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Biomedical subjects

M E Silva

Publications and source records attributed to M E Silva.

At least 37 records · Page 2Linked to original sources
PubMed1993

Vitamin D overload and experimental Trypanosoma cruzi infection: parasitological and histopathological aspects.

1. Six groups of 45-day-old, 23.0 +/- 1.7 g, female Balb/c mice were inoculated intraperitoneally with 63, 252, 440, 630, 2520 or 6300 I.U. of vitamin D for 6 days. A seventh group was inoculated with saline. Each group consisted of 30 animals. 2. All animals inoculated with the doses of 2520 and 6300 and 70% of mice which received 630 I.U. of vitamin D died 21 days after the first administration of the vitamin. The LD50 was 630 I.U. 3. The survivors were divided into two groups inoculated intraperitoneally with 5000 trypomastigotes of either Y or CL strain of Trypanosoma cruzi. 4. Based on the survival index on day 73 after infection, Vitamin D gave statistically significant protection (P < 0.01) for mice inoculated with doses of 63 or 430 I.U. of Y or CL strains, respectively. 5. On histopathological examination, inflammatory reaction and cellular and tissue parasitism were less intense in animals which received higher doses of vitamin D. 6. It is concluded that an overload of vitamin D had a protective effect against CL and Y strains of Trypanosoma cruzi infection in Balb/c mice.

Animals↗
PubMed1993

The effect of iron nutritional status on Trypanosoma cruzi infection in germfree and conventional mice.

1. Conventional (CV) and gnotobiotic (GN) female CFW mice were infected with the Y strain of Trypanosoma cruzi. 2. After infection, both CV and GN groups received injections of iron-dextran or desferrioxamine. Non-injected mice served as controls. 3. The parasitemia was more intense in iron-dextran-treated mice. 4. The iron levels in serum, liver, and spleen were: (a) not decreased by desferrioxamine and (b) increased by iron-dextran treatments. 5. An increase in leukocyte numbers was observed in all GN and CV groups after infection. 6. There was no difference in total iron binding capacity (TIBC) and iron saturation transferrin (IST) between GN and CV mice before infection. 7. In CV groups, after infection, TIBC was decreased whereas the levels of IST were increased; in GN the opposite occurred. 8. Trypanosome-specific IgG and IgM antibody levels were raised in the GN group but not in the CV group.

Animals↗
PubMed1993

Metabolic derangements in excessive insulin and sulfonylurea therapy.

Mild streptozotocin diabetic rats, characterized by normal or slightly elevated fasting blood glucose levels and glucose intolerance, treated with excessive doses of monocomponent pork insulin (0.5 U/day) (I) or glybenclamide (0.6 mg/day) (S) were compared to controls (C) and streptozotocin-diabetic rats without treatment (D). Intravenous glucose tolerance tests (0.75 g/kg) were performed in all animals and repeated after overtreatment. Insulin binding and insulin-induced D-(U-14C)-glucose transport and oxidation were also determined in isolated epididymal adipocytes. Diabetic rats showed a failure in the initial phase of insulin release and glucose intolerance as compared with (C). In overtreated rats glucose tolerance worsened (p < 0.05) after therapy. Maximal insulin binding by isolated adipocytes at tracer insulin concentration was unchanged after excessive insulin or sulfonylurea therapy. Besides, glucose transport and oxidation in the cells of overtreated rats were greater than in D and even greater than in C. These apparently divergent results, i.e. deterioration of glucose tolerance with increased insulin action in adipocytes suggest that overtreatment induces a state of resistance to hormone action in other target tissue(s) than the adipose one, possibly muscle.

Adipocytes↗
PubMed1993

Diagnostic fiberoptic bronchoscopy in patients with community-acquired pneumonia. Comparison between bronchoalveolar lavage and telescoping plugged catheter cultures.

We compared the diagnostic value of quantitative cultures of bronchoalveolar lavage (BAL) and telescoping plugged catheter (TPC) samples in 40 patients with moderately severe community-acquired pneumonia (CAP). None had received antibiotics previously. BAL quantitative cultures were performed in 13 control patients without pneumonia. In 28 (70 percent) patients, TPC cultures yielded > or = 10(3) cfu/ml of a pathogenic bacterium in pure culture. In 27 of these cases and in four additional cases, BAL cultures yielded > or = 10(3) cfu/ml. BAL cultures from the control group were sterile in seven cases, yielded normal flora in three cases, and yielded microorganisms thought to be not significant in two cases. Microbiologic agreement was reached by both TPC and BAL for 32 (84 percent) of 38 microorganisms recovered. Quantitative cultures from both techniques correlated very well (r = 0.71, p < 0.0001). We conclude that both TPC and BAL have similar accuracy to determine etiologic diagnosis of CAP. There was good qualitative and quantitative agreement between both techniques.

Adolescent↗
PubMed1993

Ultrasonographic abnormalities of the pancreas in IDDM and NIDDM patients.

OBJECTIVE: To evaluate the relationship between the type and duration of diabetes and pancreas size by ultrasonography. RESEARCH DESIGN AND METHODS: Pancreas images of 40 IDDM and 36 NIDDM patients with 0.3-34 yr of disease were compared with those of 60 normal healthy control subjects. RESULTS: The diameters +/- SD of the head, body, and tail of the pancreas in IDDM patients (1.9 +/- 0.3; 0.9 +/- 0.2; and 1.4 +/- 0.2 cm, respectively) were smaller than in NIDDM patients (2.7 +/- 0.4; 1.2 +/- 0.3; and 1.8 +/- 0.4 cm, respectively) and control group subjects (2.4 +/- 0.4; 1.1 +/- 0.3; and 1.8 +/- 0.4 cm, respectively). The pancreatic shrinkage in IDDM patients was clearly evident after 10 yr of the disease. NIDDM patients and control subjects had similar pancreatic dimensions, except for a greater body thickness in NIDDM patients with > 10 yr of disease (1.2 +/- 0.4 vs. 1.1 +/- 0.3 cm). These results were not related to differences in age, sex, and body size. Pancreas image was hypoechogenic in 72.5% of IDDM patients and hyperechogenic in 83.3% of NIDDM patients. CONCLUSIONS: Smaller pancreases in IDDM patients in comparison with NIDDM patients and control subjects were clearly demonstrated only after 10 yr of disease. Patients with NIDDM were not affected by pancreatic dimensions, except for a greater body thickness after 10 yr of disease. Pancreatic echogenicity increased with age.

Adult↗
PubMed1992

Effect of dietary chitin on cholesterol absorption and metabolism in rats.

The effect of chitin at the level of 5% in the diet on cholesterol absorption and metabolism was studied in Wistar rats fed on diet containing beef tallow (7%) and cholesterol (1%). When compared with pair-fed controls, rats fed on diet containing chitin had: (1) similar weight gain and feed efficiency, (2) lower apparent protein digestibility, (3) equivalent liver steatosis, (4) reduced levels of liver triglycerides and cholesterol, (5) similar levels of serum and fecal cholesterol, (6) higher excretion of triglycerides in feces.

Absorption↗
PubMed1992

Intragastric infection of conventional and germfree mice with Giardia lamblia.

The effects of experimental infection with Giardia lamblia were studied in 30-day old conventional and germfree CFW mice (7 animals in each group) of both sexes. Cysts were observed in the feces of both groups 6 to 7 days after intragastric infection of each animal with about 2.5 x 10(5) G. lamblia trophozoites. Fecal cyst level was statistically higher in germfree mice (about 10(5) cysts/g feces) when compared with the conventional group (about 10(4) cysts/g feces). The peak of infection in the conventional group apparently occurred on the 10th day after infection as indicated by an increase of fecal weight and by histopathological examination. Intense infiltration of the lamina propria and high reactional hyperplasia of the lymphoid component were observed in the conventional group. There was no infiltration or hyperplasia in germfree infected mice and fecal weight was relatively constant throughout the experiment. These results suggest that, as is the case for other intestinal pathogenic protozoa, the intestinal microflora is indispensable for the expression of the pathogenicity but not for the multiplication of G. lamblia.

Animals↗
PubMed1992

The acute phase of experimental infection with Trypanosoma cruzi is more severe in mice monoassociated with strict anaerobic bacteria.

1. The influence of some components of the normal human intestinal flora on the acute phase of experimental infection with strain CL of Trypanosoma cruzi was studied in 30-day-old germ-free or gnotobiotic CFW (LOB) mice monoassociated with Bacteroides fragilis, Peptostreptococcus sp or Clostridium sp by intragastric inoculation of 10(6) bacteria 10 days before the intraperitoneal infection with 5 x 10(3) trypomastigotes/g body weight. 2. Significantly earlier parasitemia peak and mortality were observed in Bacteroides fragilis- and Clostridium-associated mice (16.75 +/- 0.96 and 15.00 +/- 1.15 days, respectively) when compared with germfree animals (18.83 +/- 1.17 days). More precocious mortality (10.40 +/- 2.06 days) and, curiously, much lower blood parasitemia were observed in Peptostreptococcus-associated mice than in other gnotobiotic mice. 3. The extent of cardiac tissue parasitism decreased in the following order: germfree, B. fragilis-associated, Clostridium-associated, and Peptostreptococcus-associated animals. The levels of inflammatory reaction decreased in the following order: germfree, Peptostreptococcus-associated, Clostridium-associated, and B. fragilis-associated mice. 4. These results show that the acute phase of experimental infection with T. cruzi was more severe in mice associated with strict anaerobic bacteria when compared with germfree animals. This suggests that a normal intestinal flora may be another factor, in addition to nutritional and genetic factors, responsible for the different susceptibility of organisms of the same species infected with T. cruzi.

Acute Disease↗
PubMed1992

Effects of testosterone on growth hormone secretion and somatomedin-C generation in prepubertal growth hormone deficient male patients.

1. The role of testosterone (T) in growth was evaluated in 11 prepubertal hypopituitary males during two 15-day periods separated by a 4-week interval, i.e., before (PRE-T period) and during T ester treatment (50 mg every 5 days, 3 im doses-T period). 2. T increased growth hormone (GH) secretion, assessed by 4-h rhythm (mean +/- SEM = 1.90 +/- 0.27 vs 1.77 +/- 0.21 ng/ml; P < 0.05) and after a GHRH stimulus (3.42 +/- 0.54 vs 3.08 +/- 0.43 ng/ml; P < 0.05) as compared to the PRE-T period. 3. T also increased basal somatomedin-C (SM-C) levels (0.20 +/- 0.03 vs 0.15 +/- 0.02 U/ml; P < 0.001) and SM-C generation. After GH was administered in 4 im doses (0.01, 0.02, 0.05 and 0.1 U/kg), SM-C levels were 0.31 +/- 0.08 vs 0.24 +/- 0.07 U/ml, P < 0.001. T did not change incremental (absolute minus basal) SM-C levels (0.15 +/- 0.08 vs 0.12 +/- 0.07 U/ml; P > 0.05). 4. The results suggest that T increased plasma SM-C levels by stimulating residual GH secretion in hypopituitary males.

Adolescent↗
PubMed1992

Effect of an essential fatty acid deficient diet on experimental infection with Trypanosoma cruzi in germfree and conventional mice.

1. To investigate the possible role of essential fatty acid deficiency in host cell/parasite interaction, weanling germfree (GF) and conventional (CV) CFW mice maintained on an essential fatty acid-deficient (-) or a control (+) diet for 110 days were infected with Trypanosoma cruzi. 2. Blood parasitemia indicated that the disease was milder in the animals maintained on the essential fatty acid-deficient diet than in the GF and CV controls (maximum parasitemia: GF+ 33,300, GF-26,200, CV+ 17,100 and CV- 6,400 trypomastigotes/ml blood). 3. Survival 30 days after infection was 12% for GF+, 28% for GF-, 37% for CV+ and 65% for CV- mice. 4. Linoleic and arachidonic acid levels were significantly lower in animals kept on the essential fatty acid-deficient diet (GF-: 28.0 +/- 9.3, 23.4 +/- 8.6; CV-: 37.6 +/- 5.8, 19.9 +/- 3.6) than in controls (GF+: 164.4 +/- 48.8, 162.6 +/- 45.8; CV+: 147.1 +/- 26.5, 107.5 +/- 23.6) confirming the deficiency. 5. Before the infection, succinic dehydrogenase levels were higher in liver of all CV mice (4.52 micrograms phosphate/mg fresh tissue) than in GF mice (0.84 micrograms phosphate/mg fresh tissue), whereas the opposite was true for 5'-nucleotidase levels in brain and liver, respectively (GF: 2.84 and 3.18 micrograms phosphate/mg fresh tissue; CV: 1.25 and 1.54 micrograms phosphate/mg fresh tissue). 6. The disease was milder in deficient than in control animals in both the GF and CV groups on the basis of parasitemia and survival, indicating that fatty acid-deficient mice are partially protected against Chagas' disease. The mechanism underlying this phenomenon requires further investigation.

5'-Nucleotidase↗
PubMed1992

The life cycle of Trypanosoma cruzi under axenic conditions.

The complete life cycle of Trypanosoma cruzi under germfree (GF) conditions was achieved. The Reduvidae insects Dipetalogaster maximus, reared under axenic conditions were infected with Trypanosoma cruzi, strain CL, by feeding on GF infected mice. Axenic trypomastigotes from macerated gnotobiotic insects were used to infect GF and conventional (CV) mice by intraperitoneal, ocular, and oral routes. Infection, followed by blood parasitemia, was obtained in almost all the cases. However, Chagas' disease was more severe in GF animals when compared with CV mice.

Animals↗
PubMed1991

Effect of high sucrose diets on carcass composition in conventional and germ-free mice.

1. The effect of dietary sucrose on carcass composition was determined in conventional (CV) and germ-free (GF) mice fed on a control diet and on diets containing 20 and 40% sucrose. 2. Germ-free mice fed the control diet were heavier than their conventional counterparts. CV mice fed on sucrose diets were, however, heavier than their GF counterparts. 3. GF mice fed on high-sucrose diets showed a lower lipid content on carcass than the GF controls and their CV counterparts. 4. CV mice fed the high-sucrose diets were heavier than the conventional animals fed on the control diet. 5. The water content in the carcass of GF mice fed on high sucrose diets was higher than that of controls, as well as their CV counterparts. 6. The present results suggest different lipidogenic effect of dietary sucrose in germ-free and conventional mice.

Animal Feed↗
PubMed1991

A method for steam-sterilizing semi-solid diets for germ-free mice research.

A semi-solid corn-meal diet sterilized in glass flasks in a hospital-type autoclave is described. The values of weight gain, feed efficiency, apparent digestibility, and cecal diameters were the same for germ-free mice fed either on this diet or on a soybean meal and alfalfa diet (L-485), widely used in germ-free research. The corn-meal diet has been successfully used for eight years.

Analysis of Variance↗
PubMed1991

Immune responses of germfree mice to experimental infection with Trypanosoma cruzi.

1. The immune responses to Trypanosoma cruzi infection of germfree mice were compared to the responses of infected conventional mice. Two groups (40 animals in each group) of 2-month old female CFW germfree and conventional mice were used. The IgM and IgG which bound to the surface of T. cruzi epimastigotes determined by ELISA were significantly lower in germfree than in conventional mice (1/3 and 1/5 for IgM and IgG, respectively). 2. After infection there was a three-fold increase in the circulating levels of these immunoglobulins in germfree but not in conventional mice. Twenty-one days after T. cruzi inoculation, both IgG and IgM levels were similar in germfree and conventional animals. 3. Footpad swelling after T. cruzi-antigen inoculation was initially four-fold more intense in germfree than in conventional mice. 4. These results suggest that the reduced humoral immune response of germfree mice during the initiation of experimental Chagas' disease may be responsible for the more severe parasitism when compared to conventional mice.

Analysis of Variance↗
PubMed1990

The effect of iron deficiency and iron overload on the evolution of Chagas disease produced by three strains of Trypanosoma cruzi in CFW mice.

1. CFW mice were fed either on control diet or on iron-deficient diet. 2. After 5 months the mice were infected with CL, Y or YuYu strain of Trypanosoma cruzi. 3. On the fifth day after the infection, the mice on control diet were divided in three groups: one group remained as controls, two groups were injected either with desferrioxamine or iron-dextran. 4. The severity of the disease was evaluated by parasitemia and mortality. 5. The experimental groups were compared with the infected group fed on the control diet. 6. In mice fed on the iron-deficient diet, the disease was more severe for CL strain and less severe for Y and YuYu strains. 7. Treatment with desferrioxamine produced a less severe disease with YuYu strain and no difference with the other strains. 8. On Treatment with iron-dextran, the disease became more severe with Y and CL strains; no effect was observed with YuYu strain. 9. These findings may be due to intraspecific differences among the strains.

Animals↗
PubMed1989

Risk factors for oral cancer in Brazil: a case-control study.

A case-control study of risk factors for carcinomas of the tongue, gum, floor, and other specified parts of the mouth was conducted in 3 metropolitan areas in Brazil: São Paulo (southeast), Curitiba (south), and Goiânia (central-west). We analyzed information on demographics, occupational history, environmental exposures, tobacco smoking and alcohol drinking habits, as well as diet, oral and other health characteristics obtained from interviews with 232 cases and 464 hospital non-cancer controls matched for 5-year age-group, sex, hospital catchment area and trimester of admission. Tobacco and alcohol consumption were the strongest risk factors irrespective of the anatomical site. The adjusted relative risks (RR) for ever vs. never smokers were: 6.3, 13.9, and 7.0, for industrial-brand cigarettes, pipe, and hand-rolled cigarettes, respectively. A strong correlation was seen between number of pack-years and risk. The RR for the heaviest vs. the lowest consumption categories (greater than 100 vs. less than 1 pack-years) was 14.8. Risk levels generally decreased to those of never smokers after 10 years had elapsed since stopping smoking. The risk associated with alcohol was mostly evident for wine (cancer of the tongue) and "cachaça" (all sites), a hard liquor distilled from sugar cane. Other important risk factors were drinking "chimarrão" (a type of maté), use of a wood stove for cooking, and frequent consumption of charcoal-grilled meat and manioc. Oral hygiene characteristics represented correlates of disease risk. A significant protective effect was observed for consumption of carotene-rich vegetables and citric fruits, but not for green vegetables in general.

Age Factors↗
PubMed1989

Intragastric infection of germfree and conventional mice with Salmonella typhimurium.

The present study investigates the lethality of intragastric Salmonella typhimurium infection of germfree (GF) and conventional (CV, not germfree) mice. The introduction of only 10 viable S. typhimurium into the gastrointestinal tract of GF mice resulted in death of all animals within 8 days of inoculation. In contrast, the 50% lethal dose for CV mice was 4.7 x 10(3) viable organisms. The results demonstrate that resident microbes protect mice from the pathogenic effect of S. typhimurium infection.

Animals↗