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M Bischoff

Publications and source records attributed to M Bischoff.

At least 37 records · Page 2Linked to original sources
PubMed2001

Teicoplanin stress-selected mutations increasing sigma(B) activity in Staphylococcus aureus.

A natural rsbU mutant of Staphylococcus aureus, unable to activate the alternative transcription factor sigma(B) via the RsbU pathway and therefore forming unpigmented colonies, produced first-step teicoplanin-resistant mutants upon selection for growth in the presence of teicoplanin, of which the majority were of an intense orange color. By using an asp23 promoter-luciferase fusion as an indicator, the pigmented mutants were shown to express increased sigma(B) activity. Increased sigma(B) activity was associated with point mutations in rsbW, releasing sigma(B) from sequestration by the anti-sigma factor RsbW, or to promoter mutations increasing the sigma(B)/RsbW ratio. Genetic manipulations involving the sigB operon suggested that the mutations within the operon were associated with the increase in teicoplanin resistance. The upregulation of sigma(B) suggests that a sigma(B)-controlled gene(s) is directly or indirectly involved in the development of teicoplanin resistance in S. aureus. Carotenoids do not contribute to teicoplanin resistance, since inactivation of the dehydrosqualene synthase gene crtM abolished pigment formation without affecting teicoplanin resistance. The relevant sigma(B)-controlled target genes involved in teicoplanin resistance remain to be identified.

Anti-Bacterial Agents↗
PubMed2001

Influence of a functional sigB operon on the global regulators sar and agr in Staphylococcus aureus.

The growth phase-dependent activity profile of the alternate transcription factor sigma(B) and its effects on the expression of sar and agr were examined in three different Staphylococcus aureus strains by Northern blot analyses and by the use of reporter gene fusion experiments. Significant sigma(B) activity was detectable only in the clinical isolates MSSA1112 and Newman, carrying the wild-type rsbU allele, but not in the NCTC8325 derivative BB255, which is defective in rsbU. sigma(B) activity peaked in the late exponential phase and diminished towards the stationary phase when bacteria were grown in Luria-Bertani medium. Transcriptional analysis and a sarP1-sarP2-sarP3 (sarP1-P2-P3)-driven firefly luciferase (luc+) reporter gene fusion demonstrated a strong sigma(B) activity- and growth phase-dependent increase in sar expression that was totally absent in either rsbU or Delta rsbUVWsigB mutants. In contrast, expression of the agr locus, as measured by RNAIII levels and by an hldp::luc+ fusion, was found to be higher in the absence of sigma(B) activity, such as in rsbU or Delta rsbUVWsigB mutants, than in wild-type strains. Overexpression of sigma(B) in BB255 derivatives resulted in a clear increase in sarP1-P2-P3::luc+ expression as well as a strong decrease in hldp::luc+ expression. The data presented here suggest that sigma(B) increases sar expression while simultaneously reducing the RNAIII level in a growth phase-dependent manner.

Alleles↗
PubMed2001

Sigma(B) activity depends on RsbU in Staphylococcus aureus.

Derivatives of the widely used laboratory strain Staphylococcus aureus NCTC8325, which are natural rsbU mutants, were shown to be unable to produce RsbU, a positive regulator of the alternative sigma factor sigma(B). The lack of RsbU prevented the heat-dependent production of sigma(B)-controlled transcripts and resulted in reduced H2O2 and UV tolerance, enhanced alpha-hemolysin activity, and the inability to produce the alkaline shock protein Asp23. After 48 h of growth, rsbU mutant strains failed to accumulate staphyloxanthin, the major stationary-phase carotenoid. Transcription of Asp23 was found to be exclusively controlled by sigma(B), making it an excellent target for the study of sigma(B) activity in S. aureus. Reporter gene experiments, using the firefly luciferase gene (luc+) fused to the sigma(B)-dependent promoter(s) of asp23, revealed that sigma(B) is almost inactive in 8325 derivatives. cis complementation of the 8325 derivative BB255 with the wild-type rsbU gene from strain COL produced the rsbU(+) derivative GP268, a strain possessing a sigma(B) activity profile comparable to that of the rsbU(+) wild-type strain Newman. In GP268, the heat inducibility of sigma(B)-dependent genes, Asp23 production, alpha-hemolysin activity, pigmentation, and susceptibility to H2O2 were restored to the levels observed in strain Newman, clearly demonstrating that RsbU is needed for activation of sigma(B) in S. aureus.

Bacterial Proteins↗
PubMed2000

Toxoplasmosis, a severe complication in allogeneic hematopoietic stem cell transplantation: successful treatment strategies during a 5-year single-center experience.

Toxoplasmosis is a rare but often fatal complication that occurs after patients undergo allogeneic hematopoietic stem cell transplant. At our institution, toxoplasmosis was diagnosed in 8 of 301 patients who received stem cell transplants. Disseminated toxoplasmosis with a rapid fatal course was observed in 2 patients. Six patients had cerebral toxoplasmosis diagnosed on the basis of neurological signs and observation of the patients' mental confusion, seizures, and typical lesions (which were assessed by computed tomography, magnetic resonance imaging, or both). Seroconversion of antitoxoplasma immunoglobulin and a discovery of toxoplasma deoxyribonucleic acid in the cerebrospinal fluid (confirmed by use of polymerase chain reaction) were documented in all patients. Treatment consisted of clindamycin therapy (for 2 patients) and of pyrimethamine-clindamycin therapy, sulfadiazine therapy, or both (for 5 patients). Patients showed improvement after therapy, as assessed by clinical and radiological means. Three of 8 patients survive-1 without any residual neurological symptoms and 2 with minimal neurological symptoms.

Adult↗
PubMed2000

Kinetics of chromium(V) formation and reduction in fronds of the duckweed Spirodela polyrhiza--a low frequency EPR study.

The uptake of chromate by the duckweed Spirodela polyrhiza was investigated with atomic absorption spectroscopy and the reduction of Cr(VI) to Cr(V) was measured using low frequency EPR spectroscopy. The biphasic kinetics of the uptake was fitted to parameters of a proposed kinetic model. Another model was developed to simulate chromate reduction. The first step of chromate reduction was found to be much faster than the uptake of Cr(VI) from the free space. Most probably, this step occurs already in the cell wall or on the cell membrane surface. Further reduction of Cr(V) to Cr(III) was estimated to be slower. The disappearance of the Cr(V) signal, following transfer of the plants into a Cr-free solution, lasted several tens of hours; the kinetics was mono- or biexponential depending on the length of Cr loading. The rate constants for Cr reduction in living plants were determined for the first time.

Chromium↗
PubMed2000

Mycophenolate mofetil for the prophylaxis of acute GVHD in HLA-mismatched bone marrow transplant patients.

Mycophenolate mofetil (MMF), a new immunosuppressive drug successfully used in renal and heart transplant recipients, was used in combination with cyclosporin A (CsA), methotrexate (MTX) and prednisolone for the prophylaxis of acute graft-versus-host disease (aGVHD) after bone marrow transplantation (BMT) and peripheral blood stem cell transplantation (PBSCT) from human leukocyte antigen (HLA)-mismatched, unrelated (n = 9) and related donors (n = 4) in an open single-centre phase II study. Thirteen patients, transplanted from HLA-mismatched donors of 18-57 yr of age, received 1 g MMF daily, starting at day 10, in addition to CsA and prednisolone for aGVHD prophylaxis. All patients were engrafted between days 13 and 15. Four of the 13 patients experienced aGVHD grade I/II (n = 2) and grade III (n = 2). All patients except 3 were alive on day 100 post-transplantation. No severe adverse effects of MMF were recorded. In our pilot study, we demonstrated that MMF can be used safely for the prophylaxis of aGVHD.

Acute Disease↗
PubMed2000

Second allogeneic hematopoietic stem cell transplantation as treatment for leukemia relapsing following a first transplant.

We report 27 patients with relapsed acute or chronic leukemia who underwent a second hematopoietic stem cell transplant (HSCT) from a related or unrelated donor. Seventeen patients were diagnosed with acute myelogenous leukemia (AML), six with acute lymphocytic leukemia (ALL) and four with chronic myeloid leukemia (CML). Ages ranged from 22 to 49 years (median 37); 13 patients were female and 14 male. Relapse was diagnosed between 1 and 45 months after the first HSCT. Sixteen patients who relapsed had received an autologous transplant initially and 11 an allogeneic transplant. Ten patients relapsed within 6 months and 17 patients later than 6 months. Chemotherapy was used as reinduction for relapse after HSCT in 16 patients who had received an autologous transplant and in three who had received an allogeneic transplant, since the latter did not respond to reduction of immunosuppression to induce a graft-versus-leukemia (GVL) reaction. Five of these 19 patients (26%) achieved complete remission (CR), seven patients did not respond to chemotherapy and seven achieved a partial remission (PR). The stem cell source for the second HSCT included bone marrow (n = 12) and PBSC (n = 4) from genotypically identical unrelated donors, PBSC (n = 7) and bone marrow (n = 3) from related donors. Currently eight of the 27 patients are alive and disease-free after the second HSCT. One patient is alive and disease-free after two allogeneic transplants (day +1538), eight patients, who relapsed after an autologous transplant followed by an allogeneic transplant (days +248 to +1140), acute myeloid leukaemia (n = 6) and chronic myeloid leukemia (n = 2) are alive and disease-free. The overall disease-free survival is 30% (8/27). The overall disease-free survival of autologous transplant patients subsequently undergoing an allogeneic transplant is 43% (P = 0.049). It is suggested that a second HSCT is possible for patients with leukemia relapse following the first autologous transplant. A second transplant might also be offered to patients relapsing after the first allogeneic HSCT. Bone Marrow Transplantation (2000) 25, 41-45.

Acute Disease↗
PubMed2000

Lenograstim-mobilized peripheral blood progenitor cells in volunteer donors: an open label randomized split dose escalating study.

Mobilization of peripheral blood cell progenitor cells was investigated in 36 healthy sibling donors using three different split doses of glycosylated rhG-CSF (lenograstim). The donors were randomized into three groups: group 1 was given lenograstim at 8, group 2 at 11 and group 3 at 15 micrograms/kg/day in two split doses, subcutaneously for 4 and 5 days, respectively. Leukapheresis was performed on day 4 or 5 depending on the WBC and CD34+ cell count. We were able to demonstrate that there was a significant correlation between circulating CD34+ cells on the day of harvest and CD34+ cells in the apheresis products in all three groups. The number of CD34+ cells pre-apheresis was inversely correlated with age in group 1 and group 2. However, in group 3, the number of CD34+ cells pre-apheresis did not correlate with age. There was also a difference between the number of progenitor cells mobilized in the three dose groups regarding the time of harvest. Apheresis was performed in groups 1 and 2 on day 5 of mobilization in order to obtain a sufficient number of stem cells for allogeneic transplantation. In contrast, with the split dose of 15 micrograms/kg/day, harvest could be routinely performed on day 4 of stimulation. We conclude that lenograstim given twice a day at doses of 8, 11 and 15 micrograms/kg/day provided different CD34+ cell yields in normal donors, in particular, with regard to the time of harvest. The number of CD34+ cells pre-apheresis was not correlated with age in the group of donors mobilized with a split dose of 15 micrograms/kg/day, indicating that this dosage might also be suitable for older donors.

Adjuvants, Immunologic↗
PubMed2000

Expression and localization of nitrilase during symptom development of the clubroot disease in Arabidopsis.

The expression of nitrilase in Arabidopsis during the development of the clubroot disease caused by the obligate biotroph Plasmodiophora brassicae was investigated. A time course study showed that only during the exponential growth phase of the clubs was nitrilase prominently enhanced in infected roots compared with controls. NIT1 and NIT2 are the nitrilase isoforms predominantly expressed in clubroot tissue, as shown by investigating promoter-beta-glucuronidase fusions of each. Two peaks of beta-glucuronidase activity were visible: an earlier peak (21 d post inoculation) consisting only of the expression of NIT1, and a second peak at about 32 d post inoculation, which predominantly consisted of NIT2 expression. Using a polyclonal antibody against nitrilase, it was shown that the protein was mainly found in infected cells containing sporulating plasmodia, whereas in cells of healthy roots and in uninfected cells of inoculated roots only a few immunosignals were detected. To determine which effect a missing nitrilase isoform might have on symptom development, the P. brassicae infection in a nitrilase mutant (nit1-3) of Arabidopsis was investigated. As a comparison, transgenic plants overexpressing NIT2 under the control of the cauliflower mosaic virus 35S promoter were studied. Root galls were smaller in nit1-3 plants compared with the wild type. The phenotype of smaller clubs in the mutant was correlated with a lower free indole-3-acetic acid content in the clubs compared with the wild type. Overexpression of nitrilase did not result in larger clubs compared with the wild type. The putative role of nitrilase and auxins during symptom development is discussed.

Aminohydrolases↗
PubMed2000

[Enzootic calcinosis in 16 cows from 6 dairy farms in Unterengadin].

Enzootic calcinosis was diagnosed in 16 cows, which originated from 6 dairy farms located in the Unterengadin valley in Switzerland between 1,402 and 1,650 metres above sea level. During the winter, the cows were fed haylage, which contained up to 50 per cent golden oat-grass (Trisetum flavescens), and hay and grain. The first symptoms of enzootic calcinosis were noted in March 1998, when some of the cows developed locomotor abnormalities. Additional cases were diagnosed during the following three months. The most important clinical findings were decreased milk production, weight loss, frequent recumbency, difficulty in rising, kneeling while rising and feeding, stilted gait, arched back, shifting weight from one foot to another and reluctance to remain standing after being roused. Of the 16 cows, 5 had elevated concentrations of serum calcium and 10 had decreased concentrations of serum magnesium. All cows had normal or decreased concentrations of serum phosphorus, because the feeding of haylage containing golden oat-grass had been discontinued two months previously. In all of the cows, the most important postmortem findings were severe calcification of the aorta, iliac artery, brachiocephalic trunk and pulmonary artery.

Animals↗
PubMed1999

A second unrelated bone marrow transplant: successful quantitative monitoring of mixed chimerism using a highly discriminative PCR-STR system.

A second bone marrow transplant (BMT) might be considered as an option in patients with leukaemia with graft failure after BMT. We report the successful treatment of a patient with graft failure by a second stem cell transplant from another unrelated donor. We evaluated the usefulness of an unrelated donor as the source of the second BMT in this clinical setting. In addition to this, a penta PCR-STR system was tested and shown to be sensitive for monitoring of marrow engraftment. The conditioning regimen for the first transplantation consisted of busulfan and cyclophosphamide while anti-thymocyte globulin and CY were used for the second BMT. The patient successfully engrafted at day +11 after second BMT.

Adult↗
PubMed1999

Microbial biomass and activity in lead-contaminated soil

Microbial community diversity, potential microbial activity, and metal resistance were determined in three soils whose lead contents ranged from 0.00039 to 48 mmol of Pb kg of soil-1. Biomass levels were directly related to lead content. A molecular analysis of 16S rRNAs suggested that each soil contained a complex, diverse microbial community. A statistical analysis of the phospholipid fatty acids indicated that the community in the soil having the highest lead content was not related to the communities in the other soils. All of the soils contained active microbial populations that mineralized [14C]glucose. In all samples, 10 to 15% of the total culturable bacteria were Pb resistant and had MIC of Pb for growth of 100 to 150 &mgr;M.

Journal Article↗
PubMed1998

A second unrelated bone marrow transplant with an unrelated donor marrow: treatment of a patient with relapsed leukemia.

A second bone marrow transplant might be considered as an option in patients with leukemia relapsing after bone marrow transplantation. We report the successful treatment of a patient with relapsed ALL with a second BMT from the same unrelated donor. We evaluated the usefulness of an unrelated donor as the source of the second BMT in this clinical setting. The conditioning regimen for the first transplantation consisted of BU and CY while fractionated TBI and CY were used for the second BMT. Acute skin GVHD, grade III which developed after second BMT, was successfully treated with the use of a new immunosuppressive drug, mycophenolate mofetil. Hemorrhagic cystitis and a CMV infection developed as complications during the second BMT and were successfully treated. The patient was alive and well after the second BMT with limited chronic skin GVHD up to day +170.

Adult↗
PubMed1998

Mycophenolate mofetil for the treatment of acute and chronic GVHD in bone marrow transplant patients.

The efficacy and safety of mycophenolate mofetil (MMF) in combination with CsA and prednisolone for the treatment of acute and chronic GVHD (aGVHD and cGVHD, respectively) after BMT and PBSCT from HLA-mismatched and -matched donors was evaluated in an open single center trial. Twenty-four patients, 17-48 years of age, with acute (n = 17) and chronic GVHD (n = 7) were treated with 2 g MMF daily in addition to CsA and prednisolone. Overall grade improvement of aGVHD was found in 11 of 17 (65%) patients treated with MMF. MMF therapy in the treatment of cGVHD led to moderate improvement in three of six patients with limited cGVHD. The most common adverse hematologic events of MMF were leukopenia (n = 6), anemia (n = 4) and thrombocytopenia (n = 3). Hematological adverse events were not severe and did not require the discontinuation of MMF. In this preliminary study, we have shown that MMF can be used safely for the treatment of aGVHD. In addition, the MMF therapy resulted in significant dose reduction of prednisolone for the treatment of GVHD.

Acute Disease↗