Asunto(s)
Hematopoyesis , Megacariocitos/citología , Trombocitopenia/sangre , Animales , Mitosis , Ratas , Trombocitopenia/patologíaRESUMEN
Rats were made acutely thrombocytopenic by injection of antiplatelet serum. Marrow sections and squash preparations were made at intervals during 120 hr. Determinations were made of mitotic index, stage of maturation, ploidy level, and cell size of megakaryocytes; number and size of platelets were measured. Increased endomitosis among megakaryocytes was followed by an increase in the proportion of immature megakaryocytes, a greater average ploidy level of recognized megakaryocytes, and larger megakaryocytes. Maximum changes in these several parameters occurred between 32 and 72 hr after induction of thrombocytopenia. By 120 hr all megakarocyte parameters were near normal. For about 3 days, beginning at about 36 hr, platelet numbers increased rapidly. Average platelet size rose and returned to normal within about 60 hr. Changes in ploidy and size of megakaryocytes were measured in the immature and mature maturation stages. The results suggest that the initial stimulus in response to acute thrombocytopenia acts primarily on diploid precursors, programming them to mature into a population of megakaryocytes with an average ploidy approximately one level greater than in normal rats and a proportionate increase in cell size. The larger megakaryocytes presumably produce more platelets, accounting for a major part of the increased rate of platelet production. Since the changes in megakaryocytes begin to reverse before circulating platelet numbers have reached the normal level, reversal of the stimulus appears to be initiated by some change other than platelet mass.
Asunto(s)
Hematopoyesis , Megacariocitos/citología , Trombocitopenia/sangre , Enfermedad Aguda , Animales , Recuento de Células Sanguíneas , Plaquetas , Masculino , Índice Mitótico , Ploidias , RatasRESUMEN
After mild thrombocytopenia (about 50-100% of control platelet level), induced by injection of antiplatelet serum (APS), platelets increased at a fairly constant and moderate rate for about 4 days and reached a maximum count, greater than pretreatment levels, on the fifth day. After moderate to severe thrombocytopenia, an early moderate rate of platelet increase was succeeded within 2 days by a second more rapid rate that persisted for about 3 days. The maximum overshoot of the platelet count was usually less than twice the pretreatment level. After the largest doses of APS, the platelet count remained depressed for several days. Platelet response after acute thrombocytopenia induced with antiserum is therefore variable, depending on the level and duration of thrombocytopenia.