Benito A. González

Methotrexate withdrawal at 6 vs 12 months in juvenile idiopathic arthritis in remission: a randomized clinical trial.

CONTEXT Novel therapies have improved the remission rate in chronic inflammatory disorders including juvenile idiopathic arthritis (JIA). Therefore, strategies of tapering therapy and reliable parameters for detecting subclinical inflammation have now become challenging questions. OBJECTIVES To analyze whether longer methotrexate treatment during remission of JIA prevents flares after withdrawal of medication and whether specific biomarkers identify patients at risk for flares. DESIGN, SETTING, AND PATIENTS Prospective, open, multicenter, medication-withdrawal randomized clinical trial including 364 patients (median age, 11.0 years) with JIA recruited in 61 centers from 29 countries between February 2005 and June 2006. Patients were included at first confirmation of clinical remission while continuing medication. At the time of therapy withdrawal, levels of the phagocyte activation marker myeloid-related proteins 8 and 14 heterocomplex (MRP8/14) were determined. INTERVENTION Patients were randomly assigned to continue with methotrexate therapy for either 6 months (group 1 [n = 183]) or 12 months (group 2 [n = 181]) after induction of disease remission. MAIN OUTCOME MEASURES Primary outcome was relapse rate in the 2 treatment groups; secondary outcome was time to relapse. In a prespecified cohort analysis, the prognostic accuracy of MRP8/14 concentrations for the risk of flares was assessed. RESULTS Intention-to-treat analysis of the primary outcome revealed relapse within 24 months after the inclusion into the study in 98 of 183 patients (relapse rate, 56.7%) in group 1 and 94 of 181 (55.6%) in group 2. The odds ratio for group 1 vs group 2 was 1.02 (95% CI, 0.82-1.27; P = .86). The median relapse-free interval after inclusion was 21.0 months in group 1 and 23.0 months in group 2. The hazard ratio for group 1 vs group 2 was 1.07 (95% CI, 0.82-1.41; P = .61). Median follow-up duration after inclusion was 34.2 and 34.3 months in groups 1 and 2, respectively. Levels of MRP8/14 during remission were significantly higher in patients who subsequently developed flares (median, 715 [IQR, 320-1 110] ng/mL) compared with patients maintaining stable remission (400 [IQR, 220-800] ng/mL; P = .003). Low MRP8/14 levels indicated a low risk of flares within the next 3 months following the biomarker test (area under the receiver operating characteristic curve, 0.76; 95% CI, 0.62-0.90). CONCLUSIONS In patients with JIA in remission, a 12-month vs 6-month withdrawal of methotrexate did not reduce the relapse rate. Higher MRP8/14 concentrations were associated with risk of relapse after discontinuing methotrexate. TRIAL REGISTRATION isrctn.org Identifier: ISRCTN18186313.

Sistemática, taxonomía y domesticación de alpacas y llamas: nueva evidencia cromosómica y molecular

Four camelid species exist in South America: two wild, the guanaco (Lama guanicoe) and the vicuna (Vicugna vicugna), and two domestic, the alpaca (Lama pacos) and the llama (Lama glama). However, the origin of the domestic species has been a matter of debate. In the present study, variations in chromosome G banding patterns and in two mitochondrial gene sequences have been used to study the origin and classification of the llama and alpaca. Similar patterns in chromosome G band structure were observed in all four Lamini species, and these in turn were similar to the bands described for camels, Camelus bactrianus. However, fine and consistent differences were found in the short arms of chromosome 1, separating camels, guanacos and llamas from vicunas and alpacas. This pattern was consistent even in a hybrid guanaco x alpaca. Equivalent relationship

Mitochondrial DNA variation and systematics of the Guanaco (Lama Guanicoe, Artiodactyla: Camelidae)

Abstract Guanacos (Lama guanicoe) are the most important native herbivorous species in the South American steppes and the dominant ungulate in a fauna rich in rodents but poor in large mammal species. Between 2 and 4 subspecies are usually recognized within Lama guanicoe, based on subtle morphological differences and geographic distribution. To evaluate whether molecular variation is consistent with the latter hypotheses, we analyzed the complete cytochrome-b and partial control region mitochondrial DNA sequences of L. guanicoe from 22 localities in Peru, Bolivia, Argentina, and Chile. Sequence analyses of both genes support the monophyly of the species but failed to distinguish the occurrence of subspecies along the geographic range. Despite that, the northernmost populations (Peru and northern Chile) showed some degree of genetic differentiation with respect to southern representatives from Argentina, Bolivia, and rest of Chile. Analysis of genetic diversity also showed a strong signal of past low population size and a recent population expansion.

Tuberculin reactivity after newborn BCG immunization in mono- and dizygotic twins

SETTING Studies showing significantly higher concordance of tuberculosis among monozygotic twins than dizygotic twins have provided support for genetically determined susceptibility to tuberculosis. OBJECTIVE We wished to explore whether the development of delayed type hypersensitivity to tuberculin after newborn BCG immunization of twins suggested genetic regulation of the response to BCG in humans. DESIGN Our study population consisted of 17 monozygotic twin pairs, 18 dizygotic twin pairs, and 64 single infants 3-34 months of age from Santiago, Chile. All had a BCG scar and were tuberculin tested by one trained nurse. RESULTS The mean birth weight of both groups of twins was significantly lower than that of singletons and the percentage of individuals who failed to respond to tuberculin was approximately twice as high in twins as in singletons. After adjustment for birth weight and age by regression analysis, it was found that the distribution of tuberculin reactivity in both monozygotic and dizygotic twins was not significantly different from that of singletons. Both twin pair correlations is adjusted tuberculin reactivity were significantly greater than zero (P < 0.01) and led to a heritability estimate of 0.28. However, the monozygotic twin correlation was not significantly larger than the dizygotic twin correlation so that heritability is poorly estimated. CONCLUSION These results are consistent with a genetic regulation of the response to newborn BCG immunization in humans by a mechanism capable of producing similar responses in identical and nonidentical twins alike.

Amphibia, Anura, Leiuperidae, Pleurodema thaul : Latitudinal and altitudinal distribution extension in Chile.

The vast latitudinal extension of the Chilean territory determinates a climatic gradient which affects the distribution and diversity of its flora and fauna. From north to south, an increase of precipitation levels produces a gradual change from a desert climate (the Atacama Desert) to a temperate environment with oceanic influence in the austral extreme. Within this climatic gradient, the largest number of amphibian species, 66 % out of 56, is concentrated in central and southern Chile, between 38o and 46o S (Veloso and Navarro 1988; Ortiz and Diaz-Páez 2006). At the north of Chile, the majority of species is found in the Altiplanic zone (northeast limit of the country, 17o to 22o S) and belongs to genus Telmatobius (Formas et al. 2005). The situation is different in the coastal and interior zones of Northern Chile, where only two species have been recorded 29o S northward: Bufo atacamensis and Pleurodema thaul. Here, the Atacama Desert constitutes a natural barrier for the distribution of amphibians. On the other hand, the Andes Mountains also constitute an effective barrier for amphibian colonization on the east side of Chile.

Niche segregation between wild and domestic herbivores in Chilean Patagonia.

Competition arises when two co-occuring species share a limiting resource. Potential for competition is higher when species have coexisted for a short time, as it is the case for herbivores and livestock introduced in natural systems. Sheep, introduced in the late 19th century in Patagonia, bear a great resemblance in size and diet to the guanaco, the main native herbivore in Patagonia. In such circumstances, it could be expected that the two species compete and one of them could be displaced. We investigated spatial overlap and habitat selection by coexisting sheep and guanaco in winter and in summer. Additionally, we studied habitat selection of the guanaco in a control situation free from sheep, both in summer and winter. We also determined overlap between species in areas with different intensity of use (named preferred and marginal areas) in order to further detect the potential level of competition in the case of overlapping. Guanaco and sheep showed significantly different habitat preferences through all seasons, in spite of their spatial overlap at landscape scale. Additionally, the habitat used by guanaco was similar regardless of the presence or absence of livestock, which further indicates that sheep is not displacing guanaco where they coexist. These results suggest that habitat segregation between guanaco and sheep is due to a differential habitat selection and not to a competitive displacement process. Therefore, the potential for competition is considered low, contrary to what has been previously observed, although this could be a density-dependent result.

A case of allosuckling in wild guanacos (Lama guanicoe)

Although allosuckling, the lactation of non-filial offspring, can be a costly behavior, it has been reported in several species across a wide range of mammalian orders. Monotocous species such as ungulates exhibit this behavior less frequently than polytocous species, and most cases have been reported among captive specimens. A case of allosuckling of a free-ranging guanaco (Lama guanicoe) calf is reported. Allosuckling observed in this species may represent opportunistic behavior by the calf, supporting the “milk theft” hypothesis.

The influence of the arid Andean high plateau on the phylogeography and population genetics of guanaco (Lama guanicoe) in South America

A comprehensive study of the phylogeography and population genetics of the largest wild artiodactyl in the arid and cold‐temperate South American environments, the guanaco (Lama guanicoe) was conducted. Patterns of molecular genetic structure were described using 514 bp of mtDNA sequence and 14 biparentally inherited microsatellite markers from 314 samples. These individuals originated from 17 localities throughout the current distribution across Peru, Bolivia, Argentina and Chile. This confirmed well‐defined genetic differentiation and subspecies designation of populations geographically separated to the northwest (L. g. cacsilensis) and southeast (L. g. guanicoe) of the central Andes plateau. However, these populations are not completely isolated, as shown by admixture prevalent throughout a limited contact zone, and a strong signal of expansion from north to south in the beginning of the Holocene. Microsatellite analyses differentiated three northwestern and 4–5 southeastern populations, suggesting patterns of genetic contact among these populations. Possible genetic refuges were identified, as were source‐sink patterns of gene flow at historical and recent time scales. Conservation and management of guanaco should be implemented with an understanding of these local population dynamics while also considering the preservation of broader adaptive variation and evolutionary processes.

Application of DNA Forensic Techniques for Identifying Poached Guanacos (Lama guanicoe) in Chilean Patagonia

Abstract:  Guanaco (Lama guanicoe) is a protected and widely distributed ungulate in South America. A poacher, after killing guanacos in Valle Chacabuco, Chilean Patagonia, transported and stored the meat. Samples were retrieved by local police but the suspect argued that the meat was from a horse. Mitochondrial cytochrome b gene (774 pb), 15 loci microsatellites, and SRY gene were used to identify the species, number of animals and their population origin, and the sex of the animals, respectively. Analysis revealed that the samples came from a female (absence of SRY gene) Patagonian guanaco (assignment probability between 0.0075 and 0.0282), and clearly distinguishing it from sympatric ungulates (E‐value = 0). Based on the evidence obtained in the field in addition to forensic data, the suspect was convicted of poaching and illegally carrying fire arms. This is the first report of molecular tools being used in forensic investigations of Chilean wildlife indicating its promising future application in guanaco management and conservation.

The influence of BCG immunization on tuberculin reactivity in healthy Chilean women in the third trimester of pregnancy

SETTING Tuberculin testing is an accepted method for screening pregnant women for tuberculosis. The interpretation of tuberculin reactivity in bacillus Calmette-Guerin (BCG)-immunized pregnant women is still in debate. OBJECTIVE Four related issues were addressed: (1) The effect of pregnancy on tuberculin reactivity; (2) the effect of age differential on tuberculin reactivity; (3) the effect of repeated immunization with BCG; and (4) the risk of developing tuberculosis during pregnancy or a 3-year post-partum period. DESIGN We performed tuberculin testing in 840 healthy Chilean women in the 32nd to 34th week of pregnancy; 807 had been immunized with 1 or more doses of BCG. There were 3 age groups: 177 were < or = 19 years old, 534 were 20-29 years old, and 129 were > or = 30 years old. All women in the study were followed at least 3 years post-partum. RESULTS Women < or = 19 years old and non-pregnant women of similar age studied in the same geographical area had a similar distribution of the size of tuberculin reactions. Over 50% of all BCG-immunized women in each group had tuberculin reactions > or = 10 mm. A differential effect of different doses of BCG was significant only in 20- to 29-year-old women. None of the women in this study developed tuberculosis during pregnancy or a 3-year post-partum observation period. CONCLUSIONS Healthy, BCG-immunized pregnant women may have positive tuberculin reactions without having an increased risk for tuberculosis. The incidence of tuberculosis and the BCG immunization status need to be considered in the development of policy recommendations for diagnosis and treatment of Mycobacterium tuberculosis infection in pregnant women.