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M Pereira

Publications and source records attributed to M Pereira.

At least 19 recordsLinked to original sources
PubMed1999

trans-sialidase of Trypanosoma cruzi: location of galactose-binding site(s).

Trypanosoma cruzi expresses a trans-sialidase on its surface, which catalyzes the transfer of sialic acid from mammalian host glycans to its own surface glycoproteins. It has been proposed that the enzyme consists of three domains prior to a long C-terminal repeating sequence that is not required for enzyme activity. The first of these domains shares significant sequence identity with bacterial sialidases which catalyse the hydrolysis of sialic acid. Here we report the sequence of the N-terminal domains of the TS19y trans-sialidase gene, which was expressed in bacteria with the same specific activity as natural enzyme of T. cruzi. Various deletion mutants of TS19y, without the C-terminal tandem repeat, have been cloned and expressed and their trans-sialidase and sialidase activities measured. These experiments show that all three N-terminal domains are required for full trans-sialidase activity, though only the first is necessary for sialidase activity. Some transferase activity is observed, however, even with the shortest construct comprising the first N-terminal domain. Deletion mutants to probe the role of the N-terminal residues of the first domain suggest that the first 33 residues are also required for trans-sialidase activity, but not for sialidase activity. Molecular modelling of the first N-terminal domain of TS19y based on our structures of bacterial sialidases and site-directed mutations suggests the location of a galactose-binding site within this domain.

Amino Acid Sequence↗
PubMed1999

Phase I/II trial of (131)I-MN-14F(ab)2 anti-carcinoembryonic antigen monoclonal antibody in the treatment of patients with metastatic medullary thyroid carcinoma.

BACKGROUND: Monoclonal antibodies (MAbs) against carcinoembryonic antigen (CEA) have been recognized as targeting agents for medullary thyroid carcinoma (MTC). This Phase I/II study was initiated to determine the safety, maximum tolerated dose (MTD), and therapeutic potential of (131)I-MN-14 F(ab)2 anti-CEA MAb for patients with metastatic MTC. METHODS: Fifteen patients were enrolled in this study. Dose escalation was based on estimates of radiation dose to the bone marrow, and the radioactive dose given was determined by a pretherapy diagnostic study in which 8 mCi (0.6-20 mg) of (131)I-MN-14 F(ab)2 was administered 1 week prior to therapy. RESULTS: Three patients received an initial dose of 140 centigray (cGy) to bone marrow, 11 received 180 cGy, and 1 received 220 cGy. Myelosuppression was the only significant treatment-related dose-limiting toxicity (DLT), and the MTD appeared to be 180 cGy to the bone marrow. Human antimouse antibodies (HAMA) developed in 8 patients 2-6 weeks after therapy. Seven patients had a median of 55% reduction of tumor markers. One patient showed a dramatic improvement in the mass effect on the airways caused by 3 tumor lesions in the neck, with a 45% reduction of overall tumor burden. The disease has continued to be radiologically stable in 11 of 12 assessable patients for periods ranging from 3+ to 26+ months. CONCLUSIONS: Therapy with (131)I-MN-14 F(ab)2 is well tolerated and shows evidence of biochemical and radiologic antitumor activity. HAMA development suggests that humanized MAbs will be required in trials with repeated dose schedules. Further dose escalation, alone or in combination with other therapy modalities, is indicated for future trials, preferably with humanized anti-CEA MAbs.

Adult↗
PubMed1998

Extracellular Mg2+ inhibits both histamine-stimulated Ca(2+)-signaling and exocytosis in human tracheal secretory gland cells.

The effects of extracellular Mg2+ concentration have been investigated on the histamine-stimulated exocytotic process of human tracheal secretory gland (HTG) cells. The exocytosis of secretory granules (SG) was observed concomitantly with dynamic changes of intracellular Ca2+ ([Ca2+]i) and Mg2+ concentrations ([Mg2+]i). The rate of SG exocytosis was appraised by the decrease of quinacrine fluorescence emission. Dynamic changes of [Mg2+]i and [Ca2+]i in HTG cells were determined by the combined use of UV-microspectrofluorometry with Mag-Indo-1 and Indo-1 probes, respectively. High Mg2+ medium significantly inhibited the histamine-stimulated secretion. The influence of the extracellular and intracellular Mg2+ concentrations on [Ca2+]i was analyzed. Basal [Mg2+]i increased from 0.8 mM in a Mg(2+)-free medium to 1.7 mM in 10 mM Mg2+ medium. Histamine induced a [Mg2+]i increase which is dependent on extracellular Mg2+ concentration. The histamine stimulated [Ca2+]i rise was reduced in the presence of elevated Mg2+ extracellular medium and inhibitory effects of extracellular Mg2+ were concomitant with changes in [Mg2+]i. Our data suggest that the inhibition by extracellular Mg2+ of stimulated exocytosis is dependent on both the increase of [Mg2+]i and the inhibition of cytosolic Ca2+ influx.

Calcium↗
PubMed1998

The gene that determines resistance to tioconazole and to acridine derivatives in Aspergillus nidulans may have a corresponding gene in Trichophyton rubrum.

Understanding the genetic mechanisms involved in resistance to antifungal agents is important in the fight against pathogenic fungi. In the present investigation we studied a strain of the model fungus Aspergillus nidulans which presents resistance to tioconazole and behaves as the wild strain in the presence of other azole derivatives. Genetic analysis revealed that this resistance is due to a mutation in a single gene located on chromosome II, closely linked to the allele responsible for resistance to acriflavine and other acridine derivatives, i.e., acrA1. This result suggests that a multidrug resistance (MDR)-type mechanisms may be involved. Two tioconazole-resistant strains of the pathogenic fungus Trichophyton rubrum obtained after mutagenic treatment also became simultaneously resistant to acriflavine and ethidium bromide, suggesting the existence of a resistance mechanism similar to that observed with the acrA1 mutation in A. nidulans.

Acridines↗
PubMed1998

The areA(r) mutation of Aspergillus nidulans confers low pH sensitivity in the presence of ammonium as the only nitrogen source.

The utilization of nitrogen sources by the fungus Aspergillus nidulans is controlled by a mechanism mediated by areA, a wide domain regulatory gene. It has been verified that the strains carrying the mutant allele areAr are inhibited when growing at low pH in the presence of ammonium as the only nitrogen source. The genetic analysis of this marker showed that it apparently maps at the areA locus.

Aspergillus nidulans↗
PubMed1998

Hematopoietic recovery in cancer patients after transplantation of autologous peripheral blood CD34+ cells or unmanipulated peripheral blood stem and progenitor cells.

BACKGROUND: A study of CD34+ cell selection and transplantation was carried out with particular emphasis on characteristics of short- and long-term hematopoietic recovery. STUDY DESIGN AND METHODS: Peripheral blood stem and progenitor cells (PBPCs) were collected from 32 patients, and 17 CD34+ cell-selection procedures were carried out in 15 of the 32. One patient in whom two procedures failed to provide 1 x 10(6) CD34+ cells per kg was excluded from further analysis. After conditioning, patients received CD34+ cells (n = 10, CD34 group) or unmanipulated (n = 17, PBPC group) PBPCs containing equivalent amounts of CD34+ cells or progenitors. RESULTS: The yield of CD34+ cells was 53 percent (18-100) with a purity of 63 percent (49-82). The CD34+ fraction contained 66 percent of colony-forming units--granulocyte-macrophage (CFU-GM) and 58 percent of CFU of mixed lineages, but only 33 percent of burst-forming units-erythroid (BFU-E) (p < 0.05). Early recovery of neutrophils and reticulocytes was identical in the two groups, although a slight delay in platelet recovery may be seen with CD34+ cell selection. Late hematopoietic reconstitution, up to 1.5 years after transplant, was also similar. The two groups were thus combined for analyses of dose effects. A dose of 40 x 10(4) CFU-GM per kg ensured recovery of neutrophils to a level of 1 x 10(9) per L within 11 days, 15 x 10(4) CFU of mixed lineages per kg was associated with platelet independence within 11 days, and 100 x 10(4) BFU-E per kg predicted red cell independence within 13 days. However, a continuous effect of cell dose well beyond these thresholds was apparent, at least for neutrophil recovery. CONCLUSION: CD34+ cell selection, despite lower efficiency in collecting BFU-E, provides a suitable graft with hematopoietic capacity comparable to that of unmanipulated PBPCs. In both groups, all patients will eventually show hematopoietic recovery of all three lineages with 1 x 10(6) CD34+ cells per kg or 5 x 10(4) CFU-GM per kg, but a dose of 5 x 10(6) CD34+ cells or 40 x 10(4) CFU-GM per kg is critical to ensure rapid recovery.

Antigens, CD34↗
PubMed1998

Diagnostic electrocardiography in epidemiological studies of Chagas' disease: multicenter evaluation of a standardized method.

An electrocardiographic recording method with an associated reading guide, designed for epidemiological studies on Chagas' disease, was tested to assess its diagnostic reproducibility. Six cardiologists from five countries each read 100 electrocardiographic (ECG) tracings, including 30 from chronic chagasic patients, then reread them after an interval of 6 months. The readings were blind, with the tracings numbered randomly for the first reading and renumbered randomly for the second reading. The physicians, all experienced in interpreting ECGs from chagasic patients, followed printed instructions for reading the tracings. Reproducibility of the readings was evaluated using the kappa (kappa) index for concordance. The results showed a high degree of interobserver concordance with respect to the diagnosis of normal vs. abnormal tracings (kappa = 0.66; SE 0.02). While the interpretations of some categories of ECG abnormalities were highly reproducible, others, especially those having a low prevalence, showed lower levels of concordance. Intraobserver concordance was uniformly higher than interobserver concordance. The findings of this study justify the use by specialists of the recording of readings method proposed for epidemiological studies on Chagas' disease, but warrant caution in the interpretation of some categories of electrocardiographic alterations.

Argentina↗
PubMed1997

Acute functional iron deficiency in obese subjects during a very-low-energy all-protein diet.

We examined whether a very-low-energy all-protein diet (VLED) would produce detectable changes in iron as well as in other trace elements. Twenty-five obese patients consumed for 2 wk a VLED containing 70 g protein after a 1-wk period during which total daily energy intake was progressively reduced to 1.26 MJ. Serum iron fell sharply by approximately equal to 50% (P < 0.0001), and despite a small decrease in total-iron-binding capacity, transferrin saturation decreased from 30 +/- 11% to 18 +/- 5% (P < 0.0001). Serum ferritin did not change significantly but serum soluble transferrin receptor (sTfR), an indicator of iron deficiency, increased progressively from 4630 +/- 1110 to 6070 +/- 1390 micrograms/L (P < 0.0001). Changes in sTfR correlated inversely with prior changes in serum iron. Changes in iron metabolism did not translate into changes in erythropoiesis or red cell indexes, but the white blood cell count decreased from 7.3 +/- 1.6 to 6.2 +/- 1.9 x 10(9)/L (P < 0.002). There was no evidence of deficiency for the other trace elements and minerals tested. Daily supplementation with 200 mg Fe in 18 other subjects only partially corrected these observations despite some increase in iron stores. These results indicate that during a 2-wk VLED serum iron is significantly depressed, inducing functional tissue iron deficiency too short in duration to produce alterations in red blood cell indexes. These changes are not mediated by absolute iron deficiency, inflammation, or protein malnutrition but could be related to alterations in the iron storage and release behavior of the reticuloendothelial cell during energy deprivation alone.

Adolescent↗
PubMed1997

In vitro amphotericin B effects on growth, viability and dimorphism of Paracoccidioides brasiliensis: reversal of the treatment.

The in vitro effects of amphotericin B deoxycholate suspension (fungizone) on Paracoccidioides brasiliensis growth, cell viability and transformation were investigated. We also analyzed the protein synthesis patterns of both cellular forms, yeast and mycelium in the presence of AmB. This drug, at 30 micrograms/ml, highly inhibited yeast growth, which could be recovered depending on treatment time, where the most effective reversion was observed after 6 hr of incubation. The yeast cell viability, that had been partially affected by the drug, could also be efficiently recovered after AmB was removed. The effect of AmB on the cellular dimorphism process showed a strong reduction in the mycelium to yeast transformation (80% inhibition compared to the control without the drug). On the other hand, the transformation from yeast to mycelium in the presence of AmB was 50% affected, relative to the control. In contrast to the growth and cell viability experiments, the reversion effects on dimorphism were partial when the drug was removed, even with only 6 hr treatment. The two-dimensional gels of 35S-labeled proteins revealed a strong reduction in the three species of 80, 71 and 56 kDa in yeast and mycelium when treated with AmB.

Amphotericin B↗
PubMed1997

Analysis of chimerism following allogeneic bone marrow transplantation by fluorescent-in-situ hybridization.

Twelve patients (9 males and 3 females) with chronic myelogenous leukemia, underwent CD8+ T cell depleted allogeneic bone marrow transplantation with a sex-mismatched donor. To assess chimerism we performed fluorescent in-situ hybridization for the X and Y chromosome at different time points after BMT. Patient median age was 33 years (range, 27-48); median time to transplant was 28 months (range, 5-87). All patients received thiotepa 10 mg/kg; cyclophosphamide 120 mg/kg and 12.0 Gy of fractionated total body irradiation. CD8+ cells were depleted from the normal donor marrow with anti-CD8 murine monoclonal antibodies and immunomagnetic beads. Bone marrow aspirates were studied at <60, 60-140, 140-300, and >300 days post BMT. Hybridization was done on mononuclear cells and a median of 518 cells were counted per slide with a fluorescent microscope. The median percentage of donor cells was 99.04%, 98.21%, 98.15%, and 99.52% at <60, 60-140, 140-300, and >300 days after BMT. Mixed chimerism was a rare occurrence after CD8 depleted allogeneic BMT and occured only at low levels. Inhibition of repopulation by host hematopoietic cells may be associated with the graft-versus-leukemia effect against CML.

Adult↗
PubMed1997

Measuring the effectiveness of fiber by animal response trials.

Chemical analysis of neutral detergent fiber (NDF) provides a useful description of forages and other feeds. However, use of NDF as the sole measure of the fiber contribution of a feed has proved problematic for two classes of feeds: forages processed into differing physical forms and high fiber by-products. By-products and physically fine forages contribute to the fiber value of dairy rations, but contribute less than long forages do. Therefore, some discount factors must be assigned to these feeds if fiber requirements are to be used in balancing the carbohydrate portion of dairy diets. The effectiveness factors applied to NDF from these feeds provide an improved measure of fiber value. The assumptions and trial designs used to measure the effectiveness of NDF based on any single animal response variable are discussed, and improved approaches are suggested. The use of different response variables to measure physical and overall fiber effectiveness is discussed. Measured effectiveness of a high fiber feed differs when estimated by chewing, by the ratio of acetate to propionate, or by milk fat concentration. In all cases, inclusion of negative control treatments is necessary to measure the effect of removing fiber without introducing a substitute fiber source.

Animal Feed↗
PubMed1997

Regression of advanced refractory ovarian cancer treated with iodine-131-labeled anti-CEA monoclonal antibody.

Advanced chemotherapy-resistant ovarian cancer has a poor prognosis, thus requiring new therapeutic modalities. A complete clinical remission, using two cycles of 131I-labeled murine MN-14 anti-CEA monoclonal antibody (MAb), given intravenously, is reported in a patient with advanced ovarian cancer refractory to paclitaxel (Taxol) therapy. The patient first received radioimmunotherapy with approximately 74 mCi 131I-MN-14 IgG, followed 4 mo later by a similar dose of radiolabeled MAb. A partial remission was seen by CT 1 mo after the first radioimmunotherapy, and a further objective response was documented after the second radioimmunotherapy. CT scans performed 6 and 11 mo after the second radioimmunotherapy showed stable and minimal residual changes. However, a whole-body PET scan with [18F]fluorodeoxyglucose (FDG-PET) was negative in these regions. The CA-125 also decreased to only 13 U/ml, compared to the baseline value of 7700 U/ml. Based on CT, FDG-PET, serum CA-125 and physical exam, the patient was in complete clinical remission for 8 mo when the CA-125 levels rose. CT also showed a new suspicious lesion, presumably a peritoneal implant. No toxicity was seen after the first injection, and only Grade 1 thrombocytopenia and Grade 2 leukopenia developed after the second injection, both reversing within 6 wk. This is a report of a complete clinical remission with radiolabeled anti-CEA antibodies in a patient with chemotherapy-refractive metastatic ovarian cancer.

Aged↗
PubMed1996

Outcome of renal graft recipients with hepatitis C virus infection.

Hepatitis C virus (HCV) is a major cause of posttransplantation chronic liver disease. The aim of this study was to evaluate the prevalence of HCV in renal transplant recipients and to investigate risk and prognostic factors. Of 427 renal transplants carried out between July 1983 and January 1993, we retrospectively studied 66 (15.5%) HBsAg-negative patients with anti-HCV detected by enzyme-linked immunosorbent assay (ELISA) and recombinant immunoblot assay (RIBA). Patient and graft survivals were estimated. Anti-HCV positive patients had more time on hemodialysis and pretransplant blood transfusions (P = 0.0001) than did the seronegative population. In a mean follow-up of 52.3 +/- 27.7 months, 36 patients (54%) had biochemical evidence of liver disease, predominantly with a persistently high pattern of serum alanine aminotransferase (ALT). Pretransplantation ALT elevation was associated (P = 0.004) with chronic liver disease (CLD) in the graft recipient. None of the other variables studied predicted posttransplantation CLD. Liver failure occurred in two (3%) and was the cause of death in one of the patients. Death occurred in eight significantly more aged (P = 0.0001) patients, at 45.5 +/- 28.8 months posttransplant. In 50% of the cases, death was ascribed to sepsis. The biochemical pattern of HCV showed no predictive value for prognosis. The disease had no significant effect on the number of rejections or graft survival. The study revealed lower actuarial survival (P = 0.004) for HCV-positive patients in comparison with the seronegative population.

Adult↗
PubMed1996

[Homocysteinemia as a risk factor for cerebrovascular disorders. The role of age and homocysteine levels].

PURPOSE: To evaluate importance of homocysteinemia as risk factor of thrombotic cerebrovascular disease, in terms of age and homocysteinemia levels. METHODS: A group of patients under 55 years old (n = 35, 21 males) that had suffered a stroke 3 months to 1 year before the study, defined by clinical criteria and the presence of cerebral infarction confirmed by tomography, without history or predisponents to embolic disease. The patients were matched with a group of controls without vascular pathology of a check-up program, in terms of age and sex. Patients and controls with history of alcoholism, signs or laboratory of renal or hepatic insufficiency or with history of recent ingestion of vitamins of the group B were excluded since these conditions could influence homocysteinemia levels. We measured to patients and controls the plasmatic basal homocysteinemia and homocysteinemia 6 hours after methionine overload of 0.1 g/Kg body weigh. We estimated case-control odds ratio of hyperhomocysteinemia globally and by age groups, and odd ratio of different levels of homocysteinemia. RESULTS AND CONCLUSIONS: Hyperhomocysteinemia case-control global odds ratio was 5.7, being higher in younger patients (8.8 below and 3.5 after the age of 45 years). Homocysteinemia as a risk factor of cerebrovascular disease presented as a continuous effect: low homocysteinemia was protective, and the higher the homocysteinemia, the higher the cerebrovascular risk proved to be. In these circumstances, heterozygozyty of cysthationine beta synthase deficiency, refered as the more important cause of hyperhomocysteinemia, cannot account for most of the cases of hyperhomocysteinemia.

Adult↗
PubMed1996

Radioimmunotherapy of medullary thyroid cancer with iodine-131-labeled anti-CEA antibodies.

UNLABELLED: This study evaluates the pharmacokinetics, dosimetry, toxicity and therapeutic potential of radiolabeled NP-4 and MN-14 anti-CEA antibodies in medullary thyroid cancer (MTC). METHODS: Eighteen patients with advanced MTC entered exploratory clinical studies with therapeutic doses of 131I-labeled NP-4 and MN-14 murine monoclonal antibodies (MAbs) reactive with carcinoembryonic antigen (CEA). Doses administered ranged from 46 mCi for 131I-MN-14 lgG to 195 mCi for 131I-MN-14 F(ab)2 in patients negative for human anti-mouse antibodies (HAMA). RESULTS: The radioconjugate blood half-life (T1/2) for the whole lgG was 42.5+/-5.0 hr compared to 18.8+/- 4.1 hr for the bivalent fragments. Tumor doses of 17.5+/-11.0 and 11.4+/-6.3 cGy/mCi were estimated for 131I-MN-14 lgG and F(ab)2, respectively. Tumor/red marrow dose ratios exceeded 3:1 for most lesions. Red marrow doses of up to 350 cGy generally could be delivered with < grade 4 toxicity. Seven of 14 evaluable patients showed evidence of anti-tumor effects lasting up to 26 months, based on physical exam, tumor markers or computed tomography. CONCLUSION: This study demonstrates that anti-CEA MAbs may be suitable for radioimmunotherapy of metastatic or recurrent MTC.

Adolescent↗
PubMed1995

Characterization of Paracoccidioides brasiliensis isolates by random amplified polymorphic DNA analysis.

We initially used 25 different random primers in order to test their ability to generate random amplified polymorphic DNA fragments from the dimorphic human pathogenic fungus Paracoccidioides brasiliensis. From the tested primers we chose five to distinguish between seven isolates of this microorganism. The DNA amplification patterns allowed clear differentiation of the seven isolates into two distinct groups with only 35% genomic identity. One of these groups contained two subgroups with 81% genetic similarity. The random amplified polymorphic DNA analysis method proved to be a good tool for analyzing and comparing different genomes of P. brasiliensis isolates.

Base Sequence↗