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PubMed1964

GENETIC DISPARITY AND CANCER INDUCTION BY NORMAL TISSUE IMPLANTS IN AMPHIBIA.

Fifty percent of the implants of normal adult Triturus cristatus kidney made into the forelimbs of immature but postmetamorphic Xenopus laevis hosts initiated the formation of lymphosarcoma at the site of implantation. Donor-host genetic disparity as it relates to the intensity of the reaction, when homografts, heterografts, and xenografts are compared, appears to be one of several factors which play a role in the post-embryonic induction of both lymphosarcomas in Xenopus laevis and accessory limb structures in Triturus viridescens.

Amphibians↗

PubMed1996

Local effects of glycinergic inhibition in the spinal cord motor systems for swimming in amphibian embryos.

1. We have studied the effects of locally applying the glycinergic antagonist strychnine to rhythmically active spinal neurons in amphibian embryos during fictive swimming. Intracellular recordings were made from motoneurons and premotor interneurons in Xenopus laevis, a well-studied model system, and from motoneurons in three other species (Rana temporaria, Bufo bufo, and Triturus vulgaris). Overall, these embryos cover a range of swimming patterns from the short-cycle-period, brief-motor-root bursts of Xenopus, to the long-cycle-period, long-motor-root bursts of Rana, which are more typical of adult patterns. 2. Local strychnine application had no significant effect on the gross pattern of swimming; episode duration and the burst duration in rostral ventral roots away from the application site were unaltered, and left-right alternation was preserved. We have therefore been able to examine the effects of inhibition on individual neurons, uninfluenced by overall changes in the operation of the swimming neural circuitry. 3. In all cases strychnine blocked midcycle inhibition and significantly increased the peak on-cycle depolarization during swimming. In Rana, Bufo, and Triturus motoneurons, and in Xenopus interneurons, strychnine significantly increased the reliability of firing during swimming. In Xenopus motoneurons, where spiking was 100% reliable anyway, the timing of the spikes was advanced relative to rostral ventral root activity. These results do not provide support for postinhibitory rebound as a factor in the spike-generating process during swimming. In addition to midcycle inhibition, Xenopus motoneurons can also show a smaller, additional on-cycle inhibition that is blocked by strychnine. 4. In both Rana and Bufo the duration of caudal ventral root bursts close to the site of drug application was increased by strychnine, showing that the increased motoneuron reliability not only leads to more intense, but also more extensive, ventral root activity. 5. At the level of single neurons, glycinergic inhibition effectively reduces on-cycle excitation and in turn controls the reliability, extent, and precise timing of motoneuron firing. These changes may be the individual components underlying broader effects of inhibition described previously, such as locomotor frequency control. They also show how any modulation of inhibition in localized regions of the spinal cord could produce localized control of neuronal firing properties.

Amphibians↗

PubMed1980

Comparison of the pineal complex, retina and cerebrospinal fluid contacting neurons by immunocytochemical antirhodopsin reaction.

The presence of rhodopsin was investigated by an indirect immunocytochemical method in the pineal complex of various vertebrates (Carassius auratus, Cyprinus carpio, Hypophthalamichthys molitrix, Lucioperca lucioperca, Triturus vulgaris, Bombina bombina, Rana esculenta, Pseudemys scripta elegans, Lacerta agilis et viridis, white leghorn chickens, rat), in the retina of Lebistes reticulatus, Lucioperca lucioperca, Rana esculenta, Lacerta agilis, Pseudemys scripta elegans, the chicken and the rat, and the cerebrospinal (CSF) contacting neurons of Triturus vulgaris. The outer segments of the photoreceptor terminals of the pineal organ, frontal organ, parapineal organ of lower vertebrates and of the retina of the species investigated, were intensely stained with the antirhodopsin reaction. There was no significant positivity in the pineal organ of the reptiles, the chicken and the rat, and the parietal eye of the lizards. We failed to demonstrate any immunoreactive staining in the CSF contacting neurons of various hypothalamic areas and of the spinal cord. The light microscopic immunocytochemical results seem to contradict a photoreceptive role of the CSF contacting neurons and strengthen the view that the receptory cells of the pineal complex of lower vertebrates are involved in light perception by means of the visual pigment rhodopsin.

Amphibians↗

PubMed1995

Similar localization of immunoreactive glutamate and aspartate in the pineal organ and retina of various nonmammalian vertebrates.

The localization of immunoreactive glutamate and aspartate was compared in the pineal organ and retina of various vertebrates (Raja clavata, Carassius auratus, Salvelinus alpinus, Triturus vulgaris, Triturus cristatus, Lacerta muralis, Lacerta agilis, Lacerta viridis, Columbia livia and white leghorn chicken) by postembedding immunoelectron microscopy. Immunoreaction of both excitatory amino acids was detected in the pinealocytes in a localization similar to that of retinal photoreceptors. The reaction was intense in the axonal processes of pinealocytes as well as retinal rods and cones, further in their terminals on secondary pineal and retinal neurons. Subsequent immunoreaction on the same section showed a colocalization of glutamate and aspartate. The accumulation of these amino acids in the presynaptic part of pinealocytes suggests that they act as synaptic mediators in the neural efferentation of the pineal organ. In reptiles and birds where the hormonal efferentation of the pineal is well developed, glutamate and aspartate was also found to be accumulated in neuroendocrine terminals of pinealocytes. Therefore, glutamate and aspartate may have a role in both the hormonal and neural efferentation of the pineal organ.

Amphibians↗

PubMed1996

Neural crest cell migration and pigment pattern formation in urodele amphibians.

This review deals with research on the development and differentiation of the neural crest (NC) in amphibians carried out during the past twenty years. First, earlier studies on the migration and differentiation of NC cells in vitro are summarized. These studies include the modes of NC cell migration and their differentiation into chondroblasts, perichondral cells, neurons, Schwann cells and pigment cells (melanophores and xanthophores). Then a summary is given on the development of cranial sensory ganglia and enteric ganglia in Xenopus laevis. In the subsequent sections, mechanisms of NC cell migration are investigated in Ambystoma mexicanum, the Mexican axolotl (wild-type and white mutant) using ultrastructural, immunohistochemical and biochemical methods. In wild-type or dark axolotl embryos, pigment cells leave the NC and migrate out under the epidermis, whereas in the white mutant, pigment cells remain closely confined to the original position of the NC. This system provides an excellent model for analyzing NC cell migration in vertebrate embryos. Further sections deal with the development of larval pigment patterns in Triturus alpestris, (horizontal melanophore stripes) and Ambystoma mexicanum (vertical melanophore bars). Comparing the formation of these patterns shows that two different principles exist in the distribution of pigment derivatives of the NC: patterns following environmental cues (Triturus) and those ignoring these cues, relying solely on cell-cell interactions (Ambystoma). Other studies relate to evolutionary perspectives in pigment pattern formation. They are based on phylogenetic analyses of North American ambystomatids, combined with data on pigment patterns and their formation where such data are available. These studies have shown that vertical bars which develop from aggregates in the NC string are an evolutionary innovation, compared to the more primitive horizontal stripes lacking aggregates in the NC. Thus, in this review we show that the NC of amphibians (T. alpestris, Xenopus laevis, dark and white axolotls and other ambystomatids) may be used for various analyses concerning the migration and differentiation of its derivatives, as well as for studies on the formation and evolution of pigment patterns.

Animals↗

PubMed1976

Architecture of the marrow vasculature in three amphibian species and its significance in hematopoietic development.

Architecture of the bone marrow vasculature, particularly that of the femur, was analyzed in three amphibian species in relation to the early phylogeny of marrow hematopoiesis. A dye-injection method and histological techniques, including both serial sectioning and reconstruction methods, were used for this purpose. From these observations the following conclusions may be drawn. (1) Marrow hematopoiesis is absent from the femur of the urodelan (Triturus pyrrhogaster) and appears first in the femur of the primitive anuran (Xenopus laevis) (2) The site of primitive hematopoiesis (granulopoiesis) is the subendosteal region where the venous vascular net develops. (3) The primitive vascular architecture observed in the femur of Xenopus is characterized by the absence of a central vein. Subendosteal veins drain the blood from the bone marrow. A vein collateral to the primary artery appears in the femur of Rana catesbeiana, an advanced anuran, in which further development of both the subendosteal venous plexus and hematopoietic activity are noted. In both anura examined, the primitive blood sinuses form near the mid-shaft of the femur. The proliferation of mesenchymal elements containing dark pigment, presumably melanin, was also noted in this area. (4) The architecture of marrow vessels in Rana approaches the structure noted in mammalian bone marrow. (5) Fat tissue is observed in the urodelan bone marrow prior to the appearance of hematopoietic activity. This indicates that the formation of marrow fat is phylogenetically unrelated to the development of hematopoiesis. The present investigation on primitive hematopoiesis suggests that the development of hematopoietic activity is intimately related to the development of the marrow vasculature, particularly that of the subendosteal venous plexus. A favorable vascular arrangement may be necessary to allow active hematopoiesis.

Amphibians↗

PubMed1977

The perineural sheath in the urodele amphibian.

The perineural epithelial cells of the peripheral nerve sheath in triturus are elongated flat cells with long and thin cytoplasmic processes. Structural characteristics of the processes include a relative absence of common cytoplasmic organelles of the perinuclear cytoplasm but an abundance of vesicular profiles similar to fully formed pinocytotic vesicles. Unlike pinocytotic vesicles, vesicles of the processes often contain an 8-nm thick filament attached to their cytoplasmic face. Vesicles are also interconnected by similar filaments or by tubules. In addition, almost all vehicles appear to have openings at the cell surface, a feature not seen for pinocytotic vesicles. The concentration of exogenous peroxidase in the vesicles, and the subsequent appearance of peroxidase in the endoneural fluid, myelin sheath and axon, support the notion that the vesicles function in the exchange of substances between extraneural and endoneural fluids.

Animals↗

PubMed1978

Golgi-staining of "primary" and "secondary" motoneurons in the developing spinal cord of an amphibian.

The Golgi technique was used to study the morphology of spinal motoneurons at various stages in the early development of swimming behaviour in embryos and larvae of the palmate newt, Triturus helveticus ((Razoumowsky). The earliest motoneurons stained appeared to be associated with the Mauthner-cell system. The overall morphology of these "primary" motoneurons seems to be similar throughout the lower vertebrates and the distinctive characteristics found in earlier descriptions of those from caudate amphibia were probably due to misinterpretation. At about the time of hatching and development of low-frequency swimming behaviour, other motoneurons were found to innervate the axial musculature, cells with a central morphology different from those of the "primary" type. It was found likely that these "secondary" motoneurons innervate a separate muscle system concerned with tonic and "slow phasic" activity, while "fast phasic" acitivity in rapid swimming is supplied by "primary" cells.

Animals↗

PubMed1977

The effect of light on forelimb regeneration in the newt.

The forelimb of the newt, Triturus (Notophthalamus) viridescens, was bilaterally amputated and the animals subjected to different photoperiods during the period of regeneration, namely (1) continuous light, (2) 15 hours of light/day and (3) total darkness. Animals exposed to continuous light reached the palette regeneration stage four to five days before those kept in total darkness with the 15 hours of light/day animals being intermediate. The difference in regeneration rate was first evident in the moderate early stage (blastema accumulation stage); it then increased during subsequent stages and the difference persisted during the observation period. In an attempt to determine whether the retina was the receptor of light affected, some animals were blinded at the time of amputation and subjected to continuous light. Their rate of regeneration was similar to sighted animals subjected to continuous light but greater than sighted animals in total darkness. The pineal is discussed as the likely mediator of the photo effect.

Animals↗

PubMed1982

The epidermal melanocyte population in the skin of ultraviolet-irradiated crested newt.

The response of the epidermal melanocyte population to repeated ultraviolet (UV) exposure (wavelength spectrum 275-350 nm) has been investigated in the crested newt, Triturus cristatus carnifex. The effects of different doses of UV light were studied. The animals were killed 7 months after the first UV exposure. Only a slight decrease in the number of pigment cells was found after 85 sequential irradiations with a total dose of 1.3 x 10(5) J/m2, whereas striking decreases were observed when the same total dose was fractionated into 14 exposures or when a double dose was given in 57 exposures. The relationship between the square roots of the epidermal melanocyte densities and single doses appeared to be roughly linear, at least over the range of doses administered. The main factor in melanocyte damage seemed to be the single dose of irradiation rather than the cumulative dose administered. Decreased melanin content of the keratinocytes was observed in most irradiated animals.

Animals↗

PubMed1987

Intermittent erythropoiesis in anemic newts.

A group of 88 newts, Triturus cristatus carnifex (Laurenti), was rendered totally anemic by administering acetylphenylhydrazine (APH) in the breeding water for 48 h at a concentration of 25 mg/liter. The course of erythron restoration was followed for 5 months, sacrificing four specimens per week and analyzing the blood and spleen hemopoietic tissue. The return to the normal values of the red blood cell count occurred through marked increases in concentration at fairly regular intervals, which is best explained by a discontinuous, rhythmic erythropoiesis. This fact is strictly correlated with the intermittent mitotic activity observed in the spleen and with the periodic appearance of large quantities of immature elements in the blood smears. The APH-induced synchronization of newt erythropoietic activity revealed the approximate length of each erythropoietic cycle to be 4 to 5 weeks and the erythropoietic life span to be 50 to 60 days.

Anemia↗

PubMed1987

Periodic changes in the organs involved in the erythropoiesis of anemic newts.

In Triturus cristatus carnifex (Laurenti) newts rendered totally anemic by treatment with acetylphenylhydrazine (APH) diluted in their tank water (25 mg/liter for 48 hours, with four changes) the recovery of erythron occurs through periodic cycles of mitotic activity in the erythropoietic tissue. These cycles determine a marked increase in blood erythrocyte concentration at regular intervals of about 1 month. The consequence of this trend is the alternation of ferritin and hemosiderin accumulation phases during periods of stasis with iron mobilization phases during periods of erythropoietic activity, which is particularly evident in the Kupffer cells of the liver. Iron mobilization and erythropoietic activity are strictly related to the periodic hypertrophy of some Bowman's capsule cells in the renal corpuscle, which were previously denominated "lactate sensitive cells" (LSC). The histochemistry, location, and behavior of LSC indicate that they are probably the site of erythropoietin production in the newt.

Anemia↗

PubMed1987

Microcythemia from anemic hypoxia and normal erythropoiesis in the newt.

Specimens of the newt, Triturus cristatus carnifex (Laurenti), rendered totally anemic, restore erythron by cyclic waves of erythropoietic activity that alternate with intervals of stasis. Hemolysis is obtained by administering 25 mg/liter of acetylphenylhydrazine in the breeding water for 36 h. The first cycle of erythropoietic activity produces microcytes, which have completely differentiated by 8 weeks after treatment. However, if the animals are raised in a hyperbaric chamber at a pressure of 1.5 atmospheres, in order to compensate for hypoxia, normocytes are produced. In both cases the hematocrit and hematic concentration of hemoglobin reach analogous values, so microcythemia appears to be the only effect of hypoxia. The hemoglobin, hematocrit values, and normocyte counts in hyperbaric animals are about one-half those of the controls newts. These data, together with those on the life span of red blood cells (RBC) and time span between two successive erythropoietic cycles (2 months and 1 month, respectively), indicate that the newts normally keep only two sets (one new, one old) of RBC in circulation, whose approximate parameters can be defined as RBC count: 60,000/mm3, hematocrit: 17%, and hemoglobin: 5.4 g/100 ml.

Anemia, Hemolytic↗

PubMed1988

Sites and trend of erythropoiesis in anemic, normal, and splenectomized newts.

Newts, Triturus cristatus carnifex (Laurenti), were anesthetized by submersion in 2% chlorbutol in tap water for 15 min, splenectomized and then rendered totally anemic two months later by treatment with acetylphenylhydrazine (APH) diluted in their tanks (25 mg/liter for 36 h, changing the solution every 12 h). In the 14 weeks following hemolysis, erythron restoration occurred with the same intermittence as it did in whole animals rendered anemic by APH treatment: Beginning the second week the red blood cell count progressively increases for about one month, followed by a period of stasis which lasts about three weeks, then by a new increase, and then by a final period of stasis. Histological examination shows that erythropoietic activity occurs partly in the circulating blood and partly in erythroblasts nestled in the crypts between the muscular trabeculae of the ventricle as well as in the atrial walls. These cells, which are not part of the freely circulating elements in the blood stream, become very abundant in both whole and splenectomized anemic newts but are also present in normal animals. Newts, thus, have three sites for erythropoiesis: the spleen, the blood stream, and the heart. The other components compensate for the elimination of the spleen without determining any lack of, or delay in, erythropoietic response.

Anemia↗

PubMed1989

Relationships between spleen and respiration in the newt.

Specimens of newt, Triturus cristatus carnifex (Laurenti), anesthetized by submersion in 0.2% chlorbutol in tap water for 15 min, and then placed out of water in a damp terrarium, show hypertrophy of the spleen that in 2 hr gradually increases from 0.31 +/- 0.12%with respect to body weight to 1.56 +/- 0.26% (means and standard deviation calculated for groups of six animals). Other anesthetics either do not produce hypnosis (Veronal), do not have a prolonged enough effect (ethyl ether, chloroform), or induce vasodilatation, which prevents hypertrophy (MS-222, urethane). The spleen hypertrophy, seen histologically to be due exclusively to blood congestion, is not caused by either a pharmacological effect of the chlorbutol or by the hypnotic state, as it does not appear in submerged anesthetized animals, unless the water is constantly stirred by a magnetic agitator, and can be reversed depending on the ventilation of the animal's skin. The spleen hoards blood when oxygenation is good (in air or stirred water) and releases this supply in the bloodstream when oxygenation is insufficient (in still water). The hypoxic "diffusion boundary layer," which, in still water, forms around the immobile newts, hampers respiratory exchange and stimulates the spleen contraction. This mechanism and its relationship to oxygenation has been demonstrated statistically in unanesthetized newts as well, in both air and water, despite the interference of two contrasting factors--lung respiration and spontaneous motor activity--absent in anesthesized animals. Congestion and decongestion of the spleen are the physiological mechanisms compensating for variations in the level of oxygenation, an alternative to the "capillary recruitment" described by Poczopko and Burggren and Moalli in may amphibians that appears to be absent in newts. The newt spleen, known to play a lesser role in erythropoiesis and destruction of aged erythrocytes than that traditionally assigned to it is thus of primary importance in respiration.

Anesthesia↗

PubMed1997

Cellular mechanism of substance P in the regulation of corticosteroid secretion by newt adrenal gland.

In this work, we have studied the effects and the possible cellular mechanism of Substance P (SP) on corticosteroid secretion by the adrenal gland of the urodele crested newt, Triturus carnifex. Adrenals were in vitro superfused with SP, prostaglandin E2 (PGE2), nitric oxide (NO) donor, cyclic GMP (cGMP) analogue, and inhibitors of phospholipase A1, phospholipase A2 (PLA2), phospholipase C, adenylate cyclase (AC), cyclooxygenase (COX), NO synthase (NOS), and soluble guanylate cyclase (sGC). PGE2, corticosterone, and aldosterone release and NOS activity were determined. SP, PGE2, NO donor, and cGMP analogue increased corticosterone and aldosterone; SP and PGE2 increased NOS, and SP increased PGE2. PLA2, AC, COX, NOS, and sGC inhibitors counteracted SP and PGE2 effects, except for PLA2, which did not affect PGE2. These results suggest that SP exhibits a stimulatory role on the corticosteroidogenesis of T. carnifex adrenal gland. In particular SP enhances PLA2 activity, increasing PGE2; this prostaglandin affects AC, which, in turn, enhances NO, and the latter therefore affects sGC, with the consequent corticosteroidogenesis increase.

Adrenal Cortex Hormones↗

PubMed2002

Environmental estrogens and reproductive biology in amphibians.

In this paper, the effects of an estrogenic compound, 4-nonyl-phenol (NP), on the amphibians Rana esculenta and Triturus carnifex are described together with those on sexual differentiation in Xenopus laevis. NP increased plasma vitellogenin in male frogs and newts in a dose-related manner; moreover, inhibitory effects on gonadotropin and prolactin (PRL) secretion by pituitary were found together with an elevation of plasma androgens. NP treatment also caused a remarkable increase in number of prolactin-immunolabeled cells, suggesting that xenoestrogen might induce, at least in the newt pituitary, a PRL accumulation possibly due to a reduction of the hormone release. In addition, both NP and bisphenol A caused feminization by increasing the percentage of female phenotypes in X. laevis, and the in vivo effects were more pronounced than those of estradiol-17beta.

Amphibians↗

PubMed1980

Lactate sensitive cells in newt kidneys.

Specimens of Triturus cristatus carnifex (Laurenti), raised in 3.2 g/l solution of sodium lactate, presented hypertrophy of "lactate sensitive cells" (LSC) clustered at the vascular pole of each renal corpuscle. As seen under both the light and electron microscopes, these are specialized cells of the Bowman's capsule located at the junction between its visceral and parietal layers. The structure formed by the cells, heretofore unknown, is topographically associated with the juxtaglomerular apparatus. As lactate stimulates erythropoiesis even in normal oxygenated specimens and hypoxia induces hypertrophy of LSC in newts, it is hypothesized that the LSC are the site of erythropoietin (ESF) synthesis. A scheme of ESF biogenesis in newts, integrating the above principles, concludes the paper.

Animals↗