226
LEO LEME2
Only three promyelocyte (neutrophil) mitoses were encountered on
the 5th day of incubation (Lemez, 1955). No other mitoses of cells
belonging to the white series were found in the circulation during the
incubation period.
2. Experimental
Studies
In recent years a series of experiments has been made on mitoses,
predominantly of primitive erythrocytes. The high mitotic activity of
primitive erythrocytes and the availability throughout the year of
fertile eggs led Astaldi and Rondanelli (1955) and Bussi (1957) to
recommend the chick embryo primitive erythrocytes as a biological test
for serial screening of cytostatic drugs. Undoubtedly this recommendation and the techniques given are well founded, assuming that the
cells of the target tissue (neoplastic) are as sensitive as the chick embryo
primitive erythrocytes to the substance tested.
The stathmokinetic effect of colchicine on chick embryo erythrocytes
from the 2nd to the 9th day was studied by Astaldi et al. (1951a, b, 1952)
and from the 2nd to the 6th day by Lemez and Rychter (1956, 1958a). A
similar effect is exerted by patulin, but this can be inhibited by glutathione, cysteine, and BAL, perhaps as a consequence of the reaction of
the drugs with —SH groups on the spindle fibres (Rondanelli et al., 1957).
Analogously, a large number of 'exploded mitoses' with chromosomes
arrested at metaphase and scattered throughout the cytoplasm was
observed after exposure of primitive erythrocytes to lead nitrate. The
larger the dose and the longer the exposure, the larger was the number
of arrested mitoses (Rondanelli et al., 1958). An acridine derivative also
exhibited colchicine-like effects (Monesi, 1955). O'Connor (1952b)
treated the 4-day chick embryo primitive erythrocytes with fluoride and
iodoacetate, both of which caused chromosomes to swell, preventing
completion of mitoses (again a colchicine-like effect) due to the suppression of carbohydrate metabolism.
By studying the uptake of 32P by the DNA of embryonic erythropoietic cells from the 2nd till the 7th day of incubation, Salera et al.
(1956a, b, c, 1958) were able to calculate the duration of DNA synthesis
and to establish that this value (5-8-6 hours) remains constant in
different maturation stages of both the primitive and definitive erythrocytes during the period studied. The duration of interkinesis, calculated
on this basis, is slightly shorter in the primitive than in the definitive
erythrocytes increasing with the maturation of both lines from 15 to
22 hours and from 19 to 33 hours, respectively, while the interkinetic
period in the blood island of a young explanted blastoderm may be from
3 to 6 hours (Sabin, 1920) or from 45 minutes to 3 hours (Muller, 1930).
This is a remarkably short time for doubling the DNA content of the
LEO LEME2
Only three promyelocyte (neutrophil) mitoses were encountered on
the 5th day of incubation (Lemez, 1955). No other mitoses of cells
belonging to the white series were found in the circulation during the
incubation period.
2. Experimental
Studies
In recent years a series of experiments has been made on mitoses,
predominantly of primitive erythrocytes. The high mitotic activity of
primitive erythrocytes and the availability throughout the year of
fertile eggs led Astaldi and Rondanelli (1955) and Bussi (1957) to
recommend the chick embryo primitive erythrocytes as a biological test
for serial screening of cytostatic drugs. Undoubtedly this recommendation and the techniques given are well founded, assuming that the
cells of the target tissue (neoplastic) are as sensitive as the chick embryo
primitive erythrocytes to the substance tested.
The stathmokinetic effect of colchicine on chick embryo erythrocytes
from the 2nd to the 9th day was studied by Astaldi et al. (1951a, b, 1952)
and from the 2nd to the 6th day by Lemez and Rychter (1956, 1958a). A
similar effect is exerted by patulin, but this can be inhibited by glutathione, cysteine, and BAL, perhaps as a consequence of the reaction of
the drugs with —SH groups on the spindle fibres (Rondanelli et al., 1957).
Analogously, a large number of 'exploded mitoses' with chromosomes
arrested at metaphase and scattered throughout the cytoplasm was
observed after exposure of primitive erythrocytes to lead nitrate. The
larger the dose and the longer the exposure, the larger was the number
of arrested mitoses (Rondanelli et al., 1958). An acridine derivative also
exhibited colchicine-like effects (Monesi, 1955). O'Connor (1952b)
treated the 4-day chick embryo primitive erythrocytes with fluoride and
iodoacetate, both of which caused chromosomes to swell, preventing
completion of mitoses (again a colchicine-like effect) due to the suppression of carbohydrate metabolism.
By studying the uptake of 32P by the DNA of embryonic erythropoietic cells from the 2nd till the 7th day of incubation, Salera et al.
(1956a, b, c, 1958) were able to calculate the duration of DNA synthesis
and to establish that this value (5-8-6 hours) remains constant in
different maturation stages of both the primitive and definitive erythrocytes during the period studied. The duration of interkinesis, calculated
on this basis, is slightly shorter in the primitive than in the definitive
erythrocytes increasing with the maturation of both lines from 15 to
22 hours and from 19 to 33 hours, respectively, while the interkinetic
period in the blood island of a young explanted blastoderm may be from
3 to 6 hours (Sabin, 1920) or from 45 minutes to 3 hours (Muller, 1930).
This is a remarkably short time for doubling the DNA content of the