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A Matin

Publications and source records attributed to A Matin.

At least 19 recordsLinked to original sources
PubMed2002

Tetracycline rapidly reaches all the constituent cells of uropathogenic Escherichia coli biofilms.

We have developed a method for visualizing Escherichia coli cells that are exposed to tetracycline in a biofilm, based on a previous report that liposomes containing the E. coli TetR(B) protein fluoresce when exposed to this antibiotic. By our method, cells devoid of TetR(B) also exhibited tetracycline-dependent fluorescence. At 50 microg of tetracycline ml(-1), planktonic cells of a uropathogenic E. coli (UPEC) strain developed maximal fluorescence after 7.5 to 10 min of exposure. A similar behavior was exhibited by cells in a 24- or 48-h UPEC biofilm, as examined by confocal laser microscopy, regardless of whether they lined empty spaces or occupied densely packed regions. Further, a comparison of phase-contrast and fluorescent images of corresponding biofilm zones showed that all the cells fluoresced. Thus, all the biofilm cells were exposed to tetracycline and there were no pockets within the biofilm where the antibiotic failed to reach. It also appeared unlikely that niches of reduced exposure to the antibiotic existed within the biofilms.

Anti-Bacterial Agents↗
PubMed2001

Sensitized polygenic trait analysis.

Genetic variation in many biological processes and evolutionary adaptations is caused by polygenes--genes that act in combination to affect a particular trait. Despite the recent identification of several polygenes, many remain to be found, suggesting that new experimental and analytical methods are needed to facilitate their discovery. Here we discuss sensitized polygenetic trait analysis, a method that has emerged recently for simplifying the genetic analysis of polygenic traits. The method uses a known single gene mutation in linkage testing crosses to 'sensitize' the analysis. By increasing the frequency of affected individuals in segregating populations, linkages are more readily detected. This method has considerable potential, especially given the increasing variety of mutations that can be used to sensitize the genetic analysis of polygenic traits.

Animals↗
PubMed2001

Nuclear localization of EGF receptor and its potential new role as a transcription factor.

Epidermal growth factor receptor (EGFR) has been detected in the nucleus in many tissues and cell lines. However, the potential functions of nuclear EGFR have largely been overlooked. Here we demonstrate that nuclear EGFR is strongly correlated with highly proliferating activities of tissues. When EGFR was fused to the GAL4 DNA-binding domain, we found that the carboxy terminus of EGFR contained a strong transactivation domain. Moreover, the receptor complex bound and activated AT-rich consensus-sequence-dependent transcription, including the consensus site in cyclin D1 promoter. By using chromatin immunoprecipitation assays, we further demonstrated that nuclear EGFR associated with promoter region of cyclin D1 in vivo. EGFR might therefore function as a transcription factor to activate genes required for highly proliferating activities.

Animals↗
PubMed2000

Analysing complex genetic traits with chromosome substitution strains.

Many valuable animal models of human disease are known and new models are continually being generated in existing inbred strains,. Some disease models are simple mendelian traits, but most have a polygenic basis. The current approach to identifying quantitative trait loci (QTLs) that underlie such traits is to localize them in crosses, construct congenic strains carrying individual QTLs, and finally map and clone the genes. This process is time-consuming and expensive, requiring the genotyping of large crosses and many generations of breeding. Here we describe a different approach in which a panel of chromosome substitution strains (CSSs) is used for QTL mapping. Each of these strains has a single chromosome from the donor strain substituting for the corresponding chromosome in the host strain. We discuss the construction, applications and advantages of CSSs compared with conventional crosses for detecting and analysing QTLs, including those that have weak phenotypic effects.

Animals↗
PubMed2000

The G-protein FlhF has a role in polar flagellar placement and general stress response induction in Pseudomonas putida.

The flhF gene of Pseudomonas putida, which encodes a GTP-binding protein, is part of the flagellar-motility-chemotaxis operon. Its disruption leads to a random flagellar arrangement in the mutant (MK107) and loss of directional motility in contrast to the wild type, which has polar flagella. The return of a normal flhF allele restores polar flagella and normal motility to MK107; its overexpression triples the flagellar number but does not restore directional motility. As FlhF is homologous to the receptor protein of the signal recognition particle (SRP) pathway of membrane protein translocation, this pathway may have a role in polar flagellar placement in P. putida. MK107 is also compromised in the development of the starvation-induced general stress resistance (SGSR) and effective synthesis of several starvation and exponential phase proteins. While somewhat increased protein secretion in MK107 may contribute to its SGSR impairment, the altered protein synthesis pattern also appears to have a role.

Alleles↗
PubMed2000

Purification to homogeneity and characterization of a novel Pseudomonas putida chromate reductase.

Cr(VI) (chromate) is a widespread environmental contaminant. Bacterial chromate reductases can convert soluble and toxic chromate to the insoluble and less toxic Cr(III). Bioremediation can therefore be effective in removing chromate from the environment, especially if the bacterial propensity for such removal is enhanced by genetic and biochemical engineering. To clone the chromate reductase-encoding gene, we purified to homogeneity (>600-fold purification) and characterized a novel soluble chromate reductase from Pseudomonas putida, using ammonium sulfate precipitation (55 to 70%), anion-exchange chromatography (DEAE Sepharose CL-6B), chromatofocusing (Polybuffer exchanger 94), and gel filtration (Superose 12 HR 10/30). The enzyme activity was dependent on NADH or NADPH; the temperature and pH optima for chromate reduction were 80 degrees C and 5, respectively; and the K(m) was 374 microM, with a V(max) of 1.72 micromol/min/mg of protein. Sulfate inhibited the enzyme activity noncompetitively. The reductase activity remained virtually unaltered after 30 min of exposure to 50 degrees C; even exposure to higher temperatures did not immediately inactivate the enzyme. X-ray absorption near-edge-structure spectra showed quantitative conversion of chromate to Cr(III) during the enzyme reaction.

Biodegradation, Environmental↗
PubMed1999

pH homeostasis in acidophiles.

The acidophilic bacteria comprise an environmentally important group that includes pathogens. A fundamental requirement for existence in strongly acidic environments is generation of a large pH gradient (delta pH) to maintain the cytoplasmic pH near neutrality and safeguard the acid-labile cell constituents. These organisms require the capacity to extrude H+ across the thermodynamic barrier imposed by the delta pH. They also need special transport proteins that can function in strongly acidic environments. The quintessential device by which the acidophiles fulfil these requirements by generating a positive-inside membrane potential (delta psi) that mitigates both the force against which H+ must be extruded, as well as the influxing force of protons into the cells. The delta psi is generated through passive as well as active mechanisms. The former constitutes an H+ diffusion as well as a Donnan potential, and the latter involves electrogenic circulation of Cl-, and the operation of an electrogenic H+/K+ (Na+) antiporter.

Bacterial Physiological Phenomena↗
PubMed1999

Susceptibility to testicular germ-cell tumours in a 129.MOLF-Chr 19 chromosome substitution strain.

The identification of genes that control susceptibility to testicular germ-cell tumours (TGCTs), the most common cancer affecting young men, has been difficult. In laboratory mice, TGCTs arise from primordial germ cells in only the 129 inbred strains, and susceptibility is under multigenic control. The spontaneously arising mutation Ter (ref. 5) on mouse chromosome 18 (Refs 6,7) increases TGCT frequency on a 129/Sv background. We originally used Ter in genetic crosses to identify loci that control tumorigenesis. A genome scan of tumour-bearing progeny from backcrosses between the 129/Sv-Ter/+ and MOLF/Ei strains provided modest evidence that MOLF-derived alleles on chromosome 19 enhance development of bilateral TGCTs (ref. 9). To obtain independent evidence for linkage to the MOLF chromosome, we made an autosomal chromosome substitution strain (CSS; or 'consomic strain') in which chromosome 19 of 129/Sv+/+ was replaced by its MOLF-derived homologue. The unusually high frequency of TGCTs in this CSS (even in the absence of the Ter mutation) provides evidence confirming the genome survey results, identifies linkage for a naturally occurring strain variant allele that confers susceptibility to TGCTs and illustrates the power of CSSs in complex trait analysis.

Alleles↗
PubMed1998

Theophylline inhibits the production of nitric oxide by peripheral blood mononuclear cells from patients with asthma.

BACKGROUND: Nitric oxide (NO), a reactive free radical synthesized from L-arginine by the enzyme NO synthase (NOS), may play a role in many pathophysiologic conditions, including asthma. OBJECTIVE: The aim of this study was to investigate whether peripheral blood mononuclear cells (PBMCs) from asthmatics would spontaneously produce NO. A second objective was to ascertain whether commonly used asthma medications would modulate the production of NO. METHODS: PBMCs were isolated from 24 subjects (10 with asthma, 4 with allergic rhinitis and 10 healthy controls) and were incubated either alone or in the presence of an RNA polymerase inhibitor (actinomycin D, 1 microg/mL), a NOS inhibitor (L-NG-nitroarginine methyl ester [L-NAME], 1 mM), and L-NAME plus L-arginine (5 mM). Furthermore, PBMCs were incubated with or without addition of therapeutic concentrations of hydrocortisone (15 microg/mL), theophylline (15 microg/mL), albuterol (15 microg/mL) and ipratropium bromide (12 microg/mL). Culture supernatants were collected and assayed for NO production. RESULTS: NO production was significantly elevated in asthmatics compared with the control group (1.39+/-0.21 microM versus 0.46+/-0.01 microM; P < .05). L-NAME significantly reduced NO production in asthmatics (0.83+/-0.06 microM; P < .05), an effect completely reversed by L-arginine. Theophylline blocked NO production in asthmatics (1.39+/-0.21 microM to 0.92+/-0.11; P < .05). There was no significant effect with any of the other medications. CONCLUSION: This study suggests that theophylline may be antiinflammatory by inhibiting the L-arginine-dependent production of NO in patients with asthma.

Adult↗
PubMed1998

Testicular teratocarcinogenesis in mice--a review.

Spontaneous testicular germ cell tumours in humans and mice are remarkable for their diverse composition. These tumours are usually composed of an extraordinary variety of cell and tissue types including muscle, skin, bone, cartilage, and neuroepithelia. Their diverse composition reflects their origin from totipotent primordial germ cells at about Day 12 of fetal development. Although much is known about the development of these tumours, remarkably little is known about the genetics of the mammalian primordial germ cell lineage or about the genes that control susceptibility to spontaneous testicular germ cell tumours in humans or mice. Conventional genetic analysis of susceptible 129/Sv mice is difficult because of the large number of susceptibility genes and their low penetrance. We are taking advantage of the Ter mutation to simplify the genetic analysis. Various evidence suggests that Ter is neither necessary nor sufficient for tumourigenesis. Instead, Ter acts as a modifier, dramatically increasing tumour incidence from approximately 1% in +/+ males, to approximately 17% in Ter/+ males and approximately 94% in Ter/Ter males. Segregation analysis suggests that Ter increases tumour incidence by requiring some, but perhaps not all, of the 129/Sv-derived susceptibility genes. With standard crosses that segregate for the Ter mutation, identification not only of Ter but also of these 129/Sv-derived susceptibility genes should be possible. In this paper, we review the genetics and development of germ cell tumours in 129/Sv mice, summarize the status of Ter mapping, and provide evidence that different genetic pathways lead to unilateral and bilateral tumours.

Animals↗
PubMed1998

The Escherichia coli starvation gene cstC is involved in amino acid catabolism.

Escherichia coli strains mutant in the starvation gene cstC grow normally in a mineral salts medium but are impaired in utilizing amino acids as nitrogen sources. They are also compromised in starvation survival, where amino acid catabolism is important. The cstC gene encodes a 406-amino-acid protein that closely resembles the E. coli ArgD protein, which is involved in arginine biosynthesis. We postulate that CstC is a counterpart of ArgD in an amino acid catabolic pathway. The cstC upstream region contains several regulatory consensus sequences. Both sigmaS and sigma54 promoters are probably involved in cstC transcription and appear to compete with each other, presumably to match cstC expression to the cellular amino acid catabolic needs.

Amino Acid Sequence↗
PubMed1997

H-NS protein represses transcription of the lux systems of Vibrio fischeri and other luminous bacteria cloned into Escherichia coli.

High expression in Escherichia coli of the lux system cistron of a luminous bacteria under its own control has been accomplished only for the Vibrio fischeri lux system at high cell density. Mutation of the hns gene in E. coli has resulted in strong expression of the V. fischeri lux system at low cell density even in an rpoS-deleted strain of E. coli that emits very low levels of luminescence. The E. coli double mutant, MC4110 hns::kan rpoS::tet carrying the lux system of V. fischeri, developed high luminescence from the very early stages of cellular growth, regardless of the presence of deletion mutations in the luxI or luxR genes. Moreover, autoinducer synthesis was restored in the double mutant with the luxR-deleted system. plac-controlled V. fischeri luxCDABE genes missing luxI and luxR were dim in E. coli rpoS mutant cells, but had wild-type levels of light in the hns-deleted strain [MC4110 hns rpoS], showing that expression was independent of lux regulators in the absence of H-NS. DNA gyrase inhibitors and DNA intercalating agents also brought about the restoration of luminescence in the rpoS-deficient strain. High expression of the lux systems of Vibrio harveyi, Photobacterium leiognathi, and Xenorhabdus luminescens in E. coli MC4110 hns rpoS cells compared with that in wild-type or rpoS mutants was also accomplished. Taken together, these data suggest that the H-NS protein inhibits transcription in E. coli of the lux systems of all or most luminous bacteria at the luxC gene as well as in the luxRI region of the V. fischeri lux operon. These DNA regions are highly enriched with homopolymeric stretches of poly d(A) and poly d(T) characterizing curved DNA, a preferable site of H-NS binding. The significance of the new findings in understanding the regulatory control of the bacterial lux system is discussed.

Bacterial Proteins↗
PubMed1997

Genealogy of the 129 inbred strains: 129/SvJ is a contaminated inbred strain.

The 129 mouse is the most widely used strain in gene targeting experiments. However, numerous substrains exist with demonstrable physiological differences. In this study a set of simple sequence length polymorphisms (SSLPs) was used to determine the relatedness of selected 129 substrains. 129/SvJ was significantly different from the other 129 substrains and is more accurately classified as a recombinant congenic strain (129cX/Sv), being derived from 129/Sv and an unknown strain. This mixed genetic background could complicate gene targeting experiments by reducing homologous recombination efficiency when constructs and ES cells are not derived from the same 129 substrain. Additionally, discrepancies due to different genetic backgrounds may arise when comparing phenotypes of genes targeted in different 129-derived ES cell lines.

Agouti Signaling Protein↗
PubMed1997

The sigma S level in starving Escherichia coli cells increases solely as a result of its increased stability, despite decreased synthesis.

The sigma S level in starving (stationary phase) Escherichia coli cells increases four-to sixfold following growth in a defined or a complex medium. Chemostat-grown cells, subjected to increasing carbon starvation, also become progressively richer in sigma S content. These increases occur despite reduced transcription of the sigma S-encoding gene, rpoS, and translation of rpoS mRNA, and result solely from a large increase in the stability of the sigma protein. Previous results, based on rpoS::lacZ transcriptional and translational fusions, and on methionine incorporation in sigma S, had suggested increased synthesis of sigma S in starving cells. Alternative explanations for these results consistent with the conclusions of this paper are discussed.

Bacterial Proteins↗
PubMed1997

A bacterial model system for understanding multi-drug resistance.

Mankind stands at the crossroads, recognizing the need for a radical change in bacterial disease management. The development of several antimicrobial agents in the 1940s and 1950s allowed man to gain the upper hand in controlling these diseases. However, the horizon is now clouded by the activation in bacteria of cryptic multi-drug resistance (MDR) genes and the spread of plasmid- and integron-born MDR genes through bacterial populations. Unless remedial measures are taken, nearly all currently available antimicrobial agents are likely to soon lose their efficacies. We briefly review the bacterial MDR phenomenon and focus on a recently emerging family of small multi-drug resistance (SMR) pumps which may provide an ideal model system for understanding the MDR phenomenon in general.

Amino Acid Sequence↗