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1.
Since the first North Sea Conference (1984, Bremen), all countries bordering the North Sea made commitments to reduce discharge of hazardous substances into the North Sea. From Belgium and The Netherlands, large reductions (upto 90) in heavy metal emissions from land-based sources have been reported between 1985 and 2000. Recently, some studies in the Western Scheldt estuary (WS) have shown that total metal concentration in the water, sediments and suspended particles have decreased compared to levels in the 70s. However, data on aquatic organisms is still very limited and it is therefore difficult to confirm whether the reductions in pollution input and generally improving water quality in the WS have a corresponding impact on the levels of heavy metals in aquatic organisms. The current study measured metal concentrations in the soft tissues of mussels, Mytilus edulis (known to be good indicators of environmental metal pollution) during the period 1996–2002. Spatial (salinity and pollution gradients), temporal and seasonal variations were also studied. Results showed a down-stream decreasing trend for the metals studied (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) during all sampling campaigns. There was also a significant seasonal effect on tissue metal concentrations, with a peak observed around spring in both WS and the nearby less polluted Eastern Scheldt (ES). On temporal trends, a clear drop of metals in mussels was observed in the early 80s coinciding with the start of the efforts to reduce chemical pollution input into the North Sea. Since those early reductions, metal concentrations in mussels generally remained unchanged upto mid 90s. However, in recent times metal concentration in mussels have increased significantly, for example Cd in 2002 was almost 10 times the values in 1983 and similar to levels seen during the peak in the 70s. Other metals also increased in the 90s also reaching levels seen in the 70s. As there is no indication of recent increase in metal input into the estuary, we suggest that increased metal concentrations observed in mussels in recent years especially in the upper estuary are most likely a result of changes in physical and chemical speciation and metal bioavailability. Such changes may be caused by changes in some water quality parameters in the estuary (i.e. increased dissolved oxygen, concentration of organic matter), resulting in conditions that favour releases of sediment-bound metals into the water column. The relationship between metal content and season showed very similar annual profiles in the polluted WS and less polluted ES. Thus, seasonal variations in metal concentrations appear to be largely controlled by biological processes, while total body burdens are dependent on environmental levels and bioavailability. 相似文献
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The effect of steady-state nitrogen limitation on photo-synthetic characteristics and growth efficiency was examined in the marine haptophyte Isochrysis galbana Green. Nitrate limited chemostats were maintained at nine dilution rates, ranging from 0.18-0.96 d?1, under continuous irradiance levels of 175 μmole quanta·m?2·s?1, an irradiance level which saturated photosynthesis at all growth rates. Nitrogen limitation led to an overall reduction in pigmentation and a decrease in the cellular concentration of reaction centers; however, the optical absorption cross section, normalized to Chl a, increased. Moreover, Chl c/a ratios were higher in nitrogen-limited cells: the change in Chl c/a ratios were correlated with an increase in the functional size of Photosystem II. Both light saturated photosynthetic rates normalized per cell and specific respiratory losses were positively linearly correlated with growth rate. Light saturated photosynthetic rates normalized to Chl a remained relatively insensitive to the rate of nitrogen supply. The minimum quantum requirement for gross photosynthetic oxygen evolution increased from 12.4 to 17.0 quanta/O2. At the growth irradiance, the quantum requirement increased 88%, from 19.9 to 37.5 quauta/O2 Photosynthesis/respiration ratios remained relatively constant at dilution rates greater than 35% of the maximum relative growth rate. Consequently, net growth efficiency, defined as the ratio of the specific growth rate, μ, to specific gross photosynthesis, P, also remained relatively constant over this range of growth rates averaging 85 ± 3%. 相似文献
4.
Ronny Martinez Felix Jakob Ran Tu Petra Siegert Karl‐Heinz Maurer Ulrich Schwaneberg 《Biotechnology and bioengineering》2013,110(3):711-720
Bacillus gibsonii Alkaline Protease (BgAP) is a recently reported subtilisin protease exhibiting activity and stability properties suitable for applications in laundry and dish washing detergents. However, BgAP suffers from a significant decrease of activity at low temperatures. In order to increase BgAP activity at 15°C, a directed evolution campaign based on the SeSaM random mutagenesis method was performed. An optimized microtiter plate expression system in B. subtilis was established and classical proteolytic detection methods were adapted for high throughput screening. In parallel, the libraries were screened for increased residual proteolytic activity after incubation at 58°C. Three iterative rounds of directed BgAP evolution yielded a set of BgAP variants with increased specific activity (Kcat) at 15°C and increased thermal resistance. Recombination of both sets of amino acid substitutions resulted finally in variant MF1 with a 1.5‐fold increased specific activity (15°C) and over 100 times prolonged half‐life at 60°C (224 min compared to 2 min of the WT BgAP). None of the introduced amino acid substitutions were close to the active site of BgAP. Activity‐altering amino acid substitutions were from non‐charged to non‐charged or from sterically demanding to less demanding. Thermal stability improvements were achieved by substitutions to negatively charged amino acids in loop areas of the BgAP surface which probably fostered ionic and hydrogen bonds interactions. Biotechnol. Bioeng. 2013; 110: 711–720. © 2012 Wiley Periodicals, Inc. 相似文献
5.
Kate M. Scott Karestan C. Koenen Sergio Aguilar-Gaxiola Jordi Alonso Matthias C. Angermeyer Corina Benjet Ronny Bruffaerts Jose Miguel Caldas-de-Almeida Giovanni de Girolamo Silvia Florescu Noboru Iwata Daphna Levinson Carmen C. W. Lim Sam Murphy Johan Ormel Jose Posada-Villa Ronald C. Kessler 《PloS one》2013,8(11)
Background
Associations between lifetime traumatic event (LTE) exposures and subsequent physical ill-health are well established but it has remained unclear whether these are explained by PTSD or other mental disorders. This study examined this question and investigated whether associations varied by type and number of LTEs, across physical condition outcomes, or across countries.Methods
Cross-sectional, face-to-face household surveys of adults (18+) were conducted in 14 countries (n = 38, 051). The Composite International Diagnostic Interview assessed lifetime LTEs and DSM-IV mental disorders. Chronic physical conditions were ascertained by self-report of physician''s diagnosis and year of diagnosis or onset. Survival analyses estimated associations between the number and type of LTEs with the subsequent onset of 11 physical conditions, with and without adjustment for mental disorders.Findings
A dose-response association was found between increasing number of LTEs and odds of any physical condition onset (OR 1.5 [95% CI: 1.4–1.5] for 1 LTE; 2.1 [2.0–2.3] for 5+ LTEs), independent of all mental disorders. Associations did not vary greatly by type of LTE (except for combat and other war experience), nor across countries. A history of 1 LTE was associated with 7/11 of the physical conditions (ORs 1.3 [1.2–1.5] to 1.7 [1.4–2.0]) and a history of 5+ LTEs was associated with 9/11 physical conditions (ORs 1.8 [1.3–2.4] to 3.6 [2.0–6.5]), the exceptions being cancer and stroke.Conclusions
Traumatic events are associated with adverse downstream effects on physical health, independent of PTSD and other mental disorders. Although the associations are modest they have public health implications due to the high prevalence of traumatic events and the range of common physical conditions affected. The effects of traumatic stress are a concern for all medical professionals and researchers, not just mental health specialists. 相似文献6.
7.
Marlene Fischer Anelia Dietmann Ronny Beer Gregor Broessner Raimund Helbok Bettina Pfausler Erich Schmutzhard Peter Lackner 《PloS one》2013,8(3)
Background
Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in vascular remodeling, (neuro)inflammation, blood-brain barrier breakdown and neuronal apoptosis. Proinflammatory mechanisms are suggested to play an important role during early brain injury and cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH). This study aimed to analyze MMP-3, MMP-9, TIMP-1 and TIMP-3 in patients with SAH and their respective association with cerebral vasospasm (CVS).Methods
Blood samples were collected in 20 SAH patients on days 1 to 7, 9, 11, 13 and 15 and 20 healthy age and gender matched volunteers. Serum MMPs and TIMPs were analyzed using enzyme-linked immunosorbent assay. Doppler sonographic CVS was defined as a mean blood flow velocity above 120 cm/sec in the middle cerebral artery. When discharged from hospital and at 6 month follow-up neurological outcome was evaluated using the Glasgow Outcome Score and the modified Rankin Scale.Results
MMP-9 was higher in SAH patients compared to healthy controls (p<0.001). Patients with CVS (n = 11) had elevated MMP-9 serum levels compared to patients without CVS (n = 9, p<0.05). Higher MMP-9 was observed in the presence of cerebral ischemia associated with cerebral vasospasm (p<0.05). TIMP-1 was increased in patients with SAH on day 4 (p<0.05). There was an imbalance of the MMP-9/TIMP-1 ratio in favor of MMP-9 in SAH patients, in particular those with CVS (p<0.001). MMP-3 and TIMP-3 were significantly lower in SAH patients throughout day 4 and day 7, respectively (p<0.05). We did not find an association between MMP-, TIMP levels and neurological outcome after 6 months.Conclusions
MMP-3 and -9 are differentially regulated in SAH patients with both enzymes showing peak levels correlating with the development of CVS. The inhibitors TIMP-1 and -3 were low during the acute phase after SAH and increased later on which might suggest a preponderance of pro-inflammatory mechanisms. 相似文献8.
Lucia Vergauwen Dries Knapen An Hagenaars Gudrun De Boeck Ronny Blust 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2013,183(1):109-121
The zebrafish has become a valuable vertebrate model organism in a wide range of scientific disciplines, but current information concerning the physiological temperature response of adult zebrafish is rather scarce. In this study, zebrafish were experimentally acclimated for 28 days to 18, 26 or 34 °C and a suite of non-invasive and invasive methods was applied to determine the thermal dependence of zebrafish physiological condition. With decreasing temperature, the metabolic rate of zebrafish decreased, as shown by the decreasing oxygen uptake and ammonia excretion rates, limiting the critical swimming speed, probably due to a decreased muscle fibre power output. In response to exercise, fuel stores were mobilized to the liver as shown by the increased hepatosomatic index, liver total absolute energetic value and liver carbohydrate concentration but due to the low metabolic rate they could not be adequately addressed to power swimming activity at 18 °C. Conversely, the increased metabolic performance at high temperature came with an increased metabolic cost resulting in decreased energy status reflected particularly well by the non-invasive condition factor and invasive measures of carcass protein concentration, carcass total absolute energetic value and liver carbohydrate concentration. We showed that the combined measurement of the relative condition factor and critical swimming speed is a powerful non-invasive tool for long-term follow-up studies. Invasive methods were redundant for measuring general energy status but they provided detailed information concerning metabolic reorganization. With this study we proved that the usefulness of the zebrafish as a model organism can easily be expanded to include physiological studies and we provided a reference dataset for the selection of measures of physiological responses for future studies using the zebrafish. 相似文献
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Ronja Breitkopf Ronny Uhlig Tina Drenckhan Ralf-Jörg Fischer 《Extremophiles : life under extreme conditions》2016,20(5):653-661
Moorella thermoacetica is one of the model acetogenic bacteria for the resolution of the Wood–Ljungdahl (acetyl-CoA) pathway in which CO2 is autotrophically assimilated yielding acetyl-CoA as central intermediate. Its further conversion into acetate relies on subsequent phosphotransacetylase (PTA) and acetate kinase reactions. However, the genome of M. thermoacetica contains no pta homologous gene. It has been speculated that the moth_0864 and moth_1181 gene products sharing similarities with an evolutionarily distinct phosphotransacylase involved in 1,2-propanediol utilization (PDUL) of Salmonella enterica act as PTAs in M. thermoacetica. Here, we demonstrate specific PTA activities with acetyl-CoA as substrate of 9.05 and 2.03 U/mg for the recombinant enzymes PDUL1 (Moth_1181) and PDUL2 (Moth_0864), respectively. Both showed maximal activity at 65 °C and pH 7.6. Native proteins (90 kDa) are homotetramers composed of four subunits with apparent molecular masses of about 23 kDa. Thus, one or both PDULs of M. thermoacetica might act as PTAs in vivo catalyzing the penultimate step of the Wood–Ljungdahl pathway toward the formation of acetate. In silico analysis underlined that up to now beside of M. thermoacetica, only Sporomusa ovata contains only PDUL like classIII-PTAs but no other phosphotransacetylases or phosphotransbutyrylases (PTBs). 相似文献