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PubMed1988

Nature of moulting control in amphibians: effects of cortisol implants in toads Bufo bufo.

Implantation of cortisol pellets in a dorsal lymph sac reduced the frequency with which toads replaced the strata cornea of the epidermis. Except in a few cases, however, the replaced strata cornea were not shed as in a normal moult. The mean interval between replacements of strata cornea rose from about 9-10 days in control toads to about 18 days in intact toads bearing implants. Removal of the cortisol pellets approximately 1 month after their insertion was followed by moulting on the fourth (or fifth) day. After the first moult, the frequency of replacement of strata cornea was initially high, but returned gradually to the normal level, probably concurrently with increasing levels of endogenous adrenocortical hormones. In toads with extirpated or ectopically transplanted pars distalis of the hypophysis, implanted cortisol pellets increased the interval between replacements of strata cornea from some few days to about 14-15 days, not significantly different from the intact toads, but no sheddings occurred. It is concluded that the moulting rhythm in toads, and other amphibians, is basically a rhythm in epidermal differentiation, expressed in the frequency with which the strata cornea are being replaced. The duration of the intervals between replacements varies with the level of circulating hormones, and replacement proceeds in the absence of a corresponding rhythm in secretion of the hormones. Shedding of a replaced stratum corneum depends upon the integrated function of a complex of processes, susceptible to disruption. Such disruption presumably prevailed at the pharmacological levels of circulating hormone in the cortisol-implanted toads.

Adrenocorticotropic Hormone↗
PubMed1992

Effect of breeding state, moulting, dehydration, exposure to saturated atmosphere, and arginine vasotocin on cutaneous water permeability in the toad Bufo bufo.

Cutaneous water permeability was assessed in hydrated male toads under a variety of conditions, including dehydration and rehydration, and the effects of exogenous arginine vasotocin (AVT) were determined. Cutaneous water permeability (the rate of water uptake by toads in water) was high in toads collected in the breeding pond and declined steeply during the first week, coincident with reduced activity of the cutaneous mucus glands. The slopes of the dose-response curves relating AVT to cutaneous water influx were about the same at the transition from the breeding to the nonbreeding state, but the level of influx was higher in the breeding state. The dose-response relationship in long-term terrestrial-acclimated toads was similar to that in water-acclimated toads. The threshold dose for effect on the cutaneous water permeability was about 1 ng AVT. Dehydration had a substantially greater effect on the cutaneous water permeability than AVT. The ratio between dehydration and AVT responses tended to increase with increasing water transport capacity of the skin. Moulting and acclimation to a saturated atmosphere in fully hydrated toads more than doubled the water permeability and abolished the response to AVT. It is suggested that AVT and other factors increase the cutaneous water permeability by similar mechanisms, such as insertion of water channels in the apical membrane of the epidermal cells. The effect of AVT on the toad skin is interpreted as reflecting the general high potency of neurohypophysial hormones in stimulating the water permeability of membranes of variable permeability.

Acclimatization↗
PubMed1984

Analgesic effects of ethylketocyclazocine and morphine in rat and toad.

We have previously found rat and toad (Bufo marinus) brain to contain inverse ratios of benzomorphan-preferring (kappa/sigma) and morphine-preferring (mu) opioid receptor types. The aim of the present study was to compare in vivo pharmacologic activity of a benzomorphan, ethylketocyclazocine (EKC) and morphine sulfate (MS) in rat and toad. Footshock intensity thresholds for eliciting locomotion were determined and dose-response curves for EKC and MS analgesia were obtained. Drugs were injected subcutaneously. In rats (high mu, low kappa in brain), both compounds produced analgesia and displayed similar sensitivity to naloxone antagonism. The analgesic effects of EKC and MS may, therefore, be mediated by a common receptor type (mu) in this pain test in rats. In toads (high kappa, low mu in brain), MS produced naloxone-reversible analgesia at doses 20-fold higher than were effective in rats. Toads did not display EKC analgesia at doses below those producing motor impairment. Moreover, 50-fold higher doses were required to produce such impairment in toads. Thirty minutes following subcutaneous injection of 3H-EKC, similar concentrations were found in rat and toad brain. Uptake into brain is probably not a factor in the behavioral resistance of toads to EKC.

Analgesia↗
PubMed1994

Metabolic acidosis, prostaglandin E2 and insulin stimulates intracellular free calcium ([Ca2+]i) in isolated cells of toad urinary bladder.

It is well known that metabolic acidosis (MA), PGE2, and insulin stimulate H+ excretion in toad urinary bladder. In addition, PGE2 has been shown to increase in the toad bladder during MA. Our present experimental findings indicate that MA, PGE2 and insulin increase [Ca2+]i and this then may be the signal for stimulation of H+ excretion in this tissue. Isolated cells of the toad urinary bladder, obtained from toads in a chronic metabolic acidosis (MA) have a significantly higher intracellular Ca2+ ([Ca2+]i) than similar cells obtained from toads in normal acid-base balance. Prostaglandin E2 (PGE2) (10(-5) M) was found to stimulate [Ca2+]i in the same normal toad bladder cells, as determined by the fluorescence ratio technique using FURA 2/AM (P < 0.05). Insulin (100 mU/ml) was also found to stimulate [Ca2+]i in toad bladder cells (P < 0.01). The increase in [Ca2+]i following PGE2 stimulation was not dependent on extracellular Ca2+, whereas the increase seen following insulin stimulation was dependent on extracellular Ca2+.

Acidosis↗
PubMed1989

Changes in plasma and pituitary levels of prolactin in the toad, Bufo japonicus, throughout the year with special reference to the breeding migration.

Monthly surveys of the plasma prolactin level in Bufo japonicus at two localities, one in Tokyo and the other in Saitama Prefecture, revealed that the level was highest during the month of breeding in early spring with an additional peak recognized in autumn. The level was lowest during the winter torpid period before breeding and during the spring torpid period after breeding. The pituitary prolactin content observed in Tokyo also showed an annual cycle similar to the plasma prolactin, except that the content in winter was higher than that in summer. A further precise survey of the plasma prolactin level before and during the breeding period revealed that the level in male toads migrating toward the pond for breeding was as low as the level in torpid toads, and also that the level was elevated in only about 50% of migrating female toads. In the pond, almost all female and male toads showed high plasma prolactin levels. Soon after the females finished breeding and returned to land, the level declined to the baseline without exception. In contrast, many males retained high levels on land. The present results indicate that prolactin is not a water drive factor, at least in B. japonicus. Prolactin may, however, play a role in toad osmoregulation in water. There is a possibility that the high prolactin level in some of the migrating female toads is related to oviductal secretion, as some female toads ovulate during migration.

Acclimatization↗
PubMed2003

Comparison of dehydration and angiotensin II-stimulated cutaneous drinking in toads, Bufo punctatus.

Toads (Bufo punctatus) use a sequence of two postures to place the ventral skin on a moist surface and absorb water osmotically. First, the skin contacts the surface (seat patch down, SPD), and then the hindlimbs are abducted to maximize skin contact area (water absorption response, WR). Toads modulated behavior in response to hydration status and osmotic content of the hydration source. Dehydrated toads placed on water displayed both SPD and WR. Hydrated toads injected with angiotensin II (AII) displayed SPD longer than Ringer-injected controls but did not initiate WR and absorbed less water than dehydrated toads. These results suggest that dehydration has a more robust dipsogenic effect than AII. Dehydrated toads placed on 250 mM NaCl briefly initiated SPD but not WR. The addition of amiloride to the hyperosmotic salt solution resulted in brief display of WR but no water loss. Hydrated toads placed on 250 mM NaCl showed shorter periods of SPD behavior. The combination of AII injection and amiloride addition to the salt solution increased SPD initiation but SPD duration was short and water loss was prevented. Neither AII nor dehydration overrides chemosensory mechanisms in the skin that suppress cutaneous drinking from hypertonic solutions.

Angiotensin II↗
PubMed2006

Invasion and the evolution of speed in toads.

Cane toads (Bufo marinus) are large anurans (weighing up to 2 kg) that were introduced to Australia 70 years ago to control insect pests in sugar-cane fields. But the result has been disastrous because the toads are toxic and highly invasive. Here we show that the annual rate of progress of the toad invasion front has increased about fivefold since the toads first arrived; we find that toads with longer legs can not only move faster and are the first to arrive in new areas, but also that those at the front have longer legs than toads in older (long-established) populations. The disaster looks set to turn into an ecological nightmare because of the negative effects invasive species can have on native ecosystems; over many generations, rates of invasion will be accelerated owing to rapid adaptive change in the invader, with continual 'spatial selection' at the expanding front favouring traits that increase the toads' dispersal.

Animals↗
PubMedDate not supplied

Bufo toads and bufotenine: fact and fiction surrounding an alleged psychedelic.

This paper investigates the supposedly psychedelic Bufo toad and the allegedly psychedelic drug bufotenine, which is contained in the skin and glands of this toad. The bufo toad has held a place in human mythologies and medicines worldwide since archaic times. Used by ancient peoples for a variety of purposes, its most spectacular effects, according to lore, involve magical and shamanic or occult uses for casting spells and for divination. In the Middle Ages, the Bufo toad was celebrated as a panacea and persecuted as a powerful poison. More recently, in the 1960s the Bufo toad was resurrected as a countercultural icon, with people purportedly licking or smoking the secretions to get high. Bufotenine has been at the center of a scientific debate since its discovery in 1893. This paper examines the extensive literature surrounding the Bufo toad and bufotenine, and untangles many of the myths and the misinformation that continue to vex both science and popular reporting. Finally, to promote further investigation, a comprehensive bibliography is provided that charts the history of the Bufo toad and bufotenine.

Animals↗
PubMed2002

Lateralisation of predator avoidance responses in three species of toads.

Lateralisation of responses to presentation of a simulated predator was investigated in three species of toads: two European species (the common toad, Bufo bufo, and the green toad, Bufo viridis) and one species introduced to Australia from South America, the cane toad Bufo marinus . First a simulated snake was presented moving rapidly towards the toad in the frontal field of vision and the toad's escape responses, including jumps to the right and to the left, were recorded. No significant bias in left or right side jumping was apparent in this test. Next the simulated snake was presented in the left or right lateral field of vision in random order. Escape and defensive responses were elicited more strongly, in all three species, when the stimulus was on the toad's left side compared to its right side. Reaction times scored in the experiments with B. marinus, alone, did not differ from left to right. There were, however, species differences in the types of escape responses with respect to the laterality: B. viridis and B. marinus showed similar patterns of more sideways jumps with left presentation and more frontal jumps with right presentation. Sideways jumps were not lateralised in B. bufo, but this species showed more frontal jumps when the presentation was on the left side. These findings suggest that the selective involvement of structures located in the right side of the brain (left monocular visual field) in emotional responses (particularly fear responses) could be a phylogenetic ancient trait.

Journal Article↗
PubMed2002

Limb preference and skeletal asymmetry in the cane toad, Bufo marinus (Anura: Bufonidae).

Two forms of skeletal asymmetry were identified in a population of cane toads, Bufo marinus, an exotic species in Australia. Fluctuating asymmetry characterised the lengths and weights of the long bones of the forelimbs and hindlimbs. Directional asymmetry was observed in the structure of the pectoral girdle of the toads, with the right epicoracoid positioned ventral to the left epicoracoid in 88% of the skeletons examined. Morphological data from a cohort of individuals were correlated with limb preferences determined from 10 consecutive trials in which the toads were inverted and briefly submerged in water while bilaterally clasping the experimenter's fingers. The toad's left forelimb was released first to enable the right forelimb to exert force against the experimenter's fingers and so control righting the body of the toad in 90% of trials. Asymmetries in the long bones of the forelimbs and pectoral girdles of the toads did not correlate significantly with the strength of preference for the right forelimb, although asymmetry of the weight of the tibiafibulae did correlate significantly with percent right forelimb preference. Age, or nutritional status, was a factor in the right forelimb preference: the preference for the use of the right forelimb was strongest in toads possessing longer and heavier long bones of both the forelimbs and hindlimbs. These results provide insight into the interaction between skeletal development and lateralised motor behaviour in an anuran species.

Journal Article↗
PubMedDate not supplied

Renal response of euryhaline toad (Bufo viridis) to acute immersion in tap water, NaCl, or urea solutions.

Green toads (Bufo viridis) were acclimated to either tap water, 230 mOsmol NaCl kg-1 H2O (saline), 500 mOsmol NaCl kg-1 H2O (high saline), or 500 mmol L-1 urea. Renal functions for each acclimation group were studied on conscious animals that had one ureter chronically catheterized. Reciprocal immersion of tap-water- and saline-acclimated toads in the opposite solution did not stress the animals osmotically, and plasma osmolality increased or decreased by no more than 15%. However, urine osmolality and ionic composition changed immediately and profoundly on exposure to the other solution. Exposure of tap-water-acclimated toads to saline decreased urine flow by 30%, whereas the reciprocal immersion led to an increase of 30%. Immersion of tap-water-acclimated toads in high saline led to immediate cessation of urine flow, whereas immersion of 500 NaCl- or urea-acclimated toads in tap water led to a large increase in urine flow, with an overshoot that lasted 10 h (as a result of either salt or urea diuresis). Urine flow then stabilized at a level 5-6 times higher than the value attained at high-salt environment. On immersion of 500 urea-acclimated toads in 500 NaCl, urine flow doubled, accompanied by a change in ion composition, without change in the osmolality. In all experimental conditions, plasma potassium concentration was maintained within a narrow range. The results show that the toad's kidneys contributed efficiently both to osmo- and ionoregulation in a wide range of ambient solutions.

Animals↗
PubMed2006

Characterization of a major secretory protein in the cane toad (Bufo marinus) choroid plexus as an amphibian lipocalin-type prostaglandin D synthase.

Here we report the enzymatic and ligand-binding properties of a major secretory protein in the choroid plexus of cane toad, Bufo marinus, whose protein is homologous with lipocalin-type prostaglandin (PG) D synthase (L-PGDS) and is recombinantly expressed in Xenopus A6 cells and Escherichia coli. The toad protein bound all-trans retinal, bile pigment, and thyroid hormones with high affinities (K(d)=0.17 to 2.00 microM). The toad protein also catalysed the L-PGDS activity, which was accelerated in the presence of GSH or DTT, similar to the mammalian enzyme. The K(m) value for PGH(2) (17 microM) of the toad protein was almost the same as that of rat L-PGDS (14 microM), whereas the turnover number (6 min(-1)) was approximately 28 fold lower than that of rat L-PGDS. Site-directed mutagenesis based on a modeled structure of the toad protein revealed that Cys(59) and Thr(61) residues were crucial for the PGDS activity. The quadruple Gly(39)Ser/Ala(75)Ser/Ser(140)Thr/Phe(142)Tyr mutant of the toad protein, resembling mouse L-PGDS, showed a 1.6 fold increase in the turnover number and a shift in the optimum pH for the PGDS activity from 9.0 to 8.5. Our results suggest that the toad protein is a prototype of L-PGDS with a highly functional ligand-binding pocket and yet with a primitive catalytic pocket.

Amino Acid Sequence↗
PubMed1982

Chloride self-exchange in toad skeletal muscle in vivo and in vitro.

The exchange of cellular Cl with 36Cl has been measured in saline-perfused hindlimb muscles of the pithed toad and compared with cellular Cl exchange in isolated muscles incubated in the vitro either in toad Ringer solution or in toad plasma. In the perfused hindlimb, the rate of 36Cl efflux from muscle cells [17.0 +/- 0.9 pmol Cl.(cm2 plasma membrane.s)-1] was only 40% as fast as that of the 36Cl influx. The discrepancy between Cl influx and efflux was accompanied by a cellular accumulation of Cl against the electrochemical gradient for this anion. Concurrently, the cells took up Na in amounts at least equal to the accumulated Cl. During this accumulation of Na and Cl, the mean resting potential remained constant at a value of -89.2 +/- 1.9 (SE) mV. Na and Cl were taken up by the muscle cells of the perfused hindlimb without a concomitant decrease in cellular K content; i.e., without evidence of inhibition of the Na-K pump. The rate constant for cellular 36Cl efflux from isolated toad muscles preincubated for 3 h in vitro in toad Ringer solution was about five times faster than that of muscles in the perfused hindlimb and similar in magnitude to published values for Cl fluxes in frog muscle. Cellular Cl efflux from muscles briefly preincubated in vitro for 15 min instead of 3 h was significantly slower than after prolonged preincubation. In vitro incubation of isolated toad muscles in toad plasma slowed the cellular 36Cl efflux to values approaching those measured in the perfused hindlimb, without comparably depressing the 36Cl influx. It is suggested that the uptake of NaCl by the cells of perfused hindlimb muscle may proceed by an electroneutral inward cotransport of Na and Cl on the same carrier.

Animals↗
PubMed1989

Cardiovascular responses to denervation of pulmocutaneous baroreceptors in toads.

Toad pulmocutaneous arterial baroreceptors are connected to afferent fibers carried in the recurrent laryngeal nerves (rLNs). Bilateral rLN denervation in conscious toads (Bufo marinus) caused 34 and 78% increases in heart rate (Fh) and systemic arterial blood pressure (Pa) within 10-15 min, respectively. The variance of Pa was significantly increased 2 days after denervation, but Pa and Fh were not. In additional chronic experiments, 5 of 17 baroreceptor-denervated toads died within the 2-wk recovery period. No deaths occurred in sham-operated toads. The mean Pa, Fh, and cardiac interval (Ic), the mean variance of Pa, Fh, and Ic, and Pa and Fh responses to stress, plasma composition, and the dry-to-wet weight ratio of skeletal muscle and lung were not statistically different in denervated and sham-operated toads. However, the sensitivity of Ic to changes in Pa, exposed by intra-arterial injections of phenylephrine and nitroprusside, was attenuated in denervated toads. Postmortem examination revealed occasional pulmonary lesions, the incidence of which appeared correlated with causes of pulmonary hypertension: baroreceptor denervation and phenylephrine injections. We conclude that pulmocutaneous arterial baroreflex is tonically active but is not essential for the long-term maintenance of Pa in conscious undisturbed toads.

Animals↗
PubMed1977

Effect of hypothalamic lesions on water metabolism of the toad Bufo marinus.

The rate of cutaneous water uptake after dehydration was significantly depressed in functionally neurohypophysectomized toads (Bufo marinus), which consequently regained weight much more slowly than intact toads when returned to water. Toads bearing hypothalamic lesions were able to develop an antidiuresis when removed from water to a saturated atmosphere, but the antidiuresis was solely glmerular in origin and was established more slowly than in intact animals. The fractional reabsorption of filtrate increased significantly and the relative free water clearance decreased significantly in intact toads after removal from water. These changes in tubular function, which were not seen in lesioned toads, were responsible for the development of a more rapid and effective antidiuresis in intact animals. Injections of iso-osmotic saline, oxytocin (250 mu./100 g) and vasopressin (50 mu./100 g) had no significant effect on rates of cutaneous water uptake in both intact and lesioned toads. Injections of hyperosmotic saline, however, significantly increased rates of water uptake in both groups of toads, but to a much greater extent in the intact animals. Fluid retention arising from a marked antidiuresis occurred after the injection of vasopressin and hyperosmotic saline, and there was some evidence of an antidiuretic effect of oxytocin with the doses used here. These results and their bearing on the question of the functional significance of the neurohypophysis in anuran amphibians are discussed.

Animals↗
PubMed1999

Causes of mortality of the Wyoming toad.

Wyoming toads (Bufo baxteri) that died from January 1989 to June 1996 were submitted to the Wyoming State Veterinary Laboratory (Laramie, Wyoming, USA) for postmortem evaluation. These consisted of 108 free-ranging toads and 170 animals from six captive populations. Ninety-seven (90%) of 108 free-ranging toad carcasses were submitted during September and October. From 1989 to 1992, 27 (77%) of 35 mortalities in the captive populations occurred in October, November, and December. From 1993 to 1996, mortality in captive toads occurred without a seasonal pattern and coincided with changes in hibernation protocols that no longer mimicked natural cycles. Cause of mortality was determined in 147 (53%) of the 278 cases. Mycotic dermatitis with secondary bacterial septicemia was the most frequent diagnosis in 104 (71%) of 147 toads. Basidiobolus ranarum was found by microscopic examination of skin sections in 100 (96%) of 104 of these mortalities. This fungus was isolated from 30 (56%) of 54 free-ranging and 24 (48%) of 50 captive toads. This research documents the causes of mortality for both free-ranging and captive endangered Wyoming toads over a 7 yr period.

Age Factors↗
PubMed2000

Effect of the dry-cold season dormancy on the tonic and phasic neural control of heart rate in the toad, Bufo paracnemis.

This work examined basal heart rate and autonomic cardiac tone as well as sympathetic cardiac reactivity to hypotension induced by systemic nitroprusside injection in dormant toads (dry-cold season), Bufo paracnemis, comparing the values with those of toads collected during the active months (hot-rainy season). Autonomic tone was calculated according to the method of Lin and Horwath ('72), which allows its evaluation as a percentage of intrinsic heart rate. Specimens were maintained in an outdoors terrarium except for the week preceding surgery, when they were transferred to indoor nonclimatized tanks. The heart rate of dormant toads (27.8 +/- 2.7 beats/min) was lower than that of active toads at rest (38.6 +/- 2. 3). Cholinergic tone was higher than adrenergic tone both in active (26.2% and 7.8%, respectively) and aestivated (19.5% and 4.8%, respectively) animals. Thus, cholinergic tone and adrenergic tone were both lower in dormant animals. The reflex tachycardia elicited by nitroprusside-induced hypotension was lower in aestivated toads (9.3 +/- 0.9 beats/min) when compared to active toads (19.9 +/- 1.0), indicating a reduced sympathetic reactivity. Nitroprusside-induced hypotensions were not different in the two groups. We conclude that at rest Bufo paracnemis heart is under the influence of a double cholinergic and adrenergic tone, and that both influences, as well as the reflex adrenergic reactivity to the unloading produced by nitroprusside-induced hypotension, are reduced in aestivated toads.

Adrenergic Fibers↗
PubMed1995

TOAD-64, a gene expressed early in neuronal differentiation in the rat, is related to unc-33, a C. elegans gene involved in axon outgrowth.

Using two-dimensional gel electrophoresis we previously identified membrane-associated proteins that are upregulated over the course of neurogenesis. One of these, TOAD-64 (Turned On After Division, 64 kDa), is expressed immediately after neuronal birth and is dramatically downregulated in the adult. The gene encoding TOAD-64 has now been cloned, and its sequence shows homology to the unc-33 gene from C. elegans, mutations in which lead to aberrations in axon outgrowth. Northern and in situ hybridization show that TOAD-64 mRNA is enriched in the nervous system and is developmentally regulated in parallel with the protein. The expression of the TOAD-64 protein and gene coincident with initial neuronal differentiation and the downregulation when the majority of axon growth is complete suggests a role in axon elaboration. Three additional lines of evidence support this possibility: TOAD-64 is upregulated following neuronal induction of P19 and PC12 cells; the protein is found in lamellipodia and filopodia of growth cones; and axotomy of the sciatic nerve induces reexpression. While the sequence of TOAD-64 lacks a signal sequence and therefore is likely to encode a cytoplasmic protein, biochemical experiments demonstrate that the protein is tightly, but noncovalently, associated with membranes. The data presented here suggest that TOAD-64 could be a central element in the machinery underlying axonal outgrowth and pathfinding, perhaps playing a role in the signal transduction processes that permit growing axons to choose correct routes and targets.

Aging↗