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At least 37 records · Page 2Linked to original sources
PubMed1989

Differences in the metabolism of oxidatively modified low density lipoprotein and acetylated low density lipoprotein by human endothelial cells: inhibition of cholesterol esterification by oxidatively modified low density lipoprotein.

The rate of degradation of oxidatively modified low density lipoprotein (Ox-LDL) by human endothelial cells was similar to that of unmodified low density lipoprotein (LDL), and was approximately 2-fold greater than the rate of degradation of acetylated LDL (Ac-LDL). While LDL and Ac-LDL both stimulated cholesterol esterification in endothelial cells, Ox-LDL inhibited cholesterol esterification by 34%, demonstrating a dissociation between the degradation of Ox-LDL and its ability to stimulate cholesterol esterification. Further, while LDL and Ac-LDL resulted in a 5- and 15-fold increase in cholesteryl ester accumulation, respectively, Ox-LDL caused only a 1.3-fold increase in cholesteryl ester mass. These differences could be accounted for, in part, by the reduced cholesteryl ester content of Ox-LDL. However, when endothelial cells were incubated with Ac-LDL in the presence and absence of Ox-LDL, Ox-LDL led to a dose-dependent inhibition of cholesterol esterification without affecting the degradation of Ac-LDL. This inhibitory effect of Ox-LDL on cholesteryl ester synthesis was also manifest in normal human skin fibroblasts incubated with LDL and in LDL-receptor-negative fibroblasts incubated with unesterified cholesterol to stimulate cholesterol esterification. Further, the lipid extract from Ox-LDL inhibited cholesterol esterification in LDL-receptor negative fibroblasts. These findings suggest that the inhibition of cholesterol esterification by oxidized LDL is independent of the LDL and scavenger receptors and may be a result of translocation of a lipid component of oxidatively modified LDL across the cell membrane.

Acetylation↗
PubMed1977

T cell-mediated cytotoxicity against trinitrophenyl-modified cells: effect of glutaraldehyde treatment on the immunogenicity and antigenicity of trinitrophenyl-modified cells.

Cells treated with low concentrations of glutaraldehyde for a 10-sec interval were unable to incorporate 3H-leucine into TCA precipitable protein, respond to H-2 allogeneic cells in mixed lymphocyte reactions (MLR) and cell-mediated lympholysis (CML) assays, or display capping of cell surface immunoglobulin (Ig) with a fluoresceinated anti-Ig reagent. Such cells could stimulate and specifically block H-2 allogeneic CML activity but could not stimulate an H-2 allogeneic MLR response. Trinitrobenzenesulfonic acid (TNBS) treated spleen cells were used to sensitize syngeneic splenocytes into displaying a cytotoxic effect against trinitrophenyl (TNP)-modified target cells. Treatment of the stimulator cells with glutaraldehyde immediately after modification with TNBS did not impair their immunogenic activity. Similar treatment of TNP-modified concanavalin A-stimulated lymphoblasts that were used as inhibitors in a CML cold target competition assay allowed such cells to retain their antigenicity. Cells treated with glutaraldehyde before TNP-modification, however, were not antigenic in the cold target competition assay. These data are compatible with TNBS acting on plasma membrane molecules directly to cause cells to be antigenic and immunogenic in the CML assay rather than affecting internal cellular components.

Aldehydes↗
PubMed1990

Postoperative active specific immunization in colorectal cancer patients with virus-modified autologous tumor-cell vaccine. First clinical results with tumor-cell vaccines modified with live but avirulent Newcastle disease virus.

Sixteen patients with colorectal carcinoma Dukes' Stage B2, C, or D were treated with an autologous virus-modified tumor-cell vaccine after potential curative tumor resection (R0-Resection). An inoculum of 1 X 10(7) cells incubated with 32 hemagglutination units of nonirradiated Newcastle disease virus (NDV) was given intracutaneously up to four times at 10-day intervals. The delayed-type hypersensitivity (DTH) skin reaction was measured. The vaccination was well tolerated. In 11 of 16 patients an increasing reactivity against the vaccine was observed during the vaccination procedure. A challenge test using autologous tumor cells without NDV after the vaccination cycle revealed a specific antitumor sensibilization in 12 patients. The DTH response was not due to bacterial contamination or sensibility to the virus. Histologic examination of the vaccination site showed a dense infiltration of predominantly helper T-lymphocytes. We conclude that in most of the patients treated active, specific immunization led to a specific antitumor sensitivity.

Adult↗
PubMed1987

Identification of C8-modified deoxyinosine and N2- and C8-modified deoxyguanosine as major products of the in vitro reaction of N-hydroxy-6-aminochrysene with DNA and the formation of these adducts in isolated rat hepatocytes treated with 6-nitrochrysene and 6-aminochrysene.

Since 6-nitrochrysene and 6-aminochrysene have shown activity in carcinogenicity bioassays, we have begun an investigation of their metabolic activation pathways and the nature of the carcinogen-DNA adducts that may be formed. N-Hydroxy-6-aminochrysene (N-hydroxy-AC), a candidate proximate or ultimate carcinogen and the highest polycyclic N-hydroxy arylamine homolog studied thus far, was prepared by direct chemical synthesis and characterized by 1H-n.m.r. spectroscopy. Its rate and extent of reaction with DNA in vitro was 20-30 nmol bound/mg DNA/30 min, which is 2-10 times greater than has been reported for several other carcinogenic N-hydroxy arylamines. Three major aminochrysene-nucleoside adducts were detected in enzymatic hydrolysates of this N-hydroxy-AC-modified DNA, and these were isolated and identified by mass and 1H-n.m.r. spectroscopy as N-(deoxyinosin-8-yl)-6-aminochrysene, 5-(deoxyguanosin-N2-yl)-6-aminochrysene, and N-(deoxyguanosin-8-yl)-6-aminochrysene. These adducts accounted for 32%, 28%, and 22% respectively, of the total DNA adducts formed. We hypothesize that the deoxyinosine adduct is derived from spontaneous oxidation of the corresponding deoxyadenosine adduct prior to or during DNA isolation and adduct preparation. DNA isolated from Sprague-Dawley rat hepatocytes which had been treated with [3H]6-aminochrysene or [3H]6-nitrochrysene contained up to 12 pmol adducts/mg DNA (4 adducts per 10(6) nucleotides). High performance liquid chromatography (h.p.l.c.) analyses of enzymatic hydrolysates of this DNA indicated that the major products formed cochromatographed with the C8-deoxyinosine and C8-deoxyguanosine adducts. N-(Deoxyinosin-8-yl)-6-aminochrysene and N-(deoxyguanosin-8-yl)-6-aminochrysene accounted for 45% and 30% respectively, of the total DNA adducts formed in these cells. The preferential modification of deoxyadenosine by N-hydroxy-6-aminochrysene and the apparent facile oxidation of this adduct to a deoxyinosine derivative is thus far unique among the reactions of N-hydroxyarylamines with DNA and would not be predicted on the basis of reactivity alone.

Animals↗
PubMedDate not supplied

Comparison of a modified Edward-type medium and a modified SP4-type medium for primary isolation of Mycoplasma gallisepticum (MG) from chickens vaccinated with the F strain of MG.

The efficacy of two media, an Edward-type medium (EPJ) and a modified SP4-type medium (SP4-PS), were compared for primary isolation of Mycoplasma gallisepticum (MG) from commercial layer chickens (n = 58) vaccinated with the live F strain of MG. Three groups of chickens that differed in the interval after vaccinal exposure to the F strain (32, 41, and 102 weeks) were studied at necropsy. Mycoplasma isolation was attempted from the trachea, sinus, and cloaca using lavage and swab techniques but was successful only from the trachea and sinus. MG was isolated from 39 (8.4%) of 463 culture attempts from 58 tracheal inocula and 58 sinus inocula. Isolation of MG was successful more frequently using EPJ medium than SP4-PS medium, and isolation occurred more often from the sinus than from the trachea. Of the 58 chickens studied, 19 (33%) were shown by culture to be infected with MG. Isolation was successful only from 32- and 41-week post-vaccination exposure groups. However, all chickens studied were serologically positive for MG antibody by rapid-plate agglutination and hemagglutination-inhibition assays.

Agglutination Tests↗
PubMed1975

Immunogenic properties of modified antigen E. III. Effect of repeated injections of modified antigen on immunocompetent cells specific for native antigen.

It has been shown that ragweed antigen E loses its major antigenic determinants after denaturation in 8 M urea, but urea-denatured (UD) antigen and an alpha-polypeptide chain isolated from the denatured molecules are capable of priming mouse T cells specific for native antigen. Weekly injections of 10mug UD antigen or alpha-chain into antigen E-primed animals depressed the ongoing IgE antibody response, whereas injections of the same dose of antigen E failed to depress the antibody response. It was found by adoptive transfer experiments that helper activity of antigen E-primed splenic T cells was depressed by the treatment of the donors with either modified antigen or native antigen E. The same treatment of antigen E-primed animals depressed the DNA synthetic response of their splenic T cells to antigen E. The treatment of antigen E-primed animals with UD antigen resulted in a decrease of antigen E-specific IgE-B cells and IgG-B cells in their spleen, whereas the treatment with native antigen expanded the B cell populations. In view of the results obtained in the mouse, cellular basis for the immunologic effects of hyposensitization treatment is discussed.

Animals↗
PubMed1977

[Modified impregnation method for staining apical dendrite and spine (modified Golgi's method)].

A silver impregnation method for the demonstration of apical dendrites and spines in materials long preserved in folmalin is reported. This method is a modified version of Golgi's Silver method and consists of the following procedures: The formalin-fixed tissue blocks were incubated in a solution containing 3% potassium bichromate (150 ml), 96% ethyl alcohol (50 ml), and concentrated acetic acid (50 ml) for 24 hrs. at 37 degrees C, and 4 more days at room temperature after changing the solution twice. The tissue blocks were then kept for 5 days at room temperature in a 5% potassium bichromate solution. After making a thorough rinsing for one day in tap water and three washings in distilled water, the blocks were impregnated for 1/2 to 1 hr. in a 0.5% AgNO3 solution, for a further 4 days at room temperature in a 1% AgNO3 solution, washed three times briefly in distilled water and again impregnated for 4 to 5 days in a 2% AgNO3 solution. Following a thorough rinsing in distilled water the tissue blocks were embedded in paraffin and 50 to 100 micron sections were prepared.

Animals↗
PubMed1990

Modified reaction centers from Rhodobacter sphaeroides R26. 2: Bacteriochlorophylls with modified C-3 substituents at sites BA and BB.

Monomeric bacteriochlorophylls BA and BB in photosynthetic reaction centers from Rhodobacter sphaeroides R26 were exchanged with (13(2)-hydroxy-)bacteriochlorophylls containing a 3-vinyl- or 3-(alpha-hydroxyethyl)-substituent instead of the 3-acetyl group. The corresponding binding sites must be tolerant to the introduction of the polar residue at C-13(2) and modifications of the 3-acetyl group. According to HPLC analysis, the exchange with both pigments amounts to less than or equal to 50% of the total BChl contained in the complex, corresponding to less than or equal to 100% of the monomeric BChl alpha BA,B. The absorption spectra show significant changes in the QX and QY-region of the monomeric bacteriochlorophylls. By contrast, the absorption of the primary donor (P870) and reversible photobleaching is retained. The circular dichroism is also unchanged in the 870 nm region. The positive cd band located at around 800 nm in native reaction centers, shifts with the (blue-shifted) QY absorption(s) of BA and/or BB, whereas the position of the negative one remains nearly unaffected. The data indicate that the latter is the upper excitonic band of the primary donor, and that there is little interaction of the monomeric BA/BB with the primary donor.

Bacteriochlorophylls↗
PubMedDate not supplied

Modified taxols, 4. Synthesis and biological activity of taxols modified in the side chain.

A number of taxol derivatives substituted at the 2' position of the side chain have been prepared and their biological activities determined in KB cell culture and/or the P-388 in vivo assay. The 2'-(t-butyldimethylsilyl)taxol 5 is essentially inactive, indicating the need for a free hydroxyl group at the 2' position for activity. Epimerization of the 2' position occurred on treatment of 2'-acetyltaxol derivatives with 1,5-diazabicyclo[5.4.0]undec-7-ene, but treatment of 2'-(2,2,2-trichloroethyloxycarbonyl) taxol derivatives with DBU yielded the novel cyclization products 11 and 12 and, after deprotection at the 7 position, 13. The derivative 13 is also essentially inactive in the KB test system. Two taxols with increased H2O solubility were prepared, the 2'-(beta-alanyl) derivative 15 and the 2'-succinyl derivative 16. Although both these derivatives were active in vivo and in vitro, the former was too unstable and the latter not active enough to make suitable H2O-soluble derivatives of taxol.

Alkaloids↗
PubMed1991

Formation of C8-modified deoxyguanosine and C8-modified deoxyadenosine as major DNA adducts from 2-nitropyrene metabolism mediated by rat and mouse liver microsomes and cytosols.

2-Nitropyrene, the geometric isomer of the most studied nitropolycyclic aromatic hydrocarbon (nitro-PAH), 1-nitropyrene, is an environmental contaminant detected in ambient air and a potent direct-acting mutagen. Its metabolic activation leading to the formation of DNA adducts was studied. The activated metabolite, N-hydroxy-2-aminopyrene, was prepared and reacted with calf thymus DNA. Upon enzymatic hydrolysis of the DNA, the resulting nucleosides were separated by HPLC, and the adducts were characterized by mass and proton NMR spectral analysis. Both N-(deoxyguanosin-8-yl)-2-aminopyrene and N-(deoxyadenosin-8-yl)-2-aminopyrene, in a 5:2 ratio, were identified. These adducts were then utilized as standards to identify the DNA adducts formed from reaction of [3H]2-nitropyrene with DNA mediated by liver microsomes and cytosols of mouse and rat. In all cases, both adducts were formed. The quantities of the two adducts formed in each system were: mouse liver microsomes (11.3 pmol [3H]2-nitropyrene/mg DNA), rat liver microsomes (23), mouse liver cytosol (11.4) and rat liver cytosol (5.1). Thus, these adducts were formed in highest yield from rat liver microsomes and the lowest from rat liver cytosol. The deoxyguanosine/deoxyadenosine adduct ratio was higher from rat and mouse liver microsomes (7.8:9.2) than from rat and mouse liver cytosols (2.5:3.1). Our results represent the first direct demonstration of a C8-deoxyadenosine adduct being formed as a major product from the reaction of a nitro-PAH metabolite with DNA.

Animals↗
PubMed1986

Alkyl phosphotriester modified oligodeoxyribonucleotides. VI. NMR and UV spectroscopic studies of ethyl phosphotriester (Et) modified Rp-Rp and Sp-Sp duplexes, (d[GGAA(Et)TTCC])2.

1H NMR chemical shift assignments for the title compounds were made for all but a few H5' and H5" signals using two-dimensional nuclear Overhauser effect (2D-NOE) data, which was also used for the first time to assign absolute configuration at phosphorus. The chemical shifts were, in general, similar to those reported [Broido, M.S., et al. (1985) Eur. J. Biochem. 150, 117-128] for the B-like conformation of the unmodified, parent duplex, [d(GGAATTCC)]2. Differences in chemical shifts for corresponding protons were mostly localized to the AA(Et)TT region, and showed some stereochemical dependence. Unambiguous assignment of the phosphotriester 31P signals was achieved in a novel way using selective insensitive nucleus enhancement by polarization transfer (selective INEPT) NMR. The Rp-Rp duplex melted ca. 11 degrees C lower than either the Sp-Sp or parent duplexes, as evidenced by Tm and variable temperature 1H/31P NMR measurements. The 2D-NOE data for the Rp-Rp duplex suggested possible steric interactions between the ethyl group and the H3' of the flanking A residue. At low ionic strength, the Sp-Sp and parent duplexes had similar stability but at high ionic strength the Sp-Sp duplex was less stable.

Base Sequence↗