Evolution of a unique Plasmodium falciparum chloroquine-resistance phenotype in association with pfcrt polymorphism in Papua New Guinea and South America.
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The mechanistic basis for chloroquine resistance (CQR) in Plasmodium falciparum recently has been linked to the polymorphic gene pfcrt. Alleles associated with CQR in natural parasite isolates harbor threonine (T), as opposed to lysine (K) at amino acid 76. P. falciparum CQR strains of African and Southeast Asian origin carry pfcrt alleles encoding an amino acid haplotype of CVIET (residues 72-76), whereas most South American CQR strains studied carry an allele encoding an SVMNT haplotype; chloroquine-sensitive strains from malarious regions around the world carry a CVMNK haplotype. Upon investigating the origin of pfcrt alleles in Papua New Guinean (PNG) P. falciparum we found either the chloroquine-sensitive-associated CVMNK or CQR-associated SVMNT haplotypes previously seen in Brazilian isolates. Remarkably we did not find the CVIET haplotype observed in CQR strains from Southeast Asian regions more proximal to PNG. Further we found a previously undescribed CQR phenotype to be associated with the SVMNT haplotype from PNG and South America. This CQR phenotype is significantly less responsive to verapamil chemosensitization compared with the effect associated with the CVIET haplotype. Consistent with this, we observed that verapamil treatment of P. falciparum isolates carrying pfcrt SVMNT is associated with an attenuated increase in digestive vacuole pH relative to CVIET pfcrt-carrying isolates. These data suggest a key role for pH-dependent changes in hematin receptor concentration in the P. falciparum CQR mechanism. Our findings also suggest that P. falciparum CQR has arisen through multiple evolutionary pathways associated with pfcrt K76T. (+info)
Resolution of the early placental mammal radiation using Bayesian phylogenetics.
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Molecular phylogenetic studies have resolved placental mammals into four major groups, but have not established the full hierarchy of interordinal relationships, including the position of the root. The latter is critical for understanding the early biogeographic history of placentals. We investigated placental phylogeny using Bayesian and maximum-likelihood methods and a 16.4-kilobase molecular data set. Interordinal relationships are almost entirely resolved. The basal split is between Afrotheria and other placentals, at about 103 million years, and may be accounted for by the separation of South America and Africa in the Cretaceous. Crown-group Eutheria may have their most recent common ancestry in the Southern Hemisphere (Gondwana). (+info)
Genetic analysis reveals the wild ancestors of the llama and the alpaca.
(68/892)
The origins of South America's domestic alpaca and llama remain controversial due to hybridization, near extirpation during the Spanish conquest and difficulties in archaeological interpretation. Traditionally, the ancestry of both forms is attributed to the guanaco, while the vicuna is assumed never to have been domesticated. Recent research has, however, linked the alpaca to the vicuna, dating domestication to 6000-7000 years before present in the Peruvian Andes. Here, we examine in detail the genetic relationships between the South American camelids in order to determine the origins of the domestic forms, using mitochondrial (mt) and microsatellite DNA. MtDNA analysis places 80% of llama and alpaca sequences in the guanaco lineage, with those possessing vicuna mtDNA being nearly all alpaca or alpaca-vicuna hybrids. We also examined four microsatellites in wild known-provenance vicuna and guanaco, including two loci with non-overlapping allele size ranges in the wild species. In contrast to the mtDNA, these markers show high genetic similarity between alpaca and vicuna, and between llama and guanaco, although bidirectional hybridization is also revealed. Finally, combined marker analysis on a subset of samples confirms the microsatellite interpretation and suggests that the alpaca is descended from the vicuna, and should be reclassified as Vicugna pacos. This result has major implications for the future management of wild and domestic camelids in South America. (+info)
Analyses of genotypic diversity among North, South, and Central American isolates of sugarcane yellow leaf virus: evidence for Colombian origins and for intraspecific spatial phylogenetic variation.
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We have analyzed the genotypic diversity of sugarcane yellow leaf virus (SCYLV) collected from North, South, and Central America by fingerprinting assays and selective cDNA cloning and sequencing. One group of isolates from Colombia, designated the C-population, has been identified as residing at the root node between a separable superpopulation structure of SCYLV and other members of the family Luteoviridae, indicating that the progenitor viruses of the North, South, and Central American isolates of the SCYLV superpopulation most likely arose from a C-population structure. From a model of intrafamilial evolution (F. Moonan et al., Virology 269:156-171, 2000), a prediction could be made that within the SCYLV species, the capacity of genomic sequence divergence would range from lowest in the capsid protein open reading frame 3 (ORF 3) to highest in a region spanning across the carboxy-terminal end of the RNA-dependent RNA polymerase ORF. We have demonstrated the validity and applicability of this intrafamilial model for the prediction of intraspecies SCYLV diversity. Analysis of spatial phylogenetic variation (SPV) within the SCYLV isolates could not be assessed by application of a "partial likelihoods assessed through optimization" (PLATO)-derived intraspecies model alone. However, application of a PLATO-derived intrafamilial model with the intraspecies-derived model allowed distinction of three forms of SPV. Two of the SPV forms identified correspond to the extremes in a continuum of sequence evolution displayed in a SCYLV superpopulation structure, and the third form was diagnostic of a C-population structure. The application of these types of models has value in terms of predicting the types of SCYLV intraspecies diversity that may exist worldwide, and in general, may be useful in application for more informed design of transgenes for use in the elicitation of homology-dependent virus resistance mechanisms in transgenic plants. (+info)
Safety of blood supply for infectious diseases in Latin American countries, 1994-1997.
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The potential risk of acquiring a transfusion-transmitted infection by the human immunodeficiency virus (HIV), hepatitis B (HBV) virus, hepatitis C (HCV) virus, or Trypanosoma cruzi was estimated for seven South American and five Central American countries during the period 1994-1997. The estimates were based on official national reports of the number of donors, blood screening coverage, and prevalence of serologic markers for infectious diseases. Coverage of screening in 1997 was 100% in 12 and 11 countries for HIV and HBV respectively. Complete screening for HCV was reported by only one country in 1994 and by six in 1997. For T. cruzi, the number of countries with 100% screening coverage increased from two in 1994 to four in 1997. In 1994, three countries showed risk of transfusion-transmitted infections for HIV, seven for HBV, eight for HCV, and seven for T. cruzi. The risk of receiving an infected blood unit and acquiring a transfusion-transmitted infection has been reduced with time in 10 of the 12 countries due to improvements in screening coverage. In Uruguay, the risk was theoretically nil from 1994-1997 because at the beginning of the study period they already had 100% blood donor screening for all infectious diseases transmitted by blood. In 1994, Colombia and Venezuela had the highest health risk associated with blood transfusion (spreading index of 101 and 62, respectively); during the period 1996-1997, Costa Rica presented the highest figures (spreading index of 53 and 83, respectively). The analysis of the potential risk associated with transfusion of tainted blood highlights the need for continuous monitoring of the safety of blood supply. (+info)
Prevalence of recurrent herpes labialis and aphthous ulcers among young adults on six continents.
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The prevalence of recurrent herpes labialis (RHL) and recurrent aphthous ulcers (RAU) in young adults - - 635 armed-forces recruits and 9897 health-profession students - - in 48 institutions in 21 countries was determined by a questionnaire survey. Two or more occurrences (lifetime prevalence) of RHL were reported by 33.2% of men and 28.0% of women; the corresponding figures for RAU were 38.7% and 49.7%. North American respondents, mainly from Canada, had a significantly higher prevalence of both lesions. There were some differences in relation to profession. Approximately 15% of all the people surveyed had had herpes labialis and 25% had had aphthous ulcers at least once during the previous year. Persons with a history of recurrence of one lesion were more likely to have a history of recurrence of the other. (+info)
Very-low-birth-weight infant outcomes in 11 South American NICUs.
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OBJECTIVE: To describe and analyze outcomes in very-low-birth-weight (VLBW) infants treated in 11 Neonatal Intensive Care Units (NICUs) from four South American countries. This study is the first of a multination collaboration and can serve as a baseline for future quality and resource utilization efforts. STUDY DESIGN: Biodemographic data and multiple outcome measures were prospectively collected from October 1997 until August 1998. A logistic regression model was used to define risk factors in primary outcome measures, death, and bronchopulmonary dysplasia (BPD). Center differences were compared using chi-squared analysis. RESULTS: In 385 VLBW infants enrolled, mortality rate was 27%, with a range from 11% to 51% among NICUs. A lower BW, lower gestational age (GA), lack of antenatal steroids (AS), and air leaks (AL) were associated with increased risk of death. A lower BW, lower GA, AL, need for surfactant, necrotizing enterocolitis, and need for intubation were associated with increased risk of BPD. CONCLUSION: This study provides actual information about VLBW infants' prognosis in a SA region. Mortality rate variability among NICUs may be explained by differences in population and resources, but also by lack of implementation of proven beneficial therapies such as AS administration. (+info)