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Biomedical subjects

F Mach

Publications and source records attributed to F Mach.

At least 55 records · Page 3Linked to original sources
PubMed1997

An improved rapid troponin T test with a decreased detection limit: a multicentre study of the analytical and clinical performance in suspected myocardial damage.

In a multicentre study, we evaluated the analytical and diagnostic performance of the second version of the TROPT rapid test (TROPT 2, CARDIACT in the US). We tested TROPT 2 on 796 blood samples from 487 patients admitted on suspicion of myocardial infarction between 1 and 72 h after onset of symptoms and determined cTnT ELISA and CK MB mass in the corresponding serum samples. Frequency distributions of the results with TROPT 2 showed a detection limit of 0.18 microgram/l (for 50% positive results) as determined by the quantitative cTnT ELISA method. In a total of 796 samples the sensitivities in the detection of myocardial infarction (WHO criteria) 8-12 h after onset of symptoms were highest for cTnT ELISA (98%), followed by the rapid assay and CK MB mass (92%). A subgroup of 87 patients was primarily classified by the WHO criteria for definite infarction. Based on the maximum values within each patient time-series, diagnostic sensitivities for infarction were 100% for TROPT2, cTnT ELISA and CK MB mass. The corresponding specificities were 90%, 82% and 100%, respectively. After reclassification summarizing all cases of myocardial damage (acute and subacute myocardial infarctions and minor myocardial damage) the sensitivities were 87% (TROPT2), 100% (cTnT ELISA) and 71% (CK MB mass). The specificities of all three markers were 100%. Over 50% of all cases of minor myocardial damage were detected by TROPT 2. The clinical evaluation showed that the diagnostic performance of TROPT 2 is only slightly lower than that of cTnT ELISA.

Angina, Unstable↗
PubMed1996

Macrophages and atherosclerotic plaque stability.

Physical disruption of atheroma frequently causes coronary thrombosis. Ruptured plaques usually have thin fibrous caps overlying a large thrombogenic lipid core rich in lipid-laden macrophages. The biology of plaque monocyte-derived macrophages thus assumes critical importance in understanding plaque instability. Monocyte recruitment involves binding to leukocyte adhesion receptors on the endothelial surface such as intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. Once adherent to the endothelial surface, monocytes enter the intima at sites of lesion predilection. This process probably requires directed migration of the mononuclear cells. A number of chemoattractant molecules, such as the monocyte chemoattractant molecule-1, may participate in signaling this entry of adherent monocytes into the artery wall. Once resident in the arterial intima, monocytes accumulate lipid, via increasingly well characterized receptor-mediated uptake, and transform into macrophage foam cells. These lesional macrophages also acquire other functional properties including production of the potent procoagulant, tissue factor, apolipoprotein E, and an increasing list of cytokines (protein mediators of information and immunity) that may participate importantly in autocrine and paracrine signaling among leukocytes and vascular endothelial and smooth muscle cells. Fatty streaks seldom cause clinical events but may evolve into complicated atheromatous plaques characterized by an accumulation of smooth muscle cells and extracellular matrix and formation of a central core containing extracellular lipid. Death of macrophages, including programmed cell death or apoptosis, probably promotes formation of this thrombogenic lipid pool whose size correlates with plaque instability. Lesion complication often culminates in rupture of the fibrous cap overlying this lipid core. The integrity of the fibrous cap, and thus its resistance to rupture, depends critically on the collagenous extracellular matrix of the plaque's fibrous cap. This aspect of plaque structure in turn depends upon the balance between synthesis and degradation of the macromolecules that comprise the extracellular matrix of the cap, principally interstitial forms of collagen derived from arterial smooth muscle cells. Collagen breakdown, however, appears to depend critically on macrophages. Plaque macrophages express a variety of matrix-degrading enzymes that can contribute to the weakening of the fibrous cap. In this way, macrophages can critically influence aspects of the biology of human atheroma related to lesion stability. We hypothesize that lipid-lowering reduces clinical events, as shown in recent trials, by stabilizing lesions in part by reversing some of the maladaptive functions of macrophages described above.

Arteriosclerosis↗
PubMed1994

Heat shock proteins and the kidney.

The heat shock (HS) response is remarkably conserved during evolution and is evoked under many conditions of stress. There are a number of ways in which this ubiquitous response may be important for the understanding of renal pathophysiology. Ischemia, toxin exposure, and oxidative stress induce this response. Several models of hypertension are associated with increased susceptibility to environmental stress and increased accumulation of heat shock protein mRNA. HSP70 polymorphism has been demonstrated when comparing normotensive and hypertensive rats. Heat shock proteins may play a role in renal diseases through their important involvement in immunological processes. Several observations point to a role of the heat shock response in systemic lupus erythematosus (SLE). Autoantibodies against HSP70 and ubiquitin are found in many patients with this disease. Autoantibodies against ubiquitin and ubiquitinated histone H2A are localized to the kidney glomerular basement membrane of SLE patients with active disease. A better understanding of the HS response may thus provide important insight into renal pathophysiology and may suggest paradigms for therapeutic interventions.

Adult↗
PubMed1986

Physiological studies on pBR 322 DNA amplification in an Escherichia coli relA strain.

Amino acid limitation leads in E. coli relA cells which cannot synthesize guanosine tetraphosphate (ppGpp) under these conditions to an amplification of pBR 322 DNA. We previously proposed that ppGpp produced in E. coli relA+ cells subjected to amino acid limitation inhibits pBR 322 DNA replication (Hecker et al. 1983). In further experiments it was established that an E. coli relA strain shows plasmid amplification during amino acid limitation (arginine, threonine, leucine or histidine) only in the presence of sufficient concentrations of phosphate, ammonia and glucose. Plasmid amplification does not occur if ammonia or phosphate is depleted. We suggest that glucose, ammonia and phosphate are needed for nucleotide and deoxynucleotide synthesis as the essential prerequisite for plasmid amplification. The activity of beta-lactamase was determined as an indicator for the expression of plasmid-encoded genes. The enzyme activity remains on a low level during plasmid amplification because of arginine exhaustion. A remarkable increase in the activity of beta-lactamase was observed after resumption of growth of relA cells containing amplified plasmid DNA. The plasmid content decreased as the cells continued to grow. We found that plasmid amplification and expression of plasmid-localized genes are opposite reactions which do not occur at the same time.

Amino Acids↗
PubMed1986

Role of relA mutation in the survival of amino acid-starved Escherichia coli.

Amino acid-starved cells of Escherichia coli relA+, which contain a large number of glycogen particles, are able to survive in phosphate buffer for a longer time period than their relaxed counterparts. With regard to NH4+ starvation differences in the survival of both strains were not found. NH4+ starved cells of E. coli relA are able to synthesize glycogen but amino acid-starved cells of the relA strain are not. We suggest that the synthesis of glycogen triggered by guanosine tetraphosphate during amino acid starvation is responsible for the prolonged viability of the E. coli relA+ strain.

Amino Acids↗
PubMed1985

[Comparative cytologic studies on the effect of cetyltrimethylammonium bromide on bacterial cells].

Growing cultures of Pseudomonas aeruginosa and Bacillus megaterium show after treatment with cetyltrimethylammonium bromide (CTAB) typical concentration-dependent alterations of envelope. In Ps. aeruginosa low doses of the detergent cause perforations and lesions of the cytoplasmic membrane, by 0.016% CTAB the formation of extracellular vesicles of the outer membrane ("blebs") and the intracellular assembly of lamellar structures can be detected. These intracellular lamellar structures are artifacts of the cytoplasmic membrane after detergent application. In this case the conglomeration of bacterial cells can be demonstrated with the scanning electron microscope. The results are discussed in connection with the use of CTAB in inactivation and permeabilization of bacteria.

Anti-Infective Agents, Local↗
PubMed1984

[Formation of plasmid pBR322 oligomers as depending on a tetracycline concentration].

Escherichia coli K12 strains containing the plasmid pBR322 often show varying contents of plasmid oligomers, in which the monomer units are arranged in tandem. When the concentration of the plasmid-selective antibiotic tetracycline in the medium becomes increased selection of cells containing largely higher oligomers occurs. The number of monomer units organized in the oligomers increases with tetracycline concentration. recA- mutants are unable to generate oligomers under the same conditions and show lower tetracycline resistance. This observations suggest a selective advantage of oligomer containing cells in the presence of tetracycline as a result of higher gene dosage. But E. coli cells transformed with monomers, dimers, trimers, as well as tetramers of pBR322 are characterized by roughly the same plasmid DNA content as well as plasmid coded beta-lactamase and resistance to tetracycline.

Culture Media↗
PubMed1983

[Replication and expression of plasmid pBR 322 during discontinuous culture of a stringent and relaxed Escherichia coli strain].

The E. coli strains CP78 and CP79 carrying the plasmid pBR 322 display similar growth kinetics in discontinuous culture. During limitation of amino acids the stringent strain CP78 is able to synthesize guanosine-5'diphosphate-3'-diphosphate (ppGpp) and guanosine-5'-triphosphate-3' diphosphate, but the relaxed strain can not produce highly phosphorylated guanosine nucleotides. During the logarithmic phase of growth both strains contain similar amounts of plasmid DNA. During amino acid starvation plasmid DNA is amplified in the relaxed strain only, whereas in the stringent strain the plasmid content per cell remains constant. In stationary phase cells of CP78 a higher activity of plasmid-coded beta-lactamase than in CP79 cells was detected. Furthermore, remarkable differences between both strains were observed in the composition of proteins derived from the periplasmic fraction and separated by polyacrylamide gel electrophoresis. Our results might indicate a negative control of pBR 322 DNA replication by ppGpp during amino acid starvation.

Amino Acids↗
PubMed1983

Replication of pBR322 DNA in stringent and relaxed strains of Escherichia coli.

Synthesis of both chromosomal and plasmid (pBR322) DNA was measured in E. coli strains differing in their relA allele (relA+:CP78; relA:CP79). It was found that upon limitation of a required amino acid or after valine treatment to trigger a stringent response synthesis of pBR322 DNA was stimulated only in the relaxed strain and was inhibited in its stringent counterpart. The results suggest that replication of plasmid DNA is negatively controlled by the relA+ allele.

Chloramphenicol↗
PubMed1982

The localization of SPO1 phage resistance in the genome of Bacillus subtilis as revealed by fusion of protoplasts.

We localized the gene for resistance to phage SPO1 relatively to the markers pur B 34 and ura by means of the polyethylene-glycol induced fusion of bacterial protoplasts of three-fold auxotrophic Bacillus subtilis strains S3 and S13. By this same method, the site of some auxotrophic markers was tentatively determined. The application of the protoplast fusion technique to exact genetic analysis will not be possible until the exo- and endogenous factors influencing cell wall regeneration are standardized. Fluctuations of this kind are very significant for the determination of genetic segregation.

Adsorption↗
PubMed1982

[Cell division and macromolecular synthesis in growing spores of a temperature sensitive filamentous mutant of Bacillus subtilis].

A temperature sensitive mutant of Bacillus subtilis SB 19, strain ts 33-6 was characterized. This strain grows at 46 degrees C (restrictive temperature) with reduced intensity without septation processes. Under restrictive conditions DNA- and RNA-synthesis are remarkably reduced. DNA, however, is synthesized continuously under restrictive conditions causing the formation of multinuclear filaments. Septation, induced at permissive temperature, is not prevented under restrictive conditions. That means that under restrictive conditions initiation of septation is blocked whereas formation of septa can be observed. Shift-up experiments have shown that the initiation of septation processes occurs at an early stage of cell cycle.

Bacillus subtilis↗
PubMed1981

[Synthesis of poly(A)-containing RNA in outgrowing spores of Bacillus subtilis].

The synthesis of poly(A)-containing RNA in outgrowing spores of Bacillus subtilis was studied. A significant amount of RNA puls-labelled with 3H-uridine is polyadenylated. With the beginning of RNA synthesis in outgrowing spores labelled poly(A)-containing RNA was detected. The amount of poly(A)-RNA during the outgrowth and first cell division remains constant. Besides poly(A)-RNA the synthesis of tRNA and rRNA occurs. These results indicate a simultaneous activation of synthesis of tRNA, rRNA as well as of poly(A)-containing RNA during outgrowth of B. subtilis spores.

Bacillus subtilis↗
PubMed1981

[Lysine biosynthesis of Pseudomonas aeruginosa PAO1. III. Further characterization of lysine auxotrophic mutant of Ps. aeruginosa PAO1].

A number of lysine-auxotrophic mutants of Pseudomonas aeruginosa PAO1 were isolated through mutagenesis by means of N-methyl-N-nitrosoguaniine (Mach et al., unpublished). Using the cross feeding test and growth tests classification of lysine mutants was not possible. The investigation of diaminopimelic acid decarboxylase (DAP-DC) showed, that none of these mutants had an active enzyme, except for the mutants with a high number of revertants. The appearance of only one mutant type is attributed to the insufficient availability of DAP.

Bacterial Proteins↗