Blood, 1969, Vol. 34, No. 6, pp. 791-805.
© 1969 American Society of Hematology, Inc.
On the Development of Slowly-turning-over Cell Types
in Neonatal Rat Bone Marrow
(Studies Utilizing the Complete Tritiated Thymidine
Labeling Method Complemented by C-14
Thymidine Administration)
R. J. HAAS 1,
F. BOHNE 1, and
T. M. FLIEDNER 1
1 Abteilung für Klinische Physiologie, Zentrum für Klinische Grundlagenforschung
der Universität Ulm, Parkstrasse 11, Ulm (Donau).
1. The continuous H3-thymidine (H3-TdR) intravenous infusion of rats from
day 9 of pregnancy until term results in the labeling of every single cell
nucleus in the body of the offspring. Completely labeled newborn rats were
sacrificed at serial intervals after birth. This provided the opportunity to
follow the labeling pattern of all bone marrow cells during the development
of this organ. Cytokinetically three types of cell renewal systems could be
found: one type showed a rapid turnover losing all H3-TdR within 6 days,
e.g., erythropoietic and myelopoietic cells. Another lost most of its labeling
throughout the same time except a small but significant fraction (bone marrow
lymphocytes). The third retained a high fraction of labeled cells with a high
labeling intensity for weeks and months (reticular cells and endothelial cells).
2. A continuation of H3-TdR administration of 100 per cent labeled newborn rats throughout the first three weeks of neonatal life resulted cytokinetically in the same three different cell types. However, a larger fraction of
reticular and endothelial cells as well as bone marrow lymphocytes remained
labeled weeks and months after the last injection as compared with the first
group of 100 per cent labeled animals.
3. An administration of C14-TdR to 100 per cent labeled newborn animals
throughout the first 6 days after birth Showed that 30 to 40 per cent of the
"resting" bone marrow cells have turned into a resting state before or at least
at the time of birth. Forty per cent of these cells still had some proliferative
capacity during the first 6 days of life. Twenty per cent showed in the first
days after birth a rapid turnover whereas later on they acquired their final
cytokinetic state. The possible influence of radiation toxicity on the time of
establishment of resting cells is discussed. This approach appears of use to
study the functional properties of resting bone marrow cell types in regenerative processes and the cellular origin in the bone marrow.
Submitted on March 14, 1969
Accepted on July 10, 1969
