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Biomedical subjects

C M Silva

Publications and source records attributed to C M Silva.

At least 19 recordsLinked to original sources
PubMed2001

A survey of zearalenone in corn using Romer Mycosep 224 column and high performance liquid chromatography.

A survey of zearalenone (ZEA) in corn from various regions of Brazil was carried out by the analysis of 380 corn samples, of which 30 samples (7.8%) were found to be contaminated in the range of 46.7-719 micrograms/kg. ZEA was extracted with acetonitrile-water (84:16, v/v), cleaned-up on a Romer Mycosep 224 column, separated, detected and quantified by high performance liquid chromatography (HPLC). The in-house method characteristics of linearity, accuracy, precision, and detection limit were defined by means of recovery tests with spiked corn samples in the range of 35.8-716 micrograms/kg and the analysis of a naturally-contaminated sample (n = 7). The mean recovery for ZEA was 99.4% and the relative standard deviation (RSD) varied from 0.7 to 26.6% in the range studied. The method has been shown to be accurate, quick and reliable for determination of zearalenone in corn.

Animal Feed↗
PubMed2001

Co-occurrence of aflatoxins B1, B2, G1, G2, zearalenone and fumonisin B1 in Brazilian corn.

Two hundred and fourteen unprocessed corn samples (1997-98 harvest), collected at wholesale markets in different regions in Brazil, were surveyed for the occurrence of mycotoxins. The samples were analysed for aflatoxins B1, B2, G1, G2, zearalenone and fumonisin B1 using in-house validated methods. The occurrence of aflatoxin B1, zearalenone and fumonisin B1 was found in 38.3, 30.4 and 99.1% of the samples, respectively. Aflatoxin B1, zearalenone and fumonisin B1 contamination levels varied from 0.2 to 129, 36.8 to 719, and 200 to 6100 microg/kg, respectively. The co-occurrence of the two carcinogenic mycotoxins aflatoxin B1 and fumonisin B1 was observed in 100% of the aflatoxin-contaminated samples (82 samples). Co-occurrences of aflatoxin B1: zearalenone: fumonisin B1 and aflatoxin B1: aflatoxin B2: fumonisin B1 were found in 18 and 43 samples, respectively.

Aflatoxin B1↗
PubMed2001

Long-term prognosis of cirrhosis after spontaneous bacterial peritonitis treated with ceftriaxone.

Spontaneous bacterial peritonitis (SBP) is a frequent infection in cirrhotic patients with ascites, with a poor prognosis. The aims of this study were to determine the long-term survival of cirrhotic patients with SBP treated with ceftriaxone and to identify predictive factors related to survival. We studied 47 first episodes of SBP treated with ceftriaxone with a mean follow-up of 272 days. Nineteen variables were recorded to evaluate their relation to survival. The most frequent organism that caused SBP was Escherichia coli (40%). Spontaneous bacterial peritonitis resolution was achieved in 67% of patients. After resolution, SBP recurrence was observed in 44% of patients. The cumulative probability of survival was 68.1% at 1 month and 30.8% at 6 months. After uni-and multivariate analyses of all cases, SBP resolution ( p = 0.0001) and international normalized ratio (INR) ( p = 0.0057) were found to be related to survival. Another analysis performed after SBP resolution and SBP recurrence showed that ascitic fluid-positive culture ( p = 0.0344) and INR ( p = 0.0218) had statistical significance as variables predictive of long-term survival. We conclude that the survival of cirrhotic patients is very short after the first episode of SBP, a fact probably related to advanced liver disease, as liver dysfunction (INR) is the most important factor related to long-term patient survival.

Adult↗
PubMed2001

Action of selective serotonin reuptake inhibitor on aggressive behavior in adult rat submitted to the neonatal malnutrition.

The effect of the malnutrition during suckling on the aggressiveness was investigated in adult rats treated or not with citalopram, a selective serotonin reuptake inhibitor (SSRI). The animals were divided into two groups according to the diet used: nourished group - the rats received the control diet with 23% protein during the life; and malnourished group - the rats had its mothers submitted to diet with 7.8% protein during suckling. At 120 days of age, each group was sub-divided according to the treatment: acute - consisting a single i.p. injection of saline solution or 20-mg/Kg citalopram; chronic - consisting the single injections (1 per day during 14 days) of saline or 20 mg/Kg citalopram. The acute or chronic treatment with SSRI reduces aggressive response in nourished rats, but not in malnourished ones. Thus, the malnutrition during the critical period of brain development seems to induce durable alterations in the function of the serotoninergic neurotransmission

Aggression↗
PubMed2000

Tyrosine kinase signalling in breast cancer: epidermal growth factor receptor and c-Src interactions in breast cancer.

Both the non-receptor tyrosine kinase, c-Src, and members of the epidermal growth factor (EGF) receptor family are overexpressed in high percentages of human breast cancers. Because these molecules are plasma membrane-associated and involved in mitogenesis, it has been speculated that they function in concert with one another to promote breast cancer development and progression. Evidence to date supports a model wherein c-Src potentiates the survival, proliferation and tumorigenesis of EGF receptor family members, in part by associating with them. Phosphorylation of the EGF receptor by c-SRC is also critical for mitogenic signaling initiated by the EGF receptor itself, as well as by several G-protein coupled receptors (GPCRs), a cytokine receptor, and the estrogen receptor. Thus, c-Src appears to have pleiotropic effects on cancer cells by modulating the action of multiple growth-promoting receptors.

Breast↗
PubMed2000

Antioxidants in medicinal plant extracts. A research study of the antioxidant capacity of Crataegus, Hamamelis and Hydrastis.

The antioxidant capacity of extracts of Crataegus oxyacantha, Hamamelis virginiana, Hydrastis canadensis, plants native to Europe and North America which have long been used in herbal medicine for the treatment of cardiac and circulatory functions, has been investigated. The total antioxidant potential conferred by all hydrogen donating antioxidants present in these extracts has been assessed by the ABTS assay and the relative order of antioxidant potential has been established. Gas chromatography coupled to mass spectrometry (GC-MS) has been used for the chemical identification of the antioxidant volatile compounds present in the extracts. The GC-MS data were related to the results obtained using the ABTS assay.

Antioxidants↗
PubMed2000

Available pathways database (APD): an essential resource for combinatorial biology.

A relational database, the Available Pathways Database (APD), has been constructed of microbial natural products, their producing strains, and their biosynthetic pathways. The database allows the ready selection of donor strains for combinatorial biology experiments. It provides the same type of resource for combinatorial biology as the Available Chemicals Directory (ACD) does for combinatorial chemical library generation. Its cataloging ability can also provide insight into novel aspects of biosynthetic routes. In particular, no 10-unit Type I polyketides were found in the compilation of this edition of the APD (Version I).

Bacteria↗
PubMed2000

Anticonvulsant activity of essential oils and active principles from chemotypes of Lippia alba (Mill.) N.E. Brown.

In the present work we studied the anticonvulsive effects of the essential oils (EOs) from three chemotypes of Lippia alba (Mill.) N.E.Brown (Verbenaceae). Animals (female Swiss mice, 25 g) were treated with the EO and, 30 or 60 min after intraperitoneal (i.p.) or oral (p.o.) administration, respectively, injected with pentylenetetrazole (80 mg/kg, i.p.) and observed for 30 min. The results showed that EO I (200 and 400 mg/kg), EO II (100, 200 and 400 mg/kg), and EO III (400 mg/kg), i.p., produced an increased latency time for the first convulsion as related to controls. Death latency was greater in the groups receiving EO I (50 and 100 mg/kg), EO II (100 and 200 mg/kg), and EO III (200 mg/kg), i.p. Orally, while no effect was demonstrated with EOs at doses of 200 or 400 mg/kg, significant increases in the latency of convulsion and latency of death were observed with EO I at the highest dose (800 mg/kg). Similarly, EO III at this dose was also effective as far as latency of convulsion is concerned. Animals treated with citral (100 mg/kg, i.p.), beta-myrcene or limonene (200 mg/kg, i.p.), EOs chemical constituents, presented significant increases in the latency of convulsion and percentage of survival as compared to controls. After oral administration these effects were observed only with a higher dose (400 mg/kg). The association of EOs with diazepam significantly potentiated their effects, suggesting a similar mechanism of action and indicating that citral, beta-myrcene, and limonene are probably the EOs active compounds.

Animals↗
PubMed1999

Effect of growth hormone and induced IGF-I release on germ cell population and apoptosis in the bovine testis.

Bovine growth hormone has been used in dairy cattle to increase milk production,but it also increases the twin parturition rate. This effect is mediated by insulin-like growth factor-I (IGF-I), which prevents follicular atresia by hindering apoptosis of granulosa cells. The action of GH and IGF-I on testicular function remains unclear. The goal of this study, therefore, was to verify the effects of short-term administration of GH and induced IGF-I release on the number of testicular germ cells, testicular morphology, and apoptosis in the bovine testis. Twenty Zebu bulls were split into 2 groups. The bulls in Group 1 (n = 10) were treated with 2 subcutaneous injections of bovine GH (500 mg/bull) 7 d apart. Group 2 bulls (n = 10) received placebos under the same protocol. All of the bulls were slaughtered 14 d after the start of treatment. Fragments of the testis were collected, fixed in Bouin's solution, embedded in paraffin, and the sections stained with hematoxilin and eosin. The paraffin-embedded sections were also used for in situ detection of apoptotic cells. Blood samples were collected at slaughter to measure serum levels of IGF-I, FSH and LH. Neither the number of Stage I seminiferous epithelium germ cells and the morphometric parameters (tubular diameter, seminiferous epithelium height, and volumetric proportions of structural components) nor the blood levels of FSH and LH showed a significant difference between the 2 groups. However, the treated animals showed an increase in serum IGF-I (P<0.01). Apoptotic germ cells were detected in the testis of both groups, showing the same pattern and a stage-specific apoptosis pattern. Most of the labeled cells were spermatocytes. The localization of apoptotic germ cells did not differ between groups. These results suggest that short-term administration of GH does not affect bovine spermatogenesis in adult bulls.

Animals↗
PubMed1999

Six novel beta-galactosidase gene mutations in Brazilian patients with GM1-gangliosidosis.

GM1-gangliosidosis is a lysosomal storage disease caused by a deficiency of acid beta-galactosidase. Three clinical forms are recognized-infantile, juvenile, and adult-based on age of onset and severity of the symptoms. We have performed molecular analysis of a large cohort of GM1 patients (19 Brazilian and one Uruguayan), using nonradioactive single-strand conformation polymorphism (SSCP) and restriction enzyme analysis of genomic DNA. Six novel mutations (R121S, V240M, D491N, 638-641insT, 895-896insC, 1622-1627insG) and two previously described point mutations (R59H, R208C) were identified. Together they accounted for 90% of the disease alleles of the patients. Two mutations, 1622-1627insG and R59H, were present in 18 of 20 patients. In addition, four polymorphisms (L10P, L12L, R521C, S532G) were identified. All cases reported are infantile GM1 gangliosidosis. This report constitutes the most comprehensive molecular study to date of this disorder in infantile patients. Since GM1-gangliosidosis is the most common lysosomal storage disorder in Southern Brazil, molecular diagnosis will be important for genetic counseling, carrier detection and prenatal diagnosis in index families.

Brazil↗
PubMed1999

Signal transduction defects in growth hormone insensitivity.

Growth hormone (GH) insensitivity is a heterogeneous condition that can result from mutations within the GH receptor (GHR) and that can be inherited as both an autosomal recessive and a dominant trait. However, evidence from a small number of growth hormone binding protein (GHBP)-positive families indicates that their GH insensitivity is independent of GHR mutations. Two of these families appear to have distinct abnormalities in GH signal transduction. Studies suggest that one family (classic Laron syndrome phenotype; designated family H) have a signalling defect close to the GHR, preventing activation of both the STAT and MAPK pathways, whereas the other family (less marked phenotype; family M) have a defect in activating MAPK but not the STAT pathway. The children studied here are specifically insensitive to GH and their defect must be exclusive to this signalling system. Thus, families with GHBP-positive GH insensitivity without GHR mutations are likely to be important models in which to study the specificity of GH signal transduction and the relationship between GH insensitive phenotype and signalling defect.

Body Height↗
PubMed1998

Activation of the signal transducers and activators of transcription signaling pathway by growth hormone (GH) in skin fibroblasts from normal and GH binding protein-positive Laron Syndrome children.

We have previously described two families (H and M) with GH binding protein-positive Laron Syndrome (LS), proposed to have one or more post GHR signaling defects. In the present study, we have examined whether the signal transducers and activators of transcription (STAT) pathway is activated by GH in skin fibroblast cultures established from these LS children, to determine the level(s) at which GH insensitivity has occurred. On immunoblots, both normal and LS fibroblasts express JAK2 and STATs 1, 3, and 5. GH induced rapid tyrosine phosphorylation of a protein at approximately 93 kDa in normal fibroblasts, and Western blotting with STAT-specific antibodies revealed STAT5 activation (phosphorylation) by GH. To determine further the identity and the DNA binding characteristics of the STAT proteins that were activated by GH, EMSAs were performed using three DNA elements known to bind STAT proteins; m67, the high affinity c-sis-inducible element (SIE), the interferon response element (IRE), and the lactogenic hormone-responsive region (LHRR). GH failed to induce protein binding to the SIE or IRE in normal skin fibroblasts but did induce the formation of a specific complex with the LHRR. Induction by GH of this LHRR/protein complex, which could be supershifted partially by anti-STAT1 antisera and completely by anti-STAT5 antisera, was transient, maximal between 10 and 30 min and reduced by 60 min. GH also induced distinct LHRR/protein complexes in mouse 3T3-F442A fibroblasts and in human IM-9 lymphocytes, but supershift analysis revealed that these complexes contained STAT5 but not STAT1. Whereas no binding to the LHRR was observed in GH-treated H fibroblasts, GH induced binding to this element in M fibroblasts. These results demonstrate that 1) the JAK-STAT pathway is activated by GH in normal fibroblasts and that STATs 1 and 5 have a role in GH-dependent signaling in these cells; 2) GH activation of DNA/STAT binding is cell type- and species-specific; and 3) GH failed to activate the STAT pathway in H fibroblasts but induced STAT signaling in M fibroblasts, indicating that the site of GH resistance in the latter is likely to be located within another GH signaling pathway. These fibroblast cultures therefore provide unique models with which to further our understanding of the mechanisms of human GH signaling.

Carrier Proteins↗
PubMed1998

Growth hormone stimulation of the mitogen-activated protein kinase pathway is cell type specific.

The GH receptor is a member of the cytokine receptor superfamily. Studies in the 3T3-F442A mouse preadipocyte have shown that GH activates the Janus kinase (JAK2), the signal transducers and activators of transcription (STAT1, -3, and -5), and mitogen-activated protein (MAP) kinase. Our previous studies in the human IM-9 lymphocyte have shown that GH activates JAK2 and only STAT5 (not STAT1 or -3). In the studies presented here, we have investigated activation of the MAP kinase (MAPK) pathway in the IM-9 lymphocyte. Western blotting with antiphosphotyrosine-, anti-MAPK-, and anti-phospho-MAPK-specific antibodies as well in vitro kinase assays using a synthetic peptide substrate demonstrate that although GH (200 ng/ml) activates MAPK in 3T3-F442A cells (at 5 and 10 min of treatment), it does not activate MAPK in IM-9 lymphocytes at time points ranging from 5-60 min. Nevertheless, the phorbol ester phorbol 12-myristate 13-acetate (50 ng/ml) does activate MAPK in the IM-9 cell, and immunoprecipitation with specific antibodies indicates that this activation occurs through c-Raf-1. Although the 52- and 66-kDa forms of the adapter protein Shc are tyrosine phosphorylated in response to GH treatment in 3T3-F442A cells, we demonstrate that the predominant forms in IM-9 cells are the 52- and 46-kDa forms, and neither is tyrosine phosphorylated in response to GH. These studies further elucidate the differential signaling by GH in two cell types.

3T3 Cells↗
PubMed1996

Fluorescence resonance energy transfer between blue-emitting and red-shifted excitation derivatives of the green fluorescent protein.

We report fluorescent resonance energy transfer (FRET) between two linked variants of the green fluorescent protein (GFP). The C terminus of a red-shifted variant of GFP (RSGFP4) is fused to a flexible polypeptide linker containing a Factor X a protease cleavage site. The C terminus of this linker is in turn fused to the N terminus of a blue variant of GFP (BFP5). The gene product has spectral properties that suggest energy transfer is occurring from BFP5 to RSGFP4. Upon incubation with Factor X(a), the protein is cleaved, and the two fluorescent proteins dissociate. This is accompanied by a marked decrease in energy transfer. The RSGFP4::BFP5 fusion protein demonstrates the feasibility of using FRET between two GFP derivatives as a tool to monitor protein-protein interactions; in addition, this construct may find applications as an intracellular screen for protease inhibitors.

Animals↗
PubMed1996

Prognostic value of posterior wall thickness in childhood dilated cardiomyopathy and myocarditis.

M-mode indices of left ventricular dimension and posterior wall thickness were derived from echocardiograms of children presenting with dilated cardiomyopathy/myocarditis and were related to outcome. Echocardiograms from 16 of 18 children were manually digitized to obtain changes of left ventricular dimension and posterior wall thickness throughout the cardiac cycle. Indices of ventricular function and the ratio of end-diastolic posterior wall thickness to cavity dimensions were obtained. Patients were divided into group I (alive, n = 7), and group II (died, n = 6 or heart transplantation, n = 3) at median follow-up of 25 months. No significant difference was seen for the shortening fraction, the percentage of posterior wall thickening or the normalized peak rate of left ventricular filling. The normalized peak rate of posterior wall thinning was greater in group II. The posterior wall thickness to cavity dimension ratio was higher in group I (median = 0.19) than group II (median = 0.13) (P < 0.005). Five of six survivors, whose ventricular function improved, had ratios > 0.17. All but one with a ratio < or = 0.16 remained with a dilated heart, died or required transplantation (P = < 0.01). A relatively thicker posterior wall (ratio > 0.17) was associated with better prognosis and recovery. This index should be taken into account in decision-making regarding timing for cardiac transplantation.

Cardiomyopathy, Dilated↗
PubMed1996

Characterization and cloning of STAT5 from IM-9 cells and its activation by growth hormone.

The interaction of GH with its receptor has been shown to lead to the phosphorylation of the signal transducer and activator of transcription (STAT) family of transcription factors. We demonstrate here that GH activates the tyrosine phosphorylation of STAT5 in the human IM-9 lymphocyte cell line. Western blotting indicates that GH also activates STAT5 in human embryonic kidney cells (293), which stably express the rabbit GH receptor. Although it has been shown previously that GH activates both STATs 1 and 3 in the 3T3-F442A mouse preadipocyte cell line, we demonstrate that GH also activates STAT5 in these cells. Using electrophoretic mobility shift assay, we examined the interaction of proteins with DNA elements containing consensus STAT-binding sequences. Proteins prepared from GH-treated 3T3-F442A cells bound to the c-sis inducible element of the human c-fos gene (m67 SIE), whereas proteins from GH-treated IM-9 cells did not. However, proteins from GH-treated IM-9 cells did interact with oligonucleotides containing either an interferon response element or the lactogenic hormone-responsive region. Treatment of IM-9 cells with interferon-gamma also induced protein interactions with these elements although the complexes were distinctly different than those seen with GH treatment. Using STAT-specific antibodies, we demonstrate that the GH-induced DNA-protein complex formed with the lactogenic hormone-responsive region contained STAT5, while the interferon-gamma-induced complex contained STAT1. These results implicate STAT5 as a downstream mediator of GH action in IM-9 cells. We report here the cloning of two forms of STAT5, STAT5A and STAT5B, from an IM-9 cDNA library. Northern blot analysis demonstrated multiple-forms of STAT5 mRNA in IM-9 cells.

Adipocytes↗
PubMed1995

Red-shifted excitation mutants of the green fluorescent protein.

Using optimized combinatorial mutagenesis techniques and Digital Imaging Spectroscopy (DIS), we have isolated mutants of the cloned Aequorea victoria green fluorescent protein (GFP) that show red-shifted excitation spectra similar to that of Renilla reniformis GFP. Selective excitation of wild-type versus Red-Shifted GFP (RSGFP) enables spectral separation of these proteins. Six contiguous codons spanning the tyrosine chromophore region were randomized and sequence analysis of the mutants revealed a tyrosineglycine consensus. These mutants will enable the simultaneous analysis of two promoters or proteins per cell or organism. In consideration of the multitude of applications which are developing for GFP alone, we envisage that spectrally shifted fluorescent proteins will be of value to a diversity of research programs, including developmental and cell biology, drug-screening, and diagnostic assays.

Amino Acid Sequence↗