Biomedical subjects

Peter Langlois

Publications and source records attributed to Peter Langlois.

5 recordsLinked to original sources

PubMed2006

Very low-noise ENG amplifier system using CMOS technology.

In this paper, we describe the design and testing of a system for recording electroneurographic signals (ENG) from a multielectrode nerve cuff (MEC). This device, which is an extension of the conventional nerve signal recording cuff, enables ENG to be classified by action potential velocity. In addition to electrical measurements, we provide preliminary in vitro data obtained from frogs that demonstrate the validity of the technique for the first time. Since typical ENG signals are extremely small, on the order of 1 1 microV, very low-noise, high-gain amplifiers are required. The ten-channel system we describe was realized in a 0.8 microm CMOS technology and detailed measured results are presented. The overall gain is 10 000 and the total input-referred root mean square (rms) noise in a bandwidth 1 Hz-5 kHZ is 291 nV. The active area is 12 mm(2) and the power consumption is 24 mW from +/-2.5 V power supplies.

Action Potentials↗

PubMed2005

Prevalence of nonsyndromic oral clefts in Texas: 1995-1999.

Nonsyndromic cleft lip with/without cleft palate (NSCLP) and nonsyndromic cleft palate only (NSCPO) are common complex birth defects affecting 4,000 newborns annually. We undertook a descriptive study of oral clefts in Texas, focusing on the effect of folic acid fortification and Hispanic ethnicity on the prevalence of oral clefts as these factors have not previously been described. Data on 896 infants with NSCLP and NSCPO born between 1995 and 1999 in Texas were compared to all births in Texas during the same period. Prevalence odds ratios (POR) were calculated for maternal ethnicity, race, age, parity, public health region of residence, highest level of education, and infant gender. The effect of folic acid fortification on oral clefts was also examined. Compared with whites, adjusted POR were 0.97 (95% CI = 0.77-1.23) and 0.90 (95% CI 0.72-1.14) for NSCLP and 0.46 (95% CI = 0.30-0.72) and 0.62 (95% CI = 0.42-0.90) for NSCPO in foreign-born and US-born Hispanics, respectively. After fortification was implemented, the rate of NSCLP did not decrease. However, there was a 13% decrease in the prevalence of NSCPO (adjusted POR = 0.87, 95% CI = 0.68-1.15). Compared to whites, the rates in US-born and foreign-born Hispanic women were similar for NSCLP and much lower for NSCPO. The small reduction of 13% in NSCPO after folic acid fortification is imprecise and should be interpreted cautiously. Overall, it appears that folic acid fortification has had very little or no effect on the prevalence of oral clefts in infants born in Texas.

Adolescent↗

PubMed2005

Epidemiology of noncomplex left ventricular outflow tract obstruction malformations (aortic valve stenosis, coarctation of the aorta, hypoplastic left heart syndrome) in Texas, 1999-2001.

BACKGROUND: The left ventricular outflow tract (LVOT) malformations aortic valve stenosis (AVS), coarctation of the aorta (CoA), and hypoplastic left heart syndrome (HLHS) contribute significantly to infant mortality due to birth defects. Previous epidemiology data showed rate differences between male and female and white and black ethnic groups. The Texas Birth Defects Registry, an active surveillance program, enables study in a large, diverse population including Hispanics. METHODS: Records of children up to 1 year old with AVS, CoA, and HLHS born in Texas from 1999 to 2001, were collected from the registry. Those including additional heart defects or a chromosomal anomaly were excluded. Multivariate analysis included: infant sex; United States-Mexico border county residence; and maternal age, race/ethnicity, birthplace, and education. RESULTS: There were 910 cases among 1.08 million live births, of which 499 met inclusion criteria. Multivariate modeling of all LVOT malformations combined demonstrated lower prevalence rate ratios (PRRs) for black males (0.26) and Hispanic males (0.70). Similar results were found for CoA but not AVS or HLHS. Higher PRRs were noted for increased maternal age for LVOT (1.3 for 24-34 years; 1.7 for >34 years), AVS, and HLHS, but not CoA, and higher PRRs across all diagnoses for males (LVOT PRR, 2.4) were noted. CoA PRRs were higher in border county vs. non-border county residents (PRR, 2.1). Maternal education and birthplace were not significant factors. CONCLUSIONS: There are rate differences for males among all 3 ethnic groups. Sex and ethnic differences suggest genetic etiologies, where the ethnic differences could be used to find susceptibility loci with mapping by admixture linkage disequilibrium. Increased CoA rates along the U.S.-Mexico border suggest environmental causes that will require further monitoring.

Aortic Coarctation↗

PubMed2003

Random error and undercounting in birth defects surveillance data: implications for inference.

BACKGROUND: There has been an ongoing debate among birth defects investigators about whether or not to publish estimates of rates of birth defects with confidence intervals to allow for comparisons of rates across regions and time. A major impediment in resolving this debate has been the lack of a framework for quantifying uncertainties in the data that can be applied uniformly to birth defects surveillance programs. This report presents an overview of random error and ascertainment bias in birth defects surveillance data, and of the implications of these errors for estimation and comparisons of birth defects rates. METHODS: We consider when confidence intervals can be used as part of a strategy to make inference on rates, as well as ratios of or differences between two rates. Worth noting is that confidence intervals only address random error in the data. In the presence of undercounting of cases, estimation of rates and confidence intervals requires knowledge or an estimate of the extent of underascertainment. Rate estimates and confidence intervals that ignore such bias can be misleading. However, if it is reasonable to assume that the ascertainment bias is constant over time (or across regions), then it is possible to make valid comparisons of rates over time (or across regions) using ratio or difference estimators, even when lack of knowledge of the extent of undercounting makes estimating the absolute rate and its confidence interval problematic. Finally, sensitivity analyses can use confidence limits to determine the difference in ascertainment bias necessary to explain an apparent difference in rates. CONCLUSION: Because birth defects surveillance systems have evolved in the absence of agreed upon standards to guide the process, it is difficult to determine the extent to which the variability in rates of birth defects across programs or over time is real or due to differences in surveillance methods. Efforts to develop standards for birth defects surveillance may help to minimize the variability in prevalence of birth defects due to differences in case ascertainment methods and allow for evaluations of real temporal and spatial variations in environmental effects. In the meantime, if comparisons of rates need to be made to address public health concerns, it would be prudent to conduct only such comparisons between regions or across time when the degree of case ascertainment can be assumed to be relatively constant across regions and time.

Birth Certificates↗

PubMedDate not supplied

Linking environmental hazards and birth defects data.

The authors describe methods for linking birth certificate and birth defect registry data to potential environmental hazards and assess potential confounding factors. Cases of selected birth defects from the Texas Birth Defects Registry were linked to their respective birth/ fetal death records. Comparison births were randomly selected from the 1996-2000 Texas birth records. Maternal addresses were related through a geographic information system to boundaries of hazardous waste sites and point locations of industries. Approximately 89% of maternal addresses of case births and 88% of comparison births were successfully related in distance to these sites and industries. Maternal characteristics associated with living within one mile of these sites included belonging to any group besides non-Hispanic white and having lower education attainment (< 16 years) or a residence within the city limits. In linking environmental and health outcome databases, researchers should be aware of factors that may confound associations between exposure and outcomes.

Adult↗