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R Barra

Publications and source records attributed to R Barra.

At least 19 recordsLinked to original sources
PubMed2005

Comparison of haloacetic acids in the environment of the Northern and Southern Hemispheres.

Haloacetic acids (HAAs) are a family of compounds whose environmental concentrations have been extensively studied, primarily in Europe. Depending on the compound, their sources are believed to be both natural and anthropogenic. To better understand possible sources and contribute to the knowledge of the global distribution of these compounds, especially between the Northern and Southern Hemispheres, samples of precipitation, soils, and conifer needles were collected from Canada, Malawi, Chile, and the U.K. Precipitation samples exhibited highest HAA concentrations in collections from Canada, and lowest in those from Malawi. Malawi samples contained measurable levels of monobromoacetic acid (MBA) (56 ng/ L) unlike those from most other locations (< 9 ng/L). Soil HAA concentration levels were highest in the U.K. (e.g., 7.3 ng/g average TCA) and lowest in Malawi (0.8 ng/g average TCA), with Chile having higher levels (4.8 ng/g average TCA) than Canada (3 ng/g average TCA). Malawi soils contained small amounts of MBA (2 ng/g), in common with the two most southern of the 11 Chilean sites. Analysis of soil cores (10-cm depth sliced at 1 cm) from sites in Malawi and Chile showed that trichloroacetic acid (TCA) generally declined with depth while mono- and dichloroacetic acid (MCA and DCA) showed no trend. MCA, DCA, and TCA concentrations in archived U.K. soil samples increased by factors of 2, 4, and 5-fold over 75 years while TFA showed no consistent trend. Monochloroacetic acid (MCA) was detected in pine needles collected from Malawi. U.K. needle samples had the highest concentrations of all chloroacetic acids (CAAs): MCA, 2-18 ng/g; dichloroacetic acid (DCA), 2-38 ng/g; and trichloroacetic acid (TCA), 28-190 ng/g. Conifer needles from Canada and Chile contained CAAs at levels ranging from < 2 to 16 ng/g wet wt. Trifluoroacetic acid concentrations generally declined with increasing elevation in the samples from the Rocky Mountains in western Canada. The results indicate that concentrations of HAAs are greatest in the industrialized Northern Hemisphere but there are significant amounts of these compounds in the less industrialized Southern Hemisphere.

Acetates↗
PubMed2005

Use of Daphnia spp. for the ecotoxicological assessment of water quality in an agricultural watershed in South-Central Chile.

Because of the importance of surface waters from the Chillán River watershed (Chile) for recreation, agricultural irrigation, and the production of drinking water, local concern about river water quality has increased considerably during the last decade. Agricultural and forestry activities in the watershed, characterized by an intensive use of pesticides, are thought to play an important role in the generation of non-point-source pollution, whereas the discharge of urban wastewater from the city of Chillán constitutes a major point source of pollution. In the present investigation, acute and chronic laboratory bioassays using Daphnia spp. were conducted on surface water samples from 17 river stations located throughout the watershed. Sampling occurred on 6 occasions during a 16-month period (2000 to 2001) and included both high and low flow conditions. Almost all toxic effects observed in summer were directly related to the discharge of urban wastewater, whereas toxicity in rural areas was mainly detected during the winter period when rainfall and river flow are high. Toxicity test results were compared with measured physicochemical water-quality data. Mortality and alterations in reproductive success of Daphnia spp. were not consistently reflected in detected chemical pollution. With only one exception (atrazine), detected pesticide concentrations were below known toxicity levels. However, additive and synergistic effects of the presence of a mixture of pesticides could not be excluded as a possible cause of observed toxicity. At several stations, filtering of the water sample led to a strong decrease in toxicity, which suggests the presence of xenobiotics attached to the smaller sediment fraction. Inclusion of sediment chemical analysis and sediment toxicity testing in future work should therefore be encouraged. The presented approach provided information about the adverse effects of human activities on surface water quality in the watershed, not easily obtained from classical monitoring schemes. In specific cases, the approach may represent an economically attractive alternative to physicochemical analyses. Modifications to the proposed methodology should be introduced if the effects of intrastorm and interstorm variability of water quality are to be analyzed.

Agriculture↗
PubMed2005

Genetic and phenotypic heterogeneity in pattern dystrophy.

BACKGROUND: The pattern dystrophies (PD) represent a clinically heterogeneous family of inherited macular diseases frequently caused by mutations in the peripherin/RDS gene. Most previous studies have detailed the clinical findings in single families, making it difficult to derive data from which progression and visual outcome can be generalised. METHODS: Families were ascertained and clinically evaluated including angiography and electrophysiology where appropriate. RESULTS: In each of the six families with autosomal dominant PD, a mutation in the peripherin/RDS gene was identified, including a novel Cys250Phe variant. These data suggest that the condition is characterised by the accumulation of yellow to grey subretinal flecks, followed by pigmentary change accompanied by patches of chorioretinal atrophy. Subsequently, 50% (16/32) of individuals with PD developed poor central vision because of chorioretinal geographic atrophy or subretinal neovascularisation. The risk of these complications appears to increase with age. CONCLUSION: PD should not necessarily be considered a benign condition. Instead, patients should be counselled that there is a significant chance of losing central vision in their later years. Some elderly patients with probands showing PD may be misdiagnosed with age related macular degeneration owing to the phenotypic similarities between these conditions in the advanced state.

Adult↗
PubMed2001

Porphyrin levels in excreta of sea birds of the Chilean coasts as nondestructive biomarker of exposure to environmental pollutants.

In this preliminary study on sea birds we propose the use of porphyrins in excreta as a biomarker of exposure to contaminants. Samples of excreta were obtained from colonies of brown pelicans (Pelecanus occidentalis thagus), neotropic cormorants (Phalacrocorax olivaceus), and kelp gulls (Larus dominicanus) in three areas of the south coast of Chile with different human impact (Tubul, Talcahuano, and Valdivia). They were analyzed for porphyrin content (copro-, uro-, and protoporphyrins and total porphyrins) by a rapid fluorimetric method and by HPLC. The main outcomes of the study were: (a) kelp gulls and neotropic cormorants living in areas with high human impact showed a clear capacity to accumulate and eliminate porphyrins in the excreta; (b) species-related accumulation capacities are likely, as shown by the different levels found in different species living in the same area; (c) the porphyrin profile obtained by fluorimetry and HPLC showed a higher percentage of protoporphyrin than the other porphyrins; (d) although the fluorimetric method of Grandchamp is semiquantitative, it was found to be sensitive enough to detect differences in samples from field studies. The positive results of this preliminary study make it possible to propose this nondestructive method for a variety of field applications.

Animals↗
PubMed2001

Bioavailability of PAHs in the Biobio river (Chile): MFO activity and biliary fluorescence in juvenile Oncorhynchus mykiss.

Cytochrome P450-dependent monooxygenase (MFO) activity and levels of bile PAH metabolites were measured in fish (Oncorhynchus mykiss) exposed to Biobio river (Chile) water. Experiments were performed simultaneously in both the field and laboratory to investigate whether the river water contained notable bioavailable PAH fractions. The field experiment was conducted using fish caged for 41 days at La Mochita (Biobio river mouth) whereas the laboratory experiment involved a 21-day exposure treatment with water collected in the same area. Induction of hepatic MFO, assayed by benzo(a)pyrene monooxygenase activity (BaPMO), and levels of PAH metabolites in the bile were measured in groups of eight (field experiment) and four specimens (laboratory experiment) sampled after 5, 10, 21 and 41 days of exposure. BaPMO was induced by a factor of 23 and 25 in fish caged for 21 and 41 days, respectively. Likewise, a significant BaPMO induction was found in the fish group experimentally exposed to river water for 21 days. Biliary fluorescence measurements, recorded by fixed wavelength fluorescence (FF) and synchronous fluorescence spectroscopy (SFS), revealed significantly high levels of PAH metabolites in bile samples of fish caged for 21 and 41 days. A positive relationship was found between BaPMO activity and biliary PAH metabolites. This study provides evidences that (i) Biobio river water contains a significant bioavailable PAH fraction in terms of marked effects on fish and (ii) the biological indicators MFO activity and bile PAH metabolites represent an excellent screening methodology to assess PAH exposure.

Animals↗
PubMed2001

First report on chlorinated pesticide deposition in a sediment core from a small lake in central Chile.

This paper presents a first report on chlorinated pesticide deposition analyzed through sedimentary records in a small mesotrophic lake (Chica de San Pedro) in central Chile. The sediment core was sliced and dated using 210Pb, 137Cs and pollen analyses. Organochlorine pesticides were analyzed by gas chromatography with electron capture detection (GC-ECD). From these results, pesticide deposition over the last 50 years was estimated. No pesticides were detected below the 1940 slice of the core. Concentrations were in the range 0.640-1.4 ng/g d.w. for total DDTs, 0.046-0.362 ng/g d.w. for lindane and 0.015-0.310 ng/g d.w. for alpha-hexachlorohexane. Highest concentrations of pp'DDT were found in 1993-1996 and higher concentrations of pp'-DDE and pp'-DDD were found in the seventies (1972-1978). Total organic carbon (TOC) normalized data were used for statistical analysis. Although significant correlation was observed between concentrations of DDE and DDD, no correlation was found for DDT, suggesting that it had a different source. Factorial analysis grouped DDE together with DDD, while DDT was grouped together with gamma- and alpha-HCH. Total DDT fluxes were highest during the 1970s, while those for HCHs have been increasing in the 1990s. In Chile, organochlorine compounds were banned in 1985, and the historical deposition patterns seem to indicate that such measures have been effective. On the other hand, results point out a relatively new occurrence of pp'-DDT in the watershed, but the source remains unknown.

Chile↗
PubMed1988

A DNA-modification methylase from Bacillus stearothermophilus V.

A type II modification methylase (M BstVI) was partially purified from the thermophilic bacterium Bacillus stearothermophilus V. The methylase catalyses the transfer of methyl groups from S-adenosyl-L-methionine to unmodified double-stranded DNA. The product of methylation was identified by paper chromatography as N6-methyladenine. Since M BstVI protects DNA against cleavage by BstVI and XhoI restriction endonucleases, it follows that it methylates the adenine residue in the sequence 5'-C-T-C-G-A-G-3'.

DNA↗
PubMed1988

Resistance of Thermus spp. to Potassium Tellurite.

Two members of the genus Thermus were examined for their resistance to toxic inorganic compounds. They both proved to be fairly resistant to tellurite and selenite and to many other heavy metal salts. Cell extracts of Thermus thermophilus HB8 and of T. flavus AT-62 catalyze the reduction of K(2)TeO(3) in a reaction which is dependent on NADH oxidation.

Journal Article↗
PubMed1988

Purification and biochemical characterization of tellurite-reducing activities from Thermus thermophilus HB8.

Cell-free extracts of Thermus thermophilus HB8 catalyze the in vitro, NADH-dependent reduction of potassium tellurite (K2TeO3). Three different protein fractions with tellurite-reducing activities were identified. Two exhibited high molecular weight and were composed of at least two different polypeptides. The protein in the third fraction was purified to homogeneity and had a single polypeptide chain of 53 to 54 kilodaltons, with an isoelectric point of 8.1. Each enzyme was thermostable, the temperature optimum was 75 degrees C, and 30 mM NaCl, 1.5 M urea, or 0.004% sodium dodecyl sulfate caused 50% inhibition of the enzymes. However, 2% Triton X-100 did not have an inhibitory effect. The enzymes were also able to catalyze the reduction of sodium selenite and sodium sulfite in vitro. NADH was replaceable by NADPH. Divalent cations, such as Ca2+ and Ba2+, had no effect on the activity, while similar concentrations of Zn2+, Ni2+, and Cu2+ abolished the activity. This reductase activity could enable these bacteria both to reduce K2TeO3 and to increase their tolerance toward this salt.

Chromatography, DEAE-Cellulose↗
PubMed1987

Effects of glycyl-histidyl-lysine on Morris hepatoma 7777 cells.

Glycyl-histidyl-lysine (GHL) has been shown to have growth stimulatory effects on a number of different cell types including hepatocytes and hepatoma cells. In this study, the effects of GHL on Morris hepatoma 7777 cells were investigated. The greatest stimulatory effects on 3H-thymidine and 3H-leucine incorporation were observed at a GHL concentration of 2 ng/ml. In randomly proliferating cells, the incorporation of 3H-thymidine into DNA increased by 50% and that of 3H-leucine into protein by 29%. In addition, synergistic effects were observed when insulin and glucagon were included with GHL in the incubation mixture. Experiments with cells rendered quiescent by serum starvation indicated that cells in the G1 phase of the cell cycle are more sensitive to GHL stimulation. In these experiments, 3H-thymidine incorporation increased earlier and peaked at a higher value than in the control cells. This finding suggests that GHL may play a role in stimulating quiescent cells to re-enter the cell cycle.

Animals↗
PubMed1984

Effects of nicotinamide and structural analogs on DNA synthesis and cellular replication of rat hepatoma cells.

The effects of nicotinamide and structural analogs on DNA synthesis were studied in rat hepatoma (HTC) cells. Inhibitory effects of these compounds were observed on DNA synthesis as judged by the incorporation of [3H]-thymidine into DNA. Evidence for a marked effect on DNA integrity after preincubation with 1 mM methyl methanesulfonate was provided by a fluorometric technique with ethidium bromide. There was only a small or insignificant enhancement of this effect when hepatoma cells were incubated with nicotinamide. At concentrations of 2-20 mM, 3-aminobenzamide was observed to cause greater effects than nicotinamide on DNA synthesis and integrity and on cellular proliferation in HTC cells. Comparison of the effects of nicotinamide and 3-aminobenzamide with those of N'-methylnicotinamide suggested that some of the effects on DNA synthesis may not be mediated through inhibition of poly(ADP-ribose) synthetase. Inhibition of HTC cell proliferation was observed at a concentration of 3-aminobenzamide, 2 mM, which has been reported to be nontoxic for other cell types.

Animals↗
PubMed1982

Effects of nicotinamide, isonicotinamide, and bleomycin on DNA synthesis and repair in rat hepatocytes and hepatoma cells.

Because inhibitors of poly (ADP-ribose) synthetase have been found to influence DNA synthesis in some systems, the possibility that nicotinamide or isonicotinamide might potentiate the effect of bleomycin on DNA replication and repair was examined. After a 30-minute incubation with bleomycin (200 micrograms/ml), tritiated thymidine ([3H]dThd) incorporation into DNA was stimulated during a subsequent 30-minute incubation with hepatocytes of inbred BUF rats but was decreased in HTC cells of BUF rats. When unscheduled DNA synthesis was measured in the presence of 10 mM hydroxyurea, bleomycin (200 micrograms/ml) increased [3H]dThd incorporation in both cell types. A dose of 20 mM nicotinamide and isonicotinamide caused an approximately 50% inhibition of total [3H]dThd incorporation in HTC cells. Significant inhibitory effects of 20 mM nicotinamide and isonicotinamide on unscheduled DNA synthesis were observed after preincubation of hepatocytes and HTC cells with bleomycin. When the effects of bleomycin on DNA structure were assessed fluorometrically with ethidium bromide after mild alkaline incubation, nicotinamide and isonicotinamide did not significantly affect the damage revealed with bleomycin alone. When HTC cells were incubated for 48 hours with bleomycin (20 micrograms/ml), the increase in cell numbers was about 50% of that in control cultures. Nicotinamide and isonicotinamide also inhibited the proliferation of HTC cells, but the effects were not additive with the effect of bleomycin.

Animals↗