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Filamentous intranuclear bodies and associated multilaminate figures
545
SHORT COMMUNICATIONS
Filamentous intranuclear bodies and associated multilaminate figures Unusual intranuclear structures have been reported occasionally in a variety of cells. These structures have been both normal cytoplasmic organelles4, 5 and other structures foreign to either cell compartment z. Usually these structures were associated with neoplastic cells 3-5 or other cellular abnormalities s. Intranuclear profiles bound by a double unit membrane usually are throught to be derived from the nuclear envelope 2. Since they are believed to be continuous with the nucleal envelope and cytoplasm in another plane of section, they are called pseudoinclusions z. The present report deals with large (up to 10 #m) intranuclear bodies which were bound by a double unit membrane but contained substructures not common to the cytoplasm of the same cells. These intranuclear bodies were found in a small number of neurons in the lateral mammillary nucleus of each immature rabbit studied 6. The contents of these bodies consisted of clumps of vesicles and dense aggregations of neurofilaments. In addition, multilaminate figures occasionally were found either within or outside the intranuclear bodies (Fig. 2). In most of the tissue sections observed, the intranuclear bodies did not appear to be attached to the nuclear envelope, but one section was found in which continuity was clearly evident (Fig. 1). Because of the dilated appearance it was suspected that the intranuclear body was being pinched off to eventually lie free in the nucleoplasm. This was a tempting hypothesis for several reasons. First, the apparent lack of attachment in most cases suggested a 'free floating' body. Second, the presence of a dense mass of neurofilaments is usually associated with neuronal degenerationT, 12 which might be due to isolation from the cytoplasm proper. The multilaminate figures, which were often closely associated
Fig. 1. An intranuclear body having continuity with the nuclear envelope and the cytoplasm. Multilaminated figures (arrows) are scattered in the nucleoplasm, x 10,800. Brain Research, 33 (1971) 545-547
546
SHORT ( ' O M M U N I C A ' I IONS
Fig. 2. Two intranuclear bodies within a single neuron. A multilaminate figure (arrow) appears to have been elaborated by the adjacent intranuclear body. × 4,400. Fig. 3. A shrunken intranuclear body in contact with an enlarged nucleolus. 4,400. with the intranuclear bodies (Fig. 2), also indicated that a degenerative process was taking place. Third, rough endoplasmic reticulum was only found in the case where cytoplasmic continuity was evident (Fig. 1). Due to the presence of this normal cytoplasmic component, it was believed that this particular intranuclear body was recently formed. The more commonly occurring appearance (Fig. 2) was thought to represent a mature intranuclear body. In a few instances, shrunken intranuclear bodies were found which were completely filled with neurofilamentous material (Fig. 3), and wine thought to represent a terminal stage of these structures. This seemed more reasonable than degeneration localized to a nuclear infolding. The probability of finding an area of attachment was calculated using measurements derived from Fig. 1 and a spherical model to yield one in 750. Based upon this value it was impossible to establish from the present data that the intranuclear bodies are pinched off from the nuclear envelope. Serial ultrathin sections might resolve this question. Spontaneous neuronal degeneration is a common occurrence in neural ontogeny 8. This fact may be related to the apparent restriction of the intranuclear bodies to immature animals. Other cases of this phenomenon s have been correlated with loss of axonal projection fields but no similar correlation coulG be made in this case. A few of the simple neuronal infoldings were in contact with the nucleolus and similar nucleolar associations were made with respect to some of the intranuclear bodies (Fig. 3). Also some of the nucleoli were enlarged. Both of these changes are found in neoplastic cells2, 9 and may indicate hyperactivity of the cell. This interpretation is in agreement with the theory that neurofilamentous proliferation actually represents an abortive regeneration 7. Brain Research, 33 (1971) 545-547
SHORT COMMUNICATIONS
547
There have been several ultrastructural studies of the nucleo-cytoplasmic relationshipX,l°, 11, but none have revealed structures with any resemblance to those described in this report. Cytoplasmic invaginations into the nucleus seem to be an expression of cytoplasmic demand for nuclear R N A 11. For this reason, the most extensive invaginations would be expected in those cells involved in intensive protein production. The findings of this study are in accord with these expectations since the intranuclear bodies were found in large cells with an extensive endoplasmic reticulum and were only present during a stage of rapid growth. This observation should provide a convenient model for the study of nucleo-cytoplasmic relationships in the nervous system. This work was supported in part by VMRC-188, School of Veterinary Medicine, University of Missouri, Columbia. The authors thank Mrs. Gladys Clark for technical assistance. Department of Veterinary Anatomy, University of Missouri, Columbia, Mo. 65201 (U.S.A.)
VICTOR COX JAMES BREAZILE
1 BERNHARD, W., Ultrastructural aspects of nucleo-cytoplasmic relationship, Exp. Cell Res.,
Suppl. 6 (1958) 17-50. 2 BERNHARD,W., AND GRANBOULAN,B., The fine structure of the cancer nucleus, Exp. Cell Res., Suppl. 9 (1963) 19-53. 3 BOUTEILLE,M., KALIFAT,S. g., ANDDELARUE,J., Ultrastructural variations of nuclear bodies in human diseases, J. Ultrastruct. Res., 19 (1967) 474-486. 4 BRANDES,D., SCHOHELD,B., AND ANTON,E., Nuclear mitochondria?, Science, 149 (1965) 13731374. 5 BUCCIARELL,E., Intranuclear cisternae resembling structures of the Golgi complex, J. Cell Biol., 30 (1966) 664-665. 6 Cox, V. S., A Fine Structural Study of Retrograde Transsynaptic Degeneration, Ph.D. Thesis, Univ. of Missouri, Columbia, Mo., 1970, p. 63. 7 GRAY, E. G., AND GUILLERY,R. W., Studies of degeneration in the nervous system, Int. Rev. CytoL, 19 (1966) 162-182. 8 MONTALCINI,R. L., Events in the developing nervous system, Progr. Brain Res., 4 (1964) 1-29. 90nERLING, C., The structure of the cytoplasm, Int. Rev. Cytol., 8 (1959) 1-31. 10 SCHJEIDE,O., MCCANDLESS,A., RUTH, G., AND MUNN, R., Nuclear-cytoplasmic interactions, Nature (Lond.), 205 (1965) 156-158. 11 SHIMIZU,N., ANDISHn,S., Electron microscopicobservations on nucleolar extrusion in nerve cells of the rat hypothalamus, Z. Zellforsch., 67 (1965) 367-372. 12 WISNIEWSKI,H., TERRY, R., AND HIRANO,A., Neurofibrillary pathology, J. Neuropath. exp. Neurol., 29 (1970) 163-176. (Accepted July 12th, 1971)
Brain Research, 33 (1971) 545-547
SHORT COMMUNICATIONS
Filamentous intranuclear bodies and associated multilaminate figures Unusual intranuclear structures have been reported occasionally in a variety of cells. These structures have been both normal cytoplasmic organelles4, 5 and other structures foreign to either cell compartment z. Usually these structures were associated with neoplastic cells 3-5 or other cellular abnormalities s. Intranuclear profiles bound by a double unit membrane usually are throught to be derived from the nuclear envelope 2. Since they are believed to be continuous with the nucleal envelope and cytoplasm in another plane of section, they are called pseudoinclusions z. The present report deals with large (up to 10 #m) intranuclear bodies which were bound by a double unit membrane but contained substructures not common to the cytoplasm of the same cells. These intranuclear bodies were found in a small number of neurons in the lateral mammillary nucleus of each immature rabbit studied 6. The contents of these bodies consisted of clumps of vesicles and dense aggregations of neurofilaments. In addition, multilaminate figures occasionally were found either within or outside the intranuclear bodies (Fig. 2). In most of the tissue sections observed, the intranuclear bodies did not appear to be attached to the nuclear envelope, but one section was found in which continuity was clearly evident (Fig. 1). Because of the dilated appearance it was suspected that the intranuclear body was being pinched off to eventually lie free in the nucleoplasm. This was a tempting hypothesis for several reasons. First, the apparent lack of attachment in most cases suggested a 'free floating' body. Second, the presence of a dense mass of neurofilaments is usually associated with neuronal degenerationT, 12 which might be due to isolation from the cytoplasm proper. The multilaminate figures, which were often closely associated
Fig. 1. An intranuclear body having continuity with the nuclear envelope and the cytoplasm. Multilaminated figures (arrows) are scattered in the nucleoplasm, x 10,800. Brain Research, 33 (1971) 545-547
546
SHORT ( ' O M M U N I C A ' I IONS
Fig. 2. Two intranuclear bodies within a single neuron. A multilaminate figure (arrow) appears to have been elaborated by the adjacent intranuclear body. × 4,400. Fig. 3. A shrunken intranuclear body in contact with an enlarged nucleolus. 4,400. with the intranuclear bodies (Fig. 2), also indicated that a degenerative process was taking place. Third, rough endoplasmic reticulum was only found in the case where cytoplasmic continuity was evident (Fig. 1). Due to the presence of this normal cytoplasmic component, it was believed that this particular intranuclear body was recently formed. The more commonly occurring appearance (Fig. 2) was thought to represent a mature intranuclear body. In a few instances, shrunken intranuclear bodies were found which were completely filled with neurofilamentous material (Fig. 3), and wine thought to represent a terminal stage of these structures. This seemed more reasonable than degeneration localized to a nuclear infolding. The probability of finding an area of attachment was calculated using measurements derived from Fig. 1 and a spherical model to yield one in 750. Based upon this value it was impossible to establish from the present data that the intranuclear bodies are pinched off from the nuclear envelope. Serial ultrathin sections might resolve this question. Spontaneous neuronal degeneration is a common occurrence in neural ontogeny 8. This fact may be related to the apparent restriction of the intranuclear bodies to immature animals. Other cases of this phenomenon s have been correlated with loss of axonal projection fields but no similar correlation coulG be made in this case. A few of the simple neuronal infoldings were in contact with the nucleolus and similar nucleolar associations were made with respect to some of the intranuclear bodies (Fig. 3). Also some of the nucleoli were enlarged. Both of these changes are found in neoplastic cells2, 9 and may indicate hyperactivity of the cell. This interpretation is in agreement with the theory that neurofilamentous proliferation actually represents an abortive regeneration 7. Brain Research, 33 (1971) 545-547
SHORT COMMUNICATIONS
547
There have been several ultrastructural studies of the nucleo-cytoplasmic relationshipX,l°, 11, but none have revealed structures with any resemblance to those described in this report. Cytoplasmic invaginations into the nucleus seem to be an expression of cytoplasmic demand for nuclear R N A 11. For this reason, the most extensive invaginations would be expected in those cells involved in intensive protein production. The findings of this study are in accord with these expectations since the intranuclear bodies were found in large cells with an extensive endoplasmic reticulum and were only present during a stage of rapid growth. This observation should provide a convenient model for the study of nucleo-cytoplasmic relationships in the nervous system. This work was supported in part by VMRC-188, School of Veterinary Medicine, University of Missouri, Columbia. The authors thank Mrs. Gladys Clark for technical assistance. Department of Veterinary Anatomy, University of Missouri, Columbia, Mo. 65201 (U.S.A.)
VICTOR COX JAMES BREAZILE
1 BERNHARD, W., Ultrastructural aspects of nucleo-cytoplasmic relationship, Exp. Cell Res.,
Suppl. 6 (1958) 17-50. 2 BERNHARD,W., AND GRANBOULAN,B., The fine structure of the cancer nucleus, Exp. Cell Res., Suppl. 9 (1963) 19-53. 3 BOUTEILLE,M., KALIFAT,S. g., ANDDELARUE,J., Ultrastructural variations of nuclear bodies in human diseases, J. Ultrastruct. Res., 19 (1967) 474-486. 4 BRANDES,D., SCHOHELD,B., AND ANTON,E., Nuclear mitochondria?, Science, 149 (1965) 13731374. 5 BUCCIARELL,E., Intranuclear cisternae resembling structures of the Golgi complex, J. Cell Biol., 30 (1966) 664-665. 6 Cox, V. S., A Fine Structural Study of Retrograde Transsynaptic Degeneration, Ph.D. Thesis, Univ. of Missouri, Columbia, Mo., 1970, p. 63. 7 GRAY, E. G., AND GUILLERY,R. W., Studies of degeneration in the nervous system, Int. Rev. CytoL, 19 (1966) 162-182. 8 MONTALCINI,R. L., Events in the developing nervous system, Progr. Brain Res., 4 (1964) 1-29. 90nERLING, C., The structure of the cytoplasm, Int. Rev. Cytol., 8 (1959) 1-31. 10 SCHJEIDE,O., MCCANDLESS,A., RUTH, G., AND MUNN, R., Nuclear-cytoplasmic interactions, Nature (Lond.), 205 (1965) 156-158. 11 SHIMIZU,N., ANDISHn,S., Electron microscopicobservations on nucleolar extrusion in nerve cells of the rat hypothalamus, Z. Zellforsch., 67 (1965) 367-372. 12 WISNIEWSKI,H., TERRY, R., AND HIRANO,A., Neurofibrillary pathology, J. Neuropath. exp. Neurol., 29 (1970) 163-176. (Accepted July 12th, 1971)
Brain Research, 33 (1971) 545-547