Effect of acute restraint stress in a polytrauma rat model

Effects of sequential aeromedical evacuations following traumatic brain injury in swine

INTRODUCTION

Traumatic brain injuries (TBI) represent a significant percentage of critical injuries in military conflicts. Following injury, wounded warfighters are often subjected to multiple aeromedical evacuations (AE) and associated hypobaria, yet the impact in TBI patients remains to be characterized. This study evaluated the impact of two consecutive simulated AEs in a fluid-percussion TBI model in swine to characterize these effects.

METHODS

Following instrumentation, anesthetized Yorkshire swine underwent a frontal TBI via fluid-percussion. A hypobaric chamber was then used to simulate AE at simulated cabin pressure equivalent to 8000ft (hypobaria) in a 6 h initial flight on day 3, followed by a 9 h flight on day 6, and were monitored for 14 days. Animals in the normobaria group were subjected to the same steps at sea level while Sham animals in both groups were instrumented but not injured. Parameters measured included physiologic response, intracranial pressure (ICP), hematology, chemistry, and serum cytokines. Histopathology of brain, lung, intestine, and kidney was performed, as well as fluorojade staining to evaluate neurodegeneration. All animals were divided into sub-groups by block randomization utilizing a 2-way ANOVA to analyze independent variables.

RESULTS

Survival was 100% in all groups. Physiologic parameters were largely similar across groups as well during both 6 and 9 h AE. Animals exposed to hypobaria in both the TBI and Sham groups had elevated heart rate (HR) during the 6 h flight (p<0.05). Three animals in the TBI hypo group demonstrated leukocytosis with histologic evidence of meningeal inflammatory response. Expression of serum cytokines was low across all groups. No significant neuronal degeneration was identified in areas away from the site of injury.

CONCLUSION

Aeromedical evacuation in swine was not associated with significant differences in physiologic measures, cytokine expression or levels of neuronal degeneration. Histological examination revealed higher risk of meningeal inflammatory response and leucocytosis in swine exposed to hypobaria.

Features of the functional state of the organism of sheep under stress

The stresses that arise during routine animal husbandry procedures, such as milking, shearing, weighing, loading and hoof care, are an actual problem in animal husbandry. The components of economic damage under stress are a decrease in overall resistance and productivity, deterioration in product quality, an increase in labor costs and funds per unit of production, an increase in animal morbidity and mortality. The studies were carried out on the basis of Belozernoe farm in the Salsky district, the Rostov region. A complex of clinical and laboratory studies was performed on 18 sheep (10 Romanov and 8 Tsigay breeds) aged 2 to 3 years, before and after a planned routine shearing. Stress in sheep caused by planned shearing was clinically manifested by general depression, in some cases, subfebrile fever, moderate tachypnea and tachycardia. It was shown that stress was accompanied by anemia, the development of erythropenia and leukopenia. Immunocompetent cells in the blood of experimental animals during stress development were analyzed. Severe lymphocytopenia was found to occur after a haircut. In addition, in the blood of experimental animals under stress, a tendency to a decrease in T-total cells was noted, which was accompanied by an increase in 0-cells, which was significant in sheep of the Tsigay breed (p0.05). When analyzing the main immunoregulatory T cells in sheep under stress, a significant increase in T-suppressors was revealed with a relatively stable level of T-helpers in the blood studied. Thus, a significant (p0.05) increase in the level of T-suppressors in sheep of Romanov and Tsigay breeds was recorded; it was by 1.15 and 1.19 times higher compared with the initial data. It should be noted that we did not find any significant differences between animals of Romanov and Tsigay breeds in stress development after shearing. The obtained data should be taken into account in the further search for methods of stress correction in sheep.

Neurobiological Links between Stress, Brain Injury, and Disease

Stress, which refers to a combination of physiological, neuroendocrine, behavioral, and emotional responses to novel or threatening stimuli, is essentially a defensive adaptation under physiological conditions. However, strong and long-lasting stress can lead to psychological and pathological damage. Growing evidence suggests that patients suffering from mild and moderate brain injuries and diseases often show severe neurological dysfunction and experience severe and persistent stressful events or environmental stimuli, whether in the acute, subacute, or recovery stage. Previous studies have shown that stress has a remarkable influence on key brain regions and brain diseases. The mechanisms through which stress affects the brain are diverse, including activation of endoplasmic reticulum stress (ERS), apoptosis, oxidative stress, and excitatory/inhibitory neuron imbalance, and may lead to behavioral and cognitive deficits. The impact of stress on brain diseases is complex and involves impediment of recovery, aggravation of cognitive impairment, and neurodegeneration. This review summarizes various stress models and their applications and then discusses the effects and mechanisms of stress on key brain regions—including the hippocampus, hypothalamus, amygdala, and prefrontal cortex—and in brain injuries and diseases—including Alzheimer’s disease, stroke, traumatic brain injury, and epilepsy. Lastly, this review highlights psychological interventions and potential therapeutic targets for patients with brain injuries and diseases who experience severe and persistent stressful events.

Brain Trauma, Glucocorticoids and Neuroinflammation: Dangerous Liaisons for the Hippocampus

Glucocorticoid-dependent mechanisms of inflammation-mediated distant hippocampal damage are discussed with a focus on the consequences of traumatic brain injury. The effects of glucocorticoids on specific neuronal populations in the hippocampus depend on their concentration, duration of exposure and cell type. Previous stress and elevated level of glucocorticoids prior to pro-inflammatory impact, as well as long-term though moderate elevation of glucocorticoids, may inflate pro-inflammatory effects. Glucocorticoid-mediated long-lasting neuronal circuit changes in the hippocampus after brain trauma are involved in late post-traumatic pathology development, such as epilepsy, depression and cognitive impairment. Complex and diverse actions of the hypothalamic–pituitary–adrenal axis on neuroinflammation may be essential for late post-traumatic pathology. These mechanisms are applicable to remote hippocampal damage occurring after other types of focal brain damage (stroke, epilepsy) or central nervous system diseases without obvious focal injury. Thus, the liaisons of excessive glucocorticoids/dysfunctional hypothalamic–pituitary–adrenal axis with neuroinflammation, dangerous to the hippocampus, may be crucial to distant hippocampal damage in many brain diseases. Taking into account that the hippocampus controls both the cognitive functions and the emotional state, further research on potential links between glucocorticoid signaling and inflammatory processes in the brain and respective mechanisms is vital.

Association between serum calcium level and hemorrhagic progression in patients with traumatic intraparenchymal hemorrhage: Investigating the mediation and interaction effects of coagulopathy

In this study, we investigate the association of serum calcium with coagulopathy and hemorrhagic progression contusion (HPC) in patients with traumatic intraparenchymal hemorrhage (tIPH), and further explored the interaction and mediation effect between serum calcium as well as coagulopathy on HPC. Retrospective analyses of patients with tIPH admitted to the First Affiliated Hospital of Wenzhou Medical University between January 2016 to December 2019. The clinical data, coagulation parameters, and serum calcium levels were collected for further analysis. Multivariate logistic regression analysis was applied to identify the association of serum calcium level with coagulopathy and HPC. Causal mediation analysis (CMA) and additive interaction model were used to estimate the interaction and mediation effect between serum calcium as well as coagulopathy on HPC. Additionally, we repeated the analysis using corrected calcium. A total of 473 patients were included in this study. Of these, 54 (11.4%) patients had hypocalcemia at admission, 105 (22.2%) presented with coagulopathy, and 187 (39.5%) experienced HPC. Admission serum calcium level in patients presented with coagulopathy and HPC were 8.84 [IQR: 8.44-9.40] and 8.92 [IQR: 8.48-9.40] mg/dL respectively, which were significantly lower than that of patients without (9.10 [IQR: 8.68-9.88] and 9.12 [IQR: 8.72-9.89] mg/dL; all p < 0.001). Multivariate logistic regression analysis identified that hypocalcemia emerged as an independent risk factor for coagulopathy and HPC. However, no significant interaction was detected between hypocalcemia and coagulopathy. CMA showed that the mediator coagulopathy explained 24.4% (95% CI: 4.7-65.0%; p = 0.006) of the association between hypocalcemia and HPC. Moreover, comparable results were held using corrected calcium as well. Admission serum calcium level is associated with the HPC for patients with tIPH and this relationship is partially mediated by coagulopathy, but no significant interaction is detected. Further studies are needed to validate the findings and explore its mechanisms.