| 1. |
- Gennser, Mikael, et al.
(författare)
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Effects of dietary lipids on frequency and force in atrial muscle at 10 MPa
- 1987
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Ingår i: Undersea biomedical research. - 0093-5387. ; 14:1, s. 31-43
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Tidskriftsartikel (refereegranskat)abstract
- Spontaneously beating atrial preparations, from rats fed different lipid diets, were compressed to 10 MPa. The following observations were made: Different lipid diets altered the ratio of omega-6/omega-3 polyunsaturated fatty acids of the cardiac phospholipids. Beating frequency and twitch tension at surface pressure was unaffected by the diets. Compression to 10 MPa caused a decrease in spontaneous beating frequency and an increased twitch tension in all preparations. The decrease in beating frequency was inversely related to the omega-6/omega-3 ratio. Pressure induced increase in twitch tension was not affected by the diets. N2O dissolved in the tissue bath solution partly counteracted the pressure-induced changes.
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| 2. |
- Gennser, Mikael, et al.
(författare)
-
Effects of hydrostatic pressure and inert gases on twitch tension
- 1989
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Ingår i: Undersea biomedical research. - 0093-5387. ; 16:6, s. 415-426
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Tidskriftsartikel (refereegranskat)abstract
- Effect of pressure and inert gases on the twitch tension (Tmax) was measured on electrically stimulated and spontaneously beating rat atria. In stimulated preparations, pressurization to 10 MPa increased Tmax by 20-60% depending on the stimulating frequency (60-240 beats/min). The introduction of 5 MPa N2 or 5 MPa H2 at 10 MPa hydrostatic pressure decreased the Tmax by 17 +/- 6% and 13 +/- 6%, respectively. Gas effect did not depend on the stimulating frequency. Nitrous oxide (0.15 and 0.45 MPa) decreased Tmax both at "surface" and at 10 MPa. Nitrous oxide effect was slightly potentiated at pressure. In spontaneously beating preparations, compression to 10 and 15 MPa decreased beating frequency (BF) by 24 +/- 10% and 31 +/- 8% and increased Tmax by 60 +/- 35% and 105 +/- 33%, respectively. The tension increase is partly due to the direct pressure effect and partly due to the negative force-frequency relation in the rat atria. Introduction of inert gas increased BF and decreased Tmax. The potency of the gases was in the same order for both variables: He less than H2 less than N2.
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| 3. |
- Gennser, Mikael, et al.
(författare)
-
Effects of hydrostatic pressure, H2, N2, and He, on beating frequency of rat atria
- 1989
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Ingår i: Undersea biomedical research. - 0093-5387. ; 16:2, s. 153-164
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Tidskriftsartikel (refereegranskat)abstract
- Hydrostatic compression to 15 MPa caused a drop in spontaneous beating frequency (BF) of isolated rat atria kept in tris solution at 37 degrees C by 30.6 +/- 7.2%. Introduction of superfusing solutions equilibrated with hydrogen (PH2: 4.9, 9, and 14 MPa, respectively), increased the BF in proportion to the hydrogen content. A hydrogen partial pressure equal to the hydrostatic pressure was calculated to reduce the bradycardia by 52.0 +/- 19.5%. Effects of nitrogen (PN2: 5 and 14 MPa) and helium (PHe: 13 and 14 MPa) were also tested. Nitrogen was found to be 1.7-2 times and helium 0.2 times as effective as hydrogen in reducing the bradycardia. Preparations compressed at 27 degrees C exhibited a more pronounced bradycardia than those kept at 37 degrees C, but 5 MPa N2 and 9 MPa H2 reversed the bradycardia to the same extent at 27 degrees C as at 37 degrees C. Tests with 4 MPa H2 showed the effect on BF to be similar, whether the gas was added during an intermediate stop in the compression (4.6 MPa) or at 10 MPa pressure. An additional hydrostatic pressure increase from 10 to 12.5 MPa eliminated the BF increase of 4 MPa hydrogen added at 10 MPa. The findings are discussed in view of the possible use of hydrogen as a breathing gas in deep sea diving.
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| 4. |
- Gennser, Mikael, et al.
(författare)
-
Effects of hyperbaric pressure and temperature on atria from ectotherm animals (Rana pipiens and Anguilla anguilla)
- 1990
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Ingår i: Comparative Biochemistry and Physiology - Part A. - : Elsevier BV. - 0300-9629. ; 95:2, s. 219-228
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Tidskriftsartikel (refereegranskat)abstract
- 1. Spontaneously beating atria from frogs (R. pipiens) and eels (A. anguilla) were compressed hydraulically to 10 MPa. Effects on beating frequency and twitch tension were studied. 2. At low temperatures (8-10 degrees C) compression to 10 MPa caused a slowing of the beat frequency. No effects were noted at higher temperatures (16-24 degrees C). Twitch tension was decreased by pressure at low temperatures and increased at high temperatures. 3. Differences were noted between preparations from cold and warm acclimatized frogs, and from silver and yellow eels, respectively. 4. The effect of temperature acclimatization on pressure and temperature sensitivity is discussed in relation to data on cardiac phospholipid fatty acid composition.
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