state demonstrated dysfunctional activation of the dentate nuclei, the left inferior olivary nucleus and the left red nucleus in a 56-year-old patient with palatal myoclonus. These findings represent the first demonstration of movement-related activation of cerebellar, brainstem and midbrain nuclei in a single subject and at a spatial resolution comparable to that of anatomic MR images.

Brain Stem↗
PubMed1994

A longitudinal model of maternal self-efficacy, depression, and difficult temperament during toddlerhood.

The purpose of this study was to test a model of maternal self-efficacy during toddlerhood using a longitudinal sequential design. Participants were 126 mothers of 1-year olds (Cohort 1) and 126 mothers of 2-year olds (Cohort 2) who completed questionnaires measuring maternal self-efficacy, depression, and perceived difficult toddler temperament three times over 1 year. Data were analyzed using structural equation modeling and maximum likelihood estimation. Findings support a model whereby (a) the more depressed the mother feels, the more likely she is to rate her toddler's temperament as difficult, (b) the more difficult the child's temperament is perceived to be, the lower the mother's estimates of her parenting self-efficacy, (c) the lower the mother's self-efficacy, the greater her depression, and (d) the more depressed the mother feels at one point in time, the more likely she is to remain depressed 6 months later. Implications of the findings are discussed as they relate to self-efficacy theory and nursing intervention with parents of difficult toddlers.

Adult↗
PubMed1994

Kinematic properties of slow arm movements in Parkinson's disease.

Present pathophysiological concepts of bradykinesia stress an impairment of fast movements in Parkinson's disease. It is, however, unknown whether "bradykinetic" movements are different from slow movements of normal subjects. We recorded trajectories of unrestrained "natural" arm movements from normal subjects and patients with Parkinson's disease. The experiment required the execution of pointing movements for different movement distances and velocities. The shape of trajectories was found to be changed in Parkinson's disease. The steepness of the initial segment and the relation between steepness of the initial segment and final segment both exceeded corresponding values in normal subjects. An analysis of velocity profiles showed an impaired synchrony of vertical and horizontal velocity components. The difference from normal subjects increased with movement velocity. Parkinsonian patients suffered from a fundamental defect in the composition of complex sequences of motor programs required to perform natural arm movements.

Aged↗
PubMed1994

Repetitive magnetic nerve stimulation: technical considerations and clinical use in the assessment of neuromuscular transmission.

We assessed to what extent repetitive magnetic stimulation can replace the electrical method. Fifteen healthy subjects and 3 patients with myasthenia gravis were investigated using stimulation of the median, ulnar, axillary and accessory nerves. Single, as well as 3/sec repetitive magnetic and electrical stimuli were applied. When comparing the results of magnetic vs. electrical stimulation, amplitudes, areas and shapes of compound muscle action potentials were not significantly different. Although single magnetic stimuli were much less uncomfortable than the electrical stimuli, differences in comfort were much smaller in the repetitive protocol, because muscular contractions under the magnetic stimulation coil caused unpleasant movements of, for example, the neck. Additional problems arose from technical limitations of the prototype magnetic stimulator used: stimulation intensity was significantly limited, resulting in an inability to elicit supramaximal responses in 11 of the 154 investigations. Overheating of the stimulator coil forced us to give the coil extra time to cool down. These problems might be solved in the future by more focused stimulus geometry and introduction of cooling devices. It is concluded that magnetic stimulation can elicit responses which are equivalent to the electrical method in repetitive nerve stimulation. At present due to some shortcomings it cannot replace electrical stimulation in routine repetitive nerve stimulation.

Adult↗
PubMed1994

Relationship between cerebral blood flow velocities and cerebral electrical activity in sleep.

The dynamics of cerebral blood flow velocity during sleep were measured in the right and left middle cerebral artery of 12 and 10 healthy male volunteers, respectively. A computer-assisted pulsed (2-MHz) Doppler ultrasonography system was modified for continuous long-term and on-line recording of cerebral hemodynamics in combination with polysomnography. Mean flow velocity (MFV) decreased steadily during deepening nonrapid eye movement (NREM) sleep and increased suddenly during rapid eye movement sleep, corresponding to changes in brain function. However, spontaneous or provoked changes in sleep stage patterns as well as awakenings from NREM sleep were not regularly accompanied by corresponding changes in MFV. Differing values for MFV in subsequent sleep cycles could be shown for several sleep stages. Furthermore, MFV values in sleep stage II at the end of an NREM-sleep period were lower than in preceding slow-wave sleep. After application of short acoustic signals the electroencephalogram frequency rose, indicating an arousal, whereas MFV rapidly decreased for several seconds and then gradually returned to the prior level. These results imply an uncoupling between cerebral electrical activity and cerebral perfusion during sleep and support a dissociation in the activity of central regulatory mechanisms. In light of the proposal that cortical energy consumption can be accounted for by cerebral electrical activity, the concept that cerebral perfusion during sleep is regulated solely by the metabolic rate must be reconsidered.

Adult↗
PubMed1994

[The importance of 24-hour-blood pressure monitoring in hemodynamic and thromboembolism-induced cerebral infarcts].

Night and day blood pressure profiles of 45 patients with cerebral infarction of hemodynamic or thromboembolic origin were assessed to detect subsequent changes of circadian blood pressure variability. The data were also analysed for a possible relationship between variability of circadian blood pressure, site of cerebral infarction and activation of the autonomic nervous system. Patients with a stroke of hemodynamic origin, when compared to a control group, manifested significantly greater variability of circadian blood pressure (diastolic: -25.2 +/- 4.5% vs. -13.8 +/- 6.5%; p < 0.005). Patients who showed the greatest decrease in vasomotor reactivity (< 40%) developed a prolonged disturbance of the blood-brain barrier. This disturbance regressed slowly only after the pathological 24-hour blood pressure profile had normalized. By way of contrast, patients with cerebral infarctions due to thromboembolic events, when compared to normal individuals, showed a distinctly decreased circadian blood pressure variability (diastolic: -5.2 +/- 6.9%). Initially 40% of these patients presented a pathological increase of nocturnal blood pressure. Circadian blood pressure variability was positively correlated with serum concentration of norepinephrine (r = 0.79; p < 0.01). Patients with a stroke affecting the insular cortex manifested an increase of nocturnal blood pressure significantly more often (66.7% vs. 11.8%; p < 0.005), indicating increased sympathetic activation. They had higher serum levels of norepinephrine (540 +/- 110 pg/ml vs. 290 +/- 178 pg/ml) as compared to patients without damage to the insula and also a significantly higher incidence of prolonged QT intervals and cardiac arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗