Effects of Polystyrene Microplastics on Growth and Toxin Production of Alexandrium pacificum

Microplastics (MP) widely distributed in aquatic environments have adverse effects on aquatic organisms. Currently, the impact of MP on toxigenic red tide microalgae is poorly understood. In this study, the strain of Alexandrium pacificum ATHK, typically producing paralytic shellfish toxins (PST), was selected as the target. Effects of 1 and 0.1 μm polystyrene MP with three concentration gradients (5 mg L⁻¹, 25 mg L⁻¹ and 100 mg L⁻¹) on the growth, chlorophyll a (Chl a), photosynthetic activity (F_v/F_m) and PST production of ATHK were explored. Results showed that the high concentration (100 mg L⁻¹) of 1 μm and 0.1 μm MP significantly inhibited the growth of ATHK, and the inhibition depended on the size and concentration of MP. Contents of Chl a showed an increase with various degrees after MP exposure in all cases. The photosynthesis indicator F_v/F_m of ATHK was significantly inhibited in the first 11 days, then gradually returned to the level of control group at day 13, and finally was gradually inhibited in the 1 μm MP treatments, and promotion or inhibition to some degree also occurred at different periods after exposure to 0.1 μm MP. Overall, both particle sizes of MP at 5 and 25 mg L⁻¹ had no significant effect on cell toxin quota, and the high concentration 100 mg L⁻¹ significantly promoted the PST biosynthesis on the day 7, 11 and 15. No significant difference occurred in the cell toxin quota and the total toxin content in all treatments at the end of the experiment (day 21). All MP treatments did not change the toxin profiles of ATHK, nor did the relative molar percentage of main PST components. The growth of ATHK, Chl a content, F_v/F_m and toxin production were not affected by MP shading. This is the first report on the effects of MP on the PST-producing microalgae, which will improve the understanding of the adverse impact of MP on the growth and toxin production of A. pacificum.     

Geographical Patterns in Cyanobacteria Distribution: Climate Influence at Regional Scale

Cyanobacteria are a component of public health hazards in freshwater environments because of their potential as toxin producers. Eutrophication has long been considered the main cause of cyanobacteria outbreak and proliferation, whereas many studies emphasized the effect of abiotic parameters (mainly temperature and light) on cell growth rate or toxin production. In view of the growing concerns of global change consequences on public health parameters, this study attempts to enlighten climate influence on cyanobacteria at regional scale in Brittany (NW France). The results show that homogeneous cyanobacteria groups are associated with climatic domains related to temperature, global radiation and pluviometry, whereas microcystins (MCs) occurrences are only correlated to local cyanobacteria species composition. As the regional climatic gradient amplitude is similar to the projected climate evolution on a 30-year timespan, a comparison between the present NW and SE situations was used to extrapolate the evolution of geographical cyanobacteria distribution in Brittany. Cyanobacteria composition should shift toward species associated with more frequent Microcystins occurrences along a NW/SE axis whereas lakes situated along a SW/NE axis should transition to species (mainly Nostocales) associated with lower MCs detection frequencies.     

Bt Toxin Modification for Enhanced Efficacy

Insect-specific toxins derived from Bacillus thuringiensis (Bt) provide a valuable resource for pest suppression. Here we review the different strategies that have been employed to enhance toxicity against specific target species including those that have evolved resistance to Bt, or to modify the host range of Bt crystal (Cry) and cytolytic (Cyt) toxins. These strategies include toxin truncation, modification of protease cleavage sites, domain swapping, site-directed mutagenesis, peptide addition, and phage display screens for mutated toxins with enhanced activity. Toxin optimization provides a useful approach to extend the utility of these proteins for suppression of pests that exhibit low susceptibility to native Bt toxins, and to overcome field resistance.     

The roles of toxin A and toxin B in Clostridium difficile infection

We recently published our findings indicating that anti-TcdB antibodies were effective as treatment for C. difficile infection, but that anti-TcdA actually worsened prognosis in the gnotobiotic piglet model. To further investigate the roles of the two toxins, we administered purified toxins separately or together, systemically, to piglets and found that both toxins, either alone or together, are able to elicit severe lesions systemically and are also able to cross into the gut lumen and cause large intestinal lesions typical of infection. We also found that anti-TcdA administered before systemic challenge with TcdA again did not protect from development of disease, but, in this case, did not appear to worsen prognosis. Further work is still needed, but these findings add to the growing knowledge regarding the roles of the C. difficile toxins.     

注射A型肉毒素治疗慢性每日头痛的观察与护理

目的 观察A型肉毒素治疗慢性每日头痛(CDH)的疗效.方法60 例患者随机分为观察组和对照组.观察组采用A型肉毒素,对照组采用利多卡因加醋酸泼尼松龙注射液,两组同时进行头部固定位点和痛点一次性注射.随后在12周的不同时间段内,通过电话回访或嘱患者就诊了解情况.结果 观察组患者头痛的程度、频率、持续的时间缓解率为96.7％(P＜0.01),明显高于对照组86.6％ (P＞0.05).两组患者中除有1例出现眉毛下垂,无其他不良反应.结论 A型肉毒素注射治疗慢性每日头痛的同时,配合严密的护理观察,能使治疗安全有效进行.取得明显疗效.     

A型肉毒素对兔失副交感神经颌下腺唾液分泌的影响

BTX-A后1、2、4、12周时,静息状态颌下腺分泌量均较失副交感神经的对侧分别减少38.8%、56.5%、47.7%和38.6%,并且差异均有统计学意义(P<0.05);进食状态颌下腺分泌量均较失副交感神经的对侧减少,1周时减少46.2%,差异有统计学意义(P<0.05);分泌液中淀粉酶、钠、钾、氯离子及蛋白浓度无明显变化.结论 兔失副交感神经颌下腺内局部注射BTX-A可以抑制颌下腺的分泌.     

蛇毒毒素的抗肿瘤作用及其在医药领域的应用

目的 探讨蛇毒毒素的抗肿瘤作用及其在医药领域的应用。方法 综述蛇毒毒素的抗肿瘤组分、抗肿瘤作用及其机制的研究进展。结果 蛇毒毒素对多种肿瘤均有抑制作用,具有直接杀伤肿瘤细胞、诱导肿瘤细胞凋亡、抑制血管再生等作用。结论 对蛇毒毒素抗肿瘤组分及其作用机制进行深入研究,是当前抗肿瘤药物研究的重要方向。