Inhibitory effect of jasmonic acid and ethylene on epicotyl growth and bud induction in the maritime pine, Pinus pinaster Soland. in Ait

Two independent parameters, epicotyl height (cm) and number of induced buds were studied on Pinus pinaster explants to analyse the effects of three phytohormones (6-benzylaminopurine, jasmonic acid, ethylene) which were combined or not in 11 different treatments. Epicotyle length diminished significantly in relation to the control medium (medium without exogen phytohormones) in presence of jasmonic acid, 6-benzylaminopurine or Ethephon (which is converted to ethylene in plants) in any of treatments. Concentrations of 100 microM of jasmonic acid and Ethephon had a greater inhibitory effect than the treatments with 10 microM. In addition to that, jasmonic acid was a stronger inhibitor than Ethephon in any of the tried combinations. There were no significant differences between the control treatment and the treatment s with only 10 microM of jasmonic acid or Ethephon. However, 10 microM 6-benzylaminopurine induced bud formation. The different combinations of 6-benzylaminopurine with jasmonic acid and Ethephon showed that concentrations of 10 to 100 microM did not affect the number of induced buds. Jasmonic acid had an inhibitory effect which Ethephon only showed when combined with 100 microM of jasmonic acid and 10 microM of 6-benzylaminopurine. Three response groups were defined by cluster analysis: group 1 produced the greatest mean number of buds (4 to 5) and a mean epicotyl growth of 1 to 1.5 cm; group 2 produced 2 to 4 buds and a mean growth of 0.5 to 1.2 cm; group 3 produced only one bud and a mean epicotyl length of 1.2 to 2 cm.

Ptychodiscus brevis toxin decreases the spontaneous activity of rat right atria involving muscarinic receptors and potassium channels.

Marine dinoflagellate Ptychodiscus brevis toxin (PbTx), is known to produce toxic effects on cardiovascular system. The present experiments were conducted to evaluate the effect of synthetic phosphorus containing Ptychodiscus brevis toxin on spontaneously beating right atrium in vitro. The PbTx (0.84-84 microM) decreased the rate and force of right atrial contractions in a concentration-dependent manner. Ethanol, a vehicle present in highest concentration of PbTx, had no effect on atrial rate or force of contraction. Pretreatment with atropine blocked the PbTx-induced decrease in atrial rate and force of contraction. The tetraethylammonium, a potassium channel blocker, blocked the PbTx-induced decrease in atrial rate and force, where as, L-type of calcium channel blocker, nifedipine blocked the PbTx-induced force of contraction but not the rate changes. The results indicate that the PbTx decreased the atrial rate and force of contraction via cholinergic receptors involving K+ channel.

[Mechanism of paraoxon Effect on [[3]H] GABA uptake inhibition in brain synaptosomes of rat]

Parathion is an organophosphate compound that is frequently used as an insecticide. Paraoxon is the metabolic product of parathion which previously reported that inhibits GABA uptake by rat cerebral cortex synaptosomes. The aim of this study is to investigate possible underlying inhibitory mechanism[s] of paraoxon on GABA uptake, in synaptosomes prepared from rat cerebral cortex. After preparation of synaptosomes, kinetic studies were performed to determine the effect of paraoxon on K[m] and V[max] of GABA uptake. Acetylcholine and its antagonists [atropine and mecamylamine] were used to evaluate cholinergic dependency of GABA uptake. Type of GABA transporter involved was determined using beta-alanine and DAB A. The results of the study showed that paraoxon significantly decreased V[max] [175.2 +/- 4.23 vs. 80.4 +/- 2.03 pmol/mg protein/min, P<0.001] of GABA uptake while had no effect on its k[m] [9.80 +/- 1.02 vs. 9.09 +/- 0.92micro M in paraoxon and control groups respectively]. DABA significantly decreased GABA uptake [P<0.001] while beta-alanine had no effect. Acetylcholine had no effect on GABA uptake. On the other hand, neither atropine nor mecamylamine could reverse the inhibitory effect of paraoxon on GABA uptake. In conclusion, it seems that paraoxon acts as non-competitive anatagonist of GABA uptake, which affects kinetics of GABA uptake in nerve endings. We also conclude that the inhibitory effect of paraoxon on GABA uptake is cholinergic-independent

Differential tolerance of two morphological variants of Culex tritaeniorhynchus (Diptera: Culicidae), a Japanese encephalitis vector, to pyrethroid insecticides in Mysore, India.

Five synthetic pyrethroids, deltamethrin, cypermethrin, permethrin, alpha-cypermethrin, and lambdacyhalothrin, were tested on the larvae of 2 morphological variants of Cx. tritaeniorhynchus collected from Mysore City (ground pools) and outside Mysore (paddy fields), in Karnataka State, India. The morphological characters, ie, length and width of siphon, siphonal index, comb scale numbers, pecten teeth numbers, length of anal gills and anal gill index of larvae of two Cx. tritaeniorhynchus populations were found to be significantly different (p<0.05). To elicit further detail of these two variants, pyrethroid bioassays were undertaken. In general, the toxicity ranking of these pyrethroids tested on the Cx. tritaeniorhynchus variants from Mysore City was deltamethrin > lambdacyhalothrin > cypermethrin > permethrin > alpha-cypermethrin. However, for the rural variety it was deltamethrin > lambdacyhalothrin > alpha-cypermethrin > permethrin > cypermethrin. Of the 5 pyrethroids tested, deltamethrin was the most effective on both variants. Alpha-cypermethrin and lambdacyhalothrin were respectively 2.17 and 2.09 times more effective on the city variety (p<0.05), based on LC50 values. The results suggest that, in addition to morphological differences, the 2 tested varieties of Cx. tritaeniorhynchus also differ in susceptibility status.

Calcium modulatory properties of O,O-diphenyl O-N-cyclooctyl phosphoramidate [corrected] isolated from Ptychodiscus brevis in rat atria and smooth muscle.

Calcium modulatory activity of a marine toxin has been studied employing in vitro preparations. The toxin induced contracture in rat diaphragm was not modified by denervation, d-tubocurarine and tetrodotoxin (TTX). In contrast, varying concentrations of calcium, EGTA and ryanodine inhibited the contracture significantly. The toxin produced a series of repeating contractions in vas deferens. Experiments with TTX, adrenoceptor blockers and other agents exclude a release of neuromediators or direct stimulation of post synaptic receptors to account for the rhythmic effect in vas deferens. The dependence of rhythmicity on external Ca2+ concentration and inhibiting effect of Mn2+, ryanodine and nifedipine indicate a direct activation of voltage-sensitive calcium channel. The toxin also evoked a similar pattern of response in paced atria mediated through Ca2+ influx.

Some of the clinico-biochemical effects of organophosphorus insecticides [phoxim] in rams

Two equal groups [group I and II] of healthy adult cross-bred rams were dipped in diluted Phoxim solution [1: 2000]. The group II was injected with 5 ml of Catozal just before dipping. All rams were proved to have no troubles after dipping, whereas some attendant workers exposed diluted solution without care showed signs, including cough, irrigation of the nasopharyngeal mucosa, sneezing congestion of the eyelids with severe nasal discharge and lacrimation. Hematological analysis of rams revealed a significant increase of hematocrit in group I due to increased red cell mass [absolute polycythemia] after dipping. Biochemical investigation revealed a significant decrease of acetylcholinestrase [AChE] and albumin in groups I and II and a significant decrease of total protein in group I while a significant increase of glucose in groups I and II and a significant increase in the level of aspartate aminotransaminase [AST] activity, creatinine and blood urea nitrogen in groups I and II were recorded

(+/-)Baclofen sensitive scopolamine-induced short-term memory deficits in mice.

Possible involvement of GABA receptor systems in scopolamine-induced short-term memory deficits was investigated using latency of mice to reach shock-free zone (SFZ) and number of mistakes (descents) the animal made in 15 min as parameters for acquisition and retention of memory in passive avoidance paradigm. Atropine (1-5 mg/kg), scopolamine (0.1-0.5 mg/kg) but not pirenzepine (5-20 mg/kg) caused disruption of memory. GABA (50, 75 and 100 mg/kg) showed retention enhancing effects in scopolamine-treated and untreated animals but GABA agonist progabide (5-20 mg/kg) did not affect any of the parameter significantly. GABAA agonist, muscimol (0.05 and 0.1 mg/kg) and GABAB agonist, (+/-)baclofen (0.25, 0.5 and 1 mg/kg) and (-)baclofen (0.25 and 0.5 mg/kg) also displayed memory enhancing action. Whereas, GABAA antagonist, bicuculline produced hind limb rigidity, GABAB antagonist, CGP 35348 did not show any effect per se, but reversed the (+/-)baclofen-induced delay in latency, without affecting retention enhancing action of (+/-)baclofen. Combined administration of subeffective dose of GABA (50 mg/kg) and (+/-)baclofen (0.25 mg/kg), showed a significant improvement in acquisition and retention. However, the effect of GABA (100 mg/kg) on acquisition was reversed by bicuculline (2 mg/kg) and by CGP 35348 (100 mg/kg) while improving retention. The present study extends support to the cholinergic concept in cognitive performance and provide an evidence for the influence of GABAergic (particularly GABAB) modulation in scopolamine-induced learning and memory deficits in mice.