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Biomedical subjects

M Kuhn

Publications and source records attributed to M Kuhn.

At least 217 records · Page 12Linked to original sources
PubMed1989

2-Epimutalomycin and 28-epimutalomycin, two new polyether antibiotics from Streptomyces mutabilis. Derivatization of mutalomycin and the structure elucidation of two minor metabolites.

A number of derivatives of mutalomycin (1), a naturally occurring polyether antibiotic, have been synthesized. In the desulfurization reaction of the ethylthio derivative (5) of mutalomycin (1) with Raney-nickel we observed an unusual course of the reaction, namely the introduction of a hydroxy group instead of the usual exchange against hydrogen, leading to two reaction products, mutalomycin (1) and 28-epimutalomycin (3). The structure of 3 and 2-epimutalomycin (2), both minor metabolites from the mutalomycin fermentation, were elucidated by X-ray analysis.

Anti-Bacterial Agents↗
PubMed1989

Endothelium-dependent vasodilatation in human epicardial coronary arteries: effect of prolonged exposure to glyceryl trinitrate or SIN-1.

Human epicardial coronary arteries were obtained from the hearts of 15 patients who received cardiac transplantation for cardiomyopathy. Transverse strips of these arteries were mounted in organ baths for isometric tension recording. The arteries were constricted with prostaglandin F2 alpha and then exposed to the endothelium-dependent relaxants substance P (1 nM), bradykinin (1 nM-1 microM), and the Ca2+ ionophore A23187 (1 nM-1 microM). The effects of the endothelium-independent relaxants glyceryl trinitrate (1 nM-10 microM) and SIN-1, the active metabolite of molsidomine (1 nM-10 microM), were also tested. In control strips of human coronary arteries, all vasodilators caused concentration-dependent relaxations. Pretreatment of human coronary arteries with glyceryl trinitrate (0.5 mM for 60 min) shifted the concentration-response curve to glyceryl trinitrate to the right by a factor of approximately 800 (increase in EC50 from 10 nM to 8 microM). In contrast, endothelium-dependent relaxations to substance P, bradykinin, and A23187 and relaxations to SIN-1 were not changed significantly. Previous exposure of human coronary arteries to SIN-1 (0.5 mM for 60 min) did not modify relaxations to any of the agents tested. Our results show that (a) the responsiveness to SIN-1 is not modified in nitrate-tolerant strips of human coronary arteries, (b) prolonged exposure of human coronary arteries to SIN-1 does not cause tolerance, and (c) endothelium-dependent relaxations are not influenced by exposure of human coronary arteries to either glyceryl trinitrate or SIN-1.

Adult↗
PubMed1988

Hemolysin from Listeria--biochemistry, genetics and function in pathogenesis.

Thiol-activated hemolysins (listeriolysins) from Listeria monocytogenes (Sv4b) and Listeria ivanovii were purified to homogeneity. The N-terminal amino acid sequences of the 58 kDa listeriolysin of L. ivanovii and of a 24 kDa protein which may represent the CAMP-factor of L. ivanovii were determined. Antibodies raised against the L. ivanovii listeriolysin and anti-streptolysin O antibodies were used in Western blot analyses to detect listeriolysin(s) in virulent and avirulent Listeria strains. It was found that all virulent strains of L. monocytogenes synthesize and secrete listeriolysin (Mr 58-59 kDa), albeit in significantly variable quantities. No protein cross-reaction with anti-listeriolysin antibodies or anti-streptolysin O-antibodies was present in the supernatant of Listeria innocua, Listeria welshimeri, Listeria grayi and Listeria murrayi strains. Furthermore, the avirulent but hemolytic Listeria seeligeri did not cross-react with these antibodies. In a L. monocytogenes (strain EGD) gene bank constructed in Escherichia coli two types of hemolytic clones were identified. The first type carried recombinant plasmids with a common 2.0 kb fragment coding for a 23 kDa protein. This hemolytic activity was not activated by DTT and the 23 kDa protein did not cross react with anti-listeriolysin or anti-streptolysin antibodies. The other type of hemolytic clones was detected by using anti-streptolysin O antibodies to screen the gene bank. Some of these clones synthesized a protein of 61 kDa which cross reacted with anti-streptolysin O (or anti-listeriolysin) antibodies. By transposon Tn916 mutagenesis of L. monocytogenes two types of nonhemolytic mutants were obtained. Type I produced no extracellular protein that cross reacted with anti-listeriolysin (or anti SLO) antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1988

Microbiological investigation of an outbreak of bacteraemia due to Streptococcus faecalis in an intensive care unit.

An increased incidence of bacteraemia due to Streptococcus faecalis in a Critical Care and Trauma Centre (CCTC) during November 1985 prompted investigation. During the epidemic 21 blood cultures from five CCTC patients were positive for S. faecalis. A point prevalence culture survey revealed two more strains from wounds from two of these five patients. Fifteen strains from blood cultures and the two strains from wound sites were further characterized by conventional biotyping methods and susceptibility patterns, but they could not be differentiated from 40 unrelated control strains by these methods. The API-20S and the API-ZYM systems, however, were able to distinguish the outbreak isolates from the control strains. This investigation supports the hypothesis that S. faecalis is capable of causing cross-infection, and it may be necessary to characterize enterococci beyond routine tests to identify an outbreak due to this organism.

Adult↗
PubMed1988

ECG diagnosis of acute myocardial infarction in patients with bundle branch block.

The ECG diagnosis of myocardial infarction in the setting of bundle branch block is one that most physicians find difficult and that many erroneously believe to be impossible. Two case reports of a patient with right bundle branch block and of a patient with left bundle branch block are presented to illustrate instances in which the ECG diagnosis of myocardial infarction was both possible and essential. Methods for detecting ECG changes that indicate acute myocardial injury in the patient with bundle branch block are presented and applied to these cases.

Aged↗
PubMed1988

Single versus double chamber rate responsive cardiac pacing: comparison by cardiopulmonary noninvasive exercise testing.

A new double chamber rate responsive cardiac pacemaker (DDDMR) has been implanted in seven patients (four males and three females) with a mean age of 62 years. Indication for pacemaker treatment was complete AV block in two patients, complete AV block associated to sinus node disease in three patients and sinus node disease alone in two patients. Six patients underwent two maximal stress tests on a cycloergometer performed twice randomly starting with VVIMR or DDDMR. Basic work load of 50 watts was increased by steps of 25 watts every 2 minutes. Heart rate, respiratory frequency, blood pressure, exercise duration, maximal charge developed, oxygen consumption, rate pressure product, efficiency and Borg scale were compared. Our results show a general trend but no significant differences between all the measured parameters except for efficiency which was significantly higher with DDDMR. These results prove a slight improvement of cardiopulmonary performance in DDDMR pacing compared to VVIMR and also confirm the importance of atrial contribution to cardiac output on exercise.

Adult↗
PubMed1988

Hemolysin supports survival but not entry of the intracellular bacterium Listeria monocytogenes.

The gram-positive bacterium Listeria monocytogenes is a facultative intracellular pathogen. The only known property of L. monocytogenes which has been shown to be involved in virulence is a hemolysin, listeriolysin (J. L. Gaillard, P. Berche, and P. Sansonetti, Infect. Immun. 52:50-55, 1986; S. Kathariou, P. Metz, H. Hof, and W. Goebel, J. Bacteriol. 169:1291-1297, 1987). Using our previously obtained transposon Tn916-induced hemolysin-negative mutants of L. monocytogenes Sv1/2a (Mackaness strain), we demonstrated that the loss of hemolysin reduced significantly the rate of survival of the bacteria in mouse peritoneal macrophages but did not reduce their uptake. It was further shown that virulent L. monocytogenes strains could invade the mouse embryo fibroblast 3T6 cell line, i.e., mammalian cells which are nonprofessional phagocytes. This uptake was inhibited by cytochalasin B and hence seems to be accomplished by parasite-induced endocytosis. Hemolysin was not essential for this step. Strains of other Listeria species could not efficiently penetrate the 3T6 cells.

Animals↗
PubMed1988

Cloning of the Alcaligenes eutrophus alcohol dehydrogenase gene.

Mutants of Alcaligenes eutrophus which are altered with respect to the utilization of 2,3-butanediol and acetoin were isolated after transposon mutagenesis. The suicide vehicle pSUP5011 was used to introduce the drug resistance transposable element Tn5 into A. eutrophus. Kanamycin-resistant transconjugants of the 2,3-butanediol-utilizing parent strains CF10141 and AS141 were screened for mutants impaired in the utilization of 2,3-butanediol or acetoin. Eleven mutants were negative for 2,3-butanediol but positive for acetoin; they were unable to synthesize active fermentative alcohol dehydrogenase protein (class 1). Forty mutants were negative for 2,3-butanediol and for acetoin (class 2). Tn5-mob was also introduced into a Smr derivative of the 2,3-butanediol-nonutilizing parent strain H16. Of about 35,000 transconjugants, 2 were able to grow on 2,3-butanediol. Both mutants synthesized the fermentative alcohol dehydrogenase constitutively (class 3). The Tn5-labeled EcoRI fragments of genomic DNA of four class 1 and two class 3 mutants were cloned from a cosmid library. They were biotinylated and used as probes for the detection of the corresponding wild-type fragments in a lambda L47 and a cosmid gene bank. The gene which encodes the fermentative alcohol dehydrogenase in A. eutrophus was cloned and localized to a 2.5-kilobase (kb) SalI fragment which is located within a 11.5-kb EcoRI-fragment. The gene was heterologously expressed in A. eutrophus JMP222 and in Pseudomonas oxalaticus. The insertion of Tn5-mob in class 3 mutants mapped near the structural gene for alcohol dehydrogenase on the same 2.5-kb SalI fragment.

Acetoin↗
PubMed1988

Active and inactive forms of hemolysin (HlyA) from Escherichia coli.

The HlyA protein (Mr 110 kDa) which is the gene product of the hlyA gene encoded by the hemolysin determinant of Escherichia coli (Goebel, W. & Hedgpeth, J. (1982) J. Bacteriol. 151, 1290-1298) was observed to accumulate in the culture supernatant (in the presence of the three other Hly proteins HlyC, B and D) throughout the active growth cycle. However, the amount of extracellular HlyA protein did not correlate with the external hemolytic activity, which declined when the cells entered the stationary phase. External hemolytic activity was highly sensitive to phospholipase C and to ultrasonication. The size of the HlyA protein on SDS-PAGE was not changed by these treatments although the hemolytic activity was entirely abolished. On a polyacrylamide gel containing 2M urea but only 0.1% SDS hemolytically active HlyA migrated slightly ahead of the inactive HlyA suggesting that HlyA is more negatively charged than HlyA. Active hemolysin from unconcentrated hemolytic supernatants migrated on Sephacryl S-400 and on glycerol gradients as large complexes. Analysis of the hemolytically active fractions on SDS-PAGE yielded in both cases only HlyA (110 kDA) as major protein. An internal hemolytic activity appeared in most Escherichia coli K-12 strains in the stationary phase which was independent of the presence of HlyA or any other Hly gene product. This hemolytic activity which reached in some strains about 10% of the level determined by the hly genes was sensitive to proteinase K and disappeared upon shift of the cells to the logarithmic phase.

Chromatography↗
PubMed1988

[Determination of adenosine deaminase in 295 samples of pleural fluid].

The activity of adenosine deaminase has been measured in 295 specimens of pleural fluid from 248 patients. The effusions were due in part to pleural tubercle (n = 8), rheumatoid arthritis (n = 2) empyema (n = 4), or malignant lymphoma (n = 5); the remainder were due to effusions of other aetiologies (n = 229). The disorders of the first group of patients are known to be associated with an elevated level of ADA. The two groups of patients were compared by fixing the upper limit of normal at 50 U/l. There was a 97% specificity even though the sensitivity was only 42%. However the relative smallness of the group of patients who were suffering from tuberculosis, rheumatoid arthritis, empyema and malignant lymphoma means that the interpretation of the sensitivity of the test should be subject to caution.

Adenosine Deaminase↗
PubMed1986

[Traumatic myocardial infarct. Report of 3 cases].

Three patients aged 52, 22 and 29 years, without known previous heart disease, sustained acute myocardial infarction due to blunt chest trauma. A 52-year-old man without a history of heart disease sustained an acute non-transmural lateral myocardial infarction following blunt chest trauma during a sledging party. No coronary arteriography was performed. The clinical course during follow-up of 3 1/2 years was uncomplicated. A 22-year-old, previously asymptomatic man developed acute transmural anteroseptal infarction after a motor-cycle accident. Seven days later he died suddenly after an uncomplicated initial course. The autopsy demonstrated a complete rupture of the proximal left anterior descending artery with periarterial hemorrhage, compression of this artery by the hemorrhage and luminal thrombosis distal to the rupture. No sign of preexisting atherosclerotic coronary disease was found. A 29-year-old man admitted to the hospital after blunt chest trauma during a football game developed an acute transmural inferior infarction with an uncomplicated clinical course. Seven months later coronary arteriography demonstrated a 40% obstructive lesion of the right coronary artery, compatible with thrombosis and subsequent recanalization.

Accidents, Traffic↗