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Biomedical subjects

J L Willems

Publications and source records attributed to J L Willems.

At least 19 recordsLinked to original sources
PubMed1992

[Distinction between renal and nonrenal hematuria using immunoperoxidase staining of erythrocytes in urine for Tamm-Horsfall protein].

A recently described immunocytochemical staining method to distinguish renal from non-renal haematuria was adapted for use in the standard clinical chemical laboratory. The method is based on the observation that only in case of renal haematuria are erythrocytes in urine coated with so-called Tamm-Horsfall protein, originating from the renal tubuli. Erythrocytes in urine were stained using an indirect immunoperoxidase method, resulting in cells with dark-brown stained surfaces. The staining methods were validated with material from clinically diagnosed cases of haematuria of renal or non-renal origin and compared with scores of the number of dysmorphic erythrocytes, another method to distinguish renal from non-renal haematuria. In specimens of presumed strictly renal haematuria 86% (SD 8.7; n = 26) of the erythrocytes stained immunocytochemically. However, in specimens of haematuria originating from bleeding in the renal pelvis few cells stained (6%; SD 5.8; n = 4). In specimens of purely non-renal haematuria only 13% (SD 13.5; n = 21) stained. Immunocytochemical staining of erythrocytes permitted a much better distinction between renal and non-renal haematuria, with better sensitivity and specificity, than the inspection of erythrocyte morphology. We conclude that immunochemical staining of erythrocytes in urine is a valuable method for distinguishing renal and non-renal haematuria.

Diagnosis, Differential↗
PubMed1992

The conservative coronary angioplasty strategy after thrombolysis for acute myocardial infarction: immediate and short-term results.

The in-hospital and short-term follow-up results of a conservative coronary angioplasty approach in 354 consecutive patients treated after thrombolysis for acute myocardial infarction were compared with results obtained in 408 control noninfarcted patients treated for the classical indication of myocardial ischemia. Only 20% of the study patients underwent angioplasty during the initial hospitalization period and the clinical success rate was 93% versus 95% in the control group (p = NS). No significant differences in the total number of in-hospital untoward events were observed (10.2% and 7.6%, respectively). During a 7.4 +/- 1.5 month follow-up period, the total number of adverse events was only 16.9% in the study patients but it was 27.8% in the control group (p < 0.001). There were no significant differences in death, myocardial infarction, or coronary surgery as individual events, but repeat angioplasty was less frequent in the study group (14.0% versus 21.5%, p < 0.01). Thus in-hospital results in patients undergoing angioplasty on a deferred basis after thrombolysis for myocardial infarction were largely comparable with those results obtained in noninfarcted patients. Moreover, short-term clinical follow-up events were reduced when compared with the control group, an observation apparently largely related to the subgroup without clinical evidence of residual ischemia.

Aged↗
PubMed1992

Assessment of diagnostic ECG results using information and decision theory. Results from the CSE diagnostic study.

Information and decision theory were applied to assess the interpretation results of 15 computer programs (9 electrocardiogram and 6 vectorcardiogram) and 9 cardiologists; 8 of whom analyzed the electrocardiogram and 5 the vectorcardiogram, using a database of 1,220 clinically validated cases. The study demonstrates that information content and utility indices, by providing a comprehensive view of diagnostic performance, can enhance the insight given by the more classic statistical performance measures.

Cardiology↗
PubMed1992

Quantitative assessment of 12-lead ECG synthesis using CAVIAR.

The objective of this study is to assess the performance of patient-specific segment-specific (PSSS) synthesis in QRST complexes using CAVIAR, a new method of the serial comparison for electrocardiograms and vectorcardiograms. A collection of 250 multi-lead recordings from the Common Standards for Quantitative Electrocardiography (CSE) diagnostic pilot study is employed. QRS and ST-T segments are independently synthesized using the PSSS algorithm so that the mean-squared error between the original and estimated waveforms is minimized. CAVIAR compares the recorded and synthesized QRS and ST-T segments and calculates the mean-quadratic deviation as a measure of error. The results of this study indicate that estimated QRS complexes are good representatives of their recorded counterparts, and the integrity of the spatial information is maintained by the PSSS synthesis process. Analysis of the ST-T segments suggests that the deviations between recorded and synthesized waveforms are considerably greater than those associated with the QRS complexes. The poorer performance of the ST-T segments is attributed to magnitude normalization of the spatial loops, low-voltage passages, and noise interference. Using the mean-quadratic deviation and CAVIAR as methods of performance assessment, this study indicates that the PSSS-synthesis algorithm accurately maintains the signal information within the 12-lead electrocardiogram.

Electrocardiography↗
PubMed1992

Neurological aspects of organophosphate poisoning.

Besides their well-known anticholinesterase action resulting in a typical acute cholinergic crisis, organophosphorus (OP) agents are capable of producing several subacute or chronic neurological syndromes. The acute over-stimulation at the neuromuscular junction results in muscle fiber necrosis. The significance of this OP-induced myopathy in human intoxication is unknown. Organophosphate-induced delayed neuropathy (OPIDN) arises 1-3 weeks after exposure to some OP compounds all capable of remarkably inhibiting a distinct esterase called neuropathy target esterase (NTE) during a critical time period. An experimental hen model has been designed to screen new OP compounds as to their delayed neurotoxic effects. The recently described intermediate syndrome emerges 1-4 days after an apparently well-treated cholinergic crisis. It main clinical features are sudden respiratory paralysis, cranial motor nerve palsies, and proximal limb muscle and neck flexor weakness. Whether or not this is a separate entity in OP agent toxicology remains to be seen. Further studies are required to further determine its clinical and paraclinical characteristics and the actual type of underlying neuromuscular dysfunction involved.

Acetylcholine↗
PubMed1992

Are Wistar rats not susceptible to organophosphate-induced delayed neurotoxicity?

Male Wistar rats were sacrificed 12 weeks after single exposure to various organophosphate compounds. Peripheral nerves and skeletal muscles were examined light microscopically for the occurrence of a delayed polyneuropathy. Although unequivocal morphological hallmarks of OPIDN had been demonstrated in other rat strains using similar doses of TOCP or mipafox, we were unable to demonstrate any abnormality with these compounds. Normal findings were also obtained with fenthion, the delayed neuropathic potential of which is debated, and with paraoxon or parathion, which are both highly unlikely to cause OPIDN. These data indicate that the Wistar rat strain is highly likely to be resistant to OPIDN.

Animals↗
PubMed1979

Comparability and reproducibility of apex cardiogram recorded with six different transducer systems.

A comparison was made in 7 dogs of the results obtained by 6 different apex cardiographic transducers applied before, during, and after controlled infusion of angiotensin and isoprenaline. The electrocardiogram, internal phonocardiogram, aortic and left ventricular pressure using a Telco micromanometer, and apex cardiogram were recorded simultaneously on magnetic tape and paper. Digital computer techniques were used to derive various measurements. The comparison of the 6 transducer systems was made expecially with respect to measurements derived from the normalised derivative, calculated using total as well as developed pressure or displacement. Measurements derived from left ventricular pressure were very reproducible. Differences in results of 'contractility' indices varied between 0.5 and 1.9 per cent. Indices from the apex cardiogram using 6 different transducer systems showed variations up to 20 per cent, with mean values varying between 3.2 and 8.1 per cent. There was a systematic deviation for one transducer system, which was responsible for a significant part of the observed variability. It may be concluded that in order to assure maximal reproducibility, technical characteristics of the apex cardiograph transducer should be taken into account and an optimal recording technique should be used.

Angiotensins↗
PubMed1978

Hypotension produced by intravenous apomorphine in the anaesthetized dog is not centrally mediated.

1 Intravenous administration of apomorphine (1.25 to 20 microgram/kg) in the anaesthetized dog produced a dose-dependent decrease in blood pressure which was antagonized by haloperidol but not influenced by propranolol or atropine. 2 Intracarotid administration of apomorphine produced a systemic hypotension which was significantly smaller than that seen with intravenous injection. 3 Doses of apomorphine that caused a decrease in blood pressure on intravenous injection, had no effect on blood pressure or caused retching accompanied by an increase in blood pressure on intravertebral or intracisternal administration. The animals showed a marked hypotension on intravertebral or intracisternal injection of clonidine. 4 From these results it is concluded that the hypotension seen with intravenous apomorphine cannot be explained by a central site of action.

Animals↗