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Biomedical subjects

J W Li

Publications and source records attributed to J W Li.

At least 19 recordsLinked to original sources
PubMed2006

Evolution and molecular epidemiology of H9N2 influenza A viruses from quail in southern China, 2000 to 2005.

H9N2 influenza viruses have become established and maintain long-term endemicity in terrestrial poultry in Asian countries. Occasionally these viruses transmit to other mammals, including humans. Increasing epidemiological and laboratory findings suggest that quail may be an important host, as they are susceptible to different subtypes of influenza viruses. To better understand the role of quail in influenza virus ecology and evolution, H9N2 viruses isolated from quail during 2000 to 2005 were antigenically and genetically characterized. Our results showed that H9N2 viruses are prevalent year-round in southern China and replicate mainly asymptomatically in the respiratory tract of quail. Genetic analysis revealed that both the G1-like and Ck/Bei-like H9N2 lineages were cocirculating in quail since 2000. Phylogenetic analyses demonstrated that most of the isolates tested were double- or multiple-reassortant variants, with four G1-like and 16 Ck/Bei-like genotypes recognized. A novel genotype of G1-like virus became predominant in quail since 2003, while multiple Ck/Bei-like genotypes were introduced into quail, wherein they incorporated G1-like gene segments, but none of them became established in this host. Those Ck/Bei-like reassortants generated in quail have then been introduced into other poultry. These complex interactions form a two-way transmission system between quail and other types of poultry. The present study provides evidence that H9N2 and H5N1 subtype viruses have also exchanged gene segments to generate currently circulating reassortants of both subtypes that have pandemic potential. Continuing influenza virus surveillance in poultry is critical to understanding the genesis and emergence of potentially pandemic strains in this region.

Amino Acid Motifs↗
PubMed2001

[Separation and determination of pseudoephedrine in bufferin cold tablet by capillary electrophoresis with hydropropyl-beta-cyclodextrin as chiral selective reagent].

A method for the separation and analysis of the chiral pseudoephedrine enantiomers using capillary electrophoresis was established. The buffer solution for separation was 25 mmol/L Tris-phosphate, including 38 mmol/L hydropropyl-beta-cyclodextrin with pH value of 2.65. (1S, 2S)(+) Pseudoephedrine in Bufferin Cold tablet was determined. The method has good precision, recovery and linear relationship.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2000

Growth inhibitory effects of ATP and its derivatives on human fibroblasts immortalized with 60Co-gamma rays.

In our previous study (Katayama B et al, Int J Mol Med 2: 603-606, 1998), cell growth inhibition caused by ATP added to cultures was found to be greater in immortalized human fibroblasts than in the normal human fibroblasts. Since it has been reported that ATP affects cells via P2-purinergic receptors, growth inhibitory effects of ATP and its derivatives on immortalized human fibroblasts were investigated in the present study in order to learn what type of receptors are involved in ATP cytotoxicity. The ATP derivatives used in this study were: ATP, ADP, beta, gamma-methyleneadenosine 5'-triphosphate (MeATP), 2' & 3'-o-(4-benzoylbenzoyl) adenosine, triethylammonium salt (BzATP), adenosine 5'-o-(3-thiotriphosphate) (ATPgammaS), 2-methylthioadenosine 5'-triphosphate (2-MeSATP) and UTP. The extent of cytotoxicity induced by these drugs was found to be in the order of: ATP=ADP>ATPgammaS>MeATP=BzATP. On the other hand, neither 2-MeSATP nor UTP showed any cytotoxicity. These findings indicate that ATP may exert the cell growth inhibition by certain kinds of signal transduction via P2x or P2y purinergic receptors which affect intrinsic channels/pores of cell membrane and/or G protein activation. As a result, intracellular elevation in the concentrations of ions such as calcium and potassium, membrane depolarization, loss of endogenous ions/metabolites, and activation of inositol phospholipid-specific phospholipase C may occur. Actually, a dihydropyridine calcium channel blocker, nifedipine, and an ATP-sensitive K+-channel blocker, glybenclamide, reduced the growth inhibitory effects of ATP on the cells to some extent. The growth inhibition caused by ATP was not due to apoptosis or induction of a cyclin/CDK kinase inhibitor, P21.

Adenosine Triphosphate↗
PubMed2000

Frequent expression of soluble Fas and Fas ligand in Chinese stomach cancer and its preneoplastic lesions.

To investigate the frequency and pattern of Fas and FasL expression in the gastric mucosa at different stages of gastrocarcinogenesis, the combined examinations of pathology, immunocytochemistry and Western blot hybridisation were performed on the cancer specimens as well as their preneoplastic and non-cancerous counterparts. The frequencies of Fas and FasL expression were found to be 6.3% (1/16) and 62.5% (10/16) in non-cancerous mucosa, 60% (6/10) and 80% (8/10) in atrophic gastritis, 75% (9/12) and 83% (10/12) in intestinal metaplasia, 100% in both dysplasia Grades II (20/20) and Grade III (15/15) and 4 types of gastric carcinomas (74/74). Two forms of FasL protein in 37 kDa and 26 kDa were detected in all FasL+ cases. Soluble Fas (30 kDa) but not the membrane-type (43 kDa) is predominantly expressed in the Fas+ cases. Our data thus suggest a close correlation of soluble Fas with stomach tumour progression P<0.01. The sFas protein, together with the tumor-derived soluble and membrane FasL, may confer on the transforming and transformed gastric epithelial cells an immune advantage enabling escape from endogenous and exogenous suicide signal(s).

Fas Ligand Protein↗
PubMed2000

Expression of hyaluronan receptors CD44 and RHAMM in stomach cancers: relevance with tumor progression.

Interactions of hyaluronic acid (HA) with its binding proteins CD44 and RHAMM (receptor for HA-mediating motility) have been proposed to be important in promoting tumor progression and dissemination. However, a comparative study of their expression patterns in stomach cancer and its associated lesions is not yet available. To address this issue, the combined examinations of pathology, immunocytochemistry and Western blot hybridization were performed on advanced gastric cancer specimens as well as their preneoplastic and non-cancerous counterparts. Alternative CD44 expression was observed in the gastric mucosa with different lesions. CD44 proteins harboring variant exon 6 (CD44 v6) was detected only in cancer tissues with a total positive rate of 14% (10/74). Intracellular RHAMM molecules in Mr 93000 to 95000 were expressed in 3/31 non-cancerous mucosa. RHAMM detection rates increased along with tumor progression. Irrespective of the differences of gross and morphological pattern, majority (54/74) of cancer cases expressed multiple RHAMM isoforms in Mr 40000-45000, 64000, 70000-73000, 85000 and 93000-95000 with the appearance of cell surface immunocytochemical labeling. Among CD44 variant isoforms, v6 is more relevant with malignant transformation of gastric epithelium. Expression of RHAMM, especially the cell surface variants, is closely correlated with tumor progression (P<0.01). Expression of CD44 and RHAMM may benefit the invasion and metastasis of gastric cancer cells presumably in a reciprocal manner.

Blotting, Western↗
PubMed1999

IkappaB kinase (IKK)-associated protein 1, a common component of the heterogeneous IKK complex.

Activation of the transcription factor NF-kappaB is controlled by the sequential phosphorylation, ubiquitination, and degradation of its inhibitory subunit, IkappaB. We recently purified a large multiprotein complex, the IkappaB kinase (IKK) signalsome, which contains two regulated IkappaB kinases, IKK1 and IKK2, that can each phosphorylate IkappaBalpha and IkappaBbeta. The IKK signalsome contains several additional proteins presumably required for the regulation of the NFkappaB signal transduction cascade in vivo. In this report, we demonstrate reconstitution of IkappaB kinase activity in vitro by using purified recombinant IKK1 and IKK2. Recombinant IKK1 or IKK2 forms homo- or heterodimers, suggesting the possibility that similar IKK complexes exist in vivo. Indeed, in HeLa cells we identified two distinct IKK complexes, one containing IKK1-IKK2 heterodimers and the other containing IKK2 homodimers, which display differing levels of activation following tumor necrosis factor alpha stimulation. To better elucidate the nature of the IKK signalsome, we set out to identify IKK-associated proteins. To this end, we purified and cloned a novel component common to both complexes, named IKK-associated protein 1 (IKKAP1). In vitro, IKKAP1 associated specifically with IKK2 but not IKK1. Functional analyses revealed that binding to IKK2 requires sequences contained within the N-terminal domain of IKKAP1. Mutant versions of IKKAP1, which either lack the N-terminal IKK2-binding domain or contain only the IKK2-binding domain, disrupt the NF-kappaB signal transduction pathway. IKKAP1 therefore appears to mediate an essential step of the NF-kappaB signal transduction cascade. Heterogeneity of IKK complexes in vivo may provide a mechanism for differential regulation of NF-kappaB activation.

Amino Acid Sequence↗
PubMed1999

Cytogenetic characteristics and p53 gene status of human teratocarcinoma PA-1 cells in 407-445 passages.

To study why the human teratocarcinoma cell line PA-1 maintains a stable near-diploid karyotype even after it has been cultured for more than twenty years, p53 gene status of the cell line in 407-445 passages were investigated in detail by DNA sequence analysis and a yeast function status assay. Direct sequence analysis of RT-PCR products showed both wild and mutated bands (p53 codon 239 mutation). Consistent with the above results, the functional assay showed that one allele of the p53 gene was active (wild), while the other was inactive (mutant). In addition, the PA-1 cells expressed the p21 protein to a lesser extent than normal human fibroblasts. Though many lines of evidence have shown that mutant p53 works dominant-negatively, our results suggest that mutation in a p53 allele alone can not induce cytogenetic instability.

Aneuploidy↗
PubMed1998

A new and simple method for concentration of enteric viruses from water.

A new type of electropositive filter media particle was tested to adsorb bacteriophage f2 and enteric viruses from tap water. 3 x nutrient broth (pH 7.2) was used to elute the adsorbed viruses, and the eluate was reconcentrated by polyethylene glycol (Mw 6000) precipitation with a final concentration of 10% (wt./vol.). The adsorption of bacteriophage was reliable and efficient, and not affected by the pH value, temperature, turbidity and organic materials in water. This method gave a recovery of Polio 1 virus 96.0% for small-volume tap water; 88.7% for large-volume water; and gave a comparable recovery of HAV, Coxsackie B3 and Echo 7 from tap water. The concentration method need not acidify virus-containing water, add exogenous multivalent cation salts, or require expensive equipment.

Adsorption↗
PubMed1998

ATP inhibition of proliferation of immortalized human fibroblasts is greater than that of normal human diploid fibroblasts.

It is known that cancers develop by a multi-step process. Normal cells are first immortalized, and then transformed into tumorigenic cells. Normal human cells are very rarely immortalized, but once they are, they are relatively easily transformed into tumorigenic cells. This indicates that the immortalization step plays a critical part in the development of human cancers. Thus, elucidation of the mechanisms of this step would shed light on the process of carcinogenesis in human cells. To understand the causes of immortalization, it is important to determine the differences in cellular phenotype between immortalized and normal human cells. In this study, we found that immortalized human fibroblasts were more sensitive to the growth inhibitory effects of ATP than normal human fibroblasts. ADP was as effective as ATP, but AMP, adenosine, and phosphoric acid were not. These results indicate that a high-energy bound of ATP and ADP may contribute to the growth inhibition of the cells. When the immortalized cells were pulse-labeled with [32P]-ATP, 30-, 31-, 33- and 40-kDa membrane fraction proteins were more prominently labeled in the immortalized cells than in the normal cells. At present, the characteristics of these proteins are being investigated.

Adenosine↗
PubMed1995

Relation between age-related changes in hyper-emotionality and serotonergic neuronal activities in the rat limbic system.

To examine the relationship between higher concentrations of 5-HT and 5-HIAA in the aged rat brain and their hyper-emotionality, behavioral and neurochemical studies were performed. In the behavioral studies, under novel circumstances, the aged rats showed an significant increase in defecation. Furthermore, their locomotor activity was much less than that of young rats, and the numbers of head-dips of aged rats were significantly decreased compared to those of young rats. In the neurochemical studies, the concentrations of 5-HT and 5-HIAA in the limbic system (e.g., hippocampus, amygdala and septal area) of aged rats were much higher than those of young rats (P < 0.001) under normal conditions. The possibility that the hyper-emotionality of aged rats might be related to the hyper-activities of serotonergic neurons in their limbic system were taken into consideration when the results were analyzed.

Aging↗
PubMed1994

Polylysine domain of K-ras 4B protein is crucial for malignant transformation.

Previous studies have shown that posttranslational modifications are required for both oncogenic K-ras 4B protein membrane binding and transforming activity. In addition, Hancock et al. [Hancock, J. F., Patterson, H. & Marshall, C. J. (1990) Cell 63, 133-139] found that a polylysine domain contained at the C terminus of K-ras 4B was also absolutely essential for K-ras 4B membrane binding but, surprisingly, neither the polylysine domain nor membrane binding was required for transforming activity. We have performed similar studies, but our results are distinctly different. Our studies indicate that the polylysine domain is crucial for K-ras 4B transforming activity. Moreover, we demonstrate that although the polylysine domain increases K-ras 4B membrane binding, significant amounts of membrane binding can occur in the absence of this domain. Finally, while our studies are consistent with the notion that membrane binding is required for K-ras 4B transforming activity, we show that membrane binding, in and of itself, is not sufficient for efficient K-ras 4B transforming activity.

3T3 Cells↗
PubMed1994

[HPLC analysis of 2-(P-dimethylaminostyryl) pyridine methiodide concentration in plasma].

A reversed phase high performance liquid chromatography (RP-HPLC) method for determination of 2-(p-dimethylaminostyryl) pyridine methiodide (DSPM) concentration in rabbit plasma is reported. The stationary phase was YWG-C18H37. The mobile phase consisted of 80% CH3OH, 20% CH3COOH-CH3COONa buffer (pH 4.0, 0.20 mol/L) and (C2H5)2NH 25 mmol/L. Its flow rate was 1.0 ml/min. The column temperature and pressure was 28 degrees C and 10.13 MPa, respectively. The detect wavelength was 460 nm. The detection limit of DSPM was 2 ng or 0.08 mumol/L in plasma. The RSD (%) of within-day and between-days were less than 7%. A good linear relationship between peak area and DSPM concentration in plasma (0.68-13.65 mumol/L) was found (r = 0.9996).

Animals↗
PubMed1993

[Technetium-99m bone imaging and mechanical strength test on heterogenous inorganic bone implantation].

Two kinds of heterogenous inorganic bone (HAB), lower temperature treated HAB (LHAB) and higher temperature treated HAB (HHAB), were implanted and observed by technetium-99m bone imaging and mechanical strength test. The results confirmed that the LHAB possessed biocompatibility and osteoinductivity. Half a year after implantation, LHAB induced bone formation and bridged large osseous defect.

Animals↗
PubMed1992

Antifibrotic and uveitogenic properties of gamma interferon in the rabbit eye.

The feasibility of gamma (gamma)-interferon injection for the treatment of ocular fibrotic conditions was studied in rabbits using recombinant rabbit gamma-interferon and the cell-injection model of tractional detachment. A toxicity study revealed that intravitreal injection of greater than 10(4) units gamma-interferon consistently produced panuveitis. For tractional detachment, 250,000 rabbit dermal fibroblasts were injected intravitreally into 20 eyes; 1 day later, 5 of these eyes received intravitreal injections of 10(4) units gamma-interferon, another 5 were given 10(6) units, and the remaining 10 received balanced salt solution. Slit-lamp examination and fundus photography were performed at regular intervals for 21 days and were graded by a masked observer. The eyes were then enucleated and processed for histology. Doses of 10(4) units gamma-interferon significantly reduced the severity of detachments, but injections of 10(6) units induced panuveitis.

Animals↗
PubMed1991

Proton interactions in the resting form of cytochrome oxidase.

The effect of pH on the near-UV absorption spectrum of cytochrome oxidase has been examined. Several lines of evidence implicate a proton binding site that can modulate the optical properties of cytochrome alpha 3 in the resting enzyme. Changing the pH within the range 6.5-10.5 was found to reversibly shift the position of the Soret band over an 11-nm range. The lower pH values caused a progressive blue shift in the Soret band, whereas the high-pH range promoted a gradual red shift. Limiting band positions were approximately 416 and 427 nm. The incubation time required to reach a stable band position varied somewhat as did the actual extent of the shift. In most cases, the shift was associated with an isosbestic point. A pH titration profile for the apparent equilibrium position of the Soret band was obtained. Nonlinear least-squares fitting to a scatter plot, assuming a single acid/base group, showed an apparent pKa of 7.8. Magnetic circular dichroism (MCD) spectra of the low-pH form at 416 nm, the high-pH form at 427 nm, and the cyanide derivative at 428 nm were compared. No evidence of a high-pH-dependent low-spin transition or a change in the redox state of cytochrome a3 was found, confirming earlier work [Baker, G. M., Noguchi, M., & Palmer, G. (1987) J. Biol. Chem. 262, 595-604]. Subtraction of ferricytochrome a [spectrum taken from Vanneste, W. H. (1966) Biochemistry 5, 838-848] from a series of blue-shifting spectra showed a band at 414 nm that progressively gained amplitude and a band at 430 nm that correspondingly lost amplitude. A series of red-shifting spectra showed the opposite behavior with a clear isosbestic point being evident in both cases. The difference extinction change at 414 and 430 nm depended linearly on the position of the Soret band, both showing a reversible dependence on pH. The 430-nm band is noted to be unusually red-shifted for high-spin ferric heme a. An additional, pH-insensitive band was observed at 408-410 nm which was eliminated by treatment with cyanide. The kinetics of the pH-induced blue shift and red shift were obtained at 416 nm by using dual-wavelength method and found to be biphasic, despite the occurrence of an isosbestic point.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

[Studies on double-labelling method for determination of T lymphocyte subpopulations].

In order to determine the concurrent expression of DR and CD antigen of T lymphocyte surface markers, the fluorescence-rosette double-labelling technique was developed by employing monoclonal antibody against HLA-DR and sensitized sheep erythrocytes with OKT series of monoclonal antibodies against cell surface antigen. Its reliability was evaluated by comparison with two-step isolating technique for determining DR antigen of activated T lymphocyte subsets in 30 healthy volunteers. The result showed there was no statistic difference between results determined with two methods. The double-labelling technique was characterized by its samplity, no injury for cellular activity and ability for analysing the expression of the single antigen and double antigens on cell surface concurrently.

Adult↗