Symmetrical vascularization patterns in normal and retinoic acid treated limb regenerates of the axolotl, Ambystoma mexicanum

1998 ◽  
Vol 76 (9) ◽  
pp. 1795-1796 ◽  
Author(s):  
Steven R Scadding ◽  
Andrew Burns
Keyword(s):  
Retinoic Acid ◽  
Pattern Formation ◽  
Vascular System ◽  
Limb Regeneration ◽  
Ambystoma Mexicanum ◽  
Limb Pattern ◽  
Regeneration Blastema

The purpose of this investigation was to determine whether there were any asymmetries in the vascularization of the limb-regeneration blastema in the axolotl, Ambystoma mexicanum, that might be related to pattern formation, and to determine if retinoic acid could modify the vascular patterns of the blastema. We used acrylic casts of the vascular system of the limbs to assess the pattern of vascularization. We observed a very regular symmetrical arrangement of capillaries in the limb-regeneration blastema that did not appear to be modified by doses of retinoic acid sufficient to modify the limb pattern.

Citral, an inhibitor of retinoic acid synthesis, modifies pattern formation during limb regeneration in the axolotl Ambystoma mexicanum

1999 ◽  
Vol 77 (11) ◽  
pp. 1835-1837 ◽  
Author(s):  
Steven R Scadding
Keyword(s):  
Retinoic Acid ◽  
Pattern Formation ◽  
Limb Regeneration ◽  
Acid Synthesis ◽  
Ambystoma Mexicanum

While the effects of exogenous retinoids on amphibian limb regeneration have been studied extensively, the role of endogenous retinoids is not clear. Hence, I wished to investigate the role of endogenous retinoic acid during axolotl limb regeneration. Citral is a known inhibitor of retinoic acid synthesis. Thus, I treated regenerating limbs of the larval axolotl Ambystoma mexicanum with citral. The result of this inhibition of retinoic acid synthesis was that limb regeneration became extremely irregular and hypomorphic, with serious pattern defects, or was inhibited altogether. I conclude that endogenous retinoic acid plays an important role in pattern formation during limb regeneration.

Gap junctions in the limb regeneration blastema of the axolotl, Ambystoma mexicanum, are not distributed uniformly and are regulated by retinoic acid

1999 ◽  
Vol 77 (6) ◽  
pp. 902-909
Author(s):  
Leigh-Anne D Miller ◽  
Melissa L Farquhar ◽  
John S Greenwood ◽  
Steven R Scadding
Keyword(s):  
Retinoic Acid ◽  
Gap Junctions ◽  
Limb Regeneration ◽  
Ambystoma Mexicanum ◽  
Limb Bud ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Regeneration Blastema

Gap junctions are thought to play a role in pattern formation during limb development and regeneration by controlling the movement of small regulatory molecules between cells. An anteroposterior gradient of gap junctional communication that is higher posteriorly has been reported in the developing chick limb bud. In both the developing chick limb bud and the amphibian regenerating limb, an anteroposterior retinoic acid gradient is present, and this is also higher posteriorly. On the basis of these observations, we decided to examine the role of gap junctional communication in the regenerating amphibian limb. Gap junctions were observed in both the axolotl, Ambystoma mexicanum, limb regeneration blastema and cardiac tissue (as a positive control), using immunohistochemical labelling and laser scanning confocal microscopy. The scrape-loading/dye transfer technique for tracing the movement of a gap junction permeable dye, Lucifer yellow, showed that in blastemal epidermis there were nonuniform distributions of gap junctions in both the dorsoventral and anteroposterior axes of the blastema. Retinoic acid was found to increase gap junctional permeability in blastemal epidermis 48 h after injection and in blastemal mesenchyme 76 h after injection. The potential role of gap junctions during pattern formation in limb regeneration is discussed based on these results.

Retinoic Acid and Limb Pattern Formation in Cell Culture

1991 ◽  
pp. 105-113
Author(s):  
Hiroyuki Ide ◽  
Yasushi Ohkubo ◽  
Sumihare Noji ◽  
Shigehiko Taniguchi
Keyword(s):  
Cell Culture ◽  
Retinoic Acid ◽  
Pattern Formation ◽  
Limb Pattern

Skeletal patterns in the autopodium of native and regenerated limbs of the larval axolotl, Ambystoma mexicanum

1991 ◽  
Vol 69 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Steven R. Scadding
Keyword(s):  
Vitamin A ◽  
Significant Variation ◽  
Limb Regeneration ◽  
Ambystoma Mexicanum ◽  
Skeletal Patterning ◽  
Skeletal Pattern ◽  
Limb Pattern ◽  
Salamander Species

The purpose of this investigation was to study the autopodial skeletal patterns that are observed in native (never regenerated) and regenerated limbs of the larval axolotl, Ambystoma mexicanum. The axolotl is used widely in limb regeneration studies, and in the regenerating axolotl limb mesopodial patterns can be modified by such factors as vitamin A administration. It is also known that other salamander species show significant variation in autopodial skeletal patterning. Hence, it seemed important to determine the type and frequency of autopodial variants in both native limbs and those that have regenerated after amputation at either the stylopodial and zeugopodial levels. The results showed that native limbs exhibited a complete skeletal pattern in the majority of cases, but that variants involving loss of a phalange or reduction in the number of carpals or tarsals occurred frequently. Regenerated limb patterns were more variable than those seen in native limbs, and limbs regenerating from zeugopodial level amputations were more variable than those regenerating from stylopodial level amputation. The significance of these observations for the development and regeneration of limb pattern is discussed.

Use of retinoids to analyze the cellular basis of positional memory in regenerating amphibian limbs

1987 ◽  
Vol 65 (8) ◽  
pp. 750-761 ◽  
Author(s):  
David L. Stocum ◽  
Karen Crawford
Keyword(s):  
Retinoic Acid ◽  
Molecular Basis ◽  
Limb Regeneration ◽  
Molecular Property ◽  
Cell Recognition ◽  
Dorsoventral Axis ◽  
Modifying Agent ◽  
A Cell ◽  
Regeneration Blastema

Cells of the amphibian limb regeneration blastema inherit memories of their level of origin (positional memory) along the limb axes. These memories serve as boundaries of what is to be regenerated, thus preventing regeneration of any but the missing structures. Because of its importance in determining the boundaries of regenerate pattern, it is essential to understand the cellular and molecular basis of positional memory. One approach to this problem is to look for position-related differences in a cell or molecular property along a limb axis and then show, using an agent that modifies regenerate pattern, that the cell or molecular property and the pattern are coordinately modified. We have done this using retinoic acid (RA) as a pattern-modifying agent and an in vivo assay that detects position-related differences in a cell recognition–affinity property along the proximodistal (PD) axis of the regenerating axolotl limb. RA proximalizes positional memory in the PD axis, posteriorizes it in the anteroposterior axis, and ventralizes it in the dorsoventral axis. The level-specific PD cell recognition–affinity property is proximalized by RA, indicating that this property and positional memory are causally related. The effects of RA on positional memory may be mediated through a cellular RA-binding protein (CRABP), since the concentration of unbound (apo) CRABP molecules is highest during early stages of regeneration when the proximalizing effects of RA are greatest.

Effects of concanavalin A on limb regeneration in the axolotl Ambystoma mexicanum

1997 ◽  
Vol 75 (10) ◽  
pp. 1728-1732
Author(s):  
Steven R. Scadding
Keyword(s):  
Pattern Formation ◽  
Concanavalin A ◽  
Limb Regeneration ◽  
Ambystoma Mexicanum ◽  
Teratogenic Effect ◽  
Low Doses ◽  
Con A ◽  
Higher Doses

The purpose of this investigation was to determine the effects, if any, of concanavalin A (Con A) on the process of pattern formation during limb regeneration in the axolotl Ambystoma mexicanum. Con A was administered to regenerating axolotl forelimbs in a Hydron disk that released the Con A slowly over a period of time. The results indicate that Con A is teratogenic to the regenerating axolotl limb, causing reductions in the number, size, and quality of skeletal elements present, with increasing reductions and malformations as the dose is increased. Low doses resulted in a reduction in the number of carpals or phalanges. Higher doses resulted in more drastic malformations, including the absence of digits. The implications of this teratogenic effect of Con A on limb regeneration are discussed in the context of the possible mechanisms of pattern formation.

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