Surface contamination of hazardous drug pharmacy storage bins and pharmacy distributor shipping containers.

Purpose This study was conducted to determine whether there is contamination on exterior drug packaging using shipping totes from the distributor and carousel storage bins as surrogate markers of external packaging contamination. Methods A two-part study was conducted to measure the presence of 5-fluorouracil, ifosfamide, cyclophosphamide, docetaxel and paclitaxel using surrogate markers for external drug packaging. In Part I, 10 drug distributor shipping totes designated for transport of hazardous drugs provided a snapshot view of contamination from regular use and transit in and out of the pharmacy. An additional two totes designated for transport of non-hazardous drugs served as controls. In Part II, old carousel storage bins (i.e. those in use pre-study) were wiped for snapshot view of hazardous drug contamination on storage bins. New carousel storage bins were then put into use for storage of the five tested drugs and used for routine storage and inventory maintenance activities. Carousel bins were wiped at time intervals 0, 8, 16 and 52 weeks to measure surface contamination. Results Two of the 10 hazardous shipping totes were contaminated. Three of the five-old carousel bins were contaminated with cyclophosphamide. One of the old carousel bins was also contaminated with ifosfamide. There were no detectable levels of hazardous drugs on any of the new storage bins at time 0, 8 or 16 weeks. However, at the Week 52, there was a detectable level of 5-FU present in the 5-FU carousel bin. Conclusions Contamination of the surrogate markers suggests that external packaging for hazardous drugs is contaminated, either during the manufacturing process or during routine chain of custody activities. These results demonstrate that occupational exposure may occur due to contamination from shipping totes and storage bins, and that handling practices including use of personal protective equipment is warranted.

Microtubule amplification in the assembly of mitotic spindle and the maturation of kinetochore fibers.

Efficient assembly of a mitotic spindle and stable attachment of microtubules (k-fibers) to kinetochores are essential for the high fidelity of chromosome segregation. Both spindle assembly and k-fiber formation require robust nucleation and polymerization of microtubules mediated by the gamma-tubulin ring complex (gammaTuRC). It has been well established that centrosomes and chromatin are the two centers for microtubule nucleation. We recently demonstrate a third mechanism for microtubule nucleation and polymerization, in which the existing microtubules in the spindle act as templates to promote the formation of new microtubules. We showed that a novel spindle-associated protein, FAM29A, plays a critical role in this microtubule-dependent microtubule amplification. FAM29A associates with spindle microtubules and directly interacts with and recruits NEDD1, the targeting subunit of gammaTuRC. Spindle-associated gammaTuRC then promotes microtubule nucleation required for spindle assembly and k-fiber formation. This novel microtubule amplification pathway provides a powerful mechanism to control the local cytoskeleton structures independent of centrosomes and chromatin. We speculate that microtubule amplification not only functions in mitosis, but may also act in other physiological processes to re-enforce existing cytoskeleton structures.

FAM29A, a target of Plk1 regulation, controls the partitioning of NEDD1 between the mitotic spindle and the centrosomes.

We previously showed that FAM29A, a spindle-associated protein, promotes microtubule-dependent microtubule amplification through its interaction with and recruitment of NEDD1, the targeting subunit of the gamma-tubulin ring complex. We report here that FAM29A is regulated by Plk1, a kinase essential for spindle assembly and its bipolarity. Plk1, FAM29A and NEDD1 form three separate complexes in vivo, not one single complex. Plk1 recruits FAM29A to spindle microtubules, which, in turn, targets NEDD1 to the spindle. Plk1 also recruits NEDD1 to the centrosomes, probably through a Plk1-NEDD1 interaction, but this interaction does not contribute to targeting NEDD1 to the spindle. Altering intracellular levels of FAM29A changes the distribution of NEDD1 between the centrosomes and the spindle, indicating that FAM29A controls the partition of NEDD1 between these two mitotic structures. Thus, Plk1 promotes microtubule nucleation from the centrosomes through a FAM29A-independent pathway and from the spindle through a FAM29A-dependent pathway. FAM29A controls the relative contributions of these two pathways to microtubule polymerization during mitosis.

Mechanism, function and regulation of microtubule-dependent microtubule amplification in mitosis.

Mitotic spindle mediates the segregation of chromosomes in the cell cycle and the proper function of the spindle is crucial to the high fidelity of chromosome segregation and to the stability of the genome. Nucleation of microtubules (MTs) from centrosomes and chromatin represents two well-characterized pathways essential for the assembly of a dynamic spindle in mitosis. Recently, we identified a third MT nucleation pathway, in which existing MTs in the spindle act as a template to promote the nucleation and polymerization of MTs, thereby efficiently amplifying MTs in the spindle. We will review here our current understanding on the molecular mechanism, the physiological function and the cell-cycle regulation of MT amplification.