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161.
Summary The use of an Ussing chamber with well-defined mixing characteristics coupled to a mass spectrometer permits the concurrent evaluation of transepithelial current and oxidative metabolism with improved temporal resolution. The time-course of the amiloride-sensitive currentI
a and the rate of suprabasal CO2 productionJ
CO2
sb
were observed in 10 toad urinary bladders at short-circuit and after clamping at 100 mV, serosa positive. Following perturbation of (0100mV),I
a declined sharply within 1/2 min, remained near constant 15 min, and then increased slightly.J
CO2
sb
declined more gradually, remained near constant at 4–7 min, and then declined further. Detailed analysis revealed an early quasi-steady state with near constancy ofJ
CO2
sb
starting at 2.9±1.1 (sd) min and lasting 4.7 ±1.8 (sd) min, followed by relaxation to a later steady state at about 15 min. During the early quasi-steady state,I
a was also nearly constant. Considering that in steady statesI
a/FJ
Na
a
, the rate of transepithelial active Na transport, during the early quasi-steady state mean values ±se ofJ
Na
a
,J
CO2
sb
and (J
Na
a
/J
CO2
sb
) were, respectively, 29.9±1.7%, 59.4 ±3.2%, and 56.4±5.7% of values at short-circuit. Corresponding values during the late steady state were 41.4±6.0%, 38.2±6.1%, and 111.3±8.6%. Thus the flow ratioJ
Na
a
/J
CO2
sb
was depressed significantly during the early quasi-steady state, but returned later to the original value. The results of measurements ofI
a andJ
CO2
sb
in three hemibladders were qualitatively similar. In terms of a phenomenological black-box treatment the findings are consistent with earlier studies indicating incomplete coupling between transport and metabolism. Further studies will be required to clarify the molecular basis for these observations. 相似文献
162.
Ferdinand Bohlmann Lutz Müller Rajinder K. Gupta Robert M. King Harold Robinson 《Phytochemistry》1981,20(9):2233-2237
Out of the nineteen species of Vernonia studied, five contained highly oxygenated sesquiterpene lactones, while the rest contained predominantly triterpenes, especially lupane derivatives. 相似文献
163.
The reinvestigation of the aerial parts of Wedelia trilobata afforded, in addition to known compounds, six new eudesmanolides, two ent-kaurenic acid derivatives as well as a degraded one. A corresponding hydroxy compound was present in Gnaphalium undulatum. From Aspilia parvifolia new ent-kaurenic acid epoxides were isolated. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly. 相似文献
164.
165.
166.
167.
The aerial parts of P. canadensis afforded a new germacran-8,12-olide and several diterpenic acids. The stereochemistry of the lactone could be established only by careful 1H NMR investigations of the corresponding pyrazolines formed by addition of diazomethane, while the natural compound and its acetate only show very uncharacteristic NMR spectra. The diterpenes all belong to the rare isokaurene type. The chemotaxonomic aspects are discussed briefly. 相似文献
168.
Ferdinand Bohlmann Jürgen Ziesche Robert M. King Harold Robinson 《Phytochemistry》1980,19(12):2675-2679
The investigation of two further Senecio species and the re-investigation of S. inaequidens afforded, in addition to known compounds, seven new furanoeremophilane derivatives. Six of these are closely related to cacalol, a sesquiterpene type which predominates in the species investigated. 相似文献
169.
Ferdinand Bohlmann Christa Zdero Robert M. King Harold Robinson 《Phytochemistry》1980,19(12):2663-2668
The investigation of three Eremanthus species afforded, in addition to known compounds, several new sesquiterpenelactones, a cumambrin B isobutyrate, four lactones related to the eremantholides, two to zexbrevin and one to goyazensolide. Furthermore, a new coniferyl alcohol derivative was isolated. The overall picture of the genus is very uniform. The occurrence of eremanthine and germacranolides with a furanone ring seems to be especially typical. 相似文献
170.