Acute diffuse axonal injury following repeated mild traumatic brain injury in juvenile rats

Mild traumatic brain injuries (mTBIs) are caused by biomechanical forces being transmitted to the brain, causing neuronal connections to be subjected to sheering forces. The injury severity can be affected by a number of factors that include age and sex, however, there remains a paucity of data on how repeated mTBI (r-mTBI) impacts the female brain. In these studies, male and female juvenile rats [postnatal day (PND) 25-26] were administered a total of eight mTBIs over a 2-day period. Following each mTBI, rats were immediately assessed for acute neurological impairment. After eight mTBIs were completed, the Barnes maze was used to assess spatial learning and memory. Axonal injury was assessed using silver stain histological analyses. We found that injured females exhibited less acute neurological impairment than males. Three days after the final r-mTBI, no significant differences were observed in spatial learning and memory, with all animals showing similar times to locate the escape platform on the reversal trial, additionally there was no main effect of sex in the Barnes maze. Silver stain uptake was significantly increased in the optic tract, corpus callosum, and cortex compared with sham animals at seven days postinjury in a sex-specific manner. Females showed significant increase in all three regions following r-mTBI, whereas males only showed a significant increase in staining in the optic tract. Overall, these findings show that females may be more susceptible to axonal damage than males, and that cognitive deficits were not evident in this population following r-mTBI. These results indicate that there may be benefits in examining biomarkers that reflect axonal injury and the therapies that target reducing axonal degradation.NEW & NOTEWORTHY Diffuse axonal injury is a hallmark feature of all severities of traumatic brain injury (TBI) yet, in preclinical mild (m)TBI research no studies have yet investigated axonal damage with silver stain immunohistochemistry in female animals. This is a critical gap in the literature as recent studies suggest that females experience mTBI more frequently than males. We found that repeated mTBI (r-mTBI) caused significant diffuse axonal injury that was more pronounced in females compared with males.

The rural CPR outreach project: Medical students teach bystander CPR to secondary school students

INTRODUCTION

Prompt bystander cardiopulmonary resuscitation (CPR) can double the chance of cardiac arrest survival. Rural and remote communities experience longer emergency service wait times and have lower rates of bystander-CPR compared to their urban counterparts. Our study addresses this disparity.

METHODS

We designed a 1.5-h free hands-only CPR course tailored to secondary school students in rural and remote communities taught by medical students. We evaluated our course using pre-test and post-test surveys.

RESULTS

We taught over 300 secondary students in 5 days. Less than one-third of students had previously taken a CPR course. We found that brief CPR instruction taught by medical students was effective in both improving students' knowledge of CPR (t[528] = -26, P < 0.01) and perceived comfort in performing CPR (t[548] = -12, P < 0.01).

CONCLUSION

CPR courses taught by medical students are effective, low cost, and may help address regional health care disparities. Teaching CPR to rural/remote communities may have secondary benefits such as promoting health care careers to rural youth. We encourage other health professional programmes to consider engaging students in CPR outreach projects.

INTRODUCTION

Une réanimation cardio-pulmonaire rapide peut doubler les chances de survie en cas d'arrêt cardiaque. Les communautés rurales et éloignées connaissent des temps d'attente plus longs dans les services d'urgence et ont des taux plus faibles de RCP par rapport à leurs homologues urbains. Notre étude porte sur cette disparité.

MTHODES

Nous avons conçu un cours de RCP pratique et gratuit d'une heure et demie, adapté aux élèves du secondaire des communautés rurales et isolées et dispensé par des étudiants en médecine. Nous avons évalué notre cours à l'aide d'enquêtes pré-test et post-test.

RSULTATS

En 5 jours, nous avons enseigné à plus de 300 élèves du secondaire. Moins d'un tiers des élèves avaient déjà suivi un cours de RCP. Nous avons constaté qu'une brève formation à la RCP dispensée par des étudiants en médecine était efficace pour améliorer les connaissances des élèves en matière de RCP (t[528] = -26, P < 0,01) et la perception de leur aisance à pratiquer la RCP (t[548] = -12, P < 0,01).

CONCLUSION

Les cours de RCP dispensés par les étudiants en médecine sont efficaces, peu coûteux et peuvent contribuer à lutter contre les disparités régionales en matière de soins de santé. L'enseignement de la RCP aux communautés rurales/éloignées peut avoir des avantages secondaires tels que la promotion des carrières dans le domaine de la santé auprès des jeunes ruraux. Nous encourageons d'autres programmes professionnels de santé à envisager d'engager leurs étudiants dans des projets de sensibilisation à la RCP.

Repeated mild traumatic brain injury causes sex-specific increases in cell proliferation and inflammation in juvenile rats

Childhood represents a period of significant growth and maturation for the brain, and is also associated with a heightened risk for mild traumatic brain injuries (mTBI). There is also concern that repeated-mTBI (r-mTBI) may have a long-term impact on developmental trajectories. Using an awake closed head injury (ACHI) model, that uses rapid head acceleration to induce a mTBI, we investigated the acute effects of repeated-mTBI (r-mTBI) on neurological function and cellular proliferation in juvenile male and female Long-Evans rats. We found that r-mTBI did not lead to cumulative neurological deficits with the model. R-mTBI animals exhibited an increase in BrdU + (bromodeoxyuridine positive) cells in the dentate gyrus (DG), and that this increase was more robust in male animals. This increase was not sustained, and cell proliferation returning to normal by PID3. A greater increase in BrdU + cells was observed in the dorsal DG in both male and female r-mTBI animals at PID1. Using Ki-67 expression as an endogenous marker of cellular proliferation, a robust proliferative response following r-mTBI was observed in male animals at PID1 that persisted until PID3, and was not constrained to the DG alone. Triple labeling experiments (Iba1+, GFAP+, Brdu+) revealed that a high proportion of these proliferating cells were microglia/macrophages, indicating there was a heightened inflammatory response. Overall, these findings suggest that rapid head acceleration with the ACHI model produces an mTBI, but that the acute neurological deficits do not increase in severity with repeated administration. R-mTBI transiently increases cellular proliferation in the hippocampus, particularly in male animals, and the pattern of cell proliferation suggests that this represents a neuroinflammatory response that is focused around the mid-brain rather than peripheral cortical regions. These results add to growing literature indicating sex differences in proliferative and inflammatory responses between females and males. Targeting proliferation as a therapeutic avenue may help reduce the short term impact of r-mTBI, but there may be sex-specific considerations.