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R Wirth

Publications and source records attributed to R Wirth.

At least 19 recordsLinked to original sources
PubMed1997

Dosimetry and pathology of 237Np in female rats.

Female Sprague-Dawley rats, 10-12-week old and weighing about 240 g, were injected intravenously with 237Np-nitrate. In the toxicological study 77 rats served as controls and 28 rats per group received single doses of 5.2 and 26 kBq, respectively, per kg body weight. In addition, 12 rats of each injection level, sacrificed at defined points in time, were used for dosimetric studies. During the whole life-span the body weight and 237Np whole body-content of each animal were recorded. After death a detailed pathological examination was made of each animal in the cronical study. One day after injection 48% of the injected activity was in the skeleton, 9.3% in the liver, 3% in the kidneys and 4.4% in the rest of the organs. Whereas in all organs the activity decreased very fast, the half-life in the skeleton was about 1400 days. The bodyweights were comparable in the three groups, but the life span decreased from 800 days (control group) to 644 days after injection (26 kBq kg-1 body weight group). The main lesions in the female rats were mammary tumors (73%) and pituitary gland tumors (52%). With increasing activity the incidence of pituary gland tumors decreased and that of osteosarcomas increased from 1.3% (control group) to 32% (26 kBq kg-1 body weight group), whereas the remaining lesions showed no influence on the activity.

Animals↗
PubMed1996

Comparative analysis of 18 sex pheromone plasmids from Enterococcus faecalis: detection of a new insertion element on pPD1 and implications for the evolution of this plasmid family.

A new IS element, IS1062, related to the enterococcal IS elements IS6770 and IS1252, was detected in the 3'-terminus of the surface exclusion gene, sep1, of sex pheromone plasmid pPD1 in Enterococcus faecalis. pPD1-bearing cells lack the surface exclusion function, probably as a consequence of this insertion. Analysis of pAD1 and pPD1 sequences (7.5 kb and 2.7 kb, respectively) downstream of their aggregation substance genes revealed no similarity in these DNA regions. Detailed DNA/DNA hybridization studies using DNA probes specific for various pAD1-encoded genes needed for plasmid transfer indicated that the sex pheromone plasmids have evolved by repeated recombination and insertion of diverse transposable elements which presumably account for recent acquisition of antibiotic resistances.

Amino Acid Sequence↗
PubMed1995

[Does controlled hypotension with nitroprusside affect platelet function?].

Induced hypotension is an accepted technique to reduce intraoperative blood loss and thereby ensures satisfactory operating conditions, especially in microscopic interventions. Sodium nitroprusside (NP), which is often used for induced hypotension, was reported to inhibit platelet aggregation in vitro. Impairment of platelet function implies a higher bleeding risk, which would make the use of NP for induced hypotension questionable. METHODS. With the approval of the local ethics committee, 30 patients scheduled for nasal septum operations were included in this randomised study. For induction of anaesthesia 2 mg vecuronium, 0.1 mg fentanyl, 0.2 mg/kg etomidate, and 1 mg/kg succinylcholine were used. After tracheal intubation the patients inhaled 1.0-1.5 vol.% isoflurane in a gas mixture containing 66% nitrous oxide in oxygen. Fifteen patients received an i.v. infusion of NP for 60 min. The concentrations chosen produced a decrease of mean arterial blood pressure to 50 mm Hg. Blood samples were taken before induction of anaesthesia; after induction of anaesthesia but before beginning of the operation; and 60 min after the beginning of the operation. This time-point coincided with the end of NP administration in the study group. The last blood sample was drawn the morning after the operation. Platelet function was determined in platelet-rich plasma by a turbidometric method after adding 22 mumol/l epinephrine to induce aggregation. The spontaneous aggregation was measured in whole blood using impedance aggregometry. Data within one group were analysed using analysis of variance. Student's t-test for unpaired values served to compare data between the two groups. RESULTS. Biometric data in the two groups were comparable. The blood loss in the control group [265 (190-410) ml] significantly exceeded (P < 0.05) that in the hypotensive group [125 (75-210) ml]. No significant changes in platelet function were found throughout the study period in the patients treated with NP. In the control patients the epinephrine-induced aggregation increased significantly from 53.1 +/- 5.3% before anaesthesia to 72.1 +/- 3.3% the morning after the intervention. The spontaneous aggregation showed a significant increase from 0.718 +/- 0.338 Ohm/h before anaesthesia to 2.164 +/- 0.442 Ohm/h 60 min after the beginning of the operation. The value on the 1st postoperative day (2.266 +/- 0.448 Ohm/h) was also significantly higher than the basal value. CONCLUSIONS. In contradiction to in vitro studies using high concentrations of NP, we could not find a decrease in platelet aggregation due to hypotensive anaesthesia with this drug in vivo. In the control group a significant increase in platelet aggregation was observed, which was probably counteracted in the hypotensive patients by the interaction of NP with cyclic guanosine monophosphate (c-GMP). NP augments the intracellular concentration of c-GMP, which is known to decrease platelet aggregation.

Adolescent↗
PubMed1995

[Effect of controlled hypotension using sodium nitroprusside on platelet aggregation].

OBJECTIVE: To determine the influence of sodium nitroprusside (SNP) on platelet aggregation when this agent is used to induce hypotension during surgery. PATIENTS AND METHODS: Spontaneous platelet aggregation (SPA) determined by impedance measurement and induced platelet aggregation (IPA) determined by turbidimetry were studied in 30 subjects scheduled for elective ear, nose or throat surgery. Fifteen patients in the SNP group (SNPG) received SNP in doses adjusted to maintain a mean arterial pressure of 50 mmHg. Another 15 patients who did not receive SNP served as controls. RESULTS: SPA increased progressively in both groups. The greatest increase occurred after anesthetic induction (control group +172%, SNPG +48%); the highest level recorded was reached on the morning of the first day after surgery (control group +215%, SNPG +46%). IPA decreased after anesthetic induction (control group -21%, SNPG -40%) and stayed down throughout surgery. IPA was higher on the first morning after surgery than before the operation (control group +35%, SNPG +2%). SPA was significantly higher 60 minutes after start of surgery than before surgery in the control group; IPA and SPA were likewise higher in these patients the morning after surgery. CONCLUSIONS: Platelet aggregation increases during surgery and in the immediate postoperative period. This increase is attenuated when SPA is given to induce hypotension. SPA should be determined by measurement of impedance in whole blood when the nature of platelet aggregation during surgery is being studied, given that early increases in IPA can be masked as a result of the low sensitivity of turbidimetry.

Blood Coagulation Disorders↗
PubMed1995

Evolution of the Enterococcus faecalis sex pheromone system.

In this article we present data that form the basis of a model of the evolution of the unique Enterococcus faecalis sex pheromone system. The data indicate tht sex pheromone plasmid-encoded genes/functions, which are essential for this highly efficient plasmid collection system, are common among all sex pheromone plasmids; pAM373 seems to be only distantly related to all other pheromone plasmids. These genes appear to be restricted to sex pheromone plasmids (but see below for possible exceptions). However, the ability to produce sex pheromone-like peptides is not restricted to E. faecalis. We argue that the sex pheromone system of E. faecalis developed only once--but into at least 19 different variants--to form a system which is highly specific for this bacterium and is related to virulence.

Adhesins, Bacterial↗
PubMed1994

The sex pheromone system of Enterococcus faecalis. More than just a plasmid-collection mechanism?

The sex pheromone system of Enterococcus faecalis was discovered by observing a clumping reaction of E. faecalis strains during conjugative transfer of plasmids. It was found that only a special type of E. faecalis plasmids, the so-called sex pheromone plasmids, are transferred via this mechanism. Various experiments, especially by the group of D. B. Clewell, led to the formulation of a model describing how the sex pheromone system works. Small linear peptides, the so-called sex pheromones, are excreted by strains not possessing the corresponding sex pheromone plasmid. Donor strains harboring the plasmid do not produce the corresponding sex pheromone; they react to the presence of the peptide by production of a plasmid-encoded adhesin, the so-called aggregation substance. This adhesin allows contact between the non-motile mating partners; after conjugative transfer of the plasmid, the former recipient possesses and replicates the new plasmid. Thereby the population of E. faecalis strains is shifted to a high percentage of donor strains. This is especially true because a donor strain will still excrete sex pheromones corresponding to plasmids it does not harbor; therefore, such a strain can also function as recipient for other sex pheromone plasmids it does not possess. Various aspects of this unique plasmid collection mechanism have been studied during the last few years. The data indicate that, with the exception of pAM373, all sex pheromone plasmids possess one DNA region which is highly similar to and codes for the adhesin. It is also becoming more and more clear that regulatory functions/proteins are not conserved between different sex pheromone plasmids. Induction of adhesin synthesis needs the action of a regulatory cascade composed of unique features; at the moment we are just beginning to understand this cascade. By sequencing the first structural gene for one of those adhesins, we realized that the aggregation substance might act also as an adhesin for eucaryotic cells, probably by interaction with integrins. At least in the case of the in vitro cultured pig kidney tubulus cell line LLC-PK1 this idea could be verified. An interesting aspect of the sex pheromone system of E. faecalis is its evolution. I will discuss the idea that two different components, both of which well might contribute to virulence of the opportunistic pathogenic bacterium, were combined in the species E. faecalis to result in this unique plasmid collection system.

Adhesins, Bacterial↗
PubMed1994

Direct detection of Mycobacterium tuberculosis complex in respiratory specimens by a target-amplified test system.

A total of 938 respiratory specimens (633 sputa, 249 bronchial and tracheal aspirates, and 56 bronchoalveolar lavages) from 589 patients were tested for direct detection of Mycobacterium tuberculosis complex by the Gen-Probe amplified Mycobacterium tuberculosis direct test (MTD), and the results were compared with those of the conventional methods of fluorescence microscopy and cultivation (solid and radiometric media). One series of specimens (n = 515) was decontaminated with N-acetyl-L-cysteine (NALC)-NaOH: the other one (n = 423) was decontaminated with sodium dodecyl (lauryl) sulfate (SDS)-NaOH. Of the specimens decontaminated with NALC, 39 were MTD and culture positive, 455 were MTD and culture negative, 18 were MTD positive and culture negative, and 3 were MTD negative and culture positive, indicating a sensitivity of 92.9% and a specificity of 96.2% for the MTD. Of the specimens decontaminated with SDS, 35 were MTD and culture positive, 372 were MTD and culture negative, 15 were MTD positive and culture negative, and 1 was MTD negative and culture positive, indicating a sensitivity of 97.2% and a specificity of 96.1% for the MTD. After resolution of discrepant results by review of the patients' clinical data, the sensitivity of the MTD was 93.9%, the specificity was 97.6%, the positive predictive value was 80.7%, and the negative predictive value was 99.3% for the NALC series; the corresponding values were 97.4, 96.9, 76.0, and 99.7%, respectively, for the SDS series. In conclusion, the MTD is a highly sensitive and specific technique for detecting M. tuberculosis complex within hours in both smear-positive and smear-negative respiratory specimens.

Adult↗
PubMed1993

Sex pheromone plasmid pAD1-encoded aggregation substance of Enterococcus faecalis is positively regulated in trans by traE1.

Sex-pheromone-plasmid-bearing strains of Enterococcus faecalis react with sex pheromone to induce the expression of an adhesin, the so-called aggregation substance, on their cell surface. Here we show that, by complementation studies, for sex-pheromone plasmid pAD1, expression of the structural gene asa1, coding for an aggregation substance, is mediated by a diffusible factor encoded on pAD1. We were able to demonstrate that a small open reading frame, traE1, is sufficient for transcription of the operon containing asa1. A model for expression of asa1 under the influence of the positive regulator is presented, which is supported by our observation that regulation involves an all-or-nothing induction phenomenon, leading to cells either fully expressing asa1 or not at all.

Bacterial Proteins↗
PubMed1993

Biochemical, immunological and ultrastructural characterization of aggregation substances encoded by Enterococcus faecalis sex-pheromone plasmids.

The sex-pheromone system of Enterococcus faecalis can be viewed as a unique and highly efficient plasmid-collection mechanism. The contact needed for transfer of the conjugative sex-pheromone plasmids is mediated by an adhesin, called aggregation substance, which is encoded by these plasmids. We show here that for 17 of the 18 sex-pheromone plasmids (pAM373 being the exception) described to date, their adhesins are immunologically related to each other. In each case, we observed the presence of an N-terminal fragment of about 78 kDa in addition to the 137-kDa form of mature aggregation substance. The cross-reactions were different for the various plasmids. In the case of pPD1 the 78-kDa fragment reacted only weakly. The aggregation substance encoded by sex-pheromone plasmid pAD1 (Asa1) was characterized in detail. The conditions used for SDS/PAGE had a drastic influence on the migration behavior of mature aggregation substance and differently migrating, interconvertible forms were identified. Preliminary data indicate that Asa1 might be a glycoprotein. Antibodies were isolated which are directed against the N- and C-terminal parts of aggregation substance. They showed about the same reactivity on Western blots; however, only antibodies directed against the N-terminal part of the aggregation substance could inhibit the bacterial cell/cell contact. The reactions of the two antibody preparations with induced cells of E. faecalis was analyzed by transmission electron microscopy. The results indicated that especially the N-terminal part of aggregation substance is exposed on the cell surface of E. faecalis; the C-terminal part seems to be much less exposed.

Antibodies↗
PubMed1992

Identification of new sex pheromone plasmids in Enterococcus faecalis.

We describe the identification of the following new sex pheromone plasmids in Enterococcus faecalis: a haemolysin-bacteriocin plasmid, pIP964; three R plasmids, pIP1017, pIP1438 and pIP1440; and two cryptic conjugative plasmids, pIP1141 and pMV120. The identification was based on the formation of cell aggregates on filter membranes during conjugation, on efficient transfer in broth matings, and on a positive clumping reaction of cells carrying these plasmids. In addition these plasmids hybridized with DNA probes specific for sex pheromone-induced structural genes encoding surface proteins required for conjugative transfer of the plasmids.

DNA Probes↗
PubMed1992

Sex pheromone plasmid pAD1-encoded surface exclusion protein of Enterococcus faecalis.

During conjugative transfer of sex pheromone plasmids of Enterococcus faecalis a so-called surface exclusion protein reduces the frequency with which these plasmids are transferred to cells already possessing the same plasmid. We report here the DNA sequence of a 3.8 kb fragment of the sex pheromone plasmid pAD1 containing the structural gene sea1 for surface exclusion protein and a small open reading frame (ORF) upstream of sea1. Surface exclusion protein Sea1 was found to be highly homologous to the surface exclusion protein Sec10 encoded by the sex pheromone plasmid pCF10. Hybridization studies with DNA probes derived from the structural gene sea1 demonstrated that, with the exception of pAM373, all known sex pheromone plasmids carry a homologous gene. These studies also indicated that the genetic organization is similar in these plasmids, with the structural gene for surface exclusion protein being located 5' to that for aggregation substance.

Amino Acid Sequence↗
PubMed1992

Transcriptional control of sex-pheromone-inducible genes on plasmid pAD1 of Enterococcus faecalis and sequence analysis of a third structural gene for (pPD1-encoded) aggregation substance.

The expression of several neighbouring genes on plasmid pAD1 that are necessary for conjugation depend on induction with sex pheromone cAD1. Analyses of transcripts by Northern blot hybridization demonstrated that the genes sea1 (encoding surface exclusion protein) and asa1 (encoding aggregation substance) are transcribed independently. Both genes are organized in different operons together with neighbouring open reading frames of unknown function. Several transcripts could be identified for sea1 and asa1. Their transcriptional start sites were determined by primer extension experiments, confirming the results of the Northern blot experiments. We also could identify sea1- and iad- (encoding an inhibitory peptide counteracting sex pheromone cAD1) specific transcripts which are expressed constitutively, but to a lower extent relative to induced conditions. In addition, we localized the asp1 gene coding for aggregation substance of sex pheromone plasmid pPD1 and determined its DNA sequence, which was found to be highly homologous to asa1 (aggregation substance gene of pAD1) and prgB (aggregation substance gene of pCF10). The structural genes were found to be organized more or less identically on the three sex-pheromone plasmids pAD1, pCF10, and pPD1, and to be highly conserved. Regions supposed to be of crucial importance for regulatory functions, however, were found to differ. We also could identify some conserved DNA motifs which might be potential target sites for transcriptional regulators. In combination these data allowed us to formulate a model for the regulation of sex-pheromone-inducible genes of plasmid pAD1. Its main statement is that only in the presence of cAD1 can the gene traE1 be transcribed. The positive regulatory factor TraE1 then can trigger expression of the structural genes sea1 and asa1.

Amino Acid Sequence↗
PubMed1992

Efficacy of different irrigation methods and concentrations of root canal irrigation solutions on bacteria in the root canal.

The effectiveness of two different root canal irrigating solutions, each in two different concentrations or formulations, with two different irrigation methods was compared in vitro by means of bacterial survival determinations. 75 human root canals were enlarged, sterilized and inoculated with a mixed culture of Escherichia coli and Streptococcus mutans. After inoculation, the root canals were irrigated either manually or with an ultrasonic device for equal times (20s) with the same amount (5 ml) of sodium hypochlorite (1% and 2%), Fokalhydran I and Fokalhydran II. Sodium hypochlorite (1% and 2%) was used in a 1:100 dilution. Fokalhydran I and II were used in a 1:10 dilution. In the sodium hypochlorite group, the 1% concentration applied with a syringe proved to be most effective against Escherichia coli and Streptococcus mutans. The least effective concentration and application method against both bacteria species was obtained with 2% NaOCL and ultrasonics. Against Escherichia coli and Streptococcus mutans, a significantly lower effectiveness was found with 2% NaOCL applied with ultrasonics with respect to the rest of the sodium hypochlorite group. Fokalhydran I was significantly better than Fokalhydran II against Escherichia coli. However, no significant differences could be seen against Streptococcus mutans within this group.

Analysis of Variance↗
PubMed1992

Aggregation substance of Enterococcus faecalis mediates adhesion to cultured renal tubular cells.

The sex pheromone system of Enterococcus faecalis is a unique, highly efficient plasmid collection mechanism for this species. A crucial role in this system is played by an adhesin called aggregation substance which enables the cell-cell contact between donor and recipient strains. The existence of the amino acid motif Arg-Gly-Asp-Ser in the adhesin prompted us to look for a possible binding of E. faecalis cells expressing aggregation substance to eucaryotic cells. We were able to show that the adhesin mediated binding to cultured renal tubular cells (porcine cell line LLC-PK1) via light microscopic, electron microscopic, and enzyme-linked immunosorbent assay-based studies. Synthesis of the adhesin was induced by some component(s) of serum. These data are interpreted to mean that aggregation substance is an adhesin mediating not only cell-cell contact between different E. faecalis strains but also binding of E. faecalis to eucaryotic cells, and therefore it might contribute to virulence.

Amino Acid Sequence↗
PubMed1992

Habitual physical activity in adult IDDM patients. A study with portable motion meters.

The objective of this study was to assess the habitual physical activity of insulin-dependent diabetes mellitus (IDDM) patients on intensive insulin therapy. This case-control study consisted of 34 IDDM patients (14 on multiple injection therapy, 20 on continuous subcutaneous insulin infusion [CSII], and control subjects matched for sex, age, weight, height, body mass index, smoking behavior, and occupational status). Seven IDDM patients were studied before and after changing from multiple injection to CSII therapy. All patients were well controlled according to HbA1c. Portable motion meters were used to assess habitual physical activity during 7 consecutive days with appreciable reproducibility (coefficient of variation 1.24%) and agreement to standardized activity protocols (r = 0.96, P < 0.001). Habitual physical activity was similar in IDDM patients on injection treatment and in controls, respectively. CSII-treated patients exhibited on the average 17% less habitual physical activity than control subjects (P < 0.05). Changing from multiple injection therapy to CSII lowered habitual physical activity insignificantly in seven patients. There was no indication of decreasing physical exercise (e.g., sports) by CSII in this patient group. No correlations were found between habitual physical activity and HbA1c or body mass index, respectively. Habitual physical activity is similar in IDDM patients on multiple injection therapy and control subjects, but may decrease by CSII therapy.

Adult↗
PubMed1991

Genetic transformation of various species of Enterococcus by electroporation.

A transformation system for Enterococcus faecalis was developed which uses untreated (i.e., non-protoplasted) cells and the electroporation technique. The optimized protocol resulted in transformation efficiencies of up to 4 x 10(6) transformants per microgram of plasmid DNA. All strains of E. faecalis tested could be transformed by this method, albeit with differing transformation efficiencies. Using the protocol optimized for E. faecalis we successfully transformed Enterococcus faecium, E. hirae, E. malodoratus and E. mundtii.

Cell Division↗