HEPARIN AND MAST CELLS

1046 symptoms, their study should have compared the diagnostic yield of the two investigations in a consecutive series of patients, both investigations being done by clinicians of equal experience and competence who are blind to the result of the other? On the study design used colonoscopy could only have improved on the results of DCBE. Department of Radiology, St James’s University Hospital, Leeds LS9 7TF

P. N. E.

JAMES

SIR,-Mr Aldridge and Mr Sim restricted colonoscopy to with a barium enema showing no abnormality or only diverticular disease. Both investigations must be done on all patients with symptoms if diagnostic yields are to be compared. Colonoscopy has its limitations: it usually requires sedation; it is probably more expensive than a barium enema;1 it carries a higher (about 0-2%) risk of perforation ;2 and the caecum is not always reached, as happened in 45 % of patients in Aldridge and Sim’s series. Furthermore, a good double-contrast barium enema may occasionally reveal adenomatous polyps that have been missed by an experienced colonoscopist.3 Since 60-90% of colonic neoplasms presenting with rectal bleeding are within reach of the 60 cm flexible fibreoptic sigmoidoscope4 we suggest flexible sigmoidoscopy as the first investigation for rectal bleeding in the absence of an obvious local cause in the rectum or anus. If this is negative, a doublecontrast barium enema will give a picture of the more proximal colon. Total colonoscopy is the appropriate investigation for the few remaining undiagnosed patients, and for patients needing further endoscopic assessment or biopsy.

patients

Royal Free Hospital, London NW3 2QG

M. C. ALLISON R. E. POUNDER

1. Williams CB. The clinical yield of colonoscopy. Postgrad Med J 1984; 60: 803-10. 2. Shamir M, Schuman BM. Complications of fiberoptic endoscopy. Gastrointest Endosc 1980; 26: 86. 3. Williams CB. Polyp follow-up: How, who for and how often? Br J Surg 1985; Sept

(suppl): S25-26. 4. Goulston

bowel

KJ, Cook I, Dent OF. How important is rectal bleeding in the diagnosis of and polyps? Lancet 1986; ii: 261-64.

cancer

SIR,-Mr Aldridge and Mr Sim emphasise the lack of sensitivity of double-contrast barium enema (DCBE) in diagnosing early colorectal carcinoma. We agree. In our review of 154 consecutive patients with colorectal carcinoma in the gastrointestinal unit of a district general hospital we found that DCBE had been positive in only 31 % of patients with Dukes A, 79 % with Dukes B, and 81 % with Dukes C carcinoma. Our simultaneous figures for fibre sigmoidoscopy or colonoscopy were 84% in Dukes A, 90% in Dukes B, and 92% in Dukes C lesions. When DCBE and endoscopic examination were used in conjunction the diagnostic yield exceeded 95 % in all groups. Fibreoptic endoscopy of the large bowel in expert hands is associated with a high sensitivity and a low morbidity.’ Gilbertsen and Nelms2 have shown the procedure to be cost effective. "Open access" endoscopy without prior hospital consultation for patients with large-bowel symptoms avoided delay in diagnosis and contributed towards an increase in the yield of early cancer in our

patients. Early detection of

colorectal carcinoma is an efficient and cost-effective method of reducing mortality due to colorectal carcinoma and no effort should be spared in screening patients with

persistent large-bowel complaints. Wordsley Hospital, Wordsley, Stourbndge, West Midlands DY8 5QX

1978, 41: 1137

SIR,-Dr Scully and colleagues’ hypothesis (Sept 27, p 718) is interesting. However, the underlying premise may not be applicable

Findings from work on rodent mast cells should extrapolated to man without experimental support.

to man.

not

be

A distinction has been established between gut "mucosal" and "connective tissue" mast cells in rodents, based on their susceptibility to withstand certain fixations,1 their staining reactionsbiochemistry,3 and differences in protease content.4 There is, however, no real evidence that these findings apply in man.5,6 Use of the protease substrate D-Val-Leu-Arg MNA did not afford any clear distinction between human mast cells in the gut mucosa and those in the submucosa.7 It appears that all human mast cells contain tryptase, but in the submucosa of the gut more mast cells also contained chymotryptase than did those of the mucosal Human tryptase has fibrinogenolytic activity that complements other mast cell mediators with anticoagulant properties,9 and so Scully and colleagues’ hypothesis may be untenable. Department of Oral Pathology/Oral Medicine, King’s College School of Medicine and Dentistry, Rayne Institute,

J. R. GARRETT

London SE5 9NU

I. A. OSMAN

1. Enerback L. Mast cells in rat gastrointestinal mucosa I: Effects of fixation. Acta Pathol Microbiol Scand 1966; 66: 289-302. 2. Enerback L. Mast cells in rat gastrointestinal mucosa II: Dye-binding and metachromatic properties. Acta Pathol Microbiol Scand 1966; 66: 303-12. 3. Enerback L, Kolset SO, Kusche M, Hjerpe A, Lindahl UIF. Glycosaminoglycans in rat mucosal mast cells. Biochem J 1985; 227: 661-68. 4. Woodbury RG, Neurath H. Structure, specificity and localization of the serine proteases of connective tissue. FEBS Lett 1980; 114: 189-96. 5. Aldenborg F, Fall M, Enerbäck L. Proliferation and transepithelial migration of mucosal mast cells in interstitial cystitis. Immunology 1986; 58: 411-16. 6. Craig SS, De Blois G, Schwartz LB. Mast cells m human keloid, small intestine, and lung by an immunoperoxidase technique using a murine monoclonal antibody against tryptase. Am J Pathol (in press). 7. Garrett JR, Osman IA, Smith RE. Protease staining of mast cells m human biopsy specimens. J Histochem Cytochem (in press). 8. Irani AA, Schechter NM, Craig SS, De Blois G, Schwartz LB. Two types of human mast cells that have distinct neutral protease compositions. Proc Natl Acad Sci USA 1986; 83: 4464-68. 9. Schwartz LB, Bradford TR, Littman BH, Wintroub BU. The fibrinogenolytic activity of purified tryptase from human lung mast cells. J Immunol 1985; 135: 2762-67.

TRANSPLANTS OF PRIMATE NEURONS

SIR,-Dr Bakay and Dr King (July 19, p 163) take exception to the statement that our published data (May 17, p 1125) are the first which demonstrate "the survival and distribution of transplanted fetal monkey neurons". We knew of Bakay and colleagues’ efforts to transplant fetal nerve cells in methylphenyltetrahydropyridine (MPTP) treated rhesus monkeys but do not think either presentations at meetings or abstracts can provide sufficient data for scientific evaluation of the survival of transplanted fetal nerve cells in monkeys or of the methods used. This is why our May 17 paper did not cite, for example, our presentation at the 15th annual meeting of the Society for Neuroscience (Oct 21, 1985). Bakay and King conclude "two research teams have successfully used the same experimental treatment" but we think that our techniques differ considerably from theirs. We share the hope that grafting procedures may one day provide treatment for neurological disorders such as parkinsonism. However, it is important for the scientific evaluation of this research to be based on detailed published reports. Otherwise there will be the danger of raising premature and exaggerated hopes in patients and their families. D. E.

L. KALRA A. N. HAMLYN

SJ Prevention, screening and early diagnosis. In: DeCosse JJ, ed. Large bowel cancer. Edinburgh: Churchill Livingstone, 1981; 46-60. 2. Gilbertsen VA, Nelms JM. The prevention of invasive cancer of the rectum. Cancer 1. Winnawer

HEPARIN AND MAST CELLS

Neurobehavioral Laboratory and Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut 06510, USA; and Department of Neurobiology and Anatomy, University of Rochester School of Medicine and Dentistry, Rochester, NY

REDMOND, JR JOHN R. SLADEK, JR ROBERT H. ROTH TIMOTHY J. COLLIER JOHN D. ELSWORTH ARIEL Y. DEUTCH SUZANNE HABER