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Biomedical subjects

S S da Silva

Publications and source records attributed to S S da Silva.

17 recordsLinked to original sources
PubMed2007

Repeated-batch xylitol bioproduction using yeast cells entrapped in polyvinyl alcohol-hydrogel.

Xylose-to-xylitol conversion was investigated in a bench-scale bioreactor using Candida guilliermondii cells entrapped within polyvinyl alcohol-hydrogel beads in a system operated in repeated-batch mode with cell recycling. Yeast-viable cells were immobilized in the support using the freezing-thawing method. Bioconversion assays were performed in a stirred tank reactor operated at 400-rpm agitation speed, 30 degrees C temperature, and 1.04-vvm air flow rate. The system was explored during six successive cycles, and a small decrease in the conversion performance in the fifth cycle was observed, but the biocatalytic activity of the microorganism was recovered in the sixth cycle after washing the particles. During the process, the hydrogel beads maintained their shape and size without appreciable deterioration. Xylitol production, yield factor, and volumetric productivity increased with progressive recycling of cells and achieved their maximum values (P(F) = 39.7 g l(-1); Y(P/S) = 0.77 g g(-1); Q(P) = 0.53 g l(-1) h(-1), respectively) after the third cell recycling, probably because of cells' adaptation to the medium.

Biotechnology↗
PubMed2001

Detection of Babesia equi (Laveran, 1901) by nested polymerase chain reaction.

We describe a nested polymerase chain reaction (PCR) for the detection of Babesia equi in equine infected erythrocytes using oligonucleotides designed on the published sequence of a B. equi merozoite antigen gene (ema-1). A 102bp DNA fragment is specifically amplified from B. equi but not from Babesia caballi, Babesia bovis or Babesia bigemina DNA. In a mock infection we were able to detect down to six infected cells in 10(8) equine erythrocytes or to detect the parasite in blood with an equivalent parasitemia of 0.000006%. Furthermore, gene polymorphism was found by performing a PCR-RFLP (PCR combined with restriction fragment length polymorphism) on both the 102bp and the entire ema-1 gene DNA amplified from two B. equi isolates, Florida (USA) and Pelotas (Southern Brazil) isolates. The polymorphism was confirmed by sequencing the entire ema-1 gene from the B. equi isolate Pelotas. Our results demonstrate that the ema-1 based nested PCR is a valuable technique for routine detection of B. equi in chronically infected horses. It may be used for epidemiological and phylogenetic studies of the parasite as well as monitoring B. equi infected horses in chemotherapeutic trials.

Amino Acid Sequence↗
PubMed1999

Partial tricuspid valve transfer for repair of mitral insufficiency due to ruptured chordae tendineae.

BACKGROUND: A new technique is suggested for the reconstructive surgical treatment of mitral regurgitation. It involves partial transfer of the tricuspid valve of the patient to the mitral valve, in order to provide chordae to correct anterior leaflet prolapse of the mitral valve, secondary to rupture of the chordae tendineae. METHODS: From January 1991 to May 1997, 20 patients with mitral insufficiency due to rupture of the chordae were operated on. The prevailing cause was myxomatous degeneration (70%). Patients were in New York Heart Association functional class III and IV. RESULTS: There were no hospital deaths. Two patients were reoperated on. Eighteen patients (90%) are alive with their own valves (class I and II). Doppler echocardiogram mean values were: ejection fraction, 0.65; left atrial diameter, 4.2 cm; mitral area, 2.4 cm2; mitral transvalvular gradient, 3.3 mm Hg. No regurgitation or mild regurgitation was observed in 16 (94.1%) of the 17 cases evaluated. Mean tricuspid valvular area was 3.3 cm2. In all cases, no tricuspid regurgitation was present or it was mild. CONCLUSIONS: Partial transfer of the tricuspid valve to the mitral valve is an effective procedure for the surgical treatment of mitral valve insufficiency secondary to ruptured chordae tendineae of the anterior leaflet.

Adolescent↗
PubMed1999

Detection of genomic variability in different populations of the cattle tick Boophilus microplus in southern Brazil.

DNA from seven isolates of the cattle tick Boophilus microplus was analyzed by restriction fragment length polymorphism (RFLP). Three different cDNA clones, named P-9, P-25 and CP-12, isolated from a B. microplus cDNA library, were used as DNA probes. DNA sequences of P-9 have high similarity to ribosomal genes, whereas P-25 does not show significant homology with known sequences within databases. CP-12 is a cDNA clone encoding a cysteine endopeptidase gene. A limited degree of polymorphism was detected with P-9 and P-25, while CP-12 showed a different pattern of bands for each tick isolate. These findings suggest the existence of a complex genotypic diversity of the tick B. microplus population in endemic regions.

Animals↗
PubMed1995

Cox maze operation without cryoablation for the treatment of chronic atrial fibrillation.

BACKGROUND: From August 1993 to May 1994, 20 patients (mean age, 43 years) with atrial fibrillation underwent the maze operation without cryoablation. Ten patients had mitral stenosis, 5 had mitral insufficiency, and 5 had a mixed mitral lesion. The mean left atrial diameter as measured on echocardiograms was 6.1 cm. The cause was rheumatic in 17 patients (85%) and degenerative in 3 (15%). Seven patients had had previous episodes of thromboembolism. METHODS: Mitral valvuloplasty was performed on 7 patients, mitral commissurotomy on 4, and mitral valve replacement on 9. Thrombi were found in the left atrium of 7 patients and also in the right atrium in 2. The mean cross-clamp time was 73 minutes (range, 52 to 108 minutes). RESULTS: Patients were discharged from the hospital in good condition. Hemodynamic studies and Doppler echocardiograms showed significant reduction in the left atrial diameter (mean diameter, 4.9 cm; p < 0.01) in 18 patients. The two-channel Holter monitor showed sinus rhythm in 15 patients, atrial ectopic rhythm in 4, and atrial fibrillation in 1. Eleven patients (55%) experienced atrial fibrillation (9 in the first 3 months postoperatively), which was reversed with quinidine. Ninety percent of patients had development of an effective, synchronous, atrial systole. Six to 15 months postoperatively (average follow-up, 10 months), all patients were in functional class I, and 18 were not on a regimen of antiarrhythmic medication. CONCLUSIONS: This simplification of the maze operation has been demonstrated to be an effective alternative for the treatment of chronic atrial fibrillation.

Adolescent↗
PubMed1995

Relationships and influences between Boophilus microplus characteristics in tick-naive or repeatedly infested cattle.

Six tick-naive male Hereford calves were infested once a month for 6 months with 18,000 Boophilus microplus larvae on the back and with 400 larvae in a cloth bag glued on the lumbar region. Working with the bag ticks, 12 tick characteristics were recorded for each infestation. Each tick attribute was analyzed for significant differences with those of the first infestation (analysis of variance), and for similarity (clustering), degree of relationship (correlation), and concomitant variation (regression) against all the other attributes during the first, third, and sixth infestations. Some attributes were affected maximally by host immunity about the third infestation but recovered later (length of feeding, detachment weight, egg weight, start of oviposition, fertility efficiency index), whereas others continued to be affected until the last infestation (length of oviposition, corpse weight, start of hatching, feeding efficiency index). All analyses showed that weight at detachment and egg weight were closely related, and corpse weight was partially related to these two. All other natural characteristics were largely independent. Length of feeding showed no significant relation with weight at detachment nor length of oviposition with egg weight. These findings suggest that different tick functions are independently affected by host immunity and recommends against estimating general anti-tick resistance by the evaluation of only a few tick characteristics.

Analysis of Variance↗
PubMed1993

Inhibition and recovery of tick functions in cattle repeatedly infested with Boophilus microplus.

Six tick-naive male Hereford calves were infested with about 18,000 Boophilus microplus larvae, 400 in a cloth bag, once a month for 6 mo. Working with the bag ticks, 12 tick characteristics were recorded for each infestation. Manifestations of resistance to some attributes appeared by the second infestation, peaked by the third (detachment weight, egg weight, fertility index) or fourth (feeding length, start of oviposition), and vanished by the fifth or sixth. Resistance to corpse weight, oviposition length, start of eclosion, feeding index, and survival developed more slowly but continued until the last infestation. Lymphocyte transformation after the fifth infestation was normal for concanavalin A and augmented in only 2 calves for phytohemagglutinin. In each infestation and at the end of all infestations some calves were significantly more resistant to some tick characteristics. There was no relationship between natural resistance and the ability to mount an acquired resistance. We concluded that B. microplus can depress or evade host's immunity, that resistance to different tick functions occurs independently, that natural and acquired resistance are unrelated, and that there exist genetic differences in natural or acquired resistance to the tick among seemingly homogeneous animals.

Analysis of Variance↗
PubMedDate not supplied

Use of immobilized Candida cells on xylitol production from sugarcane bagasse.

In this study we used the yeast Candida guilliermondii FTI 20037 immobilized by entrapment in Ca-alginate beads (2.5-3 mm diameter) for xylitol production from concentrated sugarcane bagasse hemicellulosic hydrolysate in a repeated batch system. The fermentation runs were carried out in 125- and 250-ml Erlenmeyer flasks placed in an orbital shaker at 30 degrees C and 200 rpm during 72 h, keeping constant the proportion between work volume and flask total volume. According to the results, cell viability was substantially high (98%) in all fermentative cycles. The values of parameters xylitol yield and volumetric productivity increased significantly with the reutilization of the immobilized biocatalysts. The highest values of xylitol final concentration (11.05 g/l), yield factor (0.47 g/g) and volumetric productivity (0.22 g/lh) were obtained in 250-ml Erlenmeyer flasks containing 80 ml of medium plus 20 ml of immobilized biocatalysts. The support used in this study (Ca-alginate) presented stability in the experimental conditions used. The results show that the use of immobilized cells is a promising approach for increasing the xylitol production rates.

Candida↗