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R Conrad

Publications and source records attributed to R Conrad.

At least 73 records · Page 4Linked to original sources
PubMed1996

Oxidation of nitric oxide by a new heterotrophic Pseudomonas sp.

A new bacterial strain isolated from soil consumed nitric oxide (NO) under oxic conditions by oxidation to nitrate. Phenotypic and phylogenetic characterization of the new strain PS88 showed that it represents a previously unknown species of the genus Pseudomonas, closely related to Pseudomonas fluorescens and Pseudomonas putida. The heterotrophic, obligately aerobic strain PS88 was not able to denitrify or nitrify; however, strain PS88 oxidized NO to nitrate. NO was not reduced to nitrous oxide (N2O). Nitrogen dioxide (NO2) and nitrite (NO2-) as possible intermediates of NO oxidation to nitrate (NO3-) could not be detected. NO oxidation was inhibited under anoxic conditions and by high osmolarity, but not by nitrite. NO oxidation activity was inhibited by addition of formaldehyde, HgCl2, and antimycin, and by autoclaving or disintegrating the cells, indicating that the process was enzyme-mediated. However, the mechanism remains unclear. A stepwise oxidation at a metalloenzyme and a radical mechanism are discussed. NO oxidation in strain PS88 seems to be a detoxification or a co-oxidation mechanism, rather than an energy-yielding process.

Nitric Oxide↗
PubMed1996

A case of total peripheral aneosinophilia associated with complete deficiency of myeloperoxidase.

Complete and permanent absence of peripheral eosinophilic granulocytes was observed in a patient also presenting with total myeloperoxidase deficiency. The anomaly was suspected because of complete absence of the eosinophilic cluster in the display of a H*3 Technicon hematological automate and was confirmed by traditional staining of more than 100,000 leukocytes. A severe infectious problem during adolescence could be related to MPO deficiency in this patient. No specific disorder attributable to aneosinophilia was however observed subsequently.

Aged↗
PubMed1996

Soil microorganisms as controllers of atmospheric trace gases (H2, CO, CH4, OCS, N2O, and NO).

Production and consumption processes in soils contribute to the global cycles of many trace gases (CH4, CO, OCS, H2, N2O, and NO) that are relevant for atmospheric chemistry and climate. Soil microbial processes contribute substantially to the budgets of atmospheric trace gases. The flux of trace gases between soil and atmosphere is usually the result of simultaneously operating production and consumption processes in soil: The relevant processes are not yet proven with absolute certainty, but the following are likely for trace gas consumption: H2 oxidation by abiontic soil enzymes; CO cooxidation by the ammonium monooxygenase of nitrifying bacteria; CH4 oxidation by unknown methanotrophic bacteria that utilize CH4 for growth; OCS hydrolysis by bacteria containing carbonic anhydrase; N2O reduction to N2 by denitrifying bacteria; NO consumption by either reduction to N2O in denitrifiers or oxidation to nitrate in heterotrophic bacteria. Wetland soils, in contrast to upland soils are generally anoxic and thus support the production of trace gases (H2, CO, CH4, N2O, and NO) by anaerobic bacteria such as fermenters, methanogens, acetogens, sulfate reducers, and denitrifiers. Methane is the dominant gaseous product of anaerobic degradation of organic matter and is released into the atmosphere, whereas the other trace gases are only intermediates, which are mostly cycled within the anoxic habitat. A significant percentage of the produced methane is oxidized by methanotrophic bacteria at anoxic-oxic interfaces such as the soil surface and the root surface of aquatic plants that serve as conduits for O2 transport into and CH4 transport out of the wetland soils. The dominant production processes in upland soils are different from those in wetland soils and include H2 production by biological N2 fixation, CO production by chemical decomposition of soil organic matter, and NO and N2O production by nitrification and denitrification. The processes responsible for CH4 production in upland soils are completely unclear, as are the OCS production processes in general. A problem for future research is the attribution of trace gas metabolic processes not only to functional groups of microorganisms but also to particular taxa. Thus, it is completely unclear how important microbial diversity is for the control of trace gas flux at the ecosystem level. However, different microbial communities may be part of the reason for differences in trace gas metabolism, e.g., effects of nitrogen fertilizers on CH4 uptake by soil; decrease of CH4 production with decreasing temperature; or different rates and modes of NO and N2O production in different soils and under different conditions.

Animal Population Groups↗
PubMed1995

Aptamers as potential nucleic acid pharmaceuticals.

In vitro selection is a technique for the isolation of nucleic acid ligands that can bind to proteins with high affinity and specificity, and has potential applications in the development of new pharmaceuticals. This review summarizes the protein targets that have successfully elicited nucleic acid binding species (also known as "aptamers") and explores examples of how they might be developed for clinical use. In particular, the use of aptamers for the alleviation of blood clotting and the treatment of AIDS are considered.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Decreased catalase activity but unchanged superoxide dismutase activity in brains of patients with dementia of Alzheimer type.

"Oxidative stress" may be of significance in the etiopathogenesis of dementia of Alzheimer type (DAT). Therefore, we measured activities of the enzymes superoxide dismutase (SOD) and catalase (CAT), which detoxicate reactive oxygen species. Enzyme activities were measured postmortem in basal ganglia, cortical, and limbic brain regions of patients with DAT and age-matched controls. SOD activity increased with age in basal nucleus of Meynert. However, there was no significant difference in SOD activity between DAT and controls. CAT activity was independent of age and postmortem time. There were significant reductions in CAT activity in parietotemporal cortex, basal ganglia, and amygdala in DAT compared with controls (p < 0.05 to 0.01). Our findings are in line with the assumption that reactive oxygen species could contribute to the pathogenesis of DAT. Absence of these changes in basal nucleus of Meynert might reflect retrograde degeneration of cholinergic fibers.

Age Factors↗
PubMed1995

SL1 trans-splicing specified by AU-rich synthetic RNA inserted at the 5' end of Caenorhabditis elegans pre-mRNA.

In Caenorhabditis elegans, pre-mRNAs of many genes are trans-spliced to one of two spliced leaders, SL1 or SL2. Some of those that receive exclusively SL1 have been characterized as having at their 5' ends outrons, AU-rich sequences similar to introns followed by conventional 3' splice sites. Comparison of outrons from many different SL1-specific C. elegans genes has not revealed the presence of any consensus sequence that might encode SL1-specificity. In order to determine what parameters influence the splicing of SL1, we performed in vivo experiments with synthetic splice sites. Synthetic AU-rich RNA, 51 nt or longer, placed upstream of a consensus 3' splice site resulted in efficient trans-splicing. With all sequences tested, this trans-splicing was specifically to SL1. Thus, no information beyond the presence of AU-rich RNA at least as long as the minimum-length C. elegans intron, followed by a 3' splice site, is required to specify trans-splicing or for strict SL1 specificity.

Adenine↗
PubMed1994

Isozyme-specific inhibition of protein kinase C by RNA aptamers.

In vitro selection technology has been used to purify RNA aptamers from a random sequence pool that can bind to, and specifically inhibit, protein kinase C beta II. Two of the selected RNA aptamers bind to this isozyme of protein kinase C with nanomolar affinities and inhibit activation with unprecedented selectivity; the highly related, alternatively spliced beta I isozyme, which differs by 23 residues, is inhibited with 1 order of magnitude lower potency; the next most similar isozyme, alpha, shows no detectable inhibition. The production of isozyme-specific inhibitors of protein kinase C opens the possibilities for dissecting the roles of specific protein kinase Cs in the myriad of intracellular signalling pathways.

Amino Acid Sequence↗
PubMed1994

[Pseudoaneurysm of the internal carotid artery following a peritonsillar abscess].

A pseudoaneurysm of the internal carotid artery is a rare major complication of peritonsillar abscess. We present a 95-year-old women, who had a persistent bleeding from peritonsillar fossa after a routine tonsillectomy and ligation of the external carotid artery. Postoperative performed intraarterial angiography verify the diagnosis of a pseudoaneurysm of the internal carotid artery. Subsequent ligation of the internal carotid artery superior the bifurcation stops the hemorrhage. Review of literature demonstrate the importance of angiography in such cases.

Aged↗
PubMed1993

Functional analysis of a C. elegans trans-splice acceptor.

The rol-6 gene is trans-spliced to the 22 nt leader, SL1, 173 nt downstream of the transcription start. We have analyzed splicing in transformants carrying extrachromosomal arrays of rol-6 with mutations in the trans-splice acceptor site. This site is a close match to the consensus, UUUCAG, that is highly conserved in both trans-splice and intron acceptor sites in C. elegans. When the trans-splice site was inactivated by mutating the perfectly-conserved AG, trans-splicing still occurred, but at a cryptic site 20 nt upstream. We tested the frequency with which splicing switched from the normal site to the cryptic site when the pyrimidines at this site were changed to A's. Since most C. elegans 3' splice sites lack an obvious polypyrimidine tract, we hypothesized that these four pyrimidines might play this role, and indeed mutation of these bases caused splicing to switch to the cryptic site. We also demonstrated that a major reason the downstream site is normally favored is because it occurs at a boundary between A+U rich and non-A+U rich RNA. When the RNA between the two splice sites was made less A+U rich, splicing occurred preferentially at the upstream site.

Amino Acid Sequence↗
PubMed1993

Conversion of a trans-spliced C. elegans gene into a conventional gene by introduction of a splice donor site.

In Caenorhabditis elegans, pre-mRNAs that are trans-spliced are distinguished by the presence of an 'outron', intron-like RNA at the 5' end followed by a splice acceptor. We report that trans-splicing of the rol-6 gene can be completely suppressed simply by introducing a donor site into its 173 nt outron, at a site 50 nt upstream of the trans-splice site, thereby converting rol-6 into a conventional gene with a spliced intron near its 5' end. When the consensus donor site was inserted at sites further upstream it was less effective in replacing transplicing with cis-splicing. Surprisingly, the length of the intron was not the important variable, since lengthening of the 50 nt intron to 250 nt did not restore trans-splicing. Apparently the context into which the splice site was introduced determined the efficiency of its use. These results support the conclusion that the sole signal for trans-splicing is the presence of an outron. Clearly, cis- and trans-splice acceptor sites are interchangeable, allowing the possibility of competition between the two types of splicing.

Animals↗
PubMed1991

Metabolism of nitric oxide in denitrifying Pseudomonas aeruginosa and nitrate-respiring Bacillus cereus.

Suspensions of Pseudomonas aeruginosa and Bacillus cereus were continuously sparged with nitrogen to remove gaseous products of nitrate reduction. Under these conditions, P. aeruginosa denitrified nitrate to 4% NO, 47% N2O and 49% N2. B. cereus reduced nitrate to 94% nitrite, 2% NO and 5% N2O. B. cereus was unable to reduce NO or N2O as sole electron acceptor, whereas P. aeruginosa reduced NO stoichiometrically to N2O when the N2O reductase was inhibited by acetylene or when the formed N2O was immediately flushed out of the incubation vessel. The mechanism and the reason for NO production in nitrate-respiring B. cereus are unknown, but the amounts of NO released were in a similar range as in the denitrifying P. aeruginosa and thus may be of similar environmental importance.

Bacillus cereus↗
PubMed1991

Insertion of part of an intron into the 5' untranslated region of a Caenorhabditis elegans gene converts it into a trans-spliced gene.

In nematodes, the RNA products of some genes are trans-spliced to a 22-nucleotide spliced leader (SL), while the RNA products of other genes are not. In Caenorhabditis elegans, there are two SLs, SL1 and SL2, donated by two distinct small nuclear ribonucleoprotein particles in a process functionally quite similar to nuclear intron removal. We demonstrate here that it is possible to convert a non-trans-spliced gene into a trans-spliced gene by placement of an intron missing only the 5' splice site into the 5' untranslated region. Stable transgenic strains were isolated expressing a gene in which 69 nucleotides of a vit-5 intron, including the 3' splice site, were inserted into the 5' untranslated region of a vit-2/vit-6 fusion gene. The RNA product of this gene was examined by primer extension and PCR amplification. Although the vit-2/vit-6 transgene product is not normally trans-spliced, the majority of transcripts from this altered gene were trans-spliced to SL1. We termed the region of a trans-spliced mRNA precursor between the 5' end and the first 3' splice site an "outron." Our results suggest that if a transcript begins with intronlike sequence followed by a 3' splice site, this alone may constitute an outron and be sufficient to demarcate a transcript as a trans-splice acceptor. These findings leave open the possibility that specific sequences are required to increase the efficiency of trans-splicing.

Animals↗
PubMed1991

elt-1, an embryonically expressed Caenorhabditis elegans gene homologous to the GATA transcription factor family.

The short, asymmetrical DNA sequence to which the vertebrate GATA family of transcription factors binds is present in some Caenorhabditis elegans gene regulatory regions: it is required for activation of the vitellogenin genes and is also found just 5' of the TATA boxes of tra-2 and the msp genes. In vertebrates GATA-1 is specific to erythroid lineages, whereas GATA-2 and GATA-3 are present in multiple tissues. In an effort to identify the trans-acting factors that may recognize this sequence element in C. elegans, we used a degenerate oligonucleotide to clone a C. elegans homolog to this gene. We call this gene elt-1 (erythrocytelike transcription factor). It is single copy and specifies a 1.75-kb mRNA that is present predominantly, if not exclusively, in embryos. The region of elt-1 encoding two zinc fingers is remarkably similar to the DNA-binding domain of the vertebrate GATA-binding proteins. However, outside of the DNA-binding domains the amino acid sequences are quite divergent. Nevertheless, introns are located at identical or nearly identical positions in elt-1 and the mouse GATA-1 gene. In addition, elt-1 mRNA is trans-spliced to the 22-base untranslated leader, SL1. The DNA upstream of the elt-1 TATA box contains eight copies of the GATA recognition sequence within the first 300 bp, suggesting that elt-1 may be autogenously regulated. Our results suggest that the specialized role of GATA-1 in erythroid gene expression was derived after separation of the nematodes and the line that led to the vertebrates, since C. elegans lacks an erythroid lineage.

Amino Acid Sequence↗
PubMed1988

Trial of anonymous versus confidential human immunodeficiency virus testing.

Before December, 1986, all public human immunodeficiency virus (HIV) testing in Oregon was done confidentially (using names). In December, clients were offered the option of either anonymous or confidential services. As judged by questionnaire responses, the availability of anonymity increased overall demand for testing by 50%: 125% for homosexual/bisexual (gay) men, 56% for female prostitutes, 17% for intravenous drug users, and 32% for other clients. The number of gay clients who had tests increased from a mean of 42 per month during the 4 months before anonymity was available to 108 per month during the 4 months after, whereas, at public sites in Colorado or California and private sites in Oregon, the number of gay clients tested did not increase. Twice as many seropositive persons were identified during the 3 1/2 months after anonymity became available (n = 85) as in the 3 1/2 months before (n = 36). Thus, availability of anonymous HIV testing and counselling drew gay men who had not sought services under a confidential testing system.

California↗
PubMed1988

Influence of pH on microbial hydrogen metabolism in diverse sedimentary ecosystems.

Hydrogen transformation kinetic parameters were measured in sediments from anaerobic systems covering a wide range of environmental pH values to assess the influence of pH on hydrogen metabolism. The concentrations of dissolved hydrogen were measured and hydrogen transformation kinetics of the sediments were monitored in the laboratory by monitoring hydrogen consumption progress curves. The hydrogen turnover rate constants (kt) decreased directly as a function of decreasing sediment pH, and the maximum hydrogen uptake velocities (Vmax) varied as a function of pH within each of the trophic states. Conversely, the half-saturation concentrations (Km) were independent of pH. The steady-state hydrogen concentrations were at least 2 orders of magnitude lower than the half-saturation constants for hydrogen uptake. Dissolved hydrogen concentrations were at least fivefold higher in sediments from eutrophic systems than from oligotrophic and dystrophic systems. The rates of hydrogen production determined from the assumption of steady state decreased with sediment pH. These data indicate that progressively lower pH values inhibit microbial hydrogen-producing and -consuming processes within sedimentary ecosystems.

Bacteria, Anaerobic↗
PubMed1988

Prevalence of hepatitis B markers among pregnant Hispanic women in migrant/seasonal work in Oregon.

We screened 303 Hispanic pregnant women who were migrant or seasonal agricultural workers in Oregon for the presence of Hepatitis B serological markers. One carrier was identified (0.3 per cent, 95% confidence interval [CI] .02%, 2.1%). Evidence of previous HB infection was present in 5.3 per cent (16/303) of the women (95% CI 3.2%, 8.6%), rates similar to those for the general US population.

Adolescent↗