Search PubMed⌕ Search

Biomedical subjects

D St Clair

Publications and source records attributed to D St Clair.

At least 73 records · Page 4Linked to original sources
PubMed1994

Structural features of the maize sus1 gene and protein.

Genomic clones, cDNA clones, and protein of the maize (Zea mays L.) Suc synthase1 (sus1) gene were isolated and sequenced. Termini (5' and 3') of the transcribed unit were identified. The SUS1 protein was purified from tissue culture cells as a phosphorylated protein. The overall structure of sus1 is virtually identical with that of the paralogous gene, shrunken1 (sh1); however, the last intron of sh1 is missing in sus1. This intron bears much sequence similarity with the adjacent exon, suggesting that the intron arose from an internal duplication. Although the placement of the other 14 introns is identical in both genes, the introns exhibit markedly greater differences in size and sequence relative to that shown by the exons. An explanation for the differential rate of divergence of exons and introns is selection pressure for gene function. Additionally, comparisons of coding regions of plant sucrose synthases show that sh1-like and sus1-like genes can be found in all monocots so far analyzed. These latter observations point to an important role played by both genes in this group of plants.

Base Sequence↗
PubMed1993

Screening Alzheimer's disease patients for mutations in the amyloid precursor protein gene.

Over the past two years a series of different mutations has been discovered in the amyloid precursor protein (APP) gene in patients with Alzheimer's disease. All have been clustered in exons 16 and 17, a region encoding the beta A4 peptide found in the amyloid deposits of neuritic plaques and cerebral blood vessels. We have used the powerful technique of denaturing gradient gel electrophoresis to screen for mutations in exons 7, 16 and 17 of the APP gene in a cohort of 105 patients with presenile dementia of the Alzheimer type and 71 patients with autopsy-confirmed senile Alzheimer's disease. No new mutations were found, confirming earlier suggestions that APP mutations account for only a small proportion of cases of familial and sporadic Alzheimer's disease.

Adult↗
PubMed1992

Mutation in codon 713 of the beta amyloid precursor protein gene presenting with schizophrenia.

Following reports of mutations of codon 717 in exon 17 of the amyloid precursor protein (APP) gene in early-onset familial Alzheimer's disease, we screened exon 17 for new mutations in presenile dementia. The majority of the 105 patients screened had definite or probable Alzheimer's disease, but we also included atypical cases and some chronic schizophrenics. We identified a single abnormal case--a chronic schizophrenic with cognitive defects. Sequencing revealed a C to T nucleotide substitution which produces an alanine to valine change at codon 713. We were unable to detect the mutation in the remaining members of the original cohort nor in a further 100 chronic schizophrenics and 100 non-demented controls. Nonetheless, the position of the mutation in a critical portion of the APP gene suggests that it may well prove to be pathogenic.

Amino Acid Sequence↗
PubMed1991

DNA markers and biological vulnerability markers in families multiply affected with schizophrenia.

A family is reported in which the monozygotic co-twin of a schizophrenic proband was diagnosed bipolar 1 and their mother had a history of unipolar major depression. Although their clinical manifestations varied, the ill members of this family shared an abnormality in P300 not found in the asymptomatic siblings. In 14 families, linkage to the 5q11-13 region was excluded when affection status was defined solely by P300 latency independently of the clinical findings. Linkage was also excluded when the analysis was restricted to the families that had no cases of bipolar illness and when the schizophrenic phenotype was narrowly or broadly defined. It is concluded that biological markers such as P300 and eye tracking may help to clarify the overlap of different types of psychosis and help to define the phenotype for linkage analyses.

Arousal↗
PubMed1990

Association within a family of a balanced autosomal translocation with major mental illness.

282 pedigrees in the MRC Cytogenetics Registry, Edinburgh, with familial autosomal anomalies were examined for the presence of associated mental illness. In one large pedigree there were 23 cases of mental and/or behavioural disorders meeting Research Diagnostic Criteria. 34 of the 77 family members available for cytogenetic analysis carried a balanced translocation t(1:11) (q43,q21). Psychiatric diagnoses had been recorded for 16 of the 34 members with the translocation compared with only 5 of the 43 without it. The lod scores (against chance linkage of the translocation with mental illness) were greatest when the mental disorders in the phenotype were restricted to schizophrenia, schizoaffective disorder, recurrent major depression, and adolescent conduct and emotional disorders. Although the mental illness in this family may not be typical of that in the general population, the findings suggest that the q21-22 region of chromosome 11 may be a promising area to examine for genes predisposing to major mental illness.

Adolescent↗
PubMed1990

Puerperal insanity in the 19th and 20th centuries.

All patients with puerperal psychosis admitted to the Royal Edinburgh Hospital within 90 days of childbirth during the periods 1880-90 and 1971-80 were compared. The majority of cases in both groups had an affective illness with an acute presentation and a fixed interval of onset. The 19th-century cases had a more florid presentation and a greater length of admission (mean, 151 days) to the hospital than the 20th-century ones (mean, 39 days). The incidence of the disorder rose from 0.34 per 1000 childbirths per year in the 19th-century group to 1.04 in the 20th-century one, but this could be explained by nosocomial factors. Most 19th-century cases occurred in multigravid women, which questions the association of puerperal psychosis with primiparae.

Female↗
PubMed1990

Localisation of a susceptibility locus for schizophrenia on chromosome 5.

"A considerable proportion of the variance in the liability to develop schizophrenia may be genetic, but segregation analysis, to establish a mode of transmission, has not produced a consistent result. One of these studies was carried out in Iceland and made use of the large family size and extensive genealogical information present in that country. Here we demonstrate genetic linkage of two DNA polymorphisms on the long arm of human chromosome 5 to schizophrenia in seven British and Icelandic families with multiple affected members. The results indicate the existence of a gene locus with a dominant schizophrenia-susceptibility allele. Inheritance of the allele in the families studied suggests that it may also predispose to psychiatric conditions such as schizophrenia spectrum disorders and a variety of other disorders. This report provides the first strong evidence for the involvement of a single gene in the causation of schizophrenia."

Chromosomes, Human, Pair 5↗
PubMed1990

The Edinburgh cohort of HIV-positive drug users: auditory event-related potentials show progressive slowing in patients with Centers for Disease Control stage IV disease.

A two-tone auditory event-related potential (AEP) task was used to examine brain function in 206 HIV-positive individuals (infected by intravenous drug use) approximately 6-7 years after initial infection. Multiple regression analysis of AEP latency and amplitude components showed only small effects of past medical and psychiatric history, current symptoms and drug use on electrophysiological responses. HIV-positive patients had longer latency and reduced amplitude of the P300 (P3) component of the AEP compared with a normal control group, but were electrophysiologically similar to a matched control group of HIV-seronegative drug users. However, a lower P3 amplitude was seen in patients in Centers for Disease Control stage IV. One-year follow-up of 103 patients (50%) found significant lengthening of P3 latency in patients with stage IV disease but not in those with stage II or stage III disease. The results suggest that brain involvement in HIV infection can be detected electrophysiologically after the clinical diagnosis of stage IV disease.

Adult↗
PubMed1989

No linkage of chromosome 5q11-q13 markers to schizophrenia in Scottish families.

Recent work suggests that an autosomal dominant gene for schizophrenia may be located on the 5q11-q13 region of chromosome 5 (refs 1 and 2): a report of schizophrenia associated with trisomy 5q11-q13 in two members of a family of Chinese origin prompted the discovery of linkage with markers p105-599Ha and p105-153Ra in five Icelandic and two English schizophrenic families. The strongest linkage was observed when the phenotype was broadly defined to include minor psychiatric diagnoses not traditionally considered part of the schizophrenia spectrum. By contrast, no evidence was found of linkage in a single multiplex Swedish schizophrenic pedigree. To determine whether these conflicting results arise from genetic and/or uncertainties in defining the schizophrenic phenotype, we examined fifteen Scottish schizophrenic families with restriction fragment length polymorphisms that span this region. We found no evidence for linkage, regardless of how broadly or narrowly the schizophrenic phenotype is defined, and conclude that a susceptibility locus, whose presence awaits confirmation, on the proximal portion of the long arm of chromosome 5 can be responsible for only a minority of cases of familial schizophrenia.

Chromosomes, Human, Pair 5↗
PubMed1989

P300 abnormality in schizophrenic subtypes.

P300 and other long latency event-related potentials were recorded in 65 schizophrenic subjects and results were compared to findings in 119 healthy controls. Highly significant differences in P300 latency and amplitude were found between the two groups. Forty six per cent of schizophrenics had P300 latency more than two standard deviations longer than the mean for controls, 35% had a P300 amplitude smaller than the mean for controls by the same amount, and 24% were more than two standard deviations outside the mean for controls on both measures. These differences were independent of chronicity of illness, clinical subtype, family psychiatric history or the effects of neuroleptic medication. They confirm that P300 abnormality is present as a stable trait in a high proportion of schizophrenics. The status of abnormal P300 as a biological vulnerability factor for major mental illness is discussed.

Adult↗
PubMed1988

Magnetic resonance imaging in pre-senile dementia of the Alzheimer-type, multi-infarct dementia and Korsakoff's syndrome.

Magnetic resonance imaging T1 values in Alzheimer's disease (ATD) were similar to age-matched controls although frontal T1 values tended to increase intraindividually with progression of the dementia. T1 values were raised, in both cortical grey and white matter, in Korsakoff's syndrome and multi-infarct dementia. T1 values appear of little value in studying the neuropathological changes in ATD in relationship to the neuropsychological deficits, but can assist in the differential diagnosis of pre-senile dementia.

Aged↗
PubMed1988

Measuring the course of Alzheimer's disease. A longitudinal study of neuropsychological function and changes in P3 event-related potential.

On two occasions one year apart, the cognitive performance of 12 patients with presenile dementia Alzheimer type (ATD) and 14 with alcoholic Korsakoff syndrome (KS) was assessed both psychologically using the Christensen version of Luria's neuropsychological investigation and physiologically by measuring P300 (P3) and other long-latency auditory event-related potentials. All patients with ATD showed evidence of psychological deterioration and most also showed changes in auditory P3, whereas on all measures the KS group remained essentially unchanged. The extent of the changes in the ATD group varied, but in general those patients with most psychological deterioration also displayed the biggest changes in P3 wave form. There were two patterns of decline: a majority followed the traditional progressive course associated with Alzheimer disease; and in a minority, decline was slower. Methods for determining the rate of decline in individual patients with ATD, together with the prognostic implications, are discussed.

Aged↗