Indicator organisms to determine the use of chilling as a critical point in beef slaughter HACCP

End of project reportDuring chilling, temperatures of carcass surfaces at different sites change over time as do other parameters such as water activity (aw), the structure of the muscle and other tissues, as the carcass enters rigor mortis. Many of these factors are known to have a major effect on cell survival and growth and must be considered in determining the influence of chilling on bacterial survival on carcass surfaces. This study aimed to determine if chilling could be used as a critical control point (CCP) in beef slaughter in relation to pathogens such as E. coli O157:H7 and L. monocytogenes, using E. coli and Listeria innocua as pathogen indicators. The present study was designed to determine the influence of (a) chilling at 10oC for 72 h on the survival of E. coli and (b) chilling at 4oC for 72 h on the survival of L. innocua inoculated at different sites on beef carcasses. Three sites (neck, outside round and brisket) were inoculated (1) immediately after dressing while hot (E. coli and L. innocua) and (2) when cold after chilling (L. innocua). The influence of changes in surface aw was also considered and their relationship to the survival of E. coli and L. innocua over time was assessed. The data are discussed in relation to the use of chilling as a CCP in beef hazard analysis (HACCP) and the monitoring of neck temperature as the most suitable CCP.National Development Pla

Cancer, DNA repair and chromatin structure

Colorectal cancer, the most common cancer in males and females who do not smoke, is diagnosed in approximately 3,500 Scots each year. Despite having a large environmental contribution, the substantial genetic basis of colorectal tumours is still poorly understood. In this project we have adopted a number of approaches to try and further characterise this genetic contribution of colorectal cancer.To begin to understand tumour progression, we first characterised the gene ex¬ pression changes observed in various tumours using SAGE, EST and microarray data. Although many genes were identified as differentially expressed in cancers, little congruence was observed between tumour types and even expression platforms. We next compared gene expression changes observed along chromosomes to local chromatin structure, and showed that regions of constit.utively open structure generally show an increase in gene expression in cancer. Despite the lack of congruence between expression data shown previously, we illustrated that such a correlation between gene expression change in tumours and chromatin structure can be observed using various expression platforms and across a variety of tumours.congruence was observed between tumour types and even expression platforms. We next compared gene expression changes observed along chromosomes to local chromatin structure, and showed that regions of constit.utively open structure generally show an increase in gene expression in cancer. Despite the lack of congruence between expression data shown previously, we illustrated that such a correlation between gene expression change in tumours and chromatin structure can be observed using various expression platforms and across a variety of tumours.To further characterise the role of chromatin structure in tumours, we also investigated the rates of mutation and selection across chromatin categories. DNA damage and repair is a key process in cancer progression and we have shown, through inter species alignments, that although chromosomal regions of a relatively more open chromatin structure undergo lower rates of mutation, levels of purifying selection on synonymous sites are highest in regions of closed chromatin.As part of the COGS/SOCCS group the role of DNA repair in colorectal cancer was finally further investigated through a case-control association study. Tagging SNPs in genes predicted to be associated with DNA repair were selected and subsequently typed by the group in approximately 1000 cases and 1000 controls. The nature of SNPs with evidence of an association with colorectal cancer was finally characterised

Antimetabolite TTL-315 selectively kills glucose-deprived cancer cells and enhances responses to cytotoxic chemotherapy in preclinical models of cancer.

Maintaining thiol homeostasis is an imperative for cancer cell survival in the nutrient-deprived microenvironment of solid tumors. Despite this metabolic vulnerability, a selective approach has yet to be developed to disrupt thiol homeostasis in solid tumors for therapeutic purposes. In this study, we report the identification of 2-mercaptopropionyl glycine disulfide (TTL-315) as a novel antimetabolite that blocks cell survival in a manner conditional on glucose deprivation. In the presence of glucose, TTL-315 lacks cytotoxic effects in normal cells where it is detoxified by reduction to 2-mercaptopropionyl glycine, a compound with known clinical pharmacologic and safety profiles. In several rodent models of aggressive breast, lung and skin cancers, TTL-315 blocked tumor growth and cooperated with the DNA damaging drug cisplatin to trigger tumor regression. Our results offer preclinical proof of concept for TTL-315 as a novel antimetabolite to help selectively eradicate solid tumors by exploiting the glucose-deprived conditions of the tumor microenvironment