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Biomedical subjects

M Thelen

Publications and source records attributed to M Thelen.

At least 217 records · Page 12Linked to original sources
PubMed1995

A comparison of post-receptor signal transduction events in Jurkat cells transfected with either IL-8R1 or IL-8R2. Chemokine mediated activation of p42/p44 MAP-kinase (ERK-2).

The CXC chemokine, IL-8, is a potent chemoattractant of neutrophils and binds to two distinct receptors, termed IL-8R1 and IL-8R2. These receptors share high affinity for IL-8, however, only IL-8R1 is specific for IL-8 whereas IL-8R2 binds other related chemokines, including GRO alpha with high affinity. Stable Jurkat transfectants were generated expressing either functional IL-8R1 or IL-8R2 (J-IL8R1 and J-IL8R2). Both J-IL8R1 and J-IL8R2 exhibited high affinity IL-8 binding (Kd 3-5 nM) with respective receptor densities of 23,000 +/- 3,000 and 18,500 +/- 1,500. Pre-treatment of both transfectants with 1.0 micrograms/ml B. pertussis toxin (PTx) resulted in inhibition of IL-8 mediated intracellular Ca2+ mobilisation and chemotaxis, without altering the receptor's affinity for its ligand. This indicates that both receptors couple to a PTx-sensitive G-protein. Further studies showed that IL-8R1 and IL-8R2 could mediate time-dependent phosphorylation of p42/p44 MAP-kinase. In both transfectants, phosphorylation was maximal at 1-2 min after IL-8 stimulation and could be inhibited by PTx. Stimulation of J-IL8R1 and J-IL8R2 with GRO alpha revealed that this chemokine was a more potent activator of MAP-kinase in J-IL8R2, an observation reflected in the high affinity binding of GRO alpha to IL-8R2. These studies indicate that chemokines are capable of activating protein kinases and with regards to PTx-sensitivity and MAP-kinase stimulation, no significant differences between IL-8R1 and IL-8R2 post-receptor signalling occur during cell activation by IL-8.

Cell Line↗
PubMed1995

Malignant peripheral neuroectodermal tumors in urology.

During the past few years, a new tumor type has emerged in the pediatric and adolescent group of cancer patients, which has been designated malignant peripheral neuroectodermal tumor (MPNT). This tumor has some clinical and pathological signs in common with either soft-tissue sarcomas or classic Ewing's sarcoma, but is defined as a distinct entity because of its immunohistological characteristics. The tumor expresses neuronal markers, but the pattern varies: chromogranin, neuron-specific enolase, synaptophysin, protein S-100 and others. MPNT can occur in the urogenital region. The differential diagnosis on clinical grounds must include Ewing's and soft tissue sarcomas, and also Wilms' tumor and its variants. MPNT are often wide spread in the urogenital region when first diagnosed. Response to radiotherapy and combination chemotherapy is limited. Radical surgery is not always possible. The prognosis therefore remains rather poor at this time. A selection of MPNT patients is presented to demonstrate the various problems associated with this diagnosis. MRI and CT of all patients showed large tumors with direct infiltration of the surrounding structures. MRI is the best imaging modality for diagnosis and therapy monitoring in these tumors, because of its high soft-tissue contrast.

Adult↗
PubMed1995

[CT compared with SPECT in chronic recurrent pulmonary embolism: hyperdensities as signs of pulmonary artery hyperperfusion?].

UNLABELLED: Purpose of this study was to assess the aetiology of inhomogeneous lung parenchymal attenuation in patients with chronic pulmonary thromboembolism, presenting as sharply demarcated areas of increased and decreased density on computed tomography. MATERIAL AND METHODS: In 52 patients with chronic pulmonary thromboembolism, computed tomography (CT) was compared with perfusion scintigraphy (including SPECT) and agreement was assessed: "good" (all hyperdense CT segments are perfused on scan), "moderate" or "poor" (one or two resp. three or more hyperdense CT segments are not perfused). RESULTS: 44 of the 52 patients showed an inhomogeneous pulmonary attenuation on CT. Correlation of hyperdense areas with perfused lung parenchyma was graded as "good" in 26 cases, "moderate" in 14 and "poor" in 4 cases. In 40 of these 44 patients, scintigraphy revealed additional perfusion defects in homogeneously lucent areas on CT. In 6 of 8 patients with entirely homogeneous lung density on CT, SPECT revealed perfusion defects. CONCLUSION: In patients with chronic pulmonary thromboembolism, increased lung density on CT is caused by hyperperfused lung parenchyma distally to patent pulmonary arteries. SPECT proves to be more sensitive in diagnosing perfusion inhomogeneities.

Adult↗
PubMed1995

[The magnetic resonance tomographic findings following the resection arthroplasty of the caput humeri].

PURPOSE: The resection of the humeral head is normally carried out only with respect to four-part and dislocation fractures in elderly patients. The purpose of this study was to examine whether there is a correlation between the clinical results and the MRI findings. MATERIAL AND METHODS: 8 patients underwent clinical and MR examination two to 6 years after resection. RESULTS: A cartilage-like tissue formation between the remaining humeral head and the glenoid fossa, with signal intensities comparable to hyalin cartilage was found in all patients. CONCLUSION: The good functional results following resectional surgery of the humeral head can partially be related to new substitute cartilage resulting from a chondroid metaplasia.

Aged↗
PubMed1995

[A mannitol solution as an oral contrast medium in pelvic MRT].

PURPOSE: Improvement of pelvic MRI using peroral administration of an aqueous mannitol solution. METHODS: We retrospectively evaluated magnetic resonance examinations of 72 patients with suspected or proven pelvic abnormalities: In 36 patients, no bowel marking was carried out. In further 36 patients, we performed a contrast enhancement of the bowel by oral application of 1000 ml of an aqueous mannitol solution. RESULTS: 8/36 (22%) patients suffered from diarrhoea, nausea or meteorism as a result of mannitol application. In group 2, an excellent bowel marking of the small intestine could be obtained in 36/36 (100%) patients. Contrast enhancement of the bowel significantly improved delineation between intestinal structures and pelvic organs or pathologic lesions, respectively. In summary, bowel marking was desirable in 25/36 (69%) of group 1 and helpful in 26/36 (72%) of group 2. CONCLUSION: Aqueous mannitol solution is a safe bowel contrast agent and improves the diagnostic value of pelvic MRI, but in some cases delineation between marked bowel and cystic pelvic lesions may be uncertain.

Administration, Oral↗
PubMed1995

[CT and MRI in malignant peripheral neuroectodermal tumors].

To evaluate the diagnostic accuracy of CT and MRI in the diagnosis of malignant peripheral neuroectodermal tumors (MPNT), the imaging data of nine patients with immunehistochemically proven MPNT were retrospectively analyzed. The average age was 24 years (ranging from 5 to 63 years). MRI and CT of all patients showed large tumors with direct infiltration of the surrounding structures. Intratumoral calcifications were not identified. All tumors showed equal to less high signal intensity in T1- and high signal intensity in T2-weighted images. Because of its high soft-tissue contrast, MRI is the most capable imaging modality in the diagnosis and therapy-monitoring in these tumors.

Adolescent↗
PubMed1995

[Optimizing pelvic MR diagnosis with a new gastrointestinal contrast medium].

AIM: Optimization of pelvic MRI by a new concept of water-equivalent bowel contrast agent. METHODS: We performed contrast enhancement of the bowel by oral application of 1000 ml of an aqueous mannitol solution one hour before pelvic MRI. In addition we performed an enema by 250 ml of water in one patient. RESULTS: Oral and rectal contrast enhancement of the bowel was tolerated without complications by our patients. Pelvic MRI was improved by a better delineation of the bowel. CONCLUSION: The concept of water-equivalent bowel enhancement is promising. It must be assessed by further studies; in particular, it must be compared with the available concepts of positive and negative bowel contrast enhancement.

Adult↗
PubMed1995

[Conventional roentgen diagnosis of esophageal carcinoma--a determination of current status].

Conventional radiological methods in the diagnosis of esophageal carcinoma include esophagography as well as chest radiography, the latter revealing pathological findings in advanced cases. Esophagography may be used for early diagnosis, tumor staging and for follow-up examinations after irradiation and/or surgery. In particular early tumor diagnosis requires a double contrast technique with an optimal mucosal coating and distension of the esophagus. The esophagogram reveals indirect signs related to the staging from the localization and length of the tumor and from ulcerations and fistulas. In the diagnosis of recurrent tumor after surgery, esophagography is not the primary diagnostic tool. After irradiation therapy, however, it can detect intramurally growing remaining or recurrent tumor.

Adenocarcinoma↗
PubMed1995

[Computerized tomography image of pulmonary alveolar proteinosis].

Pulmonary alveolar proteinosis is a rare disease of uncertain etiology. It progresses with alveolar deposits of PAS-positive material, exhibits in the long-term interstitial changes of the lung skeleton, and can be complicated by superinfections. The computed tomographic image is characterized by geographically sharply delineated alveolar infiltrates, faint, ground-glass-like parenchymal turbidity, with well bordered interstitial structures and recesses in the subpleural space.

Adult↗
PubMed1994

Wortmannin binds specifically to 1-phosphatidylinositol 3-kinase while inhibiting guanine nucleotide-binding protein-coupled receptor signaling in neutrophil leukocytes.

Wortmannin (WT) and its derivative 17-hydroxywortmannin (HWT) inhibit at nanomolar concentrations superoxide formation and exocytosis in neutrophils stimulated with chemotactic agonists. Treatment of neutrophils with radiolabeled [3H]HWT resulted in specific and saturable binding that paralleled the inhibition of the respiratory burst. Both half-maximal binding and half-maximal inhibition were observed at 5 nM, and > 90% of maximal binding and inhibition was observed at 20 nM HWT. Fluorography of subcellular fractions that were separated on NaDodSO4/PAGE showed that [3H]HWT binds covalently to a 110-kDa cytosolic protein. The WT-binding protein was purified from human neutrophils and bovine brain homogenates by column chromatography. The pure protein was eluted from gel filtration columns with an apparent molecular mass of 200 kDa and showed a heterodimeric structure on Coomassie-stained NaDodSO4/PAGE. In addition to the 110 kDa wortmannin binding protein an equally intense band was seen migrating at 85 kDa. This band was identified on Western blots as p85 alpha, the regulatory subunit of phosphatidylinositol (PI) 3-kinase (ATP:1-phosphatidyl-1D-myo-inositol 3-phosphotransferase, EC 2.7.1.137). The purified protein contained PI 3-kinase activity that was enriched > 20,000-fold from human neutrophil cytosol during preparation. The data impose a key role for PI 3-kinase-mediated signal transduction through guanine nucleotide-binding protein-coupled receptors and suggest that 3-phosphorylated inositol phospholipids are important second messengers for immediate responses in neutrophils. Furthermore, the results show that WT is a powerful and selective tool to study the function of PI 3-kinase.

Androstadienes↗
PubMed1994

Value of routine abdominal and lymph node sonography in the follow-up of breast cancer patients.

OBJECTIVE: The aim of this study was to review usefulness and intervals for abdominal sonography during the follow-up of breast cancer patients. Additionally, we assessed the value of regional lymph node sonography in patients with possible locoregional recurrence. SUBJECTS: Retrospectively, 2657 abdominal ultrasound examinations of 414 patients and 299 sonographic examinations of the regional lymph nodes in 227 patients after surgical treatment for breast cancer were evaluated. RESULTS: Follow-up abdominal sonography revealed metastases in 6.8% of patients, and in 1% of examinations. There was no dependence on the initial T- or N-stage. At sonography of the regional lymph nodes in patients with suspicious palpatory findings metastatic nodes were found in 15.9% of patients, and in 12% of examinations. CONCLUSION: Risk-adapted follow-up intervals for abdominal sonography cannot be proposed, regular examinations are not recommended. Lymph node sonography is useful and promising in the evaluation of suspicious palpatory findings.

Abdominal Neoplasms↗
PubMed1994

Bolus-enhanced renal spiral CT: technique, diagnostic value and drawbacks.

In addition to pre- and postcontrast renal CT scans, early bolus-enhanced spiral scans during demarcation of the corticomedullary junction were acquired in 85 patients. The diagnostic value and drawbacks of the three imaging series in the evaluation of renal disease were assessed. Renal calcifications and calculus disease detected at precontrast scans (18%) were obscured after contrast administration and excretion in most cases. In the detection of renal lesions bolus-enhanced spiral CT and delayed postcontrast scans had an identical diagnostic yield (94%). Bolus-enhanced spiral CT was superior in the assessment of lesion vascularity and vascular anatomy as well as opacification of renal arteries (95%) and veins (85%). Delayed postcontrast scans were indispensable to delineate medullary or parapelvic cysts as well as anatomic abnormalities or tumors of the renal pelvis (17% of all lesions). Routine renal CT of the kidneys should consist of precontrast images and delayed postcontrast spiral scans. Bolus-enhanced spiral scans are advised to assess lesion vascularity of renal veins.

Adult↗
PubMed1994

Phospholipases and protein kinases during phagocyte activation.

Phospholipases and protein kinases are critical for the intracellular transmission and amplification of signals induced by extracellular ligands. Chemotactic activation of phagocytes through G protein coupled receptors leads to inflammatory responses of the immune cells. Downstream of G proteins, phospholipases generate precursors for eicosanoid synthesis and are involved in the functional responses. Recently, the molecular characterization of specific enzymes of the signalling cascades has gained much attention in research.

Animals↗
PubMed1994

[Reliability of imaging procedures in multi-visceral gynecologic operations of the pelvis].

Between March 1989 and December 1992, a total of 85 pelvic exenterations were performed in the Department of Gynaecology and Obstetrics of the University of Mainz. To assess the accuracy of preoperative Magnetic Resonance Imaging (MRI) and Computer Tomography (CT) with regard to tumour localisation and spread, the results of 28 MRI and 14 CT examinations were compared with the postoperative histological findings. For this widely varying patient group that had undergone a broad range of previous treatments, MRI produced an accurate forecast in 56% of cases (CT, 36%). In 33% of the patients tested, the diagnosis based on MRI was partially correct (CT, 43%), whereas the MRI results fundamentally disagreed with the actual findings in 11% of cases (CT, 21%). We conclude that both MRI and CT are of great value in the planning of operations and for informing patients about their condition; however, in individual cases, an intraoperative quick-section diagnosis is necessary to provide details of tumour spread. If the extent of tumour spread is uncertain, the results of CT and/or MRI should not deter the surgeon from the radicality of the planned operative intervention.

Adult↗