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Role of Surfactant in Other Organs
Published in Jacques R. Bourbon, Pulmonary Surfactant: Biochemical, Functional, Regulatory, and Clinical Concepts, 2019
Such a hydrophobic surface in direct contact with blood would imply an interfacial tension of about 55 dyn/cm, which translates into a collapsing pressure of about 35 mmHg for a vessel of that size.131 Thus, any loss of the glycocalyx or other natural wetting agent which could be reducing endothelial surface energy in the same way postulated20 for gastric mucus could account for the typical difference between hypertensives and normotensives. An interesting theoretical feature of such a collapsing pressure is that baroreceptors in those walls or those of similar arterioles in the aortic and carotid bodies would not “see” the elevation in pressure because they are on the convex side of the interface.131 This could provide a simple answer to the vital question in hypertension concerning why the barostat does not reset in essential hypertension. Moreover, the imposition of a collapsing pressure could explain why “mechanical tension” has been considered “the common factor” connecting many features of the blood-brain barrier.132
Chronic Constipation
Published in Peter Sagar, Andrew G. Hill, Charles H. Knowles, Stefan Post, Willem A. Bemelman, Patricia L. Roberts, Susan Galandiuk, John R.T. Monson, Michael R.B. Keighley, Norman S. Williams, Keighley & Williams’ Surgery of the Anus, Rectum and Colon, 2019
Charles H. Knowles, Adil E. Bharucha
A barostat is a rigid piston within a cylinder that is used to inflate a balloon in the colon. Because the balloon is apposed to the colonic mucosa, it can record colonic tone; manometric sensors only record phasic pressure activity. Barostat measurements revealed reduced fasting and/or postprandial colonic tone and/or compliance in 40% with normal transit constipation, 47% with STC, 53% with defaecatory disorders (DD) and normal transit and 42% with DD and slow transit.63 In another study, 43% of patients with STC had normal fasting colonic motility and motor responses to a meal and bisacodyl.70 Together, these observations suggest that normal and slow colonic transit are imperfect surrogate markers for normal and abnormal colonic motor function, respectively. Whilst normal transit constipation has been regarded as synonymous with IBS-C, 23% of patients with functional constipation or constipation predominant IBS IBS-C had delayed colonic transit.71 Hence, the relationship between colonic transit and motor functions needs to be clarified.
Upper gastrointestinal motility
Published in Nizar Zein, Bret Lashner, The Year in Gastroenterology and Hepatology, 2005
This ambitious and excellent study in a single tertiary centre examined several parameters in a large number of patients: (i) the intensity of eight dyspeptic symptoms in 438 consecutive patients with functional dyspepsia from a general gastrointestinal and speciality motility clinic over 2 years; (ii) psychosocial dimensions by questionnaire in 249 consecutive patients over 18 months (179 returned questionnaires); (iii) gastric emptying time until half-empty with 14Coctanoic acid breath test ( n = 204); and (iv) gastric sensitivity to distension and accommodation to a meal by barostat ( n = 100). Figure 2.6 summarizes the results described above in the interpretation section. Factor analysis should not be interpreted as showing the existence of four separate subgroups among patients with functional dyspepsia. Instead, in individual patients, the symptom pattern and associated physiopathological and psychopathological abnormalities will be determined by the relative contribution of each of these factors. Factor 1 is compatible with previous studies showing that functional dyspeptic patients with decreased gastric emptying are more likely to be women with symptoms of fullness, nausea and vomiting. Factor 3 is similar to ulcer-like dyspepsia 110, and gastric hypersensitivity and associated somatization suggests a global psychopathology. This study has limitations. It was performed in a tertiary centre and the findings should not be generalized to patients with functional dyspepsia in the primary or secondary care setting. The data are also of a cross-sectional nature, and the stability
Local immune response as novel disease mechanism underlying abdominal pain in patients with irritable bowel syndrome
Published in Acta Clinica Belgica, 2022
J. Aguilera-Lizarraga, M. Florens, H. Hussein, G. Boeckxstaens
Irritable bowel syndrome (IBS) is the most frequently diagnosed and most extensively evaluated functional gastrointestinal disorder (FGID) [1–3]. IBS has a negative impact on the quality of life, an enormous socio-economic burden, and an increasing prevalence that, depending on the criteria used, can reach up to 25% in the western world with higher female predominance (ratio ranging from 2:1 to 4:1) [2,3]. It is mainly characterized by abdominal pain with or without discomfort (depending on the definition used) with variable intensity and periodic exacerbations in association with altered bowel habits in the absence of structural or biochemical abnormalities that are detectable with the current diagnostic tools in clinical practice. Aberrant pain perception, or visceral hypersensitivity (VHS), is a common and pivotal hallmark of gastrointestinal disorders such as IBS. VHS is demonstrated in 60% of IBS patients and is defined as increased perception of non-noxious (i.e. allodynia) as well as noxious (i.e. hyperalgesia) stimuli arising from the viscera (i.e. the internal organs in the abdomen as the gut) [4–7]. In humans, visceral sensitivity is mainly studied using the barostat, a device allowing the assessment of visceral sensation, including pain, evoked by different distension levels (mechanical stimuli). Besides mechanical stimulation, perception of electrical, thermal, and chemical stimuli can be evaluated, as well as brain imaging techniques after mechanical stimuli.
Mechanism-based pain management in chronic pancreatitis – is it time for a paradigm shift?
Published in Expert Review of Clinical Pharmacology, 2019
Louise Kuhlmann, Søren S. Olesen, Anne E Olesen, Lars Arendt-Nielsen, Asbjørn M. Drewes
The function of pain processing and some of the underlying mechanisms can be characterized using QST. QST is comprised of a variety of stimulation modalities, at specific anatomical structures and using various evaluation methods. Well defined stimulations of skin and muscle are widely used, as the structures are easily accessible. Modalities may include mechanical stimulation (including touch, pinprick, and pressure) as well as thermal and electrical stimulation. In contrast, visceral QST, with stimulation of the gastrointestinal tract or other internal organs are unpleasant to the patient due to the invasive nature of the stimulus and more comprehensive and time-consuming to conduct [27]. Rectal distension with an electric ‘Barostat’ is occasionally used clinically in patients with, e.g., irritable bowel syndrome, but beyond this visceral QST has mainly been limited to research settings [28,29].
Adevonin, a novel synthetic antimicrobial peptide designed from the Adenanthera pavonina trypsin inhibitor (ApTI) sequence
Published in Pathogens and Global Health, 2018
Mayara S. Rodrigues, Caio F. R. de Oliveira, Luís H. O. Almeida, Simone M. Neto, Ana Paula A. Boleti, Edson L. dos Santos, Marlon H. Cardoso, Suzana M. Ribeiro, Octávio L. Franco, Fernando S. Rodrigues, Alexandre J. Macedo, Flávia R. Brust, Maria Lígia R. Macedo
Molecular dynamic simulations for adevonin were carried out in water, using the single point charge (SPC) water model. The simulations were performed using the GROMOS96 43A1 force field from the GROMACS v.5.0.4 computational package [26]. The validated tridimensional theoretical model for adevonin was used as the initial structure in the simulations and further immersed in 5,094 water molecules in a cubic box. Chloride ions were added to neutralize the system’s charge. The simulations were done under ionic strength of 0.2 M NaCl. MD simulations in sodium dodecyl sulfate (SDS) were carried out in dodecahedron boxes, where the adevonin peptide was placed into contact with a SDS micelle constituted of 100 detergents. SDS micelles were built, and their topologies generated using the CHARMM-GUI server [27]. The geometry of water molecules was constrained using the SETTLE algorithm [26]. Moreover, the LINCS algorithm was used to link all the atom-bond lengths. Particle Mesh Ewald (PME) was used for electrostatic corrections with a radius cut-off of 1.4 nm to minimize the computational simulation time. The same radius cut-off was used for van der Waals interactions. The list of the neighbors of each atom was updated every 10 simulation steps of 2 fs each. The steepest descent algorithm (50,000 steps) was applied for energy minimization. The system underwent a normalization of temperature and pressure to 300 K and 1 bar using the velocity rescaling thermostat (NVT) and the Parrinello-Rahman barostat (NPT), respectively, for 100 ps. The system with minimized energy and balanced temperature and pressure was submitted to molecular dynamics simulation during 100 ns.