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Biomedical subjects

A Oren

Publications and source records attributed to A Oren.

At least 37 records · Page 2Linked to original sources
PubMed2000

Haloterrigena thermotolerans sp. nov., a halophilic archaeon from Puerto Rico.

An extremely halophilic Archaeon belonging to the order Halobacteriales was isolated from the solar salterns of Cabo Rojo, Puerto Rico. The organism, designated strain PR5T, is rod-shaped, non-motile and requires at least 12% (w/v) NaCl to grow. The strain is highly thermotolerant: its temperature optimum is 50 degrees C and growth is possible up to 60 degrees C. Polar lipid analysis revealed the presence of the bis-sulfated glycolipid S2-DGD-1 as sole glycolipid and the absence of the glycerol diether analogue of phosphatidylglycerosulfate. Both C20,C20 and C20,C25 core lipids are present. The G+C content of the DNA is 63.3 mol%. According to 16S rDNA sequence data, strain PR5T is closely related to the representatives of the genera Haloterrigena and Natrinema, but on the basis of its phenotypic properties, 16S rDNA sequence and DNA-DNA hybridization studies, strain PR5T cannot be assigned to any of the recognized species within these genera. On the basis of its polar lipid composition, the isolate has been assigned to the genus Haloterrigena. The creation of a new species, Haloterrigena thermotolerans, is therefore proposed to accommodate this isolate. The type strain is strain PR5T (= DSM 11552T = ATCC 700275T).

Base Composition↗
PubMed2000

Change of the names Haloanaerobiales, Haloanaerobiaceae and Haloanaerobium to Halanaerobiales, Halanaerobiaceae and Halanaerobium, respectively, and further nomenclatural changes within the order Halanaerobiales.

A formal proposal is made to rename the order Haloanaerobiales as Halanaerobiales, the family Haloanaerobiaceae as Halanaerobiaceae, the genera Haloanaerobium and Haloanaerobacter as Halanaerobium and Halanaerobacter, respectively, and to change the specific epithets of Halanaerobium acetoethylicum, Halanaerobacter lacunaris, Halocella cellulolytica and Halanaerobium chitinovorans to acetethylicum, lacunarum, cellulosilytica and chitinivorans, respectively. These changes are required in view of Rule 61, Appendix 9, of the Bacteriological Code.

Bacteria, Anaerobic↗
PubMed1999

Glucocorticoid control of glial gene expression.

The glucocorticoid signaling pathway is responsive to a considerable number of internal and external signals and can therefore establish diverse patterns of gene expression. A glial-specific pattern, for example, is shown by the glucocorticoid-inducible gene glutamine synthetase. The enzyme is expressed at a particularly high level in glial cells, where it catalyzes the recycling of the neurotransmitter glutamate, and at a low level in most other cells, for housekeeping duties. Glial specificity of glutamine synthetase induction is achieved by the use of positive and negative regulatory elements, a glucocorticoid response element and a neural restrictive silencer element. Though not glial specific by themselves, these elements may establish a glial-specific pattern of expression through their mutual activity and their combined effect. The inductive activity of glucocorticoids is markedly repressed by the c-Jun protein, which is expressed at relatively high levels in proliferating glial cells. The signaling pathway of c-Jun is activated by the disruption of glia-neuron cell contacts, by transformation with v-src, and in proliferating retinal cells of early embryonic ages. The c-Jun protein inhibits the transcriptional activity of the glucocorticoid receptor and thus represses glutamine synthetase expression. This repressive mechanism might also affect the ability of glial cells to cope with glutamate neurotoxicity in injured tissues.

Animals↗
PubMed1999

Thermophilic and halophilic extremophiles.

The microbiology of extremely hot or saline habitats is a fast moving field with many new successes in the enrichment and isolation of new organisms and in an understanding of molecular factors that impart stability on thermostable and halophilic biomolecules. The results of these studies have shed new light on our understanding of prokaryotic diversity and structural biochemistry.

Adaptation, Physiological↗
PubMed1999

Isolation of Ureaplasma urealyticum and Mycoplasma hominis from public toilet bowls.

The presence of Ureaplasma urealyticum, Mycoplasma hominis, and Chlamydia trachomatis was explored in 50 public restroom toilet bowls. We used culture, antigen detection, polymerase chain reaction, and survival assay. Five bowls (10%) were contaminated with at least one organism. U. urealyticum was found in four bowls, M. hominis in three, and C. trachomatis in one. U. urealyticum survived on the toilet rim for up to 2 hours.

Chlamydia Infections↗
PubMed1999

Abnormal clotting parameters before therapeutic ERCP: do they predict major bleeding?

A total of 399 consecutive patients undergoing 598 ERCPs (endoscopic retrograde cholangiopancreatographies), including 88 pre-cut papillotomies and 206 conventional papillotomies, are described in a retrospective study. Clotting parameters, haemoglobin levels, indications for pre-cut and/or conventional papillotomy and the use of drugs assumed to interfere with blood clotting (anticoagulants, platelet-aggregation inhibitors, low-molecular-weight heparin) were evaluated in order to detect risk factors for ERCP-associated bleeding. The overall incidence of ERCP-associated bleeding was 18/598 (3.0%). The incidence of bleeding in the group without papillotomy was 7/346 (2.0%). This group consisted of patients who underwent only a diagnostic ERCP, patients who had undergone papillotomy previously, patients in whom a renewed attempt was made to extract biliary stones, and patients in whom removal or change of a stent was necessary. The incidence of papillotomy-associated bleeding was 11/252 (4.4%). Pre-cut papillotomy did and conventional papillotomy did not significantly increase the incidence of bleeding: 15.2% (P < 0.001) and 1.9% (P= 1.00) respectively. The incidence of ERCP-associated bleeding in the group not using any drugs interfering with blood clotting was 2.5%. The use of low-molecular-weight heparin (10.3%) during ERCP significantly increased the risk of bleeding (P= 0.01). However, the use of platelet aggregation inhibitors (2.4%) did not (P= 1.00). As the incidence of bleeding in patients with normal clotting parameters, including the patients with abnormal parameters which were well corrected (4.3%), was higher than in patients with abnormal haemostatic screens (2.7%), abnormal coagulation tests did not predict ERCP-associated bleeding.

Anticoagulants↗
PubMed1999

Haloarcula quadrata sp. nov., a square, motile archaeon isolated from a brine pool in Sinai (Egypt).

The motile, predominantly square-shaped, red archaeon strain 801030/1T, isolated from a brine pool in the Sinai peninsula (Egypt), was characterized taxonomically. On the basis of its polar lipid composition, the nucleotide sequences of its two 16S rRNA genes, the DNA G+C content (60.1 mol%) and its growth characteristics, the isolate could be assigned to the genus Haloarcula. However, phylogenetic analysis of the two 16S rRNA genes detected in this organism and low DNA-DNA hybridization values with related Haloarcula species showed that strain 801030/1T is sufficiently different from the recognized Haloarcula species to warrant its designation as a new species. A new species, Haloarcula quadrata, is therefore proposed, with strain 801030/1T (= DSM 11927T) as the type strain.

Base Composition↗
PubMed1999

The cytoskeletal network controls c-Jun expression and glucocorticoid receptor transcriptional activity in an antagonistic and cell-type-specific manner.

The physical and functional link between adhesion molecules and the cytoskeletal network suggests that the cytoskeleton might mediate the transduction of cell-to-cell contact signals, which often regulate growth and differentiation in an antagonistic manner. Depolymerization of the cytoskeleton in confluent cell cultures is reportedly sufficient to initiate DNA synthesis. Here we show that depolymerization of the cytoskeleton is also sufficient to repress differentiation-specific gene expression. Glutamine synthetase is a glia-specific differentiation marker gene whose expression in the retinal tissue is regulated by glucocorticoids and is ultimately dependent on glia-neuron cell contacts. Depolymerization of the actin or microtubule network in cells of the intact retina mimics the effects of cell separation, repressing glutamine synthetase induction by a mechanism that involves induction of c-Jun and inhibition of glucocorticoid receptor transcriptional activity. Depolymerization of the cytoskeleton activates JNK and p38 mitogen-activated protein kinase and induces c-Jun expression by a signaling pathway that depends on tyrosine kinase activity. Induction of c-Jun expression is restricted to Müller glial cells, the only cells in the tissue that express glutamine synthetase and maintain the ability to proliferate upon cell separation. Our results suggest that the cytoskeletal network might play a part in the transduction of cell contact signals to the nucleus.

Animals↗
PubMed1999

Bioenergetic aspects of halophilism.

Examination of microbial diversity in environments of increasing salt concentrations indicates that certain types of dissimilatory metabolism do not occur at the highest salinities. Examples are methanogenesis for H2 + CO2 or from acetate, dissimilatory sulfate reduction with oxidation of acetate, and autotrophic nitrification. Occurrence of the different metabolic types is correlated with the free-energy change associated with the dissimilatory reactions. Life at high salt concentrations is energetically expensive. Most bacteria and also the methanogenic Archaea produce high intracellular concentrations of organic osmotic solutes at a high energetic cost. All halophilic microorganisms expend large amounts of energy to maintain steep gradients of NA+ and K+ concentrations across their cytoplasmic membrane. The energetic cost of salt adaptation probably dictates what types of metabolism can support life at the highest salt concentrations. Use of KCl as an intracellular solute, while requiring far-reaching adaptations of the intracellular machinery, is energetically more favorable than production of organic-compatible solutes. This may explain why the anaerobic halophilic fermentative bacteria (order Haloanaerobiales) use this strategy and also why halophilic homoacetogenic bacteria that produce acetate from H2 + CO2 exist whereas methanogens that use the same substrates in a reaction with a similar free-energy yield do not.

Adaptation, Biological↗
PubMed1998

Fungal life in the extremely hypersaline water of the Dead Sea: first records.

The first report, to our knowledge, on the occurrence of filamentous fungi in the hypersaline (340 g salt l-1) Dead Sea is presented. Three species of filamentous fungi from surface water samples of the Dead Sea were isolated: Gymnascella marismortui (Ascomycota), which is described as a new species, Ulocladium chlamydosporum and Penicillium westlingii (Deuteromycota). G. marismortui and U. chlamydosporum grew on media containing up to 50% Dead Sea water. G. marismortui was found to be an obligate halophile growing optimally in the presence of 0.5-2 M NaCl or 10 30% (by volume) of Dead Sea water. Isolated cultures did not grow on agar media without salt, but grew on agar prepared with up to 50% Dead Sea water. This suggests that they may be adapted to life in the extremely stressful hypersaline Dead Sea.

Fungi↗
PubMed1998

Typing of halophilic Archaea and characterization of their cell surface carbohydrates by use of lectins.

Lectins are important tools for cell typing and for the study of cell surface components. They have been widely used for the analysis of carbohydrates on the surface of many eukaryotic and prokaryotic cells, but they have not yet been exploited in the study of the halophilic Archaea (family Halobacteriaceae), because of the high salinity required for the structural integrity of these microorganisms. We have defined the salt concentration threshold high enough for survival of the Archaea, but sufficiently low for lectins to bind to them. Under these conditions we studied the interactions of a series of lectins, exhibiting different sugar specificities, with diverse halophilic Archaea. Concanavalin A was the most reactive by virtue of its glucose (and mannose) binding. The other lectins varied in their interactions. The results indicate that lectins might be useful probes for both archaeal typing and analysis of their cell surface carbohydrates.

Bacterial Typing Techniques↗
PubMed1998

Paracoccus marcusii sp. nov., an orange gram-negative coccus.

Phenotypic, chemotaxonomic and 16S rDNA sequence analysis of an orange Gram-negative coccus that appeared as a contaminant on a nutrient agar plate delineated a new species of the genus Paracoccus. Phenotypic features of the strain that differ from all or most of the previously described Paracoccus species include its bright orange colour, caused by the synthesis of large amounts of carotenoids (mainly astaxanthin), and its inability to use nitrate as an electron acceptor in respiration. The name Paracoccus marcusii is proposed for this organism. The type strain is DSM 11574T.

Azo Compounds↗
PubMed1998

Halogeometricum borinquense gen. nov., sp. nov., a novel halophilic archaeon from Puerto Rico.

A novel extremely halophilic archaeon was isolated from the solar salterns of Cabo Rojo, Puerto Rico. The organism is very pleomorphic, motile and requires at least 8% (w/v) NaCl to grow. Polar lipid composition revealed the presence of a novel non-sulfate-containing glycolipid and the absence of the glycerol diether analogue of phosphatidylglycerosulfate. The G + C content of the DNA is 59 mol%. On the basis of 16S rRNA sequence data, the new isolate cannot be classified in one of the recognized genera, but occupies a position that is distantly related to the genus Haloferax. All these features justify the creation of a new genus and a new species for the family Halobacteriaceae, order Halobacteriales. The name Halogeometricum borinquense gen. nov., sp. nov. is proposed. The type strain is ATCC 700274T.

Base Composition↗
PubMed1998

Killing of Fusobacterium nucleatum, Porphyromonas gingivalis and Prevotella intermedia by protegrins.

Protegrins are broad spectrum antibiotic peptides isolated from porcine leukocytes. In this study, we (i) examine the sensitivity of Gram-negative, anaerobic periodontal pathogens to synthetic protegrins; (ii) determine the relative potencies of protegrin congeners against these bacteria; and (iii) compare the potency of protegrins with other antibiotic peptides, including magainin MSI-78, tachyplesin I, cecropin P1, human defensins HNP-1-3, and clavanin A. Synthetic L- and D-enantiomers of protegrin 1 (PG-1 and D-PG-1, respectively), and L-enantiomers of protegrins 2, 3 and 5 (PG-2, PG-3 and PG-5) were tested against Fusobacterium nucleatum, and black-pigmented organisms including Porphyromonas gingivalis and Prevotella intermedia. Strains of both F. nucleatum and the black-pigmented organisms were sensitive to PG-1, and exhibited mean ED99 of 2.2-2.3 micrograms/ml and 3.4-9.9 micrograms/ml, respectively. The D-form was statistically more potent than the L-form against these oral anaerobes, and although this difference in potency is unlikely to be of decisive therapeutic significance, the D-form may be of value given ability to resist microbial and host-derived proteases. PG-1 was more potent than magainin, tachyplesin, cecropin, defensins and clavanin under test conditions. Hypertonic salt concentrations and heat-inactivated serum were found to be inhibitory to the bactericidal activity of PG-1. PG-1 was found to induce morphologic alterations in the ultrastructural appearance of F. nucleatum consistent with damage to the bacterial membranes. We conclude that protegrins may be useful antimicrobial agents in therapy against Gram-negative anaerobic bacteria believed to be involved in chronic, adult forms of periodontal infections.

Amino Acid Sequence↗
PubMed1998

Biology of moderately halophilic aerobic bacteria.

The moderately halophilic heterotrophic aerobic bacteria form a diverse group of microorganisms. The property of halophilism is widespread within the bacterial domain. Bacterial halophiles are abundant in environments such as salt lakes, saline soils, and salted food products. Most species keep their intracellular ionic concentrations at low levels while synthesizing or accumulating organic solutes to provide osmotic equilibrium of the cytoplasm with the surrounding medium. Complex mechanisms of adjustment of the intracellular environments and the properties of the cytoplasmic membrane enable rapid adaptation to changes in the salt concentration of the environment. Approaches to the study of genetic processes have recently been developed for several moderate halophiles, opening the way toward an understanding of haloadaptation at the molecular level. The new information obtained is also expected to contribute to the development of novel biotechnological uses for these organisms.

Adaptation, Biological↗