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At least 19 recordsLinked to original sources
PubMedDate not supplied

[Cyclosporin A inhibits the response of osmotic water permeability to antidiuretic hormone in toad's bladder and to angiotensin II and antidiuretic hormone in toad's skin].

The purpose of the present study was to assess the effects of cyclosporine A (CyA) in the osmotic water flow response of isolated toad bladder to arginine-vasotocin (AVT) and to angiotensin II (Ang II) and AVT in isolated toad skin. CyA added to the dermal side of isolated toad skin or to the serosal side of toad bladder in concentrations of 0.42. 10(-6) M to 0.42. 10(-7) M had no effect on basal osmotic water permeability (Posm) but inhibited the hormonal response to AVT in both membranes (AVT 10(-10) M in toad bladder and 10(-8) to 10(-9) M in toad skin). CyA also inhibited the Posm response to Ang II (10(-7) M) in toad skin in concentrations of 0.42. 10(-6) M and 0.42. 10(-7) M. In toad bladder it could be demonstrated that the inhibitory effect was reversible. CyA in concentrations of 0.42. 10(-6) M inhibited the Posm response of toad skin to theophylline (3.2. 10(-3) M) and to dibutyryl cyclic AMP (6.3. 10(-3) M) suggesting an effect distal to the generation of cyclic AMP. These responses would support the possibility of a diuretic effect in the mammalian nephron.

Angiotensin II↗
PubMed1993

[Toad or toad cake intoxication in Taiwan: report of four cases].

The parotid glands and skin of the toad contain toxic substances. Ingestion of toad or toad cake may result in intoxication. Clinically, it may be predominantly manifested by a digitalis-like cardioactive effect. During the last six years, the National Poison Center of Taiwan has collected four cases of toad or toad cake intoxication: two cases were toad intoxication and two cases were toad cake intoxication. All four cases manifested with general weakness; three cases showed bradycardia, vomiting and diarrhea; two cases had numbness of the oral cavity; one case had excessive salivation; and two cases showed a consciousness change. In one case, an EKG showed bradycardia, and a first and second degree A-V block; this patient died of ventricular fibrillation. The prognosis in two cases was good. We lost contact with the last patient. The treatment principles in toad or toad cake intoxication is life support. If ingested, treatment is directed at prevention of absorption, including emesis, gastric lavage, activated charcoal and cathartics. Atropine, a pacemaker and other antiarrhythmic agents may be helpful in treating cardiovascular toxicity.

Adult↗
PubMed1992

Effects of atrial natriuretic peptide and toad heart extract on isolated toad Bufo arenarum aortic rings.

The vascular effects of synthetic atrial natriuretic peptide (ANP) (rANP-99-126), and toad heart extract (THE) were examined on isolated toad aortic rings from the toad Bufo arenarum. ANP inhibited contraction produced by human angiotensin II (AT II), norepinephrine (NE), and arginine vasopressin (AVP) in isolated toad aortic rings. The present data show that a relaxant effect of ANP could be obtained also in the noncontracted aortic smooth muscle of toad if it had been previously challenged with AT II or NE and allowed to return to the original basal tension. Bufo arenarum THE was able to relax the AT II-induced contraction in toad aortic rings. In toad arteries contracted with 10(-6) M AT II, ANP produced a dose-dependent relaxation with a half-maximal inhibitory concentration IC50 of 1.2 x 10(-8) M. ANP was not effective in relaxing contraction induced by high K+. The vasorelaxant effect of ANP on AT II-induced contraction was significantly increased in Ca(2+)-free medium containing 3 mM ethylene glycol bis(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA-Ringer) or by pretreatment with the calcium antagonist, diltiazem (DIL). The vasorelaxant effect of ANP on basal tension after treatment with AT II was also obtained in absence of extracellular calcium (EGTA-Ringer). These results show that Bufo arenarum contains ANP-like material and that the ANP relaxant action in the toad aorta is similar to that in mammals.

Angiotensin II↗
PubMed2000

Characterization of the spermiation response, luteinizing hormone release and sperm quality in the American toad (Bufo americanus) and the endangered Wyoming toad (Bufo baxteri).

Spermiation and LH release in response to several methods of LHRH administration were assessed in the American toad (Bufo americanus), and the most successful method was tested in the endangered Wyoming toad (Bufo baxteri). Specific objectives were to: (1) compare spermiation responses and plasma LH concentration after invasive and non-invasive LHRH treatments; (2) evaluate sperm production in response to different LHRH dosages; (3) characterize the timing of sperm release post LHRH treatment; and (4) assess sperm quality (motility, viability, morphology and acrosomal status). Male American toads were administered 4 microg LHRH by one of four routes: (1) intraperitoneal injection (i.p.); (2) subcutaneous injection (s.q.); (3) dorsal dermis absorption (d.d.a.); and (4) ventral dermis absorption (v.d.a.). Aspermic urine only was collected from saline-treated controls and d.d.a. animals. Several v.d.a. animals released spermic urine; however, all LHRH-injected toads released spermatozoa. I.p. animals produced higher sperm and LH concentrations than s.q. animals. The spermiation response in animals treated i.p. with 1 microg LHRH was similar to that in animals treated with 4 microg, but lower LHRH dosages tested produced inferior responses. Sperm production in responsive animals increased over time during the 12-h sampling interval. Regardless of treatment, most American toad spermatozoa were motile, viable, and acrosome-intact. Endangered Wyoming toads were treated i.p. with 4 microg LHRH, and spermic urine was collected. Although most spermatozoa were viable and acrosome-intact, a considerable percentage possessed structurally abnormal heads. A single i.p. injection of LHRH appears to be a reliable and safe method for controlling spermiation in toads and may be useful for assisting endangered amphibian propagation.

Acrosome↗
PubMed1988

Epidermal tissue homeostasis. III. Effect of hydrocortisone on cell pool size, cell birth rate and cell loss in normal toads and in toads deprived of the pars distalis of the pituitary gland.

It has previously been shown that in toad epidermis the cell birth rate (Kb) exceeds the rate of cell loss through moulting (Kd) and that the 'surplus' of cells seems to be removed in a controlled manner. Assuming that the epidermis is non-expanding, a Kb/Kd ratio greater than 1 indicates that cell deletion additional to desquamation takes place. In normal toads this ratio is 2-3. Following implantation of hydrocortisone pellets into intact toads (release rate, 18 micrograms/g toad/d), the Kb/Kd ratio, over a period of 14 d of hormone treatment, had increased to about 7, due mainly to an increased Kb and to a lesser extent to a decreased Kd. No change in the epidermal cell pool size had taken place. It was previously shown that, following removal of the pars distalis of the pituitary gland, the Kb/Kd ratio decreased with time, due to a decreasing Kb and an increasing Kd, eventually leading to a decreased epidermal cell pool size. In this paper it is shown that, in pars distalisectomized toads with hydrocortisone pellets implanted, the Kb/Kd ratio is restored to control levels by a restoration of the Kb as well as the Kd. The results differ from those of previous studies in which ACTH or adrenocorticosteroids were administered discontinuously (by injection). Thus, by experimental manipulation, different Kb/Kd ratios can be obtained: low (less than 1, pars distalis ablation), medium (2-3, normal toads) and high (7, hydrocortisone implantation). The potentiality of this unique situation in analysing the important question of how the 'surplus' cells are deleted is discussed.

Animals↗
PubMed1978

Evidence for involvement of microtubules in the action of vasopressin in toad urinary bladder. II. Colchicine binding properties of toad bladder epithelial cell tubulin.

Colchicine, podophyllotoxin and vinblastine have been found to inhibit the action of vasopressin on water movement in the toad urinary bladder. Tubulin is the major colchicine binding component of toad bladder epithelial cells, accounting for approximately 3.3% of the total cell protein. More than 99% of the tubulin is found in the soluble fraction after sonication, the remainder is in the particulate fraction. Similar to the characteristics of the binding of colchicine to tubulins from other sources, the binding of colchicine to toad bladder tubulin is temperature- and time-dependent, is inhibited competitively by podophyllotoxin (Ki= 5.5 x 10(-7)m), and has a binding constant of 1 X 10(6) liters/mole at 37 degrees. Binding activity decays according to first-order kinetics and is stabilized by vinblastine. The characteristics of the interactions of colchicine and podophyllotoxin with epithelial cell tubulin in vitro closely parallel the ability of these drugs to inhibit the response to vasopressin in vivo. These results, coupled with those of functional and morphological studies, support the view that the ability of these drugs to affect vasopressin-induced water movement across toad bladder epithelial cells is related to the depolymerization of cytoplasmic microtubules.

Animals↗
PubMed1993

Desensitisation of the cardiac response to somatostatin in isolated toad atria but not in whole toads.

The cardiac slowing measured in response to repeated application of somatostatin (SOM) was compared in an isolated toad sinus venosus/atrial preparation and in a whole, anaesthetised toad, Bufo marinus. Repeated doses of 0.5-1 x 10(-7) M SOM in the organ bath progressively reduced the cardiac response to 25% or less of the response to the first dose given. When preparations were allowed a recovery period of 50-80 min, the response recovered to 51.0 +/- 3.7% of the control. In contrast, the cardiac chronotropic response in anaesthetised toads to repeated intravenous injections of 2 micrograms or 1.2 nmol SOM over 3 h was not changed. Prolonged exposure to SOM (0.1-0.25 mumol/kg/h infusion), for up to 4 h in anaesthetised toads caused no significant reduction either in the cardiac responses to a bolus dose of SOM (0.6 nmol) or nerve released SOM (3 Hz for 2 min) in the presence of atropine. These opposing results suggest that the half-life of a peptide and the method of exposing receptors to a peptide are important factors in receptor desensitisation.

Anesthesia↗
PubMed2002

Studies on toad venom (3): effect of metals on the quality of toad venom torrefied on a metal plate.

To study the quality of toad venom dried on different metal plates by heating at 105 degrees C, each 20 g sample of fresh toad venom collected in Hei-Long-Jiang Province, China, was dried on (1) brass, (2) copper, (3) glass, (4) acrylic resins, (5) aluminum and (6) stainless-steel, respectively. Twelve bufadienolides, including bufalin and bufotalin, in each sample were then quantitatively analyzed by HPLC. The total levels of bufadienolides in 1000.0 mg of the dried samples were (1) > (2) > (3) > (4) > (5) > (6), varying from 303.44 mg to 420.72 mg. Besides, the color of dried venom became darker in the order of (2), (4), (6), (3), (1) and (5). Though (1) was not in good color, it was superior to the others in chemical quality. These results suggest that it is possible to dry toad venom in short period by heating it at a high temperature on a tray made of brass. This will be a better method for making high quality toad venom than the traditional method. Moreover, the removal of impurities in the fresh venom by the process of filtration through silk succeeded in raising the bufadienolides content significantly.

Amphibian Venoms↗
PubMedDate not supplied

Biosynthesis of bufadienolides in toads. VI. Experiments with [1,2-3H]cholesterol, [21-14C]coprostanol, and 5 beta-[21-14 C]pregnanolone in the toad Bufo arenarum.

[1,2-3H]Cholesterol, 5 beta-[21-14C]cholestan-3 beta-ol (coprostanol), and 3 beta-hydroxy-5 beta-[21-14C]pregnan-20-one were injected into intact Bufo arenarum toads. Arenobufagin, the main bufadienolide present in the venom of the mentioned toad, was isolated and purified by means of chromatographic procedures. The first two compounds, having an intact cholesterol side chain, were incorporated, at comparable levels, into the bufadienolide while the labeled pregnane derivative yielded non-radioactive arenobufagin. The above results support the hypothesis that cholesterol and those steroids having an intact cholesterol-type side chain are able to penetrate to the site of bufadienolide biosynthesis and are converted into bufadienolides by a still-unknown mechanism. On the other hand, those steroid derivatives bearing a degraded side chain, e.g., 20-keto-pregnanes, are not converted into bufadienolides because they are not incorporated into the bufadienolide-producing cells.

Animals↗
PubMed1984

Biosynthesis of bufadienolides in toads. V. The origin of the cholesterol used by toad parotid glands for biosynthesis of bufadienolides.

Sodium (1-14C)acetate and (5-3H) mevalonate were incubated with Bufo arenarum toad parotid gland and liver tissues. Both labelled compounds were incorporated into cholesterol produced by liver while the incubations with parotid gland produced no labelled cholesterol. Low and high density lipoproteins isolated from toad plasma were iodinated and used for binding studies. Membrane preparations of parotid gland showed high affinity binding sites for 125I-LDL and 125I-HDL. In addition, while colchicine inhibits the in vitro uptake of (3H)cholesteryl linoleate-LDL into parotid gland tissue an opposite effect was seen with (3H)cholesteryl linoleate-HDL. The above mentioned results would support the hypothesis that the cholesterol used by the parotid gland for the biosynthesis of bufadienolides would be produced in the liver, transported by the circulating lipoproteins and incorporated by the glands by a receptor-mediated mechanism.

Animals↗
PubMed2003

Identification and molecular cloning of novel trypsin inhibitor analogs from the dermal venom of the Oriental fire-bellied toad (Bombina orientalis) and the European yellow-bellied toad (Bombina variegata).

The structural diversity of polypeptides in amphibian skin secretion probably reflects different roles in dermal regulation or in defense against predators. Here we report the structures of two novel trypsin inhibitor analogs, BOTI and BVTI, from the dermal venom of the toads, Bombina orientalis and Bombina variegata. Cloning of their respective precursors was achieved from lyophilized venom cDNA libraries for the first time. Amino acid alignment revealed that both deduced peptides, consisting of 60 amino acid residues, including 10 cysteines and the reactive center motif, -CDKKC-, can be affirmed as structural homologs of the trypsin inhibitor from Bombina bombina skin.

Amino Acid Sequence↗
PubMed1995

Histological examination of the effects of corticosterone in larvae of the western toad, Bufo boreas (Anura: Bufonidae), and the Oriental fire-bellied toad, Bombina orientalis (Anura: Discoglossidae).

The effects of corticosterone (CORT)-treatment on various tissues were examined in two species of anuran larvae, the discoglossid Bombina orientalis, and the bufonid Bufo boreas. Corticosterone was administered directly into aquarium water for 15 days. After treatment, histological analyses were conducted on skin, gut, spleen, thymus, and neural and muscle tissue. Corticosterone treatment prevented sloughing of the skin, which resulted in a build-up of stratum corneum, and inhibited the development of gland nests and the subsequent formation of dermal granular and mucous glands in both species. Corticosterone treatment also decreased epithelial folding in the gut and caused vesiculation of the gut epithelial cells. The thymus of CORT-treated animals was significantly reduced in size (P < .05) and cell density (P < .05), and the spleen of CORT-treated animals was completely involuted. The brain and pituitary of CORT-treated animals had a decreased cell density (P < .05) and many pyknotic cells. An examination of muscle revealed that muscle fibers of CORT-treated animals had a decreased cross-sectional area (P < .05). The dose of CORT used (1.1 microM) was within the range used in other studies in the literature and resulted in tissue levels within the range experienced by larvae at metamorphic climax. Thus, this study is appropriate to address the histological effects of CORT in experimental manipulations and the role of increasing CORT at metamorphic climax. The data suggest that increasing endogenous CORT at metamorphosis may be involved in degeneration of larval tissue, prior to regeneration, which is stimulated by thyroid hormones.

Animals↗