Strong quenching of chlorophyll fluorescence in the desiccated state in three poikilohydric and homoiochlorophyllous moss species indicates photo-oxidative protection on highly light-exposed rocks of a tropical inselberg

The three poikilohydric and homoiochlorophyllous moss species Campylopus savannarum (C. Muell.) Mitt., Racocarpus fontinaloides (C. Muell.) Par. and Ptychomitrium vaginatum Besch. grow on sun-exposed rocks of a tropical inselberg in Brazil subject to regular drying and wetting cycles. Effective photo-oxidative protection in the light-adapted desiccated state in all three species is achieved by a reduction of ground chlorophyll fluorescence, F', to almost zero. Upon rewatering, the kinetics of the recovery of F' in air dry cushions to higher values is very fast in the first 5 min, but more than 80 min are needed until an equilibrium is reached gradually. The kinetics were not different between the three species. The three moss species, have a distinct niche occupation and form a characteristic zonation around soil vegetation islands on the rock outcrops, where C. savannarum and R. fontinaloides form an inner and outer belt, respectively, around vegetation islands and P. vaginatum occurs as small isolated cushions on bare rock. However, they were not distinguished by the reduction of F' in the dry state and the rewetting recovery kinetics and only slightly different in their photosynthetic capacity. Stable isotope ratios (delta(13)C, delta(15)N) indicate that liquid films of water limiting diffusion of CO(2) are important in determining carbon acquisition and suggest that limitation of CO(2) fixation by water films must be more pronounced over time in P. vaginatum than in the latter species. This is determined by both the micro site occupied and the form of the moss cushions.     

Freshwater snails and schistosomiasis mansoni in the state of Rio de Janeiro, Brazil: VI--Noroeste Fluminense Mesoregion

In this paper, the last of a series dealing with the survey of freshwater gastropods of the state of Rio de Janeiro, the results of collections carried out in the Noroeste Fluminense Mesoregion from 2002 to 2005 are presented and revealed the occurrence of 20 species: Antillorbis nordestensis; Biomphalaria glabrata; B. straminea; B. tenagophila; Drepanotrema anatinum; D. cimex; D. depressissimum; D. lucidum; Ferrissia sp.; Gundlachia ticaga; Gundlachia sp.; Heleobia sp.; Idiopyrgus sp.; Lymnaea columella; Melanoides tuberculatus; Physa acuta; P. marmorata; Plesiophysa guadeloupensis; Pomacea lineata; and Pomacea sp. Concerning the snail hosts of schistosomiasis the three natural vectors were identified and, although no specimens were found harbouring larval forms of Schistosoma mansoni, different kinds of cercariae had been observed.     

Comparison of the performance of three different ecophysiological life forms in a sandy coastal restinga ecosystem of SE-Brazil: a nodulated N2-fixing C3-shrub (Andira legalis (Vell.) Toledo), a CAM-shrub (Clusia hilariana Schltdl.) and a tap root C3-hemicryptophyte (Allagoptera arenaria (Gomes) O. Ktze.)

In a sandy coastal restinga ecosystem NE of Rio de Janeiro, Brazil, subject to environmental stress due to high irradiance, high temperature and low water supply, a comparative ecophysiological study of three species of different morphotypes and physiotypes was conducted during the dry season. The morphotypes were two shrubs, Clusia hilariana Schltdl. and Andira legalis (Vell.) Toledo, and the taproot hemicryptophyte Allagoptera arenaria (Gomes) O. Ktze. The physiotype differences were that C. hilariana was performing crassulacean acid metabolism (CAM), A. legalis was a nodulated N₂ fixing legume and A. arenaria had ample access to water by ground water tapping roots. All three species were light stressed and showed photoinhibition and high maximum values of non-photochemical quenching of chlorophyll fluorescence. δ¹³C values of bulk leaf organic matter (which integrate over the life span of the leaf) and instantaneous gas exchange patterns demonstrated that C. hilariana was performing CAM and the other two species C₃-photosynthesis. A. arenaria performed generous and A. legalis conserving use of water. Based on the CO₂ concentrating mechanism of CAM C. hilariana had the highest maximum rates of apparent photosynthetic electron transport, ETR_max. Uptake of atmospheric CO₂ in the afternoon (phase IV of CAM) was expressed weakly showing that the plants were under some but not severe water stress. A. legalis showed the highest levels of total N and soluble non-protein N-compounds in its organs due to N₂ fixation which, however, did not confer a higher photosynthetic capacity that must have been limited by factors other than nitrogen supply. Accumulation of amino compounds like proline and γ-aminobutyric acid in leaves of A. legalis which are known to act as osmoprotectants is likely to indicate drought stress in the dry season. Maximum net CO₂ uptake of photosynthesis was higher in the water spending A. arenaria than in A. legalis. The comparative analysis of physiological traits characterised either instantaneously or integrated over the longer term shows that in addition to morphotypic characteristics physiotypic characteristics are important for space occupation and niche acquisition of the plants in the restinga.     

Exercise training delays cardiac dysfunction and prevents calcium handling abnormalities in sympathetic hyperactivity-induced heart failure mice.

Exercise training (ET) is a coadjuvant therapy in preventive cardiology. It delays cardiac dysfunction and exercise intolerance in heart failure (HF); however, the molecular mechanisms underlying its cardioprotection are poorly understood. We tested the hypothesis that ET would prevent Ca(2+) handling abnormalities and ventricular dysfunction in sympathetic hyperactivity-induced HF mice. A cohort of male wild-type (WT) and congenic alpha(2A)/alpha(2C)-adrenoceptor knockout (alpha(2A)/alpha(2C)ARKO) mice with C57BL6/J genetic background (3-5 mo of age) were randomly assigned into untrained and exercise-trained groups. ET consisted of 8-wk swimming session, 60 min, 5 days/wk. Fractional shortening (FS) was assessed by two-dimensional guided M-mode echocardiography. The protein expression of ryanodine receptor (RyR), phospho-Ser(2809)-RyR, sarcoplasmic reticulum Ca(2+) ATPase (SERCA2), Na(+)/Ca(2+) exchanger (NCX), phospholamban (PLN), phospho-Ser(16)-PLN, and phospho-Thr(17)-PLN were analyzed by Western blotting. At 3 mo of age, no significant difference in FS and exercise tolerance was observed between WT and alpha(2A)/alpha(2C)ARKO mice. At 5 mo, when cardiac dysfunction is associated with lung edema and increased plasma norepinephrine levels, alpha(2A)/alpha(2C)ARKO mice presented reduced FS paralleled by decreased SERCA2 (26%) and NCX (34%). Conversely, alpha(2A)/alpha(2C)ARKO mice displayed increased phospho-Ser(16)-PLN (76%) and phospho-Ser(2809)-RyR (49%). ET in alpha(2A)/alpha(2C)ARKO mice prevented exercise intolerance, ventricular dysfunction, and decreased plasma norepinephrine. ET significantly increased the expression of SERCA2 (58%) and phospho-Ser(16)-PLN (30%) while it restored the expression of phospho-Ser(2809)-RyR to WT levels. Collectively, we provide evidence that improved net balance of Ca(2+) handling proteins paralleled by a decreased sympathetic activity on ET are, at least in part, compensatory mechanisms against deteriorating ventricular function in HF.     

Short-Term Functional and Morphological Changes in the Primary Cultures of Trigeminal Ganglion Cells

Several studies have proved that glial cells, as well as neurons, play a role in pain pathophysiology. Most of these studies have focused on the contribution of central glial cells (e.g., microglia and astrocytes) to neuropathic pain. Likewise, some works have suggested that peripheral glial cells, particularly satellite glial cells (SGCs), and the crosstalk between these cells and the sensory neurons located in the peripheral ganglia, play a role in the phenomenon that leads to pain. Nonetheless, the study of SGCs may be challenging, as the validity of studying those cells in vitro is still controversial. In this study, a research protocol was developed to examine the potential use of primary mixed neuronal–glia cell cultures obtained from the trigeminal ganglion cells (TGCs) of neonate mice (P10–P12). Primary cultures were established and analyzed at 4 h, 24 h, and 48 h. To this purpose, phase contrast microscopy, immunocytochemistry with antibodies against anti-βIII-tubulin and Sk3, scanning electron microscopy, and time-lapse photography were used. The results indicated the presence of morphological changes in the cultured SGCs obtained from the TGCs. The SGCs exhibited a close relationship with neurons. They presented a round shape in the first 4 h, and a more fusiform shape at 24 h and 48 h of culture. On the other hand, neurons changed from a round shape to a more ramified shape from 4 h to 48 h. Intriguingly, the expression of SK3, a marker of the SGCs, was high in all samples at 4 h, with some cells double-staining for SK3 and βIII-tubulin. The expression of SK3 decreased at 24 h and increased again at 48 h in vitro. These results confirm the high plasticity that the SGCs may acquire in vitro. In this scenario, the authors hypothesize that, at 4 h, a group of the analyzed cells remained undifferentiated and, therefore, were double-stained for SK3 and βIII-tubulin. After 24 h, these cells started to differentiate into SCGs, which was clearer at 48 h in the culture. Mixed neuronal–glial TGC cultures might be implemented as a platform to study the plasticity and crosstalk between primary sensory neurons and SGCs, as well as its implications in the development of chronic orofacial pain.     

Unique properties of a Dictyostelium discoideum carbohydrate-binding module expand our understanding of CBM–ligand interactions

Deciphering how enzymes interact, modify, and recognize carbohydrates has long been a topic of interest in academic, pharmaceutical, and industrial research. Carbohydrate-binding modules (CBMs) are noncatalytic globular protein domains attached to carbohydrate-active enzymes that strengthen enzyme affinity to substrates and increase enzymatic efficiency via targeting and proximity effects. CBMs are considered auspicious for various biotechnological purposes in textile, food, and feed industries, representing valuable tools in basic science research and biomedicine. Here, we present the first crystallographic structure of a CBM8 family member (CBM8), DdCBM8, from the slime mold Dictyostelium discoideum, which was identified attached to an endo-β-1,4-glucanase (glycoside hydrolase family 9). We show that the planar carbohydrate-binding site of DdCBM8, composed of aromatic residues, is similar to type A CBMs that are specific for crystalline (multichain) polysaccharides. Accordingly, pull-down assays indicated that DdCBM8 was able to bind insoluble forms of cellulose. However, affinity gel electrophoresis demonstrated that DdCBM8 also bound to soluble (single chain) polysaccharides, especially glucomannan, similar to type B CBMs, although it had no apparent affinity for oligosaccharides. Therefore, the structural characteristics and broad specificity of DdCBM8 represent exceptions to the canonical CBM classification. In addition, mutational analysis identified specific amino acid residues involved in ligand recognition, which are conserved throughout the CBM8 family. This advancement in the structural and functional characterization of CBMs contributes to our understanding of carbohydrate-active enzymes and protein–carbohydrate interactions, pushing forward protein engineering strategies and enhancing the potential biotechnological applications of glycoside hydrolase accessory modules.     

Comparative Study of Blood Lead Levels in Uruguayan Children (1994–2004)

Lead does not fulfill any physiological function in the human body. It is generally accepted that the blood lead level (BLL) is the best exposure index, as there is an excellent correlation between the actual exposure of the individual and the concentration of lead in blood. In Uruguay, lead contamination becomes a matter of public concern in 2001, giving rise to a sensitization in the population, which in many cases brought about a change in hygienic and dietary habits of the children. In 2004, after the leaded gasoline phasing out process in Uruguay was completed, we studied non-exposed children to correlate BLL with variables such as age, sex, area of residence, and available environmental lead data and compared these results with those from our similar screening studies 10years ago. The main result of this comparison is that BLL from children in our country had a significant decrease between 1994 and 2004.     

Increased stability of recombinant plasmids by Tn1000 insertion in chemostat cultures of recombinantEscherichia coli GT123

The stability of several pBR322-derived recombinant plasmids, carrying thethr operon fromEscherichia coli, was investigated in sulfur-limited chemostat cultures ofE. coli GT123. A marked increase in the segregational stability of one of these plasmids was observed. It is concluded that the increased stability was due to the spontaneous insertion of Tn1000 from the chromosome of the host into the plasmid.     

Gluconate metabolism of Klebsiella pneumoniae NCTC 418 grown in chemostat culture

The metabolism of gluconate by Klebsiella pneumoniae NCTC 418 was studied in continuous culture. Under all gluconate-excess conditions at low culture pH values (pH 4.5–5.5) the majority (70–90%) of the gluconate metabolized was converted to 2-oxogluconate via gluconate dehydrogenase (GADH), although specific 2-oxogluconate production rates under potassium-limited conditions were significantly lower than under other gluconate-excess conditions. At high culture pH values, metabolism shifted towards production of acetate. Levels of GADH were highest at low culture pH values and synthesis was stimulated by the presence of (high concentrations of) gluconate. An increase in activity of the tricarboxylic acid cycle was accompanied by a decrease in GADH activity in vivo and in vitro, suggesting that the GADH serves a role as an alternative energy-generating system. Anaerobic 2-oxogluconate production was found to be possible in the presence of nitrate as electron acceptor. Levels of gluconate kinase were highest when K. pneumoniae was grown under gluconate-limited conditions. Under carbon-excess conditions, levels of this enzyme correlated with the intracellular catabolic flux.Abbreviations GADH gluconate dehydrogenase (EC 1.1.99.3) - GAK gluconate kinase (EC 2.7.1.12) - GDH glucose dehydrogenase (EC 1.1.99.17) - PQQ pyrroloquinoline quinone [2,7,9-tricarboxy-1-H-pyrrolo (2,3-f) quinoline-4,5-dione] - TCA trichloroacetic acid