The effect of tumour progression on lymphocyte responses to lectins,measured by fluorescence polarization techniques

The process of fluorochromasia involves the hydrolysis by cells of fluorescein diacetate resulting in an intracellular accumulation of fluorescein. The polarization of the fluorescence of the fluorescein appears to depend on the intracellular fluorescein concentration, the distribution of fluorescein within the cell and the viscosity of the cell cytoplasm.The parameters of fluorochromasia were studied with thymocytes from normal BALB/c mice and from mice bearing an intraperitoneal NK/LY/R lymphoma. During the course of tumour proliferation, the response toT-cell mitogens increased whereas the response to other lectins,e.g. wheat germ agglutinin, decreased or remained unaltered. These changes were consistent with the corresponding increase in immunocompetent cells within the thymus, observed by microelectrophoresis. Thus this sensitive technique provides a useful quantitative assessment of the lectin-lymphoid cell interaction.     

Electroantennogram responses of male Sphinx perelegans hawkmoths to floral and ‘green-leaf volatiles’

The effects of sublethal dosages of the chloronicotinyl insecticide imidacloprid on different strains of the tobacco whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), have been studied after leaf dip and systemic application. All bioassays were performed with the insecticide susceptible strain, SUD-S, and two Spanish biotypes, ALM-2 and LMPA-2, both resistant to conventional insecticides and with a lower susceptibility towards imidacloprid. Honeydew, excreted by all strains feeding on treated and untreated cotton leaf discs was quantified by photometric analysis of its carbohydrate content. EC50-values for the depression of honeydew excretion in female adults after systemic application of imidacloprid were calculated at 0.037 ppm, 0.027 ppm and 0.048 ppm for strains SUD-S, ALM-2 and LMPA-2, respectively, indicating no significant differences between strains in feeding behaviour throughout an 48 h testing period. Depending on the strain these EC50-values were 150- to 850-times lower than LC50-values calculated for mortality in the same bioassay. Starvation tests revealed mean survival times of >48 h for female adults placed on agar without leaf discs, indicating that sublethal dosages of imidacloprid which caused antifeedant responses, were probably not covered in common 48 h systemic bioassays, used to monitor resistance to imidacloprid. Effects of sublethal dosages on honeydew excretion after leaf dip application seem to be minor. In choice situations with systemically treated and untreated leaf discs in a single container, female adults of B. tabaci showed a clear preference for the untreated leaf discs. However, when using leaf discs treated by painting the surface with imidacloprid in the same bioassay, feeding activities on treated and untreated leaf discs were not significantly different. The results of the present study demonstrate the antifeedant properties of imidacloprid on B. tabaci, which might play an essential role after soil application or seed treatment under field conditions.     

Beta carotene is associated with the regression of hamster buccal pouch carcinoma and the induction of tumor necrosis factor in macrophages

Beta carotene (250 micrograms/ml) dissolved in mineral oil applied either topically or injected locally (190 ng/ml dissolved in media) into DMBA (7,12-dimethylbenz(a)anthracene)-induced or HCPC-1 cell line-produced oral squamous cell carcinoma of the hamster buccal pouch was observed to result in the regression of these tumors. (p less than or equal to .005) Beta carotene application to tumor bearing pouches was observed to produce a dramatic increase in positively stained macrophages for tumor necrosis factor (TNF-alpha) as compared to macrophages in control pouches. Macrophages from hamsters with regressed tumor were shown to produce a significant increase in cytotoxicity to HCPC-1 tumor cells. Regression of the hamster oral carcinoma was correlated with the increased capacity of macrophages to lyse tumor cells, and related to the induction of tumor necrosis factor which was associated with the administration of the carotenoid, beta carotene.