Selective Release of Spermine and Spermidine from the Rat Striatum by N-Methyl-d-Aspartate Receptor Activation In Vivo

The intrastriatal infusion of N-methyl-D-aspartate (NMDA; 250-1,000 microM) via a dialysis cannula in anesthetized rats resulted in a marked and rapid increase in the concentrations of spermine and spermidine recovered in the dialysate. Extracellular concentrations of NMDA-released spermine and spermidine were calculated to be in the low micromolar range. Putrescine levels were not significantly affected by NMDA. The effects of NMDA (500 microM) were blocked by the previous systemic injection of MK-801 (3 mg/kg, i.p.) but were insensitive to the intrastriatal infusion of tetrodotoxin (1 microM). Intrastriatally infused kainate or quisqualate (1,000 microM) did not increase polyamine levels in the dialysate. Spermine and spermidine dialysate levels were also significantly increased by the infusion of high concentrations of K+ (greater than 100 mM), although the effects of K+ were considerably less marked than those of NMDA. Striatal polyamines are released into the extracellular space specifically by NMDA receptor activation. Because of their multiple effects on receptor- and voltage-operated cation channels, polyamines that are released by NMDA receptor activation may play an important role in phenomena already attributed to NMDA receptor stimulation, such as long-term potentiation, synaptic plasticity, and neurotoxicity.     

Effect of thioacetamide,growth hormone or partial hepatectomy on spermidine acetylase activity of rat liver cytosol

Rat liver cytosol extracts catalyzed the formation of monoacetylspermidine when incubated with acetyl-CoA and spermidine.This activity was enhanced 15-fold by administration of thioacetamide (150 mg/kg). The peak of activity occurred 18–24 h after treatment with the drug and then declined reaching control levels by 76 h. Previous studies have shown that ornithine decarboxylase activity was also greatly increased over this time period. Putrescine content in the liver was increased 80–90-fold at 18–24 h and then declined. Spermidine levels were decreased significantly over the period 12–24 h after thioacetamide treatment and then increased substantially at later times. These results are consistent with the hypothesis that, at early times after administration of thioacetamide, the increase in putrescine content is brought about both by decarboxylation of ornithine and by degradation of monoacetylspermidine.Spermidine acetylase activity was also measured in liver extracts prepared after two other physiological stimuli known to enhance ornithine decarboxylase activity were used. Both growth hormone treatment and partial hepatectomy produced an early 2–3-fold increase in the cytosolic spermidine acetylase activity.     

Exogenous Spermidine Promotes Somatic Embryogenesis of <i>Cunninghamia lanceolata</i> by Altering the Endogenous Phytohormone Content

In order to study how exogenous hormones in C. lanceolata (gymnosperm) regulate somatic embryogenesis, we measured the endogenous phytohormones of two genotypes with different somatic embryogenesis efficiency and found that an increase in endogenous concentrations of IAA and ABA may be correlated to more efficient somatic embryogenesis. By applying exogenous spermidine, we found that exogenous hormones may affect somatic embryogenesis efficiency through affecting the endogenous phytohormone content. Based on these results, further studies can be conducted whereby the concentration of exogenous hormones or the levels of endogenous phytohormones by molecular methods are regulated to promote somatic embryogenesis. Our research may benefit the long-term economic output of the forestry industry and lays the foundation to studying the molecular mechanism that controls somatic embryogenesis efficiency.     

Effect of polyamines on in vitro anther culture of Citrus clementina Hort. ex Tan

The improvement of the induction rate in Citrus anther culture is important for taking practical advantage of the haploid potential in breeding. The influence of polyamines on anther culture of Citrus clementina, cv Nules, with particular attention to the free, soluble and insoluble-conjugated polyamine levels, has been investigated. Putrescine, spermidine and putrescine plus spermidine, were added to the standard induction medium. Before culture, spermidine was the most abundant among the free polyamines detected in anthers. The exogenous supply of either putrescine or spermidine, either independently or combined, effected greater uptake and accumulation of polyamines. The addition of 2 mM spermidine to the medium stimulated gametic embryogenesis in clementine Nules, whereas putrescine did not influence embryo production. Regenerants were mostly tri-haploids; a few doubled-haploids and no haploid plants were obtained.     

In Vivo and In Vitro Effects of Some Plant Hormones on Rat Erythrocyte Carbonic Anhydrase and Glucose-6-Phosphate Dehydrogenase Activities

The present study was undertaken to determine in vivo and in vitro effects of some plant growth regulators on rat erythrocyte carbonic anhydrase (CA) and glucose-6-phosphate dehydrogenase (G6PD) activities. Both in vivo and in vitro, spermidine and kinetin did not affect enzymatic activities of CA and G6PD, whereas putrescine decreased these activities, and abscisic acid increased them. Since plants use such growth regulators, their effects should be considered on mammals consuming them since they may possess important biological effects.     

Polyamine and nitric oxide levels relate with morphogenetic evolution in somatic embryogenesis of <Emphasis Type="Italic">Ocotea catharinensis</Emphasis>

In this study we examined the effect of polyamines (PAs) putrescine (Put), spermidine (Spd) and spermine (Spm) on growth, morphology evolution, endogenous PAs levels and nitric oxide (NO) release in Ocotea catharinensis somatic embryo cultures. We observed that Spd and Spm reduced culture growth, permitted embryo morphogenetic evolution from the earliest to last embryo development stages, increased endogenous PAs levels, and induced NO release in O. catharinensis somatic embryos. On the other hand, Put had little effect on these parameters. Spd and Spm could successfully be used to promote somatic embryo maturation in O. catharinensis. The results suggest that Spd and Spm have an important role during the growth, development and morphogenetic evolution of somatic embryos, through alterations in the endogenous nitric oxide and PAs metabolism in this species.     

The citrus plant pathogen Xanthomonas citri has a dual polyamine-binding protein

ATP-Binding Cassette transporters (ABC transporters) are protein complexes involved in the import and export of different molecules, including ions, sugars, peptides, drugs, and others. Due to the diversity of substrates, they have large relevance in physiological processes such as virulence, pathogenesis, and antimicrobial resistance. In Xanthomonas citri subsp. citri, the phytopathogen responsible for the citrus canker disease, 20% of ABC transporters components are expressed under infection conditions, including the putative putrescine/polyamine ABC transporter, PotFGHI. Polyamines are ubiquitous molecules that mediate cell growth and proliferation and play important role in bacterial infections. In this work, we characterized the X. citri periplasmic-binding protein PotF (XAC2476) using bioinformatics, biophysical and structural methods. PotF is highly conserved in Xanthomonas sp. genus, and we showed it is part of a set of proteins related to the import and assimilation of polyamines in X. citri. The interaction of PotF with putrescine and spermidine was direct and indirectly shown through fluorescence spectroscopy analyses, and experiments of circular dichroism (CD) and small-angle X-ray scattering (SAXS), respectively. The protein showed higher affinity for spermidine than putrescine, but both ligands induced structural changes that coincided with the closing of the domains and increasing of thermal stability.     

Polyamines Differentially Inhibit Cyclic AMP-Dependent Protein Kinase-Mediated Phosphorylation in the Brain of the Tobacco Hornworm, Manduca sexta

The effects of the naturally occurring polyamines spermine and spermidine on phosphorylation promoted by cyclic AMP (cAMP)-dependent protein kinase (PK) (cAMP-PK; EC 2.7.1.37) were studied using the brain of the tobacco hornworm, Manduca sexta. Four particulate-associated peptides (280, 34, 21, and 19 kilodaltons) in day 1 pupal brains are endogenous substrates for a particulate type II cAMP-PK. These phosphoproteins are present in brain synaptosomal, as well as microsomal, particulate fractions but are not present in the cytosol. They are distributed throughout the CNS and PNS and are present in several nonneuronal tissues as well. Phosphorylation of these proteins via cAMP-PK was inhibited markedly by micromolar concentrations of spermine and spermidine. Other particulate-associated peptides phosphorylated via a Ca2+/calmodulin-PK or Ca2+ and cAMP-independent PKs were unaffected by polyamines, whereas the phosphorylation of a 260-kilodalton peptide was markedly enhanced. Spermine did not exert its inhibitory effect indirectly by enhancement of cAMP or ATP hydrolysis or via proteolysis, but its action appears to involve a substrate-directed inhibition of cAMP-PK-promoted phosphorylation as well as enhanced dephosphorylation. Although addition of spermine resulted in marked ribosome aggregation in synaptosomal and microsomal particulate fractions, this phenomenon was not involved in the inhibition of cAMP-PK-promoted phosphorylation.