Food For Thought: Short-Term Fasting Upregulates Glucose Transporters in Neurons and Endothelial Cells,But Not in Astrocytes

Neurochemical Research - Our group previously reported that 6-h fasting increased both insulin II mRNA expression and insulin level in rat hypothalamus. Given that insulin effects on central...     

The ER membrane complex (EMC) can functionally replace the Oxa1 insertase in mitochondria

Two multisubunit protein complexes for membrane protein insertion were recently identified in the endoplasmic reticulum (ER): the guided entry of tail anchor proteins (GET) complex and ER membrane complex (EMC). The structures of both of their hydrophobic core subunits, which are required for the insertion reaction, revealed an overall similarity to the YidC/Oxa1/Alb3 family members found in bacteria, mitochondria, and chloroplasts. This suggests that these membrane insertion machineries all share a common ancestry. To test whether these ER proteins can functionally replace Oxa1 in yeast mitochondria, we generated strains that express mitochondria-targeted Get2–Get1 and Emc6–Emc3 fusion proteins in Oxa1 deletion mutants. Interestingly, the Emc6–Emc3 fusion was able to complement an Δoxa1 mutant and restored its respiratory competence. The Emc6–Emc3 fusion promoted the insertion of the mitochondrially encoded protein Cox2, as well as of nuclear encoded inner membrane proteins, although was not able to facilitate the assembly of the Atp9 ring. Our observations indicate that protein insertion into the ER is functionally conserved to the insertion mechanism in bacteria and mitochondria and adheres to similar topological principles.

Redirecting the core subunits of the protein membrane insertion complex EMC into mitochondria rescues cells deficient for the mitochondrial Oxa1 system; this supports the hypothesis that the machinery for protein insertion into the ER membrane is functionally analogous to the YidC/Oxa1/Alb3 family of bacteria, mitochondria and chloroplasts.     

Flow cytometric sorting of sperm: Influence on fertilization and embryo/fetal development in the rabbit

Viable, intact rabbit sperm, prepared, processed, and flow cytometrically sorted, were used in this study to determine the influence of flow sorting on fertilization and embryo development. In experiment I, flow-sorted or control (unstained and unsorted) sperm were surgically inseminated into the uterine horn of hormonally primed does (10 to 12 does per time point). At 42 hr postsurgical insemination, flushed embryos were assessed for development. Fetal development was determined at day 7, day 14, and day 21 post-surgical insemination. Embryos resulting from does surgically inseminated with control sperm at 42 hr post-insemination were observed to be at the early morula stage of development (>16 cell), whereas embryos from does inseminated with flow sorted sperm were at the 8- to 16-cell stage. No difference was observed between treatments at day 7, 14, or 21, however, there was a significant decrease in fetus number per doe inseminated with flow-sorted sperm over time. In experiment II, mature oocytes were flushed from the oviducts of superovulated does and coincubated in vitro (IVF) with flow-sorted or control rabbit sperm. Oocytes observed at 6 hr post-coincubation exhibited swollen sperm heads in the cytoplasm, demonstrating that fertilization had occurred (2 PN + T). There was a higher percentage of fertilized oocytes by 8 hr post-coincubation for both control (31%) and flow-sorted sperm (31%) when used for IVF. By 10 and 12 hr post-coincubation, little difference was observed in the number of fertilized oocytes between sperm treatments (52% and 66% for control vs. 57 and 54% for flow-sorted, respectively). These studies demonstrate that flow-sorted sperm are capable of fertilizing mature oocytes under in vitro conditions. In addition they show that flow sorting may not negatively influence fertilization events, but likely interferes during early embryonic and fetal development. © 1996 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Transport and utilization of rhizoferrin bound iron in Mycobacterium smegmatis

Transport and metabolization of iron bound to the fungal siderophore rhizoferrin was analyzed by transport kinetics, Mössbauer and EPR spectroscopy. Saturation kinetics (v _max=24.4 pmol/(mg min), K _m=64.4M) and energy dependence excluded diffusion and provided evidence for a rhizoferrin transport system in M. smegmatis. Based on the spectroscopic techniques indications for intracellular presence of the ferric rhizoferrin complex were found. This feature could be of practical importance in the search of novel drugs for the treatment of mycobacterial infections. EPR and Mössbauer spectroscopy revealed different ferritin mineral cores depending on the siderophore iron source. This finding was interpreted in terms of different protein shells, i.e. two types of ferritins.     

Co-localization of beta1,6-branched oligosaccharides and coarse melanin in macrophage-melanoma fusion hybrids and human melanoma cells in vitro

Fusion hybrids between normal macrophages and Cloudman S91 melanoma cells were shown earlier to have increased metastatic potential, along with high expression of beta1,6-N-acetylglucosaminyltransferase V and beta1,6-branched oligosaccharides. Curiously, hybrids, but not parental melanoma cells, also produced 'coarse melanin'- autophagic vesicles with multiple melanosomes. As beta1,6-branched oligosaccharides were known to be associated with metastasis, and coarse melanin had been described in invasive human melanomas, we looked for potential relationships between the two. Using lectin- and immunohistochemistry, we analyzed cell lines producing coarse melanin for beta1,6-branched oligosaccharides: gp100/pmel-17 (a melanosomal structural component) and CD63 (a late endosome/lysosome component associated with melanoma and certain other human cancers). Cell lines used in this study were (i) hybrid 94-H48, a highly metastatic, macrophage-melanoma experimental fusion hybrid; (ii) 6(neo) mouse melanoma cells, the weakly metastatic, parental fusion partner; and (iii) SKmel-23, a human melanoma cell line derived from a metastasis. Coarse melanin granules were prominent both in hybrids and in SKmel-23 cells, and co-localized with stains for beta1,6-branched oligosaccharides, gp100/pmel 17, and CD63. This is the first report of this phenotype being expressed in vitro, although co-expression of beta1,6-branched oligosaccharides and coarse melanin was recently shown to be a common and pervasive characteristic in archival specimens of human melanomas, and was most prominent in metastases. The results suggest that pathways of melanogenesis in melanoma may differ significantly from those in normal melanocytes. In vitro expression of this phenotype provides new biological systems for more detailed analyses of its genesis and regulation at the molecular genetic level.     

Skin waste, vertex angle, and scar length in excisional biopsies: comparing five excision patterns--fusiform ellipse, fusiform circle, rhomboid, mosque, and S-shaped

The common excision skin pattern is either a fusiform ellipse or another pattern with dissimilar length and width. The purpose of this study was to define the most advantageous skin pattern regarding skin waste, vertex angle, and scar length. Five skin excision patterns used traditionally for closure of round lesions were analyzed: fusiform ellipse, fusiform circle, rhomboid, mosque, and S-shaped. In the analysis, the pattern characteristics were formulated by geometric principles, from which the results were compared. The smallest skin waste was found in rhomboid and mosque patterns, whereas the largest skin waste was found in the fusiform circle and ellipse. The vertex angle was found to decrease monotonously with the excision length-to-width ratio for all patterns except the mosque shape, which is zero per definition. The paradigm stating that a vertex angle of 30 degrees or less is maintained for length-to-width ratios below 4 in the surgical ellipse was found incorrect. It holds only for rhomboid and S-shaped excisions. The scar length was found almost independent of the pattern, with a variance of 3 percent. The authors conclude that the most advantageous surgical skin patterns are the rhomboid and mosque excisions.     

Thyroid receptor ligands. Part 2: Thyromimetics with improved selectivity for the thyroid hormone receptor beta

A set of thyromimetics having improved selectivity for TR-beta1 were prepared by replacing the 3'-isopropyl group of 2 and 3 with substituents having increased steric bulk. From this limited SAR study, the most potent and selective compounds identified were derived from 2 and contained a 3'-phenyl moiety bearing small hydrophobic groups meta to the biphenyl link. X-ray crystal data of 15c complexed with TR-beta1 LBD shows methionine 442 to be displaced by the bulky R3' phenyl ethyl amide side chain. Movement of this amino acid side chain provides an expanded pocket for the bulky side chain while the ligand-receptor complex retains full agonist activity.     

The EMBL Nucleotide Sequence Database: major new developments

The EMBL Nucleotide Sequence Database (http://www.ebi.ac.uk/embl/) incorporates, organizes and distributes nucleotide sequences from all available public sources. The database is located and maintained at the European Bioinformatics Institute (EBI) near Cambridge, UK. In an international collaboration with DDBJ (Japan) and GenBank (USA), data are exchanged amongst the collaborating databases on a daily basis to achieve optimal synchronization. Webin is the preferred web-based submission system for individual submitters, while automatic procedures allow incorporation of sequence data from large-scale genome sequencing centres and from the European Patent Office (EPO). Database releases are produced quarterly. Network services allow free access to the most up-to-date data collection via FTP, Email and World Wide Web interfaces. EBI's Sequence Retrieval System (SRS) integrates and links the main nucleotide and protein databases plus many other specialized molecular biology databases. For sequence similarity searching, a variety of tools (e.g. Fasta, BLAST) are available which allow external users to compare their own sequences against the latest data in the EMBL Nucleotide Sequence Database and SWISS-PROT. All resources can be accessed via the EBI home page at http://www.ebi.ac.uk.