We conducted a longitudinal cohort study to determine the association of Helicobacter pylori infection and the progression of chronic atrophic gastritis (CAG) with gastric cancer. A cohort of 4,655 healthy asymptomatic subjects was followed for a mean period of 7.7 years. H. pylori infection was established by serum specific antibodies and the presence of CAG was confirmed by serum pepsinogen. During the follow-up period, 45 gastric cancer cases were detected (incidence rate, 126/100,000 person-years). A univariate analysis after adjustment for age showed that both H. pylori and CAG were significantly associated with gastric cancer. Despite a worldwide decline in incidence, gastric cancer remains one of the leading causes of cancer-related death in Japan. [1][2][3][4] There is a marked geographic variability in the gastric cancer incidence rate; the cancer is most common in China and Japan, and one of the lowest rates is in the United States. [1][2][3][4] Many epidemiologic studies have shown that the risk of gastric cancer is strongly associated with environmental factors, such as salt, nitrates and low intake of fresh fruits and vegetables. 1,4 -8 Recent studies have indicated that Helicobacter pylori infection is also a major risk factor for the development of gastric cancer. 9 -18 The prevalence of H. pylori infection is markedly higher in Japan than in other industrialized countries, although the reasons are not fully understood. 19 -21 The observed geographic variability in gastric cancer appears to be explained by a synergistic interaction between H. pylori infection and other environmental factors.The H. pylori bacterium colonizes the stomach mucosa and triggers a series of inflammatory reactions. It is considered an important cause of chronic atrophic gastritis (CAG), 19 -23 as shown in rodent models. 24 -26 CAG is considered the first step of a sequence of mucosal changes in the stomach leading to cancer. The current model for stomach carcinogenesis begins with gastritis, proceeds to CAG, then to intestinal metaplasia, dysplasia and, finally, carcinoma. 1,27 This hypothesis is supported by a considerable number of clinicopathological and epidemiological studies in countries with a high incidence of gastric cancer. However, longitudinal cohort studies that report an association of CAG with gastric cancer and a relation between the progression of CAG and the development of gastric cancer are limited. 28 -30 In addition, the role of H. pylori infection in the above-mentioned process of stomach carcinogenesis remains unclear. To investigate these problems relating to gastric cancer development, we established a cohort of male factory workers that we followed prospectively for 8 years.CAG in a high-risk population, such as Japanese subjects, usually begins at the gastric antrum and extends proximally towards the cardia. [31][32][33] As a result, gastric secretory function diminishes as the area of functional fundic gland mucosa gets smaller. 34 CAG is a histopathological diagnosis. It is difficult, howe...

In a freshly isolated endothelial cell preparation from rabbit aorta, the regulation of the acetylcholine (ACh)-sensitive intracellular Ca2+ store and the effects of the Ca(2+)-induced Ca2+ release agonists ryanodine and caffeine were studied using fura 2 imaging fluorescence microscopy. ACh (10 mumol/L) caused a transient release of Ca2+ from an intracellular store, presumably via an inositol tris-phosphate-sensitive mechanism. This ACh response could be repeated in the presence of extracellular Ca2+ but was obtained only once in Ca(2+)-free bathing solution, which shows that a depleted intracellular Ca2+ store can be rapidly refilled from the extracellular space. Refilling can be prevented by the endoplasmic reticulum Ca(2+)-ATPase inhibitor cyclopiazonic acid (10 mumol/L), implying that Ca2+ enters the cytoplasm before accumulation in the endoplasmic reticulum. Ionomycin (10 mumol/L) caused a large Ca2+ release even after the ACh-releasable store had been emptied, indicating the existence of other ACh-insensitive stores, perhaps including the mitochondria. In one third of the cells studied, ACh induced oscillations in [Ca2+]i that were dependent on extracellular Ca2+. Also investigated were the effects of caffeine and ryanodine. In this cell preparation neither caffeine nor ryanodine induced a Ca2+ transient but instead slowly increased [Ca2+]i. It was observed that both caffeine and ryanodine were able to slowly deplete the ACh-sensitive store. These results indicate the presence of functional ryanodine receptors in native endothelial cells and demonstrate overlap between the caffeine and agonist-sensitive Ca2+ stores. We also found that caffeine was able to directly inhibit the process of ACh-induced Ca2+ release.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of cyclopiazonic acid (CPA), an inhibitor of the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA), on cytosolic Ca2+ concentration ([Ca2+]c) and membrane currents were studied in isolated urinary bladder myocytes to test the hypothesis that the sarcoplasmic reticulum (SR) buffers Ca2+, which enters the myocyte at a slow to moderate rate. Inhibition of SERCA by CPA was demonstrated by the following modifications of the caffeine-induced [Ca2+]c transients: 1) CPA prolonged the 90% decay time from peak to resting [Ca2+]c from 2.2 +/- 0.3 to 8.3 +/- 0.92 s (n = 5), 2) CPA abolished the "undershoot" of the [Ca2+]c transient that follows the washout of caffeine, and 3) CPA prevented caffeine from inducing a second [Ca2+]c transient. CPA reversibly increased resting [Ca2+]c. Starting from a control [Ca2+]c of 137 +/- 10 nM, 19 of 24 cells responded with a monotonic increase in [Ca2+]c to a steady [Ca2+]c of 238 +/- 10 nM, whereas 5 of 24 cells responded with a transient rise of [Ca2+]c to 472 nM (within 2.8 +/- 0.5 s) followed by a decay to a steady [Ca2+]c of 161 +/- 10 nM. The CPA-mediated rise in [Ca2+]c was augmented by increasing extracellular Ca2+ concentration ([Ca2+]o), suggesting a "leakage pathway" for Ca2+ influx that is unmasked by SERCA blockade. CPA reduced [Ca2+]c transients and Ca(2+)-activated K+ currents (IK,Ca), induced by depolarizing clamp steps from -60 to 0 mV, compatible with suppression of SR Ca2+ release on depletion of SR Ca2+. To reduce the contribution due to Ca(2+)-induced Ca2+ release, the cells were depolarized with a slow ramplike command (-60 to 0 mV, 15 mV/s). In 12 of these 40 cells, CPA increased [Ca2+]c and IK,Ca signals. If spontaneous transient outward currents were present, they were suppressed by CPA. CPA reduced the peak L-type Ca2+ channel current apparently through increased Ca2+ inactivation of voltage-gated Ca2+ channels. The current could be restored to control by elevating [Ca2+]o from 2.5 to 5 mM. Under these conditions, CPA increased the ramp-induced [Ca2+]c transients from 105.1 +/- 22 to 162.0 +/- 31 nM (n = 9, P < 0.05). These results suggest that Ca2+ sequestration by the SR can buffer part of the Ca2+ influx during slow depolarizations.

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