Biomedical subjects

M Thelen

Publications and source records attributed to M Thelen.

At least 19 recordsLinked to original sources

PubMed1992

MARCKS is an actin filament crosslinking protein regulated by protein kinase C and calcium-calmodulin.

AGONISTS that stimulate protein kinase C (PKC) induce profound changes in cell morphology correlating with the reorganization of submembranous actin, but no direct connection between PKC and actin assembly has been identified. The myristoylated, alanine-rich C kinase substrate (MARCKS) binds calmodulin and is a predominant, specific substrate of PKC which is phosphorylated during macrophage and neutrophil activation , growth factor-dependent mitogenesis and neurosecretion; it is redistributed from plasma membrane to cytoplasm when phosphorylated and is involved in leukocyte motility. Here we report that MARCKS is a filamentous (F) actin crosslinking protein, with activity that is inhibited by PKC-mediated phosphorylation and by binding to calcium-calmodulin. MARCKS may be a regulated crossbridge between actin and the plasma membrane, and modulation of the actin crosslinking activity of the MARCKS protein by calmodulin and phosphorylation represents a potential convergence of the calcium-calmodulin and PKC signal transduction pathways in the regulation of the actin cytoskeleton.

Actin Cytoskeleton↗

PubMed1992

[Ultrasound-proven adrenal gland tumor. References for diagnostic management].

Due to the increasing number of ultrasonographic examinations, tumors of the adrenal glands are being detected more and more often. In the present paper, suggestions for the further diagnostic evaluation are made: in the case of sonographically detected solid tumors of the adrenals, computed tomography is the next procedure of choice. If CT scan also fails to enable an unequivocal diagnosis, the next step must be laboratory investigations. Hormone-producing tumors, irrespective of size, as well as non-hormone-producing tumors larger than 6 cm in diameter or symptomatic neoplasms are all treated by surgery. In the case of an oncological patient with an asymptomatic non-hormone-producing tumor, differential diagnosis via needle aspiration should be attempted in all tumors measuring less than 6 cm in diameter. In the event of an incidental finding, fine needle aspiration is performed only in lesions measuring between 4 and 6 cm; for tumors of less than 4 cm, we consider a wait-and-see approach, with follow-up examinations at 3-month intervals to be justified.

Adrenal Gland Neoplasms↗

PubMed1992

[MR tomography in testicular processes. The significance of Gd-DTPA enhanced sequences in comparison with plain T2-weighted sequences].

The value of T1-weighted sequences after intravenous administration of Gd-DTPA and of T2-weighted sequences was compared in 43 patients suspected of having scrotal abnormalities. T2-weighted sequences gave better demonstration of the tunica albuginea and better contrast between tumor and parenchyma. The two techniques were equally sensitive for demonstrating testicular tumors but orchitis was better demonstrated on the contrast enhanced sequences. Motion artifacts were less marked in the T1-weighted sequences with contrast enhancement. In selected cases, contrast enhancement may be a valuable addition to native protocols. Our experience has indicated that MRI provides specific findings in cases of orchitis which are clinically atypical; this facilitates the decision to conservative treatment and prevents unnecessary exploration of the testes.

Adolescent↗

PubMed1992

[MR tomography of injuries of the medial collateral ligaments of the knee joint].

Frequency and characteristics of lesions of the medial collateral ligaments (MCL) were studied by MRI in 155 patients with trauma to the knee. There were abnormalities of the MCL in 38% of cases with ligamentous injuries and in 27% these were combined with meniscal tears. 11% of these patients showed isolated rupture of MCL and as a result of the MRI findings were treated conservatively. By means of T2*-weighted images the individual lesions could be accurately localised. Characteristic findings have been defined.

Humans↗

PubMed1992

[Cystic space-occupying lesions of the seminal vesicles. Their demonstration with MRT].

Between October 1990 and March 1991, 8 patients with cystic lesions in the region of the posterior bladder wall, the seminal vesicles and the prostate were examined by MRI. In all cases there was accurate characterisation of the lesion and of its anatomy. In 3 patients with abnormalities in the retrovesical space there was very good agreement with the operative findings. 4 patients were treated conservatively. In these patients there was good agreement with the findings on cystoscopy, CT and sonography.

Adult↗

PubMed1992

[Measurement error estimation in MR tomographic volumetry of the left ventricle with the multisection technic].

A multi-slice technique for MRT measurements of the left ventricular volume is much faster than the use of single-slice methods and is therefore better tolerated, leaving time for additional measurements. The end-diastolic left ventricular volume can be reliably measured by this method (123.3 +/- 13.5 ml vs. 124.1 +/- ml). The end-systolic volume is consistently overestimated by 23.7 +/- 18.3% compared with the reference value obtained by single slice measurements (47.9 +/- 8.9 ml vs 39.1 +/- 7.9 ml). Correspondingly, stroke volume and ejection fraction is underestimated on average by 10.6 +/- 9.7% and 10.6 +/- 7.6% respectively).

Adult↗

PubMed1992

[Computerized tomography analysis of gallstones: soon an essential diagnosis before nonsurgical gallstone therapy?].

Successful application of non operative procedures for gallstone therapy are limited on cholesterol stones. Therefore reliable therapeutic analysis of stone components is mandatory for planning of an adequate therapy. Computed tomographic gallstone analysis is considered to improve selection of patients significantly. However, standardized conditions for investigation of patients are not yet established. It is suggested that computerized tomography should be performed using 4 mm slides, standardized position of patients and a phantom, which allows calibration of different CT-machines.

Bile Pigments↗

PubMed1992

[Lobular carcinoma of the breast in magnetic resonance tomography. A case report].

The invasive lobular carcinoma of the breast, the incidence of which is 10-15 per cent, occupies a special position in respect of histological differentiation and biological behaviour. No MR signal enhancement was seen after contrast medium application in the tumoral tissue in the case described here, namely, an invasive lobular carcinoma of the breast of 2 cm size. Hence, it is not always possible to exclude with absolute certainty the presence especially of an invasive lobular carcinoma of the breast in the absence of contrast medium uptake.

Breast Neoplasms↗

PubMed1992

[Diagnostic goals in aortic dissection. Value of transthoracic and transesophageal echocardiography].

The combination of different ultrasound techniques like transthoracic, suprasternal, subcostal and transesophageal echocardiography have a high sensitivity and specificity in the diagnosis of aortic dissection. The limitation of this combined ultrasound technique is related to the visualization of the ascending part of the aortic arch which, cause of the interposition of the trachea, can not be visualized completely. The beginning or the end of a dissection in this part of the aorta may be misinterpreted. False negative results are rare. False positive results due to artefacts resulting from reverberations in an ectatic ascending aorta have to be taken into account. The most important diagnostic aims in acute or chronic aortic dissection can be described: 1. confirmation of the diagnosis by visualization of the intima membrane, 2. the differentiation of the true and false lumen depending on visualization of spontaneous echocardiographic contrast thrombus formation, slow or reduced reversed flow, systolic diameter reduction and signs of entry jet into the false lumen, 3. detection of intimal tear, demonstrating communication by two-dimensional or color Doppler echocardiography, 4. determination of the extent of the dissection with classification according to DeBakey type I, II and III or Stanford A and B with differentiation to communicating or non-communicating dissection, antegrade or retrograde dissection limited to the descending aorta or expanding to the ascending aorta, 5. detection of wall motion abnormalities as a sign of preexisting coronary artery disease or myocardial ischemia due to ostium occlusion by an intimal flap, coronary artery rupture or collapse of the true lumen during diastole, 6. detection and grading of aortic insufficiency, 7. detection of side branch involvement by suprasternal, subcostal and abdominal sonography, which will gain the information which side can be chosen for cannulation or catheterization at the femoral artery, 8. detection of pericardial pleural effusion and mediastinal hematoma as a sign of emergency as rupture can occur within minutes. Without surgical intervention have be performed. Based on these informations, surgery can be performed in all acute situations in type A dissection without further investigations. This decision is particularly important in patients with signs of emergency like pericardial or pleural effusion or mediastinal hematoma.

Aortic Dissection↗

PubMed1992

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American Speech-Language-Hearing Association↗

PubMed1991

[Ambulatory angiography].

Outpatient angiography is justified in selected cases; patients with risk factors must be excluded. The examination should be performed as atraumatically as possible. After angiography, the patient should be kept under observation for at least 6 hours, since most complications occur during or shortly after the intervention. Only vary rarely do complications develop after the patient has been discharged, the most serious being late hemorrhage. Facilities for rapid treatment must be provided.

Ambulatory Care↗

PubMed1991

Regulation by phosphorylation of reversible association of a myristoylated protein kinase C substrate with the plasma membrane.

Protein kinase C (PKC) transduces receptor-mediated signals by phosphorylating membrane-bound substrates which then act as effectors of specific cellular responses. The myristoylated alanine-rich C kinase substrate (MARCKS) is a specific PKC substrate which has been implicated in macrophage activation, neuro-secretion and growth factor-dependent mitogenesis. Myristoylation of MARCKS is required for effective binding to the plasma membrane where it colocalizes with PKC. Here we report that PKC-dependent phosphorylation displaces MARCKS from the membrane and that its subsequent dephosphorylation is accompanied by its reassociation with the membrane. This cycle of phosphorylation-dependent membrane attachment and detachment of a myristoylated protein represents a novel mechanism of reversible membrane targeting. As MARCKS is a calmodulin- and actin-binding protein (ref. 8, and J. Hartwig et al., manuscript submitted), the cycle of membrane attachment/detachment represents a mechanism through which PKC might reversibly regulate actin-membrane interaction.

Adenosine Triphosphate↗

PubMed1991

[Interventional angiology in the area of the thigh. Percutaneous balloon dilatation, new procedures of recanalization, stents].

The major technique of interventional angiology of the arteries of the thigh is percutaneous balloon dilatation (angioplasty). In the case of short stenoses and occlusions, the primary results and long-term success of these techniques are very good. In order to be able to successfully treat long, highly calcified, eccentric and fresh lesions using the percutaneous approach, numerous new procedures have been developed. These include local fibrinolysis, aspiration of thromboembolic material, ablation of atherosclerotic plaques using an endovascular knife, the drilling open of occlusions, the use of the laser, and implantation of vascular endoprostheses.

Angioplasty, Balloon↗

PubMed1991

[Nonsurgical recanalization of tibial arteries. Balloon dilatation, local fibrinolysis and aspiration embolectomy].

To date, percutaneous angioplasty has only rarely been employed to recanalize arteries in the lower leg. In almost all such patients, the limb has been at risk of being amputated. Since the introduction of special thin-caliber balloon catheters and concomitant drug therapy to prevent vascular spasms and thromboses, results have been markedly improved. In the case of fresh occlusions, local fibrinolysis with percutaneous aspiration embolectomy is employed.

Angioplasty, Balloon↗

PubMed1991

GM-1, a clone of the monoblastic phagocyte U937 that expresses a large respiratory burst capacity upon activation with interferon-gamma.

The human cell line U937 was cloned and screened for the responsiveness to interferon-gamma (INF-gamma). The selected subclone, named GM-1, expressed a high density of IFN-gamma receptors and showed HLA typing similar to that of the parental line but was devoid of the Y chromosome. GM-1 cells display a promyeloid phenotype as revealed by flow cytometry using a panel of murine antibodies. Following treatment with IFN-gamma GM-1 cells differentiated to a more mature monocyte stage and acquired the capacity to mount a respiratory burst. After treatment with differentiation promotors, such as phorbol 12-myristate 13-acetate (PMA), dimethyl sulfoxide (DMSO), and retinoic acid, GM-1 showed a more limited respiratory burst capacity. Superoxide release in IFN-gamma-activated cells was stimulated with f-Met-Leu-Phe, C5a, or PMA. The development of the respiratory burst capacity was accompanied with the expression of cytochrome b558, a component of the phagocyte NADPH-oxidase. GM-1 cells are useful for the study of the effects of IFN-gamma on the respiratory burst. They are more sensitive and yield a more homogenous response to IFN-gamma than U937 cells. The phenotype of GM-1 cells was stable for more than 5 years.

Antigens, CD↗

PubMed1991

MRI-assisted radiation therapy planning of brain tumors--clinical experiences in 17 patients.

A new and simple method for precise determination of lateral opposed treatment portals was developed and used in 17 patients. Compared to CT, MRI led to significant changes of portals in 59% (10/17) of cases. Individual shielding blocks could be precisely designed by use of our new method. MRI is the procedure of choice in local radiation therapy planning of brain tumors.

Adolescent↗

PubMed1991

[Regional lymph node metastases in malignant tumors of the head and neck: value of diagnostic procedures].

Sonography and computed tomography are used in staging of lymph nodes of patients with head and neck cancer. The accuracy of sonography (90%) and computed tomography (85%) is comparable or better than the palpatory accuracy (85%). The better delineation of reactive swollen cervical nodes leads to a higher sensitivity of sonography (90%) and computed tomography (84%) versus palpation (74%), but a lower specifity (palpation 94%, sonography 90%, computed tomography 86%). A literature survey shows that sonography, computed tomography and magnetic resonance imaging of cervical lymph nodes are comparable good methods.

Carcinoma, Squamous Cell↗

PubMed1991

[Diagnosis of pleural effusions and atelectases: sonography and radiology compared].

In a prospective study it was shown that chest ultrasonography is superior to conventional x-ray diagnosis of recumbent patients in diagnosing pleural effusion and lung atelectasis. In 110 supine radiographs we found a sensitivity of 47% and a specificity of 71% for right pleural effusions and a sensitivity of 55% and a specificity of 93% for left pleural effusions in comparison to 110 sonographic examinations. The results of supine radiographs in detection of atelectasis were less efficient: sensitivity for the right side: 7%; sensitivity for the left side: 13.5%. Hence, the knowledge of chest ultrasonographic diagnosis can improve the interpretation of supine radiographs.

Critical Care↗