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At least 181 records · Page 10Linked to original sources
PubMed2004

Comparative immunogenicity analysis of modified vaccinia Ankara vectors expressing native or modified forms of hepatitis C virus E1 and E2 glycoproteins.

We have evaluated in C57/Bl6 and HLA-A2.1 transgenic mice the immunogenicity of three MVA vectors expressing either native HCV E1E2 polyprotein, truncated and secreted E1 (E'1(311)) and E2 (E'2(661)) proteins, or a chimeric E1E2 heterodimer presented at the plasma membrane. Immunization induced mainly a Th1 response in HLA-A2.1 transgenic mice while a Th2-type response was detected in C57/Bl6 mice. Comparison of the three vectors shows an increase in the humoral response when antigens are secreted or membrane bound, and slightly in the cellular response when antigens are exposed on the cell surface.

Animals↗
PubMed1998

A neutron reflectivity study of polymer-modified phospholipid monolayers at the solid-solution interface: polyethylene glycol-lipids on silane-modified substrates.

The structure of polymer-decorated phospholipid monolayers at the solid-solution interface was investigated using neutron reflectometry. The monolayers were composed of distearoylphosphatidylethanolamine (DSPE) matrixed with varying amounts of DSPE-PEG (DSPE with polyethylene glycol covalently grafted to its headgroup). Mixed lipid monolayers were Langmuir-Blodgett deposited onto hydrophobic quartz or silicon substrates, previously hydrophobized by chemically grafting a robust monolayer of octadecyltrichlorosilane (OTS). We show that this method results in homogeneous and continuous phospholipid monolayers on the silanated substrates and determine that the grafted PEG chains extend away from the monolayers into the solvent phase as a function of their density, as expected from scaling theories. In addition, ligands were coupled to the end of the PEG chains and selective binding was demonstrated using fluorescence microscopy. Our results demonstrate that these constructs are ideal for further characterization and studies with well-defined monomolecular films.

Adsorption↗
PubMed2000

Modifiable risk factors and erectile dysfunction: can lifestyle changes modify risk?

OBJECTIVES: To prospectively examine whether changes in smoking, heavy alcohol consumption, sedentary lifestyle, and obesity are associated with the risk of erectile dysfunction. METHODS: Data were collected as part of a cohort study of a random sample of men 40 to 70 years old, selected from street listings in the Boston Metropolitan Area, Massachusetts. In-home interviews were completed by 1709 men at baseline in 1987 to 1989 and 1156 men at follow-up in 1995 to 1997 (average follow-up 8.8 years). Analyses included 593 men without erectile dysfunction at baseline, who were free of prostate cancer, and had not been treated for heart disease or diabetes. The incidence of moderate to complete erectile dysfunction was determined by discriminant analysis of responses to a self-administered sexual function questionnaire. RESULTS: Obesity status was associated with erectile dysfunction (P = 0.006), with baseline obesity predicting a higher risk regardless of follow-up weight loss. Physical activity status was associated with erectile dysfunction (P = 0.01), with the highest risk among men who remained sedentary and the lowest among those who remained active or initiated physical activity. Changes in smoking and alcohol consumption were not associated with the incidence of erectile dysfunction (P >0.3). CONCLUSIONS: Midlife changes may be too late to reverse the effects of smoking, obesity, and alcohol consumption on erectile dysfunction. In contrast, physical activity may reduce the risk of erectile dysfunction even if initiated in midlife. Early adoption of healthy lifestyles may be the best approach to reducing the burden of erectile dysfunction on the health and well-being of older men.

Adult↗
PubMedDate not supplied

A modular approach to the synthesis of new reagents useful in the chemical synthesis of modified DNA probes: derivatives of 3-(tert-butyldimethylsiloxy)glutaric anhydride as versatile building blocks in the synthesis of new phosphoramidites and modified solid supports.

We present a flexible and cost-efficient synthetic strategy for the preparation of a new family of phosphoramidite and solid-support reagents that can introduce a broad range of modifications into DNA probes. The key intermediate material 3 is synthesized using the inexpensive and commercially available 3-(tert-butyldimethylsiloxy)glutaric anhydride 1 and can be used as common starting material for the preparation of new labeling reagents.

Anhydrides↗
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↗
PubMed1993

Instability of the monofunctional adducts in cis-[Pt(NH3)2(N7-N-methyl-2-diazapyrenium)Cl](2+)-modified DNA: rates of cross-linking reactions in cis-platinum-modified DNA.

Single- and double-stranded oligonucleotides containing a single monofunctional cis-[Pt(NH3)2(dG)(N7-N-methyl-2-diazapyrenium)]3+ adduct have been studied at two NaCl concentrations. In 50 mM and 1 M NaCl, the adducts within the single-stranded oligonucleotides are stable. In contrast, they are unstable within the corresponding double-stranded oligonucleotides. In 50 mM NaCl, the bonds between platinum and guanine or N-methyl-2,7-diazapyrenium residues are cleaved and subsequently, intra- or interstrand cross-links are formed as in the reaction between DNA and cis-DDP. In 1 M NaCl, the main reaction is the replacement of N-methyl-2,7-diazapyrenium residues by chloride which generates double-stranded oligonucleotides containing a single monofunctional cis-[Pt(NH3)2(dG)Cl]+ adduct. The rates of closure of these monofunctional adducts to bifunctional cross-links have been studied in 60 mM NaClO4. Within d(TG.CT/AGCA), d(CG.CT/AGCG) and d(AG.CT/AGCT) (the symbol.indicates the location of the adducts in the central sequences of oligonucleotides), the half-lifes (t1/2) of the cis-[Pt(NH3)2(dG)Cl]+ adducts are respectively 12, 6 and 2.8 hr and the cross-linking reactions occur between guanine residues on the opposite strands. Within d(AG.TC/GACT), d(CG.AT/ATCG) and d(TGTG./CACA) or d(TG.TG/CACA) t1/2 are respectively 1.6, 8 and larger than 20 hr and the intrastrand cross-links are formed at the d(AG), d(GA) and d(GTG) sites, respectively. The conclusion is that the rates of conversion of cis-platinum-DNA monofunctional adducts to minor bifunctional cross-links are dependent on base sequence. The potential use of the instability of cis-[Pt(NH3)2(dG)(N7-N-methyl-2-diazapyrenium)]3+ adducts is discussed in the context of the antisense strategy.

Base Sequence↗
PubMed2005

Comparison study on PCR amplification of modified DNA by using various kinds of polymerase and modified nucleoside triphosphates.

A series of C5 substituted analogs of 2'-deoxyuridine triphosphate and 2'-deoxycytidine triphosphate were synthesized and investigated their substrate properties for thermostable DNA polymerases during polymerase chain reaction (PCR). The PCR assays indicated that the relative yield of the full-length product is dependent on whether the substitution is on dU or dC, and on the nature of the polymerase.

DNA↗