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44   First an Egg, Then a Man
     The Washington Post, Sunday, May 14, 1967

     The cultivation of tissue cells outside the body has been one
of the landmarks of experimental biology.  Known for 60 years, the
technique has come to practical use outside the research laboratory
only in the past decade.  Its main application is still for the
routine production of viruses to make vaccines.

     But diagnostic applications are now of growing importance: cell
cultures from patients are used for decisive chromosome studies in
cases of suspected mongolism or Klinefelter's disease (maldevelopment
of the testes).

     Other tests could detect certain genetic diseases of metabolism.
As we learn to make cell cultures from the early fetus, we gain a
scientific resource for rational decisions about human reproduction.
Whether to abort a pregnancy will depend in part on whether the result
is expected to be a human infant or a tragic monster.

     By reducing the stakes in a pregnancy, such techniques will
relieve many prevalent anxieties, making birth a little less like
Russian roulette. They will undoubtedly motivate many prudent couples
to attempt a pregnancy otherwise too risky for thoughtful choice.

     Cell culture has still to complete its most important
contribution to human understanding, and this will undoubtedly be in
the field of differentiation, where it has so far served to raise more
precise new questions than answers to old ones.

     The main issue is now the single cell develops into a complicated
organism with so many interdependent differentiated tissues and
organs.  By the techniques of tissue culture, it can be shown that
cells of, say, the thyroid gland, the kidney or the brain retain their
individuality when grown in separate culture.

     Differentiation of cell type is then in large part an inherent
quality of the cell, which is retained even when different cells are
sustained in the same environment.  But other evidence continues to
support the ancient rule that all the cells have the same genetic
blueprints, the same set of DNA information in the nuclei.

     We must then answer two seemingly paradoxical questions.  How
do cells with the same DNA sustain their unique tissue differentials,
i.e., remain nerve-like or kidney-like once formed?  And how are these
differentials established so precisely in the first place?

     Is it necessary to point out the practical importance of new
knowledge in such a field?  To give the crudest example, visualize
the impact on human life if a new heart could be induced to grow in
place, to substitute for a weary old one.

     The campaign toward this triumph is well under way: it is the
central challenge of contemporary biology, founded on the research
that led to the solution of the genetic code and the basic biochemical
mechanisms of heredity.  Considering the certain payoffs of another
10 or 20 years of fundamental biochemical research, it is ironic that
there should be so much talk of a "reasonable plateau" of such
research at its most crucial, ascendant moment in history.

     A plausible general theory of differentiation can already be
outlined, mainly from work with microbes just starting to be
transposed to animal and ultimately human development.  The DNA 
information is replicated rather faithfully and transmitted uniformly
to every cell.

     Genetic code research shows, however, that the readout of the DNA
goes through several steps.  First, a "transcription" of DNA segments
into RNA "messages".  Then, the "translation" of an RNA message into
the amino acid sequence of a protein.  Finally, the release of the
protein into the cell, where it may then interact with other proteins
and other cell products, or feed back to control the earlier steps
of readout of other messages.

     The crucial steps are the transcription and the translation.
Recent evidence suggests that transcription is the most importantly
vulnerable control step in microbes, but translation may have to be
considered in higher organisms.

     Recent tissue culture research has also shown that dispersed
cells rarely show their specialized capacities to the same advantage
as similar cells grown in communities.  In some cases, the
interactions between cells can be traced to soluble cell products
that accumulate in the culture field.

     In others, the evidence supports a more immediate cell-to-cell
interaction via their surface contacts.  How these interactions 
eventually signal the machinery of the genetic code inside the cell
is one of the most exciting avenues of contemporary research in
cell biology.
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