Spermidine inhibits K+ uptake without interfering with the basal activity of plasma membrane proton pump

The effect of spermidine (SPD) on the activity of plasma membrane proton pump of maize roots was studied both in an in vitro and in vivo systems. The phosphohydrolysing activity of plasma membrane. ATPase measured on isolated vesicles was not affected by the presence of SPD in a wide range of concentrations and assay conditions. Also the rate of ATP-dependent H+ accumulation into inside-out vesicles was not influenced by 0.5 mM SPD both in the presence and absence of 100 mM K+. In in vivo condition the already observed inhibition of SPD on K+ uptake (M. de Agazio et al. Plant Physiol., 87 (1988) 176–178) was confirmed at external K+ concentrations ranging from 0.1–2.0 mM without a simultaneous effect on the activity of proton pump measured as [14C]leucine accumulation and H+ extrusion. The mode of inhibition of K+ uptake exerted by SPD seems not to be related to an effect on the basal activity of plasma membrane proton pump but linked to a specific interaction with the structure(s) responsible for K+ transport through the plasma membrane

Spermidine inhibits K+ uptake without interfering with the basal activity of plasma membrane proton pump

The effect of spermidine (SPD) on the activity of plasma membrane proton pump of maize roots was studied both in an in vitro and in vivo systems. The phosphohydrolysing activity of plasma membrane. ATPase measured on isolated vesicles was not affected by the presence of SPD in a wide range of concentrations and assay conditions. Also the rate of ATP-dependent H+ accumulation into inside-out vesicles was not influenced by 0.5 mM SPD both in the presence and absence of 100 mM K+. In in vivo condition the already observed inhibition of SPD on K+ uptake (M. de Agazio et al. Plant Physiol., 87 (1988) 176\u2013178) was confirmed at external K+ concentrations ranging from 0.1\u20132.0 mM without a simultaneous effect on the activity of proton pump measured as [14C]leucine accumulation and H+ extrusion. The mode of inhibition of K+ uptake exerted by SPD seems not to be related to an effect on the basal activity of plasma membrane proton pump but linked to a specific interaction with the structure(s) responsible for K+ transport through the plasma membrane

Effect of polyamine treatments on rooting of three olive cultivar cutting

wo compact mutants from ‘Frantoio’ and ‘Leccino’, and one dwarf from ‘Leccino’ obtained from gamma irradiated plantlets were studied. Several positive morphological and physiological differences were recorded when compared to the mother plants. The results indicated the possibility of using them as new cultivars or as rootstocks

Evidence for a rapid action of levetiracetam compared to topiramate in refractory partial epilepsy.

The objective of this observational study was to compare the efficacy of levetiracetam and topiramate during the first 15 days of add-on treatment in adults with refractory partial epilepsy. Two cohorts of patients with > or =3 simple or complex partial seizures with or without secondary generalisation per month over an 8-week baseline period received levetiracetam or topiramate in two distinct phases, in addition to standard antiepileptic treatment. During the first 15 days of the therapy, levetiracetam was added at the dosage of 250 mg b.i.d. or topiramate at 25mg o.i.d. Efficacy parameters included number of seizure-free days (SFDs), mean and percent reduction in seizure frequency (in general and by type), and number of seizure-free patients in the first 15 days of treatment compared to last 15 days of the baseline period. Sixty-one patients received levetiracetam and 61 topiramate. The general characteristics of the two treatment groups were similar. The total number of SFDs during 15 days before treatment was 637 with levetiracetam and 621 with topiramate; in the 15-day evaluation period the SFDs increased to 748 (17.4%) and 668 (7.6%), respectively (ANOVA, p<0.05). Twenty-six patients (42.6%) taking levetiracetam were seizure free compared to 10 (16.4%) receiving topiramate (chi-square, p=0.003). This open-label non-controlled study suggests an early efficacy of levetiracetam as add-on therapy in patients with refractory partial epilepsy: these results appear to confirm previous indications of a rapid onset of action and seem to suggest first evaluation of the patient at the dose of 500 mg/day before increasing to the considered minimum standard dose of 1000 mg/day, as some patients could respond to the starting dose