Ultrastructural localization of binding sites for the lectins RCA I, WGA, and LTA in the preimplantation mouse embryo.

In biological tissues, specific carbohydrate moieties of the oligosaccharide chains of glycoproteins can be localized by lectin binding. Such carbohydrate moieties are among the factors that mediate cell-cell or cell-matrix interactions during pre- and postimplantation embryonic development. Binding sites for the lectins RCA I, WGA, and LTA were localized in preimplantation mouse embryos at the ultrastructural level with the help of postembedding lectin gold cytochemistry. WGA and RCA I binding sites, but no LTA binding sites, were present in the zona pellucida. WGA and RCA I binding sites were found at cell surfaces of morulae and in cells of the inner cell mass of blastocysts, suggesting that N-acetylglucosamine-, terminal beta-galactosyl-, and N-acetylgalactosamine-rich glycoproteins might be involved in cell-cell and cell-matrix interactions. WGA binding sites were found predominantly in electron lucid vesicles of the blastomeres, whereas RCA I was detected in electron dense vesicles of the compacted morula and later in the polar trophoblast cells. This allows early identification of blastomere cells that later differentiate into the polar trophoblast.

Modified growth cones in mouse neuroblastoma cultures; an electron microscopic study.

Growth cones of differentiated neuroblastoma cells in monolayer cultures were studied by electron microscopy. Morphological differentiation of the growth cone formation was induced by sodium bromide. Upon prolonged application of 10(-4) to 10(-5) M sodium bromide to the cultures, a peculiar or modified formation of the growth cone occurred. Growth cones lengthened gradually. The ultrastructure of the growth cone in contrast to the control was typified by a round to oval structure, midway being electron-dense and carrying laterally denser cytoplasmic protrusions. Bundles of microtubules, aggregates of many dense-cored vesicles, 70-150 nm in diameter, a few less electron-dense, as well as some agranular vesicles were present. Comparing the findings with previous ultrastructural accounts of growth cones of cultured ganglion cells or neuroblastoma cells, differences outnumbered similarities. The organization of the microtubule bundles and the abundance of dense-cored vesicles, sometimes extending distally was remarkable. The presence of an electron-dense substance, of unknown origin, extending laterally with the cytoplasmic protrusions has not been describe as yet.

Smooth endoplasmic reticulum and synaptic vesicles in cultured murine neuroblastoma cells.

Cultured murine neuroblastoma cells contain an extensive smooth endoplasmic reticulum (SER), also within their numerous processes and their terminals, consisting of a complex network of sacs and tubules. Both the perikaryal and the SER found within the processes and endings resemble one another morphologically. From the SER whether it is within the perikaryon or within the terminals of the neural processes, round coated vesicles with clear centers appear to form. These clusters of vesicles are 40...60nm in diameter and indistinguishable from the synaptic vesicles of normal neurons. In addition a few vesicles with clear centers with a diameter of 20...40 nm and length of 80...200 nm are encountered and appear to originate from the SER. The dense-cored vesicles do not seem to develop from the SER. There is no detectable association of the vesicles with any other cell organelle.

A simple embedding technique for monolayer neuronal cultures grown in plastic flasks.

An in situ embedding technique for monolayer cultures for subsequent ultrastructural studies is described. Dehydration is carried out in graded ethanol series without propylene oxide, and Epon is used as a final embedding medium. The advantage of this method is that the plastic flask with the embedded material can be stripped off easily without affecting the monolayer culture and that the plastic does not dissolve in Epon.

The time course of synapse formation of mouse neuroblastoma cells in monolayer cultures.

Neuroblastoma cells grown on substrates in culture develop long processes and assume the morphology of normal neurons as judged light microscopically. The development of synapses in the cultured tissue is studied by periodic electron microscopic examination of the areas of contact between cells. The initial explants are free of any apparent synaptic contacts. After 48 h in culture, simple swellings or boutons are detected at the periphery of the cells or at the end of the fine processes. These initial synaptic profiles contain a few vesicles but lack mitochondria. The synaptic vesicles appear to originate from the smooth endoplasmic reticulum. Further explants remain primitive, only the number of vesicles in the cytoplasmic swellings or boutons increases. These clusters of vesicles are 40-60 nm in diameter and morphologically distinguishable from the synaptic vesicles of normal neurons. There are no postsynaptic folds or membrane thickenings. Specialized cell contacts between cells are also present.