[The effect of a low dose of ionizing radiation and of gangliosides on the adenylate cyclase activity of the chicken thymus and thyroid in ontogeny]. / Vliianie maloi dozy ioniziruiushchei radiatsii i gangliozidov na aktivnost' adenilattsiklazy timusa i shchitovidnoi zhelezy kur v ontogeneze.

Adenylate cyclase (AC) activity was studied in thymus and thyroid gland of intact chick embryos and those irradiated with a dose of 0.029 Gy prior to incubation, and newly hatched chicks in the presence of total ganglioside fractions extracted from the same organs. Gangliosides were shown to increase the enzyme activity of thymocytes and thyrocytes during the postnatal development. It is suggested that small radiation doses potentiate the stimulatory effect of ganglioside fractions on AC.

Potentiation of radiation-induced cell kill by synthetic metalloporphyrins.

The effects of the combination of several meso-substituted, water soluble metalloporphyrins with ionizing radiation on hypoxic and oxic monolayers of Chinese hamster fibroblast (V79N) cells were studied. The metalloporphyrins tested included a series of cationic metalloporphyrins complexed with Co(III), Zn(II), Fe(III), Cu(II), Pd(II) or Mn(III) and a series of anionic porphyrins chelated with Co(III), Fe(III), Cu(II), Rh(III), Mn(III) or Sn(IV). Both cationic and anionic free porphyrins were also tested. Cationic ligands were tetrakis(4N-methylpyridyl)porphine [TMPyP], tetrakis(4N-trimethylamino phenyl)porphine [TMAP], tetrakis(4N-butylpyridyl)porphine [TBPyP] and tetrakis(3N-methylpyridyl)porphine [3TMPyP]. Anionic ligands tested were tetrakis(4-sulfonato phenyl)porphine [TPPS], tetrakis(biphenyl)porphine sulfonate [TBPS] and tetrakis(4-carboxyphenyl)porphine [TCPP]. SER calculated from survival curves and SFR from one radiation dose were used to assess the relative effectiveness of this class as non-cytotoxic hypoxic and oxic cell-kill potentiators. Comparisons were made at 100 microM, which was essentially non-toxic (greater than 70% survival) for all porphyrins tested except for Co[TMPyP] (approximately 50% survival after 1 hour at 37 degrees C under oxic conditions). The greatest effects on radiation-induced cell kill were achieved with Co[TPPS] and Co[TMPyP] with SER values of 2.3 and 2.4 respectively. Porphyrin analogs with no coordinated metal were found to be less active than the same compound with metal. The overall charge on the molecule did not systematically relate to the biological activity of the compounds tested.

Experimental study on subacute neurotoxicity of methotrexate in cats.

An experimental study on the pathogenesis of methotrexate (MTX)-related neurotoxicity including disseminated necrotizing leukoencephalopathy (DNL) was conducted in cats. MTX was administered to the cerebrospinal fluid (CSF) of adult cats using either an intracisternal intermittent instillation (ICI) model or an intraventricular continuous instillation (IVC) model. Furthermore, the synergistic effects of CSF-flow disturbance with kaolin-induced hydrocephalus, and 60Co irradiation were morphologically examined in these models. None of the animals from either the ICI and IVC groups showed DNL, but all animals showed segmental axonal degeneration, suggesting that MTX had a direct toxic effect on the axon. In the ICI groups, no apparent synergistic effect of CSF-flow disturbance and radiation was noted on this axonal change. In the IVC groups, CSF-flow disturbance augmented the degree of the axonal injury. Axonal degeneration and fibrin exudation in the walls of small blood vessels occurred in one animal of the IVC groups with CSF-flow disturbance, suggesting that a toxic effect of MTX on blood vessels is another mechanism of MTX-induced neurotoxicity.

[Mechanisms of the synergistic action of ionizing radiation and hydrogen peroxide on the viability of bacteria]. / Mekhanizmy sinergicheskogo deistviia ioniziruiushchego izlucheniia i perekisi vodoroda na zhizhnesposobnost' bakterii.

The combined effect of ionizing radiation and minor concentrations of hydrogen peroxide (0.1-0.01 M) has been studied on bacteria differing in the cell wall structure (Gy+, Gy-), radioresistance, and activity of DNA repair system. The H2O2 concentrations applied, which have a slight antibacterial action, enhance significantly the bactericidal effect of ionizing radiation producing a synergistic effect due to the decreased effectiveness of repair of DNA single-strand breaks.

[Intensification of the bactericidal action of mitomycin C and of UV irradiation with some anthracycline antibiotics]. / Usilenie bakteritsidnogo deistviia mitomitsina C i UF-oblucheniia nekotorymi antratsiklinovymi antibiotikami

Anthracycline antibiotics, such as rubomycin C (rubomycin, daunomycin), rubomycin B, carminomycin and tavromycetin (cinerubin) significantly increased the bactericidal effect of ultraviolet radiation and mitomycin C with respect to mutant 19-8 of E. coli with increased permeability of the cell membrane. This may be accounted for inhibition of DNA reparation. Beromycin, an antibiotic of the same group had no such capacity. With respect to their activity the antibiotics were arranged as follows: rubomycin C, rubomycin B, carminomycin, tavromycetin.