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Biomedical subjects

R Laufs

Publications and source records attributed to R Laufs.

At least 91 records · Page 5Linked to original sources
PubMed1995

Variable degree of slime production is linked to different levels of beta-lactam susceptibility in Staphylococcus epidermidis phase variants.

Recently we demonstrated that lack of mecA transcription was responsible for the decreased methicillin resistance phenotype of strongly slime-negative Staphylococcus epidermidis phase variants [Mempel M, Feucht H, Ziehbuhr W, Endres M, Laufs R, Grüter L (1994) Antimicrob Agents Chemother 38: 1251-1255]. In the present study we compared the beta-lactam susceptibility and the slime production capacity of 60 phenotypic variants of S. epidermidis parent strain RP62A identified by their colony morphology on congo red agar. We could show that the variable degree of slime production is linked to different levels of beta-lactam susceptibility in intermediate-stage phase variants. The increased deltahemolysin production of slime-negative phase variants may indicate an accessory gene regulator-like control.

Anti-Bacterial Agents↗
PubMed1995

Comparison of conventional autoradiography with a new DNA enzyme immunoassay for the detection of hepatitis C virus-polymerase chain reaction amplification products.

The detection of HCV-PCR amplification products by DNA enzyme immunoassay (DEIA) was compared with conventional hybridization carried out with a 32P-labelled oligonucleotide probe. The detection limit of both methods was shown to be between 100 pg and 1 ng of amplicon. All serum samples of 40 HCV-seropositive patients were positive after PCR in autoradiography, but only 38 with the DEIA technique (sensitivity 95%). There were no false-positive reactions by either method. The advantage of the DEIA method was the fast and non-radioactive detection of HCV amplicons. DEIA combines the specificity of the hybridization event with the speed of an ELISA procedure and is suitable for HCV-PCR.

Autoradiography↗
PubMed1995

Influence of exogenous interleukin-2 concentration on the isolation of human immunodeficiency virus.

A significant increase (P = 0.015) in the HIV isolation rate from plasma samples was achieved by use of 10 U/ml exogenous interleukin-2 compared to 20 U/ml. The sensitivity rose from 0% to 29% in patients negative for p24 core antigen (P = 0.031) and from 71% to 86% in patients positive for p24 core antigen in plasma (P > 0.05). Titration of infectious HIV revealed that 10 U/ml interleukin-2 is the optimal concentration to isolate low numbers of infectious particles of HIV.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Disseminated Encephalitozoon (Septata) intestinalis infection in a patient with AIDS: novel diagnostic approaches and autopsy-confirmed parasitological cure following treatment with albendazole.

Encephalitozoon intestinalis is a recently described microsporidian which causes intestinal and disseminated infections in severely immunocompromised patients with AIDS. Preliminary data suggest that albendazole can be an effective therapy for patients with E. intestinalis infection. However, relapses have been reported following treatment in some cases. These results were based upon examination of cytologic, biopsy, or stool samples with an inherent sampling bias. This report documents the first postmortem evaluation of a patient with E. intestinalis infection treated with albendazole. Antemortem microsporidial diagnosis was performed on nasal mucosal smear and duodenal biopsy specimens by electron microscopy and a newly developed indirect fluorescent-antibody method based upon in vitro cultivation of the organism. This case represents the initial report of using nasal cytologic specimens for ultrastructural and antibody-based species-level diagnosis of microsporidiosis. Following successful treatment of this infection with albendazole, the patient died of other causes. A thorough autopsy examination failed to reveal the presence of E. intestinalis in any tissue, providing confirmatory evidence for a complete parasitological cure with albendazole.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Study on reliability of commercially available hepatitis C virus antibody tests.

The serodiagnosis of hepatitis C virus (HCV) infection was analyzed by a recombinant immunoblot assay (RIBA) with recombinant proteins encoded by the viral RNA isolated from our patients in Hamburg, Germany. The HCV RNA was amplified by PCR, and proteins encoded by the viral core and the NS3, NS4, and NS5 regions were expressed subsequently in Escherichia coli. The results obtained with our UKE RIBA were compared with the results of the Abbott HCV second-generation enzyme immunoassay (EIA). Serum samples from 270 patients, which were sent to us on the suspicion of HCV hepatitis and which were negative for hepatitis A virus and hepatitis B virus antibodies, were examined. In 227 cases (84.1%), there were identical positive (204 cases, 75.6%) or negative (23 cases, 8.5%) results in both tests. In 32 cases (11.9%), the reactive Abbott second-generation HCV EIA results could not be confirmed by the UKE RIBA and the HCV PCR. In follow-up studies conducted over 1 year, these results did not change. In three cases (1.1%), the UKE RIBA presented a positive result while the Abbott second-generation HCV EIA was negative. All three cases were positive in the HCV PCR and showed seroconversion in an HCV EIA 4 to 6 weeks later. In addition, 33 patient serum samples were examined by UKE RIBA in parallel with the Ortho RIBA 2.0. In three cases (9.1%), a positive Ortho RIBA 2.0 result could not be confirmed by the UKE RIBA and the HCV PCR. All three patients were free of complaints. The UKE RIBA showed also a smaller number of indeterminate results (3.0%) than the Ortho RIBA 2.0 (24.2%). This comparison study demonstrates that the commercially available HCV antibody tests should be further improved.

Antibodies, Viral↗
PubMed1995

Tear fluid of hepatitis C virus carriers could be infectious.

For up to 20 to 40% of patients chronically infected with hepatitis C virus (HCV), the mode of transmission is still unknown. We demonstrate that tear fluid contains HCV RNA-carrying material with the properties of infectious virus and conclude that smear infection with tear fluid may play a role in HCV transmission.

Carrier State↗
PubMed1994

Characterization of different oligomeric species of the Yersinia enterocolitica outer membrane protein YadA.

The oligomeric structure of the plasmid-encoded outer membrane protein YadA of Yersinia enterocolitica was studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and sucrose gradient sedimentation, respectively. The apparent molecular weight (M(r)) of the oligomeric 200-kDa YadA species detected by SDS-PAGE varied from 152,000 to 240,000 depending on the respective acrylamide concentration. The atypical electrophoretic behavior of the 200-kDa YadA species results form an exceptionally high relative free mobility as revealed by the Ferguson plot. In contrast, the apparent M(r) of 53,000 of the YadA monomer was independent of the acrylamide concentration. An additional oligomeric 116-kDa YadA species was detected by SDS-PAGE when membrane preparations of Y. enterocolitica were solubilized in SDS at 37 degrees C. The gel-purified 116-kDa YadA species was completely converted to the 200-kDa species by heating at 100 degrees C and to the monomeric form (M(r) 53,000) by heating in the presence of 10 M urea without reducing agents, respectively. This suggests that the 116-kDa YadA species represents the native oligomeric form of YadA, whereas the 200-kDa species is only generated from native YadA during denaturation in SDS. The significance of the 116-kDa YadA species is also supported by the rather slow sedimentation at about 6 S of detergent-solubilized YadA in sucrose gradients, which probably contains only two or three monomers.

Adhesins, Bacterial↗
PubMed1994

Regulation of epidermal growth factor receptor kinase activity by polyions.

We investigated polyionic agents with regard to their effects as modulators of epidermal growth factor receptor (EGF-R) kinase activity. Many synthetic polypeptides containing glutamine as well as casein were phosphorylated, while polycationic compounds with tyrosine residues were not phosphorylatable and thus inhibited the EGF-R activity. Polyarginine, protamine sulfate, spermidine, heparin, and poly-L-lysine with a chain length of < 20.5 kDa triggered the phosphorylation of poly(Tyr1, Glu4). On the other hand, dextran sulfate and poly-L-lysine with chain lengths of > 20.5 kDa inhibited the EGF-R kinase activity. Alteration of the state of autophosphorylation of EGF-R is not in agreement with the activity of EGF-R kinase towards poly(Tyr1, Glu4). Casein and histone H1 both increased the autophosphorylation of EGF-R in a concentration-dependent manner, but only casein increased the activity of the enzyme towards an exogenous substrate. The compounds enhancing the EGF-R activity, such as poly-L-lysine, protamine, and poly-L-arginine, down-modulated the autophosphorylation reaction. We discuss the consequences of these effects as to in vivo conditions.

Amino Acid Sequence↗
PubMed1994

Greater amount of HCV-RNA in tears compared to blood.

Plasma, tear fluid and swabs from eye, nose and pharynx of 33 patients were examined for presence of hepatitis C virus (HCV) RNA by polymerase chain reaction (PCR). All samples from plasma, tear fluid and eyeswabs were found to show a positive reaction in HCV-RNA PCR. Remarkably, we regularly found greater amounts of amplification products in tear fluid and eyeswabs compared to plasma using the same conditions for sample preparation.

Base Sequence↗
PubMed1994

Lack of mecA transcription in slime-negative phase variants of methicillin-resistant Staphylococcus epidermidis.

Five phase variants (PV1 to PV5) of the well-characterized, slime-producing, methicillin-resistant, pathogenic strain of Staphylococcus epidermidis sensu strictu RP62A (ATCC 35984) were isolated by the Congo red agar method. In comparison with the parent strain, the phase variants showed a different colonial morphology on Congo red agar, a strongly reduced adherence capacity, and decreased levels of resistance to methicillin, oxacillin, and penicillin. All phase variants yielded biochemical reaction patterns and profiles in pulsed-field gel electrophoresis identical to those of parent strain RP62A, indicating a common origin. All phase variants proved to have the capacity to shift back to the original phenotype of parent strain RP62A. A search for the resistance mechanisms of strain RP62A revealed beta-lactamase production and the presence of mecA in PV1 to PV5 as well as parent strain RP62A. In Northern blots of total staphylococcal RNA, the phase variants showed no detectable mecA-specific transcription product, whereas parent strain RP62A revealed a strong signal, indicating that mecA transcription is not the mechanism responsible for the decreased methicillin resistance phenotype of phase variants PV1 to PV5.

Anti-Bacterial Agents↗
PubMed1994

Characterization of transposon mutants of biofilm-producing Staphylococcus epidermidis impaired in the accumulative phase of biofilm production: genetic identification of a hexosamine-containing polysaccharide intercellular adhesin.

The primary attachment to polymer surfaces followed by accumulation in multilayered cell clusters leads to production of Staphylococcus epidermidis biofilms, which are thought to contribute to virulence in biomaterial-related infections. We isolated Tn917 transposon mutants of biofilm-producing S. epidermidis 13-1, which were completely biofilm negative. In pulsed-field gel electrophoresis no obvious deletions of the mutants were noted. The Tn917 insertions of mutants M10 and M11 were located on different EcoRI fragments but on identical 60-kb SmaI and 17-kb BamHI chromosomal fragments. Linkage of transposon insertions of mutants M10 and M11 with the altered phenotype was demonstrated by phage transduction, whereas the several other mutants apparently represented spontaneous variants. In a primary attachment assay with polystyrene spheres, no significant difference between any of the mutants and the wild type could be detected. Cell clustering as an indication of intercellular adhesion, which is a prerequisite for accumulation in multilayered cell clusters, was not detected with any mutant. These results demonstrate that the mutants were impaired in the accumulative phase of biofilm production. Mutants M10 and M11 did not produce detectable amounts of a specific polysaccharide antigen (D. Mack, N. Siemssen, and R. Laufs, Infect. Immun. 60:2048-2057, 1992), whereas substantially reduced amounts of antigen were produced by the spontaneous variants. Hexosamine was determined as the major specific component of the antigen enriched by gel filtration of biofilm-producing S. epidermidis 1457 because almost no hexosamine was detected in material prepared from the isogenic biofilm-negative transductant 1457-M11, which differentiates the antigen from other S. epidermidis polysaccharide components. Our results provide direct genetic evidence for a function of the antigen in the accumulative phase of biofilm production by S. epidermidis by mediating intercellular adhesion.

Antigens, Bacterial↗
PubMed1994

[Risk of infection caused by homologous blood transfusion].

Compared with other nosocomial infections, transfusion-associated infectious risks are of minor relevance in the Federal Republic of Germany today. The actual spectrum of measures for an optimal degree of safety of blood components comprises a careful donor selection, highly sensitive and specific screening assays for viral parameters, inactivation and quarantine procedures for plasmatic preparations. Further possible improvements, both in the blood bank and clinical setting are discussed with regard to the inevitable residual risks of hemotherapy.

Blood Transfusion↗
PubMed1994

Prognostic significance of the hepatitis B virus-DNA concentration in patients after orthotopic liver transplantation.

Hepatitis B virus-DNA was detected by polymerase chain reaction in 9 out of 10 patients after orthotopic liver transplantation. Three of these patients were at the same time positive for hepatitis B virus-DNA by dot-blot hybridization (hepatitis B virus-DNA > 1.5 pg/ml). In these three patients HBs-antigen (HBsAg) reappeared within a mean time of 12 weeks after orthotopic liver transplantation (range 7-18 weeks). Only two of the six polymerase chain reaction-positive and dot-blot-negative patients (hepatitis B virus-DNA between 0.4 fg/ml and 1.5 pg/ml) had recurrence of HBsAg within a mean time of 54 weeks (range 52-56 weeks). Passive immunoprophylaxis with anti-HBs antibodies (serum titers > 100 IU/l) did not prevent infection of the graft in the five reinfected patients. We conclude that a low concentration of serum hepatitis B virus-DNA after orthotopic liver transplantation, which is detectable only by polymerase chain reaction, indicates a delayed infection of the graft.

Adult↗
PubMed1993

Biochemical properties of a novel 28KDA protein tyrosine kinase partially purified from the particulate fraction of rat spleen.

In this report we present some of the biochemical properties of the enzyme, here called pp28(PTK), isolated from particulate fraction of rat spleen (1). The kinase is very susceptible for polyions as regulators of the enzymatic activity. The polyanions like dextran sulfate or heparin inhibited, and polycations such as spermidin, protamin, poly-L-lysine and some random polypeptides containing tyrosine besides a basic amino acid, stimulated the enzyme markedly. The kinase showed high sensitivity towards class IA salts. In the casein phosphorylation reaction the apparent Km value for ATP was 4 microM. An unusual property is associated with autophosphorylation which leads to a reduced activity towards external substrates. Some kinase inhibitors described in the literature were tested for their potency.

Animals↗
PubMed1993

Partial purification of a tyrosine kinase activity associated with a 28-kDa phosphoprotein from the particulate fraction of rat spleen.

A phosphoprotein with associated tyrosine kinase activity has been purified from a 26,000 x g particulate fraction of rat spleen. The molecular weight of the native kinase is 85-90 kDa as estimated by gel permeation chromatography on Superdex 200 while SDS/PAGE of an autophosphorylated sample indicated a single 28-kDa band in which the radiolabel was alkali-stable. The SDS/PAGE following the incubation with 5'-p-fluorosulfonylbenzoyl[8-14C]adenosine reveals a single labeled band migrating at a molecular weight of approximately 28 kDa. The enzyme shows very restricted substrate specificity. Casein and, to a lesser degree, the random polypeptide poly(Tyr1,Glu4) were phosphorylated. The enzyme exhibits a preference for Mn2+ over Mg2+ as an activator.

Adenosine↗
PubMed1993

HIV-1-prevalence in fatalities from Hamburg, Germany.

The HIV-status of 3999 fatalities (aged 1-60 years) examined at the Institute of Forensic Medicine in Hamburg from 1989-1992 was tested. Former predictions of an enormous increase of HIV-infections, especially in the risk group of IVDA (intravenous drug addicts), did not come true. HIV-screening of fatalities is an instructive additional method of gaining information about the epidemiological development of HIV-infections.

Adult↗