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B Kemp

Publications and source records attributed to B Kemp.

At least 163 records · Page 9Linked to original sources
PubMed1992

Cerebral information processing estimated by unpredictability of the EEG.

Processing of complex information by the brain desynchronizes neuronal cells and therefore increases the unpredictability of the EEG, rather than its amplitude or power. A model of this mechanism describes the EEG as being composed of both an unpredictable fraction and a fraction that can be predicted from the past EEG. The model realistically simulates EEG of several behavioural states and suggests a simple algorithm for the computation of EEG predictability (values between 0% and 100%). Applications in sleep analysis and event-related desynchronization demonstrated that the algorithm is more accurate and artifact-resistant than the usual (spectral) power methods.

Algorithms↗
PubMed1992

Ambulatory monitoring of sleep-wakefulness patterns in healthy elderly males and females (greater than 88 years): the "Senieur" protocol.

OBJECTIVE: The study was designed to investigate sleep-wake patterns in healthy elderly men and women (greater than 88 years) using ambulatory recording techniques. DESIGN: Cross-sectional observations on 2 consecutive days. METHODS: Two consecutive 24-hour recordings were made. Each 30-second period of the recording was scored as characteristic of wakefulness, REM, and non-REM sleep (stages 1-4). SETTING: Interviews and recordings were done in the home of the elderly, not interfering with the habitual routine. PARTICIPANTS: Among eligible members of the "Senieur" protocol, screened for wellness, seven females (88-102 years) and seven males (88-98 years) volunteered to participate. MAIN OUTCOME MEASURES: Organization of sleep, sleep structure, and daytime mapping. RESULTS: There was no difference between the first and second night recording. Important gender differences were observed: males had significantly less total sleep, shorter REM latency, more transitions to wake from REM, less NREM 3 sleep, and virtually no NREM 4. Daytime napping, REM amount, and distribution did not show sex differences. Although the variability in the amount of napping was considerable, it occupied less than 10 percent of the total sleep time in both women and men. Daytime napping was unrelated to sleep characteristics. CONCLUSIONS: Ambulatory sleep-wake recordings allow an objective and critical evaluation of sleep function in normal aging. Interesting findings include a shift of REM sleep to the first part of the sleep period an increased cycle variability, and non-correlation of night-time sleep with daytime napping. In contrast to earlier findings in elderly persons, a polygraphic and subjective first-night effect was lacking.

Aged↗
PubMed1991

Variability of normal sleep patterns in 40 consecutive ambulatory sleep-wakefulness records.

Sleep-wakefulness (S-W) patterns were recorded continuously for 40 consecutive 24 h using subcutaneous chronic electrodes and an ambulatory cassette recorder in a healthy 57-year-old volunteer. Variability of sleep patterns was assessed in steady-state conditions and in the course of a scientific journey encompassing flights in both west/east and south/north directions. Data were compared with findings from age-matched laboratory control records. Polysomnographic evaluation of our sleep data shows: (1) Stability of the first 3 sleep cycles and variability of the remaining sleep period with respect to both duration and structure. Vulnerability of REM sleep to environmental interference. (2) Stability of the WASO/drowsiness cluster as an intraindividual biological trait independent of social interactions. The clinical relevance of ambulatory serial recording is stressed. (3) The role of the first sleep cycle structure in the chronobiological adaptation process is documented. Apparently travelling in south/north directions may have similar or even more polygraphic implications than west/east transfer.

Chronobiology Phenomena↗
PubMed1991

A model-based detector of vertex waves and K complexes in sleep electroencephalogram.

A model of sleep phasic events such as vertex waves, K complexes, delta waves and sleep spindles is proposed. It consists of feedback loops that are driven by white noise (simulating tonic delta and sigma activity) and by isolated random impulses, simulating vertex waves or K complexes, depending on the background tonic activity. A model-based method for the detection of sleep phasic events was implemented in a personal computer. Its performance was investigated using simulated and real whole-night EEG signals. The method was able to detect K complexes and vertex waves in a reliable way in spite of their variable shapes and in the presence of a variety of background activities. The detector appears to have superior performance to those so far reported in the literature. The performance of the detector was also compared to that of an electroencephalographer using normal sleep EEG records of 8 h duration from 6 subjects. The performance was satisfactory both in terms of accuracy and reliability. The problem of detecting K complexes in stages 3 and 4 of sleep is discussed.

Adult↗
PubMed1991

Diurnal variation of essential and physiological tremor.

Evaluations were made of the diurnal variations of tremor power at rest, after fatigue and after mass loading, and plasma norepinephrine in patients with familial essential tremor and normal subjects. Diurnal tremor power rhythms for both essential and physiological tremor pursued identical temporal profiles. Plasma norepinephrine levels followed a congruent diurnal pattern with later peak values than the peak values of tremor power. Sympathetic nervous system activity is unlikely to be the cause of diurnal tremor power variation. The consistent diurnal rhythm of tremor power may affect dosage schemes of tremorolytic drugs.

Adult↗
PubMed1990

Effect of the antidepressant Org 3770 on human sleep.

The effect of a single dose (30 mg) of Org 3770 (metirzapine) on human sleep was assessed in a double blind, placebo controlled, cross over study in 6 young, healthy male volunteers. The sleep stage classification was based on visual scoring of 24 h electroencephalographic recordings according to the criteria of Rechtschaffen and Kales. Org 3770 30 mg p.o. given 2 h before bedtime had a sleep promoting action in all subjects, resulting in a shortened time to the onset of sleep. Bedtime waking and dozing (Stage 1) were reduced in favour of deep, slow wave sleep (Stages 3 and 4). Org 3770 increased the latency of REM sleep with respect to Stage 2 sleep in all subjects. It also caused a minor reduction in waking periods during REM sleep and a lower frequency of awakenings after periods of movement. No effect of Org 3770 was observed in reaction and vigilance tests on the post treatment day. The observed effects of Org 3770 on normal human sleep suggest that it might ameliorate the sleep disturbances encountered in endogenous depression, which are characterized by a reduction in slow wave sleep, an increase in nighttime awakenings and shortening of REM sleep latency.

Adult↗
PubMed1990

Ambulatory monitoring in sleep apnoea presenting with nocturnal episodic phenomena.

Episodic nocturnal phenomena represent a separate cluster of disturbances within the classification of sleep disorders. The reported case history covers paroxysmal signs occurring secondary to a REM-dependent mixed sleep apnoea syndrome. The pathophysiology of similar episodes in elderly (non)epileptic patients is discussed. Ambulatory monitoring is an appropriate technique for investigation if respiratory and motor activity, and EEG and ECG are recorded simultaneously.

Electrocardiography↗
PubMed1990

Alternative electrode placement in (automatic) sleep scoring (Fpz-Cz/Pz-Oz versus C4-A1).

The purpose of this study is to investigate whether the international standard electrode placement (C4-A1) can be replaced by an alternative placement (Fpz-Cz/Pz-Oz) in an automatic sleep monitoring system without losing Rechtschaffen and Kales (R-K) balances. Single night-sleep polygraphic recordings of 10 patients, screened in a clinical sleep disorder setting, were recorded simultaneously with both placements, and visual sleep classification was performed separately by two independent observers. Interobserver and interplacement agreement were evaluated by way of average (dis)agreement matrices and kappa values computed for overall and individual stage scoring. Interobserver agreement for both the test and the standard electrode placements and interplacement agreement for both observers were assessed as fair to good or excellent. Scoring differences were evaluated by the rank sign test applied to clinical and theoretical difference scores. It appears that the interplacement differences are about equal to the interobserver differences, except for a slight tendency for sleep to be scored in a deeper stage with the proposed alternative placement. The data are presented and discussed in relation to current literature concepts.

Adult↗
PubMed1990

Cholinesterase risk for Iowa farmers.

Exposure to organophosphate insecticides may pose a significant risk in rural populations. The study involved 71 Iowa farmers and 28 agribusiness workers who underwent serial measurements of serum cholinesterase levels prior to and following exposure to organophosphate containing pesticides.

Agricultural Workers' Diseases↗
PubMed1989

A calmodulin-binding peptide relaxes skinned muscle from guinea-pig taenia coli.

During smooth muscle activation the calcium calmodulin complex interacts with myosin light chain kinase (MLCK) whereby activating it. A synthetic peptide analogue (RS20) corresponding to the calmodulin recognition sequence of MLCK has been synthesized and previously found to inhibit the calmodulin stimulated light chain kinase activity. Here we studied the effect of this peptide on skinned fibers from guinea pig taenia coli. Maximal contractions induced by 30 microM Ca2+ at 0.1 microM calmodulin could be completely relaxed by the peptide at 1 microM. The inhibitory effect was accompanied by partial dephosphorylation only of the regulatory myosin light chain. Relaxation could be reversed by addition of calmodulin which also increased the extent of light chain phosphorylation. The calmodulin concentration required for reversing the inhibition depended on the concentration of the inhibitory peptide suggesting that the peptide competed with MLCK for the calmodulin binding site. As the calcium-calmodulin-peptide mixture constitutes a calmodulin buffer, our results suggest, that the peptide is a calmodulin antagonist unique in terms of its potency and that less than nanomolar concentrations of free calmodulin may be required for inducing smooth muscle contractions.

Animals↗
PubMed1989

Actions of parathyroid hormone-related protein on the rat kidney in vivo.

Peptides containing residues 1-34 of parathyroid hormone-related protein (PTHrP) and of bovine parathyroid hormone (bPTH), and recombinant full-length PTHrP(1-141) were infused i.v. into anaesthetized thyroparathyroidectomized rats to compare their action and potency on the renal handling of calcium, phosphate and cyclic AMP (cAMP) in vivo. All three peptides decreased the excretion of calcium and increased the excretion of phosphate and cAMP in the urine, with PTHrP(1-34) and PTHrP(1-141) having virtually equipotent effects. Thus the essential requirements for the major physiological activity of PTHrP on the kidney are contained within the 34 amino-terminal amino acids. For all three peptides, the lowest infusion rate that increased phosphate and cAMP excretion was 0.01 nmol/kg per h, whereas the lowest infusion rate that decreased calcium excretion was 0.025 nmol/kg per h for the PTHrP peptides and 0.1 nmol/kg per h for bPTH(1-34). The response to the PTHrP peptides was maximal at an infusion rate of 0.1 nmol/kg per h for both calcium and phosphate. Since the kidney is either equally sensitive to PTHrP and bPTH(1-34), or more sensitive to PTHrP than to bPTH(1-34), the hypercalcaemia of humoral hypercalcaemia of malignancy may develop because uncontrolled secretion of PTHrP increases the renal reabsorption of calcium to such an extent that even a modest increase in the inflow of calcium into the blood raises plasma calcium concentration.

Animals↗
PubMed1988

[The Stop Snore].

Explore the source record for details and available documents.

Electric Stimulation↗
PubMed1987

A model-based monitor of human sleep stages.

Stochastic models are proposed for sleep and for the sleep related electroencephalogram (EEG), electrooculogram (EOG), and electromyogram (EMG). The evolution of sleep through its various stages is described as a Markov chain. The EEG is modelled using Wiener processes. The EOG and EMG are modelled as combinations of Poisson point processes and Gaussian processes, respectively. The EEG models contain a feedback structure that is based on physiological data. The maximum likelihood sleep stage monitor, that uses the sleep-related observations, has been derived and implemented. The agreement between automatic and human stage classifications of six sleep recordings was 70.6%, which was 4.5% worse than the average agreement between six human classifiers. Monitoring of simulated sleep suggests that the difficulty in separating wakefulness from stage 1 is due to poor modelling. If one ignores this difference, which, from a diagnostic point of view is fairly unimportant, the above mentioned agreement reaches 81.8%, which is 0.5% better than the corresponding average human vs human agreement.

Brain↗
PubMed1987

The flexor carpi radialis H-reflex in polyneuropathy: relations to conduction velocities of the median nerve and the soleus H-reflex latency.

In 80 controls latencies of flexor carpi radialis (FCR) and in 94 controls latencies of soleus H-reflexes correlated well with length of the extremity, body height and age. Multiple regression equations using latency as a variable dependent on age and body height can be best used in practice when both reflexes are employed for demonstration of proximal pathology. The majority (69%) of 93 patients with various polyneuropathies showed abnormalities in both reflexes illustrating that proximal nerve segments are frequently involved. Four per cent had abnormal FCR H-reflexes with normal soleus H-reflexes whereas the reverse was found in 19% of the patients. Abnormal FCR H-reflexes occurred with normal motor and sensory conduction velocities in the peripheral part of the median nerve in 14%, whereas the reverse was seen in 12%, indicating that FCR H-reflex examination is a valuable supplement to conventional conduction studies for detection of electrophysiologically existing pathology.

Action Potentials↗
PubMed1986

An optimal monitor of the rapid-eye-movement brain state.

A model has been proposed for the stochastic occurrence of bursts of rapid eye movements (REMs) during sleep. REM-burst are simulated by a Poisson counting process with a rate that depends on a binary Markov "sleep state". The corresponding maximum likelihood detector, that continuously monitors the current sleep state based on the observed REM-bursts, has been derived and implemented. Simulations show 97% correct decisions.

Brain↗