Glial activation in white matter following ischemia in the neonatal P7 rat brain

This study examines cell death and proliferation in the white matter after neonatal stroke. In post-natal day 7 injured rat, there was a marked reduction in myelin basic protein (MBP) immunostaining mainly corresponding to numerous pyknotic immature oligodendrocytes and TUNEL-positive astrocytes in the ipsilateral external capsule. In contrast, a substantial restoration of MBP, as indicated by the MBP ratio of left-toright, occurred in the cingulum at 48 (1.27 +- 0.12) and 72 (1.30 +- 0.18, p<0.05) hours of recovery as compared to age-matched controls (1.03 +- 0.14). Ki-67 immunostaining revealed a first peak of newly-generated cells in the dorsolateral hippocampal subventricular zone and cingulum at 72 hours after reperfusion. Double immunofluorescence revealed that most of the Ki-67-positive cells were astrocytes at 48 hours and NG2 pre-oligodendrocytes at 72 hours of recovery. Microglia infiltration occurs over several days in the cingulum and a huge quantity of macrophages reached the subcortical white matter where they engulfed immature oligodendrocytes. The overall results suggest that the persistent activation of microglia involves a chronic component of immunoinflammation, which overwhelms repair processes and contributes to cystic growth in the developing brain.Comment: 30 page

Inflammatory responses in the cerebral cortex after ischemia in the P7 neonatal Rat.

International audienceBACKGROUND AND PURPOSE: The contribution of inflammatory response to the pathogenesis of ischemic lesions in the neonate is still uncertain. This study described the chronological sequence of inflammatory changes that follow cerebral ischemia with reperfusion in the neonatal P7 rat. METHODS: P7 rats underwent left middle cerebral artery electrocoagulation associated with 1-hour left common carotid artery occlusion. The spatiotemporal pattern of cellular responses was characterized immunocytochemically with the use of antibodies against rat endogenous immunoglobulins to visualize the area of the breakdown of the blood-brain barrier. Infiltration of neutrophils and T lymphocytes was demonstrated by antibodies against myeloperoxidase and a pan-T cell marker, respectively. Antibodies ED1 and OX-42 were applied to identify microglial cells and macrophages. The response of astrocytes was shown with antibodies against glial fibrillary acidic protein. Cell survival was assessed by Bcl-2 expression. Cell death was demonstrated by DNA fragmentation with the use of the terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling (TUNEL) assay and Bax immunodetection. RESULTS: Endogenous immunoglobulin extravasation through the blood-brain barrier occurred at 2 hours of recirculation and persisted until 1 month after ischemia. Neutrophil infiltration began at 24 hours and peaked at 72 to 96 hours (30+/-3.4 neutrophils per 0.3 mm(2); P<0.0001), then disappeared at 14 days after ischemia. T cells were observed between 24 and 96 hours of reperfusion. Resident microglia-macrophages exhibited morphological remnants and expressed the cell death inhibitor Bcl-2 at 24 hours of recirculation. They became numerous within the next 48 hours and peaked at 7 days after ischemia. Phenotypic changes of resident astrocytes were apparent at 24 hours, and they proliferated between 48 hours and 7 days after ischemia. Progressively inflammatory cells showed DNA fragmentation and the cell death activator Bax expression. Cell elimination continued until there was a complete disappearance of the frontoparietal cortex. CONCLUSIONS: These data demonstrate that perinatal ischemia with reperfusion triggers acute inflammatory responses with granulocytic cell infiltration, which may be involved in accelerating the destructive processes

Radio telemetry devices to monitor breathing in non-sedated animals

Radio telemetry equipment has significantly improved over the last 10-15 years and is increasingly being used in research for monitoring a variety of physiological parameters in non-sedated animals. The aim of this review is to provide an update on the current state of development of radio telemetry for recording respiration. Our literature review found only rare reports of respiratory studies via radio telemetry. Much of this article will hence report our experience with our custom-built radio telemetry devices designed for recording respiratory signals, together with numerous other physiological signals in lambs. Our current radio telemetry system allows to record 24 simultaneous signals 24h/day for several days. To our knowledge, this is the highest number of physiological signals, which can be recorded wirelessly. Our devices have been invaluable for studying respiration in our ovine models of preterm birth, reflux laryngitis, postnatal exposure to cigarette smoke, respiratory syncytial virus infection and nasal ventilation, all of which are relevant to neonatal respiratory problems

Models for Apotosis:from Newborn to Adult

Neurodegenerative diseases are characterized by progressive impairment of brain function as a consequence of ongoing neuronal cell death. Apoptotic mechanisms have been implicated in this process, but immature brain differs from the adult in its sensitivity. To better understand the pathogenesis and developmental variations of hypoxic-ischemic neuronal death, several models have been developed and investigated to characterize cell death features in the developing brain. Involvement of apoptosis-related proteins such as Bax/Bcl-2 and caspases is overviewed during development and hypoxic-ischemic injury in various models

Brief update on hemodynamic responses in animal models of neonatal stroke and hypoxia-ischemia.

International audiencePerinatal arterial stroke is a cerebrovascular event occurring around the time of birth, with pathological or radiological evidence of focal arterial infarction mainly affecting the middle cerebral arterial territory, with an incidence of 1 in 2500 term births (Badve et al., 2012). Perinatal hypoxia–ischemia (HI) is a major cause of acute mortality, with an incidence of 2–4 per 1000 full term births (Vannucci, 2000). Perinatal brain injury induced by stroke and/or HI has been associated with permanent neuropsychological handicaps, including mental retardation, cerebral palsy, epilepsy or learning disability. No therapeutic method is available for perinatal encephalopathy apart from initiating hypothermia within 6 h after birth, but only 1 infant in 6 benefits (Azzopardi et al., 2009 and Gonzalez and Ferriero, 2009). Although these studies provide proof of concept that in this context cell death is both delayed and preventable, the protection is limited and there is still no treatment available for perinatal stroke or brain injury occurring in preterm and term infants. Clinical presentations (cause, severity, magnitude, and deteriorating speed), and inherent potentials (adaptation, preconditioning-tolerance, and intolerance) against an HI or ischemic insult are different from one infant to another. Consequently, it is incumbent on scientists in the field of neonatal brain injury to address the questions of therapeutic efficacy of an array of potential therapies in several developmentally appropriate models. Towards that end, a number of new models of neonatal HI and stroke have been introduced recently, the last being that reported by Tsuji et al. (2013). These models have been designed in the rat and mouse brain and most of them present a great variability in the lesion size and brain areas damaged, whereas this last reported model in the mouse is highly reproducible with a selective cortical infarction

A model of transient unilateral focal ischemia with reperfusion in the P7 neonatal rat: morphological changes indicative of apoptosis.

Lien full text : http://stroke.ahajournals.org/cgi/reprint/29/7/1454International audienceBACKGROUND AND PURPOSE: The mechanisms leading to delayed cell death after hypoxic-ischemic injury in the developing brain remain to be elucidated. The aim of this study was to develop a model of transient focal ischemia in the neonatal rat in an attempt to create a reperfusion phase since in the filament model of reversible middle cerebral artery occlusion, size limitations precluded performing this procedure before 14 to 18 days. We then analyze whether apoptosis or necrosis occurs in this model. METHODS: Seven-day-old Wistar rat pups (n = 96) underwent permanent left middle cerebral artery occlusion in association with 1-hour occlusion of the left common carotid artery. Evolution of the brain infarction was studied from 24 hours to 3 months on cresyl violet-stained coronal sections. Infarct volume was determined with the use of the mitochondrial stain 2,3,5-triphenyltetrazolium chloride. Neuronal death was demonstrated by the silver staining method of Gallyas et al (1980). Chromatin condensation was shown by DNA fragmentation assessed with the use of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay in cryostat sections and electron microscopic analysis. RESULTS: Almost all of the animals who survived had reproducible cortical infarcts. The mean infarct volume was 31+/-7 mm3 (mean+/-SD). The ipsilateral hemisphere showed a well-delineated lesion in the frontoparietal cortex at 3-month recovery. Argyrophilic (dying) neurons were observed a few hours after reperfusion and increased with time. Cells exhibiting DNA fragmentation were shown as early as 6 hours, increased up to and peaked at 24 to 96 hours, then progressively decreased and persisted for several days, suggesting an ongoing process. Electron microscopy analysis demonstrated high condensation and clumping of chromatin beneath nuclear membrane in shrunken neurons. CONCLUSIONS: Our study demonstrates the feasibility of performing ischemia-reperfusion in 7-day-old rats that develop progressive neuronal death with features characteristic of apoptosis. The reperfusion phase mimics events that occur during neonatal human hypoxic-ischemic encephalopathy at birth, since perinatal intensive care most often permits recirculation

Interfaces for noninvasive ventilation in the acute setting in children

International audienceThe use of noninvasive ventilation (NIV) is very specific in the acute setting as compared to its use in a chronic setting. In the Pediatric Intensive care Unit (PICU), NIV may be required around the clock and initiation has to be fast and easy. Despite the increasing use of non-invasive ventilation (NIV) and the larger choice of interfaces, data comparing the use of different interfaces for pediatric patients are scarce and recommendations for the most appropriate choice of interface are lacking. However, this choice in acute settings is crucial and a major contributor of the success of NIV. The aim of the present review was to describe the different types of interfaces available for children in the acute setting, their advantages and limitations, to highlight how to choose the optimal interface, and how to monitor the tolerance of the interface

Ischemic postconditioning in cerebral ischemia: Differences between the immature and mature brain?

Ischemic postconditioning (postC), defined as serial mechanical interruptions of blood flow at reperfusion, effectively reduces myocardial infarct size in all species tested so far, including humans. In the brain, ischemic postC leads to controversial results regardless of variations in factors such as onset time of beginning, the duration of ischemia and/or reperfusion, and the number of cycles of occlusion/reperfusion. Thus, many major issues remain to be resolved regarding its protective effects. Future studies should aim to identify the parameters that yield the strongest protection, as well as to understand why the efficacy of ischemic postC differs between models. This review will focus on initial hemodynamic changes and their consequences, and on specific features such as NO-dependent vascular tone and/or prolonged acidosis in cerebral ischemia-reperfusion in order to better understand the dynamics of ischemic postC in the developing brain