SEARCH · PubMed Health

Results for “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 1,441 records · Page 80Linked to original sources

PubMed2005

Explaining geographic variation in breast and cervical cancer incidence rates in US Hispanic women.

OBJECTIVE: This study examined geographic variation in incidence rates for two cancers common in US Hispanic women and considered some potential explanations, by using data from several high-quality cancer registries. METHODS: Age-standardized incidence rates (ASIRs) per 100,000 Hispanic women per year were analyzed for breast and cervical cancer in the population-based cancer registries of the Surveillance, Epidemiology and End Results (SEER) Program. The percentage potentially misclassified (PPM) as Hispanic, because of the frequent absence of maiden name, was estimated. Sociodemographic characteristics of the cancers and of the Hispanic population in eight areas were compared. RESULTS: The ASIRs varied from 80.9 to 113.3 for breast and 8.2 to 19.9 for cervix cancers. The PPM was higher for breast (16%) than for cervix (7%). Differences in PPM across SEER areas did not appear consistent with geographic variation in ASIRs, while some variation in ASIRs was consistent with differences in sociodemographic characteristics. Registry data on subgroups (defined by ancestry and birthplace) were too incomplete for analyses of CONCLUSIONS: Some of the geographic variation appeared to be explained by sociodemographic factors, but improvements in cancer registries are needed to analyze ASIRs for Hispanic subgroups.

Adolescent↗

PubMed2005

Long-term blood pressure monitoring and echocardiographic findings in patients with end-stage renal disease: reverse epidemiology explained?

BACKGROUND: In patients with end-stage renal disease (ESRD) hypertension is common and often leads to left ventricular (LV) hypertrophy and diastolic dysfunction, but hypotension at the onset of dialysis is associated with increased mortality. We studied blood pressure data over longer periods of time in patients on haemodialysis and related them to echocardiographic outcome, in order to elucidate these contradictory findings. METHODS: In 50 haemodialysis patients mean arterial pressure (MAP) and pulse pressure (PP) were calculated in the first three months of haemodialysis, the complete period from the start of haemodialysis until echocardiography and the last three months of haemodialysis before echocardiography. Hypertension load, pulse pressure and interdialytic weight gain were quantified and related to echocardiography. RESULTS: LV mass index was associated with MAP in all three periods, and also with the hypertension load, PP and PP load. In patients with LV dilatation, MAP and PP averaged over the complete period of dialysis were 5 to 7 mmHg higher than in patients without LV dilatation. Blood pressure parameters were the same in patients with or without LV diastolic dysfunction or systolic dysfunction. Systolic dysfunction was more frequent in patients undergoing long-term haemodialysis treatment. Interdialytic weight gain was not associated with any of the echocardiographic variables. CONCLUSION: When long-term blood pressure values are considered, hypertension is associated with parameters of early cardiac damage such as increased LV mass index and not with parameters of advanced heart failure such as systolic dysfunction. This supports the hypothesis that the presence of advanced heart failure reciprocally influences blood pressure in a negative way, thereby explaining the 'reverse epidemiology' of blood pressure and mortality in ESRD.

Adult↗

PubMed2006

Do adverse histopathologic findings in colorectal cancer patients explain disparate outcomes?

We have previously reported reduced overall and disease-free survival in black patients from a 10-year retrospective review of 668 patients from tumor registry data. This study of 213 patients reports the analysis of available archived tissue from a city hospital (n=44 patients, 53% black) and from a university medical center (n=169, 10.6% black). Two senior pathologists independently reviewed slides for predetermined histologic criteria reported to correlate with survival: tumor type, stage at diagnosis, character of invasion, vascular or perineural invasion, the presence of residual adenoma, the presence of a Crohn's-like reaction and number of nodes resected. Differences in discrete variables were compared using the Chi-squared test. Differences in continuous variables were analyzed using independent t tests. No statistically significant differences were identified in tumor stage or type by institution or race. In patients treated at the city hospital, there was a higher incidence of infiltrating tumors (85% vs. 61%, p<0.001), vascular invasion (70% vs. 36%, p<0.05) and residual adenoma (84% vs. 39%, p<0.05); however, no differences by race were identified. Blacks at both hospitals had significantly more perineural invasion (81% vs. 30%, p<0.05) and Crohn's-like reaction (64% vs. 30%, p<0.05) when compared to white patients, although there was no difference between hospitals. The total number of lymph nodes resected was higher at the university hospital (17.0 vs. 8.9, p<0.001). There were no differences in number of nodes resected at either institution by race. Histopathologic findings did not explain the apparent disparity in survival. The differences in number of nodes harvested may suggest inadequate resection or insufficient recovery of nodes by the pathologist.

Black People↗

PubMed1991

[Antiarrhythmic agents. Receptor hypothesis explains mechanisms of action].

Antiarrhythmic drugs are usually classified according to Vaughan Williams' classification I-IV. Class I includes the membrane stabilizers, class II includes the beta-blockers, drugs in class III lengthen the cardiac action potential and refractory period and class IV includes the calcium blockers. The effect of most antiarrhythmic drugs changes with heart rate and the level of myocardial depolarization, and these changes in effect can be explained by the modulated receptor hypothesis. Most class I antiarrhythmic drugs have greatest antiarrhythmic effect during periods of fast heart rate and in depolarized ischemic myocardium, and this might be attributed to greater affinity of the drugs for open or inactivated sodium channels. Most class III antiarrhythmic drugs have greatest effect during periods of slow heart rates, which may be attributed to greater affinity for closed potassium channels.

Anti-Arrhythmia Agents↗

PubMed2006

A modest model explains the distribution and abundance of Borrelia burgdorferi strains.

The distribution and abundance of Borrelia burgdorferi, including human Lyme disease strains, is a function of its interactions with vertebrate species. We present a mathematical model describing important ecologic interactions affecting the distribution and abundance of B. burgdorferi strains, marked by the allele at the outer surface protein C locus, in Ixodes scapularis ticks, the principal vector. The frequency of each strain in ticks can be explained by the vertebrate species composition, the density of each vertebrate species, the number of ticks that feed on individuals of each species, and the rate at which those ticks acquire different strains. The model results are consistent with empirical data collected in a major Lyme disease focus in New England. An applicable extension of these results would be to predict the proportion of ticks carrying human infectious strains of B. burgdorferi from disease host densities and thus predict the local risk of contracting Lyme disease.

Animals↗

PubMed2006

Individuals with diabetes mellitus with and without depressive symptoms: could social network explain the comorbidity?

OBJECTIVES: The main objective of the present study was to obtain an approximate prevalence of depressive symptoms in a community sample of persons with diabetes mellitus and to discover whether social networks could explain comorbidity of diabetes mellitus and depressive symptoms. METHOD: Subjects were persons with diabetes mellitus, members of the Diabetes Association of Ljubljana (N = 396, average age: 62.9 +/- 13.4, average duration of diabetes: 17.2 +/- 10.6). Firstly, subjects were screened with CESD (Centre for Epidemiological Studies Depression Scale) and demographic data were also gathered. Secondly, two samples (individuals with and without depressive symptoms) were compared on the basis of social network analysis. RESULTS: The prevalence of depressive symptoms was higher among persons with diabetes in comparison with general population. Individuals with depressive symptoms compared with individuals without depressive symptoms were less dissatisfied with diabetes (p = 0.011), and had better informational (p = 0.039) and instrumental support (p = 0.046), relations between them and support givers were closer (p = 0.050), more important and less conflicting (p = 0.042). Compared groups did not differ in quantitative characteristics of social networks (eg. size of the network or the network gender structure). CONCLUSIONS: The community sample results in Slovenia support the already reported association between diabetes mellitus and depression. Furthermore, social network analysis offered some potentially relevant explanation for comorbidity of diabetes mellitus and depressive symptoms.

Adult↗

PubMed2006

A model to explain the therapeutic effects of serotonin reuptake inhibitors: the role of 5-HT2 receptors.

In this article, it is posited that major depression involves an underfunctioning dopamine system resulting from hypersensitive inhibitory 5-HT2 receptors located on dopaminergic neurons. After a few weeks, treatment with most antidepressant drugs leads to a downregulation of the 5-HT2 receptors that allows for increased dopaminergic firing, which is proposed to be decisive for the antidepressant effect. However, serotonin reuptake inhibitors (SRIs) therapeutic mechanisms probably differ between different therapeutic outcomes. It is hypothesized, that in women, the use of female sex steroids leads to a downregulation of 5-HT2C receptors that contributes to atypical depressive symptoms and premenstrual dysphoria. Consequently, these conditions can be assumed to benefit from the acute increase of serotonergic neurotransmission following ingestion of an SRI rather than the secondary receptor changes, which would explain why there is a therapeutic lag time when SRIs are used to treat depression but not premenstrual dysphoric disorder. The clinical predictions derived from this hypothesis are that 5-HT2 antagonists would be an effective treatment in melancholic depression, have a fast onset of action, speed the onset of SRIs, and can be an effective augmentation for SRI-refractory patients. In contrast, in atypical depression and premenstrual dysphoria a 5-HT2 antagonist would counteract the therapeutic effect of an SRI, while 5-HT2 agonists have a therapeutic potential. It is suggested that therapeutic response to 5-HT2 antagonists/agonists may be used as a diagnostic tool to dissect subgroups of depression.

Brain↗

PubMedDate not supplied

On the unfitness of natural selection to explain sexual reproduction, and the difficulties that remain.

In its essence, the explanatory potential of the theory of natural selection is based on the iterative process of random production and variation, and subsequent non-random, directive selection. It is shown that within this explanatory framework, there is no place for the explanation of sexual reproduction. Thus in Darwinistic literature, sexual reproduction - one of nature's most salient characteristics - is often either assumed or ignored, but not explained. This fundamental and challenging gap within a complete naturalistic understanding of living beings calls for the need of a cybernetic account for sexual reproduction, meaning an understanding of the dynamic and creative potential of living beings to continuously and autonomously produce new organisms with unique and specific constellations.

Adaptation, Physiological↗

PubMedDate not supplied

Why factors rooted in the family may solely explain the urban-rural differences in schizophrenia risk estimates.

Many studies have identified urban-rural differences in schizophrenia risk. The underlying cause(s) may hypothetically include toxic exposures, diet, infections, and selective migration. In a recent study, we concluded that some of the cause(s) responsible for the urban-rural differences in schizophrenia risk are rooted in families, but some might also be rooted in individuals. First, we describe temporality as a potential methodological pitfall within this line of research, then we review studies not subject to this pitfall, and finally, we describe why factors rooted in the family may solely explain the urban-rural differences. Although other potential explanations for these differences exist, we focus on this hypothesis as it has not previously been discussed in detail. To determine the cause(s) responsible for the urban-rural differences, we need direct measurements of genetic and/or environmental factors related to urban life.

Humans↗

PubMed1991

Successful treatment of fulminant hepatitis B and fulminant hepatitis B and D coinfection explained by inhibitory effect on the immune response?

Foscarnet has been shown to inhibit the proliferation of human T and B lymphocytes in vitro. The production of lymphokines was more strongly affected than the DNA synthesis. Monocyte function was only partly inhibited by the highest foscarnet concentration tried. The influence of foscarnet on the immune system could explain the beneficial effect observed in patients with HBV-related fulminant hepatitis treated with foscarnet.

Antiviral Agents↗

PubMed1991

Differential regulation of hepatocyte-enriched transcription factors explains changes in albumin and transthyretin gene expression among hepatoma cells.

To investigate the regulation of genes whose expression is enriched in liver we studied expression of the albumin and transthyretin (TTR) genes in a series of rat hepatoma cell lines (FaO, C2, C2rev7, and H5) that express these genes at different rates. The level of expression of albumin and TTR was compared to the expression and DNA-binding activity of four transcription factors, HNF1/LFB1, C/EBP, HNF3, and HNF4, that are found at high concentrations in liver. We conclude that the levels of these factors are controlled both transcriptionally (HNF-3, HNF-4, and C/EBP) and post-transcriptionally (HNF-1/LFB1), and that the cellular concentration of these DNA-binding proteins helps explain the level of transcriptional activity observed for the genes they regulate.

Albumins↗

PubMed1991

Hormone-induced calcium oscillations in liver cells can be explained by a simple one pool model.

Hormone-induced oscillations of the free intracellular calcium concentration are thought to be relevant for frequency encoding of hormone signals. In liver cells, such Ca2+ oscillations occur in response to stimulation by hormones acting via phosphoinositide breakdown. This observation may be explained by cooperative, positive feedback of Ca2+ on its own release from one inositol 1,4,5-trisphosphate-sensitive pool, obviating oscillations of inositol 1,4,5-trisphosphate. The kinetic rate laws of the associated model have a mathematical structure reminiscent of the Brusselator, a hypothetical chemical model involving a rather improbable trimolecular reaction step, thus giving a realistic biological interpretation to this hallmark of dissipative structures. We propose that calmodulin is involved in mediating this cooperativity and positive feedback, as suggested by the presented experiments. For one, hormone-induced calcium oscillations can be inhibited by the (nonphenothiazine) calmodulin antagonists calmidazolium or CGS 9343 B. Alternatively, in cells overstimulated by hormone, as characterized by a non-oscillatory elevated Ca2+ concentration, these antagonists could again restore sustained calcium oscillations. The experimental observations, including modulation of the oscillations by extracellular calcium, were in qualitative agreement with the predictions of our mathematical model.

Animals↗

PubMed1991

What factors explain racial differences in lung volumes?

In order to examine the physical characteristics that may determine racial differences in lung volumes, we studied healthy, nonsmoking Caucasian, Chinese and Indian males of similar ages (range 18-51 yrs). We measured spirometric function, flow volume curves, lung volumes, inspiratory and expiratory muscle pressures, alveolar distensibility and diffusing capacity, together with height, weight and fat free mass. Chest shape was measured using radiographs. The mean total lung capacity and vital capacity in the Caucasian group, expressed as percentage predicted, were 5 and 10% higher than in the Chinese group and 17 and 20% higher than in the Indian group. Chinese values for these measurements were 12 and 10% greater than Indian. We found that Caucasians had higher fat free masses, higher inspiratory and expiratory muscle pressures and wider chests than the other races. The Caucasians and Chinese had longer chests than the Indians. There was no difference in alveolar distensibility or in the diffusion coefficient between the groups. These findings suggest that Caucasians have larger lung volumes than Chinese and Indians because they have increased numbers of alveoli and physically larger chest cavities, and not because of greater alveolar distensibility. Chest dimensions, together with height and race explained 90% of the variation in forced vital capacity and 86% of the variation in total lung capacity. Height multiplied by fat free mass, a "physique factor", previously suggested as the best predictive factor for forced vital capacity in Caucasians, did not account for much of the variation in forced vital capacity between Caucasians and Indians, presumably because it takes no account of differences in chest dimensions.

Adolescent↗

PubMed1991

Cancer screening by primary care physicians. Can we explain the differences?

BACKGROUND: Physicians perform cancer screening tests less often than recommended. METHODS: Forty primary care physicians were surveyed to assess their knowledge, attitudes, and experiences regarding cancer and cancer screening, and patients' medical records were reviewed to measure physicians' screening rates. RESULTS: Over 80% of physicians believed doctors should urge screening. On average, 23% of their patient visits were scheduled primarily for preventive care interventions. Screening performance scores expressed the percentage of compliance with the American Cancer Society's recommendations and demonstrated the low levels of compliance for six out of seven tests; however, there was substantial variance in performance among physicians. The best predictors of screening performance were (1) the percentage of visits scheduled primarily for prevention (mammography, and pelvic and breast examinations [P less than .05]); and (2) the number of medical journals read regularly (stool occult blood test [P less than .01], sigmoidoscopy [P less than .01], and Papanicolaou smear [P less than .02]). Also, female physicians performed more Papanicolaou smears (P less than .05) and scheduled more visits for preventive care (P less than .001). CONCLUSIONS: A small group of predictors explain large portions of the variance in cancer screening performance.

Adult↗

PubMed1991

Does racial variation in risk factors explain black-white differences in the incidence of hypertensive end-stage renal disease?

Prospectively collected data on the incidence of treated hypertensive end-stage renal disease (HT-ESRD) were analyzed to investigate whether the higher rate of HT-ESRD in blacks compared with whites is due to differences in putative ESRD risk factors. The overall age-adjusted relative risks of HT-ESRD for black compared with white residents in the Maryland Regional ESRD Registry (Network 31) Catchment Area were 7.4 (95% confidence interval, 5.9 to 9.4) and 9.9 (95% confidence interval, 7.4 to 13.1) for men and women, respectively. In a population level analysis, race-specific HT-ESRD incidence rates in the black and white populations of 13 regions in Network 31 were related to the prevalence of putative ESRD risk factors in those populations. The latter were estimated from the 1981-1982 Maryland Statewide Household Hypertension Survey. Black populations had a 5.6-fold (95% confidence interval, 3.9 to 8.1) higher unadjusted incidence of HT-ESRD than white populations. The HT-ESRD incidence in a population was also directly related to that population's prevalence of hypertension, severe hypertension, and diabetes mellitus and inversely related to measures of socioeconomic status and mean age at diagnosis of hypertension. When adjusted simultaneously for age, prevalence of hypertension, severe hypertension, diabetes, and level of education, the risk of HT-ESRD was still 4.5 (95% confidence interval, 3.2 to 6.2) times higher for black compared with white populations. Our findings failed to support the hypothesis that race-related differences in the prevalence, severity, or age at onset of hypertension, in the prevalence of diabetes or in socioeconomic status, explain the well-recognized black-white differences in the HT-ESRD incidence.

Adult↗

PubMed1990

Platelet activation may explain the storage lesion in platelet concentrates.

While the exact nature of the dysfunction of stored platelets is not known, it is generally agreed that the platelet's metabolic activity with lactate accumulation presents a significant impediment to prolonged storage. There is an increasing body of evidence that stored platelets have become activated in the preparation and handling of platelet concentrates. Changes in platelet function and structure in concentrates can be explained in terms of sequelae of activation, especially heightened metabolic activity and activation-specific changes in surface glycoproteins on stored platelets. With the use of inhibitors of platelet activation in the preparation of platelet concentrates, the loss of platelet function and integrity is less rapid and platelet metabolic rate is decreased during an extended storage period. Surface levels of glycoprotein Ib, normally decreased during prolonged storage of platelets, are well-preserved in the presence of activation inhibitors. When the use of inhibitors is combined with replacement of plasma with an artificial medium, platelets stored for up to 20 days appear to be metabolically and structurally intact and responsive to stimuli. In summary, platelet activation appears to play a major role in the generation of the storage lesion in platelet concentrates.

Blood Preservation↗

PubMed1979

Biphasic effects of ethanol on behavioral and electrophysiological parameters can be explained by functional organization of neural networks.

The biphasic effect of ethanol on the CNS is usually explained by assuming that excitatory and depressant effects are mediated by different mechanisms. The present alternative explanation states that ethanol depresses the activity of all neurons to the same extent, but that the biphasic effect can result from the functional organization of the neural network concerned. Current experimental evidence is in accordance with both explanations.

Behavior↗

PubMed1990

The stereospecificities of seven dehydrogenases from Acholeplasma laidlawii. The simplest historical model that explains dehydrogenase stereospecificity.

Stereospecificities are reported for seven dehydrogenases from Acholeplasma laidlawii, an organism from an evolutionarily distinct branch of life which has not previously been studied from a stereochemical point of view. Three of the activities examined (alcohol dehydrogenase, lactate dehydrogenase, and alanine dehydrogenase) catalyze the transfer of the pro-R (A) hydrogen from NADH. Four other activities (3-hydroxy-3-methylglutaryl-CoA reductase, glyceraldehyde-3-phosphate dehydrogenase, glucose-6-phosphate dehydrogenase, and NADH oxidase) catalyze the transfer of the pro-S (B) hydrogen from NAD(P)H. The stereospecificity of hydroxymethylglutaryl-CoA reductase is notable because it is the opposite of that of hydroxymethylglutaryl-CoA reductases from yeast and rat. These data are used to derive the simplest historical model capable of explaining available experimental facts.

Acholeplasma laidlawii↗