抗菌肽BSN-37的抑菌活性及其稳定性分析

试验旨在研究抗菌肽BSN-37的抑菌活性和稳定性。采用微量倍比稀释法测定抗菌肽BSN-37的最小抑菌浓度(MIC),菌落计数法分析抗菌肽BSN-37对大肠杆菌CVCC1568的杀菌动力学特征,扩散法测定抗菌肽BSN-37的盐离子稳定性、酸碱稳定性、血清稳定性、胰酶稳定性、热稳定性、反复冻融稳定性、室温保持稳定性、药效保持时间稳定性。结果显示,抗菌肽BSN-37对革兰氏阴性菌(大肠杆菌和沙门氏菌)的MIC为1.5625～25μg/mL,对革兰氏阳性菌(枯草芽孢杆菌和短小芽孢杆菌)的MIC为1.5625～12.5μg/mL,对真菌(白色念珠菌)没有活性;抗菌肽BSN-37可在90min内完全杀灭大肠杆菌CVCC1568;除了Fe2+和胰酶会影响抗菌肽BSN-37的抑菌活性外,在75～100℃的高温、150～250mmol/L高浓度盐离子(Na+、K+、Ca2+和Mg2+)、20%～25%饱和浓度的Cu2+、pH 4～10、20%～25%的血清、10～12次的反复冻融、10～12d室温保存等条件下仍能保持较好的抑菌活性,药效保持时间可达7.5d。本试验结果表明,抗菌肽BSN-37具有替代抗生素成为新抗菌药物的潜力,为抗菌肽BSN-37的临床应用提供了理论依据。     

人源抗菌肽LL-37对畜禽病原菌的抑菌活性及体外稳定性研究

测定LL-37对常见畜禽病原菌的抑菌活性及其体外稳定性,并与常用抗生素抑菌活性进行对比。结果表明,LL-37抗菌肽具有广谱的抑菌作用,能够有效抑制细菌生长,但在抑菌效果上弱于常用抗生素如阿莫西林等;LL-37的稳定性较差,在pH=8的碱性环境及消化酶作用的条件下,LL-37的抑菌效果大大降低。研究结果证明LL-37具有一定的抑菌效果,但其抑菌活性和稳定性还有待提高。     

抗菌肽对抗生素耐药菌株的抑菌活性研究

[目的]研究抗菌肽对抗生素耐药菌株的抑菌活性。[方法]利用抗性平板划线法从腹泻病牛血便中筛选分离出1株耐药菌,通过16S rDNA序列进行鉴定,采用琼脂孔穴扩散法通过梯度盐酸壮观霉素（spectinomycin,Spe⁺）、氨苄青霉素（ampicillin,Amp⁺）、硫酸卡那霉素（kanamycin,Kan⁺）和氯霉素（chloramphenicol,Cm⁺）试验确定该菌药敏特性,并利用1种抗菌肽制剂对该菌株进行药敏试验。[结果]经BLAST比对分析该菌16S rDNA序列,鉴定该耐药菌为科氏葡萄球菌（Staphylococcus cohnii）,此菌对Amp⁺敏感,但对试验中其他抗生素均有耐药性,各梯度抗菌肽对该耐药菌均具有明显的抑菌活性。[结论]抗菌肽能有效抑制耐药科氏葡萄球菌的生长,有望在畜牧生产中代替抗生素使用。     

抗菌肽LL-37的抑菌作用及其稳定性研究

采用微量2倍稀释法测定抗菌肽LL-37对大肠杆菌、沙门菌和金黄色葡萄球菌的最小抑菌浓度(MIC),并进一步研究温度、pH和保存时间对LL-37稳定性的影响。结果显示:LL-37对大肠杆菌、沙门菌和金黄色葡萄球菌的最小抑菌浓度分别为3.12、1.56和0.78μg/mL。热稳定性试验显示:重组抗菌肽121℃加热21 min、100℃加热3 h仍有较好的活性。酸碱稳定性试验结果显示:LL-37在pH 2.0～12.0时均具有一定的活性,pH 5.0～6.0时活性最好。此外,-20℃为此抗菌肽长期保存的最佳条件。     

大口黑鲈不同组织中抗菌肽粗提及抑菌活性测定

研究了大口黑鲈不同组织中抗菌肽的提取及其粗提物对不同菌种的抑菌作用。以新鲜的大口黑鲈为试验材料,用5％乙酸作为提取液,对大口黑鲈粘液、皮肤、肝脏、脾、卵、鳃组织进行提取,并对粗提物进行抑菌活性检测。结果表明大口黑鲈粘液、皮肤和肝脏组织提取物对嗜水气单胞菌有抑菌作用,皮肤和肝脏组织提取物对大肠杆菌有抑菌作用。肝脏组织抗菌肽提取物经SephadexG-25凝胶过滤层析柱分离后,其收集液对嗜水气单胞菌仍具有抑菌作用。大口黑鲈皮肤和肝脏组织提取物对嗜水气单胞菌、大肠杆菌均有抑菌作用。     

蝇蛆抗菌肽粗提的优化及其抑菌活性研究

为了提高蝇蛆抗菌肽粗提成功率,探讨其抑菌活性,本试验采用不同方法进行蝇蛆抗菌肽的提取,对大肠杆菌和沙门菌诱导的抗菌肽粗提液的抗菌活性及其在-20℃和-80℃下的抑菌效果进行了测定。结果显示,大肠杆菌和沙门菌诱导的蝇蛆抗菌肽浓度和抑菌圈直径均大于庆大霉素对照组;-20℃浸提匀浆液和-80℃冷冻保存过上清的蝇蛆抗菌肽对各种菌的抑菌效果显著高于其他温度。提示,经大肠杆菌和沙门菌诱导蝇蛆活体、-20℃浸提匀浆液和-80℃冷冻保存蝇蛆抗菌肽粗提液等条件均能明显提高蝇蛆抗菌肽的获得率和抑菌活性。     

蛇源抗菌肽C-BF和抗生素的抑菌活性比较及协同效应研究

研究旨在探讨蛇源抗菌肽C-BF的抗菌活性及其与抗生素和人源抗菌肽LL-37的抑菌协同作用。试验检测蛇源抗菌肽C-BF和2种畜禽常用抗生素对常见致病菌的最小抑菌浓度(MIC)与最小杀菌浓度(MBC);采用棋盘法分析蛇源抗菌肽C-BF与抗生素、人源抗菌肽LL-37联合使用效果,计算出部分抑菌浓度指数(FIC index)。结果表明:抗菌肽C-BF对革兰氏阴性菌和革兰氏阳性菌均有较强的抑菌效果;抗菌肽C-BF与抗生素联合使用对金黄色葡萄球菌表现出相加作用;与抗菌肽LL-37联合使用对大肠杆菌表现出协同效应。结果提示,蛇源抗菌肽C-BF具有成为新型饲用抗生素替代品的巨大潜力,试验可为C-BF在畜禽生产中的实际应用提供参考。     

Spinigerin α抗菌肽的分离纯化及其活性研究

Spinigerinα抗菌肽是一种源于白蚁的线性抗菌肽,包括25个氨基酸,不含半胱氨酸,呈α-螺旋结构。本研究采用凝胶加热-层析法,对Spinigerinα抗菌肽样液通过水浴加热至100℃保持20³0 min,除去不耐热的部分蛋白,经葡聚糖凝胶SephadexG-25脱盐层析分离得到Spinigerinα抗菌肽提纯物。根据SDS-聚丙烯酰胺凝胶电泳图谱绘制分子质量标准曲线,计算Spinigerinα抗菌肽的分子质量。试验结果表明:SDS-PAGE电泳表现为单一条带,其分子质量为2.74 ku;Spinigerinα抗菌肽对大肠杆菌、沙门氏菌、金黄色葡萄球菌均有抑菌作用,最小抑菌浓度分别为0.5 mg/mL、0.3 mg/mL、0.2 mg/mL。     

蝇蛆抗菌肽的诱导及其抗菌性能研究

为了探究灭活沙门氏菌对蝇蛆抗菌肽的诱导效果,试验用灭活沙门氏菌和沙门氏菌培养蝇蛆,粗提蝇蛆抗菌肽,分时间点测定其浓度及抗菌性能,同时对蝇蛆体内细菌含量进行计数。结果显示,诱导组抗菌肽浓度均高于未诱导组(P<0.05),且在24 h时浓度最高;诱导组对沙门氏菌的抑菌圈直径显著大于未诱导组(P<0.05),显著小于抗生素组(P<0.05),最低抑菌浓度(MIC)值为0.5 mg/mL;蝇蛆体内细菌含量为1.6×10⁵ CFU/g,低于国家规定标准饲料中细菌总数最低值2×10⁶ CFU/g。提示,用灭活沙门氏菌诱导蝇蛆能提高抗菌肽的表达量,且具有较强的抗菌性能及安全性。     

穿心莲水提物与10种临床常用抗菌药联用的体外抑菌试验

为研究穿心莲水提物与临床常用10种抗菌药联用对鸡致病性大肠杆菌的体外抑菌效果,本试验采用传统的水提法制备穿心莲中药液并浓缩至浓度为1 g/mL,用琼脂平板稀释法测定穿心莲水提物分别与阿莫西林、头孢曲松等10种常用抗菌药物联用对临床分离的10株鸡致病性大肠杆菌的体外抑菌作用。结果表明,穿心莲和头孢曲松、穿心莲和氟苯尼考联用100%呈现协同作用;穿心莲和头孢噻呋联用90%呈现协同作用,10%呈现无关作用;穿心莲和大观霉素联用80%呈现协同作用,20%呈现无关作用;穿心莲和林可霉素联用50%呈现协同作用,40%为无关或颉颃作用,10%为无关作用;穿心莲与阿莫西林、安普霉素、阿米卡星、多西环素、恩诺沙星联用以无关或颉颃作用为主。以上结果表明,在体外,穿心莲与头孢曲松、头孢噻呋、大观霉素、氟苯尼考联用对鸡致病性大肠杆菌呈现协同作用,与阿莫西林、安普霉素、阿米卡星、林可霉素、多西环素、恩诺沙星联用呈现无关或颉颃作用。     

Preliminary Studies on the Concentration of Na+,K+-ATPase in Skeletal Muscle of Draught Cattle in Mozambique: Effect of Sex,Age and Training

The effect of training on the potential for work in draught cattle was assessed by measuring the Na⁺,K⁺-ATPase in the muscle cell membrane and the elevation in the concentration of K⁺ in plasma during exercise. Biopsies of the semitendinosus muscle and venous blood samples were taken from the cattle used for draught work in Mozambique. No differences were found in the plasma ion or Na⁺,K⁺-ATPase concentrations in samples taken from Nguni, Africander and Angoni breeds. There were no significant differences in plasma ions (Na⁺, K⁺ and Cl^–) or muscle Na⁺,K⁺-ATPase concentrations between the Angoni males and females, although the males showed an increase in Na⁺,K⁺-ATPase with age, while the females showed a decrease. The increase in males might be attributed to their higher level of activity in the herds than that of females. After a training period of 15 days, a significant increase in Na⁺,K⁺-ATPase concentration in semitendinosus muscle was found in Angoni cattle. In females, this was significant after 8 days of training (about 30%); in males after 15 days of training (about 16%). On day 15, there was a reduction in the elevation of plasma K⁺ during the 2 h of draught work, indicating an increased capacity of the Na⁺,K⁺ pumps to maintain the extracellular K⁺ concentration in working muscles and a possible delay in the moment of fatigue.     

Antimicrobial activity of cathelicidins BMAP28, SMAP28, SMAP29, and PMAP23 against Pasteurella multocida is more broad-spectrum than host species specific

The antimicrobial activity of linear, cationic alpha-helical peptides from cattle (BMAP28), sheep (SMAP28 and SMAP29), and pigs (PMAP23) were assessed to determine if activity was selective for Pasteurella multocida from a particular animal species or broad-spectrum against all P. multocida tested. The antimicrobial activities of synthetic peptides were determined for P. multocida isolated from cattle (10 isolates), sheep (10 isolates), and pigs (10 isolates) in a broth microdilution assay. All thirty isolates of P. multocida were susceptible to BMAP28 (MICs and MBCs, 1.0-1.9 microM); SMAP28 and SMAP29 (MICs and MBCs, 0.2-0.7 microM); and PMAP23 (MICs and MBCs, 4.3 to > or = 6.8 microM). Overall, the results of this study suggest that synthesized cathelicidins from cattle, sheep, and pigs had broad-spectrum antimicrobial activity against all P. multocida.     

Time course of the incidence/multiplicity and histopathological features of murine colonic dysplasia,adenoma and adenocarcinoma induced by benzo[a]pyrene and dextran sulfate sodium

Benzo[a]pyrene (BP) is mutagenic but noncarcinogenic in the murine colon. Recently, we reported rapid induction of colonic tumors by treatment of CD2F₁ mice with BP (125 mg/kg for 5 days) followed by a colitis inducer, dextran sulfate sodium (DSS) (4% in drinking water for 1 or 2 weeks). However, there are no reports on detailed time course and histopathological features of colonic proliferative lesions in this model. Here, we show the detailed time course of colonic dysplasia, adenoma and adenocarcinoma induced by treatment with BP, DSS, and a combination of the two (BP/DSS). In the colon of mice exposed to BP/DSS, 14.6 dysplastic foci per mouse were present one week after DSS treatment (week 4). The number of dysplastic foci decreased with time to 3.1 at week 9 and thereafter remained almost constant. At week 4, 1.5 adenocarcinomas were also observed, with a marked increase in numbers with time, reaching 29.3 at week 14. In contrast, the number of dysplastic foci induced by DSS alone showed a time course similar to that following BP/DSS treatment; however, only a few tumors appeared. Neither dysplastic foci nor neoplastic lesions were induced by BP only. In mice exposed to BP/DSS, β-catenin was demonstrated immunohistochemically in the nucleus and/or cytoplasm of the tumor cells, and this translocation from the cell membrane was evident in subsets of dysplastic foci. In dysplastic foci induced by DSS alone, β-catenin was absent in the nucleus/cytoplasm. These finding suggest that aberrant β-catenin accumulation in dysplastic foci is associated with tumor progression in this BP/DSS model.