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1.
Dr. Ed. Formánek 《Plant Systematics and Evolution》1888,38(12):419-423
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Dr. Ed. Formánek 《Plant Systematics and Evolution》1888,38(6):186-190
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4.
Dr. Ed. Formánek 《Plant Systematics and Evolution》1884,34(5):157-168
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5.
Ed Echeverria 《Physiologia plantarum》1991,81(1):51-54
The sucrose content of acid lime [ Citrus aurantifolia (Christm.) Swing.] juice tissue was measured at time 0 and at various times following incubation at 15.5, 26.6 and 37.7°C. The decline in sucrose content in fruit stored at 15.5°C paralleled the expected values for a sucrose solution at pH 2.1. At higher temperatures, the in vivo sucrose content decreased at significantly lower rates than the expected values. In fruit stored at 26.6 and 37.7°C, the vacuolar pH increased 0.11 and 0.23 units, respectively. When sucrose hydrolysis was recalculated at the increased vacuolar pH of juice cells stored at 26.6 and 37.7°C, the calculated values were similar to the measured values obtained in vivo. It is concluded that within the limits of the experimental conditions, the rates of sucrose acid hydrolysis are regulated by changes in the vacuolar H+ concentration. 相似文献
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PRODUCTION AND CHARACTERIZATION OF MULTIPLE-LAYERED POPULATIONS OF ANIMAL CELLS 总被引:11,自引:5,他引:6
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Dense populations containing 129 x 106 Jensen sarcoma, 134 x 106 DON Chinese hamster, 28.9 x 106 WI-38 human diploid, 61.8 x 106 HEp-2 human carcinoma, and 67.4 x 106 WISH human amnion cells were produced from dilute inocula, 0.85 to 5.33 x 106, in 7 to 8 days in a perfusion system using replicate T-60 flasks. Perfusion rates as high as 560 ml medium/day/T-60 were required to maintain pH (to ca ±0.1 unit) and adequate nutrient supplies. The cell densities encountered are described by the term "monolayer equivalents" (M.E.), defined as number of cells per culture divided by number of cells in a monolayer. The M.E.'s for T-60 cultures containing unusually dense populations of 40 x 106 WI-38 and 250 x 106 DON cells (9-day perfusion) were 5 and 17, respectively, and numbers of cells in illustrations of stained cross-sections of membranes from these cultures were in excellent agreement. Threshold M.E.'s exist below which proliferation is the chief cellular activity and above which one or more cell functions may predominate even though proliferation persists. Cellular nutrition and metabolism may change with changes in M.E., as illustrated in different patterns of glutamic acid, proline, and glycine utilization or production in dense vs. dilute WI-38 cell populations. The results indicated that the role of contact inhibition phenomena in arresting cellular proliferation was diminished in perfusion system environments. 相似文献
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ABA stimulation of outward K+ current (I
K,out) in Vicia faba guard cells has been correlated with a rise in cytosolic pH (pH
i
). However, the underlying mechanism by which I
K,out is affected by pH
i
has remained unknown. Here, we demonstrate that pH
i
regulates outward K+ current in isolated membrane patches from Vicia faba guard cells. The stimulatory effect of alkalinizing pH
i
was voltage insensitive and independent of the two free calcium levels tested, 50 nm and 1 μm. The single-channel conductance was only slightly affected by pH
i
. Based on single-channel measurements, the kinetics of time-activated whole-cell current, and the analysis of current noise
in whole-cell recordings, we conclude that alkaline pH
i
enhances the magnitude of I
K,out by increasing the number of channels available for activation. The fact that the pH
i
effect is seen in excised patches indicates that signal transduction pathways involved in the regulation of I
K,out by pH
i
, and by implication, components of hormonal signal transduction pathways that are downstream of pH
i
, are membrane-delimited.
Received: 5 June 1996/Revised: 1 August 1996 相似文献