Kate Hendricks

Effects of hyperinsulinemia and obesity on risk of neural tube defects among Mexican Americans.

Although both maternal obesity and diabetes mellitus increase the risk for neural tube defects, it is unknown whether they are independent risk factors or manifestations of an underlying prediabetic state such as hyperinsulinemia. We investigated whether hyperinsulinemia was a risk factor for neural tube defects independent of obesity and hyperglycemia in Mexican-American women. We identified case and control women from residents delivering or terminating pregnancies in hospitals or birthing centers in any of the 14 Texas-Mexico border counties during 1995–2000. Case women had a pregnancy affected by anencephaly, spina bifida, or encephalocele; randomly selected control women had normal births, frequency matched by year and birth facility. Questionnaire and laboratory values obtained 5–6 weeks postpartum were available for 149 case and 178 control women. Both hyperinsulinemia and obesity were related to increased neural tube defect risk [odds ratio (OR) = 1.91, 95% confidence interval (CI) = 1.21–3.01 and OR = 1.73, 95% CI = 1.03–2.92, respectively]. Adjustment for obesity only slightly reduced the effect of hyperinsulinemia (OR = 1.75, 95% CI = 1.09–2.82). Alternatively, a modest effect remained for obesity after adjustment for hyperinsulinemia (OR = 1.45, 95% CI = 0.84–2.51). Hyperinsulinemia is a strong risk factor for neural tube defects and may be the driving force for the observed risk in obese women.

Bloodstream Infection Associated with Needleless Device Use and the Importance of Infection-Control Practices in the Home Health Care Setting

The influence of infection-control practices on bloodstream infection (BSI) risk was examined in a home health care setting in which three needleless devices were used consecutively. A case-control study and a retrospective cohort study were conducted. Risk factors for BSI included lower education level, younger age, having a central venous catheter (CVC) with multiple ports, or having a tunneled CVC. Among patients with a tunneled CVC, those at greatest risk had been allowed to shower rather than bathe and to get their exit site wet (P<.01). A high proportion (49%) of isolates were hydrophilic gram-negative bacteria, suggesting water sources of infection. In the cohort study, the BSI rate decreased as the frequency of changing the needleless device end cap increased from once weekly up to every 2 days, suggesting that the mechanism for BSI may involve contamination from the end cap. These findings may help to develop infection-control measures specific to home health care.

Maternal Serum B12 Levels and Risk for Neural Tube Defects in a Texas-Mexico Border Population

PURPOSE Neural tube defects (NTDs) are common birth defects that can be prevented with folate fortification and supplementation. Studies suggest that other nutrients may also be essential to neural tube closure and have a potential role in risk reduction, with vitamin B(12) mentioned most often. We determined the effect of maternal serum B(12) levels, measured postpartum, on the risk of NTDs among a high risk Mexican American population. METHODS The case-control study included 157 Mexican American women with NTD-affected pregnancies and 186 Mexican American women with normal pregnancies, who were residents of Texas-Mexico border counties and delivered during 1995 to 2000. RESULTS Compared with women in the highest vitamin B(12) quintile, women in the lowest quintile showed a strong risk effect (odds ratio (OR) = 3.0, confidence interval (CI): 1.4, 6.3); while those in the 2nd and 3rd quintiles showed moderate risk effects (OR = 1.6, CI = 0.7, 3.6 and OR = 1.7, CI = 0.8, 3.8, respectively). Adjusting for obesity, vitamin supplements, dietary folate, dietary B(12), red blood cell folate, and other covariates did not materially change these estimates. CONCLUSIONS Insufficient levels of serum B(12), which are not normally indicative of a classical vitamin B(12) deficiency nor stem from an inadequate diet, may be an important etiologic factor for NTDs in this population.

Outbreak of Shiga Toxin—Producing Escherichia coli O111:H8 Infections among Attendees of a High School Cheerleading Camp

Few US clinical laboratories screen stool specimens for Shiga toxin-producing Escherichia coli (STEC) other than E. coli O157. An outbreak of STEC O111:H8 infections indistinguishable from E. coli O157:H7 at a youth camp highlights the need to improve non-O157 STEC surveillance. Interviews of 521 (80%) of 650 attendees revealed 55 (11%) were ill; 2 developed hemolytic-uremic syndrome. Illness was associated with consuming salad during the camps first lunch meal (hazard ratio [HR], 4.68; P<.01), consuming ice provided in barrels on the camps final day (HR, 3.41; P<.01), eating cob corn (HR, 3.22; P<.01), and eating a dinner roll (HR, 2.82; P<.01). Cultures of 2 of 11 stools yielded E. coli O111:H8. Results of serologic testing and additional stool cultures demonstrated no evidence of infection with other bacterial pathogens, including E. coli O157, and supported infection with E. coli O111. Clinical laboratories should routinely screen suspect specimens for non-O157 STEC and should serotype and report Shiga-positive isolates.

Maternal stress, social support, and risk of neural tube defects among Mexican Americans.

Background: Studies suggest that maternal psychologic stress can increase the risk of congenital malformations, including neural tube defects (NTDs). We examined whether maternal stress and lack of social support contribute to NTD risk in a population living along the Texas–Mexico border. Methods: Case mothers (N = 184) were Mexican-American women with NTD-affected pregnancies who delivered during 1995 to 2000 in one of the 14 Texas counties bordering on Mexico. Control mothers (N = 225) were randomly selected from Mexican-American women residing in the same area and delivering normal live births. We measured maternal stress by tallying the number of job changes, residential moves, and major injuries occurring during the year before conception. Social support was measured using social integration and perceived emotional support scales. Results: Mothers who experienced one or more stressful life events during the year before conception had increased risks for NTDs (odds ratio [OR] = 2.9; 95% confidence interval [CI] = 1.8–4.7) compared with mothers experiencing no events. Mothers who scored low on emotional support had an elevated risk compared with those who scored high (OR = 4.6; CI = 2.2–9.7). Social support measures, such as network size and satisfaction, group interactions, and church attendance, were unrelated to NTD risk. The estimated effects were not modified or confounded by age, education, country of birth, income, obesity, vitamin supplements, dietary folate, cigarette smoking, or alcohol consumption. Conclusion: In this Mexican-American population, the occurrence of stressful life events was associated with NTD risk. These findings suggest that stress may exacerbate risk in populations with poor nutritional status and meager economic resources.

Lack of association between ZIC2 and ZIC3 genes and the risk of neural tube defects (NTDs) in Hispanic populations.

The Zic genes are a family of transcription factors that are homologous to the Drosophila odd-paired (opa) genes. Mutations in the ZIC1, ZIC2 and ZIC3 genes have been previously described, and all result in neural malformations [Brown et al., 1998; Brown et al., 2001; 2002; Carrel et al., 2001]. Several studies indicated that mutations in the ZIC2 gene might cause holoprosencephaly (HPE) inhumans [Brownet al., 1998;Brownet al., 2001]. The human ZIC2 gene is located at chromosome 13q32, which is a critical region in 13q-syndrome. Abnormalities of neural tube closure, including encephalocele and anencephaly, have been described in association with the 13q-syndrome [Brown et al., 1993, 1995]. In light ofmouse studies showing that diminished expression of the Zic2 gene also resulted in lumbosacral neural tube defects (NTDs), ZIC2 may be an excellent candidate gene for human NTDs. Studies of themousemutant, Bent tail (Bn), suggest a relationship between another Zic gene family member, Zic3, and the risk ofNTDs [Klootwijk et al., 2000].Bn is a mouse model for X-linked NTDs, as the fetuses present with exencephaly, an analogous defect of human anencephaly. Mice with Zic3 mutations were observed in more than 10% of all Bn embryos with NTDs. Mutations in human ZIC3 gene have been described in male patients with left-right axis malformations, and some of them had lumbosacral NTDs [Gebbia et al., 1997]. Carrel et al. [2001] sequenced the three exons of the ZIC3 gene in three families with X-linked spina bifida, yet failed to find mutations or any single nucleotide polymorphisms. The evidence from mouse studies and limited clinical observations suggests that the ZIC3 gene might also be worthy of study as a candidate gene for human NTDs. Brown et al. [2002] recently described a possible association between a histidine tract polymorphism in ZIC2 and NTDs. However, their sample size was relatively small, which prevented definitive conclusions. We evaluated ZIC2 and ZIC3 genes in a group of NTD patients and controls, as well as their parents, in a Hispanic population from the Texas-Mexico border region. This population has a considerably higher prevalence of NTDs (16/10,000 live births) than is generally reported in the United States (8–10/10,000 live births). NTDs were defined as spina bifida or anencephaly. The study population has been described previously [Barber et al., 2000]. Subjects were selected from births and pregnancy terminations occurring between June 1, 1995 and September 30, 1998 in a largely Hispanic population from the 14 counties along the Texas-Mexico border. Cases were identified in hospitals, birthing centers, ultrasound centers, abortion centers, prenatal clinics, genetics clinics, and by birth attendants (midwives and nonhospital physicians). An NTD was defined as spina bifida or anencephaly. Controls were healthy livebirths that occurred in the same counties during that time period. Parents of NTD cases and control infants were also included. Genomic DNA was obtained from Gutherie cards using the Puregene DNA Extraction Kit (Gentra, Minneapolis, MN). Primers designed to amplify the ZIC2 fragment encompassing the histidine tract were: upstream: 50-aac tcc aca acc agt acg gc-30; downstream: 50-gca tat agc gga aaa agg ca-30. The histidine tract polymorphismwasdetermined by the fragment sizes (117 bp or 120 bp). The upstreamprimerwas labeled at 50 end by fluorescent dye 6-FAM (Integrated DNA Technology, Coralville, IA), so that the fragment size could be determined by Genescan analysis on an ABI3100 Genetic Analyzer (Applied Biosystems, Foster City, CA). Exons

Exposure to polychlorinated biphenyls and risk of neural-tube defects in a Mexican American population.

Abstract The authors examined the association between maternal polychlorinated biphenyl (PCB) levels and risk of neural tube defects (NTDs) in Mexican American women with NTD-affected pregnancies who resided in the 14 Texas-Mexico border counties during 1995–2000 (cases). Controls were randomly selected from study area women delivering normal live births. For PCB congeners with sufficient numbers of detectab values (PCB 99, 101, 110, 118, 138, 153, 180), there was little association between the proportions with detectable PCB levels in cases and controls. Odds ratios were <1 or compatible with the null, but power was low for some congeners. All index of seven PCB congeners (105, 118, 138,153, 170, 180, 194) was also not associated with NTD risk. The maternal serum PCB levels in this study population (median PCB 153 level: 18 ng/g) were comparable to those with background exposure and do not appear to have contributed to the high prevalence of NTDs in this population.