Examination of leukaemic blasts sensitivity to cytostatic drugs using two short-term laboratory methods.

The authors examined acute leukaemia cells sensitivity to anticancer drugs using 2 short-time methods: 1. Measurement of the inhibition of 3HTdr incorporation during 2 h incubation with cytostatic; 2. Evaluation of the cell viability in short-term (5 days) liquid culture. The 37% decrease in living cells count or in the rate of 3HTdr incorporation has been evaluated as indicating sensitivity to examined drugs. Out of many determinations performed by these use of 2 mentioned methods, those executed simultaneously were compared. Comparable results were obtained to arabinoside-cytosine testing, showing ca. 94% of sensitive cases.In relation to vincristine the 3HTdr incorporation method showed more often - in 82% of cases - sensitivity as compared to only 46% tested in culture method, whereas to daunorubicine more common effect on cultured cells viability (86%) than on tritiated thymidine incorporation (40%) could be observed. These differences remain to be elucidated as to their technical or biological sources. The sensitivity to L-asparaginase was shown only in about the half of cases by both methodes.

Heterospecific activity of rat interferon.

In the experiments performed in vitro and in vivo it has been found that the rat and rat embryo fibroblasts cultured in vitro after the induction with virus produce interferon which displays the antiviral activity not only in the homologous cells but also in the heterologous ones. When analysed by chromatography on Sephadex G-100 it was shown that the rat serum contains two interferon populations differing in the molecular weight and both active in the homologous and heterologous cells. The interferon with the heterospecific activity has been used in the experimental therapy of mice infected with Encephalomyocarditis Virus (EMC), Vesicular Stomatitis Virus (VSV) and Influenza Virus, and was found to be effective.

Rat interferons. Homologous and heterologus rat serum activity.

Serum proteins from normal rat serum and induced with Sindbis virus were separated on Sephadex G-100. Interferon activity was studied in a system of homologous REC and heterologous LG cells. Proteins of normal serum as well as induced serum emerged in two peaks separated by a deep saddle. Four hours after induction, the serum gave two peaks with similar interferon activity in both cell systems. After 8-hour induction, two interferons were also obtained, but activity in the heterologous system was much lower than in the homologous system. Electrophoresis in polyacrylamide gel and on paper showed that interferon activity is connected mainly with the alpha1-globulin fraction.

Rat interferons. IV. Sialoproteins in rat serum.

Introduction of virus as inductor of interferon into rats caused a decline in serum levels of sialic acid in blood taken at the time of maximum interferon activity. Differences in the acute phase proteins were dependent on the type of virus used for induction. NDV injected intravenously did not lower serum levels of seromucoid, but given together with DMSO markedly depressed the content of this protein in the serum. Stimulation of interferon production by Sindbis virus was accompanied by a significant rise in levels of seromucoid. The same virus given together with DMSO had no effect on protein level, which remained normal, but lowered the content of sialic acid in proteins.

Rat interferons. III. Antiviral activity and effect of "priming" on interferon production in homologous and heterologous cell lines.

Studies on interferon from rat serum sensitive to pH 2-0 showed the following: 1) Its action is stronger in cultures of heterologous L cells than in rat fibroblast cultures. 2) Resistance acquired under the influence of interferon lasts longer in a heterologous than in a homologous system. 3) Actinomycin D added to cultures after 4 hours of contact with interferon inhibits its activity in L cells, and potentiates its activity in RE cells. 4) In rat embryonic cells treated with interferon, interferon production following induction with ND virus is blocked. Similar blocking was observed in cultures of L cells after 24-hour priming; after 6 hours of exposure of L cells to rat interferon, on the other hand, production of interferon was enhanced.