Kenneth Lee

Bioassays are among the ecotoxicologist's most effective weapons in the evaluation of water quality and the assessment of ecological impacts of effluents, chemicals, discharges, and emissions on the aquatic environment. Information on these assessment aids is needed throughout the international scientific and environmental management community. This comprehensive reference provides an excellent overview of the small-scale aquatic bioassay techniques and applications currently in use around the world.\nThis special volume is the result of several years of collaboration between Environment Canada and Fisheries and Oceans Canada. Internationally recognized research scientists at many institutions have contributed to this state-of-the-art examination of the exciting, environmentally important field of microscale testing in aquatic toxicology.\nMicroscale Testing in Aquatic Toxicology contains over forty chapters covering relevant principles, new techniques and recent advancements, and applications in scientific research, environmental management, academia, and the private sector.

The HIR/HPC (histone regulation/histone periodic control) negative regulators play important roles in the transcription of six of the eight core histone genes during the Saccharomyces cerevisiae cell cycle. The phenotypes of hir1 and hir2 mutants suggested that the wild-type HIR1 and HIR2 genes encode transcriptional repressors that function in the absence of direct DNA binding. When Hir1p and Hir2p were artificially tethered to yeast promoters, each protein repressed transcription, suggesting that they represent a new class of transcriptional corepressors. The two proteins might function as a complex in vivo: Hir2p required both Hir1p and another Hir protein, Hir3p, to repress transcription when it was tethered to an HTA1-lacZ reporter gene, and Hir1p and Hir2p could be coimmunoprecipitated from yeast cell extracts. Tethered Hir1p also directed the periodic transcription of the HTA1 gene and repressed HTA1 transcription in response to two cell cycle regulatory signals. Thus, it represents the first example of a transcriptional corepressor with a direct role in cell cycle-regulated transcription.

The changing landscape of the biopharmaceutical market is driving a paradigm shift toward continuous manufacturing. To date, integrated continuous bioprocessing has not been realized as enabling technologies are nascent. In this work, a fully integrated continuous process is successfully demonstrated from pilot scale bioreactor to drug substance. Comparable product quality is observed between the continuous process and a 500 L fed-batch conventional process. The continuous process generated material at a rate of 1 kg of purified mAb every 4 days, achieving a 4.6-fold increase in productivity compared to the fed-batch process A plant throughput analysis using BioSolve software shows that a fed-batch facility with 4 × 12 500 L stainless steel bioreactors and purification train of the corresponding scale can be replaced by a continuous facility consisting of 5 × 2000 L single use bioreactors and smaller purification train, with a cost reduction of 15%.