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At least 1,333 records · Page 74Linked to original sources
PubMed1986

Pharmacology of amino acid receptors on vertebrate primary afferent nerve fibres.

Structure-activity of primary afferent depolarising action (PAD) mediated by gamma-aminobutyrate (GABA) analogues suggests a difference between subsynaptic receptors located at fibre terminations within the dorsal horn and axonal receptors which are distributed throughout non-synaptic regions. The interaction of the bicuculline-sensitive GABA receptor (GABA A) ionophore complex with barbiturates and benzodiazepines suggests that at least three binding sites are required to explain the independent GABA-mimetic, GABA-potentiating and picrotoxin-reversing effects of such agents. Difficulties with explanation of the depressant effects of baclofen on spinal transmission, in terms of the bicuculline-resistant GABA (GABA B) receptor hypothesis, are mentioned. Glutamate-induced PAD of low threshold afferents is mediated indirectly through release of potassium. However, such terminals possess receptors (possibly autoreceptors for L-glutamate), activated by (+)2-amino-4-phosphonobutyrate, which cause depression of transmitter release. Primary afferent C-fibres possess receptors which are selectively activated by kainate and which mediate picrotoxin-resistant PAD. Such receptors may be involved in the presynaptic conditioning of C-fibre transmitter release. The peripheral terminals of vestibular primary afferents, in amphibia, possess excitatory amino acid receptors which are probably activated by the transmitter released from hair cells.

Animals↗
PubMed1995

Preovulatory overripeness of the oocyte as a cause of ovarian dysfunction in the human female.

A variety of gynaecological phenomena such as menstrual disorders, infertility and premature menopause are associated with ovarian dysfunction. In this paper, a factor is considered that may play a role in the aetiology of ovarian dysfunction. Animal research has shown that preovulatory overripeness of the oocyte may cause various developmental and chromosomal anomalies. Among the developmental anomalies observed in amphibia and fish are a number of gonadal aberrations, often occurring in otherwise normal specimens. This may be the consequence of a degeneration of the 'germinal cytoplasm', cytoplasmic structures located in the vegetative pole region of the oocyte, destined to become part of future primordial germ cells. Indirect evidence suggests that preovulatory overripeness of the oocyte also plays a significant role in human reproductive failure. An increased risk of preovulatory overripeness is expected during periods of endocrine irregularities, such as the first postmenarcheal years, the last premenopausal years, the first months after a pregnancy and, possibly, during certain seasons. If the overripeness-induced gonadal maldevelopment observed in animals also occurs in humans, this may explain variations in reproductive function according to month of birth, as observed in women. It is hypothesized that females conceived during periods of maternal endocrine irregularities face an increased risk of ovarian dysfunction through overripeness-induced gonadal maldevelopment.

Amphibians↗
PubMed1978

Reaction of tonofilament-like intermediate-sized filaments with antibodies raised against isolated defined polypeptides of bovine hoof prekeratin.

Total purified and reconstituted bovine hoof prekeratin, containing several polypeptides, as well as individual polypeptide size classes isolated therefrom were used as antigens in guinea pigs. The antibodies raised against these protein preparations were found to decorate the system of wavy arrays of tonofilament-like, intermediate-sized filaments present in various epithelial and epithelia-derived cells. Strong cross-reaction between different vertebrate species was noted, including amphibia. Positive results were obtained with original sera as well as with IgG fractions and antibodies made monospecific by chromatography on total bovine prekeratin covalently bound to Sepharose. Among the antisera raised against the different polypeptide size classes the most intense decoration of fibrillar arrays was obtained with antibodies against fraction 4 which contained polypeptides VI and VII.

Animals↗
PubMed1987

Vitamin A promotes DNA synthesis and mitosis in blastemas of Triturus alpestris.

Vitamin A palmitate orally administered to young, post-metamorphic Triturus alpestris (Amphibia-Urodela), for 4 and 7 days after bilateral forelimb amputation at the middle of the zeugopodium, enhanced the mean DNA content of the blastema cells. Moreover, the number of cells in mitosis was nearly twice as high in vitamin A treated animals than in control ones.

Animals↗
PubMedDate not supplied

A review of the neuroembryology of monoamine systems.

The technique of monoamine histofluorescence has been used successfully for neuroembryologic studies in a number of species ranging from amphibia to the human. Monoamine systems can be visualized early, often before final cell division and migration have taken place. Neuronal cell bodies are seen before axon terminals. Unlike the adult animal, preterminal axons can often be visualized, even in the untreated animal. Anatomical studies have shown major analogies in most of the species studied. CA-containing neuronal cell bodies are restricted to the brainstem and hypothalamus. Those neurons containing 5-HT are largely restricted to the brainstem raphe, although other cell groups may take up 5-HT, or related compounds, under experimental conditions. Monoamine nerve terminals are found throughout the entire nervous system, with some of the regions of highest density being the hypothalamus and striatum. Dynamic studies have indicated that biochemical differentiation precedes morphologic maturity, often by a long period of time. Although attempts have been made to determine a specific role of monoamines in the complex programs of neurogenesis, there is little specific data currently available.

Ambystoma mexicanum↗
PubMed1995

The rhodopsin-encoding gene of bony fish lacks introns.

A study of the sequences of the rhodopsin-encoding genes (Rh) in eight fish species from two of the major subdivisions of the teleosts reveals that no introns are present in the coding region. This contrasts with the opsin-encoding genes of all other vertebrates where either four or five introns are invariably found. Phylogenetic analysis shows that this intronless teleost Rh is homologous to the intron-containing Rh of amphibia, birds and mammals. Possible mechanisms for intron loss are discussed, including replacement by homologous conversion of Rh with a processed cDNA.

Amphibians↗
PubMed1988

Calbindin (CaBP 28 kDa) localization in the peripheral vestibular system of various vertebrates.

Previous reports on calbindin, a 28 kDa vitamin D-induced calcium-binding protein, located in the mammalian peripheral vestibular system indicated that it is specifically distributed and postulated that it could play a role in the electrophysiological functioning of the sensory cells. This immunocytochemical investigation of the distribution of calbindin in the vestibular system of various vertebrates: fishes (goldfish and sea-perch), amphibia (frog), birds (chicken) and mammals (mouse, cat and baboon), was performed to verify these observations. In the vestibular ganglion, only a few neurons were faintly immunoreactive in the fishes and the frog, while the staining was more intense but still not present in all neurons of the chicken, the mouse and the cat. All the neurons were immunoreactive in the baboon. No immunoreactivity was observed in the sensory epithelia of the fishes. All hair cells were strongly immunoreactive in the frog. In the other species, most of the hair cells in the cristae were immunostained except those situated in the peripheral areas. In the maculae, the hair cells of the striola were either the only ones stained or were more intensely stained or were more intensely stained than the others. The localization of calbindin in specific cellular types and its increasing abundance from the fishes to the mammals suggest that calbindin is associated with the capacity of sensory and nerve cells to analyze precise mechanical or biochemical stimulations.

Animals↗
PubMed1986

Effect of ethylenediaminetetraacetic acid (EDTA) on acute mercury poisoning of toad.

Studies have been carried out on the ability of EDTA (CaNa2-ethylenediaminetetraacetate) to offset the acute toxicity of mercuric chloride. The lethality of mercury was tested in female Bufo regularis species (Amphibia) which were given EDTA immediately after the Hg2+ injection. The results show that the inherent toxicity of the EDTA-mercury complex is sufficiently high for it to be ineffective as an antidote.

Alanine Transaminase↗
PubMed1987

Pharmacokinetics of kanamycin in the bullfrog, Rana catesbeiana.

1. Kanamycin disposition was studied in bullfrogs (Rana catesbeiana) following single doses IP. Both plasma t1/2 and Vd of the drug increased with increasing time after drug indicating redistribution and tight binding of kanamycin to deep tissue compartments. 2. Kanamycin was eliminated unchanged with a t1/2 plasma = 27 hr; perilymph = 89 hr; endolymph = 183 hr; aqueous humor = 54 hr; and CSF = 58 hr. 3. Kanamycin was absorbed by frogs from environmental water. 4. Environmental conditions must be carefully specified and monitored, as well as the physiological state of the animals when studying the effects of drugs on Amphibia.

Animals↗
PubMed1991

An enkephalin degrading aminopeptidase of human brain preserved during the vertebrate phylogeny.

1. A soluble human brain aminopeptidase which hydrolyses the Tyr-Gly bond of Met-enkephalin and Leu-enkephalin was identified in the brains of the following vertebrates: mammals (Callithrix jacchus and Rattus norvegicus), bird (Gallus domesticus), reptile (Tupinambis teguixin), amphibia (Bufo paracnemis), fish (Sarotherdon niloticus) and elasmobranchy (Galeocerdo cuvieri). 2. The properties of this enzyme are: molecular weight near 100,000 Da, isoelectric point near 4.9, optimum pH near 7.5, activation by dithiothreitol, strong inhibition by Cu2+, Zn2+, Ni2+, puromycin and bacitracin, hydrolysis of enkephalins and basic and neutral aminoacid-beta-naphythylamide substrates. 3. The results indicate the preservation of this human brain aminopeptidase during the course of vertebrate phylogeny.

Amino Acid Sequence↗
PubMed1993

Antitumor and antimicrobial glycoproteins from sea hares.

1. Novel antitumor and antimicrobial glycoproteins were found in the sea hares. These glycoproteins were purified to apparent homogeneity from Aplysia kurodai, Aplysia juliana and Dolabella auricularia, and designated as aplysianins, julianins and dolabellanins, respectively. 2. The nine isolated glycoproteins lysed all the tumor cells tested but did not lyse normal white and red blood cells. 3. The glycoproteins completely inhibited the synthesis of DNA and RNA by tumor cells within 2 hr and caused tumor lysis within 15 hr. 4. Tumor lysis was inhibited by the presence of N-acetylneuraminic acid, suggesting that the recognition of the sugar moiety is a key step in the cytolysis by antitumor glycoproteins from sea hares. 5. These antitumor glycoproteins, except dolabellanin P, also showed antimicrobial activities. 6. The factors were active for Gram-positive and -negative bacteria and some fungi, and their action was not cytocidal but cytostatic. 7. They exerted the antibacterial action by inhibiting nucleic acid synthesis, as does a DNA-inhibiting chemotherapeutic drug. 8. The sequence of the N-terminal part of dolabellanin A was similar to other antibacterial peptides from arthropoda, amphibia and mammals, suggesting that dolabellanin-like antibacterial peptides are common throughout the animal kingdom.

Amino Acid Sequence↗
PubMed1995

Kallikrein generates angiotensin II but not bradykinin in the plasma of the urodele, Amphiuma tridactylum.

Incubation of heat-denatured plasma from the urodele, Amphiuma tridactylum (three-toed amphiuma) or from the anurans Rana ridibunda (European green frog) and Rana catesbeiana (American bullfrog) with either glass beads, porcine pancreatic kallikrein or trypsin did not generate bradykinin-like immunoreactivity. However, peptides were generated in kallikrein-treated amphiuma plasma that contracted vascular rings from the bullfrog systemic arch and had a spasmogenic action on the bullfrog urinary bladder. These peptides which were not generated in trypsin-treated plasma, were purified to homogeneity by reverse-phase HPLC and their primary structures established as: Asp-Arg-Val-Tyr-Val-His-Pro-Phe ([Asp1,Val5]angiotensin II) and Asn-Arg-Val-Tyr-Val-His-Pro-Phe ([Asn1,Val5]angiotensin II). Incubation of synthetic [Asn1,Val5]angiotensin II with amphiuma plasma resulted in deamidation to [Asp1,Val5]angiotensin II. The data suggest, therefore that amphiuma plasma contains an L-asparagine amidohydrolase (asparaginase), as previously described for the eel. Although bradykinin-related peptides have been isolated from frog skin, this study provides evidence tha the kallikrein-kinin system may be absent from the blood of amphibia.

Amino Acid Sequence↗
PubMed1995

Infection of frog neurons with vaccinia virus permits in vivo expression of foreign proteins.

Vaccinia virus can be used to infect cells in the CNS of frogs, Xenopus laevis, and Rana pipiens, both in vivo and in vitro. In vivo infections were accomplished by injection of viral solution into the tectal ventricle of stage 40-48 tadpoles or by local injections into distinct neural regions. Infections with high titer of virus injected into the ventricle resulted in the majority of cells in the brain expressing foreign protein, while cells in the retina and optic nerve showed no expression. Infection with lower viral titers resulted in fewer infected cells that were distributed throughout the otherwise normal tissue. Intense expression of foreign protein in the brain was observed 36 hr after injection and remained high for at least 4 days. Infected animals developed normally and had the same number of cells in the optic tectum as control animals. Infection with a recombinant virus carrying the gene for Green Fluorescent Protein labels neurons, so that infected cells can be observed in vivo. Vaccinia virus provides a versatile means to alter proteins in distinct populations of neurons in amphibia.

Animals↗
PubMed2003

Sigma-class glutathione transferase from Xenopus laevis: molecular cloning, expression, and site-directed mutagenesis.

The structural gene for glutathione transferase (XlGSTS1-1) in the amphibia Xenopus laevis has been cloned from an embryo library and its nucleotide sequence has been determined. Open reading frame analysis indicated that xlgsts1 gene encodes the smallest protein of sigma class GST so far identified as being composed of only 194 amino acid residues. The recombinant XlGSTS1-1 shows a narrow range of substrate specificity as well as a significantly lower 1-chloro-2,4-dinitrobenzene conjugation capacity than that of squid sigma class GST. To compare the structural and functional differences between the squid and amphibian enzymes, several site-specific mutations were introduced in XlGSTS1-1, i.e., Ser100Asn, Phe102Tyr, Trp143Leu, Phe146Leu, and Trp148Cys. The results obtained indicate that Trp143 and Trp148 are more important determinants for the structural stability of XlGSTS1-1 rather than for its substrate specificity.

Amino Acid Sequence↗
PubMed2005

Possible autocrine regulation of chromaffin cell activity in adrenal glands of the frog by endothelin-1-induced serotonin release.

The aim of the present study was the demonstration of mechanisms of regulation of activity of chromaffin cells in the adrenal gland of Rana ridibunda (Anura-Amphibia). Previous studies have shown that endothelin-1 is an important factor for the maintenance of adrenal gland function. On the basis of these findings, frogs were injected with [Ala(1,3,11,15)]-endothelin-1 (0.025 mg/0.2 ml), which is a selective agonist of the endothelin B receptor, whereas control animals were injected with Ringer solution (0.2 ml). The adrenal glands were removed at 5, 20, and 60 min after injection and fixed, embedded in paraffin wax and stained by histological and immunohistochemical means, applied on adjacent 4-microm-thick sections. Sections were stained with hematoxylin and eosin for overall tissue analysis and, in parallel, serotonin was localized using the streptavidin-biotin complex technique while dopamine beta-hydroxylase and serotonin 2A receptors were shown by the peroxidase-antiperoxidase (PAP)-3,3'-diaminobenzidine tetrachloride (DAB) method. After injection of [Ala(1,3,11,15)]-endothelin-1, chromaffin cells secreted serotonin and synthesized dopamine beta-hydroxylase. In conclusion, these findings suggest that [Ala(1,3,11,15)]-endothelin-1 stimulates chromaffin cell activity in frog adrenal glands. Moreover, the presence of serotonin 2A receptors in chromaffin cells indicates that these cells are also targets for serotonin and that there is an autocrine signaling pathway in chromaffin cells. This is the first report providing data on the effects of endothelin-1 on chromaffin cells in frog adrenal glands.

Adrenal Glands↗
PubMed2006

Possible role of insulin-like growth factor-II C-peptide on catecholamine release and ultrastructural aspects of chromaffin cells in the adrenal gland of the frog.

The present study was undertaken to demonstrate that insulin-like growth factor-II C-peptide (IGF-II C-peptide) affects the function of the adrenal gland of Rana ridibunda (Anura, Amphibia) by stimulating chromaffin cells. Previous studies have shown that insulin-like growth factors affect adrenal gland function in mammals. On the basis of these findings, frogs were injected with IGF-II C-peptide (2.5 microg/0.2 ml), whereas control animals were injected with Ringer solution (0.2 ml). The adrenal glands were removed at 12 and 48 h after injection and fixed, embedded in paraffin wax and Epon, and examined by immunohistochemistry and transmission electron microscopy to investigate whether there were structural changes and activation of chromaffin cells in the frog adrenal gland. Sections were stained with hematoxylin and eosin for overall tissue analysis and, in parallel, serotonin was localized using the streptavidin-biotin complex technique while dopamine beta-hydroxylase was shown by the peroxidase-antiperoxidase-3, 3'-diaminobenzidine tetrachloride method. After injection of IGF-II C-peptide, chromaffin cells released serotonin and synthesized dopamine beta-hydroxylase. The most pronounced effect of IGF-II C-peptide on the chromaffin cells was observed at 12h after injection. Our results indicate that there is a possible role of IGF-II C-peptide on chromaffin cell activity enhancing catecholamine release in the adrenal gland of the frog.

Adrenal Glands↗
PubMed2006

Structural and functional analogs of the novel mammalian neuropeptide, neuromedin S (NmS), in the dermal venoms of Eurasian bombinid toads.

We report the isolation and structural characterization of two neuromedin S (NmS) analogs, (NmS-17 and NmS-33), from the dermal venoms of Eurasian bombinid toads. NmS is a novel neuromedin U (NmU)-related peptide with potent anorexigenic and circadian rhythm-modulating properties recently discovered in mammals. Cloning of NmS precursor-encoding cDNAs from skin venom-derived libraries revealed the presence of a high degree of transcript splice variation comparable to that found previously for NmU in both amphibian skin and mammalian brain. Synthetic replicates of both amphibian NmS peptides evoked robust and dose-dependent transient increases in intracellular calcium ion concentrations in CHO cells that had been stably transfected with either FM-3/GPR66 or FM-4/TGR-1 human NmU receptors. The potency and efficacy of these amphibian skin peptides at such receptors were comparable to those observed with human NmS and rat NmS. These data show that NmS and NmU genes had already diverged at the level of the Amphibia and that differential splicing of their transcribed mRNAs has been highly conserved throughout tetrapod vertebrate evolution indicative of fundamental biological function. NmS is additionally a novel neuropeptide homolog that can be added to the biologically active peptide arsenal of amphibian venom/defensive skin secretions.

Amino Acid Sequence↗
PubMed2005

The linear alometric relationship between total metabolic energy per life span and body mass of poikilothermic animals.

A linear relationship exists between total metabolic energy per life span PT(ls) (kJ) and body mass M (kg) of 54 poikilothermic species (Protozoa, Nematoda, Mollusca, Asteroidae, Insecta, Arachnoidae, Crustacea, Pisces, Amphibia, Reptilia and Snakes): PT(ls) = A(ls*)M(1.0838), where P (kJ/day) is the rate of metabolism and T(ls) (days) is the life span of animals. The linear coefficient A(ls*) = 3.7 x 10(5) kJ/kg is the total metabolic energy, exhausted during the life span per 1 kg body mass of animals. This linear coefficient can be regarded as relatively constant metabolic parameter for poikilothermic organisms, ranging from 0.1 x 10(5) to 5.5 x 10(5) kJ/kg, in spite of 17-degree differences between metabolic rate and body mass of animals. A linear relationship between total metabolic energy per life span and body mass of only 48 poikilothermic multicellular animals (without Protozoa) is: PT(ls) = A(ls*)M(0.9692) with linear coefficient A(ls*) = 2.34 x 10(5) kJ/kg. Since a power relationship exists between the rate of metabolism and body mass of animals of the type: P = aMk (a and k are the alometric constants), an empiric rule could be formulated, that life span is a time interval for which the total metabolic energy per life span becomes proportional to body mass of animals and power coefficient k becomes approximately 1.0.

Animals↗