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

The prevalence of mental retardation defined as IQ less than 70 has been estimated as ranging between 6.7-11.9 per thousand children in the Nordic countries. Etiological factors can be found in 80% of patients with severe mental retardation (IQ less than 50) and in 50% with mild mental retardation (IQ 50-70). Down's syndrome is the most common specific cause of mental retardation, followed by the Fragile X syndrome, which mainly affects boys. Since the middle of the 1980s Rett's syndrome has been recognized as the most frequent cause of progressive mental retardation in girls. Recent advances in the field of chromosomal disorders, metabolic diseases and clinical syndromes imply a need for new epidemiological research aimed at obtaining an updated picture of the heterogenous causes of mental retardation.
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PMID:[Mental retardation in children. Prevalence and etiology]. 156 94

To protect against reactive oxygen species, prokaryotic and eukaryotic cells have developed an antioxidant defence mechanism where O2- is converted to H2O2 by superoxide dismutase (Sod), and in a second step, H2O2 is converted to H2O by catalase (Cat) and/or glutathione peroxidase (Gpx). If Sod levels are increased without a concomitant Gpx increase, then the intermediate H2O2 accumulates. This intermediate could undergo the Fenton's reaction, generating hydroxyl radicals which may lead to lipid peroxidation in cells. In this study, we investigate the expression of Sod1, Gpx1 and susceptibility to lipid peroxidation during the aging process in mouse brains. We demonstrate that the mRNA levels and enzyme activity of Sod1 are higher in brains from adult mice compared to neonatal mice. Furthermore, we show that a linear increase in Sod1 mRNA and enzyme activity occurs with aging (1-100 weeks). On the contrary, we find that the mRNA and enzyme activity for Gpx1 does not increase with aging in mouse brains. In addition, our results demonstrate that the susceptibility of murine brains to lipid peroxidation increases with aging. The data in this study are consistent with the notion that reactive oxygen species may contribute to the aging process in mammalian brains. These results are discussed in relation to the normal aging process in mammals, and to the premature aging and mental retardation in Down syndrome.
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PMID:Cu/Zn superoxide dismutase mRNA and enzyme activity, and susceptibility to lipid peroxidation, increases with aging in murine brains. 159 44

The fragile X syndrome is attracting much interest because it is now recognized as the most common genetic cause of mental retardation after Down's syndrome. No effective treatment is yet available and the underlying biochemical defect is not understood. Genetic counselling is often difficult because, although it primarily affects males, one third of carrier females are also retarded. In addition, there is an important percentage of males that inherited the mutation and appear phenotypically normal. These observations have prompted extensive clinical, epidemiological and genetic studies. The more relevant points are reviewed in light of our results.
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PMID:[Importance of molecular diagnosis in the detection of healthy male transmitters of the fragile X syndrome]. 160 9

The prevalence of antibodies to hepatitis C virus (anti-HCV) was measured in a number of groups known to be at increased risk of blood-borne viral infections, using an enzyme-linked immunosorbent assay (EIA) based on a nonstructural peptide generated by recombinant DNA technology. The assay was repeatably reactive in 75.6% of men with haemophilia, 61.9% of intravenous drug users, 34.1% of homosexual men who were regular attenders at a gay sauna and 30.8% of prisoners. A lower reactivity was detected in sera collected from female prostitutes (10.4%), patients undergoing maintenance haemodialysis (5.9%), or renal transplantation (6.9%) and patients attending a sexually transmitted diseases clinic (6.2%). We also measured reactivity among inmates of a large institution for the mentally handicapped in which hepatitis B is known to be endemic, and in panels of sera which had been stored for 25-35 years. The test was positive in 41.1% of mentally handicapped patients with Down's syndrome and 7% of subjects with other forms of mental retardation. Similarly some 23% and 20% of sera collected in 1954 and 1964 from patients with a variety of illnesses were found to be reactive. As most diagnostic assays suffer from some degree of non-specificity and confirmatory tests for the anti-HCV assay were not initially available in Australia, we analysed the distribution of optical density (OD) values in the different groups, in an attempt to obtain an insight into the specificity of the results being obtained. Whereas the ODs of sera collected from patients with haemophilia and IVDU had a bimodal pattern, with two well separated sets of results on either side of the cut-off.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hepatitis C antibody testing: problems associated with non-specific binding. 172 34

Governmental officials as well as medical scientists in Taiwan have worked hard in recent years to develop and to implement various measures, such as prenatal diagnosis and neonatal screening, to lower the incidence of hereditary diseases and mental retardation in the population. An inquiry into the possibility of devising a chromosomal and biochemical screening program and to apply it routinely to all the mentally retarded school children island-wide was the major aim of the present study. A collection of 1,614 blood samples was screened for phenylketonuria (PKU), galactosemia, homocystinuria, biotinidase deficiency, and congenital hypothyroidism. The IQ of these children ranged from 50-75 (1,397 children, moderate group) to less than 50 (217 children, severe group). Six cases of PKU (one tetrahydrobiopterin deficient and five classical) and three cases of thyroid dysfunction were found. The overall incidence of these two diseases was 0.56%. Of the 1,614 blood samples, 1,323 were cultured and karyotyped successfully. One hundred and twenty-five of them had chromosome abnormalities. The majority (64 out of 125) were trisomy 21. A remarkable difference in the percentage of mentally retarded children with chromosome abnormalities was observed between the moderate (7.87%) and severe (17.51%) retarded.
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PMID:Chromosomal and biochemical screening on mentally retarded school children in Taiwan. 175 40

Significant effects on the developing brain of exposure to ionizing radiation are seen among those individuals exposed in the 8th through the 25th week after fertilization. These effects, particularly in the most sensitive period, 8-15 weeks after fertilization, manifest themselves as an increased frequency of severe mental retardation (SMR), a diminution in IQ score and in school performance, and an increase in the occurrence of seizures. Of 30 SMR cases, 18 (60%) had small heads. About 10% of the individuals with small head sizes observed among the in utero clinical sample were mentally retarded. When all of the cases of mental retardation are included in the analysis, a linear dose-response model fits the data adequately and no evidence of a threshold emerges; however, if the two probable nonradiation-related cases of Down's syndrome are excluded from the 19 SMR cases exposed 8-15 weeks after fertilization, the evidence of a threshold is stronger. The 95% lower bound of the threshold based on the new dosimetry system appears to be in the range of 0.12-0.23 Gy. In the 16-25 week period, the 95% lower bound of the threshold is 0.21 Gy both with and without inclusion of two probable nonradiation-related retarded cases. In a regression analysis of IQ scores and school performance data, a greater linearity is suggested with the new dosimetry (DS86) than with the old (T65DR), but the mean IQ score and the mean school performance of those exposed in utero to doses under 0.10 Gy are similar, and not statistically different from the means in the control group. The risk ratios for unprovoked seizures, following exposure during the 8th through the 15th week after fertilization, are 4.4 (90% confidence interval: 0.5-40.9) after 0.10-0.49 Gy and 24.9 (4.1-191.6) after 0.50 Gy or more when the mentally retarded are included and 4.4 (0.5-40.9) and 14.5 (0.4-199.6), respectively, when they are excluded.
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PMID:A review of forty-five years study of Hiroshima and Nagasaki atomic bomb survivors. Brain damage among the prenatally exposed. 176 13

The behaviour profiles of 176 mentally retarded individuals from two reception centres and nine group homes were assessed. The correlations between behaviour and age, sex, degree of mental retardation, etiology of mental retardation and medical diagnosis were assessed using the Revised Child Behaviour Profile. The severity of behaviour disturbance did not vary with age or medical diagnosis. The moderately retarded subjects presented with more severe behaviour problems, such as aggression, than the severely mentally retarded subjects. The variable most predictive of behavioural problems was etiology of the disorder. Individuals with Down's syndrome had significantly fewer behaviour disturbances and those with autism and pervasive developmental disorder had significantly more behaviour disturbances than other subjects. A psychiatric disorder was found in 10.2% of the sample. The implications of these findings are discussed with respect to public policy.
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PMID:Behaviour problems of the mentally retarded. 179 May 15

Having previously demonstrated that patients with cri du chat, 5p- syndrome, have a highly significant excess of the plasmatic and urinary relative amount of asparagine and aspartate, the authors tested the hypothesis according to which this excess could be in relation with a defect of purine metabolism. Using a previously reported in vitro assay, they found a paradoxal increase in the mitotic index in the presence of L-alanosine in lymphocyte cultures of patients with 5p- who were on no medication. They also observed particularly severe toxicity to HAT medium. This response, apparently characteristic for 5p- syndrome, was highly significant when compared to the one observed in samples of normal controls, of patients with mental retardation of various etiologies, patients with Down syndrome or with Xqfra syndrome. When patients with cri du chat syndrome received inosine with folinic acid, an inversion of their response to alanosine was observed as well as the normalization of their response to HAT medium. These findings suggest that deletion of 5p14-5p15 leads to some impairment of de novo purine synthesis, the implications of these findings are discussed.
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PMID:Metabolic anomalies in cri du chat syndrome (5p-) lymphocytes and de novo purine synthesis. 180 30

Language lateralization was assessed with a dual task procedure in 10 male right-handed patients with Down's Syndrome and relatively preserved linguistic skills. Their performance was compared with that of two control groups, with and without mental retardation, matched with Down's Syndrome individuals for sex, handedness and I.Q. Results did not support the hypothesis that mental retardation is related to specific pattern of cerebral lateralization.
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PMID:Cerebral organization for language in Down's syndrome patients. 182 31

The longevity of people with Down syndrome being served by the California Department of Developmental Services was examined in terms of a number of variables known to be related to early mortality. The findings indicated that the predictors of survival for people with Down syndrome were not different from the variables related to mortality among people with mental retardation in general. A lack of mobility or feeding skills were better predictors of an early death than were medical problems associated with congenital heart disease. Life expectancy estimates of clients with Down syndrome who lacked mobility or eating skills were found to be poor as compared to individuals who had Down syndrome but did not have these problems regardless of the presence of heart disease.
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PMID:Life expectancy of persons with Down syndrome. 182 73


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