Counting suspension

An interesting historical application of the Boltzmann equation involves examination of the number density of very small spherical globules of latex suspended in water. The particles are dishibuted in the potential gradient of the gravitational field. If an arbitrary point in the suspension is selected, the number of particles N at height h pm (1 pm= 10 m) above the reference point can be counted with a magnifying lens. In one series of measurements, the number of particles per unit volume of the suspension as a function of h was as shown in Table 3-3. 

Methods to Detect and Quantitate Viral Agents in Fluids. In order to assess the effectiveness of membrane filtration the abihty to quantitate the amount of vims present pre- and post-filtration is critical. There are a number of techniques used. The method of choice for filter challenge studies is the plaque assay which utilizes the formation of plaques, localized areas in the cell monolayer where cell death caused by viral infection in the cell has occurred on the cell monolayer. Each plaque represents the presence of a single infectious vims. Vims quantity in a sample can be determined by serial dilution until the number of plaques can be accurately counted. The effectiveness of viral removal may be determined, as in the case of bacterial removal, by comparing the vims concentration in the input suspension to the concentration of vims in the effluent. 

Fig 3 Comparison of Homogeneous Solution and Suspension Counting of Tagged HMX Samples... 

This evaluation conveniently be classified into suspension tests (section 3.1) and counting methods, although the latter themselves use suspensions of microorganisms and hence are referred to here as quantitative suspension tests (section 3.2). 

The trypsinized cell suspension is counted and diluted in complete media before assessing for survival. For each treatment set up five Petri dishes containing 200 cells per dish. 

The cell titer of each culture is counted and a sample diluted in CM 10 for assessment of posttreatment survival. For this, two 96-well microtiter plates are charged with 200 pi of a diluted cell suspension, using a multichannel pipette such that each well contains on average one cell. 

Cell titres are determined by diluting of the cell suspension in Isoton and counting an appropriate volume (usually 0.5 ml) with a Coulter counter. Two counts are made per suspension. 

The scattering models employed in data processing invariably involve the assumption of particle sphericity. Size data obtained from the analysis of suspensions of asymmetrical particles using laser diffraction tend to be somewhat more ambiguous than those obtained by electronic particle counting, where the solid volumes of the particles are detected. 

In order to prove the efficiency of the liposomal system in tumor therapy (administration of the liposomes after tumor induction), seven animals were treated with 2 x 10 B16 tumor cells (injection of a suspension in 200 pL HBSS into tail vein). After four and seven days the formulation [AVE 3 TRP-2 (10 pg TRP-2) and AVE 3 1826 CpG (1.3 pg CpG)] was given into the foot pad of the hind legs of the mice intradermally. Twenty-one days after the injection of the tumor cells, the animals were sacrificed and the metastases in the prepared lungs were counted. A second group of seven animals received the tumor cells, but no liposomal treatment was applied. Table 2 indicates the high antitumor potency of the formulation. 

Several types of testing were employed to evaluate the bactericidal efficacies of the coated substrates. Five of the coatings on circular glass cover-slips (12 mm diameter) were challenged with the bacterium Staphylococcus aureus (ATCC 6538). This was accomplished by adding a 50- jlL suspension of 10 CFU S. aureus to the surface of each sample. At predetermined contact times a 25- jlL aliquot was removed from the surface, quenched with sterile 0.02 N sodium thiosulfate, and plated on nutrient agar. The viable bacterial colonies were then counted after 48 h incubation at 37°C. Fabric samples were tested by two methods. In one, small squares (1.0-1.5 cm) were placed on a Tryptic Soy agar plate that was inoculated... 

A hemocytometer can be used to estimate exactly the number of cells in a suspension. The hemocytometer consists of two chambers, each of which is divided into nine 1.0 mm squares (Fig. D.4). A cover glass is supported 0.1 mm over these squares such that the total volume over each square is 1.0 mm x 0.1 mm or 0.1 mm or lO cm . Since 1 cm is approximately equivalent to 1 ml, the cell concentration per ml will be the average count per square x lO. ... 

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