Search PubMed⌕ Search

Biomedical subjects

R A Silva

Publications and source records attributed to R A Silva.

At least 55 records · Page 3Linked to original sources
PubMed1995

Outbreak of trypanosomosis due to Trypanosoma evansi in horses of Pantanal Mato-grossense, Brazil.

This paper reports an outbreak of trypanosomosis due to Trypanosoma evansi in horses of the Pantanal Mato-grossense region of Brazil. Forty-eight horses died (51% mortality) and abortion in one mare was recorded. The clinical signs observed were fever, anemia, conjunctivitis, edema of the legs and lower parts of the body, progressive weakness, loss of condition, and loss of appetite. The diagnosis was confirmed by morphological and biometrical studies.

Animals↗
PubMed1995

Effects of dietary n-3, n-6 and n-9 polyunsaturated fatty acids on benzo(a)pyrene-induced forestomach tumorigenesis in C57BL6J mice.

The modulating effect of dietary polyunsaturated fatty acids (PUFAs) on benzo(a)pyrene-induced forestomach tumorigenesis was assayed in mice fed with corn oil (CO), olein (O), Zizyphus mistol seed oil (MO), cod liver oil (CLO), and mixed fat (Stock diet). The fatty acid composition of liver lipids correlated well with the fatty acid composition of each diet. Only mice fed the O diet showed biochemical and clinical evidences of essential fatty acid deficiency (EFAD). Only 3 animals developed well-differentiated invading squamous cell carcinomas in the O group. The papilloma incidence was reduced in MO and CLO with respect to the O group. Forestomach papillomatosis was increased in mice fed an n-9 enriched diet in comparison to stock and CO groups. In comparison with stock mice, the frequency of multiple epidermoidal hyperplasia (MEH) was significantly decreased in the CLO group. Animals fed n-3 enriched diets (MO and CLO) showed significant antipromoting effect. These findings indicate that dietary fat can modulate tumorigenesis initiated in mouse forestomach by benzo(a)pyrene. In addition, the lack of action of an n-6 fatty acid-enriched diet in our experimental model suggests that the effect of PUFAs on tumorigenesis has target-tissue specificity. Mistol seed oil might be of potential value as a natural vegetable antipromoter nutrient.

Animals↗
PubMed1995

Protective capability of dietary Zizyphus mistol seed oil, rich in 18:3, n-3, on the development of two murine mammary gland adenocarcinomas with high or low metastatic potential.

The modulating effect of dietary Zizyphus mistol seed oil, rich in the n-3 polyunsaturated fatty acid alpha-linolenic acid, on two murine mammary gland adenocarcinomas having low (M2) and high (MM3) metastatic abilities was investigated. Following tumor subcutaneous inoculation, 165 BALB/c mice were fed on a semisynthetic diet containing 5% of mistol oil which has 25% of 18:3, n-3 (mistol group). The other group received a stock diet (C group). Tumor growth parameters such as success of tumor implants (ST), latency time (LT), tumor growth (TG), tumor volume (TV), survival, and number and sites of metastases were recorded. Fatty acid profiles of liver lipids correlated well with dietary fatty acids, with a n-3/n-6 ratio of 0.90:1 in the mistol group against 0.24:1 in the C group. None of the tumor growth parameters were worse in the mistol group with respect to the controls. On the contrary, survival in M2 hosts and tumor weight in MM3-bearing mice were significantly ameliorated. A tendency towards a diminution of total number of metastases in both types of tumor was observed in the mistol group. From these results, it is suggested that Z. mistol seed oil may be of potential value in nutritional oncology.

Adenocarcinoma↗
PubMed1995

In vivo evidence for a non-T cell origin of interleukin-5.

Eosinophil myelopoiesis is to a great extent regulated by interleukin (IL)-5. Analysis of IL-5 mRNA in spleen cell preparations by reverse transcription-polymerase chain reaction (RT-PCR) revealed the presence of message for this cytokine in uninfected severe combined immunodeficiency (SCID) mice. This message was increased following Mycobacterium avium infection. Normal BALB/c mice had higher levels of expression of IL-5 but the expression of this cytokine was reduced during M. avium infection. Anti-IL-5 monoclonal antibody administration in vivo to SCID mice reduced the number of peritoneal and splenic eosinophils. Gamma interferon (IFN-gamma) had an inhibitory effect of eosinophilopoiesis during infection of SCID mice by M. avium since neutralization of this cytokine increased the number of eosinophils detected in the peritoneal cavity of infected animals. Our results suggest that IL-5 may be produced by cells other than T cells that are both able to respond to infection and are under the control of IFN-gamma.

Animals↗
PubMed1994

Role of gamma interferon and tumor necrosis factor alpha during T-cell-independent and -dependent phases of Mycobacterium avium infection.

To design an effective immunotherapy for Mycobacterium avium infections, the protective host response to the infection must be known. Here we analyzed the role of gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) in the innate and acquired responses to M. avium infections in mice. T-cell depletion studies showed that CD4+ T cells were required for control of the infection. CD(4+)-depleted mice showed enhanced bacterial proliferation and at the same time showed a reduction in the level of expression of both IFN-gamma and TNF-alpha mRNAs in spleen cells. In contrast, M. bovis BCG immunization restricted M. avium proliferation and at the same time promoted expression of the mRNAs for the two cytokines. In vivo depletion studies using specific monoclonal antibodies showed that both IFN-gamma and TNF-alpha are involved in an early protection possibly involving NK cells, and furthermore, IFN-gamma is involved in the later T-cell-protective response to infection. In vivo neutralization of IFN-gamma during M. avium infection also blocked the priming for enhanced TNF-alpha secretion triggered by endotoxin. Both cytokines were found to be involved in the resistance expressed in BCG-immunized animals and exhibited additive bacteriostatic effects in vitro on bone marrow-derived macrophages infected with different strains of M. avium. These data suggest that both cytokines act in an additive or synergistic fashion in the induction of bacteriostasis and that IFN-gamma is also involved in priming TNF-alpha secretion.

Animals↗
PubMed1990

Electrochemistry of galvanic couples between carbon and common metallic biomaterials in the presence of crevices.

In vitro experiments were conducted upon some common metallic biomaterials and carbons, both isolated or forming galvanic couples, in a cell specially designed for crevice corrosion studies. The alloys examined were AISI 316L stainless steel, Ti6AI4V and Co-Cr-Mo. The types of carbon were glassy carbon and carbon fibre-reinforced carbon. The surface modifications were evaluated by SEM, AES and ESCA-XPS analyses. AISI 316L stainless steel suffered localized corrosion in open-circuit experiments whilst the other materials remained unattacked. Galvanic currents between metal-carbon couples were measured by zero resistance ammetry. The carbon-metal area ratio was 1:1. The results showed that 316L stainless steel and the Co-Cr-Mo alloy were prone to accelerated corrosion, whilst the Ti6AI4V alloy remained unattacked. The galvanic corrosion currents were also predicted using mixed potential theory from polarization curves obtained for each material. The experimental and theoretical values showed good agreement for the stainless steel and Co-Cr-Mo alloy. Long-term immersion tests with the same couples showed that the only metal not to suffer degradation was the Ti6AI4V alloy.

Alloys↗
PubMedDate not supplied

Circulation of eastern equine encephalitis, western equine encephalitis, Ilhéus, Maguari and Tacaiuma viruses in equines of the Brazilian Pantanal, South America.

Neutralizing antibodies to EEE (6.7%), WEE (1.2%), ILH (26.6%), MAG (28.2%) and TCM (15.7%) viruses were found in sera of 432 equines of the Brazilian Pantanal, area where undiagnosed horse deaths are frequently observed. A 4-fold rise in CF titer to EEE virus was detected in acute and convalescent sera of an encephalitis horse sacrificed in 1992. Antibodies to EEE, ILH, MAG and TCM viruses were detected in horses less than 2 years old indicating recent circulation of these viruses in the Pantanal. The evidence of recent equine encephalitis associated with rising CF titer to EEE warrants a more intensive study with attempts to isolate virus from horses with clinical manifestations of encephalitis.

Animals↗
PubMedDate not supplied

[Chagas' disease in São Paulo State: a comparative study between systematic search and inhabitants' report of bugs in the area under entomological surveillance].

Entomological surveillance of Chagas' disease in São Paulo State has adopted a scheme that uses the locality as a unit for field work. Actions are prioritized according to infestation levels obtained by systematic search of triatomine (routine actions), bugs in areas with high infestation levels and in houses whose inhabitants report the presence of the bugs (reply to notification). The most prevalent triatominic species in Sao Paulo State at present are Triatoma sordida and Panstrongylus megistus. A comparative study of infestation levels obtained in houses and surroundings in routine search and replies to notification in the two-year periods of 90/91, 92/93 and 94/95, has shown average percentage positivity of 1.3 indoors in routine activity and 6.2 in the reply to notification. For the house surroundings the values were 8.6 and 18.2 respectively, no differences being found between the two-year periods. Replies to notification showed average percentage positivity (focus) in 26% of the houses. It was verified that the notifications had come from localities with prior infestation levels equal to zero (I = O), intermediary infestation levels (I < 5) and high infestation levels (I > 5), although the percentages of positive replies to notification were higher in those localities with high prior infestation levels. These results reinforce the importance of notification in the surveillance of vector species of the invasive type like those currently prevalent in Sao Paulo State.

Animals↗
PubMedDate not supplied

The seroprevalence of equine trypanosomosis in the pantanal.

Since little information is available on the epizootiological status of Trypanosoma evansi in South America and particularly Brazil, we evaluated equine serum samples collected in 1993, 1994, 1995 and 1997 for the presence of antibodies against this trypanosome species. Our study shows corroborative evidence about the correlation among high T. evansi seroprevalence and the rainy season in the Pantanal, Brazil. The higher seroprevalence was 79.2% in horses from a ranch located in the Nhecolândia sub-region in 1994 and the lower 5.8% in animals from the same ranch in 1997. No seroprevalence was found in 1993. The possible re-introduction of T. evansi in the region as well as the relationship among our results with the outbreaks reported in 1994, are briefly discussed.

Animals↗
PubMedDate not supplied

Estimated financial impact of Trypanosoma vivax on the Brazilian pantanal and Bolivian lowlands.

The financial impact of the first outbreak of Trypanosoma vivax in the Brazilian Pantanal wetland is estimated. Results are extended to include outbreaks in the Bolivian lowlands providing a notion of the potential influence of the disease and an analytical basis. More than 11 million head of cattle, valued at more than US$3 billion are found in the Brazilian Pantanal and Bolivian lowlands. The total estimated cost of the 1995 outbreak of T. vivax is the sum of the present values of mortality, abortion, and productivity losses and treatment costs, or about 4% of total brood cow value on affected ranches. Had the outbreak gone untreated, the estimated losses would have exceeded 17% of total brood cow value.

Animals↗
PubMedDate not supplied

[Risk factors for hospitalization of children aged 1 to 4 years in Sao Luis, Maranhao, Brazil].

Risk factors for pediatric hospitalization were studied using a cross-sectional multi-stage cluster sample survey. A standardized questionnaire was answered by children's mothers or other care providers. In the municipality of São Luís, Maranhão, Brazil, 596 children aged 1 to 4 years were sampled in 50 census tracts. Design effect was calculated for each estimate. Hospitalization rate was 24. 4%. Main causes of hospitalization were pneumonia (7.3%) and diarrhea (7.1%). The Unified National Health System (SUS) and private insurance accounted for 78.1% and 18.2% of hospital admissions, respectively. After adjustment for confounding by Cox proportional hazards model modified for cross-sectional design, children whose families earned less than one minimum monthly wage and those with private insurance were at higher risk of hospitalization. Hospitalization due to outpatient-sensitive diseases accounted for most cases. The U-shaped hospitalization pattern suggests low quality of outpatient services among the poor and may be a proxy indicator for unnecessary and iatrogenic hospitalization among privately insured children.

Brazil↗
PubMedDate not supplied

[Severe acute pancreatitis, laparotomies, and planned reoperation].

Of 111 cases of acute pancreatitis studied, 13 (11.7%) patients had severe pancreatitis with infection and were submitted to planned reoperation or to open peritoneal drainage. Twelve patients were male, ages ranging from 20 to 56. The etiology was biliary in 4 patients, traumatic in 1 patient, and alcoholic in 8 patients. Early treatment included clinical support at the intensive care unit and surgical intervention was performed after the first week based on clinical signs and on ultrasound and CT scan findings. A total of 42 surgeries was performed (mean of 3.23 operations per patient). Mortality rate was 46% due to systemic complications and to multiple organ failure.

Acute Disease↗