A multicenter, double-blind study on triple therapy with lansoprazole, amoxicillin and clarithromycin for eradication of Helicobacter pylori in Japanese peptic ulcer patients

BACKGROUND

Two triple therapies with lansoprazole (LPZ)/amoxicillin (AMPC)/clarithromycin (CAM) for eradication of Helicobacter pylori were studied in multicenter, double-blind fashion to evaluate the eradication rate of H. pylori and safety of eradiation treatment in Japanese patients with H. pylori-positive active gastric ulcers or duodenal ulcers.

METHODS

Patients were randomly chosen for the control treatment of LPZ 30 mg twice a day (b.i.d.; Group A-LPZ-only) or the test treatments of LPZ 30 mg plus AMPC 750 mg and CAM 200 mg b.i.d. (Group B-LAC200) and LPZ 30 mg, AMPC 750 mg and CAM 400 mg b.i.d. (Group C-LAC400). All eradication treatments lasted for a period of 7 days. Successful eradication was assessed by culture and gastric histology 1 month after completion of the ulcer treatment.

RESULTS

The eradication rates of H. pylori in the full analysis set were 0% in Group A-LPZ-only, 87.5% in Group B-LAC200 and 89.2% in Group C-LAC400 for gastric ulcer and, 4.4% in Group A-LPZ-only, 91.1% in Group B-LAC200 and 83.7% in Group C-LAC400 for duodenal ulcer. The eradication rates of Group B-LAC200 and Group C-LAC400 were 89.2% (95% CI: 84.8-93.7%) and 86.4% (95%CI: 81.5-91.3%) in total in the full analysis set, 89% (95% CI: 84.3-93.7%) and 85.3% (95%CI: 80.1-90.5%) in the per protocol set. The eradication rates in Groups B-LAC200 and group C-LAC400 were statistically significantly higher than the rate in Group A-LPZ-only for both gastric ulcer and duodenal ulcer patients (p <.0001 for both).

CONCLUSION

A satisfactorily high H. pylori eradication rate was obtained in Japanese ulcer patients with the triple therapy regimen consisting of LPZ 30 mg, AMPC 750 mg, and CAM 200 mg b.i.d.

Spatial expression patterns of genes involved in cyclic AMP responses in Dictyostelium discoideum development

The spatial expression patterns of genes involved in cyclic adenosine monophosphate (cAMP) responses during morphogenesis in Dictyostelium discoideum were analyzed by in situ hybridization. Genes encoding adenylyl cyclase A (ACA), cAMP receptor 1, G-protein alpha2 and beta subunits, cytosolic activator of ACA (CRAC and Aimless), catalytic subunit of protein kinase A (PKA-C) and cAMP phosphodiesterases (PDE and REG-A) were preferentially expressed in the anterior prestalk (tip) region of slugs, which acts as an organizing center. MAP kinase ERK2 (extracellular signal-regulated kinase-2) mRNA, however, was enriched in the posterior prespore region. At the culmination stage, the expression of ACA, CRAC and PKA-C mRNA increased in prespore cells in contrast with the previous stage. However, no alteration in the site of expression was observed for the other mRNA analyzed. Based on these findings, two and four classes of expression patterns were catalogued for these genes during the slug and culmination stages, respectively. Promoter analyses of genes in particular classes should enhance understanding of the regulation of dynamic and coordinated gene expression during morphogenesis.

Identification and characterization of DdPDE3, a cGMP-selective phosphodiesterase from Dictyostelium

In Dictyostelium cAMP and cGMP have important functions as first and second messengers in chemotaxis and development. Two cyclic-nucleotide phosphodiesterases (DdPDE 1 and 2) have been identified previously, an extracellular dual-specificity enzyme and an intracellular cAMP-specific enzyme (encoded by the psdA and regA genes respectively). Biochemical data suggest the presence of at least one cGMP-specific phosphodiesterase (PDE) that is activated by cGMP. Using bioinformatics we identified a partial sequence in the Dictyostelium expressed sequence tag database that shows a high degree of amino acid sequence identity with mammalian PDE catalytic domains (DdPDE3). The deduced amino acid sequence of a full-length DdPDE3 cDNA isolated in this study predicts a 60 kDa protein with a 300-residue C-terminal PDE catalytic domain, which is preceded by approx. 200 residues rich in asparagine and glutamine residues. Expression of the DdPDE3 catalytic domain in Escherichia coli shows that the enzyme has Michaelis-Menten kinetics and a higher affinity for cGMP (K(m)=0.22 microM) than for cAMP (K(m)=145 microM); cGMP does not stimulate enzyme activity. The enzyme requires bivalent cations for activity; Mn(2+) is preferred to Mg(2+), whereas Ca(2+) yields no activity. DdPDE3 is inhibited by 3-isobutyl-1-methylxanthine with an IC(50) of approx. 60 microM. Overexpression of the DdPDE3 catalytic domain in Dictyostelium confirms these kinetic properties without indications of its activation by cGMP. The properties of DdPDE3 resemble those of mammalian PDE9, which also shows the highest sequence similarity within the catalytic domains. DdPDE3 is the first cGMP-selective PDE identified in lower eukaryotes.

Effects of the administration of growth hormone-releasing peptide-2 (GHRP-2) orally by gavage and in feed on growth hormone release in swine

The experiments were conducted to determine the effects of the administration of growth hormone-releasing peptide-2 (GHRP-2, also named KP102), both orally by gavage and in feed, on the release of growth hormone (GH) in swine and to investigate whether attenuation of the GH response occurs after short-term treatment with the peptide in feed. In the first experiment, saline or GHRP-2 at doses of 1, 4.5 and 9 mg/kg body weight (BW) was dissolved in 15 ml saline and administered orally as a bolus by gavage to cross-bred castrated male swine (n = 6). Orally administered GHRP-2 stimulated dose-related increases in peak concentrations of GH, with a return to basal by 120 min. After administering GHRP-2 orally, peak concentrations of GH and areas under the GH response curves (GH AUCs) for 180 min were higher (P < 0.05) than those in saline controls. In Experiment 2, GHRP-2 at doses of 0 (served as control), 1, 4.5 and 9 mg/kg BW was mixed in 150 g of feed and offered to cross-bred castrated male swine (n = 6) at 0900 hr and 1700 hr daily for a 3-d period. Administration of 1 mg/kg BW GHRP-2 to swine in feed failed to stimulate the release of GH, but GHRP-2 at doses of 4.5 and 9 mg/kg BW significantly (P < 0.05) increased plasma concentrations of GH after initial and final treatments at 0900 hr on Days 1 and 3 of treatment, respectively. Peak concentrations of GH and GH AUCs for 180 min after the initial and final treatments in the 4.5 and 9 mg/kg BW GHRP-2-treated swine were higher (P < 0.05) than those in controls. After 3 d of treatment with GHRP-2 in feed at doses of 4.5 and 9 mg/kg BW, GH responses to the peptide were maintained. The results of the present study indicate that the administration of GHRP-2 orally by gavage and in feed stimulates the release of GH in swine, and that the GH-releasing effect of the peptide does not become desensitized after short-term administration in feed.

A novel role of differentiation-inducing factor-1 in Dictyostelium development, assessed by the restoration of a developmental defect in a mutant lacking mitogen-activated protein kinase ERK2

It has been previously reported that the differentiating wild-type cells of Dictyostelium discoideum secrete a diffusible factor or factors that are able to rescue the developmental defect in the mutant lacking extracellular signal-regulated kinase 2 (ERK2), encoded by the gene erkB. In the present study, it is demonstrated that differentiation-inducing factor-1 (DIF-1) for stalk cells can mimic the role of the factor(s) and the mechanism of the action of DIF-1 in the erkB null mutant is also discussed. The mutant usually never forms multicellular aggregates, because of its defect in cyclic adenosine monophosphate (cAMP) signaling. In the presence of 100 nM DIF-1, however, the mutant cells formed tiny slugs, which eventually developed into small fruiting bodies. In contrast, DIF-1 never rescued the developmental arrest of other Dictyostelium mutants lacking adenylyl cyclase A (ACA), cAMP receptors cAR1 and cAR3, heterotrimeric G-protein, the cytosolic regulator of ACA, or the catalytic subunit of cAMP-dependent protein kinase (PKA-C). Most importantly, it was found that DIF-1 did not affect the cellular cAMP level, but rather elevated the transcriptional level of pka during the development of erkB null cells. These results suggest that DIF-1 may rescue the developmental defect in erkB null cells via the increase in PKA activity, thus giving the first conclusive evidence that DIF-1 plays a crucial role in the early events of Dictyostelium development as well as in prestalk and stalk cell induction.

Developmental changes in the spatial expression of genes involved in myosin function in Dictyostelium

We analyzed the spatial expression patterns of the genes involved in myosin function by in situ hybridization at the tipped aggregate and early culmination stages of Dictyostelium. Myosin heavy chain II mRNA was enriched in the anterior prestalk region of the tipped aggregates, whereas it disappeared from there and began to appear in both upper and lower cups of the early culminants. Similarly, mRNAs for essential light chain, regulatory light chain, myosin light chain kinase A, and myosin heavy chain kinase C were enriched in the prestalk region of the tipped aggregates. However, expression of these genes was distinctively regulated in the early culminants. These findings suggest the existence of mechanisms responsible for the expression of particular genes.

A diffusible factor involved in MAP-kinase ERK2-regulated development of Dictyostelium

Mitogen-activated protein (MAP)-kinase extracellular signal regulated kinase (ERK2) is essential for regulation of the intracellular cyclic adenosine monophosphate (cAMP) level in Dictyostelium. The mutant lacking ERK2, erk2-null, is arrested at the pre-aggregation stage, but develops into a fruiting body in a mixed population of wild-type and mutant cells. This fact implies that wild-type cells provide a certain factor that is missing in erk2-null. It was clarified that both wild-type strains KAx3 and Ax2 secreted a diffusible factor that enables erk2-null to develop. The fruiting body formed from erk2-null cells was smaller than that formed by the wild-type cells and consisted of a small sorus supported by a slender stalk with a single row of vacuolated stalk cells. The resulting spores were able to germinate and multiply on a bacterial lawn, but they were unable to develop unless the factor was provided. After 8 h of starvation, wild-type cells started to secrete the factor, which had a molecular mass of less than 3 kDa and was heat stable. The effect of this factor could not be mimicked by either cAMP or folate. Adenylyl cyclase A and cell surface cAMP receptors cAR1 and cAR3 were all indispensable components for the factor to function. Considering the molecular mass and the mode of action, this factor could be a novel one. Possible targets of this factor are discussed in terms of cAMP-dependent protein kinase activation.

The effect of NSAIDs and a COX-2 specific inhibitor on Helicobacter pylori-induced PGE2 and HGF in human gastric fibroblasts

BACKGROUND

There is compelling evidence for the pivotal role of Helicobacter pylori in the pathogenesis of gastrointestinal ulcer disease. However, despite the bacterium's toxicity, the majority of H. pylori infections are not accompanied by gastric ulcers. This implies the existence of a host mechanism offsetting H. pylori toxicity.

AIMS

To evaluate gastric fibroblasts' expression of hepatocyte growth factor (HGF), which is known to facilitate gastric ulcer healing, in the presence of H. pylori; to compare the effect on H. pylori-induced HGF expression of a COX-2 selective inhibitor with that of nonselective nonsteroidal anti-inflammatory drugs

METHODS

Human gastric fibroblasts were cultured from human gastric mucosa obtained at surgery. Prostaglandin E2 (PGE2) and HGF were measured by EIA. The expression of COX-2 mRNA was assessed by the TaqMan quantitative RT-PCR system.

RESULTS

H. pylori increased PGE2 release in gastric fibroblasts. H. pylori induced expression of COX-2 mRNA, which indicates that PG induction by H. pylori is through COX-2. Sulindac sulphide, etodolac and NS 398 all inhibited H. pylori-induced PGE2 release to the same extent. These agents also inhibited H. pylori-induced HGF release.

CONCLUSION

Gastric fibroblasts produce PG and HGF in response to the presence of H. pylori, which may be considered part of the human body's defensive reaction to H. pylori toxicity. This defensive mechanism is inhibited not only by COX-2 nonselective NSAIDs but also by a COX-2 selective inhibitor. These findings indicate the importance of COX-2 in chronic H. pylori infection.

Gastric epithelial cell proliferation and apoptosis in Helicobacter pylori-infected mice

BACKGROUND

Helicobacter pylori causes gastritis and is strongly associated with gastroduodenal ulcer and gastric cancer. The bacterium is associated with an increased rate of epithelial proliferation, which can be reversed by eradication of the organism. The mechanism of this response is not known, but this epithelial proliferation is one of the risk factors for developing gastric carcinoma. Recently, apoptosis also was found to be increased in the gastric mucosa of persons carrying H. pylori.

METHODS

cagA-positive H. pylori isolated from a human gastric ulcer was inoculated into BALB/C mice. At 4, 6, 12, 18 and 24 weeks, mice were injected with bromodeoxyuridine 5 mg/kg and killed 1 h later. Proliferation was analysed by histochemical staining for BrdU; apoptosis was examined by the TUNEL assay.

RESULTS

The number of BrdU-labelled cells in the antrum was significantly increased by H. pylori infection beginning 12 weeks after infection. The number of apoptotic cells in this tissue was increased significantly by 6 weeks after inoculation.

CONCLUSION

The proliferation observed in H. pylori infection may be a response to increased apoptosis.

The effect of growth hormone-releasing peptide-2 (KP102) administration on plasma insulin-like growth factor (IGF)-1 and IGF-binding proteins in Holstein steers on different planes of nutrition

This study was conducted to investigate the nutrition-dependent changes in insulin-like growth factor (IGF)-1 and IGF-binding proteins (IGFBPs) with growth hormone releasing peptide-2 (D-Ala-D-betaNal-Ala-Trp-D-Phe-Lys-NH(2); GHRP-2 or KP102) treatment in growing Holstein steers. Eight 13 month-old Holstein steers were grouped on two levels of feed intake (high intake (HI); 2.43% body weight or low intake (LI); 1.22%) and each group was daily injected with KP102 (12.5 microg/kg body weight/day) or saline solution into the jugular vein during 6-day period. The concentration of plasma GH showed an increase after an i.v. bolus injection of KP102 on Day 1 and Day 6 in both the LI and HI groups. Plasma IGF-1 began to increase 10 hr following an i.v. bolus injection of KP102, but this was only observed in the HI group (P < 0.05). Also, the plasma IGF-1 in the HI group with daily injections was significantly greater than the LI group from Day 1 of KP102 administration (P < 0.05). It reached maximum values of 125.1 +/- 7.6 ng/ml after Day 2, and returned to pre-injection levels after Day 4, however, no change in plasma IGF-1 was observed in LI with administration of KP102. During 6 days of treatment, plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 were significantly higher in KP102 treated steers but only in the HI group (P < 0.05). Plasma 34 kDa IGFBP-2 decreased in the HI group and did not show any change following an injection of KP102. In conclusion, the effect of stimulated endogenous GH with KP102 administration increased plasma IGF-1, 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 levels in the HI group of growing Holstein steers, but not in the LI one. Thus, we strongly believe that the plasma IGF-1 and IGFBPs response to KP102 treatment is modulated by the nutritional status of growing Holstein steers and the increased plasma IGF-1 concentration with KP102 treatment may be regulated by plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 in Holstein steers.

The effects of growth hormone-releasing peptide-2 (GHRP-2) on the release of growth hormone and growth performance in swine

The effects of GHRP-2 (also named KP102), a new growth hormone-releasing peptide, on the release of growth hormone (GH) and growth performance were examined in swine. The single intravenous (i. v.) injection of GHRP-2 at doses of 2, 10, 30 and 100 microg/kg body weight (BW) to cross-bred castrated male swine stimulated GH release in a dose-dependent manner, with a return to the baseline by 120 min. The peak GH concentrations and GH areas under the response curves (GH AUCs) for 180 min after the injections of GHRP-2 were higher (P < 0.05) than those after the injection of saline. The GH responses to repeated i.v. injections of GHRP-2 (30 microg/kg BW) at 2-h intervals for 6 h were decreased after each injection. The chronic subcutaneous (s.c.) administration of GHRP-2 (30 microg/kg BW) once daily for 30 days consistently stimulated GH release. The GH AUCs for 300 min after the injections on d 1, 10 and 30 of treatment in GHRP-2-treated swine were higher than those in saline-treated swine. However, chronic administration of GHRP-2 caused a partial attenuation of GH response between d 1 and 10 of treatment. The chronic s.c. administration of GHRP-2 also increased average daily gain for the entire treatment period by 22.35% (P < 0.05) and feed efficiency (feed/gain) by 20.64% (P < 0.01) over the saline control values, but did not significantly affect daily feed intake. These results indicate that GHRP-2 stimulates GH release and enhancing growth performance in swine.

Gastric epithelial cells stimulate Helicobacter pylori growth

Helicobacter pylori infects only human gastric epithelium, causes gastritis, and is strongly associated with gastroduodenal ulceration and gastric cancer. Colonization of the stomach with H. pylori is accompanied in the acute stage by an increased number of neutrophils in the lamina propria, indicative of gastric inflammation. It is interesting that H. pylori colonizes specifically human gastric-type epithelial cells. We studied whether the presence of gastric epithelial cells influenced H. pylori growth. H. pylori (NCTC 11637) was cultured on Skirrow agar with 7% horse blood. Kato-III cells, a human gastric cancer cell line, were cultured with RPMI 1640 plus 10% fetal bovine serum (FBS). Kato-III cells (10(5)/ml) were cultured with/ without H. pylori (10(8) cfu/ml) with RPMI 1640 + 1% FBS for 3 days. The number of Kato-III cells was counted with a hemacytometer. H. pylori with/without Kato-III cells was cultured with RPMI 1640 + 10% FBS for 2 hours, and plated on Skirrow agar. After 3 days we counted the number of H. pylori colonies. To detect the H. pylori colonies, we used a colony hybridization method. DNA of colonies was transferred to positively charged nylon membrane and hybridized by PCR with Hpl (5'-CTG-GAG-AGA-CTA-AGC-CCT-CC-3') and Hp2 (5'-ATT-ACT-GAC-GCT-GAT-TGT-GC-3')-amplified primers. We previously reported that the number of Kato-III cells was significantly decreased by co-incubation with H. pylori. The number of H. pylori colonies was significantly increased by coincubation with Kato-III cells. We conclude that the presence of human gastric epithelial cells is important for the growth of H. pylori.

Protective role of melatonin and the pineal gland in modulating water immersion restraint stress ulcer in rats

We investigated the protective effect of melatonin on stress-induced gastric lesions in rats. Fasted rats were subjected to water immersion restraint stress for 4 h and the percentage of corpus mucosa containing hemorrhagic lesions was determined. Thirty minutes before restraint stress, melatonin or vehicle was administered i.p. In another experiment, pinealectomy was performed 1 week before water immersion restraint stress. Administration of melatonin at 1 and 5 mg/kg significantly decreased gastric lesions by 46 and 74%, respectively. In contrast, pinealectomy significantly enlarged the lesion area, although this effect was counteracted by melatonin at a dose of 1 mg/kg i.p. However, this protective effect of melatonin was abolished by i.p. pretreatment with indomethacin at 5 mg/kg. These results suggest that melatonin has gastroprotective properties against stress-induced gastric injury in rats and that the pineal gland contributes to gastric protection via prostaglandin-dependent mechanisms.

Lansoprazole elevates the ratio of serum pepsinogen I v.s. pepsinogen II

In order to investigate the mechanism by which proton pump inhibitor increases serum pepsinogen levels, we evaluated the effects of ulcer location and IgG antibody against Helicobacter pylori on lansoprazole-induced elevations. Patients with endoscopically proven peptic ulcer received lansoprazole 30 mg/day for 6 or 8 weeks; pepsinogen I and II levels, along with antibody to H. pylori, were measured in fasting blood samples. We found that whether or not antibody to H. pylori was present, pepsinogen I and II levels and the I/II ratio rose significantly in lansoprazole-treated patients. Patients with stomach-body ulcers showed smaller increases in both pepsinogens than did those with ulcers in the gastric angle/antrum or in the duodenum. In conclusion, lansoprazole increases serum levels of both pepsinogens I and II, although a larger increase in pepsinogen I elevates the pepsinogen I/II ratio. The relatively small increases seen in patients with stomach-body ulcers suggest atrophic changes in the gastric mucosa in patients with stomach-body ulcer.

Chemotactic and osmotic signals share a cGMP transduction pathway in Dictyostelium discoideum

In the ameboid eukaryote Dictyostelium discoideum, chemotactic stimulation by cAMP induces an increase of intracellular cGMP and subsequently the phosphorylation of myosin heavy chain II. Resistance to high osmotic stress also requires transient increases of intracellular cGMP and phosphorylation of myosin heavy chain II, although the kinetics is much slower than for chemotaxis. To examine if chemotaxis and osmotic stress share common signaling components we systematically analyzed the osmotic cGMP response and survival in chemotactic mutants with altered cGMP signaling. Null mutants with deletions of cell surface cAMP receptors or the associated GTP-binding proteins Galpha2 and Gbeta show no cAMP-induced cGMP response and chemotaxis; in contrast, osmotic stress induces the normal cGMP accumulation and survival. The same result was obtained with the non-chemotactic mutant KI-10, which lacks the activation of guanylyl cyclase by cAMP. This indicates that these components are required for chemotaxis but not osmotic cGMP signaling and survival. The potential guanylyl cyclase null mutant KI-8 shows no chemotaxis, no osmotic cGMP increase and reduced survival in high osmolarity. Two types of cGMP-binding protein mutants, KI-4 and KI-7, also show reduced tolerance during high osmotic stress. Taken together, these observations clarify that chemotactic and osmotic signals are detected by different mechanisms, but share a cGMP signaling pathway.

cGMP potentiates receptor-stimulated Ca2+ influx in Dictyostelium discoideum

Binding of extracellular cAMP to surface receptors induces at least two responses in Dictyostelium discoideum, the G-protein-dependent activation of guanylyl cyclase, and the opening of a plasma membrane Ca2+ channel. Some experiments suggest that intracellular cGMP opens the Ca2+ channel, while others demonstrate that the channel can open in the absence of functional G-proteins (and thus in the absence of cGMP formation). We have analysed 45Ca2+ uptake in three mutants with altered cGMP formation. Mutant stmF shows a prolonged cGMP response due to deletion of an intracellular phosphodiesterase. Uptake of receptor-stimulated 45Ca2+ is enhanced about two-fold in this mutant if compared to wild-type cells, suggesting that cGMP regulates the opening of the channel. Mutant KI-7 has very low levels of surface cAMP receptors, but nevertheless an enhanced receptor-stimulated cGMP response due to a defect in the turn-off of guanylyl cyclase. This mutant shows poor receptor-stimulated 45Ca2+ uptake, suggesting that cGMP alone is not sufficient to open the Ca2+ channel. Finally, mutant KI-8 has no cGMP due to the absence of nearly all guanylyl cyclase activity. The mutant shows significant but reduced 45Ca2+ uptake (19% of wild-type; 60% if corrected for the reduced level of surface cAMP receptors), suggesting that the channel can open in the absence of cGMP. Taken together, the results demonstrate that receptor-stimulated Ca2+ influx is not directly induced by cGMP formation; it can occur in the absence of cGMP, but is potentiated two- to four-fold by cGMP.

Helicobacter pylori, neutrophils, interleukins, and gastric epithelial proliferation

Infection of Helicobacter pylori causes chronic gastritis and plays an important role in the pathogenesis of gastroduodenal ulceration. H. pylori has also been suggested to be involved in the genesis of adenocarcincoma and MALT lymphoma of the stomach. H. pylori infection is associated with increased gastric epithelial proliferation, which can be reversed by a successful eradication of the organism. Although the mechanisms of increased gastric epithelial proliferation is not known, the enhanced epithelial proliferation is important in developing gastric carcinoma. Whether or not H. pylori de nove stimulates gastric epithelial proliferation is controversial, but gastric infection with H. pylori activates a mucosal inflammatory response by consisting of large numbers of polymorphonuclear and mononuclear cells, that also includes expression of various cytokines including interleukin-8. We review the mechanisms of H. pylori in enhanced gastric epithelial cell proliferation and cytokines in patients with H. pylori infection.

[Role of Helicobacter pylori in reflux esophagitis]

It is now widely accepted that peptic ulcer disease (PUD) is a result of chronic infection of Helicobacter pylori (H. pylori). Thus, treatment of PUD should be aimed toward eradication of H. pylori with antibiotics. One the other hand, recent study from England suggested that eradication of H. pylori may provoke development of reflux esophagitis in duodenal ulcer patients. Despite duodenall ulcer patients with concomitant esophagitis is a specific type of esophagitis, it is important to recognize the development of reflux esophagitis after cure of H. pylori infection. Whether the development of reflux esophagitis is occurred in other H. pylori-related disease such as gastric ulcer remains to be studied.

cGMP as second messenger during Dictyostelium chemotaxis

The chemoattractant cAMP induces directed cell locomotion in Dictyostelium cells. Several second messenger pathways are activated upon binding of cAMP to G-protein-coupled receptors, including adenylyl cyclase, guanylyl cyclase, phospholipase C, and the opening of plasma membrane Ca2+ channels. These second messenger responses are unaltered in many chemotactic mutants, except for the cGMP response. Activation of guanylyl cyclase depends on G-proteins and is regulated by a cGMP-binding protein in a complex manner. This cGMP-binding protein also mediates intracellular functions of cGMP to activate a PKC-related kinase that phosphorylates myosin II heavy chain, thereby allowing myosin filaments to rearrange during cell movement.

Regulation of guanylyl cyclase by a cGMP-binding protein during chemotaxis in Dictyostelium discoideum

Chemoattractants transiently activate guanylyl cyclase in Dictyostelium discoideum cells. Mutant analysis demonstrates that the produced cGMP plays an essential role in chemotactic signal transduction, controlling the actomyosin-dependent motive force. Guanylyl cyclase activity is associated with the particulate fraction of a cell homogenate. The addition of the cytosol stimulates guanylyl cyclase activity, whereas the cytosol plus ATP/Mg2+ inhibits enzyme activity. We have analyzed the regulation of guanylyl cyclase in chemotactic mutants and present evidence that a cGMP-binding protein mediates both stimulation and ATP-dependent inhibition of guanylyl cyclase. Upon chromatography of cytosolic proteins, cGMP binding activity co-elutes with both guanylyl cyclase-stimulating and ATP-dependent-inhibiting activities. In addition, ATP-dependent inhibition of guanylyl cyclase activity is enhanced by the cGMP analogue 8-Br-cGMP, suggesting that a cGMP-binding protein regulates guanylyl cyclase activity. Mutant KI-4 has an aberrant cGMP binding activity with very low Kd and shows a very small chemoattractant-mediated cGMP response; the cytosol from this mutant does not stimulate guanylyl cyclase. In contrast to KI-4, the aberrant cGMP binding activity of mutant KI-7 has a very high Kd and chemoattractants induce a prolonged cGMP response. The cytosol of this mutant stimulates guanylyl cyclase activity, but ATP does not inhibit the enzyme. Thus, two previously isolated chemotactic mutants are defective in the activation and inhibition of guanylyl cyclase, respectively. The positive and negative regulation of guanylyl cyclase by its product cGMP may well explain how cells process the temporospatial information of chemotactic signals, which is necessary for sensing the direction of the chemoattractant.

Effect of long-term sucralfate ingestion on antral and fundic epithelial proliferation in the rat

Sucralfate accelerates the healing of chronic gastric ulcers, but its mechanism is not well understood. We studied the effect of long-term administration of sucralfate on gastric epithelial proliferation in the rat by means of tritiated thymidine autoradiography. Rats were treated perorally with 500 mg/kg sucralfate once a day. After 28 days, rats were injected with tritiated thymidine 1 microCi/g body weight and sacrificed 1 hr later. Autoradiographs from antral and fundic mucosae were prepared and a number of proliferative measurements were made. Long-term sucralfate administration produced an increase in tritiated thymidine labeling of epithelial cells and expansion of the proliferative zone in antral mucosa. These results indicate that long-term sucralfate ingestion stimulates gastric antral epithelial proliferation in the rat. In light of the fact that chronic gastric ulcers are usually located in the antral region in humans, this enhanced epithelial proliferation may contribute to the beneficial effect of sucralfate in accelerating the healing of gastric ulcers.

Protection against osmotic stress by cGMP-mediated myosin phosphorylation

Conventional myosin functions universally as a generator of motive force in eukaryotic cells. Analysis of mutants of the microorganism Dictyostelium discoideum revealed that myosin also provides resistance against high external osmolarities. An osmo-induced increase of intracellular guanosine 3',5'-monophosphate was shown to mediate phosphorylation of three threonine residues on the myosin tail, which caused a relocalization of myosin required to resist osmotic stress. This redistribution of myosin allowed cells to adopt a spherical shape and may provide physical strength to withstand extensive cell shrinkage in high osmolarities.

Aberrant cGMP-binding activity in non-chemotactic Dictyostelium discoideum mutants

The kinetics of cGMP-binding to the major cGMP-binding activity in Dictyostelium were investigated in 10 non-chemotactic mutants (KI mutants; KI-1 approximately 10). A wild-type cell contains about 3000 binding sites with a Kd of 1.5 nM. cGMP may dissociate from these binding sites with fast (F-type) or slow (S-type) kinetics, and DNA has been shown to promote the conversion of F- to S-type of cGMP-binding. The 10 mutants were placed in 4 classes, based on equilibrium and non-equilibrium binding properties and the effect of DNA. Class I mutants (KI-1, 3 and 8) have normal cGMP-binding properties. Class II mutants (KI-2, 6 and 7) show increased Kd values but nearly normal Bmax, normal F/S ratio and normal effects of DNA. Class III mutants (KI-4, 5 and 10) have a strongly decreased Kd and increased Bmax, nearly all binding sites are of the S-type and DNA does not affect the binding; apparently these mutants have a cGMP-binding protein locked in the S-form. cGMP-binding in class IV mutant (KI-9) is normal except that the number of binding sites is increased about 3-fold. The finding of seven mutants with altered cGMP-binding in 10 non-chemotactic mutants suggests that the cGMP-binding activity plays an important role in the chemotactic signal transduction pathway.

Immunocytochemical localization of 155 kDa myosin light chain kinase and myosin heavy chain in bovine brain

We immunocytochemically stained the bovine brain with monoclonal antibodies against 155 kDa MLCK and myosin heavy chain (MHC) and a polyclonal antibody against calmodulin. In the bovine brain, a strong immunoreactivity with the anti-MLCK antibody was observed in neurons in all layers of the cerebral cortex and basal ganglia, and astrocytes in the white matter. The antibody also stained Purkinje, granular and molecular cells in the cerebellum. An anti MHC antibody stained neurons and astrocytes in the cerebral cortex and Purkinje cells similarly to the anti-MLCK antibody, whereas the MHC immunoreactivity was detected in the cerebellar glomerulus and there was no immunostaining of MHC in the granular and outer stellate cells. These results suggest that the 155 kDa MLCK might be related not only to the Ca-calmodulin-myosin system but also other intracellular system.