Changes in cyclic-AMP phosphodiesterase activity during the formation of crown-gall tumors on potato discs

Cyclic-AMP phosphodiesterase activity was found in crown-galltumor tissue obtained from the inoculation of potato discs withAgrobacterium tumefacicns strain B6. Consistently more enzymeactivity was found, in this tumor tissue than in the correspondingnormal tissue. This difference in enzyme activity was observedwhen strains other than B6 were used to induce tumors, or whennormal and tumor potato tissue grown in culture were examinedfor phosphodiesterase activity. (Received January 27, 1978; )     

The concentration of selected cations in normal and crown-gall tumors obtained from potato discs

Crown-gall tumor tissue obtained from potato discs inoculatedwith virulent strains of Agrobacterium tumefadens containedhigher concentrations of K⁺, Mg²⁺ and Ca²⁺ than the correspondingnormal tissue. These tumors also contained higher concentrationsof these cations than normal tissue inoculated with an avirulentstrain of Agrobacterium tumefadens, or than normal tissue adjacentto the crown-gall tumors on the same potato disc. The concentrationof these cations remained significantly higher than controltissue regardless of the tumor age. 2,4-Dinitrophenol and myo-inositol,while affecting the concentration of Ca²⁺ in these tissues,had no effect on the Mg²⁺ and K⁺ concentrations. These resultssuggest increased concentrations of certain cations may be aspecific property of crown-gall tumors. (Received August 16, 1978; )     

Effects of cyclic-AMP on the formation of crown-gall tumors on the primary leaves of Phaseolus vulgris var. Pinto

Cyclic-AMP was found to inhibit the number of crown-gall tumorsthat developed on the primary leaves of Pinto beans by 30 to50%. A significant amount of inhibition was still observed whenthis nucleotide was added to the leaves up to 24 hr after theaddition of the bacterium. (Received September 17, 1974; )     

Phosphatidylethanolamide derivatives of prostaglandins E1 and E2.

Prostaglandins E1 (PGE1) and E2 (PGE2) have been coupled with the amine group of phosphatidylethanolamine (PE) by means of dicyclohexylcarbodiimide. These complexes basically mimic the relaxant and contractile effects of the corresponding free prostaglandins (PGs) on various smooth muscle preparations, but exhibit a delayed onset of action and a lower affinity for the PG receptors. The complexes are comparable with the free, parent PGs, in their intrinsic activities. The same holds true for the effects on blood pressure and on the motility of the uterus in situ. The PGE2-PE complex is hydrolysed to release obviously free PGE2 by cell-free homogenates prepared from various tissues, but not by blood plasma. The PGE2-PE complex is immunologically indistinguishable from the free PGE2.     

Effect of prostaglandins E1, E2 and F2alpha on neutrophil aggregation.

Recently we have found that chemotactic factors stimulate neutrophils in suspension to aggregate. Because of an obvious analogy to platelet aggregation, we examined the influence of three prostaglandins on this process. Prostaglandins E1, E2 and F2alpha alone did not cause aggregation of the neutrophils but were able to partially inhibit the aggregation response induced by the synthetic chemotactic tripeptide, formyl-methionyl-leucyl-phenylalanine. The minimal inhibitory concentrations for prostaglandins E1, E2 and F2alpha were 10(-7), 10(-6) and 10(-5)M, respectively. These results are similar to those found for the prostaglandin-induced inhibition of platelet aggregation. It may be, therefore, that neutrophil aggregation, like platelet aggregation, is modulated by intracellular prostaglandins and other products of arachidonic acid metabolism.     

The possible involvement of adenyl cyclase and cyclic-AMP phbsphodiesterase in the formation of crown-gall tumors on the the primary leaves of Pinto beans

Adenyl cyclase activity was found in crown-gall tumor tissueobtained from the inoculation of the primary leaves of Pintobeans with Agrobacterium tumefaciens strain B6. Consistentlymore enzyme activity was found, however, in normal leaf tissueor wounded leaf tissue inoculated with sterile broth than inthe tumor tissue. On the other hand, cyclic-AMP phosphodiesteraseactivity increased with tumor age. These two enzymes were also found in extracts of both infectiousand non-infectious strains of Agrobacterium tumefaciens, althoughno obvious correlation between the production of these enzymesand infectivity could be established. Some of the implicationsof these results will be discussed. (Received May 25, 1976; )     

The action of prostaglandins on GA3 controlled responses I. Induction of barley endosperm acid phosphatase activity by prostaglandins E1 and E2

The effect of PGE₁ and PGE₂ on the induction of acid phosphataseactivity in embryoless barley half-seeds was examined. Thesecompounds were found to promote the total amount of enzyme synthesizedas well as the amount released into the medium to nearly thesame levels obtainable when these seeds are incubated in GA₃or cyclic AMP. The enzyme induction by PGE₁ and PGE₂ was inhibited by cycloheximide,ABA, 6-methyl purine and acetylsalicyclic acid, but not by AMO-1618.A time course for the induction of acid phosphatase activityby PGE₁ and PGE₂ lagged behind by 9 hr a similar time courseobtained when seeds were incubated in GA₃ or cyclic AMP. Someof the implications of these results are discussed. (Received May 6, 1973; )     

Effects of prostaglandins E1 and E2 on activity in laryngeal and pharyngeal afferent fibers.

Prostaglandins (PG) E1 and E2 were applied topically to the receptive fields of feline laryngeal and pharyngeal sensory receptors, while action potentials were recorded from single - or few-fiber preparations of the superior laryngeal nerve. When initially dissolved in ethanol, PGs stimulated these sensory receptors. If ethanol was not used as a solvent for the PGs they did not stimulate the sensory receptors. Similarly, local application of dilute (0.025%, v/v) solutions of ethanol alone excited the receptors, whereas phosphate buffer alone did not. Thus PGE1 and PGE2 do not themselves stimulate sensory receptors in the larynx and pharynx. These findings suggest that irritant properties of PGEs on upper airways are attributable to the ethanol used as a solvent.     

Gibberellic acid regulation of adventitious shoot formation from tuber discs of potato

Summary The formation of adventitious shoots from potato tuber discs explanted onto a modified Murashige and Skoog (MS) medium containingN ⁶-benzylaminopurine (BAP) (3.0 mg/l), and α-naphthaleneacetic, acid (NAA) (0.01 mg/l), was affected by gibberellic acid (GA). The presence of GA in the explant medium was required for shoot formation and 3×10⁻¹⁰ M GA appeared optimum. However, microscopic examination of the tissue protuberances on the surface of the tuber discs from which shoots arose revealed that GA inhibited the formation of shoot meristems. Tuber discs cultured for 6 wk on MS medium containing BAP and NAA without GA did not initiate adventitious shoots that could be determined visually, but microscopic examination of the tissue protuberances revealed the presence of numerous shoot meristems. Subsequent transfer of these tuber discs to medium with GA but without BAP or NAA resulted in the formation of shoots from 100% of the recultrued dises. Thus it appears that although GA inhibits shoot meristem initiation from potato tuber discs, it is required for shoot development once meristems are initiated. This is Journal Paper 8297 of the Purdue University Agricultural Experiment Station. The research was supported by Purdue University Agricultural Experiment Station Program Improvement Funds. Potato tubers were supplied by Wm. Gehring Farms, Inc., Rensselaer, Indiana.