Studies on the Blood Coagulation (III) Ultrastructure of Human Platelets and Bird Spindle Cells -

Abstract

In order to make a phylogenetic analysis of blood coagulation in various animals including Homo sapiens, ultrastructure of bird spindle cells was studied in comparison with that of human platelets. In contras t to human platelets, the bird blood cells having a platelet-like function were spindle shaped and nucleated. Furthermore, there is no distinct difference between granulomere and hyalomere in bird spindle cell which contains characteristic large lysosomal granules instead of a granulomere-alpha in human platelets. The following fine structures of bird spindle cells were common with those of human platelets.1. There was a few granular endoplasmic reticula and ribosomes.2. Mitochondria were circular and small in size.3. Two to four Cristae mitochondriales with relatively high electron density were seen.4. Marginal bundle was composed of microtubules. The morphological feature of marginal bundle was perfectly maintained if the spindle cells were fixed at the time of blood sampling. While the marginal bundle became straight by splitting off in an unfixed cell where the nucleus was condensed and various fine structures were lost. Hence the marginal bundles in a bird spindle cell are, on the one hand, regarded as to support the morphology of platelets, and it may, on the other, provide certain coagulating factors by cytoplasmic damage when the spindle cells were destructed in the early stage of blood coagulation. Although the exact nature of coagulating factor in bird remains to be solved, a certain role played by the lysosomal granule of spindle cells in the process of blood coagulation in bird is suspected. From the observations presented here, it was not possible to trace back the phylogenetic change of cellular morphology concerning blood coagulation in mammalian, bird, and crawfish. It seems, however, to be reasonable to consider that there must be at least a certain cell, having a particular structure and function, in bird blood as well as in mammalian blood to prevent the loss of blood or body fluid. Since the marginal bundle observed in bird spindle cells, is similar to that of mammalian platelet, it must be an important morphological feature common to the cells which participate in blood coagulation.