Using network analyses to characterise Australian and Canadian frequent attenders to the emergency department.

OBJECTIVE: To explore and compare the characteristics of frequent attenders to the ED at an Australian and a Canadian tertiary hospitals by utilising a network analysis approach. METHODS: We conducted a retrospective population-based study using administrative data over the 2018 and 2019 calendar years. Participants were from a tertiary hospital in Melbourne, Australia, and Toronto, Canada. Frequent attenders were defined as patients with four or more visits in 12 months. Characteristics of younger (18-39 years), middle-aged (40-69 years) and older (70 years and older) frequent attenders were described using descriptive statistics and network analyses. RESULTS: Younger frequent attenders were characterised by mental illness and substance use, while older frequent attenders had high rates of physical (including chronic) diseases. Middle-aged frequent attenders were characterised by a combination of mental and physical illnesses. These findings were observed at both hospitals. Across all age groups, the network analyses between the Melbourne and Toronto hospitals were different. Among older frequent attender visits, more diagnoses were associated with high triage acuity at the Toronto hospital than at the Melbourne hospital. Some associations were similar at both sites, for example, the negative correlation between high triage acuity and joint pain. CONCLUSION: Younger, middle-aged and older frequent attenders have distinct characteristics, made readily apparent by using network analyses. Future interventions to reduce ED visits should consider the heterogeneity of frequent attenders who have needs specific to their age, presenting problems and jurisdiction.

A dominant-negative isoform of IKAROS expands primitive normal human hematopoietic cells.

Disrupted IKAROS activity is a recurrent feature of some human leukemias, but effects on normal human hematopoietic cells are largely unknown. Here, we used lentivirally mediated expression of a dominant-negative isoform of IKAROS (IK6) to block normal IKAROS activity in primitive human cord blood cells and their progeny. This produced a marked (10-fold) increase in serially transplantable multipotent IK6(+) cells as well as increased outputs of normally differentiating B cells and granulocytes in transplanted immunodeficient mice, without producing leukemia. Accompanying T/natural killer (NK) cell outputs were unaltered, and erythroid and platelet production was reduced. Mechanistically, IK6 specifically increased human granulopoietic progenitor sensitivity to two growth factors and activated CREB and its targets (c-FOS and Cyclin B1). In more primitive human cells, IK6 prematurely initiated a B cell transcriptional program without affecting the hematopoietic stem cell-associated gene expression profile. Some of these effects were species specific, thus identifying novel roles of IKAROS in regulating normal human hematopoietic cells.

Glutathione-dependent and -independent oxidative stress-control mechanisms distinguish normal human mammary epithelial cell subsets.

Mechanisms that control the levels and activities of reactive oxygen species (ROS) in normal human mammary cells are poorly understood. We show that purified normal human basal mammary epithelial cells maintain low levels of ROS primarily by a glutathione-dependent but inefficient antioxidant mechanism that uses mitochondrial glutathione peroxidase 2. In contrast, the matching purified luminal progenitor cells contain higher levels of ROS, multiple glutathione-independent antioxidants and oxidative nucleotide damage-controlling proteins and consume O2 at a higher rate. The luminal progenitor cells are more resistant to glutathione depletion than the basal cells, including those with in vivo and in vitro proliferation and differentiation activity. The luminal progenitors also are more resistant to H2O2 or ionizing radiation. Importantly, even freshly isolated "steady-state" normal luminal progenitors show elevated levels of unrepaired oxidative DNA damage. Distinct ROS control mechanisms operating in different subsets of normal human mammary cells could have differentiation state-specific functions and long-term consequences.