EFFECTS OF MODERATE NOISE EXPOSURE ON HEARING FUNCTION IN C57BL/6J MICE

Objective To study characteristics of hearing loss after exposure to moderate noise exposure in C57BL/6J mice. Methods Male C57BL/6J mice with normal hearing at age of 5-6 weeks were chosen for this study. The mice were randomly sclccted to be studied immediately after exposure （Group P0）, or 1 day （Group P1）, 3 days （Group P3）, 7 day （Group P7） or 14 days （P14） after exposure. Their before exposure condition served as the normal control. All mice were exposed to a broad-band white noise at 100 dB SPL for 2 hours, ABR thresholds were used to estimate hearing status at each time point. Results ABR threshold elevation was seen at every tested frequency at P0 （P〈0.01）. Elevation at high-frequencies （16 kHz and 32 kHz） was greater than at lower frequencies （4 kHz and 8 kHz, P〈0.05）. From P1 to P14, ABR thresholds continuously improved, and there was no significant difference between P14 and before exposure （P〉0.05）. Conclusion There is a frequency specific re- sponse to 100 dB SPL broad-band white noise in C57BL/6J mice, with the high-frequency being more susceptible. Hearing loss induced by moderate noise exposure appears reversible in C57BL/6J mice.

A murine model of dengue virus infection in suckling C57BL/6 and BALB/c mice

Dengue is a significant public health concern across tropical and subtropical regions worldwide,principally causing disease in children.Very young children are at increased risk of severe manifestations of dengue infection.The mechanism of dengue disease in this population is not fully understood.In this study,we present a murine model of dengue virus primary infection in suckling C57BL/6 and BALB/c mice in order to investigate disease pathogenesis.Three-day-old C57BL/6 mice intraperitoneally infected with DENV-2 NGC were more susceptible to infection than BALB/c mice,showing increased liver enzymes,extended viremia,dissemination to organs and histological alterations in liver and small intestine.Furthermore,the immune response in DENV-infected C57BL/6 mice exhibited a marked Th1 bias compared to BALB/c mice.These findings highlight the possibility of establishing an immunocompetent mouse model of DENV-2 infection in suckling mice that reproduces certain signs of disease observed in humans and that could be used to further study agerelated mechanisms of dengue pathogenesis.

Anti-leukemic and anti-angiogenic effects of D-Limonene on K562-implanted C57BL/6 mice and the chick chorioallantoic membrane model

Background: D-Limonene, a monoterpene from citrus fruit has been found to have chemopreventive and chemotherapeutic activities in various types of cancers. In this study, we evaluated the in vivo effect of D-Limonene on a K562-induced model of chronic myeloid leukemia(CML) in C57 BL/6 mice.Method: The tail vein injection model of K562 cells in immunocompromised C57 BL/6 mice was developed and evaluated for characteristics of the disease. The mice were treated with D-Limonene and evaluated for haematological parameters. We also evaluated the effect of D-Limonene on angiogenesis using the chick chorioallantoic membrane(CAM) assay.Results: In a complete blood count, a significant dose-dependent reduction in white blood cell, neutrophil and lymphocyte counts, but an elevation in red blood cell count and haemoglobin content was observed with D-Limonene treatment compared to the disease control or untreated group. In the CAM assay, D-Limonene produced a significant dose-dependent reduction in number of blood vessels in treatment groups compared to the vehicle-treated group.Conclusion: These studies suggest promising anti-leukemic and anti-angiogenic effects of D-Limonene in the treatment of CML.

Differences in action potential propagation speed and axon initial segment plasticity between neurons from Sprague-Dawley rats and C57BL/6 mice

Action potentials(APs)in neurons are generated at the axon initial segment(AIS).AP dynamics,including initiation and propagation,are intimately associated with neuronal excitability and neurotransmitter release kinetics.Most learning and memory studies at the single-neuron level have relied on the use of animal models,most notably rodents.Here,we studied AP initiation and propagation in cultured hippocampal neurons from Sprague-Dawley(SD)rats and C57BL/6(C57)mice with genetically encoded voltage indicator(GEVI)-based voltage imaging.Our data showed that APs traveled bidirectionally in neurons from both species;forward-propagating APs(fpAPs)had a different speed than backpropagating APs(bpAPs).Additionally,we observed distinct AP propagation characteristics in AISs emerging from the somatic envelope compared to those originating from dendrites.Compared with rat neurons,mouse neurons exhibited higher bpAP speed and lower fpAP speed,more distally located ankyrin G(AnkG)in AISs,and longer Nav1.2 lengths in AISs.Moreover,during AIS plasticity,AnkG and Nav1.2 showed distal shifts in location and shorter lengths of labeled AISs in rat neurons;in mouse neurons,however,they showed a longer AnkG-labeled length and more distal Nav1.2 location.Our findings suggest that hippocampal neurons in SD rats and C57 mice may have different AP propagation speeds,different AnkG and Nav1.2 patterns in the AIS,and different AIS plasticity properties,indicating that comparisons between these species must be carefully considered.

柯萨奇病毒B3诱导的病毒性心肌炎C57BL/6J小鼠模型的建立

目的：建立由柯萨奇病毒B3（CVB3）Nancy株诱导的病毒性心肌炎（VMC）C57BL/6J小鼠模型。方法：4周龄、6周龄C57BL/6J小鼠各50只,每个年龄组随机选取15只作为对照（腹腔注射PBS）,剩余35只腹腔接种含CVB3 Nancy株的病毒悬液（1×10^5PFU/只）,于感染后第14天取心脏,行HE染色和CD3、CD45免疫组化染色,进行病理学评价,检测血清白细胞介素-1β（IL-1β）、肿瘤坏死因子-α（TNF-α）水平,并做心肌组织中病毒滴度检测,采用Western blot法检测磷酸化AKT、Ik Bα、GSK3β的表达。结果：4周龄小鼠造模过程中有19只（54.3%）死亡;与对照小鼠比较,模型小鼠心肌呈现弥漫性炎性细胞浸润和片状心肌细胞变性坏死,CD3、CD45阳性细胞弥漫浸润于心肌间质,血清IL-1β、TNF-α水平明显升高（P〈0.05）,心肌组织中磷酸化AKT、Ik Bα、GSK3β表达增高（P〈0.05）。6周龄小鼠造模过程中有3只（8.6%）死亡,模型小鼠心肌组织中炎症反应轻于4周龄模型小鼠（P〈0.05）。结论：成功建立了VMC的C57BL/6J小鼠模型,4周龄C57BL/6J小鼠更适用于模型的建立。

Ultraviolet-attenuated cercariae ofSchistosoma japonicum fail to effectively induce a Th1 response in spite of up-regulating expression of cytotoxicity-related genes in C57BL/6 mice

Objective： To better understand the reason that Schistosoma japonicurn （S. japonicum） ultraviolet （UV）- radiated cercariae could not induce high level of protection in C57BL/6 mice. Methods： Microarray technology was performed to investigate the gene transcription profile in skin draining lymph nodes （sdLNs） at 1 w after exposure to attenuated cercariae （AC） or normal cercariae （NC） of S. japonicum in C57BL/6 mice. The expressions of some representative genes were further confirmed by real-time PCR. Subsequently, the expressions of Th1/Th2 cytokine genes, cytotoxicity-related genes, as well as co-stimulator genes in spleens from AC-vaccinated and NC- infected mice were analyzed by real-time PCR at w 3 and 6 post-exposure. Results： The gene expressions of Th1 cytokines, including interferon-y （IFN-γ）, interleukin （IL）-12 and tumor necrosis factor-α （TNF-α） in the sdLNs were significantly lower in AC-vaccinated mice than in NC-infected mice. Furthermore, the gene expressions of Th1- and Th2- cytokines, including IFN-γ, IL-12, TNF-α, IL-4 and IL-10, in the spleens from AC-vaccinated mice showed little changes at w 3 and 6 post-vaccination. In addition, cytotoxicity-related molecules including granzyme A, granzyme B, granzyme K, perforin 1 and Fas L were up-regulated from the early stage of vaccination, and peaked at the 3rd w after vaccination with UV-AC. Conclusion： UV-AC of S. japonicum could not ef- fectively induce a Thl response in C57BL/6 mice, which may be an explanation for the low protection against parasite challenge, and the role played by up-regulated expression of cytotoxicity-related genes in mice needs to be further investigated.

Dietary Effect of Squalene on Lipid Metabolism of Obese/Diabetes KK-<i>A^y</i>Mice and Wild-Type C57BL/6J Mice

The purpose of this study was to evaluate the influence of squalene (SQ) on plasma and hepatic lipid levels of obese/diabetic KK-Ay mice and wild-type C57BL/6J mice. SQ supplementation significantly increased the HDL cholesterol of KK-Ay mice, which was paralleled with no significant difference in the total and non-HDL cholesterol levels. The increase in HDL cholesterol was also found in the plasma of normal C57BL/6J mice, but the difference was not significant. SQ administration significantly increased neutral lipids (NL) in the liver of KK-Ay mice, while no significant difference was observed in the polar lipids and the total cholesterol levels. The increase in NL was primarily due to the increase in TAG. However, the cholesterol level significantly increased due to SQ intake in the liver of C57BL/6J mice, while no significant difference was found in other lipid levels. The present study suggests that SQ may effectively increase HDL cholesterol level, an important anti-atherosclerotic factor, especially in subjects with metabolic disorders.

Different sources of MSCs on pulmonary fibrosis in C57BL/6 mice

Since stem cell therapy is the most effective treatment in the field of tissue reparation and reconstitution,the present study aimed to explore the different sources of mesenchymal stem cells(MSCs)on the different effects of pulmonary fibrosis-related cytokines in C57BL/6 mice.For reaching this goal,we isolated MSCs from umbilical cord blood and placenta and used for stem cell therapy in a mouse model of pulmonary fibrosis model.The pulmonary fibrosis model was done by injecting bleomycin into the trachea of C57BL/6 mice.Then we assessed the degree of pulmonary fibrosis in each mouse lung tissue at weeks 1,2,3,and 4.In addition,flow cytometry was used to evaluate the frequency of CD73,CD90,CD106,CD34,CD45,CD14 cells at the mononuclear cell level;and western blotting assays revealed the expression of IκB-α.Our results showed that stem cell therapy by placenta-derived MSC had a lower level of CD34,CD45,CD14 cells at the mononuclear cell level,and that improved pulmonary fibrosis at both molecular and pathological levels.In addition,western blotting assays revealed that the expression of IκB-αwas down-regulated in MSC-treated animals.In addition,placenta-derived MSC was the most effective in improving pulmonary fibrosis in comparison to other sources.This study suggests that MSC might be a novel therapeutic approach in pulmonary fibrosis due to an enhanced anti-inflammatory effect.Also,MSC modification by gene editing could enhance their therapeutic effect in mouse pulmonary fibrosis.

C57BL/6 and DBA/1 Mice Differ in Their Response to Supplementation with 1,25D and Paricalcitol

Active vitamin D (1,25D) is a fat-soluble vitamin that is mainly produced in the skin by the conversion of 7-dehydrocholesterol under ultraviolet light stimulation.Its role in calcium homeostasis,bone growth, and prevention of rickets and osteomalacia has been known for over two hundred years.Its

Characterization of Endophytes Isolated from <i>Eclipta prostrate</i>and Roles in Regulating the Gut Microbiota of C57BL/6J Mice

Eclipta prostrata has been extensively studied for its promoting effect on human health. Previous study proved that E. prostrata possessed anti-osteoporosis function in SAMP6 mice via gut microbiota (GM). Endophytes are widespread in plants, especially in Chinese herbal medicines. However, little is known regarding the endophytes of E. prostrata. In this study, we focus on screening and identifying the endophytes from plant E. prostrata and exploring their roles in modulating GM. According to biochemical, physiological tests and 16S rDNA sequence analysis, ten endophytes were characterized in different locations of plant E. prostrata belonging to Lactococcus, Bacillus, Enterococcus, Exiguobacterium and Pantoea. The antimicrobial activity of endophytes EP01-10 was investigated via the oxford cup method. Furthermore, the acid and bile salt resistant ability of EP01-10 was detected to explore their survival ability in gastrointestinal tract. Results indicated that strains of Lactococcus, Bacillus and Exiguobacterium (EP01, 03 and 05) showed strong antimicrobial activity against Escherichia coli and Staphylococcus aureus and strains of Lactococcus, Bacillus and Enterococcus (EP01, 02, 04, 08 and 10) have the ability to survive in the gastrointestinal tract. 16S rRNA sequencing of GM in C57BL/6J mice was performed for diversity and structure analysis responded to the administration of E. prostrata extract. E. prostrata extract acted on improving the microflora diversity, particularly in increasing the abundance of Lactococcus significantly. Thus, as an endophyte, Lactococcus plays an important role in E. prostrata modulating intestinal tract. Our study suggested that endophytes of Chinese herbal medicines might be a novel target for the treatment of diseases by regulating the GM.

不同小鼠品系囊胚受体对C57BL/6胚胎干细胞种系嵌合效率的影响

目的考察不同品系的小鼠囊胚对C57BL/6胚胎干细胞种系嵌合效率的影响,进而提高通过在C57BL/6胚胎干细胞中同源重组制作基因打靶小鼠的效率。方法选取近交系B6(Cg)-Tyrc-2J和BALB/c品系及封闭群ICR作为囊胚供体鼠,通过在TLX3、Ai3K和SL三个不同基因修饰ES细胞的种系嵌合实验中,平行比较三者的囊胚利用率、嵌合鼠获得效率以及种系遗传效率等三个方面,并进一步针对囊胚来源这一因素对效率的影响进行统计学分析。结果三种ES细胞均未能通过B6(Cg)-Tyrc-2J品系囊胚的注射获得种系遗传。而BALB/c品系与ICR品系相比,囊胚利用率明显低于ICR品系(P<0.05);嵌合鼠获得效率方面,BALB/c与ICR相当(P=0.115);而种系遗传效率方面,BALB/c品系显著高于其他品系(P<0.01)。结论 BALB/c品系在C57BL/6胚胎干细胞种系嵌合效率方面确实具有优势,然而,由于BALB/c囊胚较难获得,并且存在发育延迟和透明带脆性高等问题,而ICR品系在囊胚获得和利用方面的效率明显高于BABL/c,并且也可以支持C57BL/6胚胎干细胞的种系遗传,因此也是C57BL/6胚胎干细胞囊胚注射中较好的选择。

经鼻滴入海人藻酸引起C_(57)BL/6小鼠嗅球和海马区神经元的退行性病变

目的 应用海人藻酸 (KA)在C57BL/ 6小鼠建立神经退行性病变动物模型并观察其对嗅球神经元的影响。方法 经鼻滴入KA应用尼氏和嗜银染色观察海马及嗅球的病理变化 ,免疫组化检测Cyclooxygenase 2 (COX 2 )的表达。结果 经鼻滴入KA成功地在C57BL/ 6小鼠建立了神经退行性病变动物模型 ,KA通过嗅神经引起双侧嗅球和海马损伤 ,其病变程度与小鼠体重和滴入KA剂量有关 ,同时KA引起了脑内明显的胶质细胞增生和炎症因子COX 2在嗅球部的表达。

C_(57)BL/6无毛小鼠皮肤组织学研究

目的：观察Ｃ５７ＢＬ／６无毛小鼠皮肤组织学结构。方法：１０％甲醛固定，行石蜡切片，ＨＥ染色。结果：动物表皮有一层角化过度的角质层，毛干消失，毛球结构不正常，毛囊内为一些角化物质，有的变为空囊腔。真皮深层及皮下组织内含有大量黑色素细胞，并有树突状突起。结论：Ｃ５７ＢＬ／６无毛小鼠真皮深层及皮下组织内含有大量黑色素细胞，可用于黑色素沉着疾病及黑色素瘤的研究。

C57BL/6J小鼠及鸡胚B16细胞移植瘤血管生成拟态的观察及其MMP7和MMP9的表达

【目的】探讨黑色素瘤B16细胞鸡胚和小鼠移植瘤组织中MMP7和MMP9的表达与血管生成拟态形成的关系,初步探讨宿主微环境对肿瘤细胞的影响。【方法】分别建立黑色素瘤B16细胞鸡胚和小鼠移植瘤模型,通过HE切片观察血管生成拟态的分布情况,利用免疫组化方法检测MMP7和MMP9的表达。【结果】B16细胞鸡胚和小鼠移植瘤组织中均可见血管生成拟态,并且前者显著多于后者。鸡胚移植瘤组织和小鼠移植瘤组织中MMP7的阳性细胞百分比分别为34.55±8.98和15.27±4.21,前者显著高于后者(P<0.01),MMP9的阳性细胞百分比分别为16.38±3.34和10.53±1.95,前者显著高于后者(P<0.01)。【结论】鸡胚移植瘤可用于研究肿瘤生长早期的生物学行为,MMP7和MMP9的表达可能与肿瘤生长早期血管生成拟态的形成有关。

高脂诱导的C57BL/6 (H-2b)2型糖尿病小鼠十二指肠空肠旷置术模型的建立

目的：探讨建立一种C57BL／6（H-2b）高脂诱导的2型糖尿病小鼠保留全胃的十二指肠空肠旷置术（DJB）新型降糖术式动物模型的可行性和操作要点。方法：16只C57BL／6（H-2b）高脂诱导的2型糖尿病小鼠随机分为实验组和对照组各8只，规范的术前、术中及术后操作，实验组和对照组分别行DJB和假手术，比较两组小鼠术前及术后7、14、28d平均空腹血糖，评价手术造模是否成功以及成活率。结果：术后1-28d对照组小鼠存活7只，手术组小鼠成活6只，两组成活率差异无统计学意义（P〉0．05）；与术前比较，实验组术后7d空腹血糖明显下降（P〈0．05），术后14、28d血糖趋于稳定，对照组空慢血糖术后第14、28天与术前比变化无统计学意义（P〉0．05），提示模型建立成功。结论：成功地建立C57BL／6（H-2b）高脂诱导的2型糖尿病小鼠DJB动物模型。十二指肠空肠旷置术是一种可行、安全有效的降糖术式，规范实验操作程序可以降低术中风险。

肿瘤疫苗Ad-hDCT抑制黑色素瘤B16细胞在C57BL／6小鼠脑内增殖

目的观察肿瘤疫苗Ad-hDCT预防接种对移植到C57BL/6小鼠脑实质内的黑色素瘤B16细胞增殖的抑制作用。方法 40只C57BL/6小鼠随机分为2组:Ad-BHG对照组(20只)和Ad-hDCT免疫接种组(20只)。借助小鼠脑立体定位仪行B16细胞脑内注射;采用大体观察、流式细胞术、石蜡切片HE染色及冷冻切片CD8及F4/80抗体免疫组织化学染色等方法观察肿瘤细胞的增殖情况。结果 Ad-hDCT肌肉注射后7d,小鼠外周血内hDCT特异性CD8+INF-γ+T细胞数量显著增多(P<0.01,与Ad-BHG对照组相比)。脑内移植B16细胞后16d,Ad-BHG对照组小鼠全部死亡,而Ad-hDCT免疫组小鼠长期存活率达60%,且未见行为学异常。光镜观察,Ad-BHG组小鼠脑内B16细胞生长旺盛,移植后3d可见明显肿瘤细胞团,移植后7d脑实质内可见较大的瘤块;Ad-hDCT组小鼠脑内B16细胞的增殖被显著抑制,未见瘤块形成。免疫组织化学染色结果提示,Ad-hDCT组小鼠脑内移植B16细胞后可诱导大量CD8+T细胞进入肿瘤区。同时,Ad-hDCT组小鼠脑组织内活跃的小胶质细胞显著增多。结论肿瘤疫苗Ad-hDCT能有效刺激抗原特异性细胞毒T细胞免疫反应,此类T细胞能够到达肿瘤区,发挥识别、杀伤作用,抑制黑色素瘤B16细胞在C57BL/6小鼠脑内增殖。

IL-12协同B7-1转基因细胞增强C57BL／6小鼠的抗肿瘤免疫

目的应用逆转录病毒构建了IL-12，B7-1和GM-CSF表达载体，以研究基因修饰的肿瘤细胞的癌疫苗作用。方法将三种表达载体分别转染EL-4胸腺瘤细胞并研究了该基因导入细胞的抗肿瘤免疫效果。结果当接种了EL-4／IL-12细胞后，在C57BL／6同系鼠中其基因导入细胞的肿瘤原性比较EL-4／Wt和EL-4／Neo组明显减少(P<0．01)。在EL-4／IL-12被排斥后，体内试验中实验动物诱发了抗EL-4／Wt的系统性、保护性免疫，^51Cr释放测定中，获得一个较强的抗EL-4/Wt和一个较弱的抗同系Lewis肿瘤细胞的CTL活性，体内淋巴细胞消除分析的结果提示减少的肿瘤原性主要依赖于CD4^+、CD8^+和NK细胞。用EL-4/IL-12细胞进行疫苗治疗比较用EL-4／Neo细胞能有效地延缓已建立的EL-4／Wt肿瘤细胞的生长(P<0．005)，EL-4/IL-12和EL-4／B7-1联合比用单一的转基因细胞增强了治疗效果(P<0．005)。结论应用IL-12进行血液肿瘤的治疗是有效的，IL-12和B7-1联合使用在未来人类癌症的治疗中亦可有一定的应用前景。

C57BL/6J小鼠黑色素瘤肺转移模型的构建

目的探讨建立C57BL/6 J小鼠黑色素瘤肺转移模型的影响因素,包括肿瘤的接种方式、细胞接种数量和成瘤周期。方法体外培养小鼠黑色素瘤细胞B16F10。1)取6~8周龄,雄性小鼠18只,随机分三组,每组6只,分别采取尾静脉注射、腹腔注射和皮下注射方式,每只小鼠注射100μL(3×10~6个细胞)B16F10细胞悬液,2周后,解剖小鼠并观察黑色素瘤的生长和转移情况;2)分3组,同上,经尾静脉分别注射3×10~6个细胞、1×10~6个细胞、3×10~5个细胞,2周后,解剖小鼠并观察黑色素瘤的生长和转移情况;3)分3组,同上,尾静脉注射1×10~6个细胞,分别于1周、2周、3周解剖小鼠,观察黑色素瘤的生长和转移情况。结果 1)尾静脉注射小鼠黑色素瘤细胞,小鼠发生肺转移的成功率为100%,而腹腔注射和皮下注射未发生肺转移。2)接种小鼠黑色素瘤细胞数量为1×10~6时,发生肺部转移的黑色素瘤细胞数量适中;接种细胞数量为3×10~6时,发生肺部转移的黑色素瘤细胞数量过多;接种细胞数量为3×10~5时,发生肺部转移的黑色素瘤细胞数量较少。3)尾静脉注射1×10~6个小鼠黑色素瘤细胞,饲养2周后,可以观察到黑色素瘤细胞明显的肺部转移,且不会导致小鼠死亡;饲养3周,黑色素瘤细胞肺部转移数量过多,且小鼠死亡过半;饲养1周,黑色素瘤细胞肺部转移数量较少。结论经尾静脉注射1×10~6个小鼠黑色素瘤细胞,生长2周时间,为构建C57BL/6 J小鼠黑色素瘤肺转移模型的推荐方法。

诱导C57BL/6小鼠骨髓单核细胞向破骨细胞分化的条件

目的研究诱导C57BL/6小鼠骨髓单核细胞(bone marrow-derived macrophages,BMMs)向破骨细胞分化的条件,提高诱导破骨细胞的效率。方法采用流式细胞仪鉴定BMMs表面标记物,巨噬细胞集落刺激因子(macrophage colonystimulating factor,M-CSF)与核因子κB受体活化因子配体(receptor activator of nuclear factorκB ligand,RANKL)共同诱导BMMs,4天后形成破骨细胞,通过抗酒石酸酸性磷酸酶(tartrate-resistant acid phosphatase,TRAP)与鬼笔环肽染色鉴定诱导出的破骨细胞,通过骨板吸收实验鉴定破骨细胞的骨吸收活性。结果流式细胞仪检测BMMs的CD11b阳性率为98.4%。经过4天诱导,BMMs激活、融合产生了大量的破骨细胞,呈TRAP阳性,鬼笔环肽染色可见纤维肌动蛋白环形成,骨板上形成大量不规则的骨吸收瘢痕。结论 RANKL诱导BMMs 4天可产生骨吸收活性较高的破骨细胞。