Water deficit and growth. Co-ordinating processes without an orchestrator?

Water deficit affects plant growth via reduced carbon accumulation, cell number and tissue expansion. We review the ways in which these processes are co-ordinated. Tissue expansion and its sensitivity to water deficit may be the most crucial process, involving tight co-ordination between the mechanisms which govern cell wall mechanical properties and plant hydraulics. The analyses of sensitivities, time constants and genetic correlations suggest that tissue expansion is loosely co-ordinated with cell division and carbon accumulation which may have limited direct effects on growth under water deficit. We therefore argue for essentially uncoupled mechanisms with feedbacks between them, rather than for a co-ordinated re-programming of all processes. Consequences on plant modelling and plant breeding in dry environment are discussed.     

To what extent can traditional medicine contribute a complementary or alternative solution to malaria control programmes?

Background

Sulphadoxine and pyrimethamine are anti-folate drugs that show synergistic anti-malarial effect. Point mutations in dihydrofolate reductase (dhfr) and dihydropteorate synthatase (dhps) cause anti-folate drug resistance phenotype in human malaria parasites. This study presents pattern of point mutations in dhfr/dhps genes among Indian sub-continent.

Methods

Microscopically diagnosed one hundred Plasmodium vivax field isolates were collected from five widely separated geographical regions of India. Dhfr and dhps genes were PCR amplified and sequenced. Previously published mutations data were collected and analyzed using Chi square test to identify geographical cluster of mutant/wild type genotypes.

Results

Sequence analysis revealed single (S58R), double (S58R/S117N) and quadruple (F57L/S58R/T61M/S117T/) point mutations at dhfr and single (A383G) to double (A383G/A553G) mutations at dhps in P. vivax field isolates. In addition, three new mutations were also observed at dhfr. Both, dhfr and dhps genes revealed tandem repeat variations in field isolates. Dhps revealed very low mutation frequency (14.0%) compared to dhfr (50.70%). Comparative analysis revealed a progressive increase in frequency of quadruple mutant dhfr genotype (p < 0.001) within five years in north-eastern state (Kamrup, Assam). Frequency of dhfr genotypes revealed three distinct geographical clusters of wild (northern India), double mutant (southern India), and quadruple mutant (north-eastern and island regions of India) on the Indian sub-continent.

Conclusion

Study suggests that SP may be susceptible to P. vivax in India, except Andaman and north-eastern state. The distinction of geographical regions with sensitive and resistant parasite phenotypes would be highly useful for designing and administering national anti-malarial drug policy.     

Chemical and physicochemical investigation of an aminoalkylalkoxysilane as strengthening agent for cellulosic materials

AMDES (aminopropylmethyldiethoxysilane) was used to investigate the physicochemical and chemical events related to the introduction of aminoalkylalkoxysilanes in cellulosic materials. Using (29)Si CP-MAS and (1)H NMR to study the reactivity and structural modification of AMDES in the paper it was shown that polymerization occurs in situ. The distribution of the active compound on the surface of the fibers and throughout the fibers' thickness was visualized by SEM-EDS. A relation between moisture content, fiber swelling, and uptake of AMDES was found. To better represent old and brittle documents, the paper was predegraded by oxidation with sodium hypochlorite. XRD confirmed the advanced destruction of the amorphous areas of cellulose. Adding AMDES in the oxidized paper resulted in improved mechanical properties, a roughly unmodified degree of polymerization of cellulose, but a slight increase in the yellowing, probably due to several possible reaction products such as imines, amine, amides, and Maillard reactions products. The deacidification efficacy was established and the strengthening effect was shown to arise from the interaction of AMDES with the cellulose fibers.     

Depleted genetic variation of the European ground squirrel in Central Europe in both microsatellites and the major histocompatibility complex gene: implications for conservation

Habitat fragmentation may influence the genetic make-up and adaptability of endangered populations. To facilitate genetic monitoring of the endangered European ground squirrel (EGS), we analyzed 382 individuals from 16 populations in Central Europe, covering almost half of its natural range. We tested how fragmentation affects the genetic architecture of presumably selectively neutral (12 microsatellites) and non-neutral (the major histocompatibility class II DRB gene) loci. Spatial genetic analyses defined two groups of populations, “western” and “eastern”, with a significantly higher level of habitat fragmentation in the former group. The highly fragmented western populations had significantly lower genetic diversity in both types of markers. Only one allele of the DRB gene predominated in populations of the western group, while four alleles were evenly distributed across the eastern populations. Coefficient of inbreeding values (F _IS) calculated from microsatellites were significantly higher in the western (0.27–0.79) than in eastern populations (−0.060–0.119). Inter-population differentiation was very high, but similar in both groups (western F _ST = 0.23, eastern F _ST = 0.25). The test of isolation by distance was significant for the whole dataset, as well as for the two groups analyzed separately. Comparison of genetic variability and structure on microsatellites and the DRB gene does not provide any evidence for contemporary selection on MHC genes. We suggest that genetic drift in small bottlenecked and fragmented populations may overact the role of balancing selection. Based on the resulting risk of inbreeding depression in the western populations, we support population management by crossbreeding between the western and eastern populations.     

Comparison between elementary flux modes analysis and 13C-metabolic fluxes measured in bacterial and plant cells

Background

Mitochondria are a vital component of eukaryotic cells and their dysfunction is implicated in a large number of metabolic, degenerative and age-related human diseases. The mechanism or these disorders can be difficult to elucidate due to the inherent complexity of mitochondrial metabolism. To understand how mitochondrial metabolic dysfunction contributes to these diseases, a metabolic model of a human heart mitochondrion was created.

Results

A new model of mitochondrial metabolism was built on the principle of metabolite availability using MitoMiner, a mitochondrial proteomics database, to evaluate the subcellular localisation of reactions that have evidence for mitochondrial localisation. Extensive curation and manual refinement was used to create a model called iAS253, containing 253 reactions, 245 metabolites and 89 transport steps across the inner mitochondrial membrane. To demonstrate the predictive abilities of the model, flux balance analysis was used to calculate metabolite fluxes under normal conditions and to simulate three metabolic disorders that affect the TCA cycle: fumarase deficiency, succinate dehydrogenase deficiency and α-ketoglutarate dehydrogenase deficiency.

Conclusion

The results of simulations using the new model corresponded closely with phenotypic data under normal conditions and provided insight into the complicated and unintuitive phenotypes of the three disorders, including the effect of interventions that may be of therapeutic benefit, such as low glucose diets or amino acid supplements. The model offers the ability to investigate other mitochondrial disorders and can provide the framework for the integration of experimental data in future studies.     

Bio-electrospraying primary cardiac cells: in vitro tissue creation and functional study

Manifestations of myocardial infarctions have been recognized as one of the major killers in the Western world. Therefore, advancing and developing novel cardiac tissue repair and replacement therapeutics have great implications to our health sciences and well-being. There are several approaches for forming cardiac tissues, non-jet-based and jet-based methodologies. A unique advantage of jet-based approaches is the possibility to handle living cells with a matrix for cell distribution and deposition in suspension, either as single or heterogeneous cell populations. Our previous studies on bio-electrospraying of cardiac cells have shown great promise. Here, we show for the first time the ability to bio-electrospray the three major cell types of the myocardium, both independently and simultaneously, for forming a fully functional cardiac tissue. Several samples are characterized in vitro and found to be indistinguishable in comparison to controls. Thus, we are describing a swiftly emerging novel biotechnique for direct cardiac tissue generation. Moreover, the present investigations pave the way for the development and optimization of a bio-patterning approach for the fabrication of biologically viable cardiac tissue grafts for the potential treatment of severe heart failure after myocardial infarction.     

A retinoic acid responsive Hoxa3 transgene expressed in embryonic pharyngeal endoderm, cardiac neural crest and a subdomain of the second heart field

A transgenic mouse line harbouring a β-galacdosidase reporter gene controlled by the proximal 2 kb promoter of Hoxa3 was previously generated to investigate the regulatory cues governing Hoxa3 expression in the mouse. Examination of transgenic embryos from embryonic day (E) 8.0 to E15.5 revealed regionally restricted reporter activity in the developing heart. Indeed, transgene expression specifically delineated cells from three distinct lineages: a subpopulation of the second heart field contributing to outflow tract myocardium, the cardiac neural crest cells and the pharyngeal endoderm. Manipulation of the Retinoic Acid (RA) signaling pathway showed that RA is required for correct expression of the transgene. Therefore, this transgenic line may serve as a cardiosensor line of particular interest for further analysis of outflow tract development.     

Urate oxidase purification by salting-in crystallization: towards an alternative to chromatography

Background

Rasburicase (Fasturtec® or Elitek®, Sanofi-Aventis), the recombinant form of urate oxidase from Aspergillus flavus, is a therapeutic enzyme used to prevent or decrease the high levels of uric acid in blood that can occur as a result of chemotherapy. It is produced by Sanofi-Aventis and currently purified via several standard steps of chromatography. This work explores the feasibility of replacing one or more chromatography steps in the downstream process by a crystallization step. It compares the efficacy of two crystallization techniques that have proven successful on pure urate oxidase, testing them on impure urate oxidase solutions.

Methodology/Principal Findings

Here we investigate the possibility of purifying urate oxidase directly by crystallization from the fermentation broth. Based on attractive interaction potentials which are known to drive urate oxidase crystallization, two crystallization routes are compared: a) by increased polymer concentration, which induces a depletion attraction and b) by decreased salt concentration, which induces attractive interactions via a salting-in effect. We observe that adding polymer, a very efficient way to crystallize pure urate oxidase through the depletion effect, is not an efficient way to grow crystals from impure solution. On the other hand, we show that dialysis, which decreases salt concentration through its strong salting-in effect, makes purification of urate oxidase from the fermentation broth possible.

Conclusions

The aim of this study is to compare purification efficacy of two crystallization methods. Our findings show that crystallization of urate oxidase from the fermentation broth provides purity comparable to what can be achieved with one chromatography step. This suggests that, in the case of urate oxidase, crystallization could be implemented not only for polishing or concentration during the last steps of purification, but also as an initial capture step, with minimal changes to the current process.