Light-dependence of the metabolic balance of a highly productive Philippine seagrass community

Seagrass meadows are important primary producers in SE-Asia coastal areas that are increasingly threatened by human activities resulting in a deterioration of the underwater light environment. The resilience of seagrass meadows to decreasing light availability should be approached in an integrative manner, because they shelter complex communities of primary and secondary producers. The aim of this study was to measure the in situ metabolism of a seagrass community under different levels of light availability following changes in the water column dissolved oxygen (DO) and dissolved inorganic carbon (DIC), the sediment redox potential and seagrass production. Net community production (NCP) and respiration were measured along two diel cycles to produce a balance of NCP under different light treatments. On a daily basis, at full irradiance, the community metabolism presented a net production which was close to zero, with values of −7.75 to 16.6 mmol O₂ m⁻² day⁻¹ for DO, and −56.8 to 22.7 mmol C m⁻² day⁻¹ for DIC in the first and second incubation runs, respectively. Compensation irradiance for the NCP was thus found to be close to 80% of the present light availability. Shading resulted in a general decrease in the sediment redox potential, while the initial redox potential had not recovered 6 days after exposure to full sunlight. This community appears to be in a fragile equilibrium with the environment, and any minor decrease in the water transparency would lead to a shift from an autotrophic to a heterotrophic system.     

Phylogenetic analysis of the calvaria of Homo floresiensis

Because until 2006 the Liang Bua human fossil remains were not available to the entire paleoanthropological community, the taxonomic position of Homo floresiensis was only a matter of opinion in publications. From the beginning, two schools of thought prevailed, and this situation persists today. One purports that the Liang Bua human series belongs to a local modern human (Homo sapiens sapiens) with anatomical particularities or pathologies that may be due to insular isolation/endogamy. The second argues in favour of the existence of a new species that, depending on the authors, is either a descendant of local Homo erectus, or belongs to a much more basal taxon, closer to archaic Homo or to australopithecines. Because there are no postcranial remains confidently attributed to Homo erectus in the fossil record, and because the Homo erectus type specimen is a single and partial calvaria, a cladistic analysis was undertaken using both nonmetric morphological features and metrics of the calvariae of human fossil specimens including LB1 to test if it belongs to this taxon. Our results indicate that LB1 is included in the Homo erectus clade.     

Characterization of adaptability components of Brazilian isolates of Macrophomina pseudophaseolina

Macrophomina pseudophaseolina is a new Macrophomina species reported on different crop and weed species in Brazil, India and Senegal, but to date there are no studies about its adaptability components. In this work, a collection of 62 M. pseudophaseolina isolates obtained from roots of the weed species Trianthema portulacastrum and Boerhavia diffusa collected in Northeastern Brazil, was used to: (a) study the effect of temperature and salinity on mycelial growth, (b) to determine their sensitivity to the fungicide carbendazim and (c) to assess their aggressiveness on melon and watermelon seedlings. Results showed variability among M. pseudophaseolina isolates. The optimum temperature for mycelial growth ranged between 26.4 and 38.1ºC. NaCl reduced the in vitro growth of all isolates, which were also highly sensitive to the fungicide carbendazim, exhibiting EC₅₀ values ranging from 0.013 to 0.089 mg/L a.i. Disease severity values on melon and watermelon seedlings showed that M. pseudophaseolina isolates were more aggressive in melon than in watermelon. Information about adaptability components of M. pseudophaseolina obtained in this study could be incorporated on breeding programs for melon and watermelon crops.     

Non-surgical deep intrauterine transfer of superfine open pulled straw (SOPS)-vitrified porcine embryos: Evaluation of critical steps of the procedure

Previous trials achieved extremely poor results when using the one-step warming method in a syringe in combination with non-surgical deep intrauterine transfer (NET) of superfine open pulled straw (SOPS)-vitrified embryos. This study aimed to assess the effect of the warming procedure on the in vitro and in vivo development of SOPS-vitrified embryos. The effect of the passage of the vitrified-warmed (VW) embryos through the NET catheter was also evaluated. Groups of 4 to 6 morulae and blastocysts, collected from weaned sows, were SOPS-vitrified in 1 μL of vitrification medium, warmed by the one-step warming method in a dish or in a 1-mL syringe and cultured in vitro for 48 h to evaluate the embryo survival (ES) and hatching rates (HR). Warming in syringe had a deleterious effect (P < 0.05) on the in vitro ES (60.5 ± 10.4%) and HR (39.6 ± 9.5%) of VW embryos in comparison with embryos warmed in a dish (85.4 ± 10.6% and 69.0 ± 8.4%, respectively). This decreased embryonic development was due to the increased time required between the removal of the straws from the liquid nitrogen and the contact of the embryos with the warming medium when the warming was performed in a syringe in comparison with that for the warming in a dish. After verifying that the passage of VW embryos through the NET catheter does not have a damaging effect on their further in vitro development, the negative effect of warming in a syringe was also confirmed after NET. Fifteen fresh and SOPS-vitrified embryos warmed in a syringe or in a dish were transferred to each recipient (n = 28) and recovered 24 h later to assess their developmental progression. All embryos from the syringe group were found to have degenerated at recovery. The in vivo ES and HR from the dish group (80.4 ± 3.4% and 14.2 ± 7.2%, respectively) were lower (P < 0.05) than those from the fresh group (94.0 ± 4.1% and 36.8 ± 7.8%, respectively). Combining the warming in a dish and the NET procedure, 35 VW embryos were transferred to each of 10 gilts. Five recipients farrowed an average of 10.4 ± 0.9 piglets. In conclusion, the method of one-step warming in a syringe has a negative effect on the in vitro and in vivo viability of SOPS-vitrified porcine embryos. In addition, NET of SOPS-vitrified embryos warmed by the one-step method in a dish showed promising reproductive performance of recipients. However, despite the great potential of this technology, further developments are required for large-scale commercial applications.     

Effect of Docosahexaenoic Acid and Ascorbate on Peroxidation of Retinal Membranes of ODS Rats

The ability of a range of dietary flavonoids to inhibit low-density lipoprotein (LDL) oxidation in vitro was tested using a number of different methods to assess oxidative damage to LDL. Overall quercetin was the most effective inhibitor of oxidative damage to LDL in vitro. On this basis, a diet enriched with onions and black tea was selected for a dietary intervention study that compared the effect on the Cu²⁺ ion-stimulated lag-time of LDL oxidation ex vivo in healthy human subjects of a high flavonoid diet compared with a low flavonoid diet. No significant difference was found in the Cu²⁺ ion-stimulated lag-time of LDL oxidation ex vivo between the high flavonoid and low flavonoid dietary treatments (48 ± 1.6 min compared to 49 ± 2.1 min).     

Influence of light and temperature on photoinhibition of photosynthesis inSpirulina platensis

Photoinhibition of photosynthesis and its recovery in the cyanobacteriumSpirulina platensis was studied to find how photosynthetic rates were influenced by light and temperature. By exposing cell samples from a turbidostat culture to combinations of light and temperature, a connection between light, temperature and photoinhibition was found. The experiments showed that a 10 degree increase from 20 °C to 30 °C considerably reduced the photoinhibition. At 25 °C a photon flux density of 1720 µmol m^–2 s^–1 reduced the photosynthetic rate by 50 % in 1 h, but a similarly high photon flux density had nearly no negative effect at 35 °C. Reactivation in low light from 50% photoinhibition was fast and complete in 60 min at 30 °C, while at 20 °C only about 1/6 of the full capacity was regained in the same time. Addition of the protein synthesis inhibitor streptomycin to cultures undergoing photoinhibition and regeneration indicated the presence also in this organism of a repair mechanism based on protein synthesis.Author for correspondence     

Dynamics of Long-term Anhydrobiotic Survival of Lichen-dwelling Tardigrades

It is not rare to find in references that anhydrobiotic tardigrades can survive for more than a century. However, a closer look at the empirical evidence provides very little support that tardigrades are capable of surviving dried for such a long time. In order to resolve this discrepancy, we carried out a study to evaluate the long-term survival of naturally dried tardigrades. A large fragment of dry lichen (Xanthoria parietina) was collected in the field two days after a rainy day in 1999. The dry lichen was stored inside a paper bag in the laboratory at room temperature and humidity and under atmospheric oxygen exposure. Replicates of the dry lichen were re-hydrated after various time periods of storage, with all tardigrades extracted and the survivors enumerated. Five species of tardigrades were found, but two of them only occasionally. Ramazzottius oberhaeuseri, Echiniscus testudo and Echiniscus trisetosus were sufficiently represented for statistical analysis. At the beginning of the experiment 91.1% of R. oberhaeuseri and 71.7% of Echiniscus spp. were alive. R. oberhaeuseri survived up to 1604 days, while Echiniscus spp. lived up to 1085 days. Recovery after four years of anhydrobiosis has to be considered a very good long-term survival, which is important from an ecological and evolutionary point of view.     

A re-investigation of the path of carbon in photosynthesis utilizing GC/MS methodology. Unequivocal verification of the participation of octulose phosphates in the pathway

A GC/EIMS/SIM methodology has been developed to re-examine the path of carbon in photosynthesis. Exposing isolated spinach chloroplasts to ¹³CO₂ on a solid support for a defined period followed by quenching and work-up provided a mixture of labelled sugar phosphates. After enzymatic dephosphorylation and derivatization, the Mox-TMS sugars were analysed using the above method. The purpose of the study was to try to calculate the atom% enrichment of ¹³C in as many of the individual carbons in each of the derivatized sugars as was practical using diagnostic fragment ions. In the event, only one 45 s experiment provided sufficient data to enable a range of enrichment values to be calculated. This confirmed that D-glycero-D-altro-octulose phosphate was present in the chloroplasts and was heavily labelled in the C4, C5 and C6 positions, in keeping with the hypothesis that it had an inclusive role and a labelling pattern consistent with a new modified pathway of carbon in photosynthesis.     

Specific inhibition of the aspartate aminotransferase of Plasmodium falciparum

Aspartate aminotransferases (AspATs; EC 2.6.1.1) catalyze the conversion of aspartate and α-ketoglutarate into oxaloacetate and glutamate and are key enzymes in the nitrogen metabolism of all organisms. Recent findings suggest that the plasmodial enzyme [Plasmodium falciparum aspartate aminotransferase (PfAspAT)] may also play a pivotal role in energy metabolism and in the de novo biosynthesis of pyrimidines. However, while PfAspAT is a potential drug target, the high homology between the active sites of currently available AspAT structures hinders the development of specific inhibitors of these enzymes. In this article, we report the X-ray structure of the PfAspAT homodimer at a resolution of 2.8 Å. While the overall fold is similar to the currently available structures of other AspATs, the structure presented shows a significant divergence in the conformation of the N-terminal residues. Deletion of these divergent PfAspAT N-terminal residues results in a loss of activity for the recombinant protein, and addition of a peptide containing these 13 N-terminal residues results in inhibition both in vitro and in a lysate isolated from cultured parasites, while the activity of human cytosolic AspAT is unaffected. The finding that the divergent N-terminal amino acids of PfAspAT play a role in catalytic activity indicates that specific inhibition of the enzyme may provide a lead for the development of novel compounds in the treatment of malaria. We also report on the localization of PfAspAT to the parasite cytosol and discuss the implications of the role of PfAspAT in the supply of malate to the parasite mitochondria.     

Interpretation of the toothplates of chimaeroid fishes

It has been argued that the toothplates of chimaeroid fishes exhibit a mode of growth that is fundamentally different from that of other chondrichthyans. Chimaeroid toothplates are supposed to be statodont, growing from the basal surface, whereas other chondrichthyan dentitions are lyodont, growing from the lingual towards the labial surface of the jaw. That idea is shown to be mistaken, because chimaeroid toothplates grow from the lingual surface, like other chondrichthyan dentitions. The mistake resulted from confusion about the nomenclature of toothplate surfaces, and on the choice of Chimaera as a Recent model. Callorhynchus is a more appropriate model, since it is shown to exhibit a primitive toothplate conformation, with the labial and symphysial margins of the occlusal surface bounded by a descending lamina which is applied to the margin of the jaw cartilage and grows basally throughout life. The descending lamina is well developed in toothplates of the extinct chimaeroid genera Ischyodus, Pachymylus and Brachymylus, but is much reduced in all Recent genera other than Callorhynchus. A basally-growing descending lamina also bounds the labial and symphysial margins of the principal toothplates in the Mesozoic myriacanthoids and Squaloraja. The toothplates of the Palaeozoic ‘cochliodonts' are reviewed; amongst them, the chondrenchelyids are the only forms with a basally growing descending lamina. So far as the dentition and its mode of growth arc concerned, the closest Palaeozoic relatives of chimaeroids seem to be the chondrenchelyids. The only statodont (basally growing) toothplates found in the course of this work are those of ptyctodont placoderms, which are therefore unlikely to be related to any chondrichthyans. Statodonty in its original sense (failure to shed teeth) is shown to be widespread and possibly primitive in chondrichthyans. Cochliodont and chimaeroid toothplates grow in a logarithmic spiral. Toothplates of primitive chimaeroid type, with basally growing marginal descending laminae, can develop only when the constant angle of the spiral is small (less than about 35°), and when the oral surface of the jaw grows to the same logarithmic spiral.     

Distribution of chemoreceptors to quinine on the cell surface of Paramecium caudatum

The topological distribution of the chemoreceptors to quinine in the membrane of a ciliate Paramecium caudatum were examined by conventional electrophysiological techniques. A CNR-mutant specimen defective in voltage-gated Ca channels produced a transient depolarization followed by a transient hyperpolarization and a sustained depolarization when 1 mM quinine-containing solution was applied to its entirety. A Ni²⁺-paralyzed CNR-mutant specimen produced a simple membrane depolarization in response to a local application of 1 mM quinine-containing solution to its anterior end, whereas it produced a transient membrane hyperpolarization in response to an application to its posterior end. An anterior half fragment of a CNR specimen produced a membrane depolarization whereas a posterior half fragment of the specimen produced a transient hyperpolarization upon application of 1 mM quinine-containing solution. Both anterior depolarization and posterior hyperpolarization took place prior to the contraction of the cell body. It is concluded that Paramecium caudatum possesses two kinds of chemoreceptors or two kinds of coupling of the same receptor to different signal transduction pathways to quinine which are distributed in different locations on the cell surface. Activation of the anterior receptor produces a sustained depolarizing receptor potential while activation of the posterior receptor produces a transient hyperpolarizing receptor potential.Abbreviation CNR caudatum non reversal     

On the mechanism of accumulation of cholestanol in the brain of mice with a disruption of sterol 27-hydroxylase

The rare disease cerebrotendinous xanthomatosis (CTX) is due to a lack of sterol 27-hydroxylase (CYP27A1) and is characterized by cholestanol-containing xanthomas in brain and tendons. Mice with the same defect do not develop xanthomas. The driving force in the development of the xanthomas is likely to be conversion of a bile acid precursor into cholestanol. The mechanism behind the xanthomas in the brain has not been clarified. We demonstrate here that female cyp27a1^−/− mice have an increase of cholestanol of about 2.5- fold in plasma, 6-fold in tendons, and 12-fold in brain. Treatment of cyp27a1^−/− mice with 0.05% cholic acid normalized the cholestanol levels in tendons and plasma and reduced the content in the brain. The above changes occurred in parallel with changes in plasma levels of 7α-hydroxy-4-cholesten-3-one, a precursor both to bile acids and cholestanol. Injection of a cyp27a1^−/− mouse with ²H₇-labeled 7α-hydroxy-4-cholesten-3-one resulted in a significant incorporation of ²H₇-cholestanol in the brain. The results are consistent with a concentration-dependent flux of 7α-hydroxy-4-cholesten-3-one across the blood-brain barrier in cyp27a1^−/− mice and subsequent formation of cholestanol. It is suggested that the same mechanism is responsible for accumulation of cholestanol in the brain of patients with CTX.     

Effect of genetic variants of OPTN in the pathophysiology of Paget's disease of bone

Paget's disease of bone (PDB) is the second most frequent metabolic bone disease after osteoporosis. Genetic factors play an important role in PDB, but to date PDB causing mutations were identified only in the Sequestosome 1 gene at the PDB3 locus. OPTN has been recently associated with PDB, however little is known about the effect of genetic variants in this gene in PDB pathophysiology. By sequencing OPTN in SQSTM1 non-carriers PDB patients we found 16 SNPs in regulatory, coding and non-coding regions. One of those was found to be associated with PDB in our cohort - rs2234968. Our results show that rs2238968 effect may be explained by a change in OPTN splicing that give rise to a predicted truncated protein. We also performed functional studies on the variants located in OPTN promoter – rs3829923 and the rare variant ? 9906 – to investigate putative regulators of OPTN. Our results show that OPTN expression seems to be regulated by SP1, RXR, E47, and the E2F family. In conclusion, our work suggests a potential pathophysiological role of SNPs in OPTN, giving a new perspective about the regulatory mechanisms of this gene. Ultimately we discovered a new variant associated with PDB in OPTN, reinforcing the relevance of this gene for the development of this bone disease.