Nonne-Apelt Reaction

NONNE-APELT REACTION (M. Nonne, F. Apelt), developed and proposed in 1907 by Nonne and Apelt for the qualitative determination of protein fractions in the cerebrospinal fluid. It consists of two phases: the 1st phase is the precipitation of globulins by a half-saturated solution of ammonium sulfate; the 2nd phase—after filtration in a filtrate acidified with acetic acid, albumins are precipitated by boiling. The 2nd phase of the reaction has no practical significance or application, since albumins are always found in normal fluid as well, and nowadays by the Nonne-Apelt reaction its 1st phase is understood. — T e c h n i q u e: The reagent is prepared as follows: 85.0 grams of pure neutral ammonium sulfate are boiled in 100 cubic centimeters of distilled water until dissolution ceases, then gradually cooled. Upon cooling, it is filtered, and the filtrate is used for the reaction. The reagent must be neutral; in case of its oxidation (litmus test), ammonium hydroxide solution is added to it until a neutral reaction is achieved. — R e a c t i o n: Equal amounts of cerebrospinal fluid and reagent are mixed in a test tube, and after 3 minutes the result is determined by comparing the mixture with the whole fluid in transmitted light or against a dark background. If the mixture remains transparent, the reaction is negative (-). In positive cases, various degrees of changes in transparency are discovered: traces of opalescence (±), clear opalescence (+), turbidity (++), sharp turbidity (+++). A positive Nonne-Apelt reaction is obtained in all forms of syphilis of the central nervous system, in all meningitis cases, and to a lesser extent in other organic diseases of the central nervous system. The reaction is not suitable for the etiological diagnosis of nervous diseases. Modifications of the reaction: 1. Ross-Jones modification; 1 cubic centimeter of cerebrospinal fluid is layered with the same amount of a saturated solution of ammonium sulfate, for which a pipette with the reagent, with the opening tightly blocked by a finger, is lowered to the bottom of the test tube with the cerebrospinal fluid and, cautiously removing the finger, the reagent is released, after which the pipette is also withdrawn. A white ring forms at the boundary of the liquids in pathological cases. The result is noted after 3 minutes. The reaction by this method is also performed with diluted cerebrospinal fluid (2, 4, 8, etc. times). This method gives more precise results and allows the differentiation of certain nervous system diseases. 2. Kafka modification, which consists in precipitating individual globulin fractions for which various concentrations of ammonium sulfate are used: 50% (all fractions), 40% (pseudoglobulin), 33% (euglobulin), and 28% (fibrin globulin or fibrinogen). The reaction is set up in Nissl test tubes according to the following scheme: [Table of solutions and test tubes not reproduced]. After mixing, the result is noted after 3 minutes, then after 4–5 hours, and finally after 16–24 hours of standing at room temperature and after preliminary centrifugation. Test tube 4 corresponds to the 1st phase of the Nonne-Apelt reaction. Kafka's fractional method reveals that fibrin globulins (precipitation at 28%) are most characteristic of meningitis, euglobulins (precipitation at 33%) for progressive paralysis, and pseudoglobulins (precipitation at 40% or 50%) for the remaining forms of nervous system syphilis, which is why this method acquires significance in recognizing various forms of neurolues.