Morphology of apoptosis of polymorphonuclear leukocytes isolated from juvenile bovine mammary glands

The paper describes the occurrence and morphological pattern of apoptosis o f polymorphonuclear leukocytes (PMN) of juvenile bovine mammary glands as i maged by light, fluorescence, confocal, and transmission electron microscop y. The cells were obtained by lavage of 40 juvenile bovine mammary glands s timulated with muramyl dipeptide. Twenty-four hours after the stimulation, the percentages of necrotic and apoptotic PMN were 7.9 and 4.2, respectivel y. Light, fluorescence and confocal microscopy of the apoptotic PMN showed morphological alterations including condensation of chromatin (karyopyknosi s), cell shrinking, loss of pseudopodia, and spherical shape, while transmi ssion electron microscopy revealed aggregation of chromatin, intact organel les and cell membrane, and vacuolisation of cytoplasm. The apoptotic PMN we re eventually phagocytosed by macrophages as demonstrated by electron micro scopy, and light microscopy in preparations stained for myeloperixidase, as well as by confocal microscopy. The finding of degenerating and necrotic P MN indicates that there exist two forms of death of this cell type and is s uggestive of the existence of factors alterating the apoptotic programme an d shortening the, life span of PMN.