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I Alvarez

Publications and source records attributed to I Alvarez.

At least 37 records · Page 2Linked to original sources
PubMed2004

Genetic relationships and admixture among sheep breeds from Northern Spain assessed using microsatellites.

Although many research papers have studied diversity and differentiation within livestock species, genetic relationships among neighboring populations remain poorly understood. Here we apply recent methodologies to analyze the polymorphism of 14 microsatellites in 238 unrelated individuals belonging to six sheep breeds from Northern Spain to ascertain their historical relationships and the relative genetic contributions existing between populations. Individual genotypes were analyzed to assess the existence of an underlying genetic structure. Long-term and recent migration rates were estimated to identify patterns of relative genetic contribution among breeds. The complete data set showed a strong population structure derived from both different ancestral origins and some geographical patterns of recent gene flow. Two of the analyzed breeds (Black-faced Latxa and Churra) had a marked genetic background, supporting the hypothesis that, regardless of their phenotypical similarities, they have different ancestral origins. Some of the more presumably related breeds had negative long-term admixture coefficients, showing that they diverged only recently. In addition, we show how methodologies for estimation of long-term gene flow and recent patterns of migration are complementary, providing information about migration rates on different timescales.

Animals↗
PubMed2003

The influence of process parameters for the inactivation of Listeria monocytogenes by pulsed electric fields.

The influence of the electric field strength, the treatment time, the total specific energy and the conductivity of the treatment medium on the Listeria monocytogenes inactivation by pulsed electric fields (PEF) has been investigated. L. monocytogenes inactivation increased with the field strength, treatment time and specific energy. A maximum inactivation of 4.77 log(10) cycles was observed after a treatment of 28 kV/cm, 2000 micros and 3490 kJ/kg. The lethal effect of PEF treatments on L. monocytogenes was not influenced by the conductivity of the treatment medium in a range of 2, 3 and 4 mS/cm when the total specific energy was used as a PEF control parameter. A mathematical model based on the Weibull distribution was fitted to the experimental data when the field strength (15-28 kV/cm), treatment time (0-2000 micros) and specific energy (0-3490 kJ/kg) were used as PEF control parameters. A linear relationship was obtained between the log(10) of the scale factor (b) and the electric field strength when the treatment time and the total specific energy were used to control the process. The total specific energy, in addition to the electric field strength and the treatment time, should be reported in order to evaluate the microbial inactivation by PEF.

Colony Count, Microbial↗
PubMed2003

Optimization of making barrel-fermented dry muscatel wines.

The optimization of making barrel-fermented muscatel wines requires determining what type of must clarification is most suitable for the quality of the wine, as well as what type of barrel will yield the most acceptable wines. This is achieved by adding pectolytic enzymes to clarify part of the muscatel must statically; the rest is clarified by vacuum filtration. The musts obtained are fermented in French and American oak barrels and, once fermentation has ceased, they are kept with their lees for 2 months, with periodic stirring. Eleven conventional parameters and 31 volatile compounds were quantified, and a sensory analysis of the wines was produced, which led us to conclude that static clarification with pectolytic enzymes from the muscatel musts produces the best-structured wines and the larger content of higher alcohols, esters, and terpenic compounds. The wines fermented in American oak barrels received the highest overall marks, which may be due to the greater aromatic complexity given off by the compounds in the wood.

Alcohols↗
PubMed2003

Ribosomal ITS sequences and plant phylogenetic inference.

One of the most popular sequences for phylogenetic inference at the generic and infrageneric levels in plants is the internal transcribed spacer (ITS) region of the 18S-5.8S-26S nuclear ribosomal cistron. The prominence of this source of nuclear DNA sequence data is underscored by a survey of phylogenetic publications involving comparisons at the genus level or below, which reveals that of 244 papers published over the last five years, 66% included ITS sequence data. Perhaps even more striking is the fact that 34% of all published phylogenetic hypothesis have been based exclusively on ITS sequences. Notwithstanding the many important contributions of ITS sequence data to phylogenetic understanding and knowledge of genome relationships, a number of molecular genetic processes impact ITS sequences in ways that may mislead phylogenetic inference. These molecular genetic processes are reviewed here, drawing attention to both underlying mechanism and phylogenetic implications. Among the most prevalent complications for phylogenetic inference is the existence in many plant genomes of extensive sequence variation, arising from ancient or recent array duplication events, genomic harboring of pseudogenes in various states of decay, and/or incomplete intra- or inter-array homogenization. These phenomena separately and collectively create a network of paralogous sequence relationships potentially confounding accurate phylogenetic reconstruction. Homoplasy is shown to be higher in ITS than in other DNA sequence data sets, most likely because of orthology/paralogy conflation, compensatory base changes, problems in alignment due to indel accumulation, sequencing errors, or some combination of these phenomena. Despite the near-universal usage of ITS sequence data in plant phylogenetic studies, its complex and unpredictable evolutionary behavior reduce its utility for phylogenetic analysis. It is suggested that more robust insights are likely to emerge from the use of single-copy or low-copy nuclear genes.

DNA, Ribosomal Spacer↗
PubMed2003

Inactivation of Salmonella enterica serovar enteritidis by ultrasonic waves under pressure at different water activities.

The inactivation of Salmonella enterica serovar Enteritidis by ultrasonic waves (20 kHz; 117- microm wavelength) under pressure (175 kPa) at nonlethal temperatures (manosonication [MS]) and lethal temperatures (manothermosonication [MTS]) in media of different water activities has been investigated. Heat decimal reduction time values increased 30 times when the water activity was decreased from nearly 1 to 0.96, but the MS resistance was increased only twofold. The inactivation of Salmonella serovar Enteritidis by ultrasound under pressure at low water activities was a phenomenon of the "all-or-nothing" type. A synergistic lethal effect was observed between heat and ultrasound in media with reduced water activity; the lower the water activity, the greater the synergistic effect. This work could be useful for improving sanitation and preservation treatments of foods, especially those which are sensitive to temperature and those in which components protect microorganisms to heat. It also contributes to our knowledge of microbial inactivation mechanisms by MS and MTS treatments.

Colony Count, Microbial↗
PubMed2002

Müllerian adenosarcoma of the cervix with heterologous elements: report of a case and review of the literature.

BACKGROUND: Müllerian adenosarcoma (MA) is a rare neoplasm composed of benign epithelial and malignant stromal components. Its location in the cervix and the presence of heterologous elements are extremely infrequent (to our knowledge, only 14 more cases have been reported in the English literature). We describe another case of MA of the uterine cervix with heterologous elements and review the clinical and pathological features of these tumors. CASE REPORT: A nulliparous 25-year-old woman was admitted to the hospital because of metrorrhagia and recurrent masses, dependent on the cervix, initially considered endocervical polyps. Microscopically, the last curettage performed revealed a tumor composed of two elements, epithelial and mesenchymal. The epithelial elements were benign endocervical type glands, and the mesenchymal were sarcomatous, containing minor foci of cartilage. A diagnosis of endocervical heterologous adenosarcoma was reached, and a total hysterectomy and bilateral salpingo-oophorectomy were performed. The patient is alive 2 years after the surgical procedure. Neither chemotherapy nor other adjuvant therapies have been administered, and she is clinically free of disease at the moment. CONCLUSION: Because MA with heterologous elements seems to appear at the earliest stages of the reproductive lifespan in women, commonly with a history of recurrent polyps, and because its malignant potential is uncertain, gynecologists and pathologists should be aware and think about the possibility of this tumor. Long-term follow-up is essential and so is the accumulation of individual cases to provide further experience with these unusual neoplasms.

Adenosarcoma↗
PubMed2002

Environmental factors influencing the inactivation of Listeria monocytogenes by pulsed electric fields.

AIMS: To investigate the influence of the growth phase, growth temperature, storage time, pH and aw of the treatment medium on the resistance of Listeria monocytogenes to pulsed electric fields (PEF). METHODS AND RESULTS: Square wave pulses of 2 micros at a frequency of 1 Hz and 25 and 28 kV cm(-1) were used. Cells were more PEF resistant in the stationary than in the exponential phase at both incubation temperatures investigated (4 and 35 degrees C). Cells grown at 4 degrees C were more PEF sensitive than cells grown at 35 degrees C independent of the growth phase. After a treatment of 25 kV cm(-1) and 800 micros, 1.48, 3.86 and 5.09 log10 cycles of inactivation were obtained at pH 7.0, 5.4 and 3.8, respectively. A reduction in the aw of the treatment medium protected cells against PEF treatments. CONCLUSIONS: The PEF resistance of L. monocytogenes depended on different environmental factors. The influence of growth conditions and treatment medium characteristics should be known and controlled to obtain reproducible and reliable PEF inactivation data. SIGNIFICANCE AND IMPACT OF THE STUDY: Erroneous conclusions and misinterpretation of results are possible if factors affecting the PEF resistance of L. monocytogenes are not considered during PEF inactivation studies.

Colony Count, Microbial↗
PubMed2001

Photoionization of metastable O+ ions: experiment and theory.

High-resolution absolute experimental measurements and two independent theoretical calculations were performed for photoionization of O+ ions from the 2P(o) and 2D(o) metastable levels and from the 4S(o) ground state in the photon energy range 30-35.5 eV. This is believed to be the first comparison of experiment and theory to be reported for photoionization from metastable states of ions. While there is correspondence between the predicted and measured positions and relative strengths of the resonances, the cross-section magnitudes and fine structure are sensitive to the choice of basis states.

Journal Article↗
PubMed2001

The Cys-67 residue of HLA-B27 influences cell surface stability, peptide specificity, and T-cell antigen presentation.

Cys-67 of HLA-B27 is located in the B pocket, which determines peptide-binding specificity. We analyzed effects of the Cys-67 --> Ser mutation on cell surface expression, peptide specificity, and T-cell recognition of HLA-B*2705. Surface expression was assessed with antibodies recognizing either native or unfolded HLA proteins. Whereas native B*2705 molecules predominated over unfolded ones, this ratio was reversed in the mutant, suggesting lower stability. Comparison of B*2705- and Cys-67 --> Ser-bound peptides revealed that the mutant failed to bind approximately 15% of the B*2705 ligands, while binding as many novel ones. Two peptides with Gln-2 found in both B*2705 and Cys-67 --> Ser are the first demonstration of natural B*2705 ligands lacking Arg-2. Other effects of the mutation on peptide specificity were: 1) average molecular mass of natural ligands higher than for B*2705, 2) bias against small residues at peptide position (P) 1, and 3) increased P2 permissiveness. The results suggest that the Cys-67 --> Ser mutation weakens B pocket interactions, leading to decreased stability of the mutant-peptide complexes. This may be partially compensated by interactions involving bulky P1 residues. The effect of the mutation on allorecognition was consistent with that on peptide specificity. Our results may aid understanding of the pathogenetic role of HLA-B27 in spondyloarthropathy.

Amino Acid Substitution↗
PubMed2001

Synthetic peptide vaccine against Taenia solium pig cysticercosis: successful vaccination in a controlled field trial in rural Mexico.

Taenia solium cysticercosis seriously affects human health when localised in the central nervous system (CNS) and causes great economic loss in pig husbandry in rural areas of endemic countries. Increasing the resistance to the parasite in the obligatory host pig may help in curbing transmission. Three synthetic peptides based on protein sequences of the murine parasite Taenia crassiceps, which had previously been shown to induce protection in mice against homologous challenge, were tested as a vaccine against T. solium cysticercosis in pigs. Vaccinated and unvaccinated piglets (240 in all) were distributed in pairs among the peasants' households of two rural villages in Mexico in which 14% of the native pigs were cysticercotic. Ten to twelve months later, the effect of vaccination was evaluated at necropsy. Vaccination decreased the total number of T. solium cysticerci (98.7%) and reduced the prevalence (52.6%). The natural challenge conditions used in this field trial strengthen the likelihood of successful transmission control to both pig and human through a large-scale pig vaccination program. We believe this is a major contribution in anticysticercosis vaccine development as these rather simple yet protective peptides are potentially more cost-effective to produce and less variable in results than antigens that are more complex.

Amino Acid Sequence↗
PubMed2001

Identification of novel HLA-B27 ligands derived from polymorphic regions of its own or other class I molecules based on direct generation by 20 S proteasome.

HLA-B27 is strongly associated with ankylosing spondylitis. Natural HLA-B27 ligands derived from polymorphic regions of its own or other class I HLA molecules might be involved in autoimmunity or provide diversity among HLA-B27-bound peptide repertoires from individuals. In particular, an 11-mer spanning HLA-B27 residues 169-179 is a natural HLA-B27 ligand with homology to proteins from Gram-negative bacteria. Proteasomal digestion of synthetic substrates demonstrated direct generation of the B27-(169-179) ligand. Cleavage after residue 181 generated a B27-(169-181) 13-mer that was subsequently found as a natural ligand of B*2705 and B*2704. Its binding to HLA-B27 subtypes in vivo correlated better than B27-(169-179) with association to spondyloarthropathy. Proteasomal cleavage generated also a peptide spanning B*2705 residues 150-158. This region is polymorphic among HLA-B27 subtypes and class I HLA antigens. The peptide was a natural B*2704 ligand. Since this subtype differs from B*2705 at residue 152, it was concluded that the ligand arose from HLA-B*3503, synthesized in the cells used as a source for B*2704-bound peptides. Thus, polymorphic HLA-B27 ligands derived from HLA-B27 or other class I molecules are directly produced by the 20 S proteasome in vitro, and this can be used for identification of such ligands in the constitutive HLA-B27-bound peptide pool.

Amino Acid Sequence↗
PubMed2001

Minimal alterations in the HLA-B27-bound peptide repertoire induced upon infection of lymphoid cells with Salmonella typhimurium.

OBJECTIVE: To characterize putative changes in the HLA-B27-bound peptide repertoire following infection of lymphoid cells with Salmonella typhimurium, a bacterium known to trigger reactive arthritis in HLA-B27-positive individuals. METHODS: A protocol was developed for efficient large-scale infection of lymphoblastoid cell transfectants expressing HLA-B*2705. HLA-B27-bound peptide pools were isolated from noninfected and infected B*2705+ cells and comparatively analyzed by high-performance liquid chromatography. Peptide-containing chromatographic fractions from noninfected and infected cells were systematically compared by mass spectrometry (MS) to look for putative differences at the level of individual peptides. RESULTS: The presence of B*2705 did not influence S typhimurium invasion, since this was equally efficient in nontransfected or B27-transfected cells. The chromatographic profiles of B*2705-bound peptides from noninfected and infected cells were virtually identical. A total of 808 molecular species were compared by MS. Of these, 807 were present in both infected and noninfected cells. Only one molecular species from infected cells lacked a detectable counterpart in noninfected cells. CONCLUSION: Intracellular infection of lymphoid cells by S typhimurium induces minimal alterations in the HLA-B27-bound peptide repertoire. Minor changes detectable by cytotoxic T lymphocytes, but not easily amenable to direct biochemical analysis, are not ruled out.

Arthritis, Reactive↗
PubMed2001

Large sharing of T-cell epitopes and natural ligands between HLA-B27 subtypes (B*2702 and B*2705) associated with spondyloarthritis.

HLA-B*2702 is an ankylosing spondylitis-associated allotype that differs from the more common B*2705 at residues 77, 80, and 81, in the peptide-binding site. The diversity and fine specificity of alloreactive cytolytic T-lymphocyte (CTL) raised against B*2702 were analyzed at the clonal level. Significant crossreaction with B*2705 and B*2709 indicated that the three subtypes share numerous T-cell epitopes. However, some epitopes shared by B*2702 and B*2705 were lost in B*2709, which correlates with weaker association of this subtype to disease. Clonal specificities were donor-dependent, indicating that allo-immunogenicity is variable among individuals. Anti-B*2702 CTL were little affected by single mutations mimicking B*2702/B*2705 polymorphism, but the double mutant at positions 77 and 81 was recognized worse than B*2705, suggesting a compensatory effect of residue 80. Thus, HLA-B27 polymorphism modulated alloreactivity through cooperative and compensatory effects on T-cell epitope structure. Comparison of B*2705- and B*2702-bound peptide repertoires revealed that they overlapped by 73% and 81%, respectively. This was larger than B*2702/B*2705 cross-reaction, indicating that HLA-B27 allospecificity is only partially determined by the nature of peptide repertoires. The large sharing of natural ligands and T-cell epitopes is consistent with a pathogenetic role of B*2702 and B*2705 in spondyloarthritis based on antigen presentation.

Antigen Presentation↗
PubMed2001

Variability of genetic alterations in different sites of head and neck cancer.

OBJECTIVE: Tumors arising from different sites of the head and neck area have different clinical behavior. However, most of the studies on genetic alterations in head and neck squamous cell carcinomas do not make a distinction between the sites within this area. The objective of this study is to compare the genetic alterations in three different sites of the head and neck (larynx, oropharynx, and hypopharynx). STUDY DESIGN: Prospective study. METHODS: Thirty-eight laryngeal, 29 oropharyngeal, and 37 hypopharyngeal carcinomas were studied. DNA from tumor and healthy tissue was evaluated for amplification of the oncogenes at 11q13 region (CCND1, FGF3, FGF4 and EMS1) and of the oncogenes MYC and ERBB1; for integration of the human papillomavirus (HPV) types 6b and 16; for loss of heterozygosity (LOH) at p53 and NAT2; and for the cellular DNA content. RESULTS: FGF3 and FGF4 showed a significantly higher frequency of amplification in hypopharyngeal tumors (P =.006 and P =.0002, respectively). CCND1 amplification had a nearly statistically significant (P =.072) higher frequency of amplification in hypopharyngeal tumors. Aneuploid tumors were found in a significantly lower proportion in the larynx (P =.03) compared with the other sites. For the other genetic alterations, no significant differences among the three sites were found. CONCLUSIONS: These results suggest that cancers originating from different sites in the head and neck may have different tumor biology. Therefore, they should be considered as different entities.

Aneuploidy↗
PubMed2001

Treatment of low grade gastric mucosa-associated lymphoid tissue lymphoma in stage I with Helicobacter pylori eradication. Long-term results after sequential histologic and molecular follow-up.

BACKGROUND AND OBJECTIVES: Most cases of gastric low-grade mucosa-associated lymphoid tissue (MALT) lymphoma are associated with H. pylori. In localized disease (stage I), eradication of H. pylori can result in histologic regression of the lymphoma in 50% to 100% of the patients. Moreover, in half of the apparently cured patients a monoclonal rearrangement of the IgH gene can be demonstrated. However, data on the long-term outcome of the patients are scarce. We report the evolution of a series of patients followed-up since 1994 in order to evaluate the long-term outcome of the apparently cured lymphoma. DESIGN AND METHODS: From January 1994 to July 2000, 19 consecutive patients with stage I gastric low grade MALT lymphoma were sequentially studied in our hospital. They had all been diagnosed by endoscopy and had had a complete staging (including CT-scan, contrast X-ray of the small bowel, bone marrow biopsies, immunophenotyping of bone marrow and peripheral blood and, in the later years, endoscopic ultrasonography). Diagnosis required established histologic criteria for low grade MALT lymphoma in the samples obtained by endoscopy. The investigation of H. pylori status included histologic search, serology and breath test urea-(13)C. Only patients in stage I disease associated with H. pylori were included in the study. Patients received standard triple therapy for eradication of H.pylori and after treatment were sequentially followed-up with endoscopies performed every 2-3 months in the first year, every 6 months in the second year and then yearly. Post-treatment biopsies were obtained by endoscopy for histologic studies, H. pylori cultures and molecular studies. The criteria of Wotherspoon et al. were used for the histological evaluation. Molecular studies were performed with a polymerase chain reaction analysis of the IgH gene using semi-nested procedures with consensus primers for the V(H) (Fr3A/Fr2A) and J(H) (LJH and VLJH) regions. RESULTS: After the eradication treatment, 18 of the 19 patients (94.7%) achieved histologic regression of the MALT lymphoma that occurred after a mean of 4.6 months (range 2-19). In 11 of the 18 histologically cured patients (61%) a monoclonal rearrangement of the IgH gene was demonstrated. In 2 patients the monoclonality disappeared completely, but 9 of the 11 patients (82%) had either persistent (3 patients) or intermittently persistent (5 patients) monoclonality for as long as 64 months. None of the patients who achieved a histologic remission (either with or without monoclonality) relapsed after a mean follow-up of 37 months (range 2-78). Two patients were lost to follow-up and another patient died of a gastric carcinoma; the remaining 15 patients are still in histologic remission after a mean period of 43 months (range 5-78). Ten patients studied between 1994 and the end of 1996 are in remission after a mean of 59 months (range 33-78). INTERPRETATIONS AND CONCLUSIONS: In most cases of gastric low-grade MALT lymphoma in stage I eradication of H. pylori can produce histologic regression of the lymphoma and this regression can be maintained for years. However, IgH gene monoclonality can be detected and persists in most cases. Although this persistent monoclonality seems to indicate the presence of a latent lymphoma population, over a period of 6 years it has not so far influenced the outcome. These findings indicate that in cases of localized gastric low-grade MALT lymphoma associated with H. pylori, the first step of treatment should be eradication of the H. pylori; however, a close and long follow-up is essential to determine the ultimate outcome of these patients and the possible significance of the persistent monoclonality.

Adult↗
PubMed2000

N+ charge transfer and N+2 dissociation in N2 at swarm energies.

This paper reports a drift-tube-mass-spectrometer measurement of the relative abundances of N+ and N+2 in pure nitrogen, over a ratio of electric field to gas density, E/N, from 800 to 7200 Td [1 townsend (Td)=10(-17) V cm(2)]. A proposed charge transfer dissociation scheme between the above two ions and N2 allowed us to obtain spatial rate coefficients for charge transfer and dissociation over the E/N range 800-2800 Td. Using previously measured cross sections for the above processes, and assuming a Maxwellian distribution of ion velocities, we calculated the reaction coefficients, which were found to be in good agreement with our measured values. In particular, the present results support the trend toward fairly high charge transfer cross section values for N+ energies above 10 eV. In the overlap range between 2.4 and 7.2 kTd, our concentration ratio [N(+)/N(+)(2)] is about five times smaller than that measured previously from a diffuse Townsend discharge in which electron impact is involved in addition to N+2 collisional dissociation with N2, but has the same trend. Thus it seems that, besides N+2 dissociation by electron impact, collisional dissociation becomes important at elevated values of E/N. In connection with previous discharge work in nitrogen, the present study may help explain the enhanced cathode yields observed.

Journal Article↗