Biomedical subjects

X Hu

Publications and source records attributed to X Hu.

At least 289 records · Page 16Linked to original sources

PubMed1998

[Analysis of molecular karyotype of Leishmania isolates from hilly foci and plain foci of China].

AIM: To analyse the molecular karyotypes of Leishmania isolates from hilly and plain foci of China. METHODS: Pulsed field gel electrophoresis(PFGE) was performed in 1% agarose at 6 V/cm in 0.5 x TBE at 14 degrees C with a pulse time of 60 s for 15 h and a pulse time 90 s for 9 h. RESULTS: Each isolate was resolved into 15 different EtBr-staining bands ranging in size from 200 to 2,200 kb, in which the karyotypes of 6 isolates from hilly foci were similar (including karyotypes of canine isolates similar with those of human isolates), and they were partly similar with those of L. infantum. The karyotypes of the two isolates from plain foci were similar, but the isolates from the two topographically different foci were different from each other. CONCLUSION: Homology exists between L. d. isolates from hilly foci and plain foci respectively, and exists in part between L. d. isolates from hilly foci and L. infantum; while heterogeneity exists between L. d. isolates from hilly foci and plain foci. The reservoir host, domestic dog, plays an important role as the infection source of leishmaniasis in the hilly foci of China.

Animals↗

PubMed1998

[Analysis of nuclear DNA gene types of Leishmania isolates from hilly and plain foci of China].

AIM: To analyse the nuclear DNA (nDNA) polymorphism of Leishmania isolates from hilly and plain foci of China. METHODS: nDNA were analysed by endonuclease digestion, Southern blotting and chromosomal localization. Probes were labeled with digoxigenin. RESULTS: Using gp63 gene probe, similar hybridization bands were found to be existed between nDNAs of Leishmania donovani Jiangsu human isolate and L. d. Jeddah, also between nDNAs of L. d. Sichuan human isolate and L. infantum. Using beta-tubulin gene probe, there were two similar hybridization bands existed between nDNAs of L. d. Jiangsu human isolate and L. d. Jeddah, and three similar hybridization bands existed between nDNAs of L. d. Sichuan canine isolate and L. d. Gansu canine isolate, and two similar hybridization bands existed between nDNA of L. d. Sichuan canine isolate and L. d. Wenchuan human isolate. CONCLUSION: Homology exists between L. d. Jiangsu human isolate and L. d. Jeddah from plain foci, between L. d. Sichuan human isolate from hilly foci and L. infantum, between L. d. Sichuan canine isolate and L. d. Gansu canine isolate from hilly foci. Homology as well as differences exist between L. d. Sichuan canine isolate and L. d. Wenchuan human isolate. Heterogeneity exists between isolates from hilly foci and plain foci.

Animals↗

PubMed1998

[FTIR microscope study on the change of membrane protein and lipids of erythrocyte damaged by free radicals].

The FTIR Microscope and Computer Aided Analysis were used to study not only the change of secondary structure of erythrocyte membrane protein attacked by the free radicals, but also the effect of oxygen centered free radicals on the membrane lipids in this paper. The results indicate that the content of alpha-helix in the secondary structure of protein clearly changed because of the attack of the free radicals. Damaged by free radicals in 30 minutes, the protein structure could not be restored after 3 hours. The number of the P=O (vp=0), C=O and C=C in the lipids of the membrane was changed. These changes were caused by the peroxidation of the oxygen centered free radicals.

Adult↗

PubMed1997

Tyrosine and tryptophan structure markers in hemoglobin ultraviolet resonance Raman spectra: mode assignments via subunit-specific isotope labeling of recombinant protein.

Phenyl-deuterated tyrosine (Tyr-d4) and indole-deuterated tryptophan (Trp-d5) have been selectively incorporated into hemoglobin (Hb) by expressing the gene in auxotrophic strains of Escherichia coli. Ultraviolet resonance Raman (UVRR) spectra, using 229-nm excitation, show that difference features characteristic of the Hb quaternary R --> T transition are not perturbed by the incorporation of the isotopes. All the UVRR bands between 800 and 1700 cm-1 are assigned to either Tyr or Trp except for the 1511 cm-1 band, which had been thought to arise from the Trp 2 x W18 overtone. This band does not shift upon Trp or Tyr labeling but does shift 5 cm-1 in D2O, suggesting assignment to a histidine (His) residue. Its intensification in the T-state is consistent with His protonation. The alpha- and beta-subunits were selectively labeled, by reconstitution of labeled subunits with unlabeled subunits, to make isotope hybrids. Selective Tyr labeling identified the alpha subunits as the locus of the Y8a upshift observed in Hb, supporting the previous inference that this shift is associated with the T-state H-bond involving the interfacial Tyr alpha42 [Rodgers, Su, Subramaniam, & Spiro (1992) J. Am. Chem. Soc. 114, 3697]. Selective Trp labeling showed the Trp alpha14 contributions to the T - R difference spectrum to be negligible and confirmed Trp beta37 as the locus of the W3 difference signal, and probably of the remaining Trp signals as well. The observed downshift of W17 and upshift of Wd5 in the T-state are consistent with a stronger T-state H-bond between Trp beta37 and Asp alpha94; the resulting excitation profile red shift accounts for the dominance of the Trp beta37 contribution to the T - R difference UVRR spectrum.

Crystallography, X-Ray↗

PubMed1997

Induction of glutathione S-transferase pi as a bioassay for the evaluation of potency of inhibitors of benzo(a)pyrene-induced cancer in a murine model.

There is a growing need for short-term and cost-effective bioassay to assess the efficacy of potential chemo-preventive agents. We report that the induction of glutathione (GSH) S-transferase pi (mGSTP1-1) by a chemo-preventive agent can be used as a reliable marker to assess its efficacy in retarding chemical carcinogenesis induced by benzo(a)pyrene (BP), which is a widespread environmental pollutant and believed to be a risk factor in human chemical carcinogenesis. This conclusion is based on 1) the relative contribution of mGSTP1-1 of the liver and forestomach of female A/J mice in the detoxification of the ultimate carcinogenic metabolite of BP, (+)-anti-7,8-dihydroxy-9, 10-oxy-7,8,9, 10-tetrahydrobenzo(a)pyrene [(+)-anti-BPDE]; and 2) a positive correlation between the induction of hepatic and forestomach mGSTP1-1 by 5 naturally occurring organosulfides (OSCs) from garlic (diallyl sulfide, diallyl disulfide, diallyl trisulfide, dipropyl sulfide and dipropyl disulfide) and their effectiveness in preventing BP-induced forestomach neoplasia in mice. In the liver, the combined contribution of other GSTs in the detoxification of (+)-anti-BPDE was far less than the contribution of mGSTP1-1 alone. Likewise, in the forestomach, the contribution of mGSTP1-1 far exceeded the combined contribution of other GSTs. Studies on the effects of OSCs against BP-induced forestomach neoplasia revealed a good correlation between their chemo-preventive efficacy and their ability to induce mGSTP1-1 expression in the liver (r = -0.89; p < 0.05) as well as in the forestomach (r = -0.97; p < 0.05). Our results suggest that the induction of mGSTP1-1 may be a reliable marker for evaluating the efficacy of potential inhibitors of BP-induced cancer in a murine model.

Allyl Compounds↗

PubMed1997

The orphan nuclear receptor TR2 suppresses a DR4 hormone response element of the mouse CRABP-I gene promoter.

The mouse orphan nuclear receptor TR2-11-f suppressed the expression of reporters fused to a hormone response element of the mouse cellular retinoic acid-binding protein I gene promoter. TR2-11-f was able to bind to a direct repeat with four nucleotides in the spacer (5'TGACCTTTGGGGACCT3') located within this hormone response element as homodimers. The specificity of protein-DNA interactions was demonstrated by competition in gel retardation and antibody-mediated supershift reactions. The residues critical for TR2-11-f binding were mapped to both repeated sequences, whereas the spacer and the flanking sequences were less important. The Kd and Bmax of TR2-11-f homodimer binding to this direct repeat were determined to be 2.6 nM and 0.012 nM, respectively. By using a yeast two-hybrid system, it was demonstrated that dimerization of TR2-11-f was mediated by its ligand-binding domain. The actions of TR2-11-f in regulating cellular retinoic acid-binding protein I gene will likely influence retinoic action and availability within the cells.

Animals↗

PubMed1997

Intracellular precursor interleukin (IL)-1alpha, but not mature IL-1alpha, is able to regulate human endothelial cell migration in vitro.

The human umbilical vein endothelial cell (HUVEC) has a finite lifespan in vitro, and senescent HUVEC contain elevated levels of the negative growth regulator interleukin (IL)-1alpha. IL-1alpha is translated as a signal peptide sequence-less cytosolic 31-kDa precursor (IL-1alpha p), which undergoes proteolytic activation to release the mature carboxyl terminus 17-kDa protein (IL-1alpha m). Both the IL-1alpha p and IL-1alpha m proteins are biologically active as exogenous cytokines. Interestingly, only IL-1alpha p contains a nuclear localization sequence between residues 79 and 85. To further study the role of intracellular IL-1alpha in the regulation of human endothelial cell function, a spontaneous HUVEC transformant was stably transfected with IL-1alpha p, IL-1alpha m, and the IL-1alpha p K82N mutant, which attenuates the nuclear traffic of IL-1alpha p. Interestingly, the IL-1alpha p transfectants were found to have a lower migratory potential than either IL-1alpha m or IL-1alpha p K82N transfectants, and the addition of the IL-1 receptor antagonist did not alter the migration of these cells. Immunofluorescence microscopy demonstrated that only the IL-1alpha p transfectants exhibited prominent staining for beta-catenin-associated cell-to-cell contacts, as well as pronounced vimentin intermediate filaments and actin cytoskeleton staining. These data suggest that IL-1alpha p, and not IL-1alpha m, may function as an intracellular regulator of the migratory capacity of the human endothelial cell and that the nuclear localization sequence present within IL-1alpha p may be involved in regulating this function.

Cell Movement↗

PubMed1997

Activity of four allelic forms of glutathione S-transferase hGSTP1-1 for diol epoxides of polycyclic aromatic hydrocarbons.

Allelic forms of hGSTP1-1 which differ from each other by their catalytic properties and, structurally, by the amino acid(s) in position(s) 104 or (and) 113 are known to exist in human populations. The four possible isoforms of hGSTP1-1 with isoleucine or valine in position 104 and with alanine or valine in position 113 were produced by site-directed mutagenesis of the cDNA followed by bacterial expression and purification of the proteins. Glutathione-conjugating activity was measured with the diol epoxides of benzo(a)pyrene and chrysene, as well as with the model substrate 1-chloro-2,4-dinitrobenzene. Isoenzymes with valine in position 104 were more effective with the diol epoxides of polycyclic aromatic hydrocarbons but less effective with 1-chloro-2,4-dinitrobenzene than the isoforms with isoleucine 104. In addition, the transition A113V in the presence of V104 caused a pronounced increase in catalytic efficiency for the benzo(a)pyrene but not the chrysene diol epoxide. It is proposed that amino acid 113 functions as part of a clamp that lines the mouth of the water channel leading to the active sites of the hGSTP1-1 dimer and controls the access to substrates. Therefore, the hydrophobicity and the size of residue 113 are important in co-determining the substrate specificity of the isoenzymes. The widely different activities of the allelic isoforms toward carcinogenic diol epoxides of polycyclic aromatic hydrocarbons may help to explain the correlation between cancer susceptibility and genotype at the hGSTP1 locus that has been found by others.

Alleles↗

PubMed1997

Mechanism of differential efficacy of garlic organosulfides in preventing benzo(a)pyrene-induced cancer in mice.

The mechanism of differential efficacies of diallyl sulfide (DAS), diallyl disulfide (DADS), diallyl trisulfide (DATS), dipropyl sulfide (DPS) and dipropyl disulfide (DPDS) in preventing benzo(a)pyrene (BP)-induced cancer in mice has been investigated by determining their effects on the enzymes of BP activation/inactivation pathways. With the exception of DATS, treatment of mice with other organosulfides (OSCs) caused a small but significant increase (37-44%) in hepatic ethoxyresorufin O-deethylase (EROD) activity. However, the forestomach EROD activity did not differ significantly between control and treated groups. Only DAS treatment caused a modest but statistically significant reduction (about 25%) in pulmonary EROD activity. These results suggest that while reduction of EROD activity may, at least in part, contribute to the DAS-mediated inhibition of BP-induced lung cancer, anticarcinogenic effects of OSCs against BP-induced forestomach carcinogenesis seems to be independent of this mechanism. Treatment of mice with DAS, DADS and DATS resulted in a significant increase, as compared with control, in both hepatic (3.0-, 3.2- and 4.4-fold, respectively) and forestomach (1.5-, 2.7- and 2.7-fold, respectively) glutathione transferase (GST) activity toward anti-7beta,8alpha-dihydroxy-9alpha,10alpha-oxy-7,8,9,10-tetrahydrobenzo(a)pyrene (anti-BPDE), which is the ultimate carcinogen of BP. The pulmonary GST activity was not increased by any of the OSCs. Even though epoxide hydrolase (EH) activity was differentially altered by these OSCs, a correlation between chemopreventive efficacy of OSCs and their effects on EH activity was not apparent. The results of the present study suggest that differences in the ability of OSCs to modulate GST activity toward anti-BPDE may, at least in part, account for their differential chemopreventive efficacy against BP-induced cancer in mice.

Allyl Compounds↗

PubMed1997

Differential catalytic efficiency and enantioselectivity of murine glutathione S-transferase isoenzymes in the glutathione conjugation of carcinogenic anti-diol epoxides of chrysene and benzo(g)chrysene.

The kinetics of the conjugation of carcinogenic anti-diol epoxides of chrysene (anti-CDE) and benzo(g)chrysene [anti-B(g)CDE] with glutathione (GSH) catalyzed by GSH S-transferase (GST) isoenzymes mGSTP1-1, mGSTM1-1, mGSTA3-3, mGSTA4-4, and GST 9.5 of female A/J mouse tissues has been investigated. When GST activity was measured as a function of varying anti-CDE or anti-B(g)-CDE concentrations at a fixed concentration of GSH, each isoenzyme obeyed Michaelis-Menten kinetics. The catalytic efficiencies (k(cat)/Km) of murine GSTs in the GSH conjugation of anti-CDE were in the order of GST 9.5 > mGSTP1-1 > mGSTM1-1 > mGSTA3-3 > mGSTA4-4. While each GST isoenzyme examined in the present study exhibited preference for the GSH conjugation of (+)-anti-CDE with the (R,S)-diol (S,R)-epoxide absolute configuration, which is a far more potent carcinogen than the (-)-anti-CDE [(S,R)-diol (R,S)-epoxide absolute configuration], the enantioselectivity was relatively more pronounced for mGSTP1-1 compared with other murine GSTs. Anti-B(g)CDE was a relatively poor substrate for each GST isoenzyme examined compared with anti-CDE. The catalytic efficiencies of murine GSTs in the GSH conjugation of anti-B(g)CDE were in the order of GST 9.5 > mGSTP1-1 > mGSTM1-1 > mGSTA3-3. With the exception of mGSTM1-1, all other murine GSTs exhibited preference for the GSH conjugation of anti-B(g)CDE enantiomer with the (R,S)-diol (S,R)-epoxide absolute configuration. In summary, the results of the present study indicate that the murine GSTs significantly differ in their catalytic efficiency and enantioselectivity in the GSH conjugation of both anti-CDE and anti-B(g)CDE, and that anti-B(g)CDE is a relatively poor substrate for murine GSTs compared with anti-CDE, which may partially account for the observed relatively higher carcinogenic potency of the former compound.

Animals↗

PubMed1997

Mechanism of differential catalytic efficiency of two polymorphic forms of human glutathione S-transferase P1-1 in the glutathione conjugation of carcinogenic diol epoxide of chrysene.

The kinetics of the conjugation of glutathione (GSH) with anti-1, 2-dihydroxy-3,4-oxy-1,2,3,4-tetrahydrochrysene (anti-CDE), the activated form of the widespread environmental pollutant chrysene, catalyzed by two naturally occurring polymorphic forms of the pi class human GSH S-transferase (hGSTP1-1), has been investigated. The polymorphic forms of hGSTP1-1, which differ in their primary structure by a single amino acid in position 104, exhibited preference for the GSH conjugation of (+)-anti-CDE, which is a far more potent carcinogen than (-)-anti-CDE. When concentration of anti-CDE was varied (5-200 microM and the GSH concentration was kept constant at 2 mM, both hGSTP1-1(I104) and hGSTP1-1(V104) obeyed Michaelis-Menten kinetics. However, the Vmax of GSH conjugation of anti-CDE was approximately 5.3-fold higher for the V104 variant than for the I104 form. Calculation of catalytic efficiency (kcat/Km) thus resulted in a value for hGSTP1-1(V104), 28 mM-1 s-1, that was 7.0-fold higher than that for hGSTP1-1(I104), 4 mM-1 s-1. The mechanism of the differences in the kinetic properties of hGSTP1-1 isoforms toward anti-CDE was investigated by molecular modeling of the two proteins with GSH conjugation products in their active sites. These studies revealed that the enantioselectivity of hGSTP1-1 for (+)-anti-CDE and the differential catalytic efficiencies of the V104 and I104 forms of hGSTP1-1 in the GSH conjugation of (+)-anti-CDE were due to the differences in the active-site architecture of the two proteins. The results of the present study, for the first time, provide evidence for the toxicological relevance of GSTP1-1 polymorphism in humans and suggest that the population polymorphism of hGSTP1-1 variants with disparate enzyme activities may, at least in part, account for the differential susceptibility of individuals to environmental carcinogens such as anti-CDE and possibly other similar carcinogens.

Animals↗

PubMed1997

Active site architecture of polymorphic forms of human glutathione S-transferase P1-1 accounts for their enantioselectivity and disparate activity in the glutathione conjugation of 7beta,8alpha-dihydroxy-9alpha,10alpha-ox y-7,8,9,10-tetrahydrobenzo(a)pyrene.

In this study, we demonstrate that the active site architecture of the human glutathione (GSH) S-transferase Pi (GSTP1-1) accounts for its enantioselectivity in the GSH conjugation of 7beta,8alpha-dihydroxy-9alpha,10alpha-oxy-7,8,9, 10-tetrahydrobenzo(a) pyrene (anti-BPDE), the ultimate carcinogen of benzo(a)pyrene. Furthermore, we report that the two polymorphic forms of human GSTP1-1, differing in their primary structure by a single amino acid in position 104, have disparate activity toward (+)-anti-BPDE, which can also be rationalized in terms of their active site structures. When concentration of (+)-anti-BPDE, which among four BPDE isomers is the most potent carcinogen, was varied and GSH concentration was kept constant at 2 mM (saturating concentration), both forms of hGSTP1-1 [hGSTP1-1(V104) and hGSTP1-1(I104)] obeyed Michaelis-Menten kinetics. The V(max) of GSH conjugation of (+)-anti-BPDE was approximately 3.4-fold higher for hGSTP1-1(V104) than for hGSTP1-1(I104). Adherence to Michaelis-Menten kinetics was also observed for both isoforms when (-)-anti-BPDE, which is a weak carcinogen, was used as the variable substrate. However, (-)-anti-BPDE was a relatively poor substrate for both isoforms as compared with (+)-anti-BPDE. Moreover, there were no significant differences between hGSTP1-1(V104) and hGSTP1-1(I104) in either V(max) or K(m) for (-)-anti-BPDE. The mechanism of differences in kinetic properties and enantioselectivity of hGSTP1-1 variants toward anti-BPDE was investigated by modeling of the two proteins with conjugation product molecules in their active sites. Molecular modeling studies revealed that the differences in catalytic properties of hGSTP1-1 variants as well as the enantioselectivity of hGSTP1-1 in the GSH conjugation of anti-BPDE can be rationalized in terms of the architecture of their active sites. Our results suggest that the population polymorphism of hGSTP1-1 variants with disparate enzyme activities may, at least in part, account for the differential susceptibility of individuals to carcinogens such as anti-BPDE and possibly other similar carcinogens.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed1997

Negatively charged amino acid residues play an active role in orienting the Sec-independent Pf3 coat protein in the Escherichia coli inner membrane.

The coat protein of Pseudomonas aeruginosa phage Pf3 is transiently inserted into the bacterial inner membrane with a single transmembrane anchor sequence in the N(out)C(in) orientation. The N-terminal sequence immediately flanking the membrane anchor contains one negatively charged residue, whereas the C-terminal hydrophilic segment has two positively charged residues. To investigate how the orientation of this protein is achieved, the three flanking charged amino acid residues were altered. Membrane insertion was analyzed in vivo using the accessibility to externally added protease and in vitro by testing the insertion into inverted Escherichia coli membrane vesicles. In both systems, the orientation of the protein was completely reversed for the oppositely charged mutant coat protein (RD mutant). In addition, we show in vivo that the electrochemical membrane potential is necessary for the translocation of both the wild-type and the mutant Pf3 coat proteins, suggesting that membrane insertion is driven by electrophoretic forces.

Amino Acid Sequence↗

PubMed1997

Expression of chemokine genes in rat glial cells: the effect of myelin basic protein-reactive encephalitogenic T cells.

Chemokine gene expression and chemokine activity appear to be major components of the immunopathological processes of inflammation and autoimmunity. To initiate an investigation of the role of chemokines in the pathogenesis of autoimmune inflammatory demyelination, we examined the expression of mRNA transcripts encoding four prominent chemokines, IP-10, MIP-1 alpha, MCP-1, and RANTES, in encephalitogenic rat MBP-reactive T cells, astrocytes, and microglia. Astrocytes and microglia, whether as lines or as freshly isolated cells, did not constitutively express IP-10 and MCP-1 mRNA but could be induced with LPS to also produce MIP-1 alpha and RANTES. MBP-reactive T cells were induced with MBP to produce abundant levels of MIP-1 alpha, MCP-1, and RANTES mRNA in different temporal profiles but did not express IP-10 mRNA. In an MHC-II restricted fashion, the antigen-activated MBP-reactive T cells also induced glial cells to express all four chemokines, with the chemokine gene expression greatest following T-cell interactions with MHC-compatible glia. Treatment of glial cells with TNF-alpha and IFN-gamma induced only IP-10, indicating that the expression of chemokine genes other than IP-10 requires a combination of different cytokines or direct cell-cell contact between T cells and glia. Quantitative assays revealed that activated astrocytes, the dominant glia of the CNS, express higher levels of chemokine transcripts than transcripts of the major proinflammatory cytokines TNF-alpha and IFN-gamma. These results underscore the prominent but complex expression of chemokines by cellular component of inflammatory demyelinating lesions.

Animals↗

PubMed1997

Glutathione S-transferases of female A/J mouse lung and their induction by anticarcinogenic organosulfides from garlic.

Glutathione S-transferases (GSTs) of female A/J mouse lung have been purified and characterized for their (a) structural interrelationships, (b) substrate specificities toward the ultimate carcinogenic metabolite of benzo(a)pyrene (BP), (+)-anti-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-oxy-7,8,9,10-tetrahydrobenzo(a)pyrene [(+)-anti-BPDE], and (c) induction by three naturally occurring organosulfides (OSCs)-from garlic [diallyl sulfide (DAS), diallyl trisulfide (DATS) and dipropyl sulfide (DPS)], which significantly differ in their efficacy against BP-induced lung cancer in mice. The GST activity in the lung was due to two alpha class (pI 9.4 and 6.0), two mu class (pI 8.7 and 8.6), and one pi class (pI 8.9) isoenzyme. The GST isoenzyme profile of the lung was different from that of the A/J mouse forestomach, which also is a target organ for BP-induced cancer in mice. Noticeably, an alpha class heterodimeric isoenzyme (pI 9.5) present in the forestomach of A/J mouse, which is exceptionally efficient in the glutathione (GSH) conjugation of (+)-anti-BPDE [X. Hu, S.K. Srivastava, H. Xia, Y. C. Awasthi, and S. V. Singh (1996) J. Biol. Chem. 271, 32684-32688], could not be detected in the lung. The specific activities of the lung GSTs in the GSH conjugation of (+)-anti-BPDE were in the order of GST 8.9 > GST 8.7 > GST 9.4 > GST 6.0. While DPS treatment did not increase the levels of any pulmonary GST isoenzyme, the expression of pi class GST 8.9 was significantly increased in response to both DAS and DATS administrations. Interestingly, DATS, an OSC which lacks activity against BP-induced lung cancer in mice, was a relatively more potent inducer of pi class GST isoenzyme than DAS, which is a potent inhibitor of BP-induced lung tumorigenesis. The results of the present study suggest that a mechanism(s) other than GST induction is likely to be responsible for the differential effects of DAS and DATS on BP-induced lung cancer in mice. Our results also suggest that relatively lower efficacies of the OSCs against BP-induced lung cancer than against forestomach neoplasia may be attributed to (a) a lack of expression in the lung of an isoenzyme corresponding to forestomach GST 9.5 and (b) a comparatively lower level of induction of pi type GST in the lung than in the forestomach by these OSCs.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed1997

Effects of metal ions on the substrate-specificity and activity of proton-pumping nicotinamide nucleotide transhydrogenase from Escherichia coli.

Nicotinamide nucleotide transhydrogenase catalyzes the reversible reduction of NADP+ by NADH and a concomitant proton translocation. It was demonstrated (Glavas, N.A. and Bragg, P.D. (1995) Biochim. Biophys. Acta 1231, 297-303) that the Escherichia coli transhydrogenase also catalyzed a reduction of the NAD-analogue 3-acetylpyridine-NAD+ (AcPyAD+) by NADH at low pH and in the absence of (added) NADP(H) and high salt concentrations The mechanism of this reaction has as yet not been explained. In the present study, the E. coli transhydrogenase was purified by affinity chromatography through the NADP(H)-site, rendering the pure enzyme free of NADP(H). Using this preparation it was confirmed that the enzyme readily catalyzes the above reaction. Inhibitors specific for the NADP(H)-site, e.g., palmitoyl-Coenzyme A and adenosine-2'-monophosphate-5'-diphosphoribose, strongly inhibited the reduction of AcPyAD+ by NADH, whereas an inhibitor of the NAD(H)-site, adenosine 5'-diphosphoribose, was less inhibitory. This suggests that a lack of metal ions or other ions at low pH induces an unspecific interaction of the NADP(H)-site with AcPyAD+ or NADH, presumably NADH, producing a cyclic reduction of AcPyAD+ by NADH via NAD(H) bound in the NADP(H) site. A stimulation of reduction of AcPyAD+ by NADPH by Mg2+ present during reconstitution of transhydrogenase in phospholipid vesicles was observed, but it is presently unclear whether this effect is related to that seen with the detergent-dispersed enzyme.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗

PubMed1997

Opportunistic infection and immunologic function in patients with human immunodeficiency virus-associated non-Hodgkin's lymphoma treated with chemotherapy.

BACKGROUND: The incidence of systemic non-Hodgkin's lymphoma (NHL) is higher in the population infected with human immunodeficiency virus (HIV) than in the uninfected population. Standard treatment for this cancer involves the administration of systemic chemotherapy. PURPOSE: Our objective was to determine the relative risk (RR) of opportunistic infection and the relative change in immunologic function in a cohort of patients who had HIV-associated NHL and who were treated with combination chemotherapy and to compare them with those in a matched cohort of control subjects who had advanced HIV infection but no signs of NHL. METHODS: We performed a case-control study in which the clinical course of each patient with HIV-associated NHL (n = 43; case subjects) treated with infusional cyclophosphamide, doxorubicin, and etoposide was compared with that of two patients with HIV infection but without lymphoma who were matched for CD4 lymphocyte count and prior opportunistic infection (n = 86; control subjects). The patients' medical records were reviewed for all information related to acquired immunodeficiency syndrome (AIDS)-defining opportunistic infections, survival, cause of death, and lymphocyte subset analyses. Univariate and multivariate analyses were performed to determine whether any of a number of confounding factors (e.g., age, sex, CD4 count, prior opportunistic infection, and prior antiretroviral therapy) could have influenced the risk of developing a first infectious event (defined as opportunistic infection or nonlymphoma death). All P values resulted from two-sided statistical tests. RESULTS: In the univariate analysis, a significantly greater risk for a first event was associated with being a case subject (RR = 1.8; 95% confidence intervals [CI] = 1.1-3.0; P < .05), having a low CD4 count (< 100/microL) (RR = 3.1; 95% CI = 1.8-5.4; P < .0001), being female (RR = 1.7; 95% CI = 1.1-3.3; P < .05), having prior Pneumocystis carinii pneumonia (RR = 3.5; 95% CI = 1.9-6.3; P < .0001), having any prior opportunistic infection (RR = 3.6; 95% CI = 2.1-6.4; P < .0001), and having prior antiretroviral therapy (RR = 1.9; 95% CI = 1.1-3.3; P < .05). In the multivariate analysis, however, being a case subject (RR = 2.1; 95% CI = 1.2-3.6; P < .01), having a low CD4 count (RR = 2.1; 95% CI = 1.2-3.9; P < .05), and being female (RR = 3.0; 95% CI = 1.8-5.6; P < .001) were the only characteristics associated with an increased risk of a first event. When the mean CD4 lymphocyte count at approximately 1 year was compared with that at baseline, there was a significantly greater decrease in the CD4 count among case subjects than among control subjects (mean decrease +/- standard deviation [SD] = 99/microL +/- 138/microL versus 29/microL +/- 100/microL; P = .03). CONCLUSIONS: Treatment of patients who have HIV-associated NHL with a non-steroid-containing chemotherapy regimen was associated with a significant and sustained reduction in the CD4 lymphocyte count and a twofold increase in the risk of developing opportunistic infection. IMPLICATIONS: Oncologists and other physicians who treat patients with HIV-associated NHL should be familiar with the prophylaxis, recognition, and management of opportunistic infection. In addition, there is a need to identify effective strategies for the amelioration of chemotherapy-induced immunosuppression in this population.

AIDS-Related Opportunistic Infections↗

PubMed1997

Low-flow ischemia leads to translocation of canine heart GLUT-4 and GLUT-1 glucose transporters to the sarcolemma in vivo.

BACKGROUND: Myocardial ischemia increases heart glucose utilization in vivo. However, whether low-flow ischemia leads to the translocation of glucose transporter (GLUT)-4 and/or GLUT-1 to the sarcolemma in vivo is unknown. METHODS AND RESULTS: In a canine model, we evaluated myocardial glucose metabolism in vivo and the distribution of GLUT-4 and GLUT-1 by use of immunoblotting of sarcolemma and intracellular membranes and immunofluorescence localization with confocal microscopy. In vivo glucose extraction increased fivefold (P < .001) and was associated with net lactate release in the ischemic region. Ischemia led to an increase in the sarcolemma content of both GLUT-4 (15 +/- 2% to 30 +/- 3%, P < .02) and GLUT-1 (41 +/- 4% to 58 +/- 3%, P < .03) compared with the nonischemic region and to a parallel decrease in their intracellular contents. Immunofluorescence demonstrated the presence of both GLUT-4 and GLUT-1 on cardiac myocytes. GLUT-1 had a more prominent cell surface pattern than GLUT-4, which was primarily intracellular in the nonischemic region. However, significant GLUT-4 surface labeling was found in the ischemic region. CONCLUSIONS: Translocation of the insulin-responsive GLUT-4 transporter from an intracellular storage pool to the sarcolemma occurs in vivo during acute low-flow ischemia. GLUT-1 is also present in an intracellular storage pool from which it undergoes translocation to the sarcolemma in response to ischemia. These results indicate that both GLUT-1 and GLUT-4 are important in ischemia-mediated myocardial glucose uptake in vivo.

Animals↗