Correct cell cycle regulation and terminal mitosis are critical for nervous system development. The retinoblastoma (Rb) protein is a key regulator of these processes, as Rb-/- embryos die by E15.5, exhibiting gross hematopoietic and neurological defects. The extensive apoptosis in Rb-/- embryos has been attributed to aberrant S phase entry resulting in conflicting growth control signals in differentiating cells. To assess the role of Rb in cortical development in the absence of other embryonic defects, we examined mice with telencephalon-specific Rb deletions. Animals carrying a floxed Rb allele were interbred with mice in which cre was knocked into the Foxg1 locus. Unlike germline knockouts, mice specifically deleted for Rb in the developing telencephalon survived until birth. In these mutants, Rb-/- progenitor cells divided ectopically, but were able to survive and differentiate. Mutant brains exhibited enhanced cellularity due to increased proliferation of neuroblasts. These studies demonstrate that: (i) cell cycle deregulation during differentiation does not necessitate apoptosis; (ii) Rb-deficient mutants exhibit enhanced neuroblast proliferation; and (iii) terminal mitosis may not be required to initiate differentiation.

The role of the canonical NF-kB pathway in mammary tumorigenesis was investigated using a transgenic (TG) mouse expressing a dominant-negative inhibitor of kB (IkBa SR (S32A/S36A) ) in the mammary gland under the control of the mouse mammary tumor virus promoter (MMTV). TG and control mice were subjected to a chemical carcinogenesis protocol. Hyperkeratinized squamous metaplasias (cytokeratinÀ6 þ /p63 þ ) sometimes with a basaloid island component, were found in both TG and control mice whereas luminal (cytokeratin-19 þ / MUC1 þ ) ErbB2 þ papillary and adenomatous lesions developed almost exclusively in control mice. p65/RelAand NF-kB DNA-binding activity were detected in mammary luminal lesions, but rarely in squamous metaplasias. Analysis of NF-kB family proteins and target genes using microarray data from a cohort of human mammary tumors revealed the expression of a canonical NF-kB pathway, but not non-canonical pathway proteins in HER2 þ luminal cancers. HER2 þ tumors also showed differential regulation of specific NF-kB target genes relative to basal and ER þ luminal cancers. Isolation of mammary cell populations enriched for stem and progenitor cell characteristics from an NF-kB-EGFP reporter mouse by fluorescence-activated cell sorting demonstrated that luminal progenitors contain activated NF-kB whereas the mammary stem cell-enriched population, does not. Together these data suggest that the canonical NF-kB pathway is active in normal luminal progenitor cells before transformation and is required for the formation of mammary luminal-type epithelial neoplasias.

BackgroundHealthcare-associated infections affect 10% of patients in Canadian acute-care hospitals and are significant and preventable causes of morbidity and mortality among hospitalized patients. Hand hygiene is among the simplest and most effective preventive measures to reduce these infections. However, compliance with hand hygiene among healthcare workers, specifically among physicians, is consistently suboptimal. We aim to first identify the barriers and enablers to physician hand hygiene compliance, and then to develop and pilot a theory-based knowledge translation intervention to increase physicians’ compliance with best hand hygiene practice.DesignThe study consists of three phases. In Phase 1, we will identify barriers and enablers to hand hygiene compliance by physicians. This will include: key informant interviews with physicians and residents using a structured interview guide, informed by the Theoretical Domains Framework; nonparticipant observation of physician/resident hand hygiene audit sessions; and focus groups with hand hygiene experts. In Phase 2, we will conduct intervention mapping to develop a theory-based knowledge translation intervention to improve physician hand hygiene compliance. Finally, in Phase 3, we will pilot the knowledge translation intervention in four patient care units.DiscussionIn this study, we will use a behavioural theory approach to obtain a better understanding of the barriers and enablers to physician hand hygiene compliance. This will provide a comprehensive framework on which to develop knowledge translation interventions that may be more successful in improving hand hygiene practice. Upon completion of this study, we will refine the piloted knowledge translation intervention so it can be tested in a multi-site cluster randomized controlled trial.

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The Bcl-2 gene is positively regulated by estrogen (E2) primarily through E2-response elements in the coding region and a putative p53 negative regulatory element (NRE) containing a short upstream open reading frame (uORF). The ability of mutant p53 to repress or induce Bcl-2 expression is controversial. In this study E2-receptor positive (ER(+))/wild-type p53 MCF-7cells were transfected with p53Delta291, which lacks a nuclear localization signal or a DNA binding domain mutant, p53(173L). Both p53 mutants but especially p53Delta291 increased Bcl-2 protein expression from a CMV-NRE-Bcl-2 cDNA construct in an NRE-position/orientation independent manner as well as from a 1.7 kb Bcl-2 promoter reporter gene. Bcl-2 protein expression prevented the p53Delta291-mediated increase in Bcl-2 promoter activity although immunoprecipitation demonstrated that only a small proportion of the wild-type p53 but not p53Delta91 protein interacts with Bcl-2. Unless levels of ectopically expressed mutant p53 were extremely high, stable expression of mutant p53 in MCF-7 cells moderately increased Bcl-2 protein levels. Expression of mutant p53 did not alter E2 regulation of Bcl-2, however, mutation of the uORF prevented regulation by both mutant p53 and E2. Adenovirus-mediated overexpression of WT p53 strongly reduced Bcl-2 expression in ER(-)/mut p53 MDA-MB-231 cells. Taken together these data support the position that mutant p53 behaves in a dominant "positive" manner relieving repression by WT p53 or another Bcl-2 transcriptional inhibitor in a manner independent of nuclear translocation.