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Results for “causality”

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

PubMed2005

Meiotic abnormalities in in vitro-matured marmoset monkey (Callithrix jacchus) oocytes: development of a non-human primate model to investigate causal factors.

BACKGROUND: Meiotic abnormalities are thought to be a major causal factor of low embryo development rates, for embryos developed from in vitro-matured oocytes. A new non-human primate model, in the common marmoset, is being developed to facilitate investigation of the mechanisms involved. METHODS: Oocytes were dissected from antral follicles from three size classes. They were allowed to mature in vitro for only 24 h, in order to focus the investigation on the rapidly maturing oocytes. Chromosome spreads were visualized with Giemsa staining, and spindles /chromosomes with fluorescently labelled anti-alpha-tubulin antibody combined with a DNA fluorochrome. RESULTS: 40% of the oocytes had reached metaphase II (MII) after 24 h. Of the MII oocytes selected for karyotyping, readable chromosomal spreads were obtained from 64%. Overall, 63% of these presented a normal haploid chromosome number of 23,X, with all abnormal karyotypes occurring in the oocytes from small follicles. For another group of MII oocytes, where meiotic spindles were visualized, only half of the MII oocytes displayed well-formed spindles and apparently correct chromosomal alignment. CONCLUSIONS: This work provides the first information on the normal and aneuploid MII meiotic chromosome sets for the marmoset oocyte, and demonstrates a high rate of chromosomal and spindle abnormality among rapidly maturing oocytes from small antral follicles.

Aneuploidy↗

PubMed2006

The association between atopy and factors influencing folate metabolism: is low folate status causally related to the development of atopy?

BACKGROUND: Deficiency of folate has been associated with several disorders characterized by enhanced activation of the cellular immune system (non-allergic th1 type immune response). Whether folate status is also associated with atopic disease (allergic th2 type immune response) is unknown. We aimed at examining the association between atopy and markers of impaired folate metabolism, i.e. MTHFR(C677T) genotype, plasma total homocysteine, and dietary intakes of methionine, folates, and vitamins B12, B6, and B2. METHODS: Cross-sectional population-based study of 1,671 male and female residents of Copenhagen County, Denmark, aged 30-60 years participating in a health examination during 1999-2001. Atopy was defined as positive levels of specific IgE against a panel of inhalant allergens. MTHFR(C677T) genotype was determined by PCR followed by restriction fragment length polymorphism analyses. Total homocysteine was measured by fluorescent polarization immunoassay. Dietary vitamin intakes were estimated from a semi-quantitative food frequency questionnaire. RESULTS: The prevalence of atopy was associated with MTHFR(C677T) genotype. TT individuals had a significantly higher risk of atopy compared with CC/CT individuals [odds ratio 1.76, 95% confidence interval (95% CI) 1.19-2.60]. Additionally, gene-diet interaction effects were identified. Dietary markers were negatively associated with risk of atopy in persons with the TT genotype. Total homocysteine was not related to atopy (odds ratio per 5 mumol/l = 1.12, 95% CI 0.98-1.29). CONCLUSIONS: The results suggest that an impaired folate metabolism may be causally related to the development of atopy.

Adult↗

PubMed2006

Fibrinogen and coronary heart disease: test of causality by 'Mendelian randomization'.

BACKGROUND: Blood concentrations of fibrinogen have been associated with coronary heart disease risk in epidemiological studies, but it is uncertain whether this association is causal or reflects residual confounding by other risk factors. We investigated the relationship between the single nucleotide polymorphism at position -148 in the beta-fibrinogen gene promoter (beta - 148C/T), blood fibrinogen levels, and risk of myocardial infarction (MI) in sufficiently large numbers of coronary disease cases to reliably address this question. METHODS: Genotyping and measurement of blood fibrinogen concentration were carried out in 4,685 cases of confirmed MI and 3,460 controls with no history of coronary disease. A meta-analysis of ISIS and 19 other studies of beta-fibrinogen genotypes involving a total of 12,220 coronary disease cases and 18,716 controls was conducted. RESULTS: Among the ISIS controls, mean plasma fibrinogen concentrations with the C/C, C/T and T/T genotypes were 3.34 (SE 0.015), 3.48 (0.022), and 3.60 (0.064) g/l, respectively, corresponding to an increase of 0.14 (0.024) g/l per T allele (trend P < 0.0001). In the case-control comparison, 0.14 g/l higher usual plasma fibrinogen concentration was associated with an age-adjusted and sex-adjusted risk ratio for MI of 1.17 [95% confidence interval (95% CI) 1.14-1.19; P < 0.0001]. But, after further adjustment for smoking, body mass index, and plasma apolipoprotein B/A(1) ratio, this risk ratio fell to 1.03 (95% CI 1.00-1.05; P = 0.05). Moreover, fibrinogen genotype was not significantly associated with MI incidence: risk ratio of 1.06 (95% CI 0.96-1.16) per higher-fibrinogen allele in ISIS alone and of 1.00 (95% CI 0.95-1.04) per allele in the meta-analysis. CONCLUSIONS: Genotypes that produce lifelong differences in fibrinogen concentrations do not materially influence coronary disease incidence. As these genotype-dependent differences in fibrinogen were allocated randomly at conception (Mendelian randomization), this association is not likely to be confounded by other factors. Consequently, these genetic results provide strong evidence that long-term differences in fibrinogen concentrations are not a major determinant of coronary disease risk.

Adult↗

PubMed1997

Recognizing values: a descriptive-causal method for medical/scientific discourses.

While much discussion in bioethics, philosophy of science, and philosophy of medicine concerns the proper handling and uses of value considerations, there has been little discussion about how to identify or recognize values in medical/scientific discourse. This article presents a heuristic method for identifying values in such discourses. Values are defined as descriptions or conditions that guide human action and are praise- or blameworthy. Values manifest themselves in discourses in one or more of three dimensions: linguistic, causal, and descriptive; each with distinctive "subtypes". By recognizing the various ways that values manifest in discourses, a "values scholar" can ask relevant questions of the discourse and thereby come to recognize potential evaluative meanings in the discourse. Numerous examples are provided from the author's own research program. Strengths, limitations, and paths to developing the model are briefly discussed.

Bioethics↗

PubMed2000

Evidence for a causal association between human papillomavirus and a subset of head and neck cancers.

BACKGROUND: High-risk human papillomaviruses (HPVs) are etiologic agents for anogenital tract cancers and have been detected in head and neck squamous cell carcinomas (HNSCCs). We investigated, retrospectively, an etiologic role for HPVs in a large series of patients with HNSCC. METHODS: Tumor tissues from 253 patients with newly diagnosed or recurrent HNSCC were tested for the presence of HPV genome by use of polymerase chain reaction (PCR)-based assays, Southern blot hybridization, and in situ hybridization. The viral E6 coding region was sequenced to confirm the presence of tumor-specific viral isolates. Exons 5-9 of the TP53 gene were sequenced from 166 specimens. The hazard of death from HNSCC in patients with and without HPV-positive tumors was determined by proportional hazards regression analysis. RESULTS: HPV was detected in 62 (25%) of 253 cases (95% confidence interval [CI] = 19%-30%). High-risk, tumorigenic type HPV16 was identified in 90% of the HPV-positive tumors. HPV16 was localized specifically by in situ hybridization within the nuclei of cancer cells in preinvasive, invasive, and lymph node disease. Southern blot hybridization patterns were consistent with viral integration. Poor tumor grade (odds ratio [OR] = 2.4; 95% CI = 1.2- 4.9) and oropharyngeal site (OR = 6.2; 95% CI = 3.1-12.1) independently increased the probability of HPV presence. As compared with HPV-negative oropharyngeal cancers, HPV-positive oropharyngeal cancers were less likely to occur among moderate to heavy drinkers (OR = 0.17; 95% CI = 0.05-0.61) and smokers (OR = 0.16; 95% CI = 0.02-1.4), had a characteristic basaloid morphology (OR = 18.7; 95% CI = 2.1-167), were less likely to have TP53 mutations (OR = 0.06; 95% CI = 0.01-0. 36), and had improved disease-specific survival (hazard ratio [HR] = 0.26; 95% CI = 0.07-0.98). After adjustment for the presence of lymph node disease (HR = 2.3; 95% CI = 1.4- 3.8), heavy alcohol consumption (HR = 2.6; 95% CI = 1.4-4.7), and age greater than 60 years old (HR = 1.4; 95% CI = 0.8-2.3), all patients with HPV-positive tumors had a 59% reduction in risk of death from cancer when compared with HPV-negative HNSCC patients (HR = 0.41; 95% CI = 0.20-0.88). CONCLUSIONS: These data extend recent molecular and epidemiologic studies and strongly suggest that HPV-positive oropharyngeal cancers comprise a distinct molecular, clinical, and pathologic disease entity that is likely causally associated with HPV infection and that has a markedly improved prognosis.

Adolescent↗

PubMed1994

Beliefs about illness causality among preschoolers with cancer: evidence against immanent justice.

Evaluated whether preschoolers with cancer are more or less likely than their healthy counterparts to consider illness a form of punishment for misdeeds (immanent justice). It was found that a sample of preschoolers with cancer (n = 17) rejected immanent justice as a general cause of illness, both in themselves and in others, just as frequently as healthy controls (n = 17). Both groups also rejected immanent justice in cases where misbehavior was prolonged. Children with cancer demonstrated a view of illness causality based on greater differentiation between themselves and other people, in that they were more likely than healthy controls to accept immanent justice as a cause of illness in themselves but not others, and vice versa. Finally, nearly all of the children with cancer who accepted immanent justice as a general cause of illness in themselves also attributed their cancer specifically to immanent justice.

Child, Preschool↗

PubMed2005

Integrative gene-metabolite network with implemented causality deciphers informational fluxes of sulphur stress response.

The systematic accumulation of gene expression data, although revolutionary, is insufficient in itself for an understanding of system-level physiology. In the post-genomic era, the next cognitive step is linking genes to biological processes and assembling a mosaic of data into global models of biosystem function. A dynamic network of informational flows in Arabidopsis plants perturbed by sulphur depletion is presented here. With the use of an original protocol, the first biosystem response network was reconstructed from a time series of transcript and metabolite profiles, which, on the one hand, integrates complex metabolic and transcript data and, on the other hand, possesses a causal relationship. Using the informational fluxes within this reconstruction, it was possible to link system perturbation to response endpoints. Robustness and stress tolerance, as consequences of scale-free network topology, and hubs, as potential controllers of homeostasis maintenance, were revealed. Communication paths of propagating system excitement directed to physiological endpoints, such as anthocyanin accumulation and enforced root formation were dissected from the network. An auxin regulatory circuit involved in the control of a hypo-sulphur stress response was uncovered.

Arabidopsis↗

PubMed1996

Proteinuria and blood pressure as causal components of progression to end-stage renal failure. Northern Italian Cooperative Study Group.

AIMS: To identify the prognostic factors possibly related to end-stage renal failure development. SUBJECTS AND METHODS: The prognostic factors affecting chronic renal failure progression were analysed in 456 patients who had participated in a formal, multicentre, prospective randomized trial aimed at verifying the role of protein restriction in slowing down or halting the progression of chronic renal failure. The 24-month follow-up foreseen by the protocol was completed by 311 patients and 69 reached an end-point. An inductive analysis on patient survival was made by using the Cox proportional hazard regression model, using a stepwise procedure in order to select only those factors which are significantly associated with survival. For each individual risk factor, a univariate descriptive analysis of survival was performed using the Kaplan-Meier technique. RESULTS: Underlying nephropathy, baseline plasma creatinine, proteinuria, and plasma calcium were all shown to be related to end-stage renal failure onset. Hypertensive patients (mean blood pressure > 107 mmHg) had a worst cumulative renal survival but the degree of proteinuria was even more important as a prognostic factor of renal death than hypertension. The cumulative renal survival of patients whose proteinuria decreased during the trial follow-up was better than those of patients without changes. However, the interaction between baseline lying mean blood pressure and proteinuria was not significant. CONCLUSIONS: Only primary renal disease and proteinuria were related to renal survival, being baseline plasma creatinine confounding factor. By blocking the possible causal role of proteinuria and hypertension, end-stage renal failure could be prevented in a significant percentage of patients.

Adolescent↗

PubMed2002

Transformation and transposon mutagenesis of Leifsonia xyli subsp. xyli, causal organism of ratoon stunting disease of sugarcane.

Conditions have been developed for genetic transformation and insertional mutagenesis in Leifsonia xyli subsp. xyli (Lxx), the causal organism of ratoon stunting disease (RSD), one of the most damaging and intractable diseases of sugarcane internationally. Transformation frequencies ranged from 1 to 10 colony forming units (CFU)/microg of plasmid DNA using Clavibacter/Escherichia coli shuttle vectors pCG188, pDM302, and pDM306 and ranged from 50 to 500 CFU/microg using cosmid cloning vectors pLAFR3 and pLAFR5-km. The transformation/transposition frequency was 0 to 70 CFU/microg of DNA, using suicide vectors pUCD623 and pSUP2021 containing transposable elements Tn4431 and Tn5, respectively. It was necessary to grow Lxx in media containing 0.1% glycine for electroporation and to amplify large plasmids in a dam-/dcm- E. coli strain and purify the DNA by anion exchange. To keep selection pressure at an optimum, the transformants were grown on nitrocellulose filters (0.2-microm pore size) on media containing the appropriate antibiotics. Transposon Tn4431 containing a promoterless lux operon from Vibrio fischeri and a tetracycline-resistance gene was introduced on the suicide vector pUCD623. All but 1% of the putative transposon mutants produce light, indicating transposition into functional Lxx genes. Southern blot analysis of these transformants indicates predominantly single transposon insertions at unique sites. The cosmid cloning vector pLAFR5-km was stably maintained in Lxx. The development of a transformation and transposon mutagenesis system opens the way for molecular analysis of pathogenicity determinants in Lxx.

Base Sequence↗

PubMed1998

Soft tissue tumors following traumatic injury: two observations of interest for the medicolegal causality.

Two cases of tumors of the soft tissues developing at the site of a previous traumatic injury occurring a few years earlier are reported. One was finally diagnosed as aggressive fibromatosis and the other as low-grade fibrosarcoma. Among the pathogenic mechanisms and the etiologic factors involved in such tumors, the posttraumatic causality is discussed, and in addition to the initial trauma, the role of iterative surgery in the first case and mineral muscular inclusions in the second case are examined. The different therapeutic approaches of such lesions are also reviewed.

Back Injuries↗

PubMed1998

Testing a causal model of community-based education in the Sudan.

PURPOSE: To develop and test a model of community-based education. METHOD: In 1995, after developing a hypothesized causal model for community-based education, the authors collected data for 106 students at the University of Gezira, the Sudan, who had participated over three summers in an interdisciplinary field training research and rural development course. The students rated each other on leadership, interaction with the community, subject-matter contributions, and effort. Teaching staff assessed the readiness of the community to collaborate. The students' achievement was measured by short essays measuring knowledge, supervisors' assessments of the students' performances in the community, the community's observations of the students' activities, the community's satisfaction, and a group-produced report evaluated by faculty. The effect of the students' activities on the community was measured by comparing baseline and post-intervention community health data. The students also indicated their levels of interest in the community's problems. The authors analyzed the resulting covariances using structural-equations modeling. RESULTS: After minor adaptations, the model fitted the data reasonably well. The path coefficients were quite high, particularly among the peer ratings. Leadership had a potent effect on the outcome measures, as did, to a lesser extent, the readiness of the community to collaborate with the students. CONCLUSION: This study was the first reported attempt to test a model of community-based education. Although the fit of the data to the model in the study was reasonable, further study is needed to unearth additional important elements of community-based education. This article also discusses methodologic shortcomings of the present study, such as a possible "halo effect" in the peer ratings and the retrospective nature of many of the measurements.

Ambulatory Care Facilities↗

PubMed1988

The probability that a specific cancer and a specified radiation exposure are causally related.

It is fundamental that a given cancer case cannot be attributed with absolute certainty to a prior ionizing radiation exposure, whatever the level of exposure. It is possible to estimate the probability of a causal relationship based on data and models that have been inferred from group statistics. Two types of information are needed to make these probability calculations: natural cancer incidence rates and risks of cancer induction from ionizing radiation. Cancer incidence rates for the United States are available in the report of the Surveillance, Epidemiology and End Results (SEER) program of the National Cancer Institute. Estimates of the risk of cancer induction from ionizing radiation have been published by the Advisory Committee on the Biological Effects of Ionizing Radiation (BEIR) of the National Academy of Sciences, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and the International Commission on Radiological Protection (ICRP). Using the parameters discussed above, the probability of causation formulation estimates the probability that a person who develops a particular cancer after a known quantifiable radiation exposure has the cancer as a result of the exposure. In 1985, the National Institutes of Health, responding to a U.S. Congressional mandate, published radioepidemiologic tables using the probability-of-causation method.

Humans↗

PubMed1980

Social class and suitability for psychodynamic psychotherapy A causal Model.

A causal model is postulated to mediate the connection between patients' social class and therapists' evaluations of patients' suitability for psychodynamic psychotherapy. The model postulates that patients' social class gives rise to the learning of intellectual skills cognitive styles, which lead to ways of interacting verbally with others, which in turn result in therapists' evaluations of patients suitability. Thirty psychiatric outpatients were assessed therapists during the first therapy session. One mediational pathway was discovered as postulated by the model. This pathway was found to mediate the connection between patients' social class and their subsequent attendance in psychotherapy as well. Two unexpected pathways were found to mediate therapists' judgments of suitability, one of which also mediated patients' attendance in psychotherapy. These unexpected pathways are of particular interest for the clues they offer to the ways in which psychodynamic psychotherapy may be possible and rewarding with lower-class patients.

Adult↗

PubMed1994

Posttraumatic stress disorder among Vietnam Theater Veterans. A causal model of etiology in a community sample.

Data from the National Vietnam Veterans Readjustment Study, conducted from 1986 to 1988, were used to develop and cross-validate a model of the etiology of posttraumatic stress disorder (PTSD) among a community sample of 1198 male Vietnam theater veterans. The initial model specified causal paths among five sets of variables, ordered according to their historical occurrence: a) premilitary risk factors and traumas, b) war-related and non-war-related traumas during the military, c) homecoming reception, d) postmilitary traumas, and e) PTSD. The initial model was refined and then cross-validated, leading to the specification of a final model with highly satisfactory fit and parsimony. In terms of the magnitude of their contribution to the development of PTSD, lack of support from family and friends at the time of the homecoming and exposure to combat were the two most influential contributors. Other contributing factors, in order of importance, were Hispanic ethnicity, societal rejection at the time of homecoming, childhood abuse, participation in abusive violence, and family instability. Exposure to war-related and non-war-related traumas occurred largely independently of each other, with war-related traumas contributing substantially more than non-war-related traumas to the development of PTSD. Limitations to interpretation of the results are noted due to the retrospective nature of the data and the inevitable omission of other etiological factors.

Adult↗

PubMed1980

The relation between surgical volume and mortality: an exploration of causal factors and alternative models.

A previous study of 12 procedures of varying complexity in 1,498 hospitals identified a strong negative curvilinear relationship between the volume of a particular operation and postoperative mortality. The current study uses multiple regression techniques to explore the role of other potentially important variable and alternative interpretations of the volume-mortality relationship. The dependent variable is the difference between the hospital's actual death rate and its expected death rate based upon the riskiness of its case mix. The inclusion of other variables, such as size of hospital, teaching status, geographic location and cost, improves the fit of the regression, but does not diminish the importance of volume. There is no evidence that volume accumulated over 2 years is a better measure than volume in 1 year. Experience and volume of related operations are important in some cases but not others. Several likely alternative explanations for the observed relationship were not supported: larger hospitals and those with more house staff had outcomes that were worse than expected. Large geographic differences in mortality rates remain unexplained. A simultaneous-equation model is used to test whether higher volume leads to better outcomes or better outcomes lead to higher volumes. Both causal paths are supported, but their relative importance varies with the procedure in ways that are consistent with anticipated referral patterns.

Humans↗

PubMed1983

A causal model for physician utilization: analysis of Norwegian data.

This article contains a causal model for physician utilization in Norway. The model relates enabling factors, predisposing factors, and perceived illness to physician utilization in a linear structural equation model. Our aim has been to study the effect of variables other than perceived illness on physician utilization. The results of the analysis indicate that the number of disability days because of illness and psychologic well-being are almost exclusively the only important variables in the explanation of physician utilization in Norway.

Costs and Cost Analysis↗

PubMed2000

Inflammatory aneurysm and neurocysticercosis: further evidence for a causal relationship? Case report.

OBJECTIVE AND IMPORTANCE: Two cases of inflammatory aneurysms in patients with neurocysticercosis have been reported previously. Clinical and radiographic studies suggest a causal relationship. CLINICAL PRESENTATION: A man with neurocysticercosis presented with an acute subarachnoid hemorrhage from a left middle cerebral artery aneurysm. INTERVENTION: The patient underwent a craniotomy and clipping of his aneurysm. Diffuse inflammatory changes and multiple cysticercal cysts were found throughout the left sylvian fissure. CONCLUSION: The patient had an uneventful recovery. Angiography suggested an inflammatory rather than a congenital aneurysm. Although rare, neurocysticercosis may induce aneurysm formation in the appropriate setting.

Adult↗

PubMed2002

Bladder carcinoma in a transplant recipient: evidence to implicate the BK human polyomavirus as a causal transforming agent.

The BK polyomavirus (BKV) infects most of the human population, but clinically relevant infections are mostly limited to individuals who are immunosuppressed. In transplant recipients, BKV has been associated with ureteral stenosis, interstitial nephritis, and hemorrhagic cystitis. The role of BKV in the development of human tumors is intriguing but uncertain. BKV has been identified in various tumor types including urothelial carcinoma, but the ubiquitous presence of BKV as a latent infection has confounded efforts to validate any causal role in cancer development. We report the case of a simultaneous pancreas and kidney transplant recipient who developed BKV interstitial nephritis and carcinoma of the bladder with widespread metastases. High level expression of BKV large T antigen in the primary and metastatic carcinoma, but not in the nonneoplastic urothelium, implicates BKV as an etiologic agent in the development of this tumor.

BK Virus↗