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Biomedical subjects

S Neumann

Publications and source records attributed to S Neumann.

At least 55 records · Page 3Linked to original sources
PubMed1998

Purification and properties of the F1F0 ATPase of Ilyobacter tartaricus, a sodium ion pump.

The ATPase of Ilyobacter tartaricus was solubilized from the bacterial membranes and purified. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme revealed the usual subunit pattern of a bacterial F1F0 ATPase. The polypeptides with apparent molecular masses of 56, 52, 35, 16.5, and 6.5 kDa were identified as the alpha, beta, gamma, epsilon, and c subunits, respectively, by N-terminal protein sequencing and comparison with the sequences of the corresponding subunits from the Na(+)-translocating ATPase of Propionigenium modestum. Two overlapping sequences were obtained for the polypeptides moving with an apparent molecular mass of 22 kDa (tentatively assigned as b and delta subunits). No sequence could be determined for the putative a subunit (apparent molecular mass, 25 kDa). The c subunits formed a strong aggregate with the apparent molecular mass of 50 kDa which required treatment with trichloroacetic acid for dissociation. The ATPase was inhibited by dicyclohexyl carbodiimide, and Na+ ions protected the enzyme from this inhibition. The ATPase was specifically activated by Na+ or Li+ ions, markedly at high pH. After reconstitution into proteoliposomes, the enzyme catalyzed the ATP-dependent transport of Na+, Li+, or Hi+. Proton transport was specifically inhibited by Na+ or Li+ ions, indicating a competition between these alkali ions and protons for binding and translocation across the membrane. These experiments characterize the I. tartaricus ATPase as a new member of the family of FS-ATPases, which use Na+ as the physiological coupling ion for ATP synthesis.

Amino Acid Sequence↗
PubMed1997

Evaluation of the cathetron system for recycling angioplasty catheters.

The Cathetron (Minntech Corporation, Minneapolis, MN) peracetic acid-based reprocessing method for percutaneous transluminal coronary angioplasty (PTCA) catheters was evaluated for ability to sterilize and maintain catheter integrity. The balloons and lumens of 42 catheters (140 reprocessing cycles) were inoculated with suspensions of Staphylococcus epidermidis, S. aureus, Pseudomonas aeruginosa, and Bacillus circulans. Five catheters failed the initial evaluation of mechanical integrity and were discarded. Cultures from 37 catheter lumens, balloons, and hubs (n = 349) were negative following reprocessing. The Cathetron system reliably sterilized PTCA catheter, however, further studies using different brands of catheters and evaluating catheter sterility over time under storage conditions are required.

Angioplasty, Balloon, Coronary↗
PubMed1997

Discoordinate gene expression of gyrA and gyrB in response to DNA gyrase inhibition in Escherichia coli.

The intracellular level of DNA supercoiling is regulated in Escherichia coli by a homeostatic control mechanism that includes DNA gyrase and topoisomerase I gene expression. Despite several biochemical and genetical evidence that supports the existence of a homeostatic regulation mechanism, there are only few studies focusing gyrA and gyrB gene expression in connection to the mechanism involved in the regulation of DNA supercoiling in vivo. To study DNA gyrase gene expression and to be able to isolate mutants with altered expression of DNA gyrase, we constructed a new chromosomal reporter system based on two translational fusions of gyrA and gyrB to lacZ Using this stable monitor system in a robust wild type, we simultaneously studied the influence of several inhibitors of DNA gyrase (quinolones and coumarins) on gyrA and gyrB gene expression as well as on the intracellular level of DNA supercoiling. Surprisingly, we found a delayed and differential response of gyrA and gyrB gene expression following inhibition of DNA gyrase by quinolones or coumarins. Whereas both groups of drugs were able to increase the expression of gyrA, the gyrB gene expression was only induced by the coumarins. Although the action of the quinolones was able to alter DNA supercoiling, we never observed any induction of gyrB from the chromosome. These results revealed that the gene expressio of gyrA appears to be more sensitive to alterations in DNA supercoiling than the gyrB gene expression and suggest that probably additional regulatory mechanisms on the post-translational level might be involved in the regulation of DNA supercoiling and DNA gyrase gene expression.

Aminocoumarins↗
PubMed1997

Ondansetron, droperidol and their combination for the prevention of post-operative vomiting in children.

In this study the antiemetic effects of droperidol, ondansetron and their combination were evaluated in 160 ASA Grade I and II children undergoing surgery for strabismus, who were randomly assigned to one of four groups: Group D received droperidol 75 micrograms kg-1, group O ondansetron 0.1 mg kg-1, group D+O received both droperidol 75 micrograms kg-1 and ondansetron 0.1 mg kg-1, and group N NaCl as placebo. Emesis within the first 24 h occurred in 95.0% of the children with placebo medication, compared with 32.5% (D), 40.0% (O) and 45.0% (D+O) in the groups with antiemetic prophylaxis. The differences between group N and all other groups were significant (P < 0.001). However, there were no statistically significant differences between the groups D, O and D+O. It is concluded that droperidol (75 micrograms kg-1) and ondansetron (0.1 mg kg-1) both significantly reduce PONV in children undergoing surgery for strabismus. Neither ondansetron, nor the combination D+O were superior to droperidol alone.

Adolescent↗
PubMed1997

The ssb-113 allele suppresses the dnaQ49 mutator and alters DNA supercoiling in Escherichia coli.

Mutations in the dnaQ gene, which encodes the proofreading epsilon-subunit of the DNA polymerase III holoenzyme, lead to a mutator phenotype caused by enhanced error rates during DNA replication. In this paper, we studied the influence of ssb mutations on the dnaQ49 mutator, because of the involvement of SSB protein in DNA replication. We found that the ssb-113 mutation suppresses the mutator phenotype of dnaQ49. The suppression effect resulted from an enhanced expression of the dnaQ49 allele as determined by experiments with gene fusions. S1 nuclease analysis revealed that the increased dnaQ expression is based on transcriptional activation of the dnaQP2 promoter. This seems to be the consequence of an increased DNA supercoiling in the ssb-113 mutant, which also influenced further functions that are sensitive to alterations in DNA supercoiling. These results support the hypothesis that the expression of the epsilon-subunit of DNA polymerase III may additionally be modulated by DNA supercoiling, and suggest a possible role for DNA topology in mutagenesis.

Alleles↗