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Biomedical subjects

L C de Souza

Publications and source records attributed to L C de Souza.

At least 19 recordsLinked to original sources
PubMed2004

Thermal characteristics of recombinant green fluorescent protein (GFPuv) extracted from Escherichia coli.

AIMS: The thermal stability of isolated and extracted recombinant green fluorescent protein (GFPuv) was evaluated by analysing the loss of fluorescence intensity. METHODS AND RESULTS: GFPuv was expressed by Escherichia coli, extracted by the three-phase partitioning method and purified by elution through an hydrophobic interaction column. The collected fractions were further diluted in Tris-HCl-EDTA (pH 8.0) and subjected to continuous heating at set temperatures (45-95 degrees C). From a standard curve relating fluorescence intensity to GFPuv concentration, the loss of fluorescence intensity was converted to denatured GFPuv concentration (microg ml-1). To determine the extent of the thermal stability of GFPuv, decimal reduction times (D-values), z-value and energy of activation (Ea) were calculated. CONCLUSIONS: For temperatures between 45 and 70 degrees C, extracted native GFPuv activity decreased from 11 to 75% relative to initial native protein concentration above 70 degrees C, the average decrease in GFPuv fluorescence was between 72 to 83%. SIGNIFICANCE AND IMPACT OF THE STUDY: The thermal stability of GFPuv provides the basis for its potential utility as a fluorescent biological indicator to assess the efficacy of the treatment of liquids and materials exposed to steam.

Cloning, Molecular↗
PubMed2001

Determination of dithiocarbamate fungicide residues in food by a spectrophotometric method using a vertical disulfide reaction system.

Dithiocarbamates are a class of fungicides extensively used in many crops worldwide. The current residue definition of dithiocarbamates in food for compliance with maximum residue limits, at national and international levels, is total residues arising from the use of any or each dithiocarbamate fungicide, determined as CS(2). The analytical method most frequently used to analyze dithiocarbamate residues in food for monitoring purposes was proposed more than 30 years ago. In this method, total dithiocarbamates are decomposed to CS(2), which is purified and reacted with a cupric reagent. The yellow complex formed is quantified by spectrophotometry. In this paper, a new reaction system for the purification and complexation of CS(2) is proposed. The new system is less fragile than the traditional design, is easier to assemble, and allows for a higher sample throughput, in addition to being of low cost. Recovery of added mancozeb, thiram, or ziram (0.15-8.0 mg/kg) in rice, beans, apple, banana, orange, papaya, tomato, cucumber, and potato ranged from 82 to 120%, with relative standard deviations from 0 to 10% (n = 3 or 5). Analysis of apple, tomato, and papaya samples with field-incurred dithiocarbamate residues showed comparable results using both the traditional and the new reaction systems.

Disulfides↗
PubMed2000

Evaluation of pH and calcium ion release of three root canal sealers.

The pH and calcium ion release of three root canal sealers--Sealapex, Sealer 26, and Apexit--were assessed at 24 and 48 hr, and at 7 and 30 days after spatulation. After manipulation, the sealers were placed in 1-cm-long tubes measuring 4 mm in diameter and immersed in a glass flask containing 10 ml of deionized water, which was hermetically sealed and stored at 37 degrees C. The tubes were removed at the scheduled times and the water in which they were immersed was tested for pH with a pHmeter and for released calcium by atomic absorption spectrophotometry. Starting 48 hr after immersion, Selapex produced an alklaine pH and released significantly higher calcium amounts compared with the other two sealers, with even more pronounced results after 30 days. On the basis of the results obtained, we conclude that Sealapex presented the highest calcium and hydroxyl release, especially after longer time intervals, whereas Sealer 26 showed highest release during the initial periods (i.e. during its setting time). Apexit presented the least satisfactory results.

Analysis of Variance↗
PubMed2000

[Assessment of the chronic risk for ingestion of pesticide residues in the Brazilian diet].

OBJECTIVE: To conduct a chronic dietary risk assessment of the pesticides registered in Brazil up until 1999. METHODS: The Theoretical Maximum Daily Intake (TMDI) for each pesticide was calculated using the Brazilian maximum residue limits and food consumption data from IBGE, the Brazilian Statistical Institute. The risk characterization was done comparing the TMDI with the acceptable daily intakes (ADI) from other countries and from the Codex Alimentarius. RESULTS: The TMDI was higher than the ADI (%ADI>100) at least in one Brazilian metropolitan region for 23 pesticides. Sixteen compounds are organophosphate insecticides, with methyl parathion having the TMDI exceeding the most toxicological parameter (%ADI N=9,300). Rice, beans, citrus and tomato were the commodities which most contributed to the ingestion. From the compounds under higher risk, only 6 were registered according to the Law 98.816/90, which concerns the use of pesticides in the country. CONCLUSIONS: The compounds identified in the study as presenting a potential health concern to the Brazilian consumers, and the commodities which most contributed to the ingestion, should be prioritized by the government in pesticide residue monitoring programs and in the re-registration process. In addition, residue data in food as consumed, processing factors and appropriate consumption data should be generated to allow further studies.

Brazil↗
PubMed1999

Incidence of leptospiral abortion in Brazilian dairy cattle.

We examined dams' paired serum samples and foetal kidneys (histopathologically and attempting leptospiral cultures) from 120 Brazilian Holstein abortions from 10 herds near Sao Paulo, Brazil, in 1996. Leptospiras was isolated from 15 foetuses. The Leptospira interrogans serovar hardjo was obtained from four, pomona from three and wolffi from eight foetuses. Ten of these 15 foetuses showed a four-fold rise in titres between the day of abortion and the second samples taken 15 days later. Fifty-seven other foetuses had histologic evidence of leptospires; 27 of their dams (47%) had four-fold rises in titres. In total, 72 of 120 aborted foetuses had evidence of leptospiral infection.

Abortion, Veterinary↗
PubMed1992

[Salmonellas and fecal coliforms in drinking water for animals].

Sixty small farms of Botucatu County, S. Paulo, Brazil, given over to cattle breeding were studied. These farms account for 15% of the total of 402 farms that exist in the county. The sample was drawn by simple probabilistic technique. There were found to be one hundred and thirteen drinking places located on the farms. Samples of water were taken from these drinking places and examined for bacteria of the genus Salmonella, for the determination of Most Probable Number (MNP) of fecal coliform bacteria as well as determination of the water's pH. Water temperature was measured before collection. Samples from 15 drinking places (13.3%) were positive for Salmonella. The drinking places belonged to 12 of the sixty farms studied (20%). The following serotypes were identified: S. dublin, S. newport, S. madelia, S. IV 43:g,z57:-, S. saphra, S. glostrup, S. IV ochsenzool; S. I9,12:i:- and two new serotypes S. IV 41:z52:- and S. IV 50:d:-. Of the 113 samples studied 14 (12.4%) presented MPN/100ml of fecal coliforms above 4,000. There was no relationship between MPN/100ml of fecal coliforms above 4,000 and positivity for Salmonella. Highest positivity both for Salmonella and MPN/100mL of fecal coliforms over 4,000 occurred at temperatures above 18 degrees C. As regards pH, in both situations the highest positivity occurred between 6.0 and 7.0.

Animal Husbandry↗
PubMed1992

[Technical modification of total cavo-pulmonary connection].

A variation of total cavopulmonary connection without anastomosing the superior vena cava to the right pulmonary artery branch is presented. Both vena cava flow go through an intra atrial tunnel to the right atrial appendage, which is anastomosed to the right pulmonary artery, in anatomical eligible cases.

Arteriovenous Shunt, Surgical↗
PubMed1992

[Surgical management of the aortic valve in patients older than 70 years of age].

PURPOSE: To assess the short and long-term benefits of patients who were submitted to isolated aortic valve replacement or valve replacement (VR) concomitant myocardial revascularization (MR); to evaluate the incidence of postoperative complications, hospital mortality and late mortality. METHODS: From January 1985, through December 1989, 20 consecutive patients underwent surgical intervention, 15 male (75%) and 5 female (25%), the mean age was 74.8% (ranging from 70 to 86 years old), and the aortic valve gradient ranged between 78 and 180 mmHg (mean = 97 mmHg). They presented preoperative diagnosis to have either isolated aortic stenosis (AS) or As and coronary artery disease (CAD). No patient was in NYHA functional class I; 3 patients (15%) were in class II, 14 (70%) in class III and 3 (15%) in class IV. RESULTS: The most frequent post-operative complications found were: extended intubation in 7 patients (35%), bleeding in 4 (20%), acute renal failure in 3 (15%) and ventricular arrhythmia in 3 (15%). Hospital mortality occurred in 2 patients (10%) who had been submitted to VR and concomitant MR. Late mortality occurred in 1 patient (5%). Through December 1989, 11 patients (64%) were in functional class I (NYHA), 3 (18%) in class II, 3 (18%) in class III and none in class IV. CONCLUSION: We concluded that the surgical treatment is indicate to elderly patients with isolated AS os with AS and concomitant CAD. There was a significant post-operative improvement of the functional class (NYHA) to the surviving patients.

Aged↗
PubMed1989

[Pulmonary hypertension: a serious complication in the postoperative period of tetralogy of Fallot].

Among 1,142 patients who underwent total correction of tetralogy of Fallot from May of 1960 to december of 1986, five (0.43%) presented refractory cardiac failure. Pre and postoperative control was based on symptoms and clinical signals, electrocardiogram, conventional radiographies, cardiac catheterism, cineangiocardiography, and necropsy in one case. The evolution in immediate and late postoperative periods were not good. One patient deceased in the first day after surgery: the others had complications as severe pulmonary insufficiency, diffuse and severe hypocontractibility of the right ventricle, with three late decreases. Only one patient is alive, with congestive cardiac failure hardly controllable.

Anastomosis, Surgical↗
PubMed1988

[Comparative study of various staining methods for mycobacteria].

The present paper intends to show what coloration method for mycobacteria is the better. Samples was assessed and processed by hot Ziehl-Neelsen, cold Ziehl-Neelsen, Ziehl Gabbet and Ziehl-Neelsen with alkaline metilene blue. After microscopy by five different persons the method selected were the cold Ziehl-Neelsen.

Bacteriological Techniques↗