A Method for Breaking Glass Knives Slowly

There is a general belief among electron microscopists that the speed of the break in forming the edge of a glass knife is of great importance in determining its quality. Slow breaks seem very desirable (Hayat 1970).     

Improved Methods for Making and Using Glass Knives

We have observed over time that the right side of a glass knife is the optimal cutting edge for microtomy if the counterpiece (heel opposite the edge) is controlled within 1 mm. The right cutting edge has been considered the “saw toothed” side and has not been used for ultrathin sectioning. We have observed that the right cutting edge is sharper and more durable than the left. Light and scanning electron microscopy were used to observe the cutting edge, and transmission electron microscopy was used to examine semithin and ultrathin sections of animal and plant tissues cut by the right and left sides of the cutting edge. The results indicate that the cutting edge becomes sharper and more durable from left to right. Both the quality and efficiency of ultrathin sectioning is improved by using the right cutting edge.     

A Simpler and More Economical Method for Storing Glass Knives

A recently published paper (Schoenwolf 1982) suggested the use of modified microscope slide boxes to store glass knives routinely used for ultramicrotomy. Since the microscope slide boxes cost about $10.00, require modification and may damage the fragile cutting edge unless the knife is carefully oriented, Schoenwolf's method appears to be more expensive and cumbersome than the one used routinely in the authors' laboratory.     

Producing Improved Glass Knives for Ultra-Microtomy; A Glass Breaker Featuring a Linear Fulcrum and a Device for Controlling Fracturing Velocity

Innovations include: (1) interchangeable round linear fulcra of different diameters, (2) compressible materials covering pressure sites, and (3) a screw-compression mechanism for initiating breaks and controlling fracturing velocity. The instrument consists of a cross-shaped pressure plate hinged to a rectangular metal base bearing the pressure-applying mechanism opposite the hinge. A longitudinal slot in the pressure plate parallels the long axis of the fulcrum and permits positioning of prescored glass pieces or permits scoring of an engaged glass piece by guiding a scorer inserted through the slot. Knives with straight, flawless edges have been obtained from different types of glass (up to 7/16 inch thick) including soft, pyrex and tempered. Greater than 50% yield of useable knives averaging more than 50% of flawless edge, as judged at a magnification of 220 and by ultrathin sectioning, has been obtained with the device. The instrument design and technique facilitate controllably reducing the fracturing velocity to significantly increase the width of stress-free knife edge obtained. Details of the technique, optional attachments and modifications are outlined.     

Graded Differential Photoreceptor Orientation: Ramifications for Ultramicrotomy of Retina

When sectioning small blocks of tissue from the retina of the eye, it is sometimes difficult to obtain sections which simultaneously cut squarely across the inner retinal layers and are on the long axis of the photoreceptors. This difficulty is, at least partially, due to the fact that the receptors tilt progressively relative to the tangent to the retinal curve at progressively more peripheral loci. Consideration of the graded differential orientation of the receptors indicates that, in order for the section to be simultaneously coaxial with the receptors and the inner retinal layers, the plane of the section must be parallel to and include the anterior-posterior axis of the eye, as in the case when the whole eye is sectioned through its center. It is illustrated that this criterion can be met for small blocks of retina if the block is excised along a parallel of the eye and the plane of section is perpendicular to the tangent to the retinal curve and the parallel. An approach which accomplishes this is described. Theoretical analysis suggests that distortion of apparent size of structures in the retina can become significant within a few degrees of the posterior pole if this condition in not met.     

Factors Affecting the Chemical Durability of Glass Used in the Pharmaceutical Industry

Delamination, or the generation of glass flakes in vials used to contain parenteral drug products, continues to be a persistent problem in the pharmaceutical industry. To understand all of the factors that might contribute to delamination, a statistical design of experiments was implemented to describe this loss of chemical integrity for glass vials. Phase I of this study focused on the effects of thermal exposure (prior to product filling) on the surface chemistry of glass vials. Even though such temperatures are below the glass transition temperature for the glass, and parenteral compounds are injected directly into the body, data must be collected to show that the glass was not phase separating. Phase II of these studies examined the combined effects of thermal exposure, glass chemistry, and exposure to pharmaceutically relevant molecules on glass delamination. A variety of tools was used to examine the glass and the solution contained in the vial including: scanning electron microscopy and dynamic secondary ion mass spectroscopy for the glass; and visual examination, pH measurements, laser particle counting, and inductively coupled plasma–optical emission spectrometry for the analysis of the solution. The combined results of phase I and II showed depyrogenation does not play a significant role in delamination. Terminal sterilization, glass chemistry, and solution chemistry are the key factors in the generation of glass flakes. Dissolution of silica may be an effective indicator that delamination will occur with a given liquid stored in glass. Finally, delamination should not be defined by the appearance of visible glass particulates. There is a mechanical component in the delamination process whereby the flakes must break away from the interior vial surface. Delamination should be defined by the observation of flakes on the interior surface of the vial, which can be detected by several other analytical techniques.     

Embedding Free-Floating Cells in Stained Agar for Rapid Scanning and Subsequent Ultramicrotomy

Methods we have previously used for epoxy embedding of suspended tissue culture cells, white blood cells and oral mucosal scrapings did not provide a simple means for selecting the desired specimens and facilitating their subsequent handling through embedding in an epoxy resin. We have therefore modified the agar embedding technique previously recommended for the processing of microorganisms by Kellenberger et al. (1958).     

cDNA芯片表面核酸固定化的优化

cDNA芯片技术表面核酸固定化影响因素众多,其中涉及选择载体、固定于玻片的DNA片段浓度、玻片DNA片段的固定方法、玻片预处理方法、DNA片段的变性、溶解DNA片段的点样液等等.针对这些因素进行了优化筛选实验,以便于提高cDNA芯片技术检测基因表达的效率.     

Science and Art in Preparing Tissues Embedded in Plastic for Light Microscopy, with Special Reference to Glycol Methacrylate, Glass Knives and Simple Stains

Plastic embedding preserves tissue structure much more faithfully than does paraffin. Acrylic polymerization is innocuous to dye-binding groups in sections. The water solubility of glycol methacrylate monomer and the hydrophilic properties of the polymer allow for convenience in dehydration and for versatility in staining sections. Five years of experience with glycol methacrylate (GMA) embedding for light microscopy is summarized. Methods for purifying GMA monomer are cited. Procedures for fixing, dehydrating, embedding, polymerizing, sectioning and staining, using GMA, are explained. A method is provided for making glass knives long enough to cut large blocks. Simple, reliable, quick staining methods are outlined. When compared with paraffin, GMA offers opportunities for simpler, quicker procedures and yields sections of superior quality, greater information content, and less distortion.