Biomedical subjects

W Jin

Publications and source records attributed to W Jin.

At least 91 records · Page 5Linked to original sources

PubMed1999

[Comparative studies on the absorption properties of charge transfer complexes of C60 with three organic amines].

Comparative studies on the absorption properties of charge transfer complexes of C60 with N,N-dimethylaniline, diethylamine and triethylamine in toluene, CCl4 and cyclohexane were carried out, respectively. It was found that interactions of C60 with various amines in different solvent media are all in the order: cyclohexane > CCl4 > toluene, while these interactions are different in the same solvent. Both of the molar extinction coefficients and apparent constants of CTC were determined. Meanwhile, the influences of temperature on CT interactions of C60 with various amines in different solvent media were also studied.

English Abstract↗

PubMed1998

Oral delivery of group A streptococcal cell walls augments circulating TGF-beta and suppresses streptococcal cell wall arthritis.

Oral administration of autoantigens can influence the outcome of experimental autoimmune diseases, yet little is known about nonself Ag-induced tolerance. In this study, we administered group A streptococcal cell wall (SCW) peptidoglycan-polysaccharide complexes orally and monitored the impact on SCW-induced erosive polyarthritis. Oral administration of low dose SCW (3 microg/day), initiated 7 days before an arthritogenic dose of systemic SCW, virtually eliminated the joint swelling and destruction typically observed during both the acute and chronic phases of the arthritis. High (300 microg), but not intermediate (30 microg), dose regimens also profoundly inhibited the disease. Most previous studies have demonstrated that prior feeding is required for efficacy, yet oral feeding of low dose SCW suppressed the evolution of arthritis even when administration was begun 10-15 days after induction of the arthritis. While the synovial inflammatory cell infiltration and expression of proinflammatory cytokines were markedly suppressed, no local enhancement of the regulatory cytokines IL-4, IL-10, and TGF-beta was detected. Oral administration of low dose SCW, however, up-regulated circulating levels of TGF-beta, concomitant with decreased circulating TNF-alpha and suppression of chronic arthritis. Moreover, IL-10 was increased in tolerized spleen lymphocytes, and unexpectedly, this SCW-specific IL-10 production was TGF-beta dependent. These data support a pivotal role for TGF-beta, although not necessarily in the joint, in the regulation of specific immune tolerance responsible for suppressed synovial inflammation and matrix destruction. The distant induction and up-regulation of regulatory cytokines and/or cells may contribute to the inhibition of the immune response through blunted infiltration of inflammatory cells to the joint.

Acute Disease↗

PubMed1998

cDNA cloning and characterization of sciellin, a LIM domain protein of the keratinocyte cornified envelope.

Sciellin is a precursor of the cornified envelopes of mammalian keratinizing tissues. We have cloned the cDNA encoding sciellin by screening a human keratinocyte expression library with a sciellin-specific monoclonal antibody. The composite cDNA of 2.35 kilobase pairs encodes a protein of 75.3 kDa with a pI of 10.09. The translated sequence has a central domain containing 16 repeats of 20 amino acids each that is rich in Gln and Lys residues, which are potential transglutaminase substrates, and a carboxyl domain, which contains a single LIM motif. Sciellin cDNA probes hybridize to bands of 3.4 and 4.4 kilobase pairs on Northern blots of cultured human keratinocyte RNA. The gene was mapped to human chromosome band 13q22 by fluorescence in situ hybridization. Radiation hybrid mapping demonstrated that sciellin is linked to the sequence tagged site marker WI-457 with a logarithm of the odds score of 7.77. In situ hybridization of human foreskin tissue sections demonstrated that sciellin is expressed in the stratum granulosum. Immunofluorescent staining with a polyclonal rabbit antibody made to a recombinant sciellin protein showed peripheral cytoplasmic localization in the upper cell layers of epidermis and in stratified squamous epithelia such as the oral cavity, esophagus, and vagina. Simple and columnar epithelia, with the exception of the amnion, showed no reaction.

Amino Acid Sequence↗

PubMed1998

Engagement of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) induces transforming growth factor beta (TGF-beta) production by murine CD4(+) T cells.

Evidence indicates that cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) may negatively regulate T cell activation, but the basis for the inhibitory effect remains unknown. We report here that cross-linking of CTLA-4 induces transforming growth factor beta (TGF-beta) production by murine CD4(+) T cells. CD4(+) T helper type 1 (Th1), Th2, and Th0 clones all secrete TGF-beta after antibody cross-linking of CTLA-4, indicating that induction of TGF-beta by CTLA-4 signaling represents a ubiquitous feature of murine CD4(+) T cells. Stimulation of the CD3-T cell antigen receptor complex does not independently induce TGF-beta, but is required for optimal CTLA-4-mediated TGF-beta production. The consequences of cross-linking of CTLA-4, together with CD3 and CD28, include inhibition of T cell proliferation and interleukin (IL)-2 secretion, as well as suppression of both interferon gamma (Th1) and IL-4 (Th2). Moreover, addition of anti-TGF-beta partially reverses this T cell suppression. When CTLA-4 was cross-linked in T cell populations from TGF-beta1 gene-deleted (TGF-beta1(-/-)) mice, the T cell responses were only suppressed 38% compared with 95% in wild-type mice. Our data demonstrate that engagement of CTLA-4 leads to CD4(+) T cell production of TGF-beta, which, in part, contributes to the downregulation of T cell activation. CTLA-4, through TGF-beta, may serve as a counterbalance for CD28 costimulation of IL-2 and CD4(+) T cell activation.

Abatacept↗

PubMed1998

Actinorhodin and undecylprodigiosin production in wild-type and relA mutant strains of Streptomyces coelicolor A3(2) grown in continuous culture.

The effects of growth rate and nutrient feed rate on the production of actinorhodin (Act) and undecylprodigiosin (Red) were determined in Streptomyces coelicolor A3(2) and in a congenic relA null-mutant known to be deficient in ppGpp synthesis and antibiotic production under conditions of nitrogen limitation. In the relA+ strain, Act production was inversely related to specific growth rate in continuous cultures limited by glucose, ammonium, or phosphate, while Red biosynthesis was optimal at 0.05 h-1 regardless of the specific nutrient limitation. Production of Act and Red in the relA mutant was lower than that of the parental strain, particularly under conditions of glucose- and ammonium-limitation, indicating an important and general role for ppGpp in determining the onset of the antibiotic biosynthesis under conditions of nutrient limitation. At constant growth rate, but with varying nutrient feed rates, the specific rate of Act production was adversely influenced by increasing levels of glucose, ammonium, and phosphate, with phosphate having the greatest inhibitory effect. Under the same conditions, the specific rate of Red production was stimulated by increasing glucose levels, but markedly decreased by increased levels of phosphate.

Anthraquinones↗

PubMed1998

The chick and human collagen alpha1(XII) gene promoter--activity of highly conserved regions around the first exon and in the first intron.

A single gene encodes collagen XII, an extracellular matrix protein with three large fibronectin-related subunits connected via a short collagen triple helix. Since collagen XII is a component of a specific subset of collagen fibrils in tissues bearing high tensile stress, we are interested to know how its restricted expression is regulated. To this aim, we have isolated the region around the first exon of both the chick and human collagen alpha1(XII) gene. The upstream sequences of the two genes share common features but are not related. Strong similarity starts about 100 bp 5' of the first exon and ends 100 bp into the first intron. In addition, two large conserved regions (56-63% similarity) were found in the first intron. A single major and two clusters of minor transcription start sites were identified in both the chick and human gene. To test for promoter activity, conserved fragments from the chick gene were cloned into reporter plasmids for transient transfection of fibroblasts. A 70-bp stretch containing a conserved nuclear factor-1 binding sequence just upstream of the first transcription start site was found to work as a basal promoter. An adjacent, but nonoverlapping short segment including the more downstream start sites and a conserved TATTAA sequence exhibited independent promoter activity. GC-rich sequences just 5' and 3' of the minimal promoter fragments were required for full activity. In contrast, inclusion of more upstream sequences (up to 2.4 kb) had no effect. The two conserved regions in the first intron showed no promoter activity on their own but modulated activity when linked to autologous or heterologous promoters. Specifically, one of these intronic regions might contain enhancer element(s) that respond to mechanical stress acting on the fibroblasts. We conclude that the collagen XII gene is driven by a basal promoter with two halves that can act independently; conserved control regions are located around the first exon and in the first intron.

Animals↗

PubMed1998

A novel high-affinity inhibitor for inward-rectifier K+ channels.

Inward-rectifier K+ channels are a group of highly specialized K+ channels that accomplish a variety of important biological tasks. Inward-rectifier K+ channels differ from voltage-activated K+ channels not only functionally but also structurally. Each of the four subunits of the inward-rectifier K+ channels has only two instead of six transmembrane segments compared to the voltage-activated K+ channels. Thus far, there are no high-affinity ligands that directly target any inward-rectifier K+ channel. In the present study, we identified, purified, and synthesized a protein inhibitor of the inward-rectifier K+ channels. The inhibitor, called tertiapin, blocks a G-protein-gated channel (GIRK1/4) and the ROMK1 channel with nanomolar affinities, but a closely related channel, IRK1, is insensitive to tertiapin. Mutagenesis studies show that teritapin inhibits the channel by binding to the external end of the ion conduction pore.

Amino Acid Sequence↗

PubMed1998

Desensitization of delta-opioid-induced mobilization of Ca2+ stores in NG108-15 cells.

Activation of delta-opioid receptors in NG108-15 cells induces the release of calcium from an inositol 1,4,5-trisphosphate- sensitive intracellular store. We used fura-2-based digital imaging to study the effects of prolonged exposure to agonist on opioid-induced increases in [Ca2+]i. Exposure to D-Ala2-E-Leu5 enkephalin (DADLE) (1 microM) for 30 min completely desensitized NG108-15 cells to a second DADLE-induced response. The cells recovered gradually over 25 min following washout of DADLE. The desensitization was not due to depletion of intracellular calcium stores and bradykinin failed to cross-desensitize the DADLE-evoked response, although both agonists mobilized the same Ca2+ store. Desensitization induced by 100 nM DADLE was overcome by a higher concentration of DADLE (100 microM). Treatment with 8-cpt-cAMP (0.1 mM) for 30 min did not influence the DADLE-induced increases in [CA2+]i. Phorbol dibutyrate (PdBu) (1 microM) blocked the response completely. Treatment with the inhibitor of cyclic nucleotide-dependent kinases H8 (1 microM) for 45 min did not prevent DADLE-induced desensitization. Treatment with the protein kinase C (PKC) inhibitors staurosporin (10 nM) and GF-109203X (200 nM) for 45 min reduced desensitization. However, down-regulation of PKC by 24 h exposure to PdBu (1 microM) failed to prevent the DADLE-induced desensitization in NG108-15 cells. Thus, we conclude that multiple pathways participated in desensitization of delta-receptor-mediated Ca2+ mobilization, one of which includes PKC.

Biological Transport↗

PubMed1998

Exon sequence is required for regulated RNA splicing of the human fibroblast growth factor receptor-1 alpha-exon.

Alternative RNA processing of the human fibroblast growth factor receptor-1 transcript results in receptor forms that vary in their affinity for fibroblast growth factor. An alternative RNA processing event involving recognition of the alpha-exon is deregulated during neoplastic transformation of glial cells. We have previously established a splicing reporter/transfection cell culture model system to identify sequences involved in recognition of this exon. In this study, the system was used to identify two sequence elements that differentially function to regulate splicing of this exon. Exclusion of the alpha-exon in glioblastoma cells specifically required the downstream intron sequence comprising the 5'-splice site. Replacement or mutation of this sequence increasing complementarity to U1 RNA resulted in enhanced exon recognition in SNB-19 glioblastoma cells. Sequences within the exon were found to be required for alpha-exon inclusion. Deletion and gain-of-function experiments identified a 69-nucleotide exon sequence that was specifically required for alpha-exon inclusion. These studies indicate that multiple sequences are required for the regulated recognition of the alpha-exon.

Alternative Splicing↗

PubMed1998

Purinergic receptor-induced changes in paracellular resistance across cultures of human cervical cells are mediated by two distinct cytosolic calcium-related mechanisms.

In human cervical (CaSki) cells, extracellular adenosine triphosphate (ATP) induces an acute decrease in the resistance of the lateral intercellular space (RLIS), phase I response, followed by an increase in tight junctional resistance (RTJ), phase II response. ATP also stimulates release of calcium from intracellular stores, followed by augmented calcium influx, and both effects have similar sensitivities to ATP (EC50 of 6 microM). The objective of the study was to determine the degree to which the changes in [Ca2+]i mediate the responses to ATP. 1,2-bis (2-aminophenoxy) ethane-N,N,N1,N1-tetraacetic acid (BAPTA) abrogated calcium mobilization and phase I response; in contrast, nifedipine and verapamil inhibited calcium influx and attenuated phase II response. Barium, La3+, and Mn2+ attenuated phase I response and attenuated and shortened the ionomycin-induced phase I-like decrease in RLIS, suggesting that store depletion-activated calcium entry was inhibited. Barium and La3+ also inhibited the ATP-induced phase II response, but Mn2+ had no effect on phase II response, and in the presence of low extracellular calcium it partly restored the increase in RTJ. KCl-induced membrane depolarization stimulated an acute decrease in RLIS and a late increase in RTJ similar to ATP, but only the latter was inhibited by nifedipine. KCl also induced a nifedipine-sensitive calcium influx, suggesting that acute increases in [Ca2+]i, regardless of mobilization or influx, mediate phase I response. Phase II-like increases in RTJ could be induced by treatment with diC8, and were not affected by nifedipine. Biphasic, ATP-like changes in RTE could be induced by treating the cells with ionomycin plus diC8. We conclude that calcium mobilization mediates the early decrease in RLIS, and calcium influx via calcium channels activates protein kinase C and mediates the late increase in RTJ.

Adenosine Triphosphate↗

PubMed1998

[Methodology for designing pathological models of acute renal failure].

This paper reports the methodological study on the following five pathological models of acute renal failure (ARF): 1. glycerine-induced ARF in rats; 2. noradrenaline-induced ARF in dogs; 3. ARF model caused by shutting left renal artery in dogs; 4. hydrargyrism-induced ARF in rabbits; and 5. gentamycin-induced ARF in rats.

Acute Kidney Injury↗

PubMed1998

[Determination of resibufogenin and cinobufagin in venenum Bufonis by HPLC].

OBJECTIVE: To establish a HPLC method to determine the contents of active constituents in Venenum Bufonis. METHOD: In determining the contents of resibufogenin and cinobufagin in the traditional Chinese medicine Venenum Bufonis, the mobile phase was acetonitrile-0.5% KH2PO4 solution(50:50)(pH adjusted with value phosphoric acid to 3.25 +/- 0.02). RESULT: The constituents thus determined have good linearity and separation. The average recovery of resibufogenin was 100.35%, RSD 1.86%; the average recovery of cinobufagin was 100.38%, RSD 2.09%. CONCLUSION: The method was convenient, rapid, accurate and practicable.

Amphibian Venoms↗

PubMed1998

[Azone-induced changes on corneal endothelium in rabbits].

OBJECTIVE: To investigate ocular toxic effect of azone at low concentrations in rabbits to determine whether this penetration enhancer has any value for ocular use. METHODS: 0.3%, 0.6%, 0.9% concentrations of azone in an ocular emulsion vehicle were studied. Rabbits in three experimental groups received topical 30 microl of 0.3%, 0.6%, 0.9% azone respectively three times daily for 4 weeks. Rabbits in control group 1 received 30 microl of vehicle without azone as negative control and rabbits in control group 2 received nothing as normal control. Clinical and histopathological examinations of rabbit cornea endothelial cells were made by slit-lamp biomicroscopy, light microscopy and scanning electron microscopy. RESULTS: No clinical and histopathological evidence of ocular toxicity occurred in all treated and control eyes. The concentration of azone used in this study was 3-9 times higher than that (at 0.1%) at which corneal penetration of hydrophilic compounds can be enhanced enormously. CONCLUSION: Azone has value for incorporation into ocular formulations to increase therapeutic action of many hydrophilic drugs.

Animals↗

PubMed1998

[Effects of homoharringtonine liposomes and homoharringtonine solution on glaucoma filtration surgery in rabbits].

OBJECTIVE: Homoharringtonine (HHT), a Chinese herbal drug, was used in the form of liposome or solution as an adjunct to glaucoma filtration surgery in rabbits to determine its effect in preventing closure of sclerostomy. METHODS: Forty rabbits that underwent a standard posterior-lip sclerectomy in both eyes were divided into 5 post-operative groups. Group 1 received subconjunctival HHT liposomes (0.025%). Group 2 received subconjunctival blank liposomes and served as control. Group 3 and 5 received subconjunctival HHT solution at low (0.025%) and high (0.1%) doses respectively. Group 4 received subconjunctival normal saline and served as control. Intraocular pressure, interval between operation and bleb failure, rate of scleral fistula occlusion and ocular toxicity were determined in each group. RESULTS: Subconjunctival treatment with HHT solution at a high dose transiently prolongs the survival of filtration surgery, but the subconjunctival use with HHT liposomes or HHT solution at a low dose does not significantly prolong the survival of filtration surgery in rabbits. Significant corneal haze and corneal neovascularization resulted from using HHT at a high dose. CONCLUSIONS: The success rate of rabbit filtration surgery can not be markedly increased by the postoperative use of HHT liposomes or its low dose solution. When the high dosage of HHT solution is used, transient elevation of the success rate can be obtained, however the side-effect is also significantly increased.

Animals↗

PubMed1998

[The structures elucidation of isodopharicin D and F].

Two new compounds were isolated from Isodon pharicus (Prain) Murata. Their structures were determined to be 3 alpha, 11 beta, 13 alpha-trihydroxy-entkaur-16-en-15-one (1), named isodopharicin D, and 11 beta, 13 alpha, 15 alpha-trihydroxy-entkaur-16-en-3 alpha-beta-D-glucoside (2), named isodopharicin F by chemical and spectral evidence.

Diterpenes↗

PubMed1998

[Determination of zinc, copper, iron and manganese contents in hair for MPA patients and healthy men].

In this paper the contents of zinc, copper, iron and manganese in hair for MPA patients and 38 hair-healthy men have been determined by FAAS. The results show that the hair zinc and manganese levels in MPA patients are significantly lower than that in hair-healthy men. The hair copper level in MPA patients is significantly higher than that in hair-healthy men. There are statistic difference (P < 0.05) in hair zinc, copper and menganese levels among two groups. There is no statistic difference (P > 0.05) in the iron level among the two gopups. This paper provides useful material for the research of the cause and treatment of the MPA.

Alopecia↗

PubMed1997

Mobilization of Ca2+ from intracellular stores in transfected neuro2a cells by activation of multiple opioid receptor subtypes.

In neuronal cell lines, activation of opioid receptors has been shown to mobilize intracellular Ca2+ stores. In this report, we describe the excitatory actions of opioid agonists on murine neuroblastoma neuro2a cells stably expressing either delta, mu, or kappa opioid receptors. Fura-2-based digital imaging was used to record opioid-induced increases in intracellular Ca2+ concentration ([Ca2+]i). Repeated challenges of delta, mu, or kappa opioid receptor expressing cells with 100 nM [D-Ala2,D-Leu5]-enkephalin (DADLE), [D-Ala2,N-Me-Phe4,Gly-ol]-enkephalin (DAMGO), or trans-(+/-)-3,4-dichloro N-methyl-N-(2-[1-pyrollidinyl] cyclohexyl) benzene acetamide (U-50488H), respectively, elicited reproducible Ca2+ responses. Non-transfected neuro2a cells did not respond to opioid agonists. Removal of extracellular Ca2+ from the bath prior to and during agonist challenge did not affect significantly the agonist-evoked increase in [Ca2+]i, indicating that the response resulted from the release of Ca2+ from intracellular stores. Naloxone reversibly inhibited responses in all three cell lines, confirming that they were mediated by opioid receptors. Expression of cloned opioid receptors in neuro2a cells, coupled with digital [Ca2+]i imaging, provides a model system for the study of opioid receptors and opioid-activated signaling processes. The fact that all three receptors coupled to the same intracellular signaling mechanism suggests that the primary functional difference between opioid responses in vivo results from their selective localization.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1997

Determination of cysteine by capillary zone electrophoresis with end-column amperometric detection at a gold/mercury amalgam microelectrode without deoxygenation.

Capillary zone electrophoresis was employed for the determination of cysteine using an end-column amperometric detection with a gold/mercury amalgam microelectrode, at a constant potential of 0.02-0.06 V vs. saturated calomel electrode. In this procedure deoxygenation is not necessary. The electrochemical characteristics at the microelectrode, the effect of the concentration of the buffer and the separation voltage across the capillary on the migration time and separation efficiency, and the dependence of the injection voltage and time on the detection signal, the separation efficiency and coulometric efficiency has been investigated. The calibration plot was found to be linear over four orders of magnitude and the limit of detection was 5.8 x 10(-8) mol/l (or 14.5 amol). The method was applied to the determination of cysteine in human plasma, blood and urine.

Buffers↗