Studies on the sedative effect of barbital sodium on frogs and toads from different habitats.
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Animals↗
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[Study of the mechanism of resistance of the toad to the sperm-migrating action of adrenalin observed in the male frog; trial with toad venom in the male frog].
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Amphibian Venoms↗
Systematic analysis of animals used in medieval Azerbaijan medicine.
In order to study the special composition of animals used in the medieval medicine of Azerbaijan, a wide range of medieval sources on medicine and pharmacognosy from the collection of the Institute of Manuscripts of the Azerbaijan Academy of Sciences in Baku has been studied. About 40 medieval sources from the 10-18th centuries including 17 manuscripts in Turkic, Persian and Arabic have been selected as the objects of this study. As a result, 150 species of animals described in medieval Azerbaijani books on medicine and pharmacy have been identified. Many of the identified animals are mammals, (47 species or 31% of total number of identified species). The medieval authors describe 12 species of reptiles and 4 species of Amphibians (frogs, toads, salamanders and tree-frogs (Hyla arborea). 15 species of fishes described in medieval manuscripts have been identified. The identified molluscs are cuttlefish (Sepia officinalis), mussel (Mytilus edulis), octopus (Octopus vulgaris) and snail (Helix pomatia). Most crustaceans used in medieval Azerbaijan medicine belong to Decopoda. Medieval manuscripts contain numerous names of various worms and insects (ants, flies, beetles, etc.), however their exact identification is rather difficult. As usual, medieval authors unite a number of species under one name and do not give sufficient information about their morphology. Results of the research create grounds for the idea that the recommendations of the medieval authors on the medicinal application of animals can be applied to modern medicine once they have been experimentally and clinically tested.
Animals↗
Microelectrode study of K+ accumulation by tight epithelia: I. Baseline values of split frog skin and toad urinary bladder.
Toad bladder and split frog skin were impaled with fine-tipped single- and double-barrelled K+-selective microelectrodes. In order to circumvent membrane damage induced by impaling toad bladder, a null point method was developed, involving elevations of mucosal potassium concentration. The results suggest that intracellular potassium activity of short-circuited toad bladder is approximately 82 mM, twice as large as earlier estimates. Far more stable and rigorously defined intracellular measurements were recorded from short-circuited split frog skins. The intracellular positions of the micropipette and microelectrode tips were verified by transient hyperpolarizations of the membrane potential with mucosal amiloride or by transient depolarizations with serosal barium or strophanthidin. Simultaneous impalement of distant cells with separate micropipettes demonstrated that both the baseline membrane potentials and the responses to depolarizing agents were similar, further documenting that frog skin is a functional syncytium. Measurements with double-barrelled microelectrodes and simultaneous single-barrelled microelectrodes and reference micropipettes suggest that the intracellular potassium activity is about 104 mM, lower than previously reported. Taken together with measurements of intracellular potassium concentration, this datum suggests that potassium is uniformly distributed within the epithelial cells.
Animals↗
Phosphatidylinositol-stimulated phosphorylation of an inhibitory subunit of cGMP phosphodiesterase in vertebrate rod photoreceptors.
An inhibitory subunit (P gamma) of cGMP phosphodiesterase from vertebrate rod photoreceptors (frog, toad, and bovine) was phosphorylated by cytosolic protein kinase(s) derived from intact frog rod outer segments. The phosphorylation of frog P gamma was stimulated by phosphatidylinositol but not by cAMP or cGMP. One- and two-dimensional gel electrophoresis revealed that 70-80% of P gamma was phosphorylated with 1 mol of phosphate per frog P gamma under optimal conditions. A peptide that derived from an active domain of bovine P gamma was also phosphorylated. Phosphorylation of frog P gamma was inhibited by addition of the peptide to the reaction mixture. Phosphorylation of frog P gamma was also inhibited by addition of transducin subunits or active (P gamma-less) cGMP phosphodiesterase. Okadaic acid, on the other hand, enhanced P gamma phosphorylation, suggesting the presence of protein phosphatase(s) in the cytosolic fraction. These data suggest another mechanism for the regulation of cGMP phosphodiesterase in vertebrate rod photoreceptors.
3',5'-Cyclic-GMP Phosphodiesterases↗
Amphibian respiration and olfaction and their relationships: from Robert Townson (1794) to the present.
The present review examines the developments in the elucidation of the mechanisms of amphibian respiration and olfaction. Research in these two areas has largely proceeded along independent lines, despite the fact that ventilation of the nasobuccopharyngeal cavity is a basic element in both functions. The English naturalist Robert Townson demonstrated, in the 1790s, that amphibians, contrary to general belief, ventilated the lungs by a pressure-pump mechanism. Frogs and other amphibians respire by alternatively dilating and contracting the buccopharyngeal cavity. During dilatation, with the mouth and glottis closed, air is sucked in through the open nostrils to fill the cavity. During contraction of the throat, with nostrils closed and glottis open, the air in the buccopharyngeal cavity is pressed into the lungs. During expiration, the glottis and nostrils open and air is expelled from the lungs 'by their own contraction from a state of distention'. Herholdt (1801), a Danish army surgeon, independently described the buccal pressure-pump mechanism in frogs, his experiments being confirmed by the commissioners of the Société Philomatique in Paris. Haro (1842) reintroduced a suction mechanism for amphibian respiration, which Panizza (1845) refuted: excision of the tympanic membranes prevented lung inflation, the air in the buccopharyngeal cavity leaving through the tympanum holes. Closure of the holes with the fingers restored lung inflation. The importance of cutaneous respiration in frogs and other amphibians was discovered by Spallanzani (1803), who found that frogs might survive excision of the lungs and that the amounts of exhaled carbon dioxide were small compared with those eliminated through the skin. Edwards (1824) confirmed and extended Spallanzani's findings, and Regnault & Reiset (1849) attempted to establish the relative importance of skin and lungs as respiratory organs in frogs. The problem was solved by Krogh (1904a) who measured respiration through the skin and lungs separately and simultaneously. Krogh (1904a) confirmed that carbon dioxide was chiefly eliminated through the skin, correlated with its high diffusion rate in water and tissue, whereas the pattern of oxygen uptake varied seasonally, the pulmonary uptake being lower than the cutaneous during autumn and winter, but substantially higher during the breeding period. Dolk & Postma (1927) confirmed this respiratory pattern. More recently, Hutchison and coworkers have examined the relative role of pulmonary and cutaneous gas exchange in a large number of amphibians, equipped with head masks for the separate measurement of the lung respiration in normally ventilating animals (Vinegar & Hutchison, 1965; Guimond & Hutchison, 1968; Hutchison, Whitford & Kohl, 1968; Whitford & Hutchison, 1963, 1965, 1966). As early as 1758, Rösel von Rosenhof suggested that the lungs of frogs in water functioned as hydrostatic organs that permitted the animal to float at the surface or rest on the bottom of the pond. The suggestion was inspired by observations made in the second half of the seventeenth century by members of the Royal Academy of Sciences in Paris. The French anatomists demonstrated that a tortoise, presumably the European freshwater turtle Emys orbicularis, could regulate its buoyancy by changing the volume of the lungs, to descend passively or ascend in the water. The hydrostatic function of the lungs has been repeatedly rediscovered, by Emery (1869) in the frog, by Marcacci (1895) in frogs, toads and salamanders, by Whipple (1906b) in a newt, by Willem (1920, 1931) in frogs and Xenopus laevis, by Speer 1942) in several anurans and urodeles, and finally by de Jongh (1972) in Xenopus laevis. In the second half of the nineteenth century a number of important papers appeared which confirmed and extended Townson's (1794) and Panizza's (1845) analysis of the normal respiratory movements in frogs. (ABSTRACT TRUNCATED)
Amphibians↗
ELECTRICAL EXCITABILITY OF ISOLATED FROG SKIN AND TOAD BLADDER.
When current of proper polarity and sufficient intensity is passed across isolated frog skin or toad bladder, an action potential of about 200 mv and 10 msec. duration with a sharp threshold and refractory period of several seconds' duration is elicited. Interruption of current during the action potential abolishes the response, and, as shown by appropriate bridge measurements, this occurs because the action potential results from resistance variations during the current flow. The ionic composition of the medium bathing the frog skin was varied, and it was found that the response is relatively insensitive to changes in the solution bathing the inner surface, but rapidly and reversibly affected by changes in the outer solution, particularly by replacement of sodium with potassium and by variations of calcium concentration. It was also observed that the resistance of the skin and action potential across it are reversibly altered by metabolic inhibitors and that these alterations occur independently of any changes in the intrinsic EMF of the system. From the finding that the action potential across frog skin and toad bladder results from a time-variant resistance, it is argued that this same phenomenon can be the basis of electrical excitability in general. This would attribute physical significance to the equivalent circuit commonly employed to represent the plasma membrane; i.e., the plasma membrane would be a mosaic structure of spatially separate permselective regions.
Action Potentials↗
Spontaneous larval Gnathostoma nipponicum infection in frogs.
From June 1993 to September 1997, a survey was carried out for the prevalence of larval Gnathostoma nipponicum infection in several kinds of frogs, toads, and their tadpoles collected from an endemic area of this nematode in Aomori Prefecture. Two frog species, one of 436 (0.2%) Rana nigromaculata and 51 of 147 (34.7%) R. catesbeiana were infected, and a total of 446 advanced third-stage larvae (AdL3) of G. nipponicum were recovered. These results confirmed that two frog species which can serve as the second intermediate and/or paratenic hosts in the life cycle of G. nipponicum exist in nature. This report is the first record of spontaneous infection of frogs with AdL3 of G. nipponicum.
Animals↗
Blood parasites of amphibians from Algonquin Park, Ontario.
During a 5 wk period beginning May 25, 1983, 329 amphibians, which included specimens of Rana catesbeiana Shaw, Rana clamitans Latreille, Rana septentrionalis Baird, Rana sylvatica LeConte, Hyla crucifer Wied, Bufo americanus Holbrook, and Plethodon cinereus Green, from Lake Sasajewun, Algonquin Park, Ontario, Canada were examined for blood parasites. The prevalences of species of Trypanosoma, Haemogregarina, Lankesterella, Babesiasoma, and Thrombocytozoons in these amphibians were determined. Two species of microfilaria (probably Foleyella spp.) and two intraerythrocytic forms, inclusions of an icosahedral cytoplasmic DNA virus (ICDV) and groups of rickettsial organisms, were also observed. The following are new host records: Trypanosoma ranarum (Lankester, 1871) in B. americanus; Trypanosoma ranarum (Lankester, 1871) in R. sylvatica; Trypanosoma pipientis Diamond, 1950, Babesiasoma stableri Schmittner and McGhee, 1961 and Thrombocytozoons ranarum Tchacarof, 1963 in R. septentrionalis. The aquatic frogs generally showed a much higher prevalence of infection with blood parasites than the terrestrial frogs, toads and salamanders, which is suggestive of an aquatic vector. The leech Batracobdella picta Verrill, 1872, which was found on many of the aquatic frogs, is the most likely vector in the study area. Also, an increasing prevalence of parasites was noted with increasing sizes (ages) of Rana clamitans and R. catesbeiana suggesting that longer exposure to water makes these species more likely to acquire blood parasites. The presence of Trypanosoma ranarum in B. americanus appeared to coincide with their attainment of sexual maturity.
Amphibians↗
FILAMENT LENGTHS IN STRIATED MUSCLE.
Filament lengths in resting and excited frog muscles have been measured in the electron microscope, and investigations made of the changes in length that are found under different conditions, to distinguish between those changes which arise during preparation and the actual differences in the living muscles. It is concluded that all the measured differences in filament length are caused by the preparative procedures in ways that can be simply accounted for, and that the filament lengths are the same in both resting and excited muscles at all sarcomere lengths greater than 2.1 micro, viz., A filaments, 1.6 micro; I filaments, 2.05 micro. The fine periodicity visible along the I filaments also has been measured in frog, toad, and rabbit muscles and found to be 406 A.
Aldehydes↗
Conversion of sodium channels to a form sensitive to cyclic AMP by component(s) from red cells.
Sodium transport has been measured in the isolated epithelium from colons of male Sprague-Dawley rats. Sodium transport in colons was induced by pretreating the animals with dexamethasone (6 mg kg-1) which caused the appearance of an amiloride-sensitive short circuit current within a few hours. Forskolin, a diterpene, which activates adenylate cyclase, was found to increase the cyclic adenosine monophosphate (cyclic AMP) content of rat colons and also to increase short circuit current at the same time. However, measurements of chloride and sodium fluxes across the epithelium indicated that forskolin activates chloride secretion but has no effect on sodium transport. In confirmation of (3) it was found that the amiloride-sensitive short circuit current was unchanged after the short circuit current had been increased by forskolin under a variety of conditions. The behaviour of the mammalian colon as indicated in (3) and (4) is unlike that of amphibian sodium transporting epithelia. It is shown that in toad urinary bladder forskolin increases amiloride-sensitive short circuit current. Procedures were investigated which might make sodium transport in the mammalian colon sensitive to cyclic AMP. Exposing the apical surface to sonicated suspensions of nucleated red cells (frog, toad and duck), followed by washing, gave preparations with amiloride-sensitive short circuit currents which were increased by forskolin or dibutyryl cyclic AMP. It would appear that the sodium channel in the mammalian colon, unlike that of amphibian tissues, has lost the ability to have its properties modified by cyclic AMP. Incubation of colons with sonicated suspensions of nucleated red cells apparently modifies the tissues such that sodium transport across the tissue becomes sensitive to the nucleotide.
Amiloride↗
Blockage of Na+ currents through poorly selective cation channels in the apical membrane of frog skin and toad urinary bladder.
The blockage of Na+ movements through the poorly selective cation channels in the apical membrane of frog skin (Rana temporaria) and toad urinary bladder (Bufo marinus) was investigated with noise, impedance analysis and microelectrode techniques. Na+ currents through this pathway were studied with NaCl Ringer solutions on both sides. After removal of Ca2+ and other divalent cations from the mucosal compartment, a considerable part of Isc became insensitive to amiloride. In frog skin, the inhibitory effect of amiloride in mucosal Ca(2+)-free solutions was highly variable. In some experiments a complete lack of inhibition was observed. Similarly, in the absence of amiloride, the inhibitory effect of mucosal Ca2+ varied strongly among frogs. In the absence of mucosal Ca2+, analysis of the fluctuation in Isc revealed a Lorentzian component in the power density spectrum. The corner frequency (fc) of this spontaneous Lorentzian was 12.3 Hz in frog skin and 347 Hz in the toad urinary bladder. In frog skin, nanomolar concentrations of mucosal Ca2+ induced an additional Lorentzian noise component. Its corner frequency shifted upwards with increasing mucosal Ca2+ concentration ([Ca2+]m). The relation between 2 pi fc and [Ca2+]m was linear at small [Ca2+]m whereas a parabolic increase of fc was observed at the highest [Ca2+]m. In the bladder, nanomolar concentrations of mucosal Ca2+ did not induce an additional noise component but modified the spontaneous Lorentzian noise by increasing fc proportionally with [Ca2+]m. Microelectrode recordings demonstrated that at least part of the Ca(2+)-blockable current passes through the granulosum cells and confirmed the apical localization of the poorly selective cation channel. The lack of the inhibitory effect of amiloride in Ca(2+)-free solutions seems to originate from the parallel arrangement of the amiloride- and Ca(2+)-blockable pathways and from influences of the blockage of apical channels on the basolateral membrane conductances. The latter cross-talk seems to find its origin in the voltage dependence of the basolateral membrane conductance [Garty H (1984) J Membr Biol 77:213-222; Nagel W (1985) Pflügers Arch 405 [Suppl 1]:S39-S43].
Amiloride↗
Substance P-related peptides in the hypothalamus of amphibia.
The occurrence of Substance P-(SP)-related peptides in the hypothalamus of three species of Amphibia (newt, clawed, toad, frog) was studied immunohistochemically employing the direct immunofluorescence method or a double-step technique (indirect immunofluorescence followed by the peroxidase-antiperoxidase complex method). SP-like immunopositive fibers are seen throughout the hypothalamus. They are especially abundant in the preoptic area and in the outer zone of the median eminence, suggesting a role of SP-related peptides in the hypothalamo-hypophysial regulation in these animals. Some SP-like neurons are seen in the posterior hypothalamus and in the preoptic area. In the newt, such SP-like immunopositive neurons occur frequently in the preoptic periventricular grey.
Animals↗
The extended branch-arrow model of the formation of retino-tectal connections.
This paper presents XBAM (the Extended Branch-Arrow Model), a new model of the development of the retino-tectal topographic mapping as observed in frog, toad, and goldfish visual systems. The updating process employed by XBAM is distributed in nature and depends upon interactions between branches of retinal fibers, the branches and the boundaries of the tectum and grafts, and the branches and the tectal surface. Results of computer simulation of the model are related to experimental data obtained from tectal and retinal graft and lesion studies, and comparisons are also made with other models.
Animals↗
Corticosteroid 11 beta-hydroxysteroid dehydrogenase activities in vertebrate liver.
In this paper, we examine corticosteroid 11 beta-oxidation and 11-reduction as properties of the microsomal 11 beta-hydroxysteroid dehydrogenase complex in vertebrate livers. No hepatic activity in the oxidative direction (11 beta -dehydrogenase) was found in the frog, toad, mud puppy, shark, and bird livers. In contrast, all mammalian livers had active oxidizing enzymes. Latency, defined as microsome-linked activity released by the detergent Triton DF-18, was a property of 11 beta-dehydrogenase in all mammalian livers. Mammal, bird, and dogfish livers reduced 11-dehydrocorticosteroids (11-reductase), while amphibians and bony fish did not. With the exception of rat liver, latency was a property of all the mammalian liver 11-reductases examined.
11-beta-Hydroxysteroid Dehydrogenases↗
Gonadotropin-releasing hormone in elasmobranch (electric ray, Torpedo marmorata) brain and plasma: chromatographic and immunological evidence for chicken GnRH II and novel molecular forms.
Gonadotropin-releasing hormone (GnRH) peptides in the brain, testis and plasma of an electric ray (Torpedo marmorata) were investigated by gel filtration chromatography, reverse phase high performance liquid chromatography and radioimmunoassay with region-specific antisera. In the brain, two major forms of GnRH were demonstrated. One form had identical chromatographic and immunological properties to chicken GnRH II, and the second, novel, molecular form had structural features in common with mammalian, chicken II and salmon GnRHs. A minor, early-eluting immunoreactive peak, possibly also a novel GnRH, was also evident. Immunoreactive GnRH was not detected in the testis. In the plasma, a single major early-eluting immunoreactive peak was demonstrated. This peak, identical to the minor peak observed in the brain, is likely to represent a novel form of GnRH which has immunological properties in common with mammalian, chicken II and salmon GnRHs. Immunoreactive GnRH was not detected in the plasma of species from other vertebrate classes, including rabbit, chicken, monitor lizard, clawed toad, frog, cichlid fish and lamprey. The finding of chicken GnRH II in a species of Chondrichthyes adds further support to our hypothesis that this widespread structural variant may represent an early-evolved and conserved form of GnRH. The presence of a GnRH molecular form in the plasma of the electric ray suggests that GnRH may reach target organs (pituitary and gonads) via the general circulation in some species of Chondrichthyes.
Animals↗
High-pH form of bovine rhodopsin.
Since the 1930s, the spectrum of vertebrate rhodopsin has been considered to be independent of pH (Lythgoe, R.J. 1937. J. Physiol. 89:331-358; Wald, G. 1938. J. Gen. Physiol. 21:795-832). Here I report that the spectrum of bovine rhodopsin is pH dependent. At pHs greater than 9.0, there is a shift to shorter wavelengths of its 500-nm absorption band. This shift is accounted for by the existence of a high pH form of bovine rhodopsin, with absorption maximum at 494 nm and a slightly lower extinction coefficient. The high-pH form results from the low-pH form by the deprotonation of a single group with a pK of approximately 10.2 for rhodopsin in rod disk membranes in 4.0 M KCl. The shift is observed for sheep and chicken rhodopsins, but not for frog, toad, and octopus rhodopsins. This indicates a specific amino acid difference between these rhodopsins that is potentially relevant for the mechanism of color regulation.
Animals↗
The ionic mechanisms of hyperpolarizing responses in lobster muscle fibers.
Lobster muscle fibers develop hyperpolarizing responses when subjected to sufficiently strong hyperpolarizing currents. In contrast to axons of frog, toad, and squid, the muscle fibers produce their responses without the need for prior depolarization in high external K(+). Responses begin at a threshold polarization (50 to 70 mv), the potential reaching 150 to 200 mv hyperpolarization while the current remains constant. The increased polarization develops at first slowly, then becomes rapid. It usually subsides from its peak spontaneously, falling temporarily to a potential less hyperpolarized than at threshold for the response. As long as current is applied there can be oscillatory behavior with sequential rise and subsidence of the polarization, repeating a number of times. Withdrawal of current leads to rapid return of the potential to the resting level and a small, brief depolarization. Associated with the latter, but of longer duration, is an increased conductance whose magnitude and duration increase with the antecedent current. Hyperpolarizing responses of lobster muscle fibers are due to increased membrane resistance caused by hyperpolarizing K inactivation. The oscillatory characteristic of the response is due to a delayed superimposed and prolonged increase in membrane permeability, probably for Na(+) and for either K(+) or Cl(-). The hyperpolarizing responses of other tissues also appear to result from hyperpolarizing K inactivation, on which is superimposed an increased conductance for some other ion or ions.
Animals↗