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  • Electronic Resource  (5)
  • X-ray diffraction  (3)
  • Angiotensin II
  • 1
    Electronic Resource
    Electronic Resource
    Positive inotropic action of angiotensin II in the pithed rat (1993)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 347 (1993), S. 658-663 
    Details
    ISSN: 1432-1912
    Keywords: Angiotensin II ; Myocardial contraction ; Pithed rat ; AT1 receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cardiovascular effects of angiotensin II were examined in aortic blood pressure-controlled and-uncontrolled pithed rats. Angiotensin II induced a dose-dependent increase in diastolic blood pressure, left ventricular pressure (LVP), dP/dt (the first derivative of LVP) and heart rate in pithed rats. The maximal responses for these parameters were similar to those to noradrenaline, except for the rise in diastolic blood pressure, where noradrenaline caused a greater increase than angiotensin II. After treatment with propranolol, the positive chronotropic effect of angiotensin II was abolished. Angiotensin II produced a dose-dependent increase in diastolic blood pressure, which was similar to that of vasopressin, and an increase in dP/dtmax, which proved much greater than that of vasopressin. When aortic blood pressure was controlled and the β-receptors were blocked by propranolol, angiotensin II caused a dose-dependent increase in dP/dtmax without affecting the left ventricular enddiastolic pressure. The same results were obtained after both β- and α-adrenoceptors were blocked by propranolol and phentolamine. Losartan but not PD 123177 caused parallel rightward shifts of the dose-response curve of angiotensin II for dP/dtmax in the aortic blood pressure controlled pithed rat without altering the maximal response. It is concluded that in the pithed rat angiotensin II produced an increase in myocardial contractile force which is not mediated by β- or α-adrenoceptors. The inotropic effect appears to be mediated by angiotensin receptors, of the AT1-subtype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166950
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Inhibitory effect of dithiothreitol on angiotensin II-induced contractions mediated by AT1-receptors in rat portal vein and rabbit aorta (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 349 (1994), S. 538-542 
    Details
    ISSN: 1432-1912
    Keywords: AT1-receptors ; Angiotensin II ; Dithiothreitol ; Losartan ; Rat portal vein ; Rabbit aorta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The disulfide-reducing agent dithiothreitol (DTT) has been shown to reduce angiotensin II (Ang II) subtype 1 receptor (AT,) binding sites in various tissues. Its effect on Ang II-induced contractions was studied in the rat portal vein and rabbit aorta. In the isolated rat portal vein, DTT shifted the concentration-response curve for Ang II to the right (DTT 0.5–3 mmol/l) and depressed the maximal response (DTT 1–3 mmol/l). DTT 5 mmol/l almost abolished the effect of Ang II. In the isolated rabbit aorta, the inhibitory effect of DTT was more pronounced and its pattern of effect was different,since DTT 0.3 and 0.5 mmol/l caused a progressive flattening of the concentration-response curve of Ang II. DTT (1 mmol/l) fully suppressed the effect of Ang II. A biphasic curve consisting of a high sensitivity component and a component of low sensitivity for Ang II was observed after pretreatment with DTT 1 mmol/l in the rat portal vein but not in the rabbit aorta. In the presence of DTT 1 mmol/l, the AT1-receptor antagonist losartan antagonized the high sensitivity response to Ang II in a competitive manner with a pA2 value very similar to that obtained in the absence of DTT, suggesting that this response to Ang II is mediated by those AT1-receptors which were not inactivated by DTT The biphasic curve may be explained by the occurrence of a single AT1-receptor subtype existing in two different states. Another possibility might be the involvement of two AT1-receptor subpopulations. It is concluded that disulfide bonds are critical for the functional role of AT1-receptors in Ang II-induced contractions in the rat portal vein and rabbit aorta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169144
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal equation of state of iron and Fe0.91Si0.09 (1999)
    Springer
    Physics and chemistry of minerals 26 (1999), S. 206-211 
    Details
    ISSN: 1432-2021
    Keywords: Key words Iron ; Fe ; Si alloy ; X-ray diffraction ; Equation of state ; Thermoelasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  We have carried out an in situ synchrotron X-ray diffraction study on iron and an iron-silicon alloy Fe0.91Si0.09 at simultaneously high pressure and temperature. Unit-cell volumes, measured up to 8.9 GPa and 773 K on the bcc phases of iron and Fe0.91Si0.09, are analyzed using the Birch-Murnaghan equation of state and thermal pressure approach of Anderson. Equation of state parameters on iron are found to be in agreement with results of previous studies. For both iron and Fe0.91Si0.09, thermal pressures show strong dependence on volume; the (∂KT/∂T)V values are considerably larger than those previously reported for other solids. The present results, in combination with our previous results on ɛ-FeSi, suggest a small dependency of the room-temperature bulk modulus upon the silicon content, less than 0.3 GPa for 1 wt.% silicon. We also find that substitution of silicon in iron would not appreciably change the thermoelastic properties of iron-rich Fe−Si alloys. If this behavior persists over large pressure and temperature ranges, the relative density contrast between iron and iron-rich Fe−Si alloys at conditions of the outer core of the Earth could be close to that measured at ambient conditions, i.e., 0.6% for 1 wt.% Si.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050178
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental study of the bcc-fcc phase transformations in the Fe-rich system Fe-Si at high pressures (1999)
    Springer
    Physics and chemistry of minerals 26 (1999), S. 419-424 
    Details
    ISSN: 1432-2021
    Keywords: Key words Iron ; Fe-Si alloys ; X-ray diffraction ; Phase transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract In situ X-ray diffraction experiments at high pressure were carried out up to 8.9 GPa and 1100 °C to study phase transformations of iron and two iron-silicon alloys Fe0.91Si0.09 and Fe0.83Si0.17. For iron, the transformation from the bcc phase to the fcc phase was observed at pressures 3.8–8.2 GPa and temperatures that are consistent with previous in situ X-ray diffraction studies. Reversal of the transformation of iron was found to be sensitive to temperature; hysteresis of the transformation increased from 25 °C at 3.8 GPa to 100 °C at 7.0 GPa, primarily because the bcc-fcc phase boundary has a negative Clayperon slope. In the binary system Fe-Si, the observations of the present study indicate that the ferrite (bcc phase)-stabilizing behavior of silicon persists at high pressures and that the maximum solubility of silicon in the fcc phase increases with increasing pressure: (1) the transformation from the bcc phase to the fcc phase was observed in Fe0.91Si0.09 at 6.0, 7.4 and 8.9 GPa and the temperatures measured at the onset of the transformations were 300 °C higher than those in iron at similar pressures, (2) the transformation rate in Fe0.91Si0.09 was extremely sluggish compared to that of iron, and (3) the bcc-fcc phase transformation was not observed in Fe0.91Si0.09 at 4.7 GPa up to 1000 °C and in Fe0.83Si0.17 at 8.2 GPa and 1100 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050203
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of pressure on the thermal expansion of MgO up to 8.2 GPa (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 145-148 
    Details
    ISSN: 1432-2021
    Keywords: Key words MgO ; X-ray diffraction ; Thermal expansion ; Equation of state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Isobaric volume measurements for MgO were carried out at 2.6, 5.4, and 8.2 GPa in the temperature range 300–1073 K using a DIA-type, large-volume apparatus in conjunction with synchrotron X-ray powder diffraction. Linear fit of the thermal expansion data over the experimental pressure range yields the pressure derivative, (∂α/∂P) T , of −1.04(8) × 10−6 GPa−1 K−1 and the mean zero-pressure thermal expansion α0, T  = 4.09(6) × 10−5 K−1. The α0, T value is in good agreement with results of Suzuki (1975) and Utsumi et al. (1998) over the same temperature range, whereas (∂α/∂P) T is determined for the first time on MgO by direct measurements. The cross-derivative (∂α2/∂P∂T) cannot be resolved because of large uncertainties associated with the temperature derivative of α at all pressures. The temperature derivative of the bulk modulus, (∂K T/∂T) P , of −0.025(3) GPa K−1, obtained from the measured (∂α/∂P) T value, is in accord with previous findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050001
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