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Crawford JH, Townsley MM. Steroids for Adult and Pediatric Cardiac Surgery: A Clinical Update. J Cardiothorac Vasc Anesth 2019; 33:2039-2045. [DOI: 10.1053/j.jvca.2018.11.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Indexed: 11/11/2022]
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Dhillon SK, Lear CA, Galinsky R, Wassink G, Davidson JO, Juul S, Robertson NJ, Gunn AJ, Bennet L. The fetus at the tipping point: modifying the outcome of fetal asphyxia. J Physiol 2018; 596:5571-5592. [PMID: 29774532 DOI: 10.1113/jp274949] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 04/13/2018] [Indexed: 12/13/2022] Open
Abstract
Brain injury around birth is associated with nearly half of all cases of cerebral palsy. Although brain injury is multifactorial, particularly after preterm birth, acute hypoxia-ischaemia is a major contributor to injury. It is now well established that the severity of injury after hypoxia-ischaemia is determined by a dynamic balance between injurious and protective processes. In addition, mothers who are at risk of premature delivery have high rates of diabetes and antepartum infection/inflammation and are almost universally given treatments such as antenatal glucocorticoids and magnesium sulphate to reduce the risk of death and complications after preterm birth. We review evidence that these common factors affect responses to fetal asphyxia, often in unexpected ways. For example, glucocorticoid exposure dramatically increases delayed cell loss after acute hypoxia-ischaemia, largely through secondary hyperglycaemia. This critical new information is important to understand the effects of clinical treatments of women whose fetuses are at risk of perinatal asphyxia.
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Affiliation(s)
| | - Christopher A Lear
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Robert Galinsky
- The Department of Physiology, University of Auckland, Auckland, New Zealand.,The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Victoria, Australia
| | - Guido Wassink
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Joanne O Davidson
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Sandra Juul
- Department of Pediatrics, University of Washington, Seattle, WA, USA
| | | | - Alistair J Gunn
- The Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- The Department of Physiology, University of Auckland, Auckland, New Zealand
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Bennet L, Dhillon S, Lear CA, van den Heuij L, King V, Dean JM, Wassink G, Davidson JO, Gunn AJ. Chronic inflammation and impaired development of the preterm brain. J Reprod Immunol 2018; 125:45-55. [DOI: 10.1016/j.jri.2017.11.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 11/13/2017] [Accepted: 11/24/2017] [Indexed: 12/17/2022]
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Ohshima M, Taguchi A, Tsuda H, Sato Y, Yamahara K, Harada-Shiba M, Miyazato M, Ikeda T, Iida H, Tsuji M. Intraperitoneal and intravenous deliveries are not comparable in terms of drug efficacy and cell distribution in neonatal mice with hypoxia-ischemia. Brain Dev 2015; 37:376-86. [PMID: 25034178 DOI: 10.1016/j.braindev.2014.06.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 06/23/2014] [Accepted: 06/23/2014] [Indexed: 12/18/2022]
Abstract
BACKGROUND AND PURPOSE Most therapeutic agents are administered intravenously (IV) in clinical settings and intraperitoneally (IP) in preclinical studies with neonatal rodents; however, it remains unclear whether intraperitoneal (IP) injection is truly an acceptable alternative for intravenous (IV) injection in preclinical studies. The objective of our study is to clarify the differences in the therapeutic effects of drugs and in the distribution of infused cells after an IP or IV injection in animals with brain injury. METHODS Dexamethasone or MK-801, an N-methyl-d-aspartate receptor antagonist was administered either IP or IV in a mouse model of neonatal hypoxic-ischemic encephalopathy. Green fluorescent protein-expressing mesenchymal stem cells (MSCs) or mononuclear cells (MNCs) were injected IP or IV in the mouse model. Two hours and 24h after the administration of the cells, we investigated the cell distributions by immunohistochemical staining. We also investigated distribution of IV administered MNCs labeled with 2-[18F]fluoro-2-deoxy-d-glucose in a juvenile primate, a macaque with stroke 1h after the administration. RESULTS IP and IV administration of dexamethasone attenuated the brain injury to a similar degree. IP administration of MK-801 attenuated brain injury, whereas IV administration of MK-801 did not. The IV group showed a significantly greater number of infused cells in the lungs and brains in the MSC cohort and in the spleen, liver, and lung in the MNC cohort compared to the IP group. In the macaque, MNCs were detected in the spleen and liver in large amounts, but not in the brain and lungs. CONCLUSIONS This study demonstrated that the administration route influences the effects of drugs and cell distribution. Therefore, a preclinical study may need to be performed using the optimal administration route used in a clinical setting.
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Affiliation(s)
- Makiko Ohshima
- Department of Regenerative Medicine and Tissue Engineering, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan
| | - Akihiko Taguchi
- Department of Regenerative Medicine Research, Institute of Biomedical Research Innovation, Kobe, Hyogo, Japan
| | - Hidetoshi Tsuda
- Department of Regenerative Medicine and Tissue Engineering, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan
| | - Yoshiaki Sato
- Division of Neonatology, Center for Maternal-Neonatal Care, Nagoya University Hospital, Nagoya, Aichi, Japan
| | - Kenichi Yamahara
- Department of Regenerative Medicine and Tissue Engineering, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan
| | - Mariko Harada-Shiba
- Department of Regenerative Medicine and Tissue Engineering, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan
| | - Mikiya Miyazato
- Department of Biochemistry, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan
| | - Tomoaki Ikeda
- Department of Obstetrics and Gynecology, Mie University School of Medicine, Tsu, Mie, Japan
| | - Hidehiro Iida
- Department of Investigative Radiology, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan
| | - Masahiro Tsuji
- Department of Regenerative Medicine and Tissue Engineering, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan.
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Slotkin TA, Card J, Infante A, Seidler FJ. Prenatal dexamethasone augments the sex-selective developmental neurotoxicity of chlorpyrifos: implications for vulnerability after pharmacotherapy for preterm labor. Neurotoxicol Teratol 2013; 37:1-12. [PMID: 23416428 DOI: 10.1016/j.ntt.2013.02.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 01/28/2013] [Accepted: 02/02/2013] [Indexed: 01/01/2023]
Abstract
Glucocorticoids are routinely given in preterm labor and are also elevated by maternal stress; organophosphate exposures are virtually ubiquitous, so coexposures to these two agents are pervasive. We administered dexamethasone to pregnant rats on gestational days 17-19 at a standard therapeutic dose (0.2mg/kg); offspring were then given chlorpyrifos on postnatal days 1-4, at a dose (1mg/kg) that produces barely-detectable (<10%) inhibition of brain cholinesterase activity. We evaluated indices for acetylcholine (ACh) synaptic function throughout adolescence, young adulthood and later adulthood, in brain regions possessing the majority of ACh projections and cell bodies; we measured nicotinic ACh receptor binding, hemicholinium-3 binding to the presynaptic choline transporter and choline acetyltransferase activity, all known targets for the adverse developmental effects of dexamethasone and chlorpyrifos given individually. Dexamethasone did not enhance the systemic toxicity of chlorpyrifos, as evidenced by weight gain and measurements of cholinesterase inhibition during chlorpyrifos treatment. Nevertheless, it enhanced the loss of presynaptic ACh function selectively in females, who ordinarily show sparing of organophosphate developmental neurotoxicity relative to males. Females receiving the combined treatment showed decrements in choline transporter binding and choline acetyltransferase activity that were unique (not found with either treatment alone), as well as additive decrements in nicotinic receptor binding. On the other hand, males given dexamethasone showed no augmentation of the effects of chlorpyrifos. Our findings indicate that prior dexamethasone exposure could create a subpopulation that is especially vulnerable to the adverse effects of organophosphates or other developmental neurotoxicants.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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Bennet L, Davidson JO, Koome M, Gunn AJ. Glucocorticoids and preterm hypoxic-ischemic brain injury: the good and the bad. J Pregnancy 2012; 2012:751694. [PMID: 22970371 PMCID: PMC3431094 DOI: 10.1155/2012/751694] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 07/13/2012] [Indexed: 12/20/2022] Open
Abstract
Fetuses at risk of premature delivery are now routinely exposed to maternal treatment with synthetic glucocorticoids. In randomized clinical trials, these substantially reduce acute neonatal systemic morbidity, and mortality, after premature birth and reduce intraventricular hemorrhage. However, the overall neurodevelopmental impact is surprisingly unclear; worryingly, postnatal glucocorticoids are consistently associated with impaired brain development. We review the clinical and experimental evidence on how glucocorticoids may affect the developing brain and highlight the need for systematic research.
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Affiliation(s)
- Laura Bennet
- Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland 1142, New Zealand.
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Chlorpyrifos developmental neurotoxicity: interaction with glucocorticoids in PC12 cells. Neurotoxicol Teratol 2012; 34:505-12. [PMID: 22796634 DOI: 10.1016/j.ntt.2012.07.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 06/25/2012] [Accepted: 07/08/2012] [Indexed: 11/20/2022]
Abstract
Prenatal coexposures to glucocorticoids and organophosphate pesticides are widespread. Glucocorticoids are elevated by maternal stress and are commonly given in preterm labor; organophosphate exposures are virtually ubiquitous. We used PC12 cells undergoing neurodifferentiation in order to assess whether dexamethasone enhances the developmental neurotoxicity of chlorpyrifos, focusing on models relevant to human exposures. By themselves, each agent reduced the number of cells and the combined exposure elicited a correspondingly greater effect than with either agent alone. There was no general cytotoxicity, as cell growth was actually enhanced, and again, the combined treatment evoked greater cellular hypertrophy than with the individual compounds. The effects on neurodifferentiation were more complex. Chlorpyrifos alone had a promotional effect on neuritogenesis whereas dexamethasone impaired it; combined treatment showed an overall impairment greater than that seen with dexamethasone alone. The effect of chlorpyrifos on differentiation into specific neurotransmitter phenotypes was shifted by dexamethasone. Either agent alone promoted differentiation into the dopaminergic phenotype at the expense of the cholinergic phenotype. However, in dexamethasone-primed cells, chlorpyrifos actually enhanced cholinergic neurodifferentiation instead of suppressing this phenotype. Our results indicate that developmental exposure to glucocorticoids, either in the context of stress or the therapy of preterm labor, could enhance the developmental neurotoxicity of organophosphates and potentially of other neurotoxicants, as well as producing neurobehavioral outcomes distinct from those seen with either individual agent.
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Wall SN, Lee ACC, Niermeyer S, English M, Keenan WJ, Carlo W, Bhutta ZA, Bang A, Narayanan I, Ariawan I, Lawn JE. Neonatal resuscitation in low-resource settings: what, who, and how to overcome challenges to scale up? Int J Gynaecol Obstet 2009; 107 Suppl 1:S47-62, S63-4. [PMID: 19815203 PMCID: PMC2875104 DOI: 10.1016/j.ijgo.2009.07.013] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
BACKGROUND Each year approximately 10 million babies do not breathe immediately at birth, of which about 6 million require basic neonatal resuscitation. The major burden is in low-income settings, where health system capacity to provide neonatal resuscitation is inadequate. OBJECTIVE To systematically review the evidence for neonatal resuscitation content, training and competency, equipment and supplies, cost, and key program considerations, specifically for resource-constrained settings. RESULTS Evidence from several observational studies shows that facility-based basic neonatal resuscitation may avert 30% of intrapartum-related neonatal deaths. Very few babies require advanced resuscitation (endotracheal intubation and drugs) and these newborns may not survive without ongoing ventilation; hence, advanced neonatal resuscitation is not a priority in settings without neonatal intensive care. Of the 60 million nonfacility births, most do not have access to resuscitation. Several trials have shown that a range of community health workers can perform neonatal resuscitation with an estimated effect of a 20% reduction in intrapartum-related neonatal deaths, based on expert opinion. Case studies illustrate key considerations for scale up. CONCLUSION Basic resuscitation would substantially reduce intrapartum-related neonatal deaths. Where births occur in facilities, it is a priority to ensure that all birth attendants are competent in resuscitation. Strategies to address the gap for home births are urgently required. More data are required to determine the impact of neonatal resuscitation, particularly on long-term outcomes in low-income settings.
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Affiliation(s)
- Stephen N. Wall
- Saving Newborn Lives/Save the Children USA, Washington DC and Cape Town, South Africa
| | - Anne CC Lee
- Saving Newborn Lives/Save the Children USA, Washington DC and Cape Town, South Africa
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Susan Niermeyer
- Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, CO, USA
| | - Mike English
- KEMRI-Wellcome Trust Research Programme, Nairobi, Kenya
| | | | - Wally Carlo
- University of Alabama at Birmingham, AL, USA
| | - Zulfiqar A. Bhutta
- Division of Women and Child Health, the Aga Khan University, Karachi, Pakistan
| | - Abhay Bang
- Society for Education, Action and Research in Community Health, Gadchiroli, Maharashtra, India
| | | | | | - Joy E. Lawn
- Saving Newborn Lives/Save the Children USA, Washington DC and Cape Town, South Africa
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Zhang JH, Lo T, Mychaskiw G, Colohan A. Mechanisms of hyperbaric oxygen and neuroprotection in stroke. PATHOPHYSIOLOGY 2005; 12:63-77. [PMID: 15869872 DOI: 10.1016/j.pathophys.2005.01.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Accepted: 01/18/2005] [Indexed: 11/21/2022] Open
Abstract
Cerebral vascular diseases, such as neonatal encephalopathy and focal or global cerebral ischemia, all result in reduction of blood flow to the affected regions, and cause hypoxia-ischemia, disorder of energy metabolism, activation of pathogenic cascades, and eventual cell death. Due to a narrow therapeutic window for neuroprotection, few effective therapies are available, and prognosis for patients with these neurological injuries remains poor. Hyperbaric oxygen (HBO) has been used as a primary or adjunctive therapy over the last 50 years with controversial results, both in experimental and clinical studies. In addition, the mechanisms of HBO on neuroprotection remain elusive. Early applications of HBO within a therapeutic window of 3-6h or delayed but repeated administration of HBO can either salvage injured neuronal tissues or promote neurobehavioral functional recovery. This review explores the discrepancies between experimental and clinical observations of HBO, focusing on its therapeutic window in brain injuries, and discusses the potential mechanisms of HBO neuroprotection.
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Affiliation(s)
- John H Zhang
- Department of Neurosurgery, Loma Linda University, Loma Linda, CA, USA; Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA
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Abstract
Preconditioning occurs when a subinjurious exposure renders the brain less vulnerable to a subsequent damaging exposure. In this essay, various models of preconditioning in the immature brain are discussed. Adenosine, excitatory amino acids, nitric oxide, hypoxia-inducible factor, ATP-sensitive K+ channels, caspases, heat shock proteins, inflammatory mediators and gene expression all seem to be involved in sensing, transducing and executing preconditioning resistance. Also reviewed in this essay is evidence that some subinjurious exposures render the brain more vulnerable to a subsequent damaging exposure. We believe that unraveling the mechanisms of how the developing brain becomes inherently resilient or vulnerable will offer important insights into the pathogenesis of injury. Preconditioning of the brain or induction of tolerance of the immune system might be utilized in the future to decrease CNS vulnerability and the occurrence of perinatal brain injury.
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Affiliation(s)
- Henrik Hagberg
- Department of Obstetrics and Gynecology, Institute of Women's and Children's Health, Göteborg University, Göteborg, Sweden.
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11
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Raff H, Hong JJ, Oaks MK, Widmaier EP. Adrenocortical responses to ACTH in neonatal rats: effect of hypoxia from birth on corticosterone, StAR, and PBR. Am J Physiol Regul Integr Comp Physiol 2003; 284:R78-85. [PMID: 12388447 DOI: 10.1152/ajpregu.00501.2002] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The adrenocortical response to hypoxia may be a critical component of the adaptation to this common neonatal stress. Little is known about adrenal function in vivo in hypoxic neonates. The purpose of this study was to evaluate adrenocortical responses to ACTH in suckling rat pups exposed to hypoxia from birth to 5-7 days of age compared with normoxic controls. We also evaluated potential cellular controllers of steroidogenic function in situ. In 7-day-old pups at 0800, hypoxia from birth resulted in increased basal (12.2 +/- 1.4 ng/ml; n = 12) and ACTH-stimulated (94.0 +/- 9.4 ng/ml; n = 14) corticosterone levels compared with normoxic controls (basal = 8.3 +/- 0.5 ng/ml; n = 11; stimulated = 51.3 +/- 3.8 ng/ml; n = 8). This augmentation occurred despite no significant difference in plasma ACTH levels in normoxic vs. hypoxic pups before (85 +/- 4 vs. 78 +/- 8 pg/ml) or after (481 +/- 73 vs. 498 +/- 52 pg/ml) porcine ACTH injection (20 microg/kg). This effect was similar in the afternoon at 6 days of age and even greater at 5 days of age at 0800. The aldosterone response to ACTH was not augmented by exposure to hypoxia from birth. Adrenocortical hypoxia-inducible factor (HIF)-1alpha mRNA was undetectable by RT-PCR. Steroidogenic acute regulatory (StAR) protein in adrenal subcapsules (zona fasciculata/reticularis) was augmented by exposure to hypoxia; this effect was greatest at 5 days of age. Peripheral-type benzodiazepine receptor (PBR) protein was also increased at 6 and 7 days of age in pups exposed to hypoxia from birth. We conclude that hypoxia from birth results in an augmentation of the corticosterone but not aldosterone response to ACTH. This effect appears to be mediated at least in part by an increase in controllers of mitochondrial cholesterol transport (StAR and PBR) and to occur independently of measurable changes in endogenous plasma ACTH. The augmentation of the corticosterone response to acute increases in ACTH in hypoxic pups is likely to be an important component of the overall physiological adaptation to hypoxia in the neonate.
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Affiliation(s)
- Hershel Raff
- Endocrine and Transplant Research Laboratories, St. Luke's Medical Center, and Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin 53215, USA.
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12
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Abstract
Investigations in animal models of hypoxic-ischemic injury have not translated into clinical trials of success because of the complex pathology of hypoxic-ischemic brain injury in neonates, the difficulty in defining the onset and duration and severity of the injury, the underlying predisposing disorders of the mothers or the infant, the side effects of many of the investigational drugs precluded clinical use, and many of the investigational agents interfered with only one step of the cascade of events that lead to brain injury. It is possible that a combination of therapeutic agents, including those that affect different levels of the cascade to cell death, will have the greatest neuroprotective effects. Modest hypothermia postpones secondary energy failure and can prolong the window while pharmacotherapeutic agents can be used. It is possible that in the future, sequential administration of agents or strategies that are initiated in the intrapartum period and continued postnatally will be the optimum method for treating infants who are at highest risk for brain injury following acute hypoxic-ischemic asphyxia.
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Affiliation(s)
- Seetha Shankaran
- Neonatal-Perinatal Medicine, Wayne State University School of Medicine, 3901 Beaubien Blvd, Detroit, MI 48201, USA.
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Calvert JW, Yin W, Patel M, Badr A, Mychaskiw G, Parent AD, Zhang JH. Hyperbaric oxygenation prevented brain injury induced by hypoxia-ischemia in a neonatal rat model. Brain Res 2002; 951:1-8. [PMID: 12231450 DOI: 10.1016/s0006-8993(02)03094-9] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The occurrence of hypoxia-ischemia (HI) during early fetal or neonatal stages of an individual leads to the damaging of immature neurons resulting in behavioral and psychological dysfunctions, such as motor or learning disabilities, cerebral palsy, epilepsy or even death. No effective treatment is currently available and this study is the first to use hyperbaric oxygen (HBO) as a treatment for neonatal HI. Herein, we sought out to determine if HBO is able to offer neuroprotectivity against an HI insult. Seven-day-old rat pups were subjected to unilateral carotid artery ligation followed by 2.5 h of hypoxia (8% O(2) at 37 degrees C). HBO treatment was administered by placing pups in a chamber (3 ATA for 1 h) 1 h after hypoxia exposure. Brain injury was assessed based on ipsilateral hemispheric weight divided by contralateral hemispheric weight, light microscopy, and EM. Sensorimotor functional tests were administered at 5 weeks after hypoxia exposure. After HI, the ipsilateral hemisphere was 52.65 and 57.64% (P<0.001) of the contralateral hemisphere at 2 and 6 weeks, respectively. In HBO treated groups, the ipsilateral hemisphere was 77.77 and 84.19% (P<0.001) at 2 and 6 weeks. There was much less atrophy and apoptosis in HBO treated animals under light or electron microscopy. Sensorimotor function was also improved by HBO at 5 weeks after hypoxia exposure (Chi-square, P<0.050). The results suggest that HBO is able to attenuate the effects of HI on the neonatal brain by reducing the progression of neuronal injury and increasing sensorimotor function.
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Affiliation(s)
- John W Calvert
- Department of Neurosurgery, University of Mississippi Medical Center, Jackson, MS 39216, USA
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Abrahám IM, Harkany T, Horvath KM, Luiten PG. Action of glucocorticoids on survival of nerve cells: promoting neurodegeneration or neuroprotection? J Neuroendocrinol 2001; 13:749-60. [PMID: 11578524 DOI: 10.1046/j.1365-2826.2001.00705.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Extensive studies during the past decades provided compelling evidence that glucocorticoids (GCs) have the potential to affect the development, survival and death of neurones. These observations, however, reflect paradoxical features of GCs, as they may be critically involved in both neurodegenerative and neuroprotective processes. Hence, we first address different aspects of the complex role of GCs in neurodegeneration and neuroprotection, such as concentration dependent actions of GCs on neuronal viability, anatomical diversity of GC-mediated mechanisms in the brain and species and strain differences in GC-induced neurodegeneration. Second, the modulatory action of GCs during development and ageing of the central nervous system, as well as the contribution of altered GC balance to the pathogenesis of neurodegenerative disorders is considered. In addition, we survey recent data as to the possible mechanisms underlying the neurodegenerative and neuroprotective actions of GCs. As such, two major aspects will be discerned: (i) GC-dependent offensive events, such as GC-induced inhibition of glucose uptake, increased extracellular glutamate concentration and concomitant elevation of intracellular Ca(2+), decrease in GABAergic signalling and regulation of local GC concentrations by 11 beta-hydroxysteroid dehydrogenases; and (ii) GC-related cellular defence mechanisms, such as decrease in after-hyperpolarization, increased synthesis and release of neurotrophic factors and lipocortin-1, feedback regulation of Ca(2+) currents and induction of antioxidant enzymes. The particular relevance of these mechanisms to the neurodegenerative and neuroprotective effects of GCs in the brain is discussed.
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Affiliation(s)
- I M Abrahám
- Laboratory of Molecular Neuroendocrinology, Institute of Experimental Medicine of the Hungarian Academy of Sciences, Budapest, Hungary
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O'Shea TM, Doyle LW. Perinatal glucocorticoid therapy and neurodevelopmental outcome: an epidemiologic perspective. SEMINARS IN NEONATOLOGY : SN 2001; 6:293-307. [PMID: 11972431 DOI: 10.1053/siny.2001.0065] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A relatively brief course of antenatal glucocorticoids (ACS), given to reduce the severity of respiratory distress syndrome in preterm infants, improves survival and appears to protect against brain damage. In clinical trials as well as observational studies, ACS have been associated with a decreased risk of intraventricular haemorrhage and cerebral palsy. In observational studies a decreased risk of white-matter damage, identified with cranial ultrasound, has been observed. There is some evidence, from observational studies, that repeated courses of ACS (typically given at weekly intervals) can reduce the rate of fetal head growth, and experiments in animals provide further support for this possibility. In contrast to the effects of a brief course of ACS, postnatal glucocorticoids (PCS), given to preterm infants to reduce the severity of chronic lung disease have been associated with an increased risk of neurologic impairment. Available evidence suggests that PCS does not improve survival. Further study is needed of the neurodevelopmental consequences of both multiple courses of ACS, as well as PCS.
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Affiliation(s)
- T M O'Shea
- Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
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16
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Abstract
Perinatal brain damage in the mature fetus is usually brought about by severe intrauterine asphyxia following an acute reduction of the uterine or umbilical circulation. The areas most heavily affected are the parasagittal region of the cerebral cortex and the basal ganglia. The fetus reacts to a severe lack of oxygen with activation of the sympathetic-adrenergic nervous system and a redistribution of cardiac output in favor of the central organs (brain, heart and adrenals). If the asphyxic insult persists, the fetus is unable to maintain circulatory centralization, and the cardiac output and extent of cerebral perfusion fall. Owing to the acute reduction in oxygen supply, oxidative phosphorylation in the brain comes to a standstill. The Na+/K+ pump at the cell membrane has no more energy to maintain the ionic gradients. In the absence of a membrane potential, large amounts of calcium ions flow through the voltage-dependent ion channels, down an extreme extra-/intracellular concentration gradient, into the cell. Current research suggests that the excessive increase in levels of intracellular calcium, so-called calcium overload, leads to cell damage through the activation of proteases, lipases and endonucleases. During ischemia, besides the influx of calcium ions into the cells via voltage-dependent calcium channels, more calcium enters the cells through glutamate-regulated ion channels. Glutamate, an excitatory neurotransmitter, is released from presynaptic vesicles during ischemia following anoxic cell depolarization. The acute lack of cellular energy arising during ischemia induces almost complete inhibition of cerebral protein biosynthesis. Once the ischemic period is over, protein biosynthesis returns to preischemic levels in non-vulnerable regions of the brain, while in more vulnerable areas it remains inhibited. The inhibition of protein synthesis, therefore, appears to be an early indicator of subsequent neuronal cell death. A second wave of neuronal cell damage occurs during the reperfusion phase. This cell damage is thought to be caused by the postischemic release of oxygen radicals, synthesis of nitric oxide (NO), inflammatory reactions and an imbalance between the excitatory and inhibitory neurotransmitter systems. Part of the secondary neuronal cell damage may be caused by induction of a kind of cellular suicide programme known as apoptosis. Interestingly, there is increasing evidence from recent clinical studies that perinatal brain damage is closely associated with ascending intrauterine infection before or during birth. However, a major part of this damage is likely to be of hypoxic-ischemic nature due to LPS-induced effects on fetal cerebral circulation. Knowledge of these pathophysiological mechanisms has enabled scientists to develop new therapeutic strategies with successful results in animal experiments. The potential of such therapies is discussed here, particularly the promising effects of intravenous administration of magnesium or postischemic induction of cerebral hypothermia.
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Affiliation(s)
- R Berger
- Department of Obstetrics and Gynecology, Ruhr-University, Bochum, Germany.
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Chen LE, Silver WP, Seaber AV, Korompilias AV, Urbaniak JR. Effects of dexamethasone on the contractile function of reperfused skeletal muscle. Microsurgery 2000; 17:313-20. [PMID: 9308715 DOI: 10.1002/(sici)1098-2752(1996)17:6<313::aid-micr5>3.0.co;2-i] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This study evaluated the effects of dexamethasone (DXM) on contractile function of reperfused extensor digitalis longus (EDL) muscles following 3-hour ischemia and 24-hour reperfusion. The rats were divided into four groups: normal muscle, ischemia with saline treatment, ischemia/reperfusion with saline treatment, and ischemia/reperfusion with DXM treatment groups. DXM (0.6 mg kg[-1]) or saline (3.0 ml kg[-1]) was administered at 3 hours prior to ischemia. Results showed that although contractile force in all three treated groups was significantly lower than that of normal EDL, the average isometric tetanic contractile force in the DXM-treated group was significantly greater than that in the saline-treated ischemia and ischemia/reperfusion groups. A significant difference was also seen at the peak force and at 5 seconds of the fatigue trains, and with a longer fatigue half-time (FT1/2) in the DXM-treated group than in the other two groups. Histologically, edema, inflammation and necrosis of muscle fiber were less severe in the DXM-treated group than in the saline-treated group. The results indicate that pretreatment with DXM appears to attenuate, but does not completely reverse, the contractile function deficit of ischemic skeletal muscle during the first 24 hours of reperfusion.
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Affiliation(s)
- L E Chen
- Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA
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18
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Abstract
Research from the last two decades provides directions for efforts to prevent CP in VLBW infants. The pathogenesis of CP seems to involve factors operating both during pregnancy and in the neonatal period. The most important prenatal factor appears to be intrauterine infection. Perinatal infection and other risk factors, such as the death of a co-twin, placental abruption, and cerebral ischemia, could trigger a cytokine cascade resulting in damage to the developing brain. The low frequency of intrauterine infection in mothers with preeclampsia might explain the apparent protective effect of this disorder. If the brain damage attributed to intrauterine infection and other risk factors involves cytokines as intermediates, then blockade of the proinflammatory cascade or promotion of endogenous inhibitors might prevent CP. Other potentially preventive strategies include corticosteroids given to mothers (but not those given to neonates) and thyroid hormone.
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Affiliation(s)
- T M O'Shea
- Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
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19
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Feng Y, LeBlanc MH, LeBlanc EB, Parker CC, Fratkin JD, Qian XB, Patel DM, Huang M, Smith EE, Vig PJ. Desmethyl tirilazad improves neurologic function after hypoxic ischemic brain injury in piglets. Crit Care Med 2000; 28:1431-8. [PMID: 10834691 DOI: 10.1097/00003246-200005000-00029] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Desmethyl tirilazad is a lipid-soluble free radical quencher. Deferoxamine reduces free radicals by chelating iron and reducing hydroxyl formation. Free radical inhibitors have shown promise in several hypoxic ischemic brain injury models, and we wished to see if this work could be extended to our newborn piglet model. DESIGN Randomized controlled trial. SUBJECTS Piglets (0 to 3 days old). INTERVENTION Carotid snares and arterial and venous catheters were placed under 1.5% isoflurane anesthesia. In Experiment 1, piglets were randomly assigned to receive either 3 mg/kg desmethyl tirilazad or vehicle at -15 and 90 mins. In Experiment 2, piglets were randomly assigned to receive either 20 mg/kg desmethyl tirilazad at -15 mins followed by 8 mg/kg/hr for 90 mins or 100 mg/kg deferoxamine at -15 mins or vehicle. At time 0, both carotid arteries were clamped and blood was withdrawn to reduce the blood pressure to two-thirds normal. At 15 mins, inspired oxygen was reduced to 6%. At 30 mins, the carotid snares were released, the withdrawn blood was reinfused, and the oxygen was switched to 100%. On the third day after the hypoxic ischemic injury, the animals were killed by perfusing their brains with 10% formalin. We tested the timing of lipid peroxidation and inhibition of lipid peroxidation by these agents by freezing the brains of a subset of pigs in liquid nitrogen. MEASUREMENTS Neurologic examination and brain pathology were scored by blinded observers. Thiobarbituric acid-reactive substance and oxidized and reduced glutathione were measured on frozen brains. MAIN RESULTS Desmethyl tirilazad (20 mg/kg) and 100 mg/kg deferoxamine inhibit lipid peroxidation. Desmethyl tirilazad (20 mg/kg) improves neurologic exam, but 3 mg/kg Desmethyl tirilazad or 100 mg/kg deferoxamine does not. Neither desmethyl tirilazad nor deferoxamine improves pathologic results. CONCLUSIONS High-dose desmethyl tirilazad improves neurologic function after hypoxic ischemic brain injury in the newborn piglet.
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Affiliation(s)
- Y Feng
- Department of Pediatrics, University of Mississippi Medical Center, Jackson 39216-4505, USA
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20
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Abstract
The phenomenon of ischemic tolerance has been closely associated with the expression of heat shock proteins but recently, stress tolerance not related to hsp72 has been reported. In the present study, we focused on ischemic tolerance induced by hypoxia and hyperthermia in neonatal rat brain and analyzed the expression of hsp72. In a neonatal rat model of hypoxic ischemia (H-I), preconditioning by whole-body hyperthermia or hypoxia was induced 24 h prior to the ischemia. Brain damage was histologically evaluated and the expressions of hsp72 were analyzed. Hyperthermic preconditioning at 41 degrees C for 15 min, as well as hypoxic preconditioning with 8% hypoxia for 3 h, had almost complete neuroprotective effects. However, we failed to detect the expression of hsp72 in any of preconditioning. Only the H-I insult itself induced hsp72 in the dorsal striatum and slightly in the thalamus and the hippocampus. Hyperthermic preconditioning has neuroprotective effects which are comparable to hypoxic preconditioning in immature brain. The expression of hsp72 is not likely necessary for the ischemic tolerance in immature brain.
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Affiliation(s)
- T Wada
- Department of Neurosurgery, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Japan.
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21
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Berger R, Garnier Y. Pathophysiology of perinatal brain damage. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1999; 30:107-34. [PMID: 10525170 DOI: 10.1016/s0165-0173(99)00009-0] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Perinatal brain damage in the mature fetus is usually brought about by severe intrauterine asphyxia following an acute reduction of the uterine or umbilical circulation. The areas most heavily affected are the parasagittal region of the cerebral cortex and the basal ganglia. The fetus reacts to a severe lack of oxygen with activation of the sympathetic-adrenergic nervous system and a redistribution of cardiac output in favour of the central organs (brain, heart and adrenals). If the asphyxic insult persists, the fetus is unable to maintain circulatory centralisation, and the cardiac output and extent of cerebral perfusion fall. Owing to the acute reduction in oxygen supply, oxidative phosphorylation in the brain comes to a standstill. The Na(+)/K(+) pump at the cell membrane has no more energy to maintain the ionic gradients. In the absence of a membrane potential, large amounts of calcium ions flow through the voltage-dependent ion channel, down an extreme extra-/intracellular concentration gradient, into the cell. Current research suggests that the excessive increase in levels of intracellular calcium, so-called calcium overload, leads to cell damage through the activation of proteases, lipases and endonucleases. During ischemia, besides the influx of calcium ions into the cells via voltage-dependent calcium channels, more calcium enters the cells through glutamate-regulated ion channels. Glutamate, an excitatory neurotransmitter, is released from presynaptic vesicles during ischemia following anoxic cell depolarisation. The acute lack of cellular energy arising during ischemia induces almost complete inhibition of cerebral protein biosynthesis. Once the ischemic period is over, protein biosynthesis returns to pre-ischemic levels in non-vulnerable regions of the brain, while in more vulnerable areas it remains inhibited. The inhibition of protein synthesis, therefore, appears to be an early indicator of subsequent neuronal cell death. A second wave of neuronal cell damage occurs during the reperfusion phase. This cell damage is thought to be caused by the post-ischemic release of oxygen radicals, synthesis of nitric oxide (NO), inflammatory reactions and an imbalance between the excitatory and inhibitory neurotransmitter systems. Part of the secondary neuronal cell damage may be caused by induction of a kind of cellular suicide programme known as apoptosis. Knowledge of these pathophysiological mechanisms has enabled scientists to develop new therapeutic strategies with successful results in animal experiments. The potential of such therapies is discussed here, particularly the promising effects of i.v. administration of magnesium or post-ischemic induction of cerebral hypothermia.
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Affiliation(s)
- R Berger
- Department of Obstetrics and Gynecology, University of Bochum, Bochum, Germany. richard.berger2ruhr-uni-bochum.de
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22
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Huang WL, Dunlop SA, Harper CG. Effect of exogenous corticosteroids on the developing central nervous system: a review. Obstet Gynecol Surv 1999; 54:336-42. [PMID: 10234698 DOI: 10.1097/00006254-199905000-00024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Corticosteroid therapy is used in a variety of developmental clinical settings. Prenatally, maternal administration of corticosteroids is used primarily in the prevention of respiratory distress syndrome. Postnatally, corticosteroids are used to treat a variety of infant diseases such as autoimmune hemolytic anemia and hypoglycemia. Treatment regimes often involve repeated administration, on a weekly basis prenatally and daily postnatally, despite an absence of safety data from randomized clinical trials. A large number of animal studies, the majority of which used rodents, have shown that both repeated prenatal or neonatal administration of exogenous corticosteroids has a wide range of detrimental effects on the structure and function of the developing central nervous system (CNS). None of these studies included long-term follow-up. Despite the reported detrimental effects on CNS development, a number of animal studies have shown that pretreatment with corticosteroids nevertheless protect the brain from hypoxia-ischemic injury; however, clinically such treatment is no longer favored. Studies using large animal models and with long-term follow-up should be undertaken to establish the relative risks and benefits of the repeated application of exogenous corticosteroids.
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Affiliation(s)
- W L Huang
- Department of Zoology, University of Western Australia, Nedlands, Australia.
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23
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Marret S, Bonnier C, Raymackers JM, Delpech A, Evrard P, Gressens P. Glycine antagonist and NO synthase inhibitor protect the developing mouse brain against neonatal excitotoxic lesions. Pediatr Res 1999; 45:337-42. [PMID: 10088651 DOI: 10.1203/00006450-199903000-00008] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The prevention of cerebral palsy and neuroprotection of the immature brain continue to be health care priorities. The pathophysiology of perinatal brain lesions associated with cerebral palsy seems to be multifactorial and includes pre- and perinatal factors such as preconceptional events, hormone and growth factors deficiencies, maternal infections with production of cytokines, and hypoxic/ischemic perfusion failures. Excitotoxic cascade could represent a common pathway that leads to neural cell death and subsequent brain damage. Brain injuries induced by ibotenate, a glutamatergic analog, which are essentially mediated through the N-methyl-D-aspartate receptor, mimic some aspects of the white matter cysts and transcortical necrosis observed in human perinatal brain damage. The purpose of the present study was to assess the protective role of several pharmacological agents, administered in conjunction with ibotenate, against induced excitotoxic lesions. We injected ibotenate in the developing mouse brain 5 d postnatally, after the full settlement of neuronal layers. Co-treatment with kynurenic acid, an antagonist of the facilitating glycine site of the N-methyl-D-aspartate receptor, or with N(G)-nitro-L-arginine, an inhibitor of nitric oxide synthesis, induced a dose-dependent neuroprotective effect. Conversely, zinc gluconate, a blocking agent of the channel linked to the N-methyl-D-aspartate receptor, and a free radical scavenger (U74389F), were unable to protect the developing brain against excitotoxic attack. These data help to clarify some molecular mechanisms involved in excitotoxic lesions of the developing mouse brain and permit us to envision new strategies in the prevention of cerebral palsy.
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Affiliation(s)
- S Marret
- Service de Médecine Néonatale, University of Rouen Medical School, France
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24
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Berger R, Lehmann T, Karcher J, Garnier Y, Jensen A. Low dose flunarizine protects the fetal brain from ischemic injury in sheep. Pediatr Res 1998; 44:277-82. [PMID: 9727701 DOI: 10.1203/00006450-199809000-00003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Flunarizine, a calcium channel blocker, reduced cerebral damage caused by hypoxic-ischemic insults in neonatal rats and in fetal sheep near term. However, the high dose regimen used in these studies produced cardiovascular side effects that might have counteracted the neuroprotective properties of flunarizine. Therefore, the neuroprotective effect was tested in a low dose protocol (1 mg/kg estimated body weight). Twelve fetal sheep near term were instrumented chronically. Six fetuses were pretreated with 1 mg of flunarizine per kg of estimated body weight 1 h before ischemia, whereas the remainder (n=6) received solvent. Cerebral ischemia was induced by occluding both carotid arteries for 30 min. To exclude the possibility that the neuroprotective effects of flunarizine were caused by cerebrovascular alterations we measured cerebral blood flow by injecting radiolabeled microspheres before (-1 h), during (3 min and 27 min) and after (40 min, 3 h, and 72 h) cerebral ischemia. At the end of the experiment (72 h) the ewe was given a lethal dose of sodium pentobarbitone and saturated potassium chloride i.v., and the fetal brain was perfused with formalin. Neuronal cell damage was assessed in various brain structures by light microscopy after cresyl violet/fuchsin staining using a scoring system: 1, 0-5% damage; 2, 5-50% damage; 3, 50-95% damage; 4, 95-99% damage; and 5, 100% damage. In 10 other fetal sheep effects of low dose flunarizine on circulatory centralization caused by acute asphyxia could be excluded. In the treated group neuronal cell damage was reduced significantly in many cerebral areas to varying degrees (range for control group, 1.03-2.14 versus range for treated group, 1.00-1.13; p < 0.05 to p < 0.001, respectively). There were only minor differences in blood flow to the various brain structures between groups. We conclude that pretreatment with low dose flunarizine protects the brain of fetal sheep near term from ischemic injury. This neuroprotective effect is not mediated by changes in cerebral blood flow. We further conclude that low dose flunarizine may be clinically useful as a treatment providing fetal neuroprotection, particularly because the fetal cardiovascular side effects are minimal.
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Affiliation(s)
- R Berger
- Department of Obstetrics and Gynecology, Ruhr-Universität Bochum, Germany
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25
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Perlman JM. Antenatal glucocorticoid, magnesium exposure, and the prevention of brain injury of prematurity. Semin Pediatr Neurol 1998; 5:202-10. [PMID: 9777678 DOI: 10.1016/s1071-9091(98)80035-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prevention of perinatal white matter injury with or without severe intraventricular hemorrhage (IVH) is critical to reduce cerebral palsy (CP) in premature infants. Antenatal therapies that may afford neuroprotection include glucocorticoids, which are associated with a significant reduction in severe IVH, and magnesium, which is associated with reduced CP. Potential protective mechanisms of glucocorticoids include a direct effect on brain, improved respiratory function, and more stable blood pressure hemodynamics. Because magnesium is often administered to mothers with pregnancy-induced hypertension, a condition associated with reduction in severe IVH, the independent neuroprotective role of magnesium remains unclear and warrants additional studies.
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Affiliation(s)
- J M Perlman
- Department of Pediatrics, UT Southwestern Medical School, Dallas, TX 75235-9063, USA
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26
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Macaya A, Munell F, Ferrer I, de Torres C, Reventós J. Cell death and associated c-jun induction in perinatal hypoxia-ischemia. Effect of the neuroprotective drug dexamethasone. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1998; 56:29-37. [PMID: 9602039 DOI: 10.1016/s0169-328x(98)00024-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Previous studies in a model of unilateral hypoxia-ischemia in the developing rat brain have shown induction of the mRNAs of c-fos and c-jun and presence of apoptotic DNA fragmentation. In this same model, dexamethasone confers neuroprotection if given before the insult. Since c-fos and c-jun have been involved in several models of cell death, we investigated whether the neuroprotective effect of dexamethasone could be associated with changes in expression of these genes. Rat pups, pre-treated with either 0.5 mg/kg dexamethasone or vehicle 48 h, 24 h and immediately before the injury, were subjected to ligation of the left common carotid artery followed by 3 h hypoxia. Analysis of c-fos and c-jun expression at 2 h, by means of in situ hybridization, revealed diminished induction in dexamethasone-treated animals. Jun immunoreactivity, but not Fos, and DNA fragmentation, assessed by in situ end-labeling of fragmented DNA, were present at 24 h only in vehicle-injected animals. Electrophoresis of brain extracted DNA revealed a ladder pattern in all the animals. Our results show a relationship between Jun overexpression and cell-death in the hypoxic-ischemic developing brain and suggest that dexamethasone exerts its protective effect anteceding immediate early gene induction, at some early point in post-ischemic signal transduction.
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Affiliation(s)
- A Macaya
- Biochemistry and Molecular Biology Research Center, Vall d'Hebron Hospital, Barcelona, Spain
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27
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Berkman MZ, Palaoğlu S, Erbengi T, Erbengi A. Neurotransmitter and amino acid analysis and ultrastructural observations of fetal brain cortex transplantation to adult rat brain under the effect of dexamethasone. Neurosurgery 1998; 42:1126-33; discussion 1133-4. [PMID: 9588559 DOI: 10.1097/00006123-199805000-00104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVE To conduct an investigation of fetal cortical tissue graft survival using transmission electron microscopy and analyzing neurotransmitters and amino acids and their function, with special reference to the effect of dexamethasone. METHODS Transplantation of fetal cortical brain tissue to 100 adult Wistar albino rats weighing 170 to 220 g was performed. The rats were divided into three groups. Only transplantation of fetal cortical brain tissue was performed in the first group (n=36). In the second group (n=48), dexamethasone was administered in addition to fetal cortical tissue transplantation. The third group (n=16) was used as the surgical control group. The rats were allowed to live for 6 weeks and were then decapitated. The grafts were examined by electron microscopy. Additionally, quantitative analyses of the neurotransmitters and amino acids of the grafts were conducted using high-pressure liquid chromatography. RESULTS Electron microscopic observations revealed that the grafts were still surviving at the end of the 6th week in both groups. However, in the group that received dexamethasone, neurons and their organelles were better developed than in the group that did not receive dexamethasone. Concommitantly, results of quantitative analysis in the dexamethasone group revealed statistically extremely significant higher amino acid values for glutamic acid, aspartic acid, beta-alanine, and lysine and significantly higher values for gamma-aminobutyric acid, glutamine, glycine, and serine when compared to the nondexamethasone group. CONCLUSION Dexamethasone is effective in increasing the survival and in developing the ultrastructural and functional outcome of transplanted neurons in fetal grafts.
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Affiliation(s)
- M Z Berkman
- Department of Neurosurgery, Okmeydani Social Security Hospital, Istanbul, Turkey
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28
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Affiliation(s)
- R C Vannucci
- Department of Pediatrics, Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033-0850, USA
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29
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Chumas P, Condon B, Oluoch-Olunya D, Griffiths S, Hadley D, Teasdale G. Early changes in peritumorous oedema and contralateral white matter after dexamethasone: a study using proton magnetic resonance spectroscopy. J Neurol Neurosurg Psychiatry 1997; 62:590-5. [PMID: 9219744 PMCID: PMC1074142 DOI: 10.1136/jnnp.62.6.590] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
AIMS To study the mechanism of action of steroids in patients with peritumorous oedema. METHODS To investigate early cerebral metabolic changes proton magnetic resonance spectroscopy (1H-MRS) was used before and 11 to 14 hours after treatment with dexamethasone (12 mg oral loading and 4 mg four times daily maintenance). Nine patients (two men, seven women, mean age 54) with pronounced oedema associated with various intracranial tumours (two astrocytomas, three meningiomas, two glioblastoma, and two metastases) were examined using MRI and MRS. SE1500/135 volume selected MRS (mean volume 21 ml) were performed on an oedematous region and a contralateral region. All spectra were acquired with and without water suppression. Metabolite peak area ratios were determined. RESULTS Regions of oedema had significantly (P < 0.01) higher unsuppressed water than the contralateral regions, as expected. There was no change at this early time point after dexamethasone. The ratio of the area of choline containing compounds to that creatine and phosphocreatine compounds was determined after which the serial ratios of these before and after were calculated (a serial ratio of 1.0 would indicate no change in the choline to creatine ratios after steroid administration). The mean serial ratios for the area of oedema were 1.02 (SEM 0.08) and 1.10 (0.08) for the contralateral volume of interest, indicating no significant changes. However, significant changes (P < 0.02) were found in the N-acetyl-aspartate (NAA)/choline serial ratios (0.86 (0.06) in the area of oedema, 1.20 (0.10) in contralateral brain) and the NAA/creatine serial ratios (0.86 (0.08) for the oedema, 1.25 (0.11) in contralateral brain). CONCLUSIONS Such rapid changes may be explained either by relatively large alterations in the relaxation characteristics of NAA or, more controversially, by actual changes in the amounts of NAA. It is proposed that steroids act primarily by causing early metabolic changes that are later expressed in improvements in intracranial volume relations.
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Affiliation(s)
- P Chumas
- Department of Neurosurgery, Institute of Neurological Sciences, Southern General Hospital, Glasgow, Scotland
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30
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Roohey T, Raju TN, Moustogiannis AN. Animal models for the study of perinatal hypoxic-ischemic encephalopathy: a critical analysis. Early Hum Dev 1997; 47:115-46. [PMID: 9039963 DOI: 10.1016/s0378-3782(96)01773-2] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We critically evaluated various design features from 292 animal studies related to perinatal hypoxic-ischemic encephalopathy (HIE). Rodents were the most frequently used animals in HIE research (26%), followed by piglets (23%) and sheep (22%). Asphyxia with or without ischemia was the most predominant method of producing experimental brain damage, but there were significant variations in specific details, particularly regarding the method and duration of brain insult. In 71% (207/292) of studies the CNS outcomes were tested within 24 h of experimental insult and in 29% (85/292) they were tested 24 h or more after the insult. Acute CNS metabolic end-points were assessed in 82-100% of all studies. In 90% of studies the chronological age of the animal was equivalent to that of human term newborn infant. However, in only 23% (67/292) were clinical neurological, developmental or behavioral outcomes evaluated, and in only 26% (76/292) was neuropathology assessed. While no single animal model was found to be ideal for all HIE research, some models were distinctly superior to others, depending upon the specific research question. The fetal sheep, newborn lamb and piglet models are well suited for the study of acute and subacute metabolic and physiologic endpoints, whereas the rodent and primate models could be used for long-term neurological and behavioral outcome experiments as well. We also feel that standardizing the study design features, including an HI insult method that produces consistent and predictable brain damage is urgently needed. Studies in neuro-ethology should explore how well brains of various animals compare with that of the newborn human infant. There is also a need for developing animal models that mimic clinical entities in which long-term neuro-developmental and behavioral outcomes can be assessed.
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Affiliation(s)
- T Roohey
- Department of Pediatrics, University of Illinois, Chicago 60612, USA
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31
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Tuor UI, Del Bigio MR. Protection against hypoxic-ischemic damage with corticosterone and dexamethasone: inhibition of effect by a glucocorticoid antagonist RU38486. Brain Res 1996; 743:258-62. [PMID: 9017253 DOI: 10.1016/s0006-8993(96)01054-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We investigated whether the neuroprotection provided by dexamethasone against neonatal hypoxic-ischemic damage can be inhibited by a glucocorticoid antagonist and whether corticosterone, the endogenous glucocorticoid in the rat, also provides protection. Rats (6 days old) were treated with either vehicle (0.1 ml/10 g), corticosterone (3.5-80 mg/kg, s.c.) or dexamethasone alone or in combination with RU38486 (20-80 mg/kg, s.c.) 15 min prior to dexamethasone (0.1 mg/kg, i.p.). At 7 days of age, cerebral hypoxia-ischemia was produced by right carotid artery ligation under anesthesia and subsequent exposure to 2 h of hypoxia. Damage was quantified from brains perfusion-fixed and processed 2 days later. The reduction in somatic growth, thymus weight and the relatively elevated blood glucose levels at the end of hypoxia-ischemia were inhibited by RU38486. The protective effect of dexamethasone was also prevented by RU38486 (P < 0.001). Similar to pre-treatment with dexamethasone, administration of corticosterone (40-80 mg/kg) markedly reduced the extent of infarction compared to vehicle-treated controls (P < 0.0001). Thus, the endogenous glucocorticoid in the rat also provides protection against hypoxic-ischemic damage. RU38486 inhibits the beneficial effects of dexamethasone demonstrating that the neuroprotection observed with dexamethasone is a glucocorticoid receptor-mediated effect.
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Affiliation(s)
- U I Tuor
- Biosystems, Institute for Biodiagnostics, NRCC, Winnipeg, Man, Canada.
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32
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Novack TA, Dillon MC, Jackson WT. Neurochemical mechanisms in brain injury and treatment: a review. J Clin Exp Neuropsychol 1996; 18:685-706. [PMID: 8941854 DOI: 10.1080/01688639608408292] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This article reviews cellular energy transformation processes and neurochemical events that take place at the time of brain injury and shortly thereafter emphasizing hypoxia-ischemia, cerebrovascular accident, and traumatic brain injury. New interpretations of established concepts, such as diffuse axonal injury, are discussed; specific events, such as free radical production, excess production of excitatory amino acids, and disruption of calcium homeostasis, are reviewed. Neurochemically-based interventions are also presented: calcium channel blockers, excitatory amino acid antagonists, free radical scavengers, and hypothermia treatment. Concluding remarks focus on the role of clinical neuropsychologists in validation of treatment interventions.
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Affiliation(s)
- T A Novack
- Department of Rehabilitation Medicine, University of Alabama at Birmingham 35233-7330, USA
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33
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Jansen EM, Low WC. Long-term effects of neonatal ischemic-hypoxic brain injury on sensorimotor and locomotor tasks in rats. Behav Brain Res 1996; 78:189-94. [PMID: 8864051 DOI: 10.1016/0166-4328(95)00248-0] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Perinatal ischemia and/or hypoxia in humans are major risk factors for neurologic injury that often manifest as sensorimotor and locomotor deficits throughout development and into maturity. In these studies, we utilized an established model of neonatal ischemic-hypoxia that creates unilateral striatal, cortical, and hippocampal damage (Rice III, J.E., Vanucci, R.C. and Brierley, J.B., Ann. Neurol., 9 (1981) 131-141) to investigate sensorimotor and locomotor deficits in these animals during development and as adults. Sensorimotor deficits were examined by measuring the amount of time that the animals were able to remain on a rotating treadmill. Locomotor abnormalities were assessed by measuring apomorphine-induced rotational asymmetry. Following the neonatal ischemic-hypoxic episode, at 3-9 weeks of age, animals were not able to remain on the treadmill as long as their normal littermate controls. In addition, these animals demonstrated an abnormal, ipsiversive rotational asymmetry in response to systemic administration of apomorphine. When these animals reached adulthood, the degree of atrophy in specific regions of the damaged hemisphere was quantified using measurements of cross-sectional area. The mean cross-sectional area of the striatum was decreased by 29%, the sensorimotor cortex area by 26%, and the dorsal hippocampus cross-sectional area was approximately 6% of its normal size. These data suggest that this rodent model of neonatal ischemic-hypoxic brain injury results in cerebral atrophy and long-lasting sensorimotor and locomotor deficits. These particular behavioral tasks may be used in future studies to assess locomotor and sensorimotor deficits following neonatal ischemic-hypoxic brain injury.
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Affiliation(s)
- E M Jansen
- Department of Neurosurgery, Graduate Program in Neuroscience, University of Minnesota Medical School, Minneapolis, USA
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Abstract
An extensive literature demonstrates that glucocorticoids (GCs), the adrenal steroids secreted during stress, can have a broad range of deleterious effects in the brain. The actions occur predominately, but not exclusively, in the hippocampus, a structure rich in corticosteroid receptors and particularly sensitive to GCs. The first half of this review considers three types of GC effects: a) GC-induced atrophy, in which a few weeks' exposure to high GC concentrations or to stress causes reversible atrophy of dendritic processes in the hippocampus; b) GC neurotoxicity where, over the course of months, GC exposure kills hippocampal neurons; c) GC neuroendangerment, in which elevated GC concentrations at the time of a neurological insult such as a stroke or seizure impairs the ability of neurons to survive the insult. The second half considers the rather confusing literature as to the possible mechanisms underlying these deleterious GC actions. Five broad themes are discerned: a) that GCs induce a metabolic vulnerability in neurons due to inhibition of glucose uptake; b) that GCs exacerbate various steps in a damaging cascade of glutamate excess, calcium mobilization and oxygen radical generation. In a review a number of years ago, I concluded that these two components accounted for the deleterious GC effects. Specifically, the energetic vulnerability induced by GCs left neurons metabolically compromised, and less able to carry out the costly task of containing glutamate, calcium and oxygen radicals. More recent work has shown this conclusion to be simplistic, and GC actions are shown to probably involve at least three additional components: c) that GCs impair a variety of neuronal defenses against neurologic insults; d) that GCs disrupt the mobilization of neurotrophins; e) that GCs have a variety of electrophysiological effects which can damage neurons. The relevance of each of those mechanisms to GC-induced atrophy, neurotoxicity and neuroendangerment is considered, as are the likely interactions among them.
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Affiliation(s)
- RM Sapolsky
- Department of Biological Sciences, Stanford University, Stanford, CA 94305
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McRae A, Bona E, Hagberg H. Microglia-astrocyte interactions after cortisone treatment in a neonatal hypoxia-ischemia model. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1996; 94:44-51. [PMID: 8816276 DOI: 10.1016/0165-3806(96)00043-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Microglial and astrocyte responses to glucocorticoid pretreatment in the neonate exposed to hypoxia-ischemia (HI) are largely unknown. The expression of microglial antigens and astrocytic proliferation was compared in neonatal rats exposed to HI with and without cortisone. HI was induced in 7 day old rats. One group of rats received cortisone within 24 h of birth. Immunocytochemical and immunoblot investigations were performed. Monoclonal antibodies (OX18 and OX42) were used for the detection of the major histocompatibility complex (MHC) class I antigens and complement receptor 3 (CR3) respectively. Antibodies directed against glial fibrillary acidic protein (GFAP) and microtubule associated protein II (MAP II) were used to evaluate the extent of brain damage. Cortisone treatment provoked a decline in the number of microglial cells but did not modify GFAP levels in control rats which were not exposed to HI. Neuronal damage was similar in control and cortisone treated rats exposed to HI. There were also similarities in the expression of CR3 antigens on microglia. However microglial cells expressing MHC class I antigens were less prevalent in rats exposed to HI only. Cortisone pretreatment enhanced the expression of MHC class I antigens. Astrocytic proliferation was intense in rats exposed to HI; however in rats treated with cortisone and exposed to HI there was a drastic reduction in astrocytic proliferation. In conclusion it is suggested that microglia which survive cortisone pretreatment become over-activated thereby preventing astrocytic proliferation.
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Affiliation(s)
- A McRae
- Institute of Anatomy and Cell Biology, University of Göteborg, Sweden
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Abstract
Hypoxia threatens brain function during the entire life-span starting from early fetal age up to senescence. This review compares the short-term, long-term and life-spanning effects of fetal chronic hypoxia and neonatal anoxia on several behavioural paradigms including novelty-induced spontaneous and learning behaviours. Furthermore, it reveals that perinatal hypoxia is an additional threat to neurodegeneration and decline of cognitive and other behaviours during the aging process. Prenatal hypoxia evokes a temporary delay of ingrowth of cholinergic and serotonergic fibres into the hippocampus and neocortex, and causes an enhanced neurodegeneration of 5-HT-ir axons during aging. Neonatal anoxia suppresses hippocampal ChAT activity and up-regulates muscarinic receptor sites for 3H-QNB and 3H-pirenzepine binding in the hippocampus in the early postnatal age. The altered development of axonal arborization and pre- and postsynaptic cholinergic functions may be an important underlying mechanism to explain the behavioural deficits. As far as the cellular mechanisms of perinatal hypoxia is concerned, our primary aim was to study the putative importance of Ca2+ homeostasis of developing neurons by means of pharmacological interventions and by measuring the development of immunoexpression of Ca(2+)-binding proteins. We assessed that nimodipine, an L-type calcium channel blocker, prevented or attenuated the adverse behavioural and neurochemical effects of perinatal hypoxias, while it enhanced the early postnatal development of ir-Ca(2+)-binding proteins. The results are discussed in the context of different related research areas on brain development and hypoxia and ischaemia.
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Affiliation(s)
- C Nyakas
- Department of Animal Physiology, University of Groningen, Haren, The Netherlands
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Tuor UI. Dexamethasone and the prevention of neonatal hypoxic-ischemic brain damage. Ann N Y Acad Sci 1995; 765:179-95; discussion 196-7. [PMID: 7486605 DOI: 10.1111/j.1749-6632.1995.tb16574.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- U I Tuor
- Institute for Biodiagnostics, National Research Council of Canada (NRC), Winnipeg, Manitoba
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Trembly B. Clinical potential for the use of neuroprotective agents. A brief overview. Ann N Y Acad Sci 1995; 765:1-20; discussion 26-7. [PMID: 7486597 DOI: 10.1111/j.1749-6632.1995.tb16554.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
"Stroke treatment seems to be entering a golden age ...." Fisher's observation not only applies to ischemic stroke, but to all the conditions described above, and in the future, possibly (and quite speculatively), to other neurologic diseases, such as multiple sclerosis, amyotrophic lateral sclerosis, even radiation therapy and Bell's palsy. Physicians must sharpen their criteria for decisions regarding therapy and must" ... be prepared to accept what is actually known from scientific data ... rather than to rely on instinct, clinical impression, or the need to do something rather than nothing."
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Affiliation(s)
- B Trembly
- Section of Neurosurgery, VA Medical Center, Togus, Maine 04330, USA
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Tuor UI, Chumas PD, Del Bigio MR. Prevention of hypoxic-ischemic damage with dexamethasone is dependent on age and not influenced by fasting. Exp Neurol 1995; 132:116-22. [PMID: 7720820 DOI: 10.1016/0014-4886(95)90065-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Pretreatment with the synthetic glucocorticoid dexamethasone prevents hypoxic-ischemic brain damage in 7-day-old neonatal rats. We presently characterize the response further by examining the effect of varying the age, the glucocorticoid, and the time of injection and by examining whether fasting can influence the response. Rats (n = 193) were randomized to one of 16 different treatment groups and subjected to hypoxia-ischemia (right carotid artery occlusion +8% O2 which was 3 h in duration for 7-day, 1 h for 2-week, and 30 min for 1-month-old animals). The brains were subsequently perfusion fixed and the area of infarction was measured from hematoxylin- and eosin-stained sections. Time dependence studies demonstrated that treatment with 0.1 mg/kg intraperitoneal dexamethasone 4 h prior to hypoxia reduced infarct size compared to vehicle-treated animals whereas pretreatment at either 48 h or 4 days was ineffective. Dexamethasone pretreatment (4 h) also provided neuroprotection against 4 h of hypoxia-ischemia. Fasted animals which received dexamethasone had reduced blood glucose levels yet markedly less damage than controls. Another glucocorticoid, methylprednisolone (0.7 mg/kg), also reduced infarction. In 2-week-old animals the area of infarction was reduced by pretreatment with dexamethasone, whereas in 1-month-old animals dexamethasone was ineffective. The results suggest that a glucocorticoid-mediated response intervenes in events leading to neuronal death in young animals but not older animals once myelination and synaptogenesis are complete.
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Affiliation(s)
- U I Tuor
- Biosystems, Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, Manitoba
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Antonini JM, van Dyke K, DiMatteo M, Reasor MJ. Attenuation of acute inflammatory effects of silica in rat lung by 21-aminosteroid, U74389G. Inflammation 1995; 19:9-21. [PMID: 7705890 DOI: 10.1007/bf01534376] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Chemical alteration of the glucocorticoid, methylprednisolone, has led to the introduction of a new class of compounds called the 21-aminosteroids (21-ASs). The purpose of this study was to investigate the effect of the 21-AS, U74389G, on silica-induced acute lung injury. Male Fischer 344 rats were treated intraperitoneally with saline or U74389G in a total dose of 15 mg/kg divided into three injections of 5 mg/kg separated by 4 h. Following the first treatment, animals from the two groups were intratracheally instilled with silica (10 mg/100 g body wt in 0.5 ml of saline) or saline vehicle (0.5 ml). Twenty-four hours after the instillations, bronchoalveolar lavage (BAL) was performed. In the animals not receiving U74389G, marked increases in total protein, beta-glucuronidase, and lactate dehydrogenase (LDH) activities and number of neutrophils (PMNs) were demonstrated in the BAL fluid of the silica-treated animals compared to their controls. Silica also caused dramatic increases in the luminol-dependent chemiluminescence (CL) of lung tissue and BAL cells. The CL reaction was decreased by superoxide dismutase (SOD) and N-nitro-L-arginine methyl ester hydrochloride (L-NAME), a nitric oxide (NO) synthase inhibitor. In animals treated with U74389G, there was attenuation of the silica-induced increases in biochemical, cellular, and chemiluminescent indices of damage. This study demonstrates that U74389G significantly reduces acute lung injury caused by the intratracheal instillation of silica, and this drug may be of potential value for treatment of lung diseases in which damage caused by reactive oxygen species has been implicated.
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Affiliation(s)
- J M Antonini
- Department of Pharmacology and Toxicology, Robert C. Byrd Health Sciences Center of West Virginia University, Morgantown 26506-9223
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Cottrell JE. [Pharmacologic brain protection: specific agents]. ANNALES FRANCAISES D'ANESTHESIE ET DE REANIMATION 1995; 14:134-41. [PMID: 7677279 DOI: 10.1016/s0750-7658(05)80162-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Dysfunctional sodium influx is the first step in the ischaemic cascade. It has been recently demonstrated that reducing ionic flux through voltagegated Na channels shortens the NMDA receptor activity of cultured hippocampal slices in which oxidative phosphorylation and glycolysis have been blocked. The implication of this finding is that blocking initial events in the ischaemic cascade, events which do not directly cause neuronal damage, will reduce the damage done by downstream events. It also seems intuitively reasonable to suppose that truncating initial steps of the ischaemic cascade, as distinct from blocking glutamate receptors and scavening free radicals, will reduce the probability of interfering with endogenous mechanisms of repair. Clinically useful, substantive, prophylactic, pharmacological cerebral protection will come from drugs that work upstream. And for pharmacological protection that can only be initiated subsequent to an ischaemic event, the more we learn about endogenous repair, or genetic pharmacology, the closer we will come to maximizing the benefits and minimizing the costs of downstream intervention.
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Affiliation(s)
- J E Cottrell
- Department of Anesthesiology, SUNY Health Science Center at Brooklyn, USA
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