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Biomedical subjects

Fang Yu

Publications and source records attributed to Fang Yu.

At least 37 records · Page 2Linked to original sources
PubMed2005

The rearrangement route to 3-carboxy- and 3-hydroxymethyl-2-azabicyclo[2.1.1]hexanes: 3,5-methanoprolines.

Improved stereocontrolled syntheses of 5-anti-hydroxy-3-exo-methoxycarbonyl-2-azabicyclo[2.1.1]hexanes have been effected from pyridine. The key step in the electrophilic addition-rearrangement of 2-azabicyclo[2.2.0]hex-5-ene precursors incorporates either a 3-endo-phenyl group, as an acid precursor, or a 3-endo-phenyldimethylsilylmethyl group, as a potential hydroxymethyl and acid precursor.

Journal Article↗
PubMed2005

Surface density dependence of PCR amplicon hybridization on PNA/DNA probe layers.

Surface plasmon field-enhanced fluorescence spectroscopy was employed to extensively investigate the hybridization behaviors of polymerase chain reaction (PCR) amplicons on a peptide nucleic acid (PNA) or DNA probe layer that was previously attached on a streptavidin-modified gold surface via biotin/streptavidin interaction. Despite the neutral backbone of PNA, the hybridization reactions were strongly influenced by the variation of ionic strength. The association rates exhibited a monotonic decrease with ionic strength increase and the maximum hybridization signal was achieved at an intermediate sodium concentration (approximately 100 mM). These effects were mainly ascribed to the electrostatic cross talk among the hybridized DNA molecules and the secondary structure of PCR amplicons. For the negatively charged DNA probes, the hybridization reaction was subjected additionally to the DNA/DNA electrostatic barrier, particularly in lower ionic strength range (e.g., 10 approximately 150 mM Na(+)). The electrostatic cross talk was shown to be largely reduced if the PNA probe layer was sufficiently diluted by following a strategic templated immobilization method. As a consequence, a pseudo-first-order kinetic model was applicable to describe the hybridization kinetics, and affinity constants were derived for evaluating the influence of single nucleotide polymorphisms (SNPs).

Biophysics↗
PubMed2005

Metal-enhanced up-conversion fluorescence: effective triplet-triplet annihilation near silver surface.

Up-conversion phenomena are traditionally related to two- or multiphoton processes occurring under relatively high excitation intensities. Here we present the first results of ultralow excitation intensity (in order of Wcm(-2)) continuous-wave (CW) excited up-conversion fluorescence in Kretschmann surface plasmon geometry. The active system is a blue-emitting polymer matrix blended with metalated porphyrine macrocycles. The up-conversion fluorescence is a consequence of a two-particle triplet-triplet annihilation process (TTA).

Dose-Response Relationship, Radiation↗
PubMed2005

A new diterpenoid glucopyranoside from Erythrophleum fordii.

A phytochemical investigation of the bark of Erythrophleum fordii furnished six compounds, of which one is a new diterpenoid glucopyranoside, named 15Z-[dodecahydro-18-hydroxymethyl-17,19,20-trimethyl-15(1H)-phenanthrenylidene]-acetic acid-16-O-beta-D-glucopyranoside (1). Five known compounds were identified as (+)-taxifolin (2), (-)-robinetinidol (3), palmaitic acid (4), beta-sitosterol (5) and baucosteyl (6), and were all isolated from the species for the first time. The structure of the new compound was elucidated on the basis of spectroscopic analyses and chemical methods.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Functional outcomes for older adults with cognitive impairment in a comprehensive outpatient rehabilitation facility.

The purpose of the study was to examine functional outcomes of a nurse-managed, community-based Comprehensive Outpatient Rehabilitation Facility (CORF) for frail older adults and to compare the outcomes between two groups: older adults with cognitive impairment and those with intact cognition. A retrospective cohort design using healthcare record abstraction was used for the study. Two hundred and one older adults who were admitted to the CORF from the end of 1997 to early 1999 were included in the study. Data were abstracted from healthcare records, including clinician-generated Mini-Mental State Examination, Geriatric Depression Scale, and Functional Independence Measure scores from the healthcare records and investigator-constructed measures of functional gain, rehabilitation efficiency, days of service, and discharge location. Multivariate regression analyses were performed to compare rehabilitation outcomes between the two groups. Regardless of cognitive status, all subjects improved significantly in their levels of functional dependence through participating in this outpatient rehabilitation program (P<.001). Subjects with cognitive impairment exhibited more functional dependence at baseline and discharge than did their cognitively intact counterparts. Nevertheless, there was no difference between the two groups in functional gain (P=.63), rehabilitation efficiency (P=.66), days of service (P=.83), or discharge location (P=.69). Therefore, despite their greater degree of functional dependence on admission, older adults with cognitive impairment benefited from this CORF without requiring more days of service and should thus be referred for rehabilitation services.

Aged↗
PubMed2005

Factors affecting outpatient rehabilitation outcomes in elders.

PURPOSE: To identify factors affecting outpatient rehabilitation outcomes in elders. DESIGN: A retrospective cohort design was used to explore factors affecting outpatient rehabilitation outcomes in elders. METHODS: Analyses of health records from a nurse-managed comprehensive outpatient rehabilitation facility were conducted. Data pertinent to the study were abstracted from 201 health records, including scores from three standard instruments: the Functional Independence Measure, the Mini-Mental State Examination, and the Geriatric Depression Scale, to construct study variables. Multivariate and stepwise regression analyses were performed. FINDINGS: Cognitive impairment was associated with lower admission and discharge function, but not with rehabilitation outcomes (functional gain, rehabilitation efficiency, days of service, and discharge location). Age > or = 80 years, admission function, and the interaction of age > or = 80 years and admission function affected functional gain and rehabilitation efficiency. Older age, being Black, and having more medical comorbidities were associated with days of service. None of these factors contributed to discharge location. CONCLUSIONS: Cognitive impairment was not associated with outpatient rehabilitation outcomes. Rather, age > or = 80 years and function when admitted affected functional gain and rehabilitation efficiency in elders who participated in outpatient rehabilitation services.

Activities of Daily Living↗
PubMed2005

Influence of the metal film thickness on the sensitivity of surface plasmon resonance biosensors.

The influence of the metal film thickness (i.e., the chromium adhesion promoting film and the gold film) on the sensitivity of surface plasmon resonance (SPR) signals (i.e., resonance angle shift and reflectance change) towards the thickness variation of the nonabsorbing dielectric film is investigated. The sensitivity of reflectance change decreases when a thick chromium film or a thin gold film is employed. Its linear range becomes narrower as the thickness of the metal films increases. The sensitivity and linear range of the resonance angle shift are not affected by the thickness variation of the metal films. The phenomena were theoretically explained based on the attenuated total reflection (ATR) generated evanescent field at the prism/metal interface and the SPR-generated evanescent field at the metal/dielectric interface.

Biosensing Techniques↗
PubMed2004

Surface plasmon field-enhanced fluorescence spectroscopy in PCR product analysis by peptide nucleic acid probes.

Surface plasmon field-enhanced fluorescence spectroscopy (SPFS) was recently developed for PCR product analysis, which allowed for real-time monitoring of hybridization processes and for the detection of trace amounts of PCR products, with a detection limit of 100 fmol on the peptide nucleic acid (PNA) probe surface, and 500 fmol on the DNA probe surface. By selectively labeling the strands of PCR-amplified DNA, it was shown that the heat denaturation process in combination with the application of low-salt condition substantially reduced the interference from the antisense strands and thus simplified the surface hybridization. Furthermore, SPFS was demonstrated to be capable of quantitatively discriminating the difference induced by single nucleotide substitution, even within one minute of contact time.

Antisense Elements (Genetics)↗
PubMed2004

Salusins promote cardiomyocyte growth but does not affect cardiac function in rats.

Salusin-alpha and -beta are newly found polypeptides that stimulate proliferation, hypotension and bradycardia in vascular smooth muscle cells (VSMCs) and fibroblasts. Propresalusin mRNA is widespread, and positive stains for salusins have been observed in many human tissues such as endothelium and ventricular tissue. To investigate the bio-effect of salusins on cardiovascular function, 20 nmol/kg salusin-alpha or 2 nmol/kg salusin-beta was intravenously (i.v.) injected into rats, and isolated rat hearts were perfused with 10(-12) to 10(-7) mol/l salusin-alpha or -beta. (45)Ca(2+) uptake and (3)H-Leucine incorporation were determined in cultured neonatal rat cardiomyocytes. Neither salusin-a nor -beta affected cardiac function in vivo or in vitro but salusin-beta decreased mean arterial blood pressure (MAP). The polypeptides' stimulation of (45)Ca(2+) uptake and (3)H-Leucine incorporation was concentration-dependent, and the incorporation was inhibited by nicardipine (Nic) and FK-506 [FK; an inhibitor of calcineurin (CaN)]. PD(98059) [PD; inhibitor of mitogen-activated protein kinase (MAPK)] and chelerythrine [inhibitor of protein kinase C (PKC)] inhibited salusin-stimulated (3)H-Leucine incorporation. Endothelin-1 (ET) synergistically increased salusin-induced (45)Ca(2+) uptake. Our results suggest that salusin-alpha and -beta did not directly affect cardiac function in the rat heart but that they improved calcium uptake and protein synthesis in neonatal rat cardiomyocytes through the calcium, calcineurin, MAPK and PKC signal pathways. Salusins may be regulatory factors for myocardial growth and hypertrophy.

Adenosine Triphosphatases↗
PubMed2004

Surface plasmon fluorescence immunoassay of free prostate-specific antigen in human plasma at the femtomolar level.

This study describes the development of a surface plasmon fluorescence spectroscopy (SPFS)-based sandwich immunoassay, for the detection of free prostate-specific antigen (f-PSA). The commercial CM5 chip (Biacore) was integrated into the SPFS-based assay making use of its three-dimensionally extended dextran architecture, which offers a large protein retention capacity and alleviates the metal-induced fluorescence quenching. The performance of the f-PSA assay was investigated in buffer and in human plasma, respectively. In the human plasma, the limit of detection of f-PSA was estimated to be approximately 80 fM for 40 min of contact time, which adequately meets clinical requirements.

Humans↗
PubMed2004

Attomolar sensitivity in bioassays based on surface plasmon fluorescence spectroscopy.

With the aid of a dextran matrix, the metal-induced fluorescence loss of bound fluorophores can be greatly reduced, and the distance dependence of the fluorescence yield could be largely convoluted. This is optimized for the limit of detection assessment of surface plasmon fluorescence spectroscopy. The model system was designed as a direct assay with mouse IgG covalently immobilized to the carboxymethyl dextran matrix of a CM5 sensor chip from Biacore. Time-resolved ultratrace detection of fluorophore (Alexa-Fluor 647)-labeled rabbit anti-mouse antibody down to 500 aM (10-18 M) was accomplished, corresponding to a binding rate of approximately 10 molecules mm-2 min-1.

Animals↗
PubMed2004

Surface plasmon enhanced diffraction for label-free biosensing.

Surface plasmon enhanced evanescent field at a (noble) metal/dielectric interface can be employed to enhance the diffraction efficiency of surface grating structure composed of biomolecules. Based on a Kretschmann configuration, we realized a diffraction biosensor to monitor the dynamic interaction of biological molecules in a label-free way. It was demonstrated by the binding of an anti-biotin antibody to the biotin-functionalized region of a periodically patterned surface, which generated significant optical contrast to diffract the surface plasmon field. With the aid of the synchronic surface plasmon resonance signal, a quadratic dependence of diffraction signal on the amount of bound antibody was found, which coincides with the theoretical expectation. Time-dependent measurements were conducted to estimate the density of biotin thiols on the functional region.

Antibodies, Monoclonal↗
PubMed2004

Oligonucleotide hybridization studied by a surface plasmon diffraction sensor (SPDS).

A novel label-free biosensor concept based on surface plasmon-enhanced diffraction by micro- patterned interfaces was applied to the study of hybridization reactions of target DNA oligonucleotides (15mers and 75mers) from solution to probe DNA oligonucleotides attached via streptavidin to the sensor surface. The self-referencing and quadratic signal amplification mechanism of the sensor allowed highly sensitive detection of the hybridization process. Association and dissociation processes of DNA targets could be recorded in real time and used for the quantification of their binding affinities, which differ considerably with a single base pair mismatch. An equilibrium titration approach was also applied in order to obtain the binding affinities for 15mer targets, yielding similar affinity values. The hybridization efficiencies were found to be higher for the 15mers than for the 75mers, although the latter contained the same recognition sequences. The hybridization efficiency was shown to depend on the probe density and reached nearly 100% for the 15mer fully complementary targets at a probe density of approximately 1.2 x 10(12) molecules/cm2. Using the assay as an end-point determination method, the lowest detectable coverage of a 15mer oligonucleotide was at least approximately 1.1 x 10(11) molecules/cm2. The diffraction sensing concept offers a completely novel way to integrate a reference channel in large-scale, label-free screening applications, to improve the stability and to enhance the sensitivity of microarray read-out systems.

Base Pair Mismatch↗
PubMed2004

Evanescent field in surface plasmon resonance and surface plasmon field-enhanced fluorescence spectroscopies.

The highly sensitive nature of surface plasmon resonance (SPR) spectroscopy and surface plasmon field-enhanced fluorescence spectroscopy (SPFS) are governed by the strong surface plasmon resonance-generated evanescent field at the metal/dielectric interface. The greatest evanescent field amplitude at the interface and the maximum attenuation of the reflectance are observed when a nonabsorbing dielectric is employed. An absorbing dielectric decreases the evanescent field enhancement at the interface. The SPR curve of an absorbing dielectric is characterized by a greater reflectance minimum and a broader curve, as compared to those of the nonabsorbing dielectric with the same refractive index. For a weakly absorbing dielectric, such as nanometer-thick surface-confined fluorophores, the absorption is too small to induce a significant change in the SPR curve. However, the presence of a minute amount of the fluorophore can be detected by the highly sensitive SPFS. The angle with the maximum fluorescence intensity of an SPFS curve is always smaller than the resonance angle of the corresponding SPR curve. This discrepancy is due to the differences of evanescent field distributions and their decay characteristics within the metal film and the dielectric medium. The fluorescence intensity in an SPFS curve can be expressed in terms of the evanescent field amplitude. Excellent correlations between the experimentally measured fluorescence intensities and the evanescent field amplitudes are observed.

Journal Article↗
PubMed2004

Immunosensor with self-referencing based on surface plasmon diffraction.

We propose a novel type of immunosensor based on the diffraction of surface plasmon, which allows for in situ, real-time, and label-free observation of interfacial binding events. The inherent self-referencing mechanism of surface diffraction was found to be very effective for compensating fluctuations of the bulk, demonstrated by a temperature variation experiment. Possessing a stable baseline signal, the diffraction sensor offered picomolar sensitivity in directly detecting the binding of human chorionic gonadotropin (hCG) hormone.

Journal Article↗
PubMed2004

[The relationship of angiotensin I-converting enzyme gene polymorphism with diabetic retinopathy and diabetes myocardial infarction].

OBJECTIVE: To investigate the relationship of angiotensin I-converting enzyme (ACE) gene polymorphism to diabetic retinopathy and diabetes myocardial infarction. METHODS: ACE insertion/deletion(I/D) polymorphism was determined by PCR. RESULTS: No evidence showed that ACE gene was associated with diabetic retinopathy. By comparison of the type 2 diabetes patients with myocardial infarction versus those without-myocardial infarction, it was found that the frequencies of homozygote DD (41.2% versus 33.2%) and of allele D (64.7% versus 55.0%) increased remarkably; the difference was statistically significant (P<0.05). CONCLUSION: Allele D(RR=1.50) and genotype DD(RR=1.33) seemed to be a genetic risk factor for type 2 diabetes myocardial infarction.

Adult↗