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W R Leonard

Publications and source records attributed to W R Leonard.

At least 37 records · Page 2Linked to original sources
PubMed1996

Population distributions of APOE, APOH, and APOA4 polymorphisms and their relationships with quantitative plasma lipid levels among the Evenki herders of Siberia.

We examined the distributions of seven polymorphic sites in three apolipoprotein genes (APOE, APOA4, and APOH) and their relationships with quantitative lipid levels (total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides) among the Evenki reindeer herders of central Siberia. The polymorphism data reveal several distinctive features that differentiate the Evenki from white populations: the near absence of the APOE*2 allele, the highest ever recorded frequency of the APOH*3 allele, the complete absence of the APOA*2 allele at codon 360, and significantly different frequencies at three other APOA4 polymorphic sites. Our analyses of the relationships of common apolipoprotein polymorphism and plasma lipid levels also revealed interesting results. The well-established positive association between the APOE*4 allele and LDL cholesterol level reported in white populations was not seen in the Evenki despite a comparable frequency of the APOE*4 allele. Because the Evenki have significantly lower cholesterol levels than Westernized whites, this difference in allelic effect probably reflects gene-diet interaction, which modulates the effect of APOE polymorphism on LDL cholesterol. At the APOA4 locus the HincII polymorphism at codon 127 shows a significant impact on plasma triglyceride variation in the Evenki sample: The HincII - allele was associated with higher triglyceride levels than the HincII + allele. Our data indicate that both the genetic and the environmental factors conventionally associated with cardiovascular disease risk in Western societies are different in the Evenki.

Alleles↗
PubMed1995

Growth differences between children of highland and coastal Ecuador.

This study examines patterns of growth in height and weight among children (< 60 months) of highland and coastal agricultural communities of Ecuador. Highland children are significantly shorter, but not significantly lighter than their coastal peers. Linear growth rates (cm/6 months) are comparable between the two samples. Growth rates for body weight (kg/6 m) are similar in highland and coastal boys, whereas highland girls display larger weight gains than their coastal counterparts. In both regions, linear growth is compromised to a much greater extent than growth in body weight, and growth faltering for both height and weight is most pronounced between birth and 24 months of age. The similarity in growth rates between the highland and coastal samples suggests that high altitude hypoxia plays a relatively small role in shaping growth during the first five years after birth. Rather, it appears that most of the disparity in height between the two samples can be attributed to differences established by 6 months of age. The pattern of growth retardation seen in both regions during the first 24 postnatal months is similar to that observed among impoverished populations throughout the world and is likely associated with the influence of nutritional and disease stressors. After 2 years of age, little or no "catch up" growth is seen in height, whereas improvements in weight gain are more pronounced, especially among highland girls. Ongoing research is investigating the nutritional and socio-economic correlates of growth within each region.

Altitude↗
PubMed1995

Comparison of the heart rate-monitoring and factorial methods: assessment of energy expenditure in highland and coastal Ecuadoreans.

Accurate estimates of total daily energy expenditure (TDEE) are critical to studies of the nutritional adaptation of human populations. This study compared the standard factorial method with the recently developed flex-HR technique in a sample of 32 adults (16 males, 16 females) from rural, agricultural communities of highland and coastal Ecuador. Although energy expenditures obtained from the two methods were highly correlated (r = 0.759, P < 0.0001), the 1985 FAO/WHO/UNU factorial method significantly underestimated TDEE relative to the heart rate-monitoring technique (10.27 +/- 2.54 compared with 11.91 +/- 3.96 MJ/d, P < 0.001). The degree of underestimation was greater in males, who had higher energy expenditures. Similarly, underestimation was greater in the highland farmers, who were studied during a period of heavy agricultural work. The differences in energy expenditure estimates translated into a 10% difference in estimated energy adequacy. Additional research is needed to identify the potential sources of bias in the factorial method and to further develop other techniques for accurately estimating energy expenditure under field conditions.

Adolescent↗
PubMed1995

Population relationships among historical and modern indigenous Siberians based on anthropometric characters.

A comparison of anthropometric data recently collected from a modern population of Evenki and data collected from a group of Evenki at the turn of the century by the Jesup expedition (Boas 1903) reveals a pattern of significant changes over this time period. The modern Evenki exhibit larger sitting height and biacromial breadth but smaller bizygomatic and nasal breadth and a shorter face. Although the differences in the postcranial characters might be attributable to improvements in health and nutrition over time, those of the head and face might also indicate increased gene flow, perhaps from European populations. The comparative analysis of the anthropometric data was expanded to a multivariate approach by use of canonical variate analysis. This analysis was performed using data from the 10 populations sampled during the Jesup expedition along with the data from a sample of modern Evenki. In general, a pattern of relationships emerged, reflecting known population interactions and linguistic affiliations to a certain extent. However, the sample of modern Evenki differed substantially from all the other samples in the analysis. Although such a separation of the modern Evenki from this set of historical Siberian populations may be the result of a secular trend; it is also highly probable that it reflects new patterns of gene flow resulting from interactions and events associated with Russian colonial expansion and in this century the establishment of the Soviet state.

Adolescent↗
PubMed1995

VNTR DNA variation in Siberian indigenous populations.

The VNTR loci D7S104, D11S129, D18S17, D20S15, and D21S112 in three indigenous Siberian populations were analyzed to determine the populations' genetic structure. Using the Kolmogorov-Smirnov test, we found that the Siberian indigenous populations of Surinda and Sulamai are separated at the D11S129 locus (p < 0.05). However, the population of Poligus is genetically homogeneous compared with the villages of Sulamai and Surinda. Principal component plots for the sets of VNTR loci cluster the Siberian groups together, reflecting the homogeneity of these populations. An analysis of mean per locus heterozygosity versus the distance from the centroid of distribution suggests gene flow into Sulamai but little genetic exchange with Surinda and Poligus. Ultimately, the VNTR data reflect the genetic distinctiveness of the Kets and the Evenki.

Alleles↗
PubMed1991

Household-level strategies for protecting children from seasonal food scarcity.

Although it has been widely argued that children are most severely affected during periods of food scarcity, there is little quantitative data to support this claim. The present study uses dietary intake and anthropometric data from the Andean community of Nuñoa, Peru to evaluate age-related differences in the impact of and responses to seasonal variation in food availability. Children ages 12 years and under experience smaller seasonal fluctuations in energy intake and have a more adequate pre-harvest diet than adults. Anthropometric measures (weight-for-age and skinfold thicknesses) also indicate better nutritional status in children. Protection of children against severe pre-harvest stress is important because (1) they are more vulnerable to nutritional deprivation and (2) they make substantial contributions to household production. Gender differences, however, are not apparent as nutritional adequacy is comparable in males and females. Protection of children against nutritional stress represents just one of a suite of adaptive responses to limited pre-harvest food availability exhibited within this population.

Adolescent↗
PubMed1989

Reflections on the face of Japan: a multivariate craniofacial and odontometric perspective.

Craniofacial variables for modern and prehistoric Japanese were subjected to multivariate analysis to test the relationships of the people of Japan with mainland Asian and Oceanic samples. The modern Japanese are tied to Koreans, Chinese, Southeast Asians, and the Yayoi rice agriculturalists who entered Japan in 300 B.C. Together they make up a Mainland-Asia cluster of related populations. The prehistoric Jomon foragers, the original inhabitants of the Japanese archipelago, are the direct ancestors of the modern Ainu, who made a recognizable contribution to the warrior class--the Samurai--of feudal Japan. Together, they are associated with Polynesians and Micronesians in a Jomon-Pacific cluster of related populations. Jomon-to-Ainu tooth size reduction proceeded at the same rate as that observable in the post-Pleistocene elsewhere in the Old World.

Female↗
PubMed1989

Nutritional determinants of high-altitude growth in Nuñoa, Peru.

Data on nutritional intake and patterns of physical growth in the rural Andean community of Nuñoa, Peru (elevation 4,000 m), are described and compared to data previously collected from this location. Food consumption data and selected anthropometric measures were obtained from a sample of 33 households. Estimates of caloric intake from this study are very similar to those obtained in Nuñoa during the mid- and late 1960s. However, within the present sample, upper income (i.e., middle class) individuals have significantly higher caloric intakes than those of the lower income group and also appear to have an improved diet relative to individuals of 20 years ago. Anthropometric data show that children of the upper socioeconomic status (SES) group are significantly taller and heavier than the lower SES group children. Moreover, the children of the wealthier families are taller and heavier than the children measured 20 years ago at the same location, whereas the poorer children are not. These results indicate that nutritional factors have significantly contributed to the extreme pattern of slow growth previously reported for children of Nuñoa and, moreover, demonstrate how social and environmental forces interact to create differential levels of stress that contribute to variation in biological well-being.

Altitude↗
PubMed1989

What did our ancestors eat?

Over the millennia various hominoids and hominids have subsisted on very different dietaries, depending on climate, hunting proficiency, food-processing technology, and available foods. The Australopithecines were not browsers and fruit-eaters with very high intakes of vitamin C; rather they were scavengers of kills made by other animals. The hominids who followed did include some cold-climate hunters of large game, but the amount of animal protein decreased with the advent of grain-gathering and decreased further with the introduction of cereal agriculture, with a concomitant decrease in body size. From what we know about food adequacy, preparation, and storage, the notion that the postulated "primitive" diet was generally adequate, safe, and prudent can be rejected. Over evolutionary time, many of our ancestors ate poorly, especially during climate extremes, and they were often at risk for vitamin deficiencies, food-borne diseases, and neurotoxins. Until the advent of modern processing technologies, dirt, grit, and fiber constituted a large part of most early diets.

Animals↗
PubMed1989

Protection of children from seasonal nutritional stress in an Andean agricultural community.

Patterns of seasonal variation in energy intake among small scale farmers (n = 112 individuals) of the highland community of Nuñoa, Peru are examined. Marked seasonal fluctuations in energy consumption are demonstrated with average daily energy intakes being lowest during the last few months before harvest (January-April) when locally produced foods are in shortest supply. However, seasonal energy reduction does not affect all sectors of the population equally. Children (aged 12 years and under) show the least seasonal change in energy intake and appear to be protected from energy stress during the pre-harvest period. This pattern contradicts the generally held view that children are most severely affected under conditions of food scarcity because resources must be preferentially allocated to adult males. Hence, these results emphasize the need to examine further variation in responses to nutritional stress among human populations. It appears that such variation may be dependent upon (1) the nature of the subsistence economy, and (2) aspects of division of labour within populations.

Adolescent↗
PubMed1989

Biosocial responses to seasonal food stress in highland Peru.

This paper examines patterns of seasonal variation in food consumption and responses to food stress in the highland community of Nuñoa, Peru. Dietary and anthropometric data collected from January through August of 1985 on a sample of 26 households (127 individuals) are analyzed. This study finds sharp seasonal differences in energy intake (pre-harvest = 1150 calories/day; post-harvest = 1519/day; p less than 0.01) associated with variation in the availability of locally-produced products (e.g., tubers and cereals). Seasonal energy reduction, however, does not uniformly affect all sectors of this population. Children experience little seasonal change in energy intake and have a more adequate pre-harvest diet and better nutritional status than adults. The responses used to "protect" children from energy stress and minimize the overall impact of seasonal food scarcity on this community include: 1) reduction of pre-harvest household caloric needs through emigration of adolescent and adult males, 2) preferential allocation of food to children during the pre-harvest period, 3) seasonal reduction of activity levels and the year-round use of children for many productive activities, and 4) seasonal changes in meal patterns that minimize post-prandial energy loss during periods of stress. Evaluation of similar data from other anthropological populations underscores the diversity of responses to seasonal change in food availability. Moreover, these data indicate that the protection of children from seasonal energy stress is more common than previously thought. Variation in adaptive responses to food stress appears to be dependent upon 1) the nature of the subsistence economy, 2) the relative contributions of children and adults to household production, and 3) the demographic structure of the population.

Adolescent↗
PubMed1987

Applications of the pattern variability index (sigma z) to the quantification of dysmorphogenesis in the hand.

We have generated percentiles for the pattern variability index (sigma z) of the hand in 1,088 normal infants, children, and adults and have analyzed pattern variability indices for 820 individuals representing 50 congenital malformation syndromes with respect to the normal percentiles. The majority of the affected individuals exhibited elevated sigma z values for the hand, some vastly in excess of normal, while such syndromes as Down, Turner, and the Prader-Willi syndrome were low rather than high in pattern variability of the hand.

Adult↗
PubMed1987

Evolution of P3 morphology in Australopithecus afarensis.

The Australopithecus afarensis dental sample exhibits a wide range of variation, which is most notable in the morphology of the lower third premolar (P3). P3 morphology in the A. afarensis sample ranges from the primitive sectorial extreme in AL 128-23 to the derived, bicuspid (molarized) extreme in AL 333w-1. In this paper, the degree and patterning of variation of the 20 known A. afarensis P3s are examined and the evolutionary implications are discussed. Initially, a series of dental and mandibular metric criteria are evaluated to determine whether this sample may be analyzed as a single species. From the metrics, it is clear that the single species hypothesis cannot be rejected. Next, a series of morphological criteria is devised to measure P3 molarization. Taken as a whole, the A. afarensis P3 sample displays more variation than a sample of modern hominoids (Pan troglodytes) and shows a slight trend toward increased molarization through time. When separated by sex, the A. afarensis sample still displays greater variation than the chimpanzee sample; however, only the male A. afarensis specimens show a trend toward increased molarization. Additionally, the male A. afarensis P3s are more molarized than the female, a pattern that is seen as well (though less markedly) in the chimpanzee sample. The trend toward increased molarization over time indicates selection for grinding in A. afarensis. The sexual differences parallel those seen in the postcrania (cf. Stern and Susman: Am. J. Phys. Anthropol. 60:279-318, 1983), as the females tend to retain the primitive condition, while the males display the derived morphology. Consequently, a model of sexual differences in niche exploitation, with the females exploiting a more arboreal environment, would seem to be supported by both the dental and postcranial evidence.

Africa↗
PubMed1986

Methods for measuring the strength of discriminable drug effects.

Drug discriminations can be used to investigate a variety of preclinical psychopharmacological issues. These discriminations are based on the so-called "discriminable" or "discriminative stimulus" effects of drugs. In order to conduct some types of drug discrimination studies, it is helpful or necessary to know the amount or degree of discriminability of the various drugs employed. This paper describes several methods for determining the degree of discriminability of drugs, and evaluates these methods primarily using data obtained by training rats to discriminate drug vs. no drug in a shock-escape T-maze task. The results suggest that useful indices of degree of discriminability can be computed from the rapidity with which drug discriminations are learned. Indices based on average accuracy during acquisition were found to be somewhat superior to indices based on sessions to criterion.

Animals↗
PubMed1985

Developmental and nutritional determinants of pregnancy outcome among teenagers.

To investigate the determinants of low birth weight in infants born to adolescent mothers, we studied the obstetric population attended at the Maternity Hospital of Lima, Peru. From this population, 1256 gravidas, ranging in age from 12 to 25 years, volunteered to participate in this study. Anthropometric and biochemical measurements were used to evaluate the nutritional status and physiological maturity of the mother and newborn. For analytical reasons the young teenaged mothers (less than 15 years) were classified as either still-growing or having completed their growth, depending on their height relative to their parents' height. Similarly, the young teenagers were classified as either gynecologically immature or gynecologically mature depending on whether their gynecological age was less than or greater than 2 years. Our results indicate that young still-growing teenagers, even when matched for nutritional status, have smaller newborns than adult mothers. The data also demonstrate that maternal gynecological age per se does not affect prenatal growth. As inferred from multivariate analyses, it appears that the reduction in birth weight among young teenagers can be explained in part by a decreased net availability of nutrients resulting from the competition for nutrients between the mother's growth needs and the growth needs of her fetus and by an inability of the teenage placenta to maintain placental function adequately for active fetal growth.

Adolescent↗