Nuclear inclusions in sympathetic neurons: a quantitative and ultrastructural study in the superior cervical and celiac ganglia of the cat

Loukoumasomes Are Distinct Subcellular Structures from Rods and Rings and Are Structurally Associated with MAP2 and the Nuclear Envelope in Retinal Cells

“Rods and rings” (RR) and loukoumasomes are similarly shaped, subcellular macromolecular structures with as yet unknown function. RR, so named because of their shape, are formed in response to inhibition in the GTP or CTP synthetic pathways and are highly enriched in the two key enzymes of the nucleotide synthetic pathway. Loukoumasomes also occur as linear and toroidal bodies and were initially inferred to be the same as RR, largely due to their shared shape and size and the fact that it was unclear if they shared the same subcomponents. In human retinoblastoma tissue and cells we have observed toroidal, perinuclear, macromolecular structures of similar size and antigenicity to those previously reported in neurons (neuronal-loukoumasomes). To further characterize the subcomponents of the retinal-loukoumasomes, confocal analysis following immunocytochemical staining for alpha-tubulin, beta-III tubulin and detyrosinated tubulin was performed. These studies indicate that retinal-loukoumasomes are enriched for beta-III tubulin and other tubulins associated with microtubules. Immunofluorescence together with the in situ proximity ligation assay (PLA), confirmed that beta-III tubulin colocalized with detyrosinated tubulin within loukoumasomes. Our results indicate that these tissues contain only loukoumasomes because these macromolecular structures are immunoreactive with an anti-tubulin antibody but are not recognized by the prototype anti-RR/inosine monophosphate dehydrogenase (IMPDH) antibody (It2006). To further compare the RR and retinal-loukoumasomes, retinoblastoma cells were exposed to the IMPDH-inhibitor ribavirin, a drug known to induce the formation of RR. In contrast to RR, the production of retinal-loukoumasomes was unaffected. Coimmunostaining of Y79 cells for beta-III tubulin and IMPDH indicate that these cells, when treated with ribavirin, can contain both retinal-loukoumasomes and RR and that these structures are antigenically distinct. Subcellular fractionation studies indicate that ribavirin increased the RR subcomponent, IMPDH, in the nuclear fraction of Y79 cells from 21.3 ± 5.8% (0 mM ribavirin) to 122.8 ± 7.9% (1 mM ribavirin) while the subcellular localization of the retinal-loukoumasome subcomponent tubulin went unaltered. Further characterization of retinal-loukoumasomes in retinoblastoma cells reveals that they are intimately associated with lamin folds within the nuclear envelope. Using immunofluorescence and the in situ PLA in this cell type, we have observed colocalization of beta-III tubulin with MAP2. As MAP2 is a microtubule-associated protein implicated in microtubule crosslinking, this supports a role for microtubule crosslinkers in the formation of retinal-loukoumasomes. Together, these results suggest that loukoumasomes and RR are distinct subcellular macromolecular structures, formed by different cellular processes and that there are other loukoumasome-like structures within retinal tissues and cells.

Intranuclear crystalloids in arcuate nucleus neurons after clomiphene citrate administration

The action of high doses of clomiphene citrate on the nuclei of hypothalamic arcuate neurons of male cats has been studied. Clomiphene produces an accumulation of typical crystalloid material in the nuclei. After administration of a protein-synthesis inhibitor, no such material was observed in clomiphene-treated animals. These ultrastructural features could possibly be due to a more intense protein synthesis in the hypothalamic arcuate neurons.

[Giant mitochondria in the A cells of the pancreas of a lizard: Varanus niloticus]

Pancreatic A cells of the lizard Varanus niloticus are characterized by the presence of two types of mitochondria: (a) normal, small mitochondria (about 0.4 X 1 micron), and (b) giant mitochondria, measuring up to 9 micron in length and 1 micron in diameter. Giant mitochondria show various shapes. Their matrix is filled with tubules, filaments, and dense granules. Transverse sections of tubules are polygonal in shape and about 20 nm in diameter. They are grouped in bundles. The filaments, about 9-10 nm in diameter, are arranged in parallel layers crossing each other at a 57 degree angle. In a closely related species, Varanus exanthematicus, pancreatic A cells do not show these peculiar features.

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.

Frequency and distribution of tubulo-filamentous nuclear inclusions in the celiac ganglion of the cat as revealed by serial sections

On sections at random of a cat celiac ganglion we counted 68 sections of nuclear inclusions (NI) for 320 sections of neuronal nuclei, i.e. an "apparent' frequency of 0.20. As revealed by serial sections the "actual' frequency is higher since the 5 nuclei entirely explored exhibit 19 NI. Such a study shows that each nucleus may contain at least 3 and up to 5 different tubulo-filamentous NI.