812 BRIEF NOTES
The Chemical $'ractionation of Rabbit and Swine Thymus.* BY EUGENE L.
HESS AND SAIMA E. LAGG. (From The Rheumatic Fever Research Institute,
A previous report described a gen-
eralized method for the chemical frac-
tionation of lymphatic organs (1). It was
shown that the method was applicable to
bovine thymus and to ovine and bovine
palatine tonsils. The study has now been
extended to include two additional spe-
cies, in order to ascertain the general
applicability of th~ method, and also to
include an animal common to laborato-
ries. The procedure would be much more
useful if applicable to the thymus of a
small mammal such as the rabbit, since
relevant biological studies become more
feasible, and numerous biological prob-
lems could be undertaken using data from
normal animals as a frame of reference.
Problems such as the radiation sensitivity
of lymphoid tissue (2), the antibody con-
tent of lymphatic organs (3), and the
changes in composition resulting from
the involution of the thymus under con-
ditions of stress (4), appear to be sus-
ceptible to study using chemical fraction-
ation procedures. It is the purpose of this
report to point out that the fractionation
procedure previously described (1) has
been found equally applicable to porcine
and rabbit thymus.
Materials and Methods
The thymus glands were procured from
young animals, packed in ice, and the extra-
neous tissue removed within 2 hours from
the time of slaughter. All experimental opera-
tions have beeen discussed previously (1, 5).
The preparation of extracts and symbols used
to represent the various fractions are the
* Supported by a grant from the Atomic
Energy Commission, Contract AT(11-1)366
with The Rheumatic Fever Research Insti-
tute, and by the Leukemia Society.
Received for publication, May 13, 1957.
same as used previously (1). The term
optical concentration was defined in the
previous study (1).
In our experience rabbit thymus con-
tained a much larger amount of fat dis-
persed throughout the organ than did
porcine and bovine thymus. This was
evident even with young rabbits carefully
selected with respect to age and size. Al-
together from 100 gm. of starting material,
representing the thymus glands from 18
rabbits, 42 gm. of fat were removed by
hand from cold thymus and an additional
11 gm. floated to the surface of the extracts
after centrifuging. As a consequence only
47 gm. of non-fat-containing material was
used in the rabbit experiment. The results
have been expressed, however, in terms of
100 gm. wet tissue containing no fat.
As can be seen in Fig. 1 A the electro-
phoretic pattern obtained from the total
extract (ET) using rabbit thymus was
indistinguishable from the previously
thymus. The pattern from hog thymus
is virtually identical with that seen in
Fig. 1 A.
In each subsequent fraction examined
(5.1 P, 5.1 S, 3.0 P, 3.0 S, 6.2 P, 6.2 S,
4.7 P and 4.7 S) the electrophoretic pat-
terns closely resembled those published
in the earlier study (1). For comparison
purposes patterns obtained using the
PNA-type nucleoprotein fraction 3.0 P
and fraction 4.7 S from hog thymus are
shown in Fig. 1 B and 1 C respectively.
In all cases yields of each fraction, on
a dry weight basis, were comparable to
those reported in the earlier study (1).
The optical concentrations and yields
are listed in Table I. The materials re-
maining insoluble after three extractions
(1) from bovine
J. BioPltYsle. AND BlOC~E~. CYI'OL., 1957, Vo]. 3, No. 5