Microautoradiography And Electron Probe Analysis

In biological literature, several definitions of quantitative autoradio graphy are given. The term is defined as either the determination and com parison of the density of silver grains above various structures or under varying conditions, or the determination of absolute quantities of radio activity. In both these cases, photometric measurement serves for more rapid and more exact evaluation of grain densities than would be possible by visual counting of the grains. The equipment generally used for the photometric measurement of silver grains consists of a microscope, a photocell, an electronic amplifier system and a display unit. Grains can be made accessible to photometric evaluation by various kinds of microscopic illumination: 1. Substage bright-field illumination. 2. Substage dark-field illumination. 3. Incident dark-field illumination. 4. Vertical bright-field illumination. With all these types of illumination, the relationship between the luminous flux I absorbed by the film, scattered into the objective and reflected or diffracted, and the flux 10 which is not affected by the film is used as a measure of grain density. Since these are differential measurements, the light beam I transmitted by the film is in itself a measure of grain density if the luminous flux 10 incident on the grains is kept constant. This approach has been used in a large number of measuring setups.

The aim of electron probe microanalysis of biological systems is to identify, localize, and quantify elements, mass, and water in cells and tissues. The method is based on the idea that all electrons and photons emerging from an electron beam irradiated specimen contain information on its structure and composition. In particular, energy spectroscopy of X-rays and electrons after interaction of the electron beam with the specimen is used for this purpose. However, the application of this method in biology and medicine has to overcome three specific problems: 1. The principle constituent of most cell samples is water. Since liquid water is not compatible with vacuum conditions in the electron microscope, specimens have to be prepared without disturbing the other components, in parti cular diffusible ions (elements). 2. Electron probe microanaly sis provides physical data on either dry specimens or fully hydrated, frozen specimens. This data usually has to be con verted into quantitative data meaningful to the cell biologist or physiologist. 3. Cells and tissues are not static but dynamic systems. Thus, for example, microanalysis of physiolo gical processes requires sampling techniques which are adapted to address specific biological or medical questions. During recent years, remarkable progress has been made to overcome these problems. Cryopreparation, image analysis, and electron energy loss spectroscopy are key areas which have solved some problems and offer promise for future improvements.

Ion Transport in Plants covers knowledge about ion transport in plants. The book discusses ultrastructural localization; formalism and membrane models; and membrane resistance and H+ fluxes. The text also describes ?+ fluxes in cells and organelles; Na+-?+ transport and ionic relations of the halophytes; and Cl- transport in vesicles. The ion transport in roots and the symplasm is also considered. Botanists, biochemists and biologists will find the book invaluable.

The past decade has seen a remarkable increase in the use of electron microscopy as a researm tool in biology and medicine. Thus, most institu tions of higher learning now boast several electron optical laboratories having various levels of sophistication. Training in the routine use of elec tron optical equipment and interpretation of results is no longer restricted to a few prestigious centers. On the other hand, temniques utilized by researm workers in the ultrastructural domain have become extremely diverse and complex. Although a large number of quite excellent volumes of electron microscopic temnique are now dedicated to the basic elements available whim allow the novice to acquire a reasonable introduction to the field, relatively few books have been devoted to a discussion of more ad vanced temnical aspects of the art. It was with this view that the present volume was conceived as a handy reference for workers already having some background in the field, as an information source for those wishing to shift efforts into more promising temniques, or for use as an advanced course or seminar guide. Subject matter has been mosen particularly on the basis of pertinence to present researm activities in biological electron microscopy and emphasis has been given those areas whim seem destined to greatly expand in useful ness in the near future.

In 1968, the National Bureau of Standards (NBS) published Special Publication 298 "Quantitative Electron Probe Microanalysis," which contained proceedings of a seminar held on the subject at NBS in the summer of 1967. This publication received wide interest that continued through the years far beyond expectations. The present volume, also the result of a gathering of international experts, in 1988, at NBS (now the National Institute of Standards and Technology, NIST), is intended to fulfill the same purpose. After years of substantial agreement on the procedures of analysis and data evaluation, several sharply differentiated approaches have developed. These are described in this publi cation with all the details required for practical application. Neither the editors nor NIST wish to endorse any single approach. Rather, we hope that their exposition will stimulate the dialogue which is a prerequisite for technical progress. Additionally, it is expected that those active in research in electron probe microanalysis will appreciate more clearly the areas in which further investigations are warranted.

In February, 1974, an 'International Workshop on Membrane Transport in Plants' was held at the Nuclear Research Centre, JLiI ich, West Germany. More than two hundred and fifty people, from fourteen countries, took part in this highly successful meeting. A somewhat similar meeting took place in Liverpool, England, two years ago and it became clear there that progress in the field of membrane transport in plants was now so marked that a second, and wider, meeting in Germany was more than fully justified. The members of our pro gramme committee (U. Zimmermann, Chairman, JLilich (FRG); J. Dainty,