Biomedical subjects

M L Silveira

Publications and source records attributed to M L Silveira.

4 recordsLinked to original sources

PubMed2006

Heavy metal sequential extraction methods--a modification for tropical soils.

Sequential extractions of metals can be useful to study metal distributions in various soil fractions. Although several sequential extraction procedures have been suggested in the literature, most were developed for temperate soils and may not be suitable for tropical soils with high contents of Mn and Fe oxides. The objective of this study was to develop a sequential fractionation procedure for Cu and Zn in tropical soils. Extractions were performed on surface (0-20 cm) samples of ten representative soils of Sao Paulo State, Brazil. Chemically reactive Mn forms were satisfactorily assessed by the new modified procedure. Amorphous and crystalline Fe oxides were more selectively extracted in a new two-step extraction. Soil-born Zn and Cu were primarily associated with recalcitrant soil fractions. The proposed procedure provided more detailed information on metal distribution in tropical soils and better characterization of the various components of the soil matrix. The new procedure is expected to be an important tool for predicting the potential effects of environmental changes and land application of metals on the redistribution of chemical forms of metals in tropical soils.

Copper↗

PubMed2006

Phosphorus release from a manure-impacted spodosol: effects of a water treatment residual.

Long-term depositions of animal manures affect P dynamics in soils and can pose environmental risks associated with P losses. Laboratory studies were done on P solubility characteristics in a manure-impacted Immokalee soil (sandy, siliceous, hyperthermic Arenic Alaquod) and the effectiveness of water treatment residual (WTR) in controlling P leaching. Soil samples with contrasting initial total P concentrations were prepared by mixing samples of a manure-impacted surface A horizon and a minimally P-impacted E horizon. Effects of mixing various ratios of A and E horizons, WTR rates (0, 25, 50, and 100 g kg(-1)), and depths of WTR incorporation (mixed throughout the soil column or partially incorporated) on P leaching were determined. Between 62 and 77% of total P was released from the soil mixes by successive water extractions, suggesting a considerable buffering capacity of this manure-impacted soil to resupply P into solution. Between 224 and 408 mg kg(-1) P were leached during the 36-wk leaching period in the absence of WTR. Mixing WTRs with soil reduced soluble P concentration in leachates by as much as 99.8% compared with samples without WTR. Thoroughly mixing WTR with the entire soil column (15 cm) was much more efficient than mixing WTR with only the top 7.5 cm of soil. Calcium- and Mg-P forms appear to control P release in soils without WTR, whereas sorption-desorption reactions probably determine P leaching in WTR-treated samples. Soil P distribution in various chemical forms was affected by WTR additions. Data suggest that WTR-immobilized P is stable in the long term.

Aluminum↗

PubMed1994

Urethral lengthening with anterior bladder wall flap for urinary incontinence: a new approach.

Urethral irregularity (impeding catheterization) and failure to achieve continence are common complications in surgery for urinary incontinence. We describe a surgical technique using an anterior bladder wall flap that is sutured to the posterior wall in an onlay fashion creating a flap valve mechanism. Experimental work in dogs demonstrated a significant increase in the leak point pressure in the surgical group when compared to controls (p = 0.019). Voiding cystourethrography and bladder inspection demonstrated an anterior flap valve with no fistula formation in all animals. Histological examination showed a viable anterior bladder wall flap in all cases. This technique was then applied to 6 patients with neurogenic bladder and low urethral resistance that failed to resolve with medical treatment. Urinary continence was achieved in 4 patients. In 1 patient a vesicourethral fistula developed 3 months postoperatively, since the mother failed to catheterize for 12 hours. This technique is a useful alternative in the treatment of urinary incontinence.

Adolescent↗

PubMedDate not supplied

Study of the effects of treatment with theophylline on the cognitive process and behaviour of children with bronchial asthma.

The effects of theophylline (T) on cognitive and emotional aspects were evaluated in nine children with mild bronchial asthma (7-14 years). The study was double blind crossover against placebo (P) for a period of 30 days for each. The children admitted to the study had an average IQ (80-101) and were able to perform pulmonary function studies (PFS). On days 0, 30 and 60 patients were evaluated by psychological tests (Wisc, Bender, Complex Figure A. Rey and Miss Goodenough/Machouver). PPS an T serum levels were performed on days 15 and 45. During the T period all patients had T serum levels greater than 5 mcg/ml (5 to 22). The final evaluation showed no changes in the psychological tests. Behaviour alterations were not reported by the parents. In conclusion, in this group of patients there was no influence of T on the asthmatic children's behavior. These results are in agreement with the recent data published by Schlieper et al. (J. Pediatr. 118: 449-455, 1991).

Asthma↗