We investigated the role of neuronal (type I) nitric oxide synthase (nNOS) in NMDA-mediated excitotoxicity in wild-type (SV129 and C57BL/6J) and type I NOS knock-out (nNOS Ϫ/Ϫ ) mice and examined its relationship to apoptosis. Excitotoxic lesions were produced by intrastriatal stereotactic NMDA microinjections (10-20 nmol). Lesion size was dose-and timedependent, completely blocked by MK-801 pretreatment, and smaller in nNOS knock-out mice compared with wild-type littermates (nNOS ϩ/ϩ , 11.7 Ϯ 1.7 mm 3 ; n ϭ 8; nNOS Ϫ/Ϫ , 6.4 Ϯ 1.8 mm 3 ; n ϭ 7). The density and distribution of striatal NMDA binding sites, determined by NMDA receptor autoradiography, did not differ between strains. Pharmacological inhibition of nNOS by 7-nitroindazole (50 mg/kg, i.p.) decreased NMDA lesion size by 32% in wild-type mice (n ϭ 7). Neurochemical and immunohistochemical measurements of brain nitrotyrosine, a product of peroxynitrite formation, were increased markedly in wild-type but not in the nNOS Ϫ/Ϫ mice. Moreover, elevations in 2,3-and 2,5-dihydroxybenzoic acid levels were significantly reduced in the mutant striatum, as a measure of hydroxyl radical production.The importance of apoptosis to NMDA receptor-mediated toxicity was evaluated by DNA laddering and by quantitative histochemistry [terminal deoxynucleotidyl transferasemediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) staining]. DNA laddering was first detected within lesioned tissue after 12-24 hr. TUNEL-positive cells were first observed at 12 hr, increased in number at 48 hr and 7 d, and were located predominantly in proximity to the lesion border. The density was significantly lower in nNOS Ϫ/Ϫ mice. Hence, oligonucleosomal DNA breakdown suggesting apoptosis develops as a late consequence of NMDA microinjection and is reduced in nNOS mutants. The mechanism of protection in nNOS Ϫ/Ϫ mice may relate to decreased oxygen free radical production and related NO reaction products and, in part, involves mechanisms of neuronal death associated with the delayed appearance of apoptosis.

Autoimmune hepatitis (AIH) after liver transplantation (LT) may recur and is difficult to diagnose. Our aims were to define the histopathology of and factors related to AIH recurrence. Fourteen of 475 patients received LT for AIH; 2 died perioperatively. Liver specimens (native and post-LT biopsies) from 12 other patients were reviewed and correlated with pre-and post-LT clinical course and outcome. Recurrent AIH was seen in 5 of 12 patients, 35 to 280 days post-LT as lobular hepatitis with acidophil bodies and lymphoplasmacytic infiltrate. Portal/interface hepatitis was seen with disease progression and 2 of 5 patients developed cirrhosis. Of 7 nonrecurrent patients, 1 had acquired hepatitis C with lobular/portal hepatitis and none developed cirrhosis. Histology suggestive of overlap syndrome was seen in 3 of 12 native livers with no effect on post-LT course or pathology. High-grade necroinflammation was present in native livers at LT in 5 of 5 cases with recurrent AIH and in 1 of 7 without recurrence (P < .01). Pre-LT disease duration, donor/recipient gender distribution, HLA studies, and rejection episodes did not correlate with AIH recurrence. We conclude that (1) recurrent AIH is not uncommon and was seen in 42% of patients with lymphoplasmacytic lobular, portal, and interface hepatitis; (2) acidophil bodies with lymphoplasmacytic cells are seen in early recurrent AIH; (3) recurrent AIH appears at variable time periods post-LT, and the progression is slow; and (4) high-grade inflammation in native liver at LT is a strong predictor of recurrent AIH. (HEPATOLOGY 2000;32:185-192.)

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Collagenous colitis (CC) and lymphocytic colitis (LC) are clinical syndromes characterized by the presence of chronic watery diarrhea, few or no endoscopic abnormalities and biopsies that typically show normal crypt architecture, increased mononuclear inflammation in the lamina propria, absence of neutrophils, and increased intraepithelial lymphocytes. Patients with CC also have a thickened subepithelial collagen layer. We have noted, anecdotally, that biopsy specimens from some patients with CC or LC contain certain histologic features, such as Paneth cell metaplasia (PM), that are normally seen in inflammatory bowel disease (IBD), or other types of healed colitis, and thus may cause diagnostic difficulty. Therefore, the purpose of this study was to evaluate the prevalence and significance of IBD-like morphologic features in colonic mucosal biopsies from patients with CC or LC. Five hundred thirty-one routinely processed hematoxylin and eosin-stained colonic mucosal biopsies from 150 patients with clinically, endoscopically, and histologically confirmed CC (79 patients, male/female ratio: 14/65, mean age: 60 yr) or LC (71 patients, male/female ratio: 13/58, mean age: 55 yr) were evaluated in a blinded fashion for a variety of histologic features, including active crypt inflammation (cryptitis +/- crypt abscess), surface ulceration, Paneth cell metaplasia, crypt architectural irregularity, number of intraepithelial lymphocytes, and thickness of the subepithelial collagen layer (CC only). The results were compared between CC and LC and correlated with the clinical and endoscopic data. None of the patients had or developed IBD during the study period. Active crypt inflammation was a common finding in both groups, seen in 24 of 79 CC patients (30%) and 27 of 71 LC patients (38%). Surface ulceration was not seen in any of the LC biopsies but was present in 2 of 79 (2.5%) CC patients. Paneth cell metaplasia was frequent in both groups and significantly more common in CC compared with LC patients. Forty-four percent of CC patients, but only 9 of 63 (14%) of LC patients had Paneth cell metaplasia (p <0.001). Crypt architectural irregularity, although rare, was present in 6 of 79 patients with CC (7.6%) and 3 of 71 (4.2%) patients with LC. In patients with CC, the presence of Paneth cell metaplasia was associated with more severe disease characterized by the presence of abdominal pain (p <0.001) and a higher frequency of bowel movements (>3 bowel movements/day) (p = 0.06). Also, active crypt inflammation correlated with antibiotic use at the time of clinical presentation (p = 0.04) and was present in the only two patients who had positive stool cultures (one each for and ). However, none of the other histologic findings correlated with any of the other clinical or endoscopic features, such as type of symptoms, stool consistency, type of medical treatment, associated autoimmune diseases or outcome (complete, partial, or no resolution) in either group of patients. Pathologists should be aware that some histologic features ...

1 Valproic acid, useful in the treatment of migraine, is an inhibitor of y-aminobutyric acid (GABA) aminotransferase and activator of glutamic acid decarboxylase. Its mechanism in migraine remains obscure. The effects of valproic acid (2-propylpentanoic acid) were examined on the number of cells expressing c-fos-like immunoreactivity (c-fos-LI), a marker of neuronal activation, within the trigeminal nucleus caudalis (lamina I, Io; TNC) 2 h after intracisternal injection of the irritant, capsaicin (0.1 ml; 15.25 yg ml-'), in urethane-anaesthetized Hartley guinea-pigs. Positive

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We conducted this retrospective study to evaluate the relationship between symptoms, histological findings, and treatment of collagenous (CC) and lymphocytic colitis (LC). We identified 19 CC and 12 LC patients having multiple colonoscopic procedures with colonic biopsies during their course of illness. A detailed histological review of all biopsies was performed. Clinical history, including symptoms and medications, was obtained in 25 of the 31 patients and was correlated with their histological findings. In all, 25% of the CC patients and 50% of the LC patients who had biopsies prior to their definitive diagnosis had the pathognomonic histological features on their prior biopsies to some extent (but were not recognized by the pathologists); however, these features were more pronounced on the biopsies from the procedure that established the diagnosis. Nonetheless, 10 of 12 such patients with clinical data available had symptoms and were being treated at the time of prior biopsies. Assessment of the relationship among histological, clinical and therapeutic data showed no association between symptoms or histological findings and treatment with any medication. In summary, in this sample of CC and LC patients, symptoms often precede fully developed histological features. No change in symptoms or histological findings was found to be associated with medication.

Lymphocytic colitis (LC) and collagenous colitis (CC) are diseases characterized by the presence of marked intraepithelial lymphocytosis. Both of these disorders affect primarily the colon. However, involvement of the distal small intestine has not been systematically studied. The purpose of this study was to evaluate the type and degree of intraepithelial lymphocytosis in the terminal ileum of patients with LC or CC. Terminal ileal mucosal biopsies from 22 patients with LC (male/female ratio 0.22, mean age 47 years) and 23 with CC (male/female ratio 0.43, mean age 54 years) were evaluated for the number of intraepithelial lymphocytes (IEL) per 100 epithelial cells (EC) both in the villi and crypts. The results were compared with 30 patients with inflammatory bowel disease (16 with Crohn's disease [CD], 14 with ulcerative colitis [UC]) and 24 patients (male/female ratio 0.33, mean age 44 years) without colonic pathology as normal controls. None of the patients had celiac sprue. Paired terminal ileum and colonic mucosal biopsies from 6 patients with LC, 4 with CC, 5 with CD, 5 with UC, and 10 normal controls were also immunohistochemically stained with monoclonal antibodies to CD3, CD8, CD20, and a class II MHC antigen (LN3-HLA-DR). In the villi the IEL count/100 EC was 11.8 +/- 1.8 in LC and 10.3 +/- 1.9 in CC (p = 0.3). These values were both significantly higher than in CD (2.8 +/- 0.4, p <0.001), UC (3.1 +/- 0.4, p <0.001), or normal controls (2.2 +/- 0.2, p <0.001). In the crypts the IEL count was 3.8 +/- 0.5 in LC and 3.2 +/- 0.5 in CC (p = 0.3). These values were also significantly higher than in CD (2.3 +/- 0.4, p = 0.02), UC (2.1 +/- 0.3, p = 0.02), or normal controls (1.5 +/- 0.2, p <0.001). The presence of >5 IELs/100 EC in terminal ileum biopsies was highly specific for LC and CC (specificity 98%, sensitivity 73% and 56% for LC and CC, respectively). The IEL phenotype was similar in all groups of patients and in the ileum and colon of individual patients. Intraepithelial lymphocytes were CD3+, CD8+, CD20-, and LN3-HLA-DR-, indicative of a suppressor T-cell phenotype. Intraepithelial lymphocytosis occurs in the terminal ileum in patients with LC or CC and may be helpful in diagnosing these conditions and distinguishing LC or CC from CD or UC in diagnostically difficult cases. The results suggest that the terminal ileum may be involved by a similar pathogenic process as the colon in LC and CC.