Applicability of the silver amalgam electrode in voltammetric determination of zinc and copper in gastric juice and gastric mucosa of rats

The aim of the work was to compare two analytical methods of trace analysis in respect to their applicability in heavy metals determination in biological samples. Atomic absorption spectrometry (AAS) may be considered as the method of choice in such analyses due to its accuracy, precision and low detection limit. On the other hand, voltammetric methods seem to be as useful, but rarely applied. Having in mind that there is no universal analytical method, we have compared two AAS and voltammetric methods as the tools for Zn and Cu determination in the samples collected from rat gastric juice and gastric mucosa. Construction of the renewable silver amalgam film electrode (Hg(Ag)FE) for stripping voltammetry was described. Detailed optimization of measurements procedure and sample preparation for differential pulse anodic stripping voltammetry (DP ASV) and AAS were also performed and presented. The obtained results of quantitative analysis of the chosen parameters by means of both methods are discussed

Natural development of Barrett’s oesophagus and adenocarcinoma in experimental models of gastroesophageal reflux disease

Wstęp: Do rozwoju choroby refluksowej (gastroesophageal reflux disease - GERD) dochodzi w momencie zaburzenia równowagi pomiędzy czynnikami drażniącymi reflu ksatu a czynnikami ochraniającymi błonę śluzową przełyku. Przewlekły stan zapalny przełyku może doprowadzać do poważnych powikłań w postaci metaplazji Barretta i w konsekwencji rozwoju raka przełyku. W ostatnich latach stwierdza się coraz częstsze występowanie refluksu jelitowo-żołądkowego powikłanego rozwojem gruczolakoraka przełyku, zwłaszcza w krajach o wysokim rozwoju cywilizacyjnym. Cel: Podjęcie próby stworzenia przewlekłych modeli refluksu przełykowego, które naśladują tę patologię u człowieka, w celu badania mechanizmu powstawania uszkodzeń przełykowych, ich porównanie oraz ocena przydatności do prowadzenia badań nad wieloetapowym procesem nowotworzenia bez za stosowania egzogennych kancerogenów. Stworzenie modelu przewlekłego zapalenia przełyku mogłoby się przyczynić do opracowania skutecznych metod zapobiegania i leczenia tych zmian. Materiał i metody: W badaniach wykorzystano grupę 90 szczurów rasy Wistar płci mieszanej. Eksperyment przeprowadzono w trzech zasadniczych grupach badawczych, w których wykonano: A - połączenia przełykowo-dwunastnicze bok przełyku do boku dwunastnicy, B - połączenie przełykowo-dwunastnicze koniec przełyku do boku dwunastnicy i C - połączenie przełykowo-dwunastnicze koniec przełyku do boku dwunastnicy wraz z całkowitą resekcją żołądka. Dwa pierwsze typy operacji (grupy A, B) charakteryzował refluks treści mieszanej dwunastniczo-żołądkowej, a w trzecim typie zabiegu (grupa C) uzyskano refluks treści wyłącznie alkalicznej do przełyku. Wyniki: We wszystkich trzech grupach zoperowanych zwierząt po 1-3 mies. od zabiegu obserwowano zmiany morfologiczne struktury przełyku w postaci pogrubienia błony śluzowej przełyku, nadżerek i owrzodzeń, które były wyraźnie widoczne już podczas oceny makroskopowej. W badaniu mikroskopowym u większości zwierząt stwierdzono przewlekły stan zapalny, metaplazję Barretta oraz gruczolakoraka przełyku. Wnioski: Wykonane modele doświadczalnego refleksu jelitowo-żołądkowo-przełykowego cechuje duża powtarzalność obserwacji, znikoma śmiertelność zwierząt, a uzyskane w ten sposób zmiany morfologiczne naśladują kliniczny charakter choroby. Zmiany te powstają wyłącznie na drodze naturalnego rozwoju, bez interwencji farmakologicznej w postaci np. podawania substancji kancerogennych. Opracowane modele pozwalają na systematyczne prowadzenie badań w stosunkowo długim czasie, co umożliwia poznanie patogenezy uszkodzenia przełyku, mechanizmów kancerogenezy w przebiegu GERD oraz ewentualnych sposobów zapobiegania rakowi przełyku na podłożu metaplazji Barretta.Introduction: Development of gastroesophageal reflux disease (GERD) takes place when the balance between irritant and protecting mucous membrane mechanisms is impaired. The chronic inflammation of the oesophagus results in serious complications including Barrett’s metaplasia progression into esophageal adenocarcinoma. In the last few years the incidence of chronic gastroesophageal reflux disease has been increasing, especially in highly developed countries, and this chronic disease may result in the development of oesophageal adenocarcinoma, which is also observed with increased frequency. Aim: Creation and comparison of chronic gastroesophageal reflux disease models, as well as estimation of their suitability for the investigation of the process of natural carcinogenesis in the oesophagus. Material and methods: Ninety Wistar rats were used for the study on development of chronic oesophageal inflammation. Three major groups, A - side to side anastomosis, B – side to end anastomosis and C - side to end anastomosis with total gastrectomy, were selected. In each group a different operation technique was performed to induce chronic oesophageal reflux. Groups A and B were characterized by mixed gastroduodenal reflux while group C included animals with only alkaline reflux. Results: In all three experimental models of GERD the morphological changes of the oesophageal mucosa were observed by gross inspection starting 1 month after the surgery. Under microscopic investigation chronic inflammation of the oesophageal mucosa progressing to Barrett’s metaplasia and in some cases to cancer was also confirmed. Conclusions: All experimental animal models developed due to GERD are highly reproducible and exhibit low mortality Macroscopic and microscopic assessment of oesophageal inflammation that developed in response to experimental reflux confirmed that these models are suitable and useful for determination of the pathogenesis of Barrett’s related oesophageal cancer

Endogenous prostaglandins and afferent sensory nerves in gastroprotective effect of hydrogen sulfide against stress-induced gastric lesions

Hydrogen sulfide (H2S) plays an important role in human physiology, exerting vasodilatory, neuromodulatory and anti-inflammatory effects. H2S has been implicated in the mechanism of gastrointestinal integrity but whether this gaseous mediator can affect hemorrhagic lesions induced by stress has been little elucidated. We studied the effect of the H2S precursor L-cysteine, H2S-donor NaHS, the H2S synthesizing enzyme (CSE) activity inhibitor- D,L-propargylglycine (PAG) and the gastric H2S production by CSE/CBS/3-MST activity in water immersion and restraint stress (WRS) ulcerogenesis and the accompanying changes in gastric blood flow (GBF). The role of endogenous prostaglandins (PGs) and sensory afferent nerves releasing calcitonin gene-related peptide (CGRP) in the mechanism of gastroprotection induced by H2S was examined in capsaicin-denervated rats and those pretreated with capsazepine to inhibit activity of vanilloid receptors (VR-1). Rats were pretreated with vehicle, NaHS, the donor of H2S and or L-cysteine, the H2S precursor, with or without the concurrent treatment with 1) nonselective (indomethacin) and selective cyclooxygenase (COX)-1 (SC-560) or COX-2 (rofecoxib) inhibitors. The expression of mRNA and protein for COX-1 and COX-2 were analyzed in gastric mucosa pretreated with NaHS with or without PAG. Both NaHS and L-cysteine dose-dependently attenuated severity of WRS-induced gastric lesions and significantly increased GBF. These effects were significantly reduced by pretreatment with PAG and capsaicin denervation. NaHS increased gastric H2S production via CSE/CBS but not 3-MST activity. Inhibition of COX-1 and COX-2 activity significantly diminished NaHS- and L-cysteine-induced protection and hyperemia. NaHS increased expression of COX-1, COX-2 mRNAs and proteins and raised CGRP mRNA expression. These effects of NaHS on COX-1 and COX-2 protein contents were reversed by PAG and capsaicin denervation. We conclude that H2S exerts gastroprotection against WRS-induced gastric lesions by the mechanism involving enhancement in gastric microcirculation mediated by endogenous PGs, sensory afferent nerves releasing CGRP and the activation of VR-1 receptors

Grapefruit-seed extract attenuates ethanol-and stress-induced gastric lesions via activation of prostaglandin, nitric oxide and sensory nerve pathways

AIM: Grapefruit-seed extract (GSE) containing flavonoids, possesses antibacterial and antioxidative properties but whether it influences the gastric defense mechanism and gastroprotection against ethanol- and stress-induced gastric lesions remains unknown. METHODS: We compared the effects of GSE on gastric mucosal lesions induced in rats by topical application of 100% ethanol or 3.5 h of water immersion and restraint stress (WRS) with or without (A) inhibition of cyclooxygenase (COX)-1 activity by indomethacin and rofecoxib, the selective COX-2 inhibitor, (B) suppression of NO-synthase with L-NNA (20 mg/kg ip), and (C) inactivation by capsaicin (125 mg/kg sc) of sensory nerves with or without intragastric (ig) pretreatment with GSE applied 30 min prior to ethanol or WRS. One hour after ethanol and 3.5 h after the end of WRS, the number and area of gastric lesions were measured by planimetry, the gastric blood flow (GBF) was assessed by H(2)-gas clearance technique and plasma gastrin levels and the gastric mucosal generation of PGE2, superoxide dismutase (SOD) activity and malonyldialdehyde (MDA) concentration, as an index of lipid peroxidation were determined. RESULTS: Ethanol and WRS caused gastric lesions accompanied by the significant fall in the GBF and SOD activity and the rise in the mucosal MDA content. Pretreatment with GSE (8-64 mg/kg i g) dose-dependently attenuated gastric lesions induced by 100% ethanol and WRS; the dose reducing these lesions by 50% (ID(50)) was 25 and 36 mg/kg, respectively, and this protective effect was similar to that obtained with methyl PGE2 analog (5 μg/kg i g). GSE significantly raised the GBF, mucosal generation of PGE(2), SOD activity and plasma gastrin levels while attenuating MDA content. Inhibition of PGE(2) generation with indomethacin or rofecoxib and suppression of NO synthase by L-NNA or capsaicin denervation reversed the GSE-induced protection and the accompanying hyperemia. Co-treatment of exogenous calcitonine gene-related peptide (CGRP) with GSE restored the protection and accompanying hyperemic effects of GSE in rats with capsaicin denervation. CONCLUSION: GSE exerts a potent gastroprotective activity against ethanol and WRS-induced gastric lesions via an increase in endogenous PG generation, suppression of lipid peroxidation and hyperemia possibly mediated by NO and CGRP released from sensory nerves

Novel concept in the mechanism of injury and protection of gastric mucosa : role of renina-angiotensin system and active metabolites of angiotensin

The term cytoprotection pioneered by Robert and colleagues has been introduced to describe the remarkable ability of endogenous and exogenous prostaglandins (PGs) to prevent acute gastric hemorrhagic lesions induced by noxious stimuli such as ethanol, bile acids, hiperosmolar solutions and nonsteroidal anti-inflammatory agents such as aspirin. Since that time many factors were implicated to possess gastroprotective properties such as growth factors including epidermal growth factor (EGF) and transforming factor alpha (TGFα), vasodilatory mediators such as nitric oxide (NO) and calcitonin gene related peptide (CGRP) as well as appetite gut hormones including gastrin and cholecystokinin (CCK), leptin and recently ghrelin. This protective action of gut peptides has been attributed to the release of PG but question remains whether another peptide angiotensin, the classic component of the systemic and local renin-angiotensin system (RAS) could be involved in the mechanism of gastric integrity and gastroprotection. After renin stimulation, the circulating angiotensin I is converted to angiotensin II (ANG II) by the activity of the Angiotensin Converting Enzyme (ACE). The ANG II acting via its binding to two major receptor subtypes the ANG type 1 (AT1) and type 2 (AT2) has been shown be activated during stress and to contribute to the pathogenesis of cold stress- and ischemia-reperfusion-induced gastric lesions. All bioactive angiotensin peptides can be generated not only in systemic circulation, but also locally in several tissues and organs. Recently the new functional components of RAS, such as Ang-(1-7), Ang IV, Ang-(1-12) and novel pathways ACE2 have been described suggesting the gastroprotective role for the novel ANG II metabolite, Ang-(1-7). The fact that Ang-(1-7) is produced in excessive amounts in the gastric mucosa of rodents and that pretreatment by Ang-(1-7) exhibits a potent gastroprotective activity against the gastric lesions induced by cold-restraint stress suggests that this and possibly other vasoactive metabolites of ANG II pathway could be involved in the mechanism of gastric integrity and gastroprotection. This review summarizes the novel gastroprotective factors and mechanisms associated with metabolic fate of systemic and local RAS activation with major focus to recent advancement in the angiotensin pathways in the gut integrity

In memoriam – wspomnienia pracowników Zakładu Pedagogiki Specjalnej o Profesorze Władysławie Dykciku

nie ma abstrakt