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chronic exposure to fluoxetine (prozac) causes developmental delays in rana pipiens larvae.selective serotonin reuptake inhibitors (ssris), such as fluoxetine, are among the many pharmaceuticals detected in aquatic ecosystems. although the acute effects of ssris on select organisms have been reported, little is understood about the chronic effects of these drugs on amphibians, which are particularly sensitive to environmental pollutants. serotonin plays important roles in many physiological functions, including a wide array of developmental processes. exposure to ssris during developm ...201020836066
preexposure to ultraviolet b radiation and 4-tert-octylphenol affects the response of rana pipiens tadpoles to 3,5,3'-triiodothyronine.exposure to multiple environmental stressors is negatively impacting the health of amphibians worldwide. increased exposure to ultraviolet b radiation (uvbr) and chemical pollutants may affect amphibian populations by disrupting metamorphosis; however, the actual mechanisms by which these stressors affect development remain unknown. because amphibian metamorphosis is controlled by thyroid hormones (th), changes in developmental rates by environmental stress suggest a disruption of the thyroid sy ...201020821635
chronic, dietary polybrominated diphenyl ether exposure affects survival, growth, and development of rana pipiens tadpoles.levels of polybrominated diphenyl ethers (pbdes) in the environment have been increasing rapidly over the past two decades; however, the toxicology of these compounds to aquatic organisms is poorly understood. because amphibians play a role in both aquatic and terrestrial food webs, and are currently undergoing worldwide population declines, it is of interest to determine how pbdes may affect amphibian health. this is the first study that reports chronic, dietary effects of environmentally relev ...201020821428
regulation of thyroid hormone-, oestrogen- and androgen-related genes by triiodothyronine in the brain of silurana tropicalis.amphibian metamorphosis is an excellent example of hormone-dependent control of development. thyroid hormones (ths) regulate almost all aspects of metamorphosis, including brain development and larval neuroendocrine function. sex steroids are also important for early brain function, although little is known about interactions between the two hormonal systems. in the present study, we established brain developmental profiles for thyroid hormone receptors (tralpha and trbeta), deiodinases (dio1, d ...201020626568
progesterone modulation of transmembrane helix-helix interactions between the alpha-subunit of na/k-atpase and phospholipid n-methyltransferase in the oocyte plasma membrane.progesterone binding to the surface of the amphibian oocyte initiates the meiotic divisions. our previous studies with rana pipiens oocytes indicate that progesterone binds to a plasma membrane site within the external loop between the m1 and m2 helices of the alpha-subunit of na/k-atpase, triggering a cascade of lipid second messengers and the release of the block at meiotic prophase. we have characterized this site, using a low affinity ouabain binding isoform of the alpha1-subunit.201020500835
[onconase: a ribonuclease with antitumor activity].onconase (ranpirnase) is a homologous protein obtained from rana pipiens frog eggs. the activity of onconase, and particularly its antitumor effect, is strictly connected with ribonuclease(rn-ase) activity. onconase induces cell death through the decomposition of inner cellular rna,inhibition of protein synthesis, and inhibition of cell growth and proliferation and it also specifically triggers tumor cell apoptosis. a very important mechanisms of its cytotoxicity is also its antioxidant activity ...201020173221
short-term synaptic plasticity at the main and vomeronasal olfactory receptor to mitral cell synapse in frog.synaptic responses resulting from stimulation of the main olfactory and vomeronasal (vn) nerves were measured in main and accessory olfactory bulb (aob) of frog, rana pipiens, to test the hypothesis that properties of these synapses would reflect the distinct differences in the time course of odour delivery to each of these olfactory structures. paired-pulse depression dominated responses to repetitive stimulation of the main olfactory nerve for interstimulus intervals (isi) up to several second ...200920128846
ramp acceleration and hydraulic conductivity (l(p)) of living capillaries.living mesenteric capillaries with either an intact or disrupted glycocalyx were challenged with ramp change in shear stress (deltatau). animals (rana pipiens) were divided randomly into two experimental groups, and two true capillaries (tc) per animal were investigated. the modified landis technique was combined with intravital microscopy to view individual tc and assess hydraulic conductivity (l(p)), an index of capillary function. median l(p) was 3.2 x 10(-7) for control and 11.8 x 10(-7) cm ...201020025890
monitoring transient ca2+ dynamics with large-conductance ca2+-dependent k+ channels at active zones in frog saccular hair cells.neurotransmitter release from the basolateral surface of auditory and vestibular hair cells is mediated by ca(2+) influx through voltage-gated ca(2+) channels. co-localization of large-conductance ca(2+)-activated k(+) (bk) channels at the active zones of these cells affords them with an optimal location to act as reporters of the ca(2+) concentration changes at active zones of transmitter release. in this report we use bk channels in frog (rana pipiens) hair cells to monitor dynamic changes in ...201019897018
assessment of thyroid system disruption in rana pipiens tadpoles chronically exposed to uvb radiation and 4-tert-octylphenol.many studies have considered recent increases in ultraviolet b radiation (uvbr) and endocrine disrupting chemicals polluting the environment as possible contributing factors to the reduction in amphibian populations. it has been demonstrated that exposure of amphibians to estrogenic chemicals or uvbr can affect the timing of larval development and metamorphosis. however, amphibians in the wild are exposed to multiple environmental stressors simultaneously. therefore, our study examines the effec ...200919811842
eph/ephrin gradients in the retinotectal system of rana pipiens: developmental and adult expression patterns.eph/ephrin-receptor/ligand a and b families play a variety of roles during cns development, including patterning the retinotectal projection. however, the alignment of their expression gradients with developing retinotectal maps and gradients of cellular development is not well understood in species whose midbrain tecta undergo a protracted anterior to posterior development. by using anatomical tracing methods and (3)h-thymidine neuronography, we have mapped the retinotectal projection and the s ...200919260054
critical period of sensitivity for effects of cadmium on frog growth and development.cadmium is a ubiquitous pollutant in aquatic environments that can alter organismal physiology and ecology. previous experiments found that ecological cd exposures increased the growth and development of two north american anurans. however, the generality of these effects among species, the time period over which they occur, and the mechanisms responsible remain conjectural. the goal of the present study was to determine the critical period of sensitivity of rana pipiens exposed to ecologically ...200919133712
targeted therapeutic rnases (immunornases).immunotoxins combining antibody specificity with bacterial or plant toxins are limited by their strong immunogenicity and non-specific toxicity. ribonucleases of the rnase a protein superfamily provide a solution to address these issues because they show potent antineoplastic activity on cell internalization but do not show appreciable immunogenicity or non-specific toxicity. their therapeutic value is demonstrated by rnase derived from the frog (rana pipiens), onconase (onc, alfacell, inc., new ...200919063695
nociceptin produces antinociception after spinal administration in amphibians.nociceptin, also known as orphanin fq, is a opioid-like neuropeptide that mediates its effects at the nociceptin receptor, a member of the g protein-coupled receptor superfamily. in mammals, nociceptin produces analgesia after spinal administration, however the role of nociceptin and nociceptin receptors in the modulation of noxious stimuli in non-mammalian species has not been examined. in an amphibian pain model using the acetic acid test with rana pipiens, nociceptin and nociceptin1-13 amide ...200918804120
up-regulation of brain-derived neurotrophic factor by application of fibroblast growth factor-2 to the cut optic nerve is important for long-term survival of retinal ganglion cells.application of basic fibroblast growth factor (fgf-2) to the optic nerve after axotomy promotes the survival of retinal ganglion cells (rgcs) in the frog rana pipiens and results in a rapid up-regulation of brain-derived neurotrophic factor (bdnf) and trkb synthesis by the rgcs. here we investigate whether this up-regulation is maintained over the long term and whether it is required for fgf-2's survival effect. at 6 weeks after axotomy and fgf-2 treatment, we found more rgcs immunopositive for ...200818655198
effect of temperature on residual force enhancement in single skeletal muscle fibers.it is well accepted that the steady-state isometric force following active stretching of a muscle is greater than the steady-state isometric force obtained in a purely isometric contraction at the same length. this property of skeletal muscle has been called residual force enhancement (fe). despite decades of research the mechanisms responsible for fe have remained largely unknown. based on previous studies showing increases in fe in fibers in which cross-bridges were biased towards weakly bound ...200818639880
chloride conductance in amphibian skin: regulatory control in the skin of rana pipiens.chloride conductance across the isolated skin of rana pipiens shows a voltage-activated component (g(cl)(v)) which requires the presence of mucosal cl. g(cl)(v) is normally low or dormant. it is stimulated by elevated intracellular camp, irrespective whether originating from application of ss-adrenergic agonists (isoproterenol), stimulators of the adenylyl-cyclase (forskolin), inhibitors of the phosphodiesterases (isobutyl-methyl-xanthine) or membrane-permeable camp analogues (cpt-camp). baselin ...200818599332
progesterone and subsequent polar metabolites are essential for completion of the first meiotic division in amphibian oocytes.we find that completion of the first meiotic division in rana pipiens oocytes requires the sequential action of at least two steroids: progesterone and one or more subsequent polar metabolites of progesterone. progesterone binding in vitro to oocyte surface receptors increases during the first 4-5h of exposure, followed by internalization of plasma membrane together with membrane-bound progesterone over the next hour. the internalized progesterone is metabolized to highly polar polyhydroxylated ...200818599190
larval amphibian growth and development under varying density: are parasitized individuals poor competitors?population density and infection with parasites often are important factors affecting the growth and development of individuals. how these factors co-occur and interact in nature should have important consequences for individual fitness and higher-order phenomena, such as population dynamics of hosts and their interactions with other species. however, few studies have examined the joint effects of density and parasitism on host growth and development. we examined the co-influences of rearing den ...200818157552
progesterone binding to the alpha1-subunit of the na/k-atpase on the cell surface: insights from computational modeling.progesterone triggers the resumption of meiosis in the amphibian oocyte through a signaling system at the plasma membrane. analysis of [(3)h]ouabain and [(3)h]progesterone binding to the plasma membrane of the rana pipiens oocyte indicates that progesterone competes with ouabain for a low affinity ouabain binding site on a 112kda alpha1-subunit of the membrane na/k-atpase. published amino acid sequences from both low and high affinity ouabain binding alpha1-subunits are compared, together with p ...200817936318
multiple stressor effects of herbicide, ph, and food on wetland zooplankton and a larval amphibian.interactions of herbicides and natural environmental stressors such as ph and food availability are poorly understood. we tested a chemical formulation of triclopyr (release) at environmentally relevant test concentrations (0.25 and 0.50 mg l(-1)) in combination with two levels of ph (ph 5.5 and 7.5), and two levels of food availability (high and low). population level effects of each stressor alone and in combination with the others were investigated using simocephalus vetulus, a zooplankton sp ...200817904219
onconase, an anti-tumor ribonuclease suppresses intracellular oxidative stress.onconase (onc), an antitumor ribonuclease from oocytes of a frog rana pipiens, capable of inducing apoptosis in many cell lines is synergistic with several other anticancer drugs. since cytotoxic effects of numerous drugs are modulated by reactive oxygen intermediates (roi), we have studied effects of onc on the intracellular level of oxidants in several normal cell types as well as tumor cell lines. it is demonstrated for the first time that onc substantially decreases the content of roi in all ...200717671695
interphotoreceptor retinoid-binding protein is the physiologically relevant carrier that removes retinol from rod photoreceptor outer segments.light detection by vertebrate rod photoreceptor outer segments results in the destruction of the visual pigment, rhodopsin, as its retinyl moiety is photoisomerized from 11-cis to all-trans. the regeneration of rhodopsin is necessary for vision and begins with the release of the all-trans retinal and its reduction to all-trans retinol. retinol is then transported out of the rod outer segment for further processing. we used fluorescence imaging to monitor retinol fluorescence and quantify the kin ...200717602665
cloning and bioinformatics of amphibian mu, delta, kappa, and nociceptin opioid receptors expressed in brain tissue: evidence for opioid receptor divergence in mammals.opioid agonists produce analgesia in humans and other mammals by binding to three distinct types of g protein-coupled receptors; mu (mor), delta (dor), and kappa (kor) opioid receptors. a fourth member of the opioid receptor family is the nociceptin or orphanin fq receptor (orl), however the role of the orl receptor in analgesia is less clear. in the northern grass frog, rana pipiens, systemic and central administration of morphine and selective mor, dor, and kor agonists produced dose-dependent ...200717452077
hormone cross-regulation in the tadpole brain: developmental expression profiles and effect of t3 exposure on thyroid hormone- and estrogen-responsive genes in rana pipiens.during metamorphosis, the tadpole neuroendocrine brain is a major target for the organisational effects of hormones acting via both endocrine feedback mechanisms and local hormone production. while the receptor-mediated actions of thyroid hormones in brain development have been well described, there is evidence that thyroid hormones could also be an important modulator of estrogen action during metamorphosis. to better understand hormone action and potential cross-regulation between thyroid horm ...201317400220
combining visual information from the two eyes: the relationship between isthmotectal cells that project to ipsilateral and to contralateral optic tectum using fluorescent retrograde labels in the frog, rana pipiens.the frog nucleus isthmi (homolog of the mammalian parabigeminal nucleus) is a visually responsive tegmental structure that is reciprocally connected with the ipsilateral optic tectum; cells in nucleus isthmi also project to the contralateral optic tectum. we investigated the location of the isthmotectal cells that project ipsilaterally and contralaterally using three retrograde fluorescent label solutions: alexa fluor 488 10,000 mw dextran conjugate; rhodamine b isothiocyanate; and nuclear yello ...200717335048
effects of cannabinoids on synaptic transmission in the frog neuromuscular junction.this study aimed to investigate the function of the cannabinoid receptor in the neuromuscular junction of the frog (rana pipiens). miniature end-plate potentials were recorded using the intracellular electrode recording technique in the cutaneous pectoris muscle in the presence of the cannabinoid agonists win55212-2 (win; r-(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)]-pyrolol[1,2,3de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone) and arachidonylcyclopropylamide [acpa; n-(2-cyclopropyl)-5z,8z,11z,1 ...200717267583
new insights into the passive force enhancement in skeletal muscles.the steady-state isometric force following active stretching of a muscle is always greater than the steady-state isometric force obtained in a purely isometric contraction at the same length. this phenomenon has been termed "residual force enhancement" and it is associated with an active and a passive component. the origin of these components remains a matter of scientific debate. the purpose of this work was to test the hypothesis that the passive component of the residual force enhancement is ...200717097664
change in shear stress (deltatau)/hydraulic conductivity (lp) relationship after pronase treatment of individual capillaries in situ.a complex glycoprotein meshwork covers the inner wall of blood vessels and is implicated in mechanotransduction of fluid shear stress (tau). a relationship between deltatau and capillary lp has been established. the purpose of this study was to evaluate lp in response to deltatau after exposing the capillary lumen to a mild, non-specific protease selected to disrupt its inner matrix. we hypothesized that lp would not correlate with deltatau after enzyme treatment. frogs (rana pipiens, n=69) were ...200717030043
rearing density and susceptibility of rana pipiens metamorphs to cercariae of a digenetic trematode.cercariae of many digenean trematodes target particular developmental stages of their hosts. for some digeneans that are parasites of amphibians, infection appears timed to host metamorphosis. the success and timing of metamorphosis is itself affected by a number of factors, including host density. we investigated the degree to which rearing density of rana pipiens larvae influenced time to metamorphosis and snout-to-vent length and mass at metamorphosis, as well as establishment of cercariae of ...200616883998
changes in nnos and nadph diaphorase in frog retina and tectum after axotomy and fgf-2 application.we have shown previously that application of fibroblast growth factor-2 (fgf-2) to the cut optic nerve of the frog, rana pipiens, augments the survival of retinal ganglion cells (rgcs). in this study, we examine the effects of axotomy and fgf-2 treatment upon the distribution of nitric oxide synthase (nos) and nadph diaphorase (nadph-d) activity in the frog retina and tectum. we find that nos and nadph-d are largely absent from rgcs but present in amacrine neurons and in retinorecipient tectal l ...200616808907
gonadotropin stimulation of steroid synthesis and metabolism in the rana pipiens ovarian follicle: sequential changes in endogenous steroids during ovulation, fertilization and cleavage stages.steroid synthesis and metabolism have been followed in rana pipiens ovarian follicles, denuded oocytes and eggs during ovulation, fertilization and cleavage stages (blastula formation). under physiological conditions, gonadotropin stimulation of the fully grown follicle leads to progesterone synthesis from [(3)h]acetate as well as formation of much smaller amounts of 17alpha-hydroxyprogesterone, androstenedione, pregnanedione and pregnanediol. progesterone levels increase during completion of th ...200616678716
kinetic evidence that desensitized nachr may promote transitions of active nachr to desensitized states during sustained exposure to agonists in skeletal muscle.during prolonged exposure of postjunctional nicotinic acetylcholine receptors (nachr) of skeletal muscle to acetylcholine (ach), agonist-activated nachr (nachra) gradually fall into a refractory "desensitized" state (nachrd), which no longer supports the high-conductance channel openings characteristic of the initially active nachra. in the present study, the possibility was examined that nachrd, rather than simply constituting a passive "trap" for nachra, may actively promote further conversion ...200616555103
contribution of structural peculiarities of onconase to its high stability and folding kinetics.onconase (onc) from rana pipiens is the smallest member of the ribonuclease a (rnase a) superfamily. despite a tertiary structure similar to rnase a, onc is distinguished by an extremely high thermodynamic stability. in the present paper we have probed the significance of three structural regions, which exhibit structural peculiarities in comparison to rnase a, for the stability of onc to temperature and guanidine hydrochloride induced denaturation: (i) the n-terminal pyroglutamate residue, (ii) ...200616533040
acid exposure is an immune disruptor in adult rana pipiens.acidic environments are physiological stressors for amphibians. the objective of the present study was to document the effect of an acidic environment on innate immune system function under controlled experimental conditions in rana pipiens. we developed an in vivo assay, by injecting a suspension of 1-microm fluorescent beads in fluid thioglycollate, to induce peritonitis. the number of peritoneal exudate leukocytes and their phagocytic activity did not increase with thioglycollate injection wh ...200616494242
systemic and spinal administration of the mu opioid, remifentanil, produces antinociception in amphibians.remifentanil is a relatively new opioid analgesic related to the fentanyl family of mu opioid receptor agonists and is used clinically for its unique property of having an ultra-short duration of action. however, there is little preclinical data on the analgesic (antinociceptive) effects of remifentanil and none obtained in non-mammalian animal models. the antinociceptive effects of remifentanil were assessed by using the acetic acid test in amphibians. systemic and spinal administration of remi ...200616487509
frequency selectivity of synaptic exocytosis in frog saccular hair cells.the ability to respond selectively to particular frequency components of sensory inputs is fundamental to signal processing in the ear. the frog (rana pipiens) sacculus, which is used for social communication and escape behaviors, is an exquisitely sensitive detector of sounds and ground-borne vibrations in the 5- to 200-hz range, with most afferent axons having best frequencies between 40 and 60 hz. we monitored the synaptic output of saccular sensory receptors (hair cells) by measuring the inc ...200616473940
ribonucleases as a novel pro-apoptotic anticancer strategy: review of the preclinical and clinical data for ranpirnase.cytotoxic ribonucleases (rnases), such as ranpiranase, represent a novel mechanism-based approach to anticancer therapy. these relatively small proteins selectively attack malignant cells, triggering apoptotic response and inhibiting protein synthesis. ranpirnase, originally isolated from oocytes of rana pipiens, is a member of a family of endoribonucleases. the anticancer effects of ranpiranase have been documented in both in vitro and in vivo experimental tumor models. the effects of ranpirana ...200516305992
fibroblast growth factor 2 applied to the optic nerve after axotomy up-regulates bdnf and trkb in ganglion cells by activating the erk and pka signaling pathways.application of basic fibroblast growth factor (fgf-2) to the optic nerve after axotomy promotes the survival of retinal ganglion cells (rgcs) in the frog, rana pipiens. here we investigate the effects of fgf-2 treatment upon the synthesis of brain-derived neurotrophic factor (bdnf) and its receptor, tyrosine receptor kinase b (trkb). axotomy alone increased the amounts of bdnf and trkb mrna in rgcs after 1 week and 48 h, respectively; fgf-2 treatment to the nerve accelerated and increased this u ...200616269011
long-term in vivo modulation of synaptic efficacy at the neuromuscular junction of rana pipiens frogs.prolonged changes in motor neurone activity can result in long-term changes in synaptic transmission. we investigated whether mechanisms commonly thought to be involved in determining synaptic efficacy of vertebrate motor neurones are involved in these long-term changes. the nerve supplying the cutaneous pectoris muscle was chronically stimulated via skin surface electrodes in freely moving frogs for 5-7 days. chronic stimulation induced a 50% reduction in evoked endplate potential (epp) amplitu ...200516166159
characterization of naturally occurring peptides in the skin secretion of rana pipiens frog reveal pipinin-1 as the novel insulin-releasing agent.naturally occurring insulinotropic peptides were isolated from the skin secretions of rana pipiens frogs. crude secretions (50 mg; 5-10 frogs) obtained by mild electrical stimulation of the dorsal skin surface were purified by reversed-phase high-performance liquid chromatography (hplc) yielding 80 fractions. in acute incubations with glucose-responsive brin-bd11 cells, fractions 40-47 (band 1) and fractions 60-65 (band 2) showed significant 1.7-6.7-fold increases in insulin-releasing activity ( ...200516138858
superimposed maps of the monocular visual fields in the caudolateral optic tectum in the frog, rana pipiens.the superficial layers of the frog optic tectum receive a projection from the contralateral eye that forms a point-to-point map of the visual field. the monocular part of the visual field of the contralateral eye is represented in the caudolateral region of the tectum while the binocular part of the visual field is represented in the rostromedial tectum. within the representation of the binocular field (rostromedial tectum), the maps of visual space from each eye are aligned. the tectal represen ...200715842745
treatment of jurkat acute t-lymphocytic leukemia cells by onconase (ranpirnase) is accompanied by an altered nucleocytoplasmic distribution and reduced expression of transcription factor nf-kappab.onconase (ranpirnase), a novel ribonuclease isolated from rana pipiens oocytes, was reported to suppress cancer cell growth in vitro, reduce tumor size in animals, and augment cytotoxicity of several chemotherapeutic agents. since onconase is currently in phase iii clinical trials tested in treatment of mesothelioma, much emphasis has been placed on the mechanism of its anti-tumor activity. previous studies have shown that onconase-responsive cells become arrested at the g1/s checkpoint of the c ...200415547713
in vivo expression of myosin essential light chain using plasmid expression vectors in regenerating frog skeletal muscle.it is well established that mutations in specific structural elements of the motor protein myosin are directly linked to debilitating diseases involving malfunctioning striated muscle cells. a potential way to study the relationship between myosin structure and function is to express exogenous myosin in vivo and determine contractile properties of the transgenic muscle cells. however, in vivo expression of functional levels of contractile proteins using transient transgenesis in skeletal muscle ...200515538392
opioid research in amphibians: an alternative pain model yielding insights on the evolution of opioid receptors.this review summarizes the work from our laboratory investigating mechanisms of opioid analgesia using the northern grass frog, rana pipiens. over the last dozen years, we have accumulated data on the characterization of behavioral effects after opioid administration on radioligand binding by using opioid agonist and antagonist ligands in amphibian brain and spinal cord homogenates, and by cloning and sequencing opioid-like receptor cdna from amphibian central nervous system (cns) tissues. the r ...200415464208
emi1-mediated m-phase arrest in xenopus eggs is distinct from cytostatic factor arrest.oocytes of most vertebrates arrest at metaphase of the second meiosis (meta-ii) to await fertilization, thus preventing parthenogenetic activation. this arrest is caused by a cytoplasmic activity called cytostatic factor (csf), which was first identified in the frog rana pipiens oocyte >30 years ago. csf arrest is executed by maintaining the activity of cyclin b-cdc2 at elevated levels largely through prevention of cyclin b destruction. although csf arrest is established by the mos-mitogen-activ ...200415314241
fiber order of the normal and regenerated optic tract of the frog (rana pipiens).in the normal frog, axons from the peripheral retina arising at the temporal pole course superficially in the middle stream of the diencephalic optic tract. axons from the nasal pole course in two streams running in the opposite margins of the tract, dorsonasal axons ventrally, ventronasal axons dorsally. axons from the dorsal and ventral poles of the retina occupy the intervals between the aforementioned middle and marginal streams. axons from more central regions of the retina tend to occupy d ...200415281079
force enhancement in single skeletal muscle fibres on the ascending limb of the force-length relationship.it has been assumed that force enhancement in single fibres of skeletal muscles only occurs on the descending, and not the ascending or plateau region, of the force-length relationship. this assumption has been based, however, on theoretical considerations or isolated experiments, in which neither stretch conditions nor fibre lengths were optimized for force enhancement. therefore, the purpose of this study was to investigate the residual, steady-state force enhancement following active stretch ...200415235007
effects of sublethal copper exposure on behavior and growth of rana pipiens tadpoles. 200415199983
multiple stress effects of vision herbicide, ph, and food on zooplankton and larval amphibian species from forest wetlands.as part of a multiple-tier research program, interactions of the herbicide vision (glyphosate) with two stressors, ph and food level, were examined. effects of the formulated product vision were tested at two test concentrations (0.75 and 1.50 mg acid equivalent/l), two ph levels (ph 5.5 and 7.5), and under high and low food concentrations. effects of each stressor alone and in combination were examined using two common wetland taxa: zooplankton, simocephalus vetulus, and tadpoles (gosner stage ...200415095876
an introductory biology lab that uses enzyme histochemistry to teach students about skeletal muscle fiber types.one important goal of introductory biology laboratory experiences is to engage students directly in all steps in the process of scientific discovery. even when laboratory experiences are built on principles discussed in the classroom, students often do not adequately apply this background to interpretation of results they obtain in lab. this disconnect has been described at the level of medical education (4), so it should not be surprising that educators have struggled with this same phenomenon ...200414973008
wavelength and intensity dependence of retinal evoked responses using in vivo optic nerve recording.we use a whole-animal model and wavelength-selective optical stimulation to investigate relationships between optical stimulus characteristics and neural signaling. light-emitting diodes are used to selectively stimulate rod and cone pathways in rana pipiens. a suction electrode is used to make in vivo measurements of the compound action potential from the optic nerve as the wavelength and intensity of the stimulus is varied. our results demonstrate that the cone and rod pathways can be separate ...200314960112
fatigue and recovery of dynamic and steady-state performance in frog skeletal muscle.muscle fatigue reflects alterations of both activation and cross-bridge function, which will have markedly different affects on steady-state vs. dynamic performance. such differences offer insight into the specific origins of fatigue, its mechanical manifestation, and its consequences for animal movement. these were inferred using dynamic contractions (twitches and cyclic work as might occur during locomotion) and steady-state performance with maximal, sustained activation (tetani, stiffness, an ...200414726426
effect of n-terminal and met23 mutations on the structure and dynamics of onconase.onconase (ronc), otherwise known as ranpirnase or p-30 protein, which was initially purified from extracts of rana pipiens oocytes and early embryos, exhibits anticancer activity both in vitro and in vivo and is in phase iii clinical trials for tumor therapy. we have determined the solution nmr structure of a recombinant onconase with met(-1), gln1, and leu23 residues (m-1, q1, m23l)ronc. the 20 best solution structures had a backbone root mean square deviation of 0.41 +/- 0.09 a with respect to ...200414645226
axonal sprouting in the optic nerve is not a prerequisite for successful regeneration.axonal sprouting, the production of axons additional to the parent one, occurs during optic nerve regeneration in goldfish and the frog rana pipiens, with numbers of regenerate axons exceeding normal values four- to sixfold (murray [1982] j. comp. neurol. 209:352-362; stelzner and strauss [1986] j. comp. neurol. 245:83-103). to determine whether axonal sprouting is a prerequisite for regeneration, the frog litoria moorei was examined, a species that undergoes successful optic nerve regeneration ...200312966558
fgf-2 modulates expression and distribution of gap-43 in frog retinal ganglion cells after optic nerve injury.basic fibroblast growth factor (bfgf or fgf-2) has been implicated as a trophic factor that promotes survival and neurite outgrowth of neurons. we found previously that application of fgf-2 to the proximal stump of the injured axon increases retinal ganglion cell (rgc) survival. we determine here the effect of fgf-2 on expression of the axonal growth-associated phosphoprotein (gap)-43 in retinal ganglion cells and tectum of rana pipiens during regeneration of the optic nerve. in control retinas, ...200312898535
relationship of tadpole stage to location of echinostome cercariae encystment and the consequences for tadpole survival.the effect of echinostome infections on the survival of rana pipiens tadpoles was examined in relation to developmental stage of tadpoles. individual tadpoles of gosner stages 25, 27, 32-33, and 37-39 were exposed to 1 of 4 levels of cercariae (0, 20, 50, or 100). only tadpoles at stage 25, the earliest stage infected, died within a 5-day experimental period. this stage-specific mortality rate could be explained, in part, by the stage-specific location of encystment of cercariae, which was docum ...200312880244
localization of the two constitutively expressed nitric oxide synthase isoforms (nnos and enos) in the same cell types in the saccule maculae of the frog rana pipiens by immunoelectron microscopy: evidence for a back-up system?there is growing evidence for a nitric oxide/cyclic gmp pathway of signal transduction in the vestibular system. recently, two isoforms of nitric oxide (no) synthase (nnos and enos) and no itself have been identified at the light microscopic level in the vestibulocochlear system of mice using specific antibodies and a new fluorescence indicator. in order to acquire more information about signal transduction and tissue modulation in this neuroepithelium at the cellular and subcellular levels, ult ...200312868590
effects of acid stress in adult rana pipiens.the decline in frog populations is a well-recognized worldwide phenomenon and infectious disease has been implicated as a major cause in the global decline of amphibian populations. rana pipiens are disappearing from many habitats where they used to flourish, and environmental acidification has been considered as a possible contributor to this disappearance. we present a model that integrates the results of several experiments on the effects of acid exposure on natural resistance and mortality o ...200312840835
nucleus isthmi enhances calcium influx into optic nerve fiber terminals in rana pipiens.we examined the role of nucleus isthmi in enhancing intracellular calcium concentrations in retinotectal fibers in the frog optic tectum in vitro. the intracellular calcium levels were measured using the fluorescent calcium-sensitive dye, calcium green-1 3000 mw dextran conjugate (cg-1), which was injected into one optic nerve. electrical stimulation of the labeled optic nerve alone increased tectal cg-1 fluorescence whereas electrical stimulation of nucleus isthmi alone had no effect on cg-1 fl ...200312676363
isoforms of soluble alpha-tubulin in oocytes and brain of the frog (genus rana): changes during oocyte maturation.rana oocytes have previously been shown to contain much more soluble tubulin than does the brain, suggesting different assembly and disassembly dynamics of frog oocyte tubulin compared to that in brain. by using centrifugation, sds-page, two-dimensional gel electrophoresis and western blots, probed with anti-alpha-tubulin monoclonal antibodies, polymorphic alpha-tubulins (isoforms) were compared in brains and follicle-enclosed oocytes of northern (rana pipiens) and southern (r. berlandieri) frog ...200212568348
changes in brain-derived neurotrophic factor and trkb receptor in the adult rana pipiens retina and optic tectum after optic nerve injury.in this study we used immunocytochemistry to investigate the distribution of brain-derived neurotrophic factor (bdnf) and its receptor tyrosine kinase (trkb) in retina and optic tectum of the frog rana pipiens during regeneration after axotomy. we also measured changes in bdnf mrna in retina and tectum. retrograde labeling was used to identify retinal ganglion cells (rgcs) prior to quantification of the bdnf immunoreactivity. in control animals, bdnf was found in the majority of rgcs and displac ...200212455009
cellular mechanisms of nociception in the frog.cellular mechanisms underlying defense reactions induced by noxious heat and acids were studied in frogs (rana pipiens) by measuring whole cell membrane currents in cultured dorsal root ganglion (drg) neurons. seventy-eight of 82 drg neurons exposed to 3-s ramps of increasing temperature to 48 degrees c exhibited an inward current (i(heat)) of 490 +/- 70 pa at -70 mv. i(heat) exhibited reversal at approximately 10 mv with a pronounced outward rectification, suggesting opening of nonselective cat ...200212364510
transmitter release from rana pipiens vestibular hair cells via mglurs: a role for intracellular ca(++) release.the response of the semicircular canal (scc) to the group i mglur-selective agonist dihydroxyphenylglycine (dhpg; 300 microm) - facilitation of afferent discharge rate - was dose-dependently reduced by the phospholipase c inhibitor u-73122 (1-100 microm; ic(50): 22 microm), the smooth endoplasmic reticulum ca(++) atpase inhibitor thapsigargin (100 nm-3 microm; ic(50): 500 nm), and xestospongin c (100 pm-1 microm; ic(50): 11 nm), an inositol trisphosphate receptor (ip(3)r) antagonist. ryanodine, ...200212361872
docosahexaenoic, arachidonic, palmitic, and oleic acids are differentially esterified into phospholipids of frog retina.docosahexaenoic acid (22:6n-3) is highly enriched in the retina. to determine if retinal cells take up and metabolize fatty acids in a specific manner, retinas from rana pipiens were incubated for 3 h with an equimolar mixture of tritiated 22:6n-3, arachidonic acid (20:4n-6), palmitic acid, and oleic acid. the radiolabeling of retinal lipids was determined and compared to the endogenous fatty acid content of the lipids. the results showed that in most, but not all, cases, the relative labeling w ...201312324228
small changes in whole-body corticosterone content affect larval rana pipiens fitness components.in amphibians, large changes in tissue corticosterone content (caused by treatment with large doses of hormone) alter tadpole growth and development, but the effects of smaller changes on growth, development, behavior, and morphology are unknown. in the current study, we exposed pre-metamorphic rana pipiens tadpoles to moderate doses (62 and 125 nm) of exogenous corticosterone by adding it to the rearing water. we then analyzed effects on growth, development, behavior, morphology, and the endoge ...200212161197
functional morphology of proximal hindlimb muscles in the frog rana pipiens.musculoskeletal models have become important tools in understanding motor control issues ranging from how muscles power movement to how sensory feedback supports movements. in the present study, we developed the initial musculotendon subsystem of a realistic model of the frog rana pipiens. we measured the anatomical properties of 13 proximal muscles in the frog hindlimb and incorporated these measurements into a set of musculotendon actuators. we examined whether the interaction between this mus ...200212089205
auditory stimulus optimization with feedback from fuzzy clustering of neuronal responses.the primary focus of this paper was to develop a high-performance computer system for optimizing auditory stimuli based on neuronal feedback. using the algorithm of pattern extraction (alopex) extra-cellular action potentials (aps) recorded from frog (rana pipiens) auditory neurons were used as feedback to optimize sound stimuli. this computer-based system works in real time to iteratively find the neuron's best excitatory frequency (bef). three programmable (positive and negative) threshold log ...200212075670
jumping in frogs: assessing the design of the skeletal system by anatomically realistic modeling and forward dynamic simulation.comparative musculoskeletal modeling represents a tool to understand better how motor system parameters are fine-tuned for specific behaviors. frog jumping is a behavior in which the physical properties of the body and musculotendon actuators may have evolved specifically to extend the limits of performance. little is known about how the joints of the frog contribute to and limit jumping performance. to address these issues, we developed a skeletal model of the frog rana pipiens that contained r ...200212042328
characterization of mu, kappa, and delta opioid binding in amphibian whole brain tissue homogenates.opioid agonists produce analgesia in mammals through the activation of mu, kappa, or delta opioid receptors. previous behavioral and binding studies from our laboratory using an amphibian model suggested that mu, kappa, or delta opioid agonists may activate a single type of opioid receptor in the grass frog, rana pipiens. in the present study, kinetic, saturation, and competitive binding profiles for three opioid radioligands, [(3)h]damgo ([d-ala(2),n-me-phe(4),gly(5)-ol]-enkephalin) (mu-selecti ...200211907194
influence of myosin isoforms on contractile properties of intact muscle fibers from rana pipiens.the myosin heavy chain (mhc) and myosin light chain (mlc) isoforms in skeletal muscle of rana pipiens have been well characterized. we measured the force-velocity (f-v) properties of single intact fast-twitch fibers from r. pipiens that contained mhc types 1 or 2 (mhc1 or mhc2) or coexpressed mhc1 and mhc2 isoforms. velocities were measured between two surface markers that spanned most of the fiber length. mhc and mlc isoform content was quantified after mechanics analysis by sds-page. maximal s ...200211880272
identification of myosin light chains in rana pipiens skeletal muscle and their expression patterns along single fibres.isoforms of myosin heavy chain (mhc) and myosin light chain (mlc) influence contractile kinetics of skeletal muscle. we previously showed that the four major skeletal muscle fibre types in rana pipiens (type 1, type 2, type 3 and tonic; amphibian nomenclature) contain four unique mhc isoforms. in the present study we defined the mlcs expressed in each of these r. pipiens fibre types. the mlc composition of single mhc-typed fibres was determined from western blots using a panel of monoclonal mlc ...200111815648
measurement of ca(2+) currents in intact slow skeletal muscle fibers of the frog by the three-microelectrode technique.the recording of currents passing through calcium channels in intact skeletal muscle fibers presents several difficulties. however, use of the three-microelectrode voltage-clamp technique at the end of the fiber provided us with a good approximation of current values in such fibers. using this technique, we were able to measure the calcium-channel current in slow skeletal muscle fibers of the frog (rana pipiens) and to quantify the effects of denervation on this current.200111733197
calcium sparks in intact skeletal muscle fibers of the frog.calcium sparks were studied in frog intact skeletal muscle fibers using a home-built confocal scanner whose point-spread function was estimated to be approximately 0.21 microm in x and y and approximately 0.51 microm in z. observations were made at 17-20 degrees c on fibers from rana pipiens and rana temporaria. fibers were studied in two external solutions: normal ringer's ([k(+)] = 2.5 mm; estimated membrane potential, -80 to -90 mv) and elevated [k(+)] ringer's (most frequently, [k(+)] = 13 m ...200111723160
slow atp loss and the defense of ion homeostasis in the anoxic frog brain.for most vertebrates, cutting off the oxygen supply to the brain results in a rapid (within minutes) loss of atp, the failure of atp-dependent ion-transport process, subsequent anoxic depolarization of neuronal membrane potential and consequential neuronal death. the few species that survive brain anoxia for days or months, such as the freshwater turtle trachemys scripta, avoid anoxic depolarization and maintain brain atp levels through a coordinated downregulation of brain energy demand process ...200111707503
a novel thienylhydrazone, (2-thienylidene)3,4-methylenedioxybenzoylhydrazine, increases inotropism and decreases fatigue of skeletal muscle.this study was designed to investigate the effects on single skeletal muscle fibers of a novel thienylhydrazone, referred to as lassbio-294, which is a bioisoster of pyridazinone compounds that inhibit the cyclic amp-specific phosphodiesterase (pde) 4. twitch and fatigue were analyzed in single skeletal muscle fibers isolated from either the semitendinous or the tibialis anterior muscles dissected from the frog rana pipiens. lassbio-294 (12.5-100 microm) increased twitch tension, accelerated the ...200111602667
non-specific esterase-positive dendritic cells in epithelia of the frog rana pipiens.langerhans cells are antigen-presenting cells located in epithelia and have a dendritic outline, a convoluted nucleus surrounded by an electron lucent cytoplasm with sparse organelles and occasionally containing the characteristic birbeck granule; their membrane contains class ii molecules of the major histocompatibility complex and a strong membrane reactivity for both atpase and non-specific esterase. despite increasing knowledge about mammalian langerhans cells, only a few studies have examin ...200111563545
gabaergic visual pathways in the frog rana pipiens.gamma-aminobutyric acid (gaba) is the most prevalent inhibitory neurotransmitter in the vertebrate brain. it can exert its influence either as gabaergic projection pathways or as local interneurons, which play an essential role in many visual functions. however, no gabaergic visual pathways have been studied in frogs so far. in the present study, gabaergic pathways in the central visual system of rana pipiens were investigated with double-labeling techniques, combining immunocytochemistry for ga ...200711497422
testing and comparison of non-opioid analgesics in amphibians.because of the lack of information about effective analgesics in non-mammalian vertebrates, the potency of various non-opioid agents were tested in a model of analgesia by using northern grass frogs (rana pipiens). this alternative model has been used widely for investigating opioid analgesic action. potential non-opioid analgesics tested included antipsychotic, benzodiazepine, barbiturate, antihistamine, non-steroidal anti-inflammatory (nsaid), and partial opioid agents. northern grass frogs we ...200111451391
biochemical, histological, and inhibitor studies of membrane carbonic anhydrase in frog gastric acid secretion.gastric acid secretion is dependent on carbonic anhydrase (ca). to define the role of membrane-bound ca, we used biochemical, histochemical, and pharmacological approaches in the frog (rana pipiens). ca activity and inhibition by membrane-permeant and -impermeant agents were studied in stomach homogenates and microsomal fractions. h(+) secretion in the histamine-stimulated isolated mucosa was measured before and after mucosal addition of a permeant ca inhibitor (methazolamide) and before and aft ...200111408256
pharmacology, distribution and development of muscarinic acetylcholine receptor subtypes in the optic tectum of rana pipiens.visually evoked behaviors mediated by the frog optic tectum require cholinergic activity, but the receptor subtypes through which acetylcholine acts are not yet identified. using quantitative autoradiography and scintillation spectrometry, we examined the binding of [3h]pirenzepine and [3h]af-dx 384 in the laminated optic tectum of the frog. in mammalian systems, these substances bind excitatory (m1 and m3 subtypes) and inhibitory (m2 and m4 subtypes) muscarinic acetylcholine receptors, respecti ...200111311540
toxicity of chlorypyrifos to rana pipiens embryos. 200111178655
effects of denervation on ca2+ channels in slow skeletal muscle fibers of the frog.effects of denervation on calcium channels in slow skeletal muscle fibers in the frog (rana pipiens) were studied using the three-microelectrode voltage-clamp technique in intact fibers. ca2+, ba2+, and sr2+ currents were all significantly reduced in amplitude during the first 2 weeks after denervation. after nerve section the selectivity sequence ba congruent with ca > sr was changed to ba > sr > ca and the values for relative ratio increased from 1.04 to 2.65 for ba2+ and from 0.58 to 1.20 for ...200111172890
interdependence between sodium transport, external chloride, and sodium/calcium exchanger in the isolated skin of the rana pipiens.the aim of this study was to analyze the relationship of the na+/ca2+ exchanger, cytosolic calcium, and chloride to the transepithelial transport of sodium in isolated frog skin. sodium transport was measured as amiloride-inhibitable short circuit current (scc). we studied the effect of variations in the concentrations of external chloride and of the manipulation of calcium on sensitive amiloride scc. modifications in the movement of ca2+ were induced by an ionophore, a23187, and a ca2+ channel ...200111169490
molecular species analysis of 1,2-diacylglycerol released in response to progesterone binding to the amphibian oocyte plasma membrane.progesterone, the physiological inducer of amphibian meiosis, acts within minutes at plasma membrane receptors of the rana pipiens oocyte to release 1,2-diacylglycerol (dag) from plasma and intracellular membranes. high-performance liquid chromatography (hplc) analysis of lipid extracts of uninduced oocytes indicates the presence of at least three classes of dag with a total dag content of about 150 micromol/kg wet weight. within 3-5 min after exposure to progesterone, there was a differential i ...200011152965
chromaffin-adrenocortical cell interactions: effects of chromaffin cell activation in adrenal cell cocultures.although the adrenal cortex and medulla are both involved in the maintenance of homeostasis and stress response, the functional importance of intra-adrenal interactions remains unclear. when primary cocultures of frog (rana pipiens) adrenocortical and chromaffin cells were used, selective chromaffin cell activation dramatically affected both chromaffin and adrenocortical cells. depolarization with 50 microm veratridine enhanced chromaffin cell neuronal phenotype, contacts with adrenocortical cel ...200111121377
selective opioid agonist and antagonist competition for [3h]-naloxone binding in amphibian spinal cord.opioids elicit antinociception in mammals through three distinct types of receptors designated as mu, kappa and delta. however, it is not clear what type of opioid receptor mediates antinociception in non-mammalian vertebrates. radioligand binding techniques were employed to characterize the site(s) of opioid action in the amphibian, rana pipiens. naloxone is a general opioid antagonist that has not been characterized in rana pipiens. using the non-selective opioid antagonist, [3h]-naloxone, opi ...200011082500
responses of frog skin na(+) and cl(-) transport to guanylin.a possible role for the peptide hormone guanylin was investigated in frog skin (rana pipiens) epithelium. sodium and chloride fluxes in response to this peptide were evaluated in ussing-type chambers. net and unidirectional na(+) fluxes were measured by using (22)na(+) and atomic absorption analysis of total [na(+)], whereas net cl(-) fluxes were measured by using electrometric titration for [cl(-)]. mucosal application of guanylin (0.5-2.0 micromol/l) caused marked increases in serosal to mucos ...200010958997
neuromuscular remodeling and myofiber turnover in rana pipiens' jaw muscles.larval jaw myofibers in rana pipiens degenerate during metamorphosis and are replaced by a second wave of myogenesis that provides for adult jaw function. trigeminal motoneurons that innervate larval myofibers transfer their preterminal axons to these adult successors where they establish new motor endplates. silver/acetyl-cholinesterase histochemistry was used to compare innervation patterns in the larval and adult jaw adductor muscles and to plot the time course over which these changes occur. ...199910940673
ion-chromatographic study of the possible absorption of copper and zinc by the skin of rana pipiens.frogs are known to obtain some of their nutrients (e.g., glucose and sodium) through their skin. however, no studies have been made of the possible absorption of transition metals, which exist in most river water at low-ppb (w/w) levels. therefore, this research was undertaken to evaluate the use of ion chromatography for such an investigation. solutions of copper and zinc (20 ppb in each) were chosen for use in a small-scale screening study. ten live frogs were each placed in individual baths f ...200010917432
strong association of unesterified [3h]docosahexaenoic acid and [3h-docosahexaenoyl]phosphatidate to rhodopsin during in vivo labeling of frog retinal rod outer segments.docosahexaenoic acid (dha, 22:6n-3), the most prevalent fatty acid in phospholipids of rod outer segments (ros), is essential for visual transduction and daily renewal of ros membranes. we investigated the association of [3h]dha-lipids to rhodopsin in ros from frogs (rana pipiens) after in vitro (4 hrs) and in vivo (1 day and 32 days) labeling. lipids from lyophilized ros were sequentially extracted with hexane (neutral lipids), chloroform:methanol (phospholipids) and acidified chloroform:methan ...200010905632
interaction between series compliance and sarcomere kinetics determines internal sarcomere shortening during fixed-end contraction.the interaction between contractile force and in-series compliance was investigated for the intact skeletal muscle-tendon unit (mtu) of rana pipiens semitendinosus muscles during fixed-end contraction. it was hypothesized that internal sarcomere shortening is a function of the length-force characteristics of contractile and series elastic components. the mtus (n=18) were dissected, and, while submerged in ringer's solution, muscles were activated at nine muscle lengths (-2 to +6 mm relative to o ...200010899334
basic fibroblast growth factor applied to the optic nerve after injury increases long-term cell survival in the frog retina.the neuroprotective effects of basic fibroblast growth factor (bfgf) on the long-term survival of axotomized retinal ganglion cells (rgcs) were studied in the frog rana pipiens. cell loss was quantified in different regions of the ganglion cell layer using nissl staining and tetramethylrhodamine dextran amine backfilling. all regions of the retina showed a significant decrease (32-66%) in rgc numbers between 4 and 16 weeks after axotomy. some cells showed morphological and biochemical signs of a ...200010880994
distribution and development of nicotinic acetylcholine receptor subtypes in the optic tectum of rana pipiens.acetylcholine allows the elicitation of visually evoked behaviors mediated by the frog optic tectum, but the mechanisms behind its effects are unknown. although nicotinic acetylcholine receptors (nachrs) exist in the tectum, their subtype has not been assessed. by using quantitative autoradiography, we examined the binding of [(3)h]cytisine and [(125)i]alpha-bungarotoxin in the laminated tectum. in mammalian systems, these radioligands bind with high affinity to alpha4 nachr subunits and alpha7 ...200010880991
a gender-specific mrna encoding a cytotoxic ribonuclease contains a 3' utr of unusual length and structure.a cdna (2855 nt) encoding a putative cytotoxic ribonuclease (raplr1) related to the antitumor protein onconase was cloned from a library derived from the liver of gravid female amphibian rana pipiens. the cdna was mainly comprised (83%) of 3' untranslated region (utr). secondary structure analysis predicted two unusual folding regions (ufrs) in the rna 3' utr. two of these regions (711-1442 and 1877-2130 nt) contained remarkable, stalk-like, stem-loop structures greater than 38 and 12 standard d ...200010871370
cloning and characterization of the s1 domain of four myosin isoforms from functionally divergent fiber types in adult rana pipiens skeletal muscle.the motor properties of myosin reside in the globular s1 region of the myosin heavy chain (mhc) subunit. all vertebrates express a family of mhc isoforms in skeletal muscle that have a major influence on the mechanical properties of the various fiber types. differences in molecular composition of s1 among mhc isoforms within a species have not been studied to any great detail. presently, we have isolated, cloned and sequenced the s1 subunit of four mhc isoforms from skeletal muscle in rana pipie ...200010854783
selective opioid receptor agonist and antagonist displacement of [3h]naloxone binding in amphibian brain.opioid receptor ligands have been shown to elicit antinociception in mammals through three distinct types of receptors designated as mu, delta and kappa. these opioid receptors have been characterized and cloned in several mammalian species. radioligand binding techniques were employed to characterize the sites of opioid action in the amphibian, rana pipiens. naloxone is a general opioid receptor antagonist which has not been characterized in r. pipiens. kinetic analyses of [3h]naloxone in the a ...200010844122
expression of frequenin at the frog (rana) neuromuscular junction, muscle spindle and nerve.frequenin is a calcium binding protein previously implicated in the regulation of neurotransmission in drosophila and xenopus. we have used the frog (rana pipiens) to study the localization and regulation of expression of frequenin-like molecules in the vertebrate peripheral nervous system. affinity purified antibodies to frequenin recognize molecules in the neuromuscular junction, axons in the peripheral nerve, and neuronal processes in muscle spindles. western blots of endplate regions, periph ...200010771155
dissociated adult rana pipiens motoneuron growth cones turn up concentration gradients of denervated peripheral nerve-released factors.during development of the central nervous system neuronal growth cones are attracted or repelled by concentration gradients of specific target-derived factors. although evidence suggests that gradients of target-derived factors are chemotropic for adult motoneuron growth cones, a conclusive demonstration has remained elusive. further, no preparation has been available on which to rapidly and reliably test candidate factors. the present results demonstrate that in vitro adult frog motoneuron grow ...199910624816
electrophysiological responses of frog skin to the peptides bombesin, caerulein, and physalaemin.isolated skins from the frog rana pipiens were mounted on ussing-type chambers and bathed with amphibian ringer's solution on both sides. electrical potential difference, resistance, and short-circuit current (scc) were measured by using calomel electrodes, ag-agcl electrodes, ringer's-agar bridges, and tektronix digital multimeters. under the conditions employed, scc is a measure of net na+ transport. the frog skin peptides bombesin, caerulein, and physalaemin were administered to the serosal s ...199910573296
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