| distribution and ultrastructure of somatostatin-immunoreactive cells in the pancreas of rana esculenta. | apart from a description of the general organization of the endocrine pancreas, the present study is focussed on the distribution and ultrastructural morphology of somatostatin-immunoreactive cells in the pancreas of the frog rana esculenta. for light-microscopic histochemistry, the peroxidase-antiperoxidase technique was used. for the ultrastructural investigation, we employed the immunogold method. the endocrine pancreas of r. esculenta is composed of numerous islet-like structures, which cont ... | 1995 | 7598218 |
| response of guanylate cyclase to atrial natriuretic factor in epithelial cells of the frog choroid plexus. | this study shows that the choroid plexus of rana esculenta contains a guanylate cyclase particulate (gcp), similar to that identified in mammalia, that is quite sensitive to the atrial natriuretic factor (anf). the cytochemical tests for gcp show that anf increases the enzymatic reaction products. deposits are observed on the apical portion, at the basal level and along the lateral edges of the epithelial cells, with the exclusion of some intercalary epithelial cells with reaction-lacking microv ... | 1995 | 7778097 |
| interstitial buffer capacity influences na+/h+ exchange kinetics and oxyntic cell phi in intact frog gastric mucosa. | we studied the influence of interstitial buffer capacity and co2-hco3- on oxyntic cell intracellular ph (phi) in intact frog gastric mucosa. oxyntic cells in stripped gastric mucosa of rana esculenta were loaded with the ph-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, and phi was assessed fluorometrically. in the presence of a constant serosal and luminal ph, oxyntic cell phi was dependent on the serosal but not the luminal concentration of cell-impermeable buffer ions such a ... | 1995 | 7900811 |
| comparison of melatonin-binding sites in the brain of two amphibians: an autoradiographic study. | neuroanatomic comparison of the binding capability of 2-[125i] iodomelatonin in the crested newt triturus carnifex laur. and the green frog rana esculenta, using quantitative autoradiographic techniques, revealed a heterogeneous distribution pattern. the highest and relatively high binding activities were shown to occur in the optic tracts and in the suprachiasmatic area of the hypothalamus and the optic tectum, respectively, of both species. low or no 2-[125i] iodomelatonin binding values were ... | 1995 | 7736557 |
| morphological features of different regions in frog crista ampullaris (rana esculenta). | the cellular organization of different regions of the crista epithelium from the frog posterior semicircular canal was studied by light, transmission and scanning microscopy. the sensory epithelium consists of hair cells surrounded by supporting cells and basal cells located close to the basement membrane. three types of hair cells, namely club-like, cylindrical and pear-like cells differentially distributed along the crista could be recognized on the basis of their shape. club-like cells are lo ... | 1995 | 7612357 |
| fluctuations in levels of various gangliosides in the different tracts of the oviduct of the frog (rana esculenta) during the reproductive cycle. | the ganglioside content and pattern have been followed in the different tracts (rectus, convoluted and uterine) of the frog oviduct during the reproductive cycle. the main variations we observed are: a) average higher levels of ganglioside sialic acid in the preovulatory phase, with two peaks in march and april for the convoluted and rectus tract, respectively, and a more homogenous behaviour for the uterine tract; in all three tracts of the oviduct a minimum coincident with the ovulation has be ... | 2003 | 7558766 |
| a novel neuropeptide cellular mechanism in amphibian interrenal steroidogenesis. | interrenals of female rana esculenta were incubated with gonadotropin-releasing hormone (gnrh), 9-ketoreductase inhibitor (palmitic acid), acetyl salicyclic acid, prostaglandin f2 alpha (pgf2 alpha), forskolin, isobutylmethyl xanthine (ibmx), dibutyril cyclic adenosine monophosphate (dbcamp). prostaglandin e2 (pge2), pgf2 alpha, testosterone and 17 beta-estradiol were assessed on the incubation media. in addition, in the same interrenals, 9-ketoreductase and aromatase activities were evaluated. ... | 1995 | 7544992 |
| somatostatin-immunoreactive cell in the gastrointestinal tract of the frog rana esculenta. | the morphology and topographic distribution of somatostatin-immunoreactive cells in the stomach and small intestine of the frog rana esculenta were studied at the light-microscopic level by the use of the peroxidase-antiperoxidase method. scattered immunostained cells occurred in all regions of the gastrointestinal tract investigated. in the small intestine, the number of these cells decreased gradually in the oral to anal direction, i.e. from the pyloric (antral) stomach to the entrance into th ... | 1995 | 7895281 |
| effects of gonadectomy and temperature on the n-acetyltransferase activity in the harderian gland of the green frog rana esculenta. | since, in the harderian gland (hg) of the hamster, the n-acetyltransferase (nat), the specific enzyme involved in the biosynthesis of melatonin, exhibits a sexual dimorphism, in the present study, we investigated whether such a dimorphism is present also in the hg of the green frog rana esculenta. in intact frogs, no significant differences emerged between males and females in the hg nat activity under both cold (10 degrees c) and warm (22 degrees c) temperature conditions. in female frogs, the ... | 1995 | 7858948 |
| vestibular compensation in the european green frog (rana esculenta l.) and effect of training on compensation. | compensation of the vestibular deficits following section of the ampullary nerve of a horizontal semicircular canal was studied from a behavioral point of view in the european green frog. post-rotation reactions, which are highly asymmetrical the day after the lesion, become symmetrical, as they are in intact animals, 45-60 days later. it was shown that vestibular and motor training given postoperatively did not enhance the rate at which compensation was achieved. | 1995 | 7620875 |
| a new cutaneous nerve fiber connection with the frontal nerve in the frog rana esculenta: a morphological study. | the frontal nerve arises from the frontal organ, which represents the extracranial component of the pineal complex in some lower vertebrates, and interconnects the frontal organ with the epiphysis and the brain. the existence of a previously unreported nerve branch of the frontal nerve is described here in the frog rana esculenta and called the lateral nerve. the course of the lateral nerve and its junction with the frontal nerve have been consistently detected by means of different techniques: ... | 1995 | 7542543 |
| sex steroid binding proteins in the plasma of the green frog, rana esculenta: changes during the reproductive cycle and dependence on pituitary gland and gonads. | sex steroid binding proteins (ssbp) have been reported in the plasma of female and male rana esculenta. in both sexes ssbp bind [3h]estradiol and [3h]testosterone with medium-high affinity and high specificity. using ion-exchange chromatography ssbp resolve into two peaks eluting at 0.27 m (peak i) and 0.36 m (peak ii) nacl. both peaks bind [3h]estradiol and [3h]testosterone equally well. isoelectrofocusing showed that peak i focused at ph 6.0 and 7.5, whereas peak ii focused at ph 6.0. ssbp cap ... | 1994 | 7883147 |
| immunocytochemical localization of pomc-derived peptides (adrenocorticotropic hormone, alpha-melanocyte-stimulating hormone and beta-endorphin) in the pituitary, brain and olfactory epithelium of the frog, rana esculenta, during development. | developmental stages of rana esculenta, starting with the posterior limb-bud stage (stage 26) up to a few days after metamorphosis, were examined immunohistochemically to localize cells and fibers producing some pomc-derived peptides, namely, alpha-msh, acth and beta-end. anti acth and anti alpha-msh revealed a positive reaction in the pars intermedia during all stages of development included in this study, whereas no immunoreactivity in this pituitary zone was ever evidenced with anti beta-end. ... | 1994 | 7850861 |
| detection and localization of gonadotrophin-releasing hormone (gnrh)-like material in the frog, rana esculenta, ovary. | gnrh-like material has been identified using hplc followed by ria in the ovary of rana esculenta. during the reproductive cycle three immunoreactive gnrh peaks were eluted. one of them coeluted with s-gnrh, the other two forms between gnrh and cii-gnrh. during the recovery phase s-gnrh immunoreactivity disappears. by immunocytochemistry, cii-gnrh immunostaining was localized to granulosa cells while s-gnrh was present in the perinuclear zone of the oocytes. | 1994 | 7828025 |
| [genetic instability in inheritance of electrophoretic variants, coded by the ldh-b locus, in hybrid crosses of representatives of rana esculenta l. complex (amphibia, ranidae)]. | | 1994 | 7858513 |
| action of dopamine on the ionic transport across the isolated skin of rana esculenta. | dopamine addition to the internal fluid bathing the isolated frog skin results in a strong increase of short circuit current (scc) across this tissue. the effect is dose-dependent, 10(-4) m being the dose resulting in maximal effect. the measure of transepithelial fluxes of both 22na+ and 36cl- across symmetrical parts of skin short-circuited in permanence demonstrates that this effect is due to stimulation of na+ adsorption and cl- secretion. the former effect, but not the latter one, is mimick ... | 2013 | 7534500 |
| the c-wave of the electroretinogram possesses a third component from the proximal retina. | erg and light-induced extracellular potassium ([k+]o) changes have been measured in isolated retinas of both rana esculenta and rana temporaria. the conditions of the preparations have been varied. isolated frog retinas kept receptor side-upward in a moist chamber without perfusion showed the well-known slow piii in the erg. retinas superfused from the receptor side, with o2 enrichment at their vitreal surface, however, exhibit a slow cornea-positive potential in the erg. the slow erg-potentials ... | 1994 | 7975304 |
| seasonal variations in the daily rhythm of melatonin and nat activity in the harderian gland, retina, pineal gland, and serum of the green frog, rana esculenta. | day-night variations of melatonin content and n-acetyltransferase (nat) activity were studied in the harderian gland (hg), retina, pineal gland, and serum of the green frog rana esculenta. throughout the year the retinal melatonin content was correlated with retinal nat activity and was always higher than those in the pineal gland and hg. on the other hand, in these structures diurnal fluctuations in nat activity were observed. there were clear seasonal differences in the magnitude of the noctur ... | 1994 | 7843568 |
| model of bicarbonate secretion by resting frog stomach fundus mucosa. ii. role of the oxyntopeptic cells. | in the present publication we report mainly electrophysiological studies on oxyntopeptic cells of frog gastric mucosa which aim at clarifying a possible involvement of these cells in the process of resting gastric alkali (hco3-) secretion, described in the preceding publication. the experiments were performed on intact gastric fundus mucosa of rana esculenta mounted in ussing chambers. after removal of the muscle and connective tissue layer oxyntopeptic cells were punctured from the serosal surf ... | 1994 | 7838689 |
| model of bicarbonate secretion by resting frog stomach fundus mucosa. i. transepithelial measurements. | in the present in vitro experiments on gastric fundus mucosa of rana esculenta we try to define the mechanism of alkaline secretion that is observed in summer frogs in the resting stomach (blockage of hcl secretion by ranitidine, 10(-5) mol/l). the transepithelial voltage and the rate of alkalinization (asr) of an unbuffered gastric lumen perfusate was measured as a function of serosal (and mucosal) fluid composition. asr was high (0.88 +/- s.e. 0.09 microeq.cm-2.h-1, n = 11) during serosal bath ... | 1994 | 7838688 |
| influence of gonadectomy and steroid hormone replacement therapy on the gonadotropin-releasing hormone neuronal system in the anterior preoptic area of the frog (rana esculenta) brain. | effects of gonadectomy and sex steroid replacement therapy were studied on the anterior preoptic area-located gnrh-immunoreactive neurons in males and females of the frog, rana esculenta. removal of gonads caused a drastic reduction in the immunostaining as well as in the number of gnrh neurons in the anterior preoptic area of the brain in both sexes. replacement therapy with estradiol-17 beta, testosterone, and 5 alpha-dihydrotestosterone, given alone or in combination, enhanced the somal accum ... | 1994 | 7821779 |
| [genetic defects in inheritance and the variability of locus ldh-b in hybrid populations of rana esculenta complex (amphibia, ranidae)]. | the directed ingression of lhd-b gene from r. lessonae to r. ridibunda observed during hybridization between these species was confirmed in the present study. the ingression was accompanied by decreased of the initial allele activity, segregative disturbances in heterozygotes and changes in electrophoretic mobility. the population genetic analysis has shown stable preservation of abnormal alleles in hybrid populations. the results are discussed with reference to the concept of genetic instabilit ... | 2016 | 7804099 |
| atpase activity of melanosomes in liver pigment cells of rana esculenta l. | luminometric methods show that melanosomes in liver pigment cells of rana esculenta l. have endogenous atp and atpase activity. the km value of atpase is 0.42 x 10(-8) mol/l at ph 7.0. inhibition of atpase by antimycin and by ouabain is not effective. in the presence of an excess of adp and pi, atp synthesis was observed. | 1994 | 7953071 |
| synaptic relations of the trigeminal motoneurons in a frog (rana esculenta). | the cobalt tracing technique was used to study synaptic relations of trigeminal motoneurons and the axon terminals of the mesencephalic trigeminal nucleus (vmes) in a frog (rana esculenta). most of the small calibre vmes terminals containing spherical synaptic vesicles occupied presynaptic position in axodendritic contacts. axoaxonic contacts of vmes boutons were exclusively found at the postsynaptic site. the synaptic coverage of the trigeminal motoneuron dendritic tree increased somatofugally ... | 1994 | 7803156 |
| regeneration of the testicular interstitial compartment after ethane dimethane sulfonate treatment in the hypophysectomized frog rana esculenta: independence of pituitary control. | the effects of ethane dimethane sulfonate (eds) on the testes of hypophysectomized frogs (rana esculenta) were investigated by light and electron microscopy. initial signs of interstitial cell damage were observed in eds- and eds plus pituitary homogenate (ph)-treated animals 5 days after a single injection of eds (100 mg/kg body weight). the germinal compartment in these two groups appeared disorganized adjacent to the damaged interstitial tissue only in the eds-treated animals, and by day 8, s ... | 1994 | 7926658 |
| opioid peptide modulation of stress-induced plasma steroid changes in the frog rana esculenta. | the present paper aims to evaluate whether a neuroendocrine system including opioids accounts for the effects of stress in the frog, rana esculenta. using an acute-stress paradigm, the involvement of hypothalamic opioid peptides was investigated biochemically as well as by in vivo studies. hplc and ria investigations confirm the presence of beta-endorphin-like peptides in the brain of this frog. several immunoreactive peaks are present, two of them coeluting with beta-endorphin and acetyl beta-e ... | 1994 | 7927279 |
| the isolated and perfused working heart of the frog, rana esculenta: an improved preparation. | 1. an in vitro preparation of the intact heart of the frog rana esculenta was set up. 2. the isolated heart, perfused at constant pressure, was spontaneously beating and able to generate physiological values of output pressure, cardiac output, ventricle work and power. it showed the typical phenomenon of the "hypodynamic state" after a relatively constant time from the onset of the perfusion. 3. perfusion with air-saturated saline and 99.5% oxygen-saturated saline did not show significant differ ... | 1994 | 7926601 |
| ionic selectivity of the mechano-electrical transduction channels in the hair cells of the frog sacculus. | in the isolated saccular macula of rana esculenta extracellular hair cell receptor currents evoked by mechanical stimulation of the otolithic membrane were recorded under transepithelial voltage clamp conditions. the ionic selectivity of the mechano-electrical transduction channels of the hair cells was determined by examining the effects of different concentrations of ca2+ and k+ in the apical solution on the transepithelial voltage at which the extracellular receptor current was zero (vrev). c ... | 1994 | 7914041 |
| presence of x-ag carrier in frog (rana esculenta) red blood cells. | evidence is presented that the high levels of internal l-glutamic and l-aspartic acid in frog (rana esculenta) red blood cells are due to the existence of a specific carrier for acidic amino acids of high affinity (km = 3 microm) and low capacity (vmax 0.4 mumol l-glu.kg-1 dry cell mass.10 min-1). it is na+ dependent and the incorporation of l-glutamic acid can be inhibited by l- and d-aspartate and l-cysteic acid, while d-glutamic does not inhibit. moreover, this glutamic uptake shows a bell-sh ... | 1994 | 7914933 |
| multiple sources of the pituitary pars intermedia innervation in amphibians: a dii retrograde tract-tracing study. | afferent projections to the pituitary pars intermedia were studied using the dii tract-tracing technique in two amphibian species, the urodelan triturus carnifex, and the anuran rana esculenta. after dii crystal application into the pituitary intermediate lobe, in both species cells were retrogradely labeled in the preoptic nucleus, in the supra- and retro-chiasmatic hypothalamus and in the brainstem (especially in the area indicated as locus coeruleus). the findings are discussed in relation to ... | 1994 | 8047275 |
| seasonal changes in plasma growth hormone and prolactin concentrations of the frog rana esculenta. | plasma growth hormone (gh), prolactin (prl), and vitellogenin (vtg) concentrations were determined during the annual reproductive cycle of the frog rana esculenta. plasma gh and prl were measured using a ria that employed purified bullfrog (rana catesbeiana) gh and prl as standards and radioligand, and their respective antibodies. using elisa, plasma vtg titers were related to ovarian weight. gh, prl, and vtg displayed different trends related to season and sex. in male frogs the gh and prl tren ... | 1994 | 8194739 |
| configuration of light responses in isolated retinal rods. a patch-clamp study. | the whole-cell patch-clamp technique was employed to investigate the light responses of single retinal rods of the frog (rana esculenta and r. temporaria). in the majority of experiments, completely isolated cells were studied. coupling with neighboring cells gave rise to a more complex response configuration. responses were recorded under voltage-clamp and under current-clamp conditions. stimulus response curves were measured in experiments with local stimuli illuminating only parts of the oute ... | 1994 | 8188065 |
| ultrastructural and cytochemical analysis for adenyl cyclase in frog choroid plexus. | an ultrastructural and cytochemical analysis of the anterior choroid plexus in adult rana esculenta was undertaken. the epithelial cells are implicated in the production of cephalorachidian liquid by transporting metabolites from the blood and by synthesizing and secreting activity. the epithelial cells are also capable of re-absorbing catabolites from the cephalorachidian liquid. the presence of adenylate cyclase, along the basal and lateral membranes in some epithelial cells and along the apic ... | 1994 | 8171424 |
| a phorbol ester and calcium ionophore regulate sex steroid and prostaglandin release by follicles of the anuran rana esculenta and the urodele triturus carnifex. | the aim of this work was to study the relationships among protein kinase c (pkc), calcium, prostaglandins (pgs), and sex steroids in follicles of rana esculenta and triturus carnifex. follicles, oocytes, and wall cells of follicle (theca and granulosa cells) were incubated in vitro with an activator of pkc, phorbol-12-myristate-13-acetate (pma), a calcium ionophore (a23187), an antagonist of calcium channel, verapamil, pma + a23187, prostaglandin f2 alpha (pgf2 alpha), and prostaglandin e2 (pge2 ... | 1994 | 8138111 |
| mesencephalic projections of the cochlear nucleus in the frog, rana esculenta. | the lectin phaseolus vulgaris leucoagglutinin was injected into chochlear nucleus in order to study the trajectory and projections of the auditory pathway in the frog. a strong contralateral and a weak ipsilateral fiber bundle representing the lemniscus lateralis could be followed to the torus semicircularis. the following areas of termination could be discerned in the mesencephalon: (1) each of the five subnuclei of the torus semicircularis received fibers from the cochlear nucleus, the largest ... | 1994 | 7725825 |
| regional and seasonal variations of rna synthesis in the brain of the green frog, rana esculenta. | changes of rna synthesis were demonstrated in neurons and ependymal cells of the green frog rana esculenta during the annual cycle using the mallory's trichrome stain as histochemical marker and autoradiography. since the higher affinity of the nuclei for aniline blue is consistent with the increase of rna content, the increase of rna synthesis was expressed as percentage of the blue stained nuclei (% bsn). neuronal transcription starts slowly in march or april, reaches a maximum in july and dec ... | 1994 | 7530512 |
| adaptive genetic variation in growth and development of tadpoles of the hybridogenetic rana esculenta complex. | the distribution and proportion of the sexual species rana lessonae to the hemiclonal hybrid r. esculenta among natural habitats suggests that these anurans may differ in adaptive abilities. i used a half-sib design to partition phenotypic and quantitative genetic variation in tadpole responses at two food levels into causal variance components. rana lessonae displays strong phenotypic variation across food levels. growth rate is strictly determined by environmental factors and includes weak mat ... | 1993 | 28568004 |
| characterization of the type of carbohydrate chains of the higher molecular weight (140 kda) acid phosphatase of the frog liver. | 1. the higher molecular weight, (hmw, m(r) 140 kda) acid phosphatase (acpase) of the frog liver (rana esculenta) was separated into enzymatically active components by isoelectric focusing in an immobilized ph gradient and their carbohydrate chains were analyzed by specific lectin binding after native blotting. 2. the lectin-binding patterns obtained with cona, wga, lch and pna as well as with wga and pna after desialylation indicate that the frog liver hmw acpase contains predominantly n-linked ... | 1993 | 8138034 |
| prostaglandin e2 and prostaglandin f2 alpha involvement in the corticosterone and cortisol release by the female frog, rana esculenta, during ovulation. | interrenal and ovarian tissues of rana esculenta were incubated in vitro during the preovulatory, ovulatory and postovulatory phases to study the basal release of prostaglandin e2 (pge2), prostaglandin f2 alpha (pgf2 alpha), corticosterone, and cortisol. the effects of exogenous pge2 and pgf2 alpha on interrenal and ovarian corticosteroid release were also studied. in addition, the plasma values of these four hormones were assessed during the same phases. during in vitro interrenal incubations, ... | 1993 | 8409898 |
| characterization of tension decline in different types of fatigue-resistant skeletal muscle fibres of the frog. low extracellular calcium effects. | twitch and tetanic tension have been measured in single skeletal muscle fibres (m.ileofibularis, rana esculenta and rana temporaria). on the basis of resistance to fatigue produced by repetitive tetanic stable frequency stimulation with various numbers of stimulation trains, twitch fibers were subdivided in three groups (resembling those as described by westerblad and lännergren 1986 in xenopus), that is fatigue-resistant (fr), moderately fatigued (mf) and easily fatiguing (ef). it was found fur ... | 1993 | 8181694 |
| the effects of gonadectomy and testosterone treatment on the harderian gland of the green frog, rana esculenta. | the effects of gonadectomy and testosterone treatment on the fine structure of the harderian gland in male and female green frogs were investigated in different periods of the year. gonadectomy, carried out when the glands are in the lowest secretory phase (september), causes degenerative changes consisting of a reduction of the rough endoplasmic reticulum, the appearance of autolysosomes, and an increase of nuclear heterochromatin. these effects can be prevented by testosterone treatment. no ca ... | 1993 | 8364965 |
| glycogen phosphorylase activity in the liver of the frog rana esculenta. | 1. phosphorylase activity has been assayed in liver extracts of the frog, rana esculenta, during the winter period. in native conditions, most of the phosphorylase is present as amp-independent activity and shows properties similar to those of the a form of the liver enzyme from other vertebrates. 2. it is suggested that regulation of phosphorylase activity is through interconversion between a and b forms operated by endogenous phosphorylase kinase and phosphatase. 3. kinetic studies show hyperb ... | 1993 | 8359024 |
| possible roles for prostaglandins e2 and f2 alpha in seasonal changes in ovarian steroidogenesis in the frog (rana esculenta). | concentrations of pge2, pgf2 alpha, androgens and oestradiol in plasma, and ovary weights were measured in the female frog, rana esculenta, during the annual breeding cycle. experiments were carried out in vivo to study the effects of pge2 and pgf2 alpha on plasma sex steroids during the following stages: pre-reproduction (april), reproduction (may), post-reproduction (june) and recovery (october). experiments were performed in vitro during these stages to evaluate the effects of these two prost ... | 1993 | 8345472 |
| asymmetric competition in mixed populations of tadpoles of the hybridogenetic: rana esculenta complex. | hybridogenetic rana esculenta tadpoles display tolerance to extreme environmental conditions and fit criteria of the "general-purpose" genotype. a trade-off between generality and competitive ability is assumed to occur in asexual species, but the evidence remains unclear. the purpose of my experiment was to test the competitive ability of hemiclonal hybrid rana esculenta tadpoles relative to the parental species rana lessonae. mixed and single genotype populations of r. esculenta and r. lessona ... | 1993 | 28568709 |
| opioids and testicular activity in the frog, rana esculenta. | the presence and activity of brain, pituitary and testicular beta-endorphin (beta-ep)-like material have been studied in the frog, rana esculenta, using reverse-phase high-pressure liquid chromatography, coupled with radioimmunoassay and immunocytochemistry. in-vivo and in-vitro treatments with naltrexone were carried out to assess the putative physiological activity of opioid peptides. beta-ep(1-31) and (1-27), together with their acetylated forms, have been identified in brain, pituitary and t ... | 1993 | 8492076 |
| freeze-fracture characterization of cell types at the surface of the taste organ of the frog, rana esculenta. | the ultrastructure and distribution of intramembrane particles in the chemoreceptor surface of the frog taste organ have been studied by means of freeze-fracture. sustentacular, wing, mucous cells and two different types of putative taste cells were found to reach the free surface of this chemoreceptor. each of these cell types was characterized by a different pattern and density of intramembrane particles in the free surface. wing cells displayed a relatively low number of large intramembrane p ... | 1993 | 8445408 |
| dopamine regulation of testicular activity in intact and hypophysectomized frogs, rana esculenta. | in intact frogs, both gnrha and l-dopa were able to increase testicular and plasma androgen levels and to induce spermiation. the dopamine antagonist pimozide inhibited both the effects of l-dopa but not those of gnrha. hypophysectomy reduced androgen levels, but spermiation was still induced by both gnrha and l-dopa, suggesting that these agents can directly influence the testis through a route not involving the pars distalis. again, pimozide antagonised spermiation induced by l-dopa but not th ... | 1993 | 8428613 |
| localization of fibronectin in the frog skin. | in this review, we present structural and ultrastructural localizations of fibronectin (fn) in the larval and adult skin of the frog (rana esculenta) either in in vivo or in in vitro conditions. the ventral skin of the tadpole contains membrane-associated fn-plaques disposed around the epidermal and dermal cells during their climactic rearrangement. moreover, lines of fibrillar fn are detected inside the breaks opened in the derived collagen. the ventral skin of the adult frog reveals fn distrib ... | 1993 | 8470096 |
| mammalian gonadotropin-releasing hormone increases pgf2 alpha production activating diacylglycerol lipase in rana esculenta interrenal. | the aim of the present paper was to clarify if the prostaglandin f2 alpha (pgf2 alpha) production stimulated by mammalian gonadotropin-releasing hormone (mgnrh) comes from arachidonic acid (aa) freed by diacylglycerol (dag) and/or membrane phospholipids in the interrenal of rana esculenta. interrenals of rana esculenta were incubated with inhibitors of phospholipase a1 (pla1), phospholipase a2 (pla2), phospholipase c (plc), protein kinase c (pkc) and diacylglycerol lipase (daglipase) in the pres ... | 1993 | 8452754 |
| a quantitative autoradiographic study of gabaa and benzodiazepine receptors in the brain of the frog, rana esculenta. | specific binding sites for gabaa and benzodiazepines were detected in the brain of the frog rana esculenta after the in vitro incubation of tissue sections with their respective specific agonists [3h] muscimol and [3h] flunitrazepam. conditions for the binding assay were optimized and as a result binding was saturable and specific. quantitative autoradiographic receptor measurements in the different brain sections showed that elevated levels of [3h] muscimol binding sites were found in the two l ... | 1993 | 8395952 |
| exocytosis in the lingual mucus cells of rana esculenta evoked by acetylcholine: observation of living cells by confocal laser scanning microscopy. | exocytosis of a secretory cell is believed to occur when a part of the limiting membrane of the secretory granules fuses with the luminal plasma membrane to release their contents. using a confocal laser scanning microscope, we have studied these events in living frog lingual gland cells. in a differential interference contrast (dic) mode, secretory granules were found to be stable in general, but after stimulation with acetylcholine chloride (ach) of more than 1 microm concentration, there were ... | 1993 | 8007450 |
| effects of cytochalasin b on the morphology of secretory cells of rana esculenta fungiform papilla. | the effects of cytochalasin b on the three types of secreting cells (apical, paracoronal and parietal cells) present in the fungiform papilla of the frog's tongue were studied. cytochalasin b induced morphological modifications only in the apical secreting cells, localized in the sensorial area, without affecting the paracoronal cells or the parietal cells. the morphological features of treated apical cells showed that the drug induces two different effects: a disappearance of microfilaments and ... | 1993 | 7693063 |
| hormonal control of in vitro vitellogenin synthesis in rana esculenta liver: effects of mammalian and amphibian growth hormone. | estradiol 17-beta is known to induce hepatic synthesis and secretion of vitellogenin in all species studied and in rana esculenta, previous experiments demonstrated the involvement of pituitary in these processes; indeed, in addition to estradiol 17-beta, homologous pituitary homogenate directly stimulated male and female liver to produce vitellogenin in tissue cultures. therefore, the effect of ovine growth hormone (o-gh) and rana catesbeiana growth hormone (f-gh) on hepatic vitellogenin synthe ... | 1992 | 1490586 |
| seasonal fluctuations of androgen-binding activity in the testis of the frog, rana esculenta. | an androgen-binding activity has been identified in nuclear extracts of the testis of the frog, rana esculenta. a single class of high affinity (kd = 2.5 +/- 0.6 x 10(-9) m), low-capacity binding sites was found. the binding was specific for androgens; 17 beta-estradiol displaced [3h]testosterone with an id50 of 0.1 microm. cytosolic binding activity has a low affinity and a high capacity and lacks specificity. the seasonal fluctuations in binding capacity did not correlate with the androgen pea ... | 1992 | 1490580 |
| microelectrode determination of oxyntic cell ph in intact frog gastric mucosa. effect of histamine. | intracellular ph (phi) of acid-secreting cells was measured in intact gastric fundus mucosa of rana esculenta with double-barrelled ph microelectrodes. tissues were mounted, serosal side up, between two half chambers and individual cells were impaled after microsurgical removal of the serosal muscle layer. transepithelial potential difference (vt) and resistance (rt) as well as serosal cell membrane potential (vs) and phi were continuously recorded at rest (0.1 mmol/l cimetidine) or during stimu ... | 1992 | 1488284 |
| immunocytochemical identification of some regulatory peptides (gastrin, gastrin-releasing peptide, neurotensin and vasoactive intestinal polypeptide) in the harderian gland of the green frog, rana esculenta. | the presence and distribution of gastrin-, gastrin-releasing peptide-, neurotensin- and vasoactive intestinal polypeptide-like immunoreactivity in the harderian gland of rana esculenta were studied at different times of the annual cycle. gastrin-releasing peptide, neurotensin and vasoactive intestinal polypeptide-like substances were found either in the glandular cells, or in the nerve fibers surrounding the glandular acini. gastrin-like immunoreactivity was confined to the glandular cells. the ... | 1992 | 1486611 |
| modulation of calcium current gating in frog skeletal muscle by conditioning depolarization. | 1. ca2+ inward currents were measured by voltage clamping cut skeletal muscle fibres of the frog (rana esculenta) in a double-vaseline-gap system. 2. in order to study the basis of the previously described fast gating mode induced in the ca2+ inward current by a conditioning depolarization we quantitatively analysed the response to differing features of the conditioning prepulse. 3. the faster activation seen during the second of two depolarizations was confined to the component of the inward cu ... | 1992 | 1338468 |
| intratesticular control of spermatogenesis in the frog, rana esculenta. | adult intact and hypophysectomized (pdx) frogs, rana esculenta, were treated with a gonadotropin releasing hormone agonist (gnrha, hoe 766) and/or cyproterone acetate (cpa), the antiandrogen, in order to investigate the regulation of primary spermatogonial (i spg) multiplication in vertebrates. treatment with gnrha (injections containing 900 ng administered for 12 days on alternate days) caused a significant increase of the mitotic index (mi) of i spg in pdx animals and a further mi increase of ... | 1992 | 1447555 |
| seasonal variations in acetylcholine content and the levels of cholinergic enzymes in the alimentary tract and heart of rana esculenta l. | the acetylcholine (ach) content and the relative levels of choline-acetyltransferase (chat) and acetylcholinesterase (ache) were measured in the stomach and intestinal musculature and in the heart muscles of frogs (rana esculenta l.) during hibernation (january-stage 1), low activity (april-stage 2) and high activity period (july-stage 3). the ach content doubled in the stomach from stage 1 to 2, then little change occurred. in the intestine, the ach content changed little during the stages, whi ... | 1992 | 1460236 |
| in vivo and in vitro studies on effects of beta-endorphin and naloxone on sex steroids in the water frog, rana esculenta. | the effects of beta-endorphin and its receptor antagonist, naloxone, on progesterone, androgens, and oestradiol-17 beta release in male and female rana esculenta were studied in vivo and in vitro. in the in vivo experiments the frogs underwent hypophysectomy, gonadectomy or both, or were left intact; the animals were injected with beta-endorphin or naloxone and killed after 15, 30, 90 and 240 min. in the in vitro experiments inter-renal, testis and ovary, all with and without added pituitary, we ... | 1992 | 1442140 |
| a possible role of prostaglandin e2 in reproduction of the male water frog, rana esculenta. in vivo and in vitro studies. | plasma prostaglandin e2 (pge2), prostaglandin f2 alpha (pgf2 alpha), androgens and estradiol-17 beta were measured in the male water frog, rana esculenta, during the annual sexual cycle. in vivo experiments were carried out to study the effects of pge2 and pgf2 alpha on plasma sex steroids during the following periods: prereproduction (april), reproduction (may), postreproduction (june) and recovery (october). in the same months, in vitro experiments were performed to evaluate the effects of the ... | 1992 | 1438881 |
| the nature of cl- secretion, induced by carbaryl, across the isolated skin of rana esculenta. | 1. the pesticide carbaryl induces cl- secretion through the isolated frog skin. 2. this effect is due to the activation of both processes responsible for this phenomenon: (a) na+/k+/2cl- cotransport on the serosal membrane; (b) cl- selective channels on the external membrane. 3. cl- outflux is inhibited by bumetanide (10(-5) m) on the serosal side and by diphenylamine-2-carboxylic acid (dpc) (10(-3) m) on the external side. 4. the dpc action is not mimicked by naproxen, a specific inhibitor of c ... | 1992 | 1360392 |
| distribution of calcitonin gene-related peptide immunoreactivity in the central nervous system of the frog, rana esculenta. | the distribution of calcitonin gene-related peptide (cgrp), immunoreactive structures in the central nervous system of the frog, rana esculenta, was studied using the peroxidase immunohistochemical method. immunoreactive perikarya were found in all major parts of the brain. in the forebrain, neurons of the septohippocampal formation, the amygdala, the ventromedial and posterocentral thalamic nuclei, and the cerebrospinal fluid contacting neurons in the diencephalic periventricular organ showed i ... | 1992 | 1423513 |
| in vivo and in vitro studies on the effects of mgnrh on oestradiol-17 beta inter-renal production in the female frog, rana esculenta, during the post-reproductive period. | plasma oestradiol-17 beta was measured by ria, in female, rana esculenta, submitted to hypophysectomy, gonadectomy, or both, and treated with mammalian gonadotropin-releasing hormone (mgnrh), homologous pituitary homogenate, or both, during the post-reproductive period. in addition, the oestradiol-17 beta release was measured in in vitro incubations of ovaries or interrenals treated with mgnrh, pituitary, or both, during the same period. in vivo and in vitro mgnrh and/or pituitary directly stimu ... | 1992 | 1529724 |
| effects of ca2+ and other divalent cations on k(+)-evoked force production of slow muscle fibers from rana esculenta and rana pipiens. | slow muscle fibers were dissected from cruralis muscles of rana esculenta and rana pipiens. isometric contractures were evoked by application of k(+)-rich ringer's containing ca2+, ni2+, co2+, mn2+ or mg2+. high (7.2 mmol/liter) external ca2+ concentration raised, 0 ca2+ lowered the k+ threshold. replacing ca2+ by ni2+ or co2+ had an effect similar to that of high ca2+ ringer's. in mg2+ ringer's the k+ concentration-response curve was flattened. these effects were observed already after short ex ... | 1992 | 1433275 |
| mammalian gnrh involvement in prostaglandin f2 alpha and sex steroid hormones testicular release in two amphibian species: the anuran water frog, rana esculenta, and the urodele crested newt, triturus carnifex. | the present work was carried out to study the in vitro effects of mammalian gonadotropin-releasing hormone (mgnrh) on rana esculenta and triturus carnifex testis production of prostaglandin f2 alpha (pgf2 alpha) and sex steroid hormones during the prereproduction, reproduction, and postreproduction periods. in r. esculenta, testicular pgf2 alpha release was lower during postreproduction, and mgnrh increased pgf2 alpha in prereproduction and reproduction. androgens were higher during prereproduct ... | 1992 | 1398018 |
| a possible involvement of prostaglandin f2 alpha (pgf2 alpha) in rana esculenta ovulation: effects of mammalian gonadotropin-releasing hormone on in vitro pgf2 alpha and 17 beta-estradiol production from ovary and oviduct. | the present work studied the pgf2 alpha and 17 beta-estradiol plasma levels during ovulation, and the in vitro effects of mammalian gonadotropin-releasing hormone (mgnrh) on ovarian and oviductal production of prostaglandin f2 alpha (pgf2 alpha) and 17 beta-estradiol during four different stages of the annual sexual cycle in water frog, rana esculenta. plasma levels of pgf2 alpha increased in ovulating frogs, with respect to preovulatory and postovulatory levels, while estradiol did not change. ... | 1992 | 1398010 |
| sodium nitroprusside alters dark voltage and light responses in isolated retinal rods during whole-cell recording. | dark voltage and light responses of isolated retinal rods of rana esculenta were investigated by employing the whole-cell patch-clamp technique. when the recording pipette was filled with a medium devoid of nucleotides, a spontaneous hyperpolarization of the dark voltage partly due to a diffusional loss of cgmp and its precursor gtp and a retardation in the recovery of the light responses was observed. the larger part of the retardation of the light responses was prevented by 1 mm atp. addition ... | 1992 | 1354484 |
| mitochondrial dna reveals formation of nonhybrid frogs by natural matings between hemiclonal hybrids. | the european water frog rana esculenta (rl), a natural hybrid between r. ridibunda (rr) and r. lessonae (ll), reproduces by hybridogenesis: haploid gametes usually contain an intact chromosome set of r. ridibunda (r); the lessonae nuclear genome (l) is lost from the germ line. hybridity is restored in the next generation, via fertilization by syntopic r. lessonae. matings between two hybrids (rl x rl) usually give inviable r. ridibunda (rr) progeny. the adult r. ridibunda subpopulation of trubes ... | 1992 | 1352842 |
| the msh-like activity of pineal hormone e5 in vivo and in vitro experiment. | further experiments have revealed that the polypeptidic hormone e5 has a msk-like effect, as experimentally demonstrated on the frog skin. in rana esculenta, 30-120 min after a subcutaneous injection of 0.2 mg purified e5b or e5p/100 g b.w., the skin blackened and the effect lasted for about two hours. a comparable effect was induced by incubating the fragment of frog abdominal skin with a similar solution of e5. this msk-like effect appears to be identical upon mammalian melanocytes in c57/b16 ... | 2015 | 1306087 |
| performance of tadpoles from the hybridogenetic rana esculenta complex: interactions with pond drying and interspecific competition. | the performance of three genotypes (ll, lr, rr) of tadpoles resulting from the hybrid mating system of rana lessonae (phenotype l, genotype ll) and rana esculenta (phenotype e, genotype lr) was determined in artificial ponds. the effects of interspecific competition and pond drying on growth, development, and survival of tadpoles were used to measure the performance of genotypes and the relative fitness of offspring. among the three genotypes, tadpoles from the homogametic mating rr had the lowe ... | 1992 | 28568669 |
| in vitro induction of vitellogenin synthesis in rana esculenta: role of the pituitary. | vitellogenin (vtg), a complex protein, is a precursor of yolk protein (lipovitellin and phosvitin) in all oviparous vertebrates studied to date. in amphibians, as in other oviparous vertebrates, vtg synthesis is hormonally dependent; estradiol-17 beta (e2) is especially important, although in vivo in the frog rana esculenta the pituitary may be involved in hepatic vtg synthesis and secretion. the present in vitro experiments carried out during the main phases of the annual reproductive cycle of ... | 1992 | 1398001 |
| seasonal commitment of hmgcoa reductase activity to vitellogenin production. | in female frogs (rana esculenta) during gametogenesis the cholesterol synthesized in the liver by 3-hydroxy-3-methylglutaryl coenzyme a reductase is mostly exported into the blood and taken up by the oocytes. in order to understand the fate of the neosynthesized cholesterol, female and male frogs and estrogenized male controls were injected with the labelled precursor 14c mevalonate. in females and in estrogenized controls, mevalonate-derived radioactivity is found in a plasmatic lipoprotein tha ... | 1992 | 1391685 |
| size and chirality of intracellularly applied anions affect the function of isolated photoreceptors. | the effect of intracellularly applied anions on the function of retinal rods of the frog rana esculenta was investigated by means of the whole-cell patch-clamp technique. when the recording pipette contained a medium based on potassium chloride, a slow spontaneous hyperpolarization was observed presumably due to a diffusional loss of the photoreceptor's internal transmitter cyclic guanosine monophosphate (cgmp) and its precursor guanosine triphosphate (gtp). when chloride was replaced by organic ... | 1992 | 1630887 |
| effects of intracellular signals on na+/k(+)-atpase pump activity in the frog skin epithelium. | the effects of intracellular signals (phi, na+i, ca2+i, and the electrical membrane potential), on na+ transport mediated by the na+/k+ pump were investigated in the isolated rana esculenta frog skin. in particular we focussed on phi sensitivity since protons act as an intrinsic regulator of transepithelial na+ transport (jna) by a simultaneous control of the apical membrane na+ conductance (gna) and the basolateral membrane k+ conductance (gk). phi changes which modify jna, gna and gk, do not a ... | 1992 | 1374642 |
| streptomycin blocks the afferent synapse of the isolated semicircular canals of the frog. | this study aimed to define the acute electrophysiological effects of the perilymphatic perfusion of streptomycin in the sensory apparatus of the semicircular canals of the frog. the ampullary dc potential, the vestibular nerve multiunit discharge, the nerve dc potential and the unitary epsp activity were recorded in isolated semicircular canals of the frog (rana esculenta l). the results demonstrated that perilymphatic microperfusion of streptomycin (0.1, 0.3, 1 and 3 mm) reduced both resting an ... | 1992 | 1629049 |
| morphology of epiphyseal apparatus of a ranid frog (rana esculenta) | morphological, histochemical and ultrastructural investigations on epiphyseal apparatus of rana esculenta were made. the most important findings were the following: 1) metaphyseal cartilage is localized inside proximal diaphyseal compact bone as a plug; 2) metaphyseal cartilage do not reduce in thickness during ageing; 3) metaphyseal cartilage do not show vascular invasion and do not mineralize in degenerative zone; 4) trabecular bone was not at all evident in this animal; 5) external periosteum ... | 1992 | 1515710 |
| annual variations in the binding of insulin to hepatic membranes of the frog rana esculenta. | amphibia undergo regular annual cycles of metabolic activity that are influenced by both exogenous factors and hormones. insulin binding to crude frog hepatic membranes was studied throughout the year. the general character of insulin binding was similar to that in other vertebrates; the maximum specific binding was achieved after 4 hr at 4 degrees, the optimum ph was 7.8, half-maximal displacement of bound insulin was from 9 x 10(-10) to 1 x 10(-9) m, and insulin analogs competed for the insuli ... | 1992 | 1505722 |
| testosterone induction of poly(a)(+)-rna synthesis and [35s]methionine incorporation into proteins of rana esculenta harderian gland. | the role of androgens in the cyclic secretory activity of the rana esculenta harderian gland (hg) was studied. total rna showed a dramatic increase in october and may when the nuclear androgen receptors peak. during the resumption of the secretory activity a gradual increase of poly(a)(+)-rna was detected; during the enhancement phase (may) a peak of the poly(a)(+)-rna fraction was found. in in vitro experiments testosterone increased the incorporation of [3h]uridine into the poly(a)(+)-rna frac ... | 1992 | 1375172 |
| stimulus-evoked slow potential shifts and changes in [k+]0 of the frog optic tectum. | in 17 frogs (rana esculenta var ridibunda) immobilised with succinyl choline the optic tectal surface was stimulated by trains of electrical pulses or by a flash to the contralateral eye. sustained potential shifts (spss) and changes in extracellular potassium concentration (delta[k+]0) were simultaneously recorded. in response to electrical stimulation spss of maximal amplitudes (1.19 +/- 0.1 mv) were recorded between 50 and 200 microns in depth and maximal delta[k+]0 (0.69 +/- 0.08 mm) between ... | 1992 | 1593502 |
| ovarian opioids and the reproductive cycle of the frog rana esculenta. | in mammals, proopiomelanocortin-related peptides are involved in reproductive processes both at the hypothalamo-pituitary and ovarian levels. using immunocytochemical, biochemical and physiological "in vitro" studies, we provide here evidence for a diffuse pomc-related opioid system in the frog rana esculenta. ovarian beta-endorphin (beta-ep) is expressed in thecal cells and changes during the reproductive cycle in an inverse relationship with follicular development. seasonal changes in the ovar ... | 1992 | 1573972 |
| experimental approaches to the study of degenerative and regenerative processes in the nervous tissue. i). morphological changes in the frog cerebellum after unilateral transection of the viii statoacustic nerve. | the cell density was evaluated in purkinje neuron and internal granule cell layers of the frog (rana esculenta l.) cerebellum at 3, 8, 14, or 30 days after unilateral transection of the viii statoacustic nerve. after 3 days, the cell density of the purkinje cell layer was markedly reduced, the cellular loss amounting to 30% at 30 days. in the internal granule cell layer (igl), after an abrupt decrease in the cell density at 3 and 8 days, the number of cells increased at 14 days and reached the v ... | 1992 | 1479191 |
| role of the dermal tracts in the pigment pattern of the frog. | the pigment pattern of the ventral skin of the frog rana esculenta is compared in skin fragments grown for 24 hr with or without antiserum directed to fibronectin (anti-fn). melanocyte-stimulating hormone (msh) was added to the medium during the last hour in culture in order to enhance visibility of melanophores in the ventral region of the frog skin. comparison of these two treatments provides information regarding the precise localization of melanophores in the dermal tracts and their involvem ... | 1992 | 1440581 |
| [aberrant phenotypes of the ldh-b locus in hybrid populations of the rana esculenta complex (amphibia, ranidae)]. | | 1992 | 1425192 |
| mallory stain may indicate differential rates of rna synthesis: i. a seasonal cycle in the harderian gland of the green frog (rana esculenta). | when mallory's trichrome stain is used, acinar nuclei of the harderian gland of rana esculenta display different affinities for the dye. some of the orangiophilic nuclei show affinity for aniline blue (blue nuclei). in the harderian gland of rana esculenta their number and the intensity of staining with aniline blue may vary during the year. the affinity for aniline blue disappears following digestion of paraffin sections with rnaase, but not with dnaase or trypsin. furthermore, in vitro incubat ... | 1992 | 1374668 |
| some morphological and histochemical features of the midgut myenteric plexus of the common european frog, rana esculenta. | the neuron morphology and distribution of four putative transmitters were investigated in the myenteric plexus of frog (rana esculenta) midgut. the gross morphology was revealed by nadh-diaphorase histochemistry, and the shape of the neurons by silver impregnation. nerve cells had heterogeneous distribution: they either formed ganglia or placed as solitary neurons in the duodenum, while in the rest of the midgut only solitary neurons were observed. three morphologically distinct cell types were ... | 1992 | 1374278 |
| the effect of the benzothiazepine diltiazem on force and ca2+ current in isolated frog skeletal muscle fibres. | 1. the action of the d-cis and l-cis isomers of the benzothiazepine derivative diltiazem on isometric force and l-type ca2+ inward current in short muscle fibres from toe muscles of the frog (rana esculenta and r. temporaria) was investigated under voltage clamp control with two internal microelectrodes. the experiments were performed at 10 degrees c in tea-sulphate solution, in which the concentration of ionized ca2+ was about 4 mm. 2. in the presence of diltiazem (d-cis, 0.25-30 microm; l-cis, ... | 1992 | 1323667 |
| number of mast cells in the harderian gland of the green frog, rana esculenta: the annual cycle and its relation to environmental and hormonal factors. | the harderian gland of the green frog contains mast cells. their number shows annual variations, being more numerous in the winter months. the increase of mast cell number (mcn) is matched by a marked degranulation. no sex differences are found throughout the year. manipulations of the photoperiod and temperature, either in winter or in summer, suggest that only the latter is responsible for the annual variations. exposure to higher temperatures causes a decrease in the mcn in the winter frogs, ... | 1991 | 1817144 |
| gonadotropin-releasing hormone stimulates biosynthesis of prostaglandin f2 alpha by the interrenal gland of the water frog, rana esculenta, in vitro. | the present study was carried out to evaluate the in vitro effects of mammalian gonadotropin-releasing hormone (mgnrh) on the production of prostaglandin f2 alpha (pgf2 alpha) and sex steroids (progesterone, androgens, and 17 beta-estradiol) by the interrenal gland of male and female rana esculenta during three different periods of the sexual annual cycle. in both sexes, mgnrh induced a significant increase in pgf2 alpha in the incubation medium in all examined periods. progesterone and androgen ... | 1991 | 1808024 |
| the effects of sodium removal on the two types of calcium currents in single frog atrial cells. | the effects of sodium removal on the two types of calcium currents were studied in enzymatically dispersed frog (rana esculenta) atrial myocytes with the single pipette patch-clamp technique. reduction of calcium currents was recorded when nacl was replaced either by teacl, licl, triscl, cholinecl or by mannitol. an involvement of the na-ca exchange mechanism could be ruled out since the decrease was also observed after replacing external ca with ba. the slight shift of the apparent reversal pot ... | 1991 | 1666387 |
| active urea transport independent of h+ and na+ transport in frog skin epithelium. | we investigated the relationship between h+ secretion (jh), na+ absorption (jna), and urea transport (ju) in skin of frogs (rana esculenta) adapted to running tap water, nacl (100 mm), and kcl (100 mm). in addition, cell morphological changes, particularly in the mitochondria-rich cells (mrc), were followed. nacl adaptation stimulated an active ju, reduced jna and jh, and caused a decrease in the apical surface of mrc. after kcl adaptation, jna and jh were increased and highly correlated, with a ... | 1991 | 1833990 |
| surfactant-like material on the chemoreceptorial surface of the frog's taste organ: an ultrastructural and electron spectroscopic imaging study. | tannic acid treatment was used to study the morphology of surfactant-like material (slm) in the taste organ of rana esculenta and the relation between this material and the cell types of the organ. on the surface of the taste organ slm was associated with the apical processes of wing and putative taste cells. in slm, a biphasic pattern was visible, a portion showed a lamellar periodicity (the repeating period of lamellae approximated 45 a), and a second portion showed an homogeneous electron den ... | 1991 | 1807349 |
| effects of mammalian gonadotropin-releasing hormone on plasma level of prostaglandin f2 alpha in the water frog, rana esculenta. | the present investigation was performed to evaluate the effects of mammalian gonadotropin-releasing hormone (mgnrh) on prostaglandin f2 alpha (pgf2 alpha) plasma level in adult male and female water frog, rana esculenta, during three different periods of the reproductive cycle: recovery period (october), breeding period (may), and postreproductive period (june). intact, hypophysectomized (hyp), gonadectomized (gon), and hypophysectomized-and-gonadectomized (hyp/gon) animals were injected with 0. ... | 1991 | 1778413 |
| pigment cell localizations in anuran ventral skin at climactic metamorphosis. | in anuran amphibians, the specific color pattern of the skin is expressed after metamorphosis, and its formation involves pigment cell migrations. pigment cells are differently distributed in the tadpole, larval, and froglet skin. to learn more about their fate during metamorphic climax and in the young froglet, we focused our attention on the different localizations of larval melanophores and iridophores in the ventral skin of rana esculenta before and during skin homing. localizations of melan ... | 1991 | 1750384 |
| in vitro steroid production by follicles of frog rana esculenta: mammalian gonadotropin-releasing hormone effects. | the effects of mammalian gonadotropin-releasing hormone on ovarian release of progesterone, androgens and estradiol-17 beta were studied in vitro by a superfusion system carried out on follicles of adult female rana esculenta, collected at different periods of the annual reproductive cycle. the follicles were superfused with medium alone, pituitary, mammalian gonadotropin-releasing hormone, or pituitary plus mammalian gonadotropin-releasing hormone. for follicles obtained in the prereproductive ... | 1991 | 1950598 |
| seasonal changes in plasma prostaglandin f2 alpha and sex hormones in the male water frog, rana esculenta. | prostaglandin f2 alpha (pgf2 alpha), progesterone, androgens (testosterone + dihydrotestosterone), and 17 beta-estradiol were measured in the plasma of male frogs, rana esculenta, by radioimmunoassays. plasma concentrations of pgf2 alpha were higher from october to december and peaked in march (prereproduction) and in june (postreproduction). plasma progesterone levels were relatively low but showed an increase from october to december and in june. plasma androgen titres rapidly increased in ear ... | 1991 | 1879650 |
| androgen receptor in the harderian gland of rana esculenta. | an androgen receptor has been identified in the cytosolic and nuclear extracts of the harderian gland of the frog, rana esculenta. a single class of high-affinity binding sites was found: kd = 1.9 +/- 1.3 (s.d.) nmol/l (n = 26) for the cytosolic extract and kd = 0.9 +/- 0.8 nmol/l (n = 15) for the nuclear extract. the presence of binding activity in both nuclear and cytosolic extracts and the low rate of ligand-receptor dissociation are characteristics that distinguish this receptor from a stero ... | 1991 | 2040857 |
| internalization of erythrocytes into liver parenchymal cells in naturally hibernating frogs (rana esculenta l.). | mature and intact red blood cells were found in hepatocytes of frogs during natural underground hibernation. no signs of erythrophagocytosis, e.g., separating membranes between erythrocyte and hepatocyte cytoplasm, and lysosomes, were observed. red blood cells probably penetrated into hepatocytes by ameboid-like mechanisms, which can be deduced by cytoplasmic protrusions and invaginations. most of the hepatocytes had large amounts of stored glycogen and few organelles, often segregated in conden ... | 1991 | 2022945 |
| contraction threshold and the "hump" component of charge movement in frog skeletal muscle. | the delayed component of intramembranous charge movement (hump, i gamma) was studied around the contraction threshold in cut skeletal muscle fibers of the frog (rana esculenta) in a single vaseline-gap voltage clamp. charges (q) were computed as 50-ms integrals of the on (qon) and off (qoff) of the asymmetric currents after subtracting a baseline. the hump appeared in parallel with an excess of qon over qoff by approximately 2.5 nc/mu f. caffeine (0.75 mm) not only shifted the contraction thresh ... | 1991 | 1865176 |
| the vomeronasal organ in the frog, rana esculenta. an electron microscopy study. | the ultrastructure of the vomeronasal organ (jacobson's vno) of the frog, rana esculenta, was studied under the transmission and scanning electron microscope. four cell types were identified: ciliated, bipolar, glial-like, and basal. ciliated cells are unique to the frog vno and show morphological evidence of secretion; bipolar (neuronal) cells are arranged in columns and reach the free surface of the epithelium with knobs bearing microvilli. the latter are in contact with amorphous material not ... | 1991 | 2070348 |