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At least 55 records · Page 3Linked to original sources
PubMed1987

Effects of 2,4,5-trichlorophenoxyacetic acid and quinolinic acid on 5-hydroxy-3-indoleacetic acid transport by the rabbit choroid plexus: pharmacology and electron microscopic cytochemistry.

2,4,5-Trichlorophenoxyacetic acid (2,4,5-T) reduced the uptake of 5-hydroxy-3-indoleacetic acid (5-HIAA) by the choroid plexus in a dose-related manner, while treatment with quinolinic acid at comparable concentrations did not inhibit 5-HIAA uptake. The role of carrier-mediated transport in the clearance of 5-HIAA from cerebrospinal fluid (CSF) was also evaluated in vivo by ventriculocisternal perfusion. Steady-state clearance of 5-HIAA from CSF exceeded that of inulin and was reduced competitively in the presence of 2,4,5-T. However, the clearance was not affected by quinolinic acid. The effect of 2,4,5-T on transport enzyme systems was also studied by electron microscopic cytochemistry. Na+-K+-ATPase and cytochrome oxidase activities in the choroid plexus were reduced by 2,4,5-T. Since this transport system in the choroid plexus is normally responsible for the excretion of the serotonin metabolite from the brain to the plasma, accumulation of endogenously produced organic acids in the CSF and the brain, secondary to reduced clearance by the choroid plexus, could be a contributing factor in the development of neurotoxicity.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1975

Formation of indoleacetic acid by intestinal anaerobes.

Indoleacetic acid was produced from tryptophan by only three of 23 intestinal anaerobes studied. Evidence is presented to show that the formation of indoleacetic acid proceeds through the intermediate, indolepyruvic acid, via transamination with alpha-ketoglutarate rather than by tryptamine pathway.

Anaerobiosis↗
PubMed1973

Rhythmicity in the Basipetal Transport of Indoleacetic Acid through Coleoptiles.

(14)C-Indoleacetic acid was applied to coleoptiles of corn (Zea mays) and oat (Avena sativa). The coleoptiles were detached from the endosperms at 6-minute intervals after indoleacetic acid application, and the radioactivity was determined in successive 2-millimeter regions. The rate (per cent per minute) of basipetal transport of indoleacetic acid is periodic in various regions of the coleoptile, with a period of about 20 minutes. The possible relation of this cyclic phenomenon to other rhythmic processes of similar periodicities is discussed. A distinct acropetal transport (against the concentration gradient) from the subapical region to the apical 2-millimeter region of the coleoptile was detected.The velocity of indoleacetic acid transport differs in different regions of the coleoptile. Within an entire coleoptile the velocity can be divided into three classes for corn, 41 millimeters per hour (apical), 13 millimeters per hour (mid), and 34 millimeters per hour (base), and 2 classes for oats, 28 millimeters per hour (apical) and 14 millimeters per hour (remainder). An inverse relationship between the velocity of indoleacetic acid transport, and the growth rate of the coleoptile is discussed. Corn coleoptiles exceed oat coleoptiles both in rate and in velocity of IAA transport.

Journal Article↗
PubMed1973

A red-far red reversible effect on uptake of exogenous indoleacetic Acid in etiolated rice coleoptiles.

The uptake and accumulation of exogenous indoleacetic acid-(14)C by intact rice coleoptiles were examined. The absorption of exogenous indoleacetic acid was controlled by phytochrome, while the subsequent accumulation of this indoleacetic acid in various portions of the coleoptile was complex, and the effect of red light in this system was small compared to the alteration of the uptake of indoleacetic acid by red light. The absorption of indoleacetic acid exhibited two phases: the first occurring during the first 3-hour portion of the incubation was an inhibition, while the second was a promotive effect at about the 5th hour of incubation. Both of these effects were red, far redreversible, implicating phytochrome in this effect. Neither the destruction nor the immobilization of this exogenous indoleacetic acid apeared to be greatly affected by red light irradiation. The principal interaction between phytochrome and indoleacetic acid appears to occur during the absorption of exogenous indoleacetic acid. This effect may be related to the control by phytochrome of the amount of auxin which diffuses from coleoptile tips.

Journal Article↗
PubMed1971

Cytokinin-controlled Indoleacetic Acid Oxidase Isoenzymes in Tobacco Callus Cultures.

Indoleacetic acid oxidase in tobacco callus tissues (Nicotiana tabacum L., cultivar White Gold) was resolved into seven anionic isoenzymes by polyacrylamide gel disc electrophoresis. Different concentrations of kinetin and zeatin in the presence of indoleacetic acid affected the level of this enzyme, particularly two fast-moving isoenzymes, A(5) and A(6). The optimal concentration of kinetin was 0.2 mum; increasing concentrations above this level progressively lowered the total activity of indoleacetic acid oxidase and repressed the development of isoenzymes A(5) and A(6). Actinomycin D and cycloheximide inhibited the development of these two isoenzymes under the influence of 0.2 mum kinetin, suggesting a requirement for RNA and protein synthesis. The cytokinin-promoted indoleacetic acid oxidase isoenzymes A(5) and A(6) increased with time and paralleled the dry weight increase of tobacco callus tissues, but the total activity of indoleacetic acid oxidase per unit dry weight of tobacco callus varied with time depending on the stage of plant growth.

Journal Article↗
PubMed1971

The effect of water stress on indoleacetic Acid oxidase in pea plants.

Activity of indoleacetic acid oxidase was shown to increase following a period of water stress. Two fractions of indoleacetic acid oxidase were extracted from plant extracts. Similarly, two protein peaks (determined by ultraviolet absorption) were isolated. One peak, associated with an indoleacetic acid oxidase peak, increased following water stress. The second peak, not associated with extractable indoleacetic acid oxidase, decreased after water stress. The results are discussed in terms of general growth effects.

Journal Article↗
PubMed1971

Labeled indole-macromolecular conjugates from growing stems supplied with labeled indoleacetic Acid : I. Fractionation.

Pea (Pisum sativum var. Alaska) and bean (Phaseolus vulgaris var. Red Kidney) stem sections treated with indoleacetic acid-1-(14)C, indoleacetic acid-2-(14)C, and indoleacetic acid-5-(3)H were homogenized, extracted with phenol, and the water-soluble, ethanol-insoluble material subjected to further fractionation. Following an 18-hour incubation period in indoleacetic acid-1-(14)C, most of the label was found as nonindole-(14)C in high molecular weight polysaccharide, as phenol extraction is specific for both RNA and polysaccharides. With indoleacetic acid-2-(14)C and -5-(3)H, and to a lesser extent with indoleacetic acid-1-(14)C, radioactive indoles were obtained by hydrolysis from a heterogeneous fraction between about 500 and 30,000 molecular weight, possibly polysaccharide in nature. Indoleacetic acid accounted for 8% and indole aldehyde accounted for 21% of the total radioactivity in the extract.

Journal Article↗
PubMed1982

Senescence in isolated carnation petals : effects of indoleacetic Acid and inhibitors of protein synthesis.

Indoleacetic acid induces senescence in isolated carnation (Dianthus caryophyllus, cv. White Sim) petals, increasing the duration and amount of ethylene production. This effect is inhibited by Actinomycin D, an inhibitor of RNA synthesis, and cycloheximide, a translational inhibitor of protein synthesis. The ability of petals to respond to indoleacetic acid appears to be a function of physiological age. Indoleacetic acid is capable of enhancing ethylene evolution and senescence only in specific portions of the petal.

Journal Article↗
PubMed1971

Effect of indoleacetic Acid and hydroxyproline on isoenzymes of peroxidase in wheat coleoptiles.

Indoleacetic acid at 0.017 millimolar inhibited the formation of three peroxidase isoenzymes in both soluble and wall-bound enzyme fractions of wheat coleoptile (Triticum vulgare) tissue. Hydroxyproline at 1 millimolar prevented the indoleacetic acid-induced inhibition. Indoleacetic acid oxidase activity in the soluble fraction was decreased by indoleacetic acid and was restored by hydroxyproline. Most of the indoleacetic acid oxidase activity was located in the electrophoretic zones occupied by two of the peroxidase isoenzymes influenced by indoleacetic acid and hydroxyproline. At least part of the effect of hydroxyproline on auxin-induced elongation of coleoptile tissue may be through control of auxin levels by indoleacetic acid oxidase.

Journal Article↗
PubMed1972

The relationship of the peroxidative indoleacetic Acid oxidase system to in vivo ethylene synthesis in cotton.

Since peroxidase and manganese have been implicated in both auxin destruction and ethylene production, the effect of auxins and high tissue levels of manganese on the peroxidative indoleacetic acid oxidase system and the internal level of ethylene was determined in cotton (Gossypium hirsutum L. cv. Watson GL-7). The highest level of manganese tested produced manganese toxicity symptoms, including necrotic lesions, accompanied by an increase in internal ethylene levels at about 15 days after treatment initiation. Statistically significant increases in indoleacetic acid oxidase and peroxidase activity were first observed 2 days later and were paralleled by tissue manganese levels above 7.4 milligrams per gram dry weight and internal ethylene levels of 0.77 microliters per liter air. Eight hours after application of 2,4-dichlorophenoxyacetic acid or indoleacetic acid, the internal levels of ethylene were increased to above 6.6 microliters per liter air in cotton plants, and levels of this magnitude were maintained for a 72-hour period of observation. Modification of peroxidase and indoleacetic acid oxidase activity in auxintreated plants definitely occurred well after the elevation of internal ethylene levels. While ethylene levels and indoleacetic acid oxidase activity were increased by both experimental approaches, the earlier appearance of increased ethylene indicates that the peroxidative indoleacetic acid oxidase system in cotton is not involved in ethylene synthesis or that this enzyme is not the rate-limiting factor when ethylene synthesis is increased. Ethylene, as well as auxin destruction, may be involved in some of the long term plant responses to toxic levels of manganese. The findings also suggest that auxin-induced ethylene may play a role in the elevation of peroxidase and indoleacetic acid oxidase activity eventually seen in extracts of plants treated with auxins. The data support the assumption that the enzymatic portion of the indoleacetic acid oxidase system in cotton is a peroxidase.

Journal Article↗
PubMed1966

On the ability of Taphrina deformans to produce indoleacetic acid from tryptophan by way of tryptamine.

The metabolism of tryptophan by Taphrina deformans has been studied to confirm the reported ability of this organism to produce tryptamine. Such amine production was not observed, despite use of amine oxidase inhibitors at levels which should have resulted in the accumulation of tryptamine in the medium. It has been shown that the metabolites of tryptophan include indolepyruvic acid, indolelactic acid, tryptophol, and indoleacetic acid, and that the original report of tryptamine production must be reevaluated in light of the extraction procedures employed.

Ascomycota↗