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201.
Two fundamental approaches to the comparison of classifications (e g, partitions on the same finite set of objects) can be distinguished One approach is based upon measures of metric dissimilarity while the other is based upon measures of similarity, or consensus These approaches are not necessarily simple complements of each other Instead, each captures different, limited views of comparison of two classifications The properties of these measures are clarified by their relationships to Day's complexity models and to association measures of numerical taxonomy The two approaches to comparison are equated with the use of separation and minimum value sensitive measures, suggesting the potential application of an intermediate sensitive measure to the problem of comparison of classifications Such a measure is a linear combination of separation sensitive and minimum value sensitive components The application of these intermediate measures is contrasted with the two extremes The intermediate measure for the comparison of classifications is applied to a problem of character weighting arising in the analysis of Australian stream basinsWe thank Bill Day, Mike Austin, Peter Minchin and two anonymous referees for many helpful comments We also thank P Arabie for useful discussion of consensus methods and character weighting 相似文献
202.
Basic fibroblast growth factor prevents death of lesioned cholinergic neurons in vivo 总被引:29,自引:0,他引:29
Cutting the axons of the cholinergic neurons that project to the hippocampal formation results in death of most of these cells. Previous studies have shown that administration of nerve growth factor before or at the same time as the lesion will prevent this cell death. Here we demonstrate that basic fibroblast growth factor (FGF) administered into the brain reduces the death of cholinergic neurons in the medial septum and diagonal band of Broca after transection of their axons, in both young adult and aged rats. Moreover, FGF can partially protect against death of cholinergic neurons even when administered two days after axonal transection. These results indicate a possible function for FGF in the normal support of basal forebrain cholinergic neurons, but its range of activity could be wider, for FGF also supports noncholinergic neurons in vitro, it is localized in many of the central nervous system neurons, and it is found in relatively high concentrations in the brain. 相似文献
203.
Both acute and chronic administration of morphine resulted in an increase in the percent cardiac output received by brain. However, various brain regions were affected differently by the drug treatments. The greatest increases in percent cardiac output received after chronic administration of morphine occurred in pons and cerebellum, while the greatest increases after acute administration occurred in cortex and midbrain. The changes found are in contrast with earlier studies which suggest that morphine has no effect on cerebral blood flow. 相似文献
204.
The deeper layers of the superior colliculus are involved in the initiation and execution of saccadic (high velocity) eye movements. A large population of coarsely tuned collicular neurons is active before each saccade. The mechanisms by which the signals that precisely control the direction and amplitude of a saccade are extracted from the activity of the population are unknown. It has been assumed that the exact trajectory of a saccade is determined by the activity of the entire population and that information is not extracted from only the most active cells in the population at a subsequent stage of neural processing. The trajectory of a saccade could be based on vector summation of the movement tendencies provided by each member of the population of active neurons or be determined by a weighted average of the vector contributions of each neuron in the active population. Here we present the results of experiments in which a small subset of the active population was reversibly deactivated with lidocaine. These results are consistent with the predictions of the latter population-averaging hypothesis and support the general idea that the direction, amplitude and velocity of saccadic eye movements are based on the responses of the entire population of cells active before a saccadic eye movement. 相似文献
205.
Accumulations of serotonin (5-HT) and norepinephrine (NE) were compared in control and 6-hydroxydopamine (6-OHDA) pretreated rat aorta, mesenteric and tail arteries. The distribution of these amines was corrected by subtracting tissue uptake of tritiated sorbitol in the extracellular space. 5-HT greatly accumulated both in control and 6-OHDA pretreated arteries. In contrast, NE accumulation in mesenteric and tail arteries was substantially decreased after 6-OHDA treatment. In the aorta 6-OHDA pretreatment did not affect the accumulation of both amines. These findings suggest that 5-HT accumulation in these arteries is mainly extraneuronal, and NE mainly neuronal. Since the accumulation of 5-HT in the aorta was not influenced by pretreatment with 10 microM NE, the extraneuronal uptake mechanisms for 5-HT and NE appear to be different. 相似文献
206.
Edmond W. H. Lee 《武汉大学学报:自然科学英文版》2018,23(4):323-327
The variety membership problem for two classes of non-finitely based semigroups is considered. It is shown that a finite semigroup S belongs to the variety generated by one of these non-finitely based semigroups if and only if S satisfies four certain equations that involve at most 2│S│+1 distinct variables. 相似文献
207.
Linkage of Marfan syndrome and a phenotypically related disorder to two different fibrillin genes. 总被引:55,自引:0,他引:55
B Lee M Godfrey E Vitale H Hori M G Mattei M Sarfarazi P Tsipouras F Ramirez D W Hollister 《Nature》1991,352(6333):330-334
Marfan syndrome (MFS), one of the most common genetic disorders of connective tissue, is characterized by skeletal, cardiovascular and ocular abnormalities. The incidence of the disease is about 1 in 20,000, with life expectancy severely reduced because of cardiovascular complications. As the underlying defect is unknown, MFS diagnosis is based solely on clinical criteria. Certain phenotypic features of MFS are also shared by other conditions, which may be genetically distinct entities although part of a clinical continuum. Immunohistochemical studies have implicated fibrillin, a major component of elastin-associated microfibrils, in MFS aetiology. Genetic linkage analysis with random probes has independently localized the MFS locus to chromosome 15. Here we report that these two experimental approaches converge with the cloning and mapping of the fibrillin gene to chromosome 15q15-21, and with the establishment of linkage to MFS. We also isolated a second fibrillin gene and mapped it to chromosome 5q23-31. We linked this novel gene to a condition, congenital contractural arachnodactyly, that shares some of the features of MFS. Thus, the cosegregation of two related genes with two related syndromes implies that fibrillin mutations are likely to be responsible for different MFS phenotypes. 相似文献
208.
Jae Eun Park Byoung Chul Park Hyun-A Kim Mina Song Sung Goo Park Do Hee Lee Hyeoung-Joon Kim Hyung-Kyoon Choi Jong-Tae Kim Sayeon Cho 《Cellular and molecular life sciences : CMLS》2010,67(15):2619-2629
Apoptosis signal-regulating kinase 1 (ASK1), a member of the MAP kinase kinase kinase, is activated by several death stimuli and is tightly regulated by several mechanisms such as interactions with regulatory proteins and post-translational modifications. Here, we report that dual-specificity phosphatase 13A (DUSP13A) functions as a novel regulator of ASK1. DUSP13A interacts with the N-terminal domain of ASK1 and induces ASK1-mediated apoptosis through the activation of caspase-3. DUSP13A enhances ASK1 kinase activity and thus its downstream factors. Small interfering RNA (siRNA) analyses show that knock-down of DUSP13A in human neuroblastoma SK-N-SH cells reduces ASK1 kinase activity. The phosphatase activity of DUSP13A is not required for the regulation of ASK1. This regulatory action of DSUP13 on ASK1 activity involves competition with Akt1, a negative regulator of ASK1, for binding to ASK1. Taken together, this study provides novel insights into the role of DUSP13A in the precise regulation of ASK1. 相似文献
209.
H. J. Kim M. Y. Kim J. S. Hwang H. J. Kim J. H. Lee K. C. Chang J. -H. Kim C. W. Han J.-H. Kim H. G. Seo 《Cellular and molecular life sciences : CMLS》2010,67(12):2119-2130
Activation of peroxisome proliferator-activated receptor (PPAR) δ by GW501516, a specific PPARδ ligand, significantly inhibited interleukin (IL)-1β-induced proliferation and migration of vascular smooth muscle cells (VSMCs). This effect of GW501516 was dependent on transforming growth factor-β, and was mediated through the up-regulation of IL-1 receptor antagonist. The inhibitory effect of GW501516 on VSMC proliferation was associated with cell cycle arrest at the G1 to S phase transition, which was accompanied by the induction of p21 and p53 along with decreased cyclin-dependent kinase 4 expression. Inhibition of cell migration by GW501516 was associated with the down-regulation of matrix metalloproteinase (MMP)-2 and MMP-9 in IL-1β-treated VSMCs. Inhibition of extracellular signal-regulated kinase significantly reduced the GW501516-mediated inhibition of IL-1β-stimulated VSMC proliferation. These results suggest that PPARδ plays an important role in the pathophysiology of diseases associated with the proliferation and migration of VSMCs. 相似文献
210.