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Biomedical subjects

M Thelen

Publications and source records attributed to M Thelen.

At least 325 records · Page 18Linked to original sources
PubMed1988

Percutaneous transhepatic biliary drainage: experience with 311 procedures.

Percutaneous biliary drainage was performed in 296 patients on 311 occasions using a fine-needle puncture technique. In 59%, the procedure served as postoperative decompression, and in 35% for palliation of obstruction, particularly in malignant disease. Postoperative drainage for the management of postoperative complication accounted for 2.5%. In more than 80% of the patients treated, the underlying disease was malignant obstructive jaundice. In 257 retrospectively evaluated patients the following complications were observed: cholangitis (6.6%), sepsis (3.1%), bile leakage (1.6%) with two deaths (0.7%), and subcapsular hematoma and hematoma in the hepatoduodenal ligament (1.2%). Catheter dislocations accounted for 8.5% and were eliminated by the use of self-retaining catheters. In 51 prospectively studied patients pain was encountered in 55% and cholangitis in 11.8%. The procedure is most valuable for complicated biliary obstruction, palliative drainage, and endobiliary manipulations.

Biliary Tract Neoplasms↗
PubMed1988

[Diagnostic value of sonography and computed tomography in liver metastases].

The diagnostic accuracy of sonography and computed tomography for detecting liver metastases was analysed in 526 patients with tumors and the findings were compared with those at laparotomy and at post mortem. The surgical protocols were analysed in respect of the primary tumour, the frequency of metastases and the number, localisation and size of metastases. A comparison of sonography and CT showed a higher sensitivity for CT (57.1%) compared with sonography (52.3%) although specificity was slightly higher for sonography. Liver metastases greater than 15 mm were detected by sonography (80.5%) and CT (92%), with much higher sensitivity. CT also proved superior, since the results depended less on the size, number and localisation of the deposits and on the primary tumor than did sonography.

Humans↗
PubMed1988

[Oncocytoma of the kidney. 1. Computed tomography].

The computer tomograms of 22 patients with renal oncocytomas were analysed retrospectively. Characteristic findings were: 1. solid round space-occupying lesions (22/22), 2. sharp demarcation from the kidney (20/22), 3. smooth margin (20/22), 4. hypodensity after intravenous contrast (20/20), 5. enhancement (19/19), 6. central hypodense nidus (16/22), 7. homogeneous beyond the nidus (11/22). In the presence of these criteria, the diagnosis of an oncocytoma may be suspected. Safe differentiation from a renal cell carcinoma may not always be possible.

Adenoma↗
PubMed1988

[Oncocytoma of the kidney. II. Angiography].

The angiographic findings in ten patients with renal oncocytoma are described. Characteristic features include: absence of encasement, vascular occlusions, arterio-venous shunts and contrast lakes (8/10). Spoke-wheel arrangement of tumor vessels (8/10). Homogeneous tumour contrast during the capillary phase (7/10). Sharp demarcation from the kidney and surroundings (9/10) and a peritumoral halo (4/10). If the suspicion of an oncocytoma is raised by CT examination of a space-occupying lesion (part I), angiography should be performed to confirm the diagnosis and help in planning surgical treatment.

Adenoma↗
PubMed1988

[Percutaneous transhepatic fine-caliber cholangioscopy].

Percutaneous transhepatic fine calibre cholangioscopy is described. A specially developed transparent instrument is used, which makes it unnecessary to have a steerable endoscope; visualisation of the biliary tree is of diagnostic value for assessing biliary stenoses due to tumours (choice of biopsy site, extent of intraductal radiation therapy) and for the assessment of anastomoses between the biliary system and the gut (condition of the mucosa, stenoses). In the presence of percutaneous biliary drainage, the method has little utility. Extension of the method for treating intraductal stones may be possible if in future a useful lumen can be added to the fine endoscope.

Aged↗
PubMed1988

[Malignant fibrous histiocytoma].

Malignant fibrous histiozytoma (MHF) is a pleomorphic sarcoma of ubiquituous origin. The clinical and radiological features of the tumor are illustrated by 23 patients with MFH of soft tissue and 4 MFH of bone. On conventional radiography MFH appears as a soft tissue tumor, sometimes with bone involvement; on sonography it is usually non-homogeneous and hypoechogenic with areas of necrosis. On CT the masses are homogeneous or inhomogeneous (10-60 HU.) containing areas of decreased density. Contrast enhancement was about 10-20 HU. Angiographically the tumor appears as hypo- or hypervascular with pathologic vessels. The morphology of MFH in diagnostic imaging including magnetic resonance tomography is discussed with the relevant literature.

Adolescent↗
PubMed1988

[Preoperative localization of pathologic findings in mammography].

Pre-operative localization of abnormal findings during mammography makes it easier to find the lesions if they are not palpable. Our study is based on 373 procedures, using a "harpoon" needle. Radiographs of the operative specimen showed that 66% of the lesions had been completely removed, 15% had been partially removed and 19% could not be identified unequivocally. 172 patients had subsequent mammograms. Amongst these, the lesion had been completely removed in 70%, partially removed in 14% and in 10% it was still present. In 62% dense scar formation made it impossible to be certain whether excision had been complete.

Biopsy, Needle↗
PubMed1988

Synthesis and expression in Escherichia coli of the gene encoding monocyte-derived neutrophil-activating factor: biological equivalence between natural and recombinant neutrophil-activating factor.

The neutrophil-activating factor (NAF) purified from the conditioned medium of lipopolysaccharide-stimulated human monocytes was sequenced and found to consist of 72 amino acids: SAKELRCQCIKTYSKPFHPKFIKELRVIESGPHCANTEIIVKLSDGRELCLDPKENWVQRVVEKFLKRA ENS. Purified preparations of natural NAF contained, in addition to this main form, minor amounts of three amino-terminal variants with 77 (+AVLPR), 70, and 69 residues. A gene coding for the 72-amino acid NAF was synthesized, cloned, and expressed in Escherichia coli. Western (immunologic) blot analysis of crude bacterial extracts, with an antiserum raised against natural NAF, revealed a single band that comigrated with natural NAF. Recombinant NAF purified to homogeneity had identical amino- and carboxyl-terminal sequences to the 72-amino acid natural NAF. Recombinant NAF was tested on human neutrophils and had the same activity and potency as natural NAF in inducing chemotaxis, rapidly increasing cytosolic free Ca2+, activating the respiratory burst, and releasing specific and azurophilic granular contents.

Amino Acid Sequence↗
PubMed1988

Does velocity of dilatation influence the result of dilatation? A postmortem study.

We evaluated the influence of velocity of dilatation on the success of and the vascular damage produced by dilatation. Nonatheroslerotic segments of distal superficial femoral arteries were dilated "fast" (n = 69) or "slow" (n = 45) under standard conditions with balloon catheters. The arterial wall was overstretched between 1% and more than 60%. The success of dilatation rose continuously with increasing overstretching during dilatation. The damage to the arterial wall by dilatation increased discontinuously with increasing overstretching. Dilatation success and damage patterns did not differ in the "slow" and "fast" groups.

Angioplasty, Balloon↗
PubMed1988

Tissue characterization with T1, T2, and proton density values: results in 160 patients with brain tumors.

A method by which the tissue parameters - T1, T2, and proton density - can be measured simultaneously was used in 160 patients with brain tumors to test the complete potential of magnetic resonance (MR) imaging for quantitative tissue characterization. MR tissue parameters of a wide variety of tumors, edema, white matter, and gray matter were determined. While normal brain tissues showed only small interindividual variations of tissue parameters, pathologic entities (tumor, edema) were characterized by wide ranges of T1, T2, and proton density values. The considerable overlapping of tissue parameters in different tumor entities, which were analyzed in a three-dimensional T1/T2/proton density space, indicates that a reliable diagnosis cannot be made on the basis of a quantitative evaluation of T1, T2, and proton density alone.

Adult↗
PubMed1988

Activation of monocytes by interferon-gamma has no effect on the level or affinity of the nicotinamide adenine dinucleotide-phosphate oxidase and on agonist-dependent superoxide formation.

Human monocytes purified by elutriation were cultured for 3 d in Teflon bags with or without human recombinant interferon-gamma (rIFN gamma). The cells were then collected and used in suspension to determine the rate of stimulus-dependent superoxide or hydrogen peroxide formation as a measure of the NADPH-oxidase. The treatment with IFN gamma increased this rate two- to threefold when phorbol myristate acetate (PMA) was used as the stimulus. By contrast, no IFN gamma-dependent increase in superoxide production was observed when the cells were stimulated with different concentrations of the receptor agonist N-formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe) alone or in combination with another receptor agonist, platelet-activating factor (PAF). At optimum concentrations, f-Met-Leu-Phe elicited rates of superoxide formation that could not be exceeded under other stimulatory conditions including PMA after treatment with IFN gamma. It thus appears that f-Met-Leu-Phe can lead to maximum activation of the NADPH-oxidase, and that this response is not influenced by IFN gamma. Treatment with IFN gamma also failed to affect the affinity of PMA- or f-Met-Leu-Phe-stimulated oxidase for NADPH, the Km values being 30 to 40 microM under all conditions. IFN gamma did not alter the cellular levels of cytochrome b558, as measured by low-temperature spectroscopy, and protein kinase C, as measured by [3H]phorbol dibutyrate binding, and did not appreciably influence the stimulus-dependent increase of cytosolic free calcium. These results indicate that activation of human mononuclear phagocytes by IFN gamma does not affect the level and the kinetic properties of NADPH-oxidase or its activation by receptor agonists. They confirm, however, that IFN gamma enhances the respiratory burst response to PMA.

Calcium↗
PubMed1988

Mechanism of neutrophil activation by NAF, a novel monocyte-derived peptide agonist.

The rise in cytosolic free Ca2+, shape change, superoxide formation, and granule exocytosis induced in human neutrophils by N-formyl-Met-Leu-Phe (fMLP) and by a newly discovered activating peptide, neutrophil-activating factor, termed NAF, were compared. NAF was effective in the concentration range of 0.1-10 nM and was 10- to 100-fold more potent than fMLP. In qualitative terms, the single responses to either stimulus were remarkably similar: they showed virtually identical onset and initial kinetics, and were all inhibited by pretreatment of the neutrophils with Bordetella pertussis toxin. In addition, the respiratory burst elicited by either stimulus was inhibited by 17-hydroxywortmannin and staurosporine. Two conclusions are drawn from these results: 1) neutrophil activation by NAF (as by fMLP) is dependent on a GTP-binding protein and on protein kinase C; 2) a similar, or even identical, mechanism of signal transduction must be assumed on stimulation of human neutrophils with NAF, fMLP, and other chemotactic agonists. Human monocytes, lymphocytes, and platelets did not show cytosolic free Ca2+ changes when exposed to NAF, which suggests that NAF is selective for the neutrophils.

Aminoquinolines↗
PubMed1988

[Evaluating computerized tomography and other procedures].

In computed tomography (CT) an object is scanned with X-rays from different angles. The digitally recorded data of the absorption values or profiles are used in a mathematical algorithm to reconstruct an image, which is then converted into an gray-scale image for reproduction. CT imaging replaces various modalities that give less sufficient information. It is safe, without risk, painless, faster and more cost efficient. CT reduces costs by 30 to 50%; the amount of cost reduction can be verified.

Evaluation Studies as Topic↗
PubMed1988

[Intra-arterial flow phenomena in spin echo procedures of magnetic resonance imaging and in transesophageal 2-dimensional echocardio- graphy].

In 10 pts. with mitral valve lesions dense spontaneous echographic contrast was found within the left atrium by transoesophageal echocardiography. Because of the neurologic symptoms some of the patients also had (transitoric ischemic attacks, embolism) left atrial thrombosis was suspected. The echographic phenomenon of spontaneous left atrial contrast was further examined by magnetic resonance imaging in all 10 pts. Using the spin-echo-mode the multi-echo-imaging showed dense signals in the second echo and no or few left atrial signals in the first echo in 8/10 pts. In 2/10 pts. there were no increased signals in left atrium. The missing presence of the increased signals in the first echo excluded thrombosis of the left atrium and proved blood flow effects.

Adult↗