341 TISSUE GRINDERS
There are three basic types of tissue grinders: Dounce, DUALL and Potter-Elvehjem. Dounce • Round, ball shape on lower portion of pestle. • Designed for cellular studies where the nucleus needs to remain intact. • Supplied with two pestles that are used in the same tube: — Large clearance pestle is used for the initial sample reduction. — Small clearance pestle is used to form the final homogenate. • Stainless steel version is designed to disperse particles ranging in size from 0.1 to 1.0 microns (e.g. viruses). DUALL® • Conical shape on the lower portion of the pestle: — Conical shape provides a relatively large surface area for grinding, making this type the most efficient. — Sample is progressively ground to a smaller size as the pestle is spun and lowered into the tube. — Homogenate is produced as the sample is forced through the cylindrical section of the tube. • Ground glass pestle versions are best suited for connective tissues such as muscle, heart and lung. • PTFE pestle versions should be used for homogenizing soft tissues such as brain and liver. Potter-Elvehjem • Rounded shape on the lower portion of the pestle (sometimes considered to be a Dounce style): — Sample is progressively ground smaller in the rounded section. — Homogenate is produced as the sample is forced through the cylindrical section. • Does not provide as much grinding surface as the DUALL style because of the differences in the pestles’ tip shape (round vs. conical). • Ground glass pestle versions are suited for connective tissues. • PTFE pestle versions are used with softer tissues. • Tenbroeck tissue grinders are specially modified versions of the Potter-Elvehjem style: — Hollow glass pestles allow the addition of ice water to keep samples chilled during homogenization.
Dounce
Duall®
In choosing the correct tissue grinder for a particular application, there are two rules that apply: 1. Conically shaped pestles homogenize better than pestles with a rounded shape. 2. Ground glass to ground glass surfaces homogenize better than smooth glass to smooth glass or PTFE to smooth glass. Using these rules, a glass DUALL tissue grinder produces the finest homogenate, while a glass Dounce will produce a relatively coarse homogenate.
Stated clearances for the tubes and pestles on the Tissue Grinder pages are “total,” not “annular.”
Potter-Elvehjem
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