Inhibition of rabbit lung angiotensin-converting enzyme by N alpha-[(S)-1-carboxy-3-phenylpropyl]L-alanyl-L-proline and N alpha-[(S)-1-carboxy-3-phenylpropyl]L-lysyl-L-proline

Two novel peptide analogs, N alpha-[(S)-1-carboxy-3-phenylpropyl]L-alanyl-L-proline and the corresponding L-lysyl-L-proline derivative, have been demonstrated to be potent competitive inhibitors of purified rabbit lung angiotensin-converting enzyme: Ki = 2 and 1 X 10(-10) M, respectively, at pH 7.5, 25 degrees C, and 0.3 M chloride ion. Second-order rate constants for addition of these inhibitors to enzyme under the same conditions are in the range 1-2 X 10(6) M-1 s-1; first-order rate constants for dissociation of the EI complexes are in the range 1-4 X 10(-4) s-1. The association rate constants are similar to those measured for D-3-mercapto-2-methylpropanoyl-L-proline, captopril, but the dissociation rate constants are severalfold slower and account for the higher affinity of these inhibitors for the enzyme. The dissociation constant for the EI complex containing N alpha-[(S)-1-carboxy-3-phenylpropyl]L-alanyl-L-proline is pH-dependent, and reaches a minimum at approximately pH 6: Ki = 4 +/- 1 X 10(-11) M. The pH dependence is consistent either with a model for which the protonation state of the secondary nitrogen atom in the inhibitor determines binding affinity, or one for which ionizations on the enzyme alone influence affinity for these inhibitors. The affinity of this inhibitor for the zinc-free apoenzyme is 2 X 10(4) times less than for the zinc-free apoenzyme is 2 X 10(4) times less than that for the holoenzyme. If considered as a "collected product" inhibitor, N alpha-[(S)-1-carboxy-3-phenylpropyl]L-alanyl-L-proline appears to derive an additional factor of 375 M in its affinity for the enzyme compared to that of the two products of its hypothetical hydrolysis, a consequence of favorable entropy effects.     

Production of DON-related trichothecenes byFusarium graminearum Schw from Krasnodarski krai of the USSR

34Fusarium graminearum Schw isolates produced 4-deoxynivalenol to form significant amounts of 4, 7 — dideoxynivalenol and lesser amounts of 4 — deoxynivalenol monoacetates on grain substratesin vitro. This is the first report on the capability a large group of naturally occurring isolates to produce 4,7-dideoxynivalenol. The average levels of 4,7-dideoxynivalenol on rice, corn, barley, and wheat as a substrate were respectively 26.8, 14.0, 12.8, and 10.5% of the level of 4-deoxynivalenol. 4, 7 — dideoxynivalenol was present in all examined naturally contaminated wheat kernel samples at levels of 1.7 to 7.9% of the level of 4-deoxynivalenol. These findings suggest that more attention should be given to the occurrence of 4,7-dideoxynivalenol in cereals.     

Phenylalkyl ketones as potent reversible inhibitors of interleukin-1β converting enzyme

Phenylalkyl ketones are potent reversible inhibitors of interleukin-1β converting enzyme (ICE). The extended alkyl chain ketones AcTyrValAlaAspCO(CH₂)_nPh display increased potency over the simple aryl ketone. In particular, the tetrapeptide AcTyrValAlaAspCOPh has a K_i of 10μM while AcTyrValAlaAspCO(CH₂)₅Ph has a K_i of 18.5nM.     

Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex

The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S nuclear ribosomal DNA sequence and the intervening 5.8S region were sequenced from three individuals in each of eight taxa of the Mimulus guttatus species complex. Three discrete variants, or "types," of ITS sequences were found, among which 30%-40% of sites differed, compared with 1%-2% within types. Dot plots indicate that these types were not related by conspicuous rearrangements or inversions. More than one ITS type was often found in the same taxon, and two of three ITS types span species boundaries, indicating their presence prior to speciation. These ITS sequences showed essentially no positional homology with the nearest sequenced relative, tomato. In contrast, the 5.8S region was relatively unvaried, with 8 of 162 sites varied in the sample among all eight taxa. The phylogeny inferred by the most common ITS sequence type, rooted by the two other ITS types, agreed with isozymes in showing the distinctness of M. nudatus, M. laciniatus, and M. tilingii from the other five taxa.      

中国小菇属十个新记录种

报道了小菇科小菇属真菌10个中国新记录种,香菌组：橙盖小菇Mycena aurantiidisca、黄白小菇Mycena flavoalba、粉黄小菇Mycena floridula;棘刺组：异刺小菇Mycena heteracantha;纤柄组：碱味小菇Mycena amygdalina;脆足组：粉被小菇Mycena zephirus;冬生组：绣线菊小菇Mycena speirea、冬生小菇Mycena hiemalis;小菇组：绒柄小菇Mycena flos-nivium,分别来自吉林等11个省份、自治区。提供了每个物种的形态描述和线条图,以及与相近种的讨论。共计90条自测及下载ITS序列,在采用贝叶斯法和最大似然法构建的小菇属系统发育树中,新记录种均得到分子数据支持。凭证标本存放于吉林农业大学菌物标本馆（HMJAU）。     

川芎嗪对Aβ25-35诱导体外大鼠海马神经元细胞凋亡的影响

本文通过Aβ25-35诱导体外原代培养的SD乳大鼠海马神经元,建立Aβ毒性损伤细胞模型,结合AnnexinV-FITC/PI荧光双染法流式细胞术、MTT比色法、实时荧光定量PCR及Western blot方法检测川芎嗪(tetrameth-ylpyrazine,TMP)对原代培养的海马神经元细胞活性、早期凋亡率和Bax、Bcl-2基因表达的影响。结果显示川芎嗪高、中剂量可明显增强细胞活性,增加神经元细胞的存活率(P<0.01),可显著抑制海马神经元细胞早期凋亡(P<0.01),抑制凋亡蛋白Bax的表达(P<0.01),增强抗凋亡蛋白bcl-2的表达(P<0.01)。川芎嗪可通过调节Bax/Bcl-2平衡抵抗Aβ25-35诱导的海马神经元凋亡,降低Aβ的神经元毒性,对海马神经元损伤有明显的保护作用。     

Modelling expected trout ranges under current and future water temperature regimes in the Eastern Cape,South Africa

Different values have resulted in conflicts between anglers and conservation lobbies in the management of trout in South Africa. Key to the conflict is the demarcation of boundaries to areas in which brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss currently occur, or are likely to establish following stocking for angling. To provide a longer-term perspective on these areas, we developed models to link salmonid biological thermal thresholds to elevation. These, when applied spatially using a digital elevation model with a probability of occurrence model, provided the basis for estimating potentially available thermal habitat for these two cold water species. Here, we acknowledge that other variables (stocking history; river connectivity) also play a role in understanding trout distributions. Using a simple scenario of an increase in mean daily water temperatures of 2 °C, we demonstrated that both brown and rainbow trout are likely to exhibit considerable range reductions in the future. Because it is possible that these range restrictions will result in an increasing desire to introduce trout into areas above their current distribution limits for the maintenance of angling opportunities, conservation managers should prioritise these areas, with management interventions seeking to understand what will help to limit introductions.