Biomedical subjects

J Kong

Publications and source records attributed to J Kong.

At least 19 recordsLinked to original sources

PubMed2004

Diode-end-pumped 4.2-W continuous-wave Yb:Y2O3 ceramic laser.

We report on an efficient diode-end-pumped polycrystalline Yb:Y2O3 ceramic laser. Continuous-wave output power of 4.2 W at 1078 nm was obtained under pump power of 19.5 W. The corresponding slope efficiency was 29%. The beam quality factor (M2) at full pump power was measured to be 1.63. The threshold wavelengths of the laser at various output couplings were also investigated. It was found that the threshold wavelengths shifted approximately 5 nm when the reflectivity of the output coupler changed from 90% to 99.9%, as caused by the strong reabsorption effect in the ceramic sample.

Journal Article↗

PubMed2004

Random-wavelength solid-state laser.

The spectral properties of a diode-pumped Yb:Y2O3 ceramic laser are reported. We show experimentally that the instantaneous emission wavelengths of the laser change randomly with time, whereas its emission has fixed well-defined transverse modes. The central wavelength of the laser emission also shifts prominently with the increase of intracavity light intensity. It is found that the spectral properties of the laser can be explained well based on the strong reabsorption of light in the gain medium.

Journal Article↗

PubMed2003

EGF stimulates growth by enhancing capacitative calcium entry in corneal epithelial cells.

In rabbit corneal epithelial cells (RCEC), we determined whether capacitative calcium entry (CCE) mediates the mitogenic response to epidermal growth factor, EGF. [Ca2+]i was measured with single-cell fluorescence imaging of fura2-loaded RCEC. EGF (5 ng/ml) maximally increased [Ca2+]i 4.4-fold. Following intracellular store (ICS) calcium depletion in calcium-free medium with 10 microM cyclopiazonic acid (CPA) (endoplasmic reticulum calcium ATPase inhibitor), calcium addback elicited plasma membrane Ca2+ influx as a result of activation of plasma membrane store operated channel (SOC) activity. Based on Mn2+ quench measurements of fura2 fluorescence, 5 ng/ml EGF enhanced such influx 2.3-fold, whereas with Rp-cAMPS (protein kinase A inhibitor) plus EGF it increased by 5.3-fold. In contrast, SOC activation was blocked with 100 microM 2-aminoethyldiphenylborate (2-APB, store-operated channel inhibitor). During exposure to either 50 microM UO126 (MEK-1/2 inhibitor) or 10 microM forskolin (adenylate cyclase activator), 5 ng/ml EGF failed to affect [Ca2+]i. RT-PCR detected gene expression of: 1) transient receptor potential (TRP) protein isoforms 1, 3, 4, 6 and 7; 2) IP3R isoforms 1-3. Immunocytochemistry, in conjunction with confocal and immunogold electron microscopy, detected plasma membrane localization of TRP4 expression. Inhibition of CCE with 2-APB and/or CPA, eliminated the 2.5-fold increase in intracellular [3H]-thymidine incorporation induced by EGF. Taken together, CCE in RCEC mediates the mitogenic response to EGF. EGF induces CCE through its stimulation of Erkl/2 activity, whereas PKA stimulation suppresses these effects of EGF. TRP4 may be a component of plasma membrane SOC activity, which is stimulated by ICS calcium depletion.

Animals↗

PubMed2002

Lentiviral transduction of green fluorescent protein in retinal epithelium: evidence of rejection.

This paper demonstrates lentiviral transduction of the humanized form of the Aequoria victoria gene for green fluorescent protein (GFP) into human fetal retinal pigment epithelium (RPE) in vitro and rabbit RPE in vivo. In vitro GFP expression of cultured human fetal RPE begins within two to three days after 12-16 h of maintained exposure to the virus at titers of 10(8)-10(9) infectious units (IU)/ml. Both stationary and dividing cells are transduced using a lenti viral vector with a cytomegalovirus (CMV) promoter. Expression remains stable for at least three to four months without evidence of toxicity and continues through cell division. In vivo expression is followed non-invasively in rabbit eye using a scanning laser ophthalmoscope (SLO), which can detect single fluorescing retinal cells. In vivo expression begins within a few days after a viral solution is introduced into the subretinal space. A solution of 10(9) IU/ml produces fluorescence within three to four days. Less concentrated solutions lead to slower and less expression. No expression is detectable at concentrations of 10(6) IU/ml. Within one to two weeks after introduction of the viral solution, there is evidence of rejection seen by SLO as a loss of GFP fluorescence and disruption of the RPE. Histology shows damage to the RPE layer and monocytic cell infiltrates in the choroid and subretinal space within the area receiving the viral solution. Strong GFP expression leads to rejection within two weeks. With less expression, rejection is delayed and in some cases undetectable for at least six months. If the GFP gene is not included in the viral vector or if the viral concentration is insufficient to produce detectable GFP expression, rejection is not seen. Using a rhodopsin promoter or injecting the virus intra rather than subretinally produces weak expression and no rejection. Lentivirus can induce expression of a foreign gene in the RPE. Viral induced transduction and GFP expression have no effect on the viability of the RPE in vitro. Continued expression of GFP after cell division implies chromosomal integration of the gene. In vivo expression of GFP in RPE encounters rejection. Rejection may not occur with low GFP expression. The latter occurs with low viral titers, a rhodopsin promoter or intra-retinal injection of viral solution. The results are relevant to gene therapy in retina when gene transduction leads to the expression of foreign proteins.

Animals↗

PubMed2002

The ability of the plasmid-encoded restriction and modification system LlaBIII to protect Lactococcus lactis against bacteriophages.

AIMS: To investigate the potential of the plasmid-encoded restriction and modification (R/M) system LlaBIII to protect Lactococcua lactis against bacteriophages during milk fermentations. METHODS AND RESULTS: The R/M system LlaBIII on plasmid pJW566 was cloned with a chloramphenicol cassette, resulting in plasmid pJK1. When introduced into L. lactis strains, pJK1 conferred increased phage resistance against the three most common lactococcal phage species 936, c2, and P335 and three unclassified industrial phages. The growth of the strains in RSM was not affected by the presence of plasmid pJK1. CONCLUSIONS: The plasmid-encoded R/M system LlaBIII has great ability to protect L. lactis strains against bacteriophages in milk fermentations. SIGNIFICANCE AND IMPACT OF THE STUDY: This study evaluates the ability of the LlaBIII R/M system to function as a phage defence mechanism which is an essential step prior to considering utilizing it for improving starter cultures.

Bacterial Proteins↗

PubMed2002

Breast conservation treatment in Hong Kong-early results of 203 patients: retrospective study.

OBJECTIVE: To study the clinical outcomes of patients with invasive or non-invasive breast cancer after breast conservation treatment. DESIGN: Retrospective study. SETTING: Clinical oncology department of a public hospital, Hong Kong. PATIENTS: Two hundred and three patients who received postlumpectomy radiotherapy at the Pamela Youde Nethersole Eastern Hospital between January 1994 and June 1999. INTERVENTIONS: Adjuvant radiotherapy with or without systemic adjuvant treatment. MAIN OUTCOME MEASURES: Actuarial local control rate, progression-free survival rate, disease-specific survival rate, and cosmetic score. RESULTS: The median follow-up was 3.5 years. Two of the 25 patients with carcinoma in situ only developed local recurrence; the 5-year actuarial local control rate was 91.3%. Among the 178 patients with invasive cancer, seven had a local recurrence and 12 developed distant metastases without local failure. The 5-year actuarial local control, progression-free survival, and disease-specific survival rates for patients with invasive cancer were 95.5%, 85.8%, and 95.2%, respectively. The risk of local recurrence was significantly increased for younger patients (age <40 years) and those with positive final margins. Cosmetic scores were rated good to excellent by 95.6% of patients. CONCLUSIONS: The early clinical outcomes of these patients are comparable to those in large overseas trials, which have demonstrated the equivalence of mastectomy and breast conservation treatment in terms of survival. In addition to mastectomy, with or without breast reconstruction, breast conservation treatment should be offered as an alternative to suitable Chinese women. To maximise local control, further excision or mastectomy is recommended for patients with positive final margins.

Adult↗

PubMed2001

Quantum interference and ballistic transmission in nanotube electron waveguides.

The electron transport properties of well-contacted individual single-walled carbon nanotubes are investigated in the ballistic regime. Phase coherent transport and electron interference manifest as conductance fluctuations as a function of Fermi energy. Resonance with standing waves in finite-length tubes and localized states due to imperfections are observed for various Fermi energies. Two units of quantum conductance 2G(0) = 4e(2)/h are measured for the first time, corresponding to the maximum conductance limit for ballistic transport in two channels of a nanotube.

Electron Transport↗

PubMed2001

Protein kinase C is involved in the regulation of hairless mRNA expression during mouse keratinocyte differentiation.

The hairless (hr) gene is a putative transcriptional factor whose mutations lead to hair loss in animals and humans. As a step toward understanding the role of the hr gene, we investigated the expression of hr mRNA in mouse keratinocyte differentiation. Treatment of mouse primary keratinocyte cultures with phorbol-12-myristate-13-acetate (PMA) reduced DNA synthesis and sequentially induced an up-regulation of p21Cip1/WAF1 (p21), hr and involucrin (inv) mRNAs in a time-dependent fashion, suggesting that an increase in hr gene expression is associated with keratinocyte differentiation. This up-regulation was blocked by the RNA synthesis inhibitor actinomycin D. However, an increase in hr mRNA, but not in inv mRNA, was seen in cells treated with the protein synthesis inhibitor cycloheximide, suggesting that new protein synthesis is involved in the suppression of hr transcription or in the degradation of hr mRNA in the steady state. The up-regulation of hr mRNA expression by PMA was blocked by the protein kinase C (PKC) inhibitor, GF109203X. These data indicate that PKC activation is involved in the up-regulation of hr mRNA expression during mouse keratinocyte differentiation.

Animals↗

PubMed2001

Enhancement of conflict processing activity in human brain under task relevant condition.

To investigate the working mechanism of the conflict processing system, pairs of colored numbers were sequentially presented on a screen to subjects. They were asked to determine if the magnitude or the color of the two numbers was identical. Event-related potentials (ERPs) were recorded at the same time. A negative potential peaking at 270 ms (N270) after the onset of the second number (S2) was elicited when S2 conflicted with the first number (S1) in task-relevant and (or) irrelevant attribute conflicts. The mean amplitude of the N270 was more negative in task relevant conflict than in irrelevant conflict. Therefore, the conflict processing activity can be initiated independently of the task, but is enhanced in task relevant conflict.

Adult↗

PubMed2001

Dynamic restoration of dystrophin to dystrophin-deficient myotubes.

Dystrophin domains are observed in myoblast transplantation experiments and in muscle fibers after somatic reversion in human Duchenne and mdx mouse muscular dystrophy. However, the formation and evolution of dystrophin-positive domains are not well established. Using a muscle satellite cell coculture system, we examined the dynamic restoration of dystrophin expression in dystrophin-deficient myotubes. The dystrophin-positive domains around source nuclei were clearly identified in hybrid myotubes. The occurrence of dystrophin domains was higher in myotubes differentiated from cocultures with a low concentration of normal wild-type satellite cells in relation to dystrophin-deficient satellite cells. At higher seeding ratios, the domain feature of dystrophin expression was more transitory and decreased as myotubes differentiated over time in culture. The average domain size initially increased with the addition of new nuclei by fusion early after differentiation of cocultures. However, separating dystrophin-positive domains according to their number of dystrophin-expressing contributory nuclei showed that diffusion of dystrophin contributed to domain elongation, even in early myotubes and later without fusion of additional nuclei. Diffusion occurred for all domains of one to six wild-type nuclei, and the diffusion rate was higher in domains with larger numbers of nuclei. This dynamic domain feature of dystrophin expression was also related to restoring the organization of dystrophin-associated proteins and acetylcholine receptors to hybrid myotubes. Factors regulating domain formation and diffusion therefore are important considerations in the design of strategies for both myoblast transplantation and gene therapy of Duchenne muscular dystrophy.

Animals↗

PubMed2001

NMDA receptor blockage protects against permanent noise-induced hearing loss but not its potentiation by carbon monoxide.

While a clear role has been proposed for glutamate as a putative neurotransmitter at the inner hair cell type I spiral ganglion cell synapse, the possible role of excessive glutamate release in cochlear impairment and of NMDA receptors in such a process is uncertain. The present study compares the protective effects of (+)-MK-801, an NMDA receptor antagonist, and the relatively inactive isomer (-)-MK-801 against permanent noise-induced hearing loss (NIHL). The study also asks whether (+)-MK-801 can protect against the NIHL potentiation by carbon monoxide (CO). Rats (n = 6) were exposed to 100-dB, 13.6-kHz octave-band noise for 2 h after receiving injection of (+)-MK-801 hydrogen maleate (1 mg/kg), (-)-MK-801 hydrogen maleate (1 mg/kg), or saline. Other groups of animals were exposed to the combination of noise and CO (1200 ppm) after receiving (+)-MK-801 or saline. Additional subjects received (+)-MK-801, saline or CO exposure alone. Compound action potential (CAP) threshold sensitivities were compared 4 weeks after the exposures. The results show significant protection by (+)-MK-801 against the permanent CAP threshold elevation induced by noise alone, but no protective effect of (-)-MK-801. (+)-MK-801 produced limited protection against threshold shifts induced by the combination of noise and CO. Outer hair cell (OHC) loss was not protected by (+)-MK-801 administration. The data suggest that NMDA receptor stimulation may play a role in NIHL resulting from fairly mild noise exposure. The data do not support a role for NMDA receptor stimulation in the potentiation of NIHL that results from simultaneous exposure to CO and noise.

Action Potentials↗

PubMed2001

Characterization for didodecyldimethylammonium bromide liquid crystal film entrapping catalase with enhanced direct electron transfer rate.

Direct electrochemistry for catalase (CAT) embedded in the liquid crystal film of didodecyldimethylammonium bromide (DDAB) was investigated at pyrolytic graphite (PG) electrode by voltammetric methods. The reduction reaction involved the redox couple in CAT, i.e. FeIII/FeII couple. The electron transfer between the incorporated CAT and PG electrode was found to be greatly enhanced by DDAB. The heterogeneous electron transfer rate constant k(s) was fitted as 3.0 +/- 0.4 s(-1) using the nonlinear regression analysis of the square wave voltammograms at a series of pulse heights. The pH dependence of the formal potential for CAT in DDAB film was 57 mV/pH, which suggested one-proton-transfer together with a one-electron reaction. Visible absorption and reflectance-absorbance infrared (RAIR) spectra inferred the similar heme environment of CAT in DDAB film to its native status. Circular dichroism (CD) results indicated DDAB affected slightly on the second structure of CAT.

Animals↗

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↗