A comparison of the distribution of actin and tubulin in the mammalian mitotic spindle as seen by indirect immunofluorescence

Rabbit antibodies against actin and tubulin were used in an indirect immunofluorescence study of the structure of the mitotic spindle of PtK1 cells after lysis under conditions that preserve anaphase chromosome movement. During early prophase there is no antiactin staining associated with the mitotic centers, but by late prophase, as the spindle is beginning to form, a small ball of actin antigenicity is found beside the nucleus; After nuclear envelope breakdown, the actiactin stains the region around each mitotic center, and becomes organized into fibers that run between the chromosomes and the poles. Colchicine blocks this organization, but does not disrupt the staining at the poles. At metaphase the antiactin reveals a halo of ill-defined radius around each spindle pole and fibers that run from the poles to the metaphase plate. Antitubulin shows astral rays, fibers running from chromosomes to poles, and some fibers that run across the metaphase plate. At anaphase, there is a shortening of the antiactin-stained fibers, leaving a zone which is essentially free of actin-staining fluorescence between the separating chromosomes. Antitubulin stains the region between chromosomes and poles, but also reveals substantial fibers running through the zone between separating chromosomes. Cells fixed during cytokinesis show actin in the region of the cleavage furrow, while antitubulin reveals the fibrous spindle remnant that runs between daughter cells. These results suggest that actin is a component of the mammalian mitotic spindle, that the distribution of actin differs from that of tubulin and that the distributions of these two fibrous proteins change in different ways during anaphase

Assessing similarity of dynamic geographic phenomena in spatiotemporal databases.

The growing availability of routine observations from satellite imagery and other remote sensors holds great promise for improved understanding of processes that act in the landscape. However, geographers' ability to effectively use such spatiotemporal data is challenged by large data volume and limitations of conventional data models in geographic information systems (GIS), which provide limited support for querying and exploration of spatiotemporal data other than simple comparisons of temporally referenced snapshots. Current GIS representations allow measurement of change but do not address coherent patterns of change that reflects the working of geographic events and processes. This dissertation presents a representational and query framework to overcome the limitations and enable assessing similarity of dynamic phenomena. The research includes three self contained but related studies: (1) development of a representational framework that incorporates spatiotemporal properties of geographic phenomena, (2) development of a framework to characterize events and processes that can be inferred from GIS databases, and (3) development of a method to assess similarity of events and processes based on the temporal sequences of spatiotemporal properties. Collectively the studies contribute to scientific understanding of spatiotemporal components of geographic processes and technological advances in representation and analysis

Mechanisms of Mitotic Chromosome Segregation

This book describes current knowledge about the mechanisms by which cells segregate their already duplicated chromosomes in preparation for cell division. Experts in the field treat several important aspects of this subject: (1) the history of research on mitotic mechanisms, to serve as a background; (2) assembly of the mitotic spindle; (3) Kinetochore assembly and function; (4) the mechanisms of chromosome congression to the metaphase plate; (5) the spindle assembly checkpoint; (6) mechanisms to avoid and correct erroneous chromosome attachments to the spindle; (7) a molecular perspective on spindle assembly in land plants; (8) chromosome segregation in anaphase A; (9) spindle elongation in anaphase B; and (10) the consequences of errors in chromosome segregation. Each chapter provides the reader with a comprehensive and accurate picture of current research in a form that is both readable and authoritative. The volume is suitable for scholars in this and related fields and for teaching at an advanced level