Search PubMed⌕ Search

Biomedical subjects

A Livingstone

Publications and source records attributed to A Livingstone.

63 records · Page 4Linked to original sources
PubMed1972

Two benzaldehyde dehydrogenases in bacterium N.C.I.B. 8250. Distinguishing properties and regulation.

Evidence is presented for the existence in bacterium N.C.I.B. 8250 of two inducible NAD(+)-linked benzaldehyde dehydrogenases. They may be distinguished in crude extracts by their different thermal stabilities at high pH values, benzaldehyde dehydrogenase I being much more heat-stable than benzaldehyde dehydrogenase II. Only benzaldehyde dehydrogenase I is activated by K(+) and certain other univalent cations. Gel-filtration experiments indicate that both enzymes have molecular weights of about 180000. Both enzymes are induced by growth on l-mandelate or phenylglyoxylate; only benzaldehyde dehydrogenase I is gratuitously induced by thiophenoxyacetate and only benzaldehyde dehydrogenase II is induced by benzyl alcohol, by benzaldehyde, and by a number of heterocyclic compounds which do not support growth. Mutants have been isolated that lack either benzaldehyde dehydrogenase II or benzyl alcohol dehydrogenase, or both of the enzymes. Results obtained in induction experiments with the wild-type bacterium N.C.I.B. 8250 and with the mutants show that benzaldehyde dehydrogenase II and benzyl alcohol dehydrogenase are co-ordinately regulated. Overall, the results suggest that benzaldehyde dehydrogenase I is associated with the metabolism of l-mandelate whereas benzaldehyde dehydrogenase II is associated with the metabolism of benzyl alcohol.

Alcaligenes↗
PubMed1972

Regulation of the enzymes converting L-mandelate into benzoate in bacterium N.C.I.B. 8250.

l-Mandelate is oxidized to benzoate by the enzymes l-mandelate dehydrogenase, phenylglyoxylate carboxy-lyase and benzaldehyde dehydrogenase I. Conditions have been established for measuring these three enzymes as well as benzyl alcohol dehydrogenase, benzaldehyde dehydrogenase II and catechol 1,2-oxygenase in a single cell-free extract prepared from bacterium N.C.I.B. 8250. The kinetics of induction of all these enzymes have been measured under a variety of conditions. l-Mandelate dehydrogenase, phenylglyoxylate carboxy-lyase and benzaldehyde dehydrogenase I appear to be co-ordinately regulated because (a) their differential rates of synthesis are proportional to one another under various conditions of induction and repression, (b) they are specifically and gratuitously induced by thiophenoxyacetate and a number of other compounds, and (c) mutant strains have been isolated that lack all three enzymes. Phenylglyoxylate is the primary inducer of the regulon as mutant strains lacking phenylglyoxylate carboxy-lyase form the other two enzymes in the presence of l-mandelate or phenylglyoxylate, whereas in mutant strains devoid of l-mandelate dehydrogenase activity only phenylglyoxylate induces phenylglyoxylate carboxy-lyase and benzaldehyde dehydrogenase I.

Alcaligenes↗
PubMedDate not supplied

A gene therapy/targeted radiotherapy strategy for radiation cell kill by.

BACKGROUND: Although [131I]meta-iodobenzylguanidine (MIBG) is currently one of the best agents available for targeted radiotherapy, its use is confined to a few neural crest derived tumours which accumulate the radiopharmaceutical via the noradrenaline transporter (NAT). To determine whether this drug could be used for the treatment of non-NAT expressing tumours following genetic manipulation, we previously showed that plasmid mediated transfection of NAT into a non-NAT expressing glioblastoma cell line, UVW, endowed the host cells with the capacity to actively accumulate [131I]MIBG. We now present data defining the conditions required for complete sterilisation of NAT transfected cells cultured as multicellular spheroids and treated with [131I]MIBG. METHODS: NAT transfected UVW cells, grown as monolayers and spheroids, were treated with various doses of [131I]MIBG and assessed for cell kill by clonogenic survival and measurement of spheroid volume over time (growth delay). Spheroids were left intact for different time periods to assess the effect of radiation crossfire on cell death. RESULTS AND CONCLUSIONS: Total clonogen sterilisation was observed when the cells were grown as three-dimensional spheroids and treated with 7 MBq/ml [131I]MIBG. The added benefit of radiation crossfire was demonstrated by the improvement in cell kill achieved by prolongation of the maintenance of [131I]MIBG treated spheroids in their three-dimensional form, before disaggregation and clonogenic assay. When left intact for 48 h after treatment, spheroid cure was achieved by exposure to 6 MBq/ml [131I]MIBG. These results demonstrate that the efficiency of cell kill by [131I]MIBG targeted therapy is strongly dependent on beta-particle crossfire irradiation. This gene therapy/targeted radiotherapy strategy has potential for [131I]MIBG mediated cell kill in tumours other than those derived from the neural crest.

3-Iodobenzylguanidine↗
PubMedDate not supplied

Transfectant mosaic spheroids: a new model for evaluation of tumour cell killing in targeted radiotherapy and experimental gene therapy.

BACKGROUND: We describe an in vitro tumour model for targeted radiotherapy and gene therapy that incorporates cell population heterogeneity. MATERIALS AND METHODS: Transfectant mosaic spheroids (TMS) and transfected mosaic monolayers (TMM) are composed of two cell populations derived from a single cell line. The cells of one population were transfected with the noradrenaline transporter gene (NAT), allowing active uptake of a radiolabelled targeting agent meta-[131I]iodobenzylguanidine ([131I]MIBG); the other population of cells was derived from the same parent line and transfected with a marker gene - green fluorescent protein (GFP). After treatment with [131I]MIBG, cell kill was determined in TMM by clonogenic assay and in TMS by clonogenic assay and spheroid growth delay. RESULTS: We have used the TMS model to assess the 'radiological bystander effect' (radiation cross-fire) conferred by the beta-emitting radiopharmaceutical [131I] MIBG whose cellular uptake is facilitated by the transfected gene encoding NAT. We show that cell killing by [131I]MIBG in both TMS and TMM cultures increased in direct proportion to the fraction of NAT-transfected cells and that the degree of cell killing against fraction transfected was greater in TMS, suggestive of a greater bystander effect in the three-dimensional culture system. CONCLUSIONS: TMS provide a useful model for assessment of the effectiveness of targeted radiotherapy in combination with gene therapy when less than 100% of the target cell population is expressing the NAT transgene. Further, this novel model offers the unique opportunity to investigate radiation-induced bystander effects and their contribution to cell cytotoxicity in radiotherapy and other gene therapy applications.

3-Iodobenzylguanidine↗