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Biomedical subjects

M Lieberman

Publications and source records attributed to M Lieberman.

At least 235 records · Page 13Linked to original sources
PubMed1969

Stimulation of ethylene production in tomato tissue by propionic Acid.

Propionic acid (10(-3)m) increases ethylene production by about 30 to 60% in tissue from green and half-ripe tomatoes (Lycopersicon esculentum Mill. var. Homestead) but does not increase ethylene production in tissue from ripe fruit. Stimulation is not due to the conversion of propionic acid to ethylene but appears to be secondary in nature and to operate on the endogenous ethylene-forming system. Thus conversion of methionine to ethylene in green and half-ripe tomato tissue is increased in the presence of propionic acid. Inhibitors which affect the normal endogenous ethylene-forming system similarly affect the propionic acid-stimulated system. Endogenous propionic acid may play a role in the regulation of ethylene production in tomato tissues.

Journal Article↗
PubMed1968

Effects of Kinetin, IAA, and Gibberellin on Ethylene Production, and Their Interactions in Growth of Seedlings.

Kinetin in concentrations of 10(-8) to 10(-4)m, stimulated ethylene production in 3 and 4-day old etiolated seedlings of Alaska pea (Pisum sativum L. var. Alaska). Seedlings of other species responded similarly. The response to kinetin depended on the age of the seedlings.Kinetin alone did not influence ethylene production in 6-day old stem sections, but it greatly increased the enhancing effect of IAA.Gibberellic acid had no effect on ethylene production by pea seedlings during the first 6 days of growth. Ethylene and gibberellic acid are antagonistic in their effects on growth of the seedlings; ethylene interfered severely with the action of gibberellic acid but did not completely suppress it.The inhibitors cycloheximide, cupferron, and N-ethylmaleimide, caused considerable inhibition of kinetin-induced ethylene production but were much less effective in the endogenous ethylene-forming system.

Journal Article↗
PubMed1966

Ethylene formation in rat liver microsomes.

Reduced triphosphopyridine nucleotide and pyrophosphate-dependent peroxidation of lipids in rat liver microsomes were coupled to the generation of ethylene in the presence of cuprous ions. This system suggests a model for the biogenesis of ethylene in cells.

Adenosine Triphosphate↗
PubMed1966

Stimulation of ethylene production in apple tissue slices by methionine.

Methionine can induce more than a 100% increase in ethylene production by apple tissue slices. The increased amount of ethylene derives from carbons 3 and 4 of methionine. Only post-climacteric fruit tissues are stimulated by methionine, and stimulation is optimum after 8 months' storage. Copper chelators such as sodium diethyl dithiocarbamate and cuprizone very markedly inhibit ethylene production by tissue slices. Carbon monoxide does not effect ethylene production by the slices. These data suggest that the mechanism for the conversion of methionine to ethylene, in apple tissues, is similar to the previously described model system for producing ethylene from methionine and reduced copper. Therefore, it is suggested that one of the ethylene-forming systems in tissues derives from methionine and proceeds to ethylene via a copper enzyme system which may be a peroxidase.

Journal Article↗
PubMed1965

Ethylene production from methionine.

1. A new reaction is described in which ethylene is formed from the Cu(+)-catalysed breakdown of methionine in phosphate buffer at 30 degrees in air. Some of the other products of the reaction are methionine sulphone, methionine sulphoxide, homocysteic acid, homocystine, acrolein, dimethyl disulphide, methanethiol, ethyl methyl sulphide, methane and ethane. These are considered to be produced in different reaction pathways. 2. Hydrogen peroxide is an intermediate in this reaction and can support ethylene production in the model system in anaerobic atmospheres. Cuprous copper is the active form that catalyses the formation of ethylene from an oxidized intermediate. The initial reaction is probably a Strecker degradation, but the aldehyde product is further degraded to ethylene and other products. 3. Methional (CH(3).S.CH(2).CH(2).CHO) is the most effective producer of ethylene in the model system and appears to be an intermediate in the reaction. 4. The evidence, from both tracer studies and from other precursors of ethylene in the reaction, indicates that ethylene is derived from the -CH(2).CH(2)- group of methionine.

Journal Article↗