Sara A. Barton

Admixture in Hispanics: Distribution of Ancestral Population Contributions in the Continental United States

AbstractThe effect of gene flow on Hispanic populations from different geographic regions of the United States was analyzed using six autosomal DNA markers (LDLR, GYPA, HBGG,D7S8, GC, and HLA-DQA). By region of sampling, the Hispanic populations showed different ancestry contributions, from a trihybrid structure with European, Native American, and African contributions (California, Nevada, Florida, New Jersey, and Virginia) to a dihybrid structure with European and American contributions (Southwest population) or European and African contributions (Pennsylvania and Southeast population). These findings allowed us to define two regional groups, the West and the East. In the former, Native American contributions ranged from 35.58% to 57.87%; in the East region the values ranged from 0% to 21.27%. An African influence was similar in both regions, ranging from 0% to 17.11%, with a tendency of increasing in the East region. These data reflect the different origins of the Hispanic populations that led to the present ones. In the West, Hispanics are mostly of Mexican origin, and in the East, they are predominantly of Cuban and Puerto Rican origin.

Gender and treatment differences in knowledge, health beliefs, and metabolic control in Mexican Americans with type 2 diabetes.

PURPOSE The purpose of this project was to describe metabolic control, knowledge, and health beliefs of Mexican Americans with type 2 diabetes. METHODS The study site was Starr County, Texas, a border community located on the Rio Grande River and bordering northern Mexico. Of the total sample of 360 persons, 252 agreed to participate in this intervention study and were randomized either to the treatment group or the control group that waited 1 year to begin the intervention. RESULTS The majority of individuals were Spanish-speaking females with a mean age of 54 years and a mean diabetes duration of 8 years. For those treated with diet only, males exhibited higher fasting blood glucose levels than females. Gender effects were seen for cholesterol level, with females exhibiting higher levels than males. Males expressed stronger perceptions of control and social support for diet. Bivariate relationships were found between acculturation and diabetes knowledge. The health belief subscales of control and impact on job together explained 16% of the variance in HbAlc values. CONCLUSIONS Males and females held differing beliefs about ability to control their diabetes and degree of social support for diet. The impact of gender differences on ability to integrate diabetes self-care and on effectiveness of diabetes programs has not been determined but should be considered in future research.

Estimation of nonpaternity in the Mexican population of Nuevo Leon: a validation study with blood group markers.

A method for estimating the general rate of nonpaternity in a population was validated using phenotype data on seven blood groups (A1A2BO, MNSs, Rh, Duffy, Lutheran, Kidd, and P) on 396 mother, child, and legal father trios from Nuevo León, Mexico. In all, 32 legal fathers were excluded as the possible father based on genetic exclusions at one or more loci (combined average exclusion probability of 0.694 for specific mother-child phenotype pairs). The maximum likelihood estimate of the general nonpaternity rate in the population was 0.118 +/- 0.020. The nonpaternity rates in Nuevo León were also seen to be inversely related with the socioeconomic status of the families, i.e., the highest in the low and the lowest in the high socioeconomic class. We further argue that with the moderately low (69.4%) power of exclusion for these seven blood group systems, the traditional critical values of paternity index (PI > or = 19) were not good indicators of true paternity, since a considerable fraction (307/364) of nonexcluded legal fathers had a paternity index below 19 based on the seven markers. Implications of these results in the context of genetic-epidemiological studies as well as for detection of true fathers for child-support adjudications are discussed, implying the need to employ a battery of genetic markers (possibly DNA-based tests) that yield a higher power of exclusion. We conclude that even though DNA markers are more informative, the probabilistic approach developed here would still be needed to estimate the true rate of nonpaternity in a population or to evaluate the precision of detecting true fathers.

Mortality of Mexican Americans With NIDDM: Retinopathy and other predictors in Starr County, Texas

Objective— To determine the rate and risk factors of mortality in a cohort of Mexican Americans with NIDDM. Research Design and Methods— A cohort of 353 Mexican Americans with NIDDM were identified between 1981 and 1986. All individuals underwent extensive evaluations that included physical, historical, ophthalmological, and laboratory assessments. This cohort was followed prospectively for a mean of 8 yr. Follow-up included mortality surveillance, death certificate extraction, and a combination of annual and intermediate examinations. Results— The cohort experienced 67 mortality events. One-third of all deaths were premature <65 yr of age) and most often were attributed to diseases of the heart (60.0%). In no case was diabetes listed as the cause of death, although it was listed as a contributing cause in 25.5% of cases. Men had a higher mortality rate than women. In both sexes, baseline retinopathy was identified as an important predictor of subsequent mortality. Mortality was significantly elevated in those with nonproliferative retinopathy and even further elevated in those with proliferative disease (relative risks of ≥ 4 for proliferative disease). Conclusions— Mexican Americans with NIDDM are experiencing premature and excessive mortality compared with the general population. The results clearly link microvascular complications with macrovascular disease, but this link is not explained by a more untoward profile of traditional cardiovascular risk factors. Retinopathy appears to serve as an important monitor of the progression of diabetes and when identified would warrant aggressive action to inhibit or slow the processes leading to subsequent mortality.

p53 Codon 72 Polymorphism and Risk of Cervical Cancer

Storey et al. (1998) implicated the proline/argine polymorphism of the codon 72 of the tumor-suppressor gene p53 in the development of cervical cancer (CC) with the observation that the p53 protein is more efficiently inactivated by the E6 oncoprotein of human papillomavirus in p53 arginine as compared with its proline isoform. These authors further noted that in the United Kingdom, individuals homozygous for the arginine allele were several times more susceptible to HPV-associated tumorigenesis that proline/arginine heterozygotes. Subsequent studies in different countries failed to unanimously confirm this association. Motivated by the high incidence of CC in Chile, we undertook a case control study obtaining the following frequencies for genotypes PP, AP and AA in 60 ICC cases and 53 carefully selected controls: 0.067, 0.250, 0.683 and 0.075, 0.453, 0.472 respectively. A significant difference (X2 = 3.19 p < 0.02) and an odds ratio of 2.62 supported Storey et al (1998)s results. In addition, rejecting previous hypotheses about the world distribution of the p53 codon 72 polymorphism, we conclude that this distribution most likely represents ancient human dispersal routes. Several methodological and biological explanations for the results obtained in previous negative association studies are briefly discussed.

Evidence of a Sex-Dependent Association between the MSX1 Locus and Nonsyndromic Cleft Lip with or without Cleft Palate in the Chilean Population

Prior studies have implicated an involvement of the Msx1 homeobox gene in cleft palate in mice and its homolog in humans (called MSX1 in the HOX7 gene, located on chromosome 4). In this study we present evidence of a sex-dependent association between MSX1 and nonsyndromic cleft lip/palate (NSCLP) in the Chilean population. The sample included 73 NSCLP cases, 37 from multiplex families (Mx), 36 from simplex families (Sx), and 87 controls. Polymerase chain reaction amplification of the MSX1 intragenic microsatellite (CA)n-sequence shows significant (p = 0.035) differences in the allele frequencies between NSCLP-Mx males and control males. These differences are mainly due to frequency differences in allele *2 (173 base pairs) among cases (21.9%) and controls (13.2%). When the NSCLP cases are subdivided by sex and positive family history (Mx versus Sx), the Mx males (27.8%) as well as the total NSCLP-Mx cases (25.7%) showed significantly higher frequencies of allele *2, compared to controls (11.4% and 13.2%, respectively). Analysis of the genotype data indicates that the relative risk for NSCLP is greater for persons carrying allele *2 (i.e., odds ratio [OR] larger than 1), reaching significance for all Mx cases (OR = 2.67; 95% confidence interval [CI], 1.10 to 6.52) and even more pronounced for Mx males (OR = 3.33; 95% CI, 1.08 to 10.32). Taken together, these findings support the hypothesis that the genetic variation at the MSX1 locus is a predisposing gene involved in sex-dependent susceptibility to clefting and that it also differentiates simplex from multiplex families.

Symptom-Related Self-Care of Mexican Americans With Type 2 Diabetes: Preliminary Findings of the Starr County Diabetes Education Study

Starr Country Texas, a Texas-Mexico border community, was the site of a study involving culturally-appropriate education and group support for Mexican Americans with type 2 diabetes. Data were collected from 63 subjects on frequency of diabetes-related symptoms during the previous month and on self-care symptom treatments. On average, subjects were 57-year-old females, diagnosed with diabetes for 10 years, and exhibiting HbA 1c levels of 12.5%. Almost 50% experienced excessive urination, excessive thirst, shakiness/nervousness, and numbness and/or tingling in their extremities. More than 50% of those who experienced symptoms did not view them as serious. Only one subject checked blood sugar levels when symptoms occurred. Significantly higher mean glycosylated hemoglobin levels were found for individuals who experienced dizziness and/or chest pain compared with those who did not. A variety of self-care treatments were employed, including over-the-counter medications and home remedies.

Facial Clefting and Amerindian Admixture in Populations of Santiago, Chile

Among congenital malformations, cleft lip with and/or without cleft palate has the highest relative frequencies and shows ethnic variation in prevalence. Both malformations are generally more common among the Asian than European populations. Many populations of Chile have genes of Amerindian and Spanish ancestry, with considerable variation in the degree of Amerindian admixture. Therefore, the association of clefting incidence with Amerindian admixture was investigated. The frequency of cleft lip and/or cleft palate in infants born in three private and two public maternity service clinics of Santiago, Chile, is reported. The private clinic patients have a higher socioeconomic status (SES) than those receiving the public services. They also differ in estimated Amerindian admixture. More than 200,900 consecutive birth records were reviewed. The rate of clefting malformations is 15.3 per 10,000 live births. Based on allele frequencies at the ABO and Rh blood group loci, the percentage of Amerindian admixture is higher in infants born in the public compared to those born in the private maternity service clinics. Amerindian admixture is positively correlated (Spearmans p = 0.9, P = 0.008) with clefting rate across these samples. Clefting is also associated with SES, with lower SES showing higher clefting rates. Mothers of clefting newborns also have higher estimated Amerindian admixture compared to those of normal newborns. The results support the view that in Chilean populations, susceptibility to clefting is related to Amerindian ancestry. Am. J. Hum. Biol. 9:225–232, 1997.

Risk of postmenopausal hip fracture in Mexican American women

To assess the risk of hip fracture in Mexican Americans, the ethnicity of 80 women aged 50 years and over admitted with hip fractures to a Texas hospital was compared with that of age-matched women hospitalized for other reasons. The risk of fracture for Mexican Americans was only 35 per cent that of Whites (95% CI = 19 per cent, 65 per cent). This finding was confirmed in a chart survey performed in a second hospital population. These results suggest that Mexican American women may receive less potential benefit from preventive measures for hip fracture than Whites.

The multinational andean genetic and health program—IV. Altitude and the blood pressure of the aymara

Abstract Of 2096 surveyed males and females of all ages living at three altitudes ( coastal m , sierra ~ 3000 m , and altiplano ∗ > 4000 m ), 759 were included in a study of blood pressure. Twelve groups are defined (male and female adults and children at each of three altitudes) and within each, systolic and diastolic pressures were regressed stepwise on age, ethnicity, height, weight and wt ht 2 (relative weight: adults only). Results show that in children, blood pressures depend mostly on weight or height. In male adults no consistent dependency could be found except for diastolic pressure on wt ht 2 on the coast. Female adults showed strong regressions of both blood pressures on wt ht 2 in the sierras and altiplano while age was most important on the coast. Except for persons residing near sea level, these populations do not show the ‘usual’ pattern of increased blood pressure with age. When pressures are plotted against weight, however, most of the differences between altitudes and even between sexes disappear (except, perhaps, for systolic pressure in females). We conclude that the lower blood pressures found in populations at high altitudes in this and other studies are ascribable at least partially to lower body weights due to the harshness of high altitude environments.