Biomedical subjects

P W Linders

Publications and source records attributed to P W Linders.

6 recordsLinked to original sources

PubMed1986

The use of backscattered electrons in analytical electron microscopy for the measurement of the mass of individual rat blood platelets.

The backscattered electron signal, generated in individual cells, has been used to measure the dry mass of these cells. Absolute mass values were obtained by comparing the backscattered electron signals of cells to the signals of polystyrene-latex spheres of known mass. The technique was carried out in an automated analytical scanning transmission electron microscope and applied to rat blood platelets. The resulting mass distributions agreed well with the distribution measured with a method that uses the transmitted electron signal by means of densitometric analysis of electrographs. Also the range of masses was in agreement with values deduced from data in the literature. The fully automated technique has the advantage that it is direct, fast, and that thicker specimens can be measured than is possible using the transmitted electron signal. The method is intended for use in combination with quantitative electron probe X-ray microanalysis and is then able to produce elemental mass fractions of biological specimens at the subcellular level.

Animals↗

PubMed1985

Quantitative electron probe x-ray microanalysis and densitometric mass determination of individual rat blood platelets.

An improved method for quantitative electron probe X-ray microanalysis of thin biological specimens, introduced recently, has been applied to the elemental analysis of rat blood platelets. The method uses the X-ray signal to quantify the elemental content of an object and electron scattering to determine the total dry mass of the object. Along with the dry mass distribution, data were obtained on the content and mass fraction of calcium, magnesium, and sulfur in 31 individual platelets. The mean platelet dry mass was found to be 985 fg. The mean Ca, Mg, and S contents were 1.80, 3.41, and 18.3 fg, with mean dry mass fractions of 0.195, 0.396, and 1.96%, respectively. Furthermore, these elements appear to be unevenly distributed among the platelet population.

Animals↗

PubMed1983

Mass determination of thin biological specimens using backscattered electrons. Application in quantitative X-ray microanalysis on an automated STEM system.

The capabilities of modern computerized X-ray analysis systems can be expanded to the acquisition of various signals available in the electron probe microanalyzer, in parallel with the X-rays. These facilities allow the use of backscattered electrons for the measurement of the total specimen mass thickness, which can be used in mass fraction calculations, up to a (biological) specimen thickness of 10 micron. A mass measurement procedure based on the use of backscattered electrons may become an alternative for the X-ray continuum normalization method, often used in electron probe X-ray microanalysis. A mass measurement procedure using backscattered electrons is described, and preliminary results are given.

Animals↗

PubMed1983

Calibration of transmission electron microscopic mass determination using objects with known mass distribution.

An improved calibration procedure is described for dry mass determination methods, that are based on microdensitometry of transmission electron micrographs. Polystyrene latex spheres, that are supposed to have a homogeneous mass distribution, are used for the calibration procedure. By computer fitting of the theoretically expected mass distribution to the distribution measured in a line through the centre of a sphere, a mass calibration factor is obtained. The number of measurements required for a predetermined calibration accuracy can be decreased considerably as compared to other calibration methods. Accurate calibration and reproducible adjustment of the electron optical magnification are required.

Calibration↗

PubMed1982

Improved mass determination of isolated biological objects by transmission electron microscopy and scanning microdensitometry.

A modification of the classical method of Bahr and Zeitler for dry mass determination of isolated biological objects is described. The method uses a conventional transmission electron microscope (TEM) and a computer-controlled scanning microdensitometer. The performance of the modified method has been investigated by applying it to model specimens (polystyrene latex spheres). The method offers significant improvements over the existing TEM-based mass determination method.

Computers↗

PubMed1982

Mass determination of thin biological specimens for use in quantitative electron probe X-ray microanalysis.

In the quantitative electron probe X-ray microanalysis of thin specimens the total mass thickness of a specimen is often required to express the elemental content as fractions of the total mass. In the present paper three methods for the measurement of mass thickness of thin specimens are reviewed and compared as to their applicability for use in quantitative X-ray microanalysis. The methods are based on the use of the continuum X-ray intensity, the backscattered electron intensity, and the transmitted electron intensity, respectively. From experimental results, it is concluded that the mass measurement method, based on the transmitted electron intensity, gives more accurate mass values than does the continuum X-ray method. The use of an independent mass measurement method is advantageous when low temperature oxygen plasma ashing is applied to lower X-ray analysis detection limits. In this way, elements present in ashed specimens can be expressed as fractions of the original specimen mass.

Animals↗