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PubMed1995

Cardiovascular actions of frog urotensin II in the frog, Rana catesbeiana.

The effects of synthetic frog urotensin II on cardiac output and arterial blood pressure and on the motility of isolated vascular smooth muscle were investigated in the bullfrog, Rana catesbeiana. Bolus injections of frog urotensin II (100 nmol/kg) into the left systemic arch produced a rapid and sustained fall in blood flow through the right branch of the truncus arteriosus (to 62 +/- 5% of preinjection values; n = 8). The response exhibited strong tachyphylaxis. There were no significant effects on heart rate and central arterial blood pressure but the fact that a fall in cardiac output was not accompanied by a fall in pressure suggests that the peptide produced an increase in peripheral vascular resistance. Rings of vascular smooth muscle from the proximal and distal regions of the left and right systemic arches responded to urotensin II with sustained and concentration-dependent contractions. The tissues from the different regions did not significantly differ in their maximum response and sensitivity to the peptide (EC50 values from 4.6 x 10(-9) to 6.5 x 10(-9) M; n = 6). Acetylcholine (3 x 10(-8) to 3 x 10(-6) M) significantly (P < 0.05) relaxed the rings in an endothelium-dependent manner but urotensin II did not produce relaxation at any concentration tested. The contractile effect of urotensin II (10(-7) M) was not affected by preincubation of the rings with atropine, tetrodotoxin, and somatostatin-14 but indomethacin produced a significant (P < 0.05) decrease in the amplitude of the contractions of the systemic arch (to 18 +/- 2% of control values; n = 6). Arachidonic acid (10(-5) M) also produced a sustained contraction of the rings. The data suggest an involvement of prostaglandin synthesis in the contractile action of urotensin II on isolated frog vascular smooth muscle but, unlike in mammals, urotensin II does not stimulate nitric oxide synthesis in this tissue.

Acetylcholine↗
PubMed1998

Spatial transformation of semicircular canal signals into abducens motor signals. A comparison between grass frogs and water frogs.

The spatial transformation of semicircular canal signals to extraocular motor signals was studied by recording abducens nerve responses in grass and water frogs. Both species have similar vestibular canal coordinates but dissimilar orientations of their optic axes. Before sinusoidal oscillation in darkness the static head position was systematically altered to determine the planes of head oscillation in pitch and roll associated with minimal abducens nerve responses. Measured data and known canal plane vectors were used to calculate the abducens response vector in canal coordinates. The abducens vector deviated from the horizontal canal plane vector in grass frogs by 15 degrees and in water frogs by 34 degrees but was aligned with the pulling direction of the lateral rectus muscle in each of the two species. Lesion experiments demonstrated the importance of convergent inputs from the contralateral horizontal and anterior semicircular canals for the orientation of the abducens response vector. Thus, the orientation of the optic axis and the pulling directions of extraocular muscles are taken into account by the central organization of vestibulo-ocular reflexes. Horizontal and vertical canal signals are combined species-specifically to transform the spatial coordinates of sensory signals into appropriate extraocular motor signals.

Abducens Nerve↗
PubMed1984

Drugs and the frog retina. Effect of dopaminergic agents on the pigment screening of light- and dark-adapted frogs.

This is a study, using the light and electron microscope, of the action of a dopamine agonist (apomorphine) and of a dopamine antagonist (haloperidol) on the retinal pigment screening (PS) of light- and dark-adapted frogs. Pigment screening is a phenomenon which consists of the migration of melanin granules into processes of the pigment epithelium that extend between photoreceptors, in response to changes in the conditions of illumination. In the light the pigment migrates vitreally , in the dark it aggregates sclerally . A single intravenous injection of apomorphine (0.15 mg/kg) and of haloperidol (1 mg/kg) did not induce substantial modifications in the pattern of pigment screening which was similar to that of controls both in light- and dark-adapted frogs. This suggests that dopamine is probably not directly involved in the phenomenon of pigment screening in the retina of the frog.

Animals↗
PubMed2006

Frog ANP increases the amiloride-sensitive Na(+) channel activity in urinary bladder cells of Japanese tree frog, Hyla japonica.

We examined the mechanism of amiloride-sensitive Na(+) channels (ENaC) activated by fANP in epithelial cells of frog urinary bladder by using a cell-attached patch-clamp technique. ENaC activities in the epithelial cells were significantly increased following administration of both 10(-9)M fANP and 10(-5)M 8-Br-cGMP. Both fANP and 8-Br-cGMP, however, failed to activate the ENaC in the presence of 10(-6)M amiloride. In addition, 8-Br-cGMP failed to activate the ENaC in the presence of a PKA inhibitor, KT-5720. In the next experiment, we measured both cGMP and cAMP production levels after treatment of fANP on the frog urinary bladder cells. Frog ANP significantly increased cGMP production, but not the cAMP production. Taken together, these results suggest that fANP activates ENaC through increases in cGMP production and activation of PKA.

Animals↗
PubMed1999

Protamine-like sperm nuclear basic proteins in the primitive frog Ascaphus truei and histone reversions among more advanced frogs.

Sperm nuclear basic proteins (SNBPs) that condense chromatin are very diverse. In animals, evolution of SNBPs has proceeded from lysine-rich histone H type in sponges to more arginine-rich protamine-like PL and protamine P types. Yet sporadic PL/P to H reversions are known to occur in both protostomes and deuterostomes. To determine why this is the case, we have examined SNBPs in eleven anuran species. We find that sperm of the primitive, internally fertilizing archeobatrachian frog A. truei (family Ascaphidae) has PL/P type (42 mol % arginine), with an electrophoretic profile similar to SNBPs in another archeobatrachian, externally fertilizing Leiopelma hochstetteri (family Leiopelmatidae). Cytochemistry of sperm nuclei in the advanced, externally fertilizing neobatrachian frogs Crinia signifera and C. deserticola (family Myobatrachidae) indicates that they have reverted to H type SNBPs. This is also known to be the case in externally fertilizing Rana (family Ranidae) and Silurana, a subgenus of Xenopus (family Pipidae). Such a trend, from PL/P type SNBPs in two archeobatrachians to sporadic reversions to H type in more advanced frogs, parallels the ultrastructural simplification from complex A. truei introsperm to neobatrachian aquasperm that Jamieson et al. (1993. Herpetologica 49:52-65) attribute as a secondary reversion to external fertilization.

Animals↗
PubMed1993

Vestibular endorgan of the frog after the space flight and postural alteration of the neurectomized frog--its morphological and functional resilience.

The vestibular organ of frogs returned from space were observed by SEM. Morphology of the sensory epithelia was normal, including ultrastructure, such as tip links and side links. The frogs' behavior and vestibular morphology after various types of vestibular neurectomy were studied. Vestibular neurectomy resulted in tilting posture toward that side. This tilting gradually decreased to zero and the nerve regenerated. When the same nerve was cut again after postural recovery, the tilting angle was smaller and recovery period was shorter than after the first neurectomy. When the bilateral nerves were cut and neural regeneration was inhibited on one side, tilting slowly developed toward that side. These results show that frogs' postural change is modified by both central compensation and peripheral vestibular function.

Animals↗
PubMed1987

A comparison of sodium channel kinetics in the squid axon, the frog node and the frog node with BTX using the "silent gate" model.

In this paper it is shown that the very different kinetics measured for the rise of the sodium current which follows a depolarization of the membrane in the squid giant axon, the frog node and the frog node treated with Batrachotoxin may be accurately predicted using only the measured equilibrium and static characteristics for the three preparations and the kinetics measured for the gating charge transfer. The kinetic predictions follow the use of the "silent gate" model for ion channel gating. The model is electrostatic and its chief assumptions are that the channel gate, called here the N-system, has fast kinetics and responds to the gating charge that transfers but not directly to the trans-membrane voltage applied. Because channel gating, corresponding here to the motion of the N-system, does not change its energy in the trans-membrane applied electric field the gating is electrically silent as far as gating charge transfer measurement is concerned. However the probability of gating rises with the quantity of gating charge that transfers due to the electrostatic interaction between the N-system and the gating charge, redistributed under the influence of the applied trans-membrane electric field. With these assumptions the kinetics of sodium channel gating are predictable using only the static and equilibrium characteristics of gating charge and channel activation measured as a function of membrane voltage, and the kinetics of the gating charge transfer. Because of the fast kinetics assumed for the N-system the predicted kinetics are the same for channels with any number of equivalent and independent N-systems or gates acting in parallel.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Comparative toxicity of diuron on survival and growth of Pacific treefrog, bullfrog, red-legged frog, and African clawed frog embryos and tadpoles.

The effects of the herbicide diuron on survival and growth of Pacific treefrog (Pseudacris regilla), bullfrog (Rana catesbeiana), red-legged frog (Rana aurora), and African clawed frog (Xenopus laevis) embryos and tadpoles were determined in static-renewal tests. P. regilla and X. laevis embryos had reduced growth and developed increased deformities in diuron concentrations over 20 mg/L. Hindlimb bud and forelimb development were retarded in R. aurora following 14 days exposure to diuron concentrations of > 7.6 mg/L. Mean 14-day LC50s for P. regilla and X. laevis tadpoles were 15.2 and 11.3 mg/L diuron, respectively. The 21-day LC50 for R. catesbeiana tadpoles was 12.7 mg/L diuron. The 14-day LC50 for R. aurora tadpoles was 22.2 mg/L. The lowest NOAELs calculated in embryo tests were 14.5 mg/L for P. regilla (10 days) and 7.6 mg/L diuron for X. laevis (4 days). The lowest NOAELs calculated in tadpole tests were: P. regilla, 14.5 mg/L (14 days); R. catesbeiana, 7.6 mg/L (21 days); R. aurora, 7.6 mg/L (14 days); and X. laevis, > 29.1 mg/L (14 days). Diuron concentrations having an effect on survival, growth, and malformation in the laboratory were much higher than those found in normal field spray situations; field studies would be needed to determine the hazard to amphibians in areas of localized pooling of recently applied herbicide in the environment.

Animals↗
PubMed1969

Tumor induction in developing frog kidneys by a zonal centrifuge purified fraction of the frog herpes-type virus.

Injection of frog embryos (Rana pipiens) with a zonal centrifuge purified fraction of herpes-type virus (prepared from virus-containing Lucké tumors) resulted in a high incidence of kidney tumors. This partially purified oncogenic fraction contained a high concentration of an enveloped form of the frog herpes-type virus (adjacent fractions lacked this particle and were not oncogenic), which suggests that this form of the virus plays a role in the genesis of the Lucké tumor.

Animals↗
PubMed1997

Evolution of nerve development in frogs. II. Modified development of the peripheral nervous system in the direct-developing frog Eleutherodactylus coqui (Leptodactylidae).

We use whole-mount immunohistochemistry to describe the pattern of development of cranial nerves and muscles in the direct-developing leptodactylid frog Eleutherodactylus coqui. Comparison with nerve development in the biphasically developing frogs Physalaemus pustulosus (Leptodactylidae) and Discoglossus pictus (Discoglossidae; described in a companion paper) allows us to infer the ancestral leptodactylid ontogenetic pattern and the extent to which it has been modified during the evolution of direct development in Eleutherodactylus. While early embryonic development of cranial nerves and muscles is remarkably conserved in E. coqui, most transitory embryonic and larval characters (e.g., occipital and spinal myotomes together with their innervation, the distorted course of trigeminal and facial nerves, ventral branchial arch muscles, a subset of branchial-nerve rami and the lateral-line system) never develop. However, a few larva-typical characters are recapitulated, including Rohon-Beard cells and an anastomosis between the vagal and hypoglossal nerve. In addition to the abbreviation of ontogeny by loss of larva-specific traits, dramatic dissociations and heterochronic shifts of characters can be observed in E. coqui. The onset of development of limb and trunk innervation has been pre-displaced to early embryonic stage. Moreover, the reorientation of cranial muscles and nerves corresponding to late metamorphic events in biphasically developing anurans occurs relatively much earlier and is less pronounced in E. coqui resulting in an extreme condensation of ontogeny.

Animals↗
PubMed2004

Response of the Italian agile frog (Rana latastei) to a Ranavirus, frog virus 3: a model for viral emergence in naïve populations.

Ranavirus (family Iridoviridae) is a genus of pathogens of poikilotherms, and some ranaviruses may play a role in widespread mortality of amphibians. Ecology of viral transmission in amphibians is poorly known but can be addressed through experimentation in the laboratory. In this study, we use the Ranavirus frog virus 3 (FV3) as an experimental model for pathogen emergence in naive populations of tadpoles. We simulated emerging disease by exposing tadpoles of the Italian agile frog (Rana latastei), to the North American Ranavirus FV3. We demonstrated that mortality occurred due to viral exposure, exposure of tadpoles to decreasing concentrations of FV3 in the laboratory produced dose-dependent survival rates, and cannibalism of virus-carrying carcasses increased mortality due to FV3. These experiments suggest the potential for ecological mechanisms to affect the level of exposure of tadpoles to Ranavirus and to impact transmission of viral pathogens in aquatic systems.

Amphibians↗
PubMed1979

[Physiological polymorphism of a grass frog population. III. The effect of the season on the phenotypic manifestation of frog polymorphism by the level of muscle tissue thermostability].

A study was made of the phenotypical manifestation of physiological polymorphism of the population of the grass frog by the heat resistance level of m. interphalangealis in different seasons. In autumn (starting from the 2nd half of October), throughout winter, and in summer the polymorphism of frogs is well expressed, whereas in spring (during the reproduction period) and in the first half of October (during the migration of animals to the places of hibernation) the polymorphism appears to be hidden. The latter phenomenon is due to differences in the pattern of individual seasonal changes in the heart resistance of muscles in individuals of different groups.

Animals↗
PubMed1979

[Cell proliferation and migration in the roof of the mesencephalon (tectum) in Xenopus laevis tadpoles and adult frogs normally and in brain injury. II. Cell proliferation and differentiation of the tectum in frogs].

The proliferation and directions of cell differentiation in tectum opticum were studied in the young frogs under the conditions of normal development and upon brain trauma by means of 3H-thymidine autoradiography. The same types of cells were shown to be able of proliferation in both the cases: cells of the ventricle zone and glioblasts (gliocytes) in all other tectum layers. A study of directions of the tectum proliferating cells' differentiation in the frogs has shown that the proliferating cells differentiate mainly in the ependyme tanicytes in the ventricle layer 1 and gliocytes in the other tectum layers. The trauma did not change the direction of proliferating cells' differentiation towards the formation of neurons. The complete regeneration is observed in the tectum layer 1 only.

Animals↗
PubMed1980

Rejection of skin allo- and xenografts in the grass frog, Rana temporaria and the edible frog, Rana esculenta.

The fate of orthotopic dorsal skin allo- and xenografts at 22 +!- 2 degrees C in the grass frog, Rana tempororai (Rt) and in the edible frog, R. esculenta (Re) which is an interspecific hybrid of R. ridibunda and R. lessonae. Median survival times (MSTs) in experimental groups Rt in equilibrium Rt, Re in equilibrium Re and Rt comes from Re were 28, 26 and 25 days, respectively. In R. tempororia hosts the significantly shorter viability of xenografts than allogeneic grafts may be caused by the broader spectrum of transplantation antigens of the hybrid donors. In the experimental group Re comes from Rt similar surviva times of sensitizing, second set and third set grafts were observed (24, 22, and 22 days, respectively). The first symptoms of destruction in the grafts of dorsal skin of R. temporaria were visible earlier than in the grafts of dorsal skin of R. esculenta independently of the species of the hosts. Hypotheses which could explain the differences observed are discussed.

Animals↗
PubMed1976

Frog lysozyme. I. Its identification, occurrence as isozymes, and quantitative distribution in tissues of the leopard frog, Rana pipiens.

In the course of examining the etiology of the Lucké renal adenocarcinoma of the frog, Rana pipiens, it was found that organs of the normal adult contain bacteriolytic enzymes. These enzymes all satisfied the six criteria for the identification of lysozymes and at least eight forms were separable by polyacrylamide gel electrophoresis. Their qualitative and quantitative distribution was organ-specific. All eight isozymes were found in normal kidney, while liver and spleen contained seven forms; skin, six; ovarian egg, five; and serum, two. In quantitative assays using a radial diffusion test, spleen had the greatest lysozyme concentration, followed in descending order by kidney, liver, skin, and ovary. Serum contained very low amounts. In terms of enzyme activity per animal, ovary was the highest ranking organ. As such a large number of lysozyme isozymes has not been reported in any other organism, their origins and functions are considered in the context of their presence in an ectotherm.

Animals↗
PubMed2001

Inactivation of frog virus 3 and channel catfish virus by esculentin-2P and ranatuerin-2P, two antimicrobial peptides isolated from frog skin.

While it is clear that some amphibian populations have recently experienced precipitous declines, the causes of those die-offs are complex and likely involve multiple variables. One theory suggests that environmental factors may trigger events that result in depressed immune function and increased susceptibility to infectious disease. Here we examine one aspect of innate immunity in amphibians and show that esculentin-2P (E2P) and ranatuerin-2P (R2P), two antimicrobial peptides isolated from Rana pipiens, inactivate frog virus 3, a potentially pathogenic iridovirus infecting anurans, and channel catfish herpesvirus. In contrast to mammalian antimicrobial peptides, E2P and R2P act within minutes, at temperatures as low as 0 degrees C, to inhibit viral infectivity. Moreover, these compounds appear to inactivate the virus directly and do not act by inhibiting replication in infected cells. This is the first report linking amphibian antimicrobial peptides with protection from an amphibian viral pathogen and suggests that these compounds may play a role in maintaining amphibian health.

Amphibian Proteins↗
PubMed1990

Frog virus 3-mediated translational shut-off: frog virus 3 messages are translationally more efficient than host and heterologous viral messages under conditions of increased translational stress.

Frog virus 3 rapidly and selectively blocks host cell translation while synthesizing more than 60 virus-specific polypeptides. Previous work indicated that virus infection led to activation of a kinase that phosphorylated and, as a consequence, inactivated eIF-2. Although phosphorylation of eIF-2 could explain the rapid decline in host cell translation, it could not explain how viral protein synthesis persisted in the face of host shut-off. To explain this phenomenon, we speculated that viral messages, either as a consequence of their higher translational efficiency or their greater abundance, were able to outcompete host messages for the remaining translational initiation complexes. To test this hypothesis, the relative translational efficiency of three characteristic FV3 messages was measured against that of several model messages. Translational efficiency was determined by monitoring the resistance (and hence the competitiveness) of a given transcript to increasing concentrations of salt in vitro and in vivo. In both rabbit reticulocyte lysates and wheat germ extracts, FV3 messages were more resistant to supra-optimal concentrations of potassium acetate than globin message and three BMV transcripts. In vivo, FV3 polypeptides were synthesized in the presence of salt concentrations that blocked host cell protein synthesis. These results suggest that the selective translation of FV3 messages in virus-infected cells may partly be due to the higher translational efficiency of viral messages. Structural features that contribute to translational efficiency are discussed.

Acetates↗
PubMed2004

Characterization of a peptide from skin secretions of male specimens of the frog, Leptodactylus fallax that stimulates aggression in male frogs.

During the breeding season of the mountain chicken frog Leptodactylus fallax, fighting between males results in the emergence of dominant animals that subsequently attract females to nesting sites. A peptide, termed Leptodactylus aggression-stimulating peptide (LASP), was isolated from norepinephrine-stimulated skin secretions from male specimens of L. fallax that was not present in skin secretions obtained from females. The primary structure of the peptide was established as: Gly-Leu-Trp-Asp-Asp-Leu-Lys-Ala-Ala-Ala-Lys-Lys-Val-Val-Ser-Ser-Leu-Ala-Ser-Ala-Ala-Ile-Glu-Lys-Leu NH2. LASP had no pheromone-like action on females but had a chemoattractive effect on males and stimulated aggressive behaviors, such as rearing and leaping. It is suggested that this peptide may play an important role in initiating the competitive male-male interactions that are associated with the onset of reproductive behavior in L. fallax.

Aggression↗