Search PubMed⌕ Search

Biomedical subjects

S J Yang

Publications and source records attributed to S J Yang.

At least 37 records · Page 2Linked to original sources
PubMed2000

DNA lesion and mutagenesis induced in phageM13mp2 by UVA, UVB and UVC irradiation.

Sunlight is carcinogenic and mutagenic and its genotoxic effects are believed to be the result of UV light-induced lesions in DNA. These lesions include pyrimidine dimers and (6-4) photoproducts, but it is uncertain whether the pyrimidine modifications are the sole pre-mutagenic lesions induced by UV light. Previous studies indicate that some sunlight-induced mutations in the single-stranded DNA phage M13mp2 may not be caused by these photoproducts. In this work, purified single-stranded phage DNA was exposed to UVA, UVB and UVC and the induced mutations were analyzed. All 3 types of UV light increase the mutation frequency. The mutants were sequenced and the results suggest that UVA exposure may induce formation of a non-dipyrimidine lesion in DNA.

Bacteriophage M13↗
PubMed2000

Resolution of the pathways of poliovirus type 1 transmission during an outbreak.

An outbreak of poliomyelitis with 20 cases occurred in Israel, Gaza, and the West Bank from October 1987 to October 1988. The wild type 1 poliovirus associated with the outbreak was most closely related to viruses found in the Nile Delta. The epidemiologic links among patients involved in the outbreak and patients with community-acquired infections during the outbreak were inferred from the evolutionary relationships among isolates of the outbreak virus. Complete VP1 sequences (906 nucleotides) were determined for 12 clinical and 4 sewage isolates. A total of 58 nucleotide differences were found among the 16 isolates; 74% of all substitutions were synonymous third-position transitions. An evolutionary tree, representing both the pathways of VP1 sequence evolution and the inferred chains of virus transmission during the outbreak, was constructed under the assumption that each substitution had occurred only once. The combined epidemiologic and molecular data suggest that a single founder strain was introduced into Israel from the vicinity of Gaza in the fall of 1987. Poliovirus circulation was apparently localized to southern communities during the winter and spread north by the following summer into the Hadera subdistrict of Israel, where it radiated via multiple chains of transmission into other communities in northern Israel and the West Bank. The close sequence matches (>99%) between clinical and sewage isolates from the same communities confirm the utility of environmental sampling as a tool for monitoring wild poliovirus circulation.

Base Sequence↗
PubMed2000

In vitro biomechanical analysis of three anterior thoracolumbar implants.

OBJECT: The goal of this study was to evaluate the comparative efficacy of three commonly used anterior thoracolumbar implants: the anterior thoracolumbar locking plate (ATLP), the smooth-rod Kaneda (SRK), and the Z-plate. METHODS: In vitro testing was performed using the T9-L3 segments of human cadaver spines. An L-1 corpectomy was performed, and stabilization was achieved using one of three anterior devices: the ATLP in nine spines, the SRK in 10, and the Z-plate in 10. Specimens were load tested with 1.5-, 3-, 4.5-, and 6-Nm in flexion and extension, right and left lateral bending, and right and left axial rotation. Angular motion was monitored using two video cameras that tracked light-emitting diodes attached to the vertebral bodies. Testing was performed in the intact state in spines stabilized with one of the three aforementioned devices after the devices had been fatigued to 5000 cycles at +/- 3 Nm and after bilateral facetectomy. There was no difference in the stability of the intact spines with use of the three devices. There were no differences between the SRK- and Z-plate-instrumented spines in any state. In extension testing, the mean angular rotation (+/- standard deviation) of spines instrumented with the SRK (4.7 +/- 3.2 degrees) and Z-plate devices (3.3 +/- 2.3 degrees) was more rigid than that observed in the ATLP-stabilized spines (9 +/- 4.8 degrees). In flexion testing after induction of fatigue, however, only the SRK (4.2 +/- 3.2 degrees) was stiffer than the ATLP (8.9 +/- 4.9 degrees). Also, in extension postfatigue, only the SRK (2.4 +/- 3.4 degrees) provided more rigid fixation than the ATLP (6.4 +/- 2.9 degrees). All three devices were equally unstable after bilateral facetectomy. The SRK and Z-plate anterior thoracolumbar implants were both more rigid than the ATLP, and of the former two the SRK was stiffer. CONCLUSIONS: The authors' results suggest that in cases in which profile and ease of application are not of paramount importance, the SRK has an advantage over the other two tested implants in achieving rigid fixation immediately postoperatively.

Aged↗
PubMed2000

The mechanism of contraction by 2-chloroadenosine in cat detrusor muscle cells.

PURPOSE: Four adenosine receptors (ARs), designated A1AR (A1 adenosine receptor), A2aAR (A2a adenosine receptor), A2bAR (A2b adenosine receptor), and A3AR (A3 adenosine receptor), have been cloned from various species, but the contraction mechanism via A1ARs in cat detrusor muscle cell is not well known. MATERIALS AND METHODS: We examined the cellular mechanism using an A1AR agonist 2-chloroadenosine (2-CA) in cat detrusor cell isolated by enzymatic digestion. To examine which phospholipase mediates the contraction, we used phospholipase inhibitors. RESULTS: The adenosine analog potency order is R-N6-phenylisopropyladenosine (R-PIA) > 5'-N-ethylcarbosamine adenosine (NECA) > 2-chloroadenosine (2-CA) > S-N6-phenylisopropyladenosine (S-PIA). The ratio of equi-effective concentrations of R-PIA/S-PIA was 58.2. 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 300 nM) shifted to the right the concentration-response curves of 2-CA. These results indicate A1ARs mediate 2-CA induced contraction in cat detrusor muscle. G proteins (Gi1, Gi2, Gi3, Go, Gs, and Gq) in cat detrusor muscle were detected by immunoblot analysis. Pertussis toxin (PTX) inhibited 2-CA induced contraction. In permeabilized cells, antibodies against Galphai3 antagonized 2-CA induced contraction, suggesting that the contraction is mediated by Gi3 protein. A phosphatidylinositol-specific phospholipase C (PLC) inhibitor, neomycin, reduced 2-CA induced contraction, but a phospholipase D (PLD) inhibitor, p-chloromercuribenzoic acid, and a phospholipase A2 (PLA2) inhibitor, dimethyl-eicosa-dienoic acid (DEDA), had no effect. We found the presence of the main PLC isozymes, PLC-beta1, PLC-beta3, and PLC-gamma1. 2-CA induced contraction in permeabilized cells was inhibited by PLC-beta3 but not by PLC-beta1 or PLC-gamma1 antibody. These results imply that A1ARs are coupled to PLC-beta3 via PTX-sensitive Gi3 protein. Sr2+ medium and thapsigargin, which replaces intracellular Ca2+ and deplete intracellular calcium stores respectively, inhibited 2-CA induced contraction. CONCLUSIONS: These results suggest that A1ARs mediating 2-CA induced contraction exist in cat detrusor muscle and the contraction depends on a PTX-sensitive Gi3 protein, PLC-beta3 and the release of intracellular Ca2+.

2-Chloroadenosine↗
PubMed2000

Fluorescence in situ hybridization (FISH) for detection of HER-2/neu amplification in breast cancer: a multicenter portability study.

Amplification and/or overexpression of HER-2/neu has been shown to be both a prognostic and predictive marker in breast cancer. Recent studies have also confirmed the efficacy of Herceptin (trastuzumab) as adjuvant therapy for patients with overexpression of HER-2/neu. Therefore, it is critical that precise and reproducible assays be used in the clinical laboratory setting for determination of the HER-2/neu status in patients with breast cancer. The objective of this study was to determine the portability (reproducibility between different institutions) of the PathVysion HER-2 fluorescence in situ hybridization (FISH) assay used for detection of amplification of the HER-2/neu gene in formalin-fixed, paraffin-embedded tissue sections of invasive ductal carcinoma of the breast. Study specimens consisted of one breast tumor with a normal HER-2/neu copy number, two tumors with a low level, and one tumor with a high level of HER-2/neu amplification. The PathVysion HER-2 assay was shown to be highly reproducible on different assay days (n = 3) and between different institutions (n = 5) in the detection of amplification of the HER-2/neu gene in routinely processed clinical specimens of breast carcinoma. In addition, this study examined the feasibility of enumerating FISH signals in 20 nuclei in contrast to 60 nuclei per specimen. Although a modest increase in variation was observed when analyzing 20 compared to 60 nuclei, the mean ratios were similar. Therefore, analysis of as few as 20 nuclei with this FISH HER-2/neu assay may be sufficient for determining the amplification level of the HER-2/neu gene.

Antimetabolites, Antineoplastic↗
PubMed2000

Phenotypic and functional analysis of bovine gammadelta lymphocytes.

The studies have provided the first comprehensive comparison of the factors regulating activation and proliferation of WC1+ and WC1- gammadelta T cells. The investigation has shown that accessory molecules essential for activation and function of WC1+ and WC1- gammadelta T cells and the sources and roles of cytokines in activation of gammadelta T cells through the T cell receptor (TCR). The study has also shown that the role of cytokines in activation and function of gammadelta T cells activated indirectly through cytokines secreted by ab T cells, accessory cells and antigen presenting cells (APC). Cytokines were differentially produced by subpopulations of gammadelta T cells under different conditions of activation. The investigation obtained in this study has revealed that factors account for activation and proliferation of gammadelta T cells in cultures designed to study MHC-restricted responses to antigens. Evidence obtained here has shown there is biological relevance to activation under these culture conditions that points to potential regulatory and effector functions of gammadelta T cells. The investigations have also provided the information needed to begin identifying and characterizing antigens recognized by the TCR repertoires of WC1+ and WC1- gammadelta T cells. Finally, the investigations have provided the information needed to begin analysis of the mechanisms by which gammadelta T cells modulate MHC restricted immune responses to pathogens and derived vaccines.

Animals↗
PubMed1999

Localization of a carboxylic residue possibly involved in the inhibition of vacuolar H+-pyrophosphatase by N, N'-dicyclohexylcarbodi-imide.

A vacuolar H(+)-pyrophosphatase (EC 3.6.1.1) that catalyses PP(i) hydrolysis and the electrogenic translocation of protons from the cytosol to the vacuole lumen, was purified from etiolated hypocotyls of mung bean seedlings (Vigna radiata L.). Group-specific modification was used to identify a carboxylic residue involved in the inhibition of vacuolar H(+)-pyrophosphatase. Carbodi-imides, such as N,N'-dicyclohexylcarbodi-imide (DCCD) and 1-ethyl-3-(3-dimethylamino-propyl)carbodi-imide, and Woodward's reagent K caused a progressive decline in the enzymic activity of vacuolar H(+)-pyrophosphatase in a time- and concentration-dependent manner. The stoichiometry of labelling of the vacuolar H(+)-pyrophosphatase by [(14)C]DCCD determined that DCCD modifies one carboxylic residue per subunit of the enzyme. Protection studies suggest that the DCCD-reactive carboxylic residue resides at or near the substrate-binding site. Furthermore, peptide mapping analysis reveals that Asp(283), located in the putative loop V of a tentative topological model of vacuolar H(+)-pyrophosphatase on the cytosolic side, was labelled by radioactive [(14)C]DCCD. Cytosolic loop V contains both DCCD-sensitive Asp(283) and a conserved motif sequence, rendering it a candidate for the catalytic site of vacuolar H(+)-pyrophosphatase. A topological picture of the active domain of vacuolar H(+)-pyrophosphatase is tentatively proposed.

Amino Acid Sequence↗
PubMed1999

Simple high-performance liquid chromatographic purification procedure for porcine plasma haptoglobin.

Haptoglobin is an acute-phase protein and its plasma levels increase consistently in response to infection and inflammation. Some evidence has demonstrated that haptoglobin is involved in the immune responses. In this study, we established a novel high-performance liquid chromatographic purification procedure for porcine plasma haptoglobin. The procedure required an ammonium sulfate fractionation and a HPLC Superose 12 gel-permeation chromatography. Purified porcine haptoglobin possessed one heavy (beta) and light chain (alpha) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, under reducing conditions, with a M(r) (molecular mass) of about 42,000 and 14,000 for heavy (beta) and light chains (alpha), respectively. Although the N-terminal amino acid sequence of porcine heavy chain of haptoglobin has never been reported previously, the analyses of N-terminal amino acid sequence showed a great sequence similarity to that of human and other animal species. In addition, Western blot using our specific antibody prepared against porcine M(r) 42,000 chain did react with human haptoglobin and likewise, the antibody against human haptoglobin also cross-reacted with purified porcine M(r) 42,000 chain. Thus, it confirmed that the identity of the porcine protein purified from our procedures was as haptoglobin.

Amino Acid Sequence↗
PubMed1999

Sunlight mutagenesis: changes in mutational specificity during the irradiation of phage M13mp2.

We reported previously that the mutations in phage M13mp2, a single-stranded DNA phage, induced by sunlight exposure are predominated by G-to-C transversions. We have now made an unexpected observation that an exposure to sunlight for a short period of time results in induction mainly of C-to-T transitions while a longer exposure results in the induction of G-to-C transversions. This peculiar phenomenon suggests that DNA damage formed by initial sunlight exposure can be transformed during an elongated exposure. 7, 8-Dihydro-8-oxoguanine (8-oxoG) in DNA might be involved in the shift of the mutational specificity, as 8-oxoG was formed in the phage DNA upon the sunlight exposure. We also compared the mutagenic activity of UVB irradiation with that of sunlight exposure. The results demonstrate that the genotoxic properties of sunlight and UVB in phage M13mp2 mutagenesis are different. The shift in the mutational specificity associated with the dose of the sunlight may call for general cautions in the studies of agent-induced mutagenesis.

Bacteriophage M13↗
PubMed1999

Term pregnancy in a noncommunicating rudimentary horn of an unicornuate uterus: a case report.

A case of full-term pregnancy in the noncommunicating rudimentary horn of unicornuate uterus is presented. A healthy female infant weighing 2,985 g was delivered by cesarean section at 37 weeks' gestation. The diagnosis was missed by prenatal ultrasonography and was made only at laparotomy. A retrospective analysis of our ultrasound studies revealed that the echo pattern of the nongravid uterus resembled a soft pelvic mass. Color Doppler imaging revealed prominent low-impedance uterine arcuate-radial arterial blood flow surrounding the periphery of the pelvic mass, as well as multiple areas of placental implantation with a pulsatile lacunar flow pattern. A high index of suspicion of rudimentary horn pregnancy should be borne in mind whenever late-pregnancy ultrasonography shows the above-mentioned characteristic ultrasonic findings.

Adult↗
PubMed1998

Subunit interaction of vacuolar H+-pyrophosphatase as determined by high hydrostatic pressure.

Vacuolar H+-pyrophosphatase (H+-PPase) from etiolated hypocotyls of mung bean (Vigna radiata L.) is a homodimer with a molecular mass of 145 kDa. The vacuolar H+-PPase was subjected to high hydrostatic pressure to investigate its structure and function. The inhibition of H+-PPase activity by high hydrostatic pressure has a pressure-, time- and protein-concentration-dependent manner. The Vmax value of vacuolar H+-PPase was dramatically decreased by pressurization from 293.9 to 70.2 micromol of PPi (pyrophosphate) consumed/h per mg of protein, while the Km value decreased from 0.35 to 0.08 mM, implying that the pressure treatment increased the affinity of PPi to vacuolar H+-PPase but decreased its hydrolysis. The physiological substrate and its analogues enhance high pressure inhibition of vacuolar H+-PPase. The HPLC profile reveals high pressure treatment of H+-PPase provokes the subunit dissociation from an active into inactive form. High hydrostatic pressure also induces the conformational change of vacuolar H+-PPase as determined by spectroscopic techniques. Our results indicate the importance of protein-protein interaction for this novel proton-translocating enzyme. Working models are proposed to interpret the pressure inactivation of vacuolar H+-PPase. We also suggest that association of identical subunits of vacuolar H+-PPase is not random but proceeds in a specific manner.

Cell Membrane↗
PubMed1998

Construction of full-length cDNA clones of lettuce mosaic virus (LMV) and the effects of intron-insertion on their viability in Escherichia coli and on their infectivity to plants.

A full length cDNA copy of the genomic RNA of lettuce mosaic virus (LMV) was constructed under the control of an enhanced CaMV 35S promoter and of the NOS terminator. This construct was found infectious when inoculated to lettuce plants. The intron II of the bean nitrite reductase gene was engineered into the LMV FL cDNA in order to relieve possible deleterious effects of viral sequences to Escherichia coli cells and to evaluate the effects of the presence of the intron on the FL cDNA infectivity. The intron-less FL cDNA was found to be as stable as its intron-containing counterpart in E. coli. Sequence analysis of progeny RNA derived from plants inoculated with the intron-containing FL cDNA demonstrated that the inserted intron was perfectly spliced out. The symptoms induced in lettuce by either the intron-less or the intro-containing constructs were identical to those caused by the wild-type virus. However a slight delay in the establishment of infection in lettuce and a more obvious lag in Nicotiana benthamiana were observed with the intron-containing FL cDNA.

Base Sequence↗
PubMed1998

High-pressure effects on vacuolar H+-ATPase from etiolated mung bean seedlings.

A high-hydrostatic-pressure technique was employed to study the structure-function relationship of plant vacuolar H+-ATPase from etiolated mung bean seedlings (Vigna radiata L.). When isolated vacuolar H+-ATPase was subjected to hydrostatic pressure, the activity of ATP hydrolysis was markedly inhibited in a time-, protein concentration- and pressure-dependent manner. The pressure treatment decreased both Vmax and Km of solubilized vacuolar H+-ATPase, implying an increase in ATP binding affinity, but a decrease in the ATP hydrolysis activity. Physiological substrate, Mg2+-ATP, augmented the loss of enzymatic activity upon pressure treatment. However, ADP, AMP, and Pi exerted substantial protective effects against pressurization. Steady-state ATP hydrolysis was more sensitive to pressurization than single-site ATPase activity. The inactivation of solubilized vacuolar H+-ATPase by pressure may result from changes in protein-protein interaction. The conformational change of solubilized vacuolar H+-ATPase induced by hydrostatic pressure was further determined by spectroscopic techniques. The inhibition of vacuolar H+-ATPase under pressurization involved at least two steps. Taken together, our work indicates that subunit-subunit interaction is crucial for the integrity and the function of plant vacuolar H+-ATPase. It is also suggested that the assembly of the vacuolar H+-ATPase complex is probably not random, but follows a sequestered pathway.

Adenosine Triphosphate↗
PubMed1998

Serotype-specific identification of polioviruses by PCR using primers containing mixed-base or deoxyinosine residues at positions of codon degeneracy.

We have developed a method for determining the serotypes of poliovirus isolates by PCR. Three sets of serotype-specific antisense PCR-initiating primers (primers seroPV1A, seroPV2A, and seroPV3A) were designed to pair with codons of VP1 amino acid sequences that are conserved within but that differ across serotypes. The sense polarity primers (primers seroPV1S, seroPV2S, and seroPV3S) matched codons of more conserved capsid sequences. The primers contain mixed-base and deoxyinosine residues to compensate for the high rate of degeneracy of the targeted codons. The serotypes of all polioviruses tested (48 vaccine-related isolates and 110 diverse wild isolates) were correctly identified by PCR with the serotype-specific primers. None of the genomic sequences of 49 nonpolio enterovirus reference strains were amplified under equivalent reaction conditions with any of the three primer sets. These primers are useful for the rapid screening of poliovirus isolates and for determining the compositions of cultures containing mixtures of poliovirus serotypes.

Amino Acid Sequence↗
PubMed1997

Purification and characterization of thylakoid membrane-bound inorganic pyrophosphatase from Spinacia oleracia L.

An inorganic pyrophosphatase (PPase) was purified from thylakoid membrane of spinach leaves to electrophoretic purity by methods including detergent solubilization, ammonium sulfate fractionation, and successive chromatographic techniques. Current protocol yielded about 10% recovery of total activity with a 30-fold purification. The specific activity of the purified enzyme was approximately 400 micromol PPi consumed/mg protein x h. This enzyme is a monomer with a molecular mass of 55 kDa. Several properties, including subunit composition, substrate specificity, ion requirements, inhibitor sensitivities, and amino acid composition, have been studied. Mg2+ is an essential cofactor for the thylakoid PPase. The preferred substrate for the hydrolytic reaction of PPase appears to be dimagnesium pyrophosphate. K+ could not stimulate the enzymatic activity of thylakoid PPase, while F- was a potent inhibitor. Group-specific modification of the thylakoid PPase demonstrates possible involvement of carboxylate residues in the enzymatic activity. Furthermore, antibodies raised against thylakoid PPase in a rabbit could inactivate the PPi hydrolysis of thylakoid and the purified enzyme, but not that of vacuolar H+-PPase, indicating both PPi hydrolases are structurally distinct.

Amino Acids↗
PubMed1997

Comparison of the complete nucleotide sequences of two isolates of lettuce mosaic virus differing in their biological properties.

The complete nucleotide sequences of the genomic RNAs of the 0 and E isolates of lettuce mosaic potyvirus (LMV) have been determined. These two isolates differ by their behavior towards two lettuce resistance genes and by their seed transmission properties. LMV-0 is unable to induce disease in lettuce carrying either one of the mol1 and mol2 recessive resistance genes, whereas LMV-E is able to induce disease in the same plants. The genomes of these two isolates are 10080 nucleotides (nt) in length, excluding the poly(A) tract, and encode polyproteins of 3255 amino acids (aa). The open reading frame is flanked by a 5' non-coding region of 103 nt and a 3' non-coding region of 212 nucleotides. Ten proteins were predicted. The P3 protein, with 377 aa, is the longest potyviral P3 protein characterized to date while the P1 protein, with 437 aa, is among the longest P1 proteins reported. Sequence comparisons between the two isolates demonstrated only limited sequence difference. The overall nucleotide and amino acid sequence identities between LMV-0 and LMV-E are 94 and 97% respectively. The greatest variability occurs in the P1 and in the variable N-terminal region of the coat protein, while the NIa protease domain, the NIb protein, the C-terminus of the helper component protease and the 3' non-coding region are extensively conserved. While this sequence analysis does not allow direct identification of determinants involved in the resistance breaking or in the seed transmissibility properties, these data are a first step towards the characterization of these determinants.

Amino Acid Sequence↗