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Biomedical subjects

D J Donaldson

Publications and source records attributed to D J Donaldson.

43 records · Page 3Linked to original sources
PubMed1976

X-ray induced inhibition of DNA synthesis and mitosis in internal tissues during the initiation of limb regeneration in the adult newt.

Left front limbs of adult male newts were given 2000r of X-irradiation at least four weeks prior to amputation of both forelimbs. Internal stump tissues were evaluated for the ability to incorporate 3H-thymidine and accumulate colchicine-blocked mitotic figures. In otherwise uninjured limbs, irradiation stimulated low levels of DNA synthesis which did not increase significantly after amputation. Thus, as soon as DNA synthesis increased significantly in normal limbs as a result of amputation, it was demonstrably higher than in X-rayed limbs. In general, mitotic activity in both groups reflected the DNA synthetic rates. Since others have shown that denervation at the time of amputation blocks subsequent mitosis in internal stump tissues yet allows normal levels of DNA synthesis for eight days, we conclude that X-irradiation and denervation prevent cell division in potential blastema cells by different mechanisms.

Animals↗
PubMed1975

Dedifferentiation and mitotic activity in amputated newt tails locally deprived of the spinal cord (including a note on effects of amputation level on mitosis).

The spinal cord of freshly amputated newt tails was displaced cranially by pushing several paraplast chips into the spinal canal with a glass needle. That part of the canal formerly occupied by the spinal cord was then packed with paraplast. Tails treated in this manner failed to regenerate, forming no more than a millimeter of new tissue with little or no cartilage and muscle. Dedifferentiation and early mitotic activity, however, was normal, indicating that the spinal cord exerts its effect on tail regeneration in the later stages. Amputation through the proximal region of a vertebra led to a significantly lower mitotic rate at four days than did amputation through the distal region, a situation contrary to the principle that during regeneration, elongation rate is gennerally faster from proximal than distal levels.

Amputation, Surgical↗
PubMed1975

Cancer-related aspects of regeneration research: a review.

Tissue regeneration is simply the replacement of lost cells of a tissue by those remaining. Epimorphic regeneration involves dedifferentiation of many tissues and their organization into a blastema which eventually differentiates into the missing part, usually an appendage. A detailed comparison of the cell membrane changes occurring in epimorphic regeneration, tissue regeneration and cancer can contribute to greater understanding of the differences between normal and tumor cells. Further, there is evidence that epimorphic regeneration fields may in some instances suppress tuomr induction and control existing tumors. This influence may be mediated by bioelectric fields, which are ubiquitous in nature and appear to control many cellular events. Disruption of these bioelectric fields suppresses epimorphic regeneration and may lead to cancer in mammals, while applied electric fields alter regenerative events and cause tumor regression.

Amphibians↗
PubMed1974

Protein patterns during regeneration and wound healing in the adult newt: a comparative study using gel electrophoresis.

Gel electrophoresis was performed on tissue extracts made from regenerating tails, limbs and deep razor blade wounds to the back of adult newts. In general, 3 types of changes appeared in posttrauma gels: decrease in density of some bands, increase in others, and "new" bands. Patterns were very similar in limb and tail regeneration suggesting that the two processes do not differ significantly with regard to alterations in the major soluble proteins. The patterns further indicated that certain wound-healing events also occur in regeneration. Some of these events are prolonged in the latter, while others are long-lasting in both. The results also suggest the existence of a regeneration-specific protein.

Amputation, Surgical↗