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Biomedical subjects

A G Silva

Publications and source records attributed to A G Silva.

16 recordsLinked to original sources
PubMed2004

Chagas' disease: application of TESA-blot in inconclusive sera from a Brazilian blood bank.

BACKGROUND AND OBJECTIVES: The procedure used for screening Trypanosoma cruzi-infected blood donors by using two serological techniques has frequently led to discordant results. The TESA-blot, a confirmatory test for Chagas' disease, was applied in a survey of inconclusive sera from a Brazilian blood bank. MATERIALS AND METHODS: Four hundred and forty-eight sera, obtained from blood donors at the HRU-Fundação Hemominas, were tested by using the TESA-blot assay, a Western blotting method. Of these 448 sera, 348 had previously been determined as inconclusive for Chagas' disease owing to discordance between the indirect immunofluorescence assay (IFA) and the enzyme-linked immunosorbent assay (ELISA). RESULTS: The TESA-blot was positive for 2.87% (10/348) of the inconclusive sera, and 100% positive and negative for the sera from chagasic (n=50) and non-chagasic (n=50) donors, respectively. CONCLUSIONS: Our results clearly indicate the need to improve the diagnosis of Chagas' disease in blood banks by using new confirmatory diagnostic test(s). The TESA-blot, a new test with trypomastigote fractions of the T. cruzi Y strain, has made new approaches to the confirmation of Chagas' disease possible.

Adolescent↗
PubMed1998

[Transient ischemic attacks in a patient with superior vena cava obstruction: case report].

The superior vena cava obstruction is a relatively rare condition. We report the case of a 42 year old man suffering of hypertension for about fifteen years. He reported a cervical and thoracic pain for one year, that was related to a 95% of occlusion on the right coronary artery. An angioplasty has been done but the patient still related the thoracic pain. Afterwards the patient had recurrent episodes of right hemiplegia and hypertensive emergencies that have been treated with anti-hypertensive agents. A venous disease was suspected because of cyanosis in the face especially when episodes of transient ischemic attacks occurred. A venography showed obstruction of the right jugular vein near the junction with the superior vena cava. In conclusion, it was not possible to define with certainty the relationship between the two pathologies presented by the patient, even so, we call attention to the improvement of the neurological symptoms after the control of superior vena cava obstruction with the treatment.

Adult↗
PubMed1998

Western blot detection of infectious bursal disease virus infection.

In order to evaluate the use of a Western blot methodology for the diagnosis of infectious bursal disease virus (IBDV) infection, chickens were experimentally infected with IBDV strains and tested for the presence of viral antigens and antibodies by a blocking Western blot test (bWB). The viral proteins obtained from the bursa of Fabricius (BF) were transferred to a nitrocellulose membrane after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the chicken sera obtained by heart puncture were used for the detection of these proteins. In order to eliminate nonspecific reactions, we used a rabbit anti-chicken serum (blocking tool). By the use of the bWB test, two distinct viral proteins of 43-kDa (VP2) and 32-kDa (VP3) were detected. We suggest the use of this methodology for the detection of IBDV infection in animals suspected of having IBDV reinfection and a chronic subclinical form of the disease. With the use of the rabbit anti-chicken sera for blocking, this method is practical, sensitive and less time consuming.

Animals↗
PubMed1997

Identification of a novel glucocorticoid response unit (GRU) in the 5'-flanking region of the mouse IL-2 receptor alpha gene.

Glucocorticoid hormones inhibit the production of IL-2 and upregulate mouse interleukin 2 receptor alpha (IL-2Ralpha) gene expression in T cell lines by increasing its transcription rate. Now, the authors have used functional approaches to search for regulatory elements present in the 5'-flanking region of the IL-2Ralpha gene responsible for this effect. An important regulatory region was detected between -1382 and -1100 bp from the transcription initiation site. Within this region the authors characterized two 20 bp long cis-acting regulatory elements, named G1 and G2, which are involved in the modulation of the expression of the IL-2Ralpha gene by glucocorticoids. G1 contains a relatively well-conserved GRE half palindrome site, able to bind a partially purified glucocorticoid receptor but giving rise to an unstable complex. The G2 regulatory element contains no consensus sequences of binding sites for GR nor for any other described transcriptional factors but is able to form complexes with factors present in liver or T cells. Whereas G1 or G2 alone were unable to induce a glucocorticoid-response, the contiguous presence of G1 and G2 gave rise to an efficient response. Therefore, it is postulated that the glucocorticoid-induction of IL-2Ralpha gene is mediated, at least partly, through G1 and G2 elements which constitute a novel multicomponent glucocorticoid response unit (GRU).

Animals↗
PubMed1993

Glucocorticoid hormones upregulate interleukin 2 receptor alpha gene expression.

We present evidence that glucocorticoid hormones increase expression of IL-2Rec alpha chain on T cells by regulating IL-2Rec alpha gene transcription. We have previously reported that glucocorticoids can upregulate IL-2Rec alpha mRNA and protein expression in some T cell hybrids. In the present study we show that the glucocorticoid analogue dexamethasone increases mRNA levels of the endogenous IL-2Rec alpha gene and the expression of plasmids containing 5'-flanking sequences of the IL-2Rec alpha gene linked to CAT reporter genes transiently transfected into different cell lines. We show that the dexamethasone effect depends on cis-acting regulatory elements in a segment (-1835/-802) of the mouse gene that also contains cytokine response elements and a inducible DNase I-hypersensitive site. Dexamethasone responses of IL-2Rec alpha-CAT reporter gene constructs were observed in a CTL line, in an IL-3-dependent bone marrow-derived cell line, and in COS7 monkey kidney cells. In the latter the response depended on cotransfection of a glucocorticoid receptor expression vector. The biological relevance of the glucocorticoid-mediated upregulation of the IL-2Rec alpha gene is discussed.

Animals↗
PubMed1986

Morphological alterations of small intestinal epithelium of calves caused by feeding soybean protein.

Sixteen male Holstein calves were fed milk replacer (14% solids) containing 23% crude protein from: 100% milk protein; or 66% soybean protein concentrate plus 34% milk protein as the only nutrients at 8, 9, 10, 11, 12, 12, and 12% body weight from 1 to 7 wk of age, respectively. Eight calves were sensitized to soybean by feeding 66% soybean protein concentrate plus 34% milk protein for 21 d and eight were not sensitized by feeding 100% milk protein. Afterward, each calf received one of the diets for 10 d followed by the other diet for an additional 10 d. During the 2nd wk of the initial period each calf was surgically fitted with a duodenal cannula for biopsy of intestinal mucosa. Biopsies were taken at surgery and on the last day of each period. Feeding 66% soybean protein concentrate plus 34% milk protein resulted in lower body weight gain, decreased feed efficiency, higher rectal temperatures, increased diarrhea, and villus atrophy. Diminished villi size supports other studies reporting allergic reaction to soybean protein and was associated with the poor performance observed in calves fed soybean protein.

Animals↗
PubMed1984

Influence of feeding different amounts of milk on performance, health, and absorption capability of baby calves.

The influence of feeding high milk on performance, health, and absorption capability of the small intestine was studied in Holstein calves (eight males and eight females). Animals were kept in outdoor hutches bedded with straw. Treatments consisted of two quantities of milk: 1) 4.1 kg of whole milk from 3 to 48 days of age when calves were weaned and 2) gradually increasing milk from 4.1 to 7.0 kg during the first 2 wk of treatment and feeding 7.6 kg per day thereafter until day 42. Milk was reduced gradually during the 7th wk. Intake of milk averaged 4.1 and 6.7 kg per animal per day. Commercial starter, alfalfa hay, and water were offered ad libitum to all calves. Higher milk resulted in larger weight gains (615 versus 538 g/day) and less starter intake. Total dry matter intake, feed efficiency, and scour scores were not different between treatments, but rectal temperatures were greater on high milk. Female calves fed high milk showed less xylose absorption and more days medicated than females fed less milk.

Animal Feed↗
PubMed1981

Human interleukin 2: production by both TG cells and other T cells.

We have investigated the production of interleukin 2 (IL-2) by human T cells after their stimulation by phytohaemagglutinin (PHA). T cells isolated by rosetting with sheep erythrocytes produced high levels of IL-2. Further separation of rosette-forming cells, according to the expression of Fc receptors for IgG, showed that TG and non-TG cells are equally able to produce IL-2. The release of IL-2 by TG cells did not require DNA synthesis or functional Rc gamma receptors, since positively selected TH cells produced IL-2, even though they lacked lymphoproliferative responses to PHA and antibody-dependent cell-mediated cytotoxicity.

Antibody-Dependent Cell Cytotoxicity↗
PubMedDate not supplied

Intestinal spirochetosis: first cases reported in Brazil and the use of immunohistochemistry as an aid in histopathological diagnosis.

Colonization of the colon and rectum by intestinal spirochetes is detected for the first time in Brazil in 4 of 282 (1.41%) patients who had undergone sigmoidoscopy and/or colonoscopy with a histopathological diagnosis of chronic non specific-colitis. This frequency is probably underestimated, since surgically obtained specimens were not considered in the present study. Histopathological diagnosis was performed using routine stains like hematoxylin-eosin which showed the typical, of 3-microns thick hematoxyphilic fringe on the brush border of the surface epithelium, and by silver stains like the Warthin-Starry stain. Immunohistochemical procedures using two, polyclonal, primary antibodies, one against Treponema pallidum and the other against Leptospira interrogans serovar copenhageni serogroup Icterohaemorrhagiae cross-reacted with spirochetal antigen/s producing a marked contrast of the fringe over the colonic epithelium, preserving the spiral-shaped morphology of the parasite. In one case with marked diarrhea, immunohistochemistry detected spirochetal antigen/s within a cell in an intestinal crypt, thus demonstrating that the infection can be more widely disseminated than suspected using routine stains. Immunohistochemical procedures, thus, greatly facilitate the histological diagnosis of intestinal spirochetosis and may contribute to a better understanding of the pathogenesis of the disease. Transmission and scanning electron microscopy performed in one case showed that the spirochete closely resembled the species designated as Brachyspira aalborgi.

Adolescent↗