Biomedical subjects

Enrique Vargas

Publications and source records attributed to Enrique Vargas.

6 recordsLinked to original sources

PubMed2006

An evolutionary model for identifying genetic adaptation to high altitude.

Coordinated maternal/fetal responses to pregnancy are required to ensure continuous O2 delivery to the developing organism. Mammals employ distinctive reproductive strategies that afford their young an improved chance of survival through the completion or the reproductive period. Thus, mortality prior to the end of the reproductive period is concentrated in the earliest phases of the lifecycle. At high altitude, fetal growth restriction reduces birth weight and likely compromises survival during the early postnatal period. Population variation in the frequency of the altitude-associated increase in intrauterine growth restriction (IUGR) demonstrates that multigenerational Tibetan and Andean high-altitude populations are protected compared with shorter duration, European or Han (Chinese) residents. This experiment of nature permits testing the hypothesis that genetic factors (a) influence susceptibility to altitude-associated IUGR, (b) act on maternal vascular adjustments to pregnancy determining uteroplacental blood flow, and (c) involve genes which regulate and/or are regulated by hypoxia-inducible factors (HIFs). Serial, studies during pregnancy as well as postpartum in Andean and European residents of high (3600 m) and low (300 m) altitude will permit evaluation of whether uteroplacental O2 delivery is lower in the European than Andean women and, if so, the physiological factors responsible. Comparisons of HIF-targeted vasoactive substances and SNPs in or near HIF-regulatory or targeted genes will permit determination of whether these regions are distinctive in the Andean population. Studies coupling genetic and genomic approaches with more traditional physiological measures may be productively employed for determining the genetic mechanisms influencing physiological adaptation to high altitude.

Adolescent↗

PubMed2006

Chronic mountain sickness, optimal hemoglobin, and heart disease.

For the male inhabitants of La Paz, Bolivia (3200-4100 m), and other high altitude regions in America and Asia, chronic mountain sickness (CMS) is a major health problem. Since CMS was first described by Carlos Monge in the Peruvian Andes in 1925, numerous research papers have been devoted to this topic, but many unanswered questions still exist with respect to the beginning of the disease and its cause(s). The experience with CMS has shown that an excessively high hemoglobin concentration is not favorable for high altitude acclimatization, and the hypothesis of theoretically "optimal" hematocrit and "optimal" hemoglobin has been made. The calculated optimal hemoglobin concentration of 14.7 g/dL for resting men in the Andes is discussed as theoretical and not applicable in real life. The most frequent congenital and acquired heart diseases are discussed, such as patent ductus, atrial septum defect, ventricle septum defect among congenital heart diseases and the still very frequent rheumatic valve cardiopathies and Chagas disease as acquired cardiopathies. Among the typical acquired heart diseases of the high altitude dweller, special attention is given to chronic cor pulmonale as a consequence of severe CMS with pulmonary hypertension.

Acclimatization↗

PubMed2005

Consensus statement on chronic and subacute high altitude diseases.

This is an international consensus statement of an ad hoc committee formed by the International Society for Mountain Medicine (ISMM) at the VI World Congress on Mountain Medicine and High Altitude Physiology (Xining, China; 2004) and represents the committee's interpretation of the current knowledge with regard to the most common chronic and subacute high altitude diseases. It has been developed by medical and scientific authorities from the committee experienced in the recognition and prevention of high altitude diseases and is based mainly on published, peer-reviewed articles. It is intended to include all legitimate criteria for choosing to use a specific method or procedure to diagnose or manage high altitude diseases. However, the ISMM recognizes that specific patient care decisions depend on the different geographic circumstances involved in the development of each chronic high altitude disease. These guidelines are established to inform the medical services on site who are directed to solve high altitude health problems about the definition, diagnosis, treatment, and prevention of the most common chronic high altitude diseases. The health problems associated with life at high altitude are well documented, but health policies and procedures often do not reflect current state-of-the-art knowledge. Most of the cases of high altitude diseases are preventable if on-site personnel identify the condition and implement appropriate care.

Acclimatization↗

PubMed2003

Intrauterine growth restriction, preeclampsia, and intrauterine mortality at high altitude in Bolivia.

Infant mortality and stillbirth rates in Bolivia are high and birth weights are low compared with other South American countries. Most Bolivians live at altitudes of 2500 m or higher. We sought to determine the impact of high altitude on the frequency of preeclampsia, gestational hypertension, and other pregnancy-related complications in Bolivia. We then asked whether increased preeclampsia and gestational hypertension at high altitude contributed to low birth weight and increased stillbirths. We performed a retrospective cohort study of women receiving prenatal care at low (300 m, Santa Cruz, n = 813) and high altitude (3600 m, La Paz, n = 1607) in Bolivia from 1996 to 1999. Compared with babies born at low altitude, high-altitude babies weighed less (3084 +/- 12 g versus 3366 +/- 18 g, p < 0.01) and had a greater occurrence of intrauterine growth restriction [16.8%; 95% confidence interval (CI): 14.9-18.6 versus 5.9%; 95% CI: 4.2-7.5; p < 0.01]. Preeclampsia and gestational hypertension were 1.7 times (95% CI: 1.3-2.3) more frequent at high altitude and 2.2 times (95% CI: 1.4-3.5) more frequent among primiparous women. Both high altitude and hypertensive complications independently reduced birth weight. All maternal, fetal, and neonatal complications surveyed were more frequent at high than low altitude, including fetal distress (odds ratio, 7.3; 95% CI: 3.9-13.6) and newborn respiratory distress (odds ratio, 7.3; 95% CI: 3.9-13.6; p < 0.01). Hypertensive complications of pregnancy raised the risk of stillbirth at high (odds ratio, 6.0; 95% CI: 2.2-16.2) but not at low altitude (odds ratio, 1.9; 95% CI: 0.2-17.5). These findings suggest that high altitude is an important factor worsening intrauterine mortality and maternal and infant health in Bolivia.

Adult↗

PubMed1999

Role of genetic and environmental factors in the increased blood pressures of Bolivian blacks.

The tendency toward hypertension or higher blood pressure is more common in blacks than whites. The factors that account for these differences are attributed to both environmental and genetic factors. To clarify this issue, an anthropological study of black and nonblack populations in the lowland village of Chicaloma, northeastern Bolivia at a midaltitude of 1,800 m was conducted. The study included 159 subjects, of which 79 were black and 80 were nonblack, 17-78 years. The study suggests the following: (1) the socioeconomic status of blacks as measured by an ownership index is greater than that of nonblacks, (2) blacks had higher average systolic and diastolic blood pressures than nonblacks and showed an age-associated increase in blood pressures, (3) the prevalence of hypertension was higher for blacks (7-6%) than nonblacks (1.3%), but three times lower than among blacks in the United States, (4) skin reflectance is inversely related to blood pressures so that contrary to what has been suggested the darker the skin color, the higher the blood pressures even at comparable levels of affluence. These findings together suggest that genetic factors predispose black individuals to increased blood pressures, but the expression of clinical hypertension is influenced by adverse unaccounted environmental factors. Am. J. Hum. Biol. 11:489-498, 1999. Copyright 1999 Wiley-Liss, Inc.

Journal Article↗

PubMedDate not supplied

Human physiological adaptation to pregnancy: inter- and intraspecific perspectives.

Reproductive success requires successful maternal physiological adaptation to pregnancy. An interspecific perspective reveals that the human species has modified features of our haplorhine heritage affecting the uteroplacental circulation. We speculate that such modifications - including early implantation and deep, widespread invasion of fetal (trophoblast cells) into and resultant remodeling of maternal uterine vessels - are responses to or compensation for the biomechanical constraints imposed by bipedalism which, in turn, render our species susceptible to the pregnancy complication of preeclampsia. Preeclampsia is characterized by incomplete remodeling of maternal uterine vessels as the result of shallow trophoblast invasion, which in turn reduces uteroplacental blood flow and frequently leads to intrauterine growth restriction (IUGR). Using an intraspecific perspective, we consider the fitness-related consequences of variation in uteroplacental blood flow during high-altitude pregnancy. Although birth weights are reduced at high altitudes in Bolivia, multigenerational Andean residents are relatively protected from altitude-associated IUGR. Our preliminary data suggest that Andean women have greater uteroplacental oxygen delivery than European high-altitude residents due to more complete growth and remodeling of maternal uterine vessels. Identification of the physiological and genetic mechanisms involved in such inter- and intraspecific variations in pregnancy physiology will likely be useful for understanding human evolution and contemporary challenges to successful reproduction.

Adaptation, Physiological↗