BackgroundHypoxic-ischemic encephalopathy (HIE) is a major cause of morbidity in survivors. Therapeutic hypothermia (TH) is the only available intervention, but the protection is incomplete. Preclinical studies of HIE/TH in the rodent have relied on the postnatal day (P) 7 rat whose brain approximates a 32–36 week gestation infant, less relevant for these studies. We propose that HIE and TH in the term-equivalent P10 rat will be more translational.MethodsP10–11 rat pups were subjected to unilateral hypoxia-ischemia (HI) and 4 hours recovery in normothermic (N) or hypothermic (TH) conditions. Brain damage was assessed longitudinally at 24 hours, 2 and 12 weeks. Motor function was assessed with the beam walk; recognition memory was measured by novel object recognition.ResultsNeuroprotection with TH was apparent at 2 and 12 weeks in both moderately and severely damaged animals. TH improved motor function in moderate, but not severe damage. Impaired object recognition occurred with severe damage with no evidence of protection of TH.ConclusionThis adaptation of the immature rat model of HI provides a reproducible platform to further study HIE/TH in which individual animals are followed longitudinally to provide a useful translational preclinical model.

Neonatal encephalopathy resulting from HI (hypoxia-ischaemia) continues to be a significant cause of mortality and morbidity in infants and children, affecting 1-2/1000 live term births and up to 60% of pre-term births. In order to understand the pathophysiology of this insult, as well as design therapeutic interventions, it is important to establish a relevant animal model for pre-clinical studies. One of the most frequently used models of HI-induced brain damage in immature animals is the unilateral carotid ligation/hypoxia model, initially developed in our laboratory more than 30 years ago. The original model employed the postnatal day 7 rat, whose brain is representative of that of a late gestation, pre-term [32-36 weeks GA (gestational age)] human infant. We, and others, have employed this model to characterize the pathophysiological, biochemical/energetic and neuropathological events following HI, as well as the determination of the unique characteristics of the immature brain that define its vulnerability to, and outcome from, HI. In defining the cascade of events following HI, it has become possible to identify potential targets for intervention and neuroprotection. Currently, the only available therapeutic intervention for neonatal encephalopathy in the term asphyxiated infant is therapeutic hypothermia, although this must be initiated within 6 h of birth and is at best partially effective in moderately injured infants. Ongoing pre-clinical studies are necessary to determine the basis for the partial protection afforded by hypothermia as well as the design of adjunct therapies to improve the outcome. The present review highlights the importance of using a well-characterized and relevant animal model to continue to pursue translational research in neuroprotection for the infant brain.

Mast cells are immune cells of hematopoietic origin that circulate as precursor cells prior to migration into vascularized tissues where they mature and undergo terminal differentiation in response to different cytokines within the local environment. Mast cells are well known as important regulators of inflammatory processes in peripheral tissues and recent studies support the involvement of mast cells in mediating the inflammatory response to cerebral hypoxia-ischemia in both the neonatal and adult brain. To better study mast cell function in vivo, it is important to be able to identify their environment-specific phenotype, as well as to study their interaction with other neural cells in vitro. Previous such studies of mast cells have relied on mast cells isolated from gut or bone marrow, or on a number of mast cell lines, all of which may behave differently from brain mast cells. The purpose of this study was to develop a technique for the isolation of mast cells from neonatal rat brain and to characterize these cells following hypoxia and hypoxia-ischemia. We adapted a previously described technique of coupling an antibody to the mast cell-specific FcεR1 receptor to a MACS microbead for the selective removal of intact mast cells from a neonatal brain preparation. We have isolated toluidine blue-positive brain mast cells that provide substrate for both protein analysis and in vitro studies. These cells express proteins previously used to specifically identify microglia in the brain, Iba-1 and coronin-1a. A subpopulation of mast cells in vivo also expresses Iba-1. Thus, we report a novel method for isolation of brain mast cells suitable for the study of mast cell phenotype under a variety of conditions. Further, we suggest that the use of proteins such as Iba-1 for the identification of microglia in the brain includes the caveat that mast cells may also be detected.

It is likely that most studies underestimate the prevalence of nonphysical workplace violence due to underreporting and a lack of training to identify these occurrences. Verbal abuse has been referred to as "the use of words that [are] personally insulting such as generally abusive spoken obscenities and foul language, or indicating a lack of respect for the dignity and worth of an individual." 3 The stance from the Joint Commission and the World Health Organization is that verbal abuse is a form of workplace violence and undermines the culture of safety.