Living phosphatic stromatolites in a low‐phosphorus environment: Implications for the use of phosphorus as a proxy for phosphate levels in paleo‐systems

In the geological record, fossil phosphatic stromatolites date back to the Great Oxidation Event in the Paleoproterozoic, but living phosphatic stromatolites have not been described previously. Here, we report on cyanobacterial stromatolites in a supratidal freshwater environment at Cape Recife, South African southern coast, precipitating Ca carbonate alternating with episodes of Ca phosphate deposition. In their structure and composition, the living stromatolites from Cape Recife closely resemble their fossilized analogues, showing phosphatic zonation, microbial casts, tunnel structures and phosphatic crusts of biogenic origin. The microbial communities appear to be also similar to those proposed to have formed fossil phosphatic stromatolites. Phosphatic domains in the material from Cape Recife are spatially and texturally associated with carbonate precipitates, but form distinct entities separated by sharp boundaries. Electron Probe Micro‐Analysis shows that Ca/P ratios and the overall chemical compositions of phosphatic precipitates are in the range of octacalcium phosphate, amorphous tricalcium phosphate and apatite. The coincidence in time of the emergence of phosphatic stromatolites in the fossil record with a major episode of atmospheric oxidation led to the assumption that at times of increased oxygen release the underlying increased biological production may have been linked to elevated phosphorus availability. The stromatolites at Cape Recife, however, form in an environment where ambient phosphorus concentrations do not exceed 0.28 μM, one to two orders of magnitude below the previously predicted minimum threshold of >5 μM for biogenic phosphate precipitation in paleo‐systems. Accordingly, we contest the previously proposed suitability of phosphatic stromatolites as a proxy for high ambient phosphate concentrations in supratidal to shallow ocean settings in earth history.     

Comparative study of the antioxidant activity of the essential oils of five plants against the H2O2 induced stress in Saccharomyces cerevisiae

The purpose of this work was to investigate the protective effect of five essential oils (EOs); Rosmarinus officinalis, Thymus vulgaris, Origanum compactum Benth., Eucalyptus globulus Labill. and Ocimum basilicum L.; against oxidative stress induced by hydrogen peroxide in Saccharomyces cerevisiae. The chemical composition of the EOs was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). The in vitro antioxidant activity was evaluated and the protective effect of EOs was investigated. Yeast cells were pretreated with different concentrations of EOs (6.25–25 µg/ml) for an hour then incubated with H₂O₂ (2 mM) for an additional hour. Cell viability, antioxidants (Catalase, Superoxide dismutase and Glutathione reductase) and metabolic (Succinate dehydrogenase) enzymes, as well as the level of lipid peroxidation (LPO) and protein carbonyl content (PCO) were evaluated. The chemical composition of EOs has shown the difference qualitatively and quantitatively. Indeed, O. compactum mainly contained Carvacrol, O. basilicum was mainly composed of Linalool, T. vulgaris was rich in thymol, R. officinalis had high α-Pinene amount and for E. globulus, eucalyptol was the major compound. The EOs of basil, oregano and thyme were found to possess the highest amount of total phenolic compounds. Moreover, they have shown the best protective effect on yeast cells against oxidative stress induced by H₂O₂. In addition, in a dose dependent manner of EOs in yeast medium, treated cells had lower levels of LPO, lower antioxidant and metabolic enzymes activity than cells exposed to H₂O₂ only. The cell viability was also improved. It seems that the studied EOs are efficient natural antioxidants, which can be exploited to protect against damages and serious diseases related to oxidative stress.     

Methylerythritol phosphate pathway to isoprenoids: Kinetic modeling and in silico enzyme inhibitions in Plasmodium falciparum

The methylerythritol phosphate (MEP) pathway of Plasmodium falciparum (P. falciparum) has become an attractive target for anti-malarial drug discovery. This study describes a kinetic model of this pathway, its use in validating 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) as drug target from the systemic perspective, and additional target identification, using metabolic control analysis and in silico inhibition studies. In addition to DXR, 1-deoxy-d-xylulose 5-phosphate synthase (DXS) can be targeted because it is the first enzyme of the pathway and has the highest flux control coefficient followed by that of DXR. In silico inhibition of both enzymes caused large decrement in the pathway flux. An added advantage of targeting DXS is its influence on vitamin B1 and B6 biosynthesis. Two more potential targets, 2-C-methyl-d-erythritol 2,4-cyclodiphosphate synthase and 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase, were also identified. Their inhibition caused large accumulation of their substrates causing instability of the system.     

Kidney proteome responses in the teleost fish Paralichthys olivaceus indicate a putative immune response against Streptococcus parauberis

The proteomic response to bacterial infection in a teleost fish (Paralichthys olivaceus) infected with Streptococcus parauberis was analyzed using label-free protein quantitation coupled with LC-MS(E) tandem mass spectrometry. A total of 82 proteins from whole kidney, a major lymphoid organ in this fish, were found to be differentially expressed between healthy and diseased fish analyzed 6, 24, 72 and 120 h post-infection. Among the differentially expressed proteins, those involved in mediating immune responses (e.g., heat shock proteins, cathepsins, goose-type lysozyme and complement components) were most significantly up-regulated by infection. In addition, cell division cycle 48 (CDC48) and calreticulin, which are associated with cellular recovery and glycoprotein synthesis, were up-regulated in the universal protein group, whereas the other proteins in that group were down-regulated. There was continuous activation of expression of immune-associated proteins during infection, but there was also loss of expression of proteins not involved in immune function. We expect that our findings regarding immune response at the protein level would offer new insight into the systemic response to bacterial infection of a major immune organ in teleost fish.     

L7811鼠腹水肿瘤细胞^31P核磁共振的研究

用~(31)P核磁共振技术(~(31)P-NMR)研究了L_(7811)鼠腹水肿瘤细胞和615系鼠胸腺细胞(正常对照细胞)。结果发现在肿瘤晚期阶段,L_(7811)腹水肿瘤细胞的含磷化合物未进入完全不活跃状态。此外,腹水肿瘤细胞的磷脂组成与含量亦有明显改变。因此,~(31)P-NMR谱可做为观察肿瘤细胞内能量生成和某些磷脂合成宏观动态过程的一项参考指标。     

Differentiated inhibition of DNA, RNA and protein synthesis in L1210 cells by 8-methoxypsoralen

The synthesis of DNA, RNA and protein was measured in L1210 cells following treatment with 8-methoxypsoralen in combination with long wavelength ultraviolet irradiation. The results show that the DNA synthesis is strongly inhibited (approximately 95%) at 200 ng/ml reaching a minimum within 2 hours while RNA synthesis is only weakly affected at this concentration (approximately 40% inhibition). At 2 micrograms/ml the RNA synthesis is inhibited approximately 90%. Even at this concentration only a moderate effect is seen on the protein synthesis. These results strongly indicate that the phototoxic action of 8-methoxypsoralen is primarily due to inhibition of DNA synthesis.     

Functional Analysis of the C-Terminal Region of γ-Glutamyl Kinase of Saccharomyces cerevisiae

γ-Glutamyl kinase (GK) is the rate-limiting enzyme in proline synthesis in microorganisms. Most microbial GKs contain an N-terminal kinase domain and a C-terminal pseudouridine synthase and archaeosine transglycosylase (PUA) domain. In contrast, higher eukaryotes possess a bifunctional Δ¹-pyrroline-5-carboxylate synthetase, which consists of a PUA-free GK domain and a γ-glutamyl phosphate reductase (GPR) domain. Here, to examine the role of the C-terminal region, including the PUA domain of Saccharomyces cerevisiae GK, we constructed a variety of truncated yeast GK and GK/GPR fusion proteins from which the C-terminal region was deleted. A complementation test in Escherichia coli and S. cerevisiae and enzymatic analysis of recombinant proteins revealed that a 67-residue linker sequence between a 255-residue kinase domain and a 106-residue PUA domain is essential for GK activity. It also appeared that 67 or more residues of the C-terminal region, not the PUA domain itself, are required for the full display of GK activity. Further, the GK/GPR fusion protein was functional in E. coli, but decreased stability and Mg-binding ability as compared to wild-type GK. These results suggest that the C-terminal region of S. cerevisiae GK is involved in the folding and/or the stability of the kinase domain.     

风湿性心脏病瓣膜置换术患者围术期血浆脑钠肽水平的表达及临床意义

目的:探讨风湿性心脏病瓣膜置换术患者围手术期血浆脑钠肽(BNP)水平及其临床意义。方法:选取2015年1月至2016年12月在我院接受心脏瓣膜置换术的风湿性心脏病患者98例为研究对象,分别于术前、术后12 h、24 h、48 h、术后1周进行血浆BNP、磷酸肌酸同工酶(CK-MB)、高敏C反应蛋白(hs-CRP)水平检测,观察纽约心脏病协会(NYHA)不同心功能分级、不同时间点患者血浆BNP、CK-MB、hs-CRP水平变化,同时观察并比较术后发生严重心律失常与否的患者在不同时间点血浆BNP、CK-MB、hs-CRP水平变化。结果:随NYHA心功能分级升高,患者血浆BNP、CK-MB、hs-CRP水平升高,不同NYHA心功能分级患者血浆BNP、hs-CRP水平比较差异有统计学意义(P0.05),CK-MB水平比较差异无统计学意义(P0.05);不同NYHA心功能分级患者血浆BNP、hs-CRP两两比较差异有统计学意义(P0.05),CK-MB两两比较差异无统计学意义(P0.05)。患者术后12 h、24 h、48 h血浆BNP、hs-CRP水平均显著高于术前,术后24 h、48 h血浆CK-MB水平均显著高于术前,而术后1周血浆BNP、CK-MB、hs-CRP显著低于术前(P0.05)。术后发生严重心律失常(严重心律失常组)患者16例,未发生严重心律失常(无严重心律失常组)患者82例,两组患者术后12 h、24 h、48 h血浆BNP、CK-MB、hs-CRP水平均显著高于术前(P0.05);两组患者术后1周BNP与术前比较差异无统计学意义(P0.05),而CK-MB、hs-CRP水平均显著低于术前(P0.05),但严重心律失常组术后12 h、24h、48 h、1周血浆BNP、CK-MB、hs-CRP水平均显著高于无严重心律失常组(P0.05)。结论:风湿性心脏病瓣膜置换术患者术前血浆BNP可以反映患者心功能情况,术后患者血浆BNP、CK-MB、hs-CRP异常升高,发生严重心律失常患者升高更为明显。     

Urinary and serum electrolyte changes in athletes during periodic and continuous hypokinetic and ambulatory conditions

Hypokinesia (HK) (diminished movement) induces significant electrolyte changes, but little is known about the effect of periodic hypokinesia (PHK) on minerals. The aim of this study was to measure the effect of PHK and continuous hypokinesia (CHK) on urinary and serum electrolytes. Studies were done during a 30-d period of prehypokinesia (HK) and during 364 d of PHK and CHK periods. Thirty male athletes aged 24.6±7.7 yr were chosen as subjects. They were equally divided into three groups: unrestricted ambulatory control subjects (UACS), continuously hypokinetic subjects (CHKS), and periodically hypokinetic subjects (PHKS). The UACS group experienced no changes in the daily activities and regular training and they were maintained under an average running distance of 11.7 km/d. The CHKS group was limited to an average walking distance of 0.7 km/d; and the PHKS group was limited to an average walking distance of 0.7 and running distance of 11.7 km/d for 5 d and 2 d/wk, respectively, for a period of 364 d. Urinary and serum phosphate (P), calcium (Ca), sodium (Na) and potassium (K), serum intact parathyroid hormone (iPTH), calcitonin (CT), plasma renin activity (PRA) and aldosterone (PA) levels, food and water intakes, and physical characteristics were measured. Urinary P, Ca, Na, and K loss, serum Ca, P, Na, and K, and PRA and PA values increased significantly (p≤0.01), whereas serum iPTH and CT levels decreased significantly (p≤0.01) in the PHKS and CHKS groups when compared with the UACS group. However, significant (p≤0.01) differences were observed between PHKS and CHKS groups regarding urinary and serum electrolytes, serum and plasma hormones. Food and water intakes, body weight, body fat, and peak oxygen uptake decreased significantly (p ≤ 0.01) in the CHKS group when compared with PHKS and UACS groups. Food and fluid intakes, body fat, and body weight increased significantly (p≤0.01), whereas peak oxygen uptake remained significantly (p≤0.01) higher in the PHKS group when compared with the CHKS group. Serum and urinary minerals, serum hormones, food and fluid intakes, and physical characteristics did not change significantly (p>0.01) in the UACS group when compared with their baseline control values. It was shown that both PHK and CHK induce significant serum and urinary electrolyte changes. However, urinary and serum electrolyte changes were significantly (p≤0.01) greater during PHK than CHK. It was concluded that the greater the stability of muscular activity, the smaller the serum and urinary electrolyte changes during prolonged HK.