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At least 217 records · Page 12Linked to original sources
PubMed1989

Identification of vasotocin-like immunoreactivity in chromaffin cells of the frog adrenal gland: effect of vasotocin on corticosteroid secretion.

The presence of neurohypophyseal nonapeptides in the adrenal gland of nonmammalian vertebrates and the possible action of these regulatory peptides on corticosteroid secretion have never been investigated. We have applied the indirect immunofluorescence technique to examine whether vasotocin (AVT) and/or mesotocin (MT) are located in frog adrenal (interrenal) tissue. Using antisera against AVT and tyrosine hydroxylase, we found that all chromaffin cells contain an AVT-like peptide. Labeling of consecutive sections with phenylethanolamine-N-methyltransferase or AVT antibodies showed that both noradrenaline- and adrenaline-storing cells contain AVT-like immunoreactivity. In contrast no labeling of frog adrenal slices was observed using a MT antiserum. At the ultrastructural level, the immunogold technique revealed that the AVT-immunoreactive peptide is sequestered in chromaffin granules with varying electron densities. Filtration of frog adrenal tissue extracts on Sep-Pak C-18 cartridges showed that the elution profile of the AVT-like peptide was similar to that of synthetic AVT. The apparent concentration of AVT in the adrenal was 2.7 ng/g tissue. Since chromaffin cells represent approximately one third of all interrenal cells, the actual concentration of AVT in chromaffin tissue was about 8 ng/g tissue. The role of AVT in the regulation of frog adrenal steroidogenesis was studied in vitro using perifused frog interrenal slices. Graded doses of AVT (10(-10)-10(-7) M) induced a dose-dependent stimulation of both corticosterone and aldosterone secretion. The other neurohypophyseal peptides (vasopressin, oxytocin, and MT) were also able to enhance corticosteroid secretion, but AVT was by far the most potent stimulator of steroidogenesis. Prolonged administration (4 h) of AVT induced a rapid increase in corticosterone and aldosterone output, followed by a gradual decline of corticosteroid secretion. These results show that an AVT-like peptide is stored in chromaffin granules of frog adrenal gland. Our data also indicate that synthetic AVT is a potent stimulator of corticosteroid secretion by frog interrenal cells. Since in amphibians adrenocortical and chromaffin cells are intimately intermingled, these results suggest that AVT produced by chromaffin cells may regulate corticosteroid release locally, through a cell to cell mode of communication.

Adrenal Cortex↗
PubMed1994

The frog gonadotropin-releasing hormone-I (GnRH-I) gene has a mammalian-like expression pattern and conserved domains in GnRH-associated peptide, but brain onset is delayed until metamorphosis.

Recent evidence indicates a localized origin in the olfactory placode for the mammalian forebrain neurons that express GnRH. To identify the cellular and molecular signals that induce the GnRH phenotype, we cloned and characterized a cDNA encoding the GnRH prohormone, the precursor for both GnRH-I and GnRH-associated peptide in the frog, Xenopus laevis, an embryonic model accessible to experimental manipulation. The 396-base cDNA represented a single mRNA species encoding an 89-amino acid prepro-GnRH that, unlike a recently cloned fish GnRH gene, was identical to both the mammalian GnRH decapeptide as well as multiple domains within GnRH-associated peptide. Serial section in situ hybridization histochemistry and immunocytochemistry in adult frog localized a forebrain system comprising 250-350 cell bodies whose overall neuroanatomy, including fiber projections, was very similar to that described for mammals. However, neither Northern nor in situ hybridization detected GnRH expression in midbrain, arguing that another frog gene encodes the midbrain GnRH-II expression pattern described by many others using antisera directed against the fish GnRH-I or chicken GnRH-II decapeptides. In contrast to mammals and birds, in which GnRH-expressing cells migrate into embryonic forebrain, frog GnRH cells were first detected after they reached their final position in the preoptic area during the late larval period. Thus, although previous studies proposed a complex organization for the GnRH system in the frog, our findings show that similar to mammals, there is a single gene that can account for the continuum of GnRH-I cells spanning frog forebrain. However, unlike mammals, in frogs, for unknown reasons, GnRH-I gene expression is suppressed until metamorphic climax.

Amino Acid Sequence↗
PubMed1998

Pharmacological and functional characterization of muscarinic receptors in the frog pars intermedia.

The secretion of alphaMSH from the intermediate lobe of the frog pituitary is regulated by multiple factors, including classical neurotransmitters and neuropeptides. In particular, acetylcholine (ACh), acting via muscarinic receptors, stimulates alphaMSH release from frog neurointermediate lobes (NILs) in vitro. The aim of the present study was to characterize the type of receptor and the transduction pathways involved in the mechanism of action of ACh on frog melanotrope cells. The nonselective muscarinic receptor agonists muscarine and carbachol both stimulated alphaMSH release from perifused frog NILs, whereas the M1-selective muscarinic agonist McN-A-343 was virtually devoid of effect. Both the M1>M3 antagonist pirenzepine and the M3>M1 antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide inhibited muscarine-induced alphaMSH release. Administration of a brief pulse of muscarine in the vicinity of cultured melanotrope cells provoked a 4-fold increase in the cytosolic calcium concentration ([Ca2+]i). Suppression of Ca2+ in the culture medium or addition of 3 mM Ni2+ abrogated the stimulatory effect of muscarine on [Ca2+]i and alphaMSH release. In contrast, omega-conotoxin GVIA and nifedipine did not significantly reduce the stimulatory effect of muscarine on [Ca2+]i and alphaMSH secretion. Exposure of NILs to muscarine provoked an increase in inositol phosphate formation, and this effect was dependent on extracellular Ca2+. The inhibitor of polyphosphoinositide turnover neomycin significantly attenuated the muscarine-evoked alphaMSH release. Similarly, pretreatment of frog NILs with phorbol ester markedly reduced the secretory response to muscarine. In contrast, the stimulatory effect of muscarine on alphaMSH release was not affected by the phospholipase A2 inhibitor dimethyl eicosadienoic acid or by the tyrosine kinase inhibitors lavendustin A, genistein, and tyrphostin 25. Muscarine at a high concentration (10(-4) M) only produced a 40% increase in cAMP formation. Preincubation of frog NILs with pertussis toxin did not significantly affect the muscarine-induced stimulation of alphaMSH release. These results indicate that frog melanotrope cells express a muscarinic receptor subtype pharmacologically related to the mammalian M3 receptor. Activation of this receptor causes calcium influx through Ni2+-sensitive Ca2+ channels and subsequent activation of the phopholipase C/protein kinase C transduction pathway.

Acetylcholine↗
PubMed2006

Water balance of field-excavated aestivating Australian desert frogs, the cocoon-forming Neobatrachus aquilonius and the non-cocooning Notaden nichollsi (Amphibia: Myobatrachidae).

Burrowed aestivating frogs of the cocoon-forming species Neobatrachus aquilonius and the non-cocooning species Notaden nichollsi were excavated in the Gibson Desert of central Australia. Their hydration state (osmotic pressure of the plasma and urine) was compared to the moisture content and water potential of the surrounding soil. The non-cocooning N. nichollsi was consistently found in sand dunes. While this sand had favourable water potential properties for buried frogs, the considerable spatial and temporal variation in sand moisture meant that frogs were not always in positive water balance with respect to the surrounding soil. The cocoon-forming N. aquilonius was excavated from two distinct habitat types, a claypan in which frogs had a well-formed cocoon and a dune swale where frogs did not have a cocoon. Cocoons of excavated frogs ranged in thickness from 19.4 microm to 55.61 microm and consisted of 81-229 layers. Cocooned claypan N. aquilonius were nearing exhaustion of their bladder water reserves and had a urine osmolality approaching that of the plasma. By contrast, non-cocooned N. aquilonius from the dune swale were fully hydrated, although soil moisture levels were not as high as calculated to be necessary to maintain water balance. Both species had similar plasma arginine vasotocin (AVT) concentrations ranging from 9.4 to 164 pg ml(-1), except for one cocooned N. aquilonius with a higher concentration of 394 pg ml(-1). For both species, AVT showed no relationship with plasma osmolality over the lower range of plasma osmolalities but was appreciably increased at the highest osmolality recorded. This study provides the first evidence that cocoon formation following burrowing is not obligatory in species that are capable of doing so, but that cocoon formation occurs when soil water conditions are more desiccating than for non-cocooned frogs.

Adaptation, Physiological↗
PubMed1996

Do Australian desert frogs co-accumulate counteracting solutes with urea during aestivation?

Australian desert frogs of the genera Neobatrachus, Cyclorana and Heleioporus experience significant dehydration, and iono- and osmoconcentration, during aestivation in the laboratory and accumulate substantial amounts of urea (100-200 mmol)(l-1). We expected a priori that aestivating frogs probably would not need to accumulate balancing osmolytes but would accumulate trimethylamine oxide (TMAO) or betaine as counteracting solutes to urea. These aestivating frogs did not co-accumulate a substantial quantity of any particular balancing osmolyte or counteracting solute, such as a methylamine [TMAO, trimethylamine amine (TMA), betaine, sarcosine, glycerophosphorylcholine (GPC)] or polyol (inositol, mannitol, sorbitol) in plasma or muscle relative to urea accumulation. However, for aestivating frogs, the total concentration of all measured methylamines and polyols (TMAO + TMA + betaine + sarcosine + GPC + inositol) in muscle was approximately 35-45 mmol kg-1, and so it is possible that all of these solutes have a combined counteracting osmolyte role in aestivating frogs at a ratio to urea of approximately 1:2.5, as has been described for elasmobranch fishes. Alternatively, the absence of substantial co-accumulation with urea of any particular solute suggests that aestivating frogs might not require any major extracellular or intracellular counteracting solutes (TMAO, betaine, GPC). The enzyme systems of these aestivating frogs may be insensitive to the perturbing effects of urea, or the perturbing effects of accumulated urea may be a mechanism for metabolic depression, during aestivation.

Animals↗
PubMed2002

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 realistic bones, joints and body-segment properties. We performed forward dynamic simulations of jumping to determine the minimal number of joint degrees of freedom required to produce maximal-distance jumps and to produce jumps of varied take-off angles. The forward dynamics of the models was driven with joint torque patterns determined from inverse dynamic analysis of jumping in experimental frogs. When the joints were constrained to rotate in the extension-flexion plane, the simulations produced short jumps with a fixed angle of take-off. We found that, to produce maximal-distance jumping, the skeletal system of the frog must minimally include a gimbal joint at the hip (three rotational degrees of freedom), a universal Hooke's joint at the knee (two rotational degrees of freedom) and pin joints at the ankle, tarsometatarsal, metatarsophalangeal and iliosacral joints (one rotational degree of freedom). One of the knee degrees of freedom represented a unique kinematic mechanism (internal rotation about the long axis of the tibiofibula) and played a crucial role in bringing the feet under the body so that maximal jump distances could be attained. Finally, the out-of-plane degrees of freedom were found to be essential to enable the frog to alter the angle of take-off and thereby permit flexible neuromotor control. The results of this study form a foundation upon which additional model subsystems (e.g. musculotendon and neural) can be added to test the integrative action of the neuromusculoskeletal system during frog jumping.

Animals↗
PubMed1982

Water loss and nitrogen excretion in sharp-nosed reed frogs (Hyperolius nasutus: anura, Hyperoliidae).

Sharp-nosed African reed frogs, Hyperolius nasutus Gunther, are small (0.4 g) hyperoliids which have minimal rates of evaporative water loss (4.5 mg g-1 h-1; 0.3 mg cm-2 h-1) that are only 1/10 to 1/20 that of a typical frog, Hylaregilla, of comparable size (171 mg g-1 h-1, 4.8 mg cm-2 h-1). The surface-area-specific resistance to water flux of H. nasutus dorsal skin (96-257 sec cm-1) is similar to that of other 'waterproof' frogs (300-400), of cocooned frogs (40-500), and of desert reptiles (200-1400). However, H. nasutus can greatly increase the rate of evaporative water loss during radiative heat stress by mucous gland discharge, and by exposing the ventral skin. Urea is the principal nitrogenous waste product of H. nasutus and uric acid comprises less than 1% of the total nitrogen excretion for both H. nasutus and H. regilla. Other 'waterproof' frogs, in contrast, are uricotelic. Lethal dehydration requires less than two weeks in H. nasutus, despite its low surface-area-specific rate of water loss, because of its small size and concomitantly high surface-to-volume ratio. The rate of urea accumulation during dehydration was 23 mM g-1 day-1, which is sufficiently low that urea accumulation would not be lethal before the frog had succumbed to dehydrational death. Consequently, there appears to be little or no selective advantage for uricotely in small 'waterproof' frogs, such as H. nasutus.

Animals↗
PubMed1992

Isolation and identification of intestinal bacteria from Japanese tree frog (Hlya japonica) with the special reference to anaerobic bacteria.

The bacteria in the large intestines of eight Japanese tree frogs (Hlya japonica) were enumerated by using an anaerobic culture system. The microorganisms at approximately 3.1 x 10(9) bacteria per g (wet weight) of intestinal contents were present in the intestine of all the frogs tested. No difference of the total bacteria in the frog intestine was observed between two different incubation-temperatures (room temperature and 37 degrees C). Eleven genera and 16 species were isolated from the frog intestine. In most frogs, Bacteroides (B.) caccae and B. vulgatus were detected as the predominant organisms. Escherichia coli was also present in greater numbers in the intestine. Other bacteria isolated at high dilutions were strict anaerobes, including Fusobacterium and Clostridium. Enterococcus faecalis was frequently isolated from the frog intestine. However, four genera of Bifidobacterium, Eubacterium, Peptostreptococcus, and Lactobacillus were not isolated from the frog intestine.

Animals↗
PubMed2001

Helminth communities of green frogs Rana clamitans Latreille, from southwestern Michigan.

A total of 239 green frogs Rana clamitans, collected between June 3 and August 27, 1998 from 6 locations in southwestern Michigan, was examined for helminths. Of the 26 helminth taxa found, the larval cestode Mesocestoides sp. had the highest mean intensity, followed by the larval trematode Fibricola sp. Of the helminths that mature in frogs, Haematoloechus varioplexus had the highest prevalence and Gorgodera amplicava had the highest mean intensity. Frogs from 118th Pond had the highest species richness (20), mean helminth species richness (5.2), and mean helminth abundance (153.7). Frogs from Constantine East had the highest mean helminth species diversity (0.8778) and evenness (0.6033), followed by frogs from 118th Pond. In all comparisons of mean helminth community species richness, abundance, diversity, and evenness, adult frogs had significantly higher or higher values than did juveniles at each location. Jaccard's coefficients of similarity for the helminth communities for location pairs ranged from 0.545 to 0.823. Nine and 2 core helminth taxa occurred at the local and regional levels, respectively. The differences in several helminth community measures in green frogs among locations stress the importance of local ecological conditions on helminth community structure.

Animals↗
PubMed2005

Field exposure of frog embryos and tadpoles along a pollution gradient in the Fox River and Green Bay ecosystem in Wisconsin, Usa.

We raised embryos and tadpoles of green frogs (Rana clamitans melanota) and leopard frogs (R. pipiens) in situ along a contamination gradient in the Fox River/Green Bay ecosystem (WI, USA). Differences in exposure were reflected by significant positive regressions between concentrations in sediment and in frogs of polychlorinated biphenyl (PCB) congeners and some heavy metals (Cd, Cr, and Pb), which could have predictive value for estimating exposure of amphibians to contaminants in this ecosystem and, perhaps, in others. On average, non-ortho-substituted coplanar PCBs made up a very small percentage (average, 0.2%) of the PCB congeners in all samples analyzed, with larger fractions accounted for by mono- and di-ortho congeners (average, 19%) and routine congeners (average, 81%). Hatchability of frog embryo batches and anuran species richness at the sites were negatively correlated with level of contamination, but tadpole growth and survival were not. Sediment and tissue levels of PCBs and metals generally were correlated with each other, confounding the association of effects on frogs with any particular contaminant. It is also plausible that high levels of un-ionized ammonia (NH3) reduced hatching success of green frog, but not leopard frog, embryos in the field enclosures. Other environmental factors that were present but unmeasured in the field, such as ultraviolet-B radiation as well as water flow and level fluctuations, might have caused differences in hatching success at the field sites.

Animals↗
PubMed2001

Experimental transmission of cutaneous chytridiomycosis in dendrobatid frogs.

In a series of three experiments during March-October, 1998, two species of captive-bred poison dart frogs (Dendrobates tinctorius and D. auratus) were exposed to Batrachochytrium dendrobatidis, a recently-described chytridiomycete fungus (chytrid) that was originally isolated from a blue poison dart frog (D. azureus). All frogs exposed to the chytrids developed a fatal skin disease, whereas none of the control frogs developed skin lesions. The most consistent clinical sign in chytrid-exposed frogs was excessive shedding of skin. Gross lesions were subtle, usually affected the legs and ventrum, and consisted of mild skin thickening and discoloration. Microscopic examination of shed skin pieces and/or skin imprints demonstrated the presence of chytrids and was used for ante mortem and post mortem confirmation of chytrid infection. Histologically, there was epidermal hyperkeratosis, hyperplasia, and hypertrophy associated with low to moderate numbers of chytrids in the keratinized layers. These experiments demonstrated that Batrachochytrium dendrobatidis can be a fatal pathogen in poison dart frogs. The experimentally-induced disease in these frogs resembled cases of cutaneous chytridiomycosis that have recently been described in several other species of captive and wild amphibians.

Animal Diseases↗
PubMed2003

Trichobothrial mediation of an aquatic escape response: directional jumps by the fishing spider, Dolomedes triton, foil frog attacks.

Fishing spiders (Pisauridae) frequent the surfaces of ponds and streams and thereby expose themselves to predation by a variety of aquatic and semi-aquatic vertebrates. To assess the possibility that the impressive jumps of fishing spiders from the water surface function in evading attacks by frogs, attacks by bullfrogs (Rana catesbiana) and green frogs (R. clamitans) on Dolomedes triton were studied. Both the attack dynamics of the frogs and the evasive behaviors of the spiders were recorded at 250 frames per second. A freeze-dried bullfrog, propelled toward spiders with acceleration, posture, and position that approximated the natural attack posture and dynamics, was used to assess the spiders' behavior. Qualitatively, the spiders responded to these mock-attacks just as they had to attacks by live frogs: jumping (N=29 jumps, 56.9% of instances), rearing the legs nearest the attacking frog (N=15, 29.4%), or showing no visible response (N=7, 13.7%). Spiders that jumped always did so away (in the vertical plane) from the attack (mean =137 degrees vs. vertical at 90 degrees or horizontally toward the frog at 0 degrees ). The involvement of the trichobothria (leg hairs sensitive to air movements), and the eyes as sensory mediators of the evasion response was assessed. Spiders with deactivated trichobothria were significantly impaired relative to intact and sham-deactivated spiders, and relative to spiders in total darkness. Thus, functional trichobothria, unlike the eyes, are both necessary and sufficient mediators of the evasion response. Measurements of air flow during frog attacks suggest that an exponential rise in flow velocity is the airborne signature of an attack.

Animals↗
PubMed1982

A comparative study of the effects of phenytoin and phenobarbital on electrically induced maximal seizures in frogs and mice.

This study was undertaken to compare seizure patterns and anticonvulsant effects of phenytoin in frogs (Rana pipiens) and the CF-1 strain of mice. Maximal seizures were induced with electroshock via corneal electrodes, and phenytoin anticonvulsant effects were determined by measuring the duration of tonic hindlimb extension (THE) and prevention of the THE. To control for any possible species difference that might be unique to phenytoin, the anticonvulsant effects of phenobarbital also were compared in frogs and mice. It was found that the dose-effect relationships for shortening THE duration and for prevention of THE by phenobarbital in frogs and mice were not significantly different in terms of slopes and potencies. With phenytoin, however, the dose-effect relationship for prevention of THE in mice was significantly steeper than that in frogs, whereas the slopes of the dose-effect relationships for shortening THE duration were not significantly different in these two species. Frogs decapitated 1.5 sec after electroshock exhibited THE durations equal to those in intact frogs, and phenytoin and phenobarbital efficacies in shortening THE duration were unchanged by decapitation. These results show that shortening of THE duration by both phenytoin and phenobarbital may reflect drug action in spinal or peripheral neural pathways. Also, it is suggested that phenytoin, but not phenobarbital, prevents THE by a selective action on cortical structures which are well developed in mice but are poorly developed or absent in frogs.

Animals↗
PubMed1995

Mechanism of histamine induced dispersal response in the isolated web melanophores of a frog, Rana tigerina (Daud.).

Effects of histamine and specific H1, H2 receptor agonists have been investigated on the isolated web skin melanophores of the frog, R. tigerina. Histamine, 2-methyl-histamine and 4-methyl-histamine all induced dose dependent dispersion in the frog melanophores. Reserpine treatment of the frog skin, either in vivo, or in vitro potentiated the dispersal response of the frog skin melanophores elicited by histamine. Histamine induced dispersal responses in the frog integumentary melanophores were partially blocked by mepyramine and ranitidine. Atropine failed to inhibit the dispersal response in any degree. Propranolol partially inhibited the dispersion of frog melanophores induced by histamine and 2-methyl-histamine. However, propranolol completely blocked the dispersal response of the mealnophores to 4-methyl-histamine. It is suggested that histamine induced dispersion in the frog skin melanophores in vitro is mediated partially through specific H1, H2 and beta adrenergic receptors.

Animals↗
PubMed1994

Cloning and characterization of a novel natriuretic peptide in frog (Rana catesbeiana).

C-type natriuretic peptide (CNP) is one of three members of the natriuretic peptide family. In the course of cloning frog CNP precursor cDNA, we found cDNA clones encoding a novel natriuretic peptide precursor. This novel natriuretic peptide precursor is a 118-residue peptide, carrying a 22-residue signal peptide at the N terminus and a 17-residue ring structure characteristic of the natriuretic peptide family at the C terminus. The precursor is highly homologous to mammalian CNP precursors. Its C-terminal Cys codon is directly followed by a termination codon. This feature is characteristic of CNP precursor cDNAs. The cGMP-stimulating activity of the novel natriuretic peptide was at the same level with those of frog CNP and mammalian CNPs, when rat CNP receptor was used in the cGMP assay system. Thus, this novel natriuretic peptide is structurally and functionally a member of the C-type natriuretic peptide. We designated the peptide as frog CNP II, and the previously described CNP as frog CNP I. By Northern blot analysis, expression of this novel CNP mRNA was found in brain, heart, lung, and stomach. On the other hand, frog CNP mRNA was mainly expressed in brain, where mammalian CNP mRNA is exclusively expressed. The distribution of the two frog CNPs suggests a complex system for regulating electrolyte and water balance in frog.

Amino Acid Sequence↗
PubMed1981

Fibers in spinal nerves of tree frogs: Eleutherodactylus and Hyla.

This is a study on numbers and sizes of nerve fibers as determined by electron microscope mapping of the spinal nerves of two species (in different families) of free frogs. The study provides data for comparison of fiber populations in the grass frog, Rana pipiens. In both free frogs the greatest number of fibers in the ten pairs of spinal nerves are in the second and ninth rami. The combined counts of myelinated and unmyelinated fibers in the rami on one side of the cord in Eleutherodactylus and Hyla are respectively: to the forelimb, 3,147 and 4,460 fibers; to the trunk, 334 and 1,234 fibers; and to the hindlimb, 4,335 and 6,213 fibers. With a few notable differences this distribution of fibers to regional body parts correlates closely with that found in Rana. The arboreal frogs have a relatively smaller number of medium and especially large size fibers in comparison with the aquatic-terrestrial living grass frog. The importance is stressed of examining the spinal nerves of an entirely aquatic frog with different feeding habits, such as Xenopus, for further comparison.

Animals↗
PubMed1989

Distribution of somatostatin receptors in the brain of the frog Rana ridibunda: correlation with the localization of somatostatin-containing neurons.

The biochemical characterization and anatomical distribution of somatostatin binding sites were examined in the brain of the frog Rana ridibunda, and the distribution of the receptors was compared with the location of somatostatin immunoreactive neurons. The pharmacological profile of somatostatin receptors was determined in the frog brain by means of an iodinated superagonist of somatostatin, [125I-Tyr0,DTrp8]S-14. Membrane-enriched preparations from frog brain homogenates were shown to contain high-affinity receptors (KD = 0.78 +/- 0.34 nM; Bmax = 103 + 12.7 fmoles/mg protein) with pharmacological specificity for [DTrp] substituted S14 and S28 analogs. The distribution of somatostatin-binding sites was studied by autoradiography on coronal sections of frog brain. Various densities of somatostatin receptors were detected in discrete areas of the brain. The highest concentration of binding sites was observed in the olfactory bulb, in the pallium, and in the superficial tectum. Moderate binding was observed in the striatum, amygdaloid complex, preoptic area, and cerebellum. Immunocytochemical studies of the distribution of somatostatin-28 (S28) related peptides were also conducted in the frog brain. Two antisera that recognize distinct epitopes of the somatostatin molecule have been used for immunohistochemical mapping of the peptide. Antiserum SS9 recognizes both S28 and somatostatin-14 (S14) and allowed the labelling of perikarya. Antiserum S320 recognizes the N-terminal fragment (1-12) resulting from enzymatic cleavage of S28. This latter antiserum, which does not cross-react with S28, stained mainly neuronal processes. At the infundibular level, however, both antisera stained cell bodies and fibers. Immunoreactive somatostatin-related peptides were detected in many areas of the frog brain. In the diencephalon, a heavy accumulation of perikarya and fibers was seen in the preoptic nucleus, the dorsal and ventral infundibular nuclei, and the median eminence. Immunoreactive perikarya were also observed in the telencephalon, especially in the pallium and in thalamic nuclei. Immunostained processes were detected in many telencephalic areas and in the tectum. There was good correlation between the distribution of somatostatin-immunoreactive elements and the location of somatostatin-binding sites in several areas of the brain, in particular in the median pallium, the tectum, and the interpeduncular nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Temporal and spatial localization of prothymosin alpha transcript in the Harderian gland of the frog, Rana esculenta.

The Harderian gland (hg) is the only orbital gland of the frog Rana esculenta, and it has the essential function of lubricating the eyes. The hg secretory activity is seasonal, showing the highest value in summer. There is, at present, no data on gene expression of the frog hg. This study reports, for the first time, on the temporal and spatial expression of a cDNA clone encoding for the prothymosin alpha (Prot-alpha), a highly acidic nuclear protein present in virtually all mammalian cells. Northern blot analysis revealed a single 1.7 kb transcript detected in the frog hg throughout the year, with a lowest expression in September in concomitance with the minimum secretory activity. In situ hybridization indicated that hg secretory cells express Prot-alpha transcript, and the hybridization signal was less intense in the September gland. The constant expression of the frog Prot-alpha mRNA during the whole year suggests a constitutive role for this molecule in the hg. In addition, taking into account that, in mammals, many immunomodulatory functions have been attributed to this protein, it is suggested that frog Prot-alpha might contribute to the hg immunity processes, probably acting as a protective agent against infections of the eyeball. Interestingly, although the presence of Prot-alpha gene in animals other than mammals has been considered to be highly unlikely, the present paper confirms the presence of Prot-alpha transcript in a nonmammalian vertebrate, the frog R. esculenta.

Animals↗