Since the discovery of nerve growth factor, it has been thought that neurotrophic factors are released or secreted from target cells. However, more recently it has been suggested that a specific neurotrophic factor known as brain-derived neurotrophic factor (BDNF) may reach target cells directly from pre-synaptic axons. It has not been known how these molecules get from the neuron in which they are produced to the target cells. Keigo Kohara, Akihiko Kitamura, Mieko Morishima, and Tadaharu Tsumoto have demonstrated that BDNF is transported anterogradely from presynaptic neurons to target neurons.

There are many approaches to obtaining high-resolution images and three dimensional volumetric data sets, but all have limitations. Many techniques involve reconstructing volumes of information from sections, either physical sections or optical sections. Recently, James Sharpe, Ulf Ahlgren, Paul Perry, Bill Hill, Allyson Ross, Jacob Hecksher-Sørensen, Richard Baldock, and Duncan Davidson have developed an optical technique that is analogous to computed tomography (CT). Whereas clinical CT involves an X-ray source and detector rotating around the patient, optical projection tomography (OPT) has the specimen rotating within an optical pathway.

The use of barcodes on products, combined with the computer technology to read and track the subsequent data, has revolutionized inventory control in our society. Barcodes are commonly seen on items as large as automobiles and as small as pieces of candy. But if you need to track a large number of items that are microscopic in size, such as biologically relevant molecules (think genomics, proteomics, metabolomics, etc), then you need very small barcodes. Sufficiently small rods that can be marked as barcodes have been developed by Sheila Nicewarner-Peña, Griffith Freeman, Brian Reiss, Lin He, David Peña, Ian Walton, Remy Cromer, Christine Keating, and Michael Natan.

It is widely accepted that approximately 65 million years ago, an extraterrestrial object slammed into the Yucatán Peninsula of Mexico, creating a worldwide climatic shift that wiped out the dinosaurs, and many other terrestrial and marine species. But what happened to the insects? They undoubtedly represented a larger biomass than the dinosaurs, but it's fair to say they haven't captured the public's imagination in the same way. The reason the fate of the insects has not been adequately explored is due to the paucity of the available fossil record of the insect bodies. There are a few records of insects embedded in amber or fossilized, but practically none are available from the time of mass extinction referred to as the Cretaceous-Paleocene boundary. Recently, Conrad Labandeira, Kirk Johnson, and Peter Wiif found an ingenious way to examine indirect evidence and show what happened to the insects during this time.

We're all interested in food. Food is the sustenance of life. And you're interested in microscopy, or else you would not be reading this column. So here's a web site that will appeal to both of your interests. Miloš Kaláb is the author of the web site, and he's enlisted a host of food scientists to assist him. There's no lack of expertise here!

The home page can send you to many locations, but let's begin with the site that deals with microscopy. It is said that the earliest microscopists trained their simple instruments on food, mainly to look for contaminants. We are then treated to a primer on microscopy, beginning with light microscopy, then advancing to electron microscopy.

The transmission electron microscope (TEM) was invented in the 1930's, and developments in specimen preparation in the 1950's led to its widespread use as a tool to study structure in biologic systems. Similar in principle to the light microscope, but utilizing a much shorter wavelength for better resolution, the TEM has the image-forming beam pass through the specimen. This results in a two-dimensional image which can be difficult to interpret because features from different depths of the three dimensional specimen are superimposed. Traditionally this was dealt with by cutting sections of plastic-embedded specimens so thin (in the 40 to SO nanometer range) that they effectively had only two dimensions. To allow biologists to examine structures in three dimensions, serial sections are stacked and structures reconstructed. Even though computers have made reconstruction easier, the reality is that resolution in the depth dimension is limited by the section thickness. The technique of electron tomography is emerging as a way to overcome this limitation.

Numerous microscopy techniques, based on both imaging and diffraction, exist for the measurement of grain size distributions in polycrystalline thin-film samples. The accuracy of each technique is affected by three major factors: the effective resolution of the instrument relative to the characteristic grain size, the detection of the grain size through the thickness of the film, and the recognition of boundaries between adjacent grains during post-processing. When the instrument resolution is primarily considered, the measurement technique has a practical grain size measurement range, see Fig. 1 for a comparison of ranges for several measurement techniques. In bulk metallurgy grain size analysis, methodology has been developed to represent 3-dimensionai grain structures from measurements taken on 2-dimensional images.

Recently on the microscopy list server, a question came up as to how to compensate for charging in SEM micrographs. Several good answers were suggested. Some of them were 1) recoating the sample to prevent the build up of charge on the sample in the first place, and image it again, 2) use an environmental SEM (ESEM) in the “wet” mode to eliminate the charging phenomena, 3) use a different detector, such as a backscattered electron detector, which is much less sensitive to charging phenomena, and 4) apply adjustments to the digital image using software such as Adobe PhotoshopÆ to minimize the effect of the charging problem.

Sometimes a scientist or laboratory manager has the opportunity to be involved in the design of a new building for housing sensitive instruments, such as electron microscopes. Unfortunately, few of us are trained in the necessary skills, and “learning the hard way”, by making mistakes, is not really satisfactory, given the expected lifetime of the resulting structure. It has to “right first time”!

Vibration, sound and electromagnetic interference are all huge unknowns, when it comes to microscope performance. Each manufacturer will provide you with a set of specifications which are “required” for their instrument to meet its guaranteed performance criteria.

As progress indicators in electron microscopy, advances in spatial resolution and in spectroscopy probably attract most frequent attention. Improved user-friendliness has also been significant even when judged in comparison with scanned probe microscopy. Evidence for developments in in-situ microscopy at least equally impressive can be found by comparing the relevant sections of the book by Hirsch et al. and a more recent compilation.

Peter Hirsch's research group swiftly discovered the power and frustrations of in-situ microscopy. The cine film of dislocation motion observed in the earliest diffraction contrast studies, and attributed to the thermal stresses generated by the electron beam, was extremely effective in convincing the wider community that it was indeed dislocations that were being observed.

In Ihe October, 2001 issue of Microscopy Today, Randy Tindail described and compared his experiences with service contracts offered by insurance companies versus those offered by equipment manufacturers. As a small business with limited funds, we, too, grappled with the onerous costs of service contracts on our SEM and EDS units. However, we believe that we have found an extremely cost-effective means of protecting our equipment investment against the expense of a major failure.

First, a bit of business philosophy: We believe insurance should be designed to protect the insured from catastrophe, and not be expected to take care of every minor expense or inconvenience that may develop.

In the beginning there was water-the first stain that delineated structure within a polymeric system. The polymerwas natural rubber (NR) and the system was an air-dried film of natural latex. Grenquist reported in 1929 that a dried film of natural rubber latex soaked in hot water became milky (Figure 1) and, at that stage, the latex particles could be detected by the optical microscope (OM), The contrast mechanism was provided by the absorption of water by the naturally occurring proteinaceous layers present on the congealed NR particle surfaces. There was little demand for polymer staining until the age of electron microscopy.

This article is the second of a series transcribed from the discussion taped during the Core Facility Management session. Bulleted paragraphs indicate comments by individuals attending the session.

D. Sherman: The next topic was suggested based on the discussion at last year's Core Facility Management session. Those of you who have not been involved in formal discussions on scientific ethics probably are going to have your eyes opened a bit. There is no such thing as a quick answer when it comes to ethics. What was initially brought up last year was the question of what are our responsibilities as facility managers when we see things going on that are perhaps not exactly appropriate as far as interpretation of data and such.

If we accept that the optical layouts of single-beam laser scanning confocals are generally quite similar, the most important variable is “Photon Efficiency” (PE): the fraction of photons leaving the focal plane that actually contribute to the number stored in the image memory. Unfortunately, this parameter is a function of a very large number of operator settings, design decisions and optical performance specifications (BioTechniques The 39 Steps; A Cautionary Tale about “quantitative” 3D fluorescence microscopy, April 2000 28:884-7). As a result, although all manufactures claim excellent “Photon Efficiency” none actually provide any specifications. We have to determine the PE ourselves.

Photomicrography is the combination of photography and compound microscopy. Photographers working with compound microscopes are facing many challenges (for an introduction see [1] and [2]). Digital photography offers great advantages, but also adds additional difficulties. Digital cameras have been used in photomicrography for over a decade now. Today, we have access to many excellent consumer-grade digital cameras that are most suitable for low-cost imaging systems for light microscopy. In this short paper, I summarize my experience with the Sony DSC-S70 digital camera, which comes with a nice, large Zeiss lens. (Most of the ideas presented in this paper are also valid for the DSC-S75 and DSC-S85.)

How do you comprehensively analyze the chemistry of a microstructure with an SEM equipped with an energy-dispersive x-ray spectrometer (EDXS)? Prior to the 1990's there would have been perhaps two distinct and commercially available solutions to this problem. Firstly, you could have collected a number of point spectra each with a large number of counts and individually analyzed each one. The positive aspect of this, in principle, is that for each point the elemental correlations are maintained (e.g., a given point contains Al and O). The potential problem is that the region of the point analysis in question is not representative of the microstructure as a whole or subtle differences between different points could be missed. Additionally, point analyses are quite subjective and prone to missing potentially important regions of the microstructure.

The confocal laser-scanning microscope (CLSM) has enormous potential in many biological fields. The reliability of the CLSM to obtain specific measurements and quantify fluorescence data is dependent on using a correctly aligned machine that contains a stable laser power. For many applications it is useful to know the CLSM system's performance prior to acquiring data images so the necessary resolution, sensitivity and precision can be obtained. Applications involving deconvolution, FRET and quantification necessitate that the confocal microscope is correctly configured and operating at the highest performance levels.

In 1936, Otto Scherzer published his famous theoretical paper on the correction of aberrations in round magnetic electron lenses. For fundamental reasons, the aberration coefficients are positive and to introduce negative corrections, the electron optical elements have to produce either charges or poles on the optic axis, or contain a mirror or be a multipole system. In 1997, three papers appeared with actual demonstrations of the correction of aberrations in imaging lenses, probe forming lenses and electron mirrors. It took almost two thirds of a century for this seemingly straightforward development to occur and for the promise of wavelength limited electron imaging to emerge as a practical proposition.

The use of electronic files made universally readable in Adobe Acrobat will eventually replace paper submission in nearly every avenue used by scientists, whether files go to grants agencies, to reviewers, to colleagues via e-mail, or to publishers. It's for the obvious reason of reducing paper and the costs of mailing, but also because fonts often misbehave when going across operating system platforms, and because seemingly everyone has the Acrobat Reader, A better understanding of Adobe Acrobat can go a long way toward reducing the frustration that can easily arise from using this program inappropriately and ending up with poor image resolution.

The most persistent misconception made in digital imaging among those who use our core facility involves the understanding of digital resolution; and the greatest mistakes result from a mis-use of the “Image Size” dialogue box in Adobe Photoshop. Add to that, an intractable desire to use Microsoft PowerPoint and to somehow make Photoshop and PowerPoint agree about the nature of images that open in both programs, weighted toward the miserable resolutions and compression required by PowerPoint, changes in original data become as common as dandelions on a lawn. Yet, changes in data that result from increasing or, more commonly, decreasing pixels (what is called re-sampling), can be avoided.

Resolution, as many of us have learned, is the ability to discriminate between two points in space, a phenomenon made easier by high contrast objects versus those that are low in contrast.