288 coagulant activity and concentration is not linear, par- ticularly at high concentrations. The p.c.A. values we used were calculated as a percentage of control plasma values and not as precise concentrations. The values within and between patient groups are consistent, how- ever, and therefore seem valid as an indicator of c.N.s. injury. We thank Mr and Mrs M. Dooher for financial support; Ms Kathy Barvinchak and Ms Anne Lascaris for technical assistance; Ms Cindy Cooper for her help in the preparation of the manuscript; Dr Frank Oski, Dr William Bergstrom, and Dr Richard Oates for advice; and the pwdiatric house staff. Requests for reprints should be sent to J.E.G., Upstate Medical Center, 750 East Adams Street, Syracuse, N.Y. 13210, U.S.A. REFERENCES 1. Astrup, T. Thromb. Diath. hæmorrh. 1965, 14, 401. 2. Gralnick, H. R., Abrell, E. Br. J. Hæmat. 1973, 24, 89. 3. Kramer, C. Y. Biometrics, 1956, 12, 307. 4. Niemetz, J. J. clin. Invest. 1972, 51, 307. 5. Rivers, R.P.A, Hathaway, W. E Pediat. Res. 1975, 9, 167. 6. Eiser, C., Lansdown, R. Archs Dis. Childh. 1977, 52, 525. 7. Price, R. A., Jamieson, P. A. Cancer, 1975,35, 306. 8. Brueton, M. J., Breeze, G. R., Stuart, J. J. clin. Path. 1976, 29, 341. 9. Aznar, J. A., Vilches, J. J., Mayans, J. R., Tascon, A., Monsalvez, F., Marty, M. L. Sangre, 1976, 21, 224. INCREASED ARTERIAL-TISSUE CHOLESTEROL AFTER INTESTINAL BYPASS IN SEVERE OBESITY JOHN G. KRAL GÖRAN BONDJERS Department of Surgery and Arterial Biology Group, Sahlgrenska sjukhuset, University of Göteborg, Sweden Summary Cholesterol content was measured in biopsy specimens of mesenteric artery taken at the time of jejuno-ileal bypass from 4 very obese patients aged 19, 22, 27, and 42. When their body- weight had become stable (mean 22 months) after oper- ation, biopsy specimens of the temporal artery were obtained from 3 patients and of a mesenteric artery from 1. Cholesterol content had increased significantly. The increase in arterial-tissue cholesterol was concomitant with decreases in serum high-density (H.D.L.) and low- density (L.D.L.) lipoprotein cholesterol. Introduction A LOW concentration of serum-high-density-lipopro- tein (H.D.L.) cholesterol is a risk factor for atherosclero- tic disease in man.1-3 We found that decreased serum- H.D.L. was associated with an increase in the cholesterol content of arterial-tissue biopsy specimens obtained dur- ing jejuno-ileal bypass in severely obese patients aged 20-44 years.4 Since postoperatively there was a signifi- cant decrease in serum-H.D.L.-cholesterol in these pa- tients5 we measured the cholesterol content of repeat arterial biopsy specimens. Methods Patients were screened as described elsewhere4 before being selected for jejuno-ileal bypass. They were non-alcoholic, nor- molipoproteinæmic, not using any drugs, and stable at their maximum body-weight (table i). Blood-pressure was normal. End-to-side jejuno-ileostomy (37-12.5 cm)6 was performed under routine anaesthesia, and a wedge-shaped biopsy specimen was taken from the jejunum. Cholesterol’ and D.N.A.8 were mea- TABLE I-CHARACTERISTICS OF FOUR SEVERELY OBESE PATIENTS AT JEJUNO-ILEAL BYPASS TABLE II—ARTERIAL-TISSUE CHOLESTEROL IN FOUR SEVERELY OBESE PATIENTS AT JEJUNO-ILEAL BYPASS (OP. 1) AND AT FOLLOW-UP AT STABLE BODY-WEIGHT (W.S.) sured in intima-media preparations of arterial tissue. When the patients had achieved a stable body-weight, a biopsy specimen of temporal artery was obtained in 3 of the patients. Because patient 4 was dissatisfied with the weight-loss of 23 kg and there was radiological evidence of elongation of the small intestine, a jejunal resection was per- formed and a second biopsy specimen of a mesenteric artery was obtained at the same time. Results Arterial cholesterol content increased in all patients between jejuno-ileostomy and follow-up at a stable body- weight (table n). In one (the youngest) arterial cholesterol content had more than doubled. Arterial tissue cholesterol determinations were based on 5-17 samples per biopsy (S.E.M. 0 1-0 7 mg/g). The D.N.A. content of the arterial tissue was not significantly different in specimens obtained at the two biopsies. In patient 4 a small ather- oma was found at the second operation. Discussion This study demonstrated significant increases in arte- rial-tissue cholesterol after weight reduction by jejuno- ileal bypass operations in young obese patients. We do not know how representative the mesenteric-artery biopsy specimens were of the whole arterial tree at the time of the first operation. Also it can be argued that the follow-up biopsies from the temporal artery in 3 of the patients might not be comparable with the mesen- teric arteries. However, in patient 4 we were able to obtain a specimen from the same vascular bed as in the first operation, and the same significant increase in cho- lesterol was seen as in the temporal arteries. Coincidental decreases in serum-H.D.L. and increases in arterial-tissue cholesterol, in the face of lowered total cholesterol and lowered L.D.L.-cholesterol, accord with the idea that reduced serum-H.D.L. is a risk factor for complications of atherosclerotic disease.9 Intestinal bypass operations, by excluding substantial lengths of jejuno-ileum which possibly is involved in apoprotein synthesis1o.11 may impair the synthesis of an important acceptor of tissue cholesterol. This would result in the accumulation of cholesterol in arterial tissue.