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Biomedical subjects

L Ren

Publications and source records attributed to L Ren.

At least 37 records · Page 2Linked to original sources
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↗
PubMed2000

[The study of immune effect of nine kinds of recombinant hepatitis B vaccines made in China and foreign countries].

OBJECTIVE: To study the immune effect of nine kinds of recombinant hepatitis B (FIB) vaccines. METHODS: Immunizing 715 primary school children with four genetically engineered FIB vaccines of 12 batches that were yeast HB vaccine (YDV), Chinese hamster ovary cell HB vaccine (CHO), vaccinia derived vaccine and Hansenula Polymorpha vaccine produced by USA MSD Co, USA Amgen Co, Japan, France, Argentina and Beijing, Changchun, Shenzhen of China. The anti-HBs was tested by RIA (Abbott reagent). RESULTS: Four kinds of genetically engineered HB vaccines were safe and effective. The peak of the antibody after immunization with Chinese vaccines appeared at the 7th month of the first dose. The geometric mean titre (GMT) of the anti-HBs was higher (393.60 mIU/ml) after immunized by vaccinia derived vaccine, its stability was better than the batches of CHO. The antibody titer descended in a narrow range after immunization of YDV. The vaccine containing 10 microg/dose was superior to 5 microg/dose in antibody persistence. Hansenuly polymorpha vaccine was the first time to study in China, it showed a good immune effect. CONCLUSIONS: The total immune effect of the recombinant FIB vaccines made no distinction among the products of China and USA, Japan, France and Argentina.

Antibody Formation↗
PubMed2000

[A clinical study on PA-MSHA vaccine used for adjuvant therapy of lymphoma and lung cancer].

The objective of this study was to evaluate the effectiveness and safety of pseudomonas aeruginosa MSHA vaccine (PA-MSHA vaccine) used as an immune modulator. The study was carried out after the design of a non-blind, randomized controlled trial. The malignant lymphoma patients were divided into experiment group (45 cases) and control group (43 cases). Likewise were distributed the lung cancer patients: 44 cases in experiment group and 45 cases in control group. The two experiment groups received chemotherapy + PA-MSHA vaccine. The two control groups were given chemotherapy alone. The results showed that the clinical efficacy rate was 95.56% for the exp. group and 69.77% (P < 0.01) for the control group of the malignant lymphoma cases; the clinical efficacy rate was 59.09% for the exp. group and 42.22% (P < 0.01) for the control group of the lung cancer cases. The infection rate was 17.78% for the exp. group and 37.21% (P < 0.05) for the control group of the malignant lymphoma cases; the infection rate was 15.91% for the exp. group and 40.00% (P < 0.05) for the control group of the lung cancer cases. The comprehensive immune effectiveness rates for the exp. group and control group of the malignant lymphoma cases were 77.78% and 23.26% (P < 0.01) respectively. The comprehensive immune effectiveness rates for the exp. group and control group of the lung cancer cases were 84.09% and 35.56% (P < 0.01) respectively. Adverse reactions were found in 5 cases, of which, one was given medical care while the others automatically recovered. These results indicate that PA-MSHA vaccine, as a new kind of immune modulator, can improve the effectiveness of treatment for tumor with low adverse reaction rate.

Adjuvants, Immunologic↗
PubMed2000

[Preliminary report on introducing exogenous DNA into Panax quinquefolium].

Worked aimed at introduction of Panax ginseng's exogenous DNA into Panax quinquefolium has been done continuously the past three years in our institute. The results showed that the best way of exogenous DNA introduction is via the pollen tube similarly lesser flowery organ. The suitable introducing time is at 10:00-11:00 am, and the seeds ratio is 13.21% at the experiment limits.

DNA, Plant↗
PubMed1999

Long-term survival after infection with human immunodeficiency virus type 1 (HIV-1) among homosexual men in hepatitis B vaccine trial cohorts in Amsterdam, New York City, and San Francisco, 1978-1995.

Information on long-term survival after infection with human immunodeficiency virus type 1 (HIV-1) is limited. In hepatitis B vaccine trials in Amsterdam, New York City, and San Francisco, 362 gay men were followed up to 18 years (1978-1995). The median survival time from seroconversion was 12.1 years (95% confidence interval: 11.4, 12.9). The annual risk of dying increased at a constant rate until 8 years after seroconversion and then leveled off, suggesting a group that is relatively resistant to progression. These data provide a picture of the natural history of HIV-1 infection, especially in the era prior to widespread use of highly effective treatments.

Adult↗
PubMed1999

Differential expression of inflammatory mediators in rat microglia cultured from different brain regions.

Microglial cells show a rather uniform distribution of cell numbers throughout the brain with only minor prevalences in some brain regions. Their in situ morphologies, however, may vary markedly from elongated forms observed in apposition with neuronal fibers to spherical cell bodies with sometimes extremely elaborated branching. This heterogeneity gave rise to the hypothesis that these cells are differentially conditioned by their microenvironment and, therefore, also display specific patterns of differential gene expression. In this study, microglia were isolated from 2-4 week-old mixed CNS cultures that had been prepared from neonatal rat diencephalon, tegmentum, hippocampus, cerebellum and cerebral cortex, and were investigated 24 h later. Messenger RNA levels of proteins involved in crucial immune functions of this cell type (TNF-alpha, CD4, Fcgamma receptor II, and IL-3 receptor beta-subunit) have been determined by semi-quantitative RT-PCR. The results clearly show, that three of these mRNAs (TNF-alpha, CD4, Fcgamma receptor II) are differentially expressed in microglia with hippocampal microglia displaying the highest levels of these mRNAs. The data strongly support the notion that the status of microglial gene expression depends on their localization in brain and on specific interactions with other neural cell types. Consequently, it is hypothesized that their responsiveness to signals arising in injury or disease may vary from one brain region to another.

Animals↗
PubMed1999

Error Analysis of Three Spherotensiometric Methods.

The error analysis in the determination of interfacial tension and contact angle using sphere tensiometry was fulfilled using the total differential analysis. The average error in interfacial tension for all three methods (the maximum force point method, two points method (F0 and H0/R) and process curve method) is smaller than 0.05 mN/m and average error in contact angle is smaller than 0.9 degrees. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Growth inhibition by a triple ribozyme targeted to repetitive B2 transcripts.

The B2 family represents a group of short repetitive sequences that are found throughout the rodent genome and are analogous to the human Alu sequences. Certain B2 subfamilies are transcribed by RNA polymerase III (pol III), and this transcription is in part controlled by the retinoblastoma protein. In addition to their putative role in retrotranspositional events, these actively transcribed B2 RNAs show a predicted highly stable secondary structure. Although B2 transcripts are normally confined to the nucleus, they demonstrate altered compartmentation after carcinogen treatment, in cancers, and in immortalized and/or transformed cell lines, the significance of which is unclear. Because modulation of B2 transcripts did not seem feasible with an antisense approach, we designed a triple ribozyme (TRz) construct to down-regulate B2 transcripts. The B2-targeted TRz undergoes efficient self-cleavage, resulting in liberation of the internal hammerhead Rz, which we targeted to a single-stranded region of the consensus B2 sequence. The liberated internal targeted Rz was 20 times more active than the corresponding double-G mutant construct that could not undergo self-cleavage, and 5 times more active than the same Rz flanked by nonspecific vector sequences. The B2-targeted TRz was used to develop stable transfectant clones from an SV40-immortalized hepatocyte cell line. These transfectant clones all showed variably reduced growth rates, accompanied by significant reductions in both cytoplasmic and nuclear B2 RNA levels: linear regression analyses showed that their growth rates were directly related to residual cytoplasmic B2 levels. Reverse-transcription polymerase chain reaction (RT-PCR) analyses documented efficient self-liberation of the internal targeted Rz in vivo, and showed that the relative cytoplasmic expression levels generally paralleled the magnitude of the decrease in B2 transcripts. The RT-PCR analyses further demonstrated that up to 20% of the Rz was located in the nucleus, which presumably reflects competition between autocatalytic processing and nucleocytoplasmic transport of the initial TRz transcript.

Animals↗
PubMed1999

The mutA mistranslator tRNA-induced mutator phenotype requires recA and recB genes, but not the derepression of lexA-regulated functions.

The mapping of mutA and mutC mutator alleles to the glyV and glyW glycine tRNA genes, respectively, and the subsequent discovery that the mutA phenotype is abolished in a DeltarecA strain raise the possibility that asp --> gly misinsertion may induce a novel mutagenic pathway. The recA requirement suggests three possibilities: (i) the SOS mutagenesis pathway is activated in mutA cells; (ii) loss of recA function interferes with mutA-promoted asp --> gly misinsertion; or (iii) a hitherto unrecognized recA-dependent mutagenic pathway is activated by translational stress. By assaying the expression levels of a reporter plasmid bearing a umuC :lacZ fusion, we show that the SOS regulon is not in a derepressed state in mutA cells. Neither overexpression of the lexA gene through a multicopy plasmid nor replacement of the wild-type lexA allele with the lexA1[Ind-] allele interferes with the expression of the mutA phenotype. The mutA phenotype is unaffected in cells defective for dinB, as shown here, and is unaffected in cells defective for umuD and umuC genes, as shown previously. We show that mutA-promoted asp --> gly misinsertion occurs in recA- cells and, therefore, the requirement for recA is 'downstream' of mistranslation. Finally, we show that the mutA phenotype is abolished in cells deficient for recB, suggesting that cellular recombination functions may be required for the expression of the mutator phenotype. We propose that translational stress induces a previously unrecognized mutagenic pathway in Escherichia coli.

Alleles↗
PubMed1999

Uveitis in patients treated with intravenous cidofovir.

PURPOSE: To study the characteristics of uveitis occurring during intravenous cidofovir treatment for CMV retinitis in patients with AIDS. PATIENTS AND METHODS: We retrospectively studied ten cases (16 eyes) of uveitis in patients with CMV retinitis treated with intravenous cidofovir. All the patients had ophthalmologic examinations and, if required, fundus angiographies. The median follow-up was eight months. RESULTS: Uveitis occurred after a mean of 8.5 infusions of cidofovir (range 2-17). All ten patients were on protease inhibitors. The mean CD4+ cell count was 92 +/- 51/microl and the median viral load was 3.9 log. All the eyes with uveitis had healed CMV retinitis. The first examination of the involved eyes showed inflammation of the anterior chamber (100%), vitritis (50%), posterior synechiae (75%), and low intraocular pressure (94%). Uveitis did not relapse in the seven patients who stopped cidofovir, whereas it relapsed in two of the three patients who did not stop treatment. At the end of follow-up, permanent posterior synechiae were present in 69% of the involved eyes. COMMENTS: Cidofovir therapy necessitates slit-lamp surveillance, especially in patients on HAART. Cidofovir-related uveitis requires a local steroid treatment, but if possible, cidofovir should be withdrawn.

Adult↗
PubMed1999

Significance of the anti-E2 response in self-limited and chronic hepatitis C virus infections in chimpanzees and in humans.

To determine whether there was a correlation between the kinetics or frequency of antibody to mammalian-derived hepatitis C virus (HCV) second envelope protein (E2) and development of chronicity or self-limitation of HCV infections, serial sera were examined for anti-E2, anti-HCV with confirmation with Matrix 2.0 (Abbott Laboratories, Abbott Park, IL), and reverse transcriptase-polymerase chain reaction (RT-PCR) from 6 cases of self-limited infection and 6 cases of chronic infection in chimpanzees, and from 5 cases of self-limited infection and 3 cases of chronic infection in patients. Anti-E2 developed earlier, more frequently, and to higher titer in chimpanzees and patients who were developing chronic infection than in those with self-limited infections. Thus anti-E2 is unlikely to play a role in self-limitation of the infection. However, long-term persistence of anti-E2 correlates with chronic infection. There was little or no correlation between the timing of development of anti-E2 and anti-HCV.

Animals↗