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Biomedical subjects

P Herrera

Publications and source records attributed to P Herrera.

At least 19 recordsLinked to original sources
PubMed2002

Reduced PTEN expression in the pancreas overexpressing transforming growth factor-beta 1.

PTEN is a candidate tumour suppressor gene and frequently mutated in multiple cancers, however, not in pancreatic cancer. Recently, it has been demonstrated that PTEN expression is regulated by TGF-beta1. Using TGF-beta1 transgenic mice (n=7) and wildtype littermates (n=6), as well as pancreatic tissues obtained from organ donors (n=10) and patients with pancreatic cancer (n=10), we assessed the expression of PTEN by means of immunohistochemistry and semiquantitative PCR analysis. In addition, PANC-1 cells were treated with TGF-beta1 in vitro and the levels of PTEN mRNA were determined in these cells. In human pancreatic cancers PTEN mRNA levels were significantly decreased (P<0.05). In addition, in the pancreas of TGF-beta1 transgenic mice the expression of PTEN was significantly reduced (P<0.01), as compared to wildtype littermates and incubation of PANC-1 cells with TGF-beta1 decreased PTEN mRNA levels after 24 h. Inasmuch as TGF-beta1 decreases PTEN expression in human pancreatic cancer cells and human pancreatic cancers overexpress TGF-beta1, the reduced expression of PTEN in pancreatic cancer may be mediated by TGF-beta1 overexpression. Thus, although PTEN is not mutated in pancreatic cancers, the reduction of its expression may give pancreatic cancer cells an additional growth advantage.

Animals↗
PubMed2002

BCR/ABL p210, p190 and p230 fusion genes in 250 Mexican patients with chronic myeloid leukaemia (CML).

There are two major forms of the BCR/ABL fusion gene, involving ABL exon 2, but including different exons of BCR gene. The transcripts b2a2 or b3a2 code for a p210 protein. Another fusion gene leads to the expression of an e1a2 transcript, which codes for a p190 protein. Another, less common fusion gene is c3a2[e19a2], which encodes a p230 protein. The incidence of one or the other rearrangement in chronic myeloid leukaemia (CML) patients varies in different reported series. This study was designed to determine the frequency of coexpresion of the p210, p190 and p230 transcripts in 250 Mexican patients with CML. We performed nested and multiplex reverse transcriptase polymerase chain reaction (RT-PCR) on bone marrow samples from adult patients and found that all cases were positive for some type of BCR/ABL rearrangement. In 226 (90.4%) patients it was p210, while the remaining 9.6% showed coexpression or one of the transcripts of p190/p210/p230. In 7% of patients with p210 expression there are both isoforms (b3a2/b2a2), presumably the result of alternative splicing. The rate of coexpression of the p190/p210 transcripts was 5%, which is much lower than in other reports. This may be due to the technical factors. These patients had high platelet counts, marked splenomegaly and chromosomal abnormalities in addition to Ph'. Other types of coexpression seen were p210/p230 and p190/p210/p230, in patients with high-risk clinical factors. Our study confirms the occurrence of coexpression of different BCR/ABL transcripts, although the rate (9.6%) was much lower than has been reported in other populations. This may reflect either the sensitivity of the detection techniques used or the possibility of genetic differences between the populations studied. Coexpression may be due to alternative splicing or to phenotypic variation, with clinical courses different from classical CML.

Adolescent↗
PubMed2001

General and conditional replacement of connexin43-coding DNA by a lacZ reporter gene for cell-autonomous analysis of expression.

Using the Cre/loxP system, we have circumvented early postnatal lethality and possible pleiotropic effects of general Cx43 gene deletion, in order to determine the expression and function of connexin43 (Cx43) in defined cell types. General or cell type-specific, Cre-mediated deletion of the floxed (i.e. flanked by loxP sites) Cx43-coding region led to activation of the inserted lacZ reporter gene in cells with transcriptional activity of the Cx43 gene. As deduced from lacZ expression in mice with general deletion, transcriptional activity of the Cx43 gene was not only found in a broad range of cell types known to a express Cx43, but also inpancreatic duct cells and vascular cells of the gut and skeletal muscle. Cre-mediated deletion restricted to defined cell types led to lacZ activation highlighting corresponding subsets of cells expressing Cx43, such as vascular endothelial cells, hepatic duct cells and putative neural crest cells, which were otherwise masked by strong Cx43 expression in neighbouring cells. In Cx43 expressing cell types, the floxed Cx43 allele was useful as a Cre-excision reporter for the characterization of Cre transgenes.

Animals↗
PubMed2000

Adsorption of Salmonella enteritidis by cetylpyridinium-exchanged montmorillonite clays.

Recent experiments in our laboratory have suggested that certain montmorillonite clays, when exchanged with the cationic surfactant cetylpyridinium (CP), may be useful in removing bacteria from aqueous solution. During an initial study, screening various CP-exchanged products for potential antibacterial activity, three CP-exchanged clays - CP*AAM (acid-activated montmorillonite), CP*STx-1 (Ca(++)-montmorillonite), and CP*SWy-2 (Na(+)-montmorillonite), proved to be the most effective. Binding studies were performed using 1mg each of CP-exchanged AAM, STx-1, and SWy-2 with a standardized Salmonella enteritidis solution containing approximately 40,000 colony forming units (CFU)/ml. The modified clays reduced bacterial numbers 98.1, 97.6, and 95.2%, respectively. In contrast, the parent clays only produced reductions of 39.8, 16.9, and 16.6%, respectively. Attempts were made to desorb CP from the modified clays by washing in sterile physiological saline for 24h. The resulting wash solutions failed to produce any significant reduction in bacterial colony counts; while, the washed clays retained their full antimicrobial activity. These findings suggested that the antibacterial effect of the clays is localized on the clay surface and is not due to CP dissociating from the clay. Electron microscopy revealed that the bacteria adhered to the surface of the CP-exchanged clays, but not the parent clays. Results from timed binding studies showed that the antibacterial effect was stable over the period observed. Rates of binding were positively influenced by increasing temperature, not affected by changes in pH, and negatively influenced by the presence of organic contaminants. The mechanism by which bacterial counts are reduced may involve the enhanced hydrophobicity and affinity of the CP-exchanged clay for Salmonella and the antibacterial activity of CP.

Adsorption↗
PubMed2000

Autologous peripheral blood progenitor cell transplantation with <2 x 10(6) CD34(+)/kg: an analysis of variables concerning mobilisation and engraftment.

INTRODUCTION: This study analyses the factors affecting mobilisation and engraftment in autologous peripheral blood progenitor cell transplantation according to the number of CD34(+) re-infused. MATERIALS AND METHODS: A total of 190 patients underwent mobilisation with G-CSF alone (n=113) or in combination with chemotherapy (n=77). A total of 116 patients (61%) were autografted with <2 x 10(6) CD34(+) cells/kg and 74 patients were transplanted with >2 x 10(6) CD34(+) cells/kg. Rates of granulocyte and platelet recovery were estimated using the product-limit method of Kaplan-Meier and compared using a log-rank test. The Cox regression model was used for the multivariate analysis of factors influencing engraftment. Differences between cohorts were evaluated by one-way ANOVA or Mann-Whitney tests, and multivariate analysis was performed using a stepwise lineal regression. RESULTS: Neutrophil and platelet engraftment was significantly longer with <2 x 10(6)/CD34(+)/kg (12 vs 10 days, P=0.014 and 16 vs 13 days, P=0.0001 respectively). Platelet recovery was affected by exposure to alkylating agents (P=0.04), refractory disease (P=0.02) and AML (P=0.0001), but only the last two variables remained significant in Cox regression (P<0.01). Granulocyte engraftment was longer in CML (univariate, P=0.04) and in refractory disease (multivariate, P=0.02). In patients re-infused with >2 x 10(6)/CD34(+)/kg, the Cox model did not identify prognostic factors for haematopoietic recovery. CONCLUSION: Although mobilisation schedules and disease status influenced not only the yield of progenitor cells, but also the engraftment kinetics, the number of CD34(+) re-infused was the main predictor of haematopoietic recovery. While engraftment succeeded in most of the cases, the re-infusion of >2 x 10(6)/CD34(+)/kg resulted in significantly shorter recovery times.

Adolescent↗
PubMed2000

Development and characterization of a carbon-based composite material for reducing patulin levels in apple juice.

Patulin, a heterocyclic lactone produced by various species of Penicillium and Aspergillus fungi, is often detected in apple juices and ciders. Previous research has shown the effectiveness of granular activated carbon for reducing patulin levels in aqueous solutions, apple juices, and ciders. In this study, ultrafine activated carbon was bonded onto granular quartz to produce a composite carbon adsorbent (CCA) with a high carbonaceous surface area, good bed porosity, and increased bulk density. CCA in fixed-bed adsorption columns was evaluated for efficacy in reducing patulin levels from aqueous solutions and apple juice. Columns containing 1.0, 0.5, and 0.25 g of CCA were continuously loaded with a patulin solution (10 microg/ml) and eluted at a flow rate of 1 ml/min. Results indicated that 50% breakthrough capacities for patulin on 1.0-, 0.5-, and 0.25-g CCA columns were 137.5, 38.5, and 19.9 microg, respectively. The effectiveness of CCA to adsorb patulin and prevent toxic effects was confirmed in vitro using adult hydra in culture. Hydra were sensitive to the effects of patulin, with a minimal affective concentration equal to 0.7 microg/ml; CCA adsorption prevented patulin toxicity until 76% breakthrough capacity was achieved. Fixed-bed adsorption with 1.0 g of CCA was also effective in reducing patulin concentrations (20 microg/liter) in a naturally contaminated apple juice, and breakthrough capacities were shown to increase with temperature. Additionally, CCA offered a higher initial breakthrough capacity than pelleted activated carbon when compared in parallel experiments. This study suggests that CCA used in fixed-bed adsorption systems effectively reduced patulin levels in both aqueous solutions and naturally contaminated apple juice; however, the appearance and taste of apple juice may be affected by the treatment process.

Adsorption↗
PubMed1999

Chemical modification and site-directed mutagenesis of human liver arginase: evidence that the imidazole group of histidine-141 is not involved in substrate binding.

Native and wild-type recombinant human liver arginases (EC 3.5.3.1) were photoinactivated by Rose bengal, and protection was afforded by the competitive inhibitor l-lysine. The dissociation constant for the enzyme-protector complex was essentially equal to the corresponding K(i) value. Upon mutation of His141 by phenylalanine, the enzyme activity was reduced to 6-10% of wild-type activity, with no changes in K(m) for arginine or K(i) for l-lysine or l-ornithine. The subunit composition of active enzyme was not altered by mutation, but the mutant H141F was markedly more sensitive to trypsin inactivation and completely insensitive to inactivation by diethyl pyrocarbonate (DEPC) and photoinactivation. Species with histidine groups blocked with DEPC were also insensitive to photoinactivation. We conclude that His141, which is the target for both inactivating procedures, is not involved in substrate binding, but plays a critical, albeit not essential role in the hydrolysis of enzyme-bound substrate.

Arginase↗
PubMed1999

Evidence that histidine-163 is critical for catalytic activity, but not for substrate binding to Escherichia coli agmatinase.

Agmatinase (agmatine ureohydrolase, EC 3.5.3.11) from Escherichia coli was inactivated by diethyl pyrocarbonate (DEPC) and illumination in the presence of Rose bengal. Protection against photoinactivation was afforded by the product putrescine, and the dissociation constant of the enzyme-protector complex (12 mM) was essentially equal to the K(i) value for this compound acting as a competitive inhibitor of agmatine hydrolysis. Upon mutation of His163 by phenylalanine, the agmatinase activity was reduced to 3-5% of wild-type activity, without any change in K(m) for agmatine or K(i) for putrescine inhibition. The mutant was insensitive to DEPC and dye-sensitized inactivations. We conclude that His163 plays an important role in the catalytic function of agmatinase, but it is not directly involved in substrate binding.

Catalysis↗
PubMed1999

Manganese is essential for catalytic activity of Escherichia coli agmatinase.

Purified Escherichia coli agmatinase (EC 3.5.3.11) expressed the same activity in the absence or presence of added Mn2+ (0-5mM). However, it was strongly inhibited by Co2+, Ni2+, and Zn2+ and almost half inactivated by EDTA. Partial inactivation by EDTA yielded enzyme species containing 0.85 +/- 0.1 Mn2+/subunit, and it was accompanied by a decrease in intensity of fluorescence emission and a red shift from the emission maximum of 340 nm to 346 nm, indicating the movement of tryptophane residues to a more polar environment. The activity and fluorescence properties of fully activated agmatinase were restored by incubation of dialysed species with Mn2+. Manganese-free species, obtained by treatment with EDTA and guanidinium chloride (3 M), were active only in the presence of added Mn2+. Results obtained, which represent the first demonstration of the essentiality of Mn2+ for agmatinase activity, are discussed in connection with a possible binuclear metal center in the enzyme.

Catalysis↗
PubMed1999

Immunogenicity of 2 serogroup B outer-membrane protein meningococcal vaccines: a randomized controlled trial in Chile.

CONTEXT: Meningococcal disease occurs worldwide, and serogroup B disease accounts for a large proportion of cases. Although persons younger than 4 years are at greatest risk for serogroup B meningococcal disease, vaccine efficacy has not been demonstrated in this age group. OBJECTIVE: To evaluate serum bactericidal activity (SBA) against homologous vaccine type strains and a heterologous Chilean epidemic strain of Neisseria meningitidis as a potential correlate for vaccine efficacy. DESIGN: Double-blind, randomized controlled trial conducted between March 14 and July 20, 1994. All blood samples were taken by December 1994. SETTING: Santiago, Chile, where a clonal serogroup B meningococcal disease epidemic began in 1993. PARTICIPANTS: Infants younger than 1 year (n = 187), children aged 2 to 4 years (n = 183), and adults aged 17 to 30 years (n = 173). INTERVENTION: Participants received 3 doses of outer-membrane protein (OMP) meningococcal vaccine developed in either Cuba or Norway or a control vaccine, with each dose given 2 months apart. Blood samples were obtained at baseline, prior to dose 3, and at 4 to 6 weeks after dose 3. MAIN OUTCOME MEASURE: Immune response, defined as a 4-fold or greater rise in SBA titer 4 to 6 weeks after dose 3 compared with prevaccination titer. RESULTS: Children and adult recipients of either meningococcal vaccine were more likely than controls to develop an immune response to the heterologous epidemic strain. After 3 doses of vaccine, 31% to 35% of children responded to the vaccine vs 5% to placebo; 37% to 60% of adults responded to vaccine vs 4% to placebo (P<.05 vs control for all). Infants, however, did not respond. In contrast, against homologous vaccine type strains, the response rate was 67% or higher among children and adults and 90% or higher among infants (P<.001 vs control for all). Subsequent SBA against 7 isogenic homologous target strains identified class 1 OMP as the immunodominant antigen. CONCLUSIONS: These data suggest that neither serogroup B OMP meningococcal vaccine would confer protection during a heterologous epidemic. However, epidemic strain-specific vaccines homologous for class 1 OMP are promising candidates for the control of epidemic serogroup B meningococcal disease.

Adolescent↗
PubMed1999

Expression of Bcl-2 by human bone marrow mast cells and its overexpression in mast cell leukemia.

Bcl-2 protein plays a major role in the prevention of programmed cell death of differentiating cells. In the present study, the expression of cytoplasmic bcl-2 by human Bone Marrow Mast Cells (BMMC) from both normal and pathological bone marrow samples was examined. A total of 35 subjects corresponding to 9 healthy volunteers, 8 cases of adult indolent systemic mast cell disease (SMCD), 4 cases of pediatric mastocytosis (PM), 11 cases of hematological malignancies (HM), 2 cases of reactive bone marrow, and 1 case of mast cell leukemia (MCL) were analyzed. The expression of bcl-2 was studied using quantitative three-color flow cytometry. We also studied the molecular configuration of the bcl-2 gene and other relatives by Southern blot and polymerase chain reaction (PCR) in the MCL case. Bcl-2 expression was detected in BMMC from all samples analyzed. No significant differences on the expression of bcl-2 were detected between BMMC from healthy subjects and patients with SMCD, PM, HM, and reactive bone marrow. By contrast, bcl-2 protein was overexpressed in BMMC from MCL patient without gene rearrangement. Our results show that bcl-2 protein was constitutively expressed by BMMC. BMMC from MCL display overexpression of bcl-2, which could not be related to molecular rearrangements involving the bcl-2 gene. The expression of this protein by mature MC may play a role in the prevention of MC apoptosis and thus help to explain the long survival of these cells. The overexpression of bcl-2 by BMMC in MCL may help to explain their resistance to chemotherapy-induced apoptosis.

Adult↗
PubMed1998

[Von Willebrand disease: characteristics and response to desmopressin. Study of 103 cases].

BACKGROUND: To describe the main characteristics and response to desmopressin infusion in 103 patients suffering from von Willebrand disease (vWD). PATIENTS AND METHODS: The criteria for diagnosis were (except for type 2N) the coexistence of von Willebrand factor ristocetin cofactor (vWF:RCo) activity < 50 U/dl with bleeding disease or one of the following data: von Willebrand factor antigen (vWF:Ag) activity < 50 U/dl, factor VIII (FVIII) activity < 50 U/dl or the existence of a increased bleeding time (BT). Multimeric studies of vWF were performed in 51 cases and ristocetin induced platelet aggregation (RIPA) was also performed. RESULTS: Spontaneous bleeding was found in 36 patients, while in 18 cases the diagnosis was done after surgical bleeding. Thirteen patients (6 presenting with mild bleeding) were studied for abnormalities in the routine preanestesic tests. Other 22 patients were diagnosed with vWD by familial studies. There were 3 patients with type 2B, 1 case with type 2N and other patient with type 3. BT was found increased in 26 out of 58 patients. The activities of vWF:CoR and vWF:Ag were 38.4 (9.4) U/dl and 45.8 (23.2) U/dl, respectively, while the activity of FVIII was 49.9 (20.8) U/dl. Prophylactic DDAVP (desmopressin) was infused in 32 patients. After 1 h, basal activities of vWF:CoR and vWF:Ag were increased by 3.1 (3.2) and 3.4 (3.1) times, respectively, and maintained for 3 h. FVIII activity increased 3.6 (2.3) times the basal levels decreasing after 3 h (2.9 [2.1]; p < 0.01). The BT was corrected in 8 out of ten patients. CONCLUSIONS: vWD is a major cause of surgical bleeding. Preanestesic anamnesis and coagulation tests can be useful to identify vWD. Many patients with vWD have normal BT. A failure in the response to desmopressin infusion is unusual.

Deamino Arginine Vasopressin↗
PubMed1998

[Prognostic factors in acute bacterial meningitis in children. A case control study].

BACKGROUND: The prognosis of acute bacterial meningitis continues to be poor in our country. Previous studies suggest that the delay in diagnosis has an important prognostic value. AIM: To study the influence of diagnosis timing and the clinical conditions of children with acute bacterial meningitis on admission on death and incidence of gross sequelae. PATIENTS AND METHODS: Charts of children deceased or discharged with gross sequelae as consequence of an acute bacterial meningitis were selected. To each of these cases, 4 children with the same diagnosis but discharged in good conditions were selected as controls. Variables recorded were time and number of visits previous to the diagnosis, etiology of meningitis, neurological, respiratory, digestive and hemodynamic involvement on admission. RESULTS: Fifty seven cases and 224 controls were studied. Most cases were 12 months old or less (OR 4.1, 95% CI = 1.97-8.7). Diagnosis made on the first visit or within the first 24 hours of disease, improved prognosis (OR 0.25, 95% CI = 0.07-0.78). An age of less than 12 months and a diagnosis made after more than 12 hours of disease or after more than one consultation interacted multiplying their effect on a dismal prognosis. Coma on admission (OR 7.95% CI = 3-14.3) and S Pneumoniae etiology (OR 7, CI 95% = 3.4, 14.3) were also associated with a bad prognosis. CONCLUSIONS: Early diagnosis of acute bacterial meningitis is protective for death or gross sequelae at discharge. Age, coma and S Pneumoniae etiology are the main factors associated with a poor prognosis.

Acute Disease↗
PubMed1997

Cyclosporine-induced retinal toxic blindness.

We report the case of a BMT recipient who developed blindness 22 months after BMT. Microvascular retinopathy, cortical blindness and other ocular pathologies were excluded with appropriate tests. Electrophysiological studies showed retinal damage without excluding an optic nerve lesion. The patient, who had several risk factors for neurologic-induced cyclosporine toxicity, improved with cyclosporine withdrawal. Our findings stress the need of electrophysiological tests to exclude neuroretinal damage in patients receiving cyclosporine after BMT.

Adult↗