Effects of adsorption of u.v.-inactivated parainfluenza (Sendai) virus on the incorporation of amino acids in animal host cells

Membrane damage: common mechanisms of induction and prevention

Common features in the induction of pores by various agents are as follows: induction is stochastic and progressive; damage by different agents is often synergistic and limited. The prevention of membrane damage is affected by trivalent and divalent cations, by low pH, by low ionic strength and by high osmotic pressure. The inhibitory role of protons and divalent cations is considered in greater detail: pore-forming agents can be classified into two groups: channels across planar lipid bilayers induced by the first group display voltage-sensitive, reversible inhibition by divalent cations; channels of the second group show voltage-insensitive, irreversible inhibition by divalent cations. A search for the ligands to which divalent cations and protons bind has proved elusive. Comparison with the phenomenon of 'surface conductance' through narrow apertures, that is manifest in the absence of any pore-forming agent, may prove fruitful.

Changes in paracellular and cellular ionic permeabilities of monolayers of MDCK cells infected with influenza or vesicular stomatitis viruses

MDCK cells (epithelioid line derived from the kidney of a normal dog) form monolayers which retain the properties of transporting epithelia. In these cells viruses bud asymmetrically: influenza from the apical, and vesicular stomatitis (VSV from the basolateral membrane (E. Rodríguez-Boulán and D.D. Sabatini, Proc. Natl. Acad. Sci. USA 75: 5071-5075, 1978; E. Rodríguez-Boulán and M. Pendergast, Cell 20: 45-54, 1980). In the present study, we analyzed whether these viruses affect specific ion-translocating mechanisms located in the plasma membrane. We studied the effect of infection on membrane and transepithelial conductance, passive and active unidirectional fluxes of Na+ and K+, intracellular potentials, cellular content of Na+ and K+, and formation of blisters which, in these preparations, are due to the vectorial transport of fluid. Two main observations are derived from these studies. First, infection with VSV caused an increase in transepithelial electrical conductance, due to the opening of tight junctions, 5 to 6 hr after the start of infection, coincident with the accumulation of envelope protein in the cell surface and with the rise in the curve of virus budding. Infection with influenza, on the other hand, increased the transepithelial conductance only late in the infection (12 to 14 hr) when virus production has already stopped. Second, viruses did affect membrane permeability. Yet, the changes observed may not be ascribed to a perturbation of the specific translocating mechanisms for Na+ and K+ which operate in the same region of the plasma membrane that the viruses use to penetrate and leave MDCK cells. The methods used in the present study are not suitable to decide whether the nonspecific changes in permeability elicited by the viruses occur over the whole cell membrane or are restricted to a given region.

Virally induced alterations in cellular permeability: a basis of cellular and physiological damage?

Virally induced permeability changes occur when haemolytic paramyxoviruses are added to cells; similar (though not identical) changes take place during infection of cells with viruses from several families (including paramyxoviruses). These changes occur in intact, viable cells, and precede subsequent cytopathic effects, to which they are likely to contribute. There is accumulating evidence to suggest that virally induced permeability changes may also underlie the physiological and clinical consequences of viral infection in certain situations.

Early changes in the membrane of HeLa cells adsorbing Sendai virus under conditions of fusion

Adsorption of Sendai virus at high multiplicity (500-1,000 HAU/10(6) cells) to HeLa cells grown in monolayers causes immediate changes in the ion barrier of the cell membrane, as well as changes in the morphology of the virus-treated cells. Within minutes of adsorption the cells begin to lose potassium and an extensive influx of ions into the cells occurs. Concomitantly with these changes, the cell membrane becomes depolarized, and the resting potential across its membrane decreases. Twenty to sixty minutes post adsorption the damage to the cell membrane is repaired, and both the potassium uptake and the resting potential return to their pre-exposure values. Scanning electron-micrographs of Sendai infected cells incubated at 37 degrees C show formation of bridging microvilli in a zipper-like fashion within two to five minutes post-adsorption; 30 to 60 minutes thereafter the majority of cells in the monolayer are fused. Biochemical changes induced by virus adsorption and the role of Ca++ ions in the observed effects are discussed.

Picorna- and togavirus infection of cells detected by gas chromatography

Viral infection of cells causes chemical and metabolic changes, which can be detected by gas chromatography (GC) of ether extracts of supernatant fluids and cell homogenates before any significant damage to the cells is observable microscopically. The characteristic and specific GC patterns obtained from BHK-21 and Vero cell cultures infected with encephalomyocarditis, polio, echoviruses, and a togavirus make it possible to distinguish between these infecting viruses. The appearance of 1 or 2 compounds, represented by GC peaks with TR values of 302 and 677 seconds seems to be specific for these viruses. Other peaks found in the supernatant media 1-2 hours after infection probably represent cell constituents leaking into the medium as a result of damage to the cell membrane by the invading virus.