Anti-pathogenic properties of plant peptide hormone phytosulfokines [PSK's] and its selected analogues

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.</p

Effect of haloperidol [HAL] on leucopyrokinin [LPK]-induced biphasic hyper- and hypothermic effect in rats

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

Antinociceptive effect of poneratoxin [PoTX] in rats

Poneratoxin (molecular weight 2932) is a 25 amino acid neuropeptide, isolated from an ant venom. It affects excitability of nerve and muscle fibres by changing the kinetics of the voltage-dependent sodium channel. The aim of the study was to investigate the analgetic effect of synthetic poneratoxin (PoTX) in adult female Wistar rats. In the first part of the study the animals received PoTX intracerebroventricularly. The analgetic effect was evaluated by a tail immersion test. In the second part of the experiment the analgetic effect of PoTX was blocked with naloxone, an opioid receptors antagonist. The study showed that poneratoxin exerts the analgetic effect in rats and this effect is not mediated by central opioid system. Therefore it was concluded that other mechanism is resposible for the effect of PoTX

Antinociceptive effect of MAS MT in rats

MAS MT is a myotropic decapeptide isolated from Manduca sexta. This peptide exerts stimulatory effect on insects heart-beat frequency. The present study was undertaken in order to determine a probable antinociceptive effect in rats of native synthetic decapeptide, MAS MT-I and its two analogs, heptapeptides MAS MT-II and MAS MT-III. All these peptides were applied directly into the lateral brain ventricle (icv) at three doses: 10, 25 and 50 nmol. The analgesic (antinociceptive) effect was evaluated by a tail immersion test. It was found that two doses of MAS MT-I: 25 and 50 nmol induced significant antinociceptive effect, while MAS MT-II and MAS MT-III exert a less antinociceptive effect in comparison with native MAS MT-I. Prior icv administration of naloxone, an opioid antagonist weakly blocked MAS MT-I effect. We conclude that antinociceptive effect of MAS MT-I in rats is not mediated by central opioid system

Effects of arginine substitutions on the cardioinhibitory activity of the Led-NPF-I neuropeptide

Effects of structural changes on the cardioinhibitory activity of the Led-NPF-I peptide (Ala-Arg-Gly-Pro-Gln-Leu-Arg-Leu-Arg-Phe-amide) were examined by replacing Arg residues in positions 2, 7 and 9. Replacement of L-Arg2 with another basic amino acid, such as Lys, His or D-Arg, did not abolish but rather promoted cardioinhibitory activity in giant mealworm beetle Zophobas atratus Fab. Agonistic peptides were also obtained by substitution of Arg residue in position 7 with Lys or D-Arg, and Arg in position 9 with His or D-Arg, respectively. All these analogues showed stronger cardioinhibitory effects than the native peptide at low concentration (10-9 M), and [Lys7]-, [D-Arg7]- and [D-Arg9]-Led-NPF-I also at the higher concentration (10-6 M). However, substitutions of the Arg residues in position 7 with His or in position 9 with Lys caused a loss of the cardioinhibitory activity. In addition, the replacement of Arg residues in all three positions with Lys or Orn caused a reduction of cardioinhibitory activity, although a single substitution of Arg in positions 2 or 7 with Lys yielded agonistic peptides. We conclude that the Arg2 position in the N-terminal region is more tolerant to structural modification than the other two Arg positions located in the C-terminal region