Chloroplast envelope membranes: a dynamic interface between plastids and the cytosol

Chloroplasts are bounded by a pair of outer membranes, the envelope, that is the only permanent membrane structure of the different types of plastids. Chloroplasts have had a long and complex evolutionary past and integration of the envelope membranes in cellular functions is the result of this evolution. Plastid envelope membranes contain a wide diversity of lipids and terpenoid compounds serving numerous biochemical functions and the flexibility of their biosynthetic pathways allow plants to adapt to fluctuating environmental conditions (for instance phosphate deprivation). A large body of knowledge has been generated by proteomic studies targeted to envelope membranes, thus revealing an unexpected complexity of this membrane system. For instance, new transport systems for metabolites and ions have been identified in envelope membranes and new routes for the import of chloroplast-specific proteins have been identified. The picture emerging from our present understanding of plastid envelope membranes is that of a key player in plastid biogenesis and the co-ordinated gene expression of plastid-specific protein (owing to chlorophyll precursors), of a major hub for integration of metabolic and ionic networks in cell metabolism, of a flexible system that can divide, produce dynamic extensions and interact with other cell constituents. Envelope membranes are indeed one of the most complex and dynamic system within a plant cell. In this review, we present an overview of envelope constituents together with recent insights into the major functions fulfilled by envelope membranes and their dynamics within plant cells. Special Issue of Photosynthesis Research in honor of Andrew A. Benson.     

Some physiological functions of the L-leucine dehydrogenase in Bacillus subtilis

Mutants of Bacillus subtilis constitutive for L-leucine dehydrogenase synthesis were selected. Using these mutants we could determine two functional roles for the L-leucine dehydrogenase. This enzyme liberates ammonium ions from branched chain amino acids when supplied as the sole nitrogen source. Another function is to synthesize from L-isoleucine, L-leucine, and L-valine the branched chain -keto acids which are precursors of branched chain fatty acid biosynthesis. These results together with the inducibility of the enzyme suggest that the L-leucine dehydrogenase has primarily a catabolic rather than an anabolic function in the metabolism of Bacillus subtilis.     

EVITA: a tool for the early EValuation of pharmaceutical Innovations with regard to Therapeutic Advantage

Background

New drugs are generally claimed to represent a therapeutic innovation. However, scientific evidence of a substantial clinical advantage is often lacking. This may be the result of using inadequate control groups or surrogate outcomes only in the clinical trials. In view of this, EVITA was developed as a user-friendly transparent tool for the early evaluation of the additional therapeutic value of a new drug.

Methods

EVITA does not evaluate a new compound per se but in an approved indication in comparison with existing therapeutic strategies. Placebo as a comparator is accepted only in the absence of an established therapy or if employed in an add-on strategy on top. The evaluation attributes rating points to the drug in question, taking into consideration both therapeutic benefit and risk profile. The compound scores positive points for superiority in efficiency and/or adverse effects as demonstrated in randomized controlled trials (RCTs), whilst negative points are awarded for inferiority and/or an unfavorable risk profile. The evaluation follows an algorithm considering the clinical relevance of the outcomes, the strength of the therapeutic effect and the number of RCTs performed. Categories for therapeutic aim and disease severity, although essential parts of the EVITA assessment, are attributed but do not influence the EVITA score which is presented as a color-coded bar graph. In case the available data were unsuitable for an EVITA calculation, a traffic-type yield sign is assigned instead to criticize such practice. The results are presented online http://www.evita-report.de together with all RCTs considered as well as the reasons for excluding a given RCT from the evaluation. This allows for immediate revision in response to justified criticism and simplifies the inclusion of new data.

Results

As examples, four compounds which received approval within the last years were evaluated for one of their clinical indications: lenalidomide, pioglitazone, bupropion and zoledronic acid. Only the first achieved an EVITA score above zero indicating therapeutic advantage.

Conclusions

The strength of EVITA appears to lie in its speedy assessment of the potential therapeutic advantage of a new drug for a given indication. At the same time, this approach draws attention to the typical deficits of data used for drug approval. EVITA is not intended to replace classical health technology assessment reports but rather serves as a screening tool in the sense of horizon scanning.     

Longitudinal analysis of taurine induced effects on the tear proteome of contact lens wearers and dry eye patients using a RP-RP-Capillary-HPLC-MALDI TOF/TOF MS approach

Tear proteomic studies revealed distinct similarities between contact lens wearers and dry eye patients. AMO Complete® multipurpose contact lens cleaning solutions containing taurine seem to have a beneficial effect regarding contact lens induced dry eye. To illuminate the effect of taurine on the tear proteome of contact lens wearers and sicca patients we developed a gel-based RP-RP capillary HPLC–MALDI TOF/TOF MS strategy. Two contact lens wearer groups, one using eye drops containing 0.05% taurine; the other for control physiological NaCl solution were monitored. Also, a third group of sicca patients using taurine solution was studied (N = 4 individuals/group). Tear pools of each group at six time points over 5 weeks were analyzed. In summary 267 tear proteins were identified. We found a protein subset showing a linear taurine response with R² values ≥ 0.5. Taurine effects were detected predominantly in the contact lens group demonstrated by distinct level decreases. Most protein candidates were related to inflammation. Since levels of these proteins differentiate from those of a healthy non-contact lens wearer reference they are supposed to be involved in contact lens induced dry eye and should be focused on in further studies.     

L-Homocysteine and L-homocystine stereospecifically induce endothelial nitric oxide synthase-dependent lipid peroxidation in endothelial cells

Atherothrombotic cardiovascular disease associated with hyperhomocysteinemia has been proposed to result, at least in part, from increased vascular oxidative stress. Here we characterize one mechanism by which homocyteine may induce a vascular cell type-specific oxidative stress. Our results show that L-homocysteine at micromolar levels stereospecifically increases lipid peroxidation in cultured endothelial cells, but not in vascular smooth muscle cells or when medium is incubated in the absence of cells. Consistent with these observations, homocysteine also increases the formation of intracellular reactive oxygen species. The pro-oxidant effect of homocysteine can be fully replicated by an equivalent concentration of homocystine (i.e., an oxidized form of homocysteine), but not with cysteine or glutathione. Homocyst(e)ine-dependent lipid peroxidation is independent of H(2)O(2) and alterations in glutathione peroxidase activity, but dependent on superoxide. Mechanistically, the pro-oxidant effect of homocysteine appears to involve endothelial nitric oxide synthase (eNOS), as it is blocked by the eNOS inhibitor L-N(G)-nitroarginine methyl ester. Thus, homocyst(e)ine actively promotes oxidative stress in endothelial cells via an eNOS-dependent mechanism.     

Human proximity and habitat fragmentation are key drivers of the rangewide bonobo distribution

Habitat loss and hunting threaten bonobos (Pan paniscus), Endangered (IUCN) great apes endemic to lowland rainforests of the Democratic Republic of Congo. Conservation planning requires a current, data-driven, rangewide map of probable bonobo distribution and an understanding of key attributes of areas used by bonobos. We present a rangewide suitability model for bonobos based on a maximum entropy algorithm in which data associated with locations of bonobo nests helped predict suitable conditions across the species’ entire range. We systematically evaluated available biotic and abiotic factors, including a bonobo-specific forest fragmentation layer (forest edge density), and produced a final model revealing the importance of simple threat-based factors in a data poor environment. We confronted the issue of survey bias in presence-only models and devised a novel evaluation approach applicable to other taxa by comparing models built with data from geographically distinct sub-regions that had higher survey effort. The model’s classification accuracy was high (AUC = 0.82). Distance from agriculture and forest edge density best predicted bonobo occurrence with bonobo nests more likely to occur farther from agriculture and in areas of lower edge density. These results suggest that bonobos either avoid areas of higher human activity, fragmented forests, or both, and that humans reduce the effective habitat of bonobos. The model results contribute to an increased understanding of threats to bonobo populations, as well as help identify priority areas for future surveys and determine core bonobo protection areas.     

A Pilot Study to Assess the Feasibility of Transcutaneous Glomerular Filtration Rate Measurement Using Fluorescence-Labelled Sinistrin in Dogs and Cats

In dogs and cats an assessment of renal function is often needed, however, existing methods including urine and plasma clearances are invasive, cumbersome and time consuming. This pilot study evaluated the feasibility of a transcutaneous glomerular filtration rate (GFR) measurement in dogs and cats. Additionally the optimal dose and location for the transcutaneous measurement device were investigated. Renal elimination of fluorescein-isothiocyanate-labelled sinistrin (FITC-S) was measured transcutaneously for 4 hours. The procedures were performed in awake, freely moving animals using escalating doses of FITC-S (10 mg/kg, 30 mg/kg, 50 mg/kg) with a wash-out period of at least 24 h in between. Multiple devices were placed on each animal. The resulting FITC-S disappearance curves were visually assessed to determine the most suitable location and the appropriate dose to reach an adequate transcutaneous peak signal for kinetic analysis. In both species 30 mg/kg were adequate for kinetic calculation. The most suitable place for the device was the lateral thoracic wall in dogs and the ventral abdominal wall in cats, respectively. Transcutaneous FITC-S clearance was then repeated using the optimal dose and location and in parallel with an additional plasma sinistrin clearance. Plasma elimination half-lives [min] were 26, 31 and 35, and corresponding transcutaneous elimination half-lives [min] were 26, 34 and 55, respectively in the dogs. Plasma elimination half-lives [min] were 51, 60 and 61, and corresponding transcutaneous elimination half-lives [min] were 75, 96 and 83, respectively in the cats. In conclusion, transcutaneous FITC-S clearance is a feasible method for the assessment of GFR in awake dogs and cats. It is noninvasive, well tolerated and easy to perform even in a clinical setting with results being readily available. A dose of 30 mg/kg of FITC-S seems adequate for kinetic assessment. Further studies are now needed to establish reference values and evaluate transcutaneous renal clearance in various conditions.     

Why Folkbiology Matters: Resource Conflict Despite Shared Goals and Knowledge

There is a continuing controversy over Native American fishing and hunting rights. We show that Native American (Menominee) and European American fish experts have a common knowledge base and share values and attitudes associated with fishing practices (though organized around different ethical principles). Nonetheless, perceived group differences are dramatic (especially European American perceptions of Native Americans). Cultural differences in models of nature and associated inference processes appear to mediate these stereotypes and may hold the key to reducing intergroup conflict over resources.