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451.
Mendola JD Conner IP Sharma S Bahekar A Lemieux S 《Journal of cognitive neuroscience》2006,18(3):363-375
Filling-in refers to the tendency of stabilized retinal stimuli to fade and become replaced by their background. This phenomenon is a good example of central brain mechanisms that can selectively add or delete information to/from the retinal input. Importantly, such cortical mechanisms may overlap with those that are used more generally in visual perception. In order to identify cortical areas that contribute to perceptual filling-in, we used functional magnetic resonance imaging to image activity in the visual cortex while subjects experienced filling-in. Nine subjects viewed an achromatic disc with slightly higher luminance than the background and indicated the presence or absence of filling-in by a keypress. The disc was placed in either the upper or lower left quadrant. Similar high-contrast stimuli were used to map out the retinotopic representation of the disc. Unexpectedly, the lower-field high-contrast stimulus produced more parietal cortex activation than the upper-field condition, indicating preferential representation of the lower field by attentional control mechanisms. During perceptual filling-in, we observed significant contralateral reductions in activation in lower-tier retinotopic areas V1 and V2. In contrast, increased activation was consistently observed in visual areas V3A and V4v, higher-level cortex in the intraparietal sulcus, posterior superior temporal sulcus, and the ventral occipital-temporal region, as well as the pulvinar. The filling-in activation pattern was remarkably similar for both the upper- and lower-field conditions. Behaviorally, filling-in was reported to be easier for the lower visual field, and filling-in periods were longer for the lower than the upper quadrant. We suggest this behavioral asymmetry may be partially due to the preferential parietal representation of the lower field. The results lead us to propose that perceptual filling-in recruits high-level control mechanisms to reconcile competing percepts, and alters the normal image-related signals at the first stages of cortical processing. Moreover, the overall pattern of activation during filling-in resembles that seen in other studies of perceptually bistable stimuli, including binocular rivalry, indicating common control mechanisms. 相似文献
452.
Hunt RH Xiao SD Megraud F Leon-Barua R Bazzoli F van der Merwe S Vaz Coelho LG Fock M Fedail S Cohen H Malfertheiner P Vakil N Hamid S Goh KL Wong BCY Krabshuis J Le Mair A 杜颖 戴宁 《胃肠病学》2011,16(7):423-428
世界上有一半人口感染幽门螺杆菌(H.pylori),其感染率因地理位置、种族、年龄和社会经济状况不同而存在很大差异.在发展中国家较高.发达国家较低。但总体而言,近年世界许多地区的H.pylori感染率均呈下降趋势。 相似文献
453.
O Saito CI Svensson MW Buczynski K Wegner X-Y Hua S Codeluppi RH Schaloske RA Deems EA Dennis TL Yaksh 《British journal of pharmacology》2010,160(7):1754-1764
Background and purpose:
Toll-like receptor 4 (TLR4) expressed on spinal microglia and astrocytes has been suggested to play an important role in the regulation of pain signalling. The purpose of the present work was to examine the links between TLR4, glial activation and spinal release of prostaglandin E2 (PGE2) and tumour necrosis factor (TNF), and the role these factors play in TLR4-induced tactile allodynia.Experimental approach:
Toll-like receptor 4 was activated by intrathecal (i.t.) injection of lipopolysaccharide (LPS) and KDO2-Lipid A (KDO2) to rats. Tactile allodynia was assessed using von Frey filaments and cerebrospinal fluid collected through spinal dialysis and lumbar puncture. PGE2 and TNF levels were measured by mass spectometry and elisa. Minocycline and pentoxifylline (glia inhibitors), etanercept (TNF-blocker) and ketorolac (COX-inhibitor) were given i.t. prior to injection of the TLR4-agonists, in order to determine if these agents alter TLR4-mediated nociception and the spinal release of PGE2 and TNF.Key results:
Spinal administration of LPS and KDO2 produced a dose-dependent tactile allodynia, which was attenuated by pentoxifylline, minocycline and etanercept but not ketorolac. Both TLR4 agonists induced the spinal release of PGE2 and TNF. Intrathecal pentoxifylline blunted PGE2 and TNF release, while i.t. minocycline only prevented the spinal release of TNF. The release of PGE2 induced by LPS and KDO2 was attenuated by i.t. administration of ketorolac.Conclusions and implications:
Activation of TLR4 induces tactile allodynia, which is probably mediated by TNF released by activated spinal glia. 相似文献454.
The clinical records and radiographs of 45 patients who had undergone replantation of a total hand, or a part thereof, were reviewed in order to determine the prevalence and the type of articular changes occurring distal to the site of anastomoses. In three patients, destructive joint changes were observed, consisting of bony fragmentation, spiculation, and cystic or erosive lesions. These changes, which developed between five and ten months after replantation, are most likely neuropathic or osteonecrotic in pathogenesis. 相似文献
455.
mdx muscle pathology is independent of nNOS perturbation 总被引:2,自引:0,他引:2
Crosbie RH; Straub V; Yun HY; Lee JC; Rafael JA; Chamberlain JS; Dawson VL; Dawson TM; Campbell KP 《Human molecular genetics》1998,7(5):823-829
In skeletal muscle, neuronal nitric oxide synthase (nNOS) is anchored to
the sarcolemma via the dystrophin-glycoprotein complex. When dystrophin is
absent, as in Duchenne muscular dystrophy patients and in mdx mice, nNOS is
mislocalized to the interior of the muscle fiber where it continues to
produce nitric oxide. This has led to the hypothesis that free radical
toxicity from mislocalized nNOS may contribute to mdx muscle pathology. To
test this hypothesis directly, we generated mice devoid of both nNOS and
dystrophin. Overall, the nNOS- dystrophin null mice maintained the
dystrophic characteristics of mdx mice. We evaluated the mice for several
features of the dystrophic phenotype, including membrane damage and muscle
morphology. Removal of nNOS did not alter the extent of sarcolemma damage,
which is a hallmark of the dystrophic phenotype. Furthermore, muscle from
nNOS-dystrophin null mice maintain the histological features of mdx
pathology. Our results demonstrate that relocalization of nNOS to the
cytosol does not contribute significantly to mdx pathogenesis.
相似文献
456.
Temporomandibular joint clicking with nonreducing anterior displacement of the meniscus 总被引:1,自引:0,他引:1
Patients who have temporomandibular joint (TMJ) clicking and pain are assumed to have an anterior displacement of the meniscus with reduction on opening of the jaw. On the basis of this assumption, these patients are treated nonsurgically with splint therapy. Of 301 TMJs examined, 108 (36%) produced clinically audible clicks on opening, closing, or both. Fluoroscopy and arthrotomography studies for 16 (15%) showed anteriorly displaced menisci without reduction. The mean age of this group was 32 years, with a range of 17-51 years. The duration of the patients' symptoms ranged from three months to eight years (mean 3.7 years). Bilateral degenerative joint disease was noted in 8/16 (50%). Operative findings in four patients suggested the cause of the clicking sound as a frictional impact between the degenerated surface of the condyle and the hypertrophied displaced meniscus. These observations demonstrate that an audible click may not imply a reduction of a displaced meniscus. 相似文献
457.
458.
Jones RH 《Alimentary pharmacology & therapeutics》1996,10(3):233-239
Gastrointestinal disorders are common in the general population, with annual prevalence figures ranging from 20% for irritable bowel syndrome to over 40% for dyspepsia. Less than one-third of patients consult general practitioners for these problems, and anxiety about serious disease and cancer are as important in the decision to consult as symptom severity. Gastrointestinal disorders have significant socioeconomic effects in the community, and account for 10% of the work of general practitioners in the UK. The health economics implications of management in primary care relate principally to the costs of investigation and therapy, notably antisecretory drugs, endoscopy, radiology and specialist referral. Although guidelines based on evidence and agreed between primary and secondary care physicians offer an attractive approach to rationalizing the use of resources, there is at present little health service research evidence on which to base important decisions. For example, in dyspepsia, the role of Helicobacter pylori identification and eradication in an overall management strategy in primary care has yet to be defined. An exploration of the clinical economics of gastrointestinal disorders in general practice raises a number of research questions, which will require the attention of both generalists and specialists. 相似文献
459.
New charts for height, weight, height velocity, and weight velocity are presented for clinical (as opposed to population survey) use. They are based on longitudinal-type growth curves, using the same data as in the British 1965 growth standards. In the velocity standards centiles are given for children who are early- and late-maturing as well as for those who mature at the average age (thus extending the use of the previous charts). Limits of normality for the age of occurrence of the adolescent growth spurt are given and also for the successive stages of penis, testes, and pubic hair development in boys, and for stages of breast and pubic hair development in girls. 相似文献
460.