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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Perinatal brain injury following trauma, hypoxia, and/or ischemia represents a substantial cause of pediatric disabilities including mental retardation. Such injuries lead to neuronal cell death through either necrosis or apoptosis. Numerous in vivo and in vitro studies implicate ionotropic (iGluRs) and metabotropic (mGluRs) glutamate receptors in the modulation of such cell death. Expression of glutamate receptors changes as a function of developmental age, with substantial implications for understanding mechanisms of post-injury cell death and its potential treatment. Recent findings suggest that the developing brain is more susceptible to apoptosis after injury and that such caspase mediated cell death may be exacerbated by treatment with N-methyl-D-aspartate receptor antagonists. Moreover, group I metabotropic glutamate receptors appear to have opposite effects on necrotic and apoptotic cell death. Understanding the relative roles of glutamate receptors in post-traumatic or post-ischemic cell death as a function of developmental age may lead to novel targeted approaches to the treatment of pediatric brain injury.
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PMID:Traumatic brain injury: developmental differences in glutamate receptor response and the impact on treatment. 1175 17

Cyclooxygenase-2 (COX-2) is known to be expressed in rat brain and up-regulated by ischemia. The administration of COX inhibitors before as well as soon after the ischemic insult reduces the extension of cerebral damage in rats. Overexpression of COX-2 has also been shown in the ischemic brain of adult human patients, while no information concerning COX-2 expression in neonatal ischemia is available. Intrapartum asphyxia and perinatal brain injury may result in cerebral palsy, mental retardation or epilepsy. COX-2 expression in the brain of neonates delivered after severe birth asphyxia was investigated using immunohistochemistry. Meningeal vessel walls of term and preterm babies widely expressed COX-2 immunoreactivity, as did periventricular large vessels in preterms. A number of brain cells (mature and immature cortical, periventricular and basal ganglia neurons, and oligodendrocytes of the cerebral white matter in brains from term neonates) also expressed COX-2. The present findings suggest that COX-2 may take part in enhancing neonatal brain damage via different mechanisms, such as those involving excitotoxicity and production of reactive oxygen species.
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PMID:Cyclooxygenase-2 immunoreactivity in the ischemic neonatal human brain. An autopsy study. 1184 93

A case of transverse colon volvulus in a child with mental retardation and epilepsy is described. Previously reported cases in Japanese children are reviewed. A 540 degrees, counterclockwise volvulus of the transverse colon caused ischemia requiring resection. Possible factors related to pathogenesis are discussed, and diagnostic and therapeutic measures are outlined. Volvulus of the transverse colon is extremely rare in children.
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PMID:A case of transverse colon volvulus in a child and a review of the literature in Japan. 1240 53

Cerebral hypoxia/ischemia (H/I) of the premature infant is a major cause of cerebral palsy and mental retardation. An important determinant of the ultimate outcome from this insult is the extent to which the stem cells and progenitors in the brain are affected. Irreversible injury to these cells will impair normal development of the infant's brain and, hence, its function. In the present study, we examine early intervals after H/I to identify which cells in the periventricular region are most vulnerable. At 0 h of recovery from a perinatal H/I insult, the choroid plexus shows extensive necrotic damage. The adjacent ependymal and subependymal cells are also affected. Swelling of the ependymal and medial subependymal cells is observed; however, these cells rarely sustain permanent damage. By contrast, cells in the most lateral aspect of the subventricular zone (SVZ) show more delayed, but extensive apoptotic and hybrid cell deaths. Interestingly, activated macrophages/microglia are observed adjacent to the swollen ependymal cells as well as within the affected subependyma. We conclude that the choroid plexus is an especially vulnerable structure in the immature brain, whereas the ependymal and adjacent subependymal cells are relatively resistant to damage. As the medial aspect of the SVZ contains neural stem cells, we predict that neural stem cells will be especially resistant to perinatal H/I brain damage.
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PMID:Damage to the choroid plexus, ependyma and subependyma as a consequence of perinatal hypoxia/ischemia. 1264 Jan 82

Homocystinuria is an inherited metabolic disease biochemically characterized by tissue accumulation of homocysteine (Hcy). Mental retardation, ischemia and other neurological features, whose mechanisms are still obscure are common symptoms in homocystinuric patients. In this work, we investigated the effect of Hcy administration in Wistar rats on some parameters of energy metabolism in the hippocampus, a cerebral structure directly involved with cognition. The parameters utilized were 14CO2 production, glucose uptake, lactate release and the activities of succinate dehydrogenase and cytochrome c oxidase (COX). Chronic hyperhomocysteinemia was induced by subcutaneous administration of Hcy twice a day from the 6th to the 28th day of life in doses previously determined in our laboratory. Control rats received saline in the same volumes. Rats were killed 12 h after the last injection. Results showed that Hcy administration significantly diminished 14CO2 production and glucose uptake, as well as succinate dehydrogenase and COX activities. It is suggested that impairment of brain energy metabolism may be related to the neurological symptoms present in homocystinuric patients.
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PMID:Impairment of energy metabolism in hippocampus of rats subjected to chemically-induced hyperhomocysteinemia. 1269 99

Sturge-Weber syndrome is a rare disorder that occurs with a frequency of approximately 1 per 50,000. The disease is characterized by an intracranial vascular anomaly, leptomeningeal angiomatosis, most often involving the occipital and posterior parietal lobes. Facial cutaneous vascular malformations, seizures, and glaucoma are among the most common symptoms and signs. Stasis results in ischemia underlying the leptomeningeal angiomatosis, leading to calcification and laminar cortical necrosis. The clinical course is highly variable and some children experience intractable seizures, mental retardation, and recurrent strokelike episodes. In this review, we describe the syndrome's characteristic features, clinical course, and optimal management.
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PMID:Sturge-Weber syndrome: a review. 1516 30

It is well known that neonatal hypoxic-ischemic brain injury leads to mental retardation and deficits in cognitive abilities such as learning and memory in human beings. The ameliorative effect of erythropoietin (Epo) on experimental hypoxic-ischemic brain injury in neonatal rats has been recently reported. However, the effect of Epo on cognitive abilities in the hypoxic-ischemic brain injury model is unknown. The aim of this study is to investigate the effects of Epo on learning-memory, behavior and neurodegeneration induced by hypoxia-ischemia. Seven days old Wistar Albino rat pups have been used in the study (n = 28). Experimental groups in the study were: (1) saline-treated hypoxia-ischemia group, (2) Epo-treated (i.p., 1000 U/kg) hypoxia-ischemia group, (3) sham-operated group, (4) control group. In hypoxia-ischemia groups, left common carotid artery was ligated permanently on the seventh postnatal day. Two hours after the procedure, hypoxia (92% nitrogen and 8% oxygen) was induced for 2.5 h. Epo was administered as a single dose immediately after the hypoxia period. When pups were 22 days old, learning experiments were performed using Morris water maze. On the 20th week, when brain development is accepted to be complete, learning experiments were repeated. Rats were then perfused and brains removed for macroscopic and microscopic evaluation. Epo treatment immediately after hypoxic-ischemic insult significantly improved long-term neurobehavioral achievements when tested during the subsequent phase of brain maturation and even into adulthood. Histopathological evaluation demonstrated that Epo also significantly diminished brain injury and spared hippocampal CA1 neurons. In conclusion, Epo administrated as a single dose immediately after neonatal hypoxic-ischemic insult provides benefit over a prolonged period in the still developing rat brain. Since the wide use of Epo in premature newborns, this agent may be potentially beneficial in treating asphyxial brain damage in the perinatal period.
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PMID:Erythropoietin improves long-term spatial memory deficits and brain injury following neonatal hypoxia-ischemia in rats. 1521 9

Approximately 10% of newborns are born prematurely. Of these children, more than 10% will sustain neurological injuries leading to significant learning disabilities, cerebral palsy, or mental retardation, with very low birth weight infants having an even higher incidence of brain injury. Whereas intraventricular hemorrhage was the most common form of serious neurological injury a decade ago, periventricular white matter injury (PWMI) is now the most common cause of brain injury in preterm infants. The spectrum of chronic PWMI includes focal cystic necrotic lesions (periventricular leukomalacia; PVL) and diffuse myelination disturbances. Recent neuroimaging studies support that the incidence of PVL is declining, whereas diffuse cerebral white matter injury is emerging as the predominant lesion. Factors that predispose to PVL include prematurity, hypoxia, ischemia, and inflammation. It is believed that injury to oligodendrocyte (OL) progenitors contributes to the pathogenesis of myelination disturbances in PWMI by disrupting the maturation of myelin-myelin-forming oligodendrocytes. Other potential mechanisms of injury include activation of microglia and axonal damage. Chemical mediators that may contribute to white matter injury include reactive oxygen (ROS) and nitrogen species (RNS), glutamate, cytokines, and adenosine. As our understanding of the pathogenesis of PWMI improves, it is anticipated that new strategies for directly preventing brain injury in premature infants will evolve.
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PMID:Emerging concepts in periventricular white matter injury. 1569 97

Nitric oxide (NO) and carbon monoxide (CO) synthesized from L-arginine by NO synthase and from heme by heme oxygenase, respectively, are the well-known neurotransmitters and are also involved in the regulation of vascular tone. Recent studies suggest that hydrogen sulfide (H(2)S) is the third gaseous mediator in mammals. H(2)S is synthesized from L-cysteine by either cystathionine beta-synthase (CBS) or cystathionine gamma-lyase (CSE), both using pyridoxal 5'-phosphate (vitamin B(6)) as a cofactor. H(2)S stimulates ATP-sensitive potassium channels (K(ATP)) in the vascular smooth muscle cells, neurons, cardiomyocytes and pancreatic beta-cells. In addition, H(2)S may react with reactive oxygen and/or nitrogen species limiting their toxic effects but also, attenuating their physiological functions, like nitric oxide does. In contrast to NO and CO, H(2)S does not stimulate soluble guanylate cyclase. H(2)S is involved in the regulation of vascular tone, myocardial contractility, neurotransmission, and insulin secretion. H(2)S deficiency was observed in various animal models of arterial and pulmonary hypertension, Alzheimer's disease, gastric mucosal injury and liver cirrhosis. Exogenous H(2)S ameliorates myocardial dysfunction associated with the ischemia/reperfusion injury and reduces the damage of gastric mucosa induced by anti-inflammatory drugs. On the other hand, excessive production of H(2)S may contribute to the pathogenesis of inflammatory diseases, septic shock, cerebral stroke and mental retardation in patients with Down syndrome, and reduction of its production may be of potential therapeutic value in these states.
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PMID:Hydrogen sulfide (H2S) - the third gas of interest for pharmacologists. 1737 2

Hypoxia/ischemia (H/I) brain injury at birth is an important cause of cerebral palsy, mental retardation, and epilepsy. The H/I insult also causes energy failure, oxidative stress, and unbalanced ion fluxes, leading to high induction of autopahgy in brain neurons. Since the mice unable to execute autophagy (due to brain-specific deletion of Atg7 or Atg5) die by massive loss of cerebral and cerebellar neurons with accumulation of ubiquitin aggregates, induction of neuronal autophagy after H/I injury is generally considered neuroprotective by maintaining cellular homeostasis. However, our recent results show that hippocampal pyramidal neurons undergoing caspase-dependent or -independent death following neonatal H/I injury possess abundant LC3-positive granules, and such H/I neuronal death is largely prevented by Atg7 deficiency. In the present review we discuss the roles of autophagy and other forms of programmed cell death in the neonatal H/I brain insult.
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PMID:Autophagic neuron death in neonatal brain ischemia/hypoxia. 1821 31


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