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Biomedical subjects

T Pawlik

Publications and source records attributed to T Pawlik.

At least 19 recordsLinked to original sources
PubMed2005

Role of prostaglandins in gastroprotection and gastric adaptation.

Since Robert discovery that pretreatment with prostaglandin (PG) applied in non-antisecretory dose can prevent the injury of gastric mucosa induced by necrotizing agents, much attention was paid to the role of these cyclooxygenase (COX) products in the mechanism of gastric mucosal integrity and ulcer healing. The ability of exogenous PG to attenuate or even completely prevent mucosal damage caused by corrosive substances such as absolute ethanol, hyperosmolar solutions or concentrated bile has been termed "cytoprotection". Increased generation of endogenous PG in the gastric mucosa exposed to the topical contact with "mild irritant" such as 20% ethanol, 1 mM NaCl or 5 mM taurocholate also prevented gastric injury caused by strong irritants via phenomenon of adaptive cytoprotection. Other mediators such as growth factors, nitric oxide (NO) or calcitonin gene related peptide (CGRP) as well as some gut hormones including gastrin and cholecystokinin (CCK), leptin, ghrelin and gastrin-releasing peptide (GRP) have been also found to protect gastric mucosa against the damage induced by corrosive substances. This protective action of gut hormones has been attributed to the release of PG or activation of sensory nerves because it could be abolished by the pretreatment with indomethacin or large neurotoxic dose of capsaicin and restored by the addition of exogenous PGE(2) or CGRP, respectively. Short (5 min) ischemia of the stomach applied before prolonged ischemia-reperfusion (I/R) attenuated markedly the gastric lesions produced by this I/R and also prevented the mucosal damage provoked by necrotizing substances. This protection could be abolished by the pretreatment with non-steroidal anti-inflammatory drugs (NSAID) and was accompanied by an enhancement of gastric mucosal COX-2 expression and activity. Exposure of gastric mucosa to single insult of acidified aspirin (ASA) causes severe mucosal damage with occurrence of multiple haemorrhagic lesions but with repeated application of ASA, the attenuation of mucosal lesions is observed, despite the profound inhibition of PGE(2) generation. This phenomenon called "gastric adaptation" does not appear to depend upon endogenous biosynthesis of PG but possibly involves enhanced production of growth factors increasing cell proliferation and mucosal regeneration. Unlike short lived gastroprotection by PG, NO, CGRP, mild irritants or short ischemia, gastric adaptation appears to be long-lasting phenomenon accompanied by increased resistance of the adapted mucosa to subsequent damage induced by corrosive agents.

Animals↗
PubMed2004

Brain-gut axis and its role in the control of food intake.

Gastrointestinal tract (GIT) and nervous system, both central (CNS) and enteric (ENS), are involved in two-way extrinsic communication by parasympathetic and sympathetic nerves, each comprising efferents fibers such as cholinergic and noradrenergic, respectively, and afferent sensory fibers required for gut-brain signaling. Afferent nerves are equipped with numerous sensors at their terminals in the gut related to visceral mechano- chemo- and noci-receptors, whose excitations may trigger a variety of visceral reflexes regulating GIT functions, including the appetitive behaviour. Food intake depends upon various influences from the CNS as well as from the body energy stores (adipocytes) that express and release the product of Ob gene, leptin, in proportion to fat stored and acting in long-term regulation of food intake. Leptin acts through receptors (Ob-R) present in afferent visceral nerves and hypothalamic arcuate nucleus (ARC), whose neurons are capable of expressing and releasing neuropeptide Y (NPY) and agouti related protein (AgRP) that activate the ingestive behaviour through paraventricular nucleus (PVN) (iVfeeding centerli). In addition, to this long-term regulation, a short-term regulation, on meal-to-meal basis, is secured by several gut hormones, such as cholecystokinin (CCK), peptides YY (PYY) and oxyntomodulin (OXM), released from the endocrine intestinal cells and acting via G-protein coupled receptors (GPCR) either on afferent nerves or directly on ARC neurons, which in turn inhibit expression and release of food-intake stimulating NPY and AgRP, thereby inducing satiety through inhibition of PVN. In contrast, during fasting, the GIT, especially oxyntic mucosa, expresses and releases appetite stimulating (orexigenic) factors such as ghrelin and orexins (OX) -A and OX-B, and cannabinoid CB1 agonist. Ghrelin activates growth-hormone secretagogue receptor (GHS-R) in hypothalamic ARC and stimulates growth hormone (GH) release and in vagal afferents to promote the expression and release of hypothalamic NPY and AgRP stimulating PVN and driving ingestive behaviour. The balance and interaction between anorexigenic (CCK, PYY, OXM) and orexigenic (ghrelin and OX) factors originating from GIT appears to play an important role in short-term regulation of food intake and growth hormone (GH) release. An impairment of this balance may result in disorders of feeding behaviour and weight gain (obesity) or weight loss (cachexia).

Animals↗
PubMed2004

Role of brain-gut axis in healing of gastric ulcers.

The previous studies demonstrated the pivotal role of capsaicin-sensitive peptidergic sensory neurons and vagal nerves in the maintenance of gastric mucosal integrity. The aim of the present study was: 1). to examine the effect of the functional ablation of sensory neurons with neurotoxic dose of capsaicin and surgical vagotomy on the course of healing of gastric ulcer in rat, and 2). to compare the ulcer healing action of leptin in rats with or without capsaicin-induced inactivation of sensory neurons. Three series of experiments (A, B and C) were performed in Wistar rats with gastric ulcers induced by acetic acid method. In series A, the course of ulcer healing was compared in rats with intact and capsaicin-inactivated sensory neurons. In the series B, the effect of vagotomy on the ulcer healing and accompanying changes in GBF were determined at day 8 and 16 after ulcer induction. The rats of series C, consisting of animals with intact nerves or those with capsaicin-denervation, received the 7-day treatment with exogenous leptin (10 microg/kg i.p. twice daily) to check whether blockade of sensory nerves could influence the acceleration of ulcer healing by this peptide. Capsaicin-induced ablation of sensory neurons significantly delayed ulcer healing and this was accompanied by the significant fall in the GBF and the significant rise in the gastric mucosal gene expression of IL-1beta and TNF-alpha. Vagotomy significantly delayed ulcer healing and led to decrease in GBF at ulcer margin. Treatment with exogenous leptin significantly accelerated ulcer healing, increased the GBF at ulcer margin and upregulated mRNA for iNOS and these effects were attenuated in rats with capsaicin-deactivation of sensory neurons. We conclude that: 1). vagal and sensory neurons contribute to the gastric ulcer healing process possibly due to the increase of GBF, the limitation of inflammatory response, and overexpression of TGFalpha and iNOS resulting in NO release, and 2). the acceleration of ulcer healing by leptin was attenuated in animals with capsaicin-denervation suggesting an involvement of neuropeptides released from sensory afferent nerves in the ulcer healing effect of this hormone.

Acetic Acid↗
PubMed2004

Duodenal mucosal protection by bicarbonate secretion and its mechanisms.

Proximal portion of duodenum is exposed to intermittent pulses of gastric H(+) discharged by the stomach. This review summarizes the mechanisms of duodenal mucosal integrity, mainly the role of mucus-alkaline secretion and the mucous barrier protecting surface epithelium against gastric H(+). The mucous barrier protects the leaky duodenal epithelium against each pulse of gastric H(+), which penetrates this barrier and diffuses into duodenocytes, but fails to damage them due to; a) an enhanced expression of cyclooxygenase-1 (COX-1), with release of protective prostaglandins (PG) and of nitric oxide (NO) synthase (NOS) with, however, production of NO, stimulating duodenal HCO(3)(-) secretion and b) the release of several neurotransmitters also stimulating HCO(3)(-) secretion such as vasoactive intestinal peptide (VIP), pituitary adenylate-cyclase activating polypeptide (PACAP), acetylcholine, melatonin, leptin and ghrelin released by enteric nerves and mucosal cells. At the apical duodenocyte membrane at least two HCO(3)(-)/Cl(-) anion exchangers operate in response to luminal H(+) to provide adequate extrusion of HCO(3)(-) into duodenal lumen. In the basolateral portion of duodenocyte membrane, both non-electrogenic (NBC) and electrogenic (NBC(n)) Na(+) HCO(3)(-) cotransporters are activated by the exposure to duodenal acidification, causing inward movement of HCO(3)(-) from extracellular fluid to duodenocytes. There are also at least three Na(+)/H(+) (NHE1-3) amiloride-sensitive exchangers, eliminating H(+)which diffused into these cells. The Helicobacter pylori (Hp) infection and gastric metaplasia in the duodenum with bacterium inoculating metaplastic mucosa and inhibiting HCO(3)(-) secretion by its endogenous inhibitor, asymmetric dimethyl arginine (ADMA), may result in duodenal ulcerogenesis.

Animals↗
PubMed2003

Helicobacter pylori, non-steroidal anti-inflammatory drugs and smoking in risk pattern of gastroduodenal ulcers.

BACKGROUND: Helicobacter pylori, NSAID and cigarette smoking are major risk factors for gastroduodenal ulcers. However, the results of studies on the interaction between these factors on ulcerogenesis are controversial. This study was designed to examine the association between gastroduodenal ulcers and H. pylori infection, NSAID use, smoking and age. METHODS: 5967 dyspeptic patients underwent 13C-urea breath test (UBT) and upper endoscopy, while age and dyspeptic symptoms were reported. RESULTS: Out of 5967 patients, 31.8% were ulcerated; 9.2% had gastric, 17.2% duodenal and 5.4% both gastric and duodenal ulcers. H. pylori was found in 72.5% of gastric ulcer patients, in 83.6% of duodenal ulcer patients, in 76.9% of gastroduodenal ulcer patients and in 64.8% of dyspeptic patients. The gastric, duodenal and gastroduodenal ulcers were related to H. pylori significantly and the respective ORs were: 1.44, 2.77 and 1.81. NSAID alone was used by 6.2%-12.7% of ulcer patients, tending to raise only the risk of gastric ulcer but reducing that of duodenal and gastroduodenal ulcers. The H. pylori prevalence was significantly higher in smokers (76%) than in non-smokers (67%) and the ulcer risk was also significantly higher in smokers than in non-smokers. About 20% of ulcers were 'idiopathic', i.e. without NSAID and H. pylori and the ratio of these ulcers to all ulcers significantly increased during the 5 years of the study. CONCLUSIONS: Based on multivariable logistic regression analysis we conclude that: 1) H. pylori infection, NSAID use, smoking and age play major roles in the pathogenesis of peptic ulcerations; 2) there is a negative interaction between H. pylori and NSAID on duodenal ulcers, suggesting that H. pylori reduces the development of these ulcers in NSAID users, and 3) about 20% of peptic ulcers in the Polish population are unrelated to H. pylori and NSAID use (idiopathic ulcers).

Adult↗
PubMed2003

Brain-gut axis in pancreatic secretion and appetite control.

The stimulation of exocrine pancreatic secretion that has been attributed by Pavlov exclusively to various reflexes (nervism), was then found that it depend also on numerous enterohormones, especially cholecystokinin (CCK) and secretin, released by duodeno-jejunal mucosa and originally believed to act via an endocrine pathway. Recently, CCK and other enterohormones were found to stimulate the pancreas by excitation of sensory nerves and triggering vago-vagal and entero-pancreatic reflexes. Numerous neurotransmitters and neuropeptides released by enteric nervous system (ENS) of gut and pancreas have been also implicated in the regulation of exocrine pancreas. This article was designed to review the contribution of vagal nerves and entero-hormones, especially CCK and other enterohormones, involved in the control of appetitive behavior such as leptin and ghrelin and pancreatic polypeptide family (peptide YY and neuropeptide Y). Basal secretion shows periodic fluctuations with peals controlled by ENS and by motilin and Ach. Plasma ghrelin, that is considered as hunger hormone, increases under basal conditions, while plasma leptin falls to the lowest level. Postprandial pancreatic secretion, classically divided into cephalic, gastric and intestinal phases, involves predominantly CCK, which under physiological conditions acts almost entirely by activation of vago-vagal reflexes to stimulate the exocrine pancreas, being accompanied by the fall in plasma ghrelin and increase of plasma leptin, reflecting feeding behavior. We conclude that the major role in postprandial pancreatic secretion is played by vagus and gastrin in cephalic and gastric phases and by vagus in conjunction with CCK and secretin in intestinal phase. PP, PYY somatostatin, leptin and ghrelin that affect food intake appear to participate in the feedback control of postprandial pancreatic secretion via hypothalamic centers.

Appetite Regulation↗
PubMed2002

Effect of different muscle shortening velocities during prolonged incremental cycling exercise on the plasma growth hormone, insulin, glucose, glucagon, cortisol, leptin and lactate concentrations.

BACKGROUND: Strenuous exercise was reported to involve the alteration in the release of some "stress" hormones such as growth hormone (GH), cortisol, catecholamines and appropriate adjustment of energy metabolism but the relative contribution of these hormones to metabolic response, to cycling exercise performed at different muscle shortening velocities, has not been clarified. AIMS: The purpose of this experiment was to assess the effect of applying different pedalling rates during a prolonged incremental cycling exercise test on the changes in the plasma levels of growth hormone, cortisol, insulin, glucagon and leptin in humans. MATERIAL AND METHODS: Fifteen healthy non-smoking men (means +/- SD: age 22.9 +/- 2.4 years; body mass 71.9 +/- 8.2 kg; height 178 +/- 6 cm; with VO2max of 3.896 +/- 0.544 1 x min(-1), assessed in laboratory tests, were subjects in this study. The subjects performed in two different days a prolonged incremental exercise tests at two different pedalling rates, one of them at 60 and another at 120 rev x min(-1). During this tests the power output has increased by 30 W every 6 minutes. The tests were stopped when the subject reached about 70 % of the VO2max. RESULTS AND CONCLUSIONS: We have found that choosing slow or fast pedalling rates (60 or 120 rev min(-1)), while generating the same external mechanical power output, had no effect on the pattern of changes in plasma cortisol, insulin, glucagon, glucose and leptin concentrations. But, generation of the same external mechanical power output at 120 rev min(-1) causes more stepper increase (p < 0.01) in the plasma growth hormone concentration [GH]pl and plasma lactate concentrations [La]pl when compared to that observed during cycling at 60 rev x min(-1). We have also found that the onset of a significant increase in [GH]pl during cycling at 60 rev x min(-1) was not accompanied by significant increase in [La]pl. While during cycling at 120 rev x min(-1) the onset of a significant increase in [La]pl occurred without increase in [GH]pl, but with continuation of exercise when plasma [La]pl increased, there was also a parallel rise in plasma [GH]pl, as reported before. This results indicates that the increase in [GH]pl during exercise is not closely related to the increase in [La]pl.

Adult↗
PubMed2001

Leptin in the control of gastric secretion and gut hormones in humans infected with Helicobacter pylori.

BACKGROUND: Leptin, a protein product of obese gene expressed primarily by adipocytes, provides feedback information on the size of energy stores to central OB receptors controlling the food intake, energy expenditure and body weight homeostasis. It has recently been detected in the rat stomach, especially after cholecystokinin (CCK) administration and in human stomach infected with Helicobacter pylori, but its role in gastric secretory functions in humans has not been revealed. This study was designed to determine the involvement of leptin in the control of basal, CCK- and meal-induced gastric H+ secretion and plasma gastrin and CCK levels in humans before and after an eradication of H. pylori. METHODS: Two groups (A and B) of subjects were used; group A (n = 7), for comparison of the effects of CCK and leptin on basal gastric H+ and plasma hormone (leptin, gastrin and CCK) levels, and group B (n = 6), for studies on the involvement of leptin in gastric secretory and plasma hormonal responses to vagal stimulation and gastric peptone meal before and after H. pylori eradication. RESULTS: In H. pylori-positive subjects, CCK (12-200 pmol kg(-1) h(-1)) given i.v. caused a dose-dependent increase of gastric H+ accompanied by a dose-dependent rise in plasma CCK and leptin levels. In contrast, leptin administered i.v. in graded doses (5-80 pmol kg(-1) h(-1)) resulted in a gradual inhibition of basal gastric H+ secretion and in adose-dependent increment in plasma leptin accompanied by an increase in plasma gastrin without alteration of plasma CCK level. Following eradication of H. pylori by 1-week triple therapy in group B patients, the infusion of CCK produced a significantly smaller increase in gastric H+ secretion and significantly smaller rise in plasma leptin as compared to those before the eradication. Cephalic phase stimulation of gastric secretion induced by modified sham-feeding in group B H. pylori-positive subjects increased gastric H+ secretion to about 40% of pentagastrin maximum without affecting plasma leptin, gastrin, or CCK level, while gastric peptone meal resulted in the increase in gastric H+ response reaching about 70% of pentagastrin maximum accompanied by a marked rise in plasma leptin, gastrin and CCK. The treatment with a standard dose of leptin (20 pmol kg(-1) h(-1)) failed to affect sham-feeding-induced gastric H+ secretion but reduced significantly the peptone meal-stimulated H+ secretion, while raising plasma gastrin in response to this meal. Plasma CCK under basal conditions and after sham-feeding was not affected, but plasma CCK response to gastric meal was significantly reduced by leptin infusion. Eradication of H. pylori did not affect basal or sham-feeding-induced H+ secretion but resulted in a significant fall in gastric meal-induced H+ and plasma leptin, gastrin and CCK levels. CONCLUSIONS: 1) The gastric meal and CCK enhance the release of leptin in H. pylori-positive patients and this leptin is capable of inhibiting basal and meal-stimulated gastric H+ secretion, while raising plasma gastrin and reducing the plasma CCK levels, and 2) the eradication of H. pylori reduces the postprandial gastric H+ and plasmagastrin responses as well as the release of leptin in response to CCK and meal.

Adult↗
PubMed1997

Physiological role of nitric oxide in gallbladder emptying in men.

This study was designed to determine the role of nitric oxide in gallbladder (GB) contractions in men. The studies were performed in 10 young healthy male volunteers. GB emptying was examined by ultrasonography under basal conditions and after intravenous infusion of cholecystokinin (CCK8; 12.5 pmol/kg x h) or yolk intake in tests without (saline) and with intravenous infusion of NG-monomethyl-L-arginine (L-NMMA; 4.0 micromol/kg x h) and/or L-arginine (1 mmol/kg x h). The plasma CCK level was determined by radioimmunoassay. It was found that the basal GB volume was about 27 +/- 3 ml, and after CCK8 infusion or yolk meal this volume was reduced within about 30 min by about 93 and 80%, respectively. Pretreatment with L-NMMA caused reduction of the baseline volume by about 15% and significantly augmented the GB emptying induced by CCK8 infusion and yolk intake. L-Arginine alone failed to affect basal or stimulated (CCK or yolk) emptying of the GB, but when combined with L-NMMA, it reversed the enhancement of GB contraction caused by L-NMMA. The basal plasma CCK level was 1.2 +/- 0.3 pmol/l and rose to 7.9 +/- 2.1 pmol/l with CCK8 infusion and to 4.7 +/- 1.8 pmol/l after yolk meal. No significant change in plasma CCK levels was observed in tests with L-NMMA and/or L-arginine. We conclude that under physiological conditions, the GB contractile activity is regulated predominantly by CCK, but endogenous nitric oxide has a tonic relaxing influence on this activity.

Adult↗
PubMed1993

Adenosine modulates reactive hyperemia in rat gut.

Intestinal reactive hyperemia is an abrupt blood flow increase following release from anterior mesenteric arterial occlusion. We investigated the role of adenosine in reactive hyperemia. In anesthetized rats, mesenteric arterial velocity of blood flow was determined with pulsed Doppler velocimetry and arterial pressure with a transducer. Three indices quantifying reactive hyperemias obtained following 30, 60, and 120 s arterial occlusions included duration, the volume of blood flow exceeding preocclusion blood flow, and the percentage increase in conductance. In six rat groups (half fasted and half with intrajejunal bile-oleate solutions), hyperemia parameters were determined before and after administration of either adenosine deaminase (ADA) or two adenosine receptor antagonists, namely 8-phenyltheophylline (8-PT) and 1,3-dipropyl-7-methylxanthine (DPMX). In fasted gut the three agents had variable effectiveness against reactive hyperemia, although 8-PT was the most consistent inhibitor. Instillation of intrajejunal lipid evoked a stable hyperemia and increased duration and blood flow volume after each occlusive period. ADA and 8-PT were more effective against reactive hyperemia in fed gut than in fasted gut. Our findings suggest that adenosine is a vasodilator metabolite modulating mesenteric reactive hyperemia, especially during enhanced intestinal metabolic activity.

Adenosine↗