Biomedical subjects

J Guo

Publications and source records attributed to J Guo.

At least 127 records · Page 7Linked to original sources

PubMed2000

Potentiation of benzo[a]pyrene-induced pulmonary and forestomach tumorigenesis in mice by D,L-buthionine-S,R-sulfoximine-mediated tissue glutathione depletion.

In vitro studies have suggested that the glutathione (GSH) S-transferase (GST)-catalyzed GSH conjugation is an important mechanism for the detoxification of (+)-anti-7,8-dihydroxy-9, 10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BPDE], which is the activated form of the widespread environmental pollutant benzo[a]pyrene (BP). However, in vivo experimental evidence for the importance of GSH/GST system in defense against carcinogenic effects of BP is lacking. We hypothesized that if GSH/GST were to play an important role in the detoxification of (+)-anti-BPDE, the tumorigenic activity of BP would be increased by depleting the levels of GSH, which is the required nucleophilic substrate for GST-catalyzed conjugation reactions. In the present study, we have tested the above hypothesis by determining the effect of D, L-buthionine-S,R-sulfoximine (BSO)-mediated tissue GSH depletion on BP-induced tumorigenesis of the lung and forestomach in female A/J mice. Treatment of mice with three i.p. injections of 2.5 mmol BSO/kg (12 h apart) plus 20 mM BSO in drinking water, resulted in a statistically significant reduction in hepatic, pulmonary and forestomach GSH levels. At the same time, BSO-administration caused a statistically significant increase in BP-induced pulmonary and forestomach tumor multiplicity. To the best of our knowledge, the present study is the first report that provides in vivo experimental evidence for the importance of GSH/GST system in cellular protection against carcinogenic effects of BP.

Animals↗

PubMed2000

Decreased vaginal disease in J-chain-deficient mice following herpes simplex type 2 genital infection.

J-chain-deficient (Jch(-/-)) mice were used to study the role of polymeric IgA (pIgA) in primary disease and protective immunity following genital herpes simplex type 2 (HSV-2) infection. Vaginal IgA in the Jch(-/-) mice was composed primarily of monomeric IgA and was not associated with secretory component (SC). In contrast, vaginal IgA in wild-type (WT) mice was predominantly polymeric and bound to SC. Following HSV-2 genital infection, the Jch(-/-) mice consistently exhibited fewer vaginal symptoms (P = 0.010) and mortality (P = 0.075) than did the WT mice. The variation in disease expression could not be explained by differences in local viral replication, since titers in vaginal wash fluid were comparable. To assess the effect of J chain deficiency on protective immunity, WT and Jch(-/-) mice were immunized intravaginally with attenuated HSV-2, challenged intravaginally with wild-type virus 5 weeks later, and evaluated for vaginal infection and neurological disease. Although the Jch(-/-) mice had reduced vaginal HSV-specific IgA and IgG levels following immunization, both WT and Jch(-/-) mice were protected from symptoms following wild-type virus challenge. We conclude that pIgA is not required for protective immunity against genital HSV-2 disease and that J chain deficiency offers some protection against symptoms following primary HSV-2 genital infection.

Animals↗

PubMed2000

Analysis of domains in the IKKalpha and IKKbeta proteins that regulate their kinase activity.

The IkappaB kinases IKKalpha and IKKbeta are critical in activating the NF-kappaB pathway. Although these proteins have a similar structure that includes kinase, leucine zipper, and helix-loop-helix domains, they exhibit marked differences in their kinase activity and functional properties. For example, IKKbeta has a 10-20-fold higher level of kinase activity for IkappaBalpha than does IKKalpha. Furthermore, disruption of the murine IKKbeta gene, but not the IKKalpha gene, results in severe defects in activating the NF-kappaB pathway. Mice lacking IKKbeta succumb to severe hepatic apoptosis because of failure to activate the NF-kappaB pathway, whereas mice deficient in IKKalpha exhibit skin and skeletal abnormalities and an embryonic lethal phenotype. To better characterize differences in the functional properties of these kinases, hybrid IKK proteins were constructed by domain swapping, and their kinase activity was assayed. These studies demonstrated that differences in the IKKalpha and IKKbeta helix-loop-helix domains are primarily responsible for differences in their kinase activity. In contrast, their kinase and leucine zipper domains exhibited relatively conserved function. These studies further define the properties of IKKalpha and IKKbeta, which are involved in their unique regulatory roles.

Animals↗

PubMed2000

[Effects of pre-heating on the sensitivity of K562 cell to tumor necrosis factor-alpha].

In order to study the effects of pre-heating on the sensitivity of cells to tumor necrosis factor-alpha (TNF-alpha), the K562 cells were pre-heated at 40 degrees C for different times to induce heat shock protein 70 (HSP70). To observe the effects of TNF-alpha concentration on the sensitivity of pre-heated cells, cells were pre-heated for 60 min and treated with TNF-alpha (50, 100, 200 and 400 U/ml) for 16 hours, and the cells vitalities were detected by MTT. In order to observe the effect of pre-heating time on the sensitivity of cells to TNF-alpha, the pre-heated cells were treated with 100 U/ml TNF-alpha for 24 hours. The levels of HSP70 were tested by reversed transcription-PCR(RT-PCR). The results showed that HSP70 could be induced by pre-heating, and reached its top level after 120 mins, and the sensitivity of non-heated cells to TNF-alpha was lower than that of pre-heated cells. To 100 U/ml TNF-alpha, the sensitivity was lowest after the cells were pre-heated for 120 min. The results suggested that pre-heated could induce the expression of HSP70 and inhibit the sensitivity of cell to TNF-alpha, the mechanism may be involved with the overexpression of HSP70.

HSP70 Heat-Shock Proteins↗

PubMed2000

Identification and functional characterization of a conserved, nuclear factor 1-like element in the proximal promoter region of CYP1A2 gene specifically expressed in the liver and olfactory mucosa.

CYP1A2 is a major cytochrome P-450 isoform in the liver and the olfactory mucosa but is essentially not expressed in other tissues. A nuclear factor 1 (NF-1) -like element was identified in the proximal promoter region of rat, mouse, rabbit, and human CYP1A2 genes through data base analysis. In vitro DNase I footprinting with a -211 to +81 probe from the rat CYP1A2 gene and nuclear extracts from rat liver and olfactory mucosa revealed a single protected region corresponding to the NF-1-like element at -129 to -111. Protein binding to this NF-1-like element was tissue-selective and was confirmed by in vivo footprinting in native chromatin from rat liver. Multiple DNA-binding complexes were detected in gel-shift assays using the CYP1A2 NF-1-like element and nuclear extracts from liver and olfactory mucosa, all of which were supershifted in the presence of an anti-NF1 antibody. The NF-1-like element was essential for transcriptional activity of the CYP1A2 gene in an in vitro transcription assay using nuclear extracts from the two tissues. Thus, members of the NF-1 family of transcription factors may play an important role in the tissue-selective expression of the CYP1A2 gene in the liver and olfactory mucosa.

Animals↗

PubMed2000

Induction of the human protein P56 by interferon, double-stranded RNA, or virus infection.

P56 is the most abundant protein induced by interferon (IFN) treatment of human cells. To facilitate studies on its induction pattern and cellular functions, we expressed recombinant P56 as a hexahistidine-tagged protein in Escherichia coli and purified it to apparent homogeneity using affinity chromatography. A polyclonal antibody raised against this recombinant protein was used to show that P56 is primarily a cytoplasmic protein. Cellular expression of P56 by transfection did not inhibit the replication of vesicular stomatitis virus and encephalomyocarditis virus. P56 synthesis was rapidly induced by IFN-beta, and the protein had a half-life of 6 h. IFN-gamma or poly(A)(+) could not induce the protein, but poly(I)-poly(C) or an 85-bp synthetic double-stranded RNA efficiently induced it. Similarly, infection of GRE cells, which are devoid of type I IFN genes, by vesicular stomatitis virus, encephalomyocarditis virus, or Sendai virus caused P56 induction. Surprisingly, Sendai virus could also induce P56 in the mutant cell line P2.1, which cannot respond to either IFN-alpha/beta or double-stranded RNA. Induction of P56 in the P2.1 cells and the parental U4C cells by virus infection was preceded by activation of IRF-3 as judged by its translocation to the nucleus from the cytoplasm.

Antibodies, Monoclonal↗

PubMed2000

Identification of a human brain-specific isoform of mammalian STE20-like kinase 3 that is regulated by cAMP-dependent protein kinase.

A novel isoform of mammalian STE20-like kinase 3 (MST3) with a different 5' coding region from MST3, termed MST3b, was identified by searching through expressed sequence tag data base and obtained by rapid amplification of cDNA 5'-ends. MST3b was assigned to the long arm of human chromosome 13, D13S159-D13S280, by use of the National Center for Biotechnology Information sequence-tagged sites data base. Reverse transcription-polymerase chain reaction and Northern blot analysis with a probe derived from 5' distinct sequence of MST3b revealed that the expression of MST3b mRNA is restricted to the brain, in contrast to ubiquitous distribution of MST3 transcript. Western analysis confirmed the brain-specific expression of MST3b protein. In situ hybridization of rat brain sections with a MST3b-specific probe indicated that MST3b is widely expressed in different brain regions, with especially high expression in hippocampus and cerebral cortex. When expressed in human embryonic kidney 293 (HEK293) cells, MST3b effectively phosphorylated myelin basic protein, as well as undergoing autophosphorylation. Interestingly, expression of MST3, but not MST3b, in HEK293 cells was able to activate the endogenous p42/44 mitogen-activated protein kinase (MAPK) up to 4-fold, whereas neither isoform activated p38 MAPK under the same conditions. Further experiments demonstrated that MST3b, but not MST3, was effectively phosphorylated by activation of cyclic AMP-dependent protein kinase (PKA) in both in vivo and in vitro assays. The mutation of Thr-18 into Ala in MST3b (T18A), a putative PKA phosphorylation site that is absent in MST3, abolished its phosphorylation by PKA. Consequently, expression of the T18A mutant in HEK293 cells led to partial activation of p42/44 MAPK, indicating that MST3b is under the regulation of PKA. Taken together, our data provide evidence that the two isoforms of STE20-like kinase 3 are differentially distributed and regulated.

Animals↗

PubMed2000

Lecithin vesicular carriers for transdermal delivery of cyclosporin A.

Two kinds of vesicles with and without the presence of sodium cholate (flexible vesicles and conventional vesicles) were prepared, using cyclosporin A as model drug. When applied onto the excised abdominal skin of mice non-occlusively, the enhancing effects of vesicles on the penetration of cyclosporin A were assessed by an in vitro permeation technique. The effect of sodium cholate micelles was also studied. In vivo study was carried out by topical application of vesicles onto the mice skin and drug serum concentration was detected. Results showed that after 8 h of administration, flexible vesicles transported 1.16 microg of cyclosporin A through per cm(2) mice skin and amounted to 1.88 microg 24 h later. The residual amount in the skin was 1.78+/-0.51 microg/cm(2). However, flexible vesicles failed to transport measurable amount of drug through pre-hydrated skin while deposited 2.39+/-0.26 microg/cm(2) into the skin. Conventional vesicles failed to transfer cyclosporin A into the receiver while accumulated 0. 72+/-0.19 microg/cm(2) of drug in the skin. Furthermore, 1 and 40% sodium cholate micelles precluded the transport of cyclosporin A. In vivo studies indicated that with the application of flexible vesicles, serum drug concentration of 53.43+/-9.24 ng/ml was detected 2 h later. After the stratum corneum of mouse skin has been destroyed by shaving, flexible vesicles transferred large amount of drug into blood, up to 187.32+/-53.21 ng/ml after 1 h of application. Conventional vesicles failed to deliver measurable amount of drug into the blood under normal skin condition. In conclusion, flexible vesicle is better than conventional vesicle as the carrier for transdermal delivery of cyclosporin A. Penetration and fusion have been suggested to be two major functional mechanisms. Hydration is detrimental to the enhancement effect. Stratum corneum constitutes main barrier to the transport of lipophilic cyclosporin A.

Administration, Cutaneous↗

PubMed2000

New strategies for the synthesis of biologically important tetrapyrroles. The "B,C + D + A" approach to linear tetrapyrroles.

Linear tetrapyrroles related to phytochrome (1) were prepared in enantiospecific fashion by a new strategy beginning with ring-B,C synthons of type 19 (bis-iododipyrrins). Rings A and D were elaborated by Pd(0)-mediated coupling of 19a with the appropriate alkyne acid or amide derivatives 9 and 20, followed by intramolecular cyclization (method C: BC + D + A --> ABCD).

Magnetic Resonance Spectroscopy↗

PubMed2000

Absolute stereochemistry of the strevertenes.

The CD exciton chirality method was applied to determine the absolute stereochemistry of the strevertenes, antifungal pentaene macrolides produced by Streptoverticillium sp. LL-30F848. The CD difference spectrum of strevertene A methyl ester 15-dimethylaminobenzoate showed a positive couplet between the dimethylaminobenzoate and the pentaene chromophores, and therefore established the 15R configuration. Thus, by considering the relative configurations of the remaining stereogenic centers as derived from X-ray crystallography and ROESY experiments, the absolute stereochemistry of the strevertenes is established as 2R, 3S, 5S, 7S, 11R, 13R, 14R, 15R, 26S and 27R.

Anti-Bacterial Agents↗

PubMed2000

Role of MHC class I expression and CD8(+) T cells in the evolution of iodine-induced thyroiditis in NOD-H2(h4) and NOD mice.

Dietary iodine has long been known to influence the development of human autoimmune thyroid disease. In nonobese diabetic (NOD) and NOD-H2(h4) mice elevated dietary iodine has been shown to induce autoimmune thyroid disease. Immune responses to thyroid antigens can be detected in these mouse strains, including T cell responses in the NOD-H2(h4) mouse to thyroid peroxidase. Cell transfer studies and antibody depletion experiments reveal a requirement for both CD4(+) T cells and CD8(+) T cells in the development of thyroid autoimmunity. Histological analyses of the thyroids show that following 1 week of iodine administration MHC class I expression is elevated on thyroid follicular cells and CD4(+) and CD8(+) T cells have begun to infiltrate the gland. Although MHC class II expression on thyroid epithelial cells was also elevated, the tempo of expression was slower and the extent of expression was far less than that for MHC class I. Depletion of CD8(+) T cells at early stages of disease induction inhibited not only thyroid infiltration and autoantibody production but also reduced the levels of MHC expression in the thyroid, suggesting that cytokine production by infiltrating lymphocytes was responsible for the increased MHC expression.

Adoptive Transfer↗

PubMed2000

In vitro expression of hepatitis C virus non-structure 5 antigen in the HepG2 cell line.

To establish a cell line as a model system for HCV infection and propagation in vitro, a human HepG2 cell line was incubated with a HCV RNA positive serum. The sABC immunological techniques and gold-labeled colloid electron microscopy method were employed to examine the viral proteins in those cells. The HCV non-structure 5 antigen was first detected in the HepG2 cells 72 h after incubation. The antigen was continuously observed in the cytoplasm as well on the membrane of the HepG2 cells even after 1, 2, 3 and 4 weeks after incubation. The observation of HCV non-structure 5 antigen continuously expressed in the HepG2 cells strongly indicates that the cells may have been infected by HCV virus. Therefore, the HepG2 cell line may serve as a potential host for establishment of HCV infection and propagation in vitro.

Animals↗

PubMed2000

Study on biologic activity for membrane of normal bone marrow cells with infection of epidemic hemorrhagic fever virus.

Using DPH fluorescence probe, the membrane of normal bone marrow cells with infection of epidemic hemorrhagic fever virus (EHFV) was labeled. The membrane lipid fluidity was obviously decreased from the membrane lipid fluorescence polarization. The membrane lipid fluidity of lymphocyte, monocyte and neutrophilic granulocyte was dynamically observed. After culturing the cells for 1, 6, 24 and 72 h, it was found that all the membrane lipid fluidity of the infected cells was decreased obviously with the longer the culturing time, the more obvious it. Compared with the normal control groups, there was a significant difference statistically (P < 0.05-0.01). It was suggested that the decrease of the membrane lipid fludity of normal bone marrow cell with infection of EHFV had correlation with the degree of virus invading and cell-function injury.

Bone Marrow Cells↗

PubMed2000

Amphiphysin IIm, a novel amphiphysin II isoform, is required for macrophage phagocytosis.

Phagocytosis of pathogens by macrophages initiates the innate immune response, which in turn orchestrates the adaptive immune response. Amphiphysin II participates in receptor-mediated endocytosis, in part, by recruiting the GTPase dynamin to the nascent endosome. We demonstrate here that a novel isoform of amphiphysin II associates with early phagosomes in macrophages. We have ablated the dynamin-binding site of this protein and shown that this mutant form of amphiphysin II inhibits phagocytosis at the stage of membrane extension around the bound particles. We define a signaling cascade in which PI3K is required to recruit amphiphysin II to the phagosome, and amphiphysin II in turn recruits dynamin. Thus, amphiphysin II facilitates a critical initial step in host response to infection.

Amino Acid Sequence↗

PubMed2000

Analysis of libraries encoded with GC tags: compound elution, tag decode analysis, and statistical sampling analysis.

Libraries encoded with electrophoric tags present a unique challenge with respect to library quality control and characterization. Libraries are prepared on Tentagel resin in 200-fold redundancy wherein each resin particle contains one compound per one tag set. The amount of compound present on the bead is ca. 200-500 pmole while tag levels are estimated at 0.5-1 pmol/bead. Several quality control protocols have been developed in order to accurately estimate bead yield and purity for the entire library, ensure high tag fidelity, and to determine the overall performance of individual synthons. This review provides a unique, collective portrait of Pharmacopeia's approach in assessing the quality of libraries prepared using its molecular encoding technology.

Chromatography, Liquid↗

PubMed2000

APRIL and TALL-I and receptors BCMA and TACI: system for regulating humoral immunity.

We report that the tumor neurosis factor homolog APRIL (a proliferation-inducing ligand) stimulates in vitro proliferation of primary B and T cells and increases spleen weight due to accumulation of B cells in vivo. APRIL functions via binding to BCMA (B cell maturation antigen) and TACI (transmembrane activator and CAML-interactor) and competes with TALL-I (also called BLyS or BAFF) for receptor binding. Soluble BCMA and TACI specifically prevent binding of APRIL and block APRIL-stimulated proliferation of primary B cells. BCMA-Fc also inhibits production of antibodies against keyhole limpet hemocyanin and Pneumovax in mice, indicating that APRIL and/or TALL-I signaling via BCMA and/or TACI are required for generation of humoral immunity. Thus, APRIL-TALL-I and BCMA-TACI form a two ligands-two receptors pathway involved in stimulation of B and T cell function.

Animals↗

PubMed2000

Bax expressed from a herpes viral vector enhances the efficacy of N,N'-bis(2-hydroxyethyl)-N-nitrosourea treatment in a rat glioma model.

N,N'-bis(2-hydroxyethyl)-N-nitrosourea (BCNU) is a commonly used agent for treatment of malignant gliomas. The mechanisms of cell death and the role of Bcl-2 and Bax in a BCNU-treated rat glioma cell line were investigated. Our results indicate that apoptosis occurs only at a high concentration of BCNU with elevated levels of Bax and a reversed ratio of Bax/Bcl-2. Overexpression of Bax delivered by a herpes simplex viral vector in combination with BCNU chemotherapy enhanced the efficacy of BCNU in a rat glioma model. These findings suggest that conventional treatment with BCNU may be combined with gene therapy that delivers a bax gene into the glioma cells to achieve a high level of Bax, facilitating BCNU-induced cytotoxicity.

Animals↗

PubMed2000

Evidence for antigen presentation to sensitized T cells by thyroid peroxidase (TPO)-specific B cells in mice injected with fibroblasts co-expressing TPO and MHC class II.

Injection of AKR/N mice with fibroblasts co-expressing MHC class II and TPO in the absence of adjuvant induces IgG-class TPO antibodies that resemble spontaneously arising human thyroid autoantibodies. We have used this model to examine the effect of iodide on TPO antibody induction as well as to analyse the interaction between T and B cells. Despite its importance as a major environmental factor in thyroid autoimmunity, variable iodide intake had no detectable effects on TPO antibody levels, lymphocytic infiltration of the thyroid or thyroid hormone levels. In terms of T cell responsiveness, splenocytes from TPO fibroblast-injected mice, but not from control mice, proliferated in response to TPO. Intriguingly, B cell-depleted splenocytes (mainly T cells without reduction of macrophages) proliferated in response to TPO only when co-cultured with irradiated autologous splenocytes from TPO fibroblast-injected mice but not from control mice. These data suggest that TPO-specific B cells are involved in antigen presentation to sensitized T cells and are supported by the ability of spleen cells from TPO cell-injected (but not control) mice to secrete TPO antibodies spontaneously in culture. In conclusion, we provide the first evidence for the presence of thyroid autoantigen-specific B cells and their ability to present their autoantigen to sensitized T cells in mice induced to develop TPO antibodies resembling autoantibodies in humans.

Animals↗