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Biomedical subjects

T Köhler

Publications and source records attributed to T Köhler.

At least 19 recordsLinked to original sources
PubMed1996

Comamonas testosteroni 3-ketosteroid-delta 4(5 alpha)-dehydrogenase: gene and protein characterization.

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.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1995

Headache classification based on questionnaire data: which symptoms are especially suitable?

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.

Adult↗
PubMed1995

OprK and OprM define two genetically distinct multidrug efflux systems in Pseudomonas aeruginosa.

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.

Bacterial Outer Membrane Proteins↗
PubMed1995

Evidence for an efflux pump in multidrug-resistant Campylobacter jejuni.

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.

Anti-Bacterial Agents↗
PubMed1995

Psychophysiological responses of borderline hypertensives in two experimental situations.

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.

Adult↗
PubMed1995

[Dream interpretation as access to the unconscious?--An experimental psychological evaluation].

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.

Adult↗
PubMed1994

[Early diagnosis of left ventricular dysfunction following acute myocardial infarct. Doppler echocardiography in a study of its course].

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.

Aged↗
PubMed1994

Regulation of the rpoN, ORF102 and ORF154 genes in Pseudomonas putida.

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.

Amino Acid Sequence↗
PubMed1994

Changes in the number of active sweat glands (palmar sweat index, PSI) during a distressing film.

Changes of the number of active palmar sweat glands (palmar sweat index, PSI) as assessed by the plastic finger-print method were studied in two groups of female students (n = 21 each). In both samples experiments involved an initial adaptation period, several relaxation phases and an activation period (presentation of a movie). The film was shown 10 min earlier in Group 1, for which in turn follow-up was twice as long. Prints for determination of PSI were taken every 2.5 min from the forefinger and ring finger of the left hand, and recordings of SCL, SF (number of spontaneous fluctuations) and HR were made during the corresponding intervals. Both within- and between-groups comparisons showed an increase of PSI during the activation period and a decrease afterwards. Similar effects were observed for SCL, SF and affective and somatic arousal assessed by a state questionnaire. A decrease of PSI and parameters of electrodermal activity during the first measurements indicated an initial reaction to the assessment procedure itself. Both within-subject and between-subjects correlations between PSI from both fingers showed high parallel test reliabilities, while correlations with electrodermal variables indicated a common physiological basis.

Adult↗
PubMed1994

Cross talk between catabolic pathways in Pseudomonas putida: XylS-dependent and -independent activation of the TOL meta operon requires the same cis-acting sequences within the Pm promoter.

The Pm promoter of the meta cleavage operon in the TOL (toluene degradation) plasmid pWW0 of Pseudomonas putida becomes activated by the plasmid-encoded XylS regulator in the presence of benzoate and certain substituted analogs such as 3-methylbenzoate. In the absence of XylS, Pm was still responsive to unsubstituted benzoate but with induction kinetics and a range of transcriptional activity which differed substantially from those for the XylS-mediated activation. XylS-independent induction by benzoate did not occur in a rpoN genetic background. Pm was also silent while cells were actively growing in rich medium. However, XylS-dependent transcription and XylS-independent transcription were initiated at the same nucleotide, as determined with primer extension mapping. Furthermore, a series of deletions and mutations at the Pm promoter sequence showed the same overall pattern of responsiveness to benzoate with and without XylS, thus providing genetic evidence that the same promoter structure is recognized and activated by at least two different regulators. One of them is XylS, while the other, provided by the host bacterium, could be related to the chromosome-encoded benzoate degradation pathway.

Bacterial Proteins↗
PubMed1994

Isolation and phenotypic characterization of Myxococcus xanthus mutants which are defective in sensing negative stimuli.

Myxococcus xanthus is a gram-negative gliding bacterium that exhibits a complex life cycle. Exposure of M. xanthus to chemicals like dimethyl sulfoxide (DMSO) at nondeleterious concentrations or the depletion of nutrients caused several negative responses by the cells. DMSO (> 0.1 M) or nutrient depletion triggered a repellent response: cell swarming was inhibited and FrzCD (a methyl-accepting chemotaxis protein) was demethylated; higher concentrations of DMSO (> 0.3 M) or prolonged starvation induced an additional response which involved cellular morphogenesis: DMSO caused cells to convert from rod-shaped vegetative cells to spherical, environmentally resistant "DMSO spores," and starvation induced myxospore formation in the fruiting bodies. In order to investigate the nature of these responses, we isolated a number of mutants defective in negative chemotaxis and/or sporulation. Characterization of these mutants indicated that negative chemotaxis plays an important role in colony swarming and in developmental aggregation. In addition, the results revealed some of the major interrelationships between the signal transduction pathways which respond to negative stimuli: (i) DMSO exposure and starvation were initially sensed by different systems, the neg system for DMSO and the stv system for starvation; (ii) the repellent response signals triggered by DMSO or starvation were then relayed by the frz signal transduction system; mutants defective in these responses showed altered FrzCD methylation patterns; and (iii) the morphogenesis signals in response to DMSO or starvation utilize a group of genes involved in sporulation (spo).

Bacterial Proteins↗
PubMed1994

[The significance of recurrence-inducing events for patients with chronic inflammatory bowel diseases. Results of a prospective longitudinal study over three years].

This study examined whether life event stress under general or more specific conditions (fear of separation, feeling of being under pressure, feeling of being caught between two quarreling parties, separation experiences) contribute to the aggravation of inflammatory bowel disease. Firstly, 51 patients with ulcerative colitis, 57 patients with Crohn's disease, and 60 controls were compared in terms of these variables. In addition, the IBD patients filled out questionnaires regarding life events, the specific psychological conditions mentioned above, and their symptoms several times in the three years after the first measurement. By means of group comparisons and intraindividual correlations between relapse precipitating life events and illness activity, only feelings of being under pressure showed a modest correlation to the disease activity. We conclude that the variables in question have little influence on the beginning of the relapse.

Adaptation, Psychological↗
PubMed1993

Chemotaxis plays a role in the social behaviour of Myxococcus xanthus.

Myxococcus xanthus is a Gram-negative bacterium that glides on a solid surface and displays a wide range of social behaviour including microbial development. The frz genes are homologues to the chemotaxis genes of Escherichia coli and Salmonella typhimurium and have been shown to be involved in microbial development. However, chemotaxis has never been clearly demonstrated in Myxococcus. In this study, we showed that M. xanthus exhibited tactic movements to many chemicals when they were subjected to steep and stable chemical gradients. M. xanthus was observed to spread into areas with abundant nutrients like yeast extract or Casitone and avoid areas with no nutrients or repellents (short-chain alcohols or DMSO). Responses to attractants and repellents were additive. Movement towards attractants or away from repellents required the frz genes and was correlated with methylation or demethylation of FrzCD, a methyl-accepting taxis protein. Furthermore, the frz genes were found to be required for both fruiting body formation during starvation and swarming in nutrient-rich medium. In wild-type strains, cells near the colony edge were observed to swarm towards the surrounding growth medium and to contain highly methylated FrzCD; cells near the colony centre contained mainly demethylated FrzCD and showed directed movement towards the colony edge. FrzCD was also found to be methylated during the aggregation stage of fruiting body formation on agar but largely demethylated in cells shaken in liquid starvation media. An frzE mutant failed to exhibit directed cell movements and no longer showed modification of FrzCD under these conditions. These observations suggest that M. xanthus does show chemotactic movements, that these movements require the frz genes, and that chemotaxis plays a very important role in the social behaviour of this organism.

Bacterial Proteins↗
PubMed1993

The relationship between neuroticism and blood pressure reexamined. An investigation of a nonclinical sample of military conscripts.

Given the contradictory results reported in the literature on the relationship between neuroticism and blood pressure, it was decided to reexamine this topic. This was done with a large sample very homogeneous for age, sex, food intake and life style and basically unselected in terms of medical history. In the frame of a blood donation program blood pressure was measured in 810 conscripts. In addition, subjects completed either form A or form B of the Eysenck Personality Inventory (EPI). Data from a total of 624 subjects were suitable for evaluation. No significant correlations were obtained between systolic or diastolic blood pressure and scores of neuroticism or extraversion (r = -0.10 to 0.06) nor did groups with different blood pressure values differ substantially in terms of these variables. This supports work showing that there is no essential connection between blood pressure and emotional lability as measured by the EPI.

Adult↗
PubMed1992

Phospholipase A2 inhibition by alkylbenzoylacrylic acids.

3-(4-Alkylbenzoyl)acrylic acids (ABAAs) were synthesized by acylation of alkylbenzenes with maleic anhydride and then screened in vitro for inhibition of phospholipase A2 (PLA2) from snake venom and from porcine pancreas. The inhibitory potency of ABAAs increased with the length of the alkyl residues resulting in IC50 values of between 10(-7) and 10(-4) mol/L. The most potent inhibitors of the snake venom PLA2 were the 4-(n)-hexadecyl and octadecyl (OBAA) derivatives. Kinetic experiments referred to a time-dependent inhibitory reaction. Irreversibility was examined by dilution and dialysis. A molar ratio of inactivation of OBAA of nearly 20 was estimated. Double reciprocal replots of the apparent inactivation constants to the concentration of OBAA gave a (pseudo) first order rate constant of inactivation of 2.3 min-1. For the dissociation constant of the enzyme-inhibitor intermediate, a value of 6 x 10(-6) mol/L was obtained. On the other hand, the PLA2 from porcine pancreas seemed hardly to be inhibited by ABAAs. The present data are discussed in relation to the proposed model for PLA2 inactivation by manoalide. In human PMNs leukotriene B4 and 5-HETE production was essentially reduced. In human platelets the thrombin-induced TxA2 production was reduced. Since these effects disappeared after addition of arachidonic acid, these findings refer to a PLA2 inhibition. The immunologically induced bronchospasm in guinea pigs was significantly and dose-dependently inhibited by OBAA. This indicates that ABAAs might be useful in treating allergic diseases, such as asthma, eczema, allergic shock and others.

Acrylates↗
PubMed1992

Effect of ileo-rectal anastomosis and post-valve T-caecum cannulation on growing pigs. 1. Growth performance, N-balance and intestinal adaptation.

The effects of post-valve T-caecum (PVTC) cannulation and end-to-side ileo-rectal anastomosis (IRA) on growth performance, nitrogen retention and intestinal fermentation were measured in growing pigs by comparison with a control group of intact animals. There were no differences between PVTC-pigs and intact pigs in growth performance and N balance. In IRA-animals reduced growth (P < 0.01), less efficient feed conversion (P < 0.01) and decreased N retention (P < 0.001) were found. Indices of fermentation measured in ileal digesta of PVTC- and IRA-pigs were considerably different. In IRA-animals the concentration of volatile fatty acids (VFA) was about 112-162 mmol/l, higher (P < 0.001) than in digesta of PVTC-pigs (20-31 mmol/l). The molar proportions of acetate and propionate depended (P < 0.01 and P < 0.001 respectively) on the digesta-collection technique. Concentrations and ratios of VFA measured in PVTC-pigs were similar to reported values. Diaminopimelic acid (DAPA) concentration and N:DAPA ratios measured in digesta were significantly (P < 0.05 and P < 0.001 respectively) different between treatments. All digesta variables measured showed increased microbial activity in digesta of IRA-pigs; thus, an influence on digestibility measurement can be assumed.

Adaptation, Physiological↗