Responses of the resurrection plant <Emphasis Type="Italic">Haberlea rhodopensis</Emphasis> to high irradiance

The effect of high irradiance (HI) during desiccation and subsequent rehydration of the homoiochlorophyllous desiccation-tolerant shade plant Haberlea rhodopensis was investigated. Plants were irradiated with a high quantum fluence rate (HI; 350 μmol m⁻² s⁻¹ compared to ca. 30 μmol m⁻² s⁻¹ at the natural rock habitat below trees) and subjected either to fast desiccation (tufts dehydrated with naturally occurring thin soil layers) or slow desiccation (tufts planted in pots in peat-soil dehydrated by withholding irrigation). Leaf water content was 5 % of the control after 4 d of fast and 19 d of slow desiccation. Haberlea was very sensitive to HI under all conditions. After 19 d at HI, even in well-watered plants there was a strong reduction of rates of net photosynthesis and transpiration, contents of chlorophyll (Chl) and carotenoids, as well as photosystem 2 activity (detected by the Chl fluorescence ratio R_Fd). Simultaneously, the blue/red and green/red fluorescence ratios increased considerably suggesting increased synthesis of polyphenolic compounds. Desiccation of plants in HI induced irreversible changes in the photosynthetic apparatus and leaves did not recover after rehydration regardless of fast or slow desiccation. Only young leaves survived desiccation.     

The asymmetry of transient response in compression versus release for cartilage in unconfined compression

Observations in compression tests of articular cartilage have revealed unequal load increments for compression and release of the same amplitude applied to a disk with an identical previously imposed compression (in equilibrium). The mechanism of this asymmetric transient response is investigated here using a nonlinear fibril-reinforced model. It is found that the asymmetry is predominantly produced by the fibril stiffening with its tensile strain. In addition, allowing the hydraulic permeability to decrease significantly with compressive dilatation of cartilage increases the transient fibril strain, resulting in a stronger asymmetry. Large deformation also enhances the asymmetry as a consequence of stronger fibril stiffening.     

A decade of crystallization drops: Crystallization of the cbb3 cytochrome c oxidase from Pseudomonas stutzeri

The cbb₃ cytochrome c oxidases are distant members of the superfamily of heme copper oxidases. These terminal oxidases couple O₂ reduction with proton transport across the plasma membrane and, as a part of the respiratory chain, contribute to the generation of an electrochemical proton gradient. Compared with other structurally characterized members of the heme copper oxidases, the recently determined cbb₃ oxidase structure at 3.2 Å resolution revealed significant differences in the electron supply system, the proton conducting pathways and the coupling of O₂ reduction to proton translocation. In this paper, we present a detailed report on the key steps for structure determination. Improvement of the protein quality was achieved by optimization of the number of lipids attached to the protein as well as the separation of two cbb₃ oxidase isoenzymes. The exchange of n‐dodecyl‐β‐d ‐maltoside for a precisely defined mixture of two α‐maltosides and decanoylsucrose as well as the choice of the crystallization method had a most profound impact on crystal quality. This report highlights problems frequently encountered in membrane protein crystallization and offers meaningful approaches to improve crystal quality.     

Increasing strain and strain rate strengthen transient stiffness but weaken the response to subsequent compression for articular cartilage in unconfined compression

Strain amplitude and strain rate dependent nonlinear behavior and load-induced mechanical property alterations of full-thickness bovine articular cartilage attached to bone were investigated in unconfined compression. A sequence of test compressions of finite deformation (ranging from 0.9% to 34.5% nominal strain) was performed at strain rates ranging from approximately 0.053%/s to 5.8%/s. Peak and equilibrium loads were analyzed to determine strain amplitude and strain rate dependence of linear versus nonlinear responses. The test protocol was designed to reveal changes in mechanical properties due to these finite deformations by interspersing small-amplitude witness ramps of approximately 1.1% deformation and approximately 0.44%/s strain rate between the test ramps ("witness" meaning to assess any mechanical property changes). We found that peak loads displayed high nonlinearity, stiffening with both increasing compression amplitude and more so with increasing strain rate. The response to witness ramps suggested that mechanical weakening occurred when compression amplitude reached 1.9-2.9% strain and beyond, and that weakening was much more significant at higher strain rate. These findings delineate regimes of linear versus nonlinear behavior of cartilage, and indicate the types of loads which can cause mechanical property alterations. Biological implications of this study are that strain amplitude and strain rate dependent stiffening may be essential to bear physiological loads and to protect cells and matrix from mechanical damage. Structural changes reflected by mechanical weakening at small compression could also initiate remodeling or disease processes.     

Agar yield and quality of Gracilaria chilensis (Gigartinales,Rhodophyta) in tank culture using fish effluents

Tank cultivation of Gracilaria using fish effluents has permitted a production of 48 kg m^–2 yr^–1 and can reduce the dissolved nitrogen loads in the seawater. We report the yield, gel strength, gelling and melting point of agar from Gracilaria cultivated in tanks with seawater previously utilized in intensive, land-based salmon cultures and compared to a control using directly pumped seawater, over a study period of 22 months. The results show that the highest agar yield (20 to 22%) was obtained when Gracilaria was cultivated with pure seawater as compared to the fish effluents. The gel strength, gelling and melting point were higher in the agar obtained from algae cultured with fish effluents. During the spring, the gel strength, gelling and melting point increased in tanks with fish effluents and decreased in tanks with a supply of pure seawater.     

études sur les phénomenes électrocapillaires

Sans résuméI. Analyse électrocapillaire des matières colorantes. Rev. gén. Mat. Col. 1926 Vol. 30 pp 34–45II. Phénomènes électrocapillaires et le problème du cancer. Arch. Med. Exper. 1926 Vol. I p 381III. Phénomènes électrocapillaires et l'antagonismes microbiens. Bol. Istituto Sier. Milano 1927 Vol. VI p 313.     

Yield and proliferation rate of adipose-derived stromal cells as a function of age,body mass index and harvest site—increasing the yield by use of adherent and supernatant fractions?

Background aimsAdipose-derived stem cells are easily accessed and have a relatively high density compared with other mesenchymal stromal cells. Isolation protocols of adipose-derived stem cells (ASC) rely on the cell's ability to adhere to tissue culture plastic overnight. It was evaluated whether the floating ASC fractions are also of interest for cell-based therapies. In addition, the impact of age, body mass index (BMI) and harvest site was assessed.MethodsThe surface protein profile with the use of flow cytometry, the cell yield and the doubling time of passages 4, 5 and 6 of ASC from 30 donors were determined. Adherent and supernatant fractions were compared. The impact of age, BMI and harvest site on cell yield and doubling times was determined.ResultsBoth adherent and supernatant fractions showed high mean fluorescence intensities for CD13, CD29, CD44, CD73, CD90 and CD105 and comparatively low mean fluorescence intensities for CD11b, CD62L, intracellular adhesion molecule-1 and CD34. Doubling times of adherent and supernatant fractions did not differ significantly. Whereas the old age group had a significantly lower cell yield compared with the middle aged group, BMI and harvest site had no impact on cell yield. Finally, doubling times for passages 4, 5 and 6 were not influenced by the age and BMI of the donors, nor the tissue-harvesting site.ConclusionsThe floating ASC fraction is an equivalent second cell source just like the adherent ASC fraction. Donor age, BMI and harvest site do not influence cell yield and proliferation rate.     

Photoacoustic Spectroscopy and its Application in Plant Science

The principles of photoacoustic spectroscopy are outlined. This new and still developing technique enables one to detect non-radiative de-excitation processes. It is possible to distinguish between signals emenating from different depths of the sample. In plant science photoacoustic spectroscopy has mainly been applied in photosynthesis research. Here it allows the detection of gross oxygen evolution and gives information about the energy balance of the primary photosynthetic reaction.     

Homologues of Arabidopsis Microtubule-Associated AIR9 in Trypanosomatid Parasites: Hints on Evolution and Function

AIR9 is an essential microtubule-associated protein from Arabidopsis. Sequence similarity searches indicate homologues of AIR9 in land plants and in excavate protists, including trypanosomatid parasites and Trichomonas. The AIR9-like protein from Trypanosoma brucei was recently detected in the proteome of the trypanosome flagellum, raising the possibility that trypanosomatid AIR9-like proteins also associate with microtubules. Because microtubule functions are essential to the viability of trypanosomatid parasites AIR9-like proteins may be exploited as drug targets without homology in humans. We further discuss the unexpected phylogeny of AIR9-like proteins from plants and protozoans.Key Words: plant, cortical microtubules, preprophase band, A9 domain, flagellum, ExcavataUsing a proteomic approach we recently determined that the protein encoded by the single-copy AIR9 (Auxin-Induced in Root Cultures 9) gene from Arabidopsis is a novel microtubule-associated protein (MAP). GFP-AIR9 associates with cortical microtubules of the plant interphase array and with the preprophase band (PPB). The plant-specific PPB is a transient microtubule array that marks the cortical division site and determines the plane of cytokinesis. The PPB disassembles at the onset of mitosis but leaves behind an unknown mark that during cytokinesis serves to attract the new cross-wall (the out-growing cell plate). GFP-AIR9 is not present at the PPB site during mitosis, but returns to this location when the cell plate inserts. Forming a torus, GFP-AIR9 then moves inward along the new cross-wall. By doing this, microtubule-associated AIR9 transiently behaves like a peripheral membrane protein. If cell plates are experimentally induced to insert at ectopic positions no AIR9 torus is formed. We conclude that AIR9 is capable of associating with a component of the enigmatic PPB memory.¹The 187 kDa Arabidopsis AIR9 protein consists of (seen from N- to C-terminus) a serine-rich microtubule-binding domain, a leucine-rich repeat (LRR) domain, a large region of eleven repeated A9 domains and a C-terminal region that is conserved among plant homologues (Fig. 1A). Our analyses revealed that A9 domains are likely to adopt g-immunoglobulin-like (IgG-like) folds. Using BLAST we detected AIR9 homologues in various land plants and in the genomes of the three sequenced trypanosomatid parasites.² The trypanosomatid proteins contain the LRR domain and the region of repeated A9 domains found in the Arabidopsis prototype and were therefore termed AIR9-like proteins. PSI-BLAST searches³ indicate distantly related sequences with A9 domains in several prokaryotes (mainly proteobacteria) but these proteins are lacking the LRR domain.Open in a separate windowFigure 1Domain structure of Arabidopsis AIR9 and protozoan AIR9-like proteins and phylogenetic position of AIR9-like proteins in the tree of life. (A) All AIR9-like proteins contain an LRR domain and a region of repeated A9 domains. Arabidopsis AIR9 additionally shows an N-terminal serine-rich basic region that confers microtubule binding (MT) and a C-terminal conserved region of unknown function (cc). The multicopy genome of Trichomonas harbours several genes potentially coding for AIR9-like proteins (shown in this order: gene1 {"type":"entrez-protein","attrs":{"text":"EAY10472","term_id":"121905546","term_text":"EAY10472"}}EAY10472, gene2 {"type":"entrez-protein","attrs":{"text":"EAY06037","term_id":"121901014","term_text":"EAY06037"}}EAY06037, gene3 {"type":"entrez-protein","attrs":{"text":"EAX99086","term_id":"121893848","term_text":"EAX99086"}}EAX99086, gene4 {"type":"entrez-protein","attrs":{"text":"EAY04681","term_id":"121899624","term_text":"EAY04681"}}EAY04681, gene5 {"type":"entrez-protein","attrs":{"text":"EAX86457","term_id":"121880222","term_text":"EAX86457"}}EAX86457). (B) Phylogenetic tree showing key eukaryotic taxa. All organisms found to encode AIR9-like proteins are highlighted in green. Numbers in parenthesis indicate tested genomes devoid of AIR9-like proteins. This phylogenetic tree has been redrawn and is based on results published elsewhere.^7,16,17New genomic sequence data revealed the presence of AIR9-like proteins in the human parasite Trichomonas vaginalis⁴ (Fig. 1A). We intensified our searches for AIR9-like proteins in eukaryotes using EST datasets (http://tbestdb.bcm.umontreal.ca) and genome project BLAST servers (http://genome.jgi-psf.org) revealing a curious distribution of AIR9-like proteins in the eukaryotic tree of life (Fig. 1B). AIR9-like proteins are present in land plants (including the moss Physcomitrella) and in several protists of the excavate class (Trypanosomas, Leishmania, Trichomonas, Naegleria, Seculamonas, Reclinomonas). However, AIR9 is apparently missing in all other bikont organisms: it is missing in green algae (three sequenced genomes), in red algae (two sequenced genomes) and in all Chromalveolata sequenced to date (six genomes). As stated earlier,¹ AIR9 is missing in all unikont organisms (metazoan, fungi, Amoebozoa) (Fig. 1B). This distribution of AIR9-like proteins is curious because land plants cannot be considered to be a sister group of Excavata.^5,6 This may indicate a lateral gene transfer of AIR9-like genes between both groups. However, a different scenario may be based on independent losses of AIR9-like proteins in certain groups, i.e., in green and red algae, and possibly in Chromalveolata. It will be important to establish how widespread AIR9-like proteins are among organisms of the heterogenous Excavata. Unravelling the phylogenetic relationship between the groups Plantae, Chromalveolata and Excavata may explain this curious distribution of AIR9-like proteins in the tree of life.^7–9AIR9-like proteins are found in several important human parasites. Trypanosomatid parasites are the causal agent of African trypanosomiasis (sleeping sickness), Chagas disease and leishmaniasis. Other trypanosomatid species are pathogens of crops and live stock. Vaccines for humans are missing and effective drugs without side-effects are needed.² Proteins restricted to plants and protists, as in the case of AIR9, could be exploited as drug targets against trypanosomatids -with no or little side-effects to humans.^10,11 More plant-like traits were recently reported for Trypanosoma and Leishmania and assumed to stem from lateral gene-transfer events with an endosymbiosis-derived plastid organelle.^12,13 It was speculated that trypanosomatid organisms once possessed an algal endosymbiont, but that this organelle was lost during evolution^12,14 (for a different view, however, see Ref. ¹⁰). The phylogenetic comparison of AIR9-like proteins based on the LRR domain reveals two sub-classes of AIR9-like proteins resembling the groups land plants and excavate protists, respectively (Fig. 2A). The AIR9-like protein from the moss Physcomitrella patens tightly clusters with the sub-class from land plants. This is consistent with the last common ancestor of both AIR9 sub-classes being much older than the origin of land plants, excluding the possibility of a “very late” transfer of an AIR9-like gene between land plants and protists. Our findings on the phylogenetic distribution of AIR9 do not support nor reject the possibility of a green endosymbiont in early trypanosomatid organisms. They do, however, support the idea that new drug targets in trypanosomatid parasites could be discovered by analyzing drug targets from plants.Open in a separate windowFigure 2Phylogenetic relationship of AIR9-like proteins and amino acid scans of plant and protozoan AIR9-like proteins. (A) Phylogenetic comparison based on the LRR domain reveals two subclasses of AIR9-like proteins corresponding to land plants and protozoans, respectively. (B) Amino-acid scans using a 104 amino-acid window. Note the serine-rich regions in AIR9 homologues from land plants all of which present N-terminal peaks above 20 serines in 104 amino acids. otherwise, the sequence similarity between these serine-rich regions is not statistically significant according to BLAST sequence similarity analyses [3]. Arginine plus lysine content in all plant homologues peak above 20 in 104 amino acids in N-terminal (and C-terminal) regions. The N-terminal basic region corresponds to the microtubule-binding domain found in Arabidopsis AIR9. N-terminal basic serine-rich extensions are not found in the AIR9-like proteins from trypanosomatid parasites. Some of the predicted AIR9-like proteins from Trichomonas peak with basic residues in the N-terminus. Green = plant proteins, pink = trypanosomatid proteins, white = Trichomonas proteins. Squences were obtained from protein databases, inferred from EST sequences, or derived from genomic sequences using homologous proteins as template. All sequences are available upon request.Do the AIR9-like proteins from trypanosomatids and other excavates function in a similar way to AIR9 from plants, and are they MAPs? In a remarkable study Broadhead et al¹⁵ isolated the flagellum from blood-stream Trypanosoma brucei and identified its proteome by HPLC-assisted mass-spectrometry. RNA-interference with selected proteins of the flagellar proteome established that flagellar motility is essential for viability of the blood-stream Trypanosoma.¹⁵ The flagellum of trypanosomatids consists of the 9+2 axoneme and an associated structure, the paraflagellar rod. Interestingly, the trypanosomatid AIR9-like protein (Tb11.01.8770) is among the 331 proteins of the flagellum proteome (see supplemental data by Broadhead et al Ref. ¹⁵). This raises the possibility that the AIR9-like protein from Trypanosoma binds microtubules. In Arabidopsis AIR9, the N-terminal basic serine-rich extension functions in microtubule binding.¹ The basic residues of this extension may confer binding to the acidic surface of tubulins. However, in linear alignments the microtubule binding site of Arabidopsis AIR9 appears to be only weakly conserved among land plants and no similarity to the AIR9-like proteins from protozoans is found (data not shown). We therefore scanned AIR9-like proteins from plants, trypanosomatid parasites and Trichomonas for serine-rich and basic regions. Using a 104 amino-acid window we found that all investigated plant proteins show a serine-rich and basic N-terminal extension. The AIR9-like proteins from trypanosomatid parasites do not show N-terminal serine-rich regions and the content of basic residues in these regions is far less pronounced when compared to the plant homologues. Trichomonas encodes at least five AIR9-like proteins, probably as a result of genome amplification events observed in this parasite.⁴ Interestingly, some of the putative Trichomonas AIR9-like proteins contain N-terminal basic regions (Fig. 2B). However, this is not mirrored by an elevated serine content. Taken together, these results show that all AIR9-like proteins from land plants exhibit N-terminal basic serine-rich extensions and therefore are likely to be MAPs. Further research is needed to show whether AIR9-like proteins from trypanosomatid parasites, Trichomonas and other protozoans have microtubule binding sites.