Effects of hyperthermia on intracellular calcium concentration and responses of cancerous mammary cells in culture.

Effects of hyperthermia on the intracellular calcium concentration (Cai) of an established mouse breast cancer cell line, MMT060562, were studied using fura-2 fluorescence microscopy and the whole-cell clamp technique. A sudden change of temperature from 37 to 45 degrees C induced a transient increase in the fluorescence ratio permeability of the cell membrane and inward current. Deletion of extracellular calcium abolished the fluorescence ratio response to the rise in temperature. Cai of some cells increased after hyperthermia treatment at 44-48 degrees C for 20 min, but the average increase of Cai was negligible. After hyperthermia treatment, spontaneous oscillation of Cai, chemical responses to ATP and bradykinin and the mechanically-induced spreading response diminished. However, the mechanically induced increase of Cai within the stimulated cell remained even after hyperthermia treatment. Suppression of the ATP-induced Cai response recovered to about half the original level within 12 h. Blockage of protein synthesis with cycloheximide (100 microM) had no effect on the recovery. The D-myo-inositol 1,4,5-triphosphate (IP3)-dependent increase of Cai remained intact even after hyperthermia treatment. It is concluded that hyperthermia treatment increases both the permeability of the cell membrane and Cai, but decreases the sensitivity of cells to ATP and bradykinin, presumably due to modification of the signal transduction mechanism.     

Effect of high salt treatment on influenza B viral protein synthesis in MDCK cells

Based on the information that high salt inhibits the initiation of cellular mRNA translation which depends on the function of the 5'-terminal structure of mRNA, we compared the effect of high salt on translation of host cellular mRNAs and influenza viral mRNAs, both of which are of 5'-terminal structure. Brief exposure of influenza B virus-infected MDCK cells to high salt medium resulted in a dose-dependent inhibition of viral polypeptide synthesis as well as of cellular polypeptide synthesis, but it had less effect on synthesis of viral polypeptides, particularly nonstructural protein (NS). Under these conditions the Na+ content of the infected cells was significantly increased. A similar salt effect on in vitro translation of viral and cellular mRNAs extracted from infected cells was also observed. There was no significant difference in sensitivity to hypertonic block of in vivo translation of influenza viral mRNAs and vesicular stomatitis virus mRNAs, the latter of which possess a virus-directed structure at the 5'-terminus.     

Reduction of the acetylcholine-induced K+ current in identifiedAplysia neurons by human interleukin-1 and interleukin-2

1. Effects of bath-applied recombinant human interleukin-1 (rhIL-1) and interleukin-2 (rhIL-2) on the acetylcholine (ACh)-induced K+ current recorded from identified neurons (R9 and R10) of Aplysia kurodai were investigated with voltage-clamp and pressure ejection techniques. 2. Bath-applied rhIL-1 and rhIL-2 (10-40 U/ml) reduced the ACh-induced current in the neurons without affecting the resting membrane conductance and holding current. 3. The suppressing effects of these cytokines on the current were completely reversible. 4. Heat-inactivated rhIL-1 and rhIL-2 were without effect. 5. These results suggest that the immunomodulators, IL-1 and IL-2, can modulate the ACh-induced response in the nervous system.     

Analysis of Nuclear Accumulation of Influenza NP Antigen in von Magnus Virus-Infected Cells

When 1–5C-4 cells were infected with von Magnus virus derived from influenza A/RI/5⁺ virus by four successive undiluted passages in chick embryos, virus-specific proteins were synthesized but production of infectious virus was inhibited. In these cells the synthesis of viral RNA was suppressed and the nucleoprotein (NP) antigen was found predominantly in the nucleus in contrast to standard virus-infected cells in which the antigen was distributed throughout the whole cell. The intracellular location and migration of NP were determined by isotope labeling and sucrose gradient centrifugation of subcellular fractions. In standard virus-infected cells NP polypeptide was present predominantly in the cytoplasm in the form of viral ribonucleoprotein (RNP) and intranuclear RNP was detected in reduced amounts. In contrast, in von Magnus virus-infected cells NP polypeptide was present predominantly in the nucleus in a nonassembled, soluble form and the amount of cytoplasmic RNP was considerably reduced. After short-pulse labeling NP was detected exclusively in the cytoplasm in a soluble form and after a chase a large proportion of such soluble NP was seen in the nucleus. It is suggested that a large proportion of the NP synthesized in von Magnus virus-infected cells is not assembled into cytoplasmic RNP because of the lack of available RNA and the NP migrated into the nucleus and remained there.     

Induction of two K+ currents by complement component C5a in mouse macrophages.

Puff application of complement component C5a (5 x 10(-8) M) onto peritoneal macrophages from thioglycollate-stimulated mice induced two kinds of outward current at a holding potential of -68 mV, a slowly-rising sustained outward current and a spike-like transient outward current. Quinidine (2 x 10(-4) M) and tetraethylammonium (10(-2) M) partially suppressed both types of outward current. Charybdotoxin (2 x 10(-6) M) markedly suppressed the spike-like outward current. Reversal potentials in bath solutions of different external K+ concentrations were dependent only on K+ concentrations. The transient current was not suppressed in Ca(2+)-free EGTA-containing solution, but was completely abolished in BAPTA-containing solution. One kind of single channel responding to C5a, which has a single-channel conductance of 29 pS, was recorded from cell-attached patches. These results suggest that C5a activates a Ca(2+)-dependent and another type of K+ current.