Biomedical subjects

A Uribe

Publications and source records attributed to A Uribe.

At least 19 recordsLinked to original sources

PubMed2003

Systemic lupus erythematosus in three ethnic groups. XX. Damage as a predictor of further damage.

OBJECTIVE: To examine the predictors of damage in a multiethnic cohort of systemic lupus erythematosus (SLE) patients with a specific focus on damage at baseline. PATIENTS AND METHODS: SLE patients from a multiethnic US (Hispanic, African-American and Caucasian) cohort (LUMINA: Lupus in Minority populations, Nature versus nurture) were included if they had > or =6 months of follow-up in the cohort. Damage was measured with the Systemic Lupus International Collaborating Clinics (SLICC) Damage Index (SDI). The dependent variable was the change in SDI score between study visits. Predictors were from the preceding visit. Variables known to affect damage accrual in SLE were included in the analyses. RESULTS: Three hundred and fifty-two patients (82 Hispanics, 153 African-Americans and 117 Caucasians) representing 1795 patient visits were included. Previous damage was found to be a significant predictor of subsequent damage accrual (P < 0.0001). Other variables predictive of subsequent damage accrual were disease activity (P < 0.0001), older age (P = 0.041) and use of corticosteroids (P = 0.0048). CONCLUSIONS: Once damage occurs in SLE, further damage is expected to occur. This is more likely to be the case if disease activity persists. These data have clinical implications for the management of SLE patients.

Adult↗

PubMed2002

5'-p-Fluorosulfonylbenzoyl adenosine inhibits progesterone synthesis in human placental mitochondria.

The human placental mitochondria have an ATP-diphosphohydrolase (apyrase) activity. In this paper we characterized the effect of 5'-p-fluorosulfonylbenzoyl adenosine (FSBA) on placental apyrase, and its repercussion on progesterone synthesis and oxygen consumption. Apyrase activity was inhibited by FSBA. Nucleosides tri- and diphosphates protected against FSBA inactivation, but divalent cations did not, indicating that FSBA attaches itself to an ATP-binding site of apyrase. In mitochondria, the inactivation of apyrase by FSBA was associated with inhibition of progesterone synthesis. Also, the oxygen consumption induced by ATP but not by ADP, was inhibited, clearly showing that FSBA exclusively inactivated the apyrase in human placental mitochondria. It is concluded that the apyrase activity is closely related to progesterone synthesis, probably associated with the cholesterol transport between mitochondrial membranes.

Adenosine↗

PubMed2001

A preliminary study of forensic entomology in Medellín, Colombia.

This is the first report of an ongoing study of insect succession on carrion carried out in Medellín, Colombia, using pigs (Sus scrofa) as a model to determine the insect sequence over 207 days. During this period, 2314 insects belonging to the following orders and families were collected: Diptera: Calliphoridae, Muscidae, Piophilidae, Sarcophagidae, Syrphidae, Otitidae; Hymenoptera: Apidae, Formicidae, Halictidae, Mutilidae, Vespidae; Coleoptera: Staphylinidae, Histeridae, Carabidae, Scarabaeidae, Silphidae, Dermestidae, Cleridae, Nitidulidae; Dermaptera: Forficulidae; Hemyptera: Gelastocoridae, Coreidae; Lepidoptera: Hesperiidae. Five decomposition stages were observed (fresh, bloated, active decay, advanced decay, and dry remains) and four insect ecological categories (necrophagous, predators, omnivorous, and incidental). During the fresh stage, the first insects that appeared were flies of the families Sarcophagidae and Muscidae and specimens of Formicidae (Hymenoptera). During the bloated period, species of Calliphoridae (Diptera) were predominant and the first to oviposit. During the third and fourth stages (active decay and advanced decay), the most abundant families were Calliphoridae and Muscidae, although Staphilinidae (Coleoptera) also stood out. During the last stage (dry remains), the dominant family was Formicidae (Hymenoptera) followed by Dermestidae (Coleoptera) with a large number of immature insects.

Animals↗

PubMed2001

Mitogenic action of tumour necrosis factor-alpha and interleukin-8 on explants of human duodenal mucosa.

Our aim is to examine whether tumour necrosis factor-alpha (TNF-alpha) and interleukin affect the mitotic activity in explants of human duodenal mucosa and to estimate the release of cytokines from explants incubated with TNF-alpha. Biopsy specimens of normal duodenal mucosa were taken from 19 subjects that underwent upper endoscopy for investigation of dyspeptic symptoms or chronic gastrointestinal bleeding. The specimens were processed following guidelines for organ culture technique. Paired biopsy specimens from 12 subjects were cultured for 23 h to achieve steady state and thereafter the explants were incubated 25 h with 10(-13)-10(-9) M of TNF-alpha or IL-8. Mitoses were arrested in the metaphase by adding vincristine sulphate for the last three hours. The explants were then fixed and processed for microdissection. Fifteen crypts were microdissected and the total number of metaphases was determined using the whole crypt as reference volume. The number of metaphases per crypt was also estimated in explants incubated with 10(-10) M TNF-alpha in the presence of anti-IL-8 antibodies. Additional duodenal explants from seven subjects were incubated with 10(-10) M TNF-alpha for 25 h. Thereafter the release of IL-1-beta, IL-6, IL-8 and interferon gamma (IFN-gamma) into the culture medium was measured by enzyme immunoassay and expressed as pg/mg protein. TNF-alpha and IL-8 significantly increased the number of metaphases/crypts (P<0.0001). The addition of anti-IL-8 slightly reduced the number of metaphases/crypt compared to the values observed in the explants incubated with 10(-10) M TNF-alpha alone (P<0.0001). The number of metaphases/crypt in the explants incubated with 10(-10) M TNF-alpha in the presence of anti-IL-8 antibodies was, however, markedly and significantly higher than that of the controls (P<0.000). TNF-alpha induced the release of IL-8 (P<0.01) and IL-6 (P<0.05) from the duodenal explants. TNF-alpha and IL-8 are potent mitogens to human small intestinal crypts. The mitogenic action of TNF-alpha is primarily a direct effect of the cytokine and only to a minor extent mediated by a secondary production of IL-8 in the duodenal explant. Our findings indicate that TNF-alpha and IL-8 may participate in the regulation of cell proliferation in the human small intestinal epithelium.

Cell Division↗

PubMed2001

Interleukin-1, interleukin-8, tumour necrosis factor alpha and interferon gamma stimulate DNA synthesis but have no effect on apoptosis in small-intestinal cell lines.

OBJECTIVES: Cytokines stimulate lymphocyte cell proliferation and affect cell division in several other cell types. Helicobacter pylori-induced gastritis and coeliac disease are characterized by an increased cell proliferation in association with an increased production of proinflammatory cytokines, which could contribute to these cell kinetic changes. Our aim is to examine in vitro whether cytokines usually present in the gastrointestinal mucosa affect DNA synthesis and apoptosis in a rat and a human small-intestinal cell line. METHODS: IEC-6 and FHs-74 cells were incubated for 24 h with 10(-13)-10(-9) M of tumour necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-8 (IL-8), transforming growth factor-beta (TGF-beta) and interferon gamma (IFN-gamma). IEC-6 cells were also incubated with 10(-13)-10(-9) M of interleukin-1alpha (IL-1alpha) and 10(-8) M of interleukin-1 receptor antagonist (IL-1ra). The cells were labelled with 3H-methyl thymidine for the final 4 hours, and then processed for autoradiography. DNA synthesis was evaluated by the labelling index (LI%). Apoptosis was evaluated in IEC-6 cells by changes in membrane lipid asymmetry using annexin-V binding to externalized phosphatidylserine (flow cytometry) and by estimating the caspase activity. RESULTS: TNF-alpha, IL-1beta, IL-8 and IFN-gamma significantly and markedly increased the LI, even at low concentrations (P< 0.0001), in both IEC-6 and FHs-74 cells, as did IL-1alpha in IEC-6 cells. TGF-beta significantly reduced the LI in both cell lines (P< 0.0001), whereas IL-2, IL-6 and IL-1ra did not affect DNA synthesis significantly. None of IL-1beta, IL-8, TNF-alpha or IFN-gamma affected apoptosis in IEC-6 cells. CONCLUSION: TNF-alpha, IL-1alpha, IL-1beta, IL-8 and IFN-gamma stimulated DNA synthesis in a human and a rat small-intestinal cell line. The cytokines exert their mitogenic action directly on the intestinal cells via specific receptors. Our findings indicate that pro-inflammatory cytokines may participate in the regulation of the gastrointestinal epithelial cell proliferation in health and disease.

Animals↗

PubMed2001

Enteroscopy as a tool for diagnosing gastrointestinal bleeding requiring blood transfusion.

Iron-deficiency anemia secondary to gastrointestinal blood loss is a common cause of hospitalization. In many cases, the bleeding site cannot be defined despite thorough routine examination of the gastrointestinal tract. The aim of this study was to evaluate push enteroscopy as a diagnostic tool in patients with severe anemia, secondary to recurrent gastrointestinal bleeding, that required management by transfusion. Thirty-five consecutive push enteroscopy investigations were performed in 1998 and 1999 on 25 patients (15 men, 10 women). Mean age was 57 +/- 16 years (range, 33-83). All patients had received blood transfusions because of pronounced anemia secondary to gastrointestinal bleeding. Before push enteroscopy, all patients had been investigated with esophagogastroduodenoscopy, colonoscopy, and small-bowel radiography using the double contrast technique; no bleeding site was found. In addition, 10 of 25 patients had been investigated beforehand with 99mTc-labelled red blood cell scintigraphy, and 5 of 25 with scintigraphy for Meckel diverticulum. Two patients were also investigated with angiography before the push enteroscopy, and in six patients an additional total intraoperative enteroscopy was performed, preceded by a new colonoscopy, esophagogastroduodenoscopy, and push enteroscopy. A bleeding site was disclosed in 15 of 25 (60%) patients. In 7 of 25 patients (28%) the bleeding site was found in the stomach or esophagus. even though the patients had undergone one or two esophagogastroduodenoscopies earlier with normal findings. Total intraoperative enteroscopy identified a bleeding site in four of six (67%) patients studied. Two patients had bleeding hemangiomas that were resected surgically. Two patients had small intestinal adenomas, one with adenocarcinoma in situ. Push enteroscopy performed with an overtube inserted under fluoroscopic guidance is an important diagnostic tool in patients in whom conventional examinations do not disclose bleeding sites. Interestingly, 28% of patients had bleeding within reach of the gastroscope, indicating that a new upper endoscopy should be recommended before push enteroscopy is performed. When no positive findings are seen on push enteroscopy and the patient is affected by severe, recurrent iron-deficiency anemia, total intraoperative enteroscopy should be considered.

Adenocarcinoma↗

PubMed2000

40- to 100-kD protein(s) of Helicobacter pylori stimulate DNA synthesis in epithelial cell lines without affecting apoptosis.

BACKGROUND: Previous in vitro studies have demonstrated that water extracts and sonicates of Helicobacter pylori increase DNA synthesis in a small intestinal epithelial cell line. The aim of this study was to identify mitogenic factor(s) in a water extract of a H. pylori strain and to examine their effects on DNA synthesis and apoptosis in vitro. METHODS: IEC-6 and FHs 74 cells were incubated for 24 h with different dilutions of a water extract of H. pylori (cytotoxic strain 88-23) or with 6 protein fractions obtained by gel filtration. Cells were labeled with tritiated thymidine and processed for autoradiography. DNA synthesis was evaluated by the labeling index (LI%). The proportion of IEC-6 cells undergoing apoptosis and/or necrosis was evaluated by flow cytometry using fluorescein isothiocyanate (FITC)-labeled annexin-V and propidium iodide. In vitro caspase activity was also determined as an alternative method for detection of apoptosis. RESULTS: The water extract of H. pylori 88-23 markedly increased DNA synthesis in both epithelial cell lines (p < 0.01). A marked stimulation of DNA synthesis was also observed in IEC-6 cells incubated with fraction II- containing proteins of a molecular weight ranging between 40 and 100 kD (p < 0.01). A lesser stimulation of DNA synthesis was observed in cells incubated with higher concentrations of the other protein fractions (p < 0.01). Neither the water extract of H. pylori 88-23 nor the protein fraction II (40-100 kD) induced apoptosis in IEC-6 cells. CONCLUSION: A water extract of H. pylori 88-23 and a protein fraction containing proteins with molecular weights of 40-100 kD stimulate DNA synthesis in a rat and human small intestinal cell line. Apoptosis was unaffected by the water extract and by protein fraction II, which indicate that the H. pylori-derived mitogen(s) have the capacity to directly enhance epithelial cell proliferation in vitro.

Animals↗

PubMed1999

Endogenous prostaglandins are physiological regulators of endocrine cells in the gastroduodenal mucosa of the rat.

BACKGROUND/AIM: To investigate whether endogenous prostaglandins participate in the regulation of the gastrointestinal endocrine cell system. METHODS: Sprague-Dawley rats were treated with 1 mg/kg indomethacin subcutaneously or indomethacin subcutaneously and 500 microg/kg oral prostaglandin E2 or solvents for 2 months. Endocrine cells were visualized by using immunohistochemistry and by the Sevier-Munger silver stain on specimens from the gastroduodenal mucosa, and their total volume was estimated, using standard stereological methods. Plasma and gastrointestinal tissue concentrations of regulatory peptides were analyzed by radioimmunoassay. RESULTS: Fundic mucosa. The total volume of cells stained with the Sevier-Munger silver stain (enterochromaffin-like) was increased by indomethacin, but reduced by the administration of prostaglandin E2 (P < 0.05 vs. indomethacin). Indomethacin increased the total volume of somatostatin-immunoreactive. Similarly, rats given indomethacin and prostaglandin E2 had higher values than controls. Indomethacin increased the tissue concentration of somatostatin in the gastric fundus whereas prostaglandin E2 prevented such changes (P < 0.05 vs. indomethacin). Antral mucosa. The total volume of serotonin-immunoreactive cells was reduced by indomethacin, but increased by prostaglandin E2 (P < 0.05 vs. controls and indomethacin, respectively). Duodenal mucosa. The total volume of somatostatin-immunoreactive cells was reduced in the rats given indomethacin and prostaglandin E2 (P < 0.05 vs. controls and indomethacin). Indomethacin reduced and simultaneous administration of prostaglandin E2 increased the total volume of CCK-immunoreactive cells (P < 0.05 vs. controls and indomethacin). Indomethacin reduced the total volume of serotonin-immunoreactive cells whereas the simultaneous administration of PGE2 comparatively increased their total volumes (P < 0.05 vs. indomethacin), although they were still lower than the control values. The total volume of GIP-immunoreactive cells was slightly increased in the rats given both indomethacin and indomethacin + prostaglandin E2. The tissue concentration of somatostatin in the duodenum was reduced in rats given indometacin and prostaglandin E2 (P < 0.05 vs. controls and indomethacin). CONCLUSION: Endogenous prostaglandins, particularly prostaglandin E2, regulate CCK-, enterochromaffin-like-, somatostatin-, GIP- and enterochromaffin cells in the gastroduodenal mucosa of the rat.

Administration, Oral↗

PubMed1999

Lipopolysaccharide of Escherichia coli, polyamines, and acetic acid stimulate cell proliferation in intestinal epithelial cells.

Our aim was to examine whether lipopolysaccharide of Escherichia coli, polyamines of dietetic and/or bacterial origin, and products of the bacterial metabolism influence cell proliferation in epithelial cells from the colon and small intestine. Lipopolysaccharide of Escherichia coli 0111:B4 was incubated with cultures from human colonic mucosa. The mitoses were arrested with Vincristine and the total number of metaphases per crypt was counted. In addition, lipopolysaccharide was incubated with a human colonic epithelial cell line from adenocarcinoma (LS-123 cells) and with a nontransformed small intestinal cell line from germ-free rats (IEC-6 cells) for 24 h. In the last 4 h, the cells were labeled with tritiated thymidine. The cells were incubated with putrescine, cadaverine, and spermidine at 10(-11)-10(-3) M and with acetic acid (10(-5)-10(-1) M), acetaldehyde (10(-10)-10(-4) M) and ammonium chloride (1-20 mM). Lipopolysaccharide of Escherichia coli increased the number of arrested metaphases in human colonic crypts and DNA synthesis in L-123 and IEC-6 cells (P < 0.001). All polyamines increased DNA synthesis in the colonic and small intestinal cell lines, the effects being more marked for putrescine (P < 0.001). The higher concentrations of acetic acid increased DNA synthesis in both epithelial cell lines (P < 0.001). Acetaldehyde slightly decreased DNA synthesis in LS-123 cells at cytotoxic concentrations. Ammonium chloride did not significantly affect DNA synthesis. The final concentration of nonionized ammonia was less than 3%. It is concluded that lipopolysaccharides of Escherichia coli and intraluminal factors derived from microorganisms increase cell proliferation in human colonic crypts and intestinal epithelial cell lines.

Acetaldehyde↗

PubMed1999

Presence of two enzymes, different from the F1F0-ATPase, hydrolyzing nucleotides in human term placental mitochondria.

The hydrolysis of ATP, ADP or GTP was characterized in mitochondria and submitochondrial particles since a tightly-bound ATPase associated with the inner mitochondrial membrane from the human placenta has been described. Submitochondrial particles, which are basically inner membranes, were used to define the location of this enzyme. Mitochondria treated with trypsin and specific inhibitors were also used. The oxygen consumption stimulated by ATP or ADP was 100% inhibited in intact mitochondria by low concentrations of oligomycin (0.5 microgram/mg) or venturicidine (0.1 microgram/mg), while the hydrolysis of ATP or ADP was insensitive to higher concentrations of these inhibitors but it was inhibited by vanadate. Oligomycin or venturicidine showed a different inhibition pattern in intact mitochondria in relation to the hydrolysis of ATP, ADP or GTP. When submitochondrial particles were isolated from mitochondria incubated with oligomycin or venturicidine, no further inhibition of the nucleotide hydrolysis was observed, contrasting with the partial inhibition observed in the control. By incubating the placental mitochondria with trypsin, a large fraction of the hydrolysis of nucleotides was eliminated. In submitochondrial particles obtained from mitochondria treated with trypsin or trypsin plus oligomycin, the hydrolysis of ATP was 100% sensitive to oligomycin at low concentrations, resembling the oxygen consumption; however, this preparation still showed some ADP hydrolysis. Native gel electrophoresis showed two bands hydrolyzing ADP, suggesting at least two enzymes involved in the hydrolysis of nucleotides, besides the F1F0-ATPase. It is concluded that human placental mitochondria possesses ADPase and ATP-diphosphohydrolase activities (247).

Adenosine Triphosphate↗

PubMed1999

In vitro aging of Helicobacter pylori: changes in morphology, intracellular composition and surface properties.

BACKGROUND: During the conversion from the bacillary into the coccoid form, Helicobacter pylori organisms are known to change extensively. The aim of this study was to determine some of the changes that occur regarding morphology, intracellular composition and surface properties during the aging of bacteria in vitro. MATERIALS AND METHODS: H. pylori from agar plate cultures of different ages was used in this study. The intracellular composition of the two morphological forms of the bacteria was tested by density centrifugation, DNA extraction and quantitative OD, mRNA and ATP measurements. Immunoblotting was used to observe changes in secreted/superficial protein patterns, and hydrophobicity measurements were used to observe changes in surface properties. RESULTS: All bacillary H. pylori organisms changed morphology gradually over 10 days of culture. Rods had a higher density than cocci; bacteria stored in PBS had the highest density and bacteria stored in water had the lowest. The quantitative DNA, RNA and ATP content were reduced in the aging bacteria. Fewer immunogenic proteins were expressed, and an increased surface hydrophobicity was observed in the older cultures. CONCLUSION: This study highlights several aspects of H. pylori aging in vitro and shows some of the differences that exist between bacillary and coccoid forms. This information is important for understanding the transmission and survival of H. pylori outside the human host, as the degradative changes in the intracellular composition and the surface properties shown here point to dead bacteria, and not to a viable but nonculturable form.

Adenosine Triphosphate↗

PubMed1999

Differences in cholesterol incorporation into mitochondria from hepatoma AS-30D and human term placenta.

Cholesterol transport for steroidogenesis in the human placental mitochondria is an enigma as, contrary to other steroidogenic tissues, the human placenta does not express steroidogenic acute regulatory protein (StAR), a protein known to be required for efficient utilization of cholesterol by adrenal and gonadal mitochondria. These observations suggest the possibility that cholesterol transport in human placental mitochondria involves a similar system to that present in other non-steroidogenic tissues. We studied cholesterol incorporation into mitochondria isolated from AS-30D hepatoma cells and the human placenta. Mitochondria from both sources incorporated cholesterol in vitro. There were no differences in cholesterol incorporation into hepatoma mitochondria treated with or without trypsin. In contrast, the human placental mitochondria treated with trypsin did not incorporate exogenous cholesterol. The presence of ATP increased the uptake of cholesterol by human placental mitochondria. This increase was inhibited by vanadate. These results suggest that cholesterol incorporation into human placental mitochondria is mediated by protein(s).

Adenosine Triphosphate↗

PubMed1999

Butyrate inhibits and Escherichia coli-derived mitogen(s) stimulate DNA synthesis in human hepatocytes in vitro.

Bacterial constituents and products of the bacterial metabolism pass from the gut lumen to the portal vein and may influence the homeostasis of the liver. Our aim is to examine whether DNA synthesis of human hepatocyte cell lines is affected by constituents of Escherichia coli species as well as by intracolonic products of bacterial fermentation that reach the liver via the portal vein. Supernatant solutions and bacterial cell fractions (containing either whole dead bacteria, cell walls, cytosol or non-soluble intracellular components) of E. coli K12 and of E. coli species from rat fecal flora were separated by multi-step centrifugation, French press, and microfiltration. The supernatant solution and the cell fractions were incubated with a human hepatoma cell line (Hep-G2) and with a cell line derived from non-malignant human liver cells (Chang cells) for 24 h. The cells were labeled with tritiated thymidine before processing to autoradiography. DNA synthesis was estimated by the labeling index (LI%). DNA synthesis was also estimated following incubation of Hep-G2 cells with short chain fatty acids (acetic, propionic, butyric and succinic acid), acetaldehyde, and ammonium chloride. Epidermal growth factor and a water extract of Helicobacter pylori were used as references. The fractions of E. coli from rat fecal flora containing cytosol and non-soluble intracellular components significantly increased the labeling index in both Hep-G2 and Chang cells (p < 0.05). In addition, the supernatant solution significantly increased the LI in Chang cells (p < 0.05). Epidermal growth factor increased the LI of Hep-G2 cells dose-dependently (p < 0.05). Butyric acid reduced DNA synthesis at 10(-4) M (p < 0.05). The highest doses of acetaldehyde were cytotoxic and reduced the LI. Escherichia coli species contain mitogenic factors to human hepatocytes. The mitogen(s) are present in the supernatant solution, in the cytosol and in non-soluble intracellular components. Butyrate, which is a product of bacterial fermentation of colonic substrates inhibit DNA synthesis in the hepatocyte cell lines. Our findings suggest that soluble mitogen(s) that diffuse from the microorganism to the outer environment, intracellular bacterial constituents, and products of the bacterial metabolism that reach the liver via the portal vein may influence the cell kinetic steady-state of hepatic cells.

Acetaldehyde↗

PubMed1998

Preparation and hybridization analysis of DNA/RNA from E. coli on microfabricated bioelectronic chips.

Escherichia coli were separated from a mixture containing human blood cells by means of dielectrophoresis and then subjected to electronic lysis followed by proteolytic digestion on a single microfabricated bioelectronic chip. An alternating current electric field was used to direct the bacteria to 25 microlocations above individually addressable platinum microelectrodes. The platinum electrodes were 80 microns in diameter and had center-to-center spacings of 200 microns. After the isolation, the bacteria were lysed by a series of high-voltage pulses. The lysate contained a spectrum of nucleic acids including RNA, plasmid DNA, and genomic DNA. The lysate was further examined by electronically enhanced hybridization on separate bioelectronic chips. Dielectrophoretic separation of cells followed by electronic lysis and digestion on an electronically active chip may have potential as a sample preparation process for chip-based hybridization assays in an integrated DNA/RNA analysis system.

Biosensing Techniques↗

PubMed1998

Serotonin and neuroendocrine peptides influence DNA synthesis in rat and human small intestinal cells in vitro.

Animal studies suggest a mediator role for neuroendocrine peptides and amines in regulating cell proliferation in the gastrointestinal epithelium. Our aim was to examine the effect of serotonin and selected gastrointestinal peptides on DNA synthesis in a rat and human small intestinal cell line in vitro. IEC-6 and FHs-74 cells were incubated with epidermal growth factor (EGF), insulin-like growth factor II, glucagon, substance P, neurokinin A, calcitonin gene-related peptide (GRP, CCGRP), neurotensin and serotonin. The cells were labelled with [methyl-3H] thymidine and processed for autoradiography. DNA synthesis was evaluated by the labelling index. Epidermal growth factor, insulin-like growth factor II, glucagon, and substance P increased the labelling index in a dose-related manner (P < 0.003). In contrast, a significant dose-dependent reduction of the labelling index was observed after administration of serotonin and neurokinin A (P < 0.0001). Neurotensin and CGRP did not affect the labelling index. EGF, insulin-like growth factor II, glucagon, substance P, serotonin and neurokinin A may be important physiological regulators of proliferation, of gastrointestinal cells.

Animals↗

PubMed1998

Cancer-associated strains of Helicobacter pylori stimulate DNA synthesis in IEC-6 cells.

OBJECTIVE: To determine whether water extracts of Helicobacter pylori strains, which express CagA, can influence DNA synthesis in untransformed intestinal epithelial cells in vitro. DESIGN: We used water extracts produced from H. pylori strains (A, B, C), collected from gastric mucosa of gastric cancer patients. Strain A was CagA+/VacA+ whereas strains B and C were CagA+/VacA-. Water extracts from Helicobacter mustelae and Escherichia coli were used as controls. METHODS: IEC-6 cells (small intestinal epithelial cell line from germ-free rats) were incubated with various concentrations of the bacterial extracts for 24 h. The cells were labelled with [3H]methylthymidine for 4 h and thereafter processed for autoradiography. DNA synthesis was evaluated by the labelling index (LI%). RESULTS: Water extracts from CagA-positive strains of H. pylori, with or without the capacity to produce vacuolating toxins, increased the LI in a dose-related manner (P < 0.05). The water extracts of E. coli significantly increased the LI (P < 0.001), whereas the water extracts of H. mustelae did not affect DNA synthesis. CONCLUSIONS: Cancer-associated, CagA-positive strains of H. pylori stimulate DNA synthesis in epithelial cells in vitro, independently of their ability to produce VacA toxin. Our findings suggest that unknown mitogenic components of H. pylori may contribute to the increased cell proliferation observed in the histological stages preceding gastric cancer.

Animals↗

PubMed1998

Helicobacter pylori stimulates DNA synthesis in a small intestinal cell line in vitro.

BACKGROUND: Helicobacter pylori, which causes gastritis and peptic ulcer, seems to be an important factor in the pathogenesis of gastric cancer and MALT lymphoma. Thus our aim was to examine whether H. pylori influences DNA synthesis in epithelial cells in vitro. METHODS: Sonicated and water extracts of H. pylori (cytotoxic strains NCTC 11637, 88-23 and A5, and a noncytotoxic isogenic mutant of A5, A5 vac A) were diluted to a final concentration of 1/1,000, 1/100, 1/50 and 1/10. Water extracts of Escherichia coli were used as reference. IEC-6 cells were incubated during 24 h with fragments of H. pylori or extracts of the concentrations described above. The cells were labeled with 3H-methylthymidine for 4 h and processed for autoradiography. DNA synthesis was evaluated by the labeling index (LI). RESULTS: The LI% of controls was 15.6 +/- 5.1%. All the water extracts and sonicated strains of H. pylori increased the LI% in a dose-dependent manner (p < 0.001). The highest concentrations of the sonicated strains tended to reduce the LI%, although these values were still higher than those of the control group. The water extracts of E. coli increased the LI% in a dose-dependent manner (p < 0.0001). CONCLUSION: H. pylori stimulates DNA synthesis in epithelial cells in vitro, but no association was found with the presence of cytotoxin production. Our results suggest that hitherto unknown components of H. pylori may contribute to the increase in cell proliferation observed in gastritis and to the development of MALT lymphoma and gastric cancer.

Animals↗

PubMed1997

Cell kinetic events in early indomethacin-induced gastrointestinal ulcerations in the rat.

OBJECTIVE: To follow the sequence of cell kinetic events leading to the development of ulcerations in the gastrointestinal mucosa to better define primary actions of the drug and secondary phenomena mediated by the mucosal regulatory mechanisms. DESIGN: Sprague-Dawley rats were given 4 mg/kg indomethacin subcutaneously as a single dose and killed 4h later. Additional rats were given three and five doses, twice daily, and were killed at 24h and 48h, respectively. Other groups were treated with indomethacin and oral prostaglandin E2 or placebo. All rats were killed 3h after mitotic arrest with vincristine. METHODS: Histological sections from the oxyntic mucosa and proximal and distal jejunum were evaluated using a light microscope. The total number of arrested mitoses were counted in 250 microm width area of 30 consequent fields. In addition, the thickness and proliferative zone of the mucosa were determined. The cumulative mitotic index (MI%) and the number of cells in the left column of 30 well oriented crypts and villi were estimated in the proximal and distal small intestine. RESULTS: The vast majority of rats given five doses of indomethacin developed small intestinal ulcerations and peritonitis and most of them showed haemorrhagic lesions in the oxyntic mucosa. Indomethacin reduced the number of mitotic cells in the oxyntic mucosa after three and five doses compared to controls (P<0.05). In addition, the thickness was significantly reduced in rats given five doses of indomethacin (P<0.05). These changes were prevented by the concomitant administration of prostaglandin E2. The MI% of the jejunal crypts was not affected by indomethacin but the number of villous cells was significantly lower in rats given five doses of indomethacin than in controls (P<0.05). A slight villous hyperplasia was observed in animals given three doses of indomethacin with prostaglandin E2 (P<0.05). The number of crypt cells was unaffected by treatments. CONCLUSION: Indomethacin reduced cell proliferation in the oxyntic and jejunal epithelium, and increased epithelial cell losses, which are cell kinetic mechanisms leading to development of ulcerations. The regulatory mechanisms that increase DNA synthesis need longer periods of time to be triggered and they were not apparent in this model, in which the marked cell kinetic changes induced by indomethacin produced ulcerations within 48 h.

Animals↗