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L Ding

Publications and source records attributed to L Ding.

At least 145 records · Page 8Linked to original sources
PubMed1993

bcl-2 proto-oncogene expression during human T cell development. Evidence for biphasic regulation.

To ensure that the mature T cell repertoire is MHC-restricted yet not autoreactive, cortical thymocytes that express low levels of the TCR/CD3 complex along with CD4 and CD8 (double positive cells) are subjected to positive and negative selection. Surviving cells lose either CD4 or CD8 (single positive cells) and are located primarily in the thymic medulla. bcl-2, a novel proto-oncogene that promotes cell survival by inhibiting programmed cell death (apoptosis), may be an important protein in regulating cell survival during thymocyte development. We have examined the expression of bcl-2 during T cell development by using human thymocytes. Consistent with previous studies, human thymic tissue sections stained for bcl-2 revealed occasional bcl-2+ cells within the thymic cortex and intense staining of virtually all medullary thymocytes. More quantitative western blot analysis and S1 nuclease protection assay revealed that single positive thymocytes contained approximately 2 to 3 times the level of bcl-2 protein and 3 to 4 times the level of bcl-2 mRNA as double positive thymocytes. Flow cytometric analysis of purified double positive thymocytes revealed that minimal amounts of bcl-2 protein was in fact detectable in most cells, although a small subpopulation (10-20%) contained higher levels. In contrast, brighter staining for bcl-2 was observed in virtually all single positive thymocytes. Surprisingly, CD4-CD8- thymocytes (both CD3- and CD3+) expressed the same amount of bcl-2 as did the single positive thymocytes. Because a large percentage of CD3-CD4-CD8- cells are cycling, we examined the effect of mitogenic stimulation on bcl-2 expression by double positive thymocytes by using western blot analysis. bcl-2 expression in double positive thymocytes could not be induced by cell cycle entry following stimulation with PMA and ionomycin. Our data demonstrate that bcl-2 expression is biphasic during T cell development. Both CD3-CD4-CD8- and CD3+CD4+ and CD3+CD8+ thymocytes express high levels of bcl-2. Therefore, diminished bcl-2 expression in double positive thymocytes seems to be the result of specific down-regulation in order to facilitate the selection CD4+CD8+ thymocytes.

Cell Differentiation↗
PubMed1993

Programmed cell death by bcl-2-dependent and independent mechanisms in B lymphoma cells.

Programmed cell death (PCD) or apoptosis is a common form of cellular demise during embryogenesis, tumorigenesis and clonal selection in the immune system. The bcl-2 proto-oncogene has been recently implicated as a potential physiological regulator of the PCD pathway. Gene transfer studies have shown that overexpression of bcl-2 blocks apoptosis mediated by several stimuli in cultured cell lines and promotes the survival of B and T lymphocytes in transgenic mice. However, it remains unclear whether under normal conditions bcl-2 is responsible for controlling cell death. We have investigated the role of bcl-2 in the antimembrane IgM (mIgM)-induced apoptotic death of WEHI-231 B cell lymphoma, a model that mimics clonal deletion of immature B cells by antigen. Signalling of mIgM receptors triggered downregulation of both bcl-2 RNA and protein, and induced apoptosis in WEHI-231 B cells. This effect appeared to be specific since (i) the levels of beta 2-microglobulin and beta-actin RNA remain unchanged and (ii) signalling of the apoptosis-resistant B cell lymphoma line BAL-17 with anti-mu was not associated with downregulation of bcl-2 RNA. However, stable expression of bcl-2 by transfection did not rescue WEHI-231 B cells from apoptosis, yet WEHI-231 cells overexpressing bcl-2 were more resistant to programmed cell death induced by heat-shock.(ABSTRACT TRUNCATED AT 250 WORDS)

Apoptosis↗
PubMed1993

Immunogenicity of synthetic peptides related to the core peptide sequence encoded by the human MUC1 mucin gene: effect of immunization on the growth of murine mammary adenocarcinoma cells transfected with the human MUC1 gene.

The immune response of CAF1 mice to various synthetic peptides (SP) related to the amino acid sequence (PDTRPAPGSTAPPAHGVTSA) of the tandem repeat of the MUC1 human breast mucin core peptide was evaluated. The most immunogenic preparations of the synthetic peptides were those conjugated to keyhole limpet hemocyanin (KLH) or clustered in a dendritic multiple antigenic peptide (MAP-4) configuration. The mice were immunized subcutaneously with synthetic peptides emulsified in RIBI adjuvant, employing various immunization protocols. Equivalently high IgG responses were induced using SP-KLH conjugates (GVTSAPDTRPAPGSTA-KLH) or an SP--MAP-4 chimeric configuration (SP1-6), which also included a universal malarial CST-3 T-helper epitope (SP1-6 = SAPDTRPAEKKIAKMEKASSVFNVVNS--MAP-4). These IgG antibodies bound both the appropriate MUC1 synthetic peptides and the cell surface expressed MUC1 mucin on murine mammary cells that had been transfected with the human MUC1 gene and a human breast cancer cell line that expresses cell-surface MUC1. A MAP-4 molecule, which included the entire 20-amino-acid sequence of the MUC1 tandem repeat (SP1-5 = PDTRPAPGSTAPPAHGVTSA-MAP-4) induced a poor IgG response. In contrast, all three types of molecule: SP-KLH, SP1-6 and SP1-5, were found to be good immunogens for the induction of specific delayed-type hypersensitivity (DTH) reactions measured using either synthetic peptides or MUC1-transfected cells. In addition, immunization with irradiated MUC1-transfected cells induced strong DTH reactions measured using synthetic peptides that expressed the PDTRP sequence, which has been shown to be, or to overlap, a T cell epitope in humans and a B cell epitope in mice. Finally, it was demonstrated that synthetic MUC1 peptide "vaccines" could be used both prophylactically and therapeutically to inhibit the growth of MUC1-transfected tumor cells and prolong the survival of tumor-bearing mice.

Adenocarcinoma↗
PubMed1993

Effects of weight cycling in rats allowed a choice of diet.

We examined the effects of weight cycling, produced by bouts of weight loss and regain, on body weight, body composition, dietary fat intake, and energy efficiency. Three groups of adult female Wistar rats were followed for 116 days: control rats (n = 10) were allowed ad libitum access to three mixed diets with protein as a constant proportion of energy and fat provided at 10, 30, and 50% of energy; cycled rats (n = 10) had four bouts of food restriction (50% of baseline intake for 10 days) and refeeding (18-20 days of ad libitum access to the 3 mixed diets); maturity controls (n = 10) were treated identically to controls during the first two cycles and identical to cyclers during the final two weight cycles. At the end of the experiment, we could identify no negative effects of weight cycling on any of the measures taken, and in fact body weight and percentage body fat were lower in cyclers than controls. Dietary fat intake was not altered by weight cycling. In summary, weight cycling did not promote body weight or body fat gain.

Animals↗
PubMed1993

A 9-year follow-up study of the immunogenicity and long-term efficacy of plasma-derived hepatitis B vaccine in high-risk Chinese neonates.

The long-term immunogenicity of and protection provided by a plasma-derived hepatitis B vaccine was determined in a cohort of 98 susceptible Chinese neonates immunized in 1982-1983. Within 24 hours of birth, 89 infants received the first of three 30-micrograms doses of vaccine (at 0, 1, and 6 months) and were subsequently followed up by testing for serological markers of hepatitis B virus and by determining levels of alanine aminotransferase annually for 9 years. After the primary series of vaccine doses, 74 (83%) of 89 subjects developed antibody to hepatitis B surface antigen (anti-HBs). At the 9-year follow-up, 51% of vaccinees still had levels of antibody of > or = 10 mIU/mL, considered the protective level. Seven responders to vaccine (9.4% of 74 evaluable patients) developed antibody to hepatitis B core antigen, and in six of these responders, levels of anti-HBs increased transiently. None of the vaccinees developed chronic carriage of hepatitis B surface antigen or clinical hepatitis. Immunization of high-risk neonates with a plasma-derived hepatitis B vaccine can induce long-lasting protective immunity that can prevent or modify primary infection for at least 9 years. Booster doses are not necessary during this period.

Child↗
PubMed1992

Anti-human immunodeficiency virus effects of cationic metalloporphyrin-ellipticine complexes.

A series of cationic metalloporphyrin-ellipticine complexes were found to inhibit the cytopathicity of human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus in MT-4 cells at concentrations ranging from 1.4 to 17 micrograms/mL, i.e. at a concentration that was 2.5-30-fold below the cytotoxicity threshold. These compounds were also found to inhibit syncytium formation between persistently HIV-1-infected HUT-78 and uninfected Molt/4 cells, to interfere with HIV-1 binding to the cells, and to suppress HIV-1-associated reverse transcriptase activity.

CD4 Antigens↗
PubMed1992

IL-10 inhibits mitogen-induced T cell proliferation by selectively inhibiting macrophage costimulatory function.

IL-10, a newly designated cytokine primarily produced by the Th2 subset of CD4+ T lymphocytes and Ly-1+ B lymphocytes, has recently been hypothesized to inhibit cytokine production by Th1 T cell clones by blocking accessory cell- (AC) dependent costimulatory function. To evaluate the effect of IL-10 on Con A-induced proliferative responses of resting murine T cells, purified T cells were cultured with different types of AC. The addition of IL-10 produced a 70 to 90% inhibition of resting T lymphocyte proliferation when purified populations of macrophages were used as AC, but had no effect on the AC function of T-depleted spleen cells, activated B cells, dendritic cells, or L cells. The inhibitory effects of IL-10 were inversely related to the concentration of mitogen and could be reversed by the addition of the neutralizing anti-IL-10 mAb, SXC1. The inhibition of macrophage AC function was not related to the induction of a suppressor cytokine as stimulation by mixtures of macrophages and limiting numbers of dendritic cells was not inhibited. The decrease in proliferative responses was primarily secondary to inhibition of IL-2 production although the failure of exogenous IL-2 to completely reconstitute the response suggested that IL-10 may also exert inhibitory effects on the induction of expression of a functional IL-2R. These results are most consistent with a model in which IL-10 inhibits the induction of expression on macrophages of a critical costimulatory molecule that may be constitutively expressed on other types of AC.

Animals↗
PubMed1992

Comparison of the enzymatic and biochemical properties of human insulin-degrading enzyme and Escherichia coli protease III.

The enzymatic and biochemical properties of human insulin-degrading enzyme and Escherichia coli protease III have been compared. Both enzymes were found to degrade insulin in such a way that its receptor binding activity was rapidly lost but its precipitability in trichloracetic acid was only slightly decreased. Both enzymes were also found to be inhibited by chelating agents. The bacterial enzyme, which could be purified in large amounts, was found to contain 0.6 mol of zinc per mol of enzyme but no detectable manganese. The mammalian enzyme but not the bacterial one was inhibited by a sulfhydryl alkylating agent. The two enzymes also differed in substrate specificity. The mammalian enzyme degraded insulin much better than insulin-like growth factor II, whereas the bacterial enzyme degraded them equally. The mammalian enzyme could be labeled by cross-linking to insulin = bombyxin II much greater than insulin-like growth factor I and II much greater than relaxin, while the bacterial enzyme was labeled by insulin-like growth factor II greater than insulin = insulin-like growth factor I much greater than relaxin much greater than bombyxin. Finally, sucrose gradient centrifugation and cross-linking studies both in vitro and in vivo indicated that active human enzyme partially existed as a homo- or heterodimer, whereas the bacterial enzyme was active as a monomer.

Alkylating Agents↗
PubMed1992

New variant of cytochrome b5 reductase deficiency (b5RKurashiki) in red cells, platelets, lymphocytes, and cultured fibroblasts with congenital methemoglobinemia, mental and neurological retardation, and skeletal anomalies.

A Japanese man with cytochrome b5 reductase (b5R) deficiency in various blood cell lineages (red cells, platelets, and lymphocytes) and in cultured fibroblasts demonstrated congenital methemoglobinemia associated with mental and neurological retardation, and various skeletal anomalies, such as spondylosis deformans and finger joint deformations, which have never been described in association with this enzyme deficiency. Cytochrome b5 reductase deficiency was most severe in red cells (0.3-4%) and less marked in platelets (13-27%), lymphocytes (18-31%), and fibroblasts (50%). The present case appears to be a new variant of cytochrome b5 reductase deficiency (b5RKurashiki).

Adult↗
PubMed1992

Effects of glutathione depletion using buthionine sulphoximine on the cytotoxicity in mammalian cells and human tumor cells in vitro.

An inhibitor of glutathione biosynthesis, buthionine sulphoximine (BSO), was used to deplete the endogenous thiols in mammalian cells in vitro. In this study, the cytotoxicity of BSO and BSO combined with the hypoxic cell radiosensitizer misonidazole (MISO) was investigated. Both aerobic and hypoxic cytotoxicity of MISO was found to be increased. The concentration of BSO required to reduce the colony forming ability to 50% (Cc) for the chronic cytotoxicity on V79 cells was 0.03 mmol/L under aerobic condition, while the Cc for the acute cytotoxicity on V79 cells under hypoxic and aerobic conditions was 0.4 and 0.5 mmol/L. The growth inhibition rate of human tumor cells K562 and SGC-7901 by BSO was 6.89-26.06% and 12.01-55.69%, respectively. Enhanced cytotoxicity activity was observed when BSO was used in combination with cis-dichlorodiamino Pt(II) or 5-fluorouracil.

Antibiotics, Antineoplastic↗
PubMed1991

Alpha B-crystallin exists as an independent protein in the heart and in the lens.

Alpha B-crystallin, a polypeptide of molecular mass 22 kDa, is considered to be one of two subunits (alpha A and alpha B) of the multimeric lens-specific protein, alpha-crystallin. Recent demonstrations of the extra-lenticular presence of alpha B-crystallin have suggested that outside of the lens, this polypeptide may have functions independent of alpha A. Within the lens however, as part of the protein alpha-crystallin, its function is assumed to be structural. In an effort to investigate the functional status of alpha B-crystallin in the lens, we have characterized this polypeptide in the rat heart and the human lens. Unequivocal identity of alpha B-crystallin in the rat heart and the rat lens was established by the sequence analyses of the respective cDNA clones. Size exclusion chromatography (FPLC) and immunoblotting showed that in the rat heart, alpha B-crystallin exists as an aggregate of 300-400 kDa average molecular mass, similar to that of purified alpha B-crystallin isolated from bovine lens. Interestingly, analysis of the human lens proteins by immunoblotting showed that, with age, unlike alpha A-crystallin, the alpha B subunit remains detectable in the soluble fractions derived from normal lenses as old as 82 years. Importantly, the average molecular mass of the alpha B subunit in the soluble fractions prepared from 60-80-year-old human lens nuclei was also found to be 300-400 kDa. These data lead to the conclusion that alpha B-crystallin may exist as an independent protein not only in non-lens tissues (e.g. heart) but in the lens as well.

Aging↗
PubMed1991

Purification, gene cloning, and sequence analysis of an L-isoaspartyl protein carboxyl methyltransferase from Escherichia coli.

Mammalian tissues contain protein carboxyl methyltransferases that catalyze the transfer of methyl groups from S-adenosylmethionine to the free carboxyl groups of D-aspartyl or L-isoaspartyl residues (EC 2.1.1.77). These enzymes have been postulated to play a role in the repair and/or degradation of spontaneously damaged proteins. We have now characterized a similar activity from Escherichia coli that recognizes L-isoaspartyl-containing peptides as well as protein substrates such as ovalbumin. The enzyme was purified by DEAE-cellulose, hydroxylapatite, Sephadex G-100, polyaspartate, and reversed-phase chromatography and was shown to consist of a single 24-kDa polypeptide chain. The sequence determined for the N-terminal 39 residues was used to design an oligonucleotide probe that allowed the precise localization of its structural gene (pcm) on the physical map of the E. coli chromosome at 59 min. Transformation of E. coli cells with a plasmid containing DNA from this region results in a 3-4-fold overproduction of enzyme activity. The nucleotide sequence determined for the pcm gene and its flanking regions was used to deduce a mature amino acid sequence of 207 residues with a calculated molecular weight of 23,128. This sequence shows 30.8% sequence identity with the human L-isoaspartyl/D-aspartyl methyltransferase and suggests that this enzyme catalyzes a fundamental reaction in both procaryotic and eucaryotic cells.

Amino Acid Sequence↗
PubMed1991

Syntheses and in vitro evaluation of water-soluble "cationic metalloporphyrin-ellipticine" molecules having a high affinity for DNA.

The synthesis of hybrid "cationic metalloporphyrin-intercalator" molecules is reported. These molecules are based on 9-methoxyellipticine as intercalator and tris-(4-N-methylpyridiniumyl)metalloporphyrins having a 4-aminophenyl or a 4-hydroxyphenyl group for the attachment of the linker. The effect of the length of linker (7-13 bonds), the chemical nature of the linking group (with a carboxamido or an ether function), the position of amino group between the two parts of hybrid molecules, the number of intercalator moieties (ellipticinium) covalently attached to the metalloporphyrin, and the nature of the central metal atom (Mn, Fe, Zn) on the biological activity of these hybrid molecules were studied. In addition, these molecules have a high affinity for double-stranded DNA (affinity constant of hybrid molecule 9Mn,Me = 2.3 x 10(9) M-1 for poly[d(A-T)] and 2.8 x 10(8) M-1 for poly[d(G-C)] and are cytotoxic against murine leukemia cells L1210 in vitro (IC50 of 9Mn,Me = 0.8 microM). Their cytotoxicities are dependent on the nature of central atom. Iron derivatives are less active than manganese analogues and the corresponding zinc derivatives are nearly inactive despite their same affinity for nucleic acids. These highly water-soluble hybrid molecules could be considered as efficient bleomycin models based on a cationic metalloporphyrin.

Animals↗
PubMed1991

Suppression of lymphocyte signal transduction by murine mastocytoma ascites.

The lymphocyte signal transduction, as determined by intracellular free Ca2+ mobilization of concanavalin A-stimulated T lymphocytes and of anti-immunoglobulin mu chain antibody-stimulated B lymphocytes, was suppressed in spleen cells from mice injected with murine P1.HTR mastocytoma-induced ascites and in spleen cells treated with the ascites in vitro. The suppression was observed both at the peak level and in the reactive pattern of Ca2+ influx. In the suppression, the ascites were replaceable with tumor culture supernatants or tumor homogenates. Correspondingly, primary and secondary cytotoxic T lymphocyte (CTL) responses of DBA/2 mice to allogeneic antigen were also significantly suppressed by injection of the syngeneic P1.HTR tumor-derived ascites. This new finding suggested that the mechanism of the tumorous ascites or of the tumor-derived factor-mediated immunosuppression involves at least in part the suppression of the early event of the signal transduction for lymphocyte activation.

Animals↗
PubMed1991

Dehydroandrographolide succinic acid monoester as an inhibitor against the human immunodeficiency virus.

Dehydroandrographolide succinic acid monoester (DASM) is the dehydroandrographolyl ester of succinic acid; and andrographolide, from which DASM is made, is the major diterpenoid lactone found in the Chinese medicinal herb, Andrographis paniculata. DASM has been found to be an inhibitor against the human immunodeficiency virus (HIV) in vitro. It was nontoxic to the H9 cell at the concentrations of 50-200 (average, 108) micrograms/ml and was inhibitory to the HIV-1 (IIIB) at the minimal concentration of 1.6-3.1 (average 2.0) micrograms/ml. It was also inhibitory to two other strains of HIV-1 and a strain of HIV-2. This inhibitory effect could also be demonstrated in cultures of activated human blood mononuclear cells; the 50% toxic dose and the 50% HIV inhibitory dose were about 200-greater than or equal to 400 and 0.8-2 micrograms/ml, respectively. At the subtoxic concentration, DASM partially interfered with HIV-induced cell fusion and with the binding of HIV to the H9 cell. Presumably, it also interfered with HIV replication at another unidentified step(s).

Antiviral Agents↗
PubMed1991

[Constituents of the root of Berneuxia thibetica Decne].

Three crystals have been isolated from the root of Berneuxia thibetica. On the basis of spectral data, crystals A and B have been identified as chrysosplenetin B and 22,23-dihydrospinasterone respectively, while crystal C is a mix of spinasterol and 22,23-dihydrospinasterol.

Drugs, Chinese Herbal↗
PubMed1991

Progress in studies on the antimutagenicity and anticarcinogenicity of green tea epicatechins.

An antioxidative fraction was extracted from green tea and the major compounds in the fraction identified as epicatechins. Experimental results showed that green tea epicatechin compounds (GTEC) inhibited the mutagenicity and/or chromosomal damage caused by different carcinogens in both bacterial and mammalian cells. In vitro, GTEC inhibited transformation of BALB/3T3 cells induced by BP, X-rays, or MCA/TPA. In vivo, green tea extract decreased the incidence of carcinoma in the forestomach and esophagus of mice induced by sarcosine and NaNO2. GTEC inhibited the development of gamma-glutamyl transpeptidase-positive foci in the livers of rats treated with diethyl nitrosamine (DEN) or DEN/phenobarbital. Our investigations indicate that the antimutagenic and anticarcinogenic mechanisms of GTBC are related to the following: increased glutathione-S-transferase activity; inhibition of edema, hyperplasia, and ODC activity induced by TPA; free radical scavenging; blocked tumor promoter-induced inhibition of intercellular communication; and enhanced cell-mediated immunity. GTEC might be useful in the prevention of some kinds of cancer and a variety of oxidation-related diseases.

Animals↗