Rotary microtomes

Human brain tissues, for example, are fixed postmortem with 10% formalin for 24-48 hr, dehydrated, and embedded in paraffin. Sections, cut with a rotary microtome, are mounted on coated glass slides. The sections are rinsed three times for 5 min each with 0.1 M sodium phosphate buffer (pH 7.4) and then transferred to 10-15 mM sodium citrate... 

Sectioning in Paraffine or Celloidin.—When it is necessary to study the microscopic structure of very delicate plant parts, superior results can generally be obtained by imbedding the material in paraffine or ceUoidin, which is subsequently hardened, and sectioned by means of a sliding or rotary microtome. 

Microtomes are instruments employed to facilitate the cutting of sections of organic tissues. The three most commonly used types are the hand, sliding and rotary microtomes. 

Fig. 10.—Rotary microtome. The feed mechanism is covered to protect the wearing parts from dust.

For immunocytochemistry, fixed tissue must be cut in thin sections to be viewed in the light or fluorescence microscope. There are two common ways of sectioning tissue - the cryostat for fixed frozen tissue and the rotary microtome for paraffin-embedded tissue. In animal research, select the sectioning method based on the experimental design. The method that gives the most reliable results and is the simplest should be selected. For immunocytochemistry, the cryostat is a very efficient and reliable method. The rotary microtome of paraffin-embedded material is more complex and problematic. For immunocytochemistry in animal research, the cryostat method is recommended for reasons discussed in this chapter. 

Human tissue should be fixed in 10% neutral buffered formalin and then dehydrated for embedding in paraffin. Paraffin is nonaqueous embedding medium, so the tissue blocks must have the water removed or be dehydrated. Dehydration is done in organic solvents such as alcohol, acetone, xylene, or toluene. After dehydration, the tissue blocks are embedded with liquid (warm) paraffin. When cooled, the wax embedded block is sectioned on a rotary microtome. Before immunocytochemistry can be performed on the resulting tissue sections, they must be rehydrated by processing with the same organic solvents back to water. Thus, the dehydration and rehydration steps are needed before immunohistochemistry. 

Cut 7- to 10-pm sections as ribbons on a rotary microtome using a disposable blade. 

For light microscopy, flower buds were embedded in paraffin and sectioned with a Leitz Minot 1212 rotary microtome fitted with metal blade. The sections (about 8 pm thick) were stained in fastgreen and safranin, and enclosed in DMX. 

Rotary and sledge microtomes are used with steel knives to provide sections for observation in the optical microscope. These mechanical systems provide consistent thin sections in the range of 5-40 /xm thickness. Thinner sections are cut using glass knives which provide good sections 1-4 /xm thick. 

In preparation for paraflSn infiltration water and fats are removed after fixation from the small blocks of tissue by consecutive extractions with alcohol and fat solvents, such as xylene. The tissue blocks are then placed in several changes of molten paraffin. After the displacement of xylene by paraffin is complete, the tissue blocks in paraffin are removed from the oven and hardened by cooling. Sections can be cut easily by a rotary microtome at a thickness of 5 to 7 microns (0.005 to 0.007mm.). When water-soluble carbohydrates are to be studied, it is important to cut and mount the paraffin sections on slides without exposure to water. In ordinary work, the paraffin ribbons are floated on water and lifted on slides for mounting. Paraffin is removed from the tissue sections prior to microchemical tests by consecutive baths in several changes of xylene and alcohols. 

Histological sections are performed using a standard rotary microtome at 5-7 o,m thickness after proper orientation and trimming of the paraffin block. The paraffin nbbons are separated for desired placement on slides and can be collected in either of these ways (1. or 2.) ... 

Rotationsverdampfer rotary evaporator flask Rotationsverdampferkolben rotary microtome Rotationsmikrotom rotary-piston meter Drehkolbenzahler rotary-piston pump Drehkolbenpumpe rotary vacuum filter Vakuumdrehfilter, Vakuumtrommeldrehfilter rotary vane pump Drehschieberpumpe rotating stage micros Drehtisch rotation... 

Test bar characterization. The injection-molded test bars are characterized by optical microscopy and by differential scanning calorimetry (DSC). Light microscopy is carried out in a Zeiss Axioplan 2 equipped with an AxioCam camera. The specimens are cross-sections cut from the centers of the test bars. They are 10 p,m thick. Slicing is carried out at -70 °C using a rotary cryo-microtome Leica RM 2165. A Mettler-Toledo DSC 82 P is employed. Sample mass is 5.0 0.1 mg. The samples are studied under nitrogen flux, cooled to —100 °C and heated to 280 °C at a rate of 20K/min. 

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