Separation of plant membranes by electromigration techniques

The review focuses on the multiple separating regimes that offers the free flow electrophoresis technique: free flow zone electrophoresis, isoelectric focusing, isotachophoresis, free flow step electrophoresis. Also, the feasibility to apply either interval or continuous flow electrophoresis is evaluated. The free flow zone electrophoresis regime is generally selected for the separation of cells, organelles and membranes while the other regimes find their largest fields of applications in the purification of proteins and peptides. The latter regimes present the highest resolution efficiency. Therefore, a large part of this review is devoted to the applicabilities of these different regimes to the purification of organelles and membrane vesicles at the preparative scale. Recent developments, both in instrumentation and procedures, are described. The major achievements in plant membrane fractionation obtained with free flow electrophoresis are outlined. The related procedures are both analytical and preparative: they separate tonoplast and plasma membrane simultaneously from the same homogenate, they discriminate for one type of membrane vesicles of opposite orientation, and process large quantities of membrane material by reason of the continuous flow mode. Recent advances using electromigration techniques that permit confirmation of the dynamic state of membranes, characterisation of complex membrane-dependent functions and discovery of new membrane-localised activities are presented.     

Quantitative histology of the hypertrophied human heart

Myocardial hypertrophy accompanies systemic hypertension and aortic stenosis, i.e., pressure overload. In man cardiac failure only appears after years of pressure overload, during which time cardiac function had been maintained. The structural correlates of cardiac failure have been a subject of much interest for many years. Several hypotheses relating alterations in muscle fiber alignment, capillary density, or collagen content have been offered. The application of morphometric techniques has provided essential quantitative information on the structural components of the normal and diseased heart. These data indicate that muscle fiber alignment remains normal in the pressure overloaded heart despite the presence of hypertrophy or the appearance of clinical failure. On the other hand, capillary density is decreased and collagen content is increased in hypertrophied hearts. Chemical studies on collagen concentration however have yielded inconsistent results. The relative contribution of the microcirculation and collagenous structure of the myocardium on its respective O2 availability, mechanical behavior, and deterioration in pump function will require further investigation.     

Biotic and abiotic determinants of the formation of ant mosaics in primary Neotropical rainforests

1. Ants are widespread in tropical rainforests, including in the canopy where territorially dominant arboreal species represent the main part of the arthropod biomass. 2. By mapping the territories of dominant arboreal ant species and using a null model analysis and a pairwise approach this study was able to show the presence of an ant mosaic on the upper canopy of a primary Neotropical rainforest (c. 1 ha sampled; 157 tall trees from 28 families). Although Neotropical rainforest canopies are frequently irregular, with tree crowns at different heights breaking the continuity of the territories of dominant ants, the latter are preserved via underground galleries or trails laid on the ground. 3. The distribution of the trees influences the structure of the ant mosaic, something related to the attractiveness of tree taxa for certain arboreal ant species rather than others. 4. Small‐scale natural disturbances, most likely strong winds in the area studied (presence of canopy gaps), play a role by favouring the presence of two ant species typical of secondary formations: Camponotus femoratus and Crematogaster levior, which live in parabiosis (i.e. share territories and nests but lodge in different cavities) and build conspicuous ant gardens. In addition, pioneer Cecropia myrmecophytic trees were recorded.     

Sex-biased dispersal promotes adaptive parental effects

Background  

In heterogeneous environments, sex-biased dispersal could lead to environmental adaptive parental effects, with offspring selected to perform in the same way as the parent dispersing least, because this parent is more likely to be locally adapted. We investigate this hypothesis by simulating varying levels of sex-biased dispersal in a patchy environment. The relative advantage of a strategy involving pure maternal (or paternal) inheritance is then compared with a strategy involving classical biparental inheritance in plants and in animals.     

Use of ATP bioluminescence measurements for the estimation of biomass during biological humification

Summary The development of the microflora during the humification of grape pulp has been investigated by the determination of ATP using the bioluminescence technique. Several extraction methods were tested including the use of dimethylsulphoxide, trichloroacetic acid, grinding and ultrasonification. Dimethylsulphoxide and ultrasonification for 15 sec appeared to be the most effective. The ATP extract was stabilized when it was mixed with 0.75 mM glycine, 4.4 mM Mg-EDTA, pH 7.5 and frozen. The relative error of the ATP assay by bioluminescence did not exceed 6.5%. This method allowed us to show that at least five distinct reproducible microbial phases exist during grape pulp humification. These results show that the microbial biomass changes noticeably and at distinct times during composting.     

Clinical applications of Genome Polymorphism Scans

Applications of Genome Polymorphism Scans range from the relatively simple such as gender determination and confirmation of biological relationships, to the relatively complex such as determination of autozygosity and propagation of genetic information throughout pedigrees. Unlike nearly all other clinical DNA tests, the Scan is a universal test – it covers all people and all genes. In balance, I argue that the Genome Polymorphism Scan is the most powerful, affordable clinical DNA test available today.     

Ultrastructure d'une cyanophycée aérienne calcifiée cavernicole: Geitleria calcarea Friedmann

Résumé L'ultrastructure de Geitleria calcarea Friedmann, cyanophycée filamenteuse aérienne, calcifiée et cavernicole, rarement signalée, est étudiée ici pour la première fois. La cytologie de cet organisme présente des originalités. Huit enveloppes cellulaires concentriques sont dénombrées: membrane plasmique, L I, L II, L III, L IV, enveloppe pariétale, gaine fibreuse et gaine carbonatée. La dernière est décrite à l'aide du M.E.B. Les thylacoïdes très nombreux ont une forme extrêmement contournée. Ils supportent des phycobilisomes cylindriques alternant avec des polysaccharides de même allure. L'organisation des synapses est détaillée. L'élongation est apicale et le mode de ramification est soit latéral, soit dichotomique.

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The ultrastructure of the atmophytic lime-encrusted filamentous blue-green alga Geitleria calcarea Friedmann, which grows in caves, is studied here for the first time. The cytology of this organism presents original features concerning the cellular sheath, envelopes, wall, thylacoïds and pit connections. Its filament growth is apical and its type of branching is lateral and dichotomous.

     

Comparison of basic peptides- and lipid-based strategies for the delivery of splice correcting oligonucleotides

Expression of alternatively spliced mRNA variants at specific stages of development or in specific cells and tissues contributes to the functional diversity of the human genome. Aberrations in alternative splicing were found as a cause or a contributing factor to the development, progression, or maintenance of numerous diseases. The use of antisense oligonucleotides (ON) to modify aberrant expression patterns of alternatively spliced mRNAs is a novel means of potentially controlling such diseases. Oligonucleotides can be designed to repair genetic mutations, to modify genomic sequences in order to compensate for gene deletions, or to modify RNA processing in order to improve the effects of the underlying gene mutation. Steric block ON approach have proven to be effective in experimental model for various diseases. Here, we describe our experience in investigating two strategies for ON delivery: ON conjugation with basic peptides and lipid-based particulate system (lipoplex). Basic peptides or Cell Penetrating Peptides (CPP) such as the TAT-derived peptide appear to circumvent many problems associated with ON and drug delivery. This strategy may represent the next paradigm in our ability to modulate cell function and offers a unique avenue for the treatment of disease. Lipoplexes result from the intimate interaction of ON with cationic lipids leading to ON carrying particles able to be taken up by cells and to release ON in the cytoplasm. We have used as an experimental model the correction of a splicing alteration of the mutated β-globin intron causing thalassemia. Data on cell penetration and efficacy of correction of specific steric block ON delivered either by basic peptides or lipoplex are described. A comparison of the properties of both delivery systems is made respective to the use of this new class of therapeutic molecules.