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PubMed1975

Localization of alkaline phosphatase activity of the small intestinal microvilli in various vertebrates from mammalia to fishes.

The localization of alkaline phosphatase activity in the small intestinal microvilli of the duodenum, jejunum, and ileum in various mammalia, birds, reptilia, amphibia and fishes has been investigated and compared both by light and by electron microscopes. When the incubating medium is intravitally perfused into the small intestine of living animals, deposition of azo-dye is found on the microvilli in the epithelium. Enzyme activity in the duodenal epithelium is strong in all 14 species. No appreciable differences in phosphatase activity are found among the species. In the birds and mammalia except rat, the microvilli of the jejunal and ileal epithelium shows strong alkaline phosphatase activity. In the amphibia and fishes, the jejunal epithelium of the striated border shows weak phosphatase activity. Ileal epithelium of the reptilia, amphibia and fishes shows weak or trace activity. In the glutaraldehyde-fixed material, the phosphatase activity of the duodenum in mammalia is similar in activity to that found in the intravitally perfused animal. But no azo-dye deposit can be seen on the microvilli in the jejunum of amphibia and fishes, nor the ileum of reptilia, amphibia and fishes. Furthermore, the effect of EDTA-inhibition for alkaline phosphatase in the small intestinal surface was also viewed in glutaraldehyde-fixed sections.

Alkaline Phosphatase↗
PubMed1986

Neurohypophysial peptide potencies in cultured anuran epithelia (A6).

To characterize the V2 receptor (for antidiuretic hormone), we have studied the effect of a number of neurohypophysial hormone analogues on cyclic AMP (cAMP) accumulation and short-circuit current in cultured epithelia formed by A6 cells. A6 is the designation of a continuous cell line derived from the kidney of Xenopus laevis. The order of potency for stimulating cAMP accumulation and short-circuit current in A6 epithelia is like that for stimulating water permeability in toad urinary bladder. As anticipated, arginine vasotocin (AVT), the antidiuretic hormone of Amphibia, is more potent than arginine vasopressin (AVP), the antidiuretic hormone of most mammals. The two hormones differ only in the third amino acid (Phe-3 in AVP is a substitution for Ile-3 in AVT). However, there are a number of striking differences in the responsiveness of these amphibian V2 receptors and mammalian V2 receptors to changes in the 7th, 8th, and 9th amino acids where AVT and AVP are identical. 1) Substitution of Lys-8 for Arg-8 in AVP results in marked loss of potency in Amphibia, whereas there is only modest loss of potency in mammals. 2) Desglycinamide AVP is nearly as potent as AVP in Amphibia, whereas it is inactive in mammals. 2) Tocinoic acid, lacking amino acids 7, 8, and 9, has activity in Amphibia, but pressinoic acid, lacking the same three amino acids, is inactive.

Amino Acids↗
PubMed1991

Evolution of the myelin integral membrane proteins of the central nervous system.

The predominant integral membrane protein of the CNS myelin of amphibia, reptiles, birds and mammals is proteolipid protein (PLP) and P0, the main glycoprotein in PNS myelin. Alternative splicing of the transcripts of the single genes of PLP and myelin basic protein (MBP) is the underlying mechanism by which the isoforms of the two main proteins of the myelin membrane arise. DM20 is an isoform of PLP in mammalian, avian and reptilian myelin. It does not occur in the CNS myelin of amphibia. DM20 lacks an extended hydrophilic sequence exposed on the extracytoplasmic surface of the lipid bilayer as a result of the usage of a cryptic donor splice site within exon III. We report about comparative studies on PLP and its DM20 isoform on the protein and DNA level of frog, chicken, rat CNS and the P0-related IP proteins of the CNS of trout. Chemical cleavage at tryptophan residues with N-chlorosuccinimide yields identical patterns of PLP peptides which refers to a high conservation between amphibia, birds and mammals and is totally different from the cleavage pattern of hydrophobic myelin proteins IP-1 and IP-2 of trout CNS and that of P0 of rat PNS. The N-terminal 19 amino-acid residues of IP-1 of trout CNS- and P0 of frog PNS myelin were sequenced and proved to be homologous on one hand with the P0 analogue of CNS of the shark, a cartilage fish, and on the other hand with P0 protein of PNS of birds and mammals. The complete amino-acid sequence of chicken CNS PLP was derived from its cDNA. Coding and noncoding segments of the PLP gene of frog were sequenced: there is a high degree of conservation between amphibian and mammalian PLP within the hydrophobic domains. Numerous mutations were found within the part of exon III encoding the hydrophilic domain. Base exchanges within the putative splice site in exon III explain the absence of DM20 in the protein pattern of amphibia CNS myelin. This result is being discussed in view of the membrane organization and the function of PLP.

Amino Acid Sequence↗
PubMed1993

[Occurrence of Listeria monocytogenes in snakes, tortoises, lizards and amphibians raised as pets].

Listeria (L.) spp. were isolated from fecal samples of 9 (30.0%) from 30 tortoises, of 4 (12.1%) from 33 lizards, of 3 (60.0%) from 5 amphibia and of 1 (1.3%) of 76 snakes. All animals were kept as pets. 8 isolates were identified as L. monocytogenes, whereas 4 strains were serovar 4ab (3 tortoises and 1 amphibia), 3 strains serovar 4b (2 tortoises and 1 snake) and 1 strain serovar 4e (1 amphibia). Further 4 isolates were identified as L. ivanovii serovar 5 (3 lizards and 1 tortoise), 3 strains as L. innocua serovar 6b (3 tortoises) and 2 strains as L. welshimeri serovar 6a (1 lizard) respectively serovar 6b (1 amphibia).

Amphibians↗
PubMed1987

Calbindin in vertebrate classes: immunohistochemical localization and Western blot analysis.

Calbindin immunoreactivity was investigated in various vertebrates. Positive labeling was observed in the absorptive cells of the duodenum of all birds and reptiles but not in mammals, amphibia, or fish. Staining was present in the kidney distal convoluted tubule from amphibia and higher vertebrates. Fish kidney was negative. In the central nervous system of all species investigated, cellular bodies and fibers were Calbindin positive. Their distribution was quite broad and correlates well with the previously reported mapping for chick and rat. Western blot analysis revealed two Calbindins in brain from mammals, birds, reptiles, and amphibia (27,000 and 29,000 Da). Only one band was detected in fish. We conclude that Calbindin from the evolutionary point of view is primarily a neuronal protein, with a highly conservative character.

Amphibians↗
PubMedDate not supplied

Autoinduction of nuclear hormone receptors during metamorphosis and its significance.

Metamorphosis is a most dramatic example of hormonally regulated genetic reprogramming during postembryonic development. The initiation and sustenance of the process are under the control of ecdysteroids in invertebrates and thyroid hormone, 3,3', 5-triiodothyronine, in oviparous vertebrates. Their actions are inhibited or potentiated by other endogenous or exogenous hormones - juvenile hormone in invertebrates and prolactin and glucocorticoids in vertebrates. The nuclear receptors for ecdysteroids and thyroid hormone are the most closely related members of the steroid/retinoid/thyroid hormone receptor supergene family. In many pre-metamorphic amphibia and insects, the onset of natural metamorphosis and the administration of the exogenous hormones to the early larvae are characterized by a substantial and rapid autoinduction of the respective nuclear receptors. This review will largely deal with the phenomenon of receptor autoinduction during amphibian metamorphosis, although many of its features resemble those in insect metamorphosis. In the frog Xenopus, thyroid hormone receptor autoinduction has been shown to be brought about by the direct interaction between the receptor protein and the thyroid-responsive elements in the promoter of its own gene. Three lines of evidence point towards the involvement of receptor autoinduction in the process of initiation of amphibian metamorphosis: (1) a close association between the extent of inhibition or potentiation by prolactin and glucocorticoid, respectively, and metamorphic response in whole tadpoles and in organ and cell cultures; (2) thyroid hormone fails to upregulate the expression of its own receptor in obligatorily neotenic amphibia but does so in facultatively neotenic amphibia; and (3) dominant-negative receptors known to block hormonal response prevent the autoinduction of wild-type Xenopus receptors in vivo and in cell lines. Autoinduction is not restricted to insect and amphibian metamorphic hormones but is also a characteristic of other nuclear receptors (e.g., retinoid, sex steroids, vitamin D(3) receptors) where the ligand is involved in a postembryonic developmental function. A wider significance of such receptor autoregulation is that the process may also be important for mammalian postembryonic development.

Amphibians↗
PubMed1972

Amphibian ribosomal ribonucleic acids.

1. The larger rRNA molecules of different species of amphibia do not all have the same mobility on polyacrylamide gels, and the difference appears to be one between the Anuran and Urodele amphibia. 2. Alteration of conditions of electrophoresis so as to distinguish between differences of conformation and molecular weight does not affect the results. 3. The mobility on gel electrophoresis of the rRNA precursor in two species of amphibia is similar, although the intermediate processing products differ. 4. It is suggested that the mobility differences observed represent differences of molecular weight, and are an example of the variability of the products of transcription and processing of rRNA genes in two amphibian genera.

Amphibians↗
PubMed1957

The metamorphosis of visual systems in the sea lamprey.

The life cycle of the sea lamprey, Petromyzon marinus, includes two metamorphoses. At the end of a period spent as a blind larva, buried in the mud of streams, a first metamorphosis prepares it to migrate downstream to the sea or a lake for its growth phase. Then, following a second metamorphosis, it migrates upstream as a sexually mature adult to spawn and die. The downstream migrants have a visual system based upon rhodopsin and vitamin A(1), whereas that of the upstream migrants is based upon porphyropsin and vitamin A(2). The livers contain vitamin A(1) at all stages. The sea lamprey therefore exhibits a metamorphosis of visual systems, like those observed earlier among amphibia. The presence of porphyropsin in this member of the most primitive living group of vertebrates, as in fishes and amphibia, supports the notion that porphyropsin may have been the primitive vertebrate visual pigment. Its association with fresh water existence throughout this range of organisms also is consistent with the view that the vertebrate stock originated in fresh water. The observation that in the life cycle of the lamprey rhodopsin precedes porphyropsin is not at variance with the idea that porphyropsin is the more primitive pigment, since this change is part of the second metamorphosis, marking the return to the original environment. The observation that in lampreys, fishes, and amphibia, porphyropsin maintains the same general association with fresh water, and rhodopsin with marine and terrestrial habit, suggests that a single genetic mechanism may govern this association throughout this wide span of organisms.

Animals↗
PubMed1993

Allometry of base pair specific-DNA contents in Tetrapoda.

Cells of 82 species of Tetrapoda were stained with DNA base pair specific fluorochromes (Hoechst 33258 and olivomycin) and studied by means of flow cytometry. The genome size range was about 50-fold. The class Amphibia, which had the widest range of genome size variation (about 20-fold), exhibited linear allometry in their base pair specific DNA contents (bps-C-values), i.e., the more DNA they had, the lower the quotient of AT-pairs (C(AT) = 0.13 + 0.87 x C(GC), r = +0.998). Data for Mammalia, pooled with amphibians, fell on the same allometric line at the lower extreme end of genome size range, supporting the correlation. Reptilia-Aves (or Reptilia alone) pooled with Amphibia did not conform with this relationship. Reptilia-Aves form their own line (zone); pooled with Mammalia, this group showed no regularities in the relationship of their bps-DNA contents. Besides revealing the allometry of bps-C-values, these data indicate an integral genomic feature, localization within the same regression line, which Mammalia share with Amphibia but not with recent Reptilia (and Aves). These data also suggest that the relationship between DNA base frequencies and genome size is nonlinear (reciprocal); to obtain a linear relationship, the bps-C-values should be used. It is also concluded that caution is needed when DNA-content is measured for comparative purposes using a fluorescent dye which is known to be base-pair specific. DNA content values obtained with fluorochromes with different specificity may differ as much as by a factor of 1.8, the average discrepancy level is about 14%.

Animals↗
PubMed2003

Solitary chemosensory cells in mammals?

In fish, solitary chemosensory cells (SCCs) occur in the oropharynx, gills and skin and have often been found in association with taste buds. Among amphibia, a diffuse chemosensory system has been described on the ventral skin of toads, and a structural resemblance of SCCs to taste bud cells has been reported in frogs. Putative solitary chemoreceptors have been described in mammals too, at specific sites in the digestive or respiratory apparatus. In newborn rodents, a specific set of SCCs (composed of elements positive for alpha-gustducin, a marker of chemosensory cells) is associated with the gustatory epithelium. In conclusion, the available data suggest that a SCC system is not restricted to fish but is present in amphibia and mammals as well. At our present level of knowledge, establishing a precise homology between different species is difficult. However, the data from mammals and amphibia fully confirm previous findings in fish, and the use of chemical markers to study the diffuse chemosensory systems of vertebrates seems promising.

Amphibians↗
PubMed1998

Paracrine control of steroid hormone secretion by chromaffin cells in the adrenal gland of lower vertebrates.

The adrenal glands of lower vertebrates display a notable intermingling between steroidogenic and chromaffin tissues, which increases from Pisces to Aves. As in mammals, adrenal chromaffin cells contain and release, in addition to catecholamines, serotonin and several peptides, which may affect the secretory activity of steroidogenic cells in a paracrine manner. Stimulatory molecules include serotonin, arginine-vasotocin, tachykinins, vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide and calcitonin gene-related peptide; inhibitory molecules are dopamine, somatotropic hormone-release inhibiting hormone and galanin. Epinephrine and norepinephrine appear to stimulate steroid secretion in Aves and to inhibit it in Pisces, while their action in Amphibia is controversial. Likewise, atrial natriuretic peptide exerts an anti-secretagogue action in Amphibia and a marked secretagogue effect in Pisces and Aves. The effects of opioids (enkephalins and endorphins) have scarcely been investigated and the findings obtained are highly questionable. Compared with the amazing mass of investigations carried out in mammals, studies in lower vertebrates are few, and in large part performed in Amphibia and Aves. It appears that much further work has to be done by comparative endocrinologists to fully clarify the physiological relevance of the functional interactions between chromaffin and steroidogenic cells in the adrenal glands of lower vertebrates.

Adrenal Cortex↗
PubMed2001

[Spemann's organizer--it's origin and derivatives (cellular-tissue and molecular-genetic aspects)].

In 1924 H. Spemann and H. Mangold discovered that a piece of the dorsal lip of a blastopore from Triturus cristatus, after transplantation to the ventral side of another embryo, was able to cause the neighbouring tissues to change their fate and participate in the formation of a new embryo. The dorsal lip was termed "the organizer". Since then, for as long as 75 years, attempts have been made to establish the intimate mechanisms of the organizer activity. However, no real advance was achieved in their understanding. Within the last 15 years, genetic and molecular techniques have been vastly improved, to help in tracing the fate of many cell lineages, and in compiling more exactly the fate maps for different parts of the embryo. Using these data, I have attempted to trace the fate of Spemann's organizer after the early gastrula stage. Analysis of data on inductive abilities of the organizer cells, on the use of markers, and on the observation of expression of specific genes allowed to conclude that Spemann's organizer in amphibia and its homologues in other vertebrates too are heterogeneous: they are composed of distinct cell populations able to induce primarity the development of either the head or trunk parts of the embryo. These population, determined to become the head of the trunk organizers still at the blastula stage, may be located either in the single continuous cell layer (as in amphibia and birds) or separated among different tissue germs (as in mammals). When the dorsal-ventral orientation of the embryo is established and the organizer is switched on the very early invaginating cells of the dorsal blastopore lip (in the case of amphibia) move in advance of the entire invaginating mesoderm and by the end of gastrulation occupy the place just in front of the notochord. It is supposed that the early dorsal lip and the prechordal mesoderm (PCM) are one and the same cell population, i.e. during gastrulation Spemann's organizer transfers from the lip of blastopore to the prechordal zone. The PCM seems to play an exclusive role in the formation of a head in vertebrate, because some mutations in genes expressed in the PCM result in the entire head deletion. It is supposed that spreading of differentiating signals from the PCM occurs along the main body axis in both caudal and rostral directions. After the main body plan formation the PCM is replaced by adenohypophysis. This conclusion is drawn not only from the same topology of both these structures, but also from the similarities of a set of specific genetical markers expressed in these, that makes it possible to suppose the existence of deep connections and succession between them. The adenohypophysis seems to arise directly from the PCM, or cells of the ectoderm influenced by the PCM may be subsequently transformed into humoral cells of adenohypophysis. In this interpretation, adenohypophysis and the much earlier established PCM may be considered as derivatives of Spemann's organizer. This inference is supported by the fact that all the three above structures first originate in vertebrates only.

Body Patterning↗
PubMed1977

Comparative anatomy of the topography of catecholamine containing neuron system in the brain stem from birds to teleosts.

The distribution of catecholamine (CA) containing neurons and nerve terminals in the brain stem from birds to teleosts were studied by means of histofluorescence technique of glyoxylic acid-formaldehyde combining method. The present study revealed that there exists marked differences in topography of CA neurons between higher vertebrates (birds and reptile) and lower vertebrates (amphibia and teleosts). Tegmental CA neurons in the birds and reptile are much more developed than those of amphibia and teleosts. Furthermore, huge collection of CA neurons (presumably dopamine) in the midbrain tegmentum could not be found in the amphibia and teleosts. On the other hand, distribution of CA nerve terminals in the brain stem is essentially similar throughout the vertebrate brains, though there exist modifications by secondary pattern distortions which correspond to various conditions of their lives. Some possible significance of CA neurons on development of central nervous system was discussed.

Animals↗
PubMed1977

Tumor induction by carcinogenic agents in anuran amphibian Rana temporaria.

Effects of 12 chemical cancerogenic agents have been studied in 910 anuran amphibia of the grass frog Rana temporaria. Tumors developed by administration of 8 of the agents studied. Dimethyl, diethyl and dibutylnitrosamines dissolved in water induced tumors in 44.2, 43.6 and 50% of animals, respectively; benzidine and 2-acetylaminofluorene administered subcutaneously and per os--in 46.6 and 41.2%, respectively, whereas p-dimethylaminoazobenzene and orthoaminoazotoluene (per os and subcutaneously)-in 30--33.3% of cases. Diethylstilbestrol-propionate induced tumors in 21% of cases. All the tumors developed within relatively short periods of time (15.6--31.9 weeks) and were located in the liver (hepatocellular cancer, hepatoadenomas) and the haemopoetic system (hemocytoblastosis). In control group of animals 3 amphibia developed multiple tumors of skin-cystadenopapillomas. The results obtained testify to the common mechanism of cancerogenesis in classes of vertebrates. In addition, the findings presented indicate to the suitability of amphibia as a new experimental object in oncology as well as to the applicability of these animals for purposes of express diagnostics of cancerogenicity. It may successfully serve as a biological indicator of environmental pollution with blastomogenic agents.

Animals↗
PubMed1987

[Differences in the cyto- and angioarchitectonics of the ventral horns of the spinal cord in higher and lower vertebrates].

When comparing structures of the ventral horns of the spinal cord in amphibia (Rana esculenta) and Carnivora (cat, dog), it has been stated that in the latter, together with increasing number of neurons their blood supply is improving. This is demonstrated as a growing density of the capillary network in the cerebral substance and increasing number of capillaries within 25 mcm around the neuronal bodies. Glial surrounding of the neurons changes considerably. Both in the amphibia and Carnivora astrocytes and oligodendrocytes play the role of neuronal satellites. But in the amphibia astrocytes as satellites occur much more often than oligodendrocytes. This is evidently connected with a low blood supply and with certain peculiarities of metabolic processes in the cerebral tissue.

Animals↗
PubMed1984

[The coexistence of neuropeptides and catecholamines in the adrenal gland. Research on paracrine effects on adrenal cortex cells].

The aim of the present review was to compare in mammals and amphibians the data concerning the presence of neuropeptides in the chromaffin cells and the possible action of these substances on adrenocortical cell function. Major homologies are to be found concerning the coexistence in chromaffin granules of catecholamines, Met-and Leu-enkephalins, and their precursor, proenkephalin A. However, the inhibitory action that might be exerted by enkephalins in vitro on corticosteroid production in mammalian adrenal gland, does not occur in amphibia. Dynorphin has been isolated in bovine adrenal medulla extracts; the presence of this opioid peptide has not been reported yet in amphibian interrenal tissue. All chromaffin cells of the frog interrenal gland contain VIP-like immunoreactivity whereas this neuropeptide is not contained in the adrenal medulla of mammals, exept in certain pheochromocytomas. In the frog, VIP, Metenkephalin and catecholamines are co-sequestered in the same chromaffin granules. In addition, synthetic porcine or chicken VIP stimulate in vitro the secretion of corticosteroids by frog interrenal fragments. In mammals, the steroidogenic action of VIP has been observed exclusively in tumor cell lines. The existence of somatostatin has been demonstrated in the human adrenal medulla and in pheochromocytomas, but not in amphibia. Somatostatin has been found to inhibit the response of adrenocortical cells to angiotensin II in mammals. A similar effect of somatostatin was not observed in amphibia. The coexistence of VIP and catecholamines in frog chromaffin granules and the stimulatory effect exerted by VIP on corticosteroidogenesis suggest that, in these animals, VIP may be co-liberated with noradrenaline during stress conditions, and thus may act locally on adrenocortical cells to stimulate corticosteroid secretion.

Adrenal Cortex↗
PubMed1984

[Effect of gluco- and mineralocorticoids on the structure and function of the insular apparatus of the pancreas in representatives of different classes of vertebrates].

By means of histological, historadioautographical and biochemical methods the effect produced by disturbances in hormonal balance of the adrenal cortex (corticosteroids) on the islet apparatus of the pancreas in the lamprey (Lampetra fluviatilis), the frog (Rana temporaria), the tortoise (Testudo horsfieldi), the pigeon (Columbia livia), the white rat (Rattus rattus) has been studied during autumn-winter period. Chronic injections of hydrocortisone and desoxycorticosterone-acetate are used to change the hormonal balance in the adrenal cortex. In Cyclostomata, Amphibia and Reptilia gluco- and mineralocorticoids produce similar effects by increasing glycemia level. In birds and Mammalia glucocorticoids increase glycemia level, and mineralocorticoids do not change it. An increased glucose level in the organism of the representatives of various Mammalian classes after an excess injection of glucocorticoids is accompanied with a mainfested degranulation, hypertrophy of the Golgi complex, vacuolization of aldehydefuchsin-positive B-cell. Glucocorticoides increase the level of 35S-methyonine incorporation into B-cells of Langerhans islet in the representatives of all the vertebral classes studied. Mineralocorticoids act similarly as glucocorticoids stimulating protein metabolism only in Amphibia and birds. The level of immunoreactive insulin (IRI) in response to glucocorticoids injection increases in Amphibia and Mammalia and remains unchanged in Cyclostomata, Reptilia and birds. IRI remains unchanged after injection of mineralocorticoids in all representatives of Vertebrata, besides Cyclostomata in which IRI decreases.

Animals↗
PubMed1984

[Morphology and physiology of organs of aquatic respiration in vertebrates: the gill].

The structure and function of gills has been studied in broad outline in fish and amphibia. In the fish gill, one can see two circulatory systems which are interconnected but relatively independent, which have distinct functions and which supply separate epithelia. The haemodynamic control of these two systems and the functioning of these epithelia has been examined with respect to the aquatic environment. In the amphibia, the gills continue to be functional in many cases, especially in the larvae and neotenic forms. In such cases the gills are adapted to function in concert with the lungs. When the latter are fully developed, the gills disappear. The author suggests that the role played by the gills in ionic regulation and acid-base balance in the amphibia and which has been somewhat overlooked is an important one.

Amphibians↗