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Biomedical subjects

W Chen

Publications and source records attributed to W Chen.

At least 991 records · Page 55Linked to original sources
PubMed1994

Endotoxic damage to the stria vascularis: the pathogenesis of sensorineural hearing loss secondary to otitis media?

This study presents animal experiments on endotoxin (lipopolysaccharides: LPS) damage to the inner ear with special reference to the stria vascularis. The experimental group animals (albino guinea pigs) were injected with LPS into the perilymphatic space. Pyrogen-free saline (PFS) was injected into the control group. Strial structural evaluation and hearing tests were carried out before and one, three and five days after treatment. In PFS-treated (control) ears, no significant change was found either in hearing or structure. However, thresholds of N1/P1 were elevated and latencies prolonged in LPS-treated ears. They had severe strial damage mainly to the cellular organelles. The mitochondria became swollen with a disordered, broken, degenerated or absent crest. Secondary lysosomes and autophagosomes increased in number with the presence of medulative inclusions. Na(+)-K(+)-ATPase reactant was obviously diminished. It is concluded that LPS-induced strial ototoxicity produces ion imbalance, causing changes in endolymph composition and energy failure in the organ of Corti and is also responsible for the pathogenesis of inner ear sequelae secondary to otitis media.

Animals↗
PubMed1994

Jackson-Weiss and Crouzon syndromes are allelic with mutations in fibroblast growth factor receptor 2.

Jackson-Weiss syndrome is an autosomal dominant condition characterized by craniosynostosis, foot anomalies and great phenotypic variability. Recently mutations in fibroblast growth factor receptor 2 (FGFR2) have been found in patients with another craniosynostotic syndrome, Crouzon syndrome. FGFR2 is a member of the tyrosine kinase receptor superfamily, having a high affinity for peptides that signal the transduction pathways for mitogenesis, cellular differentiation and embryogenesis. We now report an FGFR2 mutation in the conserved region of the immunoglobulin IIIc domain in the Jackson-Weiss syndrome family in which the syndrome was originally described. In addition, in four of 12 Crouzon syndrome cases, we identified two new mutations and found two previously described mutations in the same region.

Alleles↗
PubMed1994

Production of thyroid stimulation blocking antibody without TSH receptor binding activity in rabbits with experimental autoimmune thyroiditis.

When rabbits were immunized with porcine thyroid plasma membrane, some cases of produced antibodies showed the blocking activity for TSH stimulated cAMP production in cultured porcine thyroid cells in spite of negative TSH binding inhibitory immunoglobulin (TBII) activity. The inhibitory effect of these thyroid stimulation blocking antibodies (TSBAbs) on cAMP increase by forskolin and GTP gamma S in porcine thyroid cells was observed in 1 and 3 rabbits, respectively. When the blocking activity of these antibodies for stimulated cAMP production by forskolin, GTP gamma S and NaF was examined in the isolated porcine thyroid membrane, no blocking activity for these 3 stimulators except in 1 case was found. The blocking activity of these antibodies could be absorbed significantly by incubation with porcine thyroid plasma membrane as antigen. The blocking activity was not observed in rabbits immunized with porcine thyroglobulin. The present experiment demonstrated that the produced antibody in rabbits against porcine thyroid membrane had the blocking activity for TSH stimulation to thyroid cells without affecting TSH binding to its receptor. These facts suggest that this type of blocking antibody may be produced against any antigen of thyroid membrane origin except the TSH receptor.

Adenylyl Cyclases↗
PubMed1994

Studies on the action of thyroid stimulation blocking antibody (TSBAb) on thyroid cell membrane.

The effect of thyroid stimulation blocking antibody (TSBAb) on stimulated cyclic AMP (cAMP) production induced by adenylate cyclase stimulators in porcine thyroid membrane (PTM) and porcine thyroid cells (PTC) has been studied. Ten TSBAbs with high TSH binding inhibitory immunoglobulin (TBII) activities significantly blocked TSH-stimulated cAMP production in PTC. The blocking effect of TSBAb on the cAMP increase induced by forskolin or GTP-gamma S stimulation in PTC was found in a few cases. However, there was no blocking action of TSBAb on the cAMP increase stimulated by forskolin, GTP gamma S, or NaF in isolated PTM. When TSBAb-globulin was absorbed with PTM or guinea pig epididymal fat membrane (GPFM), the TBII activity in TSBAb-globulin was significantly absorbed by these membranes. A decrease of TSBAb activity (blocking activity for TSH-stimulated cAMP production in PTC) by PTM absorption, but no decrease by GPFM absorption, was found in six cases. This suggests that the potent TSBAb-neutralizing component may be associated with a non-TSH receptor site in the thyroid membrane. The other four cases showed a decrease of TSBAb activity by absorption with both PTM and GPFM. This suggests that the TSBAb-neutralizing activity may be associated with the TSH receptor site of both PTM and GPFM. The results of the present study suggest that TSBAb may block TSH action either via the TSH receptor itself or via a non-TSH receptor component of the thyroid membrane and not at a postreceptor level.

Animals↗
PubMed1994

5-Aminolevulinic acid synthesis in Escherichia coli requires expression of hemA.

hemA and hemM, which are 213 bp apart and divergently transcribed, were separately cloned. We found that hemA is required for 5-aminolevulinic acid (ALA) synthesis in two ALA- auxotrophs. Overexpression of hemM alone did not produce ALA. More ALA was produced by strains harboring a plasmid with both hemA and hemM than by those with hemA alone. We conclude that hemA alone is required for ALA synthesis but hemA and hemM are required for maximal ALA synthesis.

Aldehyde Oxidoreductases↗
PubMed1994

L-glutamine and L-asparagine stimulate Na+ -H+ exchange in porcine jejunal enterocytes.

L-Glutamine (Gln) is a major respiratory fuel and substrate for nucleic acid synthesis in mammalian intestinal cells. The structurally related amino acid, L-asparagine (Asn), stimulates the proliferative enzyme ornithine decarboxylase in colonocytes, an effect that is blocked by the Na+-H+ exchange inhibitor amiloride. In an epithelial cell line derived from newborn piglet jejunum (IPEC-J2 cells), we determined intracellular pH (pHi) by computer-assisted microfluorimetry in single cells loaded with pH-sensitive dye 2',7'-bis(2-carboxyethyl)5-(6)- carboxyfluorescein. Resting pHi in N-2-hydroxyethylpiperazine-N'-2- ethanesulfonic acid-buffered NaCl Ringer was 7.06 +/- 0.02. Removal of external Na+ caused reversible acidification; recovery of pHi from NH+4-induced acid load was Na+ dependent, amiloride inhibitable, and Cl-independent. Asn and Gln had no measurable effect on resting pHi, but pretreatment with Asn or Gln induced a consistent twofold increase in pHi recovery from an acid challenge that was not seen with L-proline, D-glutamine, or L-phenylalanine. Inhibition of Gln metabolism by aminooxyacetate abolished the stimulatory effect of Gln on the exchanger. The tumor promotor phorbol 12-myristate 13-acetate (PMA) stimulated recovery rate from acid load and also increased resting pHi. The effects of PMA and Gln on Na+-H+ exchange from acid load were additive. Stimulation of Na+-H+ exchange by PMA, but not by Gln, was inhibited by protein kinase C (PKC) inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpeperazine. We conclude that Gln metabolism stimulates Na+-H+ exchange of acid-loaded porcine enterocytes by a mechanism not requiring activation of PKC.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Lung parenchyma and type II cell morphometrics: effect of surfactant treatment on preterm ventilated lamb lungs.

The effect of exogenous surfactant treatment on lung and type II cell structure of ventilated lambs of 137-138 days gestational age was studied. Thirty-four lambs were delivered and randomized to control or 100 mg/kg of natural sheep surfactant treatment groups. Lungs from one group of lambs not treated with surfactant were fixed before ventilation, and the other animals were ventilated to maintain normal blood gas values for 3, 24, or 48 h. Morphometric assessment of the inflation-fixed lung parenchyma of ventilated lungs was compared with the architectural appearance of alveoli and alveolar ducts in the unventilated lungs. Mechanical ventilation resulted in distension of alveolar ducts accompanied by the shallowing and loss of well-defined alveoli and areas of atelectasis at 3 h. These abnormalities increased in severity after 24 and 48 h of ventilation. Surfactant treatment before ventilation significantly reduced the extent and degree of dilatation and concomitant atelectasis. The fraction of normal parenchyma was 38 +/- 7% in untreated lambs vs. 64 +/- 6% in treated lambs after 24 h of ventilation. After 48 h of ventilation, significant differences between control (39 +/- 6%) and surfactant-treated (55 +/- 6%) lambs were still evident. Alveolar type II cells contained approximately 15% lamellar bodies by volume. Neither surfactant treatment nor time of ventilation altered the volume density of lamellar bodies or other organelles, except for a decrease in glycogen from 8% in nonventilated lungs to 2.5% in lungs ventilated for 24 h. These findings indicate that a surfactant treatment at birth results in the maintenance of more normal parenchyma with less atelectasis during prolonged ventilation of the immature lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Mechanism of efficacy of 2-amino oleic acid for inhibition of calcification of glutaraldehyde-pretreated porcine bioprosthetic heart valves.

BACKGROUND: Calcification is a frequent cause of the clinical failures of glutaraldehyde-pretreated bioprosthetic heart valves (BPHV) fabricated from glutaraldehyde-cross-linked porcine aortic valves. 2-Amino oleic acid (AOA) has been shown in previous in vivo studies to be a promising anticalcification agent. Our objective was to investigate the mechanism of calcification inhibition mediated by AOA pretreatment of porcine aortic valve bioprostheses. METHODS AND RESULTS: BPHV tissues were treated with an AOA solution for 72 hours before experimentation. The diffusion of AOA across both cusp and aortic wall was evaluated. The lag time for AOA to diffuse across the aortic wall was prolonged compared with that of the cusp. An extraction study was performed to determine the stability of AOA binding; the results indicated that the binding was relatively stable regardless of solvent extraction conditions. The interaction between ionic calcium and AOA on treated tissue also was investigated by evaluating the patterns of calcium diffusion across both treated and untreated tissues. The results showed that AOA significantly reduced the diffusion of calcium. AOA inhibition of aortic valve calcification (calcium level, 5.5 +/- 3.0 mg/g of tissue compared with control; calcium level, 91.2 +/- 19.5 mg/g of tissue) but not aortic wall (calcium level, 158.7 +/- 10.3 mg/g of tissue compared with control; calcium level, 157.5 +/- 7.9 mg/g of tissue) was demonstrated on representative specimens from valves implanted in left ventricular apicoaortic shunts explanted after 150 days. CONCLUSIONS: AOA covalently binds to glutaraldehyde-pretreated bioprosthetic heart valve tissue, presumably as the result of an aldehyde-amino reaction. Covalently bound AOA diminishes Ca2+ diffusion compared with non-AOA-pretreated bioprosthetic tissues. This may explain in part the anticalcification mechanism of AOA. Furthermore, AOA inhibits calcification of porcine BPHV cusps in the circulation.

Animals↗
PubMed1994

Local delivery of dexamethasone for prevention of neointimal proliferation in a rat model of balloon angioplasty.

A periadventitial polymer system is an alternative local drug delivery technique to obtain and maintain high tissue levels of the drug at the site of vascular injury. To determine if local periadventitial delivery of dexamethasone decreases neointimal proliferation after balloon vascular injury, in three groups of Sprague-Dawley rats, 5% dexamethasone, 0.5% dexamethasone, and placebo silicone polymers were implanted around the left common carotid artery after balloon injury. In a fourth group, placebo polymers were implanted without balloon injury. Dexamethasone serum and tissue levels after polymer implantation were significantly higher in the 5% dexamethasone group compared with the 0.5% dexamethasone group. There was no neointima formation in any of the arterial segments covered with placebo polymers for 3 wk, but without balloon injury. In the arterial segments covered by the 5 and 0.5% dexamethasone polymers, there was a 76 and 75% reduction in intima/media ratios, respectively, compared with the placebo group (5% dexamethasone, 0.26 +/- 0.04; 0.5% dexamethasone, 0.27 +/- 0.03; placebo, 1.09 +/- 0.16, respectively; P < 0.0001). These results suggest that: (a) silicone polymers wrapped around the common carotid arteries for 3 wk did not, without balloon injury, stimulate neointimal proliferation in the rat model; (b) the activity of the drug-eluting polymer for suppressing intimal proliferation was chiefly, but not exclusively, site specific; and (c) transadventitial local delivery of dexamethasone at two different doses markedly inhibits neointimal proliferation after balloon vascular injury.

Administration, Topical↗
PubMed1994

Zinc-induced metallothionein synthesis could protect from gentamicin nephrotoxicity in suspended proximal tubules of rats.

We have reported that preinjection of zinc could ameliorate gentamicin-induced nephrotoxicity in vivo via the induction of metallothionein. The present project was designed to study whether preinjection of zinc could protect from the harmful effects of gentamicin on DNA synthesis, Na(+)-K(+)-ATPase activity, and free radical production in rat renal proximal tubules (PT) in vitro. PT were prepared and cultured from normal, saline-preinjected, and Zn-preinjected (Zn 10 mg/k/day s.c. 5 days) Wistar male rats weighing 80-120 g. The results showed that DNA synthesis and Na(+)-K(+)-ATPase activity were significantly suppressed in the normal and saline-preinjected rats' PT by addition of gentamicin to the media in the concentration of 12.4 mg/mL; however, these reactions were not suppressed by gentamicin in Zn-preinjected rats' PT, and malondialdehyde and hydroxyl radical production in Zn-preinjected rats' PT were significantly lower than those in the normal and saline-preinjected rats' PT (p < .01). On the other hand, the metallothionein in Zn-preinjected rats' PT was very significantly higher than that in the normal and saline-preinjected rats' PT (p < .001). Our data indicate that gentamicin-induced suppression of DNA synthesis and Na(+)-K(+)-ATPase activity in rat PT, which lead to renal injury, may be relevant to free radicals generated by gentamicin; and that preinjection of zinc could ameliorate gentamicin-induced nephrotoxicity via the induction of the metallothionein synthesis in rat PT to scavenge free radicals generated by gentamicin.

Animals↗
PubMed1994

How does autoimmunity to La and Ro initiate and spread?

Autoimmunity to La(SS-B) and Ro(SS-A) is a paradigm for understanding the normal mechanisms of B cell and T cell tolerance and development of autoimmunity to clinically important sequestered autoantigens. Epitope mapping experiments have indicated that the autoantibody response is largely self antigen-driven but have failed to elucidate why these particular autoantigens are selected. Abnormal trafficking of La or Ro peptides in polarised epithelial cells and their presentation to autoreactive T cells, or selective release of ribonucleoproteins by injured epithelial cells, could explain the targeting of salivary and lacrimal epithelium in Sjogren's syndrome. There appears to be little, if any, immune tolerance to La in the T helper and B cell compartments. Both intra-and inter-molecular spreading of the autoimmune response have been observed for La. We present a model of recruited autoimmunity whereby capture and internalisation of La/Ro ribonucleoproteins by B cells and subsequent presentation of La or Ro determinants to autoreactive T cells could lead to inter-molecular spreading of the response.

Autoantigens↗
PubMed1994

[Sharing antigenic determinant of colon carcinoma between serous and mucinous tumors of the ovary].

Expression of colon-ovarian tumor antigen (COTA) in serous and mucinous tumors of the ovary was determined immunohistochemically, using monoclonal antibody SC13A against colon carcinoma antigen as a probe. In 67 serous tumor of the ovary, the frequency of expression was 90.0% in the cystadenocarcinomas, 71.4% in the borderline cystadenomas, and only 8.0% in the cystadenomas. In 44 mucinous tumors of the ovary, the SC13A marker was expressed in 87.5% of the malignant tumors, 80.0% of the borderline tumors, and 25.8% of the benign cystadenomas. And in 20 samples of normal ovarian tissue a negative immunostaining for the SC13A was found. These findings showed that the serous and the mucinous tumors share the same antigenic determinant of colon cancer, and the percentage expression of which is significantly higher in the malignant than in the benign and the borderline tumors, as well as in the normal ovarian tissues (P < 0.005). The marker might be valuable for further studies of these tumors.

Animals↗
PubMed1994

Evaluation of the antitumor activity of human IL-4 by in vitro and in vivo assays.

The characteristics of rhuIL-4 induced cytotoxicity was detected in vitro by using 51Cr release assay and the anti-tumor activity of rhuIL-4 induced killer cell was evaluated in vivo by using a human tumor model in nude mice. huIL-4 can induce LAK activity from peripheral blood lymphocytes (PBMC) stimulated with phytohemagglutinin (PHA). Compared with the LAK activity induced by rhuIL-2, the cytotoxicity of the killer cells induced by rhuIL-4 to K562 and Raji cells was lower, but that to TBL-E, a human lymphoid leukemia cell line established in our laboratory, and PHA-activated blast cells (PHA-blasts) was of similar magnitude. In the cytotoxicity assay using PHA-blasts, the addition of PHA increased the IL-4-induced killer cell cytotoxicity by 131%, but had no effect on IL-2-induced killer cell cytotoxicity. This implies that IL-4 mainly induces CTL-like activity, while IL-2 mainly induces NK-like activity. An experimental human tumor model in nude mice was established by injection of TBL-E human leukemia cells. The anti-tumor activity of rhuIL-4 was evaluated by injection of human LAK cells induced from PHA-blasts by rhuIL-2+rhuIL-4 and human cytokines into tumor-bearing nude mice. The results showed that human LAK cells effectively inhibit the tumorigenicity of TBL-E cells in nude mice with an inhibition rate of 61%. The antitumor effect of rhuIL-2 was better than that of rIL-4, and the antitumor effect of rhuIL-2+rhuIL-4 was similar to that of rhuIL-2, though the former delayed the occurrence of tumors. Our data imply the potential application of human IL-4 in clinic, and provide an animal model to evaluate the anti-tumor activity of human cytokine(s) with species specificity.

Animals↗
PubMed1994

[Detection of Epstein-Barr virus DNA in desquamative cell of nasopharyngeal carcinoma by polymerase chain reaction].

In the study, we detected the Epstein-Barr virus (EBV) DNA from thirty-five desquamative cells and four biopsy tissues of the nasopharynx in 35 patients with nasopharyngeal carcinoma using polymerase chain reaction (PCR). Among these patients, 24 had been treated or just began to be treated by 60Co, eleven had finished or nearly finished the treatment. Twelve patients with acute/chronic tonsillitis or pharyngitis served as control. The results showed that the EBV DNA positive rate in patients without treatment or just beginning to be treated was 83.3% (20/24), finished or nearly finished the treatment 9.1% (1/11), biopsy tissues 100% (4/4), and control 8.3% (1/12). The EBV DNA positive rate of the nasopharyngeal carcinoma was significantly higher than the control (P < 0.01). These results indicated that the detection EBV DNA from desquamative cells of the nasopharyngeal carcinoma by PCR is a simple, safe, rapid, specific and sensitive technique. It is useful for making general investigation, primary diagnosis, evaluation of the curative effect of the nasopharyngeal carcinoma.

Base Sequence↗
PubMed1994

[Hydroxyapatite for laryngotracheal framework reconstruction].

This paper reported combined sternohyoid myocutaneous flap and hydroxyapatite (HA) graft for laryngotracheal reconstruction in clinical and experimental studies. HA rings were employed for reconstructing the laryngotracheal framework in 10 patients on the base of animal experiment. The implant was well taken in all cases without any rejection, resulting in excellent airways. The study demonstrates that this procedure can be used in treatment of severe laryngotracheal stenosis.

Adolescent↗
PubMed1994

[Relationship between the sex of Schistosoma japonicum and circulating antigen detection].

Single sex cercariae were used to infect rabbits and the detection of circulating membrane antigen by dot-ELISA were followed up until 1 year postinfection. 9 rabbits infected with male cercariae (worm recovery 15-133, mean 53.1) and 9 rabbits infected with female cercariae (worm recovery 1-102, mean 39.1) were examined but no positive reaction was occurred. On the contrary, 7 rabbits infected with bi-sex cercariae (worm recovery 4-161, mean 67.1) all showed positive reactions 6-10 wks post-infection. Uni-sex female worms usually could not develop to maturity within rabbits even 1 year after infection, suggesting that the life-span of uni-sex female worm might be 1 year at least in rabbits. The uni-sex male worms could develop to maturity, being usually stout. The question why no circulating membrane antigen (even CCA, unpublished data) could be detected and the nature of antigen we detected needs further investigation.

Animals↗
PubMed1994

[Invasion of Drosophila albomicans into Shanghai and areas nearby and a study on its mitochondrial DNA polymorphism].

We report the fact that D. albomicans invaded into Shanghai suddenly in the autumn of 1991. Using 9 restriction enzymes, we analyse the RFLPs of mitochondrial DNA of 29 isofemale lines belonging to 4 populations of Shanghai, Jiading, Qinpu and Nanhui. We find that all 29 haplotypes are different from each other. Comparing with the populations of Canton, Kunming, Sanhutan (Taiwan), Sumoto (Japan), and Kuala Lumper (Malaysia), we come to the conclusion that D. albomicans caught in Shanghai and areas nearby is from a few of places in the south of China-mainland. This conclusion agrees with the viewpoint that this species is on the speciation stage of migration towards north. We also discuss the mtDNA polymorphism within the species.

Animals↗