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PubMed1978

Enterobacteria of emerging pathogenic significance from clinical cases in man and animals and detection of toads and wall lizards as their reservoirs.

A total of 416 samples comprising faecal samples from diarrhoeic cases of man, calves, sheep and goats, and urine samples from patients with urinary tract infections, were examined for the presence of enterobacteria of emerging pathogenic significance. Citrobacter freundii from 20, C. intermedius biotype-a from four, Serratia marcescens (serotype 05:H13, bactericin type 16) from one and Erwinia herbicola from two human stool samples were isolated. Only two urine samples yielded C. freundii. Citrobacter freundii was isolated from 10 and C. intermedius biotype-a from two calves. From sheep and goats, two isolates of C. freundii and three of C. intermedius biotype-a were obtained. None of these samples yielded Edwarsiella tarda or Yersinia enterocolitica. The examination of 99 toads and 145 wall lizards revealed that toads were reservoirs for C. freundii, C. intermedius biotype-a and Salmonella brijbhumi, whereas wall lizards were reservoirs for C. freundii, C. intermedius biotype-a, E. herbicola, Enterobacter cloacae and Salmonella spp. These bacteria were present in the range of 2.0 x 10(6) to 6.0 x 10(11) organisms per gram of intestinal contents. In addition, toads were carriers for Edwardsiella tarda (new serotypes 04167:H1 and 05159: non-motile). None of the toads and wall lizards proved positive for C. intermedius biotype-b (C. koseri), S. marcescens and Y. entercolitica. C. freundii, C. intermedius biotype-a, E. herbicola and S. marcescens were resistant to penicillin and erythromycin whereas E. tarda isolates were also resistant to gentamycin, neomycin, colistin and sulfamethaxazole.

Animal Diseases↗
PubMed1993

Taurine in toad brain and blood under different conditions of osmolality: an immunohistochemical study.

The concentrations of taurine in blood and brain regions of the toad Bufo boreas have been measured. Most of these values are considerably lower than those found in mammals. Using an antibody prepared against conjugated taurine, the distribution of taurine in three brain regions of the toad has been visualized. The possible osmoregulatory functions of taurine have been investigated by making toads hyper- or hypo-osmotic in vivo. Induction of hypoosmolality is accompanied by a massive taurine tide in blood plasma, but has no immediate effects upon the taurine concentrations in the brain areas studied. However, histochemical visualization indicates a marked redistribution of taurine between cellular components and extracellular space of brain tissues. This may indicate that taurine has an osmoregulatory function in brain tissue under hypo-osmotic conditions. Hyperosmolality results in no elevation of the taurine concentration in blood plasma of toads, but rather in a very gradual decline of total plasma taurine content over a prolonged time period. Histochemical studies reveal little change in frontal cortex after 1 hour but deeper staining of many neurons in optic lobe accompanied by greater staining in the extracellular fluid. By 3 hours there is a depletion of taurine from all compartments of cerebral cortex tissues. No evidence of any prolonged direct osmoregulatory role for taurine is indicated under hyperosmotic conditions. A possible indirect osmoregulatory function of taurine is discussed.

Animals↗
PubMed1975

Mechanism of action of Vibrio cholerae enterotoxin. Effects on adenylate cyclase of toad and rat erythrocyte plasma membranes.

The characteristics of the cholera toxin-stimulated adenylate cyclase of toad (Bufus marinus) and rat erythrocyte plasma membranes have been examined, with special emphasis on the response to purine nucleotides, fluoride, magnesium and catecholamine hormones. Toad erythrocytes briefly exposed to low concentrations of cholera toxin (40,000 to 60,000 molecules per cell) and incubated 2 to 4 hr at 30 degrees C exhibit dramatic alterations in the kinetic and regulatory properties of adenylate cyclase. The approximate Km for ATP, Mg++ increases from about 1.8 to 3.4 mMin the toxin-stimulated enzyme. The stimulation by cholera toxin increases with increasing ATP, Mg++ concentrations, from 20 percent at low levels (0.2 mM) to 500 percent at high concentrations (greater than 3 mM). Addition of GTP, Mg++ (0.2 mM) restores normal kinetic properties to the toxin-modified enzyme, such that stimulation is most simply explained by an elevation of Vmax. GTP enhances the toxin-treated enzyme activity two- to fourfold at low ATP concentrations, but this effect disappears at high levels of the substrate. At 0.6 mM ATP and 5 mM MgC12 the apparent K alpha for GTP, Mg++ is 5 to 10 muM. The control(unstimulated) enzyme demonstrates a very small response to the guanyl nucleotide, 5'-ITP also stimulates the toxin-treated enzyme but cGMP, guanine, and the pyrimidine nucleotides have no effect. Cholera toxin also alters the activation of adenylate cyclase by free Mg++, decreasing the apparent K alpha from about 25 to 5 mM. (minus)-Epinephrine sensitizes the toad erythrocyte adenylate cyclase to GTP and also decreases the apparent K alpha for free metal. Sodium fluoride, which causes a 70- to 100-fold activation of enzyme activity, has little effect on sensitivity to GTP, and does not change the apparent K alpha for Mg++; moreover,it prevents modulation of these parameters by cholera toxin. Conversely, cholera toxin severely inhibits NaF activation, and in the presence of fluoride ion the usual three to fivefold stimulation by toxin becomes a 30 to 60 percent inhibition of activity. The toxin-stimulated enzyme can be further activated by catecholamines; in the presence of GTP the (minus)-epinephrine stimulation is enhanced by two- to threefold. The increased catecholamine stimulation of toad erythrocyte adenylate cyclase induced by cholera toxin is explained primarily by an increase in the maximal extent of activation by the hormones. Rat erythrocyte adenylate cyclase is also modified by cholera toxin. In the mammalian system the apparent affinity for the hormone appears to be increased. Cholera toxin thus induces profound and nearly permanent changes in adenylate cyclase by a unique process which mimics the stimulation by hormones in important ways, and which also accentuates the normal hormonal response. The relevance of these findings to the mechanism of action of cholera toxin is considered.

Adenylyl Cyclases↗
PubMed1976

Water permeability and lipid composition of toad urinary bladder: the influence of temperature.

The water diffusional permeability, its activation energy and the lipid composition were studied in urinary bladders from toads adapted to different temperatures. It was observed that the unidirectional water flux greatly depends on the temperature at which the experiments are performed. This dependence is greater in the animals adapted to higher temperatures. Toads adapted to cold show strong reduction in the activation energy for water diffusion permeability (from 11.4+/-1.9 kcal-mol-1 to 4.4+/-1.1kcal-mol-1) and an increase of 30% in the amount of total lipids from bladder epithelial cells. There were no significant changes in the phospholipid/cholesterol ratio, composition of the parafinic chains or protein concentration between toads adapted to both temperatures. The possibility that water translocates through the mucosal border of the toad bladder by partitioning in the polar zone and diffusioning between the hydrocarbon chains of the membrane lipids and that cold adaptation would induce a stronger "packing" of lipids in the membrane is discussed.

Acclimatization↗
PubMed1976

Thermodynamic analysis of nonelectrolyte permeation across the toad urinary bladder.

Permeability coefficients (P's) and apparent activation energies (Ealpha's) for nonelectrolyte permeation across the toad urinary bladder have been analyzed in terms of the thermodynamics of partition between membrane lipids and water. Particular attention has been paid to the contributions made by -CH2- and -OH groups: on the average, the addition of one -CH2- group to a molecule increases P fourfold, while the addition of one -OH group reduces P 500-fold. Using these changes in P, we have calculated the incremental free energies (delta delta F), enthalpies (delta delta H), and entropies (delta delta S) for partition, hydration, and solution in membrane lipids. The results for toad bladder have been compared and contrasted with those extracted from the literature for red blood cells, lecithin liposomes, and bulk phase lipid solvents. The partition of -CH2- groups into toad bladder and red cell membranes is dominated by entropy effects, i.e., a decrease in entropy of the aqueous phase that "pushes" the group out of water, and an increase in entropy of the membrane lipid that "pulls" the group into the membrane. This process resembles that in "frozen" liposome membranes. In "melted" liposomes and bulk lipid solvents the free energy of solution in the lipid is controlled by enthalpy of solution. PArtition of -OH groups in all systems is governed by hydrogen bonding between the -OH group and water. However, the solution of the -OH group in the toad bladder membranes is complex, and processes such as dimer and tetramer formation in the lipid phase may be involved. The results presented in this and the previous paper are discussed in terms of the structure of phospholipid bilayer membranes. Attention is drawn to the possible role of structural defects in the quasi-crystalline structure of the lipid (so-called 2 gl klinks) in the permeation of small molecules such as water, urea, methanol and acetamide.

Animals↗
PubMed1978

The role of cyclic AMP in parathyroid hormone action in the toad bladder.

Parathyroid hormone (PTH) inhibited active transport of inorganic phosphate and stimulated an increase in cyclic AMP concentration in the urinary bladder of the toad, Bufo marinus. Active transport of phosphate in the toad bladder was also inhibited by an analog of cyclic AMP (dibutyryl cyclic AMP) and by other drugs (pitressin and theophylline) which increase toad bladder intracellular cyclic AMP concentration. These data support the concept that cyclic AMP may be the mediator of PTH-induced phosphate transport inhibition in the toad bladder.

Animals↗
PubMed1998

Tachykinin receptors in the small intestine of the cane toad (Bufo marinus): a radioligand binding and functional study.

In this study, we have used radioligand binding and functional techniques to investigate tachykinin receptors in the small intestine of the cane toad Bufo marinus. The radioligand [125I]Bolton-Hunter [Sar9,Met(O2)11]substance P (selective at mammalian NK-1 receptors) showed no specific binding. Specific binding of [125I]Bolton-Hunter substance P ([125I]BHSP) was saturable, of high affinity (Kd 0.3 nM) and was inhibited by SP (IC50 0.64 nM) > ranakinin approximately neurokinin A (NKA) > or = SP(5-11) > or = neuropeptide gamma > or = scyliorhinin II > scyliorhinin I > or = [Sar9]-SP > or = neurokinin B approximately physalaemin approximately carassin >> SP(7-11) approximately eledoisin > or = SP(4-11) approximately SP(6-11). Binding was also inhibited by Gpp[NH]p > or = GTPgammaS > App[NH]p, indicating a G-protein coupled receptor. The order of potency of tachykinins and analogues in contracting the isolated lower small intestine was carassin (EC50 1.4 nM) > eledoisin approximately SP > or = physalaemin > or = ranakinin > SP(6-11) > scyliorhinin II > or = neuropeptide gamma > neurokinin B approximately NKA approximately scyliorhinin I > or = SP(4-11) > or = SP(5-11) > [Sar9]SP > SP(7-11). In both studies, the selective mammalian NK-1, NK-2 and NK-3 receptor agonists [Sar9,Met(O2)11]SP, [Lys5,Me-Leu9,Nle10]NKA(4-10) and senktide were weak or ineffective. There was a strong positive correlation between the pD2 and pIC50 values for mammalian tachykinins and analogues (r = 0.907), but not for the non-mammalian tachykinins, which were all full agonists but variable binding competitors. [Sar9,Met(O2)11]-SP(pD2 5.7) was approximately 25-fold less potent as an agonist than [Sar9]SP, which was itself 25-fold weaker than SP. Responses to SP were significantly reduced (n = 8, P<0.001) by the antagonist [D-Arg1,D-Trp7,9,Leu11]-SP (spantide; 1 microM). Highly selective NK-1 receptor antagonists including CP 99994 and GR 82334 (both 1 microM) were ineffective in both functional and binding studies. Tetrodotoxin (1 microM) did not inhibit contractile responses to SP, NKA and senktide. In summary, this study has shown the presence of one or more tachykinin receptor in the toad intestine. The binding site recognised by [125I]BHSP prefers SP and ranakinin. This toad "NK-1-like receptor" differs from the mammalian NK-1 receptor in having a low affinity for all mammalian NK-1 selective ligands, including antagonists. For some non-mammalian peptides, their high potency as contractile agonists relative to their poor binding affinity suggests the existence of other tachykinin receptors in the toad small intestine.

Acetylcholine↗
PubMed2002

The functionality of female reciprocal calls in the Iberian midwife toad (Alytes cisternasii): female-female acoustic competition?

Female midwife toads (genus Alytes) emit highly variable reciprocal calls of unclear function prior to and during courtship. In some species, female-female competition, expressed as physical fighting, has been reported. Males of Majorcan midwife toads (Alytes muletensis) show phonotactic response to female calls, and females of Iberian midwife toads (Alytes cisternasii) respond differently according to the male call characteristics. In this study, I test the hypothesis of female-female acoustic competition as an additional function of female reciprocal calls. Playback tests indicate that female calls are not clearly involved in female acoustic competition in the Iberian midwife toad, therefore female calls could be directed at males rather than towards competitive females.

Animals↗
PubMed2001

Failed recruitment of southern toads (Bufo terrestris) in a trace element-contaminated breeding habitat: direct and indirect effects that may lead to a local population sink.

We conducted a transplant study in which embryonic southern toads (Bufo terrestris) were held in a site polluted with coal ash (site AB; containing As, Cd, Cr, Cu, Se, and other elements) and a reference site (site R) through hatching and early larval development. To examine the remainder of the larval period, surviving larvae in AB were then transplanted to R and back-transplanted to AB, whereas surviving larvae from R were back-transplanted to R. Survival through early larval development was lower in AB than in R (34% versus 50%). However, site of hatching did not influence traits later in development (larval metabolic rate, larval morphology, duration of larval period, size at metamorphosis, or average hopping distance by metamorphs). Toads that spent the entire larval period in R had high rates of survival (70-94% of individuals transplanted after the embryonic period) regardless of where they spent the embryonic and early larval period. However, toads held in AB for the duration of the larval period suffered 100% mortality. Algal resources were scarce and their trace element concentrations high in AB compared to R, suggesting that mortality of larval toads resulted from a combination of direct toxicity (via sediment- and foodborne exposure) and indirect effects on resource abundance. The study suggests that the widespread practice of disposing of coal ash in open aquatic basins may result in sink habitats for some amphibian populations.

Animals↗
PubMed1986

Annual cycle of plasma thyroid hormone levels in the toad, Bufo japonicus.

Plasma thyroxine (T4) of the toad, Bufo japonicus formosus, was monitored monthly from March, 1981 to February, 1982. Toads were captured at Sayama, Saitama Prefecture, and individual blood samples were collected from the heart soon after capture in the field. The plasma T4 levels were minimal in November for males (0.096 ng/ml) and in December for females (0.038 ng/ml). Levels increased during the resting stage in winter and reached a peak in March, about 1 week before the breeding migration, in both males (0.48 ng/ml) and females (0.66 ng/ml). After breeding occurred in early April, the T4 levels fell rapidly to nearly the minimum in females (0.088 ng/ml) and to an intermediate level in males (0.26 ng/ml). During summer, the T4 levels were low (between 0.1 and 0.3 ng/ml) but were significantly higher than the minimum in both sexes. Males showed significantly higher T4 levels than females in January, April, October, and December. Changes in plasma T4 levels around the breeding period were studied in greater detail with toads collected in March at Shiki, Saitama Prefecture. Extremely high levels of T4 (1.72 ng/ml) were detected in both male and female toads collected in the breeding pond, showing a secondary rise of the T4 level at arrival at the breeding pond. Plasma triiodothyronine (T3) levels followed patterns similar to those of T4, although the concentrations of T3 were extremely low (between undetectable level and 116 pg/ml). The initial rise of the thyroid hormone level in winter may be related to energy metabolism at the low temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Amplexus induces surge of luteinizing hormone in male toads, Bufo japonicus.

At mating time in the wild, male toads (Bufo japonicus) exhibit a surge in circulating luteinizing hormone (LH) that is thought to result in spermiation. Experiments were performed to identify proximate control of this gonadotropin surge. Male toads migrating to a breeding pond were captured and put in plastic containers either with equal numbers of females or without females. All the males placed with the females clasped them in amplexus that lasted for about 12 hr. During this period, plasma LH and follicle-stimulating hormone levels increased progressively to about 25 and 2 times the initial levels, respectively, and then returned to the initial levels. No significant increases in plasma gonadotropin levels were observed in the males kept without females. These results suggest that the amplexus directly induced the LH surge, but do not preclude control by pheromonal or visual stimuli. To isolate effects of these factors, solitary male toads were kept with dummies of the female. The dummy was a block of "konnyaku," Japanese food whose component is mannan extracted from the root of a plant. Konnyaku is highly elastic, white in color, and virtually odorless. Thus, these dummies felt, but did not look or smell, realistic. All the males clasped their dummy and formed amplexus for 12 hr or more; an LH surge indistinguishable from that with the females was observed. It is concluded that the amplexus itself is the stimulus that induces the LH surge, and subsequent spermiation, in male toads. A strongly male-biased sex ratio, combined with a need to time spermiation precisely with actual mating, may have resulted in the evolution of this neuroendocrine reflex in male Bufo.

Animals↗
PubMed1992

Low doses of urethane effectively inhibit spinal seizures evoked by sudden cooling of toad isolated spinal cord.

The effect of low doses of urethane on three phases of spinal seizures evoked by sudden cooling (SSSC) of toad isolated spinal cord was studied. In control toads, SSSC began with a latency of 91 +/- 3 sec (mean +/- S.E.M.) exhibiting brief tremors, followed by clonic muscle contractions and finally reaching a tonic contraction (tonic phase). The latency of onset of seizures was significantly enhanced. The tonic phase was markedly abolished in toads pretreated intralymphatically with 0.15 g/kg of urethane. Tremors were the only phase observed in 55% of toads that received doses of 0.2 g/kg, and a total blockade of seizures was seen after doses of 0.25 g/kg of urethane in 50% of the preparations. A possible depressant effect of urethane on transmission mediated by excitatory amino acids is suggested.

Animals↗
PubMed1987

The characterization of the toad splenocytes which bind mouse anti-human IL-2 receptor antibody.

We have utilized two depletion protocols to characterize the spleen cells of the South African clawed toad, which bind specifically mouse-anti-human IL-2 receptor (anti-Tac) antibody and recombinant DNA produced IL-2. When the selectively lymphotoxic reagent, N-CH3-N-nitrosourea (NMU), is injected into adult toads, it removes the thymic cortex and lymphocytes throughout the body required for helper and cytotoxic cell functions. We have also used a monoclonal mouse anti-Xenopus IgM antibody to deplete toad splenocyte populations of surface (s) Ig+ cells. Freshly biopsied and cultured spleen cells were compared with respect to their capacity to bind fluorescent (Fl*-) anti-Tac antibody and its ligand, rIL-2, after a depletion protocol. The results clearly show that a phytohemagglutinin (PHA)/IL-2 sensitive splenocyte population is removed by NMU injection. While many of the remaining NMU insensitive, previously cultured cells are Tac+, they fail to bind rIL-2. Freshly biopsied spleen cells with constitutive IL-2 receptors are found in both the sIg- (T cell enriched) and sIg+ (B cell enriched) populations following panning. Moreover, both populations are able to bind the ligand with equal efficiency. Thus, constitutive IL-2 receptor bearing cells are not restricted to either the T or B cell populations. The predominant PHA activatable, rIL-2 binding cell populations of the toad appear to be T cells which are involved with helper and cytotoxic functions.

Animals↗
PubMed1987

Toad splenocytes bind human IL-2 and anti-human IL-2 receptor antibody specifically.

Human r-DNA IL-2 and fluorescent (Fl) mouse anti-human IL-2 receptor antibody have been tested separately and in competition with each other for their capacities to bind to the splenocytes of Xenopus laevis, the South African clawed toad. Binding by Fl*-mouse anti-DNP antibody of the same subclass (IgG1, kappa) was used as a control. The results of visual tests using rIL-2 coated fluorescent Covaspheres demonstrate that the human mediator will bind cells of the toad spleen. Moreover, the mediator inhibits binding of the antibody against the human IL-2 receptor, as detected by cytofluorimetry. Some of the IL-2 receptors on the toad cells appear to be constitutive, since they are expressed on freshly biopsied lymphocytes. Activation of these cells in vitro will increase the percentage of those cells able to bind both the anti-receptor antibody and rIL-2. Since the human mediator is only able to modulate in vivo immune activity in antigen-activated toads, it appears that in spite of having some constitutive IL-2 receptors, a quantitative increase in receptor expression is required before immunological behavior can be effected. More stringent controls of receptor expression may have provided an additional regulatory level as mammalian mechanisms evolved.

Animals↗
PubMed1986

Volume regulation in salt-acclimated toad (Bufo viridis): the role of urea and the urinary bladder.

Body water (weight) was studied in the euryhaline toad Bufo viridis during high salt (500 mOsm NaCl) acclimation. Plasma osmolality was greatly increased upon salt acclimation mainly by urea, and was always hyperosmotic to the ambient solution. Water content was regulated quite efficiently in slowly acclimated undisturbed toads. Repeatedly catheterized toads behaved like osmometers when transferred to hyperosmotic solutions. Total urea loss was greatly reduced in salt acclimated toads, suggesting urine was not voided under these conditions. It is concluded that urea accumulation, inhibition of the urine voiding response and the urine in the bladder are the principal factors involved in volume regulation under conditions of salt acclimation.

Acclimatization↗
PubMed1987

Comparative effects of angiotensin II on osmotic water permeability in the toad (Bufo arenarum).

The possible relationship between the renin-angiotensin system and water balance in the toad Bufo arenarum has been indirectly explored. A positive correlation was found between the hydrosmotic response of ventral pelvic toad skin to angiotensin II (A II) and some age indicators (body weight, snout-urostyle length or head width). A different hydrosmotic response for oxytocin and isoproterenol (but not for A II) was found between four cutaneous regions of toad body. We conclude that A II may not be directly involved in the regulation of water balance mediated by water absorption across the skin of Bufo arenarum toads.

Angiotensin II↗
PubMed1987

Antidiuretic responses to osmotic, ionic or volume stimulation of the brain in the unanesthetized toad, Bufo arenarum Hensel.

Single injections of 15 microliter of 1 M NaCl or 2M sucrose into the carotid system of normal unanesthetized toads induced a rapid and significant decrease of urine production. This appears to be the first report on the existence of a Verney-like phenomena in a non-mammalian vertebrate. This antidiuresis was blocked out in the hypophysectomized diencephalic lesioned animal. Concurrently, small volumes (4 microliters) of 1 M NaCl but not 2 M sucrose also induced antidiuresis when injected into the midbrain tegmentum of normal but not of hypophysectomized diencephalic lesioned toads. Larger volumes (6 microliters) of 2 M sucrose were needed to induce a similar antidiuresis in normals. Furthermore, even larger volumes (more than 8 microliters) of any of both solutions were able to induce oliguria in normal as well as in hypophysectomized toads. On the basis of these results, the following conclusion would be drawn: the brain of the toad is able to detect ionic and osmotic stimuli, these stimuli apparently affect different receptors in the brain, the antidiuresis initiated by these mechanisms is dependent on diencephalic integrity.

Animals↗
PubMed1989

Comparative ultrastructure of maturing toad (Bufo ictericus) and rabbit (Oryctolagus cuniculus) erythroid cells with regard to hemoglobin biosynthesis.

1. Toad and rabbit maturing erythroid cells were comparatively analysed with regard to their ultrastructural modifications involved in hemoglobin (Hb) biosynthesis. 2. The mitochondrial inner membrane differentiates to a lamellated body that, successively, gives rise to prehemosomal vesicles, prohemosomes, and to hemoglobinized organelles called hemosomes. 3. The prehemosomal vesicle involves ferruginous inclusions, taken as iron sources for heme biosynthesis, as well as the polypeptide globin chains, assembling themselves in the course of volume reduction. 4. From the prohemosomal stage onwards, where possibly heme biosynthesis occurs, hemosomes are formed; these organelles are presumably sites where the final Hb biosynthesis could take place. 5. All development stages leading to hemosome formation are similar in toad and rabbit erythroid cells, except that, in the toad, the structural prohemosome characteristics persist in hemosomes. 6. Through toad erythroid cell fractionation and electrophoresis of the organelle lysate supernatant, a wide and a weak cytoplasmic Hb bands were obtained; the latter coincides with the intraorganellar Hb band.

Animals↗