PubMed Health⌕ Search

Biomedical subjects

B van Dijk

Publications and source records attributed to B van Dijk.

At least 19 recordsLinked to original sources
PubMed2005

Normative findings of electrically evoked compound action potential measurements using the neural response telemetry of the Nucleus CI24M cochlear implant system.

One hundred and forty-seven adult recipients of the Nucleus 24 cochlear implant system, from 13 different European countries, were tested using neural response telemetry to measure the electrically evoked compound action potential (ECAP), according to a standardised postoperative measurement procedure. Recordings were obtained in 96% of these subjects with this standardised procedure. The group results are presented in terms of peak amplitude and latency, slope of the amplitude growth function and ECAP threshold. The effects of aetiological factors and the duration of deafness on the ECAP were also studied. While large intersubject variability and intrasubject variability (across electrodes) were found, results fell within a consistent pattern and a normative range of peak amplitudes and latencies was established. The aetiological factors had little effect on the ECAP characteristics. However, age affected ECAP amplitude and slope of the amplitude growth function significantly; i.e., the amplitude is higher in the lowest age category (15-30 years). Principal component analysis of the ECAP thresholds shows that the thresholds across 5 electrodes can be described by two factors accounting for 92% of the total variance. The two factors represent the overall level of the threshold profiles ('shift') and their slopes across the electrode array ('tilt'). Correlation between these two factors and the same factors describing the T- and C-levels appeared to be moderate, in the range of 0.5-0.6.

Action Potentials↗
PubMed2001

Alcohol dehydrogenase type 3 (ADH3) and the risk of bladder cancer.

OBJECTIVES: The polymorphic enzyme alcohol dehydrogenase (ADH) catalyses the conversion of ethanol into the carcinogenic metabolite acetaldehyde which is partly excreted into the urine. Objectives of this pilot study are to determine whether this polymorphism may be related to bladder cancer and whether it modifies the relation between alcohol intake and bladder cancer. METHODS: 120 bladder cancer patients and 133 convenience controls were recruited at the University Medical Centre Nijmegen. A self-administered questionnaire was used to assess alcohol intake and potential confounders. DNA was isolated from peripheral blood, and ADH3 genotype was determined using PCR/RFLP. People with the ADH3 genotype gamma1gamma1 were compared to people with other ADH3 genotypes. Above moderate drinkers (>14 glasses of alcohol per week) were compared to moderate drinkers. Odds ratios (ORs) and 95% confidence intervals were computed using logistic regression analyses. RESULTS: After correction for sex, age and smoking, ORs for ADH3 genotype and alcohol intake were 2.10 (1.05-4.22) and 1.21 (0.60-2.44), respectively. Moderate drinkers with the 'high-risk' (gamma1gamma1) ADH3 genotype appeared to have a threefold higher risk of bladder cancer compared to moderate drinkers with a 'low-risk' (gamma1gamma2 or gamma2gamma2) genotype. Surprisingly, the ORs for above moderate drinkers with the low-risk genotype (1.95; 95% CI: 0.85-4.48) and with the high-risk genotype (2.18; 95% CI: 0.82-5.77) were almost similar, suggesting no interaction. CONCLUSIONS: ADH3 genotype is a possible risk factor for bladder cancer. Although moderate drinkers with the gamma1gamma1 genotype seem to have the highest risk, we did not get a clear indication that ADH3 genotype modifies the relationship between alcohol intake and bladder cancer.

Aged↗
PubMed1998

How to avoid underdiagnosed asthma/chronic obstructive pulmonary disease?

The prevalence of asthma and chronic obstructive pulmonary disease (COPD) is rising in most countries, including The Netherlands. It has been suggested that a majority of these cases of (self-reported) symptoms related to asthma/COPD are not diagnosed in general practice. We compared a population screening for underdiagnosed asthma/COPD with a high-risk approach by a questionnaire form with specified questions about asthma/COPD-related symptoms. A case-controlled study including a record review was performed of cases and controls. The results of a population screening were used to classify patients as (a) asthma/COPD, (b) at risk for asthma/COPD, or (c) no asthma/COPD. Eleven hundred fifty-five patients were screened. One hundred fifty-five patients reported previous asthma/COPD-related care (cases). The difference between number of cases and controls in asthma/COPD diagnosis was chosen as main outcome measure. The population screening revealed 85 subjects with a diagnosis of asthma/COPD and 154 subjects with an increased risk. Nineteen diagnoses could be made in cases, and eight diagnoses in controls. The chart review showed that only seven cases and two controls were known to the general practitioner. From this study it can be concluded that in order to reduce the number of un- and underdiagnosed patients, all listed patients in general practice should be screened. However, if screening of all patients is not feasible, active case finding by asking a few questions about shortness of breath or wheezing to all patients in the group of listed individuals is recommended.

Adult↗
PubMed1992

The interaction of Trypanosoma congolense and Haemonchus contortus infections in trypanotolerant N'Dama cattle.

The interactions between Trypanosoma congolense and Haemonchus contortus infections were studied in N'Dama calves. A total of 38 N'Dama bulls was divided into four groups and each group infected either with H. contortus 1 week after infection with T. congolense or with T. congolense 4 weeks after infection with H. contortus, or with either infection singly. Parasitological (faecal egg counts, parasitaemia), haematological (packed cell volume, white blood cell counts, albumin) and clinical parameters (body weight change, mortality rate) were compared among the various groups. The results showed a reduced prepatent period and a markedly increased pathogenicity of H. contortus infections in animals with a concurrent T. congolense infection. The most harmful combination was a H. contortus infection 1 week after the T. congolense infection which resulted in a progressive and severe anaemia, accompanied by hypoalbuminaemia, increased weight loss and high mortality. The anaemia induced by dual infections showed a low responsiveness to chemotherapy and in several cases supportive treatment did not help recovery. The results also showed that animals with a concurrent T. congolense and H. contortus infection ran a higher risk of succumbing during the infection, and also during 10 weeks following treatment. Although infections with T. congolense alone produced no clinical signs, they were found to significantly reduce the ability of infected animals to mount a normal response to a subsequent H. contortus infection. It was concluded that the increased H. contortus egg excretion observed in animals infected with both parasites might significantly increase the risk of nematode infections and that the reduced prepatent period might necessitate more frequent anthelmintic treatments. These interactions should, therefore, be considered wherever attempts are made to control these two diseases.

Animals↗
PubMed1991

[Epileptic insult developing immediately following administration of propofol].

This article describes the occurrence of an epileptic insult immediately after the intravenous bolus administration of 200 mg propofol (Diprivan) in a healthy patient with no medical history of epilepsy or other neurological diseases. Extensive neurological examinations including EEG and CT scan did not reveal any abnormalities. We want to emphasise that even in the absence of neurological disorders propofol may induce an instantaneous epileptic insult.

Adult↗
PubMed1989

[Respiratory depression following controlled-release morphine sulfate tablets].

Controlled release morphine sulfate (MS Contin) is a relatively new oral preparation for the relief of chronic severe (cancer) pain. We describe a patient with severe neuralgia who experienced respiratory depression after ingestion of one single dose of morphine sulfate (20 mg). Administration of nalorphine chloride resulted in instant normalisation of respiratory function. This case illustrates respiratory depression as an adverse effect of MS Contin.

Aged↗
PubMed1989

Topography and homogeneity of monkey V1 studied through subdurally recorded pattern-evoked potentials.

Using small checkerboard stimulus fields, we have recorded visually evoked potentials (VEPs) in an alert rhesus monkey from an array of 35 electrodes chronically implanted between dura and arachnoid to study mass neuronal activity in striate and peristriate visual cortex. Although the principal purpose of this work was to study in detail cortical mapping in this particular animal for future intracortical recordings, we report here the usefulness of our approach for the non-invasive study of cortical processing, in particular of cortical magnification and receptive-field properties over the central 6 degrees of the visual field. The striate and extrastriate components in the pattern onset VEP both have a double negative-going waveform, with N-P-N peak latencies of 75-100-135 ms and 90-115-160 ms, respectively, for small element sizes and moderate contrasts; latencies may be 5 ms shorter for large element sizes and high contrast. We found little activity at electrode locations over visual areas beyond V2. The waveforms and timing permit some careful speculation concerning intracortical processing and VEP generation. The complex logarithmic form of the retinotopical projection provides a satisfactory model for our data, if a value of 1-1.2 degrees is used for the offset parameter a. Our data suggest that the most abundant receptive-field size in foveal striate cortex has a center diameter of 12'. This size remains constant up to 2 degrees eccentricity, and increases only slowly up to 4 degrees. The smallest receptive-field sizes seem to be independent of eccentricity throughout the central 4 degrees of V1, with a value of 4-8', in agreement with single-cell data reported by Dow et al. (1981) and Van Essen et al. (1984).

Animals↗
PubMed1988

Length-tension curves of human eye muscles during succinylcholine-induced contraction.

We have made intraoperative, continuous-registration, length-tension diagrams of detached eye muscles in 80 strabismus patients under general anaesthesia. In 47 of these we repeated the measurements after contraction evoked by succinylcholine chloride. In contracting horizontal and vertical rectus muscles, we found a linear relation between length and tension. In contracting oblique muscles, however, the relation between length and tension was frequently nonlinear. In superior oblique palsies, the superior oblique was found to be stiff after elongation and before injection of succinylcholine, and it did not contract after injection of succinylcholine. The ipsilateral inferior oblique did contract after injection of succinylcholine, but with a higher spring constant than usual (ie, contracture of the ipsilateral antagonist). In three cases the superior oblique contracted vividly after administration of succinylcholine despite the presence of excyclotropia, stereopsis, torticollis (two cases) and a hypertropia that increased in adduction, in down-gaze, in adduction and down-gaze and on ipsilateral head-tilt. In a case of general fibrosis syndrom we found almost normally contracting vertical recti, which is compatible only with a supranuclear or misdirectional cause. These cases demonstrate the usefulness of the assessment of the length-tension diagram of an eye muscle during surgery, before and during contraction evoked by succinylcholine chloride.

Humans↗
PubMed1987

Analysis of the dosage controversy in recess-resect and Faden surgery with the Robinson computer model of eye movements.

In recess-resect surgery, the dosage depends on the preoperative angle of squint and on the ratio between squint-angle reduction and dosage that the surgeon has found in previous surgery. Recommendations pertaining to this ratio vary widely among authors. Some say a recession does more than a resection, while others believe the opposite is true. Finally, most find a lower ratio at smaller preoperative angles of squint. We investigated the matter, using our modified version of the Robinson computer model of eye movements. We calculated the amounts of surgery needed to reduce 10, 15, 20, 25, and 30 degree angles of squint to zero. The increase of the ratio at large angles of squint was indeed predicted by the model. The decrease at small angles of squint, however, was not predicted by the model. We found it impossible to model the decrease of the ratio at small preoperative angles of squint. The ratios for recess and resect surgery were approximately similar. We present an inventory of the possible causes of the discrepancies. In addition, we calculated the effects of Faden surgery and found that the predictions of the computer model correspond closely to reality.

Computers↗
PubMed1986

Intraoperative length and tension curves of human eye muscles. Including stiffness in passive horizontal eye movement in awake volunteers.

Intraoperative continuous-registration length and tension curves of attached and detached eye muscles were made in 18 strabismic patients under general anesthesia. For relaxed eye muscles, we found an exponential relation between length and tension. An increased stiffness was quantified in Duane's syndrome, Graves' disease, orbital-floor fracture, and superior oblique palsy. The stiffnesses of agonist and antagonist were remarkably similar, not only in uncomplicated squint, but also when only one of the two had initially become stiffer. After intravenous administration of succinylcholine chloride, the eye muscles contracted, and the exponential length and tension curve changed into a set of straight, parallel lines. In addition, we measured stiffness in passive horizontal eye movement in awake volunteers and found 0.52 to 1.26 g/degrees (other eye in 5 degrees of adduction), confirming other published results.

Adult↗
PubMed1980

A rapid method of determining serum levels of etomidate by gas chromatography with the aid of a nitrogen detector.

A rapid method of measuring etomidate in serum is described which is suitable for the determination of serum levels during and after surgical procedures. Etomidate with the added internal standard propoxate is extracted from serum using a hexane/ether mixture. The organic layer is evaporated and the residue dissolved in acetone and injected into an OV-17 column at 220 degrees C. Resulting concentrations are linear between 0.05 and 2.0 microgram/ml serum. There is 90% recovery and the detection limit is 0.03 microgram/ml. The other drugs normally present do not interfere with the estimation. Estimations can be carried out on 20 blood samples by one person with 3 hours.

Chromatography, Gas↗
PubMed1979

A hemoperfusion column based on activated carbon granules coated with an ultrathin membrane of cellulose acetate.

A hemoperfusion system has been developed which makes use of activated carbon encapsulated with cellulose acetate. Studies have revealed that there are no stagnant flow regions in the column, there is minimal particle release and the coating is 30 A thick. The relationships between pore size, pore volume and surface area have been examined. Twenty-five patients in grade IV coma have been treated with the column for treatment of drug overdose or agricultural chemical poisoning; the clinical course of one meprobamate-poisoned patient is described in detail.

Acetates↗
PubMed1979

Etomidate-fentanyl-air anesthesia.

In 463 patients the total intravenous anesthesia technique was applied, for which sleep was induced with etomidate and analgesia was obtained with fentanyl. This technique, which prevents pollution of the air, appeared to be easily applicable and without major complications in either spontaneously breathing or ventilated patients.

Adolescent↗