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Biomedical subjects

M Brant

Publications and source records attributed to M Brant.

12 recordsLinked to original sources
PubMed2002

Enhanced DNA damage-induced p53 peptide phosphorylation and cell-cycle arrest in Sjögren's syndrome cells.

BACKGROUND: Cells from primary Sjögren's syndrome (SS) patients have been reported to show alterations in DNA repair and p53 expression. The DNA-dependent protein kinase (DNA-PK) autoantigen may be involved in both of these alterations in relation to cellular DNA damage responses. We conducted this study of cell-cycle kinetics and p53 to find additional evidence for an abnormal stress response role in the pathogenesis of SS. DESIGN: DNA-dependent protein kinase activity, p53 peptide phosphorylation and p53 protein levels were determined in gamma-irradiated long-term T lymphocyte cultures. Cell-cycle progression of peripheral blood mononuclear cells was analysed with flow cytometry. RESULTS: No significant differences in the DNA-PK activities or p53 protein levels appeared between the SS patients and the healthy individuals. However, patients with the SS hallmark Ro/SS-A and La/SS-B autoantibodies showed enhancement of both p53 peptide phosphorylation (P = 0.036) and G1 cell-cycle arrest (P = 0.015) in response to gamma radiation. CONCLUSIONS: Sjögren's syndrome cells express an enhanced G1 checkpoint function which may be mediated partly by p53 phosphorylation, suggesting that an abnormal stress response in SS is of relevance for the development of this autoimmune disease.

Adult↗
PubMed2001

Isolation and characterization of a novel IgD-binding protein from Moraxella catarrhalis.

A novel surface protein of the bacterial species Moraxella catarrhalis that displays a high affinity for IgD (MID) was solubilized in Empigen and isolated by ion exchange chromatography and gel filtration. The apparent molecular mass of monomeric MID was estimated to approximately 200 kDa by SDS-PAGE. The mid gene was cloned and expressed in Escherichia coli. The complete mid nucleotide gene sequence was determined, and the deduced amino acid sequence consists of 2123 residues. The sequence of MID has no similarity to other Ig-binding proteins and differs from all previously described outer membrane proteins of M. catarrhalis. MID was found to exhibit unique Ig-binding properties. Thus, in ELISA, dot blots, and Western blots, MID bound two purified IgD myeloma proteins, four IgD myeloma sera, and finally one IgD standard serum. No binding of MID was detected to IgG, IgM, IgA, or IgE myeloma proteins. MID also bound to the surface-expressed B cell receptor IgD, but not to other membrane molecules on human PBLs. This novel Ig-binding reagent promises to be of theoretical and practical interest in immunological research.

Adhesins, Bacterial↗
PubMed1999

Sjögren's syndrome: lymphoma predisposition coupled with a reduced frequency of t(14;18) translocations in blood lymphocytes.

Sjögren's syndrome (SS) is a systemic autoimmune disorder with a strong tumor predisposition (a 44-fold elevated incidence of non-Hodgkin's lymphoma has been reported). By polymerase chain reaction analysis of t(14;18), a key lymphomagenic event in peripheral blood lymphocytes, we found a lower frequency in a subset of 12 SS patients positive for SS-A/SS-B autoantibodies than in 21 healthy subjects and 20 SS patients lacking these SS marker autoantibodies (P < 0.001). All 14 mutants sequenced displayed signs typical of V(D)J recombinase activity. This perplexing result of a low rate of t(14;18) in a population strongly predisposed to t(14;18)-associated tumor development may be explained by a constitutive deficiency in V(D)J recombinase leading to autoimmunity and increased lymphoproliferation.

Antibodies, Antinuclear↗
PubMed1998

Abnormal DNA damage-inducible protein in cells from Sjögren's syndrome patients.

Antinuclear antibodies are commonly found in patients with Sjögren's syndrome. It has been suggested that the development of antinuclear antibodies depends on the activation of the spliceosome and other transcription-related subcellular particles, some of which have recently been shown also to function in DNA-modifying processes, such as DNA repair and V(D)J recombination. These observations add weight to a previously proposed model for the aetiology of Sjögren's syndrome. This includes the abnormal processing of the T-cell receptor and immunoglobulin genes. To test this hypothesis further, the present study on DNA-modifying proteins in Sjögren's syndrome was initiated. Gel-shift experiments using protein extracted from UV-treated Sjögren cells provided evidence of high molecular weight DNA-binding protein in six out of 12 Sjögren patients studied (but not among seven healthy controls). Some Sjögren sera displayed antibodies to protein extracts from cells treated with psoralen plus UVA radiation. These results indicate an abnormal DNA damage-inducible response in Sjögren's syndrome. It may therefore be concluded that alterations in nuclear protein may play a role in the aetiology of Sjögren's syndrome.

Antibodies, Antinuclear↗
PubMed1998

Idiopathic thromboembolism as the presenting sign of occult prostate cancer.

OBJECTIVES: Idiopathic thromboembolism has been associated with occult neoplasia; however, very limited information exists regarding a man's risk of occult prostate cancer after an idiopathic thromboembolic event. METHODS: We performed a case-control study of 209 consecutive men diagnosed with prostate cancer over a 3-year period, with 350 men diagnosed with benign prostatic hyperplasia (BPH) serving as control subjects. RESULTS: Men with idiopathic thromboembolism had a fivefold increased risk of prostate cancer compared with the BPH control group (risk ratio = 5.0, P = 0.002). The prostate-specific antigen (PSA) progression-free survival was not adversely affected after an idiopathic thromboembolic event. CONCLUSIONS: Our data suggest that men with idiopathic thromboembolism are at an increased risk for being diagnosed with prostate cancer. In men with idiopathic thromboembolism, attempts to diagnose prostate cancer, including digital rectal examination and serum PSA, warrant consideration.

Aged↗
PubMed1995

Mutational response of Fanconi anaemia cells to shuttle vector site-specific psoralen cross-links.

Fanconi anaemia (FA) is a hereditary tumour-prone disorder. FA cells exposed to DNA crosslinking agents show an increased frequency of chromosome aberrations and of deletion type mutations. The molecular basis of FA presumably is a deficiency in cellular repair of DNA adducts. In this work a shuttle vector plasmid was treated with 8-methoxypsoralen + a split dose of UVA (leading to crosslink induction), and transfected into FA lymphoblasts. The supF gene of the vector showed a mutation frequency similar to that of normal cells; however, the number of base substitutions was relatively low, whereas a high level (50%) of deletions was seen. With both normal and FA cells these deletions varied greatly in size and were randomly distributed within the supF gene. DNA cross-links were also induced using a triple helix forming 22-mer oligonucleotide linked to a psoralen molecule and being complementary to part of supF, leading to a > 30-fold increase of mutations, which were mainly position 167 single-base substitutions and showed a pattern identical to that of the normal cells. This normal response of FA cells to the site-specific DNA cross-links may reflect that not all gene sequences of FA cells are subjected to abnormal DNA repair. Alternatively, it may reflect a lower than normal genome-overall activity of a DNA cross-link repair complex, fully capable of efficiently repairing only molecules carrying relatively few adducts.

Base Sequence↗
PubMed1991

Ciprofloxacin-induced inhibition of topoisomerase II in human lymphoblastoid cells.

The antibacterial activities of the fluorinated 4-quinolones (e.g., ciprofloxacin) have been ascribed to a marked inhibition of bacterial DNA gyrase. In contrast, the influence on purified mammalian DNA enzymes, including topoisomerases, has been reported to be several orders of magnitude weaker, occurring at concentrations higher than 100 micrograms of ciprofloxacin per ml. In this study, using a nondenaturing filter elution method, a marked induction of double-strand DNA breaks in human lymphoblastoid cells exposed to 80 micrograms of ciprofloxacin per ml was seen. The proportion of single-strand versus double-strand DNA breaks was similar to that seen with the topoisomerase II inhibitory antitumor agent VP-16. The cellular recovery was more rapid after treatment with ciprofloxacin than after treatment with VP-16, displaying a normal elution profile within 15 min at 37 degrees C (60 min for VP-16). These data indicate that ciprofloxacin has an effect on intracellularly located topoisomerase II in humans.

Cell Line↗
PubMed1989

4-Quinolone antibiotics: positive genotoxic screening tests despite an apparent lack of mutation induction.

The effects of different 4-quinolone antibiotic derivatives (4-Qs) in a number of short-term tests commonly employed for the evaluation of genetic toxicity were studied. Incorporation of [3H]thymidine into mitogen-stimulated peripheral blood lymphocytes was strongly enhanced at a low concentration (1.56 micrograms/ml) for most of the tested 4-Qs, whereas DNA strand breakage in lymphoblastoid cells was evident only for ciprofloxacin (10 micrograms/ml and upwards), ofloxacin (80 micrograms/ml) and norfloxacin (160 micrograms/ml). Ciprofloxacin induced a significant amount of unscheduled DNA synthesis, but was found to be negative in a shuttle vector plasmid mutation test. Ciprofloxacin (80 micrograms/ml) did not inhibit enzymes involved in the early steps of pyrimidine biosynthesis. Cell growth was slightly depressed at a concentration of 20 micrograms/ml, becoming marked at 80 micrograms/ml. In conclusion, this study seeks to contribute to an improved evaluation of genotoxic screening test data, by focusing attention on the conflicting effects imposed by the 4-Qs on a battery of such tests.

Anti-Bacterial Agents↗
PubMedDate not supplied

Shuttle vector plasmid propagation in human peripheral blood lymphocytes facilitated by liposome-mediated transfection.

Transfection of human peripheral blood lymphocytes facilitated by a positively charged liposome preparation (Lipofectin, BRL) is 100-fold more efficient than the DEAE dextran technique for the uptake and replication of shuttle vector plasmid DNA. The yield of progeny plasmids obtained from 10 ml of blood was high enough for mutational analysis. A marked increase in the mutation frequency of the shuttle vector marker gene was noted in response to the induction of psoralen adducts in the vector. By using normal human lymphocytes, this method will permit shuttle vector analysis of DNA repair and mutagenesis in a large number of individuals. This method could also prove useful for studies of human lymphotropic viruses.

DNA Repair↗