Resin embedding temperature

Labeling in the microwave oven is usually carried out at 37°C for 15 min. Longer durations and higher temperatures may result in undesirable changes in antibody concentration and molarity of the salts and pH. After heat treatment, the sections should be kept at room temperature for at least 2 min to stabilize the antibody-antigen complexes. The step-by-step procedure for microwave heat-assisted immunolabeling of resin-embedded thin sections for electron microscopy follows (Rangell and Keller, 2000) ... 

Place the vial containing acetone and tissue in the refrigerator to raise the temperature. The tissue can now be directly stored (see Note 22), infiltrated for resin embedding, or rehydrated. After rehydration, it can be processed for immunohis-tochemistry as a wholemount, or cryoprotected and sectioned in a cryostat, prior to ICC (see Sections 3.3. and 3.4.)... 

Specimens for (S)TEM have to be transparent to the electron beam. In order to get good contrast and resolution, they have to be thin enough to minimize inelastic scattering. The required thin sections of organic materials can be obtained by ultramicrotomy eitlier after embedding into suitable resms (mostly epoxy- or methacrylate resins [H]) or directly at low temperatures by cryo-ultramicrotomy [12]. 

Carbon Composites. In this class of materials, carbon or graphite fibers are embedded in a carbon or graphite matrix. The matrix can be formed by two methods chemical vapor deposition (CVD) and coking. In the case of chemical vapor deposition (see Film deposition techniques) a hydrocarbon gas is introduced into a reaction chamber in which carbon formed from the decomposition of the gas condenses on the surface of carbon fibers. An alternative method is to mold a carbon fiber—resin mixture into shape and coke the resin precursor at high temperatures and then foUow with CVD. In both methods the process has to be repeated until a desired density is obtained. 

The poor stability on exposure to air and water, particularly at elevated temperatures, which results in a reduction in conductivity, also poses problems. In the case of polypyrrole it has been found that conductivity can, however, be maintained either by the drastic measure of storing under the protective layer of the inert gas argon or embedding polypyrrole film in a matrix of an epoxide resin-glass-fibre composite. 

III. Transmission electron microscopy of radish seeds Transmission electron microscopy (TEM) of radish seeds was done as listed below For TEM preparations, the specimens after fixation and dehydration, were embedded in Epon 812 resin (Luft, 1961). Thick sections (ca. 1mm each) were stained with 0.1% toluidine blue and observed with a Zeiss light photomicroscope. Thin sections, obtained with a diamond knife on a Supernova microtome, were sequentially stained at room temperature with 2% uranyle acetate (aqueous) for 5 min and by lead citrate for 10 min (Reynolds, 1963). Ultrastructural studies were made using a Philips CM12 transmission electrone microscope (TEM) operated at 80 KV. 

Carlemalm E, Garvito RM, Villiger W. Resin development for electron microscopy and an analysis of embedding at low temperature. JMicrosc (Oxford) 1982a 126 132-143. 

Carlemalm E, Villiger W, Hobot JA, Acetarin JD, Kellenberger E. Low temperature embedding with Lowicryl resins two new formulations and some applications. JMicrosc (Oxford) 1982b 140 55-63. 

In most cases, fixation may be carried out at room temperature. Duration of formalin fixation depends on the nature and the size of the specimen, and may vary from 15 min to 24 h. Longer fixation may be associated with a partial loss of the antigenicity of the component of interest. After formalin fixation, tissue samples are washed in three changes of the buffered saline (PBS) from 15 min to 2 h, but not longer than 24 hours on the whole, since the formaldehyde fixation is partially reversible. After washing in PBS, specimens may be either snap-frozen in liquid nitrogen for subsequent cryosectioning, or dehydrated and embedded in paraffin or synthetic resin. 

For complete polymerization, it may be necessary to continne cnring the blocks by UV for up to 2 wk at either -20°C or room temperature. Temperature for infiltration and polymerization of Lowicryl K4M can be as low as -35°C. Samples that are embedded in resins that are polymerized by UV light (Lowicryl, LR White) should not be osmicated. The osmium may interfere with the polymerization by preventing the light from penetrating the samples. 

A schematic view of a microdielectrometer sensor is shown in Fig. 8 and illustrates the electrode array, the field-effect transistors and a silicon diode temperature indicator 15) which functions as a moderate accuracy ( 2 °C) thermometer between room temperature and 250 °C. The sensor is used either by placing a small sample of resin over the electrodes, or by embedding the sensor in a reaction vessel or laminate. Since all dielectric and conductivity properties are temperature dependent, the ability to make a temperature measurement at the same point as the dielectric measurement is a useful feature of this technique. 

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