Abstract
A stathmokinetic method has been used to determine the cell cycle parameters, particularly the potential tumour doubling time, of a murine fat pad sarcoma. Additional information has been obtained by determining the percentage of labelled mitoses (PLM). A technique which simultaneously demonstrates autoradiographically labelled S phase nuclei and histochemically localized acid phosphatase activity has also been used at light microscope level to compare these parameters: acid phosphatase activity was demonstrated in tumour cells and macrophages. Single cell deletion by apoptosis has been investigated as distinct from necrosis. Condensed, dying apoptotic cells, have been found in proliferative areas of tumour that are not under physiological stress. The analysis of apoptosis indicated a previously unsuspected variation in apoptotic activity with tumour weight. Cell death by apoptosis initially rose as the tumour grew, but after the tumour reached a threshold weight it declined dramatically, and finally remained stable. This may reflect an initial attempt at autoregulation of tumour size which ultimately fails. Apoptosis was estimated to account for an average of 7% of the total cell loss rate in this tumour.
Highlights
The murine fat pad sarcoma was studied in 9-week old, female, CBA/Ht mice; tumours were supplied and implanted by the CRC Gray Laboratory
Histological observations Ischaemic necrotic tissue was found surrounded by proliferative cells (Figure 1), not necessarily at the geographical centres of the tumours
Within the necrotic zones themselves cell death was too extensive to allow for unequivocal identification of its various modes
Summary
The murine fat pad sarcoma was studied in 9-week old, female, CBA/Ht mice; tumours were supplied and implanted by the CRC Gray Laboratory. Each animal had been implanted with 0.3 ml of cell suspension of the donor tumour at 106cells ml, obtained freshly from a suitable CBA/Ht mouse. The inoculum was made by tumour homogenization in a tissue grinder and the transplant was positioned on the rear flank of the animals, dorsolaterally, after shaving the skin. To estimate the tumour growth rate, growth curves were constructed from data obtained from 29 mice over a 21-day period. The gross weight of tumour material and the net tumour weight were measured after the death of each animal. Gross weight was the total tumour weight, as excised, and the net weight concerned as far as possible, proliferative tumour material only, after removal of overt necrotic matter
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