Second messengers regulate RGS2 expression which is targeted to the nucleus.

Regulators of G-protein Signaling (RGS) proteins attenuate signaling activities of G proteins, and modulation of expression appears to be a primary mechanism for regulating RGS proteins. In human astrocytoma 1321N1 cells RGS2 expression was increased by activation of muscarinic receptors coupled to phosphoinositide signaling with carbachol, or by increased cyclic AMP production, demonstrating that both signaling systems can increase the expression of a RGS family member in a single cell type. Carbachol-stimulated increases in endogenous RGS2 protein levels appeared by immunocytochemical analysis to be largely confined to the nucleus, and this localization was confirmed by Western blot analysis which showed increased nuclear, but not cytosolic, RGS2 after carbachol treatment. Additionally, transiently expressed green fluorescent protein (GFP)-tagged, 6xHis-tagged, or unmodified RGS2 resulted in a predominant nuclear localization, as well as a distinct accumulation of RGS2 along the plasma membrane. The intranuclear localization of GFP-RGS2 was confirmed with confocal microscopy. Thus, RGS2 expression is rapidly and transiently increased by phosphoinositide signaling and by cyclic AMP, and endogenous and transfected RGS2 is largely, although not entirely, localized in the nucleus.     

Metabolomics reveals herbivore‐induced metabolites of resistance and susceptibility in maize leaves and roots

Plants respond to herbivory by reprogramming their metabolism. Most research in this context has focused on locally induced compounds that function as toxins or feeding deterrents. We developed an ultra‐high‐pressure liquid chromatography time‐of‐flight mass spectrometry (UHPLC‐TOF‐MS)‐based metabolomics approach to evaluate local and systemic herbivore‐induced changes in maize leaves, sap, roots and root exudates without any prior assumptions about their function. Thirty‐two differentially regulated compounds were identified from Spodoptera littoralis‐infested maize seedlings and isolated for structure assignment by microflow nuclear magnetic resonance (CapNMR). Nine compounds were quantified by a high throughput direct nano‐infusion tandem mass spectrometry/mass spectrometry (MS/MS) method. Leaf infestation led to a marked local increase of 1,3‐benzoxazin‐4‐ones, phospholipids, N‐hydroxycinnamoyltyramines, azealic acid and tryptophan. Only few changes were found in the root metabolome, but 1,3‐benzoxazin‐4‐ones increased in the vascular sap and root exudates. The role of N‐hydroxycinnamoyltyramines in plant–herbivore interactions is unknown, and we therefore tested the effect of the dominating p‐coumaroyltyramine on S. littoralis. Unexpectedly, p‐coumaroyltyramine was metabolized by the larvae and increased larval growth, possibly by providing additional nitrogen to the insect. Taken together, this study illustrates that herbivore attack leads to the induction of metabolites that can have contrasting effects on herbivore resistance in the leaves and roots.     

聚酸酐控释制剂的研究进展

聚酸酐材料是一种良好的生物可降解材料,它可以作为药物载体将药物递送入人体的各个器官,如脑、骨骼、血管等,也可作为基因的载体对患者进行基因治疗。聚酸酐的合成工艺简单、成本低廉,可以满足不同的用途。它奇在人体内降解为对人体无害的二元酸而排除体内,具有良好的生物相容性。文中综述了聚酸酐的合成,聚酸酐控释制剂的制备工艺、降解、体内安全性和临床应用方面的研究进展,并提出了今后的发展方向。聚酸酐在医学方面的研究和应用必将日益广泛。     

Fungi associated with rice at entre rios province, Argentina. toxigenic capacity offusarium graminearum andmicrodochium nivale isolates

A mycological survey was carried out on rice samples harvested in 1997 and 1998 from Entre Ríos province, belonging to the main production area of Argentina. The relative density and isolation frequency of the prevalent fungi were statistically compared between locations and harvest seasons. The genusAlternaria was the most prevalent component of the internal seedborne mycoflora in the two harvest seasons. Fungi belonging to the generaPhoma, Fusarium, Microdochium, Penicillium andAspergillus were also isolated. The predominant species of these genera wereAlternaria alternata, Phoma glomerata, Fusarium graminearum, Microdochium nivale, Penicillium citrinum and Aspergillus flavus.     

Climate change hastens the turnover of stream fish assemblages

Stream fish are expected to be significantly influenced by climate change, as they are ectothermic animals whose dispersal is limited within hydrographic networks. Nonetheless, they are also controlled by other physical factors that may prevent them moving to new thermally suitable sites. Using presence–absence records in 655 sites widespread throughout nine French river units, we predicted the potential future distribution of 30 common stream fish species facing temperature warming and change in precipitation regime. We also assessed the potential impacts on fish assemblages' structure and diversity. Only cold-water species, whose diversity is very low in French streams, were predicted to experience a strong reduction in the number of suitable sites. In contrast, most cool-water and warm-water fish species were projected to colonize many newly suitable sites. Considering that cold headwater streams are the most numerous on the Earth's surface, our results suggested that headwater species would undergo a deleterious effect of climate change, whereas downstream species would expand their range by migrating to sites located in intermediate streams or upstream. As a result, local species richness was forecasted to increase greatly and high turnover rates indicated future fundamental changes in assemblages' structure. Changes in assemblage composition were also positively related to the intensity of warming. Overall, these results (1) stressed the importance of accounting for both climatic and topographic factors when assessing the future distribution of riverine fish species and (2) may be viewed as a first estimation of climate change impacts on European freshwater fish assemblages.     

Lead-phase and red-stripe color morphs of red-backed salamanders Plethodon cinereus differ in hematological stress indices: A consequence of differential predation pressure?

Throughout the animal kingdom there are species that have two or more phenotypic forms or 'morphs', and many of these are amphibians. In North America, the red-backed salamander Plethodon cinereus can have either a red dorsal stripe or no dorsal stripe (lead-phase form), and evidence to date indicates the lead-phase form incurs a greater number of attacks from predators. In a recent collection of 51 P. Cinereus, blood smears of both color morphs (35 red-stripe, 16 lead-phase) were examined to obtain numbers of circulating leukocytes (via light microscopy), which can be used to indirectly estimate levels of stress hormones in vertebrates via a 'hematological stress index', which is the ratio between the number of two leukocyte types (neutrophils and lymphoeytes). Our results showed that lead-phase salamanders tended to have greater numbers of circulating neutrophils and lower numbers of circulating iymphocytes than red-stripe morphs, leading to higher average neutrophil-lymphocyte ratios in lead-phase individuals. Since the salamanders were held (refrigerated) for 7 days before sampling, we cannot be certain if this effect is a stress reaction to the captivity or the normal level for this morph. However comparison with two sets of related salamanders that were captured and sampled immediately indicates the red-stripe salamanders were either not stressed from the captivity at all, or their white blood cell distributions had returned to normal after 7 days of captivity. Taken together, our results indicate that lead-phase forms of P. Cinereus have higher stress levels than the red-stripe forms, which may be a consequence of their higher exposure to, and/or attacks from, predators. They may also indicate that the lead-phase form is less-suited to captivity than the red-stripe form of this species.     

Evolution of the secondary structures and compensatory mutations of the ribosomal RNAs of Drosophila melanogaster

This paper examines the effects of DNA sequence evolution on RNA secondary structures and compensatory mutations. Models of the secondary structures of Drosophila melanogaster 18S ribosomal RNA (rRNA) and of the complex between 2S, 5.8S, and 28S rRNAs have been drawn on the basis of comparative and energetic criteria. The overall AU richness of the D. melanogaster rRNAs allows the resolution of some ambiguities in the structures of both large rRNAs. Comparison of the sequence of expansion segment V2 in D. melanogaster 18S rRNA with the same region in three other Drosophila species and the tsetse fly (Glossina morsitans morsitans) allows us to distinguish between two models for the secondary structure of this region. The secondary structures of the expansion segments of D. melanogaster 28S rRNA conform to a general pattern for all eukaryotes, despite having highly divergent sequences between D. melanogaster and vertebrates. The 70 novel compensatory mutations identified in the 28S rRNA show a strong (70%) bias toward A-U base pairs, suggesting that a process of biased mutation and/or biased fixation of A and T point mutations or AT-rich slippage-generated motifs has occurred during the evolution of D. melanogaster rDNA. This process has not occurred throughout the D. melanogaster genome. The processes by which compensatory pairs of mutations are generated and spread are discussed, and a model is suggested by which a second mutation is more likely to occur in a unit with a first mutation as such a unit begins to spread through the family and concomitantly through the population. Alternatively, mechanisms of proofreading in stem-loop structures at the DNA level, or between RNA and DNA, might be involved. The apparent tolerance of noncompensatory mutations in some stems which are otherwise strongly supported by comparative criteria within D. melanogaster 28S rRNA must be borne in mind when compensatory mutations are used as a criterion in secondary-structure modeling. Noncompensatory mutation may extend to the production of unstable structures where a stem is stabilized by RNA- protein or additional RNA-RNA interactions in the mature ribosome. Of motifs suggested to be involved in rRNA processing, one (CGAAAG) is strongly overrepresented in the 28S rRNA sequence. The data are discussed both in the context of the forces involved with the evolution of multigene families and in the context of molecular coevolution in the rDNA family in particular.