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C Cabrera

Publications and source records attributed to C Cabrera.

16 recordsLinked to original sources
PubMed1995

Speciation of methylmercury and Hg(II) using baker's yeast biomass (Saccharomyces cerevisiae). Determination by continuous flow mercury cold vapor generation atomic absorption spectrometry.

Baker's yeast cells (Saccharomyces cerevisiae) were successfully used to selectively separate methylmercury and Hg(II). Several parameters affecting the degree of biosorption and the binding kinetics of methylmercury and Hg(II) were evaluated: solution pH, temperature, incubation time, amount of biomass and analyte, and presence of foreign ions. Methylmercury is immediately bound to the yeast cells over a wide pH and temperature range. The fraction of methylmercury bound was in all cases 100% and was unaffected by the parameters mentioned above. Hg(II) has less affinity for yeast cells and remains in solution, although the percentage of Hg(II) bound to the cell does increase at high incubation time (3 h) and biomass. Of the foreign ions tested, chloride at high concentrations strongly increases the Hg(II) binding efficiency. Methylmercury and Hg(II) are quantitatively separated under optimum conditions, i.e., 30 min incubation time at pH 7.0 and 37 degrees C. The results were compared with those obtained using a purified S. cerevisiae isolate, and no significant differences were observed. Our work suggests that the cell rapidly reduces CH3Hg+ to more volatile species, such as Hg(I) or Hg0, whereas Hg2+ is slowly bound and reduced, perhaps because of the different toxicities of the two species. The method was applied to the selective determination of CH3Hg+ and Hg(II) in spiked water samples. In all cases good recoveries were obtained.

Cations↗
PubMed1995

The role of nitric oxide in the central control of blood pressure.

In these studies blood pressure responses to intracerebroventricular (i.c.v.) infusions were recorded in anesthetized rats. NO donors caused a fall in blood pressure, whereas L-NAME, which blocks the enzyme (NOS) that produces NO, caused a rise in blood pressure. Calcium, i.c.v., stimulates NOS to lower blood pressure. The depressor action of NO is reduced by blocking the action of cGMP. This central NO/cGMP system is tonically active to maintain blood pressure at a normal level.

Amino Acid Oxidoreductases↗
PubMed1994

Radionuclide ventriculography in dynamic cardiomyoplasty.

Dynamic cardiomyoplasty improves ventricular function by increasing pump function and by limiting cardiac dilatation. The aim of this study was to assess long-term myocardial performance by radionuclide ventriculography on dilated cardiomyopathy patients subjected to cardiomyoplasty. Thirteen survivors were included. Radionuclide ventriculography was performed one week before surgery and one year later. Five patients were also studied two years following surgery. The left ventricular ejection fraction (LVEF), end-diastolic volume (EDV) and ventricular amplitude ratio (VAR) to assess mitral regurgitation were measured. Every case after one year showed a non-significant increase in LVEF. However, the decrease in EDV and in VAR was significant (p < 0.01). No significant difference in these values was found after two years. We conclude that the effects of cardiomyoplasty--reduction of cardiac dilatation, wall stress and mitral regurgitation--are more evident during the first year after surgery. Thereafter, a certain stabilization is observed.

Adult↗
PubMed1983

Segmental ejection fraction in normal subjects.

Following a modification of the area method described by Gelberg et al., left ventricular regional wall motion was studied in 30 normal subject. The left ventricular cineangiograms were filmed in the right anterior oblique projection at 48 frames/s after injection of 76% sodium-meglumine diatrizoate. The end-diastolic and end-systolic frames were each divided into 8 regions using a grid formed by longitudinal axis, which was traced from the midpoint of the aortic valve to the apex, and three equally spaced perpendiculars to the long axis. Segmental ejection fraction was estimated by determining the percent decrease in each segment area in end-systole with respect to the end-diastolic area. The mean values +/- S. D. obtained for each segment were: anterobasal 58 +/- 14%; anterolateral-proximal 59 +/- 6%; anterolateral-distal 58 +/- 4%; apical-superior 59 +/- 8%; apical-inferior 58 +/- 7%; diaphragmatic-distal 58 +/- 9%; diaphragmatic-proximal 55 +/- 6%; and posterobasal 42 +/- 15%. The values obtained are useful for comparison when evaluating left ventricular performance in patients.

Cardiac Output↗
PubMed1980

Improved endotracheal intubation technique in the rat.

A safe method for endotracheal intubation was successfully employed in rats weighing 300-400 g. A catheter from a commercial intravenous cannulation assembly was introduced into the trachea under direct visualization. A surgical operating microscope supplied magnification and light to facilitate the procedure.

Anesthesia, General↗
PubMed1975

Genesis of arrhythmias and mechanism of electrical defibrillation of the heart.

Atrial arrhythmias were induced in experiments on dogs by electrical stimulation or by local application of aconitine and methacholine to the atrium. The action of the defibrillator discharge on these arrhythmias was studied. The defibrillator discharge abolished the arrhythmias maintained by the circus movement of the excitation wave over the atria but did not abolish sinus tachycardia or ectopic aconitine tachysystoles. The threshold of the defibrillating effect depends on the existence of micro-or macro-reentries. Thmechanism of defibrillation consists of excitation of the atrial myocardium with a consequent decrease in the pathway for the circulation of excitation to below the critical size for maintaining the circus movement of the excitation wave. The axtion of the defibrillator does not inihibit the automatism of the nomotopic and heterotopic cardiac pacemakers.

Aconitum↗
PubMedDate not supplied

[Prevalence of Trypanosoma cruzi infection in Nicaraguan students. Isle of Youth Special Municipality. February, 1987].

A seroepidemiologic study on American trypanosomiasis was performed to a group of Nicaraguan students in Isle of the Youth Special Municipality, during February 1987, using indirect hemagglutination and indirect immunoflorescence techniques. The prevalence obtained with both tests and the percentage of the most frequent titer of indirect immunofluorescence are pointed out. The youth living in rural zones presented higher risk of acquiring the infection than those living in urban zones. The students coming from the Atlantic Coast, Rio San Juan and Masaya, presented the highest positive rates. Of those who were interviewed, 59% identified the Triatoma, and 13% of them manifested to have seen it inside homes. The background of being bitten by the Tritoma was present in 16.2% of those with positive results.

Adolescent↗
PubMedDate not supplied

Electrothermal atomic absorption spectrometric determination of cadmium, copper, iron, lead, and selenium in fruit slurry: analytical application to nutritional and toxicological quality control.

A method is described for direct determination of cadmium, copper, iron, lead, and selenium in slurried fruit samples by electrothermal atomic absorption spectrometry. The fresh samples were suspended in Triton X-100 and shaken with 10 g zirconia spheres until a slurry was formed. The graphite furnace conditions were optimized for each element. The detection limits were 0.3, 3.5, 15.0, 0.5, and 10.0 ng/g for Cd, Cu, Fe, Pb, and Se, respectively. Accuracy and precision were checked against sample mineralization in a microwave acid-digestion bomb. Results for analyses of National Institute of Standards and Technology standard reference materials agreed closely with certified values. Analytical application of this method was tested with 40 samples of 8 widely consumed fruit species. The mean values (referred to fresh weight of edible fraction) for each fruit species had ranges of 0.0003-0.050 microgram/g for Cd, 0.316-1.094 micrograms/g for Cu, 2.00-5.50 micrograms/g for Fe, 0.050-0.396 microgram/g for Pb, and 0.010-0.020 microgram/g for Se. The proposed method is useful for routine multielemental analysis in nutritional and toxicological quality control of fruits and similar foodstuffs.

Cadmium↗
PubMedDate not supplied

Determination of levels of lead contamination in food and feed crops.

A rapid, precise procedure is described for the determination of lead in food and feed products with electrothermal atomic absorption spectrophotometry. Samples were mineralized in a microwave acid digestion bomb in the presence of nitric acid and vanadium pentoxide. Lead concentrations were determined directly from digested samples. The detection limit was 0.04 ng/mL. Accuracy and precision were checked against National Institute of Standards and Technology standard reference material. The analytical method was tested with 51 food and feed crops from Mediterranean zones in Spain and found to be suitable for these products. Lead concentrations in samples ranged from not detectable to 2.695 micrograms/g (fresh weight).

Animal Feed↗