Tissue Penetration and Measuring Depth of Laser Doppler Flowmetry in the Gastrointestinal Application

Johansson, K.-A.; Ahn, Henrik Casimir; Lindhagen, J; Lundgren, Ove

doi:10.3109/00365528708991962

Cited by 91 publications

(46 citation statements)

References 15 publications

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“…The laser probe was held in a fixed position in the chamber solution at a distance of 1-2 mm above the mucosa by a micromanipulator. With the type and position of the probe used in these experiments, the laser light most likely penetrated through the entire thickness of the gastric wall (20). However, the recorded blood flow was mainly mucosal, because the amount of backscattered light decreases exponentially with the depth in the tissue.…”

Section: Blood Flow Measurementsmentioning

confidence: 99%

Impaired mucus-bicarbonate barrier inHelicobacter pylori-infected mice

Henriksnäs

Phillipson²,

Storm³

et al. 2006

American Journal of Physiology-Gastrointestinal and Liver Physi

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To resist the harsh intrinsic milieu, several lines of defense exist in the stomach. The aim of this study was to investigate the effect of the gastric pathogen Helicobacter pylori on these mechanisms in vivo. We used FVB/N mice expressing human ␣-1,3/4-fucosyl transferase (producing Lewis b epitopes) and inoculated with H. pylori 1. Mice were anesthetized with isoflurane or Hypnorm-midazolam, the stomach was exteriorized, and the surface of the corpus mucosa was exposed. Mucus thickness was measured with micropipettes, juxtamucosal pH (pHjm) was measured with pH-sensitive microelectrodes, blood flow was measured with laser-Doppler flowmetry, and mRNA levels of the bicarbonate transporter SLC26A9 were quantified with real-time PCR. The increase in mucosal blood flow seen in response to luminal acid (pH 1.5) in control animals (140 Ϯ 9% of control) was abolished in infected mice. The firmly adherent mucus layer was significantly thinner in infected mice (31 Ϯ 2 m) than in control mice (46 Ϯ 5 m), and no mucus accumulation occurred in infected mice. pHjm decreased significantly more on exposure to luminal acid in infected mice (luminal pH 1.5, pH jm 2.4 Ϯ 0.7) than in control mice (pHjm 6.4 Ϯ 0.5). Despite reduced pHjm, SLC26A9 mRNA expression was significantly, by increased 1.9-fold, in infected mice. The reduction in pH jm by infection with H. pylori might be due to a reduced firmly adherent mucus layer, increased mucus permeability to H ϩ , and/or inhibition of bicarbonate transport. The upregulation of SLC26A9 in H. pylori-infected epithelium might be a result of continuous inhibition of the transporter, e.g., by ammonium, a H. pylori product, which has been previously shown to inhibit SLC26A9. juxtamucosal pH; blood flow; laser-Doppler flowmetry; permeability

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Section: Blood Flow Measurementsmentioning

confidence: 99%

Impaired mucus-bicarbonate barrier inHelicobacter pylori-infected mice

Henriksnäs

Phillipson²,

Storm³

et al. 2006

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…Directional blood flow is not measured. A good correlation between LDF and radionuclide-labeled microspheres for measuring cerebral blood flow in rabbits (coefficient of 0.92) (14) (16). The signals were considered inadequate if the LDF was nonpulsatile or the measurements were less than 20 PU at baseline.…”

Section: Animal Preparationmentioning

confidence: 99%

Hydrogen Peroxide Production in Leukocytes during Cerebral Hypoxia and Reoxygenation with 100% or 21% Oxygen in Newborn Piglets

et al. 2001

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The aim of this study was to investigate whether reoxygenation with 21% O 2 rather than 100% O 2 results in reduced hydrogen peroxide (H 2 O 2 ) concentrations in neutrophils (PMN). Piglets (2-4 d old) exposed to severe hypoxia (inspired fraction of oxygen, 0.08) were randomized to resuscitation with 21 (n ϭ 13) or 100% O 2 (n ϭ 12). Five animals served as controls. H 2 O 2 concentrations in PMN in terms of rhodamine 123 (Rho 123) fluorescence intensity from arterial and superior sagittal sinus blood were quantified by flow cytometry. Laser Doppler flowmetry (LDF) was used to assess cortical blood perfusion. During hypoxia, Rho 123 increased in arterial PMN in both study groups by 15 and 32%, respectively (p Ͻ 0.05). In cerebral venous PMN, the increase was less dominant (p ϭ 0.06). Reoxygenation with 100 or 21% O 2 had no different effect on Rho 123 in arterial PMN. In cerebral venous PMN, Rho 123 was approximately 40% higher after 60 min and 30% higher after 120 min compared with corresponding data in the 21% O 2 group (p Ͻ 0.05), which were close to baseline levels. Further, O 2 treatment in both groups induced PMN accumulation in arterial blood (p Ͻ 0.05). Laser Doppler flowmetry signals increased during transient hypoxia (p Ͻ 0.0001 compared with baseline) and were normalized after reoxygenation in both study groups. The primary release of products of the sequential reduction of oxygen, superoxide radical (O 2 -) and H 2 O 2 , and the secondary production of hydroxyl radical (HO -) constitute the molecular mechanism of oxygen toxicity. Any system producing O 2 -will, as a result of the dismutase reaction, also produce H 2 O 2 . Although stable, the damaging redox properties of H 2 O 2 and its ability to form highly reactive free radicals in the presence of transition metal ions have caused the body to form defenses against it. The role of oxygen toxicity in the development of perinatal hypoxic-ischemic encephalopathy is still a matter of debate. The principal hypothesis put forward to explain this process is the oxygen free radical theory (1, 2).Stimulation of PMN during hypoxia-reoxygenation may increase the concentration of reactive oxygen species (3) in these cells. To date, the production of H 2 O 2 in PMN during hypoxia and resuscitation with pure or air-mixed O 2 has not been studied in detail. Reoxygenation is necessary to prevent further injury to neuronal tissue, but the renewed availability of O 2 to previously hypoxic brain tissue may also have detrimental effects both with respect to the microcirculation and to the parenchyma of the brain. The production of reactive oxygen metabolites may be proportional to PaO 2 , and the oxygen tension achieved during reactive hyperemia and reoxygenation with O 2 concentrations higher than 21% may generate a correspondingly higher burst of these metabolites. However, we

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“…Similar results regarding the influence of probe geometry on LDF sampling depth was obtained by Johansson et al during studies of isolated segments of feline small intestine. 3 The sampling depth has also been studied theoretically using either a Monte Carlo simulation model 4,5 or a lattice random-walk model 6 . The latter two reports did not only show that the sampling depth increases with fiber separation but also that the it is affected by the optical properties of the tissue.…”

Section: Introductionmentioning

confidence: 99%