Chiasmata and the kinetochore component Dam1 are crucial for elimination of erroneous chromosome attachments and centromere oscillation at meiosis I

Establishment of proper chromosome attachments to the spindle requires elimination of erroneous attachments, but the mechanism of this process is not fully understood. During meiosis I, sister chromatids attach to the same spindle pole (mono-oriented attachment), whereas homologous chromosomes attach to opposite poles (bi-oriented attachment), resulting in homologous chromosome segregation. Here, we show that chiasmata that link homologous chromosomes and kinetochore component Dam1 are crucial for elimination of erroneous attachments and oscillation of centromeres between the spindle poles at meiosis I in fission yeast. In chiasma-forming cells, Mad2 and Aurora B kinase, which provides time for attachment correction and destabilizes erroneous attachments, respectively, caused elimination of bi-oriented attachments of sister chromatids, whereas in chiasma-lacking cells, they caused elimination of mono-oriented attachments. In chiasma-forming cells, in addition, homologous centromere oscillation was coordinated. Furthermore, Dam1 contributed to attachment elimination in both chiasma-forming and chiasma-lacking cells, and drove centromere oscillation. These results demonstrate that chiasmata alter attachment correction patterns by enabling error correction factors to eliminate bi-oriented attachment of sister chromatids, and suggest that Dam1 induces elimination of erroneous attachments. The coincidental contribution of chiasmata and Dam1 to centromere oscillation also suggests a potential link between centromere oscillation and attachment elimination.

[Emergency coronary artery bypass grafting with warm blood cardioplegia for a patient with acute myocardial infarction and severe left ventricular dysfunction]

Emergency coronary artery bypass grafting was performed in a 61 year old man who developed acute severe cardiac and respiratory dysfunction after myocardial infarction. At operation cardiac arrest was obtained by warm blood cardioplegia in antegrade intermittent fashion. The left anterior descending artery, diagonal branch, and right coronary artery were revascularized by saphenous vein (SVG). After declamping the aorta, spontaneous heart beating was obtained and postoperative course was uneventful. Postoperative examination showed patent all SVGs and improved cardiac function. Although the delivery of the warm blood cardioplegia was controversial, our recent study revealed that the intermittent antegrade delivery of warm blood cardioplegia showed no ischemic changes of the heart during the procedure.