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Cerebral small vessel disease (CSVD) is the most common progressive vascular disease that causes vascular dementia. Aging and hypertension are major contributors to CSVD, but the pathophysiological mechanism remains unclear, mainly due to the lack of an ideal animal model. Our previous study revealed that vascular smooth muscle cell (VSMC)-specific myosin phosphatase target subunit 1 (MYPT1) knockout (MYPT1SMKO) leads to constant hypertension, prompting us to explore whether hypertensive MYPT1SMKO mice can be considered a novel CSVD animal model. Here, we found that MYPT1SMKO mice displayed age-dependent CSVD-like neurobehaviors, including decreased motion speed, anxiety, and cognitive decline. MYPT1SMKO mice exhibited remarkable white matter injury compared with control mice, as shown by the more prominent loss of myelin at 12 months of age. Additionally, MYPT1SMKO mice were found to exhibit CSVD-like small vessel impairment, including intravascular hyalinization, perivascular space enlargement, and microbleed and blood-brain barrier (BBB) disruption. Last, our results revealed that the brain of MYPT1SMKO mice was characterized by an exacerbated inflammatory microenvironment, which is similar to patients with CSVD. In light of the above structural and functional phenotypes that closely mimic the conditions of human CSVD, we suggest that MYPT1SMKO mice are a novel age- and hypertension-dependent animal model of CSVD. [ABSTRACT FROM AUTHOR]

Abstract Background Succinic acid is a building-block chemical which could be used as the precursor of many industrial products. The dissolved CO2 concentration in the fermentation broth could strongly regulate the metabolic flux of carbon and the activity of phosphoenolpyruvate (PEP) carboxykinase, which are the important committed steps for the biosynthesis of succinic acid by Actinobacillus succinogenes. Previous reports showed that succinic acid production could be promoted by regulating the supply of CO2 donor in the fermentation broth. Therefore, the effects of dissolved CO2 concentration and MgCO3 on the fermentation process should be investigated. In this article, we studied the impacts of gaseous CO2 partial pressure, dissolved CO2 concentration, and the addition amount of MgCO3 on succinic acid production by Actinobacillus succinogenes ATCC 55618. We also demonstrated that gaseous CO2 could be removed when MgCO3 was fully supplied. Results An effective CO2 quantitative mathematical model was developed to calculate the dissolved CO2 concentration in the fermentation broth. The highest succinic acid production of 61.92 g/L was obtained at 159.22 mM dissolved CO2 concentration, which was supplied by 40 g/L MgCO3 at the CO2 partial pressure of 101.33 kPa. When MgCO3 was used as the only CO2 donor, a maximal succinic acid production of 56.1 g/L was obtained, which was just decreased by 7.03% compared with that obtained under the supply of gaseous CO2 and MgCO3. Conclusions Besides the high dissolved CO2 concentration, the excessive addition of MgCO3 was beneficial to promote the succinic acid synthesis. This was the first report investigating the replaceable of gaseous CO2 in the fermentation of succinic acid. The results obtained in this study may be useful for reducing the cost of succinic acid fermentation process.

As a potential intermediary feedstock, succinic acid takes an important place in bulk chemical productions. For the first time, a method combining Plackett-Burman design (PBD), steepest ascent method (SA), and Box-Behnken design (BBD) was developed to optimize Actinobacillus succinogenes ATCC 55618 fermentation medium. First, glucose, yeast extract, and MgC[O.sub.3] were identified to be key medium components by PBD. Second, preliminary optimization was run by SA method to access the optimal region of the key medium components. Finally, the responses, that is, the production of succinic acid, were optimized simultaneously by using BBD, and the optimal concentration was located to be 84.6 g [L.sup.-1] of glucose, 14.5 g [L.sup.-1] of yeast extract, and 64.7 g [L.sup.-1] of MgC[O.sub.3]. Verification experiment indicated that the maximal succinic acid production of 52.7 ± 0.8g [L.sup.-1] was obtained under the identified optimal conditions. The result agreed with the predicted value well. Compared with that of the basic medium, the production of succinic acid and yield of succinic acid against glucose were enhanced by 67.3% and 111.1%, respectively. The results obtained in this study may be useful for the industrial commercial production of succinic acid., 1. Introduction Succinic acid is a member of the four-carbon dicarboxylic acid family in tricarboxylic acid cycle (TCA) and has a wide range of applications in the fields of surfactants, [...]

ABSTRACT To balance the flux of an engineered metabolic pathway to achieve high yield of target product is a major challenge in metabolic engineering. In previous work, the collaborative regulation of CO2 transport and fixation was investigated with co-overexpressing exogenous genes regulating both CO2 transport ( sbtA and bicA) and PEP carboxylation (phosphoenolpyruvate (PEP) carboxylase ( ppc) and carboxykinase ( pck)) under trc promoter in Escherichia coli for succinate biosynthesis. For balancing metabolic flux to maximize succinate titer, a combinatorial optimization strategy to fine-tuning CO2 transport and fixation process was implemented by promoter engineering in this study. Firstly, based on the energy matrix a synthetic promoter library containing 20 rationally designed promoters with strengths ranging from 0.8% to 100% compared with the widely used trc promoter was generated. Evaluations of rfp and cat reporter genes provided evidence that the synthetic promoters were stably and had certain applicability. Secondly, four designed promoters with different strengths were used for combinatorial assembly of single CO2 transport gene ( sbtA or bicA) and single CO2 fixation gene ( ppc or pck) expression. Three combinations, such as Tang1519 (P4- bicA + pP19- pck), Tang1522 (P4- sbtA + P4- ppc), Tang1523 (P4- sbtA + P17- ppc) with a more than 10% increase in succinate production were screened in bioreactor. Finally, based on the above results, co-expression of the four transport and fixation genes were further investigated. Co-expression of sbtA, bicA, and ppc with weak promoter P4 and pck with strong promoter P19 (AFP111/pT-P4- bicA-P4- sbtA + pACYC-P19- pck-P4- ppc) provided the best succinate production among all the combinations. The highest succinate production of 89.4 g/L was 37.5% higher than that obtained with empty vector control. This work significantly enhanced succinate production through combinatorial optimization of CO2 transport and fixation. The promoter engineering and combinatorial optimization strategies used herein represents a powerful approach to tailor-making metabolic pathways for the production of other industrially important chemicals. Biotechnol. Bioeng. 2016;113: 1531-1541. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The cell growth and total accumulation of bioactive metabolites were significantly improved by Cu2+ addition during the submerged fermentation of medicinal mushroom Ganoderma lucidum. A mathematical model, constructed by response surface methodology combination with full factorial design, was applied to study the synergic effect of Cu2+ addition concentration and addition time. The optimal Cu2+ inducement strategy for the cell growth were different from those for the biosynthesis of ganoderic acid (GA) and Ganoderma polysaccharide. A multiple additions strategy of Cu2+ by adding each 1 mM Cu2+ on day 2, 6, 8 and 2 mM Cu2+ on day 4 was developed to enhance total accumulation of GA and extracellular polysaccharides. The highest GA content reached 3.0 ± 0.1 mg per 100 mg DW, which was increased by 76.5% and 33.9% compared with the control without Cu2+ addition and the peak value predicted by the constructed mathematical model, respectively. While, relatively higher addition concentration of Cu2+ (i.e., 5 mM) on the culture of day 4 led to higher content and total production of intracellular polysaccharides. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [ABSTRACT FROM AUTHOR]

In this paper, the fundamental equations of load identification in time domain are established, using the modal coordinates based on acceleration measurement DOF as the modal normalized DOF. Then, using the preliminary identified load as driving force, structural dynamical response is calculated. On the base of comparing the structural dynamical response and the measuring acceleration in frequency domain, the component of frequency domain in the preliminary identified load is modified. Thus, the final result of load identification in time domain is obtained through inverse transform. And the modification of frequency domain in this method is very important. This method of single point exciting/single point measuring has been successfully applied to identify the practical dynamic loads on Launch Vehicle. [ABSTRACT FROM AUTHOR]

Cra (catabolite repressor/activator) is a global transcription factor (TF) that plays a pleiotropic role in controlling the transcription of several genes involved in carbon utilization and energy metabolism. Multiple studies have investigated the regulatory mechanism of Cra and its rational use for metabolic regulation, but due to the complexity of its regulation, there remain challenges in the efficient use of Cra. Here, the structure, mechanism of action, and regulatory function of Cra in carbon and nitrogen flow are reviewed. In addition, this paper highlights the application of Cra in metabolic engineering, including the promotion of metabolite biosynthesis, the regulation of stress tolerance and virulence, the use of a Cra-based biosensor, and its coupling with other transcription factors. Finally, the prospects of Cra-related regulatory strategies are discussed. This review provides guidance for the rational design and construction of Cra-based metabolic regulation systems.

The enrichment and translocation characteristics of Cd, Pb, Zn, and As by various parts of maize plants were investigated using field experiments in 22 maize varieties simultaneously under uncontaminated, low, middle, and serious heavy metal Cd, Pb, Zn, and As complex-contaminated farmland soil conditions. The relationship between the uptake of Cd, Pb, Zn, and As by maize plants and the morphological content of heavy metals in the soil was also discussed through principal component analysis and correlation analysis of the concentrations of eight heavy metals, including Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn. The results showed that:① the distribution pattern of Cd and Zn contents in different parts of the maize plant was as follows:upper stalk>lower stalk>root>seed, the distribution pattern of Pb was As follows:root>lower stalk>upper stalk>seed, and the As distribution pattern was:root>upper stalk>lower stalk>seed. The different distribution patterns were closely related to the accumulation characteristics of the crop itself and the environmental activity of Cd, Pb, Zn, and As in the soil of the study area. ② There were significant differences in Cd and Pb accumulation among 22 maize cultivars due to their genetic background ( P <0.05), which showed four trends:Cd and Pb compound high-accumulation varieties, single Cd or Pb low-accumulation varieties (low Cd and high Pb, low Pb and high Cd), and Cd and Pb compound low-accumulation varieties. Among them, the content of Cd in the grain of the three varieties exceeded the national food safety standard, and the content of Cd in the stem and leaf of 14 varieties exceeded the national food health standard. The Pb content in stems, leaves, and grains of all cultivars did not exceed the standard, but the Pb content in grains of some cultivars was close to the limit and had the risk of exceeding the standard. The content of As in the stem, leaf, and grain of different maize varieties was much lower than the standard limit value, showing a stable low-accumulation characteristic. The content of Zn in the stem and leaf of different maize varieties increased with the increase in the content of Zn in soil, but the content of Zn in grain remained within the threshold of normal plant growth. ③ Cd, Pb, Zn, and As in maize plants in the study area had a certain homology and were mainly affected by the excessive levels of Cd, Pb, Zn, and As pollutants in the soil. This showed that anthropogenic sources were brought about by mine extraction and tailings stockpiles, whereas Cu elements in maize plants were affected by certain anthropogenic pollution sources, though to a limited extent. Hg, Ni, and Cr in maize plants had a certain homology; this showed the natural source of soil parent material and weathering product accumulation. ④ The contents of Cd, Pb, Zn, and As elements in various parts of the corn plant, as well as the contents of Cr and Ni elements all had a very significant positive correlation ( P <0.01). The transport mechanisms of Cd, Pb, Zn, and As elements in the plant may have a common. However, there was a synergistic effect in the migration from the root of the corn to the upper part of the ground, and the same was true for the elements of Cr and Ni. The elements of Hg and Cd, Pb, Zn, and As in the corn stems and leaves and Hg and Cd, Hg, As, Pb, Cr, Ni, and Zn in grains all showed certain antagonistic effects. ⑤ The comparison method simultaneously satisfied the following requirements:the contents of Cd, Pb, and As in stems and leaves did not exceed the national food hygiene standards, and the contents of Cd, Pb, and As in the grains did not exceed the national food safety standards. The cluster analysis of Cd, Pb, and As in grains was a low-accumulation group, and the enrichment and transport coefficients of Cd, Pb, and As in the stems and leaves and grains were low as the optimal conditions. C18 (Xianyu 335) could be selected as the optimal maize variety with low accumulation of Cd, Pb, and As and normal Zn content in grain, which is suitable for promoting and applying in the heavy metal complex-polluted farmland around industrial and mining enterprises in north China.

In this study, a field experiment of soil passivation and low accumulation-crops was carried out for typical northern alkaline cadmium and lead compound-polluted farmland soil. Calcite was used as the main passivation material, and a small amount of slaked lime, zeolite powder, and biochar were combined to form a group passivation agent. The effects of passivators on soil physicochemical properties, bioavailability of the heavy metals Cd and Pb, and the yield and plant (stalk and seed) content of heavy metals Cd and Pb in low-accumulation maize were investigated under different grouping conditions of calcite+slaked lime (CL), calcite+zeolite (CZ), calcite+biochar (CB), and calcite+slaked lime+zeolite+biochar (CLZB). The results showed that:① all applications of passivating agent ensured the normal growth of maize and slightly increased the 1000 grain weight and maize yield. ② The effects of different calcite-based passivators on soil physical and chemical properties were different. The CL, CZ, CB, and CLZB treatments increased soil pH by 0.46, 0.25, 0.12, and 0.13 units, respectively, but had no significant correlation with soil fertility index ( P >0.05). ③ DTPA leaching and ion exchange state contents of Cd and Pb in soil could be significantly reduced by different calcite-based combinations with passivators, and the reduction rates of Cd and Pb in DTPA leaching were 49.36% and 72.55%, respectively. The reduction rates of ion exchange Cd and Pb contents were 55.39% and 78.52%, respectively. ④ The contents of Cd and Pb in stems, leaves, and grains of low-accumulation maize were further reduced by different passivating agents. The contents of Cd and Pb in the stems and leaves of maize were reduced by 45.93% and 67.00% after CLZB treatment, and the contents of Cd and Pb in grains were decreased by 25.17% and 46.62%, respectively. Moreover, the contents of Cd and Pb in DTPA extraction and ion exchange states were significantly positively correlated with the contents of Cd and Pb in corn stems, leaves, and grains ( P <0.01). The results showed that the combined use of combination passivators and low-accumulation crop varieties can obtain better restoration effects in the remediation of cadmium and lead combined-polluted farmland in the middle alkaline soil in northern China.

In order to provide technical support for the safe utilization of heavy metal-polluted farmland, we screened wheat varieties with a low accumulation of Cd in grain via a pot experiment. For this purpose, we respectively investigated the enrichment and transport characteristics of Cd in various plant parts of 119 wheat varieties under the conditions of 1.5 mg·kg -1 (low content) and 4.0 mg·kg -1 (high content) Cd-contaminated soil and explored the correlation between the Cd content of different organs of wheat and the relationship between Cd content in soil and the uptake of Cd by wheat. The results showed that:① there were significant differences in the ability to accumulate and transport Cd in roots, stems, leaves, and grains of tested wheat varieties ( P <0.05). Under the condition of low Cd content, the Cd enrichment ability of each part of the wheat plant was as follows:leaf>stem ≈root>grain; under high-content stress conditions, the Cd enrichment ability of each part of the wheat plant was:leaf>root>stem>grain; under different content conditions, the Cd transport ability of each part of the wheat plant was:leaf>stem>grain. Cd content in the wheat shoot was positively correlated with total Cd content and ion-exchangeable Cd content in soil ( P <0.01) and was closely related to strong transpiration under the pot experiment. ② The correlation coefficient r of BCF Cd of wheat roots, stems, leaves, and grain was -0.267 to -0.645, showing a very significant negative correlation ( P <0.01), indicating that with the increase in soil Cd content, the migration and accumulation degree of Cd in wheat plant organs showed a downward trend. Moreover, the negative correlation between BCF Cd and soil Cd content in stems was significantly higher than that in roots, leaves, and grains, indicating that the enrichment of Cd in wheat plants largely depended on the accumulation and transportation of stems. ③ The correlation coefficient r of Cd content between the root and stem, root and leaf, root and grain, stem and leaf, stem and grain, and leaf and grain in low-and high-content groups was 0.450-0.763, showing a very significant positive correlation ( P <0.01), indicating that there was a close transport relationship among the wheat organs, and the degree of translocation from the root to stem and stem to leaf was higher than that from the stem to grain and leaf to grain. ④ Using cluster analysis and enrichment and translocation coefficient sequencing, this study screened 16 and 11 wheat varieties with low Cd accumulation under the soil cadmium content of 1.5 mg·kg -1 and 4.0 mg·kg -1 , respectively. Among them, Luohan 7 could be used as the optimal wheat variety with low Cd accumulation under the conditions of low-, medium-, and high-Cd content.

To balance the flux of an engineered metabolic pathway to achieve high yield of target product is a major challenge in metabolic engineering. In previous work, the collaborative regulation of CO2 transport and fixation was investigated with co-overexpressing exogenous genes regulating both CO2 transport (sbtA and bicA) and PEP carboxylation (phosphoenolpyruvate (PEP) carboxylase (ppc) and carboxykinase (pck)) under trc promoter in Escherichia coli for succinate biosynthesis. For balancing metabolic flux to maximize succinate titer, a combinatorial optimization strategy to fine-tuning CO2 transport and fixation process was implemented by promoter engineering in this study. Firstly, based on the energy matrix a synthetic promoter library containing 20 rationally designed promoters with strengths ranging from 0.8% to 100% compared with the widely used trc promoter was generated. Evaluations of rfp and cat reporter genes provided evidence that the synthetic promoters were stably and had certain applicability. Secondly, four designed promoters with different strengths were used for combinatorial assembly of single CO2 transport gene (sbtA or bicA) and single CO2 fixation gene (ppc or pck) expression. Three combinations, such as Tang1519 (P4 -bicA + pP19 -pck), Tang1522 (P4 -sbtA + P4 -ppc), Tang1523 (P4 -sbtA + P17 -ppc) with a more than 10% increase in succinate production were screened in bioreactor. Finally, based on the above results, co-expression of the four transport and fixation genes were further investigated. Co-expression of sbtA, bicA, and ppc with weak promoter P4 and pck with strong promoter P19 (AFP111/pT-P4 -bicA-P4 -sbtA + pACYC-P19 -pck-P4 -ppc) provided the best succinate production among all the combinations. The highest succinate production of 89.4 g/L was 37.5% higher than that obtained with empty vector control. This work significantly enhanced succinate production through combinatorial optimization of CO2 transport and fixation. The promoter engineering and combinatorial optimization strategies used herein represents a powerful approach to tailor-making metabolic pathways for the production of other industrially important chemicals. Biotechnol. Bioeng. 2016;113: 1531-1541. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)