Quantitative X-ray microanalysis of calcium with the Camebax-TEM system in frozen, freeze-substituted and resin-embedded tissue sections. Application to molluscan glio-interstitial granules.
The relevance of the continuum method for a quantitative X-ray microanalysis of epon embedded tissue sections in the particular conditions offered by the Camebax-TEM system was tested and an improved model of specimen holder is proposed. The absolute calcium concentration [Ca] of membrane-bound intracellular glio-interstitial granules was determined by X-ray microanalysis in transmission electron microscopy of Mytilus retractor muscle. The Ca peak and background values were measured by the wavelength-dispersive spectrometer of the Camebax; the mass thickness of the section was recorded simultaneously with an added energy-dispersive detector. The tissue was frozen at approximately equal to 77 K in a mixture of liquid propane and butane, freeze-substituted in the presence of oxalic acid and embedded in epoxy resin. The calcium concentration of glio-interstitial granules can be as high as 180 mmol.kg-1 of epoxy-embedded tissue, with an average of 40 mmol.kg-1. The sampling of the data through repeated experiments is discussed and it is proposed that the cell would be the main level of variation. The Ca content of glio-interstitial granules is significantly lower in the tissues of animals submitted to high-potassium artificial sea-water for 10 min. This finding was predicted by the hypothesis that glio-interstitial tissue is a regulator of calcium concentration in extracellular spaces.
Laboratoire de Physiologie des Elements Excitables, Université Claude Bernard, Villeurbanne, France.
S
S
Blaineau
A K
AK
Julliard
J
J
Amsellem
G
G
Nicaise
D000818:Animals; D049872:Bivalvia / Q000032:analysis*; D002118:Calcium / Q000032:analysis*; D003594:Cytoplasmic Granules / Q000032:analysis; D004577:Electron Probe Microanalysis / Q000295:instrumentation; D005615:Freezing; D009132:Muscles / Q000032:analysis* / Q000648:ultrastructure; D014021:Tissue Preservation
D002118:Calcium