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D Piñero

Publications and source records attributed to D Piñero.

18 recordsLinked to original sources
PubMed2003

Long-distance colonization, isolation by distance, and historical demography in a relictual Mexican pinyon pine (Pinus nelsonii Shaw) as revealed by paternally inherited genetic markers (cpSSRs).

Pinus nelsonii is a relictual pinyon pine distributed across a wide altitudinal range in semiarid zones in Mexico near the border between the States of Nuevo León and Tamaulipas. It also occurs in small patches in the State of San Luis Potosí. Pinus nelsonii is classified in the monotypic subsection Nelsoniae, separated from other pinyon pines (subsection Cembroides), because it possesses several distinctive characters including persistent fascicle sheaths, connate needles, and a distinctive wood anatomy. In the present study, chloroplast simple sequence repeats (cpSSRs) were used to estimate genetic variation in most known populations (nine) of P. nelsonii. The genetic variation (HT = 0.73; 27 haplotypes in 256 individuals) is moderate when compared to other pine species. Population differentiation ranged between low and moderate (FST = 0.13 and RST = 0.05), as did the Nei and Goldstein genetic distances between populations. However, this pattern varied depending on whether the infinite alleles or stepwise mutation model was used. In the former case a significant isolation by distance was found, but not in the latter. A significant association between geographical and genetic structure in one clade, through a nested clade analysis, was found, which suggested long-distance colonization between 125000 and 309000 years ago. We found weak evidence for a population expansion. A mismatch distribution suggests that P. nelsonii populations underwent an expansion 4.25 times their size between 59000 and 146000 years ago. On the other hand, the populations' star-like phylogeny and a slight parabolic relationship between coalescence times and lineage number also suggest weak population expansion. Overall, this species appears to have been in demographic stasis for a large proportion of the time detected by the markers used.

Cluster Analysis↗
PubMed2001

Variation in the nrDNA ITS of Pinus subsection Cembroides: implications for molecular systematic studies of pine species complexes.

The pinyon pines (Pinus subsection Cembroides), distributed in semiarid regions of the western United States and Mexico, include a mixture of relictual and more recently evolved taxa. To investigate relationships among the pinyons, we screened and partially sequenced 3000-bp clones of the nuclear ribosomal DNA internal transcribed spacer (ITS) region for 16 taxa from subsect. Cembroides and nine representatives from four other subsections of subgenus Strobus. Restriction digests of clones reveal within-individual heterogeneity, suggesting that concerted evolution is operating slowly on the ITS in pine species. Two ITS clones were identified as pseudogenes. Tandem subrepeats in the ITS1 form stem loops comparable to those in other genera of Pinaceae and may be promoting recombination between rDNA repeats, resulting in ITS1 chimeras. Within the pinyon clade, phylogenetic structure is present, but different clones from the same (or different) individuals of a species are polyphyletic, indicating that coalescence of ITS copies within individual genomes predates evolutionary divergence in the group. At the level of subsection and above, the ITS region corresponds well with morphological and cpDNA evidence. Except for P. nelsonii, the pinyons are monophyletic, with both subsect. Cembroides and P. nelsonii forming a clade with the foxtail and bristlecone pines (subsect. Balfourianae) of western North America.

Base Sequence↗
PubMed2001

Variations in dietary iron alter behavior in developing rats.

Iron deficiency in children is associated with retardation in growth and cognitive development, and the effects on cognition may be irreversible, even with treatment. Excessive iron has also been associated with neurological disease, especially in reference to the increased iron content in the brains of Alzheimer's disease and Parkinson's disease patients. This study evaluated the effects of dietary iron deficiency and excess iron on physical activity in rats. The animal model used is developmentally sensitive and permits control of the timing as well as the duration of the nutritional insult. Hence, to study the effects of early, late and long-term iron deficiency or excess iron (supplementation), rats were either made iron deficient or supplemented on postnatal day (PND) 10-21, PND 21-35 and PND 10-35. Some iron-deficient rats were iron repleted between PND 21-35. Different measures of motor activity were taken at PND 14, 17, 20, 27 and 34. Iron-deficient and iron-supplemented rats showed decreased activity and stereotypic behavior; this was apparent for any onset and duration of the nutritional insult. Recovery from iron deficiency did not normalize these functional variables, showing that the deleterious effects of early iron deficiency persist despite subsequent adequate treatment. This study demonstrates that iron deficiency in early life leads to irreversible behavioral changes. The biological bases for these behavioral alterations are not readily apparent, because iron therapy rapidly reverses the iron losses in all brain regions.

Age Factors↗
PubMed2000

Genomic variability of Haemophilus influenzae isolated from Mexican children determined by using enterobacterial repetitive intergenic consensus sequences and PCR.

Genomic fingerprints from 92 capsulated and noncapsulated strains of Haemophilus influenzae from Mexican children with different diseases and healthy carriers were generated by PCR using the enterobacterial repetitive intergenic consensus (ERIC) sequences. A cluster analysis by the unweighted pair-group method with arithmetic averages based on the overall similarity as estimated from the characteristics of the genomic fingerprints, was conducted to group the strains. A total of 69 fingerprint patterns were detected in the H. influenzae strains. Isolates from patients with different diseases were represented by a variety of patterns, which clustered into two major groups. Of the 37 strains isolated from cases of meningitis, 24 shared patterns and were clustered into five groups within a similarity level of 1.0. One fragment of 1.25 kb was common to all meningitis strains. H. influenzae strains from healthy carriers presented fingerprint patterns different from those found in strains from sick children. Isolates from healthy individuals were more variable and were distributed differently from those from patients. The results show that ERIC-PCR provides a powerful tool for the determination of the distinctive pathogenicity potentials of H. influenzae strains and encourage its use for molecular epidemiology investigations.

Carrier State↗
PubMed1999

Phylogenetics of Pinus (Pinaceae) based on nuclear ribosomal DNA internal transcribed spacer region sequences.

A 650-bp portion of the nuclear ribosomal DNA internal transcribed spacer region was sequenced in 47 species of Pinus, representing all recognized subsections of the genus, and 2 species of Picea and Cathaya as outgroups. Parsimony analyses of these length variable sequences were conducted using a manual alignment, 13 different automated alignments, elision of the automated alignments, and exclusion of all alignment ambiguous sites. High and moderately supported clades were consistently resolved across the different analyses, while poorly supported clades were inconsistently recovered. Comparison of the topologies highlights taxa of particularly problematic placement including Pinus nelsonii and P. aristata. Within subgenus Pinus, there is moderate support for the monophyly of a narrowly circumscribed subsect. Pinus (=subsect. Sylvestres) and strong support for a clade of North and Central American hard pines. The Himalayan P. roxburghii may be sister species to these "New World hard pines," which have two well-supported subgroups, subsect. Ponderosae and a clade of the remaining five subsections. The position of subsect. Contortae conflicts with its placement in a chloroplast DNA restriction site study. Within subgenus Strobus there is consistent support for the monophyly of a broadly circumscribed subsect. Strobi (including P. krempfii and a polyphyletic subsect. Cembrae) derived from a paraphyletic grade of the remaining soft pines. Relationships among subsects. Gerardianae, Cembroides, and Balfourianae are poorly resolved. Support for the monophyly of subgenus Pinus and subgenus Strobus is not consistently obtained.

DNA, Plant↗
PubMed1999

Phylogenetic analysis of the homologous proteins of the terminal complement complex supports the emergence of C6 and C7 followed by C8 and C9.

The plasma complement system comprises several activation pathways that share a common terminal route involving the assembly of the terminal complement complex (TCC), formed by C5b-C9. The order of emergence of the homologous components of TCC (C6, C7, C8alpha, C8beta, and C9) has been determined by phylogenetic analyses of their amino acid sequences. Using all the sequence data available for C6-C9 proteins, as well as for perforins, the results suggested that these TCC components originated from a single ancestral gene and that C6 and C7 were the earliest to emerge. Our evidence supports the notion that the ancestral gene had a complex modular composition. A series of gene duplications in combination with a tendency to lose modules resulted in successive complement proteins with decreasing modular complexity. C9 and perforin apparently are the result of different selective conditions to acquire pore-forming function. Thus C9 and perforin are examples of evolutionary parallelism.

Amino Acid Sequence↗
PubMed1999

High population differentiation and genetic variation in the endangered Mexican pine Pinus Rzedowskii (Pinaceae).

Pinus rzedowskii is an endangered pine species from Michoacán (central México), which has been previously reported from only three localities. Classified within the subgenus Strobus, it exhibits intermediate morphological characters between subgenera Strobus and Pinus. We analyzed genetic aspects that could shed light on the evolution and conservation of this species. The genetic structure of nine populations was examined using 14 isozyme loci. Pinus rzedowskii has a relatively high level of genetic variation with 46.8% of the loci assayed being polymorphic, a total of 35 alleles, and a mean heterozygosity per population of 0.219. We calculated Wright's F(ST) statistic to estimate gene flow indirectly and to evaluate whether or not there was genetic structuring among populations. We found a marked differentiation among populations (F(ST) = 0.175) and significant inbreeding (F(IS) = 0.247). No pattern of isolation by distance was found. We also constructed a dendrogram based on a genetic distance matrix to obtain an overview of the possible historical relationships among populations. Finally, we found a convex relationship between the genetic distance among populations and the number of ancestral lineages, suggesting that demographically this species has not been at risk recently. Although endangered, with small and fragmented populations, P. rzedowskii shows higher levels of genetic variation than other conifer species with larger populations or similar conservation status.

Journal Article↗
PubMed1998

Biological characterization and genetic diversity of Mexican isolates of Trypanosoma cruzi.

The present work reports the in vitro biological characterization of 17 Trypanosoma cruzi isolates from southern and central México, and compares these results to those of four South American strains and one clone from Brazil. The parameters evaluated were growth rates, percentage of parasites undergoing transformation from epimastigotes to trypomastigotes, infectivity to, and in vitro killing of cultured Vero and P388 cells. Isoenzyme patterns of 11 enzymatic systems and 16 loci were also determined for the Mexican isolates. The parasites showed differences in growth, depending if they were cultured in LIT with hemin or in Grace's media. Transformation was obtained only in Grace's medium and differences were observed between the stocks. Stocks Z10 and Z21 showed the highest percentage of transformation within the Mexican isolates (39 and 41%, respectively). A second group showed percentages of transformation between 15 and 28%. In contrast, the South American strains showed higher rates of transformation (36-65%). Infection of cultured cells by isolates Z10 and H5 was evaluated in both Vero and P388 cells. Differences were observed both in the percentage of infected cells as well as in the number of amastigotes per cell. Differences in the ability to cause in vitro killing of P388 cells were also observed among the isolates. Isoenzyme analysis revealed genetic variation between the isolates, each of them with an unique zymodeme. This genetic analysis revealed, in general, a clustering based on the geographical origin of the isolates. Finally, correlation with clinical symptoms is discussed.

Animals↗
PubMed1997

[The effect of lactation time on the macronutrient and mineral composition of milk from Venezuelan women].

Human milk is considered the ideal food for the infant and it has been extensively used to estimate its nutrient requirements. The objective of this paper was to determine the effect of lactation time on the macronutrient an mineral content of milks obtained from Venezuelan women and also to compare this with the established nutrient requirements of the infant. For this purpose 83 milk samples from 45 low income mothers were analyzed at the colostrum (48 h to 54 d) and mature states of lactation (1.3 and 6 months). The results showed that colostrum had a higher protein and a lower fat content than mature milks whereas its content of energy and carbohydrate was similar to mature milk. The iron and calcium content of the milk remained unchanged during the whole study whereas Zn and Cu decreased and increased with lactation time respectively. In contrast, phosphorous and magnesium increased up to 3rd month of lactation and remained constant there after. The macronutrient content of 850 ml of the analyzed milk almost completely fulfilled the daily infant requirements established in the US (RDA) and Canada (RNI). The mineral content of this volume of milk however was insufficient to cover the infants requirements particularly those established in the US. The most notorious deficiency in these milks was in Fe since they could fulfill only 11% the infants RDA for this mineral. The infant mineral requirements established in Canada are substantially lower than those defined in the US and therefore the analyzed milks could totally fulfill the Canadian infant daily requirements of Mg, Fe and Ca and more than 70% and 80% of the requirements of Zn and P. In general, the results of this study showed that the nutrient content of the analyzed milks agree well with those reported in the literature for women from different parts of the world including developed and underdeveloped areas. At the same time they pointed out the differences in the definition of the infant nutrient requirements set by different countries and also emphasize the fact that human milk, which by definition is the natural source of nutrients for the human infant apparently is incapable of fulfilling its daily requirements.

Adolescent↗
PubMed1995

Nutritional evaluation of the soy-whey milk analog La colina.

The milk analog La colina is a product which contains mainly whey, soy protein isolate and vegetable oil, designed for infants since one year, children, adolescents and adults of all ages. The concept behind this product is to offer an alternative to milk consumption which during the last decade has decreased dramatically in Venezuela mainly due to its high price and low availability. Accordingly, the purpose of this study was to evaluate nutritionally this new product in order to determine if from a nutritional stand point it could represent a valid alternative to milk consumption. The results showed that La Colina offers the same amount of protein, energy, vitamin A, calcium, phosphorus and potassium as whole milk powder and more sodium, iron and zinc. In addition, a rat assay showed that the energy in these two products is equally available and even though the proteins in La colina are 3.9% less digestible, their quality determined by growth, PER or the nitrogen retained are excellent and identical to the quality of the proteins in milk. These results agreed with the theoretical chemical score of the proteins of this new product, which indicated that the amino acid profile of the mixture can fulfill the amino acid requirements of children, adolescents an adults. Both milk and La colina are products with a high fat content. The fat in this new product however, is vegetable oil and therefore it has a more convenient fatty acid profile than whole milk and about one third of its cholesterol. In short, these results showed that La Colina from a nutritional point of view is an excellent alternative to milk consumption.

Animals↗
PubMed1994

Genetic Structure of Rhizobium etli biovar phaseoli Associated with Wild and Cultivated Bean Plants (Phaseolus vulgaris and Phaseolus coccineus) in Morelos, Mexico.

The genetic structure of Rhizobium etli biovar phaseoli was determined for five populations in three different locations in the state of Morelos, Mexico, by using starch gel electrophoresis for five to nine polymorphic loci. Two populations were sampled during two different years from nodules of cultivated and wild common bean plants (Phaseolus vulgaris). The three other populations were associated with wild runner beans (P. coccineus) and sampled during 1988. The Rhizobium populations differ genetically both among sites and among populations within the same site in different years, as shown by differences in allelic frequencies, genetic differentiation analysis, and differences in electrotypes. The total genetic diversity for the five populations during 1988 was H = 0.487; there were also high levels of genetic variation within each population. We found the highest linkage disequilibrium in a global analysis for all the populations. At a local scale, we also found significant linkage disequilibrium in two populations, although the distribution of the D' suggest some recombination at a local scale. The other three rhizobium populations exhibit low linkage disequilibrium. A cluster analysis (UPGMA) of pairwise genetic distances showed that bacteria isolated from most wild Phaseolus spp. are grouped by population, whereas those obtained from cultivated P. vulgaris are very heterogeneous. The analysis of the genetic structure of Rhizobium strains may allow the identification of strains that are naturally well adapted to a wide range of different environments, which may be useful for agricultural purposes or as a starting point for developing improved Rhizobium strains.

Journal Article↗
PubMed1992

Hierarchical analysis of linkage disequilibrium in Rhizobium populations: evidence for sex?

Many bacterial species exhibit strong linkage disequilibrium of their chromosomal genes, which apparently indicates restricted recombination between alleles at different loci. The extent to which restricted recombination reflects limited migration between geographically isolated populations versus infrequent mixis of genotypes within populations is more difficult to determine. We examined the genetic structure of Rhizobium leguminosarum biovar phaseoli populations associated with wild and cultivated beans (Phaseolus spp.) over several spatial scales, ranging from individual host plants to throughout the Western Hemisphere. We observed significant linkage disequilibrium at scales at least as small as a cultivated plot. However, the amount of disequilibrium was much greater among isolates collected throughout the Western Hemisphere than among isolates from one area of Mexico, even when disequilibrium was quantified using an index that scales for allelic diversity. This finding suggests that limited migration between populations contributes substantially to linkage disequilibrium in Rhizobium. We also compared the genetic structure for R. leguminosarum bv. phaseoli taken from a cultivated plot with that for Escherichia coli obtained from one human host in an earlier study. Even at this fine scale, linkage disequilibrium in E. coli was very near the theoretical maximum level, whereas it was much less extreme in the local population of Rhizobium. Thus, the genetic structure for R. leguminosarum bv. phaseoli does not exclude the possibility of frequent mixis within local populations.

Enzymes↗
PubMed1991

Genetic structure of a soil population of nonsymbiotic Rhizobium leguminosarum.

The genetic structure of a population of nonsymbiotic Rhizobium leguminosarum strains was determined by the electrophoretic mobilities of eight metabolic enzymes. Nonsymbiotic strains were isolated from the rhizosphere of bean plants and characterized by growth on differential media and at different temperatures, intrinsic antibiotic resistance, the lack of homology to a nifH probe, and their inability to form nodules on bean roots. All the isolates clustered with R. leguminosarum bv. phaseoli reference strains and did not encompass any other Rhizobium taxa. Their rRNA operon restriction fragment length polymorphisms and the nucleotide sequence of a fragment of the 16S rRNA gene were also found to be identical to those of R. leguminosarum bv. phaseoli reference strains. When complemented with an R. leguminosarum bv. phaseoli symbiotic plasmid (p42d), the nonsymbiotic isolates were able to fix nitrogen in symbiosis with bean roots at levels similar to those of the parental strain. The symbiotic isolates were found at a relative frequency of 1 in 40 nonsymbiotic R. leguminosarum strains.

Base Sequence↗
PubMed1990

Primary structure of Trypanosoma cruzi small-subunit ribosomal RNA coding region: comparison with other trypanosomatids.

A Trypanosoma cruzi small subunit ribosomal RNA gene was sequenced from genomic recombinant plasmid clones. The assigned coding region was 2319 bp, the longest SSU rRNA gene described to date. On the basis of comparisons with published sequences from Crithidia fasciculata, Trypanosoma brucei, and Leishmania donovani, we conclude that the extra nucleotides in the T. cruzi gene occur in highly variable regions of rRNA genes. A phylogenetic analysis was performed with the SSU rRNA sequences from these four trypanosomatids and from Euglena gracilis as an outgroup. The Leishmania and Crithidia sequences were remarkably similar to each other (not separable statistically). Given the standard errors associated with the branching order of the two Trypanosoma species and the Leishmania-Crithidia branch, the actual topology cannot be unequivocally determined using only the ribosomal sequences analyzed here.

Animals↗
PubMed1990

Molecular evolution of class A beta-lactamases: phylogeny and patterns of sequence conservation.

We present a multiple alignment of the amino acid sequences of eight class A beta-lactamases and utilized it to propose a phylogeny, based on the nucleotide sequences of their corresponding genes. We have also used the alignment, together with the alpha-carbon co-ordinates of the Staphylococcus aureus protein, to search systematically for neighbouring residues that share the same pattern of conservation among the different members of the protein family. The distribution of invariant residues and of groups of residues with co-ordinate changes map, predominantly, at the region of the active site and at interfaces between structural elements, respectively. We have also contrasted the distribution of conserved residues with the positions which are known to differ in mutants and variants of class A beta-lactamases.

Amino Acid Sequence↗
PubMed1988

Genomic instability in Rhizobium phaseoli.

Experience from different laboratories indicates that Rhizobium strains can generate variability in regard to some phenotypic characteristics such as colony morphology or symbiotic properties. On the other hand, several reports suggest that under certain stress conditions or genetic manipulations Rhizobium cells can present genomic rearrangements. In search of frequent genomic rearrangements, we analyzed three Rhizobium strains under laboratory conditions that are not considered to cause stress in bacterial populations. DNAs from direct descendants of a single cell were analyzed in regard to the hybridization patterns obtained, using as probes different recombinant plasmids or cosmids; while most of the probes utilized did not show differences in the hybridization patterns, some of them revealed the occurrence of frequent genomic rearrangements. The implications and possible biological significance of these observations are discussed.

Cloning, Molecular↗
PubMed1987

Reiterated DNA sequences in Rhizobium and Agrobacterium spp.

Repeated DNA sequences are a general characteristic of eucaryotic genomes. Although several examples of DNA reiteration have been found in procaryotic organisms, only in the case of the archaebacteria Halobacterium halobium and Halobacterium volcanii [C. Sapienza and W. F. Doolittle, Nature (London) 295:384-389, 1982], has DNA reiteration been reported as a common genomic feature. The genomes of two Rhizobium phaseoli strains, one Rhizobium meliloti strain, and one Agrobacterium tumefaciens strain were analyzed for the presence of repetitive DNA. Rhizobium and Agrobacterium spp. are closely related soil bacteria that interact with plants and that belong to the taxonomical family Rhizobiaceae. Rhizobium species establish a nitrogen-fixing symbiosis in the roots of legumes, whereas Agrobacterium species is a pathogen in different plants. The four strains revealed a large number of repeated DNA sequences. The family size was usually small, from 2 to 5 elements, but some presented more than 10 elements. Rhizobium and Agrobacterium spp. contain large plasmids in addition to the chromosomes. Analysis of the two Rhizobium strains indicated that DNA reiteration is not confined to the chromosome or to some plasmids but is a property of the whole genome.

Cloning, Molecular↗