Fixatives coagulant

The concepts of coagulation and precipitation, common in the classical literature of fixation, are outmoded and confusing a coagulant fixative gels some, but not all proteins, while a precipitant fixative causes only certain proteins to fall out of solution. Instead, we will use terms that actually describe the chemical and physical reality of fixation at the molecular level. 

Another fixative, Kryofix (E. Merck, Darmstadt, Germany) has been recommended as a replacement for formaldehyde in immunohistochemistry by Boon and Kok (1994). Kryofix is a coagulant fixative containing 50% ethyl alcohol and polyethylene glycol (mol. wt. 300). Both ethyl alcohol and polyethylene glycol diffuse rapidly into the tissue, and the tissue fixation is completed in Kryofix in 90 sec with microwave heating. I do not have personal experience with Kryofix. 

Immunohistochemical studies demonstrate that unbuffered zinc formalin (a slow crosslinking fixative) and unbuffered acid formalin yield good preservation of antigens pi85 and TGF, whereas ethanol and methanol (two coagulating fixatives) produce good... 

Confocal laser scanning microscopy can be used in conjunction with microwave heating for examining the three-dimensional structure and cellular interrelationships in sections of paraffin-embedded tissues (Boon and Kok, 1994). Tissues are fixed with Kryofix, a coagulant fixative containing 50% ethyl alcohol and polyethylene glycol (PEG molecular weight 300) for 90 sec in a microwave oven. The use of thick paraffin sections (15 (xm) and fluorescently labeled antibodies is preferred. 

Fig.1 Detection of CD3 T-lymphocyte antigen in 16-h formalin-fixed, paraffin-embedded reactive human tonsil sections. In the absence of HIER the antigen is not detectable in the tissue fixed in neat formaldehyde, but it is stained in tissues fixed either in mixed (formaldehyde and coagulant) or in coagulative fixatives. Increasing the HIER treatment time (PC 2.50 does not substantially improve immunostaining, but adversely affects tissue morphology.

Aluminium species (alum, polyaluminium chloride, polyaluminium silica sulphate, etc.) used for charge control, pH control, as sizing mordants, broke treatment. Synthetic coagulants, fixatives (polyamines, polydadmacs, polyethyleneimines polyvinylamines) used for charge control, as sizing mordants, broke treatment, stickies treatment. 

Fest-werden, n. solidification coagulation, -wert, m. fixed value, constant, -zahl, /. fixed number, constant. 

As an even more explicit example of this effect Figure 6 shows that EPM is able to reproduce fairly well the experimentally observed dependence of the particle number on surfactant concentration for a different monomer, namely methyl methacrylate (MMA). The polymerization was carried at 80°C at a fixed concentration of ammonium persulfate initiator (0.00635 mol dm 3). Because methyl methacrylate is much more water soluble than styrene, the drop off in particle number is not as steep around the critical micelle concentration (22.) In this instance the experimental data do show a leveling off of the particle number at high and low surfactant concentrations as expected from the theory of particle formation by coagulative nucleation of precursor particles formed by homogeneous nucleation, which has been incorporated into EPM. 

Boon ME, Ouwerkerk-Noordam E, Suurmeijer AJH, et al Diagnostic parameters in liquid-based cervical cytology using a coagulant suspension fixative. Acta Cytol. 2005 49 513-519. 

Picric acid (trinitrophenol) and trinitroresorcinol, when added to fixative solutions, give greater fine structural preservation of cells (11,12). These compounds cause coagulation of proteins by forming salts with positively charged groups of proteins (11). The protein precipitates that form retain their antigenicity (3). Picric acid or trinitroresorcinol are most often added to formalde-... 

Alcohols and acetone are the simplest kinds of membrane permeabilization agents. They act by dissolving membrane lipids, thus rendering the membrane permeable to antibodies (5). Because of their coagulant effects on proteins, these solvents can be used as a one-step fixative and permeant (18). 

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