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Biomedical subjects

William R Leonard

Publications and source records attributed to William R Leonard.

At least 19 recordsLinked to original sources
PubMed2006

On the accuracy of perceived parental height in a native Amazonian society.

Studies of secular trends in adult height in rural pre-literate societies are likely to show no change owing to random measurement error in age. In such societies, adults lack birth certificates and guess when estimating their age. We assess the accuracy of perceived height of the same-sex parent to estimate secular trends. We tested the method among the Tsimane', a native Amazonian society of farmers and foragers in Bolivia. Subjects included 268 women and 287 men >20 years of age. Over half the sample reported inaccurately the height of their same-sex living parent, with a tendency to report no difference when, in fact, differences existed. Results highlight the pitfalls of using perceived parental height to examine secular trends in adult height among the Tsimane', though the method might yield accurate information in other societies. We discuss possible reasons for the low accuracy of Tsimane' estimates.

Adult↗
PubMed2006

Nutritional status and spousal empowerment among native Amazonians.

Researchers and development organizations have shown interest in individual empowerment because it presumably improves well-being. Estimates of empowerment's effects on well-being contain biases from the potential endogeneity of empowerment. Using data from a sexually egalitarian and highly autarkic society of foragers and horticulturalists in the Bolivian Amazon, the Tsimane', we overcome the problems that this poses by: (1) matching spouses' responses to the same questions about who makes decisions or who breaks ties in 10 domains to improve accuracy in measures of empowerment; and (2) using parental attributes of spouses as instrumental variables for spousal empowerment. Outcomes include two anthropometric indices of short-run nutritional status: body-mass index and age and sex-standardized z scores of mid-arm muscle area. The amount of empowerment of household heads did not affect their nutritional status or other indicators of their well-being, such as income, wealth, expenditures, happiness, social capital, or self-perceived health. It also did not affect the nutritional status of their offspring. Nor did it affect the difference in income, wealth, or monetary expenditures between spouses. The insubstantial effects persisted with other definitions of empowerment or types of regressions. We end with a discussion of why empowerment, despite its popularity in development discourse, has such tenuous links with objective indicators of well-being, and the implication of this finding for future studies of empowerment's effects.

Anthropometry↗
PubMed2006

Evaluating indices of traditional ecological knowledge: a methodological contribution.

BACKGROUND: New quantitative methods to collect and analyze data have produced novel findings in ethnobiology. A common application of quantitative methods in ethnobiology is to assess the traditional ecological knowledge of individuals. Few studies have addressed reliability of indices of traditional ecological knowledge constructed with different quantitative methods. METHODS: We assessed the associations among eight indices of traditional ecological knowledge from data collected from 650 native Amazonians. We computed Spearman correlations, Chronbach's alpha, and principal components factor analysis for the eight indices. RESULTS: We found that indices derived from different raw data were weakly correlated (rho<0.5), whereas indices derived from the same raw data were highly correlated (rho>0.5; p < 0.001). We also found a relatively high internal consistency across data from the eight indices (Chronbach's alpha = 0.78). Last, results from a principal components factor analysis of the eight indices suggest that the eight indices were positively related, although the association was low when considering only the first factor. CONCLUSION: A possible explanation for the relatively low correlation between indices derived from different raw data, but relatively high internal consistency of the eight indices is that the methods capture different aspects of an individual's traditional ecological knowledge. To develop a reliable measure of traditional ecological knowledge, researchers should collect raw data using a variety of methods and then generate an aggregated measure that contains data from the various components of traditional ecological knowledge. Failure to do this will hinder cross-cultural comparisons.

Adolescent↗
PubMed2006

Does village inequality in modern income harm the psyche? Anger, fear, sadness, and alcohol consumption in a pre-industrial society.

Researchers have found a positive association between income inequality and poor individual health. To explain the link, researchers have hypothesized that income inequality erodes community social capital, which unleashes negative emotions, stress, and stress behaviors that hurt health. Few studies have tested the hypothesized path. Here we estimate the association between (a) village income inequality and social capital, and (b) three distinct negative emotions (anger, fear, sadness) and one stress behavior (alcohol consumption). We use four quarters of panel data (2002-2003) from 655 adults in 13 villages of a foraging-farming society in the Bolivian Amazon (Tsimane'). We found that: (1) village income inequality was associated with more negative emotions but with less alcohol consumption, (2) social capital always bore a negative association with outcomes, and (3) results held up after introducing many changes to the main model. We conclude that village income inequality probably affects negative emotions and stress behaviors through other paths besides social capital because we conditioned for social capital. One such path is an innate dislike of inequality, which might have pre-human origins. Our prior research with the Tsimane' suggests that village income inequality bore an insignificant association with individual health. Therefore, village income inequality probably affects negative emotions and stress behaviors before undermining health.

Adult↗
PubMed2006

Multiparallel chiral method development screening using an 8-channel microfluidic HPLC system.

The Eksigent Express 800 8-channel microfluidic HPLC system was investigated for carrying out multiparallel screening and development of fast normal phase chiral separations. In contrast to the familiar automated sequential chiral method development approaches that often afford a next day result, the multiparallel approach offers the exciting possibility of near "real time" method development, often affording an optimized method in less than 1 h. In this study, four column types (300 microm i.d.) with two different mobile phases are screened using a universal standard gradient approach. Interestingly, parallel method optimization following initial screening was shown to sometimes lead to surprising and unanticipated outcomes, emphasizing the value of the multiparallel screening approach. A variety of standard test racemates were analyzed, with optimized separation methods for most in the 1- to 2-min range. These results compare favorably with results obtained on a single channel conventional HPLC system using 4.6-mm i.d. columns. In addition, isocratic methods developed on the microbore columns are readily translated to the larger column format.

Benzoin↗
PubMed2006

Total energy expenditure in the Yakut (Sakha) of Siberia as measured by the doubly labeled water method.

BACKGROUND: Populations in transition to a Western lifestyle display increased incidences of obesity, type 2 diabetes, and other chronic diseases; the mechanisms responsible for these changes, however, remain incompletely understood. Although reduced physical activity has been implicated, few studies have accurately quantified energy expenditure in subsistence populations. OBJECTIVE: The aim of the study was to examine the relation of total energy expenditure (TEE) and activity [physical activity level (PAL), activity energy expenditure (AEE), and weight-adjusted AEE (AEE/kg)] with body composition and lifestyle in the Yakut (Sakha), an indigenous high-latitude Siberian group. DESIGN: We measured TEE using doubly labeled water and resting metabolic rate using indirect calorimetry in 28 young adults (14 women and 14 men) from Berdygestiakh, Russia. RESULTS: The men had higher TEE (12,983 compared with 9620 kJ/d; P < 0.01), AEE (5248 compared with 3203 kJ/d; P < 0.05), AEE/kg (72.7 compared with 48.8 kJ . kg(-1) . d(-1); P < 0.05), and PAL (1.7 compared with 1.5; P = 0.09) than did the women, although this may reflect, in part, body size and composition differences. Overweight men and women had modestly higher TEEs than did lean participants; when adjusted for body size, activity levels were not significantly different between the groups. Persons with more traditional lifestyles had higher TEEs and PALs than did persons with more modernized lifestyles; this difference correlated with differences in participation in subsistence activities. CONCLUSIONS: Activity levels in the Yakut were lower than those in other subsistence groups, especially the women, and were not significantly different from those in persons in industrialized nations. Persons who participated in more subsistence activities and consumed fewer market foods had significantly higher activity levels.

Adult↗
PubMed2006

The emergence of obesity among indigenous Siberians.

Once considered a disease of affluence and confined to industrialized nations, obesity is currently emerging as a major health concern in nearly every country in the world. Available data suggest that the prevalence rate of obesity has reached unprecedented levels in most developing countries, and is increasing at a rate that far outpaces that of developed nations. This increase in obesity has also been documented among North American circumpolar populations and is associated with lifestyle changes related to economic development. While obesity has not been well studied among indigenous Siberians, recent anthropological studies indicate that obesity and its associated comorbidities are important health problems.The present study examines recent adult body composition data from four indigenous Siberian populations (Evenki, Ket, Buriat, and Yakut) with two main objectives: 1) to determine the prevalence of overweight and obesity among these groups, and 2) to assess the influence of lifestyle and socioeconomic factors on the development of excess body fat. The results of this study indicate that obesity has emerged as an important health issue among indigenous Siberians, and especially for women, whose obesity rates are considerably higher than those of men (12% vs. 7%). The present study investigated the association between lifestyle and body composition among the Yakut, and documented substantial sex differences in lifestyle correlates of obesity. Yakut men with higher incomes and who owned more luxury consumer goods were more likely to have excess body fat while, among Yakut women, affluence was not strongly associated with overweight and obesity.

Adolescent↗
PubMed2005

Physical stature of adult Tsimane' Amerindians, Bolivian Amazon in the 20th century.

We examine the association between exposure to the market and Western society on the height of adult Tsimane', a foraging-farming society in the Bolivian Amazon. As with other contemporary native peoples, we find little evidence of a significant secular change in height during 1920-1980. Female height bore a positive association with own schooling and fluency in spoken Spanish and with maternal modern human capital (schooling, writing ability, and fluency in spoken Spanish), but male heights bore no association with parental height or with modern human capital. The absence of a secular change likely reflects the persistence of traditional forms of social organization and production that protect health.

Adult↗
PubMed2005

Stereoselective syntheses of highly functionalized bicyclo[3.1.0]hexanes: a general methodology for the synthesis of potent and selective mGluR2/3 agonists.

[Chemical reaction: See text] A Et3Al mediated intramolecular epoxide opening, cyclopropanation reaction is described. The transformation provided highly functionalized bicyclo[3.1.0]hexane systems in high efficiency and with perfect H or F endo selectivity. Application of this reaction to the synthesis of mGluR2/3 agonist 1 (43% overall yield) and a few intermediates suitable for the synthesis of other bicyclo[3.1.0]hexane mGluR2/3 agonists is discussed.

Bridged Bicyclo Compounds↗
PubMed2005

Income inequality and adult nutritional status: anthropometric evidence from a pre-industrial society in the Bolivian Amazon.

Evidence has been accumulated about the adverse effects of income inequality on individual health in industrial nations, but we know less about its effect in small-scale, pre-industrial rural societies. Income inequality should have modest effects on individual health. First, norms of sharing and reciprocity should reduce the adverse effects of income inequality on individual health. Second, with sharing and reciprocity, personal income will spill over to the rest of the community, attenuating the protective role of individual income on individual health found in industrial nations. We test these ideas with data from Tsimane' Amerindians, a foraging and farming society in the Bolivian Amazon. Subjects included 479 household heads (13+ years of age) from 58 villages. Dependent variables included anthropometric indices of short-run nutritional status (body-mass index (BMI), and age- and sex-standardized z-scores of mid-arm muscle area and skinfolds). Proxies for income included area deforested per person the previous year and earnings per person in the last 2 weeks. Village income inequality was measured with the Gini coefficient. Income inequality did not correlate with anthropometric indices, most likely because of negative indirect effects from the omission of social-capital variables, which would lower the estimated impact of income inequality on health. The link between BMI and income and between skinfolds and income resembled a U and an inverted U; income did not correlate with mid-arm muscle area. The use of an experimental research design might allow for better estimates of how income inequality affects social capital and individual health.

Adolescent↗
PubMed2005

Human capital, wealth, and nutrition in the Bolivian Amazon.

We analyze anthropometric variables of a society of forager-horticulturalists in the Bolivian Amazon (Tsimane') in 2001-2002. Community variables (e.g., inequality, social capital) explain little of the variance in anthropometric indices of nutritional status, but individual-level variables (schooling, wealth) are positively correlated with nutritional status. Dietary quality (foods high in animal proteins), access to foraging technology, and traditional knowledge of medicinal plants are related to better anthropometric indices.

Adolescent↗
PubMed2003

Metabolic correlates of hominid brain evolution.

Large brain sizes in humans have important metabolic consequences as humans expend a relatively larger proportion of their resting energy budget on brain metabolism than other primates or non-primate mammals. The high costs of large human brains are supported, in part, by diets that are relatively rich in energy and other nutrients. Among living primates, the relative proportion of metabolic energy allocated to the brain is positively correlated with dietary quality. Humans fall at the positive end of this relationship, having both a very high quality diet and a large brain size. Greater encephalization also appears to have consequences for aspects of body composition. Comparative primate data indicate that humans are 'under-muscled', having relatively lower levels of skeletal muscle than other primate species of similar size. Conversely, levels of body fatness are relatively high in humans, particularly in infancy. These greater levels of body fatness and reduced levels of muscle mass allow human infants to accommodate the growth of their large brains in two important ways: (1) by having a ready supply of stored energy to 'feed the brain', when intake is limited and (2) by reducing the total energy costs of the rest of the body. Paleontological evidence indicates that the rapid brain evolution observed with the emergence of Homo erectus at approximately 1.8 million years ago was likely associated with important changes in diet and body composition.

Animals↗
PubMed2002

Declining growth status of indigenous Siberian children in post-Soviet Russia.

Human health status in Russia has declined sharply over the last decade. The massive social changes that have taken place since the fall of the Soviet Union have resulted in increasing morbidity and mortality rates. However, relatively little information is available on the changes in health and disease patterns of Russia's many indigenous populations. The present study examines anthropometric indices of growth status of young children (< 6 years; n = 155), a sensitive index of population health, in three indigenous Evenki communities of Central Siberia between 1991 and 1995. Children of the 1995 sample are significantly shorter, lighter, and leaner than those measured in 1991 and 1992. In 1995, 61 % of Evenki children were growth stunted (heightfor-age z score < -2.0), as compared to 34% in 1991 and 1992 (p < 0.001). Similarly, the prevalence of low weight-for-age (weight-for-age z score < -2.0) children in the 1995 sample was more than double that of the 1991/92 sample (43% vs. 18%; p <0.001), and the prevalence of low weight-for-height (weight-for-height z score < -2.0; "wasting") increased from 2% to 17% (p < 0.001). The levels of growth retardation observed in 1995 are comparable to those seen among impoverished third-world populations. Additionally, the declines in linear growth appear to be particularly pronounced in girls, raising the question of whether there may be differential treatment of boys and girls under these conditions of stress. Overall, these results indicate that increased economic marginalization is having a profound effect on the health and well-being of indigenous Siberian groups. Further work is necessary to determine the proximate causes of the disturbing trends, and the potential solutions and interventions.

Adult↗
PubMedDate not supplied

Energetics and evolution: an emerging research domain.

The study of energetics is important to human biology because the availability and utilization of food energy influence health, survival, and reproduction. Over the last decade, human biologists, biological anthropologists, and other evolutionary scientists have increasingly come to recognize the importance of energy dynamics in shaping evolutionary processes. Thus far, different lines of energetics research have been conducted largely in isolation from one another. This thematic collection examines topics of evolutionary energetics from several different perspectives, drawing together research from human paleontology, comparative primate and mammalian biology, human population biology, and mathematical modeling. It represents a starting point for further integrative research on human evolutionary energetics.

Animals↗
PubMedDate not supplied

Climatic influences on basal metabolic rates among circumpolar populations.

This article examines evidence for elevations in basal metabolic rate (BMR) among indigenous Northern (circumpolar) populations and considers potential mechanisms and the adaptive basis for such elevations. Data on BMR among indigenous (n = 109 males; 122 females) and nonindigenous (n = 15 males; 22 females) circumpolar groups of North America and Siberia are compiled and compared to predicted BMRs based on three different references: body surface area (Consolazio et al., 1963), body mass (Schofield, 1985), and fat-free mass (Poehlman and Toth, 1995). Regardless of which reference is used, indigenous circumpolar groups show systematic and statistically significant elevations in BMR ranging from +7% to +19% above predicted values for indigenous men and from +3 to +17% for indigenous women. Nonindigenous males also show elevations in BMR, although not to the same extent as in indigenous men (deviations = +3 to +14%), whereas nonindigenous females show no clear evidence of elevated BMRs (deviations = -7 to +5%). This pattern of variation between indigenous and nonindigenous groups suggests that both functional and genetic factors play a role in metabolic adaptation to northern climes. Recent studies on the ecology and genetics of thyroid function offer insights into the mechanisms through which indigenous circumpolar populations may regulate metabolic rates. Studies of seasonal variation in thyroid hormone levels suggest that indigenous circumpolar populations may have a greater capacity to elevate BMR during severe cold than nonindigenous groups. Recent twin studies indicate a significant genetic component of thyroid responses to environmental stressors. Further research exploring the genetics of seasonal variation in thyroid function and BMR among circumpolar groups would advance understanding of the role that selection may have played in shaping metabolic variation.

Acclimatization↗
PubMedDate not supplied

Measuring human energy expenditure: what have we learned from the flex-heart rate method?

The measurement of daily energy expenditure is an important aspect of research on human health and nutrition. Over the last 30 years, G.B. Spurr has been a leader in developing and implementing methods for more effectively assessing energy expenditure and physical activity in traditional and modernizing populations. One of his most notable contributions has been the development of the "Flex Heart Rate" (flex-HR) method. Since its inception in the late 1980s, the flex-HR method has become a standard tool for measuring daily energy expenditure in free-living human populations. This article reviews the initial development and validation of the flex-HR technique, and examines recent refinements of the method and its application to research in biomedicine and human population biology. The review and analyses highlight how the flex-HR technique has improved on earlier methods of assessing energy expenditure and greatly advanced our understanding of variability in human energy requirements.

Anthropometry↗