Biomedical subjects

R Fu

Publications and source records attributed to R Fu.

At least 19 recordsLinked to original sources

PubMed2005

Increased persistent Na(+) current and its effect on excitability in motoneurones cultured from mutant SOD1 mice.

Mutations in the enzyme superoxide dismutase 1 (SOD1) initiate a progressive motoneurone degeneration in amyotrophic lateral sclerosis (ALS). Transgenic mice overexpressing this mutation develop a similar progressive motoneurone degeneration. In spinal motoneurones cultured from presymptomatic mice expressing the glycine to alanine mutation at base pair 93 (G93A) SOD1 mutation, a marked increase in the persistent component of the Na(+) current was observed, without changes in passive properties. This increase only enhanced neuronal excitability in high input conductance cells, as low input conductance cells exhibited a compensatory outward shift in the current remaining after Na(+) blockade. High input conductance motoneurones tend to be large, so these results may explain the tendency of large motoneurones to degenerate first in ALS. Riluzole, at the therapeutic concentration used to treat ALS, decreased neuronal excitability and persistent Na(+) current in G93A motoneurones to levels observed in the control motoneurones. Aberrations in the intrinsic electrical properties may be among the first symptoms to emerge in SOD1-linked ALS.

Action Potentials↗

PubMed2005

Real time PCR on disposable PDMS chip with a miniaturized thermal cycler.

This paper presents the design and implementation of a low-cost miniature PCR device consisting of a disposable reactor chip and a miniature thermal cycler. The simple fabrication of the PCR chip by PDMS (Polydimethylsiloxane) does not need micro-machining or photolithography processes. The thermal cycler was built with a thin film heater for heating and a fan for rapid cooling. This device can perform PCR tests in a single well chip or a multiple-well chip. It can run PCR reactions of different volumes to meet specific application requirements. The smallest reaction volume tested in this work is 0.9 microL. In addition, this device fits any standard fluorescence microscope for real time detection, which makes real time PCR affordable for most research labs and clinics with a fluorescence microscope. Real-time PCR of E. coli stx1 has been demonstrated with the device described.

Computer Systems↗

PubMed2005

Ultra-wide bore 900 MHz high-resolution NMR at the National High Magnetic Field Laboratory.

Access to an ultra-wide bore (105 mm) 21.1 T magnet makes possible numerous advances in NMR spectroscopy and MR imaging, as well as novel applications. This magnet was developed, designed, manufactured and tested at the National High Magnetic Field Laboratory and on July 21, 2004 it was energized to 21.1 T. Commercial and unique homebuilt probes, along with a standard commercial NMR console have been installed and tested with many science applications to develop this spectrometer as a user facility. Solution NMR of membrane proteins with enhanced resolution, new pulse sequences for solid state NMR taking advantage of narrowed proton linewidths, and enhanced spatial resolution and contrast leading to improved animal imaging have been documented. In addition, it is demonstrated that spectroscopy of single site (17)O labeled macromolecules in a hydrated lipid bilayer environment can be recorded in a remarkably short period of time. (17)O spectra of aligned samples show the potential for using this data for orientational restraints and for characterizing unique details of cation binding properties to ion channels. The success of this NHMFL magnet illustrates the potential for using a similar magnet design as an outsert for high temperature superconducting insert coils to achieve an NMR magnet with a field >25 T.

Image Enhancement↗

PubMed2003

Skin temperature recovery from cold provocation in workers exposed to vibration: a longitudinal study.

BACKGROUND: Vibration white finger (VWF) is characterised by arterial hyperresponsiveness and vasoconstriction following cold provocation. Several years after of removal from exposure, most subjects show improved finger systolic blood pressure (FSBP) under conditions of cold challenge, but continue to report cold hands and finger blanching. AIMS: To assess the underlying reasons for the persistence of cold symptoms. METHODS: A total of 204 former users of pneumatic tools with cold related hand symptoms were evaluated and then re-evaluated a year later. Symptoms were evaluated using the Stockholm Workshop Scale. Finger systolic blood pressure per cent (FSBP%) was assessed by comparing digital blood pressure in a cold provoked and normalised state. Fingertip skin temperature was measured during cooling and occlusion and during rewarming and recovery. RESULTS: There were dramatic improvements in FSBP% (14.3 mm Hg %), modest improvement in recovered skin temperature (0.86 degrees C), and no change in symptom stage. When the most symptomatic subjects (n = 75) were compared with the less symptomatic subjects (n = 129), there were similar inter-test improvements in FSBP%. Skin temperature recovery improved in the less symptomatic (+1.49 degrees C), but did not change in the most symptomatic group (-0.12 degrees C). However, the more symptomatic group had higher temperatures at the initial test, thus qualifying the result. CONCLUSIONS: Skin temperature recovery after cold challenge in subjects with VWF remains reduced in the symptomatic subjects several years after exposure removal. This is evident even when blood pressure has increased in the setting of cold provocation. Results suggest that in VWF, the dermal circulation remains impaired, even after the restoration of arterial blood pressure in the digits.

Adult↗

PubMed2001

Functional polymer affinity matrix for purifying hexahistidine-tagged recombinant protein.

A functional polyacrylic acid (PAA) adsorbent has been prepared for metal chelate affinity chromatography. It has been found to chelate nickel ion Ni2+ strongly, and was evaluated for the ability to bind proteins containing neighbouring histidine residues. The principle of the technique was illustrated with Aeromonas hydrophila outer membrane protein OmpTS. DNA elements coding for adjacent histidines were fused to the Aeromonas hydrophila ompTS gene. Subsequent expression in E. coli resulted in the production of hybrid protein His6-OmpTS that could be purified by Ni2+-PAA affinity chromatography. The remarkable specificity found makes it an attractive addition to the range of adsorbents for metal chelate affinity chromatography.

Adsorption↗

PubMed2001

Assessment of various topical oral formulations by bone marrow transplant recipients.

Topical approaches to management of oral mucositis have the advantages of high local concentration and limited or no systemic absorption, reducing the risk of systemic complications. The acceptability of topical therapies in cancer patients has not been evaluated. Thirty-eight transplant patients assessed the acceptability of three formulations (rinse, thin gel, thick gel) of a new compound developed to prevent oral mucositis. The rinse was selected as the most acceptable formulation. The thick gel received the lowest rating. Consistency was a major determinant of overall acceptability. A neutral taste was desirable for most participants. Room temperature of the formulation was rated as completely acceptable. Most participants would be willing to use the rinse or thin gel several times per day, to retain each dose in the oral cavity for up to 5 min, and to swallow it. The support of caregivers may be needed to achieve compliance with such regimens.

Administration, Oral↗

PubMed2000

Imaging membrane protein helical wheels.

Resonance patterns have been observed in 2D solid-state NMR spectra of the transmembrane segment of M2 protein from Influenza A virus in oriented samples reflecting the helical wheel of this alpha-helix. The center of this pattern uniquely defines the helical tilt with respect to the bilayer normal without a need for resonance assignments. The distribution of resonances from amino acid specific labels around the "PISA wheel" defines the rotational orientation of the helix and yields preliminary site-specific assignments. With assignments high-resolution structural detail, such as differences in tilt and rotational orientation along the helical axis leading to an assessment of helical coiling, can be obtained.

Influenza A virus↗

PubMed2000

Inter- and intramolecular distance measurements by solid-state MAS NMR: determination of gramicidin A channel dimer structure in hydrated phospholipid bilayers.

Distance constraints are an important complement to orientational constraints. While a high-resolution monomer structure of the ion channel forming polypeptide, gramicidin A, has been solved with 120 orientational constraints, the precise geometry of the dimer interface has not been characterized. Here, using both 13C and 15N labeled gramicidin A samples in hydrated phospholipid bilayers, both inter- and intramolecular distances have been measured with a recently developed simultaneous frequency and amplitude modulation (SFAM) solid-state NMR scheme. Using this approach 15N-13C1 residual dipolar couplings across a hydrogen bond as small as 20+/-2 Hz have been characterized. While such distances are on the order of 4.2+/-0.2 A, the spectroscopy is complicated by rapid global motion of the molecular structure about the bilayer normal and channel axis. Consequently, the nominal 40 Hz dipolar coupling is averaged depending on the orientation of the internuclear vector with respect to the motional axis. The intermolecular distance confirmed the previously described monomeric structure, while the intramolecular distance across the monomer-monomer interface defined this junction and confirmed the previous model of this interface.

Bacillus↗

PubMed2000

[The lymphocyte subset and blood interleukin-2 level in children with Henoch-Schönlein purpura before and after cimetidine treatment].

The objective of this study was to evaluate the effect of cimetidine treatment on cellular immunity in children with Henoch-Schönlein purpura. T cell subset was detected by double marker flow cytometry and the level of IL-2 in peripheral blood was measured by MTT method, before and after cimetidine treatment. The results showed that CD3+, CD4+ T cell subset, CD4+/CD8+ ratio, and blood IL-2 level increased after the treatment (P < 0.05). There was no significant change in CD8+ T subset after the treatment. These findings indicate that cimetidine can promote T lymphocyte proliferation and differentiation, especially TH1 lymphocyte activity.

Adjuvants, Immunologic↗

PubMed2000

[Detection of DNA variation after space flight in Datura innoxia by random amplified polymorphic DNA markers].

OBJECTIVE: To substantiate the effect of space environment on medicinal plants, the seeds of Datura innoxia were set up in retrievable satellites. METHODS: After returning to earth, the DNA variation of different groups was detected by random amplified polymorphic DNA (RAPD) markers. RESULTS: From a pre-screening of 65 primers with 20 oligonucleotide lengths, 15 primers that produced distinct profiles for each DNA sample were selected. In contrast with the earth controlled group, 39 polymorphic bands were produced in weightless group, and its degree of gene polymorphism was 23.1%; 45 polymophic bands were produced in hit group, and its degree of gene polymorphism was 24.4%. The polymorphic bands ranged approximately from 200 to 1990 bp. CONCLUSIONS: These results indicate that weightlessness induce DNA variation to some extents in Datura innoxia, while the compound effect of weightlessness and high energy heavy ions is more notable than the effect of single weightlessness.

Cosmic Radiation↗

PubMed1999

Vicia root micronucleus assay on the clastogenicity of water samples from the Xiaoqing River in Shandong Province of the People's Republic of China.

Vicia root micronucleus assay was used to determine the clastogenicity of water samples from Xiaoqing River that passes through Jinan City. Positive results were obtained from eight water collecting sites. This indicates that the water in most areas of this river was polluted with industrial waste and municipal sewage. Results of this study proves that biomonitoring with Vicia root micronucleus test is an efficient way to assess the water quality of this river.

Biological Assay↗

PubMed1999

Capillary electrophoresis enantioseparation of drugs using beta-cyclodextrin polymer: intramolecular synergistic effect.

Enantiomers of eight basic compounds of pharmaceutical interest were studied by capillary electrophoresis (CE) using a soluble cyclodextrin (CD) polymer and native CD as chiral selectors. The effects of the polymer concentration and the pH of the buffer solution on resolution were examined. It was found that the beta-CD polymer shows higher stereoselectivity than its parent cyclodextrin. Such improvement is due to the structural difference between beta-CD and beta-CD polymer. These results suggested the existence of an intramolecular synergistic effect in CE.

Buffers↗

PubMed1999

13C selective polarization and spin diffusion in a lipid bilayer-bound polypeptide by solid-state NMR.

While (15)N solid-state NMR has proven to be very advantageous for the development of structural biological methods, (13)C spectroscopy has increased sensitivity and spectral dispersion. However, large natural abundance signals and homonuclear dipolar interactions pose significant problems. Here we have used a pair of (13)C-labeled sites in a lipid-solubilized polypeptide to show the selective polarization can be used in combination with spin diffusion to achieve simplified spectra. Both unoriented and oriented samples have been used, with the latter providing a well-resolved homonuclear dipolar splitting.

Carbon Isotopes↗

PubMed1999

Solid-state NMR and hydrogen-deuterium exchange in a bilayer-solubilized peptide: structural and mechanistic implications.

Hydrogen-deuterium exchange has been monitored by solid-state NMR to investigate the structure of gramicidin M in a lipid bilayer and to investigate the mechanisms for polypeptide insertion into a lipid bilayer. Through exchange it is possible to observe 15N-2H dipolar interactions in oriented samples that yield precise structural constraints. In separate experiments the pulse sequence SFAM was used to measure dipolar distances in this structure, showing that the dimer is antiparallel. The combined use of orientational and distance constraints is shown to be a powerful structural approach. By monitoring the hydrogen-deuterium exchange at different stages in the insertion of peptides into a bilayer environment it is shown that dimeric gramicidin is inserted into the bilayer intact, i.e., without separating into monomer units. The exchange mechanism is investigated for various sites and support for a relayed imidic acid mechanism is presented. Both acid and base catalyzed mechanisms may be operable. The nonexchangeable sites clearly define a central core to which water is inaccessible or hydroxide or hydronium ion is not even momentarily stable. This provides strong evidence that this is a nonconducting state.

Binding Sites↗

PubMed1999

Hahn-echoes from 14N in solids by the stray-field method: prospects for imaging using Long Echo-Train Summation.

We have observed Hahn-echoes resulting from Powles-Mansfield pulse-sequences for a variety of nitrogen containing solids which exhibit a range of 14N electric quadrupole coupling constants (Cq) from 0 to 4.9 MHz. Long echo-decays were frequently obtained which allowed the collection of many echoes in one echo-train, so that the method of Long Echo-Train Summation (LETS), could be used to accumulate signal. A one-dimensional STRAFI-profile is shown for solid ammonium nitrate. The spatial resolution is discussed as a function of Cq.

Ammonium Chloride↗

PubMed1999

Solid-state nuclear magnetic resonance investigation of protein and polypeptide structure.

Solid-state nuclear magnetic resonance (NMR) is rapidly emerging as a successful and important technique for protein and peptide structural elucidation from samples in anisotropic environments. Because of the diversity of nuclei and nuclear spin interactions that can be observed, and because of the broad range of sample conditions that can be studied by solid-state NMR, the potential for gaining structural constraints is great. Structural constraints in the form of orientational, distance, and torsional constraints can be obtained on proteins in crystalline, liquid-crystalline, or amorphous preparations. Great progress in the past few years has been made in developing techniques for obtaining these constraints, and now it has also been clearly demonstrated that these constraints can be assembled into uniquely defined three-dimensional structures at high resolution. Although much progress toward the development of solid-state NMR as a routine structural tool has been documented, the future is even brighter with the continued development of the experiments, of NMR hardware, and of the molecular biological methods for the preparation of labeled samples.

Anisotropy↗

PubMed1999

Correlations of structure, dynamics and function in the gramicidin channel by solid-state NMR spectroscopy.

The high resolution structure of the gramicidin A channel has been determined in a lamellar phase environment using solid-state NMR spectroscopy. While the fold is similar to previous characterizations, channel function is exquisitely dependent on structural detail. There is essentially no structural change upon cation binding and no significant change in dynamics. The cations appear to be adequately solvated in their binding site by no more than two carbonyls and no fewer than three water molecules at any one time. The relatively large number of water molecules allows for geometric flexibility and little selectivity among monovalent cations. However, the dehydration energies of cations clearly explain the selectivity for monovalent versus divalent cations. Moreover, the binding site is shown to be delocalized, resulting in a shallow potential energy well so that efficient cation conductance can be realized. The potential energy barrier at the bilayer centre has been shown to be rate limiting under certain circumstances through a correlation between conductance and the electrostatic interactions between cations at the gramicidin monomer-monomer junction and the indole dipole moments at the lipid-water interface. The dynamics are functionally important. The time-scale for carbonyl fluctuations about the C alpha-C alpha axis and kinetic rates for cation movement in the channel are the same, suggesting a correlation between molecular dynamics and kinetics. These functional correlations will be described in light of the recent K+ channel structure and the biological challenge to achieve both selectivity and efficiency.

Amino Acid Sequence↗

PubMed1999

[The application of expanded polytetrafluoroethylene in the treatment of facial depression with facial nerve palsy].

OBJECTIVE: In order to investigate the effect of expanded polytetrafluoroethylene (e-PT-FE) in repair of facial depression. METHODS: From February 1997 to July 1998. The e-PTFE was used as a filling and suspending material for facial depression and facial nerve palsy in 6 cases. They were followed up for 2-16 months. RESULTS: After filling of the facial depression, the deformed side of the face became symmetrical to that of contralateral side, and those following the suspending technique using this material the affected eyelids could close completely and the oral corners were symmetrical in its static status. CONCLUSION: The expanded PTFE was a safe, biocompatible and easily applied material, especially served as a filling or suspending material in the repair of facial depression with facial nerve palsy.

Adolescent↗