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9. Rothman KJ. Modem epidemiology. Boston: Little Brown, 1986: 171. 10. Eddy DM, Hasselblad V. FAST*PRO: software for meta-analysis by the confidence profile method. Boston: Academic Press, 1991. 11. Cox DR. Regression models and life tables. 187-202.

J R Statist Soc Ser B 1972; 34:

12. Mickey RM, Greenland S. A study of the impact of confounder-selection criteria on effect estimation. Am J Epidemiol 1989; 129: 125-37.

SJ, Ederer F. Maximum utilization of the life table method in analyzing survival. J Chron Dis 1958; 6: 699-712. 14. Kalbfleisch JD, Prentice RL. The statistical analysis of failure time data. New York: John Wiley, 1980. 13. Cutler

15. Stein ZA. HIV prevention: the need for methods women can use. Am J Public Health 1990; 80: 460-62. 16. Kreiss J, Ruminijo I, Ngugi E, Roberts P, Ndinya-Achola J, Plummer F. Efficacy of nonoxynol-9 in preventing HIV transmission. Fifth International Conference on AIDS, Montreal, Canada, June, 1989

(abstr MA036). 17. Rekart M, Manzon LM, Barnett JA, Wittenberg L, McNabb A. Nonoxynol 9: its adverse effects. Sixth International Conference on AIDS, San Francisco, June, 1990 (abstr SC36). 18. Niruthisard S, Roddy RE, Chutivongse S. The effects of frequent nonoxynol-9 use on the vaginal and cervical mucosa. Sex Transm Dis

1991; 18: 176-79.

Debrisoquine hydroxylase gene polymorphism and susceptibility to Parkinson’s disease

The pathogenesis of Parkinson’s disease may be influenced by genetic and environmental factors. Cytochrome P450 mono-oxygenases help to protect against toxic environmental compounds and individual variations in cytochrome P450 expression might, therefore, influence susceptibility to environmentally linked diseases. The frequency of mutant CYP2D6 alleles was studied in 229 patients with Parkinson’s disease and 720 controls. Individuals with a metabolic defect in the cytochrome P450 CYP2D6-debrisoquine hydroxylase gene with the poor metaboliser phenotype had a 2·54-fold (95% Cl 1·51-4·28) increased risk of Parkinson’s disease. Determination of CYP2D6 phenotype and genotype may help to identify those at greatest risk of Parkinson’s disease and may also help to identify the environmental or metabolic agents involved in the pathogenesis of this disease. Introduction

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by DNA-based genetic assays that identify up to 90% of PM individuals.5,17,18 Here we report a study that makes use of these assays. Patients and methods Caucasian patients with Parkinson’s disease were selected at random on the basis of clinical manifestations of the disease. Samples were obtained between 1988 and 1991 from the Institutes of Psychiatry and of Neurology, London, and the University Department of Neurology, Birmingham. Some samples were also obtained from the Parkinson’s Disease Society brain bank. Criteria used for diagnosis of idiopathic Parkinson’s disease have been described previously.19.2O Caucasian control samples were randomly selected from three widely separate regions: Edinburgh (n 376), Sheffield (206), and London (138). London samples were from healthy volunteers and the other samples were randomly selected from routine blood samples taken at hospital clinics. Control samples were not matched for age or sex since these are not factors in CYP2D6 genotype. No significant differences were observed in the proportion of poor metabolisers between the different regions.21 Blood samples were either frozen immediately or received at ambient temperature in ethylenediaminetetraacetic acid (EDTA) or heparin vials and stored at - 20°C until required. Any tissue samples were frozen as soon as possible after excision and stored at 70°C before DNA isolation. Genomic DNA was isolated from tissue samples, whole blood, or lymphocyte preparations as described previously.5,7 However, most blood samples were processed rapidly to provide crude cell extracts suitable for polymerase chain reaction (PCR) analysis. 01 ml whole blood was mixed with 0-75 ml 10 mmol/1 "tris" (pH 80) and 1 mmol/1 EDTA, then centrifuged at 12 000 g for 20 s. The supernatant was aspirated and the cell pellet washed twice with 0-5 ml tris-EDTA as above. The final cell pellet was resuspended in 0.1ml buffer A =

-

Cytochrome P450 mono-oxygenases metabolise several endogenous compounds and environmental chemicals that have been suggested to cause conditions such as cancer and Parkinson’s disease. Could individual variation in the cytochrome P450 responsible for the oxidation of debrisoquine (CYP2D6) therefore influence individual susceptibility to environmentally linked diseases?2,3 Cytochrome P450 CYP2D6 polymorphism is an autosomal recessive trait associated with impaired debrisoquine metabolism in 5-10% of caucasian populations.4 This metabolic defect usually reflects absence of CYP2D6 protein caused by mutations in the CYP2D6 gene in affected individuals, which results in the poor metabolisers (PM) phenotype.5-8 Reports on a possible association of debrisoquine

hydroxylase

gene

polymorphism

and

susceptibility to or conflicting

Parkinson’s disease have shown equivocal

results, sometimes attributable to the small number of patients studied but sometimes as a result of limitations of pharmacokinetic assays used to identify poor metabolisers.9-16 However, the problems associated with

Imperial Cancer Research Fund Molecular Pharmacology Group, George Square, Edinburgh EH8 9XD, UK (C. A. D. Smith, PhD, Prof C. R. Wolf, PhD); ICRF Human Genetic Resources, Clare Hall Laboratories, South Mimms (A. C. Gough, BSc, N. K. Spurr, PhD); University Department of Neurology, Institute of Psychiatry and King’s College School of Medicine and Dentistry, London (Prof P N. Leigh, FRCP, B A. Summers, MRCP); University Department of Clinical Neurology, Institute of Neurology, London (Prof A E Harding, FRCP, D M. Maranganore, MD); University Department of Neurology, Queen Elizabeth Hospital, Birmingham (S. G. Sturman, MRCP, Prof A. C. Williams, FRCP); and Department of Neuroscience, Royal Free Hospital School of Medicine and University Department of Clinical Neurology, Institute of Neurology, London (Prof A H. V. Schapira, MRCP). Correspondence to Prof C R Wolf.

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Anaivsis of G-to-A transition

Analysis

of

base-pair

deletion

PCR analysis as described in methods. The banding pattern of amplified DNA is that expected after separation of restriction fragments by polyacrylamide gel electrophoresis and ethidium bromide staining.’Use of the two PCR assays shown will identify all poor metabolisers homozygous or heterozygous for these mutant alleles or the gene deletion but not individuals (1 1.0% of PM phenotypes) who are homozygous for a gene deletion where no PCR product is obtained. The two assays are about 90% predictive of phenotype.5,17,21

homozygous or heterozygous for a combination of the G-toA transition, base-pair deletion, or gene deletion mutations. A highly significant increase in the proportion of poor metabolisers, identified by the G-to-A transition alone or a combination of the G-to-A transition and the base-pair deletion in exon 5, was found among patients with Parkinson’s disease (X2 14-79 [p

Debrisoquine hydroxylase gene polymorphism and susceptibility to Parkinson's disease.

The pathogenesis of Parkinson's disease may be influenced by genetic and environmental factors. Cytochrome P450 mono-oxygenases help to protect agains...
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