SEARCH · PubMed Health

Results for “shared variables”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources

PubMed1990

Bivariate survival models for analysis of genetic and environmental effects in twins.

Classic methods in genetics for the analysis of binary attributes, based on an assumption of a "threshold" on a normally distributed latent variable called "liability," estimate the strength of genetic and environmental effects from differences in correlations between relatives of differing genetic relatedness. Two problems that are not easily addressed by these methods are the need to take the age of onset into account (particularly in chronic diseases in which incidence rates vary considerably with age and the lengths of time at risk can vary between individuals) and the desirability of incorporating measured covariates (genetic or environmental). The standard methods of cohort analysis used in epidemiology allow for both of these features, but until recently have been restricted to independent individuals. Recent developments in survival analysis have extended the widely used "proportional hazards" model of Cox by the addition of latent variable, epsilon, reflecting the shared susceptibility of related subjects because of their shared genes or shared environment. We show how this approach can be combined with more traditional models of gene-environment interaction to allow the main effects of measured genetic markers and environmental variables to be estimated, as well as the residual variance of genetic and environment and their interactions. The approaches are applied to a cohort of female twin births in Sweden from 1886 to 1958, linked with the Swedish cancer registry from 1961 to 1982.

Adult↗

PubMed1988

Use of syllable-scale timing to discriminate words.

Assuming that only primitive, imperfect phonetic labeling of speech could be achieved by an automatic speech segmenter, words from several small vocabularies were identified using discriminant analysis, where the locations of prominent acoustic boundaries were combined in the optimum linear fashion. A set of two-syllable words that shared the same spelling in a weak alphabet (using categories like stop closure, fricative, vowel, etc.), but that differed in such features as which syllable was stressed, the tensity of the vowel, the identity of particular segments, etc., was selected. Discriminant analysis on the vector of six segmental boundaries achieved recognition accuracy 6.3 times better than chance. The words were produced by six talkers at two speaking tempos and measured by hand from sound spectrograms. Testing was performed on productions different from those used in training. When more confusable words (sharing the same stress pattern) were employed, performance was still five times better than chance. In a third experiment, the first two word sets were combined, and a subset of the variables (four of them) shared in common was employed for identification. This time recognition using temporal information was still able to do a reasonable job of discriminating the words. The results suggest that considerable information is available in segmental timing for identifying words even when the phonetic labeling of speech is weak.

Female↗

PubMed1985

Shared idiotopes among antibodies encoded by heavy-chain variable region (VH) gene members of the J558 VH family as basis for cross-reactive regulation of clones with different antigen specificity.

A wide idiotype cross-reactivity was observed among six groups of monoclonal antibodies specific for arsonate and nitrophenyl haptens, hemagglutinin of PR8 and X31 influenza viruses, dextran, A48-idiotype, and a set of six monoclonal antibodies with unknown antigenic specificity. All of these antibodies are encoded by heavy-chain variable region (VH) genes belonging to the J558 VH family. This idiotypic cross-reactivity was determined by studying the binding of these antibodies to a panel of six monoclonal anti-idiotype antibodies, each one raised against a member of the six groups of monoclonal antibodies. The administration at birth of two such monoclonal anti-idiotype antibodies induced a long-lasting suppression not only of the corresponding idiotype but also of VH-related idiotypes with different antigenic specificities. These results suggest that the idiotypes encoded by VH genes that belong to the same VH gene family are interactive one with another. The possible physiological consequences of this immunochemical cross-reactivity are discussed.

Animals↗

PubMed1991

The sharing of injecting equipment among drug users attending prescribing clinics and those using needle-exchanges.

Three groups of injecting drug-users were defined in terms of their experience of methadone treatment: treatment for periods longer than 6 months, treatment for shorter periods, and no treatment. Methadone treatment and the use of needle exchanges were related in subsequent analysis to the sharing of injecting equipment. Comparisons between groups were made on other variables believed to be associated with sharing. Significant differences were observed between treatment groups in the recency of sharing and in the use of needle-exchanges. Age and length of drug use were important factors in sharing, which was least prevalent among older respondents in long-term treatment. Regular use of needle-exchanges was associated with the passing on of used equipment to others. Subsequent analysis of regular users suggested respondents in long-term treatment were less likely to pass on their equipment than those in the other two groups.

Adolescent↗

PubMed1976

Complete amino acid sequence of the variable domains of two human IgM anti-gamma globulins (Lay/Pom) with shared idiotypic specificities.

On the basis of extensive shared idiotypic specificities, two human IgM anti-gamma-globulins (Lay/Pom) were selected for complete amino acid sequence analysis of their variable domains. Previous studies on the variable regions of the heavy chains of these proteins had shown but eight amino acid differences, only one of which was within a complementarity-determining hypervariable region. The complete amino acid sequence of the variable regions of the light chains of these two proteins is the subject of this report. Protein Lay is a typical VchiI protein with only five 'framework' differences when compared with protein Roy. Protein Pom is best classified as a VchiII, but in the 'framework' there are 16 differences between it and protein Ti. Although there are extensive differences in the first hypervariable region, the second and third light-chain hypervariable regions have an identical sequence. The finding of two identical light-chain and two identical heavy-chain hypervariable regions in these two proteins, which were selected on the basis of their combining specificities and their idiotypic cross-reactions, strongly implicates hypervariable regions in the constitution of the idiotypic determinants and the antibody combining site. Additionally, the finding of identical hypervariable regions in light chains of different V-region subgroups fulfills a prediction of the gene-interaction concept of antibody variability.

Amino Acid Sequence↗

PubMed1992

Ankyloblepharon filiforme adnatum.

We treated 4 infants with ankyloblepharon filiforme adnatum (AFA), an uncommon anomaly in which the apposing eyelid margins are connected by abnormal tissue strands. One infant had AFA alone, one had Hay-Wells syndrome, characterized by ectodermal dysplasia, and the other 2 had chromosome abnormalities, trisomy 18, and complex chromosome rearrangement, with visceral malformations. Despite heterogeneity and phenotypic variability, these developmental abnormalities shared (1) involvement of tissues growing in apposition and (2) temporal overlap of their occurrence. This suggests a common defect in the mechanism(s) that regulate tissue fusion at multiple sites during development.

Abnormalities, Multiple↗

PubMed1990

Enterococcal resistance to vancomycin and related cyclic glycopeptide antibiotics.

Enterococci belonging to various species resistant to vancomycin and related cyclic glycopeptide antibiotics have been isolated from hospitalized patients in France, the UK and the USA. All such strains examined display inducible synthesis of a membrane protein associated with resistance. The mechanism by which the membrane protein acts has not been definitively established, but it may block the access of the antibiotic to its peptidoglycan target. That the protein could be a bypass enzyme has not been ruled out. Transfer of glycopeptide resistance by conjugation to either Enterococcus faecium or Enterococcus faecalis and by transformation of Streptococcus sanguis Challis has been reported. The structural and regulatory genes encoding this resistance can be localized on plasmid and, apparently, chromosomal DNA. The plasmids encoding this resistance appear to differ from each other and have variable host ranges, but share at least some DNA sequence homology.

Aminoglycosides↗

PubMed1988

A method of quantify confounding in regression analyses applied to data on diet and CHD incidence.

We present a method to display the results of linear regression when the independent variables are highly correlated. In this method the sum of squares of regression (SSR) for pairs of variables are partitioned into orthogonal and shared components. A shared component is the reduction in the SSR of one of the variables when the other variable is added to the regression equation. This method shows how the SSR for one variable depends on the other variables present in the regression equation and explains apparent inconsistencies between forward and backward stepwise regression. To demonstrate the potential usefulness of this method we reanalyzed previously reported data on the relationship between coronary heart disease (CHD) and diet. The analysis suggested that carbohydrate and alcohol intake are negatively associated with CHD because they are associated with greater caloric intake. Protein and fat intake are also associated with greater caloric intake, but in addition they are associated with factors that increase the risk of CHD.

Alcohol Drinking↗

PubMed1976

Combined adrenorenal fusion and adrenohepatic adhesion: a case report with review of the literature and discussion of pathogenesis.

The second case of combined adrenorenal fusion and adrenohepatic adhesion on the right side is reported. It is hypothesized that the basic lesion underlying this innocuous anomaly rests in the periadrenal mesenchyme. In the case of fusion of adrenal with kidney or liver the mesenchymal defect causes 1) retardation of capsule formation with parenchymal mixing and 2) failure of local differentiation into fetal and later adult fat cells. In the case of adhesion of adrenal to kidney or liver there is no retardation of capsule formation with parenchymal mixing but only failure to differentiate locally into fat cells. Consequently, there is no physical separation of these organs by interposition of fat cells and there is variable party-wall sharing of the capsule.

Adrenal Glands↗

PubMed1990

Componential analysis as a way to investigate age-related changes in information processing.

The purpose of this paper is to alert researchers to the methods and utility of componential analysis as a means to examine age-related changes within information processing models of cognition. This analysis allows the researcher to determine which hypothesized information processing components are significant and the amount of variance shared with the dependent variable(s). Individual differences are investigated by modeling data at the individual subject level. Unstandardized regression weights are correlated with performance on a number of standardized ability tests to determine which components contribute to which abilities. The procedure combines complementary aspects of information processing analysis and psychometric analysis. Componential analysis is illustrated in this study with data from 60 individuals, aged 20 to 79, who solved verbal forced-choice analogies of the form A:B::C: (D1 or D2). Solution time and error rate data were modeled using a regression model developed by Sternberg (1977).

Adult↗

PubMed1977

On the structure of the T-cell receptor for antigen.

Antigen-binding receptors of T lymphocytes were analyzed in two different ways. First, the idiotypic properties of T helper cells are studied using anti-idiotypic antisera prepared against isolated antibodies specific for A-CHO. These anti-idiotypic antisera are defined by immunogenetic and immunochemical means with respect to their reactivity with heavy- or light-chain-associated idiotypic determinants. Second, antigen-binding receptors are isolated from enriched T-and B-lymphocyte preparations and compared with respect to their reactivity with antigen and with class- or allotype-specific anti-Ig antisera. The results provide an incomplete picture of the T-cell receptor which shares with antibodies the variable region of the heavy chain but probably no other variable or constant portion.

Animals↗

PubMedDate not supplied

Characteristics of drug abusers that discriminate needle-sharers.

To identify variables that discriminate needle-sharing among drug abusers, 224 male drug abusers were studied. They had been admitted to a 30-day inpatient drug treatment program over a 19-month period (September 1983 through March 1985). The variables examined were divided into three categories: demographic (age, race, education), personality (Minnesota Multiphasic Personality Inventory [MMPI] scores and MMPI deviant scores), and drug use patterns (drug of choice, use of single or multiple [mixed] drugs, severity of drug use, and place of use). Three variables were identified that discriminated needle-sharers from other drug abusers. Compared with other drug abusers, needle-sharers used more multiple drugs, were more likely to use a "shooting gallery," and had more problems related to drug use. No demographic or personality variables discriminated needle-sharers from nonsharers. The data suggested that needle-sharing is widespread in the drug culture. Needle-sharing was not confined to a particular racial group, educational level, or personality type. These findings can be used to structure education programs about acquired immunodeficiency syndrome (AIDS) for drug abusers. Drug treatment programs appear to provide an important opportunity to educate drug abusers about AIDS and related health issues associated with needle-sharing.

Adult↗

PubMed1992

Clonal evolution of a follicular lymphoma: evidence for antigen selection.

The potential role antigens play in growth stimulation or in clonal selection of follicular lymphomas is unknown. To study this issue, we sequenced the immunoglobulin heavy chain variable region genes expressed by a follicular lymphoma from multiple biopsy specimens and also cloned and sequenced the corresponding germ-line variable gene from this patient. Comparison to the germ-line gene revealed numerous nucleotide substitutions in all of the lymphoma variable gene sequences. Some of the substitutions may have occurred in the nonmalignant precursor B cell that gave rise to this lymphoma because they were shared among all of the variable genes, but many of the mutations accumulated as the malignant clone expanded. The mutations were distributed in such a way that strongly suggested the majority of tumor cells had been positively selected through their antigen receptor. This was especially evident for the mutations that developed late in the clonal evolution of this lymphoma. These findings indicate that antigen stimulation may be involved in the growth of follicular lymphoma tumors.

Antigens, Neoplasm↗

PubMed1991

The effect of a cost sharing provision in Japan.

This study evaluated the effect of a 10% cost sharing provision, introduced in October 1984, on demand for medical services. We analysed the data of 1701 health insurance societies, all of which joined the National Federation of Health Insurance Societies between 1983 and 1985. The case rate (per 1000 persons) and the number of serviced days (per case) were analysed as indicators of demand for inpatient, outpatient and dental medical services. The case rate was considered to be an indicator of the patient's behaviour, while the number of serviced days was influenced by the doctor's behaviour. Multiple linear regression analysis was used with each indicator to isolate the effect of the cost sharing provision, adjusted for other variables which influenced demand for medical services. The case rate was reduced significantly in all medical services. This means that a patient was discouraged from using a medical facility by the cost sharing provision. There was little difference among medical services. The number of serviced days was also reduced significantly in all medical services. There was a large difference among medical services. The effect on outpatient service was much greater than that on any other service.

Cost Sharing↗

PubMed1989

Staff perceptions of shared governance.

Future research must consider a number of potential influencing variables, focus on before and after comparisons and comparisons among types of shared governance models, and include replications and longitudinal studies. In addition, qualitative, descriptive data regarding the life of the organization will be beneficial in interpreting the more quantitative findings. The ideal of controlling all variables is simply not possible when one is studying a complex organization. With ingenuity, creativity, and a blend of methodologies, however, researchers may come considerably closer to understanding more about how and why shared governance can work effectively.

Adult↗

PubMed1988

Prognostic variability among chronic pain patients: implications for study design, interpretation, and reporting.

Chronic pain patients share many characteristics, but there is important prognostic variability among them. By selecting for certain characteristics, different recruitment methods and entry criteria for clinical or research programs may influence the likelihood of success regardless of treatment efficacy. This was demonstrated when subjects (n = 55) were recruited through lay publicity for a clinical trial of therapy for chronic back pain. In comparison to routine pain clinic patients (n=61), subjects in the clinical trial were better educated, were more often employed, had more favorable personality profiles, and were less likely to have had surgery or narcotic use (all p less than 0.004). Pain relief was significantly better for clinical trial subjects, apparently due to baseline prognostic differences rather than uniquely efficacious therapy. We conclude that chronic pain patients vary in prognostically important ways; that recruitment methods and criteria strongly influence these characteristics; and that greater attention to these details is needed when interpreting and reporting clinical research.

Adult↗

PubMed1992

Methods for inference on transmission in seroprevalence data for multiple infections.

When risk factors for an infectious disease are unknown, a method commonly employed is to investigate parallels with known infections (covariate infections). Data sets of value here are those for specified populations in which the seroprevalence of antibodies for multiple infections has been ascertained. The use of markers of covariate infections in multivariable analyses is problematic when the covariate infection is not itself an independent risk factor for the outcome of interest. In the performance of these analyses, the authors recommend the following strategy: 1) For estimates of the effects of measured risk factors on the outcome, adjustment for the covariate infection should not be done; this will avoid problems of overadjustment. 2) After control for the measured risk factors, an estimate of the "effect" of the covariate infection may be used as an indicator of the presence of unmeasured shared risk factors. 3) When shared, measured risk factors exist, the authors propose the use of methods developed for analysis of repeated measures of categorical variables to assist in inference about shared mechanisms of action of these risk factors. This analytic strategy takes advantage of the method of analogy for building understanding of transmission of new agents through their parallels with better known ones and is useful in the development of hypotheses.

Communicable Diseases↗

PubMed1988

Structural features of Ly-5 glycoproteins of the mouse and counterparts in other mammals.

The Ly-5 system of the mouse defines a set of transmembrane glycoprotein isoforms (T200, B220, etc) that hallmark various lineages and stages of hematopoietic differentiation. These isoforms are the products of a single Ly-5 gene comprising 34 exons, 32 of them (Exs-3-34) protein-coding and three (Exs-5-7) selectively represented in different isoforms (e.g., all three in isoform B220 but none in isoform T200). Probable structural features of Ly-5 glycoproteins, largely inferred from Ly-5 gene composition, are presented and compared with the rat L-CA and human LCA/T200 systems, which are phylogenetic counterparts of Ly-5 as an index of the extent and nature of structural conservation. The outer (N-terminal) region of the Ly-5 T200 isoform comprises three broadly similar domains (Exs-4, 8, 9) with salient features that jointly favor free interaction with the aqueous environment and are shared by the L-CA and human LCA/T200 systems despite an overall interspecies protein sequence similarity in this region of only about 50%. In the larger B220 isoform this region includes epitopes dictated by the selective exons Exs-5, 6, 7, these being more conserved than the shared exons Exs-4, 8, 9 and no doubt sustaining the differential functions of the respective isoforms. Comparison of the genomic sequences of Ex-5 in the Ly-5 and human systems suggests that a shift in splice donor site accounts for an extra 23 amino acids in the human Ex-5-coding domain, which is the only salient structural difference between the mouse Ly-5 and human systems. The inner extracellular region (Exs-10-16) includes subregions of high variability, but again there are shared salient interspecies similarities such as sites and numbers of Cys residues that imply a conserved, tightly-folded conformation, in contrast to the more open conformation predicted for the outer extracellular region. The transmembrane region (Ex-17) is highly conserved, as is the very large cytoplasmic region (Exs-17-34) which may interact with the plasma membrane but probably does not traverse it.

Amino Acid Sequence↗