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Biomedical subjects

X Carbonell

Publications and source records attributed to X Carbonell.

At least 19 recordsLinked to original sources
PubMed2006

Severe hypernatremic dehydration secondary to undetected lactation failure: usefulness of sodium levels in breast milk.

There is a concern that lactation failure and neonatal morbidity might be more common than previously thought. Maybe the early discharge, the lack of timely follow-up, or poor information during pregnancy or after delivery play important roles. A case of severe hypernatremic dehydration secondary to lactation failure is reported and we analyze recent recommendations.

Breast Feeding↗
PubMed2003

Expired nitric oxide in the newborn with high risk of perinatal infection.

The objective of this study is to determine expired nitric oxide (expNO) in the first 3 days of life in relation to: hours of life, gestational age, type of labor, and risk of perinatal infection. Our hypothesis has been that expNO increases in newborns with high risk of perinatal infection. Total expNO was measured in 166 newborns: 108 healthy (63 full-term and 45 preterm), 30 with low risk of perinatal infection, and 28 with high risk of perinatal infection treated with antibiotics but without positive hemoculture. Expired gas was collected using a face mask and NO concentration was determined by chemiluminescence. Total expNO neither correlated with gestational age, birth weight or serum NOx, nor changed after cesarean section, but was related to hours of life. Total expNO in the < or = 36-hour subgroups (median, interquartile range) was higher in the high-risk perinatal infection newborns ( n = 8; 5.33 (4.5-7.2) nL/min*Kg) than in healthy newborns ( n = 59; 4.13 (3.5-4.7) nL/min*kg) or low-risk perinatal infection newborns ( n = 18; 3.99 (3.4-4.7) nL/min*kg). In the 37 to 72-hour subgroups there were also differences between healthy newborns ( n = 49; 4.68 (4.1-5.3) nL/min*kg) or low-risk perinatal infection newborns on the one hand ( n = 12, 4.55 (3.9-5.2) nL/min*kg) and high risk perinatal infection newborns on the other ( n = 20; 9.69 (7.6-11.1) nL/min*kg). Then, total expNO increased in newborns with high risk of perinatal infection, regardless of hours of life.

Bacterial Infections↗
PubMed2001

Phage spread dynamics in clonal bacterial populations is depending on features of the founder cell.

Plate-cultured bacterial colonies are intriguing models to study host-parasite interactions in senescent populations. During the growth of bacteriophage-infected colonies there is a synchronous prophage induction episode among lysogenic cells that allows a dramatic but time-restricted amplification of viral particles. We report here that the dynamics of phage spread depends on the history of the lysogenic cell that establishes the clonal population, the duration of the pre-burst period being shorter when the founder, infected cell derives from older colonies. These results offer a physiologic explanation for the self-contained progression of the viral spread in closed environments, that ensures both viral dissemination but also survival of most of the host cells.

Age Factors↗
PubMed2001

Prediction of hyperbilirubinaemia in the healthy term newborn.

UNLABELLED: The aim is to establish the correlation between transcutaneous bilirubin (TCB) and serum bilirubin (TSB) and its predictive value for significant hyperbilirubinaemia > or = 290 mcmol/L (17 mg/dL). We studied a total of 2004 healthy full-term newborns, weight 3.230 g +/- 491 g; 90% received breast milk. The study was performed in two phases. In the first phase (610 newborns), the following tests were carried out: hematocrit and bilirubin in umbilical cord blood; TCB at 24 h, 48 h and between 60 h and 96 h at the forehead and over the sternum; TSB was measured along with this last test. In the second phase (1394 newborns), the predictive value of TCB and TSB was validated. The incidence of bilirubin > or = 290 mcmol/L was 2.95% and 3.2%. The correlation between TSB and TCB is high (n = 996; r = 0.92; y = 5.916 + 0.804x; p < 0.000). There was a better correlation between TCB and TSB with sternal compared to forehead determination (< 24 h: 0.81 vs 0.77; 24-48 h: 0.887 vs 0.83; and > 48 h: 0.94 vs 0.83). The study showed the scant sensitivity of umbilical cord blood bilirubin and good predictive value at 24 h of TSB > or = 102 mcmol/L (6 mg/dL) and at 48 h of TSB > or = 154 mcmol/L (9 mg/dL) and TCB > or = 13 (equivalent to 154 mcmol/L). CONCLUSION: There is a good correlation between TCB and TSB. In infants with TSB > or = 102 mcmol/L at 24 h or TSB > or = 154 mcmol/L or transcutaneous readings > or = 13 h at 48 h, a TSB test must be performed after 48 h of life.

Bilirubin↗
PubMed2000

Successful mimicry of a complex viral antigen by multiple peptide insertions in a carrier protein.

The antigenic properties of a viral peptide from the surface of foot-and-mouth disease virus particles have been successfully mimicked by multiple insertion in solvent-exposed regions of Escherichia coli beta-galactosidase. By increasing the number of viral peptides per enzyme monomer, the average IC(50) of hybrid proteins in a competitive enzyme-linked immunosorbent assay) have decreased to values close to that presented by natural virions. Moreover, the antigenic diversity of these new recombinant enzymes when measured with different anti-virus antibodies has also been largely reduced, indicating a better presentation of the epitopes located in the viral peptide. Although bivalent antibody binding could have been favoured by multiple presentation, conformational modifications of the viral peptide, due to the presence of other insertions or a cooperative antibody binding cannot be excluded. In addition, a multidimensional antigenic analysis have grouped together the multiple-inserted proteins with the native virus, suggesting that increasing the number of insertions could be a good strategy to reproduce the antigenic properties of an immunoreactive peptide in a natural multimeric disposition.

Amino Acid Sequence↗
PubMed1999

Detection of molecular interactions by using a new peptide-displaying bacteriophage biosensor.

Foreign peptides fused to the carboxy terminus of P22 tailspike protein are solvent-exposed and highly antigenic when displayed on the surface of infectious virus particles. Binding of an anti-peptide specific Fab antibody fragment enhances the infectivity of chimeric bacteriophage particles in a titre-dependent fashion. Although the precise molecular basis of this enhanced infectivity remains unclear, experimental data and modelling approaches suggest that the antibody binding might restore conformational impairments in the assembled tail protein affecting its activity and performance during infection. These results suggest that in addition to free enzymes, peptide-displaying bacteriophages could be engineered as new biosensors to detect molecular interactions by using natural viral enzymes critical for cell infection.

Bacteriophage P22↗
PubMed1999

Heat-inactivation of plasmid-encoded CI857 repressor induces gene expression from Ind- lambda prophage in recombinant Escherichia coli.

We have observed significant cell lysis upon temperature up-shift of recombinant Escherichia coli cultures harboring CI857-repressed lambda-based expression vectors. This event, that becomes evident about 30-40 min after the heat shock, takes place when using the lambda promoter system in Ind- lysogenic strains, but not in others commonly employed for recombinant gene expression. These results strongly suggest that the thermosensitive CI857 repressor, encoded by the expression vector, competes with CI Ind- molecules for binding to the prophage operator region, allowing for expression of lytic genes from the integrated Ind- viral genome upon temperature up-shift. Transcription of viral lytic genes does not include unspecific expression of a reporter sulA::lacZ gene fusion carried in the prophage genome. These results prompt, however, to carefully evaluate the limitations of expression systems based on pL/pR-CI857 in bacterial strains modified through lambda Ind- gene transfer vehicles.

Bacteriolysis↗
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

Unfolding of bacteriophage P22 tailspike protein: enhanced thermal stability of an N-terminal fusion mutant.

The tailspike protein (TSP) of bacteriophage P22 is a homotrimeric multifunctional protein responsible for cell attachment and hydrolysis of the Salmonella typhimurium host cell receptor. Despite the folding of TSP involves the formation of thermolabile intermediates, the mature protein is extremely resistant to heat and detergent denaturation. We have analyzed the thermal resistance and unfolding pathway of two mutant, functional TSPs carrying end-terminal peptide fusions. Whereas the C-terminal fusion has minor effects on the TSP stability, the presence of a 23-mer foreign peptide at the N terminus (protein ATSP) results in a significant enhancement of the thermal resistance by retarding the first transition step of the unfolding process. At 65 degrees C and in 2% SDS, the unfolding rate constant for the transition from the native to the unfolding intermediate is 9.3 x 10(-4) s(-1) for ATSP versus 1.7 x 10(-3) s(-1) for wild-type TSP. On the other hand, the electrophoretic mobility of ATSP intermediates is greatly affected, proving structural modifications induced by the fused peptide. These results suggest a critical participation of the N-terminal domain in the unfolding kinetic barriers generated during the TSP denaturation pathway.

Bacteriophage P22↗
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

Insertional mutagenesis in the tailspike protein of bacteriophage P22.

The tailspike protein (TSP) of bacteriophage P22 is a homotrimeric multifunctional protein responsible for recognition and hydrolysis of Salmonella typhimurium host receptors. Once properly folded, TSP shows an unusual stability to temperature and detergent denaturation, prompting the analysis of TSP as a framework for the positioning of heterologous protein segments. We have explored the flexibility of inner sites and both amino and carboxy termini to accommodate foreign peptides for phage display. In the examined inner sites, TSP is extremely sensitive to minor sequence modifications, the folding intermediates being rapidly degraded. However, both the amino and carboxy termini are tolerant to peptide fusions, rendering stable and functional chimeric proteins. Surprisingly, the amino terminus, which connects the tail to the neck structure, can accept large peptide fusions, and the foreign amino acid stretches are solvent-exposed and highly antigenic on assembled, infectious virus particles.

Amino Acid Sequence↗
PubMed1998

The incidence of breastfeeding in our environment.

AIMS: To establish the incidence of breastfeeding and its persistence after three and six months; to identify the factors which might modify attitudes towards breastfeeding. METHODS: An interview, administered to mothers of term born infants of adequate weight for gestational age, after a delivery of one sole foetus, between 1st March and 31st May 1997. Mothers were asked about: previous pregnancies, children and type of feeding; during this pregnancy, their intentions regarding feeding; supervision of pregnancy, and the information received regarding breastfeeding; their work situation, and educational level. Questions regarding the neonatal period referred to the kind of lactation initiated, information received, and the use of a pacifier and supplements. A two-part poll was conducted by telephone after 3 months and after 6 months, enquiring about what kind of feeding was used, the reason for change (if any), who had provided information regarding the change, degree of satisfaction, and work situation. Three hundred and twenty-nine polls were completed, accounting for 70% of the births. RESULTS: During pregnancy, 91% of mothers had intended to breastfeed, and this figure was maintained at birth. A trend towards breastfeeding was observed: 74% of those who had fed earlier children artificially started breastfeeding this time, compared with 7% of mothers who changed from breastfeeding to artificial feeding. After three months, 57% of mothers continued to breastfeed their child, and 24% after six months. High educational level exerted a positive influence on the duration of breastfeeding (OR = 1.7; p = 0.03) and the giving of supplements had a negative effect (OR = 0.4; p = 0.04). The fact that mothers work outside the home did not modify the duration of breastfeeding. CONCLUSIONS: The rate of breastfeeding is high (91%). Among mothers with previous children, there is a greater trend to change from artificial feeding to breastfeeding (74% vs 7%; p < 0.002). The mother's educational level is the most important positive factor, and the early giving of supplements the most important negative factor.

Attitude↗
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

Peptide display on functional tailspike protein of bacteriophage P22.

The tailspike protein (TSP) of Salmonella typhimurium P22 bacteriophage is a multifunctional homotrimer, 6 copies of which are non-covalently attached to the capsid to form the virion tail in the last reaction of phage assembly. An antigenic peptide of foot-and-mouth disease virus (FMDV), aa 134-156 of protein VP1, has been joined to the carboxy terminus of TSP, and produced as a fusion protein in Escherichia coli directed by the trp promoter. The resulting fusion protein is soluble, stable, non-toxic, and can be easily purified by standard procedures. Moreover, both the endorhamnosidase and capsid assembly activities of the TSP are conserved, permitting the fusion protein to reconstitute infectious viruses by in vitro association with tailless particles. In both free TSP and P22 chimeric virions, the foreign peptide is solvent-exposed and highly antigenic, indicating that P22 TSP could be an appropriate carrier protein for multimeric peptide display.

Amino Acid Sequence↗
PubMed1995

A recombinant foot-and-mouth disease virus antigen inhibits DNA replication and triggers the SOS response in Escherichia coli.

The 3D gene of foot-and-mouth disease virus encodes the viral RNA dependent RNA polymerase, also called virus infection associated (VIA) antigen, which is the most important serological marker of virus infection. This 3D gene from a serotype C1 virus has been cloned and overexpressed in Escherichia coli under the control of the strong lambda lytic promoters. The resulting 51 kDa recombinant protein has been shown to be immunoreactive with sera from infected animals. After induction of gene expression, an immediate and dramatic arrest of cell DNA synthesis occurs, similar to that produced by genotoxic doses of the drug mitomycin C. This effect does not occur during the production of either a truncated VIA antigen or other related and non-related viral proteins. The inhibition of DNA replication results in a subsequent induction of the host SOS DNA-repair response and in an increase of the mutation frequency in the surviving cells.

Capsid↗
PubMed1995

Mitomycin C stimulates thermally induced recombinant gene expression in Escherichia coli MC strains.

The effects of mitomycin C on C1857-controlled recombinant gene expression have been explored in E. coli cultures when the drug was added simultaneously to the thermal induction. A significantly improved yield of homologous, heterologous and chimeric fusion proteins was observed in E. coli MC1061 and GE864 (a MC4100 derivative) thermoinduced cells. This feature was not detected in other E. coli strains and does not involve a gene dosage mechanism but a strain-dependent stimulation of gene expression unrelated to the RecA protease activity.

DNA, Bacterial↗