C. Perriere

Presence of norepinephrine and other biogenic amines in stonefish venom

Although fish venoms exert a cardiovascular effect, the presence of adrenergic substances was not previously demonstrated. Chromatographic analysis with electrochemical detection showed the presence of substances co-migrating with norepinephrine, dopamine and tryptophan. Serotonin, which was thought to be implicated in the intense pain following fish envenomation, was not detected. Norepinephrine was identified as a component of the stonefish Synanceia verrucosa venom by gas chromatography-mass spectrometry.

Does crude venom of the stonefish (Synanceia verrucosa) activate β-adrenoceptors in the frog heart muscle?

Venom isolated from the stonefish Synanceia verrucosa was assayed in concentrations of 0.07 and 5.7 micrograms/ml on frog atrial fibres and myocytes. Venom, less than 2.9 micrograms/ml, dose-dependently increased the amplitude and the duration of the stimulated peak tension, lengthened the time constant of the relaxation phase and shortened the duration of the action potential (AP). The concentration of venom 5.7 micrograms/ml decreased the amplitude of the peak tension, induced a contracture, reduced the amplitude of the plateau and shortened its duration as well as the repolarizing phase of the AP. The positive inotropic effect induced by the venom (2.9 micrograms/ml) on the contraction was inhibited dose-dependently by propranolol but was unchanged by the alpha-adrenergic antagonists urapidil and yohimbine, the adenyl cyclase activity remaining sensitive to forskolin. Venom, adrenalin and propranolol competed for a common site. Venom (2.9 micrograms/ml) increased both the Ca and the delayed outward K currents of enzymatically isolated atrial myocytes. The data suggest that the venom activates adrenoceptors, essentially beta-adrenoceptors.

Cardiotoxicity of verrucotoxin, a protein isolated from the venom of Synanceia verrucosa

Freshly purified but unstable verrucotoxin (VTX) and a more stable proteic complex of the toxin (p-VTX) were isolated from the venom of the stonefish Synanceia verrucosa and applied to frog atrial fibres. VTX and p-VTX decreased the amplitude and the duration of the stimulated peak tension and accelerated the relaxation phase of the contraction. The negative inotropic effect of p-VTX decreased with increasing the external Ca concentration ([Ca]o) in the Ringer solution. The negative chronotropic effect induced by p-VTX was insensitive to change in [Ca]o. It is reversed by glibenclamide. p-VTX shortened the duration of the plateau and the repolarizing phase of the action potential. Glibenclamide but not tetraethylammonium reversed the p-VTX-induced shortening of the AP repolarizing phase. The data suggest that the toxin isolated from the venom of S. verrucosa inhibits Ca channels and might activate ATP-sensitive potassium channels in frog atrial heart muscle.

Biogenic amines in newly-ecdysed cockroaches

1. Simultaneous quantification (HPLC and electrochemical detection) of biological extracts have shown dopamine, N-acetyl dopamine, tryptophan, 5-hydroxytryptamine, a 5-hydroxyindolacetic acid-like substance in nervous tissue and hemolymph of Blaberus craniifer and Periplaneta americana. 2. 5-Hydroxytryptophan was only detected in head and thoraco-abdominal nerve cord. 3. Octopamine, but not N-acetyl-5-HT was quantified in the hemolymph.

Purification of a lethal fraction from the venom of the weever fish, Trachinus vipera C.V.

We report the purification of a lethal fraction of Weever fish venom using preparative electrophoresis. It was found to be composed of four identical subunits with an overall mol. wt of approximately 324,000. A 20 g mouse was killed instantly by an i.v. injection of 2 micrograms.

Effects of ecdysteroids on reproductive physiology of Nippostrongylus brasiliensis (nematoda) in vivo

1. The influence of ecdysteroids (ecdysone and ecdysterone) was investigated on the control of reproduction in the parasitic nematode Nippostrongylus brasiliensis in vivo. 2. Infestive larvae (L3) were immersed in solutions of ecdysteroids (2.2 microM) at 37 degrees C for 4 hr before injection into the host. The effect on egg-laying was observed two stages later. 3. The treatment increased egg-laying, but had no influence on the timing of the reproductive period. The greatest effect was observed with ecdysone, ecdysterone only inducing a small and non-significant stimulation under our experimental conditions. 4. The physiological role of ecdysteroids in meiosis and gonadal development in nematodes is discussed.

Proctolin promotes vitellogenesis onset in the imaginai molt decapitated cockroach Blaberus craniifer

The ovarian response of the imaginal molt decapitated cockroach, Blaberus craniifer, to nanomolar quantities of synthetic proctolin was evaluated. Sites binding anti-egg proteins were detected in the basal oocyte in 67% (18 out of 27) of the treated females, indicating that vitellogenin uptake is mediated by proctolin. The injected concentration of proctolin was consistent with a physiological role. The results suggest that proctolin, a putative neurotransmitter or neuromodulator, possibly acts on a non-excitable cell, the oocyte. At this level, the precise mechanism is discussed with respect to the calcium-dependent processes involved in both the proctolin myogenic effect and vitellogenin uptake in other species of cockroach.

Indolamines and onset of vitellogenesis in the imaginal molt-decapitated cockroach Blaberus craniifer Burm.

1. The effects of 5-hydroxytryptamine, 5-hydroxyindoleacetic acid and N-acetyl-5-hydroxytryptamine on oocytes of Blaberus craniifer, in which vitellogenesis was prevented by imaginal molt decapitation, were investigated. 2. Sites binding anti-egg-protein antibodies were detected in the periphery of basal oocytes of treated females, with individual variability. 3. In this ovoviviparous cockroach, the onset of vitellogenesis may thus not be triggered solely by juvenile hormone, and indolamines may play a role in the uptake of haemolymphatic proteins by oocytes.

Origin and function of supporting cells in the venom glands of the lesser weeverfish (Trachinus vipera)

Supporting cells in the venom glands of Trachinus vipera form a network whose meshes are filled with developed glandular cells. These supporting cells are derived from epidermal cells. A connective tissue sheath forms inside the gland, separating it into pockets. A basal lamina surrounding the pockets between the connective tissue and supporting cells can be observed similar to that between connective tissue and epidermis. The pockets are probably formed by epidermal invagination. In view of the ultrastructural observations, the supporting cells not only maintain the cohesiveness of the venom gland, as demonstrated by the presence of numerous interdigitations and desmosomes, but may also play a role in the regeneration of large glandular cells.

Indolamines in the cockroach Blaberus craniifer Burm. nervous system—II. Fed and crowded young males in comparison with females

1. Indolamines were assayed by HPLC-ECD in nervous tissue of fed and crowded young males Blaberus craniifer Burm. 2. In males, as in females housed in the same conditions, levels are depending on both age and region (= ganglia) of the central nervous system. 3. Registered sex differences are discussed in terms of anatomical, physiological and behavioral sexual dimorphism.