"Switching system"

Date:
1973
Reference:
PP/CRI/I/2/12
Catalogue details

Licence: In copyright

Credit: "Switching system". Source: Wellcome Collection.

    THE NEW YORK TIMES, FRIDAY, AUGUST 24, 1973 SULLIVAN Researchers in Cambridge, I ngland, are investigating one! f the most basic elements of® îe life process: the switch-H ig system that, in all living® . „¿lis, regulates the flow of in-F I formation needed for their I function. I In their experiments . they I have caused otherwise normal I frogs to produce, throughout I their lives, a prime constituent I of rabbit blood. In so doing the I researchers believe they have J knocked down one theory as to I how the switching is done; But the nature of the process re mains elusive. The work follows up exper iments that showed that iden- I tical frogs can be produced I in indefinite numbers from the I body cells of other frogs. Cur- 1 -ent tests at Oxford Univer sity and elsewhere are seeking jo do the same with mice a: J I rabbits. I In many-celled organisms I is evident that something shuts I off all the information in the I I except the small fraction ap- ■ plicable t I function. Thus in higher animals, i I eluding man, when an organ I I composed of dive =-n—j I cells, such as I formed, it will mot grow again« 1 if amputated, even though the® I blueprint for such a limb pre-® I sumably remains stored in t u -™ f nucleus of every body cell. ;r animals, such as sal-■ I amanders, this stored informa-1 in be retrieved and a „rown. The reason for the® I difference remains unknown. ■ I One explanation for theB I switching off of such informa-* I tion, once a cell has become« I specilaized, is that it is done by« I substances that censor the« I chemical signaling whereby op-® I erätion of.the cell is controlled.® I The signaling is done by mole-® I cules of messenger RNA (ribo-J Researchers in England Seeking Clues To 'Switching System' in Living Cells brand of bemogle , jected .into a frog egg. Hemoglobin is the substance tat binds oxygen within red ood cells so that they can irry the oxygen throughout le body. The tadpole that resulted from the injection into the frog egg began making rabbit hemoglo bin and continued doing so. into adulthood as a frog. Thus there appears to be no such oer ing system. As many have pectedj the' switching is appar ently done within the 1 archive of information, 'to the DNA (deoxyribonucleic :id) of the nucleus. The nature of this switching system is the target of elei from the body cells of oth- — frogs. Such experiments were begun by Dr. John Gurdon while he at Oxford University. He is pursuing them in a labora- . on the outskirts of ~ bridge. Frogs are produced froir . cialized body cells by removing the nucleus of such a cell and implanting it in a frog whose original nucleus been destroyed, Apparently something within the egg switches off the part of ■ Then the nucleus is in so ■ way cycled back to feed ii H the egg those commands a._ ■ design criteria needed to make® new frog. Despite the fact® it the roots of this switching® jcess seem, in this case, 1 I lie within the substance, < ■ cytoplasm, of the egg, there® ■ are, as yet, no clues as to its! ■ nature, according to Dr. Gur- ■ Biology operated® Medical Research® le outskirts of this® with Nobel I le its director, Dr. I md Dr. John Ken-® ■ drew. In Í962 they won 1' ■ prize jointly for elucidating 1 structure of hemoglobin. There are several other No-B ■ belists, including Dr. Francis H.[ IC. Crick, who shared the prize ■ (for his work, at this laboratory, I n determining the structur (DNA. Before Dr. Gurdon's I experiments, it had been Bpected, but not proved, I every cell of the body, no i ■ ter how specialized, conttained® Bin its nucleus all of the infor-F Bmation needed to produce an B entirely new individual of that (species, be it a frog or a Question on Cells Skeptics, however, ques-| oned whether the body cells •om which he derived his uclei were those of truly spe- ialized cells. There are basal slls wandering through the ■ body that seem undifferenti-1 ■ ated. Many'beieve they ■ into a wounded region and ■ give birth to the specializedL Hcells needed to make repairs. B Dr. Gurdon originally used® ié intestinal cells of tadpoles, V which subdivide very rapidly.! He did this because thf cells into which they we_. Ibe injected divide rapidly and® ideus is not primed tc ' > so too it falls behind in iti visions and the system goes® One of the obstacles t( > produce r ^efforts t rabbits in „ problem of finding nuclei from body cells that can këep pace with the rapidly dividing ;g cells of such mammals, he use of tadpole cells led ime to suspect they were not ature and fully differentiated. Dr. Gurdon believes the pos sibility that his frogs are de veloping from undifferentiated ¡nuclei has now been laid to He and Dr. Ronald A. Lasker have extracted nuclei ;from laboratory cultures of frog skin cells and produced new frogs from them. Further more, Dr. O. Ray mond Reeves, an American working in the laboratory, be lieves he has shown that the cultured cells are almost all producing keratin-like proteins, indicating a high degree of specialization. These are the proteins that form human hair and other such tissues. Dr. Reeves is now trying to - pin ,them down as the variety typ ical of frogs' skin. Early Specialization Even before the egg per forms its first subdivision, ac cording to Dr. Gurdon, the process of specialization has begun-within the cytoplasm of the egg itself. A nucleus that —'!S its way out of the egg _ _ie direction produces a cell ■line with one function. A nu- (cleus that follows another . ■ by the cytoplasm to initate ai other line of development. Dr. Gurdon's work on Mess- B enger RNA was done with Drs. ■ Charles D. Lane and Hugh R. ■ Woodland. Drs. Gurdon be- Hlieves the critical switching ■ system will eventually come u .o light by studying all the fac- :ors that control DNA replica- ion. The problem, he says 'is in designing the right ex- ■ périment. The ultimate outcome, how ever, should be-an understand- Hing of a number of questions ■ important to human welfare. ■ Notable among them is why, ■ when a salamander leg is ■ amputated, the - animals cells *e enough latent in-