Carmichael, Stephen W.

Abstract Spherical and chromatic aberrations have been the bane of optical lenses ever since they were first ground from a piece of glass. As light travels through a convex (converging) lens, the rays at the center of the optical axis are refracted (bent) less than the peripheral rays, so that the central rays are focused behind the peripheral rays. This is the essence of spherical aberration. Light of differing wavelengths (colors) interact differently with the lens so that longer wavelengths (red) are focused behind shorter wavelengths (blue). This is chromatic aberration. In the early days of light microscopy, these two inherent flaws seriously limited the quality of images.

Abstract The atomic force microscope (AFM) is proving to be as much a tool as an imaging device. Recently, Stefan Thalhammer, Robert Stark, Stefan Müller, Johannes Wienberg and Wolfgang M. Heckl have added another useful technique to this repertoire. They demonstrated that the AFM can be used to cut out an identified section of DNA and then extract that section for amplification. They began by flow sorting chromosomes, and then increased the specific amount of the target DNA with a “pre-set” in situ hybridization with chromosome-specific DMA to provide a specimen rich in chromosome 2. To identify the target area, selected chromosomes were examined with the AFM in the non-contact mode using stiff cantilevers.

Abstract The chemical analysis of secretory vesicles has long been limited by the fact that many vesicles are analyzed together, resulting in an averaging of a population. Differences between vesicles within that population could not be detected. Wouldn't it be great if vesicles could be analyzed one at a time? You guessed it, this breakthrough has been recently achieved. The technique of capillary electrophoresis (CE) was modified by Daniel Chiu, Sheri Lillard, Richard Scheller, Richard Zare, Sandra Rodriguez-Cruz, Evan Williams, Owe Orwar, Mats Sandberg, and Anders Lundqvist so that vesicles could be probed singly.

Abstract Imagine a raft in a canal between point A and point B. On that raft is a visible (fluorescent) cargo. Also, attached to that raft is a motor that will propel the raft only from A to B (anterograde transport). When the raft gets to point B, another motor is attached that can propel the raft, and its cargo, and the anterograde motor, back to point A (retrograde transport). Within a cell, the canals are microtubLiles, and a lot is known about anterograde and retrograde transport in some systems, but these phenomena have not been directly observed in a living, intact animal. Until now, that is. In a pair of very interesting papers, the laboratory of Jonathan Scholey has shown us convincing micrographs of anterograde and retrograde transport in an important animal model.

Abstract Many important discoveries in cell biology have been made by introducing specific compounds into a certain cell and observing the effect. Several methods have been used for the introduction of the compounds. For example, permeabilizing the cell by electroporation (an electric shock that has been demonstrated to poke holes in the plasma membrane), the use of biologic molecules (such as streptolysin 0) to create channels in the plasma membrane, or detergents to dissolve hoies in the plasma membrane. Several laboratories have shown these methods to be effective, but one questions the physiologic state of a holey cell. Liposomes or similar vehicles can be packed with compounds and fused with the cells of interest, but this method of introduction has drawbacks as well.

Abstract The size and precision af a tissue sample has always been a concern. As it has become possible to analyze smaller and smaller samples with molecular techniques, one must be increasingly concerned that the sample is what we think it is. So how do you dissect out a specific cell or a small group of cells? Whereas several techniques have been suggested, a group at the National Institutes of Health (NIH) have come up with an ingenious solution. Robert Bonner, Michael Emmert-Buck, Kristina Cole, Thomas Pohida, Rodrigo Chuaqui, Seth Goldstein, and Lance Liotta have published a technique they have termed Laser Capture Microdissection (LCM). With LCM, Bonner et. al. have demonstrated that a specific cell can be identified and transferred to an appropriate container for molecular analysis. Using the polymerase chain reaction (PCR), the genetic material from a single cell can be amplified for analysis. However, data from several cells (about 20) needs to be examined so that variations in the cell cycle, etc., can be averaged.

Abstract In a movie I saw recently, a young Will Shakespeare was seen to repeatedly dip the nib of a quill into a reservoir of ink and scrawl on pieces of paper until, finally, what we know as "Romeo and Juliet" was penned. As pointed out by Richard Piner, Jin Zhu, Feng Xu, Seunghun Hong, and Chad Mirkin, this technology is much older than Shakespeare, dating back about 4000 years. But even technology this old can change. As you are well aware, making devices on a smaller and smaller scale (nanofabrication) is certain to change our future way of life, Nanofabrication frequently relies on lithographic methods where a pattern is superimposed on a resistive film and the film is chemically etched to create a structure that conforms to the pattern.

Abstract Most of us have used fluorescence microscopy and are all too familiar with the advantages and disadvantages of this tool: easy identification of one or more labels that fluoresce at different wavelengths (color) against the relatively dark background of the biologic substrate, but we can't always get the spatial resolution that is needed to answer our questions. Electron microscopy, both transmission and scanning modes, offer much better spatial resolution, but present problems in localizing a label, particularly on the surface of a cell. Wouldn't it be great if an imaging technique were available that gave us the possibility of localizing one or more labels on the surface of a cell with resolution approaching electron microscopy. Karen Hedberg, Bruce Birrel, Douglas Habliston, and Hayes Griffith at the University of Oregon describe photoelectron imaging as the electron optical analogue of fluorescence microscopy, offering some of the advantages of both methods.

Abstract When I see a drawing by an earty microcopist, I am often Impressed by the amount of detail they illustrated. I am frequently amazed by the resolution they apparently were able to achieve with primitive (by today's standards) unconected optics. Were their instruments and observational skills realty that good, or were they just lucky, correctly guessing what was beneath their lens? In an amazing pictorial published in the April issue of Scientific American, Brian Ford convincingly answers this question. Ford describes the controversies surrounding descriptions by Antony van Leeuwenhoek in 1674 and Robert Brown in 1827. Both of these pioneer microscopists were often dismissed by their contemporaries and ignored for many years after their deaths. Leeuwenhoek was considered to be a man of fertile imagination whose observations of “animalcules” in pond slime were not appreciated until the time of Louis Pasteur.