Biomedical subjects

J Kong

Publications and source records attributed to J Kong.

At least 37 records · Page 2Linked to original sources

PubMed2001

[The chemical decomposition of glutamine and its effect on hybridoma cell culture].

The chemical decomposition of glutamine is a first-order reaction. Its reaction constants under storage and culture conditions were determined as 0.0009 h-1 and 0.0032 h-1 respectively. Batch culture of hybridoma cell C50 with different initial contents of glutamine helped to understand its real metabolic characteristic. The results show that when the initial concentration of glutamine is lower than 5 mmol/L, more than 80% is used by cells. And the lower the initial content, the more being used. As the initial glutamine concentration increases, the ratio of its utilization decreases. When it reaches 10 nmol/L, the ratio decreases dramatically.

Ammonia↗

PubMed2001

[Adrenomedullin and hypoxia-induced pulmonary hypertension].

OBJECTIVE: To study adrenomedullin (AM) in rat and human lung during hypoxia-induced pulmonary hypertension. METHODS: Normobaric hypoxic pulmonary hypertension animal model was adopted, pulmonary artery pressure and RVdp/dt were measured. The changes of AM contents in blood and bronchoalveolar lavage fluid were studied. The plasma levels of AM in patients with pulmonary hypertension were measured. RESULTS: During hypoxia, pulmonary artery pressure, RVdp/dt, AM contents in blood and bronchoalveolar lavage fluid in rats increased. Plasma levels of AM were significantly higher in patients with pulmonary hypertension than in the control subjects. CONCLUSIONS: AM may play an important role in developing hypoxic pulmonary hypertension in rats and human. The increase of AM level is in proportion to the extent of pulmonary hypertension.

Adrenomedullin↗

PubMed2001

[Expression of adhesion molecules on CD34(+) hematopoietic precursor cells from normal human bone marrow, cord blood and mobilized blood].

OBJECTIVE: To investigate the expression of adhesion molecules on CD(34)(+) hematopoietic precursor cells from normal human bone marrow, cord blood and mobilized peripheral blood, and the mechanism of peripheral blood precursor cells mobilization. METHODS: CD(34)(+) hematopoietic cells were separated from bone marrow, cord blood and mobilized peripheral blood by CD(34) MultiSort Kit immunomagnetic bead system. The purity was examined by FACSort. The CD(34)(+) cells and post-short-term cultured CD(34)(+) cells were labeled in an indirect immuno-fluorescence procedure with adhesion molecules CD(11a), CD(18), CD(44), CD(49d), CD(54), CD(58) and CD(62L) monoclonal antibodies and assayed by FACSort. RESULTS: The expression of CD(11a), CD(18), CD(49d), CD(54), CD(58) and CD(62L) of mobilized peripheral blood CD(34)(+) cells was lower than that of bone marrow ones, especially for CD(49d) and CD(62L). Similar to mobilized peripheral blood CD(34)(+) cells, cord blood CD(34)(+) cells also showed a lower expression of CD(11a), CD(18), CD(44), CD(49d), CD(62L) than that of bone marrow ones, especially for CD(62L), but expression of CD(54) was higher than that of bone marrow and mobilized peripheral blood CD(34)(+) cells. CONCLUSION: The expressions of cell adhesion molecules on CD(34)(+) cells in normal bone marrow, cord blood and mobilized peripheral blood were quite different, the mechanism of peripheral blood precursors mobilization might be related to downregulation of cell adhesion molecule expression.

Antigens, CD34↗

PubMed2001

[Cloning and structure analysis of a restriction and modification system, LlaBIII from Lactococcus lactis subsp. cremoris W56].

A 22.4 kb naturally occurring plasmid pJW566, isolated from L. lactis W56, was found to encode an R/M system named LlaBIII. The LlaBIII R/M system was isolated on a chloramphenicol resistant derivative of plasmid pJW566, resulting in a plasmid pJK1. Subcloning analysis showed that the LlaBIII determinant was located on a 5 kb HindIII-Sph I fragment. The fragment was sequenced. It contained a single open reading frame (ORF), corresponding to a protein of 1584 or 1576 aa. In the deduced amino acid sequence seven helicase motifs characteristic of endonuclease type I and type III and a conserved catalysis motif X in the R subunits of type I R/M systems were located in the N-terminus, followed by four conserved motifs found in DNA N6-adenine methyltransferases. The C-terminus of the deduced amino acid sequence showed no homology to known R/M systems. Therefore, this polypeptide encoded by LlaBIII is a multifunctional protein possessing putative DNA recognition, methylation and restriction activities.

Cloning, Molecular↗

PubMed2001

[The characterization of pJW566 from L. Lactis subsp. cremoris W56].

The plasmid pJW566 was isolated from L. lactis subsp. cremoris W56, one strain for Danish chadder mixed starter cultures. The strain containing plasmid pJW566 showed resistance against three common phages species 936, c2 and P335 worldwide. It was found that pJW566 encoded for an restriction and modification system, and showed strong resistance to phage CHCP412 when it was introduced into the industrial strain L. lactis CHCC2281 in milk medium. The endonuclease activity analysis indicated that the endonuclease required Mg2+, ATP, and was stimulated by AdoMet.

Animals↗

PubMed2001

[Continuous production of nisin by calcium alginate-immobilized Lactococcus lactis subsp. lacits SM526].

The attempts were made to produce nisin by immobilized cells of Lactococcus lactis subsp. lactis SM526 entrapped in calcium alginate beads. The results showed that the immobilized cell beads were intact for 90 hr under 2% of calcium alginate in 10 mmol/L CaCl2 solution. The physical stability of beads was improved by removing phosphate, citrate and acetate salts supplied in SYS3 medium. Repeated-batch fermentation utilizing immobilized cells were performed in mSYS3 medium without agitation at 32 degrees C, the concentration of nisin produced during the third cycles increased to 850 IU/mL, and the beads were still intact with little cell leakage. The immobilized beads were loaded into a sterilized glass column to continuous fermentation, nisin concentration increased to 1150 IU/mL, as high as that obtained in free-cell fermentation, and the high productivity was stable for up to 70 h under a constant supplied of the fresh mSYS3 medium.

Alginates↗

PubMed2000

Modulated chemical doping of individual carbon nanotubes.

Modulation doping of a semiconducting single-walled carbon nanotube along its length leads to an intramolecular wire electronic device. The nanotube is doped n-type for half of its length and p-type for the other half. Electrostatic gating can tune the system into p-n junctions, causing it to exhibit rectifying characteristics or negative differential conductance. The system can also be tuned into n-type, exhibiting single-electron charging and negative differential conductance at low temperatures. The low-temperature behavior is manifested by a quantum dot formed by chemical inhomogeneity along the tube.

Journal Article↗

PubMed2000

A set of canine interrepeat sequence PCR markers for high-throughput genotyping.

One hundred and sixteen interspersed repetitive DNA sequence (IRS)-PCR markers have been developed and characterized from Canis familiaris for high-throughput filter-based genotyping. We present a detailed analysis of markers produced by amplification using primers directed to the conserved regions of the C. familiaris short interspersed nuclear element (Can-SINE). The majority of IRS-PCR markers developed were moderately to highly polymorphic with mean heterozygosity (HET) and polymorphism information content (PIC) values of approximately 0.6. The HET value for 22.3% of the markers exceeded 0.7. We also demonstrate that sequence variation of Can-SINEs between breeds is significant and also represents a rich source of polymorphisms. Mapping of 73 of the markers to the existing integrated linkage-radiation hybrid map enriches the map as well as establishes the utility of the markers. The significance and utility of this new class of IRS-PCR Can-SINE-based markers for high-throughput genotyping is discussed. This method can also be extended to other species that are currently map-poor but have a sufficiently high density of SINEs to allow IRS-PCR.

Animals↗

PubMed2000

Event-related potential N270 is elicited by mental conflict processing in human brain.

We recorded event-related potentials (ERPs) in 15 subjects in order to elicit a N270 of arithmetic conflict. Subjects calculated an arithmetic problem and matched their calculation result to an answer digit. They pressed a button when the presented digit is a true answer (condition 1) and pressed another button when the answer is false (condition 2). ERP components of P90, N130, P180, N200 and late positive component (LPC) were recorded in condition 1. In condition 2, N270 was elicited between N200 and LPC and it peaked at approximately 270 ms (268.6 +/- 29.0 ms at Cz). The peak latency of LPC in condition 2 (405.7 +/- 51.3 ms) is significantly delayed than condition 1 (307.5 +/- 22.7 ms). N270 reflects the endogenous conflict processing in human brain.

Adult↗

PubMed2000

Probing trace phenols based on mediator-free alumina sol--gel-derived tyrosinase biosensor.

A novel tyrosinase biosensor has been developed for the subnanomolar detection of phenols, based on the immobilization of tyrosinase in a positively charged Al2O3 sol-gel membrane on a glassy carbon electrode. It has been found that Al2O3 sol-gel is perfectly beneficial to the immobilization of tyrosinase, because it not only possesses the general advantages of sol-gel but it also is an effective promoter of the biosensor. The large microscopic surface area, porous morphology, and hydrophilic property of the sol-gel matrix result in high enzyme loading, and the enzyme entrapped in this matrix retains its activity to a large extent. The Al2O3 sol-gel-containing surface also displays an intrinsic electrocatalytic o-quinone response and, hence, offers a high-sensitivity (127 microA mM(-1)) monitoring of phenols. The detection limit is 0.2 nM at a signal-to-noise ratio of 3, the response time is less than 4 s reaching 95% of the steady-state value, and 70% of the activity is retained after 3 months.

Biosensing Techniques↗

PubMed2000

Human brain sub-systems for discrimination of visual shapes.

To investigate whether stereo and plane visual shapes are processed in the same brain system, participants were instructed to discriminate whether two visual stimuli presented in sequence were identical and event-related potential (ERP) was recorded from their scalp. The first (S1) and the second stimuli (S2) were the same stereo shapes in condition 1, but were different in condition 3. They were the same plane shapes in condition 2, but different in condition 4. A negative component (N270) was recorded in condition 3 and 4, which showed the maximal amplitude in the right posterior scalp in condition 3 and in the anterior scalp in condition 4. A different cognition mechanism is involved in the processing of non-matched stereo and plane visual shapes.

Adult↗

PubMed2000

Reversible electromechanical characteristics of carbon nanotubes under local-probe manipulation

The effects of mechanical deformation on the electrical properties of carbon nanotubes are of interest given the practical potential of nanotubes in electromechanical devices, and they have been studied using both theoretical and experimental approaches. One recent experiment used the tip of an atomic force microscope (AFM) to manipulate multi-walled nanotubes, revealing that changes in the sample resistance were small unless the nanotubes fractured or the metal-tube contacts were perturbed. But it remains unclear how mechanical deformation affects the intrinsic electrical properties of nanotubes. Here we report an experimental and theoretical elucidation of the electromechanical characteristics of individual single-walled carbon nanotubes (SWNTs) under local-probe manipulation. We use AFM tips to deflect suspended SWNTs reversibly, without changing the contact resistance; in situ electrical measurements reveal that the conductance of an SWNT sample can be reduced by two orders of magnitude when deformed by an AFM tip. Our tight-binding simulations indicate that this effect is owing to the formation of local sp3 bonds caused by the mechanical pushing action of the tip.

Journal Article↗

PubMed2000

Intrinsic electrical properties of individual single-walled carbon nanotubes with small band gaps

Individual single-walled carbon nanotubes (SWNT) exhibiting small band gaps on the order of 10 meV are observed for the first time in electron transport measurements. Transport through the valence or conduction band of a small-gap semiconducting SWNT (SGS-SWNT) can be tuned by a nearby gate voltage. Intrinsic electrical properties of the Ohmically contacted SGS-SWNT are elucidated. An SGS-SWNT exhibits metal- or semiconductorlike characteristics depending on the Fermi level position in the band structure.

Journal Article↗

PubMed2000

Controllable reversibility of an sp(2) to sp(3) transition of a single wall nanotube under the manipulation of an AFM tip: A nanoscale electromechanical switch?

A simulation of the deflection of a single wall nanotube under the manipulation of an atomic force microscope tip revealed the key feature characterizing the deformation at relatively small bending angles to be a reversible transition from sp(2) to sp(3) bonding configurations in the bending region, leading to a 2 orders of magnitude reduction in conductance consistent with our most recent experimental observation. A local analysis elucidating the underlying physics of the findings is also discussed.

Journal Article↗

PubMed2000

Event-related brain potentials elicited by a number discrimination task.

To study the number cognition process, we recorded event-related potentials (ERPs) in 14 subjects when they were indicating whether a number pair was the same or not. The two numbers given in sequence were either the same (condition 1) or different (condition 2). After 270 ms following the onset of the second stimulus in condition 2, a negative component N270 was recorded on the scalp with the most negative amplitude at the central and occipital areas. Hemispheric asymmetry was not observed in the potential. This negative component is considered to reflect the mismatching process for numbers in the brain.

Adult↗

PubMed2000

Overexpression of neurofilament subunit NF-L and NF-H extends survival of a mouse model for amyotrophic lateral sclerosis.

Mutations in superoxide dismutase 1 (SOD1) cause amyotrophic lateral sclerosis (ALS) in a subset of patients. Neurofilaments (NFs), the most abundant protein in motoneurons, may play a role in motoneuron degeneration. To investigate this role, we crossed transgenic mice expressing SOD1 mutant G93A (G93A mice) with mice overexpressing mouse neurofilament subunit H (H mice) or L (L mice). G93A mice overexpressing either NF-L or NF-H developed ALS later and survived longer than the G93A mice on a wild type background. These results illustrate a beneficial role of neurofilaments in ALS and call into question of several hypotheses regarding the role of neurofilaments in the development of ALS.

Amyotrophic Lateral Sclerosis↗

PubMed2000

Nanotube molecular wires as chemical sensors

Chemical sensors based on individual single-walled carbon nanotubes (SWNTs) are demonstrated. Upon exposure to gaseous molecules such as NO(2) or NH(3), the electrical resistance of a semiconducting SWNT is found to dramatically increase or decrease. This serves as the basis for nanotube molecular sensors. The nanotube sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature. Sensor reversibility is achieved by slow recovery under ambient conditions or by heating to high temperatures. The interactions between molecular species and SWNTs and the mechanisms of molecular sensing with nanotube molecular wires are investigated.

Journal Article↗

PubMed2000

An amperometric biosensor based on the coimmobilization of horseradish peroxidase and methylene blue on a beta-type zeolite modified electrode.

A new biosensor for the amperometric detection of hydrogen peroxide was developed based on the coimmobilization of horseradish peroxidase (HRP) and methylene blue on a beta-type zeolite modified glassy carbon electrode without the commonly used bovine serum albumin-glutaraldehyde. The intermolecular interaction between enzyme and zeolite matrix was investigated using FT-IR. The cyclic voltammetry and amperometric measurement demonstrated that methylene blue co-immobilized with HRP in this way displayed good stability and could efficiently transfer electrons between immobilized HRP and the electrode. The sensor responded rapidly to H2O2 in the linear range from 2.5 x 10(-6) to 4.0 x 10(-3) M with a detection limit of 0.3 microM. The sensor was stable in continuous operation.

Biosensing Techniques↗