Intranuclear inclusions in neurons of the cat primary olfactory system

Intranuclear rodlets in human pancreatic islet cells

OBJECTIVES

Intranuclear rodlets (INRs) are rod-shaped intranuclear inclusions that we have described in neurons of the human brain. We recently identified these structures in pancreatic islet cells. The objectives of this study are to describe the light microscopic features and cellular pattern of distribution of INRs in human pancreatic islet cells.

METHODS

Double immunofluorescence staining was performed on 5 human pancreatic tissue samples for the detection of class III beta tubulin (C3T) to detect INRs and for promyelocytic leukemia (PML) protein to examine the relationship between PML and INRs.

RESULTS

Intranuclear rodlets were detected in 22.99% of pancreatic B cells compared with only 3.11%, 1.80%, and 1.60% of A, D, and PP cells, respectively. Twenty-four percent of C3T-immunoreactive INRs showed partial or complete immunoreactivity for PML. Promyelocytic leukemia staining within the nuclei of B cells was confined to INRs and was not present in the typical PML bodies present in other cell types. Spatially, PML and C3T staining of islet cell INRs appeared to be mutually exclusive within individual INRs.

CONCLUSIONS

Intranuclear rodlets are present within the nuclei of pancreatic islet cells, where they reside predominantly but not exclusively in B cells. Immunoreactivity of B-cell INRs for PML suggests that the functional significance of INRs may be related to that of PML and/or PML bodies. Conversely, the exclusive localization of PML staining to INRs in B cells indicates that PML's function in B cells is selectively associated with INRs. The mutually exclusive pattern of PML and C3T staining suggests dynamic interactions between these 2 proteins in B-cell INRs. In light of evidence for the involvement of INRs and of PML bodies in disease, it will be of interest to investigate these structures in animal models of diabetes and in human diabetes.

Synaptic organization of the pedunculopontine tegmental nucleus of the cat

The synaptic organization of the feline pedunculopontine tegmental nucleus (PPN) was studied electron microscopically. The bouton covering ratios were calculated in various sizes of PPN neurons, and the ratios of large neurons (56%) were found to be much higher than those of small neurons (16%). The PPN neuron dendrites usually showed some varicosities, and spines were observed on both somatic and dendritic profiles. Among a total of 1021 synapses sampled at random, axosomatic, axodendritic and axospinous synapses comprised 21.7, 61.2 and 14.1%, respectively. On the basis of the postsynaptic junction, these synapses were classified into the symmetric (66.3%) and the asymmetric (33.7%) types. The percentage of symmetric synapses was much higher on the soma (91.0%), and the large (69.4%) and medium-sized (63.2%) dendrite, while that of asymmetric synapses showed a higher value on the small dendrite (55.5%) and the dendritic spine (50.8%). Axoaxonic, dendrodendritic and dendroaxonic synapses, although not so frequent, were, in part, involved in the serial synapse or the synaptic triad. It is concluded that some PPN neurons are spiny, and that axosomatic, axodendritic and axospinous synapses are the main synaptic constituents and besides those synapses a more complex synaptic organization exists in this nucleus.

Intranuclear inclusions in rat piriform cortex: increase with age and preferential location within superficial layer II

Intranuclear inclusions have been observed in layer II neurons of rat piriform cortex. These inclusions have the form of a filamentous lattice and resemble those described by others previously. The frequency of lattice-containing nuclei shows a significant fourfold increase over a period of 3-33 months of age, with the largest increase occurring after 18 months. The incidence of these inclusions is highest in the superficial third of layer II and is significantly greater than what would be expected from the distribution of all neuronal nuclei in layer II. The presence of intranuclear lattices may be related to the high level of electrical activity in piriform cortex, and their increase with age may reflect a long-term cumulative effect of this activity.

An ultrastructural study of intranuclear rodlets in a malignant extracranial neuroepithelial neoplasm

This report describes for the first time the presence of intranuclear rodlets in a malignant extracranial neuroepithelial neoplasm. This malignant neoplasm appeared poorly differentiated by light microscopy and presented initially as a diagnostic problem. Electron microscopy revealed neoplastic cells joined by macula adherens-type junctions and containing numerous interdigitating cell processes diagnostic of a neuroepithelial neoplasm. A quantitative analysis of 500 cells revealed the presence of intranuclear rodlets in 5% of the neoplastic cells. The rodlets were composed of individual filaments that measured 7-9 nm in width. An extensive review of the literature revealed the high frequency of reported rodlets in normal neurons, normal paraneurons, neoplasms of the nervous system, and paraneuromas. The significance of this interesting structure to the physiology of the cell is discussed.

Choroid plexus carcinoma. Report of a case with immunohistochemical and ultrastructural observations

A choroid plexus carcinoma from the lateral ventricle of a ten-month-old boy was examined by light and electron microscopy. The neoplasm exhibited papillary and solid areas, invasion of adjacent brain, cytologic anaplasia, and necrosis. Intra- and extracellular PAS positive droplets were present, but no pigment was observed. No glial fibrillary acidic protein was detected within neoplastic cells. Ultrastructural examination revealed irregular nuclei with large nucleoli and occasional intranuclear filamentous rods. Cytoplasmic organelles included a moderate number of free ribosomes, rough endoplasmic reticulum, Golgi complexes, and microtubules. In some areas, numerous mitochondria filled the cytoplasm. Surface specializations included zonulae adherentes, microvilli, and clusters of cilia with a 9 + 0 microtubular pattern. Clusters of basal bodies with prominent basal feet and striated rootlets were present within the cytoplasm. Normal choroid plexus from this patient also had 9 + 0 cilia. In contrast, choroid plexus papillomas from two other infants had cilia with a 9 + 2 pattern. These observations demonstrate that both differentiated and anaplastic choroid plexus neoplasms have the potential to form cilia, and that the microtubular structure of such cilia may deviate from the usual 9 + 2 pattern.

The principal projection pathway between the olfactory bulb and the prepyriform cortex in the cat

The anatomy and neuroelectric properties of the lateral olfactory tract (LOT) were investigated in the cat. Electron micrographs were obtained from sampled areas across the rostro-caudal projection of the pathway. Fiber diameters were estimated and axon spectra were obtained from three regions corresponding to peduncle, mid-LOT, and caudal-LOT. The mean inside diameter for all measured axons was 1.13 +/- 0.53 microns. The greatest number was found in the peduncle (approximately 600,000 axons). Mid-LOT and caudal-LOT each contained approximately 250,000 axons. Unmyelinated processes were estimated to be more numerous than the myelinated axons. Synaptic structures were also observed in the LOT. Cross-sectional area measurements of the LOT were obtained from tissue prepared for light microscopy. The area decreased from about 0.3 to 0.2 mm2 across the projection from olfactory bulb to cortex. The anatomical data were used to predict the conduction properties of transmission over the LOT. The olfactory bulb mitral cells were stimulated electrically and conduction velocity and temporal dispersion were evaluated in the tract. The strength-duration and stimulus-response curves and the potential profile during stimulation were also obtained. The time constant for LOT axons was 0.3 msec. The stimulus-response curve was sigmoidal in shape for both presynaptic and postsynaptic responses. The relationship between input (the action potentials) and output (cortical postsynaptic potentials) was linear up to 90 times threshold. Action potentials were conducted at 20 m/sec across the pathway over the peduncle and decreased to about 10 m/sec in caudal aspects. The potential profile for action potentials decayed exponentially into the depths of the cortex whereas the synaptic potential was a surface negative dipole field. The axon spectra were convolved with the electrophysiological properties of the LOT to mathematically reconstruct action potentials. The empirically derived mono- and biphasic curves fitted reasonably well with experimentally derived data under various stimulus conditions.

Intranuclear rodlets in undifferentiated carcinomas of salivary glands in strain A mice in a study involving a tobacco specific nitrosamine, N-nitrosonornicotine

Undifferentiated carcinomas of the salivary glands were found in 2 of 44 (4.5%) strain A mice injected intraperitoneally with a tobacco specific nitrosamine, N-nitrosonornicotine (NNN). The presence of intranuclear rodlets (INR) in the salivary carcinomas provided the first demonstration of such structures in a non-neuronal tumor in mice. Two types of rodlets were exhibited; one was composed of fibrillar filaments arranged in bundles, and the other was much thicker, branching in form. These INR appeared to be closely associated with nuclear chromatin or nucleoli.

The Merkel cell in oral human mucosa

A study of the mucosal Merkel cells from 10 patients showed that the cell contained an intranuclear rodlet, clear cell qualities, fine desmosomes, characteristic membrane-bound Merkel granules, and cellular "horns" and had a close relationship to terminal axons. The Merkel cell is an intraepithelial cell with features of neurons and of amine-storage cells.

Cyclic AMP and ultrastructural organization of the nerve cell nucleus: stimulation of nuclear microtubules and microfilaments assembly in sympathetic neurons

As we have previously shown for electrical stimulation, in vivo cyclic AMP analogues and theophylline induce an increase (up to 8.5-fold) in the frequency of microtubular-microfilamentous inclusions in the nucleus of sympathetic neurons. These drugs, like electrical stimulation, do not modify the ultrastructural organization of such inclusions, which is briefly reviewed in the present study with the help of tilting experiments. Such data consistent with our previous opinion that microtubules and microfilaments are normal nuclear constituents of these nerve cells, their frequency being related to physiological activity. Moreover, our results may now be discussed in terms of the relationship between these nuclear inclusions and the physiological modulation of transmission through the sympathetic ganglion. Finally, as recently demonstrated in the cytoplasm, the present study shows for the first time that cyclic AMP promotes the assembly of microtubules and microfilaments in the nuclear compartment.

The ultrastructure of the sheath around chronically implanted electrodes in brain

Insulated, bipolar stainless steel electrodes were chronically implanted in various regions of the cat brain and the long-term structural changes in the tissue surrounding the electrodes were studied by light and electron microscopy. A sheath surrounded and separated the electrode from normal grey or white matter. A layer of foreign body giant cells of variable thickness was formed adjacent to the electrode. This layer was attenuated in some places so that it was unrecognizable by light microscopy. The bulk of the sheath structure consisted of collagen fibrils, leptomeningeal cells and hypertrophied astrocytes. Areas consisting of modified leptomeningeal cells with long thin processes we designated as spongy areas. These have not been previously reported using the electron microscope. Glycogen bodies were seen in leptomeningeal cells. Astrocytes became greatly enlarged and were more numerous in and around the sheath. Oligodendrocytes contained lamellar bodies, and direct continuity was shown between a lamellar body and an adjacent myelin sheath. Myelin was seen in abnormal sites (around oligodendrocytes and neurons) and in unusual configurations. Neuronal changes near the sheath included whorls and stacks of modified endoplasmic reticulum and the presence of cytoplasmic nucleolus-like bodies. Reactive, regenerative and degenerative axons were observed. Blood vessels were more numerous in the sheath and surrounding tissue than normal. Perivascular spaces were prominent even around capillaries and often plasma cells and monocytes were in these spaces. As compared to normal tissue the extracellular space is noticeably increased. Electrodes passing through ventricles were surrounded with a sheath covered with ependymal cells. This sheath was comparable in structure to the sheath present around the electrode in other locations.

Intranuclear tonofilaments in verruca vulgaris

Electron microscopic examination of a verruca vulgaris has revealed the intranuclear inclusion of tonofibrils. Although many intracellular inclusions may be related directly to the virus, nonviral inclusions may also be present.

The neurons in the primate subthalamic nucleus: a Golgi and electron microscopic study

In Golgi preparations of the adult monkey (Macaca mulatta) local interneurons and two varieties of principal neurons, radiating and elongated fusiform, are found in the subthalamic nucleus. The cell bodies of the radiating neurons have a few delicate, somatic spines some of which are occasionally bilobed and trilobed. Five to eight dendritic trunks give rise to branching, tapering dendrites, which may extend for over 400 microns. These dendrites are much thinner than the dendrites in the globus pallidus and the substantia nigra. Some neurons have many and some neurons have few dendritic spines. When numerous the dendritic spines are concentrated on the dendritic trunks and proximal dendrites. The relatively few elongated fusiform neurons are found not only in the capsule but also in the center of the nucleus. Most dendrites emerge from the opposite poles of their smooth surfaced cell bodies. They have a few dendritic spines. Some of these dendrites extend for more than 750 microsn. In 1-micron thick plastic sections lipofuscin granules are present in some but not all principal neuron cell bodies of the monkey (Macaca mulatta); but these granules are present in all principal neuron cell bodies of the pig-tail monkey (Macaca nemestrina) and of the squirrel monkey (Saimiri sciureus). The local interneurons have small cell bodies and a few relatively long undulating dendrites. The dendrites have bulbous dendritic appendages of varying complexity and beaded axon-like processes. The dendritic appendages and axon-like processes are more numerous distally and on the distal ends of the dendrites they form complex entanglements. Axons coming from the cell body have not been observed. The cell bodies of the local interneurons are identified in cresyl violet stained sections of the monkey (Macaca mulatta), in 1-micron thick plastic sections and electron micrographs of the squirrel monkey (Saimiri sciureus). They have relatively large nuclei surrounded by a thin rim of cytoplasm rich in polyribosomes.

Lattice and rodlet nuclear inclusions in Merkel cells in rabbit epidermis

A latticee or rodlet inclusion is occasionally observed in the nucleus of a Merkel cell. The lattice has the external form of a plaque or band and internally consists of alternating parallel wide and narrow layers. Filaments in wide layers run in at least two directions across the short dimension of the inclusion. In contrast, the rodlet is a bundle of parallel filaments running the long dimension of the inclusion. Filaments in lattices and rodlets possibly contract and agitate the highly folded nucleus of the Merkel cell.