THE UNIVERSITY OF WESTERN ONTARIO
FACULTY OF MEDICINE

  

RS

   

DEPARTMENT OF BACTERIOLOGY AND IMMUNOLOGY
THE HAMILTON KING MEEK MEMORIAL LABORATORY

375 SoutH STREET,
LONDON, CANADA

November 24, 1953

Dr. Joshua Lederberg,
Department of Genetics,
College of Agriculture,
University of Wisconsin,
MADISON 6, Wis., U.S.A.

Dear Lederberg:

I was delignted to get your detailed letter and to
know the problem that besets you. We have to learn a lot
about the structure of the normal nucleus before any
really useful understending can result. In the end there
will have to be an evaluation of cytological observeticns
together with the genetic observations, but it seems too
early to go as far as Werner Braun hag gone in his recent
book.

It is most interesting that you have real doubts, even
when approaching the problem from the genetic angle. We
have not been able to find a spindle, but we can find the
constellations of granules that DeLamater figures as meta-
pnase plates and spindle poles. However, all the parts that
should be achromatic prove to be chromatic - as we had sus-
pected from his pictures and hig metheds. If you take
selected chromatin patterns you could make up a series to
fit a concept of mitosis; but you could make other series to
fit almost any hypothesis. So it would seem to be worth
restricting ourselves to the observational plane.

I have done few experiments on the nuclear structure of
young coliforms and the generél impression was something like

this:- — a
WA) Ff)

 

This is remarkably similar to the pictures drawn by Hollande
in the 30's, although his nucleosome is an uncertein quantity!
We have been trying to follow the fate of these components
Dr. Joshua Lederberg - page 2

during some phage infections and they seem to behave as if
they were distinct components.

A difficulty, at the moment, is that "direct" staining
(fixed films stained for 20-30 minutes in Giemsa and diftfer-
entiated in water acidified with a drop of acetic acid)
provides information about the chromatin alone. Looked at
with & suitable filter they look very good and the elements
appear to be less fragmented than the same group hydrolyzed
in the usual way. This means that all the ideas concerning
"core" and "matrix" are really dependent upon indirect methods.
I wonder if the chromatin that is partitioned into each
daughter "nucleus" is all in one complex but connected piece.
The complexities of individual nuclei may represent various
stages in the synthesis of a new chunk rether than stages in a4
mitotic cycle. fitz-James, working on both the chemical and
cytological aspects of spore germination in B. megateriun,
feels that there is continuous production of DNA and that the
number of chromatin granules does not increase 3-~6 but rather
3~4—75-—76. There may be some chance of a quantitative
approach in that situation.

We nave always used Giemsa diluted with a phosphate buffer
of pH 7.0. Actually, we use the buffer tablets supplied for the
purpose by Gurr and have had no cause for compleint. I tried
buffering to pH 5 the other day and did not find any great
difference. I would like to know wnat the troubles were that
prompted the change of pH.

Yours sincerely,
i i {i

PGEMs mj R. G. E. Murray, M.D.
Professor