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On Maxwell's demons and the origin of evolutionary variations: an internalist perspective.

This paper defends an internalist perspective of selection based on the hypothesis that considers living evolutionary units as Maxwell's demons (MD) or Zurek's Information Gathering and Using Systems (IGUS). Individuals are considered as IGUS that extract work by means of measuring and recording processes. Interactions or measurements convert uncertainty about the environment (Shannon's information, H) into internalized information in the form of a compressed record (Chaitin's algorithmic complexity, K). The requirements of the model and the limitations inherent to its formalization are discussed. This approach offers an alternative view to the causes of evolutionary variations which goes beyond the classical Lamarckian-Darwinian controversy. I argue that random variations only apply near-to-equilibrium at the time organisms have attained structural closure, and that a speed up of mutation rates that facilitates the production of directed variations occurs far-from-equilibrium due to organisms' openness to the surrounding conditions. However, real organisms are located somewhere between the above two cases and thus, operate at an intermediate stage where there is a maximum efficiency of H/K conversion. In consequence, IGUS keep their autonomy and evolving capacity by compromising between external circumstances and inner constraints. This compromise is made possible by closure regulation. Likewise, this model explains why nature has favored the selection of agents capable of selectively recording a partial description of their environment.

Biological Evolution↗

Depressive symptoms among Hong Kong adolescents: relation to atypical sexual feelings and behaviors, gender dissatisfaction, pubertal timing, and family and peer relationships.

A representative community sample of Hong Kong boys (n = 1,024) and girls (n = 1,403), age 14-18 years, provided information regarding same-sex attraction, gender dissatisfaction, pubertal timing, early experience with sexual intercourse, and depressive symptoms. They also rated the quality of their family and peer relationships and self-perceived attractiveness. Depressive symptoms were higher in youths reporting same-sex attraction, gender dissatisfaction, early pubertal maturation, and early sexual intercourse. Family relationships were less satisfactory for those who reported same-sex attraction, gender dissatisfaction, and early sexual intercourse, and peer relationships were also worse for those who reported gender dissatisfaction. In multivariate analyses, same-sex attraction, early sexual intercourse, and early pubertal maturation were unique and direct contributors to depressive symptoms; however, gender dissatisfaction's association with depressive symptoms was largely accounted for by shared correlations with negative family and peer relationships. The multivariate model explained 11% of the variance of depressive symptoms. These findings offer a preliminary documentation of the prevalence and correlates of atypical sexual self-assessments and behavior among adolescents in Hong Kong. Such information is important if theories of sexual identity and risk factors for depressive symptoms are to have cross-cultural utility.

Adolescent↗

Prediction of marginal bone loss and tooth loss--a prospective study over 20 years.

AIM: The purpose of the study was to investigate the influence of potential risk predictors/risk factors on the longitudinal marginal bone loss and tooth loss over 20 years. MATERIAL AND METHODS: A clinical and radiographic investigation of a sample of 513 individuals was performed in 1970 and 1990. Stepwise multiple regression analyses were adopted to calculate the influence of the potential risk predictors/risk factors on the longitudinal marginal bone loss and tooth loss. RESULTS: Russell's Periodontal Index in 1970 and smoking were significantly and positively correlated to longitudinal bone loss. Russell's Periodontal Index, marginal bone loss and Plaque Index at baseline were positively and significantly correlated to the longitudinal tooth loss, whilst age, the number of missing teeth in 1970 and the number of school years showed a significant negative correlation to number of teeth lost between 1970 and 1990. CONCLUSIONS: Smoking was found to be a significant risk factor in marginal bone loss, while plaque was a risk factor in tooth loss. However, the regression models explained a low percentage of the total variance, especially for marginal bone loss.

Adolescent↗

DNA methylation and Z-DNA formation as mediators of quantitative differences in the expression of alleles.

With draft copies of several model genomes available in the near future, attention is turning towards the genetic mechanisms that determine differences between individuals. While mutations in protein coding regions affect the structure of gene products, polymorphisms outside such regions may cause quantitative differences in gene expression. Here we summarize observations indicating that such differences may be mediated by allele-specific alterations in the modification or structure of DNA. Mono-allelic expression of the rat T-cell differentiation marker RT6 in a subpopulation of cells is associated with allele-specific differences in DNA methylation in the RT6 promoter. In contrast to previously described examples of mono-allelic expression, these are determined neither stochastically nor by parental origin, but by cis-acting elements within the alleles. An attractive candidate is a rodent identifier (ID) element exclusively present in the RT6a allele. In the case of the rat nucleolin gene, a polymorphic dinucleotide repeat in the 5' region modulates promoter strength and forms left-handed Z-DNA in vivo. Models explaining putative effects of Z-DNA formation on transcription are presented. These observations suggest novel mechanisms by which repetitive DNA, an abundant source of polymorphism in the mammalian genome, may exert quantitative effects on gene expression.

ADP Ribose Transferases↗

Caregiver burden in HIV-positive and HIV-negative partners of men with AIDS.

This study examines factors associated with caregiver burden in 82 HIV-positive (HIV+) and 162 HIV-negative (HIV-) partners of men with AIDS. We expected HIV+ caregivers to report more burden than HIV- caregivers because of the toll of their disease on their resources. HIV+ caregivers did report more burden and, compared with the HIV- caregivers, they were more religious or spiritual, had less income, and coped by using more positive reappraisal and cognitive escape-avoidance and by seeking social support. Comparisons of HIV+ caregivers with 61 HIV+ partners of healthy men indicated that most differences between HIV+ and HIV- caregivers were associated with HIV seropositivity rather than caregiving. However, of the variables associated with HIV seropositivity, only religiosity or spirituality contributed independently to burden in HIV+ caregivers, suggesting a relatively weak link between HIV seropositivity and caregiver burden. The model explained 62% of the variance in burden in HIV+ caregivers and 36% of the variance in HIV- caregivers.

Acquired Immunodeficiency Syndrome↗

Predicting intentions for long-term anabolic-androgenic steroid use among men: a covariance structure model.

Long-term use of anabolic-androgenic steroids (AASs) is associated with both positive and negative effects. The authors examined possible mechanisms by which these effects contribute to AAS satisfaction and predict intentions for future AAS use. Five hundred male AAS users completed an interactive Web-based instrument assessing the psychological and physical effects of AAS use. Covariance structure modeling was used to evaluate both direct and indirect effects of AAS consequences on satisfaction with AASs and intentions for future AAS use. Results suggest that gain in muscle mass and psychological benefits from AAS use uniquely contributed to both AAS satisfaction and intentions for future use. Side effects from AAS use also uniquely contributed to AAS satisfaction, but ancillary drug use was found to partially mediate this relationship, suggesting that the satisfaction of experienced AAS users is enhanced by their mastery of side effects through the use of ancillary drugs. The final model explained 29% of the variance in intentions for future AAS use. Mechanisms for sustained AAS use and implications for intervention and prevention strategies are discussed.

Adolescent↗

Family processes within three-generation households and adolescent mothers' satisfaction with father involvement.

This investigation used a family systems perspective to examine how family dynamics within 3-generation households were associated with mothers' satisfaction with father involvement. The participants were low-income African American adolescent mothers (n=148) and grandmothers recruited at delivery and followed over 6 months. The overall model explained 68% of the variance in satisfaction with father involvement. Fathers who were involved with caregiving activities had positive relationships with adolescent mothers and grandmothers. Grandmothers served as gatekeepers; when grandmothers reported positive relationships with the 2 young parents, adolescent mothers reported positive relationships with their male partners. Mothers who reported positive partner relationships also reported high parenting efficacy and satisfaction with father involvement. Efforts to increase paternal involvement should focus on role clarification for grandmothers and fathers and on parenting activities for mothers and fathers, regardless of their romantic relationship.

Adolescent↗

Unusual location and function of the operator in the Escherichia coli galactose operon.

The operator of the gal operon is located about 60 base pairs preceding the startpoints of the transcription of the two gal promoters. This location contrasts with the location of the operator in other phage or bacterial operons where the repressor binds more closely to the respective transcription initiation sites. Models explaining how the repressor-operator interactions may control the two gal promoters are presented.

Base Sequence↗

Sequential functions of the bithorax complex of Drosophila.

The bithorax genes are a group of homoeotic genes of Drosophila whose function is related to the control of segment development. They form a gene complex in which at least seven different loci have been identified. Mutations at each of these loci produce a specific homoeotic transformation whereby a segment is transformed either in part or completely into another. In embryos completely deficient for the bithorax genes, all the thoracic and abdominal segments resemble mesothoracic segments. This observation, together with the segmental specificity of the mutant phenotypes, led Lewis to suggest a model of genetic control in which the type of development in each segment is specified by the activation of a fraction of the total number of bithorax genes. Thus, lack of activity of the bithorax genes results in mesothoracic development, activation of the bithorax (bx+) and postbithorax (pbx+) genes produces metathorax (anterior and posterior respectively), and activation of these two genes with bithoraxoid (bxd+) produces the first abdominal segment and so on. Although this model explains the genetic and developmental data, it leaves unexplained formation of the prothoracic segment. We now describe two unexpected results: deficiencies for bithorax genes can lead to segments being transformed into prothorax, and there is a temporal sequence in the function of the bithorax system.

Animals↗

Heparin kinetics: variables related to disposition and dosage.

A method to determine heparin kinetics and dosage requirements was examined in 20 patients with active thromboembolic disease. Pretreatment heparin sensitivities were determined to establish the relationship between heparin concentration and activated partial thromboplastin times (APTTs). After an initial bolus dose, serial APTTs were measured, heparin concentrations were estimated, and kinetic determinations followed. Heparin elimination rate, distribution volume, and clearance were used to calculate dosage requirements. There was a 500% range in pretreatment heparin sensitivities. Smokers had more rapid heparin elimination rates and t 1/2s than nonsmokers did. Men had more rapid drug clearances than women did. Body weight was related to heparin dosage requirements. Patients treated early after onset of symptoms required higher doses than patients in whom treatment was delayed. A multiple regression model was developed for heparin dosage requirements from body weight, sex, delay between onset of symptoms and treatment, and smoking. This statistical model explained 78% of the variance in heparin requirements.

Adolescent↗

Partitioning of oxygen during core formation on the Earth and Mars.

Core formation on the Earth and Mars involved the physical separation of metal and silicate, most probably in deep magma oceans. Although core-formation models explain many aspects of mantle geochemistry, they have not accounted for the large differences observed between the compositions of the mantles of the Earth (approximately 8 wt% FeO) and Mars (approximately 18 wt% FeO) or the smaller mass fraction of the martian core. Here we explain these differences as a consequence of the solubility of oxygen in liquid iron-alloy increasing with increasing temperature. We assume that the Earth and Mars both accreted from oxidized chondritic material. In a terrestrial magma ocean, 1,200-2,000 km deep, high temperatures resulted in the extraction of FeO from the silicate magma ocean owing to high solubility of oxygen in the metal. Lower temperatures of a martian magma ocean resulted in little or no extraction of FeO from the mantle, which thus remains FeO-rich. The FeO extracted from the Earth's magma ocean may have contributed to chemical heterogeneities in the lowermost mantle, a FeO-rich D" layer and the light element budget of the core.

Journal Article↗

A deep dynamo generating Mercury's magnetic field.

Mercury has a global magnetic field of internal origin and it is thought that a dynamo operating in the fluid part of Mercury's large iron core is the most probable cause. However, the low intensity of Mercury's magnetic field--about 1% the strength of the Earth's field--cannot be reconciled with an Earth-like dynamo. With the common assumption that Coriolis and Lorentz forces balance in planetary dynamos, a field thirty times stronger is expected. Here I present a numerical model of a dynamo driven by thermo-compositional convection associated with inner core solidification. The thermal gradient at the core-mantle boundary is subadiabatic, and hence the outer region of the liquid core is stably stratified with the dynamo operating only at depth, where a strong field is generated. Because of the planet's slow rotation the resulting magnetic field is dominated by small-scale components that fluctuate rapidly with time. The dynamo field diffuses through the stable conducting region, where rapidly varying parts are strongly attenuated by the skin effect, while the slowly varying dipole and quadrupole components pass to some degree. The model explains the observed structure and strength of Mercury's surface magnetic field and makes predictions that are testable with space missions both presently flying and planned.

Journal Article↗

Eph receptor signalling casts a wide net on cell behaviour.

Eph receptor tyrosine kinases mould the behaviour of many cell types by binding membrane-anchored ligands, ephrins, at sites of cell-cell contact. Eph signals affect both of the contacting cells and can produce diverse biological responses. New models explain how quantitative variations in the densities and signalling abilities of Eph receptors and ephrins could account for the different effects that are elicited on axon guidance, cell adhesion and cell migration during development, homeostasis and disease.

Animals↗

Predictors of weight change in middle-aged and old men.

OBJECTIVE: Studies on weight change and mortality have yielded inconclusive results. This 10-year prospective study was undertaken to improve understanding of factors affecting weight change. RESEARCH METHODS AND PROCEDURES: The subjects were 1,143 men, aged 36 to 88 years (mean, 53.3 years) at entry. A questionnaire was filled in at entry and at the end of the follow-up with queries on weight, height, weight at the age of 20, physician-diagnosed diseases, smoking, alcohol use, dietary habits, leisure physical activity, occupation, present occupational activity, living conditions (living alone or cohabiting), and former athletic status. Further information on morbidity was obtained from selected national registers. Factors predicting weight change during the study were identified by stepwise linear multiple regression analysis. RESULTS: The mean 10-year weight change was 0.8 (range, -29 to +24) kg. Age at entry (beta-coefficient, -0.17, SE 0.02), weight at entry (beta, -0.03, SE 0.01), diabetes at entry (beta, -3.55, SE 1.02), diabetes diagnosed after entry (beta, -3.94, SE 0.96), malignant cancer (beta, -1.60, SE 0.70), being a smoker (beta, - 1.59, SE 0.48), and increased physical activity (beta, - 1.27, SE 0.54) were significantly (p < 0.05) associated with weight loss in the final model. The model explained 13% of the variance of weight change. DISCUSSION: The results emphasize the complexity of weight change. Some factors associated with weight change are apparently negatively, and some positively, associated with health. This could explain the equivocal findings on weight change and mortality in the literature.

Adult↗

Maturation of dendritic cells infected by recombinant adenovirus can be delayed without impact on transgene expression.

Adenovirus-mediated gene transfer to dendritic cells is highly efficient and often used, but the relationship among cell maturation, viral infection and expression of a transferred gene remains unclear. To study this relationship, we introduced a recombinant replication-defective adenovirus encoding the gene for green fluorescent protein to normal human immature myeloid dendritic cells. We induced maturation by the addition of TNF-alpha, IL-1beta, IL-6 and prostaglandin E2 to the medium and assessed cell maturity by the levels of the secreted p40 subunit of IL-12 and of membrane-bound CD83. We quantified the efficiency of gene expression by GFP fluorescence and analyzed the data by a mixed-model analysis of variance; the model explained more than 97% of the effects. CD83 expression and p40 secretion depended solely on incubation time and maturation medium. The cells cultured in the absence of maturation medium remained immature and maintained the ability to respond to the later addition of the maturation irrespective of adenovirus infection and transferred gene expression. This expression was independent of cell maturation. In comparison with mature cells, the transferred gene was expressed in immature dendritic cells with a lag compatible with the less effective initial step (infection and/or gene transfer) in the absence of the maturation medium rather than less effective later GFP synthesis. Expression of CD83 and p40 were unaffected by adenovirus infection and transferred gene expression. Thus, immature dendritic cells infected with recombinant adenoviruses can be matured when desired after transferred gene expression.

Adenoviridae↗

Association of poorly controlled diabetes with low serum leptin in morbid obesity.

OBJECTIVES: Leptin may be involved in the regulation of body weight, food intake, and energy expenditure. In view of a possible link between leptin concentrations and diabetes that has been suggested in obese rodents, we investigated the potential relationship between serum leptin concentrations and hyperglycaemia in French patients with morbid obesity. SUBJECTS: Fasting leptin concentrations were measured in 241 morbidly obese patients with various degrees of glucose tolerance in a cross-sectional study. RESULTS: Fasting serum leptin concentrations did not differ between normoglycaemia (NG, 61.5 +/- 24.0 ng/ml) and glucose intolerant morbidly obese subjects (IGT, 56.5 +/- 18.5 ng/ml) and were slightly lower in those with controlled diabetes (55.1 +/- 30.3 ng/ml, P = 0.06 when compared to NG subjects). In contrast, leptin concentrations were 30% lower in patients with poorly controlled diabetes (43.0 +/- 22.2 ng/ml, P = 0.001 vs NG subjects). Leptin concentrations were negatively correlated with fasting glucose in all groups combined (p = -0.24, P = 0.0001) and particularly in NIDDM subjects (p = 0.31, P = 0.0054). Although leptin concentrations were higher in women than in men, similar significant correlation with fasting glucose was found when females were analyzed separately. A positive correlation was found with BMI (p = 0.25, P = 0.0001) in all groups. Multivariate analysis revealed that fasting glucose was independently associated with serum leptin concentrations (F = 12.5, P = 0.0005). Sex, age, BMI, waist/hip ratio, fasting glucose and insulin, total cholesterol and triglycerides, tested in the model, explained 42% of the leptin variability in this population. CONCLUSIONS: Poorly controlled diabetes was accompanied by a significant reduction of serum leptin concentrations in morbidly obese subjects. We suggest that a relative leptin deficiency (lower than expected for the BMI) associated with insulin deficiency in this population might contribute to a vicious cycle maintaining (or even worsening) obesity itself and/or its metabolic complications.

Adult↗

Family lifestyle and parental body mass index as predictors of body mass index in Australian children: a longitudinal study.

OBJECTIVE: To investigate associations between body mass index (BMI) and family characteristics, including lifestyle, in parents and offspring from Australian families. DESIGN AND SUBJECTS: Longitudinal survey of 219 families of Australian children who had been surveyed 3-yearly between the ages of 9 and 18 y. MEASUREMENTS: Socio-economic status, weight and height, diet from 3 day records or food frequency questionnaires, alcohol consumption, smoking habits and physical fitness in offspring (bicycle ergometry in 18-y-olds). RESULTS: In 18-y-olds, in models examining offspring's lifestyle variables, BMI was predicted negatively by physical fitness (P=0.012), and positively by alcohol intake (P=0.046) in sons while, in daughters, only a negative association with physical fitness was significant. In models including parental characteristics, BMI in 18-y-old sons and daughters was significantly predicted by mothers' and fathers' BMI, independently of offsprings' alcohol intake, smoking, physical fitness and parents' education, and, in daughters, by fathers' alcohol intake. These models explained 48% of variance in daughters and 33% in sons. In both sons and daughters, BMI over the 9 y of the survey was consistently higher in offspring with overweight or obese fathers (P=0.033 for sons, P=0.024 for daughters) or mothers (P=0.031 for sons, P=0.037 for daughters). Physical fitness at the ages of 12, 15 and 18 y was negatively related to fathers' obesity in daughters and mothers' obesity in sons. Obesity in fathers was associated with a four-fold increase in risk of obesity at the age of 18 y in both sons and daughters with an independent eight-fold increase in risk for daughters if mothers were obese. Birthweight was unrelated to overweight or obesity in the 18-y-olds. Alcohol intake in sons related significantly to alcohol intake in either parent while, for daughters, there was a significant association only with fathers' alcohol consumption. In daughters, fat intake was positively associated with fat intake score in both fathers and mothers. CONCLUSION: Parental overweight or obesity may identify children at risk for a range of unhealthy behaviours. Promotion of a healthy lifestyle targeting overweight families, particularly in lower socio-economic groups, should be a priority.

Adolescent↗

Factors associated with lead exposure in Oaxaca, Mexico.

Lead intoxication risks were studied in a community of ceramic folk art workers in Oaxaca, a southern state of Mexico, where the manufacture of low-temperature lead ceramic ware is a family tradition and often the only source of income. Variables such as household characteristics, occupation, and lead exposure risk factors were explored. Study participants' mean blood lead concentration was 43.8 microg/dl (range=8.4-99.6 microg/dl), which is over the WHO guideline of 40 microg/dl for removing workers from exposure and is the concentration over which renal damage is accelerated. Best predictors for high blood lead concentrations by multivariable regression analysis were: occupation (P<0.0001), gender (P=0.0002), and the use of glazed stoneware (P<0.0001). This model explained 18% of blood lead variation among the study group. Exposure appears to be primarily associated with antiquated pottery manufacturing techniques and the high degree of contamination prevailing at the production sites, which in most cases are their living quarters. This consequently affects the lead levels of the entire community.

Adolescent↗