Insect antifeedant activity of three new tetranortriterpenoids from Trichilia pallida.

Three new tetranortriterpenoids, methyl 6-hydroxy-11 beta-acetoxy-12 alpha-(2-methylpropanoyloxy)-3,7-dioxo-14 beta,15 beta-epoxy-1,5-meliacadien-29-oate (3), methyl 6,11 beta-dihydroxy-12 alpha-(2-methylpropanoyloxy)-3,7-dioxo-14 beta,15 beta-epoxy-1,5-meliacadien-29-oate (4), and methyl 6-hydroxy-11 beta-acetoxy-12 alpha-(2-methylbutanoyloxy)-3,7-dioxo-14 beta,15 beta-epoxy-1,5-meliacadien-29-oate (5), have been isolated from the roots of Trichilia pallida. The related compounds hirtin (1) and deacetylhirtin (2) were also obtained. Compound 4 had the greatest antifeedant activity of 1-5 when tested against larvae of four species of Lepidoptera.

Antiviral activity and metabolism of the castanospermine derivative MDL 28,574, in cells infected with herpes simplex virus type 2.

The 6-O-butanoyl derivative of castanospermine (MDL 28,574: BUCAST), an inhibitor of glycoprotein processing, blocked the growth of herpes simplex virus type-2 with the effect markedly enhanced by exposure of cells to the compound pre- as well as post-infection. The effectiveness of the derivative corresponded to an increased uptake with greatest accumulation after virus infection. Gas chromatography/mass spectrometry identified the predominant component in MDL 28,574 treated cells as castanospermine, an inhibitor of alpha-glucosidase 1. The effects of this compound on the synthesis of viral glycoprotein, gB, was determined with the increased molecular weight of the mannose-rich precursor evidence for the modulation of glycoprotein processing.

The effect of oral treatment with 6-O-butanoyl castanospermine (MDL 28,574) in the murine zosteriform model of HSV-1 infection.

Oral treatment of mice, cutaneously infected with herpes simplex virus type 1 (HSV-1) (strain SC16), with the alpha-glucosidase 1 inhibitor 6-O-butanoyl castanospermine (MDL 28,574) produced a significant delay in lesion development and reduced the amount of virus recovered from the brain. Virus load in the brains of mice, whose treatment started 2 days prior to infection, was reduced approximately 100-fold when compared to untreated controls. Treatment initiated at the time of infection, while less effective than pre-treatment, nevertheless reduced virus recovery from the brain by 10-fold. Consistent with its antiviral activity, orally administered MDL 28,574 was rapidly incorporated by brain tissue and mice fed with compound over extended periods maintained relatively high levels of drug at this site.

Quantitative transplantation assays of the rat rhabdomyosarcoma BA1112 isografts into the WAG/Rij Y rat and xenotransplantation into the athymic NCr (nu/nu) nude mouse.

Quantitative tumor cell transplantation assays have been performed to compare the transplantability of rat rhabdomyosarcoma BA1112 into isologous WAG/Rij Y rats and athymic NCr(nu/nu) nude mice. The end-point was the TD50 or the number of viable tumor cells which would transplant the tumors into half of the recipients. At Yale, two sets of 2-fold dilutions were prepared, one was sent to the MGH by Air Express. That afternoon, concurrent assays were performed at Yale using the WAG/Rij Y rat and at MGH using the NCr(nu/nu) mouse. The TD50 values were the same for iso- and xenotransplantation. Furthermore, the TD50s in rats and mice were unaffected by standard immunization procedures prior to challenge of the TD50 assay. The BA1112 (10(7) trypan blue excluding cells) grew to 10-12 mm and then completely regressed if transplanted into NCr(nu/+) mice which had received 6 Gy whole body irradiation but did not grow in control NCr(nu/+) mice. The times for the BA1112 to grow to 10 mm were the same in normal or preimmunized WAG/Rij Y rats or NCr(nu/nu) mice and in 6 Gy WBI NCr(nu/nu) mice. All of the experimental data show that the xenogenic NCr(nu/nu) mice accept the BA1112 as readily as do the isologous WAG/Rij Y rats.

Relative biological effectiveness of 241Am relative to 192Ir for continuous low-dose-rate irradiation of BA1112 rat sarcomas.

Sealed sources of 241Am have been developed for intracavitary irradiation of gynecological cancers. Relative to conventional isotopes (that is, 226Ra, 137Cs, 192Ir), 241Am allows for better shielding of dose-limiting normal tissues in the patient. In addition, the long half-life of 241Am (432 years) makes it an attractive isotope both for clinical use and for long-term radiobiology studies. Using a previously developed in vivo applicator system, BA1112 sarcomas on WAG/Rij Y rats were irradiated using 241Am or 192Ir at three different dose rates. Following in vivo treatment of the sarcomas with graded doses of radiation, cell survival curves were determined using an in vitro colony formation assay. The slopes of the resulting cell survival curves were observed to increase significantly as the dose rate increased from 0.30 to 0.60 Gy/h, then to decrease slightly as the dose rate increased from 0.60 to 0.95 Gy/h. The relative biological effectiveness (RBE) of 241Am relative to 192Ir was observed to increase linearly with increasing dose rate; the RBEs were 0.96 +/- 0.009, 1.09 +/- 0.12, and 1.17 +/- 0.11 at dose rates of 0.30, 0.60, and 0.95 Gy/h, respectively.

Effect of a perfluorochemical emulsion on the radiation response of BA1112 rhabdomyosarcomas.

The effect of treatment with a perfluorochemical emulsion (Fluosol DA, 20%), carbogen, or the combination of these two agents on the radiation response of BA1112 tumors in WAG/rij rats was examined. Fluosol and carbogen as single agents had only small effects on the tumor cell survival curve. The combination of Fluosol plus carbogen had a larger effect on tumor cell survival, reducing the hypoxic fraction of the tumor from 23 to 1.6%. The amount of sensitization was a function of the Fluosol dose, with maximal augmentation of the radiation response obtained at doses of 7.5-15 ml/kg. Carbogen pretreatments ranging from 5 to 60 min in duration all had similar effects on tumor radiosensitivity. The effect of the perfluorochemical emulsion plus carbogen on the survival of irradiated tumor cells appears to reflect changes in tumor oxygenation, rather than cytotoxic or immunological effects, since the perfluorochemical emulsion (with or without carbogen) had no effect on the viability of cells in unirradiated tumors. These experiments extend previous studies by ourselves and others using mouse tumors to show that the combination of a perfluorochemical emulsion and carbogen breathing can also increase the radiation response of a nonimmunogenic rat tumor.

Enhancement of tumor radiation response by the combination of a perfluorochemical emulsion and hyperbaric oxygen.

The presence of radioresistant hypoxic cells in tumors is believed to be one of the limiting factors in achieving local tumor control by radiotherapy. Treatment with hyperbaric oxygen during irradiation has been shown to improve the radiation response of many solid tumors in rodents and of some tumors in patients. Intravenous administration of perfluorochemical emulsions combined with oxygen breathing at atmospheric pressure has also been shown to improve the radiation response of several rodent tumors. Theoretical considerations suggest that the combination of a perfluorochemical emulsion and hyperbaric oxygen should be significantly more effective than either agent alone. This hypothesis was tested by examining the radiation response of BA1112 rhabdomyosarcomas growing in WAG/rij-Y rats. Treatment with a perfluorochemical emulsion, Fluosol-DA, plus hyperbaric oxygen (3 Atmospheres O2) significantly increased the radiation response of the malignant cells in these solid tumors. The observed changes in the tumor cell survival curve suggest that the combination of Fluosol-DA and HBO decreases the proportion of severely hypoxic cells in the tumor to less than 1.5% of the original value. The effect of the Fluosol-DA dose and the duration of pretreatment with HBO are described.