Localization of a major susceptibility locus influencing preterm birth.

Preterm birth (PTB) is a complex trait, but little is known regarding its major genetic determinants. The objective of this study is to localize genes that influence susceptibility to PTB in Mexican Americans (MAs), a minority population in the USA, using predominantly microfilmed birth certificate-based data obtained from the San Antonio Family Birth Weight Study. Only 1302 singleton births from 288 families with information on PTB and significant covariates were considered for genetic analysis. PTB is defined as a childbirth that occurs at <37 completed weeks of gestation, and the prevalence of PTB in this sample was 6.4%. An ∼10 cM genetic map was used to conduct a genome-wide linkage analysis using the program SOLAR. The heritability of PTB was high (h(2) ± SE: 0.75 ± 0.20) and significant (P = 4.5 × 10(-5)), after adjusting for the significant effects of birthweight and birth order. We found significant evidence for linkage of PTB (LOD = 3.6; nominal P = 2.3 × 10(-5); empirical P = 1.0 × 10(-5)) on chromosome 18q between markers D18S1364 and D18S541. Several other chromosomal regions (2q, 9p, 16q and 20q) were also potentially linked with PTB. A strong positional candidate gene in the 18q linked region is SERPINB2 or PAI-2, a member of the plasminogen activator system that is associated with various reproductive processes. In conclusion, to our knowledge, perhaps for the first time in MAs or US populations, we have localized a major susceptibility locus for PTB on chromosome 18q21.33-q23.

Differences in pediatric dental services under general anesthesia for Medicaid and military dependent children.

PURPOSE: This study's purpose was to compare pediatric dental services provided for Medicaid and military dependent children to determine if differences in dental treatment choices exist based on site and payment method. METHODS: Subjects included 120 Medicaid patients at the University of Texas Health Science Center at San Antonio and 120 military dependents at Lackland Air Force Base, Texas. Demographic data and treatment information were abstracted for children younger than 6 years old receiving dental treatment under general anesthesia between 2002 and 2006. Data was analyzed using Wilcoxon rank sum, Kruskal-Wallis, and Fisher's exact tests. RESULTS: The Medicaid recipients were younger (40.2 vs 49.8 months, P<.001) and more likely to be Hispanic (78% vs 30%, P<.001). The means of decayed teeth, fillings, and stainless steel crowns did not differ between sites. Medicaid children received more composite fillings (P<.001), fewer amalgam fillings (P<.001), fewer pulp therapies (P<.001), more extractions (P=.01), and fewer sealants (P<.001). Age and gender did not affect decay rates, but those of Hispanic ethnicity did experience more decay than non-Hispanics (9.5 vs 8.6, P=.02). CONCLUSION: This study found no difference in the number of less conservative, albeit more costly, procedures performed with Medicaid children at a university compared to military dependents at a military base.

Decline of tuberculosis mortality in an urban Mexican-origin population, 1935-1984.

Through a series of life table analyses, this paper describes the natural history of tuberculosis mortality in a Mexican-origin community over five decades (1935-84) during which the disease underwent a transition from a major underlying cause of death to a disease conditioned mentioned more often on death certificates as contributing to death than causing death. The decline in death rates from 1940 to 1950 was especially remarkable. Successive birth cohorts of Mexican Americans, separated by as little as five years of age, experienced distinctly lower risk of death from tuberculosis as they entered young adulthood. There was a rapid convergence in age-specific patterns of tuberculosis death rates in Mexican Americans toward those of non-Hispanic whites, so that by 1960 tuberculosis was primarily a cause of death in old age rather than young adulthood. The impact of changing environment, both through improvements of conditions within neighborhoods and through residential mobility, on birth cohorts at risk of tuberculosis needs to be examined in further research.

PIP: This study examines the history of tuberculosis mortality during 1935-84 among a Mexican-origin community in Bexar County, Texas. Data were obtained from death records of the San Antonio Metropolitan Health District. Data coding accounted for the shift in 1949 in formatting underlying cause and primary cause of death. Deaths are estimated from multiple decrement life tables for deaths by age and underlying cause in a hypothetical cohort of 100,000 newborns followed to their deaths. Cause-eliminated life tables show the distributions of deaths if tuberculosis were eliminated. Findings indicate that life expectancy of Mexican-origin people in Bexar County during 1938-42 was about 47 years for males and females. Life expectancy for Anglos was higher but still lower than the national average. By 1980, differences in life expectancies by ethnic group converged. The rapid increases in life expectancy occurred during the 1940s: 12.7 years for Mexican-origin women and 10.3 years for Mexican-origin men. The 1940 risk of tuberculosis death among Mexican-origin people was 5-7 times that of Anglos. Among the 1940s Mexican-origin population, tuberculosis caused heavy fatalities in early adulthood between the ages of 15 and 35 years. By 1960, it was a cause only in old age, as it was among Anglos. Cohort comparisons reveal that the cohort reaching the age of 15 years in 1945 had a mortality probability that was only half as great to age 20 in 1950. The mortality probability declined to near zero by age 25 in 1955. The life table proportion of deaths due to tuberculosis declined linearly and added to life expectancy until 1980. Tuberculosis was the underlying cause of death among 96% of Mexican-origin people in 1938-42 and 41% in 1983-85. Tuberculosis morbidity declined during the 1940s and 1950s due to major housing renewal, slum clearance, code enforcement, and residential mobility.

Improved identification of noisy spectra using higher-ordered correlation spectral analysis.

We used a higher-order correlation-based method of comparison for spectral identification. Higher-order correlations are an extension of the more familiar second-order cross-correlation function and have the significant advantage of being theoretically shown to eliminate noise of unknown spectral density under certain conditions. Specifically, we applied a third-order correlation technique to the identification of similar IR spectra in the presence of noise. We were able to reduce the effects of noise from a second-order correlation measurement by further processing the measurement with a third-order autocorrelation. Our results showed that the third-order correlation-based method increased the probability of detection of a spectrum in the presence of noise, when compared to using a second-order technique alone. The probability of detection increased enough at low signal-to-noise ratios that this technique may be useful when a second-order correlation technique is not acceptable. The third-order technique is applicable to a single experiment, but improved results were found by averaging the results of multiple experiments.

Emergence of diabetes mellitus in a Mexican-origin population: a multiple cause-of-death analysis.

The "New World syndrome" is comprised of disorders that are hypothesized to have resulted from an interaction of the Amerindian genotype with an environment that includes marked changes in lifestyle and diet. The principal component of the syndrome is adult-onset (noninsulin dependent) diabetes mellitus. The purpose of this paper is to describe the emergence of diabetes in a Mexican-origin population. Using a unique file of multiple-cause mortality data, we have computed standardized mortality ratios and relative standardized mortality ratios for Mexican-origin individuals and for other white persons age 30 and over from the 1930's through the middle 1980's. Results for the study population residing in Bexar County (San Antonio), Texas, show that diabetes mortality for Mexican-origin individuals did indeed increase in a pattern consistent with the New World syndrome hypothesis. This study is the first description of the emergence of diabetes using a data set with consistently defined causes of death and demographic characteristics.

Birthweight and adult health outcomes in a biethnic population in the USA.

Recent data indicate that low-birthweight adults are at a higher risk than their high-birthweight peers of developing ischemic heart disease or a cluster of conditions known as the IRS, which includes dyslipidaemias, hypertension, unfavorable body fat distribution and NIDDM. Thus far these observations have been limited to Caucasians from the United Kingdom. we extended these observations to a broader segment of the general population by studying the association of birthweight and adult health outcomes in a biethnic population of the United States. We divided a group of 564 young adult Mexican-American and non-Hispanic white men and women participants of the San Antonio Heart Study into tertiles of birthweight and compared metabolic, anthropometric, haemodynamic, and demographic characteristics across these tertile categories. Additionally, we studied birthweight as a predictor of the clustering of diseases associated with the IRS, defined as any two or more of the following conditions: hypertension, NIDDM or impaired glucose tolerance, dyslipidaemia. Normotensive, non-diabetic individuals whose birthweight was in the lowest tertile had significantly higher levels of fasting serum insulin and a more truncal fat deposition pattern than individuals whose birthweight was in the highest tertile, independently of sex, ethnicity, and current socioeconomic status. Also, the odds of expressing the IRS increased 1.72 times (95% confidence interval: 1.16-2.55) for each tertile decrease in birthweight. These findings were independent of sex, ethnicity, and current levels of socioeconomic status or obesity. In conclusion, low birthweight could be a major independent risk factor for the development of adult chronic conditions commonly associated with insulin resistance in the general population.

Secular decline in death rates due to ischemic heart disease in Mexican Americans and non-Hispanic whites in Texas, 1970-1980.

Although the decline in ischemic heart disease mortality is now entering its third decade, there has been no definitive information on the experience of Mexican Americans, the nation's second largest minority group. Earlier studies carried out in the 1970s were hampered by the unavailability of satisfactory population data beyond 1970. In the present study we have used 1970 and 1980 census data to compute death rates in Mexican Americans and non-Hispanic whites from Texas for the periods 1969-1971 and 1979-1981. All four sex-ethnic groups showed statistically significant declines in death rates due to all causes, due to total ischemic heart disease, and due to acute myocardial infarction between 1969-1971 and 1979-1981. Declines in the latter two causes of death were least marked in Mexican American men. This sex-ethnic group was also the only one that failed to show a decline in death rates due to chronic ischemic heart diseases. The fact that Mexican Americans have been shown to be less well informed about and less likely to adopt lifestyle changes aimed at reducing heart disease risk than non-Hispanic whites may account for the less striking mortality decline observed in Mexican American men, but is harder to reconcile with the apparent equal decline in Mexican American women compared with non-Hispanic whites.

Potential labor force supply and replacement in Mexico and the states of the Mexican Cession and Texas: 1980-2000.

"The purpose of this article is to carry forward the examination of potential labor force supply and replacement of men in Mexico into the 1980-1990 and 1990-2000 decades so that the possible future course of international migration between that country and the United States may be better anticipated. In addition, to provide a degree of developmental perspective, trends in potential labor force supply and replacement in Mexico since 1930-40 are presented." As a contrast, "ratios of potential labor force supply and replacement in the southwestern United States--the states of the Mexican Cession and Texas, which were formerly part of Mexico--also are shown for the 1980-1990 and 1990-2000 intervals." The results suggest that "in Mexico, the projected number of males entering the labor force ages will be about 48 percent larger in the 1980s than in the 1970s.... Fertility declined significantly in Mexico in the 1970s, and therefore the number of new entrants to the labor force ages in the 1990s will decline...." The implications for international migration between Mexico and the United States are considered.

Trends in cardiovascular mortality in Spanish-surnamed, other white, and black persons in Texas, 1970--1975.

Certain categories of cardiovascular disease have significantly declined recently as causes of death. In the present investigation we describe the variation in cardiovascular mortality in Texas by ethnicity, age and sex during 1970--1975 using age-standardized proportional mortality ratios. Specifically, the question of whether the three major ethnic groups in Texas have shared equally in any changes in cardiovascular mortality is examined. Several subcategories of cardiovascular mortality are considered. Among the sex-ethnic groups both ischemic heart disease and acute myocardial infarction mortality declined less among Spanish-surnamed males and females than in their other white and black counterparts. Chronic ischemic heart disease increased in relative importance for all groups except Spanish-surnamed females, in whom it decreased. There was no significant decrease in cerebrovascular disease mortality among Spanish-surnamed males or females as there was in the other groups. These results suggest that important differences in cause-structure of mortality are occurring in the ethnic subpopulations of Texas.

Species comparison of protein synthesis accuracy.

The average accuracy of protein synthesis in reticulocytes from several mammalian species does not correlate with longevity potential from 13 to 90 years. Isoleucine incorporation into highly purified hemoglobin chains which contain no genetically coded isoleucine was used as a direct test of protein synthesis accuracy. Since isoleucine can be incorporated into these molecules by mutations in a few cells as well as errors in most cells, the constant level of isoleucine substitution may also show that the mutation rates are not dramatically different among these species. Isoleucine substitutions in hemoglobin can be used to estimate mutations only above the level of errors, which may be as low as 1/1,000,000, but the probability of seeing a few mutant clones at any time is dependent on the number of stem cells producing reticulocytes. The number of stem cells being expressed is a reflection of the number of cell divisions per clone. If the number of cell divisions per clone is 30 or less, then isoleucine substitutions would increase when the mutation accumulation rose above 30 per million for the mutation to isoleucine at any position in the alpha or beta chain.

Amino acid substitution: its use in detection and analysis of genetic variants.

Techniques of chemical analysis, amino acid sequencing and autoradiography are being used to study the frequency of incorporation of normally noncoded amino acids into hemoglobins and seminal fluid proteins. We are studying, by the sequencing of radiolabeled proteins followed by the recovery of [3H]isoleucine phenylthiohydantoin by high-performance liquid chromatography, the frequency at which normally noncoded isoleucine is incorporated into hemoglobin because of base-substitution mutations versus translational errors. Irradiation increases the isoleucine content of human hemoglobin and the frequency of substitution of isoleucine for specific amino acids in rabbit hemoglobin. Studies to date indicate that these techniques have been developed sufficiently for initial analysis of the potential of drugs and environmental pollutants to induce base-substitution mutations in mammalian somatic cells.

Fertility differences in Peru: A reconsideration.

Abstract In a series of articles by Stycos, Heer and W. H. James, predominantly Indian areas of Peru were reported to have significantly lower levels of fertility than the economically better developed Spanish-speaking areas. Heer and James reported similar findings for Bolivia and Ecuador as well as Peru.