Carmichael, Stephen W.

Abstract Ever since membranes could be resolved within cells, the pattern of intracellular membrane trafficking has been under investigation. Images made with the transmission electron microscope revealed numerous small vesicles that appeared to be shuttling between the endoplasmic rettculum (ER) and the Golgi complex. However, these static images offered no information as to the direction trie vesicles were moving and were quite inconclusive. Nevertheless, evidence built over time to suggest that unrefined proteins were moved in small vesicles from one intracellular compartment to another. Recently, a study by John Presley, Nelson Cole, Trina Schroer, Koret Hirschberg, Kristen Zaal, and Jennifer Lippincott- Schwartz with the light microscope has challenged this view. They not only presented convincing morphologic data in their published article, but they also posted some Quicktime movies on a Web site (http://dir.nichd.nih.gov/CBMB/pb1labob.html) that are even more convincing.

Abstract It has been dogma for more than a hundred years that the light microscope cannot resolve structures that are much closer together than the length of the wavelength of light. This limit is on the order of a few hundred nanometers. This rule was “broken” by using the electron beam as the illumination source. The shorter wavelength of the electron beam gave correspondingly better resolution, down in the nanometer range. The rule was “broken” again when non-optical scanning probe microscopes (such as the scanning tunneling and atomic force microscopes) were developed. This technology gave us resolution in the sub-nanometer range, imaging individual atoms and molecules. However, scanning probe microscopes scan the surface of the specimen, excluding what's underneath from our view.

Abstract Neurons are about as polarized as cells ever get. Their axonal process can extend a distance that is up to a million times the diameter of the nerve cell body. Axons have none of the ribosomal machinery responsible for protein synthesis, so all neuronal proteins and peptides must be manufactured near the nucleus and carried out to the periphery. This distribution involves at least two distinct mechanisms, fast axonal transport, moving at almost 500 mm per day, and slow axonal transport, moving only 0.1 to 3 mm per day. It turns out that proteins of the neuronal cytoskeleton, along with many soluble cytosolic proteins, are transported exclusively by the slower process.

Abstract Recently, I had a delightfully pleasant surprise. I was attending a Human Embryology Conference in Washington, D.C., held at the National Museum of Health and Medicine, a Division of the Armed Forces Institute of Pathology. I've heard of the AFIP many times, but I had never been there, didn't even know where it was located. AFIP is located on the campus of Walter Reed Army Medical Center, which is bordered by Georgia Avenue. If you're driving, it's near the Maryland state line. If you're taking the Metro, get off at the Silver Springs stop and take a taxi.

Abstract A recent article by Matthias Rief, Filipp Oesterhelt. Berthold Heymann, and Hermann Gaub concluded with this sentence: "Single molecule force spectroscopy by AFM has proven to be a powerful addition to the nanoscopic piconewton toolbox," Everything about that conclusion is tiny. Clearly, the atomic force microscope (AFM) has given us a tool to examine structure at or near the atomic level. Earlier work from Gaub's laboratory, reviewed in this column, demonstrated that the AFM could directly measure the binding force between single molecules of biotin and avidin. This established that the AFM could be used as a tool to measure forces, not just observe structure. Their most recent experiments has added to this tiny toolbox.

Abstract All of us have looked at leaves. They're interesting. Some of us have looked at leaves under a light microscope. Still interesting. Some have looked at leaves under more powerful microscopes, and apparently they found it interesting still. Now some folks have looked more closely than ever before, and guess what? This may be the most interesting! Wendy Mechaber, Durwood Marshall, and Frances Chew of Tufts University, Richard Mechaber of GEI Consultants, Inc., and Renee Jobe of TopoMetrix turned to the atomic force microscope (AFM) to analyze the landscape of the surfaces of leaves, apparently for the first time.

Abstract We know that material within a cell is “packaged” within the Golgi apparatus. These “packages” (vesicles) bud off from the trans face of the Golgi and proceed to their destination. Just what drives this budding off process is closer to being understood, thanks to a recent report by Steven Jones, Kathryn Howell, John Henley, Hong Cao, and Mark McNwen. They presented morphologic and biochemical evidence that dynamin plays a role in this process. The dynamins are a family of 100-kD guanosine triphosphatases that are thought to be involved in the budding off of vesicles from the plasma membrane during endocytosis. Whereas some forms of dynamin are restricted to specific cells, such as neurons, the form known as dynamin II (Dyn2) is present in all tissues, including epithelium.

Abstract It has been noted by many people who have had the privilege of exploring Mayan ruins that there is a stunning blue color that has been preserved amazing well for centuries. Considering the tropical jungle is quite a hostile environment, the tenacity of this “paint” is remarkable. It had been suggested that this “paint” was made by mixing indigo dye with clay, but this did not explain its special characteristics. Recent work by Miguel José-Yacamán at the National University of Mexico and colleagues has revealed what is special about this material, which is called Maya blue paint. They collected specimens in Mexico at archeologic sites known as Jaina Island and Palenque.

Abstract Old embryos are now being looked at in a new way. About a hundred years ago, an embryologist by the name of FranMyn Paine Mall devoted his career to collecting human embryos and fetuses (an embryo becomes a fetus after 2 months of gestation) from miscarriages and abortions. These specimens form the core of what is known today as the Carnegie Collection of Human Embryos, housed in the National Museum of Health and Medicine of the Armed Forces Institute of Pathology in Washington, D.C. Whereas this is a priceless national educational resource, how do we extract the information about our embryonic development from these specimens? Classic techniques involve slicing a specimen as thinly as possible on a microtome, then reconstructing the slices in a model large enough to study. The problem is the specimen is effectively destroyed in the process. What is needed is a technique that allows whole embryos to be examined, but not destroyed.

Abstract We know from the pictographic history that the people in ancient Egypt were fond of beer and bread. Fortunately, they sent samples of these food items along with some of their more esteemed citizens to sustain them in the afterlife. Also, samples were available from rubbish heaps of ancient villages, allowing for the comparison of funerary goods with everyday foods. Additional luck was that the dry conditions have kept some samples from deteriorating even after thousands of years. Whereas they did leave us samples, they didn't leave recipes. There have been many theories about how they brewed and baked in ancient Egypt, but proof was lacking. Recently, Delwen Samuel of Cambridge University used optical and scanning electron microscopy (SEM) to determine how the ancient Egyptians brewed beer and baked bread.