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At least 1,279 records · Page 71Linked to original sources

Importance to Gas Exchange of Mass Flow of Air through Leaves.

A reanalysis of results from a recent paper on the effect of oscillation on gas exchange through leaves of cottonwood (Populus deltoides, Marsh) is presented. Mass flow of air through the leaf cannot account for the observed increase in gas exchange during oscillation in that experiment. Consideration of various published data shows that in the field, mass flow will not constitute more than a few per cent of the total exchange for most agricultural crops, but may be a significant part of the exchange for the leaves of tall trees, as they can be exposed to high winds.

Journal Article↗

High Performance Liquid Chromatography-Based Reevaluation of Disaccharides Produced upon Incubation of Sugarcane Vacuoles with UDP-Glucose.

A reanalysis of products formed after short-term incubation of sugarcane (Saccharum spp. hybrid cv H50-7209) vacuole preparations with uridine diphosphate [(14)C]glucose was performed. The results indicated that the ethanol-soluble substance previously identified as sucrose did not elute with sucrose when subjected to high performance liquid chromatography but had the same retention time as a disaccharide tentatively identified as laminaribiose.

Journal Article↗

Evaluating public commentary and scientific evidence submitted in the development of a risk assessment.

Risk assessments form the methodological basis for many public policies. A key component of the risk assessment process is the public commentary period. We conducted a case study of the California environmental tobacco smoke risk assessment to describe the contribution of the commentary to the risk assessment process. We used content analysis to examine the sources, quantity, and quality of public commentary, as well as the agency's response to the commentary. We examined the type and quality of publications cited in the commentary. Most of the comments were from critics of the risk assessment (36/44, 80%), especially tobacco industry affiliates (30/36, 83%). Critics were more likely to evoke the science evaluation criteria of study quality, reliability, and validity than were supporters. More than half the critics argued that appropriate procedures were not followed (13/23, 57%). Of the 29 commentaries on the respiratory, carcinogenic, and cardiovascular chapters, four resulted in changes to the risk assessment, such as the addition of new references or reanalysis of data. Journal articles were the most frequently cited type of reference, cited by critics (1,022/1,526 of references, 67%) and supporters (39/60, 65%). However, journal articles submitted by critics had lower impact factors than those cited by supporters (2.6 vs. 3.6, p=0.03). Participation in the public input process was not balanced among all interested parties, although this may reflect different opportunities for stakeholders to participate in stages of the process. Critics and supporters of the risk assessment used different criteria to evaluate the scientific evidence, suggesting that they were socially constructing the evidence to support their positions.

California↗

What is beyond the big five? Plenty!

In a recent analysis of personality data, Saucier and Goldberg (1998) sought to answer the question, What is beyond the Big Five? Those authors evaluated numerous clusters of English person-descriptive adjectives that have been suspected of referring to non-Big Five dimensions of personality. Their results led them to conclude that most, if not all, traits of personality can be adequately subsumed within the Big Five factor space. In contrast, our reanalysis of Saucier and Goldberg's own data, using a more realistic criterion for deciding on whether a variable does or does not fall within a particular factor space, contradicts their claim. We are led to the conclusion that there are plenty of dimensions of behavior beyond the Big Five.

Female↗

DNA synthesis in mouse epidermis: S phase cells that remain unlabeled after pulse labeling with DNA precursors progress slowly through S.

Epidermal basal cells from hairless mice were isolated after pulse labeling with tritiated DNA precursors and subjected to DNA flow cytometry combined with cell sorting. Cells were sorted from a window in the middle of the S phase, collected on glass slides, and subjected to autoradiography. Unlabeled cells in the middle of the S phase were found in normal mouse epidermis after optimal pulse labeling with tritiated thymidine [( 3H]dThd), in accordance with previous results. The proportion of unlabeled S phase cells was considerably increased among basal cells from mice treated with growth-inhibitory epidermal extracts. Reanalysis and re-sorting of cells previously sorted from mid S showed that unlabeled cells could not be accounted for by G1 contamination. Furthermore, labeling with precursors incorporated into DNA by "de novo" metabolic pathway [( 3H]Urd) did not reduce the proportion of unlabeled S phase cells, either when given alone or when given in combination with the precursor for DNA incorporated by the "salvage" pathway [( 3H]dThd). This strongly indicates that the unlabeled S phase cells do not synthesize DNA continuously, or are synthesizing DNA at a rate below the level of detection. A reduced proportion of unlabeled S phase cells was found in regenerating epidermis. This may be explained by a dilution effect caused by the 3-fold increase in the total number of cells within S phase at this condition. The observation that essentially all cells in mid S phase were labeled during 4 days of continuous labeling with [3H]dThd, indicates that cells in S phase that remain unlabeled after optimal pulse labeling are cycling, albeit slowly. Two-parameter sorting based on DNA and light scatter indicated that slowly cycling cells are larger than the average. These cells may represent a subpopulation of basal cells going through their last division cycle before differentiation.

Animals↗

Biallelic ABCA13 Loss-of-Function Variants in a Child With Neurodevelopmental Delay: A Case Report.

ABCA13 encodes ATP-binding cassette subfamily A member 13, one of the largest members of the ABC transporter family. Rare ABCA13 variants have been reported in neuropsychiatric and neurodevelopmental phenotypes, including schizophrenia, bipolar disorder, autism spectrum disorder, intellectual disability, and developmental delay; however, the mode of inheritance remains uncertain, and most published cases have focused on heterozygous variants in the context of a possible dominant or susceptibility model. We report a 5-year-old boy with neurodevelopmental delay, skeletal foot deformities, nonspecific dysmorphic features, convergent strabismus, and behavioral abnormalities. Initial genome sequencing analysis was nondiagnostic. Reanalysis after 6 months identified two rare predicted loss-of-function variants in ABCA13 in trans: c.2510del, p.(Leu837TyrfsTer21), a frameshift variant, and c.12064C>T, p.(Arg4022Ter), a nonsense variant previously reported in a patient with unexplained intellectual disability. The identification of compound heterozygous predicted loss-of-function variants supports the possibility that biallelic disruption of ABCA13 may contribute to neurodevelopmental disease, whereas previously reported heterozygous variants may represent incompletely penetrant risk alleles, susceptibility factors, or candidate findings rather than fully penetrant dominant causes. This case expands the emerging clinical and genetic spectrum associated with ABCA13 and supports further evaluation of a recessive model in patients with intellectual disability and neurodevelopmental delay.

ABCA13↗

Bayesian analysis and model selection for interval-censored survival data.

Interval-censored data occur in survival analysis when the survival time of each patient is only known to be within an interval and these censoring intervals differ from patient to patient. For such data, we present some Bayesian discretized semiparametric models, incorporating proportional and nonproportional hazards structures, along with associated statistical analyses and tools for model selection using sampling-based methods. The scope of these methodologies is illustrated through a reanalysis of a breast cancer data set (Finkelstein, 1986, Biometrics 42, 845-854) to test whether the effect of covariate on survival changes over time.

Algorithms↗

A Bayesian approach for the analysis of panel-count data with dependent termination.

We consider modeling and Bayesian analysis for panel-count data when the termination time for each subject may depend on its history of the recurrent events. We propose a fully specified semiparametric model for the joint distribution of the recurrent events and the termination time. For this model, we provide a natural motivation, derive several novel properties, and develop a Bayesian analysis based on a Markov chain Monte Carlo algorithm. Comparisons are made to other existing models and methods for panel-count data. We demonstrate the usefulness of our new models and methodologies through the reanalysis of a data set from a clinical trial.

Algorithms↗

Calibration of molecular clocks and the biogeographic history of Crypteroniaceae.

A recent molecular clock analysis concluded that Gondwanan vicariance and out-of-India dispersal best explained the distribution of Crypteroniaceae and its allies (Conti et al. 2002). A reanalysis of their data using a different molecular dating technique and calibration point is congruent with an alternative hypothesis, namely dispersal between India, Africa, and South America long after the initial break-up of Gondwana.

Biological Clocks↗

Subpopulations of slowly cycling cells in S and G2 phase in mouse epidermis.

Evidence has been presented supporting the existence of heterogeneity in cell-cycle progression in mouse epidermis, The present study was undertaken to characterize this heterogeneity in more detail. Hairless mice were continuously labelled with tritiated thymidine every 4 hr for 4 days. Basal cell suspensions were prepared from slices of mouse skin at intervals during the experiment and subjected to DNA flow cytometry. Cell-cycle analysis was combined with sorting of cells from windows in G1, S and G2 phase, and the proportion of labelled cells within each window was determined in autoradiographs. Reanalysis and resorting to control the purity of of sorted fractions were performed. Computer simulations of the data were made using a mathematical model assuming different S and G2 phase characteristics. A good fit to the data was only obtained when heterogeneity in mouse epidermal cell-cycle progression was assumed, indicating the existence of slowly traversing, distinct subpopulations of cells in G2 and S phase. These cells are assumed to contribute to about 40% of all cells in S phase and to about 70% of all in G2 phase. The estimated residence times in the resting states were 38 and 32 hr in S and G2 phase, respectively. Two-parameter sorting based on DNA and light scatter indicated that slowly cycling cells were larger than the average. There is no evidence of significant subpopulations of permanently non-proliferating keratinocytes in any of the cell-cycle phases.

Animals↗

How cryptic is the Scandinavian lynx?

A reanalysis of the existing genotypic data shows that they are compatible with the hypothesis that the present-day Scandinavian lynx represents a recent expansion from a single source. This contradicts earlier conclusions. The difference arises when it is assumed that the expansion and colonization have been stochastic processes and that the populations may not be at a drift-migration equilibrium.

Animal Migration↗

Genetics of recent habitat contraction and reduction in population size: does isolation by distance matter?

Fragmentation and loss of natural habitats are recognized as major threats to contemporary flora and fauna. Detecting past or current reductions in population size is therefore a major aim in conservation genetics. Statistical methods developed to this purpose have tended to ignore the effects of spatial population structure. However in many species, individual dispersal is restricted in space and fine-scale spatial structure such as isolation by distance (IBD) is commonly observed in continuous populations. Using a simulation-based approach, we investigated how comparative and single-point methods, traditionally used in a Wright-Fisher (WF) population context for detecting population size reduction, behave for IBD populations. We found that a complex 'quartet' of factors was acting that includes restricted dispersal, population size (i.e. habitat size), demographic history, and sampling scale. After habitat reduction, IBD populations were characterized by a stronger inertia in the loss of genetic diversity than WF populations. This inertia increases with the strength of IBD, and decreases when the sampling scale increases. Depending on the method used to detect a population size reduction, a local sampling can be more informative than a sample scaled to habitat size or vice versa. However, IBD structure led in numerous cases to incorrect inferences on population demographic history. The reanalysis of a real microsatellite data set of skink populations from fragmented and intact rainforest habitats confirmed most of our simulation results.

Alleles↗

Retinopathy of prematurity: risk factors in a prospective population-based study.

A prospective study of risk factors for retinopathy of prematurity (ROP) in all very low birthweight (less than 1500 g) infants born in New Zealand in 1986 is reported. Of 413 liveborn infants admitted to neonatal units, 338 (81.2%) survived to be discharged home. Of surviving infants, 313 (93%) were examined by indirect ophthalmoscopy, as were eight infants who died before discharge. Sixty-nine infants (21.5% of 321) had acute retinopathy. On multiple logistic regression analysis, three variables made statistically significant independent contributions to the risk of any acute retinopathy; gestational age (P less than 0.0001), principal hospital caring for the infant (P less than 0.01) and treatment with indomethacin (P less than 0.01). Only two variables, gestational age (P less than 0.0001) and hospital (P less than 0.01), made significant contributions to the risk of stage 2 or more ROP. For both categories of ROP, timing of the examination also had a statistically significant effect (P less than 0.001). After adjustment for other significant predictor variables, it was estimated that approximately 70% of infants of less than 26 weeks' gestation were at risk of ROP and nearly 50% of stage 2 or more ROP, in comparison with less than 2% of infants of 32 weeks' gestation or more; infants treated with indomethacin were over 1.5 times more likely to have ROP than infants not so treated. Failure to enforce uniform timing of examination was the most serious defect in the study; only 205 (64%) of the 321 infants were examined at the recommended time. However, reanalysis of the model with information limited to these 205 infants yielded similar risk factors. The incidence of ROP, both observed (P less than 0.05) and adjusted for other significant variables in the regression model (P less than 0.01) was lowest in the two largest level III hospitals. These hospitals also had the best survival rates after adjustment for birthweight, gestation and gender (P less than 0.01). We speculate that the larger level III units obtained better results because their size and experience enabled them to provide a better overall quality of care.

Acute Disease↗

Gc serum groups and schizophrenia.

In an epidemiological study of schizophrenia in a North Swedish isolate, Böök et al. (1978) reported an association between schizophrenia and the genetic marker Gc2. In an attempt to confirm this observation, we examined a series of schizophrenic patients from Västerbotton County in Northern Sweden. In our material there was no difference between schizophrenic patients and controls with respect to the frequencies of Gc groups or genes. A reanalysis of the material by Böök et al. (1978) showed that schizophrenics compared to controls had a significant increase in the frequency of the Gc 2-1 group, but not of the Gc2 gene. The Gc distribution in the material by Böök et al. (1978) was similar to that previously reported by us in a series of patients with cycloid psychosis.

Gene Frequency↗

Blood pressure and myotonic dystrophy.

The blood pressures of 79 consecutive patients with myotonic dystrophy have been shown to be significantly lower than those of a control series. Reanalysis of previously published data on a group of 17 myotonic dystrophy patients shows a similar result. The possibility that relative hypotension may confer a selective genetic advantage on asymptomatic gene carriers in the community is considered. It is suggested that, since patients with minimal clinical evidence of disease are also hypotensive, measurement of blood pressure may be useful as an adjunct to other methods of preclinical diagnosis of myotonic dystrophy.

Adolescent↗

XbaI polymorphism of the apolipoprotein B gene influences plasma lipid response to diet intervention.

Fresh blood samples were collected from 103 North Karelians who had in 1981-84 participated in dietary intervention studies and analysis of the XbaI restriction fragment length polymorphism (RFLP) of apolipoprotein B (apoB) was carried out. Reanalysis of the original plasma lipid and apolipoprotein data indicated that while baseline concentrations did not differ significantly between genotypes, the response to a low-fat, low-cholesterol diet was influenced by apoB XbaI genotype: reductions in total and low density lipoprotein (LDL) cholesterol, apoB and high density lipoprotein (HDL) cholesterol were greater in subjects homo- or heterozygous for the presence of the XbaI cutting site (X1X2 or X2X2 genotype, designated X2+) as compared to those lacking the cutting site (X1X1 genotype, designated X2-). The corresponding average reductions induced by dietary intervention in X2+ and X2- subjects were: for total cholesterol 1.30 and 0.99 mmol/l (p = 0.036), for LDL cholesterol 1.04 and 0.78 mmol/l (p = 0.049), for apoB 18.3 and 8.1 mg/100 ml (p = 0.012) and for HDL cholesterol 0.26 and 0.17 mmol/l (p = 0.008).

Adult↗

Histocompatibility antigens and humoral immunity to Epstein-Barr virus.

To explore possible genetic determinants of immunity to Epstein-Barr (EB) virus infection, prevalence rates and geometric mean titers (GMT) of antibody against EB viral capsid antigen (VCA) were measured in 422 adults of known HLA and ABO histocompatibility types. Deviation from the overall prevalence (87%) of anti-VCA titers > 10 was limited to subjects with HLA-A10 (95%) and those with a "blank" HLA-A locus (78%). The latter deviation was largely accounted for by the 13 subjects of HLA-A1/blank constitution (46%). Deviations from the overall mean anti-VCA titer (GMT 131.5) were found in seropositive subjects with blood group 0 (GMT 153.3) and tissue antigens HLA-A3 (GMT 150.8), HLA-B7 (GMT 152.1), HA-Bw15 (GMT 97.0), and HLA-B27 (GMT 86.4). Separate reanalysis of the data for male and female subjects verified the association of blood group 0 with elevated and HLA-B27 with reduced mean levels of anti-VCA antibody.

ABO Blood-Group System↗

HLA-DPB1 alleles correlate with risk for multiple sclerosis in Caucasoid and Cantonese patients lacking the high-risk DQB1*0602 allele.

Multiple sclerosis (MS) is a demyelinating disease associated with the HLA-DR2-related haplotype DRB1*1501, DQB1*0602 in Caucasoids and with DQB1*0602 in DR2-positive Cantonese. However, many MS patients do not have the high-risk HLA-D determinants and alternative genes may contribute to the pathogenesis of MS. One candidate gene is HLA-DPB1. Our reanalysis of five earlier reports of HLA-DPB1 antigen distributions in Caucasoid MS patients shows a consistent and highly significant increase (p = 1.5 x 10(-5)) in frequency of HLA-DPw3 in the combined data set. This study tests whether HLA-DPw3 (DPB1*0301) is also increased in frequency in Australian and Cantonese MS patients and whether any distortion in DPB1 allelic distributions can be attributed to linkage disequilibrium with DQB1*0602. PCR-RFLPs were used to determine distributions of 20 HLA-DPB1 alleles in 41 Australian MS patients and 67 controls of known DQB1*0602 status and in 11 Cantonese MS patients and 33 controls positive for HLA-DR2. HLA-DP distributions in Australian MS patients and controls positive for DQB1*0602 did not differ, but in those MS patients lacking DQB1*0602, the DPB1*0301 antigen (phenotype) frequency was significantly (p = 0.006) increased (50.0%) when compared with DQB1*0602-negative controls (9.1%). DPB1*0301 was associated (p = 0.003) with DQB1*0402 (DR8) in Caucasoid MS patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗