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Biomedical subjects

A M Ferreira

Publications and source records attributed to A M Ferreira.

At least 19 recordsLinked to original sources
PubMed2006

High EPHB2 mutation rate in gastric but not endometrial tumors with microsatellite instability.

The EPH/EFN family of receptor tyrosine kinases regulates cell adhesion and migration and has an important role in controlling cell positioning in the normal intestinal epithelium. Inactivation of EPHB2 has recently been shown to accelerate tumorigenesis in the colon and rectum, and we have previously demonstrated frequent frameshift mutations (41%) in an A9 coding microsatellite repeat in exon 17 of EPHB2 in colorectal tumors with microsatellite instability (MSI). In this study, we extended these analyses to extracolonic MSI cancers, and found frameshift EPHB2 mutations in 39% (25/64) of gastric tumors and 14% (8/56) of endometrial tumors. Regression analysis of these EPHB2 mutation data on the basis of our previously proposed statistical model identified EPHB2 as a selective target of frameshift mutations in MSI gastric cancers but not in MSI endometrial carcinomas. These results suggest a functional role for EPHB2 in gastric tumor progression, and emphasize the differences between the tumorigenic processes in MSI gastrointestinal and endometrial cancer.

DNA Mutational Analysis↗
PubMed2006

Characterization of Toxoplasma gondii from domestic animals from Minas Gerais, Brazil.

In an attempt to isolate and characterize Toxoplasma gondii from the State of Minas Gerais, Brazil, musculature samples from 72 pigs, 25 dogs, 28 free-range chickens and 50 chickens produced in industrialized farms were collected. Antibodies to T. gondii have not been detected in pigs, but were found in nine (40.9 %) out of 22 dogs, and in 15 (53.6 %) of 28 free range chickens. T. gondii was not isolated from pigs and industrialized chickens, but from eight dogs and 11 free range chickens. In order to determine T. gondii virulence, female BALB/c mice were inoculated with 10(3), 10(2), 10(1) and 10(0) tachyzoites of the 19 isolates. The strains RH (virulent) and ME49 (non-virulent) were used as references. Isolates were divided into three groups according to the virulence phenotype: five isolates were classified into virulent in mice, one into non-virulent and 13 into intermediate virulent. Nested-PCR of T. gondii SAG2 locus amplified DNA from 21 out of 22 DNA samples directly extracted from heart of free range chickens. These samples were genotyped through a PCR-RFLP assay. Seventeen (80.9 %) were classified into type I; one (4.8 %) into type III and three (14.3 %) into type I or II.

Animals↗
PubMed2006

Eosinophil cationic protein damages protoscoleces in vitro and is present in the hydatid cyst.

Eosinophils are locally recruited during the establishment and chronic phases of cystic hydatidosis. This study provides evidence that eosinophil cationic protein (ECP), one of the major components of eosinophil granules, can damage Echinococcus granulosus protoscoleces (PSC). The toxicity of ECP was investigated in vitro by following parasite viability in the presence of this protein. ECP was found to damage PSC at micromolar concentrations; the effect was blocked by specific antibodies and heparin, and was more severe than the one caused by similar concentrations of RNase A, suggesting that the cationic nature of ECP, and not its ribonuclease activity, is involved in toxicity. This observation may highlight the capacity of eosinophils to control secondary hydatidosis, derived from PSC leakage from a primary cyst. To further assess the relevance of the previous result during infection, the presence of eosinophil proteins was investigated in human hydatid cysts. ECP was found to be strongly associated with the laminated layer of the cyst wall, and present at micromolar concentrations in the hydatid fluid. Overall, these results demonstrate that eosinophils degranulate in vivo at the host-parasite interface, and that the released ECP reaches concentrations that could be harmful for the parasite.

Animals↗
PubMed2005

Developmental competence of oocytes from prepubertal Bos indicus crossbred cattle.

The aim of the present study was to evaluate the effect of age on embryogenic competence of oocytes recovered from Bos indicus crossbred calves and heifers. Cumulus-oocyte complexes (COCs) were collected from 4- to 7-month-old calves (experiment 1) and from 9- to 14-month-old heifers (experiment 2) during processing at an abattoir. In both experiments cow COCs were used as control. COCs were in vitro matured and fertilized, and the presumptive zygotes co-cultured with cumulus cells until 224 h post insemination (hpi). In experiment 1, the development rate during the first 68-72 hpi was similar (P > 0.05) between embryos derived from calves and cows. Fewer embryos from calves developed to the blastocyst stage, resulting in a lesser blastocyst production as well as lesser hatching rate (P < 0.05). The embryo development after blastocyst stage was, nevertheless, similar (P > 0.05) between blastocysts derived from calves and cows, suggesting that the development after blastocoele formation is not compromised in embryos derived from calves. In experiment 2, there were no differences (P > 0.05) on cleavage, blastocyst and hatching rates between embryos derived from prepubertal heifers and cows. The rate of blastocyst development until hatching was also similar (P > 0.05). These results indicate that oocytes from 9- to 14-month-old B. indicus crossbred heifers have the same developmental competence as oocytes derived from cows, while ocytes derived from 4- to 7-month-old B. indicus crossbred calves are less competent in developing to the blastocyst stage in vitro. It suggests that oocyte competence in B. indicus crossbred cattle is achieved around 9-14 months of age.

Aging↗
PubMed2001

Use of repetitive DNA elements to define genetic relationships among Anaplasma marginale isolates.

Anaplasma marginale genomic DNA was tested for the presence of repetitive extragenic palindromic (REP) and enterobacterial repetitive intergenic consensus (ERIC)-like sequences in order to evaluate the genetic diversity of multiple A. marginale isolates. A. marginale isolates were obtained from cattle of six different states of Brazil, from the US and an Anaplasma centrale strain was obtained from Uruguay. Patterns obtained from A. marginale isolates varied from 14 to 17 fragments by REP-polymerase chain reaction (PCR) and 6 to 14 fragments by ERIC-PCR. All A. marginale isolates presented a 0.75-kb fragment by REP and two common fragments (0.38 and 1.0 kb) by ERIC-PCR. These two fragments were not detectable in A. centrale. Both methods produced similar patterns (80%) among A. marginale isolates obtained from the same region, although some isolates within regions shared less similarity. Isolates from Parana and Pernambuco, were differentiated by these methods. The study demonstrates the presence of ERIC and REP-like elements in A. marginale isolates and shows that A. marginale isolates and strains can be differentiated by these methods.

Anaplasma↗
PubMed2001

Assessment of in vivo complement activation on the Echinococcus granulosus hydatid cyst wall.

The larval stage of the parasite Echinococcus granulosus causes hydatid disease. The hydatid cyst is potentially capable of activating host complement, since it is a large, persistent, carbohydrate-rich structure, coated with host immunoglobulins, and localized in the host's internal organs. Nonetheless, in vitro studies have suggested that the cyst surface, the hydatid cyst wall (HCW), is a poor complement activator. In this study, we assessed the occurrence of in vivo complement activation on the hydatid cyst by measuring the levels of two complement activation products, C3d and complexes bearing a C9 activation neoepitope (TCC/MAC), in extracts from HCW of human origin. Low amounts of C3d and TCC/MAC were found in HCW in comparison with their levels in normal human plasma and activated human sera, suggesting that in vivo complement activation on HCW is efficiently down-regulated. This regulation may contribute to limit host inflammation which has been observed to correlate with parasite degeneration and death.

Animals↗
PubMed2001

Virulence for BALB/c mice and antigenic diversity of eight Toxoplasma gondii strains isolated from animals and humans in Brazil.

With the purpose of establishing alternative parameters to determine the virulence of Toxoplasma gondii strains, the antigenic diversity of eight strains of the parasite isolated in Brazil was evaluated. BALB/c mice were inoculated i.p. with 10(0), 10(1), 10(2) and 10(3) tachyzoites from each strain. The mortality and time to death of the animals showed that T. gondii strains may be divided in three groups: three strains resulted in 100% of mortality, 5-10 days post inoculation (DPI); three strains resulted in 100% of mortality, 7-19 DPI and brain cysts were observed in the mice which were inoculated; two strains resulted in 0% of mortality, 30 DPI. The analysis of the antigenic profile of different T. gondii strains through Western blotting, using rabbit antiserum to T. gondii, revealed that most antigens are similar to all strains. The mAb 4C3H4 recognized antigens only in the RH, N, AS28 and ME49 strains.

Animals↗
PubMed2001

The use of sweet rolls fortified with iron bis-glycinate chelate in the prevention of iron deficiency anemia in preschool children.

The effectiveness of bread fortified with iron bis-glycinate chelate for the control of iron deficiency and iron deficiency anemia was evaluated in 89 preschool children from families of low socioeconomic level attending 2 day nurseries of the Sao Paulo City Council. During the intervention's time of 6 months the children received besides their usual center's diet, a daily supplement of two sweet rolls fortified with 2 mg each of iron from the chelate for a total daily iron intake of 4 mg. After six months of intervention there was a significant decrease in the prevalence of iron deficiency anemia from 62 to 22%. There was a mean hemoglobin improvement of 1.1 g/dL, and in children with initial hemoglobin levels < 11 g/dL the mean increase in hemoglobin was 1.42 g/dL. The total mean plasma ferritin values increased from 11.34 to 20.2 micrograms/L, and in those children originally iron depleted the ferritin values normalized. A significant increase in the "z" score for weight/height was also observed. We concluded that the use of sweet rolls fortified with 2 mg of iron from the bis-glycinate chelate is highly effective for the control of iron deficiency and iron deficiency anemia in young children.

Anemia, Iron-Deficiency↗
PubMed2000

Roles of phosphate and an enoyl radical in ferritin iron mobilization by 5-aminolevulinic acid.

5-Aminolevulinic acid (ALA), a heme precursor that accumulates in acute intermittent porphyria (AIP) and lead poisoning, undergoes enolization and subsequent iron-catalyzed oxidation at neutral pH. Iron is released from horse spleen ferritin (HoSF) by both ALA-generated O(2)(.-) and enoyl radical (ALA(z.rad)), which amplifies the chain of ALA oxidation (autocatalysis). Iron chelators such as EDTA, ATP, but not citrate, and phosphate accelerate this process and ALA-promoted iron release from HoSF is faster in horse spleen isoferritins containing larger amounts of phosphate in the core. ALA (+0.377 V versus standard hydrogen electrode) is less effective in releasing iron from ferritin than are thioglycollic acid, 6-hydroxydopamine, and N,N,N', N'-tetramethyl-p-phenylenediamine. During electrochemical one electron oxidation of ALA in a nitrogen atmosphere, spin trapping experiments with 3,5-dibromo-4-nitrosobenzenesulfonic acid demonstrated the formation of a spin adduct characterized by a six line signal, indicating a secondary carbon-centered radical and attributed to a resonant ALA&z.rad; radical. Iron is also released in such anaerobic electrochemical oxidations of ALA in the presence of ferritin, suggesting that, in addition to O(2)(*-), ALA&z.rad; can promote iron mobilization from ferritin. Hence, ALA&z.rad; may amplify the metal-catalyzed oxidation of ALA, damaging ALA-accumulating cells and possibly contributing to the symptoms of porphyria.

Adenosine Triphosphate↗
PubMed2000

How Echinococcus granulosus deals with complement.

Here, Ana Mar a Ferreira and colleagues discuss the interplay between the larval stages of Echinococcus granulosus and an important effector arm of immunity: the host complement system. During early infection, the parasite activates complement, and hence complement-dependent inflammatory responses. However, on differentiation into the hydatid cyst, the parasite exposes to the host a structure - the cyst wall - that does not activate complement strongly. Mechanisms inhibiting complement activation on the cyst wall have been elucidated, contributing to the understanding of how this large, persistent, tissue-dwelling pathogen controls the inflammatory response.

Animals↗
PubMed2000

Contribution of C5-mediated mechanisms to host defence against Echinococcus granulosus hydatid infection.

The aim of this work was to investigate the contribution of complement C5-mediated mechanisms, with an emphasis on inflammation, to host defences against Echinococcus granulosus hydatid disease. Thus, we compared the systemic and local inflammatory responses induced by the parasite, and the outcome of infection, between congenic C5-sufficient (B10.D2 n/SnJ) and C5-deficient (B10.D2 o/SnJ) mice challenged with protoscoleces. Indirect evidence of in-vivo complement activation during the establishment phase was obtained; infection induced serum amyloid P and eosinophil responses which were dependent on C5. Early recruitment of polymorphonuclear cells was not dependent on the presence of C5. The higher capacity of C5-sufficient mice to recruit eosinophils was also observed during the cystic phase of infection, and mice recruiting more eosinophils developed lower parasite masses. Analysis of the outcome of infection after 8 months showed that C5-sufficient mice were more resistant to infection than C5-deficient mice in terms of individuals with no cysts; this trend was not statistically significant. In addition, C5-deficient mice developed higher numbers of large (> 5 mm in diameter) cysts and higher cyst weights than C5-sufficient mice indicating that C5-mediated mechanisms are detrimental for parasite growth. Taken together, our results suggest that complement, through C5-mediated effectors, contributes to host defences by both restricting the establishment of infection and controlling the growth of established cysts. This contribution may, at least partially, be associated with the ability of C5a to promote eosinophil infiltration.

Animals↗
PubMed2000

Snoring in Portuguese primary school children.

OBJECTIVE: To determine the prevalence of snoring and its potential associations with sleep problems, such as daytime symptoms, medical conditions, school performance, and behavioral disturbances in Portuguese children attending primary school. METHODS: A previously validated questionnaire was sent to the parents of 1381 children attending primary schools in a parish of Coimbra, Portugal. To assess behavioral disturbances, the Portuguese version of Rutter's Children's Behavior Questionnaire for completion by teachers was used. RESULTS: Of the 988 questionnaires returned (71.5%), complete information concerning snoring was obtained for 976 children (496 girls and 480 boys; mean age: 8.1 +/- 1.5 years). Loud snoring during sleep was reported as frequent or constantly present (LSn) in 84 children (8.6%), as occasionally present in 299 children (30.6%), and as never present (NSn) by 593 children (60.8%). The LSn and NSn groups did not differ with respect to age, gender, sleep duration, time to fall asleep, frequency of night wakings, bedwetting, daytime tiredness, and school achievement. However, LSn was significantly associated with increased bedtime problems (fears and struggles), increased need for comforting activities to fall asleep, behaviors suggestive of parasomnias (sleep talking, teeth grinding, and night terrors), increased daytime sleepiness and irritability, and behavioral disturbances. Children in the LSn group were also more likely to report recurrent medical problems particularly those involving infections of the respiratory tract. CONCLUSIONS: Snoring is a common symptom in Portuguese children that is associated with behavioral daytime and sleep time disturbances. Children with loud snoring may benefit from early evaluation and intervention.

Achievement↗
PubMed2000

Mimics of copper proteins: structural and functional aspects.

The importance of copper as an essential element can be estimated by the wide range of copper proteins and enzymes playing different roles in biological systems. In the last decades many bioinorganic studies were developed on mimetic complexes of copper-dependent proteins, in order to verify the interrelations between structural and functional properties of active copper centers. Among the most studied copper ion ligand, diimine compounds have deserved special attention due their flexibility, facility of preparation, and ability to stabilize both oxidation states of this metal. In our laboratory, we have been investigating some Schiff base copper complexes as mimics of different proteins, with emphasis on functional aspects, trying to elucidate mechanisms of reaction, based on proposed intermediary species, in addition to molecular shapes. Particularly, mimics of the copper-zinc superoxide dismutase, and of monooxigenases and oxidases exhibiting dicopper sites are discussed in this work.

Copper↗
PubMed1999

Direct EPR detection of the carbonate radical anion produced from peroxynitrite and carbon dioxide.

The biological effects of peroxynitrite have been recently considered to be largely dependent on its reaction with carbon dioxide, which is present in high concentrations in intra- and extracellular compartments. Peroxynitrite anion (ONOO-) reacts rapidly with carbon dioxide, forming an adduct, nitrosoperoxocarboxylate (ONOOCO2-), whose decomposition has been proposed to produce reactive intermediates such as the carbonate radical (CO-3). Here, by the use of rapid mixing continuous flow electron paramagnetic resonance (EPR), we directly detected the carbonate radical in flow mixtures of peroxynitrite with bicarbonate-carbon dioxide over the pH range of 6-9. The radical was unambiguously identified by its EPR parameters (g = 2.0113; line width = 5.5 G) and by experiments with bicarbonate labeled with 13C. In this case, the singlet EPR signal obtained with 12C bicarbonate splits into the expected doublet because of 13C (a(13C)= 11.7 G). The singlet spectrum of the unlabeled radical was invariant between pH 6 and 9, confirming that in this pH range the detected radical is the carbonate radical anion (CO-3). Importantly, in addition to contributing to the understanding of nitrosoperoxocarboxylate decomposition pathways, this is the first report unambiguously demonstrating the formation of the carbonate radical anion at physiological pHs by direct EPR spectroscopy.

Carbon Dioxide↗
PubMed1999

Antibody response in goats experimentally infected with Toxoplasma gondii.

Serum samples of five goats inoculated with Toxoplasma gondii were analyzed using the enzyme linked immunosorbent assay (ELISA), indirect hemagglutination (IHA) and western blotting (WB). Antibodies detected by ELISA peaked between 19 and 62 days after inoculation and persisted throughout the experiment with no association to parasitaemia. Using WB, the main antigens detected had molecular weights of approximately 68, 62, 50, 48, 42, 34, 28, 26, 22 and 19 kDa. Antibody titers of between 1:256 and 1:32000 were observed using IHA, with a significant drop in activity after treatment with 2-mercapto-ethanol between days 12 and 48. This coincided with the parasitaemic period that occurs between 5 and 64 days after inoculation.

Animals↗
PubMed1999

[Prevalence of serologic markers of hepatitis B virus in hospital personnel].

OBJECTIVE: To verify the prevalence of the anti-HBc, anti-HBs and HBsAg markers of hepatitis B virus, and to identify the risk factors determining occupational infection with this virus among hospital personnel. METHODS: Samples of serum from 210 persons both male and female who work in different occupations at a hospital university, were analysed. The technique employed was the immunoenzymatic assay using commercial kits. RESULTS: As a control group, samples of serum from 45 volunteer blood donors were utilized. It was verified that 20.5% of the hospital personnel presented a positive reaction to at least one of the markers songht, as against 6.6% of the control group. The prevalence of each marker separately was: anti-HBc 8.1%, anti-HBs 5.2%, and HBsAg 2.9% in the hospital personnel; and 4.4%, 2.2% and 0.0% in the control group. The simultaneous presence of the anti-HBc and anti-HBs markers was detected in 4.3% of the workers. In the control group, the presence of the anti-HBc and anti-HBs markers was detected, isolately, with respective prevalences of 4.4% and 2.2%. Those who presented the highest rates of positivite reaction were: laboratory technicians 24.0%, nurses 23.6%, physicians 20.8%, and cleaning personnel 18.2%. CONCLUSIONS: The findings suggest that direct contact with patients and handling of blood and other body fluids are risk factors related to occupational infection with HBV. Therefore, it is recommended that hospital personnel be vaccinated against hepatitis B.

Adult↗