Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Autosomal aneuploidy in mammals adversely affects developmental processes. In human beings, for example, trisomy 21 is the most frequent aneuploidy detected among newborns and the most common known genetic cause of mental retardation. In this review, several hypotheses are discussed that have been proposed to explain the mechanisms by which aneuploidy (especially trisomy) disrupts development. These mechanisms included specific gene dosage effects, generalized disruption of genetic homeostasis, and the influence of the parental origin of the duplicated chromosome. The availability of specific chromosomal rearrangements in mice, coupled with selective breeding schemes, permits generation of aneuploidy of specific chromosomes or chromosomal segments on controlled genetic backgrounds, thus enabling the systematic study of the causes and consequences of defined aneuploidy. Phenotypic characteristics associated with a number of specific aneuploidies in the mouse are discussed. Emphasis is placed on the effects of trisomy 16. Genetic homology between mouse chromosome 16 and human chromosome 21 has led investigators to suggest that analogous mechanisms will be responsible for the developmental abnormalities produced in these respective aneuploidies. Analysis of trisomy 16 mice from the organismal to the subcellular level has revealed a number of phenotypic characteristics (particularly neurobiologic ones) shared with human trisomy 21. The dosage effects of shared genes (or their products) may contribute to the development of these features.
 ...
PMID:Developmental consequences of autosomal aneuploidy in mammals. 297 93

Murine trisomy 19 (Ts19) can be regarded as a general model of human trisomies. It is the only autosomal trisomy in the mouse that survives the perinatal period. Therefore, it is the only animal model available for postnatal investigations of trisomy-specific mental retardation. To evaluate the extent of developmental retardation during the late-embryonic and fetal period of gestation, total body weight development was documented for 60 Ts19-fetuses and compared with that of 219 euploid in utero-mates. In addition, a postnatal study on body-weight development of 77 Ts19-neonates and 74 euploid littermates was performed starting on day 1 postpartum and continuing until spontaneous death or until day 22. Forty-seven Ts19-individuals were further tested in nine behavioural test systems in order to determine their neurophysiological developmental profile. Findings were compared with age-dependent morphologic and physiologic parameters. The data obtained in the present study show a significant retardation of organ- and body-weight development in Ts19-mice starting on day 14 of gestation. Retardation of physiological parameters is progressive and persists throughout the perinatal and postnatal periods. Furthermore, the trisomic individuals showed specific behavioural abnormalities.
 ...
PMID:Behavioural and developmental abnormalities in mouse trisomy 19: an animal model of mental retardation induced by chromosome imbalance. 335 67

Among a great number of chromosomal aberrations, the absence of cerebral malformations does not explain the reason for mental retardation and will lead to interpreting as normal the echography of a fetus which, after birth, will be revealed to have a trisomy. Trisomic brain anomalies are not constant or obligatory, but some of them (holoprosencephaly for 61% of trisomy-13 and agenesis of corpus callosum for 8% of trisomy-18) have a degree of specificity. As for cerebral and cerebellar heterotopias, they cannot be considered as real malformations as they are frequently found in premature newborns and disappear with maturation, thus proving that they are a sign of immaturity. There is still a lot of work to be done before we are able to meet the request for fetal integrity formulated by contemporary couples.
 ...
PMID:Congenital malformations and chromosomal aberrations. 345 43

A 4-year-and-10-month-old girl was referred to the Child Development Center, Rhode Island Hospital, Providence, Rhode Island, USA, for evaluation because of mental retardation. She was found to have short stature, congenital heart disease and dysmorphic facial features. A chromosome analysis revealed an unbalanced translocation with trisomy of the distal part of the short arm of chromosome 2 (2p21----2pter). A balanced reciprocal translocation was identified in the maternal karyotype 46,X,t(X;2)(q28;p21). The phenotype of partial trisomy 2p is discussed.
 ...
PMID:Partial trisomy 2p. 368 57

We identified an infant male pigtail macaque monkey with a bizarre karyotype which, to the best of our knowledge, has never before been reported in any species. Examination of 107 nuclei from cultured lymphocytes revealed 81 (75.7%) to be trisomic, but with the supernumerary chromosome varying from cell to cell, trisomy 16 being the most common. A small percentage (11.2%) of the nuclei had a normal 42,XY karyotype, and the balance, with the exception of one apparent monosomic (possibly a technical artifact), had multiple chromosome abnormalities. Examination of cultured skin fibroblasts revealed a similar karyotype. We called this karyotype a mosaic variegated trisomy. At birth, the animal had a cleft lip and palate and situs inversus of the heart. He subsequently showed significant developmental delay and apparent mental retardation. There were no clinical symptoms of hematological malignancy, which often have associated acquired chromosome abnormalities such as those described here. The animal survived for 2 yr and 8 mo under intensive care.
 ...
PMID:Mosaic variegated trisomy (42,XY/43,XY, + variable) in a male pigtail macaque monkey. 373 82

A female child with mental retardation and dysmorphic features was found to have a duplication deficiency of chromosome 8: rec(8)dup q,inv(8)(p23q24), a recombinant product derived from a familial pericentric inversion, inv(8)(p23q24)mat. Clinical features of this previously undescribed inversion product are compared with other reported cases of partial trisomy for the distal long arm of chromosome 8, since this segment is thought to be primarily responsible for the phenotypic features of the trisomy 8 syndrome.
 ...
PMID:A child with a recombinant of chromosome 8 inherited from her carrier mother. 398 83

A new case of 9 p trisomy is reported in a 7-month-girl having typical morphological abnormalities and a mental retardation. During the examination, unusual ocular abnormalities were observed: pigmented linear dots of the mid peripheral retinal. Strabismus and hypertelorism were present. However, the other ocular features, blepharophimosis, correctopia, ptosis, microphthalmia, iris coloboma, unusual position of the eyelashes were not observed.
 ...
PMID:[Unusual ocular anomaly in 9 p trisomy: retinal depigmentation]. 403 67

The trisomy 5p (5p13----p ter) was identified by G-banding in a proband girl, whose mother was a balanced translocation carrier 46, XX, t(5;8) (p13;p23). Based on the clinical and cytogenetic findings, previously published and our own, it is possible to define a particular phenotype associated with the dup (5p), including (5p13), or the complete short arm. Patients were of similar phenotype: mental retardation, macrocephaly, hypotonia, mongoloid eye slant, low-set ears, depressed nasal bridge, macroglossia, longer fingers, epicanthus, thick cheeks.
 ...
PMID:[A new case of trisomy 5p]. 408 94

A service has been developed in Saskatchewan to make available the results of studies of human chromosomes, the material being forwarded to the laboratory by local transport facilities. During the first year of this project chromosome studies were requested for five doubtful cases of trisomy-21 (two were found to be normal) and for 20 definite cases of trisomy-21 in young patients (two had translocations but the parents of both these children had normal karyotypes). Eleven confirmed cases of Turner's syndrome, two of Klinefelter's syndrome, and one each of the D and E syndromes were also studied. The largest group for which studies were requested comprised 36 patients with mental retardation; only two abnormal karyotypes were encountered in this group.
 ...
PMID:A service for human chromosome studies in Saskatchewan. 590 45

The analysis of the fine structure of the chromatids permits the identification of different regions on the long arm of chromosome 21. The preponderant role of the distal third of the long arm in the syndrome of trisomy 21 is now well established. Thus, trisomy of only band 21q22 results in a state identical to that caused by complete trisomy 21. If the trisomy involves only a part of band 21q22, the intensity of the symptoms is diminished, but the appearance of the patient is still reminiscent of Down's syndrome. Monosomy for band 21q22 results in a pathologic condition in which the morphological anomalies are the inverse of those observed in trisomic patients. This syndrome, as a "contre-type" to trisomy 21, is lethal. Trisomy of the proximal long arm region of chromosome 21 (21q21 leads to 21q22) is not associated with malformations but is accompanied by mental retardation. Monosomy of the same region results in a pathologic condition, which does not have features of the contre-type of trisomy 21.
 ...
PMID:Structural variation of chromosome 21 and symptoms of Down's syndrome. 621 34


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>