Bomb calorimetry, the gold standard for assessment of intestinal absorption capacity: normative values in healthy ambulant adults.

BACKGROUND: Intestinal absorption capacity is considered to be the best method for assessing overall digestive intestinal function. Earlier reference values for intestinal function in healthy Dutch adults were based on a study that was conducted in an inpatient metabolic unit setting in a relatively small series. The present study aimed to readdress and describe the intestinal absorption capacity of healthy adults, who were consuming their usual (Western European) food and beverage diet, in a standard ambulatory setting. METHODS: Twenty-three healthy subjects (aged 22-60 years) were included in the analyses. Nutritional intake (energy and macronutrients) was determined with a 4-day nutritional diary. Subsequently, mean faecal losses of energy (by bomb calorimetry), fat, protein and carbohydrate were determined following a 3-day faecal collection. Finally, intestinal absorption capacity was calculated from the differences between intake and losses. RESULTS: Mean (SD) daily faeces production was 141 (49) g (29% dry weight), containing 891 (276) kJ [10.7 (1.3) kJ g(-1) wet faeces; 22.6 (2.5) kJ g(-1) dry faeces], 5.2 (2.2) g fat, 10.0 (3.8) g protein and 29.7 (11.7) g carbohydrates. Mean (SD) intestinal absorption capacity of healthy subjects was 89.4% (3.8%) for energy, 92.5% (3.7%) for fat, 86.9% (6.4%) for protein and 87.3% (6.6%) for carbohydrates. CONCLUSIONS: The present study provides normative values for both stool nutrient composition and intestinal energy and macronutrient absorption in healthy adults on a regular Dutch diet in an ambulatory setting. Intestinal energy absorption was found to be approximately 90%.

Systematic analysis of esophageal pressure topography in high-resolution manometry of 68 normal volunteers.

The introduction of high-resolution manometry (HRM) has been a significant advance in esophageal diagnostics. Normative values however are currently based upon a single set of published reference values, and multiple new metrics have been added over the past several years. Our goal was to provide a second set of 'normal-values' and to include all current metrics suggested by the 2012 Chicago classification. Sixty-eight subjects without foregut symptoms or previous surgery (median age 25.5 years, ranging from 20-58 years, 53% female) underwent esophageal motility assessment via an established standardized protocol. Normative thresholds were calculated for esophago-gastric junction (EGJ) characteristics (resting, relaxation, intrabolus pressure, and lengths) as well as for esophageal body strength (contraction amplitudes at multiple levels, distal contractile integral, integrity of peristalsis) and wave propagation (contractile front velocity, distal latency). Overall, our findings where strikingly similar to the previously described metrics derived from 75 control subjects of the Northwestern group. This suggests a high degree of reproducibility of HRM.

Hiatal hernia and disorders of the spine: a historical perspective.

Our understanding of esophageal disease and the foregut has evolved over the past 100 years, especially in recent times. Modern diagnostic technologies and new management paradigms have provided progressive insights into the anatomy, physiology, and normal and abnormal function of the esophagus, as well as improving patient care. Yet, the relationship between the esophagus and its close neighbor, the spine, is rarely discussed and likely underappreciated. Anatomic proximity and intertwined pathophysiology led early investigators to postulate relationships between esophageal disease and spinal abnormalities. More recent studies have illustrated a link between spinal disease and hiatal hernias. Objective radiographic measurements of kyphoscoliosis have correlated with increased hiatal hernia formation. Spinal abnormalities and disease of the esophageal hiatus are becoming more common in our aging population, with each carrying significant risk of morbidity and decreased quality of life. Operative planning and subsequent hiatal hernia repair must be undertaken in the context of these spinal abnormalities. A historical review of past publications related to the subject forms the basis for this publication, thus revealing insight and improving our understanding of the association between spinal abnormalities and hiatal hernias.

Assessment of small bowel function in critical illness: potential role of citrulline metabolism.

Small intestinal function in critically ill patients should ideally be assessed in order to determine the preferred feeding route, timing, and composition of enteral nutrition. Additionally, evaluation of small bowel function may lead to new insights aimed to maintain enterocyte integrity. Critically ill patients are likely to have impaired enterocyte function mainly as a consequence of diminished splanchnic blood flow associated with mucosal hyperpermeability and bacterial translocation, a pathological state believed to be pivotal in the development of sepsis and multiple organ dysfunction syndrome (MODS). However, feasible and validated clinical tools to reliably assess enterocyte function are lacking. This explorative review discusses the promising role of citrulline, a nonprotein amino acid almost exclusively generated by the enterocyte, as a biomarker reflecting enterocyte function in critically ill patients. Citrulline metabolism, its potential as enterocyte biomarker, and literature on citrulline in critically illness will be discussed. Finally, a novel test for enterocyte function, the citrulline generation test (enterocytic citrulline production upon stimulation with enteral or intravenous glutamine) will be considered briefly.

Recognition of the alternatively spliced segments of fibronectin by the RCJ 3.1C5.18 chondrocytic rat cell line.

OBJECTIVES: To define, for the C5.18 chondrocyte-restricted rat cell line, (1) the capacities for recognition of alternatively spliced segments of the adhesion protein fibronectin (FN), (2) the integrin subunits required for such recognition, and (3) differences in such FN recognition vs the multipotential chondroprogenitor line, RCJ 3.1. METHODS: C5.18 and RCJ 3.1 cells were tested for their capacities to adhere to recombinant alternatively spliced segments of rat FN, presented on plastic surfaces either in isolation or in partial FNs spanning the 7th through 15th type III repeats (III7-15 FNs). The effects on such adhesion of cations and integrin subunit-specific antibodies were tested. RESULTS: Despite significant augmentation in chondrocyte-specific gene expression in C5.18 relative to the RCJ 3.1 cells, the two lines exhibited similar recognition of FN spliced segments and partial isoforms. Specifically, both lines adhered to the extra type III repeat A (EIIIA) and V, but not extra type III repeat B (EIIIB), segments. There were different cation and integrin subunit requirements for adhesion to EIIIA vs V segments, and only the V segment was recognized in the context of a III7-15 FN. Such recognition was mediated via a "second" arginine-glycine-aspartic acid (RGD) sequence that is present in the V95 subsegment in rat, but not human, FN. CONCLUSION: The chondrocyte lineage-committed C5.18 cell line, similar to its multipotential chondroprogenitor, RCJ 3.1, recognizes the "cartilage-restricted" EIIIA and V segments of FN with cation, integrin, and molecular context requirements that are specific to each of these segments.

Heterophile reactive antigen in infectious mononucleosis.

Specific heterophile reactive antigen has been localized by means of indirect immunofluorescence in 12 of 13 kidney biopsy specimens obtained during the acute phase of infectious mononucleosis. I feel that this may represent the identification of infectious agent antigen. Evidence is also presented for the possible existence of two different strains of the agent of infectious mononucleosis.

Future developments in total Barrett's eradication: the surgeon's view.

Endoscopic therapies for the treatment of complicated Barret's esophagus should be embraced by the surgical community. While esophagectomy remains the standard of care for early esophageal neoplasia in many centers, endoscopic techniques are being increasingly utilizid. As refinements in both endoscopic and surgical approaches continue to evolve, accurate and contempary assessments of outcomes are critical in assuring that each is applied in appropriate circumstances.

Endoscopic and symptomatic assessment of anastomotic strictures following esophagectomy and cervical esophagogastrostomy.

BACKGROUND: Dysphagia following esophagectomy with cervical esophagogastric anastomosis is common and often can be attributed to anastomotic stricture. The prevalence, risk factors, symptomatic and endoscopic severity, and response to dilation of such strictures, however, are poorly defined. METHODS: In the present study the population consisted of 42 patients undergoing esophagectomy with gastric pull-up and cervical anastomosis. Any complaint of postoperative dysphagia was investigated with upper endoscopy. Patients undergoing endoscopy were entered into a prospective randomized trial of graduated balloon versus bougie-over-a-guidewire dilation that will be part of a future report. Dysphagia was assigned a standardized severity score, and stricture diameter pre-dilation was classified as minimal (>12 mm), mild (9-12 mm), moderate (5-8 mm), or severe (<5 mm). Outcome measures included the incidence, time to first dilation, symptomatic and endoscopic severity of anastomotic strictures, number of dilations, and influence of co-morbidities and anastomotic technique on stricture occurrence. RESULTS: Twenty-seven of 41 (66%) surviving patients underwent endoscopy and dilation. Median time to presentation was 2.4 months (min, 27 days; max, 11 months). Most patients (63%) with stricture complained of dysphagia with every meal. The majority (93%) of strictures were mild to moderate (5-12 mm), and there was no correlation between dysphagia frequency and stricture size. Tolerance of an unrestricted diet decreased with increasing stricture severity. In all, 98 dilation sessions were performed without complication. A higher stricture rate was noted following handsewn anastomoses as compared to combined stapled and handsewn anastomoses (85.7% versus 55.5%; p = 0.044). CONCLUSIONS: Most patients with symptomatic anastomotic strictures following esophagectomy with cervical esophagogastrostomy present within the first few months following surgery. Half of such strictures are minimal to mild as endoscopically assessed. Dilation is safe, and most patients experience symptomatic relief after only a few dilation sessions. A combined handsewn and stapled anastomosis may decrease the risk of stricture formation relative to a two-layer handsewn technique.

Leptin analog antagonizes leptin effects on food intake and body weight but mimics leptin-induced vagal afferent activation.

A recombinantly produced murine leptin analog (MLA) antagonizes leptin-induced signaling in cell lines that express the long form of the leptin receptor. However, the effects of MLA on the activity of leptin-sensitive neurons and on central neural controls of food intake have not been reported. Here we report effects of MLA on food intake and body weight in adult rats and on the activity of cultured rat vagal afferent neurons. Daily intracerebroventricular coinjection of MLA with exogenous leptin significantly attenuated leptin-induced reduction of 48-h food intake and body weight. Coinjection of MLA with leptin also reduced leptin-induced phosphorylation of signal transducer and activator of transcription 3 (STAT3) in the hypothalamus. In addition, chronic intracerebroventricular MLA infusion over 14 d via osmotic minipumps significantly increased daily food intake, rate of body weight gain, fat-pad mass, and circulating plasma leptin concentrations. Surprisingly, however, MLA did not antagonize leptin-evoked increases in cytosolic calcium concentrations in vagal afferent neurons in primary culture. Rather, MLA itself produced acute activation selectively in leptin-responsive vagal afferent neurons. These data suggest that MLA is an antagonist for the central effects of leptin on food intake and body weight but an agonist at sites where leptin induces acute neuronal activation. This mixed antagonist/agonist action suggests either 1) that the coupling of a single leptin receptor (ObRb) to acute activation of neurons occurs by a signaling mechanism different from those that mediate centrally evoked reductions in food intake and body weight or 2) that acute neuronal activation and centrally induced reductions of food intake and body weight are mediated by different leptin receptor subtypes.

Intravascular release of intact cellular fibronectin during oxidant-induced injury of the in vitro perfused rabbit lung.

Fibronectin (Fn) is produced by cells in blood vessels at inflammatory sites in vivo. Fn release into the circulation thus may be a marker for vascular injury. In support of this, we found that oxidant-induced vascular injury of isolated perfused rabbit lungs caused elevated circulating Fn levels. Western blot analysis indicated that Fn released from the injured blood vessels was intact, dimeric, and possessed electrophoretic mobility identical with Fn produced by fibroblasts. Unlike Fn isolated from rabbit plasma, Fn derived from lung perfusate or produced by fibroblasts reacted with antibodies raised to a synthetic peptide containing sequences from the extra type III Fn domain that is transcribed in fibroblasts but not hepatocytes. Vascular injury by protease was also associated with intravascular release of Fn, but with cleavage. Oxidant-induced vascular injury causes release of tissue-derived Fn, which can be distinguished from plasma Fn by its size and content of antigenic determinants of the extra type III domain.

The importance of symptom assessment in the surgical treatment of gastroesophageal reflux disease and Barrett's esophagus.

The "art" and science of symptom assessment in the evaluation of patients with gastroesophageal reflux disease has been under emphasized. In fact, it is critical to judgements regarding surgical versus non-surgical therapy and is much more difficult than meets the eye. Many symptoms thought to be secondary to gastroesophageal reflux are not, and some, such as asthma cough and chest pain, which are commonly thought secondary to other causes, are indeed symptoms of reflux. Diagnostic studies are helpful but far from perfect, ultimately requiring the clinician's expert judgement as the key factor in determining a successful outcome. The following outlines both an approach to the assessment of symptoms and when possible, clinical studies shedding light on their cause and interpretation.

Can clinical and endoscopic findings accurately predict early-stage adenocarcinoma?

BACKGROUND: The presentation and management of esophageal cancer are changing, as more patients are diagnosed at an earlier stage of the disease in which endoscopic treatment methods may be contemplated. Therefore, we conducted a study to determine whether symptomatic and endoscopic findings can accurately identify node-negative early-stage adenocarcinoma. METHODS: A total of 213 consecutive patients (171 men and 42 women) with resectable esophageal adenocarcinoma seen from 1992 to 2002 were evaluated. None of these patients received neoadjuvant chemotherapy or radiation therapy. Using a multivariable model, model-based probabilities of early-stage disease (T1 im/sm N0) were calculated for each combination of the following three features: no dysphagia as main symptom at presentation, tumor length

Predictive factors of coexisting cancer in Barrett's high-grade dysplasia.

BACKGROUND: Identification of high-grade dysplasia (HGD) in Barrett's esophagus has been considered an indication for esophagectomy because of the high risk for coexisting cancer. However, rigorous endoscopic surveillance programs recently have been recommended, reserving esophagectomy for patients whose cancer is identified on biopsy. This approach risks continued surveillance for patients who already have cancer unless reliable markers for the presence of occult cancer are identified. This study aimed to determine the endoscopic, histologic, and demographic features associated with the presence of occult cancer in patients with HGD. METHODS: Endoscopic, histologic, and demographic findings for 31 patients who underwent esophagectomy for HGD were reviewed. The presence of an ulcer, nodule, stricture, or raised area on preoperative endoscopy was noted. The results of endoscopic biopsies taken before resection every 1 to 2 cm along the Barrett's segment were reviewed. The HGD was categorized as unilevel if the dysplasia was limited to one level of biopsy and as multilevel if more than one level was involved. Patients were divided into two groups according to the presence or absence of cancer in the resected specimens, and these variables were compared. RESULTS: The prevalence of coexisting cancer in patients with HGD was 45% (14/31). Of the 31 patients in this study, 9 had a visible lesion. Cancer was found in the resected specimens from 7 (78%) of 9 patients with a visible lesion and 7 (32%) of 22 patients without a visible lesion (p = 0.019). Of 22 patients without a visible lesion, 10 had multilevel and 12 had unilevel HGD. The findings showed that 6 (60%) of 10 patients with multilevel HGD and 1 (8.3%) of 12 patients with unilevel HGD had cancer in the resected esophagus (p = 0.009). CONCLUSION: For patients with HGD, a lesion visible on endoscopy and/or HGD at multiple biopsy levels is associated with an increased risk for coexisting cancer. These patients should be considered for early esophagectomy.

Bravo capsule induction of esophageal hypercontractility and chest pain.

BACKGROUND: The Bravo catheter-free pH monitoring system uses a capsule attached to the esophageal mucosa to detect acid exposure. Placement of the Bravo capsule is associated with intermittent chest pain in 50% of normal volunteers. The authors hypothesized that chest pain in this setting may be attributable to hypertensive esophageal contractions induced by the Bravo capsule. METHODS: The study population consisted of 40 consecutive patients with reflux symptoms who had stationary esophageal manometry within 1 h after Bravo capsule placement. The control group consisted of 40 patients with symptomatic gastroesophageal reflux disease (GERD) from a population of patients with foregut symptoms who were computer matched to the study group for age, sex, lower esophageal sphincter (LES) pressure, LES length, and 24-h pH composite score. The patients in the control group had manometry before Bravo capsule placement. The occurrence of chest pain was assessed before and during the monitoring period by interview and review of the patient's diary. Mean contraction amplitudes in the distal third of the esophagus after 10 wet swallows were averaged. The prevalence of patients with esophageal contraction amplitudes in the distal third that exceeded the 95th percentile of normal (180 mmHg) and the mean amplitude of distal third esophageal contractions in the study and control populations were compared. In the study group, the incidence of chest pain among the patients with hypercontractility of the esophagus was compared with the incidence among those without hypercontractility. RESULTS: The mean contraction amplitude was higher in the study group (144.7 vs 105.5 mmHg; p = 0.002). The number of patients with a mean distal esophageal contraction amplitude exceeding the 95th percentile of normal also was significantly higher in the study group (13/40 vs 5/40; p = 0.03). A total of 10 patients experienced new onset of chest pain with the Bravo capsule in place, and 6 patients experienced hypertensive esophageal contractions. CONCLUSIONS: The intraesophageal Bravo capsule can cause hypertensive esophageal contractions, which may lead to chest pain.

Electrocardiographic and transmembrane potential effects of 5-iminodaunorubicin in the rat.

5-Iminodaunorubicin (5-ID) is a quinone-modified anthracycline that retains antitumor activity but lacks the usual redox-cycling effects of quinoid agents. As a test for decreased cardiotoxicity, we have compared the dose- and time-dependent effects of multiple doses of 5-ID and doxorubicin (DXR) on the rat electrocardiogram (ECG) using a signal-averaging process and have related the ECG changes induced by 5-ID to transmembrane potential alterations in myocardial preparations isolated from treated rats. 5-ID was studied at dose levels of 16, 4, and 1 mg/kg, while DXR was given at 4, 2, and 1 mg/kg. At the high- and medium-dose levels, both agents produced widening of the QRS complex, increased R- and S-wave voltage, and prolonged the Q alpha T interval. The QRS widening reversed in all surviving rats, whereas Q alpha T prolongation was reversible with 5-ID but irreversible with DXR. At the lowest dose, 5-ID had no effect on the ECG until the end of treatment. Microelectrode studies on single cells showed that QRS widening occurring with 5-ID treatment was related to a decrease in the maximum rate of depolarization (Vmax) and that Q alpha T prolongation resulted from an increase in the duration of the action potential. Electron microscopic examination showed that although these toxic changes could not be related to specific morphological alterations, in general, the more severe the electrophysiological change, the greater the ultrastructural change. The most consistent ECG change was Q alpha T prolongation. Using this parameter as a marker for cardiotoxicity, 5-ID was about 4 to 5 times less cardiotoxic than was DXR at high- and medium-dose levels and was noncardiotoxic (i.e., below a threshold for cardiotoxicity) compared with DXR at 1 mg/kg over 20 (DXR) to 35 (5-ID) treatments. The decrease in cardiotoxicity relative to DXR is consistent with previous findings that quinone redox cycling is suppressed in 5-ID. However, the ECG and transmembrane potential effects that we identified at elevated doses of 5-ID can be associated with toxic changes in cardiac cell membranes. Therefore, membrane changes other than those due to quinone redox cycling and, presumably, lipid peroxidation must underlie the electrophysiological changes and structural modifications observed with 5-ID in this study. We believe that 5-ID is a useful mechanistic probe in anthracycline cardiotoxicity studies as well as being of obvious interest for clinical trials.

Metabolic disposition of 5-iminodaunorubicin in the rat.

We determined the metabolic disposition of 5-iminodaunorubicin (IMD) in rats receiving acute doses of IMD (16 and 4 mg/kg) i.v., i.p., and p.o. Major compounds found in plasma, liver, heart, lung, and brain of the rats receiving the higher dose, i.v. or i.p., were IMD and 5-imino-13-dihydrodaunorubicin. The aglycones, 5-iminodaunorubicinone and 5-imino-13-dihydrodaunorubicinone, were minor metabolites. No deoxyaglycones of IMD were detected in any tissue. We could not detect daunorubicin or its metabolites indicating IMD was not a prodrug of daunorubicin. Highest levels of IMD and metabolites were found in lung, liver, and heart, and lowest levels were found in the plasma and brain. Plasma levels of IMD after the higher i.v. dose decayed in a biphasic manner, and we calculated alpha-phase and beta-phase halftimes of decay of 1.4 and 10 hr, respectively. Patterns of distribution of IMD and metabolites were very similar following i.v. and i.p. treatments, except for higher amounts of IMD and metabolites in the liver after the latter route. A p.o. dose of IMD (16 mg/kg) yielded plasma levels of IMD that were only about 20% of those found by the parenteral routes. Summations of all compounds in all tissues at all times after this treatment yielded less than 2% of the corresponding totals found by the other routes. Results obtained following IMD (4 mg/kg) by the three routes generally confirmed conclusions derived from the studies at the higher dose, and we found an approximate linear dose relationship between the results from the two studies. Our inability to detect the formation of deoxyaglycone metabolites of IMD in vivo is consistent with earlier in vitro findings that IMD does not participate in the oxygen-cycling phenomenon typical of daunorubicin and doxorubicin to form drug and oxygen radicals and deoxyaglycone metabolites.

Metabolic disposition of N,N-dibenzyldaunorubicin in the rat.

The more efficacious and less cardiotoxic analogue of daunorubicin, N,N-dibenzyldaunorubicin (B2D), was found to be metabolized in rats by stepwise debenzylation that was superimposed on the known anthracycline metabolism via 13-ketone reduction and deglycosidation. Using high-pressure liquid chromatography for resolution and fluorescence for detection, we observed a series of metabolites in plasma, liver, heart, muscle, and lungs of rats receiving 10 mg B2D per kg, i.v., i.p., and p.o. Rats receiving 40 mg B2D per kg, i.v., died immediately, but this dose given p.o. was not lethal during 24 hr. Patterns of B2D and metabolites varied quantitatively with tissue and route of administration. Rat liver perfusion studies indicated extensive metabolism of B2D compared with limited metabolism of doxorubicin. These observations were consistent with an observed major first-pass effect on B2D in intact rats given B2D p.o. The predominant metabolites of B2D were the glycosidic derivatives, N-benzyldaunorubicin, daunorubicin, and their 13-dihydro derivatives. These metabolites of B2D had exhibited activity against mouse leukemia P388 as did B2D and were active in in vitro tests in which B2D was essentially inactive. These results indicate that B2D acts as a prodrug for a series of active metabolites. Conversion of B2D to these metabolites was relatively more efficient after p.o. administration than following i.v. or i.p. treatments.

Fields of aberrant CpG island hypermethylation in Barrett's esophagus and associated adenocarcinoma.

Esophageal adenocarcinoma (EAC) is thought to develop through a multistage process in which Barrett's metaplasia progresses through low- and high-grade dysplasia to invasive cancer. Transcriptional silencing of tumor suppressor genes by promoter CpG island hypermethylation has been observed in many types of human cancer. Analysis of CpG island hypermethylation in EAC has thus far been limited to the CDKN2A (p16) gene. In this study, we extend the methylation analysis of EAC to include three other genes, APC, CDH1 (E-cadherin), and ESR1 (ER, estrogen receptor alpha), in addition to CDKN2A. Molecular analysis can provide insight into the complex relationships between tissues with different histologies in Barrett's esophagus and associated adenocarcinoma. Therefore, we have mapped the spatial distribution of methylation patterns in six esophagectomy cases in detail. Hypermethylation of the four CpG islands was analyzed by the MethyLight technique in 107 biopsies derived from these six patients for a total of 428 methylation analyses. Our results show that normal esophageal squamous epithelium is unmethylated at all four CpG islands. CDH1 is unmethylated in most other tissue types as well. Hypermethylation of ESR1 is seen at high frequency in inflammatory reflux esophagitis and at all subsequent stages, whereas APC and CDKN2A hypermethylation is found in Barrett's metaplasia, dysplasia, and EAC. When it occurs, hypermethylation of APC, CDKN2A, and ESR1 is usually found in a large contiguous field, suggesting either a concerted methylation change associated with metaplasia or a clonal expansion of cells with abnormal hypermethylation.

Epigenetic patterns in the progression of esophageal adenocarcinoma.

Esophageal adenocarcinoma (EAC) arises after normal squamous mucosa undergoes metaplasia to specialized columnar epithelium (intestinal metaplasia or Barrett's esophagus), which can then ultimately progress to dysplasia and subsequent malignancy. Epigenetic studies of this model have thus far been limited to the DNA methylation analysis of a few genes. In this study, we analyzed a panel of 20 genes using a quantitative, high-throughput methylation assay, METHYLIGHT: We used this broader approach to gain insight into concordant methylation behavior between genes and to generate epigenomic fingerprints for the different histological stages of EAC. Our study included a total of 104 tissue specimens from 51 patients with different stages of Barrett's esophagus and/or associated adenocarcinoma. We screened 84 of these samples with the full panel of 20 genes and found distinct classes of methylation patterns in the different types of tissue. The most informative genes were those with an intermediate frequency of significant hypermethylation [ranging from 15% (CDKN2A) to 60% (MGMT) of the samples]. This group could be further subdivided into three classes, according to the absence (CDKN2A, ESR1, and MYOD1) or presence (CALCA, MGMT, and TIMP3) of methylation in normal esophageal mucosa and stomach, or the infrequent methylation of normal esophageal mucosa accompanied by methylation in all normal stomach samples (APC). The other genes were less informative, because the frequency of hypermethylation was below 5% (ARF, CDH1, CDKN2B, GSTP1, MLH1, PTGS2, and THBS1), completely absent (CTNNB1, RB1, TGFBR2, and TYMS1), or ubiquitous (HIC1 and MTHFR), regardless of tissue type. Each class undergoes unique epigenetic changes at different steps of disease progression of EAC, suggesting a step-wise loss of multiple protective barriers against CpG island hypermethylation. The aberrant hypermethylation occurs at many different loci in the same tissues, suggestive of an overall deregulation of methylation control in EAC tumorigenesis. However, we did not find evidence for a distinct group of tumors with a CpG island methylator phenotype. Finally, we found that normal and metaplastic tissues from patients with evidence of associated dysplasia or cancer had a significantly higher incidence of hypermethylation than similar tissues from patients with no further progression of their disease. The fact that the samples from these two groups of patients were histologically indistinguishable, yet molecularly distinct, suggests that the occurrence of such hypermethylation may provide a clinical tool to identify patients with premalignant Barrett's who are at risk for further progression.

Simulation of macromolecular liquids with the adaptive resolution molecular dynamics technique.

We extend the application of the adaptive resolution technique (AdResS) to liquid systems composed of alkane chains of different lengths. The aim of the study is to develop and test the modifications of AdResS required in order to handle the change of representation of large molecules. The robustness of the approach is shown by calculating several relevant structural properties and comparing them with the results of full atomistic simulations. The extended scheme represents a robust prototype for the simulation of macromolecular systems of interest in several fields, from material science to biophysics.