Relationship between postabsorptive respiratory exchange ratio and plasma free fatty acid concentrations

The relationship between overnight postabsorptive (fasting) respiratory exchange ratio (RER) and plasma FFA concentrations was addressed using data from three separate protocols, each of which involved careful control of the antecedent diet. Protocol 1 examined the relationship between fasting RER and the previous daytime RER. In Protocol 2 fasting, RER and plasma palmitate concentrations were measured in 29 women and 31 men (body mass index <30 kg·m⁻²). Protocol 3 analyzed data from Nielsen et al. (Nielsen, S., Z. K. Guo, J. B. Albu, S. Klein, P. C. O''Brien, M. D. Jensen. 2003. Energy expenditure, sex and endogenous fuel availability in humans. J. Clin. Invest. 111: 981-988.) to understand how fasting RER and palmitate concentrations relate within individuals during four consecutive measurements. The results were as follows: 1) Fasting RER was correlated (r = 0.74, P < 0.001) with the previous day''s average RER, and less so with RER variability. 2) Fasting RER was correlated (r = −0.39, P = 0.007) with fasting plasma palmitate concentrations. 3) The pattern of the RER/palmitate relationship was similar within individuals and between individuals; a negative slope was observed significantly more often than a positive slope (χ² test; P < 0.001). Our findings suggest that, despite a fixed food quotient, the slight departures from energy equilibrium in a controlled General Clinical Research Center environment can effect plasma FFA concentrations. We suggest that including indirect calorimetry as part of FFA metabolism studies may aid in data interpretation.     

Natural,semisynthetic and synthetic tyrosinase inhibitors

Tyrosinase plays a pivotal role in the synthesis of melanin pigment synthesis on skin utilizing tyrosine as a substrate. Melanin is responsible for the protection against harmful ultraviolet irradiation, which can cause significant pathological conditions, such as skin cancers. However, it can also create esthetic problems when accumulated as hyperpigmented spots. Various skin-whitening ingredients which inhibit tyrosinase activity have been identified. Some of them, especially ones with natural product origins, possess phenolic moiety and have been employed in cosmetic products. Semi-synthetic and synthetic inhibitors have also been developed under inspiration of the natural inhibitors yet some of which have no phenolic groups. In this review, tyrosinase inhibitors with natural, semi-synthetic and synthetic origins are listed up with their structures, activities and characteristics. Further, a recent report on the adverse effect of a natural melanin synthesis inhibitor which was included in skin-whitening cosmetics is also briefly discussed.     

Role of TARP interaction in S-SCAM-mediated regulation of AMPA receptors

Scaffolding proteins are involved in the incorporation, anchoring, maintenance, and removal of AMPA receptors (AMPARs) at synapses, either through a direct interaction with AMPARs or via indirect association through auxiliary subunits of transmembrane AMPAR regulatory proteins (TARPs). Synaptic scaffolding molecule (S-SCAM) is a newly characterized member of the scaffolding proteins critical for the regulation and maintenance of AMPAR levels at synapses, and directly binds to TARPs through a PDZ interaction. However, the functional significance of S-SCAM–TARP interaction in the regulation of AMPARs has not been tested. Here we show that overexpression of the C-terminal peptide of TARP-γ2 fused to EGFP abolished the S-SCAM-mediated enhancement of surface GluA2 expression. Conversely, the deletion of the PDZ-5 domain of S-SCAM that binds TARPs greatly attenuated the S-SCAM-induced increase of surface GluA2 expression. In contrast, the deletion of the guanylate kinase domain of S-SCAM did not show a significant effect on the regulation of AMPARs. Together, these results suggest that S-SCAM is regulating AMPARs through TARPs.     

Taxonomic Review of the Genus Eudorylas Aczél (Diptera: Pipunculidae) in Korea

The Korean species of the genus Eudorylas Aczél have been studied. A total of 16 species are arranged herein. Among them, E. paraappendiculatus sp. nov. is new to science, and E. nomurai Morakote et Yano, 1990 is newly recorded in the Korean fauna.     

Efficient expression of an Epstein-Barr nuclear antigen in Drosophila cells transfected with Epstein-Barr virus DNA.

In a search for exogenous promoters which function in cultured Drosophila cells, we have co-transfected a D. melanogaster cell line with an Epstein-Barr virus (EBV) cosmid clone which encodes the Epstein-Barr nuclear antigen (EBNA-1). Here we report that Drosophila cells containing stably integrated copies of EBNA-1 encoding DNA synthesise a polypeptide of mol. wt. identical to that of authentic EBNA-1, which is detectable with EBNA-positive but not EBNA-negative human serum. As in EBV-transformed lymphoblastoid cells, this neo-antigen is associated with the nucleus of transfected cells suggesting that cellular localisation signals which operate in mammalian cells are also recognised in insect cells.     

Regulated expression of a Drosophila melanogaster heat shock locus after stable integration in a Drosophila hydei cell line.

DNA-mediated cotransformation has been used to transfer a Drosophila melanogaster heat shock locus into cultured Drosophila hydei cells by use of the copia-based selectable vector pCV2gpt and of pMH10A, a cloned 87A7 heat shock locus encoding a mutant heat shock protein (hsp). Transformed lines contain between 50 and 200 copies of both plasmids, each separately organized as a head-to-tail concatemer which is stably maintained in the transformed lines. Exposure of the cotransformants to heat shock temperatures induces the regulated expression of the hsp RNA and the mutant hsp in all the lines analyzed.     

Differential effects of 1-deoxynojirimycin on the intracellular transport of secretory glycoproteins of human hepatoma cells in culture

To investigate our earlier hypothesis that carbohydrates play a regulatory role in the intracellular transport of secretory glycoproteins, we used 1-deoxynojirimycin (DNJ), and inhibitor of glucosidase I and II of the rough endoplasmic reticulum (RER), to modify the structure of N-linked glycan moieties of secretory glycoproteins of human hepatoma (Hep G2) cells in culture. Using a pulse-chase protocol, we found that treatment of Hep G2 cultures with 1.25 mM DNJ markedly reduced the rate of secretion of ₁-protease inhibitor, ceruloplasmin, and ₂-macroglobulin, but had no effect on the export of fibronectin, -fetoprotein and transferrin, nor on albumin which lacks carbohydrate. For example, 50% of newly synthesized ₁-protease inhibitor, the glycoprotein most dramatically affected, was secreted by 27 min in control cultures versus 110 min in DNJ-treated cultures. Percoll gradient cell fractionation analyses revealed that DNJ inhibited transport of the affected secretory glycoproteins in the RER segment of the ER/Golgi pathway. For example, 50% of newly synthesized ₁-protease inhibitor was lost from the RER fraction by 10 min in untreated cells, but 70 min was required for the transport of a similar amount of protein in DNJ-treated cells. DNJ treatment also inhibited the rate at which the N-linked glycan moieties of the affected glycoproteins became resistant to endo H in the Golgi. Since the glycan moiety of secreted forms of the affected glycoproteins were fully processed to the complex structure, suggesting escape from DNJ inhibition, we concluded that removal of terminal glucose residues from the glycan chain of secretory glycoproteins is required for their transport from the RER to the Golgi. We suggest that the oligosaccharide moieties on ₁-protease inhibitor, ceruloplasmin and ₂-macroglobulin form part of the binding site for a receptor which regulates transport of these glycoproteins.