Unifying theory of hypoxia tolerance: molecular/metabolic defense and rescue mechanisms for surviving oxygen lack.

We develop a unifying theory of hypoxia tolerance based on information from two cell level models (brain cortical cells and isolated hepatocytes) from the highly anoxia tolerant aquatic turtle and from other more hypoxia sensitive systems. We propose that the response of hypoxia tolerant systems to oxygen lack occurs in two phases (defense and rescue). The first lines of defense against hypoxia include a balanced suppression of ATP-demand and ATP-supply pathways; this regulation stabilizes (adenylates) at new steady-state levels even while ATP turnover rates greatly decline. The ATP demands of ion pumping are down-regulated by generalized "channel" arrest in hepatocytes and by "spike" arrest in neurons. Hypoxic ATP demands of protein synthesis are down-regulated probably by translational arrest. In hypoxia sensitive cells this translational arrest seems irreversible, but hypoxia-tolerant systems activate "rescue" mechanisms if the period of oxygen lack is extended by preferentially regulating the expression of several proteins. In these cells, a cascade of processes underpinning hypoxia rescue and defense begins with an oxygen sensor (a heme protein) and a signal-transduction pathway, which leads to significant gene-based metabolic reprogramming-the rescue process-with maintained down-regulation of energy-demand and energy-supply pathways in metabolism throughout the hypoxic period. This recent work begins to clarify how normoxic maintenance ATP turnover rates can be drastically (10-fold) down-regulated to a new hypometabolic steady state, which is prerequisite for surviving prolonged hypoxia or anoxia. The implications of these developments are extensive in biology and medicine.

Hormones and mammary carcinogenesis in mice, rats, and humans: a unifying hypothesis.

An attempt has been made to put forward a unifying hypothesis explaining the role hormones play in the genesis of mammary cancers of different phenotypes and genotypes in mice, rats, and humans. Most mammary cancers in these species originate in luminal mammary epithelial cells lining the mammary ducts and alveoli. These cancers are histopathologically diverse and are classified on the basis of growth requirements as hormone-dependent or hormone-independent tumors. In most strains of mice, mammary cancers at the time of detection are largely of the hormone-independent type; in rats, almost all mammary cancers are hormone-dependent, while humans have both phenotypes. In spite of these differences, in vivo studies show that hormones (ovarian and pituitary) are essential for luminal mammary epithelial cell proliferation and also for the development of mammary cancers of both hormone-independent and hormone-dependent types. This article, based on our extensive in vivo and in vivo studies and on current literature, proposes a model to explain the central role of hormones in the genesis of all types of mammary cancers. The model attempts to address the following questions: (i) how hormones regulate luminal mammary epithelial cell proliferation, (ii) why hormones are required for the genesis of mammary cancers of all phenotypes and genotypes, including those which are always classified as hormone-independent tumors, and (iii) why the three species (mouse, rat, and human) have consistently different ratios of hormone-dependent to hormone-independent tumors.

Dyslexia: Success, Failure, and Self-Concept

The purpose of this study is to investigate the experience of college-aged students who have been diagnosed with dyslexia. Research has shown that many people with dyslexia experience a variety of social and emotional struggles throughout their education. Using qualitative research techniques, this study provides a description of the experience common among college students with dyslexia. Specifically, the study examines the experience of dyslexic students as it relates to attributions of successes and failures, locus of control, self-concept, and how personal knowledge about the diagnosis impacts their experience.

Parent-Child Interaction and Children's Self-Concept

This study is designed to investigate the relationships between marital communication, the quality of parents' ability to assist their children in joint problem-solving, and children's independent mastery attempts and perceived competence at problem-solving, and behavioral indicators of self-esteem. Couples' skill at regulating their own and their children's negative affect within the marital and parent-child family subsystems is hypothesized to predict the quality of their assistance, or scaffolding behavior, to their children during joint problem-solving. Further, the quality of parental scaffolding behavior is expected to predict children's independent mastery attempts, levels of perceived competence at problemsolving, and behavioral indicators of self-esteem. Families for the study will be those with children between 3 1/2 to six years of age recruited from subjects participating in a longitudinal study of communication in marriage being conducted at the Denver Center for Marital and Family Studies. Families will participate in three interaction tasks designed to tap parental scaffolding behavior during problemsolving with their children. Children will be administered self-report measures to tap their perceived competence at such problem-solving as those in the interaction tasks and parents will complete a questionnaire tapping the behavioral indicators of their child's self-esteem. Family interaction data will be coded with the use of a microanalytic coding system developed by this study, the Parent-Child Interaction Coding System. Marital communication data at three time points, premaritally, during the transition to parenthood , and concurrently, will be obtained from couples' interactions from the longitudinal study. The clinical significance of this study includes implications for training couples how to effectively regulate negative affect and offer their children sensitive assistance during joint problem-solving.

Social risk factors in Spanish youth and their impact on self-concept construction

This paper presents evidence from a psychosocial framework about the relationship among youth, work, and identity construction. The aims of this research were twofold. The first one was to analyze the working conditions of Spanish youth and their impact on individuals' biographies. The second one was to examine the effect of labor-related variables on construction / change of identity elements in Spanish youth. For this purpose, two research techniques were used: the Delphi method (103 experts sample from several entities and organizations closely related to our topic) and deep interviews (15 interviews with youths classified according to their relationship with the work market). Copyright 2007 by The Spanish Journal of Psychology.

An Introduction to Conservation Easements in the United States: A Simple Concept and a Complicated Mosaic of Law

The idea of a conservation easement – restrictions on the development and use of land designed to protect the land’s conservation or historic values – can be relatively easily understood. More significant and more challenging is the complex body of state and federal laws that shapes the creation, funding, tax treatment, enforcement, modification, and termination of conservation easements. The explosion in the number of conservation easements over the past four decades has made them one of the most popular land protection mechanisms in the United States. The National Conservation Easement Database estimates that the total number of acres encumbered by conservation easements exceeds 40 million.Because conservation easements are both novel and ubiquitous, understanding how they actual work is essential for practicing lawyers, policymakers, land trust professionals, and students of conservation. This article provides a “quick tour” through some of the most important aspects of the developing mosaic of conservation easement law. It gives the reader a sense of the complex inter-jurisdictional dynamics that shape conservation transactions and disputes about conservation easements. Professors of property law, environmental law, tax law, and environmental studies who wish to cover conservation easements in the context of a more general course can use the article to provide their students with a broad but comprehensive overview of the relevant legal and policy issues.

Coordination of aproximations in secondary school students’ understanding of limit concept

The aim of this research is to characterize the coordination of the processes of approximation related to the understanding of the limit of a function. We analyze the answers of 64 post-secondary school students to 7 problems considering the dynamic and metric conception of limit of a function. Results indicate that the metric understanding of the limit in terms of inequality supports that the student is capable of coordinating the approximations in the domain and in the range when lateral approximations coincide. However, the student is not capable of this coordination when lateral approximations do not coincide. This indicates that the metric understanding of the limit begins with the previous construction of the dynamic conception in case of coincidence of the lateral approximations in the range.

Concept and measurement: the cultural borders of meaning

Paper submitted to the Sixth International Conference on Social Science Methodology, Amsterdam, The Netherlands, August 16-20, 2004.

Social anxiety and self-concept in adolescence

This study analyzes the relationships between social anxiety and dimensions of self-concept in a sample of 2022 (50.1% males) Spanish adolescents, ranging in age from 12 to 16 year-olds. The social anxiety was assessed by the Social Phobia and Anxiety Inventory (SPAI), and self-concept was measured with the Self-Description Questionnaire II (SDQ-II). Logistic regression analyses show that adolescents with social anxiety are more likely to negatively perceive their relationship with opposite sex peers and have lower scores in self-esteem than students without social anxiety. Furthermore, in most logistic models, students with social anxiety also show a higher probability of perceiving their relation with peers of the same sex in a negative way, considering worse student, less attractive and athletic, and more emotional instable than students without social anxiety. The relevance of sex and grade in the relationship between social anxiety and self-concept in adolescence is discussed.

Unifying the observational diversity of isolated neutron stars via magneto-thermal evolution models

Observations of magnetars and some of the high magnetic field pulsars have shown that their thermal luminosity is systematically higher than that of classical radio-pulsars, thus confirming the idea that magnetic fields are involved in their X-ray emission. Here we present the results of 2D simulations of the fully coupled evolution of temperature and magnetic field in neutron stars, including the state-of-the-art kinetic coefficients and, for the first time, the important effect of the Hall term. After gathering and thoroughly re-analysing in a consistent way all the best available data on isolated, thermally emitting neutron stars, we compare our theoretical models to a data sample of 40 sources. We find that our evolutionary models can explain the phenomenological diversity of magnetars, high-B radio-pulsars, and isolated nearby neutron stars by only varying their initial magnetic field, mass and envelope composition. Nearly all sources appear to follow the expectations of the standard theoretical models. Finally, we discuss the expected outburst rates and the evolutionary links between different classes. Our results constitute a major step towards the grand unification of the isolated neutron star zoo.

An explanatory model of academic achievement based on aptitudes, goal orientations, self-concept and learning strategies

As a result of studies examining factors involved in the learning process, various structural models have been developed to explain the direct and indirect effects that occur between the variables in these models. The objective was to evaluate a structural model of cognitive and motivational variables predicting academic achievement, including general intelligence, academic self-concept, goal orientations, effort and learning strategies. The sample comprised of 341 Spanish students in the first year of compulsory secondary education. Different tests and questionnaires were used to evaluate each variable, and Structural Equation Modelling (SEM) was applied to contrast the relationships of the initial model. The model proposed had a satisfactory fit, and all the hypothesised relationships were significant. General intelligence was the variable most able to explain academic achievement. Also important was the direct influence of academic self-concept on achievement, goal orientations and effort, as well as the mediating ability of effort and learning strategies between academic goals and final achievement.

Developing pre-service teachers’ noticing of students’ understanding of the derivative concept

This research study examines the development of the ability of pre-service teachers to notice signs of students’ understanding of the derivative concept. It analyses preservice teachers’ interpretations of written solutions to problems involving the derivative concept before and after participating in a teacher training module. The results indicate that the development of this skill is linked to pre-service teachers’ progressive understanding of the mathematical elements that students use to solve problems. We have used these results to make some suggestions for teacher training programmes.

Goal Orientation Profiles and Self-Concept of Secondary School Students

The objective of this study is to identify possible combinations of multiple goals that lead to different goal orientation profiles and to determine whether there are significant group differences in self-concept dimensions. The Achievement Goals Tendencies Questionnaire (AGTQ) and the Self-Description Questionnaire-II (SDQ-II) were administered to a sample of 2,022 students of Compulsory Secondary education, ranging in age from 12 to 16 years (M = 13.81, SD = 1.35). Cluster analysis identified four profiles of motivational goals: a group of students with a generalized high motivation profile, a group of students with generalized low motivation profile, a group of students with a predominance of learning goals and achievement goals, and a last group of students with a predominance of achievement goals and social reinforcement goals. Results reveal statistically significant differences among the profiles obtained regarding self-concept dimensions.