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Biomedical subjects

F Karmeli

Publications and source records attributed to F Karmeli.

At least 73 records · Page 4Linked to original sources
PubMed1991

Gastric mucosal damage by ethanol is mediated by substance P and prevented by ketotifen, a mast cell stabilizer.

To elucidate the possible role of substance P in the pathogenesis of acute gastric mucosal damage, rats were treated intragastrically with 1.0 mL 96% ethanol, 0.6N HCl, or 25% NaCl, with or without IP coadministration of substance P, senktide, or septide (1 mumol/L per 100 g). All three peptides were found to double the mean lesion area when compared with that induced by ethanol, whereas substance P antagonist (1 mumol/L per 100 g) prevented the expansion of damage extent. The increased damage was associated with increased gastric mucosal levels of platelet activating factor, leukotriene B4, and leukotriene C4. Substance P antagonists also reduced by half the extent of the gastric damage induced by ethanol when administered by itself. WEB 2086 (platelet-activating factor antagonist; Boehringer Ingelheim KG, Germany), hydroxyzine (H1 blocker), and cimetidine (H2 blocker) reduced lesion area by 50%, but only in rats treated with both substance P and ethanol. Ketotifen (mast-cell stabilizer) (100 micrograms/100 g), administered orally 30 minutes before damage induction, totally abolished the extent of the damage induced by either ethanol or the coadministration of ethanol and peptides in the surface epithelium of the entire mucosa. The protective effect of ketotifen was accompanied by significant reduction in mucosal generation of platelet-activating factor, leukotriene C4, and leukotriene B4. Similar mucosal protection was afforded by ketotifen against damage induced by 0.6N HCl, 25% NaCl, or indomethacin. Therefore, it is suggested that substance P is involved in the pathogenesis of acute ethanol-induced gastric mucosal damage. The effective mucosal protection provided by ketotifen indicates the important role of mast cells and their mediators in the pathogenesis of acute gastric mucosal damage and may have therapeutic implications.

Animals↗
PubMed1990

The role of platelet activating factor [correction of actor] in acute gastric injury and its protection by sucralfate.

Platelet activating factor, a potent inflammatory mediator, has been reported to induce gastrointestinal damage, whereas its inhibition or antagonism is associated with mucosal protection. The aim of the present study was to elucidate the association between acute experimental gastric damage and mucosal platelet activating factor generation in the rat, and to evaluate the protective effect of sucralfate in relation to mucosal platelet activating factor formation. Gastric damage in the rat was induced by either subcutaneous injection of indomethacin 30 mg/kg or intragastric administration of aspirin 100 mg/kg, hydrochloric acid 0.6 N, taurocholate 30 mM, ethanol 96%, or sodium chloride 25%. All agents induced a significant increase in mucosal platelet activating factor levels concomitantly with induction of mucosal damage. Pretreatment with sucralfate 150 mg/rat provided a significant macroscopic and microscopic mucosal protection in all experimental models. This protection was associated with a significant decrease in mucosal platelet activating factor level in the hydrochloric acid, taurocholate, ethanol and hyperosmolar sodium chloride treated rats, whereas it remained unchanged in the aspirin and indomethacin treated rats. The data imply that platelet activating factor may have a limited role in the pathogenesis of indomethacin or aspirin induced damage, where other mechanisms such as cyclooxygenase inhibition dominate. In the damage induced by topical strong irritants, platelet activating factor may have a major pathogenetic role.

Animals↗
PubMed1990

Role of interleukin 1 in inflammatory bowel disease--enhanced production during active disease.

Interleukin 1 is a polypeptide cytokine produced by various cell types and has been shown to have a major role in inflammatory and immunological responses. In experimental colitis it proved to be a dominant mediator and a reliable marker of inflammation. The aim of the present study was to determine in vitro the extent of production and release of interleukin 1 from colonic mucosa of patients with active untreated inflammatory bowel disease. Colonic mucosal biopsy specimens were obtained during colonoscopy from 17 patients with ulcerative colitis, eight patients with Crohn's disease of the colon, and 16 normal control subjects. Interleukin 1 content was determined in fresh and 24 hour organ cultured mucosa as well as in cultured medium. Interleukin 1 content and release were significantly higher in the inflamed mucosa compared with that of control subjects. Prednisolone inhibited interleukin 1 release in a dose dependent fashion. We conclude that colonic mucosal interleukin 1 content and production is significantly raised in active inflammatory bowel disease and may have a role in the pathogenesis of the inflammatory response. Pharmacological suppression of tissue interleukin 1 production may have a beneficial therapeutic effect.

Adolescent↗
PubMed1990

Enhanced gastric and duodenal platelet-activating factor and leukotriene generation in duodenal ulcer patients.

Platelet-activating factor (PAF), leukotriene B4 (LTB4), and leukotriene C4 (LTC4) generation by gastroduodenal mucosa was assessed in duodenal ulcer patients and in normal subjects, to elucidate their possible role in the pathogenesis of peptic ulcer disease. Endoscopic fundic, antral, and duodenal biopsy specimens were obtained from 35 duodenal ulcer patients on the day the diagnosis was established and from 42 normal controls. In duodenal ulcer patients PAF generation, determined by platelet aggregation, was two- to three-fold higher than its respective generation by normal subjects. LTB4 and LTC4 synthesis by cultured antral and duodenal mucosa obtained from duodenal ulcer patients was twofold higher than their synthesis by normal subjects. Fundic LTB4 and LTC4 generation was similar in ulcer patients and controls. In 11 patients PAF, LTB4, and LTC4 generation was also assessed after 4 weeks of treatment resulting in ulcer healing and found to be significantly reduced when compared with their synthesis when the ulcer was active. These results thus suggest that PAF, LTB4, and LTC4 may have a role in the pathogenesis of duodenal ulcer, and therefore their modulation may have therapeutic benefits.

Adult↗
PubMed1990

Platelet-activating factor--a possible mediator in the pathogenesis of ulcerative colitis.

Release of platelet-activating factor (PAF) by cultured colonic mucosa of patients with ulcerative colitis and healthy controls was determined. Before stimulation with calcium ionophore or antihuman IgE, no PAF release by control mucosa and minimal PAF release by mucosa of the colitis patients were detected. After stimulation with calcium ionophore, PAF release was four to five times higher by colonic mucosa of the colitis patients than of the controls. After stimulation with antihuman IgE, PAF release was twice as high by colonic mucosa of colitis patients as by control mucosa. Prednisolone, sulphasalazine, and mesalazine inhibited PAF activity stimulated by calcium ionophore in a dose-dependent manner. The results suggest that the use of PAF antagonists in the treatment of ulcerative colitis should be investigated.

Aminosalicylic Acids↗
PubMed1990

Rectal administration of nonsteroidal antiinflammatory drugs. Effect on rat gastric ulcerogenicity and prostaglandin E2 synthesis.

Oral administration of nonsteroidal antiinflammatory drugs induces gastroduodenal mucosal damage in experimental animals as well as in humans. The aim of the present study was to evaluate the effect of rectally administered nonsteroidal antiinflammatory drugs on gastric mucosal damage, as well as on mucosal prostaglandin E2 synthesis. Fasting male rats were treated intrarectally with 0.5 ml 1% NaHCO3 solution containing several concentrations of either indomethacin, aspirin, ibuprofen, diclofenac, ketoprofen, or sulindac and concomitantly received 1 ml of 150 mM HCL intragastrically. Control rats received intrarectally the vehicle only. After 4 h, lesions in the secretory part of the stomach were scored and mucosal prostaglandin E2 synthesis was determined by the ex vivo prostaglandin generation technique. Dose-dependent mucosal damage was observed in indomethacin- and diclofenac-treated rats. Ketoprofen damage did not show dose dependency. In sulindac- and aspirin-treated rats, as well as in controls, no damage was detected. All drugs induced a significant and comparable degree of inhibition of prostaglandin E2 synthesis. There was no correlation between the severity of the mucosal damage and the inhibition of prostaglandin E2 synthesis. The ulcerogenicity of rectally administered nonsteroidal antiinflammatory drugs is therefore not directly related to the degree of inhibition of prostaglandin E2 synthesis and is probably related to the specific chemical and pharmacokinetic properties of each individual drug.

Administration, Rectal↗
PubMed1989

Colonic substance P levels are increased in ulcerative colitis and decreased in chronic severe constipation.

Substance P content was determined by radioimmunoassay in colonic mucosa from 24 patients with chronic severe constipation, 16 with active ulcerative colitis, and 28 normal controls. In patients with chronic severe constipation, the mean concentration of substance P (19.9 +/- 8.2 pg/mg) was significantly lower than in normal subjects (71 +/- 18 pg/mg). In patients with ulcerative colitis, colonic substance P concentration in inflamed mucosa (170 +/- 46 pg/mg) was significantly higher than its levels in normal subjects. Substance P may therefore have a role in the pathogenesis of clinical conditions associated with diarrhea and constipation.

Biopsy↗
PubMed1988

Effect of substance P on rat gastrointestinal transit.

The in vivo effect of substance P and related peptide analogs on gastrointestinal transit in unanesthetized rats was studied. Fasted male rats were given intragastrically 0.5 ml of a powdered charcoal (BaSo4.H2O) meal and were concomitantly injected intraperitoneally with 8 micrograms/kg of substance P or a related peptide. In control rats, the percentage of small intestine traversed by the meal 15 min after feeding was 44.9 +/- 1.4 (N = 12). Substance P, [pGlu6]SP, [pGlu6, gPhe8, mGly9]SP and [pGlu5, N-MePhe8, N-MeGly9]SP significantly accelerated intestinal transit: 59.5 +/- 3.1% (N = 7); 66.0 +/- 3.8% (N = 14), 66.8 +/- 2.4% (N = 25), and 58.4 +/- 4.4% (N = 4), respectively. Concomitant injection of [pGlu6]SP and BOC-Phe-Phe-Gly-NHOH, an inhibitor of enzyme degradation at a dose of 800 micrograms/kg lowered by 10-fold the dose of [pGlu6]SP needed to induce the same degree of intestinal transit acceleration. These results indicate that in rats, substance P and related peptides accelerate gastrointestinal transit.

Animals↗
PubMed1988

Role of platelet-activating factor in ulcerative colitis. Enhanced production during active disease and inhibition by sulfasalazine and prednisolone.

Platelet-activating factor is released from inflammatory cells. It activates neutrophils, releases secondary messengers, and mediates mucosal ulceration and ischemia in the rat. We assessed its possible role in the pathogenesis of ulcerative colitis. Colonic biopsy specimens from patients with active ulcerative colitis and controls were incubated for 4 h in Tyrode's buffer in the presence or absence of 0.2 microM calcium ionophore (A23187) or 50 microliter of antihuman immunoglobulin E. Platelet-activating factor was determined in the tissue by aggregation assay after extraction with 80% ethanol and was confirmed by thin-layer chromatography and its inactivation by phospholipases. Platelet-activating factor was not detected in normal mucosa. Only A23187 and antihuman immunoglobulin E stimulated its activity: mean +/- SE, 43.2 +/- 8.6 and 33.0 +/- 6.1 pg/10 mg wet wt, respectively. In active ulcerative colitis basal platelet-activating factor activity was 8.9 +/- 3.5 pg/10 mg wet wt. A23187 and antihuman immunoglobulin E induced significantly higher stimulation of platelet-activating factor synthesis when compared with their effects on normal mucosa: 200 +/- 28 and 70 +/- 8.3 pg/10 mg wet wt, respectively. The enhanced stimulation induced by A23187 was dose-dependently inhibited by salazopyrine, 5-amino-salicylic acid, and prednisolone, but not by sulfapyridine. It is thus suggested that platelet-activating factor may be involved in the pathogenesis of the inflammatory response in ulcerative colitis and that its inhibition by steroids, 5-aminosalicylic acid, and salazopyrine may be an additional mechanism to explain their therapeutic effects.

Adult↗
PubMed1988

No correlation between indomethacin-induced gastroduodenal damage and inhibition of gastric prostanoid synthesis.

The effect of 1 week of treatment with indomethacin 150 mg/day on human gastric prostanoid synthesis was correlated with its effect on gastric and duodenal mucosa. Before and following 1 week of treatment, endoscopic appearance of the mucosa was evaluated and scored. Following 1 week of treatment with indomethacin, antral PGE2 and 6-keto-PGF1 alpha were significantly lower than in normal subjects, but similar in patients with significant or with no mucosal damage. Co-treatment with ranitidine 150 mg b.d. or with cimetidine 400 mg b.d. reduced the mean mucosal damage score but did not affect gastric prostanoid synthesis, which was similar irrespective of the presence or absence of mucosal damage. It is therefore suggested that there is no correlation between indomethacin-induced inhibition of gastric prostanoid synthesis and its induction of mucosal damage.

Adolescent↗
PubMed1988

(2'-5')Oligoadenylate synthetase activity in intestinal mononuclear and epithelial cells of inflammatory bowel disease patients.

The activity of (2'-5')oligoadenylate synthetase, an enzyme induced by and mediating the antiviral action of interferon, was measured in extracts of intestinal mononuclear and epithelial cells isolated from patients with Crohn's disease, ulcerative colitis, and a control group. No significant differences were detected among (2'-5')oligoadenylate synthetase activities of lamina propria mononuclear cells derived from inflammatory bowel disease-involved and histologically normal control mucosa. Similarly, epithelial cells from inflammatory bowel disease and control patients expressed comparable levels of the enzyme, but these were significantly higher (p less than 0.01) than those found in autologous mononuclear cells. These results indicate that interferon is locally produced along the human intestinal mucosa under normal and inflammatory conditions. While this study supports the contention that induction of an antiviral state does not play a significant role in the pathogenesis of inflammatory bowel disease, it does not exclude the activation of the interferon system for other immunologic functions.

2',5'-Oligoadenylate Synthetase↗
PubMed1988

Somatostatin release by human gastric mucosa. Studies in peptic ulcer disease and pernicious anemia.

Somatostation has been postulated to have a paracrine modulating role in gastrin and gastric acid secretion. We applied the organ culture technique to examine somatostatin release by explants of human gastric mucosa taken from patients with active duodenal ulcer, from control subjects, and from patients with pernicious anemia. Somatostatin was found to be released at a constant rate by antral explants during 3 h of incubation. In active duodenal ulcer antral and fundic 2-h somatostatin release (18.7 +/- 2.6 pg/mg tissue (means + SE), n = 75; and 27 +/- 3 pg/mg tissue, n = 94, respectively) was significantly lower than release by control antral and fundic mucosa (83 +/- 17 pg/mg tissue, n = 39, and 72 +/- 16 pg/mg tissue, n = 42, respectively) (P less than 0.01). Somatostatin release by antral and fundic mucosa of patients with pernicious anemia was also significantly decreased (20 +/- 8 pg/mg tissue, n = 12, and 7.6 +/- 2 pg/mg tissue, n = 12, respectively) (P less than 0.05). These results imply possible impairments of the paracrine release of somatostatin in peptic ulcer disease and in pernicious anemia.

Anemia, Pernicious↗
PubMed1986

Role of endogenous gastric prostanoids in the pathogenesis and therapy of duodenal ulcer.

Synthesis of prostaglandin E2 and 6-keto prostaglandin F1 alpha by cultured antral and fundic gastric mucosa obtained from 86 patients with active duodenal ulcer who were not receiving medication was 50% lower (p less than 0.01) than their respective synthesis by cultured gastric mucosa in normal subjects. Antral and fundic prostanoid synthesis in patients receiving chronic therapy with nonsteroidal antiinflammatory drugs was almost completely inhibited. The decreased synthesis of antral and fundic prostaglandin E2 and 6-keto prostaglandin F1 alpha in duodenal ulcer patients was not affected following ulcer healing achieved after 4 wk of therapy with placebo, arbacet, misoprostol, sucralfate, and pirenzepine. In contrast, following 4 wk of therapy with ranitidine, both antral and fundic prostaglandin E2 synthesis were significantly increased when compared with their respective synthesis before therapy. These results confirm that gastric prostanoid synthesis is decreased in patients with active duodenal ulcer and in subjects treated with nonsteroidal antiinflammatory drugs, suggesting that decreased endogenous prostanoid synthesis may contribute to the pathogenesis of mucosal damage. The induction of endogenous prostanoids by ranitidine may contribute to its therapeutic effect.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Sucralfate protection against gastrointestinal damage: possible role of prostanoids.

The protective effect of sucralfate against gastric and intestinal mucosal damage was studied in rats. Sucralfate (125 mg) significantly reduced gastric mucosal lesion formation induced by s.c. administration of indomethacin (30 mg/kg) or intragastric administration of aspirin (100 mg/kg), HCl (0.6 N), NaOH (0.2 N) or sodium taurocholate (30 mM). Furthermore, when given in three doses of 125 mg each, sucralfate significantly decreased the development of small intestinal lesions induced by indomethacin in the re-fed rat. Gastric mucosal cyclooxygenase activity in sucralfate-treated rats expressed as prostaglandin E2 formation--388 +/- 140 (ng/g wet weight; mean +/- SE)--was significantly higher (P less than 0.01) than its activity in the control--264 +/- 62 (ng/g wet weight). Sucralfate also slightly, but significantly, decreased indomethacin-induced gastric mucosal cyclooxygenase inhibition. Intestinal mucosal cyclooxygenase activity was not affected by sucralfate. The results suggest that gastric and intestinal mucosal damage induced by various ulcerogens is significantly reduced by sucralfate. Sucralfate-induced stimulation of endogenous gastric mucosal prostanoid formation may in part explain its effective protective properties.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Protection by mild irritants against indomethacin-induced gastric mucosal damage in the rat: role of prostaglandin synthesis.

"Mild irritants" have been shown to protect rat gastric mucosa from damage induced by noxious topical agents, supposedly by induction of mucosal prostaglandin (PG) biosynthesis. The protective effect of NaCl 5%, ethanol 20%, NaOH 0.075 N, HCl 0.35 N, salicylic acid 100 mg/kg and paracetamol 200 mg/kg was investigated in rats treated with an ulcerogenic dose (25 mg/kg) of indomethacin; mucosal PG synthesis was simultaneously determined. Significant protection was achieved only with NaCl 5%, salicylic acid and paracetamol. Salicylic acid and paracetamol significantly decreased acid secretion and enhanced PGE2 or 6-keto PGF1 alpha generation in control rats, while a small but significant change in the indomethacin-inhibited PG synthesis was observed after treatment with NaCl 5% or salicylic acid. We conclude that protection by "mild irritants" against indomethacin-induced mucosal damage may involve increased cytoprotective PG generation, as shown for paracetamol and salicylic acid, or partial blocking of indomethacin binding at the cyclooxygenase receptor site, as shown for NaCl 5% and salicylic acid.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Interferon inhibits prostaglandin E2 synthesis and stimulates (2'-5')oligoadenylate synthetase activity in peripheral blood mononuclear cells of inflammatory bowel disease patients.

The effect of interferon (IFN) on prostaglandin E2 (PGE2) synthesis by peripheral blood mononuclear cells of normal subjects and patients with inflammatory bowel disease was studied. Exposure of peripheral blood mononuclear cells, isolated from normal subjects and patients with active ulcerative colitis and Crohn's disease, to IFN reduced the release of PGE2 in a dose-dependent manner. The inhibitory effect was observed for at least 24 h after the removal of IFN. To correlate the effect of IFN on PGE2 synthesis with a known activity of IFN, the induction of (2'-5')oligoadenylate synthetase (OAS) was also studied in the same mononuclear cells. Low basal levels of this enzyme were detected in mononuclear cells isolated from normal subjects and patients with active ulcerative colitis and Crohn's disease. Moreover, IFN treatment in vitro resulted in a similar induction of this enzyme in patients and controls. There results indicate that peripheral blood mononuclear cells of patients with active ulcerative colitis and Crohn's disease have normal response to IFN. In addition, our data do not suggest that IFN has an important role in the pathogenesis of these diseases.

2',5'-Oligoadenylate Synthetase↗
PubMed1985

(2'-5') oligo adenylate synthetase activity in leucocytes of patients with inflammatory bowel disease.

The activity of an interferon induced enzyme, (2',5') oligo adenylate synthetase, was determined in peripheral blood mononuclear cells and granulocytes of patients with inflammatory bowel disease and compared with its activity in cells isolated from normal subjects. In spite of the fact that circulating interferon is detected in patients with inflammatory bowel disease, we failed to see any increase in (2',5') oligo adenylate synthetase activity in these patients. The mean +/- SE enzyme activity given in nmol ATP incorporated into (2',5') isoadenylate oligomers by extracts of 10(5) peripheral blood mononuclear cells/21 hours was in normal subjects 1.84 +/- 0.30 (n = 27), in patients with active Crohn's disease 1.38 +/- 0.15 (n = 20) and in patients with active ulcerative colitis 1.14 +/- 0.23 (n = 21). (2',5') oligo adenylate synthetase activity in granulocytes was also similar in normal subjects and in patients with active ulcerative colitis or Crohn's disease. The enzyme activity in patients with active disease was similar both prior to and during steroid therapy. The low (2',5') oligo adenylate synthetase activity in peripheral blood mononuclear cells and granulocytes of patients with active inflammatory bowel disease may reflect decreased cellular response to interferon or a difference in the type of interferon elevated in viral diseases and in inflammatory bowel disease.

2',5'-Oligoadenylate Synthetase↗