A bovine myeloid antimicrobial peptide (BMAP‐28) kills methicillin‐resistant Staphylococcus aureus but promotes adherence of the bacteria

The cathelicidin family is one of the several families of antimicrobial peptides (AMPs). A bovine myeloid antimicrobial peptide (BMAP‐28) belongs to this family. Recently, the emergence of drug‐resistant bacteria such as methicillin‐resistant Staphylococcus aureus (MRSA) has become a big problem. AMPs are expected to be leading compounds of new antibiotics against drug‐resistant bacteria. In this study, we focused on the activity of BMAP‐28 against bacterial cell surfaces. First, we observed morphological change of MRSA caused by BMAP‐28 using a scanning probe microscope. We also studied activities of BMAP‐28 against adherence of S. aureus to fibronectin, collagen type I, collagen type IV. We confirmed whether BMAP‐28 can bind to lipoteichoic acid (LTA) of S. aureus. BMAP‐28 was indicated as damaging the cell surface of MRSA. In a particular range of concentrations, BMAP‐28 promoted adherence of S. aureus against fibronectin and collagens. It was revealed that BMAP‐28 and LTA of S. aureus bound with each other. Our study showed the potential of BMAP‐28 which can damage MRSA and interact with LTA of S. aureus but promote its adherence in some concentrations. This study provides new points of which to take notice when we use AMPs as medicines.     

猪抗病毒特异性免疫调节因子的制备及其相关性质的分析

通过获取抗人乙肝病毒特异性免疫调节因子并对其有关活性的研究,进一步探索在家畜疫苗接种过程中低分子量抗病毒免疫调节因子的特异性功能基础及免疫效应机制。用乙肝疫苗接种幼猪,致其产生特异性免疫应答,然后从其脾脏淋巴细胞中制备抗病毒免疫活性调节因子进行理化鉴定。MTT法活性检测和氨基酸组分及其含量的对比分析结果表明,制备的免疫调节因子为低分子量多肽与核酸复合物;具有特异性粘附抑制活性;在氨基酸组成上与非特异性免疫调节因子相同,但在所含氨基酸的百分含量上却有一定差异。检测结果提示,这种差异是决定其抗病毒特异性功能的化学基础。     

Contribution of AIDA-I to the pathogenicity of a porcine diarrheagenic Escherichia coli and to intestinal colonization through biofilm formation in pigs

In order to evaluate the role of the AIDA-I of porcine diarrheagenic Escherichia coli strain PD20 serogroup O143 (AIDA-I⁺, STb⁺), a mutant strain PD20M (AIDA-I⁻, STb⁺) was generated from strain PD20 by an allelic exchange procedure. In addition, the full-length aidA gene was reintroduced into strain PD20M to generate the complemented strain PD20C (pTaidA, AIDA-I⁺, STb⁺). A non-pathogenic E. coli strain PD71 was used as negative control. Each strain was inoculated to newborn pigs via stomach tube. Severity of diarrhea was evaluated clinically and intestinal colonization was assessed by histology, immunohistochemistry (IHC), and transmission electron microscopy (TEM) including immunogold electron microscopy (IGEM). The adhesion pattern to HeLa cells, bacterial auto-aggregation and biofilm formation were evaluated in vitro. Pigs infected with strains PD20 or PD20C developed diarrhea 16 and 28 h after inoculation, respectively, in contrast to pigs infected with strains PD20M or PD71. Histology, IHC, TEM and IGEM examinations showed heavy bacterial colonization with biofilm formation in the large intestine, and marked in vivo expression of AIDA-I protein in pigs infected with strains PD20 or PD20C in contrast to pigs infected with strains PD20M or PD71. The in vitro assays showed marked diffuse adherence to HeLa cells, enhanced bacterial auto-aggregation and significant biofilm formation (p < 0.05) by the AIDA-I⁺ strains, when compared to AIDA-I⁻ strains. These results demonstrate that expression of AIDA-I is essential for intestinal colonization and in vitro bacterial autoaggregation and biofilm formation. Thus, AIDA-I may be considered a significant virulence determinant in development of diarrhea caused by porcine diarrheagenic AIDA-I⁺ E. coli PD20 in piglets.     

载荷偏移对整车制动的影响

基于两轴轻型卡车,建立了载荷在不同方向上偏移时对整车制动时利用附着系数的影响的模型,同时建立了在载荷偏移状态下整车的制动减速度模型。同时以某轻型卡车为例,利用所建立的模型,采用VB编程得出整车制动时利用附着系数曲线和减速度曲线,进行模拟分析和评价,并重点模拟分析了载荷在左右方向偏移对整车制动的影响。     

益生芽孢杆菌对草鱼肠上皮细胞的黏附及对嗜水气单胞菌的抑制

为探讨益生性枯草芽孢杆菌对肠上皮细胞黏附及对嗜水气单胞菌的抑制作用,以草鱼肠上皮细胞为研究对象,检测了枯草芽孢杆菌对肠上皮细胞的黏附率、对嗜水气单胞菌的黏附抑制率和对各种生理生化指标的影响。结果显示:枯草芽孢杆菌对草鱼肠上皮细胞形态、细胞中四甲基偶氮唑盐(MTT)OD值、乳酸脱氢酶(LDH)、碱性磷酸酶(AKP)和谷草转氨酶(GOT)活性等各种生理指标无显著影响,但在孵育3h和6h后分别显著降低了Na+,K+-ATP酶和谷丙转氨酶(GPT)的活性;与嗜水气单胞菌孵育3h后,肠上皮细胞由椭圆变成不规则形态,培养液的死细胞增多,并且在多数时间点上显著降低了MTT OD值以及谷草转氨酶、Na+,K+-ATP酶和谷丙转氨酶的活性,细胞中MTT OD值和细胞上清中乳酸脱氢酶的活性显著提高(P0.05);枯草芽孢杆菌和嗜水气单胞菌共孵育对肠上皮细胞形态及各种生理指标的影响明显小于嗜水气单胞菌组;黏附抑制实验显示枯草芽孢杆菌可以显著降低嗜水气单胞菌对肠上皮细胞的黏附率。提示枯草芽孢杆菌可以抑制嗜水气单胞菌对草鱼肠上皮细胞的黏附,并减轻嗜水气单胞菌对细胞的损伤。     

啮齿类海马神经元的原代培养及方法改进

目的:通过对新生啮齿类海马神经元的分离和培养,尝试建立一个简单、稳定、高效的啮齿类海马神经元原代培养方法,为脊髓损伤的相关分子机制研究提供目的细胞。方法:取新生SD乳鼠的海马组织,通过低浓度胰酶消化制成细胞悬液、4h差速贴壁后使用无血清Neurobasal培养基培养,倒置显微镜观察细胞生长状态,免疫荧光对海马神经元相关微管蛋白-2(MAP2)行特异性染色,结合DAPI核染色鉴定神经元。结果:该方法培养的海马神经元生长状态良好,纯度较高。结论:采用低浓度胰酶消化,差速贴壁及无血清培养啮齿类海马神经元符合体外细胞实验要求,为进一步研究提供良好的目的细胞。     

In vivo adherence of Flavobacterium psychrophilum to mucosal external surfaces of rainbow trout (Oncorhynchus mykiss) fry

The adherence of Flavobacterium psychrophilum to surfaces of epithelial tissues has been inconclusively suggested as a mechanism, which enables the bacterium to invade the host. Hence, the present study aimed to examine the adherence of the cells of two colony phenotypes, smooth and rough, of F. psychrophilum to mucosal tissues of rainbow trout fry and to test the skin mucus as a nutrient for the growth of F. psychrophilum. Fish were immersed in water containing 10⁶ CFU mL^?1 F. psychrophilum for each colony phenotype. Mucosal tissue samples from fins, gills, skin and eyes, and swab samples from spleen and kidney were taken and inoculated onto TYES agar plates. Colony phenotypes of F. psychrophilum were identified and number of colonies counted. The results showed that cells of both phenotypes initially (0 h) adhered to all mucosal surfaces, but only the rough cells were still present on tissues 1 h post‐immersion. Both phenotypes showed a tissue tropism with the fin tissue being the most adhered. Furthermore, skin mucus promoted the growth of both colony phenotypes. We suggest that the growth of F. psychrophilum cells in skin mucus apparently facilitates the bacterial adherence to mucosal surfaces, and the subsequent invasion into the host.     

鸡红细胞免疫功能研究——Ⅱ.某些因素对鸡红细胞C_(3b)受体免疫粘附活性的影响

应用红细胞C_(3b)受体花环试验及红细胞免疫复合物花环试验,对攻毒后不同时间的马立克氏病鸡以及不同日龄和品种的健康鸡进行了检测.结果,马立克氏病鸡红细胞免疫粘附活性呈现先升高后降低的变化;健康鸡随日龄的不断增长,红细胞免疫粘附活性不断下降;不同品种鸡之间红细胞免疫粘附活性不同.另外,应用红细胞C_(3b)受体花环促进试验及抑制试验,对不同日龄的健康鸡及攻毒后不同时间的马立克氏病鸡进行了检测,发现健康鸡血清中存在红细胞免疫粘附促进因子及抑制因子,前者耐热,后者不耐热,且随日龄的不断增长,促进因子活性不断升高,抑制因子活性有所下降,直到促进因子活性大于抑制因子活性.而在2日龄鸡未发现有这两种因子.马立克氏病鸡随病情的不断加重,促进因子活性先升高后降低,抑制因子则不断上升,直到超过促进因子活性.     

高铜对雏鸭红细胞免疫黏附功能的影响

将1日龄天府肉鸭健雏300只随机分为6组,分别饲喂添加不同铜含量的日粮,以观察高铜对红细胞免疫黏附功能的影响。结果发现：高铜饲粮导致雏鸭红细胞C3bR花环率降低,红细胞免疫黏附能力下降,加铜剂量越高,C3bR花环率下降辐度越大。     

Initial adherence of EPEC,EHEC and VTEC to host cells

Initial adherence to host cells is the first step of the infection of enteropathogenic Escherichia coli (EPEC), enterohaemorrhagic Escherichia coli (EHEC) and verotoxigenic Escherichia coli (VTEC) strains. The importance of this step in the infection resides in the fact that (1) adherence is the first contact between bacteria and intestinal cells without which the other steps cannot occur and (2) adherence is the basis of host specificity for a lot of pathogens. This review describes the initial adhesins of the EPEC, EHEC and VTEC strains. During the last few years, several new adhesins and putative colonisation factors have been described, especially in EHEC strains. Only a few adhesins (BfpA, AF/R1, AF/R2, Ral, F18 adhesins) appear to be host and pathotype specific. The others are found in more than one species and/or pathotype (EPEC, EHEC, VTEC). Initial adherence of EPEC, EHEC and VTEC strains to host cells is probably mediated by multiple mechanisms.