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Rock glaciers manifest the creep of mountain permafrost occurring in the past or at present. Their presence and dynamics are indicators of permafrost distribution and changes in response to climate forcing. There is a complete lack of knowledge about rock glaciers in the Western Kunlun Mountains, one of the driest mountain ranges in Asia, where extensive permafrost is rapidly warming. In this study, we first mapped and quantified the kinematics of active rock glaciers based on satellite Interferometric Synthetic Aperture Radar (InSAR) and Google Earth images. Then we trained DeepLabv3+, a deep learning network for semantic image segmentation, to automate the mapping task. The well-trained model was applied for a region-wide, extensive delineation of rock glaciers from Sentinel-2 images to map the landforms that were previously missed due to the limitations of the InSAR-based identification. Finally, we mapped 413 rock glaciers across the Western Kunlun Mountains: 290 of them were active rock glaciers mapped manually based on InSAR and 123 of them were newly identified and outlined by deep learning. The rock glaciers are categorized by their spatial connection to the upslope geomorphic units. All the rock glaciers are located at altitudes between 3,390 m and 5,540 m with an average size of 0.26 km2 and a mean slope angle of 17°. The median and maximum surface downslope velocities of the active ones are 17±1 cm yr-1 and 127±6 cm yr-1, respectively. Characteristics of the inventoried rock glaciers provided insights into permafrost distribution in the Western Kunlun Mountains.

This short review presents an overview of visible-light-driven asymmetric catalysis by chiral complexes of first-row transition metals. The processes described here include dual catalysis by a chiral complex of copper, nickel, cobalt, or chromium and an additional photoredox or energy-transfer catalyst, and bifunctional catalysis by a single chiral copper or nickel catalyst. These methods allow valuable transformations with high functional group compatibility. They provide stereoselective construction of carbon–carbon or carbon–heteroatom bonds under mild conditions, and produce a diverse range of previously unknown enantioenriched compounds.1 Introduction2 Nickel-Based Photocatalytic Asymmetric Catalysis3 Copper-Based Photocatalytic Asymmetric Catalysis4 Photocatalytic Asymmetric Catalysis by Chiral Complexes of Cobalt or Chromium5 Conclusion

Taking the high volume fraction SiCp/6061Al-based composite material prepared by the powder metallurgy method under different sintering temperatures and holding times as the research object, the microstructure and interface actions are investigated by X-ray diffractometer, scanning electron microscope, transmission electron microscope, etc. The results show that as the sintering temperature increases, the interface reaction between SiC and Al intensifies, producing brittle phase Al4C3 and MgAl2O4 and MgO interface products. The nucleation and growth of Al4C3 are controlled by the sintering temperature and time. When preparing large-size workpieces with high volume fraction SiCp/6061Al-based composite materials, the sintering temperature should be controlled below [Formula: see text]C, and the holding time should not exceed 24 h.

PurposeThe desire for firms to gain competitive advantage and improve performance has resulted in the adoption of several practices. Green supply chain practices (GSCPs), just in time (JIT) and total quality management (TQM) are some of the practices adopted by firms to improve operational performance (OP) and business performance (BP). This study examines the direct influence of GSCPs, JIT and TQM on operational performance and BP. The study further analyzes the synergy of GSCPs, JIT and TQM on OP and BP.Design/methodology/approachThis study employs the quantitative approach of research by using questionnaire to gather data from manufacturing managers and supply chain managers of 140 manufacturing firms in Ghana. The research uses partial least square structural equation modeling (PLS–SEM) to analyze the survey data.FindingsThe results of the analysis show that GSCPs, TQM and JIT positively influence both OP and BP. The findings reveal that GSCPs combine with JIT and TQM to improve OP and BP significantly. However, the synergy between green supply chain and TQM creates more value for both OP and BP than the synergy between GSCPs and JIT.Originality/valueThe study proposes a research model that examines both the individual and combined influence of GSCPs, TQM and JIT on both OP and BP from the developing country perspective. The study models GSCPs as an antecedent of JIT and TQM, which has not been explored.

Since most patients with heart failure are re-admitted to the hospital, accurately identifying the risk of re-admission of patients with heart failure is important for clinical decision making and management. This study plans to develop an interpretable predictive model based on a Chinese population for predicting six-month re-admission rates in heart failure patients. Research data were obtained from the PhysioNet portal. To ensure robustness, we used three approaches for variable selection. Six different machine learning models were estimated based on selected variables. The ROC curve, prediction accuracy, sensitivity, and specificity were used to evaluate the performance of the established models. In addition, we visualized the optimized model with a nomogram. In all, 2002 patients with heart failure were included in this study. Of these, 773 patients experienced re-admission and a six-month re-admission incidence of 38.61%. Based on evaluation metrics, the logistic regression model performed best in the validation cohort, with an AUC of 0.634 (95%CI: 0.599–0.646) and an accuracy of 0.652. A nomogram was also generated. The established prediction model has good discrimination ability in predicting. Our findings are helpful and could provide useful information for the allocation of healthcare resources and for improving the quality of survival of heart failure patients.

Litchi polysaccharides are a kind of macromolecular polymers with various biological activities and a wide range of molecular weights. In this study, two separate fractions, with average molecular weights of 378.67 kDa (67.33%) and 16.96 kDa (6.95%), which were referred to as LP1 and LP2, respectively, were separated using an ultrafiltration membrane. Their physicochemical properties, and immunomodulatory and prebiotic activity were compared. The results revealed that LP2 contained more neutral sugar, arabinose, galactose and rhamnose, but less uronic acid, protein, mannose and glucose than LP1. Compared with LP1, LP2 possessed higher solubility and lower apparent viscosity. LP2 exhibited stronger stimulation on macrophage secretion of NO, TNF-α and IL-6, as well as better proliferation of Lactobacillus plantarum, Leuconostoc mesenteroides, Lactobacillus casei and Bifidobacterium adolescentis. These results suggest that an ultrafiltration membrane might be used to prepare a highly-active polysaccharide fraction from litchi pulp that may be used for food or drug development.

In large-scale MIMO system, as the number of antennas increases, the huge computational complexity makes traditional antenna selection algorithms impossible to effectively apply. This paper propose a joint transmitreceive antenna selection model based on ResNet. We utilize the optimal antenna selection algorithm to create labels for all channel matrices, which based on maximizing channel capacity criterion. Then using large-scale channel data to train a powerful residual neural network classifier. Consequently the trained model can classify the corresponding label for each channel matrix in the test set and select the optimal antenna subset. Experimental results show that the method can effectively decrease the number of antenna selection and its communication performance outperforms compared methods

A poly(vinylidene fluoride)/ethyl cellulose and amino-functionalized nano-SiO2 (PVDF-EC-(A-SiO2)) composite coated on polyethylene (PE) is developed as the functional separator of 5 V high-voltage lithium ion batteries with enhanced performance. Compared with the PE separator, the composite membrane has a uniform interconnected structure, an increased melting temperature from 138 °C (PE) to 140.8 °C, a decreased contact angle from 49.5° to 23.2°, and higher ionic conductivity from 0.34 mS cm−1 to 0.79 mS cm−1. In particular, the electrochemical window is raised to 5.3 V (vs. Li/Li+). LiNi0.5Mn1.5O4/Li batteries with this separator display a high discharge capacity of 131.6 mAh g−1 and a superior cycling stability with a capacity retention of 95.7% after 200 cycles at 0.5 C. Those results demonstrate that the PVDF-EC-(A-SiO2)/PE composite separator exhibits a good-performance in cycling stability and thermal stability, implying promising potential application in high-voltage lithium ion batteries.

Within the area of regional port clusters, this paper establishes a multi-period mixed integer programming model to optimize the empty container repositioning between public hinterlands and ports, comprehensively considering the quantitative and periodic inventory control strategy. By using Markov decision process combined with dynamic programming method, this paper dynamically optimizes the empty container inventory threshold (D;U) under quantitative strategy and S under periodical strategy at each port within the regional port clusters. On this basis, this paper optimizes the empty container repositioning scheme between public hinterlands and ports. Meanwhile, Liaoning coastal regional port cluster and its northeast hinterland are selected as the objects to solve this model and the results show that the total cost of shipping company can be saved by 14.16% and 11.92% respec- tively by the quantitative and periodical inventory control strategy. Selecting the quantity of public hinterland terminals, the empty container demand of public hinterland terminals and ports, the inventory threshold of empty containers and other factors, this paper carries on the sensitivity analysis. This paper validates inventory control strategy can weaken the shipping company in the influence of the external environment changes. And the quantitativeinventory control strategy can reduce the total cost value to a greater extent and more effective in cost control than periodical strategy.

Introduction: With an increasing number of China's aging population, Parkinson's disease (PD) increases year by year. Persons with PD exhibit abnormal balance functions, leading to motor skills difficulties, such as unstable walking or even falling. Therefore, activities of daily living and quality of life are affected. This study aims to explore the effectiveness of Tai Chi training based on the mobile phone app in improving the balance ability of persons with PD.Methods and Analysis: A randomized, single-blind, parallel controlled trial will be conducted in this study. One hundred forty-four persons with PD who meet the inclusion criteria will be randomly divided into a 1:1:1 ratio: (1) control group, (2) basic experimental group (basic app with no Tai Chi training features), and (3) balanced-enhanced experimental group (basic app with Tai Chi training features). Individuals with PD will be evaluated on balance and motor function outcomes. The primary outcome measure is the limits of stability (including the maximum excursion and direction control); the secondary outcome measures include the Unified Parkinson's Disease Rating Scale III (UPDRS-III), Berg Balance Scale (BBS), Functional Reach Test (FRT), Timed Up & Go (TUG), 6-Minute Walk Test (6MWT), and 39-item Parkinson's Disease Questionnaire (PDQ-39). Each group of patients will go through an assessment at baseline, 17 and 33 weeks.Discussion: This study will evaluate the effectiveness of the mobile phone app Tai Chi training on the balance function of persons with PD. We assume that a challenging Tai Chi project based on a mobile phone app will improve balance in the short and long term. As walking stability progresses, it is expected that daily activities and quality of life improve. These findings will be used to improve the effectiveness of future home management measures for persons with PD.Ethics and Dissemination: This study has been approved by the ethical review committee of the Shanghai University of Sport (approval number: 102772019RT056). Informed consent will be obtained from all participants or their guardians. The authors intend to submit the study findings to peer-reviewed journals or academic conferences to be published.Clinical Trial Registration: Chinese Clinical Trial Registry (ChiCTR2000029135).

Alzheimer's disease (AD) is one of the most common neurodegenerative causes of dementia, the pathology of which is still not much clear. It′s challenging to discover the disease modifying agents for the prevention and treatment of AD over the years. Emerging evidence has been accumulated to reveal the crucial role of up‐regulated glutaminyl cyclase (QC) in the initiation of AD. In the current study, the QC inhibitory potency of a library consisting of 1621 FDA‐approved compounds was assessed. A total of 54 hits, 3.33 % of the pool, exhibited QC inhibitory activities. The Ki of the top 5 compounds with the highest QC inhibitory activities were measured. Among these selected hits, compounds affecting neuronal signaling pathways and other mechanisms were recognized. Moreover, several polyphenol derivatives with QC inhibitory activities were also identified. Frameworks and subsets contained in these hits were analyzed. Taken together, our results may contribute to the discovery and development of novel QC inhibitors as potential anti‐AD agents., Up‐regulated glutaminyl cyclase (QC) has a crucial role in the initiation of Alzheimer's disease (AD).The QC inhibitory potency of a library containing 1621 FDA‐approved compounds was investigated. Molecule scaffolds and motifs contained in these hits (3.33 % of the pool) are suggested to be combined into the design of new fragment like libraries targeting QC. This approach may support the development of novel QC inhibitors as potential anti‐AD agents.

Recently, Schwarz Primitive triply periodic minimal surfaces (P-TPMS) lattice structure has received more and more attention due to its superior mechanical properties and unique topological configuration. In this paper, the effective elastic parameters and deformation behavior of the primary P-TPMS structure and its ribbed reinforced structure are studied, as well as the law of the influence of the change of relative density on them. An analytical model is developed, which can efficiently and accurately predict the effective uniaxial modulus of the ribbed P-TPMS lattice structure based on the effective uniaxial modulus of the primary P-TPMS lattice and the rib structure. By comparing the calculation results of the primary P-TPMS structure with the ribbed P-TPMS lattice structure utilizing the finite element analysis (FEA), it can be obtained that the vertical ribbed design can effectively improve the effective uniaxial modulus of the primary P-TPMS structure.

In this study, glycyrrhetinic acid (GA)-modified D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) polymeric micelles (TGA PMs) were developed for the delivery of etoposide (ETO) to hepatoma cells. GA was incorporated as a ligand because of its high affinity to the hepatocytes, while TPGS functioned as a P-gp inhibitor to reverse multidrug resistance. ETO-loaded TGA PMs (ETO-TGA PMs) displayed a mean particle size of 133.6±1.2nm with a low poly-dispersity index (0.224±0.013) and negative zeta potential (-16.30mV). The drug loading and entrapment efficiency of ETO-TGA PMs were 10.4% and 79.8%, respectively. ETO-TGA PMs also exhibited faster drug release behavior at pH 5.8 and relatively stable drug release at pH 7.4. Confocal laser scanning microscope (CLSM) observations and in vivo imaging studies revealed that TGA PMs displayed higher cellular uptake and selective accumulation at the tumor site, indicating good tumor targetability. Furthermore, ETO-TGA PMs displayed significant cytotoxicity towards HepG2 cells and higher anti-tumor efficacy (75.96%), compared to the control group. This could be due to TGA-mediated targeted drug delivery to the hepatocytes as well as P-gp inhibition. These findings suggest that TGA PMs have the potential to be used as a targeted drug delivery system for hepatic cancer therapy.

Zein/pectin core-shell nanoparticles with average diameter of about 235 nm and polydispersity index (PDI) of 0.24 were developed to encapsulate, protect and deliver resveratrol. Biopolymer nanoparticles could be formed containing up to 10.2% (w/w) resveratrol, with a particle yield of 91.7% and a resveratrol loading efficiency of 77.9%. The nanoparticles formed were spherical and had good redispersibility in aqueous solutions. The encapsulated resveratrol had a higher in vitro antioxidant activity than free resveratrol as determined by DPPH·, ABTS+ scavenging ability, and iron (III) reducing power. The encapsulated resveratrol also exhibited higher antiproliferative activity when tested using human hepatocarcinoma Bel-7402 cells than free resveratrol, with IC50 values of 17.6 μg/mL (77.2 μM) and 25.6 μg/mL (112.0 μM) respectively. The colloidal form of resveratrol developed in this study may be particularly useful for application in functional foods and beverages, as well as in dietary supplements and pharmaceutical products.

We study empty container repositioning between hinterland and seaports considering both free detention time and liner carrier cooperation. Aiming at minimizing the cost of empty container repositioning, we propose a nonlinear mixed integer programming model to obtain optimal free detention time of liner carriers and optimal time to dispatch empty containers from hinterland to seaports. Meanwhile, under the cooperation of liner carriers, the optimal quantities of empty containers repositioned from surplus ports to deficit ports are derived. To solve this model, we use CPLEX solver to get the optimal results. It is shown that when a port is judged to be a deficit port in a certain period, the liner carrier will set a shorter free detention time; otherwise, a longer free period will be set at a surplus port. Sensitivity analysis is also conducted in this paper. Results show that the increase of storage cost leads to the increase of total cost, while total cost decreases with the expansion of demand for empty containers. And poor hinterland transportation condition extends free detention time, which in turn reduces the liner carriers’ profits. Liner carriers should integrate hinterland transportation when they are short of empty containers.

Fused deposition modeling (FDM) is an important process among the available additive manufacturing technologies in various industries. Although there exists many works investigating the effects of FDM process parameters on the mechanical properties of printed materials, there are still several points need to be studied. One is the effects of process parameters on the dynamic mechanical properties of FDM-printed materials, especially in environments where the temperature often changes. The other is the mechanism by which process parameters affect the mechanical properties of printed materials. Aiming at these two points, uniaxial tensile tests and dynamic mechanical analysis are carried out respectively to characterize the tensile properties and dynamic mechanical properties of FDM-printed PLA materials under different FDM process parameters, namely printing angle, layer thickness, fill rate and nozzle temperature. Based on the experimental results explanations are given for the influence of the FDM process parameters on the mechanical properties of the printed materials.

The purpose of this study was to evaluate the antibacterial activity and mechanism of linalool against Pseudomonas aeruginosa. The determination of antibacterial activity was based on the minimum inhibitory concentration (MIC) and the minimum bactericide concentration (MBC). Further, the antibacterial mechanism was explored by a growth curve assay, scanning electron microscopy (SEM), cell membrane permeability, membrane potential and respiratory chain dehydrogenase determination. The MIC and the MBC of linalool were 431 μg/mL and 862 μg/mL, respectively. The growth curve assay showed that the growth of P. aeruginosa was inhibited. The results of SEM revealed that linalool disrupted the normal morphology of the cell. The release of nucleic acids as well as the decrease in the membrane potential proved that the membrane integrity of P. aeruginosa was destroyed. Moreover, the respiratory chain was damaged by respiratory chain dehydrogenase determination as the absorbance at 490 nm decreased. This research suggested that it was possible for linalool to become a preservative of food by destroying the cell membrane, resulting in cell death.

Utilizing the domain knowledge to improve the brain magnetic resonance image segmentation has gained much interest. The membership prior and pairwise constraints of some labeled pixels given by experts are valuable for assisting the image segmentation. This study proposes an algorithm called constrained partial-supervised fuzzy C-means by simultaneously adding the regularization terms of prior membership and pairwise constrains of labeled instances to the cost function of fuzzy C-means algorithm, and enhancing the influence of labeled instances in the clustering process, to aid the separation of unlabeled data. Experimental results on brain magnetic resonance image segmentation demonstrate that the proposed algorithm is effective for segmenting magnetic resonance image with a small amount of labeled pixels given by user.

The homeodomain transcriptional factor NKX2.1 is critical for normal morphogenesis of the lung, thyroid, and the brain. In the lung, NKX2. 1 binds to and activates the expression of pulmonary differentiation-specific genes SP-A, SP-B, and SP-C. The Nkx2.1 gene is comprised of three exons separated by two introns. In both thyroid and lung, the predominant Nkx2.1 transcript includes exons II and III and is translated into a 371 amino acid protein. A minor transcript also exists which includes all three exons. This transcript encodes a 401 amino acid isoform of NKX2.1. The 30 amino acid extension is highly conserved amongst various mammalian species. In the current study, we demonstrate that the two NKX2.1 isoforms are functionally distinct and their corresponding transcripts are expressed differentially during mouse embryonic lung development. The results demonstrate that the longer isoform of NKX2.1 exhibits reduced activity in transactivating an SP-C target promoter when compared to the truncated major NKX2.1 protein. Site directed mutagenesis of the 30 amino acid peptide extension suggests that this fragment alters the activity of 5E likely by steric interference.

Liver-specific and non-liver-specific methionine adenosyltransferase (MAT) are products of two genes (MAT1A and MAT2A, respectively) that catalyze the formation of S-adenosylmethionine (SAM), the principal methyl donor. We previously showed that MAT2A expression was associated with more rapid cell growth. Here we examined changes in hepatic MAT gene expression and related consequences after two-thirds partial hepatectomy (PH) in rats. The mRNA levels of both MAT forms increased from 3 to 6 h, but the MAT1A level then fell below baseline from 12 to 24 h, whereas the MAT2A level remained elevated up to 4 days after PH. The increase in the MAT2A mRNA level was due to increased gene transcription and mRNA stabilization. The change in the MAT1A mRNA level was posttranscriptional and did not require de novo protein synthesis. Changes in MAT activity were consistent with an increased amount of MAT isozymes. SAM levels, the ratio of SAM to S-adenosylhomocysteine (SAH), and DNA methylation fell from 6 to 24 h, whereas SAH levels increased slightly at 12 and 24 h after PH. Both increased SAM utilization and MAT2A gene expression likely contributed to the fall in SAM.

Eisai hyperbilirubinemic rats (EHBR) are mutant Sprague-Dawley rats that exhibit impaired biliary organic anion and reduced glutathione (GSH) secretion. In addition, liver GSH levels are twice that of age- matched controls. The mechanisms for the defect in biliary GSH secretion and the increase in cell GSH are not fully understood. We previously showed that canalicular membrane-enriched vesicles isolated from EHBR livers exhibited normal GSH transport. In the present study, we examined the steady-state rat canalicular reduced glutathione transporter (RcGshT) messenger RNA (mRNA) and protein levels, as well as the mechanisms for the increase in cell GSH. Both Northern and Western blot analyses of EHBR livers showed nearly identical RcGshT mRNA and polypeptide levels, respectively, as compared with controls. Treatment with phenobarbital, which increased steady-state RcGshT mRNA by five- to sixfold, RcGshT polypeptide, and biliary GSH secretion by onefold in controls, had a smaller effect on steady-state RcGshT-mRNA level in EHBR (by 1.5-fold) and did not increase RcGshT polypeptide or biliary GSH secretion. In examining possible mechanisms for increased liver GSH, both cysteine level and gamma-glutamylcysteine synthetase (GCS) activity were significantly higher than controls, while the activity of GSH synthetase was unchanged. Northern and Western blot analyses also showed increased steady-state GCS heavy subunit (GCS-HS) mRNA and polypeptide levels, respectively. In addition to liver, GSH levels in kidney, duodenal, jejunal, and ileal mucosa of EHBR were 200% to 300% of age-matched control rats. GCS activity was also increased in kidney cytosol of EHBR. Thus, the defect in biliary GSH secretion in EHBR most likely is either at the posttranslational level of RcGshT or in the inhibition exerted by retained endogenous organic anions. In addition, there is a widespread up-regulation of GSH synthesis capacity in the tissues of EHBR. (Hepatology 1996 Jul;24(1):253-8)

Methionine adenosyltransferase (MAT) is a critical cellular enzyme which catalyzes the formation of S-adenosylmethionine, the principal methyl donor. In mammals, two different genes, MAT1A and MAT2A, encode for liver-specific and non-liver-specific MAT, respectively. We have cloned and characterized a 1.4-kb 5'-flanking region of the human MAT2A (GenBank Accession No. AF039088). Two major transcriptional start sites were identified by primer extension and S1 nuclease protection analysis; one was within 10 nucleotides downstream and the other was located at 158 nucleotides upstream from the consensus TATA box, respectively. The promoter is highly GC rich (75%) in the first 300 base pairs and contains several Sp-1 binding sites, a C/EBP, a HSF2, a STATx, a c-Myb, several v-Myb, and numerous GATA consensus binding sites. The human MAT2A promoter was able to efficiently drive luciferase expression in both Jurkat and 293 cells, but sequential deletion analysis of the promoter revealed that different regions of the promoter are important for cell-specific MAT2A expression.

We have shown previously that plating primary cultures of rat hepatocytes under low density, which stimulates hepatocytes to shift from the G 0 to the G 1 phase of the cell cycle, resulted in increased levels of glutathione (GSH) and cysteine, and increased activity of γ-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in GSH synthesis (Lu et al., Am. J. Physiol. 1992;263:C1181-C1189). In the current work we examined changes in GSH homeostasis after two-thirds partial hepatectomy (PH). Male Sprague-Dawley rats underwent two-thirds PH or sham operation. GSH, oxidized glutathione (GSSG), cysteine, GSH efflux, DNA synthesis, changes in GCS subunit messenger RNA (mRNA), and protein levels were measured 12 and 24 hours after PH. Both liver GSH and cysteine levels were doubled at 12 hours and remained elevated at 24 hours after PH. GSSG levels also increased, but the ratio of GSH to GSSG levels remained unchanged. The increase in GSH and cysteine levels preceded the increase in DNA synthesis. Sinusoidal GSH efflux was unchanged after two-thirds PH, but biliary GSH efflux decreased. However, total GSH efflux was minimally altered after two-thirds PH. The increase in GSH can be largely accounted for by the increase in both cysteine availability and the activity of GCS. The steady-state mRNA and protein levels of the GCS heavy subunit were increased at 12 hours after PH. The mRNA level of the GCS light subunit was unchanged. In summary, early in the course of liver regeneration the steady-state hepatic GSH levels double because of an increase in the biosynthesis of GSH.

gamma-Glutamylcysteine synthetase (GCS) is the rate-limiting enzyme in the biosynthesis of glutathione and is composed of a heavy and a light subunit. Although the heavy subunit is enzymically active alone, the light subunit plays an important regulatory role by making the holoenzyme function more efficiently. In the current study we examined whether conditions which are known to influence gene expression of the heavy subunit also influence that of the light subunit, and the mechanisms involved. Treatment of cultured rat hepatocytes with hormones such as insulin and hydrocortisone, or plating hepatocytes under low cell density increased the steady-state mRNA level of the heavy subunit only. Treatment with diethyl maleate (DEM), buthionine sulphoximine (BSO) and t-butylhydroquinone (TBH) increased the steady state mRNA level and gene transcription rates of both subunits. These treatments share in common their ability to induce oxidative stress and activate nuclear factor kappa B (NF-kappa B). Treatment with protease inhibitors 7-amino-1-chloro-3-tosylamido-2-heptanone (TLCK) or L-1-tosylamido-2-phenylethyl chloromethyl ketone (TPCK) had no influence on the basal NF-kappa B and GCS subunit mRNA levels, but blocked the activation of NF-kappa B by DEM, BSO and TBH, and the increase in GCS heavy subunit mRNA level by BSO and TBH. On the other hand, the DEM-, BSO- and TBH-induced increase in GCS light-subunit mRNA level was unaffected by TLCK and TPCK. Thus only the heavy subunit is hormonally regulated and growth sensitive, whereas both subunits are regulated by oxidative stress. Signalling through NF-kappa B is involved only in the oxidative-stress-mediated changes in the heavy subunit gene expression.

S-adenosylmethionine synthetase (SAMS) catalyzes the formation of S-adenosylmethionine (SAM) and is essential to normal cell function. There are two forms of SAMS, liver-specific and nonliver-specific (often referred to as "kidney"), which are products of two different genes. SAMS isoenzymes differ greatly in kinetic parameters and sensitivity to inhibition by methionine analogs. The current work studied changes in SAMS and their significance in liver cancer. Northern blot analysis showed that while normal liver expresses only liver-specific SAMS, both HepG2 and HuH-7 cells express only nonliver-specific SAMS. Absence of liver-specific SAMS messenger RNA (mRNA) was not because of gene deletion or rearrangement but complete lack of gene transcription. Reverse-transcription polymerase chain reaction (RT-PCR) with liver- and kidney-specific SAMS primers showed that liver-specific SAMS mRNA was absent with only kidney SAMS mRNA present in HepG2, HuH-7, Hep3B, and HuH-1 cells, and four consecutive hepatocellular carcinoma (HCC) specimens. Normal liver tissues from the same patients express both forms of SAMS mRNA. As a result of the change in SAMS expression, SAMS activity was higher in HepG2 and HuH-7 cells at physiologically relevant methionine concentrations but lower at high (mmol/L) methionine concentrations than rat hepatocytes. Treatment with ethionine and seleno-D,L-ethionine, two inhibitors known to have I50 values 50 to 60 times lower against SAMS purified from Novikoff hepatoma cells as compared with SAMS purified from normal rat liver, resulted in increased cell lysis in HepG2 and HuH-7 cells but not cultured rat hepatocytes. These agents did not affect cellular adenosine triphosphate (ATP) levels but inhibited SAMS activity in HepG2 and HuH-7 cells when added to their protein extracts. In summary, expression of SAMS is altered in human liver cancer. This occurrence may provide a potentially exploitable target for cancer chemotherapy.

Methionine adenosyltransferase (MAT) catalyzes the formation of S-adenosylmethionine (SAM), the principal methyl donor, and is essential to normal cell function. The two forms of MAT, liver-specific and nonliver specific, are products of two different genes, MAT1A and MAT2A, respectively. Mature liver expresses mainly MAT1A. We reported a switch from MAT1A to MAT2A gene expression in human liver cancer cells (Hepatology 24:1090-1097, 1996). We also showed in a cell line model which expresses different types of MAT that expression of MAT2A was associated with more rapid cell growth and DNA synthesis (Gastroenterology 112:A1235, 1997). In the current work we examined the possible mechanisms involved. METHODS: A HUH-7 cell line model which expresses different types of MAT was established by transfection and antisense strategies. Different types of MAT differ greatly in their kinetic properties and in the feedback inhibition exerted by SAM, which strongly inhibits only the product of MAT2A. To see if differences in MAT expression resulted in changes in the steady state levels of SAM, S-adenosylhomocysteine (SAIl) and DNA methylation, these were measured using high performance liquid chromatography. These same parameters were also measured along with cell growth and DNA synthesis in untransfected HUH-7 ceils supplemented with SAM (lmM) for four days. RESULTS: Untransfected HUH-7 cells which express only MAT2A had the lowest SAM level (0.54 ± 0.003 nmol/mg protein) and SAM to SAH ratio (1.36 ± 0.13). Both SAM level and SAM to SAH ratio increased by 50-75% after MAT1A-transfection and by an additional 60-80% after MAT2A-antisense treatment. SAH levels were not significantly influenced by MAT expression. DNA methylation changed in parallel to changes in SAM level and SAM to SAH ratio. Supplementing nntransfected HUH-7 ceils with SAM in the culture medium increased SAM level, SAM to SAH ratio and DNA methylation and decreased cell growth and DNA synthesis. CONCLUSIONS: The steady state SAM level, SAM to SAH ratio and DNA methylation are influenced by the type of MAT expressed. The differences in SAM to SAH ratio and DNA methylation are most likely responsible for the differences in the rate of cell growth observed.