Distribution of dengue-2 antigens by electron immunocytochemistry.

The distribution of dengue-2 antigens was studied in infected monkey kidney cells (LLC MK2) using an indirect, horseradish peroxidase-conjugated immunoglobulin technique. This procedure allowed both light and electron microscopic examination of serial-step sections of individual cells cut in a plane perpendicular to the monolayer. Both virion and nonvirion antigens were identified on the plasma membrane with this technique. A diffuse cytoplasmic reaction product was also present. The intensity and distribution of the cytoplasmic reaction product was related to disruption of the plasma membrane.     

Sensitivity of FL cells to polio- and adenoviruses

Summary Poliovirus plaque counts on the FL strain of human amnion cells were almost double the counts on rhesus monkey kidney for the same virus preparation, repeatedly assayed over more than six months. FL cells gave more consistent results in virus assay than monkey kidney cells. Plaque counts obtained with FL cells were 2 1/2 to 5 times higher than those obtained with HeLa, Chang's conjunctiva and Detroit-6 cells.Using the chick embryo-adapted MEF-1 strain of poliovirus, FL cells and primary human amnion cells reacted similarly in respect to plaque count and morphology, while no distinct plaques were seen on monkey kidney or HeLa monolayers under comparable conditions. For infectivity assays of adenovirus suspensions based on cytopathogenic effect, FL cells were found suitable, although no plaque formation was obtained.Aided by American Cancer Society Grant E-82 and a grant from the National Foundation.     

A microiontophoretic study of the action of kainic acid and putative neurotransmitters in the rat mesencephalic trigeminal nucleus

The ‘excitotoxic’ hypothesis proposes that neurotoxic amino acids exert their effect through neuronal excitation (Olney, Ho &;Rhee, 1971).Colonnier, Steriade &;Landry (1979) have found that trigeminal mesencephalic neurons in the cat are resistant to the neurotoxic effect of kainic acid. In the present study it was found that the same neurons in the rat also resist the cytotoxic action of this amino acid. In addition, kainic acid, applied iontophoretically onto these neurons failed to alter their firing frequency. The resistance of these neurons to both neurotoxic and excitatory actions of kainic acid is consistent with the ‘excitotoxic’ hypothesis.Other putative neurotransmitters were applied by microiontophoresis on these neurons and none were found to alter their rate of discharge. Procaine however applied with relatively low ejecting currents consistently reduced their firing rates. The failure of the putative neurotransmitters tested to influence the rate of discharge of the trigeminal mesencephalic neurons suggests that the chemical synapses present on these neurons in the rat (Hinrichsen &;Larramendi, 1970) utilize another neurotransmitter from those tested. Alternatively the synapses might have a role other than the direct regulation of the firing frequency of these primary afferent neurons.