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4. Preparation and Sectioning of Specimens
- University of California Press
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55 4 Preparation and Sectioning of Specimens Ellen-Thérèse Lamm Historical Overview 57 Setting up the Lab 60 Standard Thin-Sectioning Procedure (STS) 64 STS.A. Planning and Documentation 65 STS.B. Specimen Preparation 69 STS.C. Embedding 85 STS.D. Sectioning 90 STS.E. Mounting 96 STS.F. Grinding and Polishing 101 STS.G. Curation 108 Procedure for Large Specimens (“Big Bones” [BB]) 116 BB.A. Planning and Documentation 116 BB.B. Specimen Preparation 118 BB.C. Embedding 124 BB.D. Sectioning 125 BB.E. Mounting 127 BB.F. Grinding and Polishing 129 BB.G. Curation 129 Procedure for Small Specimens (“Small Stuff” [SS]) 130 SS.A. Planning and Documentation 131 SS.B. Specimen Preparation 131 SS.C. Embedding 132 SS.D. Sectioning 137 SS.E. Mounting 138 SS.F. Grinding and Polishing 140 SS.G. Curation 141 Procedure for Radioactive Specimens 142 Troubleshooting: Some Additional Approaches 145 Cleaning and Caring for Equipment and Supplies 149 A Final Note 149 Acknowledgments 155 References 157 56 Preparation and Sectioning of Specimens After following the guidelines in Chapter 3 on how to select specimens for histological study, you now have specimens chosen and are ready to begin processing. In this chapter, we guide you through: setting up and maintaining a paleohistology lab, preparing the specimen for research, making thin-section slides, curating the slides that you produce, restoring the original fossil, caring for equipment and supplies, and staying safe while working with chemical and equipment hazards. This is not intended to be an exhaustive guide, and most people will need handson training from an experienced technician to get the best results. However, we provide here an outline of protocols with illustrated examples that will enable you to begin to undertake successful thin sectioning. This chapter also describes variations in techniques for specimens of unusual proportion—the very small to the very large. Specimens have arrived at the Museum of the Rockies (MOR) lab in containers ranging from a 00 gelatin capsule (containing a fiber found in a Mononykus field jacket) to a U.S. Armed Services Dragon missile case (housing a large and highly radioactive ceratopsian humerus). Suggested protocols for safely processing radioactive histology specimens are also presented. Fossil bone is the example material used throughout this chapter. However, these techniques are used to section a wide variety of fossilized specimens, including eggshell, teeth, ossified tendon, coprolites, and plants. With the addition of initial tissue fixation, dehydration, and clearing stages, samples of modern bone, bone with soft tissue, and extant teeth have also been successfully sectioned using the materials and methods described in “Procedures for Small Specimens.” A section on troubleshooting describes variations in protocols for specimens that are difficult to prepare because they are still in a sub-fossil state of preservation . Also included are guidelines for slide repair, a summary of all adhesives used, and a description of products used for applying coverslips and stabilizing specimens. Although “destructive sampling” is the term often applied to histological sectioning, we will show that in most cases it requires only the removal of a portion of bone that is then molded—with a cast used to restore the fossil to its original gross form. Even when an entire specimen must be sectioned, a full cast provides the same external morphological information. These techniques are detailed in the Pictorial Guides to Molding and Casting (Figures 4.13 and 4.14). 4] Project MUSE (2024-03-29 02:32 GMT) HISTORICAL OVERVIEW 57 On the other hand, the process of sectioning provides a wealth of information that can be used to answer important questions in paleontology about age, growth rate, metabolic regimes, behavior, and many additional subjects addressed in this volume (see especially Chapters 7–10). Testing these paleobiological hypotheses is worth both the effort in the histology lab and the alteration to the original specimen. Table 4.19 outlines the research projects and resulting publications that are shown in the figures throughout this chapter and Table 4.20 includes an extensive listing of all companies and supplies mentioned. Following the references cited is also a list of useful URLs that describe lapidary equipment types and operation; radiation safety resources; and a link to technical publications from Buehler Ltd. Worth noting, in addition to the information provided in the other chapters on bone structure, growth, and tissue histology, is the wide range of histological information contained in the Handbook of Histology Methods for Bone and Cartilage . With a focus on modern bone...