Functional genomic, biochemical, and genetic characterization of the Salmonella pduO gene, an ATP:cob(I)alamin adenosyltransferase gene

Salmonella enterica degrades 1,2-propanediol by a pathway dependent on coenzyme B12 (adenosylcobalamin [AdoCb1]). Previous studies showed that 1,2-propanediol utilization (pdu) genes include those for the conversion of inactive cobalamins, such as vitamin B12, to AdoCbl. However, the specific genes involved were not identified. Here we show that the pduO gene encodes a protein with ATP:cob(I)alamin adenosyltransferase activity. The main role of this protein is apparently the conversion of inactive cobalamins to AdoCbl for 1,2-propanediol degradation. Genetic tests showed that the function of the pduO gene was partially replaced by the cobA gene (a known ATP:corrinoid adenosyltransferase) but that optimal growth of S. enterica on 1,2-propanediol required a functional pduO gene. Growth studies showed that cobA pduO double mutants were unable to grow on 1,2-propanediol minimal medium supplemented with vitamin B(12) but were capable of growth on similar medium supplemented with AdoCbl. The pduO gene was cloned into a T7 expression vector. The PduO protein was overexpressed, partially purified, and, using an improved assay procedure, shown to have cob(I)alamin adenosyltransferase activity. Analysis of the genomic context of genes encoding PduO and related proteins indicated that particular adenosyltransferases tend to be specialized for particular AdoCbl-dependent enzymes or for the de novo synthesis of AdoCbl. Such analyses also indicated that PduO is a bifunctional enzyme. The possibility that genes of unknown function proximal to adenosyltransferase homologues represent previously unidentified AdoCbl-dependent enzymes is discussed.

Periodontal disease estimates in NHANES III: clinical measurement and complex sample design issues

OBJECTIVE

This paper evaluates the possibility that examiner bias or other factors contributed to an observed decline in pocket depth and gingivitis between the two three-year sequential periods of time (or phases) covered by the Third National Health and Nutrition Examination Survey (NHANES III).

METHODS

Prevalences of periodontal conditions were analyzed using data from two sets of repeat oral health examinations by examining dentists of NHANES III sample persons. The first set includes sample persons who were examined twice by the same examining dentist at an interval of one to six weeks. The second set includes sample persons who were assessed on the same day by both an examining dentist and a reference dentist. Other possible sources of error also were evaluated.

RESULTS

Overall kappa statistics measuring agreement between or within dental examiners were within the range observed for other periodontal disease surveys. While differences were found among dentists in the prevalence of pocket depth of 4 mm or more, for each group of sample persons assessed by a reference examiner-examining dentist pair, the reference examiner's periodontal measurements closely corresponded to measurements made by the examining dentists.

CONCLUSIONS

Differences between dental examiners in prevalences of periodontal conditions may be due in part to the fact that examinees were not randomly assigned to examiners. As a result, the sample persons examined by each dentist may not have been alike in characteristics thought to affect periodontal disease status. These findings suggest that the observed declines in periodontal health status between phases is not due to examiner bias. This unexplained decline may be the result of sampling variation. It is recommended that combined six-year survey results be presented whenever possible.

Comprehensive analysis of the acute toxicities induced by systemic administration of cationic lipid:plasmid DNA complexes in mice

A major limitation associated with systemic administration of cationic lipid:plasmid DNA (pDNA) complexes is the vector toxicity at the doses necessary to produce therapeutically relevant levels of transgene expression. Systematic evaluation of these toxicities has revealed that mice injected intravenously with cationic lipid:pDNA complexes develop significant, dose-dependent hematologic and serologic changes typified by profound leukopenia, thrombocytopenia, and elevated levels of serum transaminases indicative of hepatocellular necrosis. Vector administration also induced a potent inflammatory response characterized by complement activation and the induction of the cytokines IFN-gamma, TNF-alpha, IL-6, and IL-12. These toxicities were found to be transient, resolving with different kinetics to pretreatment levels by 14 days posttreatment. The toxic syndrome observed was independent of the cationic lipid:pDNA ratio, the cationic lipid species, and the level of transgene expression attained. Mechanistic studies determined that neither the complement cascade nor TNF-alpha were key mediators in the development of these characteristic toxicities. Administration of equivalent doses of the individual vector components revealed that cationic liposomes or pDNA alone did not generate the toxic responses observed with cationic lipid:pDNA complexes. Only moderate leukopenia was associated with administration of cationic liposomes or pDNA alone, while only mild thrombocytopenia was noted in pDNA-treated animals. These results establish a panel of objective parameters that can be used to quantify the acute toxicities resulting from systemic administration of cationic lipid:pDNA complexes, which in turn provides a means to compare the therapeutic indices of these vectors.

Serum total homocysteine concentration is related to self-reported heart attack or stroke history among men and women in the NHANES III

High circulating total homocysteine (tHcy) concentration, which is influenced by folate and vitamin B-12 status, is a suspected cause of cardiovascular events. This relation has been investigated in both case-control and prospective studies but has not been evaluated for different sex x age subgroups of the general U.S. population. We used data on adult (i.e., aged > or =40 y) male (n = 1097) and female (n = 1107) participants in the third National Health and Nutrition Examination Survey, excluding diabetics and those supplemented with estrogen, vitamins or minerals, to evaluate the association between serum tHcy concentration and self-report of heart attack or stroke. After adjustment for age, race-ethnicity, smoking, blood pressure, blood pressure medication, body mass index and serum concentrations of creatinine and cholesterol, past events were reported 2.4 (95% confidence interval 1.0-5.5) times as often by men with tHcy concentration of >12 micromol/L as by men with lower values. The odds ratio for women was 2.6 (95% confidence interval 1.1-6.6) after adjustment for the same factors plus menopausal status. A stronger relation in men aged < or =60 y compared with older men may help reconcile conflicting results of earlier studies.

Analysis of factors influencing the comparison of homocysteine values between the Third National Health and Nutrition Examination Survey (NHANES) and NHANES 1999+

Two important changes occurred in the time between the Third National Health and Nutrition Examination Survey (NHANES III) (1991-1994) and the later survey (NHANES 1999+) regarding total homocysteine (tHcy), i.e., a change in matrix from serum to plasma and a change in analytical methods. The goals of this study were to determine the magnitude of potential differences between plasma and serum with regard to tHcy concentrations, and between the two analytical methods used in these surveys. Optimally prepared plasma, serum allowed to clot for 30 and 60 min at room temperature and serum allowed to clot for 30 and 60 min and subjected to four freeze-thaw cycles, prepared from blood samples collected from 30 healthy people, were analyzed by both methods. Serum samples had significantly higher tHcy concentrations than plasma samples, and the difference increased with longer clotting time. Freeze-thaw cycles had little or no effect on the variability or bias in the serum sample results. The tHcy results produced by the two analytical methods were significantly different, but consistent across sample types. On average, the results of the method used in NHANES III were lower by 0.64 micromol/L; however, the relative bias varied with tHcy concentration. The tHcy results determined in surplus serum from NHANES III overestimated tHcy concentrations by approximately 10% compared with optimally prepared plasma. The average method bias was 6% between the two analytical methods. On the basis of changes in matrix and methodology, direct comparison of tHcy results between the two surveys is inappropriate.

Serum ferritin and death from all causes and cardiovascular disease: the NHANES II Mortality Study. National Health and Nutrition Examination Study

PURPOSE

The purpose of this study was to assess the association between serum ferritin and death from all causes, cardiovascular diseases (CVD), CHD and myocardial infarction (MI). Positive body iron stores have been proposed as a risk factor for coronary heart disease (CHD). While most epidemiologic studies using serum ferritin and other measures of body iron stores have not found an association between iron and heart disease risk, the hypothesis remains controversial. As a result, we examined the relationship of serum ferritin, the principle blood measure of body iron stores, to risk of death in a cohort with a standardized exam and long follow-up.

METHODS

The baseline data for this prospective cohort study were collected in 1976-1980 as part of the second National Health and Nutrition Examination Study (NHANES II) with mortality follow-up using the National Death Index (NDI) through December 31, 1992. The analytic sample (n = 1604) consisted of 128 black men, 658 white men, 100 black women and 718 white women 45-74 years of age at baseline who, based on self-reported data, were free of coronary heart disease at baseline and had no missing data. The main outcome measures were the relative risk of death for persons with serum ferritin levels: <50 microg/L; or 100-199 microg/L; or > or =200 microg/L was compared to persons with serum ferritin levels of 50-99 microg/L adjusted for possible confounding using the Cox proportional hazards model.

RESULTS

Most of the deaths were among white men (n = 254) and women (n = 168). There were relatively few deaths among black men (n = 50) and too few in women (n = 23) to reliably model. The largest number of CVD (n = 119), CHD (n = 82), and MI (n = 49) deaths were in white men while there were 69 CVD, 45 CHD and 13 MI deaths in white women. Black men with a serum ferritin level of <50 microg/L had a significantly higher adjusted risk of death from all causes (RR = 3.1 with 95% confidence limits of 1.5-6.5). There were no other statistically significant associations for all causes mortality for the other three race/sex groups. Additionally, there were no statistically significant associations between serum ferritin and any of the cardiovascular endpoints for any of the groups. There was an apparent but nonsignificant u-shaped association between serum ferritin and all causes mortality in black men and between serum ferritin and CVD death in white women. However, in both cases very wide confidence limits preclude further interpretation.

CONCLUSIONS

Overall, the results do not support the hypothesis that positive body iron stores, as measured by serum ferritin, are associated with an increased risk of CVD, CHD or MI death or between serum ferritin and all causes mortality. Most of the research to date with serum ferritin has been conducted in European men or in European American men. Our results are consistent with the primarily negative results for that race/sex group. More research is needed in women and minority groups, including an explanation of why such an association would exist in these groups but not in white men before an association can be established in them.

CDC growth charts: United States

OBJECTIVES

This report presents the revised growth charts for the United States. It summarizes the history of the 1977 National Center for Health Statistics (NCHS) growth charts, reasons for the revision, data sources and statistical procedures used, and major features of the revised charts.

METHODS

Data from five national health examination surveys collected from 1963 to 1994 and five supplementary data sources were combined to establish an analytic growth chart data set. A variety of statistical procedures were used to produce smoothed percentile curves for infants (from birth to 36 months) and older children (from 2 to 20 years), using a two-stage approach. Initial curve smoothing for selected major percentiles was accomplished with various parametric and nonparametric procedures. In the second stage, a normalization procedure was used to generate z-scores that closely match the smoothed percentile curves.

RESULTS

The 14 NCHS growth charts were revised and new body mass index-for-age (BMI-for-age) charts were created for boys and girls (http://www.cdc.gov/growthcharts). The growth percentile curves for infants and children are based primarily on national survey data. Use of national data ensures a smooth transition from the charts for infants to those for older children. These data better represent the racial/ethnic diversity and the size and growth patterns of combined breast- and formula-fed infants in the United States. New features include addition of the 3rd and 97th percentiles for all charts and extension of all charts for children and adolescents to age 20 years.

CONCLUSION

Created with improved data and statistical curve smoothing procedures, the United States growth charts represent an enhanced instrument to evaluate the size and growth of infants and children.

Hippocampal volume and everyday memory in children of very low birth weight

Children born preterm and of very low birth weight have an increased incidence of learning difficulties, but little is known about the specific nature of their cognitive deficits and the underlying neuropathology. We hypothesized that their vulnerability to hypoxic, metabolic, and nutritional insults would lead to reduced hippocampal volumes and to deficits in memory because of the role of the hippocampus in this domain of cognition. Neuropsychological and magnetic resonance imaging methods were used to investigate this hypothesis in adolescents born preterm (< or = 30 wk gestation, n = 11) or full-term (n = 8). The preterm group had significantly smaller hippocampal volumes bilaterally, despite equivalent head size, and showed specific deficits in certain aspects of everyday memory, both on objective testing and as indicated by parental questionnaires. The preterm group also had a specific deficit in numeracy. The reduced hippocampal volumes and deficits in everyday memory have previously been unrecognized, but their prevalence in a group of neurologically normal children is striking.

Diffusion and perfusion magnetic resonance imaging in childhood stroke

Two magnetic resonance imaging techniques, diffusion and perfusion imaging, are being used increasingly for evaluation of pathophysiology of stroke. This article introduces these techniques and reports some initial studies using these approaches, together with conventional T2-weighted magnetic resonance imaging, for investigation of childhood stroke. It is shown that the combination of T2-weighted and diffusion images can provide information about the timing of stroke events in childhood, and perfusion imaging can detect abnormalities not visible by other magnetic resonance imaging techniques. These magnetic resonance methods therefore should play an important role in investigation of children with stroke and could be of particular value in studies of at-risk populations of children such as those with sickle cell disease.

Internal structure and early thermal evolution of Mars from Mars Global Surveyor topography and gravity

Topography and gravity measured by the Mars Global Surveyor have enabled determination of the global crust and upper mantle structure of Mars. The planet displays two distinct crustal zones that do not correlate globally with the geologic dichotomy: a region of crust that thins progressively from south to north and encompasses much of the southern highlands and Tharsis province and a region of approximately uniform crustal thickness that includes the northern lowlands and Arabia Terra. The strength of the lithosphere beneath the ancient southern highlands suggests that the northern hemisphere was a locus of high heat flow early in martian history. The thickness of the elastic lithosphere increases with time of loading in the northern plains and Tharsis. The northern lowlands contain structures interpreted as large buried channels that are consistent with northward transport of water and sediment to the lowlands before the end of northern hemisphere resurfacing.

Warfarin-5-FU interaction--a consecutive case series

Five patients from a single institution received concomitant warfarin and 5-fluorouracil (5-FU) during a 3-year period. The mean weekly warfarin dose before starting chemotherapy was 40.66 mg and during chemotherapy it was 24 mg (p=0.0026). All patients required a warfarin dosage reduction (range 18-74%, mean 44%). Two patients were hospitalized, one with a major retroperitoneal bleed, the other for fresh-frozen plasma administration and observation. Maximum international normalized ratios (INRs) ranged from 3.66-23.7. This series confirms a common, clinically significant interaction between warfarin and 5-FU. An interaction between capecitabine, the orally available prodrug of 5-FU, and warfarin also has been reported. We recommend weekly monitoring of prothrombin time and INR for all patients receiving concomitant warfarin and 5-FU or capecitabine.

3-O-Desacyl monophosphoryl lipid A derivatives: synthesis and immunostimulant activities

The synthesis of a series of novel analogues of lipid A, the active principle of lipopolysaccharide, is reported. In these compounds, the 1-O-phosphono and (R)-3-hydroxytetradecanoyl moieties of native Salmonella minnesota R595 lipid A have been replaced with hydrogen and the length of the normal fatty acyl residues has been systematically varied. Normal fatty acid chain length in the 3-O-desacyl monophosphoryl lipid A (MLA) series is shown to be a critical determinant of iNOS gene expression in activated mouse macrophages and the induction of proinflammatory cytokines in human peripheral monocytes. Examination of pyrogenicity in rabbits and lethal toxicity in D-galactosamine-treated mice shows that toxic effects in the MLA series can be ameliorated by modifying fatty acid chain length. When used as an adjuvant for tetanus toxoid vaccines, certain MLA derivatives enhance the production of tetanus toxoid-specific antibodies in mice.

Fictive kin among oldest old African Americans in the San Francisco Bay area

OBJECTIVES

The purpose here is to identify those processes that account for the more active and supportive kinship networks among Black oldest old than found among their White age peers.

METHODS

Focused interviews were conducted with 122 Blacks 85 years and older. Both open-ended and semistructured questions were asked in order to determine how Blacks defined family and kinship membership, their expectations for kin, and the desired levels of reciprocity.

FINDINGS

A content analysis of the responses indicated that Blacks defined the boundaries of their families flexibly so as to include fictive kin, and they upgraded more distant kin into the status of primary kin. They also emphasized the importance of collateral relatives so as to expand the size of the network.

DISCUSSION

These processes use personal choices as well as immediate needs to expand the basis of relatedness beyond blood and marriage. Thus the supportive capacities of networks increase in order to serve a potentially vulnerable population.

Serum total homocysteine concentrations in the third National Health and Nutrition Examination Survey (1991-1994): population reference ranges and contribution of vitamin status to high serum concentrations

BACKGROUND

The concentration of circulating total homocysteine is a sensitive marker of inadequate folate and vitamin B12 status. Elevated homocysteine concentrations are associated with an increased risk for vascular disease.

OBJECTIVE

To identify reference ranges for serum total homocysteine concentration in U.S. residents and quantify the contribution of circulating vitamin concentrations to high homocysteine concentrations.

DESIGN

Cross-sectional prevalence study.

SETTING

United States.

PATIENTS

A nationally representative sample of 3563 male participants and 4523 female participants 12 years of age or older who participated in the third National Health and Nutrition Examination Survey.

MEASUREMENTS

Reference ranges (5th and 95th percentiles) for the total homocysteine concentration were defined among participants who were folate- and vitamin B12-replete and had normal creatinine concentrations. A high total homocysteine concentration was defined as one that exceeded the sex-specific 95th percentile for the reference sample (participants 20 to 39 years of age). The population attributable risk percentage was calculated to determine the contribution of low folate (<11 nmol/L) and vitamin B12 (<185 pmol/L) concentrations to a high homocysteine concentration.

RESULTS

Reference ranges for serum total homocysteine concentration increased with age; these ranges were 4.3 to 9.9 micromol/L for male participants and 3.3 to 7.2 micromol/L for female participants 12 to 19 years of age and from 5.9 to 15.3 micromol/L for men and 4.9 to 11.6 micromol/L for women 60 years of age or older. A high homocysteine concentration was defined as at least 11.4 micromol/L for male participants and at least 10.4 micromol/L for female participants. Approximately two thirds of the cases of high homocysteine concentrations were associated with low vitamin concentrations.

CONCLUSIONS

Upper reference limits for the serum total homocysteine concentration increased with age and were higher for male participants than for female participants at all ages. In most cases, high homocysteine concentrations were associated with low serum vitamin concentrations.

Synthesis and biological evaluation of a new class of vaccine adjuvants: aminoalkyl glucosaminide 4-phosphates (AGPs)

A novel series of acylated omega-aminoalkyl 2-amino-2-deoxy-4-phosphono-beta-D-glucopyranosides (aminoalkyl glucosaminide 4-phosphates) was synthesized and screened for immunostimulant activity. Several of these compounds enhance the production of tetanus toxoid-specific antibodies in mice and augment vaccine-induced cytotoxic T cells against EG.7-ova target cells.

Review of the Fifth American College of Chest Physicians Consensus Conference on Antithrombotic Therapy: outpatient management for adults

The recommendations of the Fifth American College of Chest Physicians (ACCP) Consensus Conference on Antithrombotic Therapy are reviewed, with a focus on outpatient anticoagulation management in adults. Numerous therapeutic recommendations have changed since the Fourth ACCP Consensus Conference on Antithrombotic Therapy. The system of grading recommendations has been modified to emphasize clinically important differences and to take into account the benefit-risk ratio of each treatment option. The International Normalized Ratio (INR) goal is now expressed as a specific target value within a range rather than simply an INR range. The recommendations of the fifth conference cover initiation of warfarin therapy, hemorrhagic complications, management of excessive anticoagulation, interruption of warfarin therapy for patients requiring surgery, nonvalvular atrial fibrillation, cardioversion in patients with atrial fibrillation, valvular heart disease, mechanical and biological prosthetic heart valves, coronary artery disease, saphenous vein and internal mammary artery bypass grafts, peripheral arterial occlusive disease, prevention of venous thromboembolism, treatment of venous thromboembolism, stroke prevention in patients with cerebrovascular disease, and pregnancy. Since the fourth consensus conference, new anticoagulation therapies and indications have emerged; the recommendations of the Fifth ACCP Consensus Conference on Antithrombotic Therapy have provided practitioners with a resource of immense value.

Serum total homocysteine concentrations in adolescent and adult Americans: results from the third National Health and Nutrition Examination Survey

BACKGROUND

The elevation of circulating total homocysteine concentrations in a fasting state is associated with an increased risk of occlusive vascular disease.

OBJECTIVE

The primary goals of this study were to describe the distribution of serum total homocysteine concentrations in the United States and to test for differences in homocysteine concentrations among sex, age, and race-ethnicity categories.

DESIGN

Using surplus sera from phase 2 of the third National Health and Nutrition Examination Survey, we measured serum total homocysteine concentrations for a nationally representative sample of 3766 males and 4819 females aged > or = 12 y.

RESULTS

Age-adjusted geometric mean total homocysteine concentrations were 9.6 and 7.9 mmol/L in non-Hispanic white males and females, 9.8 and 8.2 mmol/L in non-Hispanic black males and females, and 9.4 and 7.4 mmol/L in Mexican American males and females, respectively. Age-adjusted geometric mean total homocysteine concentrations were significantly lower in females than in males in each race-ethnicity group (P < 0.01) and were significantly lower in Mexican American females than in non-Hispanic white and non-Hispanic black females (P < 0.01). There was a significant age-sex interaction (P < 0.01), reflecting the fact that homocysteine concentrations in females tended to diverge from those in males at younger ages and converge with those in males at older ages.

CONCLUSIONS

The first data on homocysteine concentrations in a nationally representative sample of Americans confirm the age and sex differences reported previously in nonrepresentative samples. These data also indicate that differences between Mexican American and non-Hispanic females may influence circulating homocysteine concentrations.

Observations of the north polar region of Mars from the Mars orbiter laser altimeter

Elevations from the Mars Orbiter Laser Altimeter (MOLA) have been used to construct a precise topographic map of the martian north polar region. The northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5-kilometer-deep hemispheric depression that is contiguous with the area into which most outflow channels emptied. Polar cap topography displays evidence of modification by ablation, flow, and wind and is consistent with a primarily H2O composition. Correlation of topography with images suggests that the cap was more spatially extensive in the past. The cap volume of 1.2 x 10(6) to 1.7 x 10(6) cubic kilometers is about half that of the Greenland ice cap. Clouds observed over the polar cap are likely composed of CO2 that condensed out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography.

Prevalence of elevated serum transferrin saturation in adults in the United States

BACKGROUND

A population-based hemochromatosis screening program that uses serum transferrin saturation has been proposed, but few data exist on the number of U.S. adults that such a program would identify for further testing.

OBJECTIVE

To determine the prevalence of an initially elevated serum transferrin saturation and the prevalence of concurrently elevated serum transferrin saturation and serum ferritin levels in the adult population of the United States.

DESIGN

Nationally representative cross-sectional survey of the noninstitutionalized U.S. civilian population.

PARTICIPANTS

15 839 men and nonpregnant women 20 years of age and older who were examined in the third National Health and Nutrition Examination Survey (1988-1994).

MEASUREMENTS

Single measurements of serum transferrin saturations and serum ferritin levels. Cut-off values used to define elevated serum transferrin saturation ranged from greater than 45% to greater than 62%.

RESULTS

The prevalence of initially elevated serum transferrin saturation ranged from 1% to 6%. Approximately 11% to 22% of those with elevated serum transferrin saturation had concurrently elevated serum ferritin levels. The prevalence of elevated serum transferrin saturation was lower in women than in men when the same cut-off value was used to define elevated serum transferrin saturation. The prevalence of elevated serum transferrin saturation in non-Hispanic black persons and Mexican-Americans was similar to or slightly less than that in non-Hispanic white persons. The prevalence of elevated serum transferrin saturation in persons 20 to 49 years of age was as high as or higher than that in older adults.

CONCLUSIONS

A hemochromatosis screening program that uses a cut-off value of greater than 60% to define elevated serum transferrin saturation would identify an estimated 1.4 to 2.5 million U.S. adults for further testing.

Blood folate and vitamin B12: United States, 1988-94

OBJECTIVES

This report presents national estimates of serum and red blood cell (RBC) folate and serum vitamin B12 distributions for persons 4 years and over, by sociodemographic variables.

METHODS

The third National Health and Nutrition Examination Survey (NHANES III) (1988-94), provides information on the health and nutritional status of the civilian noninstitutionalized U.S. population. The analytic sample included 23,378 participants with serum folate data, 23,082 with RBC folate data, and 11,851 with serum vitamin B12 data.

RESULTS

The mean serum and RBC folate concentrations are 7.2 and 196 nanograms per milliliter (ng/mL), respectively, and the mean serum vitamin B12 concentration is 518 picograms per milliliter (pg/mL). Non-Hispanic white people have higher mean serum and RBC folate concentrations than non-Hispanic black or Mexican American people. Serum vitamin B12 concentrations are lowest for older adults, and non-Hispanic black people have higher serum B12 concentrations than non-Hispanic white individuals. Only approximately 3 percent of the population has a serum B12 concentration less than 200 pg/mL.

CONCLUSIONS

Inadequate folate status may be more prevalent among non-Hispanic black and Mexican American people. Data also suggest a modest prevalence of low serum B12 concentrations. Future assessments of folate and vitamin B12 status will be important to evaluate the impact of a recently enacted fortification policy.

Correlation of linkage data with phenotype in eight families with Stickler syndrome

The clinical findings of eight families with Stickler syndrome were analyzed and compared with the results of linkage studies using a marker for the type II collagen gene (COL2A1). In six families, there was linkage of the phenotype to COL2A1. The manifestations of the affected individuals were similar to those of the original Stickler syndrome family [Stickler et al., Mayo. Clin. Proc. 40:433-455, 1965] and resembled the phenotype of the previously reported individuals or families with Stickler syndrome in which a dominant mutation in the COL2A1 gene has been identified. Linkage to COL2A1 was excluded in the two remaining families. The most striking difference between these two types of families was the absence of severe myopia and retinal detachment in the two unliked families. In the COL2A1 unlinked families, linkage of the phenotype to genes (COL11A1 and COL11A2) that encode pro alpha chains of type XI collagen, a minor cartilage-specific collagen, was also excluded. Since Stickler syndrome can be produced by mutations in COL2A1, COL11A1, and COL11A2, our data suggest that there is at least a fourth locus for Stickler syndrome.

Distributions and trends of serum lipid levels among United States children and adolescents ages 4-19 years: data from the Third National Health and Nutrition Examination Survey

BACKGROUND

Atherosclerosis begins in childhood and progresses into adulthood. The reduction of cardiovascular risk factors, such as elevated serum total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels, in childhood may reduce cardiovascular morbidity and mortality in adulthood. Lipid distributions among children and adolescents were examined using the most recent nationally representative data.

METHODS

Data from 7,499 examinees in NHANES III (1988-1994) were used to estimate mean and percentile distributions of serum total cholesterol, LDL-C, high-density lipoprotein cholesterol (HDL-C), and triglycerides in children and adolescents aged 4 to 19 years. The estimates were analyzed by age, sex, and race/ethnic groups. Trends in mean total cholesterol were examined for 12- to 17-year-olds using data from NHES III (1966-1970), NHANES I (1971-1974), and NHANES III (1988-1994).

RESULTS

For children and adolescents 4 to 19 years of age, the 95th percentile for serum total cholesterol was 216 mg/dL and the 75th percentile was 181 mg/dL. Mean age-specific total cholesterol levels peaked at 171 mg/dL at 9-11 years of age and fell thereafter. Females had significantly higher mean total cholesterol and LDL-C levels than did males (P < 0.005). Non-Hispanic black children and adolescents had significantly higher mean total cholesterol, LDL-C, and HDL-C levels compared to non-Hispanic white and Mexican American children and adolescents. The mean total cholesterol level among 12- to 17-year-olds decreased by 7 mg/dL from 1966-1970 to 1988-1994 and is consistent with, but less than, observed trends in adults. Black females have experienced the smallest decline between surveys.

CONCLUSIONS

The findings provide a picture of the lipid distribution among U.S. children and adolescents and indicate that, like adults, adolescents have experienced a fall in total cholesterol levels. Total cholesterol levels in U.S. adolescents declined from the late 1960s to the early 1990s by an average of 7 mg/dL. This information is useful for planning programs targeting the prevention of cardiovascular disease beginning with the development of healthy lifestyles in childhood.