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Sheet Preparations (sheet + preparation)

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Medical Sciences100%

Selected Abstracts

Propagating contractions of the circular muscle evoked by slow stretch in flat sheets of guinea-pig ileum

NEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2001
S. J. H. Brookes
Flat sheet preparations of guinea-pig ileum were stretched circumferentially and the propagation of circular muscle contractions along the preparation was investigated. Slow stretch, at 100 ,m s,1, of a 50-mm long flat sheet of intestine, evoked circular muscle contraction orally, which propagated, without decrement, for up to 30 mm. This occurred despite circular muscle shortening being prevented, and in the absence of propulsion of contents. Thus, propagation in this flat sheet preparation could not explained on the basis of neuro-mechanical interactions, as previously proposed. Irrespective of the length of preparations, contraction amplitude decreased significantly in the most aboral 10,15 mm of intestine. This was not due to descending inhibitory pathways, but was associated with interruption of ascending excitatory pathways near the aboral end. Slow waves were not detected in circular muscle cells in any preparation (n=8). Smooth muscle action potentials evoked in circular muscle cells, in the presence of tetrodotoxin (TTX, 0.6 ,mol L,1), did not propagate for more than 1 mm in the longitudinal axis. Propagation of circular muscle activity, evoked by slow stretch of flat sheet preparations, reveals the presence of a mechanism other than myogenic spread or the neuro-mechanical interactions previously proposed to account for propagation; the nature of this mechanism remains to be determined. [source]

Dermal sheet preparations in the evaluation of dermal innervation in Parkinson's disease and multiple system atrophy

JOURNAL OF CUTANEOUS PATHOLOGY, Issue 3 2009
Peter Novak
Background:, Evaluation of dermal nerve fibers in conventional vertical sections is difficult because of the small number of fibers available for examination. In this study, we evaluated dermal sheet mounts for fibers in which the majority of fibers can be visualized. Methods:, We compared the dermal small fiber density in six Parkinson's disease (PD) and six multiple system atrophy (MSA) patients using dermal sheet preparations (DSP). DSP are based on epidermal-dermal separations and immunostaining of the entire dermis by the nerve growth factor receptor p75 antibody that stains both autonomic and sensory fibers. Results:, The small fiber density was reduced in PD compared with MSA (p < 0.0001), suggesting the presence of small fiber neuropathy in PD. Conclusions:, DSP offer a unique method of evaluation of dermal nerve fibers. This method can be used to evaluate small nerve fibers in many neurological disorders such as MSA and PD. [source]

Propagating contractions of the circular muscle evoked by slow stretch in flat sheets of guinea-pig ileum

NEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2001
S. J. H. Brookes
Flat sheet preparations of guinea-pig ileum were stretched circumferentially and the propagation of circular muscle contractions along the preparation was investigated. Slow stretch, at 100 ,m s,1, of a 50-mm long flat sheet of intestine, evoked circular muscle contraction orally, which propagated, without decrement, for up to 30 mm. This occurred despite circular muscle shortening being prevented, and in the absence of propulsion of contents. Thus, propagation in this flat sheet preparation could not explained on the basis of neuro-mechanical interactions, as previously proposed. Irrespective of the length of preparations, contraction amplitude decreased significantly in the most aboral 10,15 mm of intestine. This was not due to descending inhibitory pathways, but was associated with interruption of ascending excitatory pathways near the aboral end. Slow waves were not detected in circular muscle cells in any preparation (n=8). Smooth muscle action potentials evoked in circular muscle cells, in the presence of tetrodotoxin (TTX, 0.6 ,mol L,1), did not propagate for more than 1 mm in the longitudinal axis. Propagation of circular muscle activity, evoked by slow stretch of flat sheet preparations, reveals the presence of a mechanism other than myogenic spread or the neuro-mechanical interactions previously proposed to account for propagation; the nature of this mechanism remains to be determined. [source]

Dermal contributions to UVA-induced oxidative stress in skin

PHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 2 2009
Hao Ou-Yang
Background: When the skin is exposed to solar irradiation, UVA photons interact with skin tissues and induce excessive reactive oxygen species, resulting in oxidative stress. We have shown in a previous study that in vivo chemiluminescence's measurement can be used to evaluate the overall level of UVA-induced oxidative stress in human skin. However, the origin of the observed chemiluminescence signals remains unclear. Methods: UVA-induced chemiluminescence measurements were conducted: (a) in vitro on collagen solutions and solid collagen sheet preparations, (b) ex vivo on human and mouse skin biopsies, and (c) in vivo on human skin of various constitutive pigmentation levels. Fluorescence was measured on collagen in vitro as well as on skin for the in vivo experiments. Results: We found in the in vitro experiments that UVA-induced chemiluminescence increases with the presence of collagen cross-links. When dermal sides were exposed to UVA irradiation, both mouse and human skin biopsies demonstrated significantly higher chemiluminescence levels than when epidermal sides were exposed to UVA. The amount of collagen cross-links decreases slightly following UVA exposure, as shown both by in vivo fluorescence and by UVA-induced chemiluminescence. Finally, there was less measurable UVA-induced chemiluminescence in dark skin compared with light pigmented skin in vivo. Conclusions: The dermis is very sensitive to UVA photons. Dermal cross-links are potential UVA sensitizers. The oxidative stress induced by UVA and measured by chemiluminescence may largely be attributed to the breakdown of dermal collagen cross-links. [source]