PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “FROGS AND TOADS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources
PubMed2006

Comparison of ACE activity in amphibian tissues: Rana esculenta and Xenopus laevis.

Angiotensin converting enzyme (ACE) is the dipeptidyl-carboxypeptidase of the renin-angiotensin system involved in the control of blood pressure and hydromineral metabolism. It converts angiotensin I to angiotensin II, the biologically active octapeptide. Angiotensin converting enzyme-like activity has been demonstrated in a wide range of vertebrates. The presence of ACE was investigated in tissues of two amphibian species, the frog Rana esculenta and the toad Xenopus laevis. ACE activities were determined by specific substrate hydrolysis in gut, gonads, lung, kidney, heart, liver, skin, erythrocytes, and muscle homogenates and plasma by means of high performance liquid chromatography. Significant ACE activity was found in gut, gonads, lung and kidney, while that in heart, liver, skin, erythrocytes, muscle, and plasma was very low. Testis of toad contained the highest ACE activity, while that in erythrocytes of male and female frogs was notable.

Animals↗
PubMed1980

The sarcomere length--isometric tension diagram of the toad Bufo bufo sartorius.

The sarcomere length--isometric tension diagram has been determined for the toad Bufo bufo sartorius using a laser diffraction technique to measure the sarcomere width. The sarcomere width at l0 was found to be 2.37 micron. At length shorter than l0 this whole muscle exhibits a steeper decline in tension than single fibres. This discrepancy in the shape of the tension-length diagram between single frog fibres and whole toad sartorii may be due to a difference in the magnitude of the internal force which appears only at short lengths.

Animals↗
PubMed1987

Preparation and characterization of the major isotype of parvalbumin from skeletal muscle of the toad (Bufo bufo japonicus).

The major isotype of parvalbumin has been isolated from the skeletal muscle of the toad, Bufo bufo japonicus. Unlike the skeletal muscle of every frog so far examined (Rana esculenta, Rana temporaria, and Rana catesbeiana), which contains two major isotypes of parvalbumins, toad skeletal muscle has been shown to contain only one isotype, but the content of parvalbumin in toad skeletal muscle was similar to the sum of those of the two isotypes in skeletal muscles of frogs. This feature of toad skeletal muscle is advantageous to clarify the physiological role of parvalbumin. The relative molecular mass of toad parvalbumin was estimated to be 12,200 by SDS-polyacrylamide gel electrophoresis. The isoelectric point was determined to be 4.81 by polyacrylamide gel isoelectric focusing. The amino acid composition indicated that toad parvalbumin corresponds to bullfrog (R. catesbeiana) pI 4.97 parvalbumin, showing that toad parvalbumin is genetically an alpha-parvalbumin. It was also revealed by the amino acid composition that toad parvalbumin is distinctly different from any of the parvalbumins from frogs. The ultraviolet spectrum of toad parvalbumin is consistent with its amino acid composition. The ultraviolet difference spectrum of the Ca2+-loaded form vs. the metal-free form indicates that some Phe residues in the toad parvalbumin molecule are affected by a conformational change associated with Ca2+ binding. On electrophoresis in polyacrylamide gel in 14 mM Tris and 90 mM glycine, the metal-free and Mg2+-loaded forms of toad parvalbumin migrated twice as fast as the Ca2+-loaded form.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1994

The influence of ambient salinity and temperature on lipid metabolism in toad (Bufo bufo) skin. Is phosphatidylethanolamine an endogenous regulator of ion channels?

Incorporation of (32P) phosphate and (14C) acetate into frog (Rana temporaria) skin phospholipids in vitro was positively correlated to skin MR cell density. Transport across toad (Bufo bufo) skin and incorporation into skin phospholipids of the radioactive tracers were independent of transepithelial electrical potential in vitro. While all the incorporations in vitro showed (32P) and (14C) frog and toad skin phospholipid patterns dominated by phosphatidylcholine-independent of adaptational temperature and salinity--corresponding phospholipid patterns dominated by phosphatidylethanolamine (PE) were found in vivo, when toads adapted to Ringer solution were transferred to tap water containing tracer amounts of (32P) phosphate and (14C) acetate. PE could play a role in the formation of a "hydrophilic" environment and thereby, e.g. stabilise the integral membrane proteins that regulate the function of ion channels.

Animals↗
PubMed1990

Evolutionary specificity of hydrins, new hydroosmotic neuropeptides: occurrence of hydrin 2 (vasotocinyl-Gly) in the toad Bufo marinus but not in the viper Vipera aspis.

Hydrin 2 (vasotocinyl-Gly), a hydroosmotic peptide resulting from differential processing of provasotocin and recently identified in frog neurohypophysis, has been looked for in the pituitary gland of an exotic toad (Bufo marinus) and of a reptile (Vipera aspis). Hydrin 2 has been found in the amphibian but not in the reptile. This result confirms the evolutionary specificity of hydrin 2 that has been identified only in frogs and toads but not in birds and reptiles. Occurrence of hydrin 2 is explained by its regulatory function on the water permeability of the skin of anurans.

Animals↗
PubMedDate not supplied

Effects of frog-skin angiotensin II in amphibians.

The role of frog-skin angiotensin II (AII) in amphibia was studied by comparing the sodium and water permeability effects of three angiotensins (AII): frog skin (Ala-Pro-Gly-[Ile3, Val5]-Ang II), human [( Asp1, Ile5]-AII), and Japanese goosefish [( Asn1-Val5]-AII). Frog-skin AII increased the short-circuit current (SCC) significantly after it was added to the dermal side of the isolated skin of the South American frogs, Leptodactylus chaquensis and ocellatus, and the toad, Bufo arenarum, in concentrations of 10(-6) M. In frogs, the effect was significant at 15 minutes and reached 45% over control after 2 1/2 hours. The effect cannot be achieved with concentrations lower than 10(-7) M. Since amiloride (10(-4) M) blocked the SCC response, and absence of chloride in the bathing fluid did not, the effect is probably dependent on sodium transport. Human AII (10(-6) M) produced a similar response in summer frogs that had been treated with 0.1% NaCl for 14 days. Goosefish AII was ineffective at similar concentrations, and none of the angiotensins modified SCC in the toad bladder. Hydrosmotic effects could be achieved with the three angiotensins, the response being dependent on seasonal and species factors but always considerably lower than that of the neurohypophyseal peptides. Vascular reactivity of the isolated frog hindlimbs was compared by dose-response curves. Potency ratios on a molar basis against frog-skin AII was 1.136 for human AII and 1.193 for goosefish AII. The results show that the effects of the angiotensins differ in both the response of SCC to frog-skin angiotensin and its higher vascular effects.

Amphibians↗
PubMed1996

The primary structure and carbohydrate specificity of a beta-galactosyl-binding lectin from toad (Bufo arenarum Hensel) ovary reveal closer similarities to the mammalian galectin-1 than to the galectin from the clawed frog Xenopus laevis.

The detailed characterization of a galectin from the toad (Bufo arenarum Hensel) ovary in its primary structure, carbohydrate specificity, and overall biochemical properties has provided novel information pertaining to structural and evolutionary aspects of the galectin family. The lectin consists of identical single-chain polypeptide subunits composed of 134 amino acids (calculated mass, 14,797 daltons), and its N-terminal residue, alanine, is N-acetylated. When compared to the sequences of known galectins, the B. arenarum galectin exhibited the highest identity (48% for the whole molecule and 77% for the carbohydrate recognition domain (CRD)) with the bovine spleen galectin-1, but surprisingly less identity (38% for the whole molecule and 47% for the CRD) with a galectin from Xenopus laevis skin (Marschal, P., Herrmann, J., Leffler, H., Barondes, S. H., and Cooper, D. N. W. (1992) J. Biol. Chem. 267, 12942-12949). Unlike the X. laevis galectin, the binding activity of the B. arenarum galectin for N-acetyllactosamine, the human blood group A tetrasaccharide and Galbeta1,3GalNAc relative to lactose, was in agreement with that observed for the galectin-1 subgroup and those galectins having "conserved" (type I) CRDs (Ahmed, H., and Vasta, G. R. (1994) Glycobiology 4, 545-549). Moreover, the toad galectin shares three of the six cysteine residues that are conserved in all mammalian galectins-1, but not in the galectins from X. laevis, fish, and invertebrates described so far. Based on the homologies of the B. arenarum galectin with the bovine spleen galectin-1 and X. laevis skin galectin, it should be concluded that within the galectin family the correlation between conservation of primary structure and phylogenetic distances among the source species may not be a direct one as proposed elsewhere (Hirabayashi, J., and Kasai, K. (1993) Glycobiology 3, 297-304). Furthermore, galectins with conserved (type I) CRDs, represented by the B. arenarum ovary galectin, and those with "variable" (type II) CRDs, represented by the X. laevis 16-kDa galectin, clearly constitute distinct subgroups in the extant amphibian taxa and may have diverged early in the evolution of chordate lineages.

Amino Acid Sequence↗
PubMed2000

Chromogranin A-immunoreactive cells in the olfactory system of anuran amphibians.

Chromogranin A (CgA) is a member of the granin family of acidic proteins that are present in the secretory granules of many endocrine and neuroendocrine cells. The specific function(s) of these proteins is not known, but they seem to be the precursors of biologically active peptides, and they may act as helper proteins in the sorting and packaging of peptide hormones and neuropeptides. Using indirect immunohistochemistry, we have found CgA immunoreactivity in the primary olfactory epithelia, the vomeronasal epithelia, the olfactory nerves, and the olfactory bulbs of tadpoles of the American toad, Bufo americanus, and the green frog, Rana clamitans. CgA immunoreactivity was present in the early stages of larval development in toads but was not detected in toad tadpoles after the hindlimb buds formed or in toadlets or adults. In green frog tadpoles, CgA-immunoreactive cells were found in pre- and prometamorphic stages but not in late climax. CgA immunoreactivity was also absent in froglets, but it was detected in the vomeronasal epithelium but not the olfactory epithelium of adult green frogs.

Animals↗
PubMed1996

Concentration and storage of biotin in the amphibian brain.

Prominent displays of endogenous biotin reactivity can be observed at specific locations in histochemical preparations of the forebrain and midbrain in the northern leopard frog (Rana pipiens) and common American toad (Bufo americanus). At the light microscopic level, the biotin reactivity appears in clusters of darkly stained puncta of either spherical or rodlike shape in the olfactory cortex, nucleus isthmi, and hypothalamus. With the electron microscope, the biotin reactive spheres are identified as neuronal varicosities and synaptic boutons and the rods as short segments of axons. Appropriate controls demonstrate that the punctate biotin-reactive structures are sites of concentration of biotin or a biotin analog in the processes of certain neurons. These data represent the first observation on the selective concentration of a vitamin in vertebrate neurons and suggest that biotin may have specialized functions in anatomically delimited areas of the central nervous system. Localization of the densest concentration of the biotin-reactive puncta in the dorsolateral prominence of the olfactory cortex may have relevance to the functional organization of the olfactory system. The distributions of biotin-reactive puncta were observed in laboratory-housed frogs and in wild toads captured in the summer months but were sparse or absent in batches of commercially obtained frogs examined immediately upon arrival in the laboratory. Systemic administration of biotin or biocytin hydrochloride did not alter the appearance or numbers of the biotin-reactive structures either in newly received or laboratory-housed frogs. These findings suggest that the capacity of the biotin-storage mechanism in the amphibian brain may be set by environmental factors and may be readily saturable from natural dietary or enteric sources.

Animals↗