To determine whether myocyte mitotic division occurs in the adult mammalian heart and whether this cellular process is affected by aging, we measured the percentage of myocyte nuclei showing metaphase chromosomes in myocytes isolated from the left and right ventricles of rats at 8-12, 19-24, and 28-32 months after birth. Metaphase chromosomes were found at all ages in both ventricles. However, ...

The angle of cell division is critical in at least two contexts. It can determine cell fate, as it does in developing neural tissue. It can also dictate tissue architecture, as it does in many epithelia. One way to ensure the correct angle of cell division is through controlled orientation of the spindle at metaphase. What happens when that control is lost? Ongoing work suggests that the conseq...

For three species of grasshoppers the volumes of the largest and the smallest metaphase chromosome differ by a factor of 10, but the microtubules (MTs) attached to the individual kinetochores show no corresponding range in numbers. Locusta mitotic metaphase chromosomes range from 2 to 21 mum, and the average number of MTs per kinetochore is 21 with an SD of 4.6. Locusta meiotic bivalents at lat...

In Chinese hamster Don cells, fusion of an interphase cell with a metaphase cell resulted either in prophasing of the interphase nucleus, including loss of the nuclear envelope (NE), or in the formation of a double membrane around the metaphase chromosomes. Only one of these phenomena occurred in a given interphase-metaphase (I-M) binucleate cell. At pH 7.4, there was about an equal probability...

A simple and efficient method for the maintenance of Acheta domeslicus spermatocytes in vitro while permitting microscopic observation during meiotic maturation is described. The method allows the study of the factors effecting normal maturation and is applicable to other organisms. Three media are described: MM 100 contains only salts in the concentrations found in Acheta hemolymph; MMIOI cont...