共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
Here a virus, there a virus, everywhere the same virus? 总被引:22,自引:0,他引:22
There are an estimated 10(31) viruses on Earth, most of which are phages that infect bacteria. Metagenomic analyses have shown that environmental viral communities are incredibly diverse. There are an estimated 5000 viral genotypes in 200 liters of seawater and possibly a million different viral genotypes in one kilogram of marine sediment. By contrast, some culturing and molecular studies have found that viruses move between different biomes. Together, these findings suggest that viral diversity could be high on a local scale but relatively limited globally. Also, by moving between environments, viruses can facilitate horizontal gene transfer. 相似文献
3.
Nasar Meer 《Ethnic and racial studies》2016,39(3):392-396
ABSTRACTContemporary discussion about race has a tendency to set off out without first checking the rear view mirror. In Theories of Race and Ethnicity: Contemporary Debates and Perspectives, in contrast, Murji and Solomos identify what has and has not been covered, and so appeal at the outset for a ‘more sustained’ account of changing research agendas of race and ethnic relations. Taken as a whole, the collection allows the editors to contemplate ‘what factors explain the mobilizing power of ideas about race and ethnicity in the contemporary environment?' and whether indeed ‘it is the “real” rather than race that should be placed in quotation marks’. 相似文献
4.
A nation is a nation,is a state,is an ethnic group is a … . 总被引:1,自引:0,他引:1
Walker Connor 《Ethnic and racial studies》2013,36(4):377-400
5.
Available data from several completed large-scale randomized trials indicate that beta-carotene supplementation for durations up to 12 years has no overall benefit in well-nourished populations on the incidence of cardiovascular disease or the middle-to-late stages of carcinogenesis. Several important questions, however, remain unanswered. The post-trial follow-up of completed trials, together with the results of several ongoing trials of beta-carotene supplementation, will contribute reliable information to the totality of evidence from basic research, animal studies, observational epidemiologic studies, and completed trials, thus allowing more rational clinical decisions for individual patients and policy decisions for the health of the general public. 相似文献
6.
As Aurora kinases are overexpressed in a large number of cancers, and ectopic expression of Aurora generates polyploid cells containing multiple centrosomes, it has been tempting to suggest that Aurora overexpression provokes genetic instability underlying the tumorigenesis. However, examination of the evidence suggests a more complex relationship. Overexpression of Aurora-A readily transforms rat-1 and NIH3T3 cells, but not primary cells, whereas overexpression of Aurora-B induces metastasis after implantation of tumors in nude mice. Why do polyploid cells containing abnormal centrosome numbers induced by Aurora not get eliminated at cell-cycle checkpoints? Does this phenotype determine the origin of cancer or does it only promote tumor progression? Would drugs against Aurora family members be of any help for cancer treatment? These and related questions are addressed in this review (which is part of the Chromosome Segregation and Aneuploidy series). 相似文献
7.
8.
9.
In order to establish the portrait of Urbilateria, the common ancestor of triblastic metazoan, this paper focuses on the antero-posterior segmentation frequently considered as characterising the bilaterian bauplan. The synthesis presented here describes the morphological, anatomical and functional aspects of this organisation. Furthermore it analyses the conditions of its emergence during the ontogenesis of Annelids, Arthropods and Chordates and identifies its genetic bases. The provided data exhibit the unitary character of the segmentation modalities among protostomian and deuterostomian organisms. This process occurs in two phases, involving a posterior proliferative zone after the gastrulation. It shows the similarity of the expression patterns of orthologous genes, the implication of comparable signalisation and regulation pathways. The congruence of the results obtained at both structural and molecular levels reinforce the segmental organisation conception of the common ancestor of Bilaterians. 相似文献
10.
Eline K. M. Lebbe Steve Peigneur Mohitosh Maiti Prabha Devi Samuthirapandian Ravichandran Eveline Lescrinier Chris Ulens Etienne Waelkens Lisette D'Souza Piet Herdewijn Jan Tytgat 《The Journal of biological chemistry》2014,289(14):9573-9583
α-Conotoxins are peptide toxins found in the venom of marine cone snails and potent antagonists of various subtypes of nicotinic acetylcholine receptors (nAChRs). nAChRs are cholinergic receptors forming ligand-gated ion channels in the plasma membranes of certain neurons and the neuromuscular junction. Because nAChRs have an important role in regulating transmitter release, cell excitability, and neuronal integration, nAChR dysfunctions have been implicated in a variety of severe pathologies such as epilepsy, myasthenic syndromes, schizophrenia, Parkinson disease, and Alzheimer disease. To expand the knowledge concerning cone snail toxins, we examined the venom of Conus longurionis. We isolated an 18-amino acid peptide named α-conotoxin Lo1a, which is active on nAChRs. To the best of our knowledge, this is the first characterization of a conotoxin from this species. The peptide was characterized by electrophysiological screening against several types of cloned nAChRs expressed in Xenopus laevis oocytes. The three-dimensional solution structure of the α-conotoxin Lo1a was determined by NMR spectroscopy. Lo1a, a member of the α4/7 family, blocks the response to acetylcholine in oocytes expressing α7 nAChRs with an IC50 of 3.24 ± 0.7 μm. Furthermore, Lo1a shows a high selectivity for neuronal versus muscle subtype nAChRs. Because Lo1a has an unusual C terminus, we designed two mutants, Lo1a-ΔD and Lo1a-RRR, to investigate the influence of the C-terminal residue. Lo1a-ΔD has a C-terminal Asp deletion, whereas in Lo1a-RRR, a triple-Arg tail replaces the Asp. They blocked the neuronal nAChR α7 with a lower IC50 value, but remarkably, both adopted affinity for the muscle subtype α1β1δϵ. 相似文献
11.
Mammalian polyamine catabolism: a therapeutic target, a pathological problem, or both? 总被引:1,自引:0,他引:1
With the recent discovery of the polyamine catabolic enzyme spermine oxidase (SMO/PAOh1), the apparent complexity of the polyamine metabolic pathway has increased considerably. Alone or in combination with the two other known members of human polyamine catabolism, spermidine/spermine N(1)-acetyltransferase, and N(1)-acetylpolyamine oxidase (PAO), SMO/PAOh1 expression has the potential to alter polyamine homeostasis in response to normal cellular signals, drug treatment and environmental and/or cellular stressors. The activity of the oxidases producing toxic aldehydes and the reactive oxygen species (ROS) H(2)O(2), suggest a mechanism by which these oxidases can be exploited as an antineoplastic drug target. However, inappropriate activation of the pathways may also lead to pathological outcomes, including DNA damage that can lead to cellular transformation. The most recent data suggest that the two polyamine catabolic pathways exhibit distinct properties and understanding these properties should aid in their exploitation for therapeutic and/or chemopreventive strategies. 相似文献
12.
The pfam04002 annotation describes RadC as a bacterial DNA repair protein. Although the radC gene is expressed specifically during competence for genetic transformation in Streptococcus pneumoniae, we report that radC mutants exhibit normal uptake and processing of transforming DNA. They also display normal sensitivity to DNA-damaging agents, providing no support for the rad epithet. 相似文献
13.
Ebach M 《Biologist (London, England)》2003,50(1):48
The newly developing fields of phylogeography and macroecology are ignoring historical patterns at their peril. 相似文献
14.
15.
D. C. Rees 《BMJ (Clinical research ed.)》1897,2(1916):747-748
16.
17.
18.
May photoinhibition be a consequence, rather than a cause, of limited plant productivity? 总被引:1,自引:0,他引:1
William W. Adams III Onno Muller Christopher M. Cohu Barbara Demmig-Adams 《Photosynthesis research》2013,117(1-3):31-44
Photoinhibition in leaves in response to high and/or excess light, consisting of a decrease in photosynthesis and/or photosynthetic efficiency, is frequently equated to photodamage and often invoked as being responsible for decreased plant growth and productivity. However, a review of the literature reveals that photoinhibited leaves characterized for foliar carbohydrate levels were invariably found to possess high levels of sugars and starch. We propose that photoinhibition should be placed in the context of whole-plant source–sink regulation of photosynthesis. Photoinhibition may represent downregulation of the photosynthetic apparatus in response to excess light when (1) more sugar is produced in leaves than can be utilized by the rest of the plant and/or (2) more light energy is harvested than can be utilized by the chloroplast for the fixation of carbon dioxide into sugars. 相似文献
19.
Lin JS Chan CY Yang C Wang YH Chiou HY Su YC 《Experimental biology and medicine (Maywood, N.J.)》2007,232(4):557-564
Zhi-Fuzi (Radix Aconiti lateralis preparata) is prescribed fairly frequently in Chinese medicine clinical practice for treating the complications of cirrhosis. However, scientific evidence regarding its efficacy and safety has not been available until now; in addition, its treatment efficacy has not yet been evaluated in well-designed clinical trials. Hence, we investigated the hemodynamic effects of Zhi-Fuzi in conscious rats with portal vein ligation (PVL) and the safety in normal rats. Our study included 3 parts: (i) early administration during which the hemodynamic effects of low and high doses of Zhi-Fuzi (0.4 and 0.8 g/kg twice daily) and propranolol (15 and 30 mg/kg twice daily) administered for 14 days after PVL on male Sprague-Dawley rats were evaluated; (ii) late administration during which the other group of PVL rats received 2.4 g/kg of Zhi-Fuzi twice daily from the 15th to 28th postoperative day; hemodynamic effects were measured when the Zhi-Fuzi treatment was finished; and (iii) safety evaluation during which 2 groups of normal rats were administered Zhi-Fuzi (0.4 and 0.8 g/kg twice daily) for 14 days; biochemical and histopathologic studies were completed after hemodynamic measurement. In early administration the portal pressures in rats receiving low and high doses of Zhi-Fuzi, low and high doses of propranolol, and distilled water were 13.81 +/- 0.11, 11.59 +/- 0.07, 17.09 +/- 0.06, 14.52 +/- 0.29, and 20.11 +/- 0.22 mm Hg, respectively. The high dose of Zhi-Fuzi exerted more portal hypotensive effects than propranolol and simultaneously ameliorated the systemic arterial hypotension in PVL rats. The late administration of Zhi-Fuzi also significantly reduced the elevated portal pressure (14.56 +/- 0.19 vs. 19.50 +/- 0.31 mm Hg in control, P < 0.05). There were no adverse effects seen in normal rats receiving Zhi-Fuzi. The results suggest that Zhi-Fuzi is a potential drug for the prophylaxis and treatment of portal hypertension. 相似文献
20.
Summary A new chain mutant Hb-Sinai 47
His is described. The aminoacid composition of all tryptic peptides has been determined, with the exception of the insoluble core. In the fingerprint peptide T 6 which normally migrates between T 3 and T 1, moves now between T 3 and T 7. The aminoacid composition of peptide T 6 indicates a change in the aminoacid composition from Asp- to His+ in position 47.This work was supported by Grant No. GM 13714 U.S.P.H.S. 相似文献