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H Schild

Publications and source records attributed to H Schild.

At least 91 records · Page 5Linked to original sources
PubMed1999

[The quantification of the magnetization transfer contrast (MTC) effect by calculating MT quotients: does it yield additional information for the differentiation of benign and malignant diseases of the locomotor apparatus?].

PURPOSE: To investigate the potential information of the amount of magnetization-transfer effect in musculoskeletal lesions and to compare MT ratios from benign and malignant musculoskeletal lesions. MATERIAL AND METHOD: 49 patients with malignant tumors (3 osteosarcoma, 3 malignant fibrous histiocytoma, 4 chondrosarcoma, 2 Ewing sarcomas) and benign lesions (8 chondroma, 2 fibrous dysplasia, 3 osteoid-osteoma, 6 ganglion cyst, 3 cyst, 3 osteomyelitis, 4 tendinitis, 3 rotator cuff tear, 5 scar tissue) were scanned using routine MRI protocols including T1- and T2-weighted spin echo as well as T2*-weighted gradient echo (FFE) sequences at 1.5 Tesla (ACS II, Philips Medical). Additionally MTC images were generated by combining the FFE sequence and the off-resonance MT technique (-1500 Hz off-resonance frequency, 1770 degrees flip angle and 50 ms pulse duration). MT ratios were calculated as Slo-Slm/Slo. RESULTS: The MT ratio of benign lesions was 26 +/- 15%, that of malignant lesions was 22 +/- 6%. The difference was statistically not significant. As expected muscle showed a high MT ratio of 50 +/- 8%. Scar tissue demonstrated an MT ratio of 39 +/- 16% which was significantly higher than the tumor MT ratios. CONCLUSION: MTC (MT ratios) failed to show significant differences between benign and malignant lesions as was expected due to basic differences in cellularity, rate of mitosis and chromatin content. MTC might however gain more importance in separating scar tissue from recurrent tumor in the future.

Adolescent↗
PubMed1999

[Spiral CT of the head-neck area: the advantages of the early arterial phase in the detection of squamous-cell carcinomas].

PURPOSE: To determine if scanning in the arterial phase improves detection of squamous cell carcinomas in the pharynx and larynx. METHODS: In a prospective clinical study 20 patients with a pharyngeal or laryngeal carcinoma were examined with by spiral CT. 80 ml lopromid were intravenously injected as a bolus with a rate of 3 ml/sec. Two consecutive spiral CT scans were performed with start-delay times of 20 and 70 seconds respectively. Delineation and contrast enhancement of tumours, cervical lymph nodes and vessels were evaluated. The radiodensities (HU) of tumors, lymph nodes vessels, pharyngeal wall and muscle were measured. RESULTS: Comparing early and late start delay time scans tumor assessment in the early phase was better in 58%, less in 16% and equal in both scans in 26%. 82% of the pathologic lymph nodes had more peripheral enhancement than surrounding muscle tissue. During the arterial phase the measured radiodensities of the common carotid artery and jugular vein were significantly higher than in the second phase. CONCLUSION: Contrast-enhanced special CT permits accurate morphologic assessment (size, infiltration) of pharyngeal and supraglottic laryngeal squamous cell carcinoma, while pathologic lymph nodes already have a sufficient contrast enhancement for the detection.

Adult↗
PubMed1999

[MRI diagnosis in longitudinal stress fractures: differential diagnosis of Ewing sarcoma].

PURPOSE: To compare MR imaging features of stress fractures, simulating malignancies, and Ewing sarcomas. MATERIALS AND METHODS: MR imaging studies of 4 patients with longitudinal stress fractures of the tibia (n = 2) and the femur (n = 2) simulating malignancy were retrospectively compared with the MRI scans of 10 patients with histologically proven Ewing sarcoma (femur n = 5; tibia n = 3, fibula n = 1, humerus n = 1). The diagnosis of stress fractures was confirmed by follow-up examinations. An additional biopsy was performed in two patients. RESULTS: Despite negative x-ray examinations, MRI showed the fracture line in all patients with stress fractures. In these cases marrow edema was irregular and there was no well defined margin towards normal fatty marrow. In contrast Ewing sarcomas were sharply demarcated in 9/10 cases. Extraosseous enhancing soft tissue was found in Ewing sarcomas as well as in stress fractures. In stress fractures the enhancing mass was repair tissue. Areas of necrosis within the enhancing mass was seen in (8/10) Ewing sarcomas, only. In follow-up studies we observed a decrease of the marrow edema in patients with stress fractures. Occurrence of low signal areas in T1- and T2-weighted sequences within the initial enhanced extraosseous tissue corresponded to bony callus on x-rays films. CONCLUSIONS: Repair tissue in stress fractures can imitate malignancy. The irregularity of the marrow edema without well defined margins, the lack of necrosis in the small enhancing tissue and the proof of the fracture line in the MRI are criteria to differentiate stress fractures from Ewing sarcomas. Short-term follow up studies are helpful to underline the diagnosis.

Adolescent↗
PubMed1999

[Independent radiologic prognostic factors for fatal outcome of ambulatory-acquired pneumonia requiring inpatient treatment].

PURPOSE: To evaluate the independent prognostic impact of the chest radiograph for mortality from community-acquired pneumonia requiring hospitalization. METHODS: Chest radiographs of 67 patients with hospital-treated community-acquired pneumonia were analyzed with regard to the prognostic implications of radiographic patterns, extent and density of infiltrates, and its evolution during treatment. RESULTS: Non-survivors had a significantly higher extent of infiltrates (p = 0.008), density of infiltrates (p = 0.05), and radiographic spread during follow-up within 48-75 hours (p = 0.0001). In multivariate analysis, persistent or progressive infiltrates were associated with a 47-fold increase, and persistent or progressive density of infiltrates with an 18-fold increase in risk of mortality. The presence of both parameters could correctly predict 96% of survivors and 90% of non-survivors. CONCLUSIONS: The chest radiograph is an independent predictor of the severity of pneumonia. Both persistent or progressive infiltrates and persistent or progressive density of infiltrates are independently associated with mortality from community-acquired pneumonia.

Adolescent↗
PubMed1999

[MRI diagnosis of cardiac myxomas: sequence evaluation and differential diagnosis].

PURPOSE: To evaluate native and contrast enhanced T1-weighted spin (T1-SE), cine gradient echo (Cine-GE), and T2-weighted turbo spin (T2-TSE) sequences in the diagnosis and differential diagnosis of cardiac myxomas. METHODS: 15 patients with echocardiographically suspected cardiac atrial myxomas underwent 0.5 T-MR imaging of the heart with native T1-SE, contrast-enhanced T1-SE, Cine-GE, and T2-TSE sequences. MR images were evaluated for signal intensity (SI) and lesion's conspicuity. Results were confirmed histologically (14 x) or by follow-up (1 x). RESULTS: MRI revealed myxomas in 9 patients, sarcomas in three patients, and thrombi in three patients. Lesion conspicuity was better in Cine-GE and T2-TSE compared with native and contrast-enhanced T1-SE sequences. Myxomas were characterized by an intermediate SI similar to myocardium in T1-SE, high SI similar to water in T2-TSE, and low to moderately high enhancement (range 19-75%, mean 48%). CONCLUSION: Distinct SI characteristics together with anatomical-topographical features (attachment to the interatrial septum, no infiltration of myocardium and vessels) are diagnostic for cardiac myxomas. Cine-GE and T2-TSE sequences are the sequences of choice for detection of myxomas and other atrial masses. T2-TSE and contrast-enhanced T1-weighted sequences are most useful for mass characterisation and differentiation between myxomas, malignant tumors, and thrombi.

Diagnosis, Differential↗
PubMed1999

[The MRT of focal liver lesions: the value of gadolinium-enhanced dynamic studies of the whole organ with a fast 3D-turbo-gradient echo sequence].

PURPOSE: To determine the value of a dynamic Gd-enhanced ultrafast T1-weighted 3D-turbo-gradient-echo sequence (3D-TFE) in the detection and characterization of focal liver lesions. MATERIALS AND METHODS: 51 patients with 124 focal liver lesions (35 hemangiomas, 30 HCC, 24 metastases, 22 cysts, 5 FNH/adenoma, 8 other lesions) were examined using a 1.5 T system. The dynamic 3D-TFE sequence, achieving 40 slices with a thickness of 4.5 mm in a 17-s breath-hold, was compared with a fat-suppressed T2-weighted fast-spin-echo sequence (TSE SPIR), unenhanced and Gd-enhanced T1-weighted spin-echo sequences (SE), and a T1-weighted gradient-echo sequence (FFE). RESULTS: On 3D-TFE images more lesions (107/124) were identified than on T1-weighted SE (101/124) and T1-weighted FFE images (106/124), but less compared to T2-weighted TSE SPIR images (115/124). The 3D-TFE-sequence provided additional information in 65/107 (61%) detected lesions by delineating the dynamic enhancement pattern, most valuable in patients with HCCs in 90%. CONCLUSIONS: On dynamic 3D-TFE images more lesions could be depicted than on conventional T1-weighted SE and T1-weighted FFE images. Visualization of the dynamic enhancement pattern provided additional information for tumor characterization in 61% of the detected lesions on the 3D-TFE images.

Artifacts↗
PubMed1999

Differentiation of alveolitis and pulmonary fibrosis in rabbits with magnetic resonance imaging after intrabronchial administration of bleomycin.

RATIONALE AND OBJECTIVES: The authors investigate the ability of magnetic resonance imaging to differentiate alveolitis and pulmonary fibrosis by correlating magnetic resonance and pathologic findings. METHODS: Lung damage was induced in 52 rabbits by instillation of 5 mL bleomycin sulfate (10 mg/kg) into a lower-lobe bronchus using a balloon catheter. Magnetic resonance examinations were performed in a group of 7 animals 3 hours after the initial damage, and in groups of 8 animals 24 hours and 8, 14, 30, and 80 days after the initial damage. Control animals were examined 3 hours (n = 5), 24 hours, and 8 days (n = 3 for each), respectively, after the instillation of 5 mL 0.9% sodium chloride. Magnetic resonance imaging at 1.5 T included conventional T1-weighted sequences before and after injection of gadolinium-DTPA (0.1 mmol/kg), and T2-weighted fast spin echo sequences. The signal intensity and contrast enhancement of injured lung were evaluated and compared with the contralateral healthy lung and with the lungs of control animals. All animals were killed immediately after the magnetic resonance examination, and the lungs were removed and fixed before sectioning and staining. RESULTS: There was good correlation between signal intensity and contrast enhancement with magnetic resonance imaging and histologic examination. The early phase of acute alveolitis showed lesions with high signal intensity on both T1- and T2-weighted images and marked contrast enhancement after gadolinium-DTPA administration, whereas in the late fibrotic stage the lesions displayed significantly lower signal intensity and contrast enhancement. CONCLUSION: Magnetic resonance imaging can differentiate between alveolitis and fibrosis by means of signal intensity and contrast enhancement after gadolinium-DTPA administration.

Animals↗
PubMed1999

Evaluation of different models of experimentally induced liver cirrhosis for MRI research with correlation to histopathologic findings.

RATIONALE AND OBJECTIVES: Three models of experimentally induced liver cirrhosis were evaluated for MRI research on chronic liver disease. The influence of different histopathologic changes in liver fibrosis and cirrhosis on relaxation times and signal intensities was studied in vitro and in vivo. METHODS: Liver fibrosis and cirrhosis in rats was induced by oral or subcutaneous administration of carbon tetrachloride (CCl4) or by thioacetamide (TAA) in drinking water. On histology, the degree of liver fibrosis and cirrhosis, fatty infiltration, iron accumulation, and inflammatory changes were measured semiquantitatively. The amount of connective tissue was quantitatively determined by morphometry. The results were correlated with T1 and T2 relaxation times and signal intensities of the liver studied in vitro by relaxometry and in vivo by MRI. RESULTS: In both groups with CCl4 administration, histology revealed different degrees of liver fibrosis and cirrhosis. Subcutaneous injection of CCl4 also resulted in increased fatty infiltration. On the contrary, TAA produced complete liver cirrhosis in all animals. Overall, there was a good correlation between the liver T2 relaxation time and the amount of connective tissue in liver fibrosis and cirrhosis. However, the degree of liver fibrosis and cirrhosis was also strongly correlated with the degree of inflammatory changes. In the group with CCl4 administration, there was a good correlation between the fatty infiltration and the T1 relaxation time, as well as with the liver signal intensity on the T1-weighted gradient echo sequence. An increased iron accumulation was also correlated with the degree of liver fibrosis/cirrhosis; however, there was no significant influence of the iron on relaxation times or signal intensities. CONCLUSIONS: The TAA model is easier to perform and more reliable in liver cirrhosis induction than the CCl4 models. Although there is a positive correlation between the T2 relaxation times and the degree of liver fibrosis/cirrhosis, this probably results from the associated inflammatory changes and is not caused by the increased amount of connective tissue.

Animals↗
PubMed1999

A new technique for oral endotracheal airway access in rabbits under fluoroscopic control: An easy way for drug administration in chronic experiments.

Endotracheal drug administration plays an important role in rabbit models of pulmonary injury and lung disease. However, anatomical features of the oral fissure and pharynx of rabbits make orotracheal intubation a difficult task with a high failure rate. We developed a new technique for airway access in rabbits under fluoroscopic control using a balloon catheter. The procedure consists of four major steps: (1) a shortened 5-french vertebralis catheter is placed into the mesopharynx just above the epiglottic valve, (2) through the catheter lumen a guidewire is carefully moved across the epiglottis and inserted into the trachea, (3) the vertebralis catheter is replaced by a balloon catheter that subsequently is introduced into the tracheal tree over the guidewire, and (4) with the balloon catheter in the right position the guidewire is removed and the balloon is inflated so that finally the drug can be delivered. This procedure was performed in 55 New Zealand White rabbits under general anesthesia with ketamine/xylazine. In all 55 cases the procedure was performed successfully without any major complications and within a reasonably short time period. Removal of the catheter and awakening of the animals were uneventful. The described technique is a simple and safe method for airway access in rabbits and can be useful in chronic experiments for endotracheal drug administration.

Animals↗
PubMed1999

[The pathological/MR tomographic correlation and differential diagnosis of malignant kidney tumors].

PURPOSE: Evaluation of malignancy criteria in MRT of kidney tumors in correlation with the histopathological findings. MATERIALS AND METHODS: 41 patients with suspected malignant kidney tumors were examined using a T1 SE sequence (TR/TE 300/10 ms) before and after i.v. administration of 0.1 mmol/kg Gd-DTPA and a T2 SE sequence (TR/TE 5500/150 ms). The results were correlated with the pathological findings. RESULTS: 38 malignant tumors were found: 29 renal cell carcinomas (RCC), 13 with solid growth, 11 with tubulopapillary growth, and three with mixed growth forms, one cystic RCC, and one chromophobic RCC, in addition, 6 urothelial carcinomas and three other malignomas. Typical MRT criteria for RCC were an inhomogeneity of the tumor with regions of slightly increased signal intensity on the T1-weighted image (59%) and regions with reduced signal intensity on the T2-weighted image (96%) as compared with renal parenchyma; these were due to histomorphological hemorrhage and hemosiderin deposits, respectively. A further criterion for RCC was a hypointense pseudocapsule in the T2 TSE sequence in 79% of the cases. CONCLUSIONS: The low-signal nature of RCC in the T2-weighted image correlates with hemorrhage and hemosiderin deposits. The detection of a pseudocapsule is useful in the differential diagnosis of solid tumors in the kidney.

Carcinoma, Renal Cell↗
PubMed1998

Cleavage motifs of the yeast 20S proteasome beta subunits deduced from digests of enolase 1.

The 436-amino acid protein enolase 1 from yeast was degraded in vitro by purified wild-type and mutant yeast 20S proteasome particles. Analysis of the cleavage products at different times revealed a processive degradation mechanism and a length distribution of fragments ranging from 3 to 25 amino acids with an average length of 7 to 8 amino acids. Surprisingly, the average fragment length was very similar between wild-type and mutant 20S proteasomes with reduced numbers of active sites. This implies that the fragment length is not influenced by the distance between the active sites, as previously postulated. A detailed analysis of the cleavages also allowed the identification of certain amino acid characteristics in positions flanking the cleavage site that guide the selection of the P1 residues by the three active beta subunits. Because yeast and mammalian proteasomes are highly homologous, similar cleavage motifs might be used by mammalian proteasomes. Therefore, our data provide a basis for predicting proteasomal degradation products from which peptides are sampled by major histocompatibility complex class I molecules for presentation to cytotoxic T cells.

Amino Acid Sequence↗
PubMed1998

Contribution of proteasomal beta-subunits to the cleavage of peptide substrates analyzed with yeast mutants.

Proteasomes generate peptides that can be presented by major histocompatibility complex (MHC) class I molecules in vertebrate cells. Using yeast 20 S proteasomes carrying different inactivated beta-subunits, we investigated the specificities and contributions of the different beta-subunits to the degradation of polypeptide substrates containing MHC class I ligands and addressed the question of additional proteolytically active sites apart from the active beta-subunits. We found a clear correlation between the contribution of the different subunits to the cleavage of fluorogenic and long peptide substrates, with beta5/Pre2 cleaving after hydrophobic, beta2/Pup1 after basic, and beta1/Pre3 after acidic residues, but with the exception that beta2/Pup1 and beta1/Pre3 can also cleave after some hydrophobic residues. All proteolytic activities including the "branched chain amino acid-preferring" component are associated with beta5/Pre2, beta1/Pre3, or beta2/Pup1, arguing against additional proteolytic sites. Because of the high homology between yeast and mammalian 20 S proteasomes in sequence and subunit topology and the conservation of cleavage specificity between mammalian and yeast proteasomes, our results can be expected to also describe most of the proteolytic activity of mammalian 20 S proteasomes leading to the generation of MHC class I ligands.

Acetylcysteine↗
PubMed1998

The making of the dominant MHC class I ligand SYFPEITHI.

The proteasome contributes to the generation of most of the peptide ligands of MHC class I molecules. To compare the identity of the peptides generated by the proteasome with those finally presented by MHC class I molecules, we generated a monoclonal antibody recognizing the C-terminal part of the dominant H2-Kd ligand SYFPEITHI derived from the JAK1 tyrosine kinase. Immunoprecipitations of lysates from H2-Kd-expressing or non-expressing cells revealed that only in the presence of H2-Kd SYFPEITHI could be isolated. No longer potential precursor peptide containing SYFPEITHI could be detected. Surprisingly, a peptide lacking the first two amino acids, FPEITHI, was isolated independently of the presence of H2-Kd molecules. The detection of only SYFPEITHI and FPEITHI in cell lysates corresponded with the strong generation of these two peptides in in vitro digests of elongated SYFPEITHI-containing peptides with purified 20S proteasomes. Our results indicate that MHC ligands can be generated directly by the proteasome in vivo and that at least for SYFPEITHI the expression of the corresponding MHC molecule is critical for protection of the ligand in vivo.

Amino Acid Sequence↗
PubMed1998

Generation of the vesicular stomatitis virus nucleoprotein cytotoxic T lymphocyte epitope requires proteasome-dependent and -independent proteolytic activities.

The proteasome is involved in the generation of most of the MHC class I antigenic epitopes. However, it is not known if the proteasome generates the exact cytotoxic T lymphocyte (CTL) epitope or only epitope precursors which require further modification by additional proteases. Digestion of the extended vesicular stomatitis virus nucleoprotein epitope 52-59 (RGYVYQGL) by the 20S proteasome in vitro shows that the proteasome is capable of generating the correct C terminus but not the exact N terminus of the CTL epitope. This finding suggests that proteolytic activity in addition to the proteasome is required for generation of the CTL epitope. By using the proteasome inhibitor lactacystin we were able to confirm this finding in vivo. Lactacystin prevented the processing of N- and C-terminally extended epitopes, whereas the processing of only N-terminally extended epitopes was unaffected. Thus, the proteasome is necessary and sufficient for the generation of the exact C terminus of this CTL epitope, whereas the exact N terminus seems to be generated by a different protease.

Acetylcysteine↗
PubMed1998

Endoscopic manometry of esophageal varices: evaluation of a balloon technique compared with direct portal pressure measurement.

BACKGROUND/AIMS: Recently, a non-invasive endoscopic balloon technique for esophageal manometry was published. In the present study, we assess its methodological aspects together with the relationship to portal pressure. METHODS: In 20 patients with liver cirrhosis who had received an intrahepatic portosystemic stent-shunt (TIPS), we evaluated portal and variceal pressure before and after balloon occlusion of TIPS (random order). Portal pressure was measured continuously via a portal venous catheter, and variceal pressure was determined at the same time independently by two endoscopists using two balloon techniques (inflation until varix collapses; deflation until varix reappears). RESULTS: Overall, mean (+/-SD) portal pressure (28.5+/-7 mmHg) was significantly higher (p<0.001) than mean variceal pressure (24.4+/-6 mmHg). Balloon manometry-determined variceal pressure values were 10+/-15% higher with the inflation technique (26.2+/-7 mmHg) than with the balloon deflation technique (22.6+/-6 mmHg, p<0.001). Portal pressure and variceal pressure correlated significantly (p<0.001; balloon inflation: r=0.61, balloon deflation: r=0.66, mean values of inflation and deflation: r=0.68). Short-term TIPS occlusion led to mean increases of 52% and 35% in portal pressure and variceal pressure, respectively. The manometry results of both endoscopists correlated well with either balloon technique (r> or =0.93; p<0.001) and we saw no adverse effects. CONCLUSIONS: Variceal balloon manometry provides non-invasive variceal pressure data which correlate to portal pressure assessed prior to and after short-term TIPS occlusion. However, probably due to variance in collateral anatomy, variceal pressure does not exactly predict portal pressure and its acute changes in the individual patient. The averaged variceal pressure of the inflation and deflation balloon technique provides the best relation to portal pressure combined with a good interobserver reliability and warrants further clinical evaluation.

Adult↗