草地与农牧交错带退化生态系统重建及防治途径

草地不仅是草地畜牧业的基地，而且在生态环境保护与建设方面的作用尤为重要。草原与农牧交错带，即不同于西部牧区，也不同于东部农区。根据它在地理、气候、农林牧产业结构、生态、经济、文化、社会等方面具有自己独特地位的实际情况，因地制宜提出了相应之对策，为国家在西部大开发和草地与农牧交错带生态环境的恢复提供科学依据。     

Models and structures: Phenomenological and partial

In a recent paper, Suárez and Cartwright (2008) return to the example of London and London's construction of a model for superconductivity and raise a number of concerns against the account of this construction presented in French and Ladyman (1997) and elsewhere. In this discussion note, we examine the challenge they raised and offer our responses.     

Telomeres and meiosis in health and disease

The aim of this review is threefold. First, we want to report on recent observations on the role of telomeres in the alignment of homolog and non-homologues in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe and the relationship of early telomere clustering to later recombination events. Second, we compare the similarities and differences between synaptic and asynaptic yeasts. Third, we report on the increasing evidence of the effect of meiosis on telomeric sequences that suggest an induction of a specific form of recombination processes termed telomere rapid deletion.     

Telomeres and meiosis in health and disease

Meiotic dysfunction increasingly afflicts women as they age, resulting in infertility, miscarriage and handicapped offspring. How aging disrupts meiotic function in women remains unclear, but as women increasingly delay childbearing, this issue becomes urgent. Telomeres, which mediate aging in mitotic cells, may also mediate aging during meiosis. Telomeres shorten during DNA replication. In mammals, oocytes remain quiescent, but their precursors replicated during fetal oogenesis. Moreover, eggs ovulated from older women entered meiosis later during fetal oogenesis than eggs ovulated when younger, and therefore underwent more replications. Telomeres also shorten from reactive oxygen, which triggers a DNA repair response, so the prolonged interval between fetal oogenesis and ovulation in some women would further shorten telomeres. Mice normally do not exhibit age-related meiotic dysfunction (interestingly, their telomeres are manyfold longer than telomeres in women), but genetic or pharmacologic shortening of mouse telomeres recapitulates the reproductive aging phenotype of women. This has led to a telomere theory of age-related meiotic dysfunction in women, and underlined the importance to human health of a mechanistic understanding of telomeres and meiosis.     

Contrasting tail and other responses to morphine and reserpine in rats and mice

Zusammenfassung Charakteristisch verschiedene Schwanzstellungen zeigen Albino-Ratten und -Mäuse als Morphium- bzw. Reserpinreaktion. Verstärkte Schwanzreaktionen erhält man bei der Maus nach Morphium, bei der Ratte nach Reserpin. Methylphenidat erweist sich bei der Ratte antagonistisch gegen Reserpin, während im Mäuseversuch nach Reserpin injiziertes Morphium kompetitiv zu wirken scheint.

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This work was aided by a grant from the Medical Research Council.     

Linear and threshold forecasts of output and inflation using stock and housing prices

This study examines whether simple measures of Canadian equity and housing price misalignments contain leading information about output growth and inflation. Previous authors have generally found that the information content of asset prices in general, and equity and housing prices in particular, are unreliable in that they do not systematically predict future economic activity or inflation. However, earlier studies relied on simple linear relationships that would fail to pick up the potential nonlinear effects of asset price misalignments. Our results suggest that housing prices are useful for predicting GDP growth, even within a linear context. Meanwhile, both stock and housing prices can improve inflation forecasts, especially when using a threshold specification. These improvements in forecast performance are relative to the information contained in Phillips‐curve type indicators for inflation and IS‐curve type indicators for GDP growth. Copyright © 2008 John Wiley & Sons, Ltd.     

Telomeres and meiosis in health and disease

Telomeres are important segments of chromosomes that protect chromosome ends from nucleolytic degradation and fusion. At meiosis telomeres display an unprecedented behavior which involves their attachment and motility along the nuclear envelope. The movements become restricted to a limited nuclear sector during the so-called bouquet stage, which is widely conserved among species. Recent observations suggest that telomere clustering involves actin and/or microtubules, and is altered in the presence of impaired recombinogenic and chromosome related functions. This review aims to provide an overview of what is currently known about meiotic telomere attachment, dynamics and regulation in synaptic meiosis.     

Telomeres and meiosis in health and disease

Beyond their role in replication and chromosome end capping, telomeres are also thought to function in meiotic chromosome pairing, meiotic and mitotic chromosome segregation as well as in nuclear organization. Observations in both somatic and meiotic cells suggest that the positioning of telomeres within the nucleus is highly specific and believed to be dependent mainly on telomere interactions with the nuclear envelope either directly or through chromatin interacting proteins. Although little is known about the mechanism of telomere clustering, some studies show that it is an active process. Recent data have suggested a regulatory role for telomere chromatin structure in telomere movement. This review will summarize recent studies on telomere interactions with the nuclear matrix, telomere chromatin structure and factors that modify telomere chromatin structure as related to regulation of telomere movement.     

Telomeres and meiosis in health and disease

Telomeres are important segments of chromosomes that protect chromosome ends from nucleolytic degradation and fusion. At meiosis telomeres display an unprecedented behavior which involves their attachment and motility along the nuclear envelope. The movements become restricted to a limited nuclear sector during the so-called bouquet stage, which is widely conserved among species. Recent observations suggest that telomere clustering involves actin and/or microtubules, and is altered in the presence of impaired recombinogenic and chromosome related functions. This review aims to provide an overview of what is currently known about meiotic telomere attachment, dynamics and regulation in synaptic meiosis.     

Hyperbaric oxygen and testicular damage and fertility

Zusammenfassung Männliche Ratten zeigen nach einmaliger oder wiederholter stark erhöhter O₂-Zufuhr (3–5 at) Krämpfe und Lungenschäden und zum Teil Absterben. Schädigungen der Spermatogenese oder der Fertilität traten nicht auf.     

Structure and function of desmosomal proteins and their role in development and disease

Desmosomes represent major intercellular adhesive junctions at basolateral membranes of epithelial cells and in other tissues. They mediate direct cell-cell contacts and provide anchorage sites for intermediate filaments important for the maintenance of tissue architecture. There is increasing evidence now that desmosomes in addition to a simple structural function have new roles in tissue morphogenesis and differentiation. Transmembrane glycoproteins of the cadherin superfamily of Ca²⁺-dependent cell-cell adhesion molecules which mediate direct intercellular interactions in desmosomes appear to be of central importance in this respect. The complex network of proteins forming the desmosomal plaque associated with the cytoplasmic domain of the desmosomal cadherins, however, is also involved in junction assembly and regulation of adhesive strength. This re-view summarizes the structural features of these desmosomal proteins, their function during desmosome assembly and maintenance, and their role in development and disease.Received 5 February 2003; received after revision 14 March 2003; accepted 1 April 2003     

Geopsychology and geopsychopathology: Mental processes and disorders associated with geochemical and geophysical factors

Summary Temporal and regional variations in psychological processes have been associated with three geological factors. They are geochemical profiles, geomagnetic variations, and tectonic stresses. In the geochemical domain, copper, aluminum, zinc, and lithium may influence the incidence of thought disorders such as schizophrenia and senile dementia. These common elements are found in many soils and ground water. Geomagnetic variations have been correlated with enhanced anxiety, sleep disturbances, altered moods, and greater incidences of psychiatric admissions. The effects are usually brief but pervasive. Transient and very local epidemics of bizarre and unusual behaviors are sociological phenomena that sometimes precede increases in earthquake activity within a region; they have been hypothesized to be associated with tectonic strain. Many of the contemporary correlations between geological factors and human behavior are also apparent within historical data. The effects of geophysical and geochemical factors upon human behavior are not artifactual, but they are complex and often not detected by the limited scope of most studies.     

Structuralism and the conformity of mathematics and nature

Structuralists typically appeal to some variant of the widely popular ‘mapping’ account of mathematical representation to suggest that mathematics is applied in modern science to represent the world’s physical structure. However, in this paper, I argue that this realist interpretation of the ‘mapping’ account presupposes that physical systems possess an ‘assumed structure’ that is at odds with modern physical theory. Through two detailed case studies concerning the use of the differential and variational calculus in modern dynamics, I show that the formal structure that we need to assume in order to apply the mapping account is inconsistent with the way in which mathematics is applied in modern physics. The problem is that a realist interpretation of the ‘mapping’ account imposes too severe of a constraint on the conformity that must exist between mathematics and nature in order for mathematics to represent the structure of a physical system.     

Leptin signaling and circuits in puberty and fertility

Leptin is an adipocyte-derived hormone involved in a myriad of physiological process, including the control of energy balance and several neuroendocrine axes. Leptin-deficient mice and humans are obese, diabetic, and display a series of neuroendocrine and autonomic abnormalities. These individuals are infertile due to a lack of appropriate pubertal development and inadequate synthesis and secretion of gonadotropins and gonadal steroids. Leptin receptors are expressed in many organs and tissues, including those related to the control of reproductive physiology (e.g., the hypothalamus, pituitary gland, and gonads). In the last decade, it has become clear that leptin receptors located in the brain are major players in most leptin actions, including reproduction. Moreover, the recent development of molecular techniques for brain mapping and the use of genetically modified mouse models have generated crucial new findings for understanding leptin physiology and the metabolic influences on reproductive health. In the present review, we will highlight the new advances in the field, discuss the apparent contradictions, and underline the relevance of this complex physiological system to human health. We will focus our review on the hypothalamic circuitry and potential signaling pathways relevant to leptin’s effects in reproductive control, which have been identified with the use of cutting-edge technologies of molecular mapping and conditional knockouts.