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Clinicians should thus be aware that oral iron and ascorbic acid can interfere with faecal occult-blood analyses and should indicate on request forms if their patients are taking these substances.

We thank Dr H. N. Misra for suggesting that bic acid can have false-negative occult blood tests.

patients taking ascorD. P. GARRICK J. R. CLOSE W. MCMURRAY

Department of Clinical Chemistry, Wythenshawe Hospital, Manchester M23 9LT

PROLACTIN RISE AFTER A FALL IN

PLATELET MONOAMINE OXIDASE IN SCHIZOPHRENIA

SIR,-Zeller et al.have proposed that a molecular aberration of monoamine oxidase (M.A.O.) exists in schizophrenia. An altered Michaelis constant (Km) for platelet M.A.o. from schizophrenic patients has now been reported.2 This is an exciting development in the theory that M.A.o. abnormality is involved in schizophreniasince Km determinations are less subject to artifactual influences of platelet-count, non-platelet protein contamination, and enzymatic degradation than are determinations of simple platelet M.A.o. enzyme activity.

BLOOD-PRESSURE

SIR,-I read with interest the paper by Professor Stumpe and his colleagues (July 30, p. 211) on the possible role of dopamine in hypertension. I describe here an observation on the effect of intravenous infusions of adrenaline (epinephrine) on blood-pressure made while investigating adrenergic influence on cortisol release. In most subjects the concentration of

Km (X

10-7) OF PLATELET M.A.O. IN SCHIZOPHRENIC PATIENTS AND CONTROLS

* p

Platelet monoamine oxidase in schizophrenia.

821 Clinicians should thus be aware that oral iron and ascorbic acid can interfere with faecal occult-blood analyses and should indicate on request f...
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