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W Y Liu

Publications and source records attributed to W Y Liu.

At least 91 records · Page 5Linked to original sources
PubMed1987

A simple and rapid solid-phase RNA sequencing method.

A simple and rapid solid-phase RNA sequencing method has been developed based on Peattie's direct chemical method. 3'-Terminally labeled RNA was immobilized on DEAE-cellulose sheets and followed by specific modification with dimethyl sulfate, diethylpyrocarbonate, hydroxylamine (at pH 10 for the uridine and pH 5.5 for the cytidine reaction), and cleavage reaction with aniline. RNA fragments were washed from the DEAE-cellulose sheets using salt solutions, precipitated with ethanol, and separated by 15% polyacrylamide gel electrophoresis. Due to the complete removal of the impurities normally present in the solution method, the higher resolution of the sequencing bands and lower background on the autoradiograph make this solid-phase technique more efficient. This solid-phase technique is much faster and more convenient than the original method.

Animals↗
PubMed1987

Effects of ribosome dissociation on the structure of the ribosome-associated 5.8S RNA.

Diethyl pyrocarbonate reactivity and thermal denaturation were used to probe potential ribosomal interactions between tRNA and the small 5.8S and 5S rRNAs. Puromycin, an analogue of the terminal aminoacyl-adenosine portion of aminoacyl-tRNA, was observed to increase the accessibility of the 5.8S rRNA, including the highly conserved GAACp sequences. EDTA which releases both tRNA and the 5S rRNA-protein complex resulted in an even greater accessibility in the 5.8S rRNA. The thermal dissociation of whole ribosomes resulted in the release of all three RNAs, with a striking similarity in the denaturation profiles. These results strongly suggest an interdependence in the ribosome-associated structures of the small rRNAs and provide in situ evidence for the various 5S rRNA, 5.8S rRNA, and tRNA containing ribonucleoprotein complexes previously reconstituted through affinity chromatography.

Base Sequence↗
PubMed1986

A pharmacokinetic and pharmacodynamic study of a 'visiting pill' containing norethisterone.

The pharmacokinetics and pharmacodynamic effects of two doses of norethisterone (5mg and 3mg) used as a 'visiting pill' were investigated. There were no significant differences in the pharmacokinetics of the two doses except for the peak concentration achieved and the bioavailability as assessed by the area under the serum norethisterone concentration - time curve. Both doses were rapidly absorbed. Pharmacodynamic effects were minor. No change occurred in serum concentrations of total cholesterol, total triglycerides or HDL-cholesterol. The area under the serum glucose concentration--time curve and particularly the area under the serum insulin concentration--time curve were significantly increased as a result of treatment but no change occurred in the serum levels of glycosylated haemoglobin. SHBG concentrations in serum decreased on treatment whereas those of ceruloplasmin increased.

Absorption↗
PubMed1984

Prognostic value of histopathologic parameters in squamous cell carcinoma of the oropharynx.

Seventy-seven patients with squamous cell carcinoma of the oropharynx were treated by preoperative radiation therapy (4000-5000 rad) followed by surgical resection. The original biopsy specimens were evaluated for degree of keratinization, nuclear pleomorphism, frequency of mitoses, inflammatory response, vascular invasion, and pattern of invasion. Multivariant analysis (Cox regression model) and life table survival function were used to determine the relative contributions of the clinical and histologic parameters to patient outcome. The results were as follows: (1) large tumor size, nodal metastases, and male sex were found to be predictive of a poorer survival (P = 0.004, 0.0167, and 0.0237, respectively); and (2) an analysis of a combination of clinical and histologic parameters demonstrated that the pattern of invasion was the only histologic factor that was predictive of survival (P = 0.0436). Neoplasms invading as large cohesive aggregates indicated a better prognosis than neoplasms invading as thin, irregular cords or individual cells. Restricting the statistical evaluation to only histologic factors (excluding clinical factors) demonstrated that increased frequency of mitoses also correlated with poor survival (P = 0.0218). Further restriction of the analysis to T2 and T3 neoplasms that have similar survival times indicated that both frequency of mitoses and pattern of invasion were of prognostic value in predicting survival (P = 0.0127 and 0.0168, respectively).

Carcinoma, Squamous Cell↗
PubMed1984

Chemical synthesis of a biologically active gene for human immune interferon-gamma. Prospect for site-specific mutagenesis and structure-function studies.

A 453-base pair DNA duplex consisting of a gene coding for human interferon-gamma and initiation and termination signals plus appropriate restriction enzyme sites for plasmid insertion has been totally synthesized. The synthesis involved preparation of 66 oligodeoxynucleotides by a modified, solid phase phosphite procedure and enzymatic ligation of the oligonucleotides. The gene, when inserted into a previously constructed expression vector, was expressed in Escherichia coli, demonstrating functional activity for the synthetic gene. Several strategically located restriction cleavage sites have been introduced into the sequence. This provides a convenient system for site-specific mutagenesis for structure-function studies.

Amino Acid Sequence↗
PubMed1984

Genes for the alpha and beta subunits of phycocyanin.

Phycocyanin (PC) is a light-harvesting protein common to blue-green and red algae. We have isolated the genes for the two apoprotein subunits, alpha and beta, of PC from the blue-green alga Agmenellum quadruplicatum PR-6. We synthesized eight sense-strand tetradecameric oligonucleotide probes that could encode a particular pentapeptide in PC alpha from A. quadruplicatum. Only one probe hybridized with total RNA from this organism. This oligonucleotide showed homology to a unique restriction fragment when used to probe Southern blots of A. quadruplicatum DNA. The probe-homologous 3.1-kilobase pair HindIII fragment was cloned. The nucleotide sequence of a 1.7-kilobase pair segment of this clone was determined. Two open reading frames are contained in this region, which correspond in deduced amino acid sequence to PC alpha and PC beta subunits. Both coding sequences are in the same orientation, separated by 105 base pairs, with the PC beta gene 5' to the PC alpha gene. Each gene has a Shine-Dalgarno-type sequence near the initiation codon. Codon frequencies in the two genes may be correlated with the abundance of their products. The deduced amino acid sequences of the gene products show considerable homology with the alpha and beta PC subunits from other species.

Amino Acid Sequence↗
PubMed1984

Abrasion of acrylic veneers by simulated toothbrushing.

The abrasion responses were tested on four acrylic veneer materials, K + B Plus, K + B 75, Isosit, and Ivocron. The studies were performed in two independent research laboratories. Two different brushing machines were used with an abrasive slurry. The results were used for comparing the degree of abrasion for the resin materials. Three analytical methods of measuring the degree of abrasive wear were used: surface profile measurement, microscopic evaluation, and measurement of loss of volume. Isosit showed the best abrasion resistance of the four materials tested.

Acrylic Resins↗
PubMed1983

Comparison of class I (H-2) gene sequences. Derivation of unique probes for members of this multigene family.

The genes for the classical transplantation antigens are unique in that they belong to a multigene family of which each member is represented by a large number of alleles. Since all of these genes are highly related in sequence, it has been difficult to study the expression of individual members of this complex gene family. Based upon our initial suggestion that the 3' noncoding regions of these genes may be useful in identifying mRNA molecules transcribed from different loci, we have compared a large number of sequences from different inbred mouse strains and have been able to assign each of these sequences without ambiguity into distinct allelic series. Such accurate assignment has afforded the opportunity to compare the coding regions of these highly homologous genes and has led to the identification of sequences which are apparently unique to specific genes in the family. Synthetic oligonucleotides corresponding to each of the locus-specific unique regions have been used successfully to type a panel of cDNA sequences, as well as to quantitate the relative amounts of mRNA transcribed from distinct loci. The availability of these specific coding probes will allow the analysis of individual genes and their specific expression without interference from other highly homologous sequences in this multigene family.

Amino Acid Sequence↗
PubMed1983

Structure of a ribosomal 5S RNA from a mushroom, Coprinus cinereus.

The nucleotide sequence of the 5S rRNA from a mushroom, Coprinus cinereus, was determined to be: (sequence in text). This sequence is consistent with current models for the secondary structure of 5S RNAs and indicates a very high degree of sequence conservation among the most highly evolved fungi. Sequence heterogeneity was not evident in this fungus suggesting that the more highly evolved fungi may not contain the dispersed pattern of 5S rRNA genes which have been observed in intermediate fungi such as Neurospora.

Base Sequence↗