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Biomedical subjects

A Hockey

Publications and source records attributed to A Hockey.

At least 19 recordsLinked to original sources
PubMed1992

A base substitution at the splice acceptor site of intron 5 of the COL1A2 gene activates a cryptic splice site within exon 6 and generates abnormal type I procollagen in a patient with Ehlers-Danlos syndrome type VII.

The dermal type I collagen of a patient with Ehlers-Danlos type VIIB (EDS-VIIB) contained normal alpha 2(I) chains and mutant pN-alpha 2(I)' chains in which the amino-terminal propeptide (N-propeptide) remained attached to the alpha 2(I) chain. Similar alpha 2(I) chains were produced by cultured dermal fibroblasts. Amino acid sequencing of tryptic peptides, prepared from the mutant amino-terminal pN-alpha 2(I) CB1' peptide, indicated that five amino acids, including the N-proteinase (the specific proteinase that cleaves the procollagen N-propeptide) cleavage site, had been deleted from the junction of the N-propeptide and the N-telopeptide (the nonhelical domain at the amino-terminus of the alpha chains of fully processed type I polypeptide chains) of the mutant pro-alpha 2(I)' chain. The corresponding 15 nucleotides, which were deleted from approximately half of the alpha 2(I) cDNA polymerase chain reaction products, of the alpha 2(I) cDNA polymerase chain reaction products, were encoded by the +1 to +15 nucleotides of exon 6 of the normal alpha 2(I) gene (COL1A2). These 15 nucleotides were deleted in the splicing of alpha 2(I) pre-mRNA to mRNA as a result of inactivation of the 3' splice site of intron 5 by an AG to AC mutation and the activation of a cryptic AG splice acceptor site corresponding to positions +14 and +15 of exon 6. Loss of the N-proteinase cleavage site explained the persistence of the pN-alpha 2(I)' chains in the dermis and in fibroblast cultures. Collagen production by cultured dermal fibroblasts was doubled, possibly due to reduced feedback inhibition by the N-propeptides. In contrast to previously reported cases of EDS-VIIB, Lys5 of the N-telopeptide was not deleted and appeared to take part in the formation of intramolecular cross-linkages. However, increased collagen solubility and abnormal extraction profiles of the mutant type I collagen molecules indicated that collagen cross-linking was abnormal in the dermis. The proband and her son were heterozygous for the mutation. It is likely that the heterozygous loss of the N-proteinase cleavage site, with persistence of a shortened N-propeptide, was the major factor responsible for the EDS-VIIB phenotype.

Adult↗
PubMed1992

Angelman's syndrome: a neuropathological study.

We report the neuropathological findings of a 3-year-old boy with Angelman's syndrome. The main abnormalities were macroscopic consisting of small temporal and frontal lobes which also showed disorganised and irregular gyri. The occipital lobes appeared flattened but were otherwise normal as were the parietal lobes. The brain stem and cerebellum appeared normal externally. Microscopically there was irregular distribution of neurons in layer 3 and in the cerebral white matter a few subcortical ectopic neurons were present in the temporal and frontal lobes. A single "Purkinje" cell heterotopia was seen but otherwise the cerebellum appeared normal.

Abnormalities, Multiple↗
PubMed1991

Dandy-Walker malformation (variant), cystic dysplastic kidneys, and hepatic fibrosis: a distinct entity or Meckel syndrome?

Dandy-Walker malformation is an unusual finding in Meckel syndrome, which characteristically presents with encephalocele, polydactyly, and cystic renal disease. We report on a family in which three nonviable brothers had Dandy-Walker malformations (variant) with associated enlarged cystic dysplastic kidneys and hepatic fibrosis. The consistent segregation of these abnormalities in all three sibs in the absence of polydactyly and encephalocele suggested the possibility of a distinct syndrome. The clinicopathological findings of the disorder are described and discussed in the context of the phenotypic spectrum of Meckel syndrome.

Adult↗
PubMed1991

The aetiology of intellectual disability in Western Australia: a community-based study.

A register of intellectual disability is being established to assess the level and aetiology of intellectual disability in all children born and/or living in Western Australia. 1602 children aged between six and 16 years were identified who had IQs less than 70. 40 per cent had a definite genetic basis, 20 per cent an environmental cause and 40 per cent were of unknown aetiology. The insult was prenatal in 61 per cent, 10 per cent had a possible perinatal cause, 8 per cent were postnatal and for 21 per cent the timing could not be assessed. Approximately 20 per cent had concomitant cerebral palsy and 13 per cent were epileptic. A disparity was found between rural and urban areas, the prevalence being 9.9 and 6.5 per 1000 live births.

Adolescent↗
PubMed1989

Amyloid A4 protein and its precursor in Down's syndrome and Alzheimer's disease.

In patients with Alzheimer's disease, amyloid fibrils that are aggregates of A4 protein subunits are deposited in the brain. A similar process occurs at an earlier age in persons with Down's syndrome. To investigate the deposition of amyloid in these diseases, we used a radioimmunoassay to measure levels of the amyloid precursor (PreA4) in the serum of 17 patients with Down's syndrome, 15 patients with Alzheimer's disease, and 33 normal elderly controls. The mean (+/- SD) concentration of serum PreA4 was increased 1.5-fold in patients with Down's syndrome (2.49 +/- 1.13 nmol per liter) as compared with that in controls (1.68 +/- 0.49 nmol per liter; P less than 0.007); the levels in patients with Alzheimer's disease were similar to those in controls (1.83 +/- 0.78; P less than 0.98). We also found that the concentration of PreA4 in the brain tissue of two adults with Down's syndrome (100 and 190 pmol per gram) was higher than that in the brain tissue of either 26 patients with Alzheimer's disease (64.4 +/- 17.3 pmol per gram) or 17 elderly controls with neurologic disease (68.5 +/- 26.3 pmol per gram). Immunocytochemical studies of brain tissue from 26 patients with Down's syndrome showed that the deposition of A4 protein amyloid began in these patients approximately 50 years earlier than it began in 127 normal aging subjects studied previously, although the rate of deposition was the same. We conclude that, since the gene for PreA4 is on the long arm of chromosome 21, which is present in triplicate in Down's syndrome, overexpression of this gene may lead to increased levels of PreA4 and amyloid deposition in Down's syndrome. However, since increased levels of PreA4 are not present in Alzheimer's disease, additional factors must account for the amyloid deposition in that disorder.

Adolescent↗
PubMed1988

Rett syndrome: abnormal membrane-bound lamellated inclusions in neurons and oligodendroglia.

The brain biopsy of a patient with Rett syndrome showed light microscopic evidence of white matter disease. Ultrastructurally, many neurons and oligodendroglia contained membrane-bound electron-dense inclusions with a distinct lamellar and granular substructure. This substructure suggests that part of these inclusions are derived from phospholipid. If confirmed in other cases of Rett syndrome, the neurochemical study of these inclusions may contribute to an understanding of this disorder.

Brain↗
PubMed1988

Microcephaly, holoprosencephaly, hypokinesia--second report of a new syndrome.

Two still-born males whose mothers were sisters are presented. The features holoprosencephaly, hypokinesia, microcephaly, talipes, and other contractures correspond to those in the two male sibs reported by Morse et al. (1987). We suggest that our cases now provide evidence of an X-linked rather than an autosomal recessive new syndrome.

Abnormalities, Multiple↗
PubMed1988

Oculocerebral syndrome with hypopigmentation (Cross syndrome). Report of two siblings born to consanguineous parents.

In this report we describe two siblings, a 17-year-old male and his deceased sister, born to consanguineous parents, and presenting an oculocerebral syndrome with hypopigmentation as first delineated by Cross in 1967. In addition to the cutaneous hypopigmentation, both presented deep mental retardation and spastic tetraplegia with athetoid movements. A remarkable finding in this family is that a third sibling, an otherwise normal 23-year-old male, presents the same hypopigmentation with white-grey hair colour as his two severely affected siblings.

Adolescent↗
PubMed1987

Prenatal diagnosis of the fragile X using thymidine induction.

Eleven pregnancies in ten patients at risk for the fragile X were monitored by amniocentesis or chorion villus biopsy and induction of the fragile site using thymidine, methotrexate and FUdR. Three female fetuses and one male fetus were found to have the fragile X. The results obtained using thymidine induction were superior to those using methotrexate induction and probably better than those obtained using FUdR induction.

Adult↗
PubMed1986

Sensitivity to ultraviolet radiation in a dominantly inherited form of xeroderma pigmentosum.

An Australian family is described in which a mild form of xeroderma pigmentosum (XP) is inherited as an autosomal dominant trait. Studies of lymphoblastoid cells and fibroblasts from affected persons demonstrated cellular sensitivity to ultraviolet (UV) light as judged by diminished clonogenicity and higher frequencies of UV induced chromosome aberrations compared to normal controls. After UV irradiation of dominant XP cells, replicative DNA synthesis was depressed to a greater extent than normal and the level of UV induced DNA repair synthesis was lower than that in normal cells. The level of sister chromatid exchanges and the numbers of 6-thioguanine resistant mutants induced by UV irradiation were equal to those found in normal controls. Although two subjects in the family had skin cancers, this dominant form of XP is not apparently associated with high risk, or large numbers, of skin cancers in affected persons.

Adult↗
PubMed1985

De Barsy syndrome--an autosomal recessive, progeroid syndrome.

We report two families with seven siblings with de Barsy syndrome. Characteristic features include severe mental retardation, hypermobility with athetoid movements, grimacing, muscular hypotonia, laxity of small joints and brisk deep tendon reflexes, progeroid aspect with cutis laxa, atrophy of skin with hyperpigmentation, isolated depigmentations, reduction of subcutaneous fatty tissue, translucent vein pattern, short stature, frontal bossing in the young child, large prominent ears with dysplastic helices and corneal clouding or cataracts. The syndrome probably has autosomal recessive inheritance.

Abnormalities, Multiple↗