Miraculous Mysteries Of The Cell

Press, Volume CVIII, Issue 31841, 20 November 1968, Page 8

Miraculous Mysteries Of The Cell

IBU W.tt.TKB fULLIVAN) One of the most fundamental mysteries of i life concerns the manI ner in which a single i cell, so small it can I barely be seen with the ' naked eye. subdivides I into progressively more specialised cells that finally arrange themselves into a human being. A reasonably complete understanding of this process could have revolutionary applications. It might become possible to grow new organs to replace defective hearts, kidneys, or lungs. Amputated limbs might be regrown. And cancer, in which the celldividing process seems to run riot, might be controlled. For those who shun meat because it involves killing, it may be possible to grow filet steaks without the aid of living animals.

Cells “Know” Research into the mechanisms of cell division and specialisation dates back several generations. Early in the century it was found that individual cells from a complex organism "know" what thev are supposed to do. Henry V. Wilson at the University of North Carolina pushed live sponges through a cloth, breaking their tissue down into individual cells. The cells, drifting about in seawater, joined up again and began growing back into sponges. At Cambridge University in England methods were developed for growing, in glass vessels, tissues taken from higher animals. Likewise a way was found chemically to loosen the cement that holds cells together, breaking up living tissue into a host of independent cells. Finally a technique was developed for removing the nucleus from one cell and implanting it in one of another type to see what happens. It is this that has made it possible to mass-produce identical frogs in the laboratories of Oxford University. The procedure is a delicate one, for the cell nucleus cannot survive if it comes in contact Yvith any foreign material. Chemical interdependence with its surroundings are basic to the role of the nucleus and it must : always have a coating of cell material (cytoplasm). The Method The transplantation is therefore achieved by sucking at a cell with a glass tube, or pipette, whose aperture is too small to accommodate the entire ceil. The cell wall and

almost all the cytoplasm are peeled off as the nucleus is sucked into the tube, but if all goes well enough cytoplasm remains covering the nucleus to keep it alive until it is injected into another cell. In this way a body cell has been taken from a tadpole and injected into the egg of another frog whose nucleus had been destroyed by radiation. After the egg- has subdivided into many cells, but before those cells have become specialised, the incipient frog is dissolved into its component cells. These are then injected into other frog eggs which grow into frogs that are in all respects identical. In recent experiments at Oxford it has also been found that when nuclei from cells of one type are injected into cells of another type, the nuclei change their role accordingly. This shows that the behaviour of the cell is not slavishly controlled by the nucleus. There is a sort of chemical “conversation” between the nucleus and cytoplasm whose outcome lies at the roots of differentiation. Find Right Place Furthermore cells are amazingly "clevef.” They know their rightful place in the body and go there. When Dr Paul Weiss of Rockefeller University (then the Rockefeller Institute) injected pigmented skin cells into the blood of a non-pigmented [chick embyro, those cells found their way to the chick’s I skin and it was pigmented when hatched. Likewise if bone marrow cells are injected into people whose bone marrow has been killed by radiation, the new cells lodge in the marrow and begin performing their vital role. > The frog experiments I carried out by Dr John Gur-

I don at Oxford have led to speculation that people with 'desirable qualities might some day be mass produced from the body ceils of prototypes. The experiments have, in Dr [Gurdon’s view, shown that I such body cells do contain all of the genetic information needed to build a new individual. Whether it can be “turned on” by implantation in a human egg is, however, an[Other question. The shear mechanics of such a procedure. Dr Gurdon said in a recent interview, would be formidable because the egg cells of human beings and other mammals are far smaller and more delicate than those of frogs. Even in the frog transplants only a small percentage of the nuclei come through sufficiently intact to grow into a normal animal. Implications Nevertheless the fact that every living cell of the human body may. in a sense, i be a potential new individual has deep ethical implications. Attitudes on abortion, for example, are based largely on the argument that, from the moment of fertilisation, the human egg deserves the. legal

jprotection of an Individual. 1 However, if it can be demonIstrated that all human cells, [are potential egg cells, some I modification of present attitudes may occur. I If it. ultimately becomes] possible to produce identical; human beings from body cells ■ —known as vegetative reproduction—will that capability be used? Many scientistshave shuddered at the prospect, but a prominent physicist reacted differently in a [recent discussion of the subject. "If I had a son whom 1 loved." he said, “and the boy was killed in an accident, it would give me great comfort to know that from one of his [body cells an identical child could be produced." A major advantage of growing spare hearts or other organs—perhaps from par[tially specialised body cells—would be that, in case of need, 'an individual would have on hand a replacement that was' a twin of his own heart. In other words it would not be rejected as “foreign." It is such rejection that presents the chief obstacle to longterm retention of hearts and other organs transplanted frim unrelated individuals.— Copyright. 1968. “New York Times” News Service.