A procedure for obtaining thin sections of undercalcified bone biopsies embedded in methyl methacrylate.

A complex of techniques is described, including a specially designed mould and a method for flat mounting of the sections, enabling to obtain well-stretched and undamaged thin sections of undecalcified bone biopsies. Apart from a gain in polymerisation time, a clear advantage of the special mould is a more favorable temperature course in and around the tissue during the polymerisation process.     

Method for preparing thin sections of untreated equine hoof horn for electron microscopic examination

The preparation of hard tissues such as the equine hoof horn for electron microscopic examination is very difficult. In particular the penetration of fixatives and chemicals used during fixation and embedding is a problem. The objective of this study was to find and implement an alternative method enabling the preparation of high-quality thin sections of hoof horn and other hard tissue, which maintains the hard tissue ultrastructure and can be used for immuno-labeling. Compared to commonly used fixation and embedding techniques, the preparation of thin sections from untreated material method saves time and material and provides equivalent ultrastructural information. Furthermore, thin sections from untreated material are significantly larger and more homogeneous, more resistant to the electron ray, as well as more suitable for sectioning. The electron microscopical pictures obtained allow a comparison to previous test results achieved with fixed and embedded material. Using the preparation of thin sections from untreated material method, fixation and embedding artifacts are avoided, providing a clearer interpretation of the electron microscopical findings. Considerable advantages are achieved by using immunohistochemical techniques with untreated horn specimens because fixation invariably decreases antigenicity.     

Water content from analysis of freeze-dried thin sections

The analytical electron microscope and related electron beam instruments are uniquely able to measure the water content of biological tissue at a subcellular level. An analysis of the Rick procedure for quantifying this water content (Dörge et al., 1978; Rick et al., 1979) reveals a hidden assumption; namely, that the sample and standard densities, in the hydrated state, must be equal. In general this will not be valid. Equations are derived that do not invoke this hidden assumption. These equations show that errors in using the Rick technique for measuring water content should be small, a few per cent, unless the sample contains a very heterogeneous distribution of mass or the water content of the standard is a poor representation of the sample. For freeze-dried samples with extensive mass heterogeneity, such as skin, the equations for calculating water content presented in this paper should be used.     

A loop for the transfer of thin tissue sections

The construction and use of a simple wire loop for the transfer of thin tissue sections are described. The loop picks up, carries, and releases a drop of liquid containing the sections. The loop is opened and closed by manipulation of the forceps to which it is attached. This controls the attraction of the loop for the water drop and ensures reliable pickup and release of the sections.     

Effects of different epoxies on avoiding wrinkles in thin sections of botanical specimens

Fold or wrinkles appear frequently in thin sections cut from botanical material embedded in epoxy resin such as Epon 812 (Polysciences) or EM-bed-812 (Electron Microscopy Sciences). Small wrinkles may occur more or less perpendicular to the cutting direction and mostly across the cell wall, causing problems in the examination of the ultrastructure. We studied the occurrence of wrinkles and folds by methodological sectioning, with regard to block hardness, use of Formvar-support film, and chloroform vapor. Methodological sectioning or changing the block hardness did not reduce the occurrence of wrinkles in sections. Chloroform vapor improved the result as did also the use of uncoated grid. Wrinkles and folds could be avoided completely by embedding the specimens in LX-112 (Ladd) or ERL-4206 (Polysciences) low-viscosity epoxy resins, in which case Formvar-coated grids could be used, and chloroform vapor was not necessary.     

Removal of epoxy-attached thin sections from glass slides by plasma etching

Thin-sectioned samples mounted on glass slides with common petrographic epoxies cannot be easily removed (for subsequent ion-milling) by standard methods such as heating or dissolution in solvents. A method for the removal of such samples using a radio frequency (RF) generated oxygen plasma has been investigated for a number of typical petrographic and ceramic thin sections. Sample integrity and thickness were critical factors that determined the etching rate of adhesive and the survivability of the sample. Several tests were performed on a variety of materials in order to estimate possible heating or oxidation damage from the plasma. Temperatures in the plasma chamber remained below 138°C and weight changes in mineral powders etched for 76 hr were less than ±4%. A crystal of optical grade calcite showed no apparent surface damage after 48 hr of etching. Any damage from the oxygen plasma is apparently confined to the surface of the sample, and is removed during the ion-milling stage of transmission electron microscopy (TEM) sample preparation.     

A technique for obtaining ribbons of epoxy and other plastic sections for light microscope histology

A method is described by which ribbons of thick, large area sections of material embedded in epoxy resins prepared from standard recipes for electron microscopy, can be cut using conventional microtomes. The epoxy blocks are double embedded in an epoxy/polyethylene glycol mixture and ribbons are cut dry with fluorocarbon coated long-edged (‘Ralph’) glass knives. The method can also be applied to other plastic embedding media such as glycol methacrylate.     

不同断面预制桩拔桩器的研制

以移动式不抢险潜坝项目为背景,依据水射流理论研究开发了具有一定缺口的圆形和方形断面桩拔桩器.该拔桩器的箱体由弯曲成弧形的较厚钢板制成,内设10个具有流线型的喷嘴固定在横水管上.该拔桩器工作时在起吊机械的作用下做每分钟上下5～10次的往复运动,利用喷嘴出口的高压水射流破坏桩周围的泥土形成泥浆和产生井孔,减小桩土之间的摩擦...