Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Amphibia”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,603 records · Page 89Linked to original sources
PubMed1977

[Investigation of rat brain prealbumins].

12 prealbumines of rat brain water-soluble fraction were studied. Neither lipid components nor carbohydrate ones were found out in the proteins. Three of the proteins appeared to be RNA-proteids. Their subcellular distribution was investigated. The effects of temperature, salts, acids and ethanol on disc electrophoretic spectrum of brain prealbumines were closely observed. The amino acid composition, properties, compartmentation, tissue and species specificity of one of the prealbumines were studied in detail. The protein is marked as BTB-protein, as it migrates under disc electrophoresis in 7,5% polyacrylamide gel with the "witness" front of bromothemol blue (BTB). The content of BTB-protein is 0.06--0.08 gr per 100 gr of wet tissue. The protein is RNA-proteid. Its molecular weight is 10,000--20,000. BTB-protein contains 42 mole % of acidic amino acids and 5.4 mole % of alkaline ones. The protein was found in nuclear and cytoplasmic fractions. It is mainly an all-organs protein. Small amount of this protein is found in blood serum. BTB-protein can be found on the disc electrophoregramms of embryo and newborn rats brain proteins, as well as of the brain of other mammals, birds and amphibia. BTB-protein is resistant to boiling and to the effects of salts, acids, ethanol. It is suggested that BTB-protein has heterogenous structure and may be of neurophysin nature.

Amino Acids↗
PubMed1975

Adenoviruses of man and animals.

Adenoviruses are capable of causing natural infections in a wide variety of vertebrates, including amphibia, birds and mammals. Although frequently causing inapparent infections, they may be associated with diseases of varying severity and localizations. The clinico-pathological manifestations most commonly associated with adenovirus infections involve the respiratory tract and the ocular conjunctiva. Involvement of the digestive, renal and nervous systems may also be observed. A state of latency with persistence of infection for prolonged periods has been described in many hosts. Many adenovirus types are oncogemic under experimental conditions but none have been associated with naturally occurring tumours. Although the diseases caused by adenoviruses tend to be mild, this is not invariably the case and these viruses may give rise to serious epidemiological situations and represent a threat to life under certain circumstances in which the use of prophylactic vaccination may be indicated.

Adenoviridae↗
PubMedDate not supplied

[Characterization of an experimental model of monosodium- glutamate-induced convulsions in the amphibian Bufo spp].

In previous reports, Feria-Velasco et al. characterized an experimental model of convulsions in rats induced by monosodium glutamate (MSG) with evaluation of the motor behavior and neurochemical parameters. In the present work, MSG injected in toads (Bufo spp) reproduced the model of convulsions with some peculiarities. The electrocorticographic recordings in toads after MSG injection were similar to those obtained in rats after administration of convulsant agents. Most of the toads injected with MSG (81.8%) showed convulsions preceded by an episode of stereotyped movements and signs of hyperexcitability. Latency for convulsions and frequency of convulsive episodes were similar to what has been reported in rats injected with MSG. However, the duration of convulsive period was larger than that seen in rats, and no deaths were recorded in toads. The peculiar feature of amphibia regarding their cerebral structures and their blood-brain barrier (BBB) make the amphibian model, an interesting and valuable one in studying experimentally induced convulsions, as well as the role of BBB in these phenomena.

Animals↗
PubMed2006

[Role of recessive and dominant mutations in adaptation of the genus Rana to modern biosphere].

The populations of three anuran amphibian species (Amphibia, Anura) of the genus Rana (R. ridibunda Pall., R. arvalis Nilss. and R. temporaria L.) inhabiting the Yekaterinburg urban agglomeration were examined. The frequencies of two traits, morph striata and iris depigmentation, were estimated in these populations. The former trait, so-called morph striata, is phenotypically expressed as a light dorsomedial stripe. It is controlled by a dominant allele of autosomal diallelic gene striata in some species of Rana genus, exhibiting complete dominance. Striata individuals have a number of physiological features that confer them an advantage under conditions of natural and artificial geochemical anomalies. The second trait, iris depigmentation, is the result of a recessive mutation. The individuals homozygous for this trait have low viability. Thus, the dominant mutations promote rapid adaptation of their carriers. Conversely, the recessive mutations may reduce viability of an individual.

Adaptation, Biological↗
PubMed1975

Differentiation of photoreceptors in cultured optic vesicles from embryos of Rana esculenta.

Optic vesicles from embryos of Rana esculenta at a stage corresponding to stage 19 in the development of Rana pipiens were cultured for 15 days. The eyes which differentiated in vitro were much smaller than controls of the same age, due partly to the absence of the vitreous body. In many specimens a well-stratified retina surrounded by a layer of pigmented cells was found. The features of all the components of the retinal layers are described. The complete differentiation of photoreceptors, including their outer segments, is the most interesting result obtained in these organ cultures, and is in contrast with the observations previously reported for retinal tissue cultures. The authors suggest that the source of the material (amphibia instead of birds or mammals) is the main reason for this discrepancy. Frog embryo cells are practically self-sufficient since they are endowed with nutritional substances, amongst which Vit. A and antioxidative agents (Vit. E and ascorbic acid) have been indicated as the most important factors for the structural organization and integrity of the outer segments. The role played by the pigment epithelium is also discussed.

Animals↗
PubMedDate not supplied

Generation of DM-20 splice site in myelin proteolipid protein gene: a hypothesis based on analysis of the amphibian protein.

The DM-20 isoform of proteolipid protein (PLP) of central nervous system myelin is undetectable in amphibia, but readily detectable in reptiles, birds and mammals. To explain the phylogenetic origin of DM-20, it has been proposed that a donor-acceptor RNA splice site was generated by the introduction of a single base change in the codon encoding amino acid 116 of PLP. We tested this hypothesis by isolating and sequencing peptides from bullfrog PLP. One of the peptides corresponded to mammalian residues 110-122, which contain the N-terminal boundary region for the domain excluded from DM-20 in higher vertebrates. We found that the Thr115-Val116 sequence is conserved between frog and mammal. Therefore, we propose that a single base change in the third position of the codon for Thr115 would account for the appearance of the new donor-acceptor splice site. Three amino acids elsewhere in this thirteen-residue peptide were found to differ between bullfrog and mammal, which could account for the previously reported weak recognition of amphibian PLP by an antiserum specific for peptide 109-128. A second peptide from bullfrog PLP had a sequence identical to that of residues 45-52 in mammalian PLP. Our findings explain how a specific change in the myelin PLP gene could generate a new form of the PLP protein.

Amino Acid Sequence↗
PubMed1977

[Effect of a periodic growth-retarding diet on changes with age in the hypothalamo-hypophyseo-adrenal system].

Two pacemakers localized in sinoatrial and atrioventricular valves were revealed in the tench heart. In their absence, the ventricular and sometimes the atrial myocardium are capable of initialting the automaticity. Pacemaker's cells of the sinoatrial valve are surrounded by specific area similar to sinoauricular ring in amphibia or sino-caval region in mammals. Characteristics of the action potential in different parts of the tench heart are presented.

Adrenal Cortex↗
PubMed1991

Axonal microtubules: comparative anatomy in vertebrates, including man.

The microtubular density was assessed with the electron microscope in 3 microns myelinated fibers, myelin excluded, of 11 species from the following classes: Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia. The average for all species was 20.6 microtubules/microns 2. Dispersion of values was restricted as shown by a coefficient of variation of 15.8. The microtubular content of nonmedullated axons was assessed in trout, lizard, finch, and man. In the four species, the number of microtubules increased with the cross sectional area of the axon. In trout, lizard and finch, the microtubular density decreased from over 100 microtubules/microns 2 in fibers smaller than 0.1 micron 2 to about 30 in 1 micron 2 fibers; in axons of equal size, the packing of microtubules of nonmedullated was similar between them, and with reported values for peripheral axons of cat and rat. In man, the microtubular density of nonmedullated fibers exhibited only a mild decrease with the axonal size. In the finch, myelinated and nonmedullated axons overlapped in the range 0.23-0.60 micron 2 and both groups exhibited similar microtubular densities. We conclude that the packing of microtubules of the vertebrate peripheral axon is a feature largely conserved during evolution.

Animals↗
PubMedDate not supplied

[The synthesis and localization of crystallins in different cell compartments of the crystalline lens in adult frogs: immunoautoradiographic and immunofluorescent research].

The purpose of this study was to analyze immunochemically the synthesis and distribution of tissue-specific proteins, i.e., alpha-, beta- gamma- and rho-crystallins, in morphologically distinct regions of the frog (Rana temporaria L.) lens which consist of cells at various stages of differentiation, maturation and aging. Five such cell compartments can be distinguished in the lens: (1) central zone of lens epithelium (stem/clonogenic cells); (2) equatorial epithelial cells (differentiating cells); (3) lens fibers of the outer cortex (post-mitotic differentiated cells); (4) lens fibers of the deep cortex (cells without nuclei at terminal stage of differentiation); and (5) cells of the lens "nucleus" (cells formed during embryogenesis). Intact lenses and isolated lens epithelium were cultured in vitro in the presence of 35S-methionine. Then lens epithelium, outer and deep cortex, and lens nucleus were extracted with buffered saline and extracts used for immunoautoradiography. Distribution of crystallins in paraffin sections of the whole lens or isolated lens epithelium was studied using indirect immunofluorescence. Synthesis of alpha-crystallins was observed in lens epithelium and cortex, but not in lens nucleus. According to immunohistochemistry, these proteins were absent from central part of the lens epithelium: positive fluorescence was observed only in elongating cells at its periphery and in lens fibers. The data on beta-crystallins are similar except that synthesis of these proteins (traces) was detected also in lens nucleus. Synthesis of gamma-crystallins was detected in lens cortex and nucleus (traces) but not in epithelium. Immunohistochemistry showed that these proteins are absent from all regions of lens epithelium and found only in fiber cells of cortex and nucleus. Rho-crystallin was synthesized in all cell compartments of the adult lens, and all lens cells contained this protein. Our results show that cells of central lens epithelium do not contain alpha- beta- or gamma-crystallins (or the rate of their synthesis is insignificant). While cells are moving towards lens equator and elongating, synthesis of alpha- and beta-crystallins is activated. Gamma-crystallins are synthesized later, first in young lens fibers near lens equator. During embryonic development in amphibia, in contrast, gamma- and beta-crystallins are detected at earlier stages than alpha- and rho-crystallins (Mikhaĭlov et al., 1988). These data suggest that different mechanisms are involved in differentiation on lens fibers from embryonic precursor cells, on one hand, and from epithelial stem cells of adult lens, on the other.

Animals↗
PubMedDate not supplied

[Biotransformation of dimethylnitrosamine].

NDMA, one of the most widely occurring carcinogenic compounds in the environment, is present in human food (meat, vegetables, cheese and alcohol beverages), in drinking water, in drugs, in cosmetics, in tobacco and its smokes. Furthermore NDMA may be synthesized from nitrates and nitrites and endogen or exogen amines. Since the first observations of MAGEE and BARNES in 1956 on the carcinogenicity of NDMA, this compound was reported to be carcinogenic in a large number of animal species including mammals, birds, amphibia and fish. NDMA requires metabolic activation for its cytotoxic and carcinogenic actions. The major activation step is believed to be the oxygenation of the alpha-carbon catalysed by a Cytochrome P-450-dependent enzyme system commonly know as NDMA-demethylase. Studies on the enzymology of NDMA metabolism show that some Cytochrome P-450 isozymes exhibit significant NDMA-demethylase activity only at high NDMA concentrations. The form of P-450 inducible by factors such as, fasting, diabetes, ethanol consumption and pretreatment with acetone, pyrazole or isopropanol has the higher affinity for NDMA. The gene coding for this isozyme belongs tho the P-450 II E subfamily. Because NDMA-demethylase activity is decreased by monoamine oxidase inhibitors, some authors have suggested a possible role of MAO in NDMA demethylation. This view is not supported by others who don't find evidence for an involvement of MAO in NDMA metabolism. Likewise, there are contradictory reports about the existence of some NDMA demethylase activity in cytosol, nuclei and mitochondria. NDMA demethylation, followed by nonenzymatic cleavage of the hydroxylated methyl group gives formaldehyde and methyldiazohydroxide and then leads to the formation of, a methonium ion, which is able to methylate nucleophilic sites of cellular macromolecules such as, proteins, RNA and DNA. A lot of studies suggest the existence of an alternative pathway to the formation of a methylating agent, denitrosation. Although the nature of mechanisms of denitrosation is not completely known, authors think that the formation of nitrite may represent a detoxification pathway rather than an activation pathway.

Animals↗
PubMed1978

Postsynaptic facilitatory effects of theophylline on amphibian neuromyal transmission.

This study concerns the effects of theophylline on nerve-muscle transmission of the frog; it was of particular interest to evaluate the facilitatory actions of theophylline at the postsynaptic sites. At concentrations of up to 5 mM, theophylline exerted negligible effects on the end-plate resting potential or on the passive membrane characteristics. The major effects of theophylline (0.5--5.0 mM) were exerted on the end-plate potentials (EPPs), miniature EPPs, acetylcholine (ACh) potentials, and on the end-plate current. The amplitude of these parameters was markedly increased; furthermore, the half-decay time of the EPP and, particularly, of the end-plate current were markedly affected. On the other hand, the time course of the ACh potentials was not significantly affected by theophylline. Spontaneous and evoked release of ACh were not affected by theophylline (0.5--5 mM). Altogether, these results indicate that, in amphibia, the neuromyal facilitation induced by theophylline is mainly due to its postsynaptic actions. Furthermore, some of these data as well as results of others indicate that these effects of theophylline are not due to its anticholinesterase properties. It is suggested that theophylline may act directly on the cholinergic receptor or ionic conductance modulator and that it may stabilize the ACh-receptor complex.

Acetylcholine↗
PubMed1990

Details of the female and male pathway of the Keimbahn determined by enzyme histochemical and autoradiographic studies.

Autoradiographic studies and the use of enzyme histochemistry have revealed that early germ line cells (female and male PGC, oogonia, prediplotene oocytes and prospermatogonia) as well as the more advanced germ cells (diplotene oocytes, spermatogonia, spermatocytes and spermatids) show specific patterns of their DNA and RNA synthesis and their enzymatic equipment. The female and male germ lines show similar kinetics up to the arise of oocytes and T prospermatogonia (T for transitional), the final products of a first limited multiplication process of primitive gonia. In former studies we supposed that oocytes and T prospermatogonia are the first exponents of the female and male pathway of the germ line (Hilscher and Hilscher, 1989a). Recently, it could be shown--using the reverse PLM method in slides of plastic embedded material--that the first differences between female and male GC can already be stated at the end of the first proliferation wave of oogonia and multiplying prospermatogonia; that means even before the existence of oocytes and T prospermatogonia (Hilscher and Hilscher, 1989b). Oogonia and M prospermatogonia (M for multiplying) are equipped both with only one active X chromosome. While oocytes traverse the prediplotene stages of meiotic prophase T prospermatogonia prepare for a second extensive proliferation process: spermatogenesis. Oocytes in meiosis are provided with two active X chromosomes, T prospermatogonia possess only one, and the presence of the Y chromosome is not vital for them. However, the Y chromosome is required for the normal course of spermatogenesis characterized by a stock of stem cells, that are responsible for the continuous production of male gamets. The mammalian oocyte--similar as that of insects and amphibia but to a lower degree--acts as pre-embryo.

Animals↗
PubMed1990

[Metamorphosis today].

In conjunction with the 100th anniversary of birth of the Czech physiologist V. Laufberger who discovered in 1913 the possibility to induce metamorphosis in neotenous larvae of axolotls by feeding them with thyroid gland, the author gives an account on the development of knowledge regarding metamorphosis in amphibia. He analyzes the participation of endocrine glands, in particular thyroid hormones and prolactin. Special attention is devoted to mechanisms leading to resorption of the tail in tadpoles, i. e. the activation of lysosomal enzymes due to the action of thyroid hormones. Prolactin has an inhibitory effect on metamorphosis. An important part is obviously played by deiodination of the prohormone thyroxine in target tissues to active triiodothyronine. Recently it was demonstrated that during metamorphosis a significant role is played by apoptosis (controlled non-inflammatory absorption of superfluous cells).

Ambystoma↗
PubMed1990

Differential germ cell proliferation in the salamander pleurodeles waltl: controls by sexual genotype and by thermal epigenetic factor before differentiation of sexual phenotype of gonads.

In the acceptance that, during early gonadogenesis, variations of germ cell (GC) proliferation express interactions between germ and somatic cells, early events occurring before histological differentiation of gonadal sex has been detected and timed through GC counts on larvae of Pleurodeles waltl (urodele amphibia) issued from male ZZ or female ZW monosexual offspring. Gonads differentiate in accordance with sexual genotype in ZZ and ZW larvae at room temperature and in ZZ larvae at 32 degrees C whereas they are sex-reversed at 32 degrees C in ZW larvae, becoming phenotypic neomales. At both the rearing temperatures, in genital ridges, GCs do not proliferate during a period called P0 period ending earlier in ZZ than in ZW larvae. The time when proliferation starts depends on sexual genotypes and determines a ZZP0 period shorter than ZWP0 period. After P0 period, at room temperature, a moderate increase in GC number determining a P1 period is observed in both ZZ and ZW larvae, whereas a strong proliferation, determining a P2 period, occurs on a differential pattern in ZZ and ZW larvae; thus, before sexual differentiation of gonads, ZW females have more GCs than ZZ males. At 32 degrees C, GC proliferation is moderate during P1 period and does not accelerate during P2 period in ZW larvae differentiating neotestes; they have a lower GC number than ZZ larvae reared at 32 degrees C. Thus, during P2 period, at both room temperature and at 32 degrees C, GC number correlates with future phenotype of gonads. Results suggest that differential molecular events arise during early gonadogenesis and that testes may differentiate in different ways according to whether phenotype conforms to genotype or sex reversion occurs.

Animals↗
PubMed1990

[Behavior of pet animals].

Severe mistakes in pet keeping are often the result of ignorance. Many animals suffer from the care of their owners. Industry provides food in the proper composition, but the importance of the cage's interior, its size and the number of animals of the same species kept in it is often neglected. The key to a better understanding of pets is the knowledge of the ecological environment of their species. Fish, amphibia and reptiles are capable of simple acts of learning, but their potential of adaptation to their environment is determined mainly genetically, which can be observed best during the phase of their youth. Most members of these animal groups are born with a perfect behaviour program. Thus aquaria and terraria should as far as possible correspond to the needs and requirements of the species in question to its ecological niche. An aquarium should be a model of the animals' biotope. The effect of the conditions under which a pet is kept on its wellbeing is discussed in detail for the budgerigar and the guinea pig. Experiments with budgerigars showing that too small cages and the missing company of animals of the same species lead to abnormal behaviour are described. Guinea pigs live in packs. The fact how important the group and its social organization is for the individual guinea pig is documented by experimentally verified data. Furthermore the effect of the guinea pig's ontogeny under experimental conditions on the structure of a pack is discussed. Already small changes in the size of the cage or in its interior encourage the guinea pig's exploration behaviour and its mobility.

Animals↗
PubMed1990

[Innervation opf the juxtaglomerular complex (JGC) of the kidney in vertebrates].

On the base of electron microscopic investigations of kidneys, performed on some representatives of vertebrata (fishes, amphibia, reptiles, birds, mammalia) the data on their JGC innervation are presented. In the course of evolution the structure of nervous-muscular, nervous-endocrine and nervous-epithelial contacts becomes more complex. The role of the nervous factor in regulation of the systemic blood flow and water-salt metabolism acquires a greater significance in the process of development.

Amphibians↗
PubMedDate not supplied

[Inhibition of growth of B16 melanoma caused by liver regeneration].

Phenomenon of spontaneous regression of cancer indicates that recovery from malignant disease can happen without the application of any so far known therapeutic treatment. The most of the self-cured patients have undergone surgical operation which did not eliminate entire tumor or did not affect malignant tissue at all. Furthermore, regression or reversion of tumors (transformation of tumor cells into normal, nonmalignant cells) can be achieved in plants or amphibia after exposure of tumor cells to the influence of normal, regenerating tissue. Thus, it seems that during tissue regeneration certain local changes in tissue happen (synthesis of some regulatory growth factors) which induce dying of tumor cells or modify main features of malignant cells. Previously we have studied growth of murine malignant tumors in regenerating tissue of liver and skin. Obtained results indicated that under the influence of regenerating tissue anaplasia of fibrosarcoma decreases, as well as do pigmentation and the incidence of live cells in melanoma B16 tissue. Thus, it is obvious that mechanism of regenerating tissue growth control, which can also change characteristics of tumor cells, exists in mammalia, too. In order to analyse whether the same homeostatic mechanism is responsible for the phenomenon of spontaneous regression of human cancer, we have analysed the growth of melanoma B16 in back limb of nonoperated and sham or partially hepatectomized mice. Regeneration of skin and abdominal wall tissue in sham hepatectomized animals slowed down tumor growth, while liver regeneration completely inhibited tumor progression. Tumor growth inhibition was result of tumor tissue necrosis which developed around blood vessels. However, the structure and integrity of blood vessels themselves was normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

A comparison of growth regulation of mammalian with amphibian lens epithelium.

In frogs hypophysectomy causes cell proliferation in lens epithelium to subside entirely, with better than 95% of the cells arresting in G1. The phenomenon has been traced to the action of insulin-like growth factors (IGFs) whose synthesis depends on anterior pituitary hormones, most notably GH. Both GH and purified somatomedin C can reinitiate mitosis in the lenses of hypophysectomized frogs. The present studies were done to determine if growth of rat lenses is controlled as is that of amphibia. It appears this may not be so because hypophysectomy has no effect on division in the rodent system. Protein calorie malnutrition (PCM) reduced the mitotic index and this effect is much enhanced by pituitary ablation. Of interest too, were the observations that the glucocorticoid, dexamethansone, is inhibitory in frog; the effect in rat is uncertain. Injection of bovine pituitary powder has no influence on rat while stimulating the amphibian material. It is therefore possible to modify growth of rat lens epithelium in vivo but the regulating mechanism(s) appears to be distinct from that operating in frogs. Whether the difference(s) is inherent in the cells themselves or is to be sought in the access routes through which they are reached by blood borne factors (e.g. permeability of blood-aqueous barriers) is, at present, unclear.

Animals↗