Intercalary regeneration in the amphibian limb and the rule of distal transformation

Development ◽  
1980 ◽  
Vol 56 (1) ◽  
pp. 201-209
Author(s):  
M. Maden
Keyword(s):  
Normal Tissue ◽  
Sole Source ◽  
Black And White ◽  
Intercalary Regeneration ◽  
Proximal Stump ◽  
Reversed Polarity

The applicability to the amphibian limb of the rule of distal transformation, which states that tissue from any level can only become more distal, has been tested during intercalary regeneration following various types of shift-level transplantation. Following the grafting of distal blastemas to proximal levels, such that part of the presumptive pattern is missing, complete limbs nevertheless formed (Series 1). That the intercalated tissue arose entirely from the stump was shown by exchanging blastemas between black and white animals. When the proximal stump was irradiated and its contribution eliminated, intercalary deletions were produced (Series II). This was not due to the inability of irradiated and normal tissue to communicate since irradiated distal blastemas grafted onto proximal stumps still stimulated intercalary regeneration (Series III). When proximal blastemas were grafted to distal levels intercalary regenerates were obtained in about 20% of the cases (Series IV) and under these circumstances the grafted blastema was the sole source of intercalated tissue. The precise structure of these intercalated elements was impossible to ascertain, but it is suggested that they might be of reversed polarity as found in insects. These results are discussed in relation to similar experiments on the insect limb.

The polarity of the dental lamina in the regenerating salamander jaw

Development ◽  
1973 ◽  
Vol 30 (3) ◽  
pp. 635-646
Author(s):  
Heber T. Graver
Keyword(s):  
Normal Tissue ◽  
Ambystoma Maculatum ◽  
Dental Lamina ◽  
Reversed Polarity ◽  
The Right ◽  
Anterior Direction ◽  
Anterior Posterior

In ¼ and ½ amputated lower jaws of larval Ambystoma maculatum the dental lamina (DL) is replaced from both the anterior and posterior ends of the regenerate area, while in adult Triturus viridescens the DL is regenerated from the posterior stump tissues only. One-fourth and ½ mandibular jaw amputations were performed in such a manner that a short stump of jaw, devoid of DL, remained. Larvae exhibited a posterior regrowth of the DL, while in adults the lamina accumulated at the edge of the regenerate but did not enter the new tissue. Transplantation of a section of jaw from the left to the right side of the mandible resulted in the DL of the inserted piece having a reversed polarity in its new position. In both larval and adult forms, the DL of the transplant established connexions both anteriorly and posteriorly with lamina present. Transverse amputations through the inserted piece resulted in regeneration from the DL in the transplant in an anterior direction. Transplantation of a section of edentulous tissue into normal jaw tissue of the opposite side, or ttansplantation of a section of normal tissue into the edentulous area of the opposite side resulted in no anterior of posterior regrowth of the DL into the edentulous area. Collectively the results indicate that no anterior–posterior polarity exists in the DL of the larval salamander jaw, since regeneration can occur equally well in both directions. The DL of the adult salamander jaw exhibits an anterior–posterior polarity allowing for regrowth in an anterior direction only.

Nematocyte migration in hydra: evidence for contact guidance in vivo

1980 ◽  
Vol 41 (1) ◽  
pp. 33-51
Author(s):  
R.D. Campbell ◽  
B.A. Marcum
Keyword(s):  
Normal Tissue ◽  
Movement Pattern ◽  
Time Lapse ◽  
Contact Guidance ◽  
Experimental Deformation ◽  
Reversed Polarity ◽  
Bidirectional Movement ◽  
Whole Mounts

Nematocytes rapidly emigrate from normal tissue implanted into an epithelial hydra, which lacks its own nematocytes. We observed emigrating nematocytes, both in time-lapse movies and in fixed whole mounts, to learn what controls directionality. The cells migrate at speeds of 10–30 microns/min with a pseudopod forward and the capsule trailing. Migration is aligned parallel to the polyp axis, but cells move both proximally and distally and often shuttle back and forth. Thus, migration is strongly bidirectional, with a slight distal bias since at any time more cells are moving towards the tentacles. Nematocytes freely migrate through tissue of reversed polarity. No evidence was found for a chemotactic stimulus emitted from the tentacles. The bidirectional movement pattern appeared to be imposed by epithelial muscle processes, which form an axial, fibrous mat on which nematocytes migrate. Experimental deformation of the muscle alignment results in a corresponding deformation of nematocyte migration. Thus, nematocyte migration appears to be bidirectionally oriented through contact guidance by epithelial muscle processes.

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