Further studies on the nature of neural intranuclear inclusions (Roncoroni bodies) (with 2 color plates)

It is generally accepted that chromosomes are not visible in interphase except in certain diptera, amphibia and rare unicellular organisms where they are represented by polytene, giant chromosomes. Such structures are exemplified by cells in which growth is evident by increase in size while the polytene structures increase in size rather than in number. These giant chromosomes are active metabolically, synthesizing mRNA and causing increasing activity in the corresponding cells. Experimental procedures leading to increased activity in neurones were accompanied by the appearance of nuclear inclusions which behaved very much like the polytene chromosomes metabolically and, as a result, an attempt was made to determine whether they had similar chemical behavior. This proved to be demonstrable and so it is concluded that the Roncoroni body represents a metabolically active interphase chromosomal segment and may be used as a sign of such activity.