Phenytoin pretreatment prevents hypoxic-ischemic brain damage in neonatal rats

Navigating the Complexities of Traumatic Encephalopathy Syndrome (TES): Current State and Future Challenges

Chronic traumatic encephalopathy (CTE) is a unique neurodegenerative disease that is associated with repetitive head impacts (RHI) in both civilian and military settings. In 2014, the research criteria for the clinical manifestation of CTE, traumatic encephalopathy syndrome (TES), were proposed to improve the clinical identification and understanding of the complex neuropathological phenomena underlying CTE. This review provides a comprehensive overview of the current understanding of the neuropathological and clinical features of CTE, proposed biomarkers of traumatic brain injury (TBI) in both research and clinical settings, and a range of treatments based on previous preclinical and clinical research studies. Due to the heterogeneity of TBI, there is no universally agreed-upon serum, CSF, or neuroimaging marker for its diagnosis. However, as our understanding of this complex disease continues to evolve, it is likely that there will be more robust, early diagnostic methods and effective clinical treatments. This is especially important given the increasing evidence of a correlation between TBI and neurodegenerative conditions, such as Alzheimer's disease and CTE. As public awareness of these conditions grows, it is imperative to prioritize both basic and clinical research, as well as the implementation of necessary safe and preventative measures.

An update on diagnostic and prognostic biomarkers for traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a major worldwide neurological disorder of epidemic proportions. To date, there are still no FDA-approved therapies to treat any forms of TBI. Encouragingly, there are emerging data showing that biofluid-based TBI biomarker tests have the potential to diagnose the presence of TBI of different severities including concussion, and to predict outcome. Areas covered: The authors provide an update on the current knowledge of TBI biomarkers, including protein biomarkers for neuronal cell body injury (UCH-L1, NSE), astroglial injury (GFAP, S100B), neuronal cell death (αII-spectrin breakdown products), axonal injury (NF proteins), white matter injury (MBP), post-injury neurodegeneration (total Tau and phospho-Tau), post-injury autoimmune response (brain antigen-targeting autoantibodies), and other emerging non-protein biomarkers. The authors discuss biomarker evidence in TBI diagnosis, outcome prognosis and possible identification of post-TBI neurodegernative diseases (e.g. chronic traumatic encephalopathy and Alzheimer's disease), and as theranostic tools in pre-clinical and clinical settings. Expert commentary: A spectrum of biomarkers is now at or near the stage of formal clinical validation of their diagnostic and prognostic utilities in the management of TBI of varied severities including concussions. TBI biomarkers could serve as a theranostic tool in facilitating drug development and treatment monitoring.

Neuroprotective Effect of Lacosamide on Hypoxic-Ischemic Brain Injury in Neonatal Rats

BACKGROUND AND PURPOSE

Lacosamide (LCM) is an antiepileptic drug that enhances the slow inactivation of sodium channels and modulates collapsin response mediator protein-2. LCM was recently demonstrated to exert a neuroprotective effect in a murine model of traumatic brain injury and status epilepticus. Assuming the same underlying excitotoxicity-related brain injury mechanism, we hypothesized that LCM would have a neuroprotective effect in hypoxic-ischemic brain injury.

METHODS

We divided rats into three groups at each testing session: pre- or postfed with LCM, fed with normal saline, and sham. A hypoxic-ischemic brain injury was induced by subjecting 7-day-old rats to right carotid artery coagulation followed by 2.5 h of exposure to 8% oxygen. The animals were killed on postnatal day 12 to evaluate the severity of brain damage. Open field testing was also performed between week 2 and week 6, and the Morris water maze test was performed in week 7 after hypoxia-ischemia.

RESULTS

The incidence of liquefactive cerebral infarction was lower in rats prefed with LCM at 100 mg/kg/dose, with the mortality rate being higher at higher doses (200 and 300 mg/kg/dose). The infarct areas were smaller in LCM-prefed rats in several brain regions including the hemisphere, hippocampus, cortex, and striatum. Spatial learning and memory function were better in LCM-prefed rats (p<0.05). No effect was observed in postfed rats.

CONCLUSIONS

This study suggests that LCM pretreatment exerts a neuroprotective effect on hypoxia-ischemia in neonatal rats. The obtained results suggest that LCM pretreatment could be used as an effective neuroprotective method for neonates under hypoxic-ischemic conditions including heart surgery.

Role of Anticonvulsants in the Management of Posttraumatic Epilepsy

Posttraumatic seizures (PTS) have been recognized as a major complication of traumatic brain injury (TBI). The annual incidence of TBI in the United States is 1.7 million. The role of anticonvulsants in the treatment of posttraumatic epilepsy (PTE) remains uncertain. Based on current studies, however, anticonvulsants have been shown to reduce early PTS occurring within the first 7 days, but little to no benefits have been shown in late PTS occurring after 7 days. In this paper, we provide a mini review of the role of anticonvulsants and current advances in the management of PTE.

WITHDRAWN: Antiepileptic drugs for preventing seizures following acute traumatic brain injury

BACKGROUND

Seizure activity in the early post-traumatic period following head injury may cause secondary brain damage as a result of increased metabolic demands, raised intracranial pressure and excess neurotransmitter release.

OBJECTIVES

To determine the effects of prophylactic anti-epileptic agents for acute traumatic head injury.

SEARCH METHODS

We searched the Cochrane Injuries Group specialised register, MEDLINE and the registers of the Cochrane Stroke Group and Cochrane Epilepsy Group. We contacted pharmaceutical companies who manufacture anti-epileptic agents, the National Institute of Neurological Disorders and Stroke, Epilepsy Division, and the United States' National Institute of Health.

SELECTION CRITERIA

All randomised trials of anti-epileptic agents, in which study participants had a clinically defined acute traumatic head injury of any severity. Trials in which the intervention was started more than eight weeks after injury were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed the trial quality. Relative risks and 95% confidence intervals (95%CI) were calculated for each trial on an intention-to-treat basis, which included pre-drug loading exclusions. As long as statistical heterogeneity did not exist, for dichotomous data, summary relative risks and 95% confidence intervals were calculated using a fixed effects model. Where the source of heterogeneity could obviously be related to allocation concealment, drug type, or drug dose, we stratified the analyses on that dimension.

MAIN RESULTS

We identified 10 eligible randomised controlled trials, including 2036 participants, but data was unavailable for four unpublished trials, representing 631 participants and they were excluded. For the remaining six trials, the pooled relative risk (RR) for early seizure prevention was 0.34 (95%CI 0.21, 0.54); based on this estimate, for every 100 patients treated, 10 would be kept seizure free in the first week. Seizure control in the acute phase was not accompanied by a reduction in mortality (RR = 1.15; 95%CI 0.89, 1.51), a reduction in death and neurological disability (RR = 1.49; 95%CI 1.06, 2.08 for carbamazepine and RR = 0.96; 95%CI 0.72, 1.26 for phenytoin) or a reduction in late seizures (pooled RR = 1.28; 95%CI 0.90, 1.81). The pooled relative risk for skin rashes was 1.57 (95%CI 0.57, 39.88).

AUTHORS' CONCLUSIONS

Prophylactic anti-epileptics are effective in reducing early seizures, but there is no evidence that treatment with prophylactic anti-epileptics reduces the occurrence of late seizures, or has any effect on death and neurological disability. Insufficient evidence is available to establish the net benefit of prophylactic treatment at any time after injury.

Seizure heralding functional recovery in a patient with apallic syndrome: A case report with retrospective-prospective observation

BACKGROUND

It has been suggested that there exists a close relationship between seizure discharges and functional recovery from brain injury, and that paroxysmal bombardment in late seizures may herald functional recovery or may "kick-start" recovery.

CASE REPORT

We report the case of a 52-year-old patient who, following a subarachnoid hemorrhage and multiple surgeries, experienced discernible apallic syndrome of long duration. His hospitalization is well documented. The patient underwent protracted, intense rehabilitation, but he remained in this prolonged state of loss of consciousness and behavioral passivity until he experienced a series of periodic seizures. Widespread improvement in his cognitive and functional abilities coincided closely with the seizure activity. The literature on this topic is reviewed.

CONCLUSION

This case confirms the close relationship between seizure discharges and functional recovery reported in preclinical literature.

The effects of carbenoxolone, a semisynthetic derivative of glycyrrhizinic acid, on peripheral and central ischemia-reperfusion injuries in the skeletal muscle and hippocampus of rats

As carbenoxolone, a semisynthetic derivative of glycyrrhizinic acid, has a free radical scavenging property, thus the effects of carbenoxolone during ischemia-reperfusion was evaluated on an animal model of ischemia-reperfusion injury in the rat hind limb and hippocampus. Peripheral and central ischemia were induced by free-flap surgery in skeletal muscle and four-vessel-occulation (4VO) of rat, respectively. Carbenoxolone (50-200 mg/kg) and normal saline (10 ml/ kg) were administered intraperitoneally. In peripherlal ischemia, during preischemia, ischemia and reperfusion conditions the electromyographic (EMG) potentials in the muscles were recorded. The malondialdehyde (MDA) was measured by the thiobarbituric acid (TBA) test after reperfusion in peripheral and central ischemia. In peripheral ischemia, the average peak-to-peak amplitude during ischemic-reperfusion was found to be significantly larger in carbenoxolone group (100-200mg/kg) in comparison to control group. The MDA levels were recovered significantly upon carbenoxolone (100-200 mg/kg) therapy in the skeletal muscle and hippocampus of ischemic rats. These results suggest that carbenoxolone can salvage the skeletal muscle and hippocampus from acute ischemia-reperfusion injury.

Topiramate Extends the Therapeutic Window for Hypothermia-Mediated Neuroprotection After Stroke in Neonatal Rats

Background and Purpose— Critical factors influencing the neuroprotective efficacy of postischemic hypothermia include depth, duration, and time of onset of cooling. In clinical practice, there is an unavoidable lag between the hypoxic-ischemic (HI) insult and the opportunity to initiate cooling. We hypothesized that early administration of a neuroprotective agent in combination with later-onset cooling could represent an effective therapeutic intervention after neonatal HI. We evaluated whether treatment with topiramate, a clinically available anticonvulsant, increased the efficacy of delayed post-HI hypothermia in a neonatal rat stroke model.

Methods— Postnatal day 7 (P7) rats underwent right carotid artery ligation followed by 1.5 hours of exposure to 8% oxygen. Fifteen minutes post-HI, animals received injections of topiramate (30 mg/kg) or PBS. Cooling was initiated 3 hours later (“delayed hypothermia”) in all animals (3 hours, in 27°C incubator). Functional outcome (forepaw response to vibrissae stimulation) and pathology (morphometric lesion measurements) were evaluated at P15 and P35.

Results— Neither topiramate nor delayed hypothermia alone conferred protection in this protocol. Combined treatment with topiramate and delayed hypothermia improved both performance and pathological outcome in P15 and P35 rats compared with PBS-treated animals that underwent delayed hypothermia concurrently. At P15, functional measures were better in topiramate-treated animals (mean correct forepaw response 9.3/10 versus 4.8/10; P <0.001), and there was >50% reduction in tissue loss ( P <0.001); trends were similar at P35.

Conclusions— Our data provide the impetus for further evaluation of therapeutic approaches that combine drug therapy with delayed-onset cooling after neonatal HI brain injury.

AMPA-induced dark cell degeneration of cerebellar Purkinje neurons involves activation of caspases and apparent mitochondrial dysfunction

Cerebellar Purkinje neurons (PNs) are selectively vulnerable to AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepriopionic acid)-induced delayed neurotoxicity known as dark cell degeneration (DCD) that is expressed as cytoplasmic and nuclear condensation, neuron shrinkage, and failure of physiology. The present study was initiated to determine whether AMPA-receptor-induced DCD in PNs is associated with Bax translocation to the mitochondria, cytochrome C release from the mitochondria, changes in mitochondrial potential, and activation of representative initiator and executor caspases that include caspase-9, caspase-3, and caspase-7. AMPA consistently and rapidly hyperpolarized mitochondria as reflected by an increase in MitoTracker Red CMS Ros fluorescence. Increases in Bax immunoreactivity were quantitatively and temporally variable and Bax failed to localize to mitochondria. Additionally, we observed a marked increase in immunoreactivity of cytochrome C although its release from mitochondria was not apparent. Mitochondrial membrane hyperpolarization and increases in cytochrome C immunoreactivity preceded caspase activation. Immunohistochemical analyses revealed the active form of caspases-3 and -9 were markedly and significantly increased in PNs following 30 microM AMPA, and caspase-9 activation preceded caspase-3. Increases in active caspase-7 immunoreactivity were less frequently encountered in PNs. Thus DCD shares some characteristics of apoptotic programmed cell death, but lacks typical mitochondrial pathophysiology associated with classic apoptosis. These findings suggest that AMPA-induced DCD is a form of active PCD that lies on a spectrum between classical apoptosis and passive necrosis.

Anti-epileptic drugs as possible neuroprotectants in cerebral ischemia

Many similarities exist between cerebral ischemia and epilepsy regarding brain-damaging and auto-protective mechanisms that are activated following the injurious insult. Therefore, drugs that are effective in minimizing seizure-induced brain damage may also be useful in minimizing ischemic injury. Use of such drugs in stroke victims may have important clinical and financial advantages. Therefore, the authors conducted a Medline search of studies involving the use of anti-epileptic drugs (AEDs) as possible neuroprotectants and summarize the data. Most AEDs have been tested in animal models of focal or global ischemia and some were already tested in humans, for a possible neuroprotective effect. The existing data is rather scant and insufficient but it appears that only drugs that have multiple mechanisms of action seem to have some potential in conferring a degree of neuroprotection that could be clinically applicable to stroke patients. In conclusion, some of the newer AEDs show promise as possible neuroprotectants in the setup of acute ischemic stroke but more studies are needed before clinical trials in humans could be undertaken.

Perinatal brain injury: from pathogenesis to neuroprotection

Brain injury secondary to hypoxic-ischemic disease is the predominant form of all brain injury encountered in the perinatal period. The focus of this article is the most recent research developments in this field and especially those developments that should lead to the most profound effects on interventions in the first years of the new millennium. Neuronal injury is the predominant form of cellular injury in the term infant. The principal mechanisms leading to neuronal death after hypoxia-ischemia/reperfusion are initiated by energy depletion, accumulation of extracellular glutamate, and activation of glutamate receptors. The cascade of events that follows involves accumulation of cytosolic calcium and activation of a variety of calcium-mediated deleterious events. Notably this deleterious cascade, which evolves over many hours, may be interrupted even if interventions are instituted after termination of the insult, an important clinical point. Of the potential interventions, the leading candidates for application to the human infant in the relative short-term are mild hypothermia, inhibitors of free radical production, and free radical scavengers. Promising clinical data are available for the use of mild hypothermia.

Thiopental combination treatments for cerebral resuscitation after prolonged cardiac arrest in dogs. Exploratory outcome study

We postulate that mitigating the multifactorial pathogenesis of postischemic encephalopathy requires multifaceted treatments. In preparation for expensive definitive studies, we are reporting here the results of small exploratory series, compared with historic controls with the same model. We hypothesized that the brain damage mitigating effect of mild hypothermia after cardiac arrest can be enhanced with thiopental loading, and even more so with the further addition of phenytoin and methylprednisolone. Twenty-four dogs (four groups of six dogs each) received VF 12.5 min no-flow, reversed with brief cardiopulmonary bypass (CPB), controlled ventilation to 20 h, and intensive care to 96 h. Group 1 with normothermia throughout and randomized group 2 with mild hypothermia (from reperfusion to 2 h) were controls. Then, group 3 received in addition, thiopental 90 mg/kg i.v. over the first 6 h. Then, group 4 received, in addition to group 2 treatment, thiopental 30 mg/kg i.v. over the first 90 min (because the larger dose had produced cardiopulmonary complications), plus phenytoin 15 mg/kg i.v. at 15 min after reperfusion, and methylprednisolone 130 mg/kg i.v. over 20 h. All dogs survived. Best overall performance categories (OPC) achieved (OPC 1 = normal, OPC 5 = brain death) were better in group 2 than group 1 (< 0.05) and numerically better in groups 3 or 4 than in groups 1 or 2. Good cerebral outcome (OPC 1 or 2) was achieved by all six dogs only in group 4 (P < 0.05 group 4 vs. 2). Best NDS were 44 +/- 3% in group 1; 20 +/- 14% in group 2 (P = 0.002); 21 +/- 15% in group 3 (NS vs. group 2); and 7 +/- 8% in group 4 (P = 0.08 vs. group 2). Total brain histologic damage scores (HDS) at 96 h were 156 +/- 38 in group 1; 81 +/- 12 in group 2 (P < 0.001 vs. group 1); 53 +/- 25 in group 3 (P = 0.02 vs. group 2); and 48 +/- 5 in group 4 (P = 0.02 vs. group 2). We conclude that after prolonged cardiac arrest, the already established brain damage mitigating effect of mild immediate postarrest hypothermia might be enhanced by thiopental, and perhaps then further enhanced by adding phenytoin and methylprednisolone.

Anti-epileptic drugs for preventing seizures following acute traumatic brain injury

BACKGROUND

Seizure activity in the early post-traumatic period following head injury may cause secondary brain damage as a result of increased metabolic demands, raised intracranial pressure and excess neurotransmitter release.

OBJECTIVES

To determine the effects of prophylactic anti-epileptic agents for acute traumatic head injury.

SEARCH STRATEGY

We searched the Cochrane Injuries Group trials register, Medline and the databases of the Cochrane Stroke Group and Cochrane Epilepsy Group. We also contacted pharmaceutical companies who manufacture anti-epileptic agents, the National Institute of Neurological Disorders and Stroke, Epilepsy Division, and the National Institute of Health, United States.

SELECTION CRITERIA

All randomised trials of anti-epileptic agents, in which study participants had a clinically defined acute traumatic head injury of any severity. Trials in which the intervention was started more than eight weeks after injury were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed the quality of the trials. Relative risks and 95% confidence intervals were calculated for each trial on an intention to treat basis, which included pre-drug loading exclusions. As long as statistical heterogeneity did not exist, for dichotomous data, summary relative risks and 95% confidence intervals were calculated using a fixed effects model. Where the source of heterogeneity could obviously be related to allocation concealment, drug type, or drug dose, we stratified the analyses on that dimension.

MAIN RESULTS

We identified 10 eligible randomised controlled trials, including 2036 participants. Data are currently unavailable for four unpublished trials, representing 631 participants. For the remaining trials, the pooled relative risk (RR) for early seizure prevention was 0.34 (95% confidence interval 0.21 to 0.54); based on this estimate, for every 100 patients treated, 10 would be kept seizure free in the first week. Seizure control in the acute phase was not accompanied by a reduction in mortality (RR=1.15; 95% confidence interval 0.89 to 1. 51), a reduction in death and neurological disability (RR = 1.49; 95% confidence interval 1.06 to 2.08 for carbamazepine and RR= 0.96; 95% confidence interval 0.72 to 1.26 for phenytoin) or a reduction in late seizures (pooled RR =1.28; 95% confidence interval 0.90 to 1. 81). The pooled relative risk for skin rashes was 1.57 (95% confidence interval 0.57 to 39.88).

REVIEWER'S CONCLUSIONS

Prophylactic anti-epileptics are effective in reducing early seizures, but there is no evidence that treatment with prophylactic anti-epileptics reduces the occurrence of late seizures, or has any effect on death and neurological disability. Insufficient evidence is available to establish the net benefit of prophylactic treatment at any time after injury.

A submersion method to induce hypoxic damage in organotypic hippocampal cultures

Organotypic brain slices cultured on semi-porous membranes is an increasingly popular in vitro preparation for studying mechanisms of ischemic brain damage. To model in vivo hypoxia, cultured brain slices are exposed to anaerobic atmosphere by placing them into a special incubator. This requirement limits the use of in vitro ischemic models to highly specialized laboratories. Here, we describe a simple method that reproduces hypoxic injury, where cultured hippocampal slices are submerged into glucose-free deoxygenated medium for 1 h. The extent and distribution of hippocampal neuronal loss obtained with this treatment resembled that caused by hypoxia in living tissue in situ, i.e. CA1 pyramidal cell layer was most vulnerable and dentate granular cell layer was least susceptible to hypoxia as measured with fluorescence of the viability marker propidium iodide (PI). Electrophysiologic functional impairment determined by field recordings of CA1 pyramidal neurones temporally coincided with the extent of neuronal death. In addition, known neuroprotective treatments, such as hypothermia and phenytoin application ameliorated neuronal damage in a pattern similar to previously published reports. Therefore, the present in vitro model of ischemia is simple, reliable and of low cost. It is well suited for short and long-term studies of the mechanisms of hypoxic brain damage.

Vascular nitric oxide may lessen Alzheimer's risk

Estrogen deficiency, hyperinsulinemia, type II diabetes, atherosclerosis, and a past history of elevated blood pressure may be associated with increased risk of Alzheimer's disease (AD). Common to all of these risk factors is a diminished capacity of vascular endothelium to generate nitric oxide (NO). Vascular NO has the potential to enhance the membrane polarization of cerebral neurons by increasing the open probability of calcium-activated potassium channels; this may protect neurons from the excessive calcium influx, potentiated by beta-amyloid peptides that is thought to mediate neuronal damage in AD. The possibility that NO/cyclic guanosine 3', 5'-phosphate (cGMP) may modulate the synthesis or processing of the amyloid precursor protein, also merits evaluation. Practical measures for promoting vascular NO production may include increased intakes of arginine, potassium, antioxidants, and fish-oil, as well as lifestyle measures that typically lower elevated blood pressure; potential benefits of chromium, glucosamine, and silicon should also be explored. In hypertensives, angiotensin-converting enzyme (ACE) inhibitors and sodium restriction may favorably influence endothelial function. Fish-oil should have the additional benefit of antagonizing the contribution of interleukin-1 to AD pathogenesis. Ancillary anti-excitotoxic measures such as magnesium, taurine, phenytoin, and vasodilators targeting ATP-dependent potassium (KATP) channels, may likewise reduce AD risk. Most of the nutritional measures suggested here would in any case be recommendable for preservation of vascular health.

Prophylactic antiepileptic agents after head injury: a systematic review

OBJECTIVE

To determine the effectiveness and safety of prophylactic antiepileptic agents in the management of acute traumatic head injury.

METHODS

Systematic review of randomised controlled trials identified using MEDLINE, EMBASE, CINAHL, Dewent Biotechnology abstracts, and specialised databases of randomised controlled trials, by searching reference lists and contacting investigators.

RESULTS

Ten eligible randomised controlled trials were identified, including 2036 patients. The pooled relative risk (RR) for early seizure prevention was 0.34 (95% confidence interval (95%CI) 0.21-0.54); based on this estimate, for every 100 patients treated, 10 would be kept seizure free in the first week. Seizure control in the acute phase was not accompanied by a reduction in mortality (RR=1.15; 95% CI 0.89-1.51), a reduction in death and neurological disability (RR=1.49; 95% CI 1.06-2.08 for carbamazepine and RR=0.96; 95% CI 0.72-1.26 for phenytoin) or a reduction in late seizures (pooled RR=1.28; 95% CI 0.90-1.81). The pooled relative risk for skin rashes was 1.57 (95% CI 0.90-2.75).

CONCLUSIONS

Prophylactic antiepileptic drugs are effective in reducing early seizures, but there is no evidence that treatment with such drugs reduces the occurrence of late seizures, or has any effect on death and neurological disability. Insufficient evidence is available to establish the net benefit of prophylactic treatment at any time after injury.

Sodium channel modulators prevent oxygen and glucose deprivation injury and glutamate release in rat neocortical cultures

Neocortical cultures were deprived of oxygen and glucose to model ischemic neuronal injury. We used a graded series of periods of oxygen and glucose deprivation, providing graded insults. Cell death was measured by release of lactate dehydrogenase (LDH). One hundred and twenty to 240 min of deprivation caused graded increases in glutamate overflow, LDH release and 45Ca influx. Curves of LDH release with respect to deprivation time were shifted to longer intervals by treatment with tetrodotoxin (TTX; 3, 30 or 300 nM), phenytoin (10, 30 or 100 microM), lidocaine (10, 30 or 100 microM) or the N-methyl-D-aspartate antagonist CPP [3(2-carboxypiperazine-4-yl)propyl-1-phosphonic acid, 3, 10, 30 or 100 microM]. Combined treatment with TTX and CPP caused pronounced rightward shifts of LDH deprivation curves. Our results indicate that Na+ channel blockade is neuroprotective in neocortex cultures. Our results also suggest that neuroprotection with Na+ channel blockers may be due to inhibition of glutamate release.