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J L López

Publications and source records attributed to J L López.

At least 19 recordsLinked to original sources
PubMed2006

Two-dimensional electrophoresis in proteome expression analysis.

Cell proteomes are complex, given they consist of several thousand proteins. Two-dimensional electrophoresis (2DE) is unique not only for its ability to simultaneously separate thousands of proteins but also for detecting post- and co-translational modifications, which cannot be predicted from genome sequences. This review will describe the protocols applied to prepare 2D gels properly, and analyse and summarise the major challenges for successful proteome analysis using 2DE, i.e. the ability to analyse very alkaline, hydrophobic and/or low or high M(r) proteins with high resolution and the ability to detect minor components. Challenges involving sample preparation and solubilisation prior to the first dimension IEF/IPG step will be studied in depth. Sample preparation is crucial in 2DE studies and greatly influences other stages of the technique. It is the aim of this review not only to describe the challenges and limitations of 2DE but also to suggest the avenues, the evolution, the potential and the future of 2DE in proteomics.

Electrophoresis, Gel, Two-Dimensional↗
PubMed2006

Dynamics of a hepatitis B virus e antigen minus population ascribed to genotype F during the course of a chronic infection despite the presence of anti-HBs antibodies.

The in vivo evolution of genotype F HBV variants was recorded in a chronically infected patient throughout a 3-year observation period. Fluctuating levels of HBs Ag and anti-HBs antibodies were recorded, both of them cocirculating in peripheral blood samples at given times. Fifty S gene derived clones were sequenced and phylogenetically analyzed. As expected, some amino acid replacements within the S ORF were also observed within the P ORF while others were silent for the former. Such change was statistically significant for both S and P overlapping genes, which clearly indicates the appearance of a positive selection pressure. Supporting this notion, amino acid replacements were documented at both B and T cell epitopes in samples from 1997 and 1998. Several mutations were documented within and outside the "a" determinant in the major hydrophilic region. Such substitutions might have resulted from the attempt of HBV to evade both humoral and/or cellular immune response. To the best of our knowledge this unusual profile of HBV variants in presence of usually "neutralizing" anti-HBs antibodies was examined in vivo for the first time.

Amino Acid Sequence↗
PubMed2006

Short communication: Correlations between udder morphology, milk yield, and milking ability with different milking frequencies in dairy goats.

Tinerfeñ a breed goats were assigned to 2 experimental herds and milked once (n = 28) or twice (n = 24) daily to study correlations between udder morphology, milk yield, and milking ability during the middle stage of the first lactation. Pearson correlation coefficients were significantly higher between yield and measures of udder globulousness (udder volume, r = 0.79 and r = 0.59; perimeter of insertion of the udder, r = 0.47 and r = 0.37; distance between teats, r = 0.77 and r = 0.28, for goats milked once and twice daily, respectively) than for length parameters (cistern floor distance, r = 0.40 and r = -0.29; udder depth, r = -0.20 and r = 0.20). The globulousness of the udder was correlated with easier milking ability, as shown by milk fractioning (r = 0.49 to 0.70) and milk flow measures (r = 0.32 to 0.49). The results showed that the globulousness of the udder is more important than length measurements in assessing milk yield and milking ability.

Animals↗
PubMed2005

Role of proteomics in taxonomy: the Mytilus complex as a model of study.

Several strategies carried out for the application of proteomic methodologies to species and populations are summarized. Species of the genus Mytilus are used as a model organism to explain these strategies. The proteomics needed to differentiate populations, species, following some different approaches are provided. Moreover, there is an explanation of when it is most critical to carry out a rigorous analysis of this type. Sample preparation, selection of the most appropriate tissue of this organism for a comparative analysis, two-dimensional gels, computer analysis, mass spectrometry (MS) combined with two-dimensional electrophoresis (2-DE) are described. Then, the inconveniences of working with species like those of the genus Mytilus that are poorly represented in databases will be presented along with a description of how to approach this problem. Likewise, the review will include the strategy to follow when dealing with species, like mussels, that present a high degree of genetic polymorphism. The different protein-expression-based strategies used to approach the problem of differentiating Mytilus species will also be shown. Examples are presented to illustrate the use of 2-DE and MS to differenciate populations, species in taxonomic analysis.

Animals↗
PubMed2003

Genetic variability of the marine mussel Mytilus galloprovincialis assessed using two-dimensional electrophoresis.

Two-dimensional electrophoresis (2-DE) has been used to measure the degree of genetic variability of the marine mussel Mytilus galloprovincialis. Genetic polymorphisms were detected in 33 of a total of 86 polypeptides scored among the most abundant proteins from foot samples in 38 individuals. Estimates of average heterozygosity were 0.101+/-0.018 and 0.114+/-0.021 in a natural and a cultured population, respectively, from the NW of the Iberian Peninsula. These are the highest estimates of average heterozygosity reported by 2-DE in an animal species to date. We consider that these data throw open the question of the level of genetic variability detectable by two-dimensional electrophoresis. Multilocus genotype data were used to infer haplotypic frequencies by means of the EM algorithm in order to detect linkage disequilibrium between loci coding abundant proteins. Significant associations were found in 22.7% of the 406 two-locus pairs analysed. Also, clusters of loci in which all pairwise combinations exhibit statistically significant associations were detected and physical linkage between some of these loci is postulated from the linkage disequilibrium data.

Animals↗
PubMed2002

'Hbe minus' mutants of hepatitis B virus. Molecular characterization and its relation to viral genotypes.

The precore-core and S genes of HBV were directly sequenced from serum samples of 42 patients with chronic hepatitis B (16 hepatitis Be antigen [HBeAg]+and 26 anti-HBe+). Viral genotype A was identified in 12 cases, genotype D in 11 and genotype F in 19 cases. Precore mutations, mainly M1 (G1896A, stop at codon 28) were similarly found among viral genotypes A and D: seven cases (58%) and six cases (55%), respectively. The selection of M1 mutants from genotype D resulted in a more stable encapsidation signal but was less stable for genotype A precore mutants. Oddly enough, the encapsidation signal of M1 precore mutants from genotype F sequences were evenly distributed among less stable (genotype A M1 mutants) and more stable encapsidation signal (genotype D M1 mutants). This study shows that the selection of precore mutants that preclude the HBeAg expression, including the M1 mutation, does not necessarily depend on the stabilization of the encapsidation signal or the viral genotype In addition, the particular behavior of genotype F genomes at precore region is described.

Adolescent↗
PubMed2001

Phylogenetic analysis of the hepatitis B virus (HBV) genotype F including Argentine isolates.

Seven human hepatitis B virus (HBV) genotypes have been described. Genotype F, indigenous to the Americas, is the most diverging group. Our in-depth analysis of the genetic distances of this genotype included ten Argentine samples. Phylogenetic analysis on the small (S) gene of the surface antigen showed four different clusters within genotype F, which were associated with a well-defined geographical origin. Even closely connected sequences sharing a common ancestor had shown some characteristics or markers indicating geographical differentiation. Nucleotide sequences and amino acids translated according to the polymerase open reading frame (P-ORF), rather than S-ORF, yielded a more discriminating analysis.

Argentina↗
PubMed2001

Renal tolerance to cisplatin in patients 70 years and older.

The purpose of this study was to evaluate cisplatin nephrotoxicity in patients 70 years and older and to identify factors influencing nephrotoxicity occurrence. Forty-nine (N = 49) patients older than 70 years were studied retrospectively. All patients received treatment with cisplatin. Variables under study were as follows: prechemotherapy serum creatinine levels (Crb), maximum serum creatinine level during treatment (Crmax), steady serum creatinine level 3 months after treatment completion (Crstb), as well as their corresponding creatinine clearance values (CrbC, CrmaxC, CrstbC) as calculated by the Cockroft and Gault formula. Maximum creatinine increment (Imax = Crmax - Crb), stable creatinine increment (Istb = Crstb - Crb) and the corresponding clearance decrements (Dmax and Dstb) were calculated as well. The potential relationship of the above variables to cisplatin dose intensity and accumulated dose as well as to different prognostic factors were also considered. Assessment of associated conditions was carried out by means of Charlson comorbidity index. The patients' mean age was 73 years (range: 70-79 years). There were 43 men (88%) and 6 women (12%). Mean cisplatin dose intensity was 27 mg/m2/wk. A total of 157 chemotherapy courses were administered with a mean of 3.2 per patient. Mean Crb was 1.02 mg/dl (95% CI = 1.02-1.12), mean Crmax was 1.45 (95% CI = 1.34-1.46), and mean Crstb was 1.24 (95% CI = 1.16-1.32). Imax was equal to 0 in 13 patients (26%) and more than 0.4 mg/dl in 21 patients (43%). Istb was equal to 0 or negative in 22 (45%) and more than 0.4 in only 9 patients (18.3%). No significant relationship of serum creatinine levels, creatinine clearance levels, or of their increments or decrements to cisplatin dose intensity or accumulated dose were found. These levels also did not correlate with age, sex, comorbidity or Eastern Cooperative Oncology Group score. In 85% of patients, Crmax was reached between chemotherapy initiation and the third chemotherapy course, and thereafter renal function began to recover despite continued administration of cisplatin. Cisplatin is well tolerated by patients 70 years and older and dose intensity does not seem to influence renal function deterioration. Therefore, we failed to find reasons to encourage modification or limitation of cisplatin treatment in the elderly population.

Aged↗
PubMed2000

Synthesis and enzyme inhibitory activities of a series of lipidic diamine and aminoalcohol derivatives on cytosolic and secretory phospholipases A2.

We have synthesised some lipidic diamines and aminoalcohols and examined their behaviour as inhibitors of secretory and cytosolic PLA2. Some structure-activity relationships considerations have been deduced. Compound 14 was a potent and selective inhibitor of cPLA2 and compound 4 showed a dual inhibitory profile against both types of PLA2 while no cytotoxicity at 10 microM on human neutrophils or on murine macrophage line was observed for both.

Amino Alcohols↗
PubMed1999

Maximal and explosive force production capacity and balance performance in men of different ages.

A group of 32 healthy men (M) divided into three different age groups, i.e. M20 years [mean 21 (SD 1); n = 12], M40 [mean 40 (SD 2); n = 10] and M70 [mean 71 (SD 5); n = 10] volunteered as subjects for examination of maximal and explosive force production of leg extensor muscles in both isometric and dynamic actions (squat jump, SJ and counter movement jump, CMJ, and standing long-jump, SLJ). The balance test was performed on a force platform in both isometric and dynamic actions. Maximal bilateral isometric force value in M70 was lower (P < 0.001) than in M40 and as much as 46% lower (P < 0.001) than that recorded in M20 (P < 0.001). The maximal rate of force development (RFD) on the force-time curve was in M70 lower (P < 0.001) than in M40 and as much as 64% lower than in M20. The heights in SJ and CMJ and the distance in SLJ in M70 were lower (P < 0.001) than in M40 and M20 (P < 0.001). In response to modifications of the visual surroundings the older subjects were 24%-47% (P < 0.05 and P < 0.001) slower in their response time in reaching the lit centre (TT) and remained 20%-34% (P < 0.001) less time inside the centre (TC) from the overall time of lighting than M40 and M20, respectively. In both older groups the individual values of isometric RFD correlated significantly (P < 0.05) with the individual balance values of TT and TC. The present results would suggest that the capacity for explosive force production declines drastically with increasing age, even more than maximal muscle strength. Aging may also lead to impaired balance with a decrease in event detection and speed of postural adjustments. The decreased ability to develop force rapidly in older people seems to be associated with a lower capacity for neuromuscular response in controlling postural sway.

Adult↗
PubMed1999

Synthesis and inotropic activity of hydroindene derivatives.

A synthetic approach to hydroindenic inotropic agents has been developed, starting from enantiopure Hajos-Parrish (1). Hajos-Wiechert (2), and related diketones. Their transformation into C-1 formyl derivatives and other subsequent synthetic targets is described. The results of the thermodynamic equilibration between both epimers of each formyl derivative are analysed. The inotropic activities of selected compounds on right and left atrial preparations are also evaluated and discussed.

Animals↗
PubMed1999

[Adherence to very active antiretroviral treatment: impact of individualized assessment].

BACKGROUND: To determine if the intervention of individual advice improves adherence and effectiveness to highly active antiretroviral therapy. METHODS: Randomized open trial. Patients treated with zidovudine + lamivudine + indinavir were assigned (2/1) to conventional care or individual advise. Individual advise consists in adaptation to treatment to patient style of live and detailed information of therapy. Adherence were estimated with structured interview and pillo counts and were considered correct when more than 90% of prescribed drugs were taken. RESULTS: Patients 170, conventional care: 110 and IA: 60. FOLLOW-UP: 24 weeks. Baseline characteristics were similar in both groups. Correct adherence were estimated in 52.7% of conventional care and in 76.7% of individual advise (p = 0.002, relative risk: 1.45; CI 95%: 1.16-1.82). Undetectable viral load (NASBA < 50 copies/ml) in 54.5% of conventional care and in 65% of individual advise (p = 0.18, relative risk: 1.19; CI 95%: 0.93-1.53). Reduction of viral load in the conventional care group 1.02 +/- 0.5 log10/ml, and in the individual advise group 1.98 +/- 0.7 log10/ml. CONCLUSION: The individual advice improve adherence with a tendency to improve effectiveness of highly active antiretroviral therapy.

Adult↗
PubMed1999

[Investigation of HBV-DNA using the polymerase chain reaction (PCR) in HBsAg-negative, anti-HBc-positive Venezuelan donors].

OBJECTIVE: In our Center the disposal of blood with HBV positive markers is approximately 6%, being 90% AgsHB negative and anti HBc positive. With the purpose of knowing the infected capacities of these donations and to consider the possibility of using them for transfusion, the presence of the viral genoma was investigated by PCR, in a group of samples with these characteristics that were also anti sHB positive. They were correlated with the readings of the anti cHB total, with the anti cHB-IgM and with the titration of the anti sHB. MATERIALS AND METHODS: 87/100 random samples, from February to June 1996, were frozen at -30 degrees C for their later evaluation. In the serological screening were used Auszyme Monoclonal of Abbott and the Heprofile anti cHB, ADI-Diagnostic. The readings of the anti cHB was considered strong, moderate or weak according to its distance to the cut off. For the determination of the anti sHB, Hepanostika anti sHB, Organon Technika was used. They were considered with low titers (< 10 UI/L), high (> or = 10 UI/L) and very high (> or = 100 UI/L). In the determination of the anti cHB-IgM, Heprofile ADI-Diagnostic was used. For the investigation of the viral genoma, it was carried out with double PCR-ADN, using two internal and two external primers for the core-precore region. RESULTS: 70/87 (80.45%) of the samples presented high readings of anti cHB with high titers of anti sHB, being positive for anti cHB-IgM seven of them and one was HBV-ADN positive (1.42%) suggesting the possibility to be cronic carrier. In the remaining 19.55% of the samples we didn't detect positive results in the amplification assays. CONCLUSIONS: 1. The donors showed high levels of immunocompetence. 2. High titer of anti sHB doesn't guarantee the absence of viral genoma and therefore the absence of infectivity can not be sure. This doesn't allow us to come in like donors neither to use their blood in the transfusional therapy.

Blood Donors↗
PubMed1998

Distribution of hepatitis B virus genotypes in two different pediatric populations from Argentina.

Differences in pathogenesis and the probability of becoming a chronic carrier depend on the age at which hepatitis B virus (HBV) infection is acquired, ranging from 82% in infants less than 6 months of age to 15 to 30% in older children. HBV genotypes from 22 pediatric patients from two areas that differ in prevalence have been determined. Phylogenetic analysis shows a clear difference between the genotype distribution in Buenos Aires, a low-prevalence area, and that found in Gualeguay, Entre Ríos, a high-prevalence area. While the analysis allocated the sequences in the Buenos Aires group to genotypes A (36%), D (9%), and F (55%), the Gualeguay group presented exclusively genotype A isolates with very low nucleotide divergence, which suggests a strong founder viral population. The high prevalence of genotype F in the Buenos Aires group and its high intragroup heterogeneity agree with the American origin of this genotype.

Argentina↗