Lack of induced mutagenesis in E. coli or human lymphoblast cell line upon long-term sub-culturing in medium from irradiated meat

Purpose: Current study was aimed to enhance the confidence of consumers as well as entrepreneurs towards food irradiation program.

Materials and methods: In this work, safety of high dose (25?kGy) irradiated meat samples (HDIMS) was ascertained by scoring mutation frequency through a long-term sub-culturing study in Escherichia coli MG1655 cells (ATCC 700926) up to 1500 generations (at 1%), 250 generations (at 5% and 10%) and human lymphoblast thymidine kinase heterozygote (TK6) cell line (ATCC CRL-8015) [at two gene loci, tk^?/+ (thymidine kinase) and hprt⁺ (Hypoxanthine Phosphoribosyltransferase)] up to 156 generations using goat meat sample. Also these samples were assayed at further radiation doses of 10, 45 and 70?kGy at 2% concentration (in cell line), and 1% (in E. coli). Study was also performed with other meat samples such as chicken, fishes (pomfret and rohu) and shrimps by carrying out limited long-term sub-culturing trials in human lymphoblast cell line. Mutation analysis was also carried out using a novel DPAR (Differential loss of Plasmid Antibiotic Resistance) assay followed by sequencing of tc^R (tetracycline resistance) gene of pBR322 plasmid isolated from E. coli cells grown for 1500 generations on HDIMS medium and RAPD (Random Amplified Polymorphic DNA) analysis of the genome.

Results and conclusion: None of the assays exhibited any induced mutation when analyzed at regular time intervals. RAPD analysis also did not indicate any change in its nucleotide sequence, ruling out the occurrence of any silent mutation. Thus, the present findings report absence of mutagenic effect of high dose irradiated meat samples.     

腺病毒介导的HSV-tk基因治疗人脑胶质瘤SHG44的研究

目的　探讨带有ＨＳＶｔｋ 基因的重组腺病毒（Ａｄ．ｔｋ） 结合ＧＣＶ 对国人脑胶质瘤ＳＨＧ４４ 的治疗作用。方法　Ｘｇａｌ 染色比较带有报告基因ＬａｃＺ的重组腺病毒（Ａｄ．ＬａｃＺ） 转染ＳＨＧ４４ 细胞和大鼠脑胶质瘤Ｃ６ 细胞的效率,ＭＴＴ法比较Ａｄ．ｔｋ／ＧＣＶ 系统对ＳＨＧ４４ 和Ｃ６ 细胞的敏感性,ＤＮＡ片段分析细胞杀伤机制;在活体用Ａｄ．ｔｋ／ＧＣＶ 治疗ＳＨＧ４４ 移植瘤。结果　ＭＯＩ为５０ 时,Ａｄ．ＬａｃＺ感染ＳＨＧ４４ 细胞的效率近１００％ ,较Ｃ６ 细胞高;ＭＯＩ为１００ 时,Ａｄ．ｔｋ 感染的ＳＨＧ４４ 细胞对ＧＣＶ 的敏感性较Ｃ６ 细胞高,其半致死剂量（ＩＣ５０） 分别为０ ．１２ μｍｏｌ／Ｌ 和０ ．２６ μｍｏｌ／Ｌ,有凋亡机制参与其细胞杀伤;５ ×１０８ＰＦＵ 的Ａｄ．ｔｋ 肿瘤原位注射结合ＧＣＶ治疗,有效抑制ＳＨＧ４４ 移植瘤生长,肿瘤组织坏死,出血伴有纤维组织增生;与Ａｄ ．ｔｋ／ＰＢＳ组、Ａｄ．ＬａｃＺ／ＧＣＶ 组、ＰＢＳ组相比,肿瘤抑制效率分别为９２．５ ％ 、９２．６％ 、８９ ．５％ （ Ｐ＜０ ．０１） 。结论　Ａｄ．ｔｋ／ＧＣＶ系统对人脑胶质瘤细胞的感染效率和敏感性较高,治疗国人脑胶质瘤效果显著。     

The temporal profile of retinal cell genesis in the marmoset monkey

The New World marmoset monkey (Callithrix jacchus) has a relatively short gestational period compared with other primates but possesses a retina at a similar stage of maturation by birth. Previous studies have highlighted that the complex fovea of the marmoset undergoes a more rapid postnatal development in comparison with the Macaca monkey, reaching a mature stage earlier than these species. In this current study, we examined the prenatal proliferation profile of cells in the entire retina employing the thymidine analogs and also determined their phenotype by double‐label immunocytochemistry using type‐specific markers. Akin to other primate species, we demonstrate a centroperipheral gradient in the emergence of both neurons and Müller glia with cones, ganglion cells, and horizontal cells generated first in the fovea at fetal day (Fd)70–74 and with the last generated at the retinal edge at Fd115. Rods, bipolar cells, amacrine cells, displaced amacrine cells, and Müller glia were generated between Fd76 and Fd135 along the same gradient. Similar to foveal development, marmoset neuronal generation was rapid, only taking 51% of gestation whereas in Macaca this takes 81%. J. Comp. Neurol. 524:1193–1207, 2016. © 2015 Wiley Periodicals, Inc.     

结直肠癌肝转移组织中胸苷磷酸化酶表达

目的 检测胸苷磷酸化酶(TP)在人结直肠癌肝转移组织中的表达,分析该表达与肿瘤相关巨噬细胞(TAM)及与患者预后的相关性.方法 采用抗TP的单克隆抗体654-1及1C6-203、抗巨噬细胞标记物cD68的单克隆抗体PG-M1,对28例人结直肠癌肝转移标本进行免疫组织化学染色分析,对3种抗体阳性细胞进行细胞计数,计算各种阳性细胞之间,以及各种阳性细胞与患者预后的相关性.结果 28例标本中,转移癌细胞表达TP甲阳性的仅2例,癌组织中表达TP的阳性细胞主要是癌巢周围的间质细胞,特别是肿瘤相关巨噬细胞(TAM).通过对3种阳性细胞计数发现,2种TP抗体染色阳性细胞数相关(r=0.697,P<0.01);654-1阳性细胞数与TAM细胞数相关(r=0.703,P<0.01);而1C6-203阳性细胞数与TAM细胞数相关较弱,无统计学意义(r=0.359,P=0.06).16例死亡患者的术后生存时间与3种阳性细胞数目均无相关(P>0.05).结论 在人结直肠癌肝转移组织中表达TP阳性的细胞主要是TAM,组织中TP阳性细胞及CD68阳性巨噬细胞的多少与患者预后生存的时间无相关.     

6‐[(2‐Iminopyrrolidinyl)methyl]‐5‐[125I]iodouracil as a potential thymidine phosphorylase‐targeted radiopharmaceutical: synthesis and preliminary biological evaluation

Thymidine phosphorylase (TP) is expressed at higher levels in many types of malignant tumors than in adjacent nonneoplastic tissues. The aim of this study was to develop a radiolabeled TP inhibitor, 6‐[(2‐iminopyrrolidinyl)methyl]‐5‐[¹²⁵I]iodouracil ([¹²⁵I]1) as a TP‐targeted radiopharmaceutical. No‐carrier‐added [¹²⁵I]1 was synthesized by halogen exchange of the corresponding bromide (2). After purification by reverse‐phase HPLC, [¹²⁵I]1 showed a radiochemical purity of over 97%. When administered to normal mice, [¹²⁵I]1 showed a rapid clearance from the blood and a low accumulation in the thyroid and stomach, indicating good in vivo stability against deiodination. By coinjection of unlabeled 1, the uptakes in the TP‐expressing normal tissues, small intestine and liver were significantly reduced, suggesting TP‐specific modes of accumulation of [¹²⁵I]1. These findings suggest that [¹²⁵I]1 possesses the required properties for in vivo imaging of TP activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Identification of aspartic acid-203 in human thymidine phosphorylase as an important residue for both catalysis and non-competitive inhibition by the small molecule “crystallization chaperone” 5′-O-tritylinosine (KIN59)

Thymidine phosphorylase (TP) is a catabolic enzyme in thymidine metabolism that is frequently upregulated in many solid tumors. Elevated TP levels are associated with tumor angiogenesis, metastasis and poor prognosis. Therefore, the use of TP inhibitors might offer a promising strategy for cancer treatment. The tritylated inosine derivative 5′-O-tritylinosine (previously designated KIN59) is a non-competitive inhibitor of TP which was previously found to be instrumental for the crystallization of human TP. A combination of computational studies including normal mode analysis, automated ligand docking and molecular dynamics simulations were performed to define a plausible binding site for 5′-O-tritylinosine on human TP. A cavity in which 5′-O-tritylinosine could fit was identified in the vicinity of the Gly405-Val419 loop at a distance of about 11 Å from the substrate-binding site. In the X-ray crystal structure, this pocket is characterized by an intricate hydrogen-bonding network in which Asp203 was found to play an important role to afford the loop stabilization that is required for efficient enzyme catalysis. Site-directed mutagenesis of this amino acid residue afforded a mutant enzyme with a severely compromised catalytic efficiency (V_max/K_m of mutant enzyme ∼50-fold lower than for wild-type TP) and pronounced resistance to the inhibitory effect of 5′-O-tritylinosine. In contrast, the D203A mutant enzyme kept full sensitivity to the competitive inhibitors 6-aminothymine and 6-amino-5-bromouracil, which is in line with the kinetic properties of these inhibitors. Our findings reveal the existence of a previously unrecognized site in TP that can be targeted by small molecules to inhibit the catalytic activity of TP.     

Technical evaluation of thymidine kinase assay in cytosols from breast cancers

Pilot retrospective studies have pointed to the prognostic value of thymidine kinase (TK) in breast cancer. We studied the Prolifigen TK-REA assay (Sangtec Medical, Sweden), usually applied to serum, for TK analysis in breast cancer cytosols. Reproducibility was good, provided that small volume pipetting was performed carefully. The TK assay was not influenced by the short-term storage of cytosols in liquid nitrogen or at −80 °C. However, some steps appeared critical for good laboratory practice. The TK level was affected by thawing the cytosols more than twice. Tumour storage in liquid nitrogen should be preferred over storage at −80 °C. The components of the homogenisation buffer, especially sodium molybdate and KCl can have a marked influence on results. Finally, linearity problems arose with some cytosols. Thus, although assay of TK in cytosols is aparently simple, care must be taken in practice. The TK-REA kit should be standardised before widespread use in breast cancer.     

Prognostic significance of in vitro thymidine uptake in patients with colorectal carcinoma

In 127 patients with colorectal carcinoma, we measured thymidine uptake by tumor cells cultured in a semisolid medium and compared the influence of various parameters on survival by univariate and multivariate analysis. Fifty-four of the 127 carcinomas (42.5%) incorporated >1,000 cpm of tritiated thymidine per culture dish and were designated as the high-uptake group, while the other tumors (57.5%, 73/127) were designated as the low-uptake group. There was no significant correlation between high or low thymidine uptake and most of the clinicopathological characteristics of the patients. Patients in the high-uptake had a poor prognosis and a 7-year survival rate of 32.6%, which was significantly different from the rate of 69.3% in the low-uptake group (P < 0.0005). Multivariate analysis showed that thymidine uptake was one of the variables strongly associated with survival in our study population. Thus, it is concluded that thymidine uptake by tumor cells has a high capacity of predicting prognosis, independent of its relationship to other variables. Furthermore, it seems to us that thymidine uptake can help in selecting those patients with colorectal carcinoma who are most likely to benefit from perioperative adjuvant therapy. © Wiley-Liss, Inc.     

Sex differences in cell proliferation,cell death and defensive behavior following acute predator odor stress in adult rats

Males show suppressed cell proliferation in the hippocampus in response to acute stress but no studies to date have examined cell proliferation in response to acute stress in females. In the current study, we examined the effects of acute exposure to a predator odor stressor [trimethyl thiazoline (TMT); the main component of fox feces] or a control odor on cell proliferation and cell death in the dentate gyrus and on behavior in adult male and female [intact, ovariectomized (OVX) or OVX+estradiol benzoate (EB)] rats. Further, we examined whether TMT-induced changes in behavior were related to cellular changes. During TMT exposure, rats were injected with the cell synthesis marker bromodeoxyuridine and perfused 24 h later. Acute TMT exposure suppressed both cell proliferation and death in males but not in any group of females. Interestingly, in the OVX females we observed an increase in cell death that was eliminated by EB treatment. Consistent with prior studies, estradiol treatment increased cell proliferation regardless of odor condition. Regardless of sex or hormone treatment, TMT increased defensive behavior, suggesting that the behavioral response to TMT is dissociated from this cellular response. This is the first demonstration of a sex difference in cell proliferation and death in the adult dentate gyrus in response to stress.