The Malpighian tubules of the hemipteran, Triatoma infestans, grow through endopolyploidy. As a result, the number of tubule cells is constant throughout nymphal development and adult life, and nuclei with 32 degrees C and 64 degrees C Feulgen-DNA classes are maximally reached through DNA endoreplication. Feulgen-DNA classes > 64 C, with resulting giant nuclei, may occur only through nuclear and cellular fusions, elicited by stressing agents such as heat shock and fasting. Although apoptosis has been reported in cells of Malpighian tubule epithelia, especially under stress conditions, the association between cell death and the degree of polyploidy resulting from different phenomena (either development or stress) has not yet been investigated. In this study, image analysis was used to estimate the Feulgen-DNA values of apoptotic nuclei in the Malpighian tubule cells of 5th instar nymphs of T infestans subjected to heat shock at 40 degrees C for I h and fasted for 15 days before the shock. The susceptibility to apoptosis was unrelated to an exclusive degree of nuclear ploidy reached in Malpighian tubules by insect development or elicited by stress. The occurrence of apoptosis in the giant nuclei suggests that the nuclear and cellular fusion, previously assumed to be a mechanism of cell survival in blood-sucking hemipterans, may not be totally effective against stressful conditions. Ver menos

The Malpighian tubules of the hemipteran, Triatoma infestans, grow through endopolyploidy. As a result, the number of tubule cells is constant throughout nymphal development and adult life, and nuclei with 32 degrees C and 64 degrees C Feulgen-DNA classes are maximally reached through DNA endoreplication. Feulgen-DNA classes > 64 C, with resulting giant nuclei, may occur only through nuclear and cellular fusions, elicited by stressing agents such as heat shock and fasting. Although apoptosis has been reported in cells of Malpighian tubule epithelia, especially under stress conditions, the association between cell death and the degree of polyploidy resulting from different phenomena (either development or stress) has not yet been investigated. In this study, image analysis was used to estimate the Feulgen-DNA values of apoptotic nuclei in the Malpighian tubule cells of 5th instar nymphs of T infestans subjected to heat shock at 40 degrees C for I h and fasted for 15 days before the shock. The susceptibility to apoptosis was unrelated to an exclusive degree of nuclear ploidy reached in Malpighian tubules by insect development or elicited by stress. The occurrence of apoptosis in the giant nuclei suggests that the nuclear and cellular fusion, previously assumed to be a mechanism of cell survival in blood-sucking hemipterans, may not be totally effective against stressful conditions. Ver menos