Abnormal vibrissa‐related behavior and loss of barrel field inhibitory neurons in 5xFAD transgenics

A recent study reported lower anxiety in the 5xFAD transgenic mouse model of Alzheimer's disease, as measured by reduced time on the open arms of an elevated plus maze. This is important because all behaviors in experimental animals must be interpreted in light of basal anxiety and response to novel environments. We conducted a comprehensive anxiety battery in the 5xFAD transgenics and replicated the plus‐maze phenotype. However, we found that it did not reflect reduced anxiety, but rather abnormal avoidance of the closed arms on the part of transgenics and within‐session habituation to the closed arms on the part of wild‐type controls. We noticed that the 5xFAD transgenics did not engage in the whisker‐barbering behavior typical of mice of this background strain. This is suggestive of abnormal social behavior, and we suspected it might be related to their avoidance of the closed arms on the plus maze. Indeed, transgenic mice exhibited excessive home‐cage social behavior and impaired social recognition, and did not permit barbering by wild‐type mice when pair‐housed. When their whiskers were snipped the 5xFAD transgenics no longer avoided the closed arms on the plus maze. Examination of parvalbumin (PV) staining showed a 28.9% reduction in PV+ inhibitory interneurons in the barrel fields of 5xFAD mice, and loss of PV+ fibers in layers IV and V. This loss of vibrissal inhibition suggests a putatively aversive overstimulation that may be responsible for the transgenics' avoidance of the closed arms in the plus maze .     

Characterization and genetic analysis of a light- and temperature-sensitive spotted-leaf mutant in rice

A rice spotted-leaf mutant was isolated from an ethane methyl sulfonate (EMS) -induced IR64 mutant bank. The mutant, designated as spl30 (spotted-leaf30), displayed normal green leaf color under shade but exhibited red-brown lesions under natural summer field conditions. Initiation of the lesions was induced by light and the symptom was enhanced at 33 (°) C relative to 26 (°) C. Histochemical staining did not show cell death around the red-brown lesions. Chlorophyll contents in the mutant were significantly lower than those of the wild type while the ratio of chlorophyll a/b remained the same, indicating that spl30 was impaired in biosynthesis or degradation of chlorophyll. Disease reaction patterns of the mutant to Xanthomonas oryzae pv. oryzae were largely unchanged to most races tested except for a few strains. Genetic analysis showed that the mutation was controlled by a single recessive gene, tentatively named spl30(t), which co-segregated with RM15380 on chromosome 3, and was delimited to a 94 kb region between RM15380 and RM15383. Spl30(t) is likely a novel rice spotted-leaf gene since no other similar genes have been identified near the chromosomal region. The genetic data and recombination populations provided in this study will enable further fine-mapping and cloning of the gene.     

In Vitro Activity of Sodium New Houttuyfonate Alone and in Combination with Oxacillin or Netilmicin against Methicillin-Resistant Staphylococcus aureus

Background

Staphylococcus aureus can cause severe infections, including bacteremia and sepsis. The spread of methicillin-resistant Staphylococcus aureus (MRSA) highlights the need for novel treatment options. Sodium new houttuyfonate (SNH) is an analogue of houttuynin, the main antibacterial ingredient of Houttuynia cordata Thunb. The aim of this study was to evaluate in vitro activity of SNH and its potential for synergy with antibiotics against hospital-associated MRSA.

Methodology

A total of 103 MRSA clinical isolates recovered in two hospitals in Beijing were evaluated for susceptibility to SNH, oxacillin, cephalothin, meropenem, vancomycin, levofloxacin, minocycline, netilmicin, and trimethoprim/sulfamethoxazole by broth microdilution. Ten isolates were evaluated for potential for synergy between SNH and the antibiotics above by checkerboard assay. Time-kill analysis was performed in three isolates to characterize the kill kinetics of SNH alone and in combination with the antibiotics that engendered synergy in checkerboard assays. Besides, two reference strains were included in all assays.

Principal Findings

SNH inhibited all test strains with minimum inhibitory concentrations (MICs) ranging from 16 to 64 µg/mL in susceptibility tests, and displayed inhibition to bacterial growth in concentration-dependent manner in time-kill analysis. In synergy studies, the combinations of SNH-oxacillin, SNH-cephalothin, SNH-meropenem and SNH-netilmicin showed synergistic effects against 12 MRSA strains with median fractional inhibitory concentration (FIC) indices of 0.38, 0.38, 0.25 and 0.38 in checkerboard assays. In time-kill analysis, SNH at 1/2 MIC in combination with oxacillin at 1/128 to 1/64 MIC or netilmicin at 1/8 to 1/2 MIC decreased the viable colonies by ≥2log₁₀ CFU/mL.

Conclusions/Significance

SNH demonstrated in vitro antibacterial activity against 103 hospital-associated MRSA isolates. Combinations of sub-MIC levels of SNH and oxacillin or netilmicin significantly improved the in vitro antibacterial activity against MRSA compared with either drug alone. The SNH-based combinations showed promise in combating MRSA.     

Expression and purification of Mycobacterium tuberculosis ESAT-6 and MPT64 fusion protein and its immunoprophylactic potential in mouse model

The completion of Mycobacterium tuberculosis genome sequence has opened a new way for the identification and characterization of bacterial antigens, such as ESAT-6, CFP10, MPT64, and Ag85 complex, which are helpful for tuberculosis control. In this work, genes of ESAT-6 and MPT64 were fused and expressed in Escherichia coli in form of inclusion bodies with a histidine tag. The expressed fusion protein was purified by nitrilotriacetic acid (Ni-NTA) affinity chromatography under denaturing conditions, and the yield was 18mg/L of culture. In mice, the purified ESAT-6-MPT64 fusion protein elicited stronger humoral response, greater splenic lymphocyte stimulated index, and higher levels of IFN-gamma and IL-12 production than that of the single MPT64 inoculation group, and rendered modest protection on the experimental tuberculosis mouse models. In short, the ESAT-6-MPT64 fusion protein might be a potential candidate vaccine for tuberculosis.     

Bam HI DNA甲基化酶酶学性质的研究

以Lineweave-Burk plot双倒数作图法测得该酶对底物S-腺苷酰甲硫氨酸(SAM)的K_m=7.69×10~(-6)mol/L,在1mmol/LS-腺苷酰高半胱氨酸(SAH)存在下,Ki=7.33×10~(-4)mol/L,两条直线相交于纵轴,证明SAH是该酶的竞争性抑制剂。该酶最适pH为7.8,对热不稳定。同时还测定了该酶对不同DNA底物的专一性及盐浓度、代谢相关物’两价阳离子、某些酸根等对该酶调节性质的影响。以碘代乙酰胺修饰该酶的SH基’及用二硫苏糖醇(DTT)和巯基乙醇(MSH)保护该酶SH基所作的实验表明SH基是该酶活性中心所必需的,用高效液相色谱(HPLC)法证明该酶所甲基化的碱基为刘氏小球菌(M·L、DNA)分子中的胞嘧啶,且求得甲基化30min后所得甲基化水平为2.39％。同时也证明当用该酶将λDNA甲基化后,可使BamHI限制性核酸内切酶对甲基化后的λDNA丧失切割作用。     

罗汉果胚、胚乳及胚乳吸器的发育

本文采用石蜡切片与酶解分离法对罗汉果Ｓｉｒａｉｔｉａｇｒｏｓｖｅｎｏｒｉ胚、胚乳及胚乳吸器的发育过程进行观察．ａ）罗汉果胚的发育是按Ｇｅｕｍｕｒｂａｎｕｍ的分裂程序进行的．属紫菀型．但在合子分裂成球胚过程中,胚芽原细胞分化明显．故属紫菀型的变异型。ｂ）胚乳发育属核型．在球形胚阶段,在合点端和珠孔端有发育的胚乳吸器形成并进行旺盛生长,最大长度达１４２０μｍ,心形胚期．吸器活动开始减退,合点端核型胚乳吸器转变成细胞型．由胚乳本体基部膨大细胞．充当补助吸器．ｃ）酶解分离法研究胚乳吸器的发生发育有较好的应用前景。     

一株产碱性蛋白酶菌株的筛选鉴定及酶学特性研究

【目的】从丝茅草中筛选得到产蛋白酶菌株并研究驯化过程中微生物群落结构,以及探究该菌株的生长特性和蛋白酶的酶学特性。【方法】通过高通量测序探究来源于丝茅草的菌株在不同培养条件下细菌种类及丰度,通过选择性培养基来筛选能够分解酪素并产生蛋白酶的菌株,通过单因素试验方法确定环境因子对菌株生长和蛋白酶活性的影响。【结果】微生物群落结构在基础培养基和牛肉膏蛋白胨培养基中不同。通过含酪素的选择性培养基里筛选到1株产蛋白酶菌株H-16,经生理生化试验和16S r DNA鉴定知该菌株属于Escherichia marmotae,菌株H-16能产生分子量为70 k Da左右的单亚基蛋白酶。胰蛋白胨、蔗糖、30°C或35°C、p H 7分别为菌株生长的最适氮源、碳源、温度和p H。菌株H-16分泌的蛋白酶最适p H为6–8,在50°C及6%盐度以下酶活性几乎不受影响。此外,Cu(II)和Ag(I)等金属离子能够抑制蛋白酶的活性。【结论】该菌株H-16为嗜中温菌株,能够产生碱性蛋白酶。     

横纹金蛛多次产卵生物量分配初步研究

卵袋是雌蛛产卵、若蛛孵化等繁育后代的保护性场所.常见农林蜘蛛横纹金蛛(Argiopebruennichi)一般一生产卵3～6次,织制卵袋3～6个.本文对横纹金蛛的体重、卵袋生物量、卵粒数与卵粒重进行了测试研究.结果表明,随着产卵次数增加,产卵间隔时间更长,但雌蛛产卵后至下一次产卵前生物量的增量在减少,而对卵袋生物量的投...     

小鼠阴道菌群紊乱模型的建立

目的 建立小鼠阴道菌群紊乱模型,为调整阴道菌群紊乱的药物研发提供模型参考。 方法 采用雌激素化的C57BL/6小鼠经阴道以不同处理方式(链霉素50 μg/只,加德纳菌50 μL/只,链霉素50 μg/只+抗链霉素加德纳菌50 μL/只,每种处理方式各70只/组)诱导小鼠阴道菌群紊乱模型,采用细菌16S rDNA高通量测序考察造模后第1、第2、第3、第5、第7、第9、第11天内加德纳菌在阴道内的定植情况,以及阴道细菌结构和细菌生物多样性,并通过显微镜观察阴道组织的病理改变,比较3种造模方法的差异。另采用阳性药物(定君生,成分为德氏乳杆菌)对模型进行验证。 结果 采用链霉素联合抗链霉素加德纳菌能诱导形成典型的阴道菌群紊乱模型,造模后可见加德纳菌在阴道内的定植增多,优势菌以铜绿假单胞菌为主,且阴道细菌生物多样性增加,阴道组织可见明显的炎症浸润和上皮细胞坏死等病理改变。定君生能显著减少加德纳菌在阴道内的定植,减少阴道内的细菌生物多样性,并能显著改善阴道组织病理变化。 结论 采用链霉素联合抗链霉素加德纳菌诱导的小鼠阴道菌群紊乱模型方法更佳,模型的细菌学和组织病理学改变,以及对药物的反应性与临床有一定相似,具有临床应用价值。