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- Henriksnäs, Johanna, 1973-
(författare)
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Helicobacter pylori and Gastric Protection Mechanisms : An in vivo Study in Mice and Rats
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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- Samuelsson, Annika, 1964-, et al.
(författare)
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Disturbed intestinal microbiota (dysbiosis) and micro dynamics in patients treated for appendicitis and diverticulitis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: The human gut microbiota is a large dynamic bacterial community, which is influenced by for instance antibiotic treatment and hospitalization. In patients with inflammatory bowel disease the diversity of gut microbiota is thought to be less diverse. The role of the gut microbiota in acute appendicitis and diverticulitis is still unclear. To investigate the microbial diversity in patients suffering from appendicitis or diverticulitis, and the microbiota dynamics after antibiotic therapy and hospitalization we performed an open observation study.Methods and population: We have performed 16S rRNA sequence analysis on 42 individuals diagnosed with appendicitis and 18 individuals with diverticulitis as well as 33 healthy controls. Cultivation of the aerobic bacterial flora was performed as a complement to sequence analysis.Results: In sequencing data at genus level, there are distinctive differences when comparing healthy controls to patients diagnosed with appendicitis. Healthy controls have a flora dominated by Bacteroides, and Faecalibacterium, Ruminococcus and Prevotella while appendicitis patients show an intestinal flora with a higher abundance of Escherichia/Shigella and unclassified Enterobacteriaceae. The same pattern, however not quite as distinct could be seen for the diverticulitis patients. The microbial diversity increases after treatment with antibiotics and hospitalization.In the cultivated aerobic flora there was a significant loss of Escherichia coli and a significant gain of Citrobacter species, in the appendicitis group. In the appendicitis group as well as in the diverticulitis group there was a significant gain of Enterococcus faecium and Yeasts.Conclusion: The main findings of this study are that patients arriving at the emergency department with acute appendicitis or diverticulitis have an already significant disturbed fecal microbiota previous to antibiotic treatment and hospitalization.
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- Alimohammadzadeh, Rana, et al.
(författare)
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Improving the mechanical properties of CTMP fibers by combining synergistic organocatalytic/polyelectrolyte complex surface engineering with sulfite pretreatment
- 2022
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Ingår i: Proceedings of the International Mechanical Pulping Conference. ; , s. 149-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fabrication of paper-based packaging materials is increasing and the challenge is developing a sustainable process to manufacture the materials that can compete with plastics. Employing stronger fiber in production of fiber-based materials improves the efficiency of fabrication process by using a reduced amount of biomass. Cationic starch is a well-known polysaccharide that has been introduced to paper and paperboard fibers to improve the mechanical properties of lignocellulosic fibers. The polyelectrolyte (PE) multilayer method has been popularized as a new and interesting technique to enhance the adsorption of cationic starch on the fiber for improving the strength properties of chemi-thermomechanical pulp (CTMP), chemical and kraft pulps. We have shown in our previous work that the synergistic combination of organocatalysis and PE complexes improved the mechanical properties of CTMP and TMP. In this work, we chose to expand this concept by integrating it with low-dose sulfite pretreatment of wood chips in preparation of CTMP. Thus, CTMP produced by initial sulfite pre-treatment was next surface engineered by synergistic combination of organocatalysis and PE complexes using organic acids as catalysts. The CTMP pulps, which contains 0.1-0.24 wt.% sulfur, produced by our novel pulp-engineering strategy shows a dramatic strength increase (Z- strength: up to 100 %) as compared to no surface engineering. While only sulfite pre-treatment and PE-complex surface engineering were able to improve the strength properties, it was only when the organic catalysts was present that the highest strength improvements were reached. Thus, a clear synergistic effect of the catalyst was observed.
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