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PubMedDate not supplied

Cardinal vein isomerism: an embryological hypothesis to explain a persistent left superior vena cava draining into the roof of the left atrium in the absence of coronary sinus and atrial septal defect.

BACKGROUND: A persistent left superior vena cava (PLSVC) is a relatively frequent systemic venous anomaly associated with congenital heart defects. This anomaly has been explained with the persistence of the left superior cardinal vein. PLSVC usually drains into the right atrium, via coronary sinus, but it joins the left atrium in approximately 8% of the cases either directly in the setting of atrial isomerism, or via an unroofed coronary sinus, or through a coronary sinus type atrial septal defect. CASE REPORT: We describe a case of an adult patient with atria in the situs solitus, PLSVC draining into the left atrium, atresia of coronary sinus without atrial septal defect, and with additional cardiac anomalies (ventricular septal defect and discrete subaortic stenosis). CONCLUSION: A possible embryological explanation to this case rises from a right partial isomerism of the superior cardinal veins, which gives reason for both the coexistence of the PLSVC draining into the left atrium and the absence of coronary sinus, atrial septal defect, or coronary sinus ostium.

Adult↗

PubMed2002

Conflicting molecular phylogenies of European long-eared bats (Plecotus) can be explained by cryptic diversity.

Conflicting phylogenetic signals of two data sets that analyse different portions of the same molecule are unexpected and require an explanation. In the present paper we test whether (i) differential evolution of two mitochondrial genes or (ii) cryptic diversity can better explain conflicting results of two recently published molecular phylogenies on the same set of species of long-eared bats (genus Plecotus). We sequenced 1714bp of three mitochondrial regions (16S, ND1, and D-loop) of 35 Plecotus populations from 10 European countries. A likelihood ratio test revealed congruent phylogenetic signals of the three data partitions. Our phylogenetic analyses demonstrated that the existence of a previously undetected Plecotus lineage caused the incongruities of previous studies. This lineage is differentiated on the species level and lives in sympatry with its sister lineage, Plecotus auritus, in Switzerland and Northern Italy. A molecular clock indicates that all European Plecotus species are of mid or late Pliocene origin. Plecotus indet. was previously described as an intergrade between P. auritus and Plecotus austriacus since it shares morphological characters with both. It is currently known from elevations above 800 m a.s.l. in the Alps, the Dinarian Alps and the Pindos mountains in Greece. Since we could demonstrate that incongruities of two molecular analyses simply arose from the mis-identification of one lineage, we conclude that molecular phylogenetic analyses do not free systematists from a thorough inclusion of morphological and ecological data.

Animals↗

PubMed2001

The psychology of social chess and the evolution of attribution mechanisms: explaining the fundamental attribution error.

Theory of mind is the field devoted to understanding how organisms discern the mental states of others. Because mental states are not directly observable, they can only be inferred from observable features of the actor (such as behavior) and the situational context that the actor is in. Social psychologists, who study theory of mind processes under the rubric of attribution research, have shown that people often make a logical error of inference: The "fundamental attribution error" (FAE) is the tendency to assume that an actor's behavior and mental state correspond to a degree that is logically unwarranted by the situation. The social environment in which theory of mind capacities evolved may have influenced attributional processing in ways that could explain the error. In particular, the error could be caused by a psyche that is designed (1) to consider only those noncorresponding mental states (such as deception) that could have fitness consequences to the mind reader; (2) to bias inferences in a way that reduces the costs of erroneous inferences; or (3) to bias inferences in a way that yields reputational benefits. The existing literature is reviewed in light of these hypotheses.

Journal Article↗

PubMed2000

Does paternal uncertainty explain discriminative grandparental solicitude? A cross-cultural study in Greece and Germany.

Recent research on kin investment as a reproductive strategy is based on the idea that differences in grandparental caregiving directly reflect degrees of differential grandpaternal versus grandmaternal certainty. In a cross-cultural study in Greece and Germany, 544 subjects (318 Greeks, 208 Germans, 18 of other origins) were asked for an assessment of their grandparents' (GPs') caregiving. In Germany and urban Greece (modern Western societies), the maternal GPs were rated as more intensive caregivers than the paternal GPs, but this was not the case in rural Greece, where paternal GPs provided more care. However, in all groups, grandmothers were more caring than grandfathers. Thus, contrary to previous theory and research, these two effects must be clearly distinguished, and may be explained by (1) more intense female caregiving in humans (as in other viviparous mammals) and (2) a socially engendered favoring of maternal relatives in Western industrial societies as opposed to the favoring of paternal GPs seen in the patrilateral culture of rural Greece.

Journal Article↗

PubMed2003

2- and 8-alkynyladenosines: conformational studies and docking to human adenosine A3 receptor can explain their different biological behavior.

Adenosine (Ado) derivatives substituted at the C2 position with an alkynyl chain are endowed with high affinity for A(1), A(2A) and A(3) human adenosine receptors, while being less active at the low affinity A(2B) subtype. On the other hand, the introduction of an alkynyl chain at the C8 position of adenosine is detrimental for the affinity and potency at A(1), A(2A), and A(2B) receptors, while is more tolerated by the A(3) receptor. The evaluation of the stimulation of [35S]GTPgammaS binding revealed that 2-alkynyladenosines behave as adenosine receptors agonists while, on the contrary, 8-alkynyladenosines behave as antagonists. With this work we demonstrated, by means of an NMR-based and a computational conformational analysis, that 8-alkynyladenosines, differently from 2-alkynyladenosines, cannot adopt the sugar-base anti conformation required for adenosine receptor activation.Furthermore, using the recently reported X-ray crystal structure of bovine rhodopsin as template, we built a 3D model of the seven transmembrane domains of the human adenosine A(3) receptor with the homology modeling. After identification of the binding site we carried out docking experiments, demonstrating that the two class of molecules have different binding modes that explain their different degree of affinity and the shift of their activity from agonism to antagonism.

Adenosine↗

PubMed2001

A common phosphate binding site explains the unique substrate specificity of GSK3 and its inactivation by phosphorylation.

The inhibition of GSK3 is required for the stimulation of glycogen and protein synthesis by insulin and the specification of cell fate during development. Here, we demonstrate that the insulin-induced inhibition of GSK3 and its unique substrate specificity are explained by the existence of a phosphate binding site in which Arg-96 is critical. Thus, mutation of Arg-96 abolishes the phosphorylation of "primed" glycogen synthase as well as inhibition by PKB-mediated phosphorylation of Ser-9. Hence, the phosphorylated N terminus acts as a pseudosubstrate, occupying the same phosphate binding site used by primed substrates. Significantly, this mutation does not affect phosphorylation of "nonprimed" substrates in the Wnt-signaling pathway (Axin and beta-catenin), suggesting new approaches to design more selective GSK3 inhibitors for the treatment of diabetes.

Amino Acid Sequence↗

PubMed1998

Explaining geographies of health care: a critique.

This paper considers the ways in which geographers have sought to explain the spatial organisation of health care services. It does so at three interlocking scales: the global/international, the national, and the local. It considers the substantive adequacy and explanatory problems associated with different perspectives and also discusses the normative implications of alternative interpretations of patterns of health care services. The paper notes the ways in which some conventional geographies of health care, which seemed to postulate convergence towards greater egalitarianism in service provision between and within states, have been challenged by changing economic circumstances, and by a changing political and intellectual agenda. The paper also considers some emerging geographies of community-based struggles around health services and discusses their potential and limitations. Finally there is a discussion of the potential contribution, if any, of a distinctively geographical perspective on health care.

Delivery of Health Care↗

PubMed2004

Tyrosinase kinetics: discrimination between two models to explain the oxidation mechanism of monophenol and diphenol substrates.

The kinetic behaviour of tyrosinase is very complex because the enzymatic oxidation of monophenol and o-diphenol to o-quinones occurs simultaneously with the coupled non-enzymatic reactions of the latter. Both reaction types are included in the kinetic mechanism proposed for tyrosinase (Mechanism I [J. Biol. Chem. 267 (1992) 3801-3810]). We previously confirmed the validity of the rate equations by the oxidation of numerous monophenols and o-diphenols catalysed by tyrosinase from different fruits and vegetables. Other authors have proposed a simplified reaction mechanism for tyrosinase (Mechanism II [Theor. Biol. 203 (2000) 1-12]), although without deducing the rate equations. In this paper, we report new experimental work that provides the lag period value, the steady-state rate, o-diphenol concentration released to the reaction medium. The contrast between these experimental data and the respective numerical simulations of both mechanisms demonstrates the feasibility of Mechanism I. The need for the steps omitted from Mechanism II to interpret the experimental data for tyrosinase, based on the rate equations previously deduced for Mechanism I is explained.

Agaricales↗

PubMed2001

Response priming in a go/nogo task: do we have to explain the go/nogo N2 effect in terms of response activation instead of inhibition?

OBJECTIVES: In the present study, we examined the effects of response priming on the event-related potentials (ERPs) evoked by target stimuli in a go/nogo task. METHODS: In each trial, subjects were presented a cue and a target stimulus. The cue informed subjects about the following target in that trial, and therefore, also about the kind of response (right-hand response, left-hand response, no overt response) potentially to be given in that trial. RESULTS: The traditional N2 and P3 go/nogo effects were replicated: the ERPs to nogo targets were negative compared to the ERPs evoked by go targets in the N2 latency range at frontal electrode sites, and the nogo P3s were more anteriorly distributed than the go P3s. Comparing the ERPs evoked by nogo targets, we found the P3, but not the N2, to be modulated by response priming. CONCLUSIONS: These results seem to indicate that the P3, but not the N2, is associated with response inhibition, or with an evaluation/decision process with regard to the expected and/or given response. It could be speculated that the traditional go/nogo N2 effect has to be explained in terms of response activation instead of response inhibition.

Adult↗

PubMed2003

Could TCR antagonism explain associations between MHC genes and disease?

Alleles of major histocompatibility complex (MHC) loci are associated with certain types of diseases, including those of infectious and autoimmune origin. MHC products can promote susceptibility or resistance to disease by stimulating or inhibiting immune responses. Recent evidence suggests that MHC-associated peptides derived from self-proteins can act as antagonists of T-cell activation, thereby inhibiting immune responses to antigens. We suggest that self-peptide-promoted antagonism might explain some associations between MHC alleles and particular chronic diseases.

Disease Susceptibility↗

PubMed2003

Complex regional pain syndrome: mystery explained?

Complex regional pain syndrome (CRPS) is the result of changes to the somatosensory systems that process noxious, tactile, and thermal information; to the sympathetic systems that innervate skin (blood vessels, sweat glands); and to the somatomotor systems. The changes suggest that the CNS representations of the systems have been altered. Patients with CRPS also have peripheral changes (eg, oedema, signs of inflammation, sympathetic-afferent coupling [the basis for sympathetically maintained pain], and trophic changes) that cannot be explained by central changes. On the basis of clinical observation and research in human beings and animals, we hypothesise that CRPS is a systemic disease involving the CNS and peripheral nervous system. The most important question for future research is what causes CRPS? In this article, we suggest a change to the focus of research efforts and treatment. We also suggest there be diagnostic reclassification and redefinition of CRPS.

Animals↗

PubMedDate not supplied

Usefulness of psychosocial theory variables in explaining fat-related dietary behavior in Chinese Americans: association with degree of acculturation.

OBJECTIVE: To determine the usefulness of variables from psychosocial models of health behavior in explaining fat-related dietary behavior among a sample of Chinese Americans. DESIGN: A survey questionnaire was administered to a convenience sample of Chinese Americans and analyzed for descriptive statistics and relationships among variables. SUBJECTS/SETTINGS: Participants were 600 healthy individuals, ranging from 25 to 70 years of age, living in New York City. VARIABLES MEASURED: Demographic factors, degree of acculturation, food preferences, and 13 social psychological scales derived from the Theory of Planned Behavior, the Healthy Belief Model, and Social Cognitive Theory. Dependent measures assessed were intention to reduce dietary fat and behaviors related to the selection of reduced-fat diets. STATISTICAL ANALYSES: Descriptive statistics, Pearsons' correlation coefficients, t-tests, one-way analyses of variance, and multiple regression analyses were used. RESULTS: Attitude, overall health concern, and self-efficacy accounted for 58% of the variance in behavioral intention for the entire sample. Attitude, perceived barriers, and self-efficacy accounted for 19% of the variance in the prediction of dietary fat reduction behaviors. In general, a gradient was seen in the increased predictiveness of each regression model by degree of acculturation of the immigrants to American culture: predictiveness (R2) for behavior ranged from 15% for the least to 34% for the most acculturated. Acculturation was significantly related to declines in the influence of habit and of social norms. These effects were not seen by length of residency. IMPLICATIONS: Nutrition educators should assess the degree of acculturation of groups with whom they work and recognize that the degree of acculturation impacts the relative importance of various psychosocial variables in fat reduction behaviors.

Acculturation↗

PubMed2002

Does segmental difference in alpha 1-adrenoceptor subtype explain contractile difference in rat abdominal and thoracic aortae?

The cyclooxygenase inhibitor, indomethacin, depresses adrenergic agonist constriction of endothelium-denuded rat abdominal, but not thoracic, aorta. In order to explain this finding, we explored the possibility of segmental differences in the population of alpha 1-adrenoceptor (AR) subtypes. In endothelium-denuded tissues, phenylephrine elicited concentration-dependent contractions in the thoracic and abdominal aortic rings with potencies and maximal effects that, respectively, did not differ significantly (P > .05). Indomethacin (1 x 10(-5) M) inhibited phenylephrine-induced contractions only in abdominal aorta. The subtype-selective alpha 1D-AR antagonist, BMY 7378, was found to antagonize contractions to phenylephrine competitively in abdominal (pA2 8.44) and thoracic (pA2 8.56) aortic rings. These data are consistent with published alpha 1D-AR functional potency and clonal alpha 1D-AR binding affinity. In addition, cumulative concentration-contraction curves for phenylephrine were competitively antagonized in the rat abdominal and thoracic aortae by prazosin, 5-methylurapidil and WB 4101, with pA2 values of 9.39 and 9.61, 7.64 and 7.85, and 9.43 and 9.58, respectively. These compounds with varying degrees of subtype selectivity inhibited contractions of the thoracic and abdominal aortae with affinities consistent with those determined at the alpha 1D-AR subtype. The results of this study suggest that the contraction to phenylephrine of the rat abdominal and thoracic aorta is mediated via the same alpha 1D-AR subtype.

Adrenergic alpha-Agonists↗

PubMed2003

ADMA: a novel risk factor that explains excess cardiovascular event rate in patients with end-stage renal disease.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase. By competitively displacing L-arginine from the substrate binding site of NO synthase, ADMA interferes with many of the physiological functions of NO, like endothelium-dependent vasodilation and leukocyte adhesion. ADMA, like its biologically inactive regioisomer, symmetric dimethylarginine (SDMA), can be found in human plasma and urine in low concentrations. The concentrations of both dimethylarginines are increased in patients with end-stage renal disease, which may explain at least in part endothelial dysfunction and cardiovascular complications in this patient population. In addition, the metabolism of ADMA, but not SDMA, occurs via hydrolytic degradation to citrulline and dimethylamine by the enzyme dimethylarginine dimethylaminohydrolase (DDAH). Data from experimental studies suggest that ADMA inhibits vascular NO elaboration at concentrations that can be measured in plasma of patients with renal disease. Interestingly, ADMA and SDMA are poorly eliminated during hemodialysis. This is probably due to a high level of binding of both molecules to plasma proteins. High ADMA concentrations in patients with end-stage renal disease may contribute to their excess cardiovascular event rate, as in clinical studies a relationship between ADMA and carotid artery intimal thickening was found. Moreover, in a prospective study we demonstrated recently that determination of ADMA plasma concentration is useful to predict future cardiovascular event rate and total mortality in this patient population. As other researchers reported observations that are in line with our findings, there is evidence that ADMA may be a novel cardiovascular risk factor.

Arginine↗

PubMed1995

Height and body mass index in Oslo, Norway, compared to other regions of Europe: do they explain differences in the incidence of hip fracture? European Vertebral Osteoporosis Study Group.

Lean body stature and tallness have both been identified as risk factors for hip fracture. In this study, height and weight data from a multinational multicenter study were used to compare Oslo, which has some of the highest incidence rates of hip fracture ever reported, to other regions of Europe, with respect to height and body mass index. More than 17,000 subjects in six age strata (50-54, 55-59, 60-64, 65-69, 70-74, 75+ years) from 36 centers in 19 European countries were enrolled in the European Vertebral Osteoporosis Study (EVOS), which included standardized height and weight measurements. We found that men in Oslo were 4.3 cm taller than men in western Europe, 5.0 cm taller than men in eastern Europe, and 8.6 cm taller than men in southern Europe. Oslo women were also taller, by 2.2 cm compared to women in western Europe, 2.7 cm compared to women in eastern Europe, and 5.2 cm compared to women in southern Europe. In all age groups, except women aged 55-59 years, mean body mass index (BMI) was lowest in Oslo. Nearly twice as many had a BMI less than 22.0 kg/m2 in Oslo compared to the other regions combined (11.1% vs. 6.6% in men and 19.2% vs. 9.9% in women). This study indicates that the people of Oslo are taller and leaner than people in other regions of Europe. This may in part explain the higher incidence of hip fracture in the population of Oslo.

Aged↗

PubMed1993

Parental origin of mutant allele does not explain absence of gene dose in X-linked Hyp mice.

The expectation for a gene dose effect in an X-linked phenotype is that the corresponding metrical trait in heterozygous females will lie between values for affected hemizygous males and unaffected males and females. We made sequential measurements (at 30, 60, 90, 120 and 150 days) of serum phosphate concentration and tail length in mice with X-linked hypophosphatemia (genotypes: Hyp/Y, Hyp/+ and Hyp/Hyp) and in their normal litter-mates (genotypes: +/Y, +/+). We also measured renal mitochondrial 25-hydroxyvitamin D3-24-hydroxylase (24-hydroxylase) activity in 5 to 7-month-old mice fed control and low phosphate diets and representing all five genotypes. The animals were obtained by controlled breeding under uniform environmental conditions. The mutant animals all had uniformly and significantly lower serum phosphate levels, shorter tail length and higher 24-hydroxylase activity relative to unaffected litter-mates. There was no evidence of a gene dose effect because values were not significantly different among the three mutant genotypes. We also studied the influence of gamete of origin on serum phosphate, tail length and renal mitochondrial 24-hydroxylase activity in the Hyp/+ offspring of affected males (Hyp/Y) or affected females (Hyp/+ or Hyp/Hyp). We found no effect on the distribution of trait values. We conclude that parental origin of mutant allele does not explain the absence of a gene dose effect in Hyp mice.

Alleles↗

PubMed2004

The IGF2-intron3-G3072A substitution explains a major imprinted QTL effect on backfat thickness in a Meishan x European white pig intercross.

A paternally expressed QTL for muscle growth and backfat thickness (BFT) has previously been identified near the IGF2 locus on the distal tip of pig chromosome 2 (SSC2p) in three experimental F2 populations. Recently, a mutation in a regulatory element of the IGF2 gene was identified as the quantitative trait nucleotide (QTN) underlying the major QTL effect on muscle growth and BFT in crosses between Large White and Wild Boar or Pietrain. This study demonstrates that the IGF2 mutation also controls the paternally expressed QTL for backfat thickness in a cross between Meishan and European Whites. In addition, a comparison of QTL of backfat thickness measured by Hennessy grading probe (HGP) and by ultrasound measurement (USM) was made. In the USM analyses, the IFG2 mutation explains the entire QTL effect on SSC2p, whereas in the HGP analysis the presence of a second minor QTL can not be excluded. Finally, this study shows that this particular IGF2 mutation does not cause the paternally expressed QTL for teat number mapping to the same region of SSC2p as the BFT QTL.

Animals↗

PubMed2001

Variables that explain variation in prenatal care in Turkey; social class, education and ethnicity re-visited.

The extent and quality of prenatal care are important for the health of women and their babies. Recent studies suggest that women lack adequate prenatal care in contemporary Turkey. This paper uses regression models to examine the major factors impacting on the access of women to prenatal care through the 1993 Turkish Demographic and Health Survey. The findings suggest that after controlling for class, ethnicity does not explain the likelihood of a woman's access to prenatal care, partly because the predominant patriarchal ideology in Turkey determines women's access to education, which in turn determines their access to prenatal care. It can be argued that unless women's socioeconomic status in the family improves, their access to health care in general and prenatal care in particular will not increase significantly.

Educational Status↗