Jesús Aguirre-García

Role of neutrophils in innate resistance to Entamoeba histolytica liver infection in mice

In order to define the role of neutrophils in the innate resistance to Entamoeba histolytica liver infection in mice, we examined the pattern of liver lesion induced by direct injection of E. histolytica trophozoites in normal mice and in neutrophil‐depleted mice. A variety of histological lesions were found, the extent of liver damage was considerably higher in the neutrophil‐depleted mice. Livers from neutrophil‐depleted mice displayed areas of liquefactive (lytic) necrosis containing a large number of amoebae and absence of neutrophils or mononuclear cells. By contrast, in the liver of normal mice, neutrophils were seen associated to E. histolytica at early stages of infection. In both mouse groups, areas of TUNEL‐positive dead hepatocytes were observed and a characteristic internucleosomal banding pattern of genomic DNA consistent with apoptosis was detected in DNA harvested from amoebic liver lesions. These data suggest that neutrophils play an important role in the mechanisms of resistance to amoebic liver infection in mice. In addition, our histological analysis suggests that E. histolytica is capable of producing liver damage in the absence of inflammatory cells.

Age and Severity of Mucosal Lesions Influence the Performance of Serologic Markers in Helicobacter pylori–Associated Gastroduodenal Pathologies

Objective: The course of Helicobacter pylori infection and antibody response to CagA in patients with preneoplastic lesions and gastric cancer has not been thoroughly studied. We aimed to study H. pylori infection and antibody response to CagA in patients with non–atrophic gastritis, preneoplastic lesions, and gastric cancer. Methods: We studied patients attending one Oncology Hospital and one General Hospital in Mexico City. Diagnosis was based on endoscopy and histopathology in biopsies from six stomach regions. H. pylori infection was assessed by histology and serology, and antibodies against CagA were measured with immunoassay. Results: We included 618 patients, 368 with non–atrophic gastritis, 126 with precancerous lesions, and 65 with gastric cancer; in addition, 59 patients with duodenal ulcer were studied. Detection of infection and IgG against CagA had a significant increase from non–atrophic gastritis to mild and up to advanced stages of metaplasia (P < 0.05), followed by decreased infection and IgG to CagA in patients with gastric cancer (P < 0.05). However, infection and CagA antibodies were associated with young gastric cancer cases. Duodenal ulcer showed a significant association with infection detected by histology and serology, particularly among women, and a trend to associate with IgG to CagA. Conclusions: This study shows that H. pylori infection and CagA are risk markers for intestinal metaplasia. The prevalence of these risk markers decreases in gastric cancer, probably reflecting that infection decreases after advanced atrophy and metaplasia in the gastric mucosa. State of the disease, age, and sex influence the association of H. pylori infection and IgG response to CagA with gastroduodenal diseases. (Cancer Epidemiol Biomarkers Prev 2008;17(9):2498–504)

Entamoeba histolytica: acute granulomatous intestinal lesions in normal and neutrophil-depleted mice

To study the role of neutrophils in the innate resistance to Entamoeba histolytica intestinal infection in mice, animals were treated with anti-neutrophil monoclonal antibodies prior to intracecal parasite inoculation and the resulting lesions were compared with normal mice that had been equally infected. In contrast to our previous finding that neutrophils are critical in eliminating E. histolytica infection in the liver, we show here that neutrophils are not absolutely required to eliminate E. histolytica infection from the intestine. Although the neutrophils are not critical for resolution of the E. histolytica infection, neutrophils do appear to provide some measure of protection as the intestinal amoeba burden was higher at early timepoints after infection in the neutropenic animals. In addition, we found that while both the normal and the neutrophil-depleted mice developed ulcerative lesions in the colon, the neutropenic mice had an increased frequency of granulomas that formed around the amoeba. Thus, our findings appear to be the first evidence showing that granulomatous inflammation can occur after intestinal infection in mice using axenically cultured amoeba.

Reproducibilidad del diagnóstico histopatológico de lesiones precursoras del carcinoma gástrico en tres países latinoamericanos

Objective. The aim was to evaluate the concordance in the diagnosis of precursor lesions of intestinal-type gastric carcinoma among observers with different levels of experience. Material and Methods. Gastric biopsies from 1 056 cases were studied: 341 from Colombia, 382 from Mexico, and 333 from Paraguay. Pathologists without experience (A) and with experience (B) in gastrointestinal pathology, as well as experts working in an international reference center (C) participated in the diagnosis of each case. Results. The concordance (k) between pathologists with experience and those without was poor for the diagnosis of atrophic gastritis (k=0.04 to 0.12) and dysplasia (k=0.11 to 0.05), and good for the diagnosis of intestinal metaplasia (k=0.52 to 0.58). Supervision of pathologists without experience by those with experience remarkably improved the concordance in the diagnosis of atrophic gastritis (k=0.65) and intestinal metaplasia (k=0.91), and to a lesser degree, of dysplasia (k=0.28). The concordance among experts before and after the consensus meeting showed no variation in the diagnosis of atrophic gastritis (k=0.57); the concordance varied from good to excellent in the diagnosis of intestinal metaplasia (k=0.67 to 0.81) and from poor to good in that of dysplasia (k=0.18 to 0.66). Conclusion. The greatest differences arose

In vivo assessment of liver fibrosis using diffuse reflectance and fluorescence spectroscopy: A proof of concept

A novel application of diffuse reflectance and fluorescence spectroscopy in the assessment of liver fibrosis is here reported. To induce different stages of liver fibrosis, a sufficient number of male Wistar rats were differentially exposed to chronic administration with carbon tetrachloride. Then, diffuse reflectance and fluorescence spectra were in vivo measured from the liver surface of each animal by a minimal invasive laparoscopic procedure. The liver fibrosis degree was conventionally determined by means of histological examination using the Masons Trichrome stain, accompanied by hepatic expression of α-sma, and evaluation of the ALT/AST serum levels. The liver from rats exhibiting higher grades of fibrosis showed a significant increase in diffuse reflectance and fluorescence intensity when compared with control animals. At 365 nm, the diffuse reflectance spectrum exhibited an increase of 4 and 3-fold in mild and advanced fibrotic rats, respectively, when compared to the control group. Similarly, the fluorescence emission at 493 nm was 2-fold higher in fibrotic animals than in controls. By using fluorescence intensity, discrimination algorithms indicated 73% sensitivity and 94% specificity for recognition of hepatic fibrosis, while for diffuse reflectance, these values increased up to 85% and 100%, respectively. Taking into consideration there is a special need for developing new diagnostic approaches focused on detecting different stages of liver fibrosis with minimal invasiveness, these results suggest that diffuse reflectance and fluorescence spectroscopy could be worthy of further exploration in patients with liver disease.

Liver exhibits thermal variations according to the stage of fibrosis progression: A novel use of modulated‐differential scanning calorimetry for research in hepatology

Liver fibrosis results in a disproportion of the hepatic composition and architecture, characterized by a progressive accumulation of fibrillar proteins at the liver parenchyma. Modulated‐differential scanning calorimetry (mDSC) is an experimental methodology able to determine the specific thermal signature from any biological substance, based on the variation in heat flow and heat capacity. As these physicochemical properties are directly influenced by compositional and structural changes, we decided to study the thermal behavior of the liver during fibrosis using mDSC.

Pathology, Pathogenesis, and Experimental Amebiasis

The most important feature of the pathology of human amebiasis is the greatly destructive nature of the anatomical lesions produced by the protozoan Entamoeba histolytica. Recent advances on the knowledge of biochemistry, immunology, cellular and molecular biology, and genetics of this parasite, added to the use of different in vitro, in vivo, and ex vivo models to analyze host–parasite interactions or the production of intestinal and extraintestinal amebic lesions, all have given a better perception of the mechanisms of pathogenesis in amebiasis. The present chapter is divided into three parts: first, a general review of the pathology of human amebiasis; second, a short review of the mechanisms of invasion and production of damage in the host, and third, a review of the different in vivo experimental models currently available to study the mechanisms involved in amebic infection. In reference to pathogenesis, each factor, molecule or gene, or mechanism of target cell damage is reviewed individually in other chapters of this section on “Pathogenesis and Immunity” in the present book. Therefore, the meticulous or probing aspects of the studies are mentioned by each responsible and expert group of researchers. In this review, we mention in general each of the different factors of pathogenesis in amebiasis. The contributions obtained using different techniques and methodologies of experimental models are emphasized, and the subjects that still need to be unraveled to understand how this microscopic parasite has earned its well-deserved “histolytic” name are discussed.