PREFERENTIAL SILVER REACTION OF NUCLEOLAR REGIONS ADJACENT TO FIBRILLAR CENTERS IN RING-SHAPED NUCLEOLI OF LEUKEMIC LYMPHOCYTES

Silver stained proteins (SSPs) characteristic for interphasic nucleolu s organizer regions (NORs) associated with fibrillar centers (FCs) and adjacent nucleolar regions of ring shaped nucleoli in leukemic lympho cytes exhibit a different sensitivity to the mild acid extraction incl uding that with HCl. Such extractions permit a preferential visualizat ion of fibrillar centers adjacent regions (FCARs) which are believed t o represent sites of the ribosomal RNA (rRNA) transcription. The resis tance of SSPs in FCARs to the extraction with HCl seems to be due to t heir binding to other components present in these regions. The extract ibility of SSPs with HCl was influenced by the fixatives used. The lar gest resistence of SSPs to the extraction with HCl was noted after fix ation with glutaraldehyde. In contrast, the largest extractibility of these proteins was observed after fixation with unbuffered formaldehyd e.