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E Lheureux

Publications and source records attributed to E Lheureux.

7 recordsLinked to original sources
PubMed1990

Cell interactions and regeneration control.

This paper is a review of the main findings of our laboratory on the control of regeneration by cell interactions. These include results related to the role of both cell contact and local soluble factors in regeneration of the legs of insects and newts and of the parapodia and segments of nereis. The pattern of these structures is considered to be defined by positional information distributed as longitudinal and transverse positional value sequences carried by epidermal (insect) or mesenchymal (newt) cells. By associating tissues to create transverse and longitudinal discontinuities in these sequences, single or multiple regenerating structures were obtained. These structures are formed by the intercalation of cells characterized by intermediate positional values which fill the gap between the tissues in contact. Positional information may also be changed during regeneration by the nerve cord in nereis and retinoids in the newts. We describe additional cases where morphogenesis occurs without any overt discontinuity in positional information, such as from a locally injured or non-injured insect trochanter, or after deflection of nerves in nereis and newt. Regeneration following an amputation may be considered as a special case of intercalary regeneration, the first stage being the juxtaposition of normally non-contiguous cells resulting in a longitudinal or/and a transverse gap. We also report studies on local factors produced by nerves and the blastema during newt limb regeneration. The nerve factor is necessary for the division of blastemal cells. After denervation, mesenchyme differentiates in an abnormal way. The mitogenic signal from the nerves is mediated by the PKC pathway. Its production is enhanced by regeneration of cut nerve fibers. The blastema also produces growth factors. We show that the epidermal cap and mesenchyme contain acidic FGF-like factor, and that the proliferating mesenchyme stimulates nerve fibers to regrow into the blastema.

Amphibians↗
PubMed1988

The irradiated epidermis inhibits newt limb regeneration by preventing blastema growth. A histological study.

It has been established that X-ray irradiation localized to a forelimb or entire irradiation of premetamorphic Pleurodeles larvae prevented limb regeneration. Transplantation of non-irradiated skin, dermis or muscle to limb stumps of locally irradiated newts was sufficient to allow a blastema to develop. Transplantation of the same tissues to limb stumps of entirely irradiated newts yielded different results with the different graft types. Skin graft allowed a normal blastema to be established but dermis or muscle grafts did not. In order to define more precisely the role played by the epidermis in the establishment of a blastema, and in the growth of a regenerate, different combinations of limb tissues, either irradiated or not, were carried out at the level of amputated limb stumps. At four different times (8-10 days; 13-15 days; 20-23 days; 30 days or more) after amputation the stumps were examined in histological longitudinal sections to study the first events of regeneration, that is dedifferentiation and growth. Dedifferentiation occurred in both normal and irradiated tissues of mesodermal origin. The healthy mesenchymal cells began dividing and formed a growing blastema only when associated with a non-irradiated epidermis. Healthy mesenchymal cells covered with an irradiated epidermis exhibited a few mitoses after dedifferentiation, but the mitotic figures became rarer and rarer until the animals died. The lack of dense accumulation of blastemal cells in such limb stumps suggested that the healthy epidermis allows the mesenchymal cells to divide actively to constitute a growing blastema. Hence, X-ray irradiation seems to be responsible for the loss of such an epidermal mitogenic influence on the underlying mesenchymal cells.

Animals↗
PubMed1986

The effects of two retinoids on limb regeneration in Pleurodeles waltl and Triturus vulgaris.

The effects of two vitamin A analogues, retinol palmitate and retinoic acid, on pattern formation during limb regeneration in larvae of two European newts, P. waltl and T. vulgaris are described. The response of the regenerating limb to retinoid treatment differed according to the larval stage of development for P. waltl. Young larval limbs, which were anterior limb buds at the time of amputation, duplicated transversely while limbs of older larvae duplicated proximodistally. Proximodistal duplications were usually limited to the production of supernumerary carpals or a second zeugopod. Complete limbs regenerating from a distal amputation plane were rarely seen. T. vulgaris larvae regenerated limbs with either one or the other type of duplication, but never both on the same limb, at all larval stages tested. When larval P. waltl were kept in normal laboratory light during the treatment with retinol palmitate suspended in the rearing water the percentage of limbs which duplicated was very small for young larvae and increased with the age of the larvae used. Keeping the animals in the dark during the treatment period greatly increased the percentage of duplicate limbs obtained on the young larvae but not on the older larvae. This result is discussed in terms of the photodegradation of the retinoid and the length of the sensitive period for the regenerating limb. A dose-response relationship between the dose of retinol palmitate and either the percentage of limbs duplicated or the degree of duplication was not found. Such a relationship, however, was observed when retinoic acid was injected intraperitoneally into stage-54+ P. waltl larvae. Additionally, this technique revealed a peak of sensitivity to retinoic acid on the 6th day after amputation. Limb regeneration in older larvae was temporarily blocked by retinoid treatment. The limbs showed little or no regression and began blastemal development shortly after the treatment ended. Limbs of young larvae, however, often regressed. Such regressions were followed by blastemal formation and middle- to late-bud blastemas were found at the end of 11 or 14 days treatments with retinol palmitate.

Animals↗
PubMed1983

Replacement of irradiated epidermis by migration of non-irradiated epidermis in the newt limb: the necessity of healthy epidermis for regeneration.

An X-irradiated newt limb is able to regenerate if non-irradiated skin as well as non-irradiated muscle is transplanted to the stump. Non-irradiated epidermis is brought to the stump with a skin graft but not with a muscle graft. In order to know whether limb regeneration required healthy epidermis or not, a triploid skin cuff was set at the most proximal level of an irradiated limb and muscle was transplanted to the level of the midforearm. The forearm was then amputated through the muscle graft. A cytophotometrical analysis of DNA content of the epidermis cell nuclei sampled from the skin of the regenerate was undertaken to detect a migration of triploid epidermal cells. The result was a complete replacement of diploid irradiated epidermis by triploid epidermis, during the six weeks necessary for regeneration. Another investigation consisted of detecting a possible migration of non-irradiated triploid epidermis along an irradiated limb which had not been amputated. Healthy epidermis was found to migrate distally and replace irradiated epidermis in three weeks. Previous experiments involving transplantation of a non-irradiated skin cuff or muscle to an irradiated limb stump were carried out again but on animals which had been entirely irradiated to prevent any extra healthy epidermis cells from contaminating the regenerating limb epidermis. A regenerate developed from the skin graft but not from muscle graft. It is concluded that healthy epidermis must be present on the limb stump to permit the blastema to develop.

Animals↗
PubMed1977

[Importance of limb tissue associations in the development of nerve-induced supernumerary limbs in the newt Pleurodeles waltlii Michah (author's transl)].

Brachial nerve tip deviation has been carried out at various points in the upper arm and close to the limb. Some associations of cutaneous or muscular tissue from two opposite sides - dorsal and ventral or anterior and posterior - of the upper arm were made at these points. Various degrees of development of the nerve-induced supernumerary limbs were observed. When a nerve deviation was not followed by grafting of tissue from the opposite side, the supernumerary limbs did not develop or were strongly hypomorphic. A normal limb to development can occur when tissues from opposite side are associated with the ones located at the nerve tip. Such associations allow a harmonious nerve-induced supernumerary limb to develop and consequently allow all transverse axes to be established. Orientation of nerve-induced supernumerary limbs is determined by the orientation of the tissues in the area of nerve deviation. In terms of positional information, since an absence of contact between tissues from two opposite sides results in a lack of normal development, we can conclude that positional values located on either side of, the centre of, at least, one transverse axis should be in contact to allow limb development, i.e. a regenerated limb or nerve-induced supernumerary limbs or supernumerary limbs. It appears that contact between such values along any transverse axis, under sufficient nervous stimulation may give rise to a supernumerary limb.

Animals↗