The Microprobe Assay of Chemical Elements

Hall, T. A.

doi:10.1016/b978-0-12-529601-4.50024-3

Cited by 132 publications

(132 citation statements)

References 32 publications

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“…The extraneous signals can be determined and subtracted from the spectrum (87,88). The method used to convert x-ray spectra to concentrations is based on the fact that the ratio of the characteristic peak counts to the counts in the x-ray continuum generated by the specimen is proportional to elemental concentration (38) ; this has been described and validated in detail (87) . The statistical analyses (5) were also described in our previous publications (87,89,96).…”

Section: Methodsmentioning

confidence: 99%

Calcium release and ionic changes in the sarcoplasmic reticulum of tetanized muscle: an electron-probe study.

Somlyo¹,

González‐Serratos²,

Shuman³

et al. 1981

The Journal of Cell Biology

421

223

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Approximately 60-70% of the total fiber calcium was localized in the terminal cisternae (TC) in resting frog muscle as determined by electron-probe analysis of ultrathin cryosections . During a 1 .2 s tetanus, 59% (69 mmol/kg dry TC) of the calcium content of the TC was released, enough to raise total cytoplasmic calcium concentration by -1 mM . This is equivalent to the concentration of binding sites on the calcium-binding proteins (troponin and parvalbumin) in frog muscle . Calcium release was associated with a significant uptake of magnesium and potassium into the TC, but the amount of calcium released exceeded the total measured cation accumulation by 62 mEq/kg dry weight . It is suggested that most of the charge deficit is apparent, and charge compensation is achieved by movement of protons into the sarcoplasmic reticulum (SR) and/or by the movement of organic co-or counterions not measured by energy dispersive electron-probe analysis . There was no significant change in the sodium or chlorine content of the TIC during tetanus. The unchanged distribution of a permeant anion, chloride, argues against the existence of a large and sustained transSR potential during tetanus, if the chloride permeability of the in situ SR is as high as suggested by measurements on fractionated SR .The calcium content of the longitudinal SR (LSR) during tetanus did not show the LSR to be a major site of calcium storage and delayed return to the TC . The potassium concentration in the LSR was not significantly different from the adjacent cytoplasmic concentration. Analysis of small areas of I-band and large areas, including several sarcomeres, suggested that chloride is anisotropically distributed, with some of it probably bound to myosin . In contrast, the distribution of potassium in the fiber cytoplasm followed the water distribution . The mitochondrial concentration of calcium was low and did not change significantly during a tetanus. The TIC of both tetanized and resting freeze-substituted muscles contained electron-lucent circular areas . The appearance of the TIC showed no evidence of major volume changes during tetanus, in agreement with the estimates of unchanged (-72%) water content of the TIC obtained with electron-probe analysis .The release of Ca from and its subsequent return to the triadic portion of the sarcoplasmic reticulum (SR) (28,80,82) are the major determinants of the contractile cycle of striated muscle (for review, see reference 24) . Since the demonstration of the SR as the ATP-dependent relaxing factor (57), a wealth of information has been accumulated about the kinetics and THE JOURNAL OF CELL BIOLOGY " VOLUME 90 SEPTEMBER 1981 577-594 © The Rockefeller University Press -0021-9525/81/09/0577/18 $1 .00 mechanisms of calcium uptake by the SR (e.g., 41,48,63,104,106, and for review, see references 62, 102). In contrast, comparatively little is known about the mechanism of release and associated ion movements, largely because isolated SR preparations do not lend themselves to reproduction of the ph...

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Section: Methodsmentioning

confidence: 99%

Calcium release and ionic changes in the sarcoplasmic reticulum of tetanized muscle: an electron-probe study.

Somlyo¹,

González‐Serratos²,

Shuman³

et al. 1981

The Journal of Cell Biology

421

223

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“…Quantitative electron probe analysis based on the method used in this study (45,83,84) requires the accurate determination of the characteristic counts and also the X-ray continuum counts used as a measure of the dry mass of the biological…”

Section: Cryoultramicrotomy and Electron Probe Analysismentioning

confidence: 99%

Elemental distribution in striated muscle and the effects of hypertonicity: Electron probe analysis of cryo sections

Somlyo¹,

Shuman²,

Somlyo³

1977

The Journal of Cell Biology

264

172

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A method of rapid freezing in supercooled Freon 22 (monochlorodifluoromethane) followed by cryoultramicrotomy is described and shown to yield ultrathin sections in which both the cellular ultrastructure and the distribution of diffusible ions across the cell membrane are preserved and intracellular compartmentalization of diffusible ions can be quantitated. Quantitative electron probe analysis (Shuman, H., A. V. Somlyo, and A. P. . Ultramicros. 1:317-339.) of freeze-dried ultrathin cryo sections was found to provide a valid measure of the composition of cells and cellular organelles and was used to determine the ionic composition of the in situ terminal cisternae of the sarcoplasmic reticulum (SR), the distribution of C1 in skeletal muscle, and the effects of hypertonic solutions on the subcellular composition of striated muscle.There was no evidence of sequestered C1 in the terminal cisternae of resting muscles, although calcium (66 mmol/kg dry wt -+ 4.6 SE) was detected. The values of [C1]l determined with small (50-100 nm) diameter probes over cytoplasm excluding organelles and over nuclei or terminal cisternae were not significantly different. Mitochondria partially excluded C1, with a cytoplasmic/ mitochondrial C1 ratio of 2.4 -+ 0.88 SD.The elemental concentrations (mmol/kg dry wt -+ SD) of muscle fibers measured with 0.5-9-/zm diameter electron probes in normal frog striated muscle were: P, 302 -4.3; S, 189 -+ 2.9; C1, 24 -1.1; K, 404 +-4.3, and Mg, 39 +-2.1. It is concluded that: (a) in normal muscle the "excess Cl" measured with previous bulk chemical analyses and flux studies is not compartmentalized in the SR or in other cellular organelles, and (b) the cytoplasmic Cl in low [K]o solutions exceeds that predicted by a passive electrochemical distribution.Hypertonic 2.2 x NaC1, 2.5 • sucrose, or 2.2 • Na isethionate produced: (a) swollen vacuoles, frequently paired, adjacent to the Z lines and containing significantly higher than cytoplasmic concentrations of Na and Cl or S (isethionate), but no detectable Ca, and (b) granules of Ca, Mg, and P -~(6 Ca + 1 Mg)/6 P in the longitudinal SR. It is concluded that hypertonicity produces compartmentalized domains of extracellular solutes within the muscle fibers and translocates Ca into the longitudinal tubules. 828THe JOURNAL OF CELL BIOLOGY" VOLUME 74, 1977" pages 828-857 on May 11, 2018 jcb.rupress.org Downloaded from http://doi.org/10. 1083/jcb.74.3.828 Published Online: 1 September, 1977 KEY WORDS electron probe analysis 9 cryoultramicrotomy 9 striated muscle hypertonicity 9 sarcoplasmic reticulum The distribution of diffusible ions in, respectively, the extracellular space, cytoplasm, and cellular organelles, represents one of the most general problems of cell function. The main techniques available for determining the concentrations of ions in different compartments are the measurement of radio isotope ion fluxes in intact tissues and organeUe fractionation. These techniques are, however, subject to the respective uncertainties of the ultrast...

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“…However, it is important to note that the resulting thin sections afford a far superior analytical resolution (section thickness depth resolution, approximately probe diamter lateral resolution) than bulk specimens (4). This means that using 1-2 um thick sections and a probe of diameter 20 nm, measurements can be made within the cytoplasm of highly vacuolate cells or within single small (~ 10 (gym diamter) undifferentiated cells, without contamination by the ion contents of adjacent subcellular compartments or cells.…”

Section: Discussionmentioning

confidence: 99%

“…The peak (p), background under the peak (b), and continuum counts from 6.0 to 6.5 keV (c) were measured, and calculated for Na, Cl, K, and Ca in each analysis (4). To subtract b from p a linear interpolation was made from the background on either side of the appropriate Ka peak.…”

Section: Plant Growthmentioning

confidence: 99%

The regulation of ion levels within Plantago maritima roots: An examination of freeze-substituted and frozen hydrated specimens.

Harvey

Brandtner

1987

Acta Histochem. Cytochem

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Elemental distributions throughout the root radius in the absorption zone were measured by x-ray microanalysis of frozen hydrated bulk Plantago maritima root samples. Relative elemental concentrations in the cytoplasm were measured in freeze-substituted sections of undifferentiated cells and xylem parenchyma cells in the absorption zone. When grown in the presence of 200 mM NaCl, relative levels of Na+ and K+ reaching the stele are adjusted from those in the culture solution principally by an initial enhancement of the K+ level in the epidermis, and a subsequent reciprocal decrease in Na+ and increase in K+ levels at the endodermis. Mean Cl-levels do not balance those of Na+ in any of the analysed cells. Together with differences observed between control and salt grown roots in the Mg and Ca levels in the inner cortex, the regulation of Na+ and K+ reaching the xylem vessels is discussed in terms of ion pumps and ATPases, and related to the overall salinity tolerance of P. maritima. The mean relative cytoplasmic concentration ratio of Na+ : K+ was 0.6 : 1.0 in the undifferentiated cells and 1.1: 1.0 in the xylem parenchyma; in the latter the mean relative concentrations of Na+, K+ and Clwere appreciably higher than in the former. The absolute ion concentrations in the cytoplasm, and the extents of variations therein, rather than the Na+ : K+ ratio, may be correlated with the overall salinity tolerance of the plant.When grown under saline (NaCI) conditions, a salt tolerant plant which accumulates Na+ and Cl-into its shoots for osmotic adjustment must contend with the related problems of regulating the accumulation of these ions and acquiring sufficient K+ in the shoot for biochemical and osmotic purposes from a medium in which Na+ and Cl-predominate (3). It has been establishd that for a number of such plants, these problems are at least partially solved by an initial regulation of Na+ and K+ uptake at the root epidermal cells followed by further decreases in the Na+ : K+ ratio effected during radial transport to the xylem vessels (9,10,12,13). The mechanisms underlying these adjustments are not clear.As far as the root cells themselves are concerned, their various functions in the uptake and transport of ions must be carried out in a manner consistent with their own requirements. Of particular interest are the levels of Na+ and K+ in the cytoplasm. In

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The Microprobe Assay of Chemical Elements

Cited by 132 publications

References 32 publications

Calcium release and ionic changes in the sarcoplasmic reticulum of tetanized muscle: an electron-probe study.

Calcium release and ionic changes in the sarcoplasmic reticulum of tetanized muscle: an electron-probe study.

Elemental distribution in striated muscle and the effects of hypertonicity: Electron probe analysis of cryo sections

The regulation of ion levels within Plantago maritima roots: An examination of freeze-substituted and frozen hydrated specimens.

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