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PubMed1973

Initiation of Ripening in Bartlett Pear with an Antiauxin alpha(p-Chlorophenoxy)isobutyric Acid.

A vacuum infiltration technique was used to apply an anti-auxin, alpha-(p-chlorophenoxy) isobutyric acid to mature green pears (Pyrus communis var. Bartlett). Application of alpha-(p-chlorophenoxy) isobutyric acid, at 0.02, 0.2, and 2.0 mm progressively accelerated the onset of chlorophyll degradation, softening, and CO(2) evolution. The action of alpha(p-chlorophenoxy) isobutyric acid is apparently independent of ethylene, since the auxin analogue depressed ethylene evolution and could overcome ethylene deficiency in fruit ripening under hypobaric conditions.The auxin analogue decreased the Michaelis constant of indoleacetic acid oxidase in vitro, suggesting that the antiauxin action of alpha-(p-chlorophenoxy) isobutyric acid is the acceleration in the breakdown of endogenous auxins in fruit and subsequently the initiation of ripening.

Journal Article↗
PubMed1970

Antagonisms between Kinetin and Amino Acids: Experiments on the Mode of Action of Cytokinins.

The maintenance of chlorophyll in darkened first leaves of oats was used as a bioassay for cytokinins in pea (Pisum sativum) roots. No cytokinin was found (in contrast with earlier reports on sunflower roots); however, the extracts contained two or more substances antagonistic to cytokinin, i. e., promoting the yellowing in this test. Because the most active of these appeared to be an amino acid, individual amino acids were examined for their ability to modify the greening reaction. As a result, l-serine was found to have these properties. It promotes yellowing whether the greening agent is kinetin, indoleacetic acid, or adenine; it is, therefore, not functioning as a specific cytokinin antagonist. Its action is due to promoting proteolysis. Its d-isomer is inactive. l-Arginine, which alone does not cause chlorophyll retention and only weakly inhibits proteolysis, strongly antagonizes the action of l-serine, and thus prevents the yellowing; this effect is specific, and the only other effective serine antagonist found, although much weaker, is l-threonine. The action of arginine is not due to its preventing serine uptake, but rather the action parallels the serine-arginine antagonism previously described for nitrate reductase induction. A novel interpretation of the effect of amino acids on this process is therefore put forward. In studies of the RNase in darkened oat leaves, serine was found to have no effect; however, kinetin strongly inhibits the normal rise in the level of RNase which occurs in the isolated leaf. Kinetin also maintains the integrity of the cell membranes. A variety of evidence leads to the conclusion that the primary action of kinetin on the leaf is to inhibit proteolysis, rather than to promote protein synthesis.

Journal Article↗
PubMed1977

Polarity of Production of Polyphenols and Development of Various Enzyme Activities in Cut-injured Sweet Potato Root Tissue.

Investigation of polyphenol production in cut-injured sweet potato (Ipomoea batatas Lam. cv. Kokei 14) roots by histochemical and quantitative methods showed that polyphenols were produced in striking amounts in the proximal side of the tissue pieces (2 cm thick), but only in small amounts in cells of the distal side. In response to cut injury, formation of the enzymes related to polyphenol biosynthesis, phenylalanine ammonia-lyase and trans-cinnamic acid 4-hydroxylase, was also pronounced in the proximal side of the tissue pieces and slight in the distal side. The similar polarity was observed in the development of activities of various enzymes, such as NADPH-cytochrome c oxidoreductase, acid invertase, peroxidase, o-diphenol oxidase, and cytochrome c-O(2) oxidoreductase. Acropetal development of polyphenol contents and of various enzyme activities may be related to the acropetal movement of indoleacetic acid (IAA) in roots of various plants. Treatment of the distal surface of tissue pieces with IAA or 2,4-dichlorophenoxyacetic acid caused polyphenol production but treatment with gibberellic acid, abscisic acid, kinetin, or ethylene had little effect. The results suggest that IAA may play a role in the metabolic response to cut injury.

Journal Article↗
PubMed1981

Epinasty of Poinsettias-the Role of Auxin and Ethylene.

Upward physical restraint of the normally horizontal bracts of poinsettia (Euphorbia pulcherrima Willd.) resulted in increased ethylene production and epinastic curvature of the petioles after 5 days. Downward restraint caused little change in ethylene production or epinasty, indicating that the enhanced ethylene production observed in petioles bent upwards is not due to the bending stress alone. Epinasty, measured upon removal of upward physical restraint, was not affected by spraying plants with aminoxyacetic acid to reduce ethylene production or with silver thiosulfate to prevent ethylene action. Removal of the bract blades prevented the epinastic response of the petiole, and the response was restored by applying indoleacetic acid to the cut petiole end. Redistribution of auxin appears to be responsible for both the epinasty and the increased ethylene production of reoriented poinsettia bracts.

Journal Article↗
PubMed1969

Physiological Comparisons of Pith Callus With Crown-Gall and Genetic Tumors of Nicotiana glauca, N. langsdorffii, and N. glauca-langsdorffii Grown in Vitro. II. Nutritional Physiology.

Explants of genetic tumors, tumors initiated by Agrobacterium tumefaciens strains B-6 and T-37, and excised pith plugs from Nicotiana glauca, N. langsdorffii, and N. glauca-langsdorffii were cultured on Murashige and Skoog medium. All cultures, pith callus and tumors with the exception of N. langsdorffii pith grew on this medium. Addition of glutamine to the medium resulted in highly organoid growth in N. langsdorffii pith. In order to have material comparable to other pith cultures, N. langsdorffii was initiated on 2,4-dichlorophenoxyacetic acid medium, after which it grows on complete medium as amorphous pith callus. Except for the initiation of N. langsdorffii (and N. glauca) pith, the 2,4-dichlorophenoxyacetic acid medium, caused bleaching in cultures of T-37 induced tumors and death of B-6 induced tumors. Tumor cultures, except for the seedling tumor, grew well on a minimal medium lacking kinetin, indoleacetic acid, vitamins, glycine, and inositol. Glycine was necessary only in the growth of N. langsdorffii pith callus. A tissue culture model is presented which permits comparison of the various tissue types.

Journal Article↗
PubMed1978

Suberization: inhibition by washing and stimulation by abscisic Acid in potato disks and tissue culture.

Wounding of potato (Solanum tuberosum L.) tubers results in suberization, apparently triggered by the release of some chemical factor(s) at the cut surface. Suberization, as measured by diffusion resistance of the tissue surface to water vapor, was inhibited by mm concentrations of indoleacetic acid, unaffected by mm concentrations of traumatic acid, severely inhibited at mum concentrations of cytokinin, but stimulated by abscisic acid (ABA) at 10(-4)m. Thorough washing of potato disks up to 3 to 4 days after cutting resulted in severe inhibition of suberization as measured both by diffusion resistance and by the amount of the octadecene diol generated by hydrogenolysis (LiAlH(4)) of the tissue. Disks washed after 4 days did not show any inhibition of suberization. High performance liquid chromatographic analysis of the wash from fresh potato disks showed that about 14 ng of ABA was released into the wash per g of tissue. The amount of ABA released increased with time up to 4 to 6 hours of washing. The maximal amount of ABA was washed out after aging for 24 hours and after 2 days of aging ABA could no longer be found in the surface wash of the disks. Addition of ABA to the media of potato tissue cultures resulted in suberin formation whereas control cultures contained little suberin. The effect of ABA on suberization in the tissue cultures was shown to be linearly concentration-dependent up to 10(-4)m and a linear increase in suberin formation was seen up to about 8 days of culture growth on the media containing 10(-4)m ABA. From these results it is proposed that during the early phase of wound-healing ABA plays a role in triggering a chain of biochemical processes which eventually (in about 3 to 4 days) result in the formation of a suberization-inducing factor, responsible for the induction of the enzymes involved in suberin biosynthesis.

Journal Article↗
PubMed1971

Regional and subcellular changes in the concentration of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in the rat brain caused by hydrocortisone, DL- -methyl-tryptophan l-kynurenine and immobilization.

1. In agreement with previous findings on whole brain, the intraperitoneal injection of hydrocortisone, DL-alpha-methyltryptophan or L-kynurenine decreased the concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxy-indoleacetic acid (5-HIAA) in different regions of the rat brain.2. Hydrocortisone caused similar decreases in the concentrations of both 5-HT and 5-HIAA, suggesting decreased 5-HT synthesis.3. Changes in the concentration of 5-HIAA after hydrocortisone corresponded significantly to those after alpha-methyltryptophan. Changes in the concentration of 5-HT did not correspond, possibly due to falsely high 5-HT values because of interfering material derived from alpha-methyltryptophan.4. In general, kynurenine caused larger decreases in the concentration of 5-HT than in the concentration of 5-HIAA.5. In agreement with previous findings with whole brain, immobilization of rats for 5 h decreased the concentration of 5-HT and increased that of 5-HIAA in most brain regions.6. The order of the percentage decreases in the concentrations of 5-HIAA 6 h after hydrocortisone injection was, in decreasing order: hypothalamus, striatum, cerebellum, mid-brain, pons + medulla and cortex. The percentage increases after immobilization for 5 h were in the reverse order.7. The differences between the percentage decreases in the concentration of 5-HIAA after hydrocortisone and the percentage increases after immobilization were very similar in all regions except the hypothalamus. This is consistent with immobilization stress increasing the firing rate of 5-hydroxytryptaminergic neurones similarly in different regions.8. During the first 3 h of immobilization the concentrations of 5-HIAA in the hypothalamus and in the rest of the brain increased approximately in parallel. Between 3 and 5 h, 5-HIAA returned to control concentrations in the hypothalamus while continuing to rise in the rest of the brain.9. Relative changes in the concentration of 5-HT in particulate and supernatant fractions after the various treatments were comparable except 2 h after kynurenine injection when the concentration 5-HT fell in the particulate but not in the supernatant fraction. The concentration of 5-HT did fall in the latter, though more slowly than in the former fraction, suggesting a concentration of amine synthesizing organelles in particulate material.

Animals↗
PubMedDate not supplied

[Effect of ambiol and 2-chloroethylphosphonic acid on the content of phytohormones in potato leaves and tubers].

The effects of the antioxidant Ambiol and 2-chlorethylphosphonic acid (2-CEPA) on individual concentrations and concentration ratios of phytohormones, photosynthesis and photophosphorylation rates, sucrose and starch content in tubers, and plant productivity were studied in potato (Solanum tuberosum L). Ambiol increased the ratio of indoleacetic acid (IAA) to abscisic acid (ABA), IAA/ABA, and that of zeatin (Z) and zeatin riboside (ZR) to ABA, (Z + ZR)/ABA. These effects were underlain by an increase in the content of auxins and cytokinins and a decrease in ABA. Unlike Ambiol, 2-CEPA increased the level of ABA, the effect being the most pronounced in the tubers. Ambiol increased the rates of photosynthesis and noncyclic photophosphorylation in chloroplasts isolated from potato leaves. The relation of this phenomenon to auxin and cytokinin accumulation, Ambiol- and 2-CEPA-induced changes in the hormonal balance of potato tubers, carbon metabolism, and plant productivity is discussed.

Antioxidants↗
PubMed1986

Comparison of IAA-Induced and Low Temperature-Induced GA(3) Responsiveness and alpha-Amylase Production by GA(3) Insensitive Dwarf Wheat Aleurone.

Rht3-containing gibberellic acid (GA(3)) insensitive deembryonated wheat (Triticum aestivum L. var Cappelle Desprez x Minister Dwarf) aleurone, that can be made responsive to GA(3) by low temperature, can also be rendered GA(3) sensitive by preincubation with indoleacetic acid (IAA). The IAA-induced response of the dwarf selection is concentration-dependent, relatively sensitive, and similar in magnitude to that induced by low temperature. Other auxins also induce GA(3) responsiveness to a greater or lesser degree. IAA has no apparent effect on the wild type (rht, tall) selection.

Journal Article↗
PubMed1991

Physiology of Hormone Autonomous Tissue Lines Derived From Radiation-Induced Tumors of Arabidopsis thaliana.

gamma-Radiation-induced tumors of Arabidopsis thaliana L. have been produced as a novel approach to isolation of genes that regulate plant development. Tumors excised from irradiated plants are hormone autonomous in culture and have been maintained on hormone-free medium for up to 4 years. Five tumor tissue lines having different morphologies and growth rates were analyzed for auxin, cytokinin, and 1-aminocyclopropane-1-carboxylic acid (ACC) content, ethylene production, and response to exogenous growth regulators. Normal tissues and two crown gall tissue lines were analyzed for comparison. Rosettes and whole seedlings each contained approximately 30 nanograms. (gram fresh weight)(-1) free indoleacetic acid (IAA), 150 nanograms. (gram fresh weight)(-1) ester-conjugated IAA, and 10 to 20 micrograms. (gram fresh weight)(-1) amide-conjugated IAA. The crown gall lines contained similar amounts of free and ester-conjugated IAA but less amide conjugates. Whereas three of the radiation-induced tumor lines had IAA profiles similar to normal tissues, one line had 10- to 100-fold more free IAA and three- to 10-fold less amide-conjugated IAA. The fifth line had normal free IAA levels but more conjugated IAA than control tissues. Whole seedlings contained approximately 2 nanograms. (gram fresh weight)(-1) of both zeatin riboside and isopentenyladenosine. The crown gall lines had 100- to 1000-fold higher levels of each cytokinin. In contrast, the three radiation-induced tumor lines analyzed contained cytokinin levels similar to the control tissue. The radiation-induced tumor tissues produced very little ethylene, although each contained relatively high levels of ACC. Normal callus contained similar amounts of ACC but produced several times more ethylene than the radiation-induced tumor lines. Each of the radiation-induced tumor tissues displayed a unique set of responses to exogenously supplied growth regulators. Only one tumor line showed the same response as normal callus to both auxin and cytokinin feeding. In some cases, one or more tumor lines showed increased sensitivity to certain growth substances. In other cases, growth regulator feeding had no significant effect on tumor tissue growth. Morphology of the radiation-induced tumor tissues generally did not correlate with auxin to cytokinin ratio in the expected manner. The results suggest that a different primary genetic event led to the formation of each tumor and that growth and differentiation in the tumor tissue lines are uncoupled from the normal hormonal controls.

Journal Article↗
PubMed1997

Role of flavanols in yellowing beech trees of the Black Forest.

Beech leaves were sampled at the end of a prolonged hot dry period at a tree decline site in the Black Forest, Germany to investigate the potential role of flavanols in defense mechanisms against environmental stress. Green and yellowing leaves were harvested from the uppermost canopy of trees that were more than 200 years old and 30 m high. Yellowing leaves had a 7.4-fold higher concentration of total flavanols than green leaves. Green leaves contained flavanol inclusions, but during yellowing the inclusions disintegrated and the cells became filled with flavanols. Abscisic acid (ABA) stimulated the release of flavanols from intravacuolar inclusions of leaf petioles and flower pedicels. In addition, ABA caused flavanols to leach from the trichomes of beech galls. The antioxidative potential of leaf extracts, as estimated by indoleacetic acid (IAA) oxidation, was significantly higher in yellowing leaves than in green leaves. In vitro experiments revealed that (+)-catechin promoted growth of beech tissue.

Journal Article↗
PubMed1977

Alterations in brain 5-hydroxytryptamine metabolism during the 'withdrawal' phase after chronic treatment with diazepam and bromazepam.

1 Daily administration of diazepam or bromazepam (10 mg/kg) for 22 days significantly increased the activity of mid-brain tryptophan hydroxylase by 36% and 39%, respectively. The concentration of tryptophan was also enhanced in the mid-brain region of rats subjected to benzodiazepine treatment.2 Chronic therapy with either of the two anti-anxiety agents enhanced the endogenous levels of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in cerebral cortex, hypothalamus, pons-medulla, mid-brain and striatum.3 Whereas diazepam treatment decreased (13%) the activity of monoamine oxidase in mid-brain, bromazepam failed to exert any effect, suggesting that the observed elevation in 5-hydroxy-indoleacetic acid levels is not associated with enhanced deamination of 5-hydroxytryptamine.4 Discontinuation of treatment for 48 h significantly decreased the activity of mid-brain tryptophan hydroxylase to levels that were significantly lower than those seen for benzodiazepine-treated and normal rats. The concentrations of mid-brain tryptophan and 5-hydroxytryptamine were also reduced in various brain regions examined.5 Withdrawal from diazepam or bromazepam therapy further augmented the levels of brain 5-hydroxyindoleacetic acid.6 The results demonstrate that the depressant effects on behaviour of these agents are accompanied by increased metabolism of 5-hydroxytryptamine in the brain. Withdrawal from these minor tranquillizers, on the other hand, reduces the synthesis of this indoleamine.

Animals↗
PubMed1984

Effect of plant hormones on sucrose uptake by sugar beet root tissue discs.

Abscisic acid (ABA), auxins, cytokinins, gibberellic acid, alone or in combination were tested for their effects on short-term sucrose uptake in sugar beet (Beta vulgaris cv USH-20) roots. The effect of ABA on active sucrose uptake varied from no effect to the more generally observed 1.4-to 3.0-fold stimulation. A racemic mixture of ABA and its trans isomer were more stimulatory than ABA alone. Pretreating and/or simultaneously treating the tissue with K(+) or IAA prevented the ABA response while cytokinins and gibberellic acid did not. While the variable sensitivities of beet root to ABA may somehow be related to the auxin and alkali cation status of the tissue, tissue sensitivity to ABA was not correlated with ABA uptake, accumulation, or metabolic patterns. In contrast to ABA, indoleacetic acid (IAA) and other auxins strongly inhibited active sucrose uptake in beet roots. Cytokinins enhanced the auxin-induced inhibition of sucrose uptake but ABA and gibberellic acid did not modify or counteract the auxin effect. Trans-zeatin, benzyladenine, kinetin, and gibberellins had no effect on active sucrose uptake. None of the hormones or hormone mixtures tested had any significant effect on passive sucrose uptake. The effects of IAA and ABA on sucrose uptake were detectable within 1 h suggesting a rather close relationship between the physiological activities of IAA and ABA and the operation of the active transport system.

Journal Article↗
PubMed1996

Renal metabolism and effects of the glutamyl derivatives of L-dopa and 5-hydroxytryptophan in man.

1. Equimolar amounts of gamma-L-glutamyl-L-3,4-dihydroxyphenylalanine (gludopa) and gamma-L-glutamyl-5-hydroxy-L-tryptophan were infused separately and together in eight healthy, salt-replete male subjects in a placebo-controlled, cross-over study to investigate whether the administration of one amine precursor affects the renal metabolism of the other and to determine whether dopamine or 5-hydroxytryptamine would be generated preferentially. The overall effect on sodium excretion was also measured when both precursors were administered simultaneously. 2. Administration of gludopa was associated with marked increases in the urinary excretion of L-dopa, dopamine and 3,4-dihydroxyphenylacetic acid, together with a rise in the urinary excretion of sodium. gamma-L-Glutamyl-5-hydroxy-L-tryptophan, on the other hand, produced marked increases in the urinary excretion of 5-hydroxy-L-tryptophan, 5-hydroxy-tryptamine and 5-hydroxyindoleacetic acid, and this was accompanied by a slight, but non-significant, reduction in sodium excretion. About 27% of the infused dose of gludopa (on a molar basis) was recovered in the urine as dopamine whereas 15% of the given dose of gamma-L-glutamyl-5-hydroxy-L-tryptophan was excreted as 5-hydroxytryptamine. 3. The urinary excretion values of L-dopa, dopamine and 3,4-dihydroxyphenylacetic acid after the simultaneous infusion of gludopa and gamma-L-glutamyl-5-hydroxy-L-tryptophan were not significantly different from those observed after infusion of gludopa only. Similarly, the urinary excretion values of 5-hydroxy-L-tryptophan, 5-hydroxytryptamine and 5-hydroxy-indoleacetic acid during the co-infusion were similar to those measured after administration of gamma-L-glutamyl-5-hydroxy-L-tryptophan only. The net effect of the concomitant infusion of both glutamyl derivatives was an increase in urinary sodium excretion. 4. Our study in salt-replete individuals suggests that dopamine rather than 5-hydroxytryptamine was preferentially produced when equimolar amounts of their precursors were provided and that the natriuretic effect of dopamine, generated intrarenally from gludopa, was greater than the sodium retaining action of 5-hydroxytryptamine derived from gamma-L-glutamyl-5-hydroxy-L-tryptophan. Comparison of the urinary metabolite data after the separate and concomitant infusion of the two glutamyl compounds provided no evidence of competitive inhibition of synthesis of either amine.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1998

Pharmacological analysis of monoamine synthesis and catabolism in the scallop, Placopecten magellanicus.

1. The efficacies of various agents that affect monoamine synthesis, oxidation and methylation were evaluated in the scallop, Placopecten magellanicus, through the use of high performance liquid chromatography with electrochemical detection. 2. Central ganglia, labial palps and feet from animals bathed in 10(-5) M or 10(-4) M alpha-methyl-p-tyrosine for 1 day followed by 3-6 day recovery in artificial sea water had significantly reduced concentrations of 3,4-dihydroxyphenylalanine, norepinephrine, epinephrine, dopamine and 3,4-dihydroxyphenylacetic acid. 3. Central ganglia, labial palps and feet from scallops incubated in 10(-5) M or 10(-4) M para-chlorophenylalanine for 1 day followed by a 3-6 day wash in artificial sea water had significantly reduced concentrations of 5-hydroxytryptophan, 5-hydroxytryptamine and 5-hydroxy-3-indoleacetic acid. 4. Monamine oxidase inhibitors (administered at 10(-4) M for 1 day followed by a 2-day recovery) significantly decreased the concentrations of 3,4-dihydroxyphenylalanine and 5-hydroxy-3-indolacetic acid and increased the concentrations of their corresponding precursors in tissues. Deprenyl, a monoamine oxidase type B inhibitor, generally had more potent effects than pargyline, which inhibits monoamine oxidase type B and type A. Clorgyline, a monoamine oxidase type A specific inhibitor, showed few significant effects on the levels of the monoamines or their precursors or metabolites. 5. Bath application of 10(-4) M 3,5-dinitrocatechol, a blocker of catechol-O-methyl transferase, resulted in significant decreases in the concentrations of normetanephrine and metanephrine in nervous and other tissues and increased the levels of their corresponding precursors, dopamine, norepinephrine and epinephrine. 6. Generally, treatments that appeared to directly cause changes in levels of catecholaminergic compounds indirectly resulted in inverse changes in levels of indolaminergic compounds, and vice versa. This suggests an interaction between these transmitter systems. 7. The detection of monoaminergic compounds and dramatic changes in their concentrations following various drug effects strongly suggests the presence of mammalian-type metabolic pathways leading to synthesis and subsequent inactivation of monoamines.

Animals↗
PubMed1999

Isolation of tobacco isoperoxidases accumulated in cell-suspension culture medium and characterization of activities related to cell wall metabolism.

All of the most important guaiacol-type peroxidase (POX) isoforms accumulated in the culture medium of BY-2 tobacco (Nicotiana tabacum L. cv Bright Yellow 2) cells have been isolated. Five basic and two acidic isoforms were found. The four major isoforms (B2, B3, P1, and P2), all strongly basic, have been purified to homogeneity and partially sequenced. B2 and B3 are new isoforms showing high homology to only one POX isolated so far. Amino acid sequencing and specific activities indicated that basic isoPOXs constitute two pairs of strictly related isoforms (P1/P2 and B2/B3). Their specific activities measured in the presence of different substrates, as monolignols and NAD(P)H, indicated possible specialized functions in cell wall metabolism. Only P-type POXs were able to oxidize indoleacetic acid. Variations in pH could play a regulatory role by changing the relative contribution of different isoforms to total POX activity. Apart from cell culture medium, polyclonal antibodies obtained against P1 and P2 detected P1 in roots and in lower parts of stems. Immunocytochemical labeling indicated that P-type POXs were expressed in stem phloem and in phloem and epidermal cells of roots.

Amino Acid Sequence↗
PubMed1989

Hormonal characterization of a nonrooting naphthalene-acetic Acid tolerant tobacco mutant by an immunoenzymic method.

The comparative analysis of plant hormones was undertaken on a 1-naphthaleneacetic acid tolerant mutant and normal tobacco (Nicotiana tabacum cv Xanthi) plantlets. The mutant plantlet was scrubby and impaired in its root morphogenesis. Degeneration of the root meristem was studied on tissue sections; it appeared very fast (as early as the 3rd or 4th day after sowing), after which the root was further transformed into a callus. Indoleacetic acid (IAA), abscisic acid (ABA), and the isopentenyladenine (iP)- and trans-zeatin(Z)-type cytokinin levels were measured in terminal buds and root tips 13 days after sowing, by enzyme linked immunosorbent assay of high performance liquid chromatography fractions. Some differences appeared between the apical buds of the two genotypes, but the mutant tobacco differed from the wild type mainly by the presence of higher levels of IAA, ABA, and iP + isopentenyladenosine (iPA) in its small root. Thus, the IAA, ABA, and iP + iPA contents were increased by a factor of 15, 7, and 24 times, respectively, in mutant root compared to wild-type tobacco roots. Previous work has shown that the mutation impairs membrane polarization effects induced by auxin at the cell level. The present results would favor the hypothesis that the mutation has also affected the control of growth regulator accumulation in tissues.

Journal Article↗
PubMed2003

Effects of dietary lead and/or dimercaptosuccinic acid exposure on regional serotonin and serotonin metabolite content in rainbow trout (Oncorhynchus mykiss).

The lead (Pb) chelator, meso-2,3-dimercaptosuccinic acid (DMSA) may be effective in reversing some of the adverse effects of Pb exposure. Pb-induced behavioral deficits observed in fish are due to disruptions in the integrative functioning of the medulla, cerebellum, and optic tectum. Pb exposure increased serotonin (5-HT) content in all three brain regions without an effect on 5-hydroxy-3-indoleacetic acid (5-HIAA). Pb exposure followed by no Pb in the diet increased 5-HT and 5-HIAA content in all three brain regions. The replacement of dietary Pb with DMSA had no effect on 5-HT and increased 5-HIAA content. DMSA increased 5-HIAA content in all three brain regions and increased 5-HT content only the optic tectum. Treatment with DMSA may be more effective than removal of Pb from the diet in reversing Pb-induced alterations in 5-HT.

Animals↗