Thick Blood Film

THICK BLOOD FILM, a method for studying morphological elements in a hemolyzed blood drop, introduced into practice by Ross in 1903, which allows viewing 30-50 times more blood in a given period than in a thin smear. Due to its simplicity of preparation, convenience, and time savings, the thick blood film is indispensable when examining blood for malaria, spirochetes, trypanosomes, microfilariae, as well as an additional method for clinical blood examination. Method of preparing a thick blood film: 2-3 drops of blood are placed on a slide and spread with a needle or the corner of the slide to the size of a fifteen-kopeck coin. According to Huppenbauer, the drop is applied to a wet, freshly prepared smear, where it spreads evenly over the surface of the smear, forming a perfect circle; the smear is labeled with a simple pencil, which is perfectly preserved after staining. The advantage of this method is the uniformity of the drop, excluding mechanical damage to elements during spreading; in the thin smear, the stroma of erythrocytes is preserved, which allows studying changes in the shape and size of erythrocytes and the relationship of parasites to erythrocytes; the label on the smear is well preserved, the drop does not crack and adheres well to the glass. Rukhadze recommends placing the slide with a fresh drop somewhat inclined until it dries, as a result of which the blood collects along the lower edge in the form of a crescent, in which the main mass of malaria parasites accumulates. The drops are dried in the air or in an incubator for 1-2 hours and are not subsequently fixed. Staining is most often done with Giemsa solution. Staining can also be done according to Manson (preliminarily, it is necessary to hemolyze the drop with distilled water), Ioffe, and others. For mass work, the method of simultaneously processing a whole series of preparations (Barber and Kotr) is very convenient. Drops are applied closer to the edge of the slide, on the other end of which a label is made. The preparations, separated by layers of cardboard, are fastened with a rubber band from the end opposite to the drops. Staining is done by immersing the lower half of the preparations with drops into a vessel with dye; washing is done by immersing the colored part in water. In the thick blood film, the following are observed: 1) eosinophils, which are particularly well differentiated in a weakly acidic reaction of the dye solution due to their granularity; 2) basophils surrounded by a network of fibrin threads. With respect to both of these types of leukocytes, the thick blood film serves as a method for percentage counting; 3) polychromatophils in the form of a delicate gray-blue mesh; 4) parasites - plasmodia, spirochetes, trypanosomes, microfilariae; 5) endothelium in endocarditis lenta and sepsis; 6) erythrocytes; 7) Innenkörper (methemoglobin bodies) of Heinz-Ehrlich.

I. Demina. TOLUIDINE BLUE, toluidine blue, a basic thiazine dye, a dark green powder that dissolves easily in water with a blue color. In terms of its dyeing properties, toluidine blue is similar to methylene blue and Harris recommends it for vital staining of nerves. Gross recommends injecting a heated 1% solution of toluidine blue into the ear vein of a rabbit to study the excretion of dye in the renal tubules; Anikin for the same purpose uses colored agar plates, which he applies to the exposed surface of the kidney. For staining histological sections, aqueous solutions of 0.3-1.0% concentration are used. Toluidine blue is an excellent nuclear stain, it also stains well the tigroid substance of nerve cells, the granules of mast cells, the ground substance of cartilage, mucus (metachromatically); however, metachromasia usually disappears upon dehydration and to avoid this, sections should be allowed to float on the surface of a solution of the dye heated to 40°, and then they should be picked up on a slide and dried, after which the paraffin is dissolved in xylene, and the sections are mounted in Canadian balsam. Toluidine blue is also included in a number of complex stains - Mann's, Prince's, Ciaccio's, Dominici's.