Biomedical subjects

A Kurosawa

Publications and source records attributed to A Kurosawa.

At least 19 recordsLinked to original sources

PubMed2006

Investigation on the growth of coprophagy-prevented rats with supplemented vitamin B12.

The growth of coprophagy-prevented rats was compared under administration of normal levels of vitamin B12 and supplemented amounts. Two experiments in which supplemented amounts of vitamin B12 were administered were conducted under different conditions. Six rats per group were fed under coprophagy-allowed (conventional feeding) and coprophagy-prevented conditions respectively. In the first experiment, coprophagy-prevented rats were fed only feed containing recommended vitamin B12 level and forced fed hydrous faeces, vitamin B12 and folic acid respectively. In the second experiment, coprophagy-prevented rats were fed AIN-93G at the recommended vitamin B12 level (25 microg/kg diet), at 100 times the level and at 1000 times the level respectively. Body weight, feed consumption and amounts of each faeces type were determined in both experiments. In a comparison of body weight gain, we learned that coprophagy prevention reduced the values, but that there was no significant difference in the forced feeding group in the first experiment. Similar results were recognized in the second experiment. Vitamin B12 supplementation was not able to raise feed intake significantly and hence it obviously was not a severely limiting factor under the respective experimental condition which depressed feed intake.

Animal Feed↗

PubMed2004

Improvement in serum pepsinogens and gastrin in long-term monitoring after eradication of Helicobacter pylori: comparison with H. pylori-negative patients.

BACKGROUND: A decrease in pepsinogen and gastrin levels 1-3 months after Helicobacter pylori eradication is well known. However, few data are available on the long-term progression of these decreases beyond 1 year after eradication, and there has been no investigation into whether pepsinogen and gastrin levels return to normal levels as defined by data from H. pylori-negative patients with dyspepsia. AIM: We studied the effect of H. pylori eradication on pepsinogen and gastrin levels for more than 1 year, and compared levels to those in H. pylori-negative patients with dyspepsia. We also investigated the effect of H. pylori eradication on the course of atrophic corpus gastritis as reflected by histology, and on PGI levels and PG I/II ratio. METHODS: We enrolled 172 H. pylori-positive patients with dyspepsia who had undergone successful eradication therapy of more than 1 year's duration and 101 non-treated H. pylori-negative patients with dyspepsia. H. pylori status was assessed at entry and at each endoscopy after eradication by culture, histological results, the rapid urease test and the urea breath test. In both groups, patients were evaluated for fasting serum pepsinogen I and II and gastrin using a radioimmunoassay technique, and underwent detailed histological assessment according to the updated Sydney System. RESULTS: In the H. pylori-negative patients, mean serum pepsinogen I and II, I/II ratio and gastrin levels were 52.6 +/- 20.8 ng/mL, 9.2 +/- 4.2 ng/mL, 6.0 +/- 1.7 and 53.5 +/- 29.2 pg/mL, respectively. In H. pylori-positive patients with long-term eradication, pepsinogen I and II, I/II ratio and gastrin levels were 81.3 +/- 46.6 ng/mL, 25.9 +/- 17.1 ng/mL, 3.4 +/- 1.3 and 131.9 +/- 130.8 pg/mL, respectively, before treatment. At 1-3 months after eradication, serum pepsinogen I and II levels in the H. pylori-positive patients decreased to levels similar to those in the negative patients, whereas pepsinogen I/II ratio and gastrin levels remained lower and higher, respectively, than in the negative patients. Serum pepsinogen I/II ratio and gastrin levels then became similar between the groups at 12-15 months after eradication. In histological findings, inflammation and neutrophil activity decreased by 1-3 months, and atrophy in the corpus and metaplasia in the antrum decreased by 12-15 months. CONCLUSION: The results suggest that atrophic corpus gastritis and superficial gastritis are reversible, as indicated by both histological and serological findings in a long-term follow-up study.

Dyspepsia↗

PubMed2004

Oesophageal hypersensitivity in Japanese patients with non-erosive gastro-oesophageal reflux diseases.

BACKGROUND: Visceral hypersensitivity plays a major role in the pathogenesis of non-erosive oesophageal reflux disease (NERD). Prevalence of NERD differs according to the population and geographical region. Oesophageal hypersensitivity in NERD has not been well studied, especially in Japanese patients. AIM: To investigate oesophageal hypersensitivity in Japanese NERD patients. PATIENTS AND METHODS: We performed upper GI endoscopy and the modified acid perfusion test on 14 control subjects and 68 GERD patients, including 26 with NERD, 34 with erosive GERD, and six with Barrett's oesophagus. The stimulus-response function to acid was quantified by three parameters (lag time, intensity rating and the acid perfusion sensory score) and compared among four groups. RESULTS: The mean value of the lag time, intensity rating, and acid perfusion scores in NERD patients (4.6 +/- 3.4, 4.4 +/- 3.4, 27.8 +/- 26.7, respectively) were higher than in erosive GERD (3.2 +/- 3.3, 3.0 +/- 3.2, 18.2 +/- 24.8) and Barrett patients (2.5 +/- 4.0, 1.8 +/- 3.3, 15.0 +/- 28.8), and significantly higher than in the control group (1.7 +/- 2.7, 1.1 +/- 2.0, 5.4 +/- 11.8). The ratio of patients with higher sensory scores was also greater in the NERD group (57.7%) than in erosive GERD (32.3%) and Barrett group (16.7%), and significantly greater than in control group (6.7%). CONCLUSION: Our findings suggest that oesophageal sensitivity is likely to be enhanced especially in NERD patients also in Japanese population in comparison with erosive GERD, Barrett's oesophagus and controls.

Adult↗

PubMed2003

Is antimicrobial susceptibility testing necessary before second-line treatment for Helicobacter pylori infection?

BACKGROUND: An antimicrobial susceptibility test for Helicobacter pylori before second-line treatment is often performed, although whether the test is truly necessary remains unknown. PATIENTS AND METHODS: Eighty-two patients with H. pylori infection for whom first-line treatment with a 1-week proton pump inhibitor/amoxicillin-clarithromycin (AC) regimen had failed were randomly assigned to two groups: those having or not having the susceptibility test before re-treatment. The cure rates for these two groups were compared. RESULTS: Five of the 82 patients were excluded from the analysis. For 38 patients in the susceptibility-test group, we used what we considered the best regimen based on susceptibility testing: 10 patients [no resistance to clarithromycin (CAM)] received the lansoprazole-amoxicillin-clarithromycin regimen, 22 patients [19 CAM resistant, metronidazole (MNZ) susceptible; three failure of culture] were given the lansoprazole-amoxicillin-metronidazole (LAM) regimen, and six patients (both MNZ and CAM resistant) received dual therapy with omeprazole (OPZ) and amoxicillin (AMOX) in which the OPZ dose was determined by the CYP2C19 gene polymorphism. For 39 patients in the group with no susceptibility testing, LAM regimens were prescribed. The intention-to-treat (ITT)-based cure rates in the groups with and without susceptibility testing were 81.6% (95% confidence interval; 66-92%) and 92.4% (79-98%), respectively, and there was no significant difference between these two groups. CONCLUSION: Susceptibility testing is not necessarily required before second-line therapy if the first-line treatment has been performed using proton pump inhibitor/AC regimens.

Adult↗

PubMed2002

Inhibition of proliferation of gastric epithelial cells by a cyclooxygenase 2 inhibitor, JTE522, is also mediated by a PGE2-independent pathway.

BACKGROUND: Cyclooxygenase-2 (COX-2) is one of the rate-limiting enzymes for prostaglandin synthesis from arachidonic acid. Although it is known that inhibition of cyclooxygenase activity delays ulcer healing, the regulatory relationship between COX-2 and its metabolites in gastric epithelial cell proliferation is not well known. AIM: To investigate whether COX-2 has an effect on gastric mucosal cell proliferation and further studied whether such effect is mediated only by prostaglandin E2 (PGE2), a representative metabolite of arachidonates in the gastric mucosa. METHODS: Artificial wounds of defined area size were created on complete monolayer cell sheets of isolated rat gastric epithelial cells and rat gastric cell line RGM1 under the addition of arachidonic acid or a COX-2 selective inhibitor, JTE522. Repair of wounds was assessed by monitoring wound size, with cell proliferation detected using 5-bromodeoxyuridine staining. Quantity of secreted PGE2 was measured by enzyme immunoassay. RESULTS: Stimulation of foetal calf serum increased the expression of COX-2 protein and inhibition of COX-2 retarded wound healing with reduction of cell proliferation. Arachidonic acid increased PGE2 production and accelerated restoration. Combination of JTE522 and arachidonic acid resulted in a marked retardation of wound healing compared to the control, but JTE522 did not completely suppress the increase in cellular PGE2 content following the addition of arachidonate. CONCLUSIONS: The difference in the effects of JTE522 on PGE2 production and on wound healing suggest that the involvement of COX-2 in gastric epithelial cell proliferation is not mediated solely by PGE2.

Animals↗

PubMed2002

Alteration of histological gastritis after cure of Helicobacter pylori infection.

BACKGROUND: It is still disputed whether gastric atrophy or intestinal metaplasia improves after the cure of Helicobacter pylori infection. AIM: To clarify the histological changes after the cure of H. pylori infection through a literature survey. METHODS: Fifty-one selected reports from 1066 relevant articles were reviewed. The extracted data were pooled according to histological parameters of gastritis based on the (updated) Sydney system. RESULTS: Activity improved more rapidly than inflammation. Eleven of 25 reports described significant improvement of atrophy. Atrophy was not improved in one of four studies with a large sample size (> 100 samples) and in two of five studies with a long follow-up period (> 12 months), suggesting that disagreement between the studies was not totally due to sample size or follow-up period. Methodological flaws, such as patient selection, and statistical analysis based on the assumption that atrophy improves continuously and generally in all patients might be responsible for the inconsistent results. Four of 28 studies described significant improvement of intestinal metaplasia [corrected]. CONCLUSIONS: Activity and inflammation were improved after the cure of H. pylori infection. Atrophy did not improve generally among all patients, but improved in certain patients. Improvement of intestinal metaplasia was difficult to analyse due to methodological problems including statistical power.

Gastric Mucosa↗

PubMed2001

Five-day proton pump inhibitor-based quadruple therapy regimen is more effective than 7-day triple therapy regimen for Helicobacter pylori infection.

BACKGROUND: There have been no reports that describe whether 5-day quadruple therapy (rabeprazole + amoxicillin + clarithromycin + metronidazole; RACM) could substitute for standard 7-day triple therapy as a first-line therapy for Helicobacter pylori. PATIENTS AND METHODS: This study was designed as a randomized prospective single centre study. A total of 160 H. pylori-positive patients who had not received therapy were given either a 5-day RACM regimen (n=80, rabeprazole 20 mg b.d., amoxicillin 750 mg b.d., clarithromycin 200 mg b.d. and metronidazole 250 mg b.d.) or a 7-day RAC regimen (n=80, rabeprazole 20 mg b.d., amoxicillin 750 mg b.d. and clarithromycin 200 mg b.d.). Cure of the infection was assessed by a (13)C urea breath test 1 month after the completion of therapy. RESULTS: The eradication rates of the 5-day RACM regimen and the 7-day RAC regimen were 93% (95% CI: 84--97%) and 81% (95% CI: 71--89%) by intention-to-treat analysis, 94% (95% CI: 86--98%) and 83% (95% CI: 73--91%) by all-patients-treated analysis analysis and 95% (95% CI: 87--98%; P < 0.05) and 82% (95% CI: 72--90%) by per protocol analysis, respectively. No serious adverse effect was observed, and 99% of the patients reported complete compliance. CONCLUSIONS: The cure rate of the 5-day RACM regimen was more effective than the 7-day RAC regimen, suggesting that this regimen could be preferable as a first-line therapy for H. pylori infection.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2000

Comparison of the efficacy of 400mg and 800mg of clarithromycin used with lansoprazole and amoxicillin in eradication regimens for Helicobacter pylori infection in a Japanese population.

We conducted a randomized prospective comparative study to determine whether a 1-week lansoprazole-amoxicillin-clarithromycin (LAC) regimen with 800 mg of clarithromycin a day was more effective such a regimen with 400 mg daily in the Japanese population. One hundred and seventy-five Helicobacter pylori-positive patients were randomly assigned to receive one of two different 7-day regimens, one with clarithromycin 400 mg (LAC 400 regimen) and the other with clarithromycin 800 mg (LAC 800 regimen). The cure rates for both regimens were similar, although adverse effects were significantly more frequent in the LAC 800 regimen, suggesting that 400 mg of clarithromycin may be sufficient in our patient population.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2000

Addition of metronidazole to rabeprazole-amoxicillin-clarithromycin regimen for Helicobacter pylori infection provides an excellent cure rate with five-day therapy.

BACKGROUND: New triple therapy for eradication of Helicobacter pylori based on a proton pump inhibitor (PPI) provides a cure rate of approximately 90% with few adverse effects. Recently, a PPI-based quadruple therapy, which consists of a PPI plus bismuth-based triple therapy for 7 days, has been studied, and a sufficient eradication rate has been achieved. However, a shorter duration results in improved compliance. In this study, newly developed short-term, simple twice-daily quadruple therapy consisting of rabeprazole, amoxicillin, clarithromycin, and metronidazole (RACM) was compared with a PPI-based triple-therapy regimen for eradication of H. pylori. PATIENTS AND METHODS: This study was designed as a randomized open, prospective single-center study. Of a total of 105 H. pylori-positive patients, 55 received the RACM regimen for 5 days (rabeprazole, 10 mg bid; amoxicillin, 750 mg bid; clarithromycin, 200 mg bid; and metronidazole, 250 mg bid), and 50 received the RAC regimen for 5 days (rabeprazole, 10 mg bid; amoxicillin, 750 mg bid; and clarithromycin, 200 mg bid). Cure of the infection was assessed by HpSA (H. pylori stool antigen immunoassay) 1 month after completion of therapy. RESULTS: The rates of eradication of H. pylori by RACM versus RAC were 94.5% (95% CI, 85-99) versus 80.0% (95% CI, 66-90) by intention-to-treat analysis; 98.1% (95% CI, 90-100) versus 87.0% (95% CI, 74-95) by all-patients-treated analysis; and 98.1% (95% CI, 90-100) versus 86.7% (95% CI, 73-95) by per-protocol analysis. No major adverse effects were reported, and 98.0% of patients reported complete compliance. CONCLUSIONS: The simple twice-daily and short-term quadruple regimen for only 5 days provided an excellent eradication rate. Compliance with the regimen was high, and serious adverse effects were few. Therefore, the RACM regimen can be considered as safe and effective.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1996

Retinopathy in diabetic hypertensive monkeys: a pathologic study.

BACKGROUND: No satisfactory primate model of diabetic retinopathy has been produced. The clinical picture of microangiopathic retinopathy in diabetic hypertensive monkeys has been previously reported. The present study describes the pathologic findings of these animals. METHODS: Eleven eyes of six monkeys (five rhesus, one cynomolgus) were studied. Diabetes mellitus was either spontaneous or induced by streptozocin; mild arterial hypertension was either spontaneous or induced by fludrocortisone acetate. In two monkeys, the horseradish peroxidase tracer technique was employed. Trypsin flat preparations of the nasal retinal vasculature were prepared. The material was studied by light and electron microscopy. RESULTS: We divided the development of the microangiopathic retinopathy into three stages. In the early stage, background retinopathy was characterized by microvascular abnormalities and capillary dropout. Massive vascular leakage, intraretinal exudates and hemorrhage, cystoid degeneration, and cotton-wool spots were features of an exudative retinopathy in the second stage. In the final stage, chronic ischemic retinopathy was characterized by vascular occlusions and areas of retinal atrophy. CONCLUSION: Microangiopathic retinopathy in diabetic monkeys with mild hypertension presented many features of human diabetic and hypertensive retinopathy, except vitreous neovascularization.

Animals↗

PubMed1994

Effect of the selective thromboxane A2 receptor antagonist, S-1452, on antigen-induced sustained bronchial hyperresponsiveness.

Long-lasting bronchial hyperresponsiveness to i.v. acetylcholine was observed in actively sensitized guinea-pigs after aerosol ovalbumin exposure. The response became significant at 7 h post-challenge and persisted for at least 120 h compared to the response of unsensitized animals. Pretreatment of animals with the specific thromboxane A2 receptor antagonist, S-1452 (calcium (1R,2S,3S,4S)-(5Z)-7-(((phenylsulfonyl)amino)bicyclo[2.2.1] hept-2-yl)hept-5-enoate dihydrate), almost completely inhibited the onset of bronchial hyperresponsiveness, as assessed at 24 and 120 h post-challenge. However, it was ineffective when administered at 1 h post-challenge or 2 h before assessment of bronchial responsiveness. Lung vascular injury occurred transiently immediately after antigen challenge, the kinetics of injury being associated with those for the production of thromboxane B2 in bronchoalveolar lavage fluid. The vascular injury was dramatically suppressed by pretreatment with S-1452. These findings suggest that acutely generated thromboxane A2 plays an important role in the pathogenesis of antigen-induced long-lasting bronchial hyperresponsiveness, probably by producing vascular damage in the lungs.

Acetylcholine↗

PubMed1994

Contribution of thromboxane A2 to the antigen-induced immediate asthmatic response mediated by IgG1 antibody by augmentation of bronchial responsiveness in guinea-pigs.

1. IgG1-mediated anaphylactic bronchoconstriction was elicited by intravenous administration of antigen to guinea-pig 2 days after passive sensitization with IgG1-rich serum, and this response was not affected by heating the serum (at 56 degrees C, for 4 h). IgE-mediated bronchoconstriction, provoked 14 days after passive sensitization with IgE-rich serum, was completely abolished by the heating of the serum. 2. S-1452 (10 mg kg-1, p.o.), a selective thromboxane (Tx) A2 antagonist, significantly but incompletely suppressed the IgG1-mediated bronchoconstriction, but did not affect the IgE-mediated one, while diphenhydramine (5 mg kg-1, i.v.), a histamine antagonist, almost completely inhibited both IgG1- and IgE-mediated bronchoconstriction. 3. Pretreatment with propranolol (1 mg kg-1, i.v.), a beta-adrenergic blocker, in addition to diphenhydramine, caused a long-lasting bronchoconstriction following antigen challenge in both animal models. This histamine-independent bronchoconstriction was markedly suppressed by S-1452 at a low dose of 0.1 mg kg-1. 4. A significant increase in bronchial responsiveness to i.v. acetylcholine (ACh), compared to the prechallenge value, occurred as early as 3 min and persisted for 24 h after antigen challenge in the IgG1 model, but was not observed in the IgE model. S-1452 (10 mg kg-1, p.o.) inhibited the IgG1-mediated bronchial hyperresponsiveness, as assessed 60 min after antigen challenge. 5. A marked elevation of TxB2 levels was observed in bronchoalveolar lavage fluid (BALF) 3 min after antigen challenge in the IgG1 model, while levels were not changed in the IgE model. In contrast, the plasma TxB2 level assessed 1 min after antigen challenge was increased in both the IgGI and IgE models.6. The results indicate that the inhibition of IgGl- but not IgE-mediated bronchoconstriction by higher doses of S-1452 may result from the suppression of increased bronchial responsiveness to allergic mediators such as histamine, which is probably due to TxA2 generated in the airway lumen rather than in plasma. In both the IgGI and IgE models, plasma TxA2 appeared to contribute directly to the bronchoconstriction, its action being almost completely masked by histamine-mediated bronchoconstriction.

6-Ketoprostaglandin F1 alpha↗

PubMed1993

Involvement of thromboxane A2 in bronchial hyperresponsiveness but not lung inflammation induced by bacterial lipopolysaccharide in guinea pigs.

We examined both a possible association of bronchial hyperresponsiveness with lung inflammatory responses and the role of thromboxane (Tx) A2 in these responses after lipopolysaccharide (LPS) exposure in guinea pigs treated with metyrapone, a cortisol synthesis inhibitor. The increase in bronchial responsiveness to i.v. acetylcholine was transient, with a peak at 2 h after LPS exposure, which was associated with increases in TxB2 and tumor necrosis factor in bronchoalveolar lavage (BAL) fluid. However, the levels of 6-keto-prostaglandin (PG) F1 alpha, interleukin-1 and interleukin-6 in BAL fluid, and the influx of leukocytes in airway and pulmonary edema were not associated with bronchial hyperresponsiveness. Oral administration of S-1452, a selective TxA2 receptor antagonist, markedly suppressed bronchial hyperresponsiveness without affecting cellular responses, pulmonary edema and production of PGs and cytokines. These findings suggest that LPS-induced bronchial hyperresponsiveness is dependent on secondarily generated TxA2, which appears to be independent of lung inflammation.

Animals↗

PubMed1993

Effect of a novel thromboxane A2 receptor antagonist, S-1452, on postischemic brain injury in rats.

BACKGROUND AND PURPOSE: Arachidonate metabolites have been implicated in the development of cerebral injury after ischemia. Particular importance has been placed on the balance of thromboxane A2 and prostaglandin I2 because of its regulative activity on platelet functions and arterial tone. The purpose of the present study was to shed light on the role of thromboxane A2 in postischemic brain injury. METHODS: We evaluated the effects of S-1452, a novel thromboxane A2 receptor antagonist, on brain edema, infarct areas, and survival rate in rats with middle cerebral artery occlusion. A transient middle cerebral artery occlusion model was produced by inserting a piece of silicon-coated nylon thread into the internal carotid artery. RESULTS: The ratio of plasma thromboxane B2 to 6-keto-prostaglandin F1 alpha significantly rose at 0 hour (P < .05), 1 hour (P < .01), 3 hours (P < .05), and 12 hours (P < .05) and then nearly returned to the normal level at 24 hours after reperfusion following 1-hour occlusion. Pretreatment with S-1452 (5, 10, or 50 mg/kg PO) significantly attenuated the increase in postischemic water content in the cerebral cortex perfused by the anterior cerebral artery and the cerebral cortex perfused by the middle cerebral artery in a dose-dependent manner but slightly attenuated it in the caudate putamen 24 hours after reperfusion following 1-hour occlusion. Pretreatment with S-1452 (10 mg/kg PO) also significantly decreased the areas of infarction in the front parts of the cerebrum. The survival rate of animals after 2 hours of occlusion tended to be improved by treatment with S-1452 (10 mg.kg-1.d-1 PO), although there was no statistical significance. CONCLUSIONS: Our results suggest that thromboxane A2 is closely related to postischemic brain injury in the early phase of recirculation and that S-1452 may have a protective effect on postischemic brain injury.

6-Ketoprostaglandin F1 alpha↗

PubMed1992

Antiasthmatic activity of a novel thromboxane A2 antagonist, S-1452, in guinea pigs.

We examined the effect of a potent thromboxane (Tx) A2 receptor antagonist, calcium (1R, 2S, 3S, 4S)-(5Z)-7-(((phenylsulfonyl)amino)bicyclo[2.2.1] hept-2-yl)-5-heptenoate dihydrate (S-1452), on antigen- and various allergic-spasmogen-induced contractions of guinea pig lung parenchymal strips and on the increase in insufflation pressure, an index of bronchoconstriction, in anesthetized guinea pigs. In isolated guinea pig lung parenchymal strips, S-1452 showed competitive antagonism of the contractile activity of U-46619, a TxA2 mimetic, with a pA2 value of 8.9. The compound also inhibited the contraction induced by prostaglandin (PG) D2 and PGF2 alpha, but a TxA2 synthetase inhibitor, OKY-046, did not. In contrast, both drugs inhibited not only leukotriene (LT) D4-induced contraction but also antigen-induced contraction in the presence of a histamine antagonist. In anesthetized guinea pigs, oral administration of S-1452 markedly inhibited the bronchoconstrictions induced by intravenous injection of U-46619, PGD2, PGF2 alpha, LTD4 and platelet-activating factor (PAF) with ED50 values of 0.006, 0.031, 0.112, 0.033 and 0.115 mg/kg, respectively, but OKY-046 inhibited only that by LTD4 and PAF. Additionally, bronchoconstriction following intravenous injection of antigen was almost completely suppressed by S-1452 (0.1 mg/kg) and partially by OKY-046 (300 mg/kg) in passively sensitized guinea pigs which were treated with diphenydramine and propranolol. The inhibitory effect of S-1452 against U-46619-induced broncho-constriction persisted up to 7 h after oral administration.(ABSTRACT TRUNCATED AT 250 WORDS)

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1992

A novel class of platelet activating factor (PAF) antagonists. II. Modification of the 2-position of the glycerol backbone of PAF-sulfonamide isosteres.

In a continuing effort to obtain more potent platelet activating factor (PAF) antagonists, we tried to synthesize a series of PAF-sulfonamide isosteres in which the substituent at the 2-position was modified to an acetoxy equivalent other than the methoxy group. These modifications produced highly active PAF antagonists. Compound 3-[2-(5-methyl-2H-tetrazol-2-yl)-3-(octadecylcarbamoyloxy) propylaminosulfonyl]propylquinolinium iodide (52) showed the most potent activity in the in vitro inhibitory effect on PAF-induced platelet aggregation in rabbit platelet-rich plasma (IC50 = 125 nM) and also in the in vivo protective effect on PAF-induced lethality in mice, with prolonged duration of action. Optically active enantiomers of this compound were synthesized and the (S)-(-)-isomer (IC50 = 87 nM) was found to be three times more potent that the (R)-(+)-isomer (IC50 = 289 nM), clearly exemplifying the enantioselectivity in the PAF-antagonist action of this novel compound.

Animals↗

PubMed1991

Characterization and Ca2+ requirement of histamine-induced catecholamine secretion in cultured bovine chromaffin cells.

The stimulation of cultured bovine chromaffin cells with histamine induced a continuous catecholamine secretion (EC50 = 3 x 10(-7) M) via the H1 receptor, in addition to an initial catecholamine burst due to a nonspecific stimulatory effect at higher doses (greater than or equal to 10(-4) M). The continuous secretion showed little desensitization and lasted for more than 1 h. In fura-2-loaded cells, the stimulation with histamine evoked a transient rise of intracellular free Ca2+ concentration ([Ca2+]i) which lasted only for a few minutes and was followed by a sustained [Ca2+]i rise which continued for more than 20 min. The addition of an activator for the L-type voltage-sensitive Ca2+ channel, i.e., Bay K 8644 (1 microM), facilitated the sustained [Ca2+]i rise, as well as the secretion, whereas the addition of relatively high concentrations of Ca(2+)-channel blockers (10 microM) suppressed the sustained [Ca2+]i rise and part of the secretion. Removal of extracellular Ca2+ completely abolished continuous secretion and sustained [Ca2+]i rise. When the external Ca2+ level was elevated, both sustained [Ca2+]i rise and continuous secretion were enhanced in a similar Ca(2+)-dependent manner, showing saturation with around 1-3 mM Ca2+. This Ca2+ dependence was clearly different from that observed with high K+ and nicotine, which is mediated by the L-type Ca2+ channel, in which the responses showed little or no saturation when the Ca2+ level was increased. The results indicate that stimulation with histamine induces a continuous secretion via the H1 receptor, in addition to a transient and nonspecific secretion at higher doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Na(+)-dependent Ca2+ efflux inhibits stimulus-induced secretion in bovine chromaffin cells.

Stimulations of chromaffin cells with histamine and ionomycin produced rises in cellular free Ca2+ level. The removal of Na+ ions from the medium prolongated the rises without changing the magnitude. The stimulations also facilitated 45Ca2+ efflux from cells by over 3-fold. The facilitation was, however, largely abolished by the Na+ removal, indicating the Na(+)-dependent efflux is a major system to expel Ca2+ from the stimulated cells. The Na+ removal also enhanced secretions evoked by these stimuli. The results suggest the Na(+)-dependent Ca2+ efflux by lowering the elevated cellular Ca2+ plays a role in terminating the stimulus-induced secretion.

Adrenal Medulla↗