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

Fragile X syndrome is a common cause of mental retardation that results from the absence of the fragile X mental retardation protein (FMRP), an RNA binding protein whose function remains unclear. Recent in vitro work has demonstrated that the protein is translated near the synapse in an activity dependent manner [33]. We therefore asked whether expression of FMRP might be altered by neuronal activity in vivo. Using immunoblots of different sub-cellular fractions of the rat somatosensory cortex, we show that the levels of FMRP increase significantly following unilateral whisker stimulation, a model of experience dependent plasticity. This increase is greatest between 2 and 8 h after the stimulus and is seen in both a synaptosomal fraction as well as a sub-cellular fraction enriched for polyribosomal complexes. In contrast, detectable levels of FMRP within the somatosensory cortex show either a decrease or no change after a kainic acid induced seizure compared to water treated controls. Our findings demonstrate that FMRP expression levels are modulated in vivo in response to neuronal activity and suggest a role for FMRP in activity dependent plasticity.
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PMID:Sensory stimulation increases cortical expression of the fragile X mental retardation protein in vivo. 1103 25

Fmr1 knockout mice are an animal model for fragile X syndrome, the most common form of heritable mental retardation in humans. Fmr1 knockout mice exhibit macro-orchidism and cognitive and behavioural deficits reminiscent of the human phenotype. In the present study additional behavioural and cognitive testing was performed. Knockouts and control littermates were subjected to a spatial learning test using a plus-shaped water maze. Animals had to learn the position of a hidden escape platform during training trials. The position of this platform was changed during subsequent reversal trials. Previously reported deficits in reversal learning were replicated, but we also observed significant differences during the acquisition trials. A plus-shaped water maze experiment with daily changing platform positions failed to provide clear evidence for a working memory impairment, putatively underlying the spatial learning deficits. Two different test settings were used to examine the reported deficit of Fmr1 knockout mice in fear conditioning. Conditioned fear responses were observed in a contextual fear test, and the ability to acquire an emotional response was tested by means of response suppression in a conditioned emotional response procedure. Neither protocol revealed significant differences between controls and knockouts.
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PMID:Spatial learning, contextual fear conditioning and conditioned emotional response in Fmr1 knockout mice. 1109 66

The purpose of this study was to assess the reaching strategies of individuals with mental retardation under different conditions. Much about reaching has been studied from the points of view of the optimization of the reading performance and the adaptation to the object's attributes. Few studies, however, have concerned reaching among individuals with mental retardation. Eight right-handed individuals with mental retardation reached for two types of glasses, one empty and the other filled with water. We translated the position of the index finger into X-Y-Z coordinate values and examined movement time, length of trajectory, and tangential velocity under the empty and filled conditions. There was no difference between conditions on any of the variables thought in many studies for individuals without mental retardation to indicate differences between attributes. This suggests that the present individuals with mental retardation might have difficulty in using information or context for planning movement and in optimizing their reaching movement for different conditions.
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PMID:Strategies for reaching by individuals with mental retardation: empty and filled glasses. 1115 63

Mucopolysaccharidosis type VII (MPS VII) is a lysosomal storage disease caused by the lack of beta-glucuronidase (GUSB) activity. GUSB deficiency leads to the progressive accumulation of undegraded glycosaminoglycans (GAGs) in cells of most tissues, including the brain, and is associated with mental retardation. Reduction of lysosomal storage in the central nervous system and prevention of cognitive dysfunction may require intracranial delivery of a therapeutic agent during the newborn period that provides a continuous source of GUSB. Therefore, we injected recombinant adeno-associated virus encoding human GUSB into both the anterior cortex and the hippocampus of newborn MPS VII mice. Total GUSB activity in the brain approached normal levels by 18 weeks. Although GUSB activity was concentrated near the injection sites, lysosomal distension was reduced in most areas of the brain. In addition to histopathologic evidence of GAG reduction, the previously undescribed accumulation of GM2 and GM3 gangliosides in the brain was also prevented. Furthermore, GUSB expression and reduced lysosomal distension correlated with improvements in cognitive function as measured in the Morris Water Maze test. These findings indicate that localized overexpression of GUSB has positive effects on the pathology and cognitive function and does not have overt toxicity.
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PMID:Intracranial injection of recombinant adeno-associated virus improves cognitive function in a murine model of mucopolysaccharidosis type VII. 1127 77

Down's syndrome (DS) is a major cause of mental retardation, hypotonia and delayed development. Murine models of DS carrying large murine or human genomic fragments show motor alterations and memory deficits. The specific genes responsible for these phenotypic alterations have not yet been defined. DYRK1A, the human homolog of the Drosophila minibrain gene, maps to the DS critical region of human chromosome 21 and is overexpressed in DS fetal brain. DYRK1A encodes a serine-threonine kinase, probably involved in neuroblast proliferation. Mutant Drosophila minibrain flies have a reduction in both optic lobes and central brain, showing learning deficits and hypoactivity. We have generated transgenic mice (TgDyrk1A) overexpressing the full-length cDNA of Dyrk1A. TgDyrk1A mice exhibit delayed cranio-caudal maturation with functional consequences in neuromotor development. TgDyrk1A mice also show altered motor skill acquisition and hyperactivity, which is maintained to adulthood. In the Morris water maze, TgDyrk1A mice show a significant impairment in spatial learning and cognitive flexibility, indicative of hippocampal and prefrontal cortex dysfunction. In the more complex repeated reversal learning paradigm, this defect turned out to be specifically related to reference memory, whereas working memory was almost unimpaired. These alterations are comparable with those found in the partial trisomy chromosome 16 murine models of DS and suggest a causative role of DYRK1A in mental retardation and in motor anomalies of DS.
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PMID:Neurodevelopmental delay, motor abnormalities and cognitive deficits in transgenic mice overexpressing Dyrk1A (minibrain), a murine model of Down's syndrome. 1155 28

Angelman syndrome is characterized by mental retardation, seizures, ataxia, inappropriate laughter, lack of speech, a particular facial appearance, and generally a chromosome 15q11-q13 deletion. Recently, a fascination with water and water-related activities has been reported in individuals with the syndrome. We report on a 9.6-year-old male previously diagnosed with Angelman syndrome who died unexpectedly by drowning in a shallow backyard wading pool. This case further illustrates the fascination with water by individuals with Angelman syndrome and highlights that this fascination may lead to death. We wish to alert careproviders that this fascination with water and water-related activities may contribute to death and that these individuals should be closely supervised when in the presence of water.
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PMID:Drowning as a cause of death in Angelman syndrome. 1068 6

Fragile X syndrome is a common form of mental retardation caused by the absence of the FMR1 protein, FMRP. Fmr1 knockout mice exhibit a phenotype with some similarities to humans, such as macro-orchidism and behavioral abnormalities. Two homologs of FMRP have been identified, FXR1P and FXR2P. These proteins show high sequence similarity, including all functional domains identified in FMRP, such as RNA binding domains. They have an overlap in tissue distribution to that of FMRP. Interactions between the three FXR proteins have also been described. FXR2P shows high expression in brain and testis, like FMRP. To study the function of FXR2P, we generated an Fxr2 knockout mouse model. No pathological differences between knockout and wild-type mice were found in brain or testis. Given the behavioral phenotype in fragile X patients and the phenotype previously reported for the Fmr1 knockout mouse, we performed a thorough evaluation of the Fxr2 knockout phenotype using a behavioral test battery. Fxr2 knockout mice were hyperactive (i.e. traveled a greater distance, spent more time moving and moved faster) in the open-field test, impaired on the rotarod test, had reduced levels of prepulse inhibition, displayed less contextual conditioned fear, impaired at locating the hidden platform in the Morris water task and were less sensitive to a heat stimulus. Interestingly, there are some behavioral phenotypes in Fxr2 knockout mice which are similar to those observed in Fmr1 knockout mice, but there are also some different behavioral abnormalities that are only observed in the Fxr2 mutant mice. The findings implicate a role for Fxr2 in central nervous system function.
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PMID:Knockout mouse model for Fxr2: a model for mental retardation. 1187 43

Two angiotensin II (Ang II)-specific receptors, AGTR1 and AGTR2, are expressed in the mammalian brain. Ang II actions on blood pressure regulation, water electrolyte balance, and hormone secretion are primarily mediated by AGTR1. The function of AGTR2 remains unclear. Here, we show that expression of the AGTR2 gene was absent in a female patient with mental retardation (MR) who had a balanced X;7 chromosomal translocation. Additionally, 8 of 590 unrelated male patients with MR were found to have sequence changes in the AGTR2 gene, including one frameshift and three missense mutations. These findings indicate a role for AGTR2 in brain development and cognitive function.
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PMID:AGTR2 mutations in X-linked mental retardation. 1208 45

Propionic acidemia is an inherited neurometabolic disorder characterized by progressive neurological deterioration with psychomotor delay/mental retardation, convulsions and coma, and whose pathophysiology is poorly unknown. In the present study, we investigated the effect of chronic administration (from the 5th to the 28th days of life) of propionic acid (PA), the major metabolite accumulating in tissues of patients affected by propionic acidemia, on the cognitive performance of adult rats in the Morris water maze task. PA doses ranged from 1.44 to 1.92 micromol/g body weight as a function of animal age. Control rats were treated with saline in the same volumes. Chronic postnatal days (5-28) PA treatment had no effect on body weight. However, it impaired spatial performance in the water maze. We also determined the effect of ascorbic acid (AA) administered, alone or combined with PA, on the same behavioral parameters in order to test whether free radicals could be responsible for the behavioral alterations observed in PA-treated animals. AA was able to prevent the behavioral alterations provoked by PA, implying that oxidative stress may be involved in these effects. Furthermore, we also investigated the total radical-trapping antioxidant potential (TRAP) in the hippocampus of the animals. We observed that TRAP was significantly reduced in the brain of propionic acidemic rats and that co-administration of AA prevented this effect. The results provide evidence that early PA treatment induces long-lasting behavioral deficits, which are possibly caused by oxygen reactive species generation, and suggest that oxidative stress may be involved in the neuropathology of propionic acidemia.
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PMID:Ascorbic acid prevents cognitive deficits caused by chronic administration of propionic acid to rats in the water maze. 1215 Oct 37

This paper focuses on the influence of maternal nutrition on infant survival and growth and on subsequent fertility. During pregnancy, modifications in the maternal hormonal system help maintain availability of nutrients to the fetus relatively independently of maternal nutrition. When maternal dietary deficiencies reach critical levels, the effectiveness of these mechanisms in maintaining fetal nutrition decreases. Studies have confirmed the correlation of severe maternal malnutrition and lowered birth weight, neurological disorders, impaired physical growth, mental retardation, and poor school performance. Marginal nutritional status affects milk production capacity. The basis of most recommendations for lactating mothers is that the average mother produces 850 ml of milk each day. Depending on the anticipatory reserves of fat from pregnancy still available and the level of physical activity of the mother, from 2750 to 3300 Kcal/day may be needed. When the mother's energy intake is good, milk fat resembles that of her dietary fat, but when there is a shortage of food energy, the milk fatty acid pattern resembles the mother's subcutaneous fat stores. The lactose content and overall protein content of milk seem stable despite changes in the maternal diet, but the vitamin content, particularly water soluble vitamins, is very sensitive to dietary intake. Birth weight has consistently been found to be associated with infant mortality through 2 main mechanisms: maternal malnutrition may lead to a smaller placental size and decreased nutrient supply to the fetus, resulting in developmental retardation during intrauterine life, or maternal malnutrition may result in suboptimal lactation performance which will contribute to malnutrition and growth retardation of the child. Maternal nutritional status has an independent effect on the duration of postpartum amenorrhea. Improving maternal diet without concurrently introducing contraception may shorten the birth interval and consequently elevate the birthrate.
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PMID:Maternal nutrition, infant health, and subsequent fertility. 1226 49


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