RESUMEN
The effect of severe protein deficiency at weaning has been studied in bone marrow, which is a primary lymphoid organ. Our experimental model of secondary immunodeficiency in Wistar rats has shown: (1) a decreased number of viable bone marrow cells (P <.0001); (2) diminished percentage of mitosis (P <.01); and (3) severe alteration in the percentage of chromosome pairs 3, 11, and 12 bearing nucleolar organizer regions (NORs) (P <.05). This last finding indicates a poor ribosomal gene activity. These alterations were reverted after the oral administration of a 20% casein diet during 5 to 9 days. However, there were no karyotype variations between the experimental groups. We conclude from these results that severe protein deficiency at weaning alters several aspects of bone marrow cell proliferation and ribosomal gene activity as determined by the number of silver stained nucleolus organizer regions.