Caprine offspring born from fresh and frozen-thawed in vitro-produced embryos.
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Animals↗
Biomedical subjects
Y Han
Publications and source records attributed to Y Han.
An active immunization approach to generate protective catalytic antibodies.
We report that mice immunized with a phosphate immunogen produced polyclonal catalytic antibodies (PCAbs) that catalysed the hydrolysis of carbaryl, a widely used broad-spectrum carbamate insecticide that exerts toxic effects in animals and humans. The reaction catalysed by the PCAbs (IgGs) obeyed Michaelis-Menten kinetics in vitro with the following values at pH 8.0 and 25 degrees C: K(m) approximately 8.0 microM, k(cat)=4.8x10(-3)-5.8x10(-1), k(cat)/k(non-cat)=5.6x10(1)-6.8x10(3) (where k(non-cat) is the rate constant of the reaction in the absence of added catalyst). The PCAbs were also active in whole sera under physiological conditions in vitro. The PCAbs induced in vivo were also active in vivo, as immunization with the phosphate immunogen decreased the mouse blood concentration of carbaryl. To our knowledge, this is the first report demonstrating that active immunization generates antibodies possessing therapeutic catalytic function in vivo. We propose that active immunization schemes that induce enzymically active antibodies may provide a highly specific therapeutic approach for degrading toxic substances.
Animals↗
Cysteine-25 of adenylate kinase reacts with dithiothreitol to form an adduct upon aging of the enzyme.
Adenylate kinase (AK) ages in solution in the presence of DL-dithiothreitol (DTT) with a gradual activity decrease. Upon dilution with 4 M guanidine hydrochloride denatured native and aged AK, both recover to the same activity as the fresh enzyme. Mass spectroscopy and 7-chloro-4-nitrobenz-2-oxa-1,3-diazole chloride modification kinetics studies identify that the residue cysteine-25 of the enzyme reacts with DTT to form an adduct. The formation of the unusual bridging DTT adduct of AK appears to be the result of a stable DTT-protein complex. The K(M) for AMP, ADP and MgATP of the DTT-modified enzyme does not differ significantly from that of the intact enzyme, whereas the secondary and tertiary structures of the enzyme change obviously. These results indicate that cysteine-25 may not be involved directly in substrate binding, but may play an important role in maintaining secondary and tertiary structures of native AK, as well as the conformation interconversion in the catalytic cycle.
Adenylate Kinase↗
Complement is essential for protection by an IgM and an IgG3 monoclonal antibody against experimental, hematogenously disseminated candidiasis.
The incidence of life-threatening, hematogenously disseminated candidiasis, which is predominantly caused by Candida albicans, parallels the use of modern medical procedures that adversely affect the immune system. Limited antifungal drug choices and emergence of drug-resistant C. albicans strains indicate the need for novel prevention and therapeutic strategies. We are developing vaccines and Abs that enhance resistance against experimental candidiasis. However, the prevalence of serum anti-Candida Abs in candidiasis patients has led to the misconception that Abs are not protective. To explain the apparent discrepancy between such clinical observations and our work, we compared functional activities of C. albicans-specific protective and nonprotective mAbs. Both kinds of Abs are agglutinins that fix complement and are specific for cell surface mannan, but the protective Abs recognize beta-mannan, and the nonprotective Ab is specific for alpha-mannan. By several indirect and direct measures, the protective mAbs more efficiently bind complement factor C3 to the yeast cell than do nonprotective Ab. We hypothesize that the C3 deposition causes preferential association of blood-borne fungi with host phagocytic cells that are capable of killing the fungus. We conclude from these results that the protective potential of Abs is dependent on epitope specificity, serum titer, and ability to rapidly and efficiently fix complement to the fungal surface. The mechanism of protection appears to be associated with enhanced phagocytosis and killing of the fungus.
Animals↗
In vivo clearance of glucuronoxylomannan, the major capsular polysaccharide of Cryptococcus neoformans: a critical role for tissue macrophages.
Cryptococcus neoformans produces a life-threatening meningitis in patients who are immunocompromised by AIDS. A striking feature of cryptococcosis in AIDS is high serum levels of the major capsular polysaccharide, glucuronoxylomannan (GXM). Soluble GXM has numerous biologic activities that may contribute to the pathogenesis of infection. The objective of the study was to further understand in vivo processing of GXM. Mice were injected intravenously with GXM, and the tissue distribution was determined. A macrophage suicide technique that used liposome-encapsulated dichloromethylene diphosphonate determined the role of macrophages. GXM was cleared from serum with a half-life of 24-48 h but was retained for an indefinite period in tissues rich in cells of the mononuclear phagocyte system. Ablation of macrophages decreased GXM in the liver and spleen and increased serum GXM. The results identify a key role for macrophages in the clearance of GXM from serum and identify macrophages as a long-term reservoir for storage.
Animals↗
Rhenium oxo complexes of a chelating diyne ligand. Synthesis and study of the kinetics of protonation.
A series of oxo complexes, Re(O)X(diyne) (X = I, Me, Et), have been prepared from 2,7-nonadiyne and Re(O)I(3)(PPh(3))(2). Addition of B(C(6)F(5))(3) to Re(O)I(2,7-nonadiyne) (5) results in coordination of the oxo ligand to the boron. The protonation of Re(O)(X)(2-butyne)(2) and Re(O)(X)(2,7-nonadiyne)(2) with a variety of acids has been examined. With 5 and HBF(4)/Et(2)O, the ultimate product was [Re(CH(3)CN)(3)(I)(2,7-nonadiyne)](2+) (7). The conversion of 5 to 7 changes the conformation of the diyne ligand from a "chair" to a "boat" and shifts its propargylic protons considerably downfield in the (1)H NMR. The kinetics of the protonation of Re(O)I(2,7-nonadiyne) (5) by CF(3)SO(3)H in CH(3)CN have been monitored by visible spectroscopy, in a stopped-flow apparatus, and by low temperature (1)H NMR. Two second-order rate constants, presumably successive protonations, were observed in the stopped-flow, k(1) = 11.9 M(-)(1) s(-)(1) and k(2) = 3.8 M(-)(1) s(-)(1). Low temperature (1)H NMR spectroscopy indicated that the resulting solution contained a mixture of two doubly protonated intermediates X and Y, each of which slowly formed the product 7 via an acid-independent process.
Journal Article↗
Dissolution response of hydroxyapatite coatings to residual stresses.
The effect of residual stress on the dissolution of hydroxyapatite (HA) coatings was investigated. The examined coatings of 80-, 110-, and 200-microm thickness were prepared by a plasma-spraying technique under identical conditions. Residual stresses in the coatings were measured with a hole-drilling method. Dissolution of the coatings was monitored along with an examination of the phase composition. The results showed that both tensile residual stress and amorphous HA existed throughout the entire depth of the coatings and tended to increase from the surface to the interface of the coating and substrate. The thicker the coatings were, the higher the maximum residual stress was. Correspondingly, the pH value and calcium concentration of the solutions tended to increase with the coating thickness. On the basis of these phenomena and a thermodynamic analysis of the dissolution of the HA subjected to stresses, we concluded that besides structural effects, residual stress was also an important intrinsic factor influencing dissolution of HA coatings, and the dissolution can be delayed or even restrained by compressive residual stress.
Biocompatible Materials↗
Stat1-independent regulation of gene expression in response to IFN-gamma.
Although Stat1 is essential for cells to respond fully to IFN-gamma, there is substantial evidence that, in the absence of Stat1, IFN-gamma can still regulate the expression of some genes, induce an antiviral state and affect cell growth. We have now identified many genes that are regulated by IFN-gamma in serum-starved Stat1-null mouse fibroblasts. The proteins induced by IFN-gamma in Stat1-null cells can account for the substantial biological responses that remain. Some genes are induced in both wild-type and Stat1-null cells and thus are truly Stat1-independent. Others are subject to more complex regulation in response to IFN-gamma, repressed by Stat1 in wild-type cells and activated in Stat1-null cells. Many genes induced by IFN-gamma in Stat1-null fibroblasts also are induced by platelet-derived growth factor in wild-type cells and thus are likely to be involved in cell proliferation. In mouse cells expressing the docking site mutant Y440F of human IFN-gamma receptor subunit 1, the mouse Stat1 is not phosphorylated in response to human IFN-gamma, but c-myc and c-jun are still induced, showing that the Stat1 docking site is not required for Stat1-independent signaling.
Animals↗
Mesoporous aluminosilicates with ordered hexagonal structure, strong acidity, and extraordinary hydrothermal stability at high temperatures.
Highly ordered hexagonal mesoporous aluminosilicates (MAS-5) with uniform pore sizes have been successfully synthesized from assembly of preformed aluminosilcate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. The aluminosilicate precursors were obtained by heating, at 100--140 degrees C for 2--10 h, aluminasilica gels at the Al(2)O(3)/SiO(2)/TEAOH/H(2)O molar ratios of 1.0/7.0--350/10.0--33.0/500--2000. Mesoporous MAS-5 shows extraordinary stability both in boiling water (over 300 h) and in steam (800 degrees C for 2 h). Temperature-programmed desorption of ammonia shows that the acidic strength of MAS-5 is much higher than that of MCM-41 and is comparable to that of microporous Beta zeolite. In catalytic cracking of 1,3,5-triisopropylbenzene and alkylation of isobutane with butene, MAS-5 exhibits greater catalytic activity and selectivity, as compared with MCM-41 and HZSM-5. The MAS-5 samples were characterized with infrared, UV--Raman, and NMR spectroscopy and numerous other techniques. The results suggest that MAS-5 consists of both mesopores and micropores and that the pore walls of MAS-5 contain primary and secondary structural building units, similar to those of microporous zeolites. Such unique structural features might be responsible for the observed strong acidity and high thermal stability of the mesoporous aluminosilicates with well-ordered hexagonal symmetry.
Journal Article↗
A selective cysteine protease inhibitor is non-toxic and cerebroprotective in rats undergoing transient middle cerebral artery ischemia.
Ischemic neuronal injury mediated by cysteine proteases such as calpains and caspases has been demonstrated in various experimental models. Cathepsins B and L are also cysteine proteases which may contribute to neuronal death after ischemia. The authors measured in vitro and in vivo toxicity and post-ischemic cytoprotective effects of a cysteine protease inhibitor which does not block calpain or caspase but, rather, is relatively selective for cathepsins B and L. The compound belongs to the peptidyl-diazomethane family (cysteine protease inhibitor 1, termed CP-1). In vitro toxicity was measured using an assay of cell viability, and in vivo toxicity was measured by histological tissue analysis after infusion of CP-1 in rats. Two hours of middle cerebral artery (MCA) occlusion in rats was performed by the intravascular suture method. Immediately following reperfusion, intravenous infusion of CP-1 or vehicle was performed for 4 h at 0.9 ml/h. After a 7-day survival, the infarct volumes were measured. CP-1 was non-toxic to cultured glial cells to a local concentration of 200 microM, and relatively non-toxic to cultured endothelial cells at concentrations of 100-200 microM. No animal exhibited toxic effects at any of the doses used. Histologic comparisons revealed no signs of tissue toxicity. CP-1 significantly reduced hemispheric infarct volume compared to control (37+/-8.2%) at concentrations of 10, 50, and 250 microM [22+/-15%, P=0.008; 20+/-13%, P=0.002; 23+/-15%, P=0.022, respectively (mean+/-standard deviation; N=7-10 per group)]. CP-1, at the concentration of 50 microM, improved the functional score of the animals, but did not significantly alter cerebral blood flow. This study supports the hypothesis that the lysosomal cathepsins B and/or L contribute to cerebral injury after focal ischemia with reperfusion. Cysteine protease inhibitors which are relatively selective for cathepsins B and L, but not the calpains or caspases, are effective at reducing infarct volume after intravenous post-ischemic administration.
Animals↗
Embryonic brain precursors transplanted into kainate lesioned rat spinal cord.
Embryonic day 14 rat cerebral cortex-derived precursors were expanded with FGF2 and labeled with BrdU prior to being transplanted into the kainic acid-lesioned adult rat spinal cord. While these precursors give rise to cells with neuronal, astrocytic and oligodendroglial phenotypes vitro, they remained largely undifferentiated up to 12 weeks in vivo. Numerous BrdU-labeled cells were found in injured gray matter, and also lining the dilated central canal that sometimes accompanies these lesions. BrdU-labeled cells never co-expressed Map2ab, rarely co-expressed GFAP but often co-expressed nestin, even after 12 weeks in vivo. These observations suggest that the environment of the kainic acid-injured spinal cord is not hostile to transplanted embryonic cerebral cortex-derived precursors, but also is not conducive to their neuronal differentation.
Animals↗
Isolation and characterisation of a cassava catalase expressed during post-harvest physiological deterioration.
Storage roots of cassava undergo a rapid, endogenous, post-harvest deterioration response that is thought to involve oxidative processes. A cassava catalase (MecCAT1) was isolated from a root cDNA library. The transcript is expressed predominantly in roots with little expression in leaves. Catalase enzyme activity and MecCAT1 transcript expression during the post-harvest period were compared in highly susceptible and less susceptible cultivars and suggest that high levels of catalase activity may play a role in delaying the deterioration response.
Amino Acid Sequence↗
[Alteration of subcellular distribution of protein kinase C isoforms in swelling-activated multi-drug-resistant gastric cancer cells and its significance].
OBJECTIVE: To study the alteration of expression and subcellular distribution of classical protein kinase (cPKC) isoforms in gastric cancer cells SGC7901 and their multidrug-resistant cell line SGC7901/VCR under condition of swelling activation and to study the significance of such alterations. METHODS: Immuno-fluorescence technique and Western Blotting were used to determine the expression and subcellular distribution of cPKC isoforms in gastric cancer cells SGC7901 and its multidrug-resistant cell line SGC7901/VCR under normal condition and during continuous hypotonic perfusion. The co-expression of p-glycoprotein (Pgp) and protein kinase C alpha (PKC alpha) was visualized by immunofluorescence double labeling and laser confocus microscopy. RESULTS: Under the normal condition, the four isoenzymes of cPKC were expressed in both the cell membrane and the nuclei of the gastric cancer cells SGC7901 and their multidrug-resistant cell line SGC7901/VCR; PKC alpha was strongly positively expressed in the multidrug-resistant cells and positively expressed in the drug-sensitive cells; PKC beta I and PKC beta II were positively expressed in both drug-resistant and drug-sensitive cells, and PKC gamma was strongly positively expressed in both cells. In drug-resistant cell line, cell-swelling and translocation of PKC alpha and PKC gamma were observed ten minutes after continuous hypotonic perfusion. Thirty minutes after the perfusion, almost all the PKCalpha was translocated into the cell membrane of SGC7901/VCR, part of the PKC gamma was translocated into the nucleus, and the cell volume increased to two to three times as much as before. Sixty minutes later, the subcellular distribution of PKCalpha and PKC gamma and the cell volume returned to normal. In drug-sensitive cells, 10 approximately 20 minutes after the continuous hypotonic perfusion nearly all the PKCalpha was translocated into the cell membrane, part of PKC gamma was translocated into the cell membrane, and the cell volume increased to two to three times as much as before. Forty minutes later, PKCalpha and PKCgamma had basically returned to normal. The subcellular distribution of PKCbeta I and PKC beta II remained unchanged in both SGC7901 and SGC7901/VCR. Co-expression of Pgy and PKCalpha was observed in both drug-sensitive and drug-resistant cells, especially in the former. CONCLUSION: Only PKCalpha and PKC gamma isoforms play an important role in the regulation of signal transduction of Pgy and cell volume under continuous perfusion and are related to the expression of PKC alpha and Pgy. PKC beta I and PKC beta II may have nothing to do with such processes.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
High-speed counter-current chromatography separation and purification of resveratrol and piceid from Polygonum cuspidatum.
High-speed counter-current chromatography (HSCCC) was applied to the separation and purification of resveratrol and piceid from the dried roots (20.0 g) of Polygonum cuspidatium. The EtOAc extracts were separated with chloroform-methanol-water (4:3:2, v/v). Resveratrol was identified in fraction 5. The water extracts were separated first with EtOAc-EtOH-water (10:1:10, v/v) and then with the same solvent system at the modified volume ratio of 70:1:70. Yields of resveratrol and piceid obtained were 2.18% and 1.07%. Chemical structures of the purified resveratrol and piceid were confirmed by electrospray ionization MS and 1H nuclear magnetic resonance spectroscopy.
Chromatography, High Pressure Liquid↗
TNF-alpha down-regulates CXCR4 expression in primary murine astrocytes.
CXC chemokine receptor 4 (CXCR4) is a co-receptor for human immunodeficiency virus (HIV) infection and is believed to be involved in the pathogenesis of AIDS-associated neurologic disorders and brain tumors. The physiological roles of CXCR4 in developmental patterning of the nervous and hematopoietic system; gastrointestinal angiogenesis; and cardiac organogenesis were established by studies in gene-targeted mice. Studies on CXCR4 expression and regulation in neuroepithelial cells are fundamental for understanding its physiopathologic roles in the central nervous system (CNS). We show here that CXCR4 expression by primary mouse astrocytes is suppressed by exposure to tumor necrosis factor-alpha (TNF-alpha). TNF-alpha caused a pronounced down-regulation of CXCR4 mRNA in a dose- and time-dependent manner. TNF-alpha-mediated decrease of CXCR4 mRNA accumulation resulted in decreased CXCR4 protein expression. As a result, the ability of stromal cell-derived factor-1alpha (SDF-1alpha) to induce activation of MAP kinases, Erk1/2 was impaired. The half life of CXCR4 mRNA in the presence and absence of TNF-alpha stimulation was comparable, suggesting that TNF-alpha down-regulated CXCR4 mRNA at the transcriptional level. These results suggest that TNF-alpha could modulate HIV and brain tumor pathogenesis and immune-mediated inflammation in the central nervous system (CNS) by regulation of CXCR4 expression.
AIDS Dementia Complex↗
Modeling the third loop of short-chain snake venom neurotoxins: roles of the short-range and long-range interactions.
The influence of long-range interactions on local structures is an important issue in understanding protein folding process and protein structure stability. Using short-chain snake venom neurotoxin as a model system, we have studied the conformational properties of eight different loop III sequences either in the environment of one of the short-chain neurotoxin, erabutoxin b (PDB ID 1nxb), or in free state by Monte Carlo simulated annealing method. The surrounding protein structure was found to be crucial in stabilizing the loop conformation. Although all the eight peptides prefer type V beta turn in solution, three of them (KPGI, KPGV, KSGI) turn to type II beta turn and the other five (KKGI, KKGV, KNGI, KQGI, and KRGV) are confined to more rigid type V beta turn conformation in the protein structure. Using flexible tetra-glycine-peptide to screen the backbone conformational space in the protein environment also validates the results. This study shows that long-range interactions do contribute to the stability and the types of conformation for a surface loop in protein, while short-range interactions may only provide candidate conformations, which then have to be filtered by the long-range interactions further.
Amino Acid Motifs↗
Characterization and stability of hydroxyapatite coatings prepared by an electrodeposition and alkaline-treatment process.
Hydroxyapatite (HA) coatings on titanium alloy substrates were prepared by an alkaline treatment of electrodeposited precursors. The structure, residual stress, and bond strength of the coatings were investigated. Test results showed that the coatings processed in this study exhibited fairly low tensile residual stress, high crystallinity, and were free of an amorphous phase. The bond strength of the coatings increased with the decrease of current density in the range of 0.2-15 mA/cm(2), and reached 14 MPa at 0.2 mA/cm(2). Evaluation of the coatings was performed together with the evaluation of the plasma-sprayed HA coatings immersed in distilled water. It was revealed that the dissolution and bond strength degradation of the coatings were much lower than those of the plasma-sprayed HA coatings.
Alkalies↗
Flavonol glycosides from the stems of Trigonella foenum-graecum.
Two kaempferol glycosides [kaempferol 3-O-beta-D-glucosyl(1-->2)-beta-D-galactoside 7-O-beta-D-glucoside and kaempferol 3-O-beta-D-glucosyl(1-->2)-(6"-O-acetyl)-beta-D-galactoside 7-O-beta-D-glucoside] as well as the quercetin glycoside [quercetin 3-O-beta-D-glucosyl(1-->2)-beta-D-galactoside 7-O-beta-D-glucoside] were isolated from the stems of Trigonella foenum-graecum L. (Leguminosae) along with a known kaempferol glycoside, lilyn [kaempferol 3-O-beta-D-glucosyl(1-->2)-beta-D-galactoside]. Their structures were established by analysis of chemical and spectral evidence.
Fabaceae↗