Hypoxic-ischemic Events Research Articles

Youth with acquired brain injury in The Netherlands: A multi-centre study

Aim: To describe the occurrence and causes of acquired brain injury (ABI), including traumatic brain injury (TBI) and non-traumatic brain injury (NTBI), among Dutch youth and estimate incidence rates from the data.Patients: Aged 1 month–24 years, hospital diagnosed with ABI in 2008 or 2009.Methods: In three major hospitals in the southwest region of the Netherlands patients with ABI were retrospectively identified by means of diagnosis codes and specific search terms.Results: One thousand eight hundred and ninety-two patients were included: 1476 with TBI and 416 with NTBI. Causes of TBI and NTBI varied among the age groups 0–4, 5–14 and 15–24 years, with accidents (in traffic or at home) being the most common cause of TBI and hypoxic-ischemic events for NTBI, in all groups. The estimated yearly incidence rates per 100 000 for mild–moderate–severe TBI were 271.2–15.4–2.3 (0–14 years) and 261.6–27.0–7.9 (15–24 years), for mild–moderate–severe NTBI they were 95.7–11.8–1.3 (0–14 years) and 73.8–6.1–1.6 (15–24 years), respectively.Conclusion: More than 15% of TBI and NTBI in children and youth is classified as moderate or severe, with causes of TBI and NTBI varying among age groups. Based on the occurrence of ABI in three hospitals, the estimated incidence of ABI in children and youth in the southwest region of the Netherlands is substantial.

Subdural Hemorrhage and Hypoxia in Children Less than Two Years Old

The majority of subdural hemorrhages (SDH) are due to acceleration-deceleration forces associated with blunt head injury. So-called spontaneous subdural hemorrhages are described with coagulopathies, hemodialysis, hemophilia, and as extensions of hemorrhages due to other causes such as ruptured cerebral artery aneurysms. Recently, some have proposed that hypoxia causes subdural hemorrhage in infants and children. Materials and Methods Of 1,190 deaths of children younger than two years of age, we analyzed 366 that were due to asphyxial mechanisms, respiratory disease, prematurity, seizures, and perinatal hypoxic-ischemic encephalopathy. All underwent autopsy and 97% included a consultant neuropathology examination. Results Of the 366 decedents, hypoxic-ischemic encephalopathy (HIE) was diagnosed in 73 (20%) and evidence of subdural hemorrhage in 34 (9%). Of the 73 HIE deaths, 14 (19%) had SDH. Among these 14, 12 involved prematurity and/or perinatal HIE. Among the 20 fatalities with SDHs but without HIE, all were premature infants and/or had a SDH that pathologically pre-dated the putative hypoxic-ischemic event. Of the 34 SDHs, 24 were organized neomembranes and ten were organizing hemorrhages. Discussion SDHs that are not caused by acceleration-deceleration forces are routinely recognized in infants and children. Usually, they are clinically silent and may be associated with prematurity and perinatal birth events. At autopsy, subdural neomembranes frequently are incidental findings in infants and children who die from a variety of causes. This study does not support the theory that hypoxic-ischemic injury in infants and children causes subdural hemorrhage.

Effects of hypothermia on oligodendrocyte precursor cell proliferation, differentiation and maturation following hypoxia ischemia in vivo and in vitro

Hypoxic-ischemia (HI) not only causes gray matter injury but also white matter injury, leading to severe neurological deficits and mortality, and only limited therapies exist. The white matter of animal models and human patients with HI-induced brain injury contains increased oligodendrocyte precursor cells (OPCs). However, little OPC can survive and mature to repair the injured white matter. Here, we test the effects of mild hypothermia on OPC proliferation, differentiation and maturation. Animals suffered to left carotid artery ligation followed by 8% oxygen for 2h in 7-day-old rats. They were divided into a hypothermic group (rectal temperature 32–33°C for 48h) and a normothermic group (36–37°C for 48h), then animals were sacrificed at 3, 7, 14 and 42days after HI surgery. Our results showed that hypothermia successfully enhanced early OL progenitors (NG2+) and its proliferation in the corpus callosum (CC) after HI. Late OL progenitor (O4+) accumulation decreased accompanied with increased OL maturation which is detected by myelin basic protein (MBP) and proteolipid protein. (PLP) immunostaining and immunoblotting in hypothermia compared to normothermia. Additionally, using an in vitro hypoxic-ischemia model-oxygen glucose deprivation (OGD), we demonstrated that hypothermia decreased preOL accumulation and promoted OPC differentiation and maturation. Further data indicated that OPC death was significantly suppressed by hypothermia in vitro. The myelinated axons and animal behavior both markedly increased in hypothermic- compared to normothermic-animals after HI. In summary, these data suggest that hypothermia has the effects to protect OPC and to promote OL maturation and myelin repair in hypoxic–ischemic events in the neonatal rat brain. This study proposed new aspects that may contribute to elucidate the mechanism of hypothermic neuroprotection for white matter injury in neonatal rat brain injury.

Using the endocannabinoid system as a neuroprotective strategy in perinatal hypoxic-ischemic brain injury.

One of the most important causes of brain injury in the neonatal period is a perinatal hypoxic-ischemic event. This devastating condition can lead to long-term neurological deficits or even death. After hypoxic-ischemic brain injury, a variety of specific cellular mechanisms are set in motion, triggering cell damage and finally producing cell death. Effective therapeutic treatments against this phenomenon are still unavailable because of complex molecular mechanisms underlying hypoxic-ischemic brain injury. After a thorough understanding of the mechanism underlying neural plasticity following hypoxic-ischemic brain injury, various neuroprotective therapies have been developed for alleviating brain injury and improving long-term outcomes. Among them, the endocannabinoid system emerges as a natural system of neuroprotection. The endocannabinoid system modulates a wide range of physiological processes in mammals and has demonstrated neuroprotective effects in different paradigms of acute brain injury, acting as a natural neuroprotectant. The aim of this review is to study the use of different therapies to induce long-term therapeutic effects after hypoxic-ischemic brain injury, and analyze the important role of the endocannabinoid system as a new neuroprotective strategy against perinatal hypoxic-ischemic brain injury.

Neuroprotective therapies after perinatal hypoxic-ischemic brain injury.

Hypoxic-ischemic (HI) brain injury is one of the main causes of disabilities in term-born infants. It is the result of a deprivation of oxygen and glucose in the neural tissue. As one of the most important causes of brain damage in the newborn period, the neonatal HI event is a devastating condition that can lead to long-term neurological deficits or even death. The pattern of this injury occurs in two phases, the first one is a primary energy failure related to the HI event and the second phase is an energy failure that takes place some hours later. Injuries that occur in response to these events are often manifested as severe cognitive and motor disturbances over time. Due to difficulties regarding the early diagnosis and treatment of HI injury, there is an increasing need to find effective therapies as new opportunities for the reduction of brain damage and its long term effects. Some of these therapies are focused on prevention of the production of reactive oxygen species, anti-inflammatory effects, anti-apoptotic interventions and in a later stage, the stimulation of neurotrophic properties in the neonatal brain which could be targeted to promote neuronal and oligodendrocyte regeneration.

Hypoxia–Ischemia Alters Nucleotide and Nucleoside Catabolism and Na+,K+-ATPase Activity in the Cerebral Cortex of Newborn Rats

It is well known that the levels of adenosine in the brain increase dramatically during cerebral hypoxic-ischemic (HI) insults. Its levels are tightly regulated by physiological and pathophysiological changes that occur during the injury acute phase. The aim of the present study was to examine the effects of the neonatal HI event on cytosolic and ecto-enzymes of purinergic system--NTPDase, 5'-nucleotidase (5'-NT) and adenosine deaminase (ADA)--in cerebral cortex of rats immediately post insult. Furthermore, the Na(+)/K(+)-ATPase activity, adenosine kinase (ADK) expression and thiobarbituric acid reactive species (TBARS) levels were assessed. Immediately after the HI event the cytosolic NTPDase and 5'-NT activities were increased in the cerebral cortex. In synaptosomes there was an increase in the ecto-ADA activity while the Na(+)/K(+) ATPase activity presented a decrease. The difference between ATP, ADP, AMP and adenosine degradation in synaptosomal and cytosolic fractions could indicate that NTPDase, 5'-NT and ADA were differently affected after insult. Interestingly, no alterations in the ADK expression were observed. Furthermore, the Na(+)/K(+)-ATPase activity was correlated negatively with the cytosolic NTPDase activity and TBARS content. The increased hydrolysis of nucleotides ATP, ADP and AMP in the cytosol could contribute to increased adenosine levels, which could be related to a possible innate neuroprotective mechanism aiming at potentiating the ambient levels of adenosine. Together, these results may help the understanding of the mechanism by which adenosine is produced following neonatal HI injury, therefore highlighting putative therapeutical targets to minimize ischemic injury and enhance recovery.

Legal Briefs

A 37-weeks'-gestation infant whose birthweight was 3,572 g was born in 1991 to a 23-year-old G2P1 woman. A previous pregnancy with a 3-kg infant was complicated by the need for a cesarean delivery secondary to cephalopelvic disproportion (CPD). The mother was 5 ft 3 inches tall and weighed 160 pounds before the current pregnancy. After contractions began, she was admitted to the hospital. Her membranes ruptured spontaneously and resulted in clear fluid. After several hours of labor, an internal monitor was placed and an epidural was provided. The second stage of labor was 1 hour and 15 minutes. Forceps were applied. The medical records indicated mid and low forceps. The treating obstetrician denied using midforceps. Shortly after the forceps were applied, the fetal heart rate declined to ∼90 with the development of several deep variable decelerations. Shoulder dystocia developed. According to the plaintiff obstetrician, the treating obstetrician should have known about the CPD with the previous pregnancy and recognized that the pelvis was untested. The treating obstetrician stated that previous knowledge of CPD would not have influenced his decision because operative deliveries carry risks, and, because the pelvis was not tested, he considered it was good judgment to allow a vaginal delivery. The plaintiff obstetrician pointed to the record that the infant was too high when forceps were applied, and it was a risky maneuver that is known to be associated with shoulder dystocia. The fetal heart monitor was removed 5 minutes before the vaginal delivery. The infant was delivered lifeless. Resuscitation consisted of intubation, positive pressure ventilation, chest compressions, two doses of Narcan, three doses of epinephrine via the endotracheal tube, an umbilical arterial line placed at 6 minutes, as well as 6 mEq of bicarbonate at 13 minutes. The chest compressions were discontinued at 15 minutes. Apgar Scores …

γ‐Aminobutyric acid type a receptor inhibition triggers a nicotinic neuroprotective mechanism

Nicotinic acetylcholine receptor (nAChR)-mediated neuroprotection has been implicated in the treatment of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases and hypoxic ischemic events as well as other diseases hallmarked by excitotoxic and apoptotic neuronal death. Several modalities of nicotinic neuroprotection have been reported. However, although this process generally involves α4β2 and α7 subtypes, the underlying mechanisms are largely unknown. Interestingly, both activation and inhibition of α7 nAChRs have been reported to be neuroprotective. We have shown that inhibition of α7 nAChRs protects the function of acute hippocampal slices against excitotoxicity in an α4β2-dependent manner. Neuroprotection was assessed as the prevention of the N-methyl-D-aspartate-dependent loss of the area of population spikes (PSs) in the CA1 area of acute hippocampal slices. Our results support a model in which α7 AChRs control the release of γ-aminobutyric acid (GABA). Blocking either α7 or GABA(A) receptors reduces the inhibitory tone on cholinergic terminals, thereby promoting α4β2 activation, which in turn mediates neuroprotection. These results shed light on how α7 nAChR inhibition can be neuroprotective through a mechanism mediated by activation of α4β2 nAChRs.

Bench to Cribside: the Path for Developing a Neuroprotectant

The consequences of perinatal brain injury include immeasurable anguish for families and substantial ongoing costs for care and support of effected children. Factors associated with perinatal brain injury in the preterm infant include inflammation and infection, and with increasing gestational age, a higher proportion is related to hypoxic-ischemic events, such as stroke and placental abruption. Over the past decade, we have acquired new insights in the mechanisms underpinning injury and many new tools to monitor outcome in perinatal brain injury in our experimental models. By embracing these new technologies, we can expedite the screening of novel therapies. This is critical as despite enormous efforts of the research community, hypothermia is the only viable neurotherapeutic, and this procedure is limited to term birth and postcardiac arrest hypoxic-ischemic events. Importantly, experimental and preliminary data in humans also indicate a considerable therapeutic potential for melatonin against perinatal brain injury. However, even if this suggested potential is proven, the complexity of the human condition means we are likely to need additional neuroprotective and regenerative strategies. Thus, within this review, we will outline what we consider the key stages of preclinical testing and development for a neuroprotectant or regenerative neurotherapy for perinatal brain injury. We will also highlight examples of novel small animal physiological and behavioral testing that gives small animal preclinical models greater clinical relevance. We hope these new tools and an integrated bench to cribside strategic plan will facilitate the fulfillment of our overarching goal, improving the long-term brain health and quality of life for infants suffering perinatal brain injury.

Hypothermie thérapeutique contrôlée pour asphyxie périnatale : intérêt de l’électroencéphalogramme d’amplitude pour évaluer l’indication

Moderate hypothermia therapy (HT) after perinatal asphyxia of the newborn has clearly demonstrated its efficacy in reducing both mortality and long-term neurosensory sequelae. HT has now been introduced in many developed countries as a standard of care for term infants meeting the entry criteria for therapeutic cooling. However, this new therapy is only effective in case of an acute perinatal hypoxic-ischemic event. Since a number of potentially deleterious complications have been described during cooling, a strict evaluation of the newborn's status is mandatory. To help clinicians reliably select newborns who may benefit from HT, amplitude-integrated electroencephalography (aEEG) is today strongly recommended. The indication criteria for cooling include aEEG in addition to delivery history, Apgar score, cord pH and lactates, and neurological scoring for encephalopathy. We report a clinical case of a term baby girl, considered for HT in our unit, because of a clinical feature of severe neonatal encephalopathy, metabolic acidosis on cord pH, and a history of fetal distress on fetal heart rate monitoring. However, despite all these criteria, her early aEEG, like her classic EEG, showed no signs of hypoxic-ischemic encephalopathy (HIE). She was then denied HT and her early magnetic resonance imaging (MRI) exam showed no signs of HIE but typical features of a metabolic disorder (Zellweger-like syndrome). Thanks to the HT strict protocols, including early aEEG and MRI exam, the right diagnosis was rapidly made and the hypothesis of a hypoxic-ischemic event during delivery was finally ruled out.

305 Dopamine Reduces White Matter Injury in Hypoxic-Ischaemia in the Preterm Lamb

BackgroundDopamine is frequently used as inotropic agent in preterm infants. Its cardiovascular actions, as well as effects on neurovascular interactions may be neuroprotective during hypoxic-ischaemic events. Using a preterm lamb...

1072 Review of Current Opinion and Availability of Cerebral Function Monitoring and Therapeutic Hypothermia in UK Neonatal Units

Background and AimsTherapeutic hypothermia has been established as an effective treatment modality for term neonates that have suffered an acute perinatal hypoxic ischaemic event. This is a time-critical procedure which...

Therapeutic hypothermia in the prevention of hypoxic-ischaemic encephalopathy: new categories to be enrolled

Therapeutic hypothermia is now the standard of care for brain injury control in term infants with perinatal hypoxic ischemic encephalopathy (HIE). Accumulated evidence shows a reduction in mortality and long-term neurodevelopmental disability at 12–24 months of age, with more favourable effects in the less severe forms of HIE. Only few trials recruited newborns <36 weeks gestational age, or mild-to-moderate encephalopathy with base deficit (BD) <16. The new categories of patients to be enrolled should include (late) preterm infants, neonates with unexpected postnatal collapse, and newborns with stroke. Preterm HIE: Therapeutic hypothermia shows a good safety profile in clinical studies, and no adverse effects were noted in the preterm fetal animal model. Recently, it has been shown that mild hypothermia in preterm newborns with necrotizing enterocolitis (NEC) and multiple organ dysfunction syndrome (MODS) does not increase mortality, bleeding, infection, or need for inotropes in cooled newborns. A pilot study (NCT00620711) is currently recruiting newborns of > 32 but < 36 weeks gestation with standard criteria for HIE. Postnatal Collapse: The postnatal collapse (PNC) is a rare (0.03–0.5/1000 live births) but life-threatening hypoxic-ischemic event. No clinical trials of therapeutic hypothermia have specifically addressed to PNC. Nevertheless, a beneficial effect of brain cooling is expectable, and it has been proposed to include in brain hypothermia trials the infants with PNC fulfilling the entry criteria for HIE. Stroke: Perinatal arterial ischemic stroke is the most common cause of cerebral palsy (CP) in term and near-term newborn. In a systematic review and meta-analysis of animal studies of focal cerebral ischemia, hypothermia reduced the infarct size by 44%. No specific neuroprotective interventions are available for the management of acute perinatal stroke. Hypothermia may decrease seizures in newborns with encephalopathy and a focal infarct, potentially improving the long-term outcome for these infants. Concluding remarks: Future studies of therapeutic hypothermia should include the categories of newborns excluded from the published clinical trials, that is infants <36 weeks gestation, PNC or stroke, or admitted outside of the established 6-hour window, and with encephalopathy not imputable to HIE. New entry criteria will allow significant number of newborns to benefit from the treatment.

THE ROLE OF OXIDATIVE STRESS IN THE NECROTIZING ENTEROCOLITIS OF PRETERM

Introduction: Oxidative stress (OS) is strongly envolved in the pathogenesis of many preterm newborn diseases; this is due to the low efficiency of natural antioxidant systems unable to counteract the harmful effects of free radicals (FRs). Necrotizing Enterocolitis (NEC) is a multifactorial disease and it is part of the so called free radicals related diseases. Hypoxic-ischaemic events and inflammation, involved in NEC pathogenesis, are responsible of the overproduction of free radicals (FRs), generating OS. Aim: To test the hypotesis that OS marker levels in cord blood may predict the onset of NEC in high risk infants. Materials and methods: 91 preterm newborns of gestational age between 24 and 33 weeks and birth weight between 460 and 2540 grams were consecutively recruited in two italian neonatal intensive care units. Markers of potential oxidative stress risk, Non Protein Bound Iron (NPBI), and free radicals damage, Advanced Oxidation Protein Products (AOPP) and Total Hydroperoxide (TH), were measured in the cord blood. Associations between NEC and OS markers have been checked through inferential analysis (univariate logistic regression). Results: Out of 91 preterm babies, 8 developed NEC. Babies with NEC had a birth weight (BW) and a gestational age (GA) significantly lower than healthy babies (BW=1100,52 &plusmn; 444,30 vs 1320,53 &plusmn; 462,09; GA=29,02 &plusmn; 2,09 vs 30,14 &plusmn; 2,33, respec- tively. p&lt;0.005). Cord blood levels of TH and NPBI were higher in babies with NEC than in babies without, but not significantly. AOPP cord blood levels were significantly higher in babies with NEC than the babies without (AOPP=29,15 &plusmn; 20,02 vs 16,72 &plusmn; 7,34; p&lt;0.05). AOPP demonstrated a significant value for the identification of the risk of NEC (OR=1.13, CI 95%= 1.001-1.282). Conclusions: OS is strongly associated with NEC. The determination of biochemical OS markers in cord blood can be useful in identifying babies at high risk to develop NEC and in devising new strategies to bring consistent benefits to premature babies.

THE ROLE OF OXIDATIVE STRESS IN THE NECROTIZING ENTEROCOLITIS OF PRETERM

Introduction: Oxidative stress (OS) is strongly envolved in the pathogenesis of many preterm newborn diseases; this is due to the low efficiency of natural antioxidant systems unable to counteract the harmful effects of free radicals (FRs). Necrotizing Enterocolitis (NEC) is a multifactorial disease and it is part of the so called free radicals related diseases. Hypoxic-ischaemic events and inflammation, involved in NEC pathogenesis, are responsible of the overproduction of free radicals (FRs), generating OS. Aim: To test the hypotesis that OS marker levels in cord blood may predict the onset of NEC in high risk infants. Materials and methods: 91 preterm newborns of gestational age between 24 and 33 weeks and birth weight between 460 and 2540 grams were consecutively recruited in two italian neonatal intensive care units. Markers of potential oxidative stress risk, Non Protein Bound Iron (NPBI), and free radicals damage, Advanced Oxidation Protein Products (AOPP) and Total Hydroperoxide (TH), were measured in the cord blood. Associations between NEC and OS markers have been checked through inferential analysis (univariate logistic regression). Results: Out of 91 preterm babies, 8 developed NEC. Babies with NEC had a birth weight (BW) and a gestational age (GA) significantly lower than healthy babies (BW=1100,52 ± 444,30 vs 1320,53 ± 462,09; GA=29,02 ± 2,09 vs 30,14 ± 2,33, respec- tively. p<0.005). Cord blood levels of TH and NPBI were higher in babies with NEC than in babies without, but not significantly. AOPP cord blood levels were significantly higher in babies with NEC than the babies without (AOPP=29,15 ± 20,02 vs 16,72 ± 7,34; p<0.05). AOPP demonstrated a significant value for the identification of the risk of NEC (OR=1.13, CI 95%= 1.001-1.282). Conclusions: OS is strongly associated with NEC. The determination of biochemical OS markers in cord blood can be useful in identifying babies at high risk to develop NEC and in devising new strategies to bring consistent benefits to premature babies.

Endocannabinoids reduce cerebral damage after hypoxic–ischemic injury in perinatal rats

Hypoxic–ischemic (HI) insult during the perinatal period remains as one of the most common causes of brain injury and produces long-term neurological deficits, and there is a growing need for effective therapies. The aim of the present work was to perform a prospective study designed to assess the possible protector effect of two endocannabinoids: 2-arachidonoylglycerol (2AG) and anandamide (AEA) in the brain after HI injury in perinatal rat model. We evaluate their effects on cell death and check several cellular parameters. 7-days-old Wistar rats were assigned to four different experimental groups (n=7–10): Sham, HI, and HI treated with 2AG or AEA. The injury was induced by the left carotid artery ligature and subsequent exposure to 8% O2 for 120min. Immediately after the injury, treated groups received a single dose of 2AG (1mg/kg) or AEA (5mg/kg) and then animals were sacrificed 24, 72h or 7 days after the HI event. Brains fixed by perfusion were stained with Nissl for morphological studies, and non-fixed brains were dissociated and analyzed by flow cytometry to quantify apoptosis, mitochondrial state, intracellular calcium and reactive oxygen species. Our results show that both 2AG and AEA have beneficial effects after HI injury in this rat model, producing a remarkable amelioration of brain injury, reducing apoptotic cell death, contributing to the maintenance of mitochondrial functionality, and improving cellular parameters such as the influx of calcium and ROS production.

Intranasal administration of aTf protects and repairs the neonatal white matter after a cerebral hypoxic–ischemic event

Our previous studies showed that the intracerebral injection of apotransferrin (aTf) attenuates white matter damage and accelerates the remyelination process in a neonatal rat model of cerebral hypoxia-ischemia (HI) injury. However, the intracerebral injection of aTf might not be practical for clinical treatments. Therefore, the development of less invasive techniques capable of delivering aTf to the central nervous system would clearly aid in its effective clinical use. In this work, we have determined whether intranasal (iN) administration of human aTf provides neuroprotection to the neonatal mouse brain following a cerebral hypoxic-ischemic event. Apotransferrin was infused into the naris of neonatal mice and the HI insult was induced by right common carotid artery ligation followed by exposure to low oxygen concentration. Our results showed that aTf was successfully delivered into the neonatal HI brain and detected in the olfactory bulb, forebrain and posterior brain 30 min after inhalation. This treatment successfully reduced white matter damage, neuronal loss and astrogliosis in different brain regions and enhanced the proliferation and survival of oligodendroglial progenitor cells (OPCs) in the subventricular zone and corpus callosum (CC). Additionally, using an in vitro hypoxic model, we demonstrated that aTf prevents oligodendrocyte progenitor cell death by promoting their differentiation. In summary, these data suggest that iN administration of aTf has the potential to be used for clinical treatment to protect myelin and to induce remyelination in demyelinating hypoxic-ischemic events in the neonatal brain.

Magnesium sulfate treatment decreases the initial brain damage alterations produced after perinatal asphyxia in fetal lambs

The aim of this work was to analyze the effect of MgSO(4) treatment in the brain after hypoxic-ischemic (HI) injury in premature fetal lambs. Injury was induced by partial occlusion of umbilical cord for 60 min, and then the preterm lambs (80-90% of gestation) were randomly assigned to one of the following groups: control group, in which the animals were managed by conventional mechanical ventilation for 3 hr; 3 hr postpartial cord occlusion (3-hr-PCO) group, in which injured animals were managed by ventilation and then sacrificed 3 hr after HI; and MgSO(4) group, in which animals received 400 mg/kg MgSO(4) for 20 min soon after HI was induced and were managed by ventilation for 3 hr. Brains were analyzed for apoptosis by TUNEL assay. Cell viability and intracellular state studies were assessed by flow cytometry. The delayed death index was significantly increased in the 3-hr-PCO group in comparison with control. Administration of MgSO(4) elicited a delay in cell death that was similar to that in the control group. The 3-hr-PCO group showed a significantly higher concentration of reactive oxygen species, mitochondrial damage, and intracellular calcium in comparison with control and MgSO(4) - treated groups. Our results suggest that MgSO(4) treatment might have potential therapeutic benefits after the HI event.

Histological study of the protective effect of melatonin on neural cells after neonatal hypoxia-ischemia.

To minimize as much as possible the neurological consequences from hypoxic-ischemic (HI) brain injury, neuroprotective strategies are urgently required. In this sense, there is growing interest in the neuroprotective potential of melatonin after perinatal asphyxia, due to its high efficacy, low toxicity and ready cross through the blood-brain barrier. Twenty six Wistar rats at postnatal day 7 were randomly assigned to: two hypoxic-ischemic groups: pups with the left common carotid artery ligated and then submitted to hypoxia (HI group) and animals that received a dose of 15 mg/kg melatonin just after the hypoxic-ischemic event and repeated twice with an interval of 24 hours (HI+MEL group). Pups without ischemia or hypoxia were used as controls (Sham group). Seven days after surgery, brains were collected and coronal sections Nissl-stained, TUNEL-labeled, or MBP- and GFAP-immunolabeled prior to determining brain infarct area, quantify surviving neurons and evaluate oligodendroglial injury and reactive astrogliosis. The number of surviving neurons showing a well preserved architecture in HI+MEL group was similar to that observed in the Sham group. Moreover, TUNEL-positive cells only appeared in the HI group. The ratio of left-to-right hemispheric MBP immunostaining showed a significant decrease in the HI group in comparison with Sham pups, which was restored after melatonin administration. Melatonin also reduced reactive gliosis. Thus, our results suggest that treatment with melatonin after neonatal hypoxia-ischemia led to a neuroprotective effect reducing cell death, white matter demyelination and reactive astrogliosis.

Intrauterine fetal demise can be remote from the inciting insult in an animal model of hypoxia–ischemia

Fetal hypoxia-ischemia (H-I) results in significant morbidity and mortality. Little is known about the timing of death in human stillbirths. The vulnerability of the fetus varies with age at the time of insult, but it is unknown what happens to the timing of fetal death in relation to a fetal insult. We asked the question of whether the timing of fetal death was influenced by the age at which the insult occurred. Fetal H-I was achieved at three ages by sustained uterine ischemia in rabbits, mimicking the acute placental insufficiency of placental abruption. H-I at 22 d gestation (E22) resulted in fewer perinatal deaths than at E25 and E29. Fetal deaths were grouped into early and late perinatal deaths. Early perinatal death mostly occurred immediately after H-I and these fetuses delivered before term. Late perinatal death occurred between the insult and delivery at term gestation. Early perinatal death occurred more often in the E25 hypoxic-ischemic group as compared with those of the E22 hypoxic-ischemic group. There is an increasing vulnerability to hypoxia with increasing gestational age. Perinatal deaths may occur long after the episode of H-I. The timing of an intrauterine hypoxic-ischemic event cannot be inferred from the detection of fetal death.