Postischemic reperfusion: ultrastructural blood-brain barrier and hemodynamic correlative changes in an awake model of transient forebrain ischemia

Cell-specific blood-brain barrier regulation in health and disease: a focus on hypoxia

The blood-brain barrier (BBB) is a complex vascular structure consisting of microvascular endothelial cells that line the vessel wall, astrocyte end-feet, pericytes, as well as the basal lamina. BBB cells act in concert to maintain the characteristic impermeable and low paracellular flux of the brain vascular network, thus ensuring a homeostatic neuronal environment. Alterations in BBB stability that occur during injury have dire consequences on disease progression and it is clear that BBB cell-specific responses, positive or negative, must make a significant contribution to injury outcome. Reduced oxygenation, or hypoxia, is a characteristic of many brain diseases that significantly increases barrier permeability. Recent data suggest that hypoxia-inducible factor (HIF-1), the master regulator of the hypoxic response, probably mediates many hypoxic effects either directly or indirectly via its target genes. This review discusses current knowledge of physiological cell-specific regulation of barrier function, their responses to hypoxia as well as consequences of hypoxic- and HIF-1-mediated mechanisms on barrier integrity during select brain diseases. In the final sections, the potential of current advances in targeting HIF-1 as a therapeutic strategy will be overviewed.

Rat forebrain perfusion in vivo by 1 artery like the isolated kidney model: a robust recovery model permitting ischemia without anesthesia to compare multiple brain injury states

BACKGROUND

Rat brain perfusion models are critical to basic research, but they can be imprecise and/or not durable for extended outcome studies.

OBJECTIVE

To demonstrate a rat brain perfusion model that provides a simplified reliable brain perfusion circuit, reduces variables during experiment and recovery, and therefore permits more precise, reliable, and context-independent research data.

METHODS

Rat forebrain perfusion was reduced surgically to that by 1 internal carotid artery without injury to the animal. The next day, the fully awake rat was studied for brain ischemia painlessly yet in the absence of anesthesia or other interventions that might bias or alter the biochemistry of the event. This model was rigorously validated with isotope cerebral blood studies during ischemia and with histology studies at 72 hours after ischemia. The first application of this model was to compare ischemia injuries for global total, global penumbra, and global shock ischemia in a single experimental context.

RESULTS

This model is accurate, reliable, and remarkably durable. This model permits the severest brain ischemia by vessel occlusion ever demonstrated in a recovery model. It also confirms that, with conditions otherwise identical, penumbra ischemia is less injurious than total ischemia and that total ischemia is less injurious than shock ischemia.

CONCLUSION

Although meticulous in construction, this model creates ischemia more simply and more reliably than the Pulsinelli 4-vessel ischemia model that inspired it, with the inherent advantages of an isolated organ system, in which a known tissue volume is perfused at a predetermined volume and rate. This model permits robust long-term recovery.

The relationship among neurocognitive performances and biopsychosocial characteristics of elite National Football League draft picks: an exploratory investigation

Sports neuropsychology has emerged as a specialty area within the field of clinical neuropsychology. The role of the sports neuropsychologist, rooted in baseline and post-concussion testing, has evolved to include other clinical domains, including the clinical assessment of potential draft picks. There is no published information on the neurocognitive characteristics of these draft picks. We sought to determine whether elite NFL draft picks differed from NFL roster athletes on neurocognitive (ImPACT) and biopsychosocial characteristics, and given that no published data exists for this population, adopted null hypotheses. Null hypotheses were rejected for two of the four ImPACT scores, as elite draft picks scored higher on measures of visual motor speed and reaction time than roster NFL athletes. Subtle but distinct neurocognitive differences are noted when comparing elite NFL draft picks with norms from a cumulative roster of a single NFL team.

Clinical applications of the tubular retractor on spinal disorders

Tubular retractor system as a minimally invasive surgery (MIS) technique has many advantages over other conventional MIS techniques. It offers direct visualization of the operative field, anatomical familiarity to spine surgeons, and minimizing tissue trauma. With technical advancement, many spinal pathologies are being treated using this system. Namely, herniated discs, lumbar and cervical stenosis, synovial cysts, lumbar instability, trauma, and even some intraspinal tumors have all been treated through tubular retractor system. Flexible arm and easy change of the tube direction are particularly useful in contralateral spinal decompression from an ipsilateral approach. Careful attention to surgical technique through narrow space will ensure that complications are minimized and will provide improved outcomes. However, understanding detailed anatomies and keeping precise surgical orientation are essential for this technique. Authors present the technical feasibility and initial results of use a tubular retractor system as a minimally invasive technique for variaties of spinal disorders with a review of literature.