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At least 199 records · Page 11Linked to original sources

PubMed1996

Usefulness of the protection motivation theory in explaining hearing protection device use among male industrial workers.

The present study examined the usefulness of personal variables: noise annoyance, and components of the protection motivation theory (R. W. Rogers, 1983) along with social-organizational factors in explaining hearing protection device (HPD) use among Israeli manufacturing workers. Participants were 281 men exposed to harmful noise levels for which routine HPD use is required by regulation. In practice, 3 HPD user groups were identified: nonusers (n = 38), occasional users (n = 125), and regular users (n = 118). HPD use was objectively verified. HPD use was primarily related to the personal variables but not to management pressure, coworker pressure, or family support. The most powerful predictors of HPD use were perceived self-efficacy (for long-term HPD use), perceived susceptibility (to hearing loss), and noise annoyance, together explaining 48% of the outcome variance. These findings have implications for interventions aimed at motivating workers to use HPDs regularly.

Adolescent↗

PubMed2000

On measures of explained variance in nonrecursive structural equation models.

Whereas measures of explained variance in a regression and an equation of a recursive structural equation model can be simply summarized by a standard R2 measure, this is not possible in nonrecursive models in which there are reciprocal interdependencies among variables. This article provides a general approach to defining variance explained in latent dependent variables of nonrecursive linear structural equation models. A new method of its estimation, easily implemented in EQS or LISREL and available in EQS 6, is described and illustrated.

Analysis of Variance↗

PubMed2001

Explaining employees' health care costs: a prospective examination of stressful job demands, personal control, and physiological reactivity.

The authors tested the ability of stressful demands and personal control in the workplace to predict employees' subsequent health care costs in a sample of 105 full-time nurses. Both subjective and objective measures of workload demands interacted with personal control perceptions in predicting the cumulative health care costs over the ensuing 5-year period. Tonic elevations in salivary cortisol, moreover, mediated the effects of demands and control on health care costs. Neither the job demands variables nor physiological reactivity measures, however, explained subsequent mental health. The results support findings from the epidemiological literature that demonstrate an important role for employees' control in explaining occupational inequalities in coronary heart disease and mortality. The authors argue that the results also encourage control-enhancing job design interventions by suggesting that their outcomes can benefit both organizations and their members.

Adult↗

PubMed2002

Does a prosocial-selfish distinction help explain the biological affects? Comment on Buck (1999).

R. Buck (1999) argued that a conceptual distinction between prosocial and selfish motivation is necessary to understand the biological affects (consciously experienced feelings and desires having an innate neurochemical basis). However, at a biological level of analysis, a prosocial-selfish distinction is doubtful empirically and conceptually. For this reason, Buck's proposed typology of biological affects is unclear. Moreover, a prosocial-selfish distinction is not necessary to explain hemispheric differences in brain activity associated with affect. In contrast, an approach-withdrawal distinction explains some data uniquely well, although numerous exceptions imply that simple models are inadequate. To extend hemispheric models of experienced emotion, a prosocial-selfish distinction is unlikely to be explanatory, whereas an alternative account based on a distinction between verbal and nonverbal working memory may be useful.

Affect↗

PubMed2001

Mineral disequilibrium in lavas explained by convective self-mixing in open magma chambers.

Characteristic features of many porphyritic andesite and dacite lavas are that they are rich in crystals and display a range of disequilibrium features, including reversely zoned crystals, resorption surfaces, wide ranges of mineral compositions and minerals which are not in equilibrium with the surrounding rock matrix. These features are often interpreted as evidence of the mixing of magmas of contrasting composition, temperature and origin. Here, however, we propose that such features can also be caused by convection within a magma body with a single composition, that is heated from below and cooled from above. We describe petrological observations of andesite lava erupted at the Soufrière Hills volcano, Montserrat, which indicate a heating event and the intermingling of crystals that have very different thermal histories. We present experimental data on a representative groundmass composition of this lava, which indicate that it is difficult to explain the calcic compositions of plagioclase overgrowth rims and microphenocrysts unless parts of the magma were at temperatures much higher than the inferred average temperature. The concept of convective self-mixing allows us to explain the occurrence of compositions of minerals that apparently cannot coexist under equilibrium conditions.

Journal Article↗

PubMed2001

Himalayan tectonics explained by extrusion of a low-viscosity crustal channel coupled to focused surface denudation.

Recent interpretations of Himalayan-Tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the Tibetan plateau, and that ductile extrusion of high-grade metamorphic rocks between coeval normal- and thrust-sense shear zones can explain exhumation of the Greater Himalayan sequence. Here we use coupled thermal-mechanical numerical models to show that these two processes-channel flow and ductile extrusion-may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low-viscosity material. Our models provide an internally self-consistent explanation for many observed features of the Himalayan-Tibetan system.

Journal Article↗

PubMed1994

Embryonic growth and the evolution of the mammalian Y chromosome. II. Suppression of selfish Y-linked growth factors may explain escape from X-inactivation and rapid evolution of Sry.

The mammalian Y chromosome may be an attractor for selfish growth factors. A suppressor of the selfish growth effects would be expected to spread were it to have an appropriate parent-specific expression rule. A suppressor could act by boosting the resource demands of competing female embryos. This possibility may explain incidences of the escape from X-inactivation and provides a rationale for why these genes typically have Y-linked homologues. Alternatively, a suppressor could act to decrease the resource demands of males with the selfish Y. This possibility is supported by the finding that the size of male, but not female, human infants is negatively correlated to the number of X chromosomes. A protracted arms race between a selfish gene and its suppressor may ensue. Both the variation in copy number of Zfy and the unusually fast sequence evolution of Sry may be explained by such an arms race. As required by the model, human Sry is known to have an X-linked suppressor. Preliminary evidence suggests that, as predicted, rapid sequence evolution of Sry may be correlated with female promiscuity. The case for fast sequence evolution as the product of maternal/foetal conflict is strengthened by consideration of the rapid evolution of placental lactogens in both ruminants and rodents.

Animals↗

PubMed2002

Segregation at three loci explains familial and population risk in Hirschsprung disease.

Hirschsprung disease (HSCR), the most common hereditary cause of intestinal obstruction, shows considerable variation and complex inheritance. Coding sequence mutations in RET, GDNF, EDNRB, EDN3 and SOX10 lead to long-segment (L-HSCR) and syndromic HSCR but fail to explain the transmission of the much more common short-segment form (S-HSCR). We conducted a genome scan in families with S-HSCR and identified susceptibility loci at 3p21, 10q11 and 19q12 that seem to be necessary and sufficient to explain recurrence risk and population incidence. The gene at 10q11 is probably RET, supporting its crucial role in all forms of HSCR; however, coding sequence mutations are present in only 40% of linked families, suggesting the importance of noncoding variation. Here we show oligogenic inheritance of S-HSCR, the 3p21 and 19q12 loci as RET-dependent modifiers, and a parent-of-origin effect at RET. This study demonstrates by a complete genetic dissection why the inheritance pattern of S-HSCR is nonmendelian.

Alleles↗

PubMed2003

The crystal structure of the proprotein processing proteinase furin explains its stringent specificity.

In eukaryotes, many essential secreted proteins and peptide hormones are excised from larger precursors by members of a class of calcium-dependent endoproteinases, the prohormone-proprotein convertases (PCs). Furin, the best-characterized member of the mammalian PC family, has essential functions in embryogenesis and homeostasis but is also implicated in various pathologies such as tumor metastasis, neurodegeneration and various bacterial and viral diseases caused by such pathogens as anthrax and pathogenic Ebola virus strains. Furin cleaves protein precursors with narrow specificity following basic Arg-Xaa-Lys/Arg-Arg-like motifs. The 2.6 A crystal structure of the decanoyl-Arg-Val-Lys-Arg-chloromethylketone (dec-RVKR-cmk)-inhibited mouse furin ectodomain, the first PC structure, reveals an eight-stranded jelly-roll P domain associated with the catalytic domain. Contoured surface loops shape the active site by cleft, thus explaining furin's stringent requirement for arginine at P1 and P4, and lysine at P2 sites by highly charge-complementary pockets. The structure also explains furin's preference for basic residues at P3, P5 and P6 sites. This structure will aid in the rational design of antiviral and antibacterial drugs.

Amino Acid Sequence↗

PubMed2003

Palliative chemotherapy or best supportive care? A prospective study explaining patients' treatment preference and choice.

In palliative cancer treatment, the choice between palliative chemotherapy and best supportive care may be difficult. In the decision-making process, giving information as well as patients' values and preferences become important issues. Patients, however, may have a treatment preference before they even meet their medical oncologist. An insight into the patient's decision-making process can support clinicians having to inform their patients. Patients (n=207) with metastatic cancer, aged 18 years or older, able to speak Dutch, for whom palliative chemotherapy was a treatment option, were eligible for the study. We assessed the following before they consulted their medical oncologist: (1) socio-demographic characteristics, (2) disease-related variables, (3) quality-of-life indices, (4) attitudes and (5) preferences for treatment, information and participation in decision-making. The actual treatment decision, assessed after it had been made, was the main study outcome. Of 207 eligible patients, 140 patients (68%) participated in the study. At baseline, 68% preferred to undergo chemotherapy rather than wait watchfully. Eventually, 78% chose chemotherapy. Treatment preference (odds ratio (OR)=10.3, confidence interval (CI) 2.8-38.0) and a deferring style of decision-making (OR=4.9, CI 1.4-17.2) best predicted the actual treatment choice. Treatment preference (total explained variance=38.2%) was predicted, in turn, by patients' striving for length of life (29.5%), less striving for quality of life (6.1%) and experienced control over the cause of disease (2.6%). Patients' actual treatment choice was most strongly predicted by their preconsultation treatment preference. Since treatment preference is positively explained by striving for length of life, and negatively by striving for quality of life, it is questionable whether the purpose of palliative treatment is made clear. This, paradoxically, emphasises the need for further attention to the process of information giving and shared decision-making.

Adult↗

PubMed1998

Explaining the effect of ethnic group on weight concern: finding a role for family values.

OBJECTIVE: To examine the impact of ethnic group on aspects of weight concern and to assess the role of family values in explaining this association. SUBJECTS AND MEASURES: 20 Asian and 20 white daughters gave a questionnaire to their mother, father and sibling closest in age, concerning their profile characteristics (age, education) values and beliefs and completed a matched questionnaire containing additional measures of aspects of their weight concern. RESULTS: The results showed no differences between the white and Asian daughters in terms of either their restrained eating or body dissatisfaction. However, the results showed consistent differences between the members of the two family groups in terms of the value placed on achievement, child/parent relationships, competition, the role of women, and some differences in terms of materialism, the value of appearance and their idea of the perfect female body. The results were then analysed to assess the best predictors of the daughter's weight concern. Whereas restrained eating was related to the mother's rating of the value of physical appearance and the sibling's ratings of competitiveness and a non-traditional role for women (40% of the variance), the results showed that body dissatisfaction was related to the daughter's rating of materialism, having a father who preferred a thinner female body, the siblings ratings of a non-traditional role for women, degree of concordance within the family concerning the value of competitiveness and the educational level of the 'head of the family' (49% of variance). CONCLUSION: Whereas a dichotomous model of ethnicity may be insufficient to explain differences in aspects of weight concern, an expanded model of cultural beliefs may be a more powerful construct. Accordingly, the absence or presence of differences in weight concern according to ethnic group may simply reflect the extent to which the different groups chosen for analysis are differentiated by these predictive values.

Adolescent↗

PubMed2001

Utility of health belief model as a guide for explaining or predicting breast cancer screening behaviours.

AIM: The purpose of this study was to assess the utility of HBM as a theoretical guide for predicting breast cancer screening and therefore for guiding intervention studies. BACKGROUND: Breast cancer is the leading cause of death for middle age women (35-50) and the second leading cause of cancer deaths in all women in the United States (US). Early detection of breast cancer through screening is the only option available to women. However, less than half of all women in the US participate in screening. The health belief model (HBM), which specifies interactions of values and beliefs about health and their influence on choices, has been widely used to explain screening behaviour. METHODS: An integrative research review analysed 16 published descriptive studies employing HBM. Literature was located through a search of research based studies listed in Cumulative Index of Nursing and Allied Health (CINAHL), Medline, and cancer literature databases and studies cited in other references between 1990 and 1999. FINDINGS: Application of HBM was inconsistent. No study tested nonlinear relationships between variables as specified in the model. At best, the model explained 47% of the variance in screening behaviour when socioeconomic status was included. Otherwise predictive power was low, ranging from 15 to 27%. CONCLUSIONS: While the model provides some description of the values, beliefs and behaviours of middle-aged women primarily, HBM does not appear to have the power to consistently predict behaviours. Further research is needed to provide more thorough depiction of the social, nonhealth care meaning of breast cancer.

Adult↗

PubMed2003

A QSAR analysis to explain the analgesic properties of Aconitum alkaloids.

Aconitum roots are traditionally prescribed for the management of different types of painful affections in Asiatic countries. A quantitative structure-activity relationship (QSAR) analysis was performed to study the effect of chemical substitutes in the analgesic potency of alkaloids available in Chinese Aconitum roots. Using the CAChe program package for biomolecules, molecular modelling was performed in 12 alkaloids previously tested in a model of acetic acid-induced writhing in rats. The ED50 (micromol/kg) was used as the activity parameter. Structural parameters were compared between alkaloids with an aroyl/aroyloxy group at R14 and alkaloids with the aroyloxy group at R4. Single linear regression analyses were performed in order to find the parameters explaining activity. Alkaloids with an aroyl/aroyloxy group at R14 exhibited the highest potency (significantly less ED50). The stability parameters were different between groups, e.g. total energy was -8.0 +/- 0.4 in the potent analgesic alkaloids and -6.7 +/- 0.3 in the weak analgesic alkaloids (P = 0.001). The reactivity index of C2', C3' and C5' of the aromatic ring was also different between groups, e.g. the reactivity index of C5' was 40.8 +/- 0.6 in potent analgesic alkaloids and 48.1 +/- 0.6 in weaker analgesic alkaloids (P < 0.001). Several structural parameters explained analgesic activity of alkaloids, being the reactivity index of C5' on the aromatic group the most important factor (r = 0.89; P < 0.001).

Aconitum↗

PubMed1998

Assimilation of achromatic color cannot explain the brightness effects in the achromatic neon effect.

If the mouths of the pacmen of a Kanizsa square are colored, for example red, then an illusory red transparent square is seen. In many visual theories such 'neon color spreading' is explained by assimilation of chromatic and achromatic color. In this paper the achromatic case was investigated. In a two-alternative forced-choice task thirty observers judged the brightness of achromatic neon figures. The results suggest that assimilation of achromatic color inside and/or outside of the illusory figures cannot explain the brightness effects seen in achromatic neon color spreading. Although these displays may produce assimilation, it appears that contrast (perhaps acting nonlocally) is a stronger influence on their perceived brightness.

Color Perception↗

PubMed2001

Perceptual continuation and depth in visual phantoms can be explained by perceptual transparency.

We try to explain perceptual continuation and depth in the visual-phantom illusion in terms of perceptual transparency. Perceptual continuation of inducing gratings across the occluder in stationary phantoms could be explained with unique transparency, a notion proposed by Anderson (1997 Perception 26 419-453). This view is consistent with a number of previous reports including that of McCourt (1994 Vision Research 34 1609-1617) who criticized the stationary phantom illusion from the viewpoint of his counterphase lightness induction or grating induction, which might involve invalid transparency. Here we confirm that the photopic phantom illusion (Kitaoka et al, 1999 Perception 28 825-834) really gives in-phase lightness induction and involves bistable transparency. It is thus suggested that perceptual continuation and depth in the visual-phantom illusion depend on perceptual transparency.

Analysis of Variance↗

PubMed2002

Neuronal deactivation explains decreased cerebellar blood flow in response to focal cerebral ischemia or suppressed neocortical function.

Functional neuroimaging in humans with acute brain damage often reveals decreases in blood flow and metabolism in areas unaffected by the lesion. This phenomenon, termed diaschisis, is presumably caused by disruption of afferent excitatory input from the lesioned area to other brain regions. By characterizing its neurophysiological basis, we used cerebellar diaschisis to study the relationship between electrical activity and blood flow during decreased neuronal activity. Here we show that focal cerebral ischemia in rats causes diaschisis in the cerebellar cortex characterized by pronounced decreases in Purkinje cell spiking activity and small decreases in cerebellar blood flow. The findings were explained by decreased excitatory input to the cerebellar cortex, i.e., deactivation, as cerebellar neuronal excitability and vascular reactivity were preserved. Functional ablation of the cerebral cortex by either spreading depression or tetrodotoxin reproduced the changes in cerebellar function with complete recovery of Purkinje cell activity and cerebellar blood flow concomitant with recovery of neocortical function. Decreases of activity involving the contralateral frontal cortex produced the largest decrease in cerebellar electrical activity and blood flow. Our data suggest that deactivation explains the decreases in blood flow and metabolism in cerebellar diaschisis observed in human neuroimaging studies. Decreases in spiking activity were 3-7 times larger than the respective decreases in flow. Therefore, under pathological conditions, neuroimaging methods based on hemodynamic signals may only show small changes, although the underlying decrease in neuronal activity is much larger.

Animals↗

PubMed2002

The observed human sperm mutation frequency cannot explain the achondroplasia paternal age effect.

The lifelong spermatogonial stem cell divisions unique to male germ cell production are thought to contribute to a higher mutation frequency in males. The fact that certain de novo human genetic conditions (e.g., achondroplasia) increase in incidence with the age of the father is consistent with this idea. Although it is assumed that the paternal age effect is the result of an increasing frequency of mutant sperm as a man grows older, no direct molecular measurement of the germ-line mutation frequency has been made to confirm this hypothesis. Using sperm DNA from donors of different ages, we determined the frequency of the nucleotide substitution in the fibroblast growth factor receptor 3 (FGFR3) gene that causes achondroplasia. Surprisingly, the magnitude of the increase in mutation frequency with age appears insufficient to explain why older fathers have a greater chance of having a child with this condition. A number of alternatives may explain this discrepancy, including selection for sperm that carry the mutation or an age-dependent increase in premutagenic lesions that remain unrepaired in sperm and are inefficiently detected by the PCR assay.

Achondroplasia↗

PubMed2001

Explaining mortality rate plateaus.

We propose a stochastic model of aging to explain deviations from exponential growth in mortality rates commonly observed in empirical studies. Mortality rate plateaus are explained as a generic consequence of considering death in terms of first passage times for processes undergoing a random walk with drift. Simulations of populations with age-dependent distributions of viabilities agree with a wide array of experimental results. The influence of cohort size is well accounted for by the stochastic nature of the model.

Aging↗