The compound light microscope has been used by patholo gists for centuries, and remains the common tool for making a diagnosis. A half century ago, the electron microscope (EM) was introduced, and has aiso been proven to be a valuable, but expensive, tool. In the meantime, other tools and methods have worked their way into the pathologists’ armamentarium, with immunohistochemical, genetic, and molecular techniques being the most obvious examples. Josep Lloreta-Truil, Lola Ferrer, Teresa Ribalta, Marco Pavesi, and Sergio Serrano examined the literature to determine the frequency and appropriateness with which pathologists use the EM in their studies.

The code for the human genome is essentially complete, opening an expansive book about our biologic composition. But the problem is to read this book. The font size is very small, What you are reading now is 9 point font, and genetic information would correspond to approximately 10-50 point font, six orders of magnitude smaller. There are methods to derive genetic information, but recently Adam Woolley, Chantal Guillemette, Chin-Li Cheung, David Housman, and Charles Lieber have developed an elegant way to directly read genetic information with a microscope. The microscope they used was an atomic force microscope (AFM) that employed a single-walled carbon nanotube as its probe.

Over a number of years, I have found it desirable to firmly hold a sample in the SEM without the contamination problems (or sample creep) associated with carbon tape. My approach to this has been to make a small vice suitable for gripping the sample which will still fit into a standard pin-mount style sample stage. I have made a number of specimen holders over the last few years, at rock-bottom prices.

It's always refreshing to read about two old techniques being combined in a novel way to yield new information. Osamu Ohtani and Yuko Ohtani recently accomplished this. Louis Ranvier probably introduced the use of silver nitrate as a histology stain over a century ago. Whereas Ranvier is best known for describing nodes along the nerve fiber, he also demonstrated that silver nitrate stained endothelial cells, allowing their borders to be clearly visualized. In the 1970's, Takuro Murakami first used the scanning electron microscope (SEM) to examine corrosion casts of the vasculature. Much of what we currently know about the microarchitecture of blood vessels has been discovered using this technique.

The programmable array microscope (PAM) is a powerful tool combining the capabilities of nearly all previously described optical sectioning techniques in a single microscope. Not only can the user create optical sections of threedimensional objects, but the PAM's unique adaptive optical strategy allows a user to select the best sectioning method for a particular sample or experimental need. The key to the PAM is a spatial light modulator (SLM). This device, when placed in the image plane of a microscope, can be used to create optical sectioning, generate spatial encoding masks, and/or define regions of interest.

Highly localized probing of surface nanomechanical properties with a submicron resolution can be accomplished with scanning probe microscopy (SPM). The SPM ability to probe local surface topography in conjunction with mechanical, adhesive, friction, thermal, magnetic, and electric properties is unique.1 However, the quantitative probing of the nanomechanical materials properties is still a challenge and only a few examples have been published to date.

In this note, we briefly review the latest developments in the nanomechanical probing of compliant materials (predominantly polymers). We solely focus our analysis of SPM-based approach in a so-called static force spectroscopy (SFS) mode.

One of Murphy's Laws says that whenever something is published, it is immediately out of date. Project MICRO'S “Microscopy for Children: a Bibliography”, which was distributed with the December issue of this publication is no exception. I have been contacted recently about a few CD-ROMs that will interest many readers. Since the web version of the bibliography (URL below) will not be updated for a while, I am providing listings as follows.

In a pyrotechnic composition, the morphology (size, shape and surface features) of individual particles in the mixture influences both burn rate and the ease of ignition of the composition. Collectively, the larger, more rounded and smoother the particles, the lower the burn rate and the more difficult it is to ignite the composition. However, the purpose of the current investigation was only to catalogue some particle morphologies that may be useful in forensic identification of unconsumed or residual pyrotechnic evidence. In this study, potassium nitrate was chosen because of its common use in pyrotechnics and because of its similarity with other frequently used pyrotechnic oxidizers.

All samples were prepared for scanning electron microscopy using a double-sided adhesive carbon disk applied to an aluminum post. Particles were mounted to the carbon disk and sputter coated with gold.

Today's newer homes are built to be energy efficient. Better insulation, better caulking, better windows restrict heat and airflow movements. Dust and contamination getting into the house has a harder time getting out. PLM examination of dust is a direct approach to assessing the magnitude of the problem and identifying the contamination responsible. Several actual cases of dust problems in the home and the role of microscopy in solving these problems are discussed.

The Scanning Electron Microscope (SEM) with associated Energy Dispersive Spectrometer (EDS) is commonly used to characterize the structure and elemental composition of a wide variety of materials of forensic significance. When these materials are extremely limited in size, SEM/EDS is often the only suitable method for characterization available in forensic science laboratories.

Because of the inability to access SEM/EDS data from large numbers of materials, the Federal Bureau of Investigation (FBI) laboratory believes that this discipline has not realized its full potential. The usefulness of SEM/EDS has been limited by the inability to archive spectra within a utility having a true database architecture. The FBI Laboratory has designed such an X-ray database, consisting of storage, query, and display utilities unique to X-ray spectroscopy.

The colors that one sees when looking at a mineral or gemstone are due to the response of that person's eye to the energies of the light, the emission spectrum of the illumination, and, most importantly, physical phenomena in the material that cause some colors to be absorbed while others are undisturbed or enhanced. It is beyond the scope of this article to do more than touch on the physiology of the eye that allows us to see colors. Likewise, we will not dwell on the emission spectra of various light sources. Rather, we will concentrate on the various ways in which materials, especially minerals and their heights of perfection, gemstones, produce color from white light.

Fluorescence imaging of brains from older animals, particularly primates, can be hindered by the presence of lipofuscin, a strongly fluorescent pigment that accumulates with age, primarily in neuronal cells. Lipofuscin has a broad emission spectrum that overlaps emission of most fluorescent labels, is present throughout the brain and other tissues, and is very hard to quench chemically (Schnella et at.. Journal of Histochemistry and Cytochemistry, Vol. 47, 719-730, 1999). A more convenient way to eliminate lipofuscin from fluorescence images is the use image arithmetic to subtract its signal. This method takes advantage of lipofuscin's broad emission spectrum that makes it appear in all fluorescence channels.

We've used gelled agarose to cover & hold monolayer cells in place when treatment leads to cell lifting. Low-gelling temperature agarose (Type VII) (Sigma A 4018 or A 0701) can be made as a 2% stock solution in “phosphate-buffered saline” (PBS) (boiled then kept at 42° C to remain liquid). The agarose can be stored at room temperature at this time, but must be boiled and melted again before use.

Osmium tetroxide is indeed wonderful stuff. Osmium is a rare element, so disposal of used solutions should consist of recycling, not dumping, even though osmium compounds are not considered environmentally hazardous (Smith et al., 1978 Trace Metal in the Environment, vol 4. Ann Arbor Science Publishers). The colorless and soluble toxic tetroxide. is rapidly reduced by almost any kind of dirt to a black, insoluble dioxide, usually in a colloidal form that's readily dispersed by moving water if it isn't firmly stuck to the solid organic matter that brought about the reduction.

The identification of marijuana (Cannabis sativa) is a routine analysis in many forensic laboratories. An important part of this analysis is the identification of trichomes, commonly called cystolithic hairs, on plant particles. These hairs contain calcium carbonate, The very word cystolithic derives from this fact, coming from the Greek kustis and lithos meaning, “bag of stones”.

Trichomes are not unique to marijuana but are common on many species of plants. Thus, the mere presence of trichomes on a leaf surface is not sufficient. A required step in the identification of marijuana is the microscopical characterization of the cystoiithic hairs present on the leaf fragments.

Several years ago Honegger (1985) described a simple technique for removing plant cell protoplasm in order to reveal details of interfaces between plant cells and fungal structures. This technique involves the use of Ariel a commercially available washing powder (Proctor and Gamble) containing a Bacillus substilis derived protease. We since have used this technique with excellent results to examine not only the morphology of fungal haustoria inside leaf cells of various host plants but also features of the inner surface of the host cell wall with scanning electron microscopy (SEM). Here we describe the procedure we have used to prepare samples for study and provide examples of the types of images we have obtained from our samples.

This article was originally written to respond to a discussion on the Microscopy Listserver found on the Internet concerning backfilling an electron microscope with nitrogen versus laboratory air. It was expanded to include general vacuum comments, suggestions, and techniques that could be of possible value to the working microscopist.

Section thickness can be measured by placing beads of some kind on the top and bottom surfaces of the section. This is then a simple parallax problem.

Imagine the specimen in cross section. If there are two particles, one vertically above the other they are separated by the film thickness T. Tilt the film through an angle A and in plan view the particles will separate by a distance D. This can also be extended to account for two particles not vertically above each other but I'll stick to the easy case for the explanation.

Take two negatives one at zero tilt and one at tilt of A and measure the separation D. The thickness can be calculated by T=D/sinA.

The direction of the tilt axis must be known for the measurements and it is easy to see that the larger the tiit angle and the more accurately the separation is measured, the more accurate the measurement will be. Tilt at both positive and negative angles to get a more accurate result.

Various fluorescent stains and vital dyes have been used to identify dead cells in animal tissues and celi lines. In plants, fluorescein diacetate and propidium iodide have been used to label nuclei and to identify necrotic cells in plant protoplasts and 4,6-diamidino-2-phenylindole (DAPI) has been used to mark senescing cells in sections of roots. However, these dyes may be problematic when used with intact plant tissue with well-developed cells walls which may impede dye penetration. Endogenous fluorescence has been used to identify dead cells in intact and sectioned plant tissues. Published procedures typically employ ultraviolet (UV) excitation wavelengths of 340-380 nm and emission wavelengths of 400- 425 nm, thus requiring a UV filter set.