Effect of testosterone and 17-beta estradiol on limb regeneration in the newt, Notophthalmus viridescens

Gonadectomy, or injections of testosterone or 17-beta estradiol, had no apparent effect on the rate of regeneration or histological appearance of limb regenerates in the newt, Notophthalmus viridescens. Neither promotion, nor inhibition of limb regeneration was observed.     

Effect of amputation and limb regeneration on the pars distalis of the newt,Notophthalmus viridescens

Summary A study of the pituitary of the newt,Notophthalmus viridescens, during limb regeneration indicated no observable changes in histology or ultrastructure of any of the cells of the pars distalis when compared with the pars distalis of unamputated control newts.This investigation supported by a grant from the National Research Council of Canada to S.R. Scadding.     

The regeneration of newt limbs deformed in nature

Summary The regeneration of abnormal limbs from a wild newt population was examined. The abnormalities were: mirror symmetrical reduplications of digit parts, deformed wrists, or limbs with supernumerary digits. Normal regeneration resulted after amputation of the abnormal parts, regardless of the original deformity. The results suggest that the abnormalities are probably the result of local trauma to the limbs.     

The regeneration of newt limbs deformed in nature

The regeneration of abnormal limbs from a wild newt population was examined. The abnormalities were: mirror symmetrical reduplications of digit parts, deformed wrists, or limbs with supernumerary digits. Normal regeneration resulted after amputation of the abnormal parts, regardless of the original deformity. The results suggest that the abnormalities are probably the result of local trauma to the limbs.     

Effect of a dipeptide inhibiting ubiquitin-mediated protein degradation on nerve-dependent limb regeneration in the newt

The dipeptide Leu-Ala, which inhibits ubiquitin-mediated protein degradation, has been shown to act in vitro as an inhibitor of neurite outgrowth of PC12 cells (Hondermarck et al. [1992] Biochem. Biophys. Res. Commun.189: 280). Using agarose beads as vehicles, we tested, in vivo, the effect of this dipeptide (and the inactive inverse, Ala-Leu, as a control) on limb regeneration in the newt (Triturus cristatus), a nerve-dependent developmental process. Leu-Ala inhibited the growth of mid-bud blastemas without altering blastema differentiation, while Ala-Leu had no effect. Cytological observations of dipeptide-treated blastemas using Bodian staining or neurofilament antibodies showed that all the blastema tissues were unmodified except with regard to innervation. Leu-Ala-treated blastemas were devoid of nerve fibers in the epidermal cap, while the mesenchyme distal to the dipeptide impregnated bead exhibited fewer nerve fibers than did Ala-Leu-treated blastemas, which were similar to the control nontreated blastemas. Thus, Leu-Ala, in reducing blastema innervation, inhibits its growth in the same manner as surgical denervation.     

A contribution to the study of lens regeneration capacity in chick embryos

Zusammenfassung Die Linsenregeneration beim Hühnchen tritt nur auf, wenn die Embryonen am 3. oder 4. Bebrütungstage operiert worden sind. Wenn die Operation später stattfindet, tritt keine Regeneration auf.     

Nuclear chimaeras in the newt

Zusammenfassung Gruppen von 2–4 somatischen Kernen haploiderTriturus-Embryonen wurden in diploide, ungefurchte Eier injiziert, 11 haplo-diploide Mosaik-Larven entwickelten sich bis zum frühen Neurula-Stadium. Nachkommen von Kernen aus dem neuralen Ektoderm oder Chorda-Mesoderm von Spendern im Neurula-Stadium fanden sich in allen drei Keimblättern der Wirtslarve.     

The question of lens regeneration from parts of the optic vesicle in the chick embryo

Résumé Après excision du cristallin des yeux d'embryons de poulet de 48–72 h d'incubation les vésicules optiques étaient cultivées in vitro ou sur le chorio-allantoöide d'autres embryons. Elles étaient cultivées en quelques cas seules et en autres cas avec l'ectoderme céphalique. Nouveaux cristallins ne se formaient que si l'ectoderme céphalique était inclus avec la vésicule optique et si les vésicules étaient prélevées des jeunes embryons. On peut conclure que les nouveaux cristallins se forment dans l'ectoderme céphalique par induction. Nous n'avons trouvé aucune évidence de régénération du cristallin des tissus de l'oeil.

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This work was supported by a grant from the National Research Council of Canada to D. J. McCallion.     

Inhibition ofDugesia tigrina auricle regeneration by inhibitors of polyamine synthesis

Summary Results are presented that indicate polyamine synthesis inhibitors increase the flatwormDugesia tigrina's auricle regeneration time. This study serves as evidence that endogenous putrescine, spermidine, and spermine are necessary for the flatworm regeneration process.     

Remodeling and dedifferentiation of adult cardiomyocytes during disease and regeneration

Cardiomyocytes continuously generate the contractile force to circulate blood through the body. Imbalances in contractile performance or energy supply cause adaptive responses of the heart resulting in adverse rearrangement of regular structures, which in turn might lead to heart failure. At the cellular level, cardiomyocyte remodeling includes (1) restructuring of the contractile apparatus; (2) rearrangement of the cytoskeleton; and (3) changes in energy metabolism. Dedifferentiation represents a key feature of cardiomyocyte remodeling. It is characterized by reciprocal changes in the expression pattern of “mature” and “immature” cardiomyocyte-specific genes. Dedifferentiation may enable cardiomyocytes to cope with hypoxic stress by disassembly of the energy demanding contractile machinery and by reduction of the cellular energy demand. Dedifferentiation during myocardial repair might provide cardiomyocytes with additional plasticity, enabling survival under hypoxic conditions and increasing the propensity to enter the cell cycle. Although dedifferentiation of cardiomyocytes has been described during tissue regeneration in zebrafish and newts, little is known about corresponding mechanisms and regulatory circuits in mammals. The recent finding that the cytokine oncostatin M (OSM) is pivotal for cardiomyocyte dedifferentiation and exerts strong protective effects during myocardial infarction highlights the role of cytokines as potent stimulators of cardiac remodeling. Here, we summarize the current knowledge about transient dedifferentiation of cardiomyocytes in the context of myocardial remodeling, and propose a model for the role of OSM in this process.     

Cell cycle changes after denervation of the newt limb regenerate,studied in vitro

Summary The proliferation of the mesenchyme of medium bud stage blastemas ofPleurodeles, measured by³H-thymidine incorporation and mitotic index, decreases about 40–50% under denervated conditions when cultivated in vitro for 4 days; epidermis is not affected in this case. Autoradiography of blastemas after³H-thymidine long term labeling shows that 3/4 of the mesenchymal cells and 1/4 of the epidermal cells are cycling when the blastema is innervated; there is no significant change of these percentages when the blastema is denervated. The results show, contrary to in vivo experiments, that denervation does not provoke an exiting from the cell-cycle but only lengthening of the cycle of the mesenchymal cells (probably of the G₁ phase).     

Nuclear uptake of methionine-S35 in the newt embryo

Zusammenfassung In der vorliegenden Arbeit wird die Aufnahme von in DL-methionin enthaltenem S³⁵ durch die Zellkerne des Mesoderms und der Neuralplatte des Amphibien-Embryos beschrieben. Es wird auf die Ähnlichkeit hingewiesen, die mit der Aufnahme von in Glykokoll enthaltenem C¹⁴ besteht.     

Effects of tricaine methane sulphonate (M.S. 222) on the blood glucose levels in adult salamanders (Diemicytlus viridescens)

Summary Exposure to M. S. 222 results in hyperglycemia in adult newts (Diemicytlus viridescens). A combination of higher anesthetic concentrations with reduced exposure periods reduces the magnitude of this form of stress response.This work was supported by National Research Council of Canada Grant No. A9753 to S. Vethamany-Globus and No. A6933 to M. Globus.     

Mast cells and histamine in a newt,Triturus pyrrhogaster boié

Zusammenfassung Es wird nachgewiesen, dass die Mastzellen vonTriturus pyrrhogaster Boié kein Histamin enthalten, sie also im Gegensatz zur allgemeinen Annahme keine Histamozyten sind. Dieser Befund wurde sowohl biologisch am Meerschweinchendarm durch Extraktion des Histamins mit Hilfe der Codeschen Methode als auch durch den histochemischen Histaminnachweis mito-Phthalaldehyd an verschiedenen Geweben bestätigt.