The Effect of Vincristine Sulphate on the Axoplasmic Flow of Proteins in Cultured Sympathetic Neurons

Vincristine-induced changes in the retina of the isolated arterially-perfused cat eye

We have attempted to determine in this study whether the arterial administration of vincristine produces in cat the functional defects associated with hereditary and vincristine-induced night blindness in man. Using the isolated perfused cat eye, it has been possible to mimic some of the essential features of human night blindness, namely, retention of normal rhodopsin chemistry and normal photoreceptor activity, with marked suppression of the ERG b-wave. In addition, we find that vincristine produces an early, rapid fall in the c-wave, a potential that arises largely in the pigment epithelium. Ultrastructurally, it appears that many classes of retinal neuron are affected by the drug, but the principal changes in cytoarchitecture are seen in the photoreceptors. Except for the outer segments, paracrystalline deposits were found in all parts of the visual cell. The disruption of the normal microtubular organization of these cells suggests that the drug interferes with the functional integrity of the transport system by which synaptic activity is maintained. By reducing the efficacy of communication between visual cells and their second-order neurons, the electrical responses of post-synaptic elements is degraded. The route by which vinca alkaloids reach the neural retina is still uncertain, but our preliminary studies using HRP indicate that the relatively high concentration of vincristine used in this study may be responsible for compromising the blood-retinal barrier.

Ultrastructural observations on the vincristine-induced neuronal crystalloid inclusion in young rats

Vincristine-induced crystalloid inclusions were examined in the neurons and neuronal processes of young rats by the electron microscope (EM) equipped with a tilting stage. Using a computer system that reproduces three-dimensional organization, an optical transformation method was applied to the microtubules and neurofilaments in an attempt to clarify the morphological appearance and internal pattern of crystalloid inclusions. The dimensional models obtained were compared with actual EM photographs, and the characteristic ultrastructural component and morphology were drawn out. Basically, a crystalloid inclusion is composed of four strands of intermediate 10 nm neurofilaments connected to one another by four side-arms producing a circular profile on a transverse section. These four side-arms seemed to arise from nodules within the filaments at regular intervals simulating a bead-like appearance. These data did not significantly differ from those obtained from EM images. Characteristically, these crystalloid inclusions began to appear 6 h after the administration of 10(-3) M vincristine sulfate and persisted up to a period of 6 days. Beyond that, however, these inclusions were no longer demonstrable suggesting a transient state. This was in contrast to neurofibrillary tangles which appeared to be permanent changes.

Ultrastructural studies of the superior cervical trunk of the mouse: distribution, cytochemistry and stability of fibrous elements in preganglionic fibers

The ultrastructure of axons in the preganglionic cervical sympathetic trunk of the mouse is described with emphasis on the number, distribution and stability of fibrous elements in the axoplasm. Neurofilaments outnumbered microtubules in myelinated and non-myelinated axons of all sizes, and the ratio of neurofilaments to microtubules in non-myelinated axons at each point studied was fairly consistent and independent of axonal diameter. The density of neurofilaments and microtubules, however, was greater in axons of progressively smaller diameter. In non-myelinated axons and small myelinated axons neurofilaments were uniformly distributed throughout the axoplasm resulting in minimum and maximum interfilament distances of 300 angstrom and 500 angstrom respectively; the spacing of fibrous elements within any one axon was dependent upon its diameter and position with respect to the superior cervical ganglion in the preganglionic trunk. The maximum interfilament distance was also found in large myelinated axons where neurofilaments, occurring in fascicles, were separated by distances of approximately 500 angstroms. Cytochemical staining of axons with lanthanum hydroxide, ruthenium red or alkaline bismuth delineated the delicate filamentous matrix interconnecting microtubules, neurofilaments and other organelles in the axoplasm. Alkaline bismuth stain was most intense in myelinated axons where heaviest deposition of reaction product was associated with neurofilaments. Treatment in vitro of the cervical sympathetic trunk with 5 X 10(-5) M vinblastine sulfate dissociated microtubules and induced formation of crystalline arrays of "tubular" elements. A uniform center to center spacing of 250-300 angstrom was found for crystalloids in non-myelinted axons; however, in myelinated axons the center to center spacing was not uniform and varied in the range 300-600 angstrom. Neurofilaments and their surface projections were unaffected by vinblastine. Fixation in the presence of lanthanum enhanced delineation of crystalloid elements. Exposure of 0-4 degrees C for up to three hours had no consistent effect on microtubules or neurofilaments. In contrast, cold treatment disrupted the delicate axonal matrix and resulted in the formation of aggregates of coarse flocculent material in the axoplasm.

Preparation of pure neuronal and non-neuronal cultures from embryonic chick sympathetic ganglia: a new method based on both differential cell adhesiveness and the formation of homotypic neuronal aggregates

A new method has been developed for the preparation of essentially pure primary cultures of neurons and non-neuronal cells from 11-day embryonic chick sympathetic ganglia. This method utilizes (1) differences in cell-to-substrate adhesiveness between neurons and non-neuronal cells and (2) the capacity of neurons to form homotypic aggragates. The maximum difference in adhesiveness between neuronal and non-neuronal cells occurred when the ganglia were dissociated with trypsin following collection in a salt solution lacking divalent cations. This difference allowed the preparation of highly purified non-neuronal cultures and 85-90% pure neuronal cultures. Intermittent agitation during the period of cell separation markedly increased the purity of the neuronal cultures by (1) inhibiting neuronal but not non-neuronal cell attachment and (2) facilitating the formation of homotypic neuronal aggregates in the supernatant. Neuronal and non-neuronal cultures prepared under these conditions were more than 99% pure on the basis of both morphological and biochemical analyses. Both cell types exhibited attachment efficiencies greater than 95% and have been maintained for several weeks in vitro. Thus, completely isolated neuronal and non-neuronal cultures can be prepared and maintained for prolonged periods in the absence of cells of the other type.

A reduction in energy-dependent amino acid transport by microtubular inhibitors in Ehrlich ascites tumor cells

Vincristine, other periwinkle alkaloids, and colchicine partially inhibit the energy dependent transport of alpha-aminoisobutyric acid in Ehrlich ascites tumor cells. The properties of this phenomenon were characterized in detail for vincristine. Maximum depression of the steady-state intracellular alpha-aminoisobutyric acid level was achieved with a vincristine concentration of less than 0.5 muM. The inhibitory effect of vincristine increases as the extracellular alpha-aminoisobutyric acid concentration is increased reaching a maximum, however, of only approximately to 25% at a level of 5 mM, leaving a large gradient for alpha-aminoisobutyric acid across the cell membrane. Vincristine produced an asymmetrical uptake rate, while increasing the efflux of alpha-aminoisobutyric acid. Inhibition of net alpha-aminoisobutyric acid transport by vincristine was partially reversible (approximately to 40%). Colchicine (50 muM) reduced the steady-state alpha-aminoisobutyric acid level by 30%, an effect that was not reversible. Inhibition by vinleurosine and vinrosidine was comparable to that of vincristine. Addition of glucose to the medium resulted in a small, but significant, decrease in the inhibitory effects of both vincristine and colchicine. The data indicate that these agents inhibit a small component of the uphill transport of alpha-aminoisobutyric acid in Ehrlich ascites tumor cells. The inhibitory effect of vincristine cannot be attributed to an increase in the passive permeability of the cell membrane to this agent. Rather, the data along with other studies from this laboratory suggest that vincristine reduces the energy-dependent transport of alpha-aminoisobutyric acid by either inhibiting cellular energy metabolism or by inhibiting cellular energy metabolism or by inhibiting the coupling of energy-metabolism to the transport of this amino acid and raises the possibility that cellular microtubules play a role in these processes.