Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB) anion was highly lipophilic, practically insoluble in water, and durable against acid and oxidants. Partition equilibria of alkali TFPB between water and organic solvents and the stability in acid media are described and compared with the properties of the parent tetraphenylborate and of some fluorine-containing homologues.

The transport pathway of specific dietary carotenoids from the midgut lumen to the silk gland in the silkworm, Bombyx mori, is a model system for selective carotenoid transport because several genetic mutants with defects in parts of this pathway have been identified that manifest altered cocoon pigmentation. In the wild-type silkworm, which has both genes, Yellow blood (Y) and Yellow cocoon (C), lutein is transferred selectively from the hemolymph lipoprotein to the silk gland cells where it is accumulated into the cocoon. The Y gene encodes an intracellular carotenoid-binding protein (CBP) containing a lipid-binding domain known as the steroidogenic acute regulatory protein-related lipid transfer domain. Positional cloning and transgenic rescue experiments revealed that the C gene encodes Cameo2, a transmembrane protein gene belonging to the CD36 family genes, some of which, such as the mammalian SR-BI and the fruit fly ninaD, are reported as lipoprotein receptors or implicated in carotenoid transport for visual system. In C mutant larvae, Cameo2 expression was strongly repressed in the silk gland in a specific manner, resulting in colorless silk glands and white cocoons. The developmental profile of Cameo2 expression, CBP expression, and lutein pigmentation in the silk gland of the yellow cocoon strain were correlated. We hypothesize that selective delivery of lutein to specific tissue requires the combination of two components: 1) CBP as a carotenoid transporter in cytosol and 2) Cameo2 as a transmembrane receptor on the surface of the cells.All organisms exposed to light contain carotenoids, which are yellow to red C 40 hydrophobic isoprenoid pigments. Carotenoids play pivotal roles in living organisms as precursors of vitamin A, antioxidants, and colorants (1). Their potential roles in medicine have recently been investigated. For example, macular accumulation of the carotenoids lutein and zeaxanthin is associated with a decreased risk of age-related macular degeneration (2), the leading cause of blindness in the developed world. Although plants, certain fungi, and bacteria synthesize carotenoids, animals appear to be incapable of synthesizing these molecules de novo. Therefore, animals must acquire carotenoids from dietary sources, and subsequently transport them to cells of target tissues.The delivery of lipids, including carotenoids, to cells can be divided into three categories: 1) enzyme-mediated processes, such as the action of lipoprotein lipase on very low density lipoproteins, which converts a lipoprotein-bound lipid, triacylglycerol, into a water-soluble product, fatty acid, which diffuses into cells and leaves behind in the blood a lipoprotein product depleted in triacylglycerol (3); 2) receptor-mediated endocytosis, such as the uptake of low density lipoproteins by low density lipoprotein receptor, in which the entire lipoprotein particle is taken into the cell and metabolized (4); and 3) the delivery of specific lipids to specific tissues devoid of lipoprotein degradation, called selective lip...

We obtained two different clones (16 kb and 13 kb) of B. mori rDNA with intron sequence within the 28S-rRNA coding region. The sequence surrounding the intron was found to be highly conserved as indicated in several eukaryotes (Tetrahymena, Drosophila and Xenopus). The 28S rRNA-coding sequence of 16 kb and 13 kb clone was interrupted at precisely the same sites as those where the D. melanogaster rDNA interrupted by the type I and type II intron, respectively. The intron sequences of B. mori were different from those of D. melanogaster. In 16 kb clone, the intron was flanked by 14 bp duplication of the junction sequence, which was also present once within the 28S rRNA-coding region of rDNA without intron. This 14 bp sequence was identical with those surrounding the introns of Dipteran rDNAs.

The presence of long repetitive sequences is demonstrated in the genome of the silkworm, Bombyx mori. Members of this BMC1 family reveal several features typical of the L1 (long interspersed sequence one) family of mammals, except for species specific elements. The number of BMC1 elements is estimated to be approximately 3500 per haploid genome. Elements containing the full length unit of 5.1 kb are dispersed throughout the genome and their restriction sites are conserved, although most members are preferentially truncated to varying extents at their 5' ends. DNA sequencing indicates that this element contains six tandem repeats of 15 bp CpG-rich sequence in the 5' proximal region. It terminates with a 3' oligo(A) stretch, and is flanked at both ends by a 7-10 bp target sequence duplication. In addition, there is significant evidence for amino acid sequence homology with reverse transcriptase domains of other L1 families, especially F, Doc and Jockey of Drosophila melanogaster. No large open reading frame is present. The BMC1 element is suggested to be dispersed in the genome by a transposition mechanism involving RNA intermediates.

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