共查询到20条相似文献,搜索用时 15 毫秒
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A number of experimental paradigms have been used to demonstrate that NCAM, N-cadherin, and L1 stimulate axonal growth. The molecular basis of this response has been extensively studied and a range of agents that inhibit neurite outgrowth stimulated by the above CAMs, but not integrins, have now been identified. These studies pointed to the activation of a tyrosine kinase-PLCgamma cascade as being important for the neurite outgrowth responses stimulated by all three CAMs, and this was substantiated by the identification of agents that could activate the cascade and mimic the growth response. In this review we will suggest that the neurite growth response stimulated by these CAMs is mediated by activation of the fibroblast growth factor receptor (FGFR) in neurons and that this results in the recruitment and activation of PLCgamma via interactions of its SH2 domain with the activated receptor. In this context the key events downstream from activation of PLCgamma required for neurite growth appear to be the conversion of diacylglycerol (DAG) to arachidonic acid (AA) via DAG lipase activity, followed by an increased influx of calcium into the neurons. The evolutionary conservation of putative binding motifs between the above CAMs and the FGFR suggests that activation of the FGFR-PLCgamma cascade by the CAMs might involve a direct CAM-FGFR interaction. The identification of the binding motifs also allows for predictions to be made concerning whether other CAMs might directly interact with the FGFR. 相似文献
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We characterized eight aged beagles (maintained from birth in a laboratory colony) and one black Labrador using Bielschowsky's, thioflavine S, and Congo red staining, and antibodies to the beta-amyloid peptide, dystrophic neurites, and other plaque components. All plaques within these canine brains were of the diffuse subtype and were neither thioflavine S- nor Congo red-positive. The majority of plaques in the entorhinal cortex contained numerous neurons within them while plaques in the dentate gyrus did not. beta-Amyloid immunoreactivity was also present within select neurons and neuronal processes and was detected as a diffuse linear zone corresponding to the terminal fields of the perforant path. There was no significant correlation between extent of beta-amyloid accumulation and neuron number in entorhinal cortex. Neither tau-1, PHF-1, nor SMI-31-immunostaining revealed dystrophic fibers, confirming the classification of these plaques as diffuse. Canine plaques did not appear to contain bFGF- or HS-positive immunostaining. This may explain why neuritic involvement was not detected within these canine plaques. It is possible that the beta-amyloid within the canine brain has a unique primary structure or may not be in an assembly state that adversely affects neurons. 相似文献
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Rapid solidification can be achieved by quenching a thin layer of molten metal on a cold substrate, such as in melt spinning
and thermal spray deposition. An integrated model is developed to predict microstructure formation in rapidly solidified materials
through melt substrate quenching. The model solves heat and mass diffusion equations together with a moving interface that
may either be a real solid/liquid interface or an artificial dendrite tip/melt interface. For the latter case, a dendrite
growth theory is introduced at the interface. The model can also predict the transition of solidification morphology, e.g., from dendritic to planar growth. Microstructure development of Al-Cu alloy splats quenched on a copper substrate is investigated
using the model. Oscillatory planar solidification is predicted under a critical range of interfacial heat-transfer coefficient
between the splat and the substrate. Such oscillatory planar solidification leads to a banded solute structure, which agrees
with the linear stability analysis. Finally, a microstructure selection map is proposed for the melt quenching process based
on the melt undercooling and thermal contact conditions between the splat and the substrate. 相似文献
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OBJECT: Occipital encephaloceles are relatively frequently encountered. Many investigators have addressed the embryogenesis of these formations, but the dural system has never before been studied. In this retrospective analysis the authors sought to gain a better understanding of the origins of these defects. METHODS: The charts and radiological examinations, especially the magnetic resonance venography studies, were reviewed in seven patients. In six patients the straight sinus was absent. Drainage of the galenic system took place through a sinus within the falx, also known as a falcine sinus. The tentorium was not seen in five patients. CONCLUSIONS: The combination of an absent straight sinus and dysplastic tentorium is no coincidence: both develop within the same mesenchyme in the mesencephalic flexure. Distortion of the mesenchyme by a neural tube defect, causing an occipital encephalocele, will lead not only to disorders of the tentorium but also of the straight sinus. 相似文献
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TJ Newman 《Canadian Metallurgical Quarterly》1995,51(5):4212-4221
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Since 1985, the state of Minnesota, through a variety of advocacy, legislative, and interagency efforts, has made incremental gains in public policy and service development for persons with traumatic brain injury (TBI). This article reviews the roles and functions of select state programs and departments in coordinating TBI services. Key initiatives, as well as the current model of public policy and services, are outlined. Current and future service development and initiatives are discussed. Finally, specific implementation recommendations are proposed. 相似文献
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Potter Mary C.; Staub Adrian; Rado Janina; O'Connor Daniel H. 《Canadian Metallurgical Quarterly》2002,28(5):1163
When viewing a rapid sequence of pictures, observes momentarily understand the gist of each scene but have poor recognition memory for most of them (M. C. Potter, 1976). Is forgetting immediate, or does some information persist briefly? Sequences of 5 scenes were presented for 173 ms/picture; when yes-no testing began immediately, recognition was initially high but declined markedly during the 10-item test. With testing delays of 2 or 6 s, the decline over testing was less steep. When 10 or 20 pictures were presented, there was again a marked initial decline during testing. A 2-alternative forced-choice recognition test produced similar results. Both the passage of time and test interference (but not presentation interference) led to forgetting. The brief persistence of information may assist in building a coherent representation over several fixations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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MJ Kendall 《Canadian Metallurgical Quarterly》1998,12(12):803-806
Recent studies have shown that SPECT bone scintigraphy is valuable to detect meniscal tears of the knee. This has not been formally assessed in a prospective study, and no substantive study has compared bone SPECT with other noninvasive diagnostic methods. One hundred consecutive patients referred to an orthopedic surgeon with undiagnosed knee pain were assessed by clinical examination, MRI, SPECT bone scintigraphy, and arthroscopy. The MRI and SPECT bone scan findings were reported blinded to other information. Using arthroscopy as a gold standard, both MRI and SPECT showed high diagnostic ability to detect meniscal tears, with respective sensitivity rate, specificity rates, and positive and negative predictive accuracies of 80%, 71%, 84%, and 71% for MRI and 84%, 80%, 88%, and 76% for SPECT. Some meniscal tears were detected by MRI alone (n = 5) or SPECT alone (n = 8). SPECT bone scintigraphy is a suitable alternative to MRI to detect meniscal tears. The comparable diagnostic ability of SPECT bone scintigraphy implies that it can be used successfully when MRI is unavailable or unsuitable. 相似文献
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The authors present a model to account for the miscombination of features when stimuli are presented using the rapid serial visual presentation (RSVP) technique (illusory conjunctions in the time domain). It explains the distributions of responses through a mixture of trial outcomes. In some trials, attention is successfully focused on the target, whereas in others, the responses are based on partial information. Two experiments are presented that manipulated the mean processing time of the target-defining dimension and of the to-be-reported dimension, respectively. As predicted, the average origin of the responses is delayed when lengthening the target-defining dimension, whereas it is earlier when lengthening the to-be-reported dimension; in the first case the number of correct responses is dramatically reduced, whereas in the second it does not change. The results, a review of other research, and simulations carried out with a formal version of the model are all in close accordance with the predictions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献