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Biomedical subjects

Z Chen

Publications and source records attributed to Z Chen.

At least 1,207 records · Page 67Linked to original sources
PubMed1995

Exogenous interferon-gamma induces endogenous synthesis of interferon-alpha and -beta by murine macrophages for induction of nitric oxide synthase.

Murine macrophages (M phi) are activated either by interferon-gamma (IFN-gamma) or interferon-alpha/beta (IFN-alpha/beta) in combination with bacterial lipopolysaccharide (LPS) to induce synthesis of tumor necrosis factor alpha (TNF-alpha) and nitric oxide synthase (iNOS) mRNA synthesis for generation of tumor cytotoxic nitric oxide (NO). In the present study, the effect of exogenous IFN-gamma on the induction of endogenous mRNA synthesis and secretion of IFN-alpha/beta by murine M phi was investigated. Neutralizing antibodies to IFN-alpha/beta reversed TNF-alpha and NOS mRNA synthesis, as well as nitric oxide (NO)-mediated tumor cytotoxicity. Quantitative reverse transcription polymerase chain reaction (RT-PCR) revealed that treatment of M phi with IFN-gamma induced increases in both IFN-alpha and IFN-beta mRNA synthesis by approximately 2-fold and 10-fold, respectively, which corresponded to a 2-fold increase in secretion of IFN-alpha/beta by ELISA. These data indicate that exogenous IFN-gamma induces endogenous synthesis and secretion of IFN-alpha/beta by M phi, which appears to act in concert with endogenously synthesized TNF-alpha for the autocrine induction of NOS mRNA synthesis.

Animals↗
PubMed1995

Genetic control of the murine humoral response to distinct epitopes of hepatitis C virus core protein.

Recombinant hepatitis C virus (HCV) core protein from aa1-164, designated cp1-10, was used to immunize mice. Antibodies to cp1-10 were produced in all seven strains of congenic mice; none of the strains could be considered low responders relative to the others. The mouse response against individual epitopes of HCV core protein varied from one strain to another: B10.RIII (H-2r) recognized all three peptides aa13-30, aa77-90, aa129-145; B10.D2 (H-2d), B10 (H-2b) and C3H.SW (H-2b) responded to aa13-30, aa77-90; B10.M (H-2f), B10.BR (H-2k) and C3H/Hej (H-2k) reacted with aa13-30 only. Competitive inhibition of binding demonstrated that antibody to the peptide was inhibited by cp1-10 protein and the corresponding peptide only. Recombinant HCV core protein is highly immunogenic and can elicit good antibody response in mice. The aa13-30 is a major epitope of HCV core protein in mice. The humoral response to the distinct epitopes was regulated by the H-2 genes. Further analysis indicated that the I-a locus of H-2 genes determined the antibody response to aa13-30 and 77-90. These results suggest that the variation of antibody responses to HCV in humans may partially contribute to different outcomes of HCV infection.

Amino Acid Sequence↗
PubMed1995

Cross-reacting IgE antibodies recognizing latex allergens, including Hev b 1, as well as papain.

The cross-reactivity of IgE antibodies recognizing epitopes of latex allergens and papain was studied in sera of 36 latex-exposed subjects and 22 papain workers. Eight out of 24 latex-sensitized persons also showed a positive reaction to papain in the CAP assay (mostly of low or moderate degree). On the other hand, six out of the 12 sensitized papain workers also revealed IgE binding to latex allergen(s). Reciprocal inhibition experiments confirmed that groups monosensitized to one of the two allergens can be separated from a group showing partial or nearly complete immunologic cross-reactivity. Papain inhibited IgE binding by 20-33% in these subjects, whereas IgE binding to papain was strongly blocked in most cases. Comparison between the primary sequences of Hev b 1, a major latex allergen, and papain suggests that the cross-reactivity may be due to several identical trimers and tetramers.

Allergens↗
PubMed1995

Isolation and characterization of the first simian immunodeficiency virus from a feral sooty mangabey (Cercocebus atys) in West Africa.

The lineage of HIV-2-like viruses was studied in feral sooty mangabeys (SMs) by serological and genetic methods. Four feral sooty mangabeys were positive for simian immunodeficiency virus (SIV) antibodies and a new isolate, SIVsmSL92a, was obtained. Genetic analysis of gag genes showed that SIVsmSL92a was highly diverse and a distinct sequence subtype within the SIV sm/HIV-2 family. The results showed that SIVsm is the most diverse group of SIVs found thus far in a single monkey species.

Africa, Western↗
PubMed1995

The influence of scatter on the design of optimized intensity modulations.

In contrast to the traditional treatment planning process where beam parameters are adjusted in order to produce a desired dose distribution, the inverse treatment planning technique starts from the desired dose distribution and employs mathematical inversion to derive a set of optimal intensity profiles for beams with predefined directions. Crucial to the success of the inverse technique is the mathematical inversion process that yields the optimized intensity modulation. This paper systematically investigates the influence of phantom scatter in the process of designing the optimized intensity modulation and assesses its clinical consequences through the resultant treatment plans. Optimized intensity modulations and the resultant dose distributions were calculated for four prostate patients and for a simple cubic phantom under two conditions: one includes scatter and the other ignores scatter in designing the optimized intensity modulation. The effects of scatter were assessed by comparing the isodose distributions, the dose-volume histograms of the target and of the critical organs, and the tumor control probabilities and the normal tissue complication probabilities of two set prostate treatment plans. The comparison reveals that the dose homogeneity to the target is significantly improved when scatter is included in the optimization process. For prostate patients, the dose to the volume enclosed by the outer rectal contour is concomitantly reduced. Our results suggest that it is important to include the scatter in the iterative design of the optimized intensity modulations.

Biophysical Phenomena↗
PubMed1995

A displacement model for thermoluminescent dosimetry in radioimmunotherapy.

A model is developed to enable dose determination for thermoluminescent dosimeters immersed in a radioactive solution such as used in radioimmunotherapy. For low energy beta emitters used in such therapy the size of the dosimeter results in a much lower light output than when irradiated with an external Cobalt-60 (60Co) beam to the same dose as delivered to the medium. The model takes the size of the dosimeter into account and hence allows calculation of the dose in the actual medium. The application to different dosimeter sizes as well as different radionuclide energies is also illustrated. Finally, the model can be extended to dose calculation in a mixed gamma and beta irradiation geometry.

Beta Particles↗
PubMed1995

Cytotoxic effects of several hopanoids on mouse leukemia L1210 and P388 cells.

The cytotoxic effects of hopanoids, including bacteriohopane-32, 33, 34, 35-tetrol (Tetrol), bacteriohopane-32-ol (Monol), diploptene, diplopterol and acetylated Monol (AcO-Monol) isolated from Acetobacter aceti, were tested against two leukemia cell lines. Tetrol and Monol have been shown to be toxic to mouse L1210 and P388 compared to the other hopanoids. By measuring the ESR spectra of the spin labeled membranes of these cells, it was shown that the incorporation of Monol resulted in a decrease in the fluidity of the membranes. The decrease in membrane fluidity may correlate, in part, with the cytotoxicity of hopanoids against the two cell lines.

Animals↗
PubMed1995

Interactions between bacteriohopane-32,33,34,35-tetrol and liposomal membranes composed of dipalmitoylphosphatidylcholine.

The effects of bacteriohopane-32,33,34,35-tetrol (Tetrol), on liposomal membranes composed of dipalmitoyl-phosphatidylcholine (DPPC) were examined and compared with those of bacteriohopane-32-ol (Monol) and cholesterol (Chol) by means of ESR and NMR techniques. 1H-NMR spectra of Tetrol-incorporated DPPC membranes showed splitting of the signals of the choline N-methyl resonance, whereas Monol- and Chol-incorporated membranes showed not splitting of signals above the transition temperature of DPPC. It was suggested that the incorporation of Tetrol affected only the fluidity near the polar head groups of the DPPC membranes. The characteristics of the interactions between Tetrol and membranes are due to the fact that in DPPC bilayers Tetrol and Monol have an inverted orientation contrary to Chol, and that the hydroxy groups of Tetrol suppress the hydrophobic interaction between DPPC molecules whereas the methyl groups of the hopanoid ring promote this.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Effects of bacteriohopane-32-ol on the stability of various kinds of liposomal membranes.

The effects of bacteriohopane-32-ol (Monol) on the stability of various kinds of liposomal membranes composed of phosphatidylcholine (PC) were examined by measuring the release of calcein entrapped in the liposomes; these effects were then compared with those of cholesterol (Chol). Incorporation of Chol enhanced the stability of both small unilamellar vesicles (SUV) and reverse-phase evaporation vesicles (REV) by increasing their content. However, the incorporation of Monol into PC membranes produced different effects on liposome stability due to the difference in vesicle size, fatty acyl chains of phospholipids and Monol contents. At a low Monol content of dipalmitoylphosphatidylcholine (DPPC) in SUV, incorporation of Monol exerted relatively major stabilizing effect at temperatures above Tm compared with those below Tm. Furthermore, the incorporation of Monol into REV of DPPC at about 12 mol% lowered the stability of REV below Tm of DPPC while at other concentrations this was increased. This peculiar effect was not observed in SUV membranes of DPPC and membranes composed of dimyristoylphosphatidylcholine (DMPC). These results are discussed with reference to the interaction between Monol and phospholipid molecules.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

A universal calibrator for prostate specific antigen (PSA).

We describe for the first time a protocol to purify an in vitro made PSA-ACT complex to apparent homogeneity by using a combination of gel filtration and ion-exchange chromatography. The purity of the PSA-ACT complex was confirmed by gel electrophoresis and Western blot. Purification of the PSA-ACT complex was highly reproducible. An extinction coefficient of 1.0 and 280 nm (L x g-1 x cm-1) was assigned to the PSA-ACT complex based on amino acid analysis. Molecular weight was assigned by taking cDNA of ACT (plus 26% carbohydrate) and the molecular weight of PSA (28,430) which totals 89,280. Two common calibrators were made consisting of 100% PSA-ACT complex and/or 90% PSA-ACT complex plus 10% free PSA (90:10 calibrator). The 90:10 calibrator is recommended as a universal calibrator for the international standardization of PSA immunoassays.

Humans↗
PubMed1995

Isolation and characterization of intranuclear ribonucleoprotein complexes associated with double-stranded RNA adenosine deaminase from brain cells: implications for RNA-editing and hypermutation of viral RNA in the CNS.

Double-stranded RNA adenosine deaminase (DsRAD), which converts adenosine in duplex RNA to inosine, has been implicated in editing of cellular mRNA and hypermutation of viral RNA in the central nervous system (CNS). We used subcellular fractionation to show that DsRAD in bovine brain tissues is associated with high-molecular-weight ribonucleoprotein (RNP) complexes in the nuclei. DsRAD-associated RNP complexes have apparent molecular mass of up to 500 kDa and buoyant density of 1.35 to 1.42 g cc-1 in CsCl solution. In human glioma cells, DsRAD is also found exclusively in intranuclear RNP complexes that co-sediment with the largest RNA species. These DsRAD-associated RNP complexes are dissociated by RNase A or high salt. The RNA component is not essential for DsRAD activity, and the protein component can be separated by dsRNA-affinity column, gel filtration column, and glycerol gradient into enzymatically active protein species with apparent molecular mass ranging from 120 kDa to 70 kDa in polyacrylamide gel. The bovine brain DsRAD has no apparent requirement for low-molecular-weight cofactors or metal ions. These results provide insight into the native state of DsRAD in brain cells and have interesting implications for its putative roles in RNA-editing and hypermutation of viral RNA in the CNS.

Adenosine Deaminase↗