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Biomedical subjects

W Cai

Publications and source records attributed to W Cai.

At least 127 records · Page 7Linked to original sources
PubMed1991

A cellular function can enhance gene expression and plating efficiency of a mutant defective in the gene for ICP0, a transactivating protein of herpes simplex virus type 1.

ICP0 transactivates herpes simplex virus type 1 genes of all classes as well as a number of heterologous viral and cellular genes, yet it is not essential for virus replication in vitro or in vivo. Stocks of ICP0 deletion mutants, however, exhibit significantly lower plating efficiencies on standard 24-h-old Vero cell monolayers than do stocks of wild-type virus. In an attempt to determine whether the growth status of cells in the monolayer affects the ability of ICP0 mutants to initiate plaque formation, the plating efficiencies and abilities of an ICP0 null mutant (7134) and of wild-type virus (KOS) to express selected viral proteins were determined on Vero cell monolayers whose growth had been arrested either by contact inhibition-trypsinization or by isoleucine deprivation and had then been released from growth arrest. The proportion of cells cycling synchronously after release from growth arrest was assessed by flow cytometry. The results of these studies indicate that the plating efficiency of 7134 was greatest on Vero cell monolayers 8 h after release from growth arrest induced by either treatment. Monolayers of both types released from growth arrest at other times supported 7134 plaque formation less efficiently. In contrast, the plating efficiency of KOS was nearly equal on monolayers at all times after release from growth arrest. Notably, both KOS and 7134 were equally efficient in entering cells and inducing expression of the immediate-early protein ICP4 in either 8- or 24-h monolayers. Relative to KOS, however, 7134 was significantly impaired in the expression of selected early and late genes in cells at 24 h postrelease. When the plating efficiencies of 7134 and KOS were examined in 0-28 cells (Vero cells that are stably transformed with the ICP0 gene) whose growth had been arrested and then released, no differences in the plating efficiencies of the two viruses as a function of growth status were noted. These findings suggest that a cellular function expressed maximally in cells 8 h after release from growth arrest can substitute operationally for ICP0 to enhance plaque formation and viral gene expression by 7134. They further suggest that one role of ICP0 in viral infection is to facilitate virus replication in cells that do not express this function.

Animals↗
PubMed1990

[Changes in plasma TXB2 and 6-keto-PGF1 alpha and left atrial thrombosis in mitral stenosis].

This study was performed to determine the relationship between plasma concentration of thromboxane B2 (TXB2), 6-keto-prostaglandin F1a and atrial thrombosis in patients with mitral stenosis (MS). By radioimmunoassay and pathological examination, peripheral plasma TXB2 level was remarkably higher in patients with MS and persistent atrial fibrillation (AF) than in patients with MS but without AF (P less than 0.01). Plasma TXB2 level was significantly higher in patients with than in those without atrial thrombosis (P less than 0.05). There was no significant difference in plasma 6-keto-PGF1 alpha, plasma prostanoids level in peripheral venous blood correlated closely with that in left atrial blood. Patients with high plasma TXB2 level had a greater incidence of microthrombosis.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Identification of mar mutations in herpes simplex virus type 1 glycoprotein B which alter antigenic structure and function in virus penetration.

Analysis of six monoclonal antibody-resistant (mar) mutants in herpes simplex virus type 1 glycoprotein B identified two type-common (II and III) and two type-specific (I and IV) antigenic sites on this molecule. To derive additional information on the location of these sites, mar mutations were mapped and nucleotide alterations were identified by DNA sequencing. Each mutant carried a single amino acid substitution resulting from a G-to-A base transition. Alterations affecting antibody neutralization were identified at residues 473, 594, 305, and 85 for mutants in sites I through IV, respectively. Two clonally distinct site II antibodies each selected mar mutants (Gly to Arg at residue 594) that exhibited a reduction in the rate of entry (roe) into host cells. A site II mar revertant that regained sensitivity to neutralization by site II antibodies also showed normal entry kinetics. DNA sequencing of this virus identified a single base reversion of the site II mar mutation, resulting in restoration of the wild-type sequence (Arg to Gly). This finding demonstrated that the mar and roe phenotypes were the result of a single mutation. To further define structures that contributed to antibody recognition, monoclonal antibodies specific for all four sites were tested for their ability to immune precipitate a panel of linker-insertion mutant glycoprotein B molecules. Individual polypeptides that contained single insertions of 2 to 28 amino acids throughout the external domain were not recognized or were recognized poorly by antibodies specific for sites II and III, whereas no insertion affected antibody recognition of sites I and IV. mar mutations affecting either site II or III were previously shown to cause temperature-sensitive defects in glycoprotein B glycosylation, and variants altered in both these sites were temperature sensitive for virus production. Taken together, the data indicate that antigenic sites II and III are composed of higher-order structures whose integrity is linked with the ability of glycoprotein B to function in virus infectivity.

Amino Acid Sequence↗
PubMed1989

[HPLC determination of tetramethylpyrazine in human serum and its pharmacokinetic parameters].

An HPLC method for the determination of tetramethylpyrazine in serum and application of this method to tetramethylpyrazine deposition studies in human body were described. Tetramethylpyrazine was extracted from alkalinized serum with dichloromethane using methaqualone as internal standard. A RP mu-Bondapak-C18 (10 microns) column fitted with a variable-wavelength UV spectrophotometer operated at 280 nm was used. The mobile phase was methanol-water (58:42). The detection limit of the method was 0.0174 microgram/ml serum. Assay linearity was shown over the range of 0.0291-5.816 micrograms/ml serum with a regression coefficient of 0.9999. The extraction recovery was 99.84% and no interference was found from endogenous compounds, metabolites of parent drug or other commonly used drugs. For the serum concentration following oral administration of tetramethylpyrazine capsules to healthy volunteers (n = 6), the best fit was found to be with a two compartment open model. After administration of 174.5 mg dose, the pharmacokinetic parameters were as follows: Tp = 0.5102 h, Cmax = 3.114 micrograms/ml, AUC = 5.893 mg/L.h, T1/2 (Ka) = 0.1508 h, T1/2 (alpha) = 0.4855 h, T1/2 (beta) = 2.894 h, C1 = 15.7 L.h-1, Vc = 17.70 L, V = 66.77 L. The results imply that tetramethylpyrazine is absorbed rapidly, distributed widely in the body, and also eliminated at a fairly rapid rate.

Administration, Oral↗
PubMed1988

The carboxy-terminal 41 amino acids of herpes simplex virus type 1 glycoprotein B are not essential for production of infectious virus particles.

Glycoprotein B (gB) is a virally encoded protein that is found in the envelope of herpes simplex virus type 1 and membranes of cells infected with herpes simplex virus type 1. It is essential for the production of infectious virus particles. An amber mutation was introduced into the gB gene by oligonucleotide-directed mutagenesis at the codon for amino acid 863 of the protein. Virus carrying this mutation should synthesize gB molecules lacking the last 41 amino acids of the cytoplasmic domain. Immunoprecipitation of infected cell extracts demonstrated the synthesis of appropriately truncated gB molecules. Characterization of the mutant virus indicated that the loss of the carboxy-terminal 41 amino acids has little effect on gB function.

Amino Acids↗
PubMed1987

Cadmium binding to metallothioneins. Domain specificity in reactions of alpha and beta fragments, apometallothionein, and zinc metallothionein with Cd2+.

The cadmium-binding properties of rabbit liver Zn7-metallothionein (MT) 2 and apo-MT, rat liver apo-alpha MT and Zn4-alpha MT, and calf liver apo-beta MT, have been studied using circular dichroism (CD) and magnetic circular dichroism (MCD) spectroscopies. Both sets of spectra recorded during the titration of Zn7-MT 2 with Cd2+ exhibit a complicated pattern that is quite unexpected. Such behavior is not found at all in sets of spectra recorded during titrations of the apo-species (apo-MT, apo-alpha MT, and apo-beta MT), and is observed to a much lesser extent in the titration of Zn-alpha MT. Comparison between the band centers of the Cd-alpha MT and Cd-beta MT indicates that the CD spectrum of Cd7-MT is dominated by intensity from transitions that originate on Cd-S chromophores in the alpha domain, with little direct contribution from the beta domain. Analysis of the spectra recorded during titrations of Zn7-MT 2 with Cd2+ suggests: (i) that Cd2+ replaces Zn2+ in Zn7-MT isomorphously; (ii) that cadmium binds in a nonspecific, "distributed" manner across both domains; (iii) that cluster formation in the alpha domain only occurs after 4 mol eq of cadmium have been added and is indicated by the presence of a cluster-sensitive, CD spectral feature; (iv) that the characteristic derivative CD spectrum of native Cd4,Zn3-MT is only obtained from "synthetic" Cd4,Zn3-MT following a treatment cycle that allows the redistribution of cadmium into the alpha domain; warming the synthetic "native," Cd4,Zn3-MT, to 65 degrees C results in cadmium being preferentially bound in the alpha domain; and (v) Zn7-MT will bind Cd2+ quite normally at up to 65 degrees C but with greater specificity for the alpha domain compared with titrations carried out at 25 degrees C. These results suggest that the initial presence of zinc in both domains is an important factor in the lack of any domain specificity during cadmium binding to Zn-MT which contrasts the domain specific manner observed for cadmium binding to apo-MT.

Animals↗