Biomedical subjects

H G Meyer

Publications and source records attributed to H G Meyer.

At least 19 recordsLinked to original sources

PubMed2001

Degenerate ground state in a mesoscopic YBa2Cu3O(7-x) grain boundary Josephson junction.

We have measured the current-phase relationship I(varphi) of symmetric 45 degrees YBa2Cu3O7-x grain boundary Josephson junctions. Substantial deviations of the Josephson current from conventional tunnel-junction behavior have been observed: (i) The critical current exhibits, as a function of temperature T, a local minimum at a temperature T*. (ii) At T approximately T*, the first harmonic of I(phi) changes sign. (iii) For T<T*, the second harmonic of I(phi) is comparable to the first harmonic, and (iv) the ground state of the junction becomes degenerate. The results are in good agreement with a microscopic model of Josephson junctions between d-wave superconductors.

Journal Article↗

PubMed2000

GyrA sequence-based typing of Legionella.

Comparative sequence analysis of a 423-bp segment of the gyrA gene including a region homologous to the quinolone resistance-determining region (QRDR) of other species was evaluated as a novel typing method for Legionella strains. The study was performed with 29 reference strains representing 11 different Legionella species, with various serogroups, and with 13 clinical isolates of L. pneumophila. Pulsed-field gel electrophoresis and serotyping were employed for comparison of the clinical isolates. QRDR sequencing proved to be a highly discriminative tool for typing Legionellae, and permitted identification of species, serogroups and even different strains within serogroup 1. None of the isolates were resistant to quinolones in vitro and this correlated with dissence of mutations in the QRDR region. The data show that comparative sequence analysis of a short fragment of the gyrA gene is a potentially useful tool for typing of Legionella beyond the serogroup level. It is anticipated that mutations of the QRDR may arise in Legionella as a consequence of the introduction of quinolones as the agents of choice for the treatment of infections with this agent in immunocompromised patients. The employment of QRDR-typing maybe helpful in uncovering such mutations.

4-Quinolones↗

PubMed2000

Helicobacter pylori: clonal population structure and restricted transmission within families revealed by molecular typing.

Helicobacter pylori infects up to 50% of the human population worldwide. The infection occurs predominantly in childhood and persists for decades or a lifetime. H. pylori is believed to be transmitted from person to person. However, tremendous genetic diversity has been reported for these bacteria. In order to gain insight into the epidemiological basis of this phenomenon, we performed molecular typing of H. pylori isolates from different families. Fifty-nine H. pylori isolates from 27 members of nine families were characterized by using restriction fragment length polymorphism analysis of five PCR-amplified genes, by pulsed-field gel electrophoresis (PFGE) of chromosomal DNA, and by vacA and cagA genotyping. The 16S rRNA gene exhibited little allelic variation, as expected for a unique bacterial species. In contrast, the vacA, flaA, ureAB, and lspA-glmM genes were highly polymorphic, with a mean genetic diversity of 0.83, which exceeds the levels recorded for all other bacterial species. In conjunction with PFGE, 59 H. pylori isolates could be differentiated into 21 clonal types. Each individual harbored only one clone, occasionally with a clonal variant. Identical strains were always found either between siblings or between a mother and her children. Statistical analysis revealed clonality of population structure in all isolates. The results of this study suggest the possible coexistence of a large array of clonal lineages that are evolving in each individual in isolation from one another. Transmission appears to occur primarily from mother to child and perhaps between siblings.

Antigens, Bacterial↗

PubMed2000

Comparative evaluation of three different genotyping methods for investigation of nosocomial outbreaks of Legionnaires' disease in hospitals.

The increased incidence of nosocomial Legionnaires' disease in two hospitals prompted investigation of possible environmental sources. In the search for an effective DNA-typing technique for use in hospital epidemiology, the performance and convenience of three methods-SfiI macrorestriction analysis (MRA), amplified fragment length polymorphism (AFLP), and arbitrarily primed PCR (AP-PCR)-were compared. Twenty-nine outbreak-associated and eight nonassociated strains of Legionella pneumophila with 13 MRA types and subtypes were investigated. These strains comprised isolates from bronchoalveolar lavages, from environmental, patient-related sources, and type strains. All three typing methods detected one predominant genotype associated with the outbreaks in both hospitals. All of them correctly assigned epidemiologically associated, environmental isolates to their respective patient specimens. AP-PCR was the least discriminating and least reproducible technique. In contrast, AFLP was demonstrated as being the method with the best interassay reproducibility (90%) and concordance (94%) in comparison to the genotyping standard of MRA and the epidemiological data. Analysis of AFLP fragments revealed 12 different types and subtypes. Because of its simplicity and reproducibility, AFLP proved to be the most effective technique in outbreak investigation.

Bacterial Typing Techniques↗

PubMed1998

Cloning of aas, a gene encoding a Staphylococcus saprophyticus surface protein with adhesive and autolytic properties.

A gene encoding a novel cell wall-associated protein of Staphylococcus saprophyticus that binds fibronectin and to sheep erythrocytes has been cloned and sequenced. The 4392 bp open reading frame codes for an amino acid sequence that is quite similar to the Atl, an autolysin, of Staphylococcus aureus and to the AtlE of S. epidermidis. The two regions of most pronounced homology code for an N-acetyl-muramyl-L-alanine amidase and for an endo-beta-N-acetyl-D-glucosaminidase. The cloned protein lysed cells of S. saprophyticus and Micrococcus luteus exogenously. Subcloning localized the enzymatic activities to the regions of high homology and demonstrated that the interposed sequence is responsible for the adhesive activities. Two allelic replacement mutants were constructed that lacked autolytic activity and adhesive properties. The N-terminal portion of the protein contains seven highly conserved, contiguous repeats with no similarity to published sequences. It lacks the motifs typical of Gram-positive surface proteins and shows a different overall organization. This autolysin/adhesin of S. saprophyticus (Aas) appears to represent a new class of staphylococcal adhesins.

Adhesins, Bacterial↗

PubMed1997

The hemagglutinin of Staphylococcus saprophyticus binds to a protein receptor on sheep erythrocytes.

Staphylococcus saprophyticus, an important cause of urinary tract infections, produces two major surface proteins, the S. saprophyticus surface-associated protein (Ssp) and the hemagglutinin, which mediates fibronectin binding and also functions as the major adhesion of the organism. The hemagglutinating and fibronectin binding functions probably reside on different parts of the molecule. To identify a receptor on eukaryotic cells, binding and inhibition studies with acidic and neutral glycosphingolipids, carbohydrates, and proteins of sheep erythrocyte membranes were conducted. S. saprophyticus did not bind to any glycosphingolipid and no inhibition was observed when hemagglutination assays were done in the presence of carbohydrates or fibronectin. Neither treatment of erythrocytes with galactose oxidase or neuraminidase and galactose oxidase nor mild periodate oxidation of erythrocytes reduced hemagglutination. However, proteinase-treated erythrocytes were no longer agglutinated. Similarly, untreated erythrocyte membranes inhibited hemagglutination, whereas proteinase-treated membranes did not. In addition, only hemagglutinating strains bound to 60- and 21-kDa sheep erythrocyte membrane proteins on ligand blots, and these proteins inhibited hemagglutination. Our data indicate that, in contrast to many other hemagglutinins, the receptor on sheep erythrocytes for S. saprophyticus is a protein.

Animals↗

PubMed1996

The hemagglutinin of Staphylococcus saprophyticus is a major adhesin for uroepithelial cells.

The 160-kDa hemagglutinin of Staphylococcus saprophyticus also serves as a fibronectin-binding protein, and the two activities may be present on different parts of the molecule. Bacteria expressing the 160-kDa hemagglutinin bound in large numbers to histological sections of human ureters, whereas nonhemagglutinating bacteria did not bind. Binding was decreased by an antiserum to the 160-kDa protein and by a preparation of sheep erythrocyte membranes. Fibronectin had no effect. We therefore conclude that binding of S. saprophyticus to uroepithelial cells is mediated by the hemagglutinating activity of the 160-kDa surface protein.

Animals↗

PubMed1995

Expression of Staphylococcus saprophyticus surface properties is modulated by composition of the atmosphere.

Expression of two major surface proteins of Staphylococcus saprophyticus, the haemagglutinin and the Staphylococcus saprophyticus surface-associated protein (Ssp), required carefully defined culture conditions. The Ssp is produced when bacteria are grown on agar, whereas expression of the haemagglutinin requires growth in broth. We sought to identify the environmental signals that are responsible for this modulation. Varying the pH, the osmolarity of the growth medium or the temperature did not influence expression of the proteins. In contrast, growth in an anaerobic atmosphere increased haemagglutination titres and fibronectin binding (both mediated by the haemagglutinin) but suppressed production of the Ssp. As the influence of the CO2 level could be excluded, we conclude that expression of these surface proteins is probably modulated by the O2 content of the atmosphere.

Adhesins, Bacterial↗

PubMed1995

Characterization of the hemagglutinin of Staphylococcus epidermidis.

Adherence to biomaterials and production of biofilm is thought to be pivotal in the pathogenesis of prosthetic device infection by Staphylococcus epidermidis. In this study a strong association (P < .001) of hemagglutination with adherence and biofilm production was observed. Hemagglutination was not associated with cell surface hydrophobicity (P = .906). Hemagglutination inhibition studies revealed that hemagglutination was not affected by heat, pH, cation concentration, proteolytic enzymes, biologic detergent, serum proteins, or subinhibitory antibiotics. Hemagglutination was abolished by periodate oxidation and digestion with glycosidases. It was markedly inhibited by beta-lactose and its monosaccharide constituents in a concentration-dependent fashion. Hemagglutinin expression depended on the presence of glucose. Chemical analysis of a partially purified hemagglutinin preparation and cell-free hemagglutinating supernatants revealed little or no protein and small quantities of reducing sugars, pentose, ketose, hexosamine, uronic acid, and phosphate. Hemagglutinin of S. epidermidis appears to be a polysaccharide distinct from other known adhesins of S. epidermidis.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1994

Staphylococcus saprophyticus hemagglutinin binds fibronectin.

Attachment of microorganisms to host tissue is regarded as an important step in the pathogenesis of infections. Staphylococcus saprophyticus adheres to various epithelial cells and hemagglutinates sheep erythrocytes. The hemagglutinin has been identified, but a human target for this surface protein is still not known. In our report, we show that hemagglutinating strains of S. saprophyticus bind to immobilized fibronectin, whereas nonhemagglutinating strains do not. Bacterial binding was inhibited by antibody to the hemagglutinin but not by antibody to Ssp, another surface protein of S. saprophyticus. The purified hemagglutinin but not other surface proteins bound biotin-labeled fibronectin. Binding was saturable and could be inhibited by unbound hemagglutinin, unlabeled fibronectin, and by antibody to the hemagglutinin. We thus conclude that the hemagglutinin of S. saprophyticus may act as a fibronectin receptor in the human host. Heparin, the D3 peptide, or Arg-Gly-Asp-Ser (RGDS) containing peptides did not inhibit binding of fibronectin to the hemagglutinin, indicating that the binding site is different from that of Staphylococcus aureus or Treponema pallidum.

Animals↗

PubMed1994

Surface properties of Staphylococcus saprophyticus: hydrophobicity, haemagglutination and Staphylococcus saprophyticus surface-associated protein (Ssp) represent distinct entities.

Cell surface hydrophobicity may contribute to virulence in urinary tract pathogens. In this study we assess the influence of differential expression of the two major surface proteins (Ssp and the haemagglutinin) of Staphylococcus saprophyticus on cell surface hydrophobicity. The haemagglutinating strain CCM883, which does not produce Ssp, was hydrophobic regardless of the growth conditions. Strain 9325, which is non-haemagglutinating and produces Ssp, was hydrophobic only when grown in liquid media. Although these results suggest an association between the ability to express the haemagglutinin and the structure responsible for cell surface hydrophobicity, they refute any major role of Ssp and haemagglutinin in hydrophobicity. Treatment of bacteria with proteases reduces hydrophobicity, indicating that the structure mediating hydrophobicity is a protein.

Agglutination↗

PubMed1993

Identification and characterization of surface proteins from Staphylococcus saprophyticus.

Staphylococcus saprophyticus, a well known cause of urinary tract infections, possesses several properties, such as hemagglutination of sheep erythrocytes, adherence to various cell types and production of urease, which may be virulence factors. In this contribution, we summarise the present knowledge about recently discovered surface proteins of Staphylococcus saprophyticus, a 95 kDa surface-associated protein (Ssp) and the hemagglutinin, a 160 kDa surface polypeptide. We describe culture conditions conducive to production of these surface proteins and discuss the molecular and clinical implications of our findings.

Bacterial Adhesion↗

PubMed1992

Development of an antibody that binds sulfur mustard.

An antibody that binds bis(2-chloroethyl) sulfide (sulfur mustard) was developed. The immunizing antigen was prepared from the hapten 4-(2-chloroethyl)benzoic acid covalently bound to keyhole limpet hemocyanin (KLH). The antibody was monitored by a solid phase enzyme-linked immunosorbent assay (ELISA). The test antigen consisted of a second hapten, 8-chlorocaprylic acid, covalently bound to bovine serum albumin (BSA). The test antigen was absorbed to the wells of 96-well plates. The immunizing and test antigens contain a common chloroethyl moiety. Thiodiglycol, the principal hydrolysis product of sulfur mustard, does not react with the antibody. This antibody, because of its specificity, has the potential to be a valuable tool for mustard research and forensic detection.

Animals↗

PubMed1992

Staphylococcus saprophyticus hemagglutinin is a 160-kilodalton surface polypeptide.

Many strains of Staphylococcus saprophyticus cause direct hemagglutination of sheep erythrocytes. For a high proportion of clinical isolates, a surface protein (Ssp) that is apparently not involved in this property has been described. In this study, S. saprophyticus CCM883, a hemagglutinating but Ssp-negative strain, was used for the identification, purification, and characterization of a 160-kDa surface polypeptide that appears to be the major component of the hemagglutinin. Expression of the protein required the addition to the growth medium of EDTA in micromolar quantities, suggesting an inhibitory role for some unidentified metal ion. The protein was purified by means of Sephacryl S-300 chromatography, and antisera were raised in rabbits. Antibody against this protein inhibited the hemagglutination of two other, unrelated strains and was used to demonstrate, by electron microscopy, the presence of the protein on the surface of the cells. In a confirmatory experiment, the purified antigen was incubated with erythrocytes and binding was detected by the Western immunoblot technique with the antibody to the 160-kDa polypeptide. These experiments indicate that this surface protein is the hemagglutinin of S. saprophyticus.

Animals↗

PubMed1991

Anticholinesterase activity of potential therapeutic 5-(1,3,3-trimethylindolinyl) carbamates.

Six N-alkyl and N-aryl 5-(1,3,3-trimethylindolinyl) carbamates were synthesized and studied for their structure-activity relationships in inhibiting eel acetylcholinesterase (AChE). The carbamates were 5-(1,3,3-trimethylindolinyl)N,N-dimethylcarbamate (Cui Xing Ning) (I), 5-(1,3,3-trimethylindolinyl)N,N-diethylcarbamate (IV), 5-(1,3,3-trimethylindolinyl)N-ethylcarbamate (III), 5-(1,3,3-trimethylindolinyl)N,N-diethylcarbamate (IV), 5-(1,3,3-trimethylindolinyl)N-heptylcarbamate (V), and 5-(1,3,3-trimethylindolinyl)N-(3-chlorophenyl)carbamate (VI). The inhibition studies were carried out at 25.0 degrees C at pH 7.60. The rank order of the ki values for eel AChE inhibition is II > V > I > III > VI > IV. Compound II has a greater affinity for the enzyme than any irreversible inhibitor cited in the literature (Kd = 7.14 x 10(-8) M). Our findings should aid in the application of these carbamates (1) for counteracting the cholinergic problems associated with various diseases, and (2) for developing potential pretreatment compounds for organophosphate poisoning.

Acetylcholinesterase↗

PubMed1990

Intramuscular administration of atropine in the rat: jet spray versus conventional needle injection.

The characteristics of atropine plasma levels after jet spray injection were compared to those after conventional needle injection (i.m.) in 12 male rats, six per group. Blood samples were sequentially collected from the tip of the tail over a 7h period. Injection of atropine sulfate (8.0 mg kg-1) using the jet spray resulted in mean peak plasma levels of 650 ng ml-1 (95 per cent C.I. = 90) compared to 488 ng mg-1 (95 per cent C.I. = 64) using a conventional needle. Times to reach maximum concentration were 30 min (95 per cent C.I. = 12) and 58 min (95 per cent C.I. = 6) for the jet spray and needle, respectively. Histopathologic examination (5 days post-injection) of target muscle showed that minimal fiber damage resulted from using the low pressure setting on the jet spray. The results suggest that the jet spray may offer a means of increasing the antidotal benefit over that achieved with conventional techniques using presently available therapeutic formulations for acetylcholinesterase poisoning.

Animals↗

PubMed1990

pH effects in the spontaneous reactivation of phosphinylated acetylcholinesterase.

Previous studies on the spontaneous reactivation of phosphorylated and phosphonylated cholinesterases report bell-shaped curves with reaction rate maxima between pH values of 7 and 9. By way of contrast, we found reactivation rate minima in the same pH region for a phosphinylated bovine erythrocyte acetylcholinesterase and three phosphinylated eel acetylcholinesterases. To further elucidate these observations, eel acetylcholinesterase was inhibited with racemic 4-nitrophenyl ethyl(phenyl)phosphinate. The spontaneous reactivation of the inhibited enzyme over the pH range 6.00 to 9.00 was monitored following 1. both inhibition and spontaneous reactivation at the same pH, and 2. inhibition at pH 7.60 followed by spontaneous reactivation at the selected pH. The combined plots of both studies gave overlapping pH curves with minima around pH 7.60. The results indicate that the minima in the rates of the spontaneous reactivation of phosphinylated acetylcholinesterases are not the consequence of a pH-controlled change in the relative inhibition rates of the P(+)- and P(-)-enantiomers participating in the inhibition reaction. Our results suggest that the orientation of the phosphinyl group in the active site of phosphinylated acetylcholinesterase is quite different from that of the inhibitor groups in phosphonylated or phosphorylated enzyme.

Acetylcholinesterase↗

PubMed1989

Development and application of a radioimmunoassay for physostigmine.

Antiphysostigmine antibodies were produced in rabbits using a physostigmine analog, 1,3-dimethyl-3-[2- [N-methyl-N-(7-carboxyheptanoyl)] aminoethyl]-5-(N-methyl-carbamoyloxy)-2,3-dihydroindole hydrochloride, conjugated to keyhole limpet hemocyanin. These antibodies were used to develop a radioimmunoassay ranging from 0.2 to 15.0 ng/ml of physostigmine in a 0.1-ml plasma sample. A typical standard curve gave an r2 value of 0.992. This assay measures physostigmine in plasma with better sensitivity and much greater through-put than do current state-of-the-art, high-performance liquid chromatography techniques. In addition, only small volumes (100 microliters) of the plasma samples are required. Precision represented by within and among day coefficients of variance was less than 20% for 1.0 to 50.0 ng/ml and less than 22% for 0.2 ng/ml. Accuracy for the 1.0 to 50.0 ng/ml range varied less than 15% and was 22% for 0.2 ng/ml. Plasma levels of physostigmine were determined in the rat after i.m. administration of physostigmine salicylate to give a free base equivalency of 27 micrograms/kg. Estimates of the various pharmacokinetic parameters were calculated using the computer program PCNONLIN. The results were as follows: apparent volume of distribution = 5.9 liters/kg, absorption rate half-life = 2.7 min. elimination rate half-life = 17.4 min, area under the curve = 118 ng x min/ml, maximal plasma concentration = 3.5 ng/ml and time to maximal plasma concentration = 7.7 min.

Animals↗