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Phytosulfokine-α (PSK-α) (H-Tyr(SO3H)-Ile-Tyr(SO3H)-Thr-Gln- OH) (I), a sulfated growth factor universally found in both monocotyledons and dicotyledons, strongly promotes proliferation of plant cells in culture. The C-terminal truncated analog named PSK-β (Tyr(SO3H)-Ile-Tyr(SO3H)-Thr) (II) showed a 10-fold lower activity than that of the parent pentapeptide. Because PSK-α promotes proliferation and differentiation during the plant growth we undertook the studies on the influence of PSK-α on plant defense mechanisms in that period. In present studies on PSK-α (I), PSK-β (II), and its analogues, we performed a search of another biological properties. The aim of our investigation was evaluation of PSK-α, PSK-β and their selected analogues in relation to growth and development of plant pathogens, such as Phoma narcissi and Botrytis tulipae. In these studies we elaborated the synthesis of PSK-α or PSK-β and their 22 analogues modified by natural and non-natural amino acid residues. Peptides were synthesized by the solid phase method according to the Fmoc procedure on a Wang-resin. Free peptides were released from the resin by 95% TFA in the presence of EDT. Biological effect of these peptides was evaluated by test on the growth and development of pathogens of P. narcissi and B. tulipae.
The aim of present study was to evaluate mechanisms involved in thermomodulatory effect LPK in rats.Experiments were performed on adult Wistar male rats. LPK was applied either intracerebroventricularly (icv), or intraperitoneally (ip) using the similar program and technique of experiments as in our previous study. We confirmed in this paper the results of our previous reports that icv administration LPK at the dose of 20 nmol induced evident significant rectal hypothermia, while lower dose LPK of 1 nmol icv exerted significant hyperthermic effect. Peripherally applied LPK at the range of doses 10-100 nmol/100 g ip displayed slight bimodal (hyperthermic and hypothermic) effect on rectal temperature. Prior administration of haloperidol, an antagonist of central dopamine receptors blocked both effects LPK applied either icv or ip. Obtained results indicate that both hypothermic and hyperthermic effects LPK are also modulated by central dopaminergic receptors.
Continuing our studies on proctolin (Arg-Tyr-Leu-Pro-Thr) we performed the syn­thesis and biological evaluation of 52 analogues substituted in position 2, 3, 4, and 5 of the peptide chain. The peptides were bioassayed for cardiotropic activity in vitro on Tenebrio molitor and myotropic activity on foregut of Schistocerca gregaria. Twenty analogues retained 20-80% of proctolin activity.
The effect of the ant venom neuropeptide - poneratoxin (PoTX) - on neuromuscular transmission in rat diaphragm tissue was studied by means of intracellular recordings of spontaneous miniature endplate potentials (MEPPs) and of nerve evoked endplate potentials (EPPs). A 2 µM concentration of PoTX caused a pronounced but transient increase in MEPPs frequency. Moreover, within the first few minutes of PoTX administration, the area, rise time and half decay time of MEPPs gradually decreased, reaching steady values after 15-20 min. The alteration of the area, rise time and half decay time of EPPs after PoTX application was similar to that observed for MEPPs. We conclude that PoTX affects neuromuscular transmission in rat tissue, and suggest that PoTX could exert both pre- and postsynaptic effects.
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