Biology Reference
In-Depth Information
(a)
(b)
(c)
FIGURE 12.3 Types of blenders commonly used for cell homogenization: (a) Waring, Courtesy of Tiki Bar Is
Open.com ; (b) Brinkman Polytron Blender, Courtesy of LabCommerce, Inc and; (c) Virtis Tissue Homogenizer, Courtesy
of LabCommerce, Inc.
Blendor (note 'or' not 'er'). By 1954 one million Waring Blendors had been sold and even
today Waring blenders are considered the standard for the field. Soon after its introduction,
the Waring Blendor became a commonly used scientific instrument for cell homogenization.
Jonas Salk used one in developing his polio vaccine. A Waring Blendor is shown in
Figure 12.3 .
Although general food blenders are useful for many applications, they cannot efficiently
disrupt microorganisms. A step up from the simple Waring type blenders are the high speed
blade-type homogenizers including the Brinkman Polytron and the Virtis Tissue Homoge-
nizer ( Figure 12.3 ). These homogenizers employ a powerful electric motor to drive a shaft
terminated by specially designed blades that spin at high speeds. As an example, the Virtis
Cyclone IQ2 homogenizer has a 1/10HP motor mounted above a homogenizing flask/bottle.
The blades rotate at between 5,000 to 30,000 rpm and the sample volume can vary from 0.2 to
2,000 ml.
4. Osmotic Gradients
As discussed in Chapter 2 the lipid bilayer component of a cell membrane is an excellent
osmometer [15,16] . An osmometer is a device for measuring the osmotic strength of a solu-
tion. Membranes are osmometers because they are impermeable to most ions while allowing
water to readily diffuse across. The osmotic strength of one solution relative to another can be
defined by three basic classifications: hypertonic, hypotonic or isotonic. With regard to a cell,
a hypertonic solution is one having a greater solute concentration outside the cell than is
found in the cytosol. Water then leaves the cell and the cell shrinks (see Figure 2.1, Plasmol-
ysis, in Chapter 2). In contrast, a hypotonic solution is one having a lesser solute concentra-
tion outside the cell than is found in the cytosol. Water then enters the cell and the cell swells.
If the difference between the outside and cytosolic osmotic strength is sufficient, the cell may
swell until it bursts. In the case of the erythrocyte, cell disruption releases internal hemo-
globin in an easily followed process called hemolysis. As discussed previously, hemolysis
played an important role in early membrane studies (see William Hewson in Chapter 2).
Search WWH ::




Custom Search