Subcellular distribution of carbonic anhydrase in Solanum tuberosum L. leaves

The intracellular compartmentation of carbonic anhydrase (CA; EC 4.2.1.1), an enzyme that catalyses the reversible hydration of CO2 to bicarbonate, has been investigated in potato (#Solanum tuberosum$ L.) leaves. Although enzyme activity was mainly located in chloroplasts (87% of total cellular activity), significant activity (13%) was also found in the cytosol. The corresponding CA isoforms were purified either from chloroplasts or crude leaf extracts, respectively. The cytosolic isoenzyme has a molecular mass of 255 000 and is composed of eight identical subunits with an estimated Mr of 30 000. The chloroplastic isoenzyme (Mr 220 000) is also an octamer composed of two different subunits with Mr estimated at 27 000 and 27 500, respectively. The N-terminal amino acid sequences of both chloroplastic CA subunits demonstrated that they were identical except that the Mr-27 000 subunit was three amino acids shorter than that of the Mr-27 500 subunit. Cytosolic and chloroplastic CA isoenzymes were found to be similarly inhibited by monovalent anions (Cl-, I-, N3- and NO3-) and by sulfonamides (ethoxyzolamide and acetozolamide). Both CA isoforms were found to be dependent on a reducing agent such as cysteine or dithiothreitol in order to retain the catalytic activity, but 2-mercaptoethanol was found to be a potent inhibitor. A polyclonal antibody directed against a synthetic peptide corresponding to the N-terminal amino acid sequence of the chloroplastic CA monomers also recognized the cytosolic CA isoform. This antibody was used for immunocytolocalization experiments which confirmed the intracellular compartmentation of CA : within chloroplasts, CA is restricted to the stroma and appears randomly distributed in the cytosol. (Résumé d'auteur

UVB radiation induced effects on cells studied by FTIR spectroscopy

We have made a preliminary analysis of the results about the eVects on tumoral cell line (lymphoid T cell line Jurkat) induced by UVB radiation (dose of 310 mJ/cm^2) with and without a vegetable mixture. In the present study, we have used two techniques: Fourier transform infrared spectroscopy (FTIR) and flow cytometry. FTIR spectroscopy has the potential to provide the identiWcation of the vibrational modes of some of the major compounds (lipid, proteins and nucleic acids) without being invasive in the biomaterials. The second technique has allowed us to perform measurements of cytotoxicity and to assess the percentage of apoptosis. We already studied the induction of apoptotic process in the same cell line by UVB radiation; in particular, we looked for correspondences and correlations between FTIR spetroscopy and flow cytometry data finding three highly probable spectroscopic markers of apoptosis (Pozzi et al. in Radiat Res 168:698-705, 2007). In the present work, the results have shown significant changes in the absorbance and spectral pattern in the wavenumber protein and nucleic acids regions after the treatments

Cratering Experiments on the Self Armoring of Coarse-Grained Granular Targets

Recently published crater statistics on the small asteroids 25143 Itokawa and 433 Eros show a significant depletion of craters below approx. 100 m in diameter. Possible mechanisms that were brought up to explain this lack of craters were seismic crater erasure and self armoring of a coarse, boulder covered asteroid surface. While seismic shaking has been studied in this context, the concept of armoring lacks a deeper inspection and an experimental ground truth. We therefore present cratering experiments of glass bead projectiles impacting into granular glass bead targets, where the grain sizes of projectile and target are in a similar range. The impact velocities are in the range of 200 to 300 m/s. We find that craters become fainter and irregular shaped as soon as the target grains are larger than the projectile sizes and that granular craters rarely form when the size ratio between projectile and target grain is around 1:10 or smaller. In that case, we observe a formation of a strength determined crater in the first struck target grain instead. We present a simple model based on the transfer of momentum from the projectile to this first target grain, which is capable to explain our results with only a single free parameter, which is moreover well determined by previous experiments. Based on estimates of typical projectile size and boulder size on Itokawa and Eros, given that our results are representative also for km/s impact velocities, armoring should play an important role for their evolution.Comment: accepted for publication in Icaur

Changes in the Ultrastructure of Beef Muscle as Influenced by Acidic Conditions Below the Ultimate pH

Ultrastructural changes in meat incubated with different concentrations of acetic acid were investigated by transmission electron microscopy. Discs of bovine M. longissimus dorsi (48 h postmortem) were incubated at 46 C for 48 h in various acetlc acid solutions, giving discs with pH values ranging from 5.1 to 3.9 . Below pH 4. 5 , the volume of the discs increased markedly due to water absorption. Discs incubated in 0.01M acetic acid had a pH of 5.1, lower swelling ratios and shorter sarcomeres than control samples at pH 5. 5. Structural studies of the samples at pH 5.1 revealed that A-band length decreased whereas I-band length increased . There was fragmentation of thin filaments in the Z-line region and disorganization of Z-line structure. In discs treated with O.O5M acetic acid (meat pH 4.5), complete loss of M-lines was observed. Noticeable swelling also occurred across the muscle fibre axis , mainly in the A-band region, and myosin filaments were partially extracted. Z-lines were swollen, disorganized and slightly fragmented. Below pH 4. 5 , swelling became much more pronounced with further extraction of myosin filaments. Most of the actin filaments were extracted and myofibrils fused together giving an amorphous, coagulated appearance. Z-lines were partially extracted. In general, the greatest amount of swelling occurred across the muscle fibre axis although significant in creases in sarcomere length were observed at pH 4.5 and below. Cooking of control and O.01M acid treated meat discs at 80°C increased the space between myofibrils whereas minimal shrinkage was not iced in samples below pH 4.5

Infection by the castrating parasitic nematode <i>Sphaerularia bombi </i>changes gene expression in <i>Bombus terrestris </i>bumblebee queens

Parasitism can result in dramatic changes in host phenotype, which are themselves underpinned by genes and their expression. Understanding how hosts respond at the molecular level to parasites can therefore reveal the molecular architecture of an altered host phenotype. The entomoparasitic nematode Sphaerularia bombi is a parasite of bumblebee (Bombus) hosts where it induces complex behavioural changes and host castration. To examine this interaction at the molecular level, we performed genome-wide transcriptional profiling using RNA-Seq of S. bombi-infected Bombus terrestris queens at two critical time-points: during and just after overwintering diapause. We found that infection by S. bombi affects the transcription of genes underlying host biological processes associated with energy usage, translation, and circadian rhythm. We also found that the parasite affects the expression of immune genes, including members of the Toll signaling pathway providing evidence for a novel interaction between the parasite and the host immune response. Taken together, our results identify host biological processes and genes affected by an entomoparasitic nematode providing the first steps towards a molecular understanding of this ecologically important host-parasite interaction