Indirect cardiotoxic activity of the caecilian Siphonops paulensis (Gymnophiona, Amphibia) skin secretion.

The skin secretion of the caecilian S. paulensis has an indirect cardiotoxic effect. It induces a rapid blockage of electrical activity and subsequent diastolic arrest on in situ toad heart preparations. This action is not blocked by atropine and is therefore not mediated through a cholinergic mechanism. In addition, S. paulensis skin secretion is ineffective in inducing any response in isolated perfused toad heart assay, in the spontaneously beating isolated toad atria or in the electrically driven toad ventricle strip. These results, and the observation that S. paulensis skin secretion exhibits an hemolytic activity ([Schwartz, E. F., Schwartz, C. A., Sebben, A., Mendes E. G. (1997) Cardiotoxic and hemolytic activities on the caecilian Siphonops paulensis skin secretion. J. Venom. Anim. Toxins 3(1), 190]), suggest that the skin secretion cardiotoxicity could be mediated through an endogenous agent. The cardiotoxic action of S. paulensis skin secretion was investigated in isolated toad cardiac tissues in the presence of toad red blood cells (TRBC). In both atria and ventricle it evoked the same responses observed in the in situ heart. The potassium concentrations of the suspending media, as determined by atomic absorption spectroscopy were 9.5 and 11.7 times greater, respectively, in the presence of TRBC than in its absence. Given that increased levels of potassium also showed a negative inotropic effect in the isolated ventricle strip, the action of the skin secretion was attributed to the hemolytic activity, which causesan increase in K+ concentration of the medium.

Influence of body mass and environmental oxygen tension on the oxygen consumption rates of an enteropneust, Glossobalanus crozieri

The present study deals with a species of enteropneust, Glossobalanus crozieri, focusing on two aspects of its respiration: a) oxygen conssumption and body mass, and b) the influence of environmental oxygen tension on the respiratory rate. Preliminarily, the body water content was shown to be 85 per cent of the whole body weight. The regression coefficient of the oxygen consumption on the wet body mass (0.578) seems to agree with the view that in enteropneusts respiration is mainly cutaneous. The respiratory rate was significantly reduced at O2 tensions from 76 mmHg downwards, suggesting conformity rather than regulation.

Influence of body mass and environmental oxygen tension on the oxygen consumption rates of an enteropneust, Glossobalanus crozieri.

The present study deals with a species of enteropneust, Glossobalanus crozieri, focusing on two aspects of its respiration: a) oxygen consumption and body mass, and b) the influence of environmental oxygen tension on the respiratory rate. Preliminarily, the body water content was shown to be 85% of the whole body weight. The regression coefficient of the oxygen consumption on the wet body mass (0.578) seems to agree with the view that in enteropneusts respiration is mainly cutaneous. The respiratory rate was significantly reduced at O2 tensions from 76 mmHg downwards, suggesting conformity rather than regulation.

Wound repair in the Amphioxus (Branchiostoma platae), an animal deprived of inflammatory phagocytes.

The existence of phagocytes in the Amphioxus is a matter of debate since early studies of Metchnikoff, who could not induce inflammation in this animal. To reinvestigate this important phenomenon, we sectioned the distal portion of the animal and analyzed, by morphological methods, the presence of phagocytes in the wound. The analysis of the wound by optical and electron microscopy did not detect cells with morphological characteristics of phagocytes in it. The wound is completely covered by the external cuticle of the animal 24 hr after the lesion was made. A second section of the animal leads to abnormal healing of the lesion. The insertion of a surgical silk thread in the muscle of the animals results--after 13 days--in a collection of cells surrounding the foreign body. The ultrastructural analysis of these cells showed they are endothelial cells rather than specialized phagocytes. Yet, the Amphioxus is able to mount an allograph rejection when the animals are tied together by suture. This intriguing capacity of the Amphioxus to cope with tissue healing, infection, and other pathologies without phagocytes is discussed.

Spasmogenic non-cholinergic activity of a digestive gland homogenate of the amphibian snail Pomacea lineata Spix 1827.

The digestive gland of Pomacea lineata, a prosobranch gastropod mollusc inhabiting both fresh water and land, does not contain cholinomimetic compounds as do the glands of species of Aplysia, marine opisthobranch gastropods, in which both acetylcholine and urocanylcholine are present. The only pharmacological action detected for the digestive gland of Pomacea was spasmogenic activity of a crude homogenate containing 0.1 g tissue equivalents on the snail's own esophagus bathed in 10 ml of a physiological solution prepared on the basis of the animal's hemolymph composition. The spamodic activity was not blocked by atropine, bromylsergic acid diethylamide or anthazoline.

Spasmogenic non-cholinergic activity of a digestive gland homogenate of the amphibian snail Pomacea lineata spix 1827

The digestive gland of Pomacea lineata, a prosobranch gastropod mollusc inhabiting both fresh water and land, does not contain cholinomimetic compounds as do the glands species of Aplysia, marine opisthobranch gastropods, in which both acetylcholine and urocanylcholine are present. The only pharmacological detected for the digestive fland of Pomacea was spasmogenic activity of a crude homognate containing 0.1 g tissue equivalents on the snail's own esophagus bathed in 10ml of a physiological prepared on the basis of the animnal's hemolymphy composition. The spamodic activity was not blocked by atropine, bromlysergic acid diethylamide or anthazoline

The action of parotoid venom on the heart of the toad (Bufo ictericus ictericus Spix 1824) and its effects on the inhibition caused by vagal stimulation.

1. The administration of crude venom of the parotoid glands of the toad Bufo ictericus ictericus to the in situ (via abdominal vein) or isolated heart of this anuran causes both chronotropic and inotropic effects. 2. While under action of parotoid venom, the heart of the animal is insensitive to vagus nerve stimulation. 3. This blocking of vagal action is dose dependent and it is suggested that it results from a functional antagonism between the venom constituents and the acetylcholine liberated by the nerve endings on stimulation. 4. The venom constituents probably involved in this antagonism are catecholamines (adrenaline and noradrenaline), tryptamine derivatives (serotonin and bufotenidin) and genins (bufagin and bufotoxin), possibly also ATP. 5. Adrenaline, noradrenaline and serotonin, or a mixture of the three, mimic, at least partially, the blocking of vagal action caused by crude venom. 6. The blocking action of crude venom can be prevented by previously or simultaneously adding acetylcholine to the infused crude venom. This prevention is dose dependent. 7. The blocking action persists in the boiled venom and in the material dialysed from crude venom.

A tetrodotoxin-like substance found in the Brazilian frog Brachycephalus ephippium.

A tetrodotoxin-like substance, denoted ephippiotoxin, was obtained from the tissue of Brachycephalus ephippium, a small pumpkin-coloured frog collected in the Atlantic Forest of the southeast region of Brazil. Ephippiotoxin is a dialyzable substance soluble in water, methanol and ethanol, but insoluble in organic solvents such as chloroform and other apolar solvents. After treatment with active charcoal (Norit-A) and purification with ion-exchange Amberlite IRC-50 resin (NH4 + form), a freeze-dried residue was obtained, with a toxicity of c. 117 micrograms/kg (mice, i.p.). Ephippiotoxin showed the same mobility as crystalline tetrodotoxin (Sankyo) when submitted to thin-layer chromatography (silica gel G) using seven different solvent systems. White mice (20 +/- 1 g) injected i.p. with either B. ephippium tissue extracts or semi-purified toxin showed partial paralysis of the hind limbs, lethargy, altered breathing rhythm and clonic convulsions. Death occurred within 1.5-30 min after injection, depending on the dose. Ephippiotoxin induced atrioventricular diastolic blockade in the toad heart. It also inhibited the response of toad striated muscle to direct and indirect electric stimulation and blocked the compound action potential of isolated frog sciatic nerve.

The responses of isolated preparations of Bunodosoma caissarum (Correa, 1964) (Cnidaria, Anthozoa) to drugs.

Body wall strips and oral rings of Bunodosoma caissarum respond to the application of at least four categories of drugs with sustained contractions. Propionylcholine, butyrylcholine and nicotine never failed to evoke a response; acetylcholine eventually was inactive. Occasionally, a correlation between dose and response was possible. Adrenaline and noradrenaline also elicited responses, although, occasionally, both were ineffective. Tryptamine and serotonin (less) were also effective. L-Glutamate was particularly effective and its action could be depressed by GABA. Histamine, betaine, taurine and aspartate were ineffective. The results are discussed in terms of depolarization due to specific membrane receptors or to unspecific causes.

Chemical mediation in Coelenterata.

This paper reports the results of a pharmacological survey of drug action on muscle preparations of the anthozoan Bunodosoma caissarum. A critical review of previous results of drug action on Coelenterate neuromuscular junction is also given. The preparations responded only to body wall homogenates and acetylcholine. Sympathomimeticamines (adrenaline and nor-adrenaline), indolalkylamines (tryptamine, serotonin) and other drugs (tyramine, histamine, 1-glutamate and GABA) showed no action. The view that the Coelenterates do not employ acetylcholine as a neurotransmitter is discussed.