[1-13C]Glucose Metabolism in the Tumoral and Nontumoral Cerebral Tissue of a Glioma-Bearing Rat

C6 cells were used to establish a glioma-bearing rat model by stereotaxic injection in the left caudate nucleus. The tumor status was evaluated by magnetic resonance imaging and conventional histology. The glioma-bearing rats were infused for 1 h with a [1-(13)C]glucose solution. Perchloric acid extracts of the tumor and the ipsilateral and contralateral hemispheres were analyzed by 13C-NMR spectroscopy. The 13C-labeling patterns in compounds, mainly amino acids, indicated no drastic modification of carbon metabolism in both ipsilateral and contralateral hemispheres, as compared with control rats, whereas profound metabolic differences between brain tissue and tumor were observed. Glutamine C4 enrichment was lower in the glioma than in the brain [mean +/- SD values, 5.4 +/- 2.3 (n = 5) and 15.0 +/- 0.8% (n = 10), respectively] and also lower than the glutamate C4 enrichment in the glioma (mean +/- SD value, 22.6 +/- 4.2%; n = 5), indicating that tumor glutamine was neither synthesized inside the glioma nor taken up from the surrounding brain. The glutamine C4 enrichment in the serum (6.7 +/- 0.5%; n = 10) suggested that the glioma imported glutamine from the blood, a process probably connected with angiogenesis.     

The Saanen goat as an animal model for post-laryngectomy research: practical implications

A modern way of voice rehabilitation after total laryngectomy includes the use of shunt valves and tracheostoma valves. Problems of fixation to the surrounding tissue are a major drawback in the use of the shunt valve, heat and moisture exchange (HME) filters and, especially, the tracheostoma valve. To solve these problems different tissue connectors were developed. The main objective was to test the feasibility of these prototypes in a new animal model. Here we discuss the results, problems and complications of the selected Saanen goat model. In this prospective laboratory study, 19 healthy adult female Saanen goats (Capra hircus) were used and observed post-surgically for 12 weeks. Selection criteria such as comparable anatomy to humans and easy handling were used for animal model development. Also a literature search using the Medline and the ISI Web of Science databases was performed. The anatomy of the Saanen goat was investigated in a separate postmortem study. Surgery consisted of a laryngotracheal separation and implantation of a tracheo-oesophageal and tracheostoma tissue connector with fibrin tissue glue. Postoperative care consisted of frequent stoma care, monitoring appetite, weight, vital signs and administration of antibiotics, analgesics and mucolytic agents. All animals survived the surgical procedure. However, postoperative care was extensive, labour intensive and was accompanied by several complications. Eleven animals died spontaneously before the end of the experiment. The tracheostoma tissue connector caused signs of local infection in all cases. There was no evidence of infection around the tracheo-oesophageal tissue connector in 18 cases. It was concluded that the use of goats in this tracheostoma model was associated with major complications and should, therefore, only be used for short-term experiments with intensive care. Additional research is needed to see if clinical application of the tissue connectors is possible in the future.     

Plumage colour variations in the Agapornis genus: a review

The genus Agapornis consists of nine small African parrot species that are globally well known as pets, but are also found in their native habitat. Illegal trapping, poaching and habitat destruction are the main threats these birds face in the wild. In aviculture, Agapornis breeding is highly popular all across the globe. Birds are mainly selected based on their plumage colour variations but very little molecular research has been conducted on this topic. There are 30 known colour variations amongst the nine species and most of these are inherited as Mendelian traits. However, to date none of the genes or polymorphisms linked to these variations have been identified or verified. Due to unethical breeding practices, the need for the development of molecular tests such as identification verification tests or species identity tests is growing. Future research is paramount to ensure the conservation of wild populations as well as aiding breeders in improving breeding strategies.     

Birbeck Granule-Like “Organized Smooth Endoplasmic Reticulum” Resulting from the Expression of a Cytoplasmic YFP-Tagged Langerin

Langerin is required for the biogenesis of Birbeck granules (BGs), the characteristic organelles of Langerhans cells. We previously used a Langerin-YFP fusion protein having a C-terminal luminal YFP tag to dynamically decipher the molecular and cellular processes which accompany the traffic of Langerin. In order to elucidate the interactions of Langerin with its trafficking effectors and their structural impact on the biogenesis of BGs, we generated a YFP-Langerin chimera with an N-terminal, cytosolic YFP tag. This latter fusion protein induced the formation of YFP-positive large puncta. Live cell imaging coupled to a fluorescence recovery after photobleaching approach showed that this coalescence of proteins in newly formed compartments was static. In contrast, the YFP-positive structures present in the pericentriolar region of cells expressing Langerin-YFP chimera, displayed fluorescent recovery characteristics compatible with active membrane exchanges. Using correlative light-electron microscopy we showed that the coalescent structures represented highly organized stacks of membranes with a pentalaminar architecture typical of BGs. Continuities between these organelles and the rough endoplasmic reticulum allowed us to identify the stacks of membranes as a form of “Organized Smooth Endoplasmic Reticulum” (OSER), with distinct molecular and physiological properties. The involvement of homotypic interactions between cytoplasmic YFP molecules was demonstrated using an A206K variant of YFP, which restored most of the Langerin traffic and BG characteristics observed in Langerhans cells. Mutation of the carbohydrate recognition domain also blocked the formation of OSER. Hence, a “double-lock” mechanism governs the behavior of YFP-Langerin, where asymmetric homodimerization of the YFP tag and homotypic interactions between the lectin domains of Langerin molecules participate in its retention and the subsequent formation of BG-like OSER. These observations confirm that BG-like structures appear wherever Langerin accumulates and confirm that membrane trafficking effectors dictate their physiology and, illustrate the importance of molecular interactions in the architecture of intracellular membranes.     

Quantum Molecular Modeling of the Interaction Between Guanine and Alkylating Agents - 2 - Nitrogen Mustard

Abstract

The alkylation mechanism of guanine by nitrogen mustard (HN2) was studied by using a supermolecular modeling at the ab initio 6–31G level. Our computations show that interaction of guanine with the aziridinium form of HN2 necessitates a transition state for the N7 alkylation route. The pathway of N7-guanine alkylation by nitrogen and sulfur mustards is discussed on the basis of the Molecular Electrostatic Potential and HOMO-LUMO properties of these molecules.     

Diversification of South American spiny rats (Echimyidae): a multigene phylogenetic approach

Fabre, P.‐H., Galewski, T., Tilak, M.‐k. & Douzery, E.J.P. (2012) Diversification of South American spiny rats (Echimyidae): a multigene phylogenetic approach. —Zoologica Scripta, 00, 000–000. We investigated the phylogenetic relationships of 14 Echimyidae (spiny rats), one Myocastoridae (nutrias) and one Capromyidae (hutias) genera based on three newly sequenced nuclear genes (APOB, GHR and RBP3) and five previously published markers (the nuclear RAG1 and vWF, and the mitochondrial cytochrome b, 12S rRNA and 16S rRNA). We recovered a well‐supported phylogeny within the Echimyidae, although the evolutionary relationships among arboreal echimyid taxa remain unresolved. Molecular divergence times estimated using a Bayesian relaxed molecular clock suggest a Middle Miocene origin for most of the extant echimyid genera. Echimyidae seems to constitute an example of evolutionary radiation with high species diversity, yet they exhibit only narrow skull morphological changes, and the arboreal and terrestrial taxa are shown to retain numerous plesiomorphic features. The most recent common ancestor of spiny rats is inferred to be a ground‐dwelling taxon that has subsequently diverged into fossorial, semiaquatic and arboreal habitats. The arboreal clade polytomy and ancestral character estimations suggest that the colonization of the arboreal niche constituted the keystone event of the echimyid radiation. However, biogeographical patterns suggest a strong influence of allopatric speciation in addition to ecology‐driven diversification among South American spiny rats.     

Molecular Characterization of a Phage-Encoded Resistance System in Lactococcus lactis

A specific fragment of the genome of Tuc2009, a temperate lactococcal bacteriophage, was shown to contain several open reading frames, whose deduced protein products exhibited similarities to proteins known to be involved in DNA replication and modification. In this way, a putative single-stranded binding protein, replisome organizer protein, topoisomerase I, and a methylase were identified. When the genetic information coding for the putative replisome organizer protein of Tuc2009, Rep₂₀₀₉, was supplied on a high-copy-number plasmid vector, it was shown to confer a phage-encoded resistance (Per) phenotype on its lactococcal host UC509.9. The presence of this recombinant plasmid was shown to cause a marked reduction in Tuc2009 DNA replication, suggesting that the observed phage resistance was due to titration of a factor, or factors, required for Tuc2009 DNA replication. Further experiments delineated the phage resistance-conferring region to a 160-bp fragment rich in direct repeats. Gel retardation experiments, which indicated a protein-DNA interaction between this 160-bp fragment and the Rep₂₀₀₉ protein, were performed. UC509.9 strains harboring plasmids with randomly mutated versions of this fragment were shown to display a variable phage resistance phenotype, depending on the position of the mutations.     

Compensatory mechanisms mitigate the effect of warming and drought on wood formation

Because of global warming, high‐latitude ecosystems are expected to experience increases in temperature and drought events. Wood formation will have to adjust to these new climatic constraints to maintain tree mechanical stability and long‐distance water transport. The aim of this study is to understand the dynamic processes involved in wood formation under warming and drought. Xylogenesis, gas exchange, water relations and wood anatomy of black spruce [Picea mariana (Mill.) B.S.P.] saplings were monitored during a greenhouse experiment where temperature was increased during daytime or night‐time (+6 °C) combined with a drought period. The kinetics of tracheid development expressed as rate and duration of the xylogenesis sub‐processes were quantified using generalized additive models. Drought and warming had a strong influence on cell production, but little effect on wood anatomy. The increase in cell production rate under warmer temperatures, and especially during the night‐time warming at the end of the growing season, resulted in wider tree‐rings. However, the strong compensation between rates and durations of cell differentiation processes mitigates warming and drought effects on tree‐ring structure. Our results allowed quantification of how wood formation kinetics is regulated when water and heat stress increase, allowing trees to adapt to future environmental conditions.     

Both raft- and non-raft proteins associate with CHAPS-insoluble complexes: some APP in large complexes

Components of caveolae and lipid rafts are characterized by their buoyancy after detergent extraction. Using flotations in density gradients, we now show that non-raft membrane molecules are also associated with detergent-insoluble, buoyant assemblies. When Triton X-100 cellular extracts were spun to equilibrium in Nycodenz, only components of classical rafts floated. In contrast, with the zwitterionic detergent CHAPS, non-raft residents such as calnexin and APP also buoyed. When CHAPS extracts were spun in non-equilibrium (velocity) conditions, some raft components rapidly exited the input fractions while other raft markers and non-raft molecules remained relatively immobile. This pointed to size heterogeneities of CHAPS-insoluble complexes. Combined velocity/equilibrium gradients broadly divided CHAPS-insoluble membrane complexes into three size categories, which all contained cholesterol and the glycosphingolipid GM1. Large complexes were enriched in caveolin and ESA. Medium size complexes were enriched in PrP, whereas small complexes contained non-raft proteins, PrP, and some ESA. While Alzheimer's APP was primarily confined to small assemblies, a portion of its glycosylated form did buoy with large complexes. Large CHAPS-insoluble complexes resemble, but are not equal to, classical rafts. These findings extend considerably the range of detergent-insoluble membranal domains.