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Biomedical subjects

A F Wright

Publications and source records attributed to A F Wright.

At least 55 records · Page 3Linked to original sources
PubMed1996

A genome-wide search for linkage in a large bipolar family: comparison of genotyping accuracy using di- and tetranucleotide repeat microsatellite markers.

Linkage of bipolar disease to several markers mapping to chromosome 4p has been reported in an extended family multiply affected with bipolar affective disorder and no linkage was found at other locations with 106 microsatellite markers, of which 58 were dinucleotide and 48 tetranucleotide repeats [Blackwood et al. (1996), Nature Genetics, 12, 427-430]. Collecting these data provided the opportunity to assess the usefulness and accuracy of the automated linkage preprocessor (ALP) programme in a linkage study and to make a detailed comparison of di- and tetranucleotides with this semi-automated system. Genotypes were acquired using the automated linkage preprocessor (ALP) without any manual intervention at any stage of the procedure and results of analyses of these data were compared with results based on genotypes checked by visual inspection of the data. The ALP program was found to be timesaving and reliable and yielded similar results to non-automated reading using both di- and tetranucleotide repeat microsatellite markers. Tetranucleotides had fewer errors due to multiple genotypes and a lower incidence of stutter peaks making them more informative than dinucleotides in this linkage study.

Bipolar Disorder↗
PubMed1996

Recombination patterns around the breakpoints of a balanced 1;11 autosomal translocation associated with major mental illness.

The frequency and extent of pairing failure around human translocations are unknown. We have examined the pattern of recombination around the breakpoints of a balanced autosomal translocation t(1;11) (q43;q21) associated with major mental illness. DNA was available from 17 carriers and 10 non-translocation carriers with meioses involving four generations. The derivative 1 and 11 chromosomes were also isolated in somatic cell hybrids and used to confirm phase. We have genotyped pedigree members using 20 polymorphic markers within 10 cM on either side of both chromosome 1 and 11 breakpoints. We find no significant reduction of recombination in the vicinity of either breakpoint. However we estimate that there are insufficient meioses even in this large family to make a meaningful interpretation and suggest that sperm typing alone can answer these interesting questions.

Chromosome Mapping↗
PubMed1996

Ocular findings in the Laurence-Moon-Bardet-Biedl syndrome.

PURPOSE: To improve the description of the ocular part of the Laurence-Moon-Bardet-Biedl syndrome. METHODS: We examined 44 Scandinavian individuals who all had retinal dystrophy plus at least 2 more of the traditional cardinal signs of the syndrome: obesity, hypogenitalism, polydactyly and mental retardation. RESULTS: Full-field electroretinograms were obtained in 36 of the individuals and were abnormal in all. The dark adaptation thresholds were elevated by on average 3.5 log units. Symptoms of night blindness were observed at a mean age of 4 years and visual problems at daytime at 6-7 years. No one exceeding the age of 16 had a best corrected visual acuity of more than 0.1. In the fundus attenuated vessels were noted at all ages while macular pigmentations and a wax-pale optic disc appeared at age 6-7 years. Pigmentary changes in the midperiphery were noted at the earliest at 13 years of age and appeared mainly as bone spicules, however, in a minority of cases the pigmentations were atypical. Ten of the participants had been followed through a period of 9 years. Their visual acuity was reduced by on average 0.3 line (decimals) and the angle of visual fields by approximate 3 degrees (Goldmann standard object V:4e) per year through the adolescence. CONCLUSION: The ocular disease in Laurence-Mood-Bardet-Biedl syndrome presents early, the prognosis for visual function is poor and the fundus features are atypical and varying.

Adolescent↗
PubMed1996

A recombination outside the BB deletion refines the location of the X linked retinitis pigmentosa locus RP3.

Genetic loci for X-linked retinitis pigmentosa (XLRP) have been mapped between Xp11.22 and Xp22.13 (RP2, RP3, RP6, and RP15). The RP3 gene, which is responsible for the predominant form of XLRP in most Caucasian populations, has been localized to Xp21.1 by linkage analysis and the map positions of chromosomal deletions associated with the disease. Previous linkage studies have suggested that RP3 is flanked by the markers DXS1110 (distal) and OTC (proximal). Patient BB was thought to have RP because of a lesion at the RP3 locus, in addition to chronic granulomatous disease, Duchenne muscular dystrophy (DMD), mild mental retardation, and the McLeod phenotype. This patient carried a deletion extending approximately 3 Mb from DMD in Xp21.3 to Xp21.1, with the proximal breakpoint located approximately 40 kb centromeric to DXS1110. The RP3 gene, therefore, is believed to reside between DXS1110 and the proximal breakpoint of the BB deletion. In order to refine the location of RP3 and to ascertain patients with RP3, we have been analyzing several XLRP families for linkage to Xp markers. Linkage analysis in an American family of 27 individuals demonstrates segregation of XLRP with markers in Xp21.1, consistent with the RP3 subtype. One affected mate shows a recombination event proximal to DXS1110. Additional markers within the DXS1110-OTC interval show that the crossover is between two novel polymorphic markers, DXS8349 and M6, both of which are present in BB DNA and lie centromeric to the proximal breakpoint. This recombination places the XLRP mutation in this family outside the BB deletion and redefines the location of RP3.

Adult↗
PubMed1995

Automated linkage analysis in psychiatric disorders.

A genome-wide search for linkage of microsatellite markers to chromosomal loci containing genes responsible for the major psychoses is a laborious task which can be carried out with greater speed and economy by introducing automation to several steps in the procedure. We describe the use of the Automated Linkage Preprocessor (ALP) program for the computer analysis of the waveform generated by fluorescein-labelled markers after electrophoretic separation. (To obtain a copy send a request to A.F. Brown at the below MRC address or use Anonymous FTP to ftp.hgu.mrc.ac.uk. Software is in directory pub/ALP). The program runs on a PC in the Microsoft Windows environment, and is used in conjunction with an automated laser fluorescence (ALF) sequencer (Pharmacia) and its Fragment Manager software to detect and size the PCR products, filter out peaks of fluorescence due to nonallele fragments, and generate genotypes in a format suitable for direct input to standard linkage analysis programs. The method should offer the advantages of speed, accuracy, and reduced cost. Its use in linkage studies in a large family with manic-depressive illness is discussed.

Automation↗
PubMed1995

A simple method for rapid isolation of microsatellites from yeast artificial chromosomes.

Microsatellites are widely recognised as providing a rich source of polymorphic markers for genetic mapping. Consequently, highly polymorphic CA repeats tightly linked to a disease locus are invaluable tools in linkage studies. We have developed an efficient technique for cloning microsatellite repeats from a region of interest contained within a yeast artificial chromosome (YAC). The YAC material is digested with a frequent cutting restriction endonuclease and ligated to polymerase chain reaction (PCR) amplifiable catch-linkers. A 5' biotinylated (CA)11 oligonucleotide is then used to select fragments containing a complementary repeat by binding to streptavidin-coated magnetic beads. The catch-linkers enable these fragments to be PCR amplified, cloned and sequenced. Primers are then designed to amplify the repeat locus and to confirm its genomic localization and heterozygosity. We have successfully used this technique to clone a new (CA)18 microsatellite from a 360-kb YAC. The YAC contains the CYBB locus in Xp21.1 and is thought to contain at least part of the RP3 gene responsible for X-linked retinitis pigmentosa. This new CA repeat is highly polymorphic with nine alleles identified so far and a heterozygosity of 0.75.

Base Sequence↗
PubMed1995

Haplotype analysis in autosomal dominant polycystic kidney disease.

Haplotype analysis was performed in 35 autosomal dominant polycystic kidney disease (ADPKD) families typed with 13 markers close to the PKD1 locus. The identification of recombinants close to the PKD1 gene on chromosome 16p indicates that PKD1 lies between CMM65 distally and 26-6 proximally. In addition, three unlinked (PKD2) families and two families with potential new mutation were identified.

Adult↗
PubMed1995

Newly identified psychiatric illness in one general practice: 12-month outcome and the influence of patients' personality.

BACKGROUND: Relatively little is known about the natural history and outcome of psychological problems in patients who present to general practitioners. Only a small proportion of such patients are seen by specialists. Clinical experience suggests that patient personality is one of the factors influencing outcome in patients diagnosed as having psychiatric illness. AIM: This study set out to examine prospectively the progress and 12-month outcome of patients with newly identified psychiatric illness, and the association of patients' personality with outcome. METHOD: One hundred and seventy one patients with clinically significant psychiatric illness attending one practice in a Scottish new town were followed up prospectively (96 presented with psychological symptoms and 75 with somatic symptoms), and were compared with a group of 127 patients with chronic physical illness. Patients were assessed in terms of psychiatric state, social problems and personality using both computer-based and pencil and paper tests in addition to clinical assessments at each consultation during the follow-up year and structured interview one year after recruitment. RESULTS: Most of the improvement in psychiatric state scores on the 28-item general health questionnaire occurred in the first six months of the illness. Of the 171 patients with psychiatric illness 34% improved quickly and remained well, 54% had an intermittent course but had improved at 12-month follow up while 12% pursued a chronic course without improvement. The mean number of consultations in the follow-up year was 8.4 for patients presenting with psychological symptoms, 7.2 for those presenting with somatic symptoms and 6.6 for patients with chronic physical illness. The Eysenck N score proved a strong predictor of the outcome of new psychiatric illness. CONCLUSION: Only one in three patients with newly identified psychiatric illness improved quickly and and remained well, reflecting the importance of continuing care of patients with psychological problems. This study has confirmed the feasibility of simple personality testing in everyday practice and shown a link between Eysenck N score and the outcome of new psychiatric illness. The predictive value of the Eysenck N score in general practice requires further research.

Adolescent↗
PubMed1994

Automation of genetic linkage analysis using fluorescent microsatellite markers.

Automation of the typing of genetic markers offers advantages of speed, accuracy, and cost in the mapping of genetic traits and the construction of high-resolution linkage maps. We have developed an automated linkage analysis system by (i) using a robotic pipettor to set up polymerase chain reactions (PCR) to amplify microsatellites with incorporation of a single fluorescent label; (ii) using an automated sequencing apparatus for detection of the PCR products; (iii) sizing alleles automatically by the use of internal and external standards; (iv) iteratively filtering out nonallelic fragments and checking for Mendelian consistency; (v) calculating the probabilities of selected genotypes; and (vi) automatically formatting the results for input to linkage analysis programs. The method provides accurate sizing of alleles, minimizes the risk of error during manual reading and transcription of data, and increases the throughput of reliable data. It brings any inconsistencies or ambiguities in the data to the attention of the user and facilitates examination of the raw data. The ALF/ALP system, together with new, optimized microsatellite sets, particularly tetranucleotide repeats, is likely to be well-suited to fully automatic genetic linkage analysis.

Alleles↗
PubMed1994

In vitro and in vivo antitumor activity of ZENECA ZD0490, a recombinant ricin A-chain immunotoxin for the treatment of colorectal cancer.

ZENECA ZD0490 is a recombinant ricin A-chain-containing immunotoxin that recognizes an antigen that is expressed on approximately 65% of colorectal tumors. The antigen CA242 is recognized by a mouse monoclonal antibody designated C242. C242 antibody was conjugated to recombinant ricin A-chain via a methyl-hindred disulfide linker which confers in vivo stability. ZD0490 was extremely potent against colorectal cell lines CoLo201 and CoLo205, which express the CA242 antigen. ZD0490 activity was determined in vitro by both protein synthesis inhibition (50% inhibitory concentrations of 1-20 ng/ml after 24-h exposure) and clonogenic assay (76-95% cell kill after 24-h exposure to a 50% inhibitory concentration for protein synthesis inhibition; > 99.99% cell kill at 1000 ng/ml). This in vitro activity was translated to in vivo efficacy where single dose i.v. administration of 2.5 mg/kg of ZD0490 was sufficient to induce substantial growth delays of both CoLo201 and CoLo205 s.c. tumors in nude mice. This growth delay equates to between 40 and 60% inhibition of tumor protein synthesis as quantified by an in vivo [14C]leucine incorporation assay. Using this technique, it was shown that protein synthesis inhibition persisted for at least 96 h after a single dose of ZD0490. Administration of the same total dose given as daily doses over 5 days did not alter the antitumor efficacy of ZD0490 in either the growth delay or the protein synthesis inhibition assays. The in vitro and in vivo activity of ZD0490 detailed in this paper show that this novel immunotoxin is worthy of clinical evaluation, which is currently under way in the United Kingdom.

Animals↗
PubMed1994

Comparison of the cellular internalization of antibodies used either as immunotoxins or in ADEPT.

The internalization into tumor cells of two antibodies (C242 and 454A12), which make potent immunotoxins when linked to ricin A-chain, and an antibody (A5B7), which does not make a potent immunotoxin but has proven useful in ADEPT, was evaluated. The 454A12 antibody was rapidly taken into the cells, 50% of the antibody being internalized after 2 h. The C242 antibody was internalized more slowly, approx 50% being taken up by the cells in 24 h. With A5B7, less than 10% of the antibody was internalized after 24 h. Internalization of the C242 antibody was accompanied by the appearance of antibody degradation products in the cell medium after 2 h, and this degradation could be inhibited by addition of a metabolic inhibitor that prevented cell internalization. In contrast, minimal degradation of the A5B7 antibody could be detected up to 24 h after binding to the cells. In conclusion, both 454A12 and C242 antibodies, which make potent immunotoxins, were internalized into tumor cells. The A5B7 antibody, which does not make a potent immunotoxin, was not internalized, and this property may be one reason why A5B7 has proved useful for delivery of enzymes in ADEPT.

Animals↗