977 resultados para thallus anatomy


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Reading and listening involve complex psychological processes that recruit many brain areas. The anatomy of processing English words has been studied by a variety of imaging methods. Although there is widespread agreement on the general anatomical areas involved in comprehending words, there are still disputes about the computations that go on in these areas. Examination of the time relations (circuitry) among these anatomical areas can aid in understanding their computations. In this paper, we concentrate on tasks that involve obtaining the meaning of a word in isolation or in relation to a sentence. Our current data support a finding in the literature that frontal semantic areas are active well before posterior areas. We use the subject’s attention to amplify relevant brain areas involved either in semantic classification or in judging the relation of the word to a sentence to test the hypothesis that frontal areas are concerned with lexical semantics and posterior areas are more involved in comprehension of propositions that involve several words.

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The mammalian immune system must specifically recognize and eliminate foreign invaders but refrain from damaging the host. This task is accomplished in part by the production of a large number of T lymphocytes, each bearing a different antigen receptor to match the enormous variety of antigens present in the microbial world. However, because antigen receptor diversity is generated by a random mechanism, the immune system must tolerate the function of T lymphocytes that by chance express a self-reactive antigen receptor. Therefore, during early development, T cells that are specific for antigens expressed in the thymus are physically deleted. The population of T cells that leaves the thymus and seeds the secondary lymphoid organs contains helpful cells that are specific for antigens from microbes but also potentially dangerous T cells that are specific for innocuous extrathymic self antigens. The outcome of an encounter by a peripheral T cell with these two types of antigens is to a great extent determined by the inability of naive T cells to enter nonlymphoid tissues or to be productively activated in the absence of inflammation.

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Relative cerebral glucose metabolism was examined with positron-emission tomography (PET) as a measure of neuronal activation during performance of the classically conditioned eyeblink response in 12 young adult subjects. Each subject received three sessions: (i) a control session with PET scan in which unpaired presentations of the tone conditioned stimulus and corneal airpuff unconditioned stimulus were administered, (ii) a paired training session to allow associative learning to occur, and (iii) a paired test session with PET scan. Brain regions exhibiting learning-related activation were identified as those areas that showed significant differences in glucose metabolism between the unpaired control condition and well-trained state in the 9 subjects who met the learning criterion. Areas showing significant activation included bilateral sites in the inferior cerebellar cortex/deep nuclei, anterior cerebellar vermis, contralateral cerebellar cortex and pontine tegmentum, ipsilateral inferior thalamus/red nucleus, ipsilateral hippocampal formation, ipsilateral lateral temporal cortex, and bilateral ventral striatum. Among all subjects, including those who did not meet the learning criterion, metabolic changes in ipsilateral cerebellar nuclei, bilateral cerebellar cortex, anterior vermis, contralateral pontine tegmentum, ipsilateral hippocampal formation, and bilateral striatum correlated with degree of learning. The localization to cerebellum and its associated brainstem circuitry is consistent with neurobiological studies in the rabbit model of eyeblink classical conditioning and neuropsychological studies in brain-damaged humans. In addition, these data support a role for the hippocampus in conditioning and suggest that the ventral striatum may also be involved.

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Contains notes taken by Harvard student Lyman Spalding (1775-1821) from lectures on anatomy and surgery delivered by Harvard Professor John Warren (1753-1815) in 1795, as well a section entitled “Medical Observations,” which includes entries on “Vernal Debility,” or diseases occurring in the spring, and lung function. It is unclear if these are Spalding’s own writings or transcriptions from a published work. There is also text transcribed from “Elementa Medicinae,” published in 1780 by Scottish physician John Brown.

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Volume containing notes on the lectures of Henry Cline (1750-1827), a surgeon at St. Thomas's Hospital, London, England, that were kept by American medical student John Collins Warren in 1799 and 1800. The lectures were on topics including blood, blood vessels, absorbents, cellular membranes, and the nerves. There are annotations in pencil in an unknown hand throughout the volume.

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The Crimean operation has served as an occasion for Russia to demonstrate to the entire world the capabilities and the potential of information warfare. Its goal is to use difficult to detect methods to subordinate the elites and societies in other countries by making use of various kinds of secret and overt channels (secret services, diplomacy and the media), psychological impact, and ideological and political sabotage. Russian politicians and journalists have argued that information battles are necessary for “the Russian/Eurasian civilisation” to counteract “informational aggression from the Atlantic civilisation led by the USA”. This argument from the arsenal of applied geopolitics has been used for years. This text is an attempt to provide an interpretation of information warfare with the background of Russian geopolitical theory and practice.

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A method was developed to extract adenine nucleotides AMP, ADP, and ATP from marine macroalgal tissue to gain information on the cellular energy charge. Quantification was carried out by high performance liquid chromatography (HPLC). Three species from the rocky shore of the island of Helgoland (German Bight) were examined: Laminaria saccharina (Phaeophyta), Chondrus crispus (Rhodophyta), and Ulva lactuca (Chlorophyta). In L. saccharina and C. crispus, the adenylate energy charge (AEC) was determined in different thallus regions. AEC varied in relation to tissue age and function. Higher AEC values typically occurred in thallus regions with meristematic activity. Furthermore, L. saccharina and U. lactuca were exposed to UV-A and elevated UV-B radiation. The AEC was calculated and the maximal quantum yield of photosystem II (Fv/Fm) was determined as indicators for UV stress. In both species, the AEC remained at high values (0.72 ± 0.04), while Fv/Fm dropped rapidly. The results show that the photosynthesis of the phaeophyte is more resistant to UV radiation than the chlorophyte.

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The effects of biotic disturbances, like seaweed whiplash, on the diversity of benthic communities are well documented for temperate coastal systems, yet missing for Arctic benthos. In Arctic soft-bottom habitats, kelp thalli occur either continuously (e.g. trapped by sediment) or sporadically (by drifting on the sediment) after detachment from rocky shores. To explore whether a kelp thallus can disturb the structure and diversity of a coastal Arctic soft-bottom assemblage, we continuously fixed a single thallus of the kelp Saccharina latissima to or sporadically (i.e. biweekly) moved it on the sediment and compared treatment effects to unmanipulated plots (= controls). On 6 September 2013 (i.e. after 73 days of manipulation), one sediment core was taken from each of the 30 plots (n = 10), from which the number of individuals of each of the 45 encountered animal species were recorded. The continuous presence of an experimentally fixed kelp thallus significantly reduced the number of individuals on average by 27 %. This disturbance effect was even stronger, on average 49 %, where a kelp thallus was biweekly moved on the sediment. Likewise, taxon richness was lowered by an average of 19 and 36 % where a S. latissima thallus was continuously or sporadically present, respectively. While the composition of taxa was also significantly different among all treatment groups, evenness and biomass were unaffected by kelp treatments. We conclude that the presence and already movements of a single kelp thallus can promote small scale patchiness in near-shore soft-bottom assemblage structure and diversity and exemplify a significant connection between rocky and sedimentary coastal habitats.

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Mode of access: Internet.

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Mode of access: Internet.

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Mode of access: Internet.