Stepwise and large-magnitude negative shift in δ13Ccarb preceded the main marine mass extinction of the Permian–Triassic crisis interval

Large perturbations to the global carbon cycle occurred during the Permian–Triassic boundary mass extinction, the largest extinction event of the Phanerozoic Eon (542 Ma to present). Controversy concerning the pattern and mechanism of variations in the marine carbonate carbon isotope record of the Permian–Triassic crisis interval (PTCI) and their relationship to the marine mass extinction has not been resolved to date. Herein, high-resolution carbonate carbon isotope profiles (δ¹³C_carb), accompanied by lithofacies, were generated for four sections with microbialite (Taiping, Zuodeng, Cili, and Chongyang) in South China to better constrain patterns and controls on δ¹³C_carb variation in the PTCI and to test hypotheses about the temporal relationship between perturbations to the global carbon cycle and the marine mass extinction event. All four study sections exhibit a stepwise negative shift in δ¹³C_carb during the Late Permian–Early Triassic, with the shift preceding the end-Permian crisis being larger (> 3‰) than that following it (1–2‰). The pre-crisis shifts in δ¹³C_carb are widely correlatable and, hence, represent perturbations to the global carbon cycle. The comparatively smaller shifts following the crisis demonstrate that the marine mass extinction event itself had at most limited influence on the global carbon cycle, and that both Late Permian δ¹³C_carb shifts and the mass extinction must be attributed to some other cause. Their origin cannot be uniquely determined from C-isotopic data alone but appears to be most compatible with a mechanism based on episodic volcanism in combination with collapse of terrestrial ecosystems and soil erosion.     

Cloning, purification, and characterization of thermostable hypoxanthine-guanine phosphoribosyltransferase from Thermoanaerobacter tengcongensis

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT, EC 2.4.2.8) from a newly characterized thermophile Thermoanaerobacter tengcongensis was expressed in Escherichia coli and purified. Analytical gel filtration suggested that the enzyme exist as a homotetramer in solution. The optimal pH for the forward reaction was found to be 8.0 and the optimal temperature 70 degrees C. The steady-state kinetic characteristics suggest that hypoxanthine is the most effective substrate. This enzyme showed a half-life of 75min at 50 degrees C and no apparent loss of activity after 3 months at 4 degrees C.     

DNA stable pentaploid H1 (ES) cells obtained from an octaploid cell induced from tetraploid cells polyploidized using demecolcine

Pentaploid H1 (ES) cells (5H1 cells) were accidentally obtained through one‐cell cloning of octaploid H1 (ES) cells (8H1 cells) that were established from tetraploid H1 (ES) cells (4H1 cells) polyploidized using demecolcine. The number of chromosomes of 5H1 cells was 100, unlike the 40 of diploid H1 (ES) cells (2H1 cells), 80 of 4H1, and 160 of 8H1 cells. The durations of G₁, S, and G₂/M phases of 5H1 cells were 3, 7, and 6 h, respectively, almost the same as those of 2H1, 4H1, and 8H1 cells. The cell volume of 5H1 cells was half of that of 8H1 cells, suggesting that 5H1 cells were created through abnormal cell divisions of 8H1 cells. The morphology of growing 5H1 cells was a spherical cluster similar to that of 2H1 cells and differing from the flagstone‐like shape of 4H1 and 8H1 cells. Pentaploid solid tumors were formed from 5H1 cells after interperitoneal injection into the mouse abdomen, and they contained endodermal, mesodermal, and ectodermal cells as well as undifferentiated cells, suggesting both that the DNA content of 5H1 cells was retained during tumor formation and that the 5H1 cells were pluripotent. The DNA content of 5H1 cells was stable in long‐term culturing as 2H1 cells, meaning that 5H1 and 2H1 cells shared similarities in DNA structure. The excellent stability of the DNA content of 5H1 cells was explained using a hypothesis for the DNA structure of polyploid cells because the pairing of homologous chromosomes in 5H1 cells is spatially forbidden. J. Cell. Physiol. 223: 369–375, 2010. © 2010 Wiley‐Liss, Inc.     

Effect of Sulfhydryl Reagents on the Biophysical Properties of the Plasmalemma of Chara corallina

The administration of the sulfhydryl reagent N-ethyl-maleimide (NEM) to internodal cells of Chara corallina caused alterations in the biophysical properties of the plasmalemma, as measured with electrophysiological and radioactive tracer techniques. The membrane potential depolarized to, or near, the calculated Nernst potential for potassium (E_K) after 30 seconds' exposure to 0.1 millimolar NEM. During this time, the ATP level did not decrease below the control value, and the specific membrane resistance did not increase; only upon further exposure to NEM did the resistance approach the value observed in the dark. In the depolarized state, the membrane potential responded to changes in the external potassium concentration in the manner of a K⁺-electrode, but it retained it's relative insensitivity to external sodium.     

Immune response to a syngeneic mammary adenocarcinoma. III. Development of memory and suppressor functions modulating cellular cytotoxicity.

Measurement of the development of cytolytic activity by mammary tumor primed or unprimed syngeneic spleen cells on in vitro monolayers of the 13762 rat mammary tumor operationally defined several subpopulations of lymphoid cells involved in the cytotoxic response. In vitro sensitization of cells from Fischer 344 animals injected 2 to 10 days earlier with 2 x 10(7) viable tumor cells always resulted in a higher and earlier lytic response than cells from non-inoculated animals. Adoptive transfer of the same in vivo primed cells for 5 days in irradiated syngeneic hosts removed any cytotoxic cells originally present but subsequent in vitro sensitization still resulted in a higher and earlier cytolytic response. We defined such cells as "memory" cells for cytotoxicity. Memory cells were radiosensitive and specific for the immunizing target cell. In contrast to cells from animals inoculated for 3 to 10 days, cells obtained 11 and 12 days after immunization had a lower response than unprimed cells on vitro sensitization. The anamnestic response could be restored either by culturing 12-day primed cells in vitro for 2 days without antigen or by adoptive transfer for 5 days into irradiated syngeneic rats. This suggests that another population of cells is present in spleen and suppresses the conversion of memory to cytotoxic cells. A more direct measurement of suppressor cell function was obtained by coincubating tumor-primed and unprimed cells on monolayers during in vitro sensitization. Cells from animals bearing tumors for 5 to 10 days always caused an increase in the response of the mixed lymphocyte groups, whereas 11- to 13-day tumor primed cells always caused a marked decrease in the cytolytic response. These results suggest the following interpretation of the kinetics of cell-mediated cytotoxicity to syngeneic tumor inoculation. Cytotoxic cells appear about 6 days after immunization, reach peak levels 2 days later, and then decrease rapidly. Memory cells are generated at a faster rate, reach peak levels before maximum cytolytic activity, but are then functionally inhibited from converting into differentiated cytotoxic cells by a new population of suppressor cells which reach peak activity about 12 days after immunization.     

Ethanol Inhibits Basic Fibroblast Growth Factor-Mediated Proliferation of C6 Astrocytoma Cells

Abstract: Early ethanol exposure alters the proliferative activity of glial and neuronal precursors in the developing CNS. The present study tests the hypothesis that ethanol-induced alterations in cell proliferation result from interference with growth factors. An in vitro model of astroglia (C6 astrocytoma cells) was used to study the effects of ethanol on proliferation mediated by basic fibroblast growth factor (bFGF). bFGF stimulated the proliferation of C6 cells. This bFGF-enhanced proliferation was evident by increases in total cell number, DNA synthesis (as measured by [³H]thymidine incorporation), and the number of cells that took up bromodeoxyuridine. A synthetic peptide that specifically blocked the binding of bFGF to its high-affinity receptor completely abolished the proliferation-promoting effect of bFGF. The action of another mitogen for C6 cells, insulin-like growth factor-1, was not affected by this peptide. Therefore, the bFGF-stimulated proliferation was mediated through a specific bFGF receptor. Ethanol inhibited bFGF-mediated proliferation in a concentration-dependent manner. Ethanol concentrations of 100 and 200 mg/dl partially inhibited bFGF-mediated proliferation (by 58 and 74%, respectively), whereas concentrations of ≥400 mg/dl completely abolished the growth-stimulating effect of bFGF. Our data show that ethanol alters proliferative activity of C6 cells by disrupting the action of bFGF. The target of ethanol neurotoxicity is a receptor-mediated activity. bFGF can affect cell proliferation by a non-receptor-mediated intracellular pathway, but ethanol does not have an impact on this pathway.     

A family 5 β-mannanase from the thermophilic fungus Thielavia arenaria XZ7 with typical thermophilic enzyme features

A novel β-mannanase gene, man5XZ7, was cloned from thermophilic fungus Thielavia arenaria XZ7, and successfully expressed in Pichia pastoris. The gene (1,110 bp) encodes a 369-amino acid polypeptide with a molecular mass of approximately 40.8 kDa. The deduced sequence of Man5XZ7 consists of a putative 17-residue signal peptide and a catalytic module belonging to glycoside hydrolase (GH) family 5, and displays 76 % identity with the experimentally verified GH 5 endo-β-1,4-mannanase from Podospora anserina. Recombinant Man5XZ7 was optimally active at 75 °C and pH?5.0 and exhibited high activity at a wide temperature range (>50.0 % activity at 50–85 °C). Moreover, it had good adaptability to acidic to basic pH (>74.1 % activity at pH?4.0–7.0 and 25.6 % even at pH?9.0) and good stability from pH?3.0 to 10.0. These enzymatic properties showed that Man5XZ7 was a new thermophilic and alkali-tolerant β-mannanase. Further amino acid composition analysis indicated that Man5XZ7 has several characteristic features of thermophilic enzymes.     

Response of Pyropia haitanensis to agaro-oligosaccharides evidenced mainly by the activation of the eicosanoid pathway

The marine red alga Pyropia haitanensis (Protoflorideophyceae, Bangiaceae) has a nonvascular and multicellular structure and emerged earlier in evolution than other cultivatable red algae. It has been reported that lipid mediators from both the eicosanoid and octadecanoid pathways are involved in the innate immunity of other marine algae. But the defense strategies of P. haitanensis are not clearly understood. Here, we investigated the lipid defense of P. haitanensis elicited by agaro-oligosaccharides. The results indicate that the resistance of P. haitanensis was elicited and hydrogen peroxide was released by agaro-oligosaccharides. In P. haitanensis, C20 fatty acids are the essential fatty acids. Phospholipase A₂ was activated, and the free fatty acids decreased 3 h after treatment with agaro-oligosaccharides. Gas chromatography–mass spectrometry analyses revealed that the contents of volatile organic compounds increased after treatment for 3 h, which indicated that these free fatty acids were metabolized to volatile organic compounds. In conclusion, the lipid metabolic defense pathway of P. haitanensis was mainly via the C20 metabolism pathway. The C20 fatty acid was rapidly metabolized to volatile organic compounds, but not oxidized to oxylipins in response to agaro-oligosaccharides.     

Distribution of alkaline phosphatase genes in cyanobacteria and the role of alkaline phosphatase on the acquisition of phosphorus from dissolved organic phosphorus for cyanobacterial growth

Phosphorus is a vital nutrient for cyanobacterial growth. Aside from dissolved inorganic phosphorus, dissolved organic phosphorus (DOP) is used by cyanobacterial species via the activity of alkaline phosphatase (APase), which likely plays an important role in acquiring phosphorus for algal growth in the same manner as it does in other bacteria. In this work, APase genes phoA, phoD, and phoX were found distributed in the cyanobacterial strains included in the algal genome collection of the NCBI database. PhoX has a wider distribution than the classical phoA and phoD. Furthermore, multiple types of APase genes were simultaneously identified in a single strain or genome. Anabaena flos-aquae FACHB-245 was selected as a typical strain to study the performance of cyanobacteria growing on DOP. In algal growth involving AMP or lecithin, APase regulates the release of phosphorus from DOP as confirmed by the relative quantification of phoD and phoX expression levels. Our results confirmed that the distribution of APase is prevalent in cyanobacteria and thus provides a new insight into the potential role of cyanobacterial APase on phosphorus acquisition in natural environment.