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Biomedical subjects

G Li

Publications and source records attributed to G Li.

At least 199 records · Page 11Linked to original sources
PubMed2001

Potential benefits of restrictions on the transport of teenage passengers by 16 and 17 year old drivers.

OBJECTIVES: The presence of passengers is associated with fatal motor vehicle crashes of teenage drivers. A restriction against newly licensed teenage drivers carrying passengers has been included in some, but not all, graduated licensing systems. The purpose of this study was to predict the net effects on all types of road users, including vehicle occupants and non-occupants, of possible prohibitions against 16-17 year old drivers carrying passengers. METHODS: Two national datasets, a census of fatal crashes and a sample of trips in the United States, were used to compute 1995 road user death rates. Potential effects of restrictions on drivers ages 16-17 carrying passengers younger than 20 were estimated, based on road user death rates and potential choices made by passengers who would have traveled with 16-17 year old drivers if there were no restrictions. RESULTS: There were 1,181 road user deaths in 1995 involving drivers ages 16-17 whose passengers were all younger than age 20. The predicted number of lives in the United States that would be saved annually ranges from 83 to 493 (corresponding to reductions of 7-42% in road user deaths) for drivers ages 16 and 17 combined. Similar percentages of reductions (8-44%) were predicted solely for 16 year old drivers. Assuming passenger restrictions would apply to all 16 year old drivers and at least one third of 17 year old drivers, an estimated 60-344 fewer deaths per year may occur if restrictions are mandated. CONCLUSIONS: Restrictions on carrying passengers younger than 20 should be considered for inclusion in graduated licensing systems. Even if fewer than half the drivers obey the restrictions, a substantial reduction in road user deaths would be expected. Further evaluation based on real world experience is needed to confirm their efficacy.

Accidents, Traffic↗
PubMed2001

Role of SNAP-23 in trafficking of H+-ATPase in cultured inner medullary collecting duct cells.

The trafficking of H+-ATPase vesicles to the apical membrane of inner medullary collecting duct (IMCD) cells utilizes a mechanism similar to that described in neurosecretory cells involving soluble N-ethylmaleimide-sensitive factor attachment protein target receptor (SNARE) proteins. Regulated exocytosis of these vesicles is associated with the formation of SNARE complexes. Clostridial neurotoxins that specifically cleave the target (t-) SNARE, syntaxin-1, or the vesicle SNARE, vesicle-associated membrane protein-2, reduce SNARE complex formation, H+-ATPase translocation to the apical membrane, and inhibit H+ secretion. The purpose of these experiments was to characterize the physiological role of a second t-SNARE, soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP)-23, a homologue of the neuronal SNAP-25, in regulated exocytosis of H+-ATPase vesicles. Our experiments document that 25-50 nM botulinum toxin (Bot) A or E cleaves rat SNAP-23 and thereby reduces immunodetectable and (35)S-labeled SNAP-23 by >60% within 60 min. Addition of 25 nM BotE to IMCD homogenates reduces the amount of the 20 S-like SNARE complex that can be immunoprecipitated from the homogenate. Treatment of intact IMCD monolayers with BotE reduces the amount of H+-ATPase translocated to the apical membrane by 52 +/- 2% of control and reduces the rate of H+ secretion by 77 +/- 3% after acute cell acidification. We conclude that SNAP-23 is a substrate for botulinum toxin proteolysis and has a critical role in the regulation of H+-ATPase exocytosis and H+ secretion in these renal epithelial cells.

Animals↗
PubMed2001

GM-CSF mediates alveolar macrophage proliferation and type II cell hypertrophy in SP-D gene-targeted mice.

Mice deficient in surfactant protein (SP) D develop increased surfactant pool sizes and dramatic changes in alveolar macrophages and type II cells. To test the hypothesis that granulocyte-macrophage colony-stimulating factor (GM-CSF) mediates alveolar macrophage proliferation and activation and the type II cell hypertrophy seen in SP-D null mice, we bred SP-D and GM-CSF gene-targeted mice to obtain littermate double null, single null, and wild-type mice. Bronchoalveolar lavage levels of phospholipid, protein, SP-D, SP-A, and GM-CSF were measured from 1 to 4 mo. There was an approximately additive accumulation of phospholipid, total protein, and SP-A at each time point. Microscopy showed normal macrophage number and morphology in GM-CSF null mice, numerous giant foamy macrophages and hypertrophic type II cells in SP-D null mice, and large but not foamy macrophages and mostly normal type II cells in double null mice. These results suggest that the mechanisms underlying the alveolar surfactant accumulation in the SP-D-deficient and GM-CSF-deficient mice are different and that GM-CSF mediates some of the macrophage and type II cell changes seen in SP-D null mice.

Animals↗
PubMed2001

Rapid fabrication of three-dimensional porous films with biomimetic patterns by natural evaporation of amphiphilic polyacetylene solutions under ambient conditions.

A simple process for fast fabrication of thin films with biomimetic morphological structures from a group of linear homopolymers is developed. Natural evaporation of tetrahydrofuran, chloroform, and hexane-dichloromethane solutions of poly(phenylacetylene)s that contain amino acid and ethylene glycol moieties under ambient conditions instantly produces three-dimensional porous films with structural patterns reminiscent of honeycombs and radiolarian shells. Morphological analysis by optical and electronic microscopy suggests that vesicles of the amphiphilic polymers serve as building blocks in the self-organization to the biomimetic structures.

Acetylene↗
PubMed2001

Sphingosine-1-phosphate lyase has a central role in the development of Dictyostelium discoideum.

Sphingosine-1-phosphate, a product of sphingomyelin degradation, is an important element of signal transduction pathways that regulate cell proliferation and cell death. We have demonstrated additional roles for sphingosine-1-phosphate in growth and multicellular development. The specific disruption in Dictyostelium discoideum of the sphingosine-1-phosphate lyase gene, which encodes the enzyme that catalyzes sphingosine-1-phosphate degradation, results in a mutant strain with aberrant morphogenesis, as well as an increase in viability during stationary phase. The absence of sphingosine-1-phosphate lyase affects multiple stages throughout development, including the cytoskeletal architecture of aggregating cells, the ability to form migrating slugs, and the control of cell type-specific gene expression and terminal spore differentiation. This pleiotropic effect, which is due to the loss of sphingosine-1-phosphate lyase, establishes sphingolipids as pivotal regulatory molecules in a wide range of processes in multicellular development.

Actins↗
PubMed2001

Differential expression and functional analysis of Pitx2 isoforms in regulation of heart looping in the chick.

Pitx2, a bicoid-related homeobox gene, plays a crucial role in the left-right axis determination and dextral looping of the vertebrate developing heart. We have examined the differential expression and function of two Pitx2 isoforms (Pitx2a and Pitx2c) that differ in the region 5' to the homeodomain, in early chick embryogenesis. Northern blot and RT-PCR analyses indicated the existence of Pitx2a and Pitx2c but not Pitx2b in the developing chick embryos. In situ hybridization demonstrated a restricted expression of Pitx2c in the left lateral plate mesoderm (LPM), left half of heart tube and head mesoderm, but its absence in the extra-embryonic tissues where vasculogenesis occurs. RT-PCR experiments revealed that Pitx2a is absent in the left LPM, but is present in the head and extra-embryonic mesoderm. However, ectopic expression of either Pitx2c or Pitx2a via retroviral infection to the right LMP equally randomized heart looping direction. Mapping of the transcriptional activation function to the C terminus that is identical in both isoforms explained the similar results obtained by the gain-of-function approach. In contrast, elimination of Pitx2c expression from the left LMP by antisense oligonucleotide resulted in a randomization of heart looping, while treatment of embryos with antisense oligonucleotide specific to Pitx2a failed to generate similar effect. We further constructed RCAS retroviral vectors expressing dominant negative Pitx2 isoforms in which the C-terminal transcriptional activation domain was replaced by the repressor domain of the Drosophila Engrailed protein (En(r)). Ectopic expression of Pitx2c-En(r), but not Pitx2a-En(r), to the left LPM randomized the heart looping. The results thus demonstrate that Pitx2c plays a crucial role in the left-right axis determination and rightward heart looping during chick embryogenesis.

Amino Acid Sequence↗
PubMed2001

Detection of novel ALAD gene polymorphisms using denaturing high-performance liquid chromatography.

Denaturing high-performance liquid chromatography (DH-PLC), which is based on the separation of mismatched DNA heteroduplexes, is one of the most promising techniques for detecting nucleotide polymorphisms. Lead is an important environmental toxicant that can impair the cardiovascular, central nervous, renal, reproductive, and hematologic systems. Here we compare the sensitivity and efficiency of DNA polymorphism detection in the delta-aminolevulinate dehydratase (ALAD) gene encoding the principal lead-binding protein in humans by means of DHPLC and direct DNA sequencing of polymerase chain reaction amplicons. In a sample of 48 unrelated Chinese women, five novel mutations were discovered in intron 6 (G13298C). exon 7 (C13348T), intron 8 (C13847T), intron 12 (C15096T), and the 3' untranslated region of exon 13 (A15762C). The allele frequencies of C13298, T13348, T13847, T15096, and C15762 alleles were 21.3%, 2.3%. 82.1%, 62.5%, and 1.1%, respectively. All five mutations were detected by both DHPLC and direct DNA sequencing. No previously reported missense ALAD mutations were found in this Chinese population. Our study confirms that DHPLC provides an accurate method for the rapid identification of single nucleotide polymorphisms.

Adult↗
PubMed2001

Alcohol and eye diseases: a review of epidemiologic studies.

OBJECTIVE: Epidemiologic evidence for the associations of alcohol consumption with eye diseases was gathered. METHOD: A literature review was conducted. RESULTS: In addition to alcohol-induced ocular anomalies among children with fetal alcohol syndrome, epidemiologic studies in the past two decades have demonstrated that chronic alcoholism is associated with a significantly increased risk of cataract, keratitis, color vision deficiencies and corneal arcus. Moderate alcohol use, however, has been reported to be possibly protective against age-related macular degeneration, cataract and diabetic retinopathy. CONCLUSIONS: It is evident that through its biologic effects and effects on nutrient deficits alcohol plays a role in a variety of eye diseases. Information on the patient's drinking history can be clinically valuable and should be collected on a routine basis.

Alcohol Drinking↗
PubMed2001

Incorporation of horseradish peroxidase in a Kieselguhr membrane and the application to a mediator-free hydrogen peroxide sensor.

Horseradish peroxidase was incorporated in a kieselguhr membrane. The electron-transfer process of the enzyme was examined by cyclic voltammetry. It was observed that the electron-transfer reactivity of horseradish peroxidase was greatly enhanced, and that direct electrochemistry was accordingly feasible. Using the merits of the direct electron-transfer reactivity of horseradish peroxidase and its specific enzymatic catalysis towards hydrogen peroxide, an unmediated hydrogen peroxide biosensor was constructed. The calibration plot of this hydrogen peroxide sensor was linear in the range of 2.0 x 10(-6) mol/L - 6.5 x 10(-4) mol/L. The relative standard deviation was 4.1% for 6 successive determinations at a concentration of 1.0 x 10(-4) mol/L. The detection limit was 1.0 x 10(-6) mol/L.

Biosensing Techniques↗
PubMed2001

Conserved genetic findings in metastatic bladder cancer: a possible utility of allelic loss of chromosomes 9p21 and 17p13 in diagnosis.

CONTEXT: Molecular analysis of microsatellite alterations of biologically distinct tumor cell subpopulations from the same patient may aid in the determination of tumor origin and further our understanding of the genetic basis of cancer progression. DESIGN: The authors examined the pattern of allelic loss with polymorphic microsatellite markers on chromosome 9p21 (D9S161, D9S171, IFNA), regions of putative tumor suppressor gene p16, and on chromosome 17p13 (TP53), the p53 locus, in matched primary and metastatic bladder cancers from 9 patients. All patients underwent cystectomy for bladder cancer and had regional lymph node metastases at the time of surgery. Genomic DNA was prepared from primary cancers and matched synchronous lymph node metastases using a microdissection method. RESULTS: The overall frequency of allelic loss was 78% in primary cancer and 89% in paired metastatic cancer. The frequency of allelic loss in the primary cancer was 86% with D9S161, 67% with D9S171, 71% with IFNA, and 80% with TP53. The frequency of allelic loss in matched metastatic cancer was 100% with D9S161, 62% with D9S171, 71% with IFNA, and 80% with TP53. An identical pattern of allelic imbalance (allelic loss or retention) at multiple DNA loci was observed in matched primary and metastatic carcinoma in 8 (88%) cases. One case showed allelic loss in the metastasis, but not in the primary cancer. CONCLUSIONS: The pattern of allelic loss at chromosome 9p21 (p16) and 17p13 (p53) was generally maintained during cancer progression to metastasis, and identical allelic loss in primary cancer was conserved in paired metastatic carcinoma. These data suggest that these genetic changes may be useful in establishing a diagnosis and determining tumor origins in difficult cases.

Aged↗
PubMed2001

Factors associated with pilot error in aviation crashes.

BACKGROUND: The importance of pilot error in aviation crashes has long been recognized. However, understanding and preventing pilot error remains the foremost challenge in aviation safety. OBJECTIVE: This study aims to identify pilot characteristics and crash circumstances that are associated with the presence of pilot error in a large sample of aviation crashes. METHODS: Different data files compiled by the National Transportation Safety Board for 329 major airline crashes, 1,627 commuter/air taxi crashes, and 27,935 general aviation crashes for the years 1983-96 were merged; and the presence of pilot error was analyzed in relation to variables indicating the characteristics of the pilot-in-command, crash circumstance, and aircraft. Multivariate logistic regression modeling was performed to assess the associations of individual variables with the likelihood of pilot error given a crash. RESULTS: Pilot error was a probable cause in 38% of the major airline crashes, 74% of the commuter/air taxi crashes, and 85% of the general aviation crashes. Among the factors examined, instrument meteorological condition and on-airport location were each associated with a significantly increased odds of pilot error. The likelihood of pilot error decreased as pilot certificate rating increased in commuter/air taxi and general aviation crashes. Neither pilot age nor gender was independently associated with the odds of pilot error. With adjustment for pilot characteristics and crash circumstances, flight experience as measured in total flight time showed a significant protective effect on pilot error in general aviation crashes. CONCLUSIONS: The prevalence and correlates of pilot error in aviation crashes vary with the type of flight operations. Adverse weather is consistently associated with a significantly elevated likelihood of pilot error, possibly due to increased performance demand.

Accidents, Aviation↗
PubMed2001

The expression of G250/mn/CA9 antigen by flow cytometry: its possible implication for detection of micrometastatic renal cancer cells.

Monoclonal antibody (mAb) G250 is a well characterized and specific mAb to renal cell carcinoma (RCC). The gene G250 was recently cloned and was proved to be homologous to MN/CA9. The G250/MN/CA9 antigen was recently explored as a potential marker for RCC. Flow cytometry (FCM) allows quantitative analysis of cells. The present study describes a flow cytometric method to detect this antigen in human cell lines and in malignant and normal renal tissues. Twelve human carcinoma cell lines (HeLa, Colo205, HT29, BxPC3, OVCAR3, SKOV3, ACHN, A704, CAKI-2, SKRC-59, SKRC-10, and SKRC-52), 10 specimens of normal peripheral blood mononuclear cells, and 38 malignant and 36 adjacent normal renal tissues were studied. The malignant and normal renal tissues were disaggregated mechanically into a single-cell suspension, stained by mAb G250, and analyzed by FCM. All 22 of the clear cell carcinomas, 6 of 8 mixed cell carcinomas, and 3 of 6 granular cell carcinomas were positive for G250/MN/CA9 antigen. SKRC-52 and SKRC-10 were strongly positive for G250/ MN/CA9. The G250/MN/CA9 antigen could also be detected in HeLa, SKOV3, HT29, and A704 cells. One chromophobic, one chromophilic cell carcinoma, the normal renal tissues, and normal peripheral blood mononuclear cells were considered as negative. Our results further confirmed that the G250/MN/CA9 antigen was an ideal marker for RCC, especially for clear cell carcinomas, and that this antigen was present in several types of malignant cells. FCM may serve as a fast tool of immunocytochemical detection of renal cancer cells. Flow cytometric detection of renal cancer cells by using mAb G250 should be further explored.

Adult↗
PubMed2001

Frequent inactivation of the TP53 gene in esophageal squamous cell carcinoma from a high-risk population in China.

Esophageal squamous cell carcinoma (ESCC) is one of the most common fatal cancers worldwide, and north central China has some of the highest rates in the world. Previous studies from tumors in this area of China have shown high frequencies of allelic loss on chromosome 17p13-11, which includes the region where the TP53 gene is found. We examined 56 ESCC patients using single-strand conformation polymorphism and DNA sequencing to assess the frequency and spectrum of TP53 mutation and the association between allelic loss at microsatellite marker TP53 and TP53 mutations. Ninety-six % of cases were found to have at least one genetic alteration, including TP53 mutation (77%), allelic loss within the TP53 gene (73%), and/or loss of heterozygosity at the TP53 microsatellite marker (80%); 75% had two or more such alterations, including 59% with both a point mutation and an intragenic allelic loss ("two hits"). The majority of mutations observed were in exon 5, where the most common type of nucleotide substitution was a G:C-->A:T or C:G-->T:A transition, including half that occurred at CpG sites. Allelic loss was most commonly found in exon 4 but was very common in exon 5 as well. Taken together, the multiple genetic alterations of TP53 in this population at high risk for ESCC indicate that there is a very high degree of genetic instability in these tumors, that TP53 is a primary target for inactivation, and that this tumor suppressor gene plays a critical role in the carcinogenesis process for ESCC.

Adult↗
PubMed2001

Characteristics of general aviation crashes involving mature male and female pilots.

BACKGROUND: General aviation crashes in the United States were analyzed to identify differences between male and female pilots in the circumstances of their crashes and the types of pilot errors involved. METHODS: All 144 female pilots who were born between 1933 and 1942 and who were involved in general aviation crashes between 1983 and 1997 were matched 1:2 with 287 male pilots by age within 2 yr, medical certificate and pilot certificate, state or region of crash, and year of crash. RESULTS: Mechanical failure, gear up landings, improper IFR approaches, and collisions with wires or poles were more common in crashes of male pilots. Loss of control on landing/takeoff was more common in crashes of female pilots. Mishandling aircraft kinetics was the most common error of pilots of both genders and was noted more often in female pilots' crashes (81% vs. 48%) (p < 0.001). Males' crashes were more likely to involve flawed decisions (29% vs. 19% of females' crashes) (p = 0.027) or inattention (32% vs. 19%) (p = 0.004). Older pilots made fewer errors: among males age 55-63, 26% of crashes were without obvious pilot error compared with only 7% at age 40-49 (p = 0.003). CONCLUSION: There are large gender differences in the types of pilot error involved in general aviation crashes. Mishandling aircraft kinetics, poor decision making, and inattention are the most common pilot errors and merit increased attention in pilot training.

Accidents, Aviation↗
PubMed2001

[Biological removal of VOCs emissions].

The designed test conditions were following: vacancy velocity was from 0.7 cm/s to 3.5 cm/s, retention time was from 30 s to 80 s. Column activated carbon was selected as the filler of the reactor and toluene was taken as representative of VOCs. The biodegradation of toluene using biofilter reactor and the influence of concentration, flow and humidity on the toluene removal were investigated and the removal model was set up. The experimental results showed that the biofilter reactor had higher toluene removing ability. The observation of biotic community demonstrated that the microbes consisted of fungi, bacillus and spore bacillus. Of them spore bacillus was dominant.

Biodegradation, Environmental↗
PubMed2001

[Clinical study on the relationships between HBV C gene promotor gene mutation and immunological marker, HBV DNA concentration].

OBJECTIVE: To investigate the relationships between HBV infected patients immunological marker, HBV DNA concentration, and clinical symptoms. METHODS: PCR-microplate nucleotide acid hybridization-ELISA and FQ-PCR methods were applied in the analysis of HBV BCP gene mutation and HBV DNA concentration in 246 HBV infected patients. RESULTS: In patients with HBsAg+/HBeAg+/anti-HBc+, HBsAg+/anti-HBeAb+/anti-HBcAb+, and HBsAg+/anti-HBc+, the HBV DNA positive rate were 97.9% (48/49), 22.9% (25/109), 31.1% (14/45) respectively, with the overall positive rate 42.85% (98/203). And the HBV BCP gene mutation rate were 59.1% (29/49), 11% (12/109), 13.3% (6/45) respectively, with the overall mutation rate 23.15% (47/203). In HBV BCP gene mutation group HBV DNA concentration of each specimen was more than 10(6) cps/ml, which are significantly higher than other groups(P < 0.001). CONCLUSION: Re-evaluation of HBV infected patients with HBsAg+/anti-HBe+/anti-HBc+ and HBV BCP gene mutation is necessary. The immunological turnover of HBeAg indicates the immune clearance and rest of HBV only in part of HBV infected patients. The immunological marker should not be the sole factor upon which the HBV replication status, the diagnosis and prognosis of patients are determined.

Adolescent↗
PubMed2001

Protein adducts of 1,4-benzoquinone and benzene oxide among smokers and nonsmokers exposed to benzene in China.

Hemoglobin (Hb) and albumin (Alb) adducts of the benzene metabolites benzene oxide (BO) and 1,4-benzoquinone (1,4-BQ) were analyzed by gas chromatography-mass spectrometry in 43 exposed workers and 44 unexposed controls from Shanghai, China, as part of a larger cross-sectional study of benzene biomarkers. When subjects were divided into controls (n = 44) and workers exposed to </=31 ppm (n = 21) and >31 ppm (n = 22) of benzene, median 1,4-BQ-Alb adducts were 2110, 5850, and 13,800 pmol/g Alb, respectively (correlation with exposure: Spearman r = 0.762; P < 0.0001); median BO-Alb adducts were 106, 417, and 2400 pmol/g Alb, respectively (Spearman r = 0.877; P < 0.0001); and median BO-Hb adducts were 37.1, 50.5, and 136 pmol/g Hb, respectively (Spearman r = 0.757; P < 0.0001). To our knowledge, this is the first observation that adducts of 1,4-BQ are significantly correlated with benzene exposure. When compared on an individual basis, Alb adducts of 1,4-BQ and BO and Hb adducts of BO were highly correlated with each other and with urinary phenol and hydroquinone (P < 0.0001 for all of the comparisons). Although detectable in the assays, Hb adducts of 1,4-BQ and both Hb and Alb adducts of 1,2-BQ produced erratic results and are not reported. Interestingly, cigarette smoking increased Alb adducts of 1,4-BQ but not of BO, suggesting that benzene from cigarette smoke was not the primary contributor to the 1,4-BQ adducts.

Benzene↗