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91.
92.
Dynamic cortical networks of verbal and spatial working memory: effects of memory load and task practice 总被引:3,自引:5,他引:3
Working memory (WM), the ability to briefly retain and manipulate
information in mind, is central to intelligent behavior. Here we take
advantage of the high temporal resolution of electrophysiological measures
to obtain a millisecond timescale view of the activity induced in
distributed cortical networks by tasks that impose significant WM demands.
We examined how these networks are affected by the type and amount of
information to be remembered, and by the amount of task practice. Evoked
potentials (EPs) were obtained from eight subjects performing spatial and
verbal versions of a visual n-back WM task (n = 1, 2, 3) on each of three
testing days. In well-trained subjects, WM tasks elicited transient
responses reflecting different subcomponents of task processing, including
transient (lasting 0.02-0.3 s) task- sensitive and load-sensitive EPs, as
well as sustained responses (lasting 1-1.5 s), including the prestimulus
Contingent Negative Variation (CNV), and post-stimulus frontal and parietal
Slow Waves. The transient responses, with the exception of the P300,
differed between the verbal and spatial task versions, and between trials
with different response requirements. The P300 and the Slow Waves were not
affected by task version but were affected by increased WM load. These
results suggest that WM emerges from the formation of a dynamic cortical
network linking task-specific processes with non-specific, capacity-
limited, higher-order attentional processes. Practice effects on the EPs
suggested that practice led to the development of a more effective
cognitive strategy for dealing with lower-order aspects of task processing,
but did not diminish demands made on higher order processes. Thus a simple
WM task is shown to be composed of numerous elementary subsecond neural
processes whose characteristics vary with type and amount of information
being remembered, and amount of practice.
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93.
kappa opioid receptors in human microglia downregulate human immunodeficiency virus 1 expression. 总被引:2,自引:0,他引:2 下载免费PDF全文
94.
Sai-Cheong Lee Shie-Shian Huang Chao-Wei Lee Chang-Phone Fung Ning Lee Wen-Bin Shieh LK Siu 《BMC infectious diseases》2007,7(1):79
Background
Ertapenem is a once-a-day carbapenem and has excellent activity against many gram-positive and gram-negative aerobic, facultative, and anaerobic bacteria. The susceptibility of isolates of community-acquired bacteremia to ertapenem has not been reported yet. The present study assesses the in vitro activity of ertapenem against aerobic and facultative bacterial pathogens isolated from patients with community-acquired bacteremia by determining and comparing the MICs of cefepime, cefoxitin, ceftazidime, ceftriaxone, ertapenem, piperacillin, piperacillin-tazobactam, ciprofloxacin, amikacin and gentamicin. The prevalence of extended broad spectrum β-lactamases (ESBL) producing strains of community-acquired bacteremia and their susceptibility to these antibiotics are investigated. 相似文献95.
Grace?TY?Chung Rossa?WK?Chiu Jo?LK?Cheung Yongjie?Jin Stephen?SC?Chim Paul?KS?Chan YM?Dennis?LoEmail author 《BMC infectious diseases》2005,5(1):87
Background
The Severe Acute Respiratory Syndrome (SARS) was a newly emerged infectious disease which caused a global epidemic in 2002–2003. Sequence analysis of SARS-coronavirus isolates revealed that specific genotypes predominated at different periods of the epidemic. This information can be used as a footprint for tracing the epidemiology of infections and monitor viral evolution. However, direct sequencing analysis of a large number of clinical samples is cumbersome and time consuming. We present here a simple and rapid assay for the screening of SARS-coronavirus genotypes based on the use of fluorogenic oligonucleotide probes for allelic discrimination. 相似文献96.
Background
The intestinal microbiota plays an important role in immune development and homeostasis. A disturbed microbiota during early infancy is associated with an increased risk of developing inflammatory and allergic diseases later in life. The mechanisms underlying these effects are poorly understood but are likely to involve alterations in microbial production of fermentation-derived metabolites, which have potent immune modulating properties and are required for maintenance of healthy mucosal immune responses. Probiotics are beneficial bacteria that have the capacity to alter the composition of bacterial species in the intestine that can in turn influence the production of fermentation-derived metabolites. Principal among these metabolites are the short-chain fatty acids butyrate and acetate that have potent anti-inflammatory activities important in regulating immune function at the intestinal mucosal surface. Therefore strategies aimed at restoring the microbiota profile may be effective in the prevention or treatment of allergic and inflammatory diseases.Presentation of the hypothesis
Probiotic bacteria have diverse effects including altering microbiota composition, regulating epithelial cell barrier function and modulating of immune responses. The precise molecular mechanisms mediating these probiotic effects are not well understood. Short-chain fatty acids such as butyrate are a class of histone deacetylase inhibitors important in the epigenetic control of host cell responses. It is hypothesized that the biological function of probiotics may be a result of epigenetic modifications that may explain the wide range of effects observed. Studies delineating the effects of probiotics on short-chain fatty acid production and the epigenetic actions of short-chain fatty acids will assist in understanding the association between microbiota and allergic or autoimmune disorders.Testing the hypothesis
We propose that treatment with specific probiotic bacteria under in vivo conditions would offer the ideal conditions to examine the microbiological, immunological and epigenetic mechanisms of action. Advances in epigenetic technology now allow investigators to better understand the complex biological properties of probiotics and their metabolites.Implications of the hypothesis
Determining the precise mechanisms of probiotic action will lead to more specific and efficacious therapeutic strategies in the prevention or treatment of chronic inflammatory conditions. 相似文献97.
Bunyatyan N. D. Severina H. I. Mokhamad El Kayal Wassim Zalevskyi S. V. Shtrygol’ S. Yu. Shark Amjad Abu Tsyvunin V. V. Kompantsev D. V. Shevchenko A. M. Kovalenko S. N. Georgiyants V. A. Ogay M. A. Khadzhieva Z. J. 《Pharmaceutical Chemistry Journal》2020,54(1):1-6
Pharmaceutical Chemistry Journal - A search for new anticonvulsants led to a series of 2-(4-oxo-2-thioxo-1,4-dihydro-3(2H)-quinazolinyl)- acetamides that were synthesized by reacting... 相似文献
98.
Testicular neoplasms: 29 tumors studied by high-resolution US 总被引:2,自引:0,他引:2
Grantham JG; Charboneau JW; James EM; Kirschling RJ; Kvols LK; Segura JW; Wold LE 《Radiology》1985,157(3):775-780
High-resolution (10-MHz) ultrasonography produces extremely detailed anatomic images of the testis. The sonographic features most helpful in detecting tumors are mass, bright echogenic foci, and diffuse parenchymal texture change. Of 29 patients with testicular neoplasms, 21 (72%) had one or more masses, 19 (66%) had one or more echogenic foci, and nine (31%) had a diffuse parenchymal texture change. Bright echogenic foci were present in six (86%) of seven testes that had a regressed germ-cell tumor. In an attempt to define the histologic features of bright echogenic foci, we performed needle localization under real-time guidance on four operative specimens. We observed immature bone and cartilage, calcification, tubular atrophy and fibrosis, and focal noncalcific scarring. Discovery of occult testicular neoplasms was common (9/29); four patients were thought to have had "extragonadal" germ-cell tumors before abnormalities were found on the sonograms. 相似文献
99.
WH Chow LK Cheung CH ChengUniversity Medical Unit Grantham Hospital Hong Kong 《中华医学杂志(英文版)》1989,102(3):227-229
Total occlusion of the left main coronary artery (LMCA) is a rare finding in patients with stable angina pectoris. To the best of our knowledge, it has not been described in Hong Kong Chinese before. In this paper, we report the clinical and angiographic findings of a Hong Kong Chinese with this condition treated in our unit. 相似文献
100.
Two phantoms, constructed from plastic and water and appropriately proportioned to simulate the female pelvis, were used in the evaluation of the dose delivered to a conceptus from two widely used computed tomographic (CT) scanners. Doses were measured along the central axis and surface of each phantom while scanning 25 contiguous 1-cm sections. Ionization chambers were used for data acquisition. Methods for correcting for partial volume effects inside the chambers are examined. Formulas for calculating the dose to the conceptus in a wide variety of possible situations are presented. These data may be used to guide management of pregnant patients who require or have had CT examinations. 相似文献