The Human Genome Project: its relevance to ocular disease

This article describes the history of the Human Genome Project, how the human genome was sequenced, and analyses the likely impact which the results will have on the diagnosis, scientific understanding and, ultimately, treatment of ocular disease in the future.

Catabolic factors in tumour-induced cachexia

A transplantable colon adenocarcinoma of the mouse (MAC16) was utilized as a model of human cancer cachexia. The MAC16 tumour produced extensive weight loss in the host at small tumour burdens and without a reduction in either food or fluid intake. The weight loss was characterised by a decrease in both carcass fat and muscle mass which were directly proportional to the weight of the tumour. The weight loss has been correlated with the production of circulatory catabolic factors by the tumour, which degrade host muscle and adipose tissue in vitro. These factors were further characterised and have been shown to be distinct and separable by gel exclusion chromatography. The proteolytic factors (molecular weight > 150k daltons) were distinguishable from the lipolytic factors which appeared related with molecular weights of approximately 3.0, 1.5 and 0.7k daltons. Lipolytic factors of the same molecular weights were identified in other tumour models and in the body fluids of tumour-bearing animals and cancer patients. These factors were not present in healthy individuals or in patients with other weight-losing conditions. Various temperatures studied reversed the weight loss seen in the cachexia induced by the MAC16 adenocarcinoma in vivo. The effects of these treatments could be linked in vitro to the inhibition of the catabolic factors produced by the tumour. These results suggest that these factors may be responsible for the cachexia the tumour confers on its host. These factors may be useful in the understanding and therapy of cancer cachexia.

Polyunsaturated fatty acids in tumour-induced cachexia

A transplantable murine colon adenocarcinoma (MAC16) was utilised as a model of human cancer cachexia. This tumour has been found to produce extensive weight loss, characterised by depletion of host body protein and lipid stores at a small tumour burden. This weight loss has been found to be associated with production by the tumour of a lipolytic factor, activity of which was inhibited in vitro by the polyunsaturated fatty acid (PUFA) eicosapentaenoic acid (EPA). EPA has also been shown to possess anti-tumour and anti-cachectic activity in vivo, leading to the hypothesis that fatty acids mobilised by the lipolytic factor supply a growth requirement of the MAC16 tumour. In this study mobilisation and sequestration of fatty acids by the tumour was found to be non-specific, although a relationship between weight loss and arachidonic acid (AA) concentration was found in both tumour-bearing mice, and human cancer patients. The anti-tumour effect of EPA, which was found to be associated with an increase in cell loss, but not its anti-cachectic activity, was reversed by the administration of the PUFAs oleic acid (OA) and linoleic acid (LA). LA was also found to be capable of stimulating tumour growth. Inhibition of either the cyclooxygenase or lipoxygenase pathways was found to result in reduction of tumour growth, leading to the implication of one of the metabolites of LA or AA in tumour growth and cachexia. The ethyl ester of EPA was found to be inactive against the growth and cachexia of the MAC16 tumour, due to its retarded uptake compared with the free acid. The anti-proliferative agent 5-fluorouracil was found to cause tumour growth inhibition, and when given in combination with EPA, reduced the phase of tumour regrowth observed after 4 to 5 days of treatment with EPA.

Molecular identification of 26 syntaxin genes and their assignment to the different trafficking pathways in Paramecium

SNARE proteins have been classified as vesicular (v)- and target (t)-SNAREs and play a central role in the various membrane interactions in eukaryotic cells. Based on the Paramecium genome project, we have identified a multigene family of at least 26 members encoding the t-SNARE syntaxin (PtSyx) that can be grouped into 15 subfamilies. Paramecium syntaxins match the classical build-up of syntaxins, being 'tail-anchored' membrane proteins with an N-terminal cytoplasmic domain and a membrane-bound single C-terminal hydrophobic domain. The membrane anchor is preceded by a conserved SNARE domain of approximately 60 amino acids that is supposed to participate in SNARE complex assembly. In a phylogenetic analysis, most of the Paramecium syntaxin genes were found to cluster in groups together with those from other organisms in a pathway-specific manner, allowing an assignment to different compartments in a homology-dependent way. However, some of them seem to have no counterparts in metazoans. In another approach, we fused one representative member of each of the syntaxin isoforms to green fluorescent protein and assessed the in vivo localization, which was further supported by immunolocalization of some syntaxins. This allowed us to assign syntaxins to all important trafficking pathways in Paramecium.