PubMed Health⌕ Search

Biomedical subjects

L Laycock

Publications and source records attributed to L Laycock.

6 recordsLinked to original sources
PubMed1987

Australian children and the threat of nuclear war.

Seven hundred and one 10- to 13-year-old schoolchildren from 20 schools in the Hunter region of New South Wales were asked questions about the future. The questionnaire, which was in two main sections, commenced with general, open-ended questions about the children's expectations, hopes and wishes. It then moved to more specific questions which were designed to assess the children's current level of knowledge about nuclear war. In the unprompted section, 56% of the children mentioned war as one of their concerns, while 33% wrote specifically of nuclear war. In answer to specific questions, the majority (97%) of children reported being aware of the issues of nuclear armaments and nuclear war. Sixty-eight per cent of children considered that nuclear war will or might occur; 31% felt that this would be within their own lifetimes. Most of the children reported the mass media to be their source of information on these issues; very few had heard about them from family or friends. The results challenge a commonly expressed belief that children of this age are not aware of the nuclear arms situation. Awareness of this issue and its implications, which is coupled with a lack of opportunities for discussion, may be detrimental to the well-being of children.

Anxiety↗
PubMed1969

Reactions involved in the conversion of ornithine to proline in Clostridia.

An enzyme system which converts ornithine to proline was partially purified from extracts of cells of Clostridium botulinum and of Clostridium PA 3670 by fractionation with ammonium sulfate and by dialysis in the presence of 0.01 m ornithine. Nicotinamide adenine dinucleotide (NAD) was the only cofactor required for maximal activity of the partially purified system. A possible intermediate in the conversion was accumulated when a high concentration of proline was used as substrate and the NAD was maintained in the oxidized state by adding lactic dehydrogenase. Small but significant amounts of this or a similar compound were trapped with either ornithine or proline as substrate when o-aminobenzaldehyde was added to reaction mixtures. The accumulation of the o-aminobenzaldehyde reaction product was NAD-dependent with both substrates. The compound accumulated from proline was identified as Delta(1)-pyrroline-5-carboxylic acid on the basis of the melting point of the 2,4-dinitrophenylhydrazone, and by paper chromatography of the reaction product formed with o-aminobenzaldehyde. Also, extracts of C. botulinum cells oxidized reduced NAD (NADH) in the presence of the product from proline or in the presence of Delta(1)-pyrroline-5-carboxylic acid, but did not do so in the presence of the other possible intermediate, Delta(1)-pyrroline-2-carboxylic acid. (14)C-Delta(1)-pyrroline-5-carboxylic acid was reduced to (14)C-proline by these extracts in the presence of NADH. These data indicate that the conversion of ornithine to proline by C. botulinum and Clostridium PA 3679 cells involves an oxidation of ornithine to glutamic-gamma-semialdehyde which undergoes ring closure to Delta(1)-pyrroline-5-carboxylic acid. The latter compound is then reduced to proline.

Carbon Isotopes↗
PubMed1968

Proline as an intermediate in the reductive deamination of ornithine to delta-aminovaleric acid.

Fresh extracts of cells of Clostridium botulinum reduced a limited amount of ornithine to delta-aminovaleric acid, but at high substrate concentrations a considerable amount of an amino compound accumulated which was neutral at pH 4.2. Aging of the extracts at -10 C or freezing and thawing resulted in the loss of the ability to produce delta-aminovaleric acid, but the ability to produce the neutral compound was retained. This compound was separated by column chromatography, and was found to be identical to dl-proline with respect to (i) R(F) upon paper chromatography, (ii) migration rates upon paper ionophoresis, (iii) spectrum of the product of the ninhydrin reaction, (iv) oxidation with d-amino acid oxidase, and (v) rate of reduction to delta-aminovaleric acid by cell extracts. The intermediate role of proline in the reduction of ornithine to delta-aminovaleric acid was indicated by (i) rate studies with and without an added electron donor and with and without inhibitors of proline reductase, (ii) the initial accumulation of radioactive proline to the exclusion of radioactive delta-aminovaleric acid from (14)C-l-ornithine in the presence of low levels of carrier proline, and (iii) the initial accumulation of proline at low levels prior to a significant accumulation of delta-aminovaleric acid in reaction mixtures in which the latter compound was the primary product after a longer incubation time. The conversion of ornithine to proline was the rate-limiting step in the presence of a good electron donor (alanine). The mechanism of the conversion of ornithine to proline has not been established. Preliminary data indicated that it may involve an oxidation to glutamic-gamma-semialdehyde and its equilibrium product, Delta(1)-pyrroline-5-carboxylic acid.

Adenine Nucleotides↗