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K J Micklem

Publications and source records attributed to K J Micklem.

At least 37 records · Page 2Linked to original sources
PubMed1984

The effect of Ca2+ on virus-cell fusion and permeability changes.

Sendai virus-mediated permeability changes in Lettre cells or red blood cells are affected by extracellular Ca2+ in the following way: the lag period to onset of permeability changes is lengthened and the subsequent extent of leakage is reduced. Ca2+ neither stimulates nor inhibits fusion of the viral envelope to the plasma membrane of Lettre cells or red blood cells. It is concluded that Ca2+ protects cells against virally-induced permeability changes in a manner not involving membrane fusion.

Calcium↗
PubMed1983

Protein synthesis in cells infected with Semliki Forest virus is not controlled by intracellular cation changes.

Treatment of BHK cells with 1 microM nigericin results in a 55% decrease in K+ and a 3.3-fold increase in intracellular Na+; protein synthesis under these conditions is depressed by 35%. In BHK cells infected with Semliki Forest virus (SFV), protein synthesis is depressed by 76% 6.5 h after infection; intracellular K+ is unchanged, and intracellular Na+ is increased 1.8-fold at this time. These results suggest that the increase in intracellular Na+ in SFV-infected BHK cells does not adequately account for the decrease in protein synthesis, and makes it likely that an increased Na+ concentration is a consequence, not a cause, of alterations in protein synthesis in virally-infected cells. No evidence was obtained for the purported [Alonso, M. A. and Carrasco, L. (1980) Eur. J. Biochem. 109, 535-540; (1981) Eur. J. Biochem. 118, 289-294; (1981) FEBS Lett. 127, 112-114] ability of 1 microM nigericin to permeabilize' cells.

Animals↗
PubMed1983

Rat mast cells permeabilized with Sendai virus secrete histamine in response to Ca2+ buffered in the micromolar range.

In the presence of low extracellular Ca2+, Sendai virus generates permeability lesions in the membrane of rat mast cells. This causes leakage of intracellular phosphorylated metabolites and lactate dehydrogenase; it also permits uptake of normally impermeant aqueous solutes such as the complex of Ca2+ with N-hydroxyethylethylenediaminetriacetic acid. We have used this system to buffer the concentration of cytosol Ca2+ in the micromolar range and thus to cause release of the contents of the secretory granules such as histamine and beta-N-acetylglucosaminidase. We argue that such release occurs by a normal exocytotic secretory mechanism for the following reasons. (1) While leakage of cytosol components is progressively inhibited by Ca2+ in the range 1-10 microM, release of histamine is dependent on Ca2+ in this range. Higher concentrations of Ca2+ are inhibitory to both permeabilization and histamine release. (2) While leakage of phosphorylated metabolites is enhanced in metabolically inhibited cells and the leakage of lactate dehydrogenase is insensitive to metabolic inhibition, the release of histamine and beta-N-acetylglucosaminidase is strictly dependent on an intact metabolic process.

Animals↗
PubMed1983

A novel method for measuring intracellular pH and potassium concentration.

The concentration of Na+ and K+ and the pH in the cytoplasm of Lettré cells was measured by monitoring the net flux of H+, Na+, or K+ across the plasma membrane which had been rendered permeable to these ions by the action of Sendai virus. Ion flux was measured directly by analysis of cell composition, or indirectly by observing the change in membrane potential of cells treated with a specific ionophore. Cytoplasmic concentrations of cations were obtained by establishing the concentration of the cation in the medium at which addition of Sendai virus causes no change in cytoplasmic cation content. The value of Lettré-cell pH was confirmed by direct measurement employing 31P nuclear magnetic resonance, and the values of Na+ and K+ concentration were confirmed by analysis of cell cation and water content. Lettré cells suspended at 32 degrees C in Hepes-buffered saline at pH 7.3 maintain a cytosolic pH of 7.0 and contain 50 mM Na+ and 80 mM K+.

Animals↗
PubMed1983

Myxoviruses do not induce non-specific alterations in membrane permeability early on in infection.

The permeability characteristics of cells infected with myxoviruses have been studied by measuring the concentrative uptake of nutrients, the concentration of intracellular K+, and the maintenance of the Na+ gradient across the plasma membrane. Cells either show no change at all (Sendai virus-infected BHK cells and measles virus-infected Vero cells) or they show a decreased ability to concentrate nutrients, while intracellular K+ and the Na+ gradient remain unchanged (Sendai and influenza virus-infected L-1210 cells, measles virus-infected lymphocytes and mumps virus-infected L-41 cells). In no case, therefore, was a change observed that resembles the non-specific increase in membrane permeability induced by haemolytic paramyxoviruses (35, 42) or the non-specific membrane leakiness postulated to take place in infected cells (8, 9). A preliminary account of some of these findings has been presented (39).

Animals↗
PubMed1983

Effect of vesicular stomatitis virus and Semliki Forest Virus on uptake of nutrients and intracellular cation concentration.

BHK-21 cells showed an increased ability to concentrate 2-deoxy-D-glucose (dGlc) 2 to 3 h after infection with vesicular stomatitis virus (VSV) or Semliki Forest virus (SFV), which began to be released at 2 and 3 h post-infection respectively; uptake of other nutrients was not affected in this way. Intracellular Na+ was either unchanged (VSV-infected cells) or increased (SFV-infected cells); K+ content was unchanged. These results do not support the current hypothesis that a non-specific increase in membrane permeability occurs in cells infected with rhabdoviruses or togaviruses.

Animals↗
PubMed1982

Acute membrane responses to viral action.

The effects of Sendai, a paramyxovirus, on the functional activity of 3 cell types, have been studied in vitro to establish whether a virus alone can cause pathophysiological changes. Neuronal cells are depolarized and suffer a loss of excitability which was attributed to an increase in membrane conductance. Spontaneously beating cardiac cells initially stop beating and then beat more rapidly and asynchronously. Anterior pituitary cells release hormones. In all 3 cases the effects are transient and the cells recover completely.

Action Potentials↗
PubMed1982

Membrane changes during viral infection.

The effect of viruses on the surface membrane of susceptible cells during the entry and exit process has been studied. Haemolytic paramyxoviruses induce a non-specific leakage to low-molecular-weight compounds during entry; other viruses do not show this effect. During exit, no such changes occur with any virus so far studied: some viruses are released without any obvious change at all in surface membrane function; in other cases, uptake of some nutrients is altered and there is a fall in membrane potential. These results do not support the hypothesis that a generalized membrane leakiness is a prerequisite for the synthesis and release of virus particles.

Animals↗
PubMed1981

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.

Animals↗
PubMed1980

Survey of virally mediated permeability changes.

1. Sendai virus causes permeability changes when added to freshly isolated brain cells (cerebellum or ependymal cells) or to a culture of forebrain cells. 2. Sendai virus causes permeability changes when added to organ cultures of ferret lung or nasal turbinate. Influenza virus causes no permeability changes under these conditions. 3. Rabies virus and vesicular-stomatitis virus, in contrast with Sendai virus, do not cause permeability changes in BHK cells or Lettrée cells. 4. Serum from patients suffering from viral hepatitis does not cause permeability changes in human leucocytes; addition to Sendai virus causes permeability changes. 5. It is concluded that permeability changes accompanying viral entry occur only with certain types of paramyxovirus, but that there is little restriction on cell type. 6. MDBK cells infected with Sendai virus show permeability changes during viral release, similar to those that occur during viral entry. Because these changes do not appear to be restricted to paramyxoviruses, they may have considerable clinical significance.

Animals↗
PubMed1980

Changes in the surface membrane during myoblast fusion.

1. During fusion of chick-embryo myoblasts in culture, the surface membrane is affected as follows. Uptake of 2-aminoisobutyrate and 2-deoxyglucose, each of which is concentrated 20-fold relative to its concentration in the medium, is unaltered; uptake of alpha-methyl glucoside and choline (15 mM), each of which equilibrates relative to its concentration in the medium, approximately doubles. An approximate doubling also occurs in iodinatable surface protein (and in total protein) and in cell surface area as judged by light-microscopy. Adenylate cyclase (in the absence or the presence of fluoride) increases by more than 2-fold. 2. It is concluded that, during myoblast fusion cells increase in size, and this is reflected in an increased rate of simple diffusion; the rate of facilitated processes such as the uptake of amino acids and sugars, on the other hand, remains unaltered, though the activity of certain enzymes is increased. These results indicate that specific changes in the function of surface membrane occur during myoblast fusion in vitro.

Aminoisobutyric Acids↗
PubMed1980

Nature of virally mediated changes in membrane permeability to small molecules.

1. The changes in membrane permeability to small molecules caused by Sendai virus [Pasternak & Micklem (1973) J. Membr. Biol. 14, 293-303] have been further characterized. The uptake of substances that are concentrated within cells is inhibited. Choline and 2-deoxyglucose, which become phosphorylated, and aminoisobutyrate and glycine, which are driven by a Na+-linked mechanism, are examples. The uptake of each compound under conditons where its diffusion across the plasma membrane is rate-limiting is stimulated by virus. Choline, 2-deoxyglucose and amino acids at high concentration, amino acids in Na+-free medium, and most substances at low temperature, are examples. It is concluded that virally mediated decrease of uptake is due to one of two causes. Substances that are accumulated by phosphorylation are not retained because of leakage of the phosphorylated metabolites out of cells. Substances that are accumulated by linkage to a Na+ gradient are no longer accumulated because of collapse of the gradient resulting from an increased permeability to Nat 2. Increased permeability to K+ and Na+ results in (a) membrane depolarization and (b) cell swelling. The latter event leads to haemolysis (for erythrocytes) and can lead to giant-cell (polykaryon) formation (for several cell types). 3. Recovery of cells can be temporarily achieved by the addition of Ca2+; permanent recovery requires incubation for some hours at 37 degrees C. 4. The possible significance of virally mediated permeability changes, with regard to clinical situations and to cell biology, is discussed.

Amino Acids↗
PubMed1979

Manganese as a calcium probe: electron paramagnetic resonance and nuclear magnetic resonance spectroscopy of intact cells.

When Lettree cells are exposed to Mn2+, the cation becomes associated with cells in two ways: in a relatively loose and mobile manner that gives a six-line EPR spectrum designated Mnb*, and in an immobile, relatively tight manner that gives no detectable EPR specrtum, designated Mnb. Mnb* is probably on the surface of cells; most Mnb is probably inside cells. NMR measurements of Lettree cell suspensions show two water proton relaxation rates and confirm the existence of cell-associated Mn. Human erythrocytes, on the other hand, bind no Mn2+ under these conditions, as judged by EPR and NMR measurements. Virally-treated Lettree cells show an increase in Mnb (but not in Mnb*). They also show a third water proton relaxation rate.

Animals↗