Showing papers on "Toad published in 2011"

The Amazonian toad Rhaebo guttatus is able to voluntarily squirt poison from the paratoid macroglands

Abstract: Amphibian defence mechanisms commonly rely on cutaneous toxins produced in either isolated or clustered glands, such as toad parotoid macroglands. In contrast to the passive mechanism of poison liberation in other amphibians, we discovered that the Amazonian toad Rhaebo guttatus is unique because it can voluntarily squirt jets of poison from its parotoids. Amphibians commonly use toxic, cutaneous se- cretions produced by glands spread over the body as a defence against predators (Duellman and Trueb, 1994). In bufonids, these glands are grouped behind the eyes, forming a pair of pos- torbital structures, known as parotoid macrog- lands (Toledo and Jared, 1995; Tyler, Burton and Bauer, 2001). Amongst amphibians, toads provide a classic example of passive defence, based on contact between a predator's oral mu- cosa and cutaneous poisonous secretion. When threatened, they react by inflating their bodies in such a way that the parotoids become turgid and primed. When an aggressor bites a toad, it becomes the agent of its own poisoning by trig- gering the macroglands and, consequently, re- ceiving jets of poison in its mouth (Jared et al., 2009).

Larval development and metamorphosis of the olfactory and vomeronasal organs in the toad Rhinella (Bufo) arenarum (Hensel, 1867)

Abstract: Jungblut, L.D., Pozzi, A.G. and Paz, D.A. 2010. Larval development and metamorphosis of the olfactory and vomeronasal organs in the toad Rhinella (Bufo) arenarum (Hensel, 1867). — Acta Zoologica (Stockholm) 92: 305–315. The olfactory and the vomeronasal system are the two major chemosensory systems found in terrestrial vertebrates. Among tetrapods, amphibians are unique in having an aquatic larval stage, followed by metamorphosis to a terrestrial adult. In the present work, we studied the histological development of the olfactory and vomeronasal organ and associated multicellular glands of the toad Rhinella (Bufo) arenarum, from early poshatching larva to postmetamorphic toadlets. As in other bufonids, the olfactory epithelium of R. arenarum in larvae is divided into dorsal and ventral branches in the rostral and mid-nasal regions. At metamorphic climax, the larval pattern changes drastically and the adult olfactory configuration develops. Bowman’s glands appear in the olfactory epithelium of R. arenarum at the onset of metamorphic climax. The vomeronasal epithelium develops early in larval development in R. arenarum, around the time of operculum development. Interestingly, a novel sensory epithelium develops in the floor of the principal chamber of R. arenarum at metamorphic climax. This novel sensory epithelium resembles larval sensory epithelium lacking Bowman’s glands, and suggests that these animals would be able to sense not only air-borne, but also water-borne odors during their adult terrestrial life.

Resistance to tetrodotoxin in toad sympathetic nerves.

Abstract: During an investigation of the innervation of the gut of the toad (Bufo marinus), it was found that the excitatory responses of the isolated small intestine to splanchnic nerve stimulation were resistant to blockade by a wide variety of autonomic blocking drugs, including the local anaesthetic drugs procaine and cinchocaine. To check whether this response was due to a direct spread of the stimulating current to the muscle, the drug tetrodotoxin was applied. Tetrodotoxin is known to prevent the specific sodium conductance change during the action potential in nerve fibres (Narahashi, Moore & Scott, 1964; Nakamura, Nakajima & Grundfest, 1965; Kao, 1966; Takata, Moore & others, 1966), and on the other hand it has only minimal effects on action potentials in vertebrate smooth muscles (Bulbring & Tomita, 1966; Kuriyama, Osa & Toida, 1966). Because of these properties it has been possible to use tetrodotoxin to give an effective “denervation” of vertebrate smooth muscle preparations (Gershon, 1966, 1967; Bulbring & Tomita, 1966; Bell, 1968), a concentration of 5 x lo-’ g/ml sufficing to do this. However, in the present experiments it was found that tetrodotoxin in doses of up to 5 x lo4 g/ml failed to cause any reduction of the contraction of the toad intestine caused by splanchnic nerve stimulation (Fig. 1). On the other hand, the response of the intestine was abolished by cutting the splanchnic nerves between the stimulating electrodes and the muscle.

Impacts of eggs and tadpoles of the invasive cane toad (Bufo marinus) on aquatic predators in tropical Australia

Abstract: Invasive species affect native ecosystems in a variety of ways, and the magnitude of impact may depend upon many factors. In an invading species such as the cane toad (Bufo marinus), the multiphasic life history creates a potential for impact to differ between life history stages. Previous research on the impact of cane toads in Australia has focused on fatal poisoning of predators that ingest terrestrial stages of the toad, but aquatic stages (eggs, larvae) are toxic also. We exposed nine native Australian fish species and one native Australian turtle species to the eggs and larvae of toads. Strong species differences were evident, both in palatability (propensity to attack the egg or larva), and in subsequent responses (e.g. taste and reject the item, vs. ingest it). Toad eggs were less likely than toad tadpoles to be attacked, but also less likely to be rejected before ingestion (probably because the non-toxic jelly coat masks the presence of toxins in the ovum). As a result, predators were far more likely to be killed by ingesting toad eggs than toad tadpoles. Fortuitously, the spatial and temporal availability of toad egg masses restricts encounter rates with predators, so that overall ecological impact may be low despite the high vulnerability of a fish or turtle that encounters such an egg mass. Understanding such ontogenetic shifts in the nature of interactions and magnitude of impact is crucial if we are to understand the overall ecological impact of invasive species.

An interesting case of cardiotoxicity due to bufotoxin (toad toxin)

Abstract: Consumption of toads for their aphrodisiac effect is a common practice in Laos, China and in some parts of India. Toad secretions from parotid and skin contains toxin similar to cardiac glycosides. It results in bradycardia and cardiac dysfunction leading on to death in some cases. We report a case of toad poisoning in a young previously healthy male.

Peptide IC-20, encoded by skin kininogen-1 of the European yellow-bellied toad, Bombina variegata, antagonizes bradykinin-induced arterial smooth muscle relaxation.

Abstract: Objectives: The objectives were to determine if the skin secretion of the European yellow-bellied toad ( Bombina variegata ), in common with other related species, contains a bradykinin inhibitor peptide and to isolate and structurally characterize this peptide. Materials and Methods: Lyophilized skin secretion obtained from this toad was subjected to reverse phase HPLC fractionation with subsequent bioassay of fractions for antagonism of the bradykinin activity using an isolated rat tail artery smooth muscle preparation. Subsequently, the primary structure of the peptide was established by a combination of microsequencing, mass spectroscopy, and molecular cloning, following which a synthetic replicate was chemically synthesised for bioassay. Results: A single peptide of molecular mass 2300.92 Da was resolved in HPLC fractions of skin secretion and its primary structure determined as IYNAIWP-KH-NK-KPGLL-. Database interrogation with this sequence indicated that this peptide was encoded by skin kininogen-1 previously cloned from B. variegata . The blank cycles were occupied by cysteinyl (C) residues and the peptide was located toward the C-terminus of the skin kininogen, and flanked N-terminally by a classical -KR- propeptide convertase processing site. The peptide was named IC-20 in accordance (I = N-terminal isoleucine, C = C-terminal cysteine, 20 = number of residues). Like the natural peptide, its synthetic replicate displayed an antagonism of bradykinin-induced arterial smooth muscle relaxation. Conclusion: IC-20 represents a novel bradykinin antagonizing peptide from amphibian skin secretions and is the third such peptide found to be co-encoded with bradykinins within skin kininogens.

A new method of assay of human chorionic gonadotrophs utilising male toad, bufo melanostictus schneid

Abstract: THE various methods of assay of human chorionic gonadotrophin may, broadly speaking, be divided into 2 groups-first, based upon primary changes produced by the hormone in the gonads and, second, on secondary changes caused by it in the accessory reproductive organs of test animals. Assays depending on changes in the vaginal epithilium, increase in weight of uterus or of male organs, etc., belong to the laltter group and have been found to be totally unreliable and inaccurate. But the single exception of this group of tests is the inorease in weight of the prostates of immature hypophysectomised rats (Greep et dl), which is unique in that it is affected neither by the follicle-stimulating hormone nor by estrogens. I t is quite an accurate method, although cumbrous, time-taking, and needs a high degree of dexterity in its performance.

Study on Cardiotoxicity and Toxic Substance of Toad Venom in Isolated Guinea Pig Heart

Abstract: Objective:To study toad venom(BV)-induced cardiac toxicity and the toxic substances in isolated guinea-pig heart.Method:Isolated guinea pig hearts were switched to the Langendorff mode and perfused with or without BV.Measure the content of toad venom in perfused hearts using HPLC.Result:BV caused auriculo-ventricular block,supraventicular tachycardia,ventricular tachycardia,ventricular fibrillation and other arrhythmias phenomenon in isolated hearts.The cumulative doses of bufadienolides(60±11.5)μg induced cardiac arrest.Nine kinds of bufadienolides were detected by HPLC in the isolated hearts.Compare their affinity with the hearts:arenobufaginbufalintelocinobufaginhellebrigeningamabufotalincinobufalinbufotalinresibufogenindesacety-bufotalin.Conclusion:BV has cardiotoxicity on the guinea pig heart and the material basis of toad induced toxic effects may be gamabufotalin,arenobufagin and so on.

Toad skin total alkaloid and its prepn, analysis and prepn process

Abstract: The present invention provides preparation process of toad skin total alkaloid. The toad skin total alkaloid contains indole total alkaloid 50-95 wt%, cinobufagin and lipo bufogenin 0.02-0.08 wt%, and toad thetine 20-50 wt%. The present invention provides also the method of measuring toad thetine content, and the injection, powder for injection, dripping pill, capsule, oral liquid, etc with the oad skin total alkaloid as effective component and their preparation process.

The quantitative effect of the human chorionic gonadotrophin on the male toad, Bufo regularis; a method for its biological assay.

Abstract: SINCE Mainini' introduced his test for the rapid diagnosis of pregnancy utilising the male toad Bufo arenarum Hanzel, many other members of the anura in various parts of the world have been shown to be equally suitable for the test. These included Bufo marianus, B. calamita, B. vulgaris, B. regularis, B. americanus, B. melanosticus, B. stomaticus, Rana pipiens, R . esculenta and R. tegerina. However, in applying the test, a high incidence of false negative results was experienced by many workers, e.g., Mainini,l Klopper2 and Frank and P01lak.~ The original aim of this work was to find out the probable causes of such results, and thus try to discover the factors that might affect the accuracy of the test. For this purpose it was first thought advisable to investigate the sensitivity of the response of the male toad which is common in Egypt, Bufo regularis, as regards the discharge of spermatozoa in its cloaca, to known graded doses of chorionic gonadotrophin, calculated according to the toad's weight in a proper dose-weight system. When this was done it became at once evident that this response was quantal, so that a satisfactory dose-response curve could be constructed and utilised as the basis of a method for the biological assay of chorionic gonadotrophin. Robins, Parkes and Bianco4 had succeeded in using the South African male frog, Xenopus Zmis, for the assay of this hormone, and even found it many times more sensitive than the standard laboratory animals used for this purpose. Mohanty and Pabrais also reported on the use of the male toad, Bufo melanosticus Schneid, for this assay, but, as will be seen later, the technique and criteria of the method here described are different from theirs. This work was divided into three parts. Part I describes the method and the results obtained by using it to assay preparations of the chorionic gonadotrophic hormone. Part I1 comprises experiments devised to test the applicability, as well as the reliability, of this method to clinical material, and at the same time elicit its value by comparison with established methods. In Part I11 is shown the value of the author's modification of the male toad method for the diagnosis of human pregnancy, which is shown in the first part of this work, by comparing it with one of the well-known methods. PART 1 METHOD In this investigation male toads of the species Bufo regularis were employed. Their weights varied between 12 and 31.8 g., with an average of 21-9 g.

Method for removing toad cortex

Abstract: The invention discloses a method for removing toad cortices. By using the method, the speed of toad cortex removing, the concentration ratio and toad cortex quality can be obviously enhanced. The invention is realized through the following technical scheme: agent No. 1 is sprayed to the body of the toad, and medicine No.2 is smeared to the mouth of the toad; and after the cortex is removed, the toad is grasped with the right hand, the mouth of the toad gets stuck with one finger, the toad cortex is clamped out from the mouth of the toad by tweezers held with the left hand, the toad cortex is put in a half basin of cold boiled water, and the toad cortex, clamped by the tweezers, is lightly sloshed in the water until the toad cortex is completely spread.

Morphology and Some Histochemical Peculiarities of the Mucous Glands in the Integument of the Green Toads of Bufo viridis Complex (Amphibia: Bufonidae)

Abstract: We described three groups (varieties) of the mucous glands in the skin of the green toads of Bufo viridis complex basing on the morphology and histochemistry [mucopolycaccharide (MPS) composition] of their secretory epithelium and a localization of the glands in the toad integument. Our study showed that the mucous cells of three gland groups were differed in their morphology and content of the acid and neutral MPS. Only the ordinary mucous glands (group I) were found within the entire integument and only the skin of parotoid complexes contained the mucous glands of all three varieties. We consider the glands of group III as structures of full secretory maturity. Morphological and histochemical features of the glands of II (and possibly III) varieties as well as their selective distribution in the integument of the green toads permit to suppose their specific functions which need to be elucidate.

Histochemical localization of catecholamines in the urinary bladder of the toad (

Abstract: Fluorescent histochemical localization of monoamines in whole mounts of the bladder of the toad (Bufo marinus) revealed bundles of fluorescent nerves containing predominantly adrenaline. These formed a wide meshed net work about arteries but not veins. A small proportion of muscle bundles was supplied by fine varicose fluorescent nerves. Loading with adrenaline or noradrenaline increased the intensity of the fluorescence in the nerves, but produced no appreciable increase in the number of muscle bundles supplied by fluorescent nerves. Large, brilliantly fluorescent cells containing a primary monoamine were located along nerve bundles. Chronic reserpine treatment abolished the fluorescence in nerves but not in these cells. Ganglion cells showed no specific fluorescence, nor did fluorescent terminals impinge on them, but many ganglion cells contained autofluorescent granules. The significance of the presence and localization of catecholamines in the toad bladder is discussed in relation to the pharmacology of the organ and to histochemical investigations of the innervation in other vertebrate bladders.

Thiol inhibition of the effects of bradykinin upon vasopressin in the toad bladder

Abstract: Thiol inhibition of the effects of bradykinin upon vasopressin in the toad bladder Sm,-It seems that the antagonism of vasopressin and oxytocin by thiols is specific and that at least in part the thiol acts by directly affecting intracellular processes rather than solely by chemical reduction of the hormones (Handler & Orloff, 1964; Martin & Schild, 1965). Martin & Schild (1965) also presented evidence that the antagonism between thiols and these disulphide polypeptides is not typically competitive and may be caused by a reversible inactivation of essential disulphide groups in the receptor. Handler & Orloff (1964) have shown in addition that in the toad bladder preparation cysteine inhibits the response to theophylline (which does not contain a disulphide bond). In view of our recent fmding (Furtado, 1966; Furtado & Machado, 1966) that bradykinin inhibits the effects of vasopressin and oxytocin in the toad bladder, apparently acting as a specific and competitive antagonist, and considering the observation of Cirstea (1965) that at least some effects of bradykinin are potentiated by thiol compounds, we decided to further investigate the issue to see whether there was an interaction between bradykinin and thiols in the toad bladder. Both bradykinin (Furtado & Machado, 1966) and the thiol compounds (Bentley, 1964 ; Handler & Orloff, 1964) are known to inhibit the increases due to vasopressin in the movement of water as well as the net flux of sodium across the wall of the toad bladder. The interaction of these drugs was thus examined in the isolated urinary bladder of the toad, Bufo marinus, using the preparation of Bentley (1958). Each of the sacs of the bilobed bladder was mounted in a chamber with Bentley-Ringer solution bathing the serosal surface, and +-dilute Ringer within the bladder. The preparation was kept at 25 & lo, and at pH 74-7.6. The osmotic flow of water was estimated gravimetrically at 20 min intervals. The test substances were added to the serosal Ringer bath. Various doses of cysteine (cysteine hydrochloride, Eastman Kodak) (Cys) were combined with 5.0 mU/ml of vasopressin (Pitressin, Parke, Davis) (V) ; a single dose (1 .O pg/ml) of bradykinin (synthetic bradykinin, Sandoz) (BK) was also used. The dosage scheme can be diagrammatically represented as follows :