����
��ӡ
�ֺ�:
They say what doesn’t kill you makes you stronger. But sometimes what makes you stronger can kill you, at least when it comes to blood clotting. Because the stickiness that allow platelets to heal your wounds also raises your risk of heart attack.
����ɱ��������������ǿ������ʱ������Ѫ˨����ɱ�������Ŷ����ΪѪС���ճ����Ȼ������������˿ڣ���ͬʱҲ���������ಡ�ķ������ʡ�
All mammals use platelets to help prevent blood loss after traumatic injury. But birds don’t have ‘em, nor do reptiles or fish. Instead, these critters have blood cells called thrombocytes, which are about twice the size of platelets. But is bigger necessarily better when it comes to clotting? Scientists took thrombocytes from parakeets and put them to the test. The work appears in the journal Blood. [Alec A. Schmaier et al., "Occlusive thrombi arise in mammals but not birds in response to arterial injury: evolutionary insight into human cardiovascular disease"]
���в��鶯�����ܵ�����ʱ����ѪС��ֹѪ����������û��ѪС�壬���ж��������Ҳû�С�Ȼ������Щ������һ�ֽ���thrombocytes��Ѫϸ��,��ѪС���2�����Ƕ�����Ѫ��˵��Խ��Ч����һ�������𣿶Դˣ���ѧ�Ҵӳ�β����������ȡthrombocytes���в��ԡ������о������ڡ�ѪҺ����־��
They focused their attention on birds because our feathered friends have a cardiovascular system much like our own, in that blood exerts pressure on walls of blood vessels.
��ѧ����������Ϊ�о������ԭ���ǣ����ǵij���ë�����������ǵ�Ѫ��ϵͳ������֮����ѪҺ��Ѫ���ڱڵ�ʩѹ��ʽ��ͬ��
The results: parakeet thrombocytes don’t stick together like platelets do. They also don’t block blood flow in the birds’ arteries the same way that platelets do when they form clots in mice.
�о��������β���ĵ�thrombocytes������ѪС������ճ��һ������Ҳ�������������ڵ�ѪС������������ʱ���������ڵ�ѪҺ������
Which means that mice may be more likely to survive a bloodletting-pecking. But birds are far less likely to suffer from the clot formation called economy class syndrome—despite being frequent fliers.
�����ǣ������Ѫ�����������Ӿ��ò��ۺ���——�����������Ƿ�����ȥ��
�ղ�
