| growth of the pectoral girdle of the leopard frog, rana pipiens (anura: ranidae). | this article describes the growth of the anuran pectoral girdle of rana pipiens and compares skeletal development of the shoulder to that of long bones. the pectoral girdle chondrifies as two halves, each adjacent to a developing humerus. in each, the scapula and coracoid form as single foci of condensed chondrocytes that fuse, creating a cartilaginous glenoid bridge articulating with the humerus. based on histological sections, both the dermal clavicle and cleithrum begin to ossify at approxima ... | 2005 | 15744727 |
| up-regulation of acidic ribosomal phosphoprotein p0 in response to freezing or anoxia in the freeze tolerant wood frog, rana sylvatica. | natural freezing survival by the wood frog, rana sylvatica, involves multiple organ-specific, freeze-responsive changes in gene expression. the present study provides the first report of freeze-responsive genes in brain. differential screening of a cdna library made from brain of frozen wood frogs revealed a freeze-responsive clone encoding a protein of 315 amino acids that was identified as the acidic ribosomal phosphoprotein, p0 (genbank accession no. af176302). the amino acid sequence showed ... | 2005 | 15710371 |
| alteration of the hypothalamic-pituitary-gonadal axis in estrogen- and androgen-treated adult male leopard frog, rana pipiens. | gonadal steroids, in particular 5 alpha-dihydrotestosterone (dht) and 17 beta-estradiol (e2), have been shown to feed back on the hypothalamic-pituitary-gonadal (hpg) axis of the ranid frog. however, questions still remain on how dht and e2 impact two of the less-studied components of the ranid hpg axis, the hypothalamus and the gonad, and if the feedback effects are consistently negative. thus, the goal of the study was to examine the effects of dht and e2 upon the hpg axis of the gonadally-int ... | 2005 | 15642123 |
| effective population sizes and temporal stability of genetic structure in rana pipiens, the northern leopard frog. | although studies of population genetic structure are very common, whether genetic structure is stable over time has been assessed for very few taxa. the question of stability over time is particularly interesting for frogs because it is not clear to what extent frogs exist in dynamic metapopulations with frequent extinction and recolonization, or in stable patches at equilibrium between drift and gene flow. in this study we collected tissue samples from the same five populations of leopard frogs ... | 2004 | 15612296 |
| partial life-cycle toxicity and bioconcentration modeling of perfluorooctanesulfonate in the northern leopard frog (rana pipiens). | a number of recent monitoring studies have demonstrated elevated concentrations of perfluorooctanesulfonate (pfos) in humans and wildlife throughout the world. although no longer manufactured in the united states, the global distribution and relative persistence of pfos indicates a need to understand its potential ecological effects. presently, little is known concerning toxicity of pfos in chronic exposures with aquatic species. therefore, we evaluated the effects of pfos on survival and develo ... | 2004 | 15559291 |
| hydrodynamics of surface swimming in leopard frogs (rana pipiens). | the kinematics of swimming frogs have been studied extensively in the past and, based on these results, hypotheses regarding the hydrodynamics of frog swimming can be generated. to test these hypotheses we used digital particle image velocimetry (dpiv) to quantify the flow structure of the wake produced by the feet during the propulsion phase of the kick of surface swimming frogs (rana pipiens). these frogs use two different gaits, asynchronous and synchronous kicking, and the magnitude of the t ... | 2004 | 15472025 |
| assessing the toxicity and teratogenicity of pond water in north-central minnesota to amphibians. | incidence of amphibian deformities have increased in recent years, especially in the northern region of the united states. while many factors have been proposed as being responsible for generating deformities (e.g., contaminants, ultraviolet radiation [uv], parasites), no single cause has been definitively established. | 2004 | 15341313 |
| evidence that fast exocytosis can be predominantly mediated by vesicles not docked at active zones in frog saccular hair cells. | the prevailing model of neurotransmitter release stipulates that ca2+ influx triggers the rapid fusion of vesicles that are docked at presynaptic active zones. under this model, slower tonic release is supported by vesicles clustered nearby that have to translocate to the release sites before fusion. we have examined this hypothesis at the afferent synapse of saccular hair cells of the leopard frog, rana pipiens. detailed morphological measurements at this ribbon synapse show that on average 32 ... | 2004 | 15308677 |
| contribution of the submentalis muscle to feeding mechanics in the leopard frog, rana pipiens. | this study investigated the functional contributions of the submentalis muscle to the coordination of feeding behavior in the leopard frog, rana pipiens. additionally, the anatomical origins of the motor neurons innervating this muscle are identified and described. the m. submentalis is a small muscle connecting the distal mandibular tips. depending upon the anuran species studied, this muscle contributes to mandibular bending and the degree to which the tongue is protracted, or has little or no ... | 2004 | 15286946 |
| level dependence of distortion product otoacoustic emissions in the leopard frog, rana pipiens pipiens. | the inner ear of frogs holds two papillae specialized in detecting airborne sound, the amphibian papilla (ap) and the basilar papilla (bp). we measured input-output (i/o) curves of distortion product otoacoustic emissions (dpoaes) from both papillae, and compared their properties. as in other vertebrates, dpoae i/o curves showed two distinct segments, separated by a notch or kneepoint. the slope of the low-level segment was conspicuously different between the ap and the bp. for dpoae i/o curves ... | 2004 | 15157969 |
| direct and interactive effects of ecologically relevant concentrations of organic wastewater contaminants on rana pipiens tadpoles. | organic wastewater contaminants (owcs) have recently been documented in several aquatic ecosystems. we examined the effects of three owcs (caffeine, acetaminophen, and triclosan) on the activity level, startle response, survivorship, and growth of northern leopard frog (rana pipiens) tadpoles. we conducted two experiments: one on the effects of acetaminophen and triclosan alone and in combination, and the other on the effects of caffeine and acetaminophen alone and in combination. in both experi ... | 2004 | 15101040 |
| evolutionary history of the northern leopard frog: reconstruction of phylogeny, phylogeography, and historical changes in population demography from mitochondrial dna. | this study uses a combined methodological approach including phylogenetic, phylogeographic, and demographic analyses to understand the evolutionary history of the northern leopard frog, rana pipiens. we tested hypotheses concerning how (or if) known geological events and key features of the species biology influenced the contemporary geographic and genetic distribution of r. pipiens. we assayed mitochondrial dna variation from 389 individuals within 35 populations located throughout the species ... | 2004 | 15058727 |
| the physiology of hibernation in canadian leopard frogs (rana pipiens) and bullfrogs (rana catesbeiana). | canadian northern leopard frogs (rana pipiens) and bullfrogs (rana catesbeiana) were acclimated to 3 degrees c and submerged in anoxic (0-5 mmhg) and normoxic (po(2) approximately 158 mmhg) water. periodic measurements of blood po(2), pco(2), and ph were made on samples taken anaerobically from subsets of each species. blood plasma was analyzed for [na(+)], [k(+)], [cl(-)], [lactate], [glucose], total calcium, total magnesium, and osmolality. blood hematocrit was determined, and plasma bicarbona ... | 2016 | 15057718 |
| contribution of eye retraction to swallowing performance in the northern leopard frog, rana pipiens. | most anurans retract and close their eyes repeatedly during swallowing. eye retraction may aid swallowing by helping to push food back toward the esophagus, but this hypothesis has never been tested. we used behavioral observations, cineradiography, electromyography and nerve transection experiments to evaluate the contribution of eye retraction to swallowing in the northern leopard frog, rana pipiens. behavioral observations of frogs feeding on 1.5 cm long crickets reveal a high degree of varia ... | 2004 | 15010487 |
| physiology of hibernation in rana pipiens: metabolic rate, critical oxygen tension, and the effects of hypoxia on several plasma variables. | rates of o(2) consumption (.vo(2)) were determined for adult northern leopard frogs (rana pipiens) submerged at 3 degrees c at water po(2)s (p(w)o(2)) ranging from 0-160 mmhg. the critical o(2) tension (p(c)) was 36.4 mmhg. hematocrit and blood levels of po(2), glucose, lactate, ph, [na(+)], [k(+)], and osmolality were determined for frogs submerged for two days. above a p(w)o(2) of 50 mmhg, blood po(2) ranged from 1-7 mmhg, which was sufficient to allow the frogs to function entirely aerobicall ... | 2004 | 14743516 |
| effects of steroid hormones on spermatogenesis and gnrh release in male leopard frogs, rana pipiens. | several lines of evidence suggest reproduction in the ranid frogs is potently regulated by the gonadal steroids, in particular 5alpha-dihydrotestosterone (dht) and 17beta-estradiol (e(2)), and a non-gonadal steroid, the stress hormone corticosterone (cort). little is known about how these steroid hormones act upon the gnrh system to regulate the downstream reproductive events. we address these gaps in our knowledge by investigating the effects of cort, e(2), and dht administration on the in vitr ... | 2003 | 14636640 |
| ranacyclins, a new family of short cyclic antimicrobial peptides: biological function, mode of action, and parameters involved in target specificity. | we report on two new cyclic 17-residue peptides that we named ranacyclins e and t, the first isolated from rana esculenta frog skin secretions and the second discovered by screening a cdna library from rana temporaria. ranacyclins have a loop region that is homologous with that of an 18-mer peptide, plr, isolated from the skin of the northern leopard frog, rana pipiens, with no reported antimicrobial activity. here we show that ranacyclins and plr have antimicrobial and antifungal activity. howe ... | 2003 | 14636071 |
| persistence of graded epha/ephrin-a expression in the adult frog visual system. | many studies have demonstrated the involvement of the epha family of receptor tyrosine kinases and their ligands, ephrin-a2 and -a5, in the development of the temporonasal axis of the retinotectal/collicular map, but the role of these molecules in optic nerve regeneration has not been well studied. noting that the characteristic gradients of the epha/ephrin-a family that are expressed topographically in the retina and tectum of embryonic chicks and mice tend to disappear after birth, we took as ... | 2003 | 14624488 |
| physiological vulnerability of distortion product otoacoustic emissions from the amphibian ear. | the physiological vulnerability of distortion product otoacoustic emissions (dpoaes) was investigated in the leopard frog, rana pipiens pipiens. for each frog, dpoaes were recorded from the amphibian and the basilar papillae. measurements were taken before and after either the arrest of oxygen supply due to cardioectomy, or the destruction of the central nervous system (cns). dpoaes in response to high-level stimuli (> 75 db spl) were rather robust to these insults during the first two hours pos ... | 2003 | 14587603 |
| prevalence of skeletal and eye malformations in frogs from north-central united states: estimations based on collections from randomly selected sites. | skeletal malformation rates for several frog species were determined in a set of randomly selected wetlands in the north-central usa over three consecutive years. in 1998, 62 sites yielded 389 metamorphic frogs, nine (2.3%) of which had skeletal or eye malformations. a subset of the original sites was surveyed in the following 2 yr. in 1999, 1,085 metamorphic frogs were collected from 36 sites and 17 (1.6%) had skeletal or eye malformations, while in 2000, examination of 1,131 metamorphs yielded ... | 2003 | 14567211 |
| slow death in the leopard frog rana pipiens: neurotransmitters and anoxia tolerance. | while frogs such as rana temporaria are known to withstand 4-5 h anoxia at room temperature, little is known about the neurological adaptations that permit this. previous research has shown that changes in neuroactive compounds such as glutamate and dopamine in anoxia-sensitive (mammalian) brains follow a strikingly different pattern than is observed in truly anoxia-tolerant vertebrates such as the freshwater turtle. the present study measured changes in the levels of whole brain and extracellul ... | 2003 | 14555742 |
| gonadal differentiation in frogs exposed to estrogenic and antiestrogenic compounds. | exposure of amphibians to endocrine disrupting compounds (edcs) may alter differentiation of gonads, especially when exposures begin during early life stages. gonadal differentiation was observed in leopard frogs (rana pipiens) and wood frogs (rana sylvatica) exposed as tadpoles to estrogenic (estradiol, ethinylestradiol, nonylphenol) and antiestrogenic compounds (an aromatase inhibitor, flavone, and an antiestrogen, ici 182780). exposure to all compounds at micrograms/l concentrations altered g ... | 2003 | 14552012 |
| effects of hydrin 2 on cutaneous electrical properties of rana pipiens. | electrical properties were measured in isolated skin patches from leopard frogs (rana pipiens) to explore the possibility that hydrin 2 (vasotocinyl-gly) may regulate cutaneous ion transport. hydrin 2 is a neurohypophysial peptide commonly implicated in rehydration of anurans. experimental frogs were given either one or two intraperitoneal (i.p.) injections of hydrin 2 in saline solution, each calculated to achieve a final blood concentration of 81 ng/ml. after a 2-h equilibration period, the fr ... | 2003 | 14511979 |
| intact capillaries sensitive to rate, magnitude, and pattern of shear stress stimuli as assessed by hydraulic conductivity (lp). | magnitude of abrupt changes in fluid shear stress (delta tau) correlates with capillary hydraulic conductivity (lp). cultured endothelial cells differentiate between rate of change in and pattern of fluid stimulation; however, neither rate nor pattern sensitivity has been evaluated in individual capillaries. we hypothesized that lp would be greater following abrupt compared to slow delta tau and that magnitude of delta tau would correlate with lp regardless of rate. mesenteric venular capillarie ... | 2003 | 12935773 |
| the effects of nicotinic and muscarinic receptor activation on patch-clamped cells in the optic tectum of rana pipiens. | both nicotinic and muscarinic cholinergic receptors are present in the optic tectum. to begin to understand how the activation of these receptors affects visual activity patterns, we have determined the types of physiological responses induced by their activation. using tectal brain slices from the leopard frog, we found that application of nicotine (100 microm) evoked long-lasting responses in 60% of patch-clamped tectal cells. thirty percent of these responses consisted of an increase in spont ... | 2003 | 12676145 |
| a regional survey of malformed frogs in minnesota (usa) (minnesota malformed frogs). | in late 1995, school children discovered malformed frogs in a south central minnesota pond. press coverage resulted in numerous citizen reports of frog malformation across minnesota in 1996. after some initial site investigation, 3 affected frog sites and 4 nearby reference sites were selected for more detailed evaluation. field biologists made 89 visits to study sites beginning spring 1997 through fall 1999 to examine the number and type of frog malformations. over 5,100 leopard frogs (rana pip ... | 2003 | 12602621 |
| the representation of the ipsilateral eye in nucleus isthmi of the leopard frog, rana pipiens. | the retina of the leopard frog projects topographically to the superficial neuropil of the entire contralateral tectum. in the rostromedial neuropil of the tectum, there is a map of the binocular region of the visual field seen from the ipsilateral eye that is in register with the map of the binocular region of the visual field seen from the contralateral eye. the ipsilateral eye projects indirectly to the tectum through nucleus isthmi (n. isthmi), a midbrain tegmental structure. n. isthmi recei ... | 2008 | 12507333 |
| immunosuppression in the northern leopard frog (rana pipiens) induced by pesticide exposure. | an injection study and a field study were used to investigate the hypothesis that environmental xenobiotics have the potential to alter the immune function of northern leopard frogs (rana pipiens). three assays, igm-specific antibody response to keyhole limpet hemocyanin linked to dinitrophenyl (klh-dnp), zymozan induced chemiluminescence (cl) of whole blood and the delayed-type hypersensitivity (dth), were used to assay humoral, innate and cell-mediated immune endpoints. sublethal doses of ddt ... | 2003 | 12503752 |
| assessment of the risk of solar ultraviolet radiation to amphibians. i. dose-dependent induction of hindlimb malformations in the northern leopard frog (rana pipiens). | a number of environmental stressors have been hypothesized as responsible for recent increases in limb malformations in several species of north american amphibians. the purpose of this study was to generate dose-response data suitable for assessing the potential role of solar ultraviolet (uv) radiation in causing limb malformations in a species in which this phenomenon seemingly is particularly prevalent, the northern leopard frog (rana pipiens). frogs were exposed from early embryonic stages t ... | 2002 | 12144258 |
| octylphenol and uv-b radiation alter larval development and hypothalamic gene expression in the leopard frog (rana pipiens). | we assessed octylphenol (op), an estrogenic endocrine-disrupting chemical, and uv-b radiation, a known stressor in amphibian development, for their effects on hypothalamic gene expression and premetamorphic development in the leopard frog rana pipiens. newly hatched tadpoles were exposed for 10 days to op alone at two different dose levels; to subambient uv-b radiation alone; and to two combinations of op and uv-b. control animals were exposed to ethanol vehicle (0.01%) exposure, a subset of tad ... | 2002 | 11882479 |
| comparison of isometric contractile properties in hindlimb extensor muscles of the frogs rana pipiens and bufo marinus: functional correlations with differences in hopping performance. | the leopard frog (rana pipiens) is an excellent jumper that can reach high take-off velocities and accelerations. it is diurnal, using long, explosive jumps to capture prey and escape predators. the marine toad (bufo marinus) is a cryptic, nocturnal toad, typically using short, slow hops, or sometimes walking, to patrol its feeding area. typical of frogs with these different locomotor styles, rana has relatively long hindlimbs and large (by mass) hindlimb extensor muscles compared to bufo. we st ... | 2002 | 11835367 |
| role for corticoids in mediating the response of rana pipiens tadpoles to intraspecific competition. | competition is known to decrease growth and development rate in tadpoles, but the physiological basis for this phenomenon is poorly understood. we hypothesized that competition results in increased production of stress hormones and that these hormones are responsible for the suppression of growth and development. to test this hypothesis, we measured whole-body corticosterone content in premetamorphic leopard frog (rana pipiens) tadpoles raised at two different population densities and three diff ... | 2002 | 11754020 |
| effect of anoxia and adenosine on cerebral blood flow in the leopard frog (rana pipiens). | the effect of anoxia on cerebral blood velocity (cbv) on the dorsal surface of telencephalon was examined in the leopard frog, rana pipiens, using a stereomicroscope. during exposure to anoxia, a transient 228% increase in cbv velocity was seen after 20 min, but cbv fell back to basal values after a further 20 min of anoxia. topical application of 50 microm adenosine during normoxia caused a 52% increase in cbv, while 250 microm adenosine caused no further increase. at both concentrations, the e ... | 2001 | 11567784 |
| sublethal effects of chronic exposure to an organochlorine compound on northern leopard frog (rana pipiens) tadpoles. | global contamination with organochlorine compounds (ocs) has posed developmental and reproductive problems in wildlife worldwide. however, little is known about the impact of ocs or other pollutants on amphibians, despite mounting concerns about amphibian population declines and developmental deformities in the wild. wildlife populations may be affected critically by sublethal impacts of anthropogenic disturbances, yet little research has focused on such effects in amphibians. in the current stu ... | 2001 | 11501277 |
| anatomical evidence for brainstem circuits mediating feeding motor programs in the leopard frog, rana pipiens. | using injections of small molecular weight fluorescein dextran amines, combined with activity-dependent uptake of sulforhodamine 101 (sr101), brainstem circuits presumed to be involved in feeding motor output were investigated. as has been shown previously in other studies, projections to the cerebellar nuclei were identified from the cerebellar cortex, the trigeminal motor nucleus, and the vestibular nuclei. results presented here suggest an additional pathway from the hypoglossal motor nuclei ... | 2001 | 11500793 |
| cancer chemotherapy--ribonucleases to the rescue. | ribonucleases, once dismissed as uninteresting digestive enzymes, have been shown to have remarkable biological activities. onconase, from the northern leopard frog, is currently in clinical trials as a cancer chemotherapeutic. recent research has revealed some key factors responsible for the cytotoxicity of ribonucleases, and may lead to a new class of drugs. | 2001 | 11358688 |
| immunohistochemical localization of cytochrome p4501a induced by 3,3',4,4',5-pentachlorobiphenyl (pcb 126) in multiple organs of northern leopard frogs, rana pipiens. | monoclonal antibody 1-12-3 (mab 1-12-3) recognizes an epitope exclusive to cytochrome p450s in subfamily 1a (cyp1a) from all vertebrates tested so far, including one amphibian species. in this study, we first tested the utility of mab 1-12-3 for detection of presumed cyp1a proteins in hepatic microsomes of northern leopard frogs treated without or with 3,3',4,4',5-pentachlorobiphenyl (pcb 126). statistical analysis showed that ethoxyresorufin-o-deethylase (erod) activities and cyp1a equivalents ... | 2001 | 11351408 |
| integration and recovery processes contribute to the temporal selectivity of neurons in the midbrain of the northern leopard frog, rana pipiens. | this study examined the mechanisms underlying amplitude modulation selectivity in the anuran auditory midbrain. single units were recorded extracellularly in the torus semicircularis of the northern leopard frog, rana pipiens. two physiologically distinct classes of neurons were identified, based on their response latencies and their selectivities to pulse repetition rates. cells in one group had short response latencies (median = 31 ms) and responded best to pulse repetition rates below 40 hz. ... | 2000 | 11138793 |
| assessment of rates of deformity in wild frog populations using in situ cages: a case study of leopard frogs (rana pipiens) in ontario, canada. | high rates of deformity in wild amphibian populations from north-eastern north america have been increasingly reported since 1995. in the st lawrence river basin (canada) elevated frequencies of limb and eye deformities in mudpuppies (necturus maculosus) and leopard frogs (rana pipiens) were recorded in the early 1990s. a caging study was conducted during 1998 to verify the rates recorded in leopard frogs and pursue the potential causes of deformities seen in juveniles and adults. week-old leopa ... | 2001 | 23886057 |
| gabaergic inhibition shapes frequency tuning and modifies response properties in the superior olivary nucleus of the leopard frog. | the role of gamma-aminobutyric acid (gaba)ergic inhibition in shaping the excitatory frequency tuning of 74 neurons in the superior olivary nucleus of the leopard frog, rana pipiens, was studied using iontophoretic application of the gaba(a) receptor antagonist, bicuculline methiodide. for 37 neurons, bicuculline application broadened and/or changed the configuration of the excitatory frequency-tuning curve. results indicate that gaba-mediated inhibition not only sharpens the tuning curves of ne ... | 2014 | 11016782 |
| anticholinergic effects in frogs in a morris water maze analog. | we determined the effect of two doses of the centrally acting anticholinergic drug, atropine sulfate (as), on the performance of female northern leopard frogs (rana pipiens) in a visual cue analog of the morris water task. untreated frogs learned the visually cued task, while frogs treated with 150 mg/kg as were significantly slower than controls in learning to escape warm water by finding a visible platform, and there was a dose-dependent response, with frogs treated with 50 mg/kg as performing ... | 2000 | 10869602 |
| proglucagon cdnas from the leopard frog, rana pipiens, encode two glp-1-like peptides. | we have isolated and characterized proglucagon cdnas from the intestine and pancreas of the leopard frog rana pipiens. r. pipiens proglucagon encodes glucagon, glucagon-like peptides 2 (glp-2), and two glucagon-like peptide 1 (glp-1) like sequences. the pancreatic and intestinal cdnas were of identical structure and sequence suggesting that, unlike many other non-mammalian vertebrates, there is little or no alternative splicing of the proglucagon mrna in this species. a phylogenetic analysis of ... | 2000 | 10854694 |
| evidence for the anatomical origins of hypoglossal afferents in the tongue of the leopard frog, rana pipiens. | in this study, the origins of sensory neurons from the tongue that ascend in the hypoglossal nerve were identified and described in the leopard frog, rana pipiens. previous studies have shown that these afferents are used to coordinate the timing of jaw and tongue muscles, and are important in the motor control of feeding. these sensory neurons innervate the tongue bilaterally and appear to originate in the dorsal fungiform papillae of the tongue epithelium. | 2000 | 10799702 |
| hybridization in leopard frogs (rana pipiens complex): larval fitness components in single-genotype populations and mixtures. | recognizing the predominant mode of selection in hybrid systems is important in predicting the evolutionary fate of recombinant genotypes. natural selection is endogenous if hybrid genotypes are at a disadvantage relative to parental species independent of environment. alternatively, relative fitness can vary in response to environmental variation (exogenous selection), and hybrid genotypes can possess fitness values equal to or greater than that of parental species. i investigated the nature of ... | 1999 | 28565457 |
| gabaergic inhibition shapes frequency tuning and modifies response properties in the auditory midbrain of the leopard frog. | the functional role of gabaergic inhibition in shaping the frequency tuning of 96 neurons in the torus semicircularis of the leopard frog, rana pipiens, was studied using microiontophoresis of the gabaa receptor antagonist, bicuculline methiodide. bicuculline application abolished, or reduced in size, the inhibitory tuning curves of 72 neurons. in each case, there was a concommitant broadening of the excitatory tuning curve such that frequency-intensity combinations that were inhibitory under co ... | 1999 | 10573870 |
| chemolithoheterotrophy in a metazoan tissue: sulfide supports cellular work in ciliated mussel gills | hydrogen sulfide, a common constituent of marine intertidal sediments, is both a potent toxin of aerobic cellular respiration and an electron-rich molecule used by some prokaryotic organisms as a source of energy. in ciliated gills from geukensia demissa, a marine mussel from sulfide-rich sediments, sulfide oxidation supports cellular work. evidence for this comes from measurements of ciliary beat frequency (fcb) as a measure of atp turnover rate, the rate of gill oxygen consumption ( m_dot o2) ... | 1999 | 10377276 |
| alteration of leopard frog (rana pipiens) metamorphosis by the herbicide acetochlor. | based on the geographic correlation between the use of the pre-emergent herbicide acetochlor [2-chloro-n-(ethoxymethyl)-n-(2-ethyl-6-methylphenyl) acetamide] and the natural range of northern leopard frogs (rana pipiens), we investigated the effects of acetochlor (aceto) on frog metamorphosis. we specifically examined the interaction of aceto with thyroid hormone (t3) and corticosterone (cort), hormones that regulate natural metamorphosis. aceto, t3, and cort were administered via immersion. gro ... | 1999 | 10341044 |
| evaluation of hypothermia-induced analgesia and influence of opioid antagonists in leopard frogs (rana pipiens). | hypothermia results in diminished voluntary muscle activity, and is frequently used as a means of providing deep anesthesia to ectotherms and some mammals. in ectotherms, however, it is unclear if hypothermia produces true pain insensation. a needle-probe thermometer was used to demonstrate in frogs (rana pipiens) that local hypothermia (9 degrees c) could be induced by placement of a tourniqueted leg into ice water (6 degrees c) for 10 min in contrast to the contralateral nontourniqueted leg (2 ... | 1999 | 10340522 |
| role of antioxidant defenses in the tolerance of severe dehydration by anurans. the case of the leopard frog rana pipiens. | many anurans have excellent dehydration tolerance that allows endurance of the loss of up to 50-60% of total body water. one of the effects of severe dehydration is circulatory impairment due the reduced volume and increased viscosity of blood, which leads to organ hypoxia. the rehydration situation, therefore, involves a reoxygenation of tissues that may include elements of oxidative stress that resemble the injury in post-ischemic reperfusion of mammalian organs. the role of endogenous defense ... | 1998 | 9879657 |
| effects of vestibular nerve lesions on orientation turning in the leopard frog, rana pipiens. | | 1998 | 9818364 |
| antioxidant defenses and metabolic depression. the hypothesis of preparation for oxidative stress in land snails. | the roles of enzymatic antioxidant defenses in the natural tolerance of environmental stresses that impose changes in oxygen availability and oxygen consumption on animals is discussed with a particular focus on the biochemistry of estivation and metabolic depression in pulmonate land snails. despite reduced oxygen consumption and po2 during estivation, which should also mean reduced production of oxyradicals, the activities of antioxidant enzymes, such as superoxide dismutase and catalase, incr ... | 1998 | 9787804 |
| slow movement increases the survivorship of a chemically defended grasshopper in predatory encounters. | studies on insect defenses have investigated the benefits of noxious chemicals, aposematic coloration, and even gregariousness, but little information exists on the role of slow movement (as opposed to rapid escape movement and the absence of movement). using the chemically defended, slow-moving lubber grasshopper (romalea guttata) and the northern leopard frog (rana pipiens), we investigated the role of slow movement in insect defense. in a five-day experiment, frogs did not learn an aversion t ... | 1998 | 28308461 |
| the effects of telencephalic lesions on visually mediated prey orienting behavior in the leopard frog (rana pipiens). i. the effects of complete removal of one telencephalic lobe, with a comparison to the effects of unilateral tectal lobe lesions. | in this paper, we report studies aimed at characterizing the relationship between forebrain and midbrain systems involved in the control of prey orienting behavior in the leopard frog. in frogs, unilateral forebrain lesions, like unilateral tectal lobe lesions, have their most prominent effects in the contralateral monocular visual field. such lesions produce partial reductions in response frequency in the binocular visual field as well. similar sequelae follow unilateral tectal lobe removal. th ... | 1998 | 9519287 |
| effects of testosterone administration and castration on the forelimb musculature of male leopard frogs, rana pipiens. | in rana pipiens, forelimb muscles that are used by males to clasp females during amplexus are sexually dimorphic in mass, protein content, and fiber composition. this experiment examined the effects of castration and exogenous testosterone on wet mass, dry mass, and protein content of the 22 major forelimb muscles of male leopard frogs to determine whether established patterns of sexual dimorphism of the muscles are reflected in differential androgen sensitivity. muscles ranged from highly and m ... | 1998 | 9437849 |
| second messenger and camp-dependent protein kinase responses to dehydration and anoxia stresses in frogs. | the effects of whole body dehydration (up to 40% of total body water lost) or anoxia exposure (up to 2 days under n2 gas) at 5 degrees c on tissue levels of adenosine 3'-5' cyclic monophosphate (camp) and the percentage of camp-dependent protein kinase present as the free catalytic subunit (pkac), as well as the levels of the protein kinase c (pkc) second messenger, inositol 1,4,5-trisphosphate (ip3), were assessed in two anurans, the freeze-tolerant wood frog, rana sylvatica, and the freeze-int ... | 1997 | 9203370 |
| differential block of nicotinic synapses on b versus c neurones in sympathetic ganglia of frog by alpha-conotoxins mii and imi. | 1. the effects of two new acetylcholine receptor antagonists, alpha-conotoxin mii and alpha-conotoxin imi, on nicotinic synaptic transmission in the 10th paravertebral sympathetic ganglion of the leopard frog (rana pipiens) were examined. the preganglionic nerve was electrically stimulated (at low frequency, < or = 1 min-1, to avoid use-dependent changes) while compound action potentials of b and c neurones were monitored from the postganglionic nerve. 2. alpha-conotoxins mii and imi, at low mic ... | 1997 | 9134208 |
| bicarbonate and co2 transport across the skin of the leopard frog, rana pipiens: effect of pgf2alpha. | the amphibian skin represents an important organ for osmoregulation and, like the mammalian kidney, maintains acid-base balance by secreting protons or base. however, the lack of a reliable and accurate method to measure the contribution of unidirectional fluxes of hco3- ions to this mechanism has been an obstacle for the determination of the role of bicarbonate in epithelial acid-base homeostasis. recently, one of us developed a method that allows for the reliable determination of transepitheli ... | 1997 | 9124489 |
| the distribution of reduced nicotinamide adenine dinucleotide phosphate-diaphorase in the leopard frog telencephalon and related projections. | the distribution of reduced nicotinamide adenine dinucleotide phosphate-diaphorase (nadph-d) was mapped histochemically in the forebrain of rana pipiens, the leopard frog. intense staining was observed which was strikingly restricted to certain nuclear groups and fiber tracts. the densest concentrations of nadph-d stained cell bodies and fibers were observed in the granule layer of the accessory olfactory bulb and in the ventral aspect of the lateral pallium. intense staining has also been repor ... | 1997 | 9288415 |
| the roles of visual and proprioceptive information during motor program choice in frogs. | previous studies have shown that leopard frogs, rana pipiens, use tongue prehension to capture small prey and jaw prehension to capture large prey. after hypoglossal nerve transection, the frogs fail to open their mouths when attempting to feed on small prey, but open their mouths and capture large prey. here, we investigate how visual information about the prey and proprioceptive information from the tongue interact to influence the motor program choice. using pieces of earthworm of various siz ... | 1996 | 8956496 |
| single-unit responses to whole-field visual stimulation in the pretectum of rana pipiens. | visually responsive single units were recorded from the pretectal region that includes the large-celled nucleus lentiformis mesencephali (nlm) in the leopard frog, rana pipiens. during monocular stimulation of the contralateral eye, 60 single units responding to movement of a large-field, random-dot pattern were quantitatively analyzed using horizontal and vertical directions at each of four pattern velocities (0.4-40 degrees/s). all units were spontaneously active, motion sensitive, and the maj ... | 1996 | 8945761 |
| binaural inhibition is important in shaping the free-field frequency selectivity of single neurons in the inferior colliculus. | 1. we have shown previously that under free-field stimulation in the frontal field, frequency selectivity of the majority of inferior colliculus (ic) neurons became sharper when the loudspeaker was shifted to ipsilateral azimuths. these results indicated that binaural inhibition may be responsible for the direction-dependent sharpening of frequency selectivity. to test the above hypothesis directly, we investigated the frequency selectivity of ic neurons under several conditions: monaural stimul ... | 1996 | 8899629 |
| relationship between anoxia exposure and antioxidant status in the frog rana pipiens. | the biochemical adaptations of cellular antioxidant defenses that permit anoxia-tolerant animals to deal effectively with rapid and large changes in oxygen availability, and hence oxidative stress, during transitions from anoxia to normoxia provide insights into the strategies of antioxidant defense that could help to minimize reperfusion injuries to mammalian organs after anoxia/ischemia stress. the present study analyzes the effects of 30 h anoxia exposure followed by reoxygenation on the anti ... | 1996 | 8897982 |
| hopping and swimming in the leopard frog, rana pipiens: ii. a comparison of muscle activities. | electromyography (emg) was used to examine muscle activity of the major hip, knee, and ankle extensors during both hopping and swimming in leopard frogs. chronic emg electrodes were implanted for periods of 7-10 days. this permitted us to record emg activities during both hopping and swimming from the same electrode, allowing a direct comparison of the timing and amplitudes of muscle activity between the two behaviors. we could then relate these activities to the kinematics of locomotion. in bot ... | 1996 | 8843688 |
| hopping and swimming in the leopard frog, rana pipiens: i. step cycles and kinematics. | this study presents a model for the step cycle patterns used during both hopping and swimming by the leopard frog, rana pipiens. the two behaviors are essentially similar in movement pattern and in the ways they are modified from quadrupedal gaits. in hopping, there is marked hind limb extension throughout stance. the swing begins with a suspension equivalent to the leap that occurs in a galloping or bounding quadruped. following suspension, as the frog descends from the apex of its leap, the hi ... | 1996 | 8843687 |
| rapd marker estimation of genetic structure among isolated northern leopard frog populations in the south-western usa. | amphibians in the south-western united states are currently experiencing population declines. causal explanations for these population changes as well as the implementation of sound management practices requires an understanding of the genetic structure of natural amphibian populations. to this end, we estimated genetic differences within and among seven isolated populations of northern leopard frogs, rana pipiens, from arizona and southern utah using random amplified polymorphic dna (rapd) anal ... | 1996 | 8794561 |
| the involvement of the endothelium in the relaxation of the leopard frog (rana pipiens) aorta in response to acetylcholine. | 1. the vasodilator response to acetylcholine (ach) was investigated in the aortic arches of the leopard frog (rana pipiens). 2. with adrenaline pre-constricted preparations, both ach and sodium nitroprusside (snp) caused concentration-dependent relaxations. damage to the endothelial layer abolished relaxations to ach, or reduced them greatly, but had no effect on vasodilatation to snp. 3. ng-nitro-l-arginine methyl ester (l-name; 1-100 microm) concentration-dependently inhibited relaxations in r ... | 1996 | 8832080 |
| spatial and spectral dependence of the auditory periphery in the northern leopard frog. | we investigated directionalities of eardrum vibration and auditory nerve response in anesthetized northern leopard frogs (rana pipiens pipiens). simultaneous measures of eardrum velocities and firing rates from 282 auditory nerve fibers were obtained in response to free-field sounds from eight directions in the horizontal plane. sound pressure at the external surface of the ipsilateral eardrum was kept constant for each presentation direction (+/- 0.5 db). significant effects of sound direction ... | 1996 | 8592301 |
| fibronectin peptide drvphsrnsit and fibronectin receptor peptide dlyylmdl arrest gastrulation of rana pipiens. | gastrulation is characterized by dramatic cell migration which is thought to require the interaction of cell adhesion molecules with extracellular molecules. we have tested two novel peptides, a fibronectin peptide and a fibronectin receptor peptide, for their effects on gastrulation of the leopard frog rana pipiens. the fibronectin peptide drvphsrnsit corresponds to residues 1373-1383 of the cell-binding domain of fibronectin; the receptor peptide dlyylmdl corresponds to residues 124-131 of bet ... | 1995 | 7498451 |
| a novel re-regulator of cancer growth - a commentary. | tumor cells should not necessarily be viewed as 'alien invaders' that must be killed in order to cure the host harboring them. rather, the successful re-regulation of their growth, even without total tumor eradication, could provide much greater overall benefit to the host. therefore, the criteria for a meaningful evaluation of clinical benefit of cancer treatment must be re-assessed, and the length of survival and its quality should be considered the two most important parameters. tumor cells d ... | 1995 | 21597819 |
| changes in motoneuron membrane potential and reflex activity induced by sudden cooling of isolated spinal cords: differences among cold-sensitive, cold-resistant and freeze-tolerant amphibian species. | the effects of sudden cooling of the spinal cord were studied in three species of amphibians--a cold-sensitive tropical toad (bufo marinus), a cold-resistant, aquatic, hibernating frog (rana pipiens, northern leopard frog) and a freeze-tolerant frog (rana sylvatica, wood frog). ventral root (motoneuron) potentials were recorded from isolated, hemisected spinal cords of each species mounted in a sucrose-gap recording apparatus and superfused with hco3(-)-buffered ringer's solution at room tempera ... | 1995 | 7636445 |
| evaluation of use of tiletamine/zolazepam for anesthesia of bullfrogs and leopard frogs. | use of tiletamine hydrochloride and zolazepam hydrochloride (1:1 fixed ratio combination) as an anesthetic agent in 2 anuran species was studied. a dosage of 5 mg/kg of body weight, administered im, resulted in variable weak tranquilization. intramuscular administration at dosages of 10 and 20 mg/kg induced variable states of tranquilization or anesthesia in leopard frogs (rana pipiens) and bullfrogs (r catesbeiana). the dosages of 50 mg/kg induced anesthesia with greater consistency than lower ... | 1995 | 7601701 |
| classification of the temporal discharge patterns of single auditory neurons in the frog superior olivary nucleus. | temporal discharge patterns of neurons in the superior olivary nucleus (son) of the northern leopard frog (rana pipiens pipiens) were studied by evaluating peri-stimulus time histograms and interspike interval histograms generated from responses to tone bursts at the neuron's characteristic frequency and at 10 db above neuron's characteristic threshold. four basic discharge patterns were observed, i.e., primary-like, phasic-burst, phasic, and pauser. additionally, within each class, different ne ... | 1995 | 7607986 |
| metabolic effects of dehydration on an aquatic frog, rana pipiens. | cellular responses to dehydration were analyzed in six organs of leopard frogs rana pipiens. frogs at 5 degrees c endured the loss of up to 50% of their total body water content but water contents of individual organs were strongly defended. skeletal muscle water content was strongly affected by dehydration, dropping from 80.7% of wet mass in controls to 67.2% in frogs that had lost 50% of their total body water. however, water contents of internal organs dropped by only 3-8% of their wet masses ... | 1995 | 7891032 |
| acetylcholinesterase staining in the auditory brainstem nuclei of the leopard frog, rana pipiens. | we examined the distribution of acetycholinesterase (ache) in the brainstem auditory nuclei of leopard frogs (rana pipiens). numerous ache-labeled somata were observed in caudal brainstem nuclei including the dorsolateral nucleus, superior olivary nucleus, and superficial reticular nucleus. at midbrain levels, ache-labeled somata were observed in the magnocellular, principal and laminar nuclei of the torus semicircularis, though, most were located in the magnocellular nucleus. neuropil labeling, ... | 1994 | 7536314 |
| temperature dependence of two-tone rate suppression in the northern leopard frog, rana pipiens pipiens. | the existence region of two-tone rate suppression in frog low-frequency auditory-nerve fibers was found to include a suppressive region below a fiber's characteristic frequency, contrary to previous reports. in response to 3 degrees c rise in core temperature, the area and the best suppressive frequency (bsf) of the low-side suppressive region significantly increased. increasing core temperature of the frog by 6 degrees c resulted in significant changes in the high-side suppressive region: its a ... | 1994 | 7983279 |
| morphological gradients in sensory hair cells of the amphibian papilla of the frog, rana pipiens pipiens. | the sensory hair cells of the amphibian papilla (ap) of the northern leopard frog were examined in a light-microscopic analysis. hair cell length and cross-sectional area were found to vary systematically along the rostro-caudal axis of the endorgan. the ap was readily divided into three morphological regions. rostrally-located hair cells are tall, cylindrically-shaped cells with large cross-sectional areas and long stereocilia; caudally-located hair cells are short, goblet-shaped cells with sma ... | 1994 | 7852205 |
| modulating radiation cataractogenesis by hormonally manipulating lenticular growth kinetics. | there is considerable evidence that the lens epithelium is the primary site of injury leading to the development of cataracts following radiation exposure. that the damaged cells of the epithelium are the progenitors of the aberrantly differentiating fibers associated with the cataract is indisputable. so too is the observation that post-radiation proliferative activity in the lens epithelium is required for cataracts to develop. the natural hormonal regulation of lens epithelial mitotic activit ... | 1994 | 7821373 |
| diurnal change and prolonged dark effect on myeloid bodies in the retinal pigment epithelium of the leopard frog. | myeloid bodies (mbs) are multi-lamellar membrane structures which are widely distributed in the retinal pigment epithelium (rpe) of lower vertebrates. the functional significance of these organelles is not known, but they are believed to be associated with lipid processing in the retina. to determine the nature of the daily changes which occur in mbs, and to ascertain the best sampling time for mb isolation as a prelude to the biochemical characterization of these organelles, this study has asse ... | 1994 | 7956314 |
| the pattern of catecholamine response to burst activity in leopard frogs, rana pipiens. | it is well known that burst activity causes a rapid breakdown of muscle glycogen and extensive accumulation of lactate in frogs. during recovery, it has been shown that lactate is nearly totally recycled into muscle glycogen. since catecholamines are likely to play some role in the regulation of postexercise repletion of muscle glycogen, the pattern of catecholamine response was assessed in frogs during intense physical activity and the ensuing recovery period. chronically cannulated frogs were ... | 1994 | 7926648 |
| urea and salt effects on enzymes from estivating and non-estivating amphibians. | the effects of urea, cations (k+,nh4,na+,cs+,li+), and trimethylamines on the maximal activities and kinetic properties of pyruvate kinase (pk) and phosphofructokinase (pfk) from skeletal muscle were analyzed in two anuran amphibians, an estivating species, the spadefoot toad scaphiopus couchii, and a semi-aquatic species, the leopard frog rana pipiens. urea, which accumulates naturally to levels of 200-300 mm during estivation in toads, had only minor effects on the vmax, kinetic constants and ... | 1994 | 8047069 |
| experimental seizures in the frog (rana pipiens). | we investigated the effects of chemical convulsants in the leopard frog. systemic kainic acid (5-20 mg/kg) caused limbic-like seizures, with staring, catatonia, fasciculations, and severe motor seizures, which were almost always lethal. intracerebral electroencephalographic (eeg) recordings showed spike or spike-and-wave patterns at 6-8 hz that decreased in frequency and increased in amplitude, maximal at an electrode in the midline olfactory/telencephalic (olf-m) region. with time, an intericta ... | 1994 | 8174521 |
| serotonin-like immunoreactivity in the adult and developing retina of the leopard frog rana pipiens. | recent work in nonmammalian vertebrate retinas has suggested that other cell types besides the generally accepted amacrine cells may contain serotonin. we have used immunocytochemical methods to study serotonin-like immunoreactivity (5-htli) in the retina of the developing and mature frog rana pipiens. in the adult, two types of serotonin immunoreactive (5-ht-ir) cells were found in the inner nuclear layer (inl) of the retina. additionally, a large population of cells in the retinal ganglion cel ... | 1993 | 7906699 |
| adaptations of plasma membrane glucose transport facilitate cryoprotectant distribution in freeze-tolerant frogs. | natural freeze tolerance in several anuran species involves the accumulation of high concentrations of glucose as a cryoprotectant in body fluids and tissues. the present study identifies an important new molecular mechanism supporting freeze tolerance, an adaptive increase in the capacity for facilitated transport of cryoprotectant across plasma membranes by increasing the numbers and/or activity of plasma membrane glucose transporters. glucose transport by membranes isolated from liver and ske ... | 1993 | 8238604 |
| observations on the development of unusual melanization of leopard frog ventral skin. | the ontogeny of ventral pigmentation of two species of leopard frog, rana pipiens and r. chiricahuensis, was examined by light microscopy and transmission electron microscopy to reveal how the unusual melanistic ventral pigmentation of r. chiricahuensis is achieved at the cellular level. ventral skin of r. pipiens is always white. ventral skin of adult r. chiricahuensis is white when frogs are background-adapted to a white substrate, but ventral skin becomes nearly as dark colored as the dorsal ... | 1993 | 8496971 |
| anuran calling circuits: inhibition of pretrigeminal nucleus by prostaglandin. | neural correlates of mating calling and pulmonary respiration were recorded from isolated brain stems of male northern leopard frogs (rana p. pipiens) before and after exposure of the brain stems to prostaglandin f2 alpha (pg) or saline. diffusion of pg (but not saline) from a pipette directly over the pretrigeminal nuclei abolished "calling" temporarily. similar application of pg nearby had no effect. exposure of only the anterior 1/2 of the brain stem, containing the pretrigeminal nuclei but n ... | 1993 | 8440519 |
| a prey-type dependent hypoglossal feedback system in the frog rana pipiens. | nerve transection experiments combined with high-speed videography and electromyography were used to characterize a prey-type dependent hypoglossal feedback system which coordinates mouth opening and tongue protraction in the common leopard frog, rana pipiens. when feeding on small prey, sensory feedback from the tongue through the hypoglossal nerve is necessary to trigger mouth opening. if sensory feedback is prevented from reaching the brain by transection of the hypoglossal nerve, then the mo ... | 1993 | 8364717 |
| redeployment of trigeminal motor axons during metamorphosis. | as a consequence of the degeneration and replacement of the jaw muscle fibers in the leopard frog, rana pipiens, trigeminal motoneurons innervate different targets before and after metamorphosis. this investigation examined the morphological correlates of the reassignment of trigeminal motoneurons during the initial phases of myofiber turnover. specifically, silver-cholinesterase histochemistry and electron microscopy were used to 1) identify the fate of motor axons within the neuromuscular junc ... | 1992 | 1484115 |
| the inactivating potassium currents of hair cells isolated from the crista ampullaris of the frog. | 1. a-type outward currents were studied in sensory hair cells isolated from the semicircular canals (scc) of the leopard frog (rana pipiens) with whole-cell voltage- and current-clamping techniques. 2. there appear to be two classes of a-type outward-conducting potassium channels based on steady-state, kinetic, pharmacological parameters, and reversal potential. 3. the two classes of a-type currents differ in their steady-state inactivation properties as well as in the kinetics of inactivation. ... | 1992 | 1336044 |
| hibernation alters the frog's immune system. | the lymphomyeloid organs and blood leukocyte populations of the leopard frog, rana pipiens, undergo conspicuous changes during hibernation at 4 degrees c. within the blood, spleen, thymus, jugular bodies, and bone marrow there was a progressive loss of hemopoietic populations resulting in a marked lymphocyte depletion. termination of the 135-day hibernation period resulted in the restoration of all hemopoietic elements in the blood and lymphomyeloid organs within 30 days. frogs subjected to expe ... | 1992 | 1424717 |
| neural correlates of frog calling: production by two semi-independent generators. | the anterior preoptic nuclei of the isolated brainstem of male, northern leopard frogs (rana p. pipiens) were stimulated electrically and neural correlates of mating calling recorded from the rhombencephalic mating calling pattern generator. lesions of discrete areas of the brainstem showed that the mating calling generator is separable into two generators, the pretrigeminal nucleus and the classical pulmonary respiration generator (which is approximately co-extensive with the motor nuclei ix-x) ... | 1992 | 1449644 |
| directionality of phase locking in auditory nerve fibers of the leopard frog rana pipiens pipiens. | a dorsal approach to the eighth nerve and free-field stimulation were used to investigate the effect of sound direction and intensity on phase locking in auditory nerve fibers of the leopard frog rana pipiens pipiens. tuning curves of 75 auditory neurons were analyzed (fig. 2). amphibian papillar neurons, but not basilar papillar neurons, exhibit significant phase locking to short tone bursts at the characteristic frequency (cf), the degree of phase locking (vector strength) decreasing with the ... | 1992 | 1507157 |
| is there a seasonal variation in mucus transport and nutrient absorption in the leopard frog? | we postulated that as a hibernating species, frogs might have variable demands for nutrients at different seasons of the year and that this must be reflected in seasonal variations of physiologic processes related to nutrient transport and absorption. we examined the rate of mucus transport on the ciliated palate and the movement of nutrients across the intestinal lumen of leopard frogs, rana pipiens. mucus transport on the frog palate was strongly influenced by season, with maximal transport oc ... | 1992 | 1498713 |
| metabolic fate of lactate after vigorous activity in the leopard frog, rana pipiens. | although the ability of isolated frog muscle to synthesize glycogen from lactate has long been known, it has never been demonstrated that this metabolic activity occurs in the intact frog. our results clearly indicate that lactate glycogenesis in frog muscle occurs to a significant extent in vivo. during recovery from strenuous exercise, most of the lactate accumulated by frogs seems to be recycled into muscle glycogen because the lactate that disappears during recovery could account nearly stoi ... | 1992 | 1539733 |
| temporal coding in the frog auditory midbrain: the influence of duration and rise-fall time on the processing of complex amplitude-modulated stimuli. | 1. single-unit recordings were made in the auditory midbrain, the torus semicircularis (ts) of the northern leopard frog, to independently characterize the processing of different temporal attributes (signal duration, rise-fall time, and rate of amplitude modulation) of natural sounds and to investigate how these temporal variables interact to produce the observed responses to complex amplitude-modulated (am) signals. response functions, on the basis of mean spike count, were derived and categor ... | 1992 | 1552312 |
| temporal processing in the dorsal medullary nucleus of the northern leopard frog (rana pipiens pipiens). | 1. single-unit responses to different temporal acoustic parameters were characterized in the dorsal medullary nucleus (dmn) of the northern leopard frog, rana pipiens pipiens. our goal was to provide both a quantitative and a qualitative assessment of the neural representation of behaviorally relevant temporal acoustic patterns in the frog's dmn. 2. acoustic stimuli included tone bursts having different durations, rise times, or rates of amplitude modulation (am). several metrics were used to co ... | 1991 | 1661327 |
| effect of background color and low temperature on skin color and circulating alpha-msh in two species of leopard frog. | circulating levels of alpha-melanocyte stimulating hormone (alpha-msh) in two species of leopard frog, rana pipiens and r. chiricahuensis, were measured by radioimmunoassay to reveal the correlation between skin color change induced by background color and by low temperature. high levels of alpha-msh were found in both species of frog on a black background, but r. chiricahuensis had eight times higher levels than r. pipiens, r. chiricahuensis also exhibited the ability to darken its ventral surf ... | 1991 | 1879665 |
| processing of behaviorally relevant temporal parameters of acoustic stimuli by single neurons in the superior olivary nucleus of the leopard frog. | response characteristics of 130 single neurons in the superior olivary nucleus of the northern leopard frog (rana pipiens pipiens) were examined to determine their selectivity to various behaviorally relevant temporal parameters [rise-fall time, duration, and amplitude modulation (am) rate] of acoustic signals. response functions were constructed with respect to each of these variables. neurons with different temporal firing patterns such as tonic, phasic or phasic-burst firing patterns, partici ... | 1991 | 1920165 |
| prostaglandin regulation of h+ secretion in amphibian epithelia. | the role of prostaglandins in regulating h+ excretion in amphibian epithelia was investigated. the abdominal skin of the southern leopard frog rana pipiens and the urinary bladder of the toad bufo marinus were used to measure proton excretion across their mucosal surface. prostaglandin f2 alpha (pgf2 alpha) produced a dose-dependent inhibition of h+ excretion across the frog skin. frogs pretreated with ibuprofen (30 mg.kg-1.day-1 for 3 days) showed an enhanced proton excretion similar to that ob ... | 1991 | 1903604 |
| diagnostic exercise: high mortality in leopard frogs (rana pipiens). | | 1991 | 1658447 |
| classification of the temporal discharge patterns of single auditory neurons in the dorsal medullary nucleus of the northern leopard frog. | 1. the dorsal medullary nucleus (dmn) of frogs is the presumed homolog of the mammalian cochlear nucleus (cn). like the cn, the dmn is the sole target of centrally projecting primary auditory-nerve fibers and the first central auditory-processing center. to study the transformation of acoustic information in the dmn, we have utilized relatively simple stimuli--tone bursts--to detail the temporal discharge patterns of dmn neurons that can be compared with those shown by auditory-nerve fibers. 2. ... | 1990 | 2283537 |