Gastrin is a target of the beta-catenin/TCF-4 growth-signaling pathway in a model of intestinal polyposis

Mutations in the adenomatous polyposis coli (APC) tumor suppressor gene occur in most colorectal cancers and lead to activation of beta-catenin. Whereas several downstream targets of beta-catenin have been identified (c-myc, cyclin D1, PPARdelta), the precise functional significance of many of these targets has not been examined directly using genetic approaches. Previous studies have shown that the gene encoding the hormone gastrin is activated during colon cancer progression and the less-processed forms of gastrin are important colonic trophic factors. We show here that the gastrin gene is a downstream target of the beta-catenin/TCF-4 signaling pathway and that cotransfection of a constitutively active beta-catenin expression construct causes a threefold increase in gastrin promoter activity. APC(min-/+) mice overexpressing one of the alternatively processed forms of gastrin, glycine-extended gastrin, show a significant increase in polyp number. Gastrin-deficient APC(min-/+) mice, conversely, showed a marked decrease in polyp number and a significantly decreased polyp proliferation rate. Activation of gastrin by beta-catenin may therefore represent an early event in colorectal tumorigenesis and may contribute significantly toward neoplastic progression. The identification of gastrin as a functionally relevant downstream target of the beta-catenin signaling pathway provides a new target for therapeutic modalities in the treatment of colorectal cancer.

Determination of absolute stereochemistry and an alternative synthesis of homopumiliotoxin 223G: identification on chiral GC columns with the natural alkaloid

An alternative asymmetric synthesis of (+)-(lS,9aS)-homopumiliotoxin 223G (1) was accomplished via (1R,2R, 9aS)-1-(benzyloxy)-2-hydroxy-1-methyl-3[(E)-isobutylidene]++ +quinolizidi ne (4), which was synthesized according to the intramolecular nickel(II)/chromium(II)-mediated cyclization of the N-(iodoalkenyl)aldehyde 2. Compound 4 was converted to the acetate and subjected to reduction with lithium in ammonia, whereupon deprotection of the O-benzyl group and removal of the acetoxyl group occurred in a single operation to afford (+)-homopumiliotoxin 223G. The same sequence using (+/-)-4 was applied to the synthesis of racemic 223G. Gas chromatography of a sample of racemic 223G showed no separation into enantiomers on four different cyclodextrin-based chiral GC columns. We found, however, that the O-acetates of (+/-)-223G gave a nearly baseline separation on either a beta-cyclodextrin column or a permethylated beta-cyclodextrin column. The O-acetate of synthetic (+)-223G was identical on either of these two columns, with the first eluting O-acetate from acetylated (+/-)-223G and also with the acetylated 223G present in a frog skin extract, thus allowing us to confirm unambiguously the 1S,9aS absolute configurations of natural 223G.

Amino- and carboxy-terminal PEST domains mediate gastrin stabilization of rat L-histidine decarboxylase isoforms

Control of enzymatic function by peptide hormones can occur at a number of different levels and can involve diverse pathways that regulate cleavage, intracellular trafficking, and protein degradation. Gastrin is a peptide hormone that binds to the cholecystokinin B-gastrin receptor and regulates the activity of L-histidine decarboxylase (HDC), the enzyme that produces histamine. Here we show that gastrin can increase the steady-state levels of at least six HDC isoforms without affecting HDC mRNA levels. Pulse-chase experiments indicated that HDC isoforms are rapidly degraded and that gastrin-dependent increases are due to enhanced isoform stability. Deletion analysis identified two PEST domains (PEST1 and PEST2) and an intracellular targeting domain (ER2) which regulate HDC protein expression levels. Experiments with PEST domain fusion proteins demonstrated that PEST1 and PEST2 are strong and portable degradation-promoting elements which are positively regulated by both gastrin stimulation and proteasome inhibition. A chimeric protein containing the PEST domain of ornithine decarboxylase was similarly affected, indicating that gastrin can regulate the stability of other PEST domain-containing proteins and does so independently of antizyme/antizyme inhibitor regulation. At the same time, endoplasmic reticulum localization of a fluorescent chimera containing the ER2 domain of HDC was unaltered by gastrin stimulation. We conclude that gastrin stabilization of HDC isoforms is dependent upon two transferable and sequentially unrelated PEST domains that regulate degradation. These experiments revealed a novel regulatory mechanism by which a peptide hormone such as gastrin can disrupt the degradation function of multiple PEST-domain-containing proteins.

Progastrin expression predisposes mice to colon carcinomas and adenomas in response to a chemical carcinogen

BACKGROUND & AIMS

Processing intermediates of preprogastrin (gly-gastrin and progastrin), termed nonamidated gastrins, are mitogenic for several cell types including colonic epithelial cells. However, presently it is not known if nonamidated gastrins play a role in colon carcinogenesis and if the effects are similar to those of amidated gastrins.

METHODS

Colon carcinogenesis in response to azoxymethane (AOM) was examined in transgenic mice overexpressing either progastrin (hGAS) or amidated gastrin (INS-GAS), compared with that in wild-type (WT) mice.

RESULTS

In AOM-treated groups, the total number of tumors per colon was significantly higher in hGAS (4.8+/-0.34) than INS-GAS (3.0+/-0.16) and WT (2.7+/-0.35) mice. Total numbers of adenocarcinomas and adenomas per animal colon were also significantly higher in hGAS than INS-GAS and WT mice. The size of the tumors was greater in hGAS mice, resulting in a significantly higher tumor burden per mouse in the hGAS mice than INS-GAS and WT mice. Although >90% of the tumors were located in the distal half of the colon in INS-GAS and WT mice, a significant number (42%) were present at the proximal end of the colon in hGAS mice.

CONCLUSIONS

The results suggest that the risk for developing colon carcinomas and adenomas in response to AOM is significantly increased in mice expressing high levels of progastrin, but not amidated gastrins.

Synthesis and cytotoxic evaluation of a series of gamma-substituted gamma-aryloxymethyl-alpha-methylene-gamma-butyrolactones against cancer cells

PURPOSE

The main objective of this investigation was to explore the cytotoxic structure-activity relationships of gamma-substituted gamma-aryloxymethyl-alpha-methylene-gamma-butyrolactones against cancer cells.

METHODS

The target compounds were synthesized in two steps commencing with aryl-OH which was treated with a bromomethyl ketone followed by the Reformatsky-type condensation.

RESULTS

Seven types of alpha-methylene-gamma-butyrolactones were evaluated in vitro against 60 human cancer cell lines derived from nine cancer cell types. The average values of log GI50 indicated that for the aryl portion, potencies of these alpha-methylene-gamma-butyrolactones are in a decreasing order of quinolin-2(1H)-one (or 2-hydroxyquinoline, 21, -5.89) > quinoline (19, -5.79) > 2-methylquinoline (20, -5.69) >8-hydroxyquinoline (17,-5.64) > 2-naphthalene (16, -5.59) > benzene (15, -4.90). The same order was obtained for both log TGI and log LC50. However, for the gamma-substituent, the potencies are in a decreasing order of biphenyl (16f-21f) > phenyl and 4-substituted phenyl (16b-e-21b-e) > methyl (16a-21a).

CONCLUSIONS

Unlike cardiovascular activities of alpha-methylene-gamma-butyrolactones in which a gamma-methyl substituent is necessary for vasorelaxing effect while a phenyl or a halogen-substituted phenyl is prefer for the antiplatelet activities, a gamma-biphenyl substituent proved to be the best for their cytotoxicities against various cancer cell lines tested.

Telomerase activity is frequently found in metaplastic and malignant human nasopharyngeal tissues

Telomerase is a specialized ribonucleoprotein polymerase that directs the synthesis of telomere repeats at chromosome ends. Accumulating evidence has indicated that telomerase is stringently repressed in normal human somatic tissues but reactivated in cancers and immortal cells, suggesting that reactivation of telomerase plays an important role in carcinogenesis. In this study, the status of telomerase activity in diseased human nasopharyngeal lesions was determined by the telomeric repeat amplification protocol (TRAP). Fifty-four patients participated including 17 inflammation or hyperplasia, eight with squamous metaplasia, and 29 with different stages of carcinomas. Telomerase activity was detected in 1 of 17 (5.9%) inflammatory or lymphoid hyperplastic tissues, 3 of 8 (37.5%) squamous metaplastic, and 25 of 29 (86.2%) carcinoma tissues. The differences in telomerase expression in these groups is statistically significant (P < 0.001). Levels of telomerase activity correlated with tumour stage (P = 0.024). These results suggest that telomerase reactivation plays a role in the carcinogenesis of nasopharyngeal cancer. Since telomerase activity is found in the majority of nasopharyngeal cancers and a subset of metaplasia, this enzyme may be served as a reference to monitoring the status of abnormal nasopharyngeal tissues.

Concurrent enteric helminth infection modulates inflammation and gastric immune responses and reduces helicobacter-induced gastric atrophy

Helicobacter pylori is causally associated with gastritis and gastric cancer. Some developing countries with a high prevalence of infection have high gastric cancer rates, whereas in others, these rates are low. The progression of helicobacter-induced gastritis and gastric atrophy mediated by type 1 T-helper cells may be modulated by concurrent parasitic infection. Here, in mice with concurrent helminth infection, helicobacter-associated gastric atrophy was reduced considerably despite chronic inflammation and high helicobacter colonization. This correlated with a substantial reduction in mRNA for cytokines and chemokines associated with a gastric inflammatory response of type 1 T-helper cells. Thus, concurrent enteric helminth infection can attenuate gastric atrophy, a premalignant lesion.

Base- and acid-catalyzed interconversions of O-acyl- and N-acyl-ethanolamines: a cautionary note for lipid analyses

The isolation and quantification of ethanolamine containing lipids from animal tissues may expose neutral lipid extracts to acidic or basic conditions during chromatographic separations or derivatization chemistry. While investigating the acid- and base-catalyzed production of anandamide in chromatographic fractions of rat brain extracts not containing anandamide, we observed that O,N-acyl migrations are facile. O,N-acyl migrations are well documented in synthetic organic chemistry literature, but are not well described or recognized with regard to methods in lipid isolation or lipid enzyme studies. We report here the synthesis and characterization of O- and N-acyl (palmitoyl- or arachidonoyl-)ethanolamines. Their rearrangements in base and acid are quantified by liquid chromatography;-electrospray ionization mass spectrometry. The rearrangements proceed through a cyclic intermediate that is also formed during chemical reactions commonly used for derivatization of acylethanolamines for gas chromatography-mass spectrometry. The isolation and characterization of N- or O-acylethanolamines and their enzymatic formation requires awareness and consideration of the proclivity of these compounds to chemically rearrange.

Mice overexpressing progastrin are predisposed for developing aberrant colonic crypt foci in response to AOM

Recent studies show that nonamidated gastrins (Gly-gastrin and progastrin) stimulate colonic proliferation. However, the role of nonamidated vs. amidated gastrins in colon carcinogenesis has not been defined. We measured intermediate markers of carcinogenesis in transgenic mice overexpressing either progastrin (hGAS) or amidated gastrin (INS-GAS) in response to azoxymethane (AOM). The hGAS mice showed significantly higher numbers of aberrant crypt foci (140-200% increase) compared with that in wild-type (WT) and INS-GAS mice (P < 0.05) after AOM treatment. The bromodeoxyuridine-labeling index of colonic crypts also was significantly elevated in hGAS mice vs. that in WT and INS-GAS mice. The results therefore provide evidence for a mitogenic and cocarcinogenic role of nonamidated gastrins (progastrin), which is apparently not shared by the amidated gastrins. Although nonamidated gastrins are now believed to mediate mitogenic effects via novel receptors, amidated gastrins mediate biological effects via different receptor subtypes, which may explain the difference in the cocarcinogenic potential of nonamidated vs. amidated gastrins. In conclusion, our results provide strong support for a cocarcinogenic role for nonamidated gastrins in colon carcinogenesis.

Helicobacter pylori activates the histidine decarboxylase promoter through a mitogen-activated protein kinase pathway independent of pathogenicity island-encoded virulence factors

Helicobacter pylori infection of the gastric mucosa is accompanied by an activated histamine metabolism. Histamine plays a central role in the regulation of gastric acid secretion and is involved in the pathogenesis of gastroduodenal ulcerations. Histidine decarboxylase (HDC) is the rate-limiting enzyme for histamine production, and its activity is regulated through transcriptional mechanisms. The present study investigated the effect of H. pylori infection on the transcriptional activity of the human HDC (hHDC) promoter in a gastric epithelial cell line (AGS) and analyzed the underlying molecular mechanisms. Our studies demonstrate that H. pylori infection potently transactivated the hHDC promoter. The H. pylori-responsive element of the hHDC gene was mapped to the sequence +1 to +27 base pairs, which shows no homology to known cis-acting elements and also functions as a gastrin-responsive element. H. pylori regulates the activity of this element via a Raf-1/MEK/ERK pathway, which was activated in a Ras-independent manner. Furthermore, we found that H. pylori-induced transactivation of the hHDC promoter was independent of the cag pathogenicity island and the vacuolating cytotoxin A gene and therefore may be exerted through (a) new virulence factor(s). A better understanding of H. pylori-directed hHDC transcription can provide novel insights into the molecular mechanisms of H. pylori-dependent gene regulation in gastric epithelial cells and may lead to new therapeutic approaches.

Synergistic interaction between hypergastrinemia and Helicobacter infection in a mouse model of gastric cancer

BACKGROUND & AIMS

Hypergastrinemia occurs frequently in association with acid suppression and Helicobacter infection, but its role in the progression to gastric atrophy and gastric cancer has not been well defined.

METHODS

The effects of hypergastrinemia, and possible synergy with Helicobacter felis infection, were investigated in insulin-gastrin (INS-GAS) transgenic mice.

RESULTS

INS-GAS mice initially showed mild hypergastrinemia, increased maximal gastric acid secretion, and increased parietal cell number but later progressed to decreased parietal cell number and hypochlorhydria. Development of gastric atrophy was associated with increased expression of growth factors, heparin-binding epidermal growth factor and transforming growth factor alpha. At 20 months of age, INS-GAS mice showed no evidence of increased enterochromaffin-like cell number, but instead exhibited gastric metaplasia, dysplasia, carcinoma in situ, and gastric cancer with vascular invasion. Invasive gastric carcinoma was observed in 6 of 8 INS-GAS mice that were >20 months old. Helicobacter felis infection of INS-GAS mice led to accelerated (< or = 8 mo) development of intramucosal carcinoma (85%), with submucosal invasion (54%) and intravascular invasion (46%; P < or = 0.05).

CONCLUSIONS

These findings support the unexpected conclusion that chronic hypergastrinemia in mice can synergize with Helicobacter infection and contribute to eventual parietal cell loss and progression to gastric cancer.

Telomerase activity is a useful marker to distinguish malignant pancreatic cystic tumors from benign neoplasms and pseudocysts

BACKGROUND

Pancreatic serous cystadenoma, mucinous cystic neoplasms, ductal adenocarcinoma with cystic change, and pseudocysts are a spectrum of pancreatic cystic lesions. Their management strategy and prognosis are extremely diverse. Imaging study, cytology, and analysis of the tumor markers of cyst fluid are not always reliable in differentiation of these disease entities.

MATERIALS AND METHODS

Fifteen patients with pancreatic cystic neoplasms (including six mucinous cystadenocarcinomas, two mucinous cystic neoplasms with borderline malignancy, two mucinous cystadenomas, and five serous cystadenomas), 4 patients with pancreatic ductal adenocarcinomas with cystic change, and 10 patients with pseudocysts were studied. Echo-guided or computed tomography-guided biopsies of pancreatic cystic lesions and their normal counterparts were conducted on all patients prior to operation or other management. The specimens were assayed for telomerase activity by using TRAP (telomere repeat amplification protocol). The level of telomerase activity in each specimen was semiquantitated as strong, moderate, weak, and none. The final diagnoses were made from histopathological examination of surgically resected or biopsied specimens. The efficacy of telomerase activity as a tumor marker to predict malignancy of pancreatic cystic lesions was evaluated.

RESULTS

Three of the four pancreatic ductal adenocarcinomas with cystic change had strong or moderate telomerase activity; four of the six mucinous cystadenocarcinomas had moderate or weak telomerase activity; one of the two mucinous cystadenomas with borderline malignancy had weak telomerase activity; and none of their normal counterparts had detectable telomerase activity. In contrast, none of the two mucinous cystadenomas, five serous cystadenomas, and 10 pseudocysts had detectable telomerase activity. Based on these results, the sensitivity of telomerase activity for prediction of malignancy or premalignancy of pancreatic cystic lesions was 67%, the specificity was 100%, and the positive and negative predictive values were 1.0 and 0.81, respectively. The overall accuracy was 86%.

CONCLUSIONS

The differential expressions of telomerase activity have been detected specifically in malignant and premalignant pancreatic cystic tumors, but not in benign cystic neoplasms or pseudocysts. The implications of these results are that telomerase activation takes part in the malignant transformation of pancreatic cystic neoplasms and that telomerase activity is a useful marker to distinguish malignant pancreatic cystic tumors from benign neoplasms and pseudocysts.

High-salt diet induces gastric epithelial hyperplasia and parietal cell loss, and enhances Helicobacter pylori colonization in C57BL/6 mice

A high-salt diet in humans and experimental animals is known to cause gastritis, has been associated with a high risk of atrophic gastritis, and is considered a gastric tumor promoter. In laboratory rodents, salt is known to cause gastritis, and when coadministered, it promotes the carcinogenic effects of known gastric carcinogens. Because Helicobacter pylori has been associated with a progression from gastritis to gastric cancer, we designed a study to determine whether excessive dietary NaCl would have an effect on colonization and gastritis in the mouse model of H. pylori infection. Seventy-two, 8-week-old female C57BL/6 mice were infected with H. pylori strain Sydney, and 36 control mice were dosed with vehicle only. One-half of the infected and control mice were fed a high-salt diet (7.5% versus 0.25%) for 2 weeks prior to dosing and throughout the entire experiment. Twelve infected and 6 control animals from the high-salt and normal diet groups were euthanized at 4, 8, and 16 weeks. At 8 and 16 weeks postinfection (WPI), the colony-forming units per gram of tissue were significantly higher (P < 0.05) in the corpus and antrum of animals in the high-salt diet group compared with those on the normal diet. Quantitative urease was significantly higher (P < 0.05) at 4 and 8 WPI in the corpus and antrum of animals on the high-salt diet when compared with controls. At 16 WPI, mice in both the normal and the high-salt diet groups developed moderate to marked atrophic gastritis of the corpus in response to H. pylori infection. However, the gastric pits of the corpus mucosa in mice on the high-salt diet were elongated and colonized by H. pylori more frequently than those in mice on the normal diet. The high-salt diet was also associated with a significant increase in proliferation in the proximal corpus and antrum and a multifocal reduction in parietal cell numbers in the proximal corpus, resulting in the elongation of gastric pits. We conclude that excessive NaCl intake enhances H. pylori colonization in mice and in humans and that chronic salt intake may exacerbate gastritis by increasing H. pylori colonization. Furthermore, elevated salt intake may potentiate H. pylori-associated carcinogenesis by inducing proliferation, pit cell hyperplasia, and glandular atrophy.

Interferon-alpha inhibits chromogranin A promoter activity in neuroendocrine pancreatic cancer cells

Interferon-alpha (IFN-alpha) treatment can suppress the hypersecretion syndrome associated with functional neuroendocrine tumors. Chromogranin A (CgA) is a matrix protein of neuroendocrine secretory vesicles and appears to be essential for an appropriate neuroendocrine secretory function. To test the hypothesis that IFN-alpha can directly interfere with CgA gene transcription, we performed transient transfection studies in pancreatic neuroendocrine tumor cells employing CgA-luciferase reporter gene constructs showing that IFN-alpha inhibited basal and protein kinase C-dependent CgA promoter activity. Using 5'-deletion constructs in combination with mutational analysis of the proximal CgA core promoter, a cyclic AMP response element (CRE) at -71 to -64 bp was identified as the IFN-alpha response element of the CgA gene. Furthermore, functional studies indicated that IFN-alpha exerts its effect on the CgA promoter via interference with CRE binding protein (CREB)/CREB binding protein (CBP)-dependent transactivation of the CgA-CRE.

Molecular dissection of regulated secretory pathways in human gastric enterochromaffin-like cells: an immunohistochemical analysis

Enterochromaffin-like (ECL) cells regulate gastric acid secretion through vesicular release of histamine. Until now, the molecular machinery of human ECL cells involved in the formation and release of vesicles is largely unknown. We analyzed tissue samples obtained from normal human gastric mucosa (n=4) and ECLomas (n=5) immunohistochemically using the APAAP method or double immunofluorescence confocal laser microscopy. Human pheochromocytomas (n=5) were investigated in parallel and compared to ECL cells. Secretory pathways were characterized using antibodies specific for marker proteins of large dense-core vesicles (LDCVs; islet cell antigen 512, chromogranin A, pancreastatin, and vesicular monoamine transporter 2) and small synaptic vesicle (SSV) analogues (synaptophysin). Tissues were also analyzed for expression of the peptide hormone processing enzymes, carboxypeptidase E and prohormone convertase 1, as well as the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins, 25-kDa synaptosome-associated protein (SNAP25), syntaxin, and synaptobrevin. Immunoreactivity for markers of LDCVs and SSV analogues were detected in normal ECL cells and ECLomas. Both tissues also showed expression of carboxypeptidase E and prohormone convertase 1. Analysis of vesicular SNARE (v-SNARE) and target membrane SNARE (t-SNARE) proteins revealed the presence of SNAP25, syntaxin, and synaptobrevin in normal and neoplastic ECL cells. Our data suggest that ECL cells possess the two vesicle types of regulated neuroendocrine secretory pathways, LDCVs and SSV analogues. Since ECL cells also contain typical SNARE proteins, the molecular machinery underlying secretory processes in this cell type appears to be identical to the secretory apparatus of neuroendocrine cells and neurons. In addition, our findings suggest that the secretory apparatus of ECL cells is maintained during neoplastic transformation.

Activation of human histidine decarboxylase gene promoter activity by gastrin is mediated by two distinct nuclear factors

The human histidine decarboxylase gene is regulated by gastrin through a cis-acting element known as the gastrin response element (GAS-RE) that was initially localized to a site (+2 to +24) downstream of the transcriptional start site. Electrophoretic mobility shift assays using sequentially deleted DNA probes and nuclear extracts from AGS-B gastric cancer cells showed that the GAS-RE is actually composed of two overlapping binding sites (GAS-RE1, +1 to +19; and GAS-RE2, +11 to +27) that bind distinct nuclear factors. Reporter gene assays demonstrated that each element alone could confer gastrin responsiveness, but the presence of both elements was required for complete gastrin response. Stimulation of AGS-B cells with gastrin for 10-20 min resulted in a >2-fold increase in factor binding. The binding was inhibited by pretreatment of AGS-B cells with cycloheximide and the MEK1 inhibitor PD98059, indicating a requirement for protein synthesis and also indicating that activation occurs through the MEK/mitogen-activated protein kinase pathway. UV cross-linking and Southwestern blot analysis showed that GAS-RE1 bound a 52-kDa protein, whereas GAS-RE2 bound a 35-kDa protein. Hence, activation of histidine decarboxylase gene promoter activity by gastrin is most likely mediated by two separate nuclear factors.

Lessons from genetically engineered animal models. I. Physiological studies with gastrin in transgenic mice

The role of gastrin in the regulation of gastrointestinal growth and acid secretion has been addressed through recent studies involving transgenic and knockout mice. The role of gastrin as a key modulator of parietal cell function and gastric acid secretion has been confirmed through studies in mice deficient in either gastrin or the gastrin/CCK-B receptor. However, although gastrin-deficient mice show no changes in gastric proliferation, they do show reduced colonic proliferation, and rates of colonic proliferation are increased in transgenic mice overexpressing glycine-extended gastrin or progastrin. This themes article highlights recent progress in our understanding of the biology of gastrin through studies in genetically modified mice.

Genetic toxicity of cocaine

Cocaine is a widely abused drug. Recently, it has been shown to induce teratogenesis in both humans and animals. Cocaine-induced teratogenicity has been associated with reactive oxygen species (ROS), which are generated by cytochrome P450 during cocaine biotransformation. Since ROS have been reported to induce genotoxicity, it is of interest to know whether cocaine and/or its metabolites are also genotoxic. In this study, Chinese hamster ovary K1 cells were employed as a model system to investigate the genetic toxicity of cocaine in the presence or absence of rat liver S9 fraction. Cocaine-induced cytotoxicity was potentiated when S9 was present, indicating the cytochrome P450 metabolism plays a role in cocaine-mediated cytotoxicity. Cocaine treatments per se induced a few chromosome aberrations while treatments of cocaine plus S9 caused a significant increase in chromosome aberrations. In contrast, cocaine induced micronuclei (MN) formation and hypoxanthine-guanine phosphoribosyltransferase mutation only in the presence of S9. Therefore, cocaine itself is at best a weak clastogen, whereas metabolite(s) of cocaine is/are truly inducer(s) of clastogenesis and mutagenesis. Cocaine treatments alone also induced a significant increase in sister chromatid exchange frequency but the addition of S9 did not affect the results. Free radical scavengers, including superoxide dismutase and catalase, efficiently decreased the frequency of cocaine plus S9-induced MN, implying that ROS are indeed important components in cocaine-induced genotoxicity. The observation that non-toxic doses of cocaine can inhibit intercellular metabolic cooperation suggests that cocaine may also be a tumor promoter. Our data supports that cocaine could possess genotoxicity in addition to its well-known neurotoxicity and teratogenicity.

The trefoil gene family are coordinately expressed immediate-early genes: EGF receptor- and MAP kinase-dependent interregulation

The trefoil gene family of mucus cell-secreted proteins is a critical mediator of gastrointestinal mucosal restitution. Transcription of trefoil genes is induced during mucosal repair, but the regulatory mechanisms involved are unknown. Mice deficient in the intestine-specific peptide intestinal trefoil factor (ITF), in which colonic restitution is lethally impaired, showed reduced expression of the gastric trefoil genes SP and pS2, suggesting that trefoil peptides may individually regulate transcription of the entire family. In gastric cell lines, the trefoils were shown to act in a manner suggestive of immediate-early genes capable of auto- and cross-induction through cis-acting regulatory regions. Trefoil-mediated transcriptional regulation required activation of the Ras/MEK/MAP kinase signal transduction pathway. EGF receptor (EGF-R) activation was also necessary for trefoil auto- and cross-induction, and both spasmolytic polypeptide (SP) and ITF stimulation of gastric cell lines led to phosphorylation of EGF-R. Nevertheless, ITF and ITF-thioredoxin cell surface binding at 4 degrees C colocalized not with EGF-R, but with CD71, which is found in clathrin-coated pits, suggesting that integration of trefoil peptide responses may occur after internalization. As EGF-R expression is itself strongly induced after mucosal damage, the trefoil/EGF-R relationship may be pivotal in the generation and maintenance of the mucosal repair phenotype.

GC/MS analysis of anandamide and quantification of N-arachidonoylphosphatidylethanolamides in various brain regions, spinal cord, testis, and spleen of the rat

Anandamide [N-arachidonoylethanolamide (NAE)] was initially isolated from porcine brain and proposed as an endogenous ligand for cannabinoid receptors in 1992. Accumulating evidence has now suggested that, in the tissue, NAE is generated from N-arachidonoylphosphatidylethanolamides (N-ArPEs) by phosphodiesterase. In this study a sensitive and specific procedure was developed to quantify NAE and N-ArPE, including organic solvent extraction, reverse-phase C-18 cartridge separation, derivatization, and gas chromatography/mass spectrometry (GC/MS) analysis. NAE is converted by a two-step derivatization procedure to a pentafluorobenzoyl ester followed by pentafluoropropionyl acylation. Quantification was performed by isotope dilution GC/MS using deuterium-labeled NAE (NAE-2H8) as an internal standard. The same chemical derivatization was applicable to N-ArPE quantification. The separated N-ArPE fractions were converted by a two-step cleavage/derivatization procedure into the pentafluorobenzoyl ester of NAE and then to its pentafluoropropionyl amide. The derivative was quantified by GC/MS using deuterium-labeled 1,2-[2H8]dioleoyl-sn-glycero-3-phospho(arachidonoyl)ethanolamid e as an internal standard. Using these methods, we have found that endogenous NAE levels in rat brain, spleen, testis, liver, lung, and heart were below the level of quantification achievable (0.1 pmol/mg of protein) but that N-ArPE is readily quantifiable and is widely distributed in the rat CNS with the highest level in the spinal cord. The striatum, hippocampus, and accumbens contain intermediate concentrations of N-ArPE, whereas the value is lowest in the cerebellum.

Overexpression of glycine-extended gastrin in transgenic mice results in increased colonic proliferation

Gastrin is a peptide hormone involved in the growth of both normal and malignant gastrointestinal tissue. Recent studies suggest that the glycine-extended biosynthetic intermediates mediate many of these trophic effects, but the in vivo relevance of glycine-extended gastrin (G-Gly) has not been tested. We have generated mice (MTI/G-GLY) that overexpress progastrin truncated at glycine-72 to evaluate the trophic effects of G-Gly in an in vivo model. MTI/G-GLY mice have elevated serum and colonic mucosal levels of G-Gly compared with wild-type mice. MTI/G-GLY mice had a 43% increase in colonic mucosal thickness and a 41% increase in the percentage of goblet cells per crypt. MTI/G-GLY mice exhibited increased colonic proliferation compared with wild-type controls, with an expansion of the proliferative zone into the upper third of the colonic crypts. Continuous infusion of G-Gly into gastrin-deficient mice for two weeks also resulted in elevated G-Gly levels, a 10% increase in colonic mucosal thickness, and an 81% increase in colonic proliferation when compared with gastrin-deficient mice that received saline alone. To our knowledge, these studies demonstrate for the first time that G-Gly's contribute to colonic mucosal proliferation in vivo.

Polymerase chain reaction-based enzyme immunoassay for quantitation of telomerase activity: application to colorectal cancers

Telomerase is a specialized reverse transcriptase that synthesizes telomeric sequences onto human chromosomal ends. It appears to be present in the majority of primary human cancer tissues, and may have potential as a universal tumor marker. In this report, we describe a sensitive, non-radioactive, polymerase chain reaction (PCR)-based enzyme immunoassay (EIA) for the quantitation of telomerase activity in human cells. This PCR-EIA is convenient and can be easily completed within 3 h. The correlation coefficient between the results of PCR-EIA and the conventional telomeric repeat amplification protocol (TRAP) method, as measured on 4 different cell lines, was over 0.98. Evaluation of this method for clinical application was conducted with tissues obtained from patients with colorectal cancers and the results were compared with those of the conventional TRAP method. Our data indicate that telomerase activities measured by conventional TRAP and PCR-EIA are highly correlated, and we suggest that the PCR-EIA method can substitute for conventional TRAP.

Expression, crystallization and preliminary X-ray diffraction studies of N-carbamyl-D-amino-acid amidohydrolase from Agrobacterium radiobacter

The Agrobacterium radiobacter CCRC 14924 N-carbamyl-D-amino-acid amidohydrolase, the enzyme used for production of D-amino acids, was overexpressed in Escherichia coli JM109. The expressed protein was crystallized by vapour diffusion using lithium sulfate as precipitant. It crystallizes in space group P21 with unit-cell parameters a = 69.8, b = 67.9 and c = 137.8 A and beta = 96.4 degrees. There are four molecules per asymmetric unit. Crystals diffract to 2.8 A resolution using a rotating-anode source at cryogenic (113 K) temperatures.

Clinical and morphologic features of hypertrophic cardiomyopathy in elderly patients 85 years or older

We studied the distinctive morphology of the left ventricle (LV) and attempted to relate advanced age and hypertension to this characteristic feature in elderly patients with hypertrophic cardiomyopathy (HC). Fourteen elderly patients > or = 85 years old (mean age 90 +/- 5 years) with HC were compared with 45 young patients < or = 40 years (mean age 34 +/- 4 years) with this disease. More mild hypertension in the elderly (10/14, 71%) than in the young (0%), and more syncope in the young (10/45, 22%) than in the elderly (0%) were observed. Echocardiography showed that the elderly patients had relatively mild LV wall thickening, generally confined to the septum (elderly vs young: 18 +/- 4 vs 25 +/- 8 mm, p < 0.001), with more basal septal bulging (elderly vs young: 12/14, 86% vs 0%, p < 0.001) and anterior septal hypertrophy of LV (elderly vs young: 11/14, 79% vs 0%, p < 0.001). Elderly patients with mild hypertension showed a predominantly basal septal bulging (10/10, 100%) and anterior septal hypertrophy of LV (9/10, 90%). HC in elderly patients > or = 85 years old has a striking LV morphology. Mild hypertension and advanced age may contribute to the distinctive geometry.

Nosocomial infections with ceftazidime-resistant Pseudomonas aeruginosa: risk factors and outcome

Prospective studies were conducted for nosocomial Pseudomonas aeruginosa infections from February 1, 1994, to October 30, 1995. Of 97 P. aeruginosa isolates from 97 patients, 35 were resistant to ceftazidime. Logistic regression revealed previous cephalosporin or piperacillin use as independent risk factors for nosocomial ceftazidime-resistant P. aeruginosa infection. Pulsed-field gel electrophoresis revealed that four nosocomial ceftazidime-resistant P. aeruginosa infections were caused by cross-infection, probably through medical personnel.

Aldose reductase catalyzes the oxidation of naphthalene-1, 2-dihydrodiol for the formation of ortho-naphthoquinone

The oxidation of naphthalene-1,2-dihydrodiol (ND) to o-naphthoquinone (NQ) in the lens is believed to be responsible for the formation of cataracts in naphthalene-fed rats. Studies using either recombinant rat lens (RLAR) or human muscle aldose reductase (HMAR) incubated in vitro with ND in the presence of NAD(P) verified that aldose reductase (EC 1.1.1.21) is the dihydrodiol dehydrogenase that catalyzes the oxidation of ND to NQ. Kinetic studies of Vmax/Km indicated that RLAR catalyzes the NAD-dependent oxidation of ND with an optimal pH of 9.0. The corresponding activity of HMAR was lower than that of rat enzyme. The metabolite produced by the incubation of RLAR with ND in the presence of 2-mercaptoethanol and NAD in 20 mM phosphate buffer, pH 7.5, was isolated by C18 reversed-phase high-performance liquid chromatography. The elution profile showed the formation of a new peak that was identical with a peak generated when NQ was incubated under the same condition. The metabolite in both peaks was identified as 4-(2-hydroxyethylsulfanyl)-1, 2-dihydro-1,2-naphthalenedione (HNQ) by 1H and 13C NMR analyses using homonuclear correlation spectroscopy, heteronuclear multiple quantum coherence, and heteronuclear shift correlations via multiple bond connectivities as well as infrared analysis. HNQ is readily autoxidized to 2,3-dihydro-1-oxa-4-thia-9,10-phenanthrenedione. The stoichiometry of 1:1 between the consumption of ND and the formation of NADH for the formation of HNQ implies that rat lens aldose reductase catalyzes a 2e- oxidation of ND to yield the corresponding ketol, which is autoxidized to NQ.

Sp1 and CREB mediate gastrin-dependent regulation of chromogranin A promoter activity in gastric carcinoma cells

Chromogranin A (CgA) is a multifunctional acidic protein that in the stomach is expressed predominantly in enterochromaffin-like cells (ECL cells) where it is regulated by gastrin. In order to investigate the transcriptional response of the mouse CgA (mCgA) promoter to gastrin stimulation, we studied a 4.8-kilobase mCgA promoter-luciferase reporter gene construct in transiently transfected AGS-B cells. 5'-Deletion analysis and scanning mutagenesis of mCgA 5'-flanking DNA showed that a Sp1/Egr-1 site spanning -88 to -77 base pairs (bp) and a cyclic AMP-responsive element (CRE) at -71 to -64 bp are essential for gastrin-dependent mCgA transactivation. Gastrin stimulation increased cellular Sp1 protein levels and Sp1-binding to the mCgA -88 to -77 bp element, as well as binding of CREB to its consensus motif at -71 to -64 bp. Gastrin also stimulated CREB Ser-133 phosphorylation, and abundance of cellular CREB protein levels. Overexpression of either Sp1 or phosphorylated CREB transactivated the mCgA promoter dose dependently, while coexpression of both transcription factors resulted in an additive mCgA promoter response. mCgA -92 to -64 bp, comprising the Sp1/Egr-1 site and the CRE motif, conferred gastrin responsiveness to a heterologous thymidine kinase promoter system, and therefore functions as a "true" enhancer element. This report demonstrates that Sp1 and CREB mediate CCK-B/gastrin receptor-dependent gene regulation, and that the effect of gastrin on the CgA gene is brought about by cooperative action of both transcription factors.

Left ventricular filling profiles and angiotensin system activity in elite baseball players

Left ventricular (LV) filling profiles in elite baseball players has not been reported in the literature. Also, angiotensin system activity in athletes has never been reported. We used echocardiography to compare 20 male elite baseball players (aged 21.9+/-1.0 years) with those of age- and sex-matched healthy sedentary subjects. Compared with the normal group, the athlete group showed a significant increase in LV mass, LV diastolic and systolic dimension, and left atrial dimension (P<0.05, <0.001, <0.001, and <0.001, respectively). No differences in relative wall thickness or fractional shortening were found between these two groups. Diastolic filling profiles, including peak early diastolic filling velocity (E), peak late diastolic filling velocity (A), E:A ratio, early time-velocity integral (Ei), atrial time-velocity integral (Ai), Ei:Ai ratio, early filling time, deceleration time of early filling, and isovolumic relaxation time, were similar in both groups. Angiotensin system activity, including plasma renin activity, plasma aldosterone, and 24-h urinary aldosterone excretion, showed no difference between these two groups.

CONCLUSION

This study suggests that normal LV filling profile, which is mediated partly by normal angiotensin system activity, is not related to increase in LV dimension and mass in elite baseball players.

Vacuolating toxin gene polymorphism among Helicobacter pylori clinical isolates and its association with m1, m2, or chimeric vacA middle types

BACKGROUND

Helicobacter pylori vacuolating cytotoxin encoded by vacA plays an essential role in H. pylori-related pathogenesis. Specific vacA alleles are believed to be associated with increased virulence. Association among vacA polymorphism, vacA middle genotypes, and various H. pylori-related diseases was thus investigated.

METHODS

Eighty-nine isolates from patients with various gastrointestinal diseases were examined for restriction fragment length polymorphism (RFLP) of the 2.0-kb polymerase chain reaction-amplified vacA middle region. Further genetic heterogeneity was assessed with ureA-ureB RFLP.

RESULTS

Twenty-eight distinct vacA RFLPs were seen among 89 isolates. Each pattern was associated with one specific vacA middle genotype. The association of specific RFLPs with certain clinical manifestations was noted among six common groups. Further RFLP analysis of the 2.4-kb ureA-ureB segment from isolates in four popular vacA RFLPs showed high genetic variation.

CONCLUSIONS

The vacA genetic polymorphism may be associated with different gastrointestinal diseases.

Synthesis and anticancer evaluation of certain gamma-aryloxymethyl-alpha-methylene-gamma-phenyl-gamma-butyrolactones

Certain gamma-aryloxymethyl-alpha-methylene-gamma-phenyl- gamma-butyrolactones were synthesized and evaluated for their anticancer activity. These compounds demonstrated a strong growth inhibitory activity against leukemia cell lines but are relatively inactive against non-small cell lung cancers and CNS cancers. The anticancer potency for aryl portion is in an order of quinoline > 8-hydroxyquinoline > 2-methylquinoline >> naphthalene >> benzene.

Close correlation between telomerase expression and adenomatous polyp progression in multistep colorectal carcinogenesis

To investigate the role of telomerase in the multistep colorectal carcinogenesis, we examined telomerase activity in 31 adenomatous polyps and 22 paired cancer-normal mucosa specimens from non-hereditary nonpolyposis colorectal cancer patients. Telomerase activity was detected in 18% of normal mucosa, 16% of small (<1.0 cm) polyps, 20% of intermediate polyps, 71% of large (>2.0 cm) polyps, and 96% of adenocarcinoma samples (P for trend, <0.0001). High-level enzyme activities were seen in none of the normal mucosa, 5% of small polyps, 20% of intermediate polyps, 43% of large polyps, and 73% of adenocarcinoma samples (P for trend, <0.0001). These data indicate telomerase reactivation occurs with adenomatous polyp progression in multistep colorectal carcinogenesis.

Oxidative stress activates the human histidine decarboxylase promoter in AGS gastric cancer cells

Oxidant stress is thought to play a role in the pathogenesis of many gastric disorders. We have recently reported that histidine decarboxylase (HDC) promoter activity is stimulated by gastrin through a protein kinase C- and extracellular signal-regulating kinase (ERK)-dependent pathway in gastric cancer (AGS-B) cells, and this transcriptional response is mediated by a downstream cis-acting element, the gastrin response element (GAS-RE). To study the mechanism through which oxidant stress affects gastric cells, we examined the effects of hydrogen peroxide (H2O2) on HDC promoter activity and intracellular signaling in AGS-B cells. H2O2 (10 mM) specifically activated the HDC promoter 10-12-fold, and this activation was blocked by both mannitol and N-acetylcysteine. Hydrogen peroxide treatment of AGS-B cells increased the phosphorylation and kinase activity of ERK-1 and ERK-2, but did not affect Jun kinase tyrosine phosphorylation or kinase activity. In addition, treatment of AGS-B cells with H2O2 resulted in increased c-fos/c-jun mRNA expression and AP-1 activity, and also led to increased phosphorylation of epidermal growth factor receptor (EGFR) and Shc. H2O2-dependent stimulation of HDC promoter activity was completely inhibited by kinase-deficient ERKs, dominant-negative (N17 and N15) Ras, and dominant-negative Raf, and partially blocked by a dominant-negative EGFR mutant. In contrast, protein kinase C blockade did not inhibit H2O2-dependent induction of the HDC promoter. Finally, deletion analysis demonstrated that the H2O2 response element could be mapped to the GAS-RE (nucleotides 2 to 24) of the basal HDC promoter. Overall, these studies suggest that oxidant stress activates the HDC promoter through the GAS-RE, and through an Ras-, Raf-, and ERK-dependent pathway at least partially involving the EGFR.

Detection of microcalcifications in digital mammograms using wavelets

This paper presents an approach for detecting microcalcifications in digital mammograms employing wavelet-based subband image decomposition. The microcalcifications appear in small clusters of few pixels with relatively high intensity compared with their neighboring pixels. These image features can be preserved by a detection system that employs a suitable image transform which can localize the signal characteristics in the original and the transform domain. Given that the microcalcifications correspond to high-frequency components of the image spectrum, detection of microcalcifications is achieved by decomposing the mammograms into different frequency subbands, suppressing the low-frequency subband, and, finally, reconstructing the mammogram from the subbands containing only high frequencies. Preliminary experiments indicate that further studies are needed to investigate the potential of wavelet-based subband image decomposition as a tool for detecting microcalcifications in digital mammograms.

Genetic toxicity of N-methylcarbamate insecticides and their N-nitroso derivatives

N-Methylcarbamate esters are an important group of insecticides. They have lower acute toxicity to vertebrates than organophosphates, although their genotoxicity has not been adequately studied. Here we investigate the cytotoxicity and genotoxicity of N-methylcarbamate insecticides and their N-nitroso derivatives in Chinese hamster V79 cells, using the hprt locus as a marker, and also assess inhibition of gap junctional intercellular communication. N-Methylcarbamate insecticides were chemically N-nitrosated to obtain the N-nitroso derivatives. N-Nitrosation greatly increased the cytotoxicity and mutagenicity of N-methylcarbamates at the hprt locus in Chinese hamster V79 cells. The mutagenic potential of N-nitroso-N-methylcarbamates was much higher than those of many other known mutagenic nitroso compounds, as well as some non-nitroso mutagenic alkylating agents. Parental N-methylcarbamates themselves were not mutagenic, however, they inhibited gap junctional intercellular communication half as effectively as the well-studied tumor promoter 12-O-tetradecanoylphorbol-13-acetate. The findings show that N-methylcarbamate insecticides and their N-nitroso derivatives have the potential to act through mediation of epigenetic and genotoxic mechanisms respectively in the multiple stages of chemical carcinogenesis.

alpha-Methylene-gamma-butyrolactones: synthesis and vasorelaxing activity assay of coumarin, naphthalene, and quinoline derivatives

Certain alpha-methylene-gamma-butyrolactone derivatives of coumarin, naphthalene, and quinoline were synthesized and evaluated for vasorelaxing effects on isolated rat thoracic aorta. The 7-[(2,3,4,5-tetrahydro-2-methyl-4-methylene-5-oxo-2-furanyl)methoxy]-2H- 1- benzopyran-2-ones, which have an aliphatic methyl substituent at the lactone C2, were more active than their C2-phenyl counterparts against high-K+ (80 mM) medium, Ca2+ (1.9 mM)-induced vasoconstriction and the norepinephrine (NE, 3 microM)-induced phasic and tonic constrictions (2a vs. 2b; 2c vs. 2d; 2e vs. 2f; 2g vs. 2h). Although 3-chloro-7-[(2,3,4,5-tetrahydro-2-methyl-4-methylene-5-oxo-2- furanyl)methoxy]-4-methyl-2H-1-benzopyran-2-one (2g) demonstrated the most potent inhibitory activities on the NE-induced phasic and tonic constrictions at concentrations of as low as 10 micrograms/ml, it possesses both affinity for NE-receptor and intrinsic activity to trigger the vasoconstriction. However, 8-[(2,3,4,5-tetrahydro-2-methyl-4-methylene-5-oxo-2- furanyl)methoxy]quinoline (10a) and other quinoline derivatives (11a, 12a) are pure irreversible non-competitive blockers of NE-receptor with no intrinsic activity. The aromatic ring played an important role in the vasorelaxing effects of alpha-methylene-gamma-butyrolactones; naphthalene was inactive, quinolines exhibited only affinity to the alpha-receptor, and coumarins possessed both affinity and intrinsic activity.

Telomerase activity in benign and malignant human thyroid tissues

Telomerase is a specialized ribonucleoprotein polymerase that directs the synthesis of telomerase repeats at chromosome ends. Accumulating evidence has indicated that telomerase is stringently repressed in normal human somatic tissues but reactivated in cancers and immortal cells, suggesting that activation of telomerase activity plays a role in carcinogenesis and immortalization. In this work, the status of telomerase activity during the development of human thyroid cancer was determined using telomeric repeat amplification protocol (TRAP) in 14 nodular hyperplasia, 14 adenomas, 23 papillary carcinomas and 11 follicular carcinomas. Positive telomerase activity was detected in 2 of 14 nodular hyperplasias (14%), 4 of 14 adenomas (29%), 12 of 23 papillary carcinomas (52%) and 10 of 11 follicular carcinomas (91%). The cancers that are negative for telomerase activity are mostly in early stage (stage I or II). These results suggest that telomerase reactivation plays a role during the development of thyroid cancer.

Genotoxicity of propoxur and its N-nitroso derivative in mammalian cells

N-Nitroso propoxur (NP) can be synthesized from a widely used N-methylcarbamate insecticide, propoxur, in vitro in the laboratory. Because of the extensive use of aerosol propoxur, the adverse effect on cells of respiratory origin is worth elucidating. In this report, two mammalian cell cultures from respiratory tissues [a hamster lung fibroblast, V79, and a primary rat tracheal epithelial cell (RTE)], were used to investigate the genotoxicity of propoxur and NP. NP was more cytotoxic than propoxur, with LC50s (20 and six times smaller, respectively in V79 and RTE cells. NP significantly induced sister chromatid exchange (> or = 0.01 microg/ml), chromosome aberration (> or = 2.5 microg/ml) and hprt gene mutation (> or = 0.5 microg/ml) in V79 cells, and cell transformation (> or = 0.2 microg/ml) in RTE cells. Results of chromosome aberration and hprt gene mutation indicated that the major pre-mutagenic lesion induced by NP must be the O6-methylguanine adduct, which frequently mispairs with thymine and thus gives rise to a GC-->AT transition. Propoxur was not mutagenic to either type of cells. However, it inhibited gap-junctional intercellular communication in V79 cells, which indicates that propoxur could act through some epigenetic mechanisms, such as tumor promotion or cell proliferation, in the multiple process of chemical carcinogenesis.

Involvement of recF, recO, and recR genes in UV-radiation mutagenesis of Escherichia coli

The recF, recO, and recR genes were originally identified as those affecting the RecF pathway of recombination in Escherichia coli cells. Several lines of evidence suggest that the recF, recO, and recR genes function at the same step of recombination and postreplication repair. In this work, we report that null mutations in recF, recO, or recR greatly reduce UV-radiation mutagenesis (UVM) in an assay for reversion from a Trp- (trpE65) to a Trp+ phenotypes. Introduction of the defective lexA51 mutation [lexA51(Def)] and/or UmuD' into recF, recO, and recR mutants failed to restore normal UVM in the mutants. On the other hand, the presence of recA2020, a suppressor mutation for recF, recO, and recR mutations, restored normal UVM in recF, recO, and recR mutants. These results indicate an involvement of the recF, recO, and recR genes and their products in UVM, possibly by affecting the third role of RecA in UVM.

Mice lacking secretory phospholipase A2 show altered apoptosis and differentiation with Helicobacter felis infection

BACKGROUND & AIMS

Infection with Helicobacter pylori uniformly leads to a chronic superficial gastritis that may progress to atrophic gastritis, a premalignant process. A mouse model of Helicobacter felis infection was used to study possible genetic determinants of the response to infection.

METHODS

Three inbred mouse strains with known secretory phospholipase A2 (sPLA2) genotypes [BALB/c (+/+), C3H/HeJ (+/+), and C57BL/6 (-/-)] were orally infected with H. felis and examined longitudinally using routine histology, immunocytochemistry, electron microscopy, proliferating cell nuclear antigen, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, and Northern and Western blot studies.

RESULTS

Only the C57BL/6 strain showed increased gastric fundic proliferation and apoptosis in response to infection. In addition, the C57BL/6 mouse showed a marked loss of parietal and chief cells, along with a marked expansion of an aberrant gastric mucous cell lineage that stained positive for spasmolytic polypeptide. In contrast, no significant change in these cell types was observed in BALB/c and C3H/HeJ strains. Increased expression of sPLA2 was observed in BALB/c and C3H/HeJ after H. felis infection, whereas sPLA2 expression was absent in C57BL/6 mice.

CONCLUSIONS

H. felis infection leads to increased apoptosis and altered cellular differentiation in the C57BL/6 mouse, a strain that lacks gastric sPLA2 expression. Because sPLA2 has been identified recently as the MOM1 (modifier of MIN) locus that influences polyp formation in the colon, these studies suggest that sPLA2 may also influence the gastric epithelial response to Helicobacter infection.

Possible role of telomerase activation in the cancer predisposition of patients with hereditary nonpolyposis colorectal cancers

BACKGROUND

Hereditary nonpolyposis colorectal cancer syndrome (HNPCC syndrome; also called Lynch syndrome) is one of the most common cancer predisposition syndromes. Most cases of cancer associated with this syndrome are due to the inheritance of germline mutations in genes that encode proteins required for DNA mismatch repair; defects in these proteins allow mutations to accumulate more rapidly in the DNA and influence the rate of cancer development. Recent studies indicate that the reactivation of the activity of telomerase, an enzyme involved in the synthesis of chromosomal ends, in somatic cells may play a role in carcinogenesis. In this study, we evaluated the expression of telomerase in normal and cancerous colorectal tissue specimens from HNPCC and non-HNPCC patients.

METHODS

The polymerase chain reaction-based telomeric repeat amplification protocol was used to assay telomerase activity in colorectal tissue specimens from 33 non-HNPCC patients (23 normal, 26 polyps, and 37 cancer specimens) and from 24 HNPCC patients (24 normal, 0 polyps, and 28 cancer specimens).

RESULTS

Thirty-one of 37 carcinoma samples from 18 non-HNPCC patients and 27 of 28 carcinoma samples from 24 HNPCC patients were found to be positive for telomerase activity. Whereas only one of 23 normal mucosa samples from 23 non-HNPCC patients was found to have (weak) telomerase activity, eight of 24 normal mucosa samples from 24 HNPCC patients were positive for telomerase; the difference between the two groups was statistically significant (two-sided P = .0226).

IMPLICATION

This study generates the hypothesis that genetic defects in individuals with HNPCC syndrome facilitate the reactivation of telomerase activity, a process which may be associated with their predisposition to develop cancer.

Endozepine stupor. Recurring stupor linked to endozepine-4 accumulation

Recurring stupor can be caused by repeated metabolic, toxic or structural brain disturbances. Recently, cases of recurring stupor, with fast EEG activity were shown to display increased endogenous benzodiazepine-like activity during the episodes of stupor. Patients with recurring stupor underwent extensive metabolic and toxicologic screening, EEG and brain imaging. Endozepines and exogenously administered benzodiazepines were assayed in plasma and CSF by means of mass spectrometry. Flumazenil, a benzodiazepine antagonist was administered and the behavioural and EEG responses monitored. Treatment with oral flumazenil was attempted in selected cases. Twenty patients were found with recurring stupor. Episodes had begun between ages 18 and 67 years, and in nine patients, had disappeared spontaneously after 4-6 years with symptoms. Stupor lasted hours or days. Onset of the episodes and frequency were unpredictable. Patients were normal between attacks. Stupor was characterized by initial drowsiness, staggering and behavioural changes, followed by deep sleep and spontaneous recovery with post-ictal amnesia. Biochemical screening and brain imaging were always normal. Ictal EEG showed fast background activity, and flumazenil transiently awoke the patients and normalized the EEG. In the nine cases examined, endozepine-4 levels were increased during the stupor. Oral flumazenil reduced the frequency of the attacks in three of these nine patients. Recurring episodes of stupor may be due to increased endozepine-4. We propose the term 'endozepine stupor' for such episodes. Endozepine-4 is an endogenous ligand for the benzodiazepine recognition site at the GABAA receptor, with unknown molecular structure.

Magnetic resonance angiography in the diagnosis of thoracic venous obstruction

The aims of this study were to evaluate the diagnostic value of orthogonal magnetic resonance angiography (MRA) and to compare the results of MRA with those of digital subtraction venography (DSV) in thoracic venous diseases. Ten normal volunteers were evaluated using two-dimensional time-of-flight MRA in three orthogonal planes to determine the image quality of each venous segment. Twelve consecutive patients suspected of having thoracic venous disease were studied with both MRA and DSV. In the normal subjects, the plane perpendicular to the target vein provided the most consistent visualization. Using three orthogonal MRA images, a diagnostic-quality image was obtained in 175 (83%) of 210 venous segments in normal volunteers. In patients with thoracic venous obstructive disease, MRA was more effective than DSV in detecting total (84 vs 54), patent (56 vs 36), stenotic (13 vs 10), and obstructive (15 vs 8) venous segments, poststenotic or postobstructive veins (15 vs 10), thrombosis of the internal jugular vein (7 vs 2), intraluminal thrombus (5 vs 3), and azygos veins (12 vs 2). Using venous segments visible on DVS (n = 54) as the standard, the sensitivity and specificity of MRA were 94% and 100%, respectively, in detecting venous patency, and 100% and 98% in detecting complete venous obstruction. In the shoulder region, the sensitivity and specificity of MRA were 93% and 100%, respectively, in detecting venous patency, and 100% and 97% in detecting venous obstruction. We conclude that MRA with three orthogonal planes can provide relatively complete and reliable venous mapping, without the need for contrast medium.

Inhibition of telomerase activity by PKC inhibitors in human nasopharyngeal cancer cells in culture

Telomerase is a specialized ribonucleoprotein polymerase that adds hexanucleotides (TTAGGG) onto human chromosomal ends. The expression of telomerase activity has been associated with cell immortalization and the malignant phenotype in most cancers. How the telomerase activity is regulated in cancer cells is presently not known. In this work, the effects of cell cycle blockers, DNA damaging agents, TopII inhibitors and proteins kinase inhibitors on the telomerase activity were examined in cultured nasopharyngeal carcinoma cells NPC-076. Agents which interfere with tubulin assembly (Taxol and vinblastine) and agents which arrest cells at S phase (methotrexate and 5-fluorouracil) did not inhibit telomerase activity of treated cells. Agents which damage DNA (cisplatin, methyl methanesulfonate, and UV radiation) and TopII inhibitors (etoposide and daunorubicin) also did not inhibit telomerase activity of treated cells. Among the protein kinase inhibitors examined, no significant inhibition of telomerase activity was observed with cells treated with quercetin, H-89, or herbimycin A. On the other hand, two protein kinase C (PKC) inhibitors (bisindolylmaleimide I and H-7) were found to produce a big inhibition of telomerase activity in treated cells. Staurosporine produced a moderate inhibition, and sphingosine had a small inhibitory effect. The inhibition of telomerase activity by PKC inhibitors appears to be specific since the treated cells were mostly viable (i.e., greater than 75%) and still retained significant levels of protein synthesis capability. These results implicate that protein kinase C is involved in the regulation of telomerase activity in vivo.