Stimulation of Ribonucleic Acid Synthesis in Horse Lymphocytes by Exogenous Cyclic Adenosine 3′,5′-Monophosphate

Influence of whole-body hyperthermia on natural cytotoxicity of liver blood-borne sinusoidal cells

Rat liver sinusoidal cytotoxic cells were examined after exposure to in vivo and in vitro hyperthermia at 40-41 degrees C. Whole-body hyperthermia lasting for 4 h caused a decrease in the cytotoxic activity of liver sinusoidal washout cells against YAC-1 and K562 cells. Surprisingly, the percentage of washout cells with morphology of LGL (large granular lymphocyte) increased both in the liver washout and in portal blood compared to control normothermic animals. The proportions of phenotypically characterized cell subpopulations isolated from liver sinusoids did not change. Elimination of i.v. injected 125I-labelled K562 cells was decreased during hyperthermia. In vitro incubation of liver sinusoidal cytotoxic cells for 3 h at 41 degrees C decreased their cytotoxic activity by affecting the process of effector-target cell binding. However, once the effector-target cell conjugates were formed, the cytotoxic process proceeded as in normothermic conditions. These data suggest that inhibition of liver sinusoidal cytotoxic cell activity after hyperthermia may be a result of deficient target cell recognition by the effector cell.

The influence of methylxanthines on precursor incorporation into protein and RNA of mouse brain

Pentoxifyline at 1 mM had no effect on [14C]isoleucine incorporation into mouse brain tissue suspension. At 5-20 mM, this compound inhibited incorporation. The inhibition was prompt, and it was reversible. Aminophyline at 3-12 mM produced inhibition, but theophyline at 2-16 mM had no effect. Pentoxifylline inhibited the incorporation of uridine into brain RNA to the same extent and with a similar time course as its effect on protein synthesis.

Effect of adenosine 3',5'-cyclic monophosphate on the RNA and DNA synthesis and cell proliferation of rat hepatocytes in primary culture: a radioautographic study

The effect of a 24-h treatment with various doses (from 1.5-10-minus 8 to 3.0-10-minus 3 M) of adenosine 3',5'-cyclic monophospahte (cAMP) on morphometric parameters, [5--3H]uridine radioactivity concentration (URC), [methyl--3H]thymidine [Me--3H]-Tr) labelling index per hour (L.I./h) and per cent mitotic index (M.I.%) of young rat differentiated hepatocytes in primary tissue culture were investigated by morphometric and radioautographic methods. In such cells cAMP was found to induce: (1) a reduction of the apparent surface area (ASA) of total nucleoli, karyoplasm and cytoplasm; (2) significant increases in URC of all the subcellular compartments at all the dosages employed (only cAMP at 1.5-10-minus 8 M did not change karyoplasmic and cytoplasmic URC values); (3) marked increments in [Me--3H]Tdr L.I./h and M.I.% from the lowest dose up to 1.5-10-minus 4 M; at higher doses the L.I./h and M.I.% were less stimulated or approached control values. In cultured rat hepatocytes, adenosine-5'-phosphate (5'-AMP) (1.5-10-minus 4 M per 24 h) increased the karyoplasmic and total cell ASA, the lone total nucleolar URC and both the L.I./h and M.I.%. However, these metabolic effects were significantly less intense than those elicited by isomolar cAMP. Theophylline (Theo) (5.5-10-minus 5 M per 24 h) reduced the in vitro rat hepatocyte total nucleolar ASA but affected neither other morphometric nor any of the URC values. The same dose of Theo plus cAMP (1.5-10-minus M) had no morphometric effect but significantly increased the URC values of all primary rat hepatocyte compartments. Actinomycin D (DAct) (0.1 mug/ml per 24 h) plus cAMP (1.5-10-minus 4 M) decreased the cultured rat hepatocyte total nucleolar ASA but enlarged that of karyoplasm and cytoplasm and, further, markedly curtailed all the compartmental URC values. These data support the hypothesis that cAMP amplified the template activity of the liver chromatin and accelerates the flow of differentiated primary young rat hepatocytes into the various stages of the mitotic cell cycle.

Thymus adenylate cyclase activity during murine leukemogenesis

Activity of thymus adenylate cyclase was more than three times higher in leukemic AKR mice than in nonleukemic AKR mice and CBA mice. Preleukemic AKR mice that had no evidence of leukemia but were expected to soon develop the disease exhibited similarly elevated activities of thymus adenylate cyclase.