Blood, 1967, Vol. 30, No. 3, pp. 288-300.
© 1967 American Society of Hematology, Inc.
Ultrastructural Differences Between Thymic and
Lymph Node Small Lymphocytes of Mice:
Nucleolar Size and Cytoplasmic Volume
H. J. HEINIGER 1,
H. RIEDWYL 1,
H. GIGER 1,
B. SORDAT 1, and
H. COTTIER 1
1 Institute of Pathology, Institute for Mathematical Statistics, and Department
of Ophthalmology, University of Bern, Bern, Switzerland.
Ultrastructural differences between small lymphocytes of the thymic cortex
and those located in the cortical zone of lymph nodes of mice were examined
by electron microscopy and cytometric methods. The particle size analyzer
TGZ 3 (Zeiss) was used to measure the size-frequency distribution of nucleolar
cross-section diameters, and the resulting data were computed mathematically
and statistically to determine the corresponding mean volumina.
It could be shown that thymic, as compared to lymph node cortical small
lymphocytes, (1) have a smaller mean nucleolar volume (0.11µ3 versus 0.46µ3);
(2) represent a more uniform population with regard to the frequency distribution of the nucleolar cross section diameters; and (3) are of smaller size due to
less cytoplasm, while the mean nuclear volume does not differ significantly from
that of small lymphocytes located in the cortex of lymph nodes.
These findings are discussed in relation to qualitative ultrastructural peculiarities and probable differences in the magnitude of RNA turnover as estimated
by the use of tritiated cytidine. The possible significance of cytometrically
defined populations of small lymphocytes with regard to sensitized and nonsensitized cells is considered.
Submitted on November 21, 1966
Accepted on March 31, 1967
