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G B Matson

Publications and source records attributed to G B Matson.

61 records · Page 4Linked to original sources
PubMed1983

Ultraviolet-Stimulated KHCO(3) Efflux from Rose Cells: Regulation of Cytoplasmic pH.

Suspension-cultured cells of Rosa damascena that have been irradiated with ultraviolet light (254 nanometers, 2.1 x 10(4) joules per square meter) rapidly lose K(+) and HCO(3) (-) ions to the medium. If the HCO(3) (-) is derived from respiratory CO(2) inside the cell, then loss of HCO(3) (-) should be accompanied by an acidification of the cytoplasm. Estimates of the pH of control and ultraviolet-irradiated cells by (31)P-nuclear magnetic resonance spectroscopy indicated that, following irradiation, the pH of both cytoplasm and vacuole dropped by 0.2 to 0.3 units. This change was not as great as was predicted from the observed HCO(3) (-) loss. Analysis of nitrogenous compounds in the cell suggested that reduction of nitrate and synthesis of gamma-aminobutyric acid absorbed some of the protons formed by the synthesis and dissociation of bicarbonate.

Journal Article↗
PubMed1981

31P NMR reveals increased intracellular pH after fertilization in Xenopus eggs.

31P NMR spectra of mature eggs of the frog (Xenopus laevis) were taken prior to and after both fertilization and activation by a Ca2+/H+ ionophore (A23187). The eggs were constantly perfused with fresh well-buffered solution during the experiments, and the intracellular pH (pHi) was determined from the pH-dependent chemical shift of the internal Pi peak. The detection of this Pi peak in the presence of overlapping yolk phosphoprotein signals was accomplished by a T2 experiment which discriminated against the broader yolk phosphoprotein peak. The average pHi of the unfertilized, fertilized, and activated eggs was 7.42, 7.66, and 7.64, respectively. Thus, a cytoplasmic alkalinization of 0.24 pH unit occurs within 90 min 90 min after fertilization. These values are practically identical to pHi measurements made in this laboratory on Xenopus eggs by using pH-sensitive glass microelectrodes. These 31P NMR studies also indicate that extracellular pH changes as large as 3 pH units had no effect on pHi. We also found that phosphocreatine levels are very sensitive to metabolic perturbations such as oxygen depletion or metabolic inhibitor application. These treatments resulted in a rapid decrease in the phosphocreatine concentration; the ATP concentration declined only slowly after the phosphocreatine peak had disappeared.

Adenosine Triphosphate↗
PubMedDate not supplied

Use of computer simulations for quantitation of 31P ISIS MRS results.

The difficulties in quantitation of in vivo 31P spectra are exacerbated by the fact that, in general, coils with inhomogeneous B1 fields are used with in vivo samples. A general method for quantitation of in vivo 31P MRS results obtained with the ISIS localization method was developed using computer simulations. The simulation calculates the preparation of the sample magnetization throughout the sample by the ISIS pulse sequence, as well as the sensitivity of signal reception. The calculation accounts for both the B1 field and the B0 gradients applied to the sample. The sensitivity of the experiment is expressed by integration of the simulated signal over the sample, assuming a homogeneous sample. The primary advantage of this approach is that a separate localization experiment on a phantom of known concentration is not required each time parameters of the localization experiment, such as dimensions or location of the localized volume, are altered. In addition, the simulations indicate the degree of contamination (signal from outside of the localized volume) that occurs, and provide a means of comparing different executions of the ISIS experiment. Experiments were performed on phantoms to verify the simulations, and experimental results on human brain and liver are reproduced to show that this approach provides reasonable estimates of metabolite levels in terms of molar concentrations.

Computer Simulation↗