Mouse melanoma cell exosomes promote expression of Rac1 protein in fibroblasts

AIM To investigate the effect of exosomes secreted by mouse melanoma cells on the expression of Ras-related C3 botulinum toxin substrate 1 (Rac1) protein in fibroblasts. METHODS Ultracentrifugation was adopted to separete exosomes secreted by mouse melanoma B16-F10 cells. The morphological structure of exosomes was observed by negative-staining electron microscopy. The size distribution of exosomes was determined by nanoparticle tracking analysis (NTA). The exosomal markers, tumor susceptibility gene 101 (Tsg101) and tyrosinase-related protein 2 (Tyrp2), were identified by Western blot. Laser confocal microscopy was used to observe the process that mouse embryonic fibroblasts (MEF) took in exosomes during co-culture. Immunocytochemical staining and Western blot were used to detect the expression of Rac1 protein in MEF. RESULTS B16-F10 cell exosomes showed a typical tea tray-like structure, with a size range of 141~255 nm, and expressed protein markers Tsg101 and Tyrp2. The results of laser confocal microscopy showed that compared with co-culture at 0 h, a small number of exosomes appeared in the MEF at 12 h, and a large number of exosomes accumulated in the MEF after co-cultured for 24 and 36 h. Western blot analysis showed that compared with co-culture at 0 h, the expression of Rac1 protein in the MEF was significantly increased at 24 h and 36 h of co-culture (P<0.01). The results of immunocytochemical staining showed that compared with co-culture at 0 h, the positive expression level of Rac1 in the MEF cells was significantly increased at 12 h, 24 h and 36 h of co-culture (P<0.05 or P<0.01). CONCLUSION Intake of exosomes secreted by mouse melanoma cells promotes the expression of Rac1 protein in fibroblasts.     

植物病原镰刀菌产生的毒素种类及其危害

镰刀菌(Fusarium spp.)是多种重要农作物的病原体，不仅可造成农作物产量和品质的严重损失还可在离体培养条件下或植物寄主体内产生一系列被称为镰刀菌毒素的次生代谢产物。这些毒素一方面作为致病因子与镰刀菌对宿主植物的致病力密切相关，另一方面可导致家畜生产性能下降和相关病症的出现，进而影响农业生态系统并对人类健康造成威胁。鉴于镰刀菌毒素对农作物生产的影响及其对家畜和人类的毒性作用，目前已有较多关于镰刀菌侵染粮食作物后产生毒素种类的研究，但关于镰刀菌侵染豆科牧草后产生的毒素种类以及毒素在镰刀菌对豆科牧草致病力方面作用的研究则较少。本文对引起主要粮食和饲料作物病害的常见镰刀菌物种产生的主要毒素，以及这些毒素对植物、家畜和人类的危害进行了综述，并对豆科牧草中镰刀菌毒素的研究前景及意义进行了展望。     

Death of a neonatal lamb due to Clostridium perfringens type B in New Zealand

ABSTRACT

Case history and clinical findings: A flock of 20 sheep was kept within three paddocks on a single property. None of the animals in the flock had been vaccinated against any disease for at least three years. Abdominal bloating and haemorrhagic diarrhoea were observed in Lamb 1 at 24 hours-of-age. The lamb subsequently died within an hour of the onset of clinical signs. Lamb 2 was 3-days-old when observed to be recumbent with opisthotonus. The lamb was treated with dextrose, vitamins B1 and B12, and penicillin G, but died 4 hours later.

Pathological findings: Examination of Lamb 1 revealed markedly increased gas within the peritoneum and within dilated loops of intestine. The intestines were dark red and contained large quantities of haemorrhagic fluid. Histology of the intestines revealed peracute mucosal necrosis with minimal accompanying inflammation. The intestinal lumen contained cell debris, haemorrhage, and myriad large Gram-positive bacilli. The intestines of Lamb 2 did not appear bloated or reddened. However, multiple fibrin clots were visible within the pericardial sac. Histopathological examination revealed small foci of necrosis within the mucosa of the distal intestine. The necrotic foci were often associated with large numbers of large Gram-positive bacilli.

Immunohistochemsitry and molecular biology: Intestinal samples from Lamb 1 were processed for Clostridium perfringens immunohistochemistry, which revealed large numbers of intralesional, positively immunostained rods. Fragments corresponding to the expected sizes for genes encoding alpha, beta, and epsilon C. perfringens typing toxins were amplified by PCR from DNA extracted from formalin-fixed sections of intestine.

Diagnosis: Lamb dysentery due to C. perfringens type B.

Clinical relevance: C. perfringens bacteria have a worldwide distribution, but disease due to C. perfringens type B has only been diagnosed in a small number of countries and has never been reported in New Zealand or Australia. C. perfringens type B produce both beta toxin and epsilon toxins, therefore both haemorrhagic enteritis and systemic vascular damage can develop. As many animals are exposed to C. perfringens without developing disease, there must be additional unknown factors that resulted in disease in these particular sheep. Vaccines that specifically protect against C. perfringens type B are available and may be recommended for use in smaller non-commercial flocks, as in the present case.     

脱氧雪腐镰刀菌烯醇导致厌食和呕吐的机制研究进展

由镰刀菌产生的脱氧雪腐镰刀菌烯醇(DON)广泛存在于谷物及其加工产品中,对动物和人类健康有着潜在的危害。DON具有多方面的毒性作用,而厌食和呕吐是机体摄入DON后出现的最典型症状,厌食和呕吐的产生主要归因于DON对中枢神经系统和胃肠道食欲因子的影响。DON可直接作用于中枢神经系统的呕吐中枢产生呕吐反射,同时激活下丘脑神经元分泌食欲调节因子影响采食;DON可诱导肠内分泌细胞分泌肽YY、胆囊收缩素等食欲调节因子从而引发厌食;DON对中枢神经系统和胃肠道分泌的影响又可通过肠-脑轴产生关联;此外,细胞因子及肠道微生物也部分参与了反应的介导。本文综述了DON诱发机体出现厌食和呕吐的可能机制,以期为找到相应解决措施提供理论指导。     

病原菌毒素对植物的致病作用

病原菌在侵染植物的过程中产生的毒素一向被认为是致病的重要因子，然而对毒素致病作用的确定却是一个复杂的问题，毒素在一般生物测定中表现出来的对植物组织的伤害与破坏作用并不一定代表其具备致病力的密切相关，但是对于具体毒素在相应病种中的作用程度及对致病力的贡献大小还需要一些更严格的试验予以确定。     

苯甲酸在松材线虫病中的作用

在室内条件下,初步研究苯甲酸对松树和松材线虫病的作用.用不同浓度的苯甲酸溶液分别处理松枝,显示低浓度苯甲酸溶液能显著延长松枝的存活期,高浓度苯甲酸溶液处理的松枝针叶出现褐变现象,但对松枝的存活期没有影响,其症状与松材线虫病不同.分别用1.0 mmol·L-1的苯甲酸溶液和自来水培养接种松材线虫的松枝,在用苯甲酸溶液处理的接种松枝中,虽然松材线虫仍能大量增殖,但与用自来水培养的接种松枝相比,其蒸腾强度显著增强,失水萎蔫程度显著降低,存活期显著延长,这说明苯甲酸在松材线虫病树中可能起着抑制与病害相关的致病菌或提高松树抗病能力的作用.     

Correlation between Chemical Structure and Biological Activity of Host-Selective Plant Pathogen Mycotoxins

Toxin, one of the most important factors of plant fungal disease, has attracted much attention of many academicians who have been studying pathogen mycotoxin in deep research. The paper summarized chemical structures of some host-selective plant pathogen mycotoxins discovered in recent years and the correlation between biological activity and chemical structure of toxin.     

纵坑切梢小蠹伴生菌危害机理的研究

该文对纵坑切梢小蠹伴生菌Leptographium yunnanense的危害机理作了初步研究，结果表明，L.yunnanense在与小伴随侵入后，产生致病毒素对寄主树林进行危害，从而辅助纵坑切梢小蠹成功定殖于寄主树木内，该毒素在低浓度条件下仍维持一定的致病力，进一步表明伴生菌在小蠹虫成功蛀害的过程中具有重要的作用。     

类钙粘蛋白对Cry3A毒素杀虫活性的影响

将克隆的黄粉虫类钙粘蛋白基因片段在大肠杆菌中表达纯化,并分析其对Cry3A毒素杀虫活性的影响,从而探讨黄粉虫类钙粘蛋白对Cry3A毒素杀虫活性的增效作用。黄粉虫类钙粘蛋白基因片段在大肠杆菌中表达产物为包涵体,经尿素变性后,用亲和纯化法可得到较纯的重组蛋白;随着类钙粘蛋白片段与Cry3A质量比值的升高,Cry3A毒素对黄粉虫的杀虫活性也逐步提高,当其比值为1时,活性达到最大,提高了2.5倍,而黄粉虫类钙粘蛋白片段对Cry3Am的杀虫活性却没有显著性影响。研究表明,黄粉虫类钙粘蛋白对Cry3A毒素的杀虫活性具有增效作用。