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PubMed2004

Structure-activity relationships of antimicrobial peptides from the skin of Rana esculenta inhabiting in Korea.

The anuran (frogs and toads) skin is a rich source of antimicrobial peptides that can be developed therapeutically. We searched the skin secretions of Korean Rana esculenta for antimicrobial peptides, and isolated two cationic peptides with antimicrobial activity and little hemolytic activity: a 46-residue peptide of the esculentin-1 family and a 24-residue peptide of the brevinin-1 family. Their sequences showed some differences from the esculentins-1 and brevinins-1 of European Rana esculenta, indicating that sequence diversification of anuran skin antimicrobial peptides can arise from differences in habitat as well as from species differences. The 46-residue peptide named esculentin-1c had broad antimicrobial activity, while the 24-residue peptide named brevinin-1Ed exhibited limited activity. The solution structure of brevinin-1Ed was in good agreement with that of other brevinin-1-like peptides, with an amphipathic alpha-helix spanning residues 3-20, stabilized in membrane-mimetic environments. The weak bioactivity of brevinin-1Ed was attributable to the unusual presence of an anionic amino acid in the middle of the helical hydrophilic face. This report contributes to world-wide investigations of the structure-activity relationships and evolutional diversification of anuran-skin antimicrobial peptides.

Amino Acid Sequence↗

PubMed1989

Distribution of intermediate filaments in epithelial cells of the amphibian urinary bladder: an immunofluorescence study.

The distribution of intermediate filaments in toad and frog urinary bladder was studied on frozen sections by indirect immunofluorescence microscopy using specific antiprekeratin antibodies. Our results show that in both species, epithelial cells lining the urinary bladder are very rich in cytokeratin, organized as a filamentous network. In granular cells, the most abundant cells facing the urinary lumen, vasopressin promotes fusion of the membranous tubular structures located in the luminal cytoplasm with the apical cell membrane. A role for intermediate filaments in the membrane rearragements induced by vasopressin in these cells, is proposed.

Animals↗

PubMed1989

Neutral aminopeptidase: a potential marker enzyme of the amphibian urinary bladder epithelial cell apical membrane.

Antidiuretic hormone induces, in the apical plasma membrane of amphibian urinary bladder epithelial cells, the exocytotic insertion of intramembranous particle aggregates that probably contain water channels. Purification of the apical membrane is a way to characterize the aggregates. The isolation of such purified membranous fractions involves the use of specific exogenous or endogenous markers. One of them could be the neutral aminopeptidase (AP), whose activity was detected in urinary bladder. Enrichment in AP activity was observed in plasma membrane preparations compared to cell homogenates (X2.7). However, a large part of the enzyme activity was also recovered in the soluble fraction of the preparation, suggesting large proteolysis of the protein. The enzyme presents a low optimal pH (6.4) and a high specificity for proline-p-nitroanilide as compared to the AP present in kidneys and intestines. To localize the protein in the amphibian bladder epithelium, an immunological approach was necessary due to the low activity of the enzyme in this tissue. The low enzymatic activity also prevented the purification of sufficient amounts of the urinary bladder AP as antigen, and we prepared antibodies against purified AP from frog or toad kidneys where the activity is 60 times higher than in the bladder. The serum specificity was verified by spot immunodetection, Western blot, inhibition capacity of antibodies, and immunoadsorption on a solid support with the renal enzyme. The sera were found to be able to react with native as well as denatured forms of the kidney enzyme. Antibodies cross-reacted with several peptides of low molecular weight (40-60 kDa) from urinary bladder plasma membrane proteins (Western blot).(ABSTRACT TRUNCATED AT 250 WORDS)

Aminopeptidases↗

PubMed1989

Mechanisms and ecological correlates of kin recognition.

Kin recognition, which can be inferred from differential interactions amongst close relatives as compared to unrelated conspecifics, has been documented in a wide range of vertebrates and invertebrates. Kin may be discriminated by phenotypic traits (signatures) that are genetically mediated, acquired from the environment, or arise from an interaction between these two sources. The developmental mechanisms underlying recognition of relatives (or their signatures) include direct contact and familiarization, indirect familiarity (whereby previously unencountered individuals are recognized by their resemblance to familiar kin) and hypothetical recognition alleles. The biological significance and mediating mechanisms of kin recognition vary across species according to their ecology and natural history. To illustrate this point, the results of laboratory and field studies of larvae of several species of toads and frogs are reviewed.

Animal Communication↗

PubMed1978

Cytochemistry of blood cells in two West African amphibians.

Lipid, glycogen, peroxidase, acid and alkaline phosphatases were studied in the cells of blood smears in the toad and frog. While lipid and glycogen were largely confined to granulocytes and monocytes, peroxidase activity was intense in all cell types except lymphocytes in both species.

Animals↗

PubMed1978

Auditory processing in anurans.

Anurans (frogs and toads) represent an example of peripheral specialization of the auditory systems. Their inner ear contains two distinct auditory organs: the amphibian papilla and the basilar papilla. Each organ is tuned to different species-specific frequency ranges. Because of this peripheral specialization, anurans offer an excellent opportunity to explore neural decoding of complex sounds in the central auditory system.

Animal Communication↗

PubMed1985

Disease patterns in the Detroit Zoo: a study of reptilian and amphibian populations from 1973 through 1983.

A retrospective study was conducted to determine disease patterns in reptilian and amphibian populations at the Detroit Zoo from 1973 through 1983. In the reptilian population (mean +/- SD = 285.2 +/- 28), overall annual mortality rates were 1% to 40%. Mortality rates were highest in the fall months (20%) and lowest in the winter months (6%). The most frequently affected reptiles were iguana (Iguana iguana), reticulated python (Python reticulatus), rattlesnakes (Crotalus spp), common boa (Constrictor constrictor), and lizards (various genera of suborder Lacertilia). Of the 1,300 reptilian deaths from 1973 through 1983, 36.6% were caused by microbial agents, 12% by parasites, 11.6% by trauma, and 9.3% by nutritional deficiencies. The main microbial organisms that caused death were Aeromonas spp, Salmonella spp, Pseudomonas spp, Proteus spp, and Edwardsiella spp. The main parasites that caused death were Entamoeba spp and lungworms. Among amphibians, frogs and toads were the most frequently affected, and starvation and trauma were the most frequent causes of death.

Amphibians↗

PubMed1985

Brain theory and cooperative computation.

"Top-down" brain theory, based upon functional analysis of cognitive processes in terms of interacting schemas, is distinguished from "bottom-up" brain theory based on analysis of the dynamics of neural nets. "Cooperative computation" is proposed as the style of interaction of neural subsystems at various levels. Perceptual schemas are introduced as the building blocks for the representation of the perceived environment, and motor schemas serve as control systems to be coordinated into programs for the control of movement. A cooperative computation view of the design of machine vision systems is exemplified both by an algorithm for computing optic flow which offers interesting insights into the evolution of hierarchical neural structures, and by an analysis of knowledge representation for machine interpretation of visual scenes. The interaction between top-down analysis and detailed neural modelling is illustrated by the study of visuomotor coordination in frogs and toads.

Animals↗

PubMed1985

Rana computatrix: progress report, 1984.

This paper describes an approach to analyzing mechanisms of visuomotor coordination that is twofold: top-down, to offer a coordinated control program of interacting schemata (functional units, underlying behavior, which can be activated in different combinations) to achieve behavior noted by neuroethologists; and bottom-up, to provide detailed models of neural networks that are consistent with known anatomy and physiology, but that involve additional assumptions, amenable to experimental testing, to yield a network capable of exhibiting appropriate behavior. Rana computatrix, an evolving series of models of frog and toad visuomotor coordination, is described.

Animals↗

PubMed1983

Purification and physiological characterization of neurotoxins from venoms of the scorpions centruroides sculpturatus and leiurus quinquestriatus.

Several different toxins having specific effects on the kinetics of sodium channels have been isolated from the venoms of two scorpions. A combination of two steps of ion-exchange chromatography has been used to purify these toxins, whose sizes and purities have been assayed by gel filtration, urea/sodium dodecyl sulfate/polyacrylamide gel electrophoresis, and isoelectric focusing. The actions of the toxins and their relative potencies have been determined by studying the modifications they produce in action potential shape, using the sucrose-gap method, and in ionic current kinetics, measured under voltage-clamp, both assays performed on myelinated axons of frogs and toads. The venom of Leiurus quinquestriatus scorpions yielded two active neurotoxins; the major neurotoxin has a mass of approximately 7000 daltons. This major toxin affected the sodium channel inactivation process exclusively, slowing the rates of inactivation as well as preventing complete inactivation from occurring in some of the channels. Such slowed and incomplete sodium inactivation resulted in action potentials that were prolonged, from their usual duration of 5-8 msec to hundreds of milliseconds or even seconds. Five toxins were isolated from the venom of Centruroides sculpturatus Ewing scorpions, all of which also had masses of approximately 7000-7500 daltons. Four of these toxins acted primarily on the activation process of sodium channels, producing a novel increase in sodium permeability upon repolarization of the nerve membrane following a depolarizing pulse, as previously described for the crude venom [Cahalan, M. D. J. Physiol. (Lond.) 244:511-534 (1975)]. These toxins also caused repetitive firing of action potentials in single axons in response to one stimulating pulse, as well as spontaneous impulse firing. A fifth neurotoxin from C. sculpturatus venom had effects similar to those of the L. quinquestriatus toxins, slowing and preventing complete sodium inactivation. The effect of this toxin was slowly removed during external perfusion by Ringer's solution.

Action Potentials↗

PubMed1983

[Precipitation reactions between secretory products in amphibian oviducts].

The existence of precipitin reactions between some molecules in egg jellies (oviduct secretions) of tailed amphibians (Amphibia caudata) has been demonstrated by double diffusion on agarose plates. These reactions do not exist in frogs and toads (Amphibia salientia). One precipitin reaction was related to compounds with a common molecular site of interaction for all A. caudata: all cross-species reactions were possible; a common antigenic rate has been shown. Another precipitin reaction, positively demonstrated in Pleurodeles waltl, probably exists in other A. caudata. The putative influence of these reactions on egg jelly-spermatozoon interactions has been discussed. An homology between these intra-egg jelly reactions and cortical granule content-egg jelly reactions in A. salientia has been suggested.

Amphibians↗

PubMed1984

Inhibitory effects of salicylate on contractility in skeletal muscle.

Salicylate (1-5 mM) had no effect on the peak amplitude (Pt) of twitches elicited at 0.05 to 0.05 Hz, but depressed the Pt in frog and toad "toe" muscles stimulated at 5 to 10 Hz. The maximal tetanic tension (Po) was not reduced significantly by salicylate, but the time to reach Po was increased to several seconds. K-induced contractures were reduced by ca 40 and 50%, respectively, in the presence of 5 and 10 mM salicylate. Pretreatment with salicylate (5 mM) reduced the twitch potentiation by quinine, shortened the duration of twitches in caffeine-treated muscles and inhibited the caffeine- and the quinine-induced contractures. Muscles in contracture because of a previous exposure to quinine relaxed promptly upon addition of salicylate to the bathing medium. The inhibitory effects of salicylate on Pt, on Po and on K- or drug-induced contractures were reversible and were not affected by changes in pH between 7.5 and 6.5. Salicylate depressed the caffeine-rapid cooling contractures (RCC). In toad muscles, this effect was affected markedly by the order in which caffeine and salicylate were applied. Blockade of the caffeine-RCC by salicylate was enhanced by lowering the pH of the medium. Salicylamide (1-5 mM) reproduced the effects of salicylate on the caffeine- and the quinine-induced contractures and the caffeine-RCC. In addition, salicylamide reduced the twitch tension. It is proposed that salicylate and salicylamide affect Casequestration by the sarcoplasmic reticulum.

Animals↗

PubMed1984

On the frog amphibian papilla.

Comparative morphological studies in living species of frogs and toads (anurans) indicate that the amphibian papilla (a specialized auditory sensory organ of the amphibian inner ear) has undergone considerable elongation over the course of evolution. Physiological studies on the amphibian papilla of one recently-derived species (Rana catesbeiana) provide strong evidence that frequency selectivity (tuning) in that organ is accomplished by one or more traveling wave structures, in many ways analogous to that of the mammalian cochlea. I suggest that the process of elongation inferred from the comparative morphology is a direct reflection of the evolution of a single traveling wave structure (i.e., convergence on an auditory mechanism analogous to that in the mammal). One selective advantage of such a mechanism is the combination of high rejection ratio in frequency filtering and good temporal resolution of acoustical stimuli.

Animals↗

PubMed1984

Dysplastic lesions and abnormalities in amphibians associated with environmental conditions.

High incidence of developmental anomaly and tumor-like dysplasia of osteochondrous tissue of hind limbs has been detected in frogs and toads the larval development of which has taken place in water, contaminated with sewage. Correlation between frequency of dysplasia and the level of water oxidation has been noted. Study on histogenesis of the marked tumor-like dysplasia were performed. It is assumed that the major mechanism responsible for anomaly consists in cytotoxic effect of teratogenic agent and that the differentiation lesion of cartilaginous tissue is caused by blocking of maturation and death of chondrocytes.

Animals↗

PubMedDate not supplied

[Helminthological fauna of Chilean anura].

In this paper a list of the endoparasites described for the chilean frogs and toads is presented. Also it is indicated the locality of the hosts, prevalence and intensity of the infection. Nine species of parasites have been described; three trematodes: Gorgoderina chilensis in Rhinoderma darwinii, Gorgoderina valdiviensis in Caudiverbera caudiverbera, and Rudolphitrema chilensis in Eusophus roseus; two cestodes: Ophiotaenia noei in C. caudiverbera, and Baerietta chilensis in Batrachyla taeniata; three nematodes: Aplectana chilensis, and Cosmicerca chilensis in R. darwinii and Oswaldocruzia neghmei in Hylorina sylvatica, Eusophus miqueli, Eusophus vertebralis, and E. roseus, and one acanthocephala: Acanthocephalus caspanenis in Bufo spinulosus.

Animals↗

PubMed1995

Potassium conductances in cultured bovine and human retinal pigment epithelium.

PURPOSE: To identify K+ conductances on the apical and basolateral membranes in cultured monolayers of fetal bovine and human retinal pigment epithelium (RPE). METHODS: Bovine and human RPE cells were grown on a permeable substrate for an average of 4 and 25 months, respectively, mounted in a modified Ussing chamber that allowed rapid solution changes at both membranes, and perfused with modified Ringer's solutions. Conventional microelectrode recording techniques were used to record intracellularly from RPE cells. RESULTS: Electrical parameters under control conditions for bovine (n = 11) and human (n = 7) cultures respectively, were: transepithelial potential, 0.6 +/- 0.2 and 3.2 +/- 0.5 mV; Rt, 70 +/- 12 and 227 +/- 30 ohm.cm2; and Vap, -61 +/- 3 and -51 +/- 2 mV (mean +/- SEM). The relative K+ conductance (TK) was estimated from responses to 10-fold increases in [K+]o. For the apical and basal membranes, the values for TK were 0.65 and 0.37, respectively, in bovine and 0.33 and 0.45, respectively, in human RPE. Barium applied to either surface of the cultures produced membrane depolarizations and suppressed the responses significantly to K+. In bovine, a 10-fold decrease in basal [K+]o hyperpolarized Vba by 2 +/- 1 mV; a similar decrease in apical [K+]o hyperpolarized Vap by 14 +/- 1 mV. At both membranes, perfusion with Ba2+ unmasked a significant membrane depolarization induced by lowering [K+]o; this phenomenon, observed previously at the apical membrane in fresh explant bovine, frog, and toad RPE, appears to be an unmasking of Na+/K+ pump modulation by K+. CONCLUSIONS: These results indicate the presence of Ba2+ sensitive K+ conductances at the apical and basal membranes of confluent monolayers of cultured fetal human and bovine RPE and the presence of Na+/K+ pump sites at both membranes of cultured bovine cells.

Animals↗

PubMed1994

Effect of vitamin A excess on oral armature in tadpoles of toad, Bufo melanostictus (Schneider) and frog, Rana cyanophlyctis (Schneider).

Tadpoles of B. melanostictus and R. cyanophlyctis were reared in vitamin A solution. Rearing of the tadpoles of B. melanostictus in solutions containing 15, 20 and 30 IU/ml vitamin A palmitate resulted in complete disappearance of the keratinized epidermal material over the jaws and horny labial teeth. However tadpoles of the frog R. cyanophlyctis, were not affected in this way.

Animals↗

PubMed1993

[The parathyroid gland under normal and experimental conditions].

Since Sandström reported the first detailed description of the parathyroid glands of human beings in 1880, and Lever first described the ultrastructure of the parathyroid chief cells of rat in 1957, a large number of light and electron microscopic studies have been done on the parathyroid glands of numerous animal species under normal and experimental conditions. This review deals with the comparative morphology of the parathyroid glands in amphibians, reptiles, birds and mammals under normal conditions, and the problem concerning the effects of various experimental conditions on the parathyroid glands in mice, rabbits and hamsters. The parathyroid glands were recognized in all vertebrate animals higher than fish, and arose from the third and fourth branchial pouches. Several animals, such as the newt, lizard, gecko, mouse, rat, hamster and gerbil, had only two parathyroid glands, but most animals had four. In mammals, most of the parathyroid glands were closely associated with the thyroid gland, but in amphibians, reptiles and birds, the glands separated from the thyroid gland. In some mammals, the parenchymal cells of the parathyroid gland were classified under a light microscope into two main types of cells: chief cells and oxyphil cells. Examinations under an electron microscope also showed the chief cells having many cell organelles and the oxyphil cells filled with numerous mitochondria in the parathyroid glands of human beings, monkeys, cows, horses, bats and turtles. In addition, the chief cells in most animals were classified at the light microscopic level into light cells and dark cells, moreover the chief cells were also electron microscopically divided into a light and dark type showing different functional phases of a single cell type when osmium or glutaraldehyde fixative was used. However, it is widely accepted today that differences in cytoplasmic density of the chief cells are due to artifacts produced in the process of tissue preparation. The parenchymal cells of the parathyroid gland of the newt were divided into the basal cells (supporting cells) and the suprabasal cells (chief cells). In the parathyroid gland of the frog and toad, blood vessels and connective tissues were not present. In the parathyroid gland of the rabbit and hamster, the water-clear cell was observed. In the electron microscopic radioautograph of the parathyroid gland treated with 3H-leucine, most of the silver grains were seen over cisternae of the granular endoplasmic reticulum at 15 minutes, over the Golgi complexes at 30 minutes, and over secretory granules at 60 minutes.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗