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排序方式: 共有792条查询结果,搜索用时 15 毫秒
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Some properties of a newly isolated Haemophilus influenzae bacteriophage are described. The phage is morphologically distinct from previously described H. influenzae phages. 相似文献
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Huastec noncrop resource management: Implications for prehistoric rain forest management 总被引:1,自引:0,他引:1
Janis B. Alcorn 《Human ecology: an interdisciplinary journal》1981,9(4):395-417
The Huastec have interacted with elements of a diverse flora in northeastern Mexico for 30 centuries. A Huastec plant-management model is derived from patterns reflected in all anthropogenic vegetation zones, from the dooryard to the forest, and used to discuss the possible effects of human activities upon the prehistoric rain forest. Huastec plant management is discussed from an analytical perspective which views plant management as resulting from the integration of two types of plant manipulation: the manipulation of vegetation en masse and the manipulation of individual plants. Decisions about plant manipulation reflect a concern for minimal labor investment to place the resource at hand. Noncrop plant manipulation practices potentially influence the evolution of individual plants and plant communities primarily by affecting species' distribution and population parameters. Since the impact of plant-management practices clearly goes beyond domestication, ways of evaluating such practices in order to expand our understanding of ethnobotanical interactions and their impact are suggested. 相似文献
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Diana L Williams Michael W Schwartz L Scot Bastian James E Blevins Denis G Baskin 《The journal of histochemistry and cytochemistry》2008,56(3):285-293
Current evidence suggests that leptin reduces food intake in part by enhancing the hindbrain neuronal response to meal-related gastrointestinal signals, including cholecystokinin (CCK), but the phenotypes of the relevant cells are not known. To identify neurons that participate in this interaction in the rat nucleus of the solitary tract (NTS), we induced c-Fos gene expression in NTS neurons with leptin and CCK. We focused on NTS catecholamine neurons because these cells have been implicated in the feeding response to CCK. Hindbrain sections from rats that received CCK with or without leptin pretreatment were immunostained for c-Fos and tyrosine hydroxylase (TH) by a double immunofluorescence procedure. Leptin pretreatment increased the number of NTS cells expressing c-Fos-like immunoreactivity (cFLI) 3-fold relative to CCK alone, but the number of TH-positive cells with cFLI was increased 6-fold. Next, cells detected by immunofluorescence for TH were collected by laser capture microdissection and pooled for real-time quantitative PCR of c-Fos mRNA. Here, neither le0ptin nor CCK alone affected the relative amount of mRNA in the TH cell-enriched samples, but leptin plus CCK substantially increased c-Fos mRNA content. These histochemical findings identify hindbrain catecholamine cells as potential mediators of the interaction between leptin and CCK. 相似文献
788.
The potential for making functional interpretations from a single postcranial element for marsupials was investigated through morphometric analysis of the calcanea of 61 extant species from Australia and New Guinea. Extant species were grouped into locomotor categories and a canonical variates analysis was carried out on measurements of their calcanea. A relationship between measurements of the calcanea and the locomotor behavior of species was found, allowing for prediction of locomotor behavior from calcaneum morphometrics. This was applied to fossil marsupial taxa, from early–late Miocene/?Pliocene deposits at Riversleigh, in an attempt to determine their locomotor behavior. Hopping (saltatorial) taxa are distinguished from quadruped terrestrial taxa and taxa capable of climbing (arboreal and scansorial) by their relatively longer tuber calcis and wider calcaneal head, by their dorso-ventrally thicker calcaneal head, and by their calcaneocuboid facet being less steeply angled antero-posteriorly. Taxa capable of climbing are distinguished from quadruped terrestrial taxa by their shorter tuber calcis relative to the calcaneal head and by their smaller calcaneo-astragalar facet. The locomotor categories distinguished in this study (arboreal/scansorial, quadruped terrestrial, and saltatorial) highlight differences between species in their use of available substrates and thus are informative with regards to the structural components of their habitat. The results of this analysis can be used, in combination with other data, to make inferences about the habitats of paleocommunities at Riversleigh through the Miocene. The calcaneum is a dense and very robust element and, therefore, has a good chance of being preserved. This method provides a quick and easy way of inferring locomotion and has a wide potential for application to many fossil deposits because it requires only a single element. 相似文献
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Aleksandrs Pustenko Dmitrijs Stepanovs Daniela Vullo Andris Kazaks Janis Leitans 《Journal of enzyme inhibition and medicinal chemistry》2017,32(1):767-775
A new chemotype with carbonic anhydrase (CA, EC 4.2.1.1) inhibitory action has been discovered, the homo-sulfocoumarins (3H-1,2-benzoxathiepine 2,2-dioxides) which have been designed considering the (sulfo)coumarins as lead molecules. An original synthetic strategy of a panel of such derivatives led to compounds with a unique inhibitory profile and very high selectivity for the inhibition of the tumour associated (CA IX/XII) over the cytosolic (CA I/II) isoforms. Although the CA inhibition mechanism with these new compounds is unknown for the moment, we hypothesize that it may be similar to that of the sulfocoumarins, i.e. hydrolysis to the corresponding sulfonic acids which thereafter anchor to the zinc-coordinated water molecule within the enzyme active site. 相似文献