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

Mutations in X-linked genes are likely to account for the observation that more males than females are affected by mental retardation. Causative mutations have recently been identified in both syndromic X-linked mental retardation (XLMR) and in the genetically heterogeneous 'nonspecific' forms of XLMR, for which cognitive impairment is the only defining clinical feature. Proteins that function in chromatin remodelling are affected in three important syndromic forms of XLMR. In nonspecific forms of the disorder, defects have been found in signal-transduction pathways that are believed to function during neuronal maturation. These findings provide important insights into the molecular and cellular defects that underlie mental retardation.
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PMID:Monogenic causes of X-linked mental retardation. 1153 16

Congenital aniridia is due to deletions and point mutations in the PAX6 gene. We describe here a case of a mother and her two sons with a syndrome comprising congenital aniridia, ptosis, and slight mental retardation. The sons also show behavioral changes. The possibility of deletion around the PAX6 locus was excluded by polymorphism studies and fluorescence in situ hybridization analysis. Mutation screening of the PAX6 gene revealed the presence of a transversion C719A, resulting in the substitution of arginine for serine at residue 119. We suggest that this missense mutation is responsible both for aniridia and ptosis, and possibly also for the observed cognitive dysfunction in this family.
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PMID:PAX6 mutation in a family with aniridia, congenital ptosis, and mental retardation. 1155 50

Prenatal ethanol exposure may cause neurological damage and subsequent mental retardation in humans, with learning deficits similar to those following damage to the prefrontal cortex. This study examined cognitive dysfunction and cortical damage after prenatal exposure to ethanol using a chronic administration model. Pregnant Sprague-Dawley rats received one of three diets during gestation: a liquid diet containing 35% ethanol-derived calories (ETOH), an isocaloric liquid diet (ISO), or standard chow (CHOW). Subjects were obtained from ETOH dams with blood alcohol concentrations (BACs) above 90 mg/dl and corresponding ISO and CHOW controls (one male pup/litter; n=6 pups/group). At approximately 90 days of age, subjects began training on a series of unique auditory discrimination problems using a successive go/no-go procedure. A criterion of 85% accuracy determined when a rat continued to the next problem. Subjects completed a varying number of problems within a 30-session limit, after which all rats were tested on a tone/click discrimination and reversal. Subjects were then sacrificed and neuronal number in the medial prefrontal cortex (mPFC) was estimated by the optical fractionator method. Prenatal ethanol exposure induced significant cell loss in the mPFC, which was associated with significantly impaired reversal learning. Poor performance by ETOH subjects on the tone/click reversal indicates a transfer of training deficit that may reflect failures of inhibitory control.
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PMID:Prenatal ethanol exposure, generalized learning impairment, and medial prefrontal cortical deficits in rats. 1171 Dec 48

The molecular basis of human cognition is still poorly understood, but recent advances in finding genetic mutations that result in cognitive impairment may provide insights into the neurobiology of cognitive function. Here we review the progress that has been made so far and assess what has been learnt from this work on the relation between genes and cognitive processes. We review evidence that the pathway from genetic lesion to cognitive impairment can be dissected, that some genetic effects on cognition are relatively direct and we argue that the study of mental retardation syndromes is giving us new clues about the biological bases of cognition.
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PMID:Genetic effects on human cognition: lessons from the study of mental retardation syndromes. 1186 82

An evidence-based selection process for organ transplantation may be a valuable approach to improve posttransplant outcomes. This paper reviews state-of-the-art psychosocial and behavioral selection criteria and assesses their validity in view of predicting outcomes after transplantation. Psychosocial factors addressed are psychiatric disorders, mental retardation, irreversible cognitive dysfunction, and lack of social support. Behavioral selection criteria discussed are alcoholism, smoking, drug abuse, and obesity. This review reveals that the evidence concerning these selection criteria in scarce. There is a definite need for more longitudinal research to strengthen the scientific basis of the psychosocial and behavioral dimension of transplantation.
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PMID:Psychosocial and behavioral selection criteria for solid organ transplantation. 1187 Oct 47

Klinefelter syndrome (KS) has not typically been associated with mental retardation (MR), however, in recent years a growing body of evidence suggested that KS boys often experience language deficits and academic difficulties. In this study, we screened DNA samples from 1205 patients originally referred for fragile X syndrome (FRAX) testing, because of MR of unknown etiology and detected 8 KS patients. A similar number of males in the same age group were found to have FRAX; 3 of them had a family history of FRAX. Based on these findings, KS might be the most common cause of MR of unknown etiology among prepubertal males. Because of the significant benefits of early recognition and treatment of KS, we emphasize the importance of cytogenetic testing of all prepubertal males with cognitive impairment even without dysmorphic features.
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PMID:Klinefelter syndrome is a common cause for mental retardation of unknown etiology among prepubertal males. 1190 56

Piccolo belongs to a family of presynaptic cytoskeletal proteins likely to be involved in the assembly and function of presynaptic active zones as sites of neurotransmitter release. Given that abnormalities in the formation of synaptic junctions are thought to contribute to cognitive dysfunction during brain development, we have analyzed and compared the gene structure of the Piccolo gene, PCLO, from humans and mice and determined their chromosomal localization. A comparison of the deduced amino acid sequence of cDNA clones encoding Piccolo from human, mouse, rat and chicken reveals the presence of distinct homology domains. Only subsets of these are also present in the structurally related active zone protein Bassoon indicating that Piccolo and Bassoon perform related but distinct functions at active zones. Characterization of the PCLO gene reveals the presence of 25 coding exons spread over 380kb of genomic DNA. The human PCLO gene maps to 7q11.23-q21.3, a region of chromosome 7 implicated as a linkage site for autism and Williams Syndrome suggesting that alterations in the expression of Piccolo or the PCLO gene could contribute to developmental disabilities and mental retardation.
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PMID:Gene structure and genetic localization of the PCLO gene encoding the presynaptic active zone protein Piccolo. 1217 52

X-linked forms of non-specific mental retardation are complex disorders, for which mutations in several genes have recently been identified. These include OPHN1, GDI1, PAK3, IL1RAPL, TM4SF2, FMR2 and RSK2. To investigate the mechanisms through which alterations of these gene products could result in cognitive impairment, we analyzed their expression using quantitative PCR technique in two in vitro models of activity-dependent gene regulation: kainate-induced seizures and long-term synaptic potentiation (LTP). We found that the level of expression of four genes, PAK3, IL1RAPL, RSK2 and TM4SF2, was significantly up-regulated following kainate treatment. Furthermore we observed a significant increase in mRNA levels of PAK3 and IL1RAPL following LTP induction. These results suggest a possible role for these four genes in activity-dependent brain plasticity.
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PMID:Activity-dependent regulation of genes implicated in X-linked non-specific mental retardation. 1220 50

The authors review the literature on pain experience and pain assessment in people with cognitive impairments, focusing on individuals with dementia and mental retardation. The impact of cognitive impairments on pain sensation is not well understood, although some observations have been published. For example, research suggests that pain experience can be influenced by neuropathological processes in the brain and memory impairments. Reporting of pain decreases as cognitive impairment increases. In addition, poor verbal skills lead to difficulties in communicating pain. Pain assessment depends primarily on one's ability to describe the dimensions of pain. Individuals with limited ability to report pain can use pain assessment methods that rely on simple cognitive tasks. For individuals who have no ability to report pain, an outside observer must describe the discomfort experienced by interpreting the patient's body language. The authors conclude that further research is needed to develop valid and reliable assessment methods for people with cognitive impairments.
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PMID:Experience and assessment of pain in individuals with cognitive impairments. 1258 Mar 55

RS, the most common cause of profound cognitive impairment in girls and women, is composed of characteristic clinical features, including communication dysfunction, stereotypic movements, and pervasive growth failure. Neuropathologic findings indicate a failure of neuronal maturation with too small neurons and too few dendritic arbors and no evidence of a progressive neurodegenerative process. The combination of clinical and neuropathologic characteristics presents the profile of a neurodevelopmental disorder. Mutations in the gene MECP2, which encodes MeCP2, have been identified in 80% to 85% of girls and women with RS. Furthermore, the panorama of phenotypes with MECP2 mutations now extends far beyond RS to include normal girls and women, mild learning disability, autistic spectrum disorders, and X-linked mental retardation. These rapid advances in our understanding of RS over the past three decades have opened new avenues of study in developmental neurobiology.
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PMID:Rett syndrome. Current status and new vistas. 1261 84


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