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Show March of Dimes Scientists Find Armadillo Helpful in Twin Study An oddball research animal that looks like a cross " r-r" 5 between an anteater and an armored tank is causing ! " 4 - "- scientists to wonder if "identical" human twins are so - ' identical after all. - " l',' The nine-banded armadillo, which is a native of , J Texas and points south, has several child-bearing char- 1 ' , - " acteristics that are similar to those of humans. , f : , For this reason, Dr. Kurt Benirschke and colleagues at Dartmouth Medical College, Hanover, N. H., are using armadillos ar-madillos for studies of pregnancy preg-nancy and birth defects under a National Foundation-March of Dimes research grant. It takes about the same length of time nine months for baby armadillos or baby humans to develop in the womb. And in both species, the placentas are structurally sim- mal that looks like a cross " fT 1 , in armored tank is causing ! " 4 - "- ntical" human twins are so - ' , lillo, which is a native of t , i several child-bearing char- ' , ' ( ' " , to those of humans. J , , A H r ' X V - it "t'lj '' i H . ' 'A . : i , J , - .1 x e- , i I ; " .w- s- f ' Dr. Kurf Benirschke, March of Dimes grantee at Dartmouth Medical College, Hanover, N. H., studies the strange-looking armadillo. jlar. But a quirk of nature has made this odd mammal even more useful for medical research. re-search. It always has a litter of four. The four baby armadillos arma-dillos come from the same egg and are therefore always of the same sex. What has this to do with human twins? For years, scientists have believed be-lieved that identical twins those who develop through division di-vision of the same egg are exactly alike down to the very last gene. They've assumed that it was this genetic similarity that permits successful transplants trans-plants of skin or of organs between identical twins. If this theory were wholly correct, it should be easy to exchange skin grafts between identical young of the same armadillo litter since they all came from a single egg. But Dr. Benirschke and his associates, Dr. Alastaire H. Imre and Dr. John Anderson, have found that such grafts often fail to "take." This paradox has led them to suspect that the answer to graft tolerance cannot be found solely in genetic makeup. make-up. The March of Dimes researchers re-searchers think the key may lie, at least in part, in the relationship re-lationship of the embryo to the placenta the material which nourishes the unborn infant. Each armadillo quadruplet has its own isolated segment of placenta. This means that each gets a slightly different supply of nutrients, hormones and blood elements. While such differences are minute, thsy may be just enough to individualize each animal's development de-velopment so he won't accept grafts and transplants from his own littermate. Human twins, on the other hand, sometimes share a common com-mon placenta each getting exactly ex-actly the same nutrients for development. Thus they become be-come favorable candidates for any necessary organ exchange or skin graft in later life. If graft acceptance in twins is related to their sharing or not sharing the same placenta, pla-centa, some other puzzles of pregnancy may also be a little closer to solution. Why, for example, doesn't a pregnant animal "reject" its own embryo, which is actually a "foreign" substance made up of cells quite different from her own? Or does she, in some in stances? Could such a reaction lead to spontaneous abortion or a defect in the offspring? Or could it be that the exchange ex-change of substances through the placenta permits the mother moth-er to "accept" the embryo? Does this exchange also make it possible for some mothers and children to tolerate toler-ate each other's skin or organ grafts later in life? These are questions which have stumped scientists for many years. The answers, though still to come, may throw a bright new light on many problems of pregnancy, the causes of certain birth defects, de-fects, and the success or failure of organ transplants. And it may be one of the nature's more incredible creatures crea-tures dasypus novemcinctus (known familiarly as Mrs. Armadillo) who will help turn the switch on this lamp of knowledge. |