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

Down syndrome, trisomy of chromosome 21, is well investigated because it is a genetic disease with characteristic mental retardation and precocious dementia of Alzheimer type. Maternal serum markers of human chorionic gonadotrophin unconjugated estriol and amyloid precursor protein, nuchal skinfold on ultrasound and new genetic probes are developed to allow better detection of Down syndrome. The overproduction of A beta 42 because of excessive genes is thought to be a leading factor for early onset of dementia in Down syndrome adults. Animal models and transgenic mice may be helpful in determining the specific gene and pathogenesis for mental retardation and precocious dementia.
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PMID:Down syndrome. 914 96

We present a 34-year-old man with an unbalanced translocation between the long arms of chromosome 4 and chromosome 11. He had manifestations of monosomy 11(q23)--minor facial anomalies, abnormal head shape, cryptorchidism; trisomy 4(q32)--hirsutism, renal disease; and manifestations attributable to both imbalances--heart disease, musculoskeletal anomalies, and mental retardation. FISH studies showed that the chromosome 11q23.3 translocation breakpoint was distal to the rare folate sensitive fragile site (FRA11B). The patient is the oldest reported with both imbalance of 4q+ and 11q-.
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PMID:Unbalanced t(4;11)(q32;q23) in a 34-year-old man with manifestations of distal monosomy 11q and trisomy 4q syndromes. 918 74

Down syndrome, caused by trisomy of human chromosome 21 (HSA21), is the most common autosomal form of mental retardation. To understand the aetiology of the syndrome we need to identify the genes involved. We have utilised the information generated by the various EST sequencing projects to enrich the transcription map of chromosome 21. Here we report the mapping of SH3P17 to 21q22.1 and the localisation of two genes previously mapped to HSA21 by Nagase and colleagues, KIAA0136 and KIAA0179 to 21q22.2 and 21q22.3, respectively. SH3P17 has unknown function but contains four SH3 domains. KIAA0136 shows no homology to a yeast open reading frame. Further investigation of these three genes will add to our functional understanding of HSA21.
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PMID:Mapping of a novel SH3 domain protein and two proteins of unknown function to human chromosome 21. 927 76

Partial trisomy 6p is regarded as a distinct phenotype with short stature, failure to thrive, facial dysmorphisms with blepharophimosis, mental retardation and other malformations. An 18-month-old girl with typical features of partial trisomy 6p showed a de novo unbalanced translocation resulting in partial trisomy 6p21 to pter and partial monosomy 18p11 to pter. The translocation was observed in all fibroblasts analyzed, but only in 6% of the peripheral lymphocytes.
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PMID:Partial trisomy 6p from a de novo translocation (6;18) with variable mosaicism in different tissues. 929 49

We have evaluated a 3 2/12 year old girl who presented with unilateral blepharophimosis, ptosis of the eyelid, and mental retardation. Additional dysmorphic features include microcephaly, high, narrow forehead, short stubby fingers, and adduction of the right first toe. Cytogenetic analysis showed an unbalanced karyotype consisting of 46,XX,add(7)(q+) that was de novo in origin. Fluorescence in situ hybridisation (FISH) using microdissected library probe pools from chromosomes 1,2,3,7, and 3q26-qter showed that the additional material on 7q was derived from the distal end of the long arm of chromosome 3. Our results indicate that the patient had an unbalanced translocation, 46,XX,der(7)t(3;7)(q26-qter;q+) which resulted in trisomy for distal 3q. All currently reported cases of BPES (blepharophimosis-ptosis-epicanthus inversus syndrome) with associated cytogenetic abnormalities show interstitial deletions or balanced translocations involving 3q22-q23 or 3p25.3. Our patient shares similar features to BPES, except for the unilateral ptosis and absence of epicanthus inversus. It is possible that our patient has a contiguous gene defect including at least one locus for a type of blepharophimosis, further suggesting that multiple loci exist for eyelid development.
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PMID:A novel case of unilateral blepharophimosis syndrome and mental retardation associated with de novo trisomy for chromosome 3q. 932 68

In 1990, Lambotte syndrome was reported as an apparently autosomal recessive multiple congenital anomaly/mental retardation (MCA/MR) syndrome observed in 4 of 12 sibs from a probably consanguineous mating [Verloes et al., Am J Med Genet 1990; 37:119-123]. Major manifestations included intrauterine growth retardation (IUGR), microcephaly, large soft pinnae, hypertelorism, beaked nose, and extremely severe neurologic impairment, with holoprosencephaly in one instance. After the observation of a further affected child born of one unaffected sister, in situ hybridization analysis and chromosome painting techniques demonstrated a subtle t(2;4)(q37.1; p16.2) translocation in the mother, suggesting a combination of 2q/4p trisomy/monosomy in all of the affected children of the family. Many private sporadic or recurrent MCA/MR syndromes maybe due to similar symmetric translocations, undetectable by conventional banding techniques.
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PMID:Private multiple congenital anomaly syndromes may result from unbalanced subtle translocations: t(2q;4p) explains the Lambotte syndrome. 940 61

We investigated the phenomenon of long-term potentiation (LTP) in a genetic model of Down Syndrome, the segmental trisomy mouse (Ts65Dn). Ts65Dn mice survive to adulthood and have an extra chromosome that contains a segment of chromosome 16 homologous to human chromosome 21. In this study, field excitatory postsynaptic potentials (fEPSP) were recorded from the CA1 area of in vitro hippocampal slices from diploid and Ts65Dn mice, and LTP was induced by a single tetanizing pulse train (1 sec in duration) at 100 Hz. The hippocampus from both young (2 months) and older (9 months) Ts65Dn mice had a reduced LTP over a period of 60 min compared with LTP in age-matched controls. This finding may explain the reported behavioral and learning impairments in Ts65Dn mice; it suggests that this mouse model can be used to study the role of altered synaptic plasticity in mental retardation of Down Syndrome.
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PMID:Altered long-term potentiation in the young and old Ts65Dn mouse, a model for Down Syndrome. 951 25

Trisomy 22 is the most frequent trisomy, after trisomy 16, of the trisomies present in miscarriages. The children born with trisomy 22 have usually unbalanced translocations 11; 22 or mosaicisms. In a recent review Bacino et al. [1] were able to find 17 cases of children born with trisomy 22 including only 3 cases confirmed by molecular cytogenetics. We report a patient with an extra chromosome 22q- without mosaicism. This chromosomal anomaly was defined with FISH studies. The phenotype include microcephaly, microtia with pre auricular tags, hypertelorism, epicanthus, palatal cleft, short neck, winging scapulae, hypoplasia of the distal phalanges, pulmonary stenosis and mental retardation.
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PMID:De novo trisomy 22 due to an extra 22Q-chromosome. 952 16

Duplications or deletions are present in a high percentage of the gametes produced by individuals carrying balanced translocations. Preimplantation genetic diagnosis was used to examine chromosome balance in embryos from a patient having a reciprocal translocation within the short arms of chromosomes 5 and 8 (46,XX,t(5;8)(p13;p23)). This woman has two sisters with the translocation unbalanced, resulting in a partial trisomy for chromosome 5 and partial monosomy for chromosome 8 (46,XX,-8, +der(8)t(5;8)(p13;p23)) with associated mental retardation and physical abnormalities. The patient and her husband desired to have children without the abnormal chromosome balance and wished to reduce the likelihood of spontaneous abortion or need for therapeutic abortion. Fluorescence in-situ hybridization (FISH) probes for the alpha-satellite region of chromosome 8 and for a region on the short arm of chromosome 5 (5p15.2) were tested initially on lymphocytes from the patient and her sisters. The hybridization signal for chromosome 5 was detected in the expected two copies for the patient and three copies for the sisters in 87% of the cells. Two hybridization signals for chromosome 8 were detected in 96% of the cells from all individuals. Additional probe testing was done using blastomeres from polyspermic embryos. The couple then proceeded with a stimulated in-vitro fertilization (IVF) cycle and biopsies were done on 13 embryos at the 7-10-cell stage using a method of zona drilling and fluid displacement. Diagnosis was possible on at least one blastomere for nine embryos. Three embryos had nuclei with three hybridization signals for chromosome 5, three had fewer than two signals for one or both chromosomes, one was mosaic, and two had two signals for each chromosome. The latter were transferred to the patient, but pregnancy was not achieved. The results demonstrate that preimplantation genetic diagnosis for patients with reciprocal translocations can be used to identify embryos having normal chromosome balance. The potential advantages and limitations of this approach are discussed.
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PMID:Preimplantation genetic diagnosis of chromosome balance in embryos from a patient with a balanced reciprocal translocation. 954 75

Calcium is an important second messenger that affects metabolic and physiological activities of developing and mature neurons. It has been reported that electrical activity is abnormal in cultured hippocampal and DRG neurons from the trisomy 16 (Ts16) mouse, a model for Down syndrome (trisomy 21-Ts21 in human). Whole-cell voltage-clamp, radiolabeled ligand binding techniques and mRNA measurements were used to study the effect of Ts16 on voltage-dependent calcium currents in cultured fetal hippocampal neurons from the Ts16 mouse. In neither Ts16 nor control diploid neurons were low-voltage-activated calcium currents detected. However, a high-voltage-activated (HVA) calcium current was identified and shown to be dihydropyridine sensitive. The density of this HVA calcium current was 80% greater in Ts16 neurons than in control. This difference correlated with a 70% increase in binding of radiolabeled dihydropyridine, PN200-110, a marker of L-type calcium channels. However, mRNA levels encoding the alpha1C and alpha1D subunits were unchanged in the Ts16 neurons. In contrast, mRNA level of the myo-inositol transporter, the gene for which is located on mouse chromosome 16, was elevated in Ts16 neurons due to a gene-dosage effect. Therefore, it is likely that posttranscriptional regulation of dihydropyridine-sensitive voltage-dependent calcium channels is abnormal in Ts16. As dihydropyridine sensitive HVA Ca channels are implicated in heterosynaptic long-term depression and long-term potentiation, the differences reported here, if also present in the Down syndrome brain, may contribute to mental retardation in that disorder.
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PMID:Increased expression of voltage-activated calcium channels in cultured hippocampal neurons from mouse trisomy 16, a model for Down syndrome. 960 27


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