There are many techniques available that enable us to know what is happening at the surface of a living cell. These techniques have allowed us to characterize many aspects of the process of exocytosis, the fnal cellular event in secretion. Patch clamping has given us quantitative measurements of the capacitance changes as the membrane of the secretory vesicle is added to the surface of the cell during exocytosis, and the change in the opposite direction as membrane is retrieved back into the cell during endocytosis. Tiny probes have measured electrochemical changes just outside the surface of the cell as reactive molecules are released into their surroundings. Differential interference contrast microscopy has given us high resolution pictures of the cell surface during exocytosis; real-time images are suggestive of bubbles breaking the surface of a boiling pot of water. However, exocytosis is known to be proceeded by an ordered series of events that occur below the surface of the cell.

Today's clinical laboratory has a diversity of reagents and protocols from which to choose: a variety of clinical chemistry reagents, antibodies, and molecular probes, among others. These materials facilitate serum and urine analysis, histology, hematology, cytology, and a host of additional sensitive and specific assays

Regardless of the application, labs may see an array of labeling statements indicating a reagent's general use: "For Laboratory Use Only" [LUO]; "For Research Use Only" [RUO]; "For Investigational Use Only" [IUO]; "For In Vitro Diagnostic Use" [IVD]; and "Analyte Specific Reagent" [ASR]. These preparations are often employed without realizing the course manufacturer's must follow in order to provide reagents, and the reasons for these designations.

Scanning probe microscopes (SPMs) are a family of instruments used for studying the surface properties of materials on a dimensional scale ranging from the atomic to the micrometer level. As depicted in Figure 1, all SPMs work by scanning a finely tipped probe in a raster pattern over the sample surface while measuring and mapping some interaction between the probe and the surface as a function of x-y position. The piezoelectric scanners used to provide the scanning motion offer very fine positional control but have certain inherent errors that, uncorrected, can distort images, introduce artifacts, and degrade measurement accuracy.

Most electron microscopists appreciate that proper operation of the source is vital to the operation of the entire instrument. But because the gun involves a complex interplay of phenomena, few of which can be directly observed, some common misconceptions have gained currency. Typically these myths contain a kernel of truth, but they can also mislead when accepted uncritically. In this series of articles, we explore three areas of common misunderstanding relative to operation of the thermionic (tungsten filament or LaB6) gun. Field emitters are subject to very different considerations.

Post-fixing with osmium tetroxide before silver-staining sections causes problems because the OsCU can etch the deposited silver. However, it is not a good idea to perform silver enhancement after osmium tetroxide treatment because the deposited osmium can also act as a nucleating site for silver deposition, and the osmicated regions of the sample will be silver enhanced. If gold-toning is used after OsO4 post-fixation, the OSO4 can also nucleate gold particles. OsO4 should always come after silver enhancement.

The temperature of a specimen rises when the electron beam interacts with it, producing ionization and excitation of atoms and breaking molecular bonds. Energy loss in bulk materials is ultimately converted to heat, but for small particles some of the energy escapes. Of the energy lost by the electrons in the incident beam, that which is absorbed by the specimen and degraded to heat includes oscillations of valence electrons, the kinetic energy of low-energy secondary electrons, and radiationless recombination of ionized atoms or moiecuies. Energy not absorbed includes brehmsstrahlung, characteristic x-rays, and the kinetic energy of higher-energy secondary electrons. Glaeser (1979) estimated that 50% of the energy loss is confined to a distance of about 5 nm from the track of the incident electron, while the other 50% is largely due to secondary electrons having 0.5 to 5 keV kinetic energy.

In recent years there have been a growing number of facilities interested in developing remote access capabilities to a variety of microscopy systems. While certain types of microscopes, such as electron microscopes and scanning probe microscopes have been well established for telepresence microscopy, no one has yet reported on the development of similar capabilities for the confocal microscope.

At California State University, home to the CSUPERB (California State University Program for Education and Research in Biotechnology) Confocal Microscope Core Facility, we have established a remote access confocal laser scanning microscope facility that allows users with virtually any type of computer platform to connect to our system.

A large part of the preparation of semiconductor samples for SEM and TEM observations involves the creation of cross sections to expose subsurface defects and three-dimensional structure. A powerful new combination of FIB (FEI Company, Hillsboro, Oregon, http://www.feic.com ) with automated microcleaving technology (SELA, Santa Clara, California, http://www. sela.com ) now offers a comprehensive solution for fast, easy and accurate sample preparation.

Way back in 1966, when I first started my industrial career at U.S. Steel's Edgar C, Bain Laboratory for Fundamental Research (which is what it was called before it became a grease spot in Corporate America) Gene Fischione and Dick Glenn were engaged in a "moon race" of sorts to bring out some of the earliest electrolytic jet polishers. Remy Schoone helped Gene build his model; and Bob Sober helped Dick make the competition, I haven't used either one of these fine instruments in nearly thirty years, so the only connection is historical and the good feelings I have about the four nice guys who made them.

Measuring electron intensity is sometimes a useful thing to do as a part of an electron microscope study. The electron intensity recorded through a sample is one of the important pieces of information needed in determining the thickness of a thin film or the molecular weight of biological structures by electron scattering methods. Modern digital imaging systems in transmission electron microscopes allow relatively easy determination of electron intensities, but some labs don't have the expensive digital systems. Photographic film has been used traditionally to record electron microscope pictures, and film can record a very high density of spatial information.

Acetone, alcohol, and propylene oxide have different mechanical and chemical properties. They should not be chosen haphazardly but should be used with care to suit the particular demands of the embedding conditions.