Lipids, growth, and development.
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Aging↗
Biomedical subjects
R M Siervogel
Publications and source records attributed to R M Siervogel.
Obesity in children and adolescents: development of predictive equations and their application to epidemiologic studies.
Epidemiological studies of body fatness cannot be based on laboratory measures. One alternative is to analyze values related to body composition such as skinfold thicknesses, but it is better to apply an equation that accurately predicts a body composition variable. If an equation is to be developed, the choice of the dependent variable affects the selection of the independent variables to be tested for inclusion. The validation group should have a wide distribution of values for the dependent and independent variables. To develop an equation that works well on validation and with other groups, all possible sub-set regression should be applied, multicollinearity examined, and ridge and robust regression used if these are needed. An equation chosen from the literature should have been developed and tested by appropriate methods and it should be validated against data from a sub-group of the study sample.
Adolescent↗
Classification of Peruvian infants by using reference growth data.
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Growth↗
Serial analysis of plasma lipids and lipoproteins from individuals 9-21 y of age.
Total cholesterol (TC) and low-density- (LDL-C) and high-density-lipoprotein cholesterol (HDL-C) concentrations were recorded annually from 9 to 21 y of age to study tracking and predictive values for adulthood lipid concentrations associated with cardiovascular disease. The tracking coefficients for TC and LDL-C were congruent to 0.7 for 4-, 6-, and 12-y intervals, indicating good predictive value at ages 9-11 y for risk of elevated concentrations at ages 19-21 y. Tracking of HDL-C was less marked but the patterns were similar. The risk ratios for high concentrations at 19-21 y were 3.8 for TC, 2.6 for LDL-C, and 4 for HDL-C for 9-y-olds with values of 5.17 mmol/L for TC, 3.36 mmol/L for LDL-C, and 0.90 mmol/L for HDL-C, relative to 9-y-olds with values of 4.65 mmol/L for TC, 2.84 mmol/L for LDL-C, and 1.29 mmol/L for HDL-C.
Adolescent↗
Genetic analysis of patterns of growth in infant recumbent length.
A genetic basis to growth and development has been demonstrated in many heritability studies of anthropometrics. Although such measures describe the extent of growth at particular times, they do not fully address the process of growth. We applied a three-parameter curve-fitting function to serial measures of recumbent length from 569 infants (birth to 2 years of age) in 188 families enrolled in the Fels Longitudinal Study. This yielded three growth pattern parameters that represented estimated recumbent length at birth (parameter 1), rate of growth (parameter 2), and intrinsic rate of change in growth (parameter 3). The growth pattern parameter estimates for each individual were examined in a series of genetic analyses using a maximum-likelihood method for pedigree data. Significant heritabilities were found for all three growth pattern parameters: parameter 1, h2 = 0.83 +/- 0.12; parameter 2, h2 = 0.67 +/- 0.18; and parameter 3, h2 = 0.78 +/- 0.17. In addition, genotype by sex interaction was indicated for growth pattern parameters 2 and 3, suggesting that the genes influencing rate of growth and intrinsic rate of change in growth are themselves influenced by the sex of the individual.
Anthropometry↗
Reliability of B-mode ultrasonic measurements of subcutaneous adipose tissue and intra-abdominal depth: comparisons with skinfold thicknesses.
Adipose tissue deposits, particularly intra-abdominal adipose tissue, are associated with health risks such as diabetes mellitus and cardiovascular disease. Anthropometric techniques currently in use can measure subcutaneous adipose tissue (SAT) with skinfold calipers, but are limited to certain sites and cannot measure intra-abdominal adipose tissue (IAAT). Radiography, computerized tomography (CT) and magnetic resonance imaging (MRI) have been used, but they are expensive and some involve exposure to radiation. This study, which investigated the utility of B-mode ultrasound for measuring adipose tissue, found that ultrasonic measurements of SAT were as reliable as skinfold caliper measurements. Intra-observer and inter-observer coefficients of reliability for five of six ultrasonic measurements of SAT ranged from 91-98%, in comparison with coefficients of reliability ranging from 93-98% for three skinfold measurements. Coefficients of reliability for ultrasonic measurements of SAT at the paraspinal site were below 90%. Ultrasonic measurements of intra-abdominal depth (IAD), an index of IAAT, yielded an inter-observer coefficient of reliability of 64%. Ultrasound is recommended for measurement of subcutaneous adipose tissue but not for measurement of IAD.
Abdomen↗
Effects of dexamethasone on pulmonary function following extubation.
Dexamethasone is often given to intubated neonates to facilitate successful extubation. To study the effects of dexamethasone on pulmonary function immediately following extubation, we conducted a randomized, blinded, placebo-controlled trial in 51 infants. All infants had been intubated for a minimum of 3 days but no more than 30 days. Mean weight at extubation was 2.41 kg in treated infants, 2.25 kg in control infants. When infants were deemed ready for extubation, dexamethasone 0.5 mg/kg/dose or an equal volume of normal saline was given in three doses 8 hours apart. The final dose was given 1 hour before extubation. Esophageal pressure, air flow integrated to tidal volume (Vt), respiratory rate, and heart rate were measured before extubation, immediately following extubation, and every 20 minutes for 80 minutes. Total pulmonary resistance (RTP), dynamic lung compliance (CL), and minute ventilation (VE) were calculated. Forty-two infants completed the study; 19 infants received dexamethasone and 23 received placebo. There was no difference between the two groups in gestational age, weight at study, or length of intubation. Vt, RTP, VE, and CL were not significantly different between the two groups over time; however, RTP increased over time in the placebo group. Heart rate was significantly lower in the dexamethasone group. We conclude that dexamethasone appears to have limited effect on pulmonary function immediately following extubation in the population studied. Further studies should evaluate the drug effect beginning at least 1 hour after extubation.
Dexamethasone↗
Measures of body composition. Their relationship to blood pressure and use in epidemiologic research.
The association between "overweight" and increased risk of high blood pressure has long been recognized. The quantification of overweight into various aspects of body composition and the relationships of these aspects to blood pressure remain important areas of current research. The manner in which adipose tissue is distributed over the body is proving to be another important risk factor. Methodologies for assessing body composition include a variety of approaches commonly used in epidemiologic studies, ranging from simple indices (e.g., body mass index) to estimation of total body fat mass from equations based on skinfolds and other anthropometry, to newer approaches incorporating bioelectric impedance. Refined laboratory methods for assessing body composition are important in the study of small groups and in the development of predictive equations. These refined methods include the traditional approaches of hydrostatic weighing and K40 determinations, as well as newer improvements on these techniques incorporating estimates of bone mineral content and total body water. Other new sophisticated methodologies include dual-energy x-ray absorptiometry and nuclear magnetic resonance imaging. The approach to assessing body composition may vary among age groups; methodologies applicable to children may not work for the elderly.
Blood Pressure↗
Reference data on gains in weight and length during the first two years of life.
Serial data from studies of infants at the University of Iowa and from the Fels Longitudinal Study were used to develop sex-specific percentiles for increments in weight and recumbent length for selected intervals during the first 24 months of life. Weight increments are presented for 1-month intervals from birth to 6 months, 2-month intervals from birth to 12 months, and 3-month intervals from birth to 24 months. Length increments are presented for 2-month intervals from birth to 6 months, and for 3-month intervals from birth to 24 months of age. Weights and lengths at the target ages were obtained for the Iowa data by simple interpolation, and for the Fels data by fitting families of three-parameter mathematical functions to the serial data from ages 1 to 24 months. The tabular presentations are based on the Iowa data from birth to 3 months of age, on the combined Iowa and Fels data from 3 to 6 months of age, and on the Fels data from 6 to 24 months of age. We believe that these reference data will be useful in screening for deviations from normal growth and may aid in early detection of failure to thrive or excessive weight gain during early life.
Age Factors↗
Patterns of change in weight/stature2 from 2 to 18 years: findings from long-term serial data for children in the Fels longitudinal growth study.
Serial weight/stature2 (W/S2) data recorded semi-annually from 2 to 18 years in the Fels longitudinal study were analyzed to establish an approach for the investigation of long-term serial changes in body fatness during childhood and adolescence in individuals. To describe patterns of change in body fatness during childhood and adolescence, a family of mathematical models was fitted to individual serial W/S2 data recorded from 250 boys and 246 girls. The selected models fitted the W/S2 data well as judged by the root mean square errors. Based on the fitted models, variables representing patterns of change in an individual were derived. These included estimated value of W/S2 at 2 years of age (W/S(2)2yr), minimum value of W/S2 (W/S2min), age at minimum value of W/S2 (Amin), maximum velocity of W/S (Vmax), age at maximum velocity of W/S2 (AVmax), maximum value of W/S2 (W/S2max), and age at maximum value of W/S2 (Amax). There were highly significant correlations between observed W/S2 at 18 years and all the derived variables except AVmax indicating, for example, that in both sexes about 25 percent of the variation in W/S2 at 18 years could be explained by when Amin occurs or by the value of W/S2min. The negative correlations (r = -0.5) between Amin and W/S2 at 18 years suggested that the earlier children reach their nadir in W/S2, the earlier they began to increase in adiposity and the fatter they were at 18 years. Likewise, the positive correlations (r approximately 0.3 and 0.5, respectively) between the W/S(2)2yr or W/S2min and W/S2 at 18 years indicated that increased childhood adiposity may lead to increased adult adiposity.
Adipose Tissue↗
Use of the robust sib-pair method to screen for single-locus, multiple-locus, and pleiotropic effects: application to traits related to hypertension.
Robust sib-pair linkage analysis can be used as a screening tool in the search for the potential involvement of single-loci, multiple-loci, and pleiotropic effects of single loci underlying phenotypic variation. Four large families were each ascertained through one adult white male with essential hypertension. The robust sib-pair method was used to screen these families for evidence of linkage between 39 quantitative traits related to hypertension and 25 genetic marker loci. All traits were analyzed on the untransformed, square-root and log-transformed scales. Among other findings, there is a suggestion of linkage between the 6-phosphogluconate dehydrogenase locus on chromosome 1p36 and mean fifth-phase diastolic blood pressure. There may also be linkage between the following markers and traits: the adenylate kinase-1 marker and/or the Lewis blood group marker and the traits height, weight, and biacromial breadth; the glyoxylase I marker and the traits upper-arm circumference and suprailiac skinfold thickness; the ABO blood group and adenylate kinase-1 markers on chromosome 9q34 and the third component of complement marker on chromosome 19p13 and dopamine-beta-hydroxylase; and the P1 blood group and the traits weight and 1-h postload serum glucose level.
Alleles↗
Capillary blood gases in the neonate. A reassessment and review of the literature.
Heel puncture capillary blood gas (CBG) measurements continue to be used in neonates for estimating arterial blood gas values. Review of the literature reveals general agreement that CBG PO2 values are of little use in predicting arterial PO2 and that CBG pH values are reliable predictors of arterial pH; opinion varies regarding CBG PCO2. We conducted a two-part study comparing postductal arterial and CBG values. First, 50 infants were studied, each only once. All infants had umbilical arterial catheters in place. Blood was obtained simultaneously from the umbilical artery catheter and the warmed heels. Results demonstrated poor predictability of arterial values from CBG pH and PCO2 as well as for PO2. Second, to determine if variation both within and among individuals was similar, repeated measurements were made in 27 additional infants comparable to the first group. We obtained 3 to 28 simultaneous postductal arterial and CBG samples from each infant. A random-effects nested analysis of variance indicated that for pH, variation was largely the result of between-subject or within-subject replicates effects, while for PO2 and PCO2, most variation was explained by differences between the two techniques (umbilical artery catheter vs CBG). The results indicate that CBG measurements do not accurately predict arterial values in neonates. Extreme caution should be used when management decisions are based on CBG values.
Blood Gas Analysis↗
Stepwise oligogenic segregation and linkage analysis illustrated with dopamine-beta-hydroxylase activity.
A stepwise oligogenic method is developed that can be used to adjust the phenotype of a quantitative trait for the effects of a previously identified single-locus component. This method assumes that a single-locus component can be adequately identified through the use of segregation and/or linkage analysis under a 1-locus model and that the variation due to that locus can be removed from the phenotype leaving a residual that can be parameterized in terms of an additional single-locus component. Segregation and/or linkage analysis can then be used in an attempt to identify an additional single-locus component in the residual phenotype. This stepwise process can be repeated until no further single-locus effects are identified. The method is illustrated using family data on the specific activity of dopamine-beta-hydroxylase (DBH), which a number of studies have suggested may be due either to the combined effects of single-locus and multifactorial components or to the combined effects of 2 loci.
Crossing Over, Genetic↗
Alternative genetic models for the inheritance of the phenylthiocarbamide taste deficiency.
Pedigree segregation analysis was used to examine several one- and two-locus models of the inheritance of phenylthiocarbamide (PTC) taste deficiency that extend the traditional one-locus recessive model by the addition of either another allele or another locus, and in some cases predict two types of nontasters. These models allow nontaster by nontaster matings to produce taster offspring, consistent with our data and several previous studies which use the Harris and Kalmus [Annals of Eugenics 15:24-32, 1949] dilution method. The models fit our data set of 1,152 individuals from 120 families significantly better than the one-locus recessive model. The best fit was obtained with a two-locus model in which one locus controls PTC tasting and the other locus controls a more general taste ability. This model is consistent with research on the physiology of PTC tasting and with results from genetic linkage studies. Further study is suggested to evaluate better the accuracy of the proposed model.
Alleles↗
Medical student, resident, and faculty use of a computerized literature searching system.
The experiences of medical students, residents, and faculty with a computerized literature searching system were evaluated. Third-year medical students, internal medicine and family practice residents, and full-time and voluntary faculty at one medical school had the opportunity to use a full-text and bibliographic medical literature retrieval system free of charge for an eleven-month period. Subjects conducted nearly nine thousand literature searches over a period of 942 system hours. Questionnaire data showed that participants could learn to use and would use an electronic information system, felt capable of using the system, utilized the system for a variety of purposes and in a number of different ways, and viewed the system as a valuable tool in searching the medical literature. The results are discussed in the context of the educational needs of the four user-groups and medical education planning by institutions.
Computer User Training↗
Associations between plasma lipoprotein cholesterols, adiposity and adipose tissue distribution during adolescence.
Associations between changes with age in 'fat pattern' and lipoprotein cholesterols during adolescence were analyzed using serial data for 214 boys and girls between 11 and 18 years of age who were participants in the Fels Longitudinal Study. The logarithms of the ratios of the subscapular to lateral calf and the subscapular to triceps skinfold thicknesses increased with age in each sex, but the increases were greater in the boys. Plasma levels of HDL cholesterol decreased with age in the boys, but not in the girls. Within annual age-groups, neither plasma LDL cholesterol nor HDL cholesterol were correlated with percent body fat or either of the 'fat pattern' indices in each sex. In 51 children with serial data 5 years apart, changes with age in HDL cholesterol had significant negative correlations with changes in the 'fat pattern' indices that were independent of changes in percent body fat in the boys, but not in the girls. In the girls, changes in the indices were due to greater increases in the thickness of the subscapular skinfold than in the triceps and lateral calf skinfolds as percent body fat increased and were not associated with changes in levels of plasma lipoproteins. In the boys, changes in the 'fat pattern' indices were due to decreases in the thicknesses of the lateral calf and triceps skinfolds and increases in thickness of the subscapular skinfold as percent body fat decreased. These results suggest that a redistribution of adipose tissue occurs during adolescence in boys and is associated with decreases in HDL cholesterol.
Adipose Tissue↗
Linkage of a gene regulating dopamine-beta-hydroxylase activity and the ABO blood group locus.
Previous studies have presented evidence suggesting that levels of dopamine-beta-hydroxylase (DBH) activity are controlled by a gene linked to the ABO blood group locus. In this study, linkage analyses in four large families of whites and one family of blacks were performed on the untransformed and on the square root--and natural log--transformed DBH activity. In the families of white individuals, the results of both the sib-pair and lod-score linkage analyses strongly indicate that a gene regulating DBH activity is linked to the ABO blood group locus on chromosome 9q (i.e., lod score 5.88 at a recombination fraction of .0). However, the transformation used has a large effect on the maximum lod score and estimated recombination fraction. This putative gene does not appear to be polymorphic in the family of blacks.
ABO Blood-Group System↗
Fatness and fat patterns: associations with plasma lipids and blood pressures in adults, 18 to 57 years of age.
As a part of the Fels Body Composition Study (an extension of the Fels Longitudinal Study in Yellow Springs, Ohio), the hypothesis was examined that a centripetal fat pattern, characterized by a greater proportion of trunkal than extremity adiposity, was associated independent of age and per cent body fat with levels of plasma lipids and lipoprotein cholesterols and blood pressures. A cross-sectional sample of 303 white men and women, 18 to 57 years of age, measured between September 1976 and August 1979, was selected without regard to diagnosis of hypertension, hyperlipidemia, or obesity. The degree of centripetal adipose tissue distribution was indexed by the logarithm of the ratio of the subscapular to lateral calf skinfold thicknesses. Per cent body fat was estimated by densitometry. In multiple regression equations controlling for age, age2, and per cent body fat, centripetal fat pattern had a small but significant positive association with systolic blood pressure in men (R2 = 0.02, p less than 0.05). In women, centripetal fat pattern had small but significant positive associations with plasma triglycerides (R2 = 0.05, p less than 0.005), and a significant negative association with plasma high density lipoprotein cholesterol (R2 = 0.08, p less than 0.0005) after effects due to age, age2, and per cent body fat had been removed. Centripetal fat patterns appear to be associated with an "atherogenic" lipid profile in women, but the association in men is confounded with effects due to age and total body adiposity.
Adipose Tissue↗