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.

Aldehydes are the most commonly used fixatives. They serve to stabilize the fine structural details of cells and tissues prior to examination by light or electron microscopy. Research workers, technicians, pathologists and others who regularly use aldehyde fixatives frequently do not appreciate the nature and properties of these compounds or the reasons for choosing to fix a specimen in formaldehyde, glutaraldehyde or a mixture of the two. Misconceptions are widespread also about formalin and paraformaldehyde, the commercial products from which formaldehyde-containing solutions are made.

The precursor of today's light microscope was invented probably in the Netherlands about 1600. In effect it previously involved a two lens system - objective and the eyepiece. As such it was termed a compound microscope. It differed from the simple one-lens microscope of Anthony Leeuwenhoek in the 1600's. The image was so bad, however, that most microscopists preferred to use the simple one-lens microscope. Leeuwenhoek, with his one-lens microscope, magnifying up to 280X, discovered foraminifera and many other “wee beasties”, even bacteria and spermatozoa.

Several summers ago, while working at the Marine Biological Laboratory in Woods Hole, Massachusetts, George Augustine (Duke University) and I wished to look at the circulation in the giant synapse of the squid, Loligo pealei. At that time, Dr. Eugene Copeland suggested the use of India ink in order to see the circulatory system. The ink contains carbon particles that are visible under the EM. In addition, it is visible to the naked eye.

The preparation of histological sections of teeth can be both a rewarding and a frustrating experience. This is primarily due to the varying degrees of mineralization of the enamel, dentin, cementum and surrounding bone and the difficulty in retaining original relationships between the calcified and the soft tissues in the final stained section.

The tooth has a central pulp that is a gelatinous loose connective tissue. Surrounding this is dentin that forms the main bulk of the tooth, is composed chiefly of collagen fibers and is approximately 70% mineralized.

Having seen these effects often enough, and fielded questions on them from fellow AEM users, we'd like to share our speculations about surface charging effects on semiconductor and insulator surfaces. We do not claim the following to be authoritative, but just what we consider a reasonable explanation for some strange phenomena we have observed.

There appears to be some confusion as to how materials are impregnated or dried. Without getting into the exciting mathematical details best suited for persons who second language is Greek, I offer the following short explanation as to how materials are impregnated or dried.

If the object is porous, the porosity is described in terms of macropores (>50 nm), mesopores (50 - 2 nm), and micropores (2 - 0.8 nm). These three size classes of pores represent different flow mechanisms for the impregnation of porous materials. Solvent penetration of a non-porous particle by imbibing is similar mathematically to solvent penetration of micropores although the actual mechanism is quite different.

In my research, I am interested in understanding cellular morphogenetic events in early somitic myogenesis in the chicken embryo, and much of this work involves viewing fluorescently labeled cells in embryonic tissues. For this work, I am using 0.2% (weight/volume in 100% tetraglycol (Sigma)) concentrations of dil (1,1', di-octadecyl-3,3,3',3',-tetramethylindocarbocyanine perchlorate) and diO (3, 3'-dioctadecyloxacarbocyanine perchlorate) to focally label small areas (approximately 10 cells) of the epithelial somite known as the dermomyotome.

Inexpensive fixed-focus digital cameras can be used with homemade lens attachments to obtain good quality close-up images and photomicrographs. The current availability of inexpensive digital cameras with resolutions of 1024 x 768 pixels or better is brought about by technical advance and the continual introduction of competing new models and accessories. The digital camera which I use costs less than $150 now

at a liquidation sale or internet auction, and the price continues to decrease. Although more expensive digital cameras are great to have, their advanced features are not necessary for introducing young students to the digital revolution in photography and for exploring the microscopic world.