Normal and abnormal embryonic development of the anorectum in rats

Background

The embryologic and pathologic aspect of anorectal malformation (ARM) remains poorly understood. There is no universally accepted theory to explain anorectal embryology and the abnormal development that produces ARM. The aim of this study was to observe the developmental processes of anorectum in rats and to explore the abnormal embryonic development that leads to ARM.

Methods

Rat embryos with ARM were obtained by treating pregnant rats with administration of ethylenethiourea (ETU). Normal rat embryos and embryos with ARM from gestational days 12.5 to 20 were sectioned serially and sagittally and stained with H & E. The relevant structure including cloaca and urorectal septum (URS) were examined in a temporospatial sequence.

Results

Characteristics of anorectum development in ARM rat embryos treated by ETU were as follows: (1) URS never fused with cloaca membrane. (2) Dorsal cloacal membrane was maldeveloped. (3) Cloacal configuration was abnormal. (4) Tail groove never appeared. All type of ARM was the rectourethal fistula and common cloaca in ETU-treated rat embryos and was discernible on gestation day 16.

Conclusions

Absence of the tail groove and maldevelopment of the dorsal cloacal membrane, cloacal configuration, and urorectal septum are likely to be responsible for the formation of ARM. Failure of fusion of the URS with cloacal membrane is the immediate reason for rectourethral fistula or common cloaca in ETU-treated rats.     

Congenital Hydrocephalus Induced in Rats by Prenatal Administration of Ethylenethiourea

Abstract: Pregnant Wistar rats were given a single i.p. injection of 30 mg/kg ethylenethiourea (ETU) on one of gestational days 8.5 to 20.5. After rearing to postnatal day 20, the offspring were sacrificed and their brains were excised. Numerous brains removed from the pups prenatally treated with ETU on any day from gestational days 12.5 to 20.5 showed dilatation of lateral ventricle in various degrees. Histological examination revealed forking and stenosis of third ventricle in these brains. Since the degree of the third-ventricular stenosis roughly corresponded to the degree of dilatation of lateral ventricle, this anomaly is considered to be the main cause of congenital hydrocephalus induced in rats by prenatal ETU-treatment. The embryological study showed that the ependymal lining of the third ventricle was partially denuded in the fetuses 24–48 hours after ETU-treatment, and also that the denuded ependymal lining was never repaired during the following gestational days; instead, the ventricular walls fused laterally in the area where the ependymal lining had been denuded.     

乙烯硫脲对FRTL-5细胞甲状腺球蛋白合成分泌及摄碘功能的影响

目的探讨乙烯硫脲(ETU)对FRTL-5细胞的甲状腺球蛋白(TG)合成分泌和摄碘能力的影响。方法用30、150和270μg/ml乙烯硫脲处理FRTL-5细胞后,用MTT法和3H掺入法测乙烯硫脲的细胞毒性;放免法和免疫细胞化学法测乙烯硫脲对TG合成分泌的影响;RT-PCR检测乙烯硫脲对nis基因和tg基因的影响;同位素示踪法检测对细胞摄碘能力的影响。结果30～270μg/ml乙烯硫脲对FRTL-5细胞无显著细胞毒性。150μg/ml和270μg/ml乙烯硫脲显著降低培养液中TG浓度,对胞浆内TG无显著影响;使nis基因转录显著降低,对tg基因无显著影响;150μg/ml和270μg/ml乙烯硫脲显著降低细胞摄碘能力。结论乙烯硫脲可抑制FRTL-5细胞分泌TG,对TG合成无显著影响;乙烯硫脲各剂量组显著降低nis基因转录,但仅在高剂量组显著降低细胞摄碘能力。     

Micromass Culture of Midbrain Cells and its Relevance to in Vitro Mechanistic Studies*

Abstract The relationship between ethylenethiourea (ETU)-induced malformations of cultured rat whole embryos and the alterations of midbrain (MB) cells was investigated and species-specific ETU-induced alterations between rat and mouse MB cells were determined. Herefore, we developed new methods for monitoring teratogenic activities in serum fluids without heat treatment. The serum samples were prepared from rats and mice given ETU, and ETU-teratogenicity was evaluated in both species. We determined that the different sensitivity of the midbrain of the rat and mouse may be the main reason that ETU was teratogenic in rats but not in mice. Next, we showed that MB-cultures are unsuitable for estimating the teratogenic potential of arotinoids. MB differentiation was adversely affected only at concentrations which caused cell death. Finally, we demonstrated that the embryolethal action of new herbicides is not detectable in the micromass teratogenic test. However, the V79 colony assay may be useful for preliminary screening of embryolethal effects of herbicides.     

无肛胎鼠与伴发畸形

通过给妊娠１１ｄ的Ｗｉｓｔａｒ大鼠口服乙烯硫脲（ＥＴＵ），诱发胎鼠产生无肛、腰骶椎异常及体表畸形，并通过Ｘ线钼靶照像进行观察，以探讨无肛畸形伴发其他畸形的机率。结果：合并体表畸形胎鼠占无肛胎鼠的１９．５６％，伴腰骶椎异常者占６６．６％，而且发现无肛胎鼠畸形位置越高，合并腰骶椎异常及体表畸形的发生率越高，即高中低位畸形的发生率分别为５０％；３３．３％；１６．６％，这一发现对指导临床工作有重要意义。     

应用FRTL-5细胞甄别农药亚乙基硫脲、二甲戊乐灵甲状腺素干扰效应

目的　了解亚乙基硫脲 (ETU)、二甲戊乐灵对FRTL 5细胞分泌甲状腺球蛋白的影响。方法　首先用MTT法测这两种化学物的细胞毒性。然后根据细胞毒性结果确定染毒剂量并用放免法测细胞培养液甲状腺球蛋白的浓度。结果　MTT实验中 ,当二甲戊乐灵浓度大于 5ng μl,亚乙基硫脲浓度大于 36 0ng μl时 ,有明显细胞毒性。亚乙基硫脲和二甲戊乐灵在中高剂量均可引起甲状腺球蛋白浓度显著降低。结论　这两种化学物可能干扰甲状腺球蛋白的合成和分泌。     

Carcinogenicity of N-nitroso-ethylenethiourea in female mice

The nitrosation product of ethylenethiourea (ETU), N-nitroso-ETU, was tested for tumorigenicity in female ICR mice. Ten weekly oral administrations of this compound (0.66-2.64 mg/dose) caused apparently dose-dependent increases in the number of mice with pulmonary and lymphocytic neoplasms.     

Effects of food processing on pesticide residues in fruits and vegetables: A meta-analysis approach

Pesticides are widely used in food production to increase food security despite the fact that they can have negative health effects on consumers. Pesticide residues have been found in various fruits and vegetables; both raw and processed. One of the most common routes of pesticide exposure in consumers is via food consumption. Most foods are consumed after passing through various culinary and processing treatments. A few literature reviews have indicated the general trend of reduction or concentration of pesticide residues by certain methods of food processing for a particular active ingredient. However, no review has focused on combining the obtained results from different studies on different active ingredients with differences in experimental designs, analysts and analysis equipment. In this paper, we present a meta-analysis of response ratios as a possible method of combining and quantifying effects of food processing on pesticide residue levels. Reduction of residue levels was indicated by blanching, boiling, canning, frying, juicing, peeling and washing of fruits and vegetables with an average response ratio ranging from 0.10 to 0.82. Baking, boiling, canning and juicing indicated both reduction and increases for the 95% and 99.5% confidence intervals.     

Gli2基因在胎鼠后肠发育后期的表达

目的探讨胎鼠后肠发育与sonichedgehog(Shh)基因转录因子Gli2基因表达水平的关系。方法48只妊娠Wistar大鼠随机分成2组,实验组(n=24)在孕11d按125mg/kg胃管注入1%乙烯硫脲(ethylenethiourea,ETU),对照组(n=24)给予等量蒸馏水。两组分别于孕12d、14d和16d各处死8只母鼠,每只母鼠取4只体重相似的胎鼠,取其直肠1cm提取RNA,采用半定量RT_PCR法检测Gli2基因表达。结果实验组胎鼠直肠Gli2基因表达水平明显低于对照组(P<0.05),实验组Gli2基因表达呈一低水平线,而对照组随妊娠时间呈一下降的曲线。结论Gli2基因表达水平在胎鼠后肠发育中具有重要的作用。