Patients with idiopathic anal fistula (n=85) were compared with 215 control subjects, matched for age and sex, through a 180-item questionnaire. Obesity, smoking, constipation and bowel symptoms associated with IBS were more common in the patients. Endoanal ultrasound (EUS) and magnetic resonance imaging (MRI) were compared in the preoperative evaluation of anal fistula in 23 patients. For classifying the primary tract, EUS and surgical findings agreed in 14 cases, and MRI and surgery for 11: for identifying an internal opening, the corresponding figures were 17 and 10. Healing and sphincter function were studied in 42 patients operated with fistula excision and closure of the internal opening. Twenty-three patients healed primarily and another 10 after one re-operation, whereas nine required further surgery until healed. Anal resting pressure was reduced after three and 12 months, and squeeze pressure after 12 months. Eighty-three patients were randomised to surgery with or without application of gentamicin-collagen underneath the flap: 26/42 of patients randomised to gentamicin-collagen healed primarily compared with 21/41 of patients randomised to surgery only (n.s). Micro perfusion in the flap was studied by laser Doppler flowmetry during surgery in 16 patients. No correlation was seen between change in blood flow during surgery and non-healing/recurrence of the fistula. In conclusion, obesity, functional bowel symptoms and possibly smoking are more common in patients with idiopathic anal fistula than in the general population. Endoanal ultrasound is a useful tool in the preoperative evaluation of anal fistula. Advancement flap repair has a reasonably high primary recurrence rate and healing is not significantly improved by local application of gentamicin-collagen: impaired intraoperative blood perfusion of the flap is an unlikely reason for non-healing. A decrease in continence occurs also after this kind of surgery, probably due to an impaired internal anal sphincter function.

The human stomach normally contains high levels of bioactive nitric oxide (NO). This NO derives from salivary nitrate (NO3-) that is converted to nitrite (NO2-) by oral bacteria and thereafter non-enzymatically reduced in the acidic gastric lumen to NO. Nitrate is a common component in vegetables, and after ingestion it is absorbed in the small intestine. Interestingly, circulating nitrate is then concentrated by the salivary glands. Hence, intake of nitrate-rich vegetables results in high levels of NO in the stomach. The physiological effects of the high concentration of NO gas normally present in the gastric lumen have been hitherto unknown, and the present investigations were therefore conducted to address this issue. NO produced in the gastric lumen after nitrate ingestion increased gastric mucosal blood flow and the thickness of the firmly adherent mucus layer in the stomach. The blood flow and mucus layer are essential defense mechanisms that protect the mucosa from luminal acid and noxious agents. Nonsteroidal antiinflammatory drugs (NSAID) are commonly prescribed and effective drugs for treating pain and inflammation, but are associated with severe gastrointestinal side effects. We demonstrated that a nitrate-rich diet protects against NSAID-induced gastric damage, as a result of the increased formation of NO in the stomach. We also showed that the gastroprotective effect attributed to nitrate depended completely on conversion of nitrate to nitrite by the bacterial flora colonizing the tongue, and that the oral microflora is therefore important in regulating physiological conditions in the stomach. In summary, this thesis challenges the current dogma that nitrate intake is hazardous, and on the contrary suggests that dietary nitrate plays a direct role in regulating gastric homeostasis. It is likely that a sufficient supply of nitrate in the diet together with the oral microflora is essential for preventing pathological conditions in the gastrointestinal tract.

Hipertensos têm rarefação capilar e disfunção endotelial microcirculatória, tornando-se mais vulneráveis a lesões em órgãos-alvo. O estudo buscou avaliar o efeito de seis meses de tratamento farmacológico sobre densidade capilar e reatividade microvascular a estímulos fisiológicos e farmacológicos em hipertensos de baixo risco cardiovascular. Secundariamente testou-se a existência de diversidade nas respostas a diferentes estratégias anti-hipertensivas. Foram recrutados 44 pacientes, com 46,71,3 anos e 20 normotensos com 48,01,6 anos. Avaliaram-se dados antropométricos e laboratoriais e dosaram-se no soro o fator de crescimento vascular endotelial (VEGF), receptor Flt-1 para VEGF e óxido nítrico (NO). A contagem capilar foi por microscopia intravital, captando-se imagens da microcirculação no dorso da falange do dedo médio e contando os capilares com programa específico. Repetia-se o procedimento após hiperemia reativa pós-oclusiva (HRPO) para avaliar o recrutamento capilar. A reatividade vascular foi testada por fluxometria Laser Doppler, iontoforese de acetilcolina (Ach), HRPO e hiperemia térmica local (HTL). Os pacientes foram distribuídos aleatoriamente para dois grupos de tratamento: succinato de metoprolol titulado a 100 mg diários ou olmesartana medoxomila titulada a 40 mg diários, empregando-se, se necessário, a hidroclorotiazida. Os controles seguiram o mesmo protocolo inicial e após seis meses todos os testes foram repetidos nos hipertensos. As variáveis clínicas e laboratoriais basais eram semelhantes em comparação aos controles e entre os dois grupos de tratamento. Após seis meses, havia pequenas diferenças entre os grupos na relação cintura-quadril e HDL. A densidade capilar antes do tratamento era significativamente menor que no grupo controle (71,31,5 vs 80,61,8 cap/mm2 p<0,001 e HRPO 71,71,5 vs 79,52,6 cap/mm2 p<0,05) e, com o tratamento, aumentou para 75,41,1 cap/mm2 (p<0,01) no estado basal e para 76,81,1 cap/mm2 à HRPO (p<0,05). À reatividade vascular, a condutância vascular cutânea (CVC) em unidades de perfusão (UP)/mmHg era similar à HTL nos controles e hipertensos e aumentou com o tratamento nos dois subgrupos (metoprolol:1,730,2 a 1,900,2 p<0,001 e olmesartana:1,490,1 a 1,870,1 p<0,001). A CVC máxima à HRPO era menor nos hipertensos: 0,30(0,22-0,39) que nos controles: 0,39(0,31-0,49) com p<0,001. Após tratamento, aumentou para 0,41(0,29-0,51) com p<0,001. O aumento foi significativo apenas no grupo olmesartana (0,290,02 a 0,420,04 p<0,001). A diferença entre o tempo para atingir o fluxo máximo à HRPO aumentou no grupo metoprolol após tratamento 3,0 (-0,3 a 8,8) segundos versus olmesartana 0,4 (-2,1 a 2,4) segundos p<0,001. À iontoforese, a área sob a curva de fluxo (AUC) era similar nos grupos e aumentou com o tratamento, de 6087(3857-9137) para 7296(5577-10921) UP/s p=0,04. O VEGF e receptor não diferiam dos controles nem sofreram variações. A concentração de NO era maior nos hipertensos que nos controles: 64,9 (46,8-117,6) vs 50,7 (42-57,5) M/dl p=0,02 e não variou com tratamento. Em conclusão, hipertensos de baixo risco têm menor densidade e menor recrutamento capilar e ambos aumentam com tratamento. Apresentam também disfunção endotelial microcirculatória que melhora com a terapia. / Capillary rarefaction and microcirculatory endothelial dysfunction are hallmarks of hypertension, rendering patients vulnerable to target organ lesions. The study aimed at assessing the effect of a six-month treatment period upon capillary density and microvascular reactivity to physiological and pharmacological stimuli. In addition, two different treatment strategies were tested for possible differences between effects upon those variables. A total of 44 patients were recruited, mean age 46.71.3 years and 20 normotensive individuals served as controls, mean age 48.01.6 years. Anthropometrical and laboratory data were collected, as well as plasma levels of vascular endothelial growth factor (VEGF), its receptor Flt-1 and nitric oxide (NO). Capillary density was obtained by intra-vital microscopy of the dorsum of the middle phalanx before and after post-occlusive reactive hyperemia (PORH). Capillary loops were counted by a semi-automated software. Microvascular reactivity was tested by laser Doppler flowmetry (LDF), and the challenges consisted of acetylcholine iontophoresis, local thermal hyperemia (LTH) and PORH. Patients were randomly allocated to either one of two treatment arms: metoprolol succinate uptitrated to 100 mg daily or olmesartan medoxomil uptitrated to 40 mg daily, with addition of hydrochlorothiazide if necessary. Controls underwent the same initial protocol and all tests were repeated in patients after six months. Baseline clinical and laboratory parameters were similar between patients and controls and between the two treatment groups. After six months there were slight, although significant, differences between the two groups in waist/hip ratio and HDL-cholesterol. In the whole cohort, pretreatment capillary density was significantly reduced compared to controls (71.31.5 vs 80.61.8 cap/mm2 p<0.001 and PORH 71.71.5 vs 79.52.6 cap/mm2 p<0.05). After treatment it increased to 75.41.1 cap/mm2 (p<0.01) at rest and 76.81,1 cap/mm2 during PORH. During LTH, cutaneous vascular conductance (CVC) in perfusion units (PU)/ mmHg was similar in patients and controls and increased significantly in both subgroups (metoprolol: from 1.730.2 to 1.900.2 p<0,001 and olmesartan: from 1.490.1 to 1.870.1 p<0.001). Maximal CVC during PORH was reduced in hypertensive patients: 0.30 (0.22-0.39) compared to controls: 0.39(0.31-0.49) with p<0.001. After therapy it increased to 0.41(0.29-0.51) with p<0.001. The change was significant only for the olmesartan subgroup (from 0.290.02 to 0.420.04 p<0.001). After treatment, the difference in time spent to reach peak flow during PORH inreased significantly in patients taking metoprolol but not in those taking olmesartan: -3.0 (-8.8 to 0.2) and 0.4 (-2.1 to 2.4) seconds after vs before, respectively p<0,001. Area under the Ach iontophoresis flow curve (AUC) was similar in controls and hypertensive patients, and increased after treatment, from 6087 (3857-9137) to 7296 (5577-10921) PU/s p=0.04. VEGF and Flt-1 receptor were similar among all groups and did not change with treatment. NO levels were higher in hypertensive individuals than in controls: 64.9 (46.8-117.6) vs 50.7 (42.0-57.5) M/dl p=0.02 and did not change with treatment. In conclusion, low-risk hypertensive patients show reduced capillary density/recruitment, and endothelial microvascular dysfunction. Both improve with treatment

Estudos de diagnóstico de vitalidade pulpar em dentes decíduos traumatizados, através da Fluxometria Laser Doppler (FLD), têm utilizado dentes tratados endodonticamente, porém o diagnóstico clínico é realizado em dentes necrosados. O objetivo deste estudo foi avaliar a FLD como teste de vitalidade pulpar em incisivos superiores decíduos traumatizados necrosados, desvitalizados (DES), antes e após tratamento endodôntico. Foram analisados em 57 crianças, de 40 a 85 meses de idade, valores de fluxo de dois dentes: IC DES - I VIT - 1 incisivo central necrosado (leitura antes e após a endodontia) e 1 incisivo central ou lateral vitalizado (leitura repetida em 2 sessões); I VIT - I VIT - 2 incisivos centrais ou laterais vitalizados (leitura em sessão única). Foi utilizado o Fluxômetro Laser Doppler (Moor Instruments, moorLab, Axminster, Inglaterra), diodo laser emitindo no comprimento de onda de 780nm, banda Doppler em 15kHz, sonda MP13 posicionada na vestibular a 4mm da margem gengival e estabilizada com posicionador de silicone. Foram avaliados dois parâmetros: F(UA), valor de fluxo de um único dente em unidades arbitrárias; F(%), variação percentual entre pares de dentes de um mesmo paciente. Estes parâmetros foram aplicados nos grupos antes e após a endodontia: F(UA) antes, F(UA) após, F(%) antes e F(%) após. No parâmetro F(UA), para os 29 IC DES antes, a variação de fluxo foi de 2,3 a 11,1UA, a média foi de 5,4UA e o desvio-padrão de 2,5UA. Para os 29 I VIT antes, a variação foi de 4,2 a 16,1UA (9,6 ± 3,5UA). Na segunda sessão, para os 29 IC DES após, foi de 1,3 a 7,4UA (3,4 ± 1,6UA), e para os 29 I VIT após foi de 3,6 a 19,7UA (9,3 ± 3,6UA). Para os 62 I VIT analisados em única sessão, a variação foi de 5,0 a 16,5UA (9,3 ± 2,4UA). No parâmetro F(%), para os 29 pares de IC DES antes - I VIT antes a variação foi de 28,0 a 98,1% (57,4 ± 17,2%). Para os 29 pares de IC DES após - I VIT após, de 18,0 a 84,5% (37,9 ± 15,2%). Para os 31 pares de I VIT - I VIT, foi de 57,5 a 146,5% (99,9 ± 23,3%). A performance dos parâmetros foi estimada pela área sob a curva ROC (AUC). Para F(UA) antes, a AUC foi de 0,862, para F(%) antes, a AUC foi de 0,941, para F(UA) após, a AUC foi de 0,975. Seus desempenhos, considerando intervalo de confiança de 95%, foram considerados entre moderadamente acurados e altamente acurados. Para F(%) após, a AUC foi de 0,987, sendo seu desempenho altamente acurado. Após comparação das AUCs, somente foi observada diferença significante, p=0,002, entre F(UA) antes e F(UA) após. Os pontos de corte propostos foram baseados nos dados obtidos antes da endodontia: para F(UA), valores menores ou iguais a 6,5UA classificam os dentes como desvitalizados e para F(%), valores menores ou iguais a 66,9%. Conclui-se que F(UA) e F(%) são parâmetros capazes de diferenciar dentes decíduos necrosados de dentes vitalizados, assim como de diferenciar dentes tratados endodonticamente de dentes vitalizados. / Studies on diagnosis of dental pulp necrosis in traumatized primary teeth using laser Doppler flowmetry (LDF) evaluate teeth with endodontic treatment; however, clinical diagnosis is performed in teeth with pulp necrosis. The aim of this study was to evaluate the LDF as pulp vitality test in traumatized primary upper incisors, with pulp necrosis (DES), before and after endodontic treatment. The pulpal flux values of 57 children, aged from 40 to 85 months, were evaluated: IC DES - I VIT - 1 central incisor with pulp necrosis (readings before and after endodontic treatment) and 1 vital central or lateral incisor (readings in 2 sessions); Control group: I VIT - I VIT - 2 vital incisors (readings in 1 session). The Laser Doppler Flowmeter (Moor Instruments, moorLab, Axminster, UK) was used. It is a diode laser emitting at 780 nm and bandwidth at 15 kHz. A MP13 probe was placed on the buccal surface of the tooth, 4mm from the gingival margin using silicone splints. Two parameters were evaluated: F(AU), the flux value of each tooth in arbitrary units, and F(%), the percentage variation of the flux value between pairs of teeth in the same patient. The two parameters were used before and after endodontic treatment: F(AU) before, F(AU)after, F(%) before and F(%) after. In the 29 IC DES before, F(AU) ranged from 2.3 to 11.1AU; the mean was 5.4AU and the standard deviation was 2.5AU; in the 29 I VIT before, ranged from 4.2 to 16.1AU (9.6 ± 3.5AU); in the 29 IC DES after, the values ranged from 1.3 to 7.4AU (3.4 ± 1.6AU), and in the 29 I VIT after, from 3.6 to 19.7AU (9.3 ± 3.6AU). In the 62 I VIT analyzed in one session, the values ranged from 5.0 to 16.5AU (9.3 ± 2.4AU). In respect to F(%), in the 29 pairs of IC DES before - I VIT before, the values ranged from 28.0 to 98.1% (57.4 ± 17.2%); in the 29 pairs of IC DES after - I VIT after, from 18.0 to 84.5% (37.9 ± 15.2%); in the 31 pairs of I VIT - I VIT, from 57.5 to 146.5% (99.9 ± 23.3%). The performance of both tests was estimated by the area under the ROC curve (AUC). Regarding F(AU) before, the AUC was 0.862; in F(%) before, the AUC was 0.941; in F(AU) after, the AUC was 0.975. The performances were classified between moderate and highly accurate (95% Confidence Interval). Regarding F(%) after, the AUC was 0.987 and its performance was highly accurate. Comparing the AUCs, there was statistical significance (p=0.002), between F(AU) before and F(AU) after. The cut-off values were based on data before endodontic treatment. The F(AU) values that were equal to or smaller than 6.5AU, and the F(%) values that were equal to or smaller than 66.9% classified the tooth as non-vital The two parameters studied, F(AU) and F(%), are able to distinguish non-vital primary teeth from vital teeth, and to distinguish vital teeth from teeth with endodontic treatment.

The peripheral skin microcirculation reflects the overall health status of the cardiovascular system and can be examined non-invasively by laser methods to assess early cardiovascular disease (CVD) risk factors, i.e. oxidative stress and endothelial dysfunction. Examples of methods used for this task are the laser Doppler flowmetry (LDF) and laser fluorescence spectroscopy (LFS), which respectively allow tracing blood flow and the amounts of the coenzyme NAD(P)H (nicotamide adenine dinucleotide) that is involved in the cellular production of ATP (adenosine triphosphate) energy. In this work, these methods were combined with iontophoresis and PORH (post-occlusive reactive hyperaemia) reactive tests to assess skin microvascular function and oxidative stress in mice and human subjects. The main focus of the research was exploring the nonlinear dynamics of skin LDF and NAD(P)H time series by processing the signals with the wavelet transform analysis. The study of nonlinear fluctuations of the microcirculation and cell energy metabolism allows detecting dynamic oscillators reflecting the activity of microvascular factors (i.e. endothelial cells, smooth muscle cells, sympathetic nerves) and specific patterns of mitochondrial or glycolytic ATP production. Monitoring these dynamic factors is powerful for the prediction of general vascular/metabolic health conditions, and can help the study of the mechanisms at the basis of the rhythmic fluctuations of micro-vessels diameter (vasomotion). In this thesis, the microvascular and metabolic dynamic biomarkers were characterised <i>in-vivo</i> in a mouse model affected by oxidative stress and a human cohort of smokers. Data comparison, respectively, with results from control mice and non-smokers, revealed significant differences suggesting the eligibility of these markers as predictors of risk associated with oxidative stress and smoke. Moreover, a relevant link between microvascular and metabolic oscillators was observed during vasomotion induced by α-adrenergic (in mice) or PORH (in humans) stimulations, suggesting a possible role of cellular Ca²⁺oscillations of metabolic origin as drivers of vasomotion which is a theory poorly explored in literature. As future perspective, further exploration of these promising nonlinear biomarkers is required in the presence of risk factors different from smoke or oxidative stress and during vasomotion induced by stimuli different from PORH or α-adrenergic reactive challenges, to obtain a full picture on the use of these factors as predictors of risk and their role in the regulation of vasomotion.

<p>The gastrointestinal mucus gel layer and blood flow are two important mechanisms for protection at the pre-epithelial and sub-epithelial levels, respectively. <i>Helicobacter pylori</i> might circumvent these mechanisms and elicit a chronic inflammatory response with consequent ulcers in the stomach and duodenum. In this thesis, the physical state and properties of the adherent mucus gel layer was studied from the stomach to colon. Furthermore, the acute and chronic effects of <i>H. pylori</i> on the integrity of the mucus gel layer and mucosal blood flow were studied in the anesthetized rat.</p><p>A translucent mucus gel covers all studied segments of the gastrointestinal tract during fasting conditions, with the thickest layers in the colon and ileum. Carefully applied suction revealed that the mucus gel was a multi-layered structure comprising a firmly adherent layer covering the mucosa, impossible to remove, and a loosely adherent upper layer. The firmly adherent layer was thick and continuous in the corpus (80μm), antrum (154μm) and colon (116μm), but thin (<20μm) and discontinuous in the small intestine.</p><p>Following mucus removal, a rapid renewal of the loosely adherent layer ensued. The highest rate was observed in the colon with intermediate values in the small intestine. Mucus renewal in the stomach was attenuated on acute luminal application of water extracts from <i>H. pylori</i> (HPE). In animals with a chronic <i>H. pylori</i> infection the mucus renewal rate was unaffected, but the total gastric mucus gel thickness was reduced and the mucus secretory response to luminal acid (pH1) attenuated in the antrum. </p><p>HPE from type I strains acutely reduced corporal mucosal blood flow, measured with laser-Doppler flowmetry, by approximately 15%. The reduction in blood flow was mediated by a heat stable factor other than VacA and CagA. Inhibition of endogenous nitric oxide production with Nω-nitro-l-arginine augmented the decrease. However, ketotifen, a mast cell stabilizer, completely attenuated the effect of the extract as did the platelet activating factor (PAF) receptor-antagonist, WEB2086, thus depicting a detrimental role for the microvascular actions of PAF.</p>

<p>The stomach is frequently exposed to hazardous agents and to resist this harsh environment, several protective mechanisms exist. Of special interest is the gastric pathogen <i>Helicobacter pylori </i>which causes gastritis, ulcers and cancer but the mechanism leading to these diseases are still unclear. However it is very likely that <i>H. pylori </i>negatively influence the protection mechanisms that exist in the stomach. </p><p>The aims of the present investigation were first to develop an in vivo mouse model in which different protection mechanisms could be studied, and second to investigate the influence of <i>H. pylori</i> on these mechanisms. </p><p>An in vivo preparation of the gastric mucosa in mice was developed. This preparation allows studies of different gastric mucosal variables and can also be applied for studies in other gastro-intestinal organs. </p><p>Mice chronically infected with <i>H. pylori</i>, were shown to have a reduced ability of the mucosa to maintain a neutral pH at the epithelial cell surface. This could be due to the thinner inner, firmly adherent mucus gel layer, and/or to defective bicarbonate transport across the epithelium. The Cl^-/HCO₃^- exchanger SLC26A9 was inhibited by NH₄⁺, which also is produced by <i>H. pylori</i>. The mRNA levels of SLC26A9 were upregulated in infected mice, suggesting a way to overcome the inhibition of the transporter. Furthermore, the hyperemic response to acid pH 2 and 1.5 was abolished in these mice. The mechanisms by which the bacteria could alter the blood flow response might involve inhibition of the epithelial iNOS.</p><p>Water extracts of <i>H. pylori </i>(HPE) reduces the blood flow acutely through an iNOS and nerve-mediated pathway, possibly through the endogenous iNOS inhibitor ADMA. Furthermore, HPE alters the blood flow response to acid as the hyperemic response to acid pH 0.8 is accentuated in mice treated with HPE. </p>

The gastrointestinal mucus gel layer and blood flow are two important mechanisms for protection at the pre-epithelial and sub-epithelial levels, respectively. Helicobacter pylori might circumvent these mechanisms and elicit a chronic inflammatory response with consequent ulcers in the stomach and duodenum. In this thesis, the physical state and properties of the adherent mucus gel layer was studied from the stomach to colon. Furthermore, the acute and chronic effects of H. pylori on the integrity of the mucus gel layer and mucosal blood flow were studied in the anesthetized rat. A translucent mucus gel covers all studied segments of the gastrointestinal tract during fasting conditions, with the thickest layers in the colon and ileum. Carefully applied suction revealed that the mucus gel was a multi-layered structure comprising a firmly adherent layer covering the mucosa, impossible to remove, and a loosely adherent upper layer. The firmly adherent layer was thick and continuous in the corpus (80μm), antrum (154μm) and colon (116μm), but thin (&lt;20μm) and discontinuous in the small intestine. Following mucus removal, a rapid renewal of the loosely adherent layer ensued. The highest rate was observed in the colon with intermediate values in the small intestine. Mucus renewal in the stomach was attenuated on acute luminal application of water extracts from H. pylori (HPE). In animals with a chronic H. pylori infection the mucus renewal rate was unaffected, but the total gastric mucus gel thickness was reduced and the mucus secretory response to luminal acid (pH1) attenuated in the antrum. HPE from type I strains acutely reduced corporal mucosal blood flow, measured with laser-Doppler flowmetry, by approximately 15%. The reduction in blood flow was mediated by a heat stable factor other than VacA and CagA. Inhibition of endogenous nitric oxide production with Nω-nitro-l-arginine augmented the decrease. However, ketotifen, a mast cell stabilizer, completely attenuated the effect of the extract as did the platelet activating factor (PAF) receptor-antagonist, WEB2086, thus depicting a detrimental role for the microvascular actions of PAF.

The stomach is frequently exposed to hazardous agents and to resist this harsh environment, several protective mechanisms exist. Of special interest is the gastric pathogen Helicobacter pylori which causes gastritis, ulcers and cancer but the mechanism leading to these diseases are still unclear. However it is very likely that H. pylori negatively influence the protection mechanisms that exist in the stomach. The aims of the present investigation were first to develop an in vivo mouse model in which different protection mechanisms could be studied, and second to investigate the influence of H. pylori on these mechanisms. An in vivo preparation of the gastric mucosa in mice was developed. This preparation allows studies of different gastric mucosal variables and can also be applied for studies in other gastro-intestinal organs. Mice chronically infected with H. pylori, were shown to have a reduced ability of the mucosa to maintain a neutral pH at the epithelial cell surface. This could be due to the thinner inner, firmly adherent mucus gel layer, and/or to defective bicarbonate transport across the epithelium. The Cl-/HCO3- exchanger SLC26A9 was inhibited by NH4+, which also is produced by H. pylori. The mRNA levels of SLC26A9 were upregulated in infected mice, suggesting a way to overcome the inhibition of the transporter. Furthermore, the hyperemic response to acid pH 2 and 1.5 was abolished in these mice. The mechanisms by which the bacteria could alter the blood flow response might involve inhibition of the epithelial iNOS. Water extracts of H. pylori (HPE) reduces the blood flow acutely through an iNOS and nerve-mediated pathway, possibly through the endogenous iNOS inhibitor ADMA. Furthermore, HPE alters the blood flow response to acid as the hyperemic response to acid pH 0.8 is accentuated in mice treated with HPE.

Background and aims: Lung recruitment maneuvers (brief episodes of high airway pressure) are a modern treatment alternative to achieve open lung conditions under mechanical ventilation of patients with acute lung injury. It is well known that positive pressure ventilation with high airway pressures cause negative circulatory effects, and that the effects on regional vascular beds can be even more pronounced than the systemic effects. Hypoperfusion of the mesenteric vascular bed can lead to tissue ischemia and local inflammation. This intestinal inflammation has been associated with subsequent development of multiple organ dysfunction syndrome, a syndrome that still carries a high mortality and is a leading cause of death for intensive care patients. The aim of this thesis was therefore to investigate whether lung recruitment maneuvers would cause negative effects on mesenteric circulation, oxygenation or metabolism. Methods and results: In an initial study on ten patients with acute lung injury, we could demonstrate a trend towards a decreased gastric mucosal perfusion during three repeated lung recruitment maneuvers. To more closely examine this finding, we set up an oleic acid lung injury model in pigs, and in our second study we established that this model was devoid of inherent intestinal effects and was adequate for subsequent studies of intestinal effects of lung recrutiment maneuvers. In the acute lung injury model, we also tested the effect of an infusion of a vasodilating agent concurrent with the recruitment maneuvers, the hypothesis being that a vasodilating agent would prevent intestinal vasoconstriction and hypoperfusion. We could show that three repeated lung recruitment maneuvers induced short term negative effects on mesenteric oxygenation and metabolism, but that these findings were transient and short lasting. Further, the effects of prostacyclin were minor and opposing. These findings of relative little impact on the intestines of lung recruitment maneuvers, lead us to investigate the hypothesis that repeated recruitment maneuvers maybe could elicite a protective intestinal preconditioning response, a phenomenon previously described both in the rat and in the dog. However, in our fourth study, using both classical ischemic preconditioning with brief periods of intestinal ischemia or repeated lung recrutiment maneuvers, we could not demonstrate the phenomenon of intestinal preconditioning in the pig. Conclusions: We conclude, that from a mesenteric point of view, lung recruitment maneuvers are safe, and only induce transient and short lasting negative effects. We also conclude that the cause of the minor effects of lung recruitment maneuvers is not dependent on intestinal preconditioning.