Age-specific reference intervals for plasma vitamins A, E and beta-carotene and for serum zinc, retinol-binding protein and prealbumin for Sydney children aged 9-62 months

Paediatric reference intervals for blood concentrations of certain nutrients are often based on either adult data or are derived from small samples of young children. Biochemical data were obtained from 467 randomly selected, healthy preschool children aged 9-62 months in Sydney, Australia. Data were obtained for plasma vitamins A, E and beta-carotene and for serum zinc, retinol-binding protein and prealbumin. Reference intervals based on the 2.5 and 97.5 centiles for age groups 9-23, 24-35, 36-47, 48-62 months and for the total group (9-62 months) were calculated. The 2.5-97.5 centiles for the whole group were: vitamin A, 0.7-1.8 mumol/l (20.05-51.56 micrograms/dl); vitamin E, 8-30 mumol/l (0.34-1.29 mg/dl); beta-carotene, 0.1-1.1 mumol/l (5.4-59.0 micrograms/dl); zinc, 9-19 mumol/l (58.8-124.2 micrograms/dl); retinol-binding protein, 14-36 mg/l; prealbumin, 104-264 mg/l. The reference intervals reported are consistent with the findings of a number of smaller studies and are likely to be an accurate reflection of the true intervals for healthy preschool children in western developed countries.     

Opposing national stroke mortality trends in Poland and for African Americans and whites in the United States, 1968 to 1994

BACKGROUND AND PURPOSE: The United States (US) has experienced declines in stroke mortality in contrast to the increases reported for Poland. As part of the Poland and US Agreement on Cardiovascular and Cardiopulmonary Research, stroke mortality trends in Polish and US subpopulations were compared in the context of cross-population differences in competing causes of death and determinants of stroke. METHODS: Age-adjusted annual stroke, cardiovascular disease (CVD), non-CVD, and all-cause mortality rates were determined for men and women aged 35 to 64 and 65 to 74 years from 1968 to 1994 for African Americans and US whites and in Poland. Mean annual percent changes of mortality rates were estimated during 1968 to 1980 and 1981 to 1994 with the use of piecewise log-linear regression. RESULTS: US stroke mortality rates declined 3.7% to 4.8% annually during 1968 to 1980 and 2.0% to 3.1% during 1981 to 1994, with similar declines in each ethnic, gender, and age group. Polish rates increased 3.3% to 5.5% annually for all age-gender groups in Poland during 1968 to 1980. Polish men aged 35 to 64 experienced increasing rates during 1981 to 1994 (1.6% annually), while Polish women and older men experienced slight declines or little change. Only Polish men aged 35 to 64 years exhibited increases in stroke, CVD, and non-CVD mortality rates during both time intervals. CONCLUSIONS: Poland and the US experienced opposing stroke mortality rate trends between 1968 and 1994. These national and ethnic trends occurring in just one generation suggest major effects of lifestyle, socioenvironmental, and/or medical care determinants.     

The influence of health-related quality of life and social characteristics on hospital use by patients with AIDS in the Boston Health Study

OBJECTIVES: The authors examine whether health-related quality of life (HRQL) and social factors were independent predictors of future hospital use for persons with acquired immunodeficiency syndrome (AIDS). METHODS: A panel of 305 patients with AIDS treated at three provider settings in the Boston, Massachusetts area were enrolled during 1990 and 1991. Data were collected at baseline study enrollment and again 4 months later. Patient interviews, hospital bills, and medical charts were used to measure hospital use (admissions and days during the 4 months after enrollment), sociodemographic characteristics (age, gender, race, education, insurance, homelessness, alcohol use, and AIDS risk factors), disease burden (patient severity and a three-level opportunistic diseases and complications score), HRQL (patient-reported symptoms, activities of daily living, neuropsychological status, and global health assessment), system of care, and use of prophylactic drugs. Logistic regression was used to estimate the odds of admission. Total days of hospital care by patients with at least one admission were analyzed using multiple linear regression. Clinical models of hospital use were developed first from the variables measuring disease burden and system of care. Models estimating the associations between hospital use and all other predictor variables measured at baseline then were estimated using stepwise techniques, controlling for variables in the core model. RESULTS: Patients were more likely than their reference groups to be hospitalized if they had serious opportunistic diseases (adjusted odds ratio [OR] = 2.7), had poorer neuropsychological status (OR = 1.9), were non-white (OR = 2.0), or were homeless (OR = 3.3) (all P < or = 0.05). Activities of daily living were associated moderately (OR = 1.3; P = 0.07). Only system of care and neuropsychological status predicted total hospital days. CONCLUSIONS: The results indicate that future hospital use by persons with AIDS may be influenced by social and other health-related factors in addition to the more clinically related characteristics that are recorded in a medical chart. It therefore may be appropriate to assess these factors when considering options for intervention or when comparing patterns of use among patient groups or settings.     

Appearance of 1-2 Mbp giant DNA fragments as an early common response leading to cell death induced by various substances that cause oxidative stress

OBJECTIVE: To present an application of logistic regression modelling to estimate ratios of proportions, such as prevalence ratio or relative risk, and the Delta Method to estimate confidence intervals. METHOD: The Delta Method was used because it is appropriate for the estimation of variance of non-linear functions of random variables. The method is based on Taylor's series expansion and provides a good approximation of variance estimates. A computer program, utilizing the matrix module of SAS, was developed to compute the variance estimates. A practical demonstration is presented with data from a cross-sectional study carried out on a sample of 611 women, to test the hypothesis that the lack of housework sharing is associated with high scores of psychological symptoms as measured by a validated questionnaire. RESULTS: Crude and adjusted prevalence ratio estimated by logistic regression were similar to those estimated by tabular analysis. Also, ranges of the confidence intervals of the prevalence ratio according to the Delta Method were nearly equal to those obtained by the Mantel-Haenszel approach. CONCLUSIONS: The results give support to the use of the Delta Method for the estimation of confidence intervals for ratios of proportions. The method should be seen as an alternative for situations in which the need to control a large number of potential confounders limits the use of stratified analysis.     

Guidelines for Two-Parameter Weibull Analysis for Flaw-Containing Materials

Two-parameter Weibull statistics used in the analysis of mechanical data from flaw-containing materials, such as ceramics and castings, are reviewed. Guidelines to estimate Weibull parameters with the linear regression technique are provided. Moreover goodness-of-fit tests for Weibull fits and calculating confidence intervals for the estimated Weibull modulus are discussed. Methods of estimating lower bounds as well as a new hypothesis test for comparing two estimated Weibull moduli are explained. The use of these guidelines is demonstrated by using data from the literature.     

LF精炼成分预报模型的开发

采用经验计算、统计回归以及基于自学习的参考炉次法,建立了LF精炼成分的预报模型,对精炼过程中及精炼终点的钢水成分进行预报。结果表明,采用经验计算结合统计回归的方法可以预报铌、钛、碳、锰等收得率稳定的合金元素含量,采用基于自学习的参考炉次法可以预报硅、铝等收得率不稳定的合金元素含量,该模型基本满足了现场生产的要求。     

A comparison of hemodynamic parameters derived from transthoracic electrical bioimpedance with those parameters obtained by thermodilution and ventricular angiography

OBJECTIVE: To determine the limits of agreement between the cardiac output and volumetric data estimated by impedance cardiography with the cardiac output determined by thermodilution and the left ventricular ejection fraction and end-diastolic volume estimated from left ventriculography. DESIGN: A prospective study. SETTING: The cardiac catheterization laboratory of a university-affiliated teaching hospital. PATIENTS: Twenty-four patients with coronary artery disease undergoing elective left- and right heart catheterization. INTERVENTIONS: Cardiac output was measured by the thermodilution method and the ejection fraction and left ventricular volumetric data were determined by ventriculography. These same measurements were obtained by simultaneously performed impedance cardiography using a commercially available bioimpedance device. MEASUREMENTS AND MAIN RESULTS: The patients' mean cardiac output was 4.6 +/- 1.7 L/min by bioimpedance and 5.0 +/- 1.1 L/min by thermodilution. The limits of agreement between the two methods was -4.1 to 3.5 L/min. The 95% confidence intervals for the lower and upper limits of agreement were -2.7 to -5.5 L/min and 2.1 to 4.9 L/min, respectively. The mean ejection fraction was 63 +/- 8% by bioimpedance and 53 +/- 15% by ventriculography. The limits of agreement between the ejection fraction estimated by bioimpedance and ventriculography was -35% to 37%. The 95% confidence intervals for the lower and upper limits of agreement were -22% to -48% and 24% to 50%, respectively. The mean left ventricular end-diastolic volume was 108 +/- 47 mL, as estimated by bioimpedance, and 121 +/- 35 mL, as estimated by ventriculography. The limits of agreement between the left ventricular end-diastolic volume as estimated by bioimpedance and ventriculography was -139 to 113 mL. The 95% confidence intervals for the lower and upper limits of agreement were -184 to -94 mL and 68 to 158 mL, respectively. CONCLUSIONS: The 95% confidence range defining the limits of agreement between cardiac output and volumetric data estimated by bioimpedance, with the cardiac output measurement by thermodilution and the volumetric data estimated from left ventriculography, were wide, making the degree of agreement clinically unacceptable. In the opinion of the authors, impedance cardiography should not replace invasive hemodynamic monitoring at this time.     

Semicarbazide-sensitive amine oxidase (SSAO) from human and bovine cerebrovascular tissues: biochemical and immunohistological characterization

Girls actively training in sport (n=23) and girls not active in sport (n=26) were compared in terms of ages at peak height velocity (PHV) and menarche, the interval between ages at PHV and menarche, and ages at attaining stages of pubic hair and breast and the estimated duration of the stages. Subjects were longitudinally followed from about 11-18 years of age. Stature and weight were measured and stages of pubic hair and breast development were rated at approximately quarterly intervals between the initial observation and 14 years of age, at semiannual intervals until 16 years, and at irregular intervals subsequently. Age at menarche was obtained prospectively. The active girls trained 12 hours per week in rowing, track and swimming for an average of 3.9+/-1.2 years during puberty and the growth spurt. Longitudinal stature records for individual girls were fitted with kernel regression to estimate age at PHV (years). The interval between age at PHV and age at menarche was calculated. Ages at appearance of pubic hair and breast stages 3, 4 and 5 were calculated by back-interpolation, while intervals between stages 3 and 4 were calculated after log 10 transformation. Peak height velocity and menarche occur, on average, slightly later in girls active in sport, but the differences are not significant. The interval between PHV and menarche, PHV (cm/year), ages at attaining pubic hair and breast stages 3, 4 and 5, and estimated intervals between adjacent stages also do not significantly differ between girls actively training in sport and those not active in sport. Thus, regular training in sport during puberty and the adolescent spurt does not apparently influence the timing and progression of somatic and sexual maturation in girls.     

Cyclic fatigue of a model feldspathic porcelain

OBJECTIVES: This study was conducted to evaluate the fatigue parameters of a model porcelain based on the Weinstein patent using cyclic fatigue and to compare the parametric values obtained from cyclic fatigue tests with those from dynamic fatigue tests previously reported by Fairhurst et al. (1993). METHODS: Cyclical biaxial flexure of 1 mm thick and 12 mm diameter disks was performed at 37 degrees C in distilled water at a frequency of 4 Hz with constant stressing rates between a minimum and maximum stress. Three groups of samples (50, 40, 40) were tested with a maximum stress of 51, 47, and 43 MPa, respectively. The crack growth exponent, n, and the scaling constant, sigma fo, were derived from the regression constants obtained from a linear regression of the logarithm of the median time to failure with the logarithm of the maximum stress. RESULTS: No significant differences were found between the cyclic fatigue parameters, n and sigma fo, derived from the median time to failure and those obtained from dynamic fatigue data. SIGNIFICANCE: Within the limits of error in this determination, the median cyclic fatigue life can be estimated by the use of fatigue parameters obtained from dynamic fatigue testing.     

Estimation of age-specific reference ranges via smoother AVAS

This paper proposes a new non-parametric procedure to estimate age-dependent reference ranges based on Tibshirani's AVAS (additivity and variance stabilization) procedure for non-parametric estimation of transformations for regression. Several examples are given to illustrate the flexibility and applicability of the proposed method; these include alkaline phosphatase in girls, and foot length and head circumference during gestation.     

Age-dependence of the lateral diffusion coefficient of concanavalin-A receptors in the plasma membrane of ex vivo prepared brain cortical nerve cells of BN/BiRijHsd rats

A new method has been developed for ex vivo preparation of brain cortical cells of BN/BiRijHsd rats to make them suitable for the measurement of the lateral diffusion coefficient of the membrane components by means of fluorescence recovery after photobleaching (FRAP). The method involves chopping the brain cortex into pieces of less than 1 mm. These parts are stained with a fluorescent label (e.g., concanavalin-A-fluorescein, Con-A-FL conjugate) and then gently pressed onto a microscope slide using the coverslip. In the resulting specimen, the largest cells of the cortex can be recognized in phase-contrast image, sufficiently stained by the label and ready for the FRAP measurement. The lateral diffusion coefficient of Con-A-receptor proteins (Dp) was measured in such brain cell preparations of 15 female rats in four age groups (5.6-31.8 months) and 11 males in three age groups (13.8-31.8 months). Highly significant negative, linear age correlation of Dp (R=-0.9958 in females, and -0.9956 in males) were found, the regression equations being D(p female) =(8.8311-0.1425 X)(-10) and D(p male)=(9.3240-0.1630 X)(-10) cm2/s, respectively, where X is age in months. The data confirm that the lateral mobility of plasma membrane proteins represents an important biomarker of cellular aging in the brain cortical cells of BN/BiRijHsd rats.     

Item equivalence across scales: The WPPSI—R and WISC-III.

The publication of 2 Wechsler scales with multiple overlapping items, the Wechsler Preschool and Primary Scale of Intelligence—Revised (WPPSI—R) and Wechsler Intelligence Scale for Children-III (WISC-III), provided an opportunity to cross-validate items. Test–age equivalents corresponding to cumulative item raw scores were extracted from the manuals or estimated with ratio scores (and checked against regression-based values). WPPSI—R test–age equivalents correlated highly with WISC-III test–age equivalents (r?=?.88 for the 23 overlapping items), and there were few noteworthy discrepancies. These data demonstrate the validity of the WPPSI—R and WISC-III beyond the level of subtests and IQs and to the level of item makeup. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The response of heat shock proteins 25 and 72 to ischaemia in different kidney zones

Class III malocclusion with retrusive maxilla can be orthopedically corrected in the deciduous and mixed dentition, with reverse-pull headgear in combination with rapid palatal expansion. The literature recommends this procedure be carried out before the patient is 8 years old to obtain the optimal orthopedic result. This statement, however, has not been supported by scientific data. The current study examined the treatment effects of patients younger than 8 years old (5 to 8 years) and patients older than 8 years old (9 to 12 years). Thirty patients treated with maxillary protraction and expansion in the Department of Children's Dentistry and Orthodontics, University of Hong Kong were included in this study. Cephalometric radiographs were taken 6 months before the initiation of treatment (T(0)), at the initiation of treatment (T1), and after 6 months of treatment (T2). In this way, (T(2)-T1) represented cephalometric changes during the treatment period and (T1-T0) represented 6 months of growth changes without treatment. Experimental subjects served as their own control in this study. A grid system consisting of maxillary occlusal plane (OL) and a line perpendicular to OL through sella (OLp) was used for linear measurements. A total of 15 linear and 3 angular cephalometric measurements were made. A multivariate analysis of variance (MANOVA), which used age and treatment time as its factors, was used to determine effect of age and/or treatment on each cephalometric parameter. Results indicated strikingly similar therapeutic response between the younger and older age groups. These data suggest that similar skeletal response can be obtained when maxillary protraction was started either before age 8 (5 to 8 years) or after age 8 years (8 to 12 years).     

Piecewise exponential survival trees with time-dependent covariates

Survival trees methods are nonparametric alternatives to the semiparametric Cox regression in survival analysis. In this paper, a tree-based method for censored survival data with time-dependent covariates is proposed. The proposed method assumes a very general model for the hazard function and is fully nonparametric. The recursive partitioning algorithm uses the likelihood estimation procedure to grow trees under a piecewise exponential structure that handles time-dependent covariates in a parallel way to time-independent covariates. In general, the estimated hazard at a node gives the risk for a group of individuals during a specific time period. Both cross-validation and bootstrap resampling techniques are implemented in the tree selection procedure. The performance of the proposed survival trees method is shown to be good through simulation and application to real data.     

Changes in urinary excretion of type-I collagen cross-linked C-telopeptide and N-telopeptide in perimenopausal women

PURPOSE: The overall goal was to develop a simple test of random dot stereoacuity that can be used during the first 24 months of life to measure sensory outcomes following treatment of ophthalmopediatric disorders, both in the context of clinical trials and in the context of clinical management. METHODS: A series of random dot stereoacuity test cards were constructed using vectographic vertical bar stimuli with crossed disparities ranging from 1735 to 45 sec. A two-alternative, forced-choice, preferential-looking test protocol was used to measure stereoacuity in 95 healthy term infants (173 tests) over the 1.5-to-24-month age range. Success rate, validity, and tolerance limits for normal performance as a function of age were evaluated. RESULTS: The success rate was high (158 of 173 tests; 91.3%). The maturation of random dot stereoacuity was similar to that measured in earlier lab-based preferential-looking and visual evoked potential protocols; few infants younger than 2 months of age demonstrated stereopsis although by 12 months, mean stereoacuity was 2.1 log sec (120 sec). A further improvement to 1.7 log sec (56 sec) was seen during months 18 to 24, consistent with data obtained in an earlier operant random dot protocol. Tolerance limits for normal ranged from approximately 1000 sec at 6 months to 100 sec after 12 months. CONCLUSIONS: The infant random dot stereoacuity cards provide a simple, quick, and portable preferential-looking test of random dot stereoacuity for infants that has a high success rate and excellent concordance with stereoacuity outcomes from laboratory-based protocols.     

Molecular analysis of the Drosophila catalase gene

OBJECTIVE: To determine whether genetic and non-genetic components of interindividual variation in systolic and diastolic blood pressure are constant throughout the day or are time or activity dependent. METHODS: We obtained 24 h ambulatory blood pressure recordings in 263 members of 68 unrelated nuclear families (i.e. parents and their offspring) representative of the Caucasian population of Rochester, MN, USA. Using the time each patient got into bed as a reference point, we identified 198 records in which this reference point was preceded by eight consecutive active hours (out of bed) and followed by four consecutive inactive hours (in bed) in which four or more blood pressure readings taken each hour were judged to be technically satisfactory. For each hourly mean for systolic and diastolic blood pressure, we estimated total interindividual variance, variance associated with concomitant variables (generation; sex within generation strata; and age, height, weight, body mass index, and abdomen-to-hip ratio within generation and sex strata), and variance associated with additive genetic effects (i.e. the chief cause of resemblance between relatives). To assess trends in each component of interindividual blood pressure variance over the 12 h period, we estimated the slope of the linear regression line fit to the hourly estimates. RESULTS: For systolic blood pressure, total interindividual variance did not change significantly (slope of regression line = -0.23, P = 0.717). In contrast, total interindividual variance for diastolic blood pressure was greater during active hours than inactive hours (slope of regression line = -5.53, P < 0.001). For both systolic and diastolic blood pressure, variance associated with the concomitant variables was greater during active hours than during inactive hours (for systolic blood pressure slope of regression line = -2.98, P = 0.001; for diastolic blood pressure slope of regression line = -6.14, P < 0.001). Likewise, for both systolic and diastolic blood pressure, variance associated with additive genetic effects was also greater during active hours than during inactive hours (for systolic blood pressure slope of regression line = -1.65, P = 0.090; for diastolic blood pressure slope of regression line = -1.47, P = 0.018). CONCLUSIONS: This study demonstrates that components of interindividual variation in blood pressure are not constant, but are time or activity dependent.     

Tracking of markers and onset of disease among HIV-1 seroconverters

Repeated measurements on persons infected with HIV-1 indicate that infection has a dynamic impact on several markers of immune suppression and activation. The objectives of this report are: (a) to provide a statistical model for the correlation structure of serial measurements of immunological markers, and (b) to identify features of marker profiles associated with the timing of AIDS diagnoses. We analyse data obtained from 328 seroconverters participating in the Multicenter AIDS Cohort Study on whom the date of HIV-1 seroconversion is known within +/- 4.5 months. Immunological markers considered here are CD4 cell counts, serum beta 2-microglobulin and serum neopterin. The statistical model for HIV-related changes in markers consists of (1) a piecewise linear regression model for the trajectories of markers over time and (2) a two-parameter autocorrelation function that generalizes Markovian and simple random effects autocorrelation structures. Application of this model for marker measurements revealed a high degree of tracking, as the estimated autocorrelation function exhibited sub-exponential decay over time. Though current marker levels are most informative on future values, there is substantial information (memory) in previous measurements. A feature suggested by the analysis of groups formed according to the length of the AIDS-free period, is the sequential divergence of the CD4 trajectories where steeper declines occurred with a two-year lag prior to AIDS onset. For AIDS cases diagnosed 3-5 and 5-7 years after seroconversion, the rates of decline compared with those free of AIDS for at least 4 years were steeper by 95 and 46 per cent respectively at two years prior to AIDS.     

Statistical Considerations for Predicting Residual Value of Heavy Equipment

Residual value needs to be considered in owning cost calculations for used heavy construction equipment. Its dependency on factors such as manufacturer and model, equipment age, and condition rating can best be examined by analyzing real market data from equipment auctions. Macroeconomic indicators can also be included to examine any potential influence of the overall economy on auction prices. This paper discusses statistical considerations for performing such a residual value analysis. Considerations include the study type, data properties, identifying outlier observations, regression assumptions, and formulating and selecting an appropriate regression model using the adjusted coefficient of determination. A second-order polynomial of equipment age with additive factors appears promising as the final regression model. Adjusted confidence and prediction intervals are created to correctly display residual value. Cross-validation using randomly split halves of the dataset is performed. Actual data for medium track dozers are used to illustrate the validity of the methodology.     

Overweight and leanness in adulthood: prospective study of male participants in the Normative Aging Study

OBJECTIVE: Our objective was to examine the stability of body habitus over 15 years in Boston area adult males enrolled in the Normative Aging Study (NAS) and to examine stability as a function of initial leanness or obesity, age and reported body habitus at age 18. DESIGN: Prospective observational study of anthropometric/clinical measures initiated in 1961-1970, follow-up examinations at regular three and five year intervals. Subjects with complete data at entry, 5, 10 and 15 years. SUBJECTS: The 2280 Boston area subjects were aged 21-80 years (mean = 42 y) at entry. A subset (n = 350) with complete data for weight (WT) and height (HT) at four points over 15 years provided estimates of body habitus continuity. The prevalence of obesity and age of those studied were comparable to the complete sample of enrolled men (n = 1403) with any missing follow-up measures. MEASUREMENTS: Obesity was defined as body mass index (BMI) (weight in kg/height in m2) > or = 27.8 and leanness as BMI < 24.0. Three age categories at baseline (young = 25-39 y; middle = 40-49 y and old = 50-74 y) were used to examine secular and longitudinal changes. Obesity prevalence rates during late adolescence, based on self-reported weights at age 18, were compared with measured prevalence rates at entry and follow-up. Individual changes in BMI over time for each subject were estimated by linear regression and were combined to measure change in age and BMI groups. RESULTS: Weights and BMI at entry were highly correlated with 18 year values and 15 year follow-up values. New cases of obesity, defined on the basis of BMI, increased over time while the numbers of subjects classified as lean and intermediate decreased. Among oldest subjects both the lean and obese had slight but significant decreases in mean BMI. Among the lean, only the young showed consistent increments. DISCUSSION: Our results suggest consistency in body habitus among young and middle-aged obese subjects. There was little evidence of long-term reduction. In agreement with previous observations, the current findings of long-term duration in obesity suggest that preventive efforts should be focused on early years.