Actinomycin-resistant antiviral activity associated with preparations containing chicken interferon

Summary Crude and purified preparations containing chicken interferon show a 2fold antiviral activity. One is inhibited by actinomycin and leads to total inhibition if interferon is added to cells before actinomycin, the other is insensitive to actinomycin and leads to partial inhibition if interferon is added simultaneously with or after actinomycin.Work supported by the Swiss National Foundation, grant 3.399.70.The authors wish to thank Miss E. Browse, Miss U. Kohler and Mr U. Rohrer for excellent technical assistance.     

The lymphatic route. 1) Albumin and hyaluronidase modify the normal distribution of interferon in lymph and plasma

When human recombinant interferon-alpha 2 diluted in saline was injected s.c. into rabbits, the total amount recovered in thoracic lymph was less than 0.4%. Recoveries increased from 2- to 8-fold if interferon was injected in 4% albumin or with hyaluronidase, respectively. Albumin added to interferon acts as an interstitial fluid expander, thus favoring interferon absorption through lymphatics rather than blood capillaries. This strategy may increase the therapeutic index of interferon.     

The lymphatic route. 1) Albumin and hyaluronidase modify the normal distribution of interferon in lymph and plasma

Summary When human recombinant interferon-₂ diluted in saline was injected s.c. into rabbits, the total amount recovered in thoracic lymph was less than 0.4%. Recoveries increased from 2- to 8-fold if interferon was injected in 4% albumin or with hyaluronidase, respectively. Albumin added to interferon acts as an interstitial fluid expander, thus favoring interferon absorption through lymphatics rather than blood capillaries. This strategy may increase the therapeutic index of interferon.This work was supported by Ministero Pubblica Istruzione and Progetto Finalizzato Oncologia, contract No. 84.00461.44, CNR, Roma.     

The effect of actinomycin D on the production of viruses by the protoplasts of Chinese cabbage infected in vitro by the yellow mosaic virus of turnips]

Chinese Cabbage (Brassica sinensis L. var. Cantonner) protoplasts were infected by Turnip yellow mosaic virus (TYMV) and inoculated in the presence or absence of actinomycin D. Virus production was determined 40 hrs. after inoculation, the time required for the virus replication cycle to be terminated. While actinomycin D had no effect on TYMV production when present at a concentration of 1 microng/ml, a 50 to 80% inhibition of virus production was noticed at concentrations of the order of 5 to 10 microng/ml, and the inhibition reached 90% with 25 microng/ml.     

Inhibitory effect of exogenous histones on cellular growth and DNA synthesis in Chlamydomonas reinhardtii.]

The addition of exogenous histones to synchronous culture of Chlamydomonas reinhardtii, at the beginning of the cell cycle, leads to the death of the cells. The same amount of histones added in the middle of the cycle, only blocks the cell division. The mechanism of this inhibition effect of the histones could involve a block at the level of the chloroplast DNA replication.     

The reactivation of human interferons by guanidine thiocyanate

The addition of 1.5 M guanidine thiocyanate (GuSCN) reactivates inactive human leukocyte interferon. The biological activity of inactivated human fibroblast interferon can be only partially recovered with GuSCN if additional (thermal) energy is supplied.     

Potentiating effect of cycloheximide on viral interference]

The degradation of the antiviral state can be delayed in vitro by antimetabolites, when added between 5-7 hours after interferon. We explore in this chronological order whether antiviral resistance induced by Newcastle disease virus (N.D.V.) in vivo could be modified by an antimetabolite. Cycloheximide was selected for this study because of its reversible biological effect and lack of toxicity in our experimental conditions. The model system employed was Syrian Hamsters, using N.D.V. as an interferon inducer and encephalomyocarditis virus (E.M.C.) as a challenge virus. A constant and significant increase in survival of animals treated with N.D.V.+cycloheximide is probably related to a delay in the degradation of the antiviral state and not to interferon superinduction.     

The reactivation of human interferons by guanidine thiocyanate

Summary The addition of 1.5 M guanidine thiocyanate (GuSCN) reactivates inactive human leukocyte interferon. The biological activity of inactivated human fibroblast interferon can be only partially recovered with GuSCN if additional (thermal) energy is supplied.This investigation was supported by an award from the National Institutes of Health, NO1 A142520.     

On the mechanism of pyrogenic action of ricin

Summary The incubation of rabbit white blood cells with ricin, the toxic protein of castor oil seeds, leads to the production of endogenous pyrogens. This induction can be inhibited by the antibiotics actinomycin D or cycloheximide. The results are discussed in terms of disturbed corticosteroid- and Mg²⁺-levels.Acknowledgments. The author is very grateful to the Uganda National Research Council for the Research Grant No. 60.660.00 (through Makerere University, Kampala) without which the completion of his inaugurated Ph. D. Thesis would not have been possible. This paper represents a part of this Thesis.     

Effect of human interferon on viral production in a cell line chronically infected by a type D retrovirus (Mason-Pfizer virus)]

Human interferon specifically inhibits the viral multiplication in a human cell line infected by a type D retrovirus, the Mason-Pfizer virus (MPV). This inhibition is less important than for type C viruses.     

The effects of manganese and barium on the cardiac pacemaker current, if, in rabbit sino-atrial node myocytes

The isolation of ionic fluxes contributing to electric currents through cell membranes often requires block of other undesired components which can be achieved, among others, by divalent cations. Mn2+ and Ba2+ are often used, for example, to block Ca and K currents. Here we have investigated the effects of these two cations on the properties of the hyperpolarization-activated pacemaker current if, in rabbit sino-atrial node myocytes, as obtained by voltage clamp analysis. We find that 2 mM Mn2+ shifts the if activation curve by 3.2 +/- 0.3 mV towards more positive values. However, when 1 mM Ba2+ is also added, the positive shift is more than halved (1.3 +/- 0.2 mV). We find, too, that in the absence of blocking cations the ACh-induced if inhibition is slightly higher than in their presence. These results indicate that the alteration of if kinetic properties by Ba2+ plus Mn(2+)-containing solutions is minimal.     

Degradation by phytohemagglutinin of the antiviral state induced by interferon]

Phytohaemagglutinin (PHA M and P forms), when added to L 929 cells previously treated by murine interferon, degrades the antiviral state and restores virus sensitivity in the cells. This degradation depends on the amount of the lectin, the contact period with the cell and the presence of PHA membrane receptors. The importance of membrane configuration not only in the induction but also in the maintenance of the antiviral state is discussed.     

Reversible depression of spontaneous brain electrical activity induced by actinomycin D and 7-aminoactinomycin D in rats

Summary Various types of actinomycin (C, D, S₂, I and V) and 7-amino-analogue of actinomycin D were injected into the right lateral ventricle of the brain through a chronically implanted cannula. In rats but not in mice actinomycin D, actinomycin S₂ and 7-aminoactinomycin D caused depression of EEG, while cardiac and respiratory activity were maintained. This effect of the EEG was reversible and a normal EEG pattern reappeared at least 3 h after administration.     

Effets de l'actinomycine D sur le développement normal et sur les modifications expérimentales de la morphogénèse de l'oeuf de l'oursinParacentrotus lividus

Summary In the presence of actinomycin D (20–40 µg/ml), the development of the eggs of the sea urchin,Paracentrotus lividus, is slowed from the late morula and stopped at the blastula stage. The development is immediately stopped in the blastula treated with actinomycin D (20–40 µg/ml). The inhibitory effects of actinomycin D are prevented by deoxyribonucleic acid. Actinomycin D does not exert animalizing or vegetalizing effects. However, the enhancing of vegetalizing action of lithium and the weakening of animalizing effects of zinc ions and Evans blue have been observed in the presence of actinomycin D. These observations may reflect some difference in the state of dependence of differentiation of entomesodermic and ectodermic structures towards the nucleus.     

Hydrogen peroxide and hydroxyl radical involvement in the activation of caspase-3 in chemically induced apoptosis of HL-60 cells

Apoptosis of HL-60 cells induced by actinomycin D, H7, or daunorubicin was shown to involve the activation of caspase-3-like protease, 2 h after the addition of these drugs, based on microassay of enzyme activity by high-performance liquid chromatography. Catalase and a spin trap, N-t-butyl--phenylnitrone, which effectively inhibited the apoptosis induced by these drugs, also inhibited the activation of caspase-3-like protease. These results suggest that hydrogen peroxide and the hydroxyl radical are common mediators of caspase-3 activation caused by these chemicals, with apparently different functional mechanisms. Based on mitochondrial activity determined by oxygen consumption, complexes I, II, and IV were inhibited by actinomycin D. H7 inhibited complexes I and IV, 1 and 1.5 h respectively, after the addition of the drug to HL-60 cells. Daunorubicin inhibited complex IV, 1.5 h after the addition of the drug to HL-60 cells. Inhibition of complex IV by actinomycin D, H7, and daunorubicin were almost fully restored by the addition of cytochrome c. The release to the cytosol of cytochrome c by these drugs was also demonstrated by Western blot analysis. Addition of catalase inhibited the depression of complex IV activity induced by actinomycin D and H7. These observations indicate a direct relationship between hydrogen peroxide and the release of cytochrome c during apoptosis caused by actinomycin D, H7, and daunorubicin. Received 24 November 2000; received after revision 2 January 2001; accepted 30 January 2001     

Effect of dibutyryl cyclic AMP and analogs on the rate of contractions of myocytes in culture.

2O, 6N-butyryl, 3', 5'-cyclic monophosphate (dibu cAMP) when added to fetal rat heart cells in culture inhibits myocyte contraction. This inhibition is 100, 84 and 51% complete when the dibu cAMP concentration used is 2, 0.2 and 0.02 mM, respectively. The potency of dibu cAMP derivatives in myocyte contraction inhibition follows the order, dibu cAMP greater than 6N-bu cAMP greater than 2O-bu cAMP = AMP greater than butyrate. The inhibition caused by the first three chemicals is greater than 70%.     

Binding of actinomycin D and divalent cations to lipopolysaccharides ofAgrobacterium tumefaciens as studied by fluorescence spectroscopy

Summary The binding of actinomycin D and divalent cations to lipopolysaccharides ofA. tumefaciens was studied. Fluorimetric titrations revealed 2 binding sites (low and high affinity sites) for divalent cations, and 1 high-affinity site for actinomycin D.Acknowledgment. This project was financed by the Department of Science and Technology, Govt. of India (grant No. D.O. No.11 (19)/77-SERC). To whom reprint requests should be addressed.     

Assessment of the scavenging action of reduced glutathione, (+)-cyanidanol-3 and ethanol by the chemiluminescent response of the xanthine oxidase reaction

The free radical scavenging capacity of reduced glutathione (GSH), (+)-cyanidanol-3 and ethanol was assessed by their interference with the maximal chemiluminescent response produced by the xanthine oxidase reaction. GSH and (+)-cyanidanol-3 induce a progressive inhibition of chemiluminescence when increasing amounts are added to the reaction mixture. GSH and (+)-cyanidanol-3 added together at low concentrations (1 and 0.05 mM respectively) exhibit an additive effect. The addition of ethanol presents a biphasic effect. It inhibits chemiluminescence at low concentrations (10-50 mM) while at higher concentrations (75-500 mM) this effect is reversed. Estimation of the concentrations required to produce half of the maximal inhibition of chemiluminescence by these agents revealed that ethanol is less effective than GSH and (+)-cyanidanol-3 as a free radical scavenger in the system used.     

Glucose-evoked recovery of hepatic thyroxine 5'-deiodinase independent of de novo protein synthesis in fasted rat

The glucose-evoked recovery of Type I thyroxine 5'-deiodinase activity in the hepatic microsomes of fasted rat was not inhibited by either cycloheximide, puromycin or actinomycin D during 3 h after glucose feeding; however, [3H]-leucine uptake by the liver or the hepatic microsomal fraction was significantly inhibited by cycloheximide and puromycin but not by actinomycin D. These results indicate that the glucose-evoked recovery of deiodinase activity may be independent of de novo protein synthesis.