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Biomedical subjects

E Sun

Publications and source records attributed to E Sun.

At least 37 records · Page 2Linked to original sources
PubMed1998

ABT-378, a highly potent inhibitor of the human immunodeficiency virus protease.

The valine at position 82 (Val 82) in the active site of the human immunodeficiency virus (HIV) protease mutates in response to therapy with the protease inhibitor ritonavir. By using the X-ray crystal structure of the complex of HIV protease and ritonavir, the potent protease inhibitor ABT-378, which has a diminished interaction with Val 82, was designed. ABT-378 potently inhibited wild-type and mutant HIV protease (Ki = 1.3 to 3.6 pM), blocked the replication of laboratory and clinical strains of HIV type 1 (50% effective concentration [EC50], 0.006 to 0.017 microM), and maintained high potency against mutant HIV selected by ritonavir in vivo (EC50, </=0. 06 microM). The metabolism of ABT-378 was strongly inhibited by ritonavir in vitro. Consequently, following concomitant oral administration of ABT-378 and ritonavir, the concentrations of ABT-378 in rat, dog, and monkey plasma exceeded the in vitro antiviral EC50 in the presence of human serum by >50-fold after 8 h. In healthy human volunteers, coadministration of a single 400-mg dose of ABT-378 with 50 mg of ritonavir enhanced the area under the concentration curve of ABT-378 in plasma by 77-fold over that observed after dosing with ABT-378 alone, and mean concentrations of ABT-378 exceeded the EC50 for >24 h. These results demonstrate the potential utility of ABT-378 as a therapeutic intervention against AIDS.

Animals↗
PubMed1997

Inhibition of lipid peroxidation.

Lipid peroxy radicals (ROO.) were detected by electron spin resonance (ESR) at low temperature after formation by addition of H2O2 into a suspension of mice lymphocytes. If lymphocytes were treated with selenomethionine (Se-Met) prior to addition of H2O2, ROO. formation was inhibited in a fashion that was dependent on Se-Met concentration. Formation of ROO. in the spleen of mice was induced by 60Co irradiation. Animals that were supplemented with Na2SeO3 prior to irradiation exhibited a lower ROO. concentration than that of nontreated animals. Based on our experiments, we have concluded that Se has an oxygen-free radical scavenging effect. This should be a protective effect against lipid peroxy radical cellular attack.

Animals↗
PubMed1997

Ex vivo inhibition of beta-thromboglobulin release following administration to man of ABT-299, a novel prodrug of a potent platelet activating factor antagonist.

OBJECTIVE AND DESIGN: ABT-299 is a prodrug that is converted by serum esterase to a potent platelet activating factor (PAF) antagonist (A-85783). In order to evaluate the pharmacological activity of this antagonist in man the effect of ABT-299 given to healthy volunteers on ex vivo PAF-induced beta-thromboglobulin (beta-TG) release in blood was assessed. SUBJECTS: 37 healthy male volunteers, age 18 to 40 (mean age of 23.6 years) and free of medication, participated in the study. TREATMENT: Subjects were administered intravenously 0.8 mg, 2 mg, or 70 mg doses of ABT-299 (6-7 subjects per group) or placebo (9 subjects, pooled). METHODS: Peripheral blood taken over 12 h after dosing was used for ex vivo beta-TG release and, in the case of the 70 mg dose, measurement of plasma drug concentration. Data were compared by Student's t-test. RESULTS: All three doses produced highly significant inhibition (p < 0.005 compared to predose values) of PAF-induced beta-TG release (units/ml plasma +/- SEM) 12 h after drug administration (54 +/- 14 vs. 405 +/- 51, n = 8; 79 +/- 23 vs. 480 +/- 127, n = 7; 21 +/- 10 vs. 327 +/- 72, n = 6, respectively) whereas there was no significant difference in beta-TG release in the placebo group (449 +/- 90 vs. 307 +/- 49, n = 9). Inhibition was associated with the rapid appearance in plasma of A-85783 and the pyridine N-oxide metabolite of A-85783. Within 2 h, the plasma concentration of the metabolite exceeded that of the parent drug. Both the parent drug and the metabolite exhibited potent in vitro inhibition of PAF-induced beta-TG release (A2 values of 4 and 1 nM respectively). CONCLUSIONS: These studies are the first to illustrate the utility of the beta-TG release assay for assessing ex vivo activity of PAF antagonists. These studies also demonstrate that the administration of ABT-299 to man results in potent, long lasting inhibition of PAF-mediated platelet activation, due in part to the pyridine-N-oxide metabolite, and support the potential therapeutic utility of this prodrug in treating PAF-mediated diseases.

Adolescent↗
PubMed1997

Pharmacokinetic enhancement of inhibitors of the human immunodeficiency virus protease by coadministration with ritonavir.

Coadministration with the human immunodeficiency virus (HIV) protease inhibitor ritonavir was investigated as a method for enhancing the levels of other peptidomimetic HIV protease inhibitors in plasma. In rat and human liver microsomes, ritonavir potently inhibited the cytochrome P450 (CYP)-mediated metabolism of saquinavir, indinavir, nelfinavir, and VX-478. The structural features of ritonavir responsible for CYP binding and inhibition were examined. Coadministration of other protease inhibitors with ritonavir in rats and dogs produced elevated and sustained plasma drug levels 8 to 12 h after a single dose. Drug exposure in rats was elevated by 8- to 46-fold. A > 50-fold enhancement of the concentrations of saquinavir in plasma was observed in humans following a single codose of ritonavir (600 mg) and saquinavir (200 mg). These results indicate that ritonavir can favorably alter the pharmacokinetic profiles of other protease inhibitors. Combination regimens of ritonavir and other protease inhibitors may thus play a role in the treatment of HIV infection. Because of potentially substantial drug level increases, however, such combinations require further investigation to establish safe regimens for clinical use.

Animals↗
PubMed1997

Characterization of a recombinant Onchocerca volvulus antigen (Ov33) produced in yeast.

A yeast (Saccharomyces cerevisiae) expression system has been adapted to produce reagent quantities of a major Onchocerca antigen, Ov33. Using a pool of monoclonal antibodies produced against third-stage larvae, a cDNA library constructed from adult O. volvulus worms was screened. Twenty-seven cDNAs were isolated, two of which had sequence homology to Ov33, a putative aspartyl protease inhibitor, which is the immunodominant antigen of O. volvulus. These cDNAs were expressed at high levels intracellularly or through the secretory pathway of S. cerevisiae. Localization studies using antisera produced against purified recombinant protein demonstrated that Ov33 is a very abundant parasite protein present in the hypodermis, muscle, and uterus of female worms, as well as in embryonic microfilariae. The soluble recombinant protein secreted by yeast (C71) demonstrated inhibitory activity against the aspartyl protease pepsin. Antibodies to the recombinant protein-mediated leukocyte adherence to and killing of skin microfilariae. The sensitivity of a diagnostic test using recombinant Ov33 was evaluated using sera from 441 patients. The mean sensitivities for the two recombinant constructs, C27 and C71, were 82.2% and 85.4%, respectively. The combined sensitivity using both recombinant proteins was 94%.

Animals↗
PubMed1996

Capsaicin inhibits plasma membrane NADH oxidase and growth of human and mouse melanoma lines.

Hormone- and growth factor-stimulated NADH oxidase of the mammalian plasma membrane is thought to be involved in the control of normal cell proliferation. The aim of this study was to determine the effect of the naturally occurring quinone analogue capsaicin (8-methyl-N-vanillyl-6-noneamide) on the NADH oxidase activity of plasma membranes and cell growth of human primary melanocytes, the A-375 and SK-MEL-28 human melanoma cell cultures. NADH oxidase activity was inhibited preferentially in the A-375 melanoma cells but not in the primary melanocytes, by capsaicin. Inhibition of growth and the NADH oxidase by capsaicin could be induced in resistant SK-MEL-28 melanoma cells by co-administration of capsaicin with t-butyl hydroperoxide, a mild oxidising agent. Death of the inhibited cells was accompanied by nuclear changes suggestive of apoptosis. With B16 mouse melanoma, capsaicin inhibited both the NADH oxidase activity and growth in culture. Growth of B16 melanoma, transplanted in C57BL/6 mice, was significantly inhibited by capsaicin injected directly into the tumour site when co-administered with t-butyl hydroperoxide. The findings correlate the inhibition of cell surface NADH oxidase activity with inhibition of growth and capsaicin-induced apoptosis, and also suggest that the extent of inhibition may relate to the oxidation state of the plasma membrane.

Animals↗
PubMed1996

A Xenopus nodal-related gene that acts in synergy with noggin to induce complete secondary axis and notochord formation.

Using a paracrine assay to screen for signaling proteins that could respecify ectodermal tissue, we isolated a Xenopus gene related to the mouse gene nodal, a member of the TGFbeta superfamily. The gene is expressed in three regions in the early Xenopus embryo: first in the gastrula organizer, then in two stripes of cells flanking the posterior notochord in late neurulae, and finally in lateral plate mesoderm restricted to the left side of tailbud-stage embryos. Ectopic expression of the gene induces muscle formation in ectodermal explants and partial secondary axes in whole embryos. Together with noggin, another secreted protein also present in the organizer, it induces notochord formation in ectodermal explants and complete secondary axes in whole embryos. These results suggest that the nodal-related gene may act together with noggin to induce axial pattern during gastrulation and also may play a role in left-right asymmetry generation in the post-gastrula embryo.

Animals↗
PubMed1996

Genotyping of ABO blood group system by PCR and RFLP on mummies discovered at Taklamakan desert in 1912.

ABO genotyping was carried out using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) method on the dried remains of nine human mummies which had been discovered at Taklamakan desert in 1912. In all the nine mummies, ABO genotype could be determined as BO type, and ABO phenotype of the eight mummies with hair specimen could be revealed as B type using absorption-elution method. These results mean that ABO phenotype estimated from its genotype by PCR-RFLP was consistent with that by absorption-elution method in all of the eight cases examined. And in the other one child mummy, ABO phenotype could not be examined because of no hair specimen. Although it is impossible to assess the allele frequency of ABO blood group system in the populations having lived in Gao Chang at that time, the present study shows a possibility of ABO genotyping from ancient human remains.

ABO Blood-Group System↗
PubMed1995

Proton release from HeLa cells and alkalization of cytoplasm induced by diferric transferrin or ferricyanide and its inhibition by the diarylsulfonylurea antitumor drug N-(4-methylphenylsulfonyl)-N'-(4-cholorophenyl) urea (LY181984).

Proton release from HeLa cells was stimulated by an external oxidant, potassium ferricyanide, or by the growth factor diferric transferrin. This stimulated proton release was inhibited by the antitumor sulfonylurea LY181984 [N-(4-methylphenylsulfonyl)-N'-(4-chlorophenyl)urea] over the concentration range 10 nM to 1 microM. The antitumor-inactive sulfonylurea analog LY181985 [N-(4-methylphenylsulfonyl)-N'-(phenyl)urea] was without effect at 1 microM and required 10-100 microM concentrations to inhibit proton release. Diferric transferrin-induced alkalization of the cytoplasm estimated by BCECF [2',7'-bis(2-carboxyethyl)-5,(and 6)-carboxyfluorescein] fluorescence also was inhibited by 1 microM LY181984 but not by 1 microM LY181985. The inhibited component appeared to be amiloride resistant. The proton release induced by either ferricyanide or diferric transferrin was inhibited by about 35% at a near optimal amiloride concentration of 0.2 mM or at a dimethylamiloride concentration of 0.075 mM. However, the induced proton release was inhibited further by LY181984. Conversely, when proton release was inhibited fully by LY181984 at a near optimal concentration of 10 microM (50% inhibition), increasing concentrations of amiloride or dimethylamiloride resulted in additional inhibitions of 16 and 23%, respectively. However, the inhibitions by LY181984 and the amilorides were additive, suggesting that amiloride and the sulfonylureas may act independently. Evidence for an action of the sulfonylurea in inhibiting proton efflux differently from that of the amilorides came from measurements of sodium uptake either by fluorometry or by direct measurement with 22Na+. Sodium uptake was not inhibited by either LY181984 or LY181985 in HeLa cells at concentrations of LY181984 sufficient to inhibit proton efflux by 80% or more. The results show LY181984 to be a potent inhibitor of diferric transferrin- or ferricyanide-induced proton efflux and cytoplasmic alkalization in HeLa cells and that the inhibition may involve a component of proton transport that is resistant to amiloride.

Amiloride↗
PubMed1995

Onchocerca volvulus: identification and characterization of an immunogenic eggshell protein (Oveg1).

A major antigen recognized by human sera in Onchocerca volvulus infections is a parasite eggshell protein. The cDNA clone for this antigen was isolated from a lambda gt11 O. volvulus cDNA library using antisera from patients with high microfilarial counts. Sequence analysis of the cDNA clone predicts a polyglutamine repeat near the 5' end of the cDNA, and a motif of four arginines near the 3' end, reminiscent of that found in many regulatory proteins. The cDNA was subcloned into a yeast expression vector and reagent quantities of recombinant antigen produced in Saccharomyces cerevisiae. Antisera produced to the recombinant purified protein localized the antigen to the eggshell of developing microfilariae within the adult female uterus. No other sites of Oveg1 expression were noted in adult worms, but labeling was seen in internal membrane structures of L3 larvae. Sera from infected chimps recognized Oveg1 only after infections became patent. Sera from infected humans showed reactivity to Oveg1 that varied from 39 to 95%, depending upon the geographic location.

Amino Acid Sequence↗
PubMed1995

The mechanism for the effect of selenium supplementation on immunity.

Lipid peroxide (LPO) in lymphocytes from mice was evaluated by measuring substances reactive to thiobarbituric acid (TBA). The product resulting from the reaction of TBA with lymphocytes was extracted with n-butyl and fluorescence intensity was determined. The degree of lipid peroxidation, expressed as fluorescence intensity f547, was assessed for stimulation of lymphocytes with concanavalin A (Con A), and was related to lymphocyte proliferation in response to Con A if Se was administered. The lymphocyte proliferation was determined by [3H]thymidine incorporation, expressed as cpm. The effect of superoxide dismutase (SOD), added to cell culture on lymphocyte proliferation was also evaluated. It was found that LPO in lymphocytes before Con A stimulation was significantly less than that after stimulation (p < 0.001), and that SOD promoted lymphocyte proliferation dose dependently. The addition of Na2Seo3 to lymphocyte culture or supplementation in drinking water to mice decreased the produced LPO in lymphocyte in response to Con A. In the presence of Se, there is an inverse correlation between the levels of LPO in lymphocyte and the stimulated proliferation (r = -0.8902, r = -0.9439). In conclusion, active oxygen species scavenging was proposed as one of the mechanisms for Se to promote immunity.

Animals↗
PubMed1995

Effect of selenium in recovery of immunity damaged by H2O2 and 60Co radiation.

Con A stimulated lymphocytes proliferation was measured as [3H]thymidine incorporation and IgG was quantified by single radial immunodiffusion to study recovering or protecting effect of selenium (Se) on immunity attacked by exogenous active oxygen species, H2O2 and 60Co-radiation, respectively. Lipid peroxidation was also determined to observe the relation between antioxidation ability and protecting ability of Se. It was found that H2O2 injured lymphocytes immunocompetence deeply and 60Co-radiation decreased immune response capacity greatly, but that administration of Se counteracts this damage. The antioxidative ability of Se was correlated with its protecting ability.

Animals↗
PubMed1995

Composition-based prediction of dielectric properties of foods.

Prediction of accurate dielectric property data from fundamental principles for systems as complex as foods has not been possible. Simple prediction models based on easily measurable composition data can serve many useful purposes. Literature dielectric data on foods and their composition were statistically correlated. Dielectric data on salt solutions were measured to explain some of the results. When composition data were not available, standard handbook compositions were used. Inclusion of all types of foods (meats, fruits, and vegetables) inhibited any useful correlation with composition. Based on a smaller data set of meats, both dielectric constant and loss increased with water and salt content. Dielectric constant generally decreased with temperature whereas dielectric loss decreased with temperature at lower salt concentrations and increased with temperature at higher salt concentrations.

Electric Conductivity↗
PubMed1993

Computer-assisted drug discovery--a review.

A structure-based approach to new drug development is an attractive alternative to the traditional paradigm of drug discovery through screening. The elements of this approach are reviewed, with emphasis on the use of homology-built model structures. Two examples, proteases from the organisms that cause malaria and schistosomiasis, illustrate both the model-building process and the feasibility of using such models to computationally screen and identify compounds that inhibit their targets in the low micromolar range.

Computers↗
PubMed1993

Structure-based inhibitor design by using protein models for the development of antiparasitic agents.

The lack of an experimentally determined structure of a target protein frequently limits the application of structure-based drug design methods. In an effort to overcome this limitation, we have investigated the use of computer model-built structures for the identification of previously unknown inhibitors of enzymes from two major protease families, serine and cysteine proteases. We have successfully used our model-built structures to identify computationally and to confirm experimentally the activity of nonpeptidic inhibitors directed against important enzymes in the schistosome [2-(4-methoxybenzoyl)-1-naphthoic acid, Ki = 3 microM] and malaria (oxalic bis[(2-hydroxy-1-naphthylmethylene)hydrazide], IC50 = 6 microM) parasite life cycles.

Animals↗
PubMed1993

The proteases and pathogenicity of parasitic protozoa.

Protozoan parasites are among the most prevalent pathogens worldwide. Diseases like malaria, leishmaniasis, amebiasis, and trypanosomiasis affect hundreds of millions of people. Recent advances in our understanding of the biochemistry and molecular biology of these organisms has focused attention on specific parasite molecules that are key to the parasite life cycle or the pathogenesis of the diseases they produce. One group of enzymes that plays myriad roles in these processes are the parasite-derived proteases. Different types of proteases are frequently expressed at different stages of the parasite life cycle to support parasite replication and metamorphosis. Intracellular parasites such as those that produce malaria and Chagas' disease express high levels of protease activity to efficiently degrade host proteins like hemoglobin. In other instances, such as infection with Entamoeba histolytica, the causative agent of amebiasis, proteases released by the parasite can damage host cells and tissues, contributing to host tissue damage and parasite invasion. Detailed studies of these enzymes have led to model systems for the study of parasite gene regulation, parasite metabolism, and the host-parasite interplay. In some instances, proteases appear to be promising targets for the development of new antiparasitic chemotherapy.

Amino Acid Sequence↗