Cytokinin activity of N6,O2'-dibutyryl cyclic AMP and N6-butyryladenine

Adenosine 3′,5′-cyclic monophosphate (cAMP) and N6,O2′-dibutyryl adenosine 3′,5′-cyclic monophosphate (DBcAMP) were tested for relative growth promoting activity in the soybean callus bio-assay. In contrast to cAMP, DBcAMP showed cytokinin activity. N6-butyryladenine and DBcAMP were found to be equally active. Cytokinin activity of DBcAMP apparently does not depend on the ribosyl 3,5-cyclic monophosphate moiety of the molecule but is determined by the N6-butyryl side chain. In a series of N6-acyladenines (C2–C6) the optimum activity was obtained with a chain length of 4 carbon atoms

The distribution and degradation of chlormequat in wheat plants

The distribution and degradation of chlormequat chloride (2-chloro 1,2-14C ethyltrimethylammonium chloride) was determined after uptake by the roots of summer wheat seedlings. This plant regulator was readily translocated from the roots to the above ground parts and converted into choline. Choline was further metabolized to betaine which upon demethylation yielded finally glycine and serine. Both amino acids were incorporated into a protein fraction. The occurrence of radioactively labeled glycine and serine in the amino acid pool and the evolution of 14CO2 from chlormequat treated plants indicated that serine was formed from glycine under the release of 14CO2 during photorespiration. One week after the uptake period 82% of 14C chlormequat taken up by the roots was recovered as the parent compound or as breakdown products in wheat plants. In addition 5% of the amount taken up by the roots was released as 14CO2 by the leaves. Fifty per cent of the total amount of chlormequat originally present in roots and leaves was already metabolized after 7.5 days. No evidence has been obtained for the presence of unchanged chlormequat or an unknown metabolite in the nucleic acid or protein fraction

A quantitative analysis of the kinetics of cholinesterase inhibition in tissue homogenates of mice and houseflies

The paper deals with investigations on the inhibition of the cholinesterases in mouse-brain and housefly-head homogenates by O,O-dimethyl O-2,2-dichlorovinyl phosphate (DDVP). Its purpose is to explain the remarkable difference in susceptibility to DDVP between the two preparations. Several aspects of the inhibition process and the participating compounds were studied, such as (a) the relation between the amount of inhibitor used and the percentage inhibition finally obtained, (b) the reversibility of the inhibition process and the rate of reversion, (c) the rate of the inhibitory reaction and the affinity between enzyme and inhibitor, and (d) the binding of DDVP to other compounds, e.g. proteins, present in the homogenates. From the results it is concluded that the difference in susceptibility to DDVP (I50 mouse-brain-ChE = 10−7 M; I50 fly-head-ChE = 10−9 M) is mainly due to three co-operating factors: (1) Inhibition of mouse-brain-ChE by DDVP is slowly reversible, whereas fly-head-ChE is irreversibly inhibited; (2) DDVP has a much greater affinity for fly-head-ChE than for mouse-brain-ChE; (3) The concentration of DDVP is considerably reduced by reversible binding to some compound present in the mouse-brain homogenates. Horse-serum-ChE also proved to be reversibly inhibited. The paper does not, however, contain quantitative data on this preparation

A quantitative analysis of the kinetics of cholinesterase inhibition in tissue homogenates of mice and houseflies

The paper deals with investigations on the inhibition of the cholinesterases in mouse-brain and housefly-head homogenates by O,O-dimethyl O-2,2-dichlorovinyl phosphate (DDVP). Its purpose is to explain the remarkable difference in susceptibility to DDVP between the two preparations. Several aspects of the inhibition process and the participating compounds were studied, such as (a) the relation between the amount of inhibitor used and the percentage inhibition finally obtained, (b) the reversibility of the inhibition process and the rate of reversion, (c) the rate of the inhibitory reaction and the affinity between enzyme and inhibitor, and (d) the binding of DDVP to other compounds, e.g. proteins, present in the homogenates. From the results it is concluded that the difference in susceptibility to DDVP (I50 mouse-brain-ChE = 10−7 M; I50 fly-head-ChE = 10−9 M) is mainly due to three co-operating factors: (1) Inhibition of mouse-brain-ChE by DDVP is slowly reversible, whereas fly-head-ChE is irreversibly inhibited; (2) DDVP has a much greater affinity for fly-head-ChE than for mouse-brain-ChE; (3) The concentration of DDVP is considerably reduced by reversible binding to some compound present in the mouse-brain homogenates. Horse-serum-ChE also proved to be reversibly inhibited. The paper does not, however, contain quantitative data on this preparation