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

Synapse formation is a complex, incompletely understood process that has received only limited investigation in man despite the importance of synaptic dysfunction in common disorders such as epilepsy and mental retardation. This review explores synaptic differentiation, focussing on the morphologic maturation of synapses. Since differentiation depends on many antecedent developmental events, synaptogenesis can be affected by several factors: errors in neuronal proliferation, migration, and differentiation. The challenge to the neurobiologist is to detect and evaluate the minor alterations in neuronal differentiation that could account for the structural basis of the clinical manifestations. Trisomy 21 is an example of a condition in which the cytoarchitecture of the cerebral cortex is not obviously altered, yet mental retardation is consistently present; research neurobiologic techniques are making possible documentation of its structural basis. Epilepsy is another example in which examination of surgically removed cerebral cortex reveals subtle cortical dysplasias helpful in understanding the basis for the abnormal electrical discharge. Further exploration of synaptogenesis, particularly the influence of gene products and epigenetic factors on synapse maturation, will increase our understanding of the pathogenesis of conditions in which "morphology" seems normal but function is abnormal.
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PMID:Synaptic dysgenesis. 182 78

In a central institution for persons with mental retardation, the dental status in 30 adult patients with Down syndrome was compared with that in a carefully selected group of gender- and age-matched mentally retarded patients. This investigation showed an increased frequency of periodontitis in the population with Down syndrome. The caries rate, however, did not differ demonstrably between the groups. Edentulism was more frequent in patients with Down syndrome than in controls, and this fact may substantiate the observation of increased frequency of periodontitis. Caries seems to be less prevalent in institutionalized patients with mental retardation than in the population at large.
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PMID:Dental caries and periodontitis in persons with Down syndrome. 183 Dec 97

We investigated the incidence rates of several neurological diseases in childhood in a suburban Tokyo area with a total population of about 130,000. The number of liveborn babies during 1985-1989 was 6,772. The number of patients with cerebral palsy (CP) was 13 and the incidence rate was 1.9/1,000, which is equal to the results of reports from several countries. Patients with severe mental and motor retardation (SMMR) was 7 and the incidence rate was 1.0/1,000. Five out of the 7 children with SMMR always needed medical care and were always or very frequently hospitalized. Prenatal brain damage played a major role in the pathogenesis of CP and SMMR. The number of patients with Down syndrome (DS) was 9 and the incidence rate was 1.3/1,000. The number of patients with mental retardation (MR) except DS was 64 and the incidence rate was 11.6/1,000. We conclude that the incidence rates of CP, DS, SMMR, and MR still remain high and that we need further strategy to prevent pediatric neurological diseases.
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PMID:[Incidence rate of cerebral palsy, severe mental and motor retardation, and mental retardation in a suburban Tokyo area]. 183 6

The brain of a child with Down syndrome develops differently from a normal one, attaining a form reduced in size and altered in configuration. Directly related to the mental retardation are neuronal modifications manifest as alterations of cortical lamination, reduced dendritic ramifications, and diminished synaptic formation. However, selected cholinergic marker enzymes such as choline acetyl transferase and acetyl cholinesterase have shown no alterations in young children with Down syndrome. The pace of the neuronal transformations is related to stage of maturation. With early growth and development, the normal dendritic tree continuously expands. In Down syndrome, at 4 months of age, the neurons show a relatively expanded dendritic tree, but during the first year the dendrites stop growing and become atrophic relative to control neurons. Accompanying these neuronal irregularities are subtle alterations of other cell types: astrocyte, oligodendrogliocyte, microglia, and endothelial cell. In early infancy, one of the astrocytic markers, GFAP, is not altered, but there is greater expression of S-100 protein in the temporal lobe in Down syndrome. Oligodendrogliocyte dysfunction is reflected in delayed myelination in pathways of frontal and temporal lobes. Microglia appear more prominent in Down syndrome. A minority of children with Down syndrome have vascular dysplasias and focal calcification of basal ganglia. In young children, expression of beta-amyloid in Down syndrome is no different than in normal children but disappears after age two, only to reappear in adults. As some of these studies suggest, the identification of genes on chromosome 21 and the determination of the gene product allow the production of specific antibodies and, through immunohistochemical techniques, the identification of the expression of these proteins in both normal development and Down syndrome. Specifically, the localization and appearance in development of proteins such as the beta-subunit of S-100, beta-amyloid (A4 protein), superoxide dismutase, and OK-2 are providing the means for better understanding the morphogenesis of the cellular and eventually molecular basis for the mental retardation in Down syndrome.
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PMID:Growth and development of the brain in Down syndrome. 183 82

Sixty-two patients of two institutions for mentally retarded patients were immunized intradermally with 4 micrograms doses of plasma-derived hepatitis B vaccine made in Japan, initially at month 0.1 and 6. The three vaccinations induced antibodies in 93.5% (90.9% in those with Down's syndrome (DS), 94.1% in other forms of mental retardation (OMR) of the vaccinees within 9 months after the first injection, and the percentage of geometric mean titers of antibody above 10 mIU/ml was 89.3% (81.8% DS, 84.3% OMR) within 9 months. Within 2 years, the seroconversion rate showed a significantly higher decrease in subjects with DS (54.5%) than in OMR (86.3%), and the percentage of vaccines with above 10 mIU/ml also showed a significantly higher decrease in subjects with DS (36.4%) than in those with OMR (74.5%) (p less than 0.05). In the OMR patients, the antibody response persisted for 2 years, decreased remarkably in the DS patients.
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PMID:Long term observation of the effect of intradermal hepatitis B vaccination on mentally retarded patients. 183 38

The purpose of this study was to compare the periodontal condition of children with Down's syndrome and other types of mental retardation with normal children. We used two indexes: a plaque index and a gingival index. By means of the student t-test and ANOVA statistical procedure, we found the following. Mentally retarded children had a higher average intelligence than children with Down's syndrome, and significant differences existed among the three groups on both the plaque index and the gingival index, while sex had no influence on these results.
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PMID:[Survey on oral hygiene status in children with Down's syndrome and mental retardation]. 184 Mar 20

A high prevalence of the lysosomal storage disease aspartylglycosaminuria was found in a study of four birth cohorts of 12882 children in eastern Finland. Using school achievement tests and registers of mentally retarded individuals, 178 mentally retarded children were identified. Randomized urine samples from 151 of the 178 retarded children and from 101 healthy children were analyzed quantitatively for aspartylglucosamine by high-performance liquid chromatography. The results identified three affected individuals in the retarded group indicating an exceptionally high prevalence of aspartylglycosaminuria (1:3643) in the study population, consistent with a carrier frequency of 1:30. The 95% confidence limits for the prevalence are 1:4 352-1:16389. This is the highest prevalence described for any glycoproteinosis in any population and comparable to the incidence figures of the most common lysosomal storage diseases, Gaucher disease type I and Tay-Sachs disease among Ashkenazi Jews. In the study group, aspartylglycosaminuria was, after trisomy 21 (n = 19) and the fragile X syndrome (n = 6), the most common genetic cause for mental retardation.
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PMID:High prevalence of aspartylglycosaminuria among school-age children in eastern Finland. 186

We report cystinuria and symptoms of cerebellar atrophy in a 45-year-old man. His parents were first cousins, and many members of his family had stones of urinary tract or gait impairment. Neurological examination disclosed cerebellar signs resembling those of spinocerebellar degeneration. Urinalysis disclosed high cystine, lysine, ornitine and arginine output. Cystine was 1153.8 micro mol/day (normal range, 22-170); lysine, 3443.9 (normal range, 44-1000); ornitine, 283.8 (normal range, 7-40); and arginine, 154.0 (normal range, 9-50). Neurological complications reported to be associated with cystinuria include mental retardation, muscular dystrophy, hypotonia and dwarfism, mongolism, paroxysmal dyskinesia, myopathy, migraine, spastic paraplegia, multiple sclerosis, subacute combined degeneration and cranial polyneuropathy. Cerebellar signs have been reported in only two cases, and to our knowledge, this is the first case of cystinuria with cerebellar atrophy ever reported. Some common metabolic errors may have caused both disorders, although they also may have developed independently.
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PMID:[Cystinuria with symptoms of cerebellar atrophy--a case report]. 189 74

Immune abnormalities in autistic children led us to study for indirect evidence of immune activation as measured by the serum analysis of soluble interleukin-2 (sIL-2), interleukin-2 receptor (sIL-2R), T8 antigen (sT8), and interleukin-1 (sIL-1). The serum concentration of these soluble antigens was quantitated by enzyme-linked immunosorbent assays. The concentration of sIL-2 and sT8, but not of sIL-2R and sIL-1, antigens was significantly (P less than 0.05) increased in the sera of autistic children over that in the control healthy children or children with mental retardation (non-Down's syndrome). This finding indirectly indicates that the activation of a subpopulation of T cells occurs in some children with autism.
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PMID:Changes of soluble interleukin-2, interleukin-2 receptor, T8 antigen, and interleukin-1 in the serum of autistic children. 193 32

The most common genetic cause of mental retardation after Down's syndrome, the fragile X syndrome, is associated with the occurrence of a fragile site at Xq27.3. This X-linked disease is intriguing because transmission can occur through phenotypically normal males. Theories to explain this unusual phenomenon include genomic rearrangements and methylation changes associated with a local block of reactivation of the X chromosome. Using microdissected markers close to the fragile site, we have been able to test these hypotheses. We present evidence for the association of methylation with the expression of the disease. However, there is no simple relationship between the degree of methylation and either the level of expression of the fragile site or the severity of the clinical phenotype.
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PMID:Physical mapping across the fragile X: hypermethylation and clinical expression of the fragile X syndrome. 199 11


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