[The expression of neuraminidase-1 in Ewing sarcoma and its impact on sarcoma cell proliferation and migration]

Objective: To investigate the expression of neuraminidase-1 (NEU1) in Ewing sarcoma (ES) tissue and its effect on the proliferation and migration of ES cells. Methods: To obtain datasets of ES from the National Center for Biotechnology Information's High-Throughput Gene Expression Omnibus (GEO) for the analysis of NEU1 expression in ES; to acquire ES patient dataset from the International Cancer Genome Consortium (ICGC) database and apply Kaplan-Meier survival analysis to investigate the relationship between NEU1 and the prognosis of ES patients; adopting both univariate and multivariate Cox regression analysis to determine whether NEU1 is a prognostic factor for ES; adopting the Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation to analyze the potential mechanism of NEU1 in regulating the malignant biological behavior of ES; adopting the real-time fluorescence quantitative polynucleotide chain reaction (RT-qPCR) to verify the expression of NEU1 in the human bone marrow mesenchymal stem cells (hBMSC) and the ES cell line RD-ES; adopting the transfection technology to knock down the expression of NEU1 in ES cell lines and divide them into two groups: shRNA-NEU1 and shRNA-NC to explore the effects of altered NEU1 expression on ES malignant behavior; adopting the cell counting kit (CCK-8) and cell clone formation experiment to detect the proliferation ability of two groups of cells; adopting the scratch healing experiment to test the cell migration ability of the two groups. Results: We retrieved and analyzed data from the GEO database, including GSE17674 (44 ES tissues and 18 normal tissues) and GSE17679 (87 ES tissues and 18 normal tissues), and found that NEU1 expression was significantly higher in ES tissues compared to normal control tissues (P<0.001). The complete gene expression and clinical information of 56 ES patients obtained from the ICGC database revealed that the ES patients with high NEU1 expression (n=28) had a significantly lower overall survival rates at different time points compared to those with low NEU1 expression (n=28) (HR=2.830, 95%CI:1.324-6.051, P=0.005). Univariate analysis indicated that NEU1 could impact ES patient prognosis (HR=1.049, 95%CI: 1.008-1.092, P=0.019), and multivariate analysis further suggested that NEU1 could serve as a risk factor for ES prognosis (HR=1.087, 95%CI: 1.028-1.148, P=0.003). KEGG results show that MAPK signaling pathway and cell adhesion molecule signaling pathway were potential mechanisms regulating the malignant process of ES. The RT-qPCR results showed that the expression level of NEU1 in the RD-ES cell line is significantly higher than that in the control cell hBMSC (2 184.23±527.32 vs 1.00±0.08, P<0.001). The CCK-8 experiment results show that the proliferation of RD-ES cells in the NEU1 knockdown group was lower than that in the control group at 24, 48, and 72 hours (0.494±0.126 vs 0.696±0.118, 0.657±0.096 vs 1.142±0.182, 1.053±0.064 vs 1.980±0.146, all P<0.001). The results of single cell clone formation experiment show that the number of colony formation in the low expression NEU1 group was significantly lower than that in the control group (184.2±123.9 vs 362.8±78.0, P=0.021). The cell scratch healing experiment finds that the average scratch distance of the NEU1 knockdown group was significantly lower than that of the control group (19.6%±5.7% vs 56.0%±7.6%, P<0.001). Conclusion: NEU1 may be a prognostic factor in ES, and its abnormal expression in ES can affect the proliferation and migration ability of the ES cells, leading to poor prognosis in ES patients.

[Construction of Tianjin occupational disease prevention and control ability assessment system based on Delphi method]

Objective: To establish a systematic, scientific, reasonable, feasible and reliable evaluation system for occupational disease prevention and control capability, in order to provide reference for occupational disease prevention and control work in Tianjin City. Methods: In August 2022, literature review was conducted to propose indicators for the evaluation system. Two rounds of anonymous consultation with occupational health experts were conducted using the Delphi method to form expert opinions. According to the boundary value method and expert opinions, eliminate, screen, and modify the evaluation system indicators to ultimately determine the system indicators. Use Cronbach's alpha to test the reliability of the system indicators and form a Tianjin occupational disease prevention and control capability evaluation system. Results: It showed that the effective response rates of the two rounds of consultation conducted by experts in this study were 92.3% and 100.0%, respectively. The expert authority coefficients were 0.84 and 0.82, respectively. The Kendall coordination coefficient was tested for differences, and the differences were statistically significant (P<0.05). The Tianjin occupational disease prevention and control capability evaluation system includes 7 primary indicators, 17 secondary indicators, and 54 tertiary indicators. The Cronbach's alpha of the primary, second, third level indicators and all indicators were 0.91, 0.98, 0.98, 0.98 (>0.7) . Conclusion: The preliminary evaluation system for occupational disease prevention and control capacity in Tianjin City has been established, providing a reference basis for the investigation of occupational disease prevention and control capacity in Tianjin City.

Accretion around black holes: The geometry and spectra

Observations of black hole X-ray binaries and active galactic nuclei indicate that the accretion flows around black holes are composed of hot and cold gas, which have been theoretically described in terms of either a hot geometrically thick corona lying above and below a cold geometrically thin disk or an inner advection dominated accretion flow connected to an outer thin disk. This article reviews the accretion flows around black holes, with an emphasis on the physics that determines the configuration of hot and cold accreting gas, and how the configuration varies with the accretion rate and thereby produces various luminosity and spectra.

MiR-124 promotes ischemia-reperfusion induced cardiomyocyte apoptosis by targeting sphingosine kinase 1

OBJECTIVE

Ischemia-reperfusion (IR) injury of cardiomyocyte contributes to the cardiac dysfunction following myocardial infarction (MI). MiRNAs have been found to play a vital role in the pathogenesis of myocardial IR injury. In this study, the role of miR-124 in the myocardial IR injury was examined.

MATERIALS AND METHODS

Myocardial ischemia rats' model was established to examine the expression level of miR-124. The primary rat cardiomyocytes were isolated to determine in vitro oxygen-glucose deprivation and reoxygenation model. The expression of miR-124 was analyzed by quantitative Real Time-PCR (qRT-PCR). The cell viability was assessed by Cell Counting Kit-8 (CCK-8) and LDH release assay. Cell apoptosis was evaluated by flow cytometry. The expression of cleaved caspase-3, Bcl-2, and Bax was assessed by Western blot. The expression of miR-124 was manipulated by transfection with miR-124 mimics and inhibitors. The Luciferase activity assay was performed to verify whether SphK1 was a direct target of miR-124. The mRNA and protein expression of SphK1 was assessed by qRT-PCR and Western blot. The ectopic expression of SphK1 was achieved by transfecting with overexpressing plasmid.

RESULTS

Our results showed that miR-124 expression was elevated in the infarct zone. The expression level of miR-124 following OGD/R was also significantly increased. Our results showed that miR-124 mimics could enhance OGD/R-induced miR-124 increase while miR-124 inhibitors performed the opposite effect. Our findings also revealed that miR-124 mimics could augment OGD/R-induced cell death and apoptosis, while miR-124 inhibitors expressed the opposite effect. SphK1 was proposed to be a direct target of miR-124. SphK1 overexpression could abrogate the augmenting activities of miR-124 on OGD/R-induced cell injury.

CONCLUSIONS

In the pathogenesis of MI, miR-124 promotes myocardial IR-induced cell death and apoptosis in cardiomyocyte by targeting SphK1.

A novel bacteriocin BM1029: physicochemical characterization, antibacterial modes and application

AIM

Bacteriocins with antimicrobial activity are considered as potential natural bio-preservatives to control the growth of food spoilage bacteria. The aim of this work was to characterize a novel bacteriocin BM1029 discovered from Lactobacillus crustorum MN047 and evaluate its antibacterial mechanism.

METHODS AND RESULTS

Bacteriocin BM1029 was purified by cation-exchange chromatography and reversed-phase chromatography. Antibacterial activity assay showed that BM1029 is antagonistic against both Gram-positive and Gram-negative bacteria. Furthermore, it was found that BM1029 showed low haemolysis with high stability to the pretreatment with different temperatures, pH and surfactants. Moreover electron microscopy and flow cytometry suggested that BM1029 inhibit indicator strains by damaging the cell envelope integrity. Cell cycle assay suggested that BM1029 arrested cell cycle in R-phase.

CONCLUSION

The novel bacteriocin BM1029 showed high bactericidal activity against Escherichia coli and Staphylococcus aureus through a cell envelope-associated mechanism.

SIGNIFICANCE AND IMPACT OF THE STUDY

Application of BM1029 inhibited the growth of indicator strains on beef meat storage at 4°C suggesting that this bacteriocin is promising to be used as a novel preservative in food processing and preservation.

[The analysis of clinical characteristics of 34 novel coronavirus pneumonia cases in Ningxia Hui autonomous region]

Objective: To analyze the clinical characteristics of 34 COVID-19 cases and to provide the basis for the prevention and control of the epidemic disease. Methods: Thirty-four COVID-19 patients diagnosed with RT-PCR in the isolation ward of the Fourth People's Hospital of Ningxia Hui autonomous region (infectious diseases hospital) from the January 22 to February 4, 2020 were selected as the research subjects. The clinical data were collected. Excel was used to describe the relationship between clinical classification and age distribution, contact history and date of onset. SPSS 25.0 statistical software was used for analysis. The general information, clinical symptoms, blood test, virus nucleic acid test results, epidemiology, CT imaging, treatment and prognosis were analyzed. Results: There were 5 mild cases (5/34), 24 ordinary cases (24/34), 5 severe cases (5/34). The elderly was more common in severe patients. The main clinical symptoms were fever (27/34)and dry cough(26/34). The peripheral blood showed normal or decreased leukocyte count (33/34), decreased lymphocyte count (12/34). The increase of C-reactive protein (CRP) and D-dimer was related to the severity of the disease. Some patients had mild liver and kidney damage. Six patients were diagnosed through 3 or more times of nucleic acid tests. Sixteen cases had Wuhan related history,13 cases were close contacts, 5 cases had no confirmed route. The clustered infections were found in 6 families. In typical cases, CT showed single or multiple patchy ground glass shadow with thickening of interlobular septum. In severe cases, diffuse lesions of both lungs were found, with ground glass shadow, consolidation shadow and strip shadow coexisting. Thirty-four patients were treated with interferon-α and Lopinavir/Ritonavir with good prognosis. Conclusions: The clinical characteristics of COVID-19 were similar to that of general viral pneumonia but with strong infectivity. Close contact and family aggregation caused disease outbreaks. COVID-19 could not be excluded if two nucleic acid tests were negative and high-resolution CT was helpful for differential diagnosis. Early detection, early isolation, early diagnosis and early treatment are important for good prognosis. The effectiveness of antiviral drugs needs to be further verified.

Evaluation of two intensive care models in relation to successful extubation after cardiac surgery

OBJECTIVE

To compare outcomes between intensivist-directed and cardiac surgeon-directed care delivery models.

DESIGN

This retrospective, historical-control study was performed in a cohort of adult cardiac surgical patients at Zhongshan Hospital (Fudan University, China). During the first phase (March to August 2015), cardiac surgeons were in charge of postoperative care while intensivists were in charge during the second phase (September 2015-June 2016). Both phases were compared regarding successful extubation rate, intensive care unit (ICU) length of stay (LOS), and in-hospital mortality.

SETTING

Tertiary Zhongshan Hospital (Fudan University, China).

PATIENTS

Consecutive adult patients admitted to the cardiac surgical ICU (CSICU) after heart surgery.

INTERVENTIONS

Phase I patients treated by cardiac surgeons, and phase II patients treated by intensivists.

MAIN VARIABLES OF INTEREST

Successful extubation, ICU LOS and in-hospital mortality.

RESULTS

A total of 1792 (phase I) and 3007 patients (phase II) were enrolled. Most variables did not differ significantly between the two phases. However, patients in phase II had a higher successful extubation rate (99.17% vs. 98.55%; p=0.043) and a shorter median duration of mechanical ventilation (MV) (18 vs. 19h; p<0.001). In relation to patients with MV duration >48h, those in phase II had a comparatively higher successful extubation rate (p=0.033), shorter ICU LOS (p=0.038) and a significant decrease in in-hospital mortality (p=0.039).

CONCLUSIONS

The intensivist-directed care model showed improved rates of successful extubation and shorter MV durations after cardiac surgery.

[Effects of p-Phenylene diamine on liver and kidney functions of occupational exposed workers]

Objective: To study the effect of p-phenylenediamine (PPD) on liver and kidney function in occupational exposed workers. Methods: Workers in a hair dye production enterprise which used p-phenylenediamine as a raw material for production were selected as the main research population. Then we conducted a questionnaire survey on the basic conditions of workers and conducted occupational health checkups on general health status, liver and kidney function. Occupational health examination assessment results were tested in Taizhou Cancer Hospital. All data was built using EpiData 3.1 software, and statistical analysis was performed using software SPSS 20.0. Results: The liver function indicators including direct bilirubin, prealbumin, total protein, and white protein, globulin, aspartate aminotransferase, glutamyl transpeptidase, and total bilirubin in the workers exposed to high concentration of PPD were at high normal values, and these indicators were significantly different from low PPD concentration group (P<0.05) . The serum creatinine and serum uric acid in the renal function index were significantly higher in workers exposed to PPD than in workers exposed to low concentrations and in the control group (P<0.05) . Conclusion: Occupational exposed to PPD may have a hazard to the workers' liver and kidney function. Long-term occupational exposure to PPD may lead to increased cumulative exposure of workers, which may cause potential chronic liver and kidney damage in occupationally exposed populations.

[Evaluation uncertainty of power frequency electric field for a Power Project in inner Mongolia]

Objective: With the measurement and uncertainty analysis of the power frequency electric field of the main transformer in the power station, the source of uncertainty, its quantitative calculation, the synthetic assessment method and the reporting method of the measurement results are described to ensure the reliability of the power frequency electric field measurement data. Methods: Referring to the "Measurement of power frequency electric field in the workplace" (GBZ/T189.3-2007) , "Labour environment monitoring technological specification of electric power industry Partt7: Monitoring of power frequency electromagnetic fields" (DL/T 799.7-2010) and "Evaluation and Expression of Uncertainty in Measurement" (JJF 1059.1-2012) , the uncertainty of power frequency electric field measurement data of the main transformer of a power plant was analyzed and the extended uncertainty was obtained. Results: The main source of the uncertainty of power frequency electric field measurement was the measurement of repetitive operation, and the expanded uncertainty of power frequency electric field was 0.09 kV/m. Conclusion: When reporting the results of power frequency electric field measurement, the measurement uncertainty should be used simultaneously to quantify the quality of the measurement results. This method has strong practicability and operability, which can meet the requirements of uncertainty evaluation of power frequency electric field measurement results.

[Determination of p-Phenylene diamine in workplace air by elution solution-liquid chromatography]

Objective: To establish a elution solution-liquid chromatography method for determination of p-Phenylene diamine (PPD) in workplace air. Methods: p-Phenylene diamine (PPD) in the air of workplace was collected with glass fiber filters coated with dilute sulfuric acid and extracted with an aqueous EDTA solution. The target toxicant was separated with the C(18) column and analyzed with UV detector, identified by retention time, and quantified by peak area. Results: The linear range of PPD in the air of workplace was 2.00~10.00 μg/ml, with a correlation coefficient of 0.999 96. The limit of detection was 0.07 μg/ml. The lower limit of quantification was 0.23 μg/ml. The minimum detectable concentration was 0.003 1 mg/m(3) under 45.0 L sampling volume and 2.0 ml extraction solution volume. The within-run precision of different PPD concentrations was 0.15%~2.3% and the between-run precisions was 1.4%~2.6%; The extraction efficiencies was 91.4%~95.4%; The average collection efficiencies was 96.6%; The samples could be stored for 7 days isolation of air. The potential coexistence of m-Phenylene diamine and o-Phenylene diamine with p-Phenylene diamine (PPD) in the air did not interfere with the results of determination. Conclusion: This method has high sensitivity, precision, accuracy and lower limit of detection and it is applicable for determination of p-Phenylene diamine (PPD) in workplace air.

Atomic force and confocal microscopy for the study of cortical cells cultured on silicon wafers

The primary cortical cells were selected as a model to study the adherence and neural network development on chemically roughened silicon substrates without any coatings using confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). The silicon substrates have a nano-range roughness (RMS) achieved by chemical etching using hydrofluoric (HF) acid. After 7 days of culturing, the neurons were observed to connect together and form dense neural networks. Furthermore, AFM results revealed that some porous structures at a few micrometer range existed between the neuron cells and the silicon substrates. It is suggested that the porous structures are made of extracellular matrix (ECM) components and play an important role in the neuronal adhesion and neurite outgrowth on the inert silicon wafers.

Regulation of charged groups and laminin patterns for selective neuronal adhesion

Primary neuronal cultures on substrates patterned with extracellular matrix proteins such as laminin have yielded much information regarding the physiological characteristics of neuronal cells in vitro. Surface charge also influences neuronal adherence, and a positive charge can have stimulatory effects. The attraction between laminin patterns and polycation films are of interest in the study of neuronal adhesion. We cultured primary hippocampal neurons on poly(ethylenimine) (PEI) films with laminin grids and evaluated their viability and morphology by means of fluorescent microscopy after 5-7 days. The results showed that the neurons did not form networks on the laminin grids. It is inferred that the PEI films were more favourable for neuronal adhesion than the laminin grid.

AFM study of hippocampal cells cultured on silicon wafers with nano-scale surface topograph

The rat hippocampal cells were selected as model to study the interaction between the neural cells and silicon substrates using atomic force microscopy (AFM). The hippocampal cells show tight adherence on silicon wafers with nano-scale surface topograph. The lateral friction force investigated by AFM shows significant increase on the boundary around the cellular body. It is considered to relate to the cytoskeleton and cellular secretions. After ultrasonic wash in ethanol and acetone step by step, the surface of silicon wafers was observed by AFM sequentially. We have found that the culture leftovers form tight porous networks and a monolayer on the silicon wafers. It is concluded that the leftovers overspreading on the silicon substrates are the base of cell adherence on such smooth inert surfaces.

Identifying the orientation of DNA fragment in recombinant plasmid by capillary electrophoresis with a non-gel sieving solution

It was demonstrated that a capillary electrophoresis (CE) method with a non-gel sieving solution has been developed to identify the orientation of DNA fragments in recombinant plasmids in molecular biology. The influences of the concentration of sieving polymer HEC, the applied electric field strength and sampling on CE separation were analyzed concerning the optimization of separation. YO-PRO-1 was used as a DNA intercalating reagent to facilitate fluorescence detection. Under the chosen conditions (buffer, 1 x TBE containing 1 microM YO-PRO-1 and 1.2% HEC; applied electric field strength, 200 V/cm; electrokinetic sampling: time, 5 s; voltage, -6 kV), three DNA markers (phi 174/HaeIII, pBR322/HaeIII and lambda DNA/HindIII) were tested for further evaluating the relationship between the DNA size and the mobility. The established CE method conjugated with the enzymatic approach was successfully applied to identifying the DNA orientation of recombinant plasmid in transgene operations of a newly cloned gene from Arabidopsis Thaliana.

Pharmaceutical-induced cell apoptosis characterized by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) with a non-gel-sieving system was employed to characterize actinomycin D-induced cell apoptosis by measuring cellular DNA damage, termed DNA ladder, which proved to be thoroughly different from the DNA damage pattern of cell necrosis. The results by CZE analyses were identical to those obtained by conventional slab gel electrophoresis, demonstrating that CZE would be a reliable and more convenient technique for the identification of cell death with advantages of higher performance, high-speed, minute sample requirement, and advanced automation.

Characterization of phosphorylation of a novel protein kinase in rice cells by capillary electrophoresis

It was demonstrated that a separation of 20 amino acids constituting a protein and three phosphoamino acids that mostly frequently occur in eukaryotes was achieved within 15 min by capillary electrophoresis coupled with lamp-induced fluorescence detection. Fluorescein isothiocyanate was employed as the fluorescence label to facilitate the fluorescence detection of the 23 amino acid species. The fluorescent derivatization conditions and separation parameters including concentration of electrolyte, surfactant in buffer, applied voltage and sample injection were investigated in detail and optimized. The influence of buffer additives such as methanol, acetone and polyvinylpyrrolidone on separation selectivity and sensitivity were discussed. We showed that addition of 2% polyvinylpyrrolidone into the running buffer could dramatically enhance the separation selectivity of amino acids at the expense of a decrease of sensitivity of phosphoamino acids. Under the optimized conditions, the detection limits (S/N=2) ranged from 1.90 x 10(-8) M to 5.66 x 10(-8) M with an average efficiency of 620,000/m. The method was applied to characterization of the phosphorylation of a novel protein kinase RCaMBP (calcium/calmodulin-binding protein kinase) encoded by a cDNA newly isolated and cloned from rice. We verified that RCaMBP belonged to a type of Ser/Thr kinase, providing insight into its function in signal transduction.

Separation of vanadium, niobium and tantalum as ternary mixed-ligand complexes by capillary electrophoresis using chelation with 4-(2-pyridylazo)resorcinol and tartaric acid

Vanadium(V), niobium(V) and tantalum(V) were separated as ternary mixed-ligand complexes by capillary electrophoresis using 4-(2-pyridylazo)resorcinol (PAR) as the color chelating reagent. Four carboxylic acids such as tartaric acid (Tart), oxalic acid, citric acid and acetic acid were investigated as the additional ligand. The first was chosen as the best. Other parameters such as the concentration ratio of Tart to PAR, buffer concentration, injection time and applied voltage were also optimized. Under the optimized conditions, a complete separation of the three metal complexes was accomplished within 10 min. A linear calibration curve in the range of two orders of magnitude was obtained.

Evaporation of Accretion Disks around Black Holes: The Disk-Corona Transition and the Connection to the Advection-dominated Accretion Flow

We apply the disk-corona evaporation model (Meyer & Meyer-Hofmeister) originally derived for dwarf novae to black hole systems. This model describes the transition of a thin cool outer disk to a hot coronal flow. The mass accretion rate determines the location of this transition. For a number of well-studied black hole binaries, we take the mass flow rates derived from a fit of the advection-dominated accretion flow (ADAF) model to the observed spectra (for a review, see Narayan, Mahadevan, & Quataert) and determine where the transition of accretion via a cool disk to a coronal flow/ADAF would be located for these rates. We compare this with the observed location of the inner disk edge, as estimated from the maximum velocity of the Halpha emission line. We find that the transition caused by evaporation agrees with this determination in stellar disks. We also show that the ADAF and the "thin outer disk + corona" are compatible in terms of the physics in the transition region.

Low phagocytic activity of resident peritoneal macrophages in diabetic mice: relevance to the formation of advanced glycation end products

Formation of advanced glycation end products (AGEs) is accelerated in diabetic subjects along with hyperglycemia. Although several lines of evidence indicate that AGEs stimulate macrophages to secrete several cytokines and growth factors, little is known about the effect of AGEs on the primary function of macrophages, such as phagocytosis. On the other hand, impairment of the phagocytic function of monocytes/macrophages is suggested to contribute to the low resistance to infection in diabetic subjects. In the present study, we examined the effect of AGEs on the phagocytic function of macrophages. Using flow cytometric analysis of mouse resident peritoneal macrophages, we showed that AGEs suppress phagocytosis of fluorescent microspheres by cultured macrophages. In addition, experiments using streptozotocin-induced diabetic mice demonstrated a significant decrease in the phagocytic activity of resident peritoneal macrophages 12 weeks after induction of diabetes compared with age-matched control mice. The phagocytic activity of peritoneal macrophages correlated inversely with AGE content in the adjacent peritoneal tissue. Furthermore, reduced phagocytic activity of macrophages was associated with a reduction in intracellular ATP content. Because phagocytosis is an important component of the defense system, suppression of such activity by AGEs may explain, at least in part, the increased susceptibility of diabetic patients to infection.

Effect of intraperitoneal administration of heparin on advanced glycation end-products in CAPD

OBJECTIVE

To evaluate the effect of intraperitoneal (IP) administration of heparin on clearance of advanced glycation end-products (AGEs) and peritoneal dialysis efficiency.

DESIGN

Sequential self-controlled intervention study.

SETTING

University hospital, Department of Nephrology.

PATIENTS AND METHODS

Pyrraline, urea, and creatinine levels in plasma and dialysate, along with AGE-derived fluorescence intensity (excitation, 370 nm; emission, 440 nm) in dialysate were measured 0, 30, and 60 days after IP administration of heparin in 11 patients on continuous ambulatory peritoneal dialysis (CAPD). Pyrraline levels were determined by ELISA.

RESULTS

Heparin induced a significant decrease in plasma pyrraline levels; the values on days 0, 30, and 60 were 162.0+/-89.8 micromol/L, 101.1+/-32.1 micromol/L (p < 0.01), and 94.0+/-19.8 micromol/L (p < 0.001), respectively. Heparin also induced a tendency of increased dialysate pyrraline levels and a significant increase in AGE-derived fluorescence intensity in the dialysate. The values for the latter on days 0, 30, and 60 were 51.0+/-9.3 AU (arbitrary units/ mg of collagen), 73.5+/-16.0 AU (p < 0.001), and 65.6+/-15.5 AU (p < 0.01), respectively. Furthermore, heparin administration resulted in a significant (p < 0.01) increase in the dialysate/plasma ratio of urea (means 0.80, 0.90, and 0.94 on days 0, 30, and 60, respectively).

CONCLUSION

These results suggest that a beneficial effect of IP administration of heparin is in part due to its action on AGE kinetics, supporting a potential preventive strategy for peritoneal membrane distortion in CAPD.

Analysis of the forces which stabilize the active conformation of urokinase-type plasminogen activator

It was recently proposed that hydrophobic interactions control the active conformation of serine proteases in the trypsin family (Hedstrom et al. (1996) Biochemistry 35, 4515-23) rather than a charge interaction with Asp next to the active site Ser, as formerly believed. In the present study, certain site-directed mutants of the serine protease zymogen pro-urokinase (pro-UK) and its two-chain enzymatic derivative urokinase (UK) were characterized. The results provide information on the structure-function of the catalytic domain of pro-UK/UK, which is relevant to this controversy. Mutations at Asp355(c194), which eliminated its charge, induced a 6250-fold reduction in the catalytic activity of UK. By contrast, reducing the hydrophobicity at the neoterminal Ile159(c16) of UK had relatively little effect. However, when both the hydrophobicity and the size of the side chain were reduced by a glycine substitution at this position, a major reduction (9090-fold) in the catalytic efficiency of UK occurred. This effect was related to the smaller side chain increasing the cavity and the flexibility of the N-terminus and thereby interfering with its charge interaction with Asp355(c194). A similar mechanism, rather than a change in hydrophobicity, is believed also to explain the reduction in the stabilization energy of the activation domain observed in a trypsin mutant by Hedstrom et al. (1996). Although hydrophobic interaction facilitated the charge interaction with Asp355(c194), the latter was the primary force which stabilized the active conformation of UK. The charge interaction with Asp355(c194) was also found to be the principal determinant of the intrinsic catalytic activity of single-chain pro-UK. Additionally, the findings confirmed that the KM of pro-UK for its natural substrate was significantly lower than that of UK. Since this same phenomenon was also seen with each of the mutants, the substrate binding pocket of these single-chain zymogens was better formed than that of their two-chain, enzymatic derivatives.

Identification of a flexible loop region (297-313) of urokinase-type plasminogen activator, which helps determine its catalytic activity

Pro-urokinase has a much higher intrinsic catalytic activity than other zymogens of the serine protease family. Lys300(c143) in an apparent "flexible loop" region (297-313) was previously shown to be an important determinant of this intrinsic catalytic activity. This was related to the loop allowing the positive charge of Lys300(c143) to transiently interact with Asp355(c194), thereby inducing an active conformation of the protease domain (Liu, J. N., Tang, W., Sun, Z., Kung, W., Pannell, R., Sarmientos, P., and Gurewich, V. (1996) Biochemistry 35, 14070-14076). To further test this hypothesis, the charge at position 300(c143) and the flexibility of the loop were altered using site-directed mutagenesis designed according to a computer model to affect the interaction between Lys300(c143) and Asp355(c194). When the charge at Lys300(c143) but not Lys313(c156) was reduced, a significant reduction in the intrinsic catalytic activity occurred. Similarly, when the flexibility (wobbliness) of the loop was enhanced reducing the size of side chain, the intrinsic catalytic activity was also reduced. By contrast, when the loop was made less flexible, the intrinsic catalytic activity was increased. These findings were consistent with the hypothesis. The effects of these mutations on two-chain activity were less and often discordant with the intrinsic catalytic activity, indicating that they can be modulated independently. This structure-function disparity can be exploited to create a more zymogenic pro-urokinase (lower intrinsic catalytic activity) with a high catalytic activity, as exemplified by two of the mutants. The changes in intrinsic catalytic activity and two-chain activity induced by the mutations were due to changes in kcat rather than Km. Some significant structure-function differences between pro-urokinase and its highly homologous counterpart, tissue plasminogen activator, were also found.

Co-ordinated regulation of the plasma membrane calcium pump and the sarco(endo)plasmic reticular calcium pump gene expression by Ca2+

The plasma membrane calcium pump (PMCA) and sarco(endo)plasmic reticular calcium pump (SERCA) are important components of the Ca2+ homeostasis system responsible for intracellular Ca2+ signaling, yet the factors which govern their expression remain unclear. Recently, we have found that overexpression of PMCA by a gene transfection approach caused a down-regulation of the SERCA pump [Liu B.F., Xu X., Fridman R., Muallem S., Kuo T.H. Consequences of functional expression of the plasma membrane calcium pump isoform 1a. J Biol Chem 1996; 271: 5536-5544]. The results suggest an interdependence between PMCA and SERCA gene expression which has prompted us to investigate further on the mechanisms that regulate the expression of these Ca2+ pump genes in various cultured cell lines. In the present study, we have analyzed the isoforms of the PMCA and SERCA in different cells and presented evidence in favor of a co-induction of the PMCA and SERCA gene expression by second messengers, such as protein kinase C, cAMP, and Ca2+. Ectopic expression of PMCA or SERCA led to downregulation of the endogenous forms of both pumps. Changes in the level of mRNAs were paralleled by corresponding altered pump protein contents. The Ca(2+)-mediated increase of gene expression is accompanied by increased transcription rates as indicated by nuclear run-on assay. The co-ordinated induction of the PMCA and SERCA gene expression by thapsigargin was not blocked by the cytosolic application of the Ca2+ chelator BAPTA. We conclude that genes encoding components of the major Ca2+ transport pathways, including pumps and IP3 receptor channels, are regulatorally linked and this link is provided by the Ca2+ load of the ER store. This study points to the importance of gene expression as an integral component in the regulation of cellular Ca2+ homeostasis.

Inhibitory effects of tenilsetam on the Maillard reaction

It has been hypothesized that advanced Maillard reaction in vivo could explain some of the age- and diabetes-related changes. Furthermore, involvement of the Maillard reaction with Alzheimer's disease has also been suggested, as advanced glycation end products, such as pyrraline and pentosidine, were demonstrated to localize in lesions of the disease. Although aminoguanidine has been studied extensively and established as an inhibitor of the Maillard reaction, other candidates have not been investigated thoroughly. In the present study, we examined the inhibitory effect of tenilsetam [(+/-)-3-(2-thienyl)-2-piperazinone], an antidementia drug, on the Maillard reaction. Tenilsetam inhibited glucose- and fructose-induced polymerization of lysozyme in a concentration-dependent manner in vitro. Reduced enzymatic digestibility of collagen incubated with 100 mM glucose for 4 weeks was also restored to a control level by coincubation with 100 mM tenilsetam. To determine whether tenilsetam inhibits the Maillard reaction in vivo, streptozotocin-induced diabetic rats were treated with tenilsetam (50 mg/kg x day). Elevated levels of advanced glycation end-product-derived fluorescence and pyrraline in renal cortex and aorta of diabetic rats were suppressed by the administration of tenilsetam for 16 weeks. These inhibitory effects of this agent on advanced glycation in diabetic rats suggested its potential therapeutic role in controlling diabetic complications.

Accumulation of pyrraline-modified albumin in phagocytes due to reduced degradation by lysosomal enzymes

Previous studies suggested that the interaction between proteins modified by advanced glycation end products (AGEs) and cells, such as macrophages, may be involved in diabetic angiopathy. Pyrraline is one of the AGEs and known to be elevated in plasma of diabetic rats and humans, and is present in vascular lesions of diabetic and elderly subjects. We examined whether modification of albumin by pyrraline influences its degradation by macrophage-like cell line, P388D1 cells. Degradation of pyrraline-modified albumin by these cells was diminished, causing accumulation of the albumin in these cells. The susceptibility of pyrraline-modified albumin to lysosomal proteolytic enzymes was reduced by approximately 40% in vitro, while lysosomal activity in the cells per se was not affected. This phenomenon was also observed when human monocytes were used instead of P388D1 cells. Our results suggest that accumulation of pyrraline-modified albumin in P388D1 cells is due to the reduced susceptibility of the protein to lysosomal enzymatic degradation. Such alterations in the interaction between AGEs-modified protein and phagocytes may contribute to angiopathy in elderly subjects and patients with diabetes.

The exit from G(0) into the cell cycle requires and is controlled by sarco(endo)plasmic reticulum Ca2+ pump

The intracellular calcium pump sarco(endo)plasmic reticulum Ca2+ (SERCA) is responsible for the formation of the Ca2+ gradient across the endoplasmic reticulum membrane, and this gradient is used to generate the Ca2- signal during agonist-stimulated cell growth. In the present study, the role of SERCA in both cell cycle and growth control was investigated using cultured rat aortic endothelial cells (RAEC). Using a novel DNA transfection approach, cell lines were established that showed varying degree of SERCA activity through the down-regulation of the endogenous SERCA gene (B. F. Liu, X. Xu, R. Fridman, S. Muallem, and T. H. Kuo, J. Biol. Chem. 271, 1--9, 1996). Cell proliferation studies indicated that the lower SERCA expressing cells exhibited a slower growth pattern without altering the doubling time which was similar for both parental and transfected RAEC lines. G1 to S phase transition was prolonged with a smaller proportion of cells entering DNA synthesis as indicated by thymidine incorporation assay. Comparison of transfected cell lines indicated a tight coupling of SERCA activity and the length of the G1 period. Down-regulation of SERCA gene expression was accompanied by increased mRNA levels of p21 (WAF1/CIP1), a universal cell cycle inhibitor. The delay in G1 to S progression also coincided with the up-regulation of p53 mRNA and underphosphorylation of the retinoblastoma protein. This study suggests that Ca2+ metabolism in the agonist mobilizable pool controls the cell cycle through the regulation of genes operating in the critical G1 to S checkpoint.

Consequences of functional expression of the plasma membrane Ca2+ pump isoform 1a

The plasma membrane Ca2+-ATPase pump (PMCA) is an integral component of the Ca2+ signaling system which participates in signal transduction during agonist stimulated cell activation. To better understand the physiological function of the pump, isoform 1a (PMCA1a) was over-expressed in rat aortic endothelial cells using a stable transfection system under the control of a cytomegalovirus promoter. The cell lines selected after transfection with PMCA1a construct, expressed 3-4-fold increased pump protein which was mostly targeted to the plasma membrane as indicated by immunoperoxidase staining. Ca2+ uptake assays in a membrane preparation indicated a 3-4-fold increase in Ca2+ pumping activity in the transfected cells, and the expressed PMCA1a showed typical dependence on Ca2+ and calmodulin for stimulation of activity. Measurement of [Ca2+]i and [Ca2+]out showed that expression of PMCA1a had a profound effect on different aspects of the Ca2+ signal. The peak increase in [Ca2+]i evoked by ATP and/or thapsigargin was lower but the plateau phase was similar in the PMCA1a expressing cells. Accordingly, titration with ionomycin of Ca2+ content of internal stores, measurement of Ca2+ uptake into the thapsigargin- and oxalate-sensitive pool (endoplasmic reticulum) of isolated microsomes, Ca2+ uptake into streptolysin O-permeabilized cells, and analysis of SERCA mRNA and protein, showed that expression and activity of the SERCA pump was down-regulated in cells expressing PMCA1a pump. Expression of PMCA1a also down-regulated expression of the inositol 1,4,5-trisphosphate (IP3)-activated Ca2+ channel and the rate of IP3-mediated Ca2+ release in permeable cells, without affecting the affinity of the channel for IP3. On the other hand the rate of store depletion-dependent Ca2+ and Mn2+ influx (Ca2+ entry) into PMCA1a expressing cells was increased by about 2.6-fold. These changes prevented estimating the rate of pump-mediated Ca2+ efflux from changes in [Ca2+]i. Measurement of [Ca2+]out showed that the rate of Ca2+ efflux in cells expressing PMCA1a was about 1.45-fold higher than Neo controls, despite the 4-fold increase in the amount of functional pump protein. The overall study points to the flexibility, interdependence, and adaptability of the different components of the Ca2+ signaling systems to regulate the expression and activity of each component and maintain a nearly constant Ca2+ signal.

Regulation of the plasma membrane calcium pump gene expression by two signal transduction pathways

The modulation of the plasma membrane calcium pump (PMCA) gene expression is not well understood. We now present evidence that PMCA mRNA is induced by various hormones or agonists via multiple second messenger pathways that include protein kinase C-, cAMP-, and Ca(2+)-dependent mechanisms. Among several types of cultured cells examined, endothelial cells from the rat aorta (RAEC) responded to phorbol ester or angiotensin II with an 8- to 20-fold increase in the PMCA messages, while endothelial cells from the brain resistant vessel (RVEC) exhibited minimal (0- to 2-fold) response to these agonists. On the other hand, under the stimulation of cAMP or thapsigargin (a calcium mobilizing agent), the pattern of response is reversed; only RVEC responded but not RAEC. The results suggest that hormone-induced PMCA gene expression is regulated via two distinct pathways; one involves protein kinase C while the other involves Ca2+ or cAMP. Since the protein kinase A inhibitor (or the calmodulin-dependent kinase inhibitor) was able to block the stimulation elicited by either Ca2+ or cAMP, we suggest that the Ca2+ and cAMP signals share a common passage leading to the induction of PMCA mRNA. The possibility of cross-talk between the distinct second messenger pathways is also discussed.

Pleural effusion coinciding with acute exacerbations in a patient with chronic hepatitis B

A 28-yr-old man had pleural effusions coinciding with two separate episodes of acute exacerbation of chronic type B hepatitis. In both episodes, the pleural effusion was exudative with lymphocyte predominance, and there was no ascites. Hypocomplementemia was evident in the second episode when the complement level was determined, but immune complexes were not detected in the serum. The hepatitis itself was thought to be directly responsible for the pleural effusions because of meticulous exclusion of other causes and the fact that, without specific treatment, the effusions resolved completely as the hepatitis subsided.