Low temperature scanning electron microscopy and x-ray microanalysis of biological material.
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Electron Probe Microanalysis↗
Biomedical subjects
P Echlin
Publications and source records attributed to P Echlin.
Non-penetrating polymeric cryofixatives for ultrastructural and analytical studies of biological tissues.
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Animals↗
Low temperature scanning electron microscopy: a review.
Low temperature scanning electron microscopy is useful for morphological and analytical studies both in situations where low temperature techniques are used during specimen preparation and where low temperature stages are used for specimen examination and analysis. Examples are given of different low temperature specimen preparation techniques and how they may be applied to different types of specimen. There are still a number of problems associated with morphological identification in fully frozen-hydrated samples and it is important to carry out parallel studies using more conventional transmission electron microscopy and light microscopy preparation techniques. A number of criteria are presented, some or all of which may be used to establish the existence of the frozen-hydrated state.
Animals↗
Polymer cryoprotectants in the preservation of biological ultrastructure. I. Low temperature states of aqueous solutions of hydrophilic polymers.
The solid states formed by vitrified and frozen aqueous solutions of some hydrophilic polymers, able to act as biological cryoprotectants, have been studied by differential scanning calorimetry and freeze fracture electron microscopy. Glass transitions, devitrification, recrystallization and melting behaviour of aqueous solutions of polyvinylpyrrolidone, hydroxyethyl starch and dextran have been established. The vitrified polymer solutions exhibit a characteristic microspheral morphology which is not induced by the quench cooling process but is an inherent feature of the solutions themselves.
Cryoprotective Agents↗
Polymeric cryoprotectants in the preservation of biological ultrastructure. II. Physiological effects.
A study has been made of the physiological effects of three non-penetrating polymeric cryoprotective agents on sixteen different plant and animal cells and tissues. The cryoprotectants, when used at concentrations at which they are effective in preventing ice-crystal formation, generally have a lower toxicity to cells and tissue than similar concentrations of glycerol. The relatively low toxicity of these substances suggests that they would be more suitable as cryoprotectants for morphological and analytical studies than the commonly used low molecular weight compounds.
Cell Survival↗
Polymeric cryoprotectants in the preservation of biological ultrastructure. III. Morphological aspects.
Two high molecular weight polymers, polyvinylpyrrolidone (PVP) and hydroxyethyl starch (HES), have been used as cryoprotectants for preparing specimens to be freeze fractured. Solutions of 25% (w/w) suppress the formation of intracellular ice in single cells and tissue blocks from both plants and animals to the extent that fine structural details of the cell can be elucidates. The mode of action of these cryoprotectants, together with the structures they reveal and the peculiar advantages attached to their use, is discussed.
Cryoprotective Agents↗
The preparation, examination and analysis of frozen hydrated tissue sections by scanning transmission electron microscopy and x-ray microanalysis.
A method is reported for preparing, examining and analysing frozen hydrated tissue sections using transmission electron microscopy and X-ray microanalysis. Use of this method permits localization and measurement of water soluble or diffusible elements within the hydrated cell matrix. Since any change in total fresh weight of the specimen will affect the concentration of all components, great care has been taken to demonstrate that the mass neither increases nor decreases and to ensure that the tissue remains frozen-hydrated. Criteria for assessing whether or not the tissue remains frozen-hydrated are reported. After quench freezing, 1-2 mum thick sections of mouse liver were cut at 193 degrees K and picked up on a specially designed annular specimen holder covered with an aluminium coated nylon film. Using a transfer device which prevents contamination of the tissue sections while maintaining them at a low temperature (below 143 degrees K), the sections are transferred either to the vacuum evaporator cold stage or the scanning microscope cold stage. The tissue sections may be coated with an aluminium layer to improve electrical and thermal conductivity. The specimens are examined in the scanning transmission imaging mode and analysed using an energy dispersive X-ray analyser. Concentration of intra-nuclear and intra-cytoplasmic K, P, S and Cl are reported for mouse hepatocytes as ratios of the characteristic radiation to the continuum radiation used as a measure of mass. Ratios for all four elements were higher in the nucleus than the cytoplasm. Examples are given of this method as applied to plant and insect tissue.
Animals↗