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Papers by Wilma Barrionuevo

Revista de Cultura e Extensão USP, 2015

Journal of High Resolution Chromatography, 2000

Synthetic pyrethroids are increasingly being used for insect control on field crops because of th... more Synthetic pyrethroids are increasingly being used for insect control on field crops because of their advantageous environmental properties such as short field life, broad spectrum of insecticide activity, and relatively low mammalian toxicity. In the present work, experimental conditions were optimized for trace analysis of pyrethroids in water by using solid-phase microextraction followed by capillary gas chromatography. Effects of temperature, SPME-fiber diameter, and matrix were studied. SPME used off-line with a gas chromatograph electron-capture detection (GC-ECD) showed a linear response over a wide concentration range. Our results showed a strong temperature effect on pyrethroid extraction yield. The detection limit after 5 min of SPME-fiber exposure to the samples changed from 1 ppb (at 30 8C) to 0.1 ppt (at 90 8C), which is a 10000 increase in pyrethroid detection. The standard deviations of the analyte peak area ratios were typically in the range of 1-7% at 30 8C and of 3 to 15% at 90 8C. Best conditions for pyrethroids analysis were achieved using high temperature solution and a 100 lm polydimethylsiloxane fiber. No matrix (river water) influence was observed on detection of the investigated pyrethroids.

The American journal of physiology, 1999

Body mass, length, oxygen consumption (MO2) and heart rate (fH) were measured in "embryos&qu... more Body mass, length, oxygen consumption (MO2) and heart rate (fH) were measured in "embryos" (prior to hatching), "larvae" (days 10-20), "juveniles" (days 30-70 in 10-day intervals), and "adults" (day 100) of the zebrafish Danio rerio. Fish were chronically reared at either 25, 28, or 31 degreesC and then acutely exposed to hypoxia at different developmental stages. We hypothesized that at any given rearing and measurement temperature, D. rerio would maintain MO2 at lower ambient PO2 [i.e., have a lower critical partial pressure (Pcrit)] as development progressed and that at any given developmental stage individuals reared and measured at higher temperatures would show a more pronounced hypoxic bradycardia. MO2 in normoxic fish at 28 degreesC peaked at approximately 40 micromol. g-1. h-1 at day 10, thereafter falling to 4-5 micromol. g-1. h-1 at day 100. The Q10 for MO2 was 4-5 in embryos, falling to 2-3 from day 10 to day 60 and rising again to...

Brazilian Journal of Biology, 2010

In order to verify the influence of chronic and acute ambient oxygen levels from egg to adult sta... more In order to verify the influence of chronic and acute ambient oxygen levels from egg to adult stage of the zebrafish, in vivo oxygen consumption (MO2), critical tensions of oxygen (Pcrit), heart rate (fH) and total body lactate concentration (Lc) were determined for Danio rerio (Hamilton, 1822) raised at 28 °C under normoxic (7.5 mgO2.L-1 or 80 mm.Hg-1) and hypoxic conditions (4.3 mgO2.L-1) and exposed to acute hypoxia during different developmental stages. Our findings confirmed that very early stages do not respond effectively to ambient acute hypoxia. However, after the stage corresponding to the age of 30 days, D. rerio was able to respond to acute hypoxia through effective physiological mechanisms involving aerobic and anaerobic metabolism. Such responses were more efficient for the fishes reared under hypoxia which showed that D. rerio survival capability increased during acclimation to mild hypoxia. Measurements of body mass and length showed that moderate hypoxia did not aff...

Química Nova, 2001

Recebido em 18/10/99; aceito em 11/10/00 SOLID-PHASE EXTRACTION (SPE) AND SOLID-PHASE MICROEXTRAC... more Recebido em 18/10/99; aceito em 11/10/00 SOLID-PHASE EXTRACTION (SPE) AND SOLID-PHASE MICROEXTRACTION OF PYRETHROIDS IN WATER. The pyrethroids bifenthrin, permethrin, cypermethrin and deltamethrin were extracted by solid phase extraction (SPE) and solid phase microextraction (SPME). The analysis were performed on a gas chromatograph with electron capture detection (GC-ECD). Octadecil Silano-C 18 , Florisil and Silica stationary phases were studied for SPE. Better results were obtained for Florisil which gave recoveries from 80% to 108%. Pyrethroids extraction by SPME showed a linear response and a detection limit of 10 pg ml-1. Although the data showed that the two extraction methods were able to isolate the pesticide residues from water samples, the best results were obtained by using SPME which is more sensitive, faster, cheeper, being a more useful technique for the analysis of pyrethroids in drinking water.

Journal of Fish Biology, 1995

... responses of Oreoclzromis niloticus (Pisces, Cichlidae) to environmental hypoxia under differ... more ... responses of Oreoclzromis niloticus (Pisces, Cichlidae) to environmental hypoxia under differentthermal condition. Journal of Fish Biology 35, 509-519. Fritsche, R. & Nilsson, S. (1993). Cardiovascular and ventilatory control during hypoxia. In Ecophysiology (Rankin, JC & ...

Journal of Applied Ichthyology, 1998

The time-course for the thermal acclimation of aerobic metabolism was determined for juvenile and... more The time-course for the thermal acclimation of aerobic metabolism was determined for juvenile and adult P. scrqfa by following the modifications in oxygen consumption ('O?). Fish previously acclimated at 15 and 25°C and transferred to water temperature 10°C and above, showed 3-4-fold increase in '02 in the first 6 h after the change in temperature, reaching a stable '02 level in 24 and 48 h (adult and juvenile fish, respectively). Fish acclimated a t 35 and 25°C and transferred to water temperature 10°C below that to which they were previously acclimated decreased the '02 in the first 6 h after the change in water temperature (3.0-fold lower, from 35 to 25°C for both fish sizes and 6.5-and 3.0-fold lower from 25 to 15°C for juvenile and adult fish, respectively), reaching a stable '0, level in 48 h (from 25 to 15°C) and 24-72h (from 35 to 25°C). Regardless of the direction of water temperature change, P. scrofa showed partial '02 compensation and short time-course for the adjustments in aerobic metabolism, reaching a stable rate at the new water temperature in 1-3 days. These results indicate an ecological advantage for this species, mainly for the adult fish, which migrate along rivers prior to reproduction and which may experience fluctuations in water temperature, including the heated effluents from electrical power stations.

Bulletin of Environmental Contamination and Toxicology, 2002

MATERIALS AND METHODS The pyrethoids bifenthrin, permethrin, Cypermethrin and deltamethrin were p... more MATERIALS AND METHODS The pyrethoids bifenthrin, permethrin, Cypermethrin and deltamethrin were purchased from Supelco, Inc. Stock solutions were prepared by adding of 10 mg of each compound into 10 mL ethanol. A 1 mL aliquot of these stock solution was ...

Aquaculture Research, 1995

ABSTRACT Critical thermal maxima (CTMax) and minima (CTMin) were determined for Prochilodus scrof... more ABSTRACT Critical thermal maxima (CTMax) and minima (CTMin) were determined for Prochilodus scrofa Steindachner of two sizes (19.5 ±7.2 g and 249 ± 42.4 g). acclimated at 15. 20, 25, 30 and 35 ± 1°C. The CTMax and the CTMin for the smaller fish were 33.9. 36.7. 38.7, 40.3. 42.0°C and 5.0, 7.2. 9.2. 10.3. 13.4oC and for the larger (Ish 33.3, 35.7, 38.2. 40.6. 42.6°C and 6.5, 8.2. 10.8. 12.4, 14.6°C. respectively, at each acclimation temperature. The CTMin from smaller fish were significantly lower than those from larger ones but the CTMax did not show any such difference. These results indicate that P. scrofa is suitable for culture in south-eastern and even in southern Brazil where winter temperatures may drop to very low levels, mainly at night. The zone of thermal tolerance calculated by CTMax and CTMin was equivalent to 1046°C2 and 964.2°C2, respectively, for smaller and larger fish, showing a high degree of eurythermicity.

Microscopy Research and Technique, Jun 1, 2008

The analysis of histological sections has long been a valuable tool in the pathological studies. ... more The analysis of histological sections has long been a valuable tool in the pathological studies. The interpretation of tissue conditions, however, relies directly on visual evaluation of tissue slides, which may be difficult to interpret because of poor contrast or poor color differentiation. The Chromatic Contrast Visualization System (CCV) combines an optical microscope with electronically controlled light-emitting diodes (LEDs) in order to generate adjustable intensities of RGB channels for sample illumination. While most image enhancement techniques rely on software post-processing of an image acquired under standard illumination conditions, CCV produces real-time variations in the color composition of the light source itself. The possibility of covering the entire RGB chromatic range, combined with the optical properties of the different tissues, allows for a substantial enhancement in image details. Traditional image acquisition methods do not exploit these visual enhancements which results in poorer visual distinction among tissue structures. Photodynamic therapy (PDT) procedures are of increasing interest in the treatment of several forms of cancer. This study uses histological slides of rat liver samples that were induced to necrosis after being exposed to PDT. Results show that visualization of tissue structures could be improved by changing colors and intensities of the microscope light source. PDT-necrosed tissue samples are better differentiated when illuminated with different color wavelengths, leading to an improved differentiation of cells in the necrosis area. Due to the potential benefits it can bring to interpretation and diagnosis, further research in this field could make CCV an attractive technique for medical applications.