RESUMO
In this study, we developed an effective technology for the extraction of sericin from silk cocoons by deep sea water (DSW). We focused on extraction of sericin in the absence of chemical additives to obtain a safe, effective, inexpensive sericin powder. Sericin was extracted using a simple high-temperature process involving heating, condensation with Molus alba, filtering with cotton cloth, cold storage, and lyophilization. The results showed that the yield of sericin (26%) extracted by DSW was approximately 2% higher than that obtained using a chemical buffer (0.2 M Na2CO3, 24%). The marine mineral sericin M. alba (MSM) showed a size distribution of 15-250 kDa, with major peaks at 75-250 kDa with a galactose chain. Additionally, this MSM product had high antioxidant, whitening, and antibiosis effects and could be safely stored for a long time. Thus, our findings supported the use of a DSW extraction method, which was ecofriendly and yielded a proteinous, biodegradable biopolymer, for preparation of sericin.
RESUMO
Retinoid X receptors (RXRs) are highly conserved members of the nuclear hormone receptor family that mediate various physiological processes in vertebrates and invertebrates. We examined the expression patterns of RXR in the ascidian Halocynthia roretzi across a wide range of tissues and stages of embryo development, as well as the regulation of gene transcription by the ascidian RXR. H. roretzi RXR cDNA (HrRXR) was cloned from 64-cell stage embryos. The overall amino acid sequence of HrRXR showed high sequence identity with a urochordate Ciona intestinalis RXR (58%), but the ligand-binding domain of HrRXR was more similar to vertebrate orthologs than to those of invertebrate RXRs. Based on a phylogenetic analysis, HrRXR belongs to a group of urochordates that are separate from vertebrate RXRs, showing a clear evolutionary history. Real-time quantitative polymerase chain reaction and whole-mount in situ hybridization analyses revealed that the HrRXR mRNA is of maternal origin during embryogenesis, and in the examined adult tissues it is expressed in the muscles, gills, gonads, and the hepatopancreas. Immunofluorescence and immunohistochemical staining demonstrated that HrRXR is localized to the nucleus and highly expressed in the gills and hepatopancreas. Unlike human RXRα, HrRXR did not show 9-cis retinoic acid- and bexarotene (LGD1069)-dependent transactivation. While a synthetic ligand for farnesoid X receptor (FXR), GW4064, did not increase the transcriptional activation in HrRXR- or HrRXR/HrFXR-transfected HEK-293 cells, the ligand showed weak but significant activity for a single amino acid mutant of HrRXR ((Phe)231(Cys)) and HrFXR cotransfected cells. The present study suggests that the marine invertebrate chordate RXR may possess endogenous ligands that are different than vertebrate RXR ligands and which function during early embryonic stages.
