230
LEO LEME2
diminish still further the extremely short average life span of Ε I—
8 days— as compared with the average life span of adult hen erythrocytes of about 30 days (Hevesy and Ottesen, 1945; Shemin et al, 1948;
Ottesen, 1948, 1955; Rodnan et al, 1957). Brace and Altland (1956)
reported, in two chicks, an average life span of only 20 days.
Degenerative changes in primitive erythrocytes are somewhat infrequent up to the 6th day of incubation and there is histological
evidence that primitive erythrocyte production ceases after the 7th day
of incubation (Dantschakoff, 1908a). Fragmentation of primitive
elements after the 7th day cannot substantially influence their number.
The extinction of Ε I, starting with the 7th day implies that these
elements undergo destruction long before reaching full maturity; the
majority must leave the blood stream as reticulocytes, because the first
fully mature primitive erythrocytes were observed as late as the 13th
day of incubation (Lemez, 1953). Comparison of the average erythrocyte
life span in adult mammals with the maximal life span of primitive
erythrocytes in corresponding embryos reveals that the latter values are
only half the former (Lemez and Rychter, 1956). Consequently the
average life span of embryonic primitive erythrocytes in mammals must
be even shorter. With some assumptions, it can be estimated that
their average life span is about one quarter of the estimated value for
adults ; this is comparable to the findings (8:30 days) in the hen (Lemez,
1957).
2. Average Life Span of Definitive Erythrocytes
with
Round Nuclei (E
The survival curve for the definitive erythrocytes, Ε II l9 was constructed in the same way as for the primitive line (Fig. 9—curve in
background; Fig. 10A). It starts with 2-7 million on the 5th day, the
maximal value (1118-5 million) was encountered on the 11th day, and
only 11-7 million were alive on the 1st postembryonic day. From this
survival curve an average life span of 5-7 days was estimated (Lemez,
1958; Lemez and Rychter, 1959). Unfortunately, after the maximum on
the 11th day many immature elements of type Ε II X are met with in
blood smears, though their total amount in circulation is declining. This
points to continuous destruction and release into the circulation of this
erythrocyte type so that a cryptogenic turnover must be analysed. It is
supposed that the earliest red blood corpuscles to be produced also
undergo earlier destruction ; that a definitive Ε ΙΙ Χ erythroblast matures
during 24 hours into a definitive Ε II X proerythrocyte which during a
further 24 hours assumes the character of an Ε II X erythrocyte (of
course, still a reticulocyte) ; that the Ε II X elements are not destroyed at
the erythroblast or proerythrocyte stage and that after the 11th day no
LEO LEME2
diminish still further the extremely short average life span of Ε I—
8 days— as compared with the average life span of adult hen erythrocytes of about 30 days (Hevesy and Ottesen, 1945; Shemin et al, 1948;
Ottesen, 1948, 1955; Rodnan et al, 1957). Brace and Altland (1956)
reported, in two chicks, an average life span of only 20 days.
Degenerative changes in primitive erythrocytes are somewhat infrequent up to the 6th day of incubation and there is histological
evidence that primitive erythrocyte production ceases after the 7th day
of incubation (Dantschakoff, 1908a). Fragmentation of primitive
elements after the 7th day cannot substantially influence their number.
The extinction of Ε I, starting with the 7th day implies that these
elements undergo destruction long before reaching full maturity; the
majority must leave the blood stream as reticulocytes, because the first
fully mature primitive erythrocytes were observed as late as the 13th
day of incubation (Lemez, 1953). Comparison of the average erythrocyte
life span in adult mammals with the maximal life span of primitive
erythrocytes in corresponding embryos reveals that the latter values are
only half the former (Lemez and Rychter, 1956). Consequently the
average life span of embryonic primitive erythrocytes in mammals must
be even shorter. With some assumptions, it can be estimated that
their average life span is about one quarter of the estimated value for
adults ; this is comparable to the findings (8:30 days) in the hen (Lemez,
1957).
2. Average Life Span of Definitive Erythrocytes
with
Round Nuclei (E
The survival curve for the definitive erythrocytes, Ε II l9 was constructed in the same way as for the primitive line (Fig. 9—curve in
background; Fig. 10A). It starts with 2-7 million on the 5th day, the
maximal value (1118-5 million) was encountered on the 11th day, and
only 11-7 million were alive on the 1st postembryonic day. From this
survival curve an average life span of 5-7 days was estimated (Lemez,
1958; Lemez and Rychter, 1959). Unfortunately, after the maximum on
the 11th day many immature elements of type Ε II X are met with in
blood smears, though their total amount in circulation is declining. This
points to continuous destruction and release into the circulation of this
erythrocyte type so that a cryptogenic turnover must be analysed. It is
supposed that the earliest red blood corpuscles to be produced also
undergo earlier destruction ; that a definitive Ε ΙΙ Χ erythroblast matures
during 24 hours into a definitive Ε II X proerythrocyte which during a
further 24 hours assumes the character of an Ε II X erythrocyte (of
course, still a reticulocyte) ; that the Ε II X elements are not destroyed at
the erythroblast or proerythrocyte stage and that after the 11th day no