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Biomedical subjects

L Ren

Publications and source records attributed to L Ren.

At least 19 recordsLinked to original sources
PubMed2002

Treatment of antibiotics wastewater utilizing successive hydrolysis, denitrification and nitrification.

A process consisting of anaerobic hydrolysis, denitrification, and oxidation/nitrification was proposed for simultaneous removal of carbon and nitrogen from terramycin crystallizing mother solution (TCMS), and its performance was investigated by treating diluted TCMS in a lab-scale continuous flow column system. Direct denitrification-nitrification of diluted TCMS produced a significant residual of nitrate and nitrite, which disappeared 44 days after startup of anaerobic hydrolysis column. The electron donors available to denitrification were increased by 6 times after diluted TCMS was treated in the hydrolysis column under an HRT of 2.5 h or longer. The reaction rates of organics decomposition, nitrification, and denitrification were also significantly increased due to reduction of terramycin and decomposition of complicated molecules to small molecules during anaerobic hydrolysis. The specific denitrification rate and nitrification rate increased from 0.033 d(-1) and 0.01 d(-1) to 0.045 d(-1) and 0.021 d(-1) respectively after diluted TCMS (dilution ratio: 1:4) was hydrolyzed in anaerobic hydrolysis column at a hydraulic retention time (HRT) of 4 h.

Anti-Bacterial Agents↗
PubMed2001

Molecular mechanism of spectral tuning in sensory rhodopsin II.

Sensory rhodopsin II (SRII) is unique among the archaeal rhodopsins in having an absorption maximum near 500 nm, blue shifted roughly 70 nm from the other pigments. In addition, SRII displays vibronic structure in the lambda(max) absorption band, whereas the other pigments display fully broadened band maxima. The molecular origins responsible for both photophysical properties are examined here with reference to the 2.4 A crystal structure of sensory rhodopsin II (NpSRII) from Natronobacterium pharaonis. We use semiempirical molecular orbital theory (MOZYME) to optimize the chromophore within the chromophore binding site, and MNDO-PSDCI molecular orbital theory to calculate the spectroscopic properties. The entire first shell of the chromophore binding site is included in the MNDO-PSDCI SCF calculation, and full single and double configuration interaction is included for the chromophore pi-system. Through a comparison of corresponding calculations on the 1.55 A crystal structure of bacteriorhodopsin (bR), we identify the principal molecular mechanisms, and residues, responsible for the spectral blue shift in NpSRII. We conclude that the major source of the blue shift is associated with the significantly different positions of Arg-72 (Arg-82 in bR) in the two proteins. In NpSRII, this side chain has moved away from the chromophore Schiff base nitrogen and closer to the beta-ionylidene ring. This shift in position transfers this positively charged residue from a region of chromophore destabilization in bR to a region of chromophore stabilization in NpSRII, and is responsible for roughly half of the blue shift. Other important contributors include Asp-201, Thr-204, Tyr-174, Trp-76, and W402, the water molecule hydrogen bonded to the Schiff base proton. The W402 contribution, however, is a secondary effect that can be traced to the transposition of Arg-72. Indeed, secondary interactions among the residues contribute significantly to the properties of the binding site. We attribute the increased vibronic structure in NpSRII to the loss of Arg-72 dynamic inhomogeneity, and an increase in the intensity of the second excited (1)A(g)(-) -like state, which now appears as a separate feature within the lambda(max) band profile. The strongly allowed (1)B(u)(+)-like state and the higher-energy (1)A(g)(-) -like state are highly mixed in NpSRII, and the latter state borrows intensity from the former to achieve an observable oscillator strength.

Amino Acid Substitution↗
PubMed2001

Electro-Viscous Effects on Liquid Flow in Microchannels.

The presence of the electrical double layer near a solid-liquid interface results in the electro-viscous effect on pressure-driven liquid flow through microchannels. The objective of this paper is to examine the magnitude of the additional flow resistance caused by the electrokinetic effect in microchannels. Deionized ultrafiltered water, 10(-4) and 10(-2) M aqueous KCl solutions, 10(-4) M AlCl(3) solution, and 10(-4) M LiCl solution were used as the testing liquids. Carefully designed flow measurements were conducted in three silicon microchannels with a height of 14.1, 28.2, and 40.5 µm, respectively. The measured dP/dx for the pure water, the 10(-4) M KCl solution, and the 10(-4) M LiCl solution was found to be significantly higher than the prediction of the conventional laminar flow theory at the same Reynolds number. Such a high flow resistance and the resulting high apparent viscosity strongly depend on the channel's height, the ionic valence, and the concentration of the liquids. The zeta potentials for the liquid-solid systems were calculated by using the measured streaming potential data. The experimentally determined dP/dx approximately Re relationships were compared with the predictions of a theoretical electro-viscous flow model, and a good agreement was found for pure water, 10(-4) M KCl solution, and 10(-4) MAlCl(3) solution systems. The present electrokinetic flow model cannot interpret the flow characteristics of the LiCl solution. Copyright 2001 Academic Press.

Journal Article↗
PubMed2001

SwellGel: an affinity chromatography technology for high-capacity and high-throughput purification of recombinant-tagged proteins.

The revolution in genomics and proteomics is having a profound impact on drug discovery. Today's protein scientist demands a faster, easier, more reliable way to purify proteins. A high capacity, high-throughput new technology has been developed in Perbio Sciences for affinity protein purification. This technology utilizes selected chromatography media that are dehydrated to form uniform aggregates. The SwellGel aggregates will instantly rehydrate upon addition of the protein sample, allowing purification and direct performance of multiple assays in a variety of formats. SwellGel technology has greater stability and is easier to handle than standard wet chromatography resins. The microplate format of this technology provides high-capacity, high-throughput features, recovering milligram quantities of protein suitable for high-throughput screening or biophysical/structural studies. Data will be presented applying SwellGel technology to recombinant 6x His-tagged protein and glutathione-S-transferase (GST) fusion protein purification.

Binding Sites↗
PubMed2001

Retaining hard-to-reach women in HIV prevention and vaccine trials: Project ACHIEVE.

Project ACHIEVE, which conducts HIV prevention research studies, maintains a women's site in the South Bronx in NewYork City. Owing to a focused retention effort at the South Bronx site, high retention rates were achieved in a vaccine preparedness study for women at high risk of HIV infection. Comparable retention rates have been achieved in HIV vaccine trials with similar cohorts of women at this site. These results suggest that concerns about retaining hard-to-reach populations should not cause these populations to be excluded from HIV vaccine and prevention trials.

AIDS Serodiagnosis↗
PubMed2001

Cytokine-induced iNOS expression in C6 glial cells: transcriptional inhibition by ethanol.

The effect of cytokines, lipopolysaccharide, and ethanol on inducible nitric-oxide synthase (iNOS) expression was studied in C6 glial cells. Maximal induced activity, measured by the accumulation of nitrite in culture medium, occurred following treatment with lipopolysaccharide and interferon-gamma. Each cytokine alone was ineffective, whereas an optimal combination of interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma was near maximal, indicating synergistic interactions. Other combinations caused submaximal activity. Ethanol is known to suppress iNOS expression in C6 cells induced by a phorbol ester plus lipopolysaccharide. The current work shows ethanol also suppresses cytokine-induced iNOS expression and reduces interleukin-1beta and tumor necrosis factor-alpha potency without affecting interferon-gamma potency. Ethanol-mediated reductions in cytokine-induced iNOS mRNA and immunoreactive protein levels suggested an effect on gene transcription. Therefore, C6 cells stably expressing 1846 and 526 base fragments of the rat iNOS gene promoter fused to a luciferase reporter gene were prepared and characterized and used to study the effect of ethanol on iNOS promoter activity. Promoter activity in stable transfected C6 cells was inhibited by ethanol exposure with a similar concentration dependence as observed for inhibition of nitrite production, indicating that iNOS inhibition by ethanol is transcriptional. Furthermore, ethanol inhibition of the 526 base fragment activity, which lacks interferon-gamma enhancement of lipopolysaccharide-induced luciferase activity, confirmed that interferon-gamma-responsive elements do not participate in acute ethanol-induced inhibition of rat iNOS gene transcription.

Blotting, Western↗
PubMed2001

[Set up brain compartment model and simplify CBF-quantification].

In order to simplify the non-invasive quantitative evaluation of cerebral blood flow (CBF), we used computer simulation and adopted the pulse function as the input function of compartment model for calculting the mean retention fraction of 99mTc-ECD in brain from the time activity curves (n = 24). We found that there is a significant correlation between R2 (the retention fraction) from the 2-compartment model and R3 from the 3 compartment model with a correlation coefficient of 0.9836. The CBF by R2 is 29.48 +/- 1.51 ml/min per 100 g, the CBF by R3 is 29.10 +/- 1.48 ml/min per 100 g, and no significant difference between them is seen (P > 0.05, n = 24). These data indicate that the simplified two-compartment model for the mechanism of the uptake of 99mTc-ECD in brain is better. And we found that, compared with the entricular function, the pulse function may be used as a more appropriate input function for the model.

Brain↗
PubMed2001

[Studies on lignocellulolytic enzymes production and biomass degradation of Pleurotus sp2 and Trametes gallica in wheat straw cultures].

Pleurotus sp2 and Trametes gallica were selected in this assay because of their high activities of lignocellulolytic enzymes and the enzyme peaks appeared at the early stage of liquid state fermentation. Solid state fermentation was also investigated for their abilities and behaviors of enzyme-production. The capabilities and characteristics of the two strains in degrading biomass were studied. When Pleurotus sp2 was incubated in wheat straw powder containing the liquid medium of low-nitrogen, no-carbon and high inorganic salt, the activities of MnP and Lac reached the peaks on the tenth day, but the activities of hemicellulases reached the peak on the 40th day. Pleurotus sp2 caused 17.6% of biomass loss. When T. gallica was incubated in wheat straw powder containing the liquid medium of hlig-nitrogen, or low-nitrogen, no-carbon and high inorganic salt, the activities of MnP reached the peaks on the tenth day, the lac and hemicelluloses on the 40th day, and the lignin peroxidases reached the peaks on the 50th day, and it caused more than 64% of biomass loss. Among them the hemicellulose was degraded by 71.96%, and the cellulose 66.21%. T. gallica was very capable of degrading lignin of wheat straw and caused 34.37% loss during 20 days, 46. 71% loss during 30 days and 70.14% loss during 60 days. It was interesting that T. gallica degraded lignin preferentially with respect to cellulose, which was very beneficial to biopulping of paper industry.

Basidiomycota↗
PubMed2001

[Study on active constituents of traditional Chinese medicine reversing multidrug resistance of tumor cells in vitro].

OBJECTIVE: To screen drugs reversing multidrug resistance of tumor cells from active constituents of traditional Chinese medicine and to study the reversal action. METHODS: The kill effects of the drugs on tumor cell lines in vitro were determined with MTT method. The Jin's formula was used to analyse the effect of drug combination. RESULTS: 5 micrograms/ml rhynchophylline, 2 micrograms/ml jatrorrhizine and 1.25 micrograms/ml indirulin could reverse multidrug resistance for vincristine on KBv200 cell line by 16.8, 5.1 and 4 fold respectively. 1.56-12.5 micrograms/ml curcumine combining with vincristine could sensitize antitumor effect both on KB and KBv200 cell lines. CONCLUSION: All rhynchophylline, jatrorrhizine and indirulin could reverse multidrug resistance for vincristine on KBv200 cell line. Curcumine combinating vincristine could sensitize antitumor effect both on kB and kBv200 cell lines.

Antineoplastic Agents, Phytogenic↗
PubMed2001

[Bioremediation of mineral oil and polycyclic aromatic hydrocarbons (PAHs) in soils with two plant species].

With alfalfa (Medicago sativa) and paddy rice as test plants, and with pollutant level, specific bacteria, fungi and organic fertilizer as control factors, the bioremediation of mineral oil and polycyclic aromatic hydrocarbons (PAHs) in soils with two plant species was conducted. The results showed that the degradation rate of mineral oil was promoted by fertilization in alfalfa soil, but not in paddy rice soil. The degradation rate of total PAHs (11 PAH listed in USEPA) was increased by fertilization both in alfalfa and in paddy rice soil, and the promotion effect of fertilizer was better in paddy rice soil than in alfalfa soil. The fertilization rate was positively related to the rhizospheric indigenous fungi and bacteria's CFU in alfalfa soil, but only to the indigenous bacteria's CFU in paddy rice soil. The fungi and bacteria's CFU in both test soils had no positive relation with the amount of specific bacteria and fungi spiked. The degradation rate of 3-ring PAHs was enhanced in both alfalfa and paddy rice soil by fertilization, and the effect was stronger in paddy rice soil than in alfalfa soil. However, fertilization had no positive effect on the degradation of 4-ring PAHs.

Bacteria↗
PubMed2000

High prevalence of HIV infection among young men who have sex with men in New York City.

OBJECTIVE: To determine the prevalence of HIV infection and risk behaviors among young men who have sex with men (MSM) aged 15-22 years in New York City. DESIGN: An anonymous cross-sectional survey. METHODS: The 1998 Young Men's Survey in New York City (YMS-NYC), was a multistage probability survey of 541 MSM aged 15-22 years who attend public venues. After identification of venues and their associated high attendance time periods, random samples of venues and time periods were selected on a monthly basis. At each sampling event, potential participants were approached to determine eligibility. Eligible and willing men were interviewed, counselled and had a blood specimen drawn. RESULTS: Between December 1997 and September 1998, 115 sampling events were conducted. Of 612 men enrolled, 541 reported ever having had sex with a male partner. The HIV seroprevalence among the 541 MSM sampled was 12.1%. The HIV seroprevalence was 18.4% among African-Americans, 16.7% among persons of mixed race, 8.8% among Latino individuals and 3.1% among white men. HIV seroprevalence was 5.0% among 15-18 year olds and 16.4% among 19-22 year olds. A total of 65.5% of MSM were susceptible to hepatitis B virus infection (HBV). Almost half (46.1%) of the men reported unprotected anal sex in the previous 6 months and 16.3% reported ever having had an STD. Multiple regression analyses found that being older, of mixed race, black or ever having had an STD was associated with being HIV antibody positive. CONCLUSION: These data identify a large subgroup of MSM in need of effective HIV and HBV primary and secondary prevention programs.

AIDS Serodiagnosis↗
PubMed2000

Involving women in HIV vaccine efficacy trials: lessons learned from a vaccine preparedness study in New York City.

This paper identifies the recruitment strategies and human immunodeficiency virus (HIV) risk behaviors of at-risk women in an HIV vaccine preparedness study in New York City, assesses how these behaviors changed over time, and draws implications for women's involvement in HIV vaccine efficacy trials. Noninjecting HIV-1 negative women (N = 89) were recruited into an HIV vaccine preparedness study. An observational cohort study design was used. Women were recruited from clinics and community-based organizations (40%), through other study participants (24%), through newspaper advertisements (20%), and through street outreach (16%). Most women who refused (72%) also came from clinics and agencies. Retention after 12 months was 67%; after 18 months, it was 62%. The proportion of women reporting unprotected vaginal sex in the previous 3 months was 85% at baseline and declined to 70% after 12 months (P < .05). There have been no seroconversions detected. Recruitment efforts to include at-risk women in HIV vaccine efficacy trials must be diverse and actively involve community agencies. Successfully retaining these cohorts over time and detecting a high enough HIV seroincidence rate present ongoing challenges that will need to be addressed to ensure women's involvement in future trials in the US.

AIDS Vaccines↗
PubMed2000

Escherichia coli cells defective for the recN gene display constitutive elevation of mutagenesis at 3,N(4)-ethenocytosine via an SOS-induced mechanism.

The Escherichia coli UVM (UV Modulation of mutagenesis) response is a DNA damage-inducible mutagenic pathway detected as significantly increased mutagenesis at 3,N4-ethenocytosine (epsilon C) lesions borne on transfected single-stranded M13 vector DNA. All major classes of DNA-damaging agents can induce UVM, and the phenomenon is independent of previously characterized mutagenic responses in E. coli. To understand this phenomenon further, we set out to identify and characterize mutants in the UVM response. Screening a mutant bank of cells defective for 1-methyl-3-nitro-1-nitrosoguanidine-inducible genes revealed that defects in the recN gene cause a constitutive elevation of mutagenesis at epsilon C residues. In contrast to normal cells that show approximately 6% mutagenesis at epsilon C lesions, but approximately 60% upon UVM induction, recN-defective strains display approximately 50% mutagenesis at epsilon C lesion sites in untreated cells. However, the recN-mediated mutagenesis response was found to require the recA gene and the umuDC genes, and could be suppressed in the presence of a plasmid harbouring the SOS transcriptional repressor LexA. These results imply that recN cells are constitutively active for SOS mutagenesis functions. The observation that epsilonC mutagenesis is enhanced in recN cells confirms previous findings that mutagenesis at epsilonC can also be independently elevated by the SOS pathway.

Bacterial Proteins↗
PubMed2000

The Escherichia coli UVM response is accompanied by an SOS-independent error-prone DNA replication activity demonstrable in vitro.

UVM is an SOS-independent inducible response characterized by elevated mutagenesis at a site-specific 3, N4-ethenocytosine (epsilonC) residue borne on M13 single-stranded DNA transfected into Escherichia coli cells pretreated with DNA-damaging agents. By constructing and using E. coli strain AM124 (polA polB umuDC dinB lexA1[Ind-]), we show here that the UVM response is manifested in cells deficient for SOS induction, as well as for all four of the 'non-replicative' DNA polymerases, namely DNA polymerase I (polA), II (polB), IV (dinB) and V (umuDC). These results confirm that UVM represents a novel, previously unidentified cellular response to DNA-damaging agents. To address the question as to whether the UVM response is accompanied by an error-prone DNA replication activity, we applied a newly developed in vitro replication assay coupled to an in vitro mutation analysis system. In the assay, circular M13 single-stranded DNA bearing a site-specific lesion is converted to circular double-stranded replicative-form DNA in the presence of cell extracts and nucleotide precursors under conditions that closely mimic M13 replication in vivo. The newly synthesized (minus) DNA strand is selectively amplified by ligation-mediated polymerase chain reaction (LM-PCR), followed by a multiplex sequence analysis to determine the frequency and specificity of mutations. Replication of DNA bearing a site-specific epsilonC lesion by cell extracts from uninduced E. coli AM124 cells results in a mutation frequency of about 13%. Mutation frequency is elevated fivefold (to 58%) in cell extracts from UVM-induced AM124 cells, with C --> A mutations predominating over C --> T mutations, a specificity similar to that observed in vivo. These results, together with previously reported data, suggest that the UVM response is mediated through the induction of a transient error-prone DNA replication activity and that a modification of DNA polymerase III or the expression of a previously unidentified DNA polymerase may account for the UVM phenotype.

Bacterial Proteins↗
PubMed2000

Effects of lanthanum and calcium on photoelectron transport activity and the related protein complexes in chloroplast of cucumber leaves.

The effects of lanthanum and calcium ions on electron transport, dichlorephenol indophenol (DCIP) photoreduction, and oxygen evolution activities in chloroplast from cucumber (Cucumis satives L.) were determined. The lanthanum inhibited the whole electron chain-transport activity of chloroplast. DCIP photoreduction and oxygen evolution activities of the photosystem I (PSII) also decrease after treatment with La3+. But the diminished activities of PSII and chloroplast caused by La3+ could be reversed by Ca2+ and even became higher than the control level. The concentration analysis of related protein complexes to photoelectron transport in chloroplast included that La3+ induced the concentration of chlorophyll protein complexes increasing but caused some nonchlorophyll protein complexes to decompose partially. This increasing effect of La3+ on chlorophyll protein complexes results in the improvement of chlorophyll content, which will improve the absorption of photoelectron and energy transport in the process of photosynthesis.

2,6-Dichloroindophenol↗
PubMed2000

[High-dose intravitreal ganciclovir in CMV retinitis].

PURPOSE: To assess the efficacy and tolerability of high-dose (2000microg) intravitreous ganciclovir in the maintenance therapy of CMV retinitis in AIDS patients. MATERIAL: and methods: Prospective open study in a single center. The maintenance therapy of CMV retinitis consisted of a single high-dose (2000microg) intravitreous injection per week. The evaluation criteria were clinical examinations, and photographs when necessary. RESULTS: Over a 44-week period, twenty-four eyes (15 patients) have been included. The relapse rate evaluated by the survival curves method was 5% at 44 weeks. No ocular toxicity was reported after a follow-up of 24 weeks. CONCLUSION: High-dose intravitreous ganciclovir induces a prolonged remission of CMV retinitis and is well tolerated. Therefore, we recommend the use of the 2000microg dosage per intravitreous injection instead of the classical dosage of 400microg.

AIDS-Related Opportunistic Infections↗
PubMed2000

Acceptability of a stage-matched expert system intervention to increase condom use among women at high risk of HIV infection in New York City.

There is an urgent need to develop and implement effective methods for sexual behavior change to curb the spread of HIV. Condoms remain one of the most effective strategies for achieving this, yet consistent condom use is generally low, especially among those at highest risk. This article describes the acceptability of an interactive computer-based expert system designed to increase condom use in women at high risk of HIV infection. The expert system is based on the transtheoretical stages of change model. Using a computer, participants respond to questions about their attitudes and behavior toward using condoms and receive immediate feedback which is matched to their readiness to use condoms. The women were found to be at all stages of change for condom use, although a large proportion of the women (42%) were at early stages of behavior change because they were considering but not using condoms every time during sex with men. The expert system was found to be acceptable to this high-risk group of women. They almost unanimously agreed that they found the feedback useful, would return to use the system again, and would recommend it to a friend. These findings indicate that traditional intervention strategies which assume individuals are ready to use condoms consistently would be appropriate for only about one third of these women, underscoring the importance and potential utility of stage-matched interventions.

Adolescent↗