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Biomedical subjects

A Benito

Publications and source records attributed to A Benito.

At least 55 records · Page 3Linked to original sources
PubMed1999

p53 expression in locally advanced pharyngeal squamous cell carcinoma.

BACKGROUND: Prognosis for advanced head and neck squamous cell carcinoma remains poor despite advances in treatment, although a small number of patients may benefit from induction therapy leading to increased local control. Mutations of the p53 gene, which are present in a considerable percentage of head and neck squamous cell carcinomas, have been associated with poor response to chemotherapy. The role of p53 protein overexpression (which is associated with p53 gene mutations) in predicting the response to chemotherapeutic agents and survival rates is not clear. OBJECTIVE: To determine the association of p53 expression with chemotherapy response rates and disease-free survival rates in 62 patients with locally advanced pharyngeal cancer treated with induction cisplatin-5-fluorouracil chemotherapy between 1983 and 1995. DESIGN: Historical cohort. Archival tissue from biopsies done before chemotherapy was immunohistochemically stained for the p53 tumor suppressor gene (clone D0-7; DAKO Corp, Glostrup, Denmark). RESULTS: Positive staining for p53 occurred in 45 (73%) of 62 cases, with the percentage of reactive cells ranging from 35% to 98%. Chemotherapy response rates were higher in the p53-negative group (15/17 [88%]) compared with the p53-positive group (27/45 [60%]) (P =.07). The risk of recurrence was lower in the p53-negative group compared with the p53-positive group at 2, 3, and 5 years after treatment (P = .03, P = .01, and P = .007, respectively). The median relapse-free survival rates of patients in the p53-negative group was 16 months, whereas those with p53 protein expression demonstrated a median relapse-free survival time of 9 months (P = .07). In multivariate analyses, the only independent factor of relapse-free survival rates was age older than 70 years. CONCLUSION: The present study shows a trend favoring p53 overexpression as a predictive and prognostic factor in locally advanced pharyngeal cancer treated with induction chemotherapy.

Adult↗
PubMed1999

Production of engineered human pancreatic ribonucleases, solving expression and purification problems, and enhancing thermostability.

Human pancreatic ribonuclease, the homolog of bovine pancreatic ribonuclease, has a significant therapeutic potential. Its study has been hindered by the difficulty of obtaining the enzyme in a pure and homogeneous form, either from human source or using heterologous expression. Engineering of different variants of human pancreatic ribonuclease has allowed us to study and overcome some problems encountered during its heterologous production in an Escherichia coli system and its purification from inclusion bodies. The 5'-end region of the mRNA that encodes the enzyme is critical for obtaining high expression levels. The results also suggest the importance of the proline 50 residue in the recovery yields of human pancreatic ribonuclease. All the variants produced are pure and homogeneous. Their homogeneity has been demonstrated by cation-exchange and reversed-phase chromatography and by mass spectrometry analysis. Moreover, enhancement of human pancreatic ribonuclease thermal stability is observed when residues R4, K6, Q9, D16, and S17 are changed to the corresponding residues of bovine seminal ribonuclease.

Amino Acid Sequence↗
PubMed1999

Squamous cell carcinoma arising in a cutaneous epidermal cyst: case report and literature review.

Although cutaneous epidermal (infundibular) cysts are extremely common lesions, neoplastic transformation of their epithelium is quite rare. We describe a patient with a squamous cell carcinoma arising in the wall of an otherwise conventional epidermal cyst. In addition, we review the literature concluding that most of the previously reported cases may not correspond to this rare occurrence.

Adult↗
PubMed1999

Variation in resistance of natural isolates of Escherichia coli O157 to high hydrostatic pressure, mild heat, and other stresses.

Strains of Escherichia coli O157 isolated from patients with clinical cases of food-borne illness and other sources exhibited wide differences in resistance to high hydrostatic pressure. The most pressure-resistant strains were also more resistant to mild heat than other strains. Strain C9490, a representative pressure-resistant strain, was also more resistant to acid, oxidative, and osmotic stresses than the pressure-sensitive strain NCTC 12079. Most of these differences in resistance were observed only in stationary-phase cells, the only exception being acid resistance, where differences were also apparent in the exponential phase. Membrane damage in pressure-treated cells was revealed by increased uptake of the fluorescent dyes ethidium bromide and propidium iodide. When strains were exposed to the same pressure for different lengths of time, the pressure-sensitive strains took up stain sooner than the more resistant strain, which suggested that the differences in resistance may be related to susceptibility to membrane damage. Our results emphasize the importance of including stress-resistant strains of E. coli O157 when the efficacy of a novel or mild food preservation treatment is tested.

Cell Membrane↗
PubMed1999

Usefulness of seminested multiplex PCR in surveillance of imported malaria in Spain.

The use of a new PCR-based method for the diagnosis of malaria in the Spanish Malaria Reference Laboratory has promoted an increase in confirmed cases of malaria. From August 1997 to July 1998, a total of 192 whole-blood samples and 71 serum samples from 168 patients were received from the hospitals of the Spanish National Health System. Most of the patients came from west-central African countries (85%). This molecular method showed more sensitivity and specificity than microscopy, detecting 12.4% more positive samples than microscopy and 13% of mixed infections undetectable by Giemsa stain. Plasmodium falciparum was the main species detected, with 68% of the total positive malaria cases, followed by Plasmodium malariae (29%), Plasmodium vivax (14%), and Plasmodium ovale (7%), including mixed infections in all cases. This report consists of the first wide, centralized survey of malaria surveillance in Spain. The reference laboratory conducted the analysis of all imported cases in order to detect trends in acquisition. The use of a seminested multiplex PCR permitted confirmation of the origins of the infections and the Plasmodium species involved and confirmation of the effectiveness of drug treatments. This PCR also allowed the detection of the presence in Spain of primaquine-tolerant P. vivax strains from west-central Africa, as well as the detection of a P. falciparum infection induced by transfusion.

Child, Preschool↗
PubMed1999

Semi-nested, multiplex polymerase chain reaction for detection of human malaria parasites and evidence of Plasmodium vivax infection in Equatorial Guinea.

A semi-nested, multiplex polymerase chain reaction (PCR) based on the amplification of the sequences of the 18S small subunit ribosomal RNA (ssrRNA) gene was tested in a field trial in Equatorial Guinea (a hyperendemic focus of malaria in west central Africa). The method uses a primary PCR amplification reaction with a universal reverse primer and two forward primers specific for the genus Plasmodium and to mammals (the mammalian-specific primer was included as a positive control to distinguish uninfected cases from inhibition of the PCR). The second amplification is carried out with the same Plasmodium genus-specific forward primer and four specific reverse primers for each human Plasmodium species. The PCR amplified products are differentiated by fragment size after electrophoresis on a 2% agarose gel. Four villages from three regions of the island of Bioko (Equatorial Guinea) and two suspected Plasmodium vivax-P. ovale infections from the hospital of Malabo were tested by microscopy and PCR. The PCR method showed greater sensitivity and specificity than microscopic examination and confirmed the existence of a focus of P. vivax infections in Equatorial Guinea suspected by microscopic examination. It also provided evidence of several mixed infections, mainly P. falciparum and P. malariae, the two predominant species causing malaria in Equatorial Guinea.

Animals↗
PubMed1999

Prevalence of intestinal parasite infections with special reference to Entamoeba histolytica on the island of Bioko (Equatorial Guinea).

The prevalence of intestinal parasitic infections was assessed (1993 through 1995) among two different groups of persons on the island of Bioko, Equatorial Guinea. In the first group, parasitologic examinations were performed on stool specimens from a household-based sample of 557 dwellers from the rural area of the island. In the second group, 1,633 inpatients and outpatients at the General Hospital of Malabo (the capital of the country) were studied. All age groups were represented in both groups. The average prevalence of the most common protozoan and helminthic intestinal infections in rural and urban areas, respectively, was as follows: Entamoeba histolytica/E. dispar (14.9% and 32.7%, respectively), Giardia lamblia (7.2% and 8.6%), Ascaris lumbricoides (45.8% and 31.4%), and Trichuris trichiura (25.7% and 36.4%). Seventy-nine sera from patients with amebic liver abscess (suspected by ultrasonography) were studied by an immunohemagglutination assay, with 44 (56%) showing anti-E. histolytica titers > or = 1:32. Of these 79 sera, 71 were studied by an enzyme immunoassay, 86% of which were positive with titers > or = 1:64. This study showed that parasitic infections in Equatorial Guinea represent a major health problem.

Animals↗
PubMed1998

The expression of recombinant genes from bacteriophage lambda strong promoters triggers the SOS response in Escherichia coli.

The production of several non-related heterologous proteins in recombinant Escherichia coli cells promotes a significant transcription of recA and sfiA SOS DNA repair genes. The activation of the SOS system occurs when the expression of plasmid-encoded genes is directed by the strong lambda lytic promoters, but not by IPTG-controlled promoters either at 37 or at 42 degrees C, and it is linked to an extensive degradation of the proteins after their synthesis. The triggering signal for the SOS response could be an important arrest of cell DNA replication observed within the first hour after the induction of recombinant gene expression. The stimulation of this DNA repair system can partially account for the toxicity exhibited by recombinant proteins on actively producing E. coli cells.

Bacterial Proteins↗
PubMed1998

Conformational flexibility in a highly mobile protein loop of foot-and-mouth disease virus: distinct structural requirements for integrin and antibody binding.

The G-H loop of foot-and-mouth disease virus VP1 protein is a highly mobile peptide, that extends from the capsid surface and that in native virions is invisible by X-ray crystallography. In serotype C, this segment contains a hypervariable region with several continuous, overlapping, B-cell epitopes that embrace the conserved Arg-Gly-Asp (RGD) cell attachment motif. The solvent-exposed positioning of this peptide by selective insertion into different structural frameworks of E. coli beta-galactosidase, generates a spectrum of antigenic variants which react distinctively with a panel of anti-VP1 monoclonal antibodies and exhibit different efficiencies as cell ligands. The cell attachment efficiency is much less restricted by the different positioning of the viral segment at the insertion sites. A molecular model of an inserted stretch reveals a highest flexibility of the RGD tripeptide segment compared with the flanking sequences, that could allow a proper accommodation to integrin receptors even in poorly antigenic conformations. The non-converging structural requirements for RGD-mediated integrin binding and antibody recognition, explains the dynamism of the generation of neutralisation-resistant antigenic variants in the viral quasi-species, arising from a conformational space of integrin-binding competent peptides. This might be of special relevance for foot-and-moth disease virus evolution, since unlike in other picornaviruses, the cell binding motif and the major neutralising B-cell epitopes overlap in a solvent-exposed peptide accessible to the host immune system, in a virion lacking canyons and similar hiding structures.

Amino Acid Sequence↗
PubMed1998

A cell adhesion peptide from foot-and-mouth disease virus can direct cell targeted delivery of a functional enzyme.

The G-H loop of foot-and-mouth disease virus is a disordered protrusion of the VP1 protein exposed on the virion surface. This short stretch includes an arginine-glycine-aspartic acid tripeptide, a recognized integrin-binding motif, which is responsible for cell attachment and infection. Eight copies of a peptide reproducing the amino acid sequence of this FMDV ligand have been displayed in solvent-exposed regions on an enzymatically active recombinant beta-galactosidase. This viral peptide segment enables the chimeric enzyme to bind mammalian cell lines with different efficiencies, probably depending on the number of suitable cell receptors present on each of them. Moreover, it also promotes the internalization of the attached enzyme, which is transiently active inside the cells. These results suggest further exploration of the potential use of short adhesion peptides of viral origin as cell attachment tags to direct the targeted delivery of both genes and enzymes, instead of whole, infectious viruses.

Amino Acid Sequence↗
PubMed1998

Display-induced antigenic variation in recombinant peptides.

Peptide display on solvent-exposed surfaces of carrier proteins is a promising approach pursuing the identification and improvement of reactive amino acid sequences. However, the contribution of the molecular environment where the peptide is inserted on its interactive properties remains essentially unexplored. By an exhaustive antigenic analysis of the same peptide displayed on 20 structurally distinct frameworks, we show that peptide accommodation into the acceptor site has dramatic effects on its immunoreactivity. Conformational constraints can modulate the molecular recognition properties of the insert within a surprisingly wide range, probably by affecting the positioning of critical contact residues. The observed display-induced antigenic variation prompts a careful consideration of the molecular context when evaluating output amino acid sequences from screening of peptide libraries or application of directed molecular evolution technologies.

Amino Acid Sequence↗
PubMed1998

Salivary gland heterotopia in the lower neck: a report of five cases.

Heterotopic salivary gland tissue (HSGT) represents an uncommon lesion, usually presenting as a discharging sinus in the base of the neck. Diagnostic criteria and embryogenesis of this entity still remain unclear. For the purpose of clarifying both subjects, all lateral cervical anomalies undergoing surgery during a 12-year period were examined. Histological study showed salivary tissue in 10 out of 119 patients. However, only 5 of them accomplished HSGT criteria. This study presents the second largest series to date of undisputed HSGT in the lower neck. Both accessory glands and branchial cleft anomalies should be distinguished from this lesion. Neoplastic transformation in HSGT, although extremely rare, should also be considered.

Child↗
PubMed1998

Expression of Bcl-x in erythroid precursors from patients with polycythemia vera.

BACKGROUND: Deregulating the expression of Bcl-xL, an inhibitor of apoptosis, in an erythropoietin-dependent erythroblast cell line averts apoptosis induced by the withdrawal of erythropoietin. Since in polycythemia vera an abnormal clone of erythroid progenitors is independent of erythropoietin, we investigated whether the endogenous expression of Bcl-xL was deregulated in these cells. METHODS: Erythroid colonies from patients with polycythemia vera and normal subjects were cultured in the presence and absence of erythropoietin and assessed by immunocytochemical and flow-cytometric analysis with anti-Bcl-x antibodies that recognize the two species of Bcl-x (Bcl-xL and Bcl-xS). Reverse-transcriptase-polymerase-chain-reaction analysis was used to determine which one of the two species was responsible for anti-Bcl-x staining. Bone marrow mononuclear cells from 8 healthy bone marrow donors, 14 patients with polycythemia vera, 19 patients with other myeloproliferative syndromes, and 12 patients with secondary erythrocytosis were analyzed by flow cytometry with antibodies against Bcl-x and glycophorin A, an erythroid marker. RESULTS: Erythroid cells from patients with polycythemia vera survived in vitro without erythropoietin, and this finding correlated with the expression of Bcl-x protein (Bcl-xL messenger RNA was the main species of Bcl-x found), even in mature erythroblasts that normally do not express Bcl-x. The mean (+/-SD) percentage of cells positive for both glycophorin A and Bcl-x in the 14 patients with polycythemia vera (21.8+/-3.6 percent) was significantly higher than that in 8 normal donors (6.62+/-1.58 percent), 12 patients with secondary erythrocytosis (6.87+/-1.95 percent), 9 patients with essential thrombocythemia (3.81+/-0.97 percent), and 10 patients with chronic myeloid leukemia (2.7+/-0.41 percent). CONCLUSIONS: Deregulated expression of Bcl-x may contribute to the erythropoietin-independent survival of erythroid-lineage cells in polycythemia vera and thereby contribute to the pathogenesis of this disease.

Adolescent↗
PubMed1998

Megatherapy in children with high-risk Ewing's sarcoma in first complete remission.

To improve the prognosis of patients with metastatic or high-risk localized sarcoma in first CR, we explored the role of consolidation therapy with megatherapy and hematopoietic rescue. From 1986 to 1995, of 72 patients with Ewing's sarcoma from three pediatric departments, 30 were diagnosed as high-risk patients. Of these 30 patients, six did not achieve complete remission and four refused megatherapy and received multimodal treatment (chemotherapy + surgery and/or radiotherapy). The remaining 20 patients received megatherapy. There were 15 males and five females with a median age of 10.8 years (range 2-18 years). Five patients had metastatic disease at initial diagnosis, nine patients had primary tumor in the pelvis and 13 had a tumor volume greater than 100 ml. Overall disease-free survival was 62.7+/-11%; 40+/-21.9% for those with metastatic disease, 76.2+/-12.2% for those with tumor volume greater than 100 ml and 64.8+/-16.5% for those with tumor in pelvic bones. In conclusion, megatherapy has improved the outcome of this group of patients relative to that expected following conventional therapy.

Adolescent↗
PubMed1998

Progenitor cell subsets and engraftment kinetics in children undergoing autologous peripheral blood stem cell transplantation.

The main objective of the present study was to determine the role of CD34+ cell subsets in the haemopoietic recovery of children undergoing peripheral blood stem cell transplantation. For this purpose, 38 leukaphereses from 33 children with malignancies mobilized with G-CSF were analysed. Using dual-colour flow cytometry, different subpopulations of CD34+ cells were quantified and the number of each reinfused subsets correlated with haemopoietic resurgence. Multivariate analysis showed that the number of CD34+CD38- cells and CD34+CD38+ cells correlated better with time to neutrophil and platelet recovery, respectively, than the total number of CD34+ cells. Threshold values for rapid haemopoietic recovery, determined by the receiver operating characteristic analysis, were found to be 0.5 X 10(6) CD34+CD38- cells for neutrophil engraftment, and 2.0x10(6) CD34+CD38+ cells for platelet recovery. It is suggested that the analysis of CD34+ cell subsets could increase understanding of the repopulation capacity of a given leukapheresis product in peripheral blood stem cell transplantation procedures in children. In particular, this procedure could be extremely useful when low numbers of CD34+ cells are collected.

Adolescent↗