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Biomedical subjects

A Benito

Publications and source records attributed to A Benito.

At least 73 records · Page 4Linked to original sources
PubMed1998

Analysis of engraftment kinetics in pediatric patients undergoing autologous PBPC transplantation.

We sought to analyze factors that affect the engraftment kinetics following autotransplantation with PBPC mobilized by filgrastim (G-CSF). Forty-six consecutive pediatric patients with hematologic malignancies (n = 23) or solid tumors (n = 23) underwent autologous PBPC transplantation after myeloablative therapy. PBPC were mobilized using G-CSF alone. All patients received G-CSF after PBPC infusion. Factors potentially influencing the neutrophil and platelet engraftment were examined using univariate and multivariate analysis. All patients experienced rapid hematopoietic recovery, with a median of 9 days (range 7-15) to achieve a neutrophil count of 0.5 x 10(9)/L and a median of 15 days (range 9-37) to achieve a platelet count of 20 x 10(9)/L. The most important predictive factor of both platelet (p = 0.002) and neutrophil (p = 0.0001) recovery was the number of CD34+ cells infused. Patients receiving > or =5 x 10(6)/kg CD34+ cells had a more rapid hematopoietic recovery (p < 0.001) than those receiving a lower cell dose. The CD34+ cell dose is the most important predictive factor for engraftment kinetics after PBPC transplantation. Although a minimal CD34+ cell dose could not be defined, a dose > or =5 x 10(6)/kg CD34+ cells may be optimal to ensure rapid neutrophil and platelet recovery.

Adolescent↗
PubMed1998

Peripheral blood progenitor cell collection by large-volume leukapheresis in low-weight children.

Large-volume leukapheresis (LVL), defined as the processing of at least three blood volumes in a single session for peripheral blood progenitor cell (PBPC) collection, was performed in 32 small children weighing < or = 25 kg, aged 10 months to 8 years, with a variety of malignancies. Harvesting of PBPC was started after 4 days of cytokine (G-CSF, 12 micrograms/kg s.c.) alone. Procedures were performed using a continuous flow blood cell separator (COBE Spectra). The automated program of lymphocytapheresis was modified to achieve a collection rate of 0.9 ml/min. The extracorporeal line was primed with a unit of a packed red blood cells before the procedure. Acid citrate dextrose (ACD) was used as anticoagulant with an ACD inlet ratio of 1:14 and an ACD infusion rate of 1.1 ml/min/L of total blood volume. The inlet flow ranged between 6 and 35 ml/min (median 20 ml/min). A total of 37 apheresis procedures were performed (median 1, range 1-3). In 84% of patients, a single apheresis yields the minimum number of PBPC cells required for transplantation. No consistent side effects were observed, and LVL was well tolerated by children. A median of 7.7 x 10(8) kg MNC, 5.4 x 10(6)/kg CD34+, and 6.2 x 10(4)/kg CFU-GM per apheresis were harvested. Patients with neuroblastoma had a significantly lower yield than other patients. To date, 27 patients have been transplanted after myeloablative treatment, and rapid and sustained engraftment was achieved in all cases. The number of CD34+ cells infused was highly correlated with engraftment kinetics. LVL can be safely and easily performed in small children, allowing adequate PBPC collection for transplantation with rapid hematologic recovery.

Blood Specimen Collection↗
PubMed1998

Biosensor characterization of antigenic site A of foot-and-mouth disease virus presented in different vector systems.

The region 141-160 of the VP1 protein of foot-and-mouth disease virus known as site A is an immunodominant region that has been extensively studied for the purpose of developing a synthetic vaccine. In the present study, site A of foot-and-mouth disease virus was inserted in three different loops of the maltose-binding protein and its antigenicity was compared with site A presented as a conjugated synthetic peptide or inserted in beta-galactosidase. The affinity of antibodies elicited against the site A synthetic peptide was also compared with that of antibodies raised against the site A inserted within the two carrier proteins. Using biosensor technology it was possible to estimate the concentration of site A antibodies present in the various antisera and to show that site A fused to maltose-binding protein was a slightly better mimic of the epitope present in the virus particle than the synthetic peptide or the beta-galactosidase recombinant construct.

Animals↗
PubMed1998

Pathogenesis of polycythemia vera.

BACKGROUND AND OBJECTIVE: Polycythemia vera (PV) is an acquired clonal myeloproliferative disorder characterized by increased production of mature red cells. We still lack a molecular target responsible for this disorder; however, recent investigations have focused on a number of molecules involved in signal transduction pathways mediated by erythropoietin (Epo) and other growth factors. Here we review the implication of these molecules in the pathogenesis of PV. INFORMATION SOURCES: The material reviewed in this work includes articles published in journals covered by Medline. We also include data obtained in our laboratory regarding to the significance of apoptosis inhibitory proteins in erythroid development. STATE OF THE ART AND PERSPECTIVES: Overproduction of erythroid cells in PV is particular in that it occurs in the absence of a recognizable physiologic stimulus, since circulating serum levels of Epo are normal or lower than normal. Genetic analysis as well as in vitro studies, have established an essential role for Epo in the survival and maturation of committed erythroid progenitors. Epo initiates its cellular response by binding to the Epo receptor (EpoR) expressed on the surface of immature erythroblasts. Following ligand binding, EpoR is known to activate a cytoplasmic protein tyrosine kinase, Jak2 which triggers a signal transduction cascade that leads to the development of early erythroid progenitors into mature erythroblast cells. Although the mechanism underlying the increased erythroid production in PV is not well understood, a number of causes have recently came for which may provide insights not only for the pathogenesis of PV but also for a fundamental biological process: the mechanism whereby a multipotential stem cell gives rise to a particular cell lineage.

Animals↗
PubMed1998

Peripheral blood progenitor cells for autologous transplant in children.

Autologous peripheral blood progenitor cell transplantation has become an accepted procedure to support high dose chemotherapy in adults and children with cancer. The use of hematopoietic growth factors alone for mobilization of PBSC avoids the potential side effects of myelotoxic regimens and is as effective in reconstituting hematopoiesis as other mobilization methods. Many problems associated with apheresis procedures arise when PBPCs are harvested in small children. Large-volume-leukapheresis using a continuous flow blood cell separator allows us the collection of peripheral blood stem cells in children, even in the small ones. The speed of hematological recovery highly correlates with the number of CD34+ infused cells. We consider that a CD34+ cell dose of 5.0 x 10(6)/kg may be sufficient to ensure a rapid neutrophil and platelet recovery in pediatric patients mobilized by G-CSF.

Antigens, CD34↗
PubMed1998

Magnetic resonance imaging in a patient with a dual-chamber pacemaker.

The presence of an implanted cardiac pacemaker has been considered an absolute contraindication for magnetic resonance imaging due to the interactions between the pulse generators and the magnetic and radiofrequency fields generated by the magnetic resonance unit. We describe the case of a patient with a dual-chamber pacemaker who underwent two magnetic resonance imaging examinations of the head without any sequelae. Both procedures were performed with a 1 Tesla unit, with the pacemaker programmed to the AOO mode. The only interference observed was activation of the reed switch -probably due to the static magnetic field- resulting in asynchronous atrial pacing at the magnet rate. Although the general policy of never exposing a patient with a pacemaker to magnetic resonance imaging should not be revised, we think that if the testing is considered essential, it could be safely used in certain carefully selected patients.

Adenoma↗
PubMed1998

[Congenital chylothorax].

OBJECTIVE: The aim of this study was to study the prenatal diagnosis, clinical manifestations and karyotype results in congenital chylothorax. PATIENTS AND METHODS: A retrospective survey of a 20 year period was carried out. The prenatal diagnosis, maneuvers following delivery, malformations and clinical outcome were studied. RESULTS: We found 10 cases of congenital chylothorax. Four were diagnosed by prenatal ultrasound with pleural effusion and no other signs of hydrops and six were diagnosed postnatally. Of the later, five had respiratory distress and one was diagnosed by radiological procedures. In all 10 cases, postnatal thoracocentesis was performed for diagnosis and therapy, five infants required mechanical ventilation and four parenteral nutrition. One patient died 72 hours after birth and three within 24 hours of birth. The clinical outcome of the rest was successful and were placed on a medium-chain triglyceride formula that was given orally. Of the eight karyotypes studied, six trisomy 21 were found. CONCLUSIONS: The prenatal diagnosis of pleural effusion permits prompt recognition of congenital chylothorax and allow for appropriate treatment upon birth. Medical therapy including pleural drainage and total parenteral nutrition and medium-chain triglyceride formula for oral feedings is successful in the majority of cases. Down's syndrome should be considered in fetuses or newborns with pleural effusion.

Chylothorax↗
PubMed1997

The expression of Bcl-x is downregulated during differentiation of human hematopoietic progenitor cells along the granulocyte but not the monocyte/macrophage lineage.

Expression of the apoptosis inhibitory protein Bcl-x was studied in CD34+ hematopoietic precursor cells and in the promyelocytic leukemia cell line HL-60. The enriched population of CD34+ cells (more than 95%) was cultured in the presence of stem cell factor, interleukin-3 (IL-3), IL-6, and either granulocyte colony-stimulating factor or macrophage colony-stimulating factor to achieve granulocyte or monocyte/macrophage differentiation, respectively. The expression of Bcl-x increased in the early stages of both differentiation pathways. However, by day 21 of culture mature granulocytes were Bcl-x-negative, whereas monocytes/macrophages either maintained or increased the expression of Bcl-x. The pattern of Bcl-x expression in the differentiated CD34+ cells was similar to that observed in HL-60 cells differentiated along the granulocyte lineage (induced by incubation with retinoic acid), or along the monocyte/macrophage lineage (induced by incubation with phorbol diester). The bcl-x transcript predominant in HL-60 and CD34+ cells differentiated into monocytes/macrophages was bcl-xL. Although little is yet known regarding the functional significance of Bcl-x within the granulomonocytic compartment, marked changes in the pattern of its expression, as observed during granulomonocytic differentiation of HL-60 and CD34+ cells, are likely to alter the life span of mature granulocytes and monocytes/macrophages.

Antigens, CD↗
PubMed1997

Selective induction of apoptosis in cancer cells by the ether lipid ET-18-OCH3 (Edelfosine): molecular structure requirements, cellular uptake, and protection by Bcl-2 and Bcl-X(L).

The ether lipid 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3; Edelfosine) has been shown to be a rapid inducer of apoptosis in human leukemic cells and has been considered as a promising drug in cancer treatment. Here we have found that ET-18-OCH3 induced apoptosis not only in human tumor cell lines but also in primary tumor cell cultures from cancer patients. Human leukemic cells were highly sensitive to ET-18-OCH3, whereas normal cells remained unaffected. Among the distinct modifications of the ET-18-OCH3 molecule assayed, we found that substitutions in positions sn-2 and sn-3 of the glycerol backbone resulted in a complete loss of its capacity to induce apoptosis, highlighting the importance of the molecular structure of ET-18-OCH3 in its apoptotic effect. Induction of apoptosis by ET-18-OCH3 was very well correlated with the uptake of this ether lipid. ET-18-OCH3-resistant 3T3 fibroblasts became sensitive and incorporated significant amounts of the ether lipid following transformation with the SV40 virus. ET-18-OCH3-induced apoptosis as well as ET-18-OCH3 uptake were not mediated through binding of the ether lipid to the platelet-activating factor receptor. Overexpression of bcl-2 or bcl-xL by gene transfer in the human erythroleukemic HEL cells abrogated apoptosis induced by ET-18-OCH3. ET-18-OCH3 did not affect the expression of bcl-2, bcl-xL, or bax in HEL and HL-60 human leukemic cells but induced expression of c-myc, an important effector of apoptosis in several systems. Thus, ET-18-OCH3 behaves as a potent and highly selective antitumor drug able to induce an apoptotic pathway of cell death in tumor cells but not in nonmalignant cells.

Albumins↗
PubMed1997

Non-tunneled catheters for the collection and transplantation of peripheral blood stem cells in children.

We analyzed the use of non-tunneled (polyurethane, double lumen) central venous catheters (CVCs) for the collection, conditioning, transplantation and immediate post-transplantation periods in 56 children with various malignant diseases. A total of 71 leukaphereses were performed, with a mean of 1.2 apheresis per patient, following administration of granulocyte colony-stimulating factor (G-CSF) using a continuous flow blood cell separator (Cobe Spectra). The mean TBV (total blood volume) processed was 4.5 +/- 1.2 s.d. (range 2.4-7). The mean flow rate was 30.6 ml/min and the duration of a single apheresis was 327 +/- 84 s.d. (range 175-511 min). The mean purities and efficacies of collections were 77.38 +/- s.d. (range 42-100) and 42.78 +/- s.d. (range 24-80), respectively. The mean numbers of mononuclear cells (MNC) and CD34+ cells collected were 9.3 +/- 6.9 s.d. x 10(8)/kg (range 2-49) and 6.2 +/- 7.2 s.d. x 10(6)/kg (range 1-42), respectively. We observed the following complications during catheter insertion for collection: pneumothorax (1.7%), mechanical dysfunction (3.5%) that resolved with thrombolytic therapy. Complications during conditioning, transplantation and immediate post-transplantation periods were entry site infection in five patients (8.92%), catheter-related infection in two (3.57%) and catheter-related sepsis in three (5.35%). Our results indicate that the collection of PBSC with non-tunneled catheters is safe, effective and dis associated with a low incidence of complications.

Adolescent↗
PubMed1997

Apoptosis of human myeloid leukemia cells induced by an inhibitor of protein phosphatases (okadaic acid) is prevented by Bcl-2 and Bcl-X(L).

Okadaic acid, an inhibitor of serine/threonine protein phosphatases 1 and 2A has been shown to cause mitotic arrest and cell death of HL-60 and K562 cells. HL-60 cells express Bcl-2 and little or no Bcl-X(L), while K562 expresses Bcl-X(L) but not Bcl-2. Since phosphorylation/dephosphorylation reactions have been suggested to be involved in the regulation of Bcl-2, we planned to investigate whether the expression of Bcl-2, Bcl-X(L) and Bax, a protein that antagonizes the antiapoptotic function of Bcl-2, are regulated in myeloid leukemia cell lines (K562, KU812 and HL-60) treated with okadaic acid. Our results indicate that exposure of all three leukemic cell lines to nanomolar concentrations of okadaic acid causes a loss of viability by activation of an apoptotic process accompanied by a marked decrease in the expression of Bcl-2, Bcl-X(L) and Bax at both mRNA and protein level, but not of c-fos, vimentin and epsilon-globin, ruling out a non-specific effect of okadaic acid. Furthermore, constitutive expression of either Bcl-X(L) or Bcl-2 by gene transfer inhibited apoptosis triggered by okadaic acid in K562 cells. Thus, we suggest that protein phosphatases may be involved in maintaining the expression of bcl-2 family genes as part of the survival machinery of the cell.

Apoptosis↗
PubMed1997

Allogeneic peripheral blood progenitor cell (PBPC) transplantation in children with haematological malignancies.

We report on five children with haematological malignancies who underwent allogeneic peripheral blood progenitor cell (PBPC) transplantation. PBPC were harvested from HLA-identical sibling donors after G-CSF (10 micrograms/kg/d s.c.) mobilization. Aphereses were carried out on day 5 after G-CSF using a Cobe Spectra blood cell separator. All PBPC allografts were cryopreserved before transplantation. The median of CD34+ cells and CD3+ cells infused were 14.1 x 10(6)/kg recipient body weight (range 4.92-22.3) and 2.40 x 10(8)/kg recipient body weight (range 0.54 4.82), respectively. Engraftment occurred in all cases. The median time to a neutrophil count > 0.5 x 10(9)/l and a platelet count > 20 x 10(9)/l were 15 and 14 d, respectively. The incidence of severe acute graft-versus-host disease was 20%. These data suggest that allogeneic PBPC transplantation might be an alternative to bone marrow transplantation in children.

Child↗
PubMed1996

A recombinant, arginine-glycine-aspartic acid (RGD) motif from foot-and-mouth disease virus binds mammalian cells through vitronectin and, to a lower extent, fibronectin receptors.

The cell-binding abilities of a recombinant, RGD-containing peptide from foot-and-mouth disease virus (FMDV) have been characterized in HeLa and BHK cells. This peptide represents the aa sequence of the solvent-exposed G-H loop of protein VP1 which is involved in cell recognition and infection. The efficiency of the viral motif in promoting cell attachment and spreading is comparable to that shown by fibronectin or vitronectin. Cell binding is inhibited by a monoclonal antibody directed against a viral, RGD-involving B-cell epitope and also by sera against vitronectin (alpha V beta 3/beta 5) and fibronectin (alpha 5 beta 1) receptors. In addition, a synthetic RGD peptide, which is a ligand for both integrins, prevents the cell binding mediated by the FMDV domain. These data demonstrate that the FMDV RGD motif is a potent ligand for cell-receptor integrins and sufficient to promote cell attachment to susceptible cells mainly through the vitronectin receptor.

Amino Acid Sequence↗
PubMed1996

Converging antigenic structure of a recombinant viral peptide displayed on different frameworks of carrier proteins.

A peptide reproducing the G-H loop amino acid sequence of foot-and-mouth disease virus VP1 protein was fused to the solvent-exposed C-terminus of the bacteriophage P22 tailspike protein [Carbonell and Villaverde (1996) Gene, in press], a homotrimeric polypeptide with a strong beta-helical structure. This fusion does not interfere with the biological activities of the phage tail. The antigenic profile of the complex antigenic site A within the G-H loop has been determined by competitive ELISA with a panel of monoclonal antibodies directed against different overlapping B-cell epitopes. The antigenic data have been compared with those obtained with a set of 12 chimeric beta-galactosidases displaying the G-H loop on different exposed regions. A high coincidence has been evidenced between the antigenicity of the viral peptide fused to the phage protein and that of some peptides inserted in an exposed loop of the activating interface of beta-galactosidase. This indicates that completely different structural frameworks of carrier proteins can provide similar constraints that allow the recombinant peptide to successfully mimic the antigenicity, and probably conformational features, of the natural peptide on the virion surface.

Antibodies, Monoclonal↗
PubMed1996

Erythropoietin can promote erythroid progenitor survival by repressing apoptosis through Bcl-XL and Bcl-2.

Erythropoietin (Epo), the hormone that is the principal regulator of red blood cell production, interacts with high-affinity receptors on the surface of erythroid progenitor cells and maintains their survival. Epo has been shown to promote cell viability by repressing apoptosis; however, the molecular mechanism involved is unclear. In the present studies we have examined whether Epo acts as a survival factor through the regulation of the bcl-2 family of apoptosis-regulatory genes. We addressed this issue in HCD-57, a murine erythroid progenitor cell line that requires Epo for proliferation and survival. When HCD-57 cells were cultured in the absence of Epo, Bcl-2 and Bcl-XL but not Bax were downregulated, and the cells underwent apoptotic cell death. HCD-57 cells infected with a retroviral vector encoding human Bcl-XL or Bcl-2 rapidly stopped proliferating but remained viable in the absence of Epo. Furthermore, endogenous levels of bcl-2 and bcl-XL were downregulated after Epo withdrawal in HCD-57 cells that remained viable through ectopic expression of human Bcl-XL, further indicating that Epo specifically maintains the expression of bcl-2 and bcl-XL. We also show that HCD-57 rescued from apoptosis by ectopic expression of Bcl-XL can undergo erythroid differentiation in the absence of Epo, demonstrating that a survival signal but not Epo itself is necessary for erythroid differentiation of HCD-57 progenitor cells. Thus, we propose a model whereby Epo functions as a survival factor by repressing apoptosis through Bcl-XL and Bcl-2 during proliferation and differentiation of erythroid progenitors.

Animals↗