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Biomedical subjects

G A Kuypers

Publications and source records attributed to G A Kuypers.

5 recordsLinked to original sources
PubMed1981

Ultrastructural studies on cultured fibroblasts from patients with cystic fibrosis.

The ultrastructure of cultured fibroblasts of patients with cystic fibrosis (CF) was investigated and compared with control cultures. CF-fibroblasts showed a significantly increased number of pinocytotic vesicles along the plasma membrane. Other differences in ultrastructure between CF-fibroblasts and controls could not be observed. Cytochemical localisation of calcium was studied after fixation in the presence of oxalate. In CF-fibroblasts, oxalate precipitates (presumably indicating the presence of calcium) were found in the cytoplasm, often associated with membranes of the endoplasmic reticulum and Golgi vesicles, and in association with nuclear membrane and plasma membrane. In control fibroblasts, oxalate precipitates were scarce. The results are in accordance with earlier findings of elevated calcium in fibroblasts from CF-patients, and point to a localisation of at least part of the excess calcium in the cytoplasm and microsomal fraction.

Adult↗
PubMed1980

Post-mortem elemental redistribution in rat studied by x-ray microanalysis and electron microscopy.

Post-mortem elemental redistribution in various tissues from rat was studied by means of electron probe X-ray microanalysis, and correlated with morphological changes in these tissues. Pancreas, liver and cardiac muscle were removed from the animal either immediately, or after some hours after death. Elemental distribution at the cellular level was studied by X-ray microanalysis of thick cryosections. Calcium redistribution at the subcellular level was studied using tissue fixed with glutaraldehyde/oxalate. In all tissues, post-mortem redistribution of electrolytes had taken place within 2 h. The cellular concentrations of Na, Cl and Ca increased markedly, those of Mg and K decreased; no significant changes were found in the concentrations of P and S. The number of oxalate precipitates (indicating the presence of calcium) increased both in the mitochondria and in the cytoplasm and endoplasmic reticulum, reaching a maximum at 2 h. Morphological changes included mitochondrial swelling and vesiculation of the endoplasmic reticulum. Since the post-mortem ion shifts are similar to those encountered in some diseases and types of cell injury, great care has to be taken in the interpretation of X-ray microanalytical results from autopsy material.

Animals↗
PubMed1979

Kinetics of sulfate uptake by yeast.

Uptake of sulfate by yeast requires the presence of a metabolic substrate and is dependent on the time during which the cells have been metabolizing in the absence of sulfate. At low concentrations of sulfate, uptake can be described by simple saturation kinetics. Uptake of sulfate is accompanied by a net proton influx of 3 H+ and an efflux of 1 K+ for each sulfate ion taken up. Divalent cations stimulate sulfate uptake at low concentrations of sulfate; the maximal rate of uptake is not significantly affected but Km is lowered. Stimulation by divalent cations shows an optimum at a cation concentration of about 4 mM. Monovalent cations are less effective, trivalent cations are more effective in stimulating sulfate uptake. The results are qualitatively in accordance with the notion, that the effect of cations is due to an effect via the surface potential.

Biological Transport↗
PubMed1979

Mercury-induced loss of K+ from yeast cells investigated by electron probe x-ray microanalysis.

According to Passow & Rothstein (1960), the mercury-induced loss of K+ from yeast cells is an all-or-none effect. This hypothesis was tested by analysing individual yeast cells by means of energy-dispersive X-ray microanalysis. A dual effect of mercury was observed. The cell population was split into two parts: one part consisted of cells that had suffered a (nearly) complete loss of K+- the number of these cells increased with increasing concentrations of HgCl2; the other consisted of cells that had only lost part of their K+ content--these cells showed a normal distribution around a central value that decreased with increasing concentrations of HgCl2. Our analysis shows that the effect of mercury is more complex than originally suggested and that, in addition to an all-or-none effect, a gradual loss of K+ occurs.

Copper↗