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Biomedical subjects

Fei Yu

Publications and source records attributed to Fei Yu.

At least 19 recordsLinked to original sources
PubMed2007

Methylation of gibberellins by Arabidopsis GAMT1 and GAMT2.

Arabidopsis thaliana GAMT1 and GAMT2 encode enzymes that catalyze formation of the methyl esters of gibberellins (GAs). Ectopic expression of GAMT1 or GAMT2 in Arabidopsis, tobacco (Nicotiana tabacum), and petunia (Petunia hybrida) resulted in plants with GA deficiency and typical GA deficiency phenotypes, such as dwarfism and reduced fertility. GAMT1 and GAMT2 are both expressed mainly in whole siliques (including seeds), with peak transcript levels from the middle until the end of silique development. Within whole siliques, GAMT2 was previously shown to be expressed mostly in developing seeds, and we show here that GAMT1 expression is also localized mostly to seed, suggesting a role in seed development. Siliques of null single GAMT1 and GAMT2 mutants accumulated high levels of various GAs, with particularly high levels of GA(1) in the double mutant. Methylated GAs were not detected in wild-type siliques, suggesting that methylation of GAs by GAMT1 and GAMT2 serves to deactivate GAs and initiate their degradation as the seeds mature. Seeds of homozygous GAMT1 and GAMT2 null mutants showed reduced inhibition of germination, compared with the wild type, when placed on plates containing the GA biosynthesis inhibitor ancymidol, with the double mutant showing the least inhibition. These results suggest that the mature mutant seeds contained higher levels of active GAs than wild-type seeds.

Amino Acid Sequence↗
PubMed2007

Studies on Pd(0)-catalyzed cyclization of N-3,4-alkadienyl toluenesulfonamides with organic halides: selective synthesis of 2,3-dihydropyrroles, 1,2,3,6-tetrahydropyrridines, and azetidines.

The palladium-catalyzed coupling-cyclization of beta-amino allenes with organic halides ranging from aryl halide to 1-alkenyl halide was studied. 2,3-Dihydro-1H-pyrroles were obtained by reaction of 3-substituted-5-unsubstituted-3,4-allenyl amides under conditions A, while the reaction of 5-substituted-3,4-allenyl amides afforded 1,2,5,6-tetrahydropyridines and/or azetidines with high de under conditions B or C. The skeleton and relative configuration of the six-membered products were established by the X-ray diffraction studies of 10 ka. Allenyl amide 4 q reacted with 1,4-diiodobenzene 6 r to afford double cyclization product 15. The structure of its major stereoisomer was also determined by the X-ray diffraction study.

Journal Article↗
PubMed2006

Prevalence of age-related macular degeneration in Greece: the Thessaloniki Eye Study.

PURPOSE: To estimate the age- and gender-specific prevalence of age-related macular degeneration (AMD) in a population-based sample of subjects 60 years of age or older in Thessaloniki, Greece. DESIGN: Cross-sectional population-based study. METHODS: A total of 2554 subjects randomly identified from municipality registers in Thessaloniki underwent a complete ophthalmologic examination. RESULTS: Of the 3617 eligible subjects, 2554 (71%) participants completed a clinical examination. The prevalence was 2.5% for AMD, 1.4% for neovascular (NV) AMD, and 1.3% for geographic atrophy (GA). Bilateral AMD was present in 40% of AMD cases. The prevalence of AMD, NV, GA, and bilateral AMD increased with increasing age (P< .0001). No gender-specific statistically significant differences were noted. Of all participants with AMD, 67% were unaware of the diagnosis. CONCLUSIONS: The prevalence of AMD in Greece is comparable to that in other Caucasian populations. A dramatic increase in prevalence in people older than 80 years of age was observed.

Age Distribution↗
PubMed2006

Palladium(0)-catalyzed highly regio- and stereoselective addition of organoboronic acids with 1,2-allenylphosphonates forming tri- or tetrasubstituted 1(E)-alkenylphosphonates.

A highly regio- and stereoselective palladium(0)-catalyzed addition of organoboronic acids with 1,2-allenylphosphonates in the presence of HOAc forming tri- or tetrasubstituted 1(E)-alkenylphosphonates is reported in this paper. The stereoselectivity is much higher than the reported cases. The effects of different R(1), R(2), and R(3) were studied. A mechanism of this reaction is proposed on the basis of our previous study.

Journal Article↗
PubMed2006

Age-related macular degeneration is associated with an increased risk of hip fractures in the Medicare database.

PURPOSE: To explore the relationship between age-related macular degeneration (AMD) and incident hip fractures in the Medicare population. DESIGN: Prospective cohort study. METHODS: With a 5% random sample of Medicare beneficiaries in 1995, 8596 cases were coded with exudative AMD; 26,942 cases were coded with atrophic AMD, and 1,013,748 cases were coded without AMD. The Medicare claims from 1996 to 1999 were evaluated for hip fracture codes. The relationship between AMD and incident hip fractures was analyzed with multiple logistic regression models, with adjustment for baseline, ocular, and systemic covariates. RESULTS: In adjusted analyses, the risk of hip fractures was similar in cases that were coded with exudative AMD (odds ratio, 1.03; 95% confidence interval (CI), 0.95, 1.12) compared with cases with no AMD but was significantly higher in cases that were coded with atrophic AMD (odds ratio, 1.11; 95% CI, 1.06, 1.16). CONCLUSION: Medicare patients with a code for atrophic AMD had an 11% greater risk of hip fractures than did patients without a code for AMD over a four-year follow-up period.

Aged↗
PubMed2006

Longitudinal cohort study of patients with birdshot chorioretinopathy II: color vision at baseline.

PURPOSE: To describe color vision at the baseline examination of 80 participants in a longitudinal cohort study of birdshot chorioretinopathy and to identify relationships between color vision and visual acuity, symptoms, and ophthalmic signs. DESIGN: Single center cross-sectional study. METHODS: Color vision was evaluated with the desaturated Lanthony 15-Hue test. Relationships were sought between the square root of the color confusion scores (CCS) and the following factors: best-corrected visual acuity (BCVA), symptoms, cataract, vitreous inflammatory reactions, retinal vasculitis, cystoid macular edema (CME), and birdshot lesion characteristics. RESULTS: When compared with published, age-matched normal control subjects, 49 patients (61.3%; 76 eyes [47.5%]) had abnormal CCS values. Abnormal CCS values were found in nine of 51 phakic eyes (18%) with normal BCVA (>or=1.0) and without cataract. Although most eyes did not have classifiable defects, 30 eyes (18.8%) had tritan (blue-yellow) defects (88% of eyes with classifiable defects). With the use of multivariate analyses, there were significant associations between increased CCS values and the symptoms of altered color vision (P = .005) and altered contrast sensitivity (P = .015). There was a significant, but weak, relationship between CCS values and birdshot lesion morphologic condition (P = .049), but no relationships were found with other lesion characteristics or with vitreous inflammatory reactions, retinal vasculitis, or CME. CONCLUSION: The Lanthony 15-Hue test provides an objective technique to assess complaints of altered color vision in people with birdshot chorioretinopathy. Color vision can be abnormal in eyes with normal visual acuity; therefore, this parameter may be useful as an additional measure for monitoring the disease.

Adult↗
PubMed2006

Structural monitoring of oligosaccharides through 13C enrichment and NMR observation of acetyl groups.

Structural characterization of biomolecules by NMR methods frequently requires the enrichment of magnetically active isotopes at particular molecular sites. Introduction is usually achieved biosynthetically through the use of bacterial cultures grown on isotopically enriched media, but for certain types of molecules-cell-surface carbohydrates of mammalian origin, for example-this is not practical. Here we explore a means of introducing 13C-enriched sites, postisolation in natural carbohydrate products, and illustrate an ability to acquire sufficient information to select appropriate conformational models from among energetically allowed sets. The application presented involves replacement of native N-acetyl groups with 13C-labeled acetyl groups in a simple disaccharide derivative, (GlcNAc)2-OBu, or O-butyl-chitobiose. The assignment of the two acetyl groups introduced is based on a novel combination of NMR and mass spectrometry data. Structural information is obtained from chemical shift anisotropy offsets of 13C carbonyl resonances and 13C-13C dipolar couplings between the labeled methyl and carbonyl carbons of the acetyl groups. Although the application is to a relatively simple system, it lays the groundwork for application to biologically important complex carbohydrate systems.

Acetylation↗
PubMed2006

[Large-scale screening of mtDNA A1555G mutation in China and its significance in prevention of aminoglycoside antibiotic induced deafness].

OBJECTIVE: To explore the necessity of large-scale screening of mtDNA A1555G mutation in prevention of aminoglycoside antibiotic induced deafness (AAID) and to develop a feasible method to prevent AAID. METHODS: A total of 1836 patients with non-syndromic hearing impairment (NSHI), 1352 students of schools for deaf-mutes in 11 provinces and municipality in China, 413 out-patients, and 71 persons from the families with maternal relatives suffering from AAID, underwent questionnaire survey and/or PCR for A-to-G mutation at nucleotide 1555 of the mitochondrial genome. RESULTS: Sixty three patients with mtDNA A1555G mutation were found among the 1836 NSHI patients. Fifty-two maternal pedigrees were identified. 536 cases with normal hearing from these pedigrees were informed to avoid using aminoglycoside antibiotics (AmAn). CONCLUSION: Large-scale screening of mtDNA A1555G mutation and relevant health education to avoid use of AmAn are effective to prevent ototoxicity in the A1555G carriers and their maternal relatives.

Adolescent↗
PubMed2006

Immunogenicity of CTLA4 fusion anti-caries DNA vaccine in rabbits and monkeys.

Enhancement of mucosal and systemic immune responses is still a challenge for the application of DNA vaccine. Here, we show anti-caries DNA vaccines, pGJA-P and pGJA-P/VAX, encoding Streptococcus mutans antigens fused to cytotoxic T lymphocyte antigen-4 (CTLA4), which binds to B7 molecule expressed on the surfaces of antigen-presenting cells. Rabbits and monkeys were immunized via intranasal or intramuscular routes. The fusion vaccine induced accelerated and increased specific antibody responses in serum and saliva compared with non-fusion DNA vaccine in rabbits. Significant specific serum IgG and salivary IgA levels could be detected in fusion vaccine-immunized monkeys. Therefore, this study demonstrates that fusing antigens to CTLA4 results in enhancing immune efficacy and strongly suggests that it may represent a promising approach to prevent dental caries or other mucosal infectious diseases. These findings also suggest that CTLA4 fusion anti-caries DNA vaccine may be effective immunogen in primates.

Animals↗
PubMed2006

A randomized trial of chiropractic and medical care for patients with low back pain: eighteen-month follow-up outcomes from the UCLA low back pain study.

STUDY DESIGN: Randomized clinical trial. OBJECTIVES: To compare the long-term effectiveness of medical and chiropractic care for low back pain in managed care and to assess the effectiveness of physical therapy and modalities among patients receiving medical or chiropractic care. SUMMARY OF BACKGROUND DATA: Evidence comparing the long-term relative effectiveness of common treatment strategies offered to low back pain patients in managed care is lacking. METHODS: A total of 681 low back pain patients presenting to a managed-care facility were randomized to chiropractic with or without physical modalities, or medical care with or without physical therapy, and followed for 18 months. The primary outcome variables are low back pain intensity, disability, and complete remission. The secondary outcome is participants' perception of improvement in low back symptoms. RESULTS: Of the 681 patients, 610 (89.6%) were followed through 18 months. Among participants not assigned to receive physical therapy or modalities, the estimated improvements in pain and disability and 18-month risk of complete remission were a little greater in the chiropractic group than in the medical group (adjusted RR of remission = 1.29; 95% CI = 0.80-2.07). Among participants assigned to medical care, mean changes in pain and disability and risk of remission were larger in patients assigned to receive physical therapy (adjusted RR = 1.69; 95% CI = 1.08-2.66). Among those assigned to chiropractic care, however, assignment to methods was not associated with improvement or remission (adjusted RR = 0.98; 95% CI = 0.62-1.55). Compared with medical care only patients, chiropractic and physical therapy patients were much more likely to perceive improvement in their low back symptoms. However, less than 20% of all patients were pain-free at 18 months. CONCLUSIONS: Differences in outcomes between medical and chiropractic care without physical therapy or modalities are not clinically meaningful, although chiropractic may result in a greater likelihood of perceived improvement, perhaps reflecting satisfaction or lack of blinding. Physical therapy may be more effective than medical care alone for some patients, while physical modalities appear to have no benefit in chiropractic care.

Academic Medical Centers↗
PubMed2006

Extremely low penetrance of deafness associated with the mitochondrial 12S rRNA mutation in 16 Chinese families: implication for early detection and prevention of deafness.

Mutations in mitochondrial DNA (mtDNA) have been found to be associated with sensorineural hearing loss. We report here the clinical, genetic, and molecular characterization of 16 Chinese pedigrees (a total of 246 matrilineal relatives) with aminoglycoside-induced impairment. Clinical evaluation revealed the variable phenotype of hearing impairment including audiometric configuration in these subjects, although these subjects share some common features: being bilateral and sensorineural hearing impairment. Strikingly, these Chinese pedigrees exhibited extremely low penetrance of hearing loss, ranging from 4% to 18%, with an average of 8%. In particular, nineteen of 246 matrilineal relatives in these pedigrees had aminoglycoside-induced hearing loss. Mutational analysis of the mtDNA in these pedigrees showed the presence of homoplasmic 12S rRNA A1555G mutation, which has been associated with hearing impairment in many families worldwide. The extremely low penetrance of hearing loss in these Chinese families carrying the A1555G mutation strongly supports the notion that the A1555G mutation itself is not sufficient to produce the clinical phenotype. Children carrying the A1555G mutation are susceptible to the exposure of aminoglycosides, thereby inducing or worsening hearing impairment, as in the case of these Chinese families. Using those genetic and molecular approaches, we are able to diagnose whether children carry the ototoxic mtDNA mutation. Therefore, these data have been providing valuable information and technology to predict which individuals are at risk for ototoxicity, to improve the safety of aminoglycoside therapy, and eventually to decrease the incidence of deafness.

Adolescent↗
PubMed2006

Arabidopsis variegation mutants: new insights into chloroplast biogenesis.

Plant variegations are characterized by the presence of white sectors in normally green tissues and organs. Whereas the white sectors contain defective plastids that lack coloured pigments, the green sectors contain morphologically normal chloroplasts. Variegation mutants are defective in chloroplast developmental processes and arise due to mutations in nuclear or organellar genes. Despite their widespread occurrence in nature, only a few variegations have been studied at the molecular level. In this review, recent progress toward understanding two Arabidopsis variegations, immutans (im) and var2 is summarized. Both im and var2 are caused by nuclear recessive mutations and the responsible genes have been cloned and characterized. IMMUTANS functions as a chloroplast terminal oxidase that transfers electrons from the plastoquinol pool to oxygen. It appears to be a versatile electron sink, especially early in chloroplast development, when its function is crucial for carotenoid biosynthesis, and in excess light, when it serves as a 'safety valve'. IM also probably functions in chlororespiration. VAR2 encodes a chloroplast FtsH metalloprotease (termed AtFtsH2). Along with other AtFtsH proteins (AtFtsH1, 5 and 8), it forms complexes in the thylakoid membrane that are probably involved in the process of PSII repair during photoinhibition. A model has been proposed to explain the mechanism of var2 variegation, which suggests that threshold levels of FtsH complexes are required for green sector formation. It is concluded that studies on im and var2 have provided novel insights into nuclear-chloroplast interactions and, especially, into mechanisms of photoprotection.

ATP-Dependent Proteases↗
PubMed2006

Beneficial effect of brewers' yeast extract on daily activity in a murine model of chronic fatigue syndrome.

The aim of this study was to assess the effect of Brewers' yeast extract (BYE) on daily activity in a mouse model of chronic fatigue syndrome (CFS). CFS was induced by repeated injection of Brucella abortus (BA) antigen every 2 weeks. BYE was orally administered to mice in a dose of 2 g per kg per day for 2 weeks before injecting BA and for 4 weeks thereafter. We evaluated daily running activity in mice receiving BYE as compared with that in untreated mice. Weekly variation of body weight (BW) and survival in both groups was monitored during the observation period. Spleen weight (SW), SW/BW ratio, percent splenic follicular area and expression levels of interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) mRNA in spleen were determined in both groups at the time of sacrifice. The daily activity during 2 weeks after the second BA injection was significantly higher in the treated group than in the control. There was no difference in BW between both groups through the experimental course. Two mice in the control died 2 and 7 days after the second injection, whereas no mice in the treated group died. Significantly decreased SW and SW/BW ratio were observed in the treated mice together with elevation of splenic follicular area. There were suppressed IFN-gamma and IL-10 mRNA levels in spleens from the treated mice. Our results suggest that BYE might have a protective effect on the marked reduction in activity following repeated BA injection via normalization of host immune responses.

Journal Article↗
PubMed2006

Longitudinal cohort study of patients with birdshot chorioretinopathy. I. Baseline clinical characteristics.

PURPOSE: To describe baseline clinical characteristics of a cohort of 80 patients with birdshot chorioretinopathy in anticipation of a longitudinal study, and to identify relationships between visual acuity, symptoms, and ophthalmic findings. DESIGN: Single-center cross-sectional study. METHODS: A standardized examination was performed in the same order on a single day for each patient. A grading system for birdshot lesions was established prospectively to evaluate the following lesion characteristics: quantity, distribution, morphology, and pigmentation. Relationships between clinical features of disease were sought in multivariate analyses that adjusted for age, duration of uveitis, and treatment. RESULTS: Mean age at baseline examination was 55.6 years. Median best-corrected visual acuity (BCVA) was 0.8 (range, counting fingers to 1.2). There were no relationships between BCVA and any birdshot lesion characteristic. The most common cause of BCVA < or =0.4 was macular edema. Visual symptoms were present in 78 patients (97.5%), including 17 (94.4%) of 18 patients with BCVA > or =1.0 in both eyes. Blurred vision was associated with decreased BCVA (P = .02) and macular edema (P = .022). Increased lesion pigmentation was associated with complaints of blurred vision (P = .030), vibrating vision (P = .011), and nyctalopia (P = .056). CONCLUSIONS: Symptoms are common in patients with birdshot chorioretinopathy, even among those with good BCVA. Lesion pigmentation may be a marker of decreased visual function that is not reflected in central visual acuity. These findings highlight the limitation of using visual acuity measurements for monitoring patients with birdshot chorioretinopathy and as an outcome measure for studies of this disease.

Adult↗
PubMed2006

Evaluation of the effect on outcomes of the route of administration of corticosteroids in acute Vogt-Koyanagi-Harada disease.

PURPOSE: To compare the effect on outcomes of the route of administration of corticosteroids in acute Vogt-Koyanagi-Harada disease. DESIGN: Retrospective comparative interventional case series. METHODS SETTINGS: Nine international uveitis specialty clinics. STUDY POPULATION: Forty-eight patients presenting over a three-year period to a study center with acute Vogt-Koyanagi-Harada disease. INTERVENTION: Initial treatment with corticosteroid either orally (Oral only group) or intravenously followed by an oral taper (IV+Oral group). MAIN OUTCOME MEASURES: Change in visual acuity with treatment; development of ocular complications, including visually significant cataract, choroidal neovascularization, subretinal fibrosis, fundus pigment migration, nummular hypopigmented lesions, and diffuse fundus depigmentation; use of immunosuppressive therapy. RESULTS: The Oral only group comprised 15 patients (31%) and the IV+Oral group 33 patients (69%). Median follow-up was 15 months. There was no difference in duration of follow-up between groups (P = .234). There was no difference in the change in visual acuity between groups, adjusting for initial visual acuity (P = .402). There were no differences in the rates of development of visually significant cataract, fundus pigmentary changes, or in the rate of use of subsequent immunosuppressive therapy between treatment groups. No patients developed choroidal neovascularization or subretinal fibrosis over the study period. CONCLUSIONS: Route of administration of corticosteroid had no detectable effect on change in visual acuity nor on the development of visually significant complications over the study period. Prospective trials are necessary to address speed of resolution and definitively answer outcome questions.

Acute Disease↗
PubMed2006

Association of blood pressure status with the optic disk structure in non-glaucoma subjects: the Thessaloniki eye study.

PURPOSE: To study the association of blood pressure (BP) status on the optic disk structure as measured with the Heidelberg Retina Tomograph (HRT) in people without glaucoma. DESIGN: Cross-sectional population-based setting study. METHODS: Consecutive participants in the Thessaloniki Eye Study were included in this study. HRT images of the optic disk and BP measurements were taken. Hypertension was defined as a systolic BP (SBP) > or =140 mm Hg, diastolic BP (DBP) >/=90 mm Hg, or both. Subjects were classified in three groups by SBP and DBP. The Kruskal-Wallis test was used to compare the three groups with respect to the HRT parameters. Regression models adjusted for age, gender, height, disk size, intraocular pressure, cardiovascular disease, diabetes, and duration of antihypertensive treatment were used for each HRT parameter to compare values among the different groups. The P value was considered significant at <.05. RESULTS: A total of 232 subjects were included in the analysis. Rim area was significantly different among groups when DBP was considered as the criterion to classify subjects (P = .005). In regression models, cup area, and cup-to-disk (c/d) ratio were increased in subjects with normal DBP that was the result of treatment, as compared with both the high DBP and untreated normal DBP groups. CONCLUSIONS: In patients without glaucoma, the DBP <90 mm Hg that results from antihypertensive treatment is associated with increased cupping and decreased rim area of the optic disk. This information should be considered in research aiming to define the role of the BP status as an independent factor initiating optic disk changes and/or as a contributing factor to glaucoma damage.

Aged↗
PubMed2006

Contrast sensitivity and color vision in HIV-infected individuals without infectious retinopathy.

PURPOSE: To investigate the relationship between abnormal contrast sensitivity and abnormal color vision among human immunodeficiency virus (HIV)-infected individuals who have normal visual acuity and to seek host factors that predict these abnormalities. DESIGN: Noninterventional, cross-sectional study. METHODS: We evaluated 71 HIV-infected subjects with visual acuity of 20/25 or better, clear media, and no vision-threatening retinal lesions. Visual function was determined using the Pelli-Robson contrast sensitivity test and the Farnsworth-Munsell 100-Hue color test (FM-100). Results were compared with published values for normal populations and to measures of HIV disease severity. We evaluated two levels of impairment for each visual function. "Mild dysfunction" was defined as > or =1 standard deviation (SD), but <2 SD from normal means. "Abnormal" was defined as > or =2 SD from normal means. RESULTS: The prevalences of abnormal contrast sensitivity and abnormal color vision were 7.0% and 9.9%, respectively. We did not identify relationships between impaired contrast sensitivity and impaired color vision. Impaired color vision was associated with increasing age (r = 0.36, P = .002). We could not identify significant correlations between either contrast sensitivity or color vision values and the following factors: current or nadir (lowest previous) CD4+ T-lymphocyte count, HIV blood level, and Karnofsky score. CONCLUSIONS: Abnormal contrast sensitivity and abnormal color vision can occur independently in HIV-infected individuals and can be present in the absence of severe immunosuppression.

Adult↗