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Results for “Model explainability”

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At least 1,171 records · Page 65Linked to original sources

PubMed1998

Do leptin levels predict weight gain?--A 5-year follow-up study in Mauritius. Mauritius Non-communicable Disease Study Group.

OBJECTIVE: To investigate whether relative baseline leptin levels predict long-term changes in adiposity and/or its distribution. RESEARCH METHODS AND PROCEDURES: In a longitudinal study of 2888 nondiabetic Mauritians aged 25 years to 74 years who participated in population-based surveys in 1987 and 1992, changes in body mass index (BMI), waist/hip ratio (WHR), and waist circumference were compared between "hyperleptinemic," "normoleptinemic," and "hypoleptinemic" groups. "Relative leptin levels" were calculated as standardized residuals from the regression of log10 leptin on baseline BMI to provide a leptin measure independent of BMI. Analyses were performed within each sex. A linear regression model was used to assess the effect of standardized residuals on changes in BMI, WHR, and waist circumference, independent of baseline BMI, age, fasting insulin, and ethnicity. RESULTS: After adjusting for age and baseline BMI by analysis of covariance, there was no difference in changes in BMI, WHR, or waist circumference between men with low, normal, or high relative leptin levels. Among women, there was a significant difference in deltaWHR across leptin groups, such that the largest increase occurred in the "normal" leptin group. For both men and women, the linear regression models explained approximately 10% of variation in dependent variables, and the only significant independent variables were age, BMI, and being of Chinese origin, compared with Indian origin. DISCUSSION: These findings do not support a role for leptin concentration in predicting weight gain or changes in fat distribution in adults over a 5-year period.

Blood Glucose↗

PubMed2006

Evaluation of a cure process during alarm treatment for nocturnal enuresis.

Using a treatment package featuring the urine alarm, this study evaluated a treatment process for nocturnal enuresis. Children who received the training were classified into treatment successes (N = 38) and nonsuccesses (N = 19) according to a criterion (3-week continence). Their daily results were analyzed with four categories: dry with sleep (DS), dry with spontaneous awakening (DA), wet with spontaneous or alarm-forced awakening (WA), and wet with sleep (WS). In a trend analysis, an increase of DA over the treatment process was prominent for successes compared to nonsuccesses. Entering WA to a discriminant analysis, 86% of children were correctly classified into the two groups. The findings that awakening categories well distinguished successes from nonsuccesses provide support for an active avoidance model explaining the efficacy of urine-alarm treatment for nocturnal enuresis.

Child↗

PubMed1998

Antibody-induced engagement of beta2 integrins in human neutrophils causes a rapid redistribution of cytoskeletal proteins, Src-family tyrosine kinases, and p72syk that precedes de novo actin polymerization.

Beta2 integrins mediate rearrangement of the cytoskeleton and activation of selective cell functions in neutrophils. To elucidate early events following beta2 integrin ligation, we analyzed redistribution of cytoskeletal and signaling proteins as a consequence of antibody-induced integrin clustering. Incubation of neutrophils on surface-bound anti-beta2 subunit antibodies induced a very rapid (within 1 min) redistribution of the cytoskeletal proteins talin, alpha-actinin, and paxillin, and the tyrosine kinases p58(c-fgr), p53/56(lyn), and p72(syk) to a cell fraction insoluble in Triton X-100. Cytoskeletal and signaling proteins redistribution preceded de novo actin polymerization because cytochalasin B did not inhibit this redistribution. Antibody engagement of all the three distinct beta2 integrins (CD11a, CD11b, CD11c) expressed by neutrophils induced redistribution of cytoskeletal proteins and tyrosine kinases. Several tyrosine phosphorylated proteins were also rapidly redistributed as a consequence of beta2 integrin engagement and this was not affected by blocking de novo actin polymerization with cytochalasin B. In addition, genistein, an inhibitor of tyrosine kinase activities which strongly reduced protein tyrosine phosphorylation, had no effect on redistribution of cytoskeletal proteins, Src-family kinases, and p72(syk). These findings suggest that integrin-dependent cytoskeleton rearrangement in neutrophils occurs in at least two distinct steps and nucleation of some cytoskeletal proteins together with tyrosine kinases precedes rearrangement of the actin-based cytoskeleton and tyrosine kinases activation. On the basis of these and previous findings we propose a model explaining mechanisms of integrin signaling in neutrophils.

Actins↗

PubMed2006

Crystal structure and physical properties of two polymorphs of ropivacaine HCl.

The crystal structure of two polymorphs of ropivacaine HCl have been determined, as well as their relative stability up to 100 degrees C. A geometric restriction for a solid-state transition between the two polymorphs has been identified. The packing density along the H-bonded chains form the basis for a model explaining the kinetic crystallization of the metastable form. The difference in stability and physicochemical properties between the two polymorphs can be attributed to the difference in crystal structure.

2-Propanol↗

PubMed1997

Lack of relationship between preoperative measures of the severity of cirrhosis and short-term survival after liver transplantation.

The purpose of this study was to evaluate the prognostic value of clinical measures of the severity of disease in cirrhotic patients who were candidates for liver transplantation at our institution. The records of the 132 cirrhotic patients who were candidates for a first transplantation between January 1, 1987, and December 31, 1994, were reviewed. One hundred nine patients (82.6%) received grafts, and 23 (17.4%) died while on the waiting list. The variables examined included level of medical urgency at the time of enlistment, date of transplantation, serum creatinine level, variables that constitute the Child-Pugh score and Shaw's risk score (serum bilirubin and albumin, prothrombin time, ascites, encephalopathy, nutritional status, age, and operative blood loss), and 6-month survival status after transplantation. The proportion of patients who died awaiting a graft increased as a function of the Child-Pugh score at enlistment (score 5-6, 0%, n = 6; score 7-9, 7%, n = 54; score 10-11, 18%, n = 33; score 12-15, 33%, n = 39; P = .01). Six-month survival rates after transplantation were similar irrespective of the Child-Pugh score or Shaw's risk score. Stepwise multiple logistic regression models identified the degree of ascites, serum bilirubin, and operative blood loss as significant variables for the prediction of overall mortality 6 months posttransplantation (model chi 2 = 12.8; P = .025; r = 0.32), but the model explained only 10% of the outcomes observed. We concluded that the Child-Pugh score is a valid prognostic index for survival up to the time of transplantation for cirrhotic patients on the waiting list; however, clinical measures of the severity of cirrhosis are poor predictors of 6-month survival after transplantation.

Adolescent↗

PubMed2004

The role of caregiver gender and caregiver burden in nursing home placements for elderly Taiwanese survivors of stroke.

The role of caregiver gender in caregiver burden and the association between the level of caregiver burden and institutionalization of elderly stroke survivors in Taiwan were explored using a correlational, descriptive design. The convenience sample was composed of 78 male and 69 female primary caregivers of stroke survivors. Simple multiple regression and t tests were used to test the research questions. Women perceived caregiving as more burdensome than men did. Caregiver burden was most strongly associated with the characteristics of the care recipients and with institutionalization. The proposed model explained 45% and 28% of the variance in caregiver burden for male and female caregivers, respectively. It is recommended that the professional nursing role in Taiwan be expanded to include postdischarge care, respite, and home-care services to allow families to keep their elderly at home as long as possible and to provide culturally sensitive care to families that might be traumatized by having to violate ethnic Chinese cultural norms by institutionalizing family members.

Aged↗

PubMed1991

Clinical predictors of intravenous site symptoms.

The purpose of this prospective multi-site study was to determine the frequency of intravenous (IV) site symptoms and to develop a preliminary model of the factors implicated in the number of these symptoms. In a sample of 514 patients from four institutions, IV site symptoms including pain, redness, swelling, induration, and/or a venous cord were present in 205 (39.9%) of the patients. The IV catheters were in place an average of 48.7 hr. There were no significant differences in symptoms by hospital site. Using multiple regression techniques, a seven-factor model explained 18% of the variance in number of IV site symptoms. Further research is required to explore other potential causes for the numbers of IV site symptoms.

Adolescent↗

PubMed1993

Predictors of partner relationships during pregnancy and infancy.

The partner relationship of 153 women hospitalized for a high-risk pregnancy, 75 of their partners, 218 women who experienced a low-risk pregnancy and 147 of their partners was studied to determine risk-status or gender differences at pregnancy, the postpartal hospitalization, 1, 4, and 8 months following birth. A theoretical causal model predicting partner relationships was tested, followed by model respecification to derive the best explanatory model for each group. No differences were observed between low- and high-risk mothers' partner relationship; however, high-risk fathers scored lower than low-risk fathers. Partner relationships for all groups were significantly higher during pregnancy and at birth than at 4 and 8 months after birth. Respecified models explained from 26% to 63% of the variance in partner relationship during pregnancy, and from 31% to 52% at 8 months after birth.

Adult↗

PubMed2005

Importance of cell wall mannoproteins for septum formation in Saccharomyces cerevisiae.

The mannosyltransferase mutants mnn9 and mnn10 were isolated in a genetic screen for septation defects in Saccharomyces cerevisiae. Ultrastructural examination of mutant cell walls revealed markedly thin septal structures and occasional failure to construct trilaminar septa, which then led to the formation of bulky default septa at the bud neck. In the absence of a functional septation apparatus, mnn10 mutants are unable to complete cytokinesis and die as cell chains with incompletely separated cytoplasms, indicating that mannosylation defects impair the ability to form remedial septa. We could not detect N-linked glycosylation of the beta(1,3)glucan synthase Fks1p and mnn10 defects do not change the molecular weight or abundance of the protein. We discuss a model explaining the pleiotropic effects of impaired N-linked protein glycosylation on septation in S. cerevisiae.

Cell Aggregation↗

PubMed2000

A test of the validity of delinquency syndrome construct in a homogeneous sample.

This was a study of 387 adolescents who regularly attended churches affiliated with a primary Protestant denomination in a Midwestern state. The purpose was twofold: (1) to determine if the delinquency syndrome argument has validity in a sample of religious youths, by testing whether the same basic theoretical models explained crime and drug use; and (2) to examine the relative utility of sociodemographic, social control and social learning factors in explaining these two forms of delinquency. The study finds that all theoretical factors investigated are correlated significantly with both crime and use of drugs; however, some of these factors are differentially related to those two forms of delinquency. Also, social control elements did account for more additional variance in crime than did social learning or sociodemographic factors. Implications for future research are discussed in the context of limitations of the present study.

Adolescent↗

PubMed2001

A Model for Hydration Interactions between Apoferritin Molecules in Solution.

We have studied how non-DLVO forces between molecules of the globular protein apoferritin in solution affect its osmotic second virial coefficient. A model explaining the effects of the solution ionic strength and pH on the interprotein interaction is developed, to give a physical interpretation of recently published experimental findings showing that the second virial coefficient of the protein apoferritin, supported by acetate buffer, goes through a minimum as a function of ionic strength. At low ionic strengths, the apoferritin second virial coefficient initially decreases with increasing sodium ion concentration, as DLVO theory predicts. However, non-DLVO hydration forces due to overlapping of the Stern layers of the protein molecules increase the second virial coefficient with further increase of sodium ion concentration, again as found experimentally at higher ionic strengths. The non-DLVO effect arises from ionic exchange between hydrogen and sodium ions at the protein surface. An adsorption shell of hydrated sodium ions forms around the protein molecules with increasing buffer concentration. Copyright 2001 Academic Press.

Journal Article↗

PubMed2002

Effect of proton concentration on membrane potential across a weak amphoteric polymer membrane.

An amphoteric membrane consists of both positively and negatively fixed charge groups chemically bound to the polymer chains. If the external solution is changed from alkali to acid, it is possible to obtain an experimental result in which the membrane potential changes from positive to negative through the isoelectric point. It was characterized by examining the relationship between membrane potential and proton concentration (pH) obtained from both experimental and theoretical considerations. The Nernst-Planck flux equation and the Donnan equilibrium theory were also solved for a four-component system combined with the dissociation constant, in order to discuss the pH dependence of membrane potential in a weak amphoteric membrane by comparing the experimental results with the calculated results. It was proven that the calculated results substantially deviated from the theoretical results despite a similar tendency. Such a deviation was caused by the fact that the original theory disregarded the activity coefficient and the ionic mobility, which were dependent on the fixed charge concentration in a membrane. The original theoretical model was modified by adding the effect of a fixed charge group to the activity coefficient and ionic mobility. The calculated results using the modified model explained well the experimental results if the parameter called charge effectiveness, phi, was introduced into the equations. Introduction of phi into the prediction of membrane potential was already done by Kobatake et al. in a system of a strong polyelectrolyte monopolar membrane/salt aqueous solution. In this study, it was proved that phi can also be introduced into a weak amphoteric polymer membrane/salt aqueous solution system. Finally it was also concluded that the Donnan equilibrium and the Nernst-Planck flux equation were still applicable for examining the transport phenomena for the system of a weak amphoteric charged membrane and electrolyte solutions at various pH.

Journal Article↗

PubMed1997

Conformational flexibility and polymerization of vesicular stomatitis virus matrix protein.

The matrix protein of vesicular stomatitis virus (VSV) plays a pivotal role in viral assembly. We previously demonstrated the ability of M protein to self-associate at low salt concentrations. Now, we show the ability of M protein to polymerize in the presence of ZnCl2 in a nucleation-dependent manner. Analysis of kinetics revealed that the nuclei are probably made of three or four molecules of M. These results are consistent with the idea that in vitro self association of M protein is not due to amorphous aggregation but rather reflects an intrinsic ability of M to polymerize. Using attenuated total reflectance Fourier transform infrared spectroscopy, we showed that M polymerization is associated with an increase in the beta-sheet content of the protein. We propose a model explaining both the apparent M protein solubility in infected cells and how M polymerization could promote viral assembly. Data available for other negative strand viruses suggest that M polymerization may be the general basis of viral assembly.

Chlorides↗

PubMed1996

Time-dependent solutions for a cable model of an olfactory receptor neuron.

A mathematical model for an olfactory receptor neuron is investigated. The physiological and anatomical background required for the construction of a mathematical model are explained. The model, which has been described previously, has three components, including the sensory dendrite on which are found the receptor proteins themselves, and others consisting of a passive cable leading to a trigger zone and axon. In the present paper, we pursue an analytical approach for determining the change in time of the receptor potential in the important case of a subthreshold square pulse of odorant stimulation delivered uniformly at the sensory dendrite. Then, the input current increases in time to its asymptotic value. This latter condition means that we can use a Green's function approach in order to obtain accurate representations for the solution for the entire length of the nerve cell. In the case of finite cables the solution is obtained as an infinite series which is shown to converge and can be easily used to find the depolarization at all space and time points of interest. A steady-state result is obtained directly by solving the relevant ordinary differential equation. For a semi-infinite cable an explicit expression is found for the voltage as a function of time and space variables involving a single integral. However, the exact expression follows from this for the steady-state result. The analytical results obtained are compared to numerical solutions and employed to investigate the effect of varying the position of the trigger zone and the electronic length of the neuron.

Humans↗

PubMedDate not supplied

Mediators of change in physical activity following an intervention in primary care: PACE.

BACKGROUND: The current study evaluated the construct validity of a physical activity intervention in primary care by testing whether the intervention changed hypothesized mediators and whether changes in the mediators were associated with behavior change. METHODS: Matched physician offices were nonrandomly assigned to intervention or control. Apparently healthy, sedentary, adult patients (N = 255) were recruited from physician offices. The intervention was brief, behaviorally based counseling by physicians, plus a telephone follow-up 2 weeks later. Assessments of physical activity and mediators were collected at baseline and at 4- to 6-week follow-up. Hypothesized mediators were processes of change, self-efficacy, and social support for exercise. RESULTS: Patients who were counseled improved significantly more than those in the control group on behavioral and cognitive processes of change. Other changes in mediators were nonsignificant. Behavioral processes of change and self-efficacy made significant contributions to the multiple regression model explaining self-report and objective measures of physical activity. CONCLUSIONS: The intervention affected some of the targeted mediators of physical activity change. Two of three mediator variables were associated with changes in physical activity regardless of experimental condition and other variables. The construct validity of the intervention was partially supported.

Adult↗

PubMed2000

Likelihood of undergoing genetic testing for cancer risk: a population-based study.

BACKGROUND: Studies on public perceptions of genetic susceptibility testing for cancer risks are few and tend to focus on specific cancer risks of higher-risk populations, ignoring the general population and their perceived risk of getting any cancers. This study develops and tests a psychosocial model of the proximal and distal influences on likelihood of undergoing genetic susceptibility testing for cancer risk among a population-based sample. METHODS: The sample consisted of 622 adults aged 18-75 interviewed by telephone. The survey instrument included measures derived from the Health Belief Model and adaptations of existing measures from the literature. Data were analyzed using structural equation modeling techniques. RESULTS: The model suggested independent main effects for perceived benefits, perceived barriers, perceived susceptibility, and pessimism while simultaneously accounting for the effects of age, socioeconomic status, family history of cancer, and awareness of the existence of genetic susceptibility testing for cancer risk. The model explained 34% of the variance in likelihood. CONCLUSIONS: While perceived benefits, perceived barriers, perceived susceptibility, and pessimism may directly impact likelihood, they may also mediate the effects of age, socioeconomic status, family history of cancer, and awareness of cancer genetic susceptibility testing, on likelihood.

Adolescent↗

PubMed2002

Factors influencing intention to obtain a genetic test for colon cancer risk: a population-based study.

BACKGROUND: The availability of genetic testing for cancer risk has prompted an examination of the intention of the general public to undergo testing. This study expands a previous psychosocial model of factors influencing intention to undergo genetic testing for cancer in general to the context of colon cancer. METHODS: A sample of 1,836 adult residents of Vermont, New Hampshire, and Maine were interviewed via telephone. The survey instrument included measures derived from the Health Belief Model and additional psychosocial measures adapted from the literature. Structural Equation Modeling techniques were used to examine factors associated with the likelihood to undergo genetic testing. RESULTS: Perceived barriers and benefits of testing, and perceived susceptibility to colon cancer had direct associations with likelihood. Optimism and pessimism had both direct and indirect effects. Age, socioeconomic status, family history, and awareness of genetic testing had indirect effects, and acted through the other factors. The model explained 22% of the variance in likelihood. CONCLUSIONS: Perceived barriers, benefits, susceptibility, optimism, and pessimism directly influenced likelihood, and may also mediate the effect of background factors examined in this study. These findings suggest effective educational strategies to improve decision-making concerning genetic testing for colon cancer risk in the general population.

Adult↗

PubMed1994

In vivo expression and mutational analysis of the barley yellow dwarf virus readthrough gene.

The barley yellow dwarf virus (BYDV) coat protein gene is separated from an adjacent downstream open reading frame (ORF) by a single termination codon. Immunological analysis of this downstream "readthrough" region reveals multiple coat protein-readthrough products. A full-length 72-kDa (P72) coat protein-readthrough fusion product is detected in total lysates from infected cells. However, purified aphid transmissible virions contain only a 50-kDa (P50) coat protein-readthrough product. Virion-associated P50 lacks the C-terminal domain predicted by its ORF sequence. A separate 33-kDa polypeptide (P33) corresponding to the readthrough C-terminus domain is detected in the crude cellular membrane fraction. Site-directed and deletion mutational analysis demonstrate that the readthrough ORF is dispensable for BYDV replication and virion accumulation in protoplasts. In contrast, a mutant which results in a continuous fusion product of coat and readthrough sequences is not viable. Point mutations were used to map regions required for P50 and P72 synthesis. A model explaining the relationships between the three forms of the readthrough polypeptides is proposed.

Base Sequence↗