Cyrus R. Kapadia

Laser-induced fluorescence spectroscopy of human colonic mucosa: Detection of adenomatous transformation

To evaluate the potential of laser-induced fluorescence spectroscopy for the detection of premalignant lesions of the gastrointestinal tract, the hypothesis that adenomatous transformation of colonic mucosa results in an alteration of laser-induced fluorescence that enables its differentiation from normal or hyperplastic tissue was tested. A fiberoptic catheter coupled to a helium-cadmium laser (325 nm) and an optical multichannel analyzer were used to obtain fluorescence spectra (350-600 nm) from 35 normal colonic specimens and 35 resected adenomatous polyps. A score based on six wavelengths was derived by stepwise multivariate linear regression analysis of the spectra. The mean score (+/- SEM) was + 0.86 +/- 0.06 for normal mucosa and -0.86 +/- 0.06 for adenomatous polyps (P less than 0.001). Spectra from an additional 34 normal specimens, 16 adenomatous polyps, and 16 hyperplastic polyps were prospectively classified with accuracies of 100%, 100%, and 94%, respectively. The mean score for hyperplastic polyps was significantly different from adenomatous (P less than 0.001) but not from normal tissue. Thus, quantitative analysis of fluorescence spectra enables the detection of adenomatous transformation in colonic mucosa.

gastric Atrophy, Metaplasia, and Dysplasia : a Clinical Perspective

Abstract Gastric carcinoma of the intestinal type originates in dysplastic epithelium, which in turn develops in the milieu of atrophic gastritis and intestinal metaplasia. Cancers also may develop less often from gastric adenomatous polyps, which represent dysplastic epithelium arising in a raised lesion. The main causes of chronic atrophic gastritis and gastric atrophy are autoimmune due to pernicious anemia or chronic Helicobacter pylori infection. In the former condition, there is severe atrophy of the corpus (oxyntic mucosa), with the antrum being speared. In contrast, chronic atrophic gastritis consequent to H. pylori infection is a multifocal pangastritis, involving independent foci in the corpus and antrum of the stomach. For the most part, these clinical conditions are silent; the only manifestation of both these forms of chronic atrophic gastritis is cobalamin (vitamin B12) deficiency. In the case of the autoimmune gastritis of pernicious anemia, cobalamin deficiency results form the absence of intrinsic factor. When cobalamin deficiency occurs in patients with H. pylori‐related gastritis, for the most part, it is because these patients have hypochlorhydria and are therefore unable to release cobalamin from its bound form in food. Patients may have advanced neuropsychiatric manifestations of cobalamin deficiency and yet not be anemic, have a normal blood smear, and even have serum cobalamin levels in the normal range. The condition may be identified by demonstrating elevated levels of homocysteine and methylmalonic acid. Intestinal metaplasia may be of the enteric (grade I), enterocolic (grade II), or colonic (grade III) type. Grade III intestinal metaplasia has traditionally been thought of as the most sinister variety, although the extent of atrophy and metaplasia may be a better marker for premalignancy than the mere identification of small areas of grade III intestinal metaplasia. Over the years, there has been much disagreement and a high degree of interrater variability, especially between Western and Japanese pathologists, as to the different grades of dysplasia and early gastric cancer. Recent consensus conferences at Vienna and Padova have resulted in better understanding of what constitutes these lesions, and it is hoped that in the near future agreement between pathologists will improve as a consequence. For the present, it is imperative that clinicians obtain second opinions from two or more expert pathologists on biopsy specimens before arriving at a diagnosis of either low‐ or highgrade dysplasia. The former histologic diagnosis is tantamount to subjecting the patient to endoscopic surveillance and the latter is tantamount to a decision regarding the resection of the lesion, both decisions being psychologically disturbing for patients. At this time, population screening for H. pylori is not recommended in Western countries, but most experts would agree that H. pylori should be eradicated if detected as part of the appropriate investigation of a clinical disorder such as dyspepsia. Certain other specific conditions may also be considered to be precancerous, such as the gastric remnant after a partial gastrectomy and the gastric mucosa in familial adenomatous polyposis syndrome and in familial Peutz‐Jeghers syndrome and perhaps Ménétrier disease.

Intrinsic Factor-mediated Absorption of Cobalamin by Guinea Pig Ileal Cells

To investigate the fate of intrinsic factor and cobalamin during cobalamin absorption, we incubated enterocytes isolated from guinea pig ileum for periods of up to 30 min with (57)Co-labeled cyano-cobalamin bound either to human intrinsic factor or to rabbit intrinsic factor biosynthetically labeled with [(35)S]methionine. When the labeled complex was incubated for 30 min with isolated ileal cells under conditions that block cellular metabolism, virtually all cellular radioactivity could be removed by washing the cell surface with EDTA or acid. In contrast, washing removed only half the radioactivity from cells incubated at 37 degrees C in O(2). When residual cellular radioactivity was extracted and analyzed by gel filtration, 80-94% of both the (35)S and (57)Co radioactivity eluted in the same fractions as the original complex. The remaining 6-20% eluted as free [(57)Co]cobalamin or [(35)S]methionine. To examine events occurring after 30 min, we instilled into tied-off ileal loops of intact guinea pigs radiolabeled intrinsic factor-cobalamin complex and extracted nondissociable radioactivity 2-4.5 h later. The proportion of extracted (57)Co eluting as free cobalamin increased to 39-46%, that eluting as intrinsic factor-cobalamin complex declined to 22-45%, and 9-34% now eluted as a macromolecule that reacted with antitranscobalamin II antibody but not antiintrinsic factor antibody. Extracted (35)S radioactivity eluted in several peaks in addition to the intrinsic factor peak. These findings suggest that (a) after reversible attachment of intrinsic factor-cobalamin complex to its ileal surface receptor, an energy-dependent process prevents removal of the complex from the cell surface by EDTA or acid; (b) cobalamin dissociates from intrinsic factor and, as suggested by previous workers, binds to a molecule antigenically similar to transcobalamin II; and (c) intrinsic factor is slowly degraded and forms breakdown products that are detectable in ileal extracts.

Differences in laser-induced autofluorescence between adenomatous and hyperplastic polyps and normal colonic mucosa by confocal microscopy

Laser-induced autofluorescence has been used to discriminate normal from adenomatous colonic mucosa. However, few studies to date have studied the origin of colonic autofluorescence. Using confocal microscopy (excitation wavelength 488 nm), we have shown that autofluorescence at this wavelength is present predominantly in the lamina propria of normal mucosa but in the epithelium in adenomatous and hyperplastic polyps. The intensity ratio of epithelial cell to lamina propria fluorescence was significantly lower (P<0.0001) in normal mucosa (0.52±0.01) compared with either adenomatous (1.6±0.2) or hyperplastic polyps (1.7±0.15). However, the ratios were not significantly different between hyperplastic and adenomatous polyps. Thus, confocal microscopy enables the detection of the sites of autofluorescence within colonic mucosa and the quantitation of differences in fluorescence between different tissue types.

Free Intrinsic Factor in the Small Intestine in Man

Human jejunal and ileal contents and ileostomy effluents were examined for the presence of free intrinsic factor. This was detected in 9 out of 10 jejunal and three out of five ileal aspirates and in one of three ileostomy effluents studied. The intrinsic factor in the ileal effluent was shown to be physiologically active. The presence of free intrinsic factor in the small intestine has considerable physiological significance in maintaining the enterophepatic circulation of vitamin B12. It would also permit the absorption of any free vitamin B12 produced by ileal bacteria.

Intestinal pseudoobstruction in acute Lyme disease: a case report

We report here a case of acute Lyme disease in a 61-yr-old man who developed a facial nerve paralysis and a relentless intestinal pseudoobstruction 2 wk after the initial prodrome. Both the facial nerve paralysis and pseudoobstruction persisted for a month until the patient sought medical attention. Both lesions resolved only after treatment for Lyme disease was initiated. The temporal association of the pseudoobstruction with the somatic cranial neuropathy and the response of both to specific therapy for Lyme disease suggest that the former was likely the result of a reversible autonomic neuropathy or dysfunction.

Active absorption of vitamin B12 and conjugated bile salts by guinea pig ileum occurs in villous and not crypt cells

We isolated highly enriched fractions of villous and crypt cells from guinea pig intestine to determine whether this preparation provided a suitable model for comparing the transport of cobalamin and conjugated bile salts by these cell populations. The uptake of [57Co] cyanocobalamin by ileal villous cells was 30-fold greater when incubated with cobalamin bound to intrinsic factor than with free cobalamin. Intrinsic factor-mediated uptake of cobalamin could not be demonstrated using ileal crypt or jejunal villous or crypt cells. When incubated with [3H] taurocholate, the uptake by ileal villous cells was significantly greater than by ileal crypt or jejunal villous cells. These results indicate the suitability of using isolated guinea pig villous and crypt cells to examine transport processess of molecules that involve specialized mechanisms. The results also demonstrate that the undifferentiated crypt cell lacks specific transport processes necessary for the active absorption of cobalamin and taurocholate.

Evidence for involvement of cyclic nucleotides in intrinsic factor secretion by isolated rabbit gastric mucosa.

Secretion of intrinsic factor (IF) has previously been demonstrated in isolated rabbit fundic mucosa maintained in organ culture. We have now investigated the possibility that cyclic nucleotides may play a role in IF secretion. A phosphodiesterase inhibitor, 3-isobutyl methylxanthine (IBMX), stimulated IF secretion nearly fourfold while increasing tissue levels of both cyclic AMP (cAMP) and cyclic GMP (cGMP). Peak IF secretion in response to IBMX was not reached until after tissue cAMP levels were maximal. Dibutyryl cAMP and 8-Br-cAMP increased secretion by the same order of magnitude as did IBMX, whereas corresponding analogues of cGMP had no such effect. Histamine increased secretion of IF. In the presence of 40 microM IBMX, histamine elevated tissue levels of cAMP, but not of cGMP, and the stimulating effect of 10 microM histamine on IF secretion was potentiated. An H2 receptor antagonist, cimetidine, blocked the increases in IF secretion and tissue cAMP levels due to histamine, and the increase in IF secretion due to IBMX. These observations are consistent with a role for cAMP in the secretion of IF by isolated gastric mucosa.

Ultrastructure and localization of substance P and met-enkephalin immunoreactivity in the human fetal gastric antrum

SummaryThe ultrastructural localization and relations of substance P- and met-enkephalin-labeled neuronal structures were examined in the wall of the human gastric antrum during early fetal life. By 14–16 weeks of gestation, clearly discernable neural plexuses and a well developed external muscle coat were present. In the submucous coat, neural plexuses varied from immature forms consisting of 1–4 neurites partially enveloped by Schwann cell processes to more mature plexuses where neurons were completely enclosed by Schwann cell processes. Neuronal profiles with substance P- and met-enkephalin-like immunoreactivities were observed in the submucous plexus. In the myenteric plexus met-enkephalin-like immunoreactivity was seen within cell bodies and neurites. By contrast, although substance P-like immunoreactivity was observed in neurites in the myenteric plexus, no substance P-labeled somata could be identified. Unlabeled terminals were seen in contact with both unlabeled dendrites and met-enkephalinergic neurons. An increase in electron density was observed at the sites of contact. These structures probably represent early stages in the development of synaptic specializations. In addition, met-enkephalin-labeled varicosities were seen in apposition to smooth muscle cells of the circular muscle coat. This suggests that antral smooth muscle cells are directly innervated by met-enkephalin neurons.

Oxides, Onions, and Other Matters Gastrointestinal-1996-A Perspective

A selection of landmark articles for a given year in any subject risks being somewhat subjective, and subjectivity is best avoided in scientific endeavor. However, the very nature of such a selection process invites judgment. Like most judges, I, too, claim to avoid conscious bias, but no one who has ever graced the bench can claim that at the subconscious level personal bias has never crept into a decision. Similarly, deep down in the vault of my subconscious, I love a maverick. That perhaps explains why so many articles that challenge long-held beliefs have especially found favor. Among them are those that question the strength of the association of Helicobacter pylori with gastric cancer, the usefulness of surveillance endoscopy in patients with Barretts esophagus, a randomized trial that casts doubt on the preeminence of laparoscopic cholecystectomy, and a metaanalysis that concludes that corticosteroids may not be nearly as good for alcoholic hepatitis as we were once told. I have tried to resist the temptation to be too laudatory of technologic advancement, unless the benefit to the patient of such technology has been defined clearly. Thus, of all of the new technologies (endoscopic retrograde choledochopancreatography is no longer a new technology), only endoscopic ultrasonography finds a place. Articles that assess preventive strategies and are in the realm of epidemiology have received mention. All in all, 1996 was not a spectacular year for major therapeutic advances. In contrast, some notable advances have been made in the laboratory, and perhaps the most important has to do with the role of nitric oxide both in the regulation of normal function and in the genesis of disease.