| 1. |
- Ask, Per, et al.
(författare)
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Frequency content of esophageal peristaltic pressure.
- 1979
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Ingår i: American Journal of Physiology. - 0002-9513 .- 2163-5773. ; 236:3, s. E296-300
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Tidskriftsartikel (refereegranskat)abstract
- Fourier analysis of esophageal peristaltic pressure waves was performed by computer fast Fourier transform. The highest power spectral density was obtained in the frequency range below 1 Hz. The Fourier analysis showed spectral components up to about 12 Hz in the upper esophageal sphincter (UES). The significance of different frequency components was investigated by low-pass filtering at different cut-off frequencies. A reduction in the amplitude of UES contractions was obtained at a cut-off frequency of 4 Hz, whereas the cut-off frequency of 8 Hz did not show any distortion. For perfused manometry systems, only a low-compliance perfusion pump will have sufficient bandwidth for accurate recording of esophageal peristaltic pressures.
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| 2. |
- Ask, Per, et al.
(författare)
-
Peripheral nerve as an osmometer : role of the perineurium in frog sciatic nerve.
- 1983
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Ingår i: American Journal of Physiology. - 0002-9513 .- 2163-5773. ; 244:1, s. C75-81
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of volume and hydrostatic pressure in the frog sciatic nerve in vitro demonstrate that the nerve acts as an osmometer, in large part because the perineurium is a semipermeable membrane for water flow. Endoneurial hydrostatic pressure in nerves in isotonic Ringer exceeds bath pressure by about 7 mmHg. In Ringer made hypertonic by addition of sucrose, nerve volume and endoneurial pressure fall linearly in relation to 1/osmolality. The slope of the plot of pressure against volume provides a value for nerve compliance equal to 0.006 mm2/mmHg. Calculations based on the model of the nerve as an osmometer indicate that the nerve has an osmotically "inactive" volume equal to 0.19 mm3/mm, which is about 75% of the total volume of a nerve segment of unit length in normal Ringer. Perineurial hydraulic conductivity (Lp) equals 7.5 x 10(-13) cm3.s-1.dyn-1, a value characteristic of nonleaky epithelia. The perineurium is an elastic tissue with a constant modulus of elasticity equal to 3 x 10(6) dyn/cm2 when not markedly stretched and may limit nerve swelling under pathological conditions of nerve edema.
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| 3. |
- Rundquist, I, et al.
(författare)
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Sciatic nerve blood flow measured by laser Doppler flowmetry and [14C]iodoantipyrine.
- 1985
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Ingår i: American Journal of Physiology. - 0002-9513 .- 2163-5773. ; 248:3 Pt 2, s. H311-317
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Tidskriftsartikel (refereegranskat)abstract
- Blood flow was examined in sciatic nerves of pentobarbital-anesthetized rats by means of laser Doppler flowmetry (LDF) and intravenous [14C]iodoantipyrine infusion. Continuous LDF signals demonstrated slow oscillations and acute, pressure-related changes in flow. The steady-state LDF signal was related linearly to nerve blood flow, as measured with [14C]iodoantipyrine, in intact nerves and nerves stripped of the epineurium. In 14 intact nerves, nerve blood flow averaged 0.27 +/- 0.03 (SE) ml X min-1 X g-1, whereas it averaged 0.13 +/- 0.01 in 5 stripped nerves. Autoradiographs of [3H]-nicotine-infused nerves and intra-arterial injection of 57Co-labeled microspheres demonstrated that flow was not uniform throughout the nerve cross section. The results indicate that LDF can be used to examine nerve blood flow in vivo, demonstrate a linear relation between the LDF signal and flow, and establish absolute values for blood flow in intact and stripped nerves of the anesthetized rat.
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| 4. |
- Ödman, Svante, et al.
(författare)
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Peripheral nerve as an osmometer : role of endoneurial capillaries in frog sciatic nerve.
- 1987
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Ingår i: American Journal of Physiology. - 0002-9513 .- 2163-5773. ; 252:3 Pt 1, s. C335-41
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Tidskriftsartikel (refereegranskat)abstract
- The sciatic nerve of the frog was perfused in vivo with isotonic Ringer solution followed by Ringer made hypertonic by addition of sucrose or of NaCl. Nerve diameter and endoneurial hydrostatic pressure fell during hypertonic Ringer perfusion. Using a model that describes the elastic and osmotic properties of the nerve, sigma sLp, the product of the osmotic reflection coefficient at endoneurial capillaries for s equals sucrose or NaCl (which approximates 1), and of capillary hydraulic conductivity, was found to equal 73 X 10(-13) cm3 X s-1 X dyn-1. The nerve is elastic. It has a compliance K of 3.7 X 10(-5) cm2 X mmHg-1, corresponding to a modulus of elasticity E of the perineurium equal to 1.2 X 10(6) dyn X cm-2. The results indicate that the nerve behaves as an osmometer during vascular perfusion, due to the low permeability of endoneurial capillaries to small solutes such as NaCl and sucrose. A low capillary hydraulic conductivity limits bulk water flow between blood and nerve, and a low compliance limits nerve swelling and edema.
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