Dependence of growth inhibiting action of increased planting density on capacity of lettuce plants to synthesize ABA

In a series of 26 species selected from widely differing classes, 1,2-dichloro-4,5-diaminobenzene was toxic to those which did not exhibit a nutritional need for riboflavin plus vitamin B12. It failed to retard the growth of those which needed both of these vitamins. The compound was conceived as an antimetabolite of 1,2-dimethyl-4,5-diaminobenzene. This latter, which is contained within the structures of the two vitamins, was pictured as a metabolic precursor of them. It was found to have very slight activity as either riboflavin or as vitamin B12 for lactic acid bacteria and algae. The growth-inhibiting action of the dichlorodiaminobenzene was overcome competitively by the dimethyidiaminobenzene, and also, to a lesser extent, by o-phenylenediamine. The toxicity was not influenced by additions of riboflavin plus vitamin B12, except in the cases of two species, where the influence was slight. These facts were considered to support the idea that properly constructed analogs of a precursor of two or more essential participants in cell division may be able to circumvent the counteraction which the vitamin has been found to exert on an antimetabolite of its precursor. Alternate explanations of the observed data were likewise considered.

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ANTAGONISTIC GROWTH-ACTIVATING AND GROWTH-INHIBITING PRINCIPLES IN SERUM

Journal of Experimental Medicine ◽

10.1084/jem.37.5.653 ◽

1923 ◽

Vol 37 (5) ◽

pp. 653-658 ◽

Cited By ~ 18

Author(s):

Alexis Carrel ◽

Albert H. Ebeling

Keyword(s):

Proliferative Activity ◽

Antagonistic Action ◽

Inhibiting Action ◽

Inhibiting Effect ◽

Rate Of Growth ◽

Pure Cultures ◽

Growth Promoting ◽

Growth Inhibiting

The substances precipitated by CO2 from the serum of chickens 1 or 2 years old slightly increased the activity of pure cultures of a 10 year old strain of fibroblasts, an indication that a growth-promoting substance had been obtained from the serum. The rate of growth of fibroblasts was slower in serum deprived of its globulins and the increase of the inhibiting effect of the treated serum is thus manifested. It would appear that the inhibiting action of serum is referable to one or several growth-activating substances which precipitate by CO2, and to one or several growth-retarding substances which remain in the supernatant serum after the precipitate has been thrown down by centrifugation. It may be concluded that, under the conditions of the experiments: 1. A substance enhancing the proliferative activity of homologous fibroblasts is precipitated from serum by CO2. 2. The serum from which the precipitate has been removed inhibits the proliferation of homologous fibroblasts more markedly than does the original serum. The solution of the precipitate in the treated serum has about the same effect on fibroblasts as the original serum. 3. The restraining effect of serum on the activity of homologous fibroblasts is due in part to the antagonistic action of growth-activating and inhibiting substances.

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LIPOIDS AS THE GROWTH-INHIBITING FACTOR IN SERUM

Journal of Experimental Medicine ◽

10.1084/jem.42.2.143 ◽

1925 ◽

Vol 42 (2) ◽

pp. 143-154 ◽

Cited By ~ 17

Author(s):

Lillian E. Baker ◽

Alexis Carrel

Keyword(s):

Chicken Liver ◽

Embryonic Tissue ◽

Tyrode Solution ◽

Chicken Brain ◽

Inhibiting Action ◽

Inhibiting Factor ◽

Growth Inhibiting

The growth-inhibiting action of serum has been shown to be due largely to the lipoids. Serum from which the lipoids have been removed is much less inhibiting to the growth of fibroblasts in vitro than is the original serum, and only slightly more inhibiting than Tyrode solution. The lipoids extracted from the serum are toxic and more inhibiting to the growth of fibroblasts than the original serum. Lipoids extracted from chicken brain, chicken liver, egg, and embryonic tissue have likewise an inhibiting action.

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