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Biomedical subjects

C Yang

Publications and source records attributed to C Yang.

At least 19 recordsLinked to original sources
PubMed1995

Adenovirus-mediated gene transfer of wild-type p53 results in melanoma cell apoptosis in vitro and in vivo.

Gene transfer techniques may provide efficient treatment for a variety of malignant neoplasms. A replication-deficient adenovirus (Ad) vector which carries the cDNA for wild-type p53 (AdCMV.p53) was tested for its in vitro and in vivo effects on the growth of murine melanoma cell line B16-G3.26 and human melanoma cell line SK-MEL-24. The growth of B16-G3.26 cells infected with AdCMV.p53 was inhibited when compared to the uninfected cells or cells infected with the control vector AdCMV.NLS beta gal. Similarly, the growth of SK-MEL-24 cells infected with AdCMV.p53 was also below that of AdCMV.NLS beta gal-infected and uninfected controls. DNA laddering using agarose gel electrophoresis and in situ labeling of DNA fragmentation (TUNEL) showed that AdCMV.p53-infected murine and human melanoma cells underwent apoptosis. Nude mice injected s.c. either with B16-G3.26 cells or with SK-MEL-24 cells developed localized tumors. These tumors were subsequently infiltrated with either AdCMV.p53, AdCMV.NLS beta gal or saline alone. One week after infection, B16-G3.26 tumors exposed to AdCMV.p53 were 2.5 times smaller than control tumors and exhibited DNA fragmentation. A similar growth-inhibitory effect of AdCMV.p53 was observed with SK-MEL-24 tumors. Thus, Ad-mediated wild-type p53 overexpression resulted in melanoma cell apoptosis and inhibition of melanoma growth in vitro and in vivo. These gene therapy approaches may be useful in targeting rapidly growing, malignant melanomas in a clinical setting.

Adenoviridae↗
PubMed1995

The human and simian immunodeficiency virus envelope glycoprotein transmembrane subunits are palmitoylated.

The envelope proteins of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) were found to be modified by fatty acylation of the transmembrane protein subunit gp41. The precursor gp160 was also palmitoylated prior to its cleavage into the gp120 and gp41 subunits. The palmitic acid label was sensitive to treatment with hydroxylamine or 2-mercaptoethanol, indicating that the linkage is through a thioester bond. Treatment with cycloheximide did not prevent the incorporation of [3H]palmitic acid into the HIV envelope protein, indicating that palmitoylation is a posttranslation modification. In contrast to other glycoproteins, which are palmitoylated at cysteine residues within or close to the membrane-spanning hydrophobic domain, the palmitoylation of the HIV-1 envelope proteins occurs on two cysteine residues, Cys-764 and Cys-837, which are 59 and 132 amino acids, respectively, from the proposed membrane-spanning domain of gp41. Sequence comparison revealed that one of these residues (Cys-764) is conserved in the cytoplasmic domains of almost all HIV-1 isolates and is located very close to an amphipathic region which has been postulated to bind to the plasma membrane.

Amino Acid Sequence↗
PubMed1995

Adenovirus-mediated wild-type p53 expression induces apoptosis and suppresses tumorigenesis of prostatic tumor cells.

The use of replication-deficient adenoviral vectors in gene therapy may become a powerful method to achieve efficient but safe transfer of anti-tumor agents. Introduction of the wild-type p53 gene into tumor cells has, in general, been associated with growth suppression. In this study, infection of androgen-independent human prostate Tsu-pr1 cells lacking functional p53 alleles resulted in high levels of p53 protein within 10-15 h. Cells infected with AdCMV.p53 detached from the substratum, condensed, and exhibited fragmentation of nuclear DNA into nucleosomal units consistent with the process of apoptosis. These effects were evident within 24 h after infection, and the majority of cells had undergone apoptosis by 48 h, whereas cells infected with AdCMV.NLS beta Gal continued to proliferate. Uninfected or AdCMV.NLS beta Gal-infected Tsu-pr1 cells formed tumors in nude mice within 3 weeks after implantation, whereas AdCMV.p53-infected cells failed to form tumors during this period. Therefore, adenoviral-mediated antitumor therapy using the p53 gene is an efficient method to inhibit prostate tumor growth, and agents that target the cellular programmed cell death pathway may be useful in clinical applications.

Adenoviridae↗
PubMed1995

Role of mitogen-activated protein kinase phosphatase during the cellular response to genotoxic stress. Inhibition of c-Jun N-terminal kinase activity and AP-1-dependent gene activation.

Irradiation of mammalian cells with short wavelength ultraviolet light (UVC) evokes a cascade of phosphorylation events leading to altered gene expression. Both the classic mitogen-activated protein (MAP) kinases and the distantly related c-Jun N-terminal kinases (JNK) contribute to the response via phosphorylation of transcription factors including AP-1. These kinases are themselves regulated via reversible phosphorylation, and several recently identified specific MAP kinase phosphatases (MKP) have been implicated in down-regulating MAP kinase-dependent gene expression in response to mitogens. Here, we provide evidence that MKP-1 plays a role in regulating transcriptional activation in response to UVC as well as another genotoxic agent, methyl methanesulfonate (MMS). We further demonstrate that JNK is a likely target for MKP-1. JNK is shown to be activated by UVC and MMS treatment, while MAP kinase activation occurs only with UVC. Like JNK activation, MKP-1 mRNA is induced by both treatments, and elevated MKP-1 expression coincides with a decline in JNK activity. Constitutive expression of MKP-1 in vivo inhibits JNK activity and reduces UVC- and MMS-induced activation of AP-1-dependent reporter genes.

Animals↗
PubMed1995

In vitro fibrillogenesis of collagen II from pig vitreous humour.

Collagen from pig vitreous humour was fractionated into a soluble and an insoluble fraction by centrifugation. Most of the collagen II in the soluble fraction was present as pN-collagen II (procollagen II without the C-terminal propeptide), besides smaller quantities of procollagen II, collagen II and two as yet unidentified alpha-chains of collagen II. Other collagen types may be present only in trace amounts. Collagen II of the insoluble fraction, which is mostly deposited in fibrillar aggregates, consists of both pN-collagen II and collagen II. To determine the possible role of collagen II precursors in the formation of the extracellular matrix of the vitreous humour these collagen molecules were purified and in vitro fibrillogenesis was used to demonstrate that pN-collagen II could form fibrils in mixtures with collagen II. These fibrils have a reduced mass per unit length depending on the content of pN-collagen in the mixture. Cross-sections of the newly formed fibrillar aggregates revealed a flattened shape. The incomplete processing of the precursors of collagen II may be part of regulatory mechanisms possibly controlling the formation of a translucent scaffold as is required in the vitreous humour.

Animals↗
PubMed1995

Guillain-Barré syndrome in northern China. The spectrum of neuropathological changes in clinically defined cases.

The pathology of the Guillain-Barré syndrome remains controversial, and autopsied cases available for study by contemporary techniques are uncommon. Large numbers of cases clinically diagnosed as Guillain-Barré syndrome occur in northern China. In this study we examined the neuropathological changes in 12 autopsied cases from Hebei Province, China. Eleven died early in the course of their disease. In all cases tissue was specially handled and fixed for electron microscopy and for immunocytochemistry. Three of these 12 cases had typical acute inflammatory demyelinating polyneuropathy (AIDP) with lymphocytic infiltration and macrophage-mediated demyelination, reproducing the pathological picture most often reported in Guillain-Barré syndrome in North America, Europe, and Australia. Six cases had predominantly axonal involvement, characterized by Wallerian-like degeneration of nerve fibres, with only minimal demyelination and with minimal inflammation in five. Three cases, even though paralysed at the time of death, had only very mild changes in the spinal roots and sciatic nerves. Within the group of six predominantly axonal cases, there were important differences both in the severity of the abnormalities and in the classes of fibres involved. Three cases had extensive Wallerian-like degeneration of sensory as well as motor fibres [acute motor-sensory axonal neuropathy (AMSAN)], while in the other three cases the fibre degeneration affected the motor nerve fibres almost exclusively. These latter cases establish a structural basis for the clinical and electrophysiological picture termed the acute motor axonal neuropathy (AMAN) pattern. In both the AMAN and the AMSAN patterns, a prominent feature was the presence of macrophages within the periaxonal space, surrounding or displacing the axon, and surrounded by an intact myelin sheath. These studies show that the early pathological changes in cases clinically diagnosed as the Guillain-Barré syndrome are diverse and not restricted to the well-known pattern of AIDP, and that the predominant pathological patterns may differ in different parts of the world. The differences in pathological findings between acute inflammatory demyelinating polyneuropathy and the axonal patterns are likely to reflect differences in the pathogenetic mechanisms. The periaxonal macrophages in the axonal patterns suggest that an important epitope may be localized to the axolemma or periaxonal space. The mild cases indicate that severe paralysis can occur early in Guillain-Barré syndrome without prominent structural changes along the nerve, suggesting that physiological block or nerve terminal changes may be implicated.

Acute Disease↗
PubMed1995

Influence of periodontal bacteria and disease status on V beta expression in T cells.

Some bacterial antigens such as S. aureus enterotoxins can selectively stimulate T cells that express specific V beta genes of the T cell antigen receptor (TCR). The purpose of this study was to investigate whether or not periodontal bacteria could similarly alter the expression of V beta families within the TCR complex. Peripheral blood mononuclear cells (PBMNCs) were isolated from 12 patients with early onset periodontitis and 11 periodontally-healthy controls. PBMNCs were incubated in media alone, or co-cultured for 48 h with heat-inactivated A. actinomycetemcomitans, P. gingivalis and P. intermedia. Expression of five V beta families (V alpha beta 2, V beta 5, V beta 6, V beta 8, and V beta 12) was determined by use of monoclonal antibodies. Mean unstimulated expression of V alpha beta 2 and V beta 8 was significantly higher (p < 0.05) in patients than healthy controls. Co-culture with the three bacteria resulted in significant changes (increases or decreases) in V beta expression in 27% of the trials. There were no significant differences in the number or direction of changes in samples from patients and controls. When compared to unstimulated controls, 18 significant increases but no decreases in the percentage of cell expressing V alpha beta 2, V beta 5 or V beta 6 were noted following co-culture with P. intermedia. Overall, co-culture with P. intermedia significantly (p < 0.05) up-regulated expression of the five V beta families studied. These data suggest that periodontal bacteria may alter V beta expression within the T cell receptor complex.

Adult↗
PubMed1995

Stimulatory effect of bradykinin on insulin release from the perfused rat pancreas.

Rat pancreas perfusion was performed to study the effect of bradykinin on insulin release. At the perfusate glucose concentration of 6 mM, bradykinin (0.01-1 microM) increased insulin release in a concentration-dependent manner. In addition, bradykinin (1 microM) increased the glucose (10 mM)-induced insulin release. HOE-140 (0.1 microM), a bradykinin B2-receptor antagonist, decreased the baseline insulin release and abolished the bradykinin (1 microM)-induced increase in insulin release. In addition, HOE-140 (0.1 microM) attenuated the glucose (10 mM)-induced increase in insulin release. Because the blockade of bradykinin receptors by HOE-140 attenuated the glucose-induced increased insulin release, our present findings suggest that bradykinin may play a physiological role in the regulation of insulin release.

Animals↗
PubMed1995

Effect of IL-7 or IL-4 on reconstitution of donor lymphoid cells in congenic murine bone marrow transplantation.

IL-7 and IL-4 are known to influence the growth of cells of the lymphoid lineage. In this study, we investigated the effects of in vivo administration of IL-7 or IL-4 in mice subjected to congenic BM transplant. C57BL/6 Ly5.1+ mice were subjected to TBI, followed by transfer of B and T cell-depleted BM from C57BL/6 Ly5.2+ donor mice. Recipient mice were implanted with 14-day miniosmotic pumps that delivered IL-7, IL-4 or PBS and were examined for reconstitution of lymphoid cells using flow cytometry on different days. We observed no significant difference in the number of splenocytes, thymocytes and PBLs between recipient mice administered with cytokines or normal control mice. However, we observed that IL-4 infusion resulted in appearance of increased numbers of donor CD23+B220+ cells and also donor cells expressing Fc receptors for IgM (Fc micro R) and B220. Since CD23 is present only on mature B cells, our data demonstrate that following BMT, IL-4 treatment results in the development of more mature B cells compared to control mice. Additionally, we observed that IL-7 infusion resulted in significantly decreased expression of donor sIgM+B220+ cells. However, the effects of IL-7 or IL-4 were observed when the cytokines were actively administered and rapidly abated upon cessation of cytokine therapy.

Animals↗
PubMed1995

[Studies on red blood cell-mediated immunity of patients with recurrent stromal herpes simplex keratitis].

Assays of red blood cell (RBC) C3b receptor rosette and RBC immune complex (IC) rosette of 67 cases with recurrent stromal herpes simplex keratitis (HSK) were carried out. The results show that the rosette rate of RBC C3b receptor is markedly lowered and that of RBC IC receptor is significantly increased in cases with stromal HSK. In comparisons with the corresponding rates in the control group, there are significant differences (P < 0.01). The roles of RBC-mediated immunity in the immunopathogenesis of HSK were preliminarily discussed.

Adolescent↗
PubMed1994

Rab proteins form in vivo complexes with two isoforms of the GDP-dissociation inhibitor protein (GDI).

GTPases of the Rab family play a key role in the regulation of vesicular transport in eukaryotic cells. Several accessory proteins that regulate their GDP/GTP cycle as well as their subcellular localization have been identified within the past few years. The best known is Rab3A GDP dissociation inhibitor protein (GDI), originally identified as an inhibitor of GDP dissociation from Rab3A, a Rab protein specifically expressed in neuronal and neuroendocrine cells. Recent studies have pointed out a role of Rab3A GDI as a chaperone of several Rab proteins during their cycling between cytosol and membranes and Rab3A GDI has been considered so far as a general regulator of Rab function. However, cDNAs encoding potential isoforms of this protein, called GDI beta and GDI-2, have been recently isolated. In this study, we have characterized cytosolic Rab protein complexes in various cell types and tissues using Mono Q chromatography. We show that in rat brain and in insulin-secreting RINm5F cells, the majority of Rab proteins are complexed with Rab3A GDI. In contrast, in Chinese hamster ovary cells, they are mainly complexed to a protein that we have identified as GDI beta. In rat liver cytosol, Rab proteins form complexes with both isoforms. We also show that the proportion of Rab proteins complexed with either isoform depends on the relative abundance of Rab3A GDI and GDI beta in the cytosol. These findings suggest that GDI isoforms are either redundant or could be involved in the fine control of Rab function.

Amino Acid Sequence↗
PubMed1994

A unique antigenic determinant on collagen II closely associated with age related abnormal modification.

During aging, a variety of proteins undergo a non-enzymatic modification, such as oxidation, attachment of lipid peroxide, and glycation. In particular, the long-lived extracellular matrix proteins in connective tissue may be common targets for this kind of modification which, in turn, is involved in the pathogenesis of age related diseases. In the present study, we demonstrate that the age related modification on collagen II generates (a) new epitope(s). Furthermore, we established an immunochemical assay which is specifically suited to monitor the extent of abnormal modification of collagen II.

Adolescent↗
PubMed1994

Pharmacokinetics, biodistribution and tumor localization of two anti-human B-cell chronic lymphocytic leukemia monoclonal antibodies and their F(ab)'2 fragments in a xenograft model.

We investigated the pharmacokinetics, biodistribution and tumor localization of intravenously injected Dal B01 and Dal B02, two monoclonal antibodies (MoAbs) directed against tumor associated antigens on human chronic lymphocytic leukemia (CLL) B cells, and their F(ab)'2 fragments in nude mice bearing xenografts of the human B cell CLL line D10-1. More of the percentages of the injected dose (% ID) of these two MoAbs and their F(ab)'2 fragments specifically localized in the tumor xenografts than in normal tissues. Compared to intact MoAbs, their F(ab)'2 fragments had lower % ID in tumors and were cleared from circulation faster. Well-defined tumor images were obtained at 24 and 48 h after administration of [131I]Dal B02 F(ab)'2 fragment and at 96-192 h after administration of [131I]Dal B02. A comparison between intravenous and intraperitoneal routes of administration of [131I]Dal B02 did not reveal any difference in the localization of % ID in tumor or normal tissues.

Animals↗
PubMed1994

Intracellular calcium dependent activation of p72syk in platelets.

We previously demonstrated that thrombin-induced activation of p72syk was independent of intracellular Ca2+ elevation in platelets. However, our previous studies also demonstrated that activation of platelets by ionophore A23187 results in a dramatic increase in tyrosine phosphorylation of several cellular proteins. In the present study, we investigated the effect of Ca2+ elevation on the activity of p72syk. When washed porcine platelets were stimulated with ionophore A23187 and the activity of p72syk was assessed by means of an immunoprecipitation kinase assay, A23187 caused a time- and dose-dependent increase in the specific activity of p72syk. In addition, pretreatment of platelets with both aspirin and ADP scavengers or chelation of extracellular Ca2+ by EGTA had no effect on the A23187-induced activation of p72syk. These results indicate that A23187-induced activation of p72syk is independent of the formation of endoperoxide/thromboxane A2, released ADP and extracellular Ca2+, suggesting the existence of a novel pathway for activation of p72syk. Furthermore, evidence is presented which indicates a synergistic effect of A23187 and thrombin on the activation of p72syk, and an inhibitory effect of pretreatment with phorbol 12-myristate 13-acetate, a protein kinase C activator, on the activation of p72syk induced by either A23187 or thrombin.

Animals↗
PubMed1994

Chlamydia trachomatis from individuals in a sexually transmitted disease core group exhibit frequent sequence variation in the major outer membrane protein (omp1) gene.

60 cervical Chlamydia trachomatis infections identified by antigen detection from 51 prostitute women in Nairobi, Kenya were evaluated for sequence polymorphism in the major outer membrane protein (omp1) gene. DNA from clinical specimens was amplified by the polymerase chain reaction and cycle sequenced through variable domains (VD) 1, 2, and 4.37 (63%) samples had variant VD sequences, 19 (32%) samples had prototype VD sequences, and 4 (6%) samples had prototype VD sequences, and 4 (6%) samples contained omp1 sequences from two or more C. trachomatis strains. Among the 37 variant strains, 18 had two or fewer nucleotide substitutions in one or two VDs and represented point mutational drift variants. 19 strains had a larger number of nucleotide changes and displayed mosaic omp1 sequences that may have been generated by omp1 VD recombination. We conclude that the prevalence of C. trachomatis omp1 DNA polymorphism is substantial among prostitute women in Nairobi, Kenya and that this is the likely result of immune selection pressure.

Amino Acid Sequence↗