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Biomedical subjects

A Johnsen

Publications and source records attributed to A Johnsen.

At least 37 records · Page 2Linked to original sources
PubMed1991

Diagnostic value of spinal computer tomography in patients with intraspinal metastases causing complete block on myelography.

The value of post-myelographic spinal computer tomography (CT) was evaluated in cancer patients with spinal metastases causing complete myelographic block. In 22 out of 25 lumbar myelographies (88%) showing complete blockade, sufficient contrast medium had leaked proximally to allow determination of the cranial limit of the metastasis on the CT-scan. It is concluded that the post-myelographic spinal CT can replace a supplementary cervical myelography in the majority of patients with epidural metastasis, causing a complete myelographic block.

Epidural Neoplasms↗
PubMed1990

Requirements for drug monitoring of verapamil: experience from an unselected group of patients with cardiovascular disease.

Serum verapamil and metabolite concentrations were determined by HPLC in 29 patients in routine treatment with verapamil, and 23 were in steady state. Dosage levels and corresponding mean trough levels (+/- S.D.) were as follows: 120 mg daily: 79.1 (+/- 77) nmol/l, 240 mg daily: 173.3 (+/- 200.1) nmol/l, 360 mg daily: 204 (+/- 110.2) nmol/l and 480 mg daily: 361.0 (+/- 231.4) nmol/l. The variation coefficients were 97.3, 115.4, 54.0, and 62.1, respectively, thus showing considerable interpatient variation. Repeated determination of trough levels showed, in contrast, only small intrapatient variation (variation coefficient 35.8, 1.9, and 7.4, at the dosage levels 120, 240 and 340 mg per day). No significant correlation was found between serum verapamil levels age, sex, or weight. No significant effect of digoxin on the concentration of serum verapamil was found. No relation was observed between serum verapamil concentrations and desired effect or side-effects. Two patients showed no measurable serum verapamil, but one of these had detectable levels of metabolites. Such patients may represent subgroups of fast metabolizers or non-absorbers. Measurements of the metabolites nor-verapamil, D 620 and D 617 indicated saturation of the first-pass metabolism. In conclusion, therapeutic drug monitoring is not indicated during routine verapamil treatment, whereas single measurements of verapamil may be warranted in patients not responding to treatment in order to identify fast metabolizers or non-absorbers.

Adult↗
PubMed1989

Experimental studies of the influence of vigabatrin on the GABA system.

1. Studies of the influence of clinically relevant concentrations of vigabatrin on GABA-transaminase and on the release of endogenous GABA were performed in selectively cultured astrocytes and neurons. In addition, the two stereoisomers of vigabatrin were investigated separately. 2. The results indicated a preferential inhibition of neuronal GABA-transaminase by vigabatrin. 3. Only the (S)-form of vigabatrin seems to inhibit GABA-transaminase. This finding corresponds to observations in epileptic animals that the (R)-form exhibits no anticonvulsant effect. 4. Resynthesis of GABA-transaminase, following withdrawal of vigabatrin showed that maximum enzyme activity was obtained within 6 days. This finding corresponds to the persistent effect after withdrawal of the drug in patients, observed in clinical trials. 5. At a concentration of 25 microM, vigabatrin caused a significant increase in the release of endogenous GABA from cultured GABAergic neurons. Although no data on brain levels of the drugs are currently available, judging from vigabatrin blood concentrations in man and from information of brain levels in animals, following chronic treatment, it is conceivable that a sufficiently high concentration of the drug in human brain is obtained to augment GABA release.

4-Aminobutyrate Transaminase↗
PubMed1989

Cerebral computed tomography in paroxysmal atrial fibrillation.

Atrial fibrillation (AF) is associated with an increased risk of stroke. In patients with chronic AF, without clinically known cerebrovascular disease, computed tomography (CT) has revealed a high frequency of abnormal low-density areas suggesting old asymptomatic infarcts. To investigate the frequency of such lesions in paroxysmal AF, 30 patients with paroxysmal AF and 30 controls matched in sinus rhythm, without history of cerebrovascular disease, were CT scanned. Four patients with paroxysmal AF (13%) and 3 controls (10%) had abnormal CT scans with areas of low density with sharp demarcation from surrounding tissue. The abnormal areas probably reflected small, clinically silent infarcts. There were no differences between paroxysmal AF and controls in number and size of abnormal areas with apparent tissue loss. In contrast to chronic AF, the risk of such lesions in paroxysmal AF does not seem to be increased compared with matched sinus rhythm controls. This is in agreement with the clinical experience of a low risk of stroke in paroxysmal AF.

Adult↗
PubMed1988

Hemoglobin hafnia: alpha 2 (beta 116 (G18) His----Gln)2; a new hemoglobin variant mistaken for glycated hemoglobin.

Isoelectric focusing of hemolysate from patients with diabetes mellitus is routinely performed to measure their level of HbA1c (glycated hemoglobin). For a 6 year old boy with diabetes mellitus this analysis showed an HbA1c fraction of approx. 50%, which is very unlikely to occur. The possibility of a hemoglobin variant was considered, and by HPLC-separation the presence of two different beta-chains was shown. One tryptic fragment was found to deviate from the normal, and amino-acid analysis and sequence determination revealed the following amino-acid substitution: beta 116 His----Gln. It is the first reported mutation at this position. Functional studies showed almost normal behaviour, consistent with the fact that the affected persons are without any symptoms. In a family survey we found five nondiabetic members with an abnormality similar to the proband. For the variant we chose the name Hafnia, which is Latin for Copenhagen.

Amino Acid Sequence↗
PubMed1988

Neuropeptide Y in guinea pig, rabbit, rat and man. Identical amino acid sequence and oxidation of methionine-17.

Neuropeptide Y (NPY) was isolated and characterised from acid-ethanol extracts of rabbit and guinea pig brain. In both instances the chromatographic purification was a two-step procedure of gel filtration followed by reverse-phase high-performance liquid chromatography. The amino acid sequence of rabbit and guinea pig NPY was found to be identical to human and rat NPY as deduced from the cDNA structures. With the exception of the porcine peptide, all mammalian NPYs characterised to date have a methionine residue in position 17. This methionine residue is readily oxidized as indicated by the high degree of spontaneous oxidation of peptides found in the rabbit and guinea pig brain extracts and in NPY extracted from a rat phaeochromocytoma cell line. It is concluded that NPY is among the most highly conserved peptides and that NPYs containing methionine in position 17 are prone to oxidation.

Amino Acid Sequence↗
PubMed1986

Balloon-dilatation of esophageal strictures in children.

Dilatation of benign esophageal strictures by means of a balloon-catheter is a well-established procedure in adults. This method is also useful in children. The technique is described and the results of treatment in 10 children are reported. In all our patients the stricture developed after an operation for esophageal atresia with an end-to-end anastomosis. Dilatation with a balloon-catheter seems to have the same or an even better effect than the traditional dilatation with bougies. Complications following balloon-dilatations have been few and negligible in this series and dilatations can be performed using sedation instead of general anaesthesia. Therefore, this method is recommended.

Child, Preschool↗
PubMed1986

Hippuran renography and scintigraphy in children with myelomeningocele.

Long-term surveillance of the urinary tract is necessary in children with myelomeningocele and neurogenic bladder dysfunction. The results of Hippuran renography and scintigraphy were analyzed in 52 cases and compared to those of intravenous urography. In addition the radionuclide evaluation was correlated to the clinical course. It was concluded that renography is a suitable examination for the monitoring of the kidneys and upper urinary tract in these children. A decrease of renal function and drainage may occur without any changes of the clinical state.

Child↗
PubMed1985

The prognosis of surgically treated congenital hydronephrosis after diagnosis in utero.

Nine patients with a prenatal ultrasonic diagnosis of unilateral ureteropelvic junction obstruction underwent pyeloplasty in early neonatal life. Based on radiological and renographical assessment of the results, immediate postnatal intervention had no demonstrable advantage over those subjects in a control group who underwent an operation after presenting with symptoms. Half of the children in both groups had normal parenchymal function of the hydronephrotic kidney. Because of the operative complications we found it unacceptable to operate on neonates without symptoms and with normal function of the affected kidney. The advantage of prenatal diagnosis lies in the early recognition of the necessity of close surveillance. The primary indications for surgical intervention should be symptoms and impairment of the hydronephrotic kidney function.

Child↗
PubMed1984

Bronchopleural leakage treated with fibrin sealant and high-frequency positive-pressure ventilation.

In a 62-year-old man, left spontaneous pneumothorax appeared 14 days after right pneumonectomy. The large air leakage necessitated thoracotomy and resection of a bullous area in the left upper lobe. Pleurectomy was not performed. The air leakage continued for 14 more days until, at a second left thoracotomy, numerous bullae were oversewn and covered with fibrin sealant. High-frequency positive-pressure ventilation (90 respirations/min, 21 l/min) was used for the following 6 hours. After 18 hours there was no more air leakage during spontaneous ventilation and the patient made a good recovery.

Drug Combinations↗