Gel diffusion test

Five out of six patients gave a positive precipitin test. Malarial antigen was extracted from human brain for gel diffusion tests. 

From Pasteurella tularensis, a polysaccharide was extracted, but no chemical data were given. In another report,the material was thought to contain hexosamine, but qualitative tests for other sugars were negative and the substance gave several lines of precipitation in the antigen-antibody gel-diffusion test. 

Typical protocols for dermal sensitization, active systemic anaphylaxis, and passive cutaneous anaphylaxis tests are given in the article Animals in Drug Development, in this encyclopedia. In a typical gel-diffusion test, solutions of test compound, egg albumin (positive control), or vehicle (usually saline) are mixed with complete Freund s adjuvant. These mixtures are injected into animals (usually guinea pigs) of the... 

Immunological methods Methods such as gel-agglutination tests were introduced many years ago (according to Outcherlony) however they are not sufficiently sensitive. Reversed passive latex agglutination kits (SET-RPLA and TST-RPLA) are presently applied for enterotoxin detection and are more sensitive than gel diffusion (Wieneke, 1988). The ELISA technique is also very popular - toxins are detected via VIDAS STAPH ENTEROTOXIN SET and indirect double sandwich ELISA (Meyrand et al., 1998). 

Agar-diffusion tests with the anti-isomaltose, myeloma protein and several dextran preparations showed that the protein does indeed combine with a number of dextrans. Results of gel electrophoresis of the sample showed that the purified myeloma protein consisted of several multimolecular forms.107 This observation is at variance with a report that the W3129 myeloma protein isolated from the same type of serum was homogeneous.168 Additional studies are needed in order to establish whether the anti-isomaltose, myeloma protein is synthesized as a homogeneous protein or in multimolecular form. 

The third variation that exploits unsliced gels is based on the following principle the gel is, after isoelectric focusing, incubated with antiserum and the non-precipitated proteins are eluted. Further processing, e.g., staining and destaining is conventional. Methods that use slicing can be also modified in at least three different ways the individual sections can be tested by double gel diffusion, radial diffusion or immunoelectrophoresis. 

In two sensitised workers exposed to diphenylmethane diisocyanate (MDI), used for coating pipes with a polyurethane foam, tests with an MDI-human serum albumin conjugate showed the presence of specific IgE antibodies as measured by polystyrene tube radioimmunoassay (PTRIA) procedures (Zeiss et al. 1979). High levels of specific IgG antibody were found, with some cross-reactivity with a TDI-human serum albumin conjugate. The serum of one of the workers gave a positive precipitin reaction in the double diffusion test in gel. The authors suggest that these antibodies may be related to the respiratory reactions to the inhaled chemical. 

In agar gel double diffusion tests, no precipitating antibodies against HES were detected in sera of eight patients with anaphylactoid reactions to HES (Ring et al. 1976). No tests with more sensitive techniques have been performed. 

In the second series of measurements both the polymer and the silicate content of the gel were identical, the same original H+ concentration gradient was applied but the amount of HCI added to initiate the gelation of the silicates changed between 0.1550 and 0.1877 mol/1. The diffusion tests were carried out at eight different acid concentrations and the same evaluation technique and calculations were used as previously. 

This is similar to the double diffusion test in that antibody and antigen are placed in two adjacent holes cut out of an agar gel. They are caused to migrate towards one another by application of an electric field. Interaction between antibody and antigen results in a precipitation linq. This technique thus has the advantage of being much faster than the simple double diffusion test. It is used for example for the detection of Australia antigen. 

In the agar gel double diffusion test a band with two precipitin lines appeared when normal hemolysate reacted with antiserum (Fig. 1). Two precipitin lines were formed when we used the patients hemolysates in the Ouchterlony test (Fig. 1) Inspite of the deficiency of enzyme activities in the erythrocytes of our patients these precipitin lines showed a complete identity with the lines of the hemolysate from the healthy control person. 

Gel Diffusion Methods. Many types of gel reactions have been used in the detection of the enterotoxins, the most common ones being some form of either the Ouchterlony gel plate or the microslide. These methods have been used widely in the determination of the enterotoxigenicity of staphylococcal strains. The modification of the Ouchterlony gel plate test that is used in the Food Research Institute and recommended to others is the optimum sensitivity plate (OSP) method (Robbins et al., 1974 Fig. 2). It is easy to use and in conjunction with production of the enterotoxins by the membrane-over-agar or sac culture methods (Robbins et al.,1974) is of adequate sensitivity for detection of most enterotoxigenic... 

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