SEARCH · PubMed Health

Results for “Model explainability”

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 991 records · Page 55Linked to original sources

PubMed1997

Factors associated with growth of extremely premature infants during initial hospitalization.

OBJECTIVE: To quantify the factors associated with growth of very small premature infants during initial hospitalization. POPULATION: Study patients were 109 infants who were appropriate for gestational age, weighed <1000 g at birth, and were fed intravenous hyperalimentation then calcium-supplemented 81-kcal preterm formula according to a protocol. ANALYSIS: Multiple regression analysis was performed for periods of 0 to 56, 0 to 14, and 15 to 56 days of age. Growth was determined as change in weight during the period. Variables assessed in the initial model were caloric intake, protein intake, respiratory support duration, patent ductus arteriosus, dexamethasone use, infection, birth weight ratio (weight divided by expected intrauterine weight for gestation), gestational age, sex, calendar time from study start, maternal betamethasone administration, and necrotizing enterocolitis. For the 0 to 14-day period, maximum oxygen requirement for respiratory distress syndrome replaced respiratory support duration, and 5-minute Apgar score was added, whereas dexamethasone and necrotizing enterocolitis were deleted. RESULTS: Mean change in weight was 785 g for 0 to 56 days, -16 g for 0 to 14 days, and 770 g for 15 to 56 days. Mean weight was 94% (13 SD) of mean intrauterine at birth, 73% (10 SD) at 14 days, and 73% (12 SD) at 56 days. Regression models explained 85%, 43%, and 80%, respectively, of variation in growth. Of the initial variables assessed, the following were the independent prognostic determinants of growth. There was a positive association with caloric intake at 0 to 56 days and 15 to 56 days, and with protein intake at 0 to 14 days. Negative associations were found for birth weight ratio and gestational age at 0 to 56 and 0 to 14 days. Respiratory support duration was negatively associated at 15 to 56 days, and dexamethasone was negatively associated at 0 to 56 and 15 to 56 days. Formulas to predict growth were established from the final regression models. CONCLUSION: The growth failure in appropriate-for-gestational-age, <1000-g birth weight infants can be related in part to dexamethasone use and respiratory support duration. Increasing caloric intake and early protein intake improves growth. However, for the majority of these patients, early losses are not corrected completely by 56 days using currently recommended intakes.

Dexamethasone↗

PubMedDate not supplied

Predicting iron-fortified soy sauce consumption intention: application of the theory of planned behavior and health belief model.

OBJECTIVE: To identify variables that significantly predict the intention of iron ethylenediaminetetraacetic acid (NaFeEDTA)-fortified soy sauce (FeSS) consumption. DESIGN: A cross-sectional questionnaire survey, based on the Theory of Planned Behavior (TPB) and Health Belief Model (HBM), was administered, and a multistage, stratified sampling method was carried out to select study samples. SETTING: Urban and rural areas in Guizhou province, China. SUBJECTS: 636 women from rural areas and 454 from urban areas completed 1090 eligible questionnaires. VARIABLES MEASURED: Women's knowledge of FeSS; perceived severity and susceptibility of iron deficiency (ID) or iron deficiency anemia (IDA); and attitudes toward behavior, control beliefs, barriers, cues, intention to buy FeSS, health value, and health behavior identity factors were measured. ANALYSIS: A path analysis was conducted to test the goodness of fit of the model and to modify the model. Scale and factor analyses were conducted to verify the scale's reliability and construct validity. The alpha level was set at .05. RESULTS: The model explained 35% to 55% of the variance of behavioral intention. FeSS knowledge directly and indirectly affected the intention to buy FeSS. The behavioral intention was also impacted by women's health value and perception of perceived susceptibility and severity of IDA through the behavior identity and attitudes toward behavior. Cues, as an external factor, greatly affected the intention. The external control belief was a weak factor affecting intention. IMPLICATIONS FOR RESEARCH AND PRACTICE: Integrated TPB and HBM explained the behavioral intention of FeSS consumption among women in Guizhou, China. Nutrition education should emphasize behavioral attitudes and identity, and improve knowledge of FeSS and perception of ID and IDA, which would relieve anxiety about FeSS.

Adult↗

PubMed1997

Admission prediction of expected final myocardial infarct size using weighted ST-segment, Q wave, and T wave measurements.

Formulas for predicting final acute myocardial infarction (MI) size from ST-segment deviation on an initial electrocardiogram were proposed by Aldrich et al. for anterior and inferior infarct locations. This study of 529 patients who did not receive thrombolytic therapy was performed to determine the effectiveness of the Aldrich formulas for predicting final QRS MI size; to propose new formulas for predicting final MI size using ST-segment deviation, Q wave, and T wave information in a development population of 322 patients; and to evaluate the new formulas in a randomly selected population of 207 patients. The Aldrich formulas achieved correlations with final infarct size of r = .40 for anterior and r = .43 for inferior MI locations in the present population which are weaker than those previously reported. Formulas that consider electrocardiographic parameters in addition to ST-segment deviation were proposed for both anterior and inferior final MI size. In the test set of 207 patients, these models explained 16.9% and 15.2% of the variation in final MI size for anterior and inferior locations respectively. They may prove useful in assessing the extent of myocardial salvage where interventions are to be tested.

Electrocardiography↗

PubMedDate not supplied

[The efficacy of universal vaccination against the hepatitis B virus. Simulation with a mathematical model].

We present a mathematical model of the hepatitis B virus (HBV) infection in a community. The main object is to analyze the effects of two different strategies of mass vaccination: newborns or adolescents. It appears that adolescents mass vaccination produces in the short-term a bigger effect than in the newborns. Mathematically, the model is a system of non linear first order differential equations, in which each function is a related class of individuals (susceptible, infectious, carrier, immune and death by HBV) in the evolution of the HBV. The solution of system is obtained in a numerical way. It should be pointed out that the model explains neatly the herd immunity effect of the vaccine and can be used in the simulation of possible changes in the HBV infection such that generalized use of discarded needles by the drug addicted population, changes in the sexual habits, etc.

Adolescent↗

PubMed1998

Roles of calcium gradients in hyphal tip growth: a mathematical model.

A tip-high Ca2+ gradient is observed in growing fungal hyphae, but so far its role remains unknown. A mathematical model is presented, which provides evidence for the functions of such a Ca2+ gradient, in terms of its non-linear effect on the visco-elastic properties of the hyphal cytoskeleton. The model explains how the Ca2+ status at the tip may be responsible for the apical accumulation of vesicles and for an increase in the cytogel osmotic pressure, accompanied by the contraction of the cytoskeleton. The experimentally observed retraction of the spitzenkörper preceding the initiation of a branch is also reproduced, by simulating a subapical transient release of Ca2+ from internal stores.

Calcium↗

PubMed2002

Sonicated transdermal drug transport.

The following review explores the promise shown by sonicated transdermal drug transport as a novel drug delivery system in great detail. It elucidates the advantages of transdermal drug transport (TDT) over the currently prevalent modes of drug administration and then goes on to explain why despite these obvious advantages TDT is so sparingly used. This discussion includes the problems posed by the impregnable barrier--our skin, or more precisely the stratum corneum (SC), and how sonicated TDT breaches this barrier. A succinct definition of sonophoresis is included along with a description of the experimental setup and a discussion of the results. The mechanism of sonophoresis with particular emphasis on the role of cavitation (both inside and outside the skin), thermal effects, convective transport, and mechanical stresses is also included. The paper also includes a discussion on the variation of sonophoretic enhancement from drug to drug along with a recent mathematical model explaining this. The paper concludes with a section detailing possible applications of sonicated TDT in the near future.

Administration, Cutaneous↗

PubMed1977

Possible origin of gating current in nerve membrane.

The present information about gating current observed in squid giant axons points towards the distinct possibility of the current arising from the Debye relaxation of the carboxyl groups in the side chains of the globular proteins enclosing the ionic channels. These carboxyl groups form dipole chains stretching across the membrane. A dipole model is constructed to study the relaxation process under the assumption that the relaxation time tau of the dipoles is modified by dipole-dipole interaction. This model explains qualitatively some of the features of the asymmetric gating current, but is not indicative of any specific mechanism leading to the opening of the gates in the ionic channels. We speculate that the conformational change in the protein globules as a result of dipole reorientation would be the key to the mystery.

Animals↗

PubMed2000

In vivo covalent cross-linking of cellular actin by the Vibrio cholerae RTX toxin.

Enteric pathogens often export toxins that elicit diarrhea as a part of the etiology of disease, including toxins that affect cytoskeletal structure. Recently, we discovered that the intestinal pathogen Vibrio cholerae elicits rounding of epithelial cells that is dependent upon a gene we designated rtxA. Here we investigate the association of rtxA with the cell-rounding effect. We find that V. cholerae exports a large toxin, RTX (repeats-in-toxin) toxin, to culture supernatant fluids and that this toxin is responsible for cell rounding. Furthermore, we find that cell rounding is not due to necrosis, suggesting that RTX toxin is not a typical member of the RTX family of pore-forming toxins. Rather, RTX toxin causes depolymerization of actin stress fibers and covalent cross-linking of cellular actin into dimers, trimers and higher multimers. This RTX toxin-specific cross-linking occurs in cells previously rounded with cytochalasin D, indicating that G-actin is the toxin target. Although several models explain our observations, our simultaneous detection of actin cross-linking and depolymerization points toward a novel mechanism of action for RTX toxin, distinguishing it from all other known toxins.

ADP Ribose Transferases↗

PubMed2004

Computational model of dynein-dependent self-organization of microtubule asters.

Polar arrays of microtubules play many important roles in the cell. Normally, such arrays are organized by a centrosome anchoring the minus ends of the microtubules, while the plus ends extend to the cell periphery. However, ensembles of molecular motors and microtubules also demonstrate the ability to self-organize into polar arrays. We use quantitative modeling to analyze the self-organization of microtubule asters and the aggregation of motor-driven pigment granules in fragments of fish melanophore cells. The model is based on the observation that microtubules are immobile and treadmilling, and on the experimental evidence that cytoplasmic dynein motors associated with granules have the ability to nucleate MTs and attenuate their minus-end dynamics. The model explains the observed sequence of events as follows. Initially, pigment granules driven by cytoplasmic dynein motors aggregate to local clusters of microtubule minus ends. The pigment aggregates then nucleate microtubules with plus ends growing toward the fragment boundary, while the minus ends stay transiently in the aggregates. Microtubules emerging from one aggregate compete with any aggregates they encounter leading to the gradual formation of a single aggregate. Simultaneously, a positive feedback mechanism drives the formation of a single MT aster--a single loose aggregate leads to focused MT nucleation and hence a tighter aggregate which stabilizes MT minus ends more effectively leading to aster formation. We translate the model assumptions based on experimental measurements into mathematical equations. The model analysis and computer simulations successfully reproduce the observed pathways of pigment aggregation and microtubule aster self-organization. We test the model predictions by observing the self-organization in fragments of various sizes and in bi-lobed fragments. The model provides stringent constraints on rates and concentrations describing microtubule and motor dynamics, and sheds light on the role of polymer dynamics and polymer-motor interactions in cytoskeletal organization.

Animals↗

PubMed2004

Structural requirements of the N-terminal region of GLP-1-[7-37]-NH2 for receptor interaction and cAMP production.

A series of GLP-1-[7-36]-NH(2) (tGLP-1) and GLP-1-[7-37] analogs modified in position 7, 8, 9 and 36, have been designed and evaluated on murine GLP-1 receptors expressed in RIN T3 cells for both their affinity and activity. Ten of the synthesized peptides were found full agonists with activities superior or at least equal to that of the native hormone. Five of them were investigated for their plasmatic stability and the most stable, [a(8)-desR(36)]GLP-1-[7-37]- NH(2) (Compound 8), evaluated in vivo in a glucose tolerance test which confirmed a clearly longer activity than that of the native hormone. We also performed circular dichroism study and propose a hypothetical structural model explaining the most part of observed activities of GLP-1 analogs on RIN T3 cells.

Amino Acid Sequence↗

PubMed1999

Novel type of genetic rearrangement in the iduronate-2-sulfatase (IDS) gene involving deletion, duplications, and inversions.

We describe a novel type of complex genetic rearrangement in the iduronate-2-sulfatase (IDS) gene of a severely affected MPSII patient. Southern blot analysis indicated an intragenic deletion of exons 5 and 6. The deletion spans 5,581 bp. Sequencing of the deletion junctions revealed a complex rearrangement involving duplications and inversions. A remaining 20 bp fragment (c) from the intron 6 sequence and two duplicated IDS gene fragments of 314 bp (a) from intron 6/exon 7 boundary and 23 bp (b) from exon 7 were found between the deletion breakpoints. Fragments a and c were placed in an inverted orientation. We suggest that the described rearrangement is a result of a nonhomologous recombination event at sites with little homology. The proposed model explaining this recombinational event involves the formation of "tetra-loop" single-stranded DNA structure during replication. The complexity of the described rearrangement and the lack of large homologous sequences at the mutational breakpoints suggest that complex molecular intermediates are formed during illegitimate recombination.

Base Sequence↗

PubMed1987

Models for understanding the antagonism between seizures and psychosis.

1. The relationship between seizures and psychosis is reviewed using incidence and association studies, and experimental models of kindling and behavioral sensitization. 2. While there are conflicting data on the association of psychopathology with epilepsy, studies illustrating the antagonism between seizures and psychosis are examined along with the phenomenon of "Forced Normalization". 3. Electrical kindling of the amygdala provides a model of temporal lobe epilepsy while pharmacologic kindling/behavioral sensitization or dopaminergic kindling provides a model for psychosis. 4. A model explaining both the etiology and the reciprocal nature of seizures and psychosis in temporal lobe epilepsy is developed. Preictal and interictal spikes kindle both proconvulsive and inhibitory pathways of seizure expression and behaviorally relevant limbic systems. That system currently expressive, either seizure or psychosis, while under high synchronous drive would tend to fail allowing for the emergence of the opposing system.

Amygdala↗

PubMedDate not supplied

The impact of arthritis on quality of life.

This study explored the impact of pain and functional impairment on the quality of life experienced by persons with arthritis. Using a cognitive framework, a causal model was developed in which the disease-related variables interacting with demographic and social factors were hypothesized to indirectly affect quality of life through psychological mediators. Ninety-four adults--74 women and 20 men--with various forms of arthritis were interviewed in their homes. Overall, the model explained 46% of the variance in quality of life. Path analysis showed that the psychological mediators--positive self-esteem, internal control over health, perceived support, and low negative attitude toward the illness--contributed directly to a higher quality of life. Severity of arthritis-related impairment indirectly affected quality of life through the mediating variables.

Adult↗

PubMed1998

Academic achievement of African American preadolescents: the influence of teacher perceptions.

The purpose of this study was to identify the factors associated with the academic success of predominantly, middle-class African American preadolescent students. This study proposed an ecological model that considered the interaction of family environment, teacher perceptions of social skills, and student characteristics. The estimated model explained 58% of the variance in grade point average. Path analysis revealed three direct effects on grade point average, (a) grade level (negative), (b) teacher perceptions of social skills, and (c) academic ability. Findings revealed that teacher perceptions of social skills was a stronger predictor of grade point average than academic ability. Two indirect effects on grade point average were found. The first indirect effect was negative: gender predicted academic ability, which predicted teacher perceptions of social skills, which predicted grade point average. The second indirect effect was positive and it was from ability to teacher perceptions to grade point average. Implications for policy and practice are made that suggest a collaborative model of school counseling designed to "promote" the social and academic competence of African American students. Interventions that enhance teacher practices are also suggested.

Achievement↗

PubMed1993

Socioeconomic factors and mortality in small areas.

The aim of this study was to determine the extent to which variation in socioeconomic factors derived from the 1986 census could "explain" variation in standardised mortality ratio (SMR) between the 322 electoral wards and district electoral divisions (DEDs) in Dublin. Factors examined included percentage of population in the various Irish social class groupings, percentage of male unemployment, number of cars per private household and number of persons per car. Regression analysis between SMR and each of these factors individually showed a significant relationship in every case. The explanatory variables studied were all highly correlated and stepwise forward multiple regression was used to identify factors which had an independent effect. Two factors emerged as significant--percentage of persons in social classes 5 & 6 (semiskilled and unskilled) and number of cars per private household. This model explained 27.4% of the variance in SMR. We conclude that the variation of SMRs between DEDs in Dublin can partly be explained by variation in socioeconomic factors.

Humans↗

PubMed1996

The role of synapses in cortical computation.

The synapse, first introduced as physiological hypothesis by C.S. Sherrington at the close of the nineteenth century, has, 100 years on, become the nexus for anatomical and functional investigations of interneuronal communication. A number of hypotheses have been proposed that give local synaptic interactions specific roles in generating an algebra or logic for computations in the neocortex. Experimental work, however, has provided little support for such schemes. Instead, both structural and functional studies indicate that characteristically cortical functions, e.g., the identification of the motion or orientation of objects, involve computations that must be achieved with high accuracy through the collective action of hundreds or thousands of neurons connected in recurrent microcircuits. Some important principles that emerge from this collective action can effectively be captured by simple electronic models. More detailed models explain the nature of the complex computations performed by the cortical circuits and how the computations remain so remarkably robust in the face of a number of sources of noise, including variability in the anatomical connections, large variance in the synaptic responses and in the trial-to-trial output of single neurons, and weak or degraded input signals.

Animals↗

PubMed2002

The fatty acid composition of plasma phospholipids and the insulin sensitivity in elderly diabetic patients. The Pro.V.A. study.

BACKGROUND AND AIMS: The prevalence of diabetes is increasing worldwide indicating that life-style habits are important determinants for this disease. The aim of this study was to examine the effects of dietary fats on insulin sensitivity in diabetic patients. METHODS: In a randomly selected sample of population aged 65 and older, plasma phospholipid fatty acid composition was determined by gaschromatography. The plasma phospholipid fatty acid composition is a reliable marker of the type of fats present in the diet. Insulin resistance was estimated with the Homeostasis Model Assessment (HOMA). RESULTS: Body weight, height, body mass index (BMI), waist circumference, serum cholesterol as well as fasting insulin, and the HOMA index were lower in the older groups. With increasing age, there was an increase in the monounsaturated fatty acid content and a decrease in the polyunsaturated and n-6 polyunsaturated fatty acids. In the linear regression analysis, saturated fatty acids were significantly related to waist circumference, fasting glucose, fasting insulin, and HOMA. Significant relations were also obserued between HOMA and BMI, triglycerides, waist circumference, and age. Triglycerides and HDL cholesterol were strongly interrelated as well as BMI and waist circumference. In the multiple regression analysis including age, BMI, waist circumference, triglycerides, HDL cholesterol, and saturated fatty acids, the HOMA index was predicted significantly only by age, BMI, and triglycerides. This model explained 28% of the HOMA variance. CONCLUSIONS: In elderly diabetic patients insulin sensitivity is modulated by age, BMI, and triglycerides, but the type of dietary fats is not independently associated with insulin sensitivity.

Age Factors↗

PubMed1982

Adaptation in the long-wavelength pathways.

We describe and test predictions of a model of long-wavelength test sensitivity upon large, uniform backgrounds. The model explains changes in sensitivity in the red-green detection pathways strictly based upon losses of sensitivity in the receptors. We derive the prediction that field mixture data for field-mixtures of mu1 (fixed) and an addend, mu 2, must follow the same shape on different intensities of the fixed background, mu 1. This prediction is not in good agreement with the measurements.

Adaptation, Ocular↗