多胺对月季切花衰老过程中生理生化和瓶插寿命的影响

精胺处理可保持月季切花瓶插前期花瓣还原糖和蛋白质的较高水平、减缓花瓣和叶片细胞膜稼性的增加,减少共 积累以及降低乙烯释放速率,这与精胺处理后月季切花瓶插寿命提高相一致;但亚精胺处理对季切花瓶插寿命和改善观赏品质无明显影响。     

Polyamines block Ca2+-activated K+ channels in pituitary tumor cells (GH3)

The effects of the natural polyamines, putrescine, spermidine and spermine on single calcium-activated potassium channels from clonal rat pituitary tumor cells (GH3) were studied. Applied to inside-out patches, polyamines were found to reduce the current amplitude and open probability of the channels in a dose- and voltage-dependent manner, indicating that polyamines act as fast blockers which sense a fraction of the electrical field in the channel pore. The K _d for spermine was 11.2 mm for the reduction of unitary current amplitude and 0.7 mm for the reduction of the open probability. The order of effectiveness was spermine > spermidine > putrescine. From fitting -functions to current amplitude histograms, blocking and unblocking rates were determined as 11.4 × 10⁴ sec^–1 and 21.9 × 10⁴ sec^–1, respectively. The reduction of the channel open probability was relieved by an increase of the Ca²⁺ concentration of the internal solution, indicating that polyamines compete with Ca²⁺ at the Ca²⁺ sensor of the channel. Putrescine antagonized the effect of spermine on the channel current amplitude. The results suggest that polyamines at intracellular millimolar concentrations suppress ion channel activity and therefore may effect electrical discharge behavior of excitable cells.This work was supported in part by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung, P8587.     

Ultraviolet-B radiation leads to a reduction in free polyamines in Phaseolus vulgaris L.

Increasing levels of UV-B radiation (UV-B) at the Earth's surfaceare among a suite of anthropomorphic stresses that influence plant growth anddevelopment. Several stress reactions have been shown to occur in response toUV-B, including a stimulation of antioxidant pathways and altered or increasedpigmentation. Polyamines, plant growth regulators that have been shown toincrease during stress, have also been implicated in the UV-B response. Weinvestigated the effects of UV-B radiation on the UV-B sensitive legumePhaseolus vulgaris L. Top Crop over atwo-week period. Total free polyamines showed marked decreases in response toUV-B radiation, primarily due to a decrease in putrescine. The reduction infreepolyamines was correlated with UV-B induced chlorophyll loss.     

Perturbations in polyamines and related enzymes following chlordecone-potentiated bromotrichloromethane hepatotoxicity

The mechanism by which chlordecone (CD) amplifies the hepatotoxicity of halomethanes such as CCl₄, CHCl₃, and BrCCl₃ has been a subject of intense study. Recent work has shown that suppression of hepatocellular regeneration leads to accelerated progression of liver injury leading to complete hepatic failure due to an unusual interaction between individually nontoxic low-dose combination of CD and CCl₄. Since polyamines are involved in cell division, their levels reflect the extent to which there is suppression of hepatocellular regeneration during CD and CCl₄ interaction. The present studies were designed to investigate the polyamine levels and associated enzymes in livers of rats treated with BrCCl₃ alone or CD and BrCCl₃ low-dose combination in order to confirm whether the sequence of events of hepatotoxicity is similar to that seen in CCl₄ toxicity or that seen during CD and CCl₄ interaction. The extent of liver toxicity in rats fed 10 ppm chlordecone (CD) for 15 days prior to the injection of a single low dose of BrCCl₃ (15 μL/kg body weight) or after exposure to a high dose of BrCCl₃ (80 μL/kg body weight) without CD pretreatment, was similar 6 and 24 hr later as assessed by plasma transaminase levels. There was also an increase in transaminase levels, in rats exposed to a single low dose of BrCCl₃ alone (15 μL/kg body weight) but this increase was far below the high-dose exposure alone or the combination treatment. Hepatic levels of ornithine decarboxylase, S-adeno-sylmethionine decarboxylase, N¹-acetylputrescine, N¹-acetylspermidine, putrescine, spermidine, and spermine at the end of 24 hr increased after exposure to a low dose of BrCCl₃ alone as compared to exposure to a high dose alone or the low-dose combination of CD and BrCCl₃. Liver spermidine N¹-acetyltrans-ferase was elevated at 2, 6, and 24 hr after exposure to a high dose of BrCCl₃ alone as compared to treatment with a low-dose combination of CD and BrCCl₃ suggesting decreased synthesis of this enzyme, in spite of a greater need as seen from liver transaminase levels. In general, it was observed that there is significant elevation in some polyamines and related enzymes during toxicity of a low dose of BrCCl₃ which seemed to stabilize within 24 hr. This was not observed with the other two groups of rats exposed either to BrCCl₃ high dose alone or the low-dose combination of CD and BrCCl₃. Results indicate that CD and BrCCl₃ low-dose combination treatment causes increased liver toxicity resulting in compromised polyamine metabolism which is coincidental with suppressed hepatocellular regeneration leading to accelerated progressive phase of liver injury culminating in complete hepatic failure. These findings point to the possibility that the mechanism of potenti-ation of BrCCl₃ hepatotoxicity by CD is similar to that seen for CD and CCl₄ interaction.     

Changes in Polyamine Concentrations in Amygdaloid-Kindled Rats

Concentrations of the polyamines putrescine, spermidine, and spermine were investigated in the left and right amygdala and in the remaining cerebrum, in which kindling was induced by repeated application of electrical stimulation of the left amygdala of rats. In kindled rats, the concentrations of spermidine and spermine increased slightly, but elevations did not reach significant levels in any brain regions. The most profound increase was detected in the putrescine concentration in all parts of the cerebrum 1-8 h after the final stimulation. These results suggest that the increases in concentrations of polyamines, particularly of putrescine, are involved in the pathogenesis of amygdaloid kindling.     

Limited Blood-Brain Barrier Transport of Polyamines

Transport of polyamines across the blood-brain barrier of adult rats was examined by measuring the amount of radioactivity that reached the forebrain 5 s after a "bolus" intracarotid injection. The values were expressed by the brain uptake index (BUI), which is the percentage of material transported in relation to freely diffusible water in a single passage through the brain. Transport was restricted as indicated by the respective BUI values, presented as means +/- SD (number of animals): putrescine, 5.3 +/- 0.8 (11); spermidine, 6.1 +/- 1.3 (7); and spermine, 5.8 +/- 0.5 (4). A kinetic study of the transport of [14C]putrescine showed that transport due to passive diffusion accounted for the majority of the observed influx (66% at 1 mM putrescine). However, a small saturable component exists with a Km value of 4-5 mM and a Vmax of 30 nmol X min-1 X g-1. This Km value is considerably higher than the circulating levels of the polyamine in the normal mature animal, and thus is unlikely to be of physiological significance. Competition studies indicated that putrescine does not interact with carriers for adenosine, arginine, choline, or leucine.     

The fluorophenylalanine sensitive and resistant tobacco cell lines,TX1 and TX 4 1. DNA contents,chromosome numbers,nuclear ultrastructures,and effects of spermidine

Summary The two tobacco cell lines TX 1 (wild type) and TX 4 (Palmer andWidholm 1975), which are respectively sensitive and resistant to pfluorophenylalanine, were studied by light and electron microscopy and scanning cytophotometry. The two cell lines differ in the following respects: TX 1 cells exhibit spherical cells, a chromatin organization like in free-grown plants ofNicotiana tabacum, and mainly diploid and haploid DNA values. TX 4 cells show large elongated (thread-like) cells, a diffuse nuclear ultrastructure, and mainly tetraploid and octoploid DNA values. Chromosome number counts indicate that dividing TX 1 cells own a karyotype close to the diploid one, while dividing TX 4 cells are around the tetraploid state. In addition, the effects of an exogenous polyamine, spermidine, on chromatin organization were investigated. While the wild type cell line, TX1, did not respond to the treatment, the mutant, fluorophenylalanine resistant cell line, TX4, exhibited reduced nuclear size and increased chromatin condensation.     

Synthesis and characterization of new ternary Cu(II)-polyamines-ATP complexes

Four new complexes of Cu(II) of stoichiometry [Cu(ATP)(polyamine)] containing as ligands the polyamines (PA) ethylenediamine, 1,3-diaminopropane, spermidine or spermine and adenosine 5′triphosphate were prepared from aqueous solution at pH 6. The synthesis, characterization, thermogravimetric, vibrational spectroscopy, electron paramagnetic resonance analyses are described and show that these complexes have similar molecular structures. The infrared spectra and the thermal analysis are briefly discussed based on the peculiarities of the complexes. The IR spectra of the ligands and their copper complexes were used to assign the various groups and compare the shifts due to complexation. The EPR parameters values for the complexes show that Cu(II) is complexed in a similar way in the four complexes. Similarity in the coordination mode of complexes in solid state has been determined and discussed. The data obtained suggest that the four complexes present one water molecule of hydration and are complexed through two oxygen atoms from ATP and through two nitrogen atoms of each polyamine.     

On the mechanism of dormancy release in grapevine buds: a comparative study between hydrogen cyanamide and sodium azide

The effect of low doses (LD)—0.1 kJ m⁻² d⁻¹ and high doses (HD)—0.3 kJ m⁻² d⁻¹ of UV-C irradiation on free, conjugated and bound spermine, spermidine and putrescine in leaves of young pea plants after 7 and 14 days of consecutive treatment was studied. Free polyamine (PA) fractions increased mainly in LD treated plants, while conjugated fractions decreased. Bound fractions accumulated mainly at the end of the experiment (after 14 days of UV-C irradiation). The results are interpreted in relation to the possible role of endogenous bound PAs in the prevention of membrane damage induced by UV-C irradiation. Stress markers (malondialdehyde and electrolyte leakage) increased after 7 days of UV-C treatment, and reached control values by the end of the experiment (mainly after HD treatment). Malondialdehyde concentration correlated negatively with UV-C—induced bound fraction and total PAs. The results support the conclusion that endogenous PAs lessen membrane damage in young pea plants provoked by UV-C irradiation.     

Hormonal Modulation of Citrus Responses to Flooding

In this work, variations in endogenous levels of several hormones were measured in citrus under conditions of continuous flooding following a time-course design. The use of three genotypes differing in their ability to tolerate waterlogging has allowed the discrimination between common and specific hormonal responses. Data suggest an essential involvement of the aerial part in the regulation of tolerance to flooding, whereas in roots more general responses were detected. The progressive increase in leaf abscisic acid (ABA) correlating with the different tolerance of genotypes confirms the involvement of this hormone in plant responses to stress. The late increase in 1-aminocyclopropane-1-carboxylic acid, concomitant with severe leaf injury, points to ethylene as a promoter of leaf senescence in citrus. Leaf putrescine increased in all flooded genotypes, suggesting a general protective role, whereas a higher protective ability of spermidine and spermine was enforced by their exclusive accumulation in the sensitive genotype. Leaf jasmonic acid (JA) increased rapidly and transiently under flooding, suggesting a role for this hormone in triggering downstream responses. In stressed roots, while indole-3-acetic acid increased, JA and ABA levels rapidly decreased to reach almost complete depletion in all flooded citrus genotypes. This suggests that not only should the increase in the so-called stress hormones be considered a signal but also their reduction. The results contribute to the understanding of the intricate set of connections between plant hormones that regulate physiologic responses to stress.