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排序方式: 共有229条查询结果,搜索用时 15 毫秒
91.
MINOR COMPONENTS OF THE DNA OF PHYSARUM POLYCEPHALUM : Cellular Location and Metabolism 总被引:3,自引:2,他引:1
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DNA metabolism in the slime mold Physarum polycephalum was studied by centrifugation in CsCl of lysates of cultures labeled with radioactive thymidine at various times in the cell cycle. During the G2 (premitotic) phase of the cell cycle, two components of the DNA are labeled. One component is lighter (buoyant density 1.686 g/cc) than the mean of the principal DNA (1.700 g/cc), and one is heavier (approximately 1.706 g/cc). The labeled light DNA was identified chemically by its denaturability, its susceptibility to DNase, and the recovery of its radioactivity in thymine. Cell fractionation studies showed that the heavy and the principal DNA components are located in the nucleus and that the light DNA is in the cytoplasm. The light DNA comprises approximately 10% of the DNA. About ⅓–½ of the light DNA is synthesized during the S period, and the remainder is synthesized throughout G2 (there is no G1 in Physarum). The light DNA is metabolically stable. A low, variable level of incorporation of radioactive thymidine into the principal, nuclear DNA component was observed during G2. 相似文献
92.
William S. C. Gurney David A. J. Middleton Roger M. Nisbet Edward McCauley William W. Murdoch Andre DeRoos 《Theoretical population biology》1996,49(3):344-368
This paper considers the relationship between the demographic mechanisms of population control and the energetics of the individuals who comprise the population. We examine the equilibrium properties of a class of structured population models in which individuals compete for some environmental resource (such as food) and demonstrate that population demography is independent of the nature of the feedback loop which establishes the equilibrium state. We thus derive general insights into the influence exerted by individual energetic and allocation strategies on population average demographic characteristics. We show that models of individual energetics which produce apparently very similar predictions at the individual level can result in very different behaviour at the population level. In addition, we observe that different models of individual mortality can imply marked differences in population demography and that the common assumption of constant mortality can be responsible for potentially unrealistic model behaviour. Our results emphasise the substantial data requirements for parameterising and testing individual-based models. 相似文献
93.
The life cycle of T. myceliophagus was studied under spawn-running and cropping conditions. At 24o the egg to egg developmental period, when mating occurs, is 8 days, extending to 12 days at 16o. Significant damage to mushrooms occurs only when a heavy, initial infestation takes place at, or soon after, spawning. Effective control depends largely on hygiene treatments between crops. Methyl bromide fumigation or cooking-out for several hours at 66o–71o, followed by 0.01% dicofol sprays directed at the internal surfaces of the empty building, are satisfactory methods.
Zusammenfassung Der Lebenszyklus von T. myceliophagus wurde bei 16o und 24o untersucht, da diese Temperaturen gewöhnlich in den beiden Hauptphasen der gewerblichen Pilzzüchtung angewandt werden. Eine Generation entsteht innerhalb von 8 bis 12 Tagen. Da die Fruchtbarkeit der einzelnen Weibchen jedoch auf 20–25 Eier beschränkt ist, vermehrt sich die Milbe relativ langsam.Typische Schäden — Braunwerden der Sporenträger und Loslösen der Myzelmembranen — treten nur dann auf, wenn der Kompost bei oder kurz nach der Einführung des Pilzmyzels in das Bett verseucht wird.Eine effektive Kontrolle hängt von der Wirksamkeit der Behandlung zwischen den einzelnen Ernten ab. Ausräuchern des Gewächshauses samt Inhalt nach der Abernte mit Methylbromid oder mehrstündiges Heizen bei 66–71o sind zufriedenstellende Methoden. Wo dies nicht möglich ist, sollte das leere Gebäude mit 0,01% igem Dicofol ausgesprüht werden.相似文献
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Chuti Laowtammathron Eric CH Cheng Pei-Hsun Cheng Brooke R Snyder Shang-Hsun Yang Zach Johnson Chanchao Lorthongpanich Hung-Chih Kuo Rangsun Parnpai Anthony WS Chan 《BMC cell biology》2010,11(1):12
Background
Pluripotent stem cells that are capable of differentiating into different cell types and develop robust hallmark cellular features are useful tools for clarifying the impact of developmental events on neurodegenerative diseases such as Huntington's disease. Additionally, a Huntington's cell model that develops robust pathological features of Huntington's disease would be valuable for drug discovery research. 相似文献98.
99.
Camino Liquete Chiara Piroddi Evangelia G. Drakou Leigh Gurney Stelios Katsanevakis Aymen Charef Benis Egoh 《PloS one》2013,8(7)
Background
Research on ecosystem services has grown exponentially during the last decade. Most of the studies have focused on assessing and mapping terrestrial ecosystem services highlighting a knowledge gap on marine and coastal ecosystem services (MCES) and an urgent need to assess them.Methodology/Principal Findings
We reviewed and summarized existing scientific literature related to MCES with the aim of extracting and classifying indicators used to assess and map them. We found 145 papers that specifically assessed marine and coastal ecosystem services from which we extracted 476 indicators. Food provision, in particular fisheries, was the most extensively analyzed MCES while water purification and coastal protection were the most frequently studied regulating and maintenance services. Also recreation and tourism under the cultural services was relatively well assessed. We highlight knowledge gaps regarding the availability of indicators that measure the capacity, flow or benefit derived from each ecosystem service. The majority of the case studies was found in mangroves and coastal wetlands and was mainly concentrated in Europe and North America. Our systematic review highlighted the need of an improved ecosystem service classification for marine and coastal systems, which is herein proposed with definitions and links to previous classifications.Conclusions/Significance
This review summarizes the state of available information related to ecosystem services associated with marine and coastal ecosystems. The cataloging of MCES indicators and the integrated classification of MCES provided in this paper establish a background that can facilitate the planning and integration of future assessments. The final goal is to establish a consistent structure and populate it with information able to support the implementation of biodiversity conservation policies. 相似文献100.
The PHR (Pam/Highwire/RPM-1) proteins are evolutionarily conserved ubiquitin ligases that regulate axon guidance and synapse formation in Caenorhabditis elegans, Drosophila, zebrafish, and mice. In C. elegans, RPM-1 (Regulator of Presynaptic Morphology-1) functions in synapse formation, axon guidance, axon termination, and postsynaptic GLR-1 trafficking. Acting as an E3 ubiquitin ligase, RPM-1 negatively regulates a MAP kinase pathway that includes: dlk-1, mkk-4, and the p38 MAPK, pmk-3. Here we provide evidence that ppm-1, a serine/threonine phosphatase homologous to human PP2Cα(PPM1A) and PP2Cβ(PPM1B) acts as a second negative regulatory mechanism to control the dlk-1 pathway. We show that ppm-1 functions through its phosphatase activity in a parallel genetic pathway with glo-4 and fsn-1 to regulate both synapse formation in the GABAergic motorneurons and axon termination in the mechanosensory neurons. Our transgenic analysis shows that ppm-1 acts downstream of rpm-1 to negatively regulate the DLK-1 pathway, with PPM-1 most likely acting at the level of pmk-3. Our study provides insight into the negative regulatory mechanisms that control the dlk-1 pathway in neurons and demonstrates a new role for the PP2C/PPM phosphatases as regulators of neuronal development. 相似文献