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K Hahn

Publications and source records attributed to K Hahn.

At least 217 records · Page 12Linked to original sources
PubMed1988

Modeling the three-dimensional structures of bacterial aminotransferases.

The refined crystallographic structure of the "closed" conformation of chicken mitochondrial aspartate aminotransferase has been used as a template for the construction of models of the two Escherichia coli aminotransferases encoded by the tyrB and aspC genes. The main results are as follows: (1) Only minor changes are required in the coordinates of the backbone atoms to accommodate the large number of substituted side chains. (2) All deletions and insertions required to allow maximum primary sequence alignment are on the solvent-accessible surface. (3) Charged residues are all located on the surface, in contact with solvent, except for certain conserved active site residues. (4) The close packing within the hydrophobic core is maintained. (5) The interactions between the subunits are maintained. (6) Modeling of tyrosine as an external aldimine into the active sites points to several residues that could be involved in determining the substrate specificities of these aminotransferases.

Binding Sites↗
PubMed1988

Considerations on a revision of the quality factor.

A modified analytical expression is proposed for the revised quality factor that has been suggested by a liaison group of ICRP and ICRU. With this modification one obtains, for sparsely ionizing radiation, a quality factor which is proportional to the dose average of lineal energy, y. It is shown that the proposed relation between the quality factor and lineal energy can be translated into a largely equivalent dependence on LET. The choice between the reference parameters LET or y is therefore a secondary problem in an impending revision of the quality factor.

Energy Transfer↗
PubMed1986

Echocardiographic findings in patients with proved pulmonary embolism.

Echocardiographic studies were performed in 105 patients with acute and recurrent pulmonary emboli. Pulmonary embolism was confirmed by pulmonary angiography (n = 48), autopsy (n = 6), and lung perfusion scintigraphy (n = 51). Seventy of 93 patients (75%) displayed a dilated right ventricle, 38 of 91 patients (42%) had reduced left ventricular cavity dimension, 41 of 82 patients (50%) had a decreased EF slope of the mitral valve, and 78 of 101 patients (77%) showed dilatation of the right pulmonary artery. The motion of the interventricular septum was abnormal in 41 of 93 patients (44%). Right-sided thrombi were seen in 13 patients within the right pulmonary artery (n = 11) and in the right ventricle (n = 3); in one patient they were found in the superior vena cava, in the innominate vein, and the right atrium. Two patients suffered from right-sided endocarditis. Thus echocardiographic changes were frequently found in patients with proved pulmonary emboli. The echocardiographic findings of right-sided cardiac and pulmonary artery abnormalities indicate hemodynamically active pulmonary emboli.

Acute Disease↗
PubMed1986

[Diagnosis and course of synovial sarcoma. Comparison of x-ray diagnosis and bone scintigraphy].

The unfavourable prognosis of malignant synoviomas makes it essential to arrive at an early diagnosis. The early clinical symptoms and radiological appearances may be minimal and sometimes absent. It is therefore advisable to obtain bone scintigrams with perfusion and early images as well as the radiographs. The local extent of the tumour can be evaluated by ultrasound and CT. Angiography is required only if the relationship to the vessels cannot otherwise be ascertained, or if intra-arterial therapy is being considered. The final diagnosis depends on a biopsy. For subsequent observation, both scintigrams and radiographs should be obtained. It is essential to perform a three-phase scintigram. This improves the recognition of recurrences and of soft tissue or bone metastases. Most bone metastases are visible on scintigraphy, but a normal scintigram in the presence of an osteolytic lesion on a radiograph may be obtained. Pulmonary metastases can only be demonstrated radiologically.

Adolescent↗
PubMed1986

Balloon coronary angioplasty in patients with acute myocardial infarction.

After successful thrombolysis, approximately 75% of all patients will have significant coronary stenosis, which can be dilated by means of percutaneous transluminal balloon angioplasty (PTCA). In a randomized control study, 95 of our patients (Group I) had thrombolysis alone, whereas 95 others (Group II) had thrombolysis and PTCA. Both groups were comparable with respect to age, sex, infarct location, and maximal creatine kinase (CK) value. The clinical outcome during the hospital phase was better in Group II, which had a reocclusion rate of 13%, a reinfarction rate of 5%, a lethal reinfarction rate of 2%, and a cardiac death rate of 7%, compared with respective rates of 20%, 13%, 7%, and 13% in Group I. Furthermore, in Group I, residual coronary stenosis immediately after thrombolysis (75% +/- 20%) did not improve significantly until the end of the hospital phase, when it decreased to 69% +/- 21%. In Group II, stenosis (78% +/- 16%) was improved by PTCA to 33% +/- 21%, and this improvement remained constant during the hospital phase (30% +/- 26%). In Group-II patients who had an unsuccessful PTCA, stenosis was approximately the same before dilatation (83% +/- 12%), after dilatation (80% +/- 17%), and at the control study (83% +/- 17%). The end-diastolic, end-systolic, and stroke volume indices, as well as the ejection fraction, also remained unchanged. In Group I, the number of pathologic wall segments (12.2 +/- 5.0) did not improve during the hospital phase (12.2 +/- 7.9), but in Group II, the improvement was significant (14.0 +/- 5.7 vs. 10.9 +/- 8.2) (p < 0.05). PTCA seems to improve the clinical outcome, reduce the infarction and mortality rates, and enhance myocardial perfusion and performance.

Journal Article↗
PubMed1986

[PTCA and intracoronary lysis in acute myocardial infarct].

In 76% of all patients in whom thrombolysis was successful a residual stenosis exceeding 75% luminal diameter was found. Some patients suffered from single, others from multi-vessel disease. In single vessel diseases immediate intracoronary balloon dilatation of the residual stenosis is feasible. In multi-vessel diseases an aortocoronary bypass operation may follow. In a non-randomized study of 411 patients treated successfully with thrombolysis the best prognosis during the hospital phase and the subsequent 12 months was found in those who had had bypass surgery; patients treated with PTCA had the next best prognosis, and those treated with medical therapy had the worst. In a randomized study 95 patients were treated with thrombolysis alone and another 95 patients with thrombolysis plus immediate PTCA. PTCA diminished the degree of stenosis significantly (78 +/- 16% vs. 33 +/- 21%; p less than 0.001). This value remained constant during the following four weeks (30 +/- 26%). The clinical course, segmental wall motion and myocardial perfusion were more favourable in the PTCA group. No differences were found regarding spontaneous and inducible ventricular electrical vulnerability. Immediate PTCA without prior thrombolysis was performed in 27 patients with overt cardiogenic shock. The clinical mortality was significantly lower than in comparative studies. Recanalisation was successful in 24 of 27 patients. PTCA is complementary to successful thrombolysis in acute myocardial infarction to improve the prognosis and myocardial perfusion.

Aged↗