Electron microprobe calibration for measurement of intracellular water.

A set of six albumin standards has been prepared to contain tissue solids fractions ranging from approximately 10 to 38% solids. Samples of each different standard were quick frozen in cooled propane, freeze-dried at low temperature and embedded in EPON 826 containing dibromoacetophenone. Electron microprobe measurement of reduction of Br L alpha signal was plotted against tissue water fraction to provide a calibration for tissue water measurement in biological soft tissue. The relationship between electron microprobe measurement of Br L alpha and tissue water fraction was linear with correlation coefficient .991. Using the calibration established with this work, uncertainty of measurement of tissue water fraction in a tissue sample that is 80% water will be approximately 5%.

Combined energy detector-wavelength dispersive spectrometer electron probe microanalysis of biological soft tissue samples.

A Si(Li)energy detector has been coupled with a fully automated, four wavelength dispersive spectrometer electron probe microanalyzer for analysis of freeze-dried, plastic-embedded biological tissue samples. Through the use of a suitable absorber, the unwanted portion of the energy spectrum is suppressed, thus reducing overall counting rate in the energy detector to the point where it is possible to use electron beam currents with high intensities, typical of wavelength dispersive spectrometer operation, while using the configuration of highest energy detector solid angle available in our electron probe microanalyzer. The electron probe automation software has been extended to permit control of the energy detector simultaneously with control of the electron microprobe. A software stopwatch permits accurate compensation for differences between energy detector and wavelength spectrometer dead times. A region of continuum in the energy spectrum is calibrated against background for the spectrometers to provide a different number representing background for each spectrometer. This background information is provided simultaneously with on-peak data collection by treating each region of interest from the Si(Li) energy detector spectrum as an additional data line in the electron probe microanalyzer computer automation package.

Unaltered membrane properties of arterial muscle in Dahl strain genetic hypertension.

To characterize membrane properties of arterial muscle from Dahl strain hypertensive rats, we measured caudal artery contractile sensitivity to norepinephrine and serotonin, membrane potential at 16 and 37 degrees C, and intracellular potassium, sodium, and chloride content. Dahl salt-resistant (R) strain fed low- or high-salt diets and Dahl salt-sensitive (S) strain fed a low-salt diet remained normotensive. The Dahl S strain on high-salt diets became hypertensive after 4 wk of high salt feeding. There was no significant difference in the norepinephrine or serotonin effective concentration (EC) EC50, EC10, or maximum response between the hypertensive and any of the three normotensive groups. Membrane potential measured at 37 and 16 degrees C and electron-probe analysis of intracellular potassium, sodium, and chloride concentration showed no significant differences between the four groups of animals. These results that arterial muscle membrane mechanisms are not altered in genetically hypertensive Dahl salt-sensitive rats.

Freeze-dried, plastic-embedded tissue preparation: a review.

The freeze-dried, plastic-embedded specimen is a versatile type of animal soft tissue preparation, with attributes that commend it for some types of analytical and morphological studies. The preparation involves rapid freezing, freeze-drying, osmic acid vapor fixation, and embedding in an epoxy resin. This preparation, though difficult and tedious, offers some advantages for quantification and localization of water-soluble constituents in intracellular spaces. When prepared according to established protocol, there is evidence to suggest that the embedded sample faithfully retains intracellular levels of water-soluble constituents that are present at time of cryofixation. The sample can be stored easily and indefinitely and the tissue can be examined in a variety of ways. Thin sections will accept many stains for light and electron microscopy; the sample can be used for some histochemical procedures; and quantification of intracellular electrolytes is possible with electron probe microanalysis using one of several techniques. A major disadvantage of the method is the lack of satisfactory preservation of normal solute distributions in extracellular spaces. Important considerations for instruments equipped with Si(Li) energy detector systems are the decrease in mass fraction of the elements of interest due to embedding material, and complications in analysis for some elements because of the presence of osmium. This latter problem is of little consequence for analysis by wavelength spectrometers; and the increase in sample density, because of the embedding material, can be used to advantage for thick sample analysis.