Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0917816 (mental retardation)
 15,867 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We reported two patients with severe motor and intellectual disabilities syndrome, who were born to mothers having inhaled organic solvents during pregnancy. They had microcephaly, cerebral palsy, mental retardation, seizures, growth failure and minor craniofacial anomalies, variable growth deficiency including a small midface, narrow bifrontal diameter, low-set ears, thin upper lips and micrognathia. Patient 1, a male, died at 8 years and 8 months. The autopsy of his brain revealed marked cerebral atrophy and destruction of bilateral temporal lobes with ventricular enlargements. Microscopic examination revealed migration disorders with polymicrogria at the remaining cerebrum and the cerebellum as well as very thin white matter. Much hemosiderin was found around ventricles, suggesting recurrent minimal bleedings which led to more brain atrophy. Patient 2, a 5 months old male infant, had infantile spasms. On CT and MRI, he had bilateral temporal lobe defect, which might be due to the infarction of bilateral middle cerebral arteries at the prenatal period. These clinical findings are similar to those of other embryopathies, caused by alcohol, phenytoin and other agents. Hersh et al. reported five cases of toluene embryopathy in 1985 and 1988, but they did not report such central nervous system abnormalities. The pathogenesis of toluene embryopathy remains to be solved, but our cases suggested the possible teratogenesis of toluene.
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PMID:[Two cases of toluene embryopathy with severe motor and intellectual disabilities syndrome]. 929 10

Developmental neurotoxicity can be ascribed to in utero exposure to exogenous substances or to exposure of the fetus to endogenous compounds that accumulate because of genetic mutations. One of the best recognized human neuroteratogens is ethanol. The Fetal Alcohol Syndrome (FAS) is characterized by growth deficiency, particular facial features, and central nervous system (CNS) dysfunctions (mental retardation, microencephaly and brain malformations). Abuse of toluene by pregnant women can lead to an embryopathy (fetal solvent syndrome, (FSS)) whose characteristics are similar to FAS. Phenylketonuria (PKU) is a genetic defect in phenylalanine (Phe) metabolism. Offspring of phenylketonuric mothers not under strict dietary control are born with maternal PKU (mPKU), a syndrome with similar characteristics as FAS and FSS. While ethanol has been shown to cause neuronal death, no such evidence is available for toluene or Phe and/or its metabolites. On the other hand, alterations in astrocyte proliferation and maturation have been found, mostly in in vitro studies, which may represent a potential common mode of action for at least some of the CNS effects found in FAS, mPKU, and FSS. Further in vivo and in vitro studies should validate this hypothesis and elucidate possible molecular targets.
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PMID:Developmental neurotoxicity: do similar phenotypes indicate a common mode of action? A comparison of fetal alcohol syndrome, toluene embryopathy and maternal phenylketonuria. 1205 59

Neurodevelopmental disorders such as autism, attention deficit disorder, mental retardation, and cerebral palsy are common, costly, and can cause lifelong disability. Their causes are mostly unknown. A few industrial chemicals (eg, lead, methylmercury, polychlorinated biphenyls [PCBs], arsenic, and toluene) are recognised causes of neurodevelopmental disorders and subclinical brain dysfunction. Exposure to these chemicals during early fetal development can cause brain injury at doses much lower than those affecting adult brain function. Recognition of these risks has led to evidence-based programmes of prevention, such as elimination of lead additives in petrol. Although these prevention campaigns are highly successful, most were initiated only after substantial delays. Another 200 chemicals are known to cause clinical neurotoxic effects in adults. Despite an absence of systematic testing, many additional chemicals have been shown to be neurotoxic in laboratory models. The toxic effects of such chemicals in the developing human brain are not known and they are not regulated to protect children. The two main impediments to prevention of neurodevelopmental deficits of chemical origin are the great gaps in testing chemicals for developmental neurotoxicity and the high level of proof required for regulation. New, precautionary approaches that recognise the unique vulnerability of the developing brain are needed for testing and control of chemicals.
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PMID:Developmental neurotoxicity of industrial chemicals. 1787 17

The developing brain is inherently more vulnerable to injury than the adult brain because brain development is extraordinarily complex, with periods of unique susceptibility. When brain developmental processes are suspended or delayed by any external influence, virtually no potential exists for subsequent regeneration and repair. This inevitably leads to long-lasting or permanent consequences. Recent genetic studies have contributed to a better understanding of the dynamic adaptive changes that occur in the developing brain as a consequence of genetic and environmental processes. Many industrial and environmental chemicals such as lead, methyl-mercury, polychlorinated biphenyls, arsenic, and toluene are recognized causes of neurodevelopmental disorders that lead to clinical or subclinical brain dysfunction. A number of these developmental disabilities arise from interactions between environmental factors and individual gene susceptibility. In addition, neurodevelopmental disorders of unknown origin, such as mental retardation, attention deficit disorder, cerebral palsy, and autism are becoming increasingly prevalent, with costly consequences for the family and society. The aim of this review is examine brain developmental anatomy, connectivity, adaptive plasticity, and toxicity in the context of current knowledge and future trends.
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PMID:Brain development: anatomy, connectivity, adaptive plasticity, and toxicity. 1880 60