Search PubMed⌕ Search

Biomedical subjects

Y L Chang

Publications and source records attributed to Y L Chang.

At least 19 recordsLinked to original sources
PubMed1995

Soluble interleukin-2 receptor as a clinical parameter for nasopharyngeal carcinoma.

We evaluated whether the serum soluble interleukin-2 receptor (sIL-2R) may be a parameter to monitor the efficacy of treatment for nasopharyngeal carcinoma (NPC). There were 177 NPC patients and 24 healthy controls. The level of sIL-2R was measured with a sandwich ELISA kit. Higher levels of sIL-2R than for controls were found in NPC patients before treatment and in patients with distant metastasis (p < 0.001). There was, however, no difference in sIL-2R levels between controls and NPC patients after radiotherapy in relapse-free or in primary relapse. The sIL-2R levels in sequential testing revealed good correlation with clinical response. The sIL-2R levels were found to be elevated when distant metastasis was detected. Two patients had elevated sIL-2R level up to 5 months before clinical detection of metastasis. These results indicate that serial measurements of sIL-2R levels are worthwhile for NPC patients in their clinical course. The sIL-2R level proved to be an adjunct clinical parameter to monitor the efficacy of treatment of NPC.

Adult↗
PubMed1994

The primary structure of rat ribosomal protein L15.

The amino acid sequence of the rat 60S ribosomal subunit protein L15 was deduced from the sequence of nucleotides in two recombinant cDNAs. Ribosomal protein L15 has 203 amino acids, the NH2-terminal methionine is removed after translation of the mRNA, and has a molecular weight of 24,000. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 13 to 15 copies of the L15 gene. The mRNA for the protein is about 850 nucleotides in length. Rat L15 is related to ribosomal proteins from other eukaryotes. Rat L15 has the hexapeptide, TYKFFE, that also occurs in the amyloidogenic glycoprotein A4 which is associated with Alzheimer's disease and Down's Syndrome.

Amino Acid Sequence↗
PubMed1994

Intracellular calcium and myosin light chain phosphorylation during U46619-activated vascular contraction.

We investigated the relationship between [Ca2+]i, myosin light chain (LC20) phosphorylation and isometric force in guinea pig aortic strips during contractions activated by a thromboxane A2 analogue, (15S)-hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5Z, 13E-dienoic acid (U46619). Isometric force and [Ca2+]i were measured simultaneously using preloaded aequorin as the intracellular calcium indicator. LC20 phosphorylation levels were determined by two dimensional polyacrylamide gel electrophoresis in parallel preparations. Contractions induced by U46619 were accompanied by increases in [Ca2+]i and LC20 phosphorylation. The chelation of extracellular calcium with 2.5 mM EGTA significantly inhibited U46619-induced increases in [Ca2+]i, isometric force and LC20 phosphorylation. Steady-state force assumed a similar dependence on LC20 phosphorylation for contractions stimulated by potassium depolarization, alpha 1-adrenergic agonist phenylephrine and U46619 either in the presence or absence of extracellular calcium. On the contrary, the [Ca2+]i/force relation revealed that both U46619 and phenylephrine stimulated greater isometric force at lower [Ca2+]i than did KCl depolarization. The addition of a protein kinase C inhibitor, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), decreases force without significantly affecting either [Ca2+]i or LC20 phosphorylation levels. These results suggest that in guinea pig aortic smooth muscle U46619 increases the calcium sensitivity of the contractile apparatus but does not change the LC20 phosphorylation/force relation in comparison to K+ depolarization. Protein kinase C is activated during U46619-stimulated contraction and might be involved in mechanisms other than LC20 phosphorylation.

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

Epstein-Barr virus harboring in the parotid gland without tumor association.

The purpose of this study is to clarify the relationship between Epstein-Barr virus (EBV) and tumors of the major salivary gland. EBV DNA was detected by polymerase chain reaction (PCR) in parotid secretions in 56% of patients (n = 32) regardless of the presence of tumors in the parotid gland and in tumor tissues in 19% of surgical specimens (n = 21). By Southern blot-hybridization analysis, we found type A EBV in three patients and type B EBV in one patient. In situ hybridization for EBV genome was positive in surgical specimens of salivary glands in 33% of patients (n = 21). Our results suggest that this virus may not play a role in the pathogenesis of most tumors of the major salivary gland. However, two patients with lymphoepithelial carcinoma were found to have a close relationship to EBV as shown by high titers of antibodies in the sera against EBV related antigens by standard immunofluorescent technique and by the presence of many copies of EBV genome in tumor cells using in situ hybridization.

Adult↗
PubMed1993

The conformation of the sarcin/ricin loop from 28S ribosomal RNA.

The sarcin/ricin loop is a highly conserved sequence found in the RNA of all large ribosomal subunits. The cytotoxins alpha-sarcin and ricin both inactivate ribosomes by cleaving a single bond in that loop. Once it has been attacked, ribosomes no longer interact with elongation factors properly, and translation stops. We have determined the conformation of the sarcin/ricin loop by multinuclear NMR spectroscopy using E73, a 29-nucleotide RNA that has the sarcin/ricin loop sequence and that is sensitive to both toxins in vitro. The sarcin/ricin loop has a compact structure that contains several purine.purine base pairs, a GAGA tetraloop, and a bulged guanosine adjacent to a reverse Hoogsteen A.U pair. It is stabilized by an unusual set of cross-strand base-stacking interactions and imino proton to phosphate oxygen hydrogen bonds. In addition to having interesting structural features, this model explains many of the biochemical observations made about the loop's structure and its reactivity with cytotoxins, and it sheds light on the loop's interactions with elongation factors.

Animals↗
PubMed1993

Daphnoretin, a new protein kinase C activator isolated from Wikstroemia indica C.A. Mey.

Daphnoretin, a biologically active principle isolated from Wikstroemia indica C.A. Mey., caused platelet aggregation in washed rabbit platelets, platelet-rich plasma and whole blood. The aggregation of and ATP release from platelets induced by daphnoretin were similar to phorbol ester- and diacylglycerol-induced aggregation and release. The EC50 values of daphnoretin-, phorbol 12,13-dibutyrate (PDBu)- and 1-oleoyl-2-acetylglycerol (OAG)-induced platelet aggregation in washed rabbit platelets were 17.2 +/- 2.8 microM, 20.6 +/- 2.1 nM and 38.6 +/- 1.7 microM respectively. Platelet aggregation induced by daphnoretin and PDBu was not inhibited by indomethacin, BN52021 or sodium nitroprusside. ADP-scavenging systems, apyrase and phosphocreatine/creatine kinase, showed weak inhibition of the aggregation, and EGTA, triflavin, verapamil and prostaglandin E1 markedly inhibited the aggregation. Staurosporine, a potent protein kinase C inhibitor, suppressed daphnoretin-, PDBu- and OAG-induced aggregation and ATP release in a concentration-dependent manner. The IC50 values of staurosporine on daphnoretin (50 microM)-, PDBu (100 nM)- and OAG (50 microM)-induced aggregation were 37.7 +/- 8.3, 52.2 +/- 6.3 and 42.8 +/- 8.9 nM respectively. Daphnoretin did not cause significant thromboxane B2 formation in rabbit platelets. Neither daphnoretin nor PDBu caused [3H]inositol monophosphate formation or an increase in intracellular Ca2+ concentration in myo-[3H]inositol-labelled and Fura-2-loaded platelets. Platelet cytosolic protein kinase C was activated by daphnoretin and PDBu in a concentration-dependent manner with an EC50 of 12.4 +/- 1.2 microM and 18.7 +/- 1.4 nM respectively. Membrane-associated protein kinase C activity was increased by either daphnoretin or PDBu. [3H]PDBu binding to washed rabbit platelets was inhibited by daphnoretin in a concentration-dependent manner with an IC50 value of 45.2 +/- 5.2 microM. These results indicate that daphnoretin is a protein kinase C activator in rabbit platelets.

Animals↗
PubMed1993

CIS-19, a novel platelet activating factor receptor antagonist: in vitro and in vivo studies.

The effects of CIS-19 (cis-2-(3,4-dimethoxyphenyl)-6-isopropoxy-7-methoxyl-1-(N-methylforma mido)-1,2, 3,4-tetrahydronaphthalene) was determined in vitro in rabbit platelets and in vivo in rats and guinea-pigs. CIS-19 inhibited in a selective and concentration-dependent manner the aggregation and ATP release reaction of rabbit platelets induced by PAF (4 nM). The IC50 values of CIS-19 on PAF-induced aggregation of washed platelets and platelet-rich plasma were 11.3 +/- 2.7 and 16.8 +/- 3.0 microM respectively. BN52021 also inhibited PAF-induced aggregation of washed platelets with an IC50 value of 11.7 +/- 2.8 microM. CIS-19 inhibited [3H]PAF (4 nM) binding to washed rabbit platelets with an IC50 value of 1.5 +/- 0.2 microM. The concentration-response curve of PAF-induced aggregation of washed platelets was shifted rightwards by CIS-19 with pA2 and pA10 values of 7.1 (6.8-7.3 for 95% confidence limit) and 6.1 (5.8-6.2) respectively. The thromboxane B2 formation of washed platelets caused by AA, collagen or thrombin was not affected by CIS-19 of concentrations below 400 microM. CIS-19 (25 microM) completely blocked PAF-induced, but not collagen- or thrombin-induced [3H]inositol monophosphate formation of washed platelets. When CIS-19 (2.5 and 5 mg/kg) was injected i.v. into the femoral vein, it did not affect the blood pressure of rats, but antagonized PAF (2.5 micrograms/kg, i.v.)-induced hypotensive shock either preventively or curatively. CIS-19 (2.5 and 5 mg/kg) also blocked PAF (50 ng/kg)-induced, but not AA (50 micrograms/kg)-induced, bronchoconstriction in guinea-pigs. It is concluded that CIS-19 is an effective PAF receptor antagonist not only in vitro, but also in vivo.

Adenosine Triphosphate↗
PubMed1993

Possible non-sexual transmission of genital human papillomavirus infections in young women.

Human papillomaviruses were detected by an in vitro enzymatic DNA amplification method in cells obtained from vulvar swabs of 9 of 61 (14.8%) young women without prior experience of sexual intercourse and in 7 of 57 (12.3%) young women with prior experience. The prevalence of human papillomavirus DNA in these two groups of women was not significantly different (x2 = 0.16, p > 0.5; 95% confidence interval -0.165 to 0.215). These results suggest that genital human papillomavirus is not sexually transmitted in all cases and that it may be acquired by modes other than sexual contact.

Adult↗
PubMed1993

Clinical experience and model analysis on beta-2-microglobulin kinetics in high-flux hemodialysis.

Beta-2-microglobulin (beta 2M) is associated with amyloidosis. The study of beta 2M kinetics can provide information on the elimination of this uremic toxin. A beta 2M kinetic model modified from Gotch, considering the volume changes between intracellular, interstitial, and intravascular compartments and the generation stimulation and inhibition during hemodialysis is proposed. The clinical experiments on 8 stable hemodialysis patients treated with polysulfone (F80) and polymethyl methacrylate (PMMA, BK2.1p) 3 times a week were conducted. There was an 18% decrease of beta 2M clearance in the period from 30 to 180 min with a time-averaged beta 2M clearance of 48 ml/min using polysulfone dialyzers (F80). In PMMA dialyzers, there was a 64% decrease of beta 2M clearance from 30 to 180 min with a time-averaged clearance of 56.3 ml/min. During hemodialysis, the generation rate was 0.379 mg/min in polysulfone and 0.828 mg/min in PMMA dialyzers. There was a stimulation generation of 0.309 mg/min in polysulfone and 0.749 mg/min in PMMA during hemodialysis. In conclusion, we provide a beta 2M kinetic model including volume changes, polymerization, generation stimulation, and inhibition that is similar to the human physiological condition. This model can be used for further clinical study.

Blood Flow Velocity↗
PubMed1992

Prevalence of genital human papillomavirus infections in patients at a sexually transmitted diseases clinic.

The human papillomavirus was detected in cervicovaginal cells by the polymerase chain reaction in 14 of 37 (37.8%) patients attending a sexually transmitted disease (STD) clinic and in 6 of 43 healthy young women (14.0%) undergoing routine gynecologic examinations who served as controls. The results indicated that even the more malignant types of human papillomaviruses were not uncommon among the control group, and that the prevalence of human papillomavirus infection was significantly higher in STD clinic patients than in the control group. These findings confirm the suggestion that factors other than human papillomavirus infections may be involved in the pathogenesis of cervical cancer.

Ambulatory Care Facilities↗
PubMed1992

Possible transplacental transmission of human papillomaviruses.

OBJECTIVE: The objective of this study was to examine the possibility of intrauterine human papillomavirus infection of fetuses by transplacental transmission of human papillomavirus before delivery. STUDY DESIGN: Specimens of cervicovaginal cells and peripheral blood mononuclear cells were obtained from 52 consecutive pregnant women in the third trimester of pregnancy. Cord blood specimens were also obtained from the neonates born to these mothers. Presence of human papillomavirus types 16 and 18 deoxyribonucleic acid was analyzed by an in vitro enzymatic deoxyribonucleic acid amplification method. RESULTS: Human papillomavirus type 16 deoxyribonucleic acid was found in 6 (11.5%) cervicovaginal and in 9 (17.3%) peripheral blood mononuclear cell specimens. Seven cord blood specimens from neonates born to mothers who were positive for peripheral blood mononuclear cell human papillomavirus type 16 deoxyribonucleic acid were found to contain human papillomavirus type 16 deoxyribonucleic acid. One cervicovaginal and two peripheral blood mononuclear cell specimens contained human papillomavirus type 18 deoxyribonucleic acid, but none of the cord blood specimens contained human papillomavirus type 18 deoxyribonucleic acid. CONCLUSION: These results seem to suggest possible transplacental transmission of the virus and the potential association of such transmission with the status of human papillomavirus in peripheral blood mononuclear cells.

Base Sequence↗
PubMed1992

Intraneural anatomy of the median nerve provides "third web space" donor nerve graft.

To determine the feasibility of using the fascicular group to the third web space as a source of nerve graft material for bridging of median nerve gaps, a study of the intraneural anatomy of the median nerve was carried out in 23 fresh cadaver specimens. The pattern of plexus formation between the third web-space group and the remainder of the median nerve was determined. The average length of the third web-space fascicular group that could be separated from the median nerve proper prior to plexus intermingling was 24.5 cm. Cross-sectional areas of the graft and the remaining nerve were 4.43 mm2 and 13.76 mm2, respectively. The number of nerve fibers in the third web-space group was 4,847 and in the remaining median nerve, 13,486. Between February, 1989 and October, 1991, this technique has been used on 11 patients to provide donor nerve material for nerve gaps of 3 to 6 cm in the median nerve.

Adolescent↗
PubMed1992

Transcriptional regulation of precore and pregenomic RNAs of hepatitis B virus.

Hepatitis B virus (HBV) infection, either acute or chronic, has been one of the leading health problems in the world. To understand the HBV life cycle and disease process, we set out to study the regulation of viral gene expression. In this paper, we report the characterization of the HBV core promoter: two 3.5-kb transcripts, precore and pregenomic, are made from it. The latter is itself a template for viral genome replication and also encodes viral proteins essential for both viral replication and virion assembly. We identify a short sequence (from nucleotides [nt] 1744 to 1851, referred to as the basic core promoter [BCP]) that is sufficient to direct correct initiation of both precore and pregenomic messages. In addition, the two appear to be regulated in a coordinate manner. Sequences upstream of the BCP (from nt 1636 to 1744, referred to as the core upstream regulatory sequence [CURS]), have a strong stimulating effect on the BCP. Addition of the CURS to the BCP leads to a dramatic increase in both the transcription of two 3.5-kb messages and the production of 42-nm virions from transiently transfected hepatoma cells. The CURS stimulates the BCP in a position- and orientation-dependent manner. Therefore, it is unlikely that the effect is mediated through enhancer II, which has been localized to the same sequence. Deletion analysis of the CURS suggests that it contains multiple regulatory elements that control the BCP in an interactive manner. In accord with this hypothesis, the CURS is found to be bound with many distinct protein factors in footprinting experiments. Among these elements, box alpha (from nt 1646 to 1668) and box gamma delta (from nt 1671 to 1703) are two regulatory elements which individually stimulate promoter activity more than 100-fold.

Base Sequence↗
PubMed1991

Elevated levels of soluble interleukin 2 receptor and tumor necrosis factor in nasopharyngeal carcinoma.

Depressed cell-mediated immunity as a measure of the mitogenic response of mononuclear cells in patients with nasopharyngeal carcinoma is well documented, but the mechanism is still unclear. The enzyme-linked immunosorbent assay was used to measure soluble interleukin 2 receptor and tumor necrosis factor levels in 295 patients with nasopharyngeal carcinoma and 97 age-matched control subjects. Soluble interleukin 2 receptor levels in patients with nasopharyngeal carcinoma were elevated and correlated with clinical staging. Higher soluble interleukin 2 receptor levels were found in patients with bone metastasis but not in patients with intracranial involvement. The levels of tumor necrosis factor in nasopharyngeal carcinoma were higher than in control subjects but did not correlate with clinical staging. These data suggest that soluble interleukin 2 receptor levels might be more useful than soluble tumor necrosis factor levels that indicate tumor bulk. Soluble interleukin 2 receptor serves as a blocking factor that competes with interleukin 2 function, resulting in a decreased mitogenic response in patients with nasopharyngeal carcinoma. The usefulness of the levels of soluble interleukin 2 receptor to monitor the efficacy of treatment in patients with nasopharyngeal carcinoma with bone metastasis requires further study.

Adolescent↗