S. Bettini

Physiologically active factors from corpora cardiaca of Periplaneta americana

Abstract By combining gel filtration on Sephadex G-15 and G-10 and ion exchange chromatography on Cellex CM, 6 different peaks of physiological activity were separated from aqueous extracts of Periplaneta americana corpora cardiaca. The following physiological activities were assayed on the fractions; heart accelerating (HA), hyperglycaemic (HG), and increasing the frequency of the spontaneous firing recorded from nerves leaving the 6th abdominal ganglion (SFI). The 6 peaks had the following activities; (1) HA and SFI (2) HA, SFI and HG (3) HG and SFI (4) SFI (5) HA and (6) HA. Each was inactivated by treatment with trypsin. Analogies with physiologically active factors separated by other authors from similar tissue extracts are discussed, e.g. the possible identity of the active material present in peak 1 with neurohormone D of Unger and with factor P1 of Brown. None of the peaks of activity corresponds to the elution characteristics of a pure sample of 5-hydroxy-tryptamine.

The effect of scorpion venom and pure toxins on the cockroach central nervous system

Abstract The “insect toxin” separated from the venom of the scorpion Androctonus australis Hector causes block of the induced afferent transynaptic response at the sixth abdominal ganglion of the cockroach Periplaneta americana . This effect is similar to that obtained with the scorpion crude venom. The “mammal toxin” II also separated from the same venom, however, does not affect synaptic transmission. It appears that the toxicity of the “insect” and “mammal” toxins of the above venom is based on their specific affinity to the nervous systems of different groups of animals.

The effect of Latrodectus mactans tredecimguttatus venom on the endogenous activity of Periplaneta americana nerve cord.

Abstract Thoracic ganglia and cercal nerve preparations from Periplaneta americana were exposed to Latrodectus mactans tredecimguttatus venom and to its toxic protein fractions which had been electrophoretically separated. Permanent block of endogenous activity of the thoracic ganglia was observed with crude venom at a concentration of 40 μg of protein per ml, while a tenfold concentration was required to block cercal nerve preparations. The separated proteins, which were found to be toxic in vivo, induced the same effect at lower concentrations. Blocked activity may be reversed following contact with the antivenin serum.

The effect of the venom of the black widow spider Latrodectus mactans tredecimguttatus on the giant neurones of Periplaneta americana

Abstract The effects of the venom of the black widow Latrodectus mactans tredecimguttatus have been studied by intracellular recordings from giant neurones at the sixth abdominal ganglion of Periplaneta americana. The venom induces: (i) a progressive decline of the resting potential of the giant neurones; (ii) failure of synaptic transmission through a progressive reduction of the EPSP; (iii) spontaneous repetitive firing of the giant neurones; (iv) alterations of the shape and reduction in size of the propagated action potential. It is suggested that the venom causes a massive release of transmitter which in turn depolarizes the post-synaptic membrane.

Cartap activity on the cockroach nervous and neuromuscular transmission

Abstract By employing intracellular electrodes on the 6th abdominal ganglion, Cartap hydrochloride 10 −5 M caused in all experiments a block of the provoked stimulus transmission and a decrease of the cell membrane resting potential; the giant fiber conduction was not affected. In the experiments with extracellular electrodes Cartap 10 −5 M provoked a marked increase of the spontaneous activity followed by block which partially disappeared after washing. The same effects were obtained on spontaneous activity when Cartap 10 −5 M was used on the denervated 6th abdominal ganglion and in experiments conducted at 0 Ca 2+ or at 20 m M Mg 2+ . Cartap 10 −5 M did not affect the response to direct or indirect stimulation of cockroach neuromuscular preparation. These results tend to confirm that Cartap affects the postsynaptic region of the ganglionic nervous junction. The possible cause of the resting potential decrease is also discussed.

Effect of scorpion venom and its fractions on the crayfish stretch receptor organ

The effects of the crude venom of the scorpion Androctonus australis Hector and its insect toxin, mammal toxin II and the ‘crustacean fraction’ were tested on the crayfish stretch receptor organ. The ‘crustacean fraction’ was able to mimic the excitatory and blocking action of the crude venom, while the insect and mammal toxins were inactive. It is suggested that the specificity in the action of the ‘crustacean fraction’ is due to a specific affinity to a crustacean neural system.

Effect of black widow spider venom on the cockroach heart

The effect of black widow spider venom [crude gland extract (CGE), gland lumen venom (GLV), or from direct bite] on the cardiac activity of Periplaneta americana was assayed both in vivo and in vitro. It was shown that these different forms of venom in all cases blocked the cockroach heart-beat. Both CGE and GLV showed a selective activity on the heart function compared with their effect on the CNS. It is suggested that cardiac block is due to impairment of either the cardiac nerve ganglia function or the myocardial neuromuscular junctions, or of both of them. The mode of action of the toxic effects on the heart is discussed. Experiments with antiserum from CGE indicate that the antigenic fractions of CGE and GLV affecting the heart function, as well as those affecting the insect motor functions, are common to both toxic materials.

Action of Latrodectus mactans tredecimguttatus venom and fractions on cells cultivated in vitro.

The crude venom of the spider Latrodectus mactans tredecimguttatus and three of its protein fractions obtained electrophoretically (LV1, LV2 and LV3) were tested on cells cultivated in vitro, and on vertebrates and invertebrates in vivo. The crude venom exerts a cytotoxic action on KB and Amnion cells. Of the three protein fractions tested, only LV1 shows cytotoxic activity: the effect on the cells is the same as with crude venom, and the activity in reference to the protein content is ten times higher. This fraction is toxic to houseflies, and if injected intravenously, to mice. The other two fractions are devoid of cytotoxic activity. LV2 is toxic to houseflies but not to mice and guinea pigs, and LV3 injected into mice and guinea pigs produces the characteristic symptoms of Latrodectus bite in mammals. The crude venom and LV1 lack proteolytic activity. The cytotoxic activity is not associated with proteolytic activity, nor with the main toxic activity towards mammals. Neutralization experiments were performed using an antiserum prepared against Latrodectus crude venom. The cytopathic effect is neutralized by antiserum. The immunological test doses for crude venom were established in vivo and in tissue culture. Tissue cultures provide a more sensitive system of assay than the whole animal for fraction LV1 and its antibodies. Moreover tissue cultures behave as selective systems when employing crude preparations of venom, as cells react only to one component.

Acquired immune response of the house fly, Musca domestica (Linnaeus), to injected venom of the spider Latrodectus mactans tredecimguttatus (Rossi)☆

Groups of house flies have been injected with a low dose of crude venom of the spider Latrodectus mactans tredecimguttatus (Rossi), and reinjected at different time intervals with a challenge dose of venom. Mortality at 24 hours after the second injection has been compared with that of flies treated with a first injection of buffer solution followed by a challenge dose of venom. Inoculated house flies developed within 24 hours a low but significant degree of immunity against the venom. This immunity appeared to increase between 24 and 48 hours and to last for 96 hours. Latrodectus venom thus represents the second animal toxin (the first being scorpion venom) showing a protective immunological response in insects. Musca domestica (Linnaeus) is the first species of the order Diptera showing protective immunity following inoculation with a sublethal dose of an antigen.

Research on the mode of action of halogen containing thiol alkylating agents on insects. Effect of iodoacetic acid on choline acetylase

Abstract The authors have studied the action of iodoacetic acid on choline acetylase of the nervous tissue of Musca domestica and Periplaneta americana. No inhibition of enzymic activity even at high doses (8 LD50s) of iodoacetic acid has been found.