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  • 1
    Electronic Resource
    Electronic Resource
    Nerve-independent DNA synthesis and mitosis in regenerating hindlimbs of larval Xenopus laevis (1992)
    Springer
    Development genes and evolution 201 (1992), S. 128-133 
    Details
    ISSN: 1432-041X
    Keywords: Xenopus laevis ; DNA synthesis ; Mitosis ; Limb regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Xenopus laevis larvae at stage 52–53 (according to Nieuwkoop and Faber 1956) were subjected to amputation of both limbs at the thigh level as well as to repeated denervations of the right limb. Results obtained in larvae sacrificed during wound healing (1 after amputation), blastema formation (3 days) and blastema growth (5 and 7 days) showed that denervated right limbs have undergone the same histological modifications observed in innervated left limbs and have formed a regeneration blastema consisting of mesenchymal cells with a pattern of DNA synthesis and mitosis very similar to that in presence of nerves. Also, the patterns of cellular density in regenerating right and left limbs were very similar. On the whole, the data here reported show a highly remarkable degree of nerve-independence for regeneration in hindlimbs of larval Xenopus laevis at stage 52–53 and lend some substance to the hypothesis that, in early limbs, there would exist trophic factors capable of replacing those released by nerves, promoting DNA synthesis and mitosis in blastemal cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188710
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  • 2
    Electronic Resource
    Electronic Resource
    Lens formation from cornea implanted into amputated hindlimbs of Xenopus laevis larvae requires innervation or proliferating cell populations in the stump (1996)
    Springer
    Development genes and evolution 205 (1996), S. 443-449 
    Details
    ISSN: 1432-041X
    Keywords: Xenopus laevis ; Limb ; Lens formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The capacity of amputated early and late limbs of larval Xenopus laevis to promote lens-forming transformations of corneal implants in the absence of a limb regeneration blastema has been tested by implanting outer cornea fragments from donor larvae at stage 48 (according to Nieuwkoop and Faber 1956), into limb stumps of larvae at stage 52 and 57. Blastema formation has been prevented either by covering the amputation surface with the skin or by reconnecting the amputated part to the limb stump. Results show that stage 52 non-regenerating limbs could promote lens formation from corneal implants not only when innervated but also when denervated. A similar result was observed in stage 57 limbs where blastema formation was prevented by reconnecting the amputated part to the stump. In this case, relevant tissue dedifferentiation was observed in the boundary region between the stump and the autografted part of the limb. However, stage 57 limbs, where blastema formation was prevented by covering the amputation surface with skin, could promote lens formation from the outer cornea only when innervated. In this case, no relevant dedifferentiation of the stump tissues was observed. These results indicate that blastema formation is not a prerequisite for lens-forming transformations of corneal fragments implanted into amputated hindlimbs of larval X. laevis and that lens formation can be promoted by factors delivered by the nerve fibres or produced by populations of undifferentiated or dedifferentiated limb cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377225
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of thyroxine and propyl-thiouracil on hindlimb regeneration of larvalXenopus laevis (1994)
    Springer
    Development genes and evolution 203 (1994), S. 205-214 
    Details
    ISSN: 1432-041X
    Keywords: Xenopus laevis ; thyroxine ; propyl-thiouracil ; limb regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Xenopus laevis larvae at stage 53 and 55 (according to Nieuwkoop and Faber 1956) were subjected to amputation of one or both hindlimbs and reared either in thyroxine (T4) 2.5 to 10 μg/l or in propyl-thiouracil (PTU) 0.01%. Results have shown that when the limb was amputated through a nearly undifferentiated region (tarsalia level, at stage 53) or through a differentiating region (tarsalia level, at stage 55), T4 accelerated the regenerative process and enhanced the mitotic and labelling indices of blastemal cells, when compared with controls. However, PTU delayed the regenerative process and lowered the mitotic and labelling indices. When the limb was amputated through an almost differentiated region (mid-thigh level, at stage 55), T4 inhibited the conic blastema formation, while PTU did not significatively influence limb regeneration. T4 did not modify the morphogenetic properties of the regenerative blastemata, which are characteristic of the developmental stage and the degree of differentiation of the limb tissues at the amputation level. On the whole, the data show that T4, besides being indirectly responsible for the decline of the limb regenerative capacity in a proximodistal direction by promoting limb differentiation, also exerts a direct effect on the regenerative process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00636336
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  • 4
    Electronic Resource
    Electronic Resource
    The relationship of innervation and differentiation to regenerative capacity in the reamputated hindlimb of larval Xenopus laevis (1996)
    Springer
    Development genes and evolution 205 (1996), S. 252-259 
    Details
    ISSN: 1432-041X
    Keywords: Xenopus laevis ; Limb regeneration ; Reamputation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Regenerated hindlimbs of larval Xenopus laevis were reamputated at critical larval stages and levels, viz when amputation of the control limb at the same larval stage and level is followed by reduced regeneration. Reamputations were performed at the level of (1) the original plane of amputation, (2) the early regenerate (cone/palette stage), (3) the late regenerate (digit stage). Reamputation increased both the percentage rate of regeneration and the morphological complexity of the regenerates in all experimental series. Cell counts in lateral motor columns and spinal ganglia innervating the hindlimb, together with histological observations and mitotic index and labelling index determinations in reamputated and control limbs showed that improved regeneration in the reamputated limb was related to an increase in undifferentiated and proliferating cells in the stump. We did not find any evidence suggesting that renewed regeneration in reamputated anuran limbs results from an increase in innervation, as has previously been hypothesized. We support our conclusions by demonstrating an improvement in regenerationen in the reamputated and denervated hindlimbs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365803
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  • 5
    Electronic Resource
    Electronic Resource
    Xenopus laevis tadpole limb regeneration in vivo and in vitro: thyroxine directly promotes blastemal cell proliferation and morphogenesis (1995)
    Springer
    Development genes and evolution 204 (1995), S. 223-228 
    Details
    ISSN: 1432-041X
    Keywords: Xenopus laevis ; Thyroxine ; Propyl-thiouracil ; Limb renegeration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Regeneration in hindlimbs of Xenopus laevis larvae which were amputated at stage 53 and 55 through the tarsalia region is promoted by thyroxine (T4), while propyl-thiouracil (PTU) inhibits regeneration when compared to controls. In this paper, by in vivo and in vitro experiments, we demonstrate that the promoting effect of T4 on the regenerative processes of larval X. laevis hindlimbs is a direct effect of this hormone on the blastemal cells. By contrast, the inhibitory effect of PTU on the regenerative process is not due to a direct effect on blastemal cells or to a general toxic effect on the treated larvae, but is related to hypothyroidism induced by the drug. We find that: (i) an increase in blastemal cell proliferation is observed not only in blastemata of T4-treated larvae, but also in blastemata cultured in vitro in a medium supplemented with T4; (ii) the renegerative process is accelerated not only in larvae reared in T4 but also in larvae submitted to a combined treatment of T4 and PTU; (iii) inhibition of cell proliferation is observed in blastemata of PTU-reared larvae but not in blastemata cultured in vitro in a medium supplemented with PTU. Experiments on thyroidless larvae (which were submitted to transplantation of hindlimbs from larvae at stages 53 and 55 followed by amputation of their own right hindlimb and the transplanted limbs) have shown that without thyroid hormone the regenerative process is arrested at cone stage and the promoting effect of T4 treatment is dependent on limb stage and amputation level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208489
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  • 6
    Electronic Resource
    Electronic Resource
    Routine laboratory analysis for preclinical research in the pharmaceutical industry in Italy: An overview (1994)
    Springer
    Comparative clinical pathology 4 (1994), S. 136-142 
    Details
    ISSN: 1433-2981
    Keywords: Clinical chemistry ; Haematology parameters ; Procedures ; Survey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Last year, the GEET (Italian Association for Haematology and Haematochemistry in Toxicology), which covers most pharmaceutical companies and contract laboratories in Italy, carried out an explorative survey on the analytical procedures commonly used for measuring haematological and clinicochemical parameters in laboratory animals. The aim of this survey was to check the differences between methods and procedures in order to evaluate a potential standardisation among laboratories. The GEET members provided information on the experimental procedures employed and parameters evaluated in their Research Laboratories for dog and rat samples. The variables considered in this paper are blood collection (fasting, anaesthesia, site of withdrawal, anticoagulants), urine collection (water load, preservatives), nature of sample, sample storage, analytical methods and equipment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00798353
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