PubMed Health⌕ Search

Biomedical subjects

L Wan

Publications and source records attributed to L Wan.

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

Ambient sulfate concentration and chronic disease mortality in Beijing.

In this study, ecological analysis was used to assess the relationship between ambient air pollution and human mortality. All the data on environmental measures and related factors, population size and number of deaths were collected for the city of Beijing, PR China and its eight districts for the years 1980-1992. In this study the concentration of SO(4)2- was selected as a main indicator of environmental pollution for the following reasons: (i) SO(4)2- data are available to cover all urban and suburban areas in Beijing compared with other air pollutants during the study period; (ii) SO(4)2- levels indicate the concentration of sulfide (include sulfate) and acid fog in the air, and they are significantly lower in cleaner districts than in others; and (iii) analyses showed that SO(4)2- levels are significantly correlated with daily mean concentrations of sulfur dioxide and nitrogen oxide, annual coal combustion, number of households using gas fuel, counts of motor vehicles and population density. Age-standardised mortality rates due to specific diseases were calculated using the Chinese population census data in 1990. Statistically significant correlations were observed between SO(4)2- concentration and total mortality and mortality due to cardiovascular disease, malignant tumour and lung cancer (r > 0.50 in all cases). The correlations were not only found between the current SO(4)2- concentration and these mortalities, but also for SO(4)2- levels measured up to 12 years prior to death, which may suggest long-term effects of air pollution. No significant correlations were observed for mortality from respiratory diseases and cerebrovascular diseases (r = 0.30-0.50). This study indicates that the concentration of SO(4)2- in air is a useful air pollution indicator in the areas where coal is used as the main source of energy. Areas with high levels of SO(4)2- experienced higher mortality due to a variety of chronic diseases.

Air Pollutants↗
PubMed2000

Membrane-associated GAIP is a phosphoprotein and can be phosphorylated by clathrin-coated vesicles.

GAIP (G alpha interacting protein) is a member of the RGS (regulators of G protein signaling) family and accelerates the turnover of GTP bound to Galphai, Galphaq, and Galpha13. There are two pools of GAIP-a soluble and a membrane-anchored pool. The membrane-anchored pool is found on clathrin-coated vesicles (CCVs) and pits in rat liver and AtT-20 pituitary cells. By treatment of a GAIP-enriched rat liver fraction with alkaline phosphatase, we found that membrane-bound GAIP is phosphorylated. By immunoprecipitation carried out on [(32)P]orthophosphate-labeled AtT-20 pituitary cells stably expressing GAIP, (32)P-labeling was associated exclusively with the membrane pool of GAIP. Phosphoamino acid analysis revealed that phosphorylation of GAIP occurred largely on serine residues. Recombinant GAIP could be phosphorylated at its N terminus with purified casein kinase 2 (CK2). It could also be phosphorylated by isolated CCVs in vitro. Phosphorylation was Mn(2+)-dependent, using both purified CK2 and CCVs. Ser-24 was identified as one of the phosphorylation sites. Our results establish that GAIP is phosphorylated and that only the membrane pool is phosphorylated, suggesting that GAIP can be regulated by phosphorylation events taking place at the level of clathrin-coated pits and vesicles.

Animals↗
PubMed2000

Prolonged effectiveness of Norplant(R) capsule implants: a 7-year study.

Soft tubing Norplant(R) contraceptive implants were studied in 1210 women for 7 years to measure the duration of effectiveness and the magnitude of the pregnancy rates over that time. Mean age at enrollment was 27.4 years. Of the enrollees, 42% were US residents. One-sixth (16.1%) weighed >/=70 kg at the time of implant placement. At the end of 5 years, the cumulative pregnancy rate was 1.1/100; at the end of 7 years, it was 1.9/100. No pregnancies occurred to any of the 400 women who enrolled in the study at age >/=30 years and who weighed <100 kg. Among women aged 18-33 years, the 7-year Norplant pregnancy rates are comparable to the median pregnancy rates of tubal sterilization methods for women of the same age and duration of use. For women aged >/=34 years, without regard to weight at admission, the 7-year effectiveness of soft tubing Norplant equals or surpasses that of tubal sterilization. For continuing implant users, annual pregnancy rates <1.0/100 in years 6 and 7, together with low cumulative pregnancy rates, testify that Norplant capsule implants remain highly effective for 7 years.

Adolescent↗
PubMed2000

HIV-1 Nef protein binds to the cellular protein PACS-1 to downregulate class I major histocompatibility complexes.

Major-histocompatibility-complex (MHC) proteins are used to display, on the surface of a cell, peptides derived from foreign material - such as a virus - that is infecting that cell. Cytotoxic T lymphocytes then recognize and kill the infected cell. The HIV-1 Nef protein downregulates the cell-surface expression of class I MHC proteins, and probably thereby promotes immune evasion by HIV-1. In the presence of Nef, class I MHC molecules are relocalized from the cell surface to the trans-Golgi network (TGN) through as-yet-unknown mechanisms. Here we show that Nef-induced downregulation of MHC-I expression and MHC-I targeting to the TGN require the binding of Nef to PACS-1, a molecule that controls the TGN localization of the cellular protein furin. This interaction is dependent on Nef's cluster of acidic amino acids. A chimaeric integral membrane protein containing Nef as its cytoplasmic domain localizes to the TGN after internalization, in an acidic-cluster- and PACS-1-dependent manner. These results support a model in which Nef relocalizes MHC-I by acting as a connector between MHC-I's cytoplasmic tail and the PACS-1-dependent protein-sorting pathway.

Animals↗
PubMed2000

The role of tissue factor in regulating endometrial haemostasis: implications for progestin-only contraception.

Abnormal uterine bleeding accounts for the unacceptably high discontinuation rate of progestin-only contraceptives. Previously, we found that in-vivo and in-vitro decidualization of human endometrial stromal cells was associated with elevated concentrations of tissue factor (TF), the primary initiator of haemostasis. Moreover, enhanced TF expression required progesterone receptor (PR) and epidermal growth factor receptor (EGFR) mediation. In the current study, endometrial biopsies were sampled from bleeding (BL) and non-bleeding (NBL) sites under camera-directed hysteroscopic guidance after Depo-provera injections. When compared with control biopsies, immunohistochemical examination revealed that 3 months of Depo-provera contraception reduced TF concentrations at the BL sites. However, there were ample EGFR and PR concentrations at BL and NBL sites. Moreover, there was a trend towards the appearance of pathologically enlarged blood vessels at the BL sites. The use of Western blotting revealed that after 3 months of Depo-provera, concentrations of both PRB and PRA isoforms were lower at BL versus NBL sites with decreased PRA concentrations attaining statistical significance. Separate sampling of endometrial BL and NBL sites as shown here for Depo-provera contraception could prove particularly useful in identifying local factors that determine the onset of bleeding during the more protracted time-course of Norplant contraception.

Biopsy↗
PubMed2000

Characterization of dFMR1, a Drosophila melanogaster homolog of the fragile X mental retardation protein.

Fragile X syndrome is the most common inherited form of mental retardation. It is caused by loss of FMR1 gene activity due to either lack of expression or expression of a mutant form of the protein. In mammals, FMR1 is a member of a small protein family that consists of FMR1, FXR1, and FXR2. All three members bind RNA and contain sequence motifs that are commonly found in RNA-binding proteins, including two KH domains and an RGG box. The FMR1/FXR proteins also contain a 60S ribosomal subunit interaction domain and a protein-protein interaction domain which mediates homomer and heteromer formation with each family member. Nevertheless, the specific molecular functions of FMR1/FXR proteins are unknown. Here we report the cloning and characterization of a Drosophila melanogaster homolog of the mammalian FMR1/FXR gene family. This first invertebrate homolog, termed dfmr1, has a high degree of amino acid sequence identity/similarity with the defined functional domains of the FMR1/FXR proteins. The dfmr1 product binds RNA and is similar in subcellular localization and embryonic expression pattern to the mammalian FMR1/FXR proteins. Overexpression of dfmr1 driven by the UAS-GAL4 system leads to apoptotic cell loss in all adult Drosophila tissues examined. This phenotype is dependent on the activity of the KH domains. The ability to induce a dominant phenotype by overexpressing dfmr1 opens the possibility of using genetic approaches in Drosophila to identify the pathways in which the FMR1/FXR proteins function.

Amino Acid Motifs↗
PubMed2000

Effects of norplant on endometrial tissue factor expression and blood vessel structure.

Abnormal uterine bleeding after Norplant administration is primarily responsible for the high discontinuation rate of this safe and effective long-acting implantable progestin-only contraceptive agent. Although tissue factor (TF) is the primary initiator of hemostasis, previous studies indicated that Norplant-associated bleeding persists despite relatively high TF levels in the stromal compartment. Recently, we determined that progestin-enhanced TF expression during decidualization of human endometrial stromal cells involves both the epidermal growth factor receptor and progesterone receptor (PR]. The current study evaluated TF levels in endometrial bleeding (BL) and nonbleeding (NBL) sites obtained by camera-guided hysteroscopy during Norplant contraception. After 1 yr of therapy, immunohistochemical TF levels were unexpectedly higher at BL than at NBL sites. Use of immunohistochemistry and Western blotting indicated that both sites displayed elevated epidermal growth factor receptor levels and that the BL sites exhibited high levels of the PR, as well as the PR(A) and the PR(B) isoforms. Microscopic examination of 1-yr biopsies revealed that significantly larger numbers of enlarged, distended vessels were present in BL, compared with NBL sites. Elevated TF levels and abnormally enlarged blood vessels in the BL sites are consistent with the recently discovered angiogenic role of TF. By promoting aberrant angiogenesis, chronic endometrial overexpression of TF could produce fragile vessels, which are at increased risk to bleed. Analysis of endometrial BL and NBL sites, during Norplant contraception, offers the potential of elucidating local mechanisms that control enhanced TF expression, leading to abnormal angiogenesis at specific endometrial sites.

Adult↗
PubMed2000

[The construction of PQE-ARL-1 recombinant expression plasmid and the preparation and purification of ARL-1 protein].

OBJECTIVE: To further understand the function and biological activity of aldose reductase like-1 (ARL-1), and to provide the basis for the preparation of the specific antibody against ARL-1. METHODS: The ARL-1 cDNA was cloned into procaryotic expression vector PQE-30 and the recombinant ARL-1 expressed in E.coli M(15); then Ni(+)-NTA agarose columns were used to purify the ARL-1 protein. RESULTS: With the digestion of the enzymes, we identified that the ARL-1 gene was inserted into the procaryotic expression vector PQE-30. The expression products of PQE-ARL-1 (human recombinant ARL-1) showed a single protein band on SDS-PAGE. The molecular weight of ARL-1 was approximately 37.7 x 10(3) and the expression level was about 25% of the total bacterial protein. The concentration of ARL-1 protein was about 100mg/L. CONCLUSION: The construction of the recombinant plasmid PQE-ARL-1 and the preparation of the protein ARL-1 have laid a solid foundation for further studying the function of ARL-1 and preparing the specific antibody against ARL-1.

Aldehyde Reductase↗
PubMed2000

[Measurement of macrophage colony-stimulating factor during in-vitro fertilization and embryo transfer cycles].

OBJECTIVE: To explore the influences of macrophage colony-stimulating factor (M-CSF) on follicle development, ovulation, fertilization and embryo quality during in-vitro fertilization and embryo transfer (IVF-ET) cycles. METHODS: 36 patients underwent 54 cycles of controlled ovarian hyperstimulation by gonadotropin-releasing hormone agonist-human menopausal goudotropin-human chorionic gonadotropin for IVF-ET program. M-CSF concentrations in serum were measured at early follicular phase, mid-follicular phase and the day of oocyte retrieval by enzyme-linked immunosorbent assay. Follicular fluid (FF) on the day of egg retrieval was also measured for M-CSF concentration. RESULTS: M-CSF concentration in serum gradually increased throughout ovarian hyperstimulation and reached a peak on the day of oocyte retrieval. M-CSF concentration in FF was significantly higher than that in serum on the same day (P < 0.01). The M-CSF concentration in FF from follicles where oocytes could be retrieved, fertilized or with a diameter > or 16 mm, volume > or 2 ml, was significantly higher than those from follicles where oocyte could not be retrieved, fertilized or with a diameter < 16 mm, volume < 2 ml, respectively (P < 0.01). However, there was no significant difference in M-CSF concentration of FF between high and low embryo grade groups (P > 0.05). CONCLUSIONS: M-CSF may play an important role as an intraovarian regulator in the process of follicle development, maturation and ovulation. Therefore, M-CSF may exert an effect on fertilization process but not on the embryo quality.

Embryo Transfer↗
PubMed1999

Molecular characterization of the hnRNP A2/B1 proteins: tissue-specific expression and novel isoforms.

hnRNP A2/B1 proteins are among the most abundant pre-mRNA-binding proteins of vertebrates and structurally similar to hnRNP A1. We have produced two specific monoclonal antibodies against A2 and B1 and studied their molecular characteristics and in vivo expression in rat tissues. Immunoprecipitation demonstrated that the hnRNP A2/B1 complexes contain many snRNP (small nuclear ribonucleoprotein) proteins, consistent with their role in pre-mRNA splicing. RNA polymerase II inhibition causes nucleocytoplasmic shuttling of A2 and B1. In most tissues, they are localized in the nucleus; however, in the squamous epithelium of the skin and esophagus A2 is also distributed in the cytoplasm. The relative amounts of A2 and B1 are not constant among different tissues. In the adrenal, only A2 is extremely abundant in the medulla but not in the cortex. In the testis the expression of A2 and B1 are observed through spermatogenesis, and different from A1 which is stringently repressed in spermatocytes. We also found and cloned a novel testis-specific isoform of A2/B1, namely hnRNP B0. The difference of expression of A2, B1, and A1 provides new information on their in vivo roles. The diversity of A/B group hnRNP proteins may have important effects on the posttranscriptional regulation of cell-specific gene expression.

Amino Acid Sequence↗
PubMed1999

The antiviral agents, MAP30 and GAP31, are not toxic to human spermatozoa and may be useful in preventing the sexual transmission of human immunodeficiency virus type 1.

OBJECTIVE: To investigate the effects of two virucidal compounds, MAP30 (Momordica anti-human immunodeficiency virus [HIV] protein; molecular weight, 30 kd) and GAP31 (Gelonium anti-HIV protein; molecular weight, 31 kd), obtained from Momordica charantia and Gelonium multiflorum, respectively, on the motility and vitality of human spermatocytes. DESIGN: Prospective, controlled study. SETTING: New York University School of Medicine. PATIENT(S): Ten healthy men undergoing evaluation for infertility provided 10 semen specimens. INTERVENTION(S): Human sperm were treated with the anti-HIV agents, MAP30 and GAP3 1. Nonoxynol-9, a commonly used spermicide, and phosphate-buffered saline were used as the positive and negative controls, respectively. MAIN OUTCOME MEASURE(S): The motility and vitality of human spermatocytes treated with MAP30 and GAP31 at doses that inhibit HIV-1 and herpes simplex virus. RESULT(S): MAP30 and GAP31 did not inhibit the motility or vitality of human sperm cells over a dose range of 100-0.1 microg/mL, whereas nonoxynol-9 demonstrated spermicidal action on all 10 samples over the same dose range. CONCLUSION(S): The antiviral agents, MAP30 and GAP31, were not toxic to human sperm cells at the doses at which they inhibit HIV-1 and herpes simplex virus. They had no effect on the motility of spermatozoa, even at a dose of 1,000 times the maximum effective concentration. These results indicate that MAP30 and GAP31 may be useful as nonspermicidal protection against sexually transmitted diseases.

Anti-HIV Agents↗
PubMed1999

[Hepatoprotective effect of several constituents of Lonicera fulvotomentosa hsu et S. C. cheng, and L. macranthoide Hand.-Mazz. on CC1(4) and D-galactosamine induced liver injuries in mice and rats].

OBJECTIVE: To study the hepatoprotective effect of several constituents of Lonicera fulvotomentosa and L. macranthoide on CC1(4) and D-Galactosamine induced liver injury in mice and rats. METHOD: Mice and rats were given s.c. several constituents of L. fulvotomentosa and L. macranthoide, sGPT, hepatic triglycerides(TG) and malondialdehyde (MDA) were determined. RESULTS: All the compounds reduced the rise of sGPT and TG induced by CC1(4) and D-Galactosamine. Hepatic MDA formation caused by CC1(4) was also significantly decreased. CONCLUSION: Several constituents of L. fulvotomentosa and L. macranthoide are effective in decreasing CC1(4) and D-Galactosamine-induced liver injuries, and this effect appears to be due to the decrease of lipid peroxidation of CC1(4).

Alanine Transaminase↗
PubMed1998

In vitro evolution of horse heart myoglobin to increase peroxidase activity.

Random mutagenesis and screening for enzymatic activity has been used to engineer horse heart myoglobin to enhance its intrinsic peroxidase activity. A chemically synthesized gene encoding horse heart myoglobin was subjected to successive cycles of PCR random mutagenesis. The mutated myoglobin gene was expressed in Escherichia coli LE392, and the variants were screened for peroxidase activity with a plate assay. Four cycles of mutagenesis and screening produced a series of single, double, triple, and quadruple variants with enhanced peroxidase activity. Steady-state kinetics analysis demonstrated that the quadruple variant T39I/K45D/F46L/I107F exhibits peroxidase activity significantly greater than that of the wild-type protein with k1 (for H2O2 oxidation of metmyoglobin) of 1. 34 x 10(4) M-1 s-1 ( approximately 25-fold that of wild-type myoglobin) and k3 [for reducing the substrate (2, 2'-azino-di-(3-ethyl)benzthiazoline-6-sulfonic acid] of 1.4 x 10(6) M-1 s-1 (1.6-fold that of wild-type myoglobin). Thermal stability of these variants as measured with circular dichroism spectroscopy demonstrated that the Tm of the quadruple variant is decreased only slightly compared with wild-type (74.1 degreesC vs. 76.5 degreesC). The rate constants for binding of dioxygen exhibited by the quadruple variant are identical to the those observed for wild-type myoglobin (kon, 22.2 x 10(-6) M-1 s-1 vs. 22.3 x 10(-6) M-1 s-1; koff, 24.3 s-1 vs. 24.2 s-1; KO2, 0.91 x 10(-6) M-1 vs. 0.92 x 10(-6) M-1). The affinity of the quadruple variant for CO is increased slightly (kon, 0.90 x 10(-6) M-1s-1 vs. 0.51 x 10(-6) M-1s-1; koff, 5.08 s-1 vs. 3.51 s-1; KCO, 1.77 x 10(-7) M-1 vs. 1.45 x 10(-7) M-1). All four substitutions are in the heme pocket and within 5 A of the heme group.

Amino Acid Substitution↗
PubMed1998

PACS-1 defines a novel gene family of cytosolic sorting proteins required for trans-Golgi network localization.

We report the role of one member of a novel gene family, PACS-1, in the localization of trans-Golgi network (TGN) membrane proteins. PACS-1 directs the TGN localization of furin by binding to the protease's phosphorylated cytosolic domain. Antisense studies show TGN localization of furin and mannose-6-phosphate receptor, but not TGN46, is strictly dependent on PACS-1. Analyses in vitro and in vivo show PACS-1 has properties of a coat protein and connects furin to components of the clathrin-sorting machinery. Cell-free assays indicate TGN localization of furin is directed by a PACS-1-mediated retrieval step. Together, these findings explain a mechanism by which membrane proteins in mammalian cells are localized to the TGN.

Adaptor Protein Complex alpha Subunits↗
PubMed1998

Contraception with two levonorgestrel rod implants. A 5-year study in the United States and Dominican Republic.

A 5-year trial of a two-rod contraceptive implant, which releases the progestin levonorgestrel (LNG rod), was conducted at four clinics with 594 women. Mean age and weight at admission were 25.5 years and 62.4 kg, respectively. Consent to continue through 5 years was sought and obtained when the 3-year cumulative pregnancy rate proved to be 0.8 per 100. No pregnancies occurred in the fourth or fifth years. The 5-year cumulative pregnancy rate was, therefore, 0.8 per 100 with an annual average pregnancy rate below 2 per 1000 women. Prolonged bleeding/spotting (8.2% of subjects) and irregular bleeding (5.6%) were the most frequently cited medical reasons for removal. Removals for headache (4.7%) and weight change (4.0%) were the next most frequent medical reasons. Between 1% and 2% of subjects during the 5-year trial sought removals for each of the following conditions: mood changes, lower abdominal pain, depression, or pain at the implant site. The mean annual continuation rate during the study was 77 per 100. Use per woman averaged 2.96 years. Mean removal time was 5.9 +/- 0.6 min. These data indicate that, for a 5-year period, the two LNG rod implants are equivalent to the six Norplant capsule implants with respect to safety and efficacy parameters, but permit easier and more rapid implant removal.

Adolescent↗
PubMed1998

Levonorgestrel capsule implants in the United States: a 5-year study.

OBJECTIVE: To measure effectiveness, adverse event experience, and acceptability of the Food and Drug Administration-approved variant of levonorgestrel capsule implants in the United States through 5 years and to examine determinants of these outcomes. METHODS: In a prospective, multicenter study, 511 sexually active women selecting contraceptive implants were monitored four times in the 1st year, then semiannually through 5 years. Adverse events were elicited by query and physical examination, and their incidence was measured. Lifetable analyses computed pregnancy and other discontinuation rates. Cox regression models examined effects of age, parity, and preadmission desire for more children on continuation. Removal times were analyzed by analysis of variance. RESULTS: Three pregnancies occurred, yielding a 5-year cumulative rate of 1.3+/-0.8 per 100 users, an average annual rate of three per 1000 women, and an ectopic pregnancy rate of 0.6 per 1000 woman years. No pregnancies occurred to women weighing less than 79 kg. Prolonged or irregular menstrual bleeding, followed distantly by headache, weight gain, and mood changes, was the most frequent medical conditions leading to removal. Weight gain averaged 1 kg per year. Each annual continuation rate was above 80 per 100, for a cumulative 5-year rate of 39 per 100. Continuation was age-dependent, with younger women (younger than 25 years at entry) having lower 5-year continuation rates than older subjects (P < .01). Tissue trauma from deeply placed or poorly aligned implants or severe reactions to local anesthetic affected subjects in 3.1% of removals (nine cases). CONCLUSION: As measured by annual continuation rates of 80 per 100 or higher and annual pregnancy rates below one per 100, implant contraception in the United States was found to be highly acceptable and effective, year after year, regardless of the woman's age or family formation status. The cumulative 5-year pregnancy rate, 1.3 per 100, is comparable to that of tubal ligation.

Adult↗
PubMed1998

Spectroscopic and functional studies of a novel quadruple myoglobin variant with increased peroxidase activity.

A quadruple variant of horse heart myoglobin (Thr39Ile/Lys45Asp/Phe46Leu/Ile107Phe) that exhibits significantly (approximately 25-fold) greater peroxidase activity than the wild-type protein has been studied to determine its midpoint reduction potential (24(2) mV vs. SHE; pH 6.0, mu = 0.1 M, 25 degrees C) and to characterize the kinetics of its reaction with hydrogen peroxide. In addition, Fourier transform infrared (FTIR) spectra of the carbonyl and azide adducts of the protein have been obtained to gain initial insight into the effects of these substitutions on the ligand binding properties of the reduced and oxidized variant. All of the results obtained in this work are consistent with a variant heme binding pocket with increased hydrophilic character.

Animals↗