Trypanosoma cruzi in Mexican Neotropical vectors and mammals: wildlife, livestock, pets, and human population.

OBJECTIVE: To provide primary evidence of Trypanosoma cruzi landscape genetics in the Mexican Neotropics. MATERIALS AND METHODS: Trypanosoma cruzi and discrete typing units (DTU) prevalence were analyzed in landscape communities of vectors, wildlife, livestock, pets, and sympatric human populations using endpoint PCR and sequencing of all relevant amplicons from mitochondrial (kDNA) and nuclear (ME, 18S, 24Sα) gene markers. RESULTS: Although 98% of the infected sample-set (N=2 963) contained single or mixed infections of DTUI (TcI, 96.2%) and TcVI (22.6%), TcIV and TcII were also identified. Sensitivity of individual markers varied and was dependent on host taxon; kDNA, ME and 18S combined identified 95% of infections. ME genotyped 90% of vector infections, but 60% of mammals (36% wildlife), while neither 18S nor 24Sα typed more than 20% of mammal infections. CONCLUSION: Available gene fragments to identify or genotype T. cruzi are not universally sensitive for all landscape parasite populations, highlighting important T. cruzi heteroge- neity among mammal reservoir taxa and triatomine species.

Irreversible bilayer adsorption of straight semirigid rods on two-dimensional square lattices: Jamming and percolation properties.

Numerical simulations and finite-size scaling analysis have been performed to study the jamming and percolation behavior of straight semirigid rods adsorbed on two-dimensional square lattices. The depositing objects can be adsorbed on the surface forming two layers. The filling of the lattice is carried out following a generalized random sequential adsorption (RSA) mechanism. In each elementary step, (i) a set of k consecutive nearest-neighbor sites (aligned along one of two lattice axes) is randomly chosen and (ii) if each selected site is either empty or occupied by a k-mer unit in the first layer, then a new k-mer is then deposited onto the lattice. Otherwise, the attempt is rejected. The process starts with an initially empty lattice and continues until the jamming state is reached and no more objects can be deposited due to the absence of empty site clusters of appropriate size and shape. A wide range of values of k (2≤k≤64) is investigated. The study of the kinetic properties of the system shows that (1) the jamming coverage θ_{j,k} is a decreasing function with increasing k, with θ_{j,k→∞}=0.7299(21) the limit value for infinitely long k-mers and (2) the jamming exponent ν_{j} remains close to 1, regardless of the size k considered. These findings are discussed in terms of the lattice dimensionality and number of sites available for adsorption. The dependence of the percolation threshold θ_{c,k} as a function of k is also determined, with θ_{c,k}=A+Bexp(-k/C), where A=θ_{c,k→∞}=0.0457(68) is the value of the percolation threshold by infinitely long k-mers, B=0.276(25), and C=14(2). This monotonic decreasing behavior is completely different from that observed for the standard problem of straight rods on square lattices, where the percolation threshold shows a nonmonotonic k-mer size dependence. The differences between the results obtained from bilayer and monolayer phases are explained on the basis of the transversal overlaps between rods occurring in the bilayer problem. This effect (which we call a "cross-linking effect"), its consequences on the filling kinetics, and its implications in the field of conductivity of composites filled with elongated particles (or fibers) are discussed in detail. Finally, the precise determination of the critical exponents ν, ß, and γ indicates that, although the increasing in the width of the deposited layer drastically affects the behavior of the percolation threshold with k and other critical properties (such as the crossing points of the percolation probability functions), it does not alter the nature of the percolation transition occurring in the system. Accordingly, the bilayer model belongs to the same universality class as two-dimensional standard percolation model.

Irreversible multilayer adsorption of semirigid k-mers deposited on one-dimensional lattices.

Irreversible multilayer adsorption of semirigid k-mers on one-dimensional lattices of size L is studied by numerical simulations complemented by exhaustive enumeration of configurations for small lattices. The deposition process is modeled by using a random sequential adsorption algorithm, generalized to the case of multilayer adsorption. The paper concentrates on measuring the jamming coverage for different values of k-mer size and number of layers n. The bilayer problem (n≤2) is exhaustively analyzed, and the resulting tendencies are validated by the exact enumeration techniques. Then, the study is extended to an increasing number of layers, which is one of the noteworthy parts of this work. The obtained results allow the following: (i) to characterize the structure of the adsorbed phase for the multilayer problem. As n increases, the (1+1)-dimensional adsorbed phase tends to be a "partial wall" consisting of "towers" (or columns) of width k, separated by valleys of empty sites. The length of these valleys diminishes with increasing k; (ii) to establish that this is an in-registry adsorption process, where each incoming k-mer is likely to be adsorbed exactly onto an already adsorbed one. With respect to percolation, our calculations show that the percolation probability vanishes as L increases, being zero in the limit L→∞. Finally, the value of the jamming critical exponent ν_{j} is reported here for multilayer adsorption: ν_{j} remains close to 2 regardless of the considered values of k and n. This finding is discussed in terms of the lattice dimensionality.

Genetic variation and phylogeography of the Triatoma dimidiata complex evidence a potential center of origin and recent divergence of haplogroups having differential Trypanosoma cruzi and DTU infections.

The population genetics of Triatoma dimidiata haplogroups was analyzed at landscape and sub-regional scales in Chiapas and regional level across the Mexican Neotropics, and phylogeography of the complex was re-analyzed across its complete geographic range. Two contiguous fragments of the ND4 gene were analyzed due to bias from differential haplogroup specificity using a previously designed sequence. At both landscape (anthropic modification gradient) and regional (demographic, fragmentation, biogeographic, climate) scales, lowest T. dimidiata genetic diversity occurs where there is greatest historical anthropic modification, and where T. cruzi infection prevalence is significantly highest. Trypanosoma cruzi prevalence was significantly higher than expected in haplogroups 1 and 3, while lower than expected in haplogroup 2. There was also a significant difference of DTUI and DTUVI infection frequencies in both haplogroups 1 and 3, while no difference of either in haplogroup 2. All haplogroups from the Mexican Neotropics had moderate to high haplotype diversity, while greatest genetic differentiation was between haplogroups 1 and 3 (above FST = 0.868, p < 0.0001). Divergence of the complex from the MRCA was estimated between 0.97 MYA (95% HPD interval = 0.55-1.53 MYA) and 0.85 MYA (95% HPD interval = 0.42-1.5 MYA) for ND4A and both concatenated fragments, respectively, with primary divergence from the MRCA of haplogroups 2 and 3. Effective population size for Mexican haplogroups 1 and 2 increased between 0.02 and 0.03 MYA. This study supports previous ecological niche evidence for the complex´s origin surrounding the Tehuantepec Isthmus, and provides evidence for recent divergence of three primary dimidiata haplogroups, with differential T. cruzi infection frequency and DTU specificity, important components of vector capacity.

Automated identification of insect vectors of Chagas disease in Brazil and Mexico: the Virtual Vector Lab.

Identification of arthropods important in disease transmission is a crucial, yet difficult, task that can demand considerable training and experience. An important case in point is that of the 150+ species of Triatominae, vectors of Trypanosoma cruzi, causative agent of Chagas disease across the Americas. We present a fully automated system that is able to identify triatomine bugs from Mexico and Brazil with an accuracy consistently above 80%, and with considerable potential for further improvement. The system processes digital photographs from a photo apparatus into landmarks, and uses ratios of measurements among those landmarks, as well as (in a preliminary exploration) two measurements that approximate aspects of coloration, as the basis for classification. This project has thus produced a working prototype that achieves reasonably robust correct identification rates, although many more developments can and will be added, and-more broadly-the project illustrates the value of multidisciplinary collaborations in resolving difficult and complex challenges.

Landscape ecology of Trypanosoma cruzi in the southern Yucatan Peninsula.

Landscape interactions of Trypanosoma cruzi (Tc) with Triatoma dimidiata (Td) depend on the presence and relative abundance of mammal hosts. This study analyzed a landscape adjacent to the Calakmul Biosphere Reserve, composed of conserved areas, crop and farming areas, and the human community of Zoh Laguna with reported Chagas disease cases. Sylvatic mammals of the Chiroptera, Rodentia, and Marsupialia orders were captured, and livestock and pets were sampled along with T. dimidiata in all habitats. Infection by T. cruzi was analyzed using mtDNA markers, while lineage and DTU was analyzed using the mini-exon. 303 sylvatic specimens were collected, corresponding to 19 species during the rainy season and 114 specimens of 18 species during dry season. Five bats Artibeus jamaicensis, Artibeus lituratus, Sturnira lilium, Sturnira ludovici, Dermanura phaeotis (Dp) and one rodent Heteromys gaumeri were collected in the three habitats. All but Dp, and including Carollia brevicauda and Myotis keaysi, were infected with predominately TcI in the sylvatic habitat and TcII in the ecotone. Sigmodon hispidus was the rodent with the highest prevalence of infection by T. cruzi I and II in ecotone and domestic habitats. Didelphis viginiana was infected only with TcI in both domestic and sylvatic habitats; the only two genotyped human cases were TcII. Two main clades of T. cruzi, lineages I (DTU Ia) and II (DTU VI), were found to be sympatric (all habitats and seasons) in the Zoh-Laguna landscape, suggesting that no species-specific interactions occur between the parasite and any mammal host, in any habitat. We have also found mixed infections of the two principal T. cruzi clades in individuals across modified habitats, particularly in livestock and pets, and in both haplogroups of T. dimidiata. Results are contradictory to the dilution hypothesis, although we did find that most resilient species had an important role as T. cruzi hosts. Our study detected some complex trends in parasite transmission related to lineage sorting within the matrix. Intriguingly, TcIa is dominant in terrestrial small wildlife in the sylvatic habitat and is the only parasite DTU found in D. virginiana in the domestic habitat, although its frequency remained constant in sylvatic and ecotone vectors. Bats have a key role in TcVI dispersal from the sylvatic habitat, while dogs, sheep, and humans are drivers of TcVI between domestic and ecotone habitats. Overall, our results allow us to conclude that T. cruzi transmission is dependent on host availability within a highly permeable landscape in Zoh Laguna.

Research design, organization, and sample characteristics of the Maternal PKU Collaborative Study.

OBJECTIVE: The Maternal PKU Collaborative Study (MPKUCS) was initiated in 1984 by the National Institute of Child Health and Human Development (NICHD). The purpose was to assess the efficacy of dietary restriction of phenylalanine in reducing morbidity in offspring of women with hyperphenylalaninemia (HPA). A contract was awarded to Childrens Hospital Los Angeles as the Coordinating Center to provide implementation of the research protocol, data collection, and analysis. METHODS: The Study included four regional contributing centers: Childrens Hospital Los Angeles (Western Region), Boston Children's Hospital (Northeast Region), University of Illinois (Midwest Region), and University of Texas Medical Branch, Galveston (Southeast Region). Within each region, many participating clinics were responsible for obstetric care, treatment, and monitoring protocols. In 1985, Canada joined the MPKUCS, and in 1992, Germany entered. They were selected because they provided dietary supplies and strong professional services. Acquisition began in 1984 and ended in October 1995. The study included 574 pregnancies in women with HPA and 100 control subjects matched on age, race, parity, and weeks of gestation. The sample included women with blood phenylalanine values >240 micromol/L, 66% of whom had classical PKU, 22% had atypical PKU, and 12% had mild HPA. Informed consents were obtained on all participants. The women ranged in age from 15 to 36 years of age, with a mean age at conception of 23 years. Teenage pregnancies accounted for 19%. Seventy-five percent graduated from high school. Offspring included 416 newborns, 317 of whom were evaluated at 4 years of age and 289 at 6 to 7 years. Follow-up involved medical, nutritional, psychosocial, and psychological assessments. CONCLUSION: Women with PKU treated before conception and in control of their blood phenylalanine levels between 120 and 360 micromol/L (2-6 mg) exhibited normal pregnancies and neonatal outcome. Surprisingly, women who achieved control in the recommended range by 8 weeks of pregnancy also had a normal fetal outcome.

The Maternal Phenylketonuria International Study: 1984-2002.

OBJECTIVE: The purpose of this report is to review the obstetric medical, psychological, and nutritional aspects and outcome of the women and offspring enrolled in the Maternal Phenylketonuria Study, which was established to assess the efficacy of a phenylalanine (Phe)-restricted diet in preventing the morbidity associated with this disorder. METHODS: A total of 382 women with hyperphenylalaninemia (HPA) were enrolled in the study and completed 572 pregnancies. Outcome measures were analyzed with chi2, Fisher exact text, analysis of variance, t test, Wilcoxon nonparametric test, and multiple logistic regression. Outcome measures were stratified according to maternal HPA classification and the time when dietary control was achieved. RESULTS: Optimal birth outcomes occurred when maternal blood Phe levels between 120 and 360 micromol/L were achieved by 8 to 10 weeks of gestation and maintained throughout pregnancy (trimester averages of 600 micromol/L). Mothers with mild HPA achieved similar birth outcomes as mothers who were in control preconceptually and those in control by 8 to 10 weeks of pregnancy. CONCLUSIONS: Before conception, counseling and early entrance into a prenatal care program is essential in achieving optimal fetal outcome in women with HPA. The achievement of pre- and periconceptional dietary control with a Phe-restricted diet significantly decreased morbidity in the offspring of women with HPA.

Impact of the phenylalanine hydroxylase gene on maternal phenylketonuria outcome.

OBJECTIVE: The aim of the present study was to examine to what extent maternal and offspring phenylalanine hydroxylase (PAH) genotypes in conjunction with maternal IQ and dietary control during pregnancy are related to cognitive development in offspring of women with phenylketonuria (PKU). METHODS: PAH gene mutations were determined in 196 maternal PKU subjects and their offspring. The women were grouped according to PAH genotype, which predicts the metabolic phenotype (severe PKU, mild PKU, and mild hyperphenylalaninemia [MHP]). IQ was determined in both the mothers (Wechsler Adult Intelligence Scale-Revised at >18 years) and their children (Wechsler Intelligence Scale for Children-Revised at > or = 6-7 years of age). RESULTS: According to PAH genotypes, 62% of the women exhibited severe PKU, 19% exhibited mild PKU, and 19% exhibited MHP. Maternal IQ increased, and the assigned phenylalanine (Phe) levels decreased with decreasing severity of PAH genotype. In offspring of mild maternal PKU, multiple regression analysis showed offspring IQ to be significantly related to maternal IQ but not to Phe exposure during pregnancy, which was <750 micromol/L in all cases of mild PKU. In offspring of mothers with severe PKU and average Phe exposure during pregnancy of 360 to 750 micromol/L, multiple regression analysis revealed both maternal IQ and Phe exposure to be significant predictors of offspring IQ. When average Phe exposure was <360 micromol/L, cognitive development was normal (mean IQ: 105), whereas an average Phe exposure of >750 micromol/L severely depressed offspring IQ (mean IQ: 56) in this group regardless of maternal IQ. It could not be documented that the offspring PAH genotype affects cognitive development. CONCLUSION: Female individuals with severe PKU should be offered a diet for a lifetime. If good metabolic control is established, then women with PKU will have children with IQ scores that are not influenced by their disease.

Pregnancy experiences in the woman with mild hyperphenylalaninemia.

OBJECTIVE: A major issue in maternal phenylketonuria (MPKU) has been whether maternal non-PKU mild hyperphenylalaninemia (MHP) is teratogenic. Such untreated pregnancies and their outcomes are presented on this report. METHODS: Enrolled pregnancies in which the untreated prepregnancy assigned phenylalanine level (APL) was no more than 600 micro mol/L were included in the Maternal PKU Collaborative Study and were followed according to protocol. RESULTS: Forty-eight enrolled women with non-PKU MHP had mean APL 408 +/- 114 micromol/L. They had a total of 58 pregnancies that resulted in live births. Fifty were untreated. Maternal phenylalanine (Phe) levels in the untreated pregnancies decreased during pregnancy for average Phe exposure of 270 +/- 84 micromol/L, virtually identical to the level of 269 +/- 136 micromol/L in the 8 treated pregnancies. Birth measurements in the 50 offspring from untreated pregnancies were within normal limits with z scores of -0.25 for weight, 0.28 for length, and -0.63 for head circumference, although birth head circumference was negatively correlated with maternal APL (r = -0.30). Only 1 offspring had congenital heart disease. Offspring IQ was 102 +/- 15 compared with 96 +/- 14 in the mothers with untreated pregnancies and with 109 +/- 21 in control offspring. CONCLUSION: Maternal non-PKU MHP no more than 600 micromol/L does not require dietary therapy. The naturally lower Phe level during pregnancy seems to protect against teratogenesis.

Klinefelter syndrome: expanding the phenotype and identifying new research directions.

PURPOSE: The purpose of this study is to summarize new data on etiology and clinical features of Klinefelter syndrome in order to derive research priorities. METHODS: This study was conducted using critical reviews of selective topics, emphasizing less well-recognized clinical findings. RESULTS AND CONCLUSIONS: The phenotype of the prototypic 47,XXY case is well recognized: seminiferous tubule dysgenesis and androgen deficiency. Less well appreciated is the varied expressivity of 47,XXY Klinefelter syndrome, in particular neurological/cognitive perturbations like language and behavioral problems. Effective therapies are available. Reproductive technologies allow 47,XXY men to sire offspring through intracytoplasmic sperm injection (ICSI); however, genetic counseling is complex and success is low. Behavioral and expressive language difficulties are amenable to treatment by androgen therapy and psychological help. Early treatment may be imperative for optimal outcome.

Intact fetal cells in maternal plasma: are they really there?

Rare fetal cells can be recovered from maternal blood, which suggests that non-invasive prenatal diagnosis is possible. However, recovery and analysis of fetal cells from blood is complex, and sensitivity is low because of the rarity of these cells in the maternal circulation. An alternative strategy, which suggested that intact fetal cells can be found in maternal plasma by use of simple enrichment methods, has been reported. We aimed to replicate this technique. However, five independent laboratories were unable to identify any intact male cells from the plasma of 38 women known to be carrying male fetuses. Although apoptotic intact fetal cells could contribute to the detection of fetal DNA in maternal plasma, we believe that recovery of these cells is difficult and not clinically practical.