Biomedical subjects
Publications and source records attributed to T Köhler.
New color Doppler sonography with high resolution improves the detection of liver tumors and provides better information on the hepatic vessels. Echo contrast agents which pass through the lungs open up new fields of application in the investigation of blood flow.
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Fallopian tube carcinoma (FTC) is a rare but lethal gynaecological malignancy. Four out of seven FTCs were identified with three point missense mutations, one single base deletion and one silent point mutation in the p53 gene. Genital-type HPV sequences were not detected. The S-phase fraction of tumours with mutant and wild-type p53 was 25.74% (median) and 12.55% (median) respectively.
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Pseudomonas aeruginosa possesses at least two multiple drug efflux systems which are defined by the outer membrane proteins OprM and OprJ. We have found that mutants overexpressing OprM were two- and eightfold more resistant than their wild-type parent to sulfamethoxazole (SMX) and trimethoprim (TMP), respectively. For OprJ-overproducing strains, MICs of TMP increased fourfold but those of SMX were unchanged. Strains overexpressing OprM, but not those overexpressing OprJ, became hypersusceptible to TMP and SMX when oprM was inactivated. The wild-type antibiotic profile could be restored in an oprM mutant by transcomplementation with the cloned oprM gene. These results demonstrate that the mexABoprM multidrug efflux system is mainly responsible for the intrinsic resistance of P. aeruginosa to TMP and SMX.
Comamonas testosteroni delta 4(5 alpha)- and delta1-dehydrogenases [delta4(5alpha)- and delta1DH] are key enzymes in the degradation of steroids having an A:B ring fusion in a trans configuration. We previously reported the isolation of the delta1dh gene (P. Plesiat, M. Grandguillot, S. Harayama, S. Vragar, and Y. Michel Briand, J. Bacteriol. 173:7219-7227, 1991). In this study, the gene encoding delta 4(5 alpha)DH was cloned in Escherichia coli on a 16-kbp BamHI fragment by screening a genomic bank of C. testosteroni ATCC 17410 with a probe derived from delta1dh. Subcloning experiments in plasmid pUC19 mapped delta 4(5 alpha)dh immediately downstream of delta1dh. The enzyme was overexpressed 18-fold in cells of E. coli JM109 carrying a 2.5-kbp cloned fragment (plasmid pXE25). However, much higher levels of enzymatic activity (264-fold) were obtained in Pseudomonas putida KT2440, using pMMB208 as an expression vector. Studies with crude lysates of KT2440 showed that delta4(5alpha)DH exhibits higher specificity and higher activity toward delta l-androstene-3,17-dione than toward the saturated derivative 5 alpha-androstane-3,17-dione. The reaction was found to be irreversible and to use efficiently typical flavoprotein electron acceptors; optimal conditions for the enzyme activity were pH 8 and 40 degrees C. Analysis of the nucleotide sequence of the insert of pXE25 revealed an open reading frame of 1,593 bp preceded by a putative ribosome-binding site and followed by a potential transcription terminator. The amino acid sequence of the deduced peptide showed a typical flavin adenine dinucleotide-binding site in its N-terminal region, confirming the flavoproteinic structure of delta 4(5 alpha)DH. The predicted molecular mass was consistent with that of the enzyme expressed in a T7 polymerase system (60 kDa). Alignment between delta 4(5 alpha)dh and delta1dh indicated that both genes, though coding for functionally related enzymes, do not derive from a common ancestor.
In replication of a recent study, another experiment was carried out to test Freud's assumption that the elements of the dream are particularly close to the repressed unconscious and that free associations starting from them should therefore encounter successively growing resistance. 15 female subjects were asked to associate to parts of their own dreams and to those of a control subject. Skin conductance reactions (SCR) were assessed during these procedures. In addition, subjects had to report as often as possible about accompanying feelings of uneasiness during associations; this was achieved by pressing a button. Areas below SCR curves, considered as a measure of psychophysiological activation, were significantly greater during associations to own dreams. In addition, SCR values rose more often under these conditions. Feelings of uneasiness were more pronounced during associations to own dreams and such feelings increased more often under these circumstances. In spite of some difficulties implied in the experimental procedure, these findings again are in accordance with Freud's theories of dreams, resistance and repression.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
In replication of two recent studies, it was intended to show that headache symptoms obtained by means of questionnaires fit a categorial model, provided that appropriate methods of data analysis are used. In addition, the questions which are best posed to obtain a succinct classification should be determined. Configural frequency analysis (CFA) was applied to 7 answers for headache symptoms in 2 samples (n = 602 and 606). In both samples classification became more succinct when the symptoms taken into consideration were reduced to 5. Questions for the quality of pain (pulsating vs not pulsating) did not supply much information nor did the question about aggravation during physical activity in Sample I and for photophobia in Sample II enhance the succintness of the classification. Based on 5 symptoms, however, namely: (1) pain occurring in attacks; (2) unilaterality; (3) visual prodromi; (4) nausea/vomiting and (5) photophobia in Sample I, aggravation during physical activity in Sample II, CFA clearly revealed a few headache syndromes. They could easily be interpreted as migraine with aura, migraine without aura, and tension headaches. Combinations of both migraine and tension headache symptoms did not occur more often and sometimes less often than expected by chance.
Multidrug-resistant derivatives of Pseudomonas aeruginosa PAO1 were obtained after stepwise selection on tetracycline or erythromycin. Two phenotypes were generated. The tetracycline-resistant mutant (TETR) was phenotypically similar to OprM-overexpressing strains. This group displayed cross-resistance to quinolones, chloramphenicol, and all beta-lactams tested except imipenem, with no changes in the erythromycin MICs for the strains. Sodium dodecyl sulfate-polyacrylamide gels showed the overproduction of an outer membrane protein in the range of 50 kDa and a 46-kDa inner membrane protein. The erythromycin-resistant mutant (ERYR) kept its susceptibility to all beta-lactams tested with the exception of cefpirome, but it was resistant to chloramphenicol, quinolones, and tetracycline and was hypersusceptible to imipenem. This mutant also exhibited overexpression of a 50-kDa outer membrane protein that was different from OprM and of a 43-kDa inner membrane protein. The phenotype of ERYR was comparable to those of OprK- and OprJ-overexpressing strains. These strains were therefore classified as the OprK-like group. Transduction of the oprK::omega-Hg mutation of strain K613 (K. Poole, K. Krebes, C. McNally, and S. Neshat, J. Bacteriol. 175:7363-7372, 1993) into the multidrug-resistant strains resulted in the loss of multidrug resistance and the acquisition of hypersusceptibility in the OprM group, while the phenotype of the OprK-like group was unaffected. These experiments demonstrated the existence of two genetically distinct efflux systems in P. aeruginosa. The identities of the operons encoding the two efflux systems and their physiological roles are discussed.
Mechanisms of drug resistance in Campylobacter jejuni were investigated. Mutant strains 34PEFr, which was resistant to pefloxacin (128-fold increase in the MIC), and 34CTXr, which was resistant to cefotaxime (32-fold increase in the MIC) and which was derived from the susceptible parent 34s, were obtained by serial passages on pefloxacin and cefotaxime gradient plates, respectively. Both mutants showed cross-resistance to erythromycin, chloramphenicol, tetracycline, beta-lactams, and quinolones. While the quinolone resistance of strain PEFr could be explained by a mutation at codon 86 of the gyrA gene, the multidrug resistance phenotype of both strains was further investigated. Accumulation of pefloxacin, ciprofloxacin, and minocycline was measured by fluorometry and was found to be lower in the mutant strains than in the parent strain. Preincubation of the cells with carbonyl cyanide m-chlorophenylhydrazone, however, completely abolished this difference. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of outer membrane preparations from both mutant strains showed overexpression of two proteins of 55 and 39 kDa which were absent from the outer membranes of the wild-type strain. These results indicate that in C. jejuni 34PEFr and 34CTXr, multidrug resistance is associated with an efflux system with a broad specificity.
Given the contradictory reports concerning psychophysiological reactivity of hypertensives this issue was reexamined. In contrast to the large majority of studies, the hypertensive sample should not be made up of patients in medical care and the control group should be comparable in all relevant aspects other than blood pressure. Twelve male subjects with blood pressure values in the borderline range and 12 normotensive controls were recruited from a blood donation program. Experiments consisted of two parts with baseline, stress and follow-up. Stressors were a short distressing movie and mental arithmetic. Systolic and diastolic blood pressure (SBP and DBP), heart rate (HR), skin conductance level (SCL) and number of spontaneous electrodermal fluctuations (SF) were assessed in 2-min intervals, plasma adrenaline and noradrenaline once during baselines, stress 2 and follow-up 2. Hypertensives exhibited significantly higher SPB levels, and partially elevated values for DBP, HR and SCL. Response reactions to stressors, however, did not differ between groups. There was no evidence that psychophysiological adaptation during stress and recovery thereafter was impaired in hypertensives. Our results do not support the reactivity hypothesis of hypertension. Possible reasons for our failure to replicate findings from other studies are discussed.
An experiment was carried out to test Freud's assumption that the elements of the manifest dream are in particular closeness to the repressed unconscious and that free associations starting from them should therefore encounter quickly successively growing resistance. 30 female subjects were asked to associate to parts of their own dreams and of those of a control subject. Skin conductance reactions (SCR) were assessed during these procedures. The areas below the SCR curves, considered as a measure for psychophysiological activation, were significantly greater during associations to own dreams. In addition, SCR values rose significantly more often in the course of associations to the persons' own dreams than to those of other subjects. The correlation between subjectively perceived emotionality and integrated SCR values proved to be high. This justifies the use of the variable as an indicator of affective arousal. Although the experimental condition was necessarily only a rather incomplete realisation of the psychoanalytic situation, our results clearly support Freud's theory.
The prognosis of acute myocardial infarction depends on the development of left-ventricular dilatation and chronic heart failure. Serial echocardiography was performed on admission and on days 2, 4 and 6, to discover the temporal course of any early myocardial adaptation. There were 78 patients (20 women, 58 men; mean age 59 [49-69] years) with acute myocardial infarction and systemic thrombolysis, first studied up to 4 hours after onset of symptoms. The patients were divided into two groups according to infarct size as measured by creatine kinase ("area under the curve"--AUC); group 1: CK AUC < 12 IU/ml.h; group 2: CK AUC > 12 IU/ml.h. While there was no difference between the two groups on admission and on day 2, filling patterns differed significantly at the end of the first postinfarction week in that maximal early diastolic flow velocity (E) in group 1 was 0.65 m/s, but 0.73 m/s in group 2 (P < 0.05); maximal late diastolic flow velocity (A), group 1: 0.71, group 2: 0.58 m/s (P < 0.01); E/A ratio: 0.89 vs 1.22 (P < 0.001); integrated E/A ratio 1.37 vs 1.77 (P < 0.001), and the atrial component of left-ventricular filling 42 vs 36% (P < 0.001). It is concluded that the serial measurement of left-ventricular filling by Doppler echocardiography in the first post-infarction week can identify patients with impaired left-ventricular function through differences in flow pattern. Drug or interventional treatment can then be started early to prevent further left-ventricular dilatation and in this way improve prognosis.
The DNA sequence downstream of the Pseudomonas putida rpoN gene and the adjacent ORF102 was determined. This region encodes an ORF (ORF154) whose gene product was found to be homologous to a family of phosphotransferases. Insertional mutagenesis and analysis of mRNA transcripts showed that the rpoN gene is transcribed separately from the two downstream genes. The rpoN promoter was localized to an 86 nucleotide-long region upstream of the rpoN gene by examination of the expression of a series of rpoN::lacZ fusions. The expression of rpoN in P. putida was independent of the nitrogen status of the cell but was 5 times higher in the rpoN mutant than in the wild-type strain, suggesting that the expression of the rpoN gene in this organism is autoregulated.