An evaluation of 4-s-methyl-2-keto-butyric Acid as an intermediate in the biosynthesis of ethylene

Stimulation of ethylene production by cauliflower (Brassica oleracea var. botrytis L.) tissue in buffer solution containing 4-S-methyl-2-keto-butyric acid is not due to activation of the natural in vivo system. Increased ethylene production derives from an extra-cellular ethylene-forming system, catalyzed by peroxidase and other factors, which leak from the cauliflower tissue and cause the degradation of 4-S-methyl-2-keto-butyric acid. This exogenous ethylene-forming system is similar to the ethylene-forming horseradish peroxidase system which utilizes methional or 4-S-methyl-2-keto-butyric acid as substrate. We conclude that 4-S-methyl-2-keto-butyric acid is probably not an intermediate in the biosynthetic pathway between methionine and ethylene.

Focus formation by a murine sarcoma leukemia virus complex. I. Theoretical analysis

The transformation of cells in culture by a murine sarcoma-leukemia virus complex leads to the formation of identifiable foci. Titration patterns of focus counts vs. virus dilutions have been explained as being due to the interactions of three virions: leukemia, defective sarcoma, and competent hybrid. This interaction is analyzed quantitatively and equations are derived which permit determination of the composition of a sarcoma virus pseudotype as well as use of the technique for the assay of exogeneous leukemia virus. The analysis is based on the statistical distribution of virions in the culture cells and assumes that all virions have equal probability of infecting a cell and that transformation of any one cell will lead to focus formation. Limitations of the assumptions and expected measurement accuracy are discussed.

Focus formation by a murine sarcoma leukemia virus complex. II. Quantitative aspects of the interaction between radiation leukemia virus and its murine sarcoma virus pseudotype in strain C57BL mouse embryo cells

A quantitative study has been made of the interactions between radiation leukemia virus (RadLV), its murine sarcoma virus pseudotype, and their C57BL host cells. The elimination of interference phenomena by delayed infection of cells with RadLV made possible the quantitative determination of the pseudotype in terms of defective sarcoma and endogenous RadLV particles. This in turn permitted the quantitative assessment of RadLV helper activity and of the various factors which influence the accuracy and sensitivity of the helper assay.

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.

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.

Children's minimal social behavior scale (CMSBS): a short, objective measure of personality functioning (10-yr. level)

The CMSBS was administered to the following male and female Ss between their ninth and eleventh birthdays: 32 normals, 17 schizophrenics, and 32 intellectual retardates. Inter-rater reliability and diagnostic power were statistically significant for the protocols of Ss whose IQs ranged from 13 to 139. The CMSBS was shown to be a reliable measure of social responsiveness for practically the whole range of intelligence for the normal, schizophrenic, and intellectually retarded Ss of this study. Examiners needed little academic background or training, and administration required only 10 min. Scoring was simple, and the scale appeared potentially useful where large numbers of children are to be tested.

Effects of cell density and low K on action potentials of cultured chick heart cells

Hearts from 7-day-old chick embryos were separated by 0.05% trypsin and subsequently cultured in a medium containing low (1.4 mM) and normal (4.4 to 5.6 mM) potassium (K) concentration. A method was developed for controlling environmental conditions (pH, temperature, osmolarity) of 1- to 3-day. old cultured heart cells during intracellular recording with microelectrodes. No apparent differences were noted in the measurement of the several components of the action potential as a function of incubation time. Action potential configurations recorded from cells in dense areas of a culture were noticeably different from those potentials obtained in sparse areas of the same culture; the latter were similar to those of the slowly conducting cardiac junctional tissues. This difference was observed both in the presence of normal and low K. The transmembrane potential recorded from cells in densely populated areas in the normal K medium was characterized by large amplitude and steady, high resting potential whereas that recorded from cells in similar areas in the low K medium had a small amplitude, low resting potential and prominent diastolic depolarization. The tissue cultured in low K also showed a tendency to fibrillate and spontaneously defibrillate.

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.

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.