Tadpole Tail Research Articles

Changes in the rate of production of superoxide anion in tails of Rana catesbeiana tadpoles during spontaneous and triiodothyronine-induced metamorphosis

1. 1. The time course of changes in the rate of production of superoxide anion (O 2) was compared with that of β-glucuronidase in tails of Rana catesbeiana tadpoles during spontaneous and triiodothyronine (T 3)-induced metamorphosis. 2. 2. Superoxide production increases in tadpole tail tissue undergoing regression in vivo during spontaneous metamorphosis and in response to T 3 treatment. 3. 3. The specific activity of β-glucuronidase rises three-fold relative to control levels in tadpoles treated with T 3 in vivo. 4. 4. The time of onset of the rises in β-glucuronidase activity precedes the onset of tissue regression and the onset of the increase in superoxide production precedes the rise in β-glucuronidase activity.

Melanophore dispersion in northern amphibian larva induced by exposure to cold

AbstractIsolated tails from larvae of the northern amphibians Rana chensinensis and Hynobius retardatus showed light skin color in physiological salt solution at room temperature. However, when the tails were exposed to cold, they became dark. Microscopic observation revealed that exposure to cold caused reversible dispersion of melanin granules within integumental melanophores. There was no darkening, however, in the tail of the Xenopus tadpole at low temperatures, as the dispersion effect of melanophore‐stimulation hormone (MSH) on melanophores in Xenopus was blocked. Calcium ions are required for the action of MSH, but the effect of cold on melanophore dispersion observed in R. chensinensis and H. retardatus was not dependent on calcium ions. Beta adrenergic agents dispersed the melanophores of isolated tail from these amphibian larvae and propranolol antagonized the effect. However, during exposure to cold, this beta antagonist failed to inhibit the melanophore dispersion.

Locomotion in Amphibian Larvae (or “Why Aren't Tadpoles Built Like Fishes?”)

SYNOPSIS. A variety of morphological features that affect locomotion distinguish larvae of the three living amphibian orders from fishes and their larvae. The oddest amphibian larvae are anuran tadpoles. With their globose bodies, concealed forelimbs, abruptly compressed and terminally tapered tails, tadpoles not only differ radically from fishes but they—unlike caecilians or salamanders—also differ radically from their adults. Tadpoles typically have less axial musculature and much simpler myotomes than fishes. Surprisingly, in terms of mechanical (propeller) efficiency and maximum sprint speeds, tadpoles still perform as well as many teleosts of comparable sizes. From a consideration of hydromechanics, no amphibian larvae appear to be designed for sustained swimming at high speeds. High maneuverability, rather than sustainable speed, are important for amphibian larval survival. Two key features of tadpoles are the absence of caudal vertebrae and unexposed pectoral appendages. With only a notochord to serve as a skeleton, the tadpole tail is extremely flexible. Because of this exceptional flexibility, tadpoles can fold their tails up against the body and turn rapidly with virtually no displacement of their center of mass. Caudal flexibility can be regulated by muscle activity in the tadpole to effect turning. Lateral appendages are not needed for this movement and are free to develop directly into their adult morphology; the anterior ones develop under cover of an opercular fold where they do not contribute to drag. A case is presented, based on the ecology of metamorphosis, that anuran transformation should be as brief as possible. With no bone to resorb, metamorphosis of the anuran caudal appendage can, indeed, be very rapid. The basic kinematics of constant velocity straightforward swimming for tadpoles and salamander larvae is reviewed, as well as the kinematics and electromyography of starting, stopping, and turning in tadpoles. An attempt is made to relate swimming kinematics to the characteristic morphologies of amphibian larvae. Swimming speed in Rana, Bufo and Aynbystoma larvae, which swim only intermittently, is modulated by changing tail beat frequency. However, Xenopus, which swims constantly by sculling with its tail, regulates swimming speed (at low to intermediate velocities) by varying the length of the propulsive wave in its tail. Xenopus and Rana differ in the morphology of their notochord, spinal cord, spinal nerves, and spinal motor pool distribution within the spinal cord. These differences may underlie the different way these larvae regulate swimming. They may also reflect their phylogenetic history.

Cell death in the anuran tadpole tail: Thyroid hormone induces keratinization and tail-specific growth inhibition of epidermal cells

The mechanism of thyroid hormone-induced and glucocorticoid-modulated death of tail epidermal cells from tadpoles of bullfrog, Rana catesbeiana, was investigated by comparing tail epidermal cells with dorsal body epidermal cells. From morphological and biochemical criteria, there were two types of epidermal cells: basal cells and skein cells. The abundance of these cells was different between the tail and the body skin. Fifty percent of body cells and more than 95% of tail cells were skein cells. Effects of 3,3',5-triiodo-L-thyronine (T3, 10(-8) M) and cortisol (5 X 10(-7) M) were investigated with cultured epidermal cells. T3 differently regulated the keratinization of the tail and body cells. The keratinization of the tail epidermal cells was not observed without T3. T3 induced the keratinization dramatically. On the other hand, body epidermal cells were constantly undergoing keratinization without the hormone: T3 merely accelerated the rate of keratinization. Cortisol generally did not show any significant effect on keratinization. T3 showed opposite effects on DNA synthesis of the tail and body cells: suppression of tail cells and stimulation of body cells. Cortisol weakened the inhibitory effect of T3 on DNA synthesis in tail cells. Immunofluorescent micrographs with anti-BrdU showed that T3 decreased the number of cells in the S phase of the cell cycle in the case of tail cells but not of body cells. Thus, thyroid hormone plays dual roles for the tadpole epidermal cells: one is an induction and a promotion of keratinization in tail and body cells, respectively, and the other is an opposite regulation for the proliferation of both epidermal cells. These roles seem to have crucial connections to a tail-specific cell death induced by thyroid hormone.

Partial purification and characterization of cysteine proteinase from metamorphosing tadpole tails of Rana catesbeiana

1. 1. A leupeptin-sensitive proteinase was partially purified from regressing tadpole tails by acetone factionation and column chromatography on S-Sepharose. 2. 2. The enzyme degraded hemoglobin and myoglobin at pH 3.0. The enzyme also hydrolyzed Z-Phe-Arg-MCA and Boc-Val-Leu-Lys-MCA at pH 4.0. 3. 3. The enzyme activity was inhibited by leupeptin, egg cystatin, E-64 and monoiodoacetic acid and was activated by l-cysteine. 4. 4. The enzyme degraded myosin and actin in myofibrils of tadpole tails. 5. 5. The enzyme belongs to the cysteine proteinase and is possibly involved in tail degradation during the metamorphosis of tadpoles.

An electrophoretic comparison of the LDH-isozyme distribution during the development of the tadpole tails of the aquatic toad Xenopus laevis and the amphibian frog Rana temporaria

1. 1. X. laevis and R. temporaria tadpoles both have a species-specific set of LDH-isozymes, designated on a basis of their relative electrophoretic mobility: X. laevis LDH-1, -2, -3, -4 and -5; R. temporaria LDH-1, -3, -4 and -5; (LDH-1 most negative). 2. 2. LDH-1 is the major isozyme of undifferentiated tissues in both species. 3. 3. Tissue-specific isozymes develop as tissues differentiate: LDH-5 and LDH-4 are associated with white skeletal muscle; X. laevis LDH-1 and -2 with cardiac and red muscle, R. temporaria LDH-1 and -3 with cardiac muscle. 4. 4. The relatively unspecialized R. temporaria tadpole tail tissues retain high levels of LDH-1.

A comparison of the distribution of muscle type in the tadpole tails of xenopus laevis and rana temporaria: An histological and ultrastructural study

The types and the distribution of muscle fibres were analysed and compared in the tails of Xenopus laevis and Rana temporaria tadpoles. The filter feeding tadpoles of X. laevis were found to have both white muscle fibres adjacent to the notochord used for normal locomotory swimming and a superficial layer of small red fibres. The red fibres are probably used for the continuous flickering movement of the tail associated with the maintenance of the mid-water filter feeding position. R. temporaria, a grazing detritus feeding tadpole, was found to have only white muscle fibres used for normal locomotory swimming. Smaller superficial fibres were not red fibres but were thought to be immature white fibres.

Differential expression of the Ca 2+-binding protein parvalbumin during myogenesis in Xenopus laevis

We have used immunocytological techniques to examine the developmental expression of the Ca 2+-binding protein parvalbumin in Xenopus laevis embryos. Western blot experiments show that at least three different forms of parvalbumin are expressed during embryogenesis; the tadpole tail expresses one form, adult brain expresses another, mylohyoid muscle expresses both, and gastrocnemius and sartorius muscles express these two plus a third form. Parvalbumin (PV) is first detectable by immunofluorescence at stages 24–25 of development, a time when myotomal muscles are differentiating and contractile activity occurs spontaneously in embryos. At metamorphosis, PV is expressed in developing limb muscles. While the majority of skeletal muscle fibers express high levels of PV in both embryos and adults, a second fiber type has no detectable PV. The arrangement of PV-containing fibers is stereotyped in each muscle group examined. Histochemical staining of tadpole muscles indicate that PV-containing fibers correspond to fast-twitch skeletal muscles, whereas those without PV correspond to slow-twitch muscles. During tail resorption at metamorphosis, PV appears to be extruded from dying tail muscle cells and taken up by phagocytic cells.

Iodothyronine 5'-deiodinase activity in the amphibian Rana catesbeiana at different stages of the life cycle.

In a previous study, 5' deiodinase (5'D) activity was detected in skin but not in other tissues of premetamorphic tadpoles. When these tadpoles were stimulated to metamorphic climax by treatment with thyroid hormone, activity was increased in skin and was found also in gut and tail tissue. In the present study, 5'D activity was studied at various stages of spontaneous development from early prometamorphosis through metamorphic climax and including the adult frog. 5'D activity was detected in gut and skin at all stages studied and in metamorphosing tail tissue. It was minimal or absent in all other tissues examined. Activity in prometamorphic skin was comparable to that previously observed in premetamorphic skin but increased significantly during metamorphic climax and remained at this level in the adult. 5'D activity was not observed in tail tissue until resorption commenced and when present could not be correlated with tadpole stage or tail length. In both skin and tail, the 5'D activity exhibited values for Michaelis-Menten constant (Km) for rT3 and T4 in the nanomolar range. During prometamorphosis, the 5'D activity in gut exhibited a value for the rT3 Km in the micromolar range. As the tadpoles entered metamorphic climax, the rT3 Vmax of this activity in gut decreased and a second type of 5'D activity, with a Km for rT3 in the nanomolar range, was detected in this tissue. By stage XXI, only the latter component was observed, and its activity increased significantly during metamorphic climax. In the adult frog, 5'D activity in gut was comparable to that seen at the onset of climax. The adult frog also exhibited T3 5D activity in all tissues studied. These observations, together with those reported in the previous study, indicate that gut and skin are the principal T3-generating organs in anuran amphibia and suggest that increased activity of the 5'D system, at the time in the life cycle that the tissues require increased amounts of thyroid hormone, is an important part of thyroid hormone economy in this species.

Cytochemical studies of hydrogen peroxide production in the tadpole tail of Rana japonica during metamorphic climax.

The degeneration of tadpole tail tissue was investigated cytochemically by localizing the sites of hydrogen peroxide production. A cerium perhydroxide precipitation method was used. No reaction product was found in resting macrophages and intact muscle fibres during premetamorphosis. In the metamorphosis phase, extensive cerium precipitates were visualized on the outer surface of the plasma membrane of phagocytotic macrophages, fibroblasts, neutrophils, epidermal cells, muscle fibres, notochordal cells, nerve cells and capillary endothelial cells. The reaction products were localized on those parts of the plasma membranes of the macrophages that were in contact with those of adjoining cells. When catalase were added, the amount of deposits decreased. alpha-Tocopherol and indomethacin, but not dexamethasone, significantly inhibited the formation of the reaction products. These findings are taken to indicate that active oxygen is produced on the plasma membrane of activated macrophages and may play a role in the degeneration of the tail tissue.

Purification and characterization of cathepsin d-like proteinase from the tadpole tail of bullfrog, Rana catesbeiana

1. 1. An acid aspartic proteinase in the regressing tadpole tail was purified about 800-fold with a 36% recovery. 2. 2. The mol. wt of the enzyme was found to be 42,000 on gel filtration and 38,000 on sodium dodecyl sulfate polyacrylamide gel electrophoresis, respectively. 3. 3. The purified enzyme had a maximum activity at pH 3.5 and an apparent K m of 0.084% with acid-denatured hemoglobin as substrate. 4. 4. The enzyme activity was strongly inhibited by pepstatin. In addition, diazoacetylnorleucine methyl ester inactivated the enzyme in the presence of cupric ions. 5. 5. The enzyme was identified as a cathepsin D (EC. 3.4.23.5)-like proteinase.

Development of a muscle actin specified by maternal and zygotic mRNA in ascidian embryos

In this investigation, we characterize the embryonic and adult actins and describe the embryonic expression of a muscle actin in the ascidian Styela. Two-dimensional polyacrylamide gel electrophoresis showed that embryos, tadpole larvae, and adult organs contain three major and two minor isoforms of actin. Two of the major isoforms, which are present in the mantle, branchial sac, alimentary tract, and gonads of adults and in eggs, embryos, and heads and tails of tadpoles, are likely to be cytoplasmic actins. The third major isoform, which was enriched in the mantle and branchial sac of adults and localized primarily in the tails of tadpoles, is a muscle actin. The muscle actin isoform was not detected in eggs and early embryos. Radioactivity incorporation studies showed that the cytoplasmic actins were synthesized throughout early development, but muscle actin synthesis was first detected between the 16- and 64-cell stages, 2–3 hr after fertilization. Two lines of evidence indicate that embryonic muscle actin synthesis is directed in part by maternal mRNA. First, poly(A) + RNA isolated from unfertilized eggs directed the synthesis of muscle actin in an mRNA-dependent reticulocyte lysate. Second, muscle actin was synthesized in anucleate egg fragments. Arguments are also presented that muscle actin synthesis is not directed exclusively by maternal mRNA. It is concluded that embryonic and adult Styela exhibit actin heterogeneity, that one of the actin isoforms is a muscle actin, and that the muscle actin is synthesized during embryogenesis under the direction of maternal and zygotic mRNA.

Physicochemical properties of the triiodothyronine nuclear receptor from tadpole liver, intestine and tail fin

The binding of triiodothyronine (T 3) to tadpole liver, intestine, and tail fin nuclei was consistent with a single class of binding sites. The K D for the binding of T 3 to isolated nuclei from the liver (1.02 nM), intestine (1.40 nM), and tail fin (0.831 nM) nuclei were not significantly different. The number of binding sites for T 3 in the nuclei isolated from each tissue were also not significantly different. Sucrose gradient centrifugation of the salt-extracted nuclear T 3-receptor complex revealed that the s 20,w was not significantly different for the complex from the liver (3.7 S), intestine (3.9 S), or tail fin (3.9 S). Similarly, the Stokes radii of the complex from the liver (3.65 nm), intestine (3.84 nm), and tail fin (3.99 nm) were not significantly different. Molecular weights of 57000, 64000, and 67000 were calculated from the sedimentation coefficients and Stokes radii for the T 3-receptor complex from the liver, intestine, and tail fin, respectively. The similarity of the physicochemical properties of the T 3-receptor complex from each of the tissues studied is consistent with the hypothesis that the same receptor is capable of inducing tissue-specific biochemical changes.

An epidermal factor which induces thyroid hormone-dependent regression of mesenchymal tissues of the tadpole tail

Explants of tadpole tail skin secreted a factor which induces the thyroid hormone-dependent regression of the tail mesenchyme. The activity of the factor was not sensitive to digestion with trypsin or pronase. Heating at 120°C but not at 100°C for 20 min destroyed the activity. The factor came out gradually through a dialysis membrane. The factor was retarded on a Sephadex G-10 column and eluted with water after the salts fraction. We suggest that the active principle is a non-proteinaceous substance with a low molecular weight.

Observations on the interaction of prolactin and thyroxine in the tail of the bullfrog tadpole

Explants of tail fin from tadpoles of Rana catesbeina maintained in tissue culture underwent resorption when exposed to a medium containing 150 n M thyroxine (T 4). Increases in the specific activity of hexosaminidase (Hex) and of acid phosphatase (AP) were associated with this response. Ovine prolactin inhibited resorption of explants in a dose-responsive manner; however, prolactin had no influence on the specific activity of either Hex or AP cultured explants. This result contrasted with the effect of prolactin in vivo, where it inhibited both the resorption of the tail and the increase in specific activity of hydrolytic enzymes induced by T 4. The actions of both hormones, when applied in vivo, were more pronounced in the tail fin than in the muscular core of the tail at the stage of regression tested, indicating that the failure of prolactin to influence enzyme induction in vitro did not result from an incapacity of the fin to respond to prolactin in this fashion. It is suggested that the inhibition of T 4-induced enzymic activity by prolactin which is observed in the intact animal may come about in response to some related but indirect systemic action of prolactin that is lacking when explants are cultured in vitro. It is concluded that inhibition of the induction of hydrolytic enzymes is not an essential factor in the inhibitory effect of prolactin on the resorption of the tail fin.

Investigations on the role of cAMP in regulating resorption of the tail fin from tadpoles of Rana catesbeiana

Conflicting reports have appeared regarding the role of cAMP in regulating resorption of the tadpole tail during anuran metamorphosis. That cyclic nucleotide has been suggested as a mediator of the effects of both the thyroid hormones and prolactin. We tested the effects of cAMP and its derivatives dibutyryl-cAMP and 8-bromo-cAMP on explants of tail fin from tadpoles of Rana catesbeiana maintained in tissue culture. Unmodified cAMP (0.1, 2 m M) did not influence resorption. Dibutyryl-cAMP (0.1, 1 m M) and 8-bromo-cAMP (1 m M) inhibited resorption of explants induced by thyroxine (T 4). The phosphodiesterase inhibitor isobutylmethylxanthine similarly inhibited regression of explants cultured with T 4. None of these agents affected the increase in specific activity of hexosaminidase brought about by T 4. Although the effects of cAMP in anatagonizing tail resorption were simiar to those of prolactin, we found no direct effect of prolactin on levels of cAMP in cultured tail fin. Thus, the effects of prolactin appear not to be mediated by increased levels of cAMP. We conclude, however, that the elevation of cellular levels of cAMP does inhibit the resorptive action of T 4.

Regional specificity of anuran larval skin during metamorphosis: dermal specificity in development and histolysis of recombined skin grafts.

Skins from back and tail were dissected from tadpoles of Rana japonica prior to resorption of the tail and separated into epidermis and dermis by treatment with neutral protease. Homotypically and heterotypically recombined skins were constructed from the separated epidermis and dermis and transplanted into the tail of the original tadpole. Skin grafts using dermis from tail region degenerated simultaneously with resorption of the tail. However, skin grafts containing dermis from back region survived on the posterior part of the juvenile frog beyond metamorphosis. Furthermore, all epidermis underlaid with dermis from back region formed secretory glands and became flattened epithelia characteristic of adult back skin, regardless of region from which the epidermis came. Even when epidermis isolated from tail skin was cultured inside a back skin graft, the tail epidermis survived forming an epithelial cyst and developed secretory glands. These results suggest that regional specificities of anuran larval skin, i.e., development of back skin and even histolysis of tail skin, are determined by regionally specific dermis. The results also suggest that some of epidermal cells of tail skin are able to differentiate into epithelial cells similar to back skin of the adult under the influence of back dermis.

Characterization of macrophages in the tail of the anuran tadpole

AbstractMacrophage‐like cells in the tail mesenchyme of bullfrog tadpoles were isolated and characterized. These cells actively ingested latex beads into their perinuclear cytoplasm and thyroid hormone was essential for their survival in vitro. The requirement for this hormone is a unique property of these cells since other types of tail cells, such as epidermal cells and mesenchymal fibroblasts, are unable to survive in the presence of the hormone. The unusual characteristics of the cells suggest that they are indeed phagocytic macrophages and that they play a crucial role in the thyroid hormone‐dependent breakdown of the tail.

Purification and characterization of toad prolactin

Prolactin (PRL) was purified from anterior pituitary glands of adult toad ( Bufo japonicus formosus) by extraction of acetone-dried pituitary powder with acid acetone and chromatography on DEAE-cellulose and Sephadex G-100. Purification was monitored by radioimmunoassay developed for bullfrog PRL. Toad PRL thus obtained is as potent as bovine PRL in promoting collagen synthesis in the bullfrog tadpole tail fin. HPLC of the toad PRL on a reverse-phase column shows that the preparation behaves as a homogeneous protein. The hormone has a molecular weight of 23,000 as determined by SDS gel electrophoresis. The isoelectric point is 5.5 as determined by analytical electrofocusing. The amino acid composition closely resembles that of bullfrog PRL.

Hormonal regulation of growth and life span of bullfrog tadpole tail epidermal cells cultured in vitro.

Epidermal cells were dissociated from tails of the bullfrog tadpole, Rana catesbeiana, and cultured to investigate their response to steroid and thyroid hormones. Charcoal-treated serum (CTS) was used in the growth medium when cells were to be grown in the absence of steroid and thyroid hormones. The cells could be maintained for 2 weeks with a small increase in cell number in medium that contained CTS (CTS medium). Addition of cortisol to CTS medium increased both cellular attachment to the culture dishes and the proliferation of the attached cells with an optimum concentration of 5 X 10(-7) M. The cells remained viable and attached for at least a week. Cortisol stimulated the rate of protein synthesis 1.8-fold but did not alter the rate of DNA synthesis. The cells did not proliferate in the medium containing triiodothyronine (T3) and detached themselves from the dish within 5 days, which occurred in a dose-dependent manner with a maximum effect at 10(-8) M. It drastically decreased the rate of DNA synthesis but did not influence the rate of protein synthesis. These responses of cells to cortisol and T3 may reflect growth and death of tail epidermal cells in vivo at metamorphosis.