A general and efficient trnsfection proce- (12) was synthesized from L-ornithine through biscyanoethylation followed by reduction of the dinitrile; amino groups were protected as t-butoxycarbonyl (Boc) derivatives. In order for the lipid headgroup to be able to anchor itself in the minor groove of DNA, a spacer arm was required (11) between the hydrocarbon chains and the polyamine. Therefore, a glycine residue was linked to dioctadecylamine (benzyloxycarbonylglycyl-p-nitrophenol at 1 equiv plus triethylamine at 1.1 equiv in CH2Cl2 for 5 hr; H2, 10%o Pd/C in CH2Cl2/EtOH for 1 hr; 87% overall yield). See Fig. 1 for schematic

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Studies were conducted to determine the host-feeding preference of Culex quinquefasciatus Say (Diptera: Culicidae) in relation to the availability of human and domestic animals in the city of Merida, Yucatan State, Mexico. Mosquitoes were collected in the backyards of houses using resting wooden boxes. Collections were made five times per week from January to December 2005. DNA was extracted from engorged females and tested by PCR using universal avian- and mammalian-specific primers. DNA extracted from avian-derived blood was further analyzed by PCR using primers that differentiate among the birds of three avian orders: Passeriformes, Columbiformes and Galliformes. PCR products obtained from mammalian-derived blood were subjected to restriction enzyme digestion to differentiate between human-, dog-, cat-, pig-, and horse-derived blood meals. Overall, 82% of engorged mosquitoes had fed on birds, and 18% had fed on mammals. The most frequent vertebrate hosts were Galliformes (47.1%), Passeriformes (23.8%), Columbiformes (11.2%) birds, and dogs (8.8%). The overall human blood index was 6.7%. The overall forage ratio for humans was 0.1, indicating that humans were not a preferred host for Cx. quinquefasciatus in Merida.

We have investigated the role of sequence motifs in the immunoglobulin heavy chain (IgH) enhancer on its activity in myeloma and fibroblast cell-lines. In transient transfection assays the transcription stimulatory activity of the enhancer is decreased in myeloma cells by mutating the E motifs 1, 2 and 3, the core motifs C1, C2, C3 and the octamer motif (OC) and in fibroblasts by mutating E2, E3, and C2. Our results suggest that transcription factors binding to E1, C1, C3 and OC contribute in a positive manner to the tissue specificity of the IgH enhancer.