PubMed Health⌕ Search

Biomedical subjects

M Brendel

Publications and source records attributed to M Brendel.

At least 55 records · Page 3Linked to original sources
PubMed1995

SNG1--a new gene involved in nitrosoguanidine resistance in Saccharomyces cerevisiae.

We have molecularly characterized the SNG1 gene that confers hyper-resistance to the mutagen N-methyl-N'nitro-N-nitrosoguanidine (MNNG) in Saccharomyces cerevisiae when overexpressed on a multi-copy plasmid. This hyper-resistance to MNNG is not due to depletion of glutathione pools since multi-copy SNG1 containing yeast transformants contain at least wild type levels of glutathione; DNA repair seems unaffected in these transformants as the multi-copy SNG1-mediated MNNG hyper-resistance is also seen in DNA repair mutants belonging to each of the three epistasis groups of yeast repair mutants. It could be shown that SNG1 is not under control of the YAP1 encoded transcription activator that controls expression of at least two genes involved in MNNG metabolism in yeast. sng1 null mutants are viable but exhibit only slight sensitivity to MNNG, indicating that SNG1 does not encode a protein involved in a major detoxification step of this mutagen. Sequencing of the HYR-mediating passenger DNA revealed that SNG1 encodes a 547 a polypeptide containing seven transmembrane-spanning regions that may be membrane-bound. Comparison of the DNA sequence with established gene databanks revealed that SNG1 is a novel yeast gene.

Amino Acid Sequence↗
PubMed1995

Cloning, sequencing, and characterizing the Lactobacillus leichmannii pyrC gene encoding dihydroorotase.

The gene encoding dihydroorotase (DHOase) of Lactobacillus leichmannii, the third enzyme of the pyrimidine biosynthetic pathway (Genbank (EMBL) accession no X78999), was cloned by phenotypic complementation of an E coli pyrC deficient mutant after transformation with Lactobacillus leichmannii genomic library DNA. The open reading frame of the L leichmannii pyrC gene spans 1281 bp and codes for a 427 amino cid polypeptide with a calculated M(r) of 46,316 Da. Primer extension showed that the initiation site for transcription is 37 bp upstream of the putative start codon ATG and Northern blot analysis confirmed its independent transcription from the adjacent pyrB gene. Comparison of the deduced amino acid sequence of L leichmannii DHOase with sequences established for other organisms yielded 46.6% identity with the corresponding Bacillus subtilis enzyme. Highly conserved protein domains suggest importance for the enzyme's function.

Amino Acid Sequence↗
PubMed1995

Lymphocyte subsets in bronchoalveolar lavage fluid of children without bronchopulmonary disease.

Bronchoalveolar lavage (BAL) is increasingly used in the pediatric age group. However, normal values for BAL fluid (BALF) constituents are lacking. As part of an investigation to define reference values in children, we studied lymphocyte surface markers of BALF in 28 children 3 to 16 yr of age without bronchopulmonary disease. All of them were undergoing elective surgery for nonpulmonary illnesses. BAL was performed under general anaesthesia with tracheal intubation. A flexible bronchoscope (Pentax 3.5 or 4.9 mm) was wedged into the middle lobe or into one of its segments, and 3 x 1 ml/kg body weight normal saline warmed to body temperature were instilled and immediately withdrawn. The first sample was studied separately; subsequent samples were pooled for analysis. Studies on lymphocyte surface markers were performed on the pooled sample only. The distribution of B-cells, pan T-cells, and CD57 positive cells was within the range reported for adult subjects. However, CD4/CD8 ratios were lower than in adults (0.7 +/- 0.4, mean +/- SD). This decrease in the CD4/CD8 ratio was caused by an increase in CD8 cells. Comparative analysis of blood and BALF lymphocytes in a subgroup of children showed that CD4/CD8 ratios in blood were within the normal range reported for this age group and significantly higher when compared with BALF. The lower CD4/CD8 ratios in normal children have to be considered in the interpretation of BALF in children with pulmonary diseases.

Adolescent↗
PubMed1994

Complete DNA sequence of yeast chromosome II.

In the framework of the EU genome-sequencing programmes, the complete DNA sequence of the yeast Saccharomyces cerevisiae chromosome II (807 188 bp) has been determined. At present, this is the largest eukaryotic chromosome entirely sequenced. A total of 410 open reading frames (ORFs) were identified, covering 72% of the sequence. Similarity searches revealed that 124 ORFs (30%) correspond to genes of known function, 51 ORFs (12.5%) appear to be homologues of genes whose functions are known, 52 others (12.5%) have homologues the functions of which are not well defined and another 33 of the novel putative genes (8%) exhibit a degree of similarity which is insufficient to confidently assign function. Of the genes on chromosome II, 37-45% are thus of unpredicted function. Among the novel putative genes, we found several that are related to genes that perform differentiated functions in multicellular organisms of are involved in malignancy. In addition to a compact arrangement of potential protein coding sequences, the analysis of this chromosome confirmed general chromosome patterns but also revealed particular novel features of chromosomal organization. Alternating regional variations in average base composition correlate with variations in local gene density along chromosome II, as observed in chromosomes XI and III. We propose that functional ARS elements are preferably located in the AT-rich regions that have a spacing of approximately 110 kb. Similarly, the 13 tRNA genes and the three Ty elements of chromosome II are found in AT-rich regions. In chromosome II, the distribution of coding sequences between the two strands is biased, with a ratio of 1.3:1. An interesting aspect regarding the evolution of the eukaryotic genome is the finding that chromosome II has a high degree of internal genetic redundancy, amounting to 16% of the coding capacity.

Base Composition↗
PubMed1994

Isolation and characterization of three mutants with increased sensitivity to photoactivated 3-carbethoxypsoralen in Saccharomyces cerevisiae.

The complementation and genetical analysis of yeast mutants sensitive to photoactivated 3-carbethoxypsoralen define three novel recessive mutant alleles pso5-1, pso6-1, and pso7-1. Their cross-sensitivity to UV254nm, radiomimetic mutagens, and to chemicals enhancing oxidative stress suggest that these mutants are either impaired in metabolic steps protecting from oxidative stress or in mechanisms of the repair of oxygen-dependent DNA lesions. None of the three novel mutant alleles block the induction of reverse mutation by photoactivated mono- and bi-functional psoralens, nitrogen mustards, or UV254nm.

DNA Damage↗
PubMed1994

Overexpression of the SNQ3/YAP1 gene confers hyper-resistance to nitrosoguanidine in Saccharomyces cerevisiae via a glutathione-independent mechanism.

The MNNG hyper-resistance of yeast transformants containing multiple copies of the SNQ3/YAP1 yeast gene is not caused by lowered MNNG activation due to depleted pools of glutathione. On the contrary, the SNQ3/YAP1-encoded protein stimulates production of GSH, apparently by promoter activation due to the AP-1 recognition element. Expression of at least one further gene, encoding a protein with a strong detoxifying activity, must also be stimulated to explain the MNNG hyper-resistance phenotype.

Base Sequence↗
PubMed1994

Genetic effects of photoactivated psoralens during meiosis in DNA repair mutant pso3-1 of Saccharomyces cerevisiae.

The influence of the DNA repair gene PSO3 on photoactivated psoralen-induced meiotic recombination, gene conversion, reverse mutation, and on survival, was assayed in diploid strains of Saccharomyces cerevisiae homozygous for the wild-type or the pso3-1 mutant allele. Sporulation was normal in the pso3-1 diploid. Wild-type and mutant strains had the same sensitivity to photoactivated monofunctional psoralen (3-CPs + UVA) in meiosis-uncommitted and meiosis-committed stages. The mutant showed higher sensitivity to photoactivated bifunctional psoralen (8-MOP + UVA) during all stages of the meiotic cycle. Mutation induction by 3-CPs + UVA or 8-MOP + UVA in meiosis-committed cells revealed no significant differences between wild-type and the pso3-1 mutant. The status of the PSO3 gene has no influence on the kinetics of induction of gene conversion and crossing-over after 3-CPs + UVA treatment in meiosis-committed cells: gene conversion was blocked while recombination was induced. After treatment with 8-MOP + UVA gene conversion was also blocked in both strains while crossing-over could only be observed in meiosis-committed wild-type cells.

DNA Repair↗
PubMed1994

Sensitivity to nitrogen mustard in Saccharomyces cerevisiae is independently determined by regulated choline permease and DNA repair.

Sensitivity of yeast cells to the bifunctional alkylating agent nitrogen mustard (HN2) depends on two independently operating physiological mechanisms of cellular metabolism: dynamics of uptake of HN2 via choline permease, encoded in the gene HNM1/CTR, and repair of HN2-induced DNA damage. Uptake of choline and HN2 is impaired in mutant alleles of HNM1/CTR, leading to a HN2 hyper-resistant phenotype. Overexpression of HNM1/CTR leads to HN2 sensitivity higher than that of the wild type. While mutation and regulation of HNM1/CTR have pronounced effects on the cell's HN2 sensitivity, they do not interfere with repair of HN2-induced DNA damage, a process whose quality independently determines a yeast cell's sensitivity to HN2. Consequently, HNM1/CTR overexpression in an excision repair-deficient strain leads to extreme HN2 sensitivity whereas a mutational block of HNM1/CTR, in combination with excision proficiency, yields a HN2 hyper-resistant phenotype.

Biological Transport↗
PubMed1994

A single amino acid change in SNM1-encoded protein leads to thermoconditional deficiency for DNA cross-link repair in Saccharomyces cerevisiae.

Molecular characterization of a thermoconditional mutant snm1-2ts shows that the coding sequence contains three mutations, two of which are silent. The third changes amino acid glycine to arginine at position 256 thereby altering a hydrophilic domain of the protein. While sensitivity to nitrogen mustard of the mutant at 36 degrees C is very similar to that of the non-leaky allele snm1-1, multi-copy vector-mediated overexpression of snm1-2ts leads to a significantly reduced sensitivity to nitrogen mustard.

Amino Acid Sequence↗
PubMed1994

Differential cytology of bronchoalveolar lavage fluid in normal children.

Bronchoalveolar lavage (BAL) is increasingly used in the assessment of pulmonary diseases in children. However, reference values for cellular and non-cellular constituents of BAL fluid in children are lacking. We have studied the differential cytology of BAL fluid in 48 children aged 3-16 years (mean age +/- SD 7.9 +/- 3.5 yrs) undergoing elective surgery for nonpulmonary illnesses. A flexible bronchoscope (Pentax 3.5 or 4.9 mm) was wedged in the middle lobe or one of its segments. BAL was performed with 3x1 ml-kg-1 body weight of normal saline warmed to body temperature. The first sample was studied separately; subsequent samples were pooled for analysis. The mean recovery was 58 +/- 15%. Significantly more granulocytes and less lymphocytes were found in the first, as compared to the pooled, sample. Total cell counts were highly variable and ranged from 0.5-57.1 x 10(4) ml-1. Macrophages were the predominant cell type, with a mean percentage of 81.2 +/- 12.7%. The relative proportion of lymphocytes was higher than that reported in most studies of adult volunteers (16.1 +/- 2.4%). No age dependency was observed for either cell type. The mean percentage of granulocytes was 2.5 +/- 3.3%. Absolute granulocyte counts were significantly higher in children under 8 yrs of age. This study provides the first reference data on BAL differential cytology in children without pulmonary disease and will be the basis for future investigations of BAL in paediatric lung diseases.

Adolescent↗
PubMed1993

Vector YFRp1 allows transformant selection in Saccharomyces cerevisiae via resistance to formaldehyde.

Formaldehyde (FA), a chemical with low toxic potential, is used as sole selective agent for transformation in the yeast Saccharomyces cerevisiae. Neither stable auxotrophic markers in recipient cells nor defined synthetic media are needed when multicopy vector YFRp1, containing the yeast SFA gene, is employed for yeast transformation. The SFA gene gives stability to the vector and its yeast (and other) passenger genes when transformants are propagated in complex media supplemented with 3-5 mM-FA. Use of inexpensive FA and non-synthetic, undefined media will lower the cost of yeast transformant propagation considerably and thus make feasible large-volume industrial application of transformants containing YFRp1 derivatives.

Drug Resistance, Microbial↗
PubMed1993

Gene SNQ2 of Saccharomyces cerevisiae, which confers resistance to 4-nitroquinoline-N-oxide and other chemicals, encodes a 169 kDa protein homologous to ATP-dependent permeases.

The yeast gene SNQ2 confers hyper-resistance to the mutagens 4-nitroquinoline-N-oxide (4-NQO) and Triaziquone, as well as to the chemicals sulphomethuron methyl and phenanthroline when present in multiple copies in transformants of Saccharomyces cerevisiae. Subcloning and sequencing of a 5.5 kb yeast DNA fragment revealed that SNQ2 has an open reading frame of 4.5 kb. The putative encoded polypeptide of 1501 amino acids has a predicted molecular weight of 169 kDa and has several hydrophobic regions. Northern analysis showed a transcript of 5.5 kb. Haploid cells with a disrupted SNQ2 reading frame are viable. The SNQ2-encoded protein has domains believed to be involved in ATP binding and is likely to be membrane associated. It most probably serves as an ATP-dependent permease.

4-Nitroquinoline-1-oxide↗
PubMed1993

Molecular structure and genetic regulation of SFA, a gene responsible for resistance to formaldehyde in Saccharomyces cerevisiae, and characterization of its protein product.

A 3.7 kb DNA fragment of yeast chromosome IV has been sequenced that contains the SFA gene which, when present on a multi-copy plasmid in Saccharomyces cerevisiae, confers hyper-resistance to formaldehyde. The open reading frame of SFA is 1158 bp in size and encodes a polypeptide of 386 amino acids. The predicted protein shows strong homologies to several mammalian alcohol dehydrogenases and contains a sequence characteristic of binding sites for NAD. Overexpression of the SFA gene leads to enhanced consumption of formaldehyde, which is most probably the reason for the observed hyper-resistance phenotype. In sfa::LEU2 disruption mutants, sensitivity to formaldehyde is correlated with reduced degradation of the chemical. The SFA gene shares an 868 bp divergent promoter with UGX2 a gene of yet unknown function. Promoter deletion studies with a SFA promoter-lacZ gene fusion construct revealed negative interference on expression of SFA by upstream sequences. The upstream region between positions -145 and -172 is totally or partially responsible for control of inducibility of SFA by chemicals such as formaldehyde (FA), ethanol and methyl methanesulphonate. The 41 kDa SFA-encoded protein was purified from a hyper-resistant transformant; it oxidizes long-chain alcohols and, in the presence of glutathione, is able to oxidize FA. SFA is predicted to code for a long-chain alcohol dehydrogenase (glutathione-dependent formaldehyde dehydrogenase) of the yeast S. cerevisiae.

Alcohol Dehydrogenase↗
PubMed1993

Co-regulation with genes of phospholipid biosynthesis of the CTR/HNM1-encoded choline/nitrogen mustard permease in Saccharomyces cerevisiae.

An 815 bp region of the promoter of the Saccharomyces cerevisiae gene CTR/HNM1, encoding choline permease was sequenced and its regulatory function analysed by deletion studies in an in-frame promoter-lacZ construct. In addition to the TATA box, a 10 bp motif (consensus 5'-CATGTGAAAT-3') was found to be mandatory for CTR/HNM1 expression. This 'decamer' motif is located between nucleotides -262 and -271 and is identical in 9 of 10 bp with the regulatory motif found in the S. cerevisiae INO1 and CHO1 genes. Constructs with the 10 bp sequence show high constitutive expression, while elimination or alterations at three nucleotide positions, of the decamer motif in the context of an otherwise unchaged promoter leads to total loss of beta-galactosidase production. Expression of the CTR/HNM1 gene in wild-type cells is regulated by the phospholipid precursors inositol and choline; no such influence is seen in cells bearing mutations in the phospholipid regulatory genes INO2, INO4, and OPI1. There is no regulation by INO2 and OPI1 in the absence of the decamer motif. However constructs not containing this sequence (promoter intact to positions -213 or -152) are still controlled by INO4. Other substrates of the choline permease, i.e. ethanolamine, nitrogen mustard and nitrogen half mustard do not regulate expression of CTR/HNM1.

Base Sequence↗
PubMed1993

Differential interleukin-1 receptor antagonism on pancreatic beta and alpha cells. Studies in rodent and human islets and in normal rats.

The monokines interleukin-1 alpha and -beta have been implicated as effector molecules in the immune-mediated pancreatic beta-cell destruction leading to insulin-dependent diabetes mellitus. Here we investigated the effects of interleukin-1 receptor antagonism on insulin and glucagon release of rat, mouse and human islets exposed to recombinant human interleukin-1 beta, and on interleukin-1 beta induced changes in blood glucose, serum insulin and serum glucagon levels in Wistar Kyoto rats. The interleukin-1 receptor antagonist reduced the co-mitogenic effect of interleukin-1 beta on mouse and rat thymocytes with a 50% inhibitory concentration of 10- and 100-fold molar excess, respectively. Complete inhibition was obtained with a 100-1,000-fold molar excess. However, at a 100-fold molar excess the interleukin-1 receptor antagonist did not antagonise the potentiating effect of interleukin-1 beta on rat islet insulin accumulation during 3 and 6 h of exposure or of interleukin-1 beta-induced inhibition of insulin release after 24 h. In contrast, interleukin-1 beta-stimulated islet glucagon release was completely antagonised by a 100-fold molar excess of interleukin-1 receptor antagonist. A 10,000-fold molar excess of interleukin-1 receptor antagonist was needed to antagonise interleukin-1 beta stimulatory and inhibitory effects on rat beta-cell function in vitro. A 100-fold excess of interleukin-1 receptor antagonist could not counteract interleukin-1 beta effects on mouse and human beta cells, excluding species difference in the efficacy of the human interleukin-1 receptor antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗