Immunoprecipitation Assay of Alpha-fetoprotein Synthesis by Cultured Mouse Hepatoma Cells Treated with Estrogens and Glucocorticords

This investigation was to study the biosynthesis of ³H-labeled alpha-fetoprotein (AFP) by cultured mouse hepatoma (HEPA-2) cells. Both the function and regulation of this oncodevelopmental gene are unknown. However, evidence indicates that mechanisms controlling the expression of AFP involve aspects of both normal embryonic development and neoplastic transformation. The secretion of AFP was analyzed during different phases of the growth cycle to provide information on AFP production using standard culture conditions. The highest rate of secretion occurred during the stationary phase, followed by the late logarithmic and early logarithmic phases of growth, respectively. The production of AFP was then determined following the addition of glucocorticords and estrogens in an attempt to understand hormonal factors that may be involved. Studies utilizing estradiol-17β indicated that the secretion of AFP did not appear to be sensitive to this steroid even though sucrose density gradient analysis of HEPA-2 cytosol, for estrogenic receptors, revealed competitive binding moieties in the 8S and 4S regions of the gradient. In contrast, the secretion of the total complement of proteins, including AFP, was significantly stimulated by the glucocorticords, dexamethasone and corticosterone. Analysis of HEPA-2 cytosol for glucocorticord receptors revealed binding components in the 7S and 3–4S regions of the gradient. The ³H-dexamethasone binding appeared to be stereospecific since nonlabeled dexamethasone, but not nonlabeled estradiol-17β, effectively displaced the bound radioactivity. The glucocorticoid-binding component in HEPA-2 therefore displayed characteristics reported for glucocorticord receptors in normal liver and other hepatomas.     

Analysis of mosquito bloodmeals by DNA profiling

Abstract. Human specific genetic markers have been used to profile the human DNA found within a mosquito bloodmeal. In this technique, variable numbers of tandem repeat (VNTR) sequences are employed to prime amplification of human DNA in the polymerase chain reaction (PCR) and the radiolabeled products are analysed by high resolution denaturing gel electrophoresis. Matching of DNA profiles allows identification of the individual human host. Bloodmeals of 125 female Anopheles gambiae Giles mosquitoes, caught dead or alive in verandah-trap huts wherein two people had slept overnight protected by intact insecticide-impregnated bednets, were analysed: thirty-five out of thirty-nine profiles generated were identical to those of the sleepers under the nets. Thus the blood-fed mosquitoes found after impregnated nets have been used cannot, in most cases, be explained away by entry of already fed mosquitoes into the huts.     

Resistance of sugar beet to the cyst-nematode Heterodera schachtii Schm.

Lines exhibiting heritable resistance and susceptibility to beet cyst nematode were selected from a heterogeneous cultivated variety of beet but no major gene resistance was detected although many hundreds of lines of wild and cultivated varieties were tested. Recurrent selection improved the resistance of one line, selected originally for yield and non-bolting qualities, when progenies in each generation were compared with susceptible controls and with the original ancestral lines. Resistance was inherited by progenies from selections crossed with susceptible plants, but evidence of some reduction in resistance was detectable where fewer eelworms were available to invade from the soil. There was no evidence of heritable cytoplasmic influence on the resistance. Resistance is probably controlled by a polygene system in sugar beet, although immunity in Beta procumbens and B. webbiana and near-immunity in B. patellaris suggest that in other species of Beta major gene resistance may occur.     

Biting and resting behaviour of anophelines in western Venezuela and implications for control of malaria transmission

A study was conducted in three villages in western Venezuela between February 1988 and October 1989 to determine the biting and resting activity of anophelines in relation to human habits, rainfall and fenitrothion spraying of houses. Mosquitoes were collected landing on humans inside and outside experimental huts throughout the night. Only three mosquitoes were found resting in the huts in the morning, but 2470 were collected resting on vegetation in the early morning. The collections yielded eleven species of anopheline, the most abundant being Anopheles nuneztovari, comprising over 75% of the total anophelines collected, followed by An.triannulatus, An.albitarsis s.l. and An.oswaldoi. The four most abundant species showed different diel patterns of biting. For An.nuneztovari the peak of activity was close to midnight indoors and outdoors, for An.triannulatus between 19.00 and 20.00 hours outdoors, for An.albitarsis mainly before midnight indoors and outdoors and for An.oswaldoi outdoors at 19.00 hours, with an additional smaller peak indoors at midnight. Most of the human population use bednets, go to bed before 22.00 hours and are therefore most exposed to mosquitoes that bite outdoors early in the night. Fenitrothion house-spraying failed to prevent large mosquito populations developing in the wet season, presumably because of their exophilic resting habits. The possible advantages of impregnation of existing bednets with pyrethroids, and provision of nets for people who do not have them, are discussed.     

Host choice of anopheline mosquitoes in a malaria endemic area of western Venezuela

Abstract. Bloodmeals of exophilic anopheline mosquitoes collected resting on vegetation in a malaria endemic area in western Venezuela were identified by ELISA. Using a TMB peroxidase substrate in the ELISA, human bloodmeals were readily identified up to 40 h after ingestion in all laboratory-fed mosquitoes tested. Assay sensitivity declined to 75% identifiable 44 h post-feeding.
The Human Blood Index and the Feeding Index of each species differed between the three villages studied. An.triannulatus was generally more anthropophilic than An.nuneztovari and An.oswaldoi. These contrasting results emphasize the difficulties of interpreting host choice data.