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Biomedical subjects

M Lenz

Publications and source records attributed to M Lenz.

At least 55 records · Page 3Linked to original sources
PubMed1995

[MRI of the knee joint: first results of a comparison of 0,2-T specialized system and 1,5-T high field strength magnet].

PURPOSE: Diagnostic accuracy and image quality of a specialised system for MR examinations of peripheral joints were evaluated. MATERIALS AND METHODS: 20 patients with acute or chronic injuries of the knee were examined using a low-field MR system (0.2 T). For comparison, all patients were also studied with a 1.5 T high field strength magnet and all diagnoses were correlated with arthroscopic findings. RESULTS: We found compatible diagnostic accuracies (cruciate ligaments 90%, menisci 75-90%) and good image quality ratings for the low field system ("good" and "excellent" image quality in 83% of cases). CONCLUSION: The low-field MR-system offers low-cost MR examinations of peripheral joints with good image quality and reliable diagnostic information.

Adult↗
PubMed1995

[Septic ovarian vein thrombosis. Conservative management with CT-controlled follow-up].

Puerperal ovarian vein thrombophlebitis (POVT) is a rare complication during the puerperal period. A late diagnosis can lead to a high rate of morbidity and even mortality. By CT the POVT can be diagnosed early. This enables initiation of an adequate therapy with broad-spectrum antibiotics and i.v. anticoagulation well in time. In this way the disease can often be managed conservatively. CT controls can confirm the effectiveness of the therapy and are helpful in determining the duration of the i.v. anticoagulation.

Adult↗
PubMed1994

[Sclerotherapy of the internal spermatic vein in varicocele. Significance of normal anatomical variants].

During a period of four years, 386 patients with left sided varicoceles were treated by sclerotherapy of the left internal spermatic vein. This was successful in 93.8%. The most common complication was perforation of the vein in 6.2%. Technical success and complications depended on anatomical variations. Of particular significance was Bähren type IVb (competent main vein, incompetent collaterals) which occurred in 18.9%. This accounted for 66.5% of all perforations and 54.2% of unsuccessful interventions. The recurrence rate was 3.8%.

Adolescent↗
PubMed1993

Cloning, expression and mutational analysis of the urocanase gene (hutU) from Pseudomonas putida.

The histidine-utilizing hutU gene was isolated from a lambda-EMBL3 phage of a genomic library from Pseudomonas putida nicII and subcloned into the expression vector pT7-7. Escherichia coli BL21 cells were transformed with the recombinant plasmid and produced a catalytically active protein, amounting to approximately 30% of the total protein in the crude cell-free extract. The addition of NAD+ to the growth medium ensured the full occupation of active sites by the cofactor. This requires a mechanism for the transport of NAD+ into E. coli cells. Using the overproducing mutant a new, fast and efficient isolation procedure is described which yields electrophoretically homogeneous urocanase within two days. The yield of pure enzyme, based on the culture volume, has been improved 50-80-fold compared with the traditional method. To investigate the possible role of cysteine residues in the catalysis or in the tight binding of the cofactor NAD+, six different mutants were prepared. In each mutant protein, one conserved cysteine was exchanged for alanine. The resulting clones were tested for the expression of urocanase with catalytic activity; the Km and Vmax values were determined. Only Cys410 was essential for catalysis. There was no detectable reconstitution or increase of activity after the addition of NAD+, either in the essential Cys/Ala mutant or the other mutant proteins. Electrospray-mass spectroscopy of the wild-type enzyme revealed that the coenzyme is not covalently bound to the protein and computational analysis showed no typical sequence for a mononucleotide-binding domain like the Rossman fold. To obtain urocanase apoenzyme, P. putida nicII was transformed with pGP1-2 and pTET7-U and grown in nicotinate-depleted medium. Like the mutant proteins, no activation of the apoform occurred after the addition of NAD+. These observations led us to postulate a new model for the non-covalent but tight binding of NAD+ to the enzyme by 'trapping' the cofactor while folding the nascent protein.

Apoenzymes↗
PubMed1993

Diagnosis and treatment of the N0 neck in carcinomas of the upper aerodigestive tract: current status of diagnostic procedures.

Diagnostic procedures currently utilized for determining nodal status in patients with head and neck primary carcinomas are reviewed. Diagnostic procedures include clinical palpation, computed tomography, magnetic resonance imaging and ultrasound. Each technique is discussed on the basis of clinical experience at the Technical University of Munich.

Carcinoma, Squamous Cell↗
PubMed1993

[Color-coded three-dimensional reconstruction from spiral CT data sets: physical viewpoint for improvement of the method].

This paper demonstrates the possibility of improving the spatial depth impression of colour-coded three-dimensional reconstructions by modulation of colour saturation. Patients were observed with spiral computed tomography (slice thickness 10 mm, table feed 10 mm/s, reconstruction of overlapping axial images at 2 mm increment). Interesting anatomical and pathological objects (vessels, organs, tumours, metastases) were segmented, colour-coded, and reconstructed three-dimensionally. Spatial depth impression of the coloured objects could be improved by modulating not only the brightness, but also the colour saturation.

Aorta, Abdominal↗
PubMed1993

[Spiral CT in aortic aneurysms. 2D and 3D reconstructions and CT angiography].

Spiral CT was performed in 8 normals and 40 patients with alterations of the large thoracic and abdominal vessels. It proved to be the ideal basis for 2D and 3D reconstructions. In 2D reconstruction the topographic aspects of aortic aneurysms were displayed better compared to the axial scans. In 3D reconstruction the segmentation of small vessels, and vessels running parallel to the scan plane showed problems. Stenoses were displayed unsatisfactory. In patients with aortic aneurysms 3D reconstruction showed well the location and dimension of the aneurysm as well as its position to branching arteries and the intraarterial thrombus. In case of dissecting aneurysms the true and the false lumen could clearly be distinguished. Colour-coded 3D reconstruction proved to be valuable to illustrate topographic information that could be detected only with difficulty on examining the original axial scan.

Aged↗
PubMed1993

[A comparison of color duplex sonography with selective penile DSA in assessing erectile dysfunction].

42 patients with suspected vasculogenic impotence were examined via colour duplex sonography. Penile vascular anatomy was mapped and peak velocity was determined in both cavernous arteries before and after intracorporeal injection of 15 mg papaverine and 0.5 mg regitine. In all patients the results could be compared with selective penile pharmacoangiography as the gold standard. In 34/42 patients colour Duplex sonography and angiography led to an identical evaluation of penile blood supply. 4 patients were classified false-negative and 4 patients false-positive. Sensitivity and specificity were calculated for each side separately. Sensitivity was 82.4% for left side angiogram and 83.3% for right side angiogram. Specificity was 88% for left side angiogram and 87.5% for right side angiogram. Peak flow velocity was significantly diminished in pathological angiograms.

Adult↗
PubMed1993

[CT arterioportography in the spiral technic for the demonstration of liver metastases].

CT arterioportography using indirect portal venous application of contrast media is the most sensitive preoperative diagnostic technique for detection of liver metastases. Spiral CT allows continuous examination of the liver (no gap) during a single breathhold. Due to short measurement times an optimized vessel and tissue contrast can be achieved during the portal venous phase. Compared with intraoperative ultrasonography CTAP using spiral CT offers similar sensitivity (96%) in the detection of liver metastases and thus emerges as an important technique for diagnosis and follow-up of liver metastases.

Aged↗
PubMed1993

[The value of computed tomography in the diagnosis of the local and lymph node recurrences of head and neck tumors].

544 CT studies of 231 patients were evaluated retrospectively to assess the role of CT in posttherapeutic monitoring of patients with head and neck tumours. CT (80%) was inferior to clinical evaluation (87%) in diagnosing recurrent malignancy due to a lack of specificity (76 vs. 92%). With CT small recurrencies were missed. Occasionally evaluation of the oral cavity was impaired by metal artifacts (dental fillings). However with larger recurrent tumours, CT offered important additional information regarding extent, infiltration of deeper compartments and bony destruction in 51% of the cases. CT (95%) was superior to clinical evaluation (80%) in diagnosing recurrent lymph node metastases. A baseline CT study at about 6-8 weeks after the end of therapy is of great importance for follow-up studies.

Combined Modality Therapy↗