Feulgen staining of mammalian tissues fixed in picro-formol-acetic acid.

The paper describes a highly satisfactory method for in situ localization of DNA in tissues fixed in picro-formol-acetic acid or picro-formol-acetic-chromic acid mixtures following a technique in the Feulgen procedure as devised by the author. Mammalian tissues fixed in these fixatives can be hydrolysed in 6N HCl at 35 degrees C for 10 min, rinsed in water, stained with Schiff reagent after exposing the sections under UV light for 10 min, washed in water, dehydrated through a graduated series of ethanol, cleared in xylol and mounted in DPX. Sections of tissues fixed in picro-formol-acetic-chromic acid mixtures after acid hydrolysis when stained with an aqueous solution of basic fuchsin are also found to be very satisfactory for in situ localization of DNA.

Hot hydrochloric acid hydrolysis and UV Feulgen staining of rat liver sections fixed in CRAF and CRAF-like fixative.

Sections of rat liver fixed in CRAF III and Nawaschin's fixative in Dutt's modification were subjected to hydrolysis in 1N HCl at 60 degrees C for different periods of time and to Schiff's staining according to the UV Feulgen technique. The study showed that Feulgen reaction intensity depends upon time of hydrolysis, optimum coloration being possible only after 10-15 min of hydrolysis. Prolongation of hydrolysis beyond this time produced decreased staining intensity which is retained for further 35 min of hydrolysis thus forming a plateau.

Increase in Feulgen staining intensity by pre-treatment with different reagents.

In the experiments sections of rat tissues fixed in 10 per cent buffered neutral formalin for 3 hour and treated for 15 minutes with different chemical reagents such as pyridine, tributylamine, urea, tris sodium nitrite and sodium hydroxide were subjected to hydrolysis in 6 N HCl at 25 degrees C for 20 minutes and stained by the UV Feulgen technique. The results reveal a far more intense staining of the nuclei in tissues treated with any of the chemicals mentioned than in untreated controls. The possible role of these chemicals in enhancing the staining intensity is discussed.

Selective staining of animal chromosomes with synthetic dyes following iodine-dye-procedure.

The paper embodies results of the use of 51 synthetic dyes, belonging to different chemical groups for staining of animal chromosomes following iodine-dye procedure. It has been found that some of these dyes can replace gentian violet, crystal violet and safranin when used after this procedure. It has further been found that the fluorescent dyes, acriflavine and acridine yellow can also be used to stain animal chromosomes and that some of the dyes belonging to one chemical group can be successfully used whereas others of the same group are of no use.