Flatworm phylogeny from partial 18S rDNA sequences

Partial 18S rDNA sequences from 29 flatworms and 2 outgroup taxa were used in a cladistic analysis of the Platyhelminthes. Support for the clades in the resulting single most parsimonious tree was estimated through bootstrap analysis, jack-knife analysis and decay indices. The Acoelomorpha (Acoela and Nemertodermatida) were absent from the most parsimonious tree. The Acoela and the Fecampiidae form a strongly supported clade, the sister group of which may be the Tricladida. There is some support for monophyly of the rhabdocoel taxon Dalyellioida, previously regarded as paraphyletic. The sister group of the Neodermata remains unresolved. This revised version was published online in July 2006 with corrections to the Cover Date.     

Perspectives in the glycosciences – matrix-assisted laser desorption/ionization (MALDI) mass spectrometry of carbohydrates

The technique of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is reviewed with emphasis on the best type of matrix to use with carbohydrates, ways to obtain fragmentation and use of the technique for carbohydrate sequencing. © 1998 Rapid Science Ltd     

Acetic Acid, Ethanol and Steam Effects on the Growth of Botrytis cinerea in vitro and Combination of Steam and Modified Atmosphere Packaging to Control Decay in Kiwifruit

The effects of acetic acid fumigation, ethanol fumigation, and steam heat treatment on growth of Botrytis cinerea in vitro were investigated. The effect of steam heat treatments in combination with modified atmosphere packaging (MAP) on Botrytis decay development on 'Hayward' kiwifruit was also studied. The fungus was grown in Petri dishes on potato dextrose agar. Ethanol fumigation with 100  μ l/l for 3 or 6 min, or 200  μ l/l for 6 min enhanced the growth of B. cinerea . The effect of acetic acid on growth of B. cinerea was time and dosage-dependent. Fumigation with 1  μ l/l for 6 min, 2  μ l/l for 3 min, and 4  μ l/l for 3 min promoted radial growth of the fungus when compared to the growth of the untreated control. Fumigation with 2  μ l/l for 6 min delayed the growth of the fungus for the first 6 days, while fumigation with 6  μ l/l for 3 min delayed the growth of the fungus after the sixth day. Fumigation with 4 or 6  μ l/l acetic acid for 6 min, and 8  μ l/l acetic acid for 3 or 6 min resulted in complete inhibition of fungal growth. Steam heat treatment at 45°C for 6 min, and at 48, 51, and 54°C for 3 or 6 min completely inhibited fungal growth in vitro . Furthermore, steam treatments at 47, 50, and 53°C for 3 or 6 min completely inhibited decay at the stem end of kiwifruit kept at 10°C in MAP for 12 days. However, none of the steam treatments inhibited decay in wounds on the surface of the fruit kept in MAP.     

Long-term patterns of mass loss during the decomposition of leaf and fine root litter: an intersite comparison

Decomposition is a critical process in global carbon cycling. During decomposition, leaf and fine root litter may undergo a later, relatively slow phase; past long-term experiments indicate this phase occurs, but whether it is a general phenomenon has not been examined. Data from Long-term Intersite Decomposition Experiment Team, representing 27 sites and nine litter types (for a total of 234 cases) was used to test the frequency of this later, slow phase of decomposition. Litter mass remaining after up to 10 years of decomposition was fit to models that included (dual exponential and asymptotic) or excluded (single exponential) a slow phase. The resultant regression equations were evaluated for goodness of fit as well as biological realism. Regression analysis indicated that while the dual exponential and asymptotic models statistically and biologically fit more of the litter type–site combinations than the single exponential model, the latter was biologically reasonable for 27–65% of the cases depending on the test used. This implies that a slow phase is common, but not universal. Moreover, estimates of the decomposition rate of the slowly decomposing component averaged 0.139–0.221 year⁻¹ (depending on method), higher than generally observed for mineral soil organic matter, but one-third of the faster phase of litter decomposition. Thus, this material may be slower than the earlier phases of litter decomposition, but not as slow as mineral soil organic matter. Comparison of the long-term integrated decomposition rate (which included all phases of decomposition) to that for the first year of decomposition indicated the former was on average 75% that of the latter, consistent with the presence of a slow phase of decomposition. These results indicate that the global store of litter estimated using short-term decomposition rates would be underestimated by at least one-third.     

氟对镍钛拉簧的腐蚀性研究

目的:研究模拟应用氟化物防龋的口腔环境下,不同浓度氟化物对镍钛拉簧的应力衰减的影响。方法:选取两种国内常用品牌0.010 inch镍钛拉簧各40根,随机将每种拉簧平均分入四个浓度组(0.05%、0.10%、0.15%和对照组),将相同浓度组的不同品牌弹簧分别固定于间距为20 mm的四个支架的两端。将四个支架分别放入37℃人工唾液中水浴。将实验组按浓度分组放入不同浓度氟化人工唾液(0.05%、0.10%、0.15%)中处理5 min,每天三次。分别于实验前、实验后1周、2周、3周、4周用拉伸机测量每根弹簧拉伸至20 mm时的应力。对实验结果使用重复测量的方差分析。结果:时间因素对两种镍钛拉簧拉伸应力的衰减的影响有统计学意义,氟化物浓度有辅助效应,二者有交互作用。氟化物作用下不同品牌镍钛拉簧的应力腐蚀变化不同。(P0.05)。结论:1.氟化物的存在可以增加镍钛拉簧的应力衰减。2.在正畸治疗的临床工作中在使用氟化物时应考虑增加镍钛拉簧的更换频率。     

Heart rot hotel: fungal communities in red-cockaded woodpecker excavations

Tree-cavity excavators such as woodpeckers are ecosystem engineers that have potentially complex but poorly documented associations with wood decay fungi. Fungi facilitate cavity excavation by preparing and modifying excavation sites for cavity excavators. Associations between fungi and endangered red-cockaded woodpeckers (RCWs) are particularly interesting because these are the only birds that specialize in excavating into the heartwood of living pines, a process that takes years to complete. Using molecular methods, we examined fungal communities in complete and incomplete RCW excavations, and non-cavity control trees. In addition to finding a high diversity of fungi, we found three groupings of fungal communities corresponding to the three groups of trees sampled. We show that trees selected for cavity excavation by RCWs are infected by distinct fungal communities, and propose two hypotheses to explain this outcome: the bird facilitation hypothesis and the tree selection hypothesis.     

Hypoxia reduces MAX expression in endothelial cells by unproductive splicing

The MYC–MAX–MXD network is involved in the regulation of cell differentiation and proliferation. Hypoxia affects the expression levels of several members of this network, but changes specific to MAX expression have so far not been shown. We found that in endothelial cells, hypoxia induces alternative splicing of MAX, thereby increasing the expression of two MAX isoforms that differ from the wild type in their 3′ end. Isoform C is degraded by nonsense-mediated decay and isoform E encodes a highly unstable protein. The instability of isoform E is conferred by 36 isoform-specific amino acids, which have the capacity to destabilize heterologous proteins. Both splicing events are therefore unproductive and serve the purpose to downregulate the wild type protein.     

Polypyrimidine tract‐binding protein homologues from Arabidopsis underlie regulatory circuits based on alternative splicing and downstream control

Alternative splicing (AS) of precursor mRNAs is a widespread phenomenon in plants; however, many questions, especially regarding its regulation and functional implications, remain to be elucidated. In vertebrates, polypyrimidine tract‐binding proteins (PTBs) have been identified as key splicing factors influencing splice site selection and orchestrating coordinated splicing programmes during developmental processes. Here, we analysed three PTB homologues from Arabidopsis thaliana and provide evidence for their gene regulatory potential based on AS and a splicing‐independent mechanism. Our data reveal that Arabidopsis PTB homologues are subject to extensive auto‐ and cross‐regulation via AS‐coupled nonsense‐mediated decay, thereby establishing a basis for interlinking their expression. Furthermore, the multiple modes of action of Arabidopsis PTB homologues are reflected in their subcellular localization in the nucleus, cytosol and processing bodies. This work provides insight into the regulation of AS in plants and highlights the regulatory potential of the multifunctional plant PTB homologues, which might have important implications in diverse biological processes.