Showing papers on "Toad published in 1979"

Light adaptation in toad rods: requirement for an internal messenger which is not calcium.

Abstract: 1. The mechanism of light adaptation was investigated by recording intracellularly from single rods in the isolated, superfused retina of the toad, Bufo marinus. Steady background lights produce decreases in rod sensitivity and changes in response wave form similar to those previously observed in the toad eyecup. 2. The sensitivity of a dark-adapted rod is halved by a background light which bleaches about 4 rhodopsins per rod per second. Since a toad rod contains over 2000 disks, a rhodopsin bleached in one disk must alter the effectiveness of rhodopsins bleached in others. This could occur if the state of adaptation in the rod were regulated by the concentration of some diffusable substance. 3. This diffusable substance cannot be Ca2+. Increases in intracellular Ca2+, produced experimentally either by increasing extracellular Ca2+ or by facilitating Ca2+ permeability into the rod with the ionophore X537A, cause a hyperpolarization of membrane potential and a decrease in response amplitude; but they do not produce changes in sensitivity and response wave form like those produced by background light. 4. Either Ca2+ is not the internal transmitter released from the disks during excitation, or the disks release or otherwise alter the concentration of a second diffusable substance, in addition to Ca2+, which regulates the state of adaptation.

Endogenous digitalis-like activity in the plasma of the toad Bufo marinus.

Abstract: CARDIAC GLYCOSIDES derived from plants have a major role in the pharmacotherapy of cardiac disease, and, because they bind to and inhibit (Na+ + K+)ATPase, are important in studies of ion transport mechanisms. In the animal kingdom, structurally related compounds with cardiotonic activity have been shown to exist in the poison glands of bufonid toads1, but this area has received little attention. Recently we developed a sensitive radioreceptor assay for the detection of endogenous ‘digitalis-like’ agonists in animals2. This assay depends on the ability of a substance to compete with 3H-ouabain for binding to (Na+ + K+)ATPase on human red cells. Using this assay, together with assays for inhibition of K transport and (Na+ + K+)ATPase activity, we found high concentrations of ‘digitalis-like’ activity in the skin of several species of Amphibia2. Although this activity is presumably present in skin s aa protective toxin, it is possible that it might, under some circumstances, also function as an endogenous inhibitor of (Na+ + K+)ATPase. We now demonstrate, using both receptor and immunoassays, that high concentrations of digitalis-like activity are present in the plasma of the toad, Bufo marinus. As cellular (Na+ + K+)ATPase would presumably be exposed to this endogenous digitalis-like activity, it may have an important, but as yet undetermined, function in this species.

Production of tetraploid and homozygous diploid amphibians by suppression of first cleavage

Abstract: Tetraploid and genetically homozygous diploid Xenopus can be produced conveniently, in large numbers, by suppressing the first cleavage division of eggs through the application of hydrostatic pressure. The pressure-induced disruption of the mitotic spindle during the first division of a diploid zygote of the African clawed toad results in a tetraploid embryo. A homozygous diploid embryo can be derived by inhibiting the first cleavage of a parthenogenetically activated haploid egg. Both tetraploid and homozygous diploid larvae are viable and successfully undergo metamorphosis.

Possible roles for microtubules and microfilaments in ADH action on toad urinary bladder.

Abstract: Intramembranous particle aggregates in the luminal membrane of toad bladder granular cells after vasopressin stimulation have been found to correlate closely and specifically with induced alteratio...

Acid-base relationships in the blood of the toad, Bufo marinus. III. The effects of burrowing.

Abstract: When Bufo marinus burrows, the skin becomes intimately surrounded by substrate but the nares always remain exposed to the surface air. Upon entering into a state of dormancy the animal hypoventilates and this together with the loss of the skin as a respiratory site results in a rise in arterial blood P co co2 despite a probable decline in metabolism. Even though lung ventilation falls, the toad regulates blood pH and the respiratory acidosis is progressively compensated for by a progressive increase in plasma [HCO 3 -] along the course of an elevated P CO CO2 isopleth. At steady state, the acidosis is fully compensated for by a new equilibrium ratio of HCO 3 - to P CO CO2 at the same pH as the non-burrowed animal. Arousal from the dormant state at this time results in a marked lung hyperventilation and a sharp decline in body CO 2 stores

Light and scanning microscopy of the tongue and its gustatory organs in the common toad, Bufo bufo (L.).

Abstract: Unlike frogs and European tree frogs, the common toad Bufo bufo possesses a tongue lacking filiform papillae on its dorsal surface. Instead, the mucosal epithelium forms irregular, high folds, dividing the surface of the tongue into numerous separate compartments. At the bottom of those compartments occur openings of tubular glands and singular ciliated cells. In a strongly distended tongue the folds of mucosa disappear, and the regions of glandular orifices assume a shape of pocket-like recesses. The taste discs with an average diameter of 120 micrograms are localized on the top of markedly shortened fungiform papillae. The superficial layer of taste discs contains a single type of glandular supporting cells, which in part of discs show features suggesting their gradual dezintegration, probably related to the process of cellular turnover in gustatory organs.

Thyroxine and Na+ transport in toad: role in transition from poikilo- to homeothermy.

Abstract: The effects of thyroxine (T4) on Na+ transport, oxygen consumption (QO2), and Na+-K+-ATPase activity were studied in the urinary bladder and liver of the toad Bufo marinus. In the bladder, T4 in vitro (10(-8) to 10(-6) M) had no significant effect on these parameters during 15 h of incubation. When injected intraperitoneally (approximately 20 microgram/(kg body wt.day) for 6 days), T4 lowered base-line, short-circuit current by 62% (P less than 0.0025) and potential difference by 37% (P less than 0.001), increasing tissue resistance by 40% (P less than 0.02). T4 depressed QO2/DNA (-25%, P less than 0.05) with no significant effect on Na+-K+-ATPase activity. In liver, T4 increased the recovery per cell DNA of mitochondrial proteins by 32% (P less than 0.025), corresponding to an increased QO2 (stage IV) of isolated mitochondria per cell DNA (+54%, P less than 0.01). There was no significant effect on Na+-K+-ATPase activity. These results suggest that, unlike its function in the rat, T4 in the toad does not regulate cellular thermogenesis by inducing Na+-K+-ATPase. This major difference could account at least in part for the transition from poikilothermy to homeothermy. In addition, T4 has a distinct inhibitory effect on Na+ transport in the urinary bladder, which suggests an antagonism to the action of aldosterone.

Uncoupling agents distinguish between the effects of metabolic inhibitors and transport inhibitors.

Abstract: In studies with toad bladders, the uncoupling agent 2,4-dinitrophenol (DNP) reversed the inhibition of CO2 production produced by direct inhibition of transport. In contrast, DNP did not reverse the inhibition of CO2 production brought about by metabolic inhibitors. Therefore, the response to DNP distinguished between inhibition of transport and metabolism; this approach may be useful for the investigation of factors that regulate active transport.

Tissue distribution of immunoreactive somatostatin in the south african clawed toad (xenopus laevis)

Abstract: Immunoreactive somatostatin is present in the brain, gut and pancreas of the South African clawed toad, but is absent from the skin, a rich source of many other brain-gut peptides.

Toad carbonic anhydrase: purification of the enzyme from erythrocytes of Bufo marinus and comparison with the enzyme activity in the urinary bladder.

Abstract: 1. 1. Two forms of carbonic anhydrase, having isoelectric points of 6.1 and 5.8, were purified from erythrocytes of the toad, Bufo marinus, and the presence of a third form, pI = 5.4, was demonstrated. 2. 2. Each of the two purified isozymes catalyzed the hydration of CO2 and the hydrolysis of nitrophenyl acetate esters at rates characteristic of Type C (or high-activity) forms of carbonic anhydrase. 3. 3. Both forms of the erythrocyte enzyme have similar molecular weights (approx 29,000), amino acid composition, sensitivity to acetazolamide, and kinetic properties. 4. 4. The epithelium of the toad's urinary bladder also was found to contain significant amounts of carbonic anhydrase, which appears by isoelectric focusing to be indistinguishable from the enzyme isolated from the erythrocyte.

Effect of hypertonicity and colchicine on intramembranous particle aggregation in toad urinary bladder.

Abstract: Colchicine, an agent which disrupts microtubules, inhibits the vasopressin (VP)-induced increase in water permeability as well as intramembranous particle (IMP) aggregation in the luminal plasma membrane of granular cells of toad urinary bladder. However, the hydroosmotic response induced by serosal hypertonicity is not affected by colchicine. The present investigation was initiated to establish whether serosal hypertonicity is associated with IMP aggregation and whether the aggregation, if present, is altered by colchicine. The experimental half of paired hemibladders from the toad, Bufo marinus, treated with 0.1 mM colchicine for 4 h prior to exposure to serosal mannitol (240 mM) demonstrated no significant difference in osmotic water How (Jv) (1.03 × 0.18 vs. 1.13 ± 0.22μl · min−1 · cm−2; p>0.20) when compared with control hemibladders. Similarly, comparison of control and colchicine-treated bladders revealed no difference in the number of IMP aggregation sites per area of membrane (17.8 ± 2.0 vs. 24.7 ± 3.5/100μm; p>0.10), the relative area of membrane occupied by these sites (0.30 ± 0.06 vs. 0.39 ± 0.07%; p>0.10) or the mean size of the aggregates (17.0 ± 1.4 vs. 15.8 ± 1.0 × 103 μm2; p > 0.20). These results indicate that in toad bladder the increase in Jv induced by serosal hypertonicity is associated with IMP aggregation. Secondly, an intact microtubule system is not required to induce the hydroosmotic or the aggregation responses. If, as has been proposed, the cellular actions of VP and serosal hypertonicity share a common pathway to bring about an increase in osmotic water permeability and cause IMP aggregation in the luminal membrane of the granular cell, the present results suggest that the pathway begins at a step subsequent not only to the generation of cAMP, but also beyond the involvement of the microtubule system.

Larval Growth and Development of the Japanese Toad, Bufo bufo formosus, at Iwakura, Kyoto

Abstract: Yearly differences in the growth and development of the larvalJapanese common toad, Bufo bufo formesus, growing in temporary pools ina swamp at Iwakura, Kyoto, were compared for the 1977 and 1978 seasons. Tadpoles showed more rapid development in 1978 than in 1977 due to a more delayed breeding season and subsequent higher water ternperature in 1978. However, development of the 1978 larvae was retarded in the later period, resulting in similar embryonic and larval periods of 58-60 days in both years, Developmental retardation in 1978 was assumed to be the result of density effect. Tadpoles in 1977 had larger body sizes than those in 1978, especially in body weights, and such differences were presumed to be caused by a differential population density. Tadpoles delayed in development tended to have smaller body sizes than those reached at the same developmental stage earlier. Body proportions showed small yearly differences compared with absolute measurements, and were almost constant from Stages 31 to 39. This tendency indicates that body proportions are of value for systematic work. Larval survival at Iwakura was briefly noted: a female toad spawns ca. 5,OOO eggs, the average hatching rate being about 90.20/o, and 5.5-20.20/e of hatched embryos are assumed to complete metamorphosis. Whether the observed difference in metamorphic rates has significance is yet to be clarified. Introduction Tables of normal developmental stages, establishing a basis for comparing and describing anuran embryos and larvae, have been made by many authors since the end ofthe last century. LiMBAuGH and VoLpE (1957) made a complete table ofnormal developmental stages from fertilization to metamorphosis for Bufo vallicePs, and, later, GosNER (1960) modified it for other anuran species. These tables are currently used in various fields of anuran bioiogy (e.g. BEiswENGER, 1978; GAuDiN, 1978; DuELLMAN and ToFT, 1979). It has rarely been examined, however, whether or not developmental patterns of tadpoles grown under natural conditions completely fit these laboratory-made tables. Moreover, the ranges of variation both in rates of development and in the morphometrics of a given stage, have been inadequately investigated in tadpoles of the same species grown under different conditions. The Japanese common toad, Bufo bufoformosus, deposits eggs in various bodies of still water, such as ponds, pools, ditches, and rice fields (MATsui, 1975); at Iwakura, where the present investigation was performed, toads breed in temporary pools in the marsh. Different breeding seasons resulted from yearly meteorological fluctuations.

Species differences in the ouabain sensitivity of the small intestine in contractile response.

Abstract: Ouabain was examined for effect on the mechanical response of the ileum isolated from eleven animal species, dog, cat, rabbit, guinea pig, rat, vole, mouse, cock, pigeon, frog and toad. In isotonic recording, ouabain induced a sustained contraction in ileum isolated from some species. It caused a transient contraction on following by a relaxation in others. The ouabain sensitivities of a contractile response in the ilea from eleven species, as demonstrated by the estimation of ED50, was divided into four groups. That is, a high sensitive group; frog (ED50=9.0×10-8M), cat (9.3×10-8M), pigeon (3.5×10-7M) and cock (5.1×10-7M), a sensitive group; rabbit (1.1×10-6M), vole (2.3×10-6M) and guinea pig (2.7×10-6M), a low sensitive group; mouse (1.7×10-5M) and rat (9.7×10-5M) and an insensitive group; toad (>10-3M). Although ED50 in the dog was not able to be calculated, its sensitivity seems to belong to the high sensitive group. On the other hand, ED50 of acetylcholine (Ach) in thc ilea, isolated from these species were estimated in a narrow range of concentration from 5×10-9M to 5×10-8M. There were species differences in ouabain sensitivity for ileal contractile response but not in Ach sensitivity. A distinct correlation was found between the mechanical response to ouabain and the inhibitory potency of ouabain for Na, K-ATPase reported by Repke et al. These results seem to confirm that ouabain may induce a contraction by a mechanism which inhibits an electrogenic Na pump or Na, K-ATPase in the intestinal smooth muscle cell and which induces a depolarization.

Morphology, histochemistry and biochemistry of the oviduct of the toad, Bufo vulgaris (Anura, Amphibia), during the annual reproductive cycle.

Abstract: On the basis of histological and histochemical characteristics the oviduct of adult Bufo vulgaris can be separated into six zones. These characteristics include mainly the relative abundance of secretory and ciliated epithelial cells, mucosal foldings, tubular glands and the staining properties of the secretory elements. The VI zone (uterine segment) is totally deprived of tubular glands and is profoundly rich in epithelial secretory cells. These cells and the tubular glands, when well-developed, are rich in neutral and acid mucins in the preovulatory phase, whereas this content is greatly diminished after ovulation. Similarly, the weight and the length of the oviduct displays a marked seasonal pattern. The same is observed for its protein content and acid and alkaline phosphatases. These parameters show the highest values in the preovulatory period and lowest after ovulation. The toad oviduct also displays marked hydroxysteroid dehydrogenase activity along the mucosal epithelium. Its functional significance remains a matter of debate, however. A marked parallelism between the present data and those obtained by others in other amphibians indicates the existence of a common pattern of seasonal modifications correlated mainly with the release of the eggs and the formation of their multi-layered coat.