Search PubMed⌕ Search

Biomedical subjects

K Muneoka

Publications and source records attributed to K Muneoka.

At least 55 records · Page 3Linked to original sources
PubMed1987

Intercalation and the cellular origin of supernumerary limbs in Xenopus.

The hypothesis that a specialized polarizing zone controls the pattern of the anterior-posterior axis during limb development in Xenopus has been tested by analysing the cellular contribution to supernumerary limbs. Supernumerary limbs were generated by grafting hindlimb buds contralaterally between X. borealis and X. laevis to appose anterior and posterior limb tissues. Cells derived from these two species of Xenopus are readily identified by staining with quinacrine. The analysis of cellular contribution showed that supernumerary limbs consist of approximately half anterior-derived (57%) and half posterior-derived (43%) cells. These data are not consistent with the polarizing zone theory but are consistent with the hypothesis that both supernumerary limbs and normally developing limbs arise from intercalary interactions between limb bud cells with different positional values.

Animals↗
PubMed1986

Mouse embryos develop normally exo utero.

Surgical procedures are described which permit direct experimental access to postimplantation mouse embryos. These procedures arose from our finding that development proceeds normally to term after embryos have been released from the confines of the uterus, while remaining attached to it via the placenta. Embryos continue to develop exo utero, within the abdominal cavity of the mother, and are capable of surviving a variety of different surgical manipulations. This finding opens the way for experimental analyses of mouse development in vivo.

Animals↗
PubMed1986

Intrinsic control of regenerative loss in Xenopus laevis limbs.

The regenerative capability of Xenopus laevis hindlimbs was studied at different developmental stages. Three types of surgical deletion of the autopod were performed: simple amputations, 3-digit wedge-shaped deletions and 1-digit wedge-shaped deletions. The frequency of regenerative response and the digital patterns of the regenerates were analyzed. Regenerative capacity declines with developmental stage for all three types of deletions. For simple amputations this decline occurs in an orderly manner with the failure of anterior digits to regenerate at progressively later stages. A comparison between 1-digit and 3-digit deletions shows that for all stages of development, 3-digit deletions regenerate better than one-digit deletions. These data indicate that the amount of tissue removed is directly related to whether a regenerative response is observed. At any given stage, larger deletions are more likely to regenerate than smaller ones. These results are discussed with regard to the mechanisms by which growth during regeneration is controlled.

Animals↗
PubMed1986

The migration of dermal cells during blastema formation in axolotls.

Using the diploid/triploid cell marker in the axolotl (Ambystoma mexicanum) we have examined the movement of cells from the dermis into the early limb blastema. Cells of dermal origin begin to migrate beneath the wound epithelium at about 5 days postamputation, and by 10 days they are widely distributed across the amputation surface. By 15 days, a dense accumulation of blastema cells is present beneath the apical cap, and these cells are preferentially oriented in a circumferential direction. These results are discussed in relation to previous studies showing that the progeny of dermal cells become widely distributed during regeneration, and that cells of dermal origin are a major source of blastema cells. The results are also discussed in relation to ideas about how growth and patterning of the new appendage occur.

Ambystoma mexicanum↗
PubMed1986

Cellular contribution from dermis and cartilage to the regenerating limb blastema in axolotls.

Using the triploid/diploid cell marker in the axolotl, Ambystoma mexicanum, we have analyzed the extent to which cells derived from the dermis and the skeleton contribute to the regenerating limb blastema. We found that dermal cells contribute 43% of the blastemal cell population whereas cells derived from skeletal tissue contribute only 2%. When compared to the availability of cells at the plane of amputation, dermal cells overcontribute by greater than twofold whereas skeletal cells undercontribute by several-fold. These data correlate with the effects that these two tissues have on the formation of the limb pattern during regeneration; dermis has a dramatic influence on pattern and skeletal tissue has virtually no effect. It is suggested that the fibroblasts present in the dermis and in other parts of the limb form virtually all of the mesodermal tissues in the regenerate with the exception of the muscle.

Ambystoma mexicanum↗
PubMed1986

Pattern discontinuity, polarity and directional intercalation in axolotl limbs.

Axolotl limb stumps with dorsal-ventral confrontations between digits 2 and 3 but with a normal anterior-posterior pattern were created by grafting between contralateral limbs. Graft and host differed in ploidy to permit a determination of the origin of cells in the regenerated limb. After regeneration, limbs were analysed for skeletal and muscle patterns and for the distribution of marked cells in the regenerate. Regenerated limbs showed varying degrees of abnormality in their dorsal-ventral organization. Following regeneration, the original dorsal-ventral discontinuities were in some cases maintained and in others resolved. The maintenance or resolution of pattern discontinuities occurred in a position-dependent manner. Cell marker analysis indicates a relationship between the resolution of discontinuities and the extent to which cells become displaced across the original graft-host interface. These data lend support to the suggestion that circumferential intercalation is directionally biased.

Ambystoma↗
PubMed1985

A quantitative analysis of regeneration from chimaeric limb stumps in the axolotl.

We have analysed the cellular contribution and cellular displacement which occur during regeneration from chimaeric (half triploid, half diploid) lower arms in the axolotl. In general both anterior and posterior halves contribute approximately 50% of the regenerated limb cells. Deviations from equal contribution were observed only when anterior tissue was grafted, suggesting that anterior tissue is more sensitive to grafting operations. Approximately 25% of all cells in the regenerated limb were found to be displaced to the opposite side of the limb. Cellular displacement was not random; 63% of all displaced cells were found in regions adjacent to the tissue of origin.

Ambystoma↗
PubMed1984

Cellular contribution to supernumerary limbs in the axolotl, Ambystoma mexicanum.

Using the triploid cell marker, the cellular contribution from graft and stump to the supernumerary limbs which result from controlateral grafts of limb buds and regeneration blastemas in the axolotl has been analyzed. Grafts were made so as to appose anterior and posterior limb positions. Overall, the contribution from graft and stump tissue was found to be approximately equal although the position of the boundary between the two was variable from limb to limb. This result is consistent with models which suggest that intercalary regeneration is the driving force for patterning of the vertebrate limb. In addition, the pattern of cellular contribution to supernumerary limbs was consistently found to be asymmetrical in the dorsal-ventral axis. Hence, posterior limb tissue predominantly contributed cells to the posterior and dorsal part of the supernumerary limb whereas anterior limb tissue predominantly contributed cells to the anterior and ventral part of the supernumerary limb. The reason for this asymmetrical pattern remains unknown, but we suggest that it might result from a directional bias in intercalary regeneration, similar to that observed during intercalation in the proximal-distal axis of the urodele limb. Using the triploid cell marker in conjunction with a black/white pigmentation marker, the relationship between the cellular contribution boundary and the pigmentation boundary in supernumerary limbs has also been analyzed. It has been found that the positions of the two boundaries do not coincide, a result which suggests that the eventual location of pigment cells is not a good indicator of the location of nonpigment cells derived from graft and stump.

Aging↗
PubMed1984

Cellular contribution to supernumerary limbs resulting from the interaction between developing and regenerating tissues in the axolotl.

The relationship between limb development and limb regeneration is considered with regard to the mechanisms by which pattern is established during limb outgrowth. In a previous paper (Muneoka, K. and Bryant, S. V. 1982 Nature (London) 298, 369-371) the interaction between cells from the developing limb bud and the regenerating limb blastema was found to result in the production of organized supernumerary limb structures. In this paper the relative cellular contribution from developing and regenerating cells to supernumerary limbs resulting from contralateral grafts between limb buds and blastemas has been analyzed using the triploid cell marker in the axolotl. Results show that there is substantial participation from both developing and regenerating limb cells to all supernumerary limbs analyzed. These data lend further support to the hypothesis that developing and regenerating limbs utilize the same patterning mechanisms during limb outgrowth. This conclusion is discussed in terms of patterning models for developing and regenerating limbs and it is proposed that the rules of the polar coordinate model can best explain the behavior of cells during limb development as well as limb regeneration.

Ambystoma↗
PubMed1984

Improved techniques for use of the triploid cell marker in the axolotl, Ambystoma mexicanum.

Techniques for using the triploid cell marker for studying cell lineage during the development and regeneration of the axolotl limb are described. Triploid animals possess cells with three nucleoli while diploid animals possess cells with two nucleoli. We have developed a technique for isolating the limb dermis as a sheet of cells for whole-mount analysis of cellular ploidy. Whole-mount tissue preparations as well as paraffin-embedded sectioned tissues were stained specifically for nucleoli with bismuth. Cell counts from a number of triploid and diploid dermal preparations show that (1) diploid dermal cells never possess three nucleoli, (2) the frequency of trinucleolate cells in whole-mount triploid dermal preparations is not 100% but varies between animals from 30 to 76%, (3) within a single triploid animal, the frequency of trinucleolate cells in different dermal preparations is constant. These data establish the usefulness of this technique and emphasize the need for appropriate control cell counts when using the triploid cell marker in the axolotl.

Ambystoma↗
PubMed1982

Evidence that patterning mechanisms in developing and regenerating limbs are the same.

Some amphibians have the ability to form new limbs throughout their lives. The essential similarity between limb regeneration and the original development of the limb is that both involve the elaboration of new patterns of structures. While some investigators believe that the two developing systems use similar mechanisms to generate the limb pattern, others have stressed the basic differences in developing the regenerating limbs, and have concluded that different mechanisms exist. Both developing and regenerating urodele limbs can be caused to form supernumerary parts following tissue misalignment so that cells from normally disparate positions within the limb circumference confront each other (developing limbs; regenerating limbs, see ref. 11 for review). If similar mechanisms are operating, the developing limb should respond to grafts of regenerating limb tissue, and vice versa, by forming supernumerary outgrowths. If different mechanisms are operating, either the grafts should fail or the response should be disorganized. Our results with the axolotl Ambystoma mexicanum suggest that the patterning mechanisms are the same.

Ambystoma↗