Browsing by Autor "Esteban J. Parra"

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Andean and Tibetan patterns of adaptation to high altitude
(Wiley, 2013) Abigail W. Bigham; Megan J. Wilson; Colleen G. Julian; Melisa Kiyamu; Enrique Vargas; Fabiola Lèon‐Velarde; Maria C. Rivera; Carmelo Rodriquez; Vaughn A. Browne; Esteban J. Parra
These results contribute to our understanding of the unique set of adaptations developed in different highland groups to the hypoxia of high altitude. Overall, the results provide key insights into the patterns of genetic adaptation to high altitude in Andean and Tibetan populations.
Determinants of blood oxygenation during pregnancy in Andean and European residents of high altitude
(American Physiological Society, 2007) Marco Antonio Paco Vargas; Enrique Vargas; Colleen G. Julian; J. Fernando Armaza; Armando Rodríguez; Wilma Téllez; Susan Niermeyer; Megan Wilson; Esteban J. Parra; Mark D. Shriver
High altitude decreases birth weight, but this effect is diminished in long vs. short-resident, high-altitude populations. We asked whether women from long vs. short-resident, high-altitude populations had higher arterial oxygenation levels by comparing 42 Andean and 26 European residents of La Paz, Bolivia (3,600 m), serially during pregnancy (weeks 20, 30, and 36) and again 4 mo postpartum. Pregnancy raised hypoxic ventilatory sensitivity threefold, resting ventilation (.Ve), and arterial O(2) saturation (Sa(O2)) in both groups. Ancestry, as identified using 81 genetic markers, correlated with respiratory pattern, such that greater Andean ancestry was associated with higher respiratory frequency and lower tidal volume. Pregnancy increased total blood and plasma volume approximately 40% in both groups without changing red blood cell mass relative to body weight; hence, hemoglobin fell. The hemoglobin decline was compensated for by the rise in .Ve and Sa(O2) with the result that arterial O2 content (Ca(O2)) was maintained near nonpregnant levels in both groups. Birth weights were similar for all Andean and European babies, but after adjusting for variation in gestational age, maternal height and parity, Andeans weighed 209 g more than Europeans. Babies with heavier birth weights and greater ponderal indices were born to Andean women with higher Ve during pregnancy. We concluded that while maternal .Ve and arterial oxygenation were important, some factor other than higher Ca(O2) was responsible for protecting Andeans from altitude-associated reductions in fetal growth.
Effects of birthplace and individual genetic admixture on lung volume and exercise phenotypes of Peruvian Quechua
(Wiley, 2003) Tom D. Brutsaert; Esteban J. Parra; Mark D. Shriver; Alfredo Gamboa; José-Antonio Palacios; Maria C. Rivera; Ivette Rodriguez; Fabiola Lèon‐Velarde
Forced vital capacity (FVC) and maximal exercise response were measured in two populations of Peruvian males (age, 18-35 years) at 4,338 m who differed by the environment in which they were born and raised, i.e., high altitude (Cerro de Pasco, Peru, BHA, n = 39) and sea level (Lima, Peru, BSL, n = 32). BSL subjects were transported from sea level to 4,338 m, and were evaluated within 24 hr of exposure to hypobaric hypoxia. Individual admixture level (ADMIX, % Spanish ancestry) was estimated for each subject, using 22 ancestry-informative genetic markers and also by skin reflectance measurement (MEL). Birthplace accounted for the approximately 10% larger FVC (P < 0.001), approximately 15% higher maximal oxygen consumption (VO(2)max, ml.min(-1).kg(-1)) (P < 0.001), and approximately 5% higher arterial oxygen saturation during exercise (SpO(2)) (P < 0.001) of BHA subjects. ADMIX was low in both study groups, averaging 9.5 +/- 2.6% and 2.1 +/- 0.3% in BSL and BHA subjects, respectively. Mean underarm MEL was significantly higher in the BSL group (P < 0.001), despite higher ADMIX. ADMIX was not associated with any study phenotype, but study power was not sufficient to evaluate hypotheses of genetic adaptation via the ADMIX variable. MEL and FVC were positively correlated in the BHA (P = 0.035) but not BSL (P = 0.335) subjects. However, MEL and ADMIX were not correlated across the entire study sample (P = 0.282). In summary, results from this study emphasize the importance of developmental adaptation to high altitude. While the MEL-FVC correlation may reflect genetic adaptation to high altitude, study results suggest that alternate (environmental) explanations be considered.
Maternal Adaptation to High-altitude Pregnancy: An Experiment of Nature—A Review
(Elsevier BV, 2004) Lorna G. Moore; Mark D. Shriver; Lynne Bemis; B. Hickler; Megan J. Wilson; Tom D. Brutsaert; Esteban J. Parra; Enrique Vargas