姜黄素对N-甲基亚硝基脲诱发膀胱癌大鼠化学干预作用及机制分析

目的分析姜黄素对N-甲基亚硝基脲(MNU)诱导的膀胱癌大鼠模型的化学干预作用及作用机制。方法将100只SD大鼠随机分为四组,对照组(10只)、模型组(10只)、干预组(40只)和治疗组(40只),对照组等时等量的膀胱灌注生理盐水,其他三组均对大鼠进行膀胱灌注MNU,诱发SD大鼠形成膀胱癌模型(将浓度为1 mg/m L的MNU溶液灌注入膀胱内,MNU灌注时间为第2、4、6和8周,每次2 mg,每2周1次,共4次),模型组在诱发大鼠膀胱癌时膀胱灌注蒸馏水,干预组在膀胱灌注MNU时灌注姜黄素溶液(400μmol/L),即第1、3、5、7和9周膀胱灌注,第10周安乐死大鼠;治疗组在诱发大鼠膀胱癌模型后膀胱灌注姜黄素溶液(400μmol/L),即在第10、12、14、16、18周时间内持续膀胱灌注,在第19周时处死大鼠,获得的膀胱组织依次通过苏木精-伊红(HE)染色,观察病理变化;TUNEL末端标记法测定肿瘤组织中细胞凋亡情况;Western blot检测凋亡相关蛋白表达。结果模型组在第10周时膀胱癌的发生率为90%(9/10),干预组在第10周时大鼠膀胱癌的发生率为12.5%(5/40),治疗组第10周时膀胱癌的发生率为92.5%(37/40),比较干预组与模型组大鼠膀胱癌的发生率差异有显著性(P0.05),说明姜黄素对MUN诱发膀胱癌大鼠有明显的化学干预作用;在治疗组膀胱癌形成后给予姜黄素治疗,第19周膀胱癌发生率为78.4%(30/37),与治疗前的第10周比较说明姜黄素对膀胱癌有治疗作用,可以延缓膀胱癌的恶化。TUNEL实验证实姜黄素显著促进膀胱癌细胞的凋亡,抑制膀胱癌细胞的增殖。Western blot结果发现,姜黄素抑制NF-κB的激活,有效下调NF-κB调节的基因产物的表达。结论姜黄素对MNU诱导的膀胱癌大鼠模型有明显的的化学干预作用,且作用机制可能是通过抑制NF-κB的激活并且有效下调NF-κB调节的基因产物,来调节膀胱癌中相关蛋白的表达机制,即抑制增殖,诱导凋亡,进一步发挥抗癌的化学干预作用以及预防膀胱癌的复发。     

大鼠活体胸部扫描中减少图像呼吸心跳伪影序列方案的探讨

目的开发256层螺旋CT大鼠活体胸部CT扫描中减少图像呼吸、心跳伪影的序列。方法采用飞利浦Brilliance-iCT对10只SD大鼠进行胸部CT成像。每只大鼠均采用A、B两种扫描方式, A方式为常规胸部CT扫描序列,为非心电门控螺旋扫描模式,B方式为非心电门控轴扫模式。两组均在120 kV条件下扫描,扫描长度为8 cm。对所得CT数据进行横断位与冠状位肺窗与软组织窗重建,观察图像并进行测量,比较两组图像的平均CT值、图像噪声、信噪比(SNR)、和主观图像质量评分的差异,并对不同观察者间主观图像质量评分的一致性进行检验。结果分析10例大鼠胸部CT扫描数据。A、B两种扫描序列的剂量长度乘积(dose length product,DLP)值分别为144.7 mGy/cm与72.2 mGy/cm。两组间肺组织CT值与肝组织CT值差异无显著性(t值分别为-0.205、0.545,P0.05),两组图像噪声差异无显著性(t值为-0.865,P0.05),两组图像肺组织的SNR差异无显著性(t值为0.903,P0.05),但肝组织的SNR值B组高于A组,差异有显著性(t值为-2.885,P0.05)。两位医师的评分结果的相关系数为0.763,诊断结果一致性良好。A、B两种扫描方式的图像主观质量评分为(2.5±0.53)分、(4.3±0.67)分,差异有显著性(χ~2值为14.76,P0.05)。结论大鼠胸部CT扫描采用非心电门控轴扫模式可获得与胸部常规CT扫描(非心电门控螺旋扫描模式)大致相当的CT值与噪声、信噪比,但采用非心电门控轴扫模式可以有效减少大鼠胸部图像的呼吸心跳伪影,降低辐射剂量,提高图像质量,提高观察者的诊断信心。     

基于GEO数据库、TMT蛋白组学筛选绞股蓝对膀胱癌的蛋白靶点

绞股蓝(Gynostemma pentaphyllum)是传统的中药材,对于多种癌症具有显著的疗效.为筛选绞股蓝对膀胱癌的作用靶点,本研究将30只SPF级SD大鼠随机分为模型组、给药组和空白组,通过膀胱灌注N-甲基-N-亚硝基脲(MNU)建立膀胱癌模型并通过相同的方式进行膀胱灌注绞股蓝干预治疗,在第10周进行取材,通过H&E染色病理切片观察各组膀胱内肿瘤情况以明确药效.通过蛋白质组学串联质谱标签(TMT) 10重标记法检测各组膀胱组织的蛋白差异表达情况,结合GEO数据库中3组膀胱癌数据集对作用靶点进行筛选.结果 显示,绞股蓝反向调节膀胱癌335种蛋白质,其中包括55种上调和280种下调.GEO的3个膀胱癌表达谱中汇集的差异蛋白(DEGs)包含20种上调和50种下调.将GEO中DEGs与TMT蛋白质组学中膀胱癌趋势相同的蛋白进行汇集,结合绞股蓝反向调节数据,总共筛选获得了3个反向调节靶点,其中包括1种下调的靶点CNN1和2种上调的靶点KRT19、PCP4,并通过蛋白免疫印迹法进行验证.本研究结果表明,CNN1、KRT19和PCP4可能是绞股蓝治疗膀胱癌的潜在靶点,绞股蓝可能通过调节CNN1、KRT19和PCP4来抵抗膀胱癌,这为绞股蓝治疗膀胱癌提供分子机制依据.     

急性兔脑栓塞模型的建立

目的建立稳定的兔脑栓塞模型,以期为进一步开展脑栓塞的病理生理变化及影像学研究提供可靠实用的工具。方法30只健康新西兰兔,随机分成3组,其中A组3只,为空白对照组;B组5只,为假手术对照组;C组22只,为栓塞组。分离右侧颈部血管,经颈外动脉向颈内动脉注入直径约0.5~1.0 mm的SiO2颗粒10枚左右,栓塞后30 min行CT灌注检查,利用多层螺旋CT灌注成像对各组动物的脑缺血情况进行观察。24 h处死动物取脑组织进行病理研究。结果A、B组CT灌注及病理均未见异常。C组栓塞过程中3只兔死亡。16只兔CT灌注异常,表现为右侧局部CBF降低、MTT延长、CBV无明显变化或轻度上升、下降。3只兔灌注未见异常。HE染色可见8只兔脑梗塞,7只兔脑缺血,4只兔未见明显异常。结论采用该方法和技术能够建立稳定的兔脑栓塞模型,结果可靠,具有可操作性和重复性。     

THP在早期非肌层侵润性膀胱癌定位诊断与治疗中的临床应用

目的：探讨THP在早期非肌层侵润性膀胱癌定位诊断与治疗中的临床应用价值。方法：已诊断非肌层侵润性膀胱癌患者45例,术中均实行THP膀胱灌注,灌注后15min置入膀胱镜,观察膀胱内粘膜,将THP橙色染色区域作为实验组进行活检,其他未染色区域作为对照组随机活检,活检组织行病理检查。TUR—BT术后将45例患者随机分为3组。在不同的时间点开始灌注（术后即刻、术后6小时、术后7天）,比较复发率和平均复发时间。结粜：两组间比较具有统计学意义（P〈0.05）恶性粘膜吸收THP敏感度和特异度分别为100％、63．5％;TUR-BT术后即刻灌注及6小时后灌注的总复发率明显低于术后7天灌注,差异有统计学意义（P〈0．05）。结论：THP对非肌层侵润性膀胱癌早期定位诊断准确、安全性好,同时术后早期灌注THp可以降低肿瘤的复发率,值得临床推广。     

THP在早期非肌层侵润性膀胱癌定位诊断与治疗中的临床应用

目的:探讨THP在早期非肌层侵润性膀胱癌定位诊断与治疗中的临床应用价值。方法:已诊断非肌层侵润性膀胱癌患者45例,术中均实行THP膀胱灌注,灌注后15min置入膀胱镜,观察膀胱内粘膜,将THP橙色染色区域作为实验组进行活检,其他未染色区域作为对照组随机活检,活检组织行病理检查。TUR-BT术后将45例患者随机分为3组,在不同的时间点开始灌注(术后即刻、术后6小时、术后7天),比较复发率和平均复发时间。结果:两组间比较具有统计学意义(P<0.05)恶性粘膜吸收THP敏感度和特异度分别为100%、63.5%;TUR-BT术后即刻灌注及6小时后灌注的总复发率明显低于术后7天灌注,差异有统计学意义(P<0.05)。结论:THP对非肌层侵润性膀胱癌早期定位诊断准确、安全性好,同时术后早期灌注THP可以降低肿瘤的复发率,值得临床推广。     

CT对于肝脏良性占位性病变及肝癌的鉴别诊断价值分析

目的:探讨CT对于肝脏良性占位性病变及肝癌的鉴别诊断价值。方法:收取2013年3月至2016年3月我院收治的肝脏良性占位性病变及肝癌患者101例作为研究对象,按照病变类型将其分为A、B、C三组。其中A组包含原发性肝癌患者32例,B组包含肝转移癌患者28例,C组包含肝血管瘤患者41例。采用CT全肝灌注扫描模式对三组患者占位病灶组织、病灶周围组织及正常肝脏组织灌注参数进行比较。结果:三组占位病灶组织,B组患者肝动脉灌注量(HAP)最低,C组患者HAP最高;A组患者门静脉灌注量(PVP)最低,C组患者PVP最高,三组两两比较均有显著差异(P0.05)。C组总肝灌注量(TLP)明显高于A组和B组(P0.05),A、B组间无统计学差异(P0.05)。三组肝动脉灌注指数(HPI)无明显差异(P0.05);B组病灶周围组织HAP及HPI明显高于A、C组(P0.05),A、C组间无统计学差异(P0.05);三组PVP及TLP差异不显著(P0.05);三组正常肝脏组织CT灌注参数均无显著差异(P0.05)。结论:CT灌注成像对于原发性肝癌、肝转移癌及肝血管瘤具有一定的鉴别诊断价值,但明确诊断仍需结合其他检测方法进行。     

CT脑灌注剂量下X射线对体外培养的骨髓间质干细胞的影响

观察大鼠CT脑灌注剂量下的X射线照射对体外培养的骨髓间质干细胞的影响.体外大鼠培养骨髓间质细胞,分为照射组和未照射对照组,照射组细胞分别进行1～5次大鼠脑灌注条件下CT扫描.两组细胞分别做生长曲线,运用流式细胞仪检测细胞周期改变情况,以及行噻唑蓝(3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazolium romide,MTT)法检测细胞凋亡情况.5次大鼠脑灌注CT扫描下照射组细胞活性及凋亡情况与对照组细胞差异无统计学意义.常规大鼠脑灌注CT扫描对骨髓间质干细胞活性无影响.     

正常大鼠脑CT灌注成像的可重复性研究

目的:评价多层螺旋CT灌注成像对正常大鼠脑血流动力学观测结果的可重复性.方法:分别对10只健康Wistar大鼠间隔2d进行CT灌注扫描,两组原始灌注数据由2名放射科医师分别进行5次后处理得出CBF、CBV和MTT值.分析观察者内和观察者间观测结果的可重复性,以及对同一组研究对象间隔2d两次检查结果的一致性.结果:多层螺旋CT对Wistar大鼠脑所采集的灌注原始数据在观察者内和观察者间观测结果均无统计学差别(P＞0.05),并具有很好的线性(CBF和CBV值)或等级(MTT值)正相关(P＜0.01).对同一组研究对象间隔2d的两次CT灌注成像结果也存在同样好的重复性.结论:多层螺旋CT灌注成像对于Wistar大鼠脑部血流动力学观测具有很高的精密度和准确性,完全适于小型动物模型脑部血流动力学的研究.     

TUR-BT术后膀胱灌注A群链球菌联合丝裂霉素治疗高危非肌层浸润性膀胱癌的疗效观察

目的：总结经尿道膀胱肿瘤电切（TUR-BT）术后辅以沙培林（注射用A群链球菌）联合丝裂霉素（MMC）膀胱内灌注治疗高危膀胱癌的疗效。方法：回顾性研究2009年1月~2012年8月我院收治的符合高危非肌层浸润性膀胱癌患64例,观察组：TUR-BT术后行沙培林联合MMC膀胱内灌注化疗32例,对照组;MMC单药灌注32例。结果：观察组患者,平均年龄63.7岁,治疗随访时间为6~54个月,中位时间27.3个月。治疗随访期间有3例患者出现膀胱内肿瘤复发（9.3%）,1例患者疾病进展,发展为肌层浸润性膀胱癌,于术后7个月死亡（3.1%）。与对照组患者相比,疾病复发率及进展率均明显改善。结论：高危非肌层浸润膀胱癌临床复发率、进展率高,TUR-BT术后沙培林联合MMC膀胱内灌注通过局部化疗及免疫治疗联合,可有效控制疾病的复发和进展,降低患者接受膀胱部分切除或膀胱全切手术的机率,值得推广。     

Evaluation of a new model to detect bladder carcinogens or co-carcinogens; results obtained with saccharin, cyclamate and cyclophosphamide.

A sensitive rat model has been designed to detect potential weak bladder carcinogens or co-carcinogens. The test compound is given to animals which have received a single initiating, but non-carcinogenic, dose of N-methyl-N-nitrosourea (MNU). The model has been used to investigate two compounds currently under suspicion as weak bladder carcinogens, namely sodium saccharin and sodium cyclamate, and one compound known to be cytotoxic but not carcinogenic for the bladder epithelium namely cyclophosphamide. For comparison, these three compounds were also tested as solitary carcinogens in animals not pre-treated with MNU. At the very high dose levels used, sodium saccharin and sodium cyclamate were weak solitary carcinogens producing 4/253 and 3/228 bladder tumours respectively, and the first of these tumours did not appear for more than 80 weeks. When tested in the MNU/rat model more than half the animals receiving either sodium saccharin or sodium cyclamate developed bladder tumours from 10 weeks onwards. By contrast, cyclophosphamide failed to produce any tumours when tested either as a solitary carcinogen or in the MNU/rat model. It must be emphasized that the doses of saccharin and cyclamate used were far higher than those consumed by man, including diabetics, and these results should not be directly extrapolated to man without careful consideration of many other factors including negative epidemiological findings. The theoretical basis of the model is discussed and also the relevance, in terms of environmental human exposure, of detecting compounds which have a synergistic effect with other known bladder carcinogens. It appears that this model can be used to detect a carcinogenic or co-carcinogenic potential in compounds which are organotropic for the bladder more rapidly and with fewer animals than if the compounds are tested as solitary carcinogens by more conventional methods. It is suggested that it could be used to detect those compounds which require further investigation.     

N‐methyl‐N‐nitrosourea induces retinal degeneration in the rat via the inhibition of NF‐κB activation

Retinitis pigmentosa (RP) is a group of inherited neurodegenerative diseases characterized by the loss of photoreceptor cells through apoptosis. N‐methyl‐N‐nitrosourea (MNU) is an alkylating toxicant that induces photoreceptor cell death resembling hereditary RP. This study aimed to investigate the role of nuclear factor κB (NF‐κB) in MNU‐induced photoreceptor degeneration. Adult rats received a single intraperitoneal injection of MNU (60 mg/kg bodyweight). Hematoxylin and eosin staining demonstrated progressive outer nuclear layer (ONL) loss after MNU treatment. Transmission electron microscopy revealed nuclear pyknosis, chromatin margination in the photoreceptors, increased secondary lysosomes, and lobulated retinal‐pigmented epithelial cells in MNU‐treated rats. Numerous photoreceptor cells in the ONL showed positive TUNEL staining and apoptosis rate peaked at 24 hours. Enhanced depth imaging spectral‐domain optical coherence tomography showed ONL thinning and decreased choroid thickness. Electroretinograms showed decreased A wave amplitude that predominated in scotopic conditions. Western blot analysis showed that nuclear IκBα level increased, whereas nuclear NF‐κB p65 decreased significantly in the retinas of MNU‐treated rats. These findings indicate that MNU leads to selective photoreceptor degradation, and this is associated with the inhibition of NF‐κB activation.     

A relationship between nuclear DNA and RNA synthetic activities and the changes produced by n-methyl-n-nitroso urethane: A study using Amoeba proteus as a single cell model

Changes caused by a carcinogen generally vary from one cell to another even among similar types of cells. The following work investigates the degree to which damage (inhibition of division, lethality, or inherited cellular changes) caused by N-methyl-N-nitroso urethane (MNU) alters at different times during the cell cycle, and relates fluctuations in the sensitivity of cells to changes in their DNA and RNA synthetic activities—possibly in the configuration of their DNA—at the time of treatment.Studies on amoebae exposed to MNU for short periods at 50 different times in their cell cycle led to the following conclusions: amoebae are sensitive to MNU at all ages, but the dose needed to produce lethal damage to young and old cells varies by a factor of 3. Cells are most sensitive at the time of division and during the peak of DNA synthesis. Smaller changes are found during the G₂ phase, some of which occur at times of intensive RNA synthesis. Transfer of nuclei between treated and control cells proved that the changing sensitivity of the cells, as shown by both inherited changes and lethal damage, was dependent on changes in their nuclei. Though the cytoplasm could be affected directly by MNU, i.e. in the absence of a nucleus, supralethal doses 2–6 times whole cell dose were required to either kill the cell or to cause a recognizable change in the offspring of viable cells. Experiments with cells having altered nuclear/cytoplasmic ratios showed that the relative insensitivity of older cells was not due to the increased volume of their cytoplasm. However, a possible involvement of cytoplasm in the repair of nuclear damage is suggested by the ability of control cytoplasm to alleviate some nuclear damage, particularly in S phase cells.     

Methylation of DNA in rat liver and intestine by dimethylnitrosamine and N-methylnitrosourea

A chromatographic procedure for improved separation of deoxyribonucleosides and methylated deoxyribonucleosides is described. DNA was isolated from liver and small intestine of rats treated with [¹⁴C]dimethylnitrosamine ([¹⁴C]DMN) or $\text{N-[}{}^3\text{H}\text{]}\text{methyl}\text{-N-}\text{nitrosourea}$ ([³H]MNU), and the purified DNA was hydrolyzed enzymatically. The deoxyribonucleosides were chromatographed on an Aminex A-6 cation exchange column at 37°C with 0.4 M ammonium formate, pH 4.5, as eluant. In addition to showing the presence of the expected alkylated products, N⁷-methyldeoxyguanosine (determined as N⁷-methylguanine) and O⁶-methyldeoxyguanosine, several other minor methylated products were found in liver and intestinal DNA of rats treated with DMN or MNU. Two of these products are believed to be N³-methylthymidine and O⁴-methylthymidine.     

Methylnitrosourea induces neural progenitor cell apoptosis and microcephaly in mouse embryos

BACKGROUND: Prenatal exposure to methylnitrosourea (MNU), an alkylating agent, induces microcephaly in mice. However, its pathogenetic mechanism has not been clarified, especially that in the development of the cerebral cortex. METHODS: ICR mice were treated with MNU at 10 mg/kg intraperitoneally on day 13.5 or 15.5 of gestation, and the embryos were observed histologically 24 hr after treatment with MNU or at term. To clarify the pathogenesis of microcephaly and histological changes, especially apoptosis, neurogenesis, and neural migration/positioning, we performed histological analysis employing a cell‐specific labeling experiment using thymidine‐like substances (BrdU, CldU, and IdU) and markers of neurons/neural stem cells. RESULTS: Histological abnormalities of the dorsal telencephalon, and the excessive cell death of proliferative neural progenitor/stem cells were noted in the MNU‐treated embryos. The highest frequencies of cell death occurred at 36 hr after MNU treatment, and little or no neurogenesis was observed in the ventricular zone of the dorsal telencephalon. Abnormality of the radial migration was caused by the reduction of radial fibers in the radial glias. Birth‐date analysis revealed the abnormal positioning of neurons and aberrant lamination of the cerebral cortex. CONCLUSIONS: Our data suggest that prenatal exposure to MNU induces the excessive cell death of neural precursor/stem cells, and the defective development of the cerebral cortex, resulting in microcephalic abnormalities. Birth Defects Res (Part B) 89:213–222, 2010. © 2010 Wiley‐Liss, Inc.     

Androgen receptor expression in primary prostate cancers of lobund-wistar rats and in tumor-derived cell lines

Summary Prostate tumors were induced in Lobund-Wistar rats by treatment with N-methyl-N-nitrosourea (MNU) and testosterone propionate (TP). Androgen receptor (AR) expression was confirmed in 16 (100%) of the primary prostate cancers, with strong uniform staining in well-differentiated tumors and more variable AR immunoreactivity in poorly differentiated tumors. Epithelial cell lines were established from nine of the tumors. At early passages, four of the tumor cell lines tested were strongly immunoreactive for AR; however, only two of the cell lines, E2(A) and F2, have remained AR-positive. These cell lines specifically bind ³H-DHT at 40 and 19 fmol/mg protein, respectively, and express a 110 kDa AR immunoreactive protein. Proliferation in in vitro culture of both E2(A) and F2 cells was increased in the presence of 5α-dihydrotestosterone (DHT). The antiandrogen, hydroxyflutamide was able to prevent the DHT-induced growth of E2(A) but not F2 cells. Furthermore, hydroxyflutamide alone increased proliferation of F2 cells, suggesting that the androgen signalling pathway in this cell line may be abnormal. Tumorigenicity of the AR-expressing and nonexpressing cell lines was confirmed by xenograft formation following subcutaneous inoculation into intact male nude mice. In summary, carcinogen-induced prostate tumors of Lobund-Wistar rats express AR and two of nine cell lines derived from the tumors express AR. Further evaluation of AR structure in primary prostate tumors forming spontaneously or following MNU and TP induction will determine whether, as in human prostate cancers, disease progression in Lobund-Wistar rats is associated with mutations in the AR gene.     

Bladder cancer and N-methyl-N-nitrosourea. II. Sub-cellular changes associated with a single noncarcinogenic dose of MNU

The ultrastructural changes in the rat urothelium induced by a single, cytotoxic but not carcinogenic dose of N-methyl-N-nitrosourea(MNU) are described. They are compared with some aspects of the cyclophosphamide-induced response.Both MNU and cyclophosphamide produce cell necrosis, desquamation of the epithelium and haemorrhage from sub-epithelial capillaries, followed by epithelial hyperplasia. The hyperplastic epithelium appears to be de-differentiated, but the effect is reversible, and a normal-looking epithelium is re-established in 10 to 15 weeks after the MNU treatment.The significance of breaks in the basal lamina in this situation is discussed and the phagocytic potential of the epithelial cells is illustrated.     

大鼠实验性流产模型的建立及黄芪多糖对其的影响

目的应用细菌脂多糖(Lipopolysaccharides,LPS)尾静脉注射建立大鼠实验性流产动物模型,研究黄芪多糖(astragalus polysacharin,APS)对实验性流产大鼠保胎的作用。方法采用怀孕第7天Sprague-Dawley(SD)大鼠尾静脉注射LPS每只1.0μg,建立实验性大鼠流产模型,以正常怀孕大鼠尾静脉注射磷酸缓冲液(PBS)每只1.0mL作为对照组,随机将模型组大鼠分为流产模型组、APS组。APS组于怀孕4～9d口服APS2mL(150mg)/d,对照组与和流产模型组分别于4～9d口服生理盐水2mL/d。于实验第10天麻醉处死各组大鼠,计数妊娠成功比例和流产比例。结果 LPS诱导大鼠流产模型组流产比例高达8/11,而对照组和APS组流产比例分别为1/12和1/6,与流产模型组比较差异极显著(P0.01)。结论 LPS可以诱导建立大鼠流产模型,中药成分APS对实验性大鼠流产具有一定的保护作用。     

Prevention of inhibitory effects of alpha-difluoromethylornithine on rat urinary bladder carcinogenesis by exogenous putrescine

We previously demonstrated that repeated instillation of alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), inhibits (or retards) urinary bladder carcinogenesis in rats. Since ODC catalyzes the first step in polyamine synthesis, the inhibition of polyamine formation may be responsible for tumor inhibition by DFMO. The present experiment was conducted using male Fischer rats with a heterotopically transplanted urinary bladder (HTB) to determine whether the effects of DFMO are prevented by exogeneous Pu. HTBs were treated with 0.25 mg of N-methyl-N-nitrosourea (MNU) once a week for 3 weeks and the animals were then arbitrarily divided into 6 groups. Beginning one week following the last MNU treatment, all rats received twice a week instillation (0.5 ml each) as follows: Group 1 rats, normal rat urine; Group 2, 2% DFMO in urine; Group 3, 250 microM Pu and 2% DFMO in urine; Group 4, 250 microM Pu in urine; Group 5, urine for 10 weeks followed by 2% DFMO in urine; and Group 6, urine for 10 weeks followed by 250 microM Pu and 2% DFMO in urine. At 10 weeks following the last MNU instillation 5 rats from each of Groups 1 through 4 were killed for determination of urothelial polyamine levels. An additional 4 rats of Group 1 were killed at 10 weeks for histological examination. All remaining rats were killed 20 weeks after the last MNU instillation. Polyamine levels showed no significant difference among the 4 groups. The incidence of carcinoma was significantly lower in the group treated with DFMO (p less than 0.001, Group 1 vs Group 2), confirming our previous observation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of dietary zinc intake on N-methyl-N-nitrosourea-induced mammary tumorigenesis in rats

Numerous studies have shown that zinc nutrition influences the growth of several types of tumor. However, the influence of zinc nutrition on mammary tumorigenesis is not known. To study the effects of dietary zinc intake on N-methyl-N-nitrosourea (MNU)-induced mammary tumorigenesis, female Sprague-Dawley rats were fed an egg-white-based diet providing 3 (Z3), 12 (Z12), or 31 (Z31) mg zinc/kg diet ad libitum. In addition, two pair-fed controls, PFZ12 and PFZ31, were also included. Fourteen weeks after MNU injection, cumulative tumor incidence and total number of tumors were lower in Z3 rats than in Z12 and Z31 rats. Cumulative tumor incidence and total number of tumors were lower in Z3 rats than in PFZ12 rats, but were the same as in PFZ31 rats. Cumulative tumor incidence and total number of tumors were also lower in pair-fed controls than in their corresponding ad libitum controls, but were the same between the ad libitum controls. Overall, the results showed that the effect of marginal zinc deficiency on MNU-induced mammary tumorigenesis in rats was primarily the result of a reduced feed intake associated with marginal zinc deficiency rather than zinc per se.