Mutation of the cohesin related gene PDS5 causes cell death with predominant apoptotic features in Saccharomyces cerevisiae during early meiosis.

Pds5p is a cohesin related protein. It is required for maintenance of sister chromatid cohesion in mitosis and meiosis. Here we report that pds5-1 causes cell death in yeast Saccharomyces cerevisiae during early meiosis. The pds5-1 caused cell death possesses characteristics of apoptosis and necrosis, including externalization of phosphatidylserine at cytoplasmic membrane, accumulation of DNA breaks, chromatin condensation and fragmentation, nuclei fragmentation, membrane degeneration and cell size enlargement. Our results also suggest that (1) The defect of DNA repair; (2) The production of reactive oxygen species, in pds5-1 mutant are involved in pds5-1 induced cell death.

Quantitative dynamics of in vivo bone marrow neutrophil production and egress in response to injury and infection.

Production rates of blood cells from the bone marrow (BM) can be determined from pool size and residence time in the circulation only during steady state. We describe a method to evaluate changes in BM neutrophil production following severe injury. Male CD-1 mice underwent nonlethal cutaneous burn injury, a lethal burn injury with Pseudomonas aeruginosa infection, or sham treatment, and received bromodeoxyuridine (BrdU) to label proliferative cells. Rates of BM neutrophil production and release into the circulation were determined using a mathematical model that integrates BM neutrophil pool size and fraction of BrdU labeled cells as a function of time. Absolute rates could not be quantified without BrdU data for the neutrophil progenitor pool; however, relative rates could be determined. BM neutrophil production and release significantly increased after injury. After nonlethal burn, release transiently exceeded production, causing a temporary decrease in BM neutrophil stores followed by reestablishment of a steady-state BM neutrophil pool similar to sham controls. After lethal burn infection, release always exceeded production, causing complete depletion of BM neutrophils and suppression of BM neutrophil production. This method is generally applicable to estimating production rates of nonproliferating, terminally differentiated cells, arising from a stem cell pool in vivo.

Charged polymers modulate retrovirus transduction via membrane charge neutralization and virus aggregation.

The specific mechanisms of charged polymer modulation of retrovirus transduction were analyzed by characterizing their effects on virus transport and adsorption. From a standard colloidal perspective two mechanisms, charge shielding and virus aggregation, can potentially account for the experimentally observed changes in adsorption behavior and biophysical parameters due to charged polymers. Experimental testing revealed that both mechanisms could be at work depending on the characteristics of the cationic polymer. All cationic polymers enhanced adsorption and transduction via charge shielding; however, only polymers greater than 15 kDa in size were capable of enhancing these processes via the virus aggregation mechanism, explaining the higher efficiency enhancement of the high molecular weight molecules. The role of anionic polymers was also characterized and they were found to inhibit transduction via sequestration of cationic polymers, thereby preventing charge shielding and virus aggregation. Taken together, these findings suggest the basis for a revised physical model of virus transport that incorporates electrostatic interactions through both virus-cell repulsive and attractive interactions, as well as the aggregation state of the virus.

Kinetics of baculovirus replication and release using real-time quantitative polymerase chain reaction.

The study of viral-based processes is hampered by (a) their complex, transient nature, (b) the instability of products, and (c) the lack of accurate diagnostic assays. Here, we describe the use of real-time quantitative polymerase chain reaction to characterize baculoviral infection. Baculovirus DNA content doubles every 1.7 h from 6 h post-infection until replication is halted at the onset of budding. No dynamic equilibrium exists between replication and release, and the kinetics are independent of the cell density at the time of infection. No more than 16% of the intracellular virus copies bud from the cell.