Biomedical subjects

M Barboza

Publications and source records attributed to M Barboza.

7 recordsLinked to original sources

PubMed2005

Novel cysteine proteinase in Trypanosoma cruzi metacyclogenesis.

With the aim to study proteinases released to the culture medium during Trypanosoma cruzi metacyclogenesis, the presence of cysteine proteinases (CPs) was analysed in culture supernatants obtained throughout the differentiation induced by stimulation of epimastigotes with Triatoma infestans hindgut homogenate. In SDS-gelatin containing gels, an important endopeptidase activity with apparent molecular weight range between 97 and 116 kDa was encountered at pH 6, which was abolished by the specific cysteine proteinase inhibitor E-64 and TLCK, but not by pepstatin, 1,10 phenantroline or PMSF. This novel CP, named TcCPmet, showed affinity to cystatin-Sepharose, denoting its thiol-proteinase character as well as to ConA-Sepharose, indicating it contains N-linked oligosaccharides. However, it presented a different elution pattern on ConA-Sepharose than cruzipain and, in addition, it was not recognized by anti-cruzipain serum, facts that strongly suggest the different nature of both CPs. Moroever, evidence is presented indicating that TcCPmet was able to hydrolyse the same chromogenic peptides as cruzipain at optimal alkaline pH values, although with a different order of effectiveness. Our results indicate the presence of a novel CP secreted by metacyclic trypomastigotes and reinforces the important role of these enzymes in metacyclogenesis.

Animals↗

PubMed2002

Continuous cephalosporin C purification: dynamic modelling and parameter validation.

A mathematical kinetic model for the adsorption and desorption of cephalosporin C on Amberlite XAD-2 resin is proposed. The model can represent Langmuir, Freundlich or linear isotherms at equilibrium. The intrinsic kinetic parameters and adsorption isotherms as well as physical parameters such as the effective diffusivity and the external mass transfer coefficient were obtained at different temperatures and ethanol concentrations. An unfavourable cephalosporin C adsorption occurred when ethanol was present in the solution. It has been shown that at 25 degrees C the ethanol, at concentrations from 1.5% to 2.5%, decreases the cephalosporin C adsorption. However, this behaviour was not observed at 10 degrees C. The kinetic model fitted the experimental data well under different conditions. The model was validated in a continuous process of cephalosporin C purification using the same resin. The model with the validated parameters is able to predict the behaviour of the reactor system. The continuous process is composed of two stirred tank reactors with adsorber recycle. The adsorption occurs in the first stage, and elution of the product takes place in the second stage with ethanol as eluent. The dynamic behaviour of the process was described using the following parameters: hydraulic residence time for the first (theta(h1)) and second stage (theta(h2)), solid residence time (theta(s)), initial concentration of CPC (C(0)), inlet ethanol concentration (C(ET0)) and kinetics parameters.

Journal Article↗

PubMed2001

Kinetic studies of clavulanic acid recovery by ion exchange chromatography.

Clavulanic acid (CA) is a beta-lactamase inhibitor produced by strains of Streptomyces clavuligerus. Nowadays, the combination of CA with amoxycillin is the most successful example of the use of a beta-lactam antibiotic sensitive to beta-lactamases together with an inhibitor of these enzymes. Clavulanic acid is purified from fermentation broth by a series of steps consisting mainly of two-phase separation processes such as liquid-liquid extraction, adsorption or ion-exchange chromatography, among others. Amberlite IRA 400, a strong anion-exchange resin, has a very high adsorption capacity for CA (Mayer et al. 1997). This resin can be pre-treated with NaCl (chloride cycle), to remove selectively only those anions, which are able to displace chloride from the resin or with NaOH (hydroxyl cycle), to remove all species of anions. In order to decide the best operating conditions for CA recovery by ion-exchange resins and then to construct a model of this separation process, batch experiments were conducted using Amberlite IRA 400 in the chloride cycle. These runs were carried out in a 200 ml stirred tank, at two different initial solution pH, 6.2 and 4.0; the temperature was maintained at 10 degrees C and 20 degrees C during adsorption and 30 degrees C during the desorption step. It was possible, on the basis of these batch results, to model the separation process, including the adsorption kinetics, equilibrium data and mass transfer limitations.

Adsorption↗

PubMed2001

Antibodies recognizing CD24 LAP epitope on human T cells enhance CD28 and IL-2 T cell proliferation.

Membrane expression of the CD24 molecule on activated T lymphocytes is not elucidated fully. We previously described the intracellular and cell-surface expression of the CD24 sialic acid-dependent epitope(s) on phytohemagglutinin-activated peripheral blood mononuclear cells. However, the CD24 core protein was not detected previously on human T cells. This study reinvestigated the expression and role of CD24 in T cell subsets. We analyzed binding of anti-CD24 monoclonal antibodies (mAbs) to sialic and leucine-alanine-proline (LAP) epitopes in resting and activated, normal T lymphocytes. CD24 LAP and CD24 sialic epitopes were detected on activated CD4- and CD8-positive cells. Although expression of CD24 sialic epitopes remained stably expressed in interleukin (IL)-2-dependent cultures, T cell expression of the LAP epitope was transient. Anti-LAP antibodies strongly enhanced the response of T cells to a combination of anti-CD3/CD28 mAbs and enhanced proliferative response induced by recombinant IL-2. We found similarities in the tissue distribution and function of the human CD24 LAP molecule and the murine, heat-stable antigen, which suggests that CD24 might function as a signaling molecule on human T cells.

Adjuvants, Immunologic↗

PubMed1999

Mechanisms and impact of enteric infections.

The increased recognition of both old and new enteric pathogens and their potential impact requires an improved understanding of pathogenesis and effective interventions. While the overwhelming mortality (> 3 million children per year) due to diarrheal diseases is well-recognized, the potential long-term impacts of enteric infections and early childhood diarrhea morbidity are just beginning to be appreciated. Furthermore, several enteric infections are now being recognized as causes of growth shortfalls with or without diarrhea; i.e., malnutrition may be one of the greatest yet of the "emerging infectious diseases." The increased appreciation of this extended impact calls for further quantification and improved understanding of the deranged physiology. In particular, persistent diarrheal illnesses exhibit common themes of blunted villi, disruption of intestinal barrier function and varying degrees of sub-mucosal inflammation for which lactulose/mannitol permeability and fecal lactoferrin provide respective quantification. Finally, such improved understanding will allow targeted interventions among those most vulnerable, which will enable further documentation of cost effectiveness and the potential for improved human development which is critical to reducing the widening disparity and population overgrowth which increasingly threaten our global security.

Animals↗

PubMed1998

Interactions of dendritic cells with fibronectin and endothelial cells.

We studied the phenotypic characteristics of spontaneously migrated skin dendritic cells (sDC) and monocyte-derived dendritic cells (moDC), generated under different culture conditions, and their interactions with fibronectin (FN) and endothelial cells. Monocyte-derived dendritic cells were obtained after culturing monocytes with granulocyte-macrophage colony-stimulating factor (GM-CSF) (800 U/ml) and interleukin-4 (IL-4) (500 U/ml) with either 10% fetal bovine serum (FBS) or 10% allogeneic human serum (HS). Regardless of the type of serum used, the majority of moDC expressed human leucocyte antigen-DR (HLA-DR) and CD86. On day 5 of incubation, 20-67% of moDC cultured in the presence of HS (HS-moDC) expressed CD1a, b and c versus 94-97% when cultured in the presence of FBS (FBS-moDC). DC showed a differential gradient of adhesion to FN: FBS-moDC>HS-moDC>sDC approximately monocytes. Both FBS-moDC and HS-moDC were strongly positive for CD49e (alpha5-integrin) and CD29 (beta1-integrin) but negative for CD49d (alpha4-integrin). A monoclonal antibody (mAb) against CD49e blocked the adhesion of both types of moDC to FN. Although both FBS-moDC and HS-moDC attached to endothelium (a 76% and 63% increase, respectively), only HS-moDC were able to migrate through non-activated endothelium. Overall, these results suggest that spontaneously migrated sDC are less adherent to FN than moDC, that HS and FBS induce differences in CD1 expression, that HS-moDC are less adhesive to FN and endothelial cells but more motile than FBS-moDC, and that alpha5beta1-integrin is the molecule involved in moDC adhesion to FN.

Animals↗

PubMed1995

Pharmacological study of edema induced by venom of the snake Bothrops asper (terciopelo) in mice.

The effect of several drugs on the edema-forming activity of Bothrops asper venom was studied plethysmographically using the mouse foot pad assay. Bothrops asper venom induced a dose-dependent edema which developed rapidly and peaked 1 hr after envenomation. Incubation of venom with EDTA before injection resulted in a significant reduction of edema. In addition, pretreatment with prazosin, indomethacin, dexamethasone, yohimbine and mepacrine resulted in a significant reduction in edema-forming activity. However, no inhibitory effect was observed when mice were pretreated with verapamil, nordihydroguaiaretic acid, pyrilamine, cimetidine and propranolol. When drugs were administered after venom injection, only prazosin and indomethacin were effective in reducing edema. These results suggest that B. asper venom-induced edema in the mouse foot pad model is mediated, at least partially, by metalloproteinases, phospholipase A2, eicosanoid products and activation of alpha 1 and alpha 2 adrenergic receptors.

Animals↗