No abstract

Long-term organotypic cultures of rat dorsal root ganglia were cxposed to a single 40 kR dose of 184 kvp X-rays and studied in the living and fixed states by light or electron microscopy at 1-14 day intervals thereafter. Within the first 4 days following irradiation, over 30% of the neurons display chromatolytic reactions (cccentrlc nuclci, peripheral dispersal of Nissl substance, central granular zone) as well as abnormal nuclcolar changes and dissociation of ribosomes from endoplasmic reticulum cisternae. Some satellite cells undergo retraction or acute degeneration, leaving only basement membrane to cover the neuron in these areas. 8 days after irradiation, neurons also exhibit (a) arcas in which ribosomes are substantially reduced, (b) regions of cytoplasmic sequestration, (c) extensive vacuolization of granular endoplasmic rcticulum and Golgi complex, and (d) diversely altered mitochondria (including the presencc of ribosome-like particles or association with abnormal glycogen and lipid deposits). Nucleolar components become altered or reoriented and may form abnormal projections and ringlike configurations. Sizeable areas of the neuronal soma are now denuded of satellite cells; underlying these areas, nerve processes arc found abnormally invaginated into the neuronal cytoplasm. By the 14th day following irradiation, most neurons display markcd degenerative changes including extensive regions of ribosome depletion, sequestration, vacuolization, autolysis, and, in some areas, swirls of filaments, myelin figures, and heterogeneous dense bodies. These observations demonstrate that X-irradiation produces profound cytopathological changes in nervous tissue isolated from the host and that many of these changes resemble the effects of radiation on nervous tissue in vivo.

No abstract

Correlative data are presented here on the developmental history, dynamics, histochemistry, and fine structure of intranuclear rodlets in chicken sympathetic neurons from in vivo material and long-term organized tissue cultures . The rodlets consist of bundles of -70 t 10 A proteinaceous filaments closely associated with -0 .4-0 .8 µ spheroidal, granulofibrillar (gf) bodies of a related nature . These bodies are already present in the developing embryo a week or more in advance of the rodlets . In early formative stages rodlets consist of small clusters of aligned filaments contiguous with the gf-bodies. As neuronal differentiation progresses these filaments increase in number and become organized into well-ordered polyhedral arrays . Time-lapse cinemicrography reveals transient changes in rodlet contour associated with intrinsic factors, changes in form and position of the nucleolus with respect to the rodlet, and activity of the gf-bodies . With the electron microscope filaments may be seen extending between the nucleolus, gf-bodies, and rodlets ; nucleoli display circumscribed regions with fine structural features and staining reactions reminiscent of those of gf-bodies . We suggest that the latter may be derivatives of the nucleolus and that the two may act together in the assemblage and functional dynamics of the rodlet . The egress of rodlet filaments into the cytoplasm raises the possibility that these might represent a source of the cell's filamentous constituents .