Differential Response of Neural Cells to Trauma-Induced Swelling In Vitro.

Brain edema and the associated increase in intracranial pressure are major consequences of traumatic brain injury (TBI) that accounts for most early deaths after TBI. We recently showed that acute severe trauma to cultured astrocytes results in cell swelling. We further examined whether trauma induces cell swelling in neurons and microglia. We found that severe trauma also caused cell swelling in cultured neurons, whereas no swelling was observed in microglia. While severe trauma caused cell swelling in both astrocytes and neurons, mild trauma to astrocytes, neurons, and microglia failed to cell swelling. Since extracellular levels of glutamate are increased in brain post-TBI and microglia are known to release cytokine, and direct exposure of astrocytes to these molecules are known to stimulate cell swelling, we examined whether glutamate or cytokines have any additive effect on trauma-induced cell swelling. Exposure of cultured astrocytes to trauma caused cell swelling, and such swelling was potentiated by the exposure of traumatized astrocytes to glutamate and cytokines. Conditioned medium (CM) from traumatized astrocytes had no effect on neuronal swelling post-trauma, while CM from traumatized neurons and microglia potentiated the effect of trauma on astrocyte swelling. Further, trauma significantly increased the Na-K-Cl co-transporter (NKCC) activity in neurons, and that inhibition of NKCC activity diminished the trauma-induced neuronal swelling. Our results indicate that a differential sensitivity to trauma-induced cell swelling exists in neural cells and that neurons and microglia are likely to be involved in the potentiation of the astrocyte swelling post-trauma.

Non-occupational post-exposure prophylaxis in Victoria, Australia: responding to high rates of re-presentation and low rates of follow-up.

In Australia, the non-occupational post-exposure prophylaxis service in Victoria (VNPEPS) maintains a database of non-occupational post-exposure prophylaxis (NPEP) use throughout the state. Through the database the service can monitor and respond to patterns of NPEP presentation, re-presentation and follow-up as well as those who test positive for HIV. We describe a cohort of NPEP individuals from the commencement of the service to 31 December 2009. During this time, 1864 individuals presented for NPEP on 2396 occasions. The majority (85%) were men who have sex with men (MSM) presenting after receptive anal intercourse (56.1%). Repeat NPEP presentations were high (17.5%) and follow-up testing at week 12 post-NPEP was low (34%). Twenty-two patients (1.2%) tested positive for HIV at baseline presentation and six patients seroconverted to HIV during follow-up. The VNPEPS has initiated strategies to encourage behaviour change for those who re-present for NPEP, and to improve rates of week 12 follow-up.