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Biomedical subjects

A Matin

Publications and source records attributed to A Matin.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1996

Modulation of disease severity in cystic fibrosis transmembrane conductance regulator deficient mice by a secondary genetic factor.

Mice that have been made deficient for the cystic fibrosis transmembrane conductance regulator (Cftr) usually die of intestinal obstruction. We have created Cftr-deficient mice and demonstrate prolonged survival among backcross and intercross progeny with different inbred strains, suggesting that modulation of disease severity is genetically determined. A genome scan showed that the major modifier locus maps near the centromere of mouse chromosome 7. Electrophysiological studies on mice with prolonged survival show that the partial rectification of Cl- and Na+ ion transport abnormalities can be explained in part by up-regulation of a calcium-activated Cl- conductance. Identification of modifier genes in our Cftr(m1HSC)/Cftr(m1HSC) mice should provide important insight into the heterogeneous disease presentation observed among CF patients.

Animals↗
PubMed1996

Differential regulation of the mcb and emr operons of Escherichia coli: role of mcb in multidrug resistance.

The mcb operon (which is responsible for microcin B17 production) and the emr operon (which encodes a multidrug resistance pump) share a common negative regulator, EmrR. Nevertheless, compounds that induce the emr operon repress the mcb operon. The pump dedicated to microcin B17 extrusion can also protect the calls against sparfloxacin and other toxic compounds.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1996

Capacity of Helicobacter pylori to generate ionic gradients at low pH is similar to that of bacteria which grow under strongly acidic conditions.

Helicobacter pylori colonized the highly acidic human gastric mucosa. At pH 3.0 to 7.0, this bacterium maintained a nearly neutral internal pH. Its membrane potential changed reciprocally with the pH gradient so that a relatively constant proton motive force was maintained. Possible, the capacity to maintain an appropriate transmembrane ionic gradient at a low pH contributes to the pathogenic propensities of this bacterium.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1996

Regulation of Escherichia coli starvation sigma factor (sigma s) by ClpXP protease.

In Escherichia coli, starvation (stationary-phase)-mediated differentiation involves 50 or more genes and is triggered by an increase in cellular sigma s levels. Western immunoblot analysis showed that in mutants lacking the protease ClpP or its cognate ATPase-containing subunit ClpX, sigma s levels of exponential-phase cells increased to those of stationary-phase wild-type cells. Lack of other potential partners of ClpP, i.e., ClpA or ClpB, or of Lon protease had no effect. In ClpXP-proficient cells, the stability of sigma s increased markedly in stationary-phase compared with exponential-phase cells, but in ClpP-deficient cells, sigma s became virtually completely stable in both phases. There was no decrease in ClpXP levels in stationary-phase wild-type cells. Thus, sigma s probably becomes more resistant to this protease in stationary phase. The reported sigma s-stabilizing effect of the hns mutation also was not due to decreased protease levels. Studies with translational fusions containing different lengths of sigma s coding region suggest that amino acid residues 173 to 188 of this sigma factor may directly or indirectly serve as at least part of the target for ClpXP protease.

ATP-Dependent Proteases↗
PubMed1995

Liposome-mediated in vivo E1A gene transfer suppressed dissemination of ovarian cancer cells that overexpress HER-2/neu.

The HER-2/neu proto-oncogene is frequently amplified or overexpressed in many different types of human cancers, a phenomenon that has been shown to correlate with shorter survival time and lower survival rate in ovarian cancer patients. We previously reported that increased HER-2/neu expression led to more severe malignancy and increased metastatic potential in animal models and that the adenovirus 5 E1A gene repressed HER-2/neu gene expression at transcriptional level and was able to suppress tumor growth when stably transfected into human ovarian cancer SKOV-3 cells which overexpress HER-2/neu. To investigate whether the E1A gene may be used as a therapeutic agent for HER-2/neu-overexpressing human cancers in living hosts, we first developed tumor-bearing mice by injecting SKOV-3 cells that overexpress HER-2/neu intraperitonealy into female nu/nu mice. Five days later, we used cationic liposomes to directly deliver the E1A gene into adenocarcinomas that developed in the peritoneal cavity and on the mesentery of the mice that received the SKOV-3 cell injection. We found that liposome-mediated E1A gene transfer significantly inhibited growth and dissemination of ovarian cancer cells that overexpress HER-2/neu in the treated mice; about 70% of these mice survived at least 365 days, whereas all the control mice that did not receive the gene therapy developed severe tumor symptoms and died within 160 days. The results suggest that liposome-mediated E1A gene transfer may serve as an effective therapy for human ovarian cancers that overexpress HER-2/neu by directly targeting the HER-2/neu oncogene.

Adenovirus E1A Proteins↗
PubMed1995

HER-2/neu-targeting gene therapy--a review.

The HER-2/neu (also named c-erbB-2) oncogene is known to be overexpressed in many human cancers, including breast, ovarian, lung, gastric and oral cancers. In animal models, HER-2/neu overexpression was shown to enhance malignancy and metastasis phenotypes. Repression of HER-2/neu overexpression suppresses the malignant phenotypes of HER-2/neu-overexpressing cancer cells, suggesting that HER-2/neu may serve as an excellent target for developing anti-cancer agents. We have previously shown that the adenovirus-5 (Ad5) E1a gene products and the SV40 large T antigen (large T) inhibit transcription of the HER-2/neu promoter and accordingly suppresses transformation induced by HER-2/neu. In this review, we summarize our recent findings on using cationic liposomes or an Ad vector to deliver E1a or large T into tumor-bearing mice. Our results indicate that both cationic liposomes or an Ad vector can efficiently deliver E1a or large T into tumor cells in mice, and this results in suppression of tumor growth and longer survival of the mice.

Adenoviridae↗
PubMed1995

Use of starvation promoters to limit growth and selectively enrich expression of trichloroethylene- and phenol-transforming activity in recombinant Escherichia coli [corrected].

The expression of much useful bacterial activity is facilitated by rapid growth. This coupling can create problems in bacterial fermentations and in situ bioremediation. In the latter process, for example, it necessitates addition of large amounts of nutrients to contaminated environments, such as aquifers. This approach, termed biostimulation, can be technically difficult. Moreover, the resulting in situ bacterial biomass production can have undesirable consequences. In an attempt to minimize coupling between expression of biodegradative activity and growth, we used Escherichia coli starvation promoters to control toluene monooxygenase synthesis. This enzyme complex can degrade the environmental contaminants trichloroethylene (TCE) and phenol. Totally starving cell suspensions of such strains degraded phenol and TCE. Furthermore, rapid conversions occurred in the postexponential batch or very slow growth (dilution) rate chemostat cultures, and the nutrient demand and biomass formation for transforming a given amount of TCE or phenol were reduced by 60 to 90%. Strong starvation promoters have recently been clones and characterized in environmentally relevant bacteria like Pseudomonas species; thus, starvation promoter-driven degradative systems can now be constructed in such bacteria and tested for in situ efficacy.

Biodegradation, Environmental↗
PubMed1995

A carbon starvation survival gene of Pseudomonas putida is regulated by sigma 54.

By using mini-Tn5 transposon mutagenesis, two mutants of Pseudomonas putida ATCC 12633 were isolated which showed a marked increase in their sensitivity to carbon starvation; these mutants are presumably affected in the Pex type of proteins that P. putida induces upon carbon starvation (M. Givskov, L. Eberl, and S. Molin, J. Bacteriol. 176:4816-4824, 1994). The affected genes in our mutants were induced about threefold upon carbon starvation. The promoter region of the starvation gene in the mutant MK107 possessed a strong sigma 54-type-promoter sequence, and deletion analysis suggested that this was the major promoter regulating expression; this was confirmed by transcript mapping in rpoN+ and rpoN mutant backgrounds. The deletion analysis implicated a sequence upstream of the sigma 54 promoter, as well as a region downstream of the transcription start site, in the functioning of the promoter. Two sigma 70-type Pribnow boxes were also detected in the promoter region, but their transcriptional activity in the wild type was very weak. However, in a sigma 54-deficient background, these promoters became stronger. The mechanism and possible physiological role of this phenomenon and the possibility that the sequence upstream of the sigma 54 promoter may have a role in carbon sensing are discussed.

Base Sequence↗
PubMed1995

EmrR is a negative regulator of the Escherichia coli multidrug resistance pump EmrAB.

The emrAB locus of Escherichia coli encodes a multidrug resistance pump that protects the cell from several chemically unrelated antimicrobial agents, e.g., the protonophores carbonyl cyanide m-chlorophenylhydrazone (CCCP) and tetrachlorosalicyl anilide and the antibiotics nalidixic acid and thiolactomycin. The mprA gene is located immediately upstream of this locus and was shown to be a repressor of microcin biosynthesis (I. del Castillo, J. M. Gomez, and F. Moreno, J. Bacteriol. 173:3924-3929, 1991). There is a putative transcriptional terminator sequence between the mprA and emrA genes. To locate the emr promoter, single-copy lacZ operon fusions containing different regions of the emr locus were made. Only fusions containing the mprA promoter region were expressed. mprA is thus the first gene of the operon, and we propose that it be renamed emrR. Overproduction of the EmrR protein (with a multicopy vector containing the cloned emrR gene) suppressed transcription of the emr locus. A mutation in the emrR gene led to overexpression of the EmrAB pump and increased resistance to antimicrobial agents. CCCP, nalidixic acid, and a number of other structurally unrelated chemicals induced expression of the emr genes, and the induction required EmrR. We conclude that emrRAB genes constitute an operon and that EmrR serves as a negative regulator of this operon. Some of the chemicals that induce the pump serve as its substrates, suggesting that their extrusion is the natural function of the pump.

Amino Acid Sequence↗