Biomedical subjects

M Du

Publications and source records attributed to M Du.

At least 55 records · Page 3Linked to original sources

PubMed2000

Varying coordination modes and magnetic properties of copper(II) complexes with diazamesocyclic ligands by altering additional donor pendants on 1,5-diazacyclooctane.

A series of new diazamesocyclic ligands based on a diazamesocycle, 1,5-diazacyclooctane (DACO), functionalized by additional donor groups--1,5-bis(N-1-methylimidazol-2-ylmethyl)-1,5- diazacyclooctane (L1), 1-(2-hydroxybenzyl)-1,5-diazacyclooctane (HL2), 1,5-bis(2-hydroxybenzyl)-1,5-diazacyclooctane (H2L3), and 1-(N-1-methylimidazol-2-ylmethyl)-1,5-diazacyclooctane (L4)--and their Cu(II) complexes have been synthesized and characterized. Single-crystal X-ray diffraction analysis of the four Cu(II) complexes revealed that L1 forms a five-coordinate mononuclear complex, HL2 a N3- mu-bridged binuclear complex, H2L3 an oxygen mu-bridged trinuclear complex, and L4 a one-dimensional zigzag coordination polymeric complex with Cu(II). [CuL1ClO4](ClO4) (I): a = 12.194(2) A, b = 13.351(3) A, c = 14.473(3) A, beta = 107.10(3) degrees, Z = 4. [CuL2(N3)]2 (II): a = 8.1864(6) A, b = 18.141(2) A, c = 9.3307(7) A, beta = 103.662(6) degrees, Z = 2. [Cu3(L3)2Cl2] (III): a = 10.7296(13) A, b = 13.7707(17) A, c = 13.5523(17) A, beta = 106.350(3) degrees, Z = 2. ([CuL4Cl]2ClO4) infinity (IV): a = 7.279(1) A, b = 23.695(5) A, c = 19.308(4) A, beta = 100.28(3) degrees, Z = 8. All four complexes crystallize in the monoclinic crystal system with the P2(1)/c space group, and each Cu(II) center coordinated with DACO is pentacoordinated with a distorted square-pyramidal or trigonal-bipyrimidal coordination environment. In complex IV, the binuclear cation unit [CuL4Cl]2(2+) constitutes the fundamental building block of an infinite alternating zigzag chain structure, and the binuclear unit contains two types of geometries around the Cu(II) centers: the Cu(1) center is a distorted square-pyramidal environment, while the Cu(2) is a distorted trigonal-bipyramidal coordination environment. To the best of our knowledge, this is the first Cu(II) complex of a diazamesocyclic ligand with an infinite polymeric structure. The magnetic properties of complexes II, III, and IV have been investigated by variable-temperature magnetic susceptibility measurements in the solid state. The obtained parameters are 2J = 2.06 cm-1 (II), -345.56 cm-1 (III), and -2.60 cm-1 (IV), which differ greatly from ferromagnetic to weak and strong antiferromagnetic coupling. These results unequivocally indicate that the nature of the pendant arms is a key factor governing the structure and properties of the complexes; therefore, the coordination modes and properties of the metal complexes of a diazamesocycle can be controlled by altering the pendant donors on it. Magneto-structural correlation has been precisely analyzed, and the solution properties of these complexes have also been described.

Journal Article↗

PubMed2000

High-performance liquid chromatography method for the determination and quantitation of arabinosylguanine triphosphate and fludarabine triphosphate in human cells.

A gradient anion-exchange high-performance liquid chromatographic assay was developed for the simultaneous determination and quantitation of the cytotoxic triphosphates of arabinosylguanine (ara-GTP) and fludarabine (F-ara-ATP). The method was validated with respect to selectivity, recovery, linearity, precision, and accuracy using authentic standards. To test this assay in a more complex biological matrix, perchloric acid extracts of circulating human leukemia cells spiked with known concentrations of ara-GTP and F-ara-ATP were examined. Finally, to assess the clinical utility of our method, perchloric acid extracts of circulating human leukemia cells isolated from patients treated with fludarabine and nelarabine were analyzed. The range of quantitation was 0.0125-10 nmol for the ara- and native NTPs in cellular extracts. This assay should be helpful in establishing the mechanistic rationales for drug scheduling and combinations of nelarabine and fludarabine, and for correlating the therapeutic efficacy and levels of the cytotoxic triphosphates in target cells.

Arabinonucleotides↗

PubMed2000

Effects of dietary conjugated linoleic acid and linoleic:linolenic acid ratio on polyunsaturated fatty acid status in laying hens.

A study was conducted to determine the effects of dietary conjugated linoleic acid (CLA) and the ratio of linoleic:linolenic acid on long-chain polyunsaturated fatty acid status. Thirty-two 31-wk-old White Leghorn hens were randomly assigned to four diets containing 8.2% soy oil, 4.1% soy oil + 2.5% CLA (4.1% CLA source), 4.1% flax oil + 2.5% CLA, or 4.1% soy oil + 4.1% flax oil. Hens were fed the diets for 3 wk before eggs and tissues were collected for the study. Lipids were extracted from egg yolk and tissues, classes of egg yolk lipids were separated, and fatty acid concentrations of total lipids, triglyceride, phosphatidylethanolamine, and phosphatidylcholine were analyzed by gas chromatography. The concentrations of monounsaturated fatty acids and non-CLA polyunsaturated fatty acids were reduced after CLA feeding. The amount of arachidonic acid was decreased after CLA feeding in linoleic acid- and linolenic acid-rich diets, but amounts of eicosapentaenoic acid and docosahexaenoic acid were increased in the linolenic-rich diet, indicating that the synthesis or deposition of long-chain n-3 fatty acids was accelerated after CLA feeding. The increased docosahexaenoic acid and eicosapentaenoic acid contents in lipid may be compensation for the decreased arachidonic acid content. Dietary supplementation of linoleic acid increased n-6 fatty acid levels in lipids, whereas linolenic acid increased n-3 fatty acid levels. Results also suggest that CLA might not be elongated to synthesize long-chain fatty acids in significant amounts. The effect of CLA in reducing the level of n-6 fatty acids and promoting the level of n-3 fatty acids could be related to the biological effects of CLA.

Animal Nutritional Physiological Phenomena↗

PubMed2000

[1,5-Bis]

Explore the source record for details and available documents.

Journal Article↗

PubMed2000

Chloro(2-

The crystal structure of the title complex, [Cd(C(20)H(25)N(2)O(2))Cl], reveals a hydrogen-bonded dimer composed of neutral molecules. The Cd(II) center is five-coordinated by two O atoms of the pendant arms, two nitrogen donors of the 1, 5-diazacyclooctane ring and a chloride anion. The coordination geometry of the complex could be described as a distorted square pyramid. The 1,5-diazacyclooctane backbone adopts a boat/chair configuration and the two phenol/phenolato groups have a dihedral angle of 101.3 (2) degrees between them. The coordinated phenolate and phenolic groups of inversion-related molecules form strong intermolecular O-H.O hydrogen bonds.

Journal Article↗

PubMed2000

A novel three-dimensional copper(II) network via hydrogen bonds: diaquabis

The crystal structure of the title complex, [Cu(C(7)H(8)N(4))(2)(H(2)O)(2)](ClO(4))(2), consists of a discrete centrosymmetric [Cu(C(7)H(8)N(4))(2)(H(2)O)(2)](2+) cation and two perchlorate anions. The Cu(II) centre is six-coordinated by four N donors from the two pyrazole rings [Cu-N 1.998 (2) and 2.032 (3) A] and two O atoms from the water molecules occupying the apical sites [Cu-O 2.459 (3) A]. The coordination geometry of the complex can be described as octahedral. There is a unique three-dimensional network in which the perchlorate units are linked by a combination of strong O-H.O and weak C-H.O hydrogen bonds.

Journal Article↗

PubMed2000

Bis(1,5-diazacyclooctane-N,N')nickel(II) dibromide.

The crystal structure of the title complex, [Ni(C(6)H(14)N(2))(2)]Br(2), consists of discrete [Ni(C(6)H(14)N(2))(2)](2+) cations and bromide counter-anions. The Ni(II) ion is at the center of symmetry and is four-coordinated by four nitrogen donors of the mesocyclic ligand 1,5-diazacyclooctane (DACO) [Ni-N 1.935 (2)-1.937 (2) A]. The coordination geometry of Ni(II) can be considered as square planar and both DACO ligands take the boat-chair conformation. The bromide anions are hydrogen bonded with the nitrogen donors of the ligands to form a macrocycle-like ring system.

Journal Article↗

PubMed2000

Oral health services in PR China as evaluated by dentists and patients.

OBJECTIVE: To describe the function of oral health services and the delivery of oral health care in PR China. DESIGN: Cross-sectional surveys. Self-administered questionnaires gathered information on professional practices and attitudes of Chinese dentists. Patients were examined clinically for caries and services rendered. Patients were interviewed about oral health status, reason of dental visits and consumption of services, perceived need for care and self-care practices. SETTING: Wuhan City of the Hubei Province of China. SUBJECTS: Random samples of dentists (n = 250) working with child and adult patients in 1998 in Wuhan City. Each dentist had a representative sample of 20 patients attending consecutively for care enrolled in the study. RESULTS: On average, the dentists saw 12 patients per day, with most time devoted to restorative treatment and extraction. The majority of dentists held the opinion that in China little attention is given to preventive care. Forty per cent of the patients were new to the dentists and more than half attended care because of pain or acute symptoms. The reported mean number of decayed, missing, and filled teeth varied from 2.6 for 12-year-old patients to 10.7 for patients aged 65-74. Daily toothbrushing was practised by more than 90% of the patients in all age groups, however, the tradition of regular dental visits was weak. Most patients (51-75 per cent) attended for care due to acute problems or pain. CONCLUSION: The study indicated the need for reorientation of the Chinese oral health services towards prevention.

Adolescent↗

PubMed2000

Caries patterns and their relationship to infant feeding and socio-economic status in 2-4-year-old Chinese children.

AIMS: To describe the prevalence, severity and patterns of caries in 2-4-year-old children and to evaluate the association between caries experience of the children and their feeding patterns and socio-economic background in terms of mothers' education and family income. DESIGN: Cross-sectional survey. SETTING: Suburban area of Hanchuan in Hubei province, China. PARTICIPANTS: A sample of 426 children (250 boys and 176 girls). METHODS: Dental-examinations were undertaken in kindergartens using World Health Organization diagnostic criteria for dental caries. Mothers completed a short questionnaire. OUTCOME MEASURES: Prevalence of caries; rampant caries; caries in incisors; caries in incisors and/or canines and molars; mean number of decayed, missing and filled teeth/surfaces (dmft/s). RESULTS: 36% of the children had caries, 7% had rampant caries. The more extensive pattern of caries involving primary molars as well as incisors and/or canines was seen in 12% of children. Children who had been wholly bottle-fed had five times the risk of having rampant caries compared to children who were breast-fed. CONCLUSIONS: The results indicated that infant feeding practice might be a key risk factor for the development of caries at an early age in this country as elsewhere.

Bottle Feeding↗

PubMed2000

EGF stimulates gastrin promoter through activation of Sp1 kinase activity.

Epidermal growth factor (EGF) receptor activation stimulates gastrin gene expression through a GC-rich element called gastrin EGF response element (gERE). This element is bound by Sp1 family members and is a target of the ras-extracellular signal-regulated kinase (Erk) signal transduction cascade. This raised the possibility that Sp1 may be phosphorylated by kinases of this signaling pathway. Erk is capable of phosphorylating other mitogen-inducible transcription factors, e.g., Elk and Sap, suggesting that Erk may also mediate EGF-dependent phosphorylation of Sp1. This possibility was tested by studying Sp1-dependent kinase activity in extracts prepared from EGF-activated AGS cells by use of solid-phase kinase assays and immunoprecipitation of metabolically labeled Sp1. The results revealed that Sp1 kinase activity (like gastrin promoter activation) is inhibited by PD-98059 and, therefore, is dependent on mitogen-activated protein kinase kinase 1 (Mek 1). However, EGF-dependent activation of endogenous Erk did not account for most of the Sp1 kinase activity, since Erk and additional Sp1 kinase activity analyzed in a solid-phase kinase assay eluted from an ion-exchange column in different fractions. Phosphoamino acid analysis of in vivo radiolabeled Sp1 demonstrated that the kinase phosphorylates Sp1 on Ser and Thr in response to EGF. Therefore, most EGF-stimulated Sp1 kinase activity is Mek 1 dependent and distinct from Erk.

Binding Sites↗

PubMed2000

[Transgenic mice model of human hepatitis B virus x gene].

OBJECTIVE: To set up a human hepatitis B virus x (HBx) gene transgenic model. METHODS: The model was set up by microinjection, the integration and expression of the founders were identified by molecular hybridization. RESULTS: A 1,800 bp DNA fragment containing the human HBx promoter and genomic DNA was microinjected into the male pronucleus of the fertilized eggs of mice. Three hundred and thirty-eight eggs survived from microinjection were transplanted into the oviduct of 16 pseudopregnant female, 12 pseudopregnant mice got pregnant and gave birth to 74 pups. Genomic DNA were extracted from the tails of the pups, Southern blot hybridization was used for determination of the integration of human HBx gene. The 1,800 bp microinjected fragment was used as the probe, 17 mice (founders) were identified of the integration of human HBx gene. Total RNA were extracted from the livers of the founders, all 17 founders were identified of the expression of human HBx gene by using Northern blot hybridization. CONCLUSIONS: These results may provide animal models for studying on the correlation between chronic HBV infection and the development of hepatocellular carcinoma.

Animals↗

PubMed1999

ZBP-99 defines a conserved family of transcription factors and regulates ornithine decarboxylase gene expression.

Among transcription factors that regulate ornithine decarboxylase (ODC) gene expression are those that interact with GC-rich promoters, including Sp1 and ZBP-89. Sp1 functions as a transactivator and ZBP-89 as a transrepressor of both the ODC and gastrin promoters. This study reports the cloning and characterization of a second member of the ZBP family that also binds GC boxes. ZBP-99 contains four Krüppel-type zinc fingers that collectively share 91% amino acid sequence similarity and 79% sequence identity with those found in ZBP-89. In addition, there are highly conserved amino acid sequences in the carboxy-terminal segments of the two genes. In spite of their structural similarities, the two proteins are encoded at distinct loci, ZBP-89 on chromosome 3q21 and ZBP-99 on 1q32.1. The predicted open reading frame of ZBP-99 cDNA encodes a 99-kDa protein. Electrophoretic mobility shift assays showed that ZBP-99 protein specifically binds to the GC-rich promoter elements of gastrin and ODC genes. Northern blot analysis showed that a major ZBP-99 transcript of 5.6 kb is expressed ubiquitously at low levels, with elevated expression levels in placenta and in adult kidney, liver, and lymphocytes. Cotransfection of AGS gastric adenocarcinoma and HT-29 colon adenocarcinoma cells with a ZBP-99 expression construct and with an ODC reporter construct show that ZBP-99 repressed basal expression in the two cell lines by 80 and 60%, respectively. Collectively, the data suggest that ZBP-99 binds GC-rich promoters and may complement the activities mediated by ZBP-89.

Amino Acid Sequence↗

PubMed1999

A new monoclonal anti-idiotypic catalytic antibody with a CPA-like activity.

IIF9D8, a new monoclonal anti-idiotypic catalytic antibody with a CPA esterase-like activity was elicited by ID11D7, the monoclonal competitive inhibitory antibody to CPA. The hydrolysis of hippuryl-DL-phenyllactic acid by McAb IIF9D8 follows the Michaelis-Menten kinetics. The Km value and kcat are 0.036 M and 0.598 min(-1), respectively, and the rate acceleration (kcat/kuncat) is 30500. Compared with the previous McAb 32C3 induced by polyclonal antibodies to CPA, McAb IIF9D8 shows higher catalytic efficiency The catalytic antibodies with the catalytic properties similar to natural enzymes could be obtained by this approach.

Animals↗

PubMed1999

Suppression of inducible cyclooxygenase 2 gene transcription by aspirin and sodium salicylate.

The pharmacological action of salicylate cannot be explained by its inhibition of cyclooxygenase (COX) activity. In this report, the effects of aspirin and sodium salicylate on COX-2 expressions in human umbilical vein endothelial cells and foreskin fibroblasts were evaluated. Aspirin and sodium salicylate at therapeutic concentrations equipotently blocked COX-2 mRNA and protein levels induced by interleukin-1beta and phorbol 12-myristate 13-acetate. The suppressing effect was more pronounced in cultured cells deprived of fetal bovine serum for 24 h, suggesting that it may be cell cycle related. Salicylate inhibited nascent COX-2 transcript synthesis but had no effect on COX-2 mRNA stability. It inhibited COX-2 promoter activity in a concentration-dependent manner. In mice pretreated with aspirin (10 and 30 mg/kg), followed by challenge with lipopolysaccharide, COX-2 mRNA expression in peritoneal macrophages was markedly suppressed. These findings suggest that salicylate exerts its antiinflammatory action in part by suppressing COX-2 induction, thereby reducing the synthesis of proinflammatory prostaglandins.

Animals↗

PubMed1999

Sp1 phosphorylation by Erk 2 stimulates DNA binding.

EGF stimulates gene expression through a variety of signal transduction pathways that include the ras-Erk pathway. We have shown previously that EGF receptor activation stimulates gastrin gene expression through a GC-rich element called gERE. This element binds Sp1 family members and raises the possibility that the ras-Erk signal transduction cascade may target this novel EGF responsive element. Moreover, it is known that Erk 2 is capable of phosphorylating other mitogen-inducible transcription factors, e.g., Elk, Sap suggesting that Erk may also inducibly phosphorylate Sp1. To test this hypothesis directly using cotransfection experiments, we show that ras and Erk 2 activation indeed target the gERE element. The Mek 1 kinase inhibitor, PD98059, blocks 50% of EGF-inducible gastrin promoter activity. Pretreatment of the extracts with recombinant Erk2 stimulated Sp1 binding; whereas dephosphorylation reduced but did not eliminate Sp1 binding. Together, these studies demonstrate the novel finding that inducible binding of Sp1 is regulated by its state of phosphorylation. Further, gastrin promoter activation is mediated in part by the ras-Erk signaling cascade that targets Sp1.

Adenocarcinoma↗

PubMed1999

Effect of dietary conjugated linoleic acid on the composition of egg yolk lipids.

Forty-eight 27-wk-old White Leghorn hens were assigned randomly to four diets containing 0, 1.25, 2.5, or 5.0% conjugated linoleic acid (CLA). Hens were fed the CLA diets for 2 wk before eggs were collected for the study. Classes of egg yolk lipids were separated, and fatty acid concentrations in total lipid, triglyceride (TG), phosphatidylethanolamine (PE), and phosphatidylcholine (PC) were analyzed to determine the incorporation of dietary CLA isomers into different classes of egg yolk lipids. The amounts of CLA incorporated into lipid, PC, PE, and TG of egg yolk were proportional to the levels of CLA in the diet. However, more CLA was incorporated in TG than in PC and PE. The incorporation rates of different CLA isomers into different classes of lipids also were significantly different: cis-9, trans-11 and cis-10, trans-12 CLA were deposited more in TG, but cis-11, trans-13 CLA deposition in TG was significantly less. There were large differences in the concentrations of cis-8, trans-10 CLA in PC and PE. The inclusion of CLA into the diet influenced the metabolism of polyunsaturated fatty acids. The contents of 5,8,11,14-eicosatetraenoic, 9,12-octadecadienoic, and 9,12,15-octadecatrienoic acids were decreased as dietary CLA increased. Three isomers of hexadecadienoic acid were found in egg yolk lipids from hens fed 5% dietary CLA. The detection of hexadecadienoic acid isomers in lipid indicates that the utilization of CLA as an energy source after the first round of beta-oxidation may be less favorable than that of 9,12-octadecadienoic acid.

Animals↗

PubMed1999

Comparative analysis of HPLC profile of cytosolic thymidine kinase activity between hepatoma and regenerating liver in rat with reference to phosphorylation.

Thymidine kinase (TK) activity in rat hepatoma JB1 and AH136B was mainly due to cytosolic TK and was much higher than that in rat regenerating liver. Two forms of cytosolic TK, designated as TK-I and TK-II, were revealed in addition to mitochondrial TK in anion-exchange high performance liquid chromatography (HPLC) of the enzyme extract from hepatoma JB1. During incubation of the enzyme extract at 20 degrees C in the presence of phosphatase inhibitor NaF, TK-II activity remained while TK-I activity almost disappeared. Thus, TK-II appeared to be more stable than TK-I. In Western blot analysis, TK-II was much more phosphorylated and exhibiting higher specific activity than TK-I. Meanwhile, regenerating liver derived from the rat 24 h after partial hepatectomy showed only TK-I activity, which completely disappeared after incubation at 20 degrees C even in the presence of NaF. Consequently, the presence of TK-II might account for the higher TK activity in hepatomas than in regenerating liver.

Animals↗

PubMed1999

Effects of monoclonal antibody on colonization of Streptococcus sobrinus and development of dental caries in rats.

OBJECTIVE: To investigate the effect of local application of monoclonal antibody (McAb) raised against the 210KD cell surface protein antigen (PAg) of Streptococcus sobrinus on the colonization of rats' teeth and the development of dental caries. MATERIALS AND METHODS: Thirty Wistar rats were divided into 3 groups: group 1 received McAb against PAg; group 2 received unrelated mice ascites; group 3 received pure buffered saline. The bacteria were applied 6 times to the occlusal surfaces of molars and to the labial surfaces of incisors. After three applications, streptomycin-resistant S. sobrinus 6715 was applied to the teeth and the rats were fed with caries-inducing diet 2000. The number of colonized S. sobrinus was counted on the streptomycin-supplemented mutans streptocci agar and expressed as a percentage of the total colonies on BHI agar. The presence of caries was examined and scored following Keyes' procedure. RESULTS: There were significantly lower levels of colonization by S. sobrinus on rats' teeth and lower mean caries scores on the teeth treated with McAb compared with those in the control groups. CONCLUSION: Local passive immunization with McAb against PAg may be an effective way to prevent colonization by implanted S. sobrinus and development of dental caries.

Analysis of Variance↗