Metabolic engineering of plants for the synthesis of polyhydroxyalkanoates

Synthesis of polyhydroxyalkanoates (PHAs) in crop is viewed as an attractive approach for the production of this family of biodegradable plastics in large quantities and at low costs. Synthesisof PHAs containing various monomers has so far been demonstrated in the cytosol, plastids, and peroxisomes of plants. Several biochemical pathways have been modifies to achieve this, including the isoprenois pathway, the fatty acid biosynthetic pathway, and the fatty acid

Review on polyhydroxyalkanoate formation in the model plant Arabidopsis thaliana

In order to explore potential alternatives to the production of polyhydroxyalkanoates (PHAs) in bacteria, the enzymes of Alcaligenes eutrophus involved in the synthesis of polyhydroxybutyrate (PHB) have been expressed in the model plant Arabidopsis thaliana. Following the successful production of low amounts of high molecular weight PHB in plants expressing the acetoacetyl-CoA reductase and the PHB synthase in the cytoplasm of Arabidopsis cell, expression of the PHB pathway in the pastids was achieved by modifying the PHB enzymes with plastid targeting signals. This strategy resulted in a significant increase in the formation of PHB in Arabidopsis, with a maximum of 14% of the leaf dry weight . The increase in PHB production is most likely due to the higher flux in the plastids of acetyl-CoA, the precursor for PHB synthesis. A detailed study of metabolic fluxes in Arabidopsis plants producing high levels of PHB could help to determine the potential problems and limitations of PHB synthesis in Arabidopsis and could be useful for optimising strategies for the production of PHB in crop plants. The knowledge on PHB production could also be used for the production of PHAs other than PHB. Apart from PHB, no other PHAs have been produced in an eukaryotic system. Arabidopsis will therefore be used as a model system for the production in eukaryotes of more complex PHAs, such as poly(hydroxybutyrate-co-hydroxyvylerate) or medium-chain-lenght-PHAs.

Neurotoxicity of dibutyltin in aggregating brain cell cultures.

Dibutyltin (DBT) compounds are used primarily as stabilizers for polyvinyl chloride (PVC) plastics. Small quantities can be released from PVC containers into stored liquids. The neurotoxicological potential of DBT was tested in aggregating brain cell cultures after a 10-day treatment with concentrations ranging from 10(-10) to 10(-6)m, either during an early developmental period, or during a phase of advanced maturation. Changes in protein content, DNA labelling and cell type-specific enzyme activities were measured as end points. DBT caused general cytotoxicity at 10(-6)m in both immature and differentiated cultures. At 10(-7)m, it affected the myelin content and the cholinergic neurons in both states of maturation, while GABAergic neurons remained unchanged. Astrocyte and oligodendrocyte markers were diminished at 10(-7)m of DBT exclusively in immature cultures. DBT uptake by undifferentiated and differentiated cells was similar at this concentration. Whereas trimethyltin (TMT) is known to induce gliosis and triethyltin (TET) to cause demyelination and affect GABAergic neurons, DBT appeared to be more toxic than TMT, and to present a distinct toxicological pattern.

Release of vancomycin and teicoplanin from a plasticized and resorbable gelatin sponge: in vitro investigation of a new antibiotic delivery system with glycopeptides.

BACKGROUND: The aim of this study was to evaluate the efficacy of sustained release of vancomycin and teicoplanin from a resorbable gelatin glycerol sponge, in order to establish a new delivery system for local anti-infective therapy. MATERIALS AND METHODS: 60 plasticized glycerol gelatin sponges containing either 10 or 20% gelatin (w/v) were incubated in vancomycin or teicoplanin solution at 20 degrees C for either 1 or 24 h. In vitro release properties of the sponges were investigated over a period of 1 week by determining the levels of vancomycin and teicoplanin eluted in plasma using fluorescent polarization immunoassay. The rate constant and the half-life for the antibiotic release of each group were calculated by linear regression assuming first order kinetics. RESULTS: Presoaking for 24 h was associated with a significant increase in the total antibiotic release in all groups opposed to 1 h of incubation, except for the 10% sponges presoaked in teicoplanin. Doubling the gelatin content of the sponges from 10 to 20% significantly increased the total release of antibiotic load only in teicoplanin-containing sponges after 24 h incubation. In all corresponding groups investigated, release of vancomycin was more prolonged compared to teicoplanin, which allowed a gradual release beyond 5 days. The half-life (h +/- SEM) of both types of vancomycin-containing sponges was significantly prolonged by 24 h incubation in comparison to 1 h incubation (29.1 +/- 5.9 vs 5.9 +/- 1.0; p < 0.001, 30.0 +/- 2.1 vs 11.1 +/- 1.9; p < 0.001). However, neither doubling the gelatin content of the sponges nor a prolonged incubation was associated with a significantly prolonged delivery of teicoplanin. CONCLUSION: This study demonstrated a better diffusion-controlled release of vancomycin-impregnated glycerol gelatin sponges compared to those pretreated with teicoplanin. The plasticized glycerol gelatin sponge may be a promising carrier for the application of vancomycin to infected wounds for local anti-infective therapy.

Isotope ratio mass spectrometry as a tool for source inference in forensic science: a critical review

Isotope ratio mass spectrometry (IRMS) has been used in numerous fields of forensic science in a source inference perspective. This review compiles the studies published on the application of isotope ratio mass spectrometry (IRMS) to the traditional fields of forensic science so far. It completes the review of Benson et al. [1] and synthesises the extent of knowledge already gathered in the following fields: illicit drugs, flammable liquids, human provenancing, microtraces, explosives and other specific materials (packaging tapes, safety matches, plastics, etc.). For each field, a discussion assesses the state of science and highlights the relevance of the information in a forensic context. Through the different discussions which mark out the review, the potential and limitations of IRMS, as well as the needs and challenges of future studies are emphasized. The paper elicits the various dimensions of the source which can be obtained from the isotope information and demonstrates the transversal nature of IRMS as a tool for source inference.

Oeil et environnement

Résumé L'oeil est exposé à de multiples facteurs environnementaux qui influent sur le développement visuel, le confort et la santé visuelle. Une exposition excessive à la lumière solaire peut causer des pathologies de la surface oculaire et de la rétine, mais une exposition insuffisante à la lumière du jour pourrait être incriminée dans l'apparition ou la progression de la myopie. Les lumières artificielles, LED en particulier, comportent un risque accru de phototoxicité rétinienne. L'augmentation importante de la prévalence des allergies oculaires pourrait être liée à la multiplication des polluants environnementaux, comme la fumée de tabac, les dérivés de combustion de carburants ou les phtalates. Enfin, certains compléments alimentaires peuvent jouer un rôle protecteur dans certains types d'atteintes oculaire, rétinienne en particulier. Abstract The eyes are exposed to multiple environmental factors, which affect visual development, comfort, and visual health. While overexposure to sunlight can cause ocular surface and retinal pathologies, insufficient exposure to daylight could significantly contribute to myopia progression. New artificial lights, namely LED, have a higher risk of retinal phototoxicity, and could alter ocular circadian rhythm. The significant increase of prevalence of ocular allergies could be caused by the proliferation of environmental polluting substances, like tobacco smoke, fuel combustion by-products, or phtalates, which are found in many types of plastics. Finally, some dietary supplements could play a protective role in certain types of ocular pathologies, namely retinal pathologies.