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At least 649 records · Page 36Linked to original sources
PubMed1989

Electron probe X-ray microanalysis of cellular ions in the eccrine secretory coil cells during methacholine stimulation.

Intracellular concentrations of Na, K, Cl ([Na], [K] and [Cl], respectively) and other elements were determined in isolated monkey eccrine sweat secretory coil cells using quantitative electron probe X-ray microanalysis of freeze dried cryosections. The validity of the methodology was partially supported by qualitative agreement of the X-ray microanalysis data with those obtained by micro-titration with a helium glow spectrophotometer. [Na], [K] and [Cl] of the cytoplasm were the same as those in the nucleus in both clear and dark cells. [Na], [K], and [Cl] of the clear cells were also the same as those of the dark cells at rest and after stimulation with methacholine (MCh), suggesting that these two cell types behave like a functional syncytium. MCh stimulation induced a pharmacologically specific, dose-dependent decrease in [K] and [Cl] (as much as 65%), and a 3.7-fold increase in [Na]. In myoepithelial cells, a similar change in [Na] and [K] was noted after MCh stimulation although the decrease in [Cl] was only 20%. The MCh-induced change in [Na], [K] and [Cl] was almost completely inhibited by removal of Ca2+ from the medium. 10(-4) M bumetanide inhibited the MCh-induced increase in [Na], reduced the decrease in [K] by about 50%, but slightly augmented the MCh-induced decrease in [Cl]. 10(-4) M ouabain increased [Na] and decreased [K] as did MCh; however, unlike MCh, ouabain increased [Cl] by 56% after 30 min of incubation. Thus the data may be best interpreted to indicate that Ca-dependent K efflux and (perhaps also Ca-dependent) Cl efflux are the predominant initial ionic movement in muscarinic cholinergic stimulation of the eccrine sweat secretory coils and that the ouabain-sensitive Na pump plays an important role in maintenance of intracellular ions and sweat secretion.

Animals↗
PubMed2002

Magnesium transport through the basal plasma membrane of larval malpighian tubules of Drosophila hydei studied by electron probe X-ray microanalysis.

Magnesium besides calcium is the most important excretion product. In the anterior Malpighian tubules of Drosophila, excretion of magnesium takes place via the hindgut by proteoglycan containing concretions. This study reports on magnesium transport through the basal plasma membrane of the principal cells of the proximal segment of the anterior Malpighian tubules. Measurements by electron probe X-ray microanalysis indicate the existence of two antiporters which transfer magnesium in still unknown stoichiometry from the hemolymph space into the cell: Mg/H and Mg/Na.

Amiloride↗
PubMed1988

Electron probe X-ray microanalysis of the composition of hyaline articular and non-articular cartilage in young and aged rats.

Blocks of articular cartilage were taken from tibiae of young adult (8 week) and aged adult (50-60 week) rats; xiphisternal cartilage was obtained from young adult rats. Specimens were quench-frozen in nitrogen slush, freeze-fractured and examined by low-temperature scanning electron microscopy. The results of X-ray microanalysis of frozen-hydrated bulk cartilage are semi-quantitative. The composition of chondrocyte nuclei and cytoplasm are only marginally different. Xiphisternal chondrocytes contain lipid inclusions which show an absence of element peaks and are designated as being neutral lipid. Intra- and extracellular Na, P, S, Cl, K and Ca count rates are significantly different. Cartilage from older rats contains more S and Ca, and less K and Cl in the intercellular matrix than that from young rats. Intracellular K levels are lower in aged than in young rats. The intercellular matrix of xiphisternal cartilage contains larger amounts of S, Na and K, and a smaller amount of Cl compared to that of tibial articular cartilage.

Aging↗
PubMed1999

Changes in elemental content during apoptotic cell death studied by electron probe X-ray microanalysis.

Recent data suggest that changes in ionic content, primarily potassium, play a pivotal role in the progression of apoptosis. However, the changes in total element content, i.e., sodium (Na), magnesium (Mg), phosphorous (P), chlorine (Cl), potassium (K), and calcium (Ca), during apoptosis have not been evaluated. Electron probe X-ray microanalysis (EPXMA) was used to measure total element content in U937 cells before and after the induction of apoptosis. As an experimental model we used U937 cells irradiated with ultraviolet (UV) light. Apoptosis was evaluated with phase-contrast microscopy, with scanning and transmission electron microscopy, and with the fluorescent dye bisbenzimide (Hoechst 33342). Plasma membrane permeability as a measure of cell death was determined by trypan blue dye exclusion. To investigate element content with EPXMA, cells were cryoprepared, i.e., cryofixed and freeze-dried, and analyzed as whole cells using a scanning electron microscope. We found that the UV irradiation induced rapid (within 2 h) morphological changes associated with apoptosis, such as plasma membrane blebbing, condensation of the chromatin, and the formation of membrane-bound apoptotic bodies. At this time, 95% of the apoptotic cells excluded trypan blue dye. EPXMA results demonstrated that UV light-irradiated apoptotic cells (cells with membrane-bound apoptotic bodies) had a lower Cl content (P < 0.001) and K content (P < 0.001) and a higher Na content (P < 0.001) in comparison with nonirradiated control cells. Also, P and Ca content was higher in apoptotic cells than in control cells, but this difference did not reach statistical significance. No differences were found in Mg. These data indicated that morphological changes characteristic of apoptotic cell death are related with significant changes in sodium, chlorine, and potassium content. In addition, we demonstrated that these changes in elemental composition were not associated with loss of cell membrane integrity.

Apoptosis↗
PubMed1970

Electron probe x-ray microanalysis of a normal centriole.

A scanning spectrometer with lithium fluoride, ammonium dihydrogen phosphate, and gypsum crystals was used to detect the x-ray spectrum of a normal centriole, the transmitted electron image of which was used to focus the exciting electron beam to the size, shape, and position of the centriole in a 700-angstrom section of intact tissue.

Animals↗
PubMed1984

Schistosoma mansoni: electron probe X-ray microanalysis of the elemental composition of the tegument and subtegumental tissues of adult worms.

The elementary composition [Na, Mg, P, S, Cl, K, Ca and Fe] of the tegument, tegumental spines, and subtegumental tissues of adult male and female Schistosoma mansoni have been determined by electron probe X-ray microanalysis of unfixed, freeze-dried cryosections. Statistical analysis of the results suggests that there are distinct differences in the elemental composition of the tissues both between and within individual male and female worms, and between male and female worms in general. In particular, there were significant variations in the elemental contents of the tissues between individual male and female worms, which may reflect differences in the physiology and/or metabolic state of the worms. Significant differences in the elemental composition of the various tissues examined within individual worms were also found. In general, in both male and female worms, there were significantly higher elemental levels in the tegument, as opposed to the subtegumental tissues. The elemental composition of the tegumental spines in both male and female worms differed from that of the tegumental cytoplasm, although the differences in the elemental composition between spines from male and female worms reflected the differences in the elemental content between the teguments themselves. Differences in the elemental composition of the tissues between male and female worms were also found, with the female tegument containing significantly higher elemental levels (with the exception of Cl) than the male tegument. In particular, the tegument of female worms contained higher levels of calcium and, in relatively small areas, isolated calcium-containing granules. This higher tegumental calcium level in female worms may reflect a higher calcium demand by sexually mature female worms due to the presence, within the mature vitelline cells, of calcium-containing corpuscles and the production of large numbers of eggs.

Animals↗
PubMed1981

Phosphorus distribution in the nucleosome.

The spatial distribution of phosphorus within active fraction nucleosomes reveals that the path of the DNA is consistent with one and three-fourths turns of DNA supercoiled around the outside of the protein core. This phosphorus distribution, obtained with an imaging electron spectrometer in a conventional transmission electron microscope, simultaneously establishes new limits of sensitivity for elemental microanalysis.

Animals↗
PubMed1986

Preparation methods for quantitative electron probe X-ray microanalysis of rat exocrine pancreas: a review.

Pancreatic acinar cells are thought to secrete a fluid containing digestive enzymes and electrolytes and use e.g. calcium as a second messenger upon stimulation. Together with their pronounced morphological polarity, they provide a model system to study the effect of different preparation methods for quantitative biological electron probe X-ray microanalysis (EPXMA) of ultrathin sections. Several preparation methods i.e., freeze-drying and plastic-embedding, freeze-substitution (2 days) and freeze-drying of ultrathin cryosections have been applied to examine the retention of sodium, magnesium, phosphorus, sulfur, (chlorine), potassium and calcium in subcellular compartments (basal cytoplasm, apical cytoplasm, mitochondria and zymogen granules). In freeze-substituted samples the phosphorus, potassium and sulfur concentrations were 2-3 times lower in all compartments compared to freeze-dried, plastic-embedded samples. Intracellular potassium-to-sodium ratios obtained on frozen substituted and frozen-dried, plastic-embedded samples were considerably lower than for cryosections. Element gradients between adjacent organelles were large in frozen-dried cryosections, smaller in frozen-dried plastic- embedded samples and insignificant in frozen-substituted samples.

Animals↗
PubMed2000

Bioaccumulation and localization of exogenous cadmium in a teleost by electron microscopy (TEM) and its specific quantitation by electron probe X-ray microanalysis (EPMA).

A cadmium bioconcentration study was carried out in a fresh water teleost, Colisa fasciatus, to study the bioaccumulation kinetics and fate of exogenous cadmium (Cd) in biological tissues. Study shows that on exposure of the fish to a sublethal concentration of cadmium in test water, Cd uptake results in its bioconcentration in gills, liver and muscle tissues. To explore whether the accumulated Cd reaches the membranes or inside the cells, transmission electron microscopy (TEM) of the thin sections of tissues was done after histochemical localization of Cd in cells by modified SST method. TEM studies of sections of gills, liver and muscle tissues showed the deposits of exogenous Cd (visualized as dense clouds) in biological cells. This suggests the presence of free or loosely bound Cd on the membranes and inside the cells, which in the presence of Na2S is converted into insoluble metal sulfides. Electron probe X-ray microanalysis (EPMA) studies confirmed the presence of Cd on the membrane surface as well as inside the cells of bioindicator organs suggesting involvement of membrane transport of exogenous Cd inside the cells and its deposition as loosely bound insoluble metal complexes.

Animals↗