Background-L-Arginine has been shown to induce fluid secretion in human jejunum. Nitric oxide, a derivative of L-arginne is thought to have an important role as an intestinal secretagogue. Aim-To determine the effect of Larginine and the nitric oxide synthase inhibitor, nitro L-arginine methyl ester (L-NAME), on fluid and electrolyte movement in rat jejunum. Methods-A 25 cm segment ofrat jejunum was perfused in situ with iso-osmotic solutions containing either (1) saline, (2) D-arginine 20, (3) L-arginine 20, (4) L-NAME 0-1, 1, or 20 mmol/l, or (5) a combination of L-arginine 20 and L-NAME 0.1, 1, or 20 mmol/l. In further groups the effect of a subcutaneous injection of L-NAME 100 mglkg was examined in rats pretreated with either Dor L-arginine 500 mg/kg. Results-L-Arginine, unlike D-arginine, induced fluid secretion despite being better absorbed (mean -7 3 v 17-0 ,l/min/ g; p<001). L-NAME at 0.1 mmol/l had no effect on basal fluid movement but reversed L-arginine induced secretion (7.8; p<005). L-NAME at 1 and 20 mmol/l induced fluid secretion (-15.4 and -28-4, respectively), which was enhanced by the addition of L-argilnlne (-30.0 and -41-0, respectively; both p<005). A subcutaneous injection of L-NAME resulted in marked fluid secretion (-39.9) and histological evidence of intestinal ischaemia. These changes were attenuated or reversed by pretreatment with subcutaneous L-but not D-arginine. Conclusions-L-Arginine induces intestinal fluid secretion through production of nitric oxide. There is a delicate balance between the effect of nitric oxide as a secretagogue and its effect on maintaining blood flow and thus preventing intestinal ischaemia. (Gut 1996; 39: 539-544) Keywords: arginine, nitric oxide, L-NAME, intestinal transport, bowel ischaemia.Actively transported sugars and most amino acids enhance small intestinal absorption of water and electrolytes.l`However, L-arginine (L-Arg), unlike other amino acids, has been shown by us and others to induce water secretion when perfused in human jejunum.' 5 A satisfactory explanation has never been put forward to explain this phenomenon, though it has been suggested that L-Arg induced secretion by a local effect that could be inhibited by the calmodulin antagonist chlorpromazine.5Over the past few years L-Arg has been found to be the precursor of the free radical nitric oxide (NO), which has an important role as a mediator of neural, cardiovascular, and gastrointestinal function.`8 Nitric oxide is derived from the guanidino terminal of L-Arg by the action of the stereospecific enzyme nitric oxide synthase (NOS) which, in the gut, is present in the myenteric plexus9 10 and submucosal arterioles and venules."' 12 In addition, it has been shown that NO could be produced by enterocytes through both the constitutive and the inducible NOS." In vitro studies have unveiled a role for NO as a secretagogue in the ileum14 '5 and colon, [16][17][18] and in vivo studies have suggested a possible role for NO in the laxative action of castor oil,"9 magnesium sulphat...

The operation notes and pathology records of 294 consecutive patients who had right hemicolectomy for Crohn's disease were reviewed. A Meckel's diverticulum was found in 17 (5 8%) ofthese patients, 2-3 times the expected rate in the general population. At least 50% of diverticula in the normal population contain heterotopic mucosa, but none was found in those diverticula that were examined from this group. The increased prevalence of Meckel's diverticulum in patients with Crohn's disease confirms previous anecdotal reports, but the cause for the increased frequency remains unexplained. The significance of this finding is discussed. (Gut 1994; 35: 788-790) There have been suggestions that Meckel's diverticulum is found more commonly in patients diagnosed as having terminal ileal Crohn's disease than in the general population.' It is not understood why this might be. We have recently described a patient who was thought to have Crohn's disease, but at laparotomy, a Meckel's diverticulum was found at the point where the extensive terminal ileal ulceration began. The histological findings in this case were more consistent with chronic inflammation caused by acid secretion from heterotopic gastric epithelium within the diverticulum than with Crohn's disease (unpublished data).The question then arose as to whether there was a real increase in the incidence of Meckel's diverticulum in patients considered to have Crohn's disease or whether this association could, in some cases, be accounted for by acid secretion from the diverticula giving rise to peptic ulceration mimicking Crohn's disease.

A 27‐year‐old woman had a large hepatic tumor and a markedly increased serum alpha‐fetoprotein (AFP) level. A diagnosis of endodermal sinus tumor was made after a needle biopsy was performed on the liver. Clinical and radiologic examinations did not show an alternative primary site. Treatment with cisplatin, etoposide, and bleo‐mycin was started, but, after three cycles, was changed to cisplatin, vincristine, methotrexate, bleomycin, dactino‐mycin, cyclophosphamide, and etoposide because the serum AFP level was decreasing too slowly. After additional chemotherapy was given, the patient was well but had an increased AFP level and a large residual mass in the liver. A right hemihepatectomy was performed, but no viable tumor was present. The patient is alive and disease‐free 5 years later. Thus, AFP levels may be misleading in the presence of large necrotic tumors. The authors stress the need to make a diagnosis of these rare tumors early because aggressive treatment with combination chemotherapy may result in cure. Cancer 1992; 70:2260‐2262.

The varied appearances of starch particles in smears and paraffin sectionsEvidence is presented to show that maize starch particles, usually recognized in histological sections by their Maltese cross birefringence under cross-polarized light, lose this characteristic appearance when transected by the microtome blade. Such particles are, therefore, likely to be overlooked. Though maize starch usually enters the abdomen during surgery, the female genital tract is another possible route from sources such as contraceptive devices. Other types of starch particle have different shapes, sizes and surface markings and these may be distinguished from maize starch by light and electron optical methods.